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Sample records for aureus iron surface

  1. Involvement of Iron in Biofilm Formation by Staphylococcus aureus

    PubMed Central

    Huang, Hsiu-Yun; Cheng, Yi-Ching

    2012-01-01

    Staphylococcus aureus is a human pathogen that forms biofilm on catheters and medical implants. The authors' earlier study established that 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose (PGG) inhibits biofilm formation by S. aureus by preventing the initial attachment of the cells to a solid surface and reducing the production of polysaccharide intercellular adhesin (PIA). Our cDNA microarray and MALDI-TOF mass spectrometric studies demonstrate that PGG treatment causes the expression of genes and proteins that are normally expressed under iron-limiting conditions. A chemical assay using ferrozine verifies that PGG is a strong iron chelator that depletes iron from the culture medium. This study finds that adding FeSO4 to a medium that contains PGG restores the biofilm formation and the production of PIA by S. aureus SA113. The requirement of iron for biofilm formation by S. aureus SA113 can also be verified using a semi-defined medium, BM, that contains an iron chelating agent, 2, 2′-dipyridyl (2-DP). Similar to the effect of PGG, the addition of 2-DP to BM medium inhibits biofilm formation and adding FeSO4 to BM medium that contains 2-DP restores biofilm formation. This study reveals an important mechanism of biofilm formation by S. aureus SA113. PMID:22479621

  2. Passage of heme-iron across the envelope of Staphylococcus aureus.

    PubMed

    Mazmanian, Sarkis K; Skaar, Eric P; Gaspar, Andrew H; Humayun, Munir; Gornicki, Piotr; Jelenska, Joanna; Joachmiak, Andrzej; Missiakas, Dominique M; Schneewind, Olaf

    2003-02-01

    The cell wall envelope of Gram-positive pathogens functions as a scaffold for the attachment of virulence factors and as a sieve that prevents diffusion of molecules. Here the isd genes (iron-regulated surface determinant) of Staphylococcus aureus were found to encode factors responsible for hemoglobin binding and passage of heme-iron to the cytoplasm, where it acts as an essential nutrient. Heme-iron passage required two sortases that tether Isd proteins to unique locations within the cell wall. Thus, Isd appears to act as an import apparatus that uses cell wall-anchored proteins to relay heme-iron across the bacterial envelope. PMID:12574635

  3. Iron oxide surfaces

    NASA Astrophysics Data System (ADS)

    Parkinson, Gareth S.

    2016-03-01

    The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe3O4), maghemite (γ-Fe2O3), haematite (α-Fe2O3), and wüstite (Fe1-xO) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. Fe diffuses in and out from the bulk in response to the O2 chemical potential, forming sometimes complex intermediate phases at the surface. For example, α-Fe2O3 adopts Fe3O4-like surfaces in reducing conditions, and Fe3O4 adopts Fe1-xO-like structures in further reducing conditions still. It is argued that known bulk defect structures are an excellent starting point in building models for iron oxide surfaces. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe3O4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment. It is also an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed. The best understood iron oxide surface at present is probably Fe3O4(100); the structure is

  4. Iron oxide surfaces

    NASA Astrophysics Data System (ADS)

    Parkinson, Gareth S.

    2016-03-01

    The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe3O4), maghemite (γ-Fe2O3), haematite (α-Fe2O3), and wüstite (Fe1-xO) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. Fe diffuses in and out from the bulk in response to the O2 chemical potential, forming sometimes complex intermediate phases at the surface. For example, α-Fe2O3 adopts Fe3O4-like surfaces in reducing conditions, and Fe3O4 adopts Fe1-xO-like structures in further reducing conditions still. It is argued that known bulk defect structures are an excellent starting point in building models for iron oxide surfaces. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe3O4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment. It is also an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed. The best understood iron oxide surface at present is probably Fe3O4(100); the structure is

  5. Receptor-Mediated Recognition and Uptake of Iron from Human Transferrin by Staphylococcus aureus and Staphylococcus epidermidis

    PubMed Central

    Modun, Belinda; Evans, Robert W.; Joannou, Christopher L.; Williams, Paul

    1998-01-01

    Staphylococcus aureus and Staphylococcus epidermidis both recognize and bind the human iron-transporting glycoprotein, transferrin, via a 42-kDa cell surface protein receptor. In an iron-deficient medium, staphylococcal growth can be promoted by the addition of human diferric transferrin but not human apotransferrin. To determine whether the staphylococcal transferrin receptor is involved in the removal of iron from transferrin, we employed 6 M urea–polyacrylamide gel electrophoresis, which separates human transferrin into four forms (diferric, monoferric N-lobe, and monoferric C-lobe transferrin and apotransferrin). S. aureus and S. epidermidis but not Staphylococcus saprophyticus (which lacks the transferrin receptor) converted diferric human transferrin into its apotransferrin form within 30 min. During conversion, iron was removed sequentially from the N lobe and then from the C lobe. Metabolic poisons such as sodium azide and nigericin inhibited the release of iron from human transferrin, indicating that it is an energy-requiring process. To demonstrate that this process is receptor rather than siderophore mediated, we incubated (i) washed staphylococcal cells and (ii) the staphylococcal siderophore, staphyloferrin A, with porcine transferrin, a transferrin species which does not bind to the staphylococcal receptor. While staphyloferrin A removed iron from both human and porcine transferrins, neither S. aureus nor S. epidermidis cells could promote the release of iron from porcine transferrin. In competition binding assays, both native and recombinant N-lobe fragments of human transferrin as well as a naturally occurring human transferrin variant with a mutation in the C-lobe blocked binding of 125I-labelled transferrin. Furthermore, the staphylococci removed iron efficiently from the iron-loaded N-lobe fragment of human transferrin. These data demonstrate that the staphylococci efficiently remove iron from transferrin via a receptor-mediated process and

  6. Altered immune proteome of Staphylococcus aureus under iron-restricted growth conditions.

    PubMed

    Stentzel, Sebastian; Vu, Hai Chi; Weyrich, Anna Maria; Jehmlich, Nico; Schmidt, Frank; Salazar, Manuela Gesell; Steil, Leif; Völker, Uwe; Bröker, Barbara M

    2014-08-01

    Staphylococcus aureus is one of the major causative agents of severe infections, and is responsible for a high burden of morbidity and mortality. Strains of increased virulence have emerged (e.g. USA300) that can infect healthy individuals in the community and are difficult to treat. To add to the knowledge about the pathophysiology of S. aureus, the adaption to iron restriction, an important in vivo stressor, was studied and the corresponding immune response of the human host characterized. Using a combination of 1D and 2D immune proteomics, the human antibody response to the exoproteomes of S. aureus USA300Δspa grown under iron restriction or with excess iron was compared. Human antibody binding to the altered exoproteome under iron restriction showed a 2.7- to 6.2-fold increase in overall signal intensity, and new antibody specificities appeared. Quantification of the secreted bacterial proteins by gel-free proteomics showed the expected strong increase in level of proteins involved in iron acquisition during iron-restricted growth compared to iron access. This was accompanied by decreased levels of superantigens and hemolysins. The latter was corroborated by functional peripheral blood mononuclear cell proliferation assays. The present data provide a comprehensive view of S. aureus exoproteome adaptation to iron restriction. Adults have high concentrations of serum antibodies specific for some of the newly induced proteins. We conclude that iron restriction is a common feature of the microenvironment, where S. aureus interacts with the immune system of its human host. PMID:24888718

  7. Nfu facilitates the maturation of iron-sulfur proteins and participates in virulence in Staphylococcus aureus

    PubMed Central

    Mashruwala, Ameya A.; Pang, Yun Y.; Rosario-Cruz, Zuelay; Chahal, Harsimranjit K.; Benson, Meredith A.; Anzaldi-Mike, Laura L.; Skaar, Eric P.; Torres, Victor J.; Nauseef, William M.; Boyd, Jeffrey M.

    2015-01-01

    Summary The acquisition and metabolism of iron (Fe) by the human pathogen Staphylococcus aureus is critical for disease progression. S. aureus requires Fe to synthesize inorganic cofactors called iron-sulfur (Fe-S) clusters, which are required for functional Fe-S proteins. In this study we investigated the mechanisms utilized by S. aureus to metabolize Fe-S clusters. We identified that S. aureus utilizes the Suf biosynthetic system to synthesize Fe-S clusters and we provide genetic evidence suggesting that the sufU and sufB gene products are essential. Additional biochemical and genetic analyses identified Nfu as a Fe-S cluster carrier, which aids in the maturation of Fe-S proteins. We find that deletion of the nfu gene negatively impacts staphylococcal physiology and pathogenicity. A nfu mutant accumulates both increased intracellular non-incorporated Fe and endogenous reactive oxygen species (ROS) resulting in DNA damage. In addition, a strain lacking Nfu is sensitive to exogenously supplied ROS and reactive nitrogen species. Congruous with ex vivo findings, a nfu mutant strain is more susceptible to oxidative killing by human polymorphonuclear leukocytes and displays decreased tissue colonization in a murine model of infection. We conclude that Nfu is necessary for staphylococcal pathogenesis and establish Fe-S cluster metabolism as an attractive antimicrobial target. PMID:25388433

  8. Human Frataxin: Iron And Ferrochelatase Binding Surface

    SciTech Connect

    Bencze, K.Z.; Yoon, T.; Millan-Pacheco, C.; Bradley, P.B.; Pastor, N.; Cowan, J.A.; Stemmler, T.L.

    2009-06-02

    The coordinated iron structure and ferrochelatase binding surface of human frataxin have been characterized to provide insight into the protein's ability to serve as the iron chaperone during heme biosynthesis.

  9. Surface modification of high temperature iron alloys

    DOEpatents

    Park, Jong-Hee

    1995-01-01

    A method and article of manufacture of a coated iron based alloy. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700.degree. C.-1200.degree. C. to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy.

  10. Surface modification of high temperature iron alloys

    DOEpatents

    Park, J.H.

    1995-06-06

    A method and article of manufacture of a coated iron based alloy are disclosed. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700--1200 C to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy. 13 figs.

  11. Proteomic and transcriptomic profiling of Staphylococcus aureus surface LPXTG-proteins: correlation with agr genotypes and adherence phenotypes.

    PubMed

    Ythier, Mathilde; Resch, Grégory; Waridel, Patrice; Panchaud, Alexandre; Gfeller, Aurélie; Majcherczyk, Paul; Quadroni, Manfredo; Moreillon, Philippe

    2012-11-01

    Staphylococcus aureus infections involve numerous adhesins and toxins, which expression depends on complex regulatory networks. Adhesins include a family of surface proteins covalently attached to the peptidoglycan via a conserved LPXTG motif. Here we determined the protein and mRNA expression of LPXTG-proteins of S. aureus Newman in time-course experiments, and their relation to fibrinogen adherence in vitro. Experiments were performed with mutants in the global accessory-gene regulator (agr), surface protein A (Spa), and fibrinogen-binding protein A (ClfA), as well as during growth in iron-rich or iron-poor media. Surface proteins were recovered by trypsin-shaving of live bacteria. Released peptides were analyzed by liquid chromatography coupled to tandem mass-spectrometry. To unambiguously identify peptides unique to LPXTG-proteins, the analytical conditions were refined using a reference library of S. aureus LPXTG-proteins heterogeneously expressed in surrogate Lactococcus lactis. Transcriptomes were determined by microarrays. Sixteen of the 18 LPXTG-proteins present in S. aureus Newman were detected by proteomics. Nine LPXTG-proteins showed a bell-shape agr-like expression that was abrogated in agr-negative mutants including Spa, fibronectin-binding protein A (FnBPA), ClfA, iron-binding IsdA, and IsdB, immunomodulator SasH, functionally uncharacterized SasD, biofilm-related SasG and methicillin resistance-related FmtB. However, only Spa and SasH modified their proteomic and mRNA profiles in parallel in the parent and its agr- mutant, whereas all other LPXTG-proteins modified their proteomic profiles independently of their mRNA. Moreover, ClfA became highly transcribed and active in fibrinogen-adherence tests during late growth (24 h), whereas it remained poorly detected by proteomics. On the other hand, iron-regulated IsdA-B-C increased their protein expression by >10-times in iron-poor conditions. Thus, proteomic, transcriptomic, and adherence

  12. Monoclonal Antibody Targeting Staphylococcus aureus Surface Protein A (SasA) Protect Against Staphylococcus aureus Sepsis and Peritonitis in Mice.

    PubMed

    Yang, Yilong; Qian, Mengying; Yi, Shaoqiong; Liu, Shuling; Li, Bing; Yu, Rui; Guo, Qiang; Zhang, Xiaopeng; Yu, Changming; Li, Jianmin; Xu, Junjie; Chen, Wei

    2016-01-01

    Epidemic methicillin-resistant Staphylococcus aureus (MRSA) imposes an increasing impact on public health. Due to multi-antibiotics resistance in MRSA strains, there is an urgent need to develop novel therapeutics such as effective monoclonal antibodies (mAbs) against MRSA infections. Staphylococcus aureus surface protein A (SasA), a large surface-located protein (~240 kDa), is one of MSCRAMMs (microbial surface components recognizing adhesive matrix molecules) and a potential target for immunotherapeutic approaches against S. aureus infections. In the present study, we analyzed the sequence of SasA with bioinformatics tools and generated a protective monoclonal antibody (2H7) targeting the conserved domain of SasA. 2H7 was shown to recognize wild-type S. aureus and promote opsonophagocytic killing of S. aureus. In both sepsis and peritoneal infection models, prophylactic administration of 2H7 improved the survival of BALB/c mice challenged by S. aureus strain USA300 and ST239 (prevalent MRSA clones in North America and Asian countries, respectively) and enhanced bacterial clearance in kidneys. Additionally, 2H7 prophylaxis prevented the formation of intraperitoneal abscess in a murine model of peritoneal infection and therapeutic administration of 2H7 showed protective efficacy in a murine sepsis model. Our results presented here provide supporting evidences that an anti-SasA mAb might be a potential component in an antibody-based immunotherapeutic treatment of MRSA infections. PMID:26926145

  13. Monoclonal Antibody Targeting Staphylococcus aureus Surface Protein A (SasA) Protect Against Staphylococcus aureus Sepsis and Peritonitis in Mice

    PubMed Central

    Yang, Yilong; Qian, Mengying; Yi, Shaoqiong; Liu, Shuling; Li, Bing; Yu, Rui; Guo, Qiang; Zhang, Xiaopeng; Yu, Changming; Li, Jianmin; Xu, Junjie; Chen, Wei

    2016-01-01

    Epidemic methicillin-resistant Staphylococcus aureus (MRSA) imposes an increasing impact on public health. Due to multi-antibiotics resistance in MRSA strains, there is an urgent need to develop novel therapeutics such as effective monoclonal antibodies (mAbs) against MRSA infections. Staphylococcus aureus surface protein A (SasA), a large surface-located protein (~240 kDa), is one of MSCRAMMs (microbial surface components recognizing adhesive matrix molecules) and a potential target for immunotherapeutic approaches against S. aureus infections. In the present study, we analyzed the sequence of SasA with bioinformatics tools and generated a protective monoclonal antibody (2H7) targeting the conserved domain of SasA. 2H7 was shown to recognize wild-type S. aureus and promote opsonophagocytic killing of S. aureus. In both sepsis and peritoneal infection models, prophylactic administration of 2H7 improved the survival of BALB/c mice challenged by S. aureus strain USA300 and ST239 (prevalent MRSA clones in North America and Asian countries, respectively) and enhanced bacterial clearance in kidneys. Additionally, 2H7 prophylaxis prevented the formation of intraperitoneal abscess in a murine model of peritoneal infection and therapeutic administration of 2H7 showed protective efficacy in a murine sepsis model. Our results presented here provide supporting evidences that an anti-SasA mAb might be a potential component in an antibody-based immunotherapeutic treatment of MRSA infections. PMID:26926145

  14. Structural analysis of the surface polysaccharide of Staphylococcus aureus M.

    PubMed Central

    Liau, D F; Hash, J H

    1977-01-01

    The chemical structure of the surface polysaccharide from Staphylococcus aureus M was investigated by a combination of methanolytic, hydrolytic, and chromatographic techniques. The repeating unit that was most consistent with the data was a hexasaccharide composed of N-acetyl-D-aminogalacturonic acid, N-acetyl-D-fucosamine, and taurine in molar ratios of 4:2:1. A disaccharide was isolated and characterized, by combined gas-liquid chromatography-mass spectrometry, as N-acetyl-D-aminogalacturonyl-(1 leads to 3)-N-acetyl-D-fucosamine. Taurine is linked to a carboxyl group of N-acetyl-D-aminogalacturonic acid via an amide bond. PMID:873882

  15. Nanoadhesion of Staphylococcus aureus onto Titanium Implant Surfaces.

    PubMed

    Aguayo, S; Donos, N; Spratt, D; Bozec, L

    2015-08-01

    Adhesion of bacteria to dental implant surfaces is the critical initial step in the process of biofilm colonization; however, the specific nanoadhesive interactions occurring during the first contact between bacterial cells and biomaterial substrates remain poorly understood. In this report, we utilize single-cell force spectroscopy to characterize the dynamics of the initial interaction between living Staphylococcus aureus cells and machined titanium surfaces at the nanoscale. Values for maximum adhesion force were found to increase from 0-s (-0.27 ± 0.30 nN) to 60-s (-9.15 ± 0.78 nN) surface delays, with similar results observed for total adhesion work (7.39 ± 2.38 and 988.06 ± 117.08 aJ, respectively). Single unbinding events observed at higher surface delays were modeled according to the wormlike chain model, obtaining molecular contour-length predictions of 314.06 ± 9.27 nm. Average single-bond rupture forces of -0.95 ± 0.04 nN were observed at increased contact times. Short- and long-range force components of bacterial adhesion were obtained by Poisson analysis of single unbinding event peaks, yielding values of -0.75 ± 0.04 and -0.58 ± 0.15 nN, respectively. Addition of 2-mg/mL chlorhexidine to the buffer solution resulted in the inhibition of specific adhesive events but an increased overall adhesion force and work. These results suggest that initial attachment of S. aureus to smooth titanium is mostly mediated by short-range attractive forces observed at higher surface delays. PMID:26130256

  16. Iron cycling at corroding carbon steel surfaces.

    PubMed

    Lee, Jason S; McBeth, Joyce M; Ray, Richard I; Little, Brenda J; Emerson, David

    2013-01-01

    Surfaces of carbon steel (CS) exposed to mixed cultures of iron-oxidizing bacteria (FeOB) and dissimilatory iron-reducing bacteria (FeRB) in seawater media under aerobic conditions were rougher than surfaces of CS exposed to pure cultures of either type of microorganism. The roughened surface, demonstrated by profilometry, is an indication of loss of metal from the surface. In the presence of CS, aerobically grown FeOB produced tight, twisted helical stalks encrusted with iron oxides. When CS was exposed anaerobically in the presence of FeRB, some surface oxides were removed. However, when the same FeOB and FeRB were grown together in an aerobic medium, FeOB stalks were less encrusted with iron oxides and appeared less tightly coiled. These observations suggest that iron oxides on the stalks were reduced and solubilized by the FeRB. Roughened surfaces of CS and denuded stalks were replicated with culture combinations of different species of FeOB and FeRB under three experimental conditions. Measurements of electrochemical polarization resistance established different rates of corrosion of CS in aerobic and anaerobic media, but could not differentiate rate differences between sterile controls and inoculated exposures for a given bulk concentration of dissolved oxygen. Similarly, total iron in the electrolyte could not be used to differentiate treatments. The experiments demonstrate the potential for iron cycling (oxidation and reduction) on corroding CS in aerobic seawater media. PMID:24093730

  17. Expression of Multidrug Resistance Efflux Pump Gene norA Is Iron Responsive in Staphylococcus aureus

    PubMed Central

    Deng, Xin; Sun, Fei; Ji, Quanjiang; Liang, Haihua; Missiakas, Dominique; Lan, Lefu

    2012-01-01

    Staphylococcus aureus utilizes efflux transporter NorA to pump out a wide range of structurally dissimilar drugs, conferring low-level multidrug resistance. The regulation of norA expression has yet to be fully understood although past studies have revealed that this gene is under the control of the global transcriptional regulator MgrA and the two-component system ArlRS. To identify additional regulators of norA, we screened a transposon library in strain Newman expressing the transcriptional fusion norA-lacZ for altered β-galactosidase activity. We identify a transposon insertion in fhuB, a gene that encodes a ferric hydroxamate uptake system permease, and propose that the norA transcription is iron responsive. In agreement with this observation, addition of FeCl3 repressed the induction of norA-lacZ, suggesting that bacterial iron uptake plays an important role in regulating norA transcription. In addition, a fur (ferric uptake regulator) deletion exhibited compromised norA transcription and reduced resistance to quinolone compared to the wild-type strain, indicating that fur functions as a positive regulator of norA. A putative Fur box identified in the promoter region of norA was confirmed by electrophoretic mobility shift and DNase I footprint assays. Finally, by employing a siderophore secretion assay, we reveal that NorA may contribute to the export of siderophores. Collectively, our experiments uncover some novel interactions between cellular iron level and norA regulation in S. aureus. PMID:22267518

  18. Platinum Attachments on Iron Oxide Nanoparticle Surfaces

    SciTech Connect

    Palchoudhury, Soubantika; Xu, Yaolin; An, Wei; Turner, C. H.; Bao, Yuping

    2010-04-30

    Platinum nanoparticles supported on metal oxide surfaces have shown great potential as heterogeneous catalysts to accelerate electrochemical processes, such as the oxygen reduction reaction in fuel cells. Recently, the use of magnetic supports has become a promising research topic for easy separation and recovery of catalysts using magnets, such as Pt nanoparticles supported on iron oxide nanoparticles. The attachment of Pt on iron oxide nanoparticles is limited by the wetting ability of the Pt (metal) on ceramic surfaces. A study of Pt nanoparticle attachment on iron oxide nanoparticle surfaces in an organic solvent is reported, which addresses the factors that promote or inhibit such attachment. It was discovered that the Pt attachment strongly depends on the capping molecules of the iron oxide seeds and the reaction temperature. For example, the attachment of Pt nanoparticles on oleic acid coated iron oxide nanoparticles was very challenging, because of the strong binding between the carboxylic groups and iron oxide surfaces. In contrast, when nanoparticles are coated with oleic acid/tri-n-octylphosphine oxide or oleic acid/oleylamine, a significant increase in Pt attachment was observed. Electronic structure calculations were then applied to estimate the binding energies between the capping molecules and iron ions, and the modeling results strongly support the experimental observations.

  19. Discovery of an iron-regulated citrate synthase in Staphylococcus aureus.

    PubMed

    Cheung, Johnson; Murphy, Michael E P; Heinrichs, David E

    2012-12-21

    Bacteria need to scavenge iron from their environment, and this is no less important for bacterial pathogens while attempting to survive in the mammalian host. One key strategy is the synthesis of small iron chelators known as siderophores. The study of siderophore biosynthesis systems over the past several years has shed light on novel enzymology and, as such, has identified new therapeutic targets. Staphylococcus aureus, a noted human and animal pathogen, produces two citrate-based siderophores, termed staphyloferrin A and staphyloferrin B. The iron-regulated gene cluster for the biosynthesis of staphyloferrin B, sbnA-I, contains several yet uncharacterized genes. Here, we report on the identification of an enzyme, SbnG, which is annotated in the genome sequence as a metal-dependent class II aldolase. In contrast to this prediction, we report that, instead, SbnG has evolved to catalyze metal-independent citrate synthase activity using oxaloacetate and acetyl-CoA as substrates. We describe an in vitro assay to synthesize biologically active staphyloferrin B from purified enzymes and substrates, and identify several SbnG inhibitors, including metals such as calcium and magnesium. PMID:23261600

  20. Contamination of environmental surfaces by Staphylococcus aureus in a dermatological ward and its preventive measures.

    PubMed

    Oie, Shigeharu; Yanagi, Chikashige; Matsui, Hiroto; Nishida, Tomoko; Tomita, Masaaki; Kamiya, Akira

    2005-01-01

    We investigated contamination of environmental surfaces by Staphylococcus aureus from April 1 to the end of June in 2002 in the dermatological ward (37 beds) of a university hospital. For surfaces contaminated by high levels of S. aureus, disinfection methods were evaluated. 100-10(5) colony forming units (cfu) of methicillin-resistant S. aureus (MRSA) or methicillin-sensitive S. aureus (MSSA) were detected on items such as an immersion bathtub (examined area, about 900 cm2), foot washbowl, stretcher for an immersion bath, and chair for the shower. After disinfection, no S. aureus was detected on smooth surfaces such as the immersion bathtub and foot washbowl; however, S. aureus was detected even after disinfection on porous surfaces made of sponge-like materials (polyethylene foam) such as the stretcher for the immersion bath and the shower chair. Scanning electron microscopy of the porous surfaces showed formation of a large amount of coccus and bacillus biofilms on the walls of pores in the multi-pore structure. Material that is porous should not be used in patient care settings because it is not possible to disinfect it properly. PMID:15635175

  1. Tannic Acid Inhibits Staphylococcus aureus Surface Colonization in an IsaA-Dependent Manner

    PubMed Central

    Payne, David E.; Martin, Nicholas R.; Parzych, Katherine R.; Rickard, Alex H.; Underwood, Adam

    2013-01-01

    Staphylococcus aureus is a human commensal and pathogen that is capable of forming biofilms on a variety of host tissues and implanted medical devices. Biofilm-associated infections resist antimicrobial chemotherapy and attack from the host immune system, making these infections particularly difficult to treat. In order to gain insight into environmental conditions that influence S. aureus biofilm development, we screened a library of small molecules for the ability to inhibit S. aureus biofilm formation. This led to the finding that the polyphenolic compound tannic acid inhibits S. aureus biofilm formation in multiple biofilm models without inhibiting bacterial growth. We present evidence that tannic acid inhibits S. aureus biofilm formation via a mechanism dependent upon the putative transglycosylase IsaA. Tannic acid did not inhibit biofilm formation of an isaA mutant. Overexpression of wild-type IsaA inhibited biofilm formation, whereas overexpression of a catalytically dead IsaA had no effect. Tannin-containing drinks like tea have been found to reduce methicillin-resistant S. aureus nasal colonization. We found that black tea inhibited S. aureus biofilm development and that an isaA mutant resisted this inhibition. Antibiofilm activity was eliminated from tea when milk was added to precipitate the tannic acid. Finally, we developed a rodent model for S. aureus throat colonization and found that tea consumption reduced S. aureus throat colonization via an isaA-dependent mechanism. These findings provide insight into a molecular mechanism by which commonly consumed polyphenolic compounds, such as tannins, influence S. aureus surface colonization. PMID:23208606

  2. PerR Controls Oxidative Stress Resistance and Iron Storage Proteins and Is Required for Virulence in Staphylococcus aureus

    PubMed Central

    Horsburgh, Malcolm J.; Clements, Mark O.; Crossley, Howard; Ingham, Eileen; Foster, Simon J.

    2001-01-01

    The Staphylococcus aureus genome encodes three ferric uptake regulator (Fur) homologues: Fur, PerR, and Zur. To determine the exact role of PerR, we inactivated the gene by allelic replacement using a kanamycin cassette, creating strain MJH001 (perR). PerR was found to control transcription of the genes encoding the oxidative stress resistance proteins catalase (KatA), alkyl hydroperoxide reductase (AhpCF), bacterioferritin comigratory protein (Bcp), and thioredoxin reductase (TrxB). Furthermore, PerR regulates transcription of the genes encoding the iron storage proteins ferritin (Ftn) and the ferritin-like Dps homologue, MrgA. Transcription of perR was autoregulated, and PerR repressed transcription of the iron homeostasis regulator Fur, which is a positive regulator of catalase expression. PerR functions as a manganese-dependent, transcriptional repressor of the identified regulon. Elevated iron concentrations produced induction of the PerR regulon. PerR may act as a peroxide sensor, since addition of external hydrogen peroxide to 8325-4 (wild type) resulted in increased transcription of most of the PerR regulon, except for fur and perR itself. The PerR-regulated katA gene encodes the sole catalase of S. aureus, which is an important starvation survival determinant but is surprisingly not required for pathogenicity in a murine skin abscess model of infection. In contrast, PerR is not necessary for starvation survival but is required for full virulence (P < 0.005) in this model of infection. PerR of S. aureus may act as a redox sentinel protein during infection, analogous to the in vitro activities of OxyR and PerR of Escherichia coli and Bacillus subtilis, respectively. However, it differs in its response to the metal balance within the cell and has the added capability of regulating iron uptake and storage. PMID:11349039

  3. Incidence of Staphylococcus aureus and Analysis of Associated Bacterial Communities on Food Industry Surfaces

    PubMed Central

    Gutiérrez, Diana; Delgado, Susana; Vázquez-Sánchez, Daniel; Martínez, Beatriz; Cabo, Marta López; Rodríguez, Ana; Herrera, Juan J.

    2012-01-01

    Biofilms are a common cause of food contamination with undesirable bacteria, such as pathogenic bacteria. Staphylococcus aureus is one of the major bacteria causing food-borne diseases in humans. A study designed to determine the presence of S. aureus on food contact surfaces in dairy, meat, and seafood environments and to identify coexisting microbiota has therefore been carried out. A total of 442 samples were collected, and the presence of S. aureus was confirmed in 6.1% of samples. Sixty-three S. aureus isolates were recovered and typed by random amplification of polymorphic DNA (RAPD). Profiles were clustered into four groups which were related to specific food environments. All isolates harbored some potential virulence factors such as enterotoxin production genes, biofilm formation-associated genes, antibiotic resistance, or lysogeny. PCR-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprints of bacterial communities coexisting with S. aureus revealed the presence of bacteria either involved in food spoilage or of concern for food safety in all food environments. Food industry surfaces could thus be a reservoir for S. aureus forming complex communities with undesirable bacteria in multispecies biofilms. Uneven microbiological conditions were found in each food sector, which indicates the need to improve hygienic conditions in food processing facilities, particularly the removal of bacterial biofilms, to enhance the safety of food products. PMID:23023749

  4. Staphylococcus aureus Protein A Mediates Interspecies Interactions at the Cell Surface of Pseudomonas aeruginosa

    PubMed Central

    Armbruster, Catherine R.; Wolter, Daniel J.; Mishra, Meenu; Hayden, Hillary S.; Radey, Matthew C.; Merrihew, Gennifer; MacCoss, Michael J.; Burns, Jane; Wozniak, Daniel J.

    2016-01-01

    ABSTRACT While considerable research has focused on the properties of individual bacteria, relatively little is known about how microbial interspecies interactions alter bacterial behaviors and pathogenesis. Staphylococcus aureus frequently coinfects with other pathogens in a range of different infectious diseases. For example, coinfection by S. aureus with Pseudomonas aeruginosa occurs commonly in people with cystic fibrosis and is associated with higher lung disease morbidity and mortality. S. aureus secretes numerous exoproducts that are known to interact with host tissues, influencing inflammatory responses. The abundantly secreted S. aureus staphylococcal protein A (SpA) binds a range of human glycoproteins, immunoglobulins, and other molecules, with diverse effects on the host, including inhibition of phagocytosis of S. aureus cells. However, the potential effects of SpA and other S. aureus exoproducts on coinfecting bacteria have not been explored. Here, we show that S. aureus-secreted products, including SpA, significantly alter two behaviors associated with persistent infection. We found that SpA inhibited biofilm formation by specific P. aeruginosa clinical isolates, and it also inhibited phagocytosis by neutrophils of all isolates tested. Our results indicate that these effects were mediated by binding to at least two P. aeruginosa cell surface structures—type IV pili and the exopolysaccharide Psl—that confer attachment to surfaces and to other bacterial cells. Thus, we found that the role of a well-studied S. aureus exoproduct, SpA, extends well beyond interactions with the host immune system. Secreted SpA alters multiple persistence-associated behaviors of another common microbial community member, likely influencing cocolonization and coinfection with other microbes. PMID:27222468

  5. Transfer and Decontamination of S. aureus in Transmission Routes Regarding Hands and Contact Surfaces

    PubMed Central

    Arinder, Pernilla; Johannesson, Pär; Karlsson, Ingela; Borch, Elisabeth

    2016-01-01

    Hand hygiene, cleaning and disinfection are pre-requirements for hygiene management in hospital settings and the food industry. In order to facilitate risk management, different contamination scenarios and interventions need to be evaluated. In the present study data on transfer rates and reductions of Staphylococcus aureus were provided in an experimental set-up using artificial skin. Using this methodology, test persons were not exposed with pathogenic bacteria. An exposure assessment model was developed and applied to evaluate different contamination routes and hygiene interventions. The transfer rates of S. aureus from inoculated VITRO-SKIN® to fomites were calculated from blotting series. The VITRO-SKIN® was more prone to spread bacteria than fomites. When different surfaces were cleaned, the reduction of S. aureus varied between <1 and 7 log CFU. It could not be concluded that a certain coupon material, cleaning agent, cleaning wipe, soiling or humidity consistently resulted in a high or low reduction of S. aureus. The reduction of S. aureus and E. coli during hand washing was evaluated on artificial skin, VITRO-SKIN®. The reduction of E. coli on VITRO-SKIN® was similar to the log reduction obtained when washing human hands. The S. aureus count on a human hand was both calculated in different scenarios describing different contamination routes starting from a contaminated hand using the exposure assessment model, and measured on an experimental setup using VITRO-SKIN® for validation. A linear relationship was obtained between the analysed level of S. aureus and the calculated level. However, the calculated levels of S. aureus on the VITRO-SKIN® in the scenarios were 1–1.5 log lower than the analysed level. One of the scenarios was used to study the effect of interventions like hand washing and cleaning of surfaces. PMID:27280772

  6. Staphylococcus aureus transporters Hts, Sir, and Sst capture iron liberated from human transferrin by Staphyloferrin A, Staphyloferrin B, and catecholamine stress hormones, respectively, and contribute to virulence.

    PubMed

    Beasley, Federico C; Marolda, Cristina L; Cheung, Johnson; Buac, Suzana; Heinrichs, David E

    2011-06-01

    Staphylococcus aureus is a frequent cause of bloodstream, respiratory tract, and skin and soft tissue infections. In the bloodstream, the iron-binding glycoprotein transferrin circulates to provide iron to cells throughout the body, but its iron-binding properties make it an important component of innate immunity. It is well established that siderophores, with their high affinity for iron, in many instances can remove iron from transferrin as a means to promote proliferation of bacterial pathogens. It is also established that catecholamine hormones can interfere with the iron-binding properties of transferrin, thus allowing infectious bacteria access to this iron pool. The present study demonstrates that S. aureus can use either of two carboxylate-type siderophores, staphyloferrin A and staphyloferrin B, via the transporters Hts and Sir, respectively, to access the transferrin iron pool. Growth of staphyloferrin-producing S. aureus in serum or in the presence of holotransferrin was not enhanced in the presence of catecholamines. However, catecholamines significantly enhanced the growth of staphyloferrin-deficient S. aureus in human serum or in the presence of human holotransferrin. It was further demonstrated that the Sst transporter was essential for this activity as well as for the utilization of bacterial catechol siderophores. The substrate binding protein SstD was shown to interact with ferrated catecholamines and catechol siderophores, with low to submicromolar affinities. Experiments involving mice challenged intravenously with wild-type S. aureus and isogenic mutants demonstrated that the combination of Hts, Sir, and Sst transport systems was required for full virulence of S. aureus. PMID:21402762

  7. Occurrence of methicillin-resistant Staphylococcus aureus in surface waters near industrial hog operation spray fields.

    PubMed

    Hatcher, S M; Myers, K W; Heaney, C D; Larsen, J; Hall, D; Miller, M B; Stewart, J R

    2016-09-15

    Industrial hog operations (IHOs) have been identified as a source of antibiotic-resistant Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA). However, few studies have investigated the presence of antibiotic-resistant S. aureus in the environment near IHOs, specifically surface waters proximal to spray fields where IHO liquid lagoon waste is sprayed. Surface water samples (n=179) were collected over the course of approximately one year from nine locations in southeastern North Carolina and analyzed for the presence of presumptive MRSA using CHROMagar MRSA media. Culture-based, biochemical, and molecular tests, as well as matrix-assisted laser desorption/ionization-time of flight mass spectrometry were used to confirm that isolates that grew on CHROMagar MRSA media were S. aureus. Confirmed S. aureus isolates were then tested for susceptibility to 16 antibiotics and screened for molecular markers of MRSA (mecA, mecC) and livestock adaptation (absence of scn). A total of 12 confirmed MRSA were detected in 9 distinct water samples. Nine of 12 MRSA isolates were also multidrug-resistant (MDRSA [i.e., resistant to ≥3 antibiotic classes]). All MRSA were scn-positive and most (11/12) belonged to a staphylococcal protein A (spa) type t008, which is commonly associated with humans. Additionally, 12 confirmed S. aureus that were methicillin-susceptible (MSSA) were recovered, 7 of which belonged to spa type t021 and were scn-negative (a marker of livestock-adaptation). This study demonstrated the presence of MSSA, MRSA, and MDRSA in surface waters adjacent to IHO lagoon waste spray fields in southeastern North Carolina. To our knowledge, this is the first report of waterborne S. aureus from surface waters proximal to IHOs. PMID:27261430

  8. Tissue Plasminogen Activator Coating on Implant Surfaces Reduces Staphylococcus aureus Biofilm Formation

    PubMed Central

    Na, Manli; Jarneborn, Anders; Jacobsson, Gunnar; Peetermans, Marijke; Verhamme, Peter

    2015-01-01

    Staphylococcus aureus biofilm infections of indwelling medical devices are a major medical challenge because of their high prevalence and antibiotic resistance. As fibrin plays an important role in S. aureus biofilm formation, we hypothesize that coating of the implant surface with fibrinolytic agents can be used as a new method of antibiofilm prophylaxis. The effect of tissue plasminogen activator (tPA) coating on S. aureus biofilm formation was tested with in vitro microplate biofilm assays and an in vivo mouse model of biofilm infection. tPA coating efficiently inhibited biofilm formation by various S. aureus strains. The effect was dependent on plasminogen activation by tPA, leading to subsequent local fibrin cleavage. A tPA coating on implant surfaces prevented both early adhesion and later biomass accumulation. Furthermore, tPA coating increased the susceptibility of biofilm infections to antibiotics. In vivo, significantly fewer bacteria were detected on the surfaces of implants coated with tPA than on control implants from mice treated with cloxacillin. Fibrinolytic coatings (e.g., with tPA) reduce S. aureus biofilm formation both in vitro and in vivo, suggesting a novel way to prevent bacterial biofilm infections of indwelling medical devices. PMID:26519394

  9. Studies of the kinetics and mechanisms of perfluoroether reactions on iron and oxidized iron surfaces

    NASA Technical Reports Server (NTRS)

    Napier, Mary E.; Stair, Peter C.

    1992-01-01

    Polymeric perfluoroalkylethers are being considered for use as lubricants in high temperature applications, but have been observed to catalytically decompose in the presence of metals. X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) were used to explore the decomposition of three model fluorinated ethers on clean polycrystalline iron surfaces and iron surfaces chemically modified with oxygen. Low temperature adsorption of the model fluorinated ethers on the clean, oxygen modified and oxidized iron surfaces was molecular. Thermally activated defluorination of the three model compounds was observed on the clean iron surface at remarkably low temperatures, 155 K and below, with formation of iron fluoride. Preferential C-F bond scission occurred at the terminal fluoromethoxy, CF3O, of perfluoro-1-methoxy-2-ethoxy ethane and perfluoro-1-methoxy-2-ethoxy propane and at CF3/CF2O of perfluoro-1,3-diethoxy propane. The reactivity of the clean iron toward perfluoroalkylether decomposition when compared to other metals is due to the strength of the iron fluoride bond and the strong electron donating ability of the metallic iron. Chemisorption of an oxygen overlayer lowered the reactivity of the iron surface to the adsorption and decomposition of the three model fluorinated ethers by blocking active sites on the metal surface. Incomplete coverage of the iron surface with chemisorbed oxygen results in a reaction which resembles the defluorination reaction observed on the clean iron surface. Perfluoro-1-methoxy-2-ethoxy ethane reacts on the oxidized iron surface at 138 K, through a Lewis acid assisted cleavage of the carbon oxygen bond, with preferential attack at the terminal fluoromethoxy, CF3O. The oxidized iron surface did not passivate, but became more reactive with time. Perfluoro-1-methoxy-2-ethoxy propane and perfluoro-1,3-diethoxy propane desorbed prior to the observation of decomposition on the oxidized iron surface.

  10. Chemical Characterization of a New Surface Antigenic Polysaccharide from a Mutant of Staphylococcus aureus

    PubMed Central

    Wu, Teresa C. M.; Park, James T.

    1971-01-01

    A mutant of Staphylococcus aureus H was isolated by virtue of its inability to agglutinate with antibodies against teichoic acid of S. aureus. Immunological studies revealed that the mutant, S. aureus T, possessed a new surface antigen in addition to having the antigenic determinant of the wild-type strain, the ribitol teichoic acid. The presence of this additional surface component rendered strain T resistant to staphylococcal typing phages, presumably by masking the phage-receptor sites. The polymer was separated from teichoic acid by chromatography on diethylaminoethyl cellulose and was shown to be composed of two amino sugars, N-acetyl-d-fucosamine and N-acetyl-d-mannosamin uronic acid. Images PMID:5001874

  11. Lysostaphin Disrupts Staphylococcus aureus and Staphylococcus epidermidis Biofilms on Artificial Surfaces

    PubMed Central

    Wu, Julie A.; Kusuma, Caroline; Mond, James J.; Kokai-Kun, John F.

    2003-01-01

    Staphylococci often form biofilms, sessile communities of microcolonies encased in an extracellular matrix that adhere to biomedical implants or damaged tissue. Infections associated with biofilms are difficult to treat, and it is estimated that sessile bacteria in biofilms are 1,000 to 1,500 times more resistant to antibiotics than their planktonic counterparts. This antibiotic resistance of biofilms often leads to the failure of conventional antibiotic therapy and necessitates the removal of infected devices. Lysostaphin is a glycylglycine endopeptidase which specifically cleaves the pentaglycine cross bridges found in the staphylococcal peptidoglycan. Lysostaphin kills Staphylococcus aureus within minutes (MIC at which 90% of the strains are inhibited [MIC90], 0.001 to 0.064 μg/ml) and is also effective against Staphylococcus epidermidis at higher concentrations (MIC90, 12.5 to 64 μg/ml). The activity of lysostaphin against staphylococci present in biofilms compared to those of other antibiotics was, however, never explored. Surprisingly, lysostaphin not only killed S. aureus in biofilms but also disrupted the extracellular matrix of S. aureus biofilms in vitro on plastic and glass surfaces at concentrations as low as 1 μg/ml. Scanning electron microscopy confirmed that lysostaphin eradicated both the sessile cells and the extracellular matrix of the biofilm. This disruption of S. aureus biofilms was specific for lysostaphin-sensitive S. aureus, as biofilms of lysostaphin-resistant S. aureus were not affected. High concentrations of oxacillin (400 μg/ml), vancomycin (800 μg/ml), and clindamycin (800 μg/ml) had no effect on the established S. aureus biofilms in this system, even after 24 h. Higher concentrations of lysostaphin also disrupted S. epidermidis biofilms. PMID:14576095

  12. The role of serum proteins in Staphylococcus aureus adhesion to ethylene glycol coated surfaces.

    PubMed

    Schuster, Swen; Yu, Wenqi; Nega, Mulugeta; Chu, Ya-Yun; Zorn, Stefan; Zhang, Fajun; Götz, Friedrich; Schreiber, Frank

    2014-11-01

    Bacterial adhesion on implants is a first step in the development of chronic foreign body associated infections. Finding strategies to minimize bacterial adhesion may contribute to minimize such infections. It is known that surfaces with oligo-ethylene-glycol (EG3OMe) or poly-ethylene-glycol (PEG2k) terminations decrease unspecific protein adsorption and bacterial adhesion. However, little is known about the influence of serum and its components on bacterial adhesion. We therefore prepared two coatings on gold surface with HS-(CH2)11EG3OMe (EG3OMe) and PEG2k-thiol and studied the role of bovine serum albumin (BSA), γ-globulins, and serum on Staphylococcus aureus adhesion. While BSA and lysozyme showed no adherence even when applied at very high concentrations (100 mg/ml), γ-globulins adsorbed already from 10 mg/ml on. The adsorption of γ-globulins was, however, significantly decreased when it was mixed with BSA in a ratio of 3:1, as it is in the serum. Pretreatment of EG3OMe and PEG2k coatings with γ-globulins or serum strongly promoted adherence of S. aureus when resuspended in buffer, suggesting that γ-globulins play a pivotal role in promoting S. aureus adhesion by its IgG binding proteins; the finding that a spa-deletion mutant, lacking the IgG binding protein A, showed decreased adherence corroborated this. Similarly, when S. aureus was pretreated with serum or γ-globulins its adherence was also significantly decreased. Our findings show that particularly γ-globulins bind to the coated surfaces thus mediating adherence of S. aureus via its protein A. As pretreatment of S. aureus with serum or γ-globulins significantly decreased adherence, treatment of patients with γ-globulins before implant surgery might lower the risk of implant-associated infections. PMID:24980510

  13. Presence of Pseudomonas aeruginosa influences biofilm formation and surface protein expression of Staphylococcus aureus.

    PubMed

    Kumar, Amit; Ting, Yen Peng

    2015-11-01

    Although Staphylococcus aureus and Pseudomonas aeruginosa can individually colonize and infect their hosts, the commensalistic effect of the two is more tenacious and lethal. In this study, it was shown that in co-culture with P. aeruginosa, a sub-population of S. aureus exhibited improved resistance to kanamycin by selection of small colony variant (SCV) phenotype. Additionally, biofilm formation by the two bacteria was denser in the co-culture, compared with biofilm formed in individual pure cultures. Using Atomic Force Microscope (AFM) force spectroscopy for single cells, it was demonstrated that S. aureus cultured in the presence of P. aeruginosa bound more tenaciously to substrates. Surface-shaved peptides were isolated and identified using ultra-performance liquid chromatography-quadrupole-time of flight and a homology search program spider. Results indicated that serine-rich adhesin, extracellular matrix binding protein and other putative adhesion proteins could be responsible for the enhanced attachment of S. aureus in the co-culture. Besides, several other proteins were differentially expressed, indicating the occurrence of a range of other interactions. Of particular interest was a multidrug resistant protein named ABC transporter permease which is known to expel xenobiotics out of the cells. Positive regulation of this protein could be involved in the SCV selection of S. aureus in the co-culture. PMID:25925222

  14. TCA cycle activity in Staphylococcus aureus is essential for iron-regulated synthesis of staphyloferrin A, but not staphyloferrin B: the benefit of a second citrate synthase.

    PubMed

    Sheldon, Jessica R; Marolda, Cristina L; Heinrichs, David E

    2014-05-01

    Staphylococcus aureus elaborates two citrate-containing siderophores, staphyloferrin A (SA) and staphyloferrin B (SB), that enhance growth under iron-restriction, yet, paradoxically, expression of the TCA cycle citrate synthase, CitZ, is downregulated during iron starvation. Iron starvation does, however, result in expression of SbnG, recently identified as a novel citrate synthase that is encoded from within the iron-regulated SB biosynthetic locus, suggesting an important role for SbnG in staphyloferrin production. We demonstrate that during growth of S. aureus in iron-restricted media containing glucose, SB is produced but, in contrast, SA production is severely repressed; accordingly, SB-deficient mutants grow poorly in these media. Hypothesizing that reduced TCA cycle activity hinders SA production, we show that a citZ mutant is capable of SB synthesis, but not SA synthesis, providing evidence that SbnG does not generate citrate for incorporation into SA. A citZ sbnG mutant synthesizes neither staphyloferrin, is severely compromised for growth in iron-restricted media, and is significantly more impaired for virulence than either of the single-deletion mutants. We propose that SB is the more important of the two siderophores for S. aureus insofar as it is synthesized, and supports iron-restricted growth, without need of TCA cycle activity. PMID:24666349

  15. Staphylococcus pseudintermedius expresses surface proteins that closely resemble those from Staphylococcus aureus.

    PubMed

    Geoghegan, Joan A; Smith, Emma J; Speziale, Pietro; Foster, Timothy J

    2009-09-18

    Staphylococcus pseudintermedius is a commensal of dogs that is implicated in the pathogenesis of canine pyoderma. This study aimed to determine if S. pseudintermedius expresses surface proteins resembling those from Staphylococcus aureus and to characterise them. S. pseudintermedius strain 326 was shown to adhere strongly to purified fibrinogen, fibronectin and cytokeratin 10. It adhered to the alpha-chain of fibrinogen which, along with binding to cytokeratin 10, is the hallmark of clumping factor B of S. aureus, a surface protein that is in part responsible for colonisation of the human nares. Ligand-affinity blotting with cell-wall extracts demonstrated that S. pseudintermedius 326 expressed a cell-wall anchored fibronectin binding protein which recognised the N-terminal 29kDa fragment. The ability to bind fibronectin is an important attribute of pathogenic S. aureus and is associated with the ability of S. aureus to colonise skin of human atopic dermatitis patients. S. pseudintermedius genomic DNA was probed with labelled DNA amplified from the serine-aspartate repeat encoding region of clfA of S. aureus. This probe hybridised to a single SpeI fragment of S. pseudintermedius DNA. In the cell-wall extract of S. pseudintermedius 326, a 180kDa protein was discovered which bound to fibrinogen by ligand-affinity blotting and reacted in a Western blot with antibodies raised against the serine-aspartate repeat region of ClfA and the B-repeats of SdrD of S. aureus. It is proposed that this is an Sdr protein with B-repeats that has an A domain that binds to fibrinogen. Whether it is the same protein that binds cytokeratin 10 is not clear. PMID:19372010

  16. Surface Engineering of Core/Shell Iron/Iron Oxide Nanoparticles from Microemulsions for Hyperthermia

    PubMed Central

    Zhang, Guandong; Liao, Yifeng; Baker, Ian

    2011-01-01

    This paper describes the synthesis and surface engineering of core/shell-type iron/iron oxide nanoparticles for magnetic hyperthermia cancer therapy. Iron/iron oxide nanoparticles were synthesized from microemulsions of NaBH4 and FeCl3, followed by surface modification in which a thin hydrophobic hexamethyldisilazane layer - used to protect the iron core - replaced the CTAB coating on the particles. Phosphatidylcholine was then assembled on the nanoparticle surface. The resulting nanocomposite particles have a biocompatible surface and show good stability in both air and aqueous solution. Compared to iron oxide nanoparticles, the nanocomposites show much better heating in an alternating magnetic field. They are good candidates for both hyperthermia and magnetic resonance imaging applications. PMID:21833157

  17. The effect of copper(II), iron(II) sulphate, and vitamin C combinations on the weak antimicrobial activity of (+)-catechin against Staphylococcus aureus and other microbes.

    PubMed

    Holloway, Andrew C; Mueller-Harvey, Irene; Gould, Simon W J; Fielder, Mark D; Naughton, Declan P; Kelly, Alison F

    2012-12-01

    Few attempts have been made to improve the activity of plant compounds with low antimicrobial efficacy. (+)-Catechin, a weak antimicrobial tea flavanol, was combined with putative adjuncts and tested against different species of bacteria. Copper(II) sulphate enhanced (+)-catechin activity against Pseudomonas aeruginosa but not Staphylococcus aureus, Proteus mirabilis or Escherichia coli. Attempts to raise the activity of (+)-catechin against two unresponsive species, S. aureus and E. coli, with iron(II) sulphate, iron(III) chloride, and vitamin C, showed that iron(II) enhanced (+)-catechin against S. aureus, but not E. coli; neither iron(III) nor combined iron(II) and copper(II), enhanced (+)-catechin activity against either species. Vitamin C enhanced copper(II) containing combinations against both species in the absence of iron(II). Catalase or EDTA added to active samples removed viability effects suggesting that active mixtures had produced H(2)O(2)via the action of added metal(II) ions. H(2)O(2) generation by (+)-catechin plus copper(II) mixtures and copper(II) alone could account for the principal effect of bacterial growth inhibition following 30 minute exposures as well as the antimicrobial effect of (+)-catechin-iron(II) against S. aureus. These novel findings about a weak antimicrobial flavanol contrast with previous knowledge of more active flavanols with transition metal combinations. Weak antimicrobial compounds like (+)-catechin within enhancement mixtures may therefore be used as efficacious agents. (+)-Catechin may provide a means of lowering copper(II) or iron(II) contents in certain crop protection and other products. PMID:23138340

  18. Possible surface nematic order in iron pnictides

    NASA Astrophysics Data System (ADS)

    Song, Kok Wee; Koshelev, Alexei

    Nematic fluctuations play important role in the physics of the iron-based superconductors. Indications for weak precursor nematic transition has been found in the compound BaAs2-xPxFe2 [1 ]. However, high-resolution specific-heat measurements did not reveal any bulk transition [2 ]. To resolve this controversy, we consider the possibility of the surface nematic transition preceding the bulk transition. We consider the simplest model of two interacting quasi-two-dimensional electronic bands and explore the free-surface effects on the nematic order. We found that three-dimensional effects suppress the bulk nematic order and therefore this order is enhanced near the surface. [1 ]Kasahara, S., et al. ''Electronic nematicity above the structural and superconducting transition in Ba(As1-xPxFe)2.'' Nature 486.7403 (2012): 382-385. [2 ]Luo, X., et al. ''Antiferromagnetic and nematic phase transitions in Ba(As1-xPxFe)2 studied by ac microcalorimetry and SQUID magnetometry.'' Physical Review B 91.9 (2015): 094512. This work was supported by the Center for Emergent Superconductivity, an Energy FrontierResearch Center funded by the US DOE, Office of Science, under Award No. DEAC0298CH1088.

  19. Evidence of cell surface iron speciation of acidophilic iron-oxidizing microorganisms in indirect bioleaching process.

    PubMed

    Nie, Zhen-yuan; Liu, Hong-chang; Xia, Jin-lan; Yang, Yi; Zhen, Xiang-jun; Zhang, Li-Juan; Qiu, Guan-zhou

    2016-02-01

    While indirect model has been widely accepted in bioleaching, but the evidence of cell surface iron speciation has not been reported. In the present work the iron speciation on the cell surfaces of four typically acidophilic iron-oxidizing microorganism (mesophilic Acidithiobacillus ferrooxidans ATCC 23270, moderately thermophilic Leptospirillum ferriphilum YSK and Sulfobacillus thermosulfidooxidans St, and extremely thermophilic Acidianus manzaensis YN25) grown on different energy substrates (chalcopyrite, pyrite, ferrous sulfate and elemental sulfur (S(0))) were studied in situ firstly by using synchrotron-based micro- X-ray fluorescence analysis and X-ray absorption near-edge structure spectroscopy. Results showed that the cells grown on iron-containing substrates had apparently higher surface iron content than the cells grown on S(0). Both ferrous iron and ferric iron were detected on the cell surface of all tested AIOMs, and the Fe(II)/Fe(III) ratios of the same microorganism were affected by different energy substrates. The iron distribution and bonding state of single cell of A. manzaensis were then studied in situ by scanning transmission soft X-ray microscopy based on dual-energy contrast analysis and stack analysis. Results showed that the iron species distributed evenly on the cell surface and bonded with amino, carboxyl and hydroxyl groups. PMID:26645388

  20. Staphylococcus aureus Nuc2 Is a Functional, Surface-Attached Extracellular Nuclease

    PubMed Central

    Kiedrowski, Megan R.; Crosby, Heidi A.; Hernandez, Frank J.; Malone, Cheryl L.; McNamara, James O.; Horswill, Alexander R.

    2014-01-01

    Staphylococcus aureus is a prominent bacterial pathogen that causes a diverse range of acute and chronic infections. Recently, it has been demonstrated that the secreted nuclease (Nuc) enzyme is a virulence factor in multiple models of infection, and in vivo expression of nuc has facilitated the development of an infection imaging approach based on Nuc-activatable probes. Interestingly, S. aureus strains encode a second nuclease (Nuc2) that has received limited attention. With the growing interest in bacterial nucleases, we sought to characterize Nuc2 in more detail through localization, expression, and biochemical studies. Fluorescence microscopy and alkaline phosphatase localization approaches using Nuc2-GFP and Nuc2-PhoA fusions, respectively, demonstrated that Nuc2 is membrane bound with the C-terminus facing the extracellular environment, indicating it is a signal-anchored Type II membrane protein. Nuc2 enzyme activity was detectable on the S. aureus cell surface using a fluorescence resonance energy transfer (FRET) assay, and in time courses, both nuc2 transcription and enzyme activity peaked in early logarithmic growth and declined in stationary phase. Using a mouse model of S. aureus pyomyositis, Nuc2 activity was detected with activatable probes in vivo in nuc mutant strains, demonstrating that Nuc2 is produced during infections. To assess Nuc2 biochemical properties, the protein was purified and found to cleave both single- and double-stranded DNA, and it exhibited thermostability and calcium dependence, paralleling the properties of Nuc. Purified Nuc2 prevented biofilm formation in vitro and modestly decreased biomass in dispersal experiments. Altogether, our findings confirm that S. aureus encodes a second, surface-attached and functional DNase that is expressed during infections and displays similar biochemical properties to the secreted Nuc enzyme. PMID:24752186

  1. Cystic Fibrosis Isolates of Pseudomonas aeruginosa Retain Iron-Regulated Antimicrobial Activity against Staphylococcus aureus through the Action of Multiple Alkylquinolones.

    PubMed

    Nguyen, Angela T; Jones, Jace W; Cámara, Miguel; Williams, Paul; Kane, Maureen A; Oglesby-Sherrouse, Amanda G

    2016-01-01

    Cystic fibrosis (CF) is a hereditary disease that predisposes individuals to pulmonary dysfunction and chronic infections. Early infection of the CF lung with Staphylococcus aureus is common, while Pseudomonas aeruginosa becomes dominant as disease progresses. Emergence of P. aeruginosa likely depends on the action of multiple 2-alkyl-4-(1H)-quinolones (AQ) secreted by this organism. We recently showed that antimicrobial activity against S. aureus is enhanced by iron depletion and is dependent upon multiple AQ metabolites. Two of these AQs, the Pseudomonas quinolone signal [PQS; 2-heptyl-3-hydroxy-4(1H)-quinolone] and 2-heptyl-4-hydroxyquinoline (HHQ), are quorum sensing molecules that activate the expression of multiple microbicidal factors. Here we show for the first time that HHQ also exhibits innate antimicrobial activity against S. aureus. We further show that iron depletion potentiates the antistaphylococcal activity of HHQ, as well as 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO), another AQ that functions as a cytochrome B inhibitor. Notably, we found that deletion of the genes for the terminal biosynthetic steps for either PQS or HQNO results in overproduction of the HHQ intermediate, likely maintaining the ability of these mutants to mediate antimicrobial activity. Compensatory increases in HHQ were also observed in PQS-deficient CF isolates, which also retained the ability to mediate iron-regulated antimicrobial activity against S. aureus. These studies demonstrate that iron-regulated antimicrobial activity of P. aeruginosa against S. aureus is due to the cumulative effects of multiple AQ metabolites, both the production and activity of which are modulated by environmental iron levels. PMID:27512392

  2. Cystic Fibrosis Isolates of Pseudomonas aeruginosa Retain Iron-Regulated Antimicrobial Activity against Staphylococcus aureus through the Action of Multiple Alkylquinolones

    PubMed Central

    Nguyen, Angela T.; Jones, Jace W.; Cámara, Miguel; Williams, Paul; Kane, Maureen A.; Oglesby-Sherrouse, Amanda G.

    2016-01-01

    Cystic fibrosis (CF) is a hereditary disease that predisposes individuals to pulmonary dysfunction and chronic infections. Early infection of the CF lung with Staphylococcus aureus is common, while Pseudomonas aeruginosa becomes dominant as disease progresses. Emergence of P. aeruginosa likely depends on the action of multiple 2-alkyl-4-(1H)-quinolones (AQ) secreted by this organism. We recently showed that antimicrobial activity against S. aureus is enhanced by iron depletion and is dependent upon multiple AQ metabolites. Two of these AQs, the Pseudomonas quinolone signal [PQS; 2-heptyl-3-hydroxy-4(1H)-quinolone] and 2-heptyl-4-hydroxyquinoline (HHQ), are quorum sensing molecules that activate the expression of multiple microbicidal factors. Here we show for the first time that HHQ also exhibits innate antimicrobial activity against S. aureus. We further show that iron depletion potentiates the antistaphylococcal activity of HHQ, as well as 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO), another AQ that functions as a cytochrome B inhibitor. Notably, we found that deletion of the genes for the terminal biosynthetic steps for either PQS or HQNO results in overproduction of the HHQ intermediate, likely maintaining the ability of these mutants to mediate antimicrobial activity. Compensatory increases in HHQ were also observed in PQS-deficient CF isolates, which also retained the ability to mediate iron-regulated antimicrobial activity against S. aureus. These studies demonstrate that iron-regulated antimicrobial activity of P. aeruginosa against S. aureus is due to the cumulative effects of multiple AQ metabolites, both the production and activity of which are modulated by environmental iron levels. PMID:27512392

  3. Contribution of Cell Surface Hydrophobicity in the Resistance of Staphylococcus aureus against Antimicrobial Agents.

    PubMed

    Lather, Puja; Mohanty, A K; Jha, Pankaj; Garsa, Anita Kumari

    2016-01-01

    Staphylococcus aureus is found in a wide variety of habitats, including human skin, where many strains are commensals that may be clinically significant or contaminants of food. To determine the physiological characteristics of resistant strain of Staphylococcus aureus against pediocin, a class IIa bacteriocin, a resistant strain was compared with wild type in order to investigate the contribution of hydrophobicity to this resistance. Additional clumping of resistant strain relative to wild type in light microscopy was considered as an elementary evidence of resistance attainment. A delay in log phase attainment was observed in resistant strain compared to the wild type strain. A significant increase in cell surface hydrophobicity was detected for resistant strain in both hexadecane and xylene indicating the contribution of cell surface hydrophobicity as adaptive reaction against antimicrobial agents. PMID:26966577

  4. Contribution of Cell Surface Hydrophobicity in the Resistance of Staphylococcus aureus against Antimicrobial Agents

    PubMed Central

    Lather, Puja; Mohanty, A. K.; Jha, Pankaj; Garsa, Anita Kumari

    2016-01-01

    Staphylococcus aureus is found in a wide variety of habitats, including human skin, where many strains are commensals that may be clinically significant or contaminants of food. To determine the physiological characteristics of resistant strain of Staphylococcus aureus against pediocin, a class IIa bacteriocin, a resistant strain was compared with wild type in order to investigate the contribution of hydrophobicity to this resistance. Additional clumping of resistant strain relative to wild type in light microscopy was considered as an elementary evidence of resistance attainment. A delay in log phase attainment was observed in resistant strain compared to the wild type strain. A significant increase in cell surface hydrophobicity was detected for resistant strain in both hexadecane and xylene indicating the contribution of cell surface hydrophobicity as adaptive reaction against antimicrobial agents. PMID:26966577

  5. Key Role of Teichoic Acid Net Charge in Staphylococcus aureus Colonization of Artificial Surfaces

    PubMed Central

    Gross, Matthias; Cramton, Sarah E.; Götz, Friedrich; Peschel, Andreas

    2001-01-01

    Staphylococcus aureus is responsible for a large percentage of infections associated with implanted biomedical devices. The molecular basis of primary adhesion to artificial surfaces is not yet understood. Here, we demonstrate that teichoic acids, highly charged cell wall polymers, play a key role in the first step of biofilm formation. An S. aureus mutant bearing a stronger negative surface charge due to the lack of d-alanine esters in its teichoic acids can no longer colonize polystyrene or glass. The mutation abrogates primary adhesion to plastic while production of the glucosamine-based polymer involved in later steps of biofilm formation is not affected. Our data suggest that repulsive electrostatic forces can lead to reduced staphylococcal biofilm formation, which could have considerable impact on the design of novel implanted materials. PMID:11292767

  6. Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

    NASA Astrophysics Data System (ADS)

    Wu, Wei; He, Quanguo; Jiang, Changzhong

    2008-10-01

    Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed.

  7. Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

    PubMed Central

    2008-01-01

    Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed. PMID:21749733

  8. Efficiency of vanilla, patchouli and ylang ylang essential oils stabilized by iron oxide@C14 nanostructures against bacterial adherence and biofilms formed by Staphylococcus aureus and Klebsiella pneumoniae clinical strains.

    PubMed

    Bilcu, Maxim; Grumezescu, Alexandru Mihai; Oprea, Alexandra Elena; Popescu, Roxana Cristina; Mogoșanu, George Dan; Hristu, Radu; Stanciu, George A; Mihailescu, Dan Florin; Lazar, Veronica; Bezirtzoglou, Eugenia; Chifiriuc, Mariana Carmen

    2014-01-01

    Biofilms formed by bacterial cells are associated with drastically enhanced resistance against most antimicrobial agents, contributing to the persistence and chronicization of the microbial infections and to therapy failure. The purpose of this study was to combine the unique properties of magnetic nanoparticles with the antimicrobial activity of three essential oils to obtain novel nanobiosystems that could be used as coatings for catheter pieces with an improved resistance to Staphylococcus aureus and Klebsiella pneumoniae clinical strains adherence and biofilm development. The essential oils of ylang ylang, patchouli and vanilla were stabilized by the interaction with iron oxide@C14 nanoparticles to be further used as coating agents for medical surfaces. Iron oxide@C14 was prepared by co-precipitation of Fe+2 and Fe+3 and myristic acid (C14) in basic medium. Vanilla essential oil loaded nanoparticles pelliculised on the catheter samples surface strongly inhibited both the initial adherence of S. aureus cells (quantified at 24 h) and the development of the mature biofilm quantified at 48 h. Patchouli and ylang-ylang essential oils inhibited mostly the initial adherence phase of S. aureus biofilm development. In the case of K. pneumoniae, all tested nanosystems exhibited similar efficiency, being active mostly against the adherence K. pneumoniae cells to the tested catheter specimens. The new nanobiosystems based on vanilla, patchouli and ylang-ylang essential oils could be of a great interest for the biomedical field, opening new directions for the design of film-coated surfaces with anti-adherence and anti-biofilm properties. PMID:25375335

  9. The surface chemistry of iron Fischer-Tropsch catalysts

    SciTech Connect

    Dwyer, D.J.; Hardenburgh, J.H.

    1986-04-01

    The indirect conversion of coal to liquid hydrocarbons via steam gasification followed by synthesis gas (CO/H/sub 2/) chemistry has been the subject of intensive study for a number of decades. A key technological challenge facing researchers in this area is control over the product distribution during the hydrocarbon synthesis step. In the case of iron Fischer-Tropsch catalysts, it has been known that the addition of alkali to the metal catalyst has a significant impact on the product distribution. Iron catalysts treated with alkali produce less methane more alkenes and higher molecular weight products. In spite of numerous investigations, the details of this promotional effect are not understood on a molecular level. To explore the role of alkali in the surface chemistry of iron catalysts, the authors have carried out a combined surface science and catalytic kinetic study of a model iron catalyst with and without surface alkali.

  10. PolyNaSS grafting on titanium surfaces enhances osteoblast differentiation and inhibits Staphylococcus aureus adhesion.

    PubMed

    Alcheikh, A; Pavon-Djavid, G; Helary, G; Petite, H; Migonney, V; Anagnostou, F

    2013-07-01

    Titanium surface modifications to simultaneously prevent bacterial adhesion but promote bone-cell functions could be highly beneficial for improving implant osseointegration. In the present in vitro study, the effect of sulfonate groups on titanium surfaces was investigated with respect to both S. aureus adhesion and osteoblast functions pertinent to new bone formation. Commercial pure titanium (cpTi) squares were oxydized (Tiox), grafted with poly(sodium styrene sulfonate) groups (Tigraft) by covalent bonding using radical polymerization, and were characterized by infrared spectroscopy (HATR-FTIR) and colorimetry. Bacterial adhesion study showed that Tigraft exhibited high inhibition of S. aureus adhesion S at levels >90 %, when compared to cpTi (P < 0.05). In contrast osteoblasts adhesion was similar on all three titanium surfaces. While the kinetics of cell proliferation were similar on the three titanium surfaces, Alkaline phosphatase-specific activity of osteoblasts cultured on Tigraft surfaces was twofold higher than that observed on either on Tiox or cpTi surfaces (P < 0.01). More importantly, the amount and the distribution of calcium-containing nodules was different. The total area covered by calcium-containing nodules was 2.2-fold higher on the Tigraft as compared to either Tiox or cpTi surfaces (P < 0.01). These results provide evidence that poly(sodium styrene sulfonate) groups grafting on cpTi simultaneously inhibits bacteria adhesion but promote osteoblast function pertinent to new bone formation. Such modified titanium surfaces offer a promising strategy for preventing biofilm-related infections and enhancing osteointegration of implants in orthopaedic and dental applications. PMID:23625318

  11. Nanorough titanium surfaces reduce adhesion of Escherichia coli and Staphylococcus aureus via nano adhesion points.

    PubMed

    Lüdecke, Claudia; Roth, Martin; Yu, Wenqi; Horn, Uwe; Bossert, Jörg; Jandt, Klaus D

    2016-09-01

    Microbial adhesion to natural and synthetic materials surfaces is a key issue e.g. in food industry, sewage treatment and most importantly in the biomedical field. The current development and progress in nanoscale structuring of materials surfaces to control microbial adhesion requires an advanced understanding of the microbe-material-interaction. This study aimed to investigate the nanostructure of the microbe-material-interface and link it to microbial adhesion kinetics as function of titanium surface nanoroughness to gain new insight into controlling microbial adhesion via materials' surface nanoroughness. Adhesion of Escherichia coli and Staphylococcus aureus was statistically significantly reduced (p≤0.05) by 55.6 % and 40.5 %, respectively, on physical vapor deposited titanium thin films with a nanoroughness of 6nm and the lowest surface peak density compared to 2nm with the highest surface peak density. Cross-sectioning of the microbial cells with a focused ion beam (FIB) and SEM imaging provided for the first time direct insight into the titanium-microbe-interface. High resolution SEM micrographs gave evidence that the surface peaks are the loci of initial contact between the microbial cells and the material's surface. In a qualitative model we propose that the initial microbial adhesion on nanorough surfaces is controlled by the titanium surface peak density via nano adhesion points. This new understanding will help towards the design of materials surfaces for controlling microbial adhesion. PMID:27288816

  12. OXYANION SORPTION TO HIGH SURFACE AREA IRON AND ALUMINUM OXIDES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sorption of selected oxyanions (Mo, As, and P) to high surface area iron and aluminum oxides was investigated using in situ Raman and ATR-FTIR spectroscopy, batch sorption methods, electrophoretic mobility measurements, and surface complexation modeling. In situ ATR-FTIR and Raman spectra were coup...

  13. Surface-Bound Nuclease of Staphylococcus aureus: Localization of the Enzyme

    PubMed Central

    Okabayashi, Kinji; Mizuno, Den'ichi

    1974-01-01

    The cellular localization of staphylococcus nuclease, previously known as an exoenzyme, was investigated, and the following results were obtained. (i) When Staphylococcus aureus cells were converted to protoplasts by cell wall lytic enzyme L-11 (a bacteriolytic enzyme purified from Flavobacterium sp. which specifically hydrolyzes amide and peptide linkages of murein layers), over 80% of the cell-bound nuclease was released into the surrounding sucrose medium. (ii) The cell-bound nuclease was associated with the cell-wall membrane fraction of mechanically disrupted cells. (iii) The nuclease activity of cell-wall membrane fractions from cells during early and late stages of protoplast formation were compared. Less activity was found in the late stage. These results suggest that nuclease may be located at or near the surface of the cells. The distribution of cell-bound nuclease in the cell-wall membrane fraction varied with the growth conditions of S. aureus. The activity of alkaline phosphatase, another surface enzyme, was also investigated. Less of this enzyme than nuclease was released when the cells were converted to protoplasts. PMID:4587603

  14. Thin film lubrication of hexadecane confined by iron and iron oxide surfaces: A crucial role of surface structure.

    PubMed

    Ta, D T; Tieu, A K; Zhu, H T; Kosasih, B

    2015-10-28

    A comparative analysis of thin film lubrication of hexadecane between different iron and its oxide surfaces has been carried out using classical molecular dynamic simulation. An ab initio force-field, COMPASS, was applied for n-hexadecane using explicit atom model. An effective potential derived from density functional theory calculation was utilized for the interfacial interaction between hexadecane and the tribo-surfaces. A quantitative surface parameterization was introduced to investigate the influence of surface properties on the structure, rheological properties, and tribological performance of the lubricant. The results show that although the wall-fluid attraction of hexadecane on pure iron surfaces is significantly stronger than its oxides, there is a considerable reduction of shear stress of confined n-hexadecane film between Fe(100) and Fe(110) surfaces compared with FeO(110), FeO(111), Fe2O3(001), and Fe2O3(012). It was found that, in thin film lubrication of hexadecane between smooth iron and iron oxide surfaces, the surface corrugation plays a role more important than the wall-fluid adhesion strength. PMID:26520538

  15. Thin film lubrication of hexadecane confined by iron and iron oxide surfaces: A crucial role of surface structure

    NASA Astrophysics Data System (ADS)

    Ta, D. T.; Tieu, A. K.; Zhu, H. T.; Kosasih, B.

    2015-10-01

    A comparative analysis of thin film lubrication of hexadecane between different iron and its oxide surfaces has been carried out using classical molecular dynamic simulation. An ab initio force-field, COMPASS, was applied for n-hexadecane using explicit atom model. An effective potential derived from density functional theory calculation was utilized for the interfacial interaction between hexadecane and the tribo-surfaces. A quantitative surface parameterization was introduced to investigate the influence of surface properties on the structure, rheological properties, and tribological performance of the lubricant. The results show that although the wall-fluid attraction of hexadecane on pure iron surfaces is significantly stronger than its oxides, there is a considerable reduction of shear stress of confined n-hexadecane film between Fe(100) and Fe(110) surfaces compared with FeO(110), FeO(111), Fe2O3(001), and Fe2O3(012). It was found that, in thin film lubrication of hexadecane between smooth iron and iron oxide surfaces, the surface corrugation plays a role more important than the wall-fluid adhesion strength.

  16. Thin film lubrication of hexadecane confined by iron and iron oxide surfaces: A crucial role of surface structure

    SciTech Connect

    Ta, D. T.; Tieu, A. K.; Zhu, H. T. Kosasih, B.

