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Sample records for water-activating loop histidine

  1. Structural-dynamical investigation of the ZnuA histidine-rich loop: involvement in zinc management and transport.

    Science.gov (United States)

    Falconi, Mattia; Oteri, Francesco; Di Palma, Francesco; Pandey, Saurabh; Battistoni, Andrea; Desideri, Alessandro

    2011-02-01

    Comparative homology modelling techniques have been used to model the protein ZnuA from Salmonella enterica serovar Typhimurium using the 3D structure of the homologous protein from Escherichia coli. These two-domain proteins bind one Zn(2+) atom, with high affinity, in the inter-domain cleft and possess a histidine-rich loop in the N-terminal domain. Alternative structures of the ZnuA histidine-rich loop, never resolved by the X-ray diffraction method, have been modelled. A model of the apo form, one with the histidine-rich loop deleted and two alternative structures with a second zinc ion bound to the histidine-rich loop, have been generated. In all the modelled proteins, investigated through molecular dynamics simulation, the histidine-rich loop is highly mobile and its fluctuations are correlated to the ligand stability observed in the zinc sites. Based on the plasticity of the histidine-rich loop and its significant effects on protein mobility a possible role in the capture and/or transfer of the zinc ions has been suggested.

  2. Crystal Structures of Trypanosoma cruzi UDP-Galactopyranose Mutase Implicate Flexibility of the Histidine Loop in Enzyme Activation

    Energy Technology Data Exchange (ETDEWEB)

    Dhatwalia, Richa; Singh, Harkewal; Oppenheimer, Michelle; Sobrado, Pablo; Tanner, John J. (Virginia Tech); (UMC)

    2012-11-01

    Chagas disease is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi. Here we report crystal structures of the galactofuranose biosynthetic enzyme UDP-galactopyranose mutase (UGM) from T. cruzi, which are the first structures of this enzyme from a protozoan parasite. UGM is an attractive target for drug design because galactofuranose is absent in humans but is an essential component of key glycoproteins and glycolipids in trypanosomatids. Analysis of the enzyme-UDP noncovalent interactions and sequence alignments suggests that substrate recognition is exquisitely conserved among eukaryotic UGMs and distinct from that of bacterial UGMs. This observation has implications for inhibitor design. Activation of the enzyme via reduction of the FAD induces profound conformational changes, including a 2.3 {angstrom} movement of the histidine loop (Gly60-Gly61-His62), rotation and protonation of the imidazole of His62, and cooperative movement of residues located on the si face of the FAD. Interestingly, these changes are substantially different from those described for Aspergillus fumigatus UGM, which is 45% identical to T. cruzi UGM. The importance of Gly61 and His62 for enzymatic activity was studied with the site-directed mutant enzymes G61A, G61P, and H62A. These mutations lower the catalytic efficiency by factors of 10-50, primarily by decreasing k{sub cat}. Considered together, the structural, kinetic, and sequence data suggest that the middle Gly of the histidine loop imparts flexibility that is essential for activation of eukaryotic UGMs. Our results provide new information about UGM biochemistry and suggest a unified strategy for designing inhibitors of UGMs from the eukaryotic pathogens.

  3. Carboplatin binding to histidine

    NARCIS (Netherlands)

    Tanley, Simon W M; Diederichs, Kay; Kroon - Batenburg, Louise|info:eu-repo/dai/nl/070944172; Levy, Colin; Schreurs, Antoine M M|info:eu-repo/dai/nl/304847453; Helliwell, John R.

    2014-01-01

    Carboplatin is a second-generation platinum anticancer agent used for the treatment of a variety of cancers. Previous X-ray crystallographic studies of carboplatin binding to histidine (in hen egg-white lysozyme; HEWL) showed the partial conversion of carboplatin to cisplatin owing to the high NaCl

  4. Carboplatin binding to histidine

    Energy Technology Data Exchange (ETDEWEB)

    Tanley, Simon W. M. [University of Manchester, Brunswick Street, Manchester M13 9PL (United Kingdom); Diederichs, Kay [University of Konstanz, D-78457 Konstanz (Germany); Kroon-Batenburg, Loes M. J. [Utrecht University, Padualaan 8, 3584 CH Utrecht (Netherlands); Levy, Colin [University of Manchester, 131 Princess Street, Manchester M1 7DN (United Kingdom); Schreurs, Antoine M. M. [Utrecht University, Padualaan 8, 3584 CH Utrecht (Netherlands); Helliwell, John R., E-mail: john.helliwell@manchester.ac.uk [University of Manchester, Brunswick Street, Manchester M13 9PL (United Kingdom)

    2014-08-29

    An X-ray crystal structure showing the binding of purely carboplatin to histidine in a model protein has finally been obtained. This required extensive crystallization trials and various novel crystal structure analyses. Carboplatin is a second-generation platinum anticancer agent used for the treatment of a variety of cancers. Previous X-ray crystallographic studies of carboplatin binding to histidine (in hen egg-white lysozyme; HEWL) showed the partial conversion of carboplatin to cisplatin owing to the high NaCl concentration used in the crystallization conditions. HEWL co-crystallizations with carboplatin in NaBr conditions have now been carried out to confirm whether carboplatin converts to the bromine form and whether this takes place in a similar way to the partial conversion of carboplatin to cisplatin observed previously in NaCl conditions. Here, it is reported that a partial chemical transformation takes place but to a transplatin form. Thus, to attempt to resolve purely carboplatin binding at histidine, this study utilized co-crystallization of HEWL with carboplatin without NaCl to eliminate the partial chemical conversion of carboplatin. Tetragonal HEWL crystals co-crystallized with carboplatin were successfully obtained in four different conditions, each at a different pH value. The structural results obtained show carboplatin bound to either one or both of the N atoms of His15 of HEWL, and this particular variation was dependent on the concentration of anions in the crystallization mixture and the elapsed time, as well as the pH used. The structural details of the bound carboplatin molecule also differed between them. Overall, the most detailed crystal structure showed the majority of the carboplatin atoms bound to the platinum centre; however, the four-carbon ring structure of the cyclobutanedicarboxylate moiety (CBDC) remained elusive. The potential impact of the results for the administration of carboplatin as an anticancer agent are described.

  5. Carboplatin binding to histidine

    Science.gov (United States)

    Tanley, Simon W. M.; Diederichs, Kay; Kroon-Batenburg, Loes M. J.; Levy, Colin; Schreurs, Antoine M. M.; Helliwell, John R.

    2014-01-01

    Carboplatin is a second-generation platinum anticancer agent used for the treatment of a variety of cancers. Previous X-ray crystallographic studies of carboplatin binding to histidine (in hen egg-white lysozyme; HEWL) showed the partial conversion of carboplatin to cisplatin owing to the high NaCl concentration used in the crystallization conditions. HEWL co-crystallizations with carboplatin in NaBr conditions have now been carried out to confirm whether carboplatin converts to the bromine form and whether this takes place in a similar way to the partial conversion of carboplatin to cisplatin observed previously in NaCl conditions. Here, it is reported that a partial chemical transformation takes place but to a transplatin form. Thus, to attempt to resolve purely carboplatin binding at histidine, this study utilized co-crystallization of HEWL with carboplatin without NaCl to eliminate the partial chemical conversion of carboplatin. Tetragonal HEWL crystals co-crystallized with carboplatin were successfully obtained in four different conditions, each at a different pH value. The structural results obtained show carboplatin bound to either one or both of the N atoms of His15 of HEWL, and this particular variation was dependent on the concentration of anions in the crystallization mixture and the elapsed time, as well as the pH used. The structural details of the bound carboplatin molecule also differed between them. Overall, the most detailed crystal structure showed the majority of the carboplatin atoms bound to the platinum centre; however, the four-carbon ring structure of the cyclobutanedicarboxylate moiety (CBDC) remained elusive. The potential impact of the results for the administration of carboplatin as an anticancer agent are described. PMID:25195881

  6. Histidine-Containing Peptide Nucleic Acids

    DEFF Research Database (Denmark)

    2000-01-01

    Peptide nucleic acids containing histidine moieties are provided. These compounds have applications including diagnostics, research and potential therapeutics.......Peptide nucleic acids containing histidine moieties are provided. These compounds have applications including diagnostics, research and potential therapeutics....

  7. Ypq3p-dependent histidine uptake by the vacuolar membrane vesicles of Saccharomyces cerevisiae.

    Science.gov (United States)

    Manabe, Kunio; Kawano-Kawada, Miyuki; Ikeda, Koichi; Sekito, Takayuki; Kakinuma, Yoshimi

    2016-06-01

    The vacuolar membrane proteins Ypq1p, Ypq2p, and Ypq3p of Saccharomyces cerevisiae are known as the members of the PQ-loop protein family. We found that the ATP-dependent uptake activities of arginine and histidine by the vacuolar membrane vesicles were decreased by ypq2Δ and ypq3Δ mutations, respectively. YPQ1 and AVT1, which are involved in the vacuolar uptake of lysine/arginine and histidine, respectively, were deleted in addition to ypq2Δ and ypq3Δ. The vacuolar membrane vesicles isolated from the resulting quadruple deletion mutant ypq1Δypq2Δypq3Δavt1Δ completely lost the uptake activity of basic amino acids, and that of histidine, but not lysine and arginine, was evidently enhanced by overexpressing YPQ3 in the mutant. These results suggest that Ypq3p is specifically involved in the vacuolar uptake of histidine in S. cerevisiae. The cellular level of Ypq3p-HA(3) was enhanced by depletion of histidine from culture medium, suggesting that it is regulated by the substrate.

  8. Histidine adsorption on nanostructured cerium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Bercha, Sofiia [Charles University in Prague, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, CZ-18000 Prague 8 (Czech Republic); Mali, Gregor [National Institute of Chemistry, Laboratory for Inorganic Chemistry and Technology, Hajdrihova 19, SI-1001 Ljubljana (Slovenia); Khalakhan, Ivan; Skála, Tomáš [Charles University in Prague, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, CZ-18000 Prague 8 (Czech Republic); Prince, Kevin C. [Elettra-Sincrotrone Trieste S.C.p.A., in Area Science Park, Strada Statale 14, km 163.5, Basovizza, Trieste I-34149 (Italy); Matolín, Vladimír [Charles University in Prague, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, CZ-18000 Prague 8 (Czech Republic); Tsud, Nataliya, E-mail: Nataliya.Tsud@mff.cuni.cz [Charles University in Prague, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, CZ-18000 Prague 8 (Czech Republic)

    2016-10-15

    Highlights: • The surface of nanostructured ceria was functionalized by histidine. • The molecules were deposited from aqueous solution. • Polycrystalline films and nanoparticles of ceria were used as substrates. • Histidine chemisorbs on the surface via deprotonated carboxylate group. - Abstract: Histidine adsorption from neutral aqueous solution on cerium oxide substrates was studied by photoemission with use of synchrotron radiation, soft X-ray absorption spectroscopy and nuclear magnetic resonance. Polycrystalline oxide films and oxide nanoparticles were used as ceria substrates. Independent of the morphology of the support, histidine binds to the oxide through the carboxylic group while the imidazole ring does not participate in the interface formation. Compared to deposition of molecules by evaporation in vacuum, the presence of the solution during adsorption does not alter the histidine bonding to cerium oxide. The present results clearly demonstrate the applicability of the model (in-situ) studies of the histidine/CeO{sub 2} interface to the biocompatible techniques of cerium oxide functionalization.

  9. Histidine in Continuum Electrostatics Protonation State Calculations

    Science.gov (United States)

    Couch, Vernon; Stuchebruckhov, Alexei

    2014-01-01

    A modification to the standard continuum electrostatics approach to calculate protein pKas which allows for the decoupling of histidine tautomers within a two state model is presented. Histidine with four intrinsically coupled protonation states cannot be easily incorporated into a two state formalism because the interaction between the two protonatable sites of the imidazole ring is not purely electrostatic. The presented treatment, based on a single approximation of the interrelation between histidine’s charge states, allows for a natural separation of the two protonatable sites associated with the imidazole ring as well as the inclusion of all protonation states within the calculation. PMID:22072521

  10. Involvement of Histidine Residue His382 in pH Regulation of MCT4 Activity.

    Directory of Open Access Journals (Sweden)

    Shotaro Sasaki

    Full Text Available Monocarboxylate transporter 4 (MCT4 is a pH-dependent bi-directional lactate transporter. Transport of lactate via MCT4 is increased by extracellular acidification. We investigated the critical histidine residue involved in pH regulation of MCT4 function. Transport of lactate via MCT4 was measured by using a Xenopus laevis oocyte expression system. MCT4-mediated lactate transport was inhibited by Zn2+ in a pH physiological condition but not in an acidic condition. The histidine modifier DEPC (diethyl pyrocarbonate reduced MCT4 activity but did not completely inactivate MCT4. After treatment with DEPC, pH regulation of MCT4 function was completely knocked out. Inhibitory effects of DEPC were reversed by hydroxylamine and suppressed in the presence of excess lactate and Zn2+. Therefore, we performed an experiment in which the extracellular histidine residue was replaced with alanine. Consequently, the pH regulation of MCT4-H382A function was also knocked out. Our findings demonstrate that the histidine residue His382 in the extracellular loop of the transporter is essential for pH regulation of MCT4-mediated substrate transport activity.

  11. Discovery of inhibitors of bacterial histidine kinases

    NARCIS (Netherlands)

    Velikova, N.R.

    2014-01-01

    Discovery of Inhibitors of Bacterial Histidine Kinases

    Summary

    The thesis is on novel antibacterial drug discovery (http://youtu.be/NRMWOGgeysM). Using structure-based and fragment-based

  12. 21 CFR 582.5361 - Histidine.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Histidine. 582.5361 Section 582.5361 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements...

  13. Effect of dietary electrolytes and histidine on histidine metabolism and acid-base balance in rainbow trout (Salmo gairdneri)

    Science.gov (United States)

    Chiu, Y.N.; Austic, R.E.; Rumsey, G.L.

    1984-01-01

    1. Rainbow trout fingerlings were fed diets containing 1.2, 1.8 and 2.6% histidine and two mixtures of Na, K and Cl (Na + K - Cl = 0 or -200 meq/kgdiet) in a factorial design.2. Growth and efficiency of feed conversion were not affected by histidine in the diet when it contained the −200 meq/kg electrolyte mixture, but with the 0 meq/kg level, 2.6% histidine depressed both measures of response.3. Histidine increased plasma and muscle histidine levels, increased hepatic histidase activity, but did not affect hepatic histidine-pyruvate aminotransferase activity.4. Muscle-free histidine concentrations were markedly higher and lysine concentrations were lower in trout receiving 0 meq/kg than those receiving the −200 meq/kg electrolyte mixture.5. The electrolyte balance of the diet has a marked effect on the metabolism of histidine in trout.

  14. Inhibition of Transcription of the Histidine Operon In Vitro by the First Enzyme of the Histidine Pathway

    Science.gov (United States)

    Blasi, Francesco; Bruni, Carmelo B.; Avitabile, Alessandra; Deeley, Roger G.; Goldberger, Robert F.; Meyers, Marilyn M.

    1973-01-01

    An in vitro system was developed for transcription of the histidine operon of Esherichia coli carried in the genome of a defective ϕ80 transducing phage. The messenger RNA (mRNA) of the histidine operon synthesized in the in vitro system was detected by hybridization to single strands of both ϕ80 and ϕ80dhis DNA, and by competition of this hybridization with unlabeled histidine mRNA that had been synthesized in vivo (RNA extracted from cells in which the histidine operon had been derepressed). Under the conditions used, RNA complementary to the histidine operon was about 15% of the total RNA that was synthesized in vitro from the ϕ80dhis DNA template. The RNA complementary to the histidine operon was synthesized on the “sense” strand (the R strand) of ϕ80dhis in the form of a polycistronic message with a sedimentation coefficient (about 38 S) very close to that observed for the histidine mRNA synthesized in vivo. Synthesis of the histidine operon RNA appears to be subject to control in vitro. Addition of the first enzyme of the pathway for histidine biosynthesis blocked transcription of the histidine operon specifically, strongly suggesting that this enzyme acts as a regulatory protein for the histidine operon. PMID:4582195

  15. Electron Transfer from Azide Radical to Histidine Generates ...

    African Journals Online (AJOL)

    The formation of histidinyl radical (HR), which is a product of electron transfer reaction between histidine and some free radicals, was studied by pulse radiolysis. The reaction between histidine and azide radicals was found to produce HR, which has a distinct absorption spectrum with peaks at 300, 480 and 520 nm.

  16. GENERATION OF A PROTON MOTIVE FORCE BY HISTIDINE DECARBOXYLATION AND ELECTROGENIC HISTIDINE HISTAMINE ANTIPORT IN LACTOBACILLUS-BUCHNERI

    NARCIS (Netherlands)

    MOLENAAR, D; BOSSCHER, JS; TENBRINK, B; DRIESSEN, AJM; KONINGS, WN

    Lactobacillus buchneri ST2A vigorously decarboxylates histidine to the biogenic amine histamine, which is excreted into the medium. Cells grown in the presence of histidine generate both a transmembrane pH gradient, inside alkaline, and an electrical potential (DELTApsi), inside negative, upon

  17. Bacterial Histidine Kinases as Novel Antibacterial Drug Targets

    NARCIS (Netherlands)

    Bem, A.E.; Velikova, N.R.; Pellicer, M.T.; Baarlen, van P.; Marina, A.; Wells, J.M.

    2015-01-01

    Bacterial histidine kinases (HKs) are promising targets for novel antibacterials. Bacterial HKs are part of bacterial two-component systems (TCSs), the main signal transduction pathways in bacteria, regulating various processes including virulence, secretion systems and antibiotic resistance. In

  18. Histidine Residues in the Na+-coupled Ascorbic Acid Transporter-2 (SVCT2) Are Central Regulators of SVCT2 Function, Modulating pH Sensitivity, Transporter Kinetics, Na+ Cooperativity, Conformational Stability, and Subcellular Localization*

    Science.gov (United States)

    Ormazabal, Valeska; Zuñiga, Felipe A.; Escobar, Elizabeth; Aylwin, Carlos; Salas-Burgos, Alexis; Godoy, Alejandro; Reyes, Alejandro M.; Vera, Juan Carlos; Rivas, Coralia I.

    2010-01-01

    Na+-coupled ascorbic acid transporter-2 (SVCT2) activity is impaired at acid pH, but little is known about the molecular determinants that define the transporter pH sensitivity. SVCT2 contains six histidine residues in its primary sequence, three of which are exofacial in the transporter secondary structure model. We used site-directed mutagenesis and treatment with diethylpyrocarbonate to identify histidine residues responsible for SVCT2 pH sensitivity. We conclude that five histidine residues, His109, His203, His206, His269, and His413, are central regulators of SVCT2 function, participating to different degrees in modulating pH sensitivity, transporter kinetics, Na+ cooperativity, conformational stability, and subcellular localization. Our results are compatible with a model in which (i) a single exofacial histidine residue, His413, localized in the exofacial loop IV that connects transmembrane helices VII-VIII defines the pH sensitivity of SVCT2 through a mechanism involving a marked attenuation of the activation by Na+ and loss of Na+ cooperativity, which leads to a decreased Vmax without altering the transport Km; (ii) exofacial histidine residues His203, His206, and His413 may be involved in maintaining a functional interaction between exofacial loops II and IV and influence the general folding of the transporter; (iii) histidines 203, 206, 269, and 413 affect the transporter kinetics by modulating the apparent transport Km; and (iv) histidine 109, localized at the center of transmembrane helix I, might be fundamental for the interaction of SVCT2 with the transported substrate ascorbic acid. Thus, histidine residues are central regulators of SVCT2 function. PMID:20843809

  19. Loop-to-loop coupling.

    Energy Technology Data Exchange (ETDEWEB)

    Warne, Larry Kevin; Lucero, Larry Martin; Langston, William L.; Salazar, Robert Austin; Coleman, Phillip Dale; Basilio, Lorena I.; Bacon, Larry Donald

    2012-05-01

    This report estimates inductively-coupled energy to a low-impedance load in a loop-to-loop arrangement. Both analytical models and full-wave numerical simulations are used and the resulting fields, coupled powers and energies are compared. The energies are simply estimated from the coupled powers through approximations to the energy theorem. The transmitter loop is taken to be either a circular geometry or a rectangular-loop (stripline-type) geometry that was used in an experimental setup. Simple magnetic field models are constructed and used to estimate the mutual inductance to the receiving loop, which is taken to be circular with one or several turns. Circuit elements are estimated and used to determine the coupled current and power (an equivalent antenna picture is also given). These results are compared to an electromagnetic simulation of the transmitter geometry. Simple approximate relations are also given to estimate coupled energy from the power. The effect of additional loads in the form of attached leads, forming transmission lines, are considered. The results are summarized in a set of susceptibility-type curves. Finally, we also consider drives to the cables themselves and the resulting common-to-differential mode currents in the load.

  20. Optimization of cosmetic preservation: water activity reduction.

    Science.gov (United States)

    Kerdudo, A; Fontaine-Vive, F; Dingas, A; Faure, C; Fernandez, X

    2015-02-01

    Preservation of cosmetics is a prerequisite for industrialization, and among the proposed solutions, self-preserved cosmetics are of great interest. One key influencing parameter in self-preservation is water activity; its reduction can help to fight against microbial growth in cosmetic products. This work presents a study on the influence of humectants on water activity and its consequence on the preservation of cosmetic formulations. First, water-humectants mixtures were considered. The influence of glycol and glycerin content, glycol chemical structure, glycerin purity and formulation process on the water activity of the binary mixture was studied. Molecular modelling was performed for a better understanding of the impact of glycol chemistry. Then, the results were applied to five different cosmetic formulations to get optimized products. Challenge test on five strains was carried out in that sense. We showed that the higher the humectants concentration, the lower the water activity. Glycol chemical structure also influenced water activity: propan-1,2-diol was more efficient than propan-1,3-diol, certainly because of a better stabilization in water of propan-1,2-diol as shown by DFT calculation. A drop by drop introduction of glycol in water favoured aw reduction. The best water activity loss was 6.6% and was reached on the cream formulation whose preservation was improved as evidenced by challenge test. Fabrication process as well as humectants concentration were shown to influence water activity. The hydroxyl group positions as well as the presence of an alkyl group on the glycol carbon chain impacted water binding as suggested by DFT calculation. Reducing aw improved the preservation of a cosmetic cream, inhibiting or slowing down the growth of bacteria and fungi. © 2014 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  1. Electrophilic catalysis in triosephosphate isomerase: The role of histidine-95

    Energy Technology Data Exchange (ETDEWEB)

    Komives, E.A.; Chang, L.C.; Knowles, J.R. (Harvard Univ., Cambridge, MA (USA)); Lolis, E.; Tilton, R.F.; Petsko, G.A. (Massachusetts Inst. of Tech., Cambridge, MA (USA))

    1991-03-26

    Electrophilic catalysis by histidine-95 in triosephosphate isomerase has been probed by using Fourier transform infrared spectroscopy and X-ray crystallography. The carbonyl stretching frequency of dihydroxyacetone phosphate bound to the wild-type enzyme is known to be lower than that of dihydroxyacetone phosphate free in solution, and this decrease in stretching frequency has been ascribed to an enzymic electrophile that polarizes the substrate carbonyl group toward the transition state for the enolization. Infrared spectra of substrate bound to two site-directed mutants of yeast triosephosphate isomerase in which histidine-95 has been changed to glutamine or to asparagine show unperturbed carbonyl stretching frequencies between 1,732 and 1,742 cm{sup {minus}1}. The lack of carbonyl polarization when histidine-95 is removed suggests that histidine-95 is indeed the catalytic electrophile, at least for dihydroxyacetone phosphate. Kinetic studies of the glutamine mutant (H95Q) have shown that the enzyme follows a subtly different mechanism of proton transfers involving only a single acid-base catalytic group. These findings suggest an additional role for histidine-95 as a general acid-base catalyst in the wild-type enzyme. The X-ray crystal structure of the H95Q mutant with an intermediate analogue, phosphoglycolohydroxamate, bound at the active site has been solved to 2.8-{angstrom} resolution, and this structure clearly implicates glutamate-165, the catalytic base in the wild-type isomerase, as the sole acid-base catalyst for the mutant enzyme.

  2. Comparison of fractal dimension and Shannon entropy in myocytes from rats treated with histidine-tryptophan-glutamate and histidine-tryptophan cetoglutarate

    Science.gov (United States)

    de Oliveira, Marcos Aurélio Barboza; Brandi, Antônio Carlos; dos Santos, Carlos Alberto; Botelho, Paulo Henrique Husseni; Cortez, José Luís Lasso; de Godoy, Moacir Fernandes; Braile, Domingo Marcolino

    2014-01-01

    Introduction Solutions that cause elective cardiac arrest are constantly evolving, but the ideal compound has not yet been found. The authors compare a new cardioplegic solution with histidine-tryptophan-glutamate (Group 2) and other one with histidine-tryptophan-cetoglutarate (Group 1) in a model of isolated rat heart. Objective To quantify the fractal dimension and Shannon entropy in rat myocytes subjected to cardioplegia solution using histidine-tryptophan with glutamate in an experimental model, considering the caspase markers, IL-8 and KI-67. Methods Twenty male Wistar rats were anesthetized and heparinized. The chest was opened, the heart was withdrawn and 40 ml/kg of cardioplegia (with histidine-tryptophan-cetoglutarate or histidine-tryptophan-glutamate solution) was infused. The hearts were kept for 2 hours at 4ºC in the same solution, and thereafter placed in the Langendorff apparatus for 30 min with Ringer-Locke solution. Analyzes were performed for immunohistochemical caspase, IL-8 and KI-67. Results The fractal dimension and Shannon entropy were not different between groups histidine-tryptophan-glutamate and histidine-tryptophan-acetoglutarate. Conclusion The amount of information measured by Shannon entropy and the distribution thereof (given by fractal dimension) of the slices treated with histidine-tryptophan-cetoglutarate and histidine-tryptophan-glutamate were not different, showing that the histidine-tryptophan-glutamate solution is as good as histidine-tryptophan-acetoglutarate to preserve myocytes in isolated rat heart. PMID:25140464

  3. The question of histidine content in c-type cytochromes.

    Science.gov (United States)

    Cusanovich, M A; Meyer, T; Tedro, S M; Kamen, M D

    1971-03-01

    Reports that histidine may not occur in heme peptides derived from c-type cytochromes isolated from chloroplasts of Euglena gracilis and Porphyra sp. have not been substantiated in the present investigation, in which the amino acid composition and a partial sequence were determined for a heme peptide derived from the c-type cytochromes of a strain of Euglena closely related to that used in the previous studies. It is concluded that no evidence exists to challenge the generalization that histidine is always present vicinal to the hemebinding site in c-type cytochromes.

  4. Safety, absorption, and antioxidant effects of chromium histidine

    Science.gov (United States)

    Supplemental chromium has been shown to be involved in the alleviation of the metabolic syndrome, glucose intolerance, polycystic ovary syndrome, depression, excess body fat, and gestational, steroid-induced, and type 2 diabetes. Chromium amino acid complexes that contained histidine displayed cons...

  5. 21 CFR 862.1375 - Histidine test system.

    Science.gov (United States)

    2010-04-01

    ... often resulting in mental retardation and disordered speech development. (b) Classification. Class I... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Histidine test system. 862.1375 Section 862.1375...) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test Systems § 862...

  6. Formation of RNA phosphodiester bond by histidine-containing dipeptides

    DEFF Research Database (Denmark)

    Wieczorek, Rafal; Dörr, Mark; Chotera, Agata

    2013-01-01

    A new scenario for prebiotic formation of nucleic acid oligomers is presented. Peptide catalysis is applied to achieve condensation of activated RNA monomers into short RNA chains. As catalysts, L-dipeptides containing a histidine residue, primarily Ser-His, were used. Reactions were carried out ...

  7. Alternative loop rings

    CERN Document Server

    Goodaire, EG; Polcino Milies, C

    1996-01-01

    For the past ten years, alternative loop rings have intrigued mathematicians from a wide cross-section of modern algebra. As a consequence, the theory of alternative loop rings has grown tremendously. One of the main developments is the complete characterization of loops which have an alternative but not associative, loop ring. Furthermore, there is a very close relationship between the algebraic structures of loop rings and of group rings over 2-groups. Another major topic of research is the study of the unit loop of the integral loop ring. Here the interaction between loop rings and group ri

  8. Agglutination of human erythrocytes by the interaction of Zn(2+)ion with histidine-651 on the extracellular domain of band 3.

    Science.gov (United States)

    Kiyotake, Kento; Ochiai, Hideharu; Yamaguchi, Takeo

    2016-05-01

    Clustering of band 3, chloride/bicarbonate exchanger, has been reported in Zn(2+)-treated human erythrocytes. However, the agglutination of human erythrocytes is also induced by the interaction of Zn(2+)ion with histidine on band 3. Identification of histidine that interacts with Zn(2+)ion remains to be determined. The Zn(2+)-induced agglutination of human erythrocytes was unaffected by chymotrypsin cleavage of the small loop region containing His-547 in the extracellular domain of band 3. On the other hand, papain digestion of the large loop region containing His-651 in band 3 inhibited such Zn(2+)-induced agglutination. Moreover, Zn(2+)-induced erythrocyte agglutination was inhibited by the peptide (ARGWVIHPLG) containing His-651, but not by the peptide such as ARGWVIRPLG, which His-651 was substituted by arginine. Among 10 kinds of animal erythrocytes tested, interestingly, no agglutination by Zn(2+)ions was observed in cow cells only that the forth amino acid in the upstream from His-669 on the large loop of cow band 3 is aspartate (Asp-665) instead of glycine. As expected, the agglutination of human erythrocytes by Zn(2+) ions was inhibited in the presence of aspartate. These data indicate that the interaction of Zn(2+) ion with His-651 residue of band 3 plays an important role in the Zn(2+)-induced agglutination of human erythrocytes. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Fungal evaluation on green tea irradiated with different water activities

    Energy Technology Data Exchange (ETDEWEB)

    Fanaro, Gustavo B.; Duarte, Renato C.; Rodrigues, Flavio T.; Villavicencio, Anna Lucia C.H., E-mail: gbfanaro@ipen.b, E-mail: villavic@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (CTR/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Tecnologia das Radiacoes; Correa, Benedito, E-mail: correabe@usp.b [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Ciencias Biologicas. Dept. de Micologia

    2011-07-01

    The aim of this study was evaluate the fungal contamination in green tea irradiated with different radiation doses and water activities. Samples were irradiated in {sup 60}Co irradiator at doses of 0, 2.5, 5.0, 7.5 and 10.0kGy with three different water activities. In the sample with decreased water activity, the count of fungi was lower than others samples followed by original Aw and the samples with the higher water activity, however there is no difference between the increased and decreased water activities samples after the irradiation on fungi contamination at dose of 2.5 kGy. (author)

  10. Copper Complexes Of Di-, Tri-, And Tetra-Peptides Containing Tryptophan, Histidine And Arginine

    OpenAIRE

    El Naggar, A. M. [احمد محمد النجار; El-Ghaffar, S. A. A.; Zaher, M. R.

    1983-01-01

    Fifty Seven copper complexes of di-, tri-. and tetra-peptides containing tryptophan, histidine and arginine are studied spectrophotometrically. The ^a, and colour of the complexes are dependent on the sequence of the amino acid in the dipeptide methyl esters of tryptophan and arginine; and independent on the sequence of dipeptides of histidine or in any of the tri- and tetra-peptides of histidine, arginine and tryptophan. The results achieved confirmed that the nitrogen atoms of the indole nu...

  11. Manganese and cobalt binding in a multi-histidinic fragment.

    Science.gov (United States)

    Peana, Massimiliano; Medici, Serenella; Nurchi, Valeria Marina; Crisponi, Guido; Lachowicz, Joanna Izabela; Zoroddu, Maria Antonietta

    2013-12-14

    The binding of Mn(II) and Co(II) ions to a multi-histidinic peptide, the three repeats (T1R2S3R4S5H6T7S8E9G10)3 portion of Cap43 protein, has been studied. Potentiometric measurements have been used to investigate the protonation equilibria and stoichiometry of the species obtained in a wide range of pH and at a 1 : 1 ligand-to-metal molar ratio. NMR, UV-visible and EPR spectroscopy techniques have been used to investigate the role of multi-histidinic and glutamate sites in coordinating metal ions. (1)H-(1)H TOCSY, (1)H-(13)C HSQC multidimensional NMR techniques were performed to understand the details of metal binding sites and the conformational behaviour of the peptide. The effects of the peptide titration with the two metals have been followed by paramagnetic selective line-broadening in the 1D NMR spectra and the signals' disappearance in the 2D (1)H-(13)C HSQC and (1)H-(1)H TOCSY. Both ions showed common binding donor atoms: the main manganese and cobalt binding centre of the peptide fragment is associated with histidine and glutamate residues. The specific perturbation of NMR resonances indicated that the coordination involves imidazole Nε of histidine and carboxyl γ-O of glutamate residue. All the three imidazole Nε of His6, His16 and His26, as well as carboxyl γ-O of Glu9, Glu19 and Glu29, in an octahedral arrangement are involved in the coordination in the physiological pH range. The involvement of hydroxyl γ-O from the threonine (or serine) side chain can also be observed. Manganese and cobalt complexation induces important structural changes within the C-terminal portion of the ligand, constraining it to leave its disordered conformation. A model of the structure of manganese and cobalt species can be obtained from our data.

  12. Low-temperature Raman spectra of L-histidine crystal

    Energy Technology Data Exchange (ETDEWEB)

    Souda, G.P. de; Freire, P.T.C.; Mendes Filho, J.; Melo, F.E.A., E-mail: tarso@fisica.ufc.br [Universidade Federal do Ceara (UFCE), Fortaleza, CE (Brazil). Departamento de Fisica; Lima, C.L. [Universidade Federal do Piaui (UFPI), Teresina, PI (Brazil). Departamento de Fisica

    2013-07-01

    We present a Raman spectroscopy investigation of the vibrational properties of l-histidine crystals at low temperatures. The temperature dependence of the spectra show discontinuities at 165 K, which we identify with modifications in the bonds associated to both the NH{sub 3}{sup +} and CO{sub 2} − motifs indicative of a conformational phase transition that changes the intermolecular bonds. Additional evidence of such a phase transition is provided by differential scanning calorimetry measurements, which identified an enthalpic anomaly at ∼165 K. (author)

  13. Distal histidine conformational flexibility in dehaloperoxidase from Amphitrite ornata

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zuxu; de Serrano, Vesna; Betts, Laurie; Franzen, Stefan; (NCSU); (UNC)

    2009-01-28

    The enzyme dehaloperoxidase (DHP) from the terebellid polychaete Amphitrite ornata is a heme protein which has a globin fold but can function as both a hemoglobin and a peroxidase. As a peroxidase, DHP is capable of converting 2,4,6-trihalophenols to the corresponding 2,6-dihaloquinones in the presence of hydrogen peroxide. As a hemoglobin, DHP cycles between the oxy and deoxy states as it reversibly binds oxygen for storage. Here, it is reported that the distal histidine, His55, exhibits conformational flexibility in the deoxy form and is consequently observed in two solvent-exposed conformations more than 9.5 {angstrom} away from the heme. These conformations are analogous to the open conformation of sperm whale myoglobin. The heme iron in deoxy ferrous DHP is five-coordinate and has an out-of-plane displacement of 0.25 {angstrom} from the heme plane. The observation of five-coordinate heme iron with His55 in a remote solvent-exposed conformation is consistent with the hypothesis that His55 interacts with heme iron ligands through hydrogen bonding in the closed conformation. Since His55 is also displaced by the binding of 4-iodophenol in an internal pocket, these results provide new insight into the correlation between heme iron ligation, molecular binding in the distal pocket and the conformation of the distal histidine in DHP.

  14. In Silico Characterization of Histidine Acid Phytase Sequences

    Directory of Open Access Journals (Sweden)

    Vinod Kumar

    2012-01-01

    Full Text Available Histidine acid phytases (HAPhy are widely distributed enzymes among bacteria, fungi, plants, and some animal tissues. They have a significant role as an animal feed enzyme and in the solubilization of insoluble phosphates and minerals present in the form of phytic acid complex. A set of 50 reference protein sequences representing HAPhy were retrieved from NCBI protein database and characterized for various biochemical properties, multiple sequence alignment (MSA, homology search, phylogenetic analysis, motifs, and superfamily search. MSA using MEGA5 revealed the presence of conserved sequences at N-terminal “RHGXRXP” and C-terminal “HD.” Phylogenetic tree analysis indicates the presence of three clusters representing different HAPhy, that is, PhyA, PhyB, and AppA. Analysis of 10 commonly distributed motifs in the sequences indicates the presence of signature sequence for each class. Motif 1 “SPFCDLFTHEEWIQYDYLQSLGKYYGYGAGNPLGPAQGIGF” was present in 38 protein sequences representing clusters 1 (PhyA and 2 (PhyB. Cluster 3 (AppA contains motif 9 “KKGCPQSGQVAIIADVDERTRKTGEAFAAGLAPDCAITVHTQADTSSPDP” as a signature sequence. All sequences belong to histidine acid phosphatase family as resulted from superfamily search. No conserved sequence representing 3- or 6-phytase could be identified using multiple sequence alignment. This in silico analysis might contribute in the classification and future genetic engineering of this most diverse class of phytase.

