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Sample records for active site zinc

  1. Active-site zinc ligands and activated H2O of zinc enzymes.

    PubMed Central

    Vallee, B L; Auld, D S

    1990-01-01

    The x-ray crystallographic structures of 12 zinc enzymes have been chosen as standards of reference to identify the ligands to the catalytic and structural zinc atoms of other members of their respective enzyme families. Universally, H2O is a ligand and critical component of the catalytically active zinc sites. In addition, three protein side chains bind to the catalytic zinc atom, whereas four protein ligands bind to the structural zinc atom. The geometry and coordination number of zinc can vary greatly to accommodate particular ligands. Zinc forms complexes with nitrogen and oxygen just as readily as with sulfur, and this is reflected in catalytic zinc sites having a binding frequency of His much greater than Glu greater than Asp = Cys, three of which bind to the metal atom. The systematic spacing between the ligands is striking. For all catalytic zinc sites except the coenzyme-dependent alcohol dehydrogenase, the first two ligands are separated by a "short-spacer" consisting of 1 to 3 amino acids. These ligands are separated from the third ligand by a "long spacer" of approximately 20 to approximately 120 amino acids. The spacer enables formation of a primary bidentate zinc complex, whereas the long spacer contributes flexibility to the coordination sphere, which can poise the zinc for catalysis as well as bring other catalytic and substrate binding groups into apposition with the active site. The H2O is activated by ionization, polarization, or poised for displacement. Collectively, the data imply that the preferred mechanistic pathway for activating the water--e.g., zinc hydroxide or Lewis acid catalysis--will be determined by the identity of the other three ligands and their spacing. Images PMID:2104979

  2. Large zinc cation occupancy of octahedral sites in mechanically activated zinc ferrite powders

    SciTech Connect

    Oliver, S. A.; Harris, V. G.; Hamdeh, H. H.; Ho, J. C.

    2000-05-08

    The cation site occupancy of a mechanically activated nanocrystalline zinc ferrite powder was determined as (Zn{sub 0.55}{sup 2+}Fe{sub 0.18}{sup 3+}){sub tet}[Zr{sub 0.45}{sup 2+}Fe{sub 1.82}{sup 3+}]{sub oct}O{sub 4} through analysis of extended x-ray absorption fine structure measurements, showing a large redistribution of cations between sites compared to normal zinc ferrite samples. The overpopulation of cations in the octahedral sites was attributed to the ascendance in importance of the ionic radii over the crystal energy and bonding coordination in determining which interstitial sites are occupied in this structurally disordered powder. Slight changes are observed in the local atomic environment about the zinc cations, but not the iron cations, with respect to the spinel structure. The presence of Fe{sup 3+} on both sites is consistent with the measured room temperature magnetic properties. (c) 2000 American Institute of Physics.

  3. Kv3 channel assembly, trafficking and activity are regulated by zinc through different binding sites.

    PubMed

    Gu, Yuanzheng; Barry, Joshua; Gu, Chen

    2013-05-15

    Zinc, a divalent heavy metal ion and an essential mineral for life, regulates synaptic transmission and neuronal excitability via ion channels. However, its binding sites and regulatory mechanisms are poorly understood. Here, we report that Kv3 channel assembly, localization and activity are regulated by zinc through different binding sites. Local perfusion of zinc reversibly reduced spiking frequency of cultured neurons most likely by suppressing Kv3 channels. Indeed, zinc inhibited Kv3.1 channel activity and slowed activation kinetics, independent of its site in the N-terminal T1 domain. Biochemical assays surprisingly identified a novel zinc-binding site in the Kv3.1 C-terminus, critical for channel activity and axonal targeting, but not for the zinc inhibition. Finally, mutagenesis revealed an important role of the junction between the first transmembrane (TM) segment and the first extracellular loop in sensing zinc. Its mutant enabled fast spiking with relative resistance to the zinc inhibition. Therefore, our studies provide novel mechanistic insights into the multifaceted regulation of Kv3 channel activity and localization by divalent heavy metal ions.

  4. The metalloregulatory zinc site in Streptococcus pneumoniae AdcR, a zinc-activated MarR-family repressor

    PubMed Central

    Reyes-Caballero, Hermes; Guerra, Alfredo J.; Jacobsen, Faith E.; Kazmierczak, Krystyna M.; Cowart, Darin; Koppolu, Uma Mahendra Kumar; Scott, Robert A.; Winkler, Malcolm E.; Giedroc, David P.

    2010-01-01

    Streptococcus pneumoniae D39 AdcR (adhesin competence repressor) is the first metal-sensing member of the MarR (multiple antibiotic resistance repressor) family to be characterized. Expression profiling with a ΔadcR strain grown in liquid culture (brain heart infusion; BHI) under microaerobic conditions reveals upregulation of 13 genes including adcR and adcCBA, encoding a high affinity ABC uptake system for zinc, and genes encoding cell-surface zinc-binding pneumococcal histidine triad (Pht) proteins and AdcAII (Lmb, laminin binding). The ΔadcR, H108Q and H112Q adcR mutant allelic strains grown in 0.2 mM Zn(II) exhibit a slow-growth phenotype and a ≈2-fold increase in cell-associated Zn(II). Apo- and Zn(II)-bound AdcR are homodimers in solution and binding to a 28-mer DNA containing an adc operator is strongly stimulated by Zn(II) with KDNA-Zn = 2.4 ×108 M−1 (pH 6.0, 0.2 M NaCl, 25 °C). AdcR binds two Zn(II) per dimer, with step-wise Zn(II) affinities KZn1 and KZn2 of ≥109 M−1 at pH 6.0 and ≥1012 M−1 at pH 8.0. X-ray absorption spectroscopy (XAS) of the high affinity site reveals a pentacoordinate N/O complex and no cysteine coordination, the latter finding corroborated by wild-type-like functional properties of C30A AdcR. Alanine substitution of conserved residues His42 in the DNA binding domain, and His108 and His112 in the C-terminal regulatory domain, abolish high affinity Zn(II) binding and greatly reduce Zn(II)-activated binding to DNA. NMR studies reveal that these mutants adopt the same folded conformation as dimeric wild-type apo AdcR, but fail to conformationally switch upon Zn(II) binding. These studies clearly identify His42, His108 and H112 as metalloregulatory zinc ligands in S. pneumoniae AdcR. PMID:20804771

  5. Conformational changes associated with the binding of zinc acetate at the putative active site of XcTcmJ, a cupin from Xanthomonas campestris pv. campestris

    PubMed Central

    Axelrod, Herbert L.; Kozbial, Piotr; McMullan, Daniel; Krishna, S. Sri; Miller, Mitchell D.; Abdubek, Polat; Acosta, Claire; Astakhova, Tamara; Carlton, Dennis; Caruthers, Jonathan; Chiu, Hsiu-Ju; Clayton, Thomas; Deller, Marc C.; Duan, Lian; Elias, Ylva; Feuerhelm, Julie; Grzechnik, Slawomir K.; Grant, Joanna C.; Han, Gye Won; Jaroszewski, Lukasz; Jin, Kevin K.; Klock, Heath E.; Knuth, Mark W.; Kumar, Abhinav; Marciano, David; Morse, Andrew T.; Murphy, Kevin D.; Nigoghossian, Edward; Okach, Linda; Oommachen, Silvya; Paulsen, Jessica; Reyes, Ron; Rife, Christopher L.; Tien, Henry J.; Trout, Christina V.; van den Bedem, Henry; Weekes, Dana; White, Aprilfawn; Xu, Qingping; Zubieta, Chloe; Hodgson, Keith O.; Wooley, John; Elsliger, Marc-André; Deacon, Ashley M.; Godzik, Adam; Lesley, Scott A.; Wilson, Ian A.

    2010-01-01

    In the plant pathogen Xanthomonas campestris pv. campestris, the product of the tcmJ gene, XcTcmJ, encodes a protein belonging to the RmlC family of cupins. XcTcmJ was crystallized in a monoclinic space group (C2) in the presence of zinc acetate and the structure was determined to 1.6 Å resolution. Previously, the apo structure has been reported in the absence of any bound metal ion [Chin et al. (2006 ▶), Proteins, 65, 1046–1050]. The most significant difference between the apo structure and the structure of XcTcmJ described here is a reorganization of the binding site for zinc acetate, which was most likely acquired from the crystallization solution. This site is located in the conserved metal ion-binding domain at the putative active site of XcTcmJ. In addition, an acetate was also bound within coordination distance of the zinc. In order to accommodate this binding, rearrangement of a conserved histidine ligand is required as well as several nearby residues within and around the putative active site. These observations indicate that binding of zinc serves a functional role in this cupin protein. PMID:20944231

  6. Conformational changes associated with the binding of zinc acetate at the putative active site of XcTcmJ, a cupin from Xanthomonas campestris pv. campestris.

    PubMed

    Axelrod, Herbert L; Kozbial, Piotr; McMullan, Daniel; Krishna, S Sri; Miller, Mitchell D; Abdubek, Polat; Acosta, Claire; Astakhova, Tamara; Carlton, Dennis; Caruthers, Jonathan; Chiu, Hsiu Ju; Clayton, Thomas; Deller, Marc C; Duan, Lian; Elias, Ylva; Feuerhelm, Julie; Grzechnik, Slawomir K; Grant, Joanna C; Han, Gye Won; Jaroszewski, Lukasz; Jin, Kevin K; Klock, Heath E; Knuth, Mark W; Kumar, Abhinav; Marciano, David; Morse, Andrew T; Murphy, Kevin D; Nigoghossian, Edward; Okach, Linda; Oommachen, Silvya; Paulsen, Jessica; Reyes, Ron; Rife, Christopher L; Tien, Henry J; Trout, Christina V; van den Bedem, Henry; Weekes, Dana; White, Aprilfawn; Xu, Qingping; Zubieta, Chloe; Hodgson, Keith O; Wooley, John; Elsliger, Marc André; Deacon, Ashley M; Godzik, Adam; Lesley, Scott A; Wilson, Ian A

    2010-10-01

    In the plant pathogen Xanthomonas campestris pv. campestris, the product of the tcmJ gene, XcTcmJ, encodes a protein belonging to the RmlC family of cupins. XcTcmJ was crystallized in a monoclinic space group (C2) in the presence of zinc acetate and the structure was determined to 1.6 Å resolution. Previously, the apo structure has been reported in the absence of any bound metal ion [Chin et al. (2006), Proteins, 65, 1046-1050]. The most significant difference between the apo structure and the structure of XcTcmJ described here is a reorganization of the binding site for zinc acetate, which was most likely acquired from the crystallization solution. This site is located in the conserved metal ion-binding domain at the putative active site of XcTcmJ. In addition, an acetate was also bound within coordination distance of the zinc. In order to accommodate this binding, rearrangement of a conserved histidine ligand is required as well as several nearby residues within and around the putative active site. These observations indicate that binding of zinc serves a functional role in this cupin protein.

  7. Inhibitory sites in enzymes: zinc removal and reactivation by thionein.

    PubMed

    Maret, W; Jacob, C; Vallee, B L; Fischer, E H

    1999-03-02

    Thionein (T) has not been isolated previously from biological material. However, it is generated transiently in situ by removal of zinc from metallothionein under oxidoreductive conditions, particularly in the presence of selenium compounds. T very rapidly activates a group of enzymes in which zinc is bound at an inhibitory site. The reaction is selective, as is apparent from the fact that T does not remove zinc from the catalytic sites of zinc metalloenzymes. T instantaneously reverses the zinc inhibition with a stoichiometry commensurate with its known capacity to bind seven zinc atoms in the form of clusters in metallothionein. The zinc inhibition is much more pronounced than was previously reported, with dissociation constants in the low nanomolar range. Thus, T is an effective, endogenous chelating agent, suggesting the existence of a hitherto unknown and unrecognized biological regulatory system. T removes the metal from an inhibitory zinc-specific enzymatic site with a resultant marked increase of activity. The potential significance of this system is supported by the demonstration of its operations in enzymes involved in glycolysis and signal transduction.

  8. The structure of sedoheptulose-7-phosphate isomerase from Burkholderia pseudomallei reveals a zinc binding site at the heart of the active site.

    PubMed

    Harmer, Nicholas J

    2010-07-16

    Heptoses are found in the surface polysaccharides of most bacteria, contributing to structures that are essential for virulence and antibiotic resistance. Consequently, the biosynthetic enzymes for these sugars are attractive targets for novel antibiotics. The best characterized biosynthetic enzyme is GmhA, which catalyzes the conversion of sedoheptulose-7-phosphate into D-glycero-D-manno-heptopyranose-7-phosphate, the first step in the biosynthesis of heptose. Here, the structure of GmhA from Burkholderia pseudomallei is reported. This enzyme contains a zinc ion at the heart of its active site: this ion stabilizes the active, closed form of the enzyme and presents coordinating side chains as a potential acid and base to drive catalysis. A complex with the product demonstrates that the enzyme retains activity in the crystal and thus suggests that the closed conformation is catalytically relevant and is an excellent target for the development of therapeutics. A revised mechanism for the action of GmhA is postulated on the basis of this structure and the activity of B. pseudomallei GmhA mutants.

  9. Influence of zinc on bacterial populations and their proteolytic enzyme activities in freshwater environments: a cross-site comparison.

    PubMed

    Rasmussen, Lauren; Olapade, Ola A

    2016-04-01

    Temporal responses of indigenous bacterial populations and proteolytic enzyme (i.e., aminopeptidase) activities in the bacterioplankton assemblages from 3 separate freshwater environments were examined after exposure to various zinc (Zn) concentrations under controlled microcosm conditions. Zn concentrations (ranging from 0 to 10 μmol/L) were added to water samples collected from the Kalamazoo River, Rice Creek, and Huron River and examined for bacterial abundance and aminopeptidase activities at various time intervals over a 48 h incubation period in the dark. The results showed that the Zn concentrations did not significantly influence total bacterial counts directly; however, aminopeptidase activities varied significantly to increasing zinc treatments over time. Also, analysis of variance and linear regression analyses revealed significant positive relationships between bacterial numbers and their hydrolytic enzyme activities, suggesting that both probably co-vary with increasing Zn concentrations in aquatic systems. The results from this study serve as additional evidence of the ecological role of Zn as an extracellular peptidase cofactor on the dynamics of bacterial assemblages in aquatic environments.

  10. Effects of Zinc on Particulate Methane Monooxygenase Activity and Structure*

    PubMed Central

    Sirajuddin, Sarah; Barupala, Dulmini; Helling, Stefan; Marcus, Katrin; Stemmler, Timothy L.; Rosenzweig, Amy C.

    2014-01-01

    Particulate methane monooxygenase (pMMO) is a membrane-bound metalloenzyme that oxidizes methane to methanol in methanotrophic bacteria. Zinc is a known inhibitor of pMMO, but the details of zinc binding and the mechanism of inhibition are not understood. Metal binding and activity assays on membrane-bound pMMO from Methylococcus capsulatus (Bath) reveal that zinc inhibits pMMO at two sites that are distinct from the copper active site. The 2.6 Å resolution crystal structure of Methylocystis species strain Rockwell pMMO reveals two previously undetected bound lipids, and metal soaking experiments identify likely locations for the two zinc inhibition sites. The first is the crystallographic zinc site in the pmoC subunit, and zinc binding here leads to the ordering of 10 previously unobserved residues. A second zinc site is present on the cytoplasmic side of the pmoC subunit. Parallels between these results and zinc inhibition studies of several respiratory complexes suggest that zinc might inhibit proton transfer in pMMO. PMID:24942740

  11. Alternative zinc-binding sites explain the redox sensitivity of zinc-containing anti-sigma factors.

    PubMed

    Heo, Lim; Cho, Yoo-Bok; Lee, Myeong Sup; Roe, Jung-Hye; Seok, Chaok

    2013-09-01

    Certain bacterial zinc-containing anti-sigma (ZAS) factors respond sensitively to thiol-induced oxidative stress by undergoing conformational changes, which in turn reduce binding affinities for their cognate sigma factors. This redox sensitivity provides a mechanism for coping with oxidative stress by activating the transcription of antioxidant genes. Not all ZAS proteins are redox-sensitive, but the mechanism of redox sensitivity is not fully understood. Here we propose that alternative zinc-binding sites determine redox sensitivity. To support this proposal, we performed protein modeling and zinc docking on redox-sensitive and redox-insensitive ZAS proteins complexed with their cognate sigma factors. At least one strong alternative zinc-binding pocket was detected for all known redox-sensitive ZAS factors in actinomycetes, while no strong alternative zinc-binding pocket was identified in redox-insensitive ZAS factors, except for one controversial case. This hypothesis of alternative zinc-binding sites can also explain residue-specific contributions to the redox sensitivity of RsrA, a redox-sensing ZAS protein from Streptomyces coelicolor, for which alanine mutagenesis experiments are available. Our results suggest a mechanistic model for redox sensitivity as follows: zinc ion can probabilistically occupy multiple sites in redox-sensitive ZAS proteins, increasing the susceptibility of zinc-coordinating cysteine residues to oxidation. This picture of probabilistic zinc occupation agrees with a previous structure and energy analysis on zinc finger proteins, and thus it may be more widely applicable to other classes of reactive zinc-binding proteins.

  12. Analysis of zinc binding sites in protein crystal structures.

    PubMed Central

    Alberts, I. L.; Nadassy, K.; Wodak, S. J.

    1998-01-01

    The geometrical properties of zinc binding sites in a dataset of high quality protein crystal structures deposited in the Protein Data Bank have been examined to identify important differences between zinc sites that are directly involved in catalysis and those that play a structural role. Coordination angles in the zinc primary coordination sphere are compared with ideal values for each coordination geometry, and zinc coordination distances are compared with those in small zinc complexes from the Cambridge Structural Database as a guide of expected trends. We find that distances and angles in the primary coordination sphere are in general close to the expected (or ideal) values. Deviations occur primarily for oxygen coordinating atoms and are found to be mainly due to H-bonding of the oxygen coordinating ligand to protein residues, bidentate binding arrangements, and multi-zinc sites. We find that H-bonding of oxygen containing residues (or water) to zinc bound histidines is almost universal in our dataset and defines the elec-His-Zn motif. Analysis of the stereochemistry shows that carboxyl elec-His-Zn motifs are geometrically rigid, while water elec-His-Zn motifs show the most geometrical variation. As catalytic motifs have a higher proportion of carboxyl elec atoms than structural motifs, they provide a more rigid framework for zinc binding. This is understood biologically, as a small distortion in the zinc position in an enzyme can have serious consequences on the enzymatic reaction. We also analyze the sequence pattern of the zinc ligands and residues that provide elecs, and identify conserved hydrophobic residues in the endopeptidases that also appear to contribute to stabilizing the catalytic zinc site. A zinc binding template in protein crystal structures is derived from these observations. PMID:10082367

  13. Zinc ions as cytochrome C oxidase inhibitors: two sites of action.

    PubMed

    Kuznetsova, S S; Azarkina, N V; Vygodina, T V; Siletsky, S A; Konstantinov, A A

    2005-02-01

    Zinc ions are shown to be an efficient inhibitor of mitochondrial cytochrome c oxidase activity, both in the solubilized and the liposome-reconstituted enzyme. The effect of zinc is biphasic. First there occurs rapid interaction of zinc with the enzyme at a site exposed to the aqueous phase corresponding to the mitochondrial matrix. This interaction is fully reversed by EDTA and results in a partial inhibition of the enzyme activity (50-90%, depending on preparation) with an effective K(i) of approximately 10 microM. The rapid effect of zinc is observed with the solubilized enzyme, it vanishes upon incorporation of cytochrome oxidase in liposomes, and it re-appears when proteoliposomes are supplied with alamethicin that makes the membrane permeable to low molecular weight substances. Zinc presumably blocks the entrance of the D-protonic channel opening into the inner aqueous phase. Second, zinc interacts slowly (tens of minutes, hours) with a site of cytochrome oxidase accessible from the outer aqueous phase bringing about complete inhibition of the enzymatic activity. The slow phase is characterized by high affinity of the inhibitor for the enzyme: full inhibition can be achieved upon incubation of the solubilized oxidase for 24 h with zinc concentration as low as 2 microM. The rate of zinc inhibitory action in the slow phase is proportional to Zn(2+) concentration. The slow interaction of zinc with the outer surface of liposome-reconstituted cytochrome oxidase is observed only with the enzyme turning over or in the presence of weak reductants, whereas incubation of zinc with the fully oxidized proteoliposomes does not induce the inhibition. It is shown that zinc ions added to cytochrome oxidase proteoliposomes from the outside inhibit specifically the slow electrogenic phase of proton transfer, coupled to a transition of cytochrome oxidase from the oxo-ferryl to the oxidized state (the F --> O step corresponding to transfer of the 4th electron in the catalytic

  14. Zinc-induced oligomerization of zinc α2 glycoprotein reveals multiple fatty acid-binding sites.

    PubMed

    Zahid, Henna; Miah, Layeque; Lau, Andy M; Brochard, Lea; Hati, Debolina; Bui, Tam T T; Drake, Alex F; Gor, Jayesh; Perkins, Stephen J; McDermott, Lindsay C

    2016-01-01

    Zinc α2 glycoprotein (ZAG) is an adipokine with a class I MHC protein fold and is associated with obesity and diabetes. Although its intrinsic ligand remains unknown, ZAG binds the dansylated C11 fatty acid 11-(dansylamino)undecanoic acid (DAUDA) in the groove between the α1 and α2 domains. The surface of ZAG has approximately 15 weak zinc-binding sites deemed responsible for precipitation from human plasma. In the present study the functional significance of these metal sites was investigated. Analytical ultracentrifugation (AUC) and CD showed that zinc, but not other divalent metals, causes ZAG to oligomerize in solution. Thus ZAG dimers and trimers were observed in the presence of 1 and 2 mM zinc. Molecular modelling of X-ray scattering curves and sedimentation coefficients indicated a progressive stacking of ZAG monomers, suggesting that the ZAG groove may be occluded in these. Using fluorescence-detected sedimentation velocity, these ZAG-zinc oligomers were again observed in the presence of the fluorescent boron dipyrromethene fatty acid C16-BODIPY (4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-hexadecanoic acid). Fluorescence spectroscopy confirmed that ZAG binds C16-BODIPY. ZAG binding to C16-BODIPY, but not to DAUDA, was reduced by increased zinc concentrations. We conclude that the lipid-binding groove in ZAG contains at least two distinct fatty acid-binding sites for DAUDA and C16-BODIPY, similar to the multiple lipid binding seen in the structurally related immune protein CD1c. In addition, because high concentrations of zinc occur in the pancreas, the perturbation of these multiple lipid-binding sites by zinc may be significant in Type 2 diabetes where dysregulation of ZAG and zinc homoeostasis occurs.

  15. The X-ray Structure of a BAK Homodimer Reveals an Inhibitory Zinc Binding Site

    SciTech Connect

    Modoveanu,T.; Liu, Q.; Tocilj, A.; Watson, M.; Shore, G.; Gehring, K.

    2006-01-01

    BAK/BAX-mediated mitochondrial outer-membrane permeabilization (MOMP) drives cell death during development and tissue homeostasis from zebrafish to humans. In most cancers, this pathway is inhibited by BCL-2 family antiapoptotic members, which bind and block the action of proapoptotic BCL proteins. We report the 1.5 {angstrom} crystal structure of calpain-proteolysed BAK, cBAK, to reveal a zinc binding site that regulates its activity via homodimerization. cBAK contains an occluded BH3 peptide binding pocket that binds a BID BH3 peptide only weakly . Nonetheless, cBAK requires activation by truncated BID to induce cytochrome c release in mitochondria isolated from bak/bax double-knockout mouse embryonic fibroblasts. The BAK-mediated MOMP is inhibited by low micromolar zinc levels. This inhibition is alleviated by mutation of the zinc-coordination site in BAK. Our results link directly the antiapoptotic effects of zinc to BAK.

  16. Notification: Evaluation of Cherryvale, Kansas National Zinc Company site

    EPA Pesticide Factsheets

    July 12, 2012. The purpose of this memorandum is to notify you that the OIG plans to conduct a review ofthe process followed by EPA Region 7 in the handling of site related contamination at the Cherryvale, Kansas National Zinc Company site.

  17. The dynamics of zinc sites in proteins: electronic basis for coordination sphere expansion at structural sites.

    PubMed

    Daniel, A Gerard; Farrell, Nicholas P

    2014-12-01

    The functional role assumed by zinc in proteins is closely tied to the variable dynamics around its coordination sphere arising by virtue of its flexibility in bonding. Modern experimental and computational methods allow the detection and study of previously unknown features of bonding between zinc and its ligands in protein environment. These discoveries are occurring just in time as novel biological functions of zinc, which involve rather unconventional coordination trends, are emerging. In this sense coordination sphere expansion of structural zinc sites, as observed in our previous experiments, is a novel phenomenon. Here we explore the electronic and structural requirements by simulating this phenomenon in structural zinc sites using DFT computations. For this purpose, we have chosen MPW1PW91 and a mixed basis set combination as the DFT method through benchmarking, because it accurately reproduces structural parameters of experimentally characterized zinc compounds. Using appropriate models, we show that the greater ionic character of zinc coordination would allow for coordination sphere expansion if the steric and electrostatic repulsions of the ligands are attenuated properly. Importantly, through the study of electronic and structural aspects of the models used, we arrive at a comprehensive bonding model, explaining the factors that influence coordination of zinc in proteins. The proposed model along with the existing knowledge would enhance our ability to predict zinc binding sites in proteins, which is today of growing importance given the predicted enormity of the zinc proteome.

  18. Synergic Effect of Active Sites in Zinc-Modified ZSM-5 Zeolites as Revealed by High-Field Solid-State NMR Spectroscopy.

    PubMed

    Qi, Guodong; Wang, Qiang; Xu, Jun; Trébosc, Julien; Lafon, Olivier; Wang, Chao; Amoureux, Jean-Paul; Deng, Feng

    2016-12-19

    Understanding the nature of active sites in metal-supported catalysts is of great importance towards establishing their structure-property relationships. The outstanding catalytic performance of metal-supported catalysts is frequently ascribed to the synergic effect of different active sites, which is however not well spectroscopically characterized. Herein, we report the direct detection of surface Zn species and (1) H-(67) Zn internuclear interaction between Zn(2+) ions and Brønsted acid sites on Zn-modified ZSM-5 zeolites by high-field solid-state NMR spectroscopy. The observed promotion of C-H bond activation of methane is rationalized by the enhanced Brønsted acidity generated by synergic effects arising from the spatial proximity/interaction between Zn(2+) ions and Brønsted acidic protons. The concentration of synergic active sites is determined by (1) H-(67) Zn double-resonance solid-state NMR spectroscopy.

  19. The micronutrient element zinc modulates sperm activation through the SPE-8 pathway in Caenorhabditis elegans.

    PubMed

    Liu, Zhiyu; Chen, Lianwan; Shang, Yunlong; Huang, Ping; Miao, Long

    2013-05-01

    Immotile spermatids produced in the testis must undergo a series of poorly understood morphological, physiological and biochemical processes called sperm activation to become motile, fertilization-competent spermatozoa. In Caenorhabditis elegans, the spe-8 group contains sperm-specific genes active in both males and hermaphrodites, although their activity is required only for hermaphrodite self-sperm activation. The activating signal upstream of the SPE-8 signaling cascade remains unknown. Here, we show that the micronutrient zinc is sufficient to trigger sperm activation in vitro, and that extracellular zinc induces the intracellular redistribution of labile zinc. We demonstrate that other activating signals promote the similar redistribution of labile zinc, indicating that zinc might have first and/or second messenger roles during sperm activation. Moreover, zinc-induced sperm activation is SPE-8 pathway dependent. Labile zinc was enriched in the spermatheca, the normal site for self-sperm activation in hermaphrodites. High levels of zinc were also found in the secretory cells in the male gonad, suggesting that zinc might be secreted from these cells during copulation and become a component of seminal fluid, to modulate sperm activation post-copulation. These data indicate that zinc regulates sperm activation in both male and hermaphrodite C. elegans, a finding with important implications for understanding hermaphroditic evolution.

  20. Oxygen in activator centers of zinc sulfide

    SciTech Connect

    Golobeva, N.P.; Fok, M.V.

    1986-05-01

    The authors observed the sensitized luminescence of Tm and Dy without addition of Cu and Ag in samples which had been obtained by the sulfonation of zinc sulfide in hydrogen sulfide; the zinc sulfide has a copper concentration below 5.10/sup -6/ mass %. In this case the excitation can be transmitted from the ZnS lattice to the rare-earth activators mainly through defects including oxygen. The following conclusions were made. In the case of activated ZnS, oxygen is present in formations accounting for the excitation and luminescence of a number of luminophors. When an activator is introduced in the region of ZnS layer faults, where also the oxygen must be located, the positioning of the faults in close vicinity is facilitated even when the oxygen concentration of the ZnS is low. All this must be considered when models of luminescence centers of zinc sulfide are developed.

  1. Probing the Protonation State and the Redox-Active Sites of Pendant Base Iron(II) and Zinc(II) Pyridinediimine Complexes.

    PubMed

    Delgado, Mayra; Sommer, Samantha K; Swanson, Seth P; Berger, Robert F; Seda, Takele; Zakharov, Lev N; Gilbertson, John D

    2015-08-03

    Utilizing the pyridinediimine ligand [(2,6-(i)PrC6H3)N═CMe)(N((i)Pr)2C2H4)N═CMe)C5H3N] (didpa), the zinc(II) and iron(II) complexes Zn(didpa)Cl2 (1), Fe(didpa)Cl2 (2), [Zn(Hdidpa)Cl2][PF6] (3), [Fe(Hdidpa)Cl2][PF6] (4), Zn(didpa)Br2 (5), and [Zn(Hdidpa)Br2][PF6] (6), Fe(didpa)(CO)2 (7), and [Fe(Hdidpa)(CO)2][PF6] (8) were synthesized and characterized. These complexes allowed for the study of the secondary coordination sphere pendant base and the redox-activity of the didpa ligand scaffold. The protonated didpa ligand is capable of forming metal halogen hydrogen bonds (MHHBs) in complexes 3, 4, and 6. The solution behavior of the MHHBs was probed via pKa measurements and (1)H NMR titrations of 3 and 6 with solvents of varying H-bond accepting strength. The H-bond strength in 3 and 6 was calculated in silico to be 5.9 and 4.9 kcal/mol, respectively. The relationship between the protonation state and the ligand-based redox activity was probed utilizing 7 and 8, where the reduction potential of the didpa scaffold was found to shift by 105 mV upon protonation of the reduced ligand in Fe(didpa)(CO)2.

  2. Kinetics and crystal structure of a mutant Escherichia coli alkaline phosphatase (Asp-369-->Asn): a mechanism involving one zinc per active site.

    PubMed

    Tibbitts, T T; Xu, X; Kantrowitz, E R

    1994-11-01

    Using site-directed mutagenesis, an aspartate side chain involved in binding metal ions in the active site of Escherichia coli alkaline phosphatase (Asp-369) was replaced, alternately, by asparagine (D369N) and by alanine (D369A). The purified mutant enzymes showed reduced turnover rates (kcat) and increased Michaelis constants (Km). The kcat for the D369A enzyme was 5,000-fold lower than the value for the wild-type enzyme. The D369N enzyme required Zn2+ in millimolar concentrations to become fully active; even under these conditions the kcat measured for hydrolysis of p-nitrophenol phosphate was 2 orders of magnitude lower than for the wild-type enzyme. Thus the kcat/Km ratios showed that catalysis is 50 times less efficient when the carboxylate side chain of Asp-369 is replaced by the corresponding amide; and activity is reduced to near nonenzymic levels when the carboxylate is replaced by a methyl group. The crystal structure of D369N, solved to 2.5 A resolution with an R-factor of 0.189, showed vacancies at 2 of the 3 metal binding sites. On the basis of the kinetic results and the refined X-ray coordinates, a reaction mechanism is proposed for phosphate ester hydrolysis by the D369N enzyme involving only 1 metal with the possible assistance of a histidine side chain.

  3. Zinc activates damage-sensing TRPA1 ion channels

    PubMed Central

    Hu, Hongzhen; Bandell, Michael; Petrus, Matt J.; Zhu, Michael X.; Patapoutian, Ardem

    2009-01-01

    Zinc is an essential biological trace element. It is required for the structure or function of over 300 proteins, and is increasingly recognized for its role in cell signaling. However, high concentrations of zinc have cytotoxic effects, and overexposure to zinc can cause pain and inflammation through unknown mechanisms. Here we show that zinc excites nociceptive somatosensory neurons and causes nociception in mice through TRPA1, a cation channel previously shown to mediate the pungency of wasabi and cinnamon through cysteine-modification. Zinc activates TRPA1 through a novel mechanism that requires zinc influx through TRPA1 channels and subsequent activation via specific intracellular cysteine and histidine residues. TRPA1 is highly sensitive to intracellular zinc, as low nanomolar concentrations activate TRPA1 and modulate its sensitivity. These findings identify TRPA1 as a major target for the sensory effects of zinc, and support an emerging role for zinc as a signaling molecule that can modulate sensory transmission. PMID:19202543

  4. A ZnS(4) structural zinc site in the Helicobacter pylori ferric uptake regulator.

    PubMed

    Vitale, Sylvia; Fauquant, Caroline; Lascoux, David; Schauer, Kristine; Saint-Pierre, Christine; Michaud-Soret, Isabelle

    2009-06-23

    The ferric uptake regulator, Fur, is a global bacterial transcriptional regulator using iron as a cofactor to bind to specific DNA sequences. This paper describes the biochemical characterization of the native ferric uptake regulator from Helicobacter pylori (HpFur): oligomeric state, metal content, and characterization of a structural metal-binding site. HpFur contains six cysteines with two CxxC motifs, which makes it closer to Bacillus subtilis PerR (BsPerR) than to Escherichia coli Fur (EcFur). Chemical modifications of cysteine residues using iodoacetamide followed by mass spectrometry after enzymatic digestion strongly suggest that these two CxxC motifs containing cysteines 102-105 and 142-145 are involved in zinc binding in a ZnS(4) metal site. The other two cysteines (78 and 150) are not essential for DNA binding activity and do not perturb metal binding as demonstrated with the characterization of a FurC78SC150S double mutant. Chelating agent such as EDTA disrupts the dimeric structure into monomer which did not contain zinc anymore. Reconstitution of dimer from monomer requires reduction and Zn(2+) binding. Cadmium(II) substitution allows also dimer formation from monomer, and Cd(II)-substituted FurC78SC150S mutant presents a characteristic absorption of a Cd(II)Cys(4) metal-binding site. These results establish that coordination of the zinc ion in HpFur is ZnCys(4), therefore closer to the zinc site in BsPerR than in EcFur. Furthermore, the redox state of the cysteines and the zinc binding are essential to hold the H. pylori Fur in a dimeric state.

  5. Metal active site elasticity linked to activation of homocysteine in methionine synthases

    SciTech Connect

    Koutmos, Markos; Pejchal, Robert; Bomer, Theresa M.; Matthews, Rowena G.; Smith, Janet L.; Ludwig, Martha L.

    2008-04-02

    Enzymes possessing catalytic zinc centers perform a variety of fundamental processes in nature, including methyl transfer to thiols. Cobalamin-independent (MetE) and cobalamin-dependent (MetH) methionine synthases are two such enzyme families. Although they perform the same net reaction, transfer of a methyl group from methyltetrahydrofolate to homocysteine (Hcy) to form methionine, they display markedly different catalytic strategies, modular organization, and active site zinc centers. Here we report crystal structures of zinc-replete MetE and MetH, both in the presence and absence of Hcy. Structural investigation of the catalytic zinc sites of these two methyltransferases reveals an unexpected inversion of zinc geometry upon binding of Hcy and displacement of an endogenous ligand in both enzymes. In both cases a significant movement of the zinc relative to the protein scaffold accompanies inversion. These structures provide new information on the activation of thiols by zinc-containing enzymes and have led us to propose a paradigm for the mechanism of action of the catalytic zinc sites in these and related methyltransferases. Specifically, zinc is mobile in the active sites of MetE and MetH, and its dynamic nature helps facilitate the active site conformational changes necessary for thiol activation and methyl transfer.

  6. Baseline aquatic ecological risk assessment at a zinc smelter site

    SciTech Connect

    Sexton, J.E.; Becker, D.S.; Pastorok, R.A.; Ginn, T.C.; Shields, W.J.

    1995-12-31

    A baseline ecological risk assessment was conducted at the National Zinc smelter site (Bartlesville, Oklahoma). Surface water, sediments, and aquatic biota (whole fish and crayfish) in the North Tributary, West Tributary, Eliza Creek, and Sand Creek were analyzed for selected metals. Water toxicity tests (fathead minnow and cladoceran) and sediment toxicity tests (amphipod and chironomid) were also conducted. Metals in water and sediments in most of the North Tributary, West Tributary, and parts of Eliza Creek were elevated above reference values. Metal distributions in surface water showed no influence of the releases from the Site on Sand Creek, with the exception of a slight elevation of cadmium concentration relative to reference area values. In all cases, concentrations of metals in Sand Creek sediments were similar to or lower than mean reference values. Spatial distribution patterns for metals of concern in surface water were similar to those in sediments. Analyses of dissolved metals in surface water, SEM/AVS ratios for sediments, and tissue residues demonstrated that metals were bioavailable. No adverse effects were detected in the fathead minnow test for any of the site stations. A low level of toxicity was observed in the cladoceran test for several site stations. Little sediment toxicity was observed at the study area based on the amphipod survival endpoint. Sublethal effects were detected when chironomid growth at several site stations was compared with reference conditions. The ecological risks posed by surface water and sediment throughout most of the study area were not significant and bioaccumulation of metals of concern was restricted to a limited portion of the study area close to the Site.

  7. List 9 - Active CERCLIS Sites:

    EPA Pesticide Factsheets

    The List 9 displays the sequence of activities undertaken at active CERCLIS sites. An active site is one at which site assessment, removal, remedial, enforcement, cost recovery, or oversight activities are being planned or conducted.

  8. Communication between the Zinc and Nickel Sites in Dimeric HypA: Metal Recognition and pH Sensing

    SciTech Connect

    Herbst, R.; Perovic, I; Martin-Diaconescu, V; O’Brien, K; Chivers, P; Sondej Pochapsky, S; Pochapsky, T; Maroney, M

    2010-01-01

    Helicobacter pylori, a pathogen that colonizes the human stomach, requires the nickel-containing metalloenzymes urease and NiFe-hydrogenase to survive this low pH environment. The maturation of both enzymes depends on the metallochaperone, HypA. HypA contains two metal sites, an intrinsic zinc site and a low-affinity nickel binding site. X-ray absorption spectroscopy (XAS) shows that the structure of the intrinsic zinc site of HypA is dynamic and able to sense both nickel loading and pH changes. At pH 6.3, an internal pH that occurs during acid shock, the zinc site undergoes unprecedented ligand substitutions to convert from a Zn(Cys){sub 4} site to a Zn(His){sub 2}(Cys){sub 2} site. NMR spectroscopy shows that binding of Ni(II) to HypA results in paramagnetic broadening of resonances near the N-terminus. NOEs between the {beta}-CH{sub 2} protons of Zn cysteinyl ligands are consistent with a strand-swapped HypA dimer. Addition of nickel causes resonances from the zinc binding motif and other regions to double, indicating more than one conformation can exist in solution. Although the structure of the high-spin, 5-6 coordinate Ni(II) site is relatively unaffected by pH, the nickel binding stoichiometry is decreased from one per monomer to one per dimer at pH = 6.3. Mutation of any cysteine residue in the zinc binding motif results in a zinc site structure similar to that found for holo-WT-HypA at low pH and is unperturbed by the addition of nickel. Mutation of the histidines that flank the CXXC motifs results in a zinc site structure that is similar to holo-WT-HypA at neutral pH (Zn(Cys){sub 4}) and is no longer responsive to nickel binding or pH changes. Using an in vitro urease activity assay, it is shown that the recombinant protein is sufficient for recovery of urease activity in cell lysate from a HypA deletion mutant, and that mutations in the zinc-binding motif result in a decrease in recovered urease activity. The results are interpreted in terms of a model

  9. Ordered Nucleation Sites for the Growth of Zinc Oxide Nanofibers

    SciTech Connect

    Wang, J.; Ginley, D.S.; Shaheen, S.

    2006-01-01

    Organic photovoltaics (OPVs) offer a promising route to low cost photovoltaic (PV) technology that can be inexpensively manufactured on a large scale for use in power generation and commercial products. Solar power conversion efficiencies of laboratory scale OPV devices have recently reached ~5%; however, projected efficiencies of at least 10% will be required for commercialization. An analogous approach that has arisen recently that can potentially increase efficiencies employs metal oxide semiconductors as the electron acceptor, creating a hybrid organic-inorganic device. This approach offers the advantage that the conduction band of the oxide can be tuned in a systematic way through doping, thus potentially achieving higher photovoltages in the device. Additionally, nanostructures of these materials can be easily grown from precursor solutions, providing a technique to precisely control the nanoscale geometry. This work focuses on using ZnO, which is known to have high electron mobility (>100 cm2/Vs), as the electron acceptor. Nanofibers of ZnO can be grown from precursors such as zinc acetate or zinc nitrate to form arrays of nanofibers into which a conjugated polymer can be intercalated to form a composite PV device. The morphology of the nanofiber array is critical to the performance of the device, but current methods of nanofiber growth from a flat, polycrystalline nucleation layer allow for little morphological control. To overcome this limitation, we have created ordered arrays of ZnO nucleation sites with controllable size and spacing. Toluene solutions of diblock copolymer micelles with ZnCl2 incorporated into the micellar cores were spin-coated onto glass substrates and etched with an O2 plasma to yield hexagonally ordered arrays of ZnO nanoparticles that functioned as nucleation sites. Changing the concentration of ZnCl2 and the molecular weight and ratio of the diblock copolymer resulted in systematic variation in the size and spacing of the

  10. Zinc modulates PPARgamma signaling and activation of porcine endothelial cells.

    PubMed

    Meerarani, Purushothaman; Reiterer, Gudrun; Toborek, Michal; Hennig, Bernhard

    2003-10-01

    Dietary zinc has potent antioxidant and anti-inflammatory properties and is a critical component of peroxisome proliferator-activated receptor (PPAR) gene expression and regulation. To assess the protective mechanisms of PPARgamma in endothelial cell dysfunction and the role of zinc in the modulation of PPARgamma signaling, cultured porcine pulmonary artery endothelial cells were exposed to the membrane-permeable zinc chelator N,N,N'N'-tetrakis (2-pyridylmethyl)-ethylene diamine (TPEN), thiazolidinedione (TZD; PPARgamma agonist) or bisphenol A diglycidyl ether (BADGE; PPARgamma antagonist). Subsequently, endothelial cells were activated by treatment with linoleic acid (90 micro mol/L) for 6 h. Zinc chelation by TPEN increased the DNA binding activity of nuclear factor (NF)-kappaB and activator protein (AP)-1, decreased PPARgamma expression and activation as well as up-regulated interleukin (IL)-6 expression and production. These effects were fully reversed by zinc supplementation. In addition, exposure to TZD down-regulated linoleic acid-induced DNA binding activity of NF-kappaB and AP-1, whereas BADGE further induced activation of these oxidative stress-sensitive transcription factors. Most importantly, the TZD-mediated down-regulation of NF-kappaB and AP-1 and reduced inflammatory response were impaired during zinc chelation. These data suggest that zinc plays a critical role in PPARgamma signaling in linoleic acid-induced endothelial cell activation and indicate that PPARgamma signaling is impaired during zinc deficiency.

  11. 78 FR 46948 - Proposed Agreement Regarding Site Costs and Covenants Not To Sue for American Lead and Zinc Mill...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-02

    ... AGENCY Proposed Agreement Regarding Site Costs and Covenants Not To Sue for American Lead and Zinc Mill... response costs incurred at the American Lead and Zinc Mill Superfund Site near Ouray, Colorado. The... via electric mail at rudy.mike@epa.gov and should reference the American Lead and Zinc Mill Site,...

  12. Influence of extracellular zinc on M1 microglial activation

    PubMed Central

    Higashi, Youichirou; Aratake, Takaaki; Shimizu, Shogo; Shimizu, Takahiro; Nakamura, Kumiko; Tsuda, Masayuki; Yawata, Toshio; Ueba, Tetuya; Saito, Motoaki

    2017-01-01

    Extracellular zinc, which is released from hippocampal neurons in response to brain ischaemia, triggers morphological changes in microglia. Under ischaemic conditions, microglia exhibit two opposite activation states (M1 and M2 activation), which may be further regulated by the microenvironment. We examined the role of extracellular zinc on M1 activation of microglia. Pre-treatment of microglia with 30–60 μM ZnCl2 resulted in dose-dependent increases in interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNFα) secretion when M1 activation was induced by lipopolysaccharide administration. In contrast, the cell-permeable zinc chelator TPEN, the radical scavenger Trolox, and the P2X7 receptor antagonist A438079 suppressed the effects of zinc pre-treatment on microglia. Furthermore, endogenous zinc release was induced by cerebral ischaemia–reperfusion, resulting in increased expression of IL-1β, IL-6, TNFα, and the microglial M1 surface marker CD16/32, without hippocampal neuronal cell loss, in addition to impairments in object recognition memory. However, these effects were suppressed by the zinc chelator CaEDTA. These findings suggest that extracellular zinc may prime microglia to enhance production of pro-inflammatory cytokines via P2X7 receptor activation followed by reactive oxygen species generation in response to stimuli that trigger M1 activation, and that these inflammatory processes may result in deficits in object recognition memory. PMID:28240322

  13. Activation of the orphan receptor tyrosine kinase ALK by zinc.

    PubMed

    Bennasroune, Aline; Mazot, Pierre; Boutterin, Marie-Claude; Vigny, Marc

    2010-08-06

    Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase essentially and transiently expressed during development of the central and peripheral nervous system. The nature of the cognate ligand of this receptor in Vertebrates is still a matter of debate. During synaptic transmission the release of ionic zinc found in vesicles of certain glutamatergic and gabaergic terminals may act as a neuromodulator by binding to pre- or post-synaptic receptors. Recently, zinc has been shown to activate the receptor tyrosine kinase, TrkB, independently of neurotrophins. This activation occurs via increasing the Src family kinase activity. In the present study, we investigated whether the ALK activity could be modulated by extracellular zinc. We first showed that zinc alone rapidly activates ALK. This activation is dependent of ALK tyrosine kinase activity and dimerization of the receptor but is independent of Src family kinase activity. In contrast, addition of sodium pyrithione, a zinc ionophore, led to a further activation of ALK. This stronger activation is dependent of Src family kinase but independent of ALK activity and dimerization. In conclusion, zinc could constitute an endogenous ligand of ALK in vertebrates.

  14. Zinc.

    PubMed

    Barceloux, D G

    1999-01-01

    The use of zinc in metal alloys and medicinal lotions dates back before the time of Christ. Currently, most of the commercial production of zinc involves the galvanizing of iron and the manufacture of brass. Some studies support the use of zinc gluconate lozenges to treat the common cold, but there are insufficient data at this time to recommend the routine use of these lozenges. Zinc is an essential co-factor in a variety of cellular processes including DNA synthesis, behavioral responses, reproduction, bone formation, growth, and wound healing. Zinc is a relatively common metal with an average concentration of 50 mg/kg soil and a range of 10-300 mg/kg soil. Meat, seafood, dairy products, nuts, legumes, and whole grains contain relatively high concentrations of zinc. The mobility of zinc in anaerobic environments is poor and therefore severe zinc contamination occurs primarily near points sources of zinc release. The recommended daily allowance for adults is 15 mg zinc. The ingestion of 1-2 g zinc sulfate produces emesis. Zinc compounds can produce irritation and corrosion of the gastrointestinal tract, along with acute renal tubular necrosis and interstitial nephritis. Inhalation of high concentrations of zinc chloride from smoke bombs detonated in closed spaces may cause chemical pneumonitis and adult respiratory distress syndrome. In the occupational setting inhalation of fumes from zinc oxide is the most common cause of metal fume fever (fatigue, chills, fever, myalgias, cough, dyspnea, leukocytosis, thirst, metallic taste, salivation). Zinc compounds are not suspected carcinogens. Treatment of zinc toxicity is supportive. Calcium disodium ethylenediaminetetraacetate (CaNa2EDTA) is the chelator of choice based on case reports that demonstrate normalization of zinc concentrations, but there are few clinical data to confirm the efficacy of this agent.

  15. Zinc

    MedlinePlus

    ... pill" to help remove excess water from the body. Another effect of amiloride (Midamor) is that it can increase the amount of zinc in the body. Taking zinc supplements with amiloride (Midamor) might cause ...

  16. Zinc Pyrithione Improves the Antibacterial Activity of Silver Sulfadiazine Ointment

    PubMed Central

    Blanchard, Catlyn; Brooks, Lauren; Ebsworth-Mojica, Katherine; Didione, Louis; Wucher, Benjamin; Dewhurst, Stephen; Krysan, Damian

    2016-01-01

    ABSTRACT Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus are commonly associated with biofilm-associated wound infections that are recalcitrant to conventional antibiotics. As an initial means to identify agents that may have a greater propensity to improve clearance of wound-associated bacterial pathogens, we screened a Food and Drug Administration-approved drug library for members that display bactericidal activity toward 72-h-established P. aeruginosa biofilms using an adenylate kinase reporter assay for bacterial cell death. A total of 34 compounds displayed antibiofilm activity. Among these, zinc pyrithione was also shown to reduce levels of A. baumannii and S. aureus biofilm-associated bacteria and exhibited an additive effect in combination with silver sulfadiazine, a leading topical therapeutic for wound site infections. The improved antimicrobial activity of zinc pyrithione and silver sulfadiazine was maintained in an ointment formulation and led to improved clearance of P. aeruginosa, A. baumannii, and S. aureus in a murine model of wound infection. Taken together, these results suggest that topical zinc pyrithione and silver sulfadiazine combination formulations may mitigate wound-associated bacterial infections and disease progression. IMPORTANCE Topical antimicrobial ointments ostensibly mitigate bacterial wound disease and reliance on systemic antibiotics. Yet studies have called into question the therapeutic benefits of several traditional topical antibacterials, accentuating the need for improved next-generation antimicrobial ointments. Yet the development of such agents consisting of a new chemical entity is a time-consuming and expensive proposition. Considering that drug combinations are a mainstay therapeutic strategy for the treatment of other therapeutic indications, one alternative approach is to improve the performance of conventional antimicrobial ointments by the addition of a well-characterized and FDA

  17. Zinc Pyrithione Improves the Antibacterial Activity of Silver Sulfadiazine Ointment.

    PubMed

    Blanchard, Catlyn; Brooks, Lauren; Ebsworth-Mojica, Katherine; Didione, Louis; Wucher, Benjamin; Dewhurst, Stephen; Krysan, Damian; Dunman, Paul M; Wozniak, Rachel A F

    2016-01-01

    Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus are commonly associated with biofilm-associated wound infections that are recalcitrant to conventional antibiotics. As an initial means to identify agents that may have a greater propensity to improve clearance of wound-associated bacterial pathogens, we screened a Food and Drug Administration-approved drug library for members that display bactericidal activity toward 72-h-established P. aeruginosa biofilms using an adenylate kinase reporter assay for bacterial cell death. A total of 34 compounds displayed antibiofilm activity. Among these, zinc pyrithione was also shown to reduce levels of A. baumannii and S. aureus biofilm-associated bacteria and exhibited an additive effect in combination with silver sulfadiazine, a leading topical therapeutic for wound site infections. The improved antimicrobial activity of zinc pyrithione and silver sulfadiazine was maintained in an ointment formulation and led to improved clearance of P. aeruginosa, A. baumannii, and S. aureus in a murine model of wound infection. Taken together, these results suggest that topical zinc pyrithione and silver sulfadiazine combination formulations may mitigate wound-associated bacterial infections and disease progression. IMPORTANCE Topical antimicrobial ointments ostensibly mitigate bacterial wound disease and reliance on systemic antibiotics. Yet studies have called into question the therapeutic benefits of several traditional topical antibacterials, accentuating the need for improved next-generation antimicrobial ointments. Yet the development of such agents consisting of a new chemical entity is a time-consuming and expensive proposition. Considering that drug combinations are a mainstay therapeutic strategy for the treatment of other therapeutic indications, one alternative approach is to improve the performance of conventional antimicrobial ointments by the addition of a well-characterized and FDA

  18. Pyrithione, a zinc ionophore, inhibits NF-kappaB activation.

    PubMed

    Kim, C H; Kim, J H; Moon, S J; Chung, K C; Hsu, C Y; Seo, J T; Ahn, Y S

    1999-06-16

    Pyrrolidine dithiocarbamate (PDTC) suppresses NF-kappaB activity and exhibits cytotoxic effects in bovine cerebral endothelial cells (BCECs), and we have previously reported that these PDTC effects were accompanied by an increase in intracellular zinc levels. To further explore the role of zinc in the modulation of NF-kappaB activation, we studied the effect of pyrithione, a zinc ionophore, on NF-kappaB activation in BCECs. Pyrithione inhibited NF-kappaB activity in a time- and dose-dependent manner. Ca-EDTA, but not Zn-EDTA, prevented pyrithione inhibition of NF-kappaB activity. Pyrithione increased the intracellular zinc level within 15 min. This effect was also abolished by Ca-EDTA, but not by Zn-EDTA. The potency of pyrithione on NF-kappaB inhibition and zinc influx was approximately one order of magnitude more potent than PDTC. These findings establish the regulatory role of intracellular zinc levels on NF-kappaB activity in BCECs.

  19. An MSC2 Promoter-lacZ Fusion Gene Reveals Zinc-Responsive Changes in Sites of Transcription Initiation That Occur across the Yeast Genome

    PubMed Central

    Wu, Yi-Hsuan; Taggart, Janet; Song, Pamela Xiyao; MacDiarmid, Colin; Eide, David J.

    2016-01-01

    The Msc2 and Zrg17 proteins of Saccharomyces cerevisiae form a complex to transport zinc into the endoplasmic reticulum. ZRG17 is transcriptionally induced in zinc-limited cells by the Zap1 transcription factor. In this report, we show that MSC2 mRNA also increases (~1.5 fold) in zinc-limited cells. The MSC2 gene has two in-frame ATG codons at its 5’ end, ATG1 and ATG2; ATG2 is the predicted initiation codon. When the MSC2 promoter was fused at ATG2 to the lacZ gene, we found that unlike the chromosomal gene this reporter showed a 4-fold decrease in lacZ mRNA in zinc-limited cells. Surprisingly, β-galactosidase activity generated by this fusion gene increased ~7 fold during zinc deficiency suggesting the influence of post-transcriptional factors. Transcription of MSC2ATG2-lacZ was found to start upstream of ATG1 in zinc-replete cells. In zinc-limited cells, transcription initiation shifted to sites just upstream of ATG2. From the results of mutational and polysome profile analyses, we propose the following explanation for these effects. In zinc-replete cells, MSC2ATG2-lacZ mRNA with long 5’ UTRs fold into secondary structures that inhibit translation. In zinc-limited cells, transcripts with shorter unstructured 5’ UTRs are generated that are more efficiently translated. Surprisingly, chromosomal MSC2 did not show start site shifts in response to zinc status and only shorter 5’ UTRs were observed. However, the shifts that occur in the MSC2ATG2-lacZ construct led us to identify significant transcription start site changes affecting the expression of ~3% of all genes. Therefore, zinc status can profoundly alter transcription initiation across the yeast genome. PMID:27657924

  20. Dynamic HypA zinc site is essential for acid viability and proper urease maturation in Helicobacter pylori

    PubMed Central

    Johnson, Ryan C.; Hu, Heidi Q.; Merrell, D. Scott; Maroney, Michael J.

    2015-01-01

    Helicobacter pylori requires urease activity in order to survive in the acid environment of the human stomach. Urease is regulated in part by nickelation, a process that requires the HypA protein, which is a putative nickel metallochaperone that is generally associated with hydrogenase maturation. However, in H. pylori, HypA plays a dual role. In addition to an N-terminal nickel binding site, HypA proteins also contain a structural zinc site that is coordinated by two rigorously conserved CXXC sequences, which in H. pylori are flanked by His residues. These structural Zn sites are known to be dynamic, converting from Zn(Cys)4 centers at pH 7.2 to Zn(Cys)2(His)2 centers at pH 6.3 in the presence of Ni(II) ions. In this study, mutant strains of H. pylori that express zinc site variants of the HypA protein are used to show that the structural changes in the zinc site are important for the acid viability of the bacterium, and that a reduction in acid viability in these variants can be traced in large measure to deficient urease activity. This in turn leads to a model that connects the Zn(Cys)4 coordination to urease maturation. PMID:25608738

  1. Zinc ions modulate protein tyrosine phosphatase 1B activity.

    PubMed

    Bellomo, Elisa; Massarotti, Alberto; Hogstrand, Christer; Maret, Wolfgang

    2014-07-01

    Protein tyrosine phosphatases (PTPs) are key enzymes in cellular regulation. The 107 human PTPs are regulated by redox signalling, phosphorylation, dimerisation, and proteolysis. Recent findings of very strong inhibition of some PTPs by zinc ions at concentrations relevant in a cellular environment suggest yet another mechanism of regulation. One of the most extensively investigated PTPs is PTP1B (PTPN1). It regulates the insulin and leptin signalling pathway and is implicated in cancer and obesity/diabetes. The development of novel assay conditions to investigate zinc inhibition of PTP1B provides estimates of about 5.6 nM affinity for inhibitory zinc(II) ions. Analysis of three PTP1B 3D structures (PDB id: 2CM2, 3I80 and 1A5Y) identified putative zinc binding sites and supports the kinetic studies in suggesting an inhibitory zinc only in the closed and cysteinyl-phosphate intermediate forms of the enzyme. These observations gain significance with regard to recent findings of regulatory roles of zinc ions released from the endoplasmic reticulum.

  2. Zinc

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Zinc was recognized as an essential trace metal for humans during the studies of Iranian adolescent dwarfs in the early 1960s. Zinc metal existing as Zn2+ is a strong electron acceptor in biological systems without risks of oxidant damage to cells. Zn2+ functions in the structure of proteins and is ...

  3. Structural, optical and photocatalytic activity of cerium doped zinc aluminate

    NASA Astrophysics Data System (ADS)

    Sumathi, Shanmugam; Kavipriya, A.

    2017-03-01

    Zinc aluminate and cerium-doped zinc aluminate nanoparticles are synthesised by co-precipitation method. Ammonium hydroxide is used as a precipitating agent. The synthesised compounds are characterised by powder X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FT-IR), Ultraviolet diffuse reflectance spectroscopy (UV-DRS), Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and Surface area measurements. The photocatalytic activity of zinc aluminate and cerium doped zinc aluminate nanoparticles are studied under the UV light and visible light taking methylene blue as a model pollutant. The amount of catalyst, concentration of dye solution and time are optimised under UV-light. Degradation of methylene blue under the UV-light is found to be 99% in 20 min with 10 mg of cerium doped catalyst. Compared to visible light degradation, the degradation of dye under UV-light is higher. Cerium doping in zinc aluminate (ZnAl2O4:Ce3+) increased the photocatalytic activity of zinc aluminate.

  4. Copper and protons directly activate the zinc-activated channel.

    PubMed

    Trattnig, Sarah M; Gasiorek, Agnes; Deeb, Tarek Z; Ortiz, Eydith J Comenencia; Moss, Stephen J; Jensen, Anders A; Davies, Paul A

    2016-03-01

    The zinc-activated channel (ZAC) is a cationic ion channel belonging to the superfamily of Cys-loop receptors, which consists of pentameric ligand-gated ion channels. ZAC is the least understood member of this family so in the present study we sought to characterize the properties of this channel further. We demonstrate that not only zinc (Zn(2+)) but also copper (Cu(2+)) and protons (H(+)) are agonists of ZAC, displaying potencies and efficacies in the rank orders of H(+)>Cu(2+)>Zn(2+) and H(+)>Zn(2+)>Cu(2+), respectively. The responses elicited by Zn(2+), Cu(2+) and H(+) through ZAC are all characterized by low degrees of desensitization. In contrast, currents evoked by high concentrations of the three agonists comprise distinctly different activation and decay components, with transitions to and from an open state being significantly faster for H(+) than for the two metal ions. The permeabilities of ZAC for Na(+) and K(+) relative to Cs(+) are indistinguishable, whereas replacing all of extracellular Na(+) and K(+) with the divalent cations Ca(2+) or Mg(2+) results in complete elimination of Zn(2+)-activated currents at both negative and positive holding potentials. This indicates that ZAC is non-selectively permeable to monovalent cations, whereas Ca(2+) and Mg(2+) inhibit the channel. In conclusion, this is the first report of a Cys-loop receptor being gated by Zn(2+), Cu(2+) and H(+). ZAC could be an important mediator of some of the wide range of physiological functions regulated by or involving Zn(2+), Cu(2+) and H(+).

  5. Automatically activated, 300 ampere-hour silver-zinc cell

    NASA Technical Reports Server (NTRS)

    Hennigan, T. J.

    1972-01-01

    A prototype silver zinc cell is reported for which the electrolyte is being stored in a separate tank; the cell is being activated when additional power is required by collapsing the neoprene bellows container and thus forcing the electrolyte into cell through a plastic connection. A solar array is proposed as main power source for the flow actuator.

  6. The artificial zinc finger coding gene 'Jazz' binds the utrophin promoter and activates transcription.

    PubMed

    Corbi, N; Libri, V; Fanciulli, M; Tinsley, J M; Davies, K E; Passananti, C

    2000-06-01

    Up-regulation of utrophin gene expression is recognized as a plausible therapeutic approach in the treatment of Duchenne muscular dystrophy (DMD). We have designed and engineered new zinc finger-based transcription factors capable of binding and activating transcription from the promoter of the dystrophin-related gene, utrophin. Using the recognition 'code' that proposes specific rules between zinc finger primary structure and potential DNA binding sites, we engineered a new gene named 'Jazz' that encodes for a three-zinc finger peptide. Jazz belongs to the Cys2-His2 zinc finger type and was engineered to target the nine base pair DNA sequence: 5'-GCT-GCT-GCG-3', present in the promoter region of both the human and mouse utrophin gene. The entire zinc finger alpha-helix region, containing the amino acid positions that are crucial for DNA binding, was specifically chosen on the basis of the contacts more frequently represented in the available list of the 'code'. Here we demonstrate that Jazz protein binds specifically to the double-stranded DNA target, with a dissociation constant of about 32 nM. Band shift and super-shift experiments confirmed the high affinity and specificity of Jazz protein for its DNA target. Moreover, we show that chimeric proteins, named Gal4-Jazz and Sp1-Jazz, are able to drive the transcription of a test gene from the human utrophin promoter.

  7. Zinc supplementation affects the activity patterns of rural Guatemalan infants.

    PubMed

    Bentley, M E; Caulfield, L E; Ram, M; Santizo, M C; Hurtado, E; Rivera, J A; Ruel, M T; Brown, K H

    1997-07-01

    Zinc deficiency has been associated with growth deficits, reduced dietary intake and appetite, and has been hypothesized to result in reduced activity. This randomized, double-blind, placebo-controlled study examined whether 10 mg of oral zinc as zinc sulfate, given daily for up to 7 mo, affected activity patterns of 85 Guatemalan infants recruited at 6-9 mo of age. Infant activity was assessed by time sampling-observation method at 10-min intervals during a 12-h data collection period, at base line, 3 and 7 mo follow-up. Motor development and the percentage of time infants were observed in various positions (being carried, lying down, sitting, crawling, standing or walking) and engaged in various activities (eating, sleeping, resting, crying/whining or playing) were compared by treatment group. No differences in motor development were observed by treatment group. However, at follow-up 2 (after 7 mo of supplementation), zinc-supplemented infants were significantly more frequently observed sitting up compared with lying down, and were playing during 4.18 +/- 1.95% (P < 0.05) more observations than unsupplemented infants. They were also somewhat less likely to be observed crying or whining (P < 0.10) compared with those receiving the placebo. These effects are independent of other factors including infant age, motor development, sex, maternal education, family socioeconomic status and nutritional status at base line. Further research must be conducted to determine the long-term developmental importance of these differences in activity patterns associated with zinc supplementation in this setting.

  8. A zinc-binding site by negative selection induces metallodrug susceptibility in an essential chaperonin

    PubMed Central

    Cun, Shujian; Sun, Hongzhe

    2010-01-01

    GroES is an indispensable chaperonin virtually found throughout all life forms. Consequently, mutations of this protein must be critically scrutinized by natural selection. Nevertheless, the homolog from a potentially virulent gastric pathogen, Helicobacter pylori, strikingly features a histidine/cysteine-rich C terminus that shares no significant homology with other family members. Additionally, three more (H45, C51, and C53) are uniquely present in its apical domain. The statistical analyses show that these residues may have originated from negative selection, presumably driven by either dependent or independent amino acid mutations. In the absence of the C-terminal metal-binding domain, the mutant protein still exhibits a substantial capacity for zinc binding in vivo. The biochemical properties of site-directed mutants indicate that H45, C51, and C53 make up an oxidation-sensitive zinc-binding site that may donate the bound metal to a zinc acceptor. Of interest, bismuth antiulcer drugs strongly bind at this site (Kd of approximately 7 × 10-26 M), replacing the bound zinc and consequently inducing the disruption of the quaternary structure. Because biological features by negative selection are usually inert to change during evolution, this study sheds light on a promising field whereby medicines can be designed or improved to specifically target the residues that uniquely evolved in pathogenic proteins so as to retard the emergence of drug resistance. PMID:20194796

  9. Zinc coupling potentiates anti-HIV-1 activity of baicalin.

    PubMed

    Wang, Qian; Wang, Yu-Tian; Pu, Shao-Ping; Zheng, Yong-Tang

    2004-11-12

    Baicalin (BA) has been shown with anti-HIV-1 activity. Zinc is a nutrient element. The anti-HIV-1 activity of zinc complex of baicalin (BA-Zn) in vitro was studied and compared with the anti-HIV-1 activities between BA and BA-Zn in the present study. Our results suggested that BA-Zn has lower cytotoxicity and higher anti-HIV-1 activity compared with those of BA in vitro. The CC50s of BA-Zn and BA were 221.52 and 101.73 microM, respectively. The cytotoxicity of BA-Zn was about 1.2-fold lower than that of BA. The BA and BA-Zn inhibited HIV-1 induced syncytium formation, HIV-1 p24 antigen and HIV-1 RT production. The EC50s of BA-Zn on inhibiting HIV-1 induced syncytium formation (29.08 microM) and RT production (31.17 microM) were lower than those of BA (43.27 and 47.34 microM, respectively). BA-Zn was more effective than BA in inhibiting the activities of recombinant RT and HIV-1 entry into host cells. Zinc coupling enhanced the anti-HIV-1 activity of baicalin.

  10. Site-directed mutants of human RECQ1 reveal functional importance of the zinc binding domain.

    PubMed

    Sami, Furqan; Gary, Ronald K; Fang, Yayin; Sharma, Sudha

    2016-08-01

    RecQ helicases are a highly conserved family of ATP-dependent DNA-unwinding enzymes with key roles in DNA replication and repair in all kingdoms of life. The RECQ1 gene encodes the most abundant RecQ homolog in humans. We engineered full-length RECQ1 harboring point mutations in the zinc-binding motif (amino acids 419-480) within the conserved RecQ-specific-C-terminal (RQC) domain known to be critical for diverse biochemical and cellular functions of RecQ helicases. Wild-type RECQ1 contains a zinc ion. Substitution of three of the four conserved cysteine residues that coordinate zinc severely impaired the ATPase and DNA unwinding activities but retained DNA binding and single strand DNA annealing activities. Furthermore, alteration of these residues attenuated zinc binding and significantly changed the overall conformation of full-length RECQ1 protein. In contrast, substitution of cysteine residue at position 471 resulted in a wild-type like RECQ1 protein. Differential contribution of the conserved cysteine residues to the structure and functions of the RECQ1 protein is also inferred by homology modeling. Overall, our results indicate that the zinc binding motif in the RQC domain of RECQ1 is a key structural element that is essential for the structure-functions of RECQ1. Given the recent association of RECQ1 mutations with breast cancer, these results will contribute to understanding the molecular basis of RECQ1 functions in cancer etiology.

  11. Identification of off-target cleavage sites of zinc finger nucleases and TAL effector nucleases using predictive models.

    PubMed

    Fine, Eli J; Cradick, Thomas J; Bao, Gang

    2014-01-01

    Using engineered nucleases, such as Zinc Finger Nucleases (ZFNs) or Transcription Activator-Like Effector Nucleases (TALENs), to make targeted genomic modifications has become a common technique to create new model organisms and custom cell lines, and has shown great promise for disease treatment. However, these nucleases have the potential for off-target cleavage that could confound interpretation of experimental results and be detrimental for therapeutic use. Here, we describe a method to test for nuclease cleavage at potential off-target sites predicted by bioinformatics models.

  12. Arsenite binding-induced zinc loss from PARP-1 is equivalent to zinc deficiency in reducing PARP-1 activity, leading to inhibition of DNA repair

    SciTech Connect

    Sun, Xi; Zhou, Xixi; Du, Libo; Liu, Wenlan; Liu, Yang; Hudson, Laurie G.; Liu, Ke Jian

    2014-01-15

    Inhibition of DNA repair is a recognized mechanism for arsenic enhancement of ultraviolet radiation-induced DNA damage and carcinogenesis. Poly(ADP-ribose) polymerase-1 (PARP-1), a zinc finger DNA repair protein, has been identified as a sensitive molecular target for arsenic. The zinc finger domains of PARP-1 protein function as a critical structure in DNA recognition and binding. Since cellular poly(ADP-ribosyl)ation capacity has been positively correlated with zinc status in cells, we hypothesize that arsenite binding-induced zinc loss from PARP-1 is equivalent to zinc deficiency in reducing PARP-1 activity, leading to inhibition of DNA repair. To test this hypothesis, we compared the effects of arsenite exposure with zinc deficiency, created by using the membrane-permeable zinc chelator TPEN, on 8-OHdG formation, PARP-1 activity and zinc binding to PARP-1 in HaCat cells. Our results show that arsenite exposure and zinc deficiency had similar effects on PARP-1 protein, whereas supplemental zinc reversed these effects. To investigate the molecular mechanism of zinc loss induced by arsenite, ICP-AES, near UV spectroscopy, fluorescence, and circular dichroism spectroscopy were utilized to examine arsenite binding and occupation of a peptide representing the first zinc finger of PARP-1. We found that arsenite binding as well as zinc loss altered the conformation of zinc finger structure which functionally leads to PARP-1 inhibition. These findings suggest that arsenite binding to PARP-1 protein created similar adverse biological effects as zinc deficiency, which establishes the molecular mechanism for zinc supplementation as a potentially effective treatment to reverse the detrimental outcomes of arsenic exposure. - Highlights: • Arsenite binding is equivalent to zinc deficiency in reducing PARP-1 function. • Zinc reverses arsenic inhibition of PARP-1 activity and enhancement of DNA damage. • Arsenite binding and zinc loss alter the conformation of zinc finger

  13. Characterization of zinc-binding sites in human stromelysin-1: stoichiometry of the catalytic domain and identification of a cysteine ligand in the proenzyme.

    PubMed

    Salowe, S P; Marcy, A I; Cuca, G C; Smith, C K; Kopka, I E; Hagmann, W K; Hermes, J D

    1992-05-19

    A determination of the zinc stoichiometry of the catalytic domain of the human matrix metalloproteinase stromelysin-1 has been carried out using enzyme purified from recombinant Escherichia coli that express C-terminally truncated protein. Atomic absorption spectrometry revealed that both the proenzyme (prostrom255) and the mature active form (strom255) contained nearly 2 mol of Zn/mol of protein. Full-length prostromelysin purified from a mammalian cell culture line also contained zinc in excess of 1 equiv. While zinc in prostrom255 could not be removed by dialysis against o-phenanthroline, similar treatment of mature strom255 resulted in the loss of one-half of the original zinc content. The peptidase activity of the zinc-depleted protein was reduced by greater than 85% but could be restored upon addition of Zn2+ or Co2+. Addition of a thiol-containing inhibitor to a CoZn hybrid enzyme resulted in marked spectral changes in both the visible and ultraviolet regions characteristic of sulfur ligation to Co2+. This direct evidence for an integral role in catalysis and inhibitor binding confirms the location of the exchangeable metal at the active site. To examine the environment of zinc in the proenzyme, a fully cobalt-substituted proenzyme was prepared by in vivo metal replacement. The absorbance features of dicobalt prostrom255 were consistent with metal coordination by the single cysteine present in the propeptide, although the data do not allow assignment to a particular zinc site.(ABSTRACT TRUNCATED AT 250 WORDS)

  14. ZFNGenome: A comprehensive resource for locating zinc finger nuclease target sites in model organisms

    PubMed Central

    2011-01-01

    Background Zinc Finger Nucleases (ZFNs) have tremendous potential as tools to facilitate genomic modifications, such as precise gene knockouts or gene replacements by homologous recombination. ZFNs can be used to advance both basic research and clinical applications, including gene therapy. Recently, the ability to engineer ZFNs that target any desired genomic DNA sequence with high fidelity has improved significantly with the introduction of rapid, robust, and publicly available techniques for ZFN design such as the Oligomerized Pool ENgineering (OPEN) method. The motivation for this study is to make resources for genome modifications using OPEN-generated ZFNs more accessible to researchers by creating a user-friendly interface that identifies and provides quality scores for all potential ZFN target sites in the complete genomes of several model organisms. Description ZFNGenome is a GBrowse-based tool for identifying and visualizing potential target sites for OPEN-generated ZFNs. ZFNGenome currently includes a total of more than 11.6 million potential ZFN target sites, mapped within the fully sequenced genomes of seven model organisms; S. cerevisiae, C. reinhardtii, A. thaliana, D. melanogaster, D. rerio, C. elegans, and H. sapiens and can be visualized within the flexible GBrowse environment. Additional model organisms will be included in future updates. ZFNGenome provides information about each potential ZFN target site, including its chromosomal location and position relative to transcription initiation site(s). Users can query ZFNGenome using several different criteria (e.g., gene ID, transcript ID, target site sequence). Tracks in ZFNGenome also provide "uniqueness" and ZiFOpT (Zinc Finger OPEN Targeter) "confidence" scores that estimate the likelihood that a chosen ZFN target site will function in vivo. ZFNGenome is dynamically linked to ZiFDB, allowing users access to all available information about zinc finger reagents, such as the effectiveness of a given

  15. Impact of high dietary zinc on zinc accumulation, enzyme activity and proteomic profiles in the pancreas of piglets.

    PubMed

    Pieper, R; Martin, L; Schunter, N; Villodre Tudela, C; Weise, C; Klopfleisch, R; Zentek, J; Einspanier, R; Bondzio, A

    2015-04-01

    The exocrine pancreas plays an important role in zinc homeostasis. Feeding very high (2000-3000mgzinc/kg diet) levels of zinc oxide to piglets for short periods is a common practice in the swine industry to improve performance and prevent diseases. The impact on pancreatic function and possible side effects during long-term feeding of high dietary zinc levels are still poorly understood. A total of 54 weaned piglets were either fed with low (57mg/kg, LZn), normal (164mg/kg, NZn) or high (2425mg/kg, HZn) zinc concentration in the diets. After 4 weeks of feeding, ten piglets per treatment were euthanized and pancreas samples were taken. Tissue zinc concentration and metallothionein abundance was greater with HZn compared with NZn and LZn (P<0.05). Similarly, activity of α-amylase, lipase, trypsin and chymotrypsin was higher with HZn as compared with NZn and LZn diets (P<0.05), whereas elastase activity was unchanged. Total trolox equivalent antioxidative capacity of pancreas tissue was higher with HZn diets compared with the other treatments (P<0.05). Pancreatic protein profiles of NZn and HZn fed piglets were obtained by 2D-DIGE technique and revealed 15 differentially expressed proteins out of 2100 detected spots (P<0.05). The differentially expressed proteins aldose reductase, eukaryotic elongation factor II and peroxiredoxin III were confirmed by immunoblotting. Identified proteins include zinc finger-containing transcription factors and proteins mainly associated with oxidative stress response and signal transduction in HZn compared with NZn pigs. Histologic examination however showed no morphologic changes. The results suggest that long-term supply of very high dietary zinc increases zinc and metallothionein concentration, and digestive enzyme activity, but also triggers oxidative stress reactions in the pancreas of young pigs. The data provide new insights into pancreatic function under outbalanced zinc homeostasis.