    2015-10-28

    A comparative analysis of thin film lubrication of hexadecane between different iron and its oxide surfaces has been carried out using classical molecular dynamic simulation. An ab initio force-field, COMPASS, was applied for n-hexadecane using explicit atom model. An effective potential derived from density functional theory calculation was utilized for the interfacial interaction between hexadecane and the tribo-surfaces. A quantitative surface parameterization was introduced to investigate the influence of surface properties on the structure, rheological properties, and tribological performance of the lubricant. The results show that although the wall-fluid attraction of hexadecane on pure iron surfaces is significantly stronger than its oxides, there is a considerable reduction of shear stress of confined n-hexadecane film between Fe(100) and Fe(110) surfaces compared with FeO(110), FeO(111), Fe{sub 2}O{sub 3}(001), and Fe{sub 2}O{sub 3}(012). It was found that, in thin film lubrication of hexadecane between smooth iron and iron oxide surfaces, the surface corrugation plays a role more important than the wall-fluid adhesion strength.

  17. Energetics of surface confined ferritin during iron loading.

    PubMed

    Federici, Stefania; Padovani, Francesco; Poli, Maura; Rodriguez, Fernando Carmona; Arosio, Paolo; Depero, Laura E; Bergese, Paolo

    2016-09-01

    We report on the first quantitative picture on how iron loading inside ferritin molecules occurs when they are self-assembled onto solid surfaces. Recombinant human ferritin H-chain with ferroxidase activity was adsorbed onto microcantilever beams to form a stable close-packed thin film. The obtained nanomechanical system was used to track in real time the energetics of inter-ferritin surface interactions during incubation with Fe(II) for iron loading. We observed that iron loading is accompanied by increasing attractive in-plane inter-ferritin interactions able to perform a maximum surface work of 6.0±1.5mJ/m(2), corresponding to a surface energy variation per ferritin of about 40kbT. Unique to this protein surface transformation, part of the surface work is exerted by the attractive electrostatic forces arising among the new born nanosized iron cores inside the ferritin shells. The remaining work comes from subtle action of steric, bridging and depletion forces. These findings are of fundamental interest and add important information for the rational development of ferritin nanotechnology. PMID:27281237

  18. Nanostructured and Surface Polymerized Iron Particles for Magnetorheological Fluids

    NASA Astrophysics Data System (ADS)

    Hu, Ben; Fuchs, Alan; Gordaninejad, Faramarz; Evrensel, Cahit

    A novel magnetorheological fluid, in which the surface of iron particles is coated with poly (butyl acrylate) by surface initiated atom transfer radical polymerization (ATRP), is investigated. The polymer coating procedure includes two steps, which are immobilization of initiator: 2-4(-chlorosulfonylphenyl)-ethytrichlorosilane (CTCS) on the iron particles surface and graft polymerization of butyl acrylate from the surface. The surface coating is characterized by FTIR and SEM. This magnetorheological fluid has controllable off-state viscosity and high shear yield stress. Coating polymer on the iron particles surface by ATRP can significantly reduce iron particles settling and improve stability of the MR fluid. Polymerization kinetics of bulk butyl acrylate are investigated using differential scanning calorimetry (DSC). Glass transition temperature is obtained using the step-scan DSC method. The molecular weight and conversion can be controlled by the molar ratio of monomer to initiator, reaction temperature and time. The reaction is first order determined by the plot of In (M/M0) against polymerization time. The overall activation energy is found to be 126kJ/mol by Kissinger's Method.

  19. Anomalous hysteresis properties of iron films deposited on liquid surfaces

    NASA Astrophysics Data System (ADS)

    Ye, Quan-Lin; Feng, Chun-Mu; Xu, Xiao-Jun; Jin, Jin-Sheng; Xia, A.-Gen; Ye, Gao-Xiang

    2005-07-01

    A nearly free sustained iron film system, deposited on silicone oil surfaces by vapor-phase deposition method, has been fabricated and its crystal structure as well as magnetic properties has been studied. Both the temperature-dependent coercivity Hc(T) and exchange anisotropy field HE(T) of the iron films possess a maximum peak around the critical temperature Tcrit=10-15 and 4K, respectively. Our experimental results show that the anomalous hysteresis properties mainly result from the oxide surfaces of the films with spin-glass-like phase below freezing temperature Tf=30-50K.

  20. Staphylococcus aureus Surface Protein SdrE Binds Complement Regulator Factor H as an Immune Evasion Tactic

    PubMed Central

    Sharp, Julia A.; Echague, Charlene G.; Hair, Pamela S.; Ward, Michael D.; Nyalwidhe, Julius O.; Geoghegan, Joan A.; Foster, Timothy J.; Cunnion, Kenji M.

    2012-01-01

    Similar to other highly successful invasive bacterial pathogens, Staphylococcus aureus recruits the complement regulatory protein factor H (fH) to its surface to inhibit the alternative pathway of complement. Here, we report the identification of the surface-associated protein SdrE as a fH-binding protein using purified fH overlay of S. aureus fractionated cell wall proteins and fH cross-linking to S. aureus followed by mass spectrometry. Studies using recombinant SdrE revealed that rSdrE bound significant fH whether from serum or as a purified form, in both a time- and dose-dependent manner. Furthermore, rSdrE-bound fH exhibited cofactor functionality for factor I (fI)-mediated cleavage of C3b to iC3b which correlated positively with increasing amounts of fH. Expression of SdrE on the surface of the surrogate bacterium Lactococcus lactis enhanced recruitment of fH which resulted in increased iC3b generation. Moreover, surface expression of SdrE led to a reduction in C3-fragment deposition, less C5a generation, and reduced killing by polymorphonuclear cells. Thus, we report the first identification of a S. aureus protein associated with the staphylococcal surface that binds factor H as an immune evasion mechanism. PMID:22675461

  1. ASSESSMENT OF SURFACE RUNOFF FROM IRON AND STEEL MILLS

    EPA Science Inventory

    The report gives results of a program to determine if surface runoff from iron and steel mills is an environmental problem. It includes a compilation of data available before this program, information gathered from plant tours, and results of a field survey at two fully integrate...

  2. Reducing Staphylococcus aureus growth on Ti alloy nanostructured surfaces through the addition of Sn.

    PubMed

    Verissimo, Nathália C; Geilich, Benjamin M; Oliveira, Haroldo G; Caram, Rubens; Webster, Thomas J

    2015-12-01

    β-type Ti alloys containing Nb are exciting materials for numerous orthopedic and dental applications due to their exceptional mechanical properties. To improve their cytocompatibility properties (such as increasing bone growth and decreasing infection), the surfaces of such materials can be optimized by adding elements and/or nanotexturing through anodization. Because of the increasing prevalence of orthopedic implant infections, the objective of this in vitro study was to add Sn and create unique nanoscale surface features on β-type Ti alloys. Nanotubes and nanofeatures on Ti-35Nb and Ti-35Nb-4Sn alloys were created by anodization in a HF-based electrolyte and then heat treated in a furnace to promote amorphous structures and phases such as anatase, a mixture of anatase-rutile, and rutile. Samples were characterized by SEM, which indicated different morphologies dependent on the oxide content and method of modification. XPS experiments identified the oxide content which resulted in a phase transformation in the oxide layer formed onto Ti-35Nb and Ti-35Nb-4Sn alloys. Most importantly, regardless of the resulting nanostructures (nanotubes or nanofeatures) and crystalline phase, this study showed for the first time that adding Sn to β-type Ti alloys strongly decreased the adhesion of Staphylococcus aureus (S. aureus; a bacteria which commonly infects orthopedic implants leading to their failure). Thus, this study demonstrated that β-type Ti alloys with Nb and Sn have great promise to improve numerous orthopedic applications where infection may be a concern. PMID:26033413

  3. Iron migration from the anode surface in alumina electrolysis

    NASA Astrophysics Data System (ADS)

    Zhuravleva, Elena N.; Drozdova, Tatiana N.; Ponomareva, Svetlana V.; Kirik, Sergei D.

    2013-01-01

    Corrosion destruction of two-component iron-based alloys used as an anode in high-temperature alumina electrolysis in the melt of NaF/KF/AlF3 electrolyte has been considered. Ni, Si, Cu, Cr, Mn, Al, Ti in the amount of up to 10% have been tested as the dopants to an anode alloys. The composition of the corrosion products has been studied using X-ray diffraction, scanning electron microscopy and electron microprobe analysis. It has been established that the anode corrosion is induced by a surface electrochemical polarization and iron atom oxidation. Iron ions come into an exchange interaction with the fluoride components of the melted electrolyte, producing FeF2. The last interacts with oxyfluoride species transforming into the oxide forms: FeAl2O4, Fe3O4, Fe2O3. Due to the low solubility, the iron oxides are accumulated in the near-electrode sheath. The only small part of iron from anode migrates to cathode that makes an production of high purity aluminum of a real task. The alloy dopants are also subjected to corrosion in accordance with electromotive series resulting corrosion tunnels on the anode surface. The oxides are final compounds which collect in the same area. The corrosion products form an anode shell which is electronic conductor at electrolysis temperature. The electrolysis of alumina occurs beyond the corrosion shell. The rate limiting step in the corrosion is the electrolyte penetration through corrosion shell to the anode surface. The participation of the released oxygen in the corrosion has not been observed.

  4. Influence of alanine uptake on Staphylococcus aureus surface charge and its susceptibility to two cationic antibacterial agents, nisin and low molecular weight chitosan.

    PubMed

    Chen, Li-Chen; Chiang, Wen-Dee; Chen, Wei-Chiuan; Chen, Hui-Huang; Huang, Yao-Wen; Chen, Wei-Jung; Lin, Shih-Bin

    2012-12-15

    Low molecular weight chitosan (LMWC) and nisin, recognized as cationic antibacterial agents (CAAs), inhibit bacterial growth by interacting with the anionically charged cell wall. In this study, alanine uptake significantly reduced the anionic cell surface charge, as determined by the zeta potential (ZP) measurements, of Staphylococcus aureus, resulting from the incorporation of d-alanine into the cell wall. Minimum inhibitory concentration (MIC) tests and growth inhibition curves revealed that LMWC and nisin possessed inverse antibacterial activity against three strains of S. aureus, depending on the strains' net charge. A twofold reduction in the MIC value of nisin was obtained against S. aureus, inoculated in a 1.0% d- or l-alanine-augmented trypticase soy broth medium. A flocculation test demonstrated that neutralizing the anionic surface charge using d-alanine reduced the adsorption of S. aureus onto LMWC. Furthermore, the reduced surface net charge could enhance the colonization capacity of S. aureus on glass. PMID:22980819

  5. Fracture surface of hydrogen embrittlement in iron single crystals

    SciTech Connect

    Takano, N.; Kidani, K.; Hattori, Y.; Terasaki, F. )

    1993-07-01

    Hydrogen embrittlement of iron and low strength steels has been studied for a long time. Its mechanism, however has not been explained clearly yet. Fractography is often used as a method for the study of the fracture mechanism. The fracture process, for example, microvoid coalescence (MVC), cleavage, grain boundary fracture and so on, can be determined by means of fractography. Then it is possible to understand by which process hydrogen causes the embrittlement. The purpose of the present work is to investigate the characteristics of such fracture surfaces and to deduce the fracture mechanism. As for the embrittlement of iron and steels, they often occur after a fair amount of plastic deformation, which strongly depends on the crystallographic orientation and temperature. In this paper, the fracture surfaces of the hydrogen embrittlement are investigated with various crystallographic orientation and temperatures.

  6. Biofilm formation by Staphylococcus aureus from food contact surfaces in a meat-based broth and sensitivity to sanitizers

    PubMed Central

    de Souza, Evandro Leite; Meira, Quênia Gramile Silva; de Medeiros Barbosa, Isabella; Athayde, Ana Júlia Alves Aguiar; da Conceição, Maria Lúcia; de Siqueira Júnior, José Pinto

    2014-01-01

    This study assessed the capacity of adhesion, the detachment kinetic and the biofilm formation by Staphylococcus aureus isolated from food services on stainless steel and polypropylene surfaces (2 × 2 cm) when cultivated in a meat-based broth at 28 and 7 °C. It was also to study the efficacy of the sanitizers sodium hypochlorite (250 mg/L) and peracetic acid (30 mg/L) in inactivating the bacterial cells in the preformed biofilm. S. aureus strains adhered in high numbers regardless the assayed surface kind and incubation temperature over 72 h. Cells detachment of surfaces revealed high persistence over the incubation period. Number of cells needed for biofilm formation was noted at all experimental systems already after 3 days. Peracetic acid and sodium hypochlorite were not efficient in completely removing the cells of S. aureus adhered on polypropylene and stainless steel surfaces. From these results, the assayed strains revealed high capacity to adhere and form biofilm on polypropylene and stainless steel surfaces under different growth conditions. Moreover, the cells in biofilm matrix were resistant for total removal when submitted to the exposure to sanitizers. PMID:24948915

  7. Biofilm formation by Staphylococcus aureus from food contact surfaces in a meat-based broth and sensitivity to sanitizers.

    PubMed

    de Souza, Evandro Leite; Meira, Quênia Gramile Silva; de Medeiros Barbosa, Isabella; Athayde, Ana Júlia Alves Aguiar; da Conceição, Maria Lúcia; de Siqueira Júnior, José Pinto

    2014-01-01

    This study assessed the capacity of adhesion, the detachment kinetic and the biofilm formation by Staphylococcus aureus isolated from food services on stainless steel and polypropylene surfaces (2 × 2 cm) when cultivated in a meat-based broth at 28 and 7 °C. It was also to study the efficacy of the sanitizers sodium hypochlorite (250 mg/L) and peracetic acid (30 mg/L) in inactivating the bacterial cells in the preformed biofilm. S. aureus strains adhered in high numbers regardless the assayed surface kind and incubation temperature over 72 h. Cells detachment of surfaces revealed high persistence over the incubation period. Number of cells needed for biofilm formation was noted at all experimental systems already after 3 days. Peracetic acid and sodium hypochlorite were not efficient in completely removing the cells of S. aureus adhered on polypropylene and stainless steel surfaces. From these results, the assayed strains revealed high capacity to adhere and form biofilm on polypropylene and stainless steel surfaces under different growth conditions. Moreover, the cells in biofilm matrix were resistant for total removal when submitted to the exposure to sanitizers. PMID:24948915

  8. Radiation induced chemical activity at iron and copper oxide surfaces

    NASA Astrophysics Data System (ADS)

    Reiff, Sarah C.

    The radiolysis of three iron oxides, two copper oxides, and aluminum oxide with varying amounts of water were performed using gamma-rays and 5 MeV 4He ions. The adsorbed water on the surfaces was characterized using temperature programmed desorption and diffuse reflectance infrared spectroscopy, which indicated that all of the oxides had chemisorbed water on the surface. Physisorbed water was observed on the Fe2O 3 and Al2O3 surfaces as well. Molecular hydrogen was produced from adsorbed water only on Fe2O3 and Al 2O3, while the other compounds did not show any hydrogen production due to the low amounts of water on the surfaces. Slurries of varying amounts of water were also examined for hydrogen production, and they showed yields that were greater than the yield for bulk water. However, the yields of hydrogen from the copper compounds were much lower than those of the iron suggesting that the copper oxides are relatively inert to radiation induced damage to nearby water. X-ray diffraction measurements did not show any indication of changes to the bulk crystal structure due to radiolysis for any of the oxides. The surfaces of the oxides were analyzed using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). For the iron samples, FeO and Fe3O4, Raman spectroscopy revealed areas of Fe2O3 had formed following irradiation with He ions. XPS indicated the formation of a new oxygen species on the iron oxide surfaces. Raman spectroscopy of the copper oxides did not reveal any changes in the surface composition, however, XPS measurements showed a decrease in the amount of OH groups on the surface of Cu2O, while for the CuO samples the amount of OH groups were found to increase following radiolysis. Pristine Al2O3 showed the presence of a surface oxyhydroxide layer which was observed to decrease following radiolysis, consistent with the formation of molecular hydrogen.

  9. Heme Recognition By a Staphylococcus Aureus IsdE

    SciTech Connect

    Grigg, J.C.; Vermeiren, C.L.; Heinrichs, D.E.; Murphy, M.E.P.

    2009-06-03

    Staphylococcus aureus is a Gram-positive bacterial pathogen and a leading cause of hospital acquired infections. Because the free iron concentration in the human body is too low to support growth, S. aureus must acquire iron from host sources. Heme iron is the most prevalent iron reservoir in the human body and a predominant source of iron for S. aureus. The iron-regulated surface determinant (Isd) system removes heme from host heme proteins and transfers it to IsdE, the cognate substrate-binding lipoprotein of an ATP-binding cassette transporter, for import and subsequent degradation. Herein, we report the crystal structure of the soluble portion of the IsdE lipoprotein in complex with heme. The structure reveals a bi-lobed topology formed by an N- and C-terminal domain bridged by a single {alpha}-helix. The structure places IsdE as a member of the helical backbone metal receptor superfamily. A six-coordinate heme molecule is bound in the groove established at the domain interface, and the heme iron is coordinated in a novel fashion for heme transporters by Met{sup 78} and His{sup 229}. Both heme propionate groups are secured by H-bonds to IsdE main chain and side chain groups. Of these residues, His{sup 299} is essential for IsdE-mediated heme uptake by S. aureus when growth on heme as a sole iron source is measured. Multiple sequence alignments of homologues from several other Gram-positive bacteria, including the human pathogens pyogenes, Bacillus anthracis, and Listeria monocytogenes, suggest that these other systems function equivalently to S. aureus IsdE with respect to heme binding and transport.

  10. Reflection spectra and magnetochemistry of iron oxides and natural surfaces

    NASA Technical Reports Server (NTRS)

    Wasilewski, P.

    1978-01-01

    The magnetic properties and spectral characteristics of iron oxides are distinctive. Diagnostic features in reflectance spectra (0.5 to 2.4 micron) for alpha Fe2O3, gamma Fe2O3, and FeOOH include location of Fe3(+) absorption features, intensity ratios at various wavelengths, and the curve shape between 1.2 micron and 2.4 micron. The reflection spectrum of natural rock surfaces are seldom those of the bulk rock because of weathering effects. Coatings are found to be dominated by iron oxides and clay. A simple macroscopic model of rock spectra (based on concepts of stains and coatings) is considered adequate for interpretation of LANDSAT data. The magnetic properties of materials associated with specific spectral types and systematic changes in both spectra and magnetic properties are considered.

  11. Holographic surface gratings in iron-doped lithium niobate

    SciTech Connect

    Sarkisov, S. S.; Curley, M. J.; Kukhtarev, N. V.; Fields, A.; Adamovsky, G.; Smith, C. C.; Moore, L. E.

    2001-08-13

    Surface gratings associated with holographic volume gratings in photorefractive crystals of iron-doped lithium niobate have been studied using diffraction of a reflected probe beam and high-resolution phase-shifted interferometric profilometry. Both techniques show that the surface gratings exist in the form of periodical corrugations of the same period as that of the volume grating. The maximum amplitude of the periodical surface relief measured by both techniques is close to 6.5 nm. We also demonstrated that the periodical electric forces on the surface were capable of assembling polystyrene microspheres along the fringes of the grating. Large amplitude of the periodic electric field (1.6 x 10{sup 4}V/cm) is associated with the photogalvanic effect. {copyright} 2001 American Institute of Physics.

  12. Femtosecond laser surface texturing of titanium as a method to reduce the adhesion of Staphylococcus aureus and biofilm formation

    NASA Astrophysics Data System (ADS)

    Cunha, Alexandre; Elie, Anne-Marie; Plawinski, Laurent; Serro, Ana Paula; Botelho do Rego, Ana Maria; Almeida, Amélia; Urdaci, Maria C.; Durrieu, Marie-Christine; Vilar, Rui

    2016-01-01

    The aim of the present work was to investigate the possibility of using femtosecond laser surface texturing as a method to reduce the colonization of Grade 2 Titanium alloy surfaces by Staphylococcus aureus and the subsequent formation of biofilm. The laser treatments were carried out with a Yb:KYW chirped-pulse-regenerative amplification laser system with a central wavelength of 1030 nm and a pulse duration of 500 fs. Two types of surface textures, consisting of laser-induced periodic surface structures (LIPSS) and nanopillars, were produced. The topography, chemical composition and phase constitution of these surfaces were investigated by atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. Surface wettability was assessed by the sessile drop method using water and diiodomethane as testing liquids. The response of S. aureus put into contact with the laser treated surfaces in controlled conditions was investigated by epifluorescence microscopy and scanning electron microscopy 48 h after cell seeding. The results achieved show that the laser treatment reduces significantly the bacterial adhesion to the surface as well as biofilm formation as compared to a reference polished surfaces and suggest that femtosecond laser texturing is a simple and promising method for endowing dental and orthopedic titanium implants with antibacterial properties, reducing the risk of implant-associated infections without requiring immobilized antibacterial substances, nanoparticles or coatings.

  13. High potential of adhesion to biotic and abiotic surfaces by opportunistic Staphylococcus aureus strains isolated from orthodontic appliances.

    PubMed

    Merghni, Abderrahmen; Ben Nejma, Mouna; Dallel, Ines; Tobji, Samir; Ben Amor, Adel; Janel, Sébastien; Lafont, Frank; Aouni, Mahjoub; Mastouri, Maha

    2016-02-01

    Orthodontic and other oral appliances act as reservoir of opportunistic pathogens that can easily become resistant to antibiotics and cause systemic infections. The aim of this study was to investigate the ability of Staphylococcus aureus strains isolated from healthy patients with orthodontic appliances, to adhere to biotic (HeLa cells) and abiotic surfaces (polystyrene and dental alloy). Adhesive ability to polystyrene was tested by crystal violet staining and quantitative biofilm production on dental alloy surfaces was evaluated by MTT reduction assay. In addition, the presence of icaA and icaD genes was achieved by polymerase chain reaction (PCR). Qualitative biofilm production revealed that 70.6% of strains were slime producers. The metabolic activity of S. aureus biofilms on dental alloy surfaces was high and did not differ between tested strains. Moreover, all the isolates were adhesive to HeLa cells and 94% of them harbor icaA and icaD genes. Considerable adhesion and internalization capacity to the epithelial HeLa cells and strong biofilm production abilities together, with a high genotypic expression of icaA/icaD genes are an important equipment of S. aureus to colonize orthodontic appliances and eventually to disseminate towards other body areas. PMID:26620082

  14. IsdB-dependent Hemoglobin Binding Is Required for Acquisition of Heme by Staphylococcus aureus

    PubMed Central

    Pishchany, Gleb; Sheldon, Jessica R.; Dickson, Claire F.; Alam, Md Tauqeer; Read, Timothy D.; Gell, David A.; Heinrichs, David E.; Skaar, Eric P.

    2014-01-01

    Staphylococcus aureus is a Gram-positive pathogen responsible for tremendous morbidity and mortality. As with most bacteria, S. aureus requires iron to cause disease, and it can acquire iron from host hemoglobin. The current model for staphylococcal hemoglobin-iron acquisition proposes that S. aureus binds hemoglobin through the surface-exposed hemoglobin receptor IsdB. IsdB removes heme from bound hemoglobin and transfers this cofactor to other proteins of the Isd system, which import and degrade heme to release iron in the cytoplasm. Here we demonstrate that the individual components of the Isd system are required for growth on low nanomolar concentrations of hemoglobin as a sole source of iron. An in-depth study of hemoglobin binding by IsdB revealed key residues that are required for hemoglobin binding. Further, we show that these residues are necessary for heme extraction from hemoglobin and growth on hemoglobin as a sole iron source. These processes are found to contribute to the pathogenicity of S. aureus in a murine model of infection. Together these results build on the model for Isd-mediated hemoglobin binding and heme-iron acquisition during the pathogenesis of S. aureus infection. PMID:24338348

  15. Construction of super-hydrophobic iron with a hierarchical surface structure

    NASA Astrophysics Data System (ADS)

    Yuan, Zhiqing; Bin, Jiping; Wang, Xian; Wang, Menglei; Peng, Chaoyi; Xing, Suli; Xiao, Jiayu; Zeng, Jingcheng; Xiao, Ximei; Fu, Xin

    2014-04-01

    Wettability of an iron surface is crucial for the wide applications of iron in practice. In this work, a hierarchical structure highly similar to that of the underside of a bamboo leaf was constructed on an iron surface via the template method and controllable etching. After modification by stearic acid, the iron surface with hierarchical structure showed excellent water repellency, with an average contact angle of 156° and a sliding angle of 3°. X-ray diffraction (XRD) techniques and Fourier transform infrared spectroscopy (FTIR) are applied to examine the chemical components of an iron surface.

  16. Chromium boron surfaced nickel-iron base alloys

    NASA Technical Reports Server (NTRS)

    Rashid, James M. (Inventor); Friedrich, Leonard A. (Inventor); Freling, Melvin (Inventor)

    1984-01-01

    Chromium boron diffusion coatings on nickel iron alloys uniquely provide them with improvement in high cycle fatigue strength (up to 30%) and erosion resistance (up to 15 times), compared to uncoated alloy. The diffused chromium layer extends in two essential concentration zones to a total depth of about 40.times.10.sup.-6 m, while the succeeding boron layer is limited to 50-90% of the depth of the richest Cr layer nearest the surface. Both coatings are applied using conventional pack diffusion processes.

  17. Microstructural study of surface melted and chromium surface alloyed ductile iron

    NASA Astrophysics Data System (ADS)

    Sohi, M. Heydarzadeh; Ebrahimi, M.; Ghasemi, H. M.; Shahripour, A.

    2012-07-01

    In this study, ductile iron was surface melted and chromium surface alloyed via pre-placing of ferrochromium powder with different thicknesses and subsequently surface melting by tungsten inert gas (TIG) process. Optical and scanning electron microscopy, as well as micro-hardness testing and X-ray diffraction analysis were used for characterization of the treated samples. Surface melting and chromium surface alloying resulted in formation of ledeburitic structure and high chromium white cast iron in the treated layers, respectively. It was also noticed that hardness of the treated layers was considerably higher than that of the base material. Increasing thickness of ferrochromium layer increased the amount of M7C3 carbides and hardness of the alloyed layer.

  18. Surface ocean iron fertilization: The role of airborne volcanic ash and iron-flux into the Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Olgun, N.; Duggen, S.; Croot, P.; Dietze, H.

    2009-04-01

    Iron is a limiting micro-nutrient for marine primary production (MPP) in vast areas in the surface ocean. Hence, atmospheric supply of iron to the surface ocean can affect marine biogeochemical cycles, associated ocean-atmosphere exchange of CO2 and eventually climate development. Airborne volcanic ash from volcanic eruptions can be an important atmospheric iron-source in the surface ocean by releasing bio-available iron while settling through in the surface ocean. Here we present new data from time-dependent geochemical experiments with pristine (unhydrated) volcanic ash samples and natural seawater by means of Cathodic Stripping Voltammetry. Our results demonstrate that volcanic ash mobilizes significant amounts of soluble Fe within 60 minutes of contact with natural seawater. Depending on the amount of volcanic ash deposited offshore during major volcanic eruptions and the amount of iron that ash can release on contact with seawater, the calculated increase in the surface ocean Fe levels range from several nanomolar up to several hundred nanomolar (nM). Only 2 nM increase in iron concentrations can stimulate massive diatom blooms in the oceanic regions in which MPP is limited by the availability of iron (the iron-limited oceanic areas) (Wells, 2003). Therefore volcanic ash should be able to significantly affect marine phytoplankton growth in an ash fall area, acting as an iron fertilizer. Based on our new iron-release data and marine sediment core data we provide the first estimate of the flux of Fe from volcanic ash into the Pacific Ocean that covers more than 60 percent of the iron-limited oceanic regions. Our calculations show that the flux of Fe from volcanic ash is comparable to the order of magnitude of the flux of Fe from aeolian dust. Our study shows that volcanic ash is a major and so far underestimated atmospheric iron-source for the oceans and therefore an important component in marine biogeochemical iron cycles. Wells, M.L.: The level of iron

  19. Clumping Factor A Interaction with Complement Factor I Increases C3b Cleavage on the Bacterial Surface of Staphylococcus aureus and Decreases Complement-Mediated Phagocytosis▿

    PubMed Central

    Hair, Pamela S.; Echague, Charlene G.; Sholl, Amber M.; Watkins, Justin A.; Geoghegan, Joan A.; Foster, Timothy J.; Cunnion, Kenji M.

    2010-01-01

    The human complement system is important in the immunological control of Staphylococcus aureus infection. We showed previously that S. aureus surface protein clumping factor A (ClfA), when expressed in recombinant form, bound complement control protein factor I and increased factor I cleavage of C3b to iC3b. In the present study, we show that, compared to the results for the wild type, when isogenic ClfA-deficient S. aureus mutants were incubated in serum, they bound less factor I, generated less iC3b on the bacterial surface, and bound fewer C3 fragments. It has been shown previously that two amino acids in ClfA (P336 and Y338) are essential for fibrinogen binding. However, S. aureus expressing ClfA(P336A Y338S) was less virulent than ClfA-deficient strains in animal models. This suggested that ClfA contributed to S. aureus virulence by a mechanism different than fibrinogen binding. In the present study, we showed that S. aureus expressing ClfA(P336A Y338S) was more susceptible to complement-mediated phagocytosis than a ClfA-null mutant or the wild type. Unlike ClfA, ClfA(P336A Y338S) did not enhance factor I cleavage of C3b to iC3b and inhibited the cofactor function of factor H. Fibrinogen enhanced factor I binding to ClfA and the S. aureus surface. Twenty clinical S. aureus strains all expressed ClfA and bound factor I. High levels of factor I binding by clinical strains correlated with poor phagocytosis. In summary, our results suggest that the interaction of ClfA with factor I contributes to S. aureus virulence by a complement-mediated mechanism. PMID:20100856

  20. Iron

    MedlinePlus

    Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

  1. Theoretical Investigation of Hydrogen Adsorption and Dissociation on Iron and Iron Carbide Surfaces Using the ReaxFF Reactive Force Field Method

    SciTech Connect

    Zou, Chenyu; van Duin, Adri C.T.; Sorescu, Dan C.

    2012-06-01

    We have developed a ReaxFF reactive force field to describe hydrogen adsorption and dissociation on iron and iron carbide surfaces relevant for simulation of Fischer–Tropsch (FT) synthesis on iron catalysts. This force field enables large system (>>1000 atoms) simulations of hydrogen related reactions with iron. The ReaxFF force field parameters are trained against a substantial amount of structural and energetic data including the equations of state and heats of formation of iron and iron carbide related materials, as well as hydrogen interaction with iron surfaces and different phases of bulk iron. We have validated the accuracy and applicability of ReaxFF force field by carrying out molecular dynamics simulations of hydrogen adsorption, dissociation and recombination on iron and iron carbide surfaces. The barriers and reaction energies for molecular dissociation on these two types of surfaces have been compared and the effect of subsurface carbon on hydrogen interaction with iron surface is evaluated. We found that existence of carbon atoms at subsurface iron sites tends to increase the hydrogen dissociation energy barrier on the surface, and also makes the corresponding hydrogen dissociative state relatively more stable compared to that on bare iron. These properties of iron carbide will affect the dissociation rate of H{sub 2} and will retain more surface hydride species, thus influencing the dynamics of the FT synthesis process.

  2. Reduction of selenite on iron surfaces: Amicro-spectroscopic study

    NASA Astrophysics Data System (ADS)

    Scheidegger, A. M.; Grolimund, D.; Cui, D.; Devoy, J.; Spahiu, K.; Wersin, P.; Bonhoure, I.; Janousch, M.

    2003-03-01

    Under anoxie conditions zero-valent iron can react with water to produce hydrogen gas and magnetite or green rust, a highly reactive mineral phase that can induce reduction processes and thus control the speciation, the solubility, toxicity and the mobility of redox sensitive elements in (nuclear) waste repositories. In this study micro X-ray fluorescence (micro-XRF) and micro X-ray absorption spectroscopy (micro-XAS) were used to investigate the speciation of selenium that immobilized in the presence of Fe(0) and an anoxie synthetic groundwater solution. The selenium immobilization was accompanied by the formation of a green rust corrosion layer. Micro-XRF revealed that a Se-rich layer is present along the iron surfaces that were exposed to the Se(IV) solution. Micro-XAS experiments at the Se K-edge showed that Se(IV) was reduced to elemental Se(0). Thus, the reactivity of zero-valent and green rust should to be considered in assessing the long-term fate of selenium in nuclear waste repositories.

  3. Molecular Correlates of Host Specialization in Staphylococcus aureus

    PubMed Central

    Herron-Olson, Lisa; Fitzgerald, J. Ross; Musser, James M.; Kapur, Vivek

    2007-01-01

    Background The majority of Staphylococcus aureus isolates that are recovered from either serious infections in humans or from mastitis in cattle represent genetically distinct sets of clonal groups. Moreover, population genetic analyses have provided strong evidence of host specialization among S. aureus clonal groups associated with human and ruminant infection. However, the molecular basis of host specialization in S. aureus is not understood. Methodology/Principal Findings We sequenced the genome of strain ET3-1, a representative isolate of a common bovine mastitis-causing S. aureus clone. Strain ET3-1 encodes several genomic elements that have not been previously identified in S. aureus, including homologs of virulence factors from other Gram-positive pathogens. Relative to the other sequenced S. aureus associated with human infection, allelic variation in ET3-1 was high among virulence and surface-associated genes involved in host colonization, toxin production, iron metabolism, antibiotic resistance, and gene regulation. Interestingly, a number of well-characterized S. aureus virulence factors, including protein A and clumping factor A, exist as pseudogenes in ET3-1. Whole-genome DNA microarray hybridization revealed considerable similarity in the gene content of highly successful S. aureus clones associated with bovine mastitis, but not among those clones that are only infrequently recovered from bovine hosts. Conclusions/Significance Whole genome sequencing and comparative genomic analyses revealed a set of molecular genetic features that distinguish clones of highly successful bovine-associated S. aureus optimized for mastitis pathogenesis in cattle from those that infect human hosts or are only infrequently recovered from bovine sources. Further, the results suggest that modern bovine specialist clones diverged from a common ancestor resembling human-associated S. aureus clones through a combination of foreign DNA acquisition and gene decay. PMID:17971880

  4. Surface-bound iron: a metal ion buffer in the marine brown alga Ectocarpus siliculosus?

    PubMed Central

    Carrano, Carl J.

    2014-01-01

    Although the iron uptake and storage mechanisms of terrestrial/higher plants have been well studied, the corresponding systems in marine algae have received far less attention. Studies have shown that while some species of unicellular algae utilize unique mechanisms of iron uptake, many acquire iron through the same general mechanisms as higher plants. In contrast, the iron acquisition strategies of the multicellular macroalgae remain largely unknown. This is especially surprising since many of these organisms represent important ecological and evolutionary niches in the coastal marine environment. It has been well established in both laboratory and environmentally derived samples, that a large amount of iron can be ‘non-specifically’ adsorbed to the surface of marine algae. While this phenomenon is widely recognized and has prompted the development of experimental protocols to eliminate its contribution to iron uptake studies, its potential biological significance as a concentrated iron source for marine algae is only now being recognized. This study used an interdisciplinary array of techniques to explore the nature of the extensive and powerful iron binding on the surface of both laboratory and environmental samples of the marine brown alga Ectocarpus siliculosus and shows that some of this surface-bound iron is eventually internalized. It is proposed that the surface-binding properties of E. siliculosus allow it to function as a quasibiological metal ion ‘buffer’, allowing iron uptake under the widely varying external iron concentrations found in coastal marine environments. PMID:24368501

  5. Impact of growth temperature and surface type on the resistance of Pseudomonas aeruginosa and Staphylococcus aureus biofilms to disinfectants.

    PubMed

    Abdallah, Marwan; Khelissa, Oussama; Ibrahim, Ali; Benoliel, Corinne; Heliot, Laurent; Dhulster, Pascal; Chihib, Nour-Eddine

    2015-12-01

    Biofilm formation of Pseudomonas aeruginosa and Staphylococcus aureus on food-contact-surfaces represents a significant risk for the public health. In this context, the present study investigates the relationship between the environmental conditions of biofilm formation and the resistance to disinfectants. Therefore, a static biofilm reactor, called NEC-Biofilm System, was established in order to study the effect of growth temperature (20, 30 and 37°C), and of the surface type (stainless steel and polycarbonate), on biofilm resistance to disinfectants. These conditions were selected to mimic the biofilm formation on abiotic surfaces of food processing industries. The antibiofilm assays were performed on biofilms grown during 24 h. The results showed that the growth temperature influenced significantly the biofilm resistance to disinfectants. These data also revealed that the growth temperature has a significant effect on the biofilm structure of both bacteria. Furthermore, the increase of the biofilm growth temperature increased significantly the algD transcript level in sessile P. aeruginosa cells, whereas the icaA one was not affected in S. aureus cells. Overall, our findings show that the biofilm structure and matrix cannot fully explain the biofilm resistance to disinfectant agents. Nevertheless, it underlines the intimate link between environmental conditions, commonly met in food sectors, and the biofilm resistance to disinfectants. PMID:26233298

  6. SURFACE COMPLEXATION OF ACTINIDES WITH IRON OXIDES: IMPLICATIONS FOR RADIONUCLIDE TRANSPORT IN NEAR-SURFACE AQUIFERS

    SciTech Connect

    J.L. Jerden Jr.; A.J. Kropf; Y. Tsai

    2005-08-25

    The surface complexation of actinides with iron oxides plays a key role in actinide transport and retardation in geosphere-biosphere systems. The development of accurate actinide transport models therefore requires a mechanistic understanding of surface complexation reactions (i.e. knowledge of chemical speciation at mineral/fluid interfaces). Iron oxides are particularly important actinide sorbents due to their pH dependent surface charges, relatively high surface areas and ubiquity in oxic and suboxic near-surface systems. In this paper we present results from field and laboratory investigations that elucidate the mechanisms involved in binding uranium and neptunium to iron oxide mineral substrates in near neutral groundwaters. The field study involved sampling and characterizing uranium-bearing groundwaters and solids from a saprolite aquifer overlying an unmined uranium deposit in the Virginia Piedmont. The groundwaters were analyzed by inductively coupled mass spectrometry and ion chromatography and the aquifer solids were analyzed by electron microprobe. The laboratory study involved a series of batch sorption tests in which U(VI) and Np(V) were reacted with goethite, hematite and magnetite in simulated groundwaters. The pH, ionic strength, aging time, and sorbent/sorbate ratios were varied in these experiments. The oxidation state and coordination environment of neptunium in solutions and sorbents from the batch tests were characterized by X-ray absorption spectroscopy (XAS) at the Advanced Photon Source, Argonne National Laboratory. Results from this work indicate that, in oxidizing near-surface aquifers, the dissolved concentration of uranium may be limited to less than 30 parts per billion due to uptake by iron oxide mineral coatings and the precipitation of sparingly soluble U(VI) phosphate minerals. Results from the batch adsorption tests showed that, in near neutral groundwaters, a significant fraction of the uranium and neptunium adsorbed as strongly

  7. The staphylococcal surface-glycopolymer wall teichoic acid (WTA) is crucial for complement activation and immunological defense against Staphylococcus aureus infection.

    PubMed

    Kurokawa, Kenji; Takahashi, Kazue; Lee, Bok Luel

    2016-10-01

    Staphylococcus aureus is a Gram-positive bacterial pathogen that is decorated by glycopolymers, including wall teichoic acid (WTA), peptidoglycan, lipoteichoic acid, and capsular polysaccharides. These bacterial surface glycopolymers are recognized by serum antibodies and a variety of pattern recognition molecules, including mannose-binding lectin (MBL). Recently, we demonstrated that human serum MBL senses staphylococcal WTA. Whereas MBL in infants who have not yet fully developed adaptive immunity binds to S. aureus WTA and activates complement serum, MBL in adults who have fully developed adaptive immunity cannot bind to WTA because of an inhibitory effect of serum anti-WTA IgG. Furthermore, we showed that human anti-WTA IgGs purified from pooled adult serum IgGs triggered activation of classical complement-dependent opsonophagocytosis against S. aureus. Because the epitopes of WTA that are recognized by anti-WTA IgG and MBL have not been determined, we constructed several S. aureus mutants with altered WTA glycosylation. Our intensive biochemical studies provide evidence that the β-GlcNAc residues of WTA are required for the induction of anti-WTA IgG-mediated opsonophagocytosis and that both β- and α-GlcNAc residues are required for MBL-mediated complement activation. The molecular interactions of other S. aureus cell wall components and host recognition proteins are also discussed. In summary, in this review, we discuss the biological importance of S. aureus cell surface glycopolymers in complement activation and host defense responses. PMID:27424796

  8. Cleavage of Complement C3b to iC3b on the Surface of Staphylococcus aureus Is Mediated by Serum Complement Factor I

    PubMed Central

    Cunnion, K. M.; Hair, P. S.; Buescher, E. S.

    2004-01-01

    Complement-mediated opsonization of Staphylococcus aureus bearing the dominant capsule serotypes, serotypes 5 and 8, remains incompletely understood. We have previously shown that complement plays a vital role in the efficient phagocytosis of a serotype 5 S. aureus strain and that the opsonic fragments of the central complement protein C3, C3b and iC3b, were present on the bacterial surface after incubation in human serum. In the present studies, C3b and iC3b were found on several serotype 5 and 8 S. aureus strains after incubation in human serum. Using purified classical activation pathway complement proteins and the Western blot assay, we showed that when C3b was generated on the S. aureus surface no iC3b fragments were found, suggesting that other serum proteins may be required for cleaving C3b to iC3b. When C3b-coated S. aureus was incubated with serum factor I, a complement regulatory protein, iC3b was generated. Purified factor H, a serum protein cofactor for factor I, did not enhance factor I-mediated cleavage of C3b. These findings suggest that C3b cleavage to iC3b on S. aureus is mediated by serum factor I and does not require factor H. PMID:15102797

  9. Microstructural and Hardness Study of Pulsed Nd:YAG Laser Surface Alloyed Aluminum with Iron

    NASA Astrophysics Data System (ADS)

    Ansari, Mohammad; Soltani, Reza; Heydarzadeh Sohi, Mahmoud; Valefi, Zia

    2016-04-01

    In the present study, the feasibility of the formation of surface layers containing hard iron aluminides on AA6061-T6 aluminum via pre-plasma spraying with iron and subsequently double surface melting by pulsed Nd:YAG laser is studied. The effects of single and double laser surface melting on microstructure, phase formation, and hardness of the treated layers are examined. Single-step laser treatment resulted in the presence of undissolved iron particles surrounded by lump-like Al5Fe2 and needle-like Al3Fe intermetallic compounds. Double laser surface melting dissolved the retained undissolved irons and resulted in the formation of Al-Al3Fe eutectic structure. Microhardness profiles along cross section and top surface of the treated layers indicated that laser surface alloying with iron enhanced the hardness of the aluminum to more than twice of that of the base material.

  10. An in situ study of the role of surface films on granular iron in the permeable iron wall technology

    NASA Astrophysics Data System (ADS)

    Ritter, K.; Odziemkowski, M. S.; Gillham, R. W.

    2002-03-01

    Permeable walls of granular iron are a new technology developed for the treatment of groundwater contaminated with dissolved chlorinated solvents. Degradation of the chlorinated solvents involves a charge transfer process in which they are reductively dechlorinated, and the iron is oxidized. The iron used in the walls is an impure commercial material that is covered with a passive layer of Fe 2O 3, formed as a result of a high-temperature oxidation process used in the production of iron. Understanding the behaviour of this layer upon contact with solution is important, because Fe 2O 3 inhibits mechanisms involved in contaminant reduction, including electron transfer and catalytic hydrogenation. Using a glass column specially designed to allow for in situ Raman spectroscopic and open circuit potential measurements, the passive layer of Fe 2O 3 was observed to be largely removed from the commercial product, Connelly iron, upon contact with Millipore water and with a solution of Millipore water containing 1.5 mg/l trichloroethylene (TCE). It has been previously shown that Fe 2O 3 is removed from iron surfaces upon contact with solution by an autoreduction reaction; however, prior to this work, the reaction has not been shown to occur on the impure commercial iron products used in permeable granular iron walls. The rate of removal was sufficiently rapid such that the initial presence of Fe 2O 3 at the iron surface would have no consequence with respect to the performance of an in situ wall. Subsequent to the removal of Fe 2O 3 layer, magnetite and green rust formed at the iron surface as a result of corrosion in both the Millipore water and the solution containing TCE. The formation of these two species, rather than higher valency iron oxides and oxyhydroxides, is significant for the technology. The former can interfere with contaminant degradation because they inhibit electron transfer and catalytic hydrogenation. Magnetite and green rust, in contrast, will not

  11. Binding of oxygen on vacuum fractured pyrite surfaces: Reactivity of iron and sulfur surface sites

    NASA Astrophysics Data System (ADS)

    Berlich, A. G.; Nesbitt, H. W.; Bancroft, G. M.; Szargan, R.

    2013-05-01

    Synchrotron radiation excited photoelectron spectroscopy (SXPS) has been used to study the interaction of oxygen with vacuum fractured pyrite surfaces. Especially valence band spectra obtained with 30 eV photon energy were analyzed to provide a mechanism of the incipient steps of pyrite oxidation. These spectra are far more sensitive to the oxidation than sulfur or iron core level spectra. It is shown that oxygen is adsorbed on Fe(II) surface sites restoring the octahedral coordination of the Fe(II) sites. This process leads to the removal of two surface states in the valence band which are located at the low and high binding energy sides of the outer valence band, respectively. The existence of these surface states which have been proposed by calculations is experimentally proven. Furthermore, it is shown, that the sulfur sites are more reactive than expected. Sulfite like species are already formed after the lowest oxygen exposure of 10 L. This oxidation occurs at sulfur sites neighboring the Fe(II) surface sites. Oxidation of the S2 - surface sites which were considered as the most reactive species in former studies is second. No iron(III) oxides are formed during oxygen exposure, supporting the assumption that water plays an important role in the oxidation mechanism of pyrite surfaces.

  12. Surface photovoltage analysis of iron contamination in silicon processing and the relation to gate oxide integrity

    NASA Astrophysics Data System (ADS)

    Henley, Worth B.

    1995-09-01

    Surface photovoltage (SPV), a contactless optical technique for measuring minority carrier lifetime, is used to quantify the relationship between silicon iron contamination level and thin gate oxide integrity. Iron concentration levels in the range of 1 X 1010 cm-3 to 5 X 1013 cm-3 are evaluated for oxide thicknesses of 8 to 20 nm. Ramp voltage electrical breakdown and time dependant dielectric breakdown measurement on the iron contaminated gate oxide capacitors are reported. Distinct iron contamination threshold limits based on defect density and gate oxide integrity evaluate cleaning efficiencies and metallic cross contamination effects during thermal processing contamination. Iron-silicide precipitation kinetics are investigated by the lifetime analysis procedure.

  13. Random Phase Approximation in Surface Chemistry: Water Splitting on Iron.

    PubMed

    Karlický, František; Lazar, Petr; Dubecký, Matúš; Otyepka, Michal

    2013-08-13

    The reaction of water with zero-valent iron (anaerobic corrosion) is a complex chemical process involving physisorption and chemisorption events. We employ random phase approximation (RPA) along with gradient-corrected and hybrid density functional theory (DFT) functionals to study the reaction of water with the Fe atom and Fe(100) surface. We show that the involvement of the exact electron exchange and nonlocal correlation effects in RPA improves the description of all steps of the reaction on the Fe surface with respect to standard [meaning local density approximation (LDA) or generalized gradient approximation (GGA)] DFT methods. The reaction profile calculated by range-separated hybrid functional HSE06 agrees reasonably well with the RPA profile, which makes HSE06 a computationally less demanding alternative to RPA. We also investigate the reaction of the Fe atom with water using DFT, RPA, and coupled-cluster through the perturbative triples complete basis set [CCSD(T)-3s3p-DKH/CBS] method. Local DFT methods significantly underestimate reaction barriers, while the reaction kinetics and thermodynamics from RPA agree with the reference CCSD(T) data. Both systems, i.e., the Fe atom and Fe(100), provide the same reaction mechanism, indicating that anaerobic corrosion is a stepwise process involving one-electron steps, with the first reaction step (formation of the HFeOH intermediate) representing the rate-limiting step. PMID:26584120

  14. The mammalian transferrin-independent iron transport system may involve a surface ferrireductase activity.

    PubMed Central

    Jordan, I; Kaplan, J

    1994-01-01

    Mammalian cells accumulate iron from ferric citrate or ferric nitrilotriacetate through the activity of a transferrin-independent iron transport system [Sturrock, Alexander, Lamb, Craven and Kaplan (1990) J. Biol. Chem. 265, 3139-3145]. The uptake system might recognize and transport ferric-anion complexes, or cells may reduce ferric iron at the surface and then transport ferrous iron. To distinguish between these possibilities we exposed cells to either [59Fe]ferric citrate or ferric [14C]citrate and determined whether accumulation of iron was accompanied by the obligatory accumulation of citrate. In HeLa cells and human skin fibroblasts the rate of accumulation of iron was three to five times greater than that of citrate. Incubation of fibroblasts with ferric citrate or ferric ammonium citrate resulted in an enhanced accumulation of iron and citrate; the molar ratio of accumulation approaching unity. A similar rate of citrate accumulation, however, was observed when ferric citrate-incubated cells were exposed to [14C]citrate alone. Further studies demonstrated the independence of iron and citrate accumulation: addition of unlabelled citrate to cells decreased the uptake of labelled citrate without affecting the accumulation of 59Fe; iron uptake was decreased by the addition of ferrous chelators whereas the uptake of citrate was unaffected; reduction of ferric iron by ascorbate increased the uptake of iron but had no effect on the uptake of citrate. When HeLa cells were depleted of calcium, iron uptake decreased, but there was little effect on citrate uptake. These results indicate that transport of iron does not require the obligatory transport of citrate and vice versa. The mammalian transferrin-independent iron transport system appears functionally similar to iron transport systems in both the bacterial and plant kingdoms which require the activities of both a surface reductase and a ferrous metal transporter. PMID:7945215

  15. IRON

    EPA Science Inventory

    The document surveys the effects of organic and inorganic iron that are relevant to humans and their environment. The biology and chemistry of iron are complex and only partially understood. Iron participates in oxidation reduction processes that not only affect its geochemical m...

  16. A novel protein, ubiquitous in marine phytoplankton, concentrates iron at the cell surface and facilitates uptake.

    PubMed

    Morrissey, Joe; Sutak, Robert; Paz-Yepes, Javier; Tanaka, Atsuko; Moustafa, Ahmed; Veluchamy, Alaguraj; Thomas, Yann; Botebol, Hugo; Bouget, François-Yves; McQuaid, Jeffrey B; Tirichine, Leila; Allen, Andrew E; Lesuisse, Emmanuel; Bowler, Chris

    2015-02-01

    Numerous cellular functions including respiration require iron. Plants and phytoplankton must also maintain the iron-rich photosynthetic electron transport chain, which most likely evolved in the iron-replete reducing environments of the Proterozoic ocean [1]. Iron bioavailability has drastically decreased in the contemporary ocean [1], most likely selecting for the evolution of efficient iron acquisition mechanisms among modern phytoplankton. Mesoscale iron fertilization experiments often result in blooms dominated by diatoms [2], indicating that diatoms have adaptations that allow survival in iron-limited waters and rapid multiplication when iron becomes available. Yet the genetic and molecular bases are unclear, as very few iron uptake genes have been functionally characterized from marine eukaryotic phytoplankton, and large portions of diatom iron starvation transcriptomes are genes encoding unknown functions [3-5]. Here we show that the marine diatom Phaeodactylum tricornutum utilizes ISIP2a to concentrate Fe(III) at the cell surface as part of a novel, copper-independent and thermodynamically controlled iron uptake system. ISIP2a is expressed in response to iron limitation several days prior to the induction of ferrireductase activity, and it facilitates significant Fe(III) uptake during the initial response to Fe limitation. ISIP2a is able to directly bind Fe(III) and increase iron uptake when heterologously expressed, whereas knockdown of ISIP2a in P. tricornutum decreases iron uptake, resulting in impaired growth and chlorosis during iron limitation. ISIP2a is expressed by diverse marine phytoplankton, indicating that it is an ecologically significant adaptation to the unique nutrient composition of marine environments. PMID:25557662

  17. Iron impurities on Sb (111) surface and their effects on topological surface state

    NASA Astrophysics Data System (ADS)

    Han, Jinhee; Lee, Hyungjun; Choi, Hyoung Joon

    2012-02-01

    We study iron impurities on Sb (111) surface and their effects on topological surface state by using an ab-initio pseudopotential density-functional method. We implemented the spin-orbit interaction into the SIESTA in a form of additional fully non-local projectors. To calculate electronic structure of topological surface states, we consider a slab of Sb using a supercell containing 20 atomic layers with experimental bulk Sb lattice parameters. We determine atomic positions of Fe impurities on Sb (111) surface by minimizing the total energy, and calculate surface band structures near the Fermi level. To find effects of the impurity on the surface states of Sb (111) surface, we simulate ARPES spectra as a function of impurity density on the surface. From the results, we find that Fe impurity states are present near Fermi level and they strongly interact with the surface states. This work was supported by the NRF of Korea (Grant Nos. 2009-0081204 and 2011-0018306) and KISTI Supercomputing Center (Project No. KSC-2011-C2-04).

  18. Haem Recognition By a Staphylococcus Aureus NEAT Domain

    SciTech Connect

    Grigg, J.C.; Vermeiren, C.; Heinrichs, D.E.; Murphy, M.E.P.

    2009-06-01

    Successful pathogenic organisms have developed mechanisms to thrive under extreme levels of iron restriction. Haem-iron represents the largest iron reservoir in the human body and is a significant source of iron for some bacterial pathogens. NEAT (NEAr Transporter) domains are found exclusively in a family of cell surface proteins in Gram-positive bacteria. Many NEAT domain-containing proteins, including IsdA in Staphylococcus aureus, are implicated in haem binding. Here, we show that overexpression of IsdA in S. aureus enhances growth and an inactivation mutant of IsdA has a growth defect, compared with wild type, when grown in media containing haem as the sole iron source. Furthermore, the haem-binding property of IsdA is contained within the NEAT domain. Crystal structures of the apo-IsdA NEAT domain and in complex with haem were solved and reveal a clathrin adapter-like beta-sandwich fold with a large hydrophobic haem-binding pocket. Haem is bound with the propionate groups directed at the molecular surface and the iron is co-ordinated solely by Tyr(166). The phenol groups of Tyr(166) and Tyr(170) form an H-bond that may function in regulating haem binding and release. An analysis of IsdA structure-sequence alignments indicate that conservation of Tyr(166) is a predictor of haem binding by NEAT domains.

  19. Interaction of some extreme-pressure type lubricating compounds with an iron surface

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1973-01-01

    An iron surface was exposed to the extreme-pressure type lubricant benzyl chloride, dichlorophenyl phosphine, dichlorophenyl phosphine sulfide, ophenyl phosphine oxide. Iron, in the sputter-cleaned state, was exposed to these materials statically and during dynamic friction experiments. With benzyl chloride only chlorine adsorbed to the surface, and with dichlorophenyl phosphine no adsorption occurred, while the addition of sulfur to that same molecular structure resulted in the promotion of carbon and chlorine adsorption. substitution of oxygen for sulfur in the dichlorobenzyl phosphine molecule resulted in carbon, chlorine, and oxygen adsorption. With none of the phosphorus containing molecules was phosphorus detected on the surface. Sliding in an atmosphere of benzyl chloride promoted adsorption of chlorine to the iron surface. Increases in load resulted in a decrease in the surface concentration of iron chloride.

  20. Friction induced surface activity of some simple organic chlorides and hydrocarbons with iron.

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1973-01-01

    Sliding friction studies were conducted on an iron surface with exposure of that surface to various hydrocarbons and organic chlorides. The hydrocarbons included ethane, ethylene, ethyl chloride, methyl chloride and vinyl chloride. Auger cylindrical-mirror analysis was used to follow interactions of the hydrocarbon and organic chlorides with the iron surface. Results with vinyl chloride indicate friction-induced surface reactivity, adsorption to surface oxides, friction sensitivity to concentration and polymerization. Variation in the loads employed influence adsorption and, accordingly, friction. Unlike results with ethyl and vinyl chloride, friction-induced surface reactivity was not observed with ethane and ethylene.

  1. Friction-induced surface activity of some hydrocarbons with clean and oxide-covered iron

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1973-01-01

    Sliding friction studies were conducted on a clean and oxide-covered iron surface with exposure of that surface to various hydrocarbons. The hydrocarbons included ethane, ethylene ethyl chloride, methyl chloride, and vinyl chloride. Auger cylindrical mirror analysis was used to follow interactions of the hydrocarbon with the iron surface. Results with vinyl chloride indicate friction induced surface reactivity, adsorption to surface oxides, friction sensitivity to concentration and polymerization. Variation in the loads employed influence adsorption and accordingly friction. In contrast with ethyl and vinyl chloride, friction induced surface reactivity was not observed with ethane and ethylene.

  2. Polymers' surface interactions with molten iron: A theoretical study

    NASA Astrophysics Data System (ADS)

    Assadi, M. Hussein N.; Sahajwalla, Veena

    2014-10-01

    Environmental concerns are the chief drive for more innovative recycling techniques for end-of-life polymeric products. One attractive option is taking advantage of C and H content of polymeric waste in steelmaking industry. In this work, we examined the interaction of two high production polymers i.e. polyurethane and polysulfide with molten iron using ab initio molecular dynamics simulation. We demonstrate that both polymers can be used as carburizers for molten iron. Additionally, we found that light weight H2 and CHx molecules were released as by-products of the polymer-molten iron interaction. The outcomes of this study will have applications in the carburization of molten iron during ladle metallurgy and waste plastic injection in electric arc furnace.

  3. Surface characterization of iron Fischer-Tropsch catalysts

    SciTech Connect

    Kuivila, C.S.; Butt, J.B.; Stair, P.C.

    1986-01-01

    In this paper the authors address XPS characterization of the iron phases associated with Fischer-Tropsch catalysts. Results obtained for single-phase metal, oxide, and carbide samples are presented. Methods for estimating the extent of carbide formation during low conversion synthesis, and the extent of catalyst oxidation at high conversions are illustrated. This approach is used to monitor the evolution of an initially reduced, unsupported iron catalyst during synthesis at low conversion levels.

  4. The Importance of Kinetics and Redox in the Biogeochemical Cycling of Iron in the Surface Ocean

    PubMed Central

    Croot, Peter L.; Heller, Maija I.

    2012-01-01

    It is now well established that Iron (Fe) is a limiting element in many regions of the open ocean. Our current understanding of the key processes which control iron distribution in the open ocean have been largely based on thermodynamic measurements performed under the assumption of equilibrium conditions. Using this equilibrium approach, researchers have been able to detect and quantify organic complexing ligands in seawater and examine their role in increasing the overall solubility of iron. Our current knowledge about iron bioavailability to phytoplankton and bacteria is also based heavily on carefully controlled laboratory studies where it is assumed the chemical species are in equilibrium in line with the free ion association model and/or its successor the biotic ligand model. Similarly most field work on iron biogeochemistry generally consists of a single profile which is in essence a “snap-shot” in time of the system under investigation. However it is well known that the surface ocean is an extremely dynamic environment and it is unlikely if thermodynamic equilibrium between all the iron species present is ever truly achieved. In sunlit waters this is mostly due to the daily passage of the sun across the sky leading to photoredox processes which alter Fe speciation by cycling between redox states and between inorganic and organic species. Episodic deposition events, dry and wet, are also important perturbations to iron cycling as they bring in new iron to the system and alter the equilibrium between iron species and phases. Here we utilize new field data collected in the open ocean on the complexation kinetics of iron in the surface ocean to identify the important role of weak iron binding ligands (i.e., those that cannot maintain iron in solution indefinitely at seawater pH: αFeL < αFe′) in allowing transient increases in iron solubility in response to iron deposition events. Experiments with the thermal O2- source SOTS-1 also indicate the short

  5. Growth of Aerobic Ripening Bacteria at the Cheese Surface Is Limited by the Availability of Iron

    PubMed Central

    Back, Alexandre; Irlinger, Françoise

    2012-01-01

    The microflora on the surface of smear-ripened cheeses is composed of various species of bacteria and yeasts that contribute to the production of the desired organoleptic properties. The objective of the present study was to show that iron availability is a limiting factor in the growth of typical aerobic ripening bacteria in cheese. For that purpose, we investigated the effect of iron or siderophore addition in model cheeses that were coinoculated with a yeast and a ripening bacterium. Both iron and the siderophore desferrioxamine B stimulated the growth of ripening bacteria belonging to the genera Arthrobacter, Corynebacterium, and Brevibacterium. The extent of stimulation was strain dependent, and generally, the effect of desferrioxamine B was greater than that of iron. Measurements of the expression of genes related to the metabolism of iron by Arthrobacter arilaitensis Re117 by real-time reverse transcription-PCR showed that these genes were transcribed during growth in cheese. The addition of desferrioxamine B increased the expression of two genes encoding iron-siderophore ABC transport binding proteins. The addition of iron decreased the expression of siderophore biosynthesis genes and of part of the genes encoding iron-siderophore ABC transport components. It was concluded that iron availability is a limiting factor in the growth of typical cheese surface bacteria. The selection of strains with efficient iron acquisition systems may be useful for the development of defined-strain surface cultures. Furthermore, the importance of iron metabolism in the microbial ecology of cheeses should be investigated since it may result in positive or negative microbial interactions. PMID:22367081

  6. The Staphylococcus aureus Global Regulator MgrA Modulates Clumping and Virulence by Controlling Surface Protein Expression

    PubMed Central

    Crosby, Heidi A.; Schlievert, Patrick M.; Merriman, Joseph A.; King, Jessica M.; Salgado-Pabón, Wilmara; Horswill, Alexander R.

    2016-01-01

    Staphylococcus aureus is a human commensal and opportunistic pathogen that causes devastating infections in a wide range of locations within the body. One of the defining characteristics of S. aureus is its ability to form clumps in the presence of soluble fibrinogen, which likely has a protective benefit and facilitates adhesion to host tissue. We have previously shown that the ArlRS two-component regulatory system controls clumping, in part by repressing production of the large surface protein Ebh. In this work we show that ArlRS does not directly regulate Ebh, but instead ArlRS activates expression of the global regulator MgrA. Strains lacking mgrA fail to clump in the presence of fibrinogen, and clumping can be restored to an arlRS mutant by overexpressing either arlRS or mgrA, indicating that ArlRS and MgrA constitute a regulatory pathway. We used RNA-seq to show that MgrA represses ebh, as well as seven cell wall-associated proteins (SraP, Spa, FnbB, SasG, SasC, FmtB, and SdrD). EMSA analysis showed that MgrA directly represses expression of ebh and sraP. Clumping can be restored to an mgrA mutant by deleting the genes for Ebh, SraP and SasG, suggesting that increased expression of these proteins blocks clumping by steric hindrance. We show that mgrA mutants are less virulent in a rabbit model of endocarditis, and virulence can be partially restored by deleting the genes for the surface proteins ebh, sraP, and sasG. While mgrA mutants are unable to clump, they are known to have enhanced biofilm capacity. We demonstrate that this increase in biofilm formation is partially due to up-regulation of SasG, a surface protein known to promote intercellular interactions. These results confirm that ArlRS and MgrA constitute a regulatory cascade, and that they control expression of a number of genes important for virulence, including those for eight large surface proteins. PMID:27144398

  7. Surface Reactivity of Core Shell Iron-Iron Oxide Nanoclusters towards Breakdown of Carbon Tetrachloride

    NASA Astrophysics Data System (ADS)

    Tarsem S., Maninder K.; Qiang, You; Kim, Hongseok; Amonette, James E.; Baer, Donald R.

    2012-02-01

    Zero-valent iron (ZVI) is one of the technologies for groundwater remediation to reduce contaminants by removal of mobile chlorinated hydrocarbons. Iron-Iron oxide (Fe/Fe3O4) nanoclusters (NCs) made in our laboratory using cluster deposition technique have enhanced reactivity towards targeted contaminants due to the presence of ZVI protected by a passivated oxide shell. Here, we investigate the effectiveness of the Fe/Fe3O4 NCs in reducing carbon tetrachloride (CT) under laboratory conditions. The reactivity of the NCs was investigated by conducting unbuffered aqueous batch experiments to reduce CT at room temperature. Initial results show that 80% of the degradation of CT resulted in the formation of dichloromethane (DCM) and chloroform (CF); the remainder likely followed a competing pathway to yield nonhazardous products such as CO. The production of undesirable hydrogenated products such as DCM and CF suggests that the dominant reaction pathway occurs through hydrogen (H) atom transfer via H atoms generated by corrosion of the iron. Comparative experiments with ZVI NCs prepared by other methods are underway and the results will be reported. Future work is to analyze and understand factors that control the reaction pathways between desirable and undesirable products.

  8. Comparison of Methods for Evaluation of the Bactericidal Activity of Copper-Sputtered Surfaces against Methicillin-Resistant Staphylococcus aureus

    PubMed Central

    Rio, Laura; Kusiak-Nejman, Ewelina; Kiwi, John; Bétrisey, Bertrand; Pulgarin, César; Trampuz, Andrej

    2012-01-01

    Bacteria can survive on hospital textiles and surfaces, from which they can be disseminated, representing a source of health care-associated infections (HCAIs). Surfaces containing copper (Cu), which is known for its bactericidal properties, could be an efficient way to lower the burden of potential pathogens. The antimicrobial activity of Cu-sputtered polyester surfaces, obtained by direct-current magnetron sputtering (DCMS), against methicillin-resistant Staphylococcus aureus (MRSA) was tested. The Cu-polyester microstructure was characterized by high-resolution transmission electron microscopy to determine the microstructure of the Cu nanoparticles and by profilometry to assess the thickness of the layers. Sputtering at 300 mA for 160 s led to a Cu film thickness of 20 nm (100 Cu layers) containing 0.209% (wt/wt) polyester. The viability of MRSA strain ATCC 43300 on Cu-sputtered polyester was evaluated by four methods: (i) mechanical detachment, (ii) microcalorimetry, (iii) direct transfer onto plates, and (iv) stereomicroscopy. The low efficacy of mechanical detachment impeded bacterial viability estimations. Microcalorimetry provided only semiquantitative results. Direct transfer onto plates and stereomicroscopy seemed to be the most suitable methods to evaluate the bacterial inactivation potential of Cu-sputtered polyester surfaces, since they presented the least experimental bias. Cu-polyester samples sputtered for 160 s by DCMS were further tested against 10 clinical MRSA isolates and showed a high level of bactericidal activity, with a 4-log10 reduction in the initial MRSA load (106 CFU) within 1 h. Cu-sputtered polyester surfaces might be of use to prevent the transmission of HCAI pathogens. PMID:22983970

  9. Complement regulator C4BP binds to Staphylococcus aureus surface proteins SdrE and Bbp inhibiting bacterial opsonization and killing☆

    PubMed Central

    Hair, Pamela S.; Foley, Caitlin K.; Krishna, Neel K.; Nyalwidhe, Julius O.; Geoghegan, Joan A.; Foster, Timothy J.; Cunnion, Kenji M.

    2013-01-01

    Staphylococcus aureus is a premier human pathogen and the most common cause of osteoarticular, wound, and implanted device infections. We recently demonstrated S. aureus efficiently binds the classical complement regulator C4b-binding protein (C4BP) inhibiting antibody-initiated complement-mediated opsonization. Here we identify S. aureus surface protein SdrE as a C4BP-binding protein. Recombinant SdrE and recombinant bone sialoprotein-binding protein (Bbp), an allelic variant of SdrE, both efficiently bound to C4BP in heat-inactivated human serum. We previously described SdrE as binding alternative pathway regulator factor H. Recombinant SdrE and Bbp efficiently bound C4BP and factor H in serum without apparent interference. Gain of function studies utilizing Lactococcus lactis clones expressing SdrE or Bbp increased serum C4BP and factor H binding, compared with empty-vector control (WT) approximately 2-fold. Correspondingly, classical pathway-mediated C3-fragment opsonization and bacterial killing by human neutrophils decreased by half for L. lactis clones expressing SdrE or Bbp compared with WT. In summary, we identify SdrE and allelic variant Bbp as S. aureus surface proteins that bind the complement regulator C4BP inhibiting classical pathway-mediated bacterial opsonization and killing. PMID:24600566

  10. The role of airborne volcanic ash for the surface ocean biogeochemical iron-cycle: a review

    NASA Astrophysics Data System (ADS)

    Duggen, S.; Olgun, N.; Croot, P.; Hoffmann, L.; Dietze, H.; Teschner, C.

    2009-07-01

    Iron is a key micronutrient for phytoplankton growth in the surface ocean. Yet the significance of volcanism for the marine biogeochemical iron-cycle is poorly constrained. Recent studies, however, suggest that offshore deposition of airborne ash from volcanic eruptions is a way to inject significant amounts of bio-available iron into the surface ocean. Volcanic ash may be transported up to several tens of kilometres high into the atmosphere during large-scale eruptions and fine ash may encircle the globe for years, thereby reaching even the remotest and most iron-starved oceanic areas. Scientific ocean drilling demonstrates that volcanic ash layers and dispersed ash particles are frequently found in marine sediments and that therefore volcanic ash deposition and iron-injection into the oceans took place throughout much of the Earth's history. The data from geochemical and biological experiments, natural evidence and satellite techniques now available suggest that volcanic ash is a so far underestimated source for iron in the surface ocean, possibly of similar importance as aeolian dust. Here we summarise the development of and the knowledge in this fairly young research field. The paper covers a wide range of chemical and biological issues and we make recommendations for future directions in these areas. The review paper may thus be helpful to improve our understanding of the role of volcanic ash for the marine biogeochemical iron-cycle, marine primary productivity and the ocean-atmosphere exchange of CO2 and other gases relevant for climate throughout the Earth's history.

  11. Growth of Staphylococcus aureus MF 31 on the Top and Cut Surfaces of Southern Custard Pies

    PubMed Central

    Preonas, D. L.; Nelson, A. I.; Ordal, Z. John; Steinberg, M. P.; Wei, L. S.

    1969-01-01

    A Staphylococcus strain was inoculated on the top and cut surfaces of freshly baked Southern custard pies which were then packaged in a pasteboard carton and held at 30 C. Daily plate counts of surface sections 0.3 inch (0.76 cm) in thickness were made. The top surface inoculum showed a 24-hr lag time. This was due to the protective action of a top cakelike layer as shown by homogenization of the mix and coating of the surface. Substitution of all sweeteners with dextrose completely inhibited growth on the top surface. Further addition of dextrose to lower water activity (Aw) to 0.9 prevented growth on the cut surface as well, but such pies were organoleptically unacceptable. Growth on the top surface could also be prevented by 80 μg of undissociated sorbic acid per g in combination with 100 μg of undissociated propionic acid per g in the baked pie. Growth on the cakelike top surface was always retarded longer than on the cut surface provided the packaging allowed evaporation of surface moisture. Reducing the Aw of a different type of cream pie to 0.907 prevented top surface growth. It was concluded that baked cream pies with a cakelike top layer could be marketed with a “refrigerate after opening” label, provided the package maintains the moisture gradient caused by the surface skin and either a combination of 80 μg of undissociated sorbic acid per g and 100 μg undissociated propionic acid per g is present in the baked pie or the Aw of the baked pie is 0.920 or lower. Images PMID:5803631

  12. Iron

    MedlinePlus

    ... organ failure, coma, convulsions, and death. Child-proof packaging and warning labels on iron supplements have greatly ... levodopa that the body absorbs, making it less effective. Levodopa, found in Sinemet® and Stalevo®, is used ...

  13. Magnetic iron oxide nanoparticles: Synthesis and surface coating techniques for biomedical applications

    NASA Astrophysics Data System (ADS)

    Sun, Sheng-Nan; Wei, Chao; Zhu, Zan-Zan; Hou, Yang-Long; Subbu, S. Venkatraman; Xu, Zhi-Chuan

    2014-03-01

    Iron oxide nanoparticles are the most popular magnetic nanoparticles used in biomedical applications due to their low cost, low toxicity, and unique magnetic property. Magnetic iron oxide nanoparticles, including magnetite (Fe3O4) and maghemite (γ-Fe2O3), usually exhibit a superparamagnetic property as their size goes smaller than 20 nm, which are often denoted as superparamagnetic iron oxide nanoparticles (SPIONs) and utilized for drug delivery, diagnosis, therapy, and etc. This review article gives a brief introduction on magnetic iron oxide nanoparticles in terms of their fundamentals of magnetism, magnetic resonance imaging (MRI), and drug delivery, as well as the synthesis approaches, surface coating, and application examples from recent key literatures. Because the quality and surface chemistry play important roles in biomedical applications, our review focuses on the synthesis approaches and surface modifications of iron oxide nanoparticles. We aim to provide a detailed introduction to readers who are new to this field, helping them to choose suitable synthesis methods and to optimize the surface chemistry of iron oxide nanoparticles for their interests.

  14. Identification and Characterization of a Novel 38.5-Kilodalton Cell Surface Protein of Staphylococcus aureus with Extended-Spectrum Binding Activity for Extracellular Matrix and Plasma Proteins

    PubMed Central

    Hussain, Muzaffar; Becker, Karsten; von Eiff, Christof; Schrenzel, Jacques; Peters, Georg; Herrmann, Mathias

    2001-01-01

    The ability to attach to host ligands is a well-established pathogenic factor in invasive Staphylococcus aureus disease. In addition to the family of adhesive proteins bound to the cell wall via the sortase A (srtA) mechanism, secreted proteins such as the fibrinogen-binding protein Efb, the extracellular adhesion protein Eap, or coagulase have been found to interact with various extracellular host molecules. Here we describe a novel protein, the extracellular matrix protein-binding protein (Emp) initially identified in Western ligand blots as a 40-kDa protein due to its broad-spectrum recognition of fibronectin, fibrinogen, collagen, and vitronectin. Emp is expressed in the stationary growth phase and is closely associated with the cell surface and yet is extractable by sodium dodecyl sulfate. The conferring gene emp (1,023 nucleotides) encodes a signal peptide of 26 amino acids and a mature protein of a calculated molecular mass of 35.5 kDa. Using PCR, emp was demonstrated in all 240 S. aureus isolates of a defined clinical strain collection as well as in 6 S. aureus laboratory strains, whereas it is lacking in all 10 S. epidermidis strains tested. Construction of an allelic replacement mutant (mEmp50) revealed the absence of Emp in mEmp50, a significantly decreased adhesion of mEmp50 to immobilized fibronectin and fibrinogen, and restoration of these characteristics upon complementation of mEmp50. Emp expression was also demonstrable upon heterologous complementation of S. carnosus. rEmp expressed in Escherichia coli interacted with fibronectin, fibrinogen, and vitronectin in surface plasmon resonance experiments at a Kd of 21 nM, 91 nM, and 122 pM, respectively. In conclusion, the biologic characterization of Emp suggests that it is a member of the group of secreted S. aureus molecules that interact with an extended spectrum of host ligands and thereby contribute to S. aureus pathogenicity. PMID:11698365

  15. Adhesion of metals to a clean iron surface studied with LEED and Auger emission spectroscopy.

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1972-01-01

    Discussion of the results of adhesion experiments conducted with various metals contacting a clean iron surface. The metals included gold, silver, nickel, platinum, lead, tantalum, aluminum, and cobalt. Some of the metals were examined with oxygen present on their surface as well as in the clean state. The results indicate that, with the various metals contacting iron, the cohesively weaker will adhere and transfer to the cohesively stronger. The chemical activity of the metal also influenced the adhesive forces measured. With oxygen present on the metal surface, the adhesive forces measured could be correlated with the binding energy of the metal to oxygen.