  15. Approximate Loop Unrolling

    OpenAIRE

    Rodriguez-Cancio, Marcelino; Combemale, Benoit; Baudry, Benoit

    2016-01-01

    We introduce Approximate Unrolling, a loop optimization that reduces execution time and energy consumption, exploiting the existence of code regions that can endure some degree of approximation while still producing acceptable results. This work focuses on a specific kind of forgiving region: counted loops that map a given functions over the elements of an array. Approximate Unrolling transforms loops in a similar way Loop Unrolling does. However, unlike its exact counterpart, our optimizatio...

  16. Structural Insights into the HWE Histidine Kinase Family: The Brucella Blue Light-Activated Histidine Kinase Domain.

    Science.gov (United States)

    Rinaldi, Jimena; Arrar, Mehrnoosh; Sycz, Gabriela; Cerutti, María Laura; Berguer, Paula M; Paris, Gastón; Estrín, Darío Ariel; Martí, Marcelo Adrián; Klinke, Sebastián; Goldbaum, Fernando Alberto

    2016-03-27

    In response to light, as part of a two-component system, the Brucella blue light-activated histidine kinase (LOV-HK) increases its autophosphorylation, modulating the virulence of this microorganism. The Brucella histidine kinase (HK) domain belongs to the HWE family, for which there is no structural information. The HWE family is exclusively present in proteobacteria and usually coupled to a wide diversity of light sensor domains. This work reports the crystal structure of the Brucella HK domain, which presents two different dimeric assemblies in the asymmetric unit: one similar to the already described canonical parallel homodimers (C) and the other, an antiparallel non-canonical (NC) dimer, each with distinct relative subdomain orientations and dimerization interfaces. Contrary to these crystallographic structures and unlike other HKs, in solution, the Brucella HK domain is monomeric and still active, showing an astonishing instability of the dimeric interface. Despite this instability, using cross-linking experiments, we show that the C dimer is the functionally relevant species. Mutational analysis demonstrates that the autophosphorylation activity occurs in cis. The different relative subdomain orientations observed for the NC and C states highlight the large conformational flexibility of the HK domain. Through the analysis of these alternative conformations by means of molecular dynamics simulations, we also propose a catalytic mechanism for Brucella LOV-HK. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Feeding filaggrin: effects of l-histidine supplementation in atopic dermatitis.

    Science.gov (United States)

    Tan, Siao Pei; Brown, Simon B; Griffiths, Christopher Em; Weller, Richard B; Gibbs, Neil K

    2017-01-01

    Atopic dermatitis (AD), also known as eczema, is one of the most common chronic skin conditions worldwide, affecting up to 16% of children and 10% of adults. It is incurable and has significant psychosocial and economic impacts on the affected individuals. AD etiology has been linked to deficiencies in the skin barrier protein, filaggrin. In mammalian skin, l-histidine is rapidly incorporated into filaggrin. Subsequent filaggrin proteolysis releases l-histidine as an important natural moisturizing factor (NMF). In vitro studies were conducted to investigate the influence of l-histidine on filaggrin processing and barrier function in human skin-equivalent models. Our further aim was to examine the effects of daily oral l-histidine supplementation on disease severity in adult AD patients. We conducted a randomized, double-blind, placebo-controlled, crossover, nutritional supplementation pilot study to explore the effects of oral l-histidine in adult AD patients (n=24). In vitro studies demonstrated that l-histidine significantly increased both filaggrin formation and skin barrier function (Pl-histidine significantly reduced (P0.32). The clinical effect of oral l-histidine in AD was similar to that of mid-potency topical corticosteroids and combined with its safety profile suggests that it may be a safe, nonsteroidal approach suitable for long-term use in skin conditions that are associated with filaggrin deficits such as AD.

  18. Synthesis and catalytic activity of histidine-based NHC ruthenium complexes.

    Science.gov (United States)

    Monney, Angèle; Venkatachalam, Galmari; Albrecht, Martin

    2011-03-28

    Main-chain C,N-protected histidine has been successfully alkylated at both side-chain nitrogens. The corresponding histidinium salt was metallated with ruthenium(II) by a transmetalation procedure, thus providing histidine-derived NHC ruthenium complexes. These bio-inspired complexes show appreciable activity in the catalytic transfer hydrogenation of ketones.

  19. Synthesis of selectively labeled histidine and its methylderivatives with deuterium, tritium, and carbon-14.

    Science.gov (United States)

    Šamonina-Kosicka, J; Kańska, M

    2013-05-30

    Isotopologues of l-histidine and its N-methylderivatives labeled with deuterium and tritium at the 5-position in the imidazole ring were obtained using the isotope exchange method. The deuterium-labeled isotopologues [5-(2)H]-l-histidine, [5-(2)H]-N(τ) -methyl-l-histidine, [5-(2)H]-N(π) -methyl-l-histidine, and [2,5-(2)H(2)]-l-histidine were synthesized by isotope exchange method carried out in a fully deuterated medium with. The same reaction conditions were applied to synthesize [5-(3)H]-N(τ) -methyl-l-histidine, [5-(3)H]-N(π) -methyl-l-histidine, and [5-(3)H]-l-histidine with specific activity of 2.0, 5.0, and 2.6 MBq/mmol, respectively. The N(π) -[methyl-(14)C]-histamine was obtained with specific activity of 0.23 MBq/mmol in a one-step reaction by the direct methylation of histamine by [(14)C]iodomethane. Copyright © 2013 John Wiley & Sons, Ltd.

  20. Blind Loop Syndrome

    Science.gov (United States)

    ... breeding ground for bacteria. The bacteria may produce toxins as well as block the absorption of nutrients. The greater the length of small bowel involved in the blind loop, the greater the chance of bacterial overgrowth. What triggers blind loop syndrome? Blind loop ...

  1. Effects of intraperitoneally administered L-histidine on food intake, taste, and visceral sensation in rats.

    Science.gov (United States)

    Okusha, Yuka; Hirai, Yoshiyuki; Maezawa, Hitoshi; Hisadome, Kazunari; Inoue, Nobuo; Yamazaki, Yutaka; Funahashi, Makoto

    2017-07-01

    To evaluate relative factors for anorectic effects of L-histidine, we performed behavioral experiments for measuring food and fluid intake, conditioned taste aversion (CTA), taste disturbance, and c-Fos immunoreactive (Fos-ir) cells before and after i.p. injection with L-histidine in rats. Animals were injected with saline (9 ml/kg, i.p.) for a control group, and saline (9 ml/kg, i.p.) containing L-histidine (0.75, 1.5, 2.0 g/kg) for a L-histidine group. Injection of L-histidine decreased the average value of food intake, and statistically significant anorectic effects were found in animals injected with 1.5 or 2.0 g/kg L-histidine but not with 0.75 g/kg L-histidine. Taste abnormalities were not detected in any of the groups. Animals injected with 2.0 g/kg L-histidine were revealed to present with nausea by the measurement of CTA. In this group, a significant increase in the number of Fos-ir cells was detected both in the area postrema and the nucleus tractus solitarius (NTS). In the 0.75 g/kg L-histidine group, a significant increase in the number of Fos-ir cells was detected only in the NTS. When the ventral gastric branch vagotomy was performed, recovery from anorexia became faster than the sham-operated group, however, vagotomized rats injected with 2.0 g/kg L-histidine still acquired CTA. These data indicate that acute anorectic effects induced by highly concentrated L-histidine are partly caused by induction of nausea and/or visceral discomfort accompanied by neuronal activities in the NTS and the area postrema. We suggest that acute and potent effects of L-histidine on food intake require substantial amount of L-histidine in the diet.

  2. Oral administration of vitamin C and histidine attenuate cyclophosphamide-induced hemorrhagic cystitis in rats.

    Science.gov (United States)

    Farshid, Amir Abbas; Tamaddonfard, Esmaeal; Ranjbar, Sepideh

    2013-01-01

    Cyclophosphamide (CP), a widely used antineoplastic drug causes hemorrhagic cystitis (HC) mainly via induction of oxidative stress. Both vitamin C and histidine have antioxidant properties. The present study aimed to investigate the effects of oral (p.o.) administration of vitamin C and histidine on the CP-induced HC in rats. The animals were divided into two major groups I and II with four subgroups (a, b, c, and d) in each. Groups I and II were treated with intraperitoneal (i.p.) injections of normal saline and CP (200 mg/kg), respectively, thereafter, normal saline, vitamin C (200 mg/kg), histidine (200 mg/kg) and vitamin C plus histidine were p.o. administered in subgroups a, b, c, and d, respectively, three times (2, 6, and 24 h) after i.p. injections of normal saline and CP. Blood samples were assayed for total antioxidant capacity (TAC) and malondialdehyde (MDA) levels. Histopathological changes of bladder wall were investigated. The decreased TAC and increased MDA levels of plasma and the severity of hemorrhages, congestion, edema, and leukocyte infiltration of bladder induced by CP were recovered with vitamin C and histidine treatments. Combined treatment with vitamin C and histidine showed a potentiation effect. The results indicated that vitamin C and histidine attenuated the CP-induced HC by reducing of free radical-induced toxic effects.

  3. Water activity in polyol/water systems: new UNIFAC parameterization

    OpenAIRE

    Marcolli, C.; Peter, Th.

    2005-01-01

    Water activities of a series of polyol/water systems were measured with an AquaLab dew point water activity meter at 298 K. The investigated polyols with carbon numbers from n=2–7 are all in liquid state at room temperature and miscible at any molar ratio 5 with water. In aqueous solutions with the same mass concentration, the diols with lower molecular weight lead to lower water activities than those with higher molecular weights. For diols with four or more carbon atoms, the hygro...

  4. Measurement of water activity from shales through thermo hygrometer

    Energy Technology Data Exchange (ETDEWEB)

    Rabe, Claudio [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Civil. Grupo de Tecnologia e Engenharia de Petroleo (GTEP)

    2004-07-01

    This paper presents a campaign of lab tests to obtain the water activity from shales and its pore fluid originated from offshore and onshore basin. The results of water activity from shales indicate that the values rang from 0.754 to 0.923 and for the pore fluid are between 0.987 and 0.940. The results show that the water activity of interstitial water can be obtained in 6 days and the rock in 10 days using the thermo hygrometer used. The degree of saturation, water content, kind and tenor of expansible and hydratable clay mineral, total and interconnected porosity, salinity of interstitial fluid and the capillary pressure of shale samples affected the results of water activity. (author)

  5. Water activity in polyol/water systems: new UNIFAC parameterization

    Science.gov (United States)

    Marcolli, C.; Peter, Th.

    2005-06-01

    Water activities of a series of polyol/water systems were measured with an AquaLab dew point water activity meter at 298K. The investigated polyols with carbon numbers from n=2-7 are all in liquid state at room temperature and miscible at any molar ratio with water. In aqueous solutions with the same molar concentration, the diols with lower molecular weight lead to lower water activities than those with higher molecular weights. For diols with four or more carbon atoms, the hydrophilicity shows considerable differences between isomers: The 1,2-isomers - consisting of a hydrophilic and a hydrophobic part - bind less strongly to water than isomers with a more balanced distribution of the hydroxyl groups. The experimental water activities were compared with the predictions of the group contribution method UNIFAC: the model predictions overestimate the water activity of water/polyol systems of substances with two or more hydroxyl groups and can not describe the decreased binding to water of isomers with hydrophobic tails. To account for the differences between isomers, a modified UNIFAC parameterization was developed, that allows to discriminate between three types of alkyl groups depending on their position in the molecule. These new group interaction parameters were calculated using water activities of alcohol/water mixtures. This leads to a distinctly improved agreement of model predictions with experimental results while largely keeping the simplicity of the functional group approach.

  6. Water activity in polyol/water systems: new UNIFAC parameterization

    Directory of Open Access Journals (Sweden)

    C. Marcolli

    2005-01-01

    Full Text Available Water activities of a series of polyol/water systems were measured with an AquaLab dew point water activity meter at 298K. The investigated polyols with carbon numbers from n=2-7 are all in liquid state at room temperature and miscible at any molar ratio with water. In aqueous solutions with the same molar concentration, the diols with lower molecular weight lead to lower water activities than those with higher molecular weights. For diols with four or more carbon atoms, the hydrophilicity shows considerable differences between isomers: The 1,2-isomers - consisting of a hydrophilic and a hydrophobic part - bind less strongly to water than isomers with a more balanced distribution of the hydroxyl groups. The experimental water activities were compared with the predictions of the group contribution method UNIFAC: the model predictions overestimate the water activity of water/polyol systems of substances with two or more hydroxyl groups and can not describe the decreased binding to water of isomers with hydrophobic tails. To account for the differences between isomers, a modified UNIFAC parameterization was developed, that allows to discriminate between three types of alkyl groups depending on their position in the molecule. These new group interaction parameters were calculated using water activities of alcohol/water mixtures. This leads to a distinctly improved agreement of model predictions with experimental results while largely keeping the simplicity of the functional group approach.

  7. An histidine covalent receptor/butenolide complex mediates strigolactone perception

    Science.gov (United States)

    Badet-Denisot, Marie-Ange; Pillot, Jean-Paul; Cornu, David; Le Caer, Jean-Pierre; Burger, Marco; Pelissier, Frank; Retailleau, Pascal; Turnbull, Colin; Bonhomme, Sandrine; Chory, Joanne; Rameau, Catherine; Boyer, François-Didier

    2016-01-01

    Strigolactone plant hormones control plant architecture and are key players in both symbiotic and parasitic interactions. They contain an ABC tricyclic lactone connected to a butenolide group, the D-ring. The DWARF14 (D14) strigolactone receptor belongs to the superfamily of α/β-hydrolases and is known to hydrolyze the bond between the ABC lactone and the D-ring. Here we characterize the binding and catalytic functions of RAMOSUS3 (RMS3), the pea (Pisum sativum) ortholog of rice (Oryza sativa) D14 strigolactone receptor. Using novel profluorescent probes with strigolactone-like bioactivity, we show that RMS3 acts as a single-turnover enzyme that explains its apparent low enzymatic rate. We further demonstrate the formation of a covalent RMS3/D-ring complex, essential for bioactivity, in which the D-ring is attached to Histidine 247 of the catalytic triad. These results reveal an undescribed mechanism of plant hormone reception where the receptor performs an irreversible enzymatic reaction to generate its own ligand. PMID:27479744

  8. In vitro study of proteolytic degradation of rat histidine decarboxylase.

    Science.gov (United States)

    Olmo, M T; Urdiales, J L; Pegg, A E; Medina, M A; Sánchez-Jiménez, F

    2000-03-01

    Mammalian ornithine decarboxylase (ODC) is a very unstable protein which is degraded in an ATP-dependent manner by proteasome 26S, after making contact with the regulatory protein antizyme. PEST regions are sequences described as signals for protein degradation. The C-terminal PEST region of mammalian ODC is essential for its degradation by proteasome 26S. Mammalian histidine decarboxylase (HDC) is also a short-lived protein. The full primary sequence of mammalian HDC contains PEST-regions at both the N- and C-termini. Rat ODC and different truncated and full versions of rat HDC were expressed in vitro. In vitro degradation of rat ODC and rat 1-512 HDC were compared. Like ODC, rat 1-512 HDC is degraded mainly by an ATP-dependent mechanism. However, antizyme has no effect on the degradation of 1-512 HDC. The use of the inhibitors MG-132 and lactacystine significantly inhibited the degradation of 1-512 HDC, suggesting that a ubiquitin-dependent, proteasome 26S proteolytic pathway is involved. Results obtained with the different modifications of rat HDC containing all three PEST regions (full version, 1-656 HDC), only the N-terminal PEST region (1-512 HDC), or no PEST region (69-512 HDC), indicate that the N-terminal (1-69) fragment, but not the C-terminal fragment, determines that the HDC protein is a proteasome substrate in vitro.

  9. Histidine side-chain dynamics and protonation monitored by C-13 CPMG NMR relaxation dispersion

    DEFF Research Database (Denmark)

    Hass, M. A. S.; Yilmaz, A.; Christensen, Hans Erik Mølager

    2009-01-01

    the chemical shift titration experiments, and the CPMG derived exchange rates agree with those obtained previously from N-15 backbone relaxation measurements. Compared to measurements of backbone nuclei, C-13(epsilon 1) dispersion provides a more direct method to monitor interchanging protonation states...... or other kinds of conformational changes of histidine side chains or their environment. Advantages and shortcomings of using the C-13(epsilon 1) dispersion experiments in combination with chemical shift titration experiments to obtain information on exchange dynamics of the histidine side chains......The use of C-13 NMR relaxation dispersion experiments to monitor micro-millisecond fluctuations in the protonation states of histidine residues in proteins is investigated. To illustrate the approach, measurements on three specifically C-13 labeled histidine residues in plastocyanin (PCu) from...

  10. Analysis of conformational changes in rhodopsin by histidine hydrogen-deuterium exchange.

    Science.gov (United States)

    Lodowski, David T; Miyagi, Masaru

    2015-01-01

    Hydrogen-deuterium exchange (HDX) is a technique that measures the exchange of protein hydrogens for deuteriums in a D2O-containing buffer, providing readout of the structural dynamics. Histidine hydrogen-deuterium exchange mass spectrometry (His-HDX-MS) is a variation of this technique that measures the slow HDX of imidazole C2 hydrogens of histidines. This measurement, when accompanied by pH titration, provides both pK as and half-lives (t 1/2) of the HDX reaction for individual histidine residues in proteins. The pK a and t 1/2 values indicate the electrostatic environment and the degree of side-chain solvent accessibility of the histidine residues, respectively. Herein we describe an experimental protocol to characterize rhodopsin by His-HDX-MS. This technique can be used to monitor different states of rhodopsin and might be useful for monitoring longtime scale events in other GPCRs.

  11. L-histidine inhibits production of lysophosphatidic acid by the tumor-associated cytokine, autotaxin

    Directory of Open Access Journals (Sweden)

    Schiffmann Elliott

    2005-02-01

    Full Text Available Abstract Background Autotaxin (ATX, NPP-2, originally purified as a potent tumor cell motility factor, is now known to be the long-sought plasma lysophospholipase D (LPLD. The integrity of the enzymatic active site, including three crucial histidine moieties, is required for motility stimulation, as well as LPLD and 5'nucleotide phosphodiesterase (PDE activities. Except for relatively non-specific chelation agents, there are no known inhibitors of the ATX LPLD activity. Results We show that millimolar concentrations of L-histidine inhibit ATX-stimulated but not LPA-stimulated motility in two tumor cell lines, as well as inhibiting enzymatic activities. Inhibition is reversed by 20-fold lower concentrations of zinc salt. L-histidine has no significant effect on the Km of LPLD, but reduces the Vmax by greater than 50%, acting as a non-competitive inhibitor. Several histidine analogs also inhibit the LPLD activity of ATX; however, none has greater potency than L-histidine and all decrease cell viability or adhesion. Conclusion L-histidine inhibition of LPLD is not a simple stoichiometric chelation of metal ions but is more likely a complex interaction with a variety of moieties, including the metal cation, at or near the active site. The inhibitory effect of L-histidine requires all three major functional groups of histidine: the alpha amino group, the alpha carboxyl group, and the metal-binding imidazole side chain. Because of LPA's involvement in pathological processes, regulation of its formation by ATX may give insight into possible novel therapeutic approaches.

  12. In silico study of fragile histidine triad interaction domains with MDM2 and p53

    OpenAIRE

    Ameneh Eslamparast; Mohammad Hossein Ghahremani; Soroush Sardari

    2014-01-01

    Background: Fragile histidine triad (FHIT) is considered as a member of the histidine triad (HIT) nucleotide-binding protein superfamily regarded as a putative tumor suppressor executing crucial role in inhibiting p53 degradation by MDM2. Accumulating evidences indicate FHIT interaction with p53 or MDM2; however, there is no certain study deciphering functional domains of FHIT involving in the interaction with MDM2 and/or p53. In this regard, such evident interaction can spring in mind determ...

  13. The amino acid sequence around the active-site cysteine and histidine residues of stem bromelain

    Science.gov (United States)

    Husain, S. S.; Lowe, G.

    1970-01-01

    Stem bromelain that had been irreversibly inhibited with 1,3-dibromo[2-14C]-acetone was reduced with sodium borohydride and carboxymethylated with iodoacetic acid. After digestion with trypsin and α-chymotrypsin three radioactive peptides were isolated chromatographically. The amino acid sequences around the cross-linked cysteine and histidine residues were determined and showed a high degree of homology with those around the active-site cysteine and histidine residues of papain and ficin. PMID:5420046

  14. Proton transfer in histidine-tryptophan heterodimers embedded in helium droplets

    Energy Technology Data Exchange (ETDEWEB)

    Bellina, Bruno; Merthe, Daniel J.; Kresin, Vitaly V. [Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089-0484 (United States)

    2015-03-21

    We used cold helium droplets as nano-scale reactors to form and ionize, by electron bombardment and charge transfer, aromatic amino acid heterodimers of histidine with tryptophan, methyl-tryptophan, and indole. The molecular interaction occurring through an N–H ⋅ ⋅ ⋅ N hydrogen bond leads to a proton transfer from the indole group of tryptophan to the imidazole group of histidine in a radical cationic environment.

  15. The structure and dynamic properties of the complete histidine phosphotransfer domain of the chemotaxis specific histidine autokinase CheA from Thermotoga maritima

    Energy Technology Data Exchange (ETDEWEB)

    Vu, Anh; Hamel, Damon J.; Zhou Hongjun; Dahlquist, Frederick W., E-mail: dahlquist@chem.ucsb.edu [University of California Santa Barbara, Department of Chemistry and Biochemistry (United States)

    2011-09-15

    The bacterial histidine autokinase CheA contains a histidine phosphotransfer (Hpt) domain that accepts a phosphate from the catalytic domain and donates the phosphate to either target response regulator protein, CheY or CheB. The Hpt domain forms a helix-bundle structure with a conserved four-helix bundle motif and a variable fifth helix. Observation of two nearly equally populated conformations in the crystal structure of a Hpt domain fragment of CheA from Thermotoga maritima containing only the first four helices suggests more mobility in a tightly packed helix bundle structure than previously thought. In order to examine how the structures of Hpt domain homologs may differ from each other particularly in the conformation of the last helix, and whether an alternative conformation exists in the intact Hpt domain in solution, we have solved a high-resolution, solution structure of the CheA Hpt from T. maritima and characterized the backbone dynamics of this protein. The structure contains a four-helix bundle characteristic of histidine phosphotransfer domains. The position and orientation of the fifth helix resembles those in known Hpt domain crystal and solution structures in other histidine kinases. The alternative conformation that was reported in the crystal structure of the CheA Hpt from T. maritima missing the fifth helix is not detected in the solution structure, suggesting a role for the fifth helix in providing stabilizing forces to the overall structure.

  16. Introduction to Loop Heat Pipes

    Science.gov (United States)

    Ku, Jentung

    2015-01-01

    This is the presentation file for the short course Introduction to Loop Heat Pipes, to be conducted at the 2015 Thermal Fluids and Analysis Workshop, August 3-7, 2015, Silver Spring, Maryland. This course will discuss operating principles and performance characteristics of a loop heat pipe. Topics include: 1) pressure profiles in the loop; 2) loop operating temperature; 3) operating temperature control; 4) loop startup; 4) loop shutdown; 5) loop transient behaviors; 6) sizing of loop components and determination of fluid inventory; 7) analytical modeling; 8) examples of flight applications; and 9) recent LHP developments.

  17. Blind Loop Syndrome

    Science.gov (United States)

    ... of tissue that protrude through the intestinal wall (diverticulosis) Certain medical conditions, including Crohn's disease, radiation enteritis, ... History of radiation therapy to the abdomen Diabetes Diverticulosis of the small intestine A blind loop can ...

  18. Intra- and interprotein phosphorylation between two-hybrid histidine kinases controls Myxococcus xanthus developmental progression.

    Science.gov (United States)

    Schramm, Andreas; Lee, Bongsoo; Higgs, Penelope I

    2012-07-20

    Histidine-aspartate phosphorelay signaling systems are used to couple stimuli to cellular responses. A hallmark feature is the highly modular signal transmission modules that can form both simple "two-component" systems and sophisticated multicomponent systems that integrate stimuli over time and space to generate coordinated and fine-tuned responses. The deltaproteobacterium Myxococcus xanthus contains a large repertoire of signaling proteins, many of which regulate its multicellular developmental program. Here, we assign an orphan hybrid histidine protein kinase, EspC, to the Esp signaling system that negatively regulates progression through the M. xanthus developmental program. The Esp signal system consists of the hybrid histidine protein kinase, EspA, two serine/threonine protein kinases, and a putative transport protein. We demonstrate that EspC is an essential component of this system because ΔespA, ΔespC, and ΔespA ΔespC double mutants share an identical developmental phenotype. Neither substitution of the phosphoaccepting histidine residue nor deletion of the entire catalytic ATPase domain in EspC produces an in vivo mutant developmental phenotype. In contrast, substitution of the receiver phosphoaccepting residue yields the null phenotype. Although the EspC histidine kinase can efficiently autophosphorylate in vitro, it does not act as a phosphodonor to its own receiver domain. Our in vitro and in vivo analyses suggest the phosphodonor is instead the EspA histidine kinase. We propose EspA and EspC participate in a novel hybrid histidine protein kinase signaling mechanism involving both inter- and intraprotein phosphotransfer. The output of this signaling system appears to be the combined phosphorylated state of the EspA and EspC receiver modules. This system regulates the proteolytic turnover of MrpC, an important regulator of the developmental program.

  19. Intra- and Interprotein Phosphorylation between Two-hybrid Histidine Kinases Controls Myxococcus xanthus Developmental Progression*

    Science.gov (United States)

    Schramm, Andreas; Lee, Bongsoo; Higgs, Penelope I.

    2012-01-01

    Histidine-aspartate phosphorelay signaling systems are used to couple stimuli to cellular responses. A hallmark feature is the highly modular signal transmission modules that can form both simple “two-component” systems and sophisticated multicomponent systems that integrate stimuli over time and space to generate coordinated and fine-tuned responses. The deltaproteobacterium Myxococcus xanthus contains a large repertoire of signaling proteins, many of which regulate its multicellular developmental program. Here, we assign an orphan hybrid histidine protein kinase, EspC, to the Esp signaling system that negatively regulates progression through the M. xanthus developmental program. The Esp signal system consists of the hybrid histidine protein kinase, EspA, two serine/threonine protein kinases, and a putative transport protein. We demonstrate that EspC is an essential component of this system because ΔespA, ΔespC, and ΔespA ΔespC double mutants share an identical developmental phenotype. Neither substitution of the phosphoaccepting histidine residue nor deletion of the entire catalytic ATPase domain in EspC produces an in vivo mutant developmental phenotype. In contrast, substitution of the receiver phosphoaccepting residue yields the null phenotype. Although the EspC histidine kinase can efficiently autophosphorylate in vitro, it does not act as a phosphodonor to its own receiver domain. Our in vitro and in vivo analyses suggest the phosphodonor is instead the EspA histidine kinase. We propose EspA and EspC participate in a novel hybrid histidine protein kinase signaling mechanism involving both inter- and intraprotein phosphotransfer. The output of this signaling system appears to be the combined phosphorylated state of the EspA and EspC receiver modules. This system regulates the proteolytic turnover of MrpC, an important regulator of the developmental program. PMID:22661709

  20. ADI pathway and histidine decarboxylation are reciprocally regulated in Lactobacillus hilgardii ISE 5211: proteomic evidence.

    Science.gov (United States)

    Lamberti, Cristina; Purrotti, Micol; Mazzoli, Roberto; Fattori, Paolo; Barello, Cristina; Coïsson, Jean Daniel; Giunta, Carlo; Pessione, Enrica

    2011-07-01

    Amine production by amino acid decarboxylation is a common feature that is used by lactic acid bacteria (LAB) to complement lactic fermentation, since it is coupled with a proton-extruding antiport system which leads to both metabolic energy production and the attenuation of intracellular acidity. Analogous roles are played in LAB by both malolactic fermentation (MLF) and the arginine deiminase (ADI) pathway. The present investigation was aimed at establishing reciprocal interactions between amino acid decarboxylation and the two above mentioned routes. The analyses were carried out on a Lactobacillus hilgardii strain (ISE 5211) that is able to decarboxylate histidine to histamine, which had previously been isolated from wine and whose complete genome is still unknown. The 2DE proteomic approach, followed by MALDI TOF-TOF and De Novo Sequencing, was used to study the protein expression levels. The experimental evidence has indicated that malate does not influence histidine decarboxylase (HDC) biosynthesis and that histidine does not affect the malolactic enzyme level. However, the expression of the ADI route enzymes, arginine deiminase and ornithine transcarbamylase, is down-regulated by histidine: this biosynthetic repression is more important (4-fold) in cultures that are not supplemented with arginine, but is also significant (2-fold) in an arginine supplemented medium that normally induces the ADI pathway. On the other hand, arginine partially represses HDC expression, but only when histidine and arginine are both present in the culture medium. This proteomic study has also pointed out a down-regulation exerted by histidine over sugar metabolism enzymes and a GroEL stress protein. These data, together with the reciprocal antagonism between arginine deimination and histidine decarboxylation, offer clue keys to the understanding of the accumulation of lactate, amine, ammonia and ethylcarbamate in wine, with consequent implications on different health risk

  1. Multimodal mechanism of action for the Cdc34 acidic loop: a case study for why ubiquitin-conjugating enzymes have loops and tails.

    Science.gov (United States)

    Ziemba, Amy; Hill, Spencer; Sandoval, Daniella; Webb, Kristofor; Bennett, Eric J; Kleiger, Gary

    2013-11-29

    Together with ubiquitin ligases (E3), ubiquitin-conjugating enzymes (E2) are charged with the essential task of synthesizing ubiquitin chains onto protein substrates. Some 75% of the known E2s in the human proteome contain unique insertions in their primary sequences, yet it is largely unclear what effect these insertions impart on the ubiquitination reaction. Cdc34 is an important E2 with prominent roles in cell cycle regulation and signal transduction. The amino acid sequence of Cdc34 contains an insertion distal to the active site that is absent in most other E2s, yet this acidic loop (named for its four invariably conserved acidic residues) is critical for Cdc34 function both in vitro and in vivo. Here we have investigated how the acidic loop in human Cdc34 promotes ubiquitination, identifying two key molecular events during which the acidic loop exerts its influence. First, the acidic loop promotes the interaction between Cdc34 and its ubiquitin ligase partner, SCF. Second, two glutamic acid residues located on the distal side of the loop collaborate with an invariably conserved histidine on the proximal side of the loop to suppress the pKa of an ionizing species on ubiquitin or Cdc34 which greatly contributes to Cdc34 catalysis. These results demonstrate that insertions can guide E2s to their physiologically relevant ubiquitin ligases as well as provide essential modalities that promote catalysis.

  2. Feeding filaggrin: effects of L-histidine supplementation in atopic dermatitis

    Directory of Open Access Journals (Sweden)

    Tan SP

    2017-10-01

    Full Text Available Siao Pei Tan,1,2 Simon B Brown,1,2 Christopher EM Griffiths,3 Richard B Weller,1,2 Neil K Gibbs3,4 1MRC Centre for Inflammation Research, 2Department of Dermatology, The University of Edinburgh, Edinburgh, 3Dermatology Centre, Division of Musculoskeletal and Dermatological Sciences, Salford Royal NHS Foundation Trust, University of Manchester, Manchester, 4Curapel, Life Sciences Hub Wales, Cardiff, UK Abstract: Atopic dermatitis (AD, also known as eczema, is one of the most common chronic skin conditions worldwide, affecting up to 16% of children and 10% of adults. It is incurable and has significant psychosocial and economic impacts on the affected individuals. AD etiology has been linked to deficiencies in the skin barrier protein, filaggrin. In mammalian skin, l-histidine is rapidly incorporated into filaggrin. Subsequent filaggrin proteolysis releases l-histidine as an important natural moisturizing factor (NMF. In vitro studies were conducted to investigate the influence of l-histidine on filaggrin processing and barrier function in human skin-equivalent models. Our further aim was to examine the effects of daily oral l-histidine supplementation on disease severity in adult AD patients. We conducted a randomized, double-blind, placebo-controlled, crossover, nutritional supplementation pilot study to explore the effects of oral l-histidine in adult AD patients (n=24. In vitro studies demonstrated that l-histidine significantly increased both filaggrin formation and skin barrier function (P<0.01, respectively. Data from the clinical study indicated that once daily oral l-histidine significantly reduced (P<0.003 AD disease severity by 34% (physician assessment using the SCORingAD tool and 39% (patient self-assessment using the Patient Oriented Eczema Measure tool after 4 weeks of treatment. No improvement was noted with the placebo (P>0.32. The clinical effect of oral l-histidine in AD was similar to that of mid-potency topical corticosteroids

  3. Conformationally Constrained Histidines in the Design of Peptidomimetics: Strategies for the χ-Space Control

    Directory of Open Access Journals (Sweden)

    Adriano Mollica

    2011-05-01

    Full Text Available A successful design of peptidomimetics must come to terms with χ-space control. The incorporation of χ-space constrained amino acids into bioactive peptides renders the χ1 and χ2 torsional angles of pharmacophore amino acids critical for activity and selectivity as with other relevant structural features of the template. This review describes histidine analogues characterized by replacement of native α and/or β-hydrogen atoms with alkyl substituents as well as analogues with α, β-didehydro unsaturation or Cα-Cβ cyclopropane insertion (ACC derivatives. Attention is also dedicated to the relevant field of β-aminoacid chemistry by describing the synthesis of β2- and β3-models (β-hHis. Structural modifications leading to cyclic imino derivatives such as spinacine, aza-histidine and analogues with shortening or elongation of the native side chain (nor-histidine and homo-histidine, respectively are also described. Examples of the use of the described analogues to replace native histidine in bioactive peptides are also given.

  4. Structural basis of histidine kinase autophosphorylation deduced by integrating genomics, molecular dynamics, and mutagenesis.

    Science.gov (United States)

    Dago, Angel E; Schug, Alexander; Procaccini, Andrea; Hoch, James A; Weigt, Martin; Szurmant, Hendrik

    2012-06-26

    Signal transduction proteins such as bacterial sensor histidine kinases, designed to transition between multiple conformations, are often ruled by unstable transient interactions making structural characterization of all functional states difficult. This study explored the inactive and signal-activated conformational states of the two catalytic domains of sensor histidine kinases, HisKA and HATPase. Direct coupling analyses, a global statistical inference approach, was applied to >13,000 such domains from protein databases to identify residue contacts between the two domains. These contacts guided structural assembly of the domains using MAGMA, an advanced molecular dynamics docking method. The active conformation structure generated by MAGMA simultaneously accommodated the sequence derived residue contacts and the ATP-catalytic histidine contact. The validity of this structure was confirmed biologically by mutation of contact positions in the Bacillus subtilis sensor histidine kinase KinA and by restoration of activity in an inactive KinA(HisKA):KinD(HATPase) hybrid protein. These data indicate that signals binding to sensor domains activate sensor histidine kinases by causing localized strain and unwinding at the end of the C-terminal helix of the HisKA domain. This destabilizes the contact positions of the inactive conformation of the two domains, identified by previous crystal structure analyses and by the sequence analysis described here, inducing the formation of the active conformation. This study reveals that structures of unstable transient complexes of interacting proteins and of protein domains are accessible by applying this combination of cross-validating technologies.

  5. Effects of a water activity intervention programme on motor ...

    African Journals Online (AJOL)

    The aim of this study was to investigate the effect of a specially designed water activity programme on the motor competency levels of children with Down's syndrome. Six institutionalised children classified as having Down\\'s syndrome, from a school for the mentally retarded, took part in the study. The children\\'s ...

  6. Interacting Temperature and Water Activity Modulate Production of ...

    African Journals Online (AJOL)

    Online2PDF.com

    This study evaluated the effect of temperature and water activity (aw) on destruxin A (DA) production by two strains of M. ... 32. West African Journal of Applied Ecology, vol. 24 (1), 2016 water stress on destruxin production in ..... Rearing tomato whitefly and field evaluation of modified and unmodified conidia of. Beauveria ...

  7. The Cinderella loop project

    Science.gov (United States)

    Schmelz, J. T.; Beene, J.; Coyle, T.; Douglass, J.; Nasraoui, K.; O'Connor, J.; Roames, J.; Scott, M.

    2006-01-01

    The solar loop that formed off the northeast limb of the Sun on 1999 November 6 (a.k.a. the Cinderella loop) is one of the few examples of a loop on the limb observed with all three of the following imaging instruments: the Transition Region and Coronal Explorer (TRACE), the SOHO Extreme-ultraviolet Imaging Telescope (EIT), and the Yohkoh Soft X-ray Telescope (SXT). In this project we investigate the temperature differences that result when examining the Cinderella loop with one instrument compared with another. For example, what temperature differences result from the increased spatial resolution between the two EUV imagers? More specifically, given that TRACE and EIT have almost identical temperature response to coronal plasma, does the different spatial resolution of TRACE (with 0.5″ pixels) and EIT (with 2.6″ pixels) produce statistically different results? We find that the answer is no, and that our results do not change after background subtraction. In addition, the spatial resolution of EIT and SXT is similar, but the temperature responses of the two instruments are quite different. The two instruments do not seem to be viewing the same loop strands, and the plasma temperature differences are significant.