  16. Designing Hydrolytic Zinc Metalloenzymes

    PubMed Central

    2015-01-01

    Zinc is an essential element required for the function of more than 300 enzymes spanning all classes. Despite years of dedicated study, questions regarding the connections between primary and secondary metal ligands and protein structure and function remain unanswered, despite numerous mechanistic, structural, biochemical, and synthetic model studies. Protein design is a powerful strategy for reproducing native metal sites that may be applied to answering some of these questions and subsequently generating novel zinc enzymes. From examination of the earliest design studies introducing simple Zn(II)-binding sites into de novo and natural protein scaffolds to current studies involving the preparation of efficient hydrolytic zinc sites, it is increasingly likely that protein design will achieve reaction rates previously thought possible only for native enzymes. This Current Topic will review the design and redesign of Zn(II)-binding sites in de novo-designed proteins and native protein scaffolds toward the preparation of catalytic hydrolytic sites. After discussing the preparation of Zn(II)-binding sites in various scaffolds, we will describe relevant examples for reengineering existing zinc sites to generate new or altered catalytic activities. Then, we will describe our work on the preparation of a de novo-designed hydrolytic zinc site in detail and present comparisons to related designed zinc sites. Collectively, these studies demonstrate the significant progress being made toward building zinc metalloenzymes from the bottom up. PMID:24506795

  17. Molecular dynamics study of zinc binding to cysteines in a peptide mimic of the alcohol dehydrogenase structural zinc site.

    PubMed

    Brandt, Erik G; Hellgren, Mikko; Brinck, Tore; Bergman, Tomas; Edholm, Olle

    2009-02-14

    The binding of zinc (Zn) ions to proteins is important for many cellular events. The theoretical and computational description of this binding (as well as that of other transition metals) is a challenging task. In this paper the binding of the Zn ion to four cysteine residues in the structural site of horse liver alcohol dehydrogenase (HLADH) is studied using a synthetic peptide mimic of this site. The study includes experimental measurements of binding constants, classical free energy calculations from molecular dynamics (MD) simulations and quantum mechanical (QM) electron structure calculations. The classical MD results account for interactions at the molecular level and reproduce the absolute binding energy and the hydration free energy of the Zn ion with an accuracy of about 10%. This is insufficient to obtain correct free energy differences. QM correction terms were calculated from density functional theory (DFT) on small clusters of atoms to include electronic polarisation of the closest waters and covalent contributions to the Zn-S coordination bond. This results in reasonably good agreement with the experimentally measured binding constants and Zn ion hydration free energies in agreement with published experimental values. The study also includes the replacement of one cysteine residue to an alanine. Simulations as well as experiments showed only a small effect of this upon the binding free energy. A detailed analysis indicate that the sulfur is replaced by three water molecules, thereby changing the coordination number of Zn from four (as in the original peptide) to six (as in water).

  18. Induction of metallothionein I by phenolic antioxidants requires metal-activated transcription factor 1 (MTF-1) and zinc.

    PubMed Central

    Bi, Yongyi; Palmiter, Richard D; Wood, Kristi M; Ma, Qiang

    2004-01-01

    Phenolic antioxidants, such as tBHQ [2,5-di-(t-butyl)-1,4-hydroquinone], induce Mt1 (metallothionein 1) gene expression and accumulation of MT protein. Induction of Mt1 mRNA does not depend on protein synthesis, and correlates with oxidation-reduction functions of the antioxidants. In the present study, we analysed the biochemical pathway of the induction. Induction depends on the presence of MTF-1 (metal-activated transcription factor 1), a transcription factor that is required for metal-induced transcription of Mt1, but does not require nuclear factor erythroid 2-related factor 2, a tBHQ-activated CNC bZip (cap 'n' collar basic leucine zipper) protein, that is responsible for regulating genes encoding phase II drug-metabolizing enzymes. Moreover, tBHQ induces the expression of MRE-beta Geo, a reporter gene driven by five metal response elements that constitute an optimal MTF-1 binding site. Reconstitution of Mtf1 -null cells with MTF-1 restores induction by both zinc and tBHQ. Unlike activation of phase II genes by tBHQ, induction of Mt1 expression does not occur in the presence of EDTA, when cells are cultured in zinc-depleted medium, or in cells with reduced intracellular 'free' zinc due to overexpression of ZnT1, a zinc-efflux transporter, indicating that induction requires zinc. In addition, fluorescence imaging reveals that tBHQ increases cytoplasmic free zinc concentration by mobilizing intracellular zinc pools. These findings establish that phenolic antioxidants activate Mt1 transcription by a zinc-dependent mechanism, which involves MTF-1 binding to metal regulator elements in the Mt1 gene promoter. PMID:14998373

  19. Zinc-triggered induction of tissue plasminogen activator by brain-derived neurotrophic factor and metalloproteinases.

    PubMed

    Hwang, Ih-Yeon; Sun, Eun-Sun; An, Ji Hak; Im, Hana; Lee, Sun-Ho; Lee, Joo-Yong; Han, Pyung-Lim; Koh, Jae-Young; Kim, Yang-Hee

    2011-09-01

    Tissue plasminogen activator (tPA) is necessary for hippocampal long-term potentiation. Synaptically released zinc also contributes to long-term potentiation, especially in the hippocampal CA3 region. Using cortical cultures, we examined whether zinc increased the concentration and/or activity of tPA. Two hours after a 10-min exposure to 300 μM zinc, expression of tPA and its substrate, plasminogen, were significantly increased, as was the proteolytic activity of tPA. In contrast, increasing extracellular or intracellular calcium levels did not affect the expression or secretion of tPA. Changing zinc influx or chelating intracellular zinc also failed to alter tPA/plasminogen induction by zinc, indicating that zinc acts extracellularly. Zinc-mediated extracellular activation of matrix metalloproteinase (MMP) underlies the up-regulation of brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase (Trk) signaling. Consistent with these findings, co-treatment with a neutralizing antibody against BDNF or specific inhibitors of MMPs or Trk largely reversed tPA/plasminogen induction by zinc. Treatment of cortical cultures with p-aminophenylmercuric acetate, an MMP activator, MMP-2, or BDNF alone induced tPA/plasminogen expression. BDNF mRNA and protein expression was also increased by zinc and mediated by MMPs. Thus, an extracellular zinc-dependent, MMP- and BDNF-mediated synaptic mechanism may regulate the levels and activity of tPA.

  20. Mutational Analysis of the High-Affinity Zinc Binding Site Validates a Refined Human Dopamine Transporter Homology Model

    PubMed Central

    Stockner, Thomas; Montgomery, Therese R.; Kudlacek, Oliver; Weissensteiner, Rene; Ecker, Gerhard F.; Freissmuth, Michael; Sitte, Harald H.

    2013-01-01

    The high-resolution crystal structure of the leucine transporter (LeuT) is frequently used as a template for homology models of the dopamine transporter (DAT). Although similar in structure, DAT differs considerably from LeuT in a number of ways: (i) when compared to LeuT, DAT has very long intracellular amino and carboxyl termini; (ii) LeuT and DAT share a rather low overall sequence identity (22%) and (iii) the extracellular loop 2 (EL2) of DAT is substantially longer than that of LeuT. Extracellular zinc binds to DAT and restricts the transporter‚s movement through the conformational cycle, thereby resulting in a decrease in substrate uptake. Residue H293 in EL2 praticipates in zinc binding and must be modelled correctly to allow for a full understanding of its effects. We exploited the high-affinity zinc binding site endogenously present in DAT to create a model of the complete transmemberane domain of DAT. The zinc binding site provided a DAT-specific molecular ruler for calibration of the model. Our DAT model places EL2 at the transporter lipid interface in the vicinity of the zinc binding site. Based on the model, D206 was predicted to represent a fourth co-ordinating residue, in addition to the three previously described zinc binding residues H193, H375 and E396. This prediction was confirmed by mutagenesis: substitution of D206 by lysine and cysteine affected the inhibitory potency of zinc and the maximum inhibition exerted by zinc, respectively. Conversely, the structural changes observed in the model allowed for rationalizing the zinc-dependent regulation of DAT: upon binding, zinc stabilizes the outward-facing state, because its first coordination shell can only be completed in this conformation. Thus, the model provides a validated solution to the long extracellular loop and may be useful to address other aspects of the transport cycle. PMID:23436987

  1. Mutational analysis of the high-affinity zinc binding site validates a refined human dopamine transporter homology model.

    PubMed

    Stockner, Thomas; Montgomery, Therese R; Kudlacek, Oliver; Weissensteiner, Rene; Ecker, Gerhard F; Freissmuth, Michael; Sitte, Harald H

    2013-01-01

    The high-resolution crystal structure of the leucine transporter (LeuT) is frequently used as a template for homology models of the dopamine transporter (DAT). Although similar in structure, DAT differs considerably from LeuT in a number of ways: (i) when compared to LeuT, DAT has very long intracellular amino and carboxyl termini; (ii) LeuT and DAT share a rather low overall sequence identity (22%) and (iii) the extracellular loop 2 (EL2) of DAT is substantially longer than that of LeuT. Extracellular zinc binds to DAT and restricts the transporter's movement through the conformational cycle, thereby resulting in a decrease in substrate uptake. Residue H293 in EL2 praticipates in zinc binding and must be modelled correctly to allow for a full understanding of its effects. We exploited the high-affinity zinc binding site endogenously present in DAT to create a model of the complete transmemberane domain of DAT. The zinc binding site provided a DAT-specific molecular ruler for calibration of the model. Our DAT model places EL2 at the transporter lipid interface in the vicinity of the zinc binding site. Based on the model, D206 was predicted to represent a fourth co-ordinating residue, in addition to the three previously described zinc binding residues H193, H375 and E396. This prediction was confirmed by mutagenesis: substitution of D206 by lysine and cysteine affected the inhibitory potency of zinc and the maximum inhibition exerted by zinc, respectively. Conversely, the structural changes observed in the model allowed for rationalizing the zinc-dependent regulation of DAT: upon binding, zinc stabilizes the outward-facing state, because its first coordination shell can only be completed in this conformation. Thus, the model provides a validated solution to the long extracellular loop and may be useful to address other aspects of the transport cycle.

  2. Salt site performance assessment activities

    SciTech Connect

    Kircher, J.F.; Gupta, S.K.

    1983-01-01

    During this year the first selection of the tools (codes) for performance assessments of potential salt sites have been tentatively selected and documented; the emphasis has shifted from code development to applications. During this period prior to detailed characterization of a salt site, the focus is on bounding calculations, sensitivity and with the data available. The development and application of improved methods for sensitivity and uncertainty analysis is a focus for the coming years activities and the subject of a following paper in these proceedings. Although the assessments to date are preliminary and based on admittedly scant data, the results indicate that suitable salt sites can be identified and repository subsystems designed which will meet the established criteria for protecting the health and safety of the public. 36 references, 5 figures, 2 tables.

  3. Design and photocatalytic activity of nanosized zinc oxides

    NASA Astrophysics Data System (ADS)

    Gancheva, M.; Markova-Velichkova, M.; Atanasova, G.; Kovacheva, D.; Uzunov, I.; Cukeva, R.

    2016-04-01

    Zinc oxide particles with various morphologies were successfully prepared via three synthesis methods: precipitation; tribophysical treatment and sonochemistry. The as-synthesized samples were characterized by X-ray diffraction (XRD); infrared spectroscopy (IR); scanning electron microscope (SEM); BET specific surface area; electron-paramagnetic resonance (EPR), UV-Vis absorption/diffuse reflectance and X-ray photoelectron spectroscopy (XPS). Photocatalytic activities of the samples were evaluated by degradation of Malachite Green (MG) in an aqueous solution under UV and visible irradiation. The obtained ZnO powders possess crystallites size below 20 nm. The ZnO with spherical particles were obtained by precipitation method. The sonochemistry approach leads to preparation of ZnO with nanorod particles. The calculated band gaps of various ZnO powders belong to the range from 3.12 to 3.30 eV. The obtained polycrystalline zinc oxides exhibit good photocatalytic activity which is strongly influenced by the preparation conditions. The nanorod ZnO exhibits high photocatalytic activity under UV irradiation which is attributed to the morphology and the geometric surface of the particles. The ZnO obtained by precipitation has better photocatalytic efficiency under visible irradiation due to high B.E.T. specific surface area and the low level of band gap. Tribophysical treatment of a particle size-homogeneous system leads to deterioration of the photocatalytic activity of the material.

  4. Zinc Coordination Is Required for and Regulates Transcription Activation by Epstein-Barr Nuclear Antigen 1

    PubMed Central

    Aras, Siddhesh; Singh, Gyanendra; Johnston, Kenneth; Foster, Timothy; Aiyar, Ashok

    2009-01-01

    Epstein-Barr Nuclear Antigen 1 (EBNA1) is essential for Epstein-Barr virus to immortalize naïve B-cells. Upon binding a cluster of 20 cognate binding-sites termed the family of repeats, EBNA1 transactivates promoters for EBV genes that are required for immortalization. A small domain, termed UR1, that is 25 amino-acids in length, has been identified previously as essential for EBNA1 to activate transcription. In this study, we have elucidated how UR1 contributes to EBNA1's ability to transactivate. We show that zinc is necessary for EBNA1 to activate transcription, and that UR1 coordinates zinc through a pair of essential cysteines contained within it. UR1 dimerizes upon coordinating zinc, indicating that EBNA1 contains a second dimerization interface in its amino-terminus. There is a strong correlation between UR1-mediated dimerization and EBNA1's ability to transactivate cooperatively. Point mutants of EBNA1 that disrupt zinc coordination also prevent self-association, and do not activate transcription cooperatively. Further, we demonstrate that UR1 acts as a molecular sensor that regulates the ability of EBNA1 to activate transcription in response to changes in redox and oxygen partial pressure (pO2). Mild oxidative stress mimicking such environmental changes decreases EBNA1-dependent transcription in a lymphoblastoid cell-line. Coincident with a reduction in EBNA1-dependent transcription, reductions are observed in EBNA2 and LMP1 protein levels. Although these changes do not affect LCL survival, treated cells accumulate in G0/G1. These findings are discussed in the context of EBV latency in body compartments that differ strikingly in their pO2 and redox potential. PMID:19521517

  5. Preparation of silver-activated zinc sulfide thin films

    NASA Technical Reports Server (NTRS)

    Feldman, C.; Swindells, F. E.

    1968-01-01

    Silver improves luminescence and reduces contamination of zinc sulfide phosphors. The silver is added after the zinc sulfide phosphors are deposited in thin films by vapor evaporation, but before calcining, by immersion in a solution of silver salt.

  6. Charge dependent photodynamic activity of alanine based zinc phthalocyanines.

    PubMed

    Wang, Ao; Li, Yejing; Zhou, Lin; Yuan, Linxin; Lu, Shan; Lin, Yun; Zhou, Jiahong; Wei, Shaohua

    2014-12-01

    In this paper, to minimize the effects of different structure, three alanine-based zinc phthalocyanines (Pcs) of differing charges were engineered and synthesized with the same basic structure. On this premise, the relationship between nature of charge and photodynamic activity was studied. Besides, further verification and explanation of some inconsistent results were also carried out. The results showed that charge can influence the aggregation state, singlet oxygen generation ability and cellular uptake of Pcs, thereby affecting their photodynamic activity. In addition, the biomolecules inside cells may interact with Pcs of differing charges, which can also influence the aggregation state and singlet oxygen generation of the Pcs, and then influence the relationship between nature of charge and photodynamic activity.

  7. Tissue Plasminogen Activator Alters Intracellular Sequestration of Zinc through Interaction with the Transporter ZIP4

    SciTech Connect

    Emmetsberger, Jaime; Mirrione, Martine M.; Zhou, Chun; Fernandez-Monreal, Monica; Siddiq, Mustafa M.; Ji, Kyungmin; Tsirka, Stella E.

    2010-09-17

    Glutamatergic neurons contain free zinc packaged into neurotransmitter-loaded synaptic vesicles. Upon neuronal activation, the vesicular contents are released into the synaptic space, whereby the zinc modulates activity of postsynaptic neurons though interactions with receptors, transporters and exchangers. However, high extracellular concentrations of zinc trigger seizures and are neurotoxic if substantial amounts of zinc reenter the cells via ion channels and accumulate in the cytoplasm. Tissue plasminogen activator (tPA), a secreted serine protease, is also proepileptic and excitotoxic. However, tPA counters zinc toxicity by promoting zinc import back into the neurons in a sequestered form that is nontoxic. Here, we identify the zinc influx transporter, ZIP4, as the pathway through which tPA mediates the zinc uptake. We show that ZIP4 is upregulated after excitotoxin stimulation of the mouse, male and female, hippocampus. ZIP4 physically interacts with tPA, correlating with an increased intracellular zinc influx and lysosomal sequestration. Changes in prosurvival signals support the idea that this sequestration results in neuroprotection. These experiments identify a mechanism via which neurons use tPA to efficiently neutralize the toxic effects of excessive concentrations of free zinc.

  8. Zinc differentially regulates mitogen-activated protein kinases in human T cells.

    PubMed

    Hönscheid, Andrea; Dubben, Svenja; Rink, Lothar; Haase, Hajo

    2012-01-01

    Zinc is an essential nutrient with remarkable importance for immunity, in particular for T-cell function. This is, at least in part, based on an involvement of zinc ions in immune cell signal transduction; dynamic changes of the intracellular free zinc concentration have recently been recognized as signaling events. Because the molecular targets of zinc signals remain incompletely understood, we investigated the impact of elevated intracellular free zinc on mitogen-activated protein kinase (MAPK) activity and MAPK-dependent cytokine production in human T-cells. p38 was activated by treatment with zinc and the ionophore pyrithione, whereas ERK1/2 and c-Jun N-terminal kinases were unaffected. In contrast, after T-cell receptor stimulation with antibodies against CD3, ERK1/2-phosphorylation was selectively suppressed by intracellular zinc. Mechanisms that had been shown to mediate zinc-effects in other cells, such as activation of the Src kinase Lck, inhibition of the protein tyrosine phosphatase CD45 or MAPK phosphatases and cyclic nucleotide/protein kinase A signaling were not involved. This indicates that the differential impact of zinc on the MAPK families in T-cells is mediated by mechanisms that differ from the ones observed in other cell types. Further investigation of the activation of p38 by zinc demonstrated that this MAPK is responsible for the zinc-mediated activation of CREB and mRNA expression of the Th1 cytokines interferon-gamma and interleukin-2. In conclusion, regulation of MAPK activity contributes to the impact of zinc on T-cell function.

  9. A simple liposome assay for the screening of zinc ionophore activity of polyphenols.

    PubMed

    Clergeaud, Gael; Dabbagh-Bazarbachi, Husam; Ortiz, Mayreli; Fernández-Larrea, Juan B; O'Sullivan, Ciara K

    2016-04-15

    An efficient liposomal system for screening the zinc ionophore activity of a selected library consisting of the most relevant dietary polyphenols is presented. The zinc ionophore activity was demonstrated by exploring the use of zinc-specific fluorophore FluoZin-3 loaded liposomes as simple membrane tools that mimic the cell membrane. The zinc ionophore activity was demonstrated as the capacity of polyphenols to transport zinc cations across the liposome membrane and increase the zinc-specific fluorescence of the encapsulated fluorophore FluoZin-3. In addition, the zinc chelation strength of the polyphenols was also tested in a competition assay based on the fluorescence quenching of zinc-dependent fluorescence emitted by zinc-FluoZin-3 complex. Finally, the correlation between the chelation capacity and ionophore activity is demonstrated, thus underlining the sequestering or ionophoric activity that the phenolic compounds can display, thus, providing better knowledge of the importance of the structural conformation versus their biological activity. Furthermore, the assays developed can be used as tools for rapid, high-throughput screening of families of polyphenols towards different biometals.

  10. Characteristics of Zinc Phosphate Coating Activated by Different Concentrations of Nickel Acetate Solution

    NASA Astrophysics Data System (ADS)

    Abdalla, Khalid; Zuhailawati, H.; Rahmat, Azmi; Azizan, A.

    2017-02-01

    Activation pretreatment with nickel acetate solution at various concentrations was performed prior to the phosphating step to enhance the corrosion resistance of carbon steel substrates. The activation solution was studied over various concentrations: 10, 50, and 100 g/L. The effects of these concentrations on surface characteristics and microstructural evolution of the coated samples were characterized by scanning electron microscopy and energy-dispersive spectroscopy. The electrochemical behavior was evaluated using potentiodynamic polarization curves, electrochemical impedance spectroscopy, and immersion test in a 3.5 pct NaCl solution. Significant increases in the nucleation sites and surface coverage of zinc phosphate coating were observed as the concentration of activation solution reached 50 g/L. The electrochemical analysis revealed that the activation treatment with 50 g/L nickel acetate solution significantly improved the protection ability of the zinc phosphate coating. The corrosion current density of activated phosphate coating with 50 g/L was reduced by 64.64 and 13.22 pct, compared to the coatings obtained with activation solutions of 10 and 100 g/L, respectively.

  11. In vitro inhibition of superoxide anion production and superoxide dismutase activity by zinc in human spermatozoa.

    PubMed

    Gavella, M; Lipovac, V; Vucić, M; Sverko, V

    1999-08-01

    The in vitro effect of zinc on superoxide anion (O2-) generation and on SOD-like activity in spermatozoa of infertile men was investigated. The formation of superoxide anion was stimulated by NADPH and the level of superoxide anion was measured by the reduction of ferricytochrome c. Both Percoll-isolated (n = 14) and washed spermatozoa (n = 14) exposed to 1 mmol/L zinc (60 min, 37 degrees C), released less (p < 0.002 and p < 0.04, respectively) superoxide anions than did zinc-untreated spermatozoa. These results implicate a possible role for zinc as a scavenger of excessive superoxide anions produced by defective spermatozoa in semen after ejaculation. Additionally, zinc was found to dose-dependently inhibit superoxide dismutase (SOD)-like activity of spermatozoa in vitro. The inhibition of SOD-like activity by an equal concentration of zinc (1 mmol/L) was less pronounced in oligospermic (p < 0.002; n = 16) and asthenozoospermic (p < 0.0005; n = 20) than in normozoospermic samples (p < 0.0001; n = 20). This differential ability of zinc to inhibit SOD-like activity may be relevant to the physiological function of spermatozoa in fertilization. The evidence that zinc may elicit an inhibition of both superoxide anion production and SOD-like activity in human spermatozoa, indicate the existence of novel, zinc-related mechanism(s) involved in the oxidative events occurring after ejaculation, with a possible modulatory effect on germ cell function.

  12. Structure-photodynamic activity relationships of substituted zinc trisulfophthalocyanines.

    PubMed

    Cauchon, Nicole; Tian, Hongjian; Langlois, Réjean; La Madeleine, Carole; Martin, Stephane; Ali, Hasrat; Hunting, Darel; van Lier, Johan E

    2005-01-01

    To identify optimal features of metalated sulfophthalocyanine dyes for their use as photosensitizers in the photodynamic therapy of cancer, we synthesized a series of alkynyl-substituted trisulfonated phthalocyanines and compared their amphiphilic properties to a number of parameters related to their photodynamic potency. Varying the length of the substituted alkynyl side-chain modulates the hydrophobic/hydrophilic properties of the dyes providing a linear relationship between their n-octanol/water partition coefficients and retention times on reversed-phase HPLC. Aggregate formation of the dyes in aqueous solution increased with increasing hydrophobicity while monomer formation was favored by the addition of serum proteins or organic solvent. Trisulfonated zinc phthalocyanines bearing hexynyl and nonynyl substituents exhibited high cellular uptake with strong localization at the mitochondrial membranes, which coincided with effective photocytotoxicity toward EMT-6 murine mammary tumor cells. Further increase in the length of the alkynyl chains (dodecynyl, hexadecynyl) did not improve their phototoxicity, likely resulting from extensive aggregation of the dyes in aqueous medium and reduced cell uptake. Aggregation was evident from shifts in the electronic spectra and reduced capacity to generate singlet oxygen. When monomerized through the addition of Cremophor EL all sulfonated zinc phthalocyanines gave similar singlet oxygen yields. Accordingly, differences in the tendency of the dyes to aggregate do not appear to be a determining factor in their photodynamic potency. Our results confirm that the latter in particular relates to their amphiphilic properties, which facilitate cell uptake and intracellular localization at photosensitive sites such as the mitochondria. Combined, these factors play a significant role in the overall photodynamic potency of the dyes.

  13. Seasonal and spatial patterns of metals at a restored copper mine site. I. Stream copper and zinc

    USGS Publications Warehouse

    Bambic, D.G.; Alpers, C.N.; Green, P.G.; Fanelli, E.; Silk, W.K.

    2006-01-01

    Seasonal and spatial variations in metal concentrations and pH were found in a stream at a restored copper mine site located near a massive sulfide deposit in the Foothill copper-zinc belt of the Sierra Nevada, California. At the mouth of the stream, copper concentrations increased and pH decreased with increased streamflow after the onset of winter rain and, unexpectedly, reached extreme values 1 or 2 months after peaks in the seasonal hydrographs. In contrast, aqueous zinc and sulfate concentrations were highest during low-flow periods. Spatial variation was assessed in 400 m of reach encompassing an acidic, metal-laden seep. At this seep, pH remained low (2-3) throughout the year, and copper concentrations were highest. In contrast, the zinc concentrations increased with downstream distance. These spatial patterns were caused by immobilization of copper by hydrous ferric oxides in benthic sediments, coupled with increasing downstream supply of zinc from groundwater seepage.

  14. [Design, synthesis, and biological activities of histone deacetylase inhibitors with diketo ester as zinc binding group].

    PubMed

    Lu, Hui; Su, Hong; Yang, Bo; You, Qi-Dong

    2011-03-01

    Histone deacetylases (HDACs) inhibition causes hyperacetylation of histones leading to growth arrest, differentiation and apoptosis of tumor cells, representing a new strategy in cancer therapy. Many of previously reported HDACs inhibitors are hydroxamic acid derivatives, which could chelate the zinc ion in the active site in a bidentate fashion. However, hydroxamic acids occasionally have produced problems such as poor pharmacokinetics, severe toxicity and low selectivity. Herein we describe the identification of a new series of non-hydroxamate HDACs inhibitors bearing diketo ester moieties as zinc binding group. HDACs inhibition assay and antiproliferation assays in vitro against multiple cancer cell lines were used for evaluation. These compounds displayed low antiproliferative activity against solid tumor cells, while good antiproliferative activity against human leukemic monocyte lymphoma cell line U937. Compound CPUYS707 is the best with GI50 value of 0.31 micromol x L(-1) against U937 cells, which is more potent than SAHA and MS-275. HDACs inhibition activity of these compounds is lower than that expected, further evaluation is needed.

  15. Zinc and copper status of women by physical activity and menstrual status

    SciTech Connect

    Singh, A.; Deuster, P.A.; Kyle, S.B.; Moser, P.B.

    1986-03-01

    The zinc and copper status of 33 eumenorrheic (EU) and 12 amenorrheic (AM) female marathon runners and 19 EU and 8 AM nonrunners were determined from 3-day diet records and plasma and erythrocyte (RBC) levels. The study was conducted as a completely randomized 2 x 2 factorial. Mean daily zinc intakes of all groups fell below the recommended dietary allowances. Copper intakes of runners (EU = 1.3 mg; AM = 1.3 mg) were not significantly different. Menstrual status did not affect plasma zinc, RBC zinc or plasma copper levels. Physical activity however, affected RBC zinc and plasma copper levels. Both these parameters were significantly higher in runners. These findings suggest that exercise influences blood zinc and copper levels.

  16. Calcium ion gradients modulate the zinc affinity and antibacterial activity of human calprotectin.

    PubMed

    Brophy, Megan Brunjes; Hayden, Joshua A; Nolan, Elizabeth M

    2012-10-31

    Calprotectin (CP) is an antimicrobial protein produced and released by neutrophils that inhibits the growth of pathogenic microorganisms by sequestering essential metal nutrients in the extracellular space. In this work, spectroscopic and thermodynamic metal-binding studies are presented to delineate the zinc-binding properties of CP. Unique optical absorption and EPR spectroscopic signatures for the interfacial His(3)Asp and His(4) sites of human calprotectin are identified by using Co(II) as a spectroscopic probe. Zinc competition titrations employing chromophoric Zn(II) indicators provide a 2:1 Zn(II):CP stoichiometry, confirm that the His(3)Asp and His(4) sites of CP coordinate Zn(II), and reveal that the Zn(II) affinity of both sites is calcium-dependent. The calcium-insensitive Zn(II) competitor ZP4 affords dissociation constants of K(d1) = 133 ± 58 pM and K(d2) = 185 ± 219 nM for CP in the absence of Ca(II). These values decrease to K(d1) ≤ 10 pM and K(d2) ≤ 240 pM in the presence of excess Ca(II). The K(d1) and K(d2) values are assigned to the His(3)Asp and His(4) sites, respectively. In vitro antibacterial activity assays indicate that the metal-binding sites and Ca(II)-replete conditions are required for CP to inhibit the growth of both Gram-negative and -positive bacteria. Taken together, these data provide a working model whereby calprotectin responds to physiological Ca(II) gradients to become a potent Zn(II) chelator in the extracellular space.

  17. Anti-diabetic activity and safety assessment of Ayurvedic medicine, Jasada bhasma (zinc ash) in rats.

    PubMed

    Umrani, Rinku D; Agrawal, Durgashankar S; Paknikar, Kishore M

    2013-10-01

    Jasada bhasma (zinc ash) is an extensively used Ayurvedic medicine for treating diabetes mellitus. The present communication presents yet unavailable comprehensive scientific data on its physico-chemical nature vis-a-vis anti-diabetic activity and toxicity profile.Zinc ash prepared by traditional method was found to consist of 200-500 nm sized particles, predominantly zinc oxide with hexagonal wurtzite crystal structure. The effective dose range of zinc ash in oral glucose tolerance tests performed using normoglycemic Wistar rats was found to be 3-30 mg/kg. Subsequently anti-diabetic activity was assessed in streptozotocin induced type 1 and type 2 diabetic rats. Four weeks treatment with zinc ash (1, 3, 10 mg/kg) resulted in improved glucose tolerance (16-19%), lowered blood glucose levels (20-33%) and reduced serum insulin levels (27-32%). Systemic absorption was assessed by single dose pharmacokinetic study where serum zinc levels were found to be elevated (3.5 folds) after oral administration of zinc ash. Acute and sub-acute toxicity tests demonstrated safety of zinc ash up to 300 mg/kg doseie. 100 times the efficacy dose in rats. These findings, the first of their kind, provide concrete scientific evidence that justifies usage of zinc ash in diabetes treatment.

  18. Novel zinc alginate hydrogels prepared by internal setting method with intrinsic antibacterial activity.

    PubMed

    Straccia, Maria Cristina; d'Ayala, Giovanna Gomez; Romano, Ida; Laurienzo, Paola

    2015-07-10

    In this paper, a controlled gelation of alginate was performed for the first time using ZnCO3 and GDL. Uniform and transparent gels were obtained and investigated as potential wound dressings. Homogeneity, water content, swelling capability, water evaporation rate, stability in normal saline solution, mechanical properties and antibacterial activity were assessed as a function of zinc concentration. Gelation rate increased at increasing zinc content, while a decrease in water uptake and an improvement of stability were found. Release of zinc in physiological environments showed that concentration of zinc released in solution lies below the cytotoxicity level. Hydrogels showed antimicrobial activity against Escherichia coli. The hydrogel with highest zinc content was stabilized with calcium by immersion in a calcium chloride solution. The resulting hydrogel preserved homogeneity and antibacterial activity. Furthermore, it showed even an improvement of stability and mechanical properties, which makes it suitable as long-lasting wound dressing.

  19. The zinc spark is an inorganic signature of human egg activation

    PubMed Central

    Duncan, Francesca E.; Que, Emily L.; Zhang, Nan; Feinberg, Eve C.; O’Halloran, Thomas V.; Woodruff, Teresa K.

    2016-01-01

    Egg activation refers to events required for transition of a gamete into an embryo, including establishment of the polyspermy block, completion of meiosis, entry into mitosis, selective recruitment and degradation of maternal mRNA, and pronuclear development. Here we show that zinc fluxes accompany human egg activation. We monitored calcium and zinc dynamics in individual human eggs using selective fluorophores following activation with calcium-ionomycin, ionomycin, or hPLCζ cRNA microinjection. These egg activation methods, as expected, induced rises in intracellular calcium levels and also triggered the coordinated release of zinc into the extracellular space in a prominent “zinc spark.” The ability of the gamete to mount a zinc spark response was meiotic-stage dependent. Moreover, chelation of intracellular zinc alone was sufficient to induce cell cycle resumption and transition of a meiotic cell into a mitotic one. Together, these results demonstrate critical functions for zinc dynamics and establish the zinc spark as an extracellular marker of early human development. PMID:27113677

  20. Aspartate 46, a second sphere ligand to the catalytic zinc, is essential for activity of yeast alcohol dehydrogenase

    SciTech Connect

    Ganzhorn, A.J.; Plapp, B.V.

    1987-05-01

    The crystal structure of horse liver alcohol dehydrogenase (ADH) shows a hydrogen bond between the imidazole of His-67, a ligand to the active site zinc, and the carboxylate of Asp-49. Both residues are conserved in alcohol dehydrogenases. Directed mutagenesis was used to replace the homologous Asp-46 in ADH I from S. cerevisiae with asparagine. The substitution did not alter the overall structure of the enzyme, as judged by CD measurements, but the removal of a negative charge was evident in electrophoresis, and in the absorption and fluorescence spectra. The mutant and wild-type enzymes had similar zinc contents as determined by atomic absorption spectroscopy. Active site titration and steady state kinetics indicated that binding of coenzymes, substrates and substrate analogs is 4-24 fold weaker in the asparagine enzyme. The turnover numbers were reduced by a factor of 70 for ethanol oxidation and 30 for acetaldehyde reduction at pH 7.3, 30/sup 0/C. Dead end inhibition studies and the kinetic isotope effect showed that NAD and ethanol binding follow a rapid equilibrium random mechanism as opposed to the ordered mechanism found for ADH I. They conclude that the carboxyl group of Asp-46 is essential for the electrostatic environment near the active site zinc. Amidation may affect the geometry and/or coordination of the metal complex.

  1. Characterization of a bacterial community in an abandoned semiarid lead-zinc mine tailing site.

    PubMed

    Mendez, Monica O; Neilson, Julia W; Maier, Raina M

    2008-06-01

    Bacterial diversity in mine tailing microbial communities has not been thoroughly investigated despite the correlations that have been observed between the relative microbial diversity and the success of revegetation efforts at tailing sites. This study employed phylogenetic analyses of 16S rRNA genes to compare the bacterial communities present in highly disturbed, extremely (pH 2.7) and moderately (pH 5.7) acidic lead-zinc mine tailing samples from a semiarid environment with those from a vegetated off-site (OS) control sample (pH 8). Phylotype richness in these communities decreased from 42 in the OS control to 24 in the moderately acidic samples and 8 in the extremely acidic tailing samples. The clones in the extremely acidic tailing sample were most closely related to acidophiles, none of which were detected in the OS control sample. The comparison generated by this study between the bacteria present in extremely acidic tailing and that in moderately acidic tailing communities with those in an OS control soil provides a reference point from which to evaluate the successful restoration of mine tailing disposal sites by phytostabilization.

  2. Normal Modes Expose Active Sites in Enzymes

    PubMed Central

    Glantz-Gashai, Yitav; Samson, Abraham O.

    2016-01-01

    Accurate prediction of active sites is an important tool in bioinformatics. Here we present an improved structure based technique to expose active sites that is based on large changes of solvent accessibility accompanying normal mode dynamics. The technique which detects EXPOsure of active SITes through normal modEs is named EXPOSITE. The technique is trained using a small 133 enzyme dataset and tested using a large 845 enzyme dataset, both with known active site residues. EXPOSITE is also tested in a benchmark protein ligand dataset (PLD) comprising 48 proteins with and without bound ligands. EXPOSITE is shown to successfully locate the active site in most instances, and is found to be more accurate than other structure-based techniques. Interestingly, in several instances, the active site does not correspond to the largest pocket. EXPOSITE is advantageous due to its high precision and paves the way for structure based prediction of active site in enzymes. PMID:28002427

  3. The Electronic Behavior of Zinc-Finger Protein Binding Sites in the Context of the DNA Extended Ladder Model

    NASA Astrophysics Data System (ADS)

    Oiwa, Nestor; Cordeiro, Claudette; Heermann, Dieter

    2016-05-01

    Instead of ATCG letter alignments, typically used in bioinformatics, we propose a new alignment method using the probability distribution function of the bottom of the occupied molecular orbital (BOMO), highest occupied molecular orbital (HOMO) and lowest unoccupied orbital (LUMO). We apply the technique to transcription factors with Cys2His2 zinc fingers. These transcription factors search for binding sites, probing for the electronic patterns at the minor and major DNA groves. The eukaryotic Cys2His2 zinc finger proteins bind to DNA ubiquitously at highly conserved domains. They are responsible for gene regulation and the spatial organization of DNA. To study and understand these zinc finger DNA-protein interactions, we use the extended ladder in the DNA model proposed by Zhu, Rasmussen, Balatsky & Bishop (2007) te{Zhu-2007}. Considering one single spinless electron in each nucleotide π-orbital along a double DNA chain (dDNA), we find a typical pattern for the bottom of BOMO, HOMO and LUMO along the binding sites. We specifically looked at two members of zinc finger protein family: specificity protein 1 (SP1) and early grown response 1 transcription factors (EGR1). When the valence band is filled, we find electrons in the purines along the nucleotide sequence, compatible with the electric charges of the binding amino acids in SP1 and EGR1 zinc finger.

  4. Identification by site-directed mutagenesis of three essential histidine residues in membrane dipeptidase, a novel mammalian zinc peptidase.

    PubMed Central

    Keynan, S; Hooper, N M; Turner, A J

    1997-01-01

    Membrane dipeptidase (EC 3.4.13.19) is a plasma membrane zinc peptidase that is involved in the renal metabolism of glutathione and its conjugates, such as leukotriene D4. The enzyme lacks the classical signatures of other zinc-dependent hydrolases and shows no homology with any other mammalian protein. We have used site-directed mutagenesis to explore the roles of five histidine residues in pig membrane dipeptidase that are conserved among mammalian species. When expressed in COS-1 cells, the mutants H49K and H128L exhibited a specific activity and Km for the substrate Gly-D-Phe comparable with those of the wild-type enzyme. However, the mutants H20L, H152L and H198K were inactive, but were expressed at the cell surface at equivalent levels to the wild-type, as assessed by immunoblotting and immunofluorescence. These three mutants were compared with regard to their ability to bind to the competitive inhibitor cilastatin, which binds with equal efficacy to native and EDTA-treated pig kidney membrane dipeptidase. Expressed wild-type enzyme and mutants H20L and H198K were efficiently bound by cilastatin-Sepharose, but H152L failed to bind. Thus His-152 appears to be involved in the binding of substrate or inhibitor, whereas His-20 and His-198 appear to be involved in catalysis. Membrane dipeptidase shares some similarity with a dipeptidase recently cloned from Acinetobacter calcoaceticus. In particular, His-20 and His-198 of membrane dipeptidase are conserved in the bacterial enzyme, as are Glu-125 and His-219, previously shown to be required for catalytic activity. PMID:9337849

  5. Active and passive control of zinc phthalocyanine photodynamics.

    PubMed

    Sharma, Divya; Huijser, Annemarie; Savolainen, Janne; Steen, Gerwin; Herek, Jennifer L

    2013-01-01

    In this work we report on the ultrafast photodynamics of the photosensitizer zinc phthalocyanine (ZnPc) and manipulation thereof. Two approaches are followed: active control via pulse shaping and passive control via strategic manipulation in the periphery of the molecular structure. The objective of both of these control experiments is the same: to enhance the yield of the functional pathway and to minimize loss channels. The aim of the active control experiments is to increase the intersystem crossing yield in ZnPc, which is important for application in photodynamic therapy (PDT). Pulse shaping allowed an improvement in triplet to singlet ratio of 15% as compared to a transform-limited pulse. This effect is ascribed to a control mechanism that utilizes multiphoton pathways to higher-lying states from where intersystem crossing is more likely to occur. The passive control experiments are performed on ZnPc derivatives deposited onto TiO2, serving as a model system of a dye-sensitized solar cell (DSSC). Modification of the anchoring ligand of the molecular structure resulted in an increased rate for electron injection into TiO2 and slower back electron transfer, improving the DSSC efficiency.

  6. Zinc inhibits nuclear factor-kappa B activation and sensitizes prostate cancer cells to cytotoxic agents.

    PubMed

    Uzzo, Robert G; Leavis, Paul; Hatch, William; Gabai, Vladimir L; Dulin, Nickolai; Zvartau, Nadezhda; Kolenko, Vladimir M

    2002-11-01

    Prostate carcinogenesis involves transformation of zinc-accumulating normal epithelial cells to malignant cells, which do not accumulate zinc. In this study, we demonstrate by immunoblotting and immunohistochemistry that physiological levels of zinc inhibit activation of nuclear factor (NF)-kappa B transcription factor in PC-3 and DU-145 human prostate cancer cells, reduce expression of NF-kappa B-controlled antiapoptotic protein c-IAP2, and activate c-Jun NH(2)-terminal kinases. Preincubation of PC-3 cells with physiological concentrations of zinc sensitized tumor cells to tumor necrosis factor (TNF)-alpha, and paclitaxel mediated cell death as defined by terminal deoxynucleotidyl transferase-mediated nick end labeling assay. These results suggest one possible mechanism for the inhibitory effect of zinc on the development and progression of prostate malignancy and might have important consequences for the prevention and treatment of prostate cancer.

  7. Zinc distribution in blood components, inflammatory status, and clinical indexes of disease activity during zinc supplementation in inflammatory rheumatic diseases.

    PubMed

    Peretz, A; Nève, J; Jeghers, O; Pelen, F

    1993-05-01

    The effects of zinc supplementation on zinc status and on clinical and biological indicators of inflammation were investigated in 18 patients with chronic inflammatory rheumatic diseases and in 9 healthy control subjects. Patients with mild and recent onset disease were assigned to a 60-d trial to receive either 45 mg Zn (as gluconate)/d or a placebo, while control subjects received the zinc supplement. Baseline mean plasma zinc of the patients was low whereas mononuclear cell zinc content was elevated, suggesting a redistribution of the element related to the inflammatory process rather than to a zinc-deficient state. Zinc supplementation increased plasma zinc to a similar extent in patients and in control subjects, which suggested no impairment of zinc intestinal absorption as a result of the inflammatory process. On the contrary, erythrocyte and leukocyte zinc concentrations were not modified in the two groups examined. No beneficial effect of zinc treatment could be demonstrated on either clinical or inflammation indexes.

  8. Inhibition of beta-amylase activity by calcium, magnesium and zinc ions determined by spectrophotometry and isothermal titration calorimetry.

    PubMed

    Dahot, M Umar; Saboury, A A; Moosavi-Movahedi, A A

    2004-04-01

    The inhibition effect of metal ions on beta amylase activity was studied. The inhibitor-binding constant (Ki) was determined by spectrophotometric and isothermal titration calorimetric (ITC) methods. The binding of calcium, magnesium and zinc ion as inhibitors at the active site of barley beta amylase was studied at pH = 4.8 (sodium acetate 16 mM) and T = 300K. The Ki and enthalpy of binding for calcium (13.4, 13.1 mM and -14.3 kJ/mol), magnesium (18.6, 17.8mM and -17.7 kJ/mol) and zinc (17.5, 17.7 mM and -20.0 kJ/mol) were found by spectrophotometric and ITC methods respectively.

  9. Antidepressant activity of fluoxetine in the zinc deficiency model in rats involves the NMDA receptor complex.

    PubMed

    Doboszewska, Urszula; Szewczyk, Bernadeta; Sowa-Kućma, Magdalena; Młyniec, Katarzyna; Rafało, Anna; Ostachowicz, Beata; Lankosz, Marek; Nowak, Gabriel

    2015-01-01

    The zinc deficiency animal model of depression has been proposed; however, it has not been validated in a detailed manner. We have recently shown that depression-like behavior induced by dietary zinc restriction is associated with up-regulation of hippocampal N-methyl-d-aspartate receptor (NMDAR). Here we examined the effects of chronic administration of a selective serotonin reuptake inhibitor, fluoxetine (FLX), on behavioral and biochemical alterations (within NMDAR signaling pathway) induced by zinc deficiency. Male Sprague Dawley rats were fed a zinc adequate diet (ZnA, 50mg Zn/kg) or a zinc deficient diet (ZnD, 3mg Zn/kg) for 4 weeks. Then, FLX treatment (10mg/kg, i.p.) begun. Following 2 weeks of FLX administration the behavior of the rats was examined in the forced swim test (FST) and the spontaneous locomotor activity test. Twenty four hours later tissue was harvested. The proteins of NMDAR (GluN1, GluN2A and GluN2B) or AMPAR (GluA1) subunits, p-CREB and BDNF in the hippocampus (Western blot) and serum zinc level (TXRF) were examined. Depression-like behavior induced by ZnD in the FST was sensitive to chronic treatment with FLX. ZnD increased levels of GluN1, GluN2A, GluN2B and decreased pS485-GluA1, p-CREB and BDNF proteins. Administration of FLX counteracted the zinc restriction-induced changes in serum zinc level and hippocampal GluN1, GluN2A, GluN2B and p-CREB but not BDNF or pS845-GluA1 protein levels. This finding adds new evidence to the predictive validity of the proposed zinc deficiency model of depression. Antidepressant-like activity of FLX in the zinc deficiency model is associated with NMDAR complex.

  10. Antibacterial Activity of Dental Composites Containing Zinc Oxide Nanoparticles

    PubMed Central

    Sevinç, Berdan Aydin; Hanley, Luke

    2010-01-01

    The resin-based dental composites commonly used in restorations result in more plaque accumulation than other materials. Bacterial biofilm growth contributes to secondary caries and failure of resin-based dental composites. Methods to inhibit biofilm growth on dental composites have been sought for several decades. It is demonstrated here that zinc oxide nanoparticles (ZnO-NPs) blended at 10% (w/w) fraction into dental composites display antimicrobial activity and reduce growth of bacterial biofilms by roughly 80% for a single-species model dental biofilm. Antibacterial effectiveness of ZnO-NPs was assessed against Streptococcus sobrinus ATCC 27352 grown both planktonically and as biofilms on composites. Direct contact inhibition was observed by scanning electron microscopy and confocal laser scanning microscopy while biofilm formation was quantified by viable counts. An 80% reduction in bacterial counts was observed with 10% ZnO-NP-containing composites compared with their unmodified counterpart, indicating a statistically significant suppression of biofilm growth. Although, 20% of the bacterial population survived and could form a biofilm layer again, 10% ZnO-NP-containing composites maintained at least some inhibitory activity even after the third generation of biofilm growth. Microscopy demonstrated continuous biofilm formation for unmodified composites after one day growth, but only sparsely distributed biofilms formed on 10% ZnO-NP-containing composites. The minimum inhibitory concentration of ZnO-NPs suspended in S. sobrinus planktonic culture was 50 μg/ml. 10% ZnO-NP-containing composites qualitatively showed less biofilm after one day anaerobic growth of a three-species initial colonizer biofilm after when compared to unmodified composites, but did not significantly reduce growth after three days. PMID:20225252

  11. [Preparation and optimum process of walnut peel activated carbon by zinc chloride as activating agent].

    PubMed

    Liu, Xiao-hong; Wang, Xing-wei; Zhao, Bo; Lü, Jun-fang; Kang, Ni-na; Zhang, Yao-jun

    2014-12-01

    Walnut peel as raw material, zinc chloride was used as activating agent for preparation walnut peel activated carbon in the muffle furnace in this experiment, using orthogonal design. Yield, the specific surface area and iodine number of walnut peel activated carbon were determined at all designed experimental conditions and the optimum technological condition of preparation was obtained. By analysis of aperture, infrared spectra and the content of acidic group in surface with Boehm, walnut peel activated carbon of prepared at the optimum condition was characterized. The results showed the optimum technological parameters of preparation: activation temperature (600 °C), activation time (1 h), the concentration of zinc chloride (50%), the particle size (60 mesh). The specific surface area of walnut peel activated carbon obtained at optimum condition was mounting to 1258.05 m2 · g(-1), the ratio of medium porous 32.18%. Therefore, walnut peel can be used in the preparation of the high-quality activated carbon of large surface area. Agricultural wastes, as walnut peel, not only were implemented recycle, but also didn't make any pollution. Meanwhile, a cheap adsorbent was provided and it was of great significance to open a new source of activated carbon.

  12. Zinc Metalloproteinase ProA Directly Activates Legionella pneumophila PlaC Glycerophospholipid:cholesterol Acyltransferase*

    PubMed Central

    Lang, Christina; Rastew, Elena; Hermes, Björn; Siegbrecht, Enrico; Ahrends, Robert; Banerji, Sangeeta; Flieger, Antje

    2012-01-01

    Enzymes secreted by Legionella pneumophila, such as phospholipases A (PLAs) and glycerophospholipid:cholesterol acyltransferases (GCATs), may target host cell lipids and therefore contribute to the establishment of Legionnaires disease. L. pneumophila possesses three proteins, PlaA, PlaC, and PlaD, belonging to the GDSL family of lipases/acyltransferases. We have shown previously that PlaC is the major GCAT secreted by L. pneumophila and that the zinc metalloproteinase ProA is essential for GCAT activity. Here we characterized the mode of PlaC GCAT activation and determined that ProA directly processes PlaC. We further found that not only cholesterol but also ergosterol present in protozoa was palmitoylated by PlaC. Such ester formations were not induced by either PlaA or PlaD. PlaD was shown here to possess lysophospholipase A activity, and interestingly, all three GDSL enzymes transferred short chain fatty acids to sterols. The three single putative catalytic amino acids (Ser-37, Asp-398, and His-401) proved essential for all PlaC-associated PLA, lysophospholipase A, and GCAT activities. A further four cysteine residues are important for the PLA/GCAT activities as well as their oxidized state, and we therefore conclude that PlaC likely forms at least one disulfide loop. Analysis of cleavage site and loop deletion mutants suggested that for GCAT activation deletion of several amino acids within the loop is necessary rather than cleavage at a single site. Our data therefore suggest a novel enzyme inhibition/activation mechanism where a disulfide loop inhibits PlaC GCAT activity until the protein is exported to the external space where it is ProA-activated. PMID:22582391

  13. Effect of zinc supplementation on E-ADA activity, seric zinc, and cytokines levels of Trypanosoma evansi infected Wistar rats.

    PubMed

    Bottari, Nathieli B; Baldissera, Matheus D; Oliveira, Camila B; Duarte, Thiago; Duarte, Marta M M F; Leal, Marta L R; Thomé, Gustavo R; Zanini, Daniela; Schetinger, Maria Rosa C; Nunes, Matheus A G; Dressler, Valderi L; Monteiro, Silvia G; Tonin, Alexandre A; Da Silva, Aleksandro S

    2014-09-01

    The aim of this study was to evaluate the effect of zinc supplementation on the ecto-adenosine deaminase activity (E-ADA), zinc seric levels and cytokines (TNF-α, IL-1, IL-6, and IL -10) on rats experimentally infected by Trypanosoma evansi. Four groups with 10 rats each were used as negative controls (groups A and B), while the animals from the groups C and D were infected intraperitoneally with 0.1 mL of cryopreserved blood containing 1.4 × 10(4) of trypanosomes. Animals of groups B and D received two doses of Zinc (Zn) at 5 mg kg(-1), subcutaneously, on the 2nd and 7th day post-infection (PI). Blood samples were collected on days 5 (n = 5) and 15 PI (n = 5). Zn supplementation was able to increase the rat's longevity and to reduce their parasitemia. It was observed that seric Zn levels were increased on infected animals under Zn supplementation. Animals that were infected and supplemented with Zn showed changes in E-ADA activity and in cytokine levels (P < 0.05). Zn supplementation of healthy animals (Group B), increased the E-ADA activity, as well as reduced the concentration of cytokines. Infected animals from groups C and D showed increased levels of cytokines. Finally, we observed that Zn supplementation led to a modulation on cytokine's level in rats infected by T. evansi, as well as in E-ADA activity.

  14. Zinc promotes proliferation and activation of myogenic cells via the PI3K/Akt and ERK signaling cascade

    SciTech Connect

    Ohashi, Kazuya; Nagata, Yosuke; Wada, Eiji; Zammit, Peter S.; Shiozuka, Masataka; Matsuda, Ryoichi

    2015-05-01

    Skeletal muscle stem cells named muscle satellite cells are normally quiescent but are activated in response to various stimuli, such as injury and overload. Activated satellite cells enter the cell cycle and proliferate to produce a large number of myogenic progenitor cells, and these cells then differentiate and fuse to form myofibers. Zinc is one of the essential elements in the human body, and has multiple roles, including cell growth and DNA synthesis. However, the role of zinc in myogenic cells is not well understood, and is the focus of this study. We first examined the effects of zinc on differentiation of murine C2C12 myoblasts and found that zinc promoted proliferation, with an increased number of cells incorporating EdU, but inhibited differentiation with reduced myogenin expression and myotube formation. Furthermore, we used the C2C12 reserve cell model of myogenic quiescence to investigate the role of zinc on activation of myogenic cells. The number of reserve cells incorporating BrdU was increased by zinc in a dose dependent manner, with the number dramatically further increased using a combination of zinc and insulin. Akt and extracellular signal-regulated kinase (ERK) are downstream of insulin signaling, and both were phosphorylated after zinc treatment. The zinc/insulin combination-induced activation involved the phosphoinositide 3-kinase (PI3K)/Akt and ERK cascade. We conclude that zinc promotes activation and proliferation of myogenic cells, and this activation requires phosphorylation of PI3K/Akt and ERK as part of the signaling cascade. - Highlights: • Zinc has roles for promoting proliferation and inhibition differentiation of C2C12. • Zinc promotes activation of reserve cells. • Insulin and zinc synergize activation of reserve cells. • PI3K/Akt and ERK cascade affect zinc/insulin-mediated activation of reserve cells.

  15. Semenogelins I and II bind zinc and regulate the activity of prostate-specific antigen.

    PubMed

    Jonsson, Magnus; Linse, Sara; Frohm, Birgitta; Lundwall, Ake; Malm, Johan

    2005-04-15

    In semen, the gel proteins SgI and SgII (semenogelins I and II) are digested by PSA (prostate-specific antigen), resulting in liquefaction and release of motile spermatozoa. Semen contains a high concentration of Zn2+, which is known to inhibit the protease activity of PSA. We characterized the binding of Zn2+ to SgI and SgII and found evidence that these proteins are involved in regulating the activity of PSA. Intact SgI and SgII and synthetic semenogelin peptides were used in the experiments. Binding of Zn2+ was studied by radioligand blotting, titration with a zinc (II) fluorophore chelator and NMR analysis. A chromogenic substrate was used to measure the enzymatic activity of PSA. SgI and SgII bound Zn2+ with a stoichiometry of at least 10 mol (mol of protein)(-1) and with an average dissociation constant of approx. 5 microM per site. Moreover, Zn2+-inhibited PSA was activated by exposure to SgI or SgII. Since both proteins have high affinity for Zn2+ and are the dominating proteins in semen, they probably represent the major Zn2+ binders in semen, one function of which may be to regulate the activity of PSA. The system is self-regulating, and PSA is maintained in an active state by its substrate.

  16. [Interactions between natural vegetation succession and waste residue in lead-zinc tailings deposited sites].

    PubMed

    Liu, Hong-yan; Xing, Dan; Xlao, Jiu-jun; Liu, Fang

    2010-12-01

    Natural vegetation succession process and related mechanism is one of the important research contents in ecological restoration of abandoned mining land. Taking 4 lead-zinc tailings deposited sites with the recovery time being about 10 years, 20 years, 30 year, and over 40 years under similar site conditions in northwest Guizhou Provinnce as study areas, this paper studied the interactions between the natural vegetation succession and the physicochemical properties of waste residue. The results showed that with the increasing dumping time of the waste residue, the nutritional conditions of base material improved significantly, the total N, P, and K contents and the pH value increased, while the EC, bulk density, and especially, available lead and cadmium contents decreased. Meanwhile, the plant community species richness (S), diversity index (H), and evenness (J) increased correspondingly with increasing recovery time. The composition of plant communities was dominated by perennial herbaceous. In the first 20 years of recovery, the vegetation succession process was very slow, but after 30- and 40-year recovery, the vegetation coverage reached 53% and 87%, respectively. Canonical correlation analysis showed that there were significant correlations between base material properties and species diversity, and the canonical variables were the total N, P, and K contents of base material. The species diversity index was significantly negatively correlated with the available Pb and Cd contents of base material. The natural vegetation succession process in the study areas accelerated after 30 years of recovery, and the limiting factors of vegetation recovery were the nutrient deficiency and the high availability of Pb and Cd in base material.

  17. Lethal Factor Active-Site Mutations Affect Catalytic Activity In Vitro

    PubMed Central

    Hammond, S. E.; Hanna, P. C.

    1998-01-01

    The lethal factor (LF) protein of Bacillus anthracis lethal toxin contains the thermolysin-like active-site and zinc-binding consensus motif HEXXH (K. R. Klimpel, N. Arora, and S. H. Leppla, Mol. Microbiol. 13:1093–1100, 1994). LF is hypothesized to act as a Zn2+ metalloprotease in the cytoplasm of macrophages, but no proteolytic activities have been previously shown on any target substrate. Here, synthetic peptides are hydrolyzed by LF in vitro. Mass spectroscopy and peptide sequencing of isolated cleavage products separated by reverse-phase high-pressure liquid chromatography indicate that LF seems to prefer proline-containing substrates. Substitution mutations within the consensus active-site residues completely abolish all in vitro catalytic functions, as does addition of 1,10-phenanthroline, EDTA, and certain amino acid hydroxamates, including the novel zinc metalloprotease inhibitor ZINCOV. In contrast, the protease inhibitors bestatin and lysine CMK, previously shown to block LF activity on macrophages, did not block LF activity in vitro. These data provide the first direct evidence that LF may act as an endopeptidase. PMID:9573135

  18. Preliminary investigation of a sealed, remotely activated silver-zinc battery

    NASA Technical Reports Server (NTRS)

    Wheat, C. G.

    1977-01-01

    Methods necessary to provide a remotely activated, silver zinc battery capable of an extended activated stand while in a sealed condition were investigated. These requirements were to be accomplished in a battery package demonstrating an energy density of at least 35 watt hours per pound. Several methods of gas suppression were considered in view of the primary nature of this unit and utilized the electroplated dendritic zinc electrode. Amalgamation of the electrode provided the greatest suppression of gas at the zinc electrode. The approach to extending the activated stand capability of the remotely activated battery was through evaluation of three basic methods of remote, multi-cell activation; 1) the electrolyte manifold, 2) the gas manifold and 3) the individual cell. All three methods of activation can be incorporated into units which will meet the minimum energy density requirement.

  19. Esophageal carcinogenesis in the rat: zinc deficiency, DNA methylation and alkyltransferase activity.

    PubMed

    Newberne, P M; Broitman, S; Schrager, T F

    1997-01-01

    Rats fed zinc-deficient diets and given an esophageal carcinogen, methylbenzylnitrosamine, develop tumors in greater incidence and with increased frequency compared to zinc-supplemented rats. This greater susceptibility is associated with a unique esophageal lesion, parakeratosis, with markedly increased epithelial necrosis and cell proliferation. Recent studies have shown that the increased susceptibility to tumorigenesis was further associated with a number of metabolic and biochemical alterations including increased binding of the carcinogen to DNA, shifts in O6-methylguanine (O6MeG)/7-methylguanine ratios and suggestions that the promutagen O6MeG lesion is not repaired effectively in the zinc-deficient esophagus; the latter was not reflected in the amount of O6-methyltransferase activity, however. The weight of evidence supports a presumption that zinc deficiency interferes with normal DNA repair mechanisms, the nature of which is not clear. An interesting additional finding was that zinc deficiency alone was associated with esophageal tumor induction, without carcinogen, which indicates that genetic material in the zinc-deficient esophageal epithelium is damaged sufficiently, without further chemical injury, to result in loss of control of cell proliferation. Manipulation of the time of exposure to zinc deficiency and carcinogen exposure defined the initiation period as most affected by the deficiency. Furthermore, reduced carcinogen exposure (and less toxicity), along with zinc deficiency, permits development of more tumors of the endophytic type, the form more relevant to human esophageal tumors. The groundwork, as described in this paper, has now been prepared to directly address the latter issue, endophytic tumors, and the putative relation of zinc deficiency to esophageal cancer in human populations.

  20. Involvement of activation of NADPH oxidase and extracellular signal-regulated kinase (ERK) in renal cell injury induced by zinc.

    PubMed

    Matsunaga, Yoshiko; Kawai, Yoshiko; Kohda, Yuka; Gemba, Munekazu

    2005-05-01

    Zinc is employed as a supplement; however, zinc-related nephropathy is not generally known. In this study, we investigated zinc-induced renal cell injury using a pig kidney-derived cultured renal epithelial cell line, LLC-PK(1), with proximal kidney tubule-like features, and examined the involvement of free radicals and extracellular signal-regulated kinase (ERK) in the cell injury. The LLC-PK(1) cells showed early uptake of zinc (30 microM), and the release of lactate dehydrogenase (LDH), an index of cell injury, was observed 24 hr after uptake. Three hours after zinc exposure, generation of reactive oxygen species (ROS) was increased. An antioxidant, N, N'-diphenyl-p-phenylenediamine (DPPD), inhibited a zinc-related increase in ROS generation and zinc-induced renal cell injury. An NADPH oxidase inhibitor, diphenyleneiodonium (DPI), inhibited a zinc-related increase in ROS generation and cell injury. We investigated translocation from the cytosol fraction of the p67(phox) subunit, which is involved in the activation of NADPH oxidase, to the membrane fraction, and translocation was induced 3 hr after zinc exposure. We examined the involvement of ERK1/2 in the deterioration of zinc-induced renal cell injury, and the association between ERK1/2 and an increase in ROS generation. Six hours after zinc exposure, the activation (phosphorylation) of ERK1/2 was observed. An antioxidant, DPPD, inhibited the zinc-related activation of ERK1/2. An MAPK/ERK kinase (MEK1/2) inhibitor, U0126, almost completely inhibited zinc-related cell injury (the release of LDH), but did not influence ROS generation. These results suggest that early intracellular uptake of zinc by LLC-PK(1) cells causes the activation of NADPH oxidase, and that ROS generation by the activation of the enzyme leads to the deterioration of renal cell injury via the activation of ERK1/2.

  1. Hair-zinc levels determination in Algerian psoriatics using Instrumental Neutron Activation Analysis (INAA).

    PubMed

    Mansouri, A; Hamidatou Alghem, L; Beladel, B; Mokhtari, O E K; Bendaas, A; Benamar, M E A

    2013-02-01

    Psoriasis is a multifactorial skin disease with an unknown etiology. Zinc has a positive impact on psoriasis. The aim of this study is to determine hair-zinc concentration in Algerian psoriatics. 58 psoriatics and 31 normal controls of both genders were selected. Hair zinc levels were determined using Instrumental Neutron Activation Analysis technique (INAA). Student's t-test and One-Way ANOVA were applied. The average zinc concentration for controls and patients were 152 ± 53 μg/g and 167 ± 52 μg/g respectively. They are not significantly different (p>0.05). Zn concentration for males and females controls and patients were 171±27 μg/g, 151±37 μg/g and 145 ± 59 μg/g, 178 ± 58 μg/g respectively. However, for females we have observed a significant difference (p<0.05).

  2. Antibacterial Activity of Zinc Oxide-Coated Nanoporous Alumina

    DTIC Science & Technology

    2012-05-17

    2012 Available online 17 May 2012 Keywords: Aluminum oxide Zinc oxide Atomic layer deposition Nanoporous material Antibacterial material a b s t r...standard and mixed online with each sample through a tee. Isotopes (e.g., 66Zn and 115In) were evaluated in a peak hop- ping mode; a dwell time of...20 pore sizes nm and (n) 100 nm pore sizes that were examined against Staphylococcus epidermidis. several potential dermatologic applications for

  3. Zinc induces cell death in immortalized embryonic hippocampal cells via activation of Akt-GSK-3beta signaling.

    PubMed

    Min, Young Kyu; Lee, Jong Eun; Chung, Kwang Chul

    2007-01-15

    Zinc is an essential catalytic and structural element of many proteins and a signaling messenger that is released by neuronal activity at many central excitatory synapses. Excessive synaptic release of zinc followed by entry into vulnerable neurons contributes severe neuronal cell death. We have previously observed that zinc-induced neuronal cell death is accompanied by Akt activation in embryonic hippocampal progenitor (H19-7) cells. In the present study, we examined the role of Akt activation and its downstream signaling events during extracellular zinc-induced neuronal cell death. Treatment of H19-7 cells with 10 microM of zinc plus zinc ionophore, pyrithione, led to increased phosphorylation of Akt at Ser-473/Thr-308 and increased Akt kinase activity. Zinc-induced Akt activation was accompanied by increased Tyr-phosphorylated GSK-3beta as well as increased GSK-3beta kinase activity. Transient overexpression of a kinase-deficient Akt mutant remarkably suppressed GSK-3beta activation and cell death. Furthermore, tau phosphorylation, but not the degradation of beta-catenin, was dependent upon zinc-induced GSK-3beta activation and contributed to cell death. The current data suggest that, following exposure to zinc, the sequential activation of Akt and GSK-3beta plays an important role directing hippocampal neural precursor cell death.

  4. PAC-1 activates procaspase-3 in vitro through relief of zinc-mediated inhibition.

    PubMed

    Peterson, Quinn P; Goode, David R; West, Diana C; Ramsey, Kara N; Lee, Joy J Y; Hergenrother, Paul J

    2009-04-24

    The direct induction of apoptosis has emerged as a powerful anticancer strategy, and small molecules that either inhibit or activate certain proteins in the apoptotic pathway have great potential as novel chemotherapeutic agents. Central to apoptosis is the activation of the zymogen procaspase-3 to caspase-3. Caspase-3 is the key "executioner" caspase, catalyzing the hydrolysis of a multitude of protein substrates within the cell. Interestingly, procaspase-3 levels are often elevated in cancer cells, suggesting a compound that directly stimulates the activation of procaspase-3 to caspase-3 could selectively induce apoptosis in cancer cells. We recently reported the discovery of a compound, PAC-1, which enhances procaspase-3 activity in vitro and induces apoptotic death in cancer cells in culture and in mouse xenograft models. Described herein is the mechanism by which PAC-1 activates procaspase-3 in vitro. We show that zinc inhibits the enzymatic activity of procaspase-3 and that PAC-1 strongly activates procaspase-3 in buffers that contain zinc. PAC-1 and zinc form a tight complex with one another, with a dissociation constant of approximately 42 nM. The combined data indicate that PAC-1 activates procaspase-3 in vitro by sequestering inhibitory zinc ions, thus allowing procaspase-3 to autoactivate itself to caspase-3. The small-molecule-mediated activation of procaspases has great therapeutic potential and thus this discovery of the in vitro mechanism of action of PAC-1 is critical to the development and optimization of other procaspase-activating compounds.

  5. Effect of zinc on lysozyme-like activity of the seastar Marthasterias glacialis (Echinodermata, Asteroidea) mucus.

    PubMed

    Stabili, L; Pagliara, P

    2009-03-01

    Lysozyme represents the best characterized enzyme involved in the self-defense from bacteria. In this study we analysed the effects of zinc on the lysozyme-like activity of the seastar Marthasterias glacialis mucus. This activity, detected by measuring the cleared lysis area of dried Micrococcus lysodeikticus cell walls on Petri dishes, was significantly reduced in presence of zinc. The results are discussed in the light of elucidating the possible relationship between environmental contaminants and increased disease susceptibility in seastars due to the decrease of antibacterial protection. The benefits of using the test of lysozyme activity to monitoring environmental pollution are highlighted.

  6. Validated ligand mapping of ACE active site

    NASA Astrophysics Data System (ADS)

    Kuster, Daniel J.; Marshall, Garland R.

    2005-08-01

    Crystal structures of angiotensin-converting enzyme (ACE) complexed with three inhibitors (lisinopril, captopril, enalapril) provided experimental data for testing the validity of a prior active site model predicting the bound conformation of the inhibitors. The ACE active site model - predicted over 18 years ago using a series of potent ACE inhibitors of diverse chemical structure - was recreated using published data and commercial software. Comparison between the predicted structures of the three inhibitors bound to the active site of ACE and those determined experimentally yielded root mean square deviation (RMSD) values of 0.43-0.81 Å, among the distances defining the active site map. The bound conformations of the chemically relevant atoms were accurately deduced from the geometry of ligands, applying the assumption that the geometry of the active site groups responsible for binding and catalysis of amide hydrolysis was constrained. The mapping of bound inhibitors at the ACE active site was validated for known experimental compounds, so that the constrained conformational search methodology may be applied with confidence when no experimentally determined structure of the enzyme yet exists, but potent, diverse inhibitors are available.

  7. Regulation and activity of a zinc uptake regulator, Zur, in Corynebacterium diphtheriae.

    PubMed

    Smith, Kelsy F; Bibb, Lori A; Schmitt, Michael P; Oram, Diana M

    2009-03-01

    Regulation of metal ion homeostasis is essential to bacterial cell survival, and in most species it is controlled by metal-dependent transcriptional regulators. In this study, we describe a Corynebacterium diphtheriae ferric uptake regulator-family protein, Zur, that controls expression of genes involved in zinc uptake. By measuring promoter activities and mRNA levels, we demonstrate that Zur represses transcription of three genes (zrg, cmrA, and troA) in zinc-replete conditions. All three of these genes have similarity to genes involved in zinc uptake. Transcription of zrg and cmrA was also shown to be regulated in response to iron and manganese, respectively, by mechanisms that are independent of Zur. We demonstrate that the activity of the zur promoter is slightly decreased under low zinc conditions in a process that is dependent on Zur itself. This regulation of zur transcription is distinctive and has not yet been described for any other zur. An adjacent gene, predicted to encode a metal-dependent transcriptional regulator in the ArsR/SmtB family, is transcribed from a separate promoter whose activity is unaffected by Zur. A C. diphtheriae zur mutant was more sensitive to peroxide stress, which suggests that zur has a role in protecting the bacterium from oxidative damage. Our studies provide the first evidence of a zinc specific transcriptional regulator in C. diphtheriae and give new insights into the intricate regulatory network responsible for regulating metal ion concentrations in this toxigenic human pathogen.

  8. The yeast regulator of transcription protein Rtr1 lacks an active site and phosphatase activity.

    PubMed

    Xiang, Kehui; Manley, James L; Tong, Liang

    2012-07-10

    The activity of RNA polymerase II (Pol II) is controlled in part by the phosphorylation state of the C-terminal domain (CTD) of its largest subunit. Recent reports have suggested that yeast regulator of transcription protein, Rtr1, and its human homologue RPAP2, possess Pol II CTD Ser5 phosphatase activity. Here we report the crystal structure of Kluyveromyces lactis Rtr1, which reveals a new type of zinc finger protein and does not have any close structural homologues. Importantly, the structure does not show evidence of an active site, and extensive experiments to demonstrate its CTD phosphatase activity have been unsuccessful, suggesting that Rtr1 has a non-catalytic role in CTD dephosphorylation.

  9. The N-terminal zinc finger domain of Tgf2 transposase contributes to DNA binding and to transposition activity

    PubMed Central

    Jiang, Xia-Yun; Hou, Fei; Shen, Xiao-Dan; Du, Xue-Di; Xu, Hai-Li; Zou, Shu-Ming

    2016-01-01

    Active Hobo/Activator/Tam3 (hAT) transposable elements are rarely found in vertebrates. Previously, goldfish Tgf2 was found to be an autonomously active vertebrate transposon that is efficient at gene-transfer in teleost fish. However, little is known about Tgf2 functional domains required for transposition. To explore this, we first predicted in silico a zinc finger domain in the N-terminus of full length Tgf2 transposase (L-Tgf2TPase). Two truncated recombinant Tgf2 transposases with deletions in the N-terminal zinc finger domain, S1- and S2-Tgf2TPase, were expressed in bacteria from goldfish cDNAs. Both truncated Tgf2TPases lost their DNA-binding ability in vitro, specifically at the ends of Tgf2 transposon than native L-Tgf2TPase. Consequently, S1- and S2-Tgf2TPases mediated gene transfer in the zebrafish genome in vivo at a significantly (p < 0.01) lower efficiency (21%–25%), in comparison with L-Tgf2TPase (56% efficiency). Compared to L-Tgf2TPase, truncated Tgf2TPases catalyzed imprecise excisions with partial deletion of TE ends and/or plasmid backbone insertion/deletion. The gene integration into the zebrafish genome mediated by truncated Tgf2TPases was imperfect, creating incomplete 8-bp target site duplications at the insertion sites. These results indicate that the zinc finger domain in Tgf2 transposase is involved in binding to Tgf2 terminal sequences, and loss of those domains has effects on TE transposition. PMID:27251101

  10. Spacer intercalated disassembly and photodynamic activity of zinc phthalocyanine inside nanochannels of mesoporous silica nanoparticles.

    PubMed

    Ma, Xing; Sreejith, Sivaramapanicker; Zhao, Yanli

    2013-12-26

    Hydrophobic photosensitizer zinc(II) phthalocyanine (ZnPc) was loaded into adamantane (Ad) modified nanochannels of mesoporous silica nanoparticles (MSNPs). The Ad units on the surface of MSNPs were complexed with amino-substituted β-cyclodextrin to enhance the solubility of the hybrid in aqueous solution. The amino groups on β-cyclodextrin also provide functional sites for further conjugation with targeting ligands toward targeted cancer therapy. Since the intercalation of the Ad spacer isolates loaded ZnPc and prevents its aggregation inside MSNPs, ZnPc exhibits its monomeric characteristics to effectively generate cytotoxic singlet oxygen ((1)O2) upon light irradiation (675 nm) in aqueous conditions, leading to efficient photodynamic activity for successful cancer treatment in vitro. Current research presents a convenient approach to maintain the monomeric state of hydrophobic photosensitizer ZnPc by rationally utilizing multifunctional MSNPs as the carriers. The novel hybrid with targeting capability achieves active photodynamic property of monomeric ZnPc in aqueous solution under light irradiation, which may find its way for practical photodynamic therapy in the future.

  11. Genetic analysis of human immunodeficiency virus type 1 integrase and the U3 att site: unusual phenotype of mutants in the zinc finger-like domain.

    PubMed Central

    Masuda, T; Planelles, V; Krogstad, P; Chen, I S

    1995-01-01

    Retroviral integration is the step which leads to establishment of the provirus, cis- and trans-acting regions of the human immunodeficiency type 1 (HIV-1) retrovirus genome, including the attachment site (att) at the ends of the unintegrated viral DNA and the conserved domains within the integrase (IN) protein, have been identified as being important for integration. We investigated the role of each of these regions in the context of an infectious HIV-1 molecular clone through point mutagenesis of the att site and the zinc finger-like and catalytic domains of IN. The effect of each mutation on integration activity was examined by using a single-step infection system with envelope-pseudotype virus. The relative integration efficiency was estimated by monitoring the levels of viral DNA over time in the infected cells. The integration activities of catalytic domain point mutants and att site deletion mutants were estimated to be 0.5 and 5% of wild-type activity, respectively. However, in contrast with previous in vitro cell-free integration studies, alteration of the highly conserved CA dinucleotide resulted in a mutant which still retained 40% of wild-type integration activity. The relative levels of expression of each mutant, as measured by a luciferase reporter gene, correlated with levels of integration. This observation is consistent with those of previous studies indicating that integration is an obligatory step for retroviral gene expression. Interestingly, we found that three different HIV-1 constructs bearing point mutations in the zinc finger-like domain synthesized much lower levels of viral DNA after infection, suggesting impairment of these mutants before or at the initiation of reverse transcription. Western blot (immunoblot) analysis demonstrated wild-type levels of reverse transcriptase within the mutant virions. In vitro endogenous reverse transcription assays indicated that all three mutants in the zinc finger-like domain had wild-type levels of

  12. Antiviral activity of the zinc ionophores pyrithione and hinokitiol against picornavirus infections.

    PubMed

    Krenn, B M; Gaudernak, E; Holzer, B; Lanke, K; Van Kuppeveld, F J M; Seipelt, J

    2009-01-01

    We have discovered two metal ion binding compounds, pyrithione (PT) and hinokitiol (HK), that efficiently inhibit human rhinovirus, coxsackievirus, and mengovirus multiplication. Early stages of virus infection are unaffected by these compounds. However, the cleavage of the cellular eukaryotic translation initiation factor eIF4GI by the rhinoviral 2A protease was abolished in the presence of PT and HK. We further show that these compounds inhibit picornavirus replication by interfering with proper processing of the viral polyprotein. In addition, we provide evidence that these structurally unrelated compounds lead to a rapid import of extracellular zinc ions into cells. Imported Zn(2+) was found to be localized in punctate structures, as well as in mitochondria. The observed elevated level of zinc ions was reversible when the compounds were removed. As the antiviral activity of these compounds requires the continuous presence of the zinc ionophore PT, HK, or pyrrolidine-dithiocarbamate, the requirement for zinc ions for the antiviral activity is further substantiated. Therefore, an increase in intracellular zinc levels provides the basis for a new antipicornavirus mechanism.

  13. Surface magnetic contribution in zinc ferrite thin films studied by element- and site-specific XMCD hysteresis-loops

    NASA Astrophysics Data System (ADS)

    Mendoza Zélis, P.; Pasquevich, G. A.; Salcedo Rodríguez, K. L.; Sánchez, F. H.; Rodríguez Torres, C. E.