  16. Wear, corrosion, and cavitation erosion characteristics of laser-surface-alloyed gray cast iron

    NASA Astrophysics Data System (ADS)

    Bransden, Antony S.; Tomlinson, W. J.

    1990-10-01

    There is significant industrial interest in methods to improve the surface properties of cast iron. This paper describes investigations of laser treatments to enhance cast iron surfaces by alloying with the elements chromium, nickel or cobalt, or a cobalt/chromium mixture. The coatings achieved are of high integrity, low porosity and uniform in composition, microstructure and hardness. Alloyed surfaces have been subjected to corrosion testing in a range of acids and to wear and cavitation erosion in distilled and salt waters. The data show substantial improvements over those obtained from unalloyed material. Results are presented and discussed including the response of the microstructure to the testing environments.

  17. Thermal surface free energy and stress of iron

    NASA Astrophysics Data System (ADS)

    Schönecker, Stephan; Li, Xiaoqing; Johansson, Börje; Kwon, Se Kyun; Vitos, Levente

    2015-10-01

    Absolute values of surface energy and surface stress of solids are hardly accessible by experiment. Here, we investigate the temperature dependence of both parameters for the (001) and (110) surface facets of body-centered cubic Fe from first-principles modeling taking into account vibrational, electronic, and magnetic degrees of freedom. The monotonic decrease of the surface energies of both facets with increasing temperature is mostly due to lattice vibrations and magnetic disorder. The surface stresses exhibit nonmonotonic behaviors resulting in a strongly temperature dependent excess surface stress and surface stress anisotropy.

  18. Association of uranium with iron oxides typically formed on corroding steel surfaces.

    PubMed

    Dodge, C J; Francis, A J; Gillow, J B; Halada, G P; Eng, C; Clayton, C R

    2002-08-15

    Decontamination of metal surfaces contaminated with low levels of radionuclides is a major concern at Department of Energy facilities. The development of an environmentally friendly and cost-effective decontamination process requires an understanding of their association with the corroding surfaces. We investigated the association of uranium with the amorphous and crystalline forms of iron oxides commonly formed on corroding steel surfaces. Uranium was incorporated with the oxide by addition during the formation of ferrihydrite, goethite, green rust II, lepidocrocite, maghemite, and magnetite. X-ray diffraction confirmed the mineralogical form of the oxide. EXAFS analysis at the U L(III) edge showed that uranium was present in hexavalent form as a uranyl oxyhydroxide species with goethite, maghemite, and magnetite and as a bidentate inner-sphere complex with ferrihydrite and lepidocrocite. Iron was present in the ferric form with ferrihydrite, goethite, lepidocrocite, and maghemite; whereas with magnetite and green rust II, both ferrous and ferric forms were present with characteristic ferrous:total iron ratios of 0.65 and 0.73, respectively. In the presence of the uranyl ion, green rust II was converted to magnetite with concomitantreduction of uranium to its tetravalent form. The rate and extent of uranium dissolution in dilute HCl depended on its association with the oxide: uranium present as oxyhydroxide species underwent rapid dissolution followed by a slow dissolution of iron; whereas uranium present as an inner-sphere complex with iron resulted in concomitant dissolution of the uranium and iron. PMID:12214641

  19. Antibacterial Efficacy of Iron-Oxide Nanoparticles against Biofilms on Different Biomaterial Surfaces

    PubMed Central

    Thukkaram, Monica; Sitaram, Soundarya; Kannaiyan, Sathish kumar; Subbiahdoss, Guruprakash

    2014-01-01

    Biofilm growth on the implant surface is the number one cause of the failure of the implants. Biofilms on implant surfaces are hard to eliminate by antibiotics due to the protection offered by the exopolymeric substances that embed the organisms in a matrix, impenetrable for most antibiotics and immune cells. Application of metals in nanoscale is considered to resolve biofilm formation. Here we studied the effect of iron-oxide nanoparticles over biofilm formation on different biomaterial surfaces and pluronic coated surfaces. Bacterial adhesion for 30 min showed significant reduction in bacterial adhesion on pluronic coated surfaces compared to other surfaces. Subsequently, bacteria were allowed to grow for 24 h in the presence of different concentrations of iron-oxide nanoparticles. A significant reduction in biofilm growth was observed in the presence of the highest concentration of iron-oxide nanoparticles on pluronic coated surfaces compared to other surfaces. Therefore, combination of polymer brush coating and iron-oxide nanoparticles could show a significant reduction in biofilm formation. PMID:25332720

  20. Changes Found on Run-In and Scuffed Surfaces of Steel Chrome Plate, and Cast Iron

    NASA Technical Reports Server (NTRS)

    Good, J. N.; Godfrey, Douglas

    1947-01-01

    A study was made of run-in and scuffed steel, chrome-plate, and cast-iron surfaces. X-ray and electron diffraction techniques, micro-hardness determinations, and microscopy were used. Surface changes varied and were found to include three classes: chemical reaction, hardening, and crystallite-size alteration. The principal chemical reactions were oxidation and carburization.

  1. Staphylococcus aureus extracellular adherence protein contributes to biofilm formation in the presence of serum

    PubMed Central

    Thompson, Karl M.; Abraham, Nabil; Jefferson, Kimberly K.

    2010-01-01

    Staphylococcus aureus extracellular adherence protein (EAP) is secreted, but it can redock on the bacterial cell surface via neutral phosphatase (Nptase). EAP binds to certain blood proteins and to itself, and through these affinities, it contributes to adherence and aggregation. It has been demonstrated previously that EAP expression is iron regulated and it contributes to biofilm formation under iron-deplete conditions. In this study, we found that EAP and Nptase also play a role in biofilm formation under iron-replete conditions in the presence of human serum. PMID:20199571

  2. Immunopathogenesis of Staphylococcus aureus pulmonary infection

    PubMed Central

    Parker, Dane; Prince, Alice

    2013-01-01

    Staphylococcus aureus is a common human pathogen highly evolved as both a component of the commensal flora and as a major cause of invasive infection. Severe respiratory infection due to staphylococci has been increasing due to the prevalence of more virulent USA300 CA-MRSA strains in the general population. The ability of S. aureus to adapt to the milieu of the respiratory tract has facilitated its emergence as a respiratory pathogen. Its metabolic versatility, the ability to scavenge iron, coordinate gene expression, and the horizontal acquisition of useful genetic elements have all contributed to its success as a component of the respiratory flora, in hospitalized patients, as a complication of influenza and in normal hosts. The expression of surface adhesins facilitates its persistence in the airways. In addition, the highly sophisticated interactions of the multiple S. aureus virulence factors, particularly the α-hemolysin and protein A, with diverse immune effectors in the lung such as ADAM10, TNFR1, EGFR, immunoglobulin, and complement all contribute to the pathogenesis of staphylococcal pneumonia. PMID:22037948

  3. Antibody response to Staphylococcus aureus surface proteins in rabbits with persistent osteomyelitis after treatment with demineralized bone implants.

    PubMed Central

    Thomas, V L; Sanford, B A; Keogh, B S; Triplett, R G

    1989-01-01

    A rabbit model was used to study the effect of allogeneic demineralized bone powder (DBP) implants on the persistence of Staphylococcus aureus osteomyelitis. Thirty-one rabbits with chronic osteomyelitis of the tibia established by day 21, were started on systemic antibiotics followed by either no additional treatment or debridement plus either DBP (with or without supplemental antibiotics) or supplemental antibiotics only. On day 21, cultures showed a mean of 2 x 10(4) CFU/mg of debrided osseous material. By day 70, the treatment most effective in clearing infection was found in animals treated with supplemental antibiotics only (mean of 142 +/- 116 CFU/mg). In contrast, infection persisted at a 7- to 10-fold-higher level in animals receiving DBP with and without supplemental antibiotics; these results suggest that DBP contributed to persistence of infection. Longitudinal sera were tested again staphylococcal sonic extracts by immunoblot. Detection of numerous probe-positive bands indicated complex but remarkably similar antibody responses among infected animals. Antibodies attached directly to the cell surfaces of staphylococci as shown by immunogold and blocked the binding of organisms to HEp-2 and human fetal lung cells in a radioadherence assay. Antibodies could be absorbed out by intact organisms and were unreactive by immunoblot against antigens derived from cells pretreated with pronase, proteinase K, or lysostaphin. These results indicate that the major response was directed against staphylococcal cell surface proteins. Surprisingly, only one major band (molecular weight, approximately 12,000) was detected when a homologous in vivo antigen preparation was studied by immunoblot. Antibody reactive against this peptide did not appear to react with staphylococci grown in vitro. Images PMID:2643566

  4. Antibody response to Staphylococcus aureus surface proteins in rabbits with persistent osteomyelitis after treatment with demineralized bone implants.

    PubMed

    Thomas, V L; Sanford, B A; Keogh, B S; Triplett, R G

    1989-02-01

    A rabbit model was used to study the effect of allogeneic demineralized bone powder (DBP) implants on the persistence of Staphylococcus aureus osteomyelitis. Thirty-one rabbits with chronic osteomyelitis of the tibia established by day 21, were started on systemic antibiotics followed by either no additional treatment or debridement plus either DBP (with or without supplemental antibiotics) or supplemental antibiotics only. On day 21, cultures showed a mean of 2 x 10(4) CFU/mg of debrided osseous material. By day 70, the treatment most effective in clearing infection was found in animals treated with supplemental antibiotics only (mean of 142 +/- 116 CFU/mg). In contrast, infection persisted at a 7- to 10-fold-higher level in animals receiving DBP with and without supplemental antibiotics; these results suggest that DBP contributed to persistence of infection. Longitudinal sera were tested again staphylococcal sonic extracts by immunoblot. Detection of numerous probe-positive bands indicated complex but remarkably similar antibody responses among infected animals. Antibodies attached directly to the cell surfaces of staphylococci as shown by immunogold and blocked the binding of organisms to HEp-2 and human fetal lung cells in a radioadherence assay. Antibodies could be absorbed out by intact organisms and were unreactive by immunoblot against antigens derived from cells pretreated with pronase, proteinase K, or lysostaphin. These results indicate that the major response was directed against staphylococcal cell surface proteins. Surprisingly, only one major band (molecular weight, approximately 12,000) was detected when a homologous in vivo antigen preparation was studied by immunoblot. Antibody reactive against this peptide did not appear to react with staphylococci grown in vitro. PMID:2643566

  5. Redispersibility in magnetorheological fluids: Surface interactions between iron powder and wetting additives

    NASA Astrophysics Data System (ADS)

    Bombard, Antonio J. F.; Antunes, Laís S.; Gouvêa, Douglas

    2009-02-01

    Our aim in this work was to investigate the interactions between 3 carbonyl iron powders (CIP) and different wetting additives, looking for to understand how these interactions affects the rheology and redispersibility of magnetorheological fluids (MRF). The powders were named: 'A' (uncoated), 'B' (with silica coating), and 'C' (with iron III oxide coating). The additives studied were alcohols, amines and carboxylic acids or polymeric dispersants, mainly with n-octyl or n-dodecyl hydrocarbon chains. The effect of additives concentration was also studied. We conclude that the redispersibility of MRF is strongly dependent on both carbonyl iron powder surface properties and choice and concentration of dispersing additives. The type of iron powder modification also has a significant role on the viscosity of MRF formulations additionally to the known particle size effects.

  6. Reductive dehalogenation of trichloroethylene with zero-valent iron: Surface profiling microscopy and rate enhancement studies

    SciTech Connect

    Gotpagar, J.; Lyuksyutov, S.; Cohn, R.; Grulke, E.; Bhattacharyya, D.

    1999-11-23

    Mechanistic aspects of the reductive dehalogenation of trichloroethylene using zerovalent iron are studied with three different surface characterization techniques. These include scanning electron microscopy, surface profilometry, and atomic force microscopy. It was found that the pretreatment of an iron surface by chloride ions causes enhancement in the initial degradation rates. This enhancement was attributed to the increased roughness of the iron surface due to crevice corrosion obtained by pretreatment. The results indicate that the fractional active site concentration for the reactive sorption of trichloroethylene is related to the number of defects/abnormalities present on the surface of the iron. This was elucidated with the help of atomic force microscopy. Two possible mechanisms include (1) a direct hydrogenation in the presence of defects acting as catalyst and (2) an enhancement due to the two electrochemical cells operating in proximity to each other. The result of this study has potential for further research to achieve an increase in the reaction rates by surface modifications in a practical scenario.

  7. The role of airborne volcanic ash for the surface ocean biogeochemical iron-cycle: a review

    NASA Astrophysics Data System (ADS)

    Duggen, S.; Olgun, N.; Croot, P.; Hoffmann, L.; Dietze, H.; Delmelle, P.; Teschner, C.

    2010-03-01

    Iron is a key micronutrient for phytoplankton growth in the surface ocean. Yet the significance of volcanism for the marine biogeochemical iron-cycle is poorly constrained. Recent studies, however, suggest that offshore deposition of airborne ash from volcanic eruptions is a way to inject significant amounts of bio-available iron into the surface ocean. Volcanic ash may be transported up to several tens of kilometers high into the atmosphere during large-scale eruptions and fine ash may stay aloft for days to weeks, thereby reaching even the remotest and most iron-starved oceanic regions. Scientific ocean drilling demonstrates that volcanic ash layers and dispersed ash particles are frequently found in marine sediments and that therefore volcanic ash deposition and iron-injection into the oceans took place throughout much of the Earth's history. Natural evidence and the data now available from geochemical and biological experiments and satellite techniques suggest that volcanic ash is a so far underestimated source for iron in the surface ocean, possibly of similar importance as aeolian dust. Here we summarise the development of and the knowledge in this fairly young research field. The paper covers a wide range of chemical and biological issues and we make recommendations for future directions in these areas. The review paper may thus be helpful to improve our understanding of the role of volcanic ash for the marine biogeochemical iron-cycle, marine primary productivity and the ocean-atmosphere exchange of CO2 and other gases relevant for climate in the Earth's history.

  8. The Staphylococcus aureus proteome.

    PubMed

    Otto, Andreas; van Dijl, Jan Maarten; Hecker, Michael; Becher, Dörte

    2014-03-01

    Staphylococcus aureus is a Gram-positive commensal bacterium that is regarded as a major threat for modern health care systems. This relates both to the ability of S. aureus to overcome antibiotic therapy by developing high-level resistance against multiple antibiotics and this bacterium's extensive arsenal of virulence factors. Understanding the mechanisms of resistance and functional studies on stress and starvation responses are the main goals of proteomics in staphylococcal research. This review high-lights recent advances in gel-based and gel-free proteomics analyses of S. aureus and pinpoints the importance of location-specific proteomics studies targeting the cytosol, the membrane, the cell surface and the extracellular milieu in combination with integrated global proteome studies. Emerging hot topics in staphylococcal proteomics are discussed with special focus on in vivo proteomics, membrane vesicles, biofilm formation and the acquisition of absolute proteome data for systems biological modeling approaches. PMID:24439828

  9. The DUF59 Containing Protein SufT Is Involved in the Maturation of Iron-Sulfur (FeS) Proteins during Conditions of High FeS Cofactor Demand in Staphylococcus aureus.

    PubMed

    Mashruwala, Ameya A; Bhatt, Shiven; Poudel, Saroj; Boyd, Eric S; Boyd, Jeffrey M

    2016-08-01

    Proteins containing DUF59 domains have roles in iron-sulfur (FeS) cluster assembly and are widespread throughout Eukarya, Bacteria, and Archaea. However, the function(s) of this domain is unknown. Staphylococcus aureus SufT is composed solely of a DUF59 domain. We noted that sufT is often co-localized with sufBC, which encode for the Suf FeS cluster biosynthetic machinery. Phylogenetic analyses indicated that sufT was recruited to the suf operon, suggesting a role for SufT in FeS cluster assembly. A S. aureus ΔsufT mutant was defective in the assembly of FeS proteins. The DUF59 protein Rv1466 from Mycobacterium tuberculosis partially corrected the phenotypes of a ΔsufT mutant, consistent with a widespread role for DUF59 in FeS protein maturation. SufT was dispensable for FeS protein maturation during conditions that imposed a low cellular demand for FeS cluster assembly. In contrast, the role of SufT was maximal during conditions imposing a high demand for FeS cluster assembly. SufT was not involved in the repair of FeS clusters damaged by reactive oxygen species or in the physical protection of FeS clusters from oxidants. Nfu is a FeS cluster carrier and nfu displayed synergy with sufT. Furthermore, introduction of nfu upon a multicopy plasmid partially corrected the phenotypes of the ΔsufT mutant. Biofilm formation and exoprotein production are critical for S. aureus pathogenesis and vancomycin is a drug of last-resort to treat staphylococcal infections. Defective FeS protein maturation resulted in increased biofilm formation, decreased production of exoproteins, increased resistance to vancomycin, and the appearance of phenotypes consistent with vancomycin-intermediate resistant S. aureus. We propose that SufT, and by extension the DUF59 domain, is an accessory factor that functions in the maturation of FeS proteins. In S. aureus, the involvement of SufT is maximal during conditions of high demand for FeS proteins. PMID:27517714

  10. The DUF59 Containing Protein SufT Is Involved in the Maturation of Iron-Sulfur (FeS) Proteins during Conditions of High FeS Cofactor Demand in Staphylococcus aureus

    PubMed Central

    Bhatt, Shiven; Poudel, Saroj; Boyd, Eric S.; Boyd, Jeffrey M.

    2016-01-01

    Proteins containing DUF59 domains have roles in iron-sulfur (FeS) cluster assembly and are widespread throughout Eukarya, Bacteria, and Archaea. However, the function(s) of this domain is unknown. Staphylococcus aureus SufT is composed solely of a DUF59 domain. We noted that sufT is often co-localized with sufBC, which encode for the Suf FeS cluster biosynthetic machinery. Phylogenetic analyses indicated that sufT was recruited to the suf operon, suggesting a role for SufT in FeS cluster assembly. A S. aureus ΔsufT mutant was defective in the assembly of FeS proteins. The DUF59 protein Rv1466 from Mycobacterium tuberculosis partially corrected the phenotypes of a ΔsufT mutant, consistent with a widespread role for DUF59 in FeS protein maturation. SufT was dispensable for FeS protein maturation during conditions that imposed a low cellular demand for FeS cluster assembly. In contrast, the role of SufT was maximal during conditions imposing a high demand for FeS cluster assembly. SufT was not involved in the repair of FeS clusters damaged by reactive oxygen species or in the physical protection of FeS clusters from oxidants. Nfu is a FeS cluster carrier and nfu displayed synergy with sufT. Furthermore, introduction of nfu upon a multicopy plasmid partially corrected the phenotypes of the ΔsufT mutant. Biofilm formation and exoprotein production are critical for S. aureus pathogenesis and vancomycin is a drug of last-resort to treat staphylococcal infections. Defective FeS protein maturation resulted in increased biofilm formation, decreased production of exoproteins, increased resistance to vancomycin, and the appearance of phenotypes consistent with vancomycin-intermediate resistant S. aureus. We propose that SufT, and by extension the DUF59 domain, is an accessory factor that functions in the maturation of FeS proteins. In S. aureus, the involvement of SufT is maximal during conditions of high demand for FeS proteins. PMID:27517714

  11. Conserved Regions of Gonococcal TbpB Are Critical for Surface Exposure and Transferrin Iron Utilization

    PubMed Central

    Ostberg, Karen L.; DeRocco, Amanda J.; Mistry, Shreni D.; Dickinson, Mary Kathryne

    2013-01-01

    The transferrin-binding proteins TbpA and TbpB enable Neisseria gonorrhoeae to obtain iron from human transferrin. The lipoprotein TbpB facilitates, but is not strictly required for, TbpA-mediated iron acquisition. The goal of the current study was to determine the contribution of two conserved regions within TbpB to the function of this protein. Using site-directed mutagenesis, the first mutation we constructed replaced the lipobox (LSAC) of TbpB with a signal I peptidase cleavage site (LAAA), while the second mutation deleted a conserved stretch of glycine residues immediately downstream of the lipobox. We then evaluated the resulting mutants for effects on TbpB expression, surface exposure, and transferrin iron utilization. Western blot analysis and palmitate labeling indicated that the lipobox, but not the glycine-rich motif, is required for lipidation of TbpB and tethering to the outer membrane. TbpB was released into the supernatant by the mutant that produces TbpB LSAC. Neither mutation disrupted the transport of TbpB across the bacterial cell envelope. When these mutant TbpB proteins were produced in a strain expressing a form of TbpA that requires TbpB for iron acquisition, growth on transferrin was either abrogated or dramatically diminished. We conclude that surface tethering of TbpB is required for optimal performance of the transferrin iron acquisition system, while the presence of the polyglycine stretch near the amino terminus of TbpB contributes significantly to transferrin iron transport function. Overall, these results provide important insights into the functional roles of two conserved motifs of TbpB, enhancing our understanding of this critical iron uptake system. PMID:23836816

  12. Effect of iron on vanadium (001) strained surface magnetism

    NASA Astrophysics Data System (ADS)

    Elzain, M.; Al-Barwani, M.; Gismelseed, A.; Al-Rawas, A.; Yousif, A.; Widatallah, H.; Bouziane, K.; Al-Omari, I.

    2010-03-01

    The magnetism of the vanadium (001) surface has been a controversial subject on both theoretical and experiment fronts. Both strongly ferromagnetic and paramagnetic phases were reported. We have used the first principle full-potential linearized-augmented plane waves (FP-LAPW) as implemented in WIEN2k package to study the magnetic properties of strained surfaces of vanadium films as a function of film thickness. We found that for films thicker than about 11 monolayers, the magnetism of the strained surfaces converge to a constant value of about 0.15μB. Introduction of Fe monolayers and impurities at the centre of the films affects the magnetic structure of thin films but has no influence on the surface magnetism of thicker films. For Fe monolayers positioned at the centre of thick films, the Fe atoms maintain magnetic moment of order 0.86μB, a quadruple splitting of order -0.3 mm/s and a small negative isomer shift, while an Fe impurity has vanishing hyperfine fields and magnetic moment. In addition we have varied the location of the Fe monolayer and impurity within the V films and found that their position affects the surface magnetism.

  13. Combination therapy with iron chelation and vancomycin in treating murine staphylococcemia.

    PubMed

    Luo, G; Spellberg, B; Gebremariam, T; Lee, H; Xiong, Y Q; French, S W; Bayer, A; Ibrahim, A S

    2014-05-01

    Iron acquisition is a virulence factor for Staphylococcus aureus. We assessed the efficacy of the iron chelator, deferasirox (Def), alone or in combination with vancomycin (Van) against two methicillin-resistant S. aureus (MRSA) strains in vitro and in a murine bacteremia model. In vitro time-kill assays were carried out against MRSA or vancomycin-intermediate S. aureus (VISA) strains. The impact of Def on Van binding to the surface of S. aureus was measured by flow cytometry. Furthermore, we compared the efficacy of Def, Van, or both drugs in treating S. aureus bacteremia in a murine model. Combination therapy reduced MRSA and VISA viability in vitro versus either drug alone or untreated controls (p < 0.005); this outcome was correlated with enhanced Van surface binding to S. aureus cells. In vivo, Def + Van combination therapy significantly reduced the bacterial burden in mice kidneys (p = 0.005) and spleen (p < 0.001), and reduced the severity of infection with MRSA or VISA strains compared to placebo-treated mice. Our results show that Def enhances the in vitro and in vivo capacity of Van-mediated MRSA killing via a mechanism that appears to involve increased binding of Van to the staphylococcal surface. Iron chelation is a promising, novel adjunctive therapeutic strategy for MRSA and VISA infections. PMID:24292099

  14. Temperature dependence of the surface enhanced raman spectroelectrochemistry of iron in aqueous solutions.

    SciTech Connect

    Simpson, L. J.; Melendres, C. A.; Chemical Engineering

    1996-06-01

    The effect of temperature on the composition of the corrosion film on iron in aqueous sodium hydroxide and borate solutions was investigated using surface enhanced Raman spectroelectrochemistry (SERS). Fe(OH){sub 2} and Fe{sub 3}O{sub 4} were observed in the prepassivation region, while Fe{sub 3}O{sub 4} and FeOOH accounted for most of the passivated film at 25, 60 and 95 C. Fe(OH){sub 2} was found to be a stable component of the corrosion film on iron at 95 C, which is contrary to recently published theoretical calculations.

  15. Water-Mediated Proton Hopping on an Iron Oxide Surface

    SciTech Connect

    Merte, L. R.; Peng, Guowen; Bechstein, Ralf; Rieboldt, Felix; Farberow, Carrie A.; Grabow, Lars C.; Kudernatsch, Wilhelmine; Wendt, Stefen; Laegsgaard, E.; Mavrikakis, Manos; Besenbacher, Fleming

    2012-05-18

    The diffusion of hydrogen atoms across solid oxide surfaces is often assumed to be accelerated by the presence of water molecules. Here we present a high-resolution, high-speed scanning tunneling microscopy (STM) study of the diffusion of H atoms on an FeO thin film. STM movies directly reveal a water-mediated hydrogen diffusion mechanism on the oxide surface at temperatures between 100 and 300 kelvin. Density functional theory calculations and isotope-exchange experiments confirm the STM observations, and a proton-transfer mechanism that proceeds via an H3O+-like transition state is revealed. This mechanism differs from that observed previously for rutile TiO2(110), where water dissociation is a key step in proton diffusion.

  16. Removal of contaminants from aqueous solution by reaction with iron surfaces

    SciTech Connect

    Qiu, S.R.; Lai, H.F.; Roberson, M.J.; Hunt, M.L.; Amrhein, C.; Giancarlo, L.C.; Flynn, G.W.; Yarmoff, J.A.

    2000-03-07

    Irrigation drainage and industrial wastewaters often contain elevated levels of toxic oxyanions and oxycations such as selenate, chromate, and uranyl. A potential remediation method is to react contaminated water with zero-valent iron, which transforms the mobile contaminants into immobile forms. In this work, iron foil was exposed to aqueous solutions containing the relevant ions, and the reacted surfaces were characterized by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). STM images collected in situ show that the protrusions on the foil surface associated with iron oxides are smoothed out by the reaction. XPS indicates that partially reduced Se(IV) and Cr(III) are adsorbed on the surface, while uranium is deposited as U(VI), i.e., without reduction. More Se and Cr are deposited when the atmospheric gases are removed from solution because of the elimination of a competing process in which dissolved O{sub 2} increases the thickness of the iron oxide overlayer to the point where the reduction reaction is quenched. The amount of U deposited is greatly increased when the atmospheric gases are removed because of the elimination of dissolved CO{sub 2}, which can form carbonate complexes with uranium.

  17. Antimicrobial Susceptibility Profiles of Staphylococcus aureus Isolates Recovered from Humans, Environmental Surfaces, and Companion Animals in Households of Children with Community-Onset Methicillin-Resistant S. aureus Infections

    PubMed Central

    Morelli, John J.; Hogan, Patrick G.; Sullivan, Melanie L.; Muenks, Carol E.; Wang, Jeffrey W.; Thompson, Ryley M.; Burnham, Carey-Ann D.

    2015-01-01

    Our objective was to determine the antibiotic susceptibility profiles of Staphylococcus aureus isolates recovered from 110 households of children with community-onset methicillin-resistant S. aureus (MRSA) infections. Cultures were obtained from household members, household objects, and dogs and cats, yielding 1,633 S. aureus isolates. The S. aureus isolates were heterogeneous, although more than half were methicillin resistant. The highest proportion of MRSA was found in bathrooms. The majority of isolates were susceptible to antibiotics prescribed in outpatient settings. PMID:26248385

  18. Modeling ferrous ferric iron chemistry with application to martian surface geochemistry

    NASA Astrophysics Data System (ADS)

    Marion, Giles M.; Kargel, Jeffrey S.; Catling, David C.

    2008-01-01

    The Mars Global Surveyor, Mars Exploration Rover, and Mars Express missions have stimulated considerable thinking about the surficial geochemical evolution of Mars. Among the major recent mission findings are the presence of jarosite (a ferric sulfate salt), which requires formation from an acid-sulfate brine, and the occurrence of hematite and goethite on Mars. Recent ferric iron models have largely focused on 25 °C, which is a major limitation for models exploring the geochemical history of cold bodies such as Mars. Until recently, our work on low-temperature iron-bearing brines involved ferrous but not ferric iron, also obviously a limitation. The objectives of this work were to (1) add ferric iron chemistry to an existing ferrous iron model (FREZCHEM), (2) extend this ferrous/ferric iron geochemical model to lower temperatures (<0 °C), and (3) use the reformulated model to explore ferrous/ferric iron chemistries on Mars. The FREZCHEM model is an equilibrium chemical thermodynamic model parameterized for concentrated electrolyte solutions using the Pitzer approach for the temperature range from <-70 to 25 °C and the pressure range from 1 to 1000 bars. Ferric chloride and sulfate mineral parameterizations were based, in part, on experimental data. Ferric oxide/hydroxide mineral parameterizations were based exclusively on Gibbs free energy and enthalpy data. New iron parameterizations added 23 new ferrous/ferric minerals to the model for this Na-K-Mg-Ca-Fe(II)-Fe(III)-H-Cl-SO 4-NO 3-OH-HCO 3-CO 3-CO 2-O 2-CH 4-H 2O system. The model was used to develop paragenetic sequences for Rio Tinto waters on Earth and a hypothetical Martian brine derived from acid weathering of basaltic minerals. In general, model simulations were in agreement with field evidence on Earth and Mars in predicting precipitation of stable iron minerals such as jarosites, goethite, and hematite. In addition, paragenetic simulations for Mars suggest that other iron minerals such as

  19. Size-Dependent Specific Surface Area of Nanoporous Film Assembled by Core-Shell Iron Nanoclusters

    DOE PAGESBeta

    Antony, Jiji; Nutting, Joseph; Baer, Donald R.; Meyer, Daniel; Sharma, Amit; Qiang, You

    2006-01-01

    Nmore » anoporous films of core-shell iron nanoclusters have improved possibilities for remediation, chemical reactivity rate, and environmentally favorable reaction pathways. Conventional methods often have difficulties to yield stable monodispersed core-shell nanoparticles. We produced core-shell nanoclusters by a cluster source that utilizes combination of Fe target sputtering along with gas aggregations in an inert atmosphere at 7 ∘ C . Sizes of core-shell iron-iron oxide nanoclusters are observed with transmission electron microscopy (TEM). The specific surface areas of the porous films obtained from Brunauer-Emmett-Teller (BET) process are size-dependent and compared with the calculated data.« less

  20. Iron oxide and hydroxide precipitation from ferrous solutions and its relevance to Martian surface mineralogy

    NASA Technical Reports Server (NTRS)

    Posey-Dowty, J.; Moskowitz, B.; Crerar, D.; Hargraves, R.; Tanenbaum, L.

    1986-01-01

    Experiments were performed to examine if the ubiquitousness of a weak magnetic component in all Martian surface fines tested with the Viking Landers can be attributed to ferric iron precipitation in aqueous solution under oxidizing conditions at neutral pH. Ferrous solutions were mixed in deionized water and various minerals were added to separate liquid samples. The iron-bearing additives included hematite, goethite, magnetite, maghemite, lepidocrocite and potassium bromide blank at varying concentrations. IR spectroscopic scans were made to identify any precipitates resulting from bubbling oxygen throughout the solutions; the magnetic properties of the precipitates were also examined. The data indicated that the lepidocrocite may have been preferentially precipitated, then aged to maghemite. The process would account for the presumed thin residue of maghemite on the present Martian surface, long after abundant liquid water on the Martian surface vanished.

  1. Iron oxide and hydroxide precipitation from ferrous solutions and its relevance to Martian surface mineralogy

    NASA Astrophysics Data System (ADS)

    Posey-Dowty, J.; Moskowitz, B.; Crerar, D.; Hargraves, R.; Tanenbaum, L.; Dowty, E.

    1986-04-01

    Experiments were performed to examine if the ubiquitousness of a weak magnetic component in all Martian surface fines tested with the Viking Landers can be attributed to ferric iron precipitation in aqueous solution under oxidizing conditions at neutral pH. Ferrous solutions were mixed in deionized water and various minerals were added to separate liquid samples. The iron-bearing additives included hematite, goethite, magnetite, maghemite, lepidocrocite and potassium bromide blank at varying concentrations. IR spectroscopic scans were made to identify any precipitates resulting from bubbling oxygen throughout the solutions; the magnetic properties of the precipitates were also examined. The data indicated that the lepidocrocite may have been preferentially precipitated, then aged to maghemite. The process would account for the presumed thin residue of maghemite on the present Martian surface, long after abundant liquid water on the Martian surface vanished.

  2. The surface of iron molybdate catalysts used for the selective oxidation of methanol

    NASA Astrophysics Data System (ADS)

    Yeo, Benjamin R.; Pudge, Geoffrey J. F.; Bugler, Keith G.; Rushby, Alice V.; Kondrat, Simon; Bartley, Jonathan; Golunski, Stanislaw; Taylor, Stuart H.; Gibson, Emma; Wells, Peter. P.; Brookes, Catherine; Bowker, Michael; Hutchings, Graham J.

    2016-06-01

    The oxidation of methanol to formaldehyde is a major chemical process carried out catalytically and iron molybdate is one of the major catalysts for this process. In this paper we explore the nature of the active and selective surfaces of iron molybdate catalysts and show that the effective catalysts comprise molybdenum rich surfaces. We conclude that it is therefore important to maximise the surface area of these active catalysts and to this end we have studied catalysts made using a new physical grinding method with oxalic acid. For super-stoichiometric materials (Fe:Mo = 1:2.2) the reaction data show that physical mixing produces effective catalysts, possibly offering an improvement over the conventional co-precipitation method.

  3. Cohesive Relations for Surface Atoms in the Iron-Technetium Binary System

    DOE PAGESBeta

    Taylor, Christopher D.

    2011-01-01

    Iron-technetium alloys are of relevance to the development of waste forms for disposition of radioactive technetium-99 obtained from spent nuclear fuel. Corrosion of candidate waste forms is a function of the local cohesive energy () of surface atoms. A theoretical model for calculating is developed. Density functional theory was used to construct a modified embedded atom (MEAM) potential for iron-technetium. Materials properties determined for the iron-technetium system were in good agreement with the literature. To explore the relationship between local structure and corrosion, MEAM simulations were performed on representative iron-technetium alloys and intermetallics. Technetium-rich phases have lower , suggesting thatmore » these phases will be more noble than iron-rich ones. Quantitative estimates of based on numbers of nearest neighbors alone can lead to errors up to 0.5 eV. Consequently, atomistic corrosion simulations for alloy systems should utilize physics-based models that consider not only neighbor counts, but also local compositions and atomic arrangements.« less

  4. Gamma-cyclodextrin/usnic acid thin film fabricated by MAPLE for improving the resistance of medical surfaces to Staphylococcus aureus colonization

    NASA Astrophysics Data System (ADS)

    Iordache, Florin; Grumezescu, Valentina; Grumezescu, Alexandru Mihai; Curuţiu, Carmen; Diţu, Lia Mara; Socol, Gabriel; Ficai, Anton; Truşcă, Roxana; Holban, Alina Maria

    2015-05-01

    This study reports on the successful deposition of γ-cyclodextrin/usnic acid (γCD/UA) thin film by Matrix Assisted Pulsed Laser Evaporation (MAPLE) as anti-adherent coating on medical surfaces against microbial colonization. The obtained results demonstrate that these bioactive thin films inhibit Staphylococcus aureus biofilm formation at all stages, starting with their initiation. The antibiofilm effect was constant along the bacterial incubation time. Furthermore, the γCD/UA coatings show a great biocompatibility which means that this material is suitable for the development of modern medical devices with antimicrobial properties.

  5. Surface reactions of iron - enriched smectites: adsorption and transformation of hydroxy fatty acids and phenolic acids

    NASA Astrophysics Data System (ADS)

    Polubesova, Tamara; Olshansky, Yaniv; Eldad, Shay; Chefetz, Benny

    2014-05-01

    Iron-enriched smectites play an important role in adsorption and transformation of soil organic components. Soil organo-clay complexes, and in particular humin contain hydroxy fatty acids, which are derived from plant biopolymer cutin. Phenolic acids belong to another major group of organic acids detected in soil. They participate in various soil processes, and are of concern due to their allelopathic activity. We studied the reactivity of iron-enriched smectites (Fe(III)-montmorillonite and nontronite) toward both groups of acids. We used fatty acids- 9(10),16-dihydroxypalmitic acid (diHPA), isolated from curtin, and 9,10,16-trihydroxypalmitic acid (triHPA); the following phenolic acids were used: ferulic, p-coumaric, syringic, and vanillic. Adsorption of both groups of acids was measured. The FTIR spectra of fatty acid-mineral complexes indicated inner-sphere complexation of fatty acids with iron-enriched smectites (versus outer-sphere complexation with Ca(II)-montmorillonite). The LC-MS results demonstrated enhanced esterification of fatty acids on the iron-enriched smectite surfaces (as compared to Ca(II)-montmorillonite). This study suggests that fatty acids can be esterified on the iron-enriched smectite surfaces, which results in the formation of stable organo-mineral complexes. These complexes may serve as a model for the study of natural soil organo-clay complexes and humin. The reaction of phenolic acids with Fe(III)-montmorillonite demonstrated their oxidative transformation by the mineral surfaces, which was affected by molecular structure of acids. The following order of their transformation was obtained: ferulic >syringic >p-coumaric >vanillic. The LC-MS analysis demonstrated the presence of dimers, trimers, and tetramers of ferulic acid on the surface of Fe(III)-montmorillonite. Oxidation and transformation of ferulic acid were more intense on the surface of Fe(III)-montmorillonite as compared to Fe(III) in solution due to stronger complexation on

  6. Affinity capture using peptide-functionalized magnetic nanoparticles to target Staphylococcus aureus.

    PubMed

    Kuo, Fang-Yin; Lin, Wei-Lien; Chen, Yu-Chie

    2016-04-28

    Staphylococcus aureus, a commonly found pathogen, can cause food poisoning and infections. Thus, it is necessary to develop analytical methods for the rapid screening of S. aureus in suspicious samples. Magnetic nanoparticles (MNPs) are widely used as affinity probes to selectively enrich target species from complex samples because of their high specific surface area and magnetic properties. The MNP surface should be functionalized to have the capability to target specific species. We herein propose a straightforward method to functionalize aluminum oxide-coated iron oxide (Fe3O4@Al2O3) MNPs with the peptide HHHHHHDEEGLFVD (D). The peptide D was comprised of three domains: polyhistidine (H6) used as the linker, DEE added as the spacer, and GLFVD used for targeting S. aureus. D was immobilized on the surface of Fe3O4@Al2O3 MNPs through H6-Al chelation. Our results showed that the D-functionalized Fe3O4@Al2O3 MNPs (D-Fe3O4 MNPs) possess the capability to target S. aureus. The selective trapping experiments were conducted under microwave-heating for only 60 s, and sufficient bacterial cells were trapped by the MNPs to be identified by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). We demonstrated that the D-Fe3O4@Al2O3 MNPs combined with MALDI-MS can be used to rapidly characterize trace amounts of S. aureus in complex juice and egg samples. PMID:27087258

  7. Interaction of Fe(II) with phosphate and sulfate on iron oxide surfaces

    NASA Astrophysics Data System (ADS)

    Hinkle, Margaret A. G.; Wang, Zimeng; Giammar, Daniel E.; Catalano, Jeffrey G.

    2015-06-01

    Sulfate and phosphate, oxoanions common in natural systems, affect iron oxide growth and dissolution processes, the adsorption behavior of divalent cations, and iron oxide phase transformations. These oxoanions may thus influence Fe(II) adsorption behavior and subsequently alter the mechanisms and products of Fe(II)-catalyzed Fe(III) oxide recrystallization processes, such as trace metal repartitioning. In this study, the macroscopic and molecular-scale effects of the coadsorption of Fe(II) and sulfate or phosphate onto Fe(III) oxide surfaces were investigated. Macroscopic adsorption edges show that both sulfate and phosphate increase Fe(II) adsorption and that Fe(II) increases sulfate and phosphate adsorption. Attenuated total reflectance Fourier transform infrared spectroscopy shows that the cooperative adsorption behavior of oxoanions and aqueous Fe(II) likely results from a combination of ternary complexation and electrostatic interactions. Surface complexation modeling requires the inclusion of ternary complexes to simulate all conditions of the macroscopic data, further suggesting that these oxoanions and Fe(II) form ternary complexes on Fe(III) oxide surfaces. Despite clear evidence in previous research for Fe(II) oxidation upon adsorption on iron oxide surfaces, this work shows that Fe(II) also displays macroscopic and molecular-scale behaviors associated with divalent (i.e., non-oxidative) cation adsorption. Prior work has shown that metal release from iron oxides caused by ET-AE reactions is directly proportional to the macroscopically-determined Fe(II) surface coverage. Predicting the effects of sulfate and phosphate on processes controlled by ET-AE reactions at redox interfaces, such as mineral phase transformations and trace element repartitioning, may thus not require the explicit consideration of electron transfer processes.

  8. Toxicity Assessment of Silica Coated Iron Oxide Nanoparticles and Biocompatibility Improvement by Surface Engineering

    PubMed Central

    Malvindi, Maria Ada; De Matteis, Valeria; Galeone, Antonio; Brunetti, Virgilio; Anyfantis, George C.; Athanassiou, Athanassia; Cingolani, Roberto; Pompa, Pier Paolo

    2014-01-01

    We have studied in vitro toxicity of iron oxide nanoparticles (NPs) coated with a thin silica shell (Fe3O4/SiO2 NPs) on A549 and HeLa cells. We compared bare and surface passivated Fe3O4/SiO2 NPs to evaluate the effects of the coating on the particle stability and toxicity. NPs cytotoxicity was investigated by cell viability, membrane integrity, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) assays, and their genotoxicity by comet assay. Our results show that NPs surface passivation reduces the oxidative stress and alteration of iron homeostasis and, consequently, the overall toxicity, despite bare and passivated NPs show similar cell internalization efficiency. We found that the higher toxicity of bare NPs is due to their stronger in-situ degradation, with larger intracellular release of iron ions, as compared to surface passivated NPs. Our results indicate that surface engineering of Fe3O4/SiO2 NPs plays a key role in improving particles stability in biological environments reducing both cytotoxic and genotoxic effects. PMID:24465736

  9. Vaccination Against Staphylococcus aureus Pneumonia

    PubMed Central

    Spaulding, Adam R.; Salgado-Pabón, Wilmara; Merriman, Joseph A.; Stach, Christopher S.; Ji, Yinduo; Gillman, Aaron N.; Peterson, Marnie L.; Schlievert, Patrick M.

    2014-01-01

    Background. Staphylococcus aureus causes serious infections in both hospital and community settings. Attempts have been made to prevent human infection through vaccination against bacterial cell-surface antigens; thus far all have failed. Here we show that superantigens and cytolysins, when used in vaccine cocktails, provide protection from S. aureus USA100–USA400 intrapulmonary challenge. Methods. Rabbits were actively vaccinated (wild-type toxins or toxoids) or passively immunized (hyperimmune serum) against combinations of superantigens (toxic shock syndrome toxin 1, enterotoxins B and C, and enterotoxin-like X) and cytolysins (α-, β-, and γ-toxins) and challenged intrapulmonarily with multiple strains of S. aureus, both methicillin-sensitive and methicillin-resistant. Results. Active vaccination against a cocktail containing bacterial cell-surface antigens enhanced disease severity as tested by infective endocarditis. Active vaccination against secreted superantigens and cytolysins resulted in protection of 86 of 88 rabbits when challenged intrapulmonarily with 9 different S. aureus strains, compared to only 1 of 88 nonvaccinated animals. Passive immunization studies demonstrated that production of neutralizing antibodies was an important mechanism of protection. Conclusions. The data suggest that vaccination against bacterial cell-surface antigens increases disease severity, but vaccination against secreted virulence factors provides protection against S. aureus. These results advance our understanding of S. aureus pathogenesis and have important implications in disease prevention. PMID:24357631

  10. Sol–gel method as a way of carbonyl iron powder surface modification for interaction improvement

    SciTech Connect

    Małecki, P.; Kolman, K.; Pigłowski, J.; Kaleta, J.; Krzak, J.

    2015-03-15

    This article presents a method for modification of carbonyl iron particles’ surface (CIP), (d{sub 50}=4–9 µm) by silica coatings obtained using the sol–gel method. Reaction parameters were determined to obtain dry magnetic powder with homogeneous silica coatings without further processing and without any by-product in the solid or liquid phase. This approach is new among the commonly used methods of silica coating of iron particles. No attempt has been made to cover a carbonyl iron surface by silica in a waste-free method, up to date. In the current work two different silica core/shell structures were made by the sol–gel process, based on different silica precursors: tetraethoxy-silane (TEOS) and tetramethoxy-silane (TMOS). The dependence between the synthesis procedure and thickness of silica shell covering carbonyl iron particles has been described. Surface morphology of the modified magnetic particles and the coating thickness were characterized with the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Determination of the physicochemical structure of the obtained materials was performed by the energy-dispersive X-ray spectroscope (EDS), and the infrared technique (IR). The surface composition was analyzed using X-ray photoelectron spectroscopy (XPS). Additionally, distribution of particle size was measured using light microscopy. The new, efficient process of covering micro-size CIP with a nanometric silica layer was shown. Results of a performed analysis confirm the effectiveness of the presented method. - Highlights: • Proper covering CIP by sol–gel silica layer avoids agglomeration. • A new solid waste-free method of CIP coating is proposed. • Examination of the properties of modified CIP in depends on washing process. • Coatings on CIP particles doesn’t change the magnetic properties of particles.

  11. Volcanic ash as an iron-fertilizer in ocean surface water

    NASA Astrophysics Data System (ADS)

    Olgun, N.; Duggen, S.; Croot, P.; Dietze, H.; Schacht, U.; Oskarsson, N.; Siebe, C.; Auer, A.

    2007-12-01

    Surface ocean fertilisation with iron may affect the marine primary productivity, C-cycles and eventually climate development. Volcanic ash has the potential to release iron on contact with seawater and to stimulate phytoplankton growth (1,2) but the relative importance of volcanism at destructive plate margins (subduction zones, SZ) and intraplate volcanic settings (ocean islands at hot spots) remains unknown. Here we present new results from geochemical experiments with natural seawater and numerous volcanic ash samples from SZ volcanoes in the Pacific Ring of Fire (Alaska, Japan, Kamchatka, Northern and Central America and Papua New Guinea) and hot spot volcanoes (on Iceland and Hawaii). The release of iron as a function of time was determined in situ in seawater by means of Cathodic Stripping Voltammetry. Our experiments show that: A) volcanic ash from both SZ and hot spot volcanic areas mobilise significant amounts of iron, B) with the highest mobilisation rates within the first 10-20 minutes and C) indicate that volcanic ash from hot spot volcanoes mobilise less iron than volcanic ash from SZ. We propose that the higher iron-mobilisation potential of SZ volcanic ash results from higher HCl/HF ratios in SZ volcanic gases that seem to be involved in the formation of Fe-bearing soluble salt coatings (condensed gases and adsorbed aerosols) on ash particles (1,2,3). Higher HCl/HF ratios in SZ volcanic gases thus appear to be linked to the recycling of seawater through subduction of oceanic lithosphere at destructive plate margins. Together, taking into account differences in ash-fluxes from SZ and hot spot volcanoes into the oceans, our study suggests that SZ volcanic ash plays a more important role for the global surface ocean iron budget than ash from volcanoes in hot spot areas. 1 Frogner, Gislason, Oskarsson (2001). Geology, 29, 487-490. 2 Duggen, Croot, Schacht, Hofmann (2007) Geoph. Res. Letters 34, 5. 3 Oskarsson (1980), J. Volc. and Geoth. Res. 8, 251-266.

  12. Iron porphyrin polymer films: Materials for the modification of electrode surfaces and the detection of nitric oxide

    SciTech Connect

    McGuire, M.; Drew, S.M.

    1996-10-01

    We are currently investigating a new method for the detection and quantification of nitric oxide (NO) based on a carbon electrode chemically modified with an iron porphyrin polymer film. Commercially available vinyl-substituted iron porphyrin monomers can be polymerized directly onto electrode surfaces through a published electrochemical polymerization process. We are also developing a synthesis for a new vinyl-substituted monomer, iron 5,10,15-triphenyl-20-vinyl porphyrin chloride, in hopes of improving polymer film stability. The electrochemistry of NO is also being investigated at electrodes chemically modified with an iron porphyrin polymer film. We are studying the catalytic oxidation of iron porphyrin bound NO to nitrate by molecular oxygen. The reaction with molecular oxygen is preceded by a one electron reduction of the iron porphyrin-NO complex. If currents proportional to nitric oxide concentration can be measured, a new NO electrochemical sensor will be designed.

  13. Three-Dimensional Structure and Biophysical Characterization of Staphylococcus aureus Cell Surface Antigen-Manganese Transporter MntC

    SciTech Connect

    Gribenko, Alexey; Mosyak, Lidia; Ghosh, Sharmistha; Parris, Kevin; Svenson, Kristine; Moran, Justin; Chu, Ling; Li, Sheng; Liu, Tong; Woods, Jr., Virgil L.; Jansen, Kathrin U.; Green, Bruce A.; Anderson, Annaliesa S.; Matsuka, Yury V.

    2013-08-23

    MntC is a metal-binding protein component of the Mn2 +-specific mntABC transporter from the pathogen Staphylococcus aureus. The protein is expressed during the early stages of infection and was proven to be effective at reducing both S. aureus and Staphylococcus epidermidis infections in a murine animal model when used as a vaccine antigen. MntC is currently being tested in human clinical trials as a component of a multiantigen vaccine for the prevention of S. aureus infections. To better understand the biological function of MntC, we are providing structural and biophysical characterization of the protein in this work. The three-dimensional structure of the protein was solved by X-ray crystallography at 2.2 Å resolution and suggests two potential metal binding modes, which may lead to reversible as well as irreversible metal binding. Precise Mn2 +-binding affinity of the protein was determined from the isothermal titration calorimetry experiments using a competition approach. Differential scanning calorimetry experiments confirmed that divalent metals can indeed bind to MntC reversibly as well as irreversibly. Finally, Mn2 +-induced structural and dynamics changes have been characterized using spectroscopic methods and deuterium–hydrogen exchange mass spectroscopy. Results of the experiments show that these changes are minimal and are largely restricted to the structural elements involved in metal coordination. Therefore, it is unlikely that antibody binding to this antigen will be affected by the occupancy of the metal-binding site by Mn2 +.

  14. Chromate removal by surface-modified nanoscale zero-valent iron: Effect of different surface coatings and water chemistry.

    PubMed

    Dong, Haoran; He, Qi; Zeng, Guangming; Tang, Lin; Zhang, Chang; Xie, Yankai; Zeng, Yalan; Zhao, Feng; Wu, Yanan

    2016-06-01

    This study investigated the correlation between the colloidal stability and reactivity of surface-modified nano zero-valent iron (SM-nZVI) as affected by the surface coating (i.e., polyacrylic acid [PAA] and starch) under various geochemical conditions. Generally, the colloidal stability of nZVI was enhanced with increasing loading of surface coating, while there is an optimum loading for the most efficient Cr(VI) removal by SM-nZVI. At lower loadings than the optimum loading, the surface coating could enhance the particle stabilization, facilitating the Cr(VI) reduction by providing more available surface sites. However, the over-loaded surface coating on the surface of nZVI particles decreased the Cr(VI) reduction due to the occupation of the reactive sites and the inhibition of the mass transfer of Cr(VI) ions from water to the particle surface by providing the electrostatic or steric repulsion. The effects of Ca(2+) ions or humic acid (HA) on the colloidal stability and reactivity of PAA-modified nZVI (P-nZVI) and starch-modified nZVI (S-nZVI) were examined. Differing stability behavior and reactivity were observed for different SM-nZVI. It was found that the presence of Ca(2+) or HA altered surface chemistry of SM-nZVI, the particle-particle interaction and the particle-contaminant interaction, and hence influencing the stability behavior and reactivity of the particles. PMID:26970032

  15. Iron oxidation kinetics and phosphorus immobilization at the groundwater-surface water interface

    NASA Astrophysics Data System (ADS)

    van der Grift, Bas; Rozemeijer, Joachim; Griffioen, Jasper; van der Velde, Ype

    2014-05-01

    Eutrophication of freshwater environments following diffuse nutrient loads is a widely recognized water quality problem in catchments. Fluxes of non-point P sources to surface waters originate from surface runoff and flow from soil water and groundwater into surface water. The availability of P in surface waters is controlled strongly by biogeochemical nutrient cycling processes at the soil-water interface. The mechanisms and rates of the iron oxidation process with associated binding of phosphate during exfiltration of anaerobic Fe(II) bearing groundwater are among the key unknowns in P retention processes in surface waters in delta areas where the shallow groundwater is typically pH-neutral to slightly acid, anoxic, iron-rich. We developed an experimental field set-up to study the dynamics in Fe(II) oxidation and mechanisms of P immobilization at the groundwater-surface water interface in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. The exfiltrating groundwater was captured in in-stream reservoirs constructed in the ditch. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and ditch water, we quantified Fe(II) oxidation kinetics and P immobilization processes across the seasons. This study showed that seasonal changes in climatic conditions affect the Fe(II) oxidation process. In winter time the dissolved iron concentrations in the in-stream reservoirs reached the levels of the anaerobic groundwater. In summer time, the dissolved iron concentrations of the water in the reservoirs are low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into the reservoirs. Higher discharges, lower temperatures and lower pH of the exfiltrated groundwater in winter compared to summer shifts the location of the redox transition zone

  16. Facile fabrication of iron-based superhydrophobic surfaces via electric corrosion without bath

    NASA Astrophysics Data System (ADS)

    Sun, Qinghe; Liu, Hongtao; Chen, Tianchi; Wei, Yan; Wei, Zhu

    2016-04-01

    Superhydrophobic surface is of wide application in the field of catalysis, lubrication, waterproof, biomedical materials, etc. The superhydrophobic surface based on hard metal is worth further study due to its advantages of high strength and wear resistance. This paper investigates the fabrication techniques towards superhydrophobic surface on carbon steel substrate via electric corrosion and studies the properties of as-prepared superhydrophobic surface. The hydrophobic properties were characterized by a water sliding angle (SA) and a water contact angle (CA) measured by the Surface tension instrument. A Scanning electron microscope was used to analyze the structure of the corrosion surface. The surface compositions were characterized by an Energy Dispersive Spectrum. The Electrochemical workstation was used to measure its anti-corrosion property. The anti-icing performance was characterized by a steam-freezing test in Environmental testing chamber. The SiC sandpaper and 500 g weight were used to test the friction property. The research result shows that the superhydrophobic surface can be successfully fabricated by electrocorrosion on carbon steel substrate under appropriate process; the contact angle of the as-prepared superhydrophobic surface can be up to 152 ± 0.5°, and the sliding angle is 1-2°; its anti-corrosion property, anti-icing performance and the friction property all show an excellent level. This method provides the possibility of industrialization of superhydrophobic surface based on iron substrate as it can prepare massive superhydrophobic surface quickly.

  17. Recent advances in surface chemistry strategies for the fabrication of functional iron oxide based magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Turcheniuk, Kostiantyn; Tarasevych, Arkadii V.; Kukhar, Valeriy P.; Boukherroub, Rabah; Szunerits, Sabine

    2013-10-01

    The synthesis of superparamagnetic nanostructures, especially iron-oxide based nanoparticles (IONPs), with appropriate surface functional groups has been intensively researched for many high-technological applications, including high density data storage, biosensing and biomedicine. In medicine, IONPs are nowadays widely used as contrast agents for magnetic resonance imaging (MRI), in hyperthermia therapy, but are also exploited for drug and gene delivery, detoxification of biological fluids or immunoassays, as they are relatively non-toxic. The use of magnetic particles in vivo requires IONPs to have high magnetization values, diameters below 100 nm with overall narrow size distribution and long time stability in biological fluids. Due to the high surface energies of IONPs agglomeration over time is often encountered. It is thus of prime importance to modify their surface to prevent aggregation and to limit non-specific adsorption of biomolecules onto their surface. Such chemical modifications result in IONPs being well-dispersed and biocompatible, and allow for targeted delivery and specific interactions. The chemical nature of IONPs thus determines not only the overall size of the colloid, but also plays a significant role for in vivo and in vitro applications. This review discusses the different concepts currently used for the surface functionalization and coating of iron oxide nanoparticles. The diverse strategies for the covalent linking of drugs, proteins, enzymes, antibodies, and nucleotides will be discussed and the chemically relevant steps will be explained in detail.

  18. Mars surface weathering products and spectral analogs: Palagonites and synthetic iron minerals

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.; Morris, R. V.; Lauer, H. V., Jr.

    1992-01-01

    There are several hypotheses regarding the formation of Martian surface fines. These surface fines are thought to be products of weathering processes occurring on Mars. Four major weathering environments of igneous rocks on Mars have been proposed; (1) impact induced hydrothermal alterations; (2) subpermafrost igneous intrusion; (3) solid-gas surface reactions; and (4) subaerial igneous intrusion over permafrost. Although one or more of these processes may be important on the Martian surface, one factor in common for all these processes is the reaction of solid or molten basalt with water (solid, liquid, or gas). These proposed processes, with the exception of solid-gas surface reactions, are transient processes. The most likely product of transient hydrothermal processes are layer silicates, zeolites, hydrous iron oxides and palagonites. The long-term instability of hydrous clay minerals under present Martian conditions has been predicted; however, the persistence of such minerals due to slow kinetics of dehydration, or entrapment in permafrost, where the activity of water is high, can not be excluded. Anhydrous oxides of iron (e.g., hematite and maghemite) are thought to be stable under present Martian surface conditions. Oxidative weathering of sulfide minerals associated with Martian basalts has been proposed. Weathering of sulfide minerals leads to a potentially acidic permafrost and the formation of Fe(3) oxides and sulfates. Weathering of basalts under acidic conditions may lead to the formation of kaolinite through metastable halloysite and metahalloysite. Kaolinite, if present, is thought to be a thermodynamically stable phase at the Martian surface. Fine materials on Mars are important in that they influence the surface spectral properties; these fines are globally distributed on Mars by the dust storms and this fraction will have the highest surface area which should act as a sink for most of the absorbed volatiles near the surface of Mars. Therefore

  19. Peculiarities of phase transitions in the iron-nanoclay surface system studied by Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Zalutskii, A. A.

    2014-10-01

    Results of an experimental investigation of the peculiarities of phase transitions in iron compounds localized in natural low-dimensional systems (nanoclays) are reported. Conditions for observation of the phase transition by Mössbauer spectroscopy in thin films of ice adsorbed on the surface of typical clays are established for the first time. Data obtained by the proposed method for the geography of iron exchange complexes on aluminosilicate clay surface are presented.

  20. Surface chemistry and structural properties of mackinawite prepared by reaction of sulfide ions with metallic iron

    NASA Astrophysics Data System (ADS)

    Mullet, Martine; Boursiquot, Sophie; Abdelmoula, Mustapha; Génin, Jean-Marie; Ehrhardt, Jean-Jacques

    2002-03-01

    Tetragonal FeS 1- x mackinawite, has been synthesized by reacting metallic iron with a sodium sulfide solution and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), transmission Mössbauer spectroscopy (TMS) and X-ray photoelectron spectroscopy (XPS). Based on XRD and TEM analyses, synthetic mackinawite exhibits crystallization and is identical to the natural mineral. Unit cell parameters derived from XRD data are a = b = 0.3670 nm and c = 0.5049 nm. The bulk Fe:S ratio derived from the quantitative dispersive energy analysis is practically 1. XPS analyses, however, showed that mackinawite surface is composed of both Fe(II) and Fe(III) species bound to monosulfide. Accordingly, monosulfide is the dominant S species observed at the surface with lesser amount of polysulfides and elemental sulfur. TMS analysis revealed the presence of both Fe(II) and Fe(III) in the mackinawite structure, thus supporting the XPS analysis. We propose that the iron monosulfide phase synthesized by reacting metallic iron and dissolved sulfide is composed of Fe(II) and S(-II) atoms with the presence of a weathered thin layer covering the bulk material that consists of both Fe(II) and Fe(III) bound to S(-II) atoms and in a less extent of polysulfide and elemental sulfur.

  1. A Staphylococcus aureus ypfP mutant with strongly reduced lipoteichoic acid (LTA) content: LTA governs bacterial surface properties and autolysin activity

    PubMed Central

    Fedtke, Iris; Mader, Diana; Kohler, Thomas; Moll, Hermann; Nicholson, Graeme; Biswas, Raja; Henseler, Katja; Götz, Friedrich; Zähringer, Ulrich; Peschel, Andreas

    2007-01-01

    Many Gram-positive bacteria produce lipoteichoic acid (LTA) polymers whose physiological roles have remained a matter of debate because of the lack of LTA-deficient mutants. The ypfP gene responsible for biosynthesis of a glycolipid found in LTA was deleted in Staphylococcus aureus SA113, causing 87% reduction of the LTA content. Mass spectrometry and nuclear magnetic resonance spectroscopy revealed that the mutant LTA contained a diacylglycerol anchor instead of the glycolipid, whereas the remaining part was similar to the wild-type polymer except that it was shorter. The LTA mutant strain revealed no major changes in patterns of cell wall proteins or autolytic enzymes compared with the parental strain indicating that LTA may be less important in S. aureus protein attachment than previously thought. However, the autolytic activity of the mutant was strongly reduced demonstrating a role of LTA in controlling autolysin activity. Moreover, the hydrophobicity of the LTA mutant was altered and its ability to form biofilms on plastic was completely abrogated indicating a profound impact of LTA on physicochemical properties of bacterial surfaces. We propose to consider LTA and its biosynthetic enzymes as targets for new antibiofilm strategies. PMID:17640274

  2. CD66b Overexpression and Loss of C5a Receptors as Surface Markers for Staphylococcus aureus-Induced Neutrophil Dysfunction

    PubMed Central

    Schnitzler, Norbert; Grüger, Thomas; Brandenburg, Kerstin; Zinserling, Jörg; Zündorf, Josef

    2015-01-01

    Neutrophil granulocytes constitute the main component of innate immunity in the clearance of bacterial infections. However, during systemic inflammation, immunoparalysis may occur resulting in neutrophil dysfunction. This study presents a new in vitro model for analyzing the dysfunction of human peripheral blood neutrophils resulting from the interaction with Staphylococcus aureus components in whole blood. After induction of a massive complement activation by S. aureus supernatant, the neutrophils exhibit a reduced phagocytic capacity resulting in a dramatic reduction of the antibacterial activity similar to that of neutrophils isolated from septic patients. The number of phagocytozing neutrophils is drastically reduced as well as the phagocytic capacity designated by a significantly lower number of ingested microbes. This dysfunction correlates with the loss of complement component 5a receptor 1 from the neutrophil cell surface and can be further characterized by a C5a-induced CD66b overexpression. The presented in vitro model offers a new platform for preclinical testing of immunosuppressive drugs and delivers new information for the understanding of neutrophil dysfunctions under the conditions described. PMID:26176669

  3. Structural biology of heme binding in the Staphylococcus aureus Isd system.

    PubMed

    Grigg, Jason C; Ukpabi, Georgia; Gaudin, Catherine F M; Murphy, Michael E P

    2010-03-01

    Iron is an absolute requirement for nearly all organisms, but most bacterial pathogens are faced with extreme iron-restriction within their host environments. To overcome iron limitation pathogens have evolved precise mechanisms to steal iron from host supplies. Staphylococcus aureus employs the iron-responsive surface determinant (Isd) system as its primary heme-iron uptake pathway. Hemoglobin or hemoglobin-haptoglobin complexes are bound by Near iron-Transport (NEAT) domains within cell surface anchored proteins IsdB or IsdH. Heme is stripped from the host proteins and transferred between NEAT domains through IsdA and IsdC to the membrane transporter IsdEF for internalization. Once internalized, heme can be degraded by IsdG or IsdI, thereby liberating iron for the organism. Most components of the Isd system have been structurally characterized to provide insight into the mechanisms of heme binding and transport. This review summarizes recent research on the Isd system with a focus on the structural biology of heme recognition. PMID:19853304

  4. The ability of S.aureus to form biofilm on the Ti-6Al-7Nb scaffolds produced by Selective Laser Melting and subjected to the different types of surface modifications.

    PubMed

    Szymczyk, Patrycja; Junka, Adam; Ziółkowski, Grzegorz; Smutnicka, Danuta; Bartoszewicz, Marzenna; Chlebus, Edward

    2013-01-01

    The Gram-positive coccus, Staphylococcus aureus, is the leading etiologic agent of limb and life-threatening biofilm-related infections in the patients following the orthopaedic implantations. The aim of the present paper is to estimate the ability of S. aureus to form biofilm on titanium alloy (Ti-6Al-7Nb) scaffolds produced by Selective Laser Melting (SLM) and subjected to the different types of surface modifications, including ultrasonic cleaning and chemical polishing. The results obtained indicate significantly the decreased ability of S.aureus to form biofilm on the surface of scaffolds subjected to the chemical polishing in comparison to the scaffolds cleaned ultrasonically. The data provided can be useful for future applications of the SLM technology in production of Ti-6Al-7Nb medical implants. PMID:23957680

  5. Effect of thiamine hydrochloride on the redox reactions of iron at pyrite surface

    SciTech Connect

    Pesic, B.; Oliver, D.J.

    1990-01-01

    The present investigation is a part of our studies on the electro chemical aspects of pyrite bioleaching involving Thiobacillus ferrooxidans. Previously (1,2) we have examined the effect of T. ferrooxidans and their metabolic products on the redox reactions of Fe[sup 2+]/Fe[sup 3+] couple at the pyrite surface. Results obtained suggest that beyond 1. 5 days during their growth in a batch fermenter, the bacteria and their metabolic products completely cover the pyrite surface and shut down all electron transfer across the electrode-solution interface. In addition, it has been observed that the bacteria serve as the nucleation site for jarosite formation, which is found detrimental to bioleaching. In the present work we have focussed on the effect of the presence of vitamins on the redox chemistry of iron. Our examination of the effect of the presence of thiamine hydrochloride in the redox behavior of Fe[sup 2+]/Fe[sup 3+] at the pyrite surface has revealed that thiamine hydrochloride does not undergo chemical interaction with ferrous or ferric iron. However, it may adsorb onto the pyrite surface causing polarization of the pyrite electrode.

  6. Regulation of cell surface transferrin receptor-2 by iron-dependent cleavage and release of a soluble form

    PubMed Central

    Pagani, Alessia; Vieillevoye, Maud; Nai, Antonella; Rausa, Marco; Ladli, Meriem; Lacombe, Catherine; Mayeux, Patrick; Verdier, Frédérique; Camaschella, Clara; Silvestri, Laura

    2015-01-01

    Transferrin receptor-2 is a transmembrane protein whose expression is restricted to hepatocytes and erythroid cells. Transferrin receptor-2 has a regulatory function in iron homeostasis, since its inactivation causes systemic iron overload. Hepatic transferrin receptor-2 participates in iron sensing and is involved in hepcidin activation, although the mechanism remains unclear. Erythroid transferrin receptor-2 associates with and stabilizes erythropoietin receptors on the erythroblast surface and is essential to control erythrocyte production in iron deficiency. We identified a soluble form of transferrin receptor-2 in the media of transfected cells and showed that cultured human erythroid cells release an endogenous soluble form. Soluble transferrin receptor-2 originates from a cleavage of the cell surface protein, which is inhibited by diferric transferrin in a dose-dependent manner. Accordingly, the shedding of the transferrin receptor-2 variant G679A, mutated in the Arginine-Glycine-Aspartic acid motif and unable to bind diferric transferrin, is not modulated by the ligand. This observation links the process of transferrin receptor-2 removal from the plasma membrane to iron homeostasis. Soluble transferrin receptor-2 does not affect the binding of erythropoietin to erythropoietin receptor or the consequent signaling and partially inhibits hepcidin promoter activation only in vitro. Whether it is a component of the signals released by erythropoiesis in iron deficiency remains to be investigated. Our results indicate that membrane transferrin receptor-2, a sensor of circulating iron, is released from the cell membrane in iron deficiency. PMID:25637053

  7. Regulation of cell surface transferrin receptor-2 by iron-dependent cleavage and release of a soluble form.

    PubMed

    Pagani, Alessia; Vieillevoye, Maud; Nai, Antonella; Rausa, Marco; Ladli, Meriem; Lacombe, Catherine; Mayeux, Patrick; Verdier, Frédérique; Camaschella, Clara; Silvestri, Laura

    2015-04-01

    Transferrin receptor-2 is a transmembrane protein whose expression is restricted to hepatocytes and erythroid cells. Transferrin receptor-2 has a regulatory function in iron homeostasis, since its inactivation causes systemic iron overload. Hepatic transferrin receptor-2 participates in iron sensing and is involved in hepcidin activation, although the mechanism remains unclear. Erythroid transferrin receptor-2 associates with and stabilizes erythropoietin receptors on the erythroblast surface and is essential to control erythrocyte production in iron deficiency. We identified a soluble form of transferrin receptor-2 in the media of transfected cells and showed that cultured human erythroid cells release an endogenous soluble form. Soluble transferrin receptor-2 originates from a cleavage of the cell surface protein, which is inhibited by diferric transferrin in a dose-dependent manner. Accordingly, the shedding of the transferrin receptor-2 variant G679A, mutated in the Arginine-Glycine-Aspartic acid motif and unable to bind diferric transferrin, is not modulated by the ligand. This observation links the process of transferrin receptor-2 removal from the plasma membrane to iron homeostasis. Soluble transferrin receptor-2 does not affect the binding of erythropoietin to erythropoietin receptor or the consequent signaling and partially inhibits hepcidin promoter activation only in vitro. Whether it is a component of the signals released by erythropoiesis in iron deficiency remains to be investigated. Our results indicate that membrane transferrin receptor-2, a sensor of circulating iron, is released from the cell membrane in iron deficiency. PMID:25637053

  8. Friction and transfer of copper, silver, and gold to iron in the presence of various adsorbed surface films

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1979-01-01

    Sliding friction experiments were conducted with the noble metals copper, silver, and gold and two binary alloys of these metals contacting iron in the presence of various adsorbates including, oxygen, methyl mercaptan, and methyl chloride. A pin on disk specimen configuration was used with a load of 100 grams, sliding velocity of 60 mm/min; at 25 C with the surfaces saturated with the adsorbates. Auger emission spectroscopy was used to monitor surface films. Results of the experiments indicate that friction and transfer characteristics are highly specific with respect to both the noble metal and surface film present. With all three metals and films transfer of the noble metal to iron occurred very rapidly. With all metals and films transfer of the noble metal to iron continuously increased with repeated passes except for silver and copper sliding on iron sulfide.

  9. Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

    NASA Astrophysics Data System (ADS)

    Weiss, Werner; Ranke, Wolfgang

    2002-03-01

    Metal-oxide-based catalysts are used for many important synthesis reactions in the chemical industry. A better understanding of the catalyst operation can be achieved by studying elementary reaction steps on well-defined model catalyst systems. For the dehydrogenation of ethylbenzene to styrene in the presence of steam both unpromoted and potassium promoted iron-oxide catalysts are active. Here we review the work done over unpromoted single-crystalline FeO(1 1 1), Fe3O4(1 1 1) and α- Fe2O3(0 0 0 1) films grown epitaxially on Pt(1 1 1) substrates. Their geometric and electronic surface structures were characterized by STM, LEED, electron microscopy and electron spectroscopic techniques. In an integrative approach, the interaction of water, ethylbenzene and styrene with these films was investigated mainly by thermal desorption and photoelectron emission spectroscopy. The adsorption-desorption energetics and kinetics depend on the oxide surface terminations and are correlated to the electronic structures and acid-base properties of the corresponding oxide phases, which reveal insight into the nature of the active sites and into the catalytic function of semiconducting oxides in general. Catalytic studies, using a batch-reactor arrangement at high gas pressures and post-reaction surface analysis, showed that only α- Fe2O3(0 0 0 1) containing surface defects is catalytically active, whereas Fe3O4(1 1 1) is always inactive. This can be related to the elementary adsorption and desorption properties observed in ultrahigh vacuum, which indicates that the surface chemical properties of the iron-oxide films do not change significantly across the “pressure-gap”. A model is proposed according to which the active site involves a regular acidic surface site and a defect site next to it. The results on metal-oxide surface chemistry also have implications for other fields such as environmental science, biophysics and chemical sensors.

  10. Anomalous surface segregation behaviour of some 3d elements in ferromagnetic iron.

    PubMed

    Gupta, Michèle; Gupta, Raju P

    2013-10-16

    The segregation of Cr in Fe is known to be anomalous since the barrier for surface segregation of Cr is not determined by the topmost surface layer, as one would expect, but rather by the subsurface layer where the energy of segregation is much larger and endothermic. This has been attributed to a complex interaction involving the antiferromagnetism of Cr and the ferromagnetism of Fe. We report in this paper the results of our ab initio electronic structure calculations on the segregation behaviour of all the 3d elements on the (1 0 0) surface of ferromagnetic iron in the hope of better understanding this phenomenon. We find a similar behaviour for the segregation of the next antiferromagnetic 3d element Mn in Fe, where the subsurface layer is also found to block the segregation of Mn to the surface. On the other hand, ferromagnetic Co exhibits a normal segregation behaviour. The elements Sc, Cu and Ni do not form solid solutions with ferromagnetic iron. The early elements Ti and V are non-magnetic in their metallic states, but are strongly polarized by Fe, and develop magnetic moments which are aligned antiferromagnetically to those of Fe atoms. While the subsurface layer blocks the segregation of Ti to the surface, no blocking behaviour is found for the segregation of V. The segregation behaviour of all these elements is strongly correlated with the displacement of the solute atoms on the surface of Fe. The elements showing anomalous segregation behaviour are all displaced upwards on the surface, while those showing normal segregation are pulled inwards. These results indicate that the antiferromagnetism of the segregating element plays the key role in the anomalous segregation behaviour in Fe. PMID:24047767

  11. Surface plasmon resonance-induced photoactivation of gold nanoparticles as bactericidal agents against methicillin-resistant Staphylococcus aureus

    PubMed Central

    Mocan, Lucian; Ilie, Ioana; Matea, Cristian; Tabaran, Flaviu; Kalman, Ersjebet; Iancu, Cornel; Mocan, Teodora

    2014-01-01

    Systemic infections caused by methicillin-resistant Staphylococcus aureus (MRSA) and other bacteria are responsible for millions of deaths worldwide, and much of this mortality is due to the rise of antibiotic-resistant organisms as a result of natural selection. Gold nanoparticles synthesized using the standard wet chemical procedure were photoexcited using an 808 nm 2 W laser diode and further administered to MRSA bacteria. Flow cytometry, transmission electron microscopy, contrast phase microscopy, and fluorescence microscopy combined with immunochemical staining were used to examine the interaction of the photoexcited gold nano-particles with MRSA bacteria. We show here that phonon–phonon interactions following laser photoexcitation of gold nanoparticles exhibit increased MRSA necrotic rates at low concentrations and short incubation times compared with MRSA treated with gold nanoparticles alone. These unique data may represent a step forward in the study of bactericidal effects of various nanomaterials, with applications in biology and medicine. PMID:24711697

  12. Contamination of environmental surfaces by methicillin-resistant Staphylococcus aureus (MRSA) in rooms of inpatients with MRSA-positive body sites.