  8. Contribution of individual histidines to the global stability of human prolactin.

    Science.gov (United States)

    Keeler, Camille; Tettamanzi, M Cristina; Meshack, Syrus; Hodsdon, Michael E

    2009-05-01

    A member of the family of hematopoietic cytokines human prolactin (hPRL) is a 23k kDa polypeptide hormone, which displays pH dependence in its structural and functional properties. The binding affinity of hPRL for the extracellular domain of its receptor decreases 500-fold over the relatively narrow, physiologic pH range from 8 to 6; whereas, the affinity of human growth hormone (hGH), its closest evolutionary cousin, does not. Similarly, the structural stability of hPRL decreases from 7.6 to 5.6 kcal/mol from pH 8 to 6, respectively, whereas the stability of hGH is slightly increased over this same pH range. hPRL contains nine histidines, compared with hGH's three, and they are likely responsible for hPRL's pH-dependent behavior. We have systematically mutated each of hPRL's histidines to alanine and measured the effect on pH-dependent global stability. Surprisingly, a vast majority of these mutations stabilize the native protein, by as much as 2-3 kcal/mol. Changes in the overall pH dependence to hPRL global stability can be rationalized according to the predominant structural interactions of individual histidines in the hPRL tertiary structure. Using double mutant cycles, we detect large interaction free energies within a cluster of nearby histidines, which are both stabilizing and destabilizing to the native state. Finally, by comparing the structural locations of hPRL's nine histidines with their homologous residues in hGH, we speculate on the evolutionary role of replacing structurally stabilizing residues with histidine to introduce pH dependence to cytokine function.

  9. Modulating short tryptophan- and arginine-rich peptides activity by substitution with histidine.

    Science.gov (United States)

    Bacalum, Mihaela; Janosi, Lorant; Zorila, Florina; Tepes, Ana-Maria; Ionescu, Cristina; Bogdan, Elena; Hadade, Niculina; Craciun, Liviu; Grosu, Ion; Turcu, Ioan; Radu, Mihai

    2017-07-01

    High antimicrobial efficacy of short tryptophan-and arginine-rich peptides makes them good candidates in the fight against pathogens. Substitution of tryptophan and arginine by histidine could be used to modulate the peptides efficacy by optimizing their structures. The peptide (RRWWRWWRR), reported to showed good antimicrobial efficacy, was used as template, seven new analogs being designed substituting tryptophan or arginine with histidine. The peptides' efficacy was tested against E. coli, B. subtilis and S. aureus. The cytotoxicity and hemolytic effect were evaluated and the therapeutic index was inferred for each peptide. Atomic force microscopy and molecular simulation were used to analyze the effects of peptides on bacterial membrane. The substitution of tryptophan by histidine proved to strongly modulate the antimicrobial activity, mainly by changing the peptide-to-membrane binding energy. The substitution of arginine has low effect on the antimicrobial efficacy. The presence of histidine residue reduced the cytotoxic and hemolytic activity of the peptides in some cases maintaining the same efficacy against bacteria. The peptides' antimicrobial activity was correlated to the 3D-hydrophobic moment and to a simple structure-based packing parameter. The results show that some of these peptides have the potential to become good candidates to fight against bacteria. The substitution by histidine proved to fine tune the therapeutic index allowing the optimization of the peptide structure mainly by changing its binding energy and 3D-hydrophobic moment. The short tryptophan reach peptides therapeutic index can be maximized using the histidine substitution to optimize their structure. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Closing global material loops

    DEFF Research Database (Denmark)

    Prosman, Ernst-Jan; Wæhrens, Brian Vejrum; Liotta, Giacomo

    2017-01-01

    Replacing virgin materials with waste materials, a practice known as Industrial Symbiosis (IS), has been identified as a key strategy for closing material loops. This article adopts a critical view on geographic proximity and external coordinators – two key enablers of IS. By ‘uncovering’ a case...... for geographic proximity and external coordinators. In doing so, our insights into firm-level challenges of long-distance IS exchanges contribute to closing global material loops by increasing the number of potential circular pathways....

  11. Hidden-loop colostomy.

    Science.gov (United States)

    Rombeau, J L; Turnbul, R B

    1978-04-01

    Records of 15 patients having hidden-loop colostomies were reviewed. All patients had metastatic colonic cancers with impending obstructions. Six colostomies were subsequently opened because of obstructions due to cancer. All colostomy openings were done using local anesthesia in the emergency room. This technique prevented six major celiotomies and provided additional time of living without a stoma. There were two postoperative stomal prolapses, one of which necessitated reoperation. A hidden-loop colostomy is easily constructed and readily opened. It should be considered at celiotomy for selected patients who have metastatic colonic cancer with impending obstruction.

  12. Neighbor-directed histidine N(τ) alkylation. A route to imidazolium-containing phosphopeptide macrocycles

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Wen-Jian [National Cancer Inst., Frederick, MD (United States); Park, Jung-Eun [National Cancer Inst., Bethesda, MD (United States); Grant, Robert [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Lai, Christopher C. [National Cancer Inst., Frederick, MD (United States); Kelley, James A. [National Cancer Inst., Frederick, MD (United States); Yaffe, Michael B. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Lee, Kyung S. [National Cancer Inst., Bethesda, MD (United States); Burke, Terrence R. [National Cancer Inst., Frederick, MD (United States)

    2015-07-07

    Our recently discovered, selective, on-resin route to N(τ)-alkylated imidazolium-containing histidine residues affords new strategies for peptide mimetic design. In this, we demonstrate the use of this chemistry to prepare a series of macrocyclic phosphopeptides, in which imidazolium groups serve as ring-forming junctions. These cationic moieties subsequently serve to charge-mask the phosphoamino acid group that directed their formation. Furthermore, neighbor-directed histidine N(τ)-alkylation opens the door to new families of phosphopeptidomimetics for use in a range of chemical biology contexts.

  13. Cresyl saligenin phosphate makes multiple adducts on free histidine, but does not form an adduct on histidine 438 of human butyrylcholinesterase.

    Science.gov (United States)

    Liyasova, Mariya S; Schopfer, Lawrence M; Lockridge, Oksana

    2013-03-25

    Cresyl saligenin phosphate (CBDP) is a suspected causative agent of "aerotoxic syndrome", affecting pilots, crew members and passengers. CBDP is produced in vivo from ortho-containing isomers of tricresyl phosphate (TCP), a component of jet engine lubricants and hydraulic fluids. CBDP irreversibly inhibits butyrylcholinesterase (BChE) in human plasma by forming adducts on the active site serine (Ser-198). Inhibited BChE undergoes aging to release saligenin and o-cresol. The active site histidine (His-438) was hypothesized to abstract o-hydroxybenzyl moiety from the initial adduct on Ser-198. Our goal was to test this hypothesis. Mass spectral analysis of CBDP-inhibited BChE digested with Glu-C showed an o-hydroxybenzyl adduct (+106 amu) on lysine 499, a residue far from the active site, but not on His-438. Nevertheless, the nitrogen of the imidazole ring of free L-histidine formed a variety of adducts upon reaction with CBDP, including the o-hydroxybenzyl adduct, suggesting that histidine-CBDP adducts may form on other proteins. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  14. Ergothioneine, histidine, and two naturally occurring histidine dipeptides as radioprotectors against gamma-irradiation inactivation of bacteriophages T4 and P22

    Energy Technology Data Exchange (ETDEWEB)

    Hartman, P.E.; Hartman, Z.; Citardi, M.J.

    1988-05-01

    Bacteriophages P22, T4+, and T4os (osmotic shock-resistant mutant with altered capsids) were diluted in 0.85% NaCl and exposed to gamma irradiation (2.79 Gy/min) at room temperature (24 degrees C). T4+ was more sensitive to inactivation than was P22, and the T4os mutant was even more sensitive than T4+. Catalase exhibited a strong protective effect and superoxide dismutase a weaker protection, indicating that H/sub 2/O/sub 2/ or some product derived therefrom was predominant in causing inactivation of plaque formation. Low but significant (0.1-0.3 mM) reduced glutathione (GSH) enhanced phage inactivation, but a higher (1 mM) GSH concentration protected. A similar effect was found for the polyamine, spermidine. In contrast, 0.1 mM L-ergothioneine (2-thiol-L-histidine betaine) exhibited strong protection and 1 mM afforded essentially complete protection. L-Ergothioneine is present in millimolar concentrations in some fungi and is conserved up to millimolar concentrations in critical tissues when consumed by man. L-Histidine and two histidine-containing dipeptides, carnosine and anserine, protected at a concentration of 1 mM, a level at which they are present in striated muscles of various animals.

  15. THERMOPHYSICAL PROPERTIES AND WATER ACTIVITY OF TRANSFERRED CHEESE (UF

    Directory of Open Access Journals (Sweden)

    Mohsen Dalvi Esfahan

    2015-06-01

    Full Text Available Few data are available on the thermophysical properties of cheese in the ripening process.The main objective of this work was to investigate the effects of brining and temperature on the thermophysical properties, i.e., thermal conductivity, specific heat, density and water activity of UF cheese and finally we measure surface heat transfer coefficient .Then we develop models for thermophysical properties based on physical and multiple regression concept .

  16. Polymer optical fiber grating as water activity sensor

    Science.gov (United States)

    Zhang, Wei; Webb, David J.

    2014-05-01

    Controlling the water content within a product has long been required in the chemical processing, agriculture, food storage, paper manufacturing, semiconductor, pharmaceutical and fuel industries. The limitations of water content measurement as an indicator of safety and quality are attributed to differences in the strength with which water associates with other components in the product. Water activity indicates how tightly water is "bound," structurally or chemically, in products. Water absorption introduces changes in the volume and refractive index of poly(methyl methacrylate) PMMA. Therefore for a grating made in PMMA based optical fiber, its wavelength is an indicator of water absorption and PMMA thus can be used as a water activity sensor. In this work we have investigated the performance of a PMMA based optical fiber grating as a water activity sensor in sugar solution, saline solution and Jet A-1 aviation fuel. Samples of sugar solution with sugar concentration from 0 to 8%, saline solution with concentration from 0 to 22%, and dried (10ppm), ambient (39ppm) and wet (68ppm) aviation fuels were used in experiments. The corresponding water activities are measured as 1.0 to 0.99 for sugar solution, 1.0 to 0.86 for saline solution, and 0.15, 0.57 and 1.0 for the aviation fuel samples. The water content in the measured samples ranges from 100% (pure water) to 10 ppm (dried aviation fuel). The PMMA based optical fiber grating exhibits good sensitivity and consistent response, and Bragg wavelength shifts as large as 3.4 nm when the sensor is transferred from dry fuel to wet fuel.

  17. Loop Quantum Gravity

    Directory of Open Access Journals (Sweden)

    Rovelli Carlo

    1998-01-01

    Full Text Available The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a mathematically well-defined, non-perturbative and background independent quantization of general relativity, with its conventional matter couplings. Research in loop quantum gravity today forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained are: (i The computation of the physical spectra of geometrical quantities such as area and volume, which yields quantitative predictions on Planck-scale physics. (ii A derivation of the Bekenstein-Hawking black hole entropy formula. (iii An intriguing physical picture of the microstructure of quantum physical space, characterized by a polymer-like Planck scale discreteness. This discreteness emerges naturally from the quantum theory and provides a mathematically well-defined realization of Wheeler's intuition of a spacetime ``foam''. Long standing open problems within the approach (lack of a scalar product, over-completeness of the loop basis, implementation of reality conditions have been fully solved. The weak part of the approach is the treatment of the dynamics: at present there exist several proposals, which are intensely debated. Here, I provide a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  18. LAPAROSCOPIC ILEAL LOOP CONDUIT

    African Journals Online (AJOL)

    Then the right ureter was laparoscopically spa- tulated and anastomosed to the ileostomy opening using interrupted 4/0 vicryl sutures. After finishing half the circumference of the anastomotic line, a 4 Fr. ureteric catheter was introduced through the external stoma of the loop up to the site of the anastomosis with the aid of a ...

  19. Improving Loop Dependence Analysis

    DEFF Research Database (Denmark)

    Jensen, Nicklas Bo; Karlsson, Sven

    2017-01-01

    Programmers can no longer depend on new processors to have significantly improved single-thread performance. Instead, gains have to come from other sources such as the compiler and its optimization passes. Advanced passes make use of information on the dependencies related to loops. We improve th...

  20. Nalpha-(1-deoxy-D-fructos-1-yl)-L-histidine ("D-Fructose-L-histidine"): a potent copper chelator from tomato powder.

    Science.gov (United States)

    Mossine, Valeri V; Mawhinney, Thomas P

    2007-12-12

    Dried fruits and vegetables are known for their high content of D-fructose-amino acids, or Amadori compounds, which appear at the initial step of the Maillard reaction and may participate in redox reactions mediated by trace metals. In this study, we investigated complexation between Cu(II) and N(alpha)-(1-deoxy-D-fructos-1-yl)-L-histidine (D-fructose-L-histidine, FruHis). The content of FruHis in two types of commercial tomato powders was estimated by GLC-MS, using single ion monitoring of trimethylsilylated FruHis hydroxyoximate, as 40 mg/100 g, whereas the concentration of free histidine in the powder samples was about 53 mg/100 g. The Cu(II)-binding ability of FruHis was studied along with structurally related molecules L-histidine, dipeptide L-carnosine, and N(alpha)-(1-deoxy-D-fructos-1-yl)-L-arginine (FruArg) at 25 degrees C using pH-potentiometric titrations. Analysis of the titration curves showed that formation of Cu(II)-FruHis complex species occurs at pH values as low as 2 and that the complexes were redox stable in the pH range 2-10.5, at least for the time of the experiment. At physiological pH, Cu(II) and FruHis form a dominant coordination species of composition MLH-1 (log beta = 5.67), with a presumably deprotonated anomeric hydroxyl group of the fructose portion. The apparent stability constant of 1:1 complexes formed by FruHis and Cu(II) in neutral aqueous solutions is about 10(4) times higher than similar values calculated for L-histidine, L-carnosine, and FruArg. FruHis nearly completely protected hydroxyl radical-mediated fragmentation of polymeric DNA in the presence of the Cu/H2O2/ascorbate system, whereas neither of the reference compounds could inhibit the DNA fragmentation as efficiently in similar conditions. These results warrant further investigation of FruHis as a potential food-related antioxidant.

  1. Activity of two histidine decarboxylases from Photobacterium phosphoreum at different temperatures, pHs, and NaCl concentrations.

    Science.gov (United States)

    Morii, Hideaki; Kasama, Kentaro

    2004-08-01

    The major causative agent of scombroid poisoning is histamine formed by bacterial decarboxylation of histidine. The authors reported previously that histamine was exclusively formed by the psychrotrophic halophilic bacteria Photobacterium phosphoreum in scombroid fish during storage at or below 10 degrees C. Moreover, histamine-forming ability was affected by two histidine decarboxylases: constitutive and inducible enzymes. This article reports the effect of various growth and reaction conditions, such as temperature, pH, and NaCl concentration, on the activity of two histidine decarboxylases that were isolated and separated by gel chromatography from cell-free extracts of P. phosphoreum. The histidine decarboxylase activity of the cell-free extracts was highest in 7 degrees C culture; in 5% NaCl, culture growth was inhibited, and growth was best in the culture grown at pH 6.0. Moreover, percent activity of the constitutive and inducible enzymes was highest for the inducible enzyme in cultures grown at 7 degrees C and pH 7.5 and in 5% NaCl. The temperature and pH dependences of histidine decarboxylase differed between the constitutive and inducible enzymes; that is, the activity of histidine decarboxylases was optimum at 30 degrees C and pH 6.5 for the inducible enzyme and 40 degrees C and pH 6.0 for the constitutive enzyme. The differences in the temperature and pH dependences between the two enzymes extended the activity range of histidine decarboxylase under reaction conditions. On the other hand, histidine decarboxylase activity was optimum in 0% NaCl for the two enzymes. Additionally, the effects of reaction temperature, pH, and NaCl concentration on the constitutive enzyme activity of the cell-free extracts were almost the same as those on the whole histidine decarboxylase activity of the cell-free extracts, suggesting that the constitutive enzyme activity reflected the whole histidine decarboxylase activity.

  2. Histidine-mediated xylem loading of zinc is a species-wide character in Noccaea caerulescens.

    NARCIS (Netherlands)

    Kozhevnikova, A.; Seregin, I.V.; Erlikh, N.T.; Shevyreva, T.A.; Andreev, I.M.; Verweij, R.; Schat, H.

    2014-01-01

    Histidine plays a crucial role in nickel (Ni) translocation in Ni-hyperaccumulating plants. Here, we investigated its role in zinc (Zn) translocation in four accessions of the Zn hyperaccumulator, Noccaea caerulescens, using the related non-hyperaccumulator, Thlaspi arvense, as a reference. We

  3. Molecular cloning and differential IgG responses to a histidine-rich ...

    African Journals Online (AJOL)

    In order to further investigate host-parasite interactions in onchocerciasis, a major Onchocerca volvulus histidine rich antigen termed OvL3.C1 was isolated from an O. volvulus cDNA library using antibodies from putatively immune subjects living in onchocerciasis endemic communities in Cameroon. Analysis of its ...

  4. Histidine as a catalyst in organic synthesis: A facile in situ synthesis ...

    Indian Academy of Sciences (India)

    Unknown

    (Aldrich, E-Merck and Acros) and were purified prior to use either by distillation or by recrystallization. Histidine (E-Merck) ... ethylacetate (E-Merck) were purified by distillation before use. Double distilled water, .... Sandler S R and Karo W 1972 Organic functional group preparations (New York: Academic. Press) vol. 3. 4.

  5. Identification of novel bacterial histidine biosynthesis inhibitors using docking, ensemble rescoring, and whole-cell assays

    DEFF Research Database (Denmark)

    Henriksen, Signe Teuber; Liu, J.; Estiu, G.

    2010-01-01

    in the early stages of drug discovery attractive if sufficient accuracy can be achieved. Computational target identification using systems-level methods suggested the histidine biosynthesis pathway as an attractive target against S. aureus. Potential inhibitors for the pathway were identified through docking...

  6. β-Alanyl-L-Histidine, an Anti-Oxidant, Anti-fibrotic and Geno ...

    African Journals Online (AJOL)

    ... hepatic hydroxyproline, protein carbonyl, hydrogen peroxide (H2O2) levels, DNA damage, Cytochrome P4502E1 (CYP2E1) activity and transforming growth factor-β1 (TGF-β1) mRNA level. In conclusion: β-alanyl-L-histidine possesses hepatoprotective properties through reducing hepatic toxicity markers, oxidative stress, ...

  7. Histidine as a catalyst in organic synthesis: A facile in situ synthesis ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 113; Issue 4. Histidine as a catalyst in organic synthesis: A facile in situ synthesis of , N-diarylnitrones. H Mallesha K R Ravi Kumar B K Vishu Kumar K Mantelingu K S Rangappa. Organic Volume 113 Issue 4 August 2001 pp 291-296 ...

  8. Nuclear localization of the dehydrin OpsDHN1 is determined by histidine-rich motif

    Science.gov (United States)

    Hernández-Sánchez, Itzell E.; Maruri-López, Israel; Ferrando, Alejandro; Carbonell, Juan; Graether, Steffen P.; Jiménez-Bremont, Juan F.

    2015-01-01

    The cactus OpsDHN1 dehydrin belongs to a large family of disordered and highly hydrophilic proteins known as Late Embryogenesis Abundant (LEA) proteins, which accumulate during the late stages of embryogenesis and in response to abiotic stresses. Herein, we present the in vivo OpsDHN1 subcellular localization by N-terminal GFP translational fusion; our results revealed a cytoplasmic and nuclear localization of the GFP::OpsDHN1 protein in Nicotiana benthamiana epidermal cells. In addition, dimer assembly of OpsDHN1 in planta using a Bimolecular Fluorescence Complementation (BiFC) approach was demonstrated. In order to understand the in vivo role of the histidine-rich motif, the OpsDHN1-ΔHis version was produced and assayed for its subcellular localization and dimer capability by GFP fusion and BiFC assays, respectively. We found that deletion of the OpsDHN1 histidine-rich motif restricted its localization to cytoplasm, but did not affect dimer formation. In addition, the deletion of the S-segment in the OpsDHN1 protein affected its nuclear localization. Our data suggest that the deletion of histidine-rich motif and S-segment show similar effects, preventing OpsDHN1 from getting into the nucleus. Based on these results, the histidine-rich motif is proposed as a targeting element for OpsDHN1 nuclear localization. PMID:26442018

  9. Nuclear localization of the dehydrin OpsDHN1 is determined by histidine-rich motif

    Directory of Open Access Journals (Sweden)

    Itzell Euridice Hernández-Sánchez

    2015-09-01

    Full Text Available The cactus OpsDHN1 dehydrin belongs to a large family of disordered and highly hydrophilic proteins known as Late Embryogenesis Abundant (LEA proteins, which accumulate during the late stages of embryogenesis and in response to abiotic stresses. Herein, we present the in vivo OpsDHN1 subcellular localization by N-terminal GFP translational fusion; our results revealed a cytoplasmic and nuclear localization of the GFP::OpsDHN1 protein in Nicotiana benthamiana epidermal cells. In addition, dimer assembly of OpsDHN1 in planta using a Bimolecular Fluorescence Complementation (BiFC approach was demonstrated. In order to understand the in vivo role of the histidine-rich motif, the OpsDHN1-ΔHis version was produced and assayed for its subcellular localization and dimer capability by GFP fusion and BiFC assays, respectively. We found that deletion of the OpsDHN1 histidine-rich motif restricted its localization to cytoplasm, but did not affect dimer formation. In addition, the deletion of the S-segment in the OpsDHN1 protein affected its nuclear localization. Our data suggest that the deletion of histidine-rich motif and S-segment show similar effects, preventing OpsDHN1 from getting into the nucleus. Based on these results, the histidine rich motif is proposed as a targeting element for OpsDHN1 nuclear localization.

  10. Gas-phase structures and thermochemistry of neutral histidine and its conjugated acid and base.

    Science.gov (United States)

    Riffet, Vanessa; Bouchoux, Guy

    2013-04-28

    Extensive exploration of the conformational space of neutral, protonated and deprotonated histidine has been conducted at the G4MP2 level. Theoretical protonation and deprotonation thermochemistry as well as heats of formation of gaseous histidine and its ionized forms have been calculated at the G4 level considering either the most stable conformers or an equilibrium population of conformers at 298 K. These theoretical results were compared to evaluated experimental determinations. Recommended proton affinity and protonation entropy deduced from these comparisons are PA(His) = 980 kJ mol(-1) and ΔpS(His) ∼ 0 J mol(-1) K(-1), thus leading to a gas-phase basicity value of GB(His) = 947.5 kJ mol(-1). Similarly, gas phase acidity parameters are ΔacidH(o)(His) = 1373 kJ mol(-1), ΔacidS(His) ∼ 10 J mol(-1) K(-1) and ΔacidG(o)(His) = 1343 kJ mol(-1). Computed G4 heats of formation values are equal to -290, 265 and -451 kJ mol(-1) for gaseous neutral histidine and its protonated and deprotonated forms, respectively. The present computational data correct, and complete, previous thermochemical parameter estimates proposed for gas-phase histidine and its acido-basic properties.

  11. Highly Efficient Photocatalytic Hydrogen Production of Flower-like Cadmium Sulfide Decorated by Histidine

    National Research Council Canada - National Science Library

    Wang, Qizhao; Lian, Juhong; Li, Jiajia; Wang, Rongfang; Huang, Haohao; Su, Bitao; Lei, Ziqiang

    2015-01-01

    ...•4H2O and thiourea as precursors and L-Histidine as a chelating agent. The morphology, crystal phase, and photoelectrochemical performance of the flower-like CdS and pure CdS nanocrystals are carefully investigated via various characterizations...

  12. Histidine-rich glycoprotein promotes macrophage activation and inflammation in chronic liver disease

    NARCIS (Netherlands)

    Bartneck, M.; Fech, V.; Ehling, J.; Govaere, O.; Warzecha, K.T.; Hittatiya, K.; Vucur, M.; Gautheron, J.; Luedde, T.; Trautwein, C.; Lammers, Twan Gerardus Gertudis Maria; Roskams, T.; Jahnen-Dechent, W.; Tacke, F.

    2016-01-01

    Pathogen- and injury-related danger signals as well as cytokines released by immune cells influence the functional differentiation of macrophages in chronic inflammation. Recently, the liver-derived plasma protein, histidine-rich glycoprotein (HRG), was demonstrated, in mouse tumor models, to

  13. C@Fe 3 O 4 /NTA-Ni magnetic nanospheres purify histidine-tagged ...

    African Journals Online (AJOL)

    This study reports synthesis of Ni-nitrilotriacetic acid (Ni-NTA) modified carbon nanospheres containing magnetic Fe3O4 particles (C@Fe3O4), which can act as a general tool to separate and purify histidine-tagged fetidin. In this experiment, C nanospheres are prepared from glucose using the hydrothermal process, ...

  14. Muscle histidine-containing dipeptides are elevated by glucose intolerance in both rodents and men.

    Directory of Open Access Journals (Sweden)

    Sanne Stegen

    Full Text Available Muscle carnosine and its methylated form anserine are histidine-containing dipeptides. Both dipeptides have the ability to quench reactive carbonyl species and previous studies have shown that endogenous tissue levels are decreased in chronic diseases, such as diabetes.Rodent study: Skeletal muscles of rats and mice were collected from 4 different diet-intervention studies, aiming to induce various degrees of glucose intolerance: 45% high-fat feeding (male rats, 60% high-fat feeding (male rats, cafeteria feeding (male rats, 70% high-fat feeding (female mice. Body weight, glucose-tolerance and muscle histidine-containing dipeptides were assessed. Human study: Muscle biopsies were taken from m. vastus lateralis in 35 males (9 lean, 8 obese, 9 prediabetic and 9 newly diagnosed type 2 diabetic patients and muscle carnosine and gene expression of muscle fiber type markers were measured.Diet interventions in rodents (cafeteria and 70% high-fat feeding induced increases in body weight, glucose intolerance and levels of histidine-containing dipeptides in muscle. In humans, obese, prediabetic and diabetic men had increased muscle carnosine content compared to the lean (+21% (p>0.1, +30% (p<0.05 and +39% (p<0.05, respectively. The gene expression of fast-oxidative type 2A myosin heavy chain was increased in the prediabetic (1.8-fold, p<0.05 and tended to increase in the diabetic men (1.6-fold, p = 0.07, compared to healthy lean subjects.Muscle histidine-containing dipeptides increases with progressive glucose intolerance, in male individuals (cross-sectional. In addition, high-fat diet-induced glucose intolerance was associated with increased muscle histidine-containing dipeptides in female mice (interventional. Increased muscle carnosine content might reflect fiber type composition and/or act as a compensatory mechanism aimed at preventing cell damage in states of impaired glucose tolerance.

  15. Loop Quantum Cosmology.

    Science.gov (United States)

    Bojowald, Martin

    2008-01-01

    Quantum gravity is expected to be necessary in order to understand situations in which classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical spacetime inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding spacetime is then modified. One particular theory is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. The main effects are introduced into effective classical equations, which allow one to avoid the interpretational problems of quantum theory. They give rise to new kinds of early-universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function, which allows an extension of quantum spacetime beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of spacetime arising in loop quantum gravity and its application to cosmology sheds light on more general issues, such as the nature of time. Supplementary material is available for this article at 10.12942/lrr-2008-4.

  16. PAR Loop Schedule Review

    Energy Technology Data Exchange (ETDEWEB)

    Schaffer, Jr.; W.F.

    1958-04-30

    The schedule for the installation of the PAR slurry loop experiment in the South Facility of the ORR has been reviewed and revised. The design, fabrications and Installation is approximately two weeks behind schedule at this time due to many factors; however, indications are that this time can be made up. Design is estimated to be 75% complete, fabrication 32% complete and installation 12% complete.

  17. Loop Quantum Cosmology

    Directory of Open Access Journals (Sweden)

    Bojowald Martin

    2008-07-01

    Full Text Available Quantum gravity is expected to be necessary in order to understand situations in which classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical spacetime inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding spacetime is then modified. One particular theory is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. The main effects are introduced into effective classical equations, which allow one to avoid the interpretational problems of quantum theory. They give rise to new kinds of early-universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function, which allows an extension of quantum spacetime beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of spacetime arising in loop quantum gravity and its application to cosmology sheds light on more general issues, such as the nature of time.

  18. Loop Quantum Cosmology

    Directory of Open Access Journals (Sweden)

    Bojowald Martin

    2005-12-01

    Full Text Available Quantum gravity is expected to be necessary in order to understand situations where classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical space-time inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding space-time is then modified. One particular realization is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. Main effects are introduced into effective classical equations which allow to avoid interpretational problems of quantum theory. They give rise to new kinds of early universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function which allows to extend space-time beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of space-time arising in loop quantum gravity and its application to cosmology sheds new light on more general issues such as time.

  19. Cosmic string loop microlensing

    Science.gov (United States)

    Bloomfield, Jolyon K.; Chernoff, David F.

    2014-06-01

    Cosmic superstring loops within the galaxy microlens background point sources lying close to the observer-string line of sight. For suitable alignments, multiple paths coexist and the (achromatic) flux enhancement is a factor of two. We explore this unique type of lensing by numerically solving for geodesics that extend from source to observer as they pass near an oscillating string. We characterize the duration of the flux doubling and the scale of the image splitting. We probe and confirm the existence of a variety of fundamental effects predicted from previous analyses of the static infinite straight string: the deficit angle, the Kaiser-Stebbins effect, and the scale of the impact parameter required to produce microlensing. Our quantitative results for dynamical loops vary by O(1) factors with respect to estimates based on infinite straight strings for a given impact parameter. A number of new features are identified in the computed microlensing solutions. Our results suggest that optical microlensing can offer a new and potentially powerful methodology for searches for superstring loop relics of the inflationary era.

  20. Water activity and the challenge for life on early Mars.

    Science.gov (United States)

    Tosca, Nicholas J; Knoll, Andrew H; McLennan, Scott M

    2008-05-30

    In situ and orbital exploration of the martian surface has shown that acidic, saline liquid water was intermittently available on ancient Mars. The habitability of these waters depends critically on water activity (aH2O), a thermodynamic measure of salinity, which, for terrestrial organisms, has sharply defined limits. Using constraints on fluid chemistry and saline mineralogy based on martian data, we calculated the maximum aH2O for Meridiani Planum and other environments where salts precipitated from martian brines. Our calculations indicate that the salinity of well-documented surface waters often exceeded levels tolerated by known terrestrial organisms.

  1. LoopIng: a template-based tool for predicting the structure of protein loops.

    KAUST Repository

    Messih, Mario Abdel

    2015-08-06

    Predicting the structure of protein loops is very challenging, mainly because they are not necessarily subject to strong evolutionary pressure. This implies that, unlike the rest of the protein, standard homology modeling techniques are not very effective in modeling their structure. However, loops are often involved in protein function, hence inferring their structure is important for predicting protein structure as well as function.We describe a method, LoopIng, based on the Random Forest automated learning technique, which, given a target loop, selects a structural template for it from a database of loop candidates. Compared to the most recently available methods, LoopIng is able to achieve similar accuracy for short loops (4-10 residues) and significant enhancements for long loops (11-20 residues). The quality of the predictions is robust to errors that unavoidably affect the stem regions when these are modeled. The method returns a confidence score for the predicted template loops and has the advantage of being very fast (on average: 1 min/loop).www.biocomputing.it/loopinganna.tramontano@uniroma1.itSupplementary data are available at Bioinformatics online.

  2. Molecular recognition of histidine tRNA by histidyl-tRNA synthetase from hyperthermophilic archaeon, Aeropyrum pernix K1.

    Science.gov (United States)

    Nagatoyo, Yukari; Iwaki, Jun; Suzuki, Satoko; Kuno, Atsushi; Hasegawa, Tsunemi

    2005-01-01

    To investigate the recognition sites of histidine tRNA for histidyl-tRNA synthetase from an extreme hyperthermophilic archaeon, Aeropyrum pernix K1, we examined histidylation activities by using overexpressed histidyl-tRNA synthetase and various histidine tRNA transcripts that were prepared by in vitro transcription system. Results indicated that anticodon was not recognized by the histidyl-tRNA synthetase similar to that of Escherichia coli histidine tRNA recognition system. Discriminator base C73 was weekly recognized and an additional G residue was specifically recognized by the enzyme.

  3. Coupled dual loop absorption heat pump

    Science.gov (United States)

    Sarkisian, Paul H.; Reimann, Robert C.; Biermann, Wendell J.

    1985-01-01

    A coupled dual loop absorption system which utilizes two separate complete loops. Each individual loop operates at three temperatures and two pressures. This low temperature loop absorber and condenser are thermally coupled to the high temperature loop evaporator, and the high temperature loop condenser and absorber are thermally coupled to the low temperature generator.

  4. WATER ACTIVITY DATA ASSESSMENT TO BE USED IN HANFORD WASTE SOLUBILITY CALCULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    DISSELKAMP RS

    2011-01-06

    The purpose of this report is to present and assess water activity versus ionic strength for six solutes:sodium nitrate, sodium nitrite, sodium chloride, sodium carbonate, sodium sulfate, and potassium nitrate. Water activity is given versus molality (e.g., ionic strength) and temperature. Water activity is used to estimate Hanford crystal hydrate solubility present in the waste.

  5. Evidence for histidine in the active sites of ficin and stem-bromelain

    Science.gov (United States)

    Husain, S. S.; Lowe, G.

    1968-01-01

    1. Ficin and stem-bromelain are irreversibly inhibited by 1,3-dibromoacetone, a reagent designed to react first with the active-site cysteine residue and subsequently with a second nucleophile. Evidence is presented that establishes that a histidine residue is within a 5Å locus of the active-site cysteine residue in both enzymes. The histidine residue in both enzymes is alkylated at N-1 by dibromoacetone. It is suggested that, as with papain, the thiol and imidazole groups act in concert in the hydrolysis of substrates by these enzymes. 2. The inhibition of thiol-subtilisin with 1,3-dibromoacetone is shown to be due to the alkylation of a cysteine residue only. PMID:5722692

  6. Identification of a histidine acid phosphatase (phyA)-like gene in Arabidopsis thaliana.

    Science.gov (United States)

    Mullaney, E J; Ullah, A H

    1998-10-09

    A close examination of the protein sequence encoded by the Arabidopsis thaliana gene F21M12.26 reveals the gene product to be a phosphomonoesterase, acid optimum (EC 3.1.3.2). A subclass of this broad acid phosphatase is also known as 'histidine acid phosphatase. ' This is the first sequence-based evidence for a 'histidine acid phosphatase' in a dicotyledon. One important member of this class of enzymes is Aspergillus niger (ficuum) phytase, which came into prominence for its commercial application as a feed additive. The putative protein from A. thaliana gene F21M12.26 shares many important features of Aspergillus phytase, namely, size, active-site sequence, catalytic dipeptide and ten cysteine residues located in the key areas of the molecule, but lacks all nine N-glycosylation sites. Copyright 1998 Academic Press.

  7. Inactivation of histidine decarboxylase by gamma irradiation for controlling histamine formation

    Science.gov (United States)

    Pak, Won-Min; Kim, Koth-Bong-Woo-Ri; Kim, Min-Ji; Ahn, Dong-Hyun

    2017-12-01

    In this study, the effects of gamma irradiation on the survival of Morganella morganii and Photobacterium phosphoreum and the activity of their crude histidine decarboxylase (HDC) were investigated. The two strains and their crude HDC were irradiated up to 10 kGy. Viable cells of M. morganii and P. phosphoreum were not detected at any dose. The activity of crude HDC was decreased with increasing dose. In particular, the gamma irradiation at 5 and 10 kGy resulted in > 90% inactivation of crude HDC from M. morganii and P. phosphoreum, respectively. In SDS-PAGE and native PAGE, slight structural changes of crude HDC appeared with gamma irradiation. These results suggest that gamma irradiation is effective in reducing histamine production through inactivation survival of M. morganii and P. phosphoreum, and their histidine decarboxylase activity.

  8. Growth and characterization of an organic nonlinear optical material: L-Histidine malonate

    Science.gov (United States)

    Ramya, K.; Saraswathi, N. T.; Raja, C. Ramachandra

    2016-10-01

    L-Histidine malonate is one of the potential organic material for nonlinear optical applications. Single crystals of L-Histidine malonate were grown by the liquid diffusion method. The lattice parameter values were evaluated from single crystal X-ray diffraction technique. The Fourier Transform Infra Red and Raman spectral studies were employed to identify the different modes of vibrations of molecular groups in the crystal. Optical characterization and the percentage of optical transmission were recorded using UV-vis-NIR spectroscopy. The molecular structure was established by proton and carbon Nuclear magnetic resonance spectral studies. The thermal behavior of the material has been studied by Thermo gravimetric and Differential thermal plots. The second harmonic generation conversion efficiency was found out from the powder technique of Kurtz and Perry.