    2016-12-01

    Element- and site-specific magnetic hysteresis-loops measurements on a zinc ferrite (ZnFe2O4) thin film were performed by X-ray magnetic circular dichroism. Results show that iron in octahedral and tetrahedral sites of spinel structure are coupled antiferromagnetically between them, and when magnetic field is applied the magnetic moment of the ion located at octahedral sites aligns along the field direction. The magnetic measurements reveal a distinctive response of the surface with in-plane anisotropy and an effective anisotropy constant value of 12.6 kJ/m3. This effective anisotropy is due to the combining effects of demagnetizing field and, volume and surface magnetic anisotropies KV =3.1 kJ/m3 and KS =16 μJ/m2.

  14. Anticancer activity of fungal L-asparaginase conjugated with zinc oxide nanoparticles.

    PubMed

    Baskar, G; Chandhuru, J; Sheraz Fahad, K; Praveen, A S; Chamundeeswari, M; Muthukumar, T

    2015-01-01

    Demand for developing novel delivery system for cancer treatment has increased due to the side effects present in intravenous injection of L-asparaginase. Nanoparticles are used for delivering the drugs to its destination in cancer cure. Nanobiocomposite of zinc oxide nanoparticles conjugated with L-asparaginase was produced by Aspergillus terreus and was confirmed using maximum UV-Vis absorption at 340 nm in the present work. The presence of functional groups like OH, C-H, -C=N and C=O on the surface of nanobiocomposite was found from Fourier transform infrared spectrum analysis. Size of the produced nanocomposite was found in the range of 28-63 nm using scanning electron microscope. The crystalline nature of the synthesized nanobiocomposites was confirmed by X-ray diffraction analysis. The presence of zinc oxide on synthesized nanobiocomposite was confirmed by energy dispersive spectrum analysis. The anti-cancerous nature of the synthesized zinc oxide conjugated L-asparaginase nanobiocomposite on MCF-7 cell line was studied using MTT assay. The viability of the MCF-7 cells was decreased to 35.02 % when it was treated with L-asparaginase conjugated zinc oxide nanobiocomposite. Hence it is proved that the synthesized nanobiocomposites of zinc oxide conjugated L-asparaginase has good anti-cancerous activity.

  15. ANTIMICROBIAL ACTIVITY OF COPPER AND ZINC ACCUMULATED BY EASTERN OYSTER AMEBOCYTES

    EPA Science Inventory

    Fisher, William S. Submitted. Antimicrobial Activity of Copper and Zinc Accumulated by Eastern Oyster Amebocytes. J. Shellfish Res. 54 p. (ERL,GB 1196).

    The distribution of eastern oysters Crassostrea virginica near terrestrial watersheds has led to a general impression t...

  16. Bioavailability of Iron, Zinc, Phytate and Phytase Activity during Soaking and Germination of White Sorghum Varieties

    PubMed Central

    Afify, Abd El-Moneim M. R.; El-Beltagi, Hossam S.; Abd El-Salam, Samiha M.; Omran, Azza A.

    2011-01-01

    The changes in phytate, phytase activity and in vitro bioavailability of iron and zinc during soaking and germination of three white sorghum varieties (Sorghum bicolor L. Moench), named Dorado, Shandweel-6, and Giza-15 were investigated. Sorghum varieties were soaked for 20 h and germinated for 72 h after soaking for 20 h to reduce phytate content and increase iron and zinc in vitro bioavailability. The results revealed that iron and zinc content was significantly reduced from 28.16 to 32.16% and 13.78 to 26.69% for soaking treatment and 38.43 to 39.18% and 21.80 to 31.27% for germination treatments, respectively. Phytate content was significantly reduced from 23.59 to 32.40% for soaking treatment and 24.92 to 35.27% for germination treatments, respectively. Phytase enzymes will be activated during drying in equal form in all varieties. The results proved that the main distinct point is the change of phytase activity as well as specific activity during different treatment which showed no significant differences between the varieties used. The in vitro bioavailability of iron and zinc were significantly improved as a result of soaking and germination treatments. PMID:22003395

  17. Comparing zinc finger nucleases and transcription activator-like effector nucleases for gene targeting in Drosophila.

    PubMed

    Beumer, Kelly J; Trautman, Jonathan K; Christian, Michelle; Dahlem, Timothy J; Lake, Cathleen M; Hawley, R Scott; Grunwald, David J; Voytas, Daniel F; Carroll, Dana

    2013-10-03

    Zinc-finger nucleases have proven to be successful as reagents for targeted genome manipulation in Drosophila melanogaster and many other organisms. Their utility has been limited, however, by the significant failure rate of new designs, reflecting the complexity of DNA recognition by zinc fingers. Transcription activator-like effector (TALE) DNA-binding domains depend on a simple, one-module-to-one-base-pair recognition code, and they have been very productively incorporated into nucleases (TALENs) for genome engineering. In this report we describe the design of TALENs for a number of different genes in Drosophila, and we explore several parameters of TALEN design. The rate of success with TALENs was substantially greater than for zinc-finger nucleases , and the frequency of mutagenesis was comparable. Knockout mutations were isolated in several genes in which such alleles were not previously available. TALENs are an effective tool for targeted genome manipulation in Drosophila.

  18. Structural, optical, photocatalytic and antibacterial activity of zinc oxide and manganese doped zinc oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Rekha, K.; Nirmala, M.; Nair, Manjula G.; Anukaliani, A.

    2010-08-01

    Polycrystalline ZnO doped with Mn (5 and 10 at%) was prepared by the co-precipitation method. The effect of Mn doping on the photocatalytic, antibacterial activities and the influence of doping concentration on structural, optical properties of nanoparticles were studied. Structural and optical properties of the particles elucidated that the Mn 2+ ions have substituted the Zn 2+ ions without changing the Wurtzite structure of ZnO. The optical spectra showed a blue shift in the absorbance spectrum with increasing dopant concentration. The photocatalytic activities of ZnO powders were evaluated by measuring the degradation of methylene blue (MB) in water under the UV region. It was found that undoped ZnO bleaches MB much faster than manganese doped ZnO upon its exposure to the UV light. The potential toxicity of nanosized ZnO and Mn doped ZnO were investigated using both Gram positive and Gram negative bacteria as test organisms. The results showed that Mn doped ZnO nanoparticles enhanced the antibacterial activity than ZnO nanoparticles.

  19. Influence of Long-Term Zinc Administration on Spatial Learning and Exploratory Activity in Rats.

    PubMed

    Piechal, Agnieszka; Blecharz-Klin, Kamilla; Pyrzanowska, Justyna; Widy-Tyszkiewicz, Ewa

    2016-08-01

    Animal brain contains a significant amount of zinc, which is a cofactor for more than 300 enzymes. Moreover, it provides the basis for functioning of more than 2000 transcription factors, and it is necessary for memory formation and learning processes in the brain. The aim of this study was to investigate the effect of zinc supplementation on behavior in 3-month-old rats. For this purpose, the Morris water maze paradigm, hole-board, and T-maze were used. Wistar rats received a solution of ZnSO4 in drinking water at the doses of 16 mg/kg (Zn16 group) and 32 mg/kg (Zn32 group). In rats pretreated with the lower dose of zinc, the improvement of the mean escape latency was observed in comparison to the control group and Zn32 group. During memory task, both ZnSO4-supplemented groups showed an increase in crossings over the previous platform position. Furthermore, the exploratory activity in Zn16 group was improved in comparison to Zn32 and control group. In the brains of zinc-supplemented rats, we observed the higher content of zinc, both in the hippocampus and the prefrontal cortex. Hippocampal zinc level correlated positively with the mean annulus crossings of the Zn16 group during the probe trial. These findings show that the long-term administration of ZnS04 can improve learning, spatial memory, and exploratory activity in rats. Graphical Abstract Improvement of spatial learning, memory, and exploratory behavior.

  20. Correlated structural kinetics and retarded solvent dynamics at the metalloprotease active site

    SciTech Connect

    Grossman, Moran; Born, Benjamin; Heyden, Matthias; Tworowski, Dmitry; Fields, Gregg B.; Sagi, Irit; Havenith, Martina

    2011-09-18

    Solvent dynamics can play a major role in enzyme activity, but obtaining an accurate, quantitative picture of solvent activity during catalysis is quite challenging. Here, we combine terahertz spectroscopy and X-ray absorption analyses to measure changes in the coupled water-protein motions during peptide hydrolysis by a zinc-dependent human metalloprotease. These changes were tightly correlated with rearrangements at the active site during the formation of productive enzyme-substrate intermediates and were different from those in an enzyme–inhibitor complex. Molecular dynamics simulations showed a steep gradient of fast-to-slow coupled protein-water motions around the protein, active site and substrate. Our results show that water retardation occurs before formation of the functional Michaelis complex. We propose that the observed gradient of coupled protein-water motions may assist enzyme-substrate interactions through water-polarizing mechanisms that are remotely mediated by the catalytic metal ion and the enzyme active site.

  1. delta-Aminolevulinate dehydratase inhibition by 2,3-dimercaptopropanol is mediated by chelation of zinc from a site involved in maintaining cysteinyl residues in a reduced state.

    PubMed

    Emanuelli, T; Rocha, J B; Pereira, M E; Nascimento, P C; Souza, D O; Beber, F A

    1998-09-01

    The mechanisms underlying mouse delta-aminolevulinate dehydratase (ALA-D) inhibition by a chelating agent used in the treatment of heavy metal poisoning, 2,3-dimercaptopropanol (British Anti-Lewisite), were investigated. ALA-D inhibition by 2,3-dimercaptopropanol was totally reversed by 25-100 microM Zn2+, indicating that inhibition was due to chelation of zinc by 2,3-dimercaptopropanol. Our data suggested that zinc bound to a labile site (displaced by 25-40 microM EDTA or 500 microM 2,3-dimercaptopropanol) is involved in maintaining the sulfhydryl groups of ALA-D in a reduced state (essential for enzyme activity), since inhibition by these compounds was reversed by 10 mM dithiotreitol (a reducing agent). On the other hand, 10 mM dithiotreitol did not reverse ALA-D inhibition by a higher concentration of EDTA (100 microM). Accordingly, 2,3-dimercaptopropanol appears to inhibit ALA-D through a mechanism similar to that of low EDTA concentrations. Neither oxidized 2,3-dimercaptopropanol nor reactive oxygen species appeared to contribute for ALA-D inhibition by reduced 2,3-dimercaptopropanol. Taken together, these results suggest that 2,3-dimercaptopropanol inhibits ALA-D by chelating Zn2+ from a labile site that is involved in maintaining enzyme sulfhydryl groups in a reduced state. This site is compatible with the ZnB or Zn beta previously described in mammalian and bacterial ALA-D.

  2. Acrosin activity in turkey spermatozoa: assay by clinical method and effect of zinc and benzamidine on the activity.

    PubMed

    Glogowski, J; Jankowski, J; Faruga, A; Ottobre, J S; Ciereszko, A

    2001-09-15

    We optimized a clinical assay developed for measuring total acrosin activity for mammalian and fish semen for use in turkey spermatozoa. The main modifications included dilution of semen to a final concentration of 25 to 1000 x 10(3) spermatozoa, an increase of Triton X-100 concentration to 0.05% and 1 hr preincubation without substrate, Acrosin activity in turkey spermatozoa was much higher than in human spermatozoa (about 100-times) but similar to that of boar sperm. To optimize this assay for turkey spermatozoa, it was necessary to use higher Triton X-100 concentrations in the reaction mixture. There was a better catalytic efficiency at higher temperatures and a special requirement for a preincubation period for proacrosin activation. We observed high inhibition of acrosin activity by zinc added during preincubation (90% at 0.01 mM of zinc chloride). Benzamidine also inhibited turkey acrosin, and the extent of inhibition was similar for the incubation or preincubation period. When zinc ions were added during incubation, this inhibition was lower (24%). The results suggest that zinc influences proacrosin activation of turkey spermatozoa. This influence may be important for successful long-term storage of spermatozoa in the hen's oviduct.

  3. Zinc(II)-Coordination Complexes as Membrane Active Fluorescent Probes and Antibiotics

    PubMed Central

    DiVittorio, Kristy M.; Leevy, W. Matthew; O’Neil, Edward J.; Johnson, James R.; Vakulenko, Sergei; Morris, Joshua D.; Rosek, Kristine D.; Serazin, Nathan; Hilkert, Sarah; Hurley, Scott; Marquez, Manuel; Smith, Bradley D.

    2010-01-01

    Molecular probes with zinc(II)-(2,2’-dipicolylamine) coordination complexes associate with oxyanions in aqueous solution and target biomembranes that contain anionic phospholipids. This study examines a new series of coordination complexes with 2,6-bis(zinc(II)-dipicolylamine) phenoxide as the molecular recognition unit. Two lipophilic analogues are observed to partition into the membranes of zwitterionic and anionic vesicles and induce the transport of phospholipids and hydrophilic anions (carboxyfluorescein). These lipophilic zinc complexes are moderately toxic to mammalian cells. A more hydrophilic analogue does not exhibit mammalian cell toxicity (LD50 >50 µg/mL), but it is highly active against the Gram-positive bacteria Staphylococcus aureus (MIC of 1 µg/mL). Furthermore, it is active against clinically important S. aureus strains that are resistant to various antibiotics including vancomycin and oxacillin. The antibiotic action is attributed to its ability to depolarize the bacterial cell membrane. The intense bacterial staining exhibited by a fluorescent conjugate suggests that this family of zinc coordination complexes can be used as molecular probes for the detection and imaging of bacteria. PMID:18076009

  4. The Phylogeny and Active Site Design of Eukaryotic Copper-only Superoxide Dismutases

    DOE PAGES

    Peterson, Ryan L.; Galaleldeen, Ahmad; Villarreal, Johanna; ...

    2016-08-17

    In eukaryotes the bimetallic Cu/Zn superoxide dismutase (SOD) enzymes play important roles in the biology of reactive oxygen species by disproportionating superoxide anion. We reported that the fungal pathogen Candida albicans expresses a novel copper-only SOD, known as SOD5, that lacks the zinc cofactor and electrostatic loop (ESL) domain of Cu/Zn-SODs for substrate guidance. In spite of these abnormalities, C. albicans SOD5 can disproportionate superoxide at rates limited only by diffusion. Here we demonstrate that this curious copper-only SOD occurs throughout the fungal kingdom as well as in phylogenetically distant oomycetes or “pseudofungi” species. It is the only form ofmore » extracellular SOD in fungi and oomycetes, in stark contrast to the extracellular Cu/Zn-SODs of plants and animals. Through structural biology and biochemical approaches we demonstrate that these copper-only SODs have evolved with a specialized active site consisting of two highly conserved residues equivalent to SOD5 Glu-110 and Asp-113. The equivalent positions are zinc binding ligands in Cu/Zn-SODs and have evolved in copper-only SODs to control catalysis and copper binding in lieu of zinc and the ESL. Similar to the zinc ion in Cu/Zn-SODs, SOD5 Glu-110 helps orient a key copper-coordinating histidine and extends the pH range of enzyme catalysis. Furthermore, SOD5 Asp-113 connects to the active site in a manner similar to that of the ESL in Cu/Zn-SODs and assists in copper cofactor binding. Copper-only SODs are virulence factors for certain fungal pathogens; thus this unique active site may be a target for future anti-fungal strategies.« less

  5. The Phylogeny and Active Site Design of Eukaryotic Copper-only Superoxide Dismutases

    SciTech Connect

    Peterson, Ryan L.; Galaleldeen, Ahmad; Villarreal, Johanna; Taylor, Alexander B.; Cabelli, Diane E.; Hart, P. John; Culotta, Valeria C.

    2016-08-17

    In eukaryotes the bimetallic Cu/Zn superoxide dismutase (SOD) enzymes play important roles in the biology of reactive oxygen species by disproportionating superoxide anion. We reported that the fungal pathogen Candida albicans expresses a novel copper-only SOD, known as SOD5, that lacks the zinc cofactor and electrostatic loop (ESL) domain of Cu/Zn-SODs for substrate guidance. In spite of these abnormalities, C. albicans SOD5 can disproportionate superoxide at rates limited only by diffusion. Here we demonstrate that this curious copper-only SOD occurs throughout the fungal kingdom as well as in phylogenetically distant oomycetes or “pseudofungi” species. It is the only form of extracellular SOD in fungi and oomycetes, in stark contrast to the extracellular Cu/Zn-SODs of plants and animals. Through structural biology and biochemical approaches we demonstrate that these copper-only SODs have evolved with a specialized active site consisting of two highly conserved residues equivalent to SOD5 Glu-110 and Asp-113. The equivalent positions are zinc binding ligands in Cu/Zn-SODs and have evolved in copper-only SODs to control catalysis and copper binding in lieu of zinc and the ESL. Similar to the zinc ion in Cu/Zn-SODs, SOD5 Glu-110 helps orient a key copper-coordinating histidine and extends the pH range of enzyme catalysis. Furthermore, SOD5 Asp-113 connects to the active site in a manner similar to that of the ESL in Cu/Zn-SODs and assists in copper cofactor binding. Copper-only SODs are virulence factors for certain fungal pathogens; thus this unique active site may be a target for future anti-fungal strategies.

  6. An altered zinc-binding site confers resistance to a covalent inactivator of New Delhi metallo-beta-lactamase-1 (NDM-1) discovered by high-throughput screening

    PubMed Central

    Thomas, Pei W.; Spicer, Timothy; Cammarata, Michael; Brodbelt, Jennifer S.; Hodder, Peter; Fast, Walter

    2013-01-01

    Due to the global threat of antibiotic resistance mediated by New Delhi metallo-beta-lactamase-1 (NDM-1) and the lack of structurally diverse inhibitors reported for this enzyme, we developed screening and counter-screening assays for manual and automated formats. The manual assay is a trans-well absorbance-based endpoint assay in 96-well plates and has a Z’ factor of 0.8. The automated assay is an epi-absorbance endpoint assay in 384-well plates, has a Z’ factor of ≥ 0.8, good signal / baseline ratios (> 3.8), and is likely scalable for high-throughput screening (HTS). A TEM-1-based counter-screen is also presented to eliminate false positives due to assay interference or off-target activities. A pilot screen of a pharmacologically characterized compound library identified two thiol-modifying compounds as authentic NDM-1 inhibitors: p-hloromecuribenzoate (p-CMB) and nitroprusside. Recombinant NDM-1 has one Cys residue that serves as a conserved active-site primary zinc ligand and is selectively modified by p-CMB as confirmed by LC-MS/MS. However a C208D mutation results in an enzyme that maintains almost full lactamase activity, yet is completely resistant to the inhibitor. These results predict that covalent targeting of the conserved active-site Cys residue may have drawbacks as a drug design strategy. PMID:23591260

  7. A New Type of Metal-Binding Site in Cobalt- And Zinc-Containing Adenylate Kinases Isolated From Sulfate-Reducers D. Gigas And D. Desulfuricans ATCC 27774

    SciTech Connect

    Gavel, O.Y.; Bursakov, S.A.; Rocco, G.Di; Trincao, J.; Pickering, I.J.; George, G.N.; Calvete, J.J.; Brondino, C.; Pereira, A.S.; Lampreia, J.; Tavares, P.; Moura, J.J.G.; Moura, I.

    2009-05-18

    Adenylate kinase (AK) mediates the reversible transfer of phosphate groups between the adenylate nucleotides and contributes to the maintenance of their constant cellular level, necessary for energy metabolism and nucleic acid synthesis. The AK were purified from crude extracts of two sulfate-reducing bacteria (SRB), Desulfovibrio (D.) gigas NCIB 9332 and Desulfovibrio desulfuricans ATCC 27774, and biochemically and spectroscopically characterized in the native and fully cobalt- or zinc-substituted forms. These are the first reported adenylate kinases that bind either zinc or cobalt and are related to the subgroup of metal-containing AK found, in most cases, in Gram-positive bacteria. The electronic absorption spectrum is consistent with tetrahedral coordinated cobalt, predominantly via sulfur ligands, and is supported by EPR. The involvement of three cysteines in cobalt or zinc coordination was confirmed by chemical methods. Extended X-ray absorption fine structure (EXAFS) indicate that cobalt or zinc are bound by three cysteine residues and one histidine in the metal-binding site of the 'LID' domain. The sequence {sup 129}Cys-X{sub 5}-His-X{sub 15}-Cys-X{sub 2}-Cys of the AK from D. gigas is involved in metal coordination and represents a new type of binding motif that differs from other known zinc-binding sites of AK. Cobalt and zinc play a structural role in stabilizing the LID domain.

  8. Maternal dietary zinc supplementation enhances the epigenetic-activated antioxidant ability of chick embryos from maternal normal and high temperatures.

    PubMed

    Zhu, Yongwen; Liao, Xiudong; Lu, Lin; Li, Wenxiang; Zhang, Liyang; Ji, Cheng; Lin, Xi; Liu, Hsiao-Ching; Odle, Jack; Luo, Xugang

    2017-02-03

    The role of maternal dietary zinc supplementation in protecting the embryos from maternal hyperthermia-induced negative effects via epigenetic mechanisms was examined using an avian model (Gallus gallus). Broiler breeder hens were exposed to two maternal temperatures (21°C and 32°C) × three maternal dietary zinc treatments (zinc-unsupplemented control diet, the control diet + 110 mg zinc/kg inorganic or organic zinc) for 8 weeks. Maternal hyperthermia increased the embryonic mortality and induced oxidative damage evidenced by the elevated mRNA expressions of heat shock protein genes. Maternal dietary zinc deficiency damaged the embryonic development associated with the global DNA hypomethylation and histone 3 lysine 9 hyperacetylation in the embryonic liver. Supplementation of zinc in maternal diets effectively eliminated the embryonic mortality induced by maternal hyperthermia and enhanced antioxidant ability with the increased mRNA and protein expressions of metallothionein IV in the embryonic liver. The increased metallothionein IV mRNA expression was due to the reduced DNA methylation and increased histone 3 lysine 9 acetylation of the metallothionein IV promoter regardless of zinc source. These data demonstrate that maternal dietary zinc addition as an epigenetic modifier could protect the offspring embryonic development against maternal heat stress via enhancing the epigenetic-activated antioxidant ability.

  9. Zinc wave during the treatment of hypoxia is required for initial reactive oxygen species activation in mitochondria

    PubMed Central

    Slepchenko, Kira G; Lu, Qiping; Li, Yang V

    2016-01-01

    Mitochondrial reactive oxygen species (ROS) are known to accumulate during chemical hypoxia, causing adverse effects on cell function and survival. Recent studies show important role zinc accumulation plays in dysfunction associated with hypoxia. It is well known that ROS accumulation also plays a major role in cellular damage by hypoxia. In this study, fluorescent imaging and pharmacological methods were used in live HeLa cells to determine role of zinc in initial ROS accumulation in mitochondria during chemical hypoxia (oxygen glucose depravation with 4 mM sodium dithionite). Accumulation of both was observed as a very rapid phenomenon with initial rapid zinc increase (zinc wave) within 60 seconds of hypoxia onset and ROS increase within 4.5 minutes. Zinc chelation with TPEN removed the initial zinc wave which in turn abolished ROS accumulation. Influx of exogenous zinc induced rapid ROS accumulation. Inhibition of NADPH oxidase with apocynin, a NADPH oxidase inhibitor, showed significant and prolonged reduction in zinc induced ROS accumulation. We proposed a novel mechanism of intracellular zinc increase that activates NADPH oxidase which in turn triggers mitochondrial ROS production. PMID:27186322

  10. Relationships among body mass index, activities of daily living and zinc nutritional status in disabled elderly patients in nursing facilities.

    PubMed

    Kosaka, Kazue; Yamashita, Sachiko; Ando, Chinatsu; Endo, Yoriaki; Taniguchi, Keiko; Kikunaga, Shigeshi

    2013-01-01

    The purpose of this study was to examine the relationship between the zinc nutritional status and the factors associated with serum zinc concentration in the elderly patients in two nursing facilities: body mass index (BMI), the level of care, the grade of bedriddenness, and the grade of cognitive function. The estimations of the hematological constituents, physical index, and dietary survey were made based on the examination carried out of the 26 disabled elderly patients (male 6, female 20, mean age 90±6 y). The results obtained from this study can be summarized as follows: 1) The low activities of daily living (ADL) group showed a low level of serum zinc concentration, although the uptake rate of zinc by subjects was shown to be high when compared to the Dietary Reference Intakes 2010. 2) The high ADL group showed a high level of serum zinc concentration. 3) The results of multiple regression analysis among the serum zinc concentration, the determined serum ingredients, and the physical characteristics showed the significant correlation of serum zinc concentration against the BMI, the level of care, height, Alb and iron values. 4) The BMI, the level of care, the grade of bedriddenness, and the grade of cognitive function of the subjects changed according to the zinc nutritional status. These results suggested that the actual requirements of zinc of the subjects were different according to the BMI, the level of care, the grade of bedriddenness, and the grade of cognitive function.

  11. Corrosion Research And Web Site Activities

    NASA Technical Reports Server (NTRS)

    Heidersbach, Robert H.

    2001-01-01

    This report covers corrosion-related activities at the NASA Kennedy Space Center during the summer of 2000. The NASA Kennedy Space Center's corrosion web site, corrosion.ksc.nasa.gov, was updated with new information based on feedback over the past two years. The methodology for a two-year atmospheric exposure testing program to study the effectiveness of commercial chemicals sold for rinsing aircraft and other equipment was developed and some preliminary laboratory chemical analyses are presented.

  12. Corrosion Research and Web Site Activities

    NASA Technical Reports Server (NTRS)

    Heidersbach, Robert H.

    2002-01-01

    This report covers corrosion-related activities at the NASA Kennedy Space Center during the summer of 2000. The NASA Kennedy Space Center's corrosion web site, corrosion.ksc.nasa.gov, was updated with new information based on feedback over the past two years. The methodology for a two-year atmospheric exposure testing program to study the effectiveness of commercial chemicals sold for rinsing aircraft and other equipment was developed and some preliminary laboratory chemical analyses are presented.

  13. An integrative computational framework based on a two-step random forest algorithm improves prediction of zinc-binding sites in proteins.

    PubMed

    Zheng, Cheng; Wang, Mingjun; Takemoto, Kazuhiro; Akutsu, Tatsuya; Zhang, Ziding; Song, Jiangning

    2012-01-01

    Zinc-binding proteins are the most abundant metalloproteins in the Protein Data Bank where the zinc ions usually have catalytic, regulatory or structural roles critical for the function of the protein. Accurate prediction of zinc-binding sites is not only useful for the inference of protein function but also important for the prediction of 3D structure. Here, we present a new integrative framework that combines multiple sequence and structural properties and graph-theoretic network features, followed by an efficient feature selection to improve prediction of zinc-binding sites. We investigate what information can be retrieved from the sequence, structure and network levels that is relevant to zinc-binding site prediction. We perform a two-step feature selection using random forest to remove redundant features and quantify the relative importance of the retrieved features. Benchmarking on a high-quality structural dataset containing 1,103 protein chains and 484 zinc-binding residues, our method achieved >80% recall at a precision of 75% for the zinc-binding residues Cys, His, Glu and Asp on 5-fold cross-validation tests, which is a 10%-28% higher recall at the 75% equal precision compared to SitePredict and zincfinder at residue level using the same dataset. The independent test also indicates that our method has achieved recall of 0.790 and 0.759 at residue and protein levels, respectively, which is a performance better than the other two methods. Moreover, AUC (the Area Under the Curve) and AURPC (the Area Under the Recall-Precision Curve) by our method are also respectively better than those of the other two methods. Our method can not only be applied to large-scale identification of zinc-binding sites when structural information of the target is available, but also give valuable insights into important features arising from different levels that collectively characterize the zinc-binding sites. The scripts and datasets are available at http://protein.cau.edu.cn/zincidentifier/.

  14. The requirement of zinc and calcium ions for functional MMP activity in demineralized dentin matrices

    PubMed Central

    Tezvergil-Mutluay, Arzu; Agee, Kelli A.; Hoshika, Tomohiro; Carrilho, Marcela; Breschi, Lorenzo; Tjäderhane, Leo; Nishitani, Yoshihiro; Carvalho, Ricardo M.; Looney, Stephen; Tay, Franklin R.; Pashley, David H.

    2010-01-01

    The progressive degradation of resin-dentin bonds is due, in part, to the slow degradation of collagen fibrils in the hybrid layer by endogenous matrix metalloproteinases (MMPs) of the dentin matrix. In in vitro durability studies, the storage medium composition might be important because the optimum activity of MMPs requires both zinc and calcium. Objective This study evaluated the effect of different storage media on changes in matrix stiffness, loss of dry weight or solubilization of collagen from demineralized dentin beams incubated in vitro for up to 60 days. Methods Dentin beams (1×2×6mm) were completely demineralized in 10% phosphoric acid. After baseline measurements of dry mass and elastic modulus (E) (3-point bending, 15% strain) the beams were divided into 5 groups (n=11/group) and incubated at 37°C in either media containing both zinc and calcium designated as complete medium(CM), calcium-free medium, zinc-free medium, a doubled-zinc medium or water. Beams were retested at 3, 7, 14, 30, and 60 days of incubation. The incubation media was hydrolyzed with HCl for the quantitation of hydroxyproline (HOP) as an index of solubilization of collagen by MMPs. Data were analyzed using repeated measures of ANOVA. Results Both the storage medium and storage time showed significant effects on E, mass loss and HOP release (p<0.05). The incubation in CM resulted in relatively rapid and significant (p<0.05) decreases in stiffness, and increasing amounts of mass loss. The HOP content of the experimental media also increased with incubation time but was significantly lower (p<0.05) than in the control CM medium, the recommended storage medium. Conclusions The storage solutions used to age resin-dentin bonds should be buffered solutions that contain both calcium and zinc. The common use of water as an aging medium may underestimate the hydrolytic activity of endogenous dentin MMPs. PMID:20688380

  15. Diel cycles in dissolved barium, lead, iron, vanadium, and nitrite in a stream draining a former zinc smelter site near Hegeler, Illinois

    USGS Publications Warehouse

    Kay, R.T.; Groschen, G.E.; Cygan, G.; Dupre, David H.

    2011-01-01

    Diel variations in the concentrations of a number of constituents have the potential to substantially affect the appropriate sampling regimen in acidic streams. Samples taken once during the course of the day cannot adequately reflect diel variations in water quality and may result in an inaccurate understanding of biogeochemical processes, ecological conditions, and of the threat posed by the water to human health and the associated wildlife. Surface water and groundwater affected by acid drainage were sampled every 60 to 90. min over a 48-hour period at a former zinc smelter known as the Hegeler Zinc Superfund Site, near Hegeler, Illinois. Diel variations related to water quality in the aquifer were not observed in groundwater. Diel variations were observed in the temperature, pH, and concentration of dissolved oxygen, nitrite, barium, iron, lead, vanadium, and possibly uranium in surface water. Temperature, dissolved oxygen, nitrite, barium, lead, and uranium generally attained maximum values during the afternoon and minimum values during the night. Iron, vanadium, and pH generally attained minimum values during the afternoon and maximum values during the night. Concentrations of dissolved oxygen were affected by the intensity of photosynthetic activity and respiration, which are dependent upon insolation. Nitrite, an intermediary in many nitrogen reactions, may have been formed by the oxidation of ammonium by dissolved oxygen and converted to other nitrogen species as part of the decomposition of organic matter. The timing of the pH cycles was distinctly different from the cycles found in Midwestern alkaline streams and likely was the result of the photoreduction of Fe3+ to Fe 2+ and variations in the intensity of precipitation of hydrous ferric oxide minerals. Diel cycles of iron and vanadium also were primarily the result of variations in the intensity of precipitation of hydrous ferric oxide minerals. The diel variation in the concentrations of lead, uranium

  16. Improved zinc electrode and rechargeable zinc-air battery

    SciTech Connect

    Ross, P.N. Jr.

    1988-06-21

    The invention comprises an improved rechargeable zinc-air cell/battery having recirculating alkaline electrolyte and a zinc electrode comprising a porous foam support material which carries the active zinc electrode material. 5 figs.

  17. The Zinc-Dependent Protease Activity of the Botulinum Neurotoxins

    PubMed Central

    Lebeda, Frank J.; Cer, Regina Z.; Mudunuri, Uma; Stephens, Robert; Singh, Bal Ram; Adler, Michael

    2010-01-01

    The botulinum neurotoxins (BoNT, serotypes A-G) are some of the most toxic proteins known and are the causative agents of botulism. Following exposure, the neurotoxin binds and enters peripheral cholinergic nerve endings and specifically and selectively cleaves one or more SNARE proteins to produce flaccid paralysis. This review centers on the kinetics of the Zn-dependent proteolytic activities of these neurotoxins, and briefly describes inhibitors, activators and factors underlying persistence of toxin action. Some of the structural, enzymatic and inhibitor data that are discussed here are available at the botulinum neurotoxin resource, BotDB (http://botdb.abcc.ncifcrf.gov). PMID:22069621

  18. Activation of transcriptional activities of AP-1 and SRE by a new zinc-finger protein ZNF641

    SciTech Connect

    Qi Xingzhu; Li Yongqing; Xiao Jing; Yuan Wuzhou; Yan Yan; Wang Yuequn; Liang Shuyuan; Zhu Chuanbing; Chen Yingduan; Liu Mingyao . E-mail: mliu@ibt.tamhsc.edu; Wu Xiushan

    2006-01-27

    Mitogen-activated protein kinases (MAPKs) are evolutionarily conserved enzymes in cell signal transduction connecting cell-surface receptors to critical regulatory targets within cells and control cell survival, adaptation, and proliferation. Previous studies revealed that zinc-finger proteins are involved in the regulation of the MAPK signaling pathways. Here, we report the identification and characterization of a novel human zinc-finger protein, ZNF641. The cDNA of ZNF641 is 4.9 kb, encoding 438 amino acids in the nucleus. The protein is highly conserved in evolution across different vertebrate species from mouse to human. Northern blot analysis indicates that ZNF641 is expressed in most of the examined human tissues, with a high level in skeletal muscle. Overexpression of pCMV-Tag2B-ZNF641 in the COS-7 cells activates the transcriptional activities of AP-1 and SRE. Deletion analysis indicates that the linker between KRAB box and C{sub 2}H{sub 2}-type zinc-fingers represents the basal activation domain. These results suggest that ZNF641 may be a positive regulator in MAPK-mediated signaling pathways that lead to the activation of AP-1 and SRE.

  19. Antibacterial activity of silver and zinc nanoparticles against Vibrio cholerae and enterotoxic Escherichia coli.

    PubMed

    Salem, Wesam; Leitner, Deborah R; Zingl, Franz G; Schratter, Gebhart; Prassl, Ruth; Goessler, Walter; Reidl, Joachim; Schild, Stefan

    2015-01-01

    Vibrio cholerae and enterotoxic Escherichia coli (ETEC) remain two dominant bacterial causes of severe secretory diarrhea and still a significant cause of death, especially in developing countries. In order to investigate new effective and inexpensive therapeutic approaches, we analyzed nanoparticles synthesized by a green approach using corresponding salt (silver or zinc nitrate) with aqueous extract of Caltropis procera fruit or leaves. We characterized the quantity and quality of nanoparticles by UV-visible wavelength scans and nanoparticle tracking analysis. Nanoparticles could be synthesized in reproducible yields of approximately 10(8) particles/ml with mode particles sizes of approx. 90-100 nm. Antibacterial activity against two pathogens was assessed by minimal inhibitory concentration assays and survival curves. Both pathogens exhibited similar resistance profiles with minimal inhibitory concentrations ranging between 5×10(5) and 10(7) particles/ml. Interestingly, zinc nanoparticles showed a slightly higher efficacy, but sublethal concentrations caused adverse effects and resulted in increased biofilm formation of V. cholerae. Using the expression levels of the outer membrane porin OmpT as an indicator for cAMP levels, our results suggest that zinc nanoparticles inhibit adenylyl cyclase activity. This consequently deceases the levels of this second messenger, which is a known inhibitor of biofilm formation. Finally, we demonstrated that a single oral administration of silver nanoparticles to infant mice colonized with V. cholerae or ETEC significantly reduces the colonization rates of the pathogens by 75- or 100-fold, respectively.

  20. Antibacterial activity of silver and zinc nanoparticles against Vibrio cholerae and enterotoxic Escherichia coli

    PubMed Central

    Salem, Wesam; Leitner, Deborah R.; Zingl, Franz G.; Schratter, Gebhart; Prassl, Ruth; Goessler, Walter; Reidl, Joachim; Schild, Stefan

    2015-01-01

    Vibrio cholerae and enterotoxic Escherichia coli (ETEC) remain two dominant bacterial causes of severe secretory diarrhea and still a significant cause of death, especially in developing countries. In order to investigate new effective and inexpensive therapeutic approaches, we analyzed nanoparticles synthesized by a green approach using corresponding salt (silver or zinc nitrate) with aqueous extract of Caltropis procera fruit or leaves. We characterized the quantity and quality of nanoparticles by UV–visible wavelength scans and nanoparticle tracking analysis. Nanoparticles could be synthesized in reproducible yields of approximately 108 particles/ml with mode particles sizes of approx. 90–100 nm. Antibacterial activity against two pathogens was assessed by minimal inhibitory concentration assays and survival curves. Both pathogens exhibited similar resistance profiles with minimal inhibitory concentrations ranging between 5 × 105 and 107 particles/ml. Interestingly, zinc nanoparticles showed a slightly higher efficacy, but sublethal concentrations caused adverse effects and resulted in increased biofilm formation of V. cholerae. Using the expression levels of the outer membrane porin OmpT as an indicator for cAMP levels, our results suggest that zinc nanoparticles inhibit adenylyl cyclase activity. This consequently deceases the levels of this second messenger, which is a known inhibitor of biofilm formation. Finally, we demonstrated that a single oral administration of silver nanoparticles to infant mice colonized with V. cholerae or ETEC significantly reduces the colonization rates of the pathogens by 75- or 100-fold, respectively. PMID:25466205

  1. Zinc polycarboxylate dental cement for the controlled release of an active organic substance: proof of concept.

    PubMed

    Ali, Mohammad Naseem; Edwards, Mark; Nicholson, John W

    2010-04-01

    The potential of employing zinc polycarboxylate dental cement as a controlled release material has been studied. Benzalkonium chloride was used as the active ingredient, and incorporated at concentrations of 1, 2 and 3% by mass within the cement. At these levels, there was no observable effect on the speed of setting. Release was followed using an ion-selective electrode to determine changes in chloride ion concentration with time. This technique showed that the additive was released when the cured cement was placed in water, with release occurring by a diffusion mechanism for the first 3 h, but continuing beyond that for up to 1 week. Diffusion coefficients were in the range 5.62 x 10(-6) cm(2) s(-1) (for 1% concentration) to 10.90 x 10(-6) cm(2) s(-1) (for 3% concentration). Up to 3% of the total loading of benzalkonium chloride was released from the zinc polycarboxylate after a week, which is similar to that found in previous studies with glass-ionomer cement. It is concluded that zinc polycarboxylate cement is capable of acting as a useful material for the controlled release of active organic compounds.

  2. Enhanced antibacterial activity of zinc oxide nanoparticles synthesized using Petroselinum crispum extracts

    NASA Astrophysics Data System (ADS)

    Stan, Manuela; Popa, Adriana; Toloman, Dana; Silipas, Teofil-Danut; Vodnar, Dan Cristian; Katona, Gabriel

    2015-12-01

    The present contribution reports the synthesis of zinc oxide nanoparticles (ZnO NPs) using aqueous leaf and root extracts of Petroselinum crispum (parsley) and characterization of as-prepared samples. ZnO NPs are subjected to X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron paramagnetic resonance (EPR) studies. The XRD studies reveal a hexagonal wurtzite structure without supplementary diffraction lines for all ZnO samples. TEM analysis shows that the particle size is influenced by the type of plant extract. The EPR spectra indicate the presence of Mn2+ ions in ZnO sample synthesized using P. crispum leaf extract, while zinc vacancy complexes and oxygen vacancies are evidenced in all analyzed samples. ZnO NPs synthesized using P. crispum extracts exhibit increased (2-16 times) antibacterial activity as compared to chemically synthesized ZnO NPs.

  3. Enhanced antibacterial activity of zinc oxide nanoparticles synthesized using Petroselinum crispum extracts

    SciTech Connect

    Stan, Manuela Popa, Adriana; Toloman, Dana; Silipas, Teofil-Danut; Vodnar, Dan Cristian; Katona, Gabriel

    2015-12-23

    The present contribution reports the synthesis of zinc oxide nanoparticles (ZnO NPs) using aqueous leaf and root extracts of Petroselinum crispum (parsley) and characterization of as-prepared samples. ZnO NPs are subjected to X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron paramagnetic resonance (EPR) studies. The XRD studies reveal a hexagonal wurtzite structure without supplementary diffraction lines for all ZnO samples. TEM analysis shows that the particle size is influenced by the type of plant extract. The EPR spectra indicate the presence of Mn{sup 2+} ions in ZnO sample synthesized using P. crispum leaf extract, while zinc vacancy complexes and oxygen vacancies are evidenced in all analyzed samples. ZnO NPs synthesized using P. crispum extracts exhibit increased (2-16 times) antibacterial activity as compared to chemically synthesized ZnO NPs.

  4. Effects of manganese, calcium, magnesium and zinc on nickel-induced suppression of murine natural killer cell activity

    SciTech Connect

    Smialowicz, R.J.; Rogers, R.R.; Riddle, M.M.; Luebke, R.W.; Fogelson, L.D.; Rowe, D.G.

    1987-01-01

    The effects that divalent metals have on nickel-induced suppression of natural killer (NK) cell activity were studied in mice. Male CBA/J mice were given a single intramuscular injection of the following: nickel chloride, 4.5-36 ..mu..g/g; manganese chloride, 20-80 ..mu..g/g; magnesium acetate, 50-200 ..mu..g/g; zinc acetate, 2-8 ..mu..g/g; or calcium acetate, 12.5-50 ..mu..g/g. Twenty-four hours after metal injection, splenic NK cell activity was assessed using a /sup 51/Cr-release assay. Ni significantly suppressed NK activity, while Mn significantly enhanced NK activity. No alteration in NK activity was observed in mice injected with Mg, Ca, or Zn. The injection of Ni and Mn in combination at a single site resulted in the enhancement of NK activity, although this enhancement was at a level below that observed following the injection of Mn alone. Injection of Mg, Zn, or Ca in combination with Ni did not affect NK activity compared to saline controls. In contrast, the injection of Ni in one thigh followed immediately by Mn, Mg, Ca, or Zn into the other thigh resulted in significant suppression of NK activity for all metals compared with saline controls. An interesting finding was that the injection of Ni followed immediately by Mn into the opposite thigh resulted in even greater reduction in NK activity than Ni alone. Suppression of NK activity by Ni and Mn injected at separate sites was not seen when Mn injection preceded Ni injection by 1 h.

  5. Site-specific changes in zinc levels in the epididymis of rats exposed to ionizing radiation

    NASA Astrophysics Data System (ADS)

    Homma-Takeda, S.; Nishimura, Y.; Watanabe, Y.; Yukawa, M.

    2007-07-01

    The epididymis is an accessory sex organ that plays an important role in sperm maturation and storage. Trace elements, such as copper (Cu), manganese (Mn), zinc (Zn) and selenium (Se), have a pivotal role in spermatogenesis. We studied the effects of radiation on trace element levels in the epididymis in male Wistar rats using inductively coupled plasma-mass spectrometry (ICP-MS). We determined trace element concentration in segment-dissected specimens and used micro-PIXE analysis to determine Zn in epididymal sections in situ. Zn concentrations in the caput and cauda epididymis of control rats were 37.7 ± 6.5 μg/g wet weight and 18.7 ± 4.1 μg/g wet weight, respectively. At 6 h after irradiation at a single dose of 5Gy, the Zn level decreased by 33% in the caput epididymis, whereas the level did not change in the cauda segment. Similar results were obtained for Se, but not both Cu and Mn. PIXE spot analysis revealed that Zn in the lumen of the epididymal tubules decreased after irradiation.

  6. Role of zinc influx via AMPA/kainate receptor activation in metabotropic glutamate receptor-mediated calcium release.

    PubMed

    Takeda, Atsushi; Fuke, Sayuri; Minami, Akira; Oku, Naoto

    2007-05-01

    The uptake of free zinc into CA3 pyramidal cells and its significance was examined in rat hippocampal slices with ZnAF-2DA, a membrane-permeable zinc indicator. Intracellular ZnAF-2 signal in the CA3 pyramidal cell layer was increased during delivery of tetanic stimuli to the dentate granule cell layer. This increase was completely blocked in the presence of CNQX, an AMPA/kainate receptor antagonist. These results suggest that free zinc is taken up into CA3 pyramidal cells via activation of AMPA/kainate receptors. The effect of free zinc levels in the CA3 pyramidal cells on the increase in intracellular calcium via Group I metabotropic glutamate receptors was examined by regional delivery of tADA, a Group I metabotropic glutamate receptor agonist, to the stratum lucidum after blockade of AMPA/kainate receptor-mediated calcium and zinc influx. Intracellular calcium orange signal in the CA3 pyramidal cell layer was increased by tADA, whereas intracellular ZnAF-2 signal was not increased even in the presence of 100 muM zinc, suggesting that tADA induces calcium release from internal stores in CA3 pyramidal cells and is not involved in zinc uptake. The increase in calcium orange signal by tADA was enhanced by perfusion with pyrithione, a zinc ionophore that decreased basal ZnAF-2 signal in the CA3 pyramidal cell layer. It was blocked by perfusion with pyrithione and zinc that increased basal ZnAF-2 signal. The present study indicates that the increase in free calcium levels via the metabotropic glutamate receptor pathway is inversely related to free zinc levels in CA3 pyramidal cells.

  7. Photocatalytic activity of zinc modified Bi 2O 3

    NASA Astrophysics Data System (ADS)

    Hameed, Abdul; Gombac, Valentina; Montini, Tiziano; Felisari, Laura; Fornasiero, Paolo

    2009-12-01

    The surface of α-Bi 2O 3 was modified by either impregnating Zn acetate or coating with a sol-gel containing Zn hydroxide. The surface modified Bi 2O 3 powders were evaluated by UV-Visible spectroscopy, Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and surface area analysis (BET). The photocatalytic performances were evaluated for the degradation of phenol, methylene blue and methyl orange. The variations in photocatalytic activity were correlated with morphology change. The presence of ZnO does not significantly prevent the progressive formation of photocatalytically inactive (BiO) 2CO 3, while the dye decolourization capability of nanocomposite is significantly preserved with respect to that of bare Bi 2O 3.

  8. Active Sites Environmental Monitoring Program: Program plan

    SciTech Connect

    Ashwood, T.L.; Wickliff, D.S.; Morrissey, C.M.

    1992-02-01

    The Active Sites Environmental Monitoring Program (ASEMP), initiated in 1989, provides early detection and performance monitoring of transuranic (TRU) waste and active low-level waste (LLW) facilities at Oak Ridge National Laboratory (ORNL) in accordance with US Department of Energy (DOE) Order 5820.2A. Active LLW facilities in Solid Waste Storage Area (SWSA) 6 include Tumulus I and Tumulus II, the Interim Waste Management Facility (IWMF), LLW silos, high-range wells, asbestos silos, and fissile wells. The tumulus pads and IWMF are aboveground, high-strength concrete pads on which concrete vaults containing metal boxes of LLW are placed; the void space between the boxes and vaults is filled with grout. Eventually, these pads and vaults will be covered by an engineered multilayered cap. All other LLW facilities in SWSA 6 are below ground. In addition, this plan includes monitoring of the Hillcut Disposal Test Facility (HDTF) in SWSA 6, even though this facility was completed prior to the data of the DOE order. In SWSA 5 North, the TRU facilities include below-grade engineered caves, high-range wells, and unlined trenches. All samples from SWSA 6 are screened for alpha and beta activity, counted for gamma-emitting isotopes, and analyzed for tritium. In addition to these analytes, samples from SWSA 5 North are analyzed for specific transuranic elements.

  9. Pyrrolidine dithiocarbamate-zinc(II) and -copper(II) complexes induce apoptosis in tumor cells by inhibiting the proteasomal activity

    SciTech Connect

    Milacic, Vesna; Chen Di; Giovagnini, Lorena; Diez, Alejandro; Fregona, Dolores; Dou, Q. Ping

    2008-08-15

    Zinc and copper are trace elements essential for proper folding, stabilization and catalytic activity of many metalloenzymes in living organisms. However, disturbed zinc and copper homeostasis is reported in many types of cancer. We have previously demonstrated that copper complexes induced proteasome inhibition and apoptosis in cultured human cancer cells. In the current study we hypothesized that zinc complexes could also inhibit the proteasomal chymotrypsin-like activity responsible for subsequent apoptosis induction. We first showed that zinc(II) chloride was able to inhibit the chymotrypsin-like activity of a purified 20S proteasome with an IC{sub 50} value of 13.8 {mu}M, which was less potent than copper(II) chloride (IC{sub 50} 5.3 {mu}M). We then compared the potencies of a pyrrolidine dithiocarbamate (PyDT)-zinc(II) complex and a PyDT-copper(II) complex to inhibit cellular proteasomal activity, suppress proliferation and induce apoptosis in various human breast and prostate cancer cell lines. Consistently, zinc complex was less potent than copper complex in inhibiting the proteasome and inducing apoptosis. Additionally, zinc and copper complexes appear to use somewhat different mechanisms to kill tumor cells. Zinc complexes were able to activate calpain-, but not caspase-3-dependent pathway, while copper complexes were able to induce activation of both proteases. Furthermore, the potencies of these PyDT-metal complexes depend on the nature of metals and also on the ratio of PyDT to the metal ion within the complex, which probably affects their stability and availability for interacting with and inhibiting the proteasome in tumor cells.

  10. Mechanical Activation-Assisted Reductive Leaching of Cadmium from Zinc Neutral Leaching Residue Using Sulfur Dioxide

    NASA Astrophysics Data System (ADS)

    Zhang, Chun; Min, Xiaobo; Chai, Liyuan; Zhang, Jianqiang; Wang, Mi

    2015-12-01

    In this work, zinc neutral leaching residue was mechanically activated by ball-milling. The subsequent leaching behavior and kinetics of cadmium extraction in a mixed SO2-H2SO4 system were studied. Changes in the crystalline phase, lattice distortion, particle size and morphology, which were induced by mechanical activation, were also investigated. The activated samples showed different physicochemical characteristics, and cadmium extraction was found to be easier than for the un-activated samples. Under the same conditions, mechanical activation contributed to higher cadmium leaching. The cadmium extraction kinetics at 75-95°C was found to fit the shrinking core model. The raw neutral leaching residue, and the samples activated for 60 min and 120 min had a calculated activation energy of 65.02 kJ/mol, 59.45 kJ/mol and 53.46 kJ/mol, respectively. The leaching residue was characterized by ICP, XRD and SEM analysis. According to XRD analysis, the main phases in the residue were lead sulfate (PbSO4), zinc sulfide (ZnS) and cadmium sulfide (CdS).

  11. The effect of copper, zinc, mercury and cadmium on some sperm enzyme activities in the common carp (Cyprinus carpio L.).

    PubMed

    Sarosiek, Beata; Pietrusewicz, Marta; Radziwoniuk, Julita; Glogowski, Jan

    2009-11-01

    The objective of the study was to determine the effect of copper, zinc, cadmium and mercury ions (100, 10 and 1 mg/l) on the activity of some enzymes of carp spermatozoa. Acid phosphatase activity was proved to be relatively insensitive to zinc ions, while copper, mercury and cadmium ions effectively inhibited the activity of this enzyme. Beta-N-acetylglucosaminidase activity was sensitive only to mercury ions. Lactic dehydrogenase activity remained unaffected by heavy metals. Our results showed that, among the examined metals, mercury had the strongest inhibitory effect on enzymatic activities.

  12. [Structural regularities in activated cleavage sites of thrombin receptors].

    PubMed

    Mikhaĭlik, I V; Verevka, S V

    1999-01-01

    Comparison of thrombin receptors activation splitting sites sequences testifies to their similarity both in activation splitting sites of protein precursors and protein proteinase inhibitors reactive sites. In all these sites corresponded to effectory sites P2'-positions are placed by hydrophobic amino-acids only. The regularity defined conforms with previous thesis about the role of effectory S2'-site in regulation of the processes mediated by serine proteinases.

  13. Tailor-Made Zinc-Finger Transcription Factors Activate FLO11 Gene Expression with Phenotypic Consequences in the Yeast Saccharomyces cerevisiae

    PubMed Central

    Shieh, Jia-Ching; Cheng, Yu-Che; Su, Mao-Chang; Moore, Michael; Choo, Yen; Klug, Aaron

    2007-01-01

    Cys2His2 zinc fingers are eukaryotic DNA-binding motifs, capable of distinguishing different DNA sequences, and are suitable for engineering artificial transcription factors. In this work, we used the budding yeast Saccharomyces cerevisiae to study the ability of tailor-made zinc finger proteins to activate the expression of the FLO11 gene, with phenotypic consequences. Two three-finger peptides were identified, recognizing sites from the 5′ UTR of the FLO11 gene with nanomolar DNA-binding affinity. The three-finger domains and their combined six-finger motif, recognizing an 18-bp site, were fused to the activation domain of VP16 or VP64. These transcription factor constructs retained their DNA-binding ability, with the six-finger ones being the highest in affinity. However, when expressed in haploid yeast cells, only one three-finger recombinant transcription factor was able to activate the expression of FLO11 efficiently. Unlike in the wild-type, cells with such transcriptional activation displayed invasive growth and biofilm formation, without any requirement for glucose depletion. The VP16 and VP64 domains appeared to act equally well in the activation of FLO11 expression, with comparable effects in phenotypic alteration. We conclude that the functional activity of tailor-made transcription factors in cells is not easily predicted by the in vitro DNA-binding activity. PMID:17710146

  14. Zinc-sulphate-heptahydrate coated activated carbon for microbe removal from stormwater.

    PubMed

    Guest, R M; Schang, C; Deletic, A; McCarthy, D T

    2012-01-01

    There is a need to develop effective stormwater filters for passive (without any addition of chemicals or energy) and effective removal of pathogens in order to mainstream stormwater harvesting. This study focuses on the development of coated granular activated carbon (GAC) filtration material in order to develop filters for effective removal of pathogens from urban stormwater. Several laboratory trials were performed to gauge the effectiveness of the filters, which use a mixture of the zinc-sulphate-heptahydrate coated GAC and sand, on the removal of Escherichia coli (E. coli) from semi-natural stormwater. On average, a 98% removal of the inflow concentration of E. coli was achieved. Furthermore, there was also an improvement of approximately 25% in the removal of phosphorous. However, it was found that the treated material was leaching zinc. It was important to determine whether the observed removal of E. coli was indirectly caused by the sampling methodology. The results showed that the inactivation of the E. coli in the collected sample was small compared with the inactivation which actually occurred within the filter. This provides much promise to the filter, but the presence of zinc in the outflow demonstrates the need for further investigation into the stabilisation of the coating process.

  15. Characterization and identification of the sources of chromium, zinc, lead, cadmium, nickel, manganese and iron in PM10 particulates at the two sites of Kolkata, India.

    PubMed

    Karar, Kakoli; Gupta, A K; Kumar, Animesh; Biswas, Arun Kanti

    2006-09-01

    Monitoring of ambient PM10 (particulate matter which passes through a size selective impactor inlet with a 50% efficiency cut-off at 10 microm aerodynamic diameter) has been done at residential (Kasba) and industrial (Cossipore) sites of an urban region of Kolkata during November 2003 to November 2004. These sites were selected depending on the dominant anthropogenic activities. Metal constituents of atmospheric PM10 deposited on glass fibre filter paper were estimated using Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES). Chromium (Cr), zinc (Zn), lead (Pb), cadmium (Cd), nickel (Ni), manganese (Mn) and iron (Fe) are the seven toxic trace metals quantified from the measured PM10 concentrations. The 24 h average concentrations of Cr, Zn, Pb, Cd, Ni, Mn and Fe from ninety PM10 particulate samples of Kolkata were found to be 6.9, 506.1, 79.1, 3.3, 7.4, 2.4 and 103.6 ng/m3, respectively. The 24 h average PM10 concentration exceeded national ambient air quality standard (NAAQS) as specified by central pollution control board, India at both residential (Kasba) and industrial (Cossipore) areas with mean concentration of 140.1 and 196.6 microg/m3, respectively. A simultaneous meteorology study was performed to assess the influence of air masses by wind speed, wind direction, rainfall, relative humidity and temperature. The measured toxic trace metals generally showed inverse relationship with wind speed, relative humidity and temperature. Factor analysis, a receptor modeling technique has been used for identification of the possible sources contributing to the PM10. Varimax rotated factor analysis identified four possible sources of measured trace metals comprising solid waste dumping, vehicular traffic with the influence of road dust, road dust and soil dust at residential site (Kasba), while vehicular traffic with the influence of soil dust, road dust, galvanizing and electroplating industry, and tanning industry at industrial site (Cossipore).

  16. Microwave accelerated synthesis of zinc oxide nanoplates and their enhanced photocatalytic activity under UV and solar illuminations

    NASA Astrophysics Data System (ADS)

    Anas, S.; Rahul, S.; Babitha, K. B.; Mangalaraja, R. V.; Ananthakumar, S.

    2015-11-01

    Photoactive zinc based nanoplates were developed through a rapid microwave synthesis. A low temperature thermolysis reaction in a surfactant medium was initially performed for producing microwave active zinc based polar precursors. Using these precursors, the zinc oxide nanopowder having platelet morphologies were prepared. The nanoplatelets exhibited random growth with non-polar (1 0 1) surface as the major growth plane. The structural and functional features of the resultant zinc oxide samples were monitored using XRD, FTIR, TEM and PL. The photocatalytic activities of the samples were investigated through the standard photoreduction kinetics using the methylene blue dye. The catalytic efficiencies of the samples were checked both under UV and sunlight. A comparative study was also performed with the standard TiO2 sample. The analyses revealed that the microwave derived zinc oxide have higher catalytic efficiency, than the standard titania samples, both under UV and sunlight illuminations. The unique nature of the zinc oxide non-polar surfaces can be attributed due to the presence of more active two dimensional open surfaces and the higher content of oxygen defect concentrations.

  17. A modular system of DNA enhancer elements mediates tissue-specific activation of transcription by high dietary zinc in C. elegans

    PubMed Central

    Roh, Hyun Cheol; Dimitrov, Ivan; Deshmukh, Krupa; Zhao, Guoyan; Warnhoff, Kurt; Cabrera, Daniel; Tsai, Wendy; Kornfeld, Kerry

    2015-01-01

    Zinc is essential for biological systems, and aberrant zinc metabolism is implicated in a broad range of human diseases. To maintain homeostasis in response to fluctuating levels of dietary zinc, animals regulate gene expression; however, mechanisms that mediate the transcriptional response to fluctuating levels of zinc have not been fully defined. Here, we identified DNA enhancer elements that mediate intestine-specific transcriptional activation in response to high levels of dietary zinc in C. elegans. Using bioinformatics, we characterized an evolutionarily conserved enhancer element present in multiple zinc-inducible genes, the high zinc activation (HZA) element. The HZA was consistently adjacent to a GATA element that mediates expression in intestinal cells. Functional studies using transgenic animals demonstrated that this modular system of DNA enhancers mediates tissue-specific transcriptional activation in response to high levels of dietary zinc. We used this information to search the genome and successfully identified novel zinc-inducible genes. To characterize the mechanism of enhancer function, we demonstrated that the GATA transcription factor ELT-2 and the mediator subunit MDT-15 are necessary for zinc-responsive transcriptional activation. These findings define new mechanisms of zinc homeostasis and tissue-specific regulation of transcription. PMID:25552416

  18. Zinc pyrithione-mediated activation of voltage-gated KCNQ potassium channels rescues epileptogenic mutants.

    PubMed

    Xiong, Qiaojie; Sun, Haiyan; Li, Min

    2007-05-01

    KCNQ potassium channels are activated by changes in transmembrane voltage and play an important role in controlling electrical excitability. Human mutations of KCNQ2 and KCNQ3 potassium channel genes result in reduction or loss of channel activity and cause benign familial neonatal convulsions (BFNCs). Thus, small molecules capable of augmenting KCNQ currents are essential both for understanding the mechanism of channel activity and for developing therapeutics. We performed a high-throughput screen in search for agonistic compounds potentiating KCNQ potassium channels. Here we report identification of a new opener, zinc pyrithione (1), which activates both recombinant and native KCNQ M currents. Interactions with the channel protein cause an increase of single-channel open probability that could fully account for the overall conductance increase. Separate point mutations have been identified that either shift the concentration dependence or affect potentiation efficacy, thereby providing evidence for residues influencing ligand binding and downstream events. Furthermore, zinc pyrithione is capable of rescuing the mutant channels causal to BFNCs.

  19. Synthesis, characterization and enhanced antimicrobial activity of reduced graphene oxide–zinc oxide nanocomposite

    NASA Astrophysics Data System (ADS)

    Singh Rajaura, Rajveer; Sharma, Vinay; Shrivastava Ronin, Rishabh; Gupta, Deepak K.; Srivastava, Subodh; Agrawal, Kailash; Vijay, Y. K.

    2017-02-01

    In this work, we report a simple and facile one-pot chemical approach of the decoration of uniform zinc oxide nanoparticles (ZnO NPs) on reduced graphene oxide (GO) and a study of its antimicrobial activity. The nanocomposite was fully characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). TEM and SEM images clearly indicated the presence of Graphene sheets decorated with uniformly sized zinc oxide nanoparticles. Further, as an application of rGO-ZnO nanocomposites, their superior antibacterial activity was demonstrated on the Escherichia coli MTCC40 bacterial strain, using the standard disk diffusion method. This clearly showed that rGO-ZnO nanocomposites exhibited more pronounced antibacterial activity than rGO alone. This feature was revealed to be due to increased biocompatibility of PEGylated rGO-ZnO nanocomposites. In conclusion, the as-synthesized nanocomposite showed excellent antibacterial activity and has great potential for biomedical application.

  20. Activation by zinc of the human gastrin gene promoter in colon cancer cells in vitro and in vivo.

    PubMed

    Marshall, Kathryn M; Laval, Marie; Estacio, Ortis; Hudson, Damien F; Kalitsis, Paul; Shulkes, Arthur; Baldwin, Graham S; Patel, Oneel

    2015-10-01

    Over-expression of growth factors can contribute to the development and progression of cancer, and gastrins in particular have been implicated in accelerating the development of gastrointestinal cancers. Previously our group showed that hypoxia, cobalt chloride (a hypoxia mimetic) and zinc chloride could activate the expression of the gastrin gene in vitro. To characterise activation of the gastrin promoter by zinc ions further in vivo, TALEN technology was used to engineer a luciferase reporter construct into the endogenous human gastrin gene promoter in SW480 colon cancer cells. Gastrin promoter activity in the resultant Gast(luc) SW480 colon cancer cells was then measured by bioluminescence in cell culture and in tumour xenografts in SCID mice. Activation of intracellular signalling pathways was assessed by Western blotting. Activation of the gastrin promoter by zinc ions was concentration dependent in vitro and in vivo. Zinc ions significantly stimulated phosphorylation of ERK1/2 (MAPK pathway) but not of Akt (PI3K pathway). We conclude that the endogenous gastrin promoter is responsive to zinc ions, likely via activation of the MAPK pathway.

  1. Enhanced transparency, mechanical durability, and antibacterial activity of zinc nanoparticles on glass substrate

    NASA Astrophysics Data System (ADS)

    Choi, Hyung-Jin; Choi, Jin-Seok; Park, Byeong-Ju; Eom, Ji-Ho; Heo, So-Young; Jung, Min-Wook; An, Ki-Seok; Yoon, Soon-Gil

    2014-09-01

    Homogeneously distributed zinc nanoparticles (NPs) on the glass substrate were investigated for the transmittance, mechanical durability, and antibacterial effect. The buffered Ti NPs between Zn NPs and glass substrate were studied for an enhancement of the transmittance and mechanical endurance. The Ti NPs buffered Zn NPs showed a high transmittance of approximately 91.5% (at a wavelength of 550 nm) and a strong antibacterial activity for Staphylococcus aureus and Escherichia coli bacteria. The buffered Ti NPs are attractive for an excellent mechanical endurance of the Zn NPs. The Zn NPs did not require the protection layer to prevent the degradation of the performance for both the antibacterial effect and the transmittance.

  2. Examination of the role of arginine-143 in the human copper and zinc superoxide dismutase by site-specific mutagenesis.

    PubMed

    Beyer, W F; Fridovich, I; Mullenbach, G T; Hallewell, R

    1987-08-15

    The active site arginine-143 of human Cu,Zn superoxide dismutase has been replaced by lysine or by isoleucine. The mutant proteins were expressed at high levels in yeast, purified, and the amino acid substitution explored through the use of group specific reagents. The specific activities of these enzymes, measured by the xanthine oxidase/cytochrome c method and by using dry weight determination to establish protein concentration, were: native enzyme, 6570 units/mg; Lys-substituted enzyme, 2840 units/mg, Ile-substituted enzyme, 708 units/mg. The active site arginine thus plays an important, but not an essential, role in the catalytic process.

  3. Consequences and utility of the zinc-dependent metalloprotease activity of anthrax lethal toxin.

    PubMed

    Bromberg-White, Jennifer; Lee, Chih-Shia; Duesbery, Nicholas

    2010-05-01

    Anthrax is caused by the gram-positive bacterium Bacillus anthracis. The pathogenesis of this disease is dependent on the presence of two binary toxins, edema toxin (EdTx) and lethal toxin (LeTx). LeTx, the major virulence factor contributing to anthrax, contains the effector moiety lethal factor (LF), a zinc-dependent metalloprotease specific for targeting mitogen-activated protein kinase kinases. This review will focus on the protease-specific activity and function of LF, and will include a discussion on the implications and consequences of this activity, both in terms of anthrax disease, and how this activity can be exploited to gain insight into other pathologic conditions.

  4. Antioxidant, antibacterial and anti-aging activities of intracellular zinc polysaccharides from Grifola frondosa SH-05.

    PubMed

    Zhang, Chen; Gao, Zheng; Hu, Chunlong; Zhang, Jianjun; Sun, Xinyi; Rong, Chengbo; Jia, Le

    2017-02-01

    In present work, the strain of Grifola frondosa SH-05 was used as a vector of zinc biotransformation to produce the IZPS. The bioactivities including antioxidant and antibacterial activities in vitro and anti-aging properties in vivo of IZPS were investigated comparing with the IPS. The results which were in consistent with the results of histopathology assay demonstrated that the IZPS had superior antioxidant and anti-aging activities by scavenging the hydroxyl and DPPH radicals, increasing enzyme activities, decreasing the MDA contents and ameliorating the anile condition of mice. Besides, the IZPS also showed potential antibacterial activities. The IZPS with higher bioactivities was composed of were Rha, Ino and Glu with a molar ratio of 4.7:3.6:1. These conclusions indicated that the IZPS might be a potential source of natural antioxidant, antibacterial agent and anti-aging agent.

  5. Use of nanoparticulate zinc oxide as intracanal medication in endodontics: pH and antimicrobial activity.

    PubMed

    Guerreiro-Tanomaru, Juliane M; Pereira, Kamila Figueiredo; Nascimento, Camila Almeida; Bernardi, Maria Inês Basso; Tanomaru-Filho, Mario

    2013-01-01

    The aim of this study was to evaluate the pH and antimicrobial activity of micro or nanoparticulate zinc oxide (ZnO) pastes with or without calcium hydroxide (CH). The following medications were evaluated: microparticulate ZnO + polyethylene glycol (PEG) 400; nanoparticulate ZnO + PEG 400; PEG 400; CH + microparticulate ZnO + PEG 400 and CH + nanoparticulate ZnO + PEG 400. The pH was assessed between 12 hours and 28 days, using a digital pH meter. The antimicrobial activity against Enterococcus faecalis (ATCC-9212), Candida albicans (ATCC-10231), Pseudomonas aeruginosa (ATCC-27853), Staphylococcus aureus (ATCC-6538) and Kocuria rhizophila (ATCC-9341) was determined in triplicate using agar diffusion test. The results were submitted to Kruskal-Wallis/Dunn and ANOVA/Tukey tests with 5% significance. The highest pH values were found for CH+ZnO, with higher values for nanoparticulate ZnO after 12 hours and 21 days (p < 0.05). CH+ZnO medication promoted higher growth inhibition against P. aeruginosa and lower against E. faecalis. Calcium hydroxide pastes have higher pH and antimicrobial activity when associated with either micro- or nanoparticulate zinc oxide.

  6. Highly Active and Durable Nanocrystal-Decorated Bifunctional Electrocatalyst for Rechargeable Zinc-Air Batteries.

    PubMed

    Lee, Dong Un; Park, Moon Gyu; Park, Hey Woong; Seo, Min Ho; Wang, Xiaolei; Chen, Zhongwei

    2015-09-21

    A highly active and durable bifunctional electrocatalyst that consists of cobalt oxide nanocrystals (Co3 O4 NC) decorated on the surface of N-doped carbon nanotubes (N-CNT) is introduced as effective electrode material for electrically rechargeable zinc-air batteries. This active hybrid catalyst is synthesized by a facile surfactant-assisted method to produce Co3 O4 NC that are then decorated on the surface of N-CNT through hydrophobic attraction. Confirmed by half-cell testing, Co3 O4 NC/N-CNT demonstrates superior oxygen reduction and oxygen evolution catalytic activities and has a superior electrochemical stability compared to Pt/C and Ir/C. Furthermore, rechargeable zinc-air battery testing of Co3 O4 NC/N-CNT reveals superior galvanodynamic charge and discharge voltages with a significantly extended cycle life of over 100 h, which suggests its potential as a replacement for precious-metal-based catalysts for electric vehicles and grid energy storage applications.

  7. Highly durable and active non-precious air cathode catalyst for zinc air battery

    NASA Astrophysics Data System (ADS)

    Chen, Zhu; Choi, Ja-Yeon; Wang, Haijiang; Li, Hui; Chen, Zhongwei

    The electrochemical stability of non-precious FeCo-EDA and commercial Pt/C cathode catalysts for zinc air battery have been compared using accelerated degradation test (ADT) in alkaline condition. Outstanding oxygen reduction reaction (ORR) stability of the FeCo-EDA catalyst was observed compared with the commercial Pt/C catalyst. The FeCo-EDA catalyst retained 80% of the initial mass activity for ORR whereas the commercial Pt/C catalyst retained only 32% of the initial mass activity after ADT. Additionally, the FeCo-EDA catalyst exhibited a nearly three times higher mass activity compared to that of the commercial Pt/C catalyst after ADT. Furthermore, single cell test of the FeCo-EDA and Pt/C catalysts was performed where both catalysts exhibited pseudolinear behaviour in the 12-500 mA cm -2 range. In addition, 67% higher peak power density was observed from the FeCo-EDA catalyst compared with commercial Pt/C. Based on the half cell and single cell tests the non-precious FeCo-EDA catalyst is a very promising ORR electrocatalyst for zinc air battery.

  8. CHRONIC ZINC SCREENING WATER EFFECT RATIO FOR THE H-12 OUTFALL, SAVANNAH RIVER SITE

    SciTech Connect

    Coughlin, D.; Looney, B.; Millings, M.

    2009-01-13

    In response to proposed Zn limits for the NPDES outfall H-12, a Zn screening Water Effects Ratio (WER) study was conducted to determine if a full site-specific WER is warranted. Using standard assumptions for relating the lab results to the stream, the screening WER data were consistent with the proposed Zn limit and suggest that a full WER would result in a similar limit. Addition of a humate amendment to the outfall water reduced Zn toxicity, but the toxicity reduction was relatively small and unlikely to impact proposed Zn limits. The screening WER data indicated that the time and expense required to perform a full WER for Zn is not warranted.

  9. MYST protein acetyltransferase activity requires active site lysine autoacetylation.

    PubMed

    Yuan, Hua; Rossetto, Dorine; Mellert, Hestia; Dang, Weiwei; Srinivasan, Madhusudan; Johnson, Jamel; Hodawadekar, Santosh; Ding, Emily C; Speicher, Kaye; Abshiru, Nebiyu; Perry, Rocco; Wu, Jiang; Yang, Chao; Zheng, Y George; Speicher, David W; Thibault, Pierre; Verreault, Alain; Johnson, F Bradley; Berger, Shelley L; Sternglanz, Rolf; McMahon, Steven B; Côté, Jacques; Marmorstein, Ronen

    2012-01-04

    The MYST protein lysine acetyltransferases are evolutionarily conserved throughout eukaryotes and acetylate proteins to regulate diverse biological processes including gene regulation, DNA repair, cell-cycle regulation, stem cell homeostasis and development. Here, we demonstrate that MYST protein acetyltransferase activity requires active site lysine autoacetylation. The X-ray crystal structures of yeast Esa1 (yEsa1/KAT5) bound to a bisubstrate H4K16CoA inhibitor and human MOF (hMOF/KAT8/MYST1) reveal that they are autoacetylated at a strictly conserved lysine residue in MYST proteins (yEsa1-K262 and hMOF-K274) in the enzyme active site. The structure of hMOF also shows partial occupancy of K274 in the unacetylated form, revealing that the side chain reorients to a position that engages the catalytic glutamate residue and would block cognate protein substrate binding. Consistent with the structural findings, we present mass spectrometry data and biochemical experiments to demonstrate that this lysine autoacetylation on yEsa1, hMOF and its yeast orthologue, ySas2 (KAT8) occurs in solution and is required for acetylation and protein substrate binding in vitro. We also show that this autoacetylation occurs in vivo and is required for the cellular functions of these MYST proteins. These findings provide an avenue for the autoposttranslational regulation of MYST proteins that is distinct from other acetyltransferases but draws similarities to the phosphoregulation of protein kinases.

  10. MYST protein acetyltransferase activity requires active site lysine autoacetylation

    PubMed Central

    Yuan, Hua; Rossetto, Dorine; Mellert, Hestia; Dang, Weiwei; Srinivasan, Madhusudan; Johnson, Jamel; Hodawadekar, Santosh; Ding, Emily C; Speicher, Kaye; Abshiru, Nebiyu; Perry, Rocco; Wu, Jiang; Yang, Chao; Zheng, Y George; Speicher, David W; Thibault, Pierre; Verreault, Alain; Johnson, F Bradley; Berger, Shelley L; Sternglanz, Rolf; McMahon, Steven B; Côté, Jacques; Marmorstein, Ronen

    2012-01-01

    The MYST protein lysine acetyltransferases are evolutionarily conserved throughout eukaryotes and acetylate proteins to regulate diverse biological processes including gene regulation, DNA repair, cell-cycle regulation, stem cell homeostasis and development. Here, we demonstrate that MYST protein acetyltransferase activity requires active site lysine autoacetylation. The X-ray crystal structures of yeast Esa1 (yEsa1/KAT5) bound to a bisubstrate H4K16CoA inhibitor and human MOF (hMOF/KAT8/MYST1) reveal that they are autoacetylated at a strictly conserved lysine residue in MYST proteins (yEsa1-K262 and hMOF-K274) in the enzyme active site. The structure of hMOF also shows partial occupancy of K274 in the unacetylated form, revealing that the side chain reorients to a position that engages the catalytic glutamate residue and would block cognate protein substrate binding. Consistent with the structural findings, we present mass spectrometry data and biochemical experiments to demonstrate that this lysine autoacetylation on yEsa1, hMOF and its yeast orthologue, ySas2 (KAT8) occurs in solution and is required for acetylation and protein substrate binding in vitro. We also show that this autoacetylation occurs in vivo and is required for the cellular functions of these MYST proteins. These findings provide an avenue for the autoposttranslational regulation of MYST proteins that is distinct from other acetyltransferases but draws similarities to the phosphoregulation of protein kinases. PMID:22020126

  11. Gene targeting technologies in rats: zinc finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeats.

    PubMed

    Mashimo, Tomoji

    2014-01-01

    The laboratory rat has been widely used as an animal model in biomedical science for more than 150 years. Applying zinc-finger nucleases or transcription activator-like effector nucleases to rat embryos via microinjection is an efficient genome editing tool for generating targeted knockout rats. Recently, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated endonucleases have been used as an effective tool for precise and multiplex genome editing in mice and rats. In this review, the advantages and disadvantages of these site-specific nuclease technologies for genetic analysis and manipulation in rats are discussed.

  12. Activated and nonactivated forms of zinc powder: Reactivity toward chlorocarbons in water and AFM studies of surface morphologies

    SciTech Connect

    Boronina, T.N.; Lagadic, I.; Klabunde, K.J.; Sergeev, G.B.

    1998-09-01

    This work was carried out with the purpose of developing effective reagents for decontamination of groundwater contaminated with chlorocarbons. Zinc metal as a reducing agent for carbon tetrachloride (CT), chloroform (Chl), and methylene chloride (MC) in aqueous solution has been studied in some detail, especially regarding activated forms of the metal. Chlorocarbon concentrations were monitored at certain time intervals by gas chromatography/mass spectrometry (GC/MS) analysis of the headspace and water phase. Reaction mixture headspace was additionally studied by a GC/headspace analysis system to detect the formation of hydrocarbons. Chloroform, methylene chloride, methyl chloride, methane, and acetylene were found to be products from CT reduction. For methylene chloride reduction, traces of cis and trans-1,2-dichloroethene (DCE) were also found. Activated by cryo or mechanical treatment, metallic zinc caused an increase in CT dechlorination rate and conversion into methane. After the first 2.5 h, more than 20% of CT was converted into methane by cryochemically activated zinc in comparison to 1.2% by conventional zinc dust. Furthermore, CT reduction by activated zinc caused the formation of DCEs and TCE. Pathways are proposed to account for the observed methane/methylene chloride ratio and DCEs and TCE formation that include sequential reductive dechlorination through organometallic and carbonoid species on the Zn surface.