    PubMed

    Kurashige, E Jessica Ohashi; Oie, Shigeharu; Furukawa, H

    2016-01-01

    Methicillin-resistant Staphylococcus aureus (MRSA) can contaminate environmental surfaces that are frequently touched by the hands of patients with MRSA colonization/infection. There have been many studies in which the presence or absence of MRSA contamination was determined but no studies in which MRSA contamination levels were also evaluated in detail. We evaluated MRSA contamination of environmental surfaces (overbed tables, bed side rails, and curtains) in the rooms of inpatients from whom MRSA was isolated via clinical specimens. We examined the curtains within 7-14 days after they had been newly hung. The environmental surfaces were wiped using gauze (molded gauze for wiping of surface bacteria; 100% cotton, 4cm×8cm) moistened with sterile physiological saline. The MRSA contamination rate and mean counts (range) were 25.0% (6/24 samples) and 30.6 (0-255)colony-forming units (cfu)/100cm(2), respectively, for the overbed tables and 31.6% (6/19 samples) and 159.5 (0-1620)cfu/100cm(2), respectively, for the bed side rails. No MRSA was detected in 24 curtain samples. The rate of MRSA contamination of environmental surfaces was high for the overbed tables and bed side rails but low for the curtains. Therefore, at least until the 14th day of use, frequent disinfection of curtains may be not necessary. PMID:27289247

  13. New surface radiolabeling schemes of super paramagnetic iron oxide nanoparticles (SPIONs) for biodistribution studies

    NASA Astrophysics Data System (ADS)

    Nallathamby, Prakash D.; Mortensen, Ninell P.; Palko, Heather A.; Malfatti, Mike; Smith, Catherine; Sonnett, James; Doktycz, Mitchel J.; Gu, Baohua; Roeder, Ryan K.; Wang, Wei; Retterer, Scott T.

    2015-04-01

    Nanomaterial based drug delivery systems allow for the independent tuning of the surface chemical and physical properties that affect their biodistribution in vivo and the therapeutic payloads that they are intended to deliver. Additionally, the added therapeutic and diagnostic value of their inherent material properties often provides extra functionality. Iron based nanomaterials with their magnetic properties and easily tailorable surface chemistry are of particular interest as model systems. In this study the core radius of the iron oxide nanoparticles (NPs) was 14.08 +/- 3.92 nm while the hydrodynamic radius of the NPs, as determined by Dynamic Light Scattering (DLS), was between 90-110 nm. In this study, different approaches were explored to create radiolabeled NPs that are stable in solution. The NPs were functionalized with polycarboxylate or polyamine surface functional groups. Polycarboxylate functionalized NPs had a zeta potential of -35 mV and polyamine functionalized NPs had a zeta potential of +40 mV. The polycarboxylate functionalized NPs were chosen for in vivo biodistribution studies and hence were radiolabeled with 14C, with a final activity of 0.097 nCi mg-1 of NPs. In chronic studies, the biodistribution profile is tracked using low level radiolabeled proxies of the nanoparticles of interest. Conventionally, these radiolabeled proxies are chemically similar but not chemically identical to the non-radiolabeled NPs of interest. This study is novel as different approaches were explored to create radiolabeled NPs that are stable, possess a hydrodynamic radius of <100 nm and most importantly they exhibit an identical surface chemical functionality as their non-radiolabeled counterparts. Identical chemical functionality of the radiolabeled probes to the non-radiolabeled probes was an important consideration to generate statistically similar biodistribution data sets using multiple imaging and detection techniques. The radiolabeling approach described

  14. Protective efficacy of the chimeric Staphylococcus aureus vaccine candidate IC in sepsis and pneumonia models

    PubMed Central

    Yang, Liuyang; Cai, Changzhi; Feng, Qiang; Shi, Yun; Zuo, Qianfei; Yang, Huijie; Jing, Haiming; Wei, Chao; Zhuang, Yuan; Zou, Quanming; Zeng, Hao

    2016-01-01

    Staphylococcus aureus causes serious sepsis and necrotic pneumonia worldwide. Due to the spread of multidrug-resistant strains, developing an effective vaccine is the most promising method for combating S. aureus infection. In this study, based on the immune-dominant areas of the iron surface determinant B (IsdB) and clumping factor A (ClfA), we designed the novel chimeric vaccine IsdB151-277ClfA33-213 (IC). IC formulated with the AlPO4 adjuvant induced higher protection in an S. aureus sepsis model compared with the single components alone and showed broad immune protection against several clinical S. aureus isolates. Immunisation with IC induced strong antibody responses. The protective effect of antibodies was demonstrated through the opsonophagocytic assay (OPA) and passive immunisation experiment. Moreover, this new chimeric vaccine induced Th1/Th17-skewed cellular immune responses based on cytokine profiles and CD4+ T cell stimulation tests. Neutralisation of IL-17A alone (but not IFN-γ) resulted in a significant decrease in vaccine immune protection. Finally, we found that IC showed protective efficacy in a pneumonia model. Taken together, these data provide evidence that IC is a potentially promising vaccine candidate for combating S. aureus sepsis and pneumonia. PMID:26865417

  15. Toxicity of bare and surfaced functionalized iron oxide nanoparticles towards microalgae.

    PubMed

    Toh, Pey Yi; Tai, Wan Yii; Ahmad, Abdul Latif; Lim, Jit Kang; Chan, Derek Juinn Chieh

    2016-06-01

    This study investigates the toxicity of bare iron oxide nanoparticles (IONPs) and surface functionalization iron oxide nanoparticles (SF-IONPs) to the growth of freshwater microalgae Chlorella sp. This study is important due to the increased interest on the application of the magnetic responsive IONPs in various fields, such as biomedical, wastewater treatment, and microalgae harvesting. This study demonstrated that the toxicity of IONPs was mainly contributed by the indirect light shading effect from the suspending nanoparticles which is nanoparticles concentration-dependent, direct light shading effect caused by the attachment of IONPs on cell and the cell aggregation, and the oxidative stress from the internalization of IONPs into the cells. The results showed that the layer of poly(diallyldimethylammonium chloride) (PDDA) tended to mask the IONPs and hence eliminated oxidative stress toward the protein yield but it in turn tended to enhance the toxicity of IONPs by enabling the IONPs to attach on cell surfaces and cause cell aggregation. Therefore, the choice of the polymer that used for surface functionalize the IONPs is the key factor to determine the toxicity of the IONPs. PMID:26389846

  16. High-temperature superconductivity from fine-tuning of Fermi-surface singularities in iron oxypnictides

    NASA Astrophysics Data System (ADS)

    Charnukha, Aliaksei

    2015-03-01

    In the family of iron-based superconductors, 1111-type materials exhibit superconductivity with the highest transition temperature Tc=55K. Early theoretical predictions of their electronic structure revealed multiple large circular sheets of the Fermi surface. Here we use ARPES to show that two prototypical compounds of the 1111 type are at odds with this description. Their low-energy band structure is formed by the edges of several bands, which are pulled to the Fermi level from the depths of the theoretically predicted band structure by strong electronic interactions. We further demonstrate that although their low-energy electronic looks remarkably similar, the Tc differs by a factor of 2. Upon closer examination we uncover that one of the bands in the higher-Tc compound sinks to 2.3meV below the Fermi level and thus does not produce a Fermi surface. And yet we find that it hosts a superconducting energy gap 10x larger than the same band in the lower-Tc sister compound. Our results show that the Fermi-surface singularities in the iron-oxypnictides dramatically affect their low-energy electronic properties, including superconductivity, and must therefore be explicitly taken into account in any attempt to understand the pairing mechanism.

  17. Corrosion behavior of surface films on boron-implanted high purity iron and stainless steels

    NASA Technical Reports Server (NTRS)

    Kim, H. J.; Carter, W. B.; Hochman, R. F.; Meletis, E. I.

    1985-01-01

    Boron (dose, 2 x 10 to the 17th ions/sq cm) was implanted into high purity iron, AISI 316 austenitic stainless steel, and AISI 440C martensitic stainless steel, at 40 keV. The film structure of implanted samples was examined and characterized by contrast and diffraction analyses utilizing transmission electron microscopy. The effect of B(+) ion implantation on the corrosion behavior was studied using the potentiodynamic polarization technique. Tests were performed in deaerated 1 N H2SO4 and 0.1 M NaCl solutions. Scanning electron microscopy was used to examine the morphology of the corroded surfaces after testing.

  18. Surface chemical heterogeneity of bacteriogenic iron oxides from a subterranean environment.

    PubMed

    Martinez, Raul E; Smith, D Scott; Pedersen, Karsten; Ferris, F Grant

    2003-12-15

    This study quantifies the surface chemical heterogeneity of bacteriogenic iron oxides (BIOS) and its end-members (2-line ferrihydrite and intermixed intact and fragmented bacteria). On a dry weight basis, BIOS consisted of 64.5 +/- 1.8% ferrihydrite and 34.5 +/- 1.8% organic matter. Enrichment of Al, Cu, Cr, Mn, Sr, and Zn was shown in the solid versus the aqueous phase (1.9 < log Kd < 4.2). Within the solid-phase Al (69.5%), Cu (78.7%), and Zn (77.9%) were associated with the bacteria, whereas Cr (59.8%), Mn (99.8%), and Sr (79.4%) preferred ferrihydrite. Acid-base titration data from the BIOS and bacteria were fitted using FOCUS pKa spectroscopy. The bacteria spectrum with pKa's of 4.18 +/- 0.37, 4.80 +/- 0.54, 6.98 +/- 0.45, and 9.75 +/- 0.68 was similar to discrete and continuous spectra for intact and fragmented bacteria. The BIOS spectrum recorded pKa's of 4.27 +/- 0.51, 6.61 +/- 0.51, 7.89 +/- 1.10, and 9.65 +/- 0.66 and was deconvoluted to remove overlapping binding site contributions from the bacteria. The resulting residual iron oxide spectrum coincided with discrete MUSIC spectra for goethite and lepidocrocite with pKa values of 4.10 +/- 0.43, 6.53 +/- 0.45, 7.81 +/- 0.76, and 9.51 +/- 0.68. Surface site density analysis showed that acidic sites (pKa < 6) were contributed by the bacteria (37%), whereas neutral sites (6 < pKa < 8) were characteristic of the iron oxide fraction (35%). Basic sites (8 < pKa) were higher in the bacteria (57%), than in the BIOS (44%) or iron oxide fractions (47%). This analysis suggested a high degree of bacterial group masking and a similarity between the BIOS and goethite surface reactivity. An understanding of the BIOS surface chemical heterogeneity and inherent proton and metal binding capacity was obtained through the use of FOCUS apparent pKa spectroscopy. PMID:14717179

  19. Effect of surface modification on magnetization of iron oxide nanoparticle colloids.

    PubMed

    Yuan, Yuan; Rende, Deniz; Altan, Cem Levent; Bucak, Seyda; Ozisik, Rahmi; Borca-Tasciuc, Diana-Andra

    2012-09-11

    Magnetic iron oxide nanoparticles have numerous applications in the biomedical field, some more mature, such as contrast agents in magnetic resonance imaging (MRI), and some emerging, such as heating agents in hyperthermia for cancer therapy. In all of these applications, the magnetic particles are coated with surfactants and polymers to enhance biocompatibility, prevent agglomeration, and add functionality. However, the coatings may interact with the surface atoms of the magnetic core and form a magnetically disordered layer, reducing the total amount of the magnetic phase, which is the key parameter in many applications. In the current study, amine and carboxyl functionalized and bare iron oxide nanoparticles, all suspended in water, were purchased and characterized. The presence of the coatings in commercial samples was verified with X-ray photoelectron spectroscopy (XPS). The class of iron oxide (magnetite) was verified via Raman spectroscopy and X-ray diffraction. In addition to these, in-house prepared iron oxide nanoparticles coated with oleic acid and suspended in heptane and hexane were also investigated. The saturation magnetization obtained from vibrating sample magnetometry (VSM) measurements was used to determine the effective concentration of magnetic phase in all samples. The Tiron chelation test was then utilized to check the real concentration of the iron oxide in the suspension. The difference between the concentration results from VSM and the Tiron test confirmed the reduction of magnetic phase of magnetic core in the presence of coatings and different suspension media. For the biocompatible coatings, the largest reduction was experienced by amine particles, where the ratio of the effective weight of magnetic phase reported to the real weight was 0.5. Carboxyl-coated samples experienced smaller reduction with a ratio of 0.64. Uncoated sample also exhibits a reduction with a ratio of 0.6. Oleic acid covered samples show a solvent

  20. Producing ultra-thin silica coatings on iron-oxide nanoparticles to improve their surface reactivity

    NASA Astrophysics Data System (ADS)

    Kralj, Slavko; Makovec, Darko; Čampelj, Stanislav; Drofenik, Miha

    2010-07-01

    The reactivity of the relatively inert surfaces of iron-oxide magnetic nanoparticles can be significantly improved by coating the surfaces with silica. Unfortunately, however, this nonmagnetic silica layer tends to dilute the magnetic properties of the nanoparticles. Therefore, the silica layer should be as continuous, homogeneous, and as thin as possible. In this investigation we coated superparamagnetic maghemite nanoparticles by hydrolysis and the polycondensation of tetraethyl orthosilicate (TEOS), with the ethanol solution of TEOS being added to a stable suspension of citric acid-coated nanoparticles. The influences of the various parameters of the procedure on the quality of the coatings were systematically evaluated. The quality of the silica layer was characterized using electron microscopy and by performing leaching of the nanoparticles in HCl, while the surface reactivity was tested by grafting (3-aminopropyl) triethoxysilane (APS) onto the nanoparticles. We observed that the surface concentration of the grafted APS strongly increased when the nanoparticles were coated with a silica layer. The choice of experimental conditions for the coating procedure that favors the heterogeneous nucleation of silica on the surfaces of the nanoparticles enabled the preparation of very thin silica layers, less than 2 nm thick. By decreasing the amount of added TEOS to correspond to a monolayer of -Si-OH at the nanoparticles' surfaces, their surface reactivity could be very much improved, and with a reduction in their magnetization of only ˜10%.

  1. The Heme Sensor System of Staphylococcus aureus

    PubMed Central

    Stauff, Devin L.; Skaar, Eric P.

    2016-01-01

    The important human pathogen Staphylococcus aureus is able to satisfy its nutrient iron requirement by acquiring heme from host hemoglobin in the context of infection. However, heme acquisition exposes S. aureus to heme toxicity. In order to detect the presence of toxic levels of exogenous heme, S. aureus is able to sense heme through the heme sensing system (HssRS) two-component system. Upon sensing heme, HssRS directly regulates the expression of the heme-regulated ABC transporter HrtAB, which alleviates heme toxicity. Importantly, the inability to sense or respond to heme alters the virulence of S. aureus, highlighting the importance of heme sensing and detoxification to staphylococcal pathogenesis. Furthermore, potential orthologues of the Hss and Hrt systems are found in many species of Gram-positive bacteria, a possible indication that heme stress is a challenge faced by bacteria whose habitats include host tissues rich in heme. PMID:19494582

  2. The development of a new three-step protocol to determine the efficacy of disinfectant wipes on surfaces contaminated with Staphylococcus aureus.

    PubMed

    Williams, G J; Denyer, S P; Hosein, I K; Hill, D W; Maillard, J-Y

    2007-12-01

    We developed a three-step protocol to quantify the efficacy of disinfectant wipes, their ability to remove and prevent microbial transfer from surfaces and their overall antimicrobial activity. Meticillin-resistant (MRSA) or -susceptible (MSSA) Staphylococcus aureus (6-7 log(10)cfu) were inoculated onto stainless steel discs with or without organic load and dried. Grapefruit extract-containing test wipes and unmedicated control wipes were used. In step 1, wipes were mechanically rotated against surfaces for 10s at 60rpm, exerting a weight of 100+/-5g. Bacterial removal was assessed by transferring the steel discs to neutraliser, resuspending and counting remaining bacteria. In step 2, bacterial transfer from wipes was assessed by eight consecutive mechanical adpression transfers to agar/neutraliser plates. Step 3 was the measurement of antimicrobial activity by direct inoculation of the wipes for 10s followed by neutralisation and enumeration. Test wipes achieved a significantly higher bacterial cell removal than control wipes on all surfaces (P<0.05). The low bactericidal activity of the wipes (<1 log(10) reduction when directly inoculated) and the subsequent survival of bacteria on the wipes, however, led to repeated microbial transfer when initially high contamination levels were present. There were no differences between MRSA and MSSA in removal, transfer or antimicrobial activity. The three-step method is a useful tool for developing future guidelines to assess the ability of wipes to disinfect surfaces. PMID:17945392

  3. Adsorption of antimony onto iron oxyhydroxides: adsorption behavior and surface structure.

    PubMed

    Guo, Xuejun; Wu, Zhijun; He, Mengchang; Meng, Xiaoguang; Jin, Xin; Qiu, Nan; Zhang, Jing

    2014-07-15

    Antimony is detected in soil and water with elevated concentration due to a variety of industrial applications and mining activities. Though antimony is classified as a pollutant of priority interest by the United States Environmental Protection Agency (USEPA) and Europe Union (EU), very little is known about its environmental behavior and adsorption mechanism. In this study, the adsorption behaviors and surface structure of antimony (III/V) on iron oxides were investigated using batch adsorption techniques, surface complexation modeling (SCM), X-ray photon spectroscopy (XPS) and extended X-ray absorption fine structure spectroscopy (EXAFS). The adsorption isotherms and edges indicated that the affinity of Sb(V) and Sb(III) toward the iron oxides depended on the Sb species, solution pH, and the characteristics of iron oxides. Sb(V) adsorption was favored at acidic pH and decreased dramatically with increasing pH, while Sb(III) adsorption was constant over a broad pH range. When pH is higher than 7, Sb(III) adsorption by goethite and hydrous ferric oxide (HFO) was greater than Sb(V). EXAFS analysis indicated that the majority of Sb(III), either adsorbed onto HFO or co-precipitated by FeCl3, was oxidized into Sb(V) probably due to the involvement of O2 in the long duration of sample preservation. Only one Sb-Fe subshell was filtered in the EXAFS spectra of antimony adsorption onto HFO, with the coordination number of 1.0-1.9 attributed to bidentate mononuclear edge-sharing ((2)E) between Sb and HFO. PMID:24910911

  4. Electron transfer during selenium reduction by iron surfaces in aqueous solution: High resolution X-ray absorption study

    NASA Astrophysics Data System (ADS)

    Kvashnina, K. O.; Butorin, S. M.; Cui, D.; Vegelius, J.; Puranen, A.; Gens, R.; Glatzel, P.

    2009-11-01

    We present a study of selenate (SeO42-) on an iron surface in ground water solution by X-ray absorption near-edge spectroscopy. Spectral sharpening is obtained by using the high energy resolution fluorescence detection technique that also efficiently suppresses the strong fluorescence signal from the Fe surface in the highly dilute samples (Se concentration < 3 ppm). We observe fully reduced Se on polished Fe surfaces while no changes are found for Se on oxidized Fe surface.

  5. The Role of Iron-Bearing Minerals in NO2 to HONO Conversion on Soil Surfaces.

    PubMed

    Kebede, Mulu A; Bish, David L; Losovyj, Yaroslav; Engelhard, Mark H; Raff, Jonathan D

    2016-08-16

    Nitrous acid (HONO) accumulates in the nocturnal boundary layer where it is an important source of daytime hydroxyl radicals. Although there is clear evidence for the involvement of heterogeneous reactions of NO2 on surfaces as a source of HONO, mechanisms remain poorly understood. We used coated-wall flow tube measurements of NO2 reactivity on environmentally relevant surfaces (Fe (hydr)oxides, clay minerals, and soil from Arizona and the Saharan Desert) and detailed mineralogical characterization of substrates to show that reduction of NO2 by Fe-bearing minerals in soil can be a more important source of HONO than the putative NO2 hydrolysis mechanism. The magnitude of NO2-to-HONO conversion depends on the amount of Fe(2+) present in substrates and soil surface acidity. Studies examining the dependence of HONO flux on substrate pH revealed that HONO is formed at soil pH < 5 from the reaction between NO2 and Fe(2+)(aq) present in thin films of water coating the surface, whereas in the range of pH 5-8 HONO stems from reaction of NO2 with structural iron or surface complexed Fe(2+) followed by protonation of nitrite via surface Fe-OH2(+) groups. Reduction of NO2 on ubiquitous Fe-bearing minerals in soil may explain HONO accumulation in the nocturnal boundary layer and the enhanced [HONO]/[NO2] ratios observed during dust storms in urban areas. PMID:27409359

  6. The role of SO42- surface distribution in arsenic removal by iron oxy-hydroxides

    NASA Astrophysics Data System (ADS)

    Tresintsi, S.; Simeonidis, K.; Pliatsikas, N.; Vourlias, G.; Patsalas, P.; Mitrakas, M.

    2014-05-01

    This study investigates the contribution of chemisorbed SO42- in improving arsenic removal properties of iron oxy-hydroxides through an ion-exchange mechanism. An analytical methodology was developed for the accurate quantification of sulfate ion (SO42-) distribution onto the surface and structural compartments of iron oxy-hydroxides synthesized by FeSO4 precipitation. The procedure is based on the sequential determination of SO42- presence in the diffuse and Stern layers, and the structure of these materials as defined by the sulfate-rich environments during the reaction and the variation in acidity (pH 3-12). Physically sorbed SO42-, extracted in distilled water, and physically/chemically adsorbed ions on the oxy-hydroxide's surface leached by a 5 mM NaOH solution, were determined using ion chromatography. Total sulfate content was gravimetrically measured by precipitation as BaSO4. To validate the suggested method, results were verified by X-ray photoelectron and Fourier-transformed infrared spectroscopy. Results showed that low precipitation pH-values favor the incorporation of sulfate ions into the structure and the inner double layer, while under alkaline conditions ions shift to the diffuse layer.

  7. Impact of an Environmental Cleaning Intervention on the Presence of Methicillin-Resistant Staphylococcus aureus and Vancomycin-Resistant Enterococci on Surfaces in Intensive Care Unit Rooms

    PubMed Central

    Goodman, Eric R.; Platt, Richard; Bass, Richard; Onderdonk, Andrew B.; Yokoe, Deborah S.; Huang, Susan S.

    2009-01-01

    OBJECTIVES To evaluate the adequacy of discharge room cleaning and the impact of a cleaning intervention on the presence of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) on environmental surfaces in intensive care unit (ICU) rooms. DESIGN Prospective environmental study. SETTING AND SAMPLE Convenience sample of ICU rooms in an academic hospital. METHODS AND INTERVENTION The intervention consisted of (1) a change from the use of pour bottles to bucket immersion for applying disinfectant to cleaning cloths, (2) an educational campaign, and (3) feedback regarding adequacy of discharge cleaning. Cleaning of 15 surfaces was evaluated by inspecting for removal of a preapplied mark, visible only with an ultraviolet lamp (“black light”). Six surfaces were cultured for MRSA or VRE contamination. Outcomes of mark removal and culture positivity were evaluated by χ2 testing and generalized linear mixed models, clustering by room. RESULTS The black-light mark was removed from 44% of surfaces at baseline, compared with 71% during the intervention (P <.001). The intervention increased the likelihood of removal of black-light marks after discharge cleaning (odds ratio, 4.4; P < .001), controlling for ICU type (medical vs surgical) and type of surface. The intervention reduced the likelihood of an environmental culture positive for MRSA or VRE (proportion of cultures positive, 45% at baseline vs 27% during the intervention; adjusted odds ratio, 0.4; P = .02). Broad, flat surfaces were more likely to be cleaned than were doorknobs and sink or toilet handles. CONCLUSIONS Increasing the volume of disinfectant applied to environmental surfaces, providing education for Environmental Services staff, and instituting feedback with a black-light marker improved cleaning and reduced the frequency of MRSA and VRE contamination. PMID:18624666

  8. Reflectance spectroscopy of palagonite and iron-rich montmorillonite clay mixtures: Implications for the surface composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, J. B.; Handy, J.

    1991-01-01

    Because of the power of remote sensing reflectance spectroscopy in determining mineralogy, it was used as the major method of identifying possible mineral analogs of the Martian surface. A summary of proposed Martian surface compositions from reflectance spectroscopy before 1979 was presented. Since that time, iron-rich montmorillonite clay, nanocrystalline or nanophase hematite, and palagonite were suggested as Mars soil analog materials.

  9. Effects of surface condition on aqueous corrosion and environmental embrittlement of iron aluminides

    SciTech Connect

    Perrin, R.L.; Buchanan, R.A.

    1996-08-01

    Effects of retained high-temperature surface oxides, produced during thermomechanical processing and/or heat treatment, on the aqueous-corrosion and environmental-embrittlement characteristics of Fe{sub 3}Al-based iron aluminides (FA-84, FA-129 and FAL-Mo), a FeAl-based iron aluminide (FA-385), and a disordered low-aluminum Fe-Al alloy (FAPY) were evaluated. All tests were conducted at room temperature in a mild acid-chloride solution. In cyclic-anodic-polarization testing for aqueous-corrosion behavior, the surface conditions examined were: as-received (i.e., with the retained high-temperature oxides), mechanically cleaned and chemically cleaned. For all materials, the polarization tests showed the critical pitting potentials to be significantly lower in the as-received condition than in the mechanically-cleaned and chemically-cleaned conditions. These results indicate detrimental effects of the retained high-temperature oxides in terms of increased susceptibilities to localized corrosion. In 200-hour U-bend stress-corrosion-cracking tests for environmental-embrittlement behavior, conducted at open-circuit corrosion potentials and at a hydrogen-charging potential of {minus}1500 mV (SHE), the above materials (except FA-385) were examined with retained oxides and with mechanically cleaned surfaces. At the open-circuit corrosion potentials, none of the materials in either surface condition underwent cracking. At the hydrogen-charging potential, none of the materials with retained oxides underwent cracking, but FA-84, FA-129 and FAL-Mo in the mechanically cleaned condition did undergo cracking. These results suggest beneficial effects of the retained high-temperature oxides in terms of increased resistance to environmental hydrogen embrittlement.

  10. Triclosan promotes Staphylococcus aureus nasal colonization.

    PubMed

    Syed, Adnan K; Ghosh, Sudeshna; Love, Nancy G; Boles, Blaise R

    2014-01-01

    The biocide triclosan is used in many personal care products, including toothpastes, soaps, clothing, and medical equipment. Consequently, it is present as a contaminant in the environment and has been detected in some human fluids, including serum, urine, and milk. Staphylococcus aureus is an opportunistic pathogen that colonizes the noses and throats of approximately 30% of the population. Colonization with S. aureus is known to be a risk factor for several types of infection. Here we demonstrate that triclosan is commonly found in the nasal secretions of healthy adults and the presence of triclosan trends positively with nasal colonization by S. aureus. We demonstrate that triclosan can promote the binding of S. aureus to host proteins such as collagen, fibronectin, and keratin, as well as inanimate surfaces such as plastic and glass. Lastly, triclosan-exposed rats are more susceptible to nasal colonization with S. aureus. These data reveal a novel factor that influences the ability of S. aureus to bind surfaces and alters S. aureus nasal colonization. IMPORTANCE Triclosan has been used as a biocide for over 40 years, but the broader effects that it has on the human microbiome have not been investigated. We demonstrate that triclosan is present in nasal secretions of a large portion of a test population and its presence correlates with Staphylococcus aureus nasal colonization. Triclosan also promotes the binding of S. aureus to human proteins and increases the susceptibility of rats to nasal colonization by S. aureus. These findings are significant because S. aureus colonization is a known risk factor for the development of several types of infections. Our data demonstrate the unintended consequences of unregulated triclosan use and contribute to the growing body of research demonstrating inadvertent effects of triclosan on the environment and human health. PMID:24713325

  11. Methicillin-resistant Staphylococcus aureus (MRSA) contamination in bedside surfaces of a hospital ward and the potential effectiveness of enhanced disinfection with an antimicrobial polymer surfactant.

    PubMed

    Yuen, John W M; Chung, Terence W K; Loke, Alice Y

    2015-03-01

    The aim in this study was to assess the effectiveness of a quaternary ammonium chloride (QAC) surfactant in reducing surface staphylococcal contamination in a routinely operating medical ward occupied by patients who had tested positive for methicillin-resistant Staphylococcus aureus (MRSA). The QAC being tested is an antibacterial film that is sprayed onto a surface and can remain active for up to 8 h. A field experimental study was designed with the QAC plus daily hypochlorite cleaning as the experimental group and hypochlorite cleaning alone as the control group. The method of swabbing on moistened surfaces was used for sampling. It was found that 83% and 77% of the bedside surfaces of MRSA-positive and MRSA-negative patients respectively were contaminated with staphylococci at 08:00 hours, and that the staphylococcal concentrations increased by 80% at 1200 h over a 4-hour period with routine ward and clinical activities. Irrespective of the MRSA status of the patients, high-touch surfaces around the bed-units within the studied medical ward were heavily contaminated (ranged 1 to 276 cfu/cm2 amongst the sites with positive culture) with staphylococcal bacteria including MRSA, despite the implementation of daily hypochlorite wiping. However, the contamination rate dropped significantly from 78% to 11% after the application of the QAC polymer. In the experimental group, the mean staphylococcal concentration of bedside surfaces was significantly (p<0.0001) reduced from 4.4±8.7 cfu/cm2 at 08:00 hours to 0.07±0.26 cfu/cm2 at 12:00 hours by the QAC polymer. The results of this study support the view that, in addition to hypochlorite wiping, the tested QAC surfactant is a potential environmental decontamination strategy for preventing the transmission of clinically important pathogens in medical wards. PMID:25768241

  12. Persistent Staphylococcus aureus Isolates from Two Independent Cases of Bacteremia Display Increased Bacterial Fitness and Novel Immune Evasion Phenotypes

    PubMed Central

    Richards, R. L.; Haigh, R. D.; Pascoe, B.; Sheppard, S. K.; Price, F.; Jenkins, D.; Rajakumar, K.

    2015-01-01

    Staphylococcus aureus bacteremia cases are complicated by bacterial persistence and treatment failure despite the confirmed in vitro susceptibility of the infecting strain to administered antibiotics. A high incidence of methicillin-resistant S. aureus (MRSA) bacteremia cases are classified as persistent and are associated with poorer patient outcomes. It is still unclear how S. aureus evades the host immune system and resists antibiotic treatment for the prolonged duration of a persistent infection. In this study, the genetic changes and associated phenotypic traits specific to S. aureus persistent bacteremia were identified by comparing temporally dispersed isolates from persistent infections (persistent isolates) originating from two independent persistent S. aureus bacteremia cases with the initial infection isolates and with three resolved S. aureus bacteremia isolates from the same genetic background. Several novel traits were associated specifically with both independent sets of persistent S. aureus isolates compared to both the initial isolates and the isolates from resolved infections (resolved isolates). These traits included (i) increased growth under nutrient-poor conditions; (ii) increased tolerance of iron toxicity; (iii) higher expression of cell surface proteins involved in immune evasion and stress responses; and (iv) attenuated virulence in a Galleria mellonella larva infection model that was not associated with small-colony variation or metabolic dormancy such as had been seen previously. Whole-genome sequence analysis identified different single nucleotide mutations within the mprF genes of all the isolates with the adaptive persistence traits from both independent cases. Overall, our data indicate a novel role for MprF function during development of S. aureus persistence by increasing bacterial fitness and immune evasion. PMID:26056388

  13. Degradation of carbon tetrachloride by iron metal: Complexation effects on the oxide surface

    NASA Astrophysics Data System (ADS)

    Johnson, Timothy L.; Fish, William; Gorby, Yuri A.; Tratnyek, Paul G.

    1998-03-01

    Dehalogenation of chlorinated aliphatic contaminants at the surface of zero-valent iron metal (Fe 0) is mediated by the thin film of iron (hydr)oxides found on Fe 0 under environmental conditions. To evaluate the role this oxide film plays in the reduction of chlorinated methanes, carbon tetrachloride (CCl 4) degradation by Fe 0 was studied under the influence of various anions, ligands, and initial CCl 4 concentrations ([ P] o). Over the range of conditions examined in these batch experiments, the reaction kinetics could be characterized by surface-area-normalized rate constants that were pseudo-first order for CCl 4 disappearance ( kCCl 4), and zero order for the appearance of dissolved Fe 2+ ( kFe 2+). The rate of dechlorination exhibits saturation kinetics with respect to [ P] o, suggesting that CCl 4 is transformed at a limited number of reactive surface sites. Because oxidation of Fe 0 by CCl 4 is the major corrosion reaction in these systems, kFe 2+ also approaches a limiting value at high CCl 4 concentrations. The adsorption of borate strongly inhibited reduction of CCl 4, but a concomitant addition of chloride partially offset this effect by destabilizing the film. Redox active ligands (catechol and ascorbate), and those that are not redox active (EDTA and acetate), all decreased kCCl 4 (and kFe 2+). Thus, it appears that the relatively strong complexation of these ligands at the oxide-electrolyte interface blocks the sites where weak interactions with the metal oxide lead to dehalogenation of chlorinated aliphatic compounds.

  14. Correlation between surface physicochemical properties and the release of iron from stainless steel AISI 304 in biological media.

    PubMed

    Hedberg, Yolanda; Karlsson, Maria-Elisa; Blomberg, Eva; Odnevall Wallinder, Inger; Hedberg, Jonas

    2014-10-01

    Stainless steel is widely used in biological environments, for example as implant material or in food applications, where adsorption-controlled ligand-induced metal release is of importance from a corrosion, health, and food safety perspective. The objective of this study was to elucidate potential correlations between surface energy and wettability of stainless steel surfaces and the release of iron in complexing biological media. This was accomplished by studying changes in surface energies calculated from contact angle measurements, surface oxide composition (X-ray photoelectron spectroscopy), and released iron (graphite furnace atomic absorption spectroscopy) for stainless steel grade AISI 304 immersed in fluids containing bovine serum albumin or citric acid, and non-complexing fluids such as NaCl, NaOH, and HNO3. It was shown that the surface wettability and polar surface energy components were all influenced by adventitious atmospheric carbon (surface contamination of low molecular weight), rather than differences in surface oxide composition in non-complexing solutions. Adsorption of both BSA and citrate, which resulted in ligand-induced metal release, strongly influenced the wettability and the surface energy, and correlated well with the measured released amount of iron. PMID:25048358

  15. Surface-enhanced resonance Raman spectroscopy of iron-dopamine complexes

    NASA Astrophysics Data System (ADS)

    Kowalchyk, Will K.; Davis, Kevin L.; Morris, Michael D.

    1995-01-01

    Surface-enhanced resonance Raman spectroscopy (SERRS) at silver colloids is used to detect the catecholamines, 3-hydroxytyramine (dopamine) and 3,4-dihydroxyphenylacetic acid (DOPAC), in a modified Ringer's solution. Catecholamines form very strong complexes with iron(III) in solution ( Kf > 10 40) and exhibit a broad ligand-to-metal charge-transfer (LMCT) absorption in the visible (˜ 500 nm). Resonance enhancement is achieved by excitation at 532 nm from a frequency doubled Nd:YAG laser with high quality spectra attainable in 1 s. Maximum SERRS signal is observed when basic buffer is added to a dopamine sample containing 50 × 10 -6 M ferric ion. Dopamine concentrations in the nanomolar (resting level) range are obtained using this technique.

  16. Superhydrophobic surface fabricated on iron substrate by black chromium electrodeposition and its corrosion resistance property

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Feng, Haitao; Lin, Feng; Wang, Yabin; Wang, Liping; Dong, Yaping; Li, Wu

    2016-08-01

    The fabrication of superhydrophobic surface on iron substrate is carried out through 20 min black chromium electrodeposition, followed by immersing in 0.05 M ethanolic stearic acid solution for 12 h. The resultant superhydrophobic complex film is characterized by scanning electron microscope (SEM), disperse Spectrometer (EDS), atomic force microscope (AFM), water contact angle (CA), sliding angle (SA) and X-ray photoelectron spectroscope (XPS), and its corrosion resistance property is measured with cyclic voltammetry (CV), linear polarization and electrochemical impedance spectroscopy (EIS). The results show that the fabricated superhydrophobic film has excellent water repellency (CA, 158.8°; SA, 2.1°) and significantly high corrosion resistance (1.31 × 106 Ω cm-2) and excellent corrosion protection efficiency (99.94%).

  17. Surface Gasification Materials Program: Semiannual progress report for the period ending September 30, 1986. [Iron aluminide

    SciTech Connect

    Not Available

    1987-01-01

    The objective of the Surface Gasification Materials Program is to conduct research and development on materials for application to the specific needs of coal gasification systems. One of the goals of the program is to evaluate innovative fabrication methods which have the potential to lower costs and improve reliability and safety for gasifier vessels and components. Another goal is to conduct engineering-scale development and application of materials for coal gasification systems to ensure that the materials of construction for pilot plants and future large-scale plants can be properly selected and specified. This semiannual progress report covers: (1) protective coatings and claddings - application/evaluation; (2) electroslag component casting; (3) materials development for solid oxide oxygen production unit; and (4) development of iron aluminides.

  18. Determination of copper, scandium, molybdenum, tin, lead, and iron group elements in lunar surface materials

    NASA Technical Reports Server (NTRS)

    Pavlenko, L. I.; Simonova, L. V.; Karyakin, A. V.

    1974-01-01

    Distribution regularities of copper, scandium, molybdenum, tin, lead, and iron group elements were investigated in basaltoid rocks of lunar and terrestrial origin. Samples of various regolith zones taken in the area of the Sea of Fertility were analyzed, along with samples of basic and ultrabasic rocks of the East African Rift for their content of the trace admixtures listed. Data obtained on the abundance of copper, scandium, molybdenum, tin, lead, cobalt, nickel, chromium, and vanadium in Luna 16 lunar surface material were compared with the abundance of these elements in samples of lunar rocks returned by Apollo 11, Apollo 12, and Apollo 14, with the exception of scandium; its content in the latter samples was considerably higher.

  19. New Surface Radiolabeling Schemes of Super Paramagnetic Iron Oxide Nanoparticles (SPIONs) for Biodistribution Studies

    DOE PAGESBeta

    Nallathamby, Prakash D.; Mortensen, Ninell P.; Palko, Heather A.; Malfatti, Mike; Smith, Catherine; Sonnett, Jim; Doktycz, Mitchel John; Gu, Baohua; Roeder, Ryan; Wang, Wei; et al

    2015-01-01

    Nanomaterial based drug delivery systems allow for the independent tuning of the surface chemical and physical properties that affect their biodistribution in vivo and the therapeutic payloads that they are intended to deliver. Additionally, the added therapeutic and diagnostic value of their inherent material properties often provides extra functionality. Iron based nanomaterials with their magnetic properties and 10 easily tailorable surface chemistry are of particular interest as model systems. In this study the core radius of the iron oxide nanoparticles (NPs) was 14.08 3.92 nm while the hydrodynamic radius of the NPs, as determined by Dynamic Light Scattering (DLS), wasmore » between 90 110 nm. In this study, different approaches were explored to create radiolabeled NPs that are stable in solution. The NPs were functionalized with polycarboxylate or polyamine surface functional groups. Polycarboxylate 15 functionalized NPs had a zeta potential of -35 mV and polyamine functionalized NPs had a zeta potential of +40 mV. The polycarboxylate functionalized NPs were chosen for in vivo biodistribution studies and hence were radiolabeled with 14C, with a final activity of 0.097 nCi/mg-1 of NPs. In chronic studies, the biodistribution profile is tracked using low level radiolabeled proxies of the nanoparticles of interest. Conventionally, these radiolabeled proxies are chemically similar but not chemically identical to the non-20 radiolabeled NPs of interest. This study is novel as different approaches were explored to create radiolabeled NPs that are stable, possess a hydrodynamic radius of <100 nm and most importantly they exhibit an identical surface chemical functionality as their non-radiolabeled counterparts. Identical chemical functionality of the radiolabeled probes to the non-radiolabeled probes was an important consideration to generate statistically similar biodistribution data sets using multiple imaging and 25 detection techniques. The radiolabeling

  20. New Surface Radiolabeling Schemes of Super Paramagnetic Iron Oxide Nanoparticles (SPIONs) for Biodistribution Studies

    SciTech Connect

    Nallathamby, Prakash D.; Mortensen, Ninell P.; Palko, Heather A.; Malfatti, Mike; Smith, Catherine; Sonnett, Jim; Doktycz, Mitchel John; Gu, Baohua; Roeder, Ryan; Wang, Wei; Retterer, Scott T.

    2015-01-01

    Nanomaterial based drug delivery systems allow for the independent tuning of the surface chemical and physical properties that affect their biodistribution in vivo and the therapeutic payloads that they are intended to deliver. Additionally, the added therapeutic and diagnostic value of their inherent material properties often provides extra functionality. Iron based nanomaterials with their magnetic properties and 10 easily tailorable surface chemistry are of particular interest as model systems. In this study the core radius of the iron oxide nanoparticles (NPs) was 14.08 3.92 nm while the hydrodynamic radius of the NPs, as determined by Dynamic Light Scattering (DLS), was between 90 110 nm. In this study, different approaches were explored to create radiolabeled NPs that are stable in solution. The NPs were functionalized with polycarboxylate or polyamine surface functional groups. Polycarboxylate 15 functionalized NPs had a zeta potential of -35 mV and polyamine functionalized NPs had a zeta potential of +40 mV. The polycarboxylate functionalized NPs were chosen for in vivo biodistribution studies and hence were radiolabeled with 14C, with a final activity of 0.097 nCi/mg-1 of NPs. In chronic studies, the biodistribution profile is tracked using low level radiolabeled proxies of the nanoparticles of interest. Conventionally, these radiolabeled proxies are chemically similar but not chemically identical to the non-20 radiolabeled NPs of interest. This study is novel as different approaches were explored to create radiolabeled NPs that are stable, possess a hydrodynamic radius of <100 nm and most importantly they exhibit an identical surface chemical functionality as their non-radiolabeled counterparts. Identical chemical functionality of the radiolabeled probes to the non-radiolabeled probes was an important consideration to generate statistically similar biodistribution data sets using multiple imaging and 25 detection techniques. The

  1. New surface radiolabeling schemes of super paramagnetic iron oxide nanoparticles (SPIONs) for biodistribution studies†

    PubMed Central

    Nallathamby, Prakash D.; Mortensen, Ninell P.; Palko, Heather A.; Malfatti, Mike; Smith, Catherine; Sonnett, James; Doktycz, Mitchel J.; Gu, Baohua; Roeder, Ryan K.; Wang, Wei; Retterer, Scott T.

    2016-01-01

    Nanomaterial based drug delivery systems allow for the independent tuning of the surface chemical and physical properties that affect their biodistribution in vivo and the therapeutic payloads that they are intended to deliver. Additionally, the added therapeutic and diagnostic value of their inherent material properties often provides extra functionality. Iron based nanomaterials with their magnetic properties and easily tailorable surface chemistry are of particular interest as model systems. In this study the core radius of the iron oxide nanoparticles (NPs) was 14.08 ± 3.92 nm while the hydrodynamic radius of the NPs, as determined by Dynamic Light Scattering (DLS), was between 90–110 nm. In this study, different approaches were explored to create radiolabeled NPs that are stable in solution. The NPs were functionalized with polycarboxylate or polyamine surface functional groups. Polycarboxylate functionalized NPs had a zeta potential of –35 mV and polyamine functionalized NPs had a zeta potential of +40 mV. The polycarboxylate functionalized NPs were chosen for in vivo biodistribution studies and hence were radiolabeled with 14C, with a final activity of 0.097 nCi mg–1 of NPs. In chronic studies, the biodistribution profile is tracked using low-level radiolabeled proxies of the nanoparticles of interest. Conventionally, these radiolabeled proxies are chemically similar but not chemically identical to the non-radiolabeled NPs of interest. This study is novel as different approaches were explored to create radiolabeled NPs that are stable, possess a hydrodynamic radius of <100 nm and most importantly they exhibit an identical surface chemical functionality as their non-radiolabeled counterparts. Identical chemical functionality of the radiolabeled probes to the non-radiolabeled probes was an important consideration to generate statistically similar biodistribution data sets using multiple imaging and detection techniques. The radiolabeling approach

  2. Effects of surface chemistry and size on iron oxide nanoparticle delivery of oligonucleotides

    NASA Astrophysics Data System (ADS)

    Shen, Christopher

    The discovery of RNA interference and the increasing understanding of disease genetics have created a new class of potential therapeutics based on oligonucleotides. This therapeutic class includes antisense molecules, small interfering RNA (siRNA), and microRNA modulators such as antagomirs (antisense directed against microRNA) and microRNA mimics, all of which function by altering gene expression at the translational level. While these molecules have the promise of treating a host of diseases from neurological disorders to cancer, a major hurdle is their inability to enter cells on their own, where they may render therapeutic effect. Nanotechnology is the engineering of materials at the nanometer scale and has gained significant interest for nucleic acid delivery due to its biologically relevant length-scale and amenability to multifunctionality. While a number of nanoparticle vehicles have shown promise for oligonucleotide delivery, there remains a lack of understanding of how nanoparticle coating and size affect these delivery processes. This dissertation seeks to elucidate some of these factors by evaluating oligonucleotide delivery efficiencies of a panel of iron oxide nanoparticles with varying cationic coatings and sizes. A panel of uniformly-sized nanoparticles was prepared with surface coatings comprised of various amine groups representing high and low pKas. A separate panel of nanoparticles with sizes of 40, 80, 150, and 200 nm but with the same cationic coating was also prepared. Results indicated that both nanoparticle surface coating and nanoparticle hydrodynamic size affect transfection efficiency. Specific particle coatings and sizes were identified that gave superior performance. The intracellular fate of iron oxide nanoparticles was also tracked by electron microscopy and suggests that they function via the proton sponge effect. The research presented in this dissertation may aid in the rational design of improved nanoparticle delivery vectors for

  3. Iron geochemistry in surface sediments of a temperate semi-enclosed bay, North China

    NASA Astrophysics Data System (ADS)

    Zhu, Mao-Xu; Huang, Xiang-Li; Yang, Gui-Peng; Chen, Liang-Jin

    2015-11-01

    Iron (Fe) speciation and microbial reducible Fe(III) oxides (MR-Fe(III)) in surface sediments of semi-enclosed Jiaozhou Bay were quantified to reveal Fe geochemistry in the settings subjected to anthropogenic perturbations. Results indicate that sedimentary Fe in the bay is mainly of natural weathering source, without appreciable anthropogenic Fe inputs, as indicated by a generally good linear coupling of total Fe to aluminum. Among the three highly reactive Fe(III) (Fe(III)HR) pools, well crystalline Fe(III) oxides (Fe(III)wc) were always the predominant phase, followed by poorly crystalline Fe(III) oxides (Fe(III)pc), and amorphous Fe(III) oxides (Fe(III)am) were only of minor importance. The dominance of non-sulfidized Fe(II) over sulfidized Fe in the sediments points to the importance of microbial iron(III) reduction (MIR) in the free sulfide-starved conditions. High riverine inputs of TOC leads to outliers in the Fe(III)HR versus total organic carbon (TOC) ratio compared the rest of the bay. OM-dependent MIR as the common driving force has rendered all Fe(II)-bearing phases linearly coupled to TOC. MR-Fe(III) in the surface sediments covered all Fe(III)am and a fraction of less reactive Fe(III) phases, while Fe(III)wc was at most a minor contributor. Highly reactive Fe appears to be enriched to some extent in the temperate semi-enclosed bay, as in the wet-tropical counterparts.

  4. Effect of surface condition on the aqueous corrosion behavior of iron aluminies

    SciTech Connect

    Buchanan, R.A.; Perrin, R.L.

    1995-08-01

    The effects of retained high-temperature surface oxides, produced during thermomechanical processing and/or heat treatment, on the aqueous-corrosion characteristics of Fe-Al-based alloys were evaluated by electrochemical methods. Cyclic anodic polarization evaluations were conducted at room temperature in a mild acid-chloride solution (pH = 4,200 ppm Cl{sup {minus}}) on the Fe{sub 3}Al-based iron aluminides, FA-84 (Fe-28Al-2Cr-0.05B, at %), FA-129 (Fe-28Al-5Cr-0.5Nb-0.2C, at %), and FAL-Mo (Fe-28Al-5Cr-1Mo-0.04B-0.08Zr, at %), on the FeAl-based iron aluminide, FA-385 (Fe-35.65Al-0.20Mo-0.05Zr-0.11C, at %). The surface conditions evaluated were: As received (i.e. with the retained high-temperature oxides), mechanically cleaned (ground through 600-grit SiC paper), and chemically cleaned (10% HNO{sub 3}, 2%HF, at 43 {degree}C). The principal electrochemical parameter of interest was the critical putting potential with lower values indicating less resistance to chloride-induced localized corrosion. For all materials evaluated, the critical pitting potential was found to be significantly lower in the as-received condition than in the mechanically-cleaned and chemically-cleaned conditions. Mechanisms responsible for the detrimental high-temperature-oxide effect are under study.

  5. Influence of phosphorus addition on the surface tension of liquid iron and segregation of phosphorus on the surface of Fe-P alloy

    SciTech Connect

    Xue, X.M.; Jiang, H.G.; Ding, B.Z.; Hu, Z.Q.; Sui, Z.T.

    1996-02-01

    This article presents a study of the surface tension and phosphorus surface segregation in Fe-P alloys. The surface tension was measured by the sessile drop technique. The result of the dynamic surface tension for the low phosphorus content alloys shows that the alloy surface vaporization has a clear effect on the surface tension and causes a positive surface tension temperature coefficient. However, from this article, it is evident that phosphorus in liquid iron acts as a surface active element similar to arsenic. The surface segregation was determined using Auger electron spectroscopy. The result on the surface analysis of as-solidified sample indicates that the adsorption of impurity elements, such as oxygen, carbon, and nitrogen, can conceal phosphorus segregation on the free surface. Phosphorus segregation was also examined in the samples as-cleaned by Ar{sup +} and then treated 30 minutes at 650 C. Phosphorus was found to segregate extensively on the surface of the alloys. On the basis of the analysis of the published data, the surface active intensity sequence of some nonmetallic elements was arrayed, and the surface active intensity of fluorine and boron in liquid iron was estimated.

  6. A Facile Surface Passivation of Hematite Photoanodes with Iron Titanate Cocatalyst for Enhanced Water Splitting.

    PubMed

    Wang, Lei; Nguyen, Nhat Truong; Schmuki, Patrik

    2016-08-23

    The surface modification of semiconductor photoelectrodes with passivation overlayers has attracted great attention as an effective strategy to improve the charge separation and charge transfer processes across the semiconductor-electrolyte interface. In this work, a thin Fe2 TiO5 layer was decorated on nanostructured hematite nanoflake and nanocoral photoanodes (by thermal oxidation of iron foils) by a facile water-based solution method. Photoelectrochemical measurements show that the Fe2 O3 /Fe2 TiO5 heterostructure exhibits an obvious enhancement in photoelectrochemical water oxidation performance compared to the pristine hematite. For example, at 1.23 V versus the reversible hydrogen electrode (VRHE ) in 1 m KOH under AM 1.5 G (100 mW cm(-2) ) illumination, a 4-8× increase in the water oxidation photocurrent is achieved for Fe2 O3 /Fe2 TiO5 , and a considerable cathodic shift of the onset potential up to 0.53-0.62 VRHE is obtained. Moreover, the performance of the Fe2 O3 /Fe2 TiO5 heterostructure can be further improved by decoration with a SnOx layer. The enhancement in photocurrent can be attributed to the synergistic effect of Fe2 TiO5 /SnOx overlayers passivating surface states, and thus reducing surface electron-hole recombination. PMID:27348809

  7. Research of polishing process to control the iron contamination on the magnetorheological finished KDP crystal surface.

    PubMed

    Chen, Shaoshan; Li, Shengyi; Peng, Xiaoqiang; Hu, Hao; Tie, Guipeng

    2015-02-20

    A new nonaqueous and abrasive-free magnetorheological finishing (MRF) method is adopted for processing a KDP crystal. MRF polishing is easy to result in the embedding of carbonyl iron (CI) powders; meanwhile, Fe contamination on the KDP crystal surface will affect the laser induced damage threshold seriously. This paper puts forward an appropriate MRF polishing process to avoid the embedding. Polishing results show that the embedding of CI powders can be avoided by controlling the polishing parameters. Furthermore, on the KDP crystal surface, magnetorheological fluids residua inevitably exist after polishing and in which the Fe contamination cannot be removed completely by initial ultrasonic cleaning. To solve this problem, a kind of ion beam figuring (IBF) polishing is introduced to remove the impurity layer. Then the content of Fe element contamination and the depth of impurity elements are measured by time of flight secondary ion mass spectrometry. The measurement results show that there are no CI powders embedding in the MRF polished surface and no Fe contamination after the IBF polishing process, respectively. That verifies the feasibility of MRF polishing-IBF polishing (cleaning) for processing a KDP crystal. PMID:25968216

  8. Affinity capture using peptide-functionalized magnetic nanoparticles to target Staphylococcus aureus

    NASA Astrophysics Data System (ADS)

    Kuo, Fang-Yin; Lin, Wei-Lien; Chen, Yu-Chie

    2016-04-01

    Staphylococcus aureus, a commonly found pathogen, can cause food poisoning and infections. Thus, it is necessary to develop analytical methods for the rapid screening of S. aureus in suspicious samples. Magnetic nanoparticles (MNPs) are widely used as affinity probes to selectively enrich target species from complex samples because of their high specific surface area and magnetic properties. The MNP surface should be functionalized to have the capability to target specific species. We herein propose a straightforward method to functionalize aluminum oxide-coated iron oxide (Fe3O4@Al2O3) MNPs with the peptide HHHHHHDEEGLFVD (D). The peptide D was comprised of three domains: polyhistidine (H6) used as the linker, DEE added as the spacer, and GLFVD used for targeting S. aureus. D was immobilized on the surface of Fe3O4@Al2O3 MNPs through H6-Al chelation. Our results showed that the D-functionalized Fe3O4@Al2O3 MNPs (D-Fe3O4 MNPs) possess the capability to target S. aureus. The selective trapping experiments were conducted under microwave-heating for only 60 s, and sufficient bacterial cells were trapped by the MNPs to be identified by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). We demonstrated that the D-Fe3O4@Al2O3 MNPs combined with MALDI-MS can be used to rapidly characterize trace amounts of S. aureus in complex juice and egg samples.Staphylococcus aureus, a commonly found pathogen, can cause food poisoning and infections. Thus, it is necessary to develop analytical methods for the rapid screening of S. aureus in suspicious samples. Magnetic nanoparticles (MNPs) are widely used as affinity probes to selectively enrich target species from complex samples because of their high specific surface area and magnetic properties. The MNP surface should be functionalized to have the capability to target specific species. We herein propose a straightforward method to functionalize aluminum oxide-coated iron oxide (Fe3O4@Al2O3) MNPs with the

  9. ADAM10 Cell Surface Expression but Not Activity Is Critical for Staphylococcus aureus α-Hemolysin-Mediated Activation of the NLRP3 Inflammasome in Human Monocytes

    PubMed Central

    Ezekwe, Ejiofor A.D.; Weng, Chengyu; Duncan, Joseph A.

    2016-01-01

    The Staphylococcus aureus toxin, α-hemolysin, is an important and well-studied virulence factor in staphylococcal infection. It is a soluble monomeric protein that, once secreted by the bacterium, forms a heptameric pore in the membrane of a broad range of host cell types. Hemolysin was recently discovered to bind and activate a disintegrin and metalloprotease 10 (ADAM10). In epithelial and endothelial cells, ADAM10 activation is required for the toxin’s activity against these cells. In host monocytic cells, α-hemolysin activates the nucleotide-binding domain and leucine-rich repeat containing gene family, pyrin domain containing 3 (NLRP3) inflammasome leading to production of pro-inflammatory cytokines and cell death. We now show that ADAM10 is critical for α-hemolysin-mediated activation of the NLRP3 inflammasome in human monocytes as siRNA knockdown or chemical blockade of ADAM10-α-hemolysin interaction leads to diminished inflammasome activation and cell death by reducing the available ADAM10 on the cell surface. Unlike epithelial cell and endothelial cell damage, which requires α-hemolysin induced ADAM10 activation, ADAM10 protease activity was not required for NLRP3 inflammasome activation. This work confirms the importance of ADAM10 in immune activation by α-hemolysin, but indicates that host cell signal induction by the toxin is different between host cell types. PMID:27043625

  10. Immunochemical study of diverse surface antigens of a Staphylococcus aureus isolate from an osteomyelitis patient and their role in in vitro phagocytosis.

    PubMed Central

    Karakawa, W W; Young, D A

    1979-01-01

    The cellular antigens of a strain of Staphylococcus aureus, isolated from a bone fragment from osteomyelitis, were analyzed immunochemically and by interaction with human phagocytic cells. When this strain was allowed to interact with human polymorphonuclear cells in the presence of antiserum, the strain was shown to have specific antiphagocytic antigens. An acidic polysaccharide consisting of galactose and glucuronic acid was isolated from the cell surface of the organism, and in vitro opsonization tests indicated that this acidic antigen impeded in vitro phagocytosis by human polymorphonuclear cells. It was also observed that antibodies directed against the mucopeptide constituents of homologous and heterologous bacterial cell walls were effective in promoting the in vitro opsonization of the organism. In the presence of antimucopeptide serum and human polymorphonuclear cells, a variant strain was isolated from the wild type, and immunochemical analysis indicated that this strain consisted of galactose and immunodominant amino-galacturonic acid residues. In vitro phagocytosis studies employing this variant strain indicated that the homologous human convalescent serum contained higher levels of opsonins against the variant strain than the original isolate, the wild type. This observation is discussed. Images PMID:457853

  11. ULTRASOUND PRETREATMENT OF ELEMENTAL IRON: KINETIC STUDIES OF DEHALOGENATION REACTION ENHANCEMENT AND SURFACE EFFECTS. (R828598C743)

    EPA Science Inventory

    This work presents data showing the kinetic improvement afforded by ultrasound pretreatment and illustrates the physical and chemical changes that take place at the iron surface. First-order rate constants improved as much as 78% with 2 h of ultrasound pretreatment. Scann...

  12. IlsA, A Unique Surface Protein of Bacillus cereus Required for Iron Acquisition from Heme, Hemoglobin and Ferritin

    PubMed Central

    Daou, Nadine; Buisson, Christophe; Gohar, Michel; Vidic, Jasmina; Bierne, Hélène; Kallassy, Mireille; Lereclus, Didier; Nielsen-LeRoux, Christina

    2009-01-01

    The human opportunistic pathogen Bacillus cereus belongs to the B. cereus group that includes bacteria with a broad host spectrum. The ability of these bacteria to colonize diverse hosts is reliant on the presence of adaptation factors. Previously, an IVET strategy led to the identification of a novel B. cereus protein (IlsA, Iron-regulated leucine rich surface protein), which is specifically expressed in the insect host or under iron restrictive conditions in vitro. Here, we show that IlsA is localized on the surface of B. cereus and hence has the potential to interact with host proteins. We report that B. cereus uses hemoglobin, heme and ferritin, but not transferrin and lactoferrin. In addition, affinity tests revealed that IlsA interacts with both hemoglobin and ferritin. Furthermore, IlsA directly binds heme probably through the NEAT domain. Inactivation of ilsA drastically decreases the ability of B. cereus to grow in the presence of hemoglobin, heme and ferritin, indicating that IlsA is essential for iron acquisition from these iron sources. In addition, the ilsA mutant displays a reduction in growth and virulence in an insect model. Hence, our results indicate that IlsA is a key factor within a new iron acquisition system, playing an important role in the general virulence strategy adapted by B. cereus to colonize susceptible hosts. PMID:19956654

  13. Effects of high temperature surface oxides on room temperature aqueous corrosion and environmental embrittlement of iron aluminides

    SciTech Connect

    Buchanan, R.A.; Perrin, R.L.

    1996-09-01

    Studies were conducted to determine the effects of high-temperature surface oxides, produced during thermomechanical processing, heat treatment (750 {degrees}C in air, one hour) or simulated in-service-type oxidation (1000{degrees}C in air, 24 hours) on the room-temperature aqueous-corrosion and environmental-embrittlement characteristics of iron aluminides. Materials evaluated included the Fe{sub 3}Al-based iron aluminides, FA-84, FA-129, FAL and FAL-Mo, a FeAl-based iron aluminide, FA-385, and a disordered low-aluminum Fe-Al alloy, FAPY. Tests were performed in a mild acid-chloride solution to simulate aggressive atmospheric corrosion. Cyclic-anodic-polarization tests were employed to evaluate resistances to localized aqueous corrosion. The high-temperature oxide surfaces consistently produced detrimental results relative to mechanically or chemically cleaned surfaces. Specifically, the pitting corrosion resistances were much lower for the as-processed and 750{degrees} C surfaces, relative to the cleaned surfaces, for FA-84, FA-129, FAL-Mo, FA-385 and FAPY. Furthermore, the pitting corrosion resistances were much lower for the 1000{degrees}C surfaces, relative to cleaned surfaces, for FA-129, FAL and FAL-Mo.

  14. Sustaining reactivity of Fe(0) for nitrate reduction via electron transfer between dissolved Fe(2+) and surface iron oxides.

    PubMed

    Han, Luchao; yang, Li; Wang, Haibo; Hu, Xuexiang; Chen, Zhan; Hu, Chun

    2016-05-01

    The mechanism of the effects of Fe(2+)(aq) on the reduction of NO3(-) by Fe(0) was investigated. The effects of initial pH on the rate of NO3(-) reduction and the Fe(0) surface characteristics revealed Fe(2+)(aq) and the characteristics of minerals on the surface of Fe(0) played an important role in NO3(-) reduction. Both NO3(-) reduction and the decrease of Fe(2+)(aq) exhibited similar kinetics and were promoted by each other. This promotion was associated with the types of the surface iron oxides of Fe(0). Additionally, further reduction of NO3(-) produced more surface iron oxides, supplying more active sites for Fe(2+)(aq), resulting in more electron transfer between Fe(2+) and surface iron oxides and a higher reaction rate. Using the isotope specificity of (57)Fe Mossbauer spectroscopy, it was verified that the Fe(2+)(aq) was continuously converted into Fe(3+) oxides on the surface of Fe(0) and then converted into Fe3O4 via electron transfer between Fe(2+) and the pre-existing surface Fe(3+) oxides. Electrochemistry measurements confirmed that the spontaneous electron transfer between the Fe(2+) and structural Fe(3+) species accelerated the interfacial electron transfer between the Fe species and NO3(-). This study provides a new insight into the interaction between Fe species and contaminants and interface electron transfer. PMID:26835898

  15. Triclosan Promotes Staphylococcus aureus Nasal Colonization

    PubMed Central

    Syed, Adnan K.; Ghosh, Sudeshna; Love, Nancy G.; Boles, Blaise R.

    2014-01-01

    ABSTRACT The biocide triclosan is used in many personal care products, including toothpastes, soaps, clothing, and medical equipment. Consequently, it is present as a contaminant in the environment and has been detected in some human fluids, including serum, urine, and milk. Staphylococcus aureus is an opportunistic pathogen that colonizes the noses and throats of approximately 30% of the population. Colonization with S. aureus is known to be a risk factor for several types of infection. Here we demonstrate that triclosan is commonly found in the nasal secretions of healthy adults and the presence of triclosan trends positively with nasal colonization by S. aureus. We demonstrate that triclosan can promote the binding of S. aureus to host proteins such as collagen, fibronectin, and keratin, as well as inanimate surfaces such as plastic and glass. Lastly, triclosan-exposed rats are more susceptible to nasal colonization with S. aureus. These data reveal a novel factor that influences the ability of S. aureus to bind surfaces and alters S. aureus nasal colonization. PMID:24713325

  16. High-temperature superconductivity from fine-tuning of Fermi-surface singularities in iron oxypnictides

    PubMed Central

    Charnukha, A.; Evtushinsky, D. V.; Matt, C. E.; Xu, N.; Shi, M.; Büchner, B.; Zhigadlo, N. D.; Batlogg, B.; Borisenko, S. V.

    2015-01-01

    In the family of the iron-based superconductors, the REFeAsO-type compounds (with RE being a rare-earth metal) exhibit the highest bulk superconducting transition temperatures (Tc) up to 55 K and thus hold the key to the elusive pairing mechanism. Recently, it has been demonstrated that the intrinsic electronic structure of SmFe0.92Co0.08AsO (Tc = 18 K) is highly nontrivial and consists of multiple band-edge singularities in close proximity to the Fermi level. However, it remains unclear whether these singularities are generic to the REFeAsO-type materials and if so, whether their exact topology is responsible for the aforementioned record Tc. In this work, we use angle-resolved photoemission spectroscopy (ARPES) to investigate the inherent electronic structure of the NdFeAsO0.6F0.4 compound with a twice higher Tc = 38 K. We find a similarly singular Fermi surface and further demonstrate that the dramatic enhancement of superconductivity in this compound correlates closely with the fine-tuning of one of the band-edge singularities to within a fraction of the superconducting energy gap Δ below the Fermi level. Our results provide compelling evidence that the band-structure singularities near the Fermi level in the iron-based superconductors must be explicitly accounted for in any attempt to understand the mechanism of superconducting pairing in these materials. PMID:26678565

  17. Synthesis, surface modification and characterisation of biocompatible magnetic iron oxide nanoparticles for biomedical applications.

    PubMed

    Mahdavi, Mahnaz; Ahmad, Mansor Bin; Haron, Md Jelas; Namvar, Farideh; Nadi, Behzad; Rahman, Mohamad Zaki Ab; Amin, Jamileh

    2013-01-01

    Superparamagnetic iron oxide nanoparticles (MNPs) with appropriate surface chemistry exhibit many interesting properties that can be exploited in a variety of biomedical applications such as magnetic resonance imaging contrast enhancement, tissue repair, hyperthermia, drug delivery and in cell separation. These applications required that the MNPs such as iron oxide Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) having high magnetization values and particle size smaller than 100 nm. This paper reports the experimental detail for preparation of monodisperse oleic acid (OA)-coated Fe₃O₄ MNPs by chemical co-precipitation method to determine the optimum pH, initial temperature and stirring speed in order to obtain the MNPs with small particle size and size distribution that is needed for biomedical applications. The obtained nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence spectrometry (EDXRF), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), and vibrating sample magnetometer (VSM). The results show that the particle size as well as the magnetization of the MNPs was very much dependent on pH, initial temperature of Fe²⁺ and Fe³⁺ solutions and steering speed. The monodisperse Fe₃O₄ MNPs coated with oleic acid with size of 7.8 ± 1.9 nm were successfully prepared at optimum pH 11, initial temperature of 45°C and at stirring rate of 800 rpm. FTIR and XRD data reveal that the oleic acid molecules were adsorbed on the magnetic nanoparticles by chemisorption. Analyses of TEM show the oleic acid provided the Fe₃O₄ particles with better dispersibility. The synthesized Fe₃O₄ nanoparticles exhibited superparamagnetic behavior and the saturation magnetization of the Fe₃O₄ nanoparticles increased with the particle size. PMID:23807578

  18. Surface and interfacial engineering of iron oxide nanoplates for highly efficient magnetic resonance angiography.

    PubMed

    Zhou, Zijian; Wu, Changqiang; Liu, Hanyu; Zhu, Xianglong; Zhao, Zhenghuan; Wang, Lirong; Xu, Ye; Ai, Hua; Gao, Jinhao

    2015-03-24

    Magnetic resonance angiography using gadolinium-based molecular contrast agents suffers from short diagnostic window, relatively low resolution and risk of toxicity. Taking into account the chemical exchange between metal centers and surrounding protons, magnetic nanoparticles with suitable surface and interfacial features may serve as alternative T1 contrast agents. Herein, we report the engineering on surface structure of iron oxide nanoplates to boost T1 contrast ability through synergistic effects between exposed metal-rich Fe3O4(100) facets and embedded Gd2O3 clusters. The nanoplates show prominent T1 contrast in a wide range of magnetic fields with an ultrahigh r1 value up to 61.5 mM(-1) s(-1). Moreover, engineering on nanobio interface through zwitterionic molecules adjusts the in vivo behaviors of nanoplates for highly efficient magnetic resonance angiography with steady-state acquisition window, superhigh resolution in vascular details, and low toxicity. This study provides a powerful tool for sophisticated design of MRI contrast agents for diverse use in bioimaging applications. PMID:25670480

  19. Control of the interparticle spacing in superparamagnetic iron oxide nanoparticle clusters by surface ligand engineering

    NASA Astrophysics Data System (ADS)

    Dan, Wang; Bingbing, Lin; Taipeng, Shen; Jun, Wu; Fuhua, Hao; Chunchao, Xia; Qiyong, Gong; Huiru, Tang; Bin, Song; Hua, Ai

    2016-07-01

    Polymer-mediated self-assembly of superparamagnetic iron oxide (SPIO) nanoparticles allows modulation of the structure of SPIO nanocrystal cluster and their magnetic properties. In this study, dopamine-functionalized polyesters (DA-polyester) were used to directly control the magnetic nanoparticle spacing and its effect on magnetic resonance relaxation properties of these clusters was investigated. Monodisperse SPIO nanocrystals with different surface coating materials (poly(ε-caprolactone), poly(lactic acid)) of different molecular weights containing dopamine (DA) structure (DA-PCL2k, DA-PCL1k, DA-PLA1k)) were prepared via ligand exchange reaction, and these nanocrystals were encapsulated inside amphiphilic polymer micelles to modulate the SPIO nanocrystal interparticle spacing. Small-angle x-ray scattering (SAXS) was applied to quantify the interparticle spacing of SPIO clusters. The results demonstrated that the tailored magnetic nanoparticle clusters featured controllable interparticle spacing providing directly by the different surface coating of SPIO nanocrystals. Systematic modulation of SPIO nanocrystal interparticle spacing can regulate the saturation magnetization (M s) and T 2 relaxation of the aggregation, and lead to increased magnetic resonance (MR) relaxation properties with decreased interparticle spacing. Project supported by the National Key Basic Research Program of China (Grant No. 2013CB933903), the National Key Technology R&D Program of China (Grant No. 2012BAI23B08), and the National Natural Science Foundation of China (Grant Nos. 20974065, 51173117, and 50830107).

  20. Positron annihilation study of aluminum, titanium, and iron alloys surface after shot peening

    NASA Astrophysics Data System (ADS)

    Zaleski, R.; Zaleski, K.; Gorgol, M.; Wiertel, M.

    2015-08-01

    Shot peening influence on alloys based on iron, aluminum, and titanium was studied using positron annihilation lifetime spectroscopy (PALS) and residual stress measurements. The PALS spectra were analyzed assuming two lifetime components. While the residual stresses change in a similar way in all the samples, the PALS results show an opposite tendency of a component relative intensities change with the time of shot peening for the Ti alloy as compared to steel or the Al alloy. A comparison between the depth profiles of positron implantation and the residual stress distribution reveals that the positron range covers a whole depth where residual stress is observed only in the Ti alloy. Based on this observation, the evolution of the defect concentration is presumed, consisting in migration of large defects away from the surface, while only smaller ones remain close to the surface. Furthermore, the positron lifetime distribution in the Al alloy was determined using the MELT program. The results showed that the initial single, wide distribution of lifetime splits into two narrower ones with increasing shot peening time.

  1. Effects of Amines on the Surface Charge Poperties of Iron Oxides.

    SciTech Connect

    Benezeth, Pascale; Wesolowski, David J; Palmer, Donald; Machesky, Michael L.

    2009-07-01

    Specific studies detailing the effects of amines, used as pH control agents for corrosion inhibition in power plants, on the surface charge of iron oxides provide data to assess the mechanism of how these amines impact deposition rate. The current study was undertaken in order to determine accurately the dissociation constants of the relevant amines at Pressurized Water Reactor (PWR) operating conditions and to investigate the effect of sorption of two of these amines (morpholine and dimethylamine) by magnetite. The acid-dissociation equilibria of morpholine (MOR), dimethylamine (DMA) and ethanolamine (ETA) were measured potentiometrically with a hydrogen-electrode concentration cell (HECC) from 0 to 290 C in sodium trifluoromethanesulfonate (NaTr) solutions at ionic strengths up to 1 mol {center_dot} kg{sup -1}. Magnetite surface titrations were performed at an ionic strength of 0.03 mol {center_dot} kg{sup -1} (NaTr medium) in the presence or absence of morpholine and dimethylamine buffers over a wide range of pH and total amine concentrations at 150-250 C.

  2. Structural characterization and surface activities of biogenic rhamnolipid surfactants from Pseudomonas aeruginosa isolate MN1 and synergistic effects against methicillin-resistant Staphylococcus aureus.

    PubMed

    Samadi, Nasrin; Abadian, Neda; Ahmadkhaniha, Reza; Amini, Farzaneh; Dalili, Dina; Rastkari, Noushin; Safaripour, Eliyeh; Mohseni, Farzaneh Aziz

    2012-11-01

    The aim of present work was to study chemical structures and biological activities of rhamnolipid biosurfactants produced by Pseudomonas aeruginosa MN1 isolated from oil-contaminated soil. The results of liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed that total rhamnolipids (RLs) contained 16 rhamnolipid homologues. Di-lipid RLs containing C(10)-C(10) moieties were by far the most predominant congeners among mono-rhamnose (53.29 %) and di-rhamnose (23.52 %) homologues. Mono-rhamnolipids form 68.35 % of the total congeners in the RLs. Two major fractions were revealed in the thin layer chromatogram of produced RLs which were then purified by column chromatography. The retardation factors (R (f)) of the two rhamnolipid purple spots were 0.71 for RL1 and 0.46 for RL2. LC-MS/MS analysis proved that RL1 was composed of mono-RLs and RL2 consisted of di-RLs. RL1 was more surface-active with the critical micelle concentration (CMC) value of 15 mg/L and the surface tension of 25 mN/m at CMC. The results of biological assay showed that RL1 is a more potent antibacterial agent than RL2. All methicillin-resistant Staphylococcus aureus (MRSA) strains were inhibited by RLs that were independent of their antibiotic susceptibility patterns. RLs remarkably enhanced the activity of oxacillin against MRSA strains and lowered the minimum inhibitory concentrations of oxacillin to the range of 3.12-6.25 μg/mL. PMID:22644668

  3. A biological switch at the ocean surface as a cause of laminations in a Precambrian iron formation

    NASA Astrophysics Data System (ADS)

    Hashizume, K.; Pinti, D. L.; Orberger, B.; Cloquet, C.; Jayananda, M.; Soyama, H.