  9. Thiamin Pyrimidine Biosynthesis in Candida albicans: A Remarkable Reaction between Histidine and Pyridoxal Phosphate

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Rung-Yi; Huang, Siyu; Fenwick, Michael K.; Hazra, Amrita; Zhang, Yang; Rajashankar, Kanagalaghatta; Philmus, Benjamin; Kinsland, Cynthia; Sanders, Jennie Mansell; Ealick, Steven E.; Begley, Tadhg P. (Cornell); (TAM)

    2012-06-26

    In Saccharomyces cerevisiae, thiamin pyrimidine is formed from histidine and pyridoxal phosphate (PLP). The origin of all of the pyrimidine atoms has been previously determined using labeling studies and suggests that the pyrimidine is formed using remarkable chemistry that is without chemical or biochemical precedent. Here we report the overexpression of the closely related Candida albicans pyrimidine synthase (THI5p) and the reconstitution and preliminary characterization of the enzymatic activity. A structure of the C. albicans THI5p shows PLP bound at the active site via an imine with Lys62 and His66 in close proximity to the PLP. Our data suggest that His66 of the THI5 protein is the histidine source for pyrimidine formation and that the pyrimidine synthase is a single-turnover enzyme.

  10. Wilson loops as precursors

    Energy Technology Data Exchange (ETDEWEB)

    Susskind, Leonard [Department of Physics, Stanford University, Stanford, California 94305-4060 (United States); Toumbas, Nicolaos [Department of Physics, Stanford University, Stanford, California 94305-4060 (United States)

    2000-02-15

    There is substantial evidence that string theory on AdS{sub 5}xS{sub 5} is a holographic theory in which the number of degrees of freedom scales as the area of the boundary in Planck units. Precisely how the theory can describe bulk physics using only surface degrees of freedom is not well understood. A particularly paradoxical situation involves an event deep in the interior of the bulk space. The event must be recorded in the (Schroedinger picture) state vector of the boundary theory long before a signal, such as a gravitational wave, can propagate from the event to the boundary. In a previous paper with Polchinski, we argued that the ''precursor'' operators which carry information stored in the wave during the time when it vanishes in a neighborhood of the boundary are necessarily non-local. In this paper we argue that the precursors cannot be products of local gauge invariant operators such as the energy momentum tensor. In fact gauge theories have a class of intrinsically non-local operators which cannot be built from local gauge invariant objects. These are the Wilson loops. We show that the precursors can be identified with Wilson loops whose spatial size is dictated by the UV-IR connection. (c) 2000 The American Physical Society.

  11. High temperature storage loop :

    Energy Technology Data Exchange (ETDEWEB)

    Gill, David Dennis; Kolb, William J.

    2013-07-01

    A three year plan for thermal energy storage (TES) research was created at Sandia National Laboratories in the spring of 2012. This plan included a strategic goal of providing test capability for Sandia and for the nation in which to evaluate high temperature storage (>650ÀC) technology. The plan was to scope, design, and build a flow loop that would be compatible with a multitude of high temperature heat transfer/storage fluids. The High Temperature Storage Loop (HTSL) would be reconfigurable so that it was useful for not only storage testing, but also for high temperature receiver testing and high efficiency power cycle testing as well. In that way, HTSL was part of a much larger strategy for Sandia to provide a research and testing platform that would be integral for the evaluation of individual technologies funded under the SunShot program. DOEs SunShot program seeks to reduce the price of solar technologies to 6/kWhr to be cost competitive with carbon-based fuels. The HTSL project sought to provide evaluation capability for these SunShot supported technologies. This report includes the scoping, design, and budgetary costing aspects of this effort

  12. A combinatorial histidine scanning library approach to engineer highly pH-dependent protein switches.

    Science.gov (United States)

    Murtaugh, Megan L; Fanning, Sean W; Sharma, Tressa M; Terry, Alexandra M; Horn, James R

    2011-09-01

    There is growing interest in the development of protein switches, which are proteins whose function, such as binding a target molecule, can be modulated through environmental triggers. Efforts to engineer highly pH sensitive protein-protein interactions typically rely on the rational introduction of ionizable groups in the protein interface. Such experiments are typically time intensive and often sacrifice the protein's affinity at the permissive pH. The underlying thermodynamics of proton-linkage dictate that the presence of multiple ionizable groups, which undergo a pK(a) change on protein binding, are necessary to result in highly pH-dependent binding. To test this hypothesis, a novel combinatorial histidine library was developed where every possible combination of histidine and wild-type residue is sampled throughout the interface of a model anti-RNase A single domain VHH antibody. Antibodies were coselected for high-affinity binding and pH-sensitivity using an in vitro, dual-function selection strategy. The resulting antibodies retained near wild-type affinity yet became highly sensitive to small decreases in pH, drastically decreasing their binding affinity, due to the incorporation of multiple histidine groups. Several trends were observed, such as histidine "hot-spots," which will help enhance the development of pH switch proteins as well as increase our understanding of the role of ionizable residues in protein interfaces. Overall, the combinatorial approach is rapid, general, and robust and should be capable of producing highly pH-sensitive protein affinity reagents for a number of different applications. Copyright © 2011 The Protein Society.

  13. Effect of water activity on rates of serpentinization of olivine

    Science.gov (United States)

    Lamadrid, Hector M.; Rimstidt, J. Donald; Schwarzenbach, Esther M.; Klein, Frieder; Ulrich, Sarah; Dolocan, Andrei; Bodnar, Robert J.

    2017-07-01

    The hydrothermal alteration of mantle rocks (referred to as serpentinization) occurs in submarine environments extending from mid-ocean ridges to subduction zones. Serpentinization affects the physical and chemical properties of oceanic lithosphere, represents one of the major mechanisms driving mass exchange between the mantle and the Earth's surface, and is central to current origin of life hypotheses as well as the search for microbial life on the icy moons of Jupiter and Saturn. In spite of increasing interest in the serpentinization process by researchers in diverse fields, the rates of serpentinization and the controlling factors are poorly understood. Here we use a novel in situ experimental method involving olivine micro-reactors and show that the rate of serpentinization is strongly controlled by the salinity (water activity) of the reacting fluid and demonstrate that the rate of serpentinization of olivine slows down as salinity increases and H2O activity decreases.

  14. Thermodynamic Study of Water Activity of Single Strong Electrolytes

    Directory of Open Access Journals (Sweden)

    Seyed Hossein Hashemi

    2017-06-01

    Full Text Available Today, due to the natural decline of oil exploitation, the use of methods of oil recovery, has made significant progress. However, these methods are accompanied by accumulation and deposition of mineral deposits in oil field installations. In the present study, aqueous solutions, strontium sulfate, barium sulfate, manganese sulfate and nickel sulfate are studied, in terms of EUNIQUAC model and genetic algorithms. Based on the findings of this article, as temperature increases, in order to increase the solubility of the system, the ionic strength decreases; but with increasing pressure, the solubility of barium sulfate increases. Meanwhile, in this article, to evaluate water activity, aqueous solutions of manganese sulfate and nickel sulfate is studied.

  15. Functional Divergence of Poplar Histidine-Aspartate Kinase HK1 Paralogs in Response to Osmotic Stress

    Directory of Open Access Journals (Sweden)

    François Héricourt

    2016-12-01

    Full Text Available Previous works have shown the existence of protein partnerships belonging to a MultiStep Phosphorelay (MSP in Populus putatively involved in osmosensing. This study is focused on the identification of a histidine-aspartate kinase, HK1b, paralog of HK1a. The characterization of HK1b showed its ability to homo- and hetero-dimerize and to interact with a few Histidine-containing Phosphotransfer (HPt proteins, suggesting a preferential partnership in poplar MSP linked to drought perception. Furthermore, determinants for interaction specificity between HK1a/1b and HPts were studied by mutagenesis analysis, identifying amino acids involved in this specificity. The HK1b expression analysis in different poplar organs revealed its co-expression with three HPts, reinforcing the hypothesis of partnership participation in the MSP in planta. Moreover, HK1b was shown to act as an osmosensor with kinase activity in a functional complementation assay of an osmosensor deficient yeast strain. These results revealed that HK1b showed a different behaviour for canonical phosphorylation of histidine and aspartate residues. These phosphorylation modularities of canonical amino acids could explain the improved osmosensor performances observed in yeast. As conserved duplicates reflect the selective pressures imposed by the environmental requirements on the species, our results emphasize the importance of HK1 gene duplication in poplar adaptation to drought stress.

  16. The Role of Histidine-Proline-Rich Glycoprotein as Zinc Chaperone for Skeletal Muscle AMP Deaminase

    Directory of Open Access Journals (Sweden)

    Maria Ranieri-Raggi

    2014-05-01

    Full Text Available Metallochaperones function as intracellular shuttles for metal ions. At present, no evidence for the existence of any eukaryotic zinc-chaperone has been provided although metallochaperones could be critical for the physiological functions of Zn2+ metalloenzymes. We propose that the complex formed in skeletal muscle by the Zn2+ metalloenzyme AMP deaminase (AMPD and the metal binding protein histidine-proline-rich glycoprotein (HPRG acts in this manner. HPRG is a major plasma protein. Recent investigations have reported that skeletal muscle cells do not synthesize HPRG but instead actively internalize plasma HPRG. X-ray absorption spectroscopy (XAS performed on fresh preparations of rabbit skeletal muscle AMPD provided evidence for a dinuclear zinc site in the enzyme compatible with a (μ-aqua(μ-carboxylatodizinc(II core with two histidine residues at each metal site. XAS on HPRG isolated from the AMPD complex showed that zinc is bound to the protein in a dinuclear cluster where each Zn2+ ion is coordinated by three histidine and one heavier ligand, likely sulfur from cysteine. We describe the existence in mammalian HPRG of a specific zinc binding site distinct from the His-Pro-rich region. The participation of HPRG in the assembly and maintenance of skeletal muscle AMPD by acting as a zinc chaperone is also demonstrated.

  17. Metal-mediated molecular self-healing in histidine-rich mussel peptides.

    Science.gov (United States)

    Schmidt, Stephan; Reinecke, Antje; Wojcik, Felix; Pussak, Daniel; Hartmann, Laura; Harrington, Matthew James

    2014-05-12

    Mussels withstand high-energy wave impacts in rocky seashore habitats by fastening tightly to surfaces with tough and self-healing proteinaceous fibers called byssal threads. Thread mechanical behavior is believed to arise from reversibly breakable metal coordination cross-links embedded in histidine-rich protein domains (HRDs) in the principle load-bearing proteins comprising the fibrous thread core. In order to investigate HRD behavior at the molecular level, we have synthesized a histidine-rich peptide derived from mussel proteins (His5-bys) and studied its reversible adhesive self-interaction in the presence and absence of metal ions using PEG-based soft-colloidal probes (SCPs). Adhesion energies of greater than 0.3 mJ/m(2) were measured in the presence of metal ions, and the stiffness of the modified SCPs exhibited a 3-fold increase, whereas no adhesion was observed in the absence of metals. Raman spectroscopy confirmed the presence of metal-coordination via histidine residues by the peptide-supporting the role of His-metal complexes in the mechanical behavior of the byssus.

  18. Effects of phorbol ester and dexamethasone treatment on histidine decarboxylase and ornithine decarboxylase in basophilic cells.

    Science.gov (United States)

    Fajardo, I; Urdiales, J L; Medina, M A; Sanchez-Jimenez, F

    2001-05-01

    Both histamine and polyamines are important for maintaining basophilic cell function and viability. The synthesis of these biogenic amines is regulated by histidine decarboxylase and ornithine decarboxylase, respectively. In other mammalian tissues, an interplay between histamine and polyamine metabolisms has been suspected. In this report, the interplay between histamine and ornithine-derived polyamines was studied in a non-transformed mouse mast cell line (C57.1) treated with phorbol ester and dexamethasone, a treatment previously used to increase histidine decarboxylase expression in mastocytoma and basophilic leukemia. Treatment with phorbol ester and dexamethasone increased histidine decarboxylase expression and intracellular histamine levels in C57.1 mast cells to a greater extent than those found for other transformed basophilic models. The treatment also induced a reduction in ornithine decarboxylase expression, intracellular polyamine contents, and cell proliferation. These results indicate that the treatment induces a co-ordinate response of polyamine metabolism and proliferation in mast cells and other immune-related cells. The decrease in the proliferative capacity of mast cells caused by phorbol ester and dexamethasone was simultaneous to an increase in histamine production. Our results, together with those reported by other groups working with polyamine-treated mast cells, indicate an antagonism between histamine and polyamines in basophilic cells.

  19. Role of histidine for charge regulation of unstructured peptides at interfaces and in bulk.

    Science.gov (United States)

    Kurut, Anıl; Henriques, João; Forsman, Jan; Skepö, Marie; Lund, Mikael

    2014-04-01

    Histidine-rich, unstructured peptides adsorb to charged interfaces such as mineral surfaces and microbial cell membranes. At a molecular level, we investigate the adsorption mechanism as a function of pH, salt, and multivalent ions showing that (1) proton charge fluctuations are-in contrast to the majority of proteins-optimal at neutral pH, promoting electrostatic interactions with anionic surfaces through charge regulation and (2) specific zinc(II)-histidine binding competes with protons and ensures an unusually constant charge distribution over a broad pH interval. In turn, this further enhances surface adsorption. Our analysis is based on atomistic molecular dynamics simulations, coarse grained Metropolis Monte Carlo, and classical polymer density functional theory. This multiscale modeling provides a consistent picture in good agreement with experimental data on Histatin 5, an antimicrobial salivary peptide. Biological function is discussed and we suggest that charge regulation is a significant driving force for the remarkably robust activity of histidine-rich antimicrobial peptides. Copyright © 2013 Wiley Periodicals, Inc.

  20. Relationships of Dietary Histidine and Obesity in Northern Chinese Adults, an Internet-Based Cross-Sectional Study

    Directory of Open Access Journals (Sweden)

    Yan-Chuan Li

    2016-07-01

    Full Text Available Our previous studies have demonstrated that histidine supplementation significantly ameliorates inflammation and oxidative stress in obese women and high-fat diet-induced obese rats. However, the effects of dietary histidine on general population are not known. The objective of this Internet-based cross-sectional study was to evaluate the associations between dietary histidine and prevalence of overweight/obesity and abdominal obesity in northern Chinese population. A total of 2376 participants were randomly recruited and asked to finish our Internet-based dietary questionnaire for the Chinese (IDQC. Afterwards, 88 overweight/obese participants were randomly selected to explore the possible mechanism. Compared with healthy controls, dietary histidine was significantly lower in overweight (p < 0.05 and obese (p < 0.01 participants of both sexes. Dietary histidine was inversely associated with body mass index (BMI, waist circumference (WC and blood pressure in overall population and stronger associations were observed in women and overweight/obese participants. Higher dietary histidine was associated with lower prevalence of overweight/obesity and abdominal obesity, especially in women. Further studies indicated that higher dietary histidine was associated with lower fasting blood glucose (FBG, homeostasis model assessment of insulin resistance (HOMA-IR, 2-h postprandial glucose (2 h-PG, tumor necrosis factor-α (TNF-α, interleukin-1β (IL-1β, interleukin-6 (IL-6, C-reactive protein (CRP, malonaldehyde (MDA and vaspin and higher glutathione peroxidase (GSH-Px, superoxide dismutase (SOD and adiponectin of overweight/obese individuals of both sexes. In conclusion, higher dietary histidine is inversely associated with energy intake, status of insulin resistance, inflammation and oxidative stress in overweight/obese participants and lower prevalence of overweight/obesity in northern Chinese adults.

  1. Loop Quantum Gravity.

    Science.gov (United States)

    Rovelli, Carlo

    2008-01-01

    The problem of describing the quantum behavior of gravity, and thus understanding quantum spacetime, is still open. Loop quantum gravity is a well-developed approach to this problem. It is a mathematically well-defined background-independent quantization of general relativity, with its conventional matter couplings. Today research in loop quantum gravity forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained so far are: (i) The computation of the spectra of geometrical quantities such as area and volume, which yield tentative quantitative predictions for Planck-scale physics. (ii) A physical picture of the microstructure of quantum spacetime, characterized by Planck-scale discreteness. Discreteness emerges as a standard quantum effect from the discrete spectra, and provides a mathematical realization of Wheeler's "spacetime foam" intuition. (iii) Control of spacetime singularities, such as those in the interior of black holes and the cosmological one. This, in particular, has opened up the possibility of a theoretical investigation into the very early universe and the spacetime regions beyond the Big Bang. (iv) A derivation of the Bekenstein-Hawking black-hole entropy. (v) Low-energy calculations, yielding n-point functions well defined in a background-independent context. The theory is at the roots of, or strictly related to, a number of formalisms that have been developed for describing background-independent quantum field theory, such as spin foams, group field theory, causal spin networks, and others. I give here a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  2. Loop Quantum Gravity

    Directory of Open Access Journals (Sweden)

    Rovelli Carlo

    2008-07-01

    Full Text Available The problem of describing the quantum behavior of gravity, and thus understanding quantum spacetime, is still open. Loop quantum gravity is a well-developed approach to this problem. It is a mathematically well-defined background-independent quantization of general relativity, with its conventional matter couplings. Today research in loop quantum gravity forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained so far are: (i The computation of the spectra of geometrical quantities such as area and volume, which yield tentative quantitative predictions for Planck-scale physics. (ii A physical picture of the microstructure of quantum spacetime, characterized by Planck-scale discreteness. Discreteness emerges as a standard quantum effect from the discrete spectra, and provides a mathematical realization of Wheeler’s “spacetime foam” intuition. (iii Control of spacetime singularities, such as those in the interior of black holes and the cosmological one. This, in particular, has opened up the possibility of a theoretical investigation into the very early universe and the spacetime regions beyond the Big Bang. (iv A derivation of the Bekenstein–Hawking black-hole entropy. (v Low-energy calculations, yielding n-point functions well defined in a background-independent context. The theory is at the roots of, or strictly related to, a number of formalisms that have been developed for describing background-independent quantum field theory, such as spin foams, group field theory, causal spin networks, and others. I give here a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  3. Loop quantum cosmology: Recent progress

    Indian Academy of Sciences (India)

    Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like cosmological ones. This leads to several applications where loop effects play a significant role when one is sensitive to the quantum regime. As a consequence, the structure of and the approach to ...

  4. An enzymatic atavist revealed in dual pathways for water activation.

    Directory of Open Access Journals (Sweden)

    Donghong Min

    2008-08-01

    Full Text Available Inosine monophosphate dehydrogenase (IMPDH catalyzes an essential step in the biosynthesis of guanine nucleotides. This reaction involves two different chemical transformations, an NAD-linked redox reaction and a hydrolase reaction, that utilize mutually exclusive protein conformations with distinct catalytic residues. How did Nature construct such a complicated catalyst? Here we employ a "Wang-Landau" metadynamics algorithm in hybrid quantum mechanical/molecular mechanical (QM/MM simulations to investigate the mechanism of the hydrolase reaction. These simulations show that the lowest energy pathway utilizes Arg418 as the base that activates water, in remarkable agreement with previous experiments. Surprisingly, the simulations also reveal a second pathway for water activation involving a proton relay from Thr321 to Glu431. The energy barrier for the Thr321 pathway is similar to the barrier observed experimentally when Arg418 is removed by mutation. The Thr321 pathway dominates at low pH when Arg418 is protonated, which predicts that the substitution of Glu431 with Gln will shift the pH-rate profile to the right. This prediction is confirmed in subsequent experiments. Phylogenetic analysis suggests that the Thr321 pathway was present in the ancestral enzyme, but was lost when the eukaryotic lineage diverged. We propose that the primordial IMPDH utilized the Thr321 pathway exclusively, and that this mechanism became obsolete when the more sophisticated catalytic machinery of the Arg418 pathway was installed. Thus, our simulations provide an unanticipated window into the evolution of a complex enzyme.

  5. [Effects of quantum nonlocality in the water activation process].

    Science.gov (United States)

    Zatsepina, O V; Stekhin, A A; Yakovleva, G V

    2014-01-01

    The dynamic alterations of the magnetic flux density of the water volume, activated with structurally stressed calcium carbonate in micellar form have been investigated. The phase of the associated water was established to exhibit electrical and magnetic properties, recorded by in B&E meter in the frequency range of 5Hz - 2kHz. Alterations in water Eh (redox) potential and the magnetic flux density B testify to synchronous auto-oscillatory changes. This gives evidence of non-linearity of the relationship between auto-oscillatory processes excited in the water; and reflects the nonlocal in time the relationship between the states of water, manifesting in a change of water activity on the 1st and 2nd day in negative time. The mechanism of action of associated water phase is shown to be described by de Broglie concept of matter waves with taking into account delocalized in time states of phase of electron wave packet in accordance with the transactional interpretation of quantum physics.

  6. The loop gravity string

    CERN Document Server

    Freidel, Laurent; Pranzetti, Daniele

    2016-01-01

    In this work we study canonical gravity in finite regions for which we introduce a generalisation of the Gibbons-Hawking boundary term including the Immirzi parameter. We study the canonical formulation on a spacelike hypersuface with a boundary sphere and show how the presence of this term leads to an unprecedented type of degrees of freedom coming from the restoration of the gauge and diffeomorphism symmetry at the boundary. In the presence of a loop quantum gravity state, these boundary degrees of freedom localize along a set of punctures on the boundary sphere. We demonstrate that these degrees of freedom are effectively described by auxiliary strings with a 3-dimensional internal target space attached to each puncture. We show that the string currents represent the local frame field, that the string angular momenta represent the area flux and that the string stress tensor represents the two dimensional metric on the boundary of the region of interest. Finally, we show that the commutators of these broken...

  7. How long is a piece of loop?

    Directory of Open Access Journals (Sweden)

    Yoonjoo Choi

    2013-02-01

    Full Text Available Loops are irregular structures which connect two secondary structure elements in proteins. They often play important roles in function, including enzyme reactions and ligand binding. Despite their importance, their structure remains difficult to predict. Most protein loop structure prediction methods sample local loop segments and score them. In particular protein loop classifications and database search methods depend heavily on local properties of loops. Here we examine the distance between a loop’s end points (span. We find that the distribution of loop span appears to be independent of the number of residues in the loop, in other words the separation between the anchors of a loop does not increase with an increase in the number of loop residues. Loop span is also unaffected by the secondary structures at the end points, unless the two anchors are part of an anti-parallel beta sheet. As loop span appears to be independent of global properties of the protein we suggest that its distribution can be described by a random fluctuation model based on the Maxwell–Boltzmann distribution. It is believed that the primary difficulty in protein loop structure prediction comes from the number of residues in the loop. Following the idea that loop span is an independent local property, we investigate its effect on protein loop structure prediction and show how normalised span (loop stretch is related to the structural complexity of loops. Highly contracted loops are more difficult to predict than stretched loops.

  8. Membrane Topology and Heme Binding of the Histidine Kinases HrrS and ChrS in Corynebacterium glutamicum

    Directory of Open Access Journals (Sweden)

    Marc Keppel

    2018-02-01

    Full Text Available The HrrSA and the ChrSA two-component systems play a central role in the coordination of heme homeostasis in the Gram-positive soil bacterium Corynebacterium glutamicum and the prominent pathogen Corynebacterium diphtheriae, both members of the Corynebacteriaceae. In this study, we have performed a comparative analysis of the membrane topology and heme-binding characteristics of the histidine kinases HrrS and ChrS of C. glutamicum. While the cytoplasmic catalytic domains are highly conserved between HrrS and ChrS, the N-terminal sensing parts share only minor sequence similarity. PhoA and LacZ fusions of the N-terminal sensor domains of HrrS and ChrS revealed that both proteins are embedded into the cytoplasmic membrane via six α-helices. Although the overall membrane topology appeared to be conserved, target gene profiling indicated a higher sensitivity of the ChrS system to low heme levels (< 1 μM. In vitro, solubilized and purified full-length proteins bound heme in a 1:1 stoichiometry per monomer. Alanine-scanning of conserved amino acid residues in the N-terminal sensor domain revealed three aromatic residues (Y112, F115, and F118, which apparently contribute to heme binding of HrrS. Exchange of either one or all three residues resulted in an almost abolished heme binding of HrrS in vitro. In contrast, ChrS mutants only displayed a red shift of the soret band from 406 to 418 nm suggesting an altered set of ligands in the triple mutant. In line with target gene profiling, these in vitro studies suggest distinct differences in the heme-protein interface of HrrS and ChrS. Since the membrane topology mapping displayed no extensive loop regions and alanine-scanning revealed potential heme-binding residues in α-helix number four, we propose an intramembrane sensing mechanism for both proteins. Overall, we present a first comparative analysis of the ChrS and HrrS kinases functioning as transient heme sensors in the Corynebacteriaceae.

  9. WATER ACTIVITY INFLUENCE ON THE SAFE AGING PERIOD OF CONDENSED MILK

    OpenAIRE

    Ilona Šostakienė; Jūratė Blazgienė

    2010-01-01

    The majority of chemical and biological processes causing the change of nutrients and finally their spoilage are dependent on water. Microbiological growth is directly related to water activity. Water activity (aw) was introduced by an Australian microbiologist W.J. Scott in 1952. He defined this concept as a “fundamental property of water solutions” and i.e. a ratio between pure water (p0) and steam pressure solution (p). The water activity of the unsweetened condensed milk packed into canis...

  10. Combination treatment for allergic conjunctivitis - Plant derived histidine decarboxylase inhibitor and H1 antihistaminic drug.

    Science.gov (United States)

    Bakrania, Anita K; Patel, Snehal S

    2015-08-01

    Aim of present investigation was to study the effect of catechin and the combination of catechin and cetirizine in ovalbumin induced animal model of allergic conjunctivitis. Guinea pigs were divided into 5 groups: normal control, disease control, disease treated with catechin 100 mg/kg, disease treated with cetirizine 10 mg/kg, disease treated with combination of catechin and cetirizine, 50 mg/kg & 5 mg/kg respectively. Sensitization was carried out by intraperitoneal injection of ovalbumin for the period of 14 day. Simultaneously, catechin was administered orally for 14 days while, cetirizine was administered at the day of experiment. Determination of clinical scoring, mast cell and blood histamine content, histidine decarboxylase activity from stomach was carried out. Vascular permeability was measured by dye leakage after secondary challenge of allergen and conjunctival tissues were subjected for histopathological examinations. Treatment with catechin, cetirizine and combination showed significant (P < 0.05) decrease in clinical scoring and vascular permeability. While, catechin 100 mg/kg and catechin 50 mg/kg showed significant (P < 0.05) decrease in histamine content in mast and blood. The treatment also showed significant (P < 0.05) decrease in the histidine decarboxylase enzyme activity. However, cetirizine group did not show any difference in enzyme activity as well as histamine content. Histopathological examination also showed improvement in ulceration and decrease in edema and inflammation in all treatment groups. From the present study, we can conclude that catechin exhibits potent anti-allergic activity by histidine decarboxylase enzyme inhibition and combination shown significant anti-allergic activity at reduced dose by both enzyme inhibition as well as inhibition of histamine receptors. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Menkes disease and response to copper histidine: An Indian case series

    Directory of Open Access Journals (Sweden)

    Sangeetha Yoganathan

    2017-01-01

    Full Text Available Background: Menkes disease (MD is an X-linked recessive neurodegenerative disorder caused by mutations in ATP7A gene. Depending on the residual ATP7A activity, manifestation may be classical MD, occipital horn syndrome, or distal motor neuropathy. Neurological sparing is expected in female carriers. However, on rare occasions, females may manifest with classical clinical phenotype due to skewed X-chromosome inactivation, X-autosome translocation, and XO genotype. Here, we describe a small series of probands with MD and their response to copper histidine therapy. This series also includes a female with X-13 translocation manifesting neurological symptoms. Methods: The clinical profile, laboratory and radiological data, and follow-up of four children with MD were collected from the hospital database and are being presented. Results: All the four children in our series had developmental delay, recurrent respiratory tract infections, hair and skeletal changes, axial hypotonia, tortuous vessels on imaging, low serum copper, ceruloplasmin, and elevated lactate. Fetal hypokinesia and fetal growth retardation were present in two cases. Failure to thrive was present in three children and only one child had epilepsy. Subcutaneous copper histidine was administered to all children. The average time lapse in the initiation of treatment was 20.3 months, and average duration of follow-up was 14.3 months. Conclusion: We conclude that copper histidine therapy is beneficial in reversing the skin and hair changes, improving appendicular tone, socio-cognitive milestones, and improving weight gain, and immunity. Early diagnosis and management of MD are essential to have a better clinical outcome. More research is needed to explore and devise new strategies in the management of patients with MD.

  12. Increased adsorption of histidine-tagged proteins onto tissue culture polystyrene

    DEFF Research Database (Denmark)

    Holmberg, Maria; Hansen, Thomas Steen; Lind, Johan Ulrik

    2012-01-01

    In this study we compare histidine-tagged and native proteins with regards to adsorption properties. We observe significantly increased adsorption of proteins with an incorporated polyhistidine amino acid motif (HIS-tag) onto tissue culture polystyrene (TCPS) compared to similar proteins without...... a HIS-tag. The effect is not observed on polystyrene (PS). Adsorption experiments have been performed at physiological pH (7.4) and the effect was only observed for the investigated proteins that have pI values below or around 7.4. Competitive adsorption experiments with imidazole...

  13. Insufficient intake of L-histidine reduces brain histamine and causes anxiety-like behaviors in male mice.

    Science.gov (United States)

    Yoshikawa, Takeo; Nakamura, Tadaho; Shibakusa, Tetsuro; Sugita, Mayu; Naganuma, Fumito; Iida, Tomomitsu; Miura, Yamato; Mohsen, Attayeb; Harada, Ryuichi; Yanai, Kazuhiko

    2014-10-01

    L-histidine is one of the essential amino acids for humans, and it plays a critical role as a component of proteins. L-histidine is also important as a precursor of histamine. Brain histamine is synthesized from L-histidine in the presence of histidine decarboxylase, which is expressed in histamine neurons. In the present study, we aimed to elucidate the importance of dietary L-histidine as a precursor of brain histamine and the histaminergic nervous system. C57BL/6J male mice at 8 wk of age were assigned to 2 different diets for at least 2 wk: the control (Con) diet (5.08 g L-histidine/kg diet) or the low L-histidine diet (LHD) (1.28 g L-histidine/kg diet). We measured the histamine concentration in the brain areas of Con diet-fed mice (Con group) and LHD-fed mice (LHD group). The histamine concentration was significantly lower in the LHD group [Con group vs. LHD group: histamine in cortex (means ± SEs): 13.9 ± 1.25 vs. 9.36 ± 0.549 ng/g tissue; P = 0.002]. Our in vivo microdialysis assays revealed that histamine release stimulated by high K(+) from the hypothalamus in the LHD group was 60% of that in the Con group (P = 0.012). However, the concentrations of other monoamines and their metabolites were not changed by the LHD. The open-field tests showed that the LHD group spent a shorter amount of time in the central zone (87.6 ± 14.1 vs. 50.0 ± 6.03 s/10 min; P = 0.019), and the light/dark box tests demonstrated that the LHD group spent a shorter amount of time in the light box (198 ± 8.19 vs. 162 ± 14.1 s/10 min; P = 0.048), suggesting that the LHD induced anxiety-like behaviors. However, locomotor activity, memory functions, and social interaction did not differ between the 2 groups. The results of the present study demonstrated that insufficient intake of histidine reduced the brain histamine content, leading to anxiety-like behaviors in the mice. © 2014 American Society for Nutrition.

  14. Membrane permeability and the loss of germination factor from Neurospora crassa at low water activities

    Science.gov (United States)

    Charlang, G.; Horowitz, N. H.

    1974-01-01

    Neurospora crassa conidia incubating in buffer at low water activities release a germination-essential component as well as 260-nm absorbing and ninhydrin-positive materials, regardless of whether an electrolyte or nonelectrolyte is used to reduce water activity. Chloroform and antibiotics known to increase cell-membrane permeability have a similar effect. This suggests that membrane damage occurs in media of low water activity and that an increase in permeability is responsible for the release of cellular components. The damage caused in media of low water activity is nonlethal in most cases, and the conidia recover when transferred to nutrient medium.

  15. A modified suspension test for estimating the mutagenicity of samples containing free and (or) protein-bound histidine.

    Science.gov (United States)

    Liu, Bo; Jin, Jianling; Cheng, Yanfei; Zhang, Huaiqiang; Gao, Peiji

    2009-02-01

    The Ames test has not been very effective in estimating the mutagenicity of histidine-containing samples because external free and (or) protein-bound histidine in these samples would allow the histidine auxotrophs in such test samples to grow more compared with the negative controls that were used as the reference. This could give rise to a false positive.n this study, a modified suspension mutagenicity assay (MS assay) was developed. The tester strains were incubated in Luria-Bertani (LB) broth containing different concentrations of traditional Chinese medicines (TCMs) until the declining phase, and the test samples were assayed to be mutagenic or not by observing whether statistically significant differences were demonstrated in the relative reversion frequencies (RRFs) between the negative control groups and the test groups. Collectively, using LB broth as the test medium and comparing the RRFs in the declining phase made this assay less influenced by the presence of histidine in the test samples.The mutagenicity of some TCMs was measured with the MS assay. The results in MS assay were consistent with those in the mammalian bone marrow chromosomal aberration test, which indicated that the MS assay was appropriate to estimate the mutagenicity of samples containing free and (or) protein-bound histidine.

  16. Preparation of silica coated cobalt ferrite magnetic nanoparticles for the purification of histidine-tagged proteins

    Science.gov (United States)

    Aygar, Gülfem; Kaya, Murat; Özkan, Necati; Kocabıyık, Semra; Volkan, Mürvet

    2015-12-01

    Surface modified cobalt ferrite (CoFe2O4) nanoparticles containing Ni-NTA affinity group were synthesized and used for the separation of histidine tag proteins from the complex matrices through the use of imidazole side chains of histidine molecules. Firstly, CoFe2O4 nanoparticles with a narrow size distribution were prepared in an aqueous solution using the controlled co-precipitation method. In order to obtain small CoFe2O4 agglomerates, oleic acid and sodium chloride were used as dispersants. The CoFe2O4 particles were coated with silica and subsequently the surface of these silica coated particles (SiO2-CoFe2O4) was modified by amine (NH2) groups in order to add further functional groups on the silica shell. Then, carboxyl (-COOH) functional groups were added to the SiO2-CoFe2O4 magnetic nanoparticles through the NH2 groups. After that Nα,Nα-Bis(carboxymethyl)-L-lysine hydrate (NTA) was attached to carboxyl ends of the structure. Finally, the surface modified nanoparticles were labeled with nickel (Ni) (II) ions. Furthermore, the modified SiO2-CoFe2O4 magnetic nanoparticles were utilized as a new system that allows purification of the N-terminal His-tagged recombinant small heat shock protein, Tpv-sHSP 14.3.

  17. Fungal Histidine Phosphotransferase Plays a Crucial Role in Photomorphogenesis and Pathogenesis in Magnaporthe oryzae

    Directory of Open Access Journals (Sweden)

    Varsha C. Mohanan

    2017-05-01

    Full Text Available Two-component signal transduction (TCST pathways play crucial roles in many cellular functions such as stress responses, biofilm formation, and sporulation. The histidine phosphotransferase (HPt, which is an intermediate phosphotransfer protein in a two-component system, transfers a phosphate group to a phosphorylatable aspartate residue in the target protein(s, and up-regulates stress-activated MAP kinase cascades. Most fungal genomes carry a single copy of the gene coding for HPt, which are potential antifungal targets. However, unlike the histidine kinases (HK or the downstream response regulators (RR in two-component system, the HPts have not been well-studied in phytopathogenic fungi. In this study, we investigated the role of HPt in the model rice-blast fungal pathogen Magnaporthe oryzae. We found that in M. oryzae an additional isoform of the HPT gene YPD1 was expressed specifically in response to light. Further, the expression of light-regulated genes such as those encoding envoy and blue-light-harvesting protein, and PAS domain containing HKs was significantly reduced upon down-regulation of YPD1 in M. oryzae. Importantly, down-regulation of YPD1 led to a significant decrease in the ability to penetrate the host cuticle and in light-dependent conidiation in M. oryzae. Thus, our results indicate that Ypd1 plays an important role in asexual development and host invasion, and suggest that YPD1 isoforms likely have distinct roles to play in the rice-blast pathogen M. oryzae.

  18. Histidine decarboxylases and their role in accumulation of histamine in tuna and dried saury.

    Science.gov (United States)

    Kanki, Masashi; Yoda, Tomoko; Tsukamoto, Teizo; Baba, Eiichiroh

    2007-03-01

    Histamine-producing bacteria (HPB) such as Photobacterium phosphoreum and Raoultella planticola possess histidine decarboxylase (HDC), which converts histidine into histamine. Histamine fish poisoning (HFP) is attributable to the ingestion of fish containing high levels of histamine produced by HPB. Because freezing greatly decreases the histamine-producing ability of HPB, especially of P. phosphoreum, it has been speculated that HFP is caused by HDC itself from HPB cells autolyzing during frozen storage, even when HPB survive frozen storage. Here we constructed recombinant HDCs of P. phosphoreum, Photobacterium damselae, R. planticola, and Morganella morganii and investigated the ability of HDCs to produce sufficient histamine to cause HFP. To elucidate the character of these HDCs, we examined the specific activity of each recombinant HDC at various temperatures, pH levels, and NaCl concentrations. Further, we also investigated the stability of each HDC under different conditions (in reaction buffer, tuna, and dried saury) at various temperatures. P. damselae HDC readily produced sufficient histamine to cause HFP in fish samples. We consider that if HDC is implicated as an independent cause of HFP in frozen-thawed fish, the most likely causative agent is HDC of P. damselae.