  13. Activation of sputter-processed indium–gallium–zinc oxide films by simultaneous ultraviolet and thermal treatments

    PubMed Central

    Tak, Young Jun; Du Ahn, Byung; Park, Sung Pyo; Kim, Si Joon; Song, Ae Ran; Chung, Kwun-Bum; Kim, Hyun Jae

    2016-01-01

    Indium–gallium–zinc oxide (IGZO) films, deposited by sputtering at room temperature, still require activation to achieve satisfactory semiconductor characteristics. Thermal treatment is typically carried out at temperatures above 300 °C. Here, we propose activating sputter- processed IGZO films using simultaneous ultraviolet and thermal (SUT) treatments to decrease the required temperature and enhance their electrical characteristics and stability. SUT treatment effectively decreased the amount of carbon residues and the number of defect sites related to oxygen vacancies and increased the number of metal oxide (M–O) bonds through the decomposition-rearrangement of M–O bonds and oxygen radicals. Activation of IGZO TFTs using the SUT treatment reduced the processing temperature to 150 °C and improved various electrical performance metrics including mobility, on-off ratio, and threshold voltage shift (positive bias stress for 10,000 s) from 3.23 to 15.81 cm2/Vs, 3.96 × 107 to 1.03 × 108, and 11.2 to 7.2 V, respectively. PMID:26902863

  14. Synthesis, characterization, and photocatalytic activities of titanate nanotubes surface-decorated by zinc oxide nanoparticles.

    PubMed

    Wang, Li Shi; Xiao, Ming Wei; Huang, Xin Jian; Wu, Yan Dan

    2009-01-15

    Nanoscaled zinc oxide (ZnO) particles with different amounts are coated on titanate nanotubes (TNTs) by a facile chemical method at room temperature. The characterizations of XPS, TEM, XRD and UV-vis spectra confirm that pure hexagonal wurtzite ZnO nanoparticles with an average size of about 9nm are distributed on the surfaces of TNTs evenly and attached strongly. The photocatalytic activities of the ZnO-TNTs nanocomposite are superior to those of P25, ZnO, TNTs and ZnO-anatase TiO2 (TNP) nanocomposite in the oxidation of rhodamine B under UV light irradiation. A comparison of the photocatalytic activities between different catalysts is discussed. Furthermore, we also find that the ZnO-TNT nanocomposite shows very favorable recycle use potential, because they have a high sedimentation rate and their photocatalytic activity is only slightly decreased even after five times of repeated uses.

  15. Removal of toxic zinc from water/wastewater using eucalyptus seeds activated carbon: non-linear regression analysis.

    PubMed

    Senthil Kumar, Ponnusamy; Saravanan, Anbalagan; Anish Kumar, Kodyingil; Yashwanth, Ramesh; Visvesh, Sridharan

    2016-08-01

    In the present study, a novel activated carbon was prepared from low-cost eucalyptus seeds, which was utilised for the effectively removal of toxic zinc from the water/wastewater. The prepared adsorbent was studied by Fourier transform infrared spectroscopy and scanning electron microscopic characterisation studies. Adsorption process was experimentally performed for optimising the influencing factors such as adsorbent dosage, solution pH, contact time, initial zinc concentration, and temperature for the maximum removal of zinc from aqueous solution. Adsorption isotherm of zinc removal was ensued Freundlich model, and the kinetic model ensued pseudo-second order model. Langmuir monolayer adsorption capacity of the adsorbent for zinc removal was evaluated as 80.37 mg/g. The results of the thermodynamic studies suggested that the adsorption process was exothermic, thermodynamically feasible and impulsive process. Finally, a batch adsorber was planned to remove zinc from known volume and known concentration of wastewater using best obeyed model such as Freundlich. The experimental details showed the newly prepared material can be effectively utilised as a cheap material for the adsorption of toxic metal ions from the contaminated water.

  16. Biogenic synthesis of zinc oxide nanoparticles using Ruta graveolens (L.) and their antibacterial and antioxidant activities

    NASA Astrophysics Data System (ADS)

    Lingaraju, K.; Raja Naika, H.; Manjunath, K.; Basavaraj, R. B.; Nagabhushana, H.; Nagaraju, G.; Suresh, D.

    2016-06-01

    In the present investigation, green synthesis of zinc oxide nanoparticles were successfully synthesized by biological method using aqueous stem extract of Ruta graveolens act as reducing agent. Formation of ZnO nanoparticles were characterized by powder X-ray diffraction (PXRD), UV-visible spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Zinc oxide nanoparticles were subjected to biological properties such as antibacterial and antioxidant studies. The PXRD pattern reveals that ZnO sample belongs to hexagonal phase with Wurtzite structure. The UV-vis absorption spectrum shows an absorption band at 355 nm due to ZnO nanoparticles. SEM images show that the particles have spherical like structure with large surface area and the average crystallite sizes were found to be in the range ~28 nm. These observations were confirmed by TEM analysis. The ZnO nanoparticles are found to inhibit the antioxidant activity of 1,1-diphenyl-2-picrylhydrazyl free radicals effectively. ZnO Nps exhibit significant bactericidal activity against Gram -ve bacterial strains such as Klebsiella aerogenes, Pseudomonas aeruginosa, Escherichia coli and Gram +ve Staphylococcus aureus by agar well diffusion method.

  17. Structure-property-composition relationships in doped zinc oxides: enhanced photocatalytic activity with rare earth dopants.

    PubMed

    Goodall, Josephine B M; Illsley, Derek; Lines, Robert; Makwana, Neel M; Darr, Jawwad A

    2015-02-09

    In this paper, we demonstrate the use of continuous hydrothermal flow synthesis (CHFS) technology to rapidly produce a library of 56 crystalline (doped) zinc oxide nanopowders and two undoped samples, each with different particle properties. Each sample was produced in series from the mixing of an aqueous stream of basic zinc nitrate (and dopant ion or modifier) solution with a flow of superheated water (at 450 °C and 24.1 MPa), whereupon a crystalline nanoparticle slurry was rapidly formed. Each composition was collected in series, cleaned, freeze-dried, and then characterized using analytical methods, including powder X-ray diffraction, transmission electron microscopy, Brunauer-Emmett-Teller surface area measurement, X-ray photoelectron spectroscopy, and UV-vis spectrophotometry. Photocatalytic activity of the samples toward the decolorization of methylene blue dye was assessed, and the results revealed that transition metal dopants tended to reduce the photoactivity while rare earth ions, in general, increased the photocatalytic activity. In general, low dopant concentrations were more beneficial to having greater photodecolorization in all cases.

  18. Zinc Deficiency Impacts CO2 Assimilation and Disrupts Copper Homeostasis in Chlamydomonas reinhardtii*

    PubMed Central

    Malasarn, Davin; Kropat, Janette; Hsieh, Scott I.; Finazzi, Giovanni; Casero, David; Loo, Joseph A.; Pellegrini, Matteo; Wollman, Francis-André; Merchant, Sabeeha S.

    2013-01-01

    Zinc is an essential nutrient because of its role in catalysis and in protein stabilization, but excess zinc is deleterious. We distinguished four nutritional zinc states in the alga Chlamydomonas reinhardtii: toxic, replete, deficient, and limited. Growth is inhibited in zinc-limited and zinc-toxic cells relative to zinc-replete cells, whereas zinc deficiency is visually asymptomatic but distinguished by the accumulation of transcripts encoding ZIP family transporters. To identify targets of zinc deficiency and mechanisms of zinc acclimation, we used RNA-seq to probe zinc nutrition-responsive changes in gene expression. We identified genes encoding zinc-handling components, including ZIP family transporters and candidate chaperones. Additionally, we noted an impact on two other regulatory pathways, the carbon-concentrating mechanism (CCM) and the nutritional copper regulon. Targets of transcription factor Ccm1 and various CAH genes are up-regulated in zinc deficiency, probably due to reduced carbonic anhydrase activity, validated by quantitative proteomics and immunoblot analysis of Cah1, Cah3, and Cah4. Chlamydomonas is therefore not able to grow photoautotrophically in zinc-limiting conditions, but supplementation with 1% CO2 restores growth to wild-type rates, suggesting that the inability to maintain CCM is a major consequence of zinc limitation. The Crr1 regulon responds to copper limitation and is turned on in zinc deficiency, and Crr1 is required for growth in zinc-limiting conditions. Zinc-deficient cells are functionally copper-deficient, although they hyperaccumulate copper up to 50-fold over normal levels. We suggest that zinc-deficient cells sequester copper in a biounavailable form, perhaps to prevent mismetallation of critical zinc sites. PMID:23439652

  19. Anti-inflammatory activity and gastric lesions induced by zinc-tenoxicam.

    PubMed

    Nascimento, Jorge Willian L; Santos, Luiz Henrique; Nothenberg, Michael S; Coelho, Márcio M; Oga, Seizi; Tagliati, Carlos A

    2003-06-01

    Oral administration of tenoxicam or zinc-tenoxicam complex inhibited to a similar extent carrageenin-induced paw oedema and granulomatous tissue formation in rats as well as the acetic acid induced writhing response in mice. Gastric lesions induced by oral administration of zinc-tenoxicam were reduced in number and severity when compared with those induced by tenoxicam or the co-administration of tenoxicam and zinc acetate. However, after intraperitoneal administration, both zinc-tenoxicam and tenoxicam plus zinc acetate induced a reduced number of gastric lesions as compared with tenoxicam.

  20. Green synthesis, characterization, and anticancer activity of hyaluronan/zinc oxide nanocomposite

    PubMed Central

    Namvar, Farideh; Azizi, Susan; Rahman, Heshu Sulaiman; Mohamad, Rosfarizan; Rasedee, Abdullah; Soltani, Mozhgan; Rahim, Raha Abdul

    2016-01-01

    The study describes an in situ green biosynthesis of zinc oxide nanocomposite using the seaweed Sargassum muticum water extract and hyaluronan biopolymer. The morphology and optical properties of the hyaluronan/zinc oxide (HA/ZnO) nanocomposite were determined by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and ultraviolet–vis analysis. Electron microscopy and X-ray diffraction analysis showed that the zinc oxide nanoparticles were polydispersed with a mean size of 10.2±1.5 nm. The nanoparticles were mostly hexagonal in crystalline form. The HA/ZnO nanocomposite showed the absorption properties in the ultraviolet zone that is ascribed to the band gap of zinc oxide nanocomposite. In the cytotoxicity study, cancer cells, pancreatic adenocarcinoma (PANC-1), ovarian adenocarcinoma (CaOV-3), colonic adenocarcinoma (COLO205), and acute promyelocytic leukemia (HL-60) cells were treated with HA/ZnO nanocomposite. At 72 hours of treatment, the half maximal inhibitory concentration (IC50) value via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was 10.8±0.3 μg/mL, 15.4±1.2 μg/mL, 12.1±0.9 μg/mL, and 6.25±0.5 μg/mL for the PANC-1, CaOV-3, COLO-205, and HL-60 cells, respectively, showing that the composite is most toxic to the HL-60 cells. On the other hand, HA/ZnO nanocomposite treatment for 72 hours did not cause toxicity to the normal human lung fibroblast (MRC-5) cell line. Using fluorescent dyes and flow cytometry analysis, HA/ZnO nanocomposite caused G2/M cell cycle arrest and stimulated apoptosis-related increase in caspase-3 and -7 activities of the HL-60 cells. Thus, the study shows that the HA/ZnO nanocomposite produced through green synthesis has great potential to be developed into an efficacious therapeutic agent for cancers. PMID:27555781

  1. Synthesis of zinc oxide nanostructures catalytically active in the optical range without irradiation

    NASA Astrophysics Data System (ADS)

    Kasumov, M. M.

    2012-09-01

    A technique for synthesizing catalytically active zinc oxide-based nanostructures is described. The synthesis product represents a blue-gray powder. When it is introduced into a water solution of methyl orange the latter bleaches out both under daylight and in the dark. The activity of the material is measured by the Kubelka-Munk formula in the wavelength range 0.3-1.8 μm. As follows from X-ray phase analysis data, the synthesized material is a composite consisting of hexagonal structures with the parameters ZnO [ a: 3.2491, c: 5.2046] and Zn [ a: 2.6639, c: 4.9397]. A mechanism underlying the formation of a ZnO-Zn nanocomposite is suggested.

  2. Effect of aluminum and zinc on enzyme activities in the green Alga Selenastrum capricorutum

    SciTech Connect

    Kong, F.X.; Chen, Y.

    1995-11-01

    Acid rain produced by atmospheric pollution may decrease the pH value of water and increase the availability and potential toxicity of metals in water which have detrimental effects on aquatic organism, including algae, the important component of the primary production, and, thus, the entire aquatic food chain. Recent reviews of the effects of acid rain on freshwater ecosystems have emphasized research interest in soluble trivalent aluminum, although Al is rated low among trace metals in biological importance. On the other hand, zinc is an important trace element for the growth of phytoplankton and the cofactor of some enzymes. The growth response and tolerance of different species of algae to Al and Zn have been reported by Whitton who showed that algal growth would be stimulated by lower levels of the metals and totally inhibited by higher levels. These is little information, however, on the effect of Al on biochemical processes in aquatic organisms. This study investigates the influence of aluminum and zinc on several physioclogical processes in S. capricournutum, a common species of green algal in lake water. Algal growth (dry weight), ATP levels and the activities of several enzymes in the algal cells were measured after the treatment with various concentrations of Al and Zn in culture medium. Special attention is given to the relation between the enzymatic response and algal growth. 15 refs., 2 figs., 1 tab.

  3. The reduction of graphene oxide by zinc powder to produce a zinc oxide-reduced graphene oxide hybrid and its superior photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Sarkar, Sanjit; Basak, Durga

    2013-03-01

    We have synthesized for the first time ZnO/rGO hybrids from metal zinc and GO using hydrothermal technique without adding further reducing agent. The photocatalytic property of ZnO-rGO reveals that the hybrid for 50 mg of GO has the highest activity, causing a 94% degradation of methyl orange compared to 70% by only ZnO. The consistent quenching and a gradual decrease in the decay life time of the emission at ˜500 nm as the rGO content increases indicates the interfacial charge transfer process between ZnO and rGO by the defect states responsible for green emission.

  4. Coordinative modulation of human zinc transporter 2 gene expression through active and suppressive regulators.

    PubMed

    Lu, Yu-Ju; Liu, Ya-Chuan; Lin, Meng-Chieh; Chen, Yi-Ting; Lin, Lih-Yuan

    2015-04-01

    Zinc transporter 2 (ZnT2) is one of the cellular factors responsible for Zn homeostasis. Upon Zn overload, ZnT2 reduces cellular Zn by transporting it into excretory vesicles. We investigated the molecular mechanism that regulates human ZnT2 (hZnT2) gene expression. Zn induces hZnT2 expression in dose- and time-dependent manners. Overexpression of metal-responsive transcription factor 1 (MTF-1) increases hZnT2 transcription, whereas depletion of MTF-1 reduces hZnT2 expression. There are five putative metal response elements (MREs) within 1kb upstream of the hZnT2 gene. A serial deletion of the hZnT2 promoter region (from 5' to 3') shows that the two MREs proximal to the gene are essential for Zn-induced promoter activity. Further mutation analysis concludes that the penultimate MRE (MREb) supports the metal-induced promoter activity. The hZnT2 promoter has also a zinc finger E-box binding homeobox (ZEB) binding element. Mutation or deletion of this ZEB binding element elevates the basal and Zn-induced hZnT2 promoter activities. Knockdown of ZEB1 mRNA enhances the hZnT2 transcript level in HEK-293 cells. In MCF-7 (ZEB-deficient) cells, expression of ZEB proteins attenuates the Zn-induced hZnT2 expression. However, expressions of MTF-1 target genes such as human ZnT1 and metallothionein IIA were not affected. Our study shows the expression of the hZnT2 gene is coordinately regulated via active and suppressive modulators.

  5. Experimental phasing using zinc anomalous scattering

    SciTech Connect

    Cha, Sun-Shin; An, Young Jun; Jeong, Chang-Sook; Kim, Min-Kyu; Lee, Sung-Gyu; Lee, Kwang-Hoon; Oh, Byung-Ha

    2012-09-01

    The surface of proteins can be charged with zinc ions and the anomalous signals from these zinc ions can be used for structure determination of proteins. Zinc is a suitable metal for anomalous dispersion phasing methods in protein crystallography. Structure determination using zinc anomalous scattering has been almost exclusively limited to proteins with intrinsically bound zinc(s). Here, it is reported that multiple zinc ions can easily be charged onto the surface of proteins with no intrinsic zinc-binding site by using zinc-containing solutions. Zn derivatization of protein surfaces appears to be a largely unnoticed but promising method of protein structure determination.

  6. Autism phenotypes in ZnT3 null mice: Involvement of zinc dyshomeostasis, MMP-9 activation and BDNF upregulation.

    PubMed

    Yoo, Min Heui; Kim, Tae-Youn; Yoon, Young Hee; Koh, Jae-Young

    2016-06-29

    To investigate the role of synaptic zinc in the ASD pathogenesis, we examined zinc transporter 3 (ZnT3) null mice. At 4-5 weeks of age, male but not female ZnT3 null mice exhibited autistic-like behaviors. Cortical volume and neurite density were significantly greater in male ZnT3 null mice than in WT mice. In male ZnT3 null mice, consistent with enhanced neurotrophic stimuli, the level of BDNF as well as activity of MMP-9 was increased. Consistent with known roles for MMPs in BDNF upregulation, 2.5-week treatment with minocycline, an MMP inhibitor, significantly attenuated BDNF levels as well as megalencephaly and autistic-like behaviors. Although the ZnT3 null state removed synaptic zinc, it rather increased free zinc in the cytosol of brain cells, which appeared to increase MMP-9 activity and BDNF levels. The present results suggest that zinc dyshomeostasis during the critical period of brain development may be a possible contributing mechanism for ASD.

  7. Autism phenotypes in ZnT3 null mice: Involvement of zinc dyshomeostasis, MMP-9 activation and BDNF upregulation

    PubMed Central

    Yoo, Min Heui; Kim, Tae-Youn; Yoon, Young Hee; Koh, Jae-Young

    2016-01-01

    To investigate the role of synaptic zinc in the ASD pathogenesis, we examined zinc transporter 3 (ZnT3) null mice. At 4–5 weeks of age, male but not female ZnT3 null mice exhibited autistic-like behaviors. Cortical volume and neurite density were significantly greater in male ZnT3 null mice than in WT mice. In male ZnT3 null mice, consistent with enhanced neurotrophic stimuli, the level of BDNF as well as activity of MMP-9 was increased. Consistent with known roles for MMPs in BDNF upregulation, 2.5-week treatment with minocycline, an MMP inhibitor, significantly attenuated BDNF levels as well as megalencephaly and autistic-like behaviors. Although the ZnT3 null state removed synaptic zinc, it rather increased free zinc in the cytosol of brain cells, which appeared to increase MMP-9 activity and BDNF levels. The present results suggest that zinc dyshomeostasis during the critical period of brain development may be a possible contributing mechanism for ASD. PMID:27352957

  8. Copper and zinc induction of lipid peroxidation and effects on antioxidant enzyme activities in the microalga Pavlova viridis (Prymnesiophyceae).

    PubMed

    Li, Mei; Hu, Changwei; Zhu, Qin; Chen, Li; Kong, Zhiming; Liu, Zhili

    2006-01-01

    The metal-induced lipid peroxidation and response of antioxidative enzymes have been investigated in the marine microalga Pavlova viridis to understand the mechanisms of metal resistance in algal cells. We have analyzed superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) activities and glutathione (GSH) contents in microalgal cells grown at different concentrations of copper and zinc. In response to each metal, lipid peroxidation was enhanced with the increase of concentrations, as an indication of the oxidative damage caused by metal concentration assayed in the microalgae cells. Exposure of P. viridis to the two metals caused changes in enzyme activities in a different manner, depending on the metal assayed: after copper treatments, total SOD activity was enhanced, while it was reduced after zinc exposure. Copper and zinc stimulated the activities of CAT and GSH whereas GPX showed a remarkable increase in activity in response to copper treatments and decrease after zinc treatments. These results suggest that an activation of some antioxidant enzymes was enhanced to counteract the oxidative stress induced by the two metals.

  9. Effects of the seminal plasma zinc content and catalase activity on the semen quality of water buffalo (Bubalus bubalis) bulls.

    PubMed

    Alavi-Shoushtari, S M; Rezai, S Asri; Ansari, M H Kh; Khaki, A

    2009-01-15

    In order to determine zinc and catalase content of seminal plasma in the buffalo and to study their associations with the semen characteristics, 54 semen samples were collected from 10 buffalo bulls; semen volume and sperm concentration, gross and progressive motility and viability were evaluated, seminal plasma was then harvested by centrifugation and its zinc content was estimated by atomic absorption spectrophotometer and its catalase activity determined by using a commercial kit. The zinc content of the seminal plasma (Mean +/- SEM) was recorded as 154.40 +/- 1.74 mg L(-1), while, the mean catalase value was 32.00 +/- 0.42 U mL(-1). The mean zinc values was highly correlated with sperm progressive motility and viability and with catalase values (p = 0.000 for all) and also was associated with gross motility (p = 0.020) and negatively with abnormal morphology (p = 0.049). The catalase values were highly associated with sperm progressive motility, viability and zinc content (p = 0.000 for all) and was associated with sperm gross motility (p = 0.024). For further clarification of these correlations, the samples were categorized in three groups of excellent (Ex, >90% motile, n = 33), good (Go, 80-89% motile, n = 15) and moderate (Mo, <79% motile, n = 6) according to their percentage of sperm motility. The mean progressive motility in Ex group was 92.54 +/- 0.51%, in Go group was 81.66 +/- 0.62% and in Mo group was 71.66 +/- 1.05%. The mean zinc and catalase values were recorded as 161.07 +/- 1.63 mg L(-1) and 33.41 +/- 0.34 U mL(-1) in Ex, 146.70 +/- 1.91 mg L(-1) and 31.01 +/- 0.67 in Go and 136.42 +/- 4.97 mg L(-1) and 26.51 +/- 0.87 U mL(-1) in Mo groups. The mean zinc value in Ex group was highly associated with sperm motility, viability and catalase values, in Go group was associated with catalase values and highly associated with sperm abnormal morphology and in Mo group it was highly associations with catalase values only. The mean catalase value in Ex group

  10. Cadmium restores in vitro splicing activity inhibited by zinc-depletion.

    PubMed

    Lee, Myeong Jin; Ayaki, Hitoshi; Goji, Junko; Kitamura, Keiko; Nishio, Hisahide

    2006-10-01

    Zinc (Zn)-depletion inhibits the second step of RNA splicing, namely exon-ligation. To investigate the effects of cadmium (Cd) and other metal ions on RNA splicing inhibited by Zn-depletion, we measured in vitro splicing activities in the presence of these metals. Zn-depletion in the splicing reaction mixture was achieved by addition of a Zn-chelator, 1,10-phenanthroline. Cd(II) at 1, 5 and 10 microM restored the splicing activity to 2, 24 and 72% of that in the control reaction mixture, while higher concentrations of Cd(II) decreased the splicing activity, and more than 50 microM Cd(II) showed a complete absence of spliced products. Hg(II) also restored the splicing activity, albeit to a lesser extent, since 5 and 10 microM Hg(II) restored the splicing activity to 3 and 4% of the control value. The other metal ions examined in this study, Co(II), Cu(II), Mg(II) and Mn(II), did not show any restoration of the splicing activity. We concluded that Cd(II) could restore the in vitro splicing activity inhibited by Zn-depletion, although higher concentrations of Cd(II) prevented progress of the RNA splicing reaction. These results suggest that Cd(II) has a bifunctional property regarding RNA splicing, and is stimulatory at low concentrations and inhibitory at high concentrations.

  11. Genome Wide Association Mapping of Grain Arsenic, Copper, Molybdenum and Zinc in Rice (Oryza sativa L.) Grown at Four International Field Sites

    PubMed Central

    Norton, Gareth J.; Douglas, Alex; Lahner, Brett; Yakubova, Elena; Guerinot, Mary Lou; Pinson, Shannon R. M.; Tarpley, Lee; Eizenga, Georgia C.; McGrath, Steve P.; Zhao, Fang-Jie; Islam, M. Rafiqul; Islam, Shofiqul; Duan, Guilan; Zhu, Yongguan; Salt, David E.; Meharg, Andrew A.; Price, Adam H.

    2014-01-01

    The mineral concentrations in cereals are important for human health, especially for individuals who consume a cereal subsistence diet. A number of elements, such as zinc, are required within the diet, while some elements are toxic to humans, for example arsenic. In this study we carry out genome-wide association (GWA) mapping of grain concentrations of arsenic, copper, molybdenum and zinc in brown rice using an established rice diversity panel of ∼300 accessions and 36.9 k single nucleotide polymorphisms (SNPs). The study was performed across five environments: one field site in Bangladesh, one in China and two in the US, with one of the US sites repeated over two years. GWA mapping on the whole dataset and on separate subpopulations of rice revealed a large number of loci significantly associated with variation in grain arsenic, copper, molybdenum and zinc. Seventeen of these loci were detected in data obtained from grain cultivated in more than one field location, and six co-localise with previously identified quantitative trait loci. Additionally, a number of candidate genes for the uptake or transport of these elements were located near significantly associated SNPs (within 200 kb, the estimated global linkage disequilibrium previously employed in this rice panel). This analysis highlights a number of genomic regions and candidate genes for further analysis as well as the challenges faced when mapping environmentally-variable traits in a highly genetically structured diversity panel. PMID:24586963

  12. Genome wide association mapping of grain arsenic, copper, molybdenum and zinc in rice (Oryza sativa L.) grown at four international field sites.

    PubMed

    Norton, Gareth J; Douglas, Alex; Lahner, Brett; Yakubova, Elena; Guerinot, Mary Lou; Pinson, Shannon R M; Tarpley, Lee; Eizenga, Georgia C; McGrath, Steve P; Zhao, Fang-Jie; Islam, M Rafiqul; Islam, Shofiqul; Duan, Guilan; Zhu, Yongguan; Salt, David E; Meharg, Andrew A; Price, Adam H

    2014-01-01

    The mineral concentrations in cereals are important for human health, especially for individuals who consume a cereal subsistence diet. A number of elements, such as zinc, are required within the diet, while some elements are toxic to humans, for example arsenic. In this study we carry out genome-wide association (GWA) mapping of grain concentrations of arsenic, copper, molybdenum and zinc in brown rice using an established rice diversity panel of ∼ 300 accessions and 36.9 k single nucleotide polymorphisms (SNPs). The study was performed across five environments: one field site in Bangladesh, one in China and two in the US, with one of the US sites repeated over two years. GWA mapping on the whole dataset and on separate subpopulations of rice revealed a large number of loci significantly associated with variation in grain arsenic, copper, molybdenum and zinc. Seventeen of these loci were detected in data obtained from grain cultivated in more than one field location, and six co-localise with previously identified quantitative trait loci. Additionally, a number of candidate genes for the uptake or transport of these elements were located near significantly associated SNPs (within 200 kb, the estimated global linkage disequilibrium previously employed in this rice panel). This analysis highlights a number of genomic regions and candidate genes for further analysis as well as the challenges faced when mapping environmentally-variable traits in a highly genetically structured diversity panel.

  13. Removal of lead from aqueous solution by activated carbon prepared from Enteromorpha prolifera by zinc chloride activation.

    PubMed

    Li, Yanhui; Du, Qiuju; Wang, Xiaodong; Zhang, Pan; Wang, Dechang; Wang, Zonghua; Xia, Yanzhi

    2010-11-15

    Activated carbon was prepared from Enteromorpha prolifera (EP) by zinc chloride activation. The physico-chemical properties of EP-activated carbon (EPAC) were characterized by thermal stability, zeta potential and Boehm titration methods. The examination showed that EPAC has a porous structure with a high surface area of 1688 m(2)/g. Batch adsorption experiments were carried out to study the effect of various parameters such as initial pH, adsorbent dosage, contact time and temperature on Pb(II) ions adsorption properties by EPAC. The kinetic studies showed that the adsorption data followed a pseudo second-order kinetic model. The isotherm analysis indicated that the adsorption data can be represented by Freundlich isotherm model. Thermodynamic studies indicated that the adsorption reaction was a spontaneous and endothermic process.

  14. Study of the effects of oral zinc supplementation on peroxynitrite levels, arginase activity and NO synthase activity in seminal plasma of Iraqi asthenospermic patients

    PubMed Central

    2014-01-01

    Background Low concentrations of nitric oxide (NO) are necessary for the biology and physiology of spermatozoa, but high levels of NO are toxic and have negative effects on sperm functions. Although several studies have considered the relationship between infertility and semen NO concentrations, no study on the effects of asthenospermia treatments such as oral zinc supplementation on concentrations of NO, which are important in fertility, has been reported. Studies have shown that oral zinc supplementation develops sperm count, motility and the physical characteristics of sperm in animals and in some groups of infertile men. The present study was conducted to study the effect of zinc supplementation on the quantitative and qualitative characteristics of semen, along with enzymes of the NO pathway in the seminal plasma of asthenospermic patients. Methods Semen samples were obtained from 60 fertile and 60 asthenozoospermic infertile men of matched age. The subfertile group was treated with zinc sulfate; each participant took two capsules (220 mg per capsule) per day for 3 months. Semen samples were obtained (before and after zinc sulfate supplementation). After liquefaction of the seminal fluid at room temperature, routine semen analyses were performed. The stable metabolites of NO (nitrite) in seminal plasma were measured by nitrophenol assay. Arginase activity and NO synthase activity were measured spectrophotometrically. Results Peroxynitrite levels, arginase activity, NO synthase activity and various sperm parameters were compared among fertile controls and infertile patients (before and after treatment with zinc sulfate). Peroxynitrite levels and NO synthase activity were significantly higher in the infertile patients compared to the fertile group. Conversely, arginase activity was significantly higher in the fertile group than the infertile patients. Peroxynitrite levels, arginase activity and NO synthase activity of the infertile patient were restored to

  15. Evaluation of novel reactive MgO activated slag binder for the immobilisation of lead and zinc.

    PubMed

    Jin, Fei; Al-Tabbaa, Abir

    2014-12-01

    Although Portland cement is the most widely used binder in the stabilisation/solidification (S/S) processes, slag-based binders have gained significant attention recently due to their economic and environmental merits. In the present study, a novel binder, reactive MgO activated slag, is compared with hydrated lime activated slag in the immobilisation of lead and zinc. A series of lead or zinc-doped pastes and mortars were prepared with metal to binder ratio from 0.25% to 1%. The hydration products and microstructure were studied by X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The major hydration products were calcium silicate hydrate and hydrotalcite-like phases. The unconfined compressive strength was measured up to 160 d. Findings show that lead had a slight influence on the strength of MgO-slag paste while zinc reduced the strength significantly as its concentration increased. Leachate results using the TCLP tests revealed that the immobilisation degree was dependent on the pH and reactive MgO activated slag showed an increased pH buffering capacity, and thus improved the immobilisation efficiency compared to lime activated slag. It was proposed that zinc was mainly immobilised within the structure of the hydrotalcite-like phases or in the form of calcium zincate, while lead was primarily precipitated as the hydroxide. It is concluded, therefore, that reactive MgO activated slag can serve as clinker-free alternative binder in the S/S process.

  16. Structure of Saccharomyces cerevisiae Rtr1 reveals an active site for an atypical phosphatase.

    PubMed

    Irani, Seema; Yogesha, S D; Mayfield, Joshua; Zhang, Mengmeng; Zhang, Yong; Matthews, Wendy L; Nie, Grace; Prescott, Nicholas A; Zhang, Yan Jessie

    2016-03-01

    Changes in the phosphorylation status of the carboxyl-terminal domain (CTD) of RNA polymerase II (RNAPII) correlate with the process of eukaryotic transcription. The yeast protein regulator of transcription 1 (Rtr1) and the human homolog RNAPII-associated protein 2 (RPAP2) may function as CTD phosphatases; however, crystal structures of Kluyveromyces lactis Rtr1 lack a consensus active site. We identified a phosphoryl transfer domain in Saccharomyces cerevisiae Rtr1 by obtaining and characterizing a 2.6 Å resolution crystal structure. We identified a putative substrate-binding pocket in a deep groove between the zinc finger domain and a pair of helices that contained a trapped sulfate ion. Because sulfate mimics the chemistry of a phosphate group, this structural data suggested that this groove represents the phosphoryl transfer active site. Mutagenesis of the residues lining this groove disrupted catalytic activity of the enzyme assayed in vitro with a fluorescent chemical substrate, and expression of the mutated Rtr1 failed to rescue growth of yeast lacking Rtr1. Characterization of the phosphatase activity of RPAP2 and a mutant of the conserved putative catalytic site in the same chemical assay indicated a conserved reaction mechanism. Our data indicated that the structure of the phosphoryl transfer domain and reaction mechanism for the phosphoryl transfer activity of Rtr1 is distinct from those of other phosphatase families.

  17. Structure of Saccharomyces cerevisiae Rtr1 reveals an active site for an atypical phosphatase

    PubMed Central

    Mayfield, Joshua; Zhang, Mengmeng; Zhang, Yong; Matthews, Wendy L.; Nie, Grace; Prescott, Nicholas A.; Zhang, Yan Jessie

    2016-01-01

    Changes in the phosphorylation status of the carboxyl-terminal domain (CTD) of RNA polymerase II (RNAPII) correlate with the process of eukaryotic transcription. The yeast protein regulator of transcription 1 (Rtr1) and the human homolog RNAPII-associated protein 2 (RPAP2) may function as CTD phosphatases; however, crystal structures of Kluyveromyces lactis Rtr1 lack a consensus active site. We identified a phosphoryl transfer domain in Saccharomyces cerevisiae Rtr1 by obtaining and characterizing a 2.6 Å resolution crystal structure. We identified a putative substrate-binding pocket in a deep groove between the zinc finger domain and a pair of helices that contained a trapped sulfate ion. Because sulfate mimics the chemistry of a phosphate group, this structural data suggested that this groove represents the phosphoryl transfer active site. Mutagenesis of the residues lining this groove disrupted catalytic activity of the enzyme assayed in vitro with a fluorescent chemical substrate, and expression of the mutated Rtr1 failed to rescue growth of yeast lacking Rtr1. Characterization of the phosphatase activity of RPAP2 and a mutant of the conserved putative catalytic site in the same chemical assay indicated a conserved reaction mechanism. Our data indicated that the structure of the phosphoryl transfer domain and reaction mechanism for the phosphoryl transfer activity of Rtr1 is distinct from those of other phosphatase families. PMID:26933063

  18. Activation of caspase-3 in HL-60 cells treated with pyrithione and zinc.

    PubMed

    Kondoh, Masuo; Tasaki, Emi; Takiguchi, Masufumi; Higashimoto, Minoru; Watanabe, Yoshiteru; Sato, Masao

    2005-04-01

    The transition metal zinc (Zn) is an endogenous regulator of apoptosis. The ability of Zn to modulate apoptosis is believed to be mediated by the regulation of caspase activity. Previously, we reported that an acute influx of labile Zn induced apoptosis via activation of caspase in human leukemia HL-60 cells treated with a Zn ionophore (Py, pyrithione) and Zn at 1 and 25 microM, respectively. In the present study, we investigated the involvement of caspase-3 in Py (1 microM)/Zn (25 microM)-induced apoptosis in HL-60 cells. Pro-caspase-3 is an inactive form of caspase-3. The processing of pro-caspase-3, a sign of caspase-3 activation, occurred 6 h after treatment with Py/Zn. Proteolysis of poly (ADP-ribose) polymerase (PARP), a substrate of caspase-3, was also observed 6 h after treatment with Py/Zn. We also confirmed the elevation of caspase-3 activity as an index of the cleavage of amino acid sequences recognized by activated caspase-3. An inhibitor of caspase-3 attenuated the appearance of the DNA ladder. Taken together, these results indicate that the activation of caspase-3 is partly responsible for the induction of apoptosis in Py/Zn-treated HL-60 cells.

  19. In vitro Antioxidant Activities of Sodium Zinc and
Sodium Iron Chlorophyllins from Pine Needles

    PubMed Central

    Zhan, Ruzhen; Wu, Jian

    2014-01-01

    Summary Chlorophyll was extracted from pine needles, and then sodium zinc chlorophyllin (SZC) and sodium iron chlorophyllin (SIC) were synthesised by saponification, purification and substitution reaction, using sodium copper chlorophyllin (SCC) as a control. Their crystalline structures were verified by atomic absorbance spectroscopy, UV-VIS spectroscopy and HPLC. Moreover, their antioxidant activities were evaluated and compared with that of ascorbic acid through four biochemical assays: DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity, reducing power, inhibition of β-carotene bleaching and O2– scavenging activity. SZC had better antioxidant properties at a lower dosage than SIC and SCC in all assays. In the β-carotene bleaching assay, EC50 of SZC, SIC and SCC was 0.04, 0.38 and 0.90 mg/mL, respectively, much lower than that of ascorbic acid (4.0 mg/mL). SZC showed a better result (p<0.05) than ascorbic acid in the O2– scavenging activity assay. The results obtained from reducing power determination were also excellent: the absorbance values were all about 1.0 at 0.5 mg/mL, about half of that of ascorbic acid. In the investigation of DPPH radical scavenging activity, all chlorophyllins had lower activities than ascorbic acid. These results demonstrated the potential bioactivities of chlorophyll derivatives and supported their possible role in human health protection and disease prevention. PMID:27904324

  20. Characteristics of activated carbon prepared from pistachio-nut shell by zinc chloride activation under nitrogen and vacuum conditions.

    PubMed

    Lua, Aik Chong; Yang, Ting

    2005-10-15

    Activated carbons with well-developed pore structures were prepared from pistachio-nut shells by chemical activation using zinc chloride under both nitrogen atmosphere and vacuum conditions. The effects of preparation parameters on the carbon pore structure were studied in order to optimize these parameters. It was found that under vacuum conditions, the characteristics of the activated carbons produced are better than those under nitrogen atmosphere. The impregnation ratio, the activation temperature, and the activation hold time are the important parameters that influence the characteristics of the activated carbons. The optimum experimental conditions for preparing predominantly microporous activated carbons with high pore surface area and micropore volume are an impregnation ratio of 0.75, an activation temperature of 400 degrees C, and a hold time of 1 h. Under these conditions, the BET surface areas of the carbons activated under nitrogen atmosphere and vacuum conditions were 1635.37 and 1647.16 m2/g, respectively. However, at a ZnCl2 impregnation ratio of 1.5, a furnace temperature of 500 degrees C, and a hold time of 2 h, the predominantly mesoporous activated carbon prepared under vacuum condition had a BET surface area of 2527 m2/g. Fourier transform infrared spectra were used to detect changes in the surface functional groups of the samples during the different preparation stages.

  1. Synthesis and characterisation of flower shaped zinc oxide nanostructures and its antimicrobial activity.

    PubMed

    Mohan Kumar, Kesarla; Mandal, Badal Kumar; Appala Naidu, Etcherla; Sinha, Madhulika; Siva Kumar, Koppala; Sreedhara Reddy, Pamanji

    2013-03-01

    Flower shaped Zinc Oxide nanostructures was synthesized using a simple method without using any structure directing agents. Elemental analysis, crystalline nature, shape and size were examined using Powder X-ray Diffraction (XRD), scanning electron microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM) and Energy Dispersive X-ray Spectroscopy (EDAX). XRD revealed the formation of hexagonal ZnO nanostructures. SEM and TEM analyses revealed the formation of crystalline ZnO flowers in which a bunch of ZnO nanorods assembled together to form a leaf like structure followed by flower shaped ZnO nanostructures. Thus synthesised ZnO nanostructures showed good antimicrobial activity towards gram-positive bacteria Staphylococcus aureus as well as gram-negative bacteria Escherichia coli with a MIC/MBC of 25mg/L.

  2. Effect of arbuscular mycorrhizal (G. etunicatum) fungus on antioxidant enzymes activity under zinc toxicity in lettuce plants.

    PubMed

    Farshian, Shadi; Khara, Jalil; Parviz, Malekzadeh

    2007-06-01

    Zinc is one of the eight trace elements which are essential for the normal healthy growth and reproduction of crop plants. Plants possess cellular mechanisms that may be involved in the detoxification of heavy metals and thus confer plants a better tolerance against them. Arbuscular mycorrhizal fungi colonization is one of these mechanisms. Here, the effect of mycorrhizal fungus G. etunicatum on Zn toxicity tolerance through enhanced activity of some of antioxidant enzymes has been studied. Treatments were applied in triplicates of two factorial analyses: (a) mycorrhizal and non-mycorrhizal; (b) 5 levels of Zinc (0, 1.5, 3.5, 5.5, 7.5 mM). Zinc was added to modified Hoagland's nutrient solution (with half P concentration). Plants were grown in growth chamber for 10 weeks. Toxicity symptoms such as necrosis and chlorosis appeared on the leaves. Activity of detoxifying enzymes Guaiacol peroxidase (GUPX) and Ascorbate peroxidase (APX) were measured. GPX activity in roots and shoots of mycorrhizal and non-mycorrhizal plants was increased. Also, APX activity increased in roots and shoots ofmycorrhizal and non-mycorrhizal plants. Root length colonization (RLC) was measured by gridline intersect method. Mycorrhizal colonization decreased due to Zinc exposure. The results indicate the probable role of arbuscular mycorrhizal colonization in stress tolerance.

  3. Texaphyrins and water-soluble zinc(II) ionophores: development, mechanism of anticancer activity, and synergistic effects

    PubMed Central

    Preihs, Christian; Magda, Darren J.

    2014-01-01

    Texaphyrins, first prepared by Sessler and coworkers in the 1980s, represent early examples of expanded porphyrins. This class of pentaaza, oligopyrrolic macrocycles demonstrates excellent tumor localization and metal-chelating properties. In biological milieus, texaphyrins act as redox mediators and are able to produce reactive oxygen species. Furthermore, texaphyrins have been shown to upregulate zinc in vivo, an important feature that inspired us to develop new zinc ionophores that might allow the same function to be elicited but via a simpler chemical means. In this review, the basic properties of texaphyrins and the zinc ionophores they helped spawn will be discussed in the cadre of developing an understanding that could lead to the preparation of new, redox-active anticancer agents. PMID:25295224

  4. Functional Diversity and Microbial Activity of Forest Soils that Are Heavily Contaminated by Lead and Zinc.

    PubMed

    Pająk, Marek; Błońska, Ewa; Frąc, Magdalena; Oszust, Karolina

    The objective of this study was to assess the impact of metal contamination on microbial functional diversity and enzyme activity in forest soils. This study involved the evaluation of the influence of the texture, carbon content and distance to the source of contamination on the change in soil microbial activity, which did not investigate in previous studies. The study area is located in southern Poland near the city of Olkusz around the flotation sedimentation pond of lead and zinc at the Mining and Metallurgical Company "ZGH Bolesław, Inc.". The central point of the study area was selected as the middle part of the sedimentation pond. The experiment was conducted over a regular 500 × 500-m grid, where 33 sampling points were established. Contents of organic carbon and trace elements (Zn, Pb and Cd), pH and soil texture were investigated. The study included the determination of dehydrogenase and urease activities and microbial functional diversity evaluation based on the community-level physiological profiling approach by Biolog EcoPlate. The greatest reduction in the dehydrogenase and urease activities was observed in light sandy soils with Zn content >220 mg · kg(-1) and a Pb content > 100 mg · kg(-1). Soils with a higher concentration of fine fraction, despite having the greatest concentrations of metals, were characterized by high rates of Biolog®-derived parameters and a lower reduction of enzyme activity.

  5. Preparation and Biological Activity of New Collagen Composites, Part I: Collagen/Zinc Titanate Nanocomposites.

    PubMed

    Albu, Madalina G; Vladkova, Todorka G; Ivanova, Iliana A; Shalaby, Ahmed S A; Moskova-Doumanova, Veselina S; Staneva, Anna D; Dimitriev, Yanko B; Kostadinova, Anelya S; Topouzova-Hristova, Tanya I

    2016-09-01

    The aim of this investigation was to develop new antimicrobial collagen/zinc titanate (ZnTiO3) biomaterials using a sol-gel cryogenic draying technology in keeping the native collagen activity. Broad-spectrum antimicrobial activity was demonstrated against Firmicutes (Staphylococcus epidermidis, Bacillus cereus, and Candida lusitaniae) and Gracilicutes (Escherichia coli, Salmonella enterica, and Pseudomonas putida) microorganisms. The antimicrobial activity as well as the cytotoxicity were specific for the different test microorganisms (Gram-positive and Gram-negative bacteria and fungi) and model eukaryotic cells (osteosarcoma, fibroblast, and keratinocyte cells), respectively, and both were depending on the ZnTiO3 concentration. Three mechanisms of the antimicrobial action were supposed, including (i) mechanical demolition of the cell wall and membrane by the crystal nanoparticles of the ZnTiO3 entrapped in the collagen matrix, (ii) chelation of its metal ions, and (iii) formation of free oxygen radicals due to the interaction between the microbial cells and antimicrobial agent. It was concluded that the optimal balance between antimicrobial activity and cytotoxicity could be achieved by a variation of the ZnTiO3 concentration. The antifungal and broad-spectrum antibacterial activity of the studied collagen/ZnTiO3 nanocomposites, combined with a low cytotoxicity, makes them a promising anti-infection biomaterial.

  6. Zinc and iron concentration and SOD activity in human semen and seminal plasma.

    PubMed

    Marzec-Wróblewska, Urszula; Kamiński, Piotr; Lakota, Paweł; Szymański, Marek; Wasilow, Karolina; Ludwikowski, Grzegorz; Kuligowska-Prusińska, Magdalena; Odrowąż-Sypniewska, Grażyna; Stuczyński, Tomasz; Michałkiewicz, Jacek

    2011-10-01

    The aim of the present study was to measure zinc (Zn) and iron (Fe) concentration in human semen and superoxide dismutase (SOD) activity in seminal plasma and correlate the results with sperm quality. Semen samples were obtained from men (N = 168) undergoing routine infertility evaluation. The study design included two groups based on the ejaculate parameters. Group I (n = 39) consisted of males with normal ejaculate (normozoospermia), and group II (n = 129) consisted of males with pathological spermiogram. Seminal Zn and Fe were measured in 162 samples (group I, n = 38; group II, n = 124) and SOD activity in 149 samples (group I, n = 37; group II, n = 112). Correlations were found between SOD activity and Fe and Zn concentration, and between Fe and Zn concentration. SOD activity was negatively associated with volume of semen and positively associated with rapid progressive motility, nonprogressive motility, and concentration. Negative correlation was stated between Fe concentration and normal morphology. Mean SOD activity in seminal plasma of semen from men of group I was higher than in seminal plasma of semen from men of group II. Fe concentration was higher in teratozoospermic males than in males with normal morphology of spermatozoa in group II. Our results suggest that Fe may influence spermatozoa morphology.

  7. The active site of ribulose-bisphosphate carboxylase/oxygenase

    SciTech Connect

    Hartman, F.C.

    1991-01-01

    The active site of ribulose-bisphosphate carboxylase/oxygenase requires interacting domains of adjacent, identical subunits. Most active-site residues are located within the loop regions of an eight-stranded {beta}/{alpha}-barrel which constitutes the larger C-terminal domain; additional key residues are located within a segment of the smaller N-terminal domain which partially covers the mouth of the barrel. Site-directed mutagenesis of the gene encoding the enzyme from Rhodospirillum rubrum has been used to delineate functions of active-site residues. 6 refs., 2 figs.

  8. DOE site performance assessment activities. Radioactive Waste Technical Support Program

    SciTech Connect

    Not Available

    1990-07-01

    Information on performance assessment capabilities and activities was collected from eight DOE sites. All eight sites either currently dispose of low-level radioactive waste (LLW) or plan to dispose of LLW in the near future. A survey questionnaire was developed and sent to key individuals involved in DOE Order 5820.2A performance assessment activities at each site. The sites surveyed included: Hanford Site (Hanford), Idaho National Engineering Laboratory (INEL), Los Alamos National Laboratory (LANL), Nevada Test Site (NTS), Oak Ridge National Laboratory (ORNL), Paducah Gaseous Diffusion Plant (Paducah), Portsmouth Gaseous Diffusion Plant (Portsmouth), and Savannah River Site (SRS). The questionnaire addressed all aspects of the performance assessment process; from waste source term to dose conversion factors. This report presents the information developed from the site questionnaire and provides a comparison of site-specific performance assessment approaches, data needs, and ongoing and planned activities. All sites are engaged in completing the radioactive waste disposal facility performance assessment required by DOE Order 5820.2A. Each site has achieved various degrees of progress and have identified a set of critical needs. Within several areas, however, the sites identified common needs and questions.

  9. WRNIP1 accumulates at laser light irradiated sites rapidly via its ubiquitin-binding zinc finger domain and independently from its ATPase domain

    SciTech Connect

    Nomura, Hironoshin; Yoshimura, Akari; Edo, Takato; Kanno, Shin-ichiro; Tada, Syusuke; Seki, Masayuki; Yasui, Akira; Enomoto, Takemi

    2012-01-27

    Highlights: Black-Right-Pointing-Pointer WRNIP1 accumulates in laser light irradiated sites very rapidly via UBZ domain. Black-Right-Pointing-Pointer The ATPase domain of WRNIP1 is dispensable for its accumulation. Black-Right-Pointing-Pointer The accumulation of WRNIP1 seems not to be dependent on the interaction with WRN. -- Abstract: WRNIP1 (Werner helicase-interacting protein 1) was originally identified as a protein that interacts with the Werner syndrome responsible gene product. WRNIP1 contains a ubiquitin-binding zinc-finger (UBZ) domain in the N-terminal region and two leucine zipper motifs in the C-terminal region. In addition, it possesses an ATPase domain in the middle of the molecule and the lysine residues serving as ubiquitin acceptors in the entire of the molecule. Here, we report that WRNIP1 accumulates in laser light irradiated sites very rapidly via its ubiquitin-binding zinc finger domain, which is known to bind polyubiquitin and to be involved in ubiquitination of WRNIP1 itself. The accumulation of WRNIP1 in laser light irradiated sites also required the C-terminal region containing two leucine zippers, which is reportedly involved in the oligomerization of WRNIP1. Mutated WRNIP1 with a deleted ATPase domain or with mutations in lysine residues, which serve as ubiquitin acceptors, accumulated in laser light irradiated sites, suggesting that the ATPase domain of WRNIP1 and ubiquitination of WRNIP1 are dispensable for the accumulation.

  10. Savannah River Site prioritization of transition activities

    SciTech Connect

    Finley, R.H.

    1993-11-01

    Effective management of SRS conversion from primarily a production facility to other missions (or Decontamination and Decommissioning (D&D)) requires a systematic and consistent method of prioritizing the transition activities. This report discusses the design of a prioritizing method developed to achieve systematic and consistent methods of prioritizing these activities.

  11. Catalysis by a de novo zinc-mediated protein interface: implications for natural enzyme evolution and rational enzyme engineering.

    PubMed

    Der, Bryan S; Edwards, David R; Kuhlman, Brian

    2012-05-08

    Here we show that a recent computationally designed zinc-mediated protein interface is serendipitously capable of catalyzing carboxyester and phosphoester hydrolysis. Although the original motivation was to design a de novo zinc-mediated protein-protein interaction (called MID1-zinc), we observed in the homodimer crystal structure a small cleft and open zinc coordination site. We investigated if the cleft and zinc site at the designed interface were sufficient for formation of a primitive active site that can perform hydrolysis. MID1-zinc hydrolyzes 4-nitrophenyl acetate with a rate acceleration of 10(5) and a k(cat)/K(M) of 630 M(-1) s(-1) and 4-nitrophenyl phosphate with a rate acceleration of 10(4) and a k(cat)/K(M) of 14 M(-1) s(-1). These rate accelerations by an unoptimized active site highlight the catalytic power of zinc and suggest that the clefts formed by protein-protein interactions are well-suited for creating enzyme active sites. This discovery has implications for protein evolution and engineering: from an evolutionary perspective, three-coordinated zinc at a homodimer interface cleft represents a simple evolutionary path to nascent enzymatic activity; from a protein engineering perspective, future efforts in de novo design of enzyme active sites may benefit from exploring clefts at protein interfaces for active site placement.

  12. Safety Oversight of Decommissioning Activities at DOE Nuclear Sites

    SciTech Connect

    Zull, Lawrence M.; Yeniscavich, William

    2008-01-15

    The Defense Nuclear Facilities Safety Board (Board) is an independent federal agency established by Congress in 1988 to provide nuclear safety oversight of activities at U.S. Department of Energy (DOE) defense nuclear facilities. The activities under the Board's jurisdiction include the design, construction, startup, operation, and decommissioning of defense nuclear facilities at DOE sites. This paper reviews the Board's safety oversight of decommissioning activities at DOE sites, identifies the safety problems observed, and discusses Board initiatives to improve the safety of decommissioning activities at DOE sites. The decommissioning of former defense nuclear facilities has reduced the risk of radioactive material contamination and exposure to the public and site workers. In general, efforts to perform decommissioning work at DOE defense nuclear sites have been successful, and contractors performing decommissioning work have a good safety record. Decommissioning activities have recently been completed at sites identified for closure, including the Rocky Flats Environmental Technology Site, the Fernald Closure Project, and the Miamisburg Closure Project (the Mound site). The Rocky Flats and Fernald sites, which produced plutonium parts and uranium materials for defense needs (respectively), have been turned into wildlife refuges. The Mound site, which performed R and D activities on nuclear materials, has been converted into an industrial and technology park called the Mound Advanced Technology Center. The DOE Office of Legacy Management is responsible for the long term stewardship of these former EM sites. The Board has reviewed many decommissioning activities, and noted that there are valuable lessons learned that can benefit both DOE and the contractor. As part of its ongoing safety oversight responsibilities, the Board and its staff will continue to review the safety of DOE and contractor decommissioning activities at DOE defense nuclear sites.

  13. Lead concentration in the blood of the general population living near a lead-zinc mine site, Nigeria: Exposure pathways.

    PubMed

    Bello, Olanrewaju; Naidu, Ravi; Rahman, Mohammad Mahmudur; Liu, Yanju; Dong, Zhaomin

    2016-01-15

    Lead (Pb) poisoning in children is a major public health catastrophe worldwide. This report summarises both exposure pathways and blood Pb levels in children below 7 years of age and adults (above 18 years) from the Adudu community living near a lead-zinc mine in Nasawara, Nigeria. The average and median blood Pb levels in children and adults were 2.1 and 1.3 μg/dL, 3.1 and 1.8 μg/dL, respectively. However, Pb in 14% of adults' blood exceeded 5 μg/dL, which is the recommended threshold blood Pb concentration in adults as established by the Centers for Disease Control and Prevention (CDC). Furthermore 68% of adults' blood exceeded blood Pb action level of 2 μg/dL. For children, 11.4% and 31% of the blood samples exceeded 5 μg/dL and 2 μg/dL, respectively, while no safe blood Pb level in children has been recommended. In Nasawara, a significant difference (p<0.05) was observed between the various age groups in children with 2-4 years old having the highest levels and 6 year old children having the lowest Pb levels. Although this study did not detect elevated levels of Pb in children's blood in regions such as Zamfara, Nigeria and Kabwe, Zambia, a high percentage of samples exceeded 2 μg/dL. Soils, floor dusts, water and crops also reveal that Pb contamination in the study area could potentially be the major cause of blood Pb in the community exposed to mining. This study also observed a significant correlation between water Pb levels of adults and blood Pb levels, suggesting that water is the major exposure pathway. This analysis highlights the need to properly manage mining activities so that the health of communities living in the vicinity of a Pb-Zn mine is not compromised.

  14. Controlled Orientation of Active Sites in a Nanostructured Multienzyme Complex

    PubMed Central

    Lim, Sung In; Yang, Byungseop; Jung, Younghan; Cha, Jaehyun; Cho, Jinhwan; Choi, Eun-Sil; Kim, Yong Hwan; Kwon, Inchan

    2016-01-01

    Multistep cascade reactions in nature maximize reaction efficiency by co-assembling related enzymes. Such organization facilitates the processing of intermediates by downstream enzymes. Previously, the studies on multienzyme nanocomplexes assembled on DNA scaffolds demonstrated that closer interenzyme distance enhances the overall reaction efficiency. However, it remains unknown how the active site orientation controlled at nanoscale can have an effect on multienzyme reaction. Here, we show that controlled alignment of active sites promotes the multienzyme reaction efficiency. By genetic incorporation of a non-natural amino acid and two compatible bioorthogonal chemistries, we conjugated mannitol dehydrogenase to formate dehydrogenase with the defined active site arrangement with the residue-level accuracy. The study revealed that the multienzyme complex with the active sites directed towards each other exhibits four-fold higher relative efficiency enhancement in the cascade reaction and produces 60% more D-mannitol than the other complex with active sites directed away from each other. PMID:28004799

  15. Zinc Enzymes.

    ERIC Educational Resources Information Center

    Bertini, I.; And Others

    1985-01-01

    Discusses the role of zinc in various enzymes concerned with hydration, hydrolysis, and redox reactions. The binding of zinc to protein residues, properties of noncatalytic zinc(II) and catalytic zinc, and the reactions catalyzed by zinc are among the topics considered. (JN)

  16. Hedgehog Pathway Antagonist 5E1 Binds Hedgehog at the Pseudo-active Site

    PubMed Central

    Maun, Henry R.; Wen, Xiaohui; Lingel, Andreas; de Sauvage, Frederic J.; Lazarus, Robert A.; Scales, Suzie J.; Hymowitz, Sarah G.

    2010-01-01

    Proper hedgehog (Hh) signaling is crucial for embryogenesis and tissue regeneration. Dysregulation of this pathway is associated with several types of cancer. The monoclonal antibody 5E1 is a Hh pathway inhibitor that has been extensively used to elucidate vertebrate Hh biology due to its ability to block binding of the three mammalian Hh homologs to the receptor, Patched1 (Ptc1). Here, we engineered a murine:human chimeric 5E1 (ch5E1) with similar Hh-binding properties to the original murine antibody. Using biochemical, biophysical, and x-ray crystallographic studies, we show that, like the regulatory receptors Cdon and Hedgehog-interacting protein (Hhip), ch5E1 binding to Sonic hedgehog (Shh) is enhanced by calcium ions. In the presence of calcium and zinc ions, the ch5E1 binding affinity increases 10–20-fold to tighter than 1 nm primarily because of a decrease in the dissociation rate. The co-crystal structure of Shh bound to the Fab fragment of ch5E1 reveals that 5E1 binds at the pseudo-active site groove of Shh with an epitope that largely overlaps with the binding site of its natural receptor antagonist Hhip. Unlike Hhip, the side chains of 5E1 do not directly coordinate the Zn2+ cation in the pseudo-active site, despite the modest zinc-dependent increase in 5E1 affinity for Shh. Furthermore, to our knowledge, the ch5E1 Fab-Shh complex represents the first structure of an inhibitor antibody bound to a metalloprotease fold. PMID:20504762

  17. Zinc affects differently growth, photosynthesis, antioxidant enzyme activities and phytochelatin synthase expression of four marine diatoms.

    PubMed

    Nguyen-Deroche, Thi Le Nhung; Caruso, Aurore; Le, Thi Trung; Bui, Trang Viet; Schoefs, Benoît; Tremblin, Gérard; Morant-Manceau, Annick

    2012-01-01

    Zinc-supplementation (20 μM) effects on growth, photosynthesis, antioxidant enzyme activities (superoxide dismutase, ascorbate peroxidase, catalase), and the expression of phytochelatin synthase gene were investigated in four marine diatoms (Amphora acutiuscula, Nitzschia palea, Amphora coffeaeformis and Entomoneis paludosa). Zn-supplementation reduced the maximum cell density. A linear relationship was found between the evolution of gross photosynthesis and total chlorophyll content. The Zn treatment decreased the electron transport rate except in A. coffeaeformis and in E. paludosa at high irradiance. A linear relationship was found between the efficiency of light to evolve oxygen and the size of the light-harvesting antenna. The external carbonic anhydrase activity was stimulated in Zn-supplemented E. paludosa but was not correlated with an increase of photosynthesis. The total activity of the antioxidant enzymes did not display any clear increase except in ascorbate peroxidase activity in N. palea. The phytochelatin synthase gene was identified in the four diatoms, but its expression was only revealed in N. palea, without a clear difference between control and Zn-supplemented cells. Among the four species, A. paludosa was the most sensitive and A. coffeaeformis, the most tolerant. A. acutiuscula seemed to be under metal starvation, whereas, to survive, only N. palea developed several stress responses.

  18. A unique geometry of the active site of angiotensin-converting enzyme consistent with structure-activity studies

    NASA Astrophysics Data System (ADS)

    Mayer, Dorica; Naylor, Christopher B.; Motoc, Ioan; Marshall, Garland R.

    1987-04-01

    Previous structure-activity studies of captopril and related active angiotensin-converting enzyme (ACE) inhibitors have led to the conclusion that the basic structural requirements for inhibition of ACE involve (a) a terminal carboxyl group; (b) an amido carbonyl group; and (c) different types of effective zinc (Zn) ligand functional groups. Such structural requirements common to a set of compounds acting at the same receptor have been used to define a pharmacophoric pattern of atoms or groups of atoms mutually oriented in space that is necessary for ACE inhibition from a stereochemical point of view. A unique pharmacophore model (within the resolution of approximately 0.15 Å) was observed using a method for systematic search of the conformational hyperspace available to the 28 structurally different molecules under study. The method does not assume a common molecular framework, and, therefore, allows comparison of different compounds that is independent of their absolute orientation. Consequently, by placing the carboxyl binding group, the binding site for amido carbonyl, and the Zn atom site in positions determined by ideal binding geometry with the inhibitors' functional groups, it was possible to clearly specify a geometry for the active site of ACE.

  19. Zinc as Allosteric Ion Channel Modulator: Ionotropic Receptors as Metalloproteins.

    PubMed

    Peralta, Francisco Andrés; Huidobro-Toro, Juan Pablo

    2016-07-02

    Zinc is an essential metal to life. This transition metal is a structural component of many proteins and is actively involved in the catalytic activity of cell enzymes. In either case, these zinc-containing proteins are metalloproteins. However, the amino acid residues that serve as ligands for metal coordination are not necessarily the same in structural proteins compared to enzymes. While crystals of structural proteins that bind zinc reveal a higher preference for cysteine sulfhydryls rather than histidine imidazole rings, catalytic enzymes reveal the opposite, i.e., a greater preference for the histidines over cysteines for catalysis, plus the influence of carboxylic acids. Based on this paradigm, we reviewed the putative ligands of zinc in ionotropic receptors, where zinc has been described as an allosteric modulator of channel receptors. Although these receptors do not strictly qualify as metalloproteins since they do not normally bind zinc in structural domains, they do transitorily bind zinc at allosteric sites, modifying transiently the receptor channel's ion permeability. The present contribution summarizes current information showing that zinc allosteric modulation of receptor channels occurs by the preferential metal coordination to imidazole rings as well as to the sulfhydryl groups of cysteine in addition to the carboxyl group of acid residues, as with enzymes and catalysis. It is remarkable that most channels, either voltage-sensitive or transmitter-gated receptor channels, are susceptible to zinc modulation either as positive or negative regulators.

  20. Zinc as Allosteric Ion Channel Modulator: Ionotropic Receptors as Metalloproteins

    PubMed Central

    Peralta, Francisco Andrés; Huidobro-Toro, Juan Pablo

    2016-01-01

    Zinc is an essential metal to life. This transition metal is a structural component of many proteins and is actively involved in the catalytic activity of cell enzymes. In either case, these zinc-containing proteins are metalloproteins. However, the amino acid residues that serve as ligands for metal coordination are not necessarily the same in structural proteins compared to enzymes. While crystals of structural proteins that bind zinc reveal a higher preference for cysteine sulfhydryls rather than histidine imidazole rings, catalytic enzymes reveal the opposite, i.e., a greater preference for the histidines over cysteines for catalysis, plus the influence of carboxylic acids. Based on this paradigm, we reviewed the putative ligands of zinc in ionotropic receptors, where zinc has been described as an allosteric modulator of channel receptors. Although these receptors do not strictly qualify as metalloproteins since they do not normally bind zinc in structural domains, they do transitorily bind zinc at allosteric sites, modifying transiently the receptor channel’s ion permeability. The present contribution summarizes current information showing that zinc allosteric modulation of receptor channels occurs by the preferential metal coordination to imidazole rings as well as to the sulfhydryl groups of cysteine in addition to the carboxyl group of acid residues, as with enzymes and catalysis. It is remarkable that most channels, either voltage-sensitive or transmitter-gated receptor channels, are susceptible to zinc modulation either as positive or negative regulators. PMID:27384555

  1. Zinc and prostatic cancer

    PubMed Central

    Song, Yang; Ho, Emily

    2014-01-01

    Purpose of review Aim to understand the connection between zinc and prostatic cancer, and to summarize the recent findings about the functions of zinc in the maintenance of prostate health. Recent findings Contradictory findings have been reported by epidemiologic studies examining the association between zinc intake and the risk of prostate cancer. However, a growing body of experimental evidence support that high zinc levels are essential for prostate health. The possible mechanisms include the effects of zinc on the inhibition of terminal oxidation, induction of mitochondrial apoptogenesis, and suppression of NFκB activity. The most recent finding is the effects of zinc in the maintenance of DNA integrity in normal prostate epithelial cells (PrEC) by modulating the expression and activity of DNA repair and damage response proteins, especially p53. Zinc depletion in PrEC increased p53 expression but compromised p53 DNA binding activity resulting an impaired DNA repair function. Moreover, recent findings support the role of zinc transporters as tumor suppressors in the prostate. Summary Future studies need to discover sensitive and specific zinc biomarkers and perform more in vivo studies on the effects of zinc on prostate functions in normal animals or prostate cancer models. PMID:19684515

  2. Application of native-state electrospray mass spectrometry to identify zinc-binding sites on engineered hemoglobin.

    PubMed

    Lippincott, J; Fattor, T J; Lemon, D D; Apostol, I

    2000-09-10

    We report the utility of native-state mass spectrometry to detect zinc ion binding to the engineered hemoglobin rHb52. Various preparations of this recombinant hemoglobin had significantly different oxygen affinities. Detailed characterization of denatured globins did not show any difference between analyzed hemoglobin molecules. However, when solutions of intact hemoglobin pseudotetramers were analyzed by native-state electrospray mass spectrometry, a significant shift in the mass spectrum was observed, indicating labile modification of hemoglobin. Using collision-induced dissociation (CID), we found a mass gain of 63 Da located on the beta-globin. EDTA treatment of modified hemoglobin prior to the infusion removed the modification and restored the predicted oxygen affinity. Ion-trap fragmentation of the +8 charged ion of modified beta-globin showed a neutral loss of 96+/-1 Da, consistent with neutral loss of zinc sulfide. These findings indicated zinc binding to the beta-globin through a cysteine residue. Involvement of Cys93 was confirmed by kinetics of cysteine residue reactivity with dithiodipyridine and peptide mapping. Presence of zinc was confirmed by ICP-MS metal analysis.

  3. Perspective: On the active site model in computational catalyst screening

    NASA Astrophysics Data System (ADS)

    Reuter, Karsten; Plaisance, Craig P.; Oberhofer, Harald; Andersen, Mie

    2017-01-01

    First-principles screening approaches exploiting energy trends in surface adsorption represent an unparalleled success story in recent computational catalysis research. Here we argue that our still limited understanding of the structure of active sites is one of the major bottlenecks towards an ever extended and reliable use of such computational screening for catalyst discovery. For low-index transition metal surfaces, the prevalently chosen high-symmetry (terrace and step) sites offered by the nominal bulk-truncated crystal lattice might be justified. For more complex surfaces and composite catalyst materials, computational screening studies will need to actively embrace a considerable uncertainty with respect to what truly are the active sites. By systematically exploring the space of possible active site motifs, such studies might eventually contribute towards a targeted design of optimized sites in future catalysts.

  4. Diffusional correlations among multiple active sites in a single enzyme.

    PubMed

    Echeverria, Carlos; Kapral, Raymond

    2014-04-07

    Simulations of the enzymatic dynamics of a model enzyme containing multiple substrate binding sites indicate the existence of diffusional correlations in the chemical reactivity of the active sites. A coarse-grain, particle-based, mesoscopic description of the system, comprising the enzyme, the substrate, the product and solvent, is constructed to study these effects. The reactive and non-reactive dynamics is followed using a hybrid scheme that combines molecular dynamics for the enzyme, substrate and product molecules with multiparticle collision dynamics for the solvent. It is found that the reactivity of an individual active site in the multiple-active-site enzyme is reduced substantially, and this effect is analyzed and attributed to diffusive competition for the substrate among the different active sites in the enzyme.

  5. A zinc-dependent DNA-binding activity co-operates with cAMP-responsive-element-binding protein to activate the human thyroglobulin enhancer.

    PubMed Central

    Berg, V; Vassart, G; Christophe, D

    1997-01-01

    Footprinting experiments involving the human thyroglobulin gene enhancer and thyroid nuclear extracts revealed a protected region called X2, containing an incomplete cAMP-responsive element (CRE). Band-shift experiments identified two binding activities recognizing the X2 element: a CRE-binding protein (CREB)/activating transcription factor (ATF) relative that binds the half CRE motif and a second factor that interacts with a G-rich motif located just upstream from the CRE. The first factor appears to be CREB itself, as indicated by the supershifting when using an antibody directed against CREB, and the second DNA-binding activity involved was shown to be zinc-dependent and exhibited an apparent molecular mass of 42-44 kDa in South-Western blotting experiments. This factor may represent a novel entity, which we named CAF, for 'CREB Associated Factor'. Three copies of X2 sequence conferred a strong cAMP-dependent transcriptional activation to a heterologous promoter in transient transfection assay in cAMP-stimulated primary thyrocytes and HeLa cells. Transfection experiments of constructs containing the X2 element mutated in either the CRE or the G-rich site showed that both motifs were required for this transcription activating function. Moreover, the combination of several individual X2 elements mutated in either the CRE or the G-rich motif did not exhibit full transcriptional activity. This suggests that, in the context of the X2 element, CREB requires a close interaction with CAF to achieve both basal and cAMP-dependent transcriptional activation. PMID:9163323

  6. Antifungal activity of zinc oxide nanoparticles against Botrytis cinerea and Penicillium expansum.

    PubMed

    He, Lili; Liu, Yang; Mustapha, Azlin; Lin, Mengshi

    2011-03-20

    Antifungal activities of zinc oxide nanoparticles (ZnO NPs) and their mode of action against two postharvest pathogenic fungi (Botrytis cinerea and Penicillium expansum) were investigated in this study. ZnO NPs with sizes of 70 ± 15 nm and concentrations of 0, 3, 6 and 12 mmol l(-1) were used. Traditional microbiological plating, scanning electron microscopy (SEM), and Raman spectroscopy were used to study antifungal activities of ZnO NPs and to characterize the changes in morphology and cellular compositions of fungal hyphae treated with ZnO NPs. Results show that ZnO NPs at concentrations greater than 3 mmol l(-1) can significantly inhibit the growth of B. cinerea and P. expansum. P. expansum was more sensitive to the treatment with ZnO NPs than B. cinerea. SEM images and Raman spectra indicate two different antifungal activities of ZnO NPs against B. cinerea and P. expansum. ZnO NPs inhibited the growth of B. cinerea by affecting cellular functions, which caused deformation in fungal hyphae. In comparison, ZnO NPs prevented the development of conidiophores and conidia of P. expansum, which eventually led to the death of fungal hyphae. These results suggest that ZnO NPs could be used as an effective fungicide in agricultural and food safety applications.

  7. Shape-control of Zinc Oxide nanoparticles: enhancing photocatalytic activity under UV irradiation

    NASA Astrophysics Data System (ADS)

    Montero-Muñoz, M.; Ramos-Ibarra, J. E.; Rodríguez-Páez, J. E.; Ramirez, A.; Huamaní-Coaquira, J. A.

    2017-01-01

    Zinc oxide (ZnO) nanostructures with different sizes and morphologies were synthesized using the Controlled Precipitation Method. It follows a standard process, but with different synthesis and washing solvents to modify the features related to the photocatalytic activity. The solid phase evolution during aging step was followed using Infrared Spectroscopy (FTIR) and the solids obtained, after the washing process, were characterized using X-ray diffraction (XRD). The Rietveld refinement indicates a Wurtzite phase (space group P63mc) as majority phase with lattice parameters a = 3.2530 Å and c = 5.2125 Å. Scanning electron microscopy (SEM) image shows a sponge-like morphology for the sample synthesized with ethylene glycol as solvent, acidified with nitric acid and washed with water. The sample synthesized and washed with water shows a needle-like morphology; and the sample synthesized in acetic acid and washed with water shows particles with undefined morphology. The optical properties of the as-prepared ZnO samples were investigated by UV-vis absorption spectroscopy. Finally, the photocatalytic activity of ZnO powders was studied from the initial rate of decomposition of H2O2 in aqueous solution. The best results were obtained with samples synthesized and washed with water; the influence of all the solvents on the morphology of ZnO samples and the effect of the morphologies on the photocatalytic activity are discussed.

  8. Chemically derived defects in zinc oxide nanocrystals and their enhanced photo-electrocatalytic activities.

    PubMed

    Prakash, Anand; Bahadur, D

    2014-10-21

    This paper reports the influence of surface defects on the photocatalytic degradation of methylene blue (MB) for zinc oxide (ZnO) nanocrystals (NCs) synthesized in different organic solvents. A simple chemical approach has been adopted for the promotion of oxygen vacancies in pristine ZnO using solvents namely dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and dimethylsulfoxide (DMSO). This alters the growth of NCs through the promotion of oxygen vacancies depending on the fact that the solvent with minimum viscosity supports faster nucleation and growth exhibiting maximum surface defects. DMF with minimum viscosity results in largest particle size and superior photocatalytic activity. Further, X-ray diffraction, UV-visible reflectance spectroscopy and transmission electron microscopy confirm that the DMF supports the faster growth of NCs as compared to NMP and DMSO. Electron paramagnetic resonance, Raman, X-ray photoelectron, and photoluminescence spectroscopies confirm different states of oxygen vacancies in the NCs and their dependence on the nature of solvents. The photocatalytic activities of these NCs were investigated against the degradation of MB as a model dye. The results show that the oxygen defects at the surface of NCs are more responsible for higher photocatalytic activity than the specific surface area of NCs. The electrochemical investigations of MB degradation suggest that these defects upon interaction with MB influence the storage capacity and charge-discharge profiles of NCs. During degradation, MB passivates these defects, which has been explained in terms of increased charge-discharge time and storage capacity.

  9. Zinc poisoning

    MedlinePlus

    ... other materials to make industrial items such as paint, dyes, and more. These combination substances can be ... Compounds used to make paint, rubber, dyes, wood preservatives, and ... Zinc chloride Zinc oxide (relatively nonharmful) Zinc ...

  10. Zinc modulation of calcium activity at the photoreceptor terminal: a calcium imaging study.

    PubMed

    Anastassov, Ivan; Shen, Wen; Ripps, Harris; Chappell, Richard L

    2013-07-01

    There is abundant experimental evidence that zinc ions (Zn(2+)) are present in the synaptic vesicles of vertebrate photoreceptors, and that they are co-released with glutamate. Here we show that increasing the concentration of extracellular zinc (2 μM-2 mM) suppresses the entry of calcium into the synaptic terminals of isolated salamander double cones. The resultant dose-dependent curve was fit by an inverse Hill equation having an IC50 of 38 μM, and Hill coefficient of 1.1. Because there is currently no reliable way to measure the concentration of extracellular zinc, it is not known whether the zinc released under normal circumstances is of physiological significance. In an attempt to circumvent this problem we used zinc chelators to reduce the available pool of endogenous zinc. This enabled us to determine how the absence of zinc affected calcium entry. We found that when intra- or extra-cellular zinc was chelated by 250 μM of membrane-permeable TPEN or 500 μM of membrane-impermeable histidine, there was a significant rise in the depolarization-induced intracellular calcium level within photoreceptor terminals. This increase in internal [Ca(2+)] will undoubtedly lead to a concomitant increase in glutamate release. In addition, we found that blocking the L-type calcium channels that are expressed on the synaptic terminals of photoreceptors with 50 μM nicardipine or 100 μM verapamil abolished the effects of zinc chelation. These findings are a good indication that, when released in vivo, the zinc concentration is sufficient to suppress voltage-gated calcium channels, and reduce the rate of glutamate release from photoreceptor terminals.