    2016-07-01

    Banded iron formations (BIFs) exhibit alternating silica- and iron-rich laminae, potentially reflecting the dynamics of the paleo-environments in which they were formed, although the exact mechanism remains unclear. Here the formation of a 2.7-2.9 Ga BIF from Dharwar Craton, India, is deciphered by analyzing the inter-band variations of the redox-sensitive isotope biomarkers, 15N/14N and 56Fe/54Fe. Organic matter with δ15N values as high as + 12.0 ± 0.8 ‰ appears to be trapped in silica. Iron oxides exhibit systematically positive δ56Fe values, ranging between + 0.80 ± 0.05 ‰ and + 1.67 ± 0.02 ‰. Compared to the iron-rich bands, silica-rich bands, which show higher δ56Fe values, exhibit an order of magnitude higher concentrations of 15N-rich organic nitrogen, normalized by the abundances of its host silica. The presence of 15N-rich organic matter may imply the emergence of a modern-like biological nitrogen cycle that requires the formation of oxidized nitrogen compounds. The higher concentration of 15N-rich organic nitrogen for the silica-rich bands possibly suggests that the photosynthetic activity was higher during the formation periods of these bands. The heavier iron isotope compositions of the silica-rich bands cannot be explained alone by iron oxidation through probable pathways. The relative 56Fe-enrichment in silica-rich bands is explained here by the progressive dissolution of iron oxides to the ocean, through iron reduction by 15N-rich organic matter actively produced at the ocean surface. The formation of iron-rich bands possibly corresponds to periods of reduced biological productivity, when precipitated iron was not effectively dissolved to the ocean. The observed shift in the organic concentration between Fe- and Si-rich bands could be the switch that triggered the BIF laminations. This shift could conceivably represent periodic fluctuations in the oxygen generation, which possibly occurred over periods of millennia, at the dawn of the

  4. Photoemission from real iron surfaces and its relationship to light penetration of the overlayer

    NASA Astrophysics Data System (ADS)

    Momose, Yoshihiro; Suzuki, Daisuke; Sakurai, Takao; Nakayama, Keiji

    2015-02-01

    We report the photoemission from real iron surfaces at elevated temperatures, called thermally assisted photoemission (TAPE), and its relationship to the X-ray photoelectron spectroscopy (XPS) results. TAPE measurements were carried out using a Geiger counter under a gaseous atmosphere of He containing 1 % isobutane vapor at normal atmospheric pressure. A sample was initially heated to temperatures ranging from 25 to 353 °C under light irradiation at a certain wavelength of 200, 210, 220, and 230 nm, and then, wavelength was scanned from 300 to 170 nm at the final temperature. The values of a constant related to electron photoemission probability, αA, where A is identical with the Richardson constant, and photothreshold (photoelectric work function), ϕ, were obtained from a plot of the square root of the electron photoemission intensity against the photon energy; the αA values increased with temperature, and the ϕ values also increased with temperature. From the Arrhenius plot, the αA was found to have an activation energy Δ E αA = 0.096 eV. The activation energies of the surface oxygen component ratio Z = O2-/(OH + O2-) and the surface elemental composition ratio X = Fe/(O + N + C + Fe) obtained from the XPS data were also determined from their Arrhenius plots: Δ E Z = 0.113 eV and Δ E X = 0.039 eV, respectively. From a close resemblance between the latter activation energies and those of the Δ E αA and the Δ E a = 0.112-0.040 eV for the quantum yields (Momose et al. in Appl Phys A. doi: 10.1007/s00339-014-8589-7, 2014), it was found that the increase in the intensity of the TAPE with temperature was strongly associated with the increase in the values of Z and X with temperature. It was therefore concluded that the ability of the surface overlayer to pass the incident light became a rate-determining step to start the photoemission, which was decisively controlled by the temperature-dependent surface oxygen components and surface compositions. The

  5. Reflectance Spectroscopy of Palagonite and Iron-Rich Montmorillonite Clay Mixtures: Implications for the Surface Composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, James; Handy, Jonathan

    1992-01-01

    Mixtures of a Hawaiian palagonite and an iron-rich, montmorillonite clay (15.8 +/- 0.4 wt% Fe as Fe2O3) were evaluated as Mars surface spectral analogs from their diffuse reflectance spectra. The presence of the 2.2 microns absorption band in the reflectance spectrum of clays and its absence in the Mars spectrum have been interpreted as indicating that highly crystalline aluminous hydroxylated clays cannot be a major mineral component of the soil on Mars. The palagonite sample used in this study does not show this absorption feature in its spectrum. In mixtures of palagonite and iron-rich montmorillonite, the 2.2 microns Al-OH clay lattice band is not seen below 15 wt% montmorillonite. This suggests the possibility that iron-rich montmorillonite clay may be present in the soil of Mars at up to 15 wt% in combination with palagonite, and remain undetected in remotely sensed spectra of Mars.

  6. Controls on dissolved cobalt in surface waters of the Sargasso Sea: Comparisons with iron and aluminum

    NASA Astrophysics Data System (ADS)

    Shelley, R. U.; Sedwick, P. N.; Bibby, T. S.; Cabedo-Sanz, P.; Church, T. M.; Johnson, R. J.; Macey, A. I.; Marsay, C. M.; Sholkovitz, E. R.; Ussher, S. J.; Worsfold, P. J.; Lohan, M. C.

    2012-06-01

    Dissolved cobalt (dCo), iron (dFe) and aluminum (dAl) were determined in water column samples along a meridional transect (˜31°N to 24°N) south of Bermuda in June 2008. A general north-to-south increase in surface concentrations of dFe (0.3-1.6 nM) and dAl (14-42 nM) was observed, suggesting that aerosol deposition is a significant source of dFe and dAl, whereas no clear trend was observed for near-surface dCo concentrations. Shipboard aerosol samples indicate fractional solubility values of 8-100% for aerosol Co, which are significantly higher than corresponding estimates of the solubility of aerosol Fe (0.44-45%). Hydrographic observations and analysis of time series rain samples from Bermuda indicate that wet deposition accounts for most (>80%) of the total aeolian flux of Co, and hence a significant proportion of the atmospheric input of dCo to our study region. Our aerosol data imply that the atmospheric input of dCo to the Sargasso Sea is modest, although this flux may be more significant in late summer. The water column dCo profiles reveal a vertical distribution that predominantly reflects `nutrient-type' behavior, versus scavenged-type behavior for dAl, and a hybrid of nutrient- and scavenged-type behavior for dFe. Mesoscale eddies also appear to impact on the vertical distribution of dCo. The effects of biological removal of dCo from the upper water column were apparent as pronounced sub-surface minima (21 ± 4 pM dCo), coincident with maxima in Prochlorococcus abundance. These observations imply that Prochlorococcus plays a major role in removing dCo from the euphotic zone, and that the availability of dCo may regulate Prochlorococcus growth in the Sargasso Sea.

  7. Nonequilibrium Molecular Dynamics Simulations of Organic Friction Modifiers Adsorbed on Iron Oxide Surfaces.

    PubMed

    Ewen, James P; Gattinoni, Chiara; Morgan, Neal; Spikes, Hugh A; Dini, Daniele

    2016-05-10

    For the successful development and application of lubricants, a full understanding of the nanoscale behavior of complex tribological systems is required, but this is difficult to obtain experimentally. In this study, we use nonequilibrium molecular dynamics (NEMD) simulations to examine the atomistic structure and friction properties of commercially relevant organic friction modifier (OFM) monolayers adsorbed on iron oxide surfaces and lubricated by a thin, separating layer of hexadecane. Specifically, acid, amide, and glyceride OFMs, with saturated and Z-unsaturated hydrocarbon tail groups, are simulated at various surface coverages and sliding velocities. At low and medium coverage, the OFMs form liquidlike and amorphous monolayers, respectively, which are significantly interdigitated with the hexadecane lubricant, resulting in relatively high friction coefficients. At high coverage, solidlike monolayers are formed for all of the OFMs, which, during sliding, results in slip planes between well-defined OFM and hexadecane layers, yielding a marked reduction in the friction coefficient. When present at equal surface coverage, OFMs with saturated and Z-unsaturated tail groups are found to yield similar structure and friction behavior. OFMs with glyceride head groups yield significantly lower friction coefficients than amide and particularly carboxylic acid head groups. For all of the OFMs and coverages simulated, the friction coefficient is found to increase linearly with the logarithm of sliding velocity; however, the gradient of this increase depends on the coverage. The structure and friction details obtained from these simulations agree well with experimental results and also shed light on the relative tribological performance of these OFMs through nanoscale structural variations. This has important implications in terms of the applicability of NEMD to aid the development of new formulations to control friction. PMID:27064962

  8. Temporal fluctuations in grain size, organic materials and iron concentrations in intertidal surface sediment of San Francisco Bay

    USGS Publications Warehouse

    Thomson-Becker, E. A.; Luoma, S.N.

    1985-01-01

    The physical and chemical characteristics of the oxidized surface sediment in an estuary fluctuate temporally in response to physical forces and apparently-fluctuating inputs. These characteristics, which include grain size and concentrations of organic materials and iron, will influence both trace-metal geochemistry and bioavailability. Temporal trends in the abundance of fine particles, total organic carbon content (TOC), absorbance of extractable organic material (EOM), and concentration of extractable iron in the sediment of San Francisco Bay were assessed using data sets containing approximately monthly samples for periods of two to seven years. Changes in wind velocity and runoff result in monthly changes in the abundance of fine particles in the intertidal zone. Fine-grained particles are most abundant in the late fall/early winter when runoff is elevated and wind velocities are low; particles are coarser in the summer when runoff is low and wind velocities are consistently high. Throughout the bay, TOC is linearly related to fine particle abundance (r = 0.61). Temporal variability occurs in this relationship, as particles are poor in TOC relative to percent of fine particles in the early rainy season. Iron-poor particles also appear to enter the estuary during high runoff periods; while iron is enriched on particle surfaces in the summer. Concentrations of extractable iron and absorbance of EOM vary strongly from year to year. Highest absorbances of EOM occurred in the first year following the drought in 1976-77, and in 1982 and 1983 when river discharge was unusually high. Extractable-iron concentrations were also highest in 1976-77, but were very low in 1982 and 1983. ?? 1985 Dr W. Junk Publishers.

  9. Exploring Staphylococcus aureus pathways to disease for vaccine development

    PubMed Central

    DeDent, Andrea; Kim, Hwan Keun; Missiakas, Dominique; Schneewind, Olaf

    2012-01-01

    Staphylococcus aureus is a commensal of the human skin or nares and a pathogen that frequently causes skin and soft tissue infections as well as bacteremia and sepsis. Recent efforts in understanding the molecular mechanisms of pathogenesis revealed key virulence strategies of S. aureus in host tissues: bacterial scavenging of iron, induction of coagulation pathways to promote staphylococcal agglutination in the vasculature, and suppression of innate and adaptive immune responses. Advances in all three areas have been explored for opportunities in vaccine design in an effort to identify the critical protective antigens of S. aureus. Human clinical trials with specific subunit vaccines have failed, yet provide important insights for the design of future trials that must address the current epidemic of S. aureus infections with drug-resistant isolates (MRSA, methicillin-resistant S. aureus). PMID:22130613

  10. On the Chemical Synthesis and Physical Properties of Iron Pyrite, Especially the (100) Surface

    NASA Astrophysics Data System (ADS)

    Macpherson, Hector Alexander

    Given that iron pyrite (cubic FeS2, fool's gold) is a semiconductor with a ˜1 eV band gap, it has long been investigated for use in technological applications, especially photovoltaics. Unfortunately, numerous measurements indicate that it's properties, as currently synthesized at least, do not allow for effective devices. Photovoltages far below theoretical expectation are found as well as below band gap optical absorption. From a scientific standpoint, our understanding of the cause of these observations, the form of the density of states for instance, remains mired in uncertainty. In this work we have attempted to gain insight into this problem by creating ensembles of pyrite nanocrystals that can then be treated and measured with well-developed wet-chemical nanocrystal techniques. Specifically, we interpret the existing literature to advocate that the surface states of this material dominate its observed electrical properties. In an effort to better understand the most prevalent surface, the (100) face, we developed a synthesis that nucleates small (< 20 nm) pyrite nanoparticles and then changes chemical conditions to grow all other faces besides {100} to extinction, creating ˜37 nm nanocubes. The optical properties of these nanocubes are measured and the phenomenon of resonance light scattering (RLS) is observed. This phenomenon, along with the poor colloidal dispersibility of these nanocubes is then used to promote the idea that an unusual dynamic electronic phenomenon exists on these surfaces. This phenomenon is found to be passivated by introducing charged ligands to the surfaces of these particles. Additionally, after this surface treatment, two very sharp absorption features are observed at 0.73 and 0.88 eV. In connection with recent theoretical work, these transitions are taken as evidence that the (100) surface of pyrite is spin-polarized with each absorption peak being the signal of band edge absorption across a spin-selected direct band gap. A

  11. Displaying structural property and inheritance of cast iron surfacing on steel base

    NASA Astrophysics Data System (ADS)

    Shveev, I. A.

    2016-06-01

    Graphite inclusions heredity in deposited layer from remelted special cast iron billets was established. The possibility of controlling the structural state and the quality of the deposited layer due to technological parameters of welding and heat treatment of parts is shown. Ways of improving cast iron wear resistance durability are proposed.

  12. Inhibition of Staphylococcus aureus Adhesion to the Surface of a Reticular Heavyweight Polypropylene Mesh Soaked in a Combination of Chlorhexidine and Allicin: An In vitro Study

    PubMed Central

    Pérez-Köhler, Bárbara; García-Moreno, Francisca; Bayon, Yves; Pascual, Gemma; Bellón, Juan Manuel

    2015-01-01

    Introduction Presoaking meshes for hernia repair with antiseptics prior to implantation could decrease the adhesion of microorganisms to the material surface and reduce the risk of antibiotic resistances. In this work, we evaluate chlorhexidine and allicin (natural antiseptic not yet tested for these purposes) against vancomycin as antiseptics to be used in the pretreatment of a heavyweight polypropylene mesh using an in vitro model of bacterial contamination. Methods Solutions of saline, vancomycin (40 µg/mL), allicin (1,000 µg/mL), chlorhexidine (2%-0.05%) and the combination allicin-chlorhexidine (900 µg/mL-0.05%) were analyzed with agar diffusion tests in the presence of 106 CFU Staphylococcus aureus ATCC25923. Additionally, sterile fragments of Surgipro (1 cm2) were soaked with the solutions and cultured onto contaminated agar plates for 24/48/72 h. The antimicrobial material DualMesh Plus was utilized as positive control. At every time, the inhibition zones were measured and the bacterial adhesion to the mesh surface quantified (sonication, scanning electron microscopy). Cytotoxicity of the treatments was examined (alamarBlue) using rabbit skin fibroblasts. Results The largest zones of inhibition were created by allicin-chlorhexidine. Chlorhexidine was more effective than vancomycin, and allicin lost its effectiveness after 24 h. No bacteria adhered to the surface of the DualMesh Plus or the meshes soaked with vancomycin, chlorhexidine and allicin-chlorhexidine. On the contrary, saline and allicin allowed adherence of high loads of bacteria. Vancomycin had no toxic effects on fibroblasts, while allicin and chlorhexidine exerted high toxicity. Cytotoxicity was significantly reduced with the allicin-chlorhexidine combination. Conclusions The use of antiseptics such as chlorhexidine, alone or combined with others like allicin, could represent an adequate prophylactic strategy to be used for hernia repair materials because soaking with these agents provides

  13. The impact of changing surface ocean conditions on the dissolution of aerosol iron

    NASA Astrophysics Data System (ADS)

    Fishwick, Matthew P.; Sedwick, Peter N.; Lohan, Maeve C.; Worsfold, Paul J.; Buck, Kristen N.; Church, Thomas M.; Ussher, Simon J.

    2014-11-01

    The proportion of aerosol iron (Fe) that dissolves in seawater varies greatly and is dependent on aerosol composition and the physicochemical conditions of seawater, which may change depending on location or be altered by global environmental change. Aerosol and surface seawater samples were collected in the Sargasso Sea and used to investigate the impact of these changing conditions on aerosol Fe dissolution in seawater. Our data show that seawater temperature, pH, and oxygen concentration, within the range of current and projected future values, had no significant effect on the dissolution of aerosol Fe. However, the source and composition of aerosols had the most significant effect on the aerosol Fe solubility, with the most anthropogenically influenced samples having the highest fractional solubility (up to 3.2%). The impact of ocean warming and acidification on aerosol Fe dissolution is therefore unlikely to be as important as changes in land usage and fossil fuel combustion. Our experimental results also reveal important changes in the size distribution of soluble aerosol Fe in solution, depending on the chemical conditions of seawater. Under typical conditions, the majority (77-100%) of Fe released from aerosols into ambient seawater existed in the colloidal (0.02-0.4 µm) size fraction. However, in the presence of a sufficient concentration of strong Fe-binding organic ligands (10 nM) most of the aerosol-derived colloidal Fe was converted to soluble Fe (<0.02 µm). This finding highlights the potential importance of organic ligands in retaining aerosol Fe in a biologically available form in the surface ocean.

  14. Genotoxicity assessment of magnetic iron oxide nanoparticles with different particle sizes and surface coatings

    NASA Astrophysics Data System (ADS)

    Liu, Yanping; Xia, Qiyue; Liu, Ying; Zhang, Shuyang; Cheng, Feng; Zhong, Zhihui; Wang, Li; Li, Hongxia; Xiao, Kai

    2014-10-01

    Magnetic iron oxide nanoparticles (IONPs) have been widely used for various biomedical applications such as magnetic resonance imaging and drug delivery. However, their potential toxic effects, including genotoxicity, need to be thoroughly understood. In the present study, the genotoxicity of IONPs with different particle sizes (10, 30 nm) and surface coatings (PEG, PEI) were assessed using three standard genotoxicity assays, the Salmonella typhimurium reverse mutation assay (Ames test), the in vitro mammalian chromosome aberration test, and the in vivo micronucleus assay. In the Ames test, SMG-10 (PEG coating, 10 nm) showed a positive mutagenic response in all the five test bacterial strains with and without metabolic activation, whereas SEI-10 (PEI coating, 10 nm) showed no mutagenesis in all tester strains regardless of metabolic activation. SMG-30 (PEG coating, 30 nm) was not mutagenic in the absence of metabolic activation, and became mutagenic in the presence of metabolic activation. In the chromosomal aberration test, no increase in the incidence of chromosomal aberrations was observed for all three IONPs. In the in vivo micronucleus test, there was no evidence of increased micronuclei frequencies for all three IONPs, indicating that they were not clastogenic in vivo. Taken together, our results demonstrated that IONPs with PEG coating exhibited mutagenic activity without chromosomal and clastogenic abnormalities, and smaller IONPs (SMG-10) had stronger mutagenic potential than larger ones (SMG-30); whereas, IONPs with SEI coating (SEI-10) were not genotoxic in all three standard genotoxicity assays. This suggests that the mutagenicity of IONPs depends on their particle size and surface coating.

  15. Genotoxicity assessment of magnetic iron oxide nanoparticles with different particle sizes and surface coatings.

    PubMed

    Liu, Yanping; Xia, Qiyue; Liu, Ying; Zhang, Shuyang; Cheng, Feng; Zhong, Zhihui; Wang, Li; Li, Hongxia; Xiao, Kai

    2014-10-24

    Magnetic iron oxide nanoparticles (IONPs) have been widely used for various biomedical applications such as magnetic resonance imaging and drug delivery. However, their potential toxic effects, including genotoxicity, need to be thoroughly understood. In the present study, the genotoxicity of IONPs with different particle sizes (10, 30 nm) and surface coatings (PEG, PEI) were assessed using three standard genotoxicity assays, the Salmonella typhimurium reverse mutation assay (Ames test), the in vitro mammalian chromosome aberration test, and the in vivo micronucleus assay. In the Ames test, SMG-10 (PEG coating, 10 nm) showed a positive mutagenic response in all the five test bacterial strains with and without metabolic activation, whereas SEI-10 (PEI coating, 10 nm) showed no mutagenesis in all tester strains regardless of metabolic activation. SMG-30 (PEG coating, 30 nm) was not mutagenic in the absence of metabolic activation, and became mutagenic in the presence of metabolic activation. In the chromosomal aberration test, no increase in the incidence of chromosomal aberrations was observed for all three IONPs. In the in vivo micronucleus test, there was no evidence of increased micronuclei frequencies for all three IONPs, indicating that they were not clastogenic in vivo. Taken together, our results demonstrated that IONPs with PEG coating exhibited mutagenic activity without chromosomal and clastogenic abnormalities, and smaller IONPs (SMG-10) had stronger mutagenic potential than larger ones (SMG-30); whereas, IONPs with SEI coating (SEI-10) were not genotoxic in all three standard genotoxicity assays. This suggests that the mutagenicity of IONPs depends on their particle size and surface coating. PMID:25274166

  16. Microcalorimetric Studies of Surface Acid/Base Properties of Magnesium Iron Catalysts Prepared from Hydrotalcite-Type Precursors

    NASA Astrophysics Data System (ADS)

    Tu, Mai; Shen, Jianyi; Chen, Yi

    1997-01-01

    Magnesium-iron mixed oxides with Mg/Fe molar ratios 1,3, and 6 were prepared from hydrotalcite-type precursors. Microcalorimetric adsorption of NH 3and CO 2showed that the surface acidity and basicity of the mixed oxides after calcination at 673 K are similar despite the different Mg/Fe ratios. Increasing calcination temperature from 673 to 773 K significantly decreased the surface area of the 3 Mg/Fe oxide, but the densities of both the acid and base sites were not changed. Mössbauer spectroscopy revealed that the reduction of the 3 Mg/Fe oxide (Fe 2O 3/MgO) in H 2at 673 K converted all Fe 3+to Fe 2+. The resulted FeO/MgO exhibited the same acidity as that of the Fe 2O 3/MgO, but the basicity of the FeO/MgO was greatly enhanced. Reduction at 773 K resulted in the formation of 76% Fe 2+and 24% Fe 0as detected by Mössbauer spectroscopy. The Fe/FeO/MgO sample formed exhibited very low heat for the adsorption of NH 3(40 kJ/mol) indicating that all iron atoms on the surface are Fe 0. However, a substantial basicity remained on the surface of this sample that may account for its high olefin selectivity compared with pure iron catalyst in the Fischer-Tropsch synthesis.

  17. Surface catalysis of uranium(VI) reduction by iron(II)

    NASA Astrophysics Data System (ADS)

    Liger, Emmanuelle; Charlet, Laurent; Van Cappellen, Philippe

    1999-10-01

    Colloidal hematite (α-Fe2O3) is used as model solid to investigate the kinetic effect of specific adsorption interactions on the chemical reduction of uranyl (UVIO22+) by ferrous iron. Acid-base titrations and Fe(II) and uranyl adsorption experiments are performed on hematite suspensions, under O2- and CO2-free conditions. The results are explained in terms of a constant capacitance surface complexation model of the hematite-aqueous solution interface. Two distinct Fe(II) surface complexes are required to reproduce the data: (≡FeIIIOFeII)+ (or ≡FeIIIOFeII(OH2)n+) and ≡FeIIIOFeIIOH0 (or ≡FeIIIOFeII(OH2)n-1OH0). The latter complex represents a significant fraction of total adsorbed Fe(II) at pH > 6.5. Uranyl binding to the hematite particles is characterized by a sharp adsorption edge between pH 4 and pH 5.5. Because of the absence of competing aqueous carbonate complexes, uranyl remains completely adsorbed at pH > 7. A single mononuclear surface complex accounts for the adsorption of uranyl over the entire range of experimental conditions. Although thermodynamically feasible, no reaction between uranyl and Fe(II) is observed in homogeneous solution at pH 7.5, for periods of up to three days. In hematite suspensions, however, surface-bound uranyl reacts on a time scale of hours. Based on Fourier Transformed Infrared spectra, chemical reduction of U(VI) is inferred to be the mechanism responsible for the disappearance of uranyl. The kinetics of uranyl reduction are quantified by measuring the decrease with time of the concentration of U(VI) extractable from the hematite particles by NaHCO3. In the presence of excess Fe(II), the initial rate of U(VI) reduction exhibits a first-order dependence on the concentration of adsorbed uranyl. The pseudo-first-order rate constant varies with pH (range, 6-7.5) and the total (dissolved + adsorbed) concentration of Fe(II) (range, 2-160 μM). When analyzing the rate data in terms of the calculated surface speciation, the

  18. Mapping Ultra-weak Protein-Protein Interactions between Heme Transporters of Staphylococcus aureus

    PubMed Central

    Abe, Ryota; Caaveiro, Jose M. M.; Kozuka-Hata, Hiroko; Oyama, Masaaki; Tsumoto, Kouhei

    2012-01-01

    Iron is an essential nutrient for the proliferation of Staphylococcus aureus during bacterial infections. The iron-regulated surface determinant (Isd) system of S. aureus transports and metabolizes iron porphyrin (heme) captured from the host organism. Transportation of heme across the thick cell wall of this bacterium requires multiple relay points. The mechanism by which heme is physically transferred between Isd transporters is largely unknown because of the transient nature of the interactions involved. Herein, we show that the IsdC transporter not only passes heme ligand to another class of Isd transporter, as previously known, but can also perform self-transfer reactions. IsdA shows a similar ability. A genetically encoded photoreactive probe was used to survey the regions of IsdC involved in self-dimerization. We propose an updated model that explicitly considers self-transfer reactions to explain heme delivery across the cell wall. An analogous photo-cross-linking strategy was employed to map transient interactions between IsdC and IsdE transporters. These experiments identified a key structural element involved in the rapid and specific transfer of heme from IsdC to IsdE. The resulting structural model was validated with a chimeric version of the homologous transporter IsdA. Overall, our results show that the ultra-weak interactions between Isd transporters are governed by bona fide protein structural motifs. PMID:22427659

  19. Environmental application of millimeter-scale sponge iron (s-Fe(0)) particles (II): the effect of surface copper.

    PubMed

    Ju, Yongming; Liu, Xiaowen; Liu, Runlong; Li, Guohua; Wang, Xiaoyan; Yang, Yanyan; Wei, Dongyang; Fang, Jiande; Dionysiou, Dionysios D

    2015-04-28

    To enhance the catalytic reactivity of millimeter-scale particles of sponge iron (s-Fe(0)), Cu(2+) ions were deposited on the surface of s-Fe(0) using a simple direct reduction reaction, and the catalytic properties of the bimetallic system was tested for removal of rhodamine B (RhB) from an aqueous solution. The influence of Cu(0) loading, catalyst dosage, particle size, initial RhB concentration, and initial pH were investigated, and the recyclability of the catalyst was also assessed. The results demonstrate that the 3∼5 millimeter s-Fe(0) particles (s-Fe(0)(3∼5mm)) with 5wt% Cu loading gave the best results. The removal of RhB followed two-step, pseudo-first-order reaction kinetics. Cu(0)-s-Fe(0) showed excellent stability after five reuse cycles. Cu(0)-s-Fe(0) possesses great advantages compared to nanoscale zero-valent iron, iron power, and iron flakes as well as its bimetals. The surface Cu(0) apparently catalyzes the production of reactive hydrogen atoms for indirect reaction and generates Fe-Cu galvanic cells that enhance electron transfer for direct reaction. This bimetallic catalyst shows great potential for the pre-treatment of recalcitrant wastewaters. Additionally, some oxides containing iron element are selected to simulate the adsorption process. The results prove that the adsorption process of FeOOH, Fe2O3 and Fe3O4 played minor role for the removal of RhB. PMID:25668301

  20. Final Report: The Impact of Carbonate on Surface Protonation, Electron Transfer and Crystallization Reactions in Iron Oxide Nanoparticles and Colloids

    SciTech Connect

    Dixon, David Adams

    2013-07-02

    This project addresses key issues of importance in the geochemical behavior of iron oxides and in the geochemical cycling of carbon and iron. For Fe, we are specifically studying the influence of carbonate on electron transfer reactions, solid phase transformations, and the binding of carbonate to reactive sites on the edges of particles. The emphasis on carbonate arises because it is widely present in the natural environment, is known to bind strongly to oxide surfaces, is reactive on the time scales of interest, and has a speciation driven by acid-base reactions. The geochemical behavior of carbonate strongly influences global climate change and CO{sub 2} sequestration technologies. Our goal is to answer key questions with regards to specific site binding, electron transfer reactions, and crystallization reactions of iron oxides that impact both the geochemical cycling of iron and CO{sub 2} species. Our work is focused on the molecular level description of carbonate chemistry in solution including the prediction of isotope fractionation factors. We have also done work on critical atmospheric species.

  1. Environmental application of millimetre-scale sponge iron (s-Fe(0)) particles (III): The effect of surface silver.

    PubMed

    Ju, Yongming; Yu, Yunjiang; Wang, Xiaoyan; Zhang, Sukun; Liu, Runlong; Fu, Jianping; Han, Jinglei; Fang, Jiande; Dionysiou, Dionysios D

    2015-12-15

    To enhance the dechlorination reactivity of millimetric sponge iron (s-Fe(0)), a facile one-pot method was used to decorate s-Fe(0) with Ag(+) ions under ambient conditions. The results recorded by X-ray diffraction patterns, X-ray photoelectron spectra and high-resolution transmission electron microscopy demonstrated that the growth of Ag(0) was dominated primarily by (111) plane with a mean length of ∼20 nm. The roles of Ag(0) loading, catalyst dosage, particle size, initial pH and contaminant concentration were assessed during the removal of pentachlorophenol (PCP). Catalyst recyclability was also studied. The results revealed that 3-5mm s-Fe(0) particles with 5 wt% Ag(0) loading exhibited the best performance with a dose of 3.0 g per 60 mL PCP solution. In addition, the dechlorination of PCP followed two-step, pseudo-first-order reaction kinetics, and Ag(0)-s-Fe(0) was advantageous compared with bimetals of nanoscale zero-valent iron, iron power and iron flakes. The dechlorination mechanism of PCP over Ag(0)-s-Fe(0) was attributed to the surface Ag(0) decoration, which catalyzed the formation of reactive hydrogen atoms for indirect reaction, and the direct electron transfer via Fe-Ag(0) galvanic cells for direct reaction. This suggests that Ag-based bimetals of s-Fe(0) have great potential in the pretreatment of organic halogen compounds in aqueous solution. PMID:26276702

  2. Modulation of Staphylococcus aureus spreading by water.

    PubMed

    Lin, Mei-Hui; Ke, Wan-Ju; Liu, Chao-Chin; Yang, Meng-Wei

    2016-01-01

    Staphylococcus aureus is known to spread rapidly and form giant colonies on the surface of soft agar and animal tissues by a process called colony spreading. So far, the mechanisms underlying spreading remain poorly understood. This study investigated the spreading phenomenon by culturing S. aureus and its mutant derivatives on Tryptic Soy Agarose (TSA) medium. We found that S. aureus extracts water from the medium and floats on water at 2.5 h after inoculation, which could be observed using phase contrast microscopy. The floating of the bacteria on water could be verified by confocal microscopy using an S. aureus strain that constitutively expresses green fluorescence protein. This study also found that as the density of bacterial colony increases, a quorum sensing response is triggered, resulting in the synthesis of the biosurfactants, phenolic-soluble modulins (PSMs), which weakens water surface tension, causing water to flood the medium surface to allow the bacteria to spread rapidly. This study reveals a mechanism that explains how an organism lacking a flagellar motor is capable of spreading rapidly on a medium surface, which is important to the understanding of how S. aureus spreads in human tissues to cause infections. PMID:27125382

  3. Modulation of Staphylococcus aureus spreading by water

    PubMed Central

    Lin, Mei-Hui; Ke, Wan-Ju; Liu, Chao-Chin; Yang, Meng-Wei

    2016-01-01

    Staphylococcus aureus is known to spread rapidly and form giant colonies on the surface of soft agar and animal tissues by a process called colony spreading. So far, the mechanisms underlying spreading remain poorly understood. This study investigated the spreading phenomenon by culturing S. aureus and its mutant derivatives on Tryptic Soy Agarose (TSA) medium. We found that S. aureus extracts water from the medium and floats on water at 2.5 h after inoculation, which could be observed using phase contrast microscopy. The floating of the bacteria on water could be verified by confocal microscopy using an S. aureus strain that constitutively expresses green fluorescence protein. This study also found that as the density of bacterial colony increases, a quorum sensing response is triggered, resulting in the synthesis of the biosurfactants, phenolic-soluble modulins (PSMs), which weakens water surface tension, causing water to flood the medium surface to allow the bacteria to spread rapidly. This study reveals a mechanism that explains how an organism lacking a flagellar motor is capable of spreading rapidly on a medium surface, which is important to the understanding of how S. aureus spreads in human tissues to cause infections. PMID:27125382

  4. Corrosion related properties of iron (100) surface in liquid lead and bismuth environments: A first-principles study

    NASA Astrophysics Data System (ADS)

    Song, Chi; Li, Dong-Dong; Xu, Yi-Chun; Pan, Bi-Cai; Liu, Chang-Song; Wang, Zhi-Guang

    2014-05-01

    The corrosion of steels in liquid metal lead (Pb) and bismuth (Bi) is a critical challenge in the development of accelerator driven systems (ADS). Using a first-principles method with a slab model, we theoretically investigate the interaction between the Pb (Bi) atom and the iron (Fe) (100) surface to assess the fundamental corrosion properties. Our investigation demonstrates that both Pb and Bi atoms favorably adsorb on the (100) surface. Such an adsorption decreases the energy required for the dissociation of an Fe atom from the surface, enhancing the dissolution tendency significantly. The segregation of six common alloying elements (Cr, Al, Mn, Ni, Nb, and Si) to the surface and their impacts on the corrosion properties are also considered. The present results reveal that Si seems to have a relatively good performance to stabilize the surface and alleviate the dissolving trend caused by Pb and Bi.

  5. The role of SO{sub 4}{sup 2−} surface distribution in arsenic removal by iron oxy-hydroxides

    SciTech Connect

    Tresintsi, S.; Simeonidis, K.; Pliatsikas, N.; Vourlias, G.; Patsalas, P.; Mitrakas, M.

    2014-05-01

    This study investigates the contribution of chemisorbed SO{sub 4}{sup 2−} in improving arsenic removal properties of iron oxy-hydroxides through an ion-exchange mechanism. An analytical methodology was developed for the accurate quantification of sulfate ion (SO{sub 4}{sup 2−}) distribution onto the surface and structural compartments of iron oxy-hydroxides synthesized by FeSO{sub 4} precipitation. The procedure is based on the sequential determination of SO{sub 4}{sup 2−} presence in the diffuse and Stern layers, and the structure of these materials as defined by the sulfate-rich environments during the reaction and the variation in acidity (pH 3–12). Physically sorbed SO{sub 4}{sup 2−}, extracted in distilled water, and physically/chemically adsorbed ions on the oxy-hydroxide's surface leached by a 5 mM NaOH solution, were determined using ion chromatography. Total sulfate content was gravimetrically measured by precipitation as BaSO{sub 4}. To validate the suggested method, results were verified by X-ray photoelectron and Fourier-transformed infrared spectroscopy. Results showed that low precipitation pH-values favor the incorporation of sulfate ions into the structure and the inner double layer, while under alkaline conditions ions shift to the diffuse layer. - Graphical abstract: An analytical methodology for the accurate quantification of sulfate ions (SO{sub 4}{sup 2−}) distribution onto the diffuse layer, the Stern layer and the structure of iron oxy-hydroxides used as arsenic removal agents. - Highlights: • Quantification of sulfate ions presence in FeOOH surface compartments. • Preparation pH defines the distribution of sulfates. • XPS and FTIR verify the presence of SO{sub 4}{sup 2−} in the structure, the Stern layer the diffuse layer of FeOOH. • Chemically adsorbed sulfates control the arsenic removal efficiency of iron oxyhydroxides.

  6. Antimicrobial Peptide P60.4Ac-Containing Creams and Gel for Eradication of Methicillin-Resistant Staphylococcus aureus from Cultured Skin and Airway Epithelial Surfaces.

    PubMed

    Haisma, Elisabeth M; Göblyös, Anikó; Ravensbergen, Bep; Adriaans, Alwin E; Cordfunke, Robert A; Schrumpf, Jasmijn; Limpens, Ronald W A L; Schimmel, Kirsten J M; den Hartigh, Jan; Hiemstra, Pieter S; Drijfhout, Jan Wouter; El Ghalbzouri, Abdoelwaheb; Nibbering, Peter H

    2016-07-01

    We previously found the LL-37-derived peptide P60.4Ac to be effective against methicillin-resistant Staphylococcus aureus (MRSA) on human epidermal models (EMs). The goal of this study was to identify the preferred carrier for this peptide for topical application on skin and mucosal surfaces. We prepared P60.4Ac in three formulations, i.e., a water-in-oil cream with lanolin (Softisan 649), an oil-in-water cream with polyethylene glycol hexadecyl ether (Cetomacrogol), and a hydroxypropyl methylcellulose (hypromellose) 4000 gel. We tested the antimicrobial efficacy of the peptide in these formulations against mupirocin-resistant and -sensitive MRSA strains on EMs and bronchial epithelial models (BEMs). The cytotoxic effects of formulated P60.4Ac on these models were determined using histology and WST-1 and lactate dehydrogenase assays. Moreover, we assessed the stability of the peptide in these formulations with storage for up to 3 months. Killing of MRSA by P60.4Ac in the two creams was less effective than that by P60.4Ac in the hypromellose gel. In agreement with those findings, P60.4Ac in the hypromellose gel was highly effective in eradicating the two MRSA strains from EMs. We found that even 0.1% (wt/wt) P60.4Ac in the hypromellose gel killed >99% of the viable planktonic bacteria and >85% of the biofilm-associated bacteria on EMs. Hypromellose gels containing 0.1% and 0.5% (wt/wt) P60.4Ac effectively reduced the numbers of viable MRSA cells from BEMs by >90%. No cytotoxic effects of P60.4Ac in the hypromellose gel with up to 2% (wt/wt) P60.4Ac on keratinocytes in EMs and in the hypromellose gel with up to 0.5% (wt/wt) P60.4Ac on epithelial cells in BEMs were observed. High-performance liquid chromatography analysis showed that P60.4Ac was stable in the Softisan cream and the hypromellose gel but not in the Cetomacrogol cream. We conclude that P60.4Ac formulated in hypromellose gel is both stable and highly effective in eradicating MRSA from colonized EMs and

  7. The specific reactive surface area of granular zero-valent iron in metal contaminant removal: Column experiments and modelling.

    PubMed

    Statham, Tom M; Mason, Lachlan R; Mumford, Kathryn A; Stevens, Geoffrey W

    2015-06-15

    A series of dynamic-flow kinetic experiments were conducted to assess the removal rates of aqueous Cu(2+) and Zn(2+) ions by zero-valent iron (ZVI), a promising material for inclusion in cold-climate remediation applications. The influence of experimental parameters on contaminant removal rates, including aqueous flow rate, operating temperature, and the concentrations of ZVI, salt and dissolved oxygen, was investigated. A mass transport model has been developed that accounts (i) aqueous-phase dispersion processes, (ii) film diffusion of contaminant ions to the reactive ZVI surface and (iii) the reactive removal mechanism itself. Regression to the experimental data indicated that when oxygen is present in the solution feed Cu(2+) and Zn(2+) removal processes were limited by film diffusion. In de-aerated solutions film diffusion still controls Cu(2+) removal but a first-order surface reaction provides a better model for Zn(2+) kinetics. Using air as the equilibrium feed gas, the reactive proportion of the total surface area for contaminant removal was calculated to be 97% and 64% of the active spherically-assumed geometric area associated with ZVI media for Cu(2+) and Zn(2+), respectively. Relative to a gas absorption area, determined in previous studies, the reactive proportion is less than 0.41% of the unreacted ZVI total surface area. These findings suggest that only part of the iron oxyhydroxide surface is reacting during ZVI based metal contaminant removal. PMID:25839833

  8. Size-controlled synthesis of superparamagnetic iron oxide nanoparticles and their surface coating by gold for biomedical applications

    NASA Astrophysics Data System (ADS)

    Maleki, H.; Simchi, A.; Imani, M.; Costa, B. F. O.

    2012-11-01

    The size mono-dispersity, saturation magnetization, and surface chemistry of magnetic nanoparticles (NPs) are recognized as critical factors for efficient biomedical applications. Here, we performed modified water-in-oil inverse nano-emulsion procedure for preparation of stable colloidal superparamagnetic iron oxide NPs (SPIONs) with high saturation magnetization. To achieve mono-dispersed SPIONs, optimization process was probed on several important factors including molar ratio of iron salts [Fe3+ and Fe2+], the concentration of ammonium hydroxide as reducing agent, and molar ratio of water to surfactant. The biocompatibility of the obtained NPs, at various concentrations, was evaluated via MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay and the results showed that the NPs were non-toxic at concentrations <0.1 mg/mL. Surface functionalization was performed by conformal coating of the NPs with a thin shell of gold (˜4 nm) through chemical reduction of attached gold salts at the surface of the SPIONs. The Fe3O4 core/Au shell particles demonstrate strong plasmon resonance absorption and can be separated from solution using an external magnetic field. Experimental data from both physical and chemical determinations of the changes in particle size, surface plasmon resonance optical band, phase components, core-shell surface composition, and magnetic properties have confirmed the formation of the mono-dispersed core-shell nanostructure.

  9. Towards advanced structural analysis of iron oxide clusters on the surface of γ-Al2O3 using EXAFS

    NASA Astrophysics Data System (ADS)

    Boubnov, Alexey; Roppertz, Andreas; Kundrat, Matthew D.; Mangold, Stefan; Reznik, Boris; Jacob, Christoph R.; Kureti, Sven; Grunwaldt, Jan-Dierk

    2016-11-01

    Iron oxide centres are structurally investigated in 0.1% Fe/γ-Al2O3, which is known as highly active catalyst, for instance in the oxidation of CO. The sample was characterised by using X-ray absorption spectroscopy (XAS) in terms of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), Mössbauer spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). These analyses evidenced high dispersion of the iron oxide entities without significant presence of bulk-like aggregates associated with the low Fe content of the catalyst. A library of structural models of Al2O3-supported surface Fe was created as input for EXAFS fitting. Additionally, several model structures of Fe substituting Al ions in bulk γ-Al2O3 were created with optimised geometry based on density-functional theory (DFT) calculations. From EXAFS refinement of the best 8 out of 24 models, it was found that the trivalent Fe ions are coordinated by 4-5 oxygen atoms and are located on octahedral lattice sites of the exposed surfaces of γ-Al2O3. These iron oxide species exist mainly as a mixture of monomeric and binuclear species and due to the low concentration represent suitable model systems as alternative to single crystal systems for structure-function relationships.

  10. Effect of surface-modified superparamagnetic iron oxide nanoparticles (SPIONS) on mast cell infiltration: An acute in vivo study.

    PubMed

    Sabareeswaran, Arumugam; Ansar, Ereath Beeran; Harikrishna Varma, Parimanathu Rama Varma; Mohanan, Parayanthala Vilappil; Kumary, Thrikkovil Variathu

    2016-08-01

    Extensive use of superparamagnetic iron oxide nanoparticles (SPIONS) in theranostics prompted us to investigate the acute changes in cell morphology and function following intravenous administration of surface-modified SPIONS in a rat model. Dextran-coated (DEX) and polyethylene glycol-coated (PEG) SPIONS were synthesized and characterized, and cytocompatibility was evaluated in vitro. Haematological, histopathological, ultrastructural and oxidative stress analyses were carried out 24h post intravenous administration in vivo. In test groups, SGPT and SGOT enzymes were significantly altered when compared to saline-only controls. Anti-oxidant imbalance and lipid peroxidation were observed in all major organs. Histology revealed iron-laden Kupffer cells and macrophages in liver and lung respectively. Iron overload was observed in the convoluted tubules of the kidney. Mast cell infiltration and distribution were observed differentially in test groups. Although surface modification of SPIONS improved biocompatibility in vitro, they affected anti-oxidant and tissue nitrite levels, which greatly influenced mast cell infiltration in vivo. PMID:27013127

  11. Differential proteomics analysis of the surface heterogeneity of dextran iron oxide nanoparticles and the implications for their in vivo clearance

    PubMed Central

    Simberg, Dmitri; Park, Ji-Ho; Karmali, Priya P.; Zhang, Wan-Ming; Merkulov, Sergei; McCrae, Keith; Bhatia, Sangeeta; Sailor, Michael; Ruoslahti, Erkki

    2009-01-01

    In order to understand the role of plasma proteins in the rapid liver clearance of dextran-coated superparamagnetic iron oxide (SPIO) in vivo, we analyzed the full repertoire of SPIO-binding blood proteins using novel two-dimensional differential mass spectrometry approach. The identified proteins showed specificity for surface domains of the nanoparticles: mannan-binding lectins bound to the dextran coating, histidine-rich glycoprotein and kininogen bound to the iron oxide part, and the complement lectin and contact clotting factors were secondary binders. Nanoparticle clearance studies in knockout mice suggested that these proteins, as well as several previously identified opsonins, do not play a significant role in the SPIO clearance. However, both the dextran coat and the iron oxide core remained accessible to specific probes after incubation of SPIO in plasma, suggesting that the nanoparticle surface could be available for recognition by macrophages, regardless of protein coating. These data provide guidance to rational design of bioinert, long-circulating nanoparticles. PMID:19394687

  12. ELECTRON MICROSCOPE ANALYSIS OF YOUNG AND OLD RED BLOOD CELLS STAINED WITH COLLOIDAL IRON FOR SURFACE CHARGE EVALUATION

    PubMed Central

    Marikovsky, Y.; Danon, D.

    1969-01-01

    Human and rabbit red blood cells, separated into "young" and "old" age groups by differential flotation on phthalate esters, were fixed with glutaraldehyde and labeled with colloidal ferric oxide. Electron micrographs of thin sections of young cells showed a uniform and dense depostion of positive iron particles. Old cells showed particles deposited irregularly, leaving unlabeled gaps on the membrane surface. Red cells incubated with 10 units/ml receptor-destroying enzyme (RDE) demonstrate a reduced labeling, similar to that of old cells. After neuraminic acid had been removed from red cells by 20 units/ml RDE, no iron particles were found on membrane surfaces. The different labeling of young, old, and RDE-treated human and rabbit red cells was correlated with their electric mobility and agglutinability by poly-L-lysine. The contradiction between the apparent similarity in charge density of human and rabbit red cells as estimated by density of iron particles and the markedly lower electric mobility of rabbit red cells is discussed. PMID:4186411

  13. Electron microscope analysis of young and old red blood cells stained with colloidal iron for surface charge evaluation.

    PubMed

    Marikovsky, Y; Danon, D

    1969-10-01

    Human and rabbit red blood cells, separated into "young" and "old" age groups by differential flotation on phthalate esters, were fixed with glutaraldehyde and labeled with colloidal ferric oxide. Electron micrographs of thin sections of young cells showed a uniform and dense depostion of positive iron particles. Old cells showed particles deposited irregularly, leaving unlabeled gaps on the membrane surface. Red cells incubated with 10 units/ml receptor-destroying enzyme (RDE) demonstrate a reduced labeling, similar to that of old cells. After neuraminic acid had been removed from red cells by 20 units/ml RDE, no iron particles were found on membrane surfaces. The different labeling of young, old, and RDE-treated human and rabbit red cells was correlated with their electric mobility and agglutinability by poly-L-lysine. The contradiction between the apparent similarity in charge density of human and rabbit red cells as estimated by density of iron particles and the markedly lower electric mobility of rabbit red cells is discussed. PMID:4186411

  14. Staphylococcus aureus Induces Release of Bradykinin in Human Plasma

    PubMed Central

    Mattsson, Eva; Herwald, Heiko; Cramer, Henning; Persson, Kristin; Sjöbring, Ulf; Björck, Lars

    2001-01-01

    Staphylococcus aureus is a prominent human pathogen. Here we report that intact S. aureus bacteria activate the contact system in human plasma in vitro, resulting in a massive release of the potent proinflammatory and vasoactive peptide bradykinin. In contrast, no such effect was recorded with Streptococcus pneumoniae. In the activation of the contact system, blood coagulation factor XII and plasma kallikrein play central roles, and a specific inhibitor of these serine proteinases inhibited the release of bradykinin by S. aureus in human plasma. Furthermore, fragments of the cofactor H-kininogen of the contact system efficiently blocked bradykinin release. The results suggest that activation of the contact system at the surface of S. aureus and the subsequent release of bradykinin could contribute to the hypovolemic hypotension seen in patients with severe S. aureus sepsis. The data also suggest that the contact system could be used as a target in the treatment of S. aureus infections. PMID:11349054

  15. Prebiotic polymerization: Oxidative polymerization of 2, 3-dimercapto-1-propanol on the surface of iron(III) hydroxide oxide

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1995-01-01

    The oxidation of 2, 3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the Fe(OH)O phase. Reactions carried out at the same ratio of dithiol to Fe(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

  16. Prebiotic Polymerization: Oxidative Polymerization of 2,3 Dimercapto-1- Propanol on the Surface of Iron(III) Hydroxide Oxide

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1995-01-01

    The oxidation of 2,3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the FE(OH)O phase. Reactions carried out at the same ratio of dithiol to FE(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

  17. Prebiotic Oxidative Polymerization of 2,3 Dimercaptopropanol on the Surface of Iron(III) Hydroxide Oxide

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1994-01-01

    The oxidation of 2,3-Dimercapto-1-propanol by ferric ions on the surface of iron (III) hydroxide oxide yielded polydisulfide polymers. This polymerization occured readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron (III) hydroxide oxide (20 mg, 160 micro mole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the mineral phase. Reactions at higher dithiol concentrations with the same ratio of dithiol to mineral gave a higher yield of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis will be discussed.

  18. Epidemiology of Staphylococcus aureus during space flight

    NASA Technical Reports Server (NTRS)

    Pierson, D. L.; Chidambaram, M.; Heath, J. D.; Mallary, L.; Mishra, S. K.; Sharma, B.; Weinstock, G. M.

    1996-01-01

    Staphylococcus aureus was isolated over 2 years from Space Shuttle mission crewmembers to determine dissemination and retention of bacteria. Samples before and after each mission were from nasal, throat, urine, and feces and from air and surface sampling of the Space Shuttle. DNA fingerprinting of samples by digestion of DNA with SmaI restriction endonuclease followed by pulsed-field gel electrophoresis showed S. aureus from each crewmember had a unique fingerprint and usually only one strain was carried by an individual. There was only one instance of transfer between crewmembers. Strains from interior surfaces after flight matched those of crewmembers, suggesting microbial fingerprinting may have forensic application.

  19. High speed CO2 laser surface modification of iron/cobalt co-doped boroaluminosilicate glass and the impact on surface roughness, gloss and wettability

    NASA Astrophysics Data System (ADS)

    Hodgson, S. D.; Waugh, D. G.; Gillett, A.; Lawrence, J.

    2016-07-01

    A preliminary study into the impact of high speed laser processing on the surface of iron and cobalt co-doped glass substrates using a 60 W continuous wave (cw) CO2 laser. Two types of processing, termed fill-processing and line-processing, were trialled. In fill-processed samples the surface roughness of the glass was found to increase linearly with laser power from an S a value of 20.8 nm–2.1 μm at a processing power of 54 W. With line processing, a more exponential-like increase was observed with a roughness of 4 μm at 54 W. The change in surface properties of the glass, such as gloss and wettability, have also been measured. The contact angle of water was found to increase after laser processing by up to 64°. The surface gloss was varied between 45 and 100 gloss units (GUs).

  20. Slippery liquid-infused porous surface based on perfluorinated lubricant/iron tetradecanoate: Preparation and corrosion protection application

    NASA Astrophysics Data System (ADS)

    Yang, Shengsheng; Qiu, Ri; Song, Hongqing; Wang, Peng; Shi, Zhiqiang; Wang, Yanfang

    2015-02-01

    Corrosion and fouling have been two major enemies for materials immersed in seawater. Fluid including gas and liquid as coating for marine corrosion protection has attracted much attention, since it can also exert antifouling capability in seawater environment. Combining gas and solid phases, superhydrophobic surface is promising to protect the underlying metal from corrosion. However, the intrinsically short sustainability in underwater environment has hindered its practical application, so that its corrosion protection ability is only temporary. Originated from liquid and solid phases, slippery liquid-infused porous surface (SLIPS) has spurred wide interest due to its prominent performance in different fields. However, the exploration of corrosion protection efficiency from SLIPS remains rare. In this research, SLIPS is constructed onto steel surface via a facile two-step protocol. First, based on a dissolution-deposition strategy, iron tetradecanoate is formed by an electrochemical route. After that, fluid lubricant is infused onto the deposit, whose rough surface acts as the reservoir to entrap the fluid to form a static liquid coating. Compared to the bare and hydrophobic deposit covering low alloy steel, the SLIPS composed perfluorinated lubricant and iron tetradecanoate endows good corrosion protection property.

  1. Influence of iron solubility and charged surface-active compounds on lipid oxidation in fatty acid ethyl esters containing association colloids.

    PubMed

    Homma, Rika; Johnson, David R; McClements, D Julian; Decker, Eric A

    2016-05-15

    The impact of iron compounds with different solubilities on lipid oxidation was studied in the presence and absence of association colloids. Iron (III) sulfate only accelerated lipid oxidation in the presence of association colloids while iron (III) oleate accelerated oxidation in the presence and absence of association colloids. Further, iron (III) oxide retarded lipid oxidation both with and without association colloids. The impact of charged association colloids on lipid oxidation in ethyl oleate was also investigated. Association colloids consisting of the anionic surface-active compound dodecyl sulphosuccinate sodium salt (AOT), cationic surface-active compound hexadecyltrimethylammonium bromide (CTAB), and nonionic surface-active compound 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton X-100) retarded, promoted, and had no effect on lipid oxidation rates, respectively. These results indicate that the polarity of metal compounds and the charge of association colloids play a big role in lipid oxidation. PMID:26776045

  2. 35. GREY IRON TUMBLERS, IN THE GREY IRON FOUNDRY ROTATE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    35. GREY IRON TUMBLERS, IN THE GREY IRON FOUNDRY ROTATE CASTINGS WITH SHOT TO REMOVE AND SURFACE OXIDES AND REMAINING EXCESS METALS. - Stockham Pipe & Fittings Company, Grey Iron Foundry, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

  3. Synthesis and Characterization of Surface Grafted Poly(N-isopropylacrylamide) and Poly(Carboxylic Acid)– Iron Particles via Atom Transfer Radical Polymerization for Biomedical Applications

    PubMed Central

    Sutrisno, Joko; Fuchs, Alan; Evrensel, Cahit

    2014-01-01

    This research relates to the preparation and characterization of surface grafted poly(N-isopropylacrylamide) and poly(carboxylic acid)–micron-size iron particles via atom transfer radical polymerization (ATRP). The surface grafted polymers–iron particles result in multifunctional materials which can be used in biomedical applications. The functionalities consist of cell targeting, imaging, drug delivery, and immunological response. The multifunctional materials are synthesized in two steps. First, surface grafting is used to place polymer molecules on the iron particles surface. The second step, is conjugation of the bio-molecules onto the polymer backbone. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy were used to confirm the presence of polymers on the iron particles. The thickness of the grafted polymers and glass transition temperature of the surface grafted polymers were determined by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The covalent bond between grafted polymers and iron particles caused higher glass transition temperature as compared with non-grafted polymers. The ability to target the bio-molecule and provide fluorescent imaging was simulated by conjugation of rat immunoglobulin and fluorescein isothiocyanate (FITC) labeled anti-rat. The fluorescence intensity was determined using flow cytometry and conjugated IgG-FITC anti-rat on iron particles which was imaged using a fluorescence microscopy. PMID:25382869

  4. SURFACE COMPLEXATION MODEL TO DESCRIBE COMPETITIVE ARSENIC ADSORPTION ONTO IRON OXIDES

    EPA Science Inventory

    The output of this work would be a set of self-consistent model parameters that would describe the adsorption of arsenic onto iron oxides in the presence of other solutes. The model could be used to predict the potential for removal of arsenic from drinking water by adsorpt...

  5. Staphylococcus aureus biofilms

    PubMed Central

    Archer, Nathan K; Mazaitis, Mark J; Costerton, J William; Leid, Jeff G; Powers, Mary Elizabeth

    2011-01-01

    Increasing attention has been focused on understanding bacterial biofilms and this growth modality's relation to human disease. In this review we explore the genetic regulation and molecular components involved in biofilm formation and maturation in the context of the Gram-positive cocci, Staphylococcus aureus. In addition, we discuss diseases and host immune responses, along with current therapies associated with S. aureus biofilm infections and prevention strategies. PMID:21921685

  6. Surface Functionalization of Magnetic Iron Oxide Nanoparticles for MRI Applications – Effect of Anchoring Group and Ligand Exchange Protocol

    PubMed Central

    Smolensky, Eric D.; Park, Hee-Yun E.; Berquó, Thelma S.; Pierre, Valérie C.

    2011-01-01

    Hydrophobic magnetite nanoparticles synthesized from thermal decomposition of iron salts must be rendered hydrophilic for their application as MRI contrast agents. This process requires refunctionalizing the surface of the nanoparticles with a hydrophilic organic coating such as polyethylene glycol. Two parameters were found to influence the magnetic behavior and relaxivity of the resulting hydrophilic iron oxide nanoparticles: the functionality of the anchoring group and the protocol followed for the functionalization. Nanoparticles coated with PEGs via a catecholate-type anchoring moiety maintain the saturation magnetization and relaxivity of the hydrophobic magnetite precursor. Other anchoring functionalities, such as phosphonate, carboxylate, and dopamine decrease the magnetization and relaxivity of the contrast agent. The protocol for functionalizing the nanoparticles also influences the magnetic behavior of the material. Nanoparticles refunctionalized according to a direct biphasic protocol exhibit higher relaxivity than those refunctionalized according to a two-step procedure which first involves stripping the nanoparticles. This research presents the first systematic study of both the binding moiety and the functionalization protocol on the relaxivity and magnetization of water-soluble coated iron oxide nanoparticles used as MRI contrast agents. PMID:21861279

  7. Effect of surface charge on the colloidal stability and in vitro uptake of carboxymethyl dextran-coated iron oxide nanoparticles

    PubMed Central

    Ayala, Vanessa; Herrera, Adriana P.; Latorre-Esteves, Magda; Torres-Lugo, Madeline

    2013-01-01

    Nanoparticle physicochemical properties such as surface charge are considered to play an important role in cellular uptake and particle–cell interactions. In order to systematically evaluate the role of surface charge on the uptake of iron oxide nanoparticles, we prepared carboxymethyl-substituted dextrans with different degrees of substitution, ranging from 38 to 5 groups per chain, and reacted them using carbodiimide chemistry with amine–silane-coated iron oxide nanoparticles with narrow size distributions in the range of 33–45 nm. Surface charge of carboxymethyl-substituted dextran-coated nano-particles ranged from −50 to 5 mV as determined by zeta potential measurements, and was dependent on the number of carboxymethyl groups incorporated in the dextran chains. Nanoparticles were incubated with CaCo-2 human colon cancer cells. Nanoparticle–cell interactions were observed by confocal laser scanning microscopy and uptake was quantified by elemental analysis using inductively coupled plasma mass spectroscopy. Mechanisms of internalization were inferred using pharmacological inhibitors for fluid-phase, clathrin-mediated, and caveola-mediated endocytosis. Results showed increased uptake for nanoparticles with greater negative charge. Internalization patterns suggest that uptake of the most negatively charged particles occurs via non-specific interactions. PMID:24470787

  8. Factors controlling synthesis of iron oxide nanoparticles and the effect of surface charge on magnetic hyperthermia

    NASA Astrophysics Data System (ADS)

    Qi, Bin

    Iron oxide nanoparticles (IONPs) have been widely studied in the theranostics application due to their promising magnetic properties, low cytotoxicity and attractive biocompatibility. Despite the numerous studies on the kinetic mechanisms of IONPs synthesis and thus the resulting size, shape and crystallinity; there are still considerable unsolved issues in quantitatively depicting the dependence between particle morphology and the reaction conditions. To begin to explain some of these phenomena, the kinetic mechanism for the morphology and crystalline changes of IONPs with the ligand/precursor ratio in nanoparticle synthesis was investigated. During the synthesis of nanoparticles via thermal decomposition of iron precursors, the capping ligand-precursor ratio influences the resulting size of the iron oxide nanoparticles. As the molar ratio of aliphatic amines to iron precursor is increased, the average diameter of the synthesized iron oxide nanoparticles decreases. This trend is opposite to previously reported results. We investigated this phenomenon by independently varying the ligand chain length, the ligand-precursor molar ratio, and the degree of saturation of the aliphatic chain. Nuclear magnetic resonance spectra of precursor illustrated the presence of a primary amine peak before heating and the peak absence after heating, potentially indicating that the primary amine acts as reducing agent to promote the decomposition of the iron precursor. We hypothesize that the amine groups play a dominant role in the nucleation of the particles, while the chain length and degree of aliphatic saturation have only a minor effect on particle size. The nanoparticles' size and crystallinity were characterized with high resolution transmission electron microscopy, dynamic light scattering, and X-ray diffraction, and the magnetic properties were characterized by magnetometry. Known ligand/precursor ratio effects on the IONPs size distribution, here in, we report that the

  9. Application of EDS microanalysis in the identification of inhomogeneities in surface protective layers on ductile cast iron parts

    NASA Astrophysics Data System (ADS)

    Boroń, Ł.; Tchórz, A.

    2010-02-01

    In this study, the results of the application of both scanning electron microscopy and EDS microanalysis in investigations of the process of the protective layer formation on the surface of ductile cast iron (the substrate material) turbine blades are presented. The turbine blades, designated for operation in an aggressive environment, were coated with protective chromium carbide layers using plasma spraying methods. The first turbine blade was coated using a standard plasma spraying technique, followed by superficial remelting treatment, while the second one was coated using a modified plasma technology, i.e., HVOF (High Velocity Oxy Fuel) spraying technique.

  10. Manganese Doping of Magnetic Iron Oxide Nanoparticles: Tailoring Surface Reactivity for a Regenerable Heavy Metal Sorbent

    SciTech Connect

    Warner, Cynthia L.; Chouyyok, Wilaiwan; Mackie, Katherine E.; Neiner, Doinita; Saraf, Laxmikant; Droubay, Timothy C.; Warner, Marvin G.; Addleman, Raymond S.

    2012-02-28

    A method for tuning the analyte affinity of magnetic, inorganic nanostructured sorbents for heavy metal contaminants is described. The manganese-doped iron oxide nanoparticle sorbents have a remarkably high affinity compared to the precursor material. Sorbent affinity can be tuned toward an analyte of interest simply by adjustment of the dopant quantity. The results show that following the Mn doping process there is a large increase in affinity and capacity for heavy metals (i.e., Co, Ni, Zn, As, Ag, Cd, Hg, and Tl). Capacity measurements were carried out for the removal of cadmium from river water and showed significantly higher loading than the relevant commercial sorbents tested for comparison. The reduction in Cd concentration from 100 ppb spiked river water to 1 ppb (less than the EPA drinking water limit of 5 ppb for Cd) was achieved following treatment with the Mn-doped iron oxide nanoparticles. The Mn-doped iron oxide nanoparticles were able to load 1 ppm of Cd followed by complete stripping and recovery of the Cd with a mild acid wash. The Cd loading and stripping is shown to be consistent through multiple cycles with no loss of sorbent performance.

  11. The evaluation of the influence of laser treatment parameters on the type of thermal effects in the surface layer microstructure of gray irons

    NASA Astrophysics Data System (ADS)

    Paczkowska, Marta

    2016-01-01

    The aim of the presented research was to create a laser heat treatment (LHT) diagram presenting singular modifications such as remelting, alloying, hardening from the solid state, tempering the surface layer of gray iron in individual ranges of laser beam parameters (power density and its interaction time). A synthesis of such different thermal phenomena taking place in gray irons surface layer resulting from LHT was the aim of this analysis. The performed research allowed specifying similar, previously created diagrams concerning different engineering materials in general. The created LHT diagram presents singular modifications in the surface layer of gray iron in individual ranges of laser beam parameters. This diagram allows distinguishing ranges of laser beam parameters that could be useful in selecting the LHT parameters or forecasting their effects in the gray iron surface layer. It has been observed that it is possible to achieve the modification of the surface layer of gray iron by applying values of laser beam power density lower than the values of density presented in previously created diagrams related to the influence of LHT parameters on their effects in the surface layer referring to different groups of engineering materials. The limit of the laser beam density was defined resulting in the modification of the surface layer for interaction time t<0.2 s (remelting or alloying) and t>0.2 s (hardening from the solid state). It is not possible to achieve melting or hardening of the surface layer in gray irons using a laser beam density of less than 10 W mm-2. Hardening is possible only with the interaction time longer than 0.2 s and the power beam density between 10 and 40 W mm-2. Tempering of the surface layer is possible with the density of nearly 10 W mm-2 but only with a relatively long interaction time (i.e. 4 s).

  12. A Novel Cell-Associated Protection Assay Demonstrates the Ability of Certain Antibiotics To Protect Ocular Surface Cell Lines from Subsequent Clinical Staphylococcus aureus Challenge▿†

    PubMed Central

    Wingard, J. B.; Romanowski, E. G.; Kowalski, R. P.; Mah, F. S.; Ling, Y.; Bilonick, R. A.; Shanks, R. M. Q.

    2011-01-01

    In vivo effectiveness of topical antibiotics may depend on their ability to associate with epithelial cells to provide continued protection, but this contribution is not measured by standard antibiotic susceptibility tests. We report a new in vitro method that measures the ability of test antibiotics azithromycin (AZM), erythromycin (ERY), tetracycline (TET), and bacitracin (BAC) to associate with mammalian cells and to protect these cells from destruction by bacteria. Mammalian cell lines were grown to confluence using antibiotic-free medium and then incubated in medium containing a single antibiotic (0 to 512 μg/ml). After incubation, the cells were challenged with Staphylococcus aureus ocular isolates, without antibiotics added to the culture medium. Epithelial cell layer integrity was assessed by gentian violet staining, and the minimum cell layer protective concentration (MCPC) of an antibiotic sufficient to protect the mammalian cells from S. aureus was determined. Staining was also quantified and analyzed. Bacterial viability was determined by culture turbidity and growth on agar plates. Preincubation of Chang and human corneal limbal epithelial cells with AZM, ERY, and TET at ≥64 μg/ml provided protection against AZM-susceptible S. aureus strains, with increasing protection at higher concentrations. TET toxicity was demonstrated at >64 μg/ml, whereas AZM displayed toxicity to one cell line at 512 μg/ml. BAC failed to show consistent protection at any dose, despite bacterial susceptibility to BAC as determined by traditional antibiotic susceptibility testing. A range of antibiotic effectiveness was displayed in this cell association assay, providing data that may be considered in addition to traditional testing when determining therapeutic dosing regimens. PMID:21628536

  13. Structure and friction of stearic acid and oleic acid films adsorbed on iron oxide surfaces in squalane.

    PubMed

    Doig, Michael; Warrens, Chris P; Camp, Philip J

    2014-01-14

    The structure and friction of fatty acid surfactant films adsorbed on iron oxide surfaces lubricated by squalane are examined using large-scale molecular dynamics simulations. The structures of stearic acid and oleic acid films under static and shear conditions, and at various surface coverages, are described in detail, and the effects of unsaturation in the tail group are highlighted. At high surface coverage, the measured properties of stearic acid and oleic acid films are seen to be very similar. At low and intermediate surface coverages, the presence of a double bond, as in oleic acid, is seen to give rise to less penetration of lubricant in to the surfactant film and less layering of the lubricant near to the film. The kinetic friction coefficient is measured as a function of shear rate within the hydrodynamic (high shear rate) lubrication regime. Lubricant penetration and layering are observed to be correlated with friction coefficient. The friction coefficient with oleic acid depends only weakly on surface coverage, while stearic acid admits more lubricant penetration, and its friction coefficient increases significantly with decreasing surface coverage. Connections between film structure and friction are discussed. PMID:24364665

  14. Superparamagnetic iron oxide coated on the surface of cellulose nanospheres for the rapid removal of textile dye under mild condition

    NASA Astrophysics Data System (ADS)

    Qin, Yunfeng; Qin, Zongyi; Liu, Yannan; Cheng, Miao; Qian, Pengfei; Wang, Qian; Zhu, Meifang

    2015-12-01

    Magnetic composite nanoparticles (MNPs) were prepared by anchoring iron oxide (Fe3O4) on the surface of carboxyl cellulose nanospheres through a facile chemical co-precipitation method. The as-prepared MNPs were characterized by atomic force microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, wide-angle X-ray diffraction measurement, thermal gravity analysis and vibrating sample magnetometry. These MNPs were of a generally spherical shape with a narrow size distribution, and exhibited superparamagnetic behaviors with high saturation magnetization. High efficient removal of Navy blue in aqueous solution was demonstrated at room temperature in a Fenton-like system containing the MNPs and H2O2, which benefited from small particle size, large surface area, high chemical activity, and good dispersibility of the MNPs. The removal efficiency of Navy blue induced by the MNPs prepared at a weight ratio of cellulose to iron of 1:2 were 90.6% at the first minute of the degradation reaction, and 98.0% for 5 min. Furthermore, these MNPs could be efficiently recycled and reused by using an external magnetic field. The approach presented in this paper promotes the use of renewable natural resources as templates for the preparation and stabilization of various inorganic nanomaterials for the purpose of catalysis, magnetic resonance imaging, biomedical and other potential applications.

  15. XPS study of the room temperature surface oxidation of zirconium and its binary alloys with tin, chromium and iron

    NASA Astrophysics Data System (ADS)

    Kumar, Lalit; Sarma, D. D.; Krummacher, S.

    1988-07-01

    Surface oxidation of pure zirconium and its dilute binary alloys with tin, chromium and iron has been investigated by X-ray photoelectron spectroscopy with a view to comparing their oxidation behaviour at room temperature. Mostly suboxides of zirconium are formed during the initial stages of oxidation at oxygen exposures < 10 L, while at higher exposures ZrO 2 is the dominant oxide species formed together with two suboxides. The relative XPS intensity of these two suboxides shows a broad and weak maximum in the exposure range 20-30 L. Pure zirconium as well as its dilute alloys exhibit a decreasing rate of oxidation with increasing oxygen exposures. No significant difference is observed in the surface oxidation behaviour of pure zirconium and its dilute binary alloys at room temperature.

  16. A novel co-culture model of murine K12 osteosarcoma cells and S. aureus on common orthopedic implant materials: 'the race to the surface' studied in vitro.

    PubMed

    McConda, David B; Karnes, Jonathan M; Hamza, Therwa; Lindsey, Brock A

    2016-07-01

    Infection is a major cause of orthopedic implant failure. There are few studies assessing both tissue cell and bacterial adherence on common orthopedic implant materials in a co-culture environment. An in vitro co-culture model was created using K12 osteosarcoma cells and Staphylococcus aureus in a medium incubated over metal disks for 48 h. The results showed that, in the presence of S. aureus, there were fewer osteosarcoma cells attached to the disks for all substrata tested. There were significantly more osteosarcoma cells adhering to the cobalt chrome than the stainless steel and titanium disks. Overall, in the presence of osteosarcoma cells, there were more bacteria adhering to the disks for all the substrata tested, with significantly more bacteria adhering to the stainless steel disks compared to cobalt chrome and titanium disks. Scanning electron microscopy verified that osteosarcoma cells and bacteria were adherent to the metal disks after incubation for 48 h. Furthermore, the observation that more bacteria were in the co-culture than in the control sample suggests that the osteosarcoma cells serve as a nutrient source for the bacteria. Future models assessing the interaction of osteogenic cells with bacteria on a substratum would be improved if the model accounted for the role of the immune system in secondary bone healing. PMID:27142312

  17. Residual Stress, Structure and Other Properties Formation by Combined Thermo-Hardening Processing of Surface Layer of Gray Cast Iron Parts

    NASA Astrophysics Data System (ADS)

    Rakhimyanov, Kh M.; Nikitin, Yu V.; Semenova, Yu S.; Eremina, A. S.

    2016-04-01

    The proposed combined thermo-hardening processing of gray cast iron enables to control the surface layer structure and mechanical properties formation. The processing includes high-speed heating by low-temperature plasma source and ultrasonic surface plastic deformation. The algorithm of calculation the stress-strain state of a surface layer at combined processing of gray cast iron is developed. This algorithm is based on method of sections. The ultrasonic surface deformation contribution is determined during formation of residual stresses. It is established that the combination of the thermal and deformation effects on the material provides an additional increment of microhardness and increase of surface layer thickness. Experimental results shows that the features of structural and phase transformations in a surface layer are revealed without a surface melting by energy of low-temperature plasma. The top of a layer does not contain inclusions of graphite that testifies to change of structural transformations in conditions of combined processing.

  18. Surface- and tip-enhanced Raman spectroscopy reveals spin-waves in iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Rodriguez, Raul D.; Sheremet, Evgeniya; Deckert-Gaudig, Tanja; Chaneac, Corinne; Hietschold, Michael; Deckert, Volker; Zahn, Dietrich R. T.

    2015-05-01

    Nanomaterials have the remarkable characteristic of displaying physical properties different from their bulk counterparts. An additional degree of complexity and functionality arises when oxide nanoparticles interact with metallic nanostructures. In this context the Raman spectra due to plasmonic enhancement of iron oxide nanocrystals are here reported showing the activation of spin-waves. Iron oxide nanoparticles on gold and silver tips are found to display a band around 1584 cm-1 attributed to a spin-wave magnon mode. This magnon mode is not observed for nanoparticles deposited on silicon (111) or on glass substrates. Metal-nanoparticle interaction and the strongly localized electromagnetic field contribute to the appearance of this mode. The localized excitation that generates this mode is confirmed by tip-enhanced Raman spectroscopy (TERS). The appearance of the spin-waves only when the TERS tip is in close proximity to a nanocrystal edge suggests that the coupling of a localized plasmon with spin-waves arises due to broken symmetry at the nanoparticle border and the additional electric field confinement. Beyond phonon confinement effects previously reported in similar systems, this work offers significant insights on the plasmon-assisted generation and detection of spin-waves optically induced.Nanomaterials have the remarkable characteristic of displaying physical properties different from their bulk counterparts. An additional degree of complexity and functionality arises when oxide nanoparticles interact with metallic nanostructures. In this context the Raman spectra due to plasmonic enhancement of iron oxide nanocrystals are here reported showing the activation of spin-waves. Iron oxide nanoparticles on gold and silver tips are found to display a band around 1584 cm-1 attributed to a spin-wave magnon mode. This magnon mode is not observed for nanoparticles deposited on silicon (111) or on glass substrates. Metal-nanoparticle interaction and the strongly

  19. Evaluation of Surface Roughness and Power Consumption in Machining FCD 450 Cast Iron using Coated and Uncoated Irregular Milling Tools

    NASA Astrophysics Data System (ADS)

    Razlan Yusoff, Ahmad; Arsyad, Fitriyanti

    2016-02-01

    In this project, the effects of different cutting parameters on surface roughness and power consumption when machining FCD450 cast iron were studied using coated and uncoated irregular milling tool geometry of variable helix and pitch. Their responses on roughness and power consumption were evaluated based on the spindle speed, feed rate, and depth of cut, machining length and machining time. Results showed that except spindle speed and machining length, other parameters such as feed rate, axial and radial depth of cut and also machining time proportionate with surface roughness. The power consumption proportionately increase for all cutting parameters except feedrate. It is showed that the average decrement 27.92 percent for surface roughness and average decrement 9.32 percent for power consumption by using coated compared to uncoated tool. Optimum cutting parameters for both minimum surface roughness and power consumption can be determined. The coated tools performed better than uncoated milling tools for responses of surface roughness and power consumption to increase machining productivity and profit.