  19. Histidine Decarboxylases and Their Role in Accumulation of Histamine in Tuna and Dried Saury▿

    Science.gov (United States)

    Kanki, Masashi; Yoda, Tomoko; Tsukamoto, Teizo; Baba, Eiichiroh

    2007-01-01

    Histamine-producing bacteria (HPB) such as Photobacterium phosphoreum and Raoultella planticola possess histidine decarboxylase (HDC), which converts histidine into histamine. Histamine fish poisoning (HFP) is attributable to the ingestion of fish containing high levels of histamine produced by HPB. Because freezing greatly decreases the histamine-producing ability of HPB, especially of P. phosphoreum, it has been speculated that HFP is caused by HDC itself from HPB cells autolyzing during frozen storage, even when HPB survive frozen storage. Here we constructed recombinant HDCs of P. phosphoreum, Photobacterium damselae, R. planticola, and Morganella morganii and investigated the ability of HDCs to produce sufficient histamine to cause HFP. To elucidate the character of these HDCs, we examined the specific activity of each recombinant HDC at various temperatures, pH levels, and NaCl concentrations. Further, we also investigated the stability of each HDC under different conditions (in reaction buffer, tuna, and dried saury) at various temperatures. P. damselae HDC readily produced sufficient histamine to cause HFP in fish samples. We consider that if HDC is implicated as an independent cause of HFP in frozen-thawed fish, the most likely causative agent is HDC of P. damselae. PMID:17220267

  20. Fine-tuning of proton sponges by precise diaminoethanes and histidines in pDNA polyplexes.

    Science.gov (United States)

    Lächelt, Ulrich; Kos, Petra; Mickler, Frauke M; Herrmann, Annika; Salcher, Eveline E; Rödl, Wolfgang; Badgujar, Naresh; Bräuchle, Christoph; Wagner, Ernst

    2014-01-01

    The cationizable nature of 'proton-sponge' transfection agents facilitates pDNA delivery in several steps. Protonated amines account for electrostatic DNA binding and cellular uptake, buffering amines mediate polyplex escape from acidifying intracellular vesicles. As demonstrated with a sequence-defined library of oligo(ethanamino)amides containing selected oligoethanamino acids and histidines, the total protonation capacity as well as the cationization pH profile within the endolysosomal range have critical impact on gene transfer. Building blocks with even numbered amine groups (Gtt, Sph) exhibited higher total endolysosomal buffer capacity than odd number (Stp) analogs. Within the endolysosomal range, Gtt has the highest buffer capacity around pH5, whereas Stp has its maximum around pH7. Histidines increased the total buffer capacity, resulted in a more continuous cationization pH profile and greatly improved transgene expression in vitro and in vivo. Using receptor targeted and polyethylene glycol shielded polyplexes, better endosomal escape and >100-fold enhanced transfection was detected. Proton-sponge transfection agents for pDNA delivery are characterized in this study, demonstrating over 100-fold enhanced transection and better endosomal escape by using receptor targeted and polyethylene glycol shielded polyplexes. © 2013.

  1. Novel Organotin(IV) Schiff Base Complexes with Histidine Derivatives: Synthesis, Characterization, and Biological Activity

    Science.gov (United States)

    Garza-Ortiz, Ariadna; Camacho-Camacho, Carlos; Sainz-Espuñes, Teresita; Rojas-Oviedo, Irma; Gutiérrez-Lucas, Luis Raúl; Gutierrez Carrillo, Atilano; Vera Ramirez, Marco A.

    2013-01-01

    Five novel tin Schiff base complexes with histidine analogues (derived from the condensation reaction between L-histidine and 3,5-di-tert-butyl-2-hydroxybenzaldehyde) have been synthesized and characterized. Characterization has been completed by IR and high-resolution mass spectroscopy, 1D and 2D solution NMR (1H, 13C  and 119Sn), as well as solid state 119Sn NMR. The spectroscopic evidence shows two types of structures: a trigonal bipyramidal stereochemistry with the tin atom coordinated to five donating atoms (two oxygen atoms, one nitrogen atom, and two carbon atoms belonging to the alkyl moieties), where one molecule of ligand is coordinated in a three dentate fashion. The second structure is spectroscopically described as a tetrahedral tin complex with four donating atoms (one oxygen atom coordinated to the metal and three carbon atoms belonging to the alkyl or aryl substituents), with one molecule of ligand attached. The antimicrobial activity of the tin compounds has been tested against the growth of bacteria in vitro to assess their bactericidal properties. While pentacoordinated compounds 1, 2, and 3 are described as moderate effective to noneffective drugs against both Gram-positive and Gram-negative bacteria, tetracoordinated tin(IV) compounds 4 and 5 are considered as moderate effective and most effective compounds, respectively, against the methicillin-resistant Staphylococcus aureus strains (Gram-positive). PMID:23864839

  2. Arabidopsis histidine kinase 5 regulates salt sensitivity and resistance against bacterial and fungal infection.

    Science.gov (United States)

    Pham, Jasmine; Liu, Jasmine; Bennett, Mark H; Mansfield, John W; Desikan, Radhika

    2012-04-01

    • The ability of plants to adapt to multiple stresses imposed by the natural environment requires cross-talk and fine-tuning of stress signalling pathways. The hybrid histidine kinase Arabidopsis histidine kinase 5 (AHK5) is known to mediate stomatal responses to exogenous and endogenous signals in Arabidopsis thaliana. The purpose of this study was to determine whether the function of AHK5 in stress signalling extends beyond stomatal responses. • Plant growth responses to abiotic stresses, tissue susceptibility to bacterial and fungal pathogens, and hormone production and metabolism of reactive oxygen species were monitored in a T-DNA insertion mutant of AHK5. • The findings of this study indicate that AHK5 positively regulates salt sensitivity and contributes to resistance to the bacterium Pseudomonas syringae pv. tomato DC3000 and the fungal pathogen Botrytis cinerea. • This is the first report of a role for AHK5 in the regulation of survival following challenge by a hemi-biotrophic bacterium and a necrotrophic fungus, as well as in the growth response to salt stress. The function of AHK5 in regulating the production of hormones and redox homeostasis is discussed. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

  3. Selective histamine uptake rescues photo- and mechanoreceptor function of histidine decarboxylase-deficient Drosophila mutant.

    Science.gov (United States)

    Melzig, J; Burg, M; Gruhn, M; Pak, W L; Buchner, E

    1998-09-15

    In insects, histamine is found both in the peripheral nervous system (PNS) and in the CNS and is known to function as a fast neurotransmitter in photoreceptors that have been shown to express selectively the hdc gene. This gene codes for histidine decarboxylase (HDC), the enzyme for histamine synthesis. Fast neurotransmission requires the efficient removal of the transmitter from the synaptic cleft. Here we identify in Drosophila photo- and mechanoreceptors a histamine uptake mechanism that can restore the function of these receptors in mutants unable to synthesize histamine. When apparent null mutants for the hdc gene imbibe aqueous histamine solution or are genetically "rescued" by a transgene ubiquitously expressing histidine decarboxylase under heat-shock control, sufficient amounts of histamine selectively accumulate in photo- and mechanoreceptors to generate near-normal electrical responses in second-order visual interneurons and qualitatively to restore wild-type visual and mechanosensory behavior. This strongly supports the proposal that histamine functions as a fast neurotransmitter also in a certain class of mechanoreceptors. A set of CNS-intrinsic neurons that in the wild type contain high concentrations of histamine apparently lacks this uptake mechanism. We therefore speculate that histamine of intrinsic neurons may function as a neuromodulator rather than as a fast transmitter.

  4. Fungal histidine phosphotransferase plays a crucial role in photomorphogenesis and pathogenesis in Magnaporthe oryzae

    Science.gov (United States)

    Mohanan, Varsha C.; Chandarana, Pinal M.; Chattoo, Bharat. B.; Patkar, Rajesh N.; Manjrekar, Johannes

    2017-05-01

    Two-component signal transduction (TCST) pathways play crucial roles in many cellular functions such as stress responses, biofilm formation and sporulation. The histidine phosphotransferase (HPt), which is an intermediate phosphotransfer protein in a two-component system, transfers a phosphate group to a phosphorylatable aspartate residue in the target protein(s), and up-regulates stress-activated MAP kinase cascades. Most fungal genomes carry a single copy of the gene coding for HPt, which are potential antifungal targets. However, unlike the histidine kinases (HK) or the downstream response regulators (RR) in two-component system, the HPts have not been well studied in phytopathogenic fungi. In this study, we investigated the role of HPt in the model rice-blast fungal pathogen Magnaporthe oryzae. We found that in M. oryzae an additional isoform of the HPT gene YPD1 was expressed specifically in response to light. Further, the expression of light-regulated genes such as those encoding envoy and blue-light-harvesting protein, and PAS domain containing HKs was significantly reduced upon down-regulation of YPD1 in M. oryzae. Importantly, down-regulation of YPD1 led to a significant decrease in the ability to penetrate the host cuticle and in light-dependent conidiation in M. oryzae. Thus, our results indicate that Ypd1 plays an important role in asexual development and host invasion, and suggest that YPD1 isoforms likely have distinct roles to play in the rice-blast pathogen M. oryzae.

  5. Glycerol enhances fungal germination at the water-activity limit for life

    NARCIS (Netherlands)

    Stevenson, Andrew; Hamill, Philip G; Medina, Ángel; Kminek, Gerhard; Rummel, John D; Dijksterhuis, Jan; Timson, David J; Magan, Naresh; Leong, Su-Lin L; Hallsworth, John E

    2016-01-01

    For the most-extreme fungal xerophiles, metabolic activity and cell division typically halts between 0.700 and 0.640 water activity (approximately 70.0-64.0% relative humidity). Here, we investigate whether glycerol can enhance xerophile germination under acute water-activity regimes, using an

  6. Glycerol enhances fungal germination at the water-activity limit for life

    NARCIS (Netherlands)

    Stevenson, Andrew; Hamill, Philip G; Medina, Ángel; Kminek, Gerhard; Rummel, John D; Dijksterhuis, Jan; Timson, David J; Magan, Naresh; Leong, Su-Lin L; Hallsworth, John E

    2017-01-01

    For the most-extreme fungal xerophiles, metabolic activity and cell division typically halts between 0.700 and 0.640 water activity (approximately 70.0-64.0% relative humidity). Here, we investigate whether glycerol can enhance xerophile germination under acute water-activity regimes, using an

  7. Effect of Water Activity on the Free Fatty Acid Value of Crude Palm ...

    African Journals Online (AJOL)

    The influence of water activity, aw on the storage quality of palm oil was examined. Equal proportions of palm oil were put in three different water activity media for a period of 21 days at room temperature. A fourth sample representing the control was placed by the window in the laboratory. Aliquots were withdrawn at an ...

  8. Kinetics of acrylamide formation/elimination reactions as affected by water activity.

    Science.gov (United States)

    De Vleeschouwer, Kristel; Van der Plancken, Iesel; Van Loey, Ann; Hendrickx, Marc E

    2007-01-01

    The influence of water activity on the kinetics of acrylamide formation and elimination reaction was investigated using low-moisture equimolar asparagine-glucose model systems, which were heated at temperatures between 120 and 200 degrees C for variable heating times. To determine the water content corresponding to the water activities tested, a sorption moisture isotherm was constructed experimentally. The acrylamide concentrations measured at different water activities could be modeled on the basis of a reaction scheme including not only acrylamide formation and elimination reactions but also an alternative Maillard reaction between both reactants. The corresponding rate constants and activation energies were estimated using nonlinear regression analysis. Whereas the rate constant for acrylamide formation varied only slightly with the initial water activity of the model system, the elimination rate constant showed a clear minimum around a water activity of 0.82. The opposite trend, namely, a maximum at a water activity of 0.82, was found for the Maillard reaction rate constant as a function of water activity, which confirms data from literature. The activation energies for the different reactions changed in a comparable way as the corresponding rate constant with water activity.

  9. Study of loop-loop and loop-edge dislocation interactions in bcc iron

    DEFF Research Database (Denmark)

    Osetsky, Y.N.; Bacon, D.J.; Gao, F.

    2000-01-01

    that the evolution of heterogeneities such as dislocation decoration and rafts has serious impacts on the mechanical properties on neutron-irradiated metals. In the present work, atomic-scale computer modelling (ASCM) has been applied to study the mechanisms for the formation of such microstructure in bcc iron....... It is shown that glissile clusters with parallel Burgers vectors interact strongly and can form extended immobile complexes, i.e., rafts. Similar attractive interaction exists between dislocation loops and an edge dislocation. These two mechanisms may be responsible for the formation of extended complexes...... of dislocation loops below the extra half-plane of edge dislocations. The interaction energies between loops and between an edge dislocation and loops has been calculated as a function of distance using ASCM and the results for long-range interactions are in good agreement with the results of isotropic...

  10. N -loop running should be combined with N -loop matching

    Science.gov (United States)

    Braathen, Johannes; Goodsell, Mark D.; Krauss, Manuel E.; Opferkuch, Toby; Staub, Florian

    2018-01-01

    We investigate the high-scale behavior of Higgs sectors beyond the Standard Model, pointing out that the proper matching of the quartic couplings before applying the renormalization group equations (RGEs) is of crucial importance for reliable predictions at larger energy scales. In particular, the common practice of leading-order parameters in the RGE evolution is insufficient to make precise statements on a given model's UV behavior, typically resulting in uncertainties of many orders of magnitude. We argue that, before applying N -loop RGEs, a matching should even be performed at N -loop order in contrast to common lore. We show both analytical and numerical results where the impact is sizable for three minimal extensions of the Standard Model: a singlet extension, a second Higgs doublet and finally vector-like quarks. We highlight that the known two-loop RGEs tend to moderate the running of their one-loop counterparts, typically delaying the appearance of Landau poles. For the addition of vector-like quarks we show that the complete two-loop matching and RGE evolution hints at a stabilization of the electroweak vacuum at high energies, in contrast to results in the literature.

  11. Neighbor-directed Histidine N(τ)–Alkylation: A Route to Imidazolium-containing Phosphopeptide Macrocycles

    Science.gov (United States)

    Qian, Wen-Jian; Park, Jung-Eun; Grant, Robert; Lai, Christopher C.; Kelley, James A.; Yaffe, Michael B.; Lee, Kyung S.; Burke, Terrence R.

    2016-01-01

    Our recently discovered, selective, on-resin route to N(τ)-alkylated imidazolium-containing histidine residues affords new strategies for peptide mimetic design. In our current work, we demonstrate the use of this chemistry to prepare a series of macrocyclic phosphopeptides, in which imidazolium groups serve as ring-forming junctions. Interestingly, these cationic moieties subsequently serve to charge-mask the phosphoamino acid group that directed their formation. Neighbor-directed histidine N(τ)-alkylation opens the door to new families of phosphopeptidomimetics for use in a range of chemical biology contexts. PMID:26152807

  12. Kalman Orbit Optimized Loop Tracking

    Science.gov (United States)

    Young, Lawrence E.; Meehan, Thomas K.

    2011-01-01

    Under certain conditions of low signal power and/or high noise, there is insufficient signal to noise ratio (SNR) to close tracking loops with individual signals on orbiting Global Navigation Satellite System (GNSS) receivers. In addition, the processing power available from flight computers is not great enough to implement a conventional ultra-tight coupling tracking loop. This work provides a method to track GNSS signals at very low SNR without the penalty of requiring very high processor throughput to calculate the loop parameters. The Kalman Orbit-Optimized Loop (KOOL) tracking approach constitutes a filter with a dynamic model and using the aggregate of information from all tracked GNSS signals to close the tracking loop for each signal. For applications where there is not a good dynamic model, such as very low orbits where atmospheric drag models may not be adequate to achieve the required accuracy, aiding from an IMU (inertial measurement unit) or other sensor will be added. The KOOL approach is based on research JPL has done to allow signal recovery from weak and scintillating signals observed during the use of GPS signals for limb sounding of the Earth s atmosphere. That approach uses the onboard PVT (position, velocity, time) solution to generate predictions for the range, range rate, and acceleration of the low-SNR signal. The low- SNR signal data are captured by a directed open loop. KOOL builds on the previous open loop tracking by including feedback and observable generation from the weak-signal channels so that the MSR receiver will continue to track and provide PVT, range, and Doppler data, even when all channels have low SNR.

  13. Study of the Open Loop and Closed Loop Oscillator Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Imel, George R. [Idaho State Univ., Pocatello, ID (United States); Baker, Benjamin [Idaho National Lab. (INL), Idaho Falls, ID (United States); Riley, Tony [Knolls Atomic Power Lab. (KAPL), Schenectady, NY (United States); Langbehn, Adam [Puget Sound Naval Base, Bremerton, WA (United States); Aryal, Harishchandra [Idaho State Univ., Pocatello, ID (United States); Benzerga, M. Lamine [Idaho State Univ., Pocatello, ID (United States)

    2015-04-11

    This report presents the progress and completion of a five-year study undertaken at Idaho State University of the measurement of very small worth reactivity samples comparing open and closed loop oscillator techniques.The study conclusively demonstrated the equivalency of the two techniques with regard to uncertainties in reactivity values, i.e., limited by reactor noise. As those results are thoroughly documented in recent publications, in this report we will concentrate on the support work that was necessary. For example, we describe in some detail the construction and calibration of a pilot rod for the closed loop system. We discuss the campaign to measure the required reactor parameters necessary for inverse-kinetics. Finally, we briefly discuss the transfer of the open loop technique to other reactor systems.

  14. Vertically Polarized Omnidirectional Printed Slot Loop AntennaPrinted Slot Loop Antenna (invited)

    DEFF Research Database (Denmark)

    Kammersgaard, Nikolaj Peter Iversen; Kvist, Søren Helstrup; Thaysen, Jesper

    2015-01-01

    A novel verticall A novel vertically polarized dpolarize , omnidirection omnidirectional l , printed slot loop antenna h sprinted slot loop antenna has been designed, simulated, fabricated, and measured. The slot loop works as a magnetic loop. The loop is loaded with inductors to insure uniform a...

  15. Closed loop obstruction: pictorial essay.

    Science.gov (United States)

    Mbengue, A; Ndiaye, A; Soko, T O; Sahnoun, M; Fall, A; Diouf, C T; Régent, D; Diakhaté, I C

    2015-02-01

    Closed loop obstruction occurs when a segment of bowel is incarcerated at two contiguous points. The diagnosis is based on multiple transitional zones. The incarcerated loops appear in U or C form or present a radial layout around the location of the obstruction. It's very important to specify the type of obstruction because, in patients with simple bowel obstruction, a conservative approach is often advised. On the other hand, a closed loop obstruction immediately requires a surgical approach because of its high morbidity and the risk of death in case of a late diagnosis. Copyright © 2013 Éditions françaises de radiologie. Published by Elsevier Masson SAS. All rights reserved.

  16. Effective potential at three loops

    Science.gov (United States)

    Martin, Stephen P.

    2017-11-01

    I present the effective potential at three-loop order for a general renormalizable theory, using the MS ¯ renormalization scheme and Landau gauge fixing. As applications and illustrative points of reference, the results are specialized to the supersymmetric Wess-Zumino model and to the standard model. In each case, renormalization group scale invariance provides a consistency check. In the Wess-Zumino model, the required vanishing of the minimum vacuum energy yields an additional check. For the standard model, I carry out the resummation of Goldstone boson contributions, which provides yet more opportunities for nontrivial checks, and obtain the minimization condition for the Higgs vacuum expectation value at full three-loop order. An infrared divergence due to doubled photon propagators appears in the three-loop standard model effective potential, but it does not affect the minimization condition or physical observables and can be eliminated by resummation.

  17. Divalent metal binding by histidine-rich glycoprotein differentially regulates higher order oligomerisation and proteolytic processing.

    Science.gov (United States)

    Priebatsch, Kristin M; Poon, Ivan K H; Patel, Kruti K; Kvansakul, Marc; Hulett, Mark D

    2017-01-01

    The serum protein histidine-rich glycoprotein (HRG) has been implicated in tissue injury and tumour growth. Several HRG functions are regulated by the divalent metal Zn2+ , including ligand binding and proteolytic processing that releases active HRG fragments. Although HRG can bind divalent metals other than Zn2+ , the impact of these divalent metals on the biophysical properties of HRG remains poorly understood. We now show that HRG binds Zn2+ , Ni2+ , Cu2+ and Co2+ with micromolar affinities, but differing stoichiometries, and regulate the release of specific HRG fragments during proteolysis. Furthermore, HRG binding to Zn2+ promotes HRG dimer formation in a Zn2+ -concentration- and pH-dependent manner. Our data highlight the complex divalent metal-dependent regulatory mechanisms that govern HRG function. © 2016 Federation of European Biochemical Societies.

  18. Crystal structure of a bicupin protein HutD involved in histidine utilization in Pseudomonas.

    Science.gov (United States)

    Gerth, M L; Liu, Y; Jiao, W; Zhang, X-X; Baker, E N; Lott, J S; Rainey, P B; Johnston, J M

    2017-08-01

    Cupins form one of the most functionally diverse superfamilies of proteins, with members performing a wide range of catalytic, non-catalytic, and regulatory functions. HutD is a predicted bicupin protein that is involved in histidine utilization (Hut) in Pseudomonas species. Previous genetic analyses have suggested that it limits the upper level of Hut pathway expression, but its mechanism of action is unknown. Here, we have determined the structure of PfluHutD at 1.74 Å resolution in several crystallization conditions, and identified N-formyl-l-glutamate (FG, a Hut pathway intermediate) as a potential ligand in vivo. Proteins 2017; 85:1580-1588. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  19. Using Poly-L-Histidine Modified Glassy Carbon Electrode to Trace Hydroquinone in the Sewage Water

    Directory of Open Access Journals (Sweden)

    Bin Wang

    2014-01-01

    Full Text Available A sensitive voltammetric method for trace measurements of hydroquinone in the sewage water is described. The poly-L-histidine is prepared to modify the glassy carbon electrode in order to improve the electrochemical catalysis of interesting substances such as hydroquinone. The influence of the base solution, pH value, and scanning speed on the tracing of hydroquinone is discussed, and the experimental procedures and conditions are optimized. The laboratory results show that it is possible to construct a linear calibration curve between the peak current of hydroquinone on modified electrode and its concentration at the level of 0.00001 mol/L. The potential limitation of the method is suggested by a linear peaking shift model as well. The method was successfully applied to the determination of hydroquinone in the actual sample of industrial waste water.

  20. Quantum Chemical Mass Spectrometry: Verification and Extension of the Mobile Proton Model for Histidine

    Science.gov (United States)

    Cautereels, Julie; Blockhuys, Frank

    2017-06-01

    The quantum chemical mass spectrometry for materials science (QCMS2) method is used to verify the proposed mechanism for proton transfer - the Mobile Proton Model (MPM) - by histidine for ten XHS tripeptides, based on quantum chemical calculations at the DFT/B3LYP/6-311+G* level of theory. The fragmentations of the different intermediate structures in the MPM mechanism are studied within the QCMS2 framework, and the energetics of the proposed mechanism itself and those of the fragmentations of the intermediate structures are compared, leading to the computational confirmation of the MPM. In addition, the calculations suggest that the mechanism should be extended from considering only the formation of five-membered ring intermediates to include larger-ring intermediates. [Figure not available: see fulltext.

  1. Deep-vein thrombosis is not associated with the P/S186 polymorphism of histidine-rich glycoprotein

    NARCIS (Netherlands)

    Rattink, A.P.; Hennis, B.C.; Lievers, C.J.A.; Maat, M.P.M. de; Bertina, R.; Mennen, L.I.; Rosendaal, F.R.

    1999-01-01

    Background: In several studies, higher plasma levels of histidine-rich glycoprotein (HRG) have been observed in patients with venous thrombosis than in healthy subjects. Apart from environmental factors, such as the use of oral contraceptives, the plasma HRG levels are mainly determined genetically.

  2. Chromium III histidinate exposure modulates antioxidant gene expression in HaCaT human keratinocytes exposed to oxidative stress

    Science.gov (United States)

    While the toxicity of hexavalent chromium is well established, trivalent Cr (Cr(III)) is an essential nutrient involved in insulin and glucose homeostasis. Recently, antioxidant effects of chromium (III) histidinate (Cr(III)His) were reported in HaCaT human keratinocytes exposed to oxidative stress...

  3. Influence of histidine incorporation on buffer capacity and gene transfection efficiency of HPMA-co-oligolysine brush polymers.

    Science.gov (United States)

    Shi, Julie; Schellinger, Joan G; Johnson, Russell N; Choi, Jennifer L; Chou, Brian; Anghel, Ersilia L; Pun, Suzie H

    2013-06-10

    One of the major intracellular barriers to nonviral gene delivery is efficient endosomal escape. The incorporation of histidine residues into polymeric constructs has been found to increase endosomal escape via the proton sponge effect. Statistical and diblock copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA), oligolysine, and oligohistidine were synthesized via reversible-addition fragmentation chain transfer (RAFT) polymerization and tested for in vitro transfection efficiency, buffering ability, and polyplex uptake mechanism via the use of chemical endocytic inhibitors. Interestingly, histidine-containing statistical and diblock polymers exhibited increased buffer capacity in different endosomal pH ranges. Statistical copolymers transfected better than block copolymers that contained similar amounts of histidine. In addition, only the polymer containing the highest incorporation of oligohistidine residues led to increases in transfection efficiency over the HPMA-oligolysine base polymer. Thus, for these polymer architectures, high histidine incorporation may be required for efficient endosomal escape. Furthermore, inhibitor studies indicate that nonacidified caveolae-mediated endocytosis may be the primary route of transfection for these copolymers, suggesting that alternative approaches for increasing endosomal escape may be beneficial for enhancing transfection efficiency with these HPMA-oligolysine copolymers.

  4. Implication of citrate, malate and histidine in the accumulation and transport of nickel in Mesembryanthemum crystallinum and Brassica juncea.

    Science.gov (United States)

    Amari, Taoufik; Lutts, Stanley; Taamali, Manel; Lucchini, Giorgio; Sacchi, Gian Attilio; Abdelly, Chedly; Ghnaya, Tahar

    2016-04-01

    Citrate, malate and histidine have been involved in many processes including metal tolerance and accumulation in plants. These molecules have been frequently reported to be the potential nickel chelators, which most likely facilitate metal transport through xylem. In this context, we assess here, the relationship between organics acids and histidine content and nickel accumulation in Mesembryanthemum crystallinum and Brassica juncea grown in hydroponic media added with 25, 50 and 100 µM NiCl2. Results showed that M. crystallinum is relatively more tolerant to Ni toxicity than B. juncea. For both species, xylem transport rate of Ni increased with increasing Ni supply. A positive correlation was established between nickel and citrate concentrations in the xylem sap. In the shoot of B. juncea, citric and malic acids concentrations were significantly higher than in the shoot of M. crystallinum. Also, the shoots and roots of B. juncea accumulated much more histidine. In contrast, a higher root citrate concentration was observed in M. crystallinum. These findings suggest a specific involvement of malic and citric acid in Ni translocation and accumulation in M. crystallinum and B. juncea. The high citrate and histidine accumulation especially at 100µM NiCl2, in the roots of M. crystallinum might be among the important factors associated with the tolerance of this halophyte to toxic Ni levels. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. LISA Pathfinder: OPD loop characterisation

    Science.gov (United States)

    Born, Michael; LPF Collaboration

    2017-05-01

    The optical metrology system (OMS) of the LISA Pathfinder mission is measuring the distance between two free-floating test masses with unprecedented precision. One of the four OMS heterodyne interferometers reads out the phase difference between the reference and the measurement laser beam. This phase from the reference interferometer is common to all other longitudinal interferometer read outs and therefore subtracted. In addition, the phase is fed back via the digital optical pathlength difference (OPD) control loop to keep it close to zero. Here, we analyse the loop parameters and compare them to on-ground measurement results.

  6. Chinese Magic in Loop Integrals

    OpenAIRE

    Ward, B. F. L.

    2011-01-01

    We present an approach to higher point loop integrals using Chinese magic in the virtual loop integration variable. We show, using the five point function in the important e^+e^-\\to f\\bar{f}+\\gamma process for ISR as a pedagogical vehicle, that we get an expression for it directly reduced to one scalar 5-point function and 4-, 3-, and 2- point integrals, thereby avoiding the computation of the usual three tensor 5-pt Passarino-Veltman reduction. We argue that this offers potential for greater...

  7. High-energy collision-induced dissociation of histidine ions, [His+H](+) and [His-H](-) , and histidine dimer [His2 +H]().

    Science.gov (United States)

    Khreis, Jusuf M; Reitshammer, Julia; Vizcaino, Violaine; Klawitter, Kevin; Feketeová, Linda; Denifl, Stephan

    2017-11-06

    Histidine (His) is an essential amino acid, whose side group consists of aromatic imidazole moiety that can bind a proton or metal cation and act as a donor in intermolecular interactions in many biological processes. While the dissociation of His monomer ions is well known, information on the kinetic energy released in the dissociation has been missing. Using a new home built electrospray ionization (ESI) source adapted to a double focusing mass spectrometer of BxE geometry, we investigated the fragmentation reactions of protonated and deprotonated His, [His+H](+) and [His-H](-) , and the protonated His dimer [His2 +H](+) , accelerated to 6 keV in a high-energy collision with He gas. We have evaluated the kinetic energy release (KER) for the observed dissociation channels. ESI of the His solution in positive mode led to the formation of His clusters [Hisn +H](+) , n = 1 - 6, with notably enhanced stability of the tetramer. [His+H](+) dissociates predominantly by loss of (H2 O+CO) with a KER of 278 meV, while the dominant dissociation channel of [His-H](-) involves loss of NH3 with a high KER of 769 meV. Dissociation of [His2 +H](+) is dominated by loss of the monomer but smaller losses are also observed. The KER for HCOOH loss from both [His+H](+) and [His-H](-) is similar at 278 and 249 meV, respectively, which suggest the collision-induced dissociation takes place via a similar mechanism. The loss of COOH and C2 H5 NO2 from the dimer suggests that the dimer of His binds through a shared proton between the imidazole moieties. This article is protected by copyright. All rights reserved.

  8. A Novel Protective Function for Cytokinin in the Light Stress Response Is Mediated by the ARABIDOPSIS HISTIDINE KINASE2 and ARABIDOPSIS HISTIDINE KINASE3 Receptors1[W

    Science.gov (United States)

    Cortleven, Anne; Nitschke, Silvia; Klaumünzer, Marion; AbdElgawad, Hamada; Asard, Han; Grimm, Bernhard; Riefler, Michael; Schmülling, Thomas

    2014-01-01

    Cytokinins are plant hormones that regulate diverse processes in plant development and responses to biotic and abiotic stresses. In this study, we show that Arabidopsis (Arabidopsis thaliana) plants with a reduced cytokinin status (i.e. cytokinin receptor mutants and transgenic cytokinin-deficient plants) are more susceptible to light stress compared with wild-type plants. This was reflected by a stronger photoinhibition after 24 h of high light (approximately 1,000 µmol m−2 s−1), as shown by the decline in maximum quantum efficiency of photosystem II photochemistry. Photosystem II, especially the D1 protein, is highly sensitive to the detrimental impact of light. Therefore, photoinhibition is always observed when the rate of photodamage exceeds the rate of D1 repair. We demonstrate that in plants with a reduced cytokinin status, the D1 protein level was strongly decreased upon light stress. Inhibition of the D1 repair cycle by lincomycin treatment indicated that these plants experience stronger photodamage. The efficiency of photoprotective mechanisms, such as nonenzymatic and enzymatic scavenging systems, was decreased in plants with a reduced cytokinin status, which could be a cause for the increased photodamage and subsequent D1 degradation. Additionally, slow and incomplete recovery in these plants after light stress indicated insufficient D1 repair. Mutant analysis revealed that the protective function of cytokinin during light stress depends on the ARABIDOPSIS HISTIDINE KINASE2 (AHK2) and AHK3 receptors and the type B ARABIDOPSIS RESPONSE REGULATOR1 (ARR1) and ARR12. We conclude that proper cytokinin signaling and regulation of specific target genes are necessary to protect leaves efficiently from light stress. PMID:24424319

  9. A novel protective function for cytokinin in the light stress response is mediated by the Arabidopsis histidine kinase2 and Arabidopsis histidine kinase3 receptors.

    Science.gov (United States)

    Cortleven, Anne; Nitschke, Silvia; Klaumünzer, Marion; Abdelgawad, Hamada; Asard, Han; Grimm, Bernhard; Riefler, Michael; Schmülling, Thomas

    2014-03-01

    Cytokinins are plant hormones that regulate diverse processes in plant development and responses to biotic and abiotic stresses. In this study, we show that Arabidopsis (Arabidopsis thaliana) plants with a reduced cytokinin status (i.e. cytokinin receptor mutants and transgenic cytokinin-deficient plants) are more susceptible to light stress compared with wild-type plants. This was reflected by a stronger photoinhibition after 24 h of high light (approximately 1,000 µmol m(-2) s(-1)), as shown by the decline in maximum quantum efficiency of photosystem II photochemistry. Photosystem II, especially the D1 protein, is highly sensitive to the detrimental impact of light. Therefore, photoinhibition is always observed when the rate of photodamage exceeds the rate of D1 repair. We demonstrate that in plants with a reduced cytokinin status, the D1 protein level was strongly decreased upon light stress. Inhibition of the D1 repair cycle by lincomycin treatment indicated that these plants experience stronger photodamage. The efficiency of photoprotective mechanisms, such as nonenzymatic and enzymatic scavenging systems, was decreased in plants with a reduced cytokinin status, which could be a cause for the increased photodamage and subsequent D1 degradation. Additionally, slow and incomplete recovery in these plants after light stress indicated insufficient D1 repair. Mutant analysis revealed that the protective function of cytokinin during light stress depends on the Arabidopsis histidine KINASE2 (AHK2) and AHK3 receptors and the type B Arabidopsis response regulator1 (ARR1) and ARR12. We conclude that proper cytokinin signaling and regulation of specific target genes are necessary to protect leaves efficiently from light stress.

  10. Novel mutations and clinical outcomes of copper-histidine therapy in Menkes disease patients.

    Science.gov (United States)

    Kim, Ja Hye; Lee, Beom Hee; Kim, Yoo-Mi; Choi, Jin-Ho; Kim, Gu-Hwan; Cheon, Chong Kun; Yoo, Han-Wook

    2015-02-01

    Menkes disease is a very rare X-linked copper metabolism disorder that results from an ATP7A gene mutation. With the advent of subcutaneous copper-histidine therapy, the early diagnosis of Menkes disease becomes of utmost importance for patients' prognosis. In the present study, the clinical characteristics of 12 Korean patients with Menkes disease (11 males and 1 female from 11 unrelated families) were described along with the mutation spectrum. Only 2 male patients were diagnosed in the neonatal period, and the other male patients were diagnosed at age 4.3 ± 1.9 months. The presenting signs included depigmented kinky hair, neurologic deficits, and hypotonia. Serum copper and ceruloplasmin levels were markedly decreased. Intracranial vessels were dilated with tortuosity and accompanied by regional cerebral infarctions, even at an early age. Of note, the female patient was diagnosed at age 18 months, during the evaluation for developmental delay, by characteristic MRA findings, biochemical profiles, and genetic evaluation. A total of 11 ATP7A mutations were identified, including five previously unreported mutations. Most mutations were truncated (except 1 missense mutation), including 3 frameshift, 2 nonsense, 3 large deletion, and 2 splice-site variants. The age at commencement of copper-histidine treatment was variable among patients age 7.3 ± 7.5 (0.5-27) months. Despite the treatment, seven patients died before age 5 years, and the remaining patients were severely retarded in neurodevelopment. The poor outcomes of our patients might be related to delayed therapy, but severe ATP7A mutations should be noted as well.

  11. Refolding and purification of histidine-tagged protein by artificial chaperone-assisted metal affinity chromatography.

    Science.gov (United States)

    Dong, Xiao-Yan; Chen, Li-Jun; Sun, Yan

    2009-07-03

    This article has proposed an artificial chaperone-assisted immobilized metal affinity chromatography (AC-IMAC) for on-column refolding and purification of histidine-tagged proteins. Hexahistidine-tagged enhanced green fluorescent protein (EGFP) was overexpressed in Escherichia coli, and refolded and purified from urea-solubilized inclusion bodies by the strategy. The artificial chaperone system was composed of cetyltrimethylammonium bromide (CTAB) and beta-cyclodextrin (beta-CD). In the refolding process, denatured protein was mixed with CTAB to form a protein-CTAB complex. The mixture was then loaded to IMAC column and the complex was bound via metal chelating to the histidine tag. This was followed by washing with a refolding buffer containing beta-CD that removed CTAB from the bound protein and initiated on-column refolding. The effect of the washing time (i.e., on-column refolding time) on mass and fluorescence recoveries was examined. Extensive studies by comparison with other related refolding techniques have proved the advantages of AC-IMAC. In the on-column refolding, the artificial chaperone system suppressed protein interactions and facilitated protein folding to its native structure. So, the on-column refolding by AC-IMAC led to 99% pure EGFP with a fluorescence recovery of 80%. By comparison at a similar final EGFP concentration (0.6-0.8 mg/mL), this fluorescence recovery value was not only much higher than direct dilution (14%) and AC-assisted refolding (26%) in bulk solutions, but also superior to its partner, IMAC (60%). The operating conditions would be further optimized to improve the refolding efficiency.