  11. Antimicrobial activity of zinc and titanium dioxide nanoparticles against biofilm-producing methicillin-resistant Staphylococcus aureus

    NASA Astrophysics Data System (ADS)

    Jesline, A.; John, Neetu P.; Narayanan, P. M.; Vani, C.; Murugan, Sevanan

    2015-02-01

    Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major nosocomial pathogens responsible for a wide spectrum of infections and the emergence of bacterial resistance to antibiotics has lead to treatment drawbacks towards large number of drugs. Formation of biofilms is the main contributing factor to antibiotic resistance. The development of reliable processes for the synthesis of zinc oxide nanoparticles is an important aspect of nanotechnology today. Zinc oxide and titanium dioxide nanoparticles comprise well-known inhibitory and bactericidal effects. Emergence of antimicrobial resistance by pathogenic bacteria is a major health problem in recent years. This study was designed to determine the efficacy of zinc and titanium dioxide nanoparticles against biofilm producing methicillin-resistant S. aureus. Biofilm production was detected by tissue culture plate method. Out of 30 MRSA isolates, 22 isolates showed strong biofilm production and 2 showed weak and moderate biofilm formation. Two strong and weak biofilm-producing methicillin-resistant S. aureus isolates were subjected to antimicrobial activity using commercially available zinc and titanium dioxide nanoparticles. Thus, the nanoparticles showed considerably good activity against the isolates, and it can be concluded that they may act as promising, antibacterial agents in the coming years.

  12. Robotics at Savannah River site: activity report

    SciTech Connect

    Byrd, J.S.

    1984-09-01

    The objectives of the Robotics Technology Group at the Savannah River Laboratory are to employ modern industrial robots and to develop unique automation and robotic systems to enhance process operations at the Savannah River site (SRP and SRL). The incentives are to improve safety, reduce personnel radiation exposure, improve product quality and productivity, and to reduce operating costs. During the past year robotic systems have been installed to fill chemical dilution vials in a SRP laboratory at 772-F and remove radioactive waste materials in the SRL Californium Production Facility at 773-A. A robotic system to lubricate an extrusion press has been developed and demonstrated in the SRL robotics laboratory and is scheduled for installation at the 321-M fuel fabrication area. A mobile robot was employed by SRP for a radiation monitoring task at a waste tank top in H-Area. Several other robots are installed in the SRL robotics laboratories and application development programs are underway. The status of these applications is presented in this report.

  13. Bio-Fabrication of zinc oxide nanoparticles using leaf extract of Parthenium hysterophorus L. and its size-dependent antifungal activity against plant fungal pathogens

    NASA Astrophysics Data System (ADS)

    Rajiv, P.; Rajeshwari, Sivaraj; Venckatesh, Rajendran

    2013-08-01

    The study reports the synthesis and characterization of zinc oxide nanoparticles from weed plant by a novel method. The aim of this work is to synthesize zinc oxide nanoparticles from Parthenium hysterophorus L. by inexpensive, ecofriendly and simple method. Highly stable, spherical and hexagonal zinc oxide nanoparticles were synthesized by using different concentrations of 50% and 25% parthenium leaf extracts. Both the concentrations of the leaf extract act as reducing and capping agent for conversion of nanoparticles. Formation of zinc oxide nanoparticles have been confirmed by UV-Vis absorption spectroscopy, X-ray diffraction (XRD), Fourier trans-form infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis with energy dispersive X-ray analysis (EDX). SEM, TEM and EDX analysis reveals that spherical and hexagonal zinc oxide nanoparticle sizes were 27 ± 5 nm and 84 ± 2 nm respectively and chemical composition of zinc oxide were present. We synthesized different sized zinc oxide nanoparticles and explored the size-dependent antifungal activity against plant fungal pathogens. Highest zone of inhibition was observed in 25 μg/ml of 27 ± 5 nm size zinc oxide nanoparticles against Aspergillus flavus and Aspergillus niger. Parthenium mediated zinc oxide nanoparticles were synthesized and proved to be good antifungal agents and environment friendly.

  14. Zinc rescues obesity-induced cardiac hypertrophy via stimulating metallothionein to suppress oxidative stress-activated BCL10/CARD9/p38 MAPK pathway.

    PubMed

    Wang, Shudong; Gu, Junlian; Xu, Zheng; Zhang, Zhiguo; Bai, Tao; Xu, Jianxiang; Cai, Jun; Barnes, Gregory; Liu, Qiu-Ju; Freedman, Jonathan H; Wang, Yonggang; Liu, Quan; Zheng, Yang; Cai, Lu

    2017-02-03

    Obesity often leads to obesity-related cardiac hypertrophy (ORCH), which is suppressed by zinc-induced inactivation of p38 mitogen-activated protein kinase (p38 MAPK). In this study, we investigated the mechanisms by which zinc inactivates p38 MAPK to prevent ORCH. Mice (4-week old) were fed either high fat diet (HFD, 60% kcal fat) or normal diet (ND, 10% kcal fat) containing variable amounts of zinc (deficiency, normal and supplement) for 3 and 6 months. P38 MAPK siRNA and the p38 MAPK inhibitor SB203580 were used to suppress p38 MAPK activity in vitro and in vivo, respectively. HFD activated p38 MAPK and increased expression of B-cell lymphoma/CLL 10 (BCL10) and caspase recruitment domain family member 9 (CARD9). These responses were enhanced by zinc deficiency and attenuated by zinc supplement. Administration of SB203580 to HFD mice or specific siRNA in palmitate-treated cardiomyocytes eliminated the HFD and zinc deficiency activation of p38 MAPK, but did not significantly impact the expression of BCL10 and CARD9. In cultured cardiomyocytes, inhibition of BCL10 expression by siRNA prevented palmitate-induced increased p38 MAPK activation and atrial natriuretic peptide (ANP) expression. In contrast, inhibition of p38 MAPK prevented ANP expression, but did not affect BCL10 expression. Deletion of metallothionein abolished the protective effect of zinc on palmitate-induced up-regulation of BCL10 and phospho-p38 MAPK. HFD and zinc deficiency synergistically induce ORCH by increasing oxidative stress-mediated activation of BCL10/CARD9/p38 MAPK signalling. Zinc supplement ameliorates ORCH through activation of metallothionein to repress oxidative stress-activated BCL10 expression and p38 MAPK activation.

  15. Overexpression of the zinc finger protein MZF1 inhibits hematopoietic development from embryonic stem cells: correlation with negative regulation of CD34 and c-myb promoter activity.

    PubMed Central

    Perrotti, D; Melotti, P; Skorski, T; Casella, I; Peschle, C; Calabretta, B

    1995-01-01

    Zinc finger genes encode proteins that act as transcription factors. The myeloid zinc finger 1 (MZF1) gene encodes a zinc finger protein with two DNA-binding domains that recognize two distinct consensus sequences, is preferentially expressed in hematopoietic cells, and may be involved in the transcriptional regulation of hematopoiesis-specific genes. Reverse transcription-PCR analysis of human peripheral blood CD34+ cells cultured under lineage-restricted conditions demonstrated MZF1 expression during both myeloid and erythroid differentiation. Sequence analysis of the 5'-flanking region of the CD34 and c-myb genes, which are a marker of and a transcriptional factor required for hematopoietic proliferation and differentiation, respectively, revealed closely spaced MZF1 consensus binding sites found by electrophoretic mobility shift assays to interact with recombinant MZF1 protein. Transient or constitutive MZF1 expression in different cell types resulted in specific inhibition of chloramphenicol acetyltransferase activity driven by the CD34 or c-myb 5'-flanking region. To determine whether transcriptional modulation by MZF1 activity plays a role in hematopoietic differentiation, constructs containing the MZF1 cDNA under the control of different promoters were transfected into murine embryonic stem cells which, under defined in vitro culture conditions, generate colonies of multiple hematopoietic lineages. Constitutive MZF1 expression interfered with the ability of embryonic stem cells to undergo hematopoietic commitment and erythromyeloid colony formation and prevented the induced expression of CD34 and c-myb mRNAs during differentiation of these cells. These data indicate that MZF1 plays a critical role in hematopoiesis by modulating the expression of genes involved in this process. PMID:7565760

  16. Active sites of thioredoxin reductases: why selenoproteins?

    PubMed

    Gromer, Stephan; Johansson, Linda; Bauer, Holger; Arscott, L David; Rauch, Susanne; Ballou, David P; Williams, Charles H; Schirmer, R Heiner; Arnér, Elias S J

    2003-10-28

    Selenium, an essential trace element for mammals, is incorporated into a selected class of selenoproteins as selenocysteine. All known isoenzymes of mammalian thioredoxin (Trx) reductases (TrxRs) employ selenium in the C-terminal redox center -Gly-Cys-Sec-Gly-COOH for reduction of Trx and other substrates, whereas the corresponding sequence in Drosophila melanogaster TrxR is -Ser-Cys-Cys-Ser-COOH. Surprisingly, the catalytic competence of these orthologous enzymes is similar, whereas direct Sec-to-Cys substitution of mammalian TrxR, or other selenoenzymes, yields almost inactive enzyme. TrxRs are therefore ideal for studying the biology of selenocysteine by comparative enzymology. Here we show that the serine residues flanking the C-terminal Cys residues of Drosophila TrxRs are responsible for activating the cysteines to match the catalytic efficiency of a selenocysteine-cysteine pair as in mammalian TrxR, obviating the need for selenium. This finding suggests that the occurrence of selenoenzymes, which implies that the organism is selenium-dependent, is not necessarily associated with improved enzyme efficiency. Our data suggest that the selective advantage of selenoenzymes is a broader range of substrates and a broader range of microenvironmental conditions in which enzyme activity is possible.

  17. Very high specific activity ⁶⁶/⁶⁸Ga from zinc targets for PET.

    PubMed

    Engle, J W; Lopez-Rodriguez, V; Gaspar-Carcamo, R E; Valdovinos, H F; Valle-Gonzalez, M; Trejo-Ballado, F; Severin, G W; Barnhart, T E; Nickles, R J; Avila-Rodriguez, M A

    2012-08-01

    This work describes the production of very high specific activity (66/68)Ga from (nat)Zn(p,n) and (66)Zn(p,n) using proton irradiations between 7 and 16 MeV, with emphasis on (66)Ga for use with common bifunctional chelates. Principal radiometallic impurities are (65)Zn from (p,x) and (67)Ga from (p,n). Separation of radiogallium from target material is accomplished with cation exchange chromatography in hydrochloric acid solution. Efficient recycling of Zn target material is possible using electrodeposition of Zn from its chloride form, but these measures are not necessary to achieve high specific activity or near-quantitative radiolabeling yields from natural targets. Inductively coupled plasma mass spectroscopy (ICP-MS) measures less than 2 ppb non-radioactive gallium in the final product, and the reactivity of (66)Ga with common bifunctional chelates, decay corrected to the end of irradiation, is 740 GBq/μmol (20 Ci/μmol) using natural zinc as a target material. Recycling enriched (66)Zn targets increased the reactivity of (66)Ga with common bifunctional chelates.

  18. Zinc oxide nanoparticles cause inhibition of microbial denitrification by affecting transcriptional regulation and enzyme activity.

    PubMed

    Zheng, Xiong; Su, Yinglong; Chen, Yinguang; Wan, Rui; Liu, Kun; Li, Mu; Yin, Daqiang

    2014-12-02

    Over the past few decades, human activities have accelerated the rates and extents of water eutrophication and global warming through increasing delivery of biologically available nitrogen such as nitrate and large emissions of anthropogenic greenhouse gases. In particular, nitrous oxide (N2O) is one of the most important greenhouse gases, because it has a 300-fold higher global warming potential than carbon dioxide. Microbial denitrification is a major pathway responsible for nitrate removal, and also a dominant source of N2O emissions from terrestrial or aquatic environments. However, whether the release of zinc oxide nanoparticles (ZnO NPs) into the environment affects microbial denitrification is largely unknown. Here we show that the presence of ZnO NPs lead to great increases in nitrate delivery (9.8-fold higher) and N2O emissions (350- and 174-fold higher in the gas and liquid phases, respectively). Our data further reveal that ZnO NPs significantly change the transcriptional regulations of glycolysis and polyhydroxybutyrate synthesis, which causes the decrease in reducing powers available for the reduction of nitrate and N2O. Moreover, ZnO NPs substantially inhibit the gene expressions and catalytic activities of key denitrifying enzymes. These negative effects of ZnO NPs on microbial denitrification finally cause lower nitrate removal and higher N2O emissions, which is likely to exacerbate water eutrophication and global warming.

  19. POZ domain transcription factor, FBI-1, represses transcription of ADH5/FDH by interacting with the zinc finger and interfering with DNA binding activity of Sp1.

    PubMed

    Lee, Dong-Kee; Suh, Dongchul; Edenberg, Howard J; Hur, Man-Wook

    2002-07-26

    The POZ domain is a protein-protein interaction motif that is found in many transcription factors, which are important for development, oncogenesis, apoptosis, and transcription repression. We cloned the POZ domain transcription factor, FBI-1, that recognizes the cis-element (bp -38 to -22) located just upstream of the core Sp1 binding sites (bp -22 to +22) of the ADH5/FDH minimal promoter (bp -38 to +61) in vitro and in vivo, as revealed by electrophoretic mobility shift assay and chromatin immunoprecipitation assay. The ADH5/FDH minimal promoter is potently repressed by the FBI-1. Glutathione S-transferase fusion protein pull-down showed that the POZ domains of FBI-1, Plzf, and Bcl-6 directly interact with the zinc finger DNA binding domain of Sp1. DNase I footprinting assays showed that the interaction prevents binding of Sp1 to the GC boxes of the ADH5/FDH promoter. Gal4-POZ domain fusions targeted proximal to the GC boxes repress transcription of the Gal4 upstream activator sequence-Sp1-adenovirus major late promoter. Our data suggest that POZ domain represses transcription by interacting with Sp1 zinc fingers and by interfering with the DNA binding activity of Sp1.

  20. Assessing the antimicrobial activity of zinc oxide thin films using disk diffusion and biofilm reactor

    NASA Astrophysics Data System (ADS)

    Gittard, Shaun D.; Perfect, John R.; Monteiro-Riviere, Nancy A.; Wei, Wei; Jin, Chunming; Narayan, Roger J.

    2009-03-01

    The electronic and chemical properties of semiconductor materials may be useful in preventing growth of microorganisms. In this article, in vitro methods for assessing microbial growth on semiconductor materials will be presented. The structural and biological properties of silicon wafers coated with zinc oxide thin films were evaluated using atomic force microscopy, X-ray photoelectron spectroscopy, and MTT viability assay. The antimicrobial properties of zinc oxide thin films were established using disk diffusion and CDC Biofilm Reactor studies. Our results suggest that zinc oxide and other semiconductor materials may play a leading role in providing antimicrobial functionality to the next-generation medical devices.

  1. Antiurolithiatic Activity of Extract and Oleanolic Acid Isolated from the Roots of Lantana camara on Zinc Disc Implantation Induced Urolithiasis.

    PubMed

    Vyas, Narendra; Argal, Ameeta

    2013-01-01

    The present study was done to evaluate the antiurolithiatic activity of ethanolic extract of roots (ELC 200 mg/kg) and oleanolic acid (OA 60 mg/kg, O.A. 80 mg/kg, O.A. 100 mg/kg) isolated from roots of Lantana camara in albino wistar male rats using zinc disc implantation induced urolithiatic model. The group in which only zinc disc was implanted without any treatment showed increase in calcium output (23  ± 2.7 mg/dL). Cystone receiving animals showed significant protection from such change (P < 0.01). Treatment with OA and ELC significantly reduced the calcium output at a dose of OA 60 mg/kg (P < 0.01), OA 80 mg/kg (P < 0.01), ELC 200 mg/kg (P < 0.01), and OA 100 mg/kg (P < 0.001), as compared with zinc disc implanted group. The average weight of zinc discs along with the deposited crystals in the only disc implanted group was found to be 111 ± 8.6 mg. Group that received Cystone 500 mg/kg showed significant reduction in the depositions (P < 0.001). Similarly, the rats which received OA and ELC showed reduced formation of depositions around the zinc disc (P < 0.001). The X-ray images of rats also showed significant effect of OA and ELC on urolitiasis. Thus, OA and ELC showed promising antiurolithiatic activity in dose dependant manner.

  2. Removal of Zinc Form Carbonic Anhydrase: A Kinetics Experiment for Upper-Level Chemistry Laboratories

    ERIC Educational Resources Information Center

    Williams, Kathryn R.; Adhyaru, Bhavin

    2004-01-01

    An experiment on kinetics of deactivation of carbonic anhydrase by removal of zinc is demonstrated. Carbonic anhydrase, the enzyme that catalyzes the interconversion of carbon dioxide and bicarbonate, requires on Zn(II) ion in its active site, and removal of the zinc cofactor by complexion to another ligand leaves the apoenzyme, which is totally…

  3. Crystallographic snapshots of active site metal shift in E. coli fructose 1,6-bisphosphate aldolase

    PubMed Central

    Tran, Huyen-Thi; Lee, Seon-Hwa; Ho, Thien-Hoang; Hong, Seung-Hye; Huynh, Kim-Hung; Ahn, Yeh-Jin; Oh, Deok-Kun; Kang, Lin-Woo

    2016-01-01

    Fructose 1,6-bisphosphate aldolase (FBA) is important for both glycolysis and gluconeogenesis in life. Class II (zinc dependent) FBA is an attractive target for the development of antibiotics against protozoa, bacteria, and fungi, and is also widely used to produce various high-value stereoisomers in the chemical and pharmaceutical industry. In this study, the crystal structures of class II Escherichia coli FBA (EcFBA) were determined from four different crystals, with resolutions between 1.8 Å and 2.0 Å. Native EcFBA structures showed two separate sites of Zn1 (interior position) and Zn2 (active site surface position) for Zn2+ ion. Citrate and TRIS bound EcFBA structures showed Zn2+ position exclusively at Zn2. Crystallographic snapshots of EcFBA structures with and without ligand binding proposed the rationale of metal shift at the active site, which might be a hidden mechanism to keep the trace metal cofactor Zn2+ within EcFBA without losing it. PMID:27733232

  4. Community Update on Site Activities, July 19, 2013

    EPA Pesticide Factsheets

    In an effort to engage and inform community members interested in the New Bedford Harbor Superfund Site cleanup, EPA will be issuing periodic topic-based fact sheets that will provide background information and updates about ongoing activities.

  5. Zinc(II) complexes with heterocyclic ether, acid and amide. Crystal structure, spectral, thermal and antibacterial activity studies

    NASA Astrophysics Data System (ADS)

    Jabłońska-Wawrzycka, Agnieszka; Rogala, Patrycja; Czerwonka, Grzegorz; Hodorowicz, Maciej; Stadnicka, Katarzyna

    2016-02-01

    The reaction of zinc salts with heterocyclic ether (1-ethoxymethyl-2-methylimidazole (1-ExMe-2-MeIm)), acid (pyridine-2,3-dicarboxylic acid (2,3-pydcH2)) and amide (3,5-dimethylpyrazole-1-carboxamide (3,5-DMePzCONH2)) yielded three new zinc complexes formulated as [Zn(1-ExMe-2-MeIm)2Cl2] 1, fac-[Zn(H2O)6][Zn(2,3-pydcH)3]22 and [Zn(3,5-DMePz)2(NCO)2] 3. Complexes of 1 and 3 are four-coordinated with a tetrahedron as coordination polyhedron. However, compound 2 forms an octahedral cation-anion complex. The complex 3 was prepared by eliminating of the carboxamide group from the ligand and then the 3,5-dimethylpyrazole (3,5-DMePz) and isocyanates formed were employed as new ligands. The IR and X-ray studies have confirmed a bidentate fashion of coordination of the 2,3-pydcH and monodentate fashion of coordination of the 1-ExMe-2-MeIm and 3,5-DMePz to the Zn(II) ions. The crystal packing of Zn(II) complexes are stabilized by intermolecular classical hydrogen bonds of O-H⋯O and N-H⋯O types. The most interesting feature of the supramolecular architecture of complexes is the existence of C-H⋯O, C-H⋯Cl and C-H⋯π interactions and π⋯π stacking, which also contributes to structural stabilisation. The correlation between crystal structure and thermal stability of zinc complexes is observed. In all compounds the fragments of ligands donor-atom containing go in the last steps. Additionally, antimicrobial activities of compounds were carried out against certain Gram-positive and Gram-negative bacteria and counts of CFU (colony forming units) were also determined. The achieved results confirmed a significant antibacterial activity of some tested zinc complexes. On the basis of the Δ log CFU values the antibacterial activity of zinc complexes follows the order: 3 > 2 > 1. Influence a number of N-donor atoms in zinc environment on antibacterial activity is also observed.

  6. Utilization of zinc chloride for surface modification of activated carbon derived from Jatropha curcas L. for absorbent material.

    PubMed

    Pratumpong, P; Toommee, S

    2016-12-01

    The objective of this research is to produce the low-cost activated carbon from Jatropha curcas L. by chemical activation using zinc chloride ZnCl2. The effects of the impregnation ratio on the surface and chemical properties of activated carbon were investigated. The impregnation ratio was selected at the range of 1:1-10:1 for investigation. The optimum conditions resulted in an activated carbon with a carbon content of 80% wt, while the specific surface area evaluated using nitrogen adsorption isotherm corresponds to 600 m(2)/g.

  7. Synthesis and Enhanced Photocatalytic Activity of Ce-Doped Zinc Oxide Nanorods by Hydrothermal Method

    NASA Astrophysics Data System (ADS)

    Aisah, N.; Gustiono, D.; Fauzia, V.; Sugihartono, I.; Nuryadi, R.

    2017-02-01

    Zinc oxide (ZnO) is a n-type semiconductor material which has a wide direct band gap energy of ∼ 3.3 eV, and other interesting optical properties, hence it’s potentially applied to various fields such as electronics, optoelectronics, sensors, photonic devices, and also photocatalyst. Dopant in ZnO nanostructures is an effective way to improve ZnO’s structural properties in various applications. In this study, undoped and Ce doped ZnO nanorods were synthesized on ITO coated glass substrates by ultrasonic spray pyrolysis for seeding deposition and hydrothermal methods at a temperature of 95 0C for 2 hours for growth. X-ray diffraction, field emission scanning electron microscopy (FESEM), UV-VIS and Photoluminescence spectroscopy were used to characterize the crystal structure, surface morphology and optical properties of ZnO nanorods and the photocatalytic activity test for methylene blue degradation. The experimental results showed that 3% Cerium dopant has produced hexagonal morphology ZnO nanorod growing more uniform on (002) crystal planes, increased the intensity of ultraviolet absorbance thereby increase the degradation speed of methylene blue.

  8. The impact of zinc oxide nanoparticles on the bacterial microbiome of activated sludge systems

    NASA Astrophysics Data System (ADS)

    Meli, K.; Kamika, I.; Keshri, J.; Momba, M. N. B.

    2016-12-01

    The expected growth in nanomaterial applications could result in increased amounts of nanoparticles entering municipal sewer systems, eventually ending up in wastewater treatment plants and therefore negatively affecting microbial populations and biological nutrient removal. The aim of this study was to ascertain the impact of zinc oxide nanoparticles (nZnO) on the bacterial microbiome of an activated sludge system. A metagenomic approach combined with the latest generation Illumina MiSeq platform and RDP pipeline tools were used to identify and classify the bacterial microbiome of the sludge. Results revealed a drastic decrease in the number of operational taxonomic units (OTUs) from 27 737 recovered in the nZnO-free sample to 23 743, 17 733, and 13 324 OTUs in wastewater samples exposed to various concentrations of nZnO (5, 10 and 100 mg/L nZnO, respectively). These represented 12 phyla, 21 classes, 30 orders, 54 families and 51 genera, completely identified at each taxonomic level in the control samples; 7-15-25-28-20 for wastewater samples exposed to 5 mg/L nZnO; 9-15-24-31-23 for those exposed to 10 mg/L and 7-11-19-26-17 for those exposed 100 mg/L nZnO. A large number of sequences could not be assigned to specific taxa, suggesting a possibility of novel species to be discovered.

  9. Active sensing and damage detection using piezoelectric zinc oxide-based nanocomposites.

    PubMed

    Meyers, Frederick N; Loh, Kenneth J; Dodds, John S; Baltazar, Arturo

    2013-05-10

    This study investigated the design and performance of piezoelectric nanocomposite-based interdigitated transducers (IDTs) for active sensing and damage detection. First, thin films that are highly piezoelectric and mechanically flexible were designed by embedding zinc oxide (ZnO) nanoparticles in a poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) piezo-polymer matrix. Second, the suspended nanoparticle solutions were then spin coated onto patterned comb electrodes to fabricate the IDTs. The films were then poled to align their electric domains and to increase their permanent piezoelectricity. Upon IDT fabrication, its sensing and actuation of Lamb waves on an aluminum pipe was validated. These results were also compared to data obtained from commercial Macro Fiber Composite IDT transducers. In the last phase of this work, damage detection was demonstrated by mounting these nanocomposite sensors and actuators (using a pitch-catch setup) onto an aluminum pipe and plate. Damage was simulated by tightening a band clamp around the pipe and by drilling holes in the plate. A damage index calculation was used to compare results corresponding to different levels of damage applied to the plate (i.e., different drilled hole depths), and good correlation was observed. Thus, ZnO/PVDF-TrFE transducers were shown to have the potential for use as piezoelectric transducers for structural health monitoring and damage detection.

  10. Active sensing and damage detection using piezoelectric zinc oxide-based nanocomposites

    NASA Astrophysics Data System (ADS)

    Meyers, Frederick N.; Loh, Kenneth J.; Dodds, John S.; Baltazar, Arturo

    2013-05-01

    This study investigated the design and performance of piezoelectric nanocomposite-based interdigitated transducers (IDTs) for active sensing and damage detection. First, thin films that are highly piezoelectric and mechanically flexible were designed by embedding zinc oxide (ZnO) nanoparticles in a poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) piezo-polymer matrix. Second, the suspended nanoparticle solutions were then spin coated onto patterned comb electrodes to fabricate the IDTs. The films were then poled to align their electric domains and to increase their permanent piezoelectricity. Upon IDT fabrication, its sensing and actuation of Lamb waves on an aluminum pipe was validated. These results were also compared to data obtained from commercial Macro Fiber Composite IDT transducers. In the last phase of this work, damage detection was demonstrated by mounting these nanocomposite sensors and actuators (using a pitch-catch setup) onto an aluminum pipe and plate. Damage was simulated by tightening a band clamp around the pipe and by drilling holes in the plate. A damage index calculation was used to compare results corresponding to different levels of damage applied to the plate (i.e., different drilled hole depths), and good correlation was observed. Thus, ZnO/PVDF-TrFE transducers were shown to have the potential for use as piezoelectric transducers for structural health monitoring and damage detection.

  11. Evaluation of photodynamic activity, photostability and in vitro drug release of zinc phthalocyanine-loaded nanocapsules.

    PubMed

    de Souza, Thiane Deprá; Ziembowicz, Francieli Isa; Müller, Debora Friedrich; Lauermann, Sâmera Cristina; Kloster, Carmen Luisa; Santos, Roberto Christ Vianna; Lopes, Leonardo Quintana Soares; Ourique, Aline Ferreira; Machado, Giovanna; Villetti, Marcos Antonio

    2016-02-15

    Nanocapsule formulations containing zinc phthalocyanine (ZnPc) were investigated as drug delivery systems for use in photodynamic therapy (PDT). ZnPc loaded chitosan, PCL, and PCL coated with chitosan nanocapsules were prepared and characterized by means of their physicochemical properties, photodynamic activity, photostability and drug release profile. All formulations presented nanometric hydrodynamic radius, around 100 nm, low polydispersity index (0.08-0.24), slightly negative zeta potential for PCL nanoparticles and positive zeta potential for suspension containing chitosan. Encapsulation efficiencies were higher than 99%. The capacity of ZnPc loaded nanocapsules to produce cytotoxic singlet oxygen ((1)O2) by irradiation with red laser was monitored using 1.3-diphenylisobenzofuran as a probe. The singlet oxygen quantum yields (ΦΔ) for ZnPc loaded chitosan nanocapsules were high and similar to that of the standard (ZnPc in DMSO), displaying excellent ability to generate (1)O2. The photosensitizer loaded nanocapsules are photostable in the timescale usually utilized in PDT and only a small photobleaching event was observed when a light dose of 610J/cm(2) was applied. The in vitro drug release studies of ZnPc from all nanocapsules demonstrated a sustained release profile controlled by diffusion, without burst effect. The nature of the polymer and the core type of the nanocapsules regulated ZnPc release. Thus, the nanocapsules developed in this work are a promising strategy to be employed in PDT.

  12. Antineoplastic activity of ouabain and pyrithione zinc in acute myeloid leukemia.

    PubMed

    Tailler, M; Senovilla, L; Lainey, E; Thépot, S; Métivier, D; Sébert, M; Baud, V; Billot, K; Fenaux, P; Galluzzi, L; Boehrer, S; Kroemer, G; Kepp, O

    2012-07-26

    Despite recent progress in the treatment of acute myeloid leukemia (AML), the prognosis of this rather heterogeneous disease remains poor and novel chemotherapeutics that specifically target leukemic cells must be developed. To address this need at the preclinical level, we implemented a high content imaging-based screen for the identification of small agents that induce AML cell death in vitro. Among a panel of 1040 Food and Drug Administration-approved agents, we identified pyrithione zinc (PZ) and ouabain (OUA) as potential antileukemic compounds. Both PZ and OUA efficiently induced cell death associated with apoptotic chromatin condensation and inhibition of nuclear factor-κB survival signaling, leading to reduced expression of antiapoptotic proteins, in several AML cell lines. PZ- and OUA-induced cell death was associated with the permeabilization of the outer mitochondrial membrane and led to the release of cytochrome c followed by caspase activation. Both PZ and OUA exerted significant anticancer effects in vivo, on human AML cells xenografts as well as ex vivo, on CD34(+) (but not CD34(-)) malignant myeloblasts from AML patients. Altogether, our results suggest that PZ and OUA may exhibit antileukemic effects by inducing the apoptotic demise of AML cells.

  13. The impact of zinc oxide nanoparticles on the bacterial microbiome of activated sludge systems

    PubMed Central

    Meli, K.; Kamika, I.; Keshri, J.; Momba, M. N. B.

    2016-01-01

    The expected growth in nanomaterial applications could result in increased amounts of nanoparticles entering municipal sewer systems, eventually ending up in wastewater treatment plants and therefore negatively affecting microbial populations and biological nutrient removal. The aim of this study was to ascertain the impact of zinc oxide nanoparticles (nZnO) on the bacterial microbiome of an activated sludge system. A metagenomic approach combined with the latest generation Illumina MiSeq platform and RDP pipeline tools were used to identify and classify the bacterial microbiome of the sludge. Results revealed a drastic decrease in the number of operational taxonomic units (OTUs) from 27 737 recovered in the nZnO-free sample to 23 743, 17 733, and 13 324 OTUs in wastewater samples exposed to various concentrations of nZnO (5, 10 and 100 mg/L nZnO, respectively). These represented 12 phyla, 21 classes, 30 orders, 54 families and 51 genera, completely identified at each taxonomic level in the control samples; 7-15-25-28-20 for wastewater samples exposed to 5 mg/L nZnO; 9-15-24-31-23 for those exposed to 10 mg/L and 7-11-19-26-17 for those exposed 100 mg/L nZnO. A large number of sequences could not be assigned to specific taxa, suggesting a possibility of novel species to be discovered. PMID:27966634

  14. Electrodeposition, characterization, and antibacterial activity of zinc/silver particle composite coatings

    NASA Astrophysics Data System (ADS)

    Reyes-Vidal, Y.; Suarez-Rojas, R.; Ruiz, C.; Torres, J.; Ţălu, Ştefan; Méndez, Alia; Trejo, G.

    2015-07-01

    Composite coatings consisting of zinc and silver particles (Zn/AgPs) with antibacterial activity were prepared using an electrodeposition technique. The morphology, composition, and structure of the Zn/AgPs composite coatings were analyzed using scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), inductively coupled plasma (ICP) spectrometry, and X-ray diffraction (XRD). The antibacterial properties of the coatings against the microorganisms Escherichia coli as a model Gram-negative bacterium and Staphylococcus aureus as a model Gram-positive bacterium were studied quantitatively and qualitatively. The results revealed that the dispersant cetyltrimethylammonium bromide (CTAB) assisted in the formation of a stable suspension of Ag particles in the electrolytic bath for 24 h. Likewise, a high concentration of CTAB in the electrolytic bath promoted an increase in the number of Ag particles occluded in the Zn/AgPs coatings. The Zn/AgPs coatings that were obtained were compact, smooth, and shiny materials. Antimicrobial tests performed on the Zn/AgPs coatings revealed that the inhibition of bacterial growth after 30 min of contact time was between 91% and 98% when the AgPs content ranged from 4.3 to 14.0 mg cm-3.

  15. Colorimetric cholesterol sensor based on peroxidase like activity of zinc oxide nanoparticles incorporated carbon nanotubes.

    PubMed

    Hayat, Akhtar; Haider, Waqar; Raza, Yousuf; Marty, Jean Louis

    2015-10-01

    A sensitive and selective colorimetric method based on the incorporation of zinc oxide nanoparticles (ZnO NPs) on the surface of carbon nanotubes (CNTs) was shown to posses synergistic peroxidase like activity for the detection of cholesterol. The proposed nanocomposite catalyzed the oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) in the presence of hydrogen peroxide (H2O2) to produce a green colored product which can be monitored at 405 nm. H2O2 is the oxidative product of cholesterol in the presence of cholesterol oxidase. Therefore, the oxidation of cholesterol can be quantitatively related to the colorimetric response by combining these two reactions. Under the optimal experimental conditions, the colorimetric response was proportional to the concentration of cholesterol in the range of 0.5-500 nmol/L, with a detection limit of 0.2 nmol/L. The applicability of the proposed assays was demonstrated for the determination of cholesterol in milk powder samples with good recovery results.

  16. Synthesis, characterization and anticancer activity of kaempferol-zinc(II) complex.

    PubMed

    Tu, Lv-Ying; Pi, Jiang; Jin, Hua; Cai, Ji-Ye; Deng, Sui-Ping

    2016-06-01

    According to the previous studies, the anticancer activity of flavonoids could be enhanced when they are coordinated with transition metal ions. In this work, kaempferol-zinc(II) complex (kaempferol-Zn) was synthesized and its chemical properties were characterized by UV-VIS, FT-IR, (1)H NMR, elemental analysis, electrospray mass spectrometry (ES-MS) and fluorescence spectroscopy, which showed that the synthesized complex was coordinated with a Zn(II) ion via the 3-OH and 4-oxo groups. The anticancer effects of kaempferol-Zn and free kaempferol on human oesophageal cancer cell line (EC9706) were compared. MTT results demonstrated that the killing effect of kaempferol-Zn was two times higher than that of free kaempferol. Atomic force microscopy (AFM) showed the morphological and ultrastructural changes of cellular membrane induced by kaempferol-Zn at subcellular or nanometer level. Moreover, flow cytometric analysis indicated that kaempferol-Zn could induce apoptosis in EC9706 cells by regulating intracellular calcium ions. Collectively, all the data showed that kaempferol-Zn might be served as a kind of potential anticancer agent.

  17. Enhanced oxidative stress resistance through activation of a zinc deficiency transcription factor in Brachypodium distachyon.

    PubMed

    Glover-Cutter, Kira M; Alderman, Stephen; Dombrowski, James E; Martin, Ruth C

    2014-11-01

    Identification of viable strategies to increase stress resistance of crops will become increasingly important for the goal of global food security as our population increases and our climate changes. Considering that resistance to oxidative stress is oftentimes an indicator of health and longevity in animal systems, characterizing conserved pathways known to increase oxidative stress resistance could prove fruitful for crop improvement strategies. This report argues for the usefulness and practicality of the model organism Brachypodium distachyon for identifying and validating stress resistance factors. Specifically, we focus on a zinc deficiency B. distachyon basic leucine zipper transcription factor, BdbZIP10, and its role in oxidative stress in the model organism B. distachyon. When overexpressed, BdbZIP10 protects plants and callus tissue from oxidative stress insults, most likely through distinct and direct activation of protective oxidative stress genes. Increased oxidative stress resistance and cell viability through the overexpression of BdbZIP10 highlight the utility of investigating conserved stress responses between plant and animal systems.

  18. Interaction of mining activities and aquatic environment: A review from Greek mine sites.

    NASA Astrophysics Data System (ADS)

    Vasileiou, Eleni; Kallioras, Andreas

    2016-04-01

    In Greece a significant amount of mineral and ore deposits have been recorded accompanied by large industrial interest and a long mining history. Today many active and/or abandoned mine sites are scattered within the country; while mining activities take place in different sites for exploiting various deposits (clay, limestone, slate, gypsum, kaolin, mixed sulphide ores (lead, zinc, olivine, pozzolan, quartz lignite, nickel, magnesite, aluminum, bauxite, gold, marbles etc). The most prominent recent ones are: (i) the lignite exploitation that is extended in the area of Ptolemais (Western Macedonia) and Megalopolis (Central Peloponnese); and (ii) the major bauxite deposits located in central Greece within the Parnassos-Ghiona geotectonic zone and on Euboea Island. In the latter area, significant ores of magnesite were exploited and mixed sulphide ores. Centuries of intensive mining exploitation and metallurgical treatment of lead-silver deposits in Greece, have also resulted in significant abandoned sites, such as the one in Lavrion. Mining activities in Lavrio, were initiated in ancient times and continued until the 1980s, resulting in the production of significant waste stockpiles deposited in the area, crucial for the local water resources. Ιn many mining sites, environmental pressures are also recorded after the mine closure to the aquatic environment, as the surface waters flow through waste dump areas and contaminated soils. This paper aims to the geospatial visualization of the mining activities in Greece, in connection to their negative (surface- and/or ground-water pollution; overpumping due to extensive dewatering practices) or positive (enhanced groundwater recharge; pit lakes, improvement of water budget in the catchment scale) impacts on local water resources.

  19. Influence of triethyl phosphate on phosphatase activity in shooting range soil: Isolation of a zinc-resistant bacterium with an acid phosphatase.

    PubMed

    Story, Sandra; Brigmon, Robin L

    2017-03-01

    Phosphatase-mediated hydrolysis of organic phosphate may be a viable means of stabilizing heavy metals via precipitation as a metal phosphate in bioremediation applications. We investigated the effect of triethyl phosphate (TEP) on soil microbial-phosphatase activity in a heavy-metal contaminated soil. Gaseous TEP has been used at subsurface sites for bioremediation of organic contaminants but not applied in heavy-metal contaminated areas. Little is known about how TEP affects microbial activity in soils and it is postulated that TEP can serve as a phosphate source in nutrient-poor groundwater and soil/sediments. Over a 3-week period, TEP amendment to microcosms containing heavy-metal contaminated soil resulted in increased activity of soil acid-phosphatase and repression of alkaline phosphatase, indicating a stimulatory effect on the microbial population. A soil-free enrichment of microorganisms adapted to heavy-metal and acidic conditions was derived from the TEP-amended soil microcosms using TEP as the sole phosphate source and the selected microbial consortium maintained a high acid-phosphatase activity with repression of alkaline phosphatase. Addition of 5mM zinc to soil-free microcosms had little effect on acid phosphatase but inhibited alkaline phosphatase. One bacterial member from the consortium, identified as Burkholderia cepacia sp., expressed an acid-phosphatase activity uninhibited by high concentrations of zinc and produced a soluble, indigo pigment under phosphate limitation. The pigment was produced in a phosphate-free medium and was not produced in the presence of TEP or phosphate ion, indicative of purple acid-phosphatase types that are pressed by bioavailable phosphate. These results demonstrate that TEP amendment was bioavailable and increased overall phosphatase activity in both soil and soil-free microcosms supporting the possibility of positive outcomes in bioremediation applications.

  20. Novel conductive polypyrrole/zinc oxide/chitosan bionanocomposite: synthesis, characterization, antioxidant, and antibacterial activities

    PubMed Central

    Ebrahimiasl, Saeideh; Zakaria, Azmi; Kassim, Anuar; Basri, Sri Norleha

    2015-01-01

    An antibacterial and conductive bionanocomposite (BNC) film consisting of polypyrrole (Ppy), zinc oxide (ZnO) nanoparticles (NPs), and chitosan (CS) was electrochemically synthesized on indium tin oxide (ITO) glass substrate by electrooxidation of 0.1 M pyrrole in aqueous solution containing appropriate amounts of ZnO NPs uniformly dispersed in CS. This method enables the room temperature electrosynthesis of BNC film consisting of ZnO NPs incorporated within the growing Ppy/CS composite. The morphology of Ppy/ZnO/CS BNC was characterized by scanning electron microscopy. ITO–Ppy/CS and ITO–Ppy/ZnO/CS bioelectrodes were characterized using the Fourier transform infrared technique, X-ray diffraction, and thermogravimetric analysis. The electrical conductivity of nanocomposites was investigated by a four-probe method. The prepared nanocomposites were analyzed for antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl assay. The results demonstrated that the antioxidant activity of nanocomposites increased remarkably by addition of ZnO NPs. The electrical conductivity of films showed a sudden decrease for lower weight ratios of ZnO NPs (5 wt%), while it was increased gradually for higher ratios (10, 15, and 20 wt%). The nanocomposites were analyzed for antibacterial activity against Gram-positive and Gram-negative bacteria. The results indicated that the synthesized BNC is effective against all of the studied bacteria, and its effectiveness is higher for Pseudomonas aeruginosa. The thermal stability and physical properties of BNC films were increased by an increase in the weight ratio of ZnO NPs, promising novel applications for the electrically conductive polysaccharide-based nanocomposites, particularly those that may exploit the antimicrobial nature of Ppy/ZnO/CS BNCs. PMID:25565815

  1. Antibacterial activity and interaction mechanism of electrospun zinc-doped titania nanofibers.

    PubMed

    Amna, Touseef; Hassan, M Shamshi; Barakat, Nasser A M; Pandeya, Dipendra Raj; Hong, Seong Tshool; Khil, Myung-Seob; Kim, Hak Yong

    2012-01-01

    In this study, a biological evaluation of the antimicrobial activity of Zn-doped titania nanofibers was carried out using Escherichia coli ATCC 52922 (Gram negative) and Staphylococcus aureus ATCC 29231 (Gram positive) as model organisms. The utilized Zn-doped titania nanofibers were prepared by the electrospinning of a sol-gel composed of zinc nitrate, titanium isopropoxide, and polyvinyl acetate; the obtained electrospun nanofibers were vacuum dried at 80°C and then calcined at 600°C. The physicochemical properties of the synthesized nanofibers were determined by X-ray diffraction pattern, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron probe microanalysis, thermogravimetry, and transmission electron microscopy (TEM). The antibacterial activity and the acting mechanism of Zn-doped titania nanofibers against bacteria were investigated by calculation of minimum inhibitory concentration and analyzing the morphology of the bacterial cells following the treatment with nanofibers solution. Our investigations reveal that the lowest concentration of Zn-doped titania nanofibers solution inhibiting the growth of S. aureus ATCC 29231 and E. coli ATCC 52922 strains is found to be 0.4 and 1.6 μg/ml, respectively. Furthermore, Bio-TEM analysis demonstrated that the exposure of the selected microbial strains to the nanofibers led to disruption of the cell membranes and leakage of the cytoplasm. In conclusion, the combined results suggested doping promotes antimicrobial effect; synthesized nanofibers possess a very large surface-to-volume ratio and may damage the structure of the bacterial cell membrane, as well as depress the activity of the membranous enzymes which cause bacteria to die in due course.

  2. Antiurolithiatic activity of Abelmoschus moschatus seed extracts against zinc disc implantation-induced urolithiasis in rats

    PubMed Central

    Pawar, Anil T.; Vyawahare, Niraj S.

    2016-01-01

    Background: The commonly used techniques for removing renal calculi are associated with the risk of acute renal injury and increase in stone recurrence which indicates an urgent need for alternate therapy. Objectives: The aim was to evaluate the antiurolithiatic activity of Abelmoschus moschatus seed extracts in rats. Materials and Methods: Urolithiasis was induced by surgical implantations of zinc disc in the urinary bladders of rats. Upon postsurgical recovery, different doses of chloroform (CAM) and methanolic (MAM) extracts of A. moschatus seeds (viz., 100, 200 and 400 mg/kg body weight) were administered to disc implanted rats for the period of 7 days by the oral route. Antiurolithiatic activity was evaluated by measuring various dimensions of stones and estimating levels of various biomarkers in serum and urine samples. Results: A significant decrease in urinary output was observed in disc implanted animals, which was prevented by the treatment with extracts. Supplementation with extracts caused significant improvement in glomerular filtration rate and urinary total protein excretion. The elevated levels of serum creatinine, uric acid, and blood urea nitrogen were also prevented by the extracts. The extracts significantly reduced deposition of calculi deposition around the implanted disc. This antiurolithiatic potential is observed at all doses (100, 200, and 400 mg/kg) of MAM, whereas only higher dose (400 mg/kg) of CAM showed significant antiurolithiatic potential. Conclusion: The extracts of A. moschatus seeds possessed significant antiurolithiatic activity. The possible mechanism underlying this effect is mediated collectively through diuretic, antioxidant, and free-radical scavenging effects of the plant. PMID:27057124

  3. Enhanced photodynamic leishmanicidal activity of hydrophobic zinc phthalocyanine within archaeolipids containing liposomes

    PubMed Central

    Perez, Ana Paula; Casasco, Agustina; Schilrreff, Priscila; Defain Tesoriero, Maria Victoria; Duempelmann, Luc; Altube, Maria Julia; Higa, Leticia; Morilla, Maria Jose; Petray, Patricia; Romero, Eder L

    2014-01-01

    In this work, the in vitro anti-Leishmania activity of photodynamic liposomes made of soybean phosphatidylcholine, sodium cholate, total polar archaeolipids (TPAs) extracted from the hyperhalophile archaea Halorubrum tebenquichense and the photosensitizer zinc phthalocyanine (ZnPcAL) was compared to that of ultradeformable photodynamic liposomes lacking TPAs (ZnPcUDLs). We found that while ZnPcUDLs and ZnPcALs (130 nm mean diameter and −35 mV zeta potential) were innocuous against promastigotes, a low concentration (0.01 μM ZnPc and 7.6 μM phospholipids) of ZnPcALs irradiated at a very low-energy density (0.2 J/cm2) eliminated L. braziliensis amastigotes from J774 macrophages, without reducing the viability of the host cells. In such conditions, ZnPcALs were harmless for J774 macrophages, HaCaT keratinocytes, and bone marrow-derived dendritic cells. Therefore, topical photodynamic treatment would not likely affect skin-associated lymphoid tissue. ZnPcALs were extensively captured by macrophages, but ZnPcUDLs were not, leading to 2.5-fold increased intracellular delivery of ZnPc than with ZnPcUDLs. Despite mediating low levels of reactive oxygen species, the higher delivery of ZnPc and the multiple (caveolin- and clathrin-dependent plus phagocytic) intracellular pathway followed by ZnPc would have been the reason for the higher antiamastigote activity of ZnPcALs. The leishmanicidal activity of photodynamic liposomal ZnPc was improved by TPA-containing liposomes. PMID:25045264

  4. Enhanced photodynamic leishmanicidal activity of hydrophobic zinc phthalocyanine within archaeolipids containing liposomes.

    PubMed

    Perez, Ana Paula; Casasco, Agustina; Schilrreff, Priscila; Tesoriero, Maria Victoria Defain; Duempelmann, Luc; Pappalardo, Juan Sebastián; Altube, Maria Julia; Higa, Leticia; Morilla, Maria Jose; Petray, Patricia; Romero, Eder L

    2014-01-01

    In this work, the in vitro anti-Leishmania activity of photodynamic liposomes made of soybean phosphatidylcholine, sodium cholate, total polar archaeolipids (TPAs) extracted from the hyperhalophile archaea Halorubrum tebenquichense and the photosensitizer zinc phthalocyanine (ZnPcAL) was compared to that of ultradeformable photodynamic liposomes lacking TPAs (ZnPcUDLs). We found that while ZnPcUDLs and ZnPcALs (130 nm mean diameter and -35 mV zeta potential) were innocuous against promastigotes, a low concentration (0.01 μM ZnPc and 7.6 μM phospholipids) of ZnPcALs irradiated at a very low-energy density (0.2 J/cm(2)) eliminated L. braziliensis amastigotes from J774 macrophages, without reducing the viability of the host cells. In such conditions, ZnPcALs were harmless for J774 macrophages, HaCaT keratinocytes, and bone marrow-derived dendritic cells. Therefore, topical photodynamic treatment would not likely affect skin-associated lymphoid tissue. ZnPcALs were extensively captured by macrophages, but ZnPcUDLs were not, leading to 2.5-fold increased intracellular delivery of ZnPc than with ZnPcUDLs. Despite mediating low levels of reactive oxygen species, the higher delivery of ZnPc and the multiple (caveolin- and clathrin-dependent plus phagocytic) intracellular pathway followed by ZnPc would have been the reason for the higher antiamastigote activity of ZnPcALs. The leishmanicidal activity of photodynamic liposomal ZnPc was improved by TPA-containing liposomes.

  5. Novel conductive polypyrrole/zinc oxide/chitosan bionanocomposite: synthesis, characterization, antioxidant, and antibacterial activities.

    PubMed

    Ebrahimiasl, Saeideh; Zakaria, Azmi; Kassim, Anuar; Basri, Sri Norleha

    2015-01-01

    An antibacterial and conductive bionanocomposite (BNC) film consisting of polypyrrole (Ppy), zinc oxide (ZnO) nanoparticles (NPs), and chitosan (CS) was electrochemically synthesized on indium tin oxide (ITO) glass substrate by electrooxidation of 0.1 M pyrrole in aqueous solution containing appropriate amounts of ZnO NPs uniformly dispersed in CS. This method enables the room temperature electrosynthesis of BNC film consisting of ZnO NPs incorporated within the growing Ppy/CS composite. The morphology of Ppy/ZnO/CS BNC was characterized by scanning electron microscopy. ITO-Ppy/CS and ITO-Ppy/ZnO/CS bioelectrodes were characterized using the Fourier transform infrared technique, X-ray diffraction, and thermogravimetric analysis. The electrical conductivity of nanocomposites was investigated by a four-probe method. The prepared nanocomposites were analyzed for antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl assay. The results demonstrated that the antioxidant activity of nanocomposites increased remarkably by addition of ZnO NPs. The electrical conductivity of films showed a sudden decrease for lower weight ratios of ZnO NPs (5 wt%), while it was increased gradually for higher ratios (10, 15, and 20 wt%). The nanocomposites were analyzed for antibacterial activity against Gram-positive and Gram-negative bacteria. The results indicated that the synthesized BNC is effective against all of the studied bacteria, and its effectiveness is higher for Pseudomonas aeruginosa. The thermal stability and physical properties of BNC films were increased by an increase in the weight ratio of ZnO NPs, promising novel applications for the electrically conductive polysaccharide-based nanocomposites, particularly those that may exploit the antimicrobial nature of Ppy/ZnO/CS BNCs.

  6. Antibacterial activity of root canal filling materials for primary teeth: zinc oxide and eugenol cement, Calen paste thickened with zinc oxide, Sealapex and EndoREZ.

    PubMed

    Queiroz, Alexandra Mussolino de; Nelson-Filho, Paulo; Silva, Léa Assed Bezerra da; Assed, Sada; Silva, Raquel Assed Bezerra da; Ito, Izabel Yoko

    2009-01-01

    This study evaluated in vitro the antibacterial activity of 4 root canal filling materials for primary teeth - zinc oxide and eugenol cement (ZOE), Calen paste thickened with zinc oxide (Calen/ZO), Sealapex sealer and EndoREZ sealer - against 5 bacterial strains commonly found in endodontic infections (Kocuria rhizophila, Enterococcus faecalis, Streptococcus mutans, Escherichia coli and Staphylococcus aureus) using the agar diffusion test (agar-well technique). Calen paste, 1% chlorhexidine digluconate (CHX) and distilled water served as controls. Seven wells per dish were made at equidistant points and immediately filled with the test and control materials. After incubation of the plates at 37 degrees C for 24 h, the diameter of the zones of bacterial growth inhibition produced around the wells was measured (in mm) with a digital caliper under reflected light. Data were analyzed statistically by analysis of variance and Tukey's post-hoc test (alpha=0.05). There were statistically significant differences (p<0.0001) among the zones of bacterial growth inhibition produced by the different materials against all target microorganisms. K. rhizophila was inhibited more effectively (p<0.05) by ZOE, while Calen/ZO had its highest antibacterial activity against E. faecalis (p<0.05). S. mutans was inhibited by Calen/ZO, Sealapex and ZOE in the same intensity (p>0.05). E. coli was inhibited more effectively (p<0.05) by ZOE, followed by Calen/ZO and Sealapex. Calen/ZO and ZOE were equally effective (p>0.05) against S. aureus, while Sealapex had the lowest antibacterial efficacy (p<0.05) against this microorganism. EndoREZ presented antibacterial activity only against K. rhizophila and S. aureus. The Calen paste and Calen/ZO produced larger zones of inhibition than 1% CHX when the marker microorganism was E faecalis. In conclusion, the in vitro antibacterial activity of the 4 root canal filling materials for primary teeth against bacterial strains commonly found in endodontic

  7. Crystal structure of Clostridium botulinum neurotoxin protease in a product-bound state: Evidence for noncanonical zinc protease activity.

    PubMed

    Segelke, Brent; Knapp, Mark; Kadkhodayan, Saloumeh; Balhorn, Rod; Rupp, Bernhard

    2004-05-04

    Clostridium botulinum neurotoxins (BoNTs), the most potent toxins known, disrupt neurotransmission through proteolysis of proteins involved in neuroexocytosis. The light chains of BoNTs are unique zinc proteases that have stringent substrate specificity and require exceptionally long substrates. We have determined the crystal structure of the protease domain from BoNT serotype A (BoNT/A). The structure reveals a homodimer in a product-bound state, with loop F242-V257 from each monomer deeply buried in its partner's catalytic site. The loop, which acts as a substrate, is oriented in reverse of the canonical direction for other zinc proteases. The Y249-Y250 peptide bond of the substrate loop is hydrolyzed, leaving the Y249 product carboxylate coordinated to the catalytic zinc. From the crystal structure of the BoNT/A protease, detailed models of noncanonical binding and proteolysis can be derived which we propose are also consistent with BoNT/A binding and proteolysis of natural substrate synaptosome-associated protein of 25 kDa (SNAP-25). The proposed BoNT/A substrate-binding mode and catalytic mechanism are markedly different from those previously proposed for the BoNT serotype B.

  8. Identification of putative active site residues of ACAT enzymes.

    PubMed

    Das, Akash; Davis, Matthew A; Rudel, Lawrence L

    2008-08-01

    In this report, we sought to determine the putative active site residues of ACAT enzymes. For experimental purposes, a particular region of the C-terminal end of the ACAT protein was selected as the putative active site domain due to its high degree of sequence conservation from yeast to humans. Because ACAT enzymes have an intrinsic thioesterase activity, we hypothesized that by analogy with the thioesterase domain of fatty acid synthase, the active site of ACAT enzymes may comprise a catalytic triad of ser-his-asp (S-H-D) amino acid residues. Mutagenesis studies revealed that in ACAT1, S456, H460, and D400 were essential for activity. In ACAT2, H438 was required for enzymatic activity. However, mutation of D378 destabilized the enzyme. Surprisingly, we were unable to identify any S mutations of ACAT2 that abolished catalytic activity. Moreover, ACAT2 was insensitive to serine-modifying reagents, whereas ACAT1 was not. Further studies indicated that tyrosine residues may be important for ACAT activity. Mutational analysis showed that the tyrosine residue of the highly conserved FYXDWWN motif was important for ACAT activity. Furthermore, Y518 was necessary for ACAT1 activity, whereas the analogous residue in ACAT2, Y496, was not. The available data suggest that the amino acid requirement for ACAT activity may be different for the two ACAT isozymes.

  9. Serum Zinc and Adiponectin Levels in Patients with Polycystic Ovary Syndrome, Adjusted for Anthropometric, Biochemical, Dietary Intake, and Physical Activity Measures.

    PubMed

    Mazloomi, Sahar; Alizadeh, Narges; Aminzare, Majid; Niroomand, Soudabeh; Mousavi, Seyedeh Neda

    2017-02-03

    Previous studies have shown that serum zinc and adiponectin levels are associated with insulin resistance in the polycystic ovary syndrome (PCOS) patients. But there is no study to evaluate serum zinc and adiponectin levels as predictor markers of PCOS, adjusted for anthropometric, biochemical, dietary intake, and physical activity measures. Ninety-one new PCOS cases (based on the Rotterdam criteria) and 85 healthy control women participated and individually matched based on age. Food intake of all participants obtained by the food frequency and physical activity level was assessed by the International Physical Activity Questionnaires. Serum glucose, lipid profile, androgens, insulin, adiponectin, and zinc concentrations were measured at the fasting state. Weight, BMI, waist circumference, and body fat, as well as serum levels of DHEAS, insulin, TG, LDL cholesterol (LDL.C), homeostasis model assessment of insulin resistance (HOMA-IR), and LH/FSH ratio, were significantly higher in the PCOS compared with those of the healthy control women. Serum levels of zinc and adiponectin were significantly lower in the PCOS than those of the healthy control women. Results of the logistic regression model showed significant effects of adiponectin, zinc, and LH/FSH ratio on the PCOS, adjusted for anthropometric and biochemical measures (p < 0.05). In the present study, serum level of zinc had significant correlation with adiponectin in the PCOS patients, and serum levels of zinc, adiponectin, and LH/FSH ratio had significant effects on the PCOS occurrence.

  10. Methanopyrus kandleri topoisomerase V contains three distinct AP lyase active sites in addition to the topoisomerase active site

    PubMed Central

    Rajan, Rakhi; Osterman, Amy; Mondragón, Alfonso

    2016-01-01

    Topoisomerase V (Topo-V) is the only topoisomerase with both topoisomerase and DNA repair activities. The topoisomerase activity is conferred by a small alpha-helical domain, whereas the AP lyase activity is found in a region formed by 12 tandem helix-hairpin-helix ((HhH)2) domains. Although it was known that Topo-V has multiple repair sites, only one had been mapped. Here, we show that Topo-V has three AP lyase sites. The atomic structure and Small Angle X-ray Scattering studies of a 97 kDa fragment spanning the topoisomerase and 10 (HhH)2 domains reveal that the (HhH)2 domains extend away from the topoisomerase domain. A combination of biochemical and structural observations allow the mapping of the second repair site to the junction of the 9th and 10th (HhH)2 domains. The second site is structurally similar to the first one and to the sites found in other AP lyases. The 3rd AP lyase site is located in the 12th (HhH)2 domain. The results show that Topo-V is an unusual protein: it is the only known protein with more than one (HhH)2 domain, the only known topoisomerase with dual activities and is also unique by having three AP lyase repair sites in the same polypeptide. PMID:26908655

  11. Methanopyrus kandleri topoisomerase V contains three distinct AP lyase active sites in addition to the topoisomerase active site.

    PubMed

    Rajan, Rakhi; Osterman, Amy; Mondragón, Alfonso

    2016-04-20

    Topoisomerase V (Topo-V) is the only topoisomerase with both topoisomerase and DNA repair activities. The topoisomerase activity is conferred by a small alpha-helical domain, whereas the AP lyase activity is found in a region formed by 12 tandem helix-hairpin-helix ((HhH)2) domains. Although it was known that Topo-V has multiple repair sites, only one had been mapped. Here, we show that Topo-V has three AP lyase sites. The atomic structure and Small Angle X-ray Scattering studies of a 97 kDa fragment spanning the topoisomerase and 10 (HhH)2 domains reveal that the (HhH)2 domains extend away from the topoisomerase domain. A combination of biochemical and structural observations allow the mapping of the second repair site to the junction of the 9th and 10th (HhH)2 domains. The second site is structurally similar to the first one and to the sites found in other AP lyases. The 3rd AP lyase site is located in the 12th (HhH)2 domain. The results show that Topo-V is an unusual protein: it is the only known protein with more than one (HhH)2 domain, the only known topoisomerase with dual activities and is also unique by having three AP lyase repair sites in the same polypeptide.

  12. Hepatic cells' mitotic and peritoneal macrophage phagocytic activities during Trypanosoma musculi infection in zinc-deficient mice.

    PubMed Central

    Humphrey, P. A.; Ashraf, M.; Lee, C. M.

    1997-01-01

    The effects of zinc deficiency on hepatic cell mitotic and peritoneal macrophage phagocytic activities were examined in mice infected with Trypanosoma musculi or immunized with parasitic products. On a full-complement or pair-fed diet, infected and homogenate-inoculated mice showed mitotic activity gains of 7.9% to 80.3% and 6.5% to 99.0%, respectively. Infected and homogenate-inoculated mice on a zinc-deficient diet showed 21.8% to 95.7% and 17.2% to 65.2%, respectively, more dividing liver cells compared with controls. In comparison to controls, macrophages isolated from infected and homogenate-immunized mice on full-complement or pair-fed diets had phagocytized 13.4% to 31.4% more latex particles from day 50 to 80. In the zinc-deficient group, macrophages isolated from infected mice had significant numbers of phagocytized latex particles (1.8% to 38.5%) from day 20 to day 80 compared with controls. The homogenate-immunized mice also had increased numbers (18.6 to 30.8%) of phagocytized latex particles. PMID:9145631

  13. Mechanochemical synthesis and in vitro anti-Helicobacter pylori and uresase inhibitory activities of novel zinc(II)-famotidine complex.

    PubMed

    Amin, Muhammad; Iqbal, Mohammad S; Hughes, Roy W; Khan, Safyan A; Reynolds, Paul A; Enne, Virve I; Sajjad-ur-Rahman; Mirza, Akmal S

    2010-06-01

    The mechanochemical synthesis and characterization of a zinc complex with famotidine is described. The complex was characterized by microanalysis and a number of spectroscopic techniques. The complex was of M:L dihydrate type. Derivatization of famotidine with zinc appears to enhance the activity of the drug by inhibiting the growth of Helicobacter pylori (two reference and 34 clinical isolates). The complex inhibited the growth of H. pylori in an MIC range of 1-8 microg mL(-1). The anti-H. pylori activity of the zinc-famotidine complex against antibiotic-resistant strains was nearly comparable to that of antibiotic-susceptible strains. The complex was found to be far less toxic than the parent drug, as demonstrated by its higher LD(50) value. In the human urease enzyme inhibition assay the complex exhibited significant inhibition. The new complex appears to be more useful in eradicating both the antibiotic-susceptible and antibiotic-resistant strains of H. pylori.

  14. Improvement in the electrical performance and bias-stress stability of dual-active-layered silicon zinc oxide/zinc oxide thin-film transistor

    NASA Astrophysics Data System (ADS)

    Liu, Yu-Rong; Zhao, Gao-Wei; Lai, Pai-To; Yao, Ruo-He

    2016-08-01

    Si-doped zinc oxide (SZO) thin films are deposited by using a co-sputtering method, and used as the channel active layers of ZnO-based TFTs with single and dual active layer structures. The effects of silicon content on the optical transmittance of the SZO thin film and electrical properties of the SZO TFT are investigated. Moreover, the electrical performances and bias-stress stabilities of the single- and dual-active-layer TFTs are investigated and compared to reveal the effects of the Si doping and dual-active-layer structure. The average transmittances of all the SZO films are about 90% in the visible light region of 400 nm-800 nm, and the optical band gap of the SZO film gradually increases with increasing Si content. The Si-doping can effectively suppress the grain growth of ZnO, revealed by atomic force microscope analysis. Compared with that of the undoped ZnO TFT, the off-state current of the SZO TFT is reduced by more than two orders of magnitude and it is 1.5 × 10-12 A, and thus the on/off current ratio is increased by more than two orders of magnitude. In summary, the SZO/ZnO TFT with dual-active-layer structure exhibits a high on/off current ratio of 4.0 × 106 and superior stability under gate-bias and drain-bias stress. Projected supported by the National Natural Science Foundation of China (Grant Nos. 61076113 and 61274085), the Natural Science Foundation of Guangdong Province (Grant No. 2016A030313474), and the University Development Fund (Nanotechnology Research Institute, Grant No. 00600009) of the University of Hong Kong, China.

  15. Studies on the activation energy from the ac conductivity measurements of rubber ferrite composites containing manganese zinc ferrite

    NASA Astrophysics Data System (ADS)

    Hashim, Mohd.; Alimuddin; Kumar, Shalendra; Shirsath, Sagar E.; Mohammed, E. M.; Chung, Hanshik; Kumar, Ravi

    2012-11-01

    Manganese zinc ferrites (MZF) have resistivities between 0.01 and 10 Ω m. Making composite materials of ferrites with either natural rubber or plastics will modify the electrical properties of ferrites. The moldability and flexibility of these composites find wide use in industrial and other scientific applications. Mixed ferrites belonging to the series Mn(1-x)ZnxFe2O4 were synthesized for different ‘x’ values in steps of 0.2, and incorporated in natural rubber matrix (RFC). From the dielectric measurements of the ceramic manganese zinc ferrite and rubber ferrite composites, ac conductivity and activation energy were evaluated. A program was developed with the aid of the LabVIEW package to automate the measurements. The ac conductivity of RFC was then correlated with that of the magnetic filler and matrix by a mixture equation which helps to tailor properties of these composites.

  16. Deep Sequencing of Random Mutant Libraries Reveals the Active Site of the Narrow Specificity CphA Metallo-β-Lactamase is Fragile to Mutations

    PubMed Central

    Sun, Zhizeng; Mehta, Shrenik C.; Adamski, Carolyn J.; Gibbs, Richard A.; Palzkill, Timothy

    2016-01-01

    CphA is a Zn2+-dependent metallo-β-lactamase that efficiently hydrolyzes only carbapenem antibiotics. To understand the sequence requirements for CphA function, single codon random mutant libraries were constructed for residues in and near the active site and mutants were selected for E. coli growth on increasing concentrations of imipenem, a carbapenem antibiotic. At high concentrations of imipenem that select for phenotypically wild-type mutants, the active-site residues exhibit stringent sequence requirements in that nearly all residues in positions that contact zinc, the substrate, or the catalytic water do not tolerate amino acid substitutions. In addition, at high imipenem concentrations a number of residues that do not directly contact zinc or substrate are also essential and do not tolerate substitutions. Biochemical analysis confirmed that amino acid substitutions at essential positions decreased the stability or catalytic activity of the CphA enzyme. Therefore, the CphA active - site is fragile to substitutions, suggesting active-site residues are optimized for imipenem hydrolysis. These results also suggest that resistance to inhibitors targeted to the CphA active site would be slow to develop because of the strong sequence constraints on function. PMID:27616327

  17. Preparation of activated carbon from dried pods of Prosopis cineraria with zinc chloride activation for the removal of phenol.

    PubMed

    Nath, Kaushik; Panchani, Suresh; Bhakhar, M S; Chatrola, Sandip

    2013-06-01

    Utilization of agrowaste materials for the production of activated carbon, as an excellent adsorbent with large surface area, is well established industrially, for dephenolation of wastewater. In the present work, dried pods of Prosopis cineraria-a novel and low-cost agrowaste material-were used to prepare activated carbons by zinc chloride activation. Batch adsorption experiments were carried out to study the effects of various physicochemical parameters such as initial phenol concentration, adsorbent dose, initial solution pH, and temperature. Pseudo-first-order second-order and diffusion kinetic models were used to identify the possible mechanisms of such adsorption process. The Langmuir and Freundlich equations were used to analyze the adsorption equilibrium. Maximum removal efficiency of 86 % was obtained with 25 mg L(-1) of initial phenol concentration. The favorable pH for maximum phenol adsorption was 4.0. Freundlich equation represented the adsorption equilibrium data more ideally than the Langmuir. The maximum adsorption capacity obtained was 78.32 mg g(-1) at a temperature of 30 °C and 25 mg L(-1) initial phenol concentration. The adsorption was spontaneous and endothermic. The pseudo-second-order model, an indication of chemisorption mechanism, fitted the experimental data better than the pseudo-first-order Lagergren model. Regeneration of spent activated carbon was carried out using Pseudomonas putida MTCC 2252 as the phenol-degrading microorganism. Maximum regeneration up to 57.5 % was recorded, when loaded phenol concentration was 25 mg L(-1). The data obtained in this study would be useful in designing and fabricating an efficient treatment plant for phenol-rich effluents.

  18. Green synthesis of nano zinc oxide and evaluation of its impact on germination and metabolic activity of Solanum lycopersicum.

    PubMed

    Singh, Ajey; Singh, N B; Hussain, Imtiyaz; Singh, Himani; Yadav, Vijaya; Singh, S C

    2016-09-10

    In the present study, zinc oxide nanoparticles (ZnO NPs) were rapidly synthesized at room temperature by treating zinc acetate dihydrate with the flower extract of Elaeagnus angustifolia (Russian olive). The formation of ZnO NPs was primarily confirmed by UV-visible absorption spectrum in the range of 250-700nm. XRD analysis and DLS particle size analyzer revealed the size of ZnO NPs. The FTIR spectrum revealed the presence of phytochemicals in the flower extract mediated ZnO NPs. Moreover, the morphology of the ZnO NPs was determined using SEM. Seeds of Solanum lycopersicum (tomato) were separately treated with different concentrations of synthesized ZnO NPs and zinc sulphate (ZnSO4) salt suspensions (common zinc supplement). The effect of these treatments on seed germination, seedling vigor, chlorophyll, protein and sugar contents as well as on the activities of lipid peroxidation and antioxidant enzyme were studied. Leaves of plants treated with 6.1mM concentration of ZnO NPs recorded maximum reflectance while it was minimum in plants treated with 1.2mM concentration of NPs. The effect of synthesized ZnO NPs on seedling vigor, pigment, protein and sugar content was found affirmative at lower concentrations contrary to control and ZnSO4 salt. The inhibitory effect at higher concentration of NPs indicated importance in the precise application of NPs, in Zn deficient system, where plant response varies with concentration. To the best of our knowledge this is the first report on Elaeagnus angustifolia mediated synthesis of ZnO NPs and their effects on germination and physiological activity of tomato.

  19. Activity prediction of substrates in NADH-dependent carbonyl reductase by docking requires catalytic constraints and charge parameterization of catalytic zinc environment

    NASA Astrophysics Data System (ADS)

    Dhoke, Gaurao V.; Loderer, Christoph; Davari, Mehdi D.; Ansorge-Schumacher, Marion; Schwaneberg, Ulrich; Bocola, Marco

    2015-11-01

    Molecular docking of substrates is more challenging compared to inhibitors as the reaction mechanism has to be considered. This becomes more pronounced for zinc-dependent enzymes since the coordination state of the catalytic zinc ion is of greater importance. In order to develop a predictive substrate docking protocol, we have performed molecular docking studies of diketone substrates using the catalytic state of carbonyl reductase 2 from Candida parapsilosis (CPCR2). Different docking protocols using two docking methods (AutoDock Vina and AutoDock4.2) with two different sets of atomic charges (AM1-BCC and HF-RESP) for catalytic zinc environment and substrates as well as two sets of vdW parameters for zinc ion were examined. We have selected the catalytic binding pose of each substrate by applying mechanism based distance criteria. To compare the performance of the docking protocols, the correlation plots for the binding energies of these catalytic poses were obtained against experimental Vmax values of the 11 diketone substrates for CPCR2. The best correlation of 0.73 was achieved with AutoDock4.2 while treating catalytic zinc ion in optimized non-bonded (NBopt) state with +1.01 charge on the zinc ion, compared to 0.36 in non-bonded (+2.00 charge on the zinc ion) state. These results indicate the importance of catalytic constraints and charge parameterization of catalytic zinc environment for the prediction of substrate activity in zinc-dependent enzymes by molecular docking. The developed predictive docking protocol described here is in principle generally applicable for the efficient in silico substrate spectra characterization of zinc-dependent ADH.

  20. Promoter-proximal polyadenylation sites reduce transcription activity

    PubMed Central

    Andersen, Pia K.; Lykke-Andersen, Søren; Jensen, Torben Heick

    2012-01-01

    Gene expression relies on the functional communication between mRNA processing and transcription. We previously described the negative impact of a point-mutated splice donor (SD) site on transcription. Here we demonstrate that this mutation activates an upstream cryptic polyadenylation (CpA) site, which in turn causes reduced transcription. Functional depletion of U1 snRNP in the context of the wild-type SD triggers the same CpA event accompanied by decreased RNA levels. Thus, in accordance with recent findings, U1 snRNP can shield premature pA sites. The negative impact of unshielded pA sites on transcription requires promoter proximity, as demonstrated using artificial constructs and supported by a genome-wide data set. Importantly, transcription down-regulation can be recapitulated in a gene context devoid of splice sites by placing a functional bona fide pA site/transcription terminator within ∼500 base pairs of the promoter. In contrast, promoter-proximal positioning of a pA site-independent histone gene terminator supports high transcription levels. We propose that optimal communication between a pA site-dependent gene terminator and its promoter critically depends on gene length and that short RNA polymerase II-transcribed genes use specialized termination mechanisms to maintain high transcription levels. PMID:23028143

  1. Active chemisorption sites in functionalized ionic liquids for carbon capture.

    PubMed

    Cui, Guokai; Wang, Jianji; Zhang, Suojiang

    2016-07-25

    Development of novel technologies for the efficient and reversible capture of CO2 is highly desired. In the last decade, CO2 capture using ionic liquids has attracted intensive attention from both academia and industry, and has been recognized as a very promising technology. Recently, a new approach has been developed for highly efficient capture of CO2 by site-containing ionic liquids through chemical interaction. This perspective review focuses on the recent advances in the chemical absorption of CO2 using site-containing ionic liquids, such as amino-based ionic liquids, azolate ionic liquids, phenolate ionic liquids, dual-functionalized ionic liquids, pyridine-containing ionic liquids and so on. Other site-containing liquid absorbents such as amine-based solutions, switchable solvents, and functionalized ionic liquid-amine blends are also investigated. Strategies have been discussed for how to activate the existent reactive sites and develop novel reactive sites by physical and chemical methods to enhance CO2 absorption capacity and reduce absorption enthalpy. The carbon capture mechanisms of these site-containing liquid absorbents are also presented. Particular attention has been paid to the latest progress in CO2 capture in multiple-site interactions by amino-free anion-functionalized ionic liquids. In the last section, future directions and prospects for carbon capture by site-containing ionic liquids are outlined.

  2. Photodynamic activity of substituted zinc trisulfophthalocyanines: role of plasma membrane damage.

    PubMed

    Cauchon, Nicole; Nader, Moni; Bkaily, Ghassan; van Lier, Johan E; Hunting, Darel

    2006-01-01

    We recently reported that variations in cellular phototoxicity among a series of alkynyl-substituted zinc trisulfophthalocyanines (ZnPcS3Cn) correlates with their hydrophobicity, with the most amphiphilic derivatives showing the highest cell uptake and phototoxicity. In this study we address the role of the plasma membrane in the photodynamic response as it relates to the overall hydrophobicity of the photosensitizer. The membrane tracker dye 1-[4(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), which is incorporated into plasma membranes by endocytosis, was used to establish plasma membrane uptake by EMT-6 cells of the ZnPcS3C, by colocalization, and TMA-DPH membrane uptake rates after photodynamic therapy were used to quantify membrane damage. TMA-DPH colocalization patterns show plasma membrane uptake of the photosensitizers after short 1 h incubation periods. TMA-DPH plasma membrane uptake rates after illumination of the photosensitizer-treated cells show a parabolic relationship with photosensitizer hydrophobicity that correlates well with the phototoxicity of the ZnPcS3C,. After a 1 h incubation period, overall phototoxicity correlates closely with the postillumination rate of TMA-DPH incorporation into the cell membrane, suggesting a major role of plasma membrane damage in the overall PDT effect. In contrast, after a 24 h incubation, phototoxicity shows a stronger but imperfect correlation with total cellular photosensitizer uptake rather than TMA-DPH membrane uptake, suggesting a partial shift in the cellular damage responsible for photosensitization from the plasma membrane to intracellular targets. We conclude that plasma membrane localization of the amphiphilic ZnPcS3C6-C9 is a major factor in their overall photodynamic activity.

  3. Zinc oxide nanoparticles and monocytes: Impact of size, charge and solubility on activation status

    SciTech Connect

    Prach, Morag; Stone, Vicki; Proudfoot, Lorna

    2013-01-01

    Zinc oxide (ZnO) particle induced cytotoxicity was dependent on size, charge and solubility, factors which at sublethal concentrations may influence the activation of the human monocytic cell line THP1. ZnO nanoparticles (NP; average diameter 70 nm) were more toxic than the bulk form (< 44 μm mesh) and a positive charge enhanced cytotoxicity of the NP despite their relatively high dissolution. A positive charge of the particles has been shown in other studies to have an influence on cell viability. Centrifugal filtration using a cut off of 5 kDa and Zn element analysis by atomic absorption spectroscopy confirmed that exposure of the ZnO particles and NP to 10% foetal bovine serum resulted in a strong association of the Zn{sup 2+} ion with protein. This association with protein may influence interaction of the ZnO particles and NP with THP1 cells. After 24 h exposure to the ZnO particles and NP at sublethal concentrations there was little effect on immunological markers of inflammation such as HLA DR and CD14, although they may induce a modest increase in the adhesion molecule CD11b. The cytokine TNFα is normally associated with proinflammatory immune responses but was not induced by the ZnO particles and NP. There was also no effect on LPS stimulated TNFα production. These results suggest that ZnO particles and NP do not have a classical proinflammatory effect on THP1 cells. -- Highlights: ► ZnO is cytotoxic to THP-1 monocytes. ► ZnO nanoparticles are more toxic than the bulk form. ► Positive charge enhances ZnO nanoparticle cytotoxicity. ► Sublethal doses of ZnO particles do not induce classical proinflammatory markers.