  20. Investigation of interparticle forces in natural waters: effects of adsorbed humic acids on iron oxide and alumina surface properties.

    PubMed

    Sander, Sylvia; Mosley, Luke M; Hunter, Keith A

    2004-09-15

    The nature of interparticle forces acting on colloid particle surfaces with adsorbed surface films of the internationally used humic acid standard material, Suwannee River Humic Acid (SHA), has been investigated using an atomic force microscope (AFM). Two particle surfaces were used, alumina and a hydrous iron oxide film coated onto silica particles. Adsorbed SHA dominated the interactive forces for both surface types when present. At low ionic strength and pH > 4, the force curves were dominated by electrostatic repulsion of the electrical double layers, with the extent of repulsion decreasing as electrolyte (NaCl) concentration increased, scaling with the Debye length (kappa(-1)) of the electrolyte according to classical theory. At pH approximately 4, electrostatic forces were largely absent, indicating almost complete protonation of carboxylic acid (-COOH) functional groups on the adsorbed SHA. Under these conditions and also at high electrolyte concentration ([NaCl] > 0.1 M), the absence of electrostatic forces allowed observation of repulsion forces arising from steric interaction of adsorbed SHA as the oxide surfaces approached closely to each other (separation < 10 nm). This steric barrier shrank as electrolyte concentration increased, implying tighter coiling of the adsorbed SHA molecules. In addition, adhesive bridging between surfaces was observed only in the presence of SHA films, implying a strong energy barrier to spontaneous detachment of the surfaces from each other once joined. This adhesion was especially strong in the presence of Ca2+ which appears to bridge SHA layers on each surface. Overall, our results show that SHA is a good model for the NOM adsorbed on colloids. PMID:15487789

  1. An investigation of the kinetics for hydrogen chemisorption on iron metal surfaces

    NASA Technical Reports Server (NTRS)

    Shanabarger, M. R.

    1980-01-01

    A quasi-isothermal approach was used to study the kinetics of hydrogen and hydrogen sulfide chemisorption onto iron film in an effort to understand the environmental degradation of steels. The coverage of chemisorbed hydrogen or chemisorbed sulfur was observed as a function of time for fixed conditions of substrate temperature. Auger electron spectroscopy was used to observe the sulfur and chemisorption-induced resistance change was employed to monitor hydrogen coverage. To compare the results obtained from studying the kinetics by two different techniques, the kinetics of oxygen chemisorption onto iron films was also studied. A reaction model utilized to interpret the H2/Fe2 chemisorption kinetics was applied to data from an earlier study on the desorption kinetics for H2 chemisorbed onto nicket films in the vicinity of the Curie temperature of the film. This analysis permitted a separation of the gross desorption process into individual components so that the influence of the magnetic phase transition on the rate constants could be determined.

  2. The impact of surface dynamo magnetic fields on the solar iron abundance

    NASA Astrophysics Data System (ADS)

    Shchukina, N.; Trujillo Bueno, J.

    2015-07-01

    Most chemical abundance determinations ignore that the solar photosphere is significantly magnetized by the ubiquitous presence of a small-scale magnetic field. A recent investigation has suggested that there should be a significant impact on the derived iron abundance, owing to the magnetically induced changes on the photospheric temperature and density structure (indirect effect). The three-dimensional (3D) photospheric models used in that investigation have non-zero net magnetic flux values and stem from magneto-convection simulations without small-scale dynamo action. Here we address the same problem by instead using 3D models of the quiet solar photosphere that result from a state-of-the-art magneto-convection simulation with small-scale dynamo action, where the net magnetic flux is zero. One of these 3D models has negligible magnetization, while the other is characterized by a mean field strength of 160 Gauss in the low photosphere. With such 3D models we carried out spectral synthesis for a large set of Fe i lines to derive abundance corrections, taking the above-mentioned indirect effect and the Zeeman broadening of the intensity profiles (direct effect) into account. We conclude that if the magnetism of the quiet solar photosphere is mainly produced by a small-scale dynamo, then its impact on the determination of the solar iron abundance is negligible. Table 1 is available in electronic form at http://www.aanda.org

  3. Chelator free gallium-68 radiolabelling of silica coated iron oxide nanorods via surface interactions.

    PubMed

    Burke, Benjamin P; Baghdadi, Neazar; Kownacka, Alicja E; Nigam, Shubhanchi; Clemente, Gonçalo S; Al-Yassiry, Mustafa M; Domarkas, Juozas; Lorch, Mark; Pickles, Martin; Gibbs, Peter; Tripier, Raphaël; Cawthorne, Christopher; Archibald, Stephen J

    2015-09-28

    The commercial availability of combined magnetic resonance imaging (MRI)/positron emission tomography (PET) scanners for clinical use has increased demand for easily prepared agents which offer signal or contrast in both modalities. Herein we describe a new class of silica coated iron-oxide nanorods (NRs) coated with polyethylene glycol (PEG) and/or a tetraazamacrocyclic chelator (DO3A). Studies of the coated NRs validate their composition and confirm their properties as in vivo T2 MRI contrast agents. Radiolabelling studies with the positron emitting radioisotope gallium-68 (t1/2 = 68 min) demonstrate that, in the presence of the silica coating, the macrocyclic chelator was not required for preparation of highly stable radiometal-NR constructs. In vivo PET-CT and MR imaging studies show the expected high liver uptake of gallium-68 radiolabelled nanorods with no significant release of gallium-68 metal ions, validating our innovation to provide a novel simple method for labelling of iron oxide NRs with a radiometal in the absence of a chelating unit that can be used for high sensitivity liver imaging. PMID:26292197

  4. Surface complexation modeling and spectroscopic evidence of antimony adsorption on iron-oxide-rich red earth soils.

    PubMed

    Vithanage, Meththika; Rajapaksha, Anushka Upamali; Dou, Xiaomin; Bolan, Nanthi S; Yang, Jae E; Ok, Yong Sik

    2013-09-15

    Few studies have investigated surface complexation of antimony (Sb) on natural sorbents. In addition, intrinsic acidic constants, speciation, and spectroscopic data are scarce for Sb sorption in soil. Only simple sorption models have been proposed to describe the sorption of Sb(V) on specific mineral surfaces. This study therefore assessed the mechanisms of Sb(III) and Sb(V) adsorption on natural red earth (NRE), a naturally occurring iron coated sand, at various pHs and Sb loadings. The Sb(V) adsorption followed typical anion adsorption curve with adsorption reaching maximum around pH 4-5, while no pH dependence was observed for Sb(III) sorption. The FT-IR spectra revealed that shifts in absorbance of the hydroxyl groups in iron-oxide were related to the Fe-O-Sb bonds and provided evidence for inner sphere bond formation. Direct evidence on the strong interaction of Sb(III) and Sb(V) with ≡Fe-O and ≡Al-O was observed from the decrease in Fe-2p, Al-2p, and Si-2p peaks of the X-ray photoelectron spectroscopy (XPS) data before and after Sb(V) and Sb(III) adsorption on NRE. Successful data modeling using the 2-pK diffuse double layer model (DDLM) with the FITEQL revealed that sorption occurs through the formation of bidentate mononuclear and binuclear complexes. Model simulations showed a high affinity to the ≡FeOH sites at high Sb loadings, whereas at low loadings, both≡ FeOH and ≡AlOH sites showed similar affinities to Sb. In the case of Sb(V), multilayer formation was also revealed in addition to surface complexation by the isotherm data fitted with the Freundlich model and two sites Langmuir equations, which indicated heterogeneous multilayer adsorption of Sb(V) on NRE. PMID:23791229

  5. Emergent nesting of the Fermi surface from local-moment description of iron-pnictide high-Tc superconductors

    NASA Astrophysics Data System (ADS)

    Rodriguez, Jose P.; Araujo, Miguel A. N.; Sacramento, Pedro D.

    2014-07-01

    We uncover the low-energy spectrum of a t-J model for electrons on a square lattice of spin-1 iron atoms with 3dxz and 3dyz orbital character by applying Schwinger-boson-slave-fermion mean-field theory and by exact diagonalization of one hole roaming over a 4 × 4 × 2 lattice. Hopping matrix elements are set to produce hole bands centered at zero two-dimensional (2D) momentum in the free-electron limit. Holes can propagate coherently in the t-J model below a threshold Hund coupling when long-range antiferromagnetic order across the d + = 3d(x + iy)z and d - = 3d(x - iy)z orbitals is established by magnetic frustration that is off-diagonal in the orbital indices. This leads to two hole-pocket Fermi surfaces centered at zero 2D momentum. Proximity to a commensurate spin-density wave (cSDW) that exists above the threshold Hund coupling results in emergent Fermi surface pockets about cSDW momenta at a quantum critical point (QCP). This motivates the introduction of a new Gutzwiller wavefunction for a cSDW metal state. Study of the spin-fluctuation spectrum at cSDW momenta indicates that the dispersion of the nested band of one-particle states that emerges is electron-type. Increasing Hund coupling past the QCP can push the hole-pocket Fermi surfaces centered at zero 2D momentum below the Fermi energy level, in agreement with recent determinations of the electronic structure of mono-layer iron-selenide superconductors.

  6. Fur is required for the activation of virulence gene expression through the induction of the sae regulatory system in Staphylococcus aureus

    PubMed Central

    Johnson, Miranda; Sengupta, Mrittika; Purves, Joanne; Tarrant, Emma; Williams, Peter H.; Cockayne, Alan; Muthaiyan, Arunachalam; Stephenson, Robert; Ledala, Nagender; Wilkinson, Brian J.; Jayaswal, Radheshyam K.; Morrissey, Julie A.

    2010-01-01

    Our previous studies showed that both Sae and Fur are required for the induction of eap and emp expression in low iron. In this study, we show that expression of sae is also iron-regulated, as sae expression is activated by Fur in low iron. We also demonstrate that both Fur and Sae are required for full induction of the oxidative stress response and expression of non-covalently bound surface proteins in low-iron growth conditions. In addition, Sae is required for the induced expression of the important virulence factors isdA and isdB in low iron. Our studies also indicate that Fur is required for the induced expression of the global regulators Agr and Rot in low iron and a number of extracellular virulence factors such as the haemolysins which are also Sae- and Agr-regulated. Hence, we show that Fur is central to a complex regulatory network that is required for the induced expression of a number of important S. aureus virulence determinants in low iron. PMID:20705504

  7. Chemically modified nanoparticles surface for sensing bacterial loading--experimental study based on fluorescence stimulation by iron ions.

    PubMed

    Poiata, Antoniea; Creanga, Dorina E; Nadejde, Claudia; Fifere, Nicușor; Airinei, Anton

    2013-10-01

    The influence of iron ions supplied from magnetite nanoparticles with chemically modified surface on Pseudomonas aeruginosa germ was aimed--with experimental and theoretical approach of the intensity of the fluorescent signal emitted by the pyoverdine like siderophores. As the coated magnetic nanoparticles could function as probes, the possibility of designing a chemical device was considered based on the sensing of iron reduction from Fe(3+) into the more soluble Fe(2+), for detecting various levels of contamination (10 ÷ 10(8) cell/ml) of biological specimens and environmental samples. The proposed mathematical model estimated the fluorescence intensity due to siderophore synthesized by Pseudomonas, considering that the parameter describing the ion-bacteria interaction depends differently on the cell density for different magnetite nanoparticle coatings: linear dependence was found in the case of sodium oleate coating while power function was revealed for tetramethyl ammonium coating of magnetite nanocores, in both cases magnetite suspension being supplied in the same concentration (0.1 μl/ml). The calculated values of fluorescence intensity fitted the experimental data corresponding to magnetite supplied bacteria with graph slopes close to the unit and correlation coefficients of 0.999 and 0.996, while for the control samples, where that parameter was zeroed, correlation coefficient was found of 0.999. PMID:23186558

  8. Relating the Surface Properties of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) to Their Bactericidal Effect towards a Biofilm of Streptococcus mutans

    PubMed Central

    Javanbakht, Taraneh; Laurent, Sophie; Stanicki, Dimitri; Wilkinson, Kevin J.

    2016-01-01

    This study was designed to determine the effects of superparamagnetic iron oxide nanoparticles (SPIONs) on the biological activity of a bacterial biofilm (Streptococcus mutans). Our hypothesis was that the diffusion of the SPIONs into biofilms would depend on their surface properties, which in turn would largely be determined by their surface functionality. Bare, positively charged and negatively charged SPIONs, with hydrodynamic diameters of 14.6 ± 1.4 nm, 20.4 ± 1.3 nm and 21.2 ± 1.6 nm were evaluated. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and electrophoretic mobility (EPM) measurements were used to confirm that carboxylic functional groups predominated on the negatively charged SPIONS, whereas amine functional groups predominated on the positively charged particles. Transmission electron microscopy (TEM) showed the morphology and sizes of SPIONs. Scanning electron microscopy (SEM) and EPM measurements indicated that the surfaces of the SPIONs were covered with biomolecules following their incubation with the biofilm. Bare SPIONs killed bacteria less than the positively charged SPIONs at the highest exposure concentrations, but the toxicity of the bare and positively charged SPIONs was the same for lower SPION concentrations. The positively charged SPIONs were more effective in killing bacteria than the negatively charged ones. Nonetheless, electrophoretic mobilities of all three SPIONs (negative, bare and positively charged) became more negative following incubation with the (negatively-charged) biofilm. Therefore, while the surface charge of SPIONS was important in determining their biological activity, the initial surface charge was not constant in the presence of the biofilm, leading eventually to SPIONS with fairly similar surface charges in situ. The study nonetheless suggests that the surface characteristics of the SPIONS is an important parameter controlling the efficiency of antimicrobial agents. The analysis of the CFU/mL values

  9. Relating the Surface Properties of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) to Their Bactericidal Effect towards a Biofilm of Streptococcus mutans.

    PubMed

    Javanbakht, Taraneh; Laurent, Sophie; Stanicki, Dimitri; Wilkinson, Kevin J

    2016-01-01

    This study was designed to determine the effects of superparamagnetic iron oxide nanoparticles (SPIONs) on the biological activity of a bacterial biofilm (Streptococcus mutans). Our hypothesis was that the diffusion of the SPIONs into biofilms would depend on their surface properties, which in turn would largely be determined by their surface functionality. Bare, positively charged and negatively charged SPIONs, with hydrodynamic diameters of 14.6 ± 1.4 nm, 20.4 ± 1.3 nm and 21.2 ± 1.6 nm were evaluated. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and electrophoretic mobility (EPM) measurements were used to confirm that carboxylic functional groups predominated on the negatively charged SPIONS, whereas amine functional groups predominated on the positively charged particles. Transmission electron microscopy (TEM) showed the morphology and sizes of SPIONs. Scanning electron microscopy (SEM) and EPM measurements indicated that the surfaces of the SPIONs were covered with biomolecules following their incubation with the biofilm. Bare SPIONs killed bacteria less than the positively charged SPIONs at the highest exposure concentrations, but the toxicity of the bare and positively charged SPIONs was the same for lower SPION concentrations. The positively charged SPIONs were more effective in killing bacteria than the negatively charged ones. Nonetheless, electrophoretic mobilities of all three SPIONs (negative, bare and positively charged) became more negative following incubation with the (negatively-charged) biofilm. Therefore, while the surface charge of SPIONS was important in determining their biological activity, the initial surface charge was not constant in the presence of the biofilm, leading eventually to SPIONS with fairly similar surface charges in situ. The study nonetheless suggests that the surface characteristics of the SPIONS is an important parameter controlling the efficiency of antimicrobial agents. The analysis of the CFU/mL values

  10. Surface Modified Iron Oxide Nanoparticles as Fe Source Precursor to Induce the Formation of Prussian Blue Nanocubes.

    PubMed

    Hu, Sunling; Zhang, Xiaoqing; Zang, Fengchao; Zhang, Yu; Zhang, Wei; Wu, Yihang; Song, Mengjie; Wang, Yuehua; Gu, Ning

    2016-02-01

    Nano-sized Prussian blue (PB) cubes were synthesized at room temperature by simply stirring the mixture of surface modified iron oxide nanoparticles (IONPs) and potassium ferrocyanide in an aqueous acid solution. The nanocubes were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The influence of different molecules modified on the surface of IONPs on the cube formation was discussed. The surface modification with dimercaptosuccinic acid (DMSA), 3-aminopropyltriethoxysilane (APTS) and citric acid (CA) all displayed a key role in the formation precess of PB nanocubes, but which could not be formed as bare IONPs or Fe3+ were used as precursor. Combined with the reaction process tracing with UV-vis absorption spectroscopy and TEM, a possible kinetically controlled growth mechanism was proposed where slower formation rate of amorphous PB due to very low release rate of Fe ions from the surface modified IONPs and subsequent recrystallization are responsible for the obtained PB nanocubes. The peroxidase-like catalytic activity of the synthesized nanocubes was investigated and catalysis was found to follow Michaelis-Menten kinetics. The potential of using such PB nanocubes as an effective MRI contrast agent was also demonstrated. PMID:27433710

  11. Analysis of the global ocean sampling (GOS) project for trends in iron uptake by surface ocean microbes.

    PubMed

    Toulza, Eve; Tagliabue, Alessandro; Blain, Stéphane; Piganeau, Gwenael

    2012-01-01

    Microbial metagenomes are DNA samples of the most abundant, and therefore most successful organisms at the sampling time and location for a given cell size range. The study of microbial communities via their DNA content has revolutionized our understanding of microbial ecology and evolution. Iron availability is a critical resource that limits microbial communities' growth in many oceanic areas. Here, we built a database of 2319 sequences, corresponding to 140 gene families of iron metabolism with a large phylogenetic spread, to explore the microbial strategies of iron acquisition in the ocean's bacterial community. We estimate iron metabolism strategies from metagenome gene content and investigate whether their prevalence varies with dissolved iron concentrations obtained from a biogeochemical model. We show significant quantitative and qualitative variations in iron metabolism pathways, with a higher proportion of iron metabolism genes in low iron environments. We found a striking difference between coastal and open ocean sites regarding Fe(2+) versus Fe(3+) uptake gene prevalence. We also show that non-specific siderophore uptake increases in low iron open ocean environments, suggesting bacteria may acquire iron from natural siderophore-like organic complexes. Despite the lack of knowledge of iron uptake mechanisms in most marine microorganisms, our approach provides insights into how the iron metabolic pathways of microbial communities may vary with seawater iron concentrations. PMID:22363520

  12. Orientation dependences of surface morphologies and energies of iron-gallium alloys

    NASA Astrophysics Data System (ADS)

    Costa, Marcio; Wang, Hui; Hu, Jun; Wu, Ruqian; Na, Suok-Min; Chun, Hyunsuk; Flatau, Alison B.

    2016-05-01

    We investigated the surface energies of several low-index surfaces of the D03-type FeGa alloys (Galfenol), using density functional theory (DFT) simulations and contact angle measurements. DFT calculations predict that (1) the Ga-covered (110) surface of Galfenol is more stable in the Ga-rich condition, while Ga-covered (001) surface of Galfenol become more favorable in Ga-poor condition; and (2) a full Ga overlayer tends to form on top of Galfenol surfaces regardless their orientation, both in agreement with the experimental observation. We also studied Ga segregation in the bcc Fe matrix in order to explore the possibility of Ga precipitation away from Fe. It was found that the Fe-Ga separation is unlikely to occur since Ga diffusion toward the surface is effectively self-stopped once the Ga overlayers form on the facets.

  13. Laser ablation of iron-rich black films from exposed granite surfaces

    NASA Astrophysics Data System (ADS)

    Delgado Rodrigues, J.; Costa, D.; Mascalchi, M.; Osticioli, I.; Siano, S.

    2014-10-01

    Here, we investigated the potential of laser removal of iron-rich dark films from weathered granite substrates, which represents a very difficult conservation problem because of the polymineralic nature of the stone and of its complex deterioration mechanisms. As often occurs, biotite was the most critical component because of its high optical absorption, low melting temperature, and pronounced cleavage, which required a careful control of the photothermal and photomechanical effects to optimize the selective ablation of the mentioned unwanted dark film. Different pulse durations and wavelengths Nd:YAG lasers were tested and optimal irradiation conditions were determined through thorough analytical characterisations. Besides addressing a specific conservation problem, the present work provides information of general valence in laser uncovering of encrusted granite.

  14. Fermi surface nesting and spin density wave instability in the overdoped superconducting iron pnictides

    NASA Astrophysics Data System (ADS)

    Jiang, Hong-Min; Yao, Zi-Jian; Zhang, Fu-Chun

    2012-11-01

    The nesting of electron Fermi pocket with one of the two hole pockets around the Brillouin zone center has been attributed to the spin density wave (SDW) instability in the parent compound of superconducting iron pnictides. We propose here that the second hole Fermi pocket may be nested with the electron pocket in the doped case, which results in a new SDW instability. Our work is motivated by and may explain the recent scanning tunneling spectroscopy (STM) measurements on NaFe1-xCoxAs, which show an asymmetric gap-like feature near the Fermi level in the overdoped regime (Zhou X. et al., Phys. Rev. Lett., 109 (2012) 037002). We use a multi-band model to examine this feature within random phase approximation to include the coupling between the itinerant electron and the local spins.

  15. Surface modified superparamagnetic iron oxide nanoparticles: as a new carrier for bio-magnetically targeted therapy.

    PubMed

    Liang, Sheng; Wang, Yongxian; Yu, Junfeng; Zhang, Chunfu; Xia, Jiaoyun; Yin, Duanzhi

    2007-12-01

    Amino-functionalized superparamagnetic iron oxide nanoparticles (SPION) were synthesized by coprecipitation method. The particles were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron micrographs (SEM), transmission electron micrographs (TEM) and atomic force micrographs (AFM). The size of the modified particles varied in the range 10-15 nm and did not change significantly after modification. Hepama-1, an excellent humanized monoclonal antibody directed against liver cancer, was conjugated to the SPION to prepare immuno-magnetic nanoparticles (IMN). A direct labeling method was employed to radiolabel IMN with rhenium-188. The radiolabeling efficiency was about 90% with good in vitro stability. (188)Re labeled IMN could markedly kill SMMC-7721 liver cancer cells. Such SPION might be very useful for bio-magnetically targeted radiotherapy in liver cancer treatment. PMID:17562137

  16. Inhibition of nitrate reduction by NaCl adsorption on a nano-zero-valent iron surface during a concentrate treatment for water reuse.

    PubMed

    Hwang, Yuhoon; Kim, Dogun; Shin, Hang-Sik

    2015-01-01

    Nanoscale zero-valent iron (NZVI) has been considered as a possible material to treat water and wastewater. However, it is necessary to verify the effect of the matrix components in different types of target water. In this study, different effects depending on the sodium chloride (NaCl) concentration on reductions of nitrates and on the characteristics of NZVI were investigated. Although NaCl is known as a promoter of iron corrosion, a high concentration of NaCl (>3 g/L) has a significant inhibition effect on the degree of NZVI reactivity towards nitrate. The experimental results were interpreted by a Langmuir-Hinshelwood-Hougen-Watson reaction in terms of inhibition, and the decreased NZVI reactivity could be explained by the increase in the inhibition constant. As a result of a chloride concentration analysis, it was verified that 7.7-26.5% of chloride was adsorbed onto the surface of NZVI. Moreover, the change of the iron corrosion product under different NaCl concentrations was investigated by a surface analysis of spent NZVI. Magnetite was the main product, with a low NaCl concentration (0.5 g/L), whereas amorphous iron hydroxide was observed at a high concentration (12 g/L). Though the surface was changed to permeable iron hydroxide, the Fe(0) in the core was not completely oxidized. Therefore, the inhibition effect of NaCl could be explained as the competitive adsorption of chloride and nitrate. PMID:25358487

  17. A Surface-Charge Study on Cellular-Uptake Behavior of F3-Peptide-Conjugated Iron Oxide Nanoparticles

    PubMed Central

    Zhang, Yu; Yang, Mo; Park, Ji-Ho; Singelyn, Jennifer; Ma, Huiqing; Sailor, Michael J.; Ruoslahti, Erkki; Ozkan, Mihrimah

    2011-01-01

    Surface-charge measurements of mammalian cells in terms of Zeta potential are demonstrated as a useful biological characteristic in identifying cellular interactions with specific nanomaterials. A theoretical model of the changes in Zeta potential of cells after incubation with nanoparticles is established to predict the possible patterns of Zeta-potential change to reveal the binding and internalization effects. The experimental results show a distinct pattern of Zeta potential change that allows the discrimination of human normal breast epithelial cells (MCF-10A) from human cancer breast epithelial cells (MCF-7) when the cells are incubated with dextran coated iron oxide nanoparticles that contain tumor-homing F3 peptides, where the tumor-homing F3 peptide specifically bound to nucleolin receptors that are overexpressed in cancer breast cells. PMID:19554564

  18. Iron Test

    MedlinePlus

    ... detect and help diagnose iron deficiency or iron overload. In people with anemia , these tests can help ... also be ordered when iron deficiency or iron overload is suspected. Early iron deficiency often goes unnoticed. ...

  19. Thermodynamic stability and structures of iron chloride surfaces: A first-principles investigation

    SciTech Connect

    Saraireh, Sherin A.; Altarawneh, Mohammednoor

    2014-08-07

    In this study, we report a comprehensive density functional theory investigation of the structure and thermodynamic stability of FeCl{sub 2} and FeCl{sub 3} surfaces. Calculated lattice constants and heats of formation for bulk FeCl{sub 2} and FeCl{sub 3} were found to be in relatively good agreement with experimental measurements. We provide structural parameters for 15 distinct FeCl{sub 2} and FeCl{sub 3} surfaces along the three low-index orientations. The optimized geometries for all surfaces are compared with analogous bulk values. Ab initio atomistic thermodynamic calculations have been carried out to assess the relative thermodynamic stability of FeCl{sub 2} and FeCl{sub 3} surfaces under practical operating conditions of temperatures and pressures. The FeCl{sub 2} (100-Cl) surface is found to afford the most stable configuration at all experimentally accessible gas phase conditions.

  20. Iron dissolution from volcanic ash in low-pH atmospheric water: a key control on volcanic iron input to the surface ocean?

    NASA Astrophysics Data System (ADS)

    Maters, E.; Delmelle, P.; Ayris, P. M.; Opfergelt, S.

    2012-12-01

    A low concentration of dissolved iron (Fe) limits phytoplankton growth in approximately 30% of the ocean. The input of soluble Fe to these High-Nutrient Low-Chlorophyll (HNLC) regions has the potential to boost primary production and thereby enhance the drawdown of atmospheric carbon dioxide (CO2). Over geological timescales, volcanic activity may alter the flux of Fe to the surface ocean and so contribute to modulating atmospheric CO2 concentrations, ultimately impacting the global climate. Ocean Fe fertilisation has also recently been found to contribute to century-scale carbon sequestration via the export of biomass to the seafloor. Atmospherically deposited volcanic ash is now increasingly seen as an intermittent source of Fe to the surface ocean. Understanding the process of Fe release from ash in solution is key for assessing the potential for ash, particularly that produced by large but rare explosive eruptions or during sustained periods of intense volcanism, to fertilise the marine environment. Previous studies have measured the release of Fe from ash in near-neutral pH solution, but the influence of interaction between ash and acidic cloud- or rainwater during transport on Fe release is poorly understood. In this study, seven volcanic ash samples ranging from tephrite to rhyolite (49-74 wt.% SiO2) were leached in pH 1 H2SO4 in batch reactors for 336 h, at a 1:500 ash-to-solution ratio, to investigate Fe release under acidic conditions. Major element concentrations were measured by inductively coupled plasma- atomic emission spectroscopy (ICP-AES) across a time series of ash leachates. Changes in ash surface composition induced by contact with acid solution were assessed by X-ray photoelectron spectroscopy (XPS). The Fe2+/Fe3+ ratio in ash leachates was also determined for the first time, using the Ferrozine method. The ash samples released 42 to 411 μmol m-2 of Fe over 336 h of leaching. High initial Fe release rates (>1 μmol m-2 h-1) sustained for up

  1. Detection of Remarkably Low Isotopic Ratio of Iron in Anthropogenic Aerosols and Evaluation of its Contribution to the Surface Ocean

    NASA Astrophysics Data System (ADS)

    Kurisu, M.; Iizuka, T.; Sakata, K.; Uematsu, M.; Takahashi, Y.

    2015-12-01

    It has been reported that phytoplankton growth in the High Nutrient-Low Chlorophyll (HNLC) regions is limited by dissolved iron (DFe) concentration (e.g., Martin and Fitzwater, 1988). Aerosol is known as one of the dominant sources of DFe to the ocean and classified into two origins such as anthropogenic and natural. A series of recent studies showed that Fe in anthropogenic aerosols is more soluble than that in natural aerosols (Takahashi et al., 2013) and has lower isotopic ratio (Mead et al., 2013). However, the difference between Fe isotopic ratio (δ56Fe: [(56Fe/54Fe)sample/(56Fe/54Fe)IRMM-14]-1) of two origins reported in Mead et al. (2013) is not so large compared with the standard deviation. Therefore, the aim of this study is to determine Fe species and δ56Fe in anthropogenic aerosols more accurately and to evaluate its contribution to the ocean surface. Iron species were determined by X-ray absorption fine structure (XAFS) analysis, while δ56Fe in size-fractionated aerosols were measured by MC-ICP-MS (NEPTUNE Plus) after chemical separation using anion exchange resin. Dominant Fe species in the samples were, ferrihydrite, hematite, and biotite. It was also revealed that coarse particles contained a larger amount of biotite and that fine particles contained a larger amount of hematite, which suggested that anthropogenic aerosols were emitted during combustion processes. In addition, results of Fe isotopic ratio analysis suggested that δ56Fe of coarse particles were around +0.25‰, whereas that of fine particles were -0.5 ˜ -2‰, which was lower than the δ56Fe in anthropogenic aerosol by Mead et al. (2013). The size-fractionated sampling made it possible to determine the δ56Fe in anthropogenic aerosol. Soluble component in fine particles extracted by simulated rain water also showed much lower δ56Fe (δ56Fe = -3.9±0.12‰), suggesting that anthropogenic Fe has much lower isotopic ratio. The remarkably low δ56Fe may be caused by the

  2. Effects of 1000 C oxide surfaces on room temperature aqueous corrosion and environmental embrittlement of iron aluminides

    SciTech Connect

    Buchanan, R.A.; Perrin, R.L.

    1997-12-01

    Results of electrochemical aqueous-corrosion studies at room temperature indicate that retained in-service-type high-temperature surface oxides (1000 C in air for 24 hours) on FA-129, FAL and FAL-Mo iron aluminides cause major reductions in pitting corrosion resistance in a mild acid-chloride solution designed to simulate aggressive atmospheric corrosion. Removal of the oxides by mechanical grinding restores the corrosion resistance. In a more aggressive sodium tetrathionate solution, designed to simulate an aqueous environment contaminated by sulfur-bearing combustion products, only active corrosion occurs for both the 1000 C oxide and mechanically cleaned surfaces at FAL. Results of slow-strain-rate stress-corrosion-cracking tests on FA-129, FAL and FAL-Mo at free-corrosion and hydrogen-charging potentials in the mild acid chloride solution indicate somewhat higher ductilities (on the order of 50%) for the 1000 C oxides retard the penetration of hydrogen into the metal substrates and, consequently, are beneficial in terms of improving resistance to environmental embrittlement. In the aggressive sodium tetrathionate solution, no differences are observed in the ductilities produced by the 1000 C oxide and mechanically cleaned surfaces for FAL.

  3. In-situ deposition of silver-iron oxide nanoparticles on the surface of fly ash for water purification.

    PubMed

    Joshi, Mahesh Kumar; Pant, Hem Raj; Liao, Nina; Kim, Jun Hee; Kim, Han Joo; Park, Chan Hee; Kim, Cheol Sang

    2015-09-01

    In this study, a fly ash based composite, Ag-iron oxide/fly ash, was synthesized via a facile one-pot hydrothermal process using fly ash, ferrous chloride, and silver nitrate as precursors. Field emission scanning electron microscopy (FE-SEM), EDX, transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), Photoluminescence (PL) and Brunauer-Emmett-Teller (BET) surface area measurement confirmed the formation of composite particle. FA provided a suitable surface for the in-situ deposition of Fe3O4 and Ag NPs during hydrothermal treatment. As a result, the particle size of Fe3O4 and Ag NPs was sufficiently decreased, and the surface area of the NPs as well as, a whole matrix was increased. The antimicrobial activity of the composite was accessed by Escherichia coli inhibition assay. Lead(II) ion adsorption efficiency of the composite was analyzed from a series of batch adsorption experiments (the effects of concentration, contact time, pH and adsorbent dose on the adsorption of Pb(II) ion from aqueous solution). Results indicated that as-synthesized composite has high antibacterial capacity, and the metal ions uptake efficiency compared to fly ash particle. Furthermore, incorporation Fe3O4 NPs onto the fly ash make it easily separable from a reaction system using an external magnet. The composite synthesis protocol is a simple method that utilizes a readily available industrial byproduct to produce a unique composite for environmental remediation. PMID:25985419

  4. Crack initiation and near-threshold surface fatigue crack propagation behavior of the iron-base superalloy A-286

    NASA Astrophysics Data System (ADS)

    Daeubler, M. A.; Thompson, A. W.; Bernstein, I. M.

    1988-02-01

    The fatigue behavior of the iron-base superalloy A-286 was studied at room temperature in air for three aging conditions: underaged, peak aged, and overaged. A fatigue strength at 107 cycles of about 200 MPa, independent of aging condition, was measured for an applied load ratio of R =0.1. Surface crack initiation and propagation were measured using hourglass specimens. Surface cracks were invariably initiated in slip bands orientated between 45 and 55 deg to the load axis, and an average ratio of crack depth to crack length of about 0.45 for these semi-elliptical cracks was measured. These earliest observable short surface cracks grew at an accelerated propagation rate in the near-threshold regime but were retarded in a transition stage, resulting in a minimum in crack growth rate. This behavior was correlated to the interaction of the crack with specific microstructure features. Following this minimum, the crack growth accelerated again with increasing Δ K and appeared to converge with the crack growth behavior expected for long through cracks. The crack propagation rate at fixed Δ K was lowest in underaged, compared to peak aged and overaged microstructures. The minimum and trends in crack growth rate appeared to depend on the development of roughness-induced closure.

  5. Solution structure of the NEAT (NEAr Transporter) domain from IsdH/HarA: the human hemoglobin receptor in Staphylococcus aureus.

    PubMed

    Pilpa, Rosemarie M; Fadeev, Evgeny A; Villareal, Valerie A; Wong, Melissa L; Phillips, Martin; Clubb, Robert T

    2006-07-01

    During infections the pathogen Staphylococcus aureus procures the essential nutrient iron from its host using iron-regulated surface determinant (Isd) proteins, which scavenge heme bound iron from host hemoproteins. Four Isd proteins are displayed in the cell wall, where they function as receptors for host proteins and heme. Each of the receptors contains one or more copies of a recently discovered domain called NEAT (NEAr Transporter) that has been shown to mediate protein binding. Here we report the three-dimensional solution structure of the NEAT domain from the IsdH/HarA protein, which is the hemoglobin receptor in the Isd system. This is the first structure of a NEAT domain and reveals that they adopt a beta sandwich fold that consists of two five-stranded antiparallel beta sheets. Although unrelated at the primary sequence level, our results indicate that NEAT domains belong to the immunoglobulin superfamily. Binding studies indicate that two IsdH/HarA NEAT domains bind a single molecule of methemoglobin, while the distantly related NEAT domain from the S. aureus IsdC protein binds only heme. A comparison of their primary sequences in light of the new structure is used to predict the hemoglobin and heme binding surfaces on NEAT domains. PMID:16762363

  6. Orientation dependences of surface morphologies and energies of iron-gallium alloys

    NASA Astrophysics Data System (ADS)

    Costa, Marcio; Wang, Hui; Hu, Jun; Wu, Ruqian; Na, Suok-Min; Chun, Hyunsuk; Flatau, Alison B.; University of California, Irvine Collaboration; University of Maryland Collaboration

    Magnetostrictive Fe-Ga alloys (Galfenol) are very promising rare-earth free materials for applications in sensors, actuators, energy-harvesters and spintronic devices. Investigation on surface energies of Galfenol based on density functional calculations (DFT) and contact angle measurements may provide fundamental understandings and guidance to further optimize the performance of Galfenol. DFT calculations predict that Ga-covered (110) surface of Galfenol is more stable in Ga-rich condition, while Ga-covered (001) surface of Galfenol surface become more favorable in Ga-poor condition. Moreover, a full Ga overlayer tends to form on top of Gafenol surfaces regardless their orientation, both in agreement with the experimental observation. Further studies on Ga segregation in the Fe bcc matrix demonstrate that the Fe-Ga separation is unlikely to occur since Ga diffusion toward the surface is effectively self-stopped once the Ga overlayers form on the facets. This work was supported by the National Science Foundation through the SUSCHEM-Collaborative Research program (Grant Numbers: DMR-1310494 at UCI and DMR-1310447 at UMD). Work at UCI was also supported by the ONR (Grant Number: N00014-13-1-0445).

  7. Effect of phosphorous surface segregation on iron-zinc reaction kinetics during hot-dip galvanizing

    SciTech Connect

    Jordan, C.E.; Zuhr, R.; Marder, A.R.

    1997-12-01

    Phosphorous was ion implanted on one surface of a large grain (10 to 20 mm) low-carbon steel sheet in order to study the effect of surface segregation on the formation of Fe-Zn phases during galvanizing. Both an Al-free and a 0.20 wt pct Al-Zn bath at 450 C were used in this investigation. It was found that P surface segregation did not affect the kinetics of Fe-Zn phase growth for the total alloy layer or the individual Fe-Zn gamma, delta, and zeta phase alloy layers in the 0.00 wt pct Al-Zn baths. In the 0.20 wt pct Al-Zn bath, the Fe{sub 2}Al{sub 5} inhibition layer formed with kinetics, showing linear growth on both the P-ion implanted and non-P-ion implanted surfaces. Fe-Zn phase growth only occurred after extended reaction times on both surfaces and was found to directly correspond to the location of substrate grain boundary sites. These results indicate that P surface segregation does not affect the growth of Fe-Zn phases or the Fe{sub 2}Al{sub 5} inhibition layer. It was shown that in the 0.20 wt pct Al-Zn bath, substrate grain boundaries are the dominant steel substrate structural feature that controls the kinetics of Fe-Zn alloy phase growth.

  8. Human immunoglobulin G recognizing fibrinogen-binding surface proteins is protective against both Staphylococcus aureus and Staphylococcus epidermidis infections in vivo.

    PubMed

    Vernachio, John H; Bayer, Arnold S; Ames, Brenda; Bryant, Dawn; Prater, Bradley D; Syribeys, Peter J; Gorovits, Elena L; Patti, Joseph M

    2006-02-01

    A human donor-selected immunoglobulin G for intravenous injection (IGIV) product with elevated titers against the staphylococcal fibrinogen-binding MSCRAMM proteins ClfA and SdrG (INH-A21) was tested in vitro and in vivo. INH-A21 contained a significantly increased ability to inhibit the fibrinogen-binding activity of recombinant forms of both ClfA and SdrG. Evaluation of the opsonizing potential of INH-A21 was evaluated using fluorescently labeled bacteria; this assay indicated an increase in phagocytic activity compared to normal IGIV. The prophylactic efficacy of INH-A21 against an intraperitoneal challenge of methicillin-resistant Staphylococcus epidermidis (MRSE) was evaluated in a neonatal rat model. INH-A21 was also evaluated for prophylactic and therapeutic efficacy in a rabbit model of catheter-induced aortic valve infective endocarditis caused by either MRSE or methicillin-resistant Staphylococcus aureus (MRSA). Results from the in vivo models demonstrated potent prophylactic and therapeutic efficacy against both MRSE and MRSA. These data suggest that INH-A21 may be an important tool for the prevention and treatment of staphylococcal infections, especially in high-risk populations. PMID:16436704

  9. Human Immunoglobulin G Recognizing Fibrinogen-Binding Surface Proteins Is Protective against both Staphylococcus aureus and Staphylococcus epidermidis Infections In Vivo

    PubMed Central

    Vernachio, John H.; Bayer, Arnold S.; Ames, Brenda; Bryant, Dawn; Prater, Bradley D.; Syribeys, Peter J.; Gorovits, Elena L.; Patti, Joseph M.

    2006-01-01

    A human donor-selected immunoglobulin G for intravenous injection (IGIV) product with elevated titers against the staphylococcal fibrinogen-binding MSCRAMM proteins ClfA and SdrG (INH-A21) was tested in vitro and in vivo. INH-A21 contained a significantly increased ability to inhibit the fibrinogen-binding activity of recombinant forms of both ClfA and SdrG. Evaluation of the opsonizing potential of INH-A21 was evaluated using fluorescently labeled bacteria; this assay indicated an increase in phagocytic activity compared to normal IGIV. The prophylactic efficacy of INH-A21 against an intraperitoneal challenge of methicillin-resistant Staphylococcus epidermidis (MRSE) was evaluated in a neonatal rat model. INH-A21 was also evaluated for prophylactic and therapeutic efficacy in a rabbit model of catheter-induced aortic valve infective endocarditis caused by either MRSE or methicillin-resistant Staphylococcus aureus (MRSA). Results from the in vivo models demonstrated potent prophylactic and therapeutic efficacy against both MRSE and MRSA. These data suggest that INH-A21 may be an important tool for the prevention and treatment of staphylococcal infections, especially in high-risk populations. PMID:16436704

  10. Sensitive and rapid detection of staphylococcus aureus in milk via cell binding domain of lysin.

    PubMed

    Yu, Junping; Zhang, Yun; Zhang, Yun; Li, Heng; Yang, Hang; Wei, Hongping

    2016-03-15

    Staphylococcus aureus (S. aureus) is an important food-borne pathogen in dairy products contaminated through raw ingredients or improper food handling. Rapid detection of S. aureus with high sensitivity is of significance for food quality and safety. In this study, a new method was developed for detecting S. aureus in milk by coupling immunomagnetic separation with enzyme linked cell wall binding domain (CBD) of lysin plyV12, which can bind to S. aureus with high affinity. There are millions of binding sites present on the cell surface of S. aureus for the CBD attachment, which greatly improves the detection sensitivity. The method has the overall testing time of only 1.5h with the detection limit of 4 × 10(3)CFU/mL in spiked milk. Because it is simple, rapid and sensitive, this method could be used for the detection of S. aureus in various food samples. PMID:26433070

  11. Surface, electrical and mechanical modifications of PMMA after implantation with laser produced iron plasma ions

    NASA Astrophysics Data System (ADS)

    Ahmed, Qazi Salman; Bashir, Shazia; Jalil, Sohail Abdul; Shabbir, Muhammad Kaif; Mahmood, Khaliq; Akram, Mahreen; Khalid, Ayesha; Yaseen, Nazish; Arshad, Atiqa

    2016-07-01

    Laser Produced Plasma (LPP) was employed as an ion source for the modifications in surface, electrical and mechanical properties of poly methyl (methacrylate) PMMA. For this purpose Nd:YAG laser (532 nm, 6 ns, 10 Hz) at a fluence of 12.7 J/cm2 was employed to generate Fe plasma. The fluence and energy measurements of laser produced Fe plasma ions were carried out by employing Thomson Parabola Technique in the presence of magnetic field strength of 0.5 T, using CR-39 as Solid State Nuclear Track Detector (SSNTD). It has been observed that ion fluence ejecting from ablated plasma was maximum at an angle of 5° with respect to the normal to the Fe target surface. PMMA substrates were irradiated with Fe ions of constant energy of 0.85 MeV at various ion fluences ranging from 3.8 × 106 ions/cm2 to 1.8 × 108 ions/cm2 controlled by varying laser pulses from 3000 to 7000. Optical microscope and Scanning Electron Microscope (SEM) were utilized for the analysis of surface features of irradiated PMMA. Results depicted the formation of chain scission, crosslinking, dendrites and star like structures. To explore the electrical behavior, four probe method was employed. The electrical conductivity of ion irradiated PMMA was increased with increasing ion fluence. The surface hardness was measured by shore D hardness tester and results showed the monotonous increment in surface hardness with increasing ion fluence. The increasing trend of surface hardness and electrical conductivity with increasing Fe ion fluence has been well correlated with the surface morphology of ion implanted PMMA. The temperature rise of PMMA surface due to Fe ion irradiation is evaluated analytically and comes out to be in the range of 1.72 × 104 to 1.82 × 104 K. The values of total Linear Energy Transfer (LET) or stopping power of 0.8 MeV Fe ions in PMMA is 61.8 eV/Å and their range is 1.34 μm evaluated by SRIM simulation.

  12. Iron sulfides and sulfur species produced at hematite surfaces in the presence of sulfate-reducing bacteria 1

    NASA Astrophysics Data System (ADS)

    Neal, Andrew L.; Techkarnjanaruk, Somkiet; Dohnalkova, Alice; McCready, David; Peyton, Brent M.; Geesey, Gill G.

    2001-01-01

    In the presence of sulfate-reducing bacteria ( Desulfovibrio desulfuricans) hematite (α-Fe 2O 3) dissolution is affected potentially by a combination of enzymatic (hydrogenase) reduction and hydrogen sulfide oxidation. As a consequence, ferrous ions are free to react with excess H 2S to form insoluble ferrous sulfides. X-ray photoelectron spectra indicate binding energies similar to ferrous sulfides having pyrrhotite-like structures (Fe2 p3/2 708.4 eV; S2 p3/2 161.5 eV). Other sulfur species identified at the surface include sulfate, sulfite and polysulfides. Thin film X-ray diffraction identifies a limited number of peaks, the principal one of which may be assigned to the hexagonal pyrrhotite (102) peak (d = 2.09 Å; 2θ = 43.22°), at the hematite surface within 3 months exposure to sulfate-reducing bacteria (SRB). High-resolution transmission electron microscopy identifies the presence of a hexagonal structure associated with observed crystallites. Although none of the analytical techniques employed provide unequivocal evidence as to the nature of the ferrous sulfide formed in the presence of SRB at hematite surfaces, we conclude from the available evidence that a pyrrhotite stiochiometry and structure is the best description of the sulfides we observe. Such ferrous sulfide production is inconsistent with previous reports in which mackinawite and greigite were products of biological sulfate reduction (Rickard 1969a; Herbert et al., 1998; Benning et al., 1999). The apparent differences in stoichiometry may be related to sulfide activity at the mineral surface, controlled in part by H 2S autooxidation in the presence of iron oxides. Due to the relative stability of pyrrhotite at low temperatures, ferrous sulfide dissolution is likely to be reduced compared to the more commonly observed products of SRB activity. Additionally, biogenic pyrrhotite formation will also have implications for geomagnetic field behavior of sediments.

  13. Size and Surface Functionalization of Iron Oxide Nanoparticles Influence the Composition and Dynamic Nature of Their Protein Corona

    PubMed Central

    2015-01-01

    Nanoparticles (NPs) adsorb proteins when in the biological matrix, and the resulted protein corona could affect NP-cell interactions. The corona has a dynamic nature with the adsorbed proteins constantly exchanging with the free proteins in the matrix at various rates. The rapidly exchanging proteins compose the soft corona, which responds more dynamically to environment changes than the hard corona established by the ones with slow exchange rates. In the present study, the corona formed on the superparamagnetic iron oxide NPs (SPIONs) in human serum was studied by flow field-flow fractionation and ultracentrifugation, which rapidly differentiated the corona proteins based on their exchange rates. By varying the surface hydrophobicity of the SPIONs with a core size around 10 nm, we found out that, the more hydrophobic surface ligand attracted proteins with higher surface hydrophobicity and formed a more dynamic corona with a larger portion of the involved proteins with fast exchange rates. Increasing the core diameter of the SPIONs but keeping the surface ligand the same could also result in a more dynamic corona. A brief investigation of the effect on the cellular uptake of SPIONs using one selected corona protein, transferrin, was conducted. The result showed that, only the stably bound transferrin could significantly enhance cellular uptake, while transferrin bound in a dynamic nature had negligible impact. Our study has led to a better understanding of the relationship between the particle properties and the dynamic nature of the corona, which can help with design of nanomaterials with higher biocompatibility and higher efficacy in biosystems for biomedical applications. PMID:25144382

  14. Understanding Surface Processes on Mars Through Study of Iron Oxides/Oxyhydroxides: Clues to Surface Alteration and Aqueous Processes

    NASA Technical Reports Server (NTRS)

    Bishop, J. L.; Mancinelli, R. L.; Dyar, M. D.; Parente, M.; Drief, A.; Lane, M. D.; Murad, E.

    2006-01-01

    We are performing oxidation and reduction reactions on hydrated ferric oxide minerals in order to investigate how these might alter under a variety of conditions on the surface of Mars. Preliminary experiments on ferrihydrite and goethite showed that heating these minerals in a dry oxidizing environment produces fine-grained hematite, while heating these minerals in a reducing environment produces fine-grained magnetite. Under Mars-like oxidation levels this magnetite then oxidizes to maghemite. These reactions are dependent on the presence of water and organic material that can act as a reductant. We are using reflectance and Mossbauer spectroscopy to characterize the reaction products and TEM to analyze the sample texture. Our preliminary results indicate that magnetite and maghemite could be formed in the soil on Mars from ferrihydrite and goethite if organics were present on early Mars.

  15. Reflectance spectroscopy and GEX simulation of palagonite and iron-rich montmorillonite clay mixtures: Implications for the surface composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, J. B.; Handy, J.; Quinn, R.

    1992-01-01

    Because of the power of remote sensing reflectance spectroscopy in determining mineralogy, it has been used as the major method of identifying a possible mineral analogue of the martian surface. A summary of proposed martian surface compositions from reflectance spectroscopy before 1979 was presented by Singer et al. Since that time, iron-rich montmorillonite clay, nanocrystalline or nanophase hematite, and palagonite have been suggested as Mars soil analogue materials. Palagonite in petrological terms is best described as an amorphous, hydrated, ferric iron, silica gel. Montmorillonite is a member of the smectite clay group, and its structure is characterized by an octahedral sheet in coordination with two tetrahedral sheets in which oxygen atoms are shared. The crystal unity of montmorillonite is well defined in contrast to palagonite where it is considered amorphous or poorly crystalline at best. Because of the absence of the diagnostic strong 2.2-micron reflectance band characteristic of clays in the near-infrared (NIR) spectrum of Mars and palagonite and based upon a consideration of wide wavelength coverage (0.3-50 microns), Roush et al. concluded that palagonite is a more likely Mars surface analogue. In spite of the spectral agreement of palagonite and the Mars reflectance spectrum in the 2.2-micron region, palagonite shows poor correspondence with the results of the Viking LR experiment. In contrast, iron-rich montmorillonite clays show relatively good agreement with the results of the Viking LR experiment. This spectral study was undertaken to evaluate the spectral properties of mixtures of palagonite and Mars analogue iron-rich montmorillonite clay (16-18 wt. percent Fe as Fe2O3) as a Mars surface mineralogical model. Mixtures of minerals as Mars surface analogue materials have been studied before, but the mixtures were restricted to crystalline clays and iron oxides.

  16. Contribution of coated humic acids calculated through their surface coverage on nano iron oxides for ofloxacin and norfloxacin sorption.

    PubMed

    Peng, Hongbo; Liang, Ni; Li, Hao; Chen, Fangyuan; Zhang, Di; Pan, Bo; Xing, Baoshan

    2015-09-01

    Sorption of organic contaminants on organo-mineral complexes has been investigated extensively, but the sorption contribution of mineral particles was not properly addressed before calculating KOC, especially for ionic organic contaminants. We measured the surface coverage of a humic acid (HA) on nano iron oxides (n-Fe2O3) in a series of synthesized organo-mineral complexes. The contribution of the coated HA to ofloxacin (OFL) and norfloxacin (NOR) sorption in HA-n-Fe2O3 complexes was over 80% of the total sorption with the surface coverage of 36% and fOC of 1.6%. All the coated HA showed higher sorption to NOR and OFL in comparison to the original HA, suggesting HA fractionation and/or physical re-conformation during organo-mineral complex formation. The decreased KOC with multilayer coating may suggest the importance of site-specific interactions for OFL sorption, while the increased KOC with multilayer coating may suggest the importance of partitioning in hydrophobic region for NOR sorption. PMID:25978351

  17. Solvent-surface interactions control the phase structure in laser-generated iron-gold core-shell nanoparticles.

    PubMed

    Wagener, Philipp; Jakobi, Jurij; Rehbock, Christoph; Chakravadhanula, Venkata Sai Kiran; Thede, Claas; Wiedwald, Ulf; Bartsch, Mathias; Kienle, Lorenz; Barcikowski, Stephan

    2016-01-01

    This work highlights a strategy for the one-step synthesis of FeAu nanoparticles by the pulsed laser ablation of alloy targets in the presence of different solvents. This method allows particle generation without the use of additional chemicals; hence, solvent-metal interactions could be studied without cross effects from organic surface ligands. A detailed analysis of generated particles via transmission electron microscopy in combination with EDX elemental mapping could conclusively verify that the nature of the used solvent governs the internal phase structure of the formed nanoparticles. In the presence of acetone or methyl methacrylate, a gold shell covering a non-oxidized iron core was formed, whereas in aqueous media, an Au core with an Fe3O4 shell was generated. This core-shell morphology was the predominant species found in >90% of the examined nanoparticles. These findings indicate that fundamental chemical interactions between the nanoparticle surface and the solvent significantly contribute to phase segregation and elemental distribution in FeAu nanoparticles. A consecutive analysis of resulting Fe@Au core-shell nanoparticles revealed outstanding oxidation resistance and fair magnetic and optical properties. In particular, the combination of these features with high stability magnetism and plasmonics may create new opportunities for this hybrid material in imaging applications. PMID:27004738

  18. Effects of Iron-Oxide Nanoparticle Surface Chemistry on Uptake Kinetics and Cytotoxicity in CHO-K1 Cells

    PubMed Central

    Hanot, Camille C.; Choi, Young Suk; Anani, Tareq B.; Soundarrajan, Dharsan; David, Allan E.

    2015-01-01

    Superparamagnetic iron-oxide nanoparticles (SPIONs) show great promise for multiple applications in biomedicine. While a number of studies have examined their safety profile, the toxicity of these particles on reproductive organs remains uncertain. The goal of this study was to evaluate the cytotoxicity of starch-coated, aminated, and PEGylated SPIONs on a cell line derived from Chinese Hamster ovaries (CHO-K1 cells). We evaluated the effect of particle diameter (50 and 100 nm) and polyethylene glycol (PEG) chain length (2k, 5k and 20k Da) on the cytotoxicity of SPIONs by investigating cell viability using the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and sulforhodamine B (SRB) assays. The kinetics and extent of SPION uptake by CHO-K1 cells was also studied, as well as the resulting generation of intracellular reactive oxygen species (ROS). Cell toxicity profiles of SPIONs correlated strongly with their cellular uptake kinetics, which was strongly dependent on surface properties of the particles. PEGylation caused a decrease in both uptake and cytotoxicity compared to aminated SPIONs. Interestingly, 2k Da PEG-modifed SPIONs displayed the lowest cellular uptake and cytotoxicity among all studied particles. These results emphasize the importance of surface coatings when engineering nanoparticles for biomedical applications. PMID:26729108

  19. Nonreciprocity of spin waves in magnonic crystals created by surface acoustic waves in structures with yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Kryshtal, R. G.; Medved, A. V.

    2015-12-01

    Experimental results of investigations of nonreciprocity for surface magnetostatic spin waves (SMSW) in the magnonic crystal created by surface acoustic waves (SAW) in yttrium iron garnet films on a gallium gadolinium garnet substrate as without metallization and with aluminum films with different electrical conductivities (thicknesses) are presented. In structures without metallization, the frequency of magnonic gaps is dependent on mutual directions of propagation of the SAW and SMSW, showing nonreciprocal properties for SMSW in SAW - magnonic crystals even with the symmetrical dispersion characteristic. In metalized SAW - magnonic crystals the shift of the magnonic band gaps frequencies at the inversion of the biasing magnetic field was observed. The frequencies of magnonic band gaps as functions of SAW frequency are presented. Measured dependencies, showing the decrease of magnonic gaps frequency and the expansion of the magnonic band gap width with the decreasing of the metal film conductivity are given. Such nonreciprocal properties of the SAW - magnonic crystals are promising for signal processing in the GHz range.

  20. Effects of bionic units on the fatigue wear of gray cast iron surface with different shapes and distributions

    NASA Astrophysics Data System (ADS)

    Chen, Zhi-kai; Lu, Shu-chao; Song, Xi-bin; Zhang, Haifeng; Yang, Wan-shi; Zhou, Hong

    2015-03-01

    To improve the fatigue wear resistance of gray cast iron (GCI), GCI samples were modified by a laser to imitate the unique structure of some soil animals alternating between soft and hard phases; the hard phase resists the deformation and the soft phase releases the deformation. Using the self-controlled fatigue wear test method, the fatigue wear behaviors of treated and untreated samples were investigated and compared experimentally. The results show that the bionic non-smooth surface obtains a beneficial effect on improving the fatigue wear resistance of a sample, and the fatigue wear resistance of the bionic sample assembled with reticulate units (60°+0°), whose mass loss was reduced by 62%, was superior to the others. Meanwhile, a finite element (FE) was used to simulate the compression and the distributions of strain and stress on the non-smooth surface was inferred. From these results, we understood that the functions of the bionic unit such as reducing strain and stress, and also obstructing the closure and propagation of cracks were the main reasons for improving the fatigue wear property of GCI.

  1. Solvent-surface interactions control the phase structure in laser-generated iron-gold core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Wagener, Philipp; Jakobi, Jurij; Rehbock, Christoph; Chakravadhanula, Venkata Sai Kiran; Thede, Claas; Wiedwald, Ulf; Bartsch, Mathias; Kienle, Lorenz; Barcikowski, Stephan

    2016-03-01

    This work highlights a strategy for the one-step synthesis of FeAu nanoparticles by the pulsed laser ablation of alloy targets in the presence of different solvents. This method allows particle generation without the use of additional chemicals; hence, solvent-metal interactions could be studied without cross effects from organic surface ligands. A detailed analysis of generated particles via transmission electron microscopy in combination with EDX elemental mapping could conclusively verify that the nature of the used solvent governs the internal phase structure of the formed nanoparticles. In the presence of acetone or methyl methacrylate, a gold shell covering a non-oxidized iron core was formed, whereas in aqueous media, an Au core with an Fe3O4 shell was generated. This core-shell morphology was the predominant species found in >90% of the examined nanoparticles. These findings indicate that fundamental chemical interactions between the nanoparticle surface and the solvent significantly contribute to phase segregation and elemental distribution in FeAu nanoparticles. A consecutive analysis of resulting Fe@Au core-shell nanoparticles revealed outstanding oxidation resistance and fair magnetic and optical properties. In particular, the combination of these features with high stability magnetism and plasmonics may create new opportunities for this hybrid material in imaging applications.

  2. Solvent-surface interactions control the phase structure in laser-generated iron-gold core-shell nanoparticles

    PubMed Central

    Wagener, Philipp; Jakobi, Jurij; Rehbock, Christoph; Chakravadhanula, Venkata Sai Kiran; Thede, Claas; Wiedwald, Ulf; Bartsch, Mathias; Kienle, Lorenz; Barcikowski, Stephan

    2016-01-01

    This work highlights a strategy for the one-step synthesis of FeAu nanoparticles by the pulsed laser ablation of alloy targets in the presence of different solvents. This method allows particle generation without the use of additional chemicals; hence, solvent-metal interactions could be studied without cross effects from organic surface ligands. A detailed analysis of generated particles via transmission electron microscopy in combination with EDX elemental mapping could conclusively verify that the nature of the used solvent governs the internal phase structure of the formed nanoparticles. In the presence of acetone or methyl methacrylate, a gold shell covering a non-oxidized iron core was formed, whereas in aqueous media, an Au core with an Fe3O4 shell was generated. This core-shell morphology was the predominant species found in >90% of the examined nanoparticles. These findings indicate that fundamental chemical interactions between the nanoparticle surface and the solvent significantly contribute to phase segregation and elemental distribution in FeAu nanoparticles. A consecutive analysis of resulting Fe@Au core-shell nanoparticles revealed outstanding oxidation resistance and fair magnetic and optical properties. In particular, the combination of these features with high stability magnetism and plasmonics may create new opportunities for this hybrid material in imaging applications. PMID:27004738

  3. Chemical force microscopy investigation of phosphate adsorption on the surfaces of iron(III) oxyhydroxide particles.

    PubMed

    Kreller, D I; Gibson, G; vanLoon, G W; Horton, J H

    2002-10-15

    Phosphate-modified AFM tips were prepared by the deposition of self-assembled monolayers (SAMs) of bis(11-thioundecyl) phosphate on Au-coated silicon nitride cantilevers. The properties of the PO(2)H-terminated SAMs were investigated by studying the pH-dependent force interactions of the tips with phosphate- and carboxylic acid-terminated SAM control surfaces. The PO(2)H functional groups had a pK(a) of approximately 5.0. A chemical force microscopy (CFM) study was conducted on the interactions between the probes and the surfaces of hydrous ferric oxide particles prepared in our laboratory by hydrolytic precipitation from FeCl(3). The forces between PO(2)H probes and the hydrous ferric oxide surfaces were seen to exhibit a strong pH dependence, with maximum attractive forces occurring for pH values between 5 and 8. The effects of postprecipitation of the hydrous ferric oxide colloids with orthophosphate, H(2)PO(4)(-), dimethylphosphate, (CH(3)O)(2)PO(2)H (DMP), and tannic acid (TA) on the adhesive interactions between the PO(2)H tips and the solids were also investigated. Attenuated total reflectance infrared spectroscopy (ATR-IR) was used to verify the presence of surface-adsorbed species and zeta potentiometric measurements to determine surface charge on the colloids. We show that the method of chemical force titration using phosphate-terminated tips can differentiate between these various colloids and that it shows promise as a general method for studying this environmentally important class of compounds. PMID:12702389

  4. Molecular Basis of Virulence in Staphylococcus aureus Mastitis

    PubMed Central

    Le Maréchal, Caroline; Seyffert, Nubia; Jardin, Julien; Hernandez, David; Jan, Gwenaël; Rault, Lucie; Azevedo, Vasco; François, Patrice; Schrenzel, Jacques; van de Guchte, Maarten; Even, Sergine; Berkova, Nadia; Thiéry, Richard; Fitzgerald, J. Ross

    2011-01-01

    Background S. aureus is one of the main pathogens involved in ruminant mastitis worldwide. The severity of staphylococcal infection is highly variable, ranging from subclinical to gangrenous mastitis. This work represents an in-depth characterization of S. aureus mastitis isolates to identify bacterial factors involved in severity of mastitis infection. Methodology/Principal Findings We employed genomic, transcriptomic and proteomic approaches to comprehensively compare two clonally related S. aureus strains that reproducibly induce severe (strain O11) and milder (strain O46) mastitis in ewes. Variation in the content of mobile genetic elements, iron acquisition and metabolism, transcriptional regulation and exoprotein production was observed. In particular, O11 produced relatively high levels of exoproteins, including toxins and proteases known to be important in virulence. A characteristic we observed in other S. aureus strains isolated from clinical mastitis cases. Conclusions/Significance Our data are consistent with a dose-dependant role of some staphylococcal factors in the hypervirulence of strains isolated from severe mastitis. Mobile genetic elements, transcriptional regulators, exoproteins and iron acquisition pathways constitute good targets for further research to define the underlying mechanisms of mastitis severity. PMID:22096559

  5. Expanded Glucose Import Capability Affords Staphylococcus aureus Optimized Glycolytic Flux during Infection

    PubMed Central

    Vitko, Nicholas P.; Grosser, Melinda R.; Khatri, Dal; Lance, Thurlow R.

    2016-01-01

    ABSTRACT Acquisition of numerous virulence determinants affords Staphylococcus aureus greater pathogenicity than other skin-colonizing staphylococci in humans. Additionally, the metabolic adaptation of S. aureus to nonrespiratory conditions encountered during infection (e.g., hypoxia, nitric oxide, iron chelation) has been implicated as contributing to S. aureus virulence. Specifically, S. aureus has been shown to ferment glycolytic substrates in nonrespiratory environments encountered within the host. Here, we show that S. aureus has acquired unique carbohydrate transporters that facilitate the maximal uptake of host sugars and serve to support nonrespiratory growth in inflamed tissue. The carbohydrate substrates of 11 S. aureus transporters were identified, and at least four of their genes encode S. aureus glucose transporters (glcA, glcB, glcC, and glcU). Moreover, two transporter genes (glcA and glcC) are unique to S. aureus and contribute disproportionately to the nonrespiratory growth of S. aureus on glucose. Targeted inactivation of sugar transporters reduced glucose uptake and attenuated S. aureus in a murine model of skin and soft tissue infections. These data expand the evidence for metabolic adaptation of S. aureus to invasive infection and demonstrate the specific requirement for the fermentation of glucose over all other available carbohydrates. Ultimately, acquisition of foreign genes allows S. aureus to adopt a metabolic strategy resembling that of infiltrating host immune cells: high glycolytic flux coupled to lactate excretion. PMID:27329749

  6. The Effect of Hydrogen on the Bonding and Dissociation of Carbon Monoxide on AN IRON(100) Surface

    NASA Astrophysics Data System (ADS)

    Nassir, Mohamed Husain

    1993-01-01

    Adsorption and coadsorption of CO and H _2 on Fe(100) was studied using the following six methods: Temperature programmed desorption (TPD), x -ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), high resolution electron energy loss spectroscopy (HREELS), single reflection Fourier transform infrared spectroscopy (FTIR) and low-energy electron diffraction (LEED). The binding and dissociation of CO on a clean and hydrogen presaturated Fe(100) surface were investigated to provide better understanding of the first step in the Fischer-Tropsch synthesis, an important industrial catalytic reaction for converting CO and hydrogen to hydrocarbon. CO adsorbs molecularly on the clean surface in three states alpha_1, alpha_2 and alpha_3 . At temperatures above 350 K but below 440 K, CO is bound to the surface only in the highly perturbed alpha_3 state (pi -bonded geometry). The CO alpha_3 molecules are believed to occupy the 4-fold hollow sites. When the surface temperature is raised above 440 K, a fraction of the alpha_3 desorbs and the remainder dissociates. The dissociation fragments replace the CO alpha_3 molecules in the 4-fold hollow sites. These fragments recombine at higher temperatures and appear as beta CO. The bonding and dissociation of CO in the alpha_3 received more attention because it is believed that this state is a precursor to dissociation. A model describing the partitioning between desorption and dissociation is proposed in which the dissociation fragments displace the strongly bound CO in the beta -bonded state. The stoichiometry of this reaction at saturation requires that only half the original CO adsorbed in the beta-bonded CO state can dissociate. Presaturating the surface with hydrogen affects the bonding and dissociation of CO on the iron surface. One effect is to weaken CO-Fe bonds which results in a very weakly bound state (alpha^' _1). In addition to the alpha ^'_1 state, presaturating the surface with hydrogen

  7. Iron mineralogy of the surface of Mars from the 1 μm band spectral properties

    NASA Astrophysics Data System (ADS)

    Carrozzo, F. G.; Altieri, F.; Bellucci, G.; Poulet, F.; D'Aversa, E.; Bibring, J.-P.

    2012-10-01

    We study the 1 μm absorption from OMEGA/MEX spectra to map Martian iron mineralogy at a global scale. This band is covered on the left by the VNIR (visible and near infrared) OMEGA channel and on the right by the SWIR (short wavelengths infrared) one. We first perform a systematic spatial coregistration of the two channels after an improvement of the VNIR radiometric calibration. The update of the VNIR Instrumental Transfer Function (ITF) and the internal stray-light estimation is based on the spectra of the Phobos red units and of the water ice north polar cap of Mars, which have been fitted according to an iterative process. The level of the signal in the blue wavelength range, previously systematically overestimated due to a stray-light residual and the general shape of the spectrum for λ > 0.7 μm are improved . Global maps of the 1 μm signature have been derived from 9 new spectral indices. The largest values of the 1 μm band integral are found in Noachian terrains and in the dunes around the north polar cap. In the south polar region, an area centered at ˜155°W and ˜83°S is mapped as a distinctive spectral unit, dominated by pyroxene. The northern lowlands of Mars together with other dark terrains located in the northern hemisphere show very low values of some spectral indices due to the negative spectral slope in the NIR. This behavior is consistent with the presence of weathered basalts with a possible glassy or amorphous component. Among the hydrated terrains, the only ones that can be isolated by studying the 1 μm band are those located in Terra Meridiani, Aram Chaos and Capri Chasma, enriched in sulfate and hematite. On the other hand, the sulfates of the dark dunes surrounding the northern polar cap and the phyllosilicates of the bright hydrated deposits of Mawrth Vallis cannot be isolated combining the parameters used in this study. This suggests that their distinctive mineralogy does not affect the 1 μm band, remaining similar to the global

  8. Molecular Cloning and Analysis of a Putative Siderophore ABC Transporter from Staphylococcus aureus

    PubMed Central

    Morrissey, Julie A.; Cockayne, Alan; Hill, Philip J.; Williams, Paul

    2000-01-01

    From a mass-excised Staphylococcus aureus λZapII expression library, we cloned an operon encoding a novel ABC transporter with significant homology to bacterial siderophore transporter systems. The operon encodes four genes designated sstA, -B, -C, and -D encoding two putative cytoplasmic membrane proteins (sstA and sstB), an ATPase (sstC), and a membrane-bound 38-kDa lipoprotein (sstD). The sst operon is preceded by two putative Fur boxes, which indicated that expression of the sst operon was likely to be iron dependent. SstD was overexpressed in Escherichia coli, purified by Triton X-114 phase partitioning, and used to generate monospecific antisera in rats. Immunoblotting studies located SstD in the membrane fraction of S. aureus and showed that expression of the lipoprotein was reduced under iron-rich growth conditions. Triton X-114 partitioning studies on isolated membranes provided additional biochemical evidence that SstD in S. aureus is a lipoprotein. Immunoreactive polypeptides of approximately 38 kDa were detected in a wide range of staphylococcal species, but no antigenic homolog was detected in Bacillus subtilis. Expression of SstD in vivo was confirmed by immunoblotting studies with S. aureus recovered from a rat intraperitoneal chamber implant model. To further define the contribution of SstD in promoting growth of S. aureus in vitro and in vivo, we used antisense RNA technology to modulate expression of SstD. Expression of antisense sstD RNA in S. aureus resulted in a decrease in SstD expression under both iron-rich and iron-restricted growth conditions. However, this reduction in SstD levels did not affect the growth of S. aureus in vitro in an iron-limited growth medium or when grown in an intraperitoneal rat chamber implant model in vivo. PMID:11035736

  9. Reducing phosphorus loading of surface water using iron-coated sand.

    PubMed

    Groenenberg, Jan E; Chardon, Wim J; Koopmans, Gerwin F

    2013-01-01

    Phosphorus losses from agricultural soils is an important source of P in surface waters leading to surface water quality impairment. In addition to reducing P inputs, mitigation measures are needed to reduce P enrichment of surface waters. Because drainage of agricultural land by pipe drainage is an important pathway of P to surface waters, removing P from drainage water has a large potential to reduce P losses. In a field trial, we tested the performance of a pipe drain enveloped with Fe-coated sand, a side product of the drinking water industry with a high ability to bind P, to remove P from the drainage water. The results of this trial, encompassing more than one hydrological season, are very encouraging because the efficiency of this mitigation measure to remove P amounted to 94%. During the trial, the pipe drains were below the groundwater level for a prolonged time. Nevertheless, no reduction of Fe(III) in the Fe-coated sand occurred, which was most likely prevented by reduction of Mn oxides present in this material. The enveloped pipe drain was estimated to be able to lower the P concentration in the effluent to the desired water quality criterion for about 14 yr. Manganese oxides are expected to be depleted after 5 to 10 yr. The performance of the enveloped pipe drain, both in terms of its ability to remove P to a sufficiently low level and the stability of the Fe-coated sand under submerged conditions in the long term, needs prolonged experimental research. PMID:23673760

  10. Grafting densely-packed poly( n-butyl methacrylate) chains from an iron substrate by aryl diazonium surface-initiated ATRP: XPS monitoring

    NASA Astrophysics Data System (ADS)

    Matrab, Tarik; Save, Maud; Charleux, Bernadette; Pinson, Jean; Cabet-deliry, Eva; Adenier, Alain; Chehimi, Mohamed M.; Delamar, Michel

    2007-06-01

    Poly( n-butyl methacrylate), PBMA, chains were grafted by atom transfer radical polymerization (ATRP) from the surface of iron plates using electrochemically attached initiators based on diazonium salts providing an iron/polyphenylene/PBMA structure. This surface-initiated ATRP procedure was controlled by the addition of a small proportion of Cu ++ deactivator, but in the absence of any sacrificial initiator. Combined XPS, IR and AFM experiments provide a powerful means for the characterization of the obtained complex iron/polyphenylene/PBMA layered structure. It is possible to measure the thickness of the brominated aryl structure covalently attached to iron. Concerning the PBMA brushes, their presence on the surface was confirmed by IRRAS. The brominated chain end could be traced by XPS testifying for the ATRP character of the polymerization and the thickness of the polymer brushes was determined. The controlled living ATRP character of the polymerization is confirmed through a linear correlation between the thickness of the layer and the degree of polymerization. Measurement of the grafting density of PBMA chains indicates that they are compactly packed and that, approximately, one brominated aryl chain out of two efficiently initiates ATRP.

  11. Iron phthalocyanine on Cu(111): Coverage-dependent assembly and symmetry breaking, temperature-induced homocoupling, and modification of the adsorbate-surface interaction by annealing.