  12. In silico study of fragile histidine triad interaction domains with MDM2 and p53

    Directory of Open Access Journals (Sweden)

    Ameneh Eslamparast

    2014-01-01

    Full Text Available Background: Fragile histidine triad (FHIT is considered as a member of the histidine triad (HIT nucleotide-binding protein superfamily regarded as a putative tumor suppressor executing crucial role in inhibiting p53 degradation by MDM2. Accumulating evidences indicate FHIT interaction with p53 or MDM2; however, there is no certain study deciphering functional domains of FHIT involving in the interaction with MDM2 and/or p53. In this regard, such evident interaction can spring in mind determining important domains of FHIT binding to MDM2 with regard to p53. Materials and Methods: Since there were not any previous studies appraising complete three-dimensional structures of target molecules, molecular modeling was carried out to construct three-dimensional models of full FHIT, MDM2, P53 and also FHIT segments. Truncated structures of FHIT were created to reveal critical regions engaging in FHIT interaction. Results: Given the shape and shape/electrostatic total energy, FHIT structures (β1-5, (β3-7, α1, and (β5-7, α1 appeared to be better candidates than other structures in interaction with full MDM2. Furthermore, FHIT structures (β6-7, (β6-7, α1, (β4-7, α1 were considered to be better than other structures in interaction with p53. FHIT truncates that interact with MDM2 presented lower energy levels than FHIT truncates interacting with p53. Conclusion: These findings are beneficial to understand the mechanism of the FHIT-MDM2-p53 complex activation for designing inhibitory compounds.

  13. Mercury(II) binds to both of chymotrypsin's histidines, causing inhibition followed by irreversible denaturation/aggregation.

    Science.gov (United States)

    Stratton, Amanda; Ericksen, Matthew; Harris, Travis V; Symmonds, Nick; Silverstein, Todd P

    2017-02-01

    The toxicity of mercury is often attributed to its tight binding to cysteine thiolate anions in vital enzymes. To test our hypothesis that Hg(II) binding to histidine could be a significant factor in mercury's toxic effects, we studied the enzyme chymotrypsin, which lacks free cysteine thiols; we found that chymotrypsin is not only inhibited, but also denatured by Hg(II). We followed the aggregation of denatured enzyme by the increase in visible absorbance due to light scattering. Hg(II)-induced chymotrypsin precipitation increased dramatically above pH 6.5, and free imidazole inhibited this precipitation, implicating histidine-Hg(II) binding in the process of chymotrypsin denaturation/aggregation. Diethylpyrocarbonate (DEPC) blocked chymotrypsin's two histidines (his40 and his57 ) quickly and completely, with an IC50 of 35 ± 6 µM. DEPC at 350 µM reduced the hydrolytic activity of chymotrypsin by 90%, suggesting that low concentrations of DEPC react with his57 at the active site catalytic triad; furthermore, DEPC below 400 µM enhanced the Hg(II)-induced precipitation of chymotrypsin. We conclude that his57 reacts readily with DEPC, causing enzyme inhibition and enhancement of Hg(II)-induced aggregation. Above 500 µM, DEPC inhibited Hg(II)-induced precipitation, and [DEPC] >2.5 mM completely protected chymotrypsin against precipitation. This suggests that his40 reacts less readily with DEPC, and that chymotrypsin denaturation is caused by Hg(II) binding specifically to the his40 residue. Finally, we show that Hg(II)-histidine binding may trigger hemoglobin aggregation as well. Because of results with these two enzymes, we suggest that metal-histidine binding may be key to understanding all heavy metal-induced protein aggregation. © 2017 The Protein Society.

  14. Loss of the histidine kinase DhkD results in mobile mounds during development of Dictyostelium discoideum.

    Directory of Open Access Journals (Sweden)

    Charles K Singleton

    Full Text Available Histidine kinases are receptors for sensing cellular and environmental signals, and in response to the appropriate cue they initiate phosphorelays that regulate the activity of response regulators. The Dictyostelium discoideum genome encodes 15 histidine kinases that function to regulate several processes during the multicellular developmental program, including the slug to culmination transition, osmoregulation, and spore differentiation. While there are many histidine kinases, there is only a single response regulator, RegA. Not surprisingly given the ubiquitous involvement of cAMP in numerous processes of development in Dictyostelium, RegA is a cAMP phosphodiesterase that is activated upon receiving phosphates through a phosphorelay. Hence, all of the histidine kinases characterized to date regulate developmental processes through modulating cAMP production. Here we investigate the function of the histidine kinase DhkD.The dhkD gene was disrupted, and the resulting cells when developed gave a novel phenotype. Upon aggregation, which occurred without streaming, the mounds were motile, a phenotype termed the pollywog stage. The pollywog phenotype was dependent on a functional RegA. After a period of random migration, the pollywogs attempted to form fingers but mostly generated aberrant structures with no tips. While prestalk and prespore cell differentiation occurred with normal timing, proper patterning did not occur. In contrast, wild type mounds are not motile, and the cAMP chemotactic movement of cells within the mound facilitates proper prestalk and prespore patterning, tip formation, and the vertical elongation of the mound into a finger.We postulate that DhkD functions to ensure the proper cAMP distribution within mounds that in turn results in patterning, tip formation and the transition of mounds to fingers. In the absence of DhkD, aberrant cell movements in response to an altered cAMP distribution result in mound migration, a lack of

  15. Dirac Induction for loop groups

    NARCIS (Netherlands)

    Posthuma, H.

    2011-01-01

    Using a coset version of the cubic Dirac operators for affine Lie algebras, we give an algebraic construction of the Dirac induction homomorphism for loop group representations. With this, we prove a homogeneous generalization of the Weyl-Kac character formula and show compatibility with Dirac

  16. Loop quantum cosmology and singularities.

    Science.gov (United States)

    Struyve, Ward

    2017-08-15

    Loop quantum gravity is believed to eliminate singularities such as the big bang and big crunch singularity. This belief is based on studies of so-called loop quantum cosmology which concerns symmetry-reduced models of quantum gravity. In this paper, the problem of singularities is analysed in the context of the Bohmian formulation of loop quantum cosmology. In this formulation there is an actual metric in addition to the wave function, which evolves stochastically (rather than deterministically as the case of the particle evolution in non-relativistic Bohmian mechanics). Thus a singularity occurs whenever this actual metric is singular. It is shown that in the loop quantum cosmology for a homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker space-time with arbitrary constant spatial curvature and cosmological constant, coupled to a massless homogeneous scalar field, a big bang or big crunch singularity is never obtained. This should be contrasted with the fact that in the Bohmian formulation of the Wheeler-DeWitt theory singularities may exist.

  17. Loop quantum gravity and observations

    CERN Document Server

    Barrau, A

    2014-01-01

    Quantum gravity has long been thought to be completely decoupled from experiments or observations. Although it is true that smoking guns are still missing, there are now serious hopes that quantum gravity phenomena might be tested. We review here some possible ways to observe loop quantum gravity effects either in the framework of cosmology or in astroparticle physics.

  18. Scalar one-loop integrals

    NARCIS (Netherlands)

    Veltman, M.J.G.; Hooft, G. 't

    1979-01-01

    The completely general one-loop scalar one-, two-, three- and four-point functions are studied. Also an integral occurring in connection with soft bremsstrahlung is considered. Formulas in terms of Spence functions are given. An expansion for Spence functions with complex argument is presented.

  19. Two loops in eleven dimensions

    CERN Document Server

    Green, Michael B.; Vanhove, Pierre; Green, Michael B.; Kwon, Hwang-h.; Vanhove, Pierre

    2000-01-01

    The two-loop Feynman diagram contribution to the four-graviton amplitude of eleven-dimensional supergravity compactified on a two-torus, T^2, is analyzed in detail. The Schwinger parameter integrations are re-expressed as integration over the moduli space of a second torus, \\hat T^2, which enables the leading low-momentum contribution to be evaluated in terms of maps of \\hat T^2 into T^2. The ultraviolet divergences associated with boundaries of moduli space are regularized in a manner that is consistent with the expected duality symmetries of string theory. This leads to an exact expression for terms of order contraction of four Weyl tensors), thereby extending earlier results for the R^4 term that were based on the one-loop eleven-dimensional amplitude. Precise agreement is found with terms in type IIA and IIB superstring theory that arise from the low energy expansion of the tree-level and one-loop string amplitudes and predictions are made for the coefficients of certain two-loop string theory terms as we...

  20. INFLUENCE OF THE COMPOSITION OF MILK POWDER ON WATER ACTIVITY APPLYING THE GAB MODEL

    Directory of Open Access Journals (Sweden)

    Julio Gil

    2016-03-01

    Full Text Available The use of sorption isotherms at 25°C, for analyze the influence of water activity (aw of the different compositions of whole milk, skim and low in lactose powder, was study. Precisely the latter incorporating previous work can extend the differential behavior of the various components. The work can establish the relationship between the moisture content of the milk powders studied, with its water activity (aw. The experimental results are evaluated with reference model GAB, noting that the layout of the isotherms and the model parameters were successfully adjusted to the values obtained. The clear influence of the presence of monosaccharides (glucose and galactose in the reduced-lactose milk, which reduce the water activity aw from greater value of 0.4 due to the higher solubility of these, is observed. The fat content in whole milk, not being adsorbent is manifested in higher values for water activity.

  1. Dataset of water activity measurements of alcohol:water solutions using a Tunable Diode Laser.

    Science.gov (United States)

    Allan, Matthew; Mauer, Lisa J

    2017-06-01

    The data presented in this article are related to the research article entitled "RH-temperature phase diagrams of hydrate forming deliquescent crystalline ingredients" (Allan and Mauer, 2017) [1]. The data are water activity measurements of alcohol:water solutions (methanol:water and ethanol:water solutions at varying molar ratios) at different temperatures collected using the Tunable Diode Laser by Decagon Devices. The measured water activities of ethanol:water solutions were correlated to the initial volumetric ratios to produce polynomial equations that can be used to calculate the needed initial volumetric ratios for water activity controlled solutions. The data sets and polynomial equations are provided to enable extended analyses and applications of the data and calculations for generating and using controlled water activity solutions containing alcohol. An example application of these data is described in the research article mentioned above.

  2. INFLUENCE OF THE COMPOSITION OF MILK POWDER ON WATER ACTIVITY APPLYING THE GAB MODEL

    OpenAIRE

    Julio Gil; Paola Yacanto; Silvana Muratona; Clidia R. Abaca; Sylvia M. Esquenoni

    2016-01-01

    The use of sorption isotherms at 25°C, for analyze the influence of water activity (aw) of the different compositions of whole milk, skim and low in lactose powder, was study. Precisely the latter incorporating previous work can extend the differential behavior of the various components. The work can establish the relationship between the moisture content of the milk powders studied, with its water activity (aw). The experimental results are evaluated with reference model GAB, noting that the...

  3. Glycerol enhances fungal germination at the water-activity limit for life

    OpenAIRE

    Stevenson, Andrew; Hamill, Philip G.; Medina, Ángel; Kminek, Gerhard; Rummel, John D.; Dijksterhuis, Jan; Timson, David J.; Magan, Naresh; Leong, Su-lin L.; Hallsworth, John E.

    2016-01-01

    For the most-extreme fungal xerophiles, metabolic activity and cell division typically halts between 0.700 and 0.640 water activity (approximately 70.0-64.0% relative humidity). Here, we investigate whether glycerol can enhance xerophile germination under acute water-activity regimes, using an experimental system which represents the biophysical limit of Earth's biosphere. Spores of a variety of species including Aspergillus penicillioides, Eurotium halophilicum, Xerochrysium xerophilium (for...

  4. Critical water activity and amorphous state for optimal preservation of lyophilised lactic acid bacteria

    OpenAIRE

    Passot, Stéphanie; Cenard, Stéphanie; Douania, Inès; Trelea, Ioan Cristian; Fonseca, Fernanda

    2012-01-01

    International audience; The aim of this study was to investigate the influence of the water activity on the stability of lyophilised lactic acid bacteria, especially in the solid glassy region. Lactobacillus bulgaricus CFL1 was co-lyophilised with sucrose and stored under controlled relative humidity at 25 °C. Glass transition temperature (T g), water activity, water content and loss of specific acidification activity during storage were determined. The rates of bacteria degradation were anal...

  5. Dietary histidine requirement to reduce the risk and severity of cataracts is higher than the requirement for growth in Atlantic salmon smolts, independently of the dietary lipid source.

    Science.gov (United States)

    Remø, S C; Hevrøy, E M; Olsvik, P A; Fontanillas, R; Breck, O; Waagbø, R

    2014-05-28

    The present study was carried out to investigate whether the dietary histidine requirement to reduce cataract development is higher than that for growth in Atlantic salmon smolts (Salmo salar L.) after seawater transfer and whether dietary vegetable oils contribute to cataractogenesis. Duplicate groups of salmon smolts were fed ten experimental diets with either fish oil (FO) or a vegetable oil (VO) mix replacing 70 % FO and histidine at five target levels (10, 12, 14, 16 and 18 g His/kg diet) for 13 weeks after seawater transfer. The VO diet-fed fish exhibited somewhat inferior growth and feed intakes compared with the FO diet-fed fish, irrespective of the dietary histidine concentration. Both cataract prevalence and severity were negatively correlated with the dietary histidine concentration, while lens N-acetyl-histidine (NAH) concentrations were positively correlated with it. The fatty acid profiles of muscle, heart and lens reflected that of the dietary oils to a descending degree and did not affect the observed cataract development. Muscle, heart and brain histidine concentrations reflected dietary histidine concentrations, while the corresponding tissue imidazole (anserine, carnosine and NAH) concentrations appeared to saturate differently with time. The expression level of liver histidase was not affected by the dietary histidine concentration, while the liver antioxidant response was affected in the VO diet-fed fish on a transcriptional level. The lowest severity of cataracts could be achieved by feeding 13·4 g His/kg feed, independently of the dietary lipid source. However, the present study also suggests that the dietary histidine requirement to minimise the risk of cataract development is 14·4 g His/kg feed.

  6. Modified Continuous Loop Technique for microvascular anastomosis

    Directory of Open Access Journals (Sweden)

    Kumar Pramod

    2001-01-01

    Full Text Available A modified method of continuous loop technique for microvascular anastomosis is described. The handling of loop is easier & even last suture is placed under vision. This makes the microvascular anastomosis easier and simpler.

  7. A True Open-Loop Synchronization Technique

    DEFF Research Database (Denmark)

    Golestan, Saeed; Vidal, Ana; Yepes, Alejandro G.

    2016-01-01

    Synchronization techniques can be broadly classified into two major categories: Closed-loop and open-loop methods. The open-loop synchronization (OLS) techniques, contrary to the closed-loop ones, are unconditionally stable and benefit from a fast dynamic response. Their performance, however, tends...... is to develop a true OLS (and therefore, unconditionally stable) technique without any need for the calculation of sine and cosine functions. The effectiveness of the proposed synchronization technique is confirmed through the simulation and experimental results....

  8. Estimation of complex permittivity using loop antenna

    DEFF Research Database (Denmark)

    Lenler-Eriksen, Hans-Rudolph; Meincke, Peter

    2004-01-01

    A method for estimating the complex permittivity of materials in the vicinity of a loop antenna is proposed. The method is based on comparing measured and numerically calculated input admittances for the loop antenna.......A method for estimating the complex permittivity of materials in the vicinity of a loop antenna is proposed. The method is based on comparing measured and numerically calculated input admittances for the loop antenna....

  9. Loop connectors in dentogenic diastema

    Directory of Open Access Journals (Sweden)

    Sanjna Nayar

    2015-01-01

    Full Text Available Patients with a missing tooth along with diastema have limited treatment options to restore the edentulous space. The use of a conventional fixed partial denture (FPD to replace the missing tooth may result in too wide anterior teeth leading to poor esthetics. Loss of anterior teeth with existing diastema may result in excess space available for pontic. This condition presents great esthetic challenge for prosthodontist. If implant supported prosthesis is not possible because of inadequate bone support, FPD along with loop connector may be a treatment option to maintain the diastema and provide optimal esthetic restoration. Here, we report a clinical case where FPD along with loop connector was used to achieve esthetic rehabilitation in maxillary anterior region in which midline diastema has been maintained.

  10. Processing of alpha4 integrin by the proprotein convertases: histidine at position P6 regulates cleavage.

    Science.gov (United States)

    Bergeron, Eric; Basak, Ajoy; Decroly, Etienne; Seidah, Nabil G

    2003-07-15

    The proprotein convertases (PCs) participate in the limited proteolysis of integrin alpha4 subunit at the H(592)VISKR(597) downward arrow ST site (where underlined residues indicate positively charged amino acids important for PC-mediated cleavage and downward arrow indicates the cleavage site), since this cleavage is inhibited by the serpin alpha1-PDX (alpha1-antitrypsin Portland). Co-expression of alpha4 with each convertase in LoVo (furin-deficient human colon carcinoma) cells revealed that furin and proprotein convertase 5A (PC5A) are the best pro-alpha4 convertases. In agreement, processing of endogenous pro-alpha4 in human lymphoblastoid CEM-T4 cells was enhanced greatly in stable transfectants overexpressing either enzyme. In many leucocyte cell lines, the expression of furin closely correlated with the endogenous processing efficacy, suggesting that furin is a candidate pro-alpha4 convertase. Mutational analysis showed that replacement of P1 Arg(597) with alanine (R597A) abrogated cleavage, whereas the P6 mutant H592R is even better processed by the endogenous convertases of Chinese-hamster ovary CHO-K1 cells. In vitro kinetic studies using synthetic peptides confirmed the importance of a positively charged residue at P6 and showed that wild-type alpha4 processing is performed best by furin and PC5A at acidic and neutral pHs, respectively. Biosynthetic analysis of pro-alpha4 and its H592R and H592K mutants in the presence or absence of the weak base, NH(4)Cl, revealed that the P6 histidine residue renders its processing by furin sensitive to cellular pH. This suggests that pro-alpha4 cleavage occurs preferentially in acidic compartments. In conclusion, although the accepted furin processing motif is Arg-Xaa-(Lys/Arg)-Arg downward arrow, our data further extend it to include a regulatory histidine residue at P6 in precursors that lack a basic residue at P4.

  11. Oxidative Stress Tolerance by Calcium and Histidine in Two Tomato Cultivars Under Nickel Stress

    Directory of Open Access Journals (Sweden)

    Mozafari H.

    2014-05-01

    Full Text Available We investigated calcium (Ca and L-histidine (His interaction on nickel (Ni-induced oxidative stress tolerance in two tomato (Solanum lycopersicum Mill. cultivars including Cal-J N3 and Petoearly CH. CaCl2 (0 and 300 µM and L-histidine (0 and 300 µM effects on the oxidative responses in these cultivars cultured were compared in the hydroponic media under Ni stress (NiSO4; 0,150 and 300 µM. The activities of antioxidative enzymes including catalase (CAT, guaiacol peroxidase (GPX, ascorbate peroxidase (APX, superoxide dismutase (SOD and total content of proteins, malondialdehyde (MDA, other aldehydes, H2O2, Ca2+, Ni2+, ascorbate (ASC, dehydroascorbate (DHA and electrolytes leakage (EL were determined. The obtained results indicated that the application of Ca and His generally reduced oxidative markers such as the contents of EL, H2O2, MDA and activity of CAT as well as the Ni2+content of root and shoot organs under nickel toxicity, while application of Ni treatment without Ca+His increased these oxidative parameters and accumulation of Ni2+, compared to the control. Applying Ni without Ca and His has resulted in reduction of GPX, APX and SOD activities as well as concentrations of root and shoot Ca2+and ASC in the two mentioned cultivars. Application of Ca and His lead to the elevated contents of Ca2+ and ASC, increased activities of GPX, APX and SOD as well as inhibition of Ni2+ accumulation differently in both cultivars. Ca and His also alleviated the adverse effects of Ni stress on the selected investigated parameters especially in Petoearly CH cultivar. Thus, interaction of Ca and His appeared to improve adaptive responses to Ni stress leading to decreasing Ni-induced oxidative stress in the tomato plants. Therefore, our results suggest that Ca+His alleviated nickel-induced oxidative stress by uptake and inhibition of translocation of Ni2+ plus Ni chelating mechanism improvement in the tomato cultivars.

  12. Structural and Functional Analysis of the Escherichia coli Acid-Sensing Histidine Kinase EvgS.

    Science.gov (United States)

    Sen, Hrishiraj; Aggarwal, Nikhil; Ishionwu, Chibueze; Hussain, Nosheen; Parmar, Chandni; Jamshad, Mohammed; Bavro, Vassiliy N; Lund, Peter A

    2017-09-15

    The EvgS/EvgA two-component system of Escherichia coli is activated in response to low pH and alkali metals and regulates many genes, including those for the glutamate-dependent acid resistance system and a number of efflux pumps. EvgS, the sensor kinase, is one of five unconventional histidine kinases (HKs) in E. coli and has a large periplasmic domain and a cytoplasmic PAS domain in addition to phospho-acceptor, HK and dimerization, internal receiver, and phosphotransfer domains. Mutations that constitutively activate the protein at pH 7 map to the PAS domain. Here, we built a homology model of the periplasmic region of EvgS, based on the structure of the equivalent region of the BvgS homologue, to guide mutagenesis of potential key residues in this region. We show that histidine 226 is required for induction and that it is structurally colocated with a proline residue (P522) at the top of the predicted transmembrane helix that is expected to play a key role in passing information to the cytoplasmic domains. We also show that the constitutive mutations in the PAS domain can be further activated by low external pH. Expression of the cytoplasmic part of the protein alone also gives constitutive activation, which is lost if the constitutive PAS mutations are present. These findings are consistent with a model in which EvgS senses both external and internal pH and is activated by a shift from a tight inactive to a weak active dimer, and we present an analysis of the purified cytoplasmic portion of EvgS that supports this. IMPORTANCE One of the ways bacteria sense their environment is through two-component systems, which have one membrane-bound protein to do the sensing and another inside the cell to turn genes on or off in response to what the membrane-bound protein has detected. The membrane-bound protein must thus be able to detect the stress and signal this detection event to the protein inside the cell. To understand this process, we studied a protein that helps

  13. Metabolic profiling of plasma amino acids shows that histidine increases following the consumption of pork

    Directory of Open Access Journals (Sweden)

    Samman S

    2014-06-01

    Full Text Available Samir Samman,1 Ben Crossett,2 Miles Somers,1 Kirstine J Bell,1 Nicole T Lai,1,3 David R Sullivan,3 Peter Petocz4 1Discipline of Nutrition and Metabolism, 2Discipline of Proteomics and Biotechnology, School of Molecular Bioscience, University of Sydney, Sydney, NSW, Australia; 3Department of Clinical Biochemistry, Royal Prince Alfred Hospital, Sydney, NSW, Australia; 4Department of Statistics, Macquarie University, Sydney, NSW, Australia Abstract: Amino acid (AA status is determined by factors including nutrition, metabolic rate, and interactions between the metabolism of AA, carbohydrates, and lipids. Analysis of the plasma AA profile, together with markers of glucose and lipid metabolism, will shed light on metabolic regulation. The objectives of this study were to investigate the acute responses to the consumption of meals containing either pork (PM or chicken (CM, and to identify relationships between plasma AA and markers of glycemic and lipemic control. A secondary aim was to explore AA predictors of plasma zinc concentrations. Ten healthy adults participated in a postprandial study on two separate occasions. In a randomized cross-over design, participants consumed PM or CM. The concentrations of 21 AA, glucose, insulin, triglycerides, nonesterified fatty acids, and zinc were determined over 5 hours postprandially. The meal composition did not influence glucose, insulin, triglyceride, nonesterified fatty acid, or zinc concentrations. Plasma histidine was higher following the consumption of PM (P=0.014, with consistently higher changes observed after 60 minutes (P<0.001. Greater percentage increases were noted at limited time points for valine and leucine + isoleucine in those who consumed CM compared to PM. In linear regression, some AAs emerged as predictors of the metabolic responses, irrespective of the meal that was consumed. The present study demonstrates that a single meal of PM or CM produces a differential profile of AA in the

  14. Solution Equilibria between Aluminum(III) Ion and L-histidine or L-tyrosine

    Science.gov (United States)

    Jelic, Ratomir; Dzajevic, Dragana; Cvijovic, Mirjana

    2002-01-01

    Toxic effects due to high aluminum body loads were observed in a number of conditions following ingestion of Al-containing antacids. Bio-availability of aluminum depends not only on the solubility of the ingested salt but also on the physico-chemical properties of the soluble Al complexes formed in body fluids. Amino acids may, upon interaction with Al-salts, form absorbable Al-complexes. Hence, complex formation equilibria between Al3+ and either, L- histidine or L-tyrosine were studied by glass electrode potentiometric (0.1 mol/L LiCl ionic medium, 298 K), proton NMR and uv spectrophotometric measurements. Non linear least squares treatment of the potentiometric data indicates that in the concentration ranges: 0.5≤CA1≤2.0 ; 1.0≤CHis≤10.0; 2.5≤PH≤6.5, in Al3+ + His solutions, the following complexes (with log overall stability constants given in parenthesis) are formed: Al(HHis)3+(12.21±0.08); Al(His)2+, (7.25±0.08); and Al(HHis)His2+, (20.3±0.1). In Al3+ + Tyr solutions in the concentration range 1.0≤CTyr≤3.0 mmol/L and ligand to metal concentration ratio from 2:1 to 3:1, in the pH interval from 3.0 to 6.5 the formation of the following complexes was detected: Al(HTyr)2+, (12.72±0.09); Al(Tyr)2+, (10.16±0.03) and Al(OH)2Tyr , (2.70±0.05). Proton NMR data indicate that in Al(His)2+ complex histidine acts as a monodentate ligand but its bidentate coordination is possible with carboxylate oxygen and imidazole 1-nitrogen as donors. In Al(HTyr)3+ complex tyrosine is a monodentate ligand with carboxylate oxygen as donor. The mechanism of the formation of complexes in solution is discussed as well as their possible role in aluminum toxicity. PMID:18476000

  15. Chiral logarithms to five loops

    OpenAIRE

    Bissegger, Moritz; Fuhrer, Andreas

    2006-01-01

    We investigate two specific Green functions in the framework of chiral perturbation theory. We show that, using analyticity and unitarity, their leading logarithmic singularities can be evaluated in the chiral limit to any desired order in the chiral expansion, with a modest calculational cost. The claim is illustrated with an evaluation of the leading logarithm for the scalar two-point function to five-loop order.

  16. Glycerol enhances fungal germination at the water-activity limit for life.

    Science.gov (United States)

    Stevenson, Andrew; Hamill, Philip G; Medina, Ángel; Kminek, Gerhard; Rummel, John D; Dijksterhuis, Jan; Timson, David J; Magan, Naresh; Leong, Su-Lin L; Hallsworth, John E

    2017-03-01

    For the most-extreme fungal xerophiles, metabolic activity and cell division typically halts between 0.700 and 0.640 water activity (approximately 70.0-64.0% relative humidity). Here, we investigate whether glycerol can enhance xerophile germination under acute water-activity regimes, using an experimental system which represents the biophysical limit of Earth's biosphere. Spores from a variety of species, including Aspergillus penicillioides, Eurotium halophilicum, Xerochrysium xerophilum (formerly Chrysosporium xerophilum) and Xeromyces bisporus, were produced by cultures growing on media supplemented with glycerol (and contained up to 189 mg glycerol g dry spores-1 ). The ability of these spores to germinate, and the kinetics of germination, were then determined on a range of media designed to recreate stresses experienced in microbial habitats or anthropogenic systems (with water-activities from 0.765 to 0.575). For A. penicillioides, Eurotium amstelodami, E. halophilicum, X. xerophilum and X. bisporus, germination occurred at lower water-activities than previously recorded (0.640, 0.685, 0.651, 0.664 and 0.637 respectively). In addition, the kinetics of germination at low water-activities were substantially faster than those reported previously. Extrapolations indicated theoretical water-activity minima below these values; as low as 0.570 for A. penicillioides and X. bisporus. Glycerol is present at high concentrations (up to molar levels) in many types of microbial habitat. We discuss the likely role of glycerol in expanding the water-activity limit for microbial cell function in relation to temporal constraints and location of the microbial cell or habitat. The findings reported here have also critical implications for understanding the extremes of Earth's biosphere; for understanding the potency of disease-causing microorganisms; and in biotechnologies that operate at the limits of microbial function. © 2016 The Authors. Environmental Microbiology

  17. Homo- and Heteroligand Nickel(II Complexes with Benzoic and para-Methoxybenzoic Acid Hydrazides and L-Histidine

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    N.V. Troshanin

    2017-03-01

    Full Text Available Complex formation of nickel(II with benzoic, para-methoxybenzoic acid hydrazides, and L-histidine have been studied by the methods of pH-metric titrimetry, spectrophotometry, and mathematical modelling in aqueous solutions with 1.0 mol dm–3 KNO3 as background at 298 K. Dissociation constants of ligands, as well as composition, formation constants, and spectral parameters of homo- and heteroligand complexes have been determined. It has been shown that stability of the complexes formed with para-methoxybenzoic acid hydrazide is higher than with benzoic acid hydrazide, which is consistent with the electron-donor properties of the methoxy group. Extra stabilization of the nickel(II heteroligand complexes with benzoic (para-methoxybenzoic acid hydrazide and L-histidine has been discovered and interpreted.

  18. A Rhizobium radiobacter Histidine Kinase Can Employ Both Boolean AND and OR Logic Gates to Initiate Pathogenesis.

    Science.gov (United States)

    Fang, Fang; Lin, Yi-Han; Pierce, B Daniel; Lynn, David G

    2015-10-12

    The molecular logic gates that regulate gene circuits are necessarily intricate and highly regulated, particularly in the critical commitments necessary for pathogenesis. We now report simple AND and OR logic gates to be accessible within a single protein receptor. Pathogenesis by the bacterium Rhizobium radiobacter is mediated by a single histidine kinase, VirA, which processes multiple small molecule host signals (phenol and sugar). Mutagenesis analyses converged on a single signal integration node, and finer functional analyses revealed that a single residue could switch VirA from a functional AND logic gate to an OR gate where each of two signals activate independently. Host range preferences among natural strains of R. radiobacter correlate with these gate logic strategies. Although the precise mechanism for the signal integration node requires further analyses, long-range signal transmission through this histidine kinase can now be exploited for synthetic signaling circuits. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Role of histidine-related compounds to intracellular buffering in fish skeletal muscle.

    Science.gov (United States)

    Abe, H; Dobson, G P; Hoeger, U; Parkhouse, W S

    1985-10-01

    Histidine-related compounds (HRC) were analyzed in fish skeletal muscle as a means of identifying their precise role in intracellular buffering. Fish muscle was used because it contains two functionally and spatially distinct fiber types, red and white. Two fish species, rainbow trout (Salmo gairdneri) and the Pacific blue marlin (Makaira nigricans), were studied because these species demonstrate widely different activity patterns. Marlin red and white muscle buffer capacity was two times higher than trout with white muscle, buffering being two times greater than red in both species. Buffer capacity was highest in the 6.5-7.5 pH range for all tissues, which corresponded to their high anserine levels. The titrated HRC buffering was greater than the observed HRC buffering, which suggested that not all HRC were available to absorb protons. The HRC contribution to total cellular buffering varied from a high of 62% for marlin white to a low of 7% for trout red. The other principal buffers were found to be phosphate and protein with taurine contributing within red muscle in the 7.0-8.0 pH range. HRC were found to be dominant in skeletal muscle buffering by principally accounting for the buffering capacity differences found between the species and fiber types.

  20. Rational Design of Selective Adenine-Based Scaffolds for Inactivation of Bacterial Histidine Kinases.

    Science.gov (United States)

    Goswami, Manibarsha; Wilke, Kaelyn E; Carlson, Erin E

    2017-10-12

    Bacterial histidine kinases (HKs) are quintessential regulatory enzymes found ubiquitously in bacteria. Apart from their regulatory roles, they are also involved in the production of virulence factors and conferring resistance to various antibiotics in pathogenic microbes. We have previously reported compounds that inhibit multiple HKs by targeting the conserved catalytic and ATP-binding (CA) domain. Herein, we conduct a detailed structure-activity relationship assessment of adenine-based inhibitors using biochemical and docking methods. These studies have resulted in several observations. First, interaction of an inhibitor's amine group with the conserved active-site Asp is essential for activity and likely dictates its orientation in the binding pocket. Second, a N-NH-N triad in the inhibitor scaffold is highly preferred for binding to conserved Gly:Asp:Asn residues. Lastly, hydrophobic electron-withdrawing groups at several positions in the adenine core enhance potency. The selectivity of these inhibitors was tested against heat shock protein 90 (HSP90), which possesses a similar ATP-binding fold. We found that groups that target the ATP-lid portion of the catalytic domain, such as a six-membered ring, confer selectivity for HKs.

  1. The Rational Design, Synthesis, and Antimicrobial Properties of Thiophene Derivatives That Inhibit Bacterial Histidine Kinases.

    Science.gov (United States)

    Boibessot, Thibaut; Zschiedrich, Christopher P; Lebeau, Alexandre; Bénimèlis, David; Dunyach-Rémy, Catherine; Lavigne, Jean-Philippe; Szurmant, Hendrik; Benfodda, Zohra; Meffre, Patrick

    2016-10-13

    The emergence of multidrug-resistant bacteria emphasizes the urgent need for novel antibacterial compounds targeting unique cellular processes. Two-component signal transduction systems (TCSs) are commonly used by bacteria to couple environmental stimuli to adaptive responses, are absent in mammals, and are embedded in various pathogenic pathways. To attenuate these signaling pathways, we aimed to target the TCS signal transducer histidine kinase (HK) by focusing on their highly conserved adenosine triphosphate-binding domain. We used a structure-based drug design strategy that begins from an inhibitor-bound crystal structure and includes a significant number of structurally simplifiying "intuitive" modifications to arrive at the simple achiral, biaryl target structures. Thus, ligands were designed, leading to a series of thiophene derivatives. These compounds were synthesized and evaluated in vitro against bacterial HKs. We identified eight compounds with significant inhibitory activities against these proteins, two of which exhibited broad-spectrum antimicrobial activity. The compounds were also evaluated as adjuvants for the treatment of resistant bacteria. One compound was found to restore the sensivity of these bacteria to the respective antibiotics.

  2. Histidine-rich glycoprotein can prevent development of mouse experimental glioblastoma.

    Directory of Open Access Journals (Sweden)

    Maria Kärrlander

    Full Text Available Extensive angiogenesis, formation of new capillaries from pre-existing blood vessels, is an important feature of malignant glioma. Several antiangiogenic drugs targeting vascular endothelial growth factor (VEGF or its receptors are currently in clinical trials as therapy for high-grade glioma and bevacizumab was recently approved by the FDA for treatment of recurrent glioblastoma. However, the modest efficacy of these drugs and emerging problems with anti-VEGF treatment resistance welcome the development of alternative antiangiogenic therapies. One potential candidate is histidine-rich glycoprotein (HRG, a plasma protein with antiangiogenic properties that can inhibit endothelial cell adhesion and migration. We have used the RCAS/TV-A mouse model for gliomas to investigate the effect of HRG on brain tumor development. Tumors were induced with platelet-derived growth factor-B (PDGF-B, in the presence or absence of HRG. We found that HRG had little effect on tumor incidence but could significantly inhibit the development of malignant glioma and completely prevent the occurrence of grade IV tumors (glioblastoma.

  3. Hypothalamic L-Histidine Decarboxylase Is Up-Regulated During Chronic REM Sleep Deprivation of Rats.

    Directory of Open Access Journals (Sweden)

    Gloria E Hoffman

    Full Text Available A competition of neurobehavioral drives of sleep and wakefulness occurs during sleep deprivation. When enforced chronically, subjects must remain awake. This study examines histaminergic neurons of the tuberomammillary nucleus of the posterior hypothalamus in response to enforced wakefulness in rats. We tested the hypothesis that the rate-limiting enzyme for histamine biosynthesis, L-histidine decarboxylase (HDC, would be up-regulated during chronic rapid eye movement sleep deprivation (REM-SD because histamine plays a major role in maintaining wakefulness. Archived brain tissues of male Sprague Dawley rats from a previous study were used. Rats had been subjected to REM-SD by the flowerpot paradigm for 5, 10, or 15 days. For immunocytochemistry, rats were transcardially perfused with acrolein-paraformaldehyde for immunodetection of L-HDC; separate controls used carbodiimide-paraformaldehyde for immunodetection of histamine. Immunolocalization of histamine within the tuberomammillary nucleus was validated using carbodiimide. Because HDC antiserum has cross-reactivity with other decarboxylases at high antibody concentrations, titrations localized L-HDC to only tuberomammillary nucleus at a dilution of ≥ 1:300,000. REM-SD increased immunoreactive HDC by day 5 and it remained elevated in both dorsal and ventral aspects of the tuberomammillary complex. Our results suggest that up-regulation of L-HDC within the tuberomammillary complex during chronic REM-SD may be responsible for maintaining wakefulness.