  4. Active Sites Environmental Monitoring Program: Mid-FY 1991 report

    SciTech Connect

    Ashwood, T.L.; Wickliff, D.S.; Morrissey, C.M.

    1991-10-01

    This report summarizes the activities of the Active Sites Environmental Monitoring Program (ASEMP) from October 1990 through March 1991. The ASEMP was established in 1989 by Solid Waste Operations and the Environmental Sciences Division to provide early detection and performance monitoring at active low-level radioactive waste (LLW) disposal sites in Solid Waste Storage Area (SWSA) 6 and transuranic (TRU) waste storage sites in SWSA 5 as required by chapters II and III of US Department of Energy Order 5820.2A. Monitoring results continue to demonstrate the no LLW is being leached from the storage vaults on the tumulus pads. Loading of vaults on Tumulus II began during this reporting period and 115 vaults had been loaded by the end of March 1991.

  5. Antimicrobial activity of zinc oxide particles on five micro-organisms of the Challenge Tests related to their physicochemical properties.

    PubMed

    Pasquet, Julia; Chevalier, Yves; Couval, Emmanuelle; Bouvier, Dominique; Noizet, Gaëlle; Morlière, Cécile; Bolzinger, Marie-Alexandrine

    2014-01-02

    Zinc oxide is commonly used in pharmaceutical products to prevent or treat topical or systemic diseases owing to its antimicrobial properties, but it is scarcely used as preservative in topical formulations. The aim of this work was to investigate the antimicrobial activity of zinc oxide (ZnO) powders on the five microbial strains used for Challenge Tests in order to evaluate this inorganic compound as a preservative in topical formulation and assess relationships between the structural parameters of ZnO particles and their antimicrobial activity. For this purpose, the physicochemical characteristics of three ZnO grades were measured and their antimicrobial efficacy against the following micro-organisms - Escherichia coli; Staphylococcus aureus; Pseudomonas aeruginosa; Candida albicans; Aspergillus brasiliensis - was assessed using disc diffusion susceptibility tests and a broth dilution method. The comprehensive dataset of physicochemical characteristics and antimicrobial activities (MIC and MBC) is discussed regarding methodological issues related to the particulate nature of ZnO and structure-activity relationships. Every ZnO grade showed bactericidal and antifungal activity against the five tested micro-organisms in a concentration dependent manner. ZnO particles with smaller size, larger specific area and higher porosity exhibit higher antimicrobial activity. Such trends are related to their mechanisms of antimicrobial activity.

  6. Ayurvedic medicine zinc bhasma: physicochemical evaluation, anti-diabetic activity and safety assessment.

    PubMed

    Umrani, Rinku D; Paknikar, Kishore M

    2011-02-01

    Bhasmas are unique Ayurvedic metallic preparations used for medicinal purposes since ancient times. With increasing knowledge of risk of nanomaterials, it becomes imperative to assess the safety of nanoparticulate Ayurvedic medicines using toxicity models. In this study, zinc bhasma was characterized using modern physicochemical techniques. In vitro toxicity test revealed no major cytotoxicity at all the dose levels tested. No behavioral abnormality, clinical signs and mortality was seen indicating no adverse effects. SGOT, SGPT and serum urea were also not significantly altered indicating no major organ toxicity. In the current study, zinc bhasma appears safe for human use.

  7. Active and regulatory sites of cytosolic 5'-nucleotidase.

    PubMed

    Pesi, Rossana; Allegrini, Simone; Careddu, Maria Giovanna; Filoni, Daniela Nicole; Camici, Marcella; Tozzi, Maria Grazia

    2010-12-01

    Cytosolic 5'-nucleotidase (cN-II), which acts preferentially on 6-hydroxypurine nucleotides, is essential for the survival of several cell types. cN-II catalyses both the hydrolysis of nucleotides and transfer of their phosphate moiety to a nucleoside acceptor through formation of a covalent phospho-intermediate. Both activities are regulated by a number of phosphorylated compounds, such as diadenosine tetraphosphate (Ap₄A), ADP, ATP, 2,3-bisphosphoglycerate (BPG) and phosphate. On the basis of a partial crystal structure of cN-II, we mutated two residues located in the active site, Y55 and T56. We ascertained that the ability to catalyse the transfer of phosphate depends on the presence of a bulky residue in the active site very close to the aspartate residue that forms the covalent phospho-intermediate. The molecular model indicates two possible sites at which adenylic compounds may interact. We mutated three residues that mediate interaction in the first activation site (R144, N154, I152) and three in the second (F127, M436 and H428), and found that Ap₄A and ADP interact with the same site, but the sites for ATP and BPG remain uncertain. The structural model indicates that cN-II is a homotetrameric protein that results from interaction through a specific interface B of two identical dimers that have arisen from interaction of two identical subunits through interface A. Point mutations in the two interfaces and gel-filtration experiments indicated that the dimer is the smallest active oligomerization state. Finally, gel-filtration and light-scattering experiments demonstrated that the native enzyme exists as a tetramer, and no further oligomerization is required for enzyme activation.

  8. Critical zinc[sup +2] activities for sour orange determined with chelator-buffered nutrient solutions

    SciTech Connect

    Swietlik, D.; Zhang, L. )

    1994-07-01

    Chelator-buffered nutrient solutions were used to study the effect of different levels of Zn activity in the rhizosphere on growth and nutritive responses of various tissues of sour orange seedlings. The seedlings were grown for 3 months in a growth chamber in a hydroponic culture containing from 5 to 69 [mu]m and 5 to 101 [mu]m total Zn in Expts. 1 and 2, respectively. Zn[sup +2] activities were calculated with a computerized chemical equilibrium model, and buffered by inclusion of a chelator, diethylenetriamine pentaacetate (DTPA), at 74 and 44 [mu]m in excess of the sum of Fe, Mn, Zn, Cu, Ni, and Co in Expts. 1 and 2, respectively. The use of DTPA-buffered solutions proved successful in imposing varying degrees of Zn deficiency. The deficiency was confirmed by leaf symptomatology, leaf chemical analyses, i.e., <16 mg[center dot]kg[sup [minus]1] Zn, and responses to foliar sprays and application of Zn to the roots. Growth parameters varied in their sensitivity to Zn deficiency, i.e., root dry weight < leaf number and white root growth < stem dry weight < leaf dry weight < shoot elongation and leaf area. The critical activities, expressed as pZn = [minus]log(Zn[sup +2]), were [approximately]10.2 [+-] 0.2 for root dry weight, 10.1 [+-] 0.2 for leaf number and white root growth, 10.0 [+-] 0.2 for stem dry weight, 9.9 [+-] 0.2 for leaf dry weight, and 9.8 [+-] 0.2 for shoot growth and leaf area. Increases in growth were observed in response to Zn applications even in the absence of visible Zn-deficiency symptoms. Seedlings containing > 23 mg[center dot]kg[sup [minus]1] Zn in leaves did not respond to further additions of Zn to the nutrient solution. Zinc foliar sprays were less effective than Zn applications to the roots in alleviating severe Zn deficiency because foliar-absorbed Zn was not translocated from the top of the roots and thus could not correct Zn deficiency in the roots.

  9. BAX Activation is Initiated at a Novel Interaction Site

    PubMed Central

    Gavathiotis, Evripidis; Suzuki, Motoshi; Davis, Marguerite L.; Pitter, Kenneth; Bird, Gregory H.; Katz, Samuel G.; Tu, Ho-Chou; Kim, Hyungjin; Cheng, Emily H.-Y.; Tjandra, Nico; Walensky, Loren D.

    2008-01-01

    BAX is a pro-apoptotic protein of the BCL-2 family stationed in the cytosol until activated by a diversity of stress stimuli to induce cell death. Anti-apoptotic proteins such as BCL-2 counteract BAX-mediated cell death. Although an interaction site that confers survival functionality has been defined for anti-apoptotic proteins, an activation site has not been identified for BAX, rendering its explicit trigger mechanism unknown. We previously developed Stabilized Alpha-Helix of BCL-2 domains (SAHBs) that directly initiate BAX-mediated mitochondrial apoptosis. Here we demonstrate by NMR analysis that BIM SAHB binds BAX at an interaction site that is distinct from the canonical binding groove characterized for anti-apoptotic proteins. The specificity of the BIM SAHB-BAX interaction is highlighted by point mutagenesis that abrogates functional activity, confirming that BAX activation is initiated at this novel structural location. Thus, we have now defined a BAX interaction site for direct activation, establishing a new target for therapeutic modulation of apoptosis. PMID:18948948

  10. Enhancement of Odor-Induced Activity in the Canine Brain by Zinc Nanoparticles: A Functional MRI Study in Fully Unrestrained Conscious Dogs.

    PubMed

    Jia, Hao; Pustovyy, Oleg M; Wang, Yun; Waggoner, Paul; Beyers, Ronald J; Schumacher, John; Wildey, Chester; Morrison, Edward; Salibi, Nouha; Denney, Thomas S; Vodyanoy, Vitaly J; Deshpande, Gopikrishna

    2016-01-01

    Using noninvasive in vivo functional magnetic resonance imaging (fMRI), we demonstrate that the enhancement of odorant response of olfactory receptor neurons by zinc nanoparticles leads to increase in activity in olfaction-related and higher order areas of the dog brain. To study conscious dogs, we employed behavioral training and optical motion tracking for reducing head motion artifacts. We obtained brain activation maps from dogs in both anesthetized state and fully conscious and unrestrained state. The enhancement effect of zinc nanoparticles was higher in conscious dogs with more activation in higher order areas as compared with anesthetized dogs. In conscious dogs, voxels in the olfactory bulb and hippocampus showed higher activity to odorants mixed with zinc nanoparticles as compared with pure odorants, odorants mixed with gold nanoparticles as well as zinc nanoparticles alone. These regions have been implicated in odor intensity processing in other species including humans. If the enhancement effect of zinc nanoparticles observed in vivo are confirmed by future behavioral studies, zinc nanoparticles may provide a way for enhancing the olfactory sensitivity of canines for detection of target substances such as explosives and contraband substances at very low concentrations, which would otherwise go undetected.

  11. Removal of residual colonic ciprofloxacin in the rat by activated charcoal entrapped within zinc-pectinate beads.

    PubMed

    Khoder, Mouhamad; Tsapis, Nicolas; Domergue-Dupont, Valérie; Gueutin, Claire; Fattal, Elias

    2010-10-09

    Residual antibiotics reaching the colon have many deleterious effects on the colonic microbiota including the selection of new antibiotic resistances. In order to avoid the selection of ciprofloxacin resistance, intestine or colon-targeted zinc-pectinate beads containing activated charcoal (AC) were designed for the inactivation of residual ciprofloxacin in the gastrointestinal tract of rats. Bead stability after oral administration was adjusted by tuning the concentration of zinc in the gelling bath and the number of washings. Intestine and colon-targeted beads were administered along with 50mg/kg of ciprofloxacin and ciprofloxacin was dosed in the plasma and the feces using HPLC. Ciprofloxacin pharmacokinetics was not affected by the oral co-administration of beads. The co-administration of intestine-targeted beads led to a significant decrease of the residual fecal free ciprofloxacin with a pronounced dose effect. Our study suggests the rat model is not appropriate for the investigation of bacteria responsive colon-targeted beads probably due to the important anatomical and physiological differences between human and rat gastrointestinal tracts. The ability of AC loaded zinc-pectinate beads to selectively decrease the intestinal residual fraction of ciprofloxacin could provide a better protection of the intestinal microbiota and may prevent the emergence of ciprofloxacin resistance in the gastrointestinal tract.

  12. Jasada bhasma, a Zinc-Based Ayurvedic Preparation: Contemporary Evidence of Antidiabetic Activity Inspires Development of a Nanomedicine

    PubMed Central

    2015-01-01

    The roles of metals in human physiology are well established. It is also known that many metals are required in trace amounts for normal metabolism and their deficiency leads to diseases. In Ayurveda, metal-based preparations, that is, bhasmas, are indicated for the treatment of several diseases. Standard textbooks of Ayurveda recommend Jasada bhasma (zinc based bhasma) as the treatment of choice for diabetes. Modern medicine also recognizes the important role of zinc in glucose homeostasis. Yet, studies that validate the use of Jasada bhasma are few and uncomprehensive. There is an imminent need for a systematic study on physicochemical characterization, pharmacological efficacy, and toxicity assessment of several bhasma preparations to generate scientific evidence of their utility and safety. Interestingly, recent studies suggest that bhasmas comprise submicronic particles or nanoparticles. Thus a bhasma-inspired new drug discovery approach could emerge in which several metal based nanomedicines could be developed. This would help in utilizing the age old, time-tested wisdom of Ayurveda in modern medicine. One such study on antidiabetic activity of Jasada bhasma and the corresponding new drug, namely, zinc oxide nanoparticles, is briefly discussed, as an example. PMID:25866533

  13. Geochemical and mineralogical characterization of the abandoned Valzinco (lead-zinc) and Mitchell (gold) mine sites prior to reclamation, Spotsylvania County, Virginia

    USGS Publications Warehouse

    Hammarstrom, Jane M.; Johnson, Adam N.; Seal, Robert R., II; Meier, Allen L.; Briggs, Paul L.; Piatak, Nadine M.

    2006-01-01

    The Virginia gold-pyrite belt, part of the central Virginia volcanic-plutonic belt, hosts numerous abandoned metal mines. The belt extends from about 50 km south of Washington, D.C., for approximately 175 km to the southwest into central Virginia. The rocks that comprise the belt include metamorphosed volcanic and clastic (noncarbonate) sedimentary rocks that were originally deposited during the Ordovician). Deposits that were mined can be classified into three broad categories: 1. volcanic-associated massive sulfide deposits, 2. low-sulfide quartz-gold vein deposits, 3. gold placer deposits, which result from weathering of the vein deposits The massive sulfide deposits were historically mined for iron and pyrite (sulfur), zinc, lead, and copper but also yielded byproduct gold and silver. The most intensely mineralized and mined section of the belt is southwest of Fredericksburg, in the Mineral district of Louisa and Spotsylvania counties. The Valzinco Piatak lead-zinc mine and the Mitchell gold prospect are abandoned sites in Spotsylvania County. As a result of environmental impacts associated with historic mining, both sites were prioritized for reclamation under the Virginia Orphaned Land Program administered by the Virginia Department of Mines, Minerals, and Energy (VDMME). This report summarizes geochemical data for all solid sample media, along with mineralogical data, and results of weathering experiments on Valzinco tailings and field experiments on sediment accumulation in Knights Branch. These data provide a framework for evaluating water-rock interactionsand geoenvironmental signatures of long-abandoned mines developed in massive sulfide deposits and low-sulfide gold-quartz vein deposits in the humid temperate ecosystem domain in the eastern United States.

  14. Involvement of novel autophosphorylation sites in ATM activation.

    PubMed

    Kozlov, Sergei V; Graham, Mark E; Peng, Cheng; Chen, Philip; Robinson, Phillip J; Lavin, Martin F

    2006-08-09

    ATM kinase plays a central role in signaling DNA double-strand breaks to cell cycle checkpoints and to the DNA repair machinery. Although the exact mechanism of ATM activation remains unknown, efficient activation requires the Mre11 complex, autophosphorylation on S1981 and the involvement of protein phosphatases and acetylases. We report here the identification of several additional phosphorylation sites on ATM in response to DNA damage, including autophosphorylation on pS367 and pS1893. ATM autophosphorylates all these sites in vitro in response to DNA damage. Antibodies against phosphoserine 1893 revealed rapid and persistent phosphorylation at this site after in vivo activation of ATM kinase by ionizing radiation, paralleling that observed for S1981 phosphorylation. Phosphorylation was dependent on functional ATM and on the Mre11 complex. All three autophosphorylation sites are physiologically important parts of the DNA damage response, as phosphorylation site mutants (S367A, S1893A and S1981A) were each defective in ATM signaling in vivo and each failed to correct radiosensitivity, genome instability and cell cycle checkpoint defects in ataxia-telangiectasia cells. We conclude that there are at least three functionally important radiation-induced autophosphorylation events in ATM.

  15. Resonant active sites in catalytic ammonia synthesis: A structural model

    NASA Astrophysics Data System (ADS)

    Cholach, Alexander R.; Bryliakova, Anna A.; Matveev, Andrey V.; Bulgakov, Nikolai N.

    2016-03-01

    Adsorption sites Mn consisted of n adjacent atoms M, each bound to the adsorbed species, are considered within a realistic model. The sum of bonds Σ lost by atoms in a site in comparison with the bulk atoms was used for evaluation of the local surface imperfection, while the reaction enthalpy at that site was used as a measure of activity. The comparative study of Mn sites (n = 1-5) at basal planes of Pt, Rh, Ir, Fe, Re and Ru with respect to heat of N2 dissociative adsorption QN and heat of Nad + Had → NHad reaction QNH was performed using semi-empirical calculations. Linear QN(Σ) increase and QNH(Σ) decrease allowed to specify the resonant Σ for each surface in catalytic ammonia synthesis at equilibrium Nad coverage. Optimal Σ are realizable for Ru2, Re2 and Ir4 only, whereas other centers meet steric inhibition or unreal crystal structure. Relative activity of the most active sites in proportion 5.0 × 10- 5: 4.5 × 10- 3: 1: 2.5: 3.0: 1080: 2270 for a sequence of Pt4, Rh4, Fe4(fcc), Ir4, Fe2-5(bcc), Ru2, Re2, respectively, is in agreement with relevant experimental data. Similar approach can be applied to other adsorption or catalytic processes exhibiting structure sensitivity.

  16. Effect of zinc supplementation on superoxide dismutase activity in patients with ulcerative rectocolitis.

    PubMed

    Paz Matias, Juliana; Costa e Silva, Danilla Michelle; Clímaco Cruz, Kyria Jayanne; Gomes da Silva, Kelcylene; Monte Feitosa, Mayara; Oliveira Medeiros, Leydiane Gleici; do Nascimento Marreiro, Dilina; do Nascimento Nogueira, Nadir

    2014-12-17

    Introducción: La colitis ulcerosa se caracteriza por la inflamación difusa de la mucosa y el estrés oxidativo. De esta forma, el cuerpo activa el sistema de defensa antioxidante en un intento de reducir la producción excesiva de especies reactivas de oxígeno, así como poder neutralizarlos. Objetivo: Este estudio evaluó el efecto de la suplementación de zinc sobre la actividad de la enzima superóxido dismutasa en pacientes con colitis ulcerosa. Métodos: El estudio incluyó 24 pacientes, con edades comprendidas entre 20 y 59 años y con diagnóstico de colitis ulcerosa en fase de remisión de la enfermedad. Los pacientes fueron divididos en dos grupos: experimental - deficiencia de zinc (n = 12) y control - normales o con altos contenido de zinc (n = 12). El grupo experimental se sometió a tratamiento con suplemento de drogas, en forma de gluconato de zinc (30 mg Zn / día), administrada diariamente por la mañana en ayunas durante 60 días. Las concentraciones en plasma y los eritrocitos de zinc se determinaron por espectrofotometría de absorción atómica de llama. La actividad de la superóxido dismutasa (SOD) se determinó por el método de eritrocitos in vitro utilizando el kit de Randox. Resultados y Discusión: La suplementación de zinc causó un aumento significativo en las concentraciones plasmáticas de mineral y mostró una reducción significativa en los eritrocitos, permaneciendo dentro de los límites normales. La actividad de SOD fue mayor en los pacientes de los grupos experimentales y de control, sin diferencias después de la suplementación. Conclusión: El estudio evidenció que la administración de suplementos de zinc mejora la condición homeostática del mineral, sin ningún cambio en la actividad de SOD, como un marcador de estrés oxidativo en pacientes con colitis ulcerosa.

  17. Development of nanoporous structure in carbons by chemical activation with zinc chloride.

    PubMed

    Rajbhandari, Rinita; Shrestha, Lok Kumar; Pokharel, Bhadra Prasad; Pradhananga, Raja Ram

    2013-04-01

    Series of activated carbons (ACs) have been prepared from Lapsi (Choerospondias axillaris) seed powder (LSP) by chemical activation with zinc chloride (ZnCI2) and the effects of ZnCl2 impregnation ratio, carbonization time, and precursor sources on the structure and properties of ACs have been systematically investigated. Carbonization was carried out at 400 degrees C and the ratio of LSP and ZnCI2 was varied from LSP:ZnCl2 = 1:0.25 (AC-0.25), 1:0.50 (AC-0.50) 1:1 (AC-1), 1:2 (AC-2), and 1:4 (AC-4). The ACs were characterized by Fourier transform-infrared (FTIR) spectroscopy, Raman scattering, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Surface properties (effective surface areas, pore volumes, and pore size distributions) were studied by nitrogen adsorption-desorption measurements. The electrochemical and vapor sensing properties were investigated by cyclic voltammetry, and quartz crystal microbalance (QCM) method, respectively. All the ACs are amorphous materials containing oxygenated surface functional groups and having nanoporous (microporous and mesoporous) structures. We found that surface properties depend on the LSP:ZnCI2 ratio, carbonization time, and also on the precursor type. The effective surface area increased significantly with increasing LSP:ZnCI2 ratio from 1:0.25 to 1:0.5 and then remain apparently constant. However, total pore volume increased continuously with ZnCI2 ratio. Increase in the carbonization time above 4 h decreased both the surface area and pore volume. ACs prepared from bamboo and coconut shell showed better surface properties compared to AC prepared from sugarcane; surface area and pore volume of the former systems are nearly double of the later system. AC derived from LSP (AC-4) showed excellent electrochemical performance giving specific capacitance value of 328 F/g in 1 M H2SO4 solution demonstrating the potential use of this material for supercapacitor electrodes. Our

  18. Magnetic properties and adsorptive performance of manganese–zinc ferrites/activated carbon nanocomposites

    SciTech Connect

    Zhang, B.B.; Xu, J.C.; Xin, P.H.; Han, Y.B.; Hong, B.; Jin, H.X.; Jin, D.F.; Peng, X.L.; Li, J.; Gong, J.; Ge, H.L.; Zhu, Z.W.; Wang, X.Q.

    2015-01-15

    Owing to the unique microstructure and high specific surface area, activated carbon (AC) could act as an excellent adsorbent for wastewater treatment and good carrier for functional materials. In this paper, manganese–zinc ferrites (Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}: MZF) were anchored into AC by hydrothermal method, resulting in the excellent magnetic response for AC nanocomposites in wastewater treatment. All results demonstrated the magnetic nanoparticles presented a spinel phase structure and existed in the pores of AC. The saturation magnetization (Ms) of MZF/AC nanocomposites increased with the ferrites content, while the pore volume and specific surface area declined. The Sample-5 possessed the specific surface area of 1129 m{sup 2} g{sup −1} (close to 1243 m{sup 2} g{sup −1} of AC) and Ms of 3.96 emu g{sup −1}. Furthermore, the adsorptive performance for organic dyes was studied and 99% methylene blue was adsorbed in 30 min. The magnetic AC nanocomposites could be separated easily from solution by magnetic separation technique. - Graphical abstract: The Sample-5 presented both good magnetic response and high BET surface area up to 1129 m{sup 2} g{sup −1} (close to AC of 1243 m{sup 2} g{sup −1}), which could be separated completely for about 60 s. MZF/AC nanocomposites (Sample-3, 4, 5) in our work could be used as the magnetic absorbents, which could be separated easily by an outer magnet after the MB adsorption. - Highlights: • Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} (MZF) as few as possible was implanted into activated carbon (AC) for the higher surface area. • Sample-5 possessed the high specific surface area (1129 m{sup 2} g{sup −1}) and the suitable Ms (3.96 emu g{sup −1}). • Methylene blue was adsorbed almost completely by MZF/AC nanocomposites in 30 min. • MZF/AC nanocomposites were separated easily from solution by magnetic separation technique.

  19. Antitumor activity of photodynamic therapy performed with nanospheres containing zinc-phthalocyanine

    PubMed Central

    2013-01-01

    Background The increasing incidence of cancer and the search for more effective therapies with minimal collateral effects have prompted studies to find alternative new treatments. Among these, photodynamic therapy (PDT) has been proposed as a very promising new modality in cancer treatment with the lowest rates of side effects, revealing itself to be particularly successful when the photosensitizer is associated with nanoscaled carriers. This study aimed to design and develop a new formulation based on albumin nanospheres containing zinc-phthalocyanine tetrasulfonate (ZnPcS4-AN) for use in the PDT protocol and to investigate its antitumor activity in Swiss albino mice using the Ehrlich solid tumor as an experimental model for breast cancer. Methods Ehrlich tumor’s volume, histopathology and morphometry were used to assess the efficacy of intratumoral injection of ZnPcS4-AN in containing tumor aggressiveness and promoting its regression, while the toxicity of possible treatments was assessed by animal weight, morphological analysis of the liver and kidneys, hemogram, and serum levels of total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transferase (GGT), alkaline phosphatase, creatinine and urea. In order to evaluate the efficacy of PDT, groups of animals treated with intratumoral injection of doxorubicin (Dox) were also investigated. Results Intratumoral injection of ZnPcS4-AN was found to be efficient in mediating PDT to refrain tumor aggressiveness and to induce its regression. Although tumor volume reduction was not significant, PDT induced a remarkable increase in the necrosis area seen in the tumor’s central region, as in other experimental groups, including tumor and Dox treated groups, but also in the tumor’s peripheral region. Further, PDT showed minimal adverse effects. Indeed, the use of ZnPcS4-AN in mediating PDT revealed anti-neoplastic activity similar to that

  20. Zinc-Induced Polymerization of Killer-Cell Ig-like Receptor into Filaments Promotes Its Inhibitory Function at Cytotoxic Immunological Synapses.

    PubMed

    Kumar, Santosh; Rajagopalan, Sumati; Sarkar, Pabak; Dorward, David W; Peterson, Mary E; Liao, Hsien-Shun; Guillermier, Christelle; Steinhauser, Matthew L; Vogel, Steven S; Long, Eric O

    2016-04-07

    The inhibitory function of killer cell immunoglobulin-like receptors (KIR) that bind HLA-C and block activation of human natural killer (NK) cells is dependent on zinc. We report that zinc induced the assembly of soluble KIR into filamentous polymers, as detected by electron microscopy, which depolymerized after zinc chelation. Similar KIR filaments were isolated from lysates of cells treated with zinc, and membrane protrusions enriched in zinc were detected on whole cells by scanning electron microscopy and imaging mass spectrometry. Two independent mutations in the extracellular domain of KIR, away from the HLA-C binding site, impaired zinc-driven polymerization and inhibitory function. KIR filaments formed spontaneously, without the addition of zinc, at functional inhibitory immunological synapses of NK cells with HLA-C(+) cells. Adding to the recent paradigm of signal transduction through higher order molecular assemblies, zinc-induced polymerization of inhibitory KIR represents an unusual mode of signaling by a receptor at the cell surface.

  1. High-pressure Gas Activation for Amorphous Indium-Gallium-Zinc-Oxide Thin-Film Transistors at 100 °C

    NASA Astrophysics Data System (ADS)

    Kim, Won-Gi; Tak, Young Jun; Du Ahn, Byung; Jung, Tae Soo; Chung, Kwun-Bum; Kim, Hyun Jae

    2016-03-01

    We investigated the use of high-pressure gases as an activation energy source for amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs). High-pressure annealing (HPA) in nitrogen (N2) and oxygen (O2) gases was applied to activate a-IGZO TFTs at 100 °C at pressures in the range from 0.5 to 4 MPa. Activation of the a-IGZO TFTs during HPA is attributed to the effect of the high-pressure environment, so that the activation energy is supplied from the kinetic energy of the gas molecules. We reduced the activation temperature from 300 °C to 100 °C via the use of HPA. The electrical characteristics of a-IGZO TFTs annealed in O2 at 2 MPa were superior to those annealed in N2 at 4 MPa, despite the lower pressure. For O2 HPA under 2 MPa at 100 °C, the field effect mobility and the threshold voltage shift under positive bias stress were improved by 9.00 to 10.58 cm2/V.s and 3.89 to 2.64 V, respectively. This is attributed to not only the effects of the pressurizing effect but also the metal-oxide construction effect which assists to facilitate the formation of channel layer and reduces oxygen vacancies, served as electron trap sites.

  2. Solution NMR characterization of Sgf73(1-104) indicates that Zn ion is required to stabilize zinc finger motif

    SciTech Connect

    Lai, Chaohua; Wu, Minhao; Li, Pan; Shi, Chaowei; Tian, Changlin; Zang, Jianye

    2010-07-02

    Zinc finger motif contains a zinc ion coordinated by several conserved amino acid residues. Yeast Sgf73 protein was identified as a component of SAGA (Spt/Ada/Gcn5 acetyltransferase) multi-subunit complex and Sgf73 protein was known to contain two zinc finger motifs. Sgf73(1-104), containing the first zinc finger motif, was necessary to modulate the deubiquitinase activity of SAGA complex. Here, Sgf73(1-104) was over-expressed using bacterial expression system and purified for solution NMR (nuclear magnetic resonance) structural studies. Secondary structure and site-specific relaxation analysis of Sgf73(1-104) were achieved after solution NMR backbone assignment. Solution NMR and circular dichroism analysis of Sgf73(1-104) after zinc ion removal using chelation reagent EDTA (ethylene-diamine-tetraacetic acid) demonstrated that zinc ion was required to maintain stable conformation of the zinc finger motif.

  3. Chemical Modification of Papain and Subtilisin: An Active Site Comparison

    ERIC Educational Resources Information Center

    St-Vincent, Mireille; Dickman, Michael

    2004-01-01

    An experiment using methyle methanethiosulfonate (MMTS) and phenylmethylsulfonyl flouride (PMSF) to specifically modify the cysteine and serine residues in the active sites of papain and subtilism respectively is demonstrated. The covalent modification of these enzymes and subsequent rescue of papain shows the beginning biochemist that proteins…

  4. Spectroscopic studies of the active site of galactose oxidase

    SciTech Connect

    Knowles, P.F.; Brown, R.D. III; Koenig, S.H.

    1995-07-19

    X-ray absorption and EPR spectroscopy have been used to probe the copper site structure in galactose oxidase at pH 4.5 and 7.0. the results suggest that there are no major differences in the structure of the tetragonal Cu(II) site at these pH values. Analysis of the extended X-ray absorption fine structure (EXAFS) indicates that four N,O scatterers are present at approximately 2 {Angstrom}; these are presumably the equatorial ligands. In addition, the EXAFS data establish that oxidative activation to produce the active-site tyrosine radical does not cause major changes in the copper coordination environment. Therefore results obtained on the one-electron reduced enzyme, containing Cu(II) but not the tyrosine radical, probably also apply to the catalytically active Cu(II)/tyrosine radical state. Solvent water exchange, inhibitor binding, and substrate binding have been probed via nuclear magnetic relaxation dispersion (NMRD) measurements. The NMRD profile of galactose oxidase is quantitatively consistent with the rapid exchange of a single, equatorial water ligand with a Cu(II)-O separation of about 2.4 {Angstrom}. Azide and cyanide displace this coordinated water. The binding of azide and the substrate dihydroxyacetone produce very similar effects on the NMRD profile of galactose oxidase, indicating that substrates also bind to the active site Cu(II) in an equatorial position.

  5. Energy transfer at the active sites of heme proteins

    SciTech Connect

    Dlott, D.D.; Hill, J.R.

    1995-12-31

    Experiments using a picosecond pump-probe apparatus at the Picosecond Free-electron Laser Center at Stanford University, were performed to investigate the relaxation of carbon monoxide bound to the active sites of heme proteins. The significance of these experiments is two-fold: (1) they provide detailed information about molecular dynamics occurring at the active sites of proteins; and (2) they provide insight into the nature of vibrational relaxation processes in condensed matter. Molecular engineering is used to construct various molecular systems which are studied with the FEL. We have studied native proteins, mainly myoglobin obtained from different species, mutant proteins produced by genetic engineering using recombinant DNA techniques, and a variety of model systems which mimic the structures of the active sites of native proteins, which are produced using molecular synthesis. Use of these different systems permits us to investigate how specific molecular structural changes affect dynamical processes occurring at the active sites. This research provides insight into the problems of how different species needs are fulfilled by heme proteins which have greatly different functionality, which is induced by rather small structural changes.

  6. The zinc fingers of the SR-like protein ZRANB2 are single-stranded RNA-binding domains that recognize 5′ splice site-like sequences

    SciTech Connect

    Loughlin, Fionna E.; Mansfield, Robyn E.; Vaz, Paula M.; McGrath, Aaron P.; Setiyaputra, Surya; Gamsjaeger, Roland; Chen, Eva S.; Morris, Brian J.; Guss, J. Mitchell; Mackay, Joel P.

    2009-09-02

    The alternative splicing of mRNA is a critical process in higher eukaryotes that generates substantial proteomic diversity. Many of the proteins that are essential to this process contain arginine/serine-rich (RS) domains. ZRANB2 is a widely-expressed and highly-conserved RS-domain protein that can regulate alternative splicing but lacks canonical RNA-binding domains. Instead, it contains 2 RanBP2-type zinc finger (ZnF) domains. We demonstrate that these ZnFs recognize ssRNA with high affinity and specificity. Each ZnF binds to a single AGGUAA motif and the 2 domains combine to recognize AGGUAA(N{sub x})AGGUAA double sites, suggesting that ZRANB2 regulates alternative splicing via a direct interaction with pre-mRNA at sites that resemble the consensus 5{prime} splice site. We show using X-ray crystallography that recognition of an AGGUAA motif by a single ZnF is dominated by side-chain hydrogen bonds to the bases and formation of a guanine-tryptophan-guanine 'ladder.' A number of other human proteins that function in RNA processing also contain RanBP2 ZnFs in which the RNA-binding residues of ZRANB2 are conserved. The ZnFs of ZRANB2 therefore define another class of RNA-binding domain, advancing our understanding of RNA recognition and emphasizing the versatility of ZnF domains in molecular recognition.

  7. The in vitro ejection of zinc from human immunodeficiency virus (HIV) type 1 nucleocapsid protein by disulfide benzamides with cellular anti-HIV activity.

    PubMed Central

    Tummino, P J; Scholten, J D; Harvey, P J; Holler, T P; Maloney, L; Gogliotti, R; Domagala, J; Hupe, D

    1996-01-01

    Several disulfide benzamides have been shown to possess wide-spectrum antiretroviral activity in cell culture at low micromolar to submicromolar concentrations, inhibiting human immunodeficiency virus (HIV) type 1 (HIV-1) clinical and drug-resistant strains along with HIV-2 and simian immunodeficiency virus [Rice, W. G., Supko, J. G., Malspeis, L., Buckheit, R. W., Jr., Clanton, D., Bu, M., Graham, L., Schaeffer, C. A., Turpin, J. A., Domagala, J., Gogliotti, R., Bader, J. P., Halliday, S. M., Coren, L., Sowder, R. C., II, Arthur, L. O. & Henderson, L. E. (1995) Science 270, 1194-1197]. Rice and coworkers have proposed that the compounds act by "attacking" the two zinc fingers of HIV nucleocapsid protein. Shown here is evidence that low micromolar concentrations of the anti-HIV disulfide benzamides eject zinc from HIV nucleocapsid protein (NCp7) in vitro, as monitored by the zinc-specific fluorescent probe N-(6-methoxy-8-quinoyl)-p-toluenesulfonamide (TSQ). Structurally similar disulfide benzamides that do not inhibit HIV-1 in culture do not eject zinc, nor do analogs of the antiviral compounds with the disulfide replaced with a methylene sulfide. The kinetics of NCp7 zinc ejection by disulfide benzamides were found to be nonsaturable and biexponential, with the rate of ejection from the C-terminal zinc finger 7-fold faster than that from the N-terminal. The antiviral compounds were found to inhibit the zinc-dependent binding of NCp7 to HIV psi RNA, as studied by gel-shift assays, and the data correlated well with the zinc ejection data. Anti-HIV disulfide benzamides specifically eject NCp7 zinc and abolish the protein's ability to bind psi RNA in vitro, providing evidence for a possible antiretroviral mechanism of action of these compounds. Congeners of this class are under advanced preclinical evaluation as a potential chemotherapy for acquired immunodeficiency syndrome. Images Fig. 7 PMID:8577770

  8. Stress-responsive mitogen-activated protein kinases interact with the EAR motif of a poplar zinc finger protein and mediate its degradation through the 26S proteasome.

    PubMed

    Hamel, Louis-Philippe; Benchabane, Meriem; Nicole, Marie-Claude; Major, Ian T; Morency, Marie-Josée; Pelletier, Gervais; Beaudoin, Nathalie; Sheen, Jen; Séguin, Armand

    2011-11-01

    Mitogen-activated protein kinases (MAPKs) contribute to the establishment of plant disease resistance by regulating downstream signaling components, including transcription factors. In this study, we identified MAPK-interacting proteins, and among the newly discovered candidates was a Cys-2/His-2-type zinc finger protein named PtiZFP1. This putative transcription factor belongs to a family of transcriptional repressors that rely on an ERF-associated amphiphilic repression (EAR) motif for their repression activity. Amino acids located within this repression motif were also found to be essential for MAPK binding. Close examination of the primary protein sequence revealed a functional bipartite MAPK docking site that partially overlaps with the EAR motif. Transient expression assays in Arabidopsis (Arabidopsis thaliana) protoplasts suggest that MAPKs promote PtiZFP1 degradation through the 26S proteasome. Since features of the MAPK docking site are conserved among other EAR repressors, our study suggests a novel mode of defense mechanism regulation involving stress-responsive MAPKs and EAR repressors.

  9. Activation of phenylalanine hydroxylase by phenylalanine does not require binding in the active site.

    PubMed

    Roberts, Kenneth M; Khan, Crystal A; Hinck, Cynthia S; Fitzpatrick, Paul F

    2014-12-16

    Phenylalanine hydroxylase (PheH), a liver enzyme that catalyzes the hydroxylation of excess phenylalanine in the diet to tyrosine, is activated by phenylalanine. The lack of activity at low levels of phenylalanine has been attributed to the N-terminus of the protein's regulatory domain acting as an inhibitory peptide by blocking substrate access to the active site. The location of the site at which phenylalanine binds to activate the enzyme is unknown, and both the active site in the catalytic domain and a separate site in the N-terminal regulatory domain have been proposed. Binding of catecholamines to the active-site iron was used to probe the accessibility of the active site. Removal of the regulatory domain increases the rate constants for association of several catecholamines with the wild-type enzyme by ∼2-fold. Binding of phenylalanine in the active site is effectively abolished by mutating the active-site residue Arg270 to lysine. The k(cat)/K(phe) value is down 10⁴ for the mutant enzyme, and the K(m) value for phenylalanine for the mutant enzyme is >0.5 M. Incubation of the R270K enzyme with phenylalanine also results in a 2-fold increase in the rate constants for catecholamine binding. The change in the tryptophan fluorescence emission spectrum seen in the wild-type enzyme upon activation by phenylalanine is also seen with the R270K mutant enzyme in the presence of phenylalanine. Both results establish that activation of PheH by phenylalanine does not require binding of the amino acid in the active site. This is consistent with a separate allosteric site, likely in the regulatory domain.

  10. Green synthesis, characterization and antimicrobial activities of zinc oxide nanoparticles from the leaf extract of Azadirachta indica (L.)

    NASA Astrophysics Data System (ADS)

    Elumalai, K.; Velmurugan, S.

    2015-08-01

    The synthesis of metal and semiconductor nanoparticles is an expanding research area due to the potential applications in the development of novel technologies. Especially, biologically synthesized nanomaterial has become an important branch of nanotechnology. The present work, described the synthesis of zinc oxide nanoparticles (ZnO NPs) using leaf aqueous extract of Azadirachta indica (L.) and its antimicrobial activities. The nanoparticles was obtain characterized by UV-Vis spectroscopy, Photoluminescence (PL), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM) analysis, Energy dispersive X-ray analysis (EDAX), Field emission scanning electron microscopy (FESEM) and Atomic force microscope (AFM) analysis. In this study we also investigated antimicrobial activity of green synthesized ZnO NPs. The results depicted concentration of ZnO NPs was increased (50, 100, 200 μg/mL) and also increase in antimicrobial activities was due to the increase of H2O2 concentration from the surface of ZnO. However, green synthesized ZnO NPs was more potent than Bare ZnO and leaf of A. indica. Finally concluded the zinc oxide nanoparticles exhibited an interesting antimicrobial activity with both Gram positive and Gram negative bacterial and yeast at micromolar concentration.

  11. Changes in active site histidine hydrogen bonding trigger cryptochrome activation.

    PubMed

    Ganguly, Abir; Manahan, Craig C; Top, Deniz; Yee, Estella F; Lin, Changfan; Young, Michael W; Thiel, Walter; Crane, Brian R

    2016-09-06

    Cryptochrome (CRY) is the principal light sensor of the insect circadian clock. Photoreduction of the Drosophila CRY (dCRY) flavin cofactor to the anionic semiquinone (ASQ) restructures a C-terminal tail helix (CTT) that otherwise inhibits interactions with targets that include the clock protein Timeless (TIM). All-atom molecular dynamics (MD) simulations indicate that flavin reduction destabilizes the CTT, which undergoes large-scale conformational changes (the CTT release) on short (25 ns) timescales. The CTT release correlates with the conformation and protonation state of conserved His378, which resides between the CTT and the flavin cofactor. Poisson-Boltzmann calculations indicate that flavin reduction substantially increases the His378 pKa Consistent with coupling between ASQ formation and His378 protonation, dCRY displays reduced photoreduction rates with increasing pH; however, His378Asn/Arg variants show no such pH dependence. Replica-exchange MD simulations also support CTT release mediated by changes in His378 hydrogen bonding and verify other responsive regions of the protein previously identified by proteolytic sensitivity assays. His378 dCRY variants show varying abilities to light-activate TIM and undergo self-degradation in cellular assays. Surprisingly, His378Arg/Lys variants do not degrade in light despite maintaining reactivity toward TIM, thereby implicating different conformational responses in these two functions. Thus, the dCRY photosensory mechanism involves flavin photoreduction coupled to protonation of His378, whose perturbed hydrogen-bonding pattern alters the CTT and surrounding regions.

  12. Changes in active site histidine hydrogen bonding trigger cryptochrome activation

    PubMed Central

    Ganguly, Abir; Manahan, Craig C.; Top, Deniz; Yee, Estella F.; Lin, Changfan; Young, Michael W.; Thiel, Walter; Crane, Brian R.

    2016-01-01

    Cryptochrome (CRY) is the principal light sensor of the insect circadian clock. Photoreduction of the Drosophila CRY (dCRY) flavin cofactor to the anionic semiquinone (ASQ) restructures a C-terminal tail helix (CTT) that otherwise inhibits interactions with targets that include the clock protein Timeless (TIM). All-atom molecular dynamics (MD) simulations indicate that flavin reduction destabilizes the CTT, which undergoes large-scale conformational changes (the CTT release) on short (25 ns) timescales. The CTT release correlates with the conformation and protonation state of conserved His378, which resides between the CTT and the flavin cofactor. Poisson-Boltzmann calculations indicate that flavin reduction substantially increases the His378 pKa. Consistent with coupling between ASQ formation and His378 protonation, dCRY displays reduced photoreduction rates with increasing pH; however, His378Asn/Arg variants show no such pH dependence. Replica-exchange MD simulations also support CTT release mediated by changes in His378 hydrogen bonding and verify other responsive regions of the protein previously identified by proteolytic sensitivity assays. His378 dCRY variants show varying abilities to light-activate TIM and undergo self-degradation in cellular assays. Surprisingly, His378Arg/Lys variants do not degrade in light despite maintaining reactivity toward TIM, thereby implicating different conformational responses in these two functions. Thus, the dCRY photosensory mechanism involves flavin photoreduction coupled to protonation of His378, whose perturbed hydrogen-bonding pattern alters the CTT and surrounding regions. PMID:27551082

  13. Chlorovirus PBCV-1 Encodes an Active Copper-Zinc Superoxide Dismutase

    PubMed Central

    Kang, Ming; Duncan, Garry A.; Kuszynski, Charles; Oyler, George; Zheng, Jiayin; Becker, Donald F.

    2014-01-01

    ABSTRACT Superoxide dismutases (SODs) are metalloproteins that protect organisms from toxic reactive oxygen species by catalyzing the conversion of superoxide anion to hydrogen peroxide and molecular oxygen. Chlorovirus PBCV-1 encodes a 187-amino-acid protein that resembles a Cu-Zn SOD with all of the conserved amino acid residues for binding copper and zinc (named cvSOD). cvSOD has an internal Met that results in a 165-amino-acid protein (named tcvSOD). Both cvSOD and tcvSOD recombinant proteins inhibited nitroblue tetrazolium reduction of superoxide anion generated in a xanthine-xanthine oxidase system in solution. tcvSOD was chosen for further characterization because it was easier to produce. Recombinant tcvSOD also inhibited a riboflavin photochemical reduction system in a polyacrylamide gel assay, which was blocked by the Cu-Zn SOD inhibitor cyanide but not by azide, which inhibits Fe and Mn SODs. A kcat/Km value for cvSOD was determined by stop-flow spectrophotometry as 1.28 × 108 M−1 s−1, suggesting that cvSOD-catalyzed O2− dismutation was not a diffusion controlled encounter. The cvsod gene was expressed as a late gene, and cvSOD activity was detected in purified virions. Superoxide accumulated rapidly during virus infection, and circumstantial evidence indicates that cvSOD aids its decomposition to benefit virus replication. Cu-Zn SOD homologs have been described to occur in 3 other families of large DNA viruses, poxviruses, baculoviruses, and mimiviruses, which group as a clade. Interestingly, cvSOD does not group in the same clade as the other virus SODs but instead groups in an expanded clade that includes Cu-Zn SODs from many cellular organisms. IMPORTANCE Virus infection often leads to an increase in toxic reactive oxygen species in the host, which can be detrimental to virus replication. Viruses have developed various ways to overcome this barrier. As reported in this article, the chloroviruses often encode and package a functional Cu

  14. Oxygen dependence of two-photon activation of zinc and copper phthalocyanine tetrasulfonate in Jurkat cells.

    PubMed

    Mir, Youssef; van Lier, Johan E; Paquette, Benoit; Houde, Daniel

    2008-01-01

    Photodynamic therapy (PDT), the use of light-activated drugs, is a promising treatment of cancer as well as several nonmalignant conditions. However, the efficacy of one-photon (1-gamma) PDT is limited by hypoxia, which can prevent the production of the cytotoxic singlet oxygen ((1)O(2)) species, leading to tumor resistance to PDT. To solve this problem, we propose an irradiation protocol based on a simultaneous, two-photon (2-gamma) excitation of the photosensitizer (Ps). Excitation of the Ps triplet state leads to an upper excited triplet state T(n) with distinct photochemical properties, which could inflict biologic damage independent of the presence of molecular oxygen. To determine the potential of a 2-gamma excitation process, Jurkat cells were incubated with zinc or copper phthalocyanine tetrasulfonate (ZnPcS(4) or CuPcS(4)). ZnPcS(4) is a potent (1)O(2) generator in 1-gamma PDT, while CuPcS(4) is inactive under these conditions. Jurkat cells incubated with either ZnPcS(4) or CuPcS(4) were exposed to a 670 nm continuous laser (1-gamma PDT), 532 nm pulsed-laser light (2-gamma PDT), or a combination of 532 and 670 nm (2-gamma PDT). The efficacy of ZnPcS(4) to photoinactivate the Jurkat cells decreased as the concentration of oxygen decreased for both the 1-gamma and 2-gamma protocols. In the case of CuPcS(4), cell phototoxicity was measured only following 2-gamma irradiation, and its efficacy also decreased at a lower oxygen concentration. Our results suggest that for CuPcS(4) the T(n) excited state can be populated after 2-gamma irradiation at 532 nm or the combination of 532 and 670 nm light. Dependency of phototoxicity upon aerobic conditions for both 1-gamma and 2-gamma PDT suggests that reactive oxygen species play an important role in 1-gamma and 2-gamma PDT.

  15. Anti-urolithiatic activity of standardized extract of Biophytum sensitivum against zinc disc implantation induced urolithiasis in rats.

    PubMed

    Pawar, Anil Tukaram; Vyawahare, Niraj S

    2015-01-01

    Biophytum sensitivum (L.) DC (family: Oxalidaceae) has been used in the Indian indigenous system of medicine, Ayurveda, for the treatment of various health aliments including renal calculi. The present study was undertaken to investigate the anti-urolithiatic activity of standardized methanolic extract of whole plant of B. sensitivum (MBS) in rats. Urolithiasis was induced by surgical implantations of zinc disc in the urinary bladders of rats. Upon postsurgical recovery, different doses of MBS (viz., 100, 200, and 400 mg/kg body weight) were administered to zinc disc-implanted rats for the period of 7 days by the oral route. Anti-urolithiatic activity was evaluated by measuring various dimensions of stones and estimating levels of various biomarkers in serum and urine samples. A significant decrease in urinary output was observed in the disc-implanted animals, which was prevented by the MBS treatment. Supplementation with MBS caused significant improvement in glomerular filtration rate and protein excretion. The elevated levels of serum creatinine, uric acid, and blood urea nitrogen were also prevented by the MBS treatment. The MBS treatment showed reduced formation of deposition around the implanted zinc disc. The higher dose of MBS (400 mg/kg) found more effective. These results indicate that the administration of MBS significantly prevents the growth of urinary stones. The possible mechanism underlying this effect is mediated collectively through diuretic, antioxidant and anti-inflammatory effects of the plant. The results concluded that the methanolic extract of whole plant of B. sensitivum possessed significant anti-urolithiatic activity.

  16. Anti-urolithiatic activity of standardized extract of Biophytum sensitivum against zinc disc implantation induced urolithiasis in rats

    PubMed Central

    Pawar, Anil Tukaram; Vyawahare, Niraj S.

    2015-01-01

    Biophytum sensitivum (L.) DC (family: Oxalidaceae) has been used in the Indian indigenous system of medicine, Ayurveda, for the treatment of various health aliments including renal calculi. The present study was undertaken to investigate the anti-urolithiatic activity of standardized methanolic extract of whole plant of B. sensitivum (MBS) in rats. Urolithiasis was induced by surgical implantations of zinc disc in the urinary bladders of rats. Upon postsurgical recovery, different doses of MBS (viz., 100, 200, and 400 mg/kg body weight) were administered to zinc disc-implanted rats for the period of 7 days by the oral route. Anti-urolithiatic activity was evaluated by measuring various dimensions of stones and estimating levels of various biomarkers in serum and urine samples. A significant decrease in urinary output was observed in the disc-implanted animals, which was prevented by the MBS treatment. Supplementation with MBS caused significant improvement in glomerular filtration rate and protein excretion. The elevated levels of serum creatinine, uric acid, and blood urea nitrogen were also prevented by the MBS treatment. The MBS treatment showed reduced formation of deposition around the implanted zinc disc. The higher dose of MBS (400 mg/kg) found more effective. These results indicate that the administration of MBS significantly prevents the growth of urinary stones. The possible mechanism underlying this effect is mediated collectively through diuretic, antioxidant and anti-inflammatory effects of the plant. The results concluded that the methanolic extract of whole plant of B. sensitivum possessed significant anti-urolithiatic activity. PMID:26605159

  17. Probing the promiscuous active site of myo-inositol dehydrogenase using synthetic substrates, homology modeling, and active site modification.

    PubMed

    Daniellou, Richard; Zheng, Hongyan; Langill, David M; Sanders, David A R; Palmer, David R J

    2007-06-26

    The active site of myo-inositol dehydrogenase (IDH, EC 1.1.1.18) from Bacillus subtilis recognizes a variety of mono- and disaccharides, as well as 1l-4-O-substituted inositol derivatives. It catalyzes the NAD+-dependent oxidation of the axial alcohol of these substrates with comparable kinetic constants. We have found that 4-O-p-toluenesulfonyl-myo-inositol does not act as a substrate for IDH, in contrast to structurally similar compounds such as those bearing substituted benzyl substituents in the same position. X-ray crystallographic analysis of 4-O-p-toluenesulfonyl-myo-inositol and 4-O-(2-naphthyl)methyl-myo-inositol, which is a substrate for IDH, shows a distinct difference in the preferred conformation of the aryl substituent. Conformational analysis of known substrates of IDH suggests that this conformational difference may account for the difference in reactivity of 4-O-p-toluenesulfonyl-myo-inositol in the presence of IDH. A sequence alignment of IDH with the homologous glucose-fructose oxidoreductase allowed the construction of an homology model of inositol dehydrogenase, to which NADH and 4-O-benzyl-scyllo-inosose were docked and the active site energy minimized. The active site model is consistent with all experimental results and suggests that a conserved tyrosine-glycine-tyrosine motif forms the hydrophobic pocket adjoining the site of inositol recognition. Y233F and Y235F retain activity, while Y233R and Y235R do not. A histidine-aspartate pair, H176 and D172, are proposed to act as a dyad in which H176 is the active site acid/base. The enzyme is inactivated by diethyl pyrocarbonate, and the mutants H176A and D172N show a marked loss of activity. Kinetic isotope effect experiments with D172N indicate that chemistry is rate-determining for this mutant.

  18. Role of sensitivity of zinc oxide nanorods (ZnO-NRs) based photosensitizers in hepatocellular site of biological tissue

    NASA Astrophysics Data System (ADS)

    Atif, M.; Fakhar-E-Alam, M.; Alsalhi, M. S.

    2011-11-01

    Zinc oxide nanorods (ZnO-NRs) with high surface to volume ratio and bio compatibility are used as an efficient photosensitizer carrier system for achievement of Hepatocellular cancer cell (HepG2) necrosis within few minutes. Present study highlights the role of effectiveness of ZnO-NRs in photodynamic therapy (PDT). We have grown the ZnO-NRs on the tip of borosilicate glass capillaries (0.5 μm diameter). The grown ZnO-NRs were conjugated using Photofrin® and ALA for the efficient intracellular drug delivery, which produces reactive oxygen species (ROS) via photochemical reactions leading to cell death within few minutes after exposing UV light (240 nm). Viability of controlled and treated HepG2 cells with optimum dose of light (UV-visible) has been assessed by neutral red assay (NRA). The results were verified by staining of mitochondria using Mitotracker® red as an efficient dye as well as ROS detection. ZnO-NRs based Phogem® (PG) treated normal liver tissues of Sprague-Dawley rats were used as comparative experimental model. Morphological apoptotic changes in liver tissue of Sprague-Dawley rats before and after ZnO-NRs conjugated with photosensitizer (PS)-mediated PDT were investigated by microscopic examination.

  19. Site-specific host gene modification by zinc finger nucleases: pointing the way to drug free control of HIV-1?

    PubMed Central

    Sasson, Sarah C; Kelleher, Anthony D

    2014-01-01

    Anti-retroviral therapy (ART) for human immunodeficiency virus-1 (HIV-1) infection has transformed its clinical course with spectacular reductions in morbidity and mortality, turning this once fatal diagnosis into a manageable chronic infection. However, ART has its limitations. Current ART does not eliminate the virus. Interruption of therapy results in rapid rebound of the virus, and such rebounds are associated with excess morbidity and mortality. This means that therapy once started is for life. This raises the issues of drug resistance due to suboptimal compliance, cumulative toxicities and mounting costs. Efforts to control the virus through novel interventions, particularly through cell or gene therapy have had a resurgence of interest as a single patient was apparently cured by an allogeneic stem cell transplantation from a donor who carried homozygous mutations that disable expression of the HIV-1 co-receptor CCR5. This paper reviews the state of play of gene therapy for HIV infection in the context of a recent paper showing the safety and feasibility of an approach that involves the ex vivo disruption of the ccr5 gene in autologous CD4 T cells using a virally delivered zinc finger nuclease, before their expansion and reinfusion. Although there are still considerable challenges, this approach may point towards a future drug free therapy for HIV-1 infection. PMID:25505967

  20. The active site structure and mechanism of phosphoenolpyruvate utilizing enzymes

    SciTech Connect

    Cheng, K.C.

    1989-01-01

    Arginine specific reagents showed irreversible inhibition of avian liver mitochondrial phosphoenolpyruvate carboxykinase. Potent protection against modification was elicited by CO{sub 2} or CO{sub 2} in the presence of other substrates. Labeling of enzyme with (7-{sup 14}C) phenylglyoxal showed that 1 or 2 arginines are involved in CO{sub 2} binding and activation. Peptide map studies showed this active site arginine residues is located at position 289. Histidine specific reagents showed pseudo first order inhibition of avian mitochondrial phosphoenolpyruvate carboxykinase activity. The best protection against modification was elicited by IDP or IDP and Mn{sup +2}. One histidine residue is at or near the phosphoenolpyruvate binding site as demonstrated in the increased absorbance at 240 nm and proton relaxation rate studies. Circular dichroism studies reveal that enzyme structure was perturbed by diethylpyrocarbonate modification. Metal binding studies suggest that this enzyme has only one metal binding site. The putative binding sites from several GTP and phosphoenolpyruvate utilizing enzymes are observed in P-enolpyruvate carboxykinase from different species.

  1. Behavioral Abnormality Induced by Enhanced Hypothalamo-Pituitary-Adrenocortical Axis Activity under Dietary Zinc Deficiency and Its Usefulness as a Model.

    PubMed

    Takeda, Atsushi; Tamano, Haruna; Nishio, Ryusuke; Murakami, Taku

    2016-07-16

    Dietary zinc deficiency increases glucocorticoid secretion from the adrenal cortex via enhanced hypothalamo-pituitary-adrenocortical (HPA) axis activity and induces neuropsychological symptoms, i.e., behavioral abnormality. Behavioral abnormality is due to the increase in glucocorticoid secretion rather than disturbance of brain zinc homeostasis, which occurs after the increase in glucocorticoid secretion. A major target of glucocorticoids is the hippocampus and their actions are often associated with disturbance of glutamatergic neurotransmission, which may be linked to behavioral abnormality, such as depressive symptoms and aggressive behavior under zinc deficiency. Glucocorticoid-mediated disturbance of glutamatergic neurotransmission in the hippocampus is also involved in the pathophysiology of, not only psychiatric disorders, such as depression, but also neurodegenerative disorders, e.g., Alzheimer's disease. The evidence suggests that zinc-deficient animals are models for behavioral and psychological symptoms of dementia (BPSD), as well as depression. To understand validity to apply zinc-deficient animals as a behavioral abnormality model, this paper deals with the effect of antidepressive drugs and herbal medicines on hippocampal dysfunctions and behavioral abnormality, which are induced by enhanced HPA axis activity under dietary zinc deficiency.

  2. Evaluation and comparison of zinc absorption level from 2-Alkyle 3-Hydroxy pyranon-zinc complexes and zinc sulfate in rat in vivo

    PubMed Central

    Akbar, Badii; Niloufar, Nekouei; Abolfazl, Mostafavi; Lofollah, Saghaei; Ali, Khodarahmi Qadam; Soheyla, Valadian

    2013-01-01

    Background: Although zinc sulfate has been used to improve disorders originated from zinc deficiency, its low compliance is due to gastrointestinal complications; therefore, other zinc compounds have been suggested as replacers for zinc deficient people. The objective of this study was to evaluate and compare the absorption of ethyl and methyl zinc-maltol with that of zinc sulfate to substitute zinc sulfate with those complexes. Materials and Methods: After five weeks of being fed by zinc deficient food, zinc deficient rats were divided into four groups randomly receiving medicinal solutions of zinc sulfate, zinc ethyl maltol and zinc methyl maltol using feeding tube method for two weeks while the control was received distilled water. Serum zinc concentration and ALP (Alkaline Phosphatase) and LDH (Lactate Dehydrogenase) activity of rats were determined before and after the study. Statistical analyses were performed using SPSS 11.5. The study was conducted from 2008 to 2010. Results: Serum zinc concentration and enzyme activity in all groups receiving drug solution increased. The most and least increase were in zinc sulfate and zinc methyl maltol groups, respectively. The difference between zinc methyl maltol and zinc sulfate group was significant (P < 0.05); however, this difference was not significant in the case of zinc ethyl maltol. Conclusion: Zinc ethyl maltol can be a suitable and preferable substitute for zinc sulfate. PMID:24223392

  3. On the active site of mononuclear B1 metallo β-lactamases: a computational study

    NASA Astrophysics Data System (ADS)

    Sgrignani, Jacopo; Magistrato, Alessandra; Dal Peraro, Matteo; Vila, Alejandro J.; Carloni, Paolo; Pierattelli, Roberta

    2012-04-01

    Metallo-β-lactamases (MβLs) are Zn(II)-based bacterial enzymes that hydrolyze β-lactam antibiotics, hampering their beneficial effects. In the most relevant subclass (B1), X-ray crystallography studies on the enzyme from Bacillus Cereus point to either two zinc ions in two metal sites (the so-called `3H' and `DCH' sites) or a single Zn(II) ion in the 3H site, where the ion is coordinated by Asp120, Cys221 and His263 residues. However, spectroscopic studies on the B1 enzyme from B. Cereus in the mono-zinc form suggested the presence of the Zn(II) ion also in the DCH site, where it is bound to an aspartate, a cysteine, a histidine and a water molecule. A structural model of this enzyme in its DCH mononuclear form, so far lacking, is therefore required for inhibitor design and mechanistic studies. By using force field based and mixed quantum-classical (QM/MM) molecular dynamics (MD) simulations of the protein in aqueous solution we constructed such structural model. The geometry and the H-bond network at the catalytic site of this model, in the free form and in complex with two common β-lactam drugs, is compared with experimental and theoretical findings of CphA and the recently solved crystal structure of new B2 MβL from Serratia fonticola (Sfh-I). These are MβLs from the B2 subclass, which features an experimentally well established mono-zinc form, in which the Zn(II) is located in the DCH site. From our simulations the ɛɛδ and δɛδ protomers emerge as possible DCH mono-zinc reactive species, giving a novel contribution to the discussion on the MβL reactivity and to the drug design process.

  4. 46 CFR 148.330 - Zinc ashes; zinc dross; zinc residues; zinc skimmings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Zinc ashes; zinc dross; zinc residues; zinc skimmings... Materials § 148.330 Zinc ashes; zinc dross; zinc residues; zinc skimmings. (a) The shipper must inform the cognizant Coast Guard Captain of the Port in advance of any cargo transfer operations involving zinc...

  5. 46 CFR 148.330 - Zinc ashes; zinc dross; zinc residues; zinc skimmings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Zinc ashes; zinc dross; zinc residues; zinc skimmings... Materials § 148.330 Zinc ashes; zinc dross; zinc residues; zinc skimmings. (a) The shipper must inform the cognizant Coast Guard Captain of the Port in advance of any cargo transfer operations involving zinc...

  6. 46 CFR 148.330 - Zinc ashes; zinc dross; zinc residues; zinc skimmings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Zinc ashes; zinc dross; zinc residues; zinc skimmings... Materials § 148.330 Zinc ashes; zinc dross; zinc residues; zinc skimmings. (a) The shipper must inform the cognizant Coast Guard Captain of the Port in advance of any cargo transfer operations involving zinc...

  7. 46 CFR 148.330 - Zinc ashes; zinc dross; zinc residues; zinc skimmings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Zinc ashes; zinc dross; zinc residues; zinc skimmings... Materials § 148.330 Zinc ashes; zinc dross; zinc residues; zinc skimmings. (a) The shipper must inform the cognizant Coast Guard Captain of the Port in advance of any cargo transfer operations involving zinc...

  8. Trans-synaptic zinc mobilization improves social interaction in two mouse models of autism through NMDAR activation

    PubMed Central

    Lee, Eun-Jae; Lee, Hyejin; Huang, Tzyy-Nan; Chung, Changuk; Shin, Wangyong; Kim, Kyungdeok; Koh, Jae-Young; Hsueh, Yi-Ping; Kim, Eunjoon

    2015-01-01

    Genetic aspects of autism spectrum disorders (ASDs) have recently been extensively explored, but environmental influences that affect ASDs have received considerably less attention. Zinc (Zn) is a nutritional factor implicated in ASDs, but evidence for a strong association and linking mechanism is largely lacking. Here we report that trans-synaptic Zn mobilization rapidly rescues social interaction in two independent mouse models of ASD. In mice lacking Shank2, an excitatory postsynaptic scaffolding protein, postsynaptic Zn elevation induced by clioquinol (a Zn chelator and ionophore) improves social interaction. Postsynaptic Zn is mainly derived from presynaptic pools and activates NMDA receptors (NMDARs) through postsynaptic activation of the tyrosine kinase Src. Clioquinol also improves social interaction in mice haploinsufficient for the transcription factor Tbr1, which accompanies NMDAR activation in the amygdala. These results suggest that trans-synaptic Zn mobilization induced by clioquinol rescues social deficits in mouse models of ASD through postsynaptic Src and NMDAR activation. PMID:25981743

  9. ROS-dependent anticandidal activity of zinc oxide nanoparticles synthesized by using egg albumen as a biotemplate

    NASA Astrophysics Data System (ADS)

    Shoeb, M.; Singh, Braj R.; Khan, Javed A.; Khan, Wasi; Singh, Brahma N.; Singh, Harikesh B.; Naqvi, Alim H.

    2013-09-01

    Zinc oxide nanoparticles (ZnO NPs) have attracted great attention because of their superior optical properties and wide application in biomedical science. However, little is known about the anticandidal activity of ZnO NPs against Candida albicans (C. albicans). This study was designed to develop the green approach to synthesize ZnO NPs using egg white (denoted as EtZnO NPs) and investigated its possible mechanism of antimicrobial activity against C. albicans 077. It was also notable that anticandidal activity of EtZnO NPs is correlated with reactive oxygen species (ROS) production in a dose dependent manner. Protection of histidine against ROS clearly suggests the implication of ROS in anticandidal activity of EtZnO NPs. This green approach based on egg white-mediated synthesis of ZnO NPs paves the way for developing cost effective, eco-friendly and promising antimicrobial nanomaterial for applications in medicine.

  10. Trans-synaptic zinc mobilization improves social interaction in two mouse models of autism through NMDAR activation.

    PubMed

    Lee, Eun-Jae; Lee, Hyejin; Huang, Tzyy-Nan; Chung, Changuk; Shin, Wangyong; Kim, Kyungdeok; Koh, Jae-Young; Hsueh, Yi-Ping; Kim, Eunjoon

    2015-05-18

    Genetic aspects of autism spectrum disorders (ASDs) have recently been extensively explored, but environmental influences that affect ASDs have received considerably less attention. Zinc (Zn) is a nutritional factor implicated in ASDs, but evidence for a strong association and linking mechanism is largely lacking. Here we report that trans-synaptic Zn mobilization rapidly rescues social interaction in two independent mouse models of ASD. In mice lacking Shank2, an excitatory postsynaptic scaffolding protein, postsynaptic Zn elevation induced by clioquinol (a Zn chelator and ionophore) improves social interaction. Postsynaptic Zn is mainly derived from presynaptic pools and activates NMDA receptors (NMDARs) through postsynaptic activation of the tyrosine kinase Src. Clioquinol also improves social interaction in mice haploinsufficient for the transcription factor Tbr1, which accompanies NMDAR activation in the amygdala. These results suggest that trans-synaptic Zn mobilization induced by clioquinol rescues social deficits in mouse models of ASD through postsynaptic Src and NMDAR activation.

  11. Phosphorylation of zinc channel ZIP7 drives MAPK, PI3K and mTOR growth and proliferation signalling.

    PubMed

    Nimmanon, T; Ziliotto, S; Morris, S; Flanagan, L; Taylor, K M

    2017-02-16

    Zinc is an essential trace element participating in diverse biological processes. Cellular zinc levels are strictly controlled by two families of transport proteins: ZIP channels (SLC39A) and ZnT transporters (SLC30A). ZIP channels increase cytosolic zinc levels by importing zinc into cells or releasing zinc from intracellular stores such as the ER. Among all the 14 human members of the ZIP family, ZIP7 is a gatekeeper of zinc release from intracellular stores, requiring post-translational activation by phosphorylation on residues S275 and S276, resulting in activation of multiple downstream pathways. Employing site-directed mutagenesis, we investigated the importance of these individual serine residues as well as other predicted phosphorylation sites on ZIP7, showing that all four sites are required for maximal ZIP7 activation. Using phosphor-protein arrays, we also discovered the major signalling pathways that were activated as a direct result of ZIP7-mediated zinc release from intracellular stores. These data reveal the role of ZIP7-mediated zinc release from intracellular stores in driving major pathways, such as MAPK, mTOR and PI3K-AKT, involved in providing cell survival and proliferation and often over activated in cancer.

  12. Target selectivity of vertebrate notch proteins. Collaboration between discrete domains and CSL-binding site architecture determines activation probability.

    PubMed

    Ong, Chin-Tong; Cheng, Hui-Teng; Chang, Li-Wei; Ohtsuka, Toshiyuki; Kageyama, Ryoichiro; Stormo, Gary D; Kopan, Raphael

    2006-02-24

    All four mammalian Notch proteins interact with a single DNA-binding protein (RBP-jkappa), yet they are not equivalent in activating target genes. Parallel assays of three Notch-responsive promoters in several cell lines revealed that relative activation strength is dependent on protein module and promoter context more than the cellular context. Each Notch protein reads binding site orientation and distribution on the promoter differently; Notch1 performs extremely well on paired sites, and Notch3 prefers single sites in conjunction with a proximal zinc finger transcription factor. Although head-head sites can elicit a Notch response on their own, use of CBS (CSL binding site) in tail-tail orientation is context-dependent. Bias for specific DNA elements is achieved by interplay between the N-terminal RAM (RBP-jkappa-associated molecule/ankyrin region), which interprets CBS proximity and orientation, and the C-terminal transactivation domain that interacts specifically with the transcription machinery or nearby factors. To confirm the prediction that modular design underscores the evolution of functional divergence between Notch proteins, we generated a synthetic Notch protein (Notch1 ankyrin with Notch3 transactivation domain) that displayed superior signaling strength on the hes5 promoter. Consistent with the prediction that "preferred" targets (Hes1) should respond faster and at lower Notch concentration than other targets, we showed that Hes5-GFP was extinguished fast and recovered slowly, whereas Hes1-GFP was inhibited late and recovered quickly after a pulse of DAPT in metanephroi cultures.

  13. Identification of Ice Nucleation Active Sites on Silicate Dust Particles

    NASA Astrophysics Data System (ADS)

    Zolles, Tobias; Burkart, Julia; Häusler, Thomas; Pummer, Bernhard; Hitzenberger, Regina; Grothe, Hinrich

    2015-04-01

    Mineral dusts originating from Earth's crust are known to be important atmospheric ice nuclei. In agreement with earlier studies, feldspar was found as the most active of the tested natural mineral dusts [1-3]. Nevertheless, among those structures K-feldspar showed by far the highest ice nucleation activity. In this study, the reasons for its activity and the difference in the activity of the different feldspars were investigated in closer details. Conclusions are drawn from scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, and oil-immersion freezing experiments. We give a potential explanation of the increased ice nucleation activity of K-feldspar. The ice nucleating sites are very much dependent on the alkali ion present by altering the water structure and the feldspar surface. The higher activity of K-feldspar can be attributed to the presence of potassium ions on the surface and surface bilayer. The alkali-ions have different hydration shells and thus an influence on the ice nucleation activity of feldspar. Chaotropic behavior of Calcium and Sodium ions are lowering the ice nucleation potential of the other feldspars, while kosmotropic Potassium has a neutral or even positive effect. Furthermore we investigated the influence of milling onto the ice nucleation of quartz particles. The ice nucleation activity can be increased by mechanical milling, by introducing more molecular, nucleation active defects to the particle surface. This effect is larger than expected by plane surface increase. [1] Atkinson et al. The Importance of Feldspar for Ice Nucleation by Mineral Dust in Mixed-Phase Clouds. Nature 2013, 498, 355-358. [2] Yakobi-Hancock et al.. Feldspar Minerals as Efficient Deposition Ice Nuclei. Atmos. Chem. Phys. 2013, 13, 11175-11185. [3] Zolles et al. Identification of Ice Nucleation Active Sites on Feldspar Dust Particles. J. Phys. Chem. A 2015 accepted.

  14. Identification of Ftr1 and Zrt1 as iron and zinc micronutrient transceptors for activation of the PKA pathway in Saccharomyces cerevisiae

    PubMed Central

    Schothorst, Joep; Zeebroeck, Griet V.; Thevelein, Johan M.

    2017-01-01

    Multiple types of nutrient transceptors, membrane proteins that combine a transporter and receptor function, have now been established in a variety of organisms. However, so far all established transceptors utilize one of the macronutrients, glucose, amino acids, ammonium, nitrate, phosphate or sulfate, as substrate. This is also true for the Saccharomyces cerevisiae transceptors mediating activation of the PKA pathway upon re-addition of a macronutrient to glucose-repressed cells starved for that nutrient, re-establishing a fermentable growth medium. We now show that the yeast high-affinity iron transporter Ftr1 and high-affinity zinc transporter Zrt1 function as transceptors for the micronutrients iron and zinc. We show that replenishment of iron to iron-starved cells or zinc to zinc-starved cells triggers within 1-2 minutes a rapid surge in trehalase activity, a well-established PKA target. The activation with iron is dependent on Ftr1 and with zinc on Zrt1, and we show that it is independent of intracellular iron and zinc levels. Similar to the transceptors for macronutrients, Ftr1 and Zrt1 are strongly induced upon iron and zinc starvation, respectively, and they are rapidly downregulated by substrate-induced endocytosis. Our results suggest that transceptor-mediated signaling to the PKA pathway may occur in all cases where glucose-repressed yeast cells have been starved first for an essential nutrient, causing arrest of growth and low activity of the PKA pathway, and subsequently replenished with the lacking nutrient to re-establish a fermentable growth medium. The broadness of the phenomenon also makes it likely that nutrient transceptors use a common mechanism for signaling to the PKA pathway. PMID:28357393

  15. Face the Edges: Catalytic Active Sites of Nanomaterials

    PubMed Central

    Ni, Bing

    2015-01-01

    Edges are special sites in nanomaterials. The atoms residing on the edges have different environments compared to those in other parts of a nanomaterial and, therefore, they may have different properties. Here, recent progress in nanomaterial fields is summarized from the viewpoint of the edges. Typically, edge sites in MoS2 or metals, other than surface atoms, can perform as active centers for catalytic reactions, so the method to enhance performance lies in the optimization of the edge structures. The edges of multicomponent interfaces present even more possibilities to enhance the activities of nanomaterials. Nanoframes and ultrathin nanowires have similarities to conventional edges of nanoparticles, the application of which as catalysts can help to reduce the use of costly materials. Looking beyond this, the edge structures of graphene are also essential for their properties. In short, the edge structure can influence many properties of materials. PMID:27980960

  16. The Association between Provider Practice and Knowledge of ORS and Zinc Supplementation for the Treatment of Childhood Diarrhea in Bihar, Gujarat and Uttar Pradesh, India: A Multi-Site Cross-Sectional Study

    PubMed Central

    Lamberti, Laura M.; Fischer Walker, Christa L.; Taneja, Sunita; Mazumder, Sarmila; Black, Robert E.

    2015-01-01

    Introduction Programs aimed at reducing the burden of diarrhea among children under-five in low-resource settings typically allocate resources to training community-level health workers, but studies have suggested that provider knowledge does not necessarily translate into adequate practice. A diarrhea management program implemented in Bihar, Gujarat and Uttar Pradesh, India trained private sector rural medical practitioners (RMPs) and public sector Accredited Social Health Activists (ASHAs) and Anganwadi workers (AWWs) in adequate treatment of childhood diarrhea with oral rehydration salts (ORS) and zinc. We used cross-sectional program evaluation data to determine the association between observed diarrhea treatment practices and reported knowledge of ORS and zinc among each provider cadre. Methods We conducted principal components analysis on providers’ responses to diarrhea treatment questions in order to generate a novel scale assessing ORS/zinc knowledge. We subsequently regressed a binary indicator of whether ORS/zinc was prescribed during direct observation onto the resulting knowledge scores, controlling for other relevant knowledge predictors. Results There was a positive association between ORS/zinc knowledge score and prescribing ORS and zinc to young children with diarrhea among private sector RMPs (aOR: 2.32; 95% CI: 1.29-4.17) and public sector ASHAs and AWWs (aOR 2.48; 95% CI: 1.90-3.24). Controlling for knowledge score, receipt of training in the preceding 6 months was a good predictor of adequate prescribing in the public but not the private sector. In the public sector, direct access to ORS and zinc supplies was also highly associated with prescribing. Conclusions To enhance the management of childhood diarrhea in India, programmatic activities should center on increasing knowledge of ORS and zinc among public and private sector providers through biannual trainings but should also focus on ensuring sustained access to an adequate supply chain

  17. Active sites in char gasification: Final technical report

    SciTech Connect

    Wojtowicz, M.; Lilly, W.D.; Perkins, M.T.; Hradil, G.; Calo, J.M.; Suuberg, E.M.