    PubMed

    Snezhkova, Olesia; Bischoff, Felix; He, Yuanqin; Wiengarten, Alissa; Chaudhary, Shilpi; Johansson, Niclas; Schulte, Karina; Knudsen, Jan; Barth, Johannes V; Seufert, Knud; Auwärter, Willi; Schnadt, Joachim

    2016-03-01

    We have examined the geometric and electronic structures of iron phthalocyanine assemblies on a Cu(111) surface at different sub- to mono-layer coverages and the changes induced by thermal annealing at temperatures between 250 and 320 °C by scanning tunneling microscopy, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy. The symmetry breaking observed in scanning tunneling microscopy images is found to be coverage dependent and to persist upon annealing. Further, we find that annealing to temperatures between 300 and 320 °C leads to both desorption of iron phthalocyanine molecules from the surface and their agglomeration. We see clear evidence of temperature-induced homocoupling reactions of the iron phthalocyanine molecules following dehydrogenation of their isoindole rings, similar to what has been observed for related tetrapyrroles on transition metal surfaces. Finally, spectroscopy indicates a modified substrate-adsorbate interaction upon annealing with a shortened bond distance. This finding could potentially explain a changed reactivity of Cu-supported iron phthalocyanine in comparison to that of the pristine compound. PMID:26957171

  12. Iron phthalocyanine on Cu(111): Coverage-dependent assembly and symmetry breaking, temperature-induced homocoupling, and modification of the adsorbate-surface interaction by annealing

    NASA Astrophysics Data System (ADS)

    Snezhkova, Olesia; Bischoff, Felix; He, Yuanqin; Wiengarten, Alissa; Chaudhary, Shilpi; Johansson, Niclas; Schulte, Karina; Knudsen, Jan; Barth, Johannes V.; Seufert, Knud; Auwärter, Willi; Schnadt, Joachim

    2016-03-01

    We have examined the geometric and electronic structures of iron phthalocyanine assemblies on a Cu(111) surface at different sub- to mono-layer coverages and the changes induced by thermal annealing at temperatures between 250 and 320 °C by scanning tunneling microscopy, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy. The symmetry breaking observed in scanning tunneling microscopy images is found to be coverage dependent and to persist upon annealing. Further, we find that annealing to temperatures between 300 and 320 °C leads to both desorption of iron phthalocyanine molecules from the surface and their agglomeration. We see clear evidence of temperature-induced homocoupling reactions of the iron phthalocyanine molecules following dehydrogenation of their isoindole rings, similar to what has been observed for related tetrapyrroles on transition metal surfaces. Finally, spectroscopy indicates a modified substrate-adsorbate interaction upon annealing with a shortened bond distance. This finding could potentially explain a changed reactivity of Cu-supported iron phthalocyanine in comparison to that of the pristine compound.

  13. Self-assembly of Iron Oxide Nanoparticles on Liquid Surfaces by Using Miscible Solvent Pairs

    NASA Astrophysics Data System (ADS)

    Hu, Jiayang; Zhang, Datong; Kennedy, Kathleen M.; Herman, Irving P.

    Nanoparticle (NP) self-assembly on liquid-air interfaces by using immiscible solvent pairs is a fast and effective way to prepare two-dimensional (2D) close-packed superlattices. However, this technique is limited by the number of available solvent pairs that are immiscible with each other while being different in the dispersity of NPs. Here, we report forming 2D superlattices using toluene/dimethyl sulfoxide miscible solvent pairs. In-situ small angle X-ray scattering patterns from NP layers sitting on the meniscus agree with patterns expected from 2D tilted closed packed superlattices. Real time optical microscopy shows that after drop casting, most of NPs coagulate immediately and sink to the bottom over several days, but leave a continuous ML on the surface, without forming 3D clusters that are usually seen in the immiscible techniques generated by the ``coffee ring'' effect. TEM images show that NPs nucleate simultaneously on different parts on the liquid surface until they touch, therefore covering the whole surface.

  14. Variations in the abundance of iron on Mercury's surface from MESSENGER X-Ray Spectrometer observations

    NASA Astrophysics Data System (ADS)

    Weider, Shoshana Z.; Nittler, Larry R.; Starr, Richard D.; McCoy, Timothy J.; Solomon, Sean C.

    2014-06-01

    We present measurements of Mercury's surface composition from the analysis of MESSENGER X-Ray Spectrometer data acquired during 55 large solar flares, which each provide a statistically significant detection of Fe X-ray fluorescence. The Fe/Si data display a clear dependence on phase angle, for which the results are empirically corrected. Mercury's surface has a low total abundance of Fe, with a mean Fe/Si ratio of ˜0.06 (equivalent to ˜1.5 wt% Fe). The absolute Fe/Si values are subject to a number of systematic uncertainties, including the phase-angle correction and possible mineral mixing effects. Individual Fe/Si measurements have an intrinsic error of ˜10%. Observed Fe/Si values display small variations (significant at two standard deviations) from the planetary average value across large regions in Mercury's southern hemisphere. Larger differences are observed between measured Fe/Si values from more spatially resolved footprints on volcanic smooth plains deposits in the northern hemisphere and from those in surrounding terrains. Fe is most likely contained as a minor component in sulfide phases (e.g., troilite, niningerite, daubréelite) and as Fe metal, rather than within mafic silicates. Variations in surface reflectance (i.e., differences in overall reflectance and spectral slope) across Mercury are unlikely to be caused by variations in the abundance of Fe.

  15. Influence of manganese incorporation on structure, surface and As(III)/As(V) removal capacity of iron oxy-hydroxides

    NASA Astrophysics Data System (ADS)

    Tresintsi, Sofia; Simeonidis, Konstantinos; Mitrakas, Manassis

    2013-04-01

    Iron oxy-hydroxides are well defined As(V) adsorbents dominating in water treatment market. The main drawback of these adsorbents, as well as of all commercial one, is their significantly low adsorption capacity for As(III). A breakthrough for improving As(III) adsorption of iron oxy-hydroxides may come by the MnO2incorporation. However, MnO2 decreases the total arsenic capacity proportionally to its percentage since its efficiency for As(V) is much lower than that of an iron oxy-hydroxide. It is concluded that an ideal adsorbent capable for high and simultaneous As(III) and As(V) removal should be consisted of a binary Fe(III)-Mn(IV) oxy-hydroxide both efficient for As(III) oxidation, due to Mn(IV) presence, and capture of As(V) due to a high positively surface charge density. This work studies the optimum parameters at the synthesis of single Fe and binary Fe/Mn oxy-hydroxides in a continuous flow kilogram-scale production reactor through the precipitation of FeSO4 in the pH range 3-12, under intense oxidative conditions using H2O2/KMnO4, that maximize arsenic adsorption. The evaluation of their efficiency was based on its As(III) and As(V) adsorption capacity (Q10-index) at equilibrium concentration equal to drinking water regulation limit (Ce= 10 μg/L) in NSF challenge water. The pH of synthesis was found to decisively affect, the structure, surface configuration and Q10-index. As a result, both single Fe and binary Fe/Mn oxy-hydroxides prepared at pH 4, which consist of schwertmannite and Mn(IV)-feroxyhyte respectively, were qualified according to their highest Q10-index of 13±0.5 μg As(V)/ mg for a residual arsenic concentration of 10 μg/L at an equilibrium pH 7. The high surface charge and the activation of an ion-exchange mechanism between SO42- adsorbed in the Stern layer and arsenate ions were found to significantly contribute to the increased adsorption capacity. The Q10-index for As(III) of Fe/Mn adsorbent at equilibrium pH 7 was 6.7 μg/mg, which

  16. Abundance of Iron on Mercury's Surface from MESSENGER X-Ray Spectrometer Data

    NASA Astrophysics Data System (ADS)

    Weider, S. Z.; Nittler, L. R.; Starr, R. D.; Evans, L. G.; McCoy, T. J.; Solomon, S. C.

    2012-12-01

    Early orbital results from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) X-Ray Spectrometer (XRS) revealed that Mercury's surface has a low Fe content. The reported Fe/Si ratios (~0.03 to 0.15) gave an upper limit of ~4 wt% Fe. This limit is consistent with the bulk estimate provided by the Gamma-Ray Spectrometer (Fe/Si: ~0.12) and the upper limit of ~6 wt % FeO in silicate minerals that is constrained by reflectance spectroscopy. Reliable Fe abundance estimates are difficult to obtain from XRS data for several reasons, including: (i) strong solar flares are required to excite Fe X-ray fluorescence, and such flares occur rarely; and (ii) energetic particle events often accompany the strongest solar flares, causing fluorescence of the instrument's Cu collimators and spectral contamination close to the Fe K lines at 6.4-7 keV. Forward modeling of XRS data from more than 30 flares during the first year of MESSENGER's orbit reveal that Fe is ubiquitously lower on Mercury (Fe/Si ranging from 0.02 to 0.18, with a peak in the distribution at ~0.06, or ~1.5 wt% Fe) than on other terrestrial planets. Although the abundance of Mg across the surface of Mercury is known to vary according to geological terrain, our data indicate that this variation is not a result of Fe substitution for Mg in mafic silicates. A correlation between Ca and S (and to a lesser extent between Mg and S) has previously been reported from the XRS data. Mercury's high S contents likely reflect the presence of abundant sulfide minerals, such as oldhamite (Ca,Mg,Fe)S. Our data reveal further correlations between Fe and Ca, and between Fe and Mg, suggesting that sulfides (most likely troilite, FeS, and/or oldhamite) are a major carrier of Fe on Mercury's surface. The low Fe content of Mercury's surface supports the very low FeO contents that are predicted from both melting experiments on enstatite chondrites and from thermodynamic modeling. However, even the few wt% Fe on

  17. On the ion-bombardment reduction mechanism. [of iron ions in lunar surface

    NASA Technical Reports Server (NTRS)

    Yin, L.; Tsang, T.; Adler, I.

    1976-01-01

    Recent laboratory studies of solar-wind reduction mechanisms on the lunar surface are discussed, emphasizing the effects of the electronic configurations of transition metals and the effects of covalent bonding. A series of experiments is described which involved argon ion bombardment of extremely thin targets consisting of simple halides and cyanides of first-row transition metals. Experimental results are summarized which imply that the cyanides generally have much higher reduction efficiencies than the halides. It is suggested that although reduction and sputtering take place concurrently under ion bombardment, they may actually be two independent processes.

  18. Surface Interrogation Scanning Electrochemical Microscopy of Ni(1-x)Fe(x)OOH (0 < x < 0.27) Oxygen Evolving Catalyst: Kinetics of the "fast" Iron Sites.

    PubMed

    Ahn, Hyun S; Bard, Allen J

    2016-01-13

    Nickel-iron mixed metal oxyhydroxides have attracted significant attention as an oxygen evolution reaction (OER) catalyst for solar fuel renewable energy applications. Here, we performed surface-selective and time-dependent redox titrations to directly measure the surface OER kinetics of Ni(IV) and Fe(IV) in NiOOH, FeOOH, and Ni(1-x)Fe(x)OOH (0 < x < 0.27) electrodes. Most importantly, two types of surface sites exhibiting "fast" and "slow" kinetics were found, where the fraction of "fast" sites in Ni(1-x)Fe(x)OOH matched the iron atom content in the film. This finding provides experimental support to the theory-proposed model of active sites in Ni(1-x)Fe(x)OOH. The OER rate constant of the "fast" site was 1.70 s(-1) per atom. PMID:26645678

  19. Expression of fibronectin binding protein A (FnBPA) from Staphylococcus aureus at the cell surface of Lactococcus lactis improves its immunomodulatory properties when used as protein delivery vector.

    PubMed

    Almeida, Juliana F; Breyner, Natalia M; Mahi, Miloud; Ahmed, Bensoltane; Benbouziane, Bouasria; Boas, Priscilla C B Vilas; Miyoshi, Anderson; Azevedo, Vasco; Langella, Philippe; Bermúdez-Humarán, Luis G; Chatel, Jean-Marc

    2016-03-01

    A recombinant strain of Lactococcus lactis displaying a cell-surface anchored fibronectin binding protein A (FnBPA) from Staphylococcus aureus (LL-FnBPA) had been shown to be more efficient in delivering plasmid than its wild-type counterpart both in vitro and in vivo, and have the ability to orientate the immune response toward a Th2 profile in a context of a DNA vaccination. The aim of this work was to test whether this LL-FnBPA strain could shape the immune response after mucosal administration in mice. For this, we used a mouse model of human papilloma virus (HPV)-induced cancer and a L. lactis strain displaying at its cell surface both HPV-16-E7 antigen (LL-E7) and FnBPA (LL-E7+FnBPA). Our results revealed a more efficient systemic Th1 immune response with recombinant LL-E7+FnBPA. Furthermore, mice vaccinated with LL-E7+FnBPA were better protected when challenged with HPV-16-induced tumors. Altogether, the results suggest that FnBPA displays adjuvant properties when used in the context of mucosal delivery using L. lactis as a live vector. PMID:26854905

  20. Aft2, a novel transcription regulator, is required for iron metabolism, oxidative stress, surface adhesion and hyphal development in Candida albicans.

    PubMed

    Xu, Ning; Cheng, Xinxin; Yu, Qilin; Qian, Kefan; Ding, Xiaohui; Liu, Ruming; Zhang, Biao; Xing, Laijun; Li, Mingchun

    2013-01-01

    Morphological transition and iron metabolism are closely relevant to Candida albicans pathogenicity and virulence. In our previous study, we demonstrated that C. albicans Aft2 plays an important role in ferric reductase activity and virulence. Here, we further explored the roles of C. albicans Aft2 in numerous cellular processes. We found that C. albicans Aft2 exhibited an important role in iron metabolism through bi-directional regulation effects on iron-regulon expression. Deletion of AFT2 reduced cellular iron accumulation under iron-deficient conditions. Furthermore, both reactive oxygen species (ROS) generation and superoxide dismutase (SOD) activity were remarkably increased in the aft2Δ/Δ mutant, which were thought to be responsible for the defective responses to oxidative stress. However, we found that over-expression of C. albicans AFT2 under the regulation of the strong PGK1 promoter could not effectively rescue Saccharomyces cerevisiae aft1Δ mutant defects in some cellular processes, such as cell-wall assembly, ion homeostasis and alkaline resistance, suggesting a possibility that C. albicans Aft2 weakened its functional role of regulating some cellular metabolism during the evolutionary process. Interestingly, deletion of AFT2 in C. albicans increased cell surface hydrophobicity, cell flocculation and the ability of adhesion to polystyrene surfaces. In addition, our results also revealed that C. albicans Aft2 played a dual role in regulating hypha-specific genes under solid and liquid hyphal inducing conditions. Deletion of AFT2 caused an impaired invasive growth in solid medium, but an increased filamentous aggregation and growth in liquid conditions. Moreover, iron deficiency and environmental cues induced nuclear import of Aft2, providing additional evidence for the roles of Aft2 in transcriptional regulation. PMID:23626810

  1. Surface-Correlated Nanophase Iron Metal in Lunar Soils: Petrography and Space Weathering Effects

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; Wentworth, Susan J.; McKay, David S.

    1998-01-01

    Space weathering is a term used to include all of the processes that act on material exposed at the surface of a planetary or small body. In the case of the Moon, it includes a variety of processes that formed the lunar regolith, caused the maturation of lunar soils, and formed patina on rock surfaces. The processes include micrometeorite impact and reworking, implantation of solar wind and flare particles, radiation damage and chemical effects from solar particles and cosmic rays, interactions with the lunar atmosphere, and sputtering erosion and deposition. Space weathering effects collectively result in a reddened continuum slope, lowered albedo, and attenuated absorption features in reflectance spectra of lunar soils as compared to finely comminuted rocks from the same Apollo sites. Understanding these effects is critical in order to fully integrate the lunar sample collection with remotely sensed data from recent robotic missions (e.g., Lunar Prospector, Clementine, Galileo). Our objective is to determine the origin of space weathering effects in lunar soils through combined electron microscopy and microspectrophotometry techniques applied to individual soil particles from <20 pm size factions (dry-sieved) of mature lunar soils. It has been demonstrated that it is the finest size fraction (<25 pm) of lunar soils that dominates the optical properties of the bulk soils.

  2. Role of Surface Precipitation in Copper Sorption by the Hydrous Oxides of Iron and Aluminum.

    PubMed

    Karthikeyan; Elliott; Chorover

    1999-01-01

    Isotherms were developed at pH 6.9 for adsorption (ADS) and coprecipitation (CPT) of Cu by hydrous oxides of Fe (HFO) and Al (HAO) to study the role of sorbate/sorbent ratio in metal cation removal. For low sorbate/sorbent conditions, HFO had a higher Cu retention capacity than HAO regardless of contact methodology. For either oxide, CPT was consistently more effective than ADS in removing Cu from solution. At high sorbate/sorbent ratios, surface precipitation dominates and the oxide's net cation retention capacity depends on the nature and solubility of the precipitate formed at the oxide-water interface. X-ray diffraction patterns and isotherms of HAO for both ADS and CPT suggest formation of a solid solution [e.g., CuAl2O4(s)] with dramatically lower solubility than Cu(OH)2(s) precipitated in bulk solution. In contrast, Cu precipitated on the HFO surface exhibited a solubility comparable to the bulk precipitated Cu(OH)2(s). Therefore, at high sorbate/sorbent ratios, HAO has a higher Cu "apparent" sorption capacity than HFO. The relative utility of these oxides as metal scavengers thus depends markedly on sorbate/sorbent conditions. Copyright 1999 Academic Press. PMID:9878138

  3. Mapping Electrochemical Heterogeneity at Iron Oxide Surfaces: A Local Electrochemical Impedance Study.

    PubMed

    Lucas, Marie; Boily, Jean-François

    2015-12-22

    Alternating current scanning electrochemical microscopy (AC-SECM) was used for the first time to map key electrochemical attributes of oriented hematite (α-Fe2O3) single crystal surfaces at the micron-scale. Localized electrochemical impedance spectra (LEIS) of the (001) and (012) faces provided insight into the spatial variations of local double layer capacitance (C(dl)) and charge transfer resistance (R(ad)). These parameters were extracted by LEIS measurements in the 0.4-8000 Hz range to probe the impedance response generated by the redistribution of water molecules and charge carriers (ions) under an applied AC. These were attributed to local variations in the local conductivity of the sample surfaces. Comparison with global EIS measurements on the same samples uncovered highly comparable frequency-resolved processes, that were broken down into contributions from the bulk hematite, the interface as well as the microelectrode/tip assembly. This work paves the way for new studies aimed at mapping electrochemical processes at the mesoscale on this environmentally and technologically important material. PMID:26625255

  4. Tribological effect of iron oxide residual on the DLC film surface under seawater and saline solutions

    NASA Astrophysics Data System (ADS)

    Costa, R. P. C.; Marciano, F. R.; Lima-Oliveira, D. A.; Corat, E. J.; Trava-Airoldi, V. J.

    2011-04-01

    This paper discusses the seawater and saline solutions effects on the tribological behavior of diamond-like carbon (DLC) films. The adsorption of Fe on DLC surface is one of the mechanisms that is believed to be the cause of the decrease in dispersive component of the surface energy and increase of the I D/I G ratio leading to low friction coefficient and wear rate under corrosive environments. Tribological behaviors DLC films were experimentally evaluated under corrosive environments by using steel ball and DLC coated steel flat under rotational sliding conditions. The DLC films were prepared on 440 stainless steel disks by DC-pulsed PECVD using methane as a precursor gas. Two different set of tribological system was assembled, one when the liquids and the pairs were put inside of a stainless steel vessel and others inside of a PTFE. Every tribological test was performed under 10 N normal load120 mms - 1 of sliding speed. The friction coefficients were evaluated during 1000 cycles.

  5. Reactions and reaction intermediates on iron surfaces. III. Reactions of aldehydes and ketones on Fe(100)

    SciTech Connect

    Benziger, J.B.; Madix, R.J.

    1982-01-01

    The reactions of formaldehyde, acetaldehyde, and acetone on Fe(100) were studied by temperature-programmed reaction spectroscopy and X-ray photoelectron spectroscopy (XPS). Formaldehyde and acetaldehyde were observed to react with adsorbed hydrogen to form adsorbed alkoxy intermediates. These reactions occurred at low temperature (ca. 200 K). In the absence of adsorbed hydrogen, formaldehyde and acetaldehyde decomposed to adsorbed CO and hydrogen. This reaction was also observed at low temperatures. On an initially clean surface the aldehydes first decomposed, forming adsorbed hydrogen which subsequently reacted with adsorbed aldehyde to form an alkoxy intermediate. The alkoxy intermediates reacted to form CO and H/sub 2/ primarily, with lesser amounts of alcohol, aldehyde, and hydrocarbon products. Acetone reacted differently from the aldehydes and did not appear to form an alkoxy intermediate. XPS results suggested that acetone and acetaldehyde did not adsorb in their keto form on the surface and it is suggested that they adsorbed as enol intermediates. The distinct reaction behavior of acetone may be due to these enol intermediates.

  6. Oxidation rate of iron sulfides as affected by surface area, morphology, oxygen concentration and autotrophic bacteria

    SciTech Connect

    Pugh, C.E.

    1984-05-01

    The relationship between surface area and rate of oxidation of Fe sulphides (pyrite and marcasite) separated from Texas lignite was studied. The reaction kinetics with respect to Fe sulphide morphology and particle size were evaluated. The oxygen concentration and the presence of autotrophic Fe and S-oxidizing bacteria (thiobacillus ferro-oxidans) on the rate of oxidation were also evaluated. The formation of sulphate from Fe sulphide was selected to measure the rate of oxidation. Relative reaction rates for different morphological forms of Fe sulphide were: marcasite > framboidal pyrite > massive pyrite. As the surface area of pyrite doubled, reaction rate increased by a factor of 1.5. Sulphate production for the 5 to 2 ..mu..m fraction was twice that of the 50 to 20 ..mu..m fraction. Reaction rate was approximately fivefold greater for non-inoculated treatments at 20% O/sub 2/ compared with 0% O/sub 2/ and was approximately ninefold greater for the same treatment inoculated with T. ferro-oxidans.

  7. Remarkable doping effects beyond altering Fermi surface on the superconductivity of iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Ye, Z. R.; Zhang, Y.; Chen, F.; Xu, M.; Jiang, J.; Niu, X. H.; Wen, C. H. P.; Xie, B. P.; Feng, D. L.; Xing, L. Y.; Wang, X. C.; Jin, C. Q.

    2014-03-01

    The superconductivity in Fe-based superconductors could be achieved by doping the parent compounds. Previous researches were focusing on the charge carrier density or Fermi surface alteration by doping only. However, the dominating factors based on Fermiology have many inconsistencies, which indicates that some other effects induced by doping are neglected. Using ARPES, we have established the microscopic and more comprehensive picture of doping on the electronic structure beyond altering Fermi surface. We have figured out other two critical effects of doping, scattering and changing correlation. With doping, the dxy-related band around the zone center is found to be much more sensitive than the dxz/dyz-related bands and the strength of the impurity scattering strongly depends on the position of dopants, which resembles the case in cuprates. On the other hand, we observed that the electron correlation decreases with doping, which is universal in various systems of Fe-based superconductors. Moderate electron correlation is critical for the high Tc. The two effects we observed here both are very important for the superconductivity, and explain a lot of previous mysteries and unresolved issues.

  8. Iron Chelation

    MedlinePlus

    ... iron overload and need treatment. What is iron overload? Iron chelation therapy is used when you have ... may want to perform: How quickly does iron overload happen? This is different for each person. It ...

  9. Iron oxide magnetic nanoparticles with versatile surface functions based on dopamine anchors.

    PubMed

    Mazur, Mykola; Barras, Alexandre; Kuncser, Victor; Galatanu, Andrei; Zaitzev, Vladimir; Turcheniuk, Kostiantyn V; Woisel, Patrice; Lyskawa, Joel; Laure, William; Siriwardena, Aloysius; Boukherroub, Rabah; Szunerits, Sabine

    2013-04-01

    The synthesis of multifunctional magnetic nanoparticles (MF-MPs) is one of the most active research areas in advanced materials as their multifunctional surfaces allow conjugation of biological and chemical molecules, thus making it possible to achieve target-specific diagnostic in parallel to therapeutics. We report here a simple strategy to integrate in a one-step reaction several reactive sites onto the particles. The preparation of MF-MPs is based on their simultaneous modification with differently functionalized dopamine derivatives using simple solution chemistry. The formed MF-MPs show comparable magnetic properties to those of naked nanoparticles with almost unaltered particle size of around 25 nm. The different termini, amine, azide and maleimide functions, enable further functionalization of MF-MPs by the grafting-on approach. Michael addition, Cu(i) catalyzed « click » chemistry and amidation reactions are performed on the MF-MPs integrating subsequently 6-(ferrocenyl)-hexanethiol, horseradish peroxidase (HRP) and mannose. PMID:23420060

  10. Iron oxide magnetic nanoparticles with versatile surface functions based on dopamine anchors

    NASA Astrophysics Data System (ADS)

    Mazur, Mykola; Barras, Alexandre; Kuncser, Victor; Galatanu, Andrei; Zaitzev, Vladimir; Turcheniuk, Kostiantyn V.; Woisel, Patrice; Lyskawa, Joel; Laure, William; Siriwardena, Aloysius; Boukherroub, Rabah; Szunerits, Sabine

    2013-03-01

    The synthesis of multifunctional magnetic nanoparticles (MF-MPs) is one of the most active research areas in advanced materials as their multifunctional surfaces allow conjugation of biological and chemical molecules, thus making it possible to achieve target-specific diagnostic in parallel to therapeutics. We report here a simple strategy to integrate in a one-step reaction several reactive sites onto the particles. The preparation of MF-MPs is based on their simultaneous modification with differently functionalized dopamine derivatives using simple solution chemistry. The formed MF-MPs show comparable magnetic properties to those of naked nanoparticles with almost unaltered particle size of around 25 nm. The different termini, amine, azide and maleimide functions, enable further functionalization of MF-MPs by the grafting-on approach. Michael addition, Cu(i) catalyzed « click » chemistry and amidation reactions are performed on the MF-MPs integrating subsequently 6-(ferrocenyl)-hexanethiol, horseradish peroxidase (HRP) and mannose.

  11. Kinetics of homogeneous and surface-catalyzed mercury(II) reduction by iron(II)

    USGS Publications Warehouse

    Amirbahman, Aria; Kent, Douglas B.; Curtis, Gary P.; Marvin-DiPasquale, Mark C.

    2013-01-01

    Production of elemental mercury, Hg(0), via Hg(II) reduction is an important pathway that should be considered when studying Hg fate in environment. We conducted a kinetic study of abiotic homogeneous and surface-catalyzed Hg(0) production by Fe(II) under dark anoxic conditions. Hg(0) production rate, from initial 50 pM Hg(II) concentration, increased with increasing pH (5.5–8.1) and aqueous Fe(II) concentration (0.1–1 mM). The homogeneous rate was best described by the expression, rhom = khom [FeOH+] [Hg(OH)2]; khom = 7.19 × 10+3 L (mol min)−1. Compared to the homogeneous case, goethite (α-FeOOH) and hematite (α-Fe2O3) increased and γ-alumina (γ-Al2O3) decreased the Hg(0) production rate. Heterogeneous Hg(0) production rates were well described by a model incorporating equilibrium Fe(II) adsorption, rate-limited Hg(II) reduction by dissolved and adsorbed Fe(II), and rate-limited Hg(II) adsorption. Equilibrium Fe(II) adsorption was described using a surface complexation model calibrated with previously published experimental data. The Hg(0) production rate was well described by the expression rhet = khet [>SOFe(II)] [Hg(OH)2], where >SOFe(II) is the total adsorbed Fe(II) concentration; khet values were 5.36 × 10+3, 4.69 × 10+3, and 1.08 × 10+2 L (mol min)−1 for hematite, goethite, and γ-alumina, respectively. Hg(0) production coupled to reduction by Fe(II) may be an important process to consider in ecosystem Hg studies.

  12. Optimization of Fenton-based treatment of petroleum refinery wastewater with scrap iron using response surface methodology

    NASA Astrophysics Data System (ADS)

    Saber, Ali; Hasheminejad, Hasti; Taebi, Amir; Ghaffari, Ghasem

    2014-09-01

    The ever-increasing number and production capacity of petroleum refineries in recent years have intensified the need for developing an effective and practical method for treating their wastewaters. In this study, the application of Fenton process with scrap iron powder was investigated for the treatment of a bio-refractory petroleum refinery effluent. Response surface methodology was employed with a cubic IV optimal design to optimize the process using chemical oxygen demand (COD) removal as the target response. H2O2/COD, and H2O2/Fe mass ratios as well as pH were considered as the relevant parameters. A COD removal of more than 83 % was achieved under optimal conditions (H2O2/COD 10.03, H2O2/Fe 2.66 and pH 3.0) within 90 min. Kinetics studies were conducted to investigate the effect of reaction time on COD removal. In addition, the role of post-coagulation on COD removal under optimal conditions was investigated and it was found that 37 % of COD removal occurred due to coagulation, indicating its high potential in the Fenton process.

  13. Disruption of N-Αcyl Homoserine Lactone-Mediated Cell Signaling and Iron Acquisition in Epiphytic Bacteria by Leaf Surface Compounds▿

    PubMed Central

    Karamanoli, Katerina; Lindow, Steven E.

    2006-01-01

    Since N-acyl homoserine lactones (AHLs) are key mediators of cell density-dependent regulation of traits involved in virulence and epiphytic fitness in gram-negative bacteria such as Pseudomonas syringae, a variety of plant species were examined to determine their production of leaf surface compounds that could interact with these signaling systems. Leaf washings of 17 of 52 plant species tested stimulated or inhibited AHL-dependent traits in at least one of the bacterial reporter strains used. The active compounds from most plants could be distinguished from known AHLs due to different patterns of mobility during C8 and C18 reverse-phase thin-layer chromatography (TLC) and normal-phase TLC compared to the patterns for authentic bacterial AHLs. All plant extracts were also tested to determine their abilities to sequester iron and trigger bacterial siderophore synthesis on a medium containing abundant iron. Leaf washings from 16 of the 52 plant species, as well as tannic acid solutions, stimulated pyoverdine synthesis in P. syringae in a high-iron medium. These preparations also inhibited the growth of a P. syringae mutant unable to produce pyoverdine siderophores but not the growth of the wild-type bacterium. The stimulation of siderophore production and the growth inhibition by plant extracts and purified tannins were both reversed by addition of ferric chloride to culture media, indicating that iron was made unavailable by the compounds released onto the leaf surface. PMID:16997987

  14. The use of multiple pseudo-physiological solutions to simulate the degradation behavior of pure iron as a metallic resorbable implant: a surface-characterization study.

    PubMed

    Tolouei, Ranna; Harrison, Jerome; Paternoster, Carlo; Turgeon, Stephane; Chevallier, Pascale; Mantovani, Diego

    2016-07-20

    Understanding the interactions of a pure iron surface with biological elements, such as ions and proteins in an aqueous medium, is essential for an accurate in vitro assessment of corrosion patterns. In fact, the synergy of chlorides, carbonates, phosphates and complex organic molecules present in the body environment is a key factor affecting both in vivo and in vitro degradation of materials, especially iron and its alloys. The aim of this work was the assessment of degradation patterns of pure iron in 5 commercial pseudo-physiological solutions by a thorough study of degraded surface chemistry and morphology. It also provides a methodological basis to understand the short-term degradation mechanism of degradable iron depending on the surrounding physiological media. The standard static immersion corrosion test was modified to adapt the procedure to pseudo-physiological solutions. After a 14-day static immersion test, the surfaces of samples were investigated by scanning electron microscopy, stylus profilometry and atomic force microscopy techniques. The chemistry and phase composition of the degraded layers were evaluated, respectively, by X-ray photoelectron spectrometry and X-ray diffractometry. The morphology and composition of the degradation layers were found to be different for the test-solutions: for phosphate-rich solutions, the formation of an adherent passive layer was found; degradation mechanisms related to general corrosion were predominant for all the other solutions. In conclusion, the chemical composition of the used medium plays a fundamental role in the degradation pattern of pure iron, so that direct comparisons of solutions with different ion concentrations, as reported in the literature, need to be carefully assessed. PMID:27381258

  15. Dynamics of polyelectrolyte adsorption on surfaces: Applications in the detection of iron in water

    NASA Astrophysics Data System (ADS)

    Gammana, Madhira N.

    Layer by layer (LbL) self assembly is a simple multilayer thin (nanometer scale) film fabricating technique. The mechanism of film growth remains a topic of much controversy. For example, several models have been proposed to explain the origin of linear and exponential film growth that are attributed to differences in the dynamic processes that occur at the molecular level during film formation. The problem is that there are no methods that directly measure the dynamics of polymer formation during LbL film formation. In this thesis, I describe the essential elements of an ATR-IR spectroscopic method that was developed to enable measurement of the dynamics of the mass adsorbed and polyelectrolyte conformation during the formation of PEM's. In particular, I followed the sequential adsorption of Sodium polyacrylate (NaPA) and Poly (diallyldimethylammonium) chloride (PDADMAC) from deionized (DI) water and as a function of ionic strength to show that polymer diffusion occurs between layers when adsorbed from DI water. In contrast, a denser layer occurs with no polymer interdiffusion for deposition from 0.02M ionic strength solutions of NaPA and PDADMAC. While the mass deposited increased with ionic strength, linear multilayer growth in films were observed in all cases. This finding disputes a common viewpoint that interdiffusion of polymer layers is a key feature of exponential film growth. The theme of polymer layer adsorption was used in the detection of Fe 3+ in seawater. A new approach, developed previously in Tripp's group, utilized "vertical amplification" in which a block copolymer assembled on membranes provided multiple anchoring points extending from the surface for attaching a siderophore, desferrioxamine B (DFB). The Fe3+ chelates with the siderophore producing a red color that can be quantified by visible spectroscopy. However, the rate of Fe3+ uptake was found to be dependent on flow rate. The origin of this flow rate dependence was identified by the work

  16. Colloidally stable surface-modified iron oxide nanoparticles: Preparation, characterization and anti-tumor activity

    NASA Astrophysics Data System (ADS)

    Macková, Hana; Horák, Daniel; Donchenko, Georgiy Viktorovich; Andriyaka, Vadim Ivanovich; Palyvoda, Olga Mikhailovna; Chernishov, Vladimir Ivanovich; Chekhun, Vasyl Fedorovich; Todor, Igor Nikolaevich; Kuzmenko, Oleksandr Ivanovich

    2015-04-01

    Maghemite (γ-Fe2O3) nanoparticles were obtained by co-precipitation of Fe(II) and Fe(III) chlorides and subsequent oxidation with sodium hypochlorite and coated with poly(N,N-dimethylacrylamide-co-acrylic acid) [P(DMAAm-AA)]. They were characterized by a range of methods including transmission electron microscopy (TEM), elemental analysis, dynamic light scattering (DLS) and zeta potential measurements. The effect of superparamagnetic P(DMAAm-AA)-γ-Fe2O3 nanoparticles on oxidation of blood lipids, glutathione and proteins in blood serum was detected using 2-thiobarbituric acid and the ThioGlo fluorophore. Finally, mice received magnetic nanoparticles administered per os and the antitumor activity of the particles was tested on Lewis lung carcinoma (LLC) in male mice line C57BL/6 as an experimental in vivo metastatic tumor model; the tumor size was measured and the number of metastases in lungs was determined. Surface-modified γ-Fe2O3 nanoparticles showed higher antitumor and antimetastatic activities than commercial CuFe2O4 particles and the conventional antitumor agent cisplatin.

  17. Lunar Meteorite Queen Alexandra Range 93069 and the Iron Concentration of the Lunar Highlands Surface

    NASA Technical Reports Server (NTRS)

    Korotev, Randy L.; Jolliff, Bradley L.; Rockow, Kaylynn M.

    1996-01-01

    Lunar meteorite Queen Alexandra Range 93069 is a clast-rich, glassy-matrix regolith breccia of ferroan, highly aluminous bulk composition. It is similar in composition to other feldspathic lunar meteorites but differs in having higher concentrations of siderophile elements and incompatible trace elements. Based on electron microprobe analyses of the fusion crust, glassy matrix, and clasts, and instrumental neutron activation analysis of breccia fragments, QUE 93069 is dominated by nonmare components of ferroan, noritic- anorthosite bulk composition. Thin section QUE 93069,31 also contains a large, impact-melted, partially devitrified clast of magnesian, anorthositic-norite composition. The enrichment in Fe, Sc, and Cr and lower Mg/Fe ratio of lunar meteorites Yamato 791197 and Yamato 82192/3 compared to other feldspathic lunar meteorites can be attributed to a small proportion (5-10%) of low-Ti mare basalt. It is likely that the non- mare components of Yamato 82192/3 are similar to and occur in similar abundance to those of Yamato 86032, with which it is paired. There is a significant difference between the average FeO concentration of the lunar highlands surface as inferred from the feldspathic lunar meteorites (mean: approx. 5.0%; range: 4.3-6.1 %) and a recent estimate based on data from the Clementine mission (3.6%).

  18. Surface chemistry and wear behavior of single-crystal silicon carbide sliding against iron at temperatures to 1500 C in vacuum

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron and Auger electron spectroscopy analyses and morphological studies of wear and metal transfer were conducted with a single-crystal silicon carbide 0001 surface in contact with iron at various temperatures to 1500 C in a vacuum of 10 to the minus 8th power pascal. The results indicate that below 800 C, carbide-carbon and silicon are primarily seen on the silicon carbide surface. Above 800 C the graphite increases rapidly with increase in temperature. The outermost surficial layer, which consists mostly of graphite and little silicon at temperatures above 1200 C is about 2 nm thick. A thicker layer, which consists of a mixture of graphite, carbide, and silicon is approximately 100 nm thick. The closer the surface sliding temperature is to 800 C, the more the metal transfer produced. Above 800 C, there was a transfer of rough, discontinuous, and thin iron debris instead of smooth, continuous and thin iron film which was observed to transfer below 800 C. Two kinds of fracture pits were observed on the silicon carbide surface: (1) a pit with a spherical asperity; and (2) multiangular shaped pits.

  19. A humanized monoclonal antibody targeting Staphylococcus aureus.

    PubMed

    Patti, Joseph M

    2004-12-01

    This current presentation describes the in vitro and in vivo characterization of Aurexis (tefibazumab), a humanized monoclonal antibody that exhibits a high affinity and specificity and for the Staphylococcus aureus MSCRAMM (Microbial Surface Components Recognizing Adhesive Matrix Molecules) protein ClfA. Aurexis inhibited ClfA binding to human fibrinogen, and enhanced the opsonophagocytic uptake of ClfA-coated beads. Preclinical in vivo testing revealed that a single administration of Aurexis significantly protected against an IV challenge with a methicillin resistant S. aureus (MRSA) strain in murine septicemia and rabbit infective endocarditis (IE) models. Safety and pharmacokinetic data from a 19-patient phase I study support continued evaluation of Aurexis in phase II studies. PMID:15576200

  20. A New Insight into Neutrino Energy Loss by Electron Capture of Iron Group Nuclei in Magnetar Surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Jing-Jing; Gu, Wei-Min

    2016-06-01

    Based on the relativistic mean-field effective interactions theory, and the Lai dong model, we discuss the influences of superstrong magnetic fields (SMFs) on electron Fermi energy, nuclear blinding energy, and single-particle level structure in magnetar surfaces. Using the Shell-Model Monte Carlo method and the Random Phase Approximation theory, we analyze the neutrino energy loss rates (NELRs) by electron capture for iron group nuclei in SMFs. First, when B 12 < 100, we find that the SMFs have a slight influence on the NELRs for most nuclides at relativistic low temperatures (e.g., T 9 = 0.233); nevertheless, the NELRs increase by more than four orders of magnitude at relativistic high temperatures (e.g., T 9 = 15.53). When B 12 > 100, the NELRs decrease by more than three orders of magnitude (e.g., at T 9 = 15.53 for 52–61Fe, 55–60Co, and 56–63Ni). Second, for a certain value of magnetic field and temperature, the NELRs increase by more than four orders of magnitude when {ρ }7≤slant {10}3, but as the density increases (i.e., when {ρ }7\\gt {10}3), there is almost no influence on the density of NELRs. For the density around {ρ }7={10}2, there is an abrupt increase in NELRs when B 12 ≥ 103.5. Such jumps are an indication that the underlying shell structure has changed due to single-particle behavior by SMFs. Finally, we compare our NELRs with those of Fuller et al. (FFN) and Nabi & Klapdor-Kleingrothaus (NKK). For the case without SMFs, one finds that our rates for certain nuclei are close to about five orders of magnitude lower than FFN and NKK at relativistic low temperatures (e.g., T 9 = 1). However, at a relativistic high temperature (e.g., T 9 = 3), our results are in good agreement with NKK, but about one order of magnitude lower than FFN. For the case with SMFs, our NELRs for some iron group nuclei can be about five orders of magnitude higher than those of FFN and NKK. (Note that B 12, T 9, and ρ 7 are in units of 1012 G, 109 K, and {10}7 {{g

  1. Laser treatment of dual matrix cast iron with presence of WC particles at the surface: Influence of self-annealing on stress fields

    NASA Astrophysics Data System (ADS)

    Yilbas, B. S.; Akhtar, S. S.; Karatas, C.; Boran, K.

    2016-01-01

    Laser control melting of dual matrix cast iron surface is carried out. A carbon film containing 15% WC particles is formed at the surface prior to the laser treatment and the spiral tracks are adopted for laser scanning at the workpiece surface. Morphological, metallurgical, microhardness, and scratch resistance of the laser treated surface are examined using analytical tools. Temperature and stress fields in the laser irradiated region are predicted incorporating ABAQUS finite element code. Predictions of temperature and residual stress at the laser treated surface are validated with the thermocouple and the X-ray diffraction data. It is found that surface temperature and residual stress predictions agree well with their counterparts corresponding to thermocouple data and findings of X-ray diffraction technique. Laser treated surface is free from asperities including voids and micro-cracks despite the mismatch of thermal expansion coefficients of WC and dual matrix cast iron. This behavior is attributed to the self-annealing effects of recently formed spiral tracks on the previously formed tracks during the laser treatment process; in which case, the self-annealing effect modifies the cooling rates and lowers thermal stress levels in the laser treated layer. Laser treated layer consists of a dense region composing of fine grains and WC particles, dendritic and featherlike structures below the dense layer, and the heat affected zone.

  2. Use of response surface methodology for optimizing process parameters for high inulinase production by the marine yeast Cryptococcus aureus G7a in solid-state fermentation and hydrolysis of inulin.

    PubMed

    Sheng, Jun; Chi, Zhenming; Yan, Kuirang; Wang, Xianghong; Gong, Fang; Li, Jing

    2009-04-01

    The optimization of process parameters for high inulinase production by the marine yeast strain Cryptococcus aureus G7a in solid-state fermentation (SSF) was carried out using central composite design (CCD), one of the response surface methodologies (RSMs). We found that moisture, inoculation size, the amount ratio of wheat bran to rice husk, temperature and pH had great influence on inulinase production by strain G7a. Therefore, the CCD was used to evaluate the influence of the five factors on the inulinase production by strain G7a. Then, five levels of the five factors above were further optimized using the CCD. Finally, the optimal parameters obtained with the RSM were the initial moisture 61.5%, inoculum 2.75%, the amount ratio of wheat bran to rice husk 0.42, temperature 29 degrees C, pH 5.5. Under the optimized conditions, 420.9 U g(-1) of dry substrate of inulinase activity was reached in the solid-state fermentation culture of strain G7a within 120 h whereas the predicted maximum inulinase activity of 436.2 U g(-1) of inulinase activity of 436.2 U g(-1) of dry weight was derived from the RSM regression. This is the highest inulinase activity produced by the yeast strain reported so far. A large amount of monosaccharides and oligosaccharides were detected after inulin hydrolysis by the crude inulinase. PMID:18726619

  3. Surface-Plasmon-Enhanced Photodriven CO2 Reduction Catalyzed by Metal-Organic-Framework-Derived Iron Nanoparticles Encapsulated by Ultrathin Carbon Layers.

    PubMed

    Zhang, Huabin; Wang, Tao; Wang, Junjie; Liu, Huimin; Dao, Thang Duy; Li, Mu; Liu, Guigao; Meng, Xianguang; Chang, Kun; Shi, Li; Nagao, Tadaaki; Ye, Jinhua

    2016-05-01

    Highly efficient utilization of solar light with an excellent reduction capacity is achieved for plasmonic Fe@C nanostructures. By carbon layer coating, the optimized catalyst exhibits enhanced selectivity and stability applied to the solar-driven reduction of CO2 into CO. The surface-plasmon effect of iron particles is proposed to excite CO2 molecules, and thereby facilitates the final reaction activity. PMID:27001900

  4. Bioaccessibility of micron-sized powder particles of molybdenum metal, iron metal, molybdenum oxides and ferromolybdenum--Importance of surface oxides.

    PubMed

    Mörsdorf, Alexander; Odnevall Wallinder, Inger; Hedberg, Yolanda

    2015-08-01

    The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO2, and MoO3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys. PMID:26032492

  5. Role of GapC in the pathogenesis of Staphylococcus aureus.

    PubMed

    Kerro-Dego, Oudessa; Prysliak, Tracy; Perez-Casal, Jose; Potter, Andrew A

    2012-05-01

    Staphylococcus aureus is recognized worldwide as a major pathogen causing clinical or subclinical intramammary infections in lactating cows, sheep and goats. S. aureus produces a wide arsenal of cell surface and extracellular proteins involved in virulence. Among these are two conserved proteins with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity named glyceraldehyde-3-phosphate dehydrogenase-B (GapB) and -C (GapC). In this study, we used the S. aureus wild type strain RN6390 and its isogenic gapC mutant H330 in in vitro and in vivo studies and determined that the S. aureus GapC protein plays a role on adherence to and internalization into bovine mammary epithelial (MAC-T) cells. In addition, we found that S. aureus H330 did not caused mastitis after an experimental infection of ovine mammary glands. Together, these results show that GapC is important in the pathogenesis of S. aureus mastitis. PMID:22176759

  6. In-Situ ATR-FTIR and Surface Complexation Modeling Study of the Adsorption of Dimethylarsenic Acid and p-Arsanilic Acid on Iron Oxides

    NASA Astrophysics Data System (ADS)

    Goldberg, S. R.; Al-Abadleh, H.; Mitchell, W.

    2010-12-01

    Arsenic is an element that exists naturally in many rocks and minerals around the world, accumulates in petroleum, shale, and coal deposits as a result of biogeochemical processes, and is found in fly ash from fuel combustion. Arsenic compounds in their organic and inorganic forms pose both health and environmental risks. The environmental fate of arsenic compounds is controlled to a large extent by their surface interactions with inorganic and organic surfaces. We report results from applying the triple layer surface complexation model to adsorption isotherm and pH-envelope experimental data of dimethylarsenic acid, DMA, and p-arsanilic acid, p-AsA on the iron oxides, hematite and goethite. Ligand exchange reactions were based on the interpretation of ATR-FTIR spectra of DMA and p-AsA surface complexes. Surface coverage of the organoarsenicals was quantified in-situ from the spectral component at 840 cm-1. The best model fit to the DMA adsorption data was obtained using an outer-sphere complex, whereas for p-AsA, best model fit was obtained using two monodentate inner-sphere surface complexes. The significance of the results is discussed in relation to improving modeling tools used by environmental regulators. Accurate predictive modeling tools are needed for effective design of arsenic removal technologies using iron oxide minerals.

  7. Iron Depletion Enhances Production of Antimicrobials by Pseudomonas aeruginosa

    PubMed Central

    Nguyen, Angela T.; Jones, Jace W.; Ruge, Max A.; Kane, Maureen A.

    2015-01-01

    ABSTRACT Cystic fibrosis (CF) is a heritable disease characterized by chronic, polymicrobial lung infections. While Staphylococcus aureus is the dominant lung pathogen in young CF patients, Pseudomonas aeruginosa becomes predominant by adulthood. P. aeruginosa produces a variety of antimicrobials that likely contribute to this shift in microbial populations. In particular, secretion of 2-alkyl-4(1H)-quinolones (AQs) contributes to lysis of S. aureus in coculture, providing an iron source to P. aeruginosa both in vitro and in vivo. We previously showed that production of one such AQ, the Pseudomonas quinolone signal (PQS), is enhanced by iron depletion and that this induction is dependent upon the iron-responsive PrrF small RNAs (sRNAs). Here, we demonstrate that antimicrobial activity against S. aureus during coculture is also enhanced by iron depletion, and we provide evidence that multiple AQs contribute to this activity. Strikingly, a P. aeruginosa ΔprrF mutant, which produces very little PQS in monoculture, was capable of mediating iron-regulated growth suppression of S. aureus. We show that the presence of S. aureus suppresses the ΔprrF1,2 mutant's defect in iron-regulated PQS production, indicating that a PrrF-independent iron regulatory pathway mediates AQ production in coculture. We further demonstrate that iron-regulated antimicrobial production is conserved in multiple P. aeruginosa strains, including clinical isolates from CF patients. These results demonstrate that iron plays a central role in modulating interactions of P. aeruginosa with S. aureus. Moreover, our studies suggest that established iron regulatory pathways of these pathogens are significantly altered during polymicrobial infections. IMPORTANCE Chronic polymicrobial infections involving Pseudomonas aeruginosa and Staphylococcus aureus are a significant cause of morbidity and mortality, as the interplay between these two organisms exacerbates infection. This is in part due to enhanced

  8. agr function in clinical Staphylococcus aureus isolates

    PubMed Central

    Traber, Katrina E.; Lee, Elsie; Benson, Sarah; Corrigan, Rebecca; Cantera, Mariela; Shopsin, Bo; Novick, Richard P.

    2016-01-01

    The accessory gene regulator (agr) of Staphylococcus aureus is a global regulator of the staphylococcal virulon, which includes secreted virulence factors and surface proteins. The agr locus is important for virulence in a variety of animal models of infection, and has been assumed by inference to have a major role in human infection. Although most human clinical S. aureus isolates are agr+, there have been several reports of agr-defective mutants isolated from infected patients. Since it is well known that the agr locus is genetically labile in vitro, we have addressed the question of whether the reported agr-defective mutants were involved in the infection or could have arisen during post-isolation handling. We obtained a series of new staphylococcal isolates from local clinical infections and handled these with special care to avoid post-isolation mutations. Among these isolates, we found a number of strains with non-haemolytic phenotypes owing to mutations in the agr locus, and others with mutations elsewhere. We have also obtained isolates in which the population was continuously heterogeneous with respect to agr functionality, with agr+ and agr− variants having otherwise indistinguishable chromosomal backgrounds. This finding suggested that the agr− variants arose by mutation during the course of the infection. Our results indicate that while most clinical isolates are haemolytic and agr+, non-haemolytic and agr− strains are found in S. aureus infections, and that agr+ and agr− variants may have a cooperative interaction in certain types of infections. PMID:18667559

  9. Exotoxins of Staphylococcus aureus

    PubMed Central

    Dinges, Martin M.; Orwin, Paul M.; Schlievert, Patrick M.

    2000-01-01

    This article reviews the literature regarding the structure and function of two types of exotoxins expressed by Staphylococcus aureus, pyrogenic toxin superantigens (PTSAgs) and hemolysins. The molecular basis of PTSAg toxicity is presented in the context of two diseases known to be caused by these exotoxins: toxic shock syndrome and staphylococcal food poisoning. The family of staphylococcal PTSAgs presently includes toxic shock syndrome toxin-1 (TSST-1) and most of the staphylococcal enterotoxins (SEs) (SEA, SEB, SEC, SED, SEE, SEG, and SEH). As the name implies, the PTSAgs are multifunctional proteins that invariably exhibit lethal activity, pyrogenicity, superantigenicity, and the capacity to induce lethal hypersensitivity to endotoxin. Other properties exhibited by one or more staphylococcal PTSAgs include emetic activity (SEs) and penetration across mucosal barriers (TSST-1). A detailed review of the molecular mechanisms underlying the toxicity of the staphylococcal hemolysins is also presented. PMID:10627489

  10. Effects of iron deficiency on iron binding and internalization into acidic vacuoles in Dunaliella salina.

    PubMed

    Paz, Yakov; Shimoni, Eyal; Weiss, Meira; Pick, Uri

    2007-07-01

    Uptake of iron in the halotolerant alga Dunaliella salina is mediated by a transferrin-like protein (TTf), which binds and internalizes Fe(3+) ions. Recently, we found that iron deficiency induces a large enhancement of iron binding, which is associated with accumulation of three other plasma membrane proteins that associate with TTf. In this study, we characterized the kinetic properties of iron binding and internalization and identified the site of iron internalization. Iron deficiency induces a 4-fold increase in Fe binding, but only 50% enhancement in the rate of iron uptake and also increases the affinity for iron and bicarbonate, a coligand for iron binding. These results indicate that iron deprivation leads to accumulation and modification of iron-binding sites. Iron uptake in iron-sufficient cells is preceded by an apparent time lag, resulting from prebound iron, which can be eliminated by unloading iron-binding sites. Iron is tightly bound to surface-exposed sites and hardly exchanges with medium iron. All bound iron is subsequently internalized. Accumulation of iron inhibits further iron binding and internalization. The vacuolar inhibitor bafilomycin inhibits iron uptake and internalization. Internalized iron was localized by electron microscopy within vacuolar structures that were identified as acidic vacuoles. Iron internalization is accompanied by endocytosis of surface proteins into these acidic vacuoles. A novel kinetic mechanism for iron uptake is proposed, which includes two pools of bound/compartmentalized iron separated by a rate-limiting internalization stage. The major parameter that is modulated by iron deficiency is the iron-binding capacity. We propose that excessive iron binding in iron-deficient cells serves as a temporary reservoir for iron that is subsequently internalized. This mechanism is particularly suitable for organisms that are exposed to large fluctuations in iron availability. PMID:17513481

  11. The long-term effects of copper surface area on menstrual blood loss and iron status in women fitted with an IUD.

    PubMed

    Larsson, G; Milsom, I; Jonasson, K; Lindstedt, G; Rybo, G

    1993-11-01

    The long-term effects of copper surface area on menstrual blood loss (MBL) and iron status (hemoglobin, hematocrit, red cell count and indices, and serum ferritin) were evaluated in 25 healthy women who were observed for a period of 3 years following insertion of an intrauterine device. MBL was determined objectively by the alkaline hematin method. The women (mean age 37.2 +/- 1.6 yr, range 27-46 yr) were fitted with a Multiload intrauterine device (IUD) with a copper surface area of either 250 mm2 (MLCu-250, n = 13) or 375 mm2 (MLCu-375, n = 12). MBL prior to IUD insertion was 55 +/- 8 ml for women subsequently fitted with a MLCu-250 and 59 +/- 9 ml for women fitted with a MLCu-375. An increase in MBL was recorded at all measurement points following IUD insertion (MLCu-250/MLCu-375: 3 months: 55/49%; 6 months: 58/49%; 12 months: 64/41%; 24 months: 55/49%; 36 months: 47/39%, NS). There were no significant differences in iron status parameters before IUD insertion between groups nor were there any significant changes recorded in any of these parameters after IUD insertion. Our findings that the increase in copper surface area from 250 mm2 to 375 mm2 had no effect on MBL were thus substantiated by the hematological findings. Based on the results of the present study, women from developed countries apparently tolerate an increased MBL of approximately 45% without developing anemia. Iron stores were unchanged indicating an adequate adaptive increase in intestinal iron absorption. PMID:8275696

  12. Influence of Gas Composition and Exposure Cycle on the Formation of Surface and Subsurface Oxides in Iron-Aluminum-Based Alloys at High Temperatures

    NASA Astrophysics Data System (ADS)

    Bott, June H.; Yin, Hogbin; Sridhar, Seetharaman; Auinger, Michael

    2016-04-01

    The slab reheating process of binary iron-aluminum alloys and an industrial TRIP steel grade has been investigated in both dry and wet atmospheres. The presence of water vapor has a significant effect on the overall scale growth and internal corrosion depth. Heating rate greatly influences the porosity of the surface oxide layer with the surface getting more porous at faster heating rates. Nitride formation could be suppressed in the presence of water vapor, leading to a reduction of internal corrosion depth and a better formability of the final material. Experimental results were compared to thermodynamic predictions and critically discussed.

  13. Influence of Gas Composition and Exposure Cycle on the Formation of Surface and Subsurface Oxides in Iron-Aluminum-Based Alloys at High Temperatures

    NASA Astrophysics Data System (ADS)

    Bott, June H.; Yin, Hogbin; Sridhar, Seetharaman; Auinger, Michael

    2016-08-01

    The slab reheating process of binary iron-aluminum alloys and an industrial TRIP steel grade has been investigated in both dry and wet atmospheres. The presence of water vapor has a significant effect on the overall scale growth and internal corrosion depth. Heating rate greatly influences the porosity of the surface oxide layer with the surface getting more porous at faster heating rates. Nitride formation could be suppressed in the presence of water vapor, leading to a reduction of internal corrosion depth and a better formability of the final material. Experimental results were compared to thermodynamic predictions and critically discussed.

  14. The effects of novel surface treatments on the wear and fatigue properties of steel and chilled cast iron

    NASA Astrophysics Data System (ADS)

    Carroll, Jason William

    Contact fatigue driven wear is a principal design concern for gear and camshaft engineering of power systems. To better understand how to engineer contact fatigue resistant surfaces, the effects of electroless nickel and hydrogenated diamond-like-carbon (DLC) coatings on the fatigue life at 108 cycles of SAE 52100 steel were studied using ultrasonic fatigue methods. The addition of DLC and electroless nickel coatings to SAE 52100 bearing steel had no effect on the fatigue life. Different inclusion types were found to affect the stress intensity value beyond just the inclusion size, as theorized by Murakami. The difference in stress intensity values necessary to propagate a crack for Ti (C,N) and alumina inclusions was due to the higher driving force for crack extension at the Ti (C,N) inclusions and was attributed to differences in the shape of the inclusion: rhombohedral for the Ti (C,N) versus spherical for the oxides. A correction factor was added to the Murakami equation to account for inclusion type. The wear properties of DLC coated SAE 52100 and chilled cast iron were studied using pin-on-disk tribometry and very high cycle ultrasonic tribometry. A wear model that includes sliding thermal effects as well as thermodynamics consistent with the wear mechanism for DLCs was developed based on empirical results from ultrasonic wear testing to 108 cycles. The model fit both ultrasonic and classic tribometer data for wear of DLCs. Finally, the wear properties of laser hardened steels - SAE 8620, 4140, and 52100 - were studied at high contact pressures and low numbers of cycles. A design of experiments was conducted to understand how the laser processing parameters of power, speed, and beam size, as well as carbon content of the steel, affected surface hardness. A hardness maximum was found at approximately 0.7 wt% carbon most likely resulting from increased amounts of retained austenite. The ratcheting contact fatigue model of Kapoor was found to be useful in

  15. Midtemperature Solar Systems Test Facility predictions for thermal performance based on test data. Alpha Solarco Model 104 solar collector with 0. 125-inch Schott low-iron glass reflector surface

    SciTech Connect

    Harrison, T.D.

    1981-04-01

    Thermal performance predictions based on test data are presented for the Alpha Solarco Model 104 solar collector, with 0.125-inch Schott low-iron glass reflector surface, for three output temperatures at five cities in the United States.

  16. Menaquinone biosynthesis potentiates haem toxicity in Staphylococcus aureus

    PubMed Central

    Wakeman, Catherine A.; Hammer, Neal D.; Stauff, Devin L.; Attia, Ahmed S.; Anzaldi, Laura L.; Dikalov, Sergey I.; Calcutt, M. Wade; Skaar, Eric P.

    2012-01-01

    Summary Staphylococcus aureus is a pathogen that infects multiple anatomical sites leading to a diverse array of diseases. Although vertebrates can restrict the growth of invading pathogens by sequestering iron within haem, S. aureus surmounts this challenge by employing high-affinity haem uptake systems. However, the presence of excess haem is highly toxic, necessitating tight regulation of haem levels. To overcome haem stress, S. aureus expresses the detoxification system HrtAB. In this work, a transposon screen was performed in the background of a haem-susceptible, HrtAB-deficient S. aureus strain to identify the substrate transported by this putative pump and the source of haem toxicity. While a recent report indicates that HrtAB exports haem itself, the haem-resistant mutants uncovered by the transposon selection enabled us to elucidate the cellular factors contributing to haem toxicity. All mutants identified in this screen inactivated the menaquinone (MK) biosynthesis pathway. Deletion of the final steps of this pathway revealed that quinone molecules localizing to the cell membrane potentiate haem-associated superoxide production and subsequent oxidative damage. These data suggest a model in which membrane-associated haem and quinone molecules form a redox cycle that continuously generates semiquinones and reduced haem, both of which react with atmospheric oxygen to produce superoxide. PMID:23043465

  17. Evidence of a reduction reaction of oxidized iron/cobalt by boron atoms diffused toward naturally oxidized surface of CoFeB layer during annealing

    SciTech Connect

    Sato, Soshi Honjo, Hiroaki; Niwa, Masaaki; Ikeda, Shoji; Ohno, Hideo; Endoh, Tetsuo

    2015-04-06

    We have investigated the redox reaction on the surface of Ta/CoFeB/MgO/CoFeB magnetic tunnel junction stack samples after annealing at 300, 350, and 400 °C for 1 h using angle-resolved X-ray photoelectron spectroscopy for precise analysis of the chemical bonding states. At a capping tantalum layer thickness of 1 nm, both the capping tantalum layer and the surface of the underneath CoFeB layer in the as-deposited stack sample were naturally oxidized. By comparison of the Co 2p and Fe 2p spectra among the as-deposited and annealed samples, reduction of the naturally oxidized cobalt and iron atoms occurred on the surface of the CoFeB layer. The reduction reaction was more significant at higher annealing temperature. Oxidized cobalt and iron were reduced by boron atoms that diffused toward the surface of the top CoFeB layer. A single CoFeB layer was prepared on SiO{sub 2}, and a confirmatory evidence of the redox reaction with boron diffusion was obtained by angle-resolved X-ray photoelectron spectroscopy analysis of the naturally oxidized surface of the CoFeB single layer after annealing. The redox reaction is theoretically reasonable based on the Ellingham diagram.

  18. Use of near infrared correlation spectroscopy for quantitation of surface iron, absorbed water and stored electronic energy in a suite of Mars soil analog materials

    NASA Technical Reports Server (NTRS)

    Coyne, Lelia M.; Banin, Amos; Carle, Glenn; Orenberg, James; Scattergood, Thomas

    1989-01-01

    A number of questions concerning the surface mineralogy and the history of water on Mars remain unresolved using the Viking analyses and Earth-based telescopic data. Identification and quantitation of iron-bearing clays on Mars would elucidate these outstanding issues. Near infrared correlation analysis, a method typically applied to qualitative and quantitative analysis of individual constituents of multicomponent mixtures, is adapted here to selection of distinctive features of a small, highly homologous series of Fe/Ca-exchanged montmorillonites and several kalinites. Independently determined measures of surface iron, relative humidity and stored electronic energy were used as constituent data for linear regression of the constituent vs. reflectance data throughout the spectral region 0.68 to 2.5 micrometers. High correlations were found in appropriate regions for all three constituents, though that with stored energy is still considered tenuous. Quantitation was improved using 1st and 2nd derivative spectra. High resolution data over a broad spectral range would be required to quantitatively identify iron-bearing clays by remotely sensed reflectance.

  19. Antibacterial activity and cytocompatibility of titanium oxide coating modified by iron ion implantation.

    PubMed

    Tian, Yaxin; Cao, Huiliang; Qiao, Yuqin; Meng, Fanhao; Liu, Xuanyong

    2014-10-01

    In this work, zero valent iron nanoparticles (Fezero-NPs) and iron oxide nanoparticles (Feox-NPs) were synthesized at the subsurface and surface regions of titanium oxide coatings (TOCs) by plasma immersion ion implantation. This novel Fe-NPs/TOC system showed negligible iron releasing, great electron storage capability and excellent cytocompatibility in vitro. Importantly, the system showed selective antibacterial ability which can kill Staphylococcus aureus under dark conditions but has no obvious antibacterial effect against Escherichia coli. Owing to a bipolar Schottky barrier between Fezero-NPs/TOC and Fezero-NPs/Feox-NPs, electrons could be captured by the Fezero-NPs bounded at the subsurface region of the coating. This electron storage capability of the Fe-NPs/TOC system induced extracellular electron transportation and accumulation of adequate valence-band holes (h(+)) at the external side, which caused oxidation damage to S. aureus cells in the dark. No obvious biocide effect against E. coli resulted from lack of electron transfer ability between E. coli and substrate materials. This work may open up a novel and controlled strategy to design coatings of implants with antibacterial ability and cytocompatibility for medical applications. PMID:24914826

  20. Iron overdose

    MedlinePlus

    Iron is an ingredient in many mineral and vitamin supplements. Iron supplements are also sold by themselves. Types include: Ferrous sulfate (Feosol, Slow Fe) Ferrous gluconate (Fergon) Ferrous fumarate (Femiron, Feostat) Other products may also contain iron.

  1. Application of Polypyrrole Multi-Walled Carbon Nanotube Composite Layer for Detection of Mercury, Lead and Iron Ions Using Surface Plasmon Resonance Technique

    PubMed Central

    Sadrolhosseini, Amir Reza; Noor, A. S. M.; Bahrami, Afarin; Lim, H. N.; Talib, Zainal Abidin; Mahdi, Mohd. Adzir

    2014-01-01

    Polypyrrole multi-walled carbon nanotube composite layers were used to modify the gold layer to measure heavy metal ions using the surface plasmon resonance technique. The new sensor was fabricated to detect trace amounts of mercury (Hg), lead (Pb), and iron (Fe) ions. In the present research, the sensitivity of a polypyrrole multi-walled carbon nanotube composite layer and a polypyrrole layer were compared. The application of polypyrrole multi-walled carbon nanotubes enhanced the sensitivity and accuracy of the sensor for detecting ions in an aqueous solution due to the binding of mercury, lead, and iron ions to the sensing layer. The Hg ion bonded to the sensing layer more strongly than did the Pb and Fe ions. The limitation of the sensor was calculated to be about 0.1 ppm, which produced an angle shift in the region of 0.3° to 0.6°. PMID:24733263

  2. Application of polypyrrole multi-walled carbon nanotube composite layer for detection of mercury, lead and iron ions using surface plasmon resonance technique.

    PubMed

    Sadrolhosseini, Amir Reza; Noor, A S M; Bahrami, Afarin; Lim, H N; Talib, Zainal Abidin; Mahdi, Mohd Adzir

    2014-01-01

    Polypyrrole multi-walled carbon nanotube composite layers were used to modify the gold layer to measure heavy metal ions using the surface plasmon resonance technique. The new sensor was fabricated to detect trace amounts of mercury (Hg), lead (Pb), and iron (Fe) ions. In the present research, the sensitivity of a polypyrrole multi-walled carbon nanotube composite layer and a polypyrrole layer were compared. The application of polypyrrole multi-walled carbon nanotubes enhanced the sensitivity and accuracy of the sensor for detecting ions in an aqueous solution due to the binding of mercury, lead, and iron ions to the sensing layer. The Hg ion bonded to the sensing layer more strongly than did the Pb and Fe ions. The limitation of the sensor was calculated to be about 0.1 ppm, which produced an angle shift in the region of 0.3° to 0.6°. PMID:24733263

  3. Protease inhibitors decrease IgG shedding from Staphylococcus aureus, increasing complement activation and phagocytosis efficiency.

    PubMed

    Fernandez Falcon, Maria F; Echague, Charlene G; Hair, Pamela S; Nyalwidhe, Julius O; Cunnion, Kenji M

    2011-10-01

    Staphylococcus aureus is a major pathogen for immunologically intact humans and its pathogenesis is a model system for evasion of host defences. Antibodies and complement are essential elements of the humoral immune system for prevention and control of S. aureus infections. The specific hypothesis for the proposed research is that S. aureus modifies humoral host defences by cleaving IgG that has bound to the bacterial surface, thereby inhibiting opsonophagocytosis. S. aureus was coated with pooled, purified human IgG and assayed for the shedding of cleaved IgG fragments using ELISA and Western blot analysis. Surface-bound IgG was shed efficiently from S. aureus in the absence of host blood proteins. Broad-spectrum protease inhibitors prevented cleavage of IgG from the S. aureus surface, suggesting that staphylococcal proteases are responsible for IgG cleavage. Serine protease inhibitors and cysteine protease inhibitors decreased the cleavage of surface-bound IgG; however, a metalloprotease inhibitor had no effect. Using protease inhibitors to prevent the cleavage of surface-bound IgG increased the binding of complement C3 fragments on the surface of S. aureus, increased the association with human neutrophils and increased phagocytosis by human neutrophils. PMID:21636671

  4. Staphylococcus aureus dry stress survivors have a heritable fitness advantage in subsequent dry exposure.

    PubMed

    Maudsdotter, Lisa; Imai, Saki; Ohniwa, Ryosuke L; Saito, Shinji; Morikawa, Kazuya

    2015-06-01

    Staphylococcus aureus is a major cause of hospital-acquired infections. The ability to survive on abiotic surfaces is an important characteristic that facilitates transmission between human hosts. We found that S. aureus survivors of dry surface incubation are resistant to subsequent dry stress exposure. Survivors also had reduced sensitivity to the disinfectant chlorhexidine gluconate, but not to ethanol. By using a set of mutants in cardiolipin synthase genes, we further demonstrated that the housekeeping cardiolipin synthase, Cls2, was significant for survival on dry surface. Taken together, this study provides insights into S. aureus survival outside of a host. PMID:25749710

  5. Ceftaroline-Heteroresistant Staphylococcus aureus

    PubMed Central

    Saravolatz, Stephanie N.; Martin, Hayley; Pawlak, Joan; Johnson, Leonard B.

    2014-01-01

    Heteroresistance refers to the presence, within a large population of antimicrobial-susceptible microorganisms, of subpopulations with lesser susceptibilities. Ceftaroline is a novel cephalosporin with activity against methicillin-resistant Staphylococcus aureus (MRSA). The aim of this study was to detect the prevalence of ceftaroline heteroresistance in vitro in a select group of S. aureus strains. There were 57 isolates selected for evaluation, 20 MRSA, 20 vancomycin-intermediate S. aureus (VISA), 7 daptomycin-nonsusceptible S. aureus (DNSSA), 6 linezolid-nonsusceptible S. aureus (LNSSA), and 4 heteroresistant VISA (hVISA) isolates. MICs and minimal bactericidal concentrations were determined using the broth microdilution method according to CLSI guidelines. All of the isolates were analyzed by pulsed-field gel electrophoresis. The staphylococcal cassette chromosome mec element (SCCmec) types were determined by a multiplex PCR. Population analysis profiles (PAPs) were performed to determine heteroresistance for all of the isolates using plates made by adding various amounts of ceftaroline to brain heart infusion agar. The frequencies of resistant subpopulations were 1 in 104 to 105 organisms. We determined that 12 of the 57 (21%) isolates tested were ceftaroline-heteroresistant S. aureus (CHSA). CHSA occurred among strains with reduced susceptibilities to vancomycin, daptomycin, and linezolid but occurred in none of the USA-300 isolates tested. Evaluation of the heteroresistant strains demonstrated that the phenotype was unstable. Further studies are needed to determine whether CHSA has a role in clinical failures and to determine the implications of our study findings. PMID:24637680

  6. Influence of carvacrol and thymol on the physiological attributes, enterotoxin production and surface characteristics of Staphylococcus aureus strains isolated from foods

    PubMed Central

    Souza, E.L.; Oliveira, C.E.V.; Stamford, T.L.M.; Conceição, M.L.; Neto, N.J. Gomes

    2013-01-01

    This study evaluated the influence of the phenolic compounds carvacrol (CAR) and thymol (THY) on some physiological characteristics and on the modulation of the secretion of some staphylococcal virulence factors, that is, coagulase and enterotoxin. This study also investigated possible mechanisms for the establishment of the anti-staphylococcal activity of these compounds. Sublethal concentrations (0.3 and 0.15 μL/mL) of CAR and THY inhibited the activity of the enzymes coagulase and lipase and led to a decrease in salt tolerance. At the tested sublethal concentrations, both CAR and THY led to a total suppression of enterotoxin production. The loss of a 260-nm-absorbing material and an efflux of potassium ions occurred immediately after the addition of CAR and THY at 0.6 and 1.2 μL/mL and increased up to 120 min of exposure. Electron microscopy of cells exposed to CAR and THY (0.6 μL/mL) revealed that individual cells appeared to be deformed, with projections of cellular material. The observations of leakage of cellular material and an altered cell surface suggest that gross damage to a cell’s cytoplasmic membrane, which results in a disruption in protein secretion, could be responsible for the anti-staphylococcal properties of CAR and THY. PMID:24159280

  7. Effect of thiamine hydrochloride on the redox reactions of iron at pyrite surface. [Fourth quarterly techical progress report, September 1990--November 1990

    SciTech Connect

    Pesic, B.; Oliver, D.J.

    1990-12-31

    The present investigation is a part of our studies on the electro chemical aspects of pyrite bioleaching involving Thiobacillus ferrooxidans. Previously (1,2) we have examined the effect of T. ferrooxidans and their metabolic products on the redox reactions of Fe{sup 2+}/Fe{sup 3+} couple at the pyrite surface. Results obtained suggest that beyond 1. 5 days during their growth in a batch fermenter, the bacteria and their metabolic products completely cover the pyrite surface and shut down all electron transfer across the electrode-solution interface. In addition, it has been observed that the bacteria serve as the nucleation site for jarosite formation, which is found detrimental to bioleaching. In the present work we have focussed on the effect of the presence of vitamins on the redox chemistry of iron. Our examination of the effect of the presence of thiamine hydrochloride in the redox behavior of Fe{sup 2+}/Fe{sup 3+} at the pyrite surface has revealed that thiamine hydrochloride does not undergo chemical interaction with ferrous or ferric iron. However, it may adsorb onto the pyrite surface causing polarization of the pyrite electrode.

  8. Enhanced photocatalytic performance of Hemin (chloro(protoporhyinato)iron(III)) anchored TiO2 photocatalyst for methyl orange degradation: A surface modification method

    NASA Astrophysics Data System (ADS)

    Devi, L. Gomathi; ArunaKumari, M. L.

    2013-07-01

    TiO2 was prepared by sol-gel method through the hydrolysis of TiCl4 and its surface derivatization was carried out with molecular catalyst like Hemin (chloro(protoporhyinato)iron(III)). Catalyst was characterized by various analytical techniques like UV-vis spectroscopy, FT-IR, FE-SEM and XRD. The anchoring of Hemin on titania surface is confirmed by FT-IR spectra through the linkage of Odbnd Csbnd Osbnd Ti bond and also by TGA-DSC and elemental analysis. The photocatalytic activity of the surface modified catalyst is tested for the degradation of methyl orange (MO) as a model compound under UV light. The Hemin impregnated TiO2 (H-TiO2) in presence of H2O2 shows an excellent photocatalytic activity compared to pristine TiO2, Hemin, H2O2, TiO2/H2O2, and Hemin/H2O2 systems. The enhancement in the photocatalytic activity is attributed to the presence of iron (III) porphyrin ring on the TiO2 surface, which reduces the electron-hole recombination rate and also by acting as a mediator for continuous production of enriched concentration of hydroxyl radicals along with various other reactive free radicals.