  4. Partial alanine scan of mast cell degranulating peptide (MCD): importance of the histidine- and arginine residues.

    Science.gov (United States)

    Buku, Angeliki; Mendlowitz, Milton; Condie, Barry A; Price, Joseph A

    2004-06-01

    The influence of the two histidine and two arginine residues of mast cell degranulating peptide (MCD) in activity and binding was studied by replacing these amino acids in the MCD sequence with L-alanine. Their histamine releasing activity was determined on rat peritoneal mast cells. Their binding affinity to the FcepsilonRIalpha binding subunit of the human mast cell receptor protein, was carried out using fluorescence polarization. The histamine assay showed that replacement of His13 by Ala o ccurred without loss of activity compared with the activity of MCD. Alanine substitutions for Arg7 and His8 resulted in an approximately 40 fold increase, and for Arg16 in a 14-fold increase in histamine-releasing activity of MCD. The binding affinities of the analogs were tested by competitive displacement of bound fluorescent MCD peptide from the FcepsilonRIalpha binding protein of the mast cell receptor by the Ala analogs using fluorescence polarization. The analogs Ala8 (for His) and Ala16 (for Arg) showed the same binding affinities as MCD, whereas analog Ala7 (for Arg) and analog Ala13 (for His) showed slightly better binding affinity than the parent compound. This study showed that the introduction of alanine residues in these positions resulted in MCD agonists of diverse potency. These findings will be useful in further MCD structure-activity studies.

  5. Acute hyponatremia after cardioplegia by histidine-tryptophane-ketoglutarate – a retrospective study

    Directory of Open Access Journals (Sweden)

    Lindner Gregor

    2012-06-01

    Full Text Available Abstract Background Hyponatremia is the most common electrolyte disorder in hospitalized patients and is known to be associated with increased mortality. The administration of antegrade single-shot, up to two liters, histidine-tryptophane-ketoglutarate (HTK solution for adequate electromechanical cardiac arrest and myocardial preservation during minimally invasive aortic valve replacement (MIAVR is a standard procedure. We aimed to determine the impact of HTK infusion on electrolyte and acid–base balance. Methods In this retrospective analysis we reviewed data on patient characteristics, type of surgery, arterial blood gas analysis during surgery and intra-/postoperative laboratory results of patients receiving surgery for MIAVR at a large tertiary care university hospital. Results A total of 25 patients were included in the study. All patients were normonatremic at start of surgery. All patients developed hyponatremia after administration of HTK solution with a significant drop of serum sodium of 15 mmol/L (p  Conclusions Acute hyponatremia during cardioplegia with HTK solution is isotonic and should probably not be corrected without presence of hypotonicity as confirmed by measurement of serum osmolality.

  6. Identification of Plasmodium falciparum isolates lacking histidine-rich protein 2 and 3 in Eritrea.

    Science.gov (United States)

    Menegon, Michela; L'Episcopia, Mariangela; Nurahmed, Abduselam M; Talha, Albadawi A; Nour, Bakri Y M; Severini, Carlo

    2017-11-01

    The histidine-rich protein 2 of Plasmodium falciparum is the most common malaria antigen targeted by rapid diagnostic tests for the specific diagnosis of P. falciparum. Recently, pfhrp2 gene deletions have been documented in P. falciparum isolates from South America and some multiple endemic countries in Africa and Asia. Parasites with such gene deletions can produce false negative diagnostic results using HRP2-based rapid diagnostic kits. In the present work, the prevalence of P. falciparum parasites lacking pfhrp2, pfhrp3, which produces a second P. falciparum antigen that is recognized by PfHRP2 -based rapid diagnostic tests, and their flanking genes was evaluated in 135 P. falciparum isolates from Gash Barka region and in 9 isolates from Debub region, in Eritrea. In the analyzed samples, 56% (81/144) of isolates were pfhrp2/pfhrp3 positive, while 9.7% (14/144) showed deletion of exon 2 of pfhrp2 gene and 43% (62/144) of isolates lacked the pfhrp3 gene. These results suggest that the pfhrp2 and pfhrp3 deletion phenomenon is present in a considerable proportion in the study areas, thus making the HRP2/3 based rapid diagnostic tests not completely reliable for malaria diagnosis in Eritrea. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Functional reconstitution of Staphylococcus aureus truncated AgrC histidine kinase in a model membrane system.

    Directory of Open Access Journals (Sweden)

    Lina Wang

    Full Text Available The integral membrane protein AgrC is a histidine kinase whose sensor domains interact with an autoinducing peptide, resulting in a series of downstream responses. In this study, truncated AgrCTM5-6C and AgrCTM5-6C-GFP with GFP as a reporter gene were produced using a bacterial system. Purified AgrCTM5-6C and AgrCTM5-6C-GFP were reconstituted into liposomes by a detergent-mediated method. To achieve high-yield protein incorporation, we investigated the effect of different detergents on protein reconstitution efficiency. The highest incorporation was found with N,N-dimethyldode-cylamine N-oxide during complete liposome solubilization, which resulted in a yield of 85±5%. The COOH-terminus of the protein AgrCTM5-6C was almost exclusively oriented towards the inside of the vesicles. AgrCTM5-6C in proteoliposomes exhibited approximately a 6-fold increase in constitutive activity compared with AgrCTM5-6C in detergent micelles. The reconstitution of AgrCTM5-6C or AgrCTM5-6C-GFP was characterized using dynamic light scattering, fluorescence microscopy, and transmission electron microscopy. Based on the results, the optimal conditions for protein incorporation were defined. These findings contribute to the study of membrane protein structure and function in vitro using a reconstitution system.

  8. Corticotropin-releasing hormone receptor-1 and histidine decarboxylase expression in chronic urticaria.

    Science.gov (United States)

    Papadopoulou, Nikoletta; Kalogeromitros, Demetrios; Staurianeas, Nikolaos G; Tiblalexi, Despina; Theoharides, Theoharis C

    2005-11-01

    Certain skin disorders, such as contact dermatitis and chronic urticaria, are characterized by inflammation involving mast cells and worsen by stress. The underlying mechanism of this effect, however, is not known. The skin appears to have the equivalent of a hypothalamic-pituitary-adrenal (HPA) axis, including local expression of corticotropin-releasing hormone (CRH) and its receptors (CRH-R). We have reported that acute stress and intradermal administration of CRH stimulate skin mast cells and increase vascular permeability through CRH-R1 activation. In this study, we investigated the expression of CRH-R1, the main CRH-R subtype in human skin, and the mast cell related gene histidine decarboxylase (HDC), which regulates the production of histamine, in normal and pathological skin biopsies. Quantitative real time PCR revealed that chronic urticaria expresses high levels of CRH-R1 and HDC as compared to normal foreskin, breast skin and cultured human keratinocytes. The lichen simplex samples had high expression of CRH-R1, but low HDC. These results implicate CRH-R in chronic urticaria, which is often exacerbated by stress.

  9. DNA binding and cleavage studies of copper(II) complexes with 2'-deoxyadenosine modified histidine moiety.

    Science.gov (United States)

    Borowska, Justyna; Sierant, Malgorzata; Sochacka, Elzbieta; Sanna, Daniele; Lodyga-Chruscinska, Elzbieta

    2015-09-01

    This work is focused on the study of DNA binding and cleavage properties of 2'-deoxyadenosines modified with ester/amide of histidine (his(6)dA ester, his(6)dA amide) and their copper(II) complexes. To determine the coordination mode of the complex species potentiometric and spectroscopic (UV-visible, CD, EPR) studies have been performed. The analysis of electronic absorption and fluorescence spectra has been used to find the nature of the interactions between the compounds and calf thymus DNA (CT-DNA). There is significant influence of the -NH2 and -OCH3 groups on binding of the ligands or the complexes to DNA. Only amide derivative and its complex reveal intercalative ability. In the case of his(6)dA ester and Cu(II)-his(6)dA ester the main interactions can be groove binding. DNA cleavage activities of the compounds have been examined by gel electrophoresis. The copper complexes have promoted the cleavage of plasmid DNA, but none of the ligands exhibited any chemical nuclease activity. The application of different scavengers of reactive oxygen species provided a conclusion that DNA cleavage caused by copper complexes might occur via hydrolytic pathway.

  10. Large Variation in Detection of Histidine-Rich Protein 2 in Plasmodium falciparum Isolates from Colombia

    Science.gov (United States)

    Pava, Zuleima; Echeverry, Diego F.; Díaz, Gustavo; Murillo, Claribel

    2010-01-01

    Most rapid diagnostic tests (RDTs) available use histidine-rich protein 2 (HRP2) as a target. However, it has been reported that sequence variations of this protein affects its sensitivity. Currently, there is insufficient evidence for HRP2 variability in Plasmodium falciparum isolates from Colombia and its relationship with RDT performance. To determine possible geographic differences and their effects on the performance of RDTs, 22 blood samples from patients with P. falciparum malaria from Tumaco and Buenaventura, Colombia were assessed by measurement of HRP2 concentration by an HRP2 enzyme-linked immunosorbent assay, RDTs, and thick blood smear. Statistical analysis showed an association between RDT performance and HRP2 concentrations. No significant difference was found between locations. A large variation of antigen concentration in samples was found at same parasitemia. In contrast to previously reports, there was no correlation between initial parasitemia and HRP2 concentration. Our results indicate that antigen quantity should be studied more carefully because the sensitivity of the RDT is affected more by antigen concentration than by parasitemia. PMID:20889875

  11. Effect of Abiotic Stresses on Histidine kinases Gene Expression in Zea mays L. cv. SC. 704

    Directory of Open Access Journals (Sweden)

    Javadmanesh, Susan

    2013-02-01

    Full Text Available UV-B radiation and osmotic stress (like drought and salinity have a significant effect on physiology, morphology, biochemistry and molecular biology. To cope with such stimuli, plants must be able to effectively sense, respond to and adapt to changes in their biological activities. Hence, signal transduction pathways play important role in response to environmental stimuli. In this study, the expression of three Histidine Kinases including ZmHK1, ZmHK2 and ZmHK3a was studied in maize plants exposed to 8 days drought, salinity and UV-B stresses applying transcript approach. The semi-quantitative RT-PCR analyses of ZmHKs showed up-regulation of ZmHK1 and ZmHK3 agenes after 8 days exposure to applied stresses except salinity in leaves, although, their regulation was more prominent during drought stress. Astonishingly, exposure to these stresses showed down-regulation of all genes in maize roots. However, the ZmHK1 behavior was quite different from two other homologues and showed up-regulation in combined stresses. We suggest that ZmHK1 and ZmHK3a, as cytokinin transmembrane receptors, sense osmolarity changes in cells caused by dehydration. Our data supports the involvement of ZmHK homologues under these stresses in maize and provides a gene expression dynamics during the stress which will be valuable for further studies of the molecular mechanisms of stress tolerance in maize.

  12. Detection of histidine decarboxylase in rat aorta and cultured rat aortic smooth muscle cells.

    Science.gov (United States)

    Tippens, A S; Davis, S V; Hayes, J R; Bryda, E C; Green, T L; Gruetter, C A

    2004-08-01

    Having previously demonstrated release of histamine from mast-cell-deficient rat aorta, the objective of this study was to determine and localize histamine synthesis capability in the aorta by detecting histidine decarboxylase (HDC), the enzyme that catalyzes histamine formation. Experiments were conducted with nested reverse transcription-polymerase chain reaction (nRT-PCR) to detect HDC mRNA and with immunofluorescence and western blot analysis to detect HDC protein in rat aorta, cultured rat aortic smooth muscle (RASMC) and endothelial cells (RAEC). Gel electrophoresis of nRT-PCR products indicated HDC mRNA in liver, aorta and RASMC but not in RAEC or kidney. Sequence analysis confirmed that the band observed in RASMC was the target HDC amplicon. Immunofluorescence indicated the presence of HDC protein in RASMC and not in RAEC. Western Blot analysis revealed HDC protein (55 kDa) in liver, aorta, RASMC but not in RAEC or kidney. The results of this study are the first to demonstrate the presence of HDC mRNA and protein in rat aorta and more specifically in RASMC, indicative of their capability to synthesize histamine. Copyright 2004 Birkhäuser Verlag, Basel

  13. Detection of histidine decarboxylase mRNA in human vascular smooth muscle and endothelial cells.

    Science.gov (United States)

    Tippens, A S; Gruetter, C A

    2004-06-01

    The objective of this study was to investigate histamine synthesis capability of human vascular smooth muscle and endothelial cells by detecting histidine decarboxylase (HDC) mRNA. HDC catalyzes exclusively the formation of histamine in mammalian cells. Experiments utilizing nested reverse transcription-polymerase chain reaction (nRT-PCR) were conducted to detect the presence of HDC mRNA. Human aortic smooth muscle cells (HAoSMC) and human aortic endothelial cells (HAEC) were cultured and RNA was extracted and amplified using two sets of HDC-specific primers. Rat liver and kidney RNA were isolated and amplified to serve as positive and negative controls, respectively. Gel electrophoresis of HAoSMC, HAEC and liver mRNA revealed bands coinciding with an expected product size of 440 base pairs. Sequence analysis revealed that the observed bands were the appropriate HDC amplicons. These findings are the first to indicate the presence of HDC mRNA in vascular smooth muscle cells and confirm the presence of HDC mRNA in endothelial cells which is consistent with an ability of these cell types to synthesize histamine in the vascular wall.

  14. Effects of grain, fructose, and histidine on ruminal pH and fermentation products during an induced subacute acidosis protocol.

    Science.gov (United States)

    Golder, H M; Celi, P; Rabiee, A R; Heuer, C; Bramley, E; Miller, D W; King, R; Lean, I J

    2012-04-01

    The effects of grain, fructose, and histidine on ruminal pH and fermentation products were studied in dairy cattle during an induced subacute acidosis protocol. Thirty Holstein heifers were randomly allocated to 5 treatment groups: (1) control (no grain); (2) grain [fed at a crushed triticale dry matter intake (DMI) of 1.2% of body weight (BW)]; (3) grain (0.8% of BW DMI)+fructose (0.4% of BW DMI); (4) grain (1.2% of BW DMI)+histidine (6 g/head); and (5) grain (0.8% of BW DMI)+fructose (0.4% of BW DMI)+histidine (6 g/head) in a partial factorial arrangement. Heifers were fed 1 kg of grain daily with ad libitum access to ryegrass silage and alfalfa hay for 10 d. Feed was withheld for 14 h before challenge day, on which heifers were fed 200 g of alfalfa hay and then the treatment diets immediately thereafter. Rumen samples were collected 5 min after diet ingestion, 60 min later, and at 3 subsequent 50-min intervals. Grain decreased ruminal pH and increased ammonia, total volatile fatty acid (VFA), acetate, butyrate, propionate, and valerate concentrations compared with controls. The addition of grain had no effect on ruminal D- and L-lactate concentrations. Fructose markedly decreased ruminal pH and markedly increased D- and L-lactate concentrations. Fructose increased total VFA and butyrate and decreased valerate concentrations. Although histidine did not have a marked effect on ruminal fermentation, increased concentrations of histamine were observed following feeding. This study demonstrates that the substitution of some grain for fructose can lower ruminal pH and increase VFA and lactate concentrations, warranting further investigation into the role of sugars on the risk of acidosis in dairy cattle. Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  15. Resonance Raman investigation of the effects of copper binding to iron-mesoporphyrin.histidine-rich glycoprotein complexes

    OpenAIRE

    Larsen, R W; Nunez, D J; Morgan, W. T.; Muhoberac, B B; Ondrias, M.R.

    1992-01-01

    Histidine-rich glycoprotein (HRG) binds both hemes and metal ions simultaneously with evidence for interaction between the two. This study uses resonance Raman and optical absorption spectroscopies to examine the heme environment of the 1:1 iron-mesoporphyrin.HRG complex in its oxidized, reduced and CO-bound forms in the absence and presence of copper. Significant perturbation of Fe(3+)-mesoporphyrin.HRG is induced by Cu2+ binding to the protein. Specifically, high frequency heme resonance Ra...

  16. Synthesis of novel chitosan resin possessing histidine moiety and its application to the determination of trace silver by ICP-AES coupled with triplet automated-pretreatment system.

    Science.gov (United States)

    Hosoba, Minako; Oshita, Koji; Katarina, Rosi K; Takayanagi, Toshio; Oshima, Mitsuko; Motomizu, Shoji

    2009-04-20

    A novel chitosan resin, cross-linked chitosan functionalized with histidine moiety (histidine-type chitosan resin), was synthesized for the collection and concentration of trace silver in aquatic samples. A triplet automated-pretreatment system (Triplet Auto-Pret System) installed mini-columns packed with the synthesized histidine-type chitosan resin was coupled with an inductively coupled plasma-atomic emission spectrometry (ICP-AES) for a rapid and sensitive analysis. Adsorption behavior of 50 elements on the histidine-type chitosan resin was examined. A trace amount of Ag(I) was shown a good adsorption in wide pH regions (pH 5-9), and Ag(I) adsorbed was readily recovered with 1 M nitric acid solution. The limit of detection (3sigma) for silver was 0.03 microg L(-1). The system was successfully applied to river water and dipped water in silver coated container.

  17. Multiplication of microbes below 0.690 water activity: implications for terrestrial and extraterrestrial life.

    Science.gov (United States)

    Stevenson, Andrew; Burkhardt, Jürgen; Cockell, Charles S; Cray, Jonathan A; Dijksterhuis, Jan; Fox-Powell, Mark; Kee, Terence P; Kminek, Gerhard; McGenity, Terry J; Timmis, Kenneth N; Timson, David J; Voytek, Mary A; Westall, Frances; Yakimov, Michail M; Hallsworth, John E

    2015-02-01

    Since a key requirement of known life forms is available water (water activity; aw ), recent searches for signatures of past life in terrestrial and extraterrestrial environments have targeted places known to have contained significant quantities of biologically available water. However, early life on Earth inhabited high-salt environments, suggesting an ability to withstand low water-activity. The lower limit of water activity that enables cell division appears to be ∼ 0.605 which, until now, was only known to be exhibited by a single eukaryote, the sugar-tolerant, fungal xerophile Xeromyces bisporus. The first forms of life on Earth were, though, prokaryotic. Recent evidence now indicates that some halophilic Archaea and Bacteria have water-activity limits more or less equal to those of X. bisporus. We discuss water activity in relation to the limits of Earth's present-day biosphere; the possibility of microbial multiplication by utilizing water from thin, aqueous films or non-liquid sources; whether prokaryotes were the first organisms able to multiply close to the 0.605-aw limit; and whether extraterrestrial aqueous milieux of ≥ 0.605 aw can resemble fertile microbial habitats found on Earth. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

  18. WATER ACTIVITY INFLUENCE ON THE SAFE AGING PERIOD OF CONDENSED MILK

    Directory of Open Access Journals (Sweden)

    Ilona Šostakienė

    2010-01-01

    Full Text Available The majority of chemical and biological processes causing the change of nutrients and finally their spoilage are dependent on water. Microbiological growth is directly related to water activity. Water activity (aw was introduced by an Australian microbiologist W.J. Scott in 1952. He defined this concept as a “fundamental property of water solutions” and i.e. a ratio between pure water (p0 and steam pressure solution (p. The water activity of the unsweetened condensed milk packed into canister remains unchanged during the storage period (aw.= 0,902. The water activity in the sweetened condensed milk slightly increases after 18 months (aw.= 0,784, after 18 months aw = 0,787. Though water activity does not actually change the storage of such a product and does not create a possibility for the growth of microorganisms. However, milk is a system of array compounds and a limitless storage of such a product is impossible. It is determined that the allowed storage period of 12 months is justified as after this period a major part of milk changes become accelerated

  19. Effect of water activity and temperature on the growth of Eurotium species isolated from animal feeds.

    Science.gov (United States)

    Greco, Mariana; Pardo, Alejandro; Pose, Graciela; Patriarca, Andrea

    Xerophilic fungi represent a serious problem due to their ability to grow at low water activities causing the spoiling of low and intermediate moisture foods, stored goods and animal feeds, with the consequent economic losses. The combined effect of water activity and temperature of four Eurotium species isolated from animal feeds was investigated. Eurotium amstelodami, Eurotium chevalieri, Eurotium repens and Eurotium rubrum were grown at 5, 15, 25, 37 and 45°C on malt extract agar adjusted with glycerol in the range 0.710-0.993 of water activities. The cardinal model proposed by Rosso and Robinson (2001) was applied to fit growth data, with the variable water activity at fixed temperatures, obtaining three cardinal water activities (a wmin , a wmax , a wopt ) and the specific growth rate at the optimum a w (μ opt ). A probabilistic model was also applied to define the interface between growth and no-growth. The cardinal model provided an adequate estimation of the optimal a w to grow and the maximum growth rate. The probabilistic model showed a good performance to fit growth/no-growth cases in the predicted range. The results presented here could be applied to predict Eurotium species growth in animal feeds. Copyright © 2017 Asociación Española de Micología. Publicado por Elsevier España, S.L.U. All rights reserved.

  20. Analysis of the effect of water activity on ice formation using a new thermodynamic framework

    Science.gov (United States)

    Barahona, D.

    2014-07-01

    In this work a new thermodynamic framework is developed and used to investigate the effect of water activity on the formation of ice within supercooled droplets. The new framework is based on a novel concept where the interface is assumed to be made of liquid molecules "trapped" by the solid matrix. It also accounts for the change in the composition of the liquid phase upon nucleation. Using this framework, new expressions are developed for the critical ice germ size and the nucleation work with explicit dependencies on temperature and water activity. However unlike previous approaches, the new model does not depend on the interfacial tension between liquid and ice. The thermodynamic framework is introduced within classical nucleation theory to study the effect of water activity on the ice nucleation rate. Comparison against experimental results shows that the new approach is able to reproduce the observed effect of water activity on the nucleation rate and the freezing temperature. It allows for the first time a phenomenological derivation of the constant shift in water activity between melting and nucleation. The new framework offers a consistent thermodynamic view of ice nucleation, simple enough to be applied in atmospheric models of cloud formation.

  1. Chemical Looping Technology: Oxygen Carrier Characteristics.

    Science.gov (United States)

    Luo, Siwei; Zeng, Liang; Fan, Liang-Shih

    2015-01-01

    Chemical looping processes are characterized as promising carbonaceous fuel conversion technologies with the advantages of manageable CO2 capture and high energy conversion efficiency. Depending on the chemical looping reaction products generated, chemical looping technologies generally can be grouped into two types: chemical looping full oxidation (CLFO) and chemical looping partial oxidation (CLPO). In CLFO, carbonaceous fuels are fully oxidized to CO2 and H2O, as typically represented by chemical looping combustion with electricity as the primary product. In CLPO, however, carbonaceous fuels are partially oxidized, as typically represented by chemical looping gasification with syngas or hydrogen as the primary product. Both CLFO and CLPO share similar operational features; however, the optimum process configurations and the specific oxygen carriers used between them can vary significantly. Progress in both CLFO and CLPO is reviewed and analyzed with specific focus on oxygen carrier developments that characterize these technologies.

  2. Does aluminium bind to histidine? An NMR investigation of amyloid β12 and amyloid β16 fragments.

    Science.gov (United States)

    Narayan, Priya; Krishnarjuna, Bankala; Vishwanathan, Vinaya; Jagadeesh Kumar, Dasappa; Babu, Sudhir; Ramanathan, Krishna Venkatachala; Easwaran, Kalpathy Ramaier Katchap; Nagendra, Holenarasipur Gundurao; Raghothama, Srinivasarao

    2013-07-01

    Aluminium and zinc are known to be the major triggering agents for aggregation of amyloid peptides leading to plaque formation in Alzheimer's disease. While zinc binding to histidine in Aβ (amyloid β) fragments has been implicated as responsible for aggregation, not much information is available on the interaction of aluminium with histidine. In the NMR study of the N-terminal Aβ fragments, DAEFRHDSGYEV (Aβ12) and DAEFRHDSGYEVHHQK (Aβ16) presented here, the interactions of the fragments with aluminium have been investigated. Significant chemical shifts were observed for few residues near the C-terminus when aluminium chloride was titrated with Aβ12 and Aβ16 peptides. Surprisingly, it is nonhistidine residues which seem to be involved in aluminium binding. Based on NMR constrained structure obtained by molecular modelling, aluminium-binding pockets in Aβ12 were around charged residues such as Asp, Glu. The results are discussed in terms of native structure propagation, and the relevance of histidine residues in the sequences for metal-binding interactions. We expect that the study of such short amyloid peptide fragments will not only provide clues for plaque formation in aggregated conditions but also facilitate design of potential drugs for these targets. © 2013 John Wiley & Sons A/S.

  3. On-line affinity selection of histidine-containing peptides using a polymeric monolithic support for capillary electrophoresis.

    Science.gov (United States)

    Vizioli, Nora M; Rusell, Maria Lucía; Carbajal, Maria Laura; Carducci, Clyde N; Grasselli, Mariano

    2005-08-01

    An on-line affinity selection method using a polymeric monolithic support is proposed for the retention of histidine-containing peptides and their subsequent separation by capillary zone electrophoresis (CZE). Monolithic capillary columns were prepared in fused-silica capillaries of 150 mum inner diameter (ID) by ionizing radiation-initiated in situ polymerization and cross-linking of diethylene glycol dimethacrylate and glycidyl methacrylate, and chemically modified with iminodiacetic acid (IDA) and copper ion. Monolithic microextractors were coupled on-line near the inlet of the separation capillary (fused-silica capillary, 75 mum ID x 28 cm from the microextractor to the detector). Model peptide mixtures of histidine-containing and histidine-noncontaining peptides were assessed. Peptides were released from the sorbent by a 5 mM imidazole solution and then separated by CZE with ultraviolet detection. Relative standard deviation values for migration times and corrected peak areas were found to be lower than 5.8 and 10.5%, respectively. IDA-Cu(II) ion modified monolithic microextractors showed a chromatographic behavior and could be reused at least 25 times. The use of monolithic supports proved to be an advantageous alternative to packed particles for the preparation of microextractors.

  4. Aminooxy analog of histamine is an efficient inhibitor of mammalian L-histidine decarboxylase: combined in silico and experimental evidence.

    Science.gov (United States)

    Castro-Oropeza, R; Pino-Ángeles, A; Khomutov, M A; Urdiales, J L; Moya-García, A A; Vepsäläinen, J; Persson, L; Sarabia, F; Khomutov, A; Sánchez-Jiménez, F

    2014-03-01

    Histamine plays highlighted roles in the development of many common, emergent and rare diseases. In mammals, histamine is formed by decarboxylation of L-histidine, which is catalyzed by pyridoxal-5'-phosphate (PLP) dependent histidine decarboxylase (HDC, EC 4.1.1.22). The limited availability and stability of the protein have delayed the characterization of its structure-function relationships. Our previous knowledge on mammalian HDC, derived from both in silico and experimental approaches, indicates that an effective competitive inhibitor should be capable to form an "external aldimine-like structure" and have an imidazole group, or its proper mimetic, which provides additional affinity of PLP-inhibitor adduct to the HDC active center. This is confirmed using HEK-293 cells transfected to express human HDC and the aminooxy analog of histidine, 4(5)-aminooxymethylimidazole (O-IMHA, IC₅₀ ≈ 2 × 10(-7) M) capable to form a PLP-inhibitor complex (oxime) in the enzyme active center. Taking advantage of the availability of the human HDC X-ray structure, we have also determined the potential interactions that could stabilize this oxime in the active site of mammalian HDC.

  5. Histidine-iridium(III) coordination-based peptide luminogenic cyclization and cyclo-RGD peptides for cancer-cell targeting.

    Science.gov (United States)

    Ma, Xiaochuan; Jia, Junli; Cao, Rui; Wang, Xiaobo; Fei, Hao

    2014-12-24

    In the field of peptide drug discovery, structural constraining and fluorescent labeling are two sought-after techniques important for both basic research and pharmaceutical development. In this work, we describe an easy-to-use approach for simultaneous peptide cyclization and luminescent labeling based on iridium(III)-histidine coordination (Ir-HH cyclization). Using a series of model peptides with histidine flanking each terminus, the binding activity and reaction kinetics of Ir-HH cyclization of different ring sizes were characterized. In the series, Ir-HAnH (n = 2, 3) with moderate ring sizes provides appropriate flexibility and proper distance between histidines for cyclic formation, which leads to the best binding affinity and structural stability in physiological conditions, as compared to other Ir-HH-cyclized peptides with smaller (n = 0, 1) or larger (n = 4, 5) ring sizes. Ir-HRGDH, an Ir-HH-cyclized peptide containing integrin targeting motif Arg-Gly-Asp (RGD), showed better targeting affinity than its linear form and enhanced membrane permeability in comparison with fluorescein-labeled cyclic RGDyK peptide. Cell death inducing peptide KLA-linked Ir-HRGDH (Ir-HRGDH-KLA) showed dramatically enhanced cytotoxicity and high selectivity for cancer cells versus noncancer cells. These data demonstrate that the method conveniently combines structural constraining of peptides with luminescent imaging capabilities, which facilitates functional and intracellular characterization of potential peptide-based drug leads, thus introducing a new tool to meet emerging needs in medicinal research.

  6. Alkali metals in addition to acidic pH activate the EvgS histidine kinase sensor in Escherichia coli.

    Science.gov (United States)

    Eguchi, Yoko; Utsumi, Ryutaro

    2014-09-01

    Two-component signal transduction systems (TCSs) in bacteria perceive environmental stress and transmit the information via phosphorelay to adjust multiple cellular functions for adaptation. The EvgS/EvgA system is a TCS that confers acid resistance to Escherichia coli cells. Activation of the EvgS sensor initiates a cascade of transcription factors, EvgA, YdeO, and GadE, which induce the expression of a large group of acid resistance genes. We searched for signals activating EvgS and found that a high concentration of alkali metals (Na(+), K(+)) in addition to low pH was essential for the activation. EvgS is a histidine kinase, with a large periplasmic sensor region consisting of two tandem PBPb (bacterial periplasmic solute-binding protein) domains at its N terminus. The periplasmic sensor region of EvgS was necessary for EvgS activation, and Leu152, located within the first PBPb domain, was involved in the activation. Furthermore, chimeras of EvgS and PhoQ histidine kinases suggested that alkali metals were perceived at the periplasmic sensor region, whereas the cytoplasmic linker domain, connecting the transmembrane region and the histidine kinase domain, was required for low-pH perception. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  7. Chiral recognition of proteins having L-histidine residues on the surface with lanthanide ion complex incorporated-molecularly imprinted fluorescent nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Uzun, Lokman, E-mail: lokman@hacettepe.edu.tr [Hacettepe University, Department of Chemistry, 06381, Ankara (Turkey); Uzek, Recep; Şenel, Serap [Hacettepe University, Department of Chemistry, 06381, Ankara (Turkey); Say, Ridvan [Anadolu University, Department of Chemistry, 26470, Eskisehir (Turkey); Denizli, Adil [Hacettepe University, Department of Chemistry, 06381, Ankara (Turkey)

    2013-08-01

    In this study, lanthanide ion complex incorporated molecularly imprinted fluorescent nanoparticles were synthesized. A combination of three novel approaches was applied for the purpose. First, lanthanide ions [Terbium(III)] were complexed with N-methacryloyl-L-histidine (MAH), polymerizable derivative of L-histidine amino acid, in order to incorporate the complex directly into the polymeric backbone. At the second stage, L-histidine molecules imprinted nanoparticles were utilized instead of whole protein imprinting in order to avoid whole drawbacks such as fragility, complexity, denaturation tendency, and conformation dependency. At the third stage following the first two steps mentioned above, imprinted L-histidine was coordinated with cupric ions [Cu(II)] to conduct the study under mild conditions. Then, molecularly imprinted fluorescent nanoparticles synthesized were used for L-histidine adsorption from aqueous solution to optimize conditions for adsorption and fluorimetric detection. Finally, usability of nanoparticles was investigated for chiral biorecognition using stereoisomer, D-histidine, racemic mixture, D,L-histidine, proteins with surface L-histidine residue, lysozyme, cytochrome C, or without ribonuclease A. The results revealed that the proposed polymerization strategy could make significant contribution to the solution of chronic problems of fluorescent component introduction into polymers. Additionally, the fluorescent nanoparticles reported here could be used for selective separation and fluorescent monitoring purposes. Highlights: • Lanthanide ion complex incorporated molecularly imprinted fluorescent nanoparticles • Direct incorporation of the fluorescent complex into polymeric backbone. • Imprinting by assistance of cupric ion coordination into nanoparticles • Evaluation of the chiral biorecognition ability of nanoparticles • Simultaneous selective separation and fluorescent monitoring.

  8. Immunocytochemical staining of endogenous nuclear proteins with the HIS-1 anti-poly-histidine monoclonal antibody: a potential source of error in His-tagged protein detection.

    Science.gov (United States)

    Chilumuri, Amrutha; Markiv, Anatoliy; Milton, Nathaniel G N

    2014-07-01

    Histidine-tagged proteins are widely used in biochemical studies and frequently detected with antibodies specific for the histidine tag. Immunocytochemistry is widely used in studies with overexpressed proteins to determine cellular localization and in the case of histidine-tagged proteins can be carried out with anti-polyhistidine antibodies. Recent studies have suggested that polyhistidine sequences are present within a small number of human proteins and may direct expression to the nucleus and nuclear speckles compartments of the cell. In this study immunocytochemical staining of human SH-SY5Y neuroblastoma cell lines with the HIS-1 anti-polyhistidine monoclonal antibody were determined. Results showed that the HIS-1 anti-polyhistidine monoclonal antibody stained endogenous nuclear proteins in SH-SY5Y cells. The stained proteins were contained within the nuclear membrane, but were not directly linked to DNA. In a histidine-tagged catalase overexpressing cell line the HIS-1 anti-polyhistidine monoclonal antibody showed nuclear staining, whilst staining with the CAT-505 anti-catalase monoclonal antibody showed primarily cytoplasmic staining. These results suggest that anti-polyhistidine antibody staining shows significant cross-reactivity with endogenous nuclear proteins in SH-SY5Y neuroblastoma cells and may not be suitable for localization studies of histidine-tagged proteins. Immunocytochemical studies with anti-polyhistidine antibodies and localization of histidine-tagged proteins must be confirmed with protein specific antibodies or other methodology. Copyright © 2014 Elsevier GmbH. All rights reserved.

  9. Imidazole Nitrogens of Two Histidine Residues Participating in N-H···N Hydrogen Bonds in Protein Structures: Structural Bioinformatics Approach Combined with Quantum Chemical Calculations.

    Science.gov (United States)

    Iyer, Abhishek Hariharan; Krishna Deepak, R N V; Sankararamakrishnan, Ramasubbu

    2018-01-25

    Protein structures are stabilized by different types of hydrogen bonds. However, unlike the DNA double helical structure, the N-H···N type of hydrogen bonds is relatively rare in proteins. N-H···N hydrogen bonds formed by imidazole groups of two histidine residues have not been investigated. We have systematically analyzed 5333 high-resolution protein structures with resolution 1.8 Å or better and identified 285 histidine pairs in which the nitrogen atoms of the imidazole side chains can potentially participate in N-H···N hydrogen bonds. The histidine pairs were further divided into two groups, neutral-neutral and protonated-neutral, depending on the protonation state of the donor histidine. Quantum chemical calculations were performed on imidazole groups adopting the same geometry observed in the protein structures. Average interaction energies between the interacting imidazole groups are -6.45 and -22.5 kcal/mol for neutral-neutral and protonated-neutral, respectively. Hydrogen bond interaction between the imidazole moieties is further confirmed by natural bond orbital analyses of the model compounds. Histidine residues involved in N-H···N hydrogen bonds are relatively more buried and have low B-factor values in the protein structures. N-H···N hydrogen bond formed by a pair of buried histidine residues can significantly contribute to the structural stability of proteins.

  10. Singularities in loop quantum cosmology.

    Science.gov (United States)

    Cailleteau, Thomas; Cardoso, Antonio; Vandersloot, Kevin; Wands, David

    2008-12-19

    We show that simple scalar field models can give rise to curvature singularities in the effective Friedmann dynamics of loop quantum cosmology (LQC). We find singular solutions for spatially flat Friedmann-Robertson-Walker cosmologies with a canonical scalar field and a negative exponential potential, or with a phantom scalar field and a positive potential. While LQC avoids big bang or big rip type singularities, we find sudden singularities where the Hubble rate is bounded, but the Ricci curvature scalar diverges. We conclude that the effective equations of LQC are not in themselves sufficient to avoid the occurrence of curvature singularities.

  11. Closed-loop neuromorphic benchmarks

    CSIR Research Space (South Africa)

    Stewart, TC

    2015-11-01

    Full Text Available the study was exempt from ethical approval procedures.) Did the study presented in the manuscript involve human or animal subjects: No I v i w 1Closed-loop Neuromorphic Benchmarks Terrence C. Stewart 1,∗, Travis DeWolf 1, Ashley Kleinhans 2 and Chris..._link335 program from ev3dev-c (https://github.com/in4lio/ev3dev-c). This allows the EV3 to336 listen for UDP commands that tell it to set motor values and read sensor values. Communication with337 a PC was over a USB link (although the system also...

  12. Holomorphic curves in loop groups

    Energy Technology Data Exchange (ETDEWEB)

    Guest, M.A.; Pressley, A.N.