    1987-09-01

    Among the key variables in the design of gasifiers and combustors is the reactivity of the chars which must be gasified or combusted. Significant loss of unburned char is unacceptable in virtually any process; the provision of sufficient residence time for complete conversion is essential. A very wide range of reactivities are observed, depending upon the nature of the char in a process. The current work focuses on furthering the understanding of gasification reactivities of chars. It has been well established that the reactivity of char to gasification generally depends upon three principal factors: (1) the concentration of ''active sites'' in the char; (2) mass transfer within the char; and (3) the type and concentration of catalytic impurities in the char. The present study primarily addresses the first factor. The subject of this research is the origin, nature, and fate of active sites in chars derived from parent hydrocarbons with coal-like structure. The nature and number of the active sites and their reactivity towards oxygen are examined in ''model'' chars derived from phenol-formaldehyde type resins. How the active sites are lost by the process of thermal annealing during heat treatment of chars are studied, and actual rate for the annealing process is derived. Since intrinsic char reactivities are of primary interest in the present study, a fair amount of attention was given to the model char synthesis and handling so that the effect of catalytic impurities and oxygen-containing functional groups in the chemical structure of the material were minimized, if not completely eliminated. The project would not be considered complete without comparing characteristic features of synthetic chars with kinetic behavior exhibited by natural chars, including coal chars.

  18. Nest predation increases with parental activity: Separating nest site and parental activity effects

    USGS Publications Warehouse

    Martin, T.E.; Scott, J.; Menge, C.

    2000-01-01

    Alexander Skutch hypothesized that increased parental activity can increase the risk of nest predation. We tested this hypothesis using ten open-nesting bird species in Arizona, USA. Parental activity was greater during the nestling than incubation stage because parents visited the nest frequently to feed their young during the nestling stage. However, nest predation did not generally increase with parental activity between nesting stages across the ten study species. Previous investigators have found similar results. We tested whether nest site effects might yield higher predation during incubation because the most obvious sites are depredated most rapidly. We conducted experiments using nest sites from the previous year to remove parental activity. Our results showed that nest sites have highly repeatable effects on nest predation risk; poor nest sites incurred rapid predation and caused predation rates to be greater during the incubation than nestling stage. This pattern also was exhibited in a bird species with similar (i.e. controlled) parental activity between nesting stages. Once nest site effects are taken into account, nest predation shows a strong proximate increase with parental activity during the nestling stage within and across species. Parental activity and nest sites exert antagonistic influences on current estimates of nest predation between nesting stages and both must be considered in order to understand current patterns of nest predation, which is an important source of natural selection.

  19. Nest predation increases with parental activity: separating nest site and parental activity effects.

    PubMed Central

    Martin, T E; Scott, J; Menge, C

    2000-01-01

    Alexander Skutch hypothesized that increased parental activity can increase the risk of nest predation. We tested this hypothesis using ten open-nesting bird species in Arizona, USA. Parental activity was greater during the nestling than incubation stage because parents visited the nest frequently to feed their young during the nestling stage. However, nest predation did not generally increase with parental activity between nesting stages across the ten study species. Previous investigators have found similar results. We tested whether nest site effects might yield higher predation during incubation because the most obvious sites are depredated most rapidly. We conducted experiments using nest sites from the previous year to remove parental activity. Our results showed that nest sites have highly repeatable effects on nest predation risk; poor nest sites incurred rapid predation and caused predation rates to be greater during the incubation than nestling stage. This pattern also was exhibited in a bird species with similar (i.e. controlled) parental activity between nesting stages. Once nest site effects are taken into account, nest predation shows a strong proximate increase with parental activity during the nestling stage within and across species. Parental activity and nest sites exert antagonistic influences on current estimates of nest predation between nesting stages and both must be considered in order to understand current patterns of nest predation, which is an important source of natural selection. PMID:11413645

  20. Active site amino acid sequence of human factor D.

    PubMed

    Davis, A E

    1980-08-01

    Factor D was isolated from human plasma by chromatography on CM-Sephadex C50, Sephadex G-75, and hydroxylapatite. Digestion of reduced, S-carboxymethylated factor D with cyanogen bromide resulted in three peptides which were isolated by chromatography on Sephadex G-75 (superfine) equilibrated in 20% formic acid. NH2-Terminal sequences were determined by automated Edman degradation with a Beckman 890C sequencer using a 0.1 M Quadrol program. The smallest peptide (CNBr III) consisted of the NH2-terminal 14 amino acids. The other two peptides had molecular weights of 17,000 (CNBr I) and 7000 (CNBr II). Overlap of the NH2-terminal sequence of factor D with the NH2-terminal sequence of CNBr I established the order of the peptides. The NH2-terminal 53 residues of factor D are somewhat more homologous with the group-specific protease of rat intestine than with other serine proteases. The NH2-terminal sequence of CNBr II revealed the active site serine of factor D. The typical serine protease active site sequence (Gly-Asp-Ser-Gly-Gly-Pro was found at residues 12-17. The region surrounding the active site serine does not appear to be more highly homologous with any one of the other serine proteases. The structural data obtained point out the similarities between factor D and the other proteases. However, complete definition of the degree of relationship between factor D and other proteases will require determination of the remainder of the primary structure.

  1. Brownian aggregation rate of colloid particles with several active sites

    SciTech Connect

    Nekrasov, Vyacheslav M.; Yurkin, Maxim A.; Chernyshev, Andrei V.; Polshchitsin, Alexey A.; Yakovleva, Galina E.; Maltsev, Valeri P.

    2014-08-14

    We theoretically analyze the aggregation kinetics of colloid particles with several active sites. Such particles (so-called “patchy particles”) are well known as chemically anisotropic reactants, but the corresponding rate constant of their aggregation has not yet been established in a convenient analytical form. Using kinematic approximation for the diffusion problem, we derived an analytical formula for the diffusion-controlled reaction rate constant between two colloid particles (or clusters) with several small active sites under the following assumptions: the relative translational motion is Brownian diffusion, and the isotropic stochastic reorientation of each particle is Markovian and arbitrarily correlated. This formula was shown to produce accurate results in comparison with more sophisticated approaches. Also, to account for the case of a low number of active sites per particle we used Monte Carlo stochastic algorithm based on Gillespie method. Simulations showed that such discrete model is required when this number is less than 10. Finally, we applied the developed approach to the simulation of immunoagglutination, assuming that the formed clusters have fractal structure.

  2. [Mechanism of arginine deiminase activity by site-directed mutagenesis].

    PubMed

    Li, Lifeng; Ni, Ye; Sun, Zhihao

    2012-04-01

    Arginine deiminase (ADI) has been studied as a potential anti-cancer agent for inhibiting arginine-auxotrophic tumors (such as melanomas and hepatocellular carcinomas) in phase III clinical trials. In this work, we studied the molecular mechanism of arginine deiminase activity by site-directed mutagenesis. Three mutation sites, A128, H404 and 1410, were introduced into wild-type ADI gene by QuikChange site-directed mutagenesis method, and four ADI mutants M1 (A128T), M2 (H404R), M3 (I410L), and M4 (A128T, H404R) were obtained. The ADI mutants were individually expressed in Escherichia coli BL21 (DE3), and the enzymatic properties of the purified mutant proteins were determined. The results show that both A128T and H404R had enhanced optimum pH, higher activity and stability of ADI under physiological condition (pH 7.4), as well as reduced K(m) value. This study provides an insight into the molecular mechanism of the ADI activity, and also the experimental evidence for the rational protein evolution in the future.

  3. Potential sites of CFTR activation by tyrosine kinases

    PubMed Central

    Billet, Arnaud; Jia, Yanlin; Jensen, Timothy J.; Hou, Yue-Xian; Chang, Xiu-Bao; Riordan, John R.; Hanrahan, John W.

    2016-01-01

    ABSTRACT The CFTR chloride channel is tightly regulated by phosphorylation at multiple serine residues. Recently it has been proposed that its activity is also regulated by tyrosine kinases, however the tyrosine phosphorylation sites remain to be identified. In this study we examined 2 candidate tyrosine residues near the boundary between the first nucleotide binding domain and the R domain, a region which is important for channel function but devoid of PKA consensus sequences. Mutating tyrosines at positions 625 and 627 dramatically reduced responses to Src or Pyk2 without altering the activation by PKA, suggesting they may contribute to CFTR regulation. PMID:26645934

  4. Chitosan/zinc oxide-polyvinylpyrrolidone (CS/ZnO-PVP) nanocomposite for better thermal and antibacterial activity.

    PubMed

    Karpuraranjith, M; Thambidurai, S

    2017-03-06

    A new biopolymer based ZnO-PVP nanocomposite was successfully synthesized by single step in situ precipitation method using chitosan as biosurfactant, zinc chloride as a source material, PVP as stabilizing agent and sodium hydroxide as precipitating agent. The chemical bonding and crystalline behaviors of chitosan, zinc oxide and PVP were confirmed by FT-IR and XRD analysis. The biopolymer connected ZnO particles intercalated PVP matrix was layer and rod like structure appeared in nanometer range confirmed by HR-SEM and TEM analysis. The surface topography image of CS/ZnO-PVP nanocomposite was obtained in the average thickness of 12nm was confirmed by AFM analysis. Thermal stability of cationic biopolymer based ZnO intercalated PVP has higher stability than CS-PVP and chitosan. Consequently, antimicrobial activity of chitosan/ZnO-PVP matrix acts as a better microbial inhibition activity than PVP-ZnO nanocomposite. The obtained above results demonstrate that CS and ZnO intercalated PVP matrix has better reinforced effect than other components. Therefore, Chitosan/ZnO-PVP nanocomposite may be a promising material for the biomedical applications.

  5. Low-Temperature Photochemically Activated Amorphous Indium-Gallium-Zinc Oxide for Highly Stable Room-Temperature Gas Sensors.

    PubMed

    Jaisutti, Rawat; Kim, Jaeyoung; Park, Sung Kyu; Kim, Yong-Hoon

    2016-08-10

    We report on highly stable amorphous indium-gallium-zinc oxide (IGZO) gas sensors for ultraviolet (UV)-activated room-temperature detection of volatile organic compounds (VOCs). The IGZO sensors fabricated by a low-temperature photochemical activation process and exhibiting two orders higher photocurrent compared to conventional zinc oxide sensors, allowed high gas sensitivity against various VOCs even at room temperature. From a systematic analysis, it was found that by increasing the UV intensity, the gas sensitivity, response time, and recovery behavior of an IGZO sensor were strongly enhanced. In particular, under an UV intensity of 30 mW cm(-2), the IGZO sensor exhibited gas sensitivity, response time and recovery time of 37%, 37 and 53 s, respectively, against 750 ppm concentration of acetone gas. Moreover, the IGZO gas sensor had an excellent long-term stability showing around 6% variation in gas sensitivity over 70 days. These results strongly support a conclusion that a low-temperature solution-processed amorphous IGZO film can serve as a good candidate for room-temperature VOCs sensors for emerging wearable electronics.

  6. Zinc-phosphate nanoparticles with reversibly attached TNF-α analogs: an interesting concept for potential use in active immunotherapy

    NASA Astrophysics Data System (ADS)

    Hribar, Gorazd; Žnidaršič, Andrej; Bele, Marjan; Maver, Uroš; Caserman, Simon; Gaberšček, Miran; Gaberc-Porekar, Vladka

    2011-07-01

    The authors' intention was to prepare nanometer-sized zinc-phosphate nanoparticles that would be capable of binding histidine-rich TNF-α analogs onto their surface via a coordinative bond. Zinc-phosphate nanoparticles with a size of around 60 nm were prepared by a wet precipitation method and characterized using SEM, EDX, XRD, and DLS. First, BSA was bound as a testing protein, afterward two TNF-α analogs with decreased activity were bound to the described nanoparticles. The efficiency of binding and the existence of coordinative bond were confirmed with SDS-PAGE analysis. During binding, particle storage, and release experiments, the prepared TNF-α analogs retained their biological activity—hence the epitopes necessary for formation of antibodies stayed intact. The particle size did not change within a period of 2 weeks. No significant agglomeration was observed, the particles could be quickly dispersed in ultrasound. The present nanoparticles and the general approach of coordinative binding are widely applicable for natural and engineered histidine-rich proteins. The nanoparticles bearing appropriate TNF-α analogs could also be potentially used for active immunotherapy to tackle the chronic inflammatory diseases associated with pathogenically elevated levels of TNF-α.

  7. MSK1 activity is controlled by multiple phosphorylation sites

    PubMed Central

    McCOY, Claire E.; Campbell, David G.; Deak, Maria; Bloomberg, Graham B.; Arthur, J. Simon C.

    2004-01-01

    MSK1 (mitogen- and stress-activated protein kinase) is a kinase activated in cells downstream of both the ERK1/2 (extracellular-signal-regulated kinase) and p38 MAPK (mitogen-activated protein kinase) cascades. In the present study, we show that, in addition to being phosphorylated on Thr-581 and Ser-360 by ERK1/2 or p38, MSK1 can autophosphorylate on at least six sites: Ser-212, Ser-376, Ser-381, Ser-750, Ser-752 and Ser-758. Of these sites, the N-terminal T-loop residue Ser-212 and the ‘hydrophobic motif’ Ser-376 are phosphorylated by the C-terminal kinase domain of MSK1, and their phosphorylation is essential for the catalytic activity of the N-terminal kinase domain of MSK1 and therefore for the phosphorylation of MSK1 substrates in vitro. Ser-381 is also phosphorylated by the C-terminal kinase domain, and mutation of Ser-381 decreases MSK1 activity, probably through the inhibition of Ser-376 phosphorylation. Ser-750, Ser-752 and Ser-758 are phosphorylated by the N-terminal kinase domain; however, their function is not known. The activation of MSK1 in cells therefore requires the activation of the ERK1/2 or p38 MAPK cascades and does not appear to require additional signalling inputs. This is in contrast with the closely related RSK (p90 ribosomal S6 kinase) proteins, whose activity requires phosphorylation by PDK1 (3-phosphoinositide-dependent protein kinase 1) in addition to phosphorylation by ERK1/2. PMID:15568999

  8. Diel Sampling of Groundwater and Surface Water for Trace Elements and Select Water-Quality Constituents at a Former Zinc Smelter Site near Hegeler, Illinois, August 1-3, 2007

    USGS Publications Warehouse

    Kay, Robert T.; Groschen, George E.; Dupre, David H.; Drexler, Timothy D.; Thingvold, Karen L.; Rosenfeld, Heather J.

    2009-01-01

    Surface water can exhibit substantial diel variations in the concentration of a number of constituents. Sampling regimens that do not characterize diel variations in water quality can result in an inaccurate understanding of site conditions and of the threat posed by the site to human health and the environment. Surface- and groundwater affected by acid drainage were sampled every 60 to 90 minutes over a 48-hour period at a former zinc smelter known as the Hegeler Zinc Superfund Site, in Hegeler, Ill. Groundwater-quality data from a well at the site indicate stable, low pH, weakly oxidizing geochemical conditions in the aquifer. With the exceptions of temperature and pH, no constituents exhibited diel variations in groundwater. Variations in temperature and pH likely were not representative of conditions in the aquifer. Surface water was sampled at a site on Grape Creek. Diel variations were observed in temperature, dissolved oxygen, pH, and specific conductance, and in the concentrations of nitrite, barium, iron, lead, vanadium, and possibly uranium. Concentrations during the diel cycles varied by about an order of magnitude for nitrite and varied by about a factor of two for barium, iron, lead, vanadium, and uranium. Temperature, dissolved oxygen, specific conductance, nitrite, barium, lead, and uranium generally reached maximum values during the afternoon and minimum values during the night. Iron, vanadium, and pH generally reached minimum values during the afternoon and maximum values during the night. These variations would need to be accounted for during sampling of surface-water quality in similar hydrologic settings. The temperature variations in surface water were affected by variations in air temperature. Concentrations of dissolved oxygen were affected by variations in the intensity of photosynthetic activity and respiration. Nitrite likely was formed by the oxidation of ammonium by dissolved oxygen and degraded by its anaerobic oxidation by ammonium or

  9. QM/MM X-ray Refinement of Zinc Metalloenzymes

    PubMed Central

    Li, Xue; Hayik, Seth A.; Merz, Kenneth M.

    2010-01-01

    Zinc metalloenzymes play an important role in biology. However, due to the limitation of molecular force field energy restraints used in X-ray refinement at medium or low resolutions, the precise geometry of the zinc coordination environment can be difficult to distinguish from ambiguous electron density maps. Due to the difficulties involved in defining accurate force fields for metal ions, the QM/MM (Quantum-Mechanical /Molecular-Mechanical) method provides an attractive and more general alternative for the study and refinement of metalloprotein active sites. Herein we present three examples that indicate that QM/MM based refinement yields a superior description of the crystal structure based on R and Rfree values and on the inspection of the zinc coordination environment. It is concluded that QM/MM refinement is a useful general tool for the improvement of the metal coordination sphere in metalloenzyme active sites. PMID:20116858

  10. Intracellular zinc distribution in mitochondria, ER and the Golgi apparatus.

    PubMed

    Lu, Qiping; Haragopal, Hariprakash; Slepchenko, Kira G; Stork, Christian; Li, Yang V

    2016-01-01

    Zinc (Zn(2+)) is required for numerous cellular functions. As such, the homeostasis and distribution of intracellular zinc can influence cellular metabolism and signaling. However, the exact distribution of free zinc within live cells remains elusive. Previously we showed the release of zinc from thapsigargin/IP3-sensitive endoplasmic reticulum (ER) storage in cortical neurons. In the present study, we investigated if other cellular organelles also contain free chelatable zinc and function as organelle storage for zinc. To identify free zinc within the organelles, live cells were co-stained with Zinpyr-1, a zinc fluorescent dye, and organelle-specific fluorescent dyes (MitoFluor Red 589: mitochondria; ER Tracker Red: endoplasmic reticulum; BODIPY TR ceramide: Golgi apparatus; Syto Red 64: nucleus). We examined organelles that represent potential storing sites for intracellular zinc. We showed that zinc fluorescence staining was co-localized with MitoFluor Red 589, ER Tracker Red, and BODIPY TR ceramide respectively, suggesting the presence of free zinc in mitochondria, endoplasmic reticulum, and the Golgi apparatus. On the other hand, cytosol and nucleus had nearly no detectable zinc fluorescence. It is known that nucleus contains high amount of zinc binding proteins that have high zinc binding affinity. The absence of zinc fluorescence suggests that there is little free zinc in these two regions. It also indicates that the zinc fluorescence detected in mitochondria, ER and Golgi apparatus represents free chelatable zinc. Taken together, our results support that these organelles are potential zinc storing organelles during cellular zinc homeostasis.

  11. Calculation of the Slip System Activity in Deformed Zinc Single Crystals Using Digital 3-D Image Correlation Data

    SciTech Connect

    Florando, J; Rhee, M; Arsenlis, A; LeBlanc, M; Lassila, D

    2006-02-21

    A 3-D image correlation system, which measures the full-field displacements in 3 dimensions, has been used to experimentally determine the full deformation gradient matrix for two zinc single crystals. Based on the image correlation data, the slip system activity for the two crystals has been calculated. The results of the calculation show that for one crystal, only the primary slip system is active, which is consistent with traditional theory. The other crystal however, shows appreciable deformation on slip systems other than the primary. An analysis has been conducted which confirms the experimental observation that these other slip system deform in such a manner that the net result is slip which is approximately one third the magnitude and directly orthogonal to the primary system.

  12. Current activities handbook: formerly utilized sites remedial action program

    SciTech Connect

    1981-02-27

    This volume is one of a series produced under contract with the DOE, by Politech Corporation to develop a legislative and regulatory data base to assist the FUSRAP management in addressing the institutional and socioeconomic issues involved in carrying out the Formerly Utilized Sites Remedial Action Program. This Information Handbook series contains information about all relevant government agencies at the Federal and state levels, the pertinent programs they administer, each affected state legislature, and current Federal and state legislative and regulatory initiatives. This volume is a compilation of information about the activities each of the thirteen state legislatures potentially affected by the Formerly Utilized Sites Remedial Action Program. It contains a description of the state legislative procedural rules and a schedule of each legislative session; a summary of pending relevant legislation; the name and telephone number of legislative and state agency contacts; and the full text of all bills identified.

  13. Vitamin K epoxide reductase: homology, active site and catalytic mechanism.

    PubMed

    Goodstadt, Leo; Ponting, Chris P

    2004-06-01

    Vitamin K epoxide reductase (VKOR) recycles reduced vitamin K, which is used subsequently as a co-factor in the gamma-carboxylation of glutamic acid residues in blood coagulation enzymes. VKORC1, a subunit of the VKOR complex, has recently been shown to possess this activity. Here, we show that VKORC1 is a member of a large family of predicted enzymes that are present in vertebrates, Drosophila, plants, bacteria and archaea. Four cysteine residues and one residue, which is either serine or threonine, are identified as likely active-site residues. In some plant and bacterial homologues the VKORC1 homologous domain is fused with domains of the thioredoxin family of oxidoreductases. These might reduce disulfide bonds of VKORC1-like enzymes as a prerequisite for their catalytic activities.

  14. Synthesis and in vitro anticancer activity of zinc(II) phthalocyanines conjugated with coumarin derivatives for dual photodynamic and chemotherapy.

    PubMed

    Zhou, Xiao-Qin; Meng, Lu-Bo; Huang, Qi; Li, Jun; Zheng, Ke; Zhang, Feng-Ling; Liu, Jian-Yong; Xue, Jin-Ping

    2015-02-01

    The combination of photodynamic therapy and chemotherapy is a promising strategy to overcome growing problems in contemporary medicine, such as low therapeutic efficacy and drug resistance. Four zinc(II) phthalocyanine-coumarin conjugates were synthesized and characterized. In these complexes, zinc(II) phthalocyanine was used as the photosensitizing unit, and a coumarin derivative was selected as the cytostatic moiety; the two components were linked via a tri(ethylene glycol) chain. These conjugates exhibit high photocytotoxicity against HepG2 human hepatocarcinoma cells, with low IC50 values in the range of 0.014-0.044 μM. The high photodynamic activities of these conjugates are in accordance with their low aggregation tendency and high cellular uptake. One of these conjugates exhibits high photocytotoxicity and significantly higher chemocytotoxicity. The results clearly show that the two antitumor components in these conjugates work in a cooperative fashion. As shown by confocal microscopy, the conjugates can localize in the mitochondria and lysosomes, and one of the conjugates can also localize in the cell nuclei.

  15. RETRACTED: Green synthesis of zinc oxide nanoparticles using Moringa oleifera leaf extract and evaluation of its antimicrobial activity.

    PubMed

    Elumalai, K; Velmurugan, S; Ravi, S; Kathiravan, V; Ashokkumar, S

    2015-05-15

    The development of semiconductor materials made a considerable progress of catalytic technologies. In the present study, a simple and eco-friendly chemical direction for the synthesis of zinc oxide nanoparticles (ZnO NPs) using leaf extract of Moringa oleifera has been used. The prepared ZnO NPs were characterized various techniques such as UV-Vis absorption spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR) and photoluminescence spectroscopy (PL). XRD analysis revealed the wurtzite hexagonal structure of ZnO NPs. FT-IR confirmed the presence of functional groups of both leaf extract and ZnO NPs. The particles size, morphology and topography determined from FE-SEM. The intense and narrow width of zinc and oxygen have high purity and crystalline were identified using EDX. UV-Vis absorption showed the characteristic absorption peak of ZnO NPs. The results of antimicrobial activities revealed that maximum zones of inhibition was observed Gram (+ve) positive bacteria and followed by the Gram (-ve) negative bacteria and fungal at concentration of 200μg/mL of ZnO NPs.

  16. Determination of spatial distributions of zinc and active biomass in microbial biofilms by two-photon laser scanning microscopy.

    PubMed

    Hu, Zhiqiang; Hidalgo, Gabriela; Houston, Paul L; Hay, Anthony G; Shuler, Michael L; Abruña, Héctor D; Ghiorse, William C; Lion, Leonard W

    2005-07-01

    The spatial distributions of zinc, a representative transition metal, and active biomass in bacterial biofilms were determined using two-photon laser scanning microscopy (2P-LSM). Application of 2P-LSM permits analysis of thicker biofilms than are amenable to observation with confocal laser scanning microscopy and also provides selective excitation of a smaller focal volume with greater depth localization. Thin Escherichia coli PHL628 biofilms were grown in a minimal mineral salts medium using pyruvate as the carbon and energy source under batch conditions, and thick biofilms were grown in Luria-Bertani medium using a continuous-flow drip system. The biofilms were visualized by 2P-LSM and shown to have heterogeneous structures with dispersed dense cell clusters, rough surfaces, and void spaces. Contrary to homogeneous biofilm model predictions that active biomass would be located predominantly in the outer regions of the biofilm and inactive or dead biomass (biomass debris) in the inner regions, significant active biomass fractions were observed at all depths in biofilms (up to 350 microm) using live/dead fluorescent stains. The active fractions were dependent on biofilm thickness and are attributed to the heterogeneous characteristics of biofilm structures. A zinc-binding fluorochrome (8-hydroxy-5-dimethylsulfoamidoquinoline) was synthesized and used to visualize the spatial location of added Zn within biofilms. Zn was distributed evenly in a thin (12 microm) biofilm but was located only at the surface of thick biofilms, penetrating less than 20 microm after 1 h of exposure. The relatively slow movement of Zn into deeper biofilm layers provides direct evidence in support of the concept that thick biofilms may confer resistance to toxic metal species by binding metals at the biofilm-bulk liquid interface, thereby retarding metal diffusion into the biofilm (G. M. Teitzel and M. R. Park, Appl. Environ. Microbiol. 69:2313-2320, 2003).

  17. The effects of oral zinc sulphate during radiotherapy on anti-oxidant enzyme activities in patients with head and neck cancer: a prospective, randomised, placebo-controlled study.

    PubMed

    Ertekin, M V; Koç, M; Karslioğlu, I; Sezen, O; Taysi, S; Bakan, N

    2004-07-01

    The purpose was to determine the effects of oral zinc sulphate along with radiotherapy on anti-oxidant enzyme activities in patients with head and neck cancer. Thirty patients with head and neck cancer were randomly assigned to receive either zinc sulphate capsules (including 50 mg zinc) (n = 15) or placebo (n = 15) three times a day, starting on the day of the first radiotherapy fraction and continuing throughout the scheduled radiotherapy course including weekends and 6 weeks after radiotherapy. The patients were treated with telecobalt radiation at conventional fractionation of 2 Gy/fraction and five fractions/ week in 20-35 fractions for a period of 4-7 weeks. Blood samples for biochemical parameters were collected after an overnight fast (12 h) before radiotherapy, the first day and 6 weeks after radiotherapy. In the placebo group, three patients were excluded. No difference was detected in any final measurement activities of erythrocyte anti-oxidant enzyme such as copper-zinc superoxide dismutase (Cu-Zn SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in the direct comparison between the zinc sulphate and the placebo group, except erythrocyte SOD activities measured the first day after radiotherapy (p < 0.03). In the respective measurement analysis of the groups in themselves, in the zinc sulphate group, while the statistical analysis for the activities of erythrocyte CAT and GSH-Px were significantly different (chi2 = 12.4, p < 0.05; chi2 = 8.9, p < 0.05, respectively) before radiotherapy, the first day and 6 weeks after radiotherapy, the activities of SOD did not differ (chi2 = 4.2, p > 0.05). In these three measurements, there was no statistical significance in the activities of enzymes in erythrocyte Cu-Zn SOD, CAT and GSH-Px in the placebo group. Before radiotherapy, plasma zinc levels were normal in 16 patients (59.2%) and were lower in 11 patients (40.8%) compared with laboratory levels. It would be worthwhile studying the effect of oral zinc

  18. Biomarkers of Nutrition for Development (BOND)-Zinc Review.

    PubMed

    King, Janet C; Brown, Kenneth H; Gibson, Rosalind S; Krebs, Nancy F; Lowe, Nicola M; Siekmann, Jonathan H; Raiten, Daniel J

    2016-03-09

    Zinc is required for multiple metabolic processes as a structural, regulatory, or catalytic ion. Cellular, tissue, and whole-body zinc homeostasis is tightly controlled to sustain metabolic functions over a wide range of zinc intakes, making it difficult to assess zinc insufficiency or excess. The BOND (Biomarkers of Nutrition for Development) Zinc Expert Panel recommends 3 measurements for estimating zinc status: dietary zinc intake, plasma zinc concentration (PZC), and height-for-age of growing infants and children. The amount of dietary zinc potentially available for absorption, which requires an estimate of dietary zinc and phytate, can be used to identify individuals and populations at risk of zinc deficiency. PZCs respond to severe dietary zinc restriction and to zinc supplementation; they also change with shifts in whole-body zinc balance and clinical signs of zinc deficiency. PZC cutoffs are available to identify individuals and populations at risk of zinc deficiency. However, there are limitations in using the PZC to assess zinc status. PZCs respond less to additional zinc provided in food than to a supplement administered between meals, there is considerable interindividual variability in PZCs with changes in dietary zinc, and PZCs are influenced by recent meal consumption, the time of day, inflammation, and certain drugs and hormones. Insufficient data are available on hair, urinary, nail, and blood cell zinc responses to changes in dietary zinc to recommend these biomarkers for assessing zinc status. Of the potential functional indicators of zinc, growth is the only one that is recommended. Because pharmacologic zinc doses are unlikely to enhance growth, a growth response to supplemental zinc is interpreted as indicating pre-existing zinc deficiency. Other functional indicators reviewed but not recommended for assessing zinc nutrition in clinical or field settings because of insufficient information are the activity or amounts of zinc-dependent enzymes

  19. Crystal structure of Helicobacter pylori neutrophil-activating protein with a di-nuclear ferroxidase center in a zinc or cadmium-bound form

    SciTech Connect

    Yokoyama, Hideshi; Tsuruta, Osamu; Akao, Naoya; Fujii, Satoshi

    2012-06-15

    Highlights: Black-Right-Pointing-Pointer Structures of a metal-bound Helicobacter pylori neutrophil-activating protein were determined. Black-Right-Pointing-Pointer Two zinc ions were tetrahedrally coordinated by ferroxidase center (FOC) residues. Black-Right-Pointing-Pointer Two cadmium ions were coordinated in a trigonal-bipyramidal and octahedral manner. Black-Right-Pointing-Pointer The second metal ion was more weakly coordinated than the first at the FOC. Black-Right-Pointing-Pointer A zinc ion was found in one negatively-charged pore suitable as an ion path. -- Abstract: Helicobacter pylori neutrophil-activating protein (HP-NAP) is a Dps-like iron storage protein forming a dodecameric shell, and promotes adhesion of neutrophils to endothelial cells. The crystal structure of HP-NAP in a Zn{sup 2+}- or Cd{sup 2+}-bound form reveals the binding of two zinc or two cadmium ions and their bridged water molecule at the ferroxidase center (FOC). The two zinc ions are coordinated in a tetrahedral manner to the conserved residues among HP-NAP and Dps proteins. The two cadmium ions are coordinated in a trigonal-bipyramidal and distorted octahedral manner. In both structures, the second ion is more weakly coordinated than the first. Another zinc ion is found inside of the negatively-charged threefold-related pore, which is suitable for metal ions to pass through.

  20. Mapping intermolecular interactions and active site conformations: from human MMP-1 crystal structure to molecular dynamics free energy calculations.

    PubMed

    Nash, Anthony; Birch, Helen L; de Leeuw, Nora H

    2017-02-01

    The zinc-dependent Matrix Metalloproteinases (MMPs) found within the extracellular matrix (ECM) of vertebrates are linked to pathological processes such as arthritis, skin ulceration and cancer. Although a general backbone proteolytic mechanism is understood, crystallographic data continue to suggest an active site that is too narrow to encompass the respective substrate. We present a fully parameterised Molecular Dynamics (MD) study of the structural properties of an MMP-1-collagen crystallographic structure (Protein Data Bank - 4AUO), followed by an exploration of the free energy surface of a collagen polypeptide chain entering the active site, using a combined meta-dynamics and umbrella sampling (MDUS) approach. We conclude that the interactions between MMP-1 and the collagen substrate are in good agreement with a number of experimental studies. As such, our unrestrained MD simulations and our MDUS results, which indicate an energetic barrier for a local uncoiling and insertion event, can inform future investigations of the collagen-peptide non-bonded association steps with the active site prior to proteolytic mechanisms. The elucidation of such free energy barriers provides a better understanding of the role of the enzyme in the ECM and is important in the design of future MMP inhibitors.

  1. Zinc-induced Self-association of Complement C3b and Factor H

    PubMed Central

    Nan, Ruodan; Tetchner, Stuart; Rodriguez, Elizabeth; Pao, Po-Jung; Gor, Jayesh; Lengyel, Imre; Perkins, Stephen J.

    2013-01-01

    The sub-retinal pigment epithelial deposits that are a hallmark of age-related macular degeneration contain both C3b and millimolar levels of zinc. C3 is the central protein of complement, whereas C3u is formed by the spontaneous hydrolysis of the thioester bridge in C3. During activation, C3 is cleaved to form active C3b, then C3b is inactivated by Factor I and Factor H to form the C3c and C3d fragments. The interaction of zinc with C3 was quantified using analytical ultracentrifugation and x-ray scattering. C3, C3u, and C3b associated strongly in >100 μm zinc, whereas C3c and C3d showed weak association. With zinc, C3 forms soluble oligomers, whereas C3u and C3b precipitate. We conclude that the C3, C3u, and C3b association with zinc depended on the relative positions of C3d and C3c in each protein. Computational predictions showed that putative weak zinc binding sites with different capacities exist in all five proteins, in agreement with experiments. Factor H forms large oligomers in >10 μm zinc. In contrast to C3b or Factor H alone, the solubility of the central C3b-Factor H complex was much reduced at 60 μm zinc and even more so at >100 μm zinc. The removal of the C3b-Factor H complex by zinc explains the reduced C3u/C3b inactivation rates by zinc. Zinc-induced precipitation may contribute to the initial development of sub-retinal pigment epithelial deposits in the retina as well as reducing the progression to advanced age-related macular degeneration in higher risk patients. PMID:23661701

  2. X-ray absorption edge spectroscopy of Co(II)-binding sites of copper- and zinc-containing proteins.

    PubMed

    Desideri, A; Comin, F; Morpurgo, L; Cocco, D; Calabrese, L; Mondovi, B; Maret, W; Rotilio, G

    1981-10-28

    X-ray absorption near-edge spectroscopy (XANES) of Co(II) in three derivatives of superoxide dismutase, namely [Cu(II)-Co(II)], [Cu(I)-Co(II)] and [...-Co(II)], suggests a tetrahedral coordination of the metal for all compounds. Significant differences, detected in the spectrum of the [Cu(II)-Co(II)] derivative as compared to the other species, indicate that a conformational change and/or a different charge of the imidazole bridging the two metal sites in superoxide dismutase occur in coincidence with the change of copper valence. The XANES spectra of the cobalt derivatives of alcohol dehydrogenase, carbonic anhydrase and stellacyanin show features that can be accounted for by an increasing degree of covalency in the metal first sphere of coordination, in the following order: alcohol dehydrogenase greater than stellacyanin greater than superoxide dismutase greater than or equal to carbonic anhydrase.

  3. The potential of phytoremediation using hyperaccumulator plants: a case study at a lead-zinc mine site.

    PubMed

    Lorestani, Bahareh; Cheraghi, Mehrdad; Yousefi, Nafiseh

    2012-09-01

    Contamination with heavy metals is one of the most pressing threats to water and soil resources, as well as human health. Phytoremediation might potentially be used to remediate metal-contaminated sites. A major advance in the development of phytoremediation for heavy metal affected soils was the discovery of heavy metal hyperaccumulation in plants. This study applied several established criteria to identify hyperaccumulator plants. A case study was conducted at a mining area in the Hamedan province in the west central region of Iran. The results indicated that plant metal accumulation differed among species and plant parts. Plant species grown in substrata with elevated metal levels contained significantly higher metal levels. Using the most common criteria, Euphorbia macroclada and Centaurea virgata can be classified as hyperaccumulators of specific heavy metals measured in this study and they might potentially be used for the phytoremediation of contaminated soils.

  4. Identification of covalent active site inhibitors of dengue virus protease

    PubMed Central

    Koh-Stenta, Xiaoying; Joy, Joma; Wang, Si Fang; Kwek, Perlyn Zekui; Wee, John Liang Kuan; Wan, Kah Fei; Gayen, Shovanlal; Chen, Angela Shuyi; Kang, CongBao; Lee, May Ann; Poulsen, Anders; Vasudevan, Subhash G; Hill, Jeffrey; Nacro, Kassoum

    2015-01-01

    Dengue virus (DENV) protease is an attractive target for drug development; however, no compounds have reached clinical development to date. In this study, we utilized a potent West Nile virus protease inhibitor of the pyrazole ester derivative class as a chemical starting point for DENV protease drug development. Compound potency and selectivity for DENV protease were improved through structure-guided small molecule optimization, and protease-inhibitor binding interactions were validated biophysically using nuclear magnetic resonance. Our work strongly suggests that this class of compounds inhibits flavivirus protease through targeted covalent modification of active site serine, contrary to an allosteric binding mechanism as previously described. PMID:26677315

  5. Zinc-induced modulation of SRSF6 activity alters Bim splicing to promote generation of the most potent apoptotic isoform BimS.

    PubMed

    Hara, Hirokazu; Takeda, Tatsuya; Yamamoto, Nozomi; Furuya, Keisuke; Hirose, Kazuya; Kamiya, Tetsuro; Adachi, Tetsuo

    2013-07-01

    Bim is a member of the pro-apoptotic BH3-only Bcl-2 family of proteins. Bim gene undergoes alternative splicing to produce three predominant splicing variants (BimEL, BimL and BimS). The smallest variant BimS is the most potent inducer of apoptosis. Zinc (Zn(2+)) has been reported to stimulate apoptosis in various cell types. In this study, we examined whether Zn(2+) affects the expression of Bim in human neuroblastoma SH-SY5Y cells. Zn(2+) triggered alterations in Bim splicing and induced preferential generation of BimS, but not BimEL and BimL, in a dose- and time-dependent manner. Other metals (cadmium, cobalt and copper) and stresses (oxidative, endoplasmic reticulum and genotoxic stresses) had little or no effect on the expression of BimS. To address the mechanism of Zn(2+)-induced preferential generation of BimS, which lacks exon 4, we developed a Bim mini-gene construct. Deletion analysis using the Bim mini-gene revealed that predicted binding sites of the SR protein SRSF6, also known as SRp55, are located in the intronic region adjacent to exon 4. We also found that mutations in the predicted SRSF6-binding sites abolished generation of BimS mRNA from the mutated Bim mini-gene. In addition, a UV cross-linking assay followed by Western blotting showed that SRSF6 directly bound to the predicted binding site and Zn(2+) suppressed this binding. Moreover, Zn(2+) stimulated SRSF6 hyper-phosphorylation. TG003, a cdc2-like kinase inhibitor, partially prevented Zn(2+)-induced generation of BimS and SRSF6 hyper-phosphorylation. Taken together, our findings suggest that Zn(2+) inhibits the activity of SRSF6 and promotes elimination of exon 4, leading to preferential generation of BimS.

  6. Maternal and Umbilical Cord Blood Levels of Zinc and Copper in Active Labor Versus Elective Caesarean Delivery at Khartoum Hospital, Sudan.

    PubMed

    Elhadi, Alaeldin; Rayis, Duria A; Abdullahi, Hala; Elbashir, Leana M; Ali, Naji I; Adam, Ishag

    2016-01-01

    A case-control study was conducted in Khartoum Hospital Sudan to determine maternal and umbilical cord blood levels of zinc and copper in active labor versus elective cesarean delivery. Cases were women delivered vaginally and controls were women delivered by elective cesarean (before initiation of labor). Paired maternal and cord zinc and copper were measured using atomic absorption spectrophotometry. The two groups (52 paired maternal and cord in each arm) were well matched in their basic characteristics. In comparison with cesarean delivery, the median (interquartile range) of both maternal [87.0 (76.1-111.4) vs. 76.1 (65.2-88.3) μg/dL, P = 0.004] and cord zinc [97.8 (87.0-114.1) vs. 81.5(65.2-110.2) μg/dL P = 0.034] levels were significantly higher in the vaginal delivery. While there was no significant difference in the maternal copper [78.8 (48.1-106.1) vs. 92.4 (51.9-114.9) μg/dL, P = 0.759], the cord copper [43.5(29.9-76.1) vs. 32.2(21.7-49.6) μg/dL, P = 0.019] level was significantly higher in vaginal delivery. There was no significant correlation between zinc (both maternal and cord) and copper. While the cord zinc was significantly correlated with maternal zinc, there was no significant correlation between maternal and cord copper. The current study showed significantly higher levels of maternal and cord zinc and cord copper in women who delivered vaginally compared with caesarean delivery.

  7. Zinc pyrithione salvages reperfusion injury by inhibiting NADPH oxidase activation in cardiomyocytes.

    PubMed

    Kasi, Viswanath; Bodiga, Sreedhar; Kommuguri, Upendra Nadh; Sankuru, Suneetha; Bodiga, Vijaya Lakshmi

    2011-07-01

    Zinc pyrithione (ZPT), has a strong anti-apoptotic effect when administered just before reperfusion. Because oxidative stress has been proposed to contribute to myocardial reperfusion injury, we tested whether ZPT can reduce the production of reactive oxygen species during reoxygenation in cultured neonatal rat cardiac myocytes and evaluated the role of NADPH oxidase in hypoxia/reoxygenation (H/R) injury. The cells were subjected to 8h of simulated ischemia, followed by either 30 min or 16 h of reoxygenation. ZPT when started just before reoxygenation significantly reduced superoxide generation, LDH release and improved cell survival compared to H/R. Attenuation of the ROS production by ZPT paralleled its capacity to prevent pyknotic nuclei formation. In addition, ZPT reversed the H/R-induced expression of NOX2 and p47(phox) phosphorylation indicating that ZPT directly protects cardiomyocytes from reperfusion injury by a mechanism that attenuates NADPH oxidase mediated intracellular oxidative stress.

  8. Evolutionary conservation of zinc finger transcription factor binding sites in promoters of genes co-expressed with WT1 in prostate cancer

    PubMed Central

    Eisermann, Kurtis; Tandon, Sunpreet; Bazarov, Anton; Brett, Adina; Fraizer, Gail; Piontkivska, Helen

    2008-01-01

    Background Gene expression analyses have led to a better understanding of growth control of prostate cancer cells. We and others have identified the presence of several zinc finger transcription factors in the neoplastic prostate, suggesting a potential role for these genes in the regulation of the prostate cancer transcriptome. One of the transcription factors (TFs) identified in the prostate cancer epithelial cells was the Wilms tumor gene (WT1). To rapidly identify coordinately expressed prostate cancer growth control genes that may be regulated by WT1, we used an in silico approach. Results Evolutionary conserved transcription factor binding sites (TFBS) recognized by WT1, EGR1, SP1, SP2, AP2 and GATA1 were identified in the promoters of 24 differentially expressed prostate cancer genes from eight mammalian species. To test the relationship between sequence conservation and function, chromatin of LNCaP prostate cancer and kidney 293 cells were tested for TF binding using chromatin immunoprecipitation (ChIP). Multiple putative TFBS in gene promoters of placental mammals were found to be shared with those in human gene promoters and some were conserved between genomes that diverged about 170 million years ago (i.e., primates and marsupials), therefore implicating these sites as candidate binding sites. Among those genes coordinately expressed with WT1 was the kallikrein-related peptidase 3 (KLK3) gene commonly known as the prostate specific antigen (PSA) gene. This analysis located several potential WT1 TFBS in the PSA gene promoter and led to the rapid identification of a novel putative binding site confirmed in vivo by ChIP. Conversely for two prostate growth control genes, androgen receptor (AR) and vascular endothelial growth factor (VEGF), known to be transcriptionally regulated by WT1, regulatory sequence conservation was observed and TF binding in vivo was confirmed by ChIP. Conclusion Overall, this targeted approach rapidly identified important candidate

  9. Experimental and computational active site mapping as a starting point to fragment-based lead discovery.

    PubMed

    Behnen, Jürgen; Köster, Helene; Neudert, Gerd; Craan, Tobias; Heine, Andreas; Klebe, Gerhard

    2012-02-06

    Small highly soluble probe molecules such as aniline, urea, N-methylurea, 2-bromoacetate, 1,2-propanediol, nitrous oxide, benzamidine, and phenol were soaked into crystals of various proteins to map their binding pockets and to detect hot spots of binding with respect to hydrophobic and hydrophilic properties. The selected probe molecules were first tested at the zinc protease thermolysin. They were then applied to a wider range of proteins such as protein kinase A, D-xylose isomerase, 4-diphosphocytidyl-2C-methyl-D-erythritol synthase, endothiapepsin, and secreted aspartic protease 2. The crystal structures obtained clearly show that the probe molecules populate the protein binding pockets in an ordered fashion. The thus characterized, experimentally observed hot spots of binding were subjected to computational active site mapping using HotspotsX. This approach uses knowledge-based pair potentials to detect favorable binding positions for various atom types. Good agreement between the in silico hot spot predictions and the experimentally observed positions of the polar hydrogen bond forming functional groups and hydrophobic portions was obtained. Finally, we compared the observed poses of the small-molecule probes with those of much larger structurally related ligands. They coincide remarkably well with the larger ligands, considering their spatial orientation and the experienced interaction patterns. This observation confirms the fundamental hypothesis of fragment-based lead discovery: that binding poses, even of very small molecular probes, do not significantly deviate or move once a ligand is grown further into the binding site. This underscores the fact that these probes populate given hot spots and can be regarded as relevant seeds for further design.

  10. Facile synthesis of pegylated zinc(II) phthalocyanines via transesterification and their in vitro photodynamic activities.

    PubMed

    Bai, Ming; Lo, Pui-Chi; Ye, Jing; Wu, Chi; Fong, Wing-Ping; Ng, Dennis K P

    2011-10-21

    Treatment of 4,5-bis[4-(methoxycarbonyl)phenoxy]phthalonitrile and 4,5-bis[3,5-bis(methoxycarbonyl)phenoxy]phthalonitrile with an excess of 1,3-diiminoisoindoline in the presence of Zn(OAc)(2)·2H(2)O and 1,8-diazabicyclo[5.4.0]undec-7-ene in triethylene glycol monomethyl ether or polyethylene glycol monomethyl ether (with an average molecular weight of 550) led to "3 + 1" mixed cyclisation and transesterification in one pot, affording the corresponding di-β-substituted zinc(II) phthalocyanines in 7-23% yield. As shown by absorption spectroscopy, these compounds were essentially non-aggregated in N,N-dimethylformamide and could generate singlet oxygen effectively. The singlet oxygen quantum yields (Φ(Δ) = 0.53-0.57) were comparable with that of the unsubstituted zinc(II) phthalocyanine (Φ(Δ) = 0.56). These compounds in Cremophor EL emulsions also exhibited photocytotoxicity against HT29 human colorectal adenocarcinoma and HepG2 human hepatocarcinoma cells with IC(50) values in the range of 0.25-3.72 μM. The analogue with four triethylene glycol chains was the most potent photosensitiser and localised preferentially in the mitochondria of HT29 cells. The bis(polyethylene glycol)-counterpart could form surfactant-free nanoparticles both in water and in the culture medium. The hydrodynamic radii, as determined by dynamic laser light scattering, ranged from 6.3 to 79.8 nm depending on the preparation methods and conditions. The photocytotoxicity of these nanoparticles (IC(50) = 0.43-0.56 μM) was comparable with that of the Cremophor EL-formulated system (IC(50) = 0.34 μM).

  11. Target-classification approach applied to active UXO sites

    NASA Astrophysics Data System (ADS)

    Shubitidze, F.; Fernández, J. P.; Shamatava, Irma; Barrowes, B. E.; O'Neill, K.

    2013-06-01

    This study is designed to illustrate the discrimination performance at two UXO active sites (Oklahoma's Fort Sill and the Massachusetts Military Reservation) of a set of advanced electromagnetic induction (EMI) inversion/discrimination models which include the orthonormalized volume magnetic source (ONVMS), joint diagonalization (JD), and differential evolution (DE) approaches and whose power and flexibility greatly exceed those of the simple dipole model. The Fort Sill site is highly contaminated by a mix of the following types of munitions: 37-mm target practice tracers, 60-mm illumination mortars, 75-mm and 4.5'' projectiles, 3.5'', 2.36'', and LAAW rockets, antitank mine fuzes with and without hex nuts, practice MK2 and M67 grenades, 2.5'' ballistic windshields, M2A1-mines with/without bases, M19-14 time fuzes, and 40-mm practice grenades with/without cartridges. The site at the MMR site contains targets of yet different sizes. In this work we apply our models to EMI data collected using the MetalMapper (MM) and 2 × 2 TEMTADS sensors. The data for each anomaly are inverted to extract estimates of the extrinsic and intrinsic parameters associated with each buried target. (The latter include the total volume magnetic source or NVMS, which relates to size, shape, and material properties; the former includes location, depth, and orientation). The estimated intrinsic parameters are then used for classification performed via library matching and the use of statistical classification algorithms; this process yielded prioritized dig-lists that were submitted to the Institute for Defense Analyses (IDA) for independent scoring. The models' classification performance is illustrated and assessed based on these independent evaluations.

  12. High-pressure Gas Activation for Amorphous Indium-Gallium-Zinc-Oxide Thin-Film Transistors at 100 °C

    PubMed Central

    Kim, Won-Gi; Tak, Young Jun; Du Ahn, Byung; Jung, Tae Soo; Chung, Kwun-Bum; Kim, Hyun Jae

    2016-01-01

    We investigated the use of high-pressure gases as an activation energy source for amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs). High-pressure annealing (HPA) in nitrogen (N2) and oxygen (O2) gases was applied to activate a-IGZO TFTs at 100 °C at pressures in the range from 0.5 to 4 MPa. Activation of the a-IGZO TFTs during HPA is attributed to the effect of the high-pressure environment, so that the activation energy is supplied from the kinetic energy of the gas molecules. We reduced the activation temperature from 300 °C to 100 °C via the use of HPA. The electrical characteristics of a-IGZO TFTs annealed in O2 at 2 MPa were superior to those annealed in N2 at 4 MPa, despite the lower pressure. For O2 HPA under 2 MPa at 100 °C, the field effect mobility and the threshold voltage shift under positive bias stress were improved by 9.00 to 10.58 cm2/V.s and 3.89 to 2.64 V, respectively. This is attributed to not only the effects of the pressurizing effect but also the metal-oxide construction effect which assists to facilitate the formation of channel layer and reduces oxygen vacancies, served as electron trap sites. PMID:26972476

  13. Upregulation of KCC2 Activity by Zinc-Mediated Neurotransmission via the mZnR/GPR39 Receptor

    PubMed Central

    Chorin, Ehud; Vinograd, Ofir; Fleidervish, Ilya; Gilad, David; Herrmann, Sharon; Sekler, Israel; Aizenman, Elias; Hershfinkel, Michal

    2011-01-01

    Vesicular Zn2+ regulates postsynaptic neuronal excitability upon its corelease with glutamate. We previously demonstrated that synaptic Zn2+ acts via a distinct metabotropic zinc-sensing receptor (mZnR) in neurons to trigger Ca2+ responses in the hippocampus. Here, we show that physiological activation of mZnR signaling induces enhanced K+/Cl− cotransporter 2 (KCC2) activity and surface expression. As KCC2 is the major Cl− outward transporter in neurons, Zn2+ also triggers a pronounced hyperpolarizing shift in the GABAA reversal potential. Mossy fiber stimulation-dependent upregulation of KCC2 activity is eliminated in slices from Zn2+ transporter 3-deficient animals, which lack synaptic Zn2+. Importantly, activity-dependent ZnR signaling and subsequent enhancement of KCC2 activity are also absent in slices from mice lacking the G-protein-coupled receptor GPR39, identifying this protein as the functional neuronal mZnR. Our work elucidates a fundamentally important role for synaptically released Zn2+ acting as a neurotransmitter signal via activation of a mZnR to increase Cl− transport, thereby enhancing inhibitory tone in postsynaptic cells. PMID:21900570

  14. Effect of nano-zinc oxide on nitrogenase activity in legumes: an interplay of concentration and exposure time

    NASA Astrophysics Data System (ADS)

    Kumar, Praveen; Burman, Uday; Santra, P.

    2015-07-01

    Experiments were carried out to study the effect of zinc oxide nanoparticles (nano-ZnO) on nitrogenase activity in legumes. In the first experiment, nodulated roots of cluster bean, moth bean, green gram and cowpea were dipped in Hoagland solution containing 1.5 and 10 μg mL-1 of nano-ZnO for 24 h. Nitrogenase activity in cluster bean, green gram and cowpea roots increased after dipping in solution containing 1.5 μg mL-1 nano-ZnO, but decreased in roots dipped in solution containing 10 μg mL-1 nano-ZnO. However, in moth bean roots, nitrogenase activity decreased after dipping in solution containing either concentration of nano-ZnO. In the second experiment, nodulated roots of green gram were dipped in Hoagland solution containing 1, 4, 6, 8 and 10 μg mL-1 nano-ZnO for 6-30 h before estimating nitrogenase activity. Results showed that an interactive effect of nano-ZnO concentration and exposure time influenced nitrogenase activity. The possible reasons behind this effect have been discussed. A model [ A = 3.44 + 0.46 t - 0.01 t 2 - 0.002 tc 2 ( R 2 = 0.81)] involving linear and power components was developed to simulate the response of nitrogenase activity in green gram roots to the concentration and exposure time of nano-ZnO.

  15. Cadmium tolerance and accumulation of Elsholtzia argyi origining from a zinc/lead mining site - a hydroponics experiment.

    PubMed

    Li, Siliang; Wang, Fengping; Ru, Mei; Ni, Wuzhong

    2014-01-01

    In this study, a hydroponics experiment was conducted to investigate the characteristics of Cd tolerance and accumulation of Elsholtzia argyi natively growing on the soil with high levels of heavy metals in a Zn/Pb mining site. Seedlings of E. argyi grown for 4 weeks and then were treated with 0(CK), 5,10,15, 20, 25, 30, 40, 50,100 umM Cd for 21 days. Each treatment had three replications. No visual toxic symptoms on shoots of E. argyi were observed at Cd level < or = 50 muM. The results indicated that the dry biomass of each tissue and the whole plants of the treatments with < or =40 umM cadmium were similar to that of the control, implying that E. argyi was a cadmium tolerant plant. The results also showed that the shoot Cd concentration significantly (P < 0.05) increased with the increase in the Cd level in nutrient solution. The shoot Cd concentration of the treatment with 40 umM Cd was as high as 237.9 mg kg(-1), which was higher than 100 mg kg(-1), normally used as the threshold concentration for identifying the Cd hyperaccumulating plant. It could be concluded that E. argyi was a Cd tolerant and accumulating plant species.

  16. Identification of Phosphorylation Sites Altering Pollen Soluble Inorganic Pyrophosphatase Activity.

    PubMed

    Eaves, Deborah J; Haque, Tamanna; Tudor, Richard L; Barron, Yoshimi; Zampronio, Cleidiane G; Cotton, Nicholas P J; de Graaf, Barend H J; White, Scott A; Cooper, Helen J; Franklin, F Christopher H; Harper, Jeffery F; Franklin-Tong, Vernonica E

    2017-03-01

    Protein phosphorylation regulates numerous cellular processes. Identifying the substrates and protein kinases involved is vital to understand how these important posttranslational modifications modulate biological function in eukaryotic cells. Pyrophosphatases catalyze the hydrolysis of inorganic phosphate (PPi) to inorganic phosphate Pi, driving biosynthetic reactions; they are essential for low cytosolic inorganic phosphate. It was suggested recently that posttranslational regulation of Family I soluble inorganic pyrophosphatases (sPPases) may affect their activity. We previously demonstrated that two pollen-expressed sPPases, Pr-p26.1a and Pr-p26.1b, from the flowering plant Papaver rhoeas were inhibited by phosphorylation. Despite the potential significance, there is a paucity of data on sPPase phosphorylation and regulation. Here, we used liquid chromatographic tandem mass spectrometry to map phosphorylation sites to the otherwise divergent amino-terminal extensions on these pollen sPPases. Despite the absence of reports in the literature on mapping phosphorylation sites on sPPases, a database survey of various proteomes identified a number of examples, suggesting that phosphorylation may be a more widely used mechanism to regulate these enzymes. Phosphomimetic mutants of Pr-p26.1a/b significantly and differentially reduced PPase activities by up to 2.5-fold at pH 6.8 and 52% in the presence of Ca(2+) and hydrogen peroxide over unmodified proteins. This indicates that phosphoregulation of key sites can inhibit the catalytic responsiveness of these proteins in concert with key intracellular events. As sPPases are essential for many metabolic pathways in eukaryotic cells, our findings identify the phosphorylation of sPPases as a potential master regulatory mechanism that could be used to attenuate metabolism.

  17. Evidence for segmental mobility in the active site of pepsin

    SciTech Connect

    Pohl, J.; Strop, P.; Senn, H.; Foundling, S.; Kostka, V.

    1986-05-01

    The low hydrolytic activity (k/sub cat/ < 0.001 s/sup -1/) of chicken pepsin (CP) towards tri- and tetrapeptides is enhanced at least 100 times by modification of its single sulfhydryl group of Cys-115, with little effect on K/sub m/-values. Modification thus simulates the effect of secondary substrate binding on pepsin catalysis. The rate of Cys-115 modification is substantially decreased in the presence of some competitive inhibitors, suggesting its active site location. Experiments with CP alkylated at Cys-115 with Acrylodan as a fluorescent probe or with N-iodoacetyl-(4-fluoro)-aniline as a /sup 19/F-nmr probe suggest conformation change around Cys-115 to occur on substrate or substrate analog binding. The difference /sup 1/H-nmr spectra (500 MHz) of unmodified free and inhibitor-complexed CP reveal chemical shifts almost exclusively in the aromatic region. The effects of Cu/sup + +/ on /sup 19/F- and /sup 1/H-nmr spectra have been studied. Examination of a computer graphics model of CP based on E. parasitica pepsin-inhibitor complex X-ray coordinates suggests that Cys-115 is located near the S/sub 3//S/sub 5/ binding site. The results are interpreted in favor of segmental mobility of this region important for pepsin substrate binding and catalysis.

  18. First Principles Computational Study of the Active Site of Arginase

    SciTech Connect

    Ivanov, Ivaylo; Klien, Micheal

    2004-01-14

    Ab initio density functional theory (DFT) methods were used to investigate the structural features of the active site of the binuclear enzyme rat liver arginase. Special emphasis was placed on the crucial role of the second shell ligand interactions. These interactions were systematically studied by performing calculations on models of varying size. It was determined that a water molecule, and not hydroxide, is the bridging exogenous ligand. The carboxylate ligands facilitate the close approach of the Mn (II) ions by attenuating the metal-metal electrostatic repulsion. Of the two metals, MnA was shown to carry a larger positive charge. Analysis of the electronic properties of the active site revealed that orbitals involving the terminal Asp234 residue, as well as the flexible -1,1 bridging Asp232, lie at high energies, suggesting weaker coordination. This is reflected in certain structural variability present in our models and is also consistent with recent experimental findings. Finally, implications of our findings for the biological function of the enzyme are delineated.

  19. Brain-derived neurotrophic factor but not vesicular zinc promotes TrkB activation within mossy fibers of mouse hippocampus in vivo.

    PubMed

    Helgager, Jeffrey; Huang, Yang Zhong; Mcnamara, James O

    2014-12-01

    The neurotrophin receptor, TrkB receptor tyrosine kinase, is critical to central nervous system (CNS) function in health and disease. Elucidating the ligands mediating TrkB activation in vivo will provide insights into its diverse roles in the CNS. The canonical ligand for TrkB is brain-derived neurotrophic factor (BDNF). A diversity of stimuli also can activate TrkB in the absence of BDNF, a mechanism termed transactivation. Zinc, a divalent cation packaged in synaptic vesicles along with glutamate in axons of mammalian cortical neurons, can transactivate TrkB in neurons and heterologous cells in vitro. Yet the contributions of BDNF and zinc to TrkB activation in vivo are unknown. To address these questions, we conducted immunohistochemical (IHC) studies of the hippocampal mossy fiber axons and boutons using an antibody selective for pY816 of TrkB, a surrogate measure of TrkB activation. We found that conditional deletion of BDNF resulted in a reduction of pY816 in axons and synaptic boutons of hippocampal mossy fibers, thereby implicating BDNF in activation of TrkB in vivo. Unexpectedly, pY816 immunoreactivity was increased in axons but not synaptic boutons of mossy fibers in ZnT3 knockout mice that lack vesicular zinc. Marked increases of BDNF content were evident within the hippocampus of ZnT3 knockout mice and genetic elimination of BDNF reduced pY816 immunoreactivity in these mice, implicating BDNF in enhanced TrkB activation mediated by vesicular zinc depletion. These findings support the conclusion that BDNF but not vesicular zinc activates TrkB in hippocampal mossy fiber axons under physiological conditions.

  20. Ultrasonic assisted removal of sunset yellow from aqueous solution by zinc hydroxide nanoparticle loaded activated carbon: Optimized experimental design.

    PubMed

    Roosta, M; Ghaedi, M; Sahraei, R; Purkait, M K

    2015-01-01

    The efficiency of zinc hydroxide nanoparticle loaded on activated carbon (Zn(OH)2-NP-AC) in the removal of sunset yellow from aqueous solutions using ultrasonic-assisted adsorption method was investigated. This nanomaterial was characterized using different techniques such as SEM, XRD and UV-vis spectrophotometer. A central composite design (CCD) was used for the optimization of significant factors using response surface methodology (RSM). Under the best conditions (5.2 min of sonication time, pH3, 0.023 g of adsorbent and 30 mg L(-1) of SY), Langmuir model was fitting the experimental equilibrium data well. The small amount of proposed adsorbent (0.023 g) is applicable for the successful removal of SY (>97%) in short time (5 min) with high adsorption capacity (83-114 mg g(-1)).

  1. Interaction Between Yeasts and Zinc

    NASA Astrophysics Data System (ADS)

    Nicola, Raffaele De; Walker, Graeme

    Zinc is an essential trace element in biological systems. For example, it acts as a cellular membrane stabiliser, plays a critical role in gene expression and genome modification and activates nearly 300 enzymes, including alcohol dehydrogenase. The present chapter will be focused on the influence of zinc on cell physiology of industrial yeast strains of Saccharomyces cerevisiae, with special regard to the uptake and subsequent utilisation of this metal. Zinc uptake by yeast is metabolism-dependent, with most of the available zinc translocated very quickly into the vacuole. At cell division, zinc is distributed from mother to daughter cells and this effectively lowers the individual cellular zinc concentration, which may become zinc depleted at the onset of the fermentation. Zinc influences yeast fermentative performance and examples will be provided relating to brewing and wine fermentations. Industrial yeasts are subjected to several stresses that may impair fermentation performance. Such stresses may also impact on yeast cell zinc homeostasis. This chapter will discuss the practical implications for the correct management of zinc bioavailability for yeast-based biotechnologies aimed at improving yeast growth, viability, fermentation performance and resistance to environmental stresses

  2. C-H Activation on Co,O Sites: Isolated Surface Sites versus Molecular Analogs.

    PubMed

    Estes, Deven P; Siddiqi, Georges; Allouche, Florian; Kovtunov, Kirill V; Safonova, Olga V; Trigub, Alexander L; Koptyug, Igor V; Copéret, Christophe

    2016-11-16

    The activation and conversion of hydrocarbons is one of the most important challenges in chemistry. Transition-metal ions (V, Cr, Fe, Co, etc.) isolated on silica surfaces are known to catalyze such processes. The mechanisms of these processes are currently unknown but are thought to involve C-H activation as the rate-determining step. Here, we synthesize well-defined Co(II) ions on a silica surface using a metal siloxide precursor followed by thermal treatment under vacuum at 500 °C. We show that these isolated Co(II) sites are catalysts for a number of hydrocarbon conversion reactions, such as the dehydrogenation of propane, the hydrogenation of propene, and the trimerization of terminal alkynes. We then investigate the mechanisms of these processes using kinetics, kinetic isotope effects, isotopic labeling experiments, parahydrogen induced polarization (PHIP) NMR, and comparison with a molecular analog. The data are consistent with all of these reactions occurring by a common mechanism, involving heterolytic C-H or H-H activation via a 1,2 addition across a Co-O bond.

  3. Polarizability of the active site of cytochrome c reduces the activation barrier for electron transfer

    PubMed Central

    Dinpajooh, Mohammadhasan; Martin, Daniel R.; Matyushov, Dmitry V.

    2016-01-01

    Enzymes in biology’s energy chains operate with low energy input distributed through multiple electron transfer steps between protein active sites. The general challenge of biological design is how to lower the activation barrier without sacrificing a large negative reaction free energy. We show that this goal is achieved through a large polarizability of the active site. It is polarized by allowing a large number of excited states, which are populated quantum mechanically by electrostatic fluctuations of the protein and hydration water shells. This perspective is achieved by extensive mixed quantum mechanical/molecular dynamics simulations of the half reaction of reduction of cytochrome c. The barrier for electron transfer is consistently lowered by increasing the number of excited states included in the Hamiltonian of the active site diagonalized along the classical trajectory. We suggest that molecular polarizability, in addition to much studied electrostatics of permanent charges, is a key parameter to consider in order to understand how enzymes work. PMID:27306204

  4. Zinc Binding to the Tyr402 and His402 Allotypes of Complement Factor H: Possible Implications for Age-Related Macular Degeneration

    PubMed Central

    Nan, Ruodan; Farabella, Irene; Schumacher, Felix F.; Miller, Ami; Gor, Jayesh; Martin, Andrew C.R.; Jones, David T.; Lengyel, Imre; Perkins, Stephen J.

    2011-01-01

    The Tyr402His polymorphism of complement factor H (FH) with 20 short complement regulator (SCR) domains is associated with age-related macular degeneration (AMD). How FH contributes to disease pathology is not clear. Both FH and high concentrations of zinc are found in drusen deposits, the key feature of AMD. Heterozygous FH is inhibited by zinc, which causes FH to aggregate. Here, zinc binding to homozygous FH was studied. By analytical ultracentrifugation, large amounts of oligomers were observed with both the native Tyr402 and the AMD-risk His402 homozygous allotypes of FH and both the recombinant SCR-6/8 allotypes with Tyr/His402. X-ray scattering also showed that both FH and SCR-6/8 allotypes strongly aggregated at > 10 μM zinc. The SCR-1/5 and SCR-16/20 fragments were less likely to bind zinc. These observations were supported by bioinformatics predictions. Starting from known zinc binding sites in crystal structures, we predicted 202 putative partial surface zinc binding sites in FH, most of which were in SCR-6. Metal site prediction web servers also suggested that SCR-6 and other domains bind zinc. Predicted SCR-6/8 dimer structures showed that zinc binding sites could be formed at the protein–protein interface that would lead to daisy-chained oligomers. It was concluded that zinc binds weakly to FH at multiple surface locations, most probably within the functionally important SCR-6/8 domains, and this explains why zinc inhibits FH activity. Given the high pathophysiological levels of bioavailable zinc present in subretinal deposits, we discuss how zinc binding to FH may contribute to deposit formation and inflammation associated with AMD. PMID:21396937

  5. Metals on the move: zinc ions in cellular regulation and in the coordination dynamics of zinc proteins.

    PubMed

    Maret, Wolfgang

    2011-06-01

    Homeostatic control maintains essential transition metal ions at characteristic cellular concentrations to support their physiological functions and to avoid adverse effects. Zinc is especially widely used as a catalytic or structural cofactor in about 3000 human zinc proteins. In addition, the homeostatic control of zinc in eukaryotic cells permits functions of zinc(II) ions in regulation and in paracrine and intracrine signaling. Zinc ions are released from proteins through ligand-centered reactions in zinc/thiolate coordination environments, and from stores in cellular organelles, where zinc transporters participate in zinc loading and release. Muffling reactions allow zinc ions to serve as signaling ions (second messengers) in the cytosol that is buffered to picomolar zinc ion concentrations at steady-state. Muffling includes zinc ion binding to metallothioneins, cellular translocations of metallothioneins, delivery of zinc ions to transporter proteins, and zinc ion fluxes through cellular membranes with the result of removing the additional zinc ions from the cytosol and restoring the steady-state. Targets of regulatory zinc ions are proteins with sites for transient zinc binding, such as membrane receptors, enzymes, protein-protein interactions, and sensor proteins that control gene expression. The generation, transmission, targets, and termination of zinc ion signals involve proteins that use coordination dynamics in the inner and outer ligand spheres to control metal ion association and dissociation. These new findings establish critically important functions of zinc ions and zinc metalloproteins in cellular control.

  6. Structural Basis for Autoregulation of the Zinc Transporter YiiP

    SciTech Connect

    Lu, M.; Chai, J; Fu, D

    2009-01-01

    Zinc transporters have crucial roles in cellular zinc homeostatic control. The 2.9-A resolution structure of the zinc transporter YiiP from Escherichia coli reveals a richly charged dimer interface stabilized by zinc binding. Site-directed fluorescence resonance energy transfer (FRET) measurements and mutation-activity analysis suggest that zinc binding triggers hinge movements of two electrically repulsive cytoplasmic domains pivoting around four salt bridges situated at the juncture of the cytoplasmic and transmembrane domains. These highly conserved salt bridges interlock transmembrane helices at the dimer interface, where they are well positioned to transmit zinc-induced interdomain movements to reorient transmembrane helices, thereby modulating coordination geometry of the active site for zinc transport. The cytoplasmic domain of YiiP is a structural mimic of metal-trafficking proteins and the metal-binding domains of metal-transporting P-type ATPases. The use of this common structural module to regulate metal coordination chemistry may enable a tunable transport activity in response to cytoplasmic metal fluctuations.

  7. SRC-DEPENDENT PHOSPHORYLATION OF THE EPIDERMAL GROWTH FACTOR RECEPTOR ON TYROSINE 845 IS REQUIRED FOR ZINC-INDUCED RAS ACTIVATION

    EPA Science Inventory

    Src-dependent Phosphorylation of the Epidermal Growth Factor Receptor on Tyrosine 845 Is Required for Zinc-induced Ras Activation
    Weidong Wu 1 , Lee M. Graves 2 , Gordon N. Gill 3 , Sarah J. Parsons 4 , and James M. Samet 5
    1 Center for Environmental Medicine and Lung Biolo...

  8. Active Sites Environmental Monitoring Program: Program plan. Revision 1

    SciTech Connect

    Ashwood, T.L.; Wickliff, D.S.; Morrissey, C.M.

    1992-02-01

    The Active Sites Environmental Monitoring Program (ASEMP), initiated in 1989, provides early detection and performance monitoring of transuranic (TRU) waste and active low-level waste (LLW) facilities at Oak Ridge National Laboratory (ORNL) in accordance with US Department of Energy (DOE) Order 5820.2A. Active LLW facilities in Solid Waste Storage Area (SWSA) 6 include Tumulus I and Tumulus II, the Interim Waste Management Facility (IWMF), LLW silos, high-range wells, asbestos silos, and fissile wells. The tumulus pads and IWMF are aboveground, high-strength concrete pads on which concrete vaults containing metal boxes of LLW are placed; the void space between the boxes and vaults is filled with grout. Eventually, these pads and vaults will be covered by an engineered multilayered cap. All other LLW facilities in SWSA 6 are below ground. In addition, this plan includes monitoring of the Hillcut Disposal Test Facility (HDTF) in SWSA 6, even though this facility was completed prior to the data of the DOE order. In SWSA 5 North, the TRU facilities include below-grade engineered caves, high-range wells, and unlined trenches. All samples from SWSA 6 are screened for alpha and beta activity, counted for gamma-emitting isotopes, and analyzed for tritium. In addition to these analytes, samples from SWSA 5 North are analyzed for specific transuranic elements.

  9. Physically adsorbed fullerene layer on positively charged sites on zinc oxide cathode affords efficiency enhancement in inverted polymer solar cell.

    PubMed

    Cheng, Yu-Shan; Liao, Sih-Hao; Li, Yi-Lun; Chen, Show-An

    2013-07-24

    We present a novel idea for overcoming the drawback of poor contact between the ZnO cathode and active layer interface in an inverted polymer solar cell (i-PSC), simply by incorporating an electron-acceptor self-assembled monolayer (SAM)--tetrafluoroterephthalic acid (TFTPA)--on the ZnO cathode surface to create an electron-poor surface of TFTPA on ZnO. The TFTPA molecules on ZnO are anchored on the ZnO surface by reacting its carboxyl groups with hydroxyl groups on the ZnO surface, such that the tetrafluoroterephthalate moieties lay on the surface with plane-on electron-poor benzene rings acting as positive charge centers. Upon coating a layer of fullerenes on top of it, the fullerene molecules can be physically adsorbed by Coulombic interaction and facilitate a promoted electron collection from the bulk. The active layer is composed of the mid bandgap polymer poly(3-hexylthiophene) (P3HT) or low bandgap polymer, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl

  10. Enzyme activity as an indicator of soil-rehabilitation processes at a zinc and lead ore mining and processing area.

    PubMed

    Ciarkowska, Krystyna; Sołek-Podwika, Katarzyna; Wieczorek, Jerzy

    2014-01-01

    The activities of soil enzymes in relation to the changes occurring in the soil on a degraded area in southern Poland after zinc and lead mining were analyzed. An evaluation of the usefulness of urease and invertase activities for estimating the progress of the rehabilitation processes in degraded soil was performed. The data show that the soil samples differed significantly in organic carbon (0.68-104.0 g kg(-1)) and total nitrogen (0.03-8.64 g kg(-1)) content in their surface horizons. All of the soil samples (apart from one covered with forest) had very high total concentrations of zinc (4050-10,884 mg kg(-1)), lead (959-6661 mg kg(-1)) and cadmium (24.4-174.3 mg kg(-1)) in their surface horizons, and similar concentrations in their deeper horizons. Nevertheless, the amounts of the soluble forms of the above-mentioned heavy metals were quite low and they accounted for only a small percentage of the total concentrations: 1.4% for Zn, 0.01% for Pb and 2.6% for Cd. Urease activities were ranked as follows: soil from flotation settler (0.88-1.78 μg N-NH4(+) 2h(-1) g(-1))activity (2.14-5.73 μg N-NH4(+) 2h(-1) g(-1)). Invertase activities were similar in soil that was undisturbed by mining and in soil from old slag heaps, ranging from 20.5 to 77.1mg of the inverted sugar, but they were much lower in soil from the flotation settler (0.12-6.95 mg of the inverted sugar). The results demonstrated that heavy pollution with Zn, Pb and Cd slightly decreased the activities of urease and invertase. It is thought that it resulted from the enzyme reactions occurring in slightly acidic or alkaline soil conditions. Under such conditions, heavy metals occur mainly in insoluble forms. The activities of these enzymes are strongly dependent on the content and decomposition of organic matter in the soil.

  11. What every dentist should know about zinc.

    PubMed

    Patel, Amar; von Fraunhofer, J Anthony; Bashirelahi, Nasir

    2011-01-01

    Zinc plays an important role in human physiology, from its involvement in the proper function of the immune system to its role in cellular growth, cell proliferation, and cell apoptosis as well as its essential role in the activity of numerous zinc-binding proteins. However, zinc also plays a key pathophysiological role in major neurological disorders and diabetes. Zinc deficiency is a worldwide problem, whereas excessive intake of zinc is relatively rare. Many patients are exposed to zinc on a regular basis through dentistry as a result of its use in certain restorative materials, mouthwashes, toothpastes and, notably, denture adhesives. Of particular importance to dental professionals are various case reports concerning the neurologic effects of excess zinc intake by patients who routinely use large quantities of zinc-containing denture adhesives. This review presents relevant information concerning the use of zinc in dentistry.

  12. Zinc in innate and adaptive tumor immunity

    PubMed Central

    2010-01-01

    Zinc is important. It is the second most abundant trace metal with 2-4 grams in humans. It is an essential trace element, critical for cell growth, development and differentiation, DNA synthesis, RNA transcription, cell division, and cell activation. Zinc deficiency has adverse consequences during embryogenesis and early childhood development, particularly on immune functioning. It is essential in members of all enzyme classes, including over 300 signaling molecules and transcription factors. Free zinc in immune and tumor cells is regulated by 14 distinct zinc importers (ZIP) and transporters (ZNT1-8). Zinc depletion induces cell death via apoptosis (or necrosis if apoptotic pathways are blocked) while sufficient zinc levels allows maintenance of autophagy. Cancer cells have upregulated zinc importers, and frequently increased zinc levels, which allow them to survive. Based on this novel synthesis, approaches which locally regulate zinc levels to promote survival of immune cells and/or induce tumor apoptosis are in order. PMID:21087493

  13. Active Site and Laminarin Binding in Glycoside Hydrolase Family 55*

    PubMed Central

    Bianchetti, Christopher M.; Takasuka, Taichi E.; Deutsch, Sam; Udell, Hannah S.; Yik, Eric J.; Bergeman, Lai F.; Fox, Brian G.