  9. Performance of the Chromogenic Medium CHROMagar Staph Aureus and the Staphychrom Coagulase Test in the Detection and Identification of Staphylococcus aureus in Clinical Specimens

    PubMed Central

    Carricajo, Anne; Treny, Axel; Fonsale, Nathalie; Bes, Michele; Reverdy, Marie Elisabeth; Gille, Yves; Aubert, Gerald; Freydiere, Anne Marie

    2001-01-01

    CHROMagar Staph aureus (CSAM) (CHROMagar Microbiology, Paris, France) is a new chromogenic medium designed to enable detection of colonies of Staphylococcus aureus by their pink color. A total of 775 specimens were cultured in parallel on CHROMagar Staph aureus and conventional media. Among the 267 S. aureus strains recovered on at least one medium, 263 were isolated on CSAM medium (sensitivity, 98.5%), and 245 (sensitivity, 91.8%) were isolated on conventional media. The specificity of presumptive identification of S. aureus on the basis of pink colony color on CSAM medium was 97% (493 of 508). This specificity increased to 100% when coagulase detection with the Staphychrom coagulase test was added and to 98.8% when S. aureus surface components were detected by agglutination in the Pastorex Staph Plus test. Susceptibility testing of 67 S. aureus strains, performed in parallel on pink CSAM colonies and on colonies grown on blood agar, gave similar results. Thus, rapid and accurate recognition and identification of S. aureus isolates were achieved with CSAM as the primary isolation medium, followed by the staphylocoagulase Staphychrom test. Antimicrobial susceptibility testing (disk-diffusion method or ATB STAPH System) can be performed directly on pink CSAM colonies. PMID:11427572

  10. RATES OF IRON OXIDATION AND ARSENIC SORPTION DURING GROUND WATER-SURFACE WATER MIXING AT A HAZARDOUS WASTE SITE

    EPA Science Inventory

    The fate of arsenic discharged from contaminated ground water to a pond at a hazardous waste site is controlled, in part, by the rate of ferrous iron oxidation-precipitation and arsenic sorption. Laboratory experiments were conducted using site-derived water to assess the impact...

  11. Partial oxidation (“aging”) and surface modification decrease the toxicity of nano-sized zero valent iron.

    EPA Science Inventory

    Nanosize zero-valent iron (nZVI) is used as a redox-active catalyst for in situ remediation of contaminated ground waters. In aqueous environments, nZVI oxidizes over time (i.e., “ages”) to magnetite and other oxides. For remediation, hi...

  12. Functionally distinct NEAT (NEAr Transporter) domains within the Staphylococcus aureus IsdH/HarA protein extract heme from methemoglobin.

    PubMed

    Pilpa, Rosemarie M; Robson, Scott A; Villareal, Valerie A; Wong, Melissa L; Phillips, Martin; Clubb, Robert T

    2009-01-01

    The pathogen Staphylococcus aureus uses iron-regulated surface determinant (Isd) proteins to scavenge the essential nutrient iron from host hemoproteins. The IsdH protein (also known as HarA) is a receptor for hemoglobin (Hb), haptoglobin (Hp), and the Hb-Hp complex. It contains three NEAT (NEAr Transporter) domains: IsdH(N1), IsdH(N2), and IsdH(N3). Here we show that they have different functions; IsdH(N1) binds Hb and Hp, whereas IsdH(N3) captures heme that is released from Hb. The staphylococcal IsdB protein also functions as an Hb receptor. Primary sequence homology to IsdH indicates that it will also employ functionally distinct NEAT domains to bind heme and Hb. We have used site-directed mutagenesis and surface plasmon resonance methods to localize the Hp and Hb binding surface on IsdH(N1). High affinity binding to these structurally unrelated proteins requires residues located within a conserved aromatic motif that is positioned at the end of the beta-barrel structure. Interestingly, this site is quite malleable, as other NEAT domains use it to bind heme. We also demonstrate that the IsdC NEAT domain can capture heme directly from Hb, suggesting that there are multiple pathways for heme transfer across the cell wall. PMID:18984582

  13. Short- and Long-Term Effects of Prenatal Exposure to Iron Oxide Nanoparticles: Influence of Surface Charge and Dose on Developmental and Reproductive Toxicity

    PubMed Central

    Di Bona, Kristin R.; Xu, Yaolin; Gray, Marquita; Fair, Douglas; Hayles, Hunter; Milad, Luckie; Montes, Alex; Sherwood, Jennifer; Bao, Yuping; Rasco, Jane F.

    2015-01-01

    Iron oxide nanoparticles (NPs) are commonly utilized for biomedical, industrial, and commercial applications due to their unique properties and potential biocompatibility. However, little is known about how exposure to iron oxide NPs may affect susceptible populations such as pregnant women and developing fetuses. To examine the influence of NP surface-charge and dose on the developmental toxicity of iron oxide NPs, Crl:CD1(ICR) (CD-1) mice were exposed to a single, low (10 mg/kg) or high (100 mg/kg) dose of positively-charged polyethyleneimine-Fe2O3-NPs (PEI-NPs), or negatively-charged poly(acrylic acid)-Fe2O3-NPs (PAA-NPs) during critical windows of organogenesis (gestation day (GD) 8, 9, or 10). A low dose of NPs, regardless of charge, did not induce toxicity. However, a high exposure led to charge-dependent fetal loss as well as morphological alterations of the uteri (both charges) and testes (positive only) of surviving offspring. Positively-charged PEI-NPs given later in organogenesis resulted in a combination of short-term fetal loss (42%) and long-term alterations in reproduction, including increased fetal loss for second generation matings (mice exposed in utero). Alternatively, negatively-charged PAA-NPs induced fetal loss (22%) earlier in organogenesis to a lesser degree than PEI-NPs with only mild alterations in offspring uterine histology observed in the long-term. PMID:26694381

  14. Short- and Long-Term Effects of Prenatal Exposure to Iron Oxide Nanoparticles: Influence of Surface Charge and Dose on Developmental and Reproductive Toxicity.

    PubMed

    Di Bona, Kristin R; Xu, Yaolin; Gray, Marquita; Fair, Douglas; Hayles, Hunter; Milad, Luckie; Montes, Alex; Sherwood, Jennifer; Bao, Yuping; Rasco, Jane F

    2015-01-01

    Iron oxide nanoparticles (NPs) are commonly utilized for biomedical, industrial, and commercial applications due to their unique properties and potential biocompatibility. However, little is known about how exposure to iron oxide NPs may affect susceptible populations such as pregnant women and developing fetuses. To examine the influence of NP surface-charge and dose on the developmental toxicity of iron oxide NPs, Crl:CD1(ICR) (CD-1) mice were exposed to a single, low (10 mg/kg) or high (100 mg/kg) dose of positively-charged polyethyleneimine-Fe₂O₃-NPs (PEI-NPs), or negatively-charged poly(acrylic acid)-Fe₂O₃-NPs (PAA-NPs) during critical windows of organogenesis (gestation day (GD) 8, 9, or 10). A low dose of NPs, regardless of charge, did not induce toxicity. However, a high exposure led to charge-dependent fetal loss as well as morphological alterations of the uteri (both charges) and testes (positive only) of surviving offspring. Positively-charged PEI-NPs given later in organogenesis resulted in a combination of short-term fetal loss (42%) and long-term alterations in reproduction, including increased fetal loss for second generation matings (mice exposed in utero). Alternatively, negatively-charged PAA-NPs induced fetal loss (22%) earlier in organogenesis to a lesser degree than PEI-NPs with only mild alterations in offspring uterine histology observed in the long-term. PMID:26694381

  15. Cutaneous Immune Defenses Against Staphylococcus aureus Infections

    PubMed Central

    Choi, Ji Hae; Seo, Ho Seong; Lim, Sang Young; Park, Kyungho

    2014-01-01

    Staphylococcus aureus (S. aureus) is a virulent bacterium that abundantly colonizes inflammatory skin diseases. Since S. aureus infections occur in an impaired skin barrier, it is important to understand the protective mechanism through cutaneous immune responses against S. aureus infections and the interaction with Staphylococcal virulence factors. In this review, we summarize not only the pathogenesis and key elements of S. aureus skin infections, but also the cutaneous immune system against its infections and colonization. The information obtained from this area may provide the groundwork for further immunomodulatory therapies or vaccination strategies to prevent S. aureus infections. PMID:26064853

  16. Streptomyces-derived actinomycin D inhibits biofilm formation by Staphylococcus aureus and its hemolytic activity.

    PubMed

    Lee, Jin-Hyung; Kim, Yong-Guy; Lee, Kayeon; Kim, Chang-Jin; Park, Dong-Jin; Ju, Yoonjung; Lee, Jae-Chan; Wood, Thomas K; Lee, Jintae

    2016-01-01

    Staphylococcus aureus is a versatile human pathogen that produces diverse virulence factors, and its biofilm cells are difficult to eradicate due to their inherent ability to tolerate antibiotics. The anti-biofilm activities of the spent media of 252 diverse endophytic microorganisms were investigated using three S. aureus strains. An attempt was made to identify anti-biofilm compounds in active spent media and to assess their anti-hemolytic activities and hydrophobicities in order to investigate action mechanisms. Unlike other antibiotics, actinomycin D (0.5 μg ml(-1)) from Streptomyces parvulus significantly inhibited biofilm formation by all three S. aureus strains. Actinomycin D inhibited slime production in S. aureus and it inhibited hemolysis by S. aureus and caused S. aureus cells to become less hydrophobic, thus supporting its anti-biofilm effect. In addition, surface coatings containing actinomycin D prevented S. aureus biofilm formation on glass surfaces. Given these results, FDA-approved actinomycin D warrants further attention as a potential antivirulence agent against S. aureus infections. PMID:26785934

  17. Staphylococcus aureus Deficient in Lipidation of Prelipoproteins Is Attenuated in Growth and Immune Activation

    PubMed Central

    Stoll, Hartmut; Dengjel, Jörn; Nerz, Christiane; Götz, Friedrich

    2005-01-01

    A lipoprotein diacylglyceryl transferase (lgt) deletion mutant of Staphylococcus aureus SA113 was constructed. The lipoprotein and prelipoprotein expression, the growth behavior, and the ability of the mutant to elicit an immune response in various host cells were studied. In the wild type, the majority of [14C]palmitate-labeled lipoproteins were located in the membrane fraction, although some lipoproteins were also present on the cell surface and in the culture supernatant. The lgt mutant completely lacked palmitate-labeled lipoproteins and released high amounts of some unmodified prelipoproteins, e.g., the oligopeptide-binding protein OppA, the peptidyl-prolyl cis-trans isomerase PrsA, and the staphylococcal iron transporter SitC, into the culture supernatant. The growth of the lgt mutant was hardly affected in rich medium but was retarded under nutrient limitation. The lgt mutant and its crude lysate induced much fewer proinflammatory cytokines and chemokines in human monocytic (MonoMac6), epithelial (pulmonary A549), and endothelial (human umbilical vein endothelial) cells than the wild type. However, in whole blood samples, the culture supernatant of the lgt mutant was equal or even superior to the wild-type supernatant in tumor necrosis factor alpha induction. Lipoprotein fractionation experiments provided evidence that a small proportion of the mature lipoproteins are released by the S. aureus wild type despite the lipid anchor and are trapped in part by the cell wall, thereby exposing the immune-activating lipid structure on the cell surface. Bacterial lipoproteins appear to be essential for a complete immune stimulation by gram-positive bacteria. PMID:15784587

  18. Variational calculation of ground-state energy of iron atoms and condensed matter in strong magnetic fields. [at neutron star surfaces

    NASA Technical Reports Server (NTRS)

    Flowers, E. G.; Ruderman, M. A.; Lee, J.-F.; Sutherland, P. G.; Hillebrandt, W.; Mueller, E.

    1977-01-01

    Variational calculations of the binding energies of iron atoms and condensed matter in strong magnetic fields (greater than 10 to the 12th gauss). These calculations include the electron exchange energy. The cohesive energy of the condensed matter, which is the difference between these two binding energies, is of interest in pulsar theories and in the description of the surfaces of neutron stars. It is found that the cohesive energy ranges from 2.6 keV to 8.0 keV.

  19. Reverse micelle synthesis of nanoscale metal containing catalysts. [Nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide nanoscale powders

    SciTech Connect

    Darab, J.G.; Fulton, J.L.; Linehan, J.C.

    1993-03-01

    The need for morphological control during the synthesis of catalyst precursor powders is generally accepted to be important. In the liquefaction of coal, for example, iron-bearing catalyst precursor particles containing individual crystallites with diameters in the 1-100 nanometer range are believed to achieve good dispersion through out the coal-solvent slurry during liquefaction 2 runs and to undergo chemical transformations to catalytically active iron sulfide phases. The production of the nanoscale powders described here employs the confining spherical microdomains comprising the aqueous phase of a modified reverse micelle (MRM) microemulsion system as nanoscale reaction vessels in which polymerization, electrochemical reduction and precipitation of solvated salts can occur. The goal is to take advantage of the confining nature of micelles to kinetically hinder transformation processes which readily occur in bulk aqueous solution in order to control the morphology and phase of the resulting powder. We have prepared a variety of metal, alloy, and metal- and mixed metal-oxide nanoscale powders from appropriate MRM systems. Examples of nanoscale powders produced include Co, Mo-Co, Ni[sub 3]Fe, Ni, and various oxides and oxyhydroxides of iron. Here, we discuss the preparation and characterization of nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide MRM nanoscale powders. We have used extended x-ray absorption fine structure (EXAFS) spectroscopy to study the chemical polymerization process in situ, x-ray diffraction (XRD), scanning and transmission electron microcroscopies (SEM and TEM), elemental analysis and structural modelling to characterize the nanoscale powders produced. The catalytic activity of these powders is currently being studied.

  20. [Vancomycin-resistant Staphylococcus aureus].

    PubMed

    Rodríguez, Carlos Andrés; Vesga, Omar

    2005-12-01

    The evolution and molecular mechanisms of vancomycin resistance in Staphylococcus aureus were reviewed. Case reports and research studies on biochemestry, electron microscopy and molecular biology of Staphylococcus aureus were selected from Medline database and summarized in the following review. After almost 40 years of successful treatment of S. aureus with vancomycin, several cases of clinical failures have been reported (since 1997). S. aureus strains have appeared with intermediate susceptibility (MIC 8-16 microg/ml), as well as strains with heterogeneous resistance (global MIC < or =4 microg/ml), but with subpopulations of intermediate susceptibility. In these cases, resistance is mediated by cell wall thickening with reduced cross linking. This traps the antibiotic before it reaches its major target, the murein monomers in the cell membrane. In 2002, a total vancomycin resistant strain (MIC > or =32 microg/ml) was reported with vanA genes from Enterococcus spp. These genes induce the change of D-Ala-D-Ala terminus for D-Ala-D-lactate in the cell wall precursors, leading to loss of affinity for glycopeptides. Vancomycin resistance in S. aureus has appeared; it is mediated by cell wall modifications that trap the antibiotic before it reaches its action site. In strains with total resistance, Enterococcus spp. genes have been acquired that lead to modification of the glycopeptide target. PMID:16433184

  1. Heterologously Expressed Staphylococcus aureus Fibronectin-Binding Proteins Are Sufficient for Invasion of Host Cells

    PubMed Central

    Sinha, Bhanu; Francois, Patrice; Que, Yok-Ai; Hussain, Muzaffar; Heilmann, Christine; Moreillon, Philippe; Lew, Daniel; Krause, Karl-Heinz; Peters, Georg; Herrmann, Mathias

    2000-01-01

    Staphylococcus aureus invasion of mammalian cells, including epithelial, endothelial, and fibroblastic cells, critically depends on fibronectin bridging between S. aureus fibronectin-binding proteins (FnBPs) and the host fibronectin receptor integrin α5β1 (B. Sinha et al., Cell. Microbiol. 1:101–117, 1999). However, it is unknown whether this mechanism is sufficient for S. aureus invasion. To address this question, various S. aureus adhesins (FnBPA, FnBPB, and clumping factor [ClfA]) were expressed in Staphylococcus carnosus and Lactococcus lactis subsp. cremoris. Both noninvasive gram-positive microorganisms are genetically distinct from S. aureus, lack any known S. aureus surface protein, and do not bind fibronectin. Transformants of S. carnosus and L. lactis harboring plasmids coding for various S. aureus surface proteins (FnBPA, FnBPB, and ClfA) functionally expressed adhesins (as determined by bacterial clumping in plasma, specific latex agglutination, Western ligand blotting, and binding to immobilized and soluble fibronectin). FnBPA or FnBPB but not of ClfA conferred invasiveness to S. carnosus and L. lactis. Invasion of 293 cells by transformants was comparable to that of strongly invasive S. aureus strain Cowan 1. Binding of soluble and immobilized fibronectin paralleled invasiveness, demonstrating that the amount of accessible surface FnBPs is rate limiting. Thus, S. aureus FnBPs confer invasiveness to noninvasive, apathogenic gram-positive cocci. Furthermore, FnBP-coated polystyrene beads were internalized by 293 cells, demonstrating that FnBPs are sufficient for invasion of host cells without the need for (S. aureus-specific) coreceptors. PMID:11083807

  2. Iron deficiency.

    PubMed

    Scrimshaw, N S

    1991-10-01

    The world's leading nutritional problem is iron deficiency. 66% of children and women aged 15-44 years in developing countries have it. Further, 10-20% of women of childbearing age in developed countries are anemic. Iron deficiency is identified with often irreversible impairment of a child's learning ability. It is also associated with low capacity for adults to work which reduces productivity. In addition, it impairs the immune system which reduces the body's ability to fight infection. Iron deficiency also lowers the metabolic rate and the body temperature when exposed to cold. Hemoglobin contains nearly 73% of the body's iron. This iron is always being recycled as more red blood cells are made. The rest of the needed iron does important tasks for the body, such as binds to molecules that are reservoirs of oxygen for muscle cells. This iron comes from our diet, especially meat. Even though some plants, such as spinach, are high in iron, the body can only absorb 1.4-7% of the iron in plants whereas it can absorb 20% of the iron in red meat. In many developing countries, the common vegetarian diets contribute to high rates of iron deficiency. Parasitic diseases and abnormal uterine bleeding also promote iron deficiency. Iron therapy in anemic children can often, but not always, improve behavior and cognitive performance. Iron deficiency during pregnancy often contributes to maternal and perinatal mortality. Yet treatment, if given to a child in time, can lead to normal growth and hinder infections. However, excess iron can be damaging. Too much supplemental iron in a malnourished child promotes fatal infections since the excess iron is available for the pathogens use. Many countries do not have an effective system for diagnosing, treating, and preventing iron deficiency. Therefore a concerted international effort is needed to eliminate iron deficiency in the world. PMID:1745900

  3. Experimental Staphylococcus aureus brain abscess.

    PubMed

    Enzmann, D R; Britt, R R; Obana, W G; Stuart, J; Murphy-Irwin, K

    1986-01-01

    The virulent organism Staphylococcus aureus produced brain abscesses that were quantitatively and qualitatively different from those caused by less virulent organisms. S. aureus abscesses created larger lesions, as earlier ependymitis, delayed progress toward healing, and caused areas of inflammatory escape outside the collagen capsule. Imaging tests revealed similar findings: the abscesses were larger, had more extensive central necrosis, and showed earlier evidence of ependymitis. This virulent organism also demonstrated that white matter is more susceptible than overlying gray matter to destruction by infection. The pattern of spread and other histologic findings suggest that collagen capsule formation has less of an infection "containment" function than was previously thought. PMID:3085444

  4. [Protein toxins of Staphylococcus aureus].

    PubMed

    Shamsutdinov, A F; Tiurin, Iu A

    2014-01-01

    Main scientific-research studies regarding protein bacterial toxins of the most widespread bacteria that belong to Staphylococcus spp. genus and in particular the most pathogenic species for humans--Staphylococcus aureus, are analyzed. Structural and biological properties of protein toxins that have received the name of staphylococcus pyrogenic toxins (PTSAg) are presented. Data regarding genetic regulation of secretion and synthesis of these toxins and 3 main regulatory genetic systems (agr--accessory gene regulator, xpr--extracellular protein regulator, sar--staphylococcal accessory regulator) that coordinate synthesis of the most important protein toxins and enzymes for virulence of S. aureus, are presented. PMID:25051707

  5. Preparation and characterization of antibacterial Senegalia (Acacia) senegal/iron-silica bio-nanocomposites

    NASA Astrophysics Data System (ADS)

    Şişmanoğlu, Tuba; Karakuş, Selcan; Birer, Özgür; Soylu, Gülin Selda Pozan; Kolan, Ayşen; Tan, Ezgi; Ürk, Öykü; Akdut, Gizem; Kilislioglu, Ayben

    2015-11-01

    Many studies that research bio-nanocomposites utilize techniques that involve the dispersion of strengthening components like silica, metal and metal oxides through a host biopolymer matrix. The biggest success factor for the bio-nanocomposite is having a smooth integration of organic and inorganic phases. This interattraction between the surfaces of inorganic particles and organic molecules are vital for good dispersion. In this study, a novel biodegradable antibacterial material was developed using gum arabic from Senegalia senegal (stabilizer), silica (structure reinforcer) and zero valent iron particles. Silica particles work to not only strengthen the mechanical properties of the Senegalia senegal but also prevent the accumulation of ZVI nanoparticles due to attraction between hydroxyl groups and FeO. The gum arabic/Fe-SiO2 bio-nanocomposite showed effective antibacterial property against the Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Using Scanning electron microscopy, homogeneous dispersion and uniform particle size was viewed in the biopolymer. X-ray diffraction studies of iron particles organization in Senegalia senegal also showed that the main portion of iron was crystalline and in the form of FeO and Fe0. X-ray photoelectron spectroscopy was used to evaluate the chemical composition of the surface but no appreciable peak was measured for the iron before Ar etching. These results suggest that the surface of iron nanoparticles consist mainly of a layer of iron oxides in the form of FeO. Thermal gravimetric analysis was used to determine the thermal stability and absorbed moisture content.

  6. Final Technical Report. Reactivity of Iron-Bearing Minerals and CO2 Sequestration and Surface Chemistry of Pyrite. An Interdisciplinary Approach

    SciTech Connect

    Strongin, Daniel

    2014-12-31

    Over the course of the scientific program, two areas of research were pursued: reactions of iron oxides with supercritical CO2 and sulfide and surface reactivity of pyrite. The latter area of interest was to understand the chemistry that results when supercritical CO2 (scCO2 ) with H2 S and/or SO2 in deep saline formations (DFS) contacts iron bearing minerals. Understanding the complexities the sulfur co-injectants introduce is a critical step in developing CO2 sequestration as a climate-mitigating strategy. The research strategy was to understand macroscopic observations of this chemistry with an atomic/molecular level view using surface analytical techniques. Research showed that the exposure of iron (oxyhdr)oxides (which included ferrihydrite, goethite, and hematite) to scCO2 in the presence of sulfide led to reactions that formed siderite (FeCO3). The results have important implications for the sequestration of CO2 via carbonation reactions in the Earth’s subsurface. An earlier area of focus in the project was to understand pyrite oxidation in microscopic detail. This understanding was used to understand macroscopic observations of pyrite reactivity. Results obtained from this research led to a better understanding how pyrite reacts in a range of chemical environments. Geochemical and modern surface science techniques were used to understand the chemistry of pyrite in important environmental conditions. The program relied on a strong integration the results of these techniques to provide a fundamental understanding to the macroscopic chemistry exhibited by pyrite in the environment. Major achievements during these studies included developing an understanding of the surface sites on pyrite that controlled its reactivity under oxidizing conditions. In particular sulfur anion vacancies and/or ferric sites were sites of reactivity. Studies also showed that the

  7. Growth promotion of the opportunistic human pathogen, Staphylococcus lugdunensis, by heme, hemoglobin, and coculture with Staphylococcus aureus

    PubMed Central

    Brozyna, Jeremy R; Sheldon, Jessica R; Heinrichs, David E

    2014-01-01

    Staphylococcus lugdunensis is both a commensal of humans and an opportunistic pathogen. Little is currently known about the molecular mechanisms underpinning the virulence of this bacterium. Here, we demonstrate that in contrast to S. aureus,S. lugdunensis makes neither staphyloferrin A (SA) nor staphyloferrin B (SB) in response to iron deprivation, owing to the absence of the SB gene cluster, and a large deletion in the SA biosynthetic gene cluster. As a result, the species grows poorly in serum-containing media, and this defect was complemented by introduction of the S. aureusSA gene cluster into S. lugdunensis. S. lugdunensis expresses the HtsABC and SirABC transporters for SA and SB, respectively; the latter gene set is found within the isd (heme acquisition) gene cluster. An isd deletion strain was significantly debilitated for iron acquisition from both heme and hemoglobin, and was also incapable of utilizing ferric-SB as an iron source, while an hts mutant could not grow on ferric-SA as an iron source. In iron-restricted coculture experiments, S. aureus significantly enhanced the growth of S. lugdunensis, in a manner dependent on staphyloferrin production by S. aureus, and the expression of the cognate transporters by S. lugdunensis. PMID:24515974

  8. Enhancing Electrochemical Water-Splitting Kinetics by Polarization-Driven Formation of Near-Surface Iron(0): An In Situ XPS Study on Perovskite-Type Electrodes**

    PubMed Central

    Opitz, Alexander K; Nenning, Andreas; Rameshan, Christoph; Rameshan, Raffael; Blume, Raoul; Hävecker, Michael; Knop-Gericke, Axel; Rupprechter, Günther; Fleig, Jürgen; Klötzer, Bernhard

    2015-01-01

    In the search for optimized cathode materials for high-temperature electrolysis, mixed conducting oxides are highly promising candidates. This study deals with fundamentally novel insights into the relation between surface chemistry and electrocatalytic activity of lanthanum ferrite based electrolysis cathodes. For this means, near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and impedance spectroscopy experiments were performed simultaneously on electrochemically polarized La0.6Sr0.4FeO3−δ (LSF) thin film electrodes. Under cathodic polarization the formation of Fe0 on the LSF surface could be observed, which was accompanied by a strong improvement of the electrochemical water splitting activity of the electrodes. This correlation suggests a fundamentally different water splitting mechanism in presence of the metallic iron species and may open novel paths in the search for electrodes with increased water splitting activity. PMID:25557533

  9. Enhancing electrochemical water-splitting kinetics by polarization-driven formation of near-surface iron(0): an in situ XPS study on perovskite-type electrodes.

    PubMed

    Opitz, Alexander K; Nenning, Andreas; Rameshan, Christoph; Rameshan, Raffael; Blume, Raoul; Hävecker, Michael; Knop-Gericke, Axel; Rupprechter, Günther; Fleig, Jürgen; Klötzer, Bernhard

    2015-02-23

    In the search for optimized cathode materials for high-temperature electrolysis, mixed conducting oxides are highly promising candidates. This study deals with fundamentally novel insights into the relation between surface chemistry and electrocatalytic activity of lanthanum ferrite based electrolysis cathodes. For this means, near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and impedance spectroscopy experiments were performed simultaneously on electrochemically polarized La0.6 Sr0.4 FeO3-δ (LSF) thin film electrodes. Under cathodic polarization the formation of Fe(0) on the LSF surface could be observed, which was accompanied by a strong improvement of the electrochemical water splitting activity of the electrodes. This correlation suggests a fundamentally different water splitting mechanism in presence of the metallic iron species and may open novel paths in the search for electrodes with increased water splitting activity. PMID:25557533

  10. Brain iron homeostasis.

    PubMed

    Moos, Torben

    2002-11-01

    transferrin were, however, restricted to areas situated in close proximity to the ventricular and pial surfaces. In particular, transferrin injected into the ventricles was never observed in regions distant from the CSF. It was concluded that choroid plexus-derived transferrin is not likely to play a significant role for binding and transporting iron in the brain interstitium. Transferrin secretion from oligodendrocytes probably plays the key role in this process. In the third part of the thesis, the uptake of iron by neurons devoid of projections beyond the blood-brain barrier and glia is addressed. Given the fact that the demonstration of plasma proteins in brain sections can be hampered by several methodological factors, a mapping of the cellular distribution of transferrin in the brain was performed employing extensive use of tissue-processing and staining protocols. In order to aid in the understanding of cellular iron uptake in the intact brain, attempts were made to identify iron, transferrin, and transferrin receptors at the light microscopic level. Consistent with the widespread distribution of transferrin receptors in neurons, the ligand transferrin was also found in neurons throughout the CNS. When examined at high resolution, transferrin was found to be distributed to the cytoplasm of neurons, exhibiting a dotted appearance, which is probably consistent with a distribution in the endosomallysosomal system. In contrast to the consistent presence of transferrin receptors on neurons, it was not possible to detect transferrin receptors on glial cells. Related to these observations, the presence of non-transferrin-bound iron in the brain suggests that glial cells may take it up by a mechanism that does not involve the transferrin receptor. The widespread distribution of ferritin in glial cells clearly indicates that the glial cells acquire iron. Dietary iron-overload did not change the distribution of transferrin receptors or ferritin in the brain. By contrast, iron

  11. Targeting Staphylococcus aureus Toxins: A Potential form of Anti-Virulence Therapy

    PubMed Central

    Kong, Cin; Neoh, Hui-min; Nathan, Sheila

    2016-01-01

    Staphylococcus aureus is an opportunistic pathogen and the leading cause of a wide range of severe clinical infections. The range of diseases reflects the diversity of virulence factors produced by this pathogen. To establish an infection in the host, S. aureus expresses an inclusive set of virulence factors such as toxins, enzymes, adhesins, and other surface proteins that allow the pathogen to survive under extreme conditions and are essential for the bacteria’s ability to spread through tissues. Expression and secretion of this array of toxins and enzymes are tightly controlled by a number of regulatory systems. S. aureus is also notorious for its ability to resist the arsenal of currently available antibiotics and dissemination of various multidrug-resistant S. aureus clones limits therapeutic options for a S. aureus infection. Recently, the development of anti-virulence therapeutics that neutralize S. aureus toxins or block the pathways that regulate toxin production has shown potential in thwarting the bacteria’s acquisition of antibiotic resistance. In this review, we provide insights into the regulation of S. aureus toxin production and potential anti-virulence strategies that target S. aureus toxins. PMID:26999200

  12. Direct detection of nasal Staphylococcus aureus carriage via helicase-dependent isothermal amplification and chip hybridization

    PubMed Central

    2012-01-01

    Background The bacterium Staphylococcus aureus constitutes one of the most important causes of nosocomial infections. One out of every three individuals naturally carries S. aureus in their anterior nares, and nasal carriage is associated with a significantly higher infection rate in hospital settings. Nasal carriage can be either persistent or intermittent, and it is the persistent carriers who, as a group, are at the highest risk of infection and who have the highest nasal S. aureus cell counts. Prophylactic decolonization of S. aureus from patients’ noses is known to reduce the incidence of postsurgical infections, and there is a clear rationale for rapid identification of nasal S. aureus carriers among hospital patients. Findings A molecular diagnostic assay was developed which is based on helicase-dependent target amplification and amplicon detection by chip hybridization to a chip surface, producing a visible readout. Nasal swabs from 70 subjects were used to compare the molecular assay against culturing on “CHROMagar Staph aureus” agar plates. The overall relative sensitivity was 89%, and the relative specificity was 94%. The sensitivity rose to 100% when excluding low-count subjects (<100 S. aureus colony-forming units per swab). Conclusions This molecular assay is much faster than direct culture and has sensitivity that is appropriate for identification of high-count (>100 S. aureus colony-forming units per swab) nasal S. aureus carriers who are at greatest risk for nosocomial infections. PMID:22882800

  13. The therapeutic effect of chlorogenic acid against Staphylococcus aureus infection through sortase A inhibition

    PubMed Central

    Wang, Lin; Bi, Chongwei; Cai, Hongjun; Liu, Bingrun; Zhong, Xiaobo; Deng, Xuming; Wang, Tiedong; Xiang, Hua; Niu, Xiaodi; Wang, Dacheng

    2015-01-01

    The emergence and wide spread of multi-drug resistant Staphylococcus aureus (S. aureus) requires the development of new therapeutic agents with alternative modes of action. Anti-virulence strategies are hoped to meet that need. Sortase A (SrtA) has attracted great interest as a potential drug target to treat infections caused by S. aureus, as many of the surface proteins displayed by SrtA function as virulence factors by mediating bacterial adhesion to specific organ tissues, invasion of host cells, and evasion of the host-immune responses. It has been suggested that inhibitors of SrtA might be promising candidates for the treatment and/or prevention of S. aureus infections. In this study, we report that chlorogenic acid (CHA), a natural compound that lacks significant anti-S. aureus activity, inhibit the activity of SrtA in vitro (IC50 = 33.86 ± 5.55 μg/ml) and the binding of S. aureus to fibrinogen (Fg). Using molecular dynamics simulations and mutagenesis assays, we further demonstrate that CHA binds to the binding sites of C184 and G192 in the SrtA. In vivo studies demonstrated that CHA prevent mice from S. aureus-induced renal abscess, resulting in a significant survival advantage. These findings indicate that CHA is a promising therapeutic compound against SrtA during S. aureus infections. PMID:26528244

  14. Sharp transition from ripple patterns to a flat surface for ion beam erosion of Si with simultaneous co-deposition of iron

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Brötzmann, M.; Hofsäss, H.

    2012-09-01

    We investigate pattern formation on Si by sputter erosion under simultaneous co-deposition of Fe atoms, both at off-normal incidence, as function of the Fe surface coverage. The patterns obtained for 5 keV Xe ion irradiation at 30° incidence angle are analyzed with atomic force microscopy. Rutherford backscattering spectroscopy of the local steady state Fe content of the Fe-Si surface layer allows a quantitative correlation between pattern type and Fe coverage. With increasing Fe coverage the patterns change, starting from a flat surface at low coverage (< 2×1015 Fe/cm2) over dot patterns (2-8×1015 Fe/cm2), ripples patterns (8-17×1015 Fe/cm2), pill bug structures (1.8×1016 Fe/cm2) and a rather flat surface with randomly distributed weak pits at high Fe coverage (>1.8×1016 Fe/cm2). Our results confirm the observations by Macko et al. for 2 keV Kr ion irradiation of Si with Fe co-deposition. In particular, we also find a sharp transition from pronounced ripple patterns with large amplitude (rms roughness ˜ 18 nm) to a rather flat surface (rms roughness ˜ 0.5 nm). Within this transition regime, we also observe the formation of pill bug structures, i.e. individual small hillocks with a rippled structure on an otherwise rather flat surface. The transition occurs within a very narrow regime of the steady state Fe surface coverage between 1.7 and 1.8×1016 Fe/cm2, where the composition of the mixed Fe-Si surface layer of about 10 nm thickness reaches the stoichiometry of FeSi2. Phase separation towards amorphous iron silicide is assumed as the major contribution for the pattern formation at lower Fe coverage and the sharp transition from ripple patterns to a flat surface.

  15. A Non-Electrostatic Surface Complexation Approach to Modeling Radionuclide Migration at the Nevada Test Site: I. Iron Oxides and Calcite

    SciTech Connect

    Zavarin, M; Bruton, C J

    2004-12-17

    Reliable quantitative prediction of contaminant transport in subsurface environments is critical to evaluating the risks associated with radionuclide migration. As part of the Underground Test Area (UGTA) project, radionuclide transport away from various underground nuclear tests conducted in the saturated zone at the Nevada Test Site (NTS) is being examined. In the near-field environment, reactive transport simulations must account for changes in water chemistry and mineralogy as a function of time and their effect on radionuclide migration. Unlike the K{sub d} approach, surface complexation (SC) reactions, in conjunction with ion exchange and precipitation, can be used to describe radionuclide reactive transport as a function of changing environmental conditions. They provide a more robust basis for describing radionuclide retardation in geochemically dynamic environments. The interaction between several radionuclides considered relevant to the UGTA project and iron oxides and calcite are examined in this report. The interaction between these same radionuclides and aluminosilicate minerals is examined in a companion report (Zavarin and Bruton, 2004). Selection criteria for radionuclides were based on abundance, half-life, toxicity to human and environmental health, and potential mobility at NTS (Tompson et al., 1999). Both iron oxide and calcite minerals are known to be present at NTS in various locations and are likely to affect radionuclide migration from the near-field. Modeling the interaction between radionuclides and these minerals was based on surface complexation. The effectiveness of the most simplified SC model, the one-site Non-Electrostatic Model (NEM), to describe sorption under various solution conditions is evaluated in this report. NEM reactions were fit to radionuclide sorption data available in the literature, as well as sorption data recently collected for the UGTA project, and a NEM database was developed. For radionuclide-iron oxide sorption

  16. Role of surface chemistry and morphology in the reactive adsorption of H₂S on iron (hydr)oxide/graphite oxide composites.

    PubMed

    Arcibar-Orozco, Javier A; Wallace, Rajiv; Mitchell, Joshua K; Bandosz, Teresa J

    2015-03-10

    Composites of magnetite and two-line ferrihydrite with graphite oxide (GO) were synthesized and tested as hydrogen sulfide adsorbents. Exhausted and initial composites were characterized by the adsorption of nitrogen, X-ray diffraction, potentiometric titration, thermal analysis, and FTIR. The addition of GO increased the surface area of the composites due to the formation of new micropores. The extent of the increase depended on the nature of the iron (hydr)oxide and the content of GO. The addition of GO did not considerably change the crystal structure but increased the number of acidic functional groups. While for the magnetite composites an increase in the H2S adsorption capacity after GO addition was found, the opposite effect was recorded for the ferrihydrite composites. That increase in the adsorption capacity was linked to the affinity of the composites to adsorb water in mesopores of specific sizes in which the reaction with basic surface groups takes place. Elemental sulfur and ferric and ferrous sulfates were detected on the surface of the exhausted samples. A redox reactive adsorption mechanism is proposed to govern the retention of hydrogen sulfide on the surface of the composites. The incorporation of GO enhances the chemical retention of H2S due to the incorporation of OH reactive groups and an increase in surface heterogeneity. PMID:25675243

  17. Adsorption of silane films on iron surfaces: Characterization of films and development of novel silane-based pretreatments to replace chromates and phosphates

    NASA Astrophysics Data System (ADS)

    Zhang, Chunbin

    This work mainly consists of three parts. The first part deals with characterization of silane films on metal surfaces (iron) by various analytical techniques. The second part describes the development of novel silane-based pretreatments of cold rolled steel (CRS) which may be used for the replacement of pretreatments based on phosphating with chromating as a final rinse. The third part focuses on the corrosion performance of polyurethane-power-paint-coated CRS panels by means of electrochemical impedance spectroscopy. In the first part of this work, films deposited on polished iron surfaces from solutions of gamma-aminopropyltriethoxysilane (gamma-APS), 1,2-bis(triethoxysilyl) ethane (BTSE), their mixtures, and other silanes were characterized by means of ellipsometry, Reflection-Absorption Infrared Spectroscopy, Time-of-Flight Secondary Ion Mass Spectrometry, and etc. The purpose of the second part of this work was to develop novel silane-based pretreatments that can replace the commercially used phosphating pretreatment with a chromate final rinse for CRS for the benefit of a cleaner environment. The corrosion performance of the coated CRS panels was studied by means of a cyclic corrosion test and the standard ASTM salt spray test B117. A novel silane-based pretreatment, namely, a two step silane treatment, which used two silanes, one organofunctional silane (gamma-APS) and one non-functional silane (BTSE), was developed. Results obtained from cyclic corrosion and salt spray tests showed that the two step silane treatment provided corrosion performance for CRS panels equal to the commercially used iron phosphating pretreatment with a chromate final rinse. In the third part of this work, electrochemical impedance spectroscopy (EIS) was employed to study the corrosion performance of CRS panels that were coated with polyurethane powder paint. The purpose was to study the effects of various pretreatments and pH on the performance of the paint-CRS systems during

  18. Survival of Staphylococcus aureus on fomites.

    PubMed

    Cuesta, Alicia; Nastri, Natalia; Bernat, Maria; Brusca, Maria; Turcot, Liliana; Nastri, Maria; Rosa, Alcira C

    2008-01-01

    The aim of this study was to evaluate duration of survival of Staphylococcus aureus on contaminated standardized fomites, such as sterilization paper (SP) and polyester previously sterilized in a steam autoclave, and to determine the potential inhibitory effects of the substrates (fabrics used to manufacture garments and special wrapping paper used in the dental setting) using the bacteriostasis test. The test was performed on two types of sterile standardized samples (T1 and T2). Sterility of the samples was validated following the protocol in use at the Department of Microbiology, after which the samples were inoculated with 50 microl of a calibrated suspension of Staphylococcus aureus (reference strain ATCC 25923) in the exponential growth phase, in a final concentration of 10(7) cfu/ml and 10(6) cfu/ml). The samples were incubated at 27 degrees C and survival and concentration of microorganisms attached to the surface of the substrates was determined at the following experimental time points: immediately post-contamination, and 3 hours, 24 hours, 3 days, and 7 days post-contamination. Recovery was determined and expressed as a percentage; the bacteriostasis test was performed and showed negative results. Our results suggest that the quantity of recovered microorganisms varies according to the type of substrate and that there is a relation between survival and incubation time of the inoculated substrate serving as an artificial niche. PMID:19177850

  19. Oxygen and iron isotope constraints on near-surface fractionation effects and the composition of lunar mare basalt source regions

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Spicuzza, Michael J.; Craddock, Paul R.; Day, James M. D.; Valley, John W.; Dauphas, Nicolas; Taylor, Lawrence A.

    2010-11-01

    Oxygen and iron isotope analyses of low-Ti and high-Ti mare basalts are presented to constrain their petrogenesis and to assess stable isotope variations within lunar mantle sources. An internally-consistent dataset of oxygen isotope compositions of mare basalts encompasses five types of low-Ti basalts from the Apollo 12 and 15 missions and eight types of high-Ti basalts from the Apollo 11 and 17 missions. High-precision whole-rock δ 18O values (referenced to VSMOW) of low-Ti and high-Ti basalts correlate with major-element compositions (Mg#, TiO 2, Al 2O 3). The observed oxygen isotope variations within low-Ti and high-Ti basalts are consistent with crystal fractionation and match the results of mass-balance models assuming equilibrium crystallization. Whole-rock δ 56Fe values (referenced to IRMM-014) of high-Ti and low-Ti basalts range from 0.134‰ to 0.217‰ and 0.038‰ to 0.104‰, respectively. Iron isotope compositions of both low-Ti and high-Ti basalts do not correlate with indices of crystal fractionation, possibly owing to small mineral-melt iron fractionation factors anticipated under lunar reducing conditions. The δ 18O and δ 56Fe values of low-Ti and the least differentiated high-Ti mare basalts are negatively correlated, which reflects their different mantle source characteristics (e.g., the presence or absence of ilmenite). The average δ 56Fe values of low-Ti basalts (0.073 ± 0.018‰, n = 8) and high-Ti basalts (0.191 ± 0.020‰, n = 7) may directly record that of their parent mantle sources. Oxygen isotope compositions of mantle sources of low-Ti and high-Ti basalts are calculated using existing models of lunar magma ocean crystallization and mixing, the estimated equilibrium mantle olivine δ 18O value, and equilibrium oxygen-fractionation between olivine and other mineral phases. The differences between the calculated whole-rock δ 18O values for source regions, 5.57‰ for low-Ti and 5.30‰ for high-Ti mare basalt mantle source regions

  20. Cell wall sorting of lipoproteins in Staphylococcus aureus.

    PubMed Central

    Navarre, W W; Daefler, S; Schneewind, O

    1996-01-01

    Many surface proteins are thought to be anchored to the cell wall of gram-positive organisms via their C termini, while the N-terminal domains of these molecules are displayed on the bacterial surface. Cell wall anchoring of surface proteins in Staphylococcus aureus requires both an N-terminal leader peptide and a C-terminal cell wall sorting signal. By fusing the cell wall sorting of protein A to the C terminus of staphylococcal beta-lactamase, we demonstrate here that lipoproteins can also be anchored to the cell wall of S. aureus. The topology of cell wall-anchored beta-lactamase is reminiscent of that described for Braun's murein lipoprotein in that the N terminus of the polypeptide chain is membrane anchored whereas the C-terminal end is tethered to the bacterial cell wall. PMID:8550464

  1. Specific Bonds between an Iron Oxide Surface and Outer Membrane Cytochromes MtrC and OmcA from Shewanella oneidensis MR-1

    SciTech Connect

    Lower, Brian H.; Shi, Liang; Yongsunthon, Ruchirej; Droubay, Timothy C.; Mccready, David E.; Lower, Steven

    2007-07-31

    Shewanella oneidensis MR-1 is purported to express outer membrane cytochromes (e.g., MtrC and OmcA) that transfer electrons directly to Fe(III) in a mineral during anaerobic respiration.  A prerequisite for this type of reaction would be the formation of a stable bond between a cytochrome and an iron oxide surface.  Atomic force microscopy (AFM) was used to detect whether a specific bond forms between a hematite (Fe2O3) thin film, created with oxygen plasma assisted molecular beam epitaxy (MBE), and recombinant MtrC or OmcA molecules coupled to gold substrates.  Force spectra displayed a unique force signature indicative of a specific bond between each cytochrome and the hematite surface.  The strength of the OmcA-hematite bond was approximately twice as strong as the MtrC-hematite bond, but direct binding to hematite was twice as favorable for MtrC.  Reversible folding/unfolding reactions were observed for mechanically denatured MtrC molecules bound to hematite.  The force measurements for the hematite-cytochrome pairs were compared to spectra collected between an iron oxide and S. oneidensis under anaerobic conditions.  There is a strong correlation between the whole cell and pure protein force spectra suggesting that the unique binding attributes of each cytochrome complement one another and allow both MtrC and OmcA to play a prominent role in the transfer of electrons to Fe(III) in minerals.  Finally, by comparing the magnitude of binding force for the whole cell vs. pure protein data, we were able to estimate that a single bacterium of S. oneidensis (2 x 0.5 μm) expresses ~104 cytochromes on its outer surface

  2. Laser surface texturing of cast iron steel: dramatic edge burr reduction and high speed process optimisation for industrial production using DPSS picosecond lasers

    NASA Astrophysics Data System (ADS)

    Bruneel, David; Kearsley, Andrew; Karnakis, Dimitris

    2015-07-01

    In this work we present picosecond DPSS laser surface texturing optimisation of automotive grade cast iron steel. This application attracts great interest, particularly in the automotive industry, to reduce friction between moving piston parts in car engines, in order to decrease fuel consumption. This is accomplished by partially covering with swallow microgrooves the inner surface of a piston liner and is currently a production process adopting much longer pulse (microsecond) DPSS lasers. Lubricated interface conditions of moving parts require from the laser process to produce a very strictly controlled surface topography around the laser formed grooves, whose edge burr height must be lower than 100 nm. To achieve such a strict tolerance, laser machining of cast iron steel was investigated using an infrared DPSS picosecond laser (10ps duration) with an output power of 16W and a repetition rate of 200 kHz. The ultrashort laser is believed to provide a much better thermal management of the etching process. All studies presented here were performed on flat samples in ambient air but the process is transferrable to cylindrical geometry engine liners. We will show that reducing significantly the edge burr below an acceptable limit for lubricated engine production is possible using such lasers and remarkably the process window lies at very high irradiated fluences much higher that the single pulse ablation threshold. This detailed experimental work highlights the close relationship between the optimised laser irradiation conditions as well as the process strategy with the final size of the undesirable edge burrs. The optimised process conditions are compatible with an industrial production process and show the potential for removing extra post)processing steps (honing, etc) of cylinder liners on the manufacturing line saving time and cost.

  3. Specific bonds between an iron oxide surface and outer membrane cytochromes MtrC and OmcA from Shewanella oneidensis MR-1.

    PubMed

    Lower, Brian H; Shi, Liang; Yongsunthon, Ruchirej; Droubay, Timothy C; McCready, David E; Lower, Steven K

    2007-07-01

    Shewanella oneidensis MR-1 is purported to express outer membrane cytochromes (e.g., MtrC and OmcA) that transfer electrons directly to Fe(III) in a mineral during anaerobic respiration. A prerequisite for this type of reaction would be the formation of a stable bond between a cytochrome and an iron oxide surface. Atomic force microscopy (AFM) was used to detect whether a specific bond forms between a hematite (Fe(2)O(3)) thin film, created with oxygen plasma-assisted molecular beam epitaxy, and recombinant MtrC or OmcA molecules coupled to gold substrates. Force spectra displayed a unique force signature indicative of a specific bond between each cytochrome and the hematite surface. The strength of the OmcA-hematite bond was approximately twice that of the MtrC-hematite bond, but direct binding to hematite was twice as favorable for MtrC. Reversible folding/unfolding reactions were observed for mechanically denatured MtrC molecules bound to hematite. The force measurements for the hematite-cytochrome pairs were compared to spectra collected for an iron oxide and S. oneidensis under anaerobic conditions. There is a strong correlation between the whole-cell and pure-protein force spectra, suggesting that the unique binding attributes of each cytochrome complement one another and allow both MtrC and OmcA to play a prominent role in the transfer of electrons to Fe(III) in minerals. Finally, by comparing the magnitudes of binding force for the whole-cell versus pure-protein data, we were able to estimate that a single bacterium of S. oneidensis (2 by 0.5 microm) expresses approximately 10(4) cytochromes on its outer surface. PMID:17468239

  4. Specific Bonds between an Iron Oxide Surface and Outer Membrane Cytochromes MtrC and OmcA from Shewanella oneidensis MR-1▿

    PubMed Central

    Lower, Brian H.; Shi, Liang; Yongsunthon, Ruchirej; Droubay, Timothy C.; McCready, David E.; Lower, Steven K.

    2007-01-01

    Shewanella oneidensis MR-1 is purported to express outer membrane cytochromes (e.g., MtrC and OmcA) that transfer electrons directly to Fe(III) in a mineral during anaerobic respiration. A prerequisite for this type of reaction would be the formation of a stable bond between a cytochrome and an iron oxide surface. Atomic force microscopy (AFM) was used to detect whether a specific bond forms between a hematite (Fe2O3) thin film, created with oxygen plasma-assisted molecular beam epitaxy, and recombinant MtrC or OmcA molecules coupled to gold substrates. Force spectra displayed a unique force signature indicative of a specific bond between each cytochrome and the hematite surface. The strength of the OmcA-hematite bond was approximately twice that of the MtrC-hematite bond, but direct binding to hematite was twice as favorable for MtrC. Reversible folding/unfolding reactions were observed for mechanically denatured MtrC molecules bound to hematite. The force measurements for the hematite-cytochrome pairs were compared to spectra collected for an iron oxide and S. oneidensis under anaerobic conditions. There is a strong correlation between the whole-cell and pure-protein force spectra, suggesting that the unique binding attributes of each cytochrome complement one another and allow both MtrC and OmcA to play a prominent role in the transfer of electrons to Fe(III) in minerals. Finally, by comparing the magnitudes of binding force for the whole-cell versus pure-protein data, we were able to estimate that a single bacterium of S. oneidensis (2 by 0.5 μm) expresses ∼104 cytochromes on its outer surface. PMID:17468239

  5. Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP) and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP

    NASA Astrophysics Data System (ADS)

    Sugimura, K.; Miyajima, Y.; Sonehara, M.; Sato, T.; Hayashi, F.; Zettsu, N.; Teshima, K.; Mizusaki, H.

    2016-05-01

    This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO2) was successfully deposited on the CIP-surface by using hydrolysis of TEOS (Si(OC2H5)4). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.

  6. Chitosan-Iron Oxide Coated Graphene Oxide Nanocomposite Hydrogel: A Robust and Soft Antimicrobial Biofilm.

    PubMed

    Konwar, Achyut; Kalita, Sanjeeb; Kotoky, Jibon; Chowdhury, Devasish

    2016-08-17

    We report a robust biofilm with antimicrobial properties fabricated from chitosan-iron oxide coated graphene oxide nanocomposite hydrogel. For the first time, the coprecipitation method was used for the successful synthesis of iron oxide coated graphene oxide (GIO) nanomaterial. After this, films were fabricated by the gel-casting technique aided by the self-healing ability of the chitosan hydrogel network system. Both the nanomaterial and the nanocomposite films were characterized by techniques such as scanning electron microscopy, FT-IR spectroscopy, X-ray diffraction, and vibrating sample magnetometry. Measurements of the thermodynamic stability and mechanical properties of the films indictaed a significant improvement in their thermal and mechanical properties. Moreover, the stress-strain profile indicated the tough nature of the nanocomposite hydrogel films. These improvements, therefore, indicated an effective interaction and good compatibility of the GIO nanomaterial with the chitosan hydrogel matrix. In addition, it was also possible to fabricate films with tunable surface properties such as hydrophobicity simply by varying the loading percentage of GIO nanomaterial in the hydrogel matrix. Fascinatingly, the chitosan-iron oxide coated graphene oxide nanocomposite hydrogel films displayed significant antimicrobial activities against both Gram-positive and Gram-negative bacterial strains, such as methicillin-resistant Staphylococcus aureus, Staphylococcus aureus, and Escherichia coli, and also against the opportunistic dermatophyte Candida albicans. The antimicrobial activities of the films were tested by agar diffusion assay and antimicrobial testing based on direct contact. A comparison of the antimicrobial activity of the chitosan-GIO nanocomposite hydrogel films with those of individual chitosan-graphene oxide and chitosan-iron oxide nanocomposite films demonstrated a higher antimicrobial activity for the former in both types of tests. In vitro hemolysis

  7. Total and labile metals in surface sediments of the tropical river-estuary system of Marabasco (Pacific coast of Mexico): Influence of an iron mine.

    PubMed

    Marmolejo-Rodríguez, Ana Judith; Prego, Ricardo; Meyer-Willerer, Alejandro; Shumilin, Evgueni; Cobelo-García, Antonio

    2007-01-01

    Marabasco is a tropical river-estuary system comprising the Marabasco river and the Barra de Navidad Lagoon. The river is impacted by the Peña Colorada iron mine, which produces 3.5 million tons of pellets per year. Thirteen surface sediment samples were collected in May 2005 (dry season) in order to establish background levels of Al, Cd, Co, Cu, Fe, Ni, Pb, and Zn in the system and to ascertain the potential mobility of metals in the sediments. Analyses were carried out in the fraction finer than 63 microm, and labile metals extracted according the BCR procedure. Certified reference materials were used for validation of methods. Total concentrations of Cd, Co, Cu, Ni, Pb, and Zn were in the range of 0.05-0.34, 6-95, 0.7-31, 9-26, 2-18, and 53-179 mgkg(-1), respectively; Al and Fe ranges of 24-127, and 26-69 mgg(-1) correspondingly. Cadmium was found to be significantly labile in the sediments (20-100%), followed by Co (0-35%), Ni (3-16%) and Zn (0-25%), whereas the labile fraction for Cu, Fe and Pb was almost negligible (<4%). According with the total metal concentrations, background levels and normalised enrichment factors (NEF) of the metals studied, the impact of the Peña Colorada iron mine on the Marabasco system is lower than expected when compared with other similar World systems influenced by mining activities. PMID:17997460

  8. Application of response surface methodology (RSM) for the removal of methylene blue dye from water by nano zero-valent iron (NZVI).

    PubMed

    Khosravi, Morteza; Arabi, Simin

    2016-01-01

    In this study, iron zero-valent nanoparticles were synthesized, characterized and studied for removal of methylene blue dye in water solution. The reactions were mathematically described as the function of parameters such as nano zero-valent iron (NZVI) dose, pH, contact time and initial dye concentration, and were modeled by the use of response surface methodology. These experiments were carried out as a central composite design consisting of 30 experiments determined by the 2(4) full factorial designs with eight axial points and six center points. The results revealed that the optimal conditions for dye removal were NZVI dose 0.1-0.9 g/L, pH 3-11, contact time 20-100 s, and initial dye concentration 10-50 mg/L, respectively. Under these optimal values of process parameters, the dye removal efficiency of 92.87% was observed, which very close to the experimental value (92.21%) in batch experiment. In the optimization, R(2) and R(2)adj correlation coefficients for the model were evaluated as 0.96 and 0.93, respectively. PMID:27438238

  9. Influence of the shape and surface oxidation in the magnetization reversal of thin iron nanowires grown by focused electron beam induced deposition

    PubMed Central

    Córdoba, Rosa; Magén, César; Snoeck, Etienne; Koopmans, Bert

    2015-01-01

    Summary Iron nanostructures grown by focused electron beam induced deposition (FEBID) are promising for applications in magnetic sensing, storage and logic. Such applications require a precise design and determination of the coercive field (H C), which depends on the shape of the nanostructure. In the present work, we have used the Fe2(CO)9 precursor to grow iron nanowires by FEBID in the thickness range from 10 to 45 nm and width range from 50 to 500 nm. These nanowires exhibit an Fe content between 80 and 85%, thus giving a high ferromagnetic signal. Magneto-optical Kerr characterization indicates that H C decreases for increasing thickness and width, providing a route to control the magnetization reversal field through the modification of the nanowire dimensions. Transmission electron microscopy experiments indicate that these wires have a bell-type shape with a surface oxide layer of about 5 nm. Such features are decisive in the actual value of H C as micromagnetic simulations demonstrate. These results will help to make appropriate designs of magnetic nanowires grown by FEBID. PMID:26199835

  10. Influence of the shape and surface oxidation in the magnetization reversal of thin iron nanowires grown by focused electron beam induced deposition.

    PubMed

    Rodríguez, Luis A; Deen, Lorenz; Córdoba, Rosa; Magén, César; Snoeck, Etienne; Koopmans, Bert; De Teresa, José M

    2015-01-01

    Iron nanostructures grown by focused electron beam induced deposition (FEBID) are promising for applications in magnetic sensing, storage and logic. Such applications require a precise design and determination of the coercive field (H C), which depends on the shape of the nanostructure. In the present work, we have used the Fe2(CO)9 precursor to grow iron nanowires by FEBID in the thickness range from 10 to 45 nm and width range from 50 to 500 nm. These nanowires exhibit an Fe content between 80 and 85%, thus giving a high ferromagnetic signal. Magneto-optical Kerr characterization indicates that H C decreases for increasing thickness and width, providing a route to control the magnetization reversal field through the modification of the nanowire dimensions. Transmission electron microscopy experiments indicate that these wires have a bell-type shape with a surface oxide layer of about 5 nm. Such features are decisive in the actual value of H C as micromagnetic simulations demonstrate. These results will help to make appropriate designs of magnetic nanowires grown by FEBID. PMID:26199835

  11. CO2-Brine-Iron-bearing Clay Mineral Interactions: Surface Area Changes and Fracture-Filling Potentials in Geologic CO2 Sequestration

    NASA Astrophysics Data System (ADS)

    Jun, Y.; Hu, Y.

    2011-12-01

    Geologic carbon dioxide sequestration (GCS) is a promising option to reduce anthropogenic CO2 emission from coal-fired power plants. The injected CO2 in GCS sites can induce dissolution of rocks and secondary mineral formation, potentially change the physical properties of the geological formations, and thus influence the transport and injectivity of CO2. However, most of the relevant studies are based on hydrological transport, using simulation models rather than studying actual interfacial chemical reactions. The mechanisms and kinetics of interfacial reactions among supercritical CO2 (scCO2)-saline water-rock surfaces at the molecular scale and their impacts on CO2 leakage have not been well understood. This research investigated the effects of various environmental factors (such as temperature, pressure, salinity, and different metal ion and organic-containing brine) on the dissolution and surface morphological changes of clay minerals. In this work, iron-bearing clay mineral, biotite [K(Mg,Fe)3AlSi3O10(OH,F)2], was used for model clay minerals in potential GCS sites. Both fluid/solid chemistry analysis and interfacial topographic studies were conducted to investigate the dissolution/precipitation on clay mineral surfaces under GCS conditions in high salinity systems. Using atomic force microscopy (AFM) and scanning electron microscopy (SEM), the interfacial surface morphology changes were observed. Shortly after a CO2 pressure of 102 atm is applied at 95oC, in situ pH of solutions was 3.15 ± 0.10. The early intrinsic dissolution rates of biotite were 8.4 ± 2.8 × 10-13 and 11.2 ± 3.0 × 10-13 mol Si m-2s-1 in water and NaCl solution, respectively. At the early stage of reaction, fast growth of fibrous illite on biotite basal planes was observed. After 22-70 h reaction, the biotite basal surface cracked, resulting in illite detaching from the surfaced. Later, the cracked surface layer was released into solution, thus the inner layer was exposed as a renewed

  12. X-ray magnetic circular dichroism photoemission electron microscopy of focused ion beam-induced magnetic patterns on iron-rhodium surfaces

    NASA Astrophysics Data System (ADS)

    Tohki, Atsushi; Aikoh, Kazuma; Shinoda, Ryoichi; Ohkochi, Takuo; Kotsugi, Masato; Nakamura, Tetsuya; Kinoshita, Toyohiko; Iwase, Akihiro; Matsui, Toshiyuki

    2013-05-01

    Iron-rhodium (FeRh) thin films were irradiated with a 30 keV Ga ion beam using a focused ion beam system to produce micrometer scale ferromagnetic square dot arrays. Two-dimensional magnetic square dot arrays with dimensions of 30 × 30, 10 × 10, and 5 × 5 μm were successfully produced on the FeRh surface, which was confirmed by magnetic force microscopy. The results of photoemission electron microscopy combined with X-ray magnetic circular dichroism revealed that the magnetization of the magnetic square dots could be controlled by changing the amount of irradiation. The magnetic domain structure of the magnetic square dots with sides of 5-30 μm was found to be a single domain structure, which was possibly influenced by the interaction between ferromagnetic and antiferromagnetic interfaces.

  13. Mixed-valence iron minerals on Venus: Fe(2+)-Fe(3+) oxides and oxy-silicates formed by surface-atmosphere interactions

    NASA Technical Reports Server (NTRS)

    Burns, Roger G.; Straub, Darcy W.

    1992-01-01

    Inferences from these investigations are that Fe(3+)-bearing minerals such as hematite magnesioferrite, acmite, and epidote are thermodynamically unstable, and that magnetite is the predominant mixed-valence iron oxide mineral on venus. Recently, the Fe(2+)-Fe(3+) silicate mineral laihunite was proposed to be a reaction product of olivine with the venusian atmosphere. This possibility is discussed further here. We suggest that other mixed-valence Fe(2+)-Fe(3+)-Oz-OH(-) silicates could also result from surface-atmosphere interactions on Venus. Topics discussed include the following: (1) conversion of hematite to magnetite; (2) stability of laihunite; (3) the possible existence of oxy-amphiboles and oxy-micas on Venus; and (4) other mixed-valence Fe(2+)-Fe(3+) silicates likely to exist on Venus.

  14. Surface Gasification Materials Program semiannual progress report for the period ending March 31, 1986. [Fe/sub 3/Al (iron aluminides)

    SciTech Connect

    Not Available

    1986-06-01

    The objective of the Surface Gasification Materials Program is to conduct research and development on materials for application to the specific needs of coal gasification systems. One of the goals of the program is to evaluate innovative fabrication methods which have the potential to lower costs and improve reliability and safety for gasifier vessels and components. Another goal is to conduct engineering-scale development and application of materials for coal gasification systems to ensure that the materials of construction for pilot plants and future large-scale plants can be properly selected and specified. Contents of this semiannual progress report include: (1) protective coatings and claddings - application/evaluation; (2) corrosion of structural ceramics in coal gasification environments; (3) electroslag component casting; and (4) development of iron aluminides. 8 figs., 14 tabs.

  15. Seasonal Control of Surface-Water Dissolved Iron Concentrations by Suspended Particle Concentrations on the Northern Gulf of Alaska Continental Shelf and Slope

    NASA Astrophysics Data System (ADS)

    Crusius, J.; Schroth, A. W.; Campbell, R.; Cullen, J. T.; Dillman, D.; Resing, J.

    2012-12-01

    The continental shelf region of the northern Gulf of Alaska (GoA) supports a productive ecosystem including an important commercial fishery. Downwelling winds during most of the year imply that some mechanism other than upwelling must be supplying the essential nutrients iron and nitrate. Although it is well known that iron limits productivity offshore in the GoA, we have a poor understanding of the controls on Fe supply. Data from cruises from 2010 provide some new insight into the mechanisms of Fe supply. Cruises were carried out along a transect extending from the mouth of the Copper River to ~40 km beyond the shelf break three times per year including early April, early May, and late July. High-resolution surface-water sampling was carried out, as well as bottle casts at 5 stations. High, fairly uniform concentrations of "total dissolvable iron" (TDFe; unfiltered sample acidified to pH=1.7) as well as "dissolved" Fe (dFe) were observed spanning the shelf in April, suggesting sediment resuspension is an important source of dFe to surface waters at that time. By contrast, high dFe and TDFe concentrations in late July coincide with low-salinity surface water, which in this location indicates a glacial meltwater source. Throughout spring and summer high particle concentrations across much of the shelf appear to "buffer" dFe concentrations to ~3 nmol/kg, which are close to those observed by Lippiatt et al (2010) in the region. This is consistent with dFe concentrations being determined by the organic ligand concentrations that, in turn, are fairly constant. In late July, surface water dFe concentrations are ~0.5 nmol/kg on the outer shelf and up to ~50 km further offshore. These dFe concentrations on the outer shelf are much lower in July than earlier in the year, owing to Fe removal by phytoplankton uptake and by scavenging, as well as by the lack of particulate Fe sources to surface waters in July. However, the high surface-water dFe observed ~50 km beyond the

  16. A Tactile Response in Staphylococcus aureus

    PubMed Central

    Lower, Steven K.; Yongsunthon, Ruchirej; Casillas-Ituarte, Nadia N.; Taylor, Eric S.; DiBartola, Alex C.; Lower, Brian H.; Beveridge, Terrance J.; Buck, Andrew W.; Fowler, Vance G.

    2010-01-01

    It is well established that bacteria are able to respond to temporal gradients (e.g., by chemotaxis). However, it is widely held that prokaryotes are too small to sense spatial gradients. This contradicts the common observation that the vast majority of bacteria live on the surface of a solid substrate (e.g., as a biofilm). Herein we report direct experimental evidence that the nonmotile bacterium Staphylococcus aureus possesses a tactile response, or primitive sense of touch, that allows it to respond to spatial gradients. Attached cells recognize their substrate interface and localize adhesins toward that region. Braille-like avidity maps reflect a cell's biochemical sensory response and reveal ultrastructural regions defined by the actual binding activity of specific proteins. PMID:21044577

  17. Surface decoration of amine-rich carbon nitride with iron nanoparticles for arsenite (As(III)) uptake: The evolution of the Fe-phases under ambient conditions.

    PubMed

    Georgiou, Y; Mouzourakis, E; Bourlinos, A B; Zboril, R; Karakassides, M A; Douvalis, A P; Bakas, Th; Deligiannakis, Y

    2016-07-15

    A novel hybrid material (gC3N4-rFe) consisting of amine-rich graphitic carbon nitride (gC3N4), decorated with reduced iron nanoparticles (rFe) is presented. XRD and TEM show that gC3N4-rFe bears aggregation-free Fe-nanoparticles (10nm) uniformly dispersed over the gC3N4 surface. In contrast, non-supported iron nanoparticles are strongly aggregated, with non-uniform size distribution (20-100nm). (57)Fe-Mössbauer spectroscopy, dual-mode electron paramagnetic resonance (EPR) and magnetization measurements, allow a detailed mapping of the evolution of the Fe-phases after exposure to ambient O2. The as-prepared gC3N4-rFe bears Fe(2+) and Fe° phases, however only after long exposure to ambient O2, a Fe-oxide layer is formed around the Fe° core. In this [Fe°/Fe-oxide] core-shell configuration, the gC3N4-rFe hybrid shows enhanced As(III) uptake capacity of 76.5mgg(-1), i.e., ca 90% higher than the unmodified carbonaceous support, and 300% higher than the non-supported Fe-nanoparticles. gC3N4-rFe is a superior As(III) sorbent i.e., compared to its single counterparts or vs. graphite/graphite oxide or activated carbon analogues (11-36mgg(-1)). The present results demonstrate that the gC3N4 matrix is not simply a net that holds the particles, but rather an active component that determines particle formation dynamics and ultimately their redox profile, size and surface dispersion homogeneity. PMID:27037479

  18. Haemin represses the haemolytic activity of Staphylococcus aureus in an Sae-dependent manner.

    PubMed

    Schmitt, Julia; Joost, Insa; Skaar, Eric P; Herrmann, Mathias; Bischoff, Markus

    2012-10-01

    Staphylococcus aureus is a major human pathogen and a common cause of nosocomial infections. This facultative pathogen produces a large arsenal of virulence factors, including the haemolysins, which allow the bacterium to lyse erythrocytes and thereby release large amounts of the haem-containing haemoglobin. The released haem is thought to be the main iron source of this organism during the course of infection, and is considered to be crucial for bacterial proliferation in vivo. High concentrations of haem and its degradation products, on the other hand, are known to be toxic for S. aureus, making it essential for the pathogen to tightly control haem release from red blood cells. Here we show that S. aureus responds to haemin by downregulating the expression of haemolysins. Subinhibitory concentrations of haemin were found to significantly reduce transcription of the haemolysin genes hlb (encoding β-haemolysin) and hlgA (encoding the S-class component of γ-haemolysin), while hla (encoding α-haemolysin) and RNAIII (encoding δ-haemolysin) transcription did not appear to be affected. The presence of haemin also reduced the haemolytic potential of the supernatants of S. aureus LS1 cultures. Inactivation of the sae locus in LS1 abolished the haemin effect on the transcription of haemolysin genes, indicating that the two-component regulatory system is required for this regulatory effect. Iron limitation, on the other hand, was found to induce the expression of haemolysins, and this effect was again abolished in the sae mutant, indicating that S. aureus modulates its haemolysin production in response to iron and haem availability in an Sae-dependent manner. PMID:22859613

  19. Hyperspectral surface materials map of quadrangle 3364, Pasaband (417) and Markaz-e Kajiran (418) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  20. Hyperspectral surface materials map of quadrangle 3266, Uruzgan (519) and Moqur (520) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Giles, Stuart A.; Johnson, Michaela R.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  1. Hyperspectral surface materials map of quadrangle 3770, Faizabad (217) and Parkhaw (218) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Giles, Stuart A.; Johnson, Michaela R.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  2. Hyperspectral surface materials map of quadrangle 3362, Shindand (415) and Tulak (416) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Giles, Stuart A.; Johnson, Michaela R.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  3. Hyperspectral surface materials map of quadrangle 3562, Khawja-Jir (403) and Murghab (404) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  4. Hyperspectral surface materials map of quadrangle 3568, Pul-e Khumri (503) and Charikar (504) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  5. Hyperspectral surface materials map of quadrangle 3366, Gizab (513) and Nawer (514) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  6. Hyperspectral surface materials map of quadrangle 3564, Jowand (405) and Gurziwan (406) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  7. Hyperspectral surface materials map of quadrangle 3570, Tagab-e-Munjan (505) and Asmar-Kamdesh (506) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  8. Hyperspectral surface materials map of quadrangle 3264, Naw Zad-Musa Qala (423) and Dihrawud (424) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  9. Hyperspectral surface materials map of quadrangle 3368, Ghazni (515) and Gardez (516) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  10. Hyperspectral surface materials map of quadrangle 3162, Chakhansur (603) and Kotalak (604) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  11. Hyperspectral surface materials map of quadrangle 3566, Sangcharak (501) and Sayghan-o-Kamard (502) quadrangles, Afghanistan, showing iron-bearing minerals and other material

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Giles, Stuart A.; Johnson, Michaela R.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  12. Hyperspectral surface materials map of quadrangle 3260, Dasht-e-Chah-e-Mazar (419) and Anar Darah (420) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  13. Hyperspectral Surface Materials Map of Quadrangle 3268, Khayr Kot (521) and Urgun (522) Quadrangles, Afghanistan, Showing Iron-bearing Minerals and Other Materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Giles, Stuart A.; Johnson, Michaela R.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  14. Hyperspectral surface materials map of quadrangle 3262, Farah (421) and Hokumat-e-pur-Chaman (422) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  15. Hyperspectral surface materials map of quadrangle 3166, Jaldak (701) and Maruf-Nawa (702) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Giles, Stuart A.; Johnson, Michaela R.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  16. Hyperspectral surface materials map of quadrangle 3164, Lashkar Gah (605) and Kandahar (606) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  17. Hyperspectral surface materials map of quadrangle 3462, Herat (409) and Chishti Sharif (410) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  18. Hyperspectral surface materials map of quadrangle 3464, Shahrak (411) and Kasi (412) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  19. Hyperspectral surface materials map of quadrangle 3466, La`l wa Sar Jangal (507) and Bamyan (508) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Giles, Stuart A.; Johnson, Michaela R.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  20. Hyperspectral surface materials map of quadrangle 3468, Chak-e Wardak-Siyahgird (509) and Kabul (510) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Giles, Stuart A.; Johnson, Michaela R.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  1. Hyperspectral surface materials map of quadrangle 3670, Jurm-Kishim (223) and Zebak (224) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, Todd M.; Kokaly, Raymond F.; Livo, Keith E.; Johnson, Michaela R.; Giles, Stuart A.

    2013-01-01

    This map shows the spatial distribution of selected iron-bearing minerals and other materials derived from analysis of airborne HyMap™ imaging spectrometer (hyperspectral) data of Afghanistan collected in late 2007. This map is one in a series of U.S. Geological Survey/Afghanistan Geological Survey quadrangle maps covering Afghanistan. Flown at an altitude of 50,000 feet (15,240 meters (m)), the HyMap™ imaging spectrometer measured reflected sunlight in 128 channels, covering wavelengths between 0.4 and 2.5 μm. The data were georeferenced, atmospherically corrected and converted to apparent surface reflectance, empirically adjusted using ground-based reflectance measurements, and combined into a mosaic with 23-m pixel spacing. Variations in water vapor and dust content of the atmosphere, in solar angle, and in surface elevation complicated correction; therefore, some classification differences may be present between adjacent flight lines. The reflectance spectrum of each pixel of HyMap™ imaging spectrometer data was compared to the reference materials in a spectral library of minerals, vegetation, water, and other materials. Minerals occurring abundantly at the surface and those having unique spectral features were easily detected and discriminated, while minerals having slightly different compositions but similar spectral features were less easily discriminated; thus, some map classes consist of several minerals having similar spectra, such as “Goethite and jarosite.” A designation of “Not classified” was assigned to the pixel when there was no match with reference spectra.

  2. Hyperspectral surface materials map of quadrangle 3470, Jalalabad (511) and Chaghasaray (512) quadrangles, Afghanistan, showing iron-bearing minerals and other materials

    USGS Publications Warehouse

    King, Trude V.V.; Hoefen, T