    1988-09-01

    It was observed by Atiyah that there is a correspondence between based gauge equivalence classes of SU/sub n/-instantons over S/sup 4/ of charge d on the one hand, and based holomorphic curves of genus zero in ..cap omega..SU/sub n/ of degree d on the other hand. In this paper we study the parameter space of such holomorphic curves which have the additional property that they lie entirely in the subgroup ..cap omega../sub alg/SU/sub n/ of algebraic loops. We describe a cell decomposition of this parameter space, and compute its complex dimension to be (2n-1)d.

  13. Instrument Qualification of Custom Fabricated Water Activity Meter for Hot Cell Use

    Energy Technology Data Exchange (ETDEWEB)

    McCoskey, Jacob K. [Hanford Site (HNF), Richland, WA (United States)

    2014-01-22

    This report describes a custom fabricated water activity meter and the results of the qualification of this meter as described in the laboratory test plan LAB-PLN-11-00012, Testing and Validation of an Enhanced Acquisition and Control System. It was calibrated against several NaOH solutions of varying concentrations to quantify the accuracy and precision of the instrument at 20 °C and 60 °C. Also, a schematic and parts list of the equipment used to make the water activity meter will be presented in this report.

  14. Measuring water activity of aviation fuel using a polymer optical fiber Bragg grating

    Science.gov (United States)

    Zhang, Wei; Webb, David J.; Carpenter, Mark; Williams, Colleen

    2014-05-01

    Poly(methyl methacrylate) (PMMA) based polymer optical fiber Bragg gratings have been used for measuring water activity of aviation fuel. Jet A-1 samples with water content ranging from 100% ERH (wet fuel) to 10 ppm (dried fuel), have been conditioned and calibrated for measurement. The PMMA based optical fiber grating exhibits consistent response and a good sensitivity of 59±3pm/ppm (water content in mass). This water activity measurement allows PMMA based optical fiber gratings to detect very tiny amounts of water in fuels that have a low water saturation point, potentially giving early warning of unsafe operation of a fuel system.

  15. Gauge theory loop operators and Liouville theory

    Energy Technology Data Exchange (ETDEWEB)

    Drukker, Nadav [Humboldt Univ. Berlin (Germany). Inst. fuer Physik; Gomis, Jaume; Okuda, Takuda [Perimeter Inst. for Theoretical Physics, Waterloo, ON (Canada); Teschner, Joerg [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2009-10-15

    We propose a correspondence between loop operators in a family of four dimensional N=2 gauge theories on S{sup 4} - including Wilson, 't Hooft and dyonic operators - and Liouville theory loop operators on a Riemann surface. This extends the beautiful relation between the partition function of these N=2 gauge theories and Liouville correlators found by Alday, Gaiotto and Tachikawa. We show that the computation of these Liouville correlators with the insertion of a Liouville loop operator reproduces Pestun's formula capturing the expectation value of a Wilson loop operator in the corresponding gauge theory. We prove that our definition of Liouville loop operators is invariant under modular transformations, which given our correspondence, implies the conjectured action of S-duality on the gauge theory loop operators. Our computations in Liouville theory make an explicit prediction for the exact expectation value of 't Hooft and dyonic loop operators in these N=2 gauge theories. The Liouville loop operators are also found to admit a simple geometric interpretation within quantum Teichmueller theory as the quantum operators representing the length of geodesics. We study the algebra of Liouville loop operators and show that it gives evidence for our proposal as well as providing definite predictions for the operator product expansion of loop operators in gauge theory. (orig.)

  16. Signal Sensing and Transduction by Histidine Kinases as Unveiled through Studies on a Temperature Sensor.

    Science.gov (United States)

    Abriata, Luciano A; Albanesi, Daniela; Dal Peraro, Matteo; de Mendoza, Diego

    2017-06-20

    Histidine kinases (HK) are the sensory proteins of two-component systems, responsible for a large fraction of bacterial responses to stimuli and environmental changes. Prototypical HKs are membrane-bound proteins that phosphorylate cognate response regulator proteins in the cytoplasm upon signal detection in the membrane or periplasm. HKs stand as potential drug targets but also constitute fascinating systems for studying proteins at work, specifically regarding the chemistry and mechanics of signal detection, transduction through the membrane, and regulation of catalytic outputs. In this Account, we focus on Bacillus subtilis DesK, a membrane-bound HK part of a two-component system that maintains appropriate membrane fluidity at low growth temperatures. Unlike most HKs, DesK has no extracytoplasmic signal-sensing domains; instead, sensing is carried out by 10 transmembrane helices (coming from two protomers) arranged in an unknown structure. The fifth transmembrane helix from each protomer connects, without any of the intermediate domains found in other HKs, into the dimerization and histidine phosphotransfer (DHp) domain located in the cytoplasm, which is followed by the ATP-binding domains (ABD). Throughout the years, genetic, biochemical, structural, and computational studies on wild-type, mutant, and truncated versions of DesK allowed us to dissect several aspects of DesK's functioning, pushing forward a more general understanding of its own structure/function relationships as well as those of other HKs. We have shown that the sensing mechanism is rooted in temperature-dependent membrane properties, most likely a combination of thickness, fluidity, and water permeability, and we have proposed possible mechanisms by which DesK senses these properties and transduces the signals. X-ray structures and computational models have revealed structural features of TM and cytoplasmic regions in DesK's kinase- and phosphatase-competent states. Biochemical and genetic

  17. A Histidine Aspartate Ionic Lock Gates the Iron Passage in Miniferritins from Mycobacterium smegmatis*

    Science.gov (United States)

    Williams, Sunanda Margrett; Chandran, Anu V.; Vijayabaskar, Mahalingam S.; Roy, Sourav; Balaram, Hemalatha; Vishveshwara, Saraswathi; Vijayan, Mamannamana; Chatterji, Dipankar

    2014-01-01

    Dps (DNA-binding protein from starved cells) are dodecameric assemblies belonging to the ferritin family that can bind DNA, carry out ferroxidation, and store iron in their shells. The ferritin-like trimeric pore harbors the channel for the entry and exit of iron. By representing the structure of Dps as a network we have identified a charge-driven interface formed by a histidine aspartate cluster at the pore interface unique to Mycobacterium smegmatis Dps protein, MsDps2. Site-directed mutagenesis was employed to generate mutants to disrupt the charged interactions. Kinetics of iron uptake/release of the wild type and mutants were compared. Crystal structures were solved at a resolution of 1.8–2.2 Å for the various mutants to compare structural alterations vis à vis the wild type protein. The substitutions at the pore interface resulted in alterations in the side chain conformations leading to an overall weakening of the interface network, especially in cases of substitutions that alter the charge at the pore interface. Contrary to earlier findings where conserved aspartate residues were found crucial for iron release, we propose here that in the case of MsDps2, it is the interplay of negative-positive potentials at the pore that enables proper functioning of the protein. In similar studies in ferritins, negative and positive patches near the iron exit pore were found to be important in iron uptake/release kinetics. The unique ionic cluster in MsDps2 makes it a suitable candidate to act as nano-delivery vehicle, as these gated pores can be manipulated to exhibit conformations allowing for slow or fast rates of iron release. PMID:24573673

  18. Virulence Effects and Signaling Partners Modulated by Brucella melitensis Light-sensing Histidine Kinase

    Science.gov (United States)

    Gourley, Christopher R.

    The facultative intracellular pathogen Brucella melitensis utilizes diverse virulence factors. A Brucella light sensing histidine kinase can influence in vitro virulence of the bacteria during intracellular infection. First, we demonstrated that the B. melitensis light sensing kinase (BM-LOV-HK) affects virulence in an IRF-1-/- mouse model of infection. Infection with a Δ BM-LOV-HK strain resulted in less bacterial colonization of IRF-1-/- spleens and extended survivorship compared to mice infected with wild type B. melitensis 16M. Second, using PCR arrays, we observed less expression of innate and adaptive immune system activation markers in ΔBM-LOV-HK infected mouse spleens than wild type B. melitensis 16M infected mouse spleens 6 days after infection. Third, we demonstrated by microarray analysis of B. melitensis that deletion of BM-LOV-HK alters bacterial gene expression. Downregulation of genes involved in control of the general stress response system included the alternative sigma factor RpoE1 and its anti-anti sigma factor PhyR. Conversely, genes involved in flagella production, quorum sensing, and the type IV secretion system (VirB operon) were upregulated in the Δ BM-LOV-HK strain compared to the wild type B. melitensis 16M. Analysis of genes differentially regulated in Δ BM-LOV-HK versus the wild type strain indicated an overlap of 110 genes with data from previous quorum sensing regulator studies of Δ vjbR and/ΔblxR(babR) strains. Also, several predicted RpoE1 binding sites located upstream of genes were differentially regulated in the ΔBM-LOV-HK strain. Our results suggest BM-LOV-HK is important for in vivo Brucella virulence, and reveals that BM-LOV-HK directly or indirect regulates members of the Brucella quorum sensing, type IV secretion, and general stress systems.

  19. Histidine-Rich Glycoprotein Uptake and Turnover Is Mediated by Mononuclear Phagocytes

    Science.gov (United States)

    Tugues, Sònia; Orlova, Anna; Bhoi, Sujata; Padhan, Narendra; Åkerud, Peter; Honjo, Satoshi; Selvaraju, Ram Kumar; Mazzone, Massimiliano; Tolmachev, Vladimir; Claesson-Welsh, Lena

    2014-01-01

    Histidine-rich glycoprotein (HRG) is implicated in tumor growth and metastasis by regulation of angiogenesis and inflammation. HRG is produced by hepatocytes and carried to tissues via the circulation. We hypothesized that HRG's tissue distribution and turnover may be mediated by inflammatory cells. Biodistribution parameters were analyzed by injection of radiolabeled, bioactive HRG in the circulation of healthy and tumor-bearing mice. 125I-HRG was cleared rapidly from the blood and taken up in tissues of healthy and tumor-bearing mice, followed by degradation, to an increased extent in the tumor-bearing mice. Steady state levels of HRG in the circulation were unaffected by the tumor disease both in murine tumor models and in colorectal cancer (CRC) patients. Importantly, stromal pools of HRG, detected in human CRC microarrays, were associated with inflammatory cells. In agreement, microautoradiography identified 125I-HRG in blood vessels and on CD45-positive leukocytes in mouse tissues. Moreover, radiolabeled HRG bound in a specific, heparan sulfate-independent manner, to differentiated human monocytic U937 cells in vitro. Suppression of monocyte differentiation by systemic treatment of mice with anti-colony stimulating factor-1 neutralizing antibodies led to reduced blood clearance of radiolabeled HRG and to accumulation of endogenous HRG in the blood. Combined, our data show that mononuclear phagocytes have specific binding sites for HRG and that these cells are essential for uptake of HRG from blood and distribution of HRG in tissues. Thereby, we confirm and extend our previous report that inflammatory cells mediate the effect of HRG on tumor growth and metastatic spread. PMID:25243896

  20. Diversity of plasmids encoding histidine decarboxylase gene in Tetragenococcus spp. isolated from Japanese fish sauce.

    Science.gov (United States)

    Satomi, Masataka; Furushita, Manabu; Oikawa, Hiroshi; Yano, Yutaka

    2011-07-15

    Nineteen isolates of histamine producing halophilic bacteria were isolated from four fish sauce mashes, each mash accumulating over 1000 ppm of histamine. The complete sequences of the plasmids encoding the pyruvoyl dependent histidine decarboxylase gene (hdcA), which is harbored in histamine producing bacteria, were determined. In conjunction, the sequence regions adjacent to hdcA were analyzed to provide information regarding its genetic origin. As reference strains, Tetragenococcus halophilus H and T. muriaticus JCM10006(T) were also studied. Phenotypic and 16S rRNA gene sequence analyses identified all isolates as T. halophilus, a predominant histamine producing bacteria present during fish sauce fermentation. Genetic analyses (PCR, Southern blot, and complete plasmid sequencing) of the histamine producing isolates confirmed that all the isolates harbored approximately 21-37 kbp plasmids encoding a single copy of the hdc cluster consisting of four genes related to histamine production. Analysis of hdc clusters, including spacer regions, indicated >99% sequence similarity among the isolates. All of the plasmids sequenced encoded traA, however genes related to plasmid conjugation, namely mob genes and oriT, were not identified. Two putative mobile genetic elements, ISLP1-like and IS200-like, respectively, were identified in the up- and downstream region of the hdc cluster of all plasmids. Most of the sequences, except hdc cluster and two adjacent IS elements, were diverse among plasmids, suggesting that each histamine producers harbored a different histamine-related plasmid. These results suggested that the hdc cluster was not spread by clonal dissemination depending on the specific plasmid and that the hdc cluster in tetragenococcal plasmid was likely encoded on transformable elements. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Construction of histidine-tagged yeast mitochondrial cytochrome c oxidase for facile purification of mutant forms.

    Science.gov (United States)

    Meunier, Brigitte; Maréchal, Amandine; Rich, Peter R

    2012-06-01

    Yeast CcO (cytochrome c oxidase) has been developed as a facile system for the production and analysis of mutants of a mitochondrial form of CcO for mechanistic studies. First, a 6H tag (His6 tag) was fused to the C-terminus of a nuclear-encoded subunit of CcO from yeast Saccharomyces cerevisiae. This allowed efficient purification of a WT (wild-type) mitochondrial CcO, 6H-WT (yeast CcO with a 6H tag on the nuclear-encoded Cox13 subunit), with a recovery yield of 45%. Its catalytic-centre activity [≈180 e·s(-1) (electrons per s)], UV-visible signatures of oxidized and reduced states and ability to form the P(M) ['peroxy' (but actually a ferryl/radical state)] and F (ferryl) intermediates confirm normal functioning of the histidine-tagged protein. Point mutations were introduced into subunit I of the 6H-WT strain. All mutants were screened for their ability to assemble CcO and grow on respiratory substrate. One such mutant [6H-E243DI (the 6H-WT strain with an additional mutation of E243D in mitochondrial DNA-encoded subunit I)] was purified and showed ~50% of the 6H-WT catalytic-centre activity, consistent with the effects of the equivalent mutation in bacterial oxidases. Mutations in both the D and the H channels affect respiratory growth and these effects are discussed in terms of their putative roles in CcO mechanism.

  2. Histidine Regulates Seed Oil Deposition through Abscisic Acid Biosynthesis and β-Oxidation1

    Science.gov (United States)

    2016-01-01

    The storage compounds are deposited into plant seeds during maturation. As the model oilseed species, Arabidopsis (Arabidopsis thaliana) has long been studied for seed oil deposition. However, the regulation of this process remains unclear. Through genetic screen with a seed oil body-specific reporter, we isolated low oil1 (loo1) mutant. LOO1 was mapped to HISTIDINE BIOSYNTHESIS NUMBER 1A (HISN1A). HISN1A catalyzes the first step of His biosynthesis. Oil significantly decreased, and conversely proteins markedly increased in hisn1a mutants, indicating that HISN1A regulates both oil accumulation and the oil-protein balance. HISN1A was predominantly expressed in embryos and root tips. Accordingly, the hisn1a mutants exhibited developmental phenotype especially of seeds and roots. Transcriptional profiling displayed that β-oxidation was the major metabolic pathway downstream of HISN1A. β-Oxidation was induced in hisn1a mutants, whereas it was reduced in 35S:HISN1A-transgenic plants. In plants, seed storage oil is broken-down by β-oxidation, which is controlled by abscisic acid (ABA). We found that His activated genes of ABA biosynthesis and correspondingly advanced ABA accumulation. Exogenous ABA rescued the defects of hisn1a mutants, whereas mutation of ABA DEFICIENT2, a key enzyme in ABA biosynthesis, blocked the effect of His on β-oxidation, indicating that ABA mediates His regulation in β-oxidation. Intriguingly, structural analysis showed that a potential His-binding domain was present in the general amino acid sensors GENERAL CONTROL NON-DEREPRESSIBLE2 and PII, suggesting that His may serve as a signal molecule. Taken together, our study reveals that His promotes plant seed oil deposition through ABA biosynthesis and β-oxidation. PMID:27493214

  3. Histidine Regulates Seed Oil Deposition through Abscisic Acid Biosynthesis and β-Oxidation.

    Science.gov (United States)

    Ma, Huimin; Wang, Shui

    2016-10-01

    The storage compounds are deposited into plant seeds during maturation. As the model oilseed species, Arabidopsis (Arabidopsis thaliana) has long been studied for seed oil deposition. However, the regulation of this process remains unclear. Through genetic screen with a seed oil body-specific reporter, we isolated low oil1 (loo1) mutant. LOO1 was mapped to HISTIDINE BIOSYNTHESIS NUMBER 1A (HISN1A). HISN1A catalyzes the first step of His biosynthesis. Oil significantly decreased, and conversely proteins markedly increased in hisn1a mutants, indicating that HISN1A regulates both oil accumulation and the oil-protein balance. HISN1A was predominantly expressed in embryos and root tips. Accordingly, the hisn1a mutants exhibited developmental phenotype especially of seeds and roots. Transcriptional profiling displayed that β-oxidation was the major metabolic pathway downstream of HISN1A β-Oxidation was induced in hisn1a mutants, whereas it was reduced in 35S:HISN1A-transgenic plants. In plants, seed storage oil is broken-down by β-oxidation, which is controlled by abscisic acid (ABA). We found that His activated genes of ABA biosynthesis and correspondingly advanced ABA accumulation. Exogenous ABA rescued the defects of hisn1a mutants, whereas mutation of ABA DEFICIENT2, a key enzyme in ABA biosynthesis, blocked the effect of His on β-oxidation, indicating that ABA mediates His regulation in β-oxidation. Intriguingly, structural analysis showed that a potential His-binding domain was present in the general amino acid sensors GENERAL CONTROL NON-DEREPRESSIBLE2 and PII, suggesting that His may serve as a signal molecule. Taken together, our study reveals that His promotes plant seed oil deposition through ABA biosynthesis and β-oxidation. © 2016 American Society of Plant Biologists. All Rights Reserved.

  4. A Duo of Potassium-Responsive Histidine Kinases Govern the Multicellular Destiny of Bacillus subtilis

    Science.gov (United States)

    de Oña, Paula; Kunert, Maritta; Leñini, Cecilia; Gallegos-Monterrosa, Ramses; Mhatre, Eisha; Vileta, Darío; Hölscher, Theresa; Kuipers, Oscar P.

    2015-01-01

    ABSTRACT Multicellular biofilm formation and surface motility are bacterial behaviors considered mutually exclusive. However, the basic decision to move over or stay attached to a surface is poorly understood. Here, we discover that in Bacillus subtilis, the key root biofilm-controlling transcription factor Spo0A~Pi (phosphorylated Spo0A) governs the flagellum-independent mechanism of social sliding motility. A Spo0A-deficient strain was totally unable to slide and colonize plant roots, evidencing the important role that sliding might play in natural settings. Microarray experiments plus subsequent genetic characterization showed that the machineries of sliding and biofilm formation share the same main components (i.e., surfactin, the hydrophobin BslA, exopolysaccharide, and de novo-formed fatty acids). Sliding proficiency was transduced by the Spo0A-phosphorelay histidine kinases KinB and KinC. We discovered that potassium, a previously known inhibitor of KinC-dependent biofilm formation, is the specific sliding-activating signal through a thus-far-unnoticed cytosolic domain of KinB, which resembles the selectivity filter sequence of potassium channels. The differential expression of the Spo0A~Pi reporter abrB gene and the different levels of the constitutively active form of Spo0A, Sad67, in Δspo0A cells grown in optimized media that simultaneously stimulate motile and sessile behaviors uncover the spatiotemporal response of KinB and KinC to potassium and the gradual increase in Spo0A~Pi that orchestrates the sequential activation of sliding, followed by sessile biofilm formation and finally sporulation in the same population. Overall, these results provide insights into how multicellular behaviors formerly believed to be antagonistic are coordinately activated in benefit of the bacterium and its interaction with the host. PMID:26152584

  5. Impact of chromium histidinate on high fat diet induced obesity in rats

    Directory of Open Access Journals (Sweden)

    Tuzcu Zeynep

    2011-05-01

    Full Text Available Abstract Background Chromium (Cr is an essential trace element that has garnered interest for use as a weight loss aid, but its molecular mechanism in obesity is not clear. In this study, an attempt has been made to investigate the effects of chromium histidinate (CrHis on glucose transporter-2 (GLUT-2, nuclear factor erythroid 2-related factor 2 (Nrf2, heme oxygenase-1 (HO-1, nuclear factor-kappa B (NF-κB p65 and the oxidative stress marker 4-hydroxynonenal adducts (HNE expressions in liver of rats fed high fat diet (HFD. Methods Male Wistar rats (n = 40, 8 wk-old were divided into four groups. Group I was fed a standard diet (12% of calories as fat; Group II was fed a standard diet and supplemented with 110 μg CrHis/kg BW/d; Group III was fed a HFD (40% of calories as fat; Group IV was fed HFD and supplemented with 110 μg CrHis/kg BW/d. Results Rats fed HFD possessed greater serum insulin (40 vs.33 pmol/L and glucose (158 vs. 143 mg/dL concentration and less liver Cr (44 vs.82 μg/g concentration than rats fed the control diet. However, rats supplemented with CrHis had greater liver Cr and serum insulin and lower glucose concentration in rats fed HFD (P P P Conclusion These findings demonstrate that supplementation of CrHis is protective against obesity, at least in part, through Nrf2-mediated induction of HO-1 in rats fed high fat diet.

  6. Survival of bacteria in nuclear waste buffer materials. The influence of nutrients, temperature and water activity

    Energy Technology Data Exchange (ETDEWEB)

    Pedersen, K.; Motamedi, M. [Goeteborg Univ. (Sweden). Dept. of General and Marine Microbiology; Karnland, O. [Clay Technology AB, Lund (Sweden)

    1995-12-01

    The concept of deep geological disposal of spent fuel is common to many national nuclear waste programs. Long-lived radioactive waste will be encapsulated in canisters made of corrosion resistant materials e.g. copper and buried several hundred meters below ground in a geological formation. Different types of compacted bentonite clay, or mixtures with sand, will be placed as a buffer around the waste canisters. A major concern for the performance of the canisters is that sulphate-reducing bacteria (SRB) may be present in the clay and induce corrosion by production of hydrogen sulphide. This report presents data on viable counts of SRB in the bedrock of Aespoe hard rock laboratory. A theoretical background on the concept water activity is given, together with basic information about SRB. Some results on microbial populations from a full scale buffer test in Canada is presented. These results suggested water activity to be a strong limiting factor for survival of bacteria in compacted bentonite. As a consequence, experiments were set up to investigate the effect from water activity on survival of SRB in bentonite. Here we show that survival of SRB in bentonite depends on the availability of water and that compacting a high quality bentonite to a density of 2.0 g/cm{sup 3}, corresponding to a water activity (a{sub w}) of 0.96, prevented SRB from surviving in the clay. 24 refs.

  7. Is there a common water-activity limit for the three domains of life?

    NARCIS (Netherlands)

    Stevenson, Andrew; Cray, Jonathan A; Williams, Jim P; Santos, Ricardo; Sahay, Richa; Neuenkirchen, Nils; McClure, Colin D; Grant, Irene R; Houghton, Jonathan Dr; Quinn, John P; Timson, David J; Patil, Satish V; Singhal, Rekha S; Antón, Josefa; Dijksterhuis, Jan; Hocking, Ailsa D; Lievens, Bart; Rangel, Drauzio E N; Voytek, Mary A; Gunde-Cimerman, Nina; Oren, Aharon; Timmis, Kenneth N; McGenity, Terry J; Hallsworth, John E

    2014-01-01

    Archaea and Bacteria constitute a majority of life systems on Earth but have long been considered inferior to Eukarya in terms of solute tolerance. Whereas the most halophilic prokaryotes are known for an ability to multiply at saturated NaCl (water activity (aw) 0.755) some xerophilic fungi can

  8. Effect of pH, temperature and water activity on the inhibition of ...

    African Journals Online (AJOL)

    WiN 7

    2012-01-31

    Jan 31, 2012 ... Effect of pH, temperature and water activity on the inhibition of Botrytis cinerea by Bacillus amyloliquefaciens isolates. Hamdache Ahlem1, Ezziyyani Mohammed2, Alain Badoc3 and Lamarti Ahmed1*. 1Département de Biologie, Faculté des Sciences, Equipe de Biotechnologies Végétales. M‟hannech II ...

  9. Determination of moisture content and water activity in algae and fish by thermoanalytical techniques

    Directory of Open Access Journals (Sweden)

    Vilma Mota da Silva

    2008-01-01

    Full Text Available The water content in seafoods is very important since it affects their sensorial quality, microbiological stability, physical characteristics and shelf life. In this study, thermoanalytical techniques were employed to develop a simple and accurate method to determine water content (moisture by thermogravimetry (TG and water activity from moisture content values and freezing point depression using differential scanning calorimetry (DSC. The precision of the results suggests that TG is a suitable technique to determine moisture content in biological samples. The average water content values for fish samples of Lutjanus synagris and Ocyurus chrysurus species were 76.4 ± 5.7% and 63.3 ± 3.9%, respectively, while that of Ulva lactuca marine algae species was 76.0 ± 4.4%. The method presented here was also successfully applied to determine water activity in two species of fish and six species of marine algae collected in the Atlantic coastal waters of Bahia, in Brazil. Water activity determined in fish samples ranged from 0.946 - 0.960 and was consistent with values reported in the literature, i.e., 0.9 - 1.0. The water activity values determined in marine algae samples lay within the interval of 0.974 - 0.979.

  10. Predicting the initial freezing point and water activity of meat products from composition data

    NARCIS (Netherlands)

    Sman, van der R.G.M.; Boer, E.P.J.

    2005-01-01

    In this paper we predict the water activity and initial freezing point of food products (meat and fish) based on their composition. The prediction is based on thermodynamics (the Clausius-Clapeyron equation, the Ross equation and an approximation of the Pitzer equation). Furthermore, we have taken

  11. Analysis of the Effect of Water Activity on Ice Formation Using a New Theory of Nucleation

    Science.gov (United States)

    Barahona, Donifan

    2013-01-01

    In this work a new theory of nucleation is developed and used to investigate the effect of water activity on the formation of ice within super-cooled droplets. The new theory is based on a novel concept where the interface is assumed to be made of liquid molecules trapped by the solid matrix. Using this concept new expressions are developed for the critical ice germ size and the nucleation work, with explicit dependencies on temperature and water activity. However unlike previous approaches, the new theory does not depend on the interfacial tension between liquid and ice. Comparison against experimental results shows that the new theory is able to reproduce the observed effect of water activity on nucleation rate and freezing temperature. It allows for the first time a theoretical derivation of the constant shift in water activity between melting and nucleation. The new theory offers a consistent thermodynamic view of ice nucleation, simple enough to be applied in atmospheric models of cloud formation.

  12. Low-water activity foods: increased concern as vehicles of foodborne pathogens

    NARCIS (Netherlands)

    Beuchat, L.R.; Komitopoulou, E.; Beckers, H.; Betts, R.P.; Bourdichon, F.; Fanning, S.; Joosten, H.M.L.J.; Kuile, ter B.H.

    2013-01-01

    Foods and food ingredients with low water activity (aw) have been implicated with increased frequency in recent years as vehicles for pathogens that have caused outbreaks of illnesses. Some of these foodborne pathogens can survive for several months, even years, in low-aw foods and in dry food

  13. Low-water activity foods: increased concern as vehicles of foodborne pathogens

    NARCIS (Netherlands)

    Beuchat, L.R.; Komitopoulou, E.; Beckers, H.; Betts, R.P.; Bourdichon, F.; Fanning, S.; Joosten, H.M.; ter Kuile, B.H.

    2013-01-01

    Foods and food ingredients with low water activity (a(w)) have been implicated with increased frequency in recent years as vehicles for pathogens that have caused outbreaks of illnesses. Some of these foodborne pathogens can survive for several months, even years, in low-a(w) foods and in dry food

  14. Determination of moisture content and water activity in algae and fish by thermoanalytical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Vilma Mota da; Silva, Luciana Almeida; Andrade, Jailson B. de [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil). Inst. de Quimica]. E-mail: jailsong@ufba.br; Veloso, Marcia C. da Cunha [Centro Federal de Educacao Tecnologica da Bahia (CEFET-BA), Salvador, BA (Brazil)); Santos, Gislaine Vieira [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil). Inst. de Biologia

    2008-07-01

    The water content in seafoods is very important since it affects their sensorial quality, microbiological stability, physical characteristics and shelf life. In this study, thermoanalytical techniques were employed to develop a simple and accurate method to determine water content (moisture) by thermogravimetry (TG) and water activity from moisture content values and freezing point depression using differential scanning calorimetry (DSC). The precision of the results suggests that TG is a suitable technique to determine moisture content in biological samples. The average water content values for fish samples of Lutjanus synagris and Ocyurus chrysurus species were 76.4 {+-} 5.7% and 63.3 {+-} 3.9%, respectively, while that of Ulva lactuca marine algae species was 76.0 {+-} 4.4%. The method presented here was also successfully applied to determine water activity in two species of fish and six species of marine algae collected in the Atlantic coastal waters of Bahia, in Brazil. Water activity determined in fish samples ranged from 0.946 - 0.960 and was consistent with values reported in the literature, i.e., 0.9 - 1.0. The water activity values determined in marine algae samples lay within the interval of 0.974 - 0.979. (author)

  15. The genome of the square archaeon Haloquadratum walsbyi : life at the limits of water activity

    NARCIS (Netherlands)

    Bolhuis, Henk; Palm, Peter; Wende, Andy; Falb, Michaela; Rampp, Markus; Rodriguez-Valera, Francisco; Pfeiffer, Friedhelm; Oesterhelt, Dieter

    2006-01-01

    Background: The square halophilic archaeon Haloquadratum walsbyi dominates NaCl- saturated and MgCl2 enriched aquatic ecosystems, which imposes a serious desiccation stress, caused by the extremely low water activity. The genome sequence was analyzed and physiological and physical experiments were

  16. Is there a common water-activity limit for the three domains of life?

    Science.gov (United States)

    Stevenson, Andrew; Cray, Jonathan A; Williams, Jim P; Santos, Ricardo; Sahay, Richa; Neuenkirchen, Nils; McClure, Colin D; Grant, Irene R; Houghton, Jonathan DR; Quinn, John P; Timson, David J; Patil, Satish V; Singhal, Rekha S; Antón, Josefa; Dijksterhuis, Jan; Hocking, Ailsa D; Lievens, Bart; Rangel, Drauzio E N; Voytek, Mary A; Gunde-Cimerman, Nina; Oren, Aharon; Timmis, Kenneth N; McGenity, Terry J; Hallsworth, John E

    2015-01-01

    Archaea and Bacteria constitute a majority of life systems on Earth but have long been considered inferior to Eukarya in terms of solute tolerance. Whereas the most halophilic prokaryotes are known for an ability to multiply at saturated NaCl (water activity (aw) 0.755) some xerophilic fungi can germinate, usually at high-sugar concentrations, at values as low as 0.650–0.605 aw. Here, we present evidence that halophilic prokayotes can grow down to water activities of Eurotium spp.). We also manipulated the balance of chaotropic and kosmotropic stressors for the extreme, xerophilic fungi Aspergillus penicilloides and X. bisporus and, via this approach, their established water-activity limits for mycelial growth (∼0.65) were reduced to 0.640. Furthermore, extrapolations indicated theoretical limits of 0.632 and 0.636 aw for A. penicilloides and X. bisporus, respectively. Collectively, these findings suggest that there is a common water-activity limit that is determined by physicochemical constraints for the three domains of life. PMID:25500507

  17. Multiplication of microbes below 0.690 water activity : implications for terrestrial and extraterrestrial life

    NARCIS (Netherlands)

    Stevenson, Andrew; Burkhardt, Jürgen; Cockell, Charles S; Cray, Jonathan A; Dijksterhuis, Jan; Fox-Powell, Mark; Kee, Terence P; Kminek, Gerhard; McGenity, Terry J; Timmis, Kenneth N; Timson, David J; Voytek, Mary A; Westall, Frances; Yakimov, Michail M; Hallsworth, John E

    Since a key requirement of known life forms is available water (water activity; aw ), recent searches for signatures of past life in terrestrial and extraterrestrial environments have targeted places known to have contained significant quantities of biologically available water. However, early life

  18. Water Content or Water Activity: What Rules Crispy Behavior in Bread Crust?

    NARCIS (Netherlands)

    Nieuwenhuijzen, van N.H.; Primo-Martin, C.; Meinders, M.B.J.; Tromp, R.H.; Hamer, R.J.; Vliet, van T.

    2008-01-01

    A dry crust loses its crispness when water migrates into the crust. It is not clear if it is the amount of water absorbed or the water activity (aw) that leads to a loss of crispness. The hysteresis effect observed when recording a water sorption isotherm allowed us to study the effects of aw and

  19. Water content or water activity: What rules crispy behavior in bread crust?

    NARCIS (Netherlands)

    Nieuwenhuijzen, N.H. van; Primo-Martín, C.; Meinders, M.B.J.; Tromp, R.H.; Hamer, R.J.; Vliet, T. van

    2008-01-01

    A dry crust loses its crispness when water migrates into the crust. It is not clear if it is the amount of water absorbed or the water activity (a w) that leads to a loss of crispness. The hysteresis effect observed when recording a water sorption isotherm allowed us to study the effects of aw and

  20. Conidia of Penicillium rubens formed at low water activities can attract more water.

    Science.gov (United States)

    van Laarhoven, Karel A; Peeters, Loes H M; Bekker, Mirjam; Huinink, Hendrik P; Adan, Olaf C G

    2017-09-04

    To address the problem of indoor fungal growth, understanding the influence of moisture conditions on the fungal colonization process is crucial. This paper explores the influence of past moisture conditions on current processes. Specifically, it studies the growth and water sorption of conidia of Penicillium rubens formed at lower water activities (ranging from 0.86 to 0.99). For the first time, dynamic vapor sorption (DVS) is applied as a tool to quantify the water sorption of conidia as a function of the water activity at conidiation. Furthermore, growth experiments on agar and gypsum substrates are reported that relate hyphal growth rates of the mycelium from pretreated conidia to the water activity at conidiation. No effect of the conidiation water activity on mycelial growth rates is found on either gypsum or agar. It is found, however, that conidia formed at lower activities have a higher dry weight and attract more water from humid air. It is shown that both phenomena can be explained by conidia from lower activities carrying higher amounts of compatible solutes, glycerol in particular. The enhanced sorption observed in this study might constitute a mechanism through which solute reserves contribute to survival during the early steps of fungal colonization. © 2017 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

  1. Extremophilic fungi in arctic ice: a relationship between adaptation to low temperature and water activity

    DEFF Research Database (Denmark)

    Gunde-Cimerman, N.; Sonjak, S.; Zalar, P.

    2003-01-01

    Little is known about fungal diversity in extremely cold regions. Low temperatures induce the formation of ice crystals and therefore also the creation of low water activity (a(w)). These are the dominant factors in external chemistry that influence microbial biota in cold regions. Therefore, we ...

  2. The effect of water activity and temperature on the production of some mycotoxins

    NARCIS (Netherlands)

    Northolt, M.D.

    1979-01-01

    Preventing mold from growing and producing mycotoxins requires knowledge of the conditions under which each of the toxinogenic molds becomes active. In this investigation the relation between fungal growth and mycotoxin formation and the factors water activity and temperature is studied.

  3. Polyakov loop modeling for hot QCD

    Science.gov (United States)

    Fukushima, Kenji; Skokov, Vladimir

    2017-09-01

    We review theoretical aspects of quantum chromodynamics (QCD) at finite temperature. The most important physical variable to characterize hot QCD is the Polyakov loop, which is an approximate order parameter for quark deconfinement in a hot gluonic medium. Additionally to its role as an order parameter, the Polyakov loop has rich physical contents in both perturbative and non-perturbative sectors. This review covers a wide range of subjects associated with the Polyakov loop from topological defects in hot QCD to model building with coupling to the Polyakov loop.

  4. Vertically Polarized Omnidirectional Printed Slot Loop Antenna

    DEFF Research Database (Denmark)

    Kammersgaard, Nikolaj Peter Iversen; Kvist, Søren H.; Thaysen, Jesper

    2015-01-01

    A novel vertically polarized omnidirectional printed slot loop antenna has been designed, simulated, fabricated and measured. The slot loop works as a magnetic loop. The loop is loaded with inductors to insure uniform and in-phase fields in the slot in order to obtain an omnidirectional radiation...... pattern. The antenna is designed for the 2.45 GHz Industrial, Scientific and Medical band. Applications of the antenna are many. One is for on-body applications since it is ideal for launching a creeping waves due to the polarization....

  5. Nonlinear Bayesian Tracking Loops for Multipath Mitigation

    Directory of Open Access Journals (Sweden)

    Pau Closas

    2012-01-01

    Full Text Available This paper studies Bayesian filtering techniques applied to the design of advanced delay tracking loops in GNSS receivers with multipath mitigation capabilities. The analysis includes tradeoff among realistic propagation channel models and the use of a realistic simulation framework. After establishing the mathematical framework for the design and analysis of tracking loops in the context of GNSS receivers, we propose a filtering technique that implements Rao-Blackwellization of linear states and a particle filter for the nonlinear partition and compare it to traditional delay lock loop/phase lock loop-based schemes.

  6. Soft Neutrosophic Loops