    2015-01-01

    The Carbohydrate Active Enzyme (CAZy) database indicates that glycoside hydrolase family 55 (GH55) contains both endo- and exo-β-1,3-glucanases. The founding structure in the GH55 is PcLam55A from the white rot fungus Phanerochaete chrysosporium (Ishida, T., Fushinobu, S., Kawai, R., Kitaoka, M., Igarashi, K., and Samejima, M. (2009) Crystal structure of glycoside hydrolase family 55 β-1,3-glucanase from the basidiomycete Phanerochaete chrysosporium. J. Biol. Chem. 284, 10100–10109). Here, we present high resolution crystal structures of bacterial SacteLam55A from the highly cellulolytic Streptomyces sp. SirexAA-E with bound substrates and product. These structures, along with mutagenesis and kinetic studies, implicate Glu-502 as the catalytic acid (as proposed earlier for Glu-663 in PcLam55A) and a proton relay network of four residues in activating water as the nucleophile. Further, a set of conserved aromatic residues that define the active site apparently enforce an exo-glucanase reactivity as demonstrated by exhaustive hydrolysis reactions with purified laminarioligosaccharides. Two additional aromatic residues that line the substrate-binding channel show substrate-dependent conformational flexibility that may promote processive reactivity of the bound oligosaccharide in the bacterial enzymes. Gene synthesis carried out on ∼30% of the GH55 family gave 34 active enzymes (19% functional coverage of the nonredundant members of GH55). These active enzymes reacted with only laminarin from a panel of 10 different soluble and insoluble polysaccharides and displayed a broad range of specific activities and optima for pH and temperature. Application of this experimental method provides a new, systematic way to annotate glycoside hydrolase phylogenetic space for functional properties. PMID:25752603

  14. An Active Site Water Network in the Plasminogen Activator Pla from Yersinia pestis

    SciTech Connect

    Eren, Elif; Murphy, Megan; Goguen, Jon; van den Berg, Bert

    2010-08-13

    The plasminogen activator Pla from Yersinia pestis is an outer membrane protease (omptin) that is important for the virulence of plague. Here, we present the high-resolution crystal structure of wild-type, enzymatically active Pla at 1.9 {angstrom}. The structure shows a water molecule located between active site residues D84 and H208, which likely corresponds to the nucleophilic water. A number of other water molecules are present in the active site, linking residues important for enzymatic activity. The R211 sidechain in loop L4 is close to the nucleophilic water and possibly involved in the stabilization of the oxyanion intermediate. Subtle conformational changes of H208 result from the binding of lipopolysaccharide to the outside of the barrel, explaining the unusual dependence of omptins on lipopolysaccharide for activity. The Pla structure suggests a model for the interaction with plasminogen substrate and provides a more detailed understanding of the catalytic mechanism of omptin proteases.

  15. An active site water network in the plasminogen activator pla from Yersinia pestis.

    PubMed

    Eren, Elif; Murphy, Megan; Goguen, Jon; van den Berg, Bert

    2010-07-14

    The plasminogen activator Pla from Yersinia pestis is an outer membrane protease (omptin) that is important for the virulence of plague. Here, we present the high-resolution crystal structure of wild-type, enzymatically active Pla at 1.9 A. The structure shows a water molecule located between active site residues D84 and H208, which likely corresponds to the nucleophilic water. A number of other water molecules are present in the active site, linking residues important for enzymatic activity. The R211 sidechain in loop L4 is close to the nucleophilic water and possibly involved in the stabilization of the oxyanion intermediate. Subtle conformational changes of H208 result from the binding of lipopolysaccharide to the outside of the barrel, explaining the unusual dependence of omptins on lipopolysaccharide for activity. The Pla structure suggests a model for the interaction with plasminogen substrate and provides a more detailed understanding of the catalytic mechanism of omptin proteases.

  16. Zinc ionophores pyrithione inhibits herpes simplex virus replication through interfering with proteasome function and NF-κB activation.

    PubMed

    Qiu, Min; Chen, Yu; Chu, Ying; Song, Siwei; Yang, Na; Gao, Jie; Wu, Zhiwei

    2013-10-01

    Pyrithione (PT), known as a zinc ionophore, is effective against several pathogens from the Streptococcus and Staphylococcus genera. The antiviral activity of PT was also reported against a number of RNA viruses. In this paper, we showed that PT could effectively inhibit herpes simplex virus types 1 and 2 (HSV-1 and HSV-2). PT inhibited HSV late gene (Glycoprotein D, gD) expression and the production of viral progeny, and this action was dependent on Zn(2+). Further studies showed that PT suppressed the expression of HSV immediate early (IE) gene, the infected cell polypeptide 4 (ICP4), but had less effect on another regulatory IE protein, ICP0. It was found that PT treatment could interfere with cellular ubiquitin-proteasome system (UPS), leading to the inhibition of HSV-2-induced IκB-α degradation to inhibit NF-κB activation and enhanced promyelocytic leukemia protein (PML) stability in nucleus. However, PT did not show direct inhibition of 26S proteasome activity. Instead, it induced Zn(2+) influx, which facilitated the dysregulation of UPS and the accumulation of intracellular ubiquitin-conjugates. UPS inhibition by PT caused disruption of IκB-α degradation and NF-κB activation thus leading to marked reduction of viral titer.

  17. Zinc sulfide liquefaction catalyst

    DOEpatents

    Garg, Diwakar

    1984-01-01

    A process for the liquefaction of carbonaceous material, such as coal, is set forth wherein coal is liquefied in a catalytic solvent refining reaction wherein an activated zinc sulfide catalyst is utilized which is activated by hydrogenation in a coal derived process solvent in the absence of coal.

  18. Active Site Loop Conformation Regulates Promiscuous Activity in a Lactonase from Geobacillus kaustophilus HTA426

    PubMed Central

    Zhang, Yu; An, Jiao; Yang, Guang-Yu; Bai, Aixi; Zheng, Baisong; Lou, Zhiyong; Wu, Geng; Ye, Wei; Chen, Hai-Feng; Feng, Yan; Manco, Giuseppe

    2015-01-01

    Enzyme promiscuity is a prerequisite for fast divergent evolution of biocatalysts. A phosphotriesterase-like lactonase (PLL) from Geobacillus kaustophilus HTA426 (GkaP) exhibits main lactonase and promiscuous phosphotriesterase activities. To understand its catalytic and evolutionary mechanisms, we investigated a “hot spot” in the active site by saturation mutagenesis as well as X-ray crystallographic analyses. We found that position 99 in the active site was involved in substrate discrimination. One mutant, Y99L, exhibited 11-fold improvement over wild-type in reactivity (kcat/Km) toward the phosphotriesterase substrate ethyl-paraoxon, but showed 15-fold decrease toward the lactonase substrate δ-decanolactone, resulting in a 157-fold inversion of the substrate specificity. Structural analysis of Y99L revealed that the mutation causes a ∼6.6 Å outward shift of adjacent loop 7, which may cause increased flexibility of the active site and facilitate accommodation and/or catalysis of organophosphate substrate. This study provides for the PLL family an example of how the evolutionary route from promiscuity to specificity can derive from very few mutations, which promotes alteration in the conformational adjustment of the active site loops, in turn draws the capacity of substrate binding and activity. PMID:25706379

  19. Effect of calcium chloride, zinc chloride, and water infusion on metmyoglobin reducing activity and fresh lamb color.

    PubMed

    Bekhit, A E D; Ilian, M A; Morton, J D; Vanhanan, L; Sedcole, J R; Bickerstaffe, R

    2005-09-01

    Calcium chloride (CaCl2), zinc chloride (ZnCl2), or water infusions were used to investigate the biochemical factors that affect fresh lamb color, and to examine the role of metmyoglobin-reducing activity in regulating this important quality attribute. Immediately after exsanguination, lamb carcasses (n = 6 per treatment) were infused (10% of BW) with 0.3 M CaCl2, 0.05 M ZnCl2, or water via a catheter inserted into the left carotid artery. The right LM was excised at 24-h postmortem and divided into two halves. The caudal portion was cut into 2.5-cm-thick chops and displayed for 6 d under 1,076 lx of white fluorescent lighting at 2 degrees C, whereas the cranial half was vacuum-packaged and stored at 2 degrees C for 3 wk before retail display. Objective color measurements and samples for biochemical analysis were taken at 0, 1, 3, and 6 d of display. In infused carcasses, pH decline was more rapid (P < 0.05) than in untreated controls, and it was greatest for CaCl2-infused carcasses. Calcium chloride-infused carcasses had lower (P < 0.01) NAD and higher (P < 0.001) NADPH concentrations than water- and ZnCl2-infused or untreated control carcasses. The negative effects of calcium infusion on fresh lamb color, higher (P < 0.01) metmyoglobin accumulation rate, and lower (P < 0.01) L*, a*, and b* color measurements could be explained by the lower amounts of unbound water (P < 0.01), shorter sarcomere length (P < 0.01), lower NAD concentrations (P < 0.01), and higher lipid peroxidation (P < 0.01). Zinc and water-infusions produced less (P < 0.01) lipid oxidation and improved the color and color stability of fresh lamb (P < 0.001). Rate of lipid oxidation in LM chops was greater (P < 0.01) after 3 wk of vacuum-packaged storage than 24-h postmortem. Metmyoglobin-reducing activities (sarcoplasmic and myofibrillar) were decreased in response to infusion treatments (P < 0.001), and ZnCl2 infusion resulted in the lowest metmyoglobin-reducing activities (P < 0.001). A

  20. Characterization of the active site of ADP-ribosyl cyclase.

    PubMed

    Munshi, C; Thiel, D J; Mathews, I I; Aarhus, R; Walseth, T F; Lee, H C

    1999-10-22

    ADP-ribosyl cyclase synthesizes two Ca(2+) messengers by cyclizing NAD to produce cyclic ADP-ribose and exchanging nicotinic acid with the nicotinamide group of NADP to produce nicotinic acid adenine dinucleotide phosphate. Recombinant Aplysia cyclase was expressed in yeast and co-crystallized with a substrate, nicotinamide. x-ray crystallography showed that the nicotinamide was bound in a pocket formed in part by a conserved segment and was near the central cleft of the cyclase. Glu(98), Asn(107) and Trp(140) were within 3.5 A of the bound nicotinamide and appeared to coordinate it. Substituting Glu(98) with either Gln, Gly, Leu, or Asn reduced the cyclase activity by 16-222-fold, depending on the substitution. The mutant N107G exhibited only a 2-fold decrease in activity, while the activity of W140G was essentially eliminated. The base exchange activity of all mutants followed a similar pattern of reduction, suggesting that both reactions occur at the same active site. In addition to NAD, the wild-type cyclase also cyclizes nicotinamide guanine dinucleotide to cyclic GDP-ribose. All mutant enzymes had at least half of the GDP-ribosyl cyclase activity of the wild type, some even 2-3-fold higher, indicating that the three coordinating amino acids are responsible for positioning of the substrate but not absolutely critical for catalysis. To search for the catalytic residues, other amino acids in the binding pocket were mutagenized. E179G was totally devoid of GDP-ribosyl cyclase activity, and both its ADP-ribosyl cyclase and the base exchange activities were reduced by 10,000- and 18,000-fold, respectively. Substituting Glu(179) with either Asn, Leu, Asp, or Gln produced similar inactive enzymes, and so was the conversion of Trp(77) to Gly. However, both E179G and the double mutant E179G/W77G retained NAD-binding ability as shown by photoaffinity labeling with [(32)P]8-azido-NAD. These results indicate that both Glu(179) and Trp(77) are crucial for catalysis and

  1. Synthesis and characterization of zinc oxide nanorods and its photocatalytic activities towards degradation of 2,4-D.

    PubMed

    Meenakshi, G; Sivasamy, A

    2017-01-01

    Semiconductor zinc oxide nanorods (NRZnO) were prepared by sol-gel technique using zinc acetate as the precursor and ammonia as the precipitating agent. The prepared photocatalyst were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), UV-Visible diffuse reflectance spectroscopy (UV-Vis-DRS), X-ray photoelectron spectroscopy (XPS), Field Emission-Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM), High Resolution-Tunneling Microscope (HR-TEM), Brunauer, Emmett and Teller (BET) and electron paramagnetic resonance spectroscopy (EPR) analysis. Particle size of the prepared photocatalyst was established by XRD and FE-SEM analysis. The morphology and the formation of uniform NRZnO was controlled by the temperature, entire concentration of precursors, duration of aging process. High surface roughness and porosity confirmed by AFM analysis. Band gap energy of the synthesized photocatalyst (3.2eV) was determined by using diffuse reflectance spectroscopy. The in-situ production of OH radicals by the prepared photocatalyst was confirmed by electron paramagnetic resonance spectroscopy (EPR) spin trapping technique. The photocatalytic activity of prepared NRZnO was evaluated by photo degradation of 2, 4-dichlorophenoxyacetic acid (2, 4-D) under UV and visible light irradiations. Experimental parameter such as effect of pH, catalyst dosage, initial 2, 4- D concentrations and addition of different electrolytes on the degradation of 2, 4-D was also studied in detail. Neutral pH was found to be the optimum and catalyst dosage of 30mg/10ml resulted in higher percentage of degradation. The photo degraded samples were analyzed by chemical oxygen demand (COD) analysis, UV-Visible spectroscopy. Reusability of the prepared photocatalyst was tested upto three cycles without affecting its performance. The experimental shown the rate of degradation follows pseudo-first order rate kinetics with respect to 2, 4 D.

  2. Mutations inducing an active-site aperture in Rhizobium sp. sucrose isomerase confer hydrolytic activity.

    PubMed

    Lipski, Alexandra; Watzlawick, Hildegard; Ravaud, Stéphanie; Robert, Xavier; Rhimi, Moez; Haser, Richard; Mattes, Ralf; Aghajari, Nushin

    2013-02-01

    Sucrose isomerase is an enzyme that catalyzes the production of sucrose isomers of high biotechnological and pharmaceutical interest. Owing to the complexity of the chemical synthesis of these isomers, isomaltulose and trehalulose, enzymatic conversion remains the preferred method for obtaining these products. Depending on the microbial source, the ratio of the sucrose-isomer products varies significantly. In studies aimed at understanding and explaining the underlying molecular mechanisms of these reactions, mutations obtained using a random-mutagenesis approach displayed a major hydrolytic activity. Two of these variants, R284C and F164L, of sucrose isomerase from Rhizobium sp. were therefore crystallized and their crystal structures were determined. The three-dimensional structures of these mutants allowed the identification of the molecular determinants that favour hydrolytic activity compared with transferase activity. Substantial conformational changes resulting in an active-site opening were observed, as were changes in the pattern of water molecules bordering the active-site region.

  3. Zinc transporter 7 deficiency affects lipid synthesis in adipocytes by inhibiting insulin-dependent Akt activity and glucose uptake

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mice deficient for zinc transporter 7 (Znt7) are mildly zinc deficient, accompanied with low body weight gain and body fat accumulation. To investigate the underlying mechanism of Znt7 deficiency in body adiposity, we investigated fatty acid composition and insulin sensitivity in visceral (epididyma...

  4. Osteogenic activity and antibacterial effect of zinc oxide/carboxylated graphene oxide nanocomposites: Preparation and in vitro evaluation.

    PubMed

    Chen, Junyu; Zhang, Xin; Cai, He; Chen, Zhiqiang; Wang, Tong; Jia, Lingling; Wang, Jian; Wan, Qianbing; Pei, Xibo

    2016-11-01

    The aim of this study was to prepare nanocomposites of carboxylated graphene oxide (GO-COOH) sheets decorated with zinc oxide (ZnO) nanoparticles (NPs) and investigate their advantages in the field of bone tissue engineering. First, ZnO/GO-COOH nanocomposites were synthesized by facile reactions, including the carboxylation of graphene oxide (GO) and the nucleation of ZnO on GO-COOH sheets. The synthesized ZnO/GO-COOH nanocomposites were then characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, and transmission electron microscopy (TEM). The biocompatibility, osteogenic activity and antibacterial effect of ZnO/GO-COOH nanocomposites were further investigated. In the nanocomposites, ZnO nanoparticles with a size of approximately 12nm were uniformly decorated on GO-COOH sheets. Compared with GO-COOH and the control group, ZnO/GO-COOH nanocomposites significantly enhanced ALP activity, osteocalcin production and extracellular matrix mineralization as well as up-regulated osteogenic-related genes (ALP, OCN, and Runx2) in MG63 osteoblast-like cells. Moreover, ZnO/GO-COOH nanocomposites had an antibacterial effect against Streptococcus mutans. These results indicated that ZnO/GO-COOH nanocomposites exhibited both osteogenic activity and antibacterial effect and had great potential for designing new biomaterials in the field of bone tissue engineering.

  5. Multi-reporter selection for the design of active and more specific zinc-finger nucleases for genome editing

    PubMed Central

    Oakes, Benjamin L.; Xia, Danny F.; Rowland, Elizabeth F.; Xu, Denise J.; Ankoudinova, Irina; Borchardt, Jennifer S.; Zhang, Lei; Li, Patrick; Miller, Jeffrey C.; Rebar, Edward J.; Noyes, Marcus B.

    2016-01-01

    Engineered nucleases have transformed biological research and offer great therapeutic potential by enabling the straightforward modification of desired genomic sequences. While many nuclease platforms have proven functional, all can produce unanticipated off-target lesions and have difficulty discriminating between homologous sequences, limiting their therapeutic application. Here we describe a multi-reporter selection system that allows the screening of large protein libraries to uncover variants able to discriminate between sequences with substantial homology. We have used this system to identify zinc-finger nucleases that exhibit high cleavage activity (up to 60% indels) at their targets within the CCR5 and HBB genes and strong discrimination against homologous sequences within CCR2 and HBD. An unbiased screen for off-target lesions using a novel set of CCR5-targeting nucleases confirms negligible CCR2 activity and demonstrates minimal off-target activity genome wide. This system offers a straightforward approach to generate nucleases that discriminate between similar targets and provide exceptional genome-wide specificity. PMID:26738816

  6. Bis(hinokitiolato)zinc complex ([Zn(hkt)2]) activates Akt/protein kinase B independent of insulin signal transduction.

    PubMed

    Naito, Yuki; Yoshikawa, Yutaka; Masuda, Kazufumi; Yasui, Hiroyuki

    2016-07-01

    Since many Zn complexes have been developed to enhance the insulin-like activity and increase the exposure and residence of Zn in the animal body, these complexes are recognized as one of the new candidates with action mechanism different from existing anti-diabetic drugs. However, the molecular mechanism by which Zn complexes exert an anti-DM effect is unknown. Therefore, we evaluated the activity of Zn complexes, especially related to the phosphorylation of insulin signaling pathway components. We focused on the insulin-like effects of the bis(hinokitiolato)zinc complex, [Zn(hkt)2], using 3T3-L1 adipocytes. [Zn(hkt)2] was taken up by cells and induced Akt phosphorylation in a time-dependent manner. Additionally, it showed inhibitory activity against PTP1B and PTEN, which are major negative regulators of insulin signaling. It did not promote the phosphorylation of IR (insulin receptor)-β or IRS (insulin receptor substrate)-1 by itself, but in combination with insulin, it enhanced the phosphorylation of IRβ. We conclude that [Zn(hkt)2] has effects on the proteins of insulin signaling pathway without insulin receptor mediation, and [Zn(hkt)2] promotes insulin function and shows the anti-DM effects. Thus, [Zn(hkt)2] may be the basis for improved DM treatments.

  7. A Three-Photon Active Organic Fluorophore for Deep Tissue Ratiometric Imaging of Intracellular Divalent Zinc.

    PubMed

    Philips, Divya Susan; Sreejith, Sivaramapanicker; He, Tingchao; Menon, Nishanth Venugopal; Anees, Palapuravan; Mathew, Jomon; Sajikumar, Sreedharan; Kang, Yuejun; Stuparu, Mihaiela Corina; Sun, Handong; Zhao, Yanli; Ajayaghosh, Ayyappanpillai

    2016-05-20

    Deep tissue bioimaging with three-photon (3P) excitation using near-infrared (NIR) light in the second IR window (1.0-1.4 μm) could provide high resolution images with an improved signal-to-noise ratio. Herein, we report a photostable and nontoxic 3P excitable donor-π-acceptor system (GMP) having 3P cross-section (σ3 ) of 1.78×10(-80)  cm(6)  s(2)  photon(-2) and action cross-section (σ3 η3 ) of 2.31×10(-81)  cm(6)  s(2)  photon(-2) , which provides ratiometric fluorescence response with divalent zinc ions in aqueous conditions. The probe signals the Zn(2+) binding at 530 and 600 nm, respectively, upon 1150 nm excitation with enhanced σ3 of 1.85×10(-80)  cm(6)  s(2)  photon(-2) and σ3 η3 of 3.33×10(-81)  cm(6)  s(2)  photon(-2) . The application of this probe is demonstrated for ratiometric 3P imaging of Zn(2+) in vitro using HuH-7 cell lines. Furthermore, the Zn(2+) concentration in rat hippocampal slices was imaged at 1150 nm excitation after incubation with GMP, illustrating its potential as a 3P ratiometric probe for deep tissue Zn(2+) ion imaging.

  8. Site-specific PEGylation of lidamycin and its antitumor activity

    PubMed Central

    Li, Liang; Shang, Boyang; Hu, Lei; Shao, Rongguang; Zhen, Yongsu

    2015-01-01

    In this study, N-terminal site-specific mono-PEGylation of the recombinant lidamycin apoprotein (rLDP) of lidamycin (LDM) was prepared using a polyethyleneglycol (PEG) derivative (Mw 20 kDa) through a reactive terminal aldehyde group under weak acidic conditions (pH 5.5). The biochemical properties of mPEG-rLDP-AE, an enediyne-integrated conjugate, were analyzed by SDS-PAGE, RP-HPLC, SEC-HPLC and MALDI-TOF. Meanwhile, in vitro and in vivo antitumor activity of mPEG-rLDP-AE was evaluated by MTT assays and in xenograft model. The results indicated that mPEG-rLDP-AE showed significant antitumor activity both in vitro and in vivo. After PEGylation, mPEG-rLDP still retained the binding capability to the enediyne AE and presented the physicochemical characteristics similar to that of native LDP. It is of interest that the PEGylation did not diminish the antitumor efficacy of LDM, implying the possibility that this derivative may function as a payload to deliver novel tumor-targeted drugs. PMID:26579455

  9. Activating human genes with zinc finger proteins, transcription activator-like effectors and CRISPR/Cas9 for gene therapy and regenerative medicine.

    PubMed

    Gersbach, Charles A; Perez-Pinera, Pablo

    2014-08-01

    New technologies have recently been developed to control the expression of human genes in their native genomic context by engineering synthetic transcription factors that can be targeted to any DNA sequence. The ability to precisely regulate any gene as it occurs naturally in the genome provides a means to address a variety of diseases and disorders. This approach also circumvents some of the traditional challenges of gene therapy. In this editorial, we review the technologies that have enabled targeted human gene activation, including the engineering of transcription factors based on zinc finger proteins, transcription activator-like effectors and the CRISPR/Cas9 system. Additionally, we highlight examples in which these methods have been developed for therapeutic applications and discuss challenges and opportunities.

  10. Allosteric site-mediated active site inhibition of PBP2a using Quercetin 3-O-rutinoside and its combination.

    PubMed

    Rani, Nidhi; Vijayakumar, Saravanan; P T V, Lakshmi; Arunachalam, Annamalai

    2016-08-01

    Recent crystallographic study revealed the involvement of allosteric site in active site inhibition of penicillin binding protein (PBP2a), where one molecule of Ceftaroline (Cef) binds to the allosteric site of PBP2a and paved way for the other molecule (Cef) to bind at the active site. Though Cef has the potency to inhibit the PBP2a, its adverse side effects are of major concern. Previous studies have reported the antibacterial property of Quercetin derivatives, a group of natural compounds. Hence, the present study aims to evaluate the effect of Quercetin 3-o-rutinoside (Rut) in allosteric site-mediated active site inhibition of PBP2a. The molecular docking studies between allosteric site and ligands (Rut, Que, and Cef) revealed a better binding efficiency (G-score) of Rut (-7.790318) and Cef (-6.194946) with respect to Que (-5.079284). Molecular dynamic (MD) simulation studies showed significant changes at the active site in the presence of ligands (Rut and Cef) at allosteric site. Four different combinations of Rut and Cef were docked and their G-scores ranged between -6.320 and -8.623. MD studies revealed the stability of the key residue (Ser403) with Rut being at both sites, compared to other complexes. Morphological analysis through electron microscopy confirmed that combination of Rut and Cefixime was able to disturb the bacterial cell membrane in a similar fashion to that of Rut and Cefixime alone. The results of this study indicate that the affinity of Rut at both sites were equally good, with further validations Rut could be considered as an alternative for inhibiting MRSA growth.

  11. Zinc: indications in brain disorders.

    PubMed

    Prakash, Atish; Bharti, Kanchan; Majeed, Abu Bakar A

    2015-04-01

    Zinc is the authoritative metal which is present in our body, and reactive zinc metal is crucial for neuronal signaling and is largely distributed within presynaptic vesicles. Zinc also plays an important role in synaptic function. At cellular level, zinc is a modulator of synaptic activity and neuronal plasticity in both development and adulthood. Different importers and transporters are involved in zinc homeostasis. ZnT-3 is a main transporter involved in zinc homeostasis in the brain. It has been found that alterations in brain zinc status have been implicated in a wide range of neurological disorders including impaired brain development and many neurodegenerative disorders such as Alzheimer's disease, and mood disorders including depression, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and prion disease. Furthermore, zinc has also been implicated in neuronal damage associated with traumatic brain injury, stroke, and seizure. Understanding the mechanisms that control brain zinc homeostasis is thus critical to the development of preventive and treatment strategies for these and other neurological disorders.

  12. Extensive site-directed mutagenesis reveals interconnected functional units in the alkaline phosphatase active site

    PubMed Central

    Sunden, Fanny; Peck, Ariana; Salzman, Julia; Ressl, Susanne; Herschlag, Daniel

    2015-01-01

    Enzymes enable life by accelerating reaction rates to biological timescales. Conventional studies have focused on identifying the residues that have a direct involvement in an enzymatic reaction, but these so-called ‘catalytic residues’ are embedded in extensive interaction networks. Although fundamental to our understanding of enzyme function, evolution, and engineering, the properties of these networks have yet to be quantitatively and systematically explored. We dissected an interaction network of five residues in the active site of Escherichia coli alkaline phosphatase. Analysis of the complex catalytic interdependence of specific residues identified three energetically independent but structurally interconnected functional units with distinct modes of cooperativity. From an evolutionary perspective, this network is orders of magnitude more probable to arise than a fully cooperative network. From a functional perspective, new catalytic insights emerge. Further, such comprehensive energetic characterization will be necessary to benchmark the algorithms required to rationally engineer highly efficient enzymes. DOI: http://dx.doi.org/10.7554/eLife.06181.001 PMID:25902402

  13. A split active site couples cap recognition by Dcp2 to activation

    PubMed Central

    Floor, Stephen N.; Jones, Brittnee N.; Hernandez, Gail A.; Gross, John D.

    2010-01-01

    Decapping by Dcp2 is an essential step in 5′-3′ mRNA decay. In yeast, decapping requires an open-to-closed transition in Dcp2, though the link between closure and catalysis remains elusive. Here we show using NMR that cap binds conserved residues on both the catalytic and regulatory domains of Dcp2. Lesions in the cap-binding site on the regulatory domain reduce the catalytic step two orders of magnitude and block formation of the closed state whereas Dcp1 enhances the catalytic step by a factor of ten and promotes closure. We conclude that closure occurs during the rate-limiting catalytic step of decapping, juxtaposing the cap-binding region of each domain to form a composite active site. This work suggests a model for regulation of decapping, where coactivators trigger decapping by stabilizing a labile composite active site. PMID:20711189

  14. In vitro permeation and biological activity of punicalagin and zinc (II) across skin and mucous membranes prone to Herpes simplex virus infection.

    PubMed

    Houston, David M J; Robins, Bethan; Bugert, Joachim J; Denyer, Stephen P; Heard, Charles M

    2017-01-01

    Coadministration of pomegranate rind extract (PRE) and zinc (II) ions has recently been reported as a potential new topical treatment for Herpes simplex virus (HSV) infections. In the current work we examined the in vitro topical delivery of punicalagin (major phytochemical of PRE) and zinc from hydrogels across epithelial membranes that can become infected with HSV. Porcine epidermal, buccal and vaginal mucous membranes were excised and mounted in Franz diffusion cells and dosed with a simple hydrogel containing PRE and zinc sulphate (ZnSO4). The permeation of punicalagin and zinc were determined by HPLC and ICPMS respectively; punicalagin was also determined in the basal layers by reverse tape stripping. Receptor phases from the epidermal membrane experiment were also used to challenge HSV-1 in Vero host cells, and ex vivo porcine skin was used to probe COX-2 modulation. Punicalagin and zinc permeated each of the three test membranes, with significantly greater amounts of both delivered across the epidermal membrane. The amounts of punicalagin permeating the buccal and vaginal membranes were similar, although the amount of zinc permeating the vaginal membrane was comparatively very large - it is known that zinc interacts with vaginal mucosa. The punicalagin recovered by reverse tape stripping of the epidermal, buccal and vaginal membranes gave 0.47±0.016, 0.45±0.052 and 0.51±0.048nMcm(-2) respectively, and were statistically the same (p<0.05). A 2.5 log reduction was achieved against HSV-1 using diffusion cell receptor phase, and COX-2 expression was reduced by 64% in ex vivo skin after 6h. Overall, a hydrogel containing 1.25mgmL(-1) PRE and 0.25M ZnSO4 was able to topically deliver both the major bioactive compound within PRE and Zn (II) across all membranes and into the site specific region of Herpes simplex vesicular clusters, while maintaining potentiated virucidal and anti-inflammatory properties. This novel therapeutic system therefore has potential for

  15. Carbonic anhydrase activity and photosynthetic rate in the tree species Paulownia tomentosa Steud. Effect of dimethylsulfoxide treatment and zinc accumulation in leaves.

    PubMed

    Lazova, Galia N; Naidenova, Tsveta; Velinova, Katya

    2004-03-01

    The enzyme carbonic anhydrase (CA) (EC 4.2.1.1) catalyzes the reversible conversion of CO2 to HCO3- and has been shown to be involved in photosynthesis. The enzyme has been shown in animals, plants, eubacteria and viruses, but similar reports on the evidence for CA activity in tree plants does not be appear to be available. In the preliminary analyses of the work, the CA activity in leaf extracts from the tree species Paulownia tomentosa Steud. (introduced in Bulgaria) is described. A connection between CA activity and the rate of photosynthetic CO2 fixation is shown. In the second portion of the work, the effect of 10(-4) mol/L and 10(-2) mol/L dimethylsulfoxide (DMSO) on the zinc accumulation in leaves is demonstrated. It is suggested that CA activity is an indicator of the level of physiologically active zinc in leaves of P. tomentosa Steud. A connection between the process of zinc accumulation in leaves and the activity of the enzymes CA and glycolate oxidase (GO) (EC 1.1.3.1) is established.

  16. Metal-Organic Frameworks as Highly Active Electrocatalysts for High-Energy Density, Aqueous Zinc-Polyiodide Redox Flow Batteries.

    PubMed

    Li, Bin; Liu, Jian; Nie, Zimin; Wang, Wei; Reed, David; Liu, Jun; McGrail, Pete; Sprenkle, Vincent

    2016-07-13

    The new aqueous zinc-polyiodide redox flow battery (RFB) system with highly soluble active materials as well as ambipolar and bifunctional designs demonstrated significantly enhanced energy density, which shows great potential to reduce RFB cost. However, the poor kinetic reversibility and electrochemical activity of the redox reaction of I3(-)/I(-) couples on graphite felts (GFs) electrode can result in low energy efficiency. Two nanoporous metal-organic frameworks (MOFs), MIL-125-NH2 and UiO-66-CH3, that have high surface areas when introduced to GF surfaces accelerated the I3(-)/I(-) redox reaction. The flow cell with MOF-modified GFs serving as a positive electrode showed higher energy efficiency than the pristine GFs; increases of about 6.4% and 2.7% occurred at the current density of 30 mA/cm(2) for MIL-125-NH2 and UiO-66-CH3, respectively. Moreover, UiO-66-CH3 is more promising due to its excellent chemical stability in the weakly acidic electrolyte. This letter highlights a way for MOFs to be used in the field of RFBs.

  17. Effect of reaction parameters on photoluminescence and photocatalytic activity of zinc sulfide nanosphere synthesized by hydrothermal route

    NASA Astrophysics Data System (ADS)

    Chanu, T. Inakhunbi; Samanta, Dhrubajyoti; Tiwari, Archana; Chatterjee, Somenath

    2017-01-01

    Zinc Sulfide (ZnS) nanospheres have been synthesized using amino acid, L-Histidine as a capping agent by hydrothermal method. The as prepared ZnS have been characterised using X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), Photoluminescence (PL), Fourier Transform Infra-Red spectroscopy (FTIR), UV-vis absorption spectroscopy and X-ray Photo Electron Spectroscopy (XPS). Effect of reaction parameters on particle size has been investigated. The morphology and size of the ZnS can be tuned based on the reaction parameters. ZnS nanosphere with a particle size of 5 nm is obtained when the reaction parameters are kept at 120 °C for 3 h. The PL of ZnS shows multiple defect emissions arising from interstitials/vacancies. Particle size of ZnS nanoparticles plays an important role in determining the photo catalytic activity. A chronological study on synthesis of ZnS nanosphere and its photo catalytic activity under the sunlight are discussed here, which reveals the photo degradation of Rhodamine B (RhB) upto 87% as observed with ZnS nanosphere having a particle size of 5 nm.

  18. Silver and zinc oxide nanostructures loaded on activated carbon as new adsorbents for removal of methylene green: a comparative study.

    PubMed

    Ghaedi, M; Karimi, H; Yousefi, F

    2014-09-01

    In this study, the removal of methylene green (MG) from aqueous solution based on two new adsorbents including silver nanoparticles and zinc oxide nanorods loaded on activated carbon (Ag-NP-AC and ZnO-NR-AC, respectively) has been carried out. The dependency of removal process to variables such as contact time, pH, amount of adsorbents, and initial MG concentration were examined and optimized. It was found that the maximum MG removal percentage was achieved at pH = 7.0 following stirring at 400 r min(-1) for 7 and 6 min for Ag-NP-AC and ZnO-NR-AC, respectively. Equilibrium data were well fitted with the Langmuir model having maximum adsorption capacity of 166.7 and 200 mg g(-1) for Ag-NP-AC and ZnO-NR-AC, respectively. Thermodynamic parameters of MG adsorption on Ag-NP-AC such as enthalpy and entropy changes, activation energy, sticking probability, and Gibbs free energy changes show the spontaneous and endothermic nature of the removal process. Among different conventional kinetic models, the pseudo second-order kinetics in addition to particle diffusion mechanism is the best and efficient model for the prediction and explanation of experimental data of MG adsorption onto both adsorbents.

  19. Synthesis of water-dispersible zinc oxide quantum dots with antibacterial activity and low cytotoxicity for cell labeling

    NASA Astrophysics Data System (ADS)

    Hsu, Shan-hui; Lin, Ying Yi; Huang, Sherry; Lem, Kwok Wai; Huong Nguyen, Dinh; Lee, Dai Soo

    2013-11-01

    Typical photoluminescent semiconductor nanoparticles, called quantum dots (QDs), have potential applications in biological labeling. When used to label stem cells, QDs may impair the differentiation capacity of the stem cells. In this study, we synthesized zinc oxide (ZnO) QDs in methanol with an average size of ∼2 nm. We then employed two different types of polyethylene glycol (PEG) molecules (SH-PEG-NH2 and NH2-PEG-NH2) to conjugate ZnO QDs and made them water-dispersible. Fourier transform infrared spectroscopy spectra indicated the attachment of PEG molecules on ZnO QDs. No obvious size alteration was observed for ZnO QDs after PEG conjugation. The water-dispersible ZnO QDs still retained the antibacterial activity and fluorescence intensity. The cytotoxicity evaluation revealed that ZnO QDs at higher concentrations decreased cell viability but were generally safe at 30 ppm or below. Cell lines of hepatocytes (HepG2), osteoblasts (MC3T3-E1) and mesenchymal stem cells (MSCs) were successfully labeled by the water-dispersible ZnO QDs at 30 ppm. The ZnO QD-labeled MSCs maintained their stemness and differentiation capacity. Therefore, we conclude that the water-dispersible ZnO QDs developed in this study have antibacterial activity, low cytotoxicity, and proper labeling efficiency, and can be used to label a variety of cells including stem cells.

  20. Facile fabrication and characterization of chitosan-based zinc oxide nanoparticles and evaluation of their antimicrobial and antibiofilm activity

    NASA Astrophysics Data System (ADS)

    Dhillon, Gurpreet Singh; Kaur, Surinder; Brar, Satinder Kaur

    2014-06-01

    The present investigation deals with the facile synthesis and characterization of chitosan (CTS)-based zinc oxide (ZnO) nanoparticles (NPs) and their antimicrobial activities against pathogenic microorganisms. ZnO-CTS NPs were synthesized through two different methods: nano spray drying and precipitation, using various organic compounds (citric acid, glycerol, starch and whey powder) as stabilizers. Both the synthesis methods were simple and were devoid of any chemical usage. The detailed characterization of the NPs was carried out using UV-Vis spectroscopy, dynamic light scattering particle size analysis, zeta potential measurements and scanning electron microscopy, which confirmed the fabrication of NPs with different shapes and sizes. Antimicrobial assay of synthesized ZnO-CTS NPs was carried out against different pathogenic microbial strains ( Candida albicans, Micrococcus luteus and Staphylococcus aureus). The significant ( p < 0.05) inhibition of growth was observed for both M. luteus and S. aureus with ZnO-CTS NPs (with a concentration ranging from 0.625 to 0.156 mg/ml) as compared to control treatment. ZnO-CTS NPs also showed significant biofilm inhibition activity ( p < 0.05) against M. luteus and S. aureus. The study demonstrated the potential of ZnO-CTS NPs as antimicrobial and antibiofilm agents.

  1. Photophysical behavior and photodynamic therapy activity of conjugates of zinc monocarboxyphenoxy phthalocyanine with human serum albumin and chitosan

    NASA Astrophysics Data System (ADS)

    Oluwole, David O.; Prinsloo, Earl; Nyokong, Tebello

    2017-02-01

    Zinc monocarboxyphenoxy phthalocyanine (ZnMCPPc) was linked to human serum albumin (HSA) and chitosan via amide bond formation. The photophysical behavior and photodynamic therapy (PDT) activity (against human breast adenocarcinoma cell line (MCF-7 cells) of ZnMCPPc alone and its conjugates were investigated. The conjugates showed improved fluorescence, triplet and singlet oxygen quantum yields when compared to ZnMCPPc alone. The in vitro dark cytotoxicity and PDT studies were carried out at a dose of 3.6 μg/mL to 57.1 μg/mL. The in vitro dark cytotoxicity studies of ZnMCPPc showed cell viability < 50% at 28.6 μg/mL and 57.1 μg/mL, while the conjugates showed > 50% in all their tested concentrations (3.6 to 57.1) μg/mL. Thus, conjugation of ZnMCPPc to HSA and chitosan improves its dark cytotoxicity, an important criteria for molecules meant for photodynamic therapy. Complex 1 showed the most efficacious PDT activity with cell viability < 50% at concentration range of (14.3 to 57.1) μg/mL in comparison to the conjugates which only showed < 50% cell viability at 28.6 μg/mL and 57.1 μg/mL for 1-HSA and 57.1 μg/mL for 1-Chitosan.

  2. Multiple interferon stimulated genes synergize with the zinc finger antiviral protein to mediate anti-alphavirus activity.

    PubMed

    Karki, Sophiya; Li, Melody M H; Schoggins, John W; Tian, Suyan; Rice, Charles M; MacDonald, Margaret R

    2012-01-01

    The zinc finger antiviral protein (ZAP) is a host factor that mediates inhibition of viruses in the Filoviridae, Retroviridae and Togaviridae families. We previously demonstrated that ZAP blocks replication of Sindbis virus (SINV), the prototype Alphavirus in the Togaviridae family at an early step prior to translation of the incoming genome and that synergy between ZAP and one or more interferon stimulated genes (ISGs) resulted in maximal inhibitory activity. The present study aimed to identify those ISGs that synergize with ZAP to mediate Alphavirus inhibition. Using a library of lentiviruses individually expressing more than 350 ISGs, we screened for inhibitory activity in interferon defective cells with or without ZAP overexpression. Confirmatory tests of the 23 ISGs demonstrating the largest infection reduction in combination with ZAP revealed that 16 were synergistic. Confirmatory tests of all potentially synergistic ISGs revealed 15 additional ISGs with a statistically significant synergistic effect in combination with ZAP. These 31 ISGs are candidates for further mechanistic studies. The number and diversity of the identified ZAP-synergistic ISGs lead us to speculate that ZAP may play an important role in priming the cell for optimal ISG function.

  3. Silver nanoparticles in combination with acetic acid and zinc oxide quantum dots for antibacterial activities improvement-A comparative study

    NASA Astrophysics Data System (ADS)

    Sedira, Sofiane; Ayachi, Ahmed Abdelhakim; Lakehal, Sihem; Fateh, Merouane; Achour, Slimane

    2014-08-01

    Due to their remarkable antibacterial/antivirus properties, silver nanoparticles (Ag NPs) and zinc oxide quantum dots (ZnO Qds) have been widely used in the antimicrobial field. The mechanism of action of Ag NPs on bacteria was recently studied and it has been proven that Ag NPs exerts their antibacterial activities mainly by the released Ag+. In this work, Ag NPs and ZnO Qds were synthesized using polyol and hydrothermal method, respectively. It was demonstrated that Ag NPs can be oxidized easily in aqueous solution and the addition of acetic acid can increase the Ag+ release which improves the antibacterial activity of Ag NPs. A comparative study between bactericidal effect of Ag NPs/acetic acid and Ag NPs/ZnO Qds on Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia and Staphylococcus aureus was undertaken using agar diffusion method. The obtained colloids were characterized using UV-vis spectroscopy, Raman spectrometry, X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM).

  4. Preparation and characterization of active emulsified films based on chitosan-carboxymethyl cellulose containing zinc oxide nano particles.

    PubMed

    Noshirvani, Nooshin; Ghanbarzadeh, Babak; Mokarram, Reza Rezaei; Hashemi, Mahdi; Coma, Véronique

    2017-03-04

    Active nanocomposites based on carboxymethyl cellulose-chitosan-oleic acid (CMC-CH-OL) incorporated with different concentrations (0.5-2wt.%) of zinc oxide nanoparticles (ZnO NPs) were produced by casting method. The effects of ZnO NPs on the morphological, mechanical, thermal, physical and antifungal properties of the films were studied. New interaction between ZnO NPs and polymer matrix were confirmed by Fourier Transform infrared. After addition of ZnO NPs, tensile strength, lightness (L*) and thermal stability decreased however, elongation at break, contact angle, a* (greenness) and b* (yellowness) of the nanocomposite films increased in comparison to the films without nano-filler. UV transmittance at 280nm decreased from 17.3% to 0.2, 0.1 and 0.1 for the nanocomposite films containing 0.5, 1 and 2wt.% ZnO NPs, respectively, suggesting higher UV blocking properties. Disc diffusion test showed considerable antifungal properties of the active nanocomposite films against Aspergillus niger, especially in CMC-CH-OL-ZnO 2wt.% by more than 40% fungal growth inhibition.

  5. DNA inhibits catalysis by the carboxyltransferase subunit of acetyl-CoA carboxylase: implications for active site communication.

    PubMed

    Benson, Brian K; Meades, Glen; Grove, Anne; Waldrop, Grover L

    2008-01-01

    Acetyl-CoA carboxylase (ACC) catalyzes the first committed step in the synthesis of long-chain fatty acids. The crystal structure of the Escherichia coli carboxyltransferase component of ACC revealed an alpha(2)beta(2) subunit composition with two active sites and, most importantly, a unique zinc domain in each alphabeta pair that is absent in the eukaryotic enzyme. We show here that carboxyltransferase binds DNA. Half-maximal saturation of different single-stranded or double-stranded DNA constructs is seen at 0.5-1.0 muM, and binding is cooperative and nonspecific. The substrates (malonyl-CoA and biocytin) inhibit DNA:carboxyltransferase complex formation. More significantly, single-stranded DNA, double-stranded DNA, and heparin inhibit the reaction catalyzed by carboxyltransferase, with single-stranded DNA and heparin acting as competitive inhibitors. However, double-inhibition experiments revealed that both DNA and heparin can bind the enzyme in the presence of a bisubstrate analog (BiSA), and the binding of BiSA has a very weak synergistic effect on the binding of the second inhibitor (DNA or heparin) and vice versa. In contrast, DNA and heparin can also bind to the enzyme simultaneously, but the binding of either molecule has a strong synergistic effect on binding of the other. An important mechanistic implication of these observations is that the dual active sites of ACC are functionally connected.

  6. Effects of zinc and influence of Acremonium lolii on growth parameters, chlorophyll a fluorescence and antioxidant enzyme activities of ryegrass (Lolium perenne L. cv Apollo).

    PubMed

    Bonnet, M; Camares, O; Veisseire, P

    2000-05-01

    The effects of zinc on growth, mineral content, chlorophyll a fluorescence, and detoxifying enzyme activity (ascorbate peroxidase (APX), EC 1.11.1.11; superoxide dismutase (SOD), EC 1.15.1.1) of ryegrass infected or not by Acremonium lolii, and treated with nutrient solution containing 0-50 mM ZnSO(4) were studied. The introduction of zinc induces stress with a decrease in growth at 1, 5 and 10 mM ZnSO(4) and a cessation of growth at 50 mM ZnSO(4), in ryegrass plants infected by A. lolii or not. This decrease in growth may be due to an accumulation of zinc in leaves. Nevertheless, symbiotic plants showed higher values in tiller number, an advantage conferred by the fungus. After 24 d of Zn exposure, leaf fresh weights and leaf water content were lower in plants growing with Zn in the culture medium and no advantage was conferred by the fungus to its host. An increase in Zn supply resulted in a decrease of the Ca, K, Mg, and Cu content of the leaves, a reduction in the quantum yield of electron flow throughout photosystem II (DeltaF/F(1)(m))and a lowering of the efficiency of photosynthetic energy conversion (F(v)/F(m)), compared to control plants. To counter this zinc stress, detoxifying enzymes APX and SOD increased (100%) when Zn reached the value of 50 mM in the nutrient solution. At 10 mM ZnSO(4), the presence of the fungus in the plant led to an increase in the threshold toxicity of plants to zinc by a diminution of APX activity.

  7. Activity and leaching features of zinc-aluminum ferrites in catalytic wet oxidation of phenol.

    PubMed

    Xu, Aihua; Yang, Min; Qiao, Ruiping; Du, Hongzhang; Sun, Chenglin

    2007-08-17

    A series of ZnFe(2-x)Al(x)O(4) spinel type catalysts prepared by sol-gel method have been characterized and tested for catalytic wet oxidation (CWO) of phenol with pure oxygen. The iron species existed in these materials as aggregated iron oxide clusters and Fe3+ species in octahedral sites. With a decrease in iron content the concentration of the first iron species decreased and the latter increased. Complete phenol conversions and high chemical oxygen demand (COD) removals were obtained for all catalysts during phenol degradation at mild reaction conditions (160 degrees C and 1.0 MPa of oxygen pressure). Increasing with the concentration of Fe3+ species in octahedral sites, induction period became significantly shortened. After phenol was completely degraded, the concomitant recycling of the leaching Fe3+ ions back to the catalyst surface was observed, and in this case it is possible to perform successful CWO reactions with some cycles. It is also suggested that during the reaction the Fe3+ cations coordinated in octahedral sites in the ZnFe(2-x)Al(x)O(4) catalysts are resistant to acid leaching, but the reduced Fe2+ cations become much more labile, leading to increased Fe leaching.

  8. Effects of heavy metals on the expression of a zinc-inducible metallothionein-III gene and antioxidant enzyme activities in Crassostrea gigas.

    PubMed

    Cong, Ming; Wu, Huifeng; Liu, Xiaoli; Zhao, Jianmin; Wang, Xuan; Lv, Jiasen; Hou, Lin

    2012-10-01

    Sequestration by metallothioneins and antioxidant defense are two kinds of important defense mechanisms employed by mollusks to minimize adverse effects caused by heavy metal contaminants in marine environment. In the present study, a novel metallothionein gene, CgMT-III, was cloned from Crassostrea gigas, consisting of eighteen conserved cysteine residues and encoding a MT III-like protein with two tandem β domains. The expression level of CgMT-III transcript induced by zinc was much higher than that induced by cadmium exposure. It suggested that CgMT-III was perhaps mainly involved in homeostatic control of zinc metabolism, which was distinct from previously identified MTs in C. gigas. Among the tested antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), SOD and GPx showed varying up-regulations in a tissue-specific manner, while CAT activities were inhibited in both gill and hepatopancreas from C. gigas exposed to heavy metals. It can be inferred that CgMT-III was mainly involved in zinc homeostasis, and CgMT-III gene together with CAT enzyme could be potential biomarkers to indicate heavy metal, especially zinc pollution in marine organisms.

  9. Characterization of Active Site Residues of Nitroalkane Oxidase†

    PubMed Central

    Valley, Michael P.; Fenny, Nana S.; Ali, Shah R.; Fitzpatrick, Paul F.

    2010-01-01

    The flavoenzyme nitroalkane oxidase catalyzes the oxidation of primary and secondary nitrolkanes to the corresponding aldehydes and ketones plus nitrite. The structure of the enzyme shows that Serl71 forms a hydrogen bond to the flavin N5, suggesting that it plays a role in catalysis. Cys397 and Tyr398 were previously identified by chemical modification as potential active site residues. To more directly probe the roles of these residues, the S171A, S171V, S171T, C397S, and Y398F enzymes have been characterized with nitroethane as substrate. The C397S and Y398 enzymes were less stable than the wild-type enzyme, and the C397S enzyme routinely contained a substoichiometric amount of FAD. Analysis of the steady-state kinetic parameters for the mutant enzymes, including deuterium isotope effects, establishes that all of the mutations result in decreases in the rate constants for removal of the substrate proton by ~5-fold and decreases in the rate constant for product release of ~2-fold. Only the S171V and S171T mutations alter the rate constant for flavin oxidation. These results establish that these residues are not involved in catalysis, but rather are required for maintaining the protein structure. PMID:20056514

  10. Detection limit for activation measurements in ultralow background sites

    NASA Astrophysics Data System (ADS)

    Trache, Livius; Chesneanu, D.; Margineanu, R.; Pantelica, A.; Ghita, D. G.; Burducea, I.; Straticiuc, M.; Tang, X. D.

    2014-09-01

    We used 12C +13C fusion at the beam energies E = 6, 7 and 8 MeV to determine the sensitivity and the limits of activation method measurements in ultralow background sites. A 13C beam of 0.5 μA from the 3 MV Tandem accelerator of the Horia Hulubei National Institute of Physics and Nuclear Engineering - IFIN HH impinged on thick graphite targets. After about 24 hrs of irradiation targets were measured in two different laboratories: one with a heavy shielded Ge detector in the institute (at the surface) and one located underground in the microBequerel laboratory, in the salt mine of Slanic-Prahova, Romania. The 1369- and 2754 keV peaks from 24Na deactivation were clearly observed in the γ-ray spectra obtained for acquisitions lasting a few hours, or a few days. Determination of the detection limit in evaluating the cross sections for the target irradiated at Ec . m = 3 MeV indicates the fact that it is possible to measure gamma spectrum in underground laboratory down to Ec . m = 2 . 6 MeV. Cleaning the spectra with beta-gamma coincidences and increasing beam intensity 20 times will take as further down. The measurements are motivated by the study of the 12 C +12 C reaction at astrophysical energies.

  11. Disturbance opens recruitment sites for bacterial colonization in activated sludge.

    PubMed

    Vuono, David C; Munakata-Marr, Junko; Spear, John R; Drewes, Jörg E

    2016-01-01

    Little is known about the role of immigration in shaping bacterial communities or the factors that may dictate success or failure of colonization by bacteria from regional species pools. To address these knowledge gaps, the influence of bacterial colonization into an ecosystem (activated sludge bioreactor) was measured through a disturbance gradient (successive decreases in the parameter solids retention time) relative to stable operational conditions. Through a DNA sequencing approach, we show that the most abundant bacteria within the immigrant community have a greater probability of colonizing the receiving ecosystem, but mostly as low abundance community members. Only during the disturbance do some of these bacterial populations significantly increase in abundance beyond background levels and in few cases become dominant community members post-disturbance. Two mechanisms facilitate the enhanced enrichment of immigrant populations during disturbance: (i) the availability of resources left unconsumed by established species and (ii) the increased availability of niche space for colonizers to establish and displace resident populations. Thus, as a disturbance decreases local diversity, recruitment sites become available to promote colonization. This work advances our understanding of microbial resource management and diversity maintenance in complex ecosystems.

  12. Public health assessment for Sandoval Zinc Company, Sandoval, Marion County, Illinois, Region 5: CERCLIS number ILD053980454. Final report

    SciTech Connect

    Not Available

    1999-06-10

    The Sandoval Zinc site occupies about 13 acres southeast of Sandoval in Marion County, Illinois. It is an abandoned primary and secondary zinc smelter that was next to a coal mining operation. Smelting waste may have been transported off the site and used as fill in Sandoval and other nearby communities. Airborne emissions occurred during regular operations and accidental fires. Surface water runoff transported wastes from the site into adjacent ditches, creeks, ponds, and farm properties. Overall, the Sandoval Zinc site poses no apparent public health hazard to most of the population in Sandoval. The site may be a public health hazard to preschool children with excessive hand-to-mouth activity exposed to residential surface soils with high levels of lead. However, blood sample results from children in a day care near the site did not show elevated levels of lead.

  13. Effect of effective mass and spontaneous polarization on photocatalytic activity of wurtzite and zinc-blende ZnS

    SciTech Connect

    Dong, Ming; Zhang, Jinfeng; Yu, Jiaguo

    2015-10-01

    Semiconductor zinc sulphide (ZnS) has two common phases: hexagonal wurtzite and cubic zinc-blende structures. The crystal structures, energy band structures, density of states (DOS), bond populations, and optical properties of wurtzite and zinc-blende ZnS were investigated by the density functional theory of first-principles. The similar band gaps and DOS of wurtzite and zinc-blende ZnS were found and implied the similarities in crystal structures. However, the distortion of ZnS{sub 4} tetrahedron in wurtzite ZnS resulted in the production of spontaneous polarization and internal electric field, which was beneficial for the transfer and separation of photogenerated electrons and holes.

  14. Cytotoxic activity, X-ray crystal structures and spectroscopic characterization of cobalt(II), copper(II) and zinc(II) coordination compounds with 2-substituted benzimidazoles.

    PubMed

    Sánchez-Guadarrama, Obdulia; López-Sandoval, Horacio; Sánchez-Bartéz, Francisco; Gracia-Mora, Isabel; Höpfl, Herbert; Barba-Behrens, Noráh

    2009-09-01

    Herein we present the synthesis, structural and spectroscopic characterization of coordination compounds of cobalt(II), copper(II) and zinc(II) with 2-methylbenzimidazole (2mbz), 2-phenylbenzimidazole (2phbz), 2-chlorobenzimidazole (2cbz), 2-benzimidazolecarbamate (2cmbz) and 2-guanidinobenzimidazole (2gbz). Their cytotoxic activity was evaluated using human cancer cell lines, PC3 (prostate), MCF-7 (breast), HCT-15 (colon), HeLa (cervic-uterine), SKLU-1 (lung) and U373 (glioblastoma), showing that the zinc(II) and copper(II) compounds [Zn(2mbz)(2)Cl(2)].0.5H(2)O, [Zn(2cmbz)(2)Cl(2)].EtOH, [Cu(2cmbz)Br(2)].0.7H(2)O and [Cu(2gbz)Br(2)] had significant cytotoxic activity. The isostructural cobalt(II) complexes showed not significant activity. The cytotoxic activity is related to the presence of halides in the coordination sphere of the metal ion. Recuperation experiments with HeLa cells, showed that the cells recuperated after removing the copper(II) compounds and, on the contrary, the cells treated with the zinc(II) compounds did not. These results indicate that the mode of action of the coordination compounds is different.

  15. 21 CFR 73.2995 - Luminescent zinc sulfide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Luminescent zinc sulfide. 73.2995 Section 73.2995... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2995 Luminescent zinc sulfide. (a) Identity. The color additive luminescent zinc sulfide is zinc sulfide containing a copper activator....

  16. 21 CFR 73.2995 - Luminescent zinc sulfide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Luminescent zinc sulfide. 73.2995 Section 73.2995... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2995 Luminescent zinc sulfide. (a) Identity. The color additive luminescent zinc sulfide is zinc sulfide containing a copper activator....

  17. 21 CFR 73.2995 - Luminescent zinc sulfide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Luminescent zinc sulfide. 73.2995 Section 73.2995... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2995 Luminescent zinc sulfide. (a) Identity. The color additive luminescent zinc sulfide is zinc sulfide containing a copper activator....

  18. 21 CFR 73.2995 - Luminescent zinc sulfide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Luminescent zinc sulfide. 73.2995 Section 73.2995... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2995 Luminescent zinc sulfide. (a) Identity. The color additive luminescent zinc sulfide is zinc sulfide containing a copper activator....

  19. 21 CFR 73.2995 - Luminescent zinc sulfide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Luminescent zinc sulfide. 73.2995 Section 73.2995... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2995 Luminescent zinc sulfide. (a) Identity. The color additive luminescent zinc sulfide is zinc sulfide containing a copper activator....

  20. 40 CFR 61.154 - Standard for active waste disposal sites.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 9 2012-07-01 2012-07-01 false Standard for active waste disposal... for Asbestos § 61.154 Standard for active waste disposal sites. Each owner or operator of an active... visible emissions to the outside air from any active waste disposal site where asbestos-containing...

  1. 40 CFR 61.154 - Standard for active waste disposal sites.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 9 2014-07-01 2014-07-01 false Standard for active waste disposal... for Asbestos § 61.154 Standard for active waste disposal sites. Each owner or operator of an active... visible emissions to the outside air from any active waste disposal site where asbestos-containing...

  2. 10 CFR 63.16 - Review of site characterization activities. 2

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... IN A GEOLOGIC REPOSITORY AT YUCCA MOUNTAIN, NEVADA Licenses Preapplication Review § 63.16 Review of... conduct of site characterization activities at the Yucca Mountain site, DOE shall report the nature and... activities at the Yucca Mountain site, NRC staff shall be permitted to visit and inspect the locations...

  3. 10 CFR 63.16 - Review of site characterization activities. 2

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... IN A GEOLOGIC REPOSITORY AT YUCCA MOUNTAIN, NEVADA Licenses Preapplication Review § 63.16 Review of... conduct of site characterization activities at the Yucca Mountain site, DOE shall report the nature and... activities at the Yucca Mountain site, NRC staff shall be permitted to visit and inspect the locations...

  4. 10 CFR 63.16 - Review of site characterization activities. 2

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... IN A GEOLOGIC REPOSITORY AT YUCCA MOUNTAIN, NEVADA Licenses Preapplication Review § 63.16 Review of... conduct of site characterization activities at the Yucca Mountain site, DOE shall report the nature and... activities at the Yucca Mountain site, NRC staff shall be permitted to visit and inspect the locations...

  5. 10 CFR 63.16 - Review of site characterization activities. 2

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... IN A GEOLOGIC REPOSITORY AT YUCCA MOUNTAIN, NEVADA Licenses Preapplication Review § 63.16 Review of... conduct of site characterization activities at the Yucca Mountain site, DOE shall report the nature and... activities at the Yucca Mountain site, NRC staff shall be permitted to visit and inspect the locations...

  6. 10 CFR 63.16 - Review of site characterization activities. 2

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... IN A GEOLOGIC REPOSITORY AT YUCCA MOUNTAIN, NEVADA Licenses Preapplication Review § 63.16 Review of... conduct of site characterization activities at the Yucca Mountain site, DOE shall report the nature and... activities at the Yucca Mountain site, NRC staff shall be permitted to visit and inspect the locations...

  7. Robotics and Automation Activities at the Savannah River Site: A Site Report for SUBWOG 39F

    SciTech Connect

    Teese, G.D.

    1995-09-28

    The Savannah River Site has successfully used robots, teleoperators, and remote video to reduce exposure to ionizing radiation, improve worker safety, and improve the quality of operations. Previous reports have described the use of mobile teleoperators in coping with a high level liquid waste spill, the removal of highly contaminated equipment, and the inspection of nuclear reactor vessels. This report will cover recent applications at the Savannah River, as well as systems which SRS has delivered to other DOE site customers.

  8. Curative effect of topical treatment of digital dermatitis with a gel containing activated copper and zinc chelate

    PubMed Central

    Holzhauer, M.; Bartels, C. J.; van Barneveld, M.; Vulders, C.; Lam, T.

    2011-01-01

    The efficacy of two topical treatments for painful ulcerative stage (M2) of bovine digital dermatitis (BDD) lesions was compared in a clinical trial conducted on five dairy farms in 2009 to 2010. The first treatment was a water-based gel with active components copper and zinc (Intra Hoof-fit gel [IHF]) and the second treatment was a topical chlortetracycline spray (CTC spray). The experimental unit for this study was the hindleg with the presence of a BDD lesion. Cure was defined as the transition of an M2 lesion into a healed (M0) or a non-painful chronic stage (M4) of BDD at D28. On day 0, cows with M2 BDD lesions were photographed and were treated with either IHF or CTC. Subsequently, feet were photographed and scored on D28. The cure rate of M2 BDD lesions treated with IHF at D28 was 0.92 (CI 0.84 to 0.96) and was significantly better than for M2 BDD lesions treated with CTC, which was 0.58 (CI 0.47 to 0.68). PMID:21957114

  9. Dynamics of an Active-Site Flap Contributes to Catalysis in a JAMM Family Metallo Deubiquitinase.

    PubMed

    Bueno, Amy N; Shrestha, Rashmi K; Ronau, Judith A; Babar, Aditya; Sheedlo, Michael J; Fuchs, Julian E; Paul, Lake N; Das, Chittaranjan

    2015-10-06

    The endosome-associated deubiquitinase (DUB) AMSH is a member of the JAMM family of zinc-dependent metallo isopeptidases with high selectivity for Lys63-linked polyubiquitin chains, which play a key role in endosomal-lysosomal sorting of activated cell surface receptors. The catalytic domain of the enzyme features a flexible flap near the active site that opens and closes during its catalytic cycle. Structural analysis of its homologues, AMSH-LP (AMSH-like protein) and the fission yeast counterpart, Sst2, suggests that a conserved Phe residue in the flap may be critical for substrate binding and/or catalysis. To gain insight into the contribution of this flap in substrate recognition and catalysis, we generated mutants of Sst2 and characterized them using a combination of enzyme kinetics, X-ray crystallography, molecular dynamics simulations, and isothermal titration calorimetry (ITC). Our analysis shows that the Phe residue in the flap contributes key interactions during the rate-limiting step but not to substrate binding, since mutants of Phe403 exhibit a defect only in kcat but not in KM. Moreover, ITC studies show Phe403 mutants have similar KD for ubiquitin compared to the wild-type enzyme. The X-ray structures of both Phe403Ala and the Phe403Trp, in both the free and ubiquitin bound form, reveal no appreciable structural change that might impair substrate or alter product binding. We observed that the side chain of the Trp residue is oriented identically with respect to the isopeptide moiety of the substrate as the Phe residue in the wild-type enzyme, so the loss of activity seen in this mutant cannot be explained by the absence of a group with the ability to provide van der Waals interactions that facilitate the hyrdolysis of the Lys63-linked diubiquitin. Molecular dynamics simulations indicate that the flap in the Trp mutant is quite flexible, allowing almost free rotation of the indole side chain. Therefore, it is possible that these different dynamic

  10. GAS HYDRATES AT TWO SITES OF AN ACTIVE CONTINENTAL MARGIN.

    USGS Publications Warehouse

    Kvenvolden, K.A.

    1985-01-01

    Sediment containing gas hydrates from two distant Deep Sea Drilling Project sites (565 and 568), located about 670 km apart on the landward flank of the Middle America Trench, was studied to determine the geochemical conditions that characterize the occurrence of gas hydrates. Site 565 was located in the Pacific Ocean offshore the Nicoya Peninsula of Costa Rica in 3,111 m of water. The depth of the hole at this site was 328 m, and gas hydrates were recovered from 285 and 319 m. Site 568 was located about 670 km to the northwest offshore Guatemala in 2,031 m of water. At this site the hole penetrated to 418 m, and gas hydrates were encountered at 404 m.

  11. Genome wide association mapping of grain arsenic, copper, molybdenum, and zinc in rice (Oryza sativa L.) grown at four international field sites

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The mineral concentrations in cereals are important for human health, especially for individuals who consume a cereal subsistence diet. A number of elements, such as zinc, are required within the diet, while some elements are toxic to humans, for example arsenic. In this study we carried out genome-...

  12. Lidar research activities and observations at NARL site, Gadanki, India

    NASA Astrophysics Data System (ADS)

    Yellapragada, Bhavani Kumar

    2016-05-01

    The National Atmospheric Research Laboratory (NARL), a unit of Department of Space (DOS), located at Gadanki village (13.5°N, 79.2°E, 370 m AMSL) in India, is involved in the development of lidar remote sensing technologies for atmospheric research. Several advanced lidar technologies employing micropulse, polarization, Raman and scanning have been developed at this site and demonstrated for atmospheric studies during the period between 2008 and 2015. The technology of micropulse lidar, operates at 532 nm wavelength, was successfully transferred to an industry and the commercial version has been identified for Indian Lidar network (I-LINK) programme. Under this lidar network activity, several lidar units were installed at different locations in India to study tropospheric aerosols and clouds. The polarization sensitive lidar technology was realized using a set of mini photomultiplier tube (PMT) units and has the capability to operate during day and night without a pause. The lidar technology uses a compact flashlamp pumped Qswitched laser and employs biaxial configuration between the transmitter and receiver units. The lidar technology has been utilized for understanding the polarization characteristics of boundary layer aerosols during the mixed layer development. The demonstrated Raman lidar technology, uses the third harmonic wavelength of Nd:YAG laser, provides the altitude profiles of aerosol backscattering, extinction and water vapor covering the boundary layer range and allows operation during nocturnal periods. The Raman lidar derived height profiles of aerosol backscattering and extinction coefficient, lidar ratio, and watervapor mixing ratio inform the tropical boundary layer aerosol characteristics. The scanning lidar technology uses a near infrared laser wavelength for probing the lower atmosphere and has been utilized for high resolution cloud profiling during convective periods. The lidar technology is also used for rain rate measurement during

  13. Dynamically achieved active site precision in enzyme catalysis.

    PubMed

    Klinman, Judith P

    2015-02-17

    CONSPECTUS: The grand challenge in enzymology is to define and understand all of the parameters that contribute to enzymes' enormous rate accelerations. The property of hydrogen tunneling in enzyme reactions has moved the focus of research away from an exclusive focus on transition state stabilization toward the importance of the motions of the heavy atoms of the protein, a role for reduced barrier width in catalysis, and the sampling of a protein conformational landscape to achieve a family of protein substates that optimize enzyme-substrate interactions and beyond. This Account focuses on a thermophilic alcohol dehydrogenase for which the chemical step of hydride transfer is rate determining across a wide range of experimental conditions. The properties of the chemical coordinate have been probed using kinetic isotope effects, indicating a transition in behavior below 30 °C that distinguishes nonoptimal from optimal C-H activation. Further, the introduction of single site mutants has the impact of either enhancing or eliminating the temperature dependent transition in catalysis. Biophysical probes, which include time dependent hydrogen/deuterium exchange and fluorescent lifetimes and Stokes shifts, have also been pursued. These studies allow the correlation of spatially resolved transitions in protein motions with catalysis. It is now possible to define a long-range network of protein motions in ht-ADH that extends from a dimer interface to the substrate binding domain across to the cofactor binding domain, over a distance of ca. 30 Å. The ongoing challenge to obtaining spatial and temporal resolution of catalysis-linked protein motions is discussed.

  14. Electric Field-aided Selective Activation for Indium-Gallium-Zinc-Oxide Thin Film Transistors

    PubMed Central

    Lee, Heesoo; Chang, Ki Soo; Tak, Young Jun; Jung, Tae Soo; Park, Jeong Woo; Kim, Won-Gi; Chung, Jusung; Jeong, Chan Bae; Kim, Hyun Jae

    2016-01-01

    A new technique is proposed for the activation of low temperature amorphous InGaZnO thin film transistor (a-IGZO TFT) backplanes through application of a bias voltage and annealing at 130 °C simultaneously. In this ‘electrical activation’, the effects of annealing under bias are selectively focused in the channel region. Therefore, electrical activation can be an effective method for lower backplane processing temperatures from 280 °C to 130 °C. Devices fabricated with this method exhibit equivalent electrical properties to those of conventionally-fabricated samples. These results are analyzed electrically and thermodynamically using infrared microthermography. Various bias voltages are applied to the gate, source, and drain electrodes while samples are annealed at 130 °C for 1 hour. Without conventional high temperature annealing or electrical activation, current-voltage curves do not show transfer characteristics. However, electrically activated a-IGZO TFTs show superior electrical characteristics, comparable to the reference TFTs annealed at 280 °C for 1 hour. This effect is a result of the lower activation energy, and efficient transfer of electrical and thermal energy to a-IGZO TFTs. With this approach, superior low-temperature a-IGZO TFTs are fabricated successfully. PMID:27725695

  15. Electric Field-aided Selective Activation for Indium-Gallium-Zinc-Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Lee, Heesoo; Chang, Ki Soo; Tak, Young Jun; Jung, Tae Soo; Park, Jeong Woo; Kim, Won-Gi; Chung, Jusung; Jeong, Chan Bae; Kim, Hyun Jae

    2016-10-01

    A new technique is proposed for the activation of low temperature amorphous InGaZnO thin film transistor (a-IGZO TFT) backplanes through application of a bias voltage and annealing at 130 °C simultaneously. In this ‘electrical activation’, the effects of annealing under bias are selectively focused in the channel region. Therefore, electrical activation can be an effective method for lower backplane processing temperatures from 280 °C to 130 °C. Devices fabricated with this method exhibit equivalent electrical properties to those of conventionally-fabricated samples. These results are analyzed electrically and thermodynamically using infrared microthermography. Various bias voltages are applied to the gate, source, and drain electrodes while samples are annealed at 130 °C for 1 hour. Without conventional high temperature annealing or electrical activation, current-voltage curves do not show transfer characteristics. However, electrically activated a-IGZO TFTs show superior electrical characteristics, comparable to the reference TFTs annealed at 280 °C for 1 hour. This effect is a result of the lower activation energy, and efficient transfer of electrical and thermal energy to a-IGZO TFTs. With this approach, superior low-temperature a-IGZO TFTs are fabricated successfully.

  16. Occupancy of the Zinc-binding Site by Transition Metals Decreases the Substrate Affinity of the Human Dopamine Transporter by an Allosteric Mechanism*

    PubMed Central

    Li, Yang; Mayer, Felix P.; Hasenhuetl, Peter S.; Burtscher, Verena; Schicker, Klaus; Sitte, Harald H.; Freissmuth, Michael; Sandtner, Walter

    2017-01-01

    The human dopamine transporter (DAT) has a tetrahedral Zn2+-binding site. Zn2+-binding sites are also recognized by other first-row transition metals. Excessive accumulation of manganese or of copper can lead to parkinsonism because of dopamine deficiency. Accordingly, we examined the effect of Mn2+, Co2+, Ni2+, and Cu2+ on transport-associated currents through DAT and DAT-H193K, a mutant with a disrupted Zn2+-binding site. All transition metals except Mn2+ modulated the transport cycle of wild-type DAT with affinities in the low micromolar range. In this concentration range, they were devoid of any action on DAT-H193K. The active transition metals reduced the affinity of DAT for dopamine. The affinity shift was most pronounced for Cu2+, followed by Ni2+ and Zn2+ (= Co2+). The extent of the affinity shift and the reciprocal effect of substrate on metal affinity accounted for the different modes of action: Ni2+ and Cu2+ uniformly stimulated and inhibited, respectively, the substrate-induced steady-state currents through DAT. In contrast, Zn2+ elicited biphasic effects on transport, i.e. stimulation at 1 μm and inhibition at 10 μm. A kinetic model that posited preferential binding of transition metal ions to the outward-facing apo state of DAT and a reciprocal interaction of dopamine and transition metals recapitulated all experimental findings. Allosteric activation of DAT via the Zn2+-binding site may be of interest to restore transport in loss-of-function mutants. PMID:28096460

  17. The influence of zinc(II) on thioredoxin/glutathione disulfide exchange: QM/MM studies to explore how zinc(II) accelerates exchange in higher dielectric environments.

    PubMed

    Kurian, Roby; Bruce, Mitchell R M; Bruce, Alice E; Amar, François G

    2015-08-01

    QM/MM studies were performed to explore the energetics of exchange reactions of glutathione disulfide (GSSG) and the active site of thioredoxin [Cys32-Gly33-Pro34-Cys35] with and without zinc(II), in vacuum and solvated models. The activation energy for exchange, in the absence of zinc, is 29.7 kcal mol(-1) for the solvated model. This is 3.3 kcal mol(-1) higher than the activation energy for exchange in the gas phase, due to ground state stabilization of the active site Cys-32 thiolate in a polar environment. In the presence of zinc, the activation energy for exchange is 4.9 kcal mol(-1) lower than in the absence of zinc (solvated models). The decrease in activation energy is attributed to stabilization of the charge-separated transition state, which has a 4-centered, cyclic arrangement of Zn-S-S-S with an estimated dipole moment of 4.2 D. A difference of 4.9 kcal mol(-1) in activation energy would translate to an increase in rate by a factor of about 4000 for zinc-assisted thiol-disulfide exchange. The calculations are consistent with previously reported experimental results, which indicate that metal-thiolate, disulfide exchange rates increase as a function of solvent dielectric. This trend is opposite to that observed for the influence of the dielectric environment on the rate of thiol-disulfide exchange in the absence of metal. The results suggest a dynamic role for zinc in thiol-disulfide exchange reactions, involving accessible cysteine sites on proteins, which may contribute to redox regulation and mechanistic pathways during oxidative stress.

  18. Generic phosphatase activity detection using zinc mediated aggregation modulation of polypeptide-modified gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Selegård, Robert; Enander, Karin; Aili, Daniel

    2014-11-01

    A challenge in the design of plasmonic nanoparticle-based colorimetric assays is that the change in colloidal stability, which generates the colorimetric response, is often directly linked to the biomolecular recognition event. New assay strategies are hence required for every type of substrate and enzyme of interest. Here, a generic strategy for monitoring of phosphatase activity is presented where substrate recognition is completely decoupled from the nanoparticle stability modulation mechanism, which enables detection of a wide range of enzymes using different natural substrates with a single simple detection scheme. Phosphatase activity generates inorganic phosphate that forms an insoluble complex with Zn2+. In a sample containing a preset concentration of Zn2+, phosphatase activity will markedly reduce the concentration of dissolved Zn2+ from the original value, which in turn affects the aggregation of gold nanoparticles functionalized with a designed Zn2+ responsive polypeptide. The change in nanoparticle stability thus provides a rapid and sensitive readout of the phosphatase activity. The assay is not limited to a particular enzyme or enzyme substrate, which is demonstrated using three completely different phosphatases and five different substrates, and thus constitutes a highly interesting system for drug screening and diagnostics.A challenge in the design of plasmonic nanoparticle-based colorimetric assays is that the change in colloidal stability, which generates the colorimetric response, is often directly linked to the biomolecular recognition event. New assay strategies are hence required for every type of substrate and enzyme of interest. Here, a generic strategy for monitoring of phosphatase activity is presented where substrate recognition is completely decoupled from the nanoparticle stability modulation mechanism, which enables detection of a wide range of enzymes using different natural substrates with a single simple detection scheme

  19. Zinc phosphide

    Integrated Risk Information System (IRIS)

    Zinc phoshide ; CASRN 1314 - 84 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Ef

  20. Zinc interactions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The most common and probably the most harmful micronutrient deficiency of commercial pecan enterprises is zinc deficiency. A review is presented of how orchard nutrient element management practices potentially influence tree Zn nutrition. Findings provide background information on how to reduce th...

  1. Zinc cyanide

    Integrated Risk Information System (IRIS)

    Zinc cyanide ; CASRN 557 - 21 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effe

  2. Subclinical zinc deficiency impairs pancreatic digestive enzyme activity and digestive capacity of weaned piglets.

    PubMed

    Brugger, Daniel; Windisch, Wilhelm M

    2016-08-01

    This study investigated the effects of short-term subclinical Zn deficiency on exocrine pancreatic activity and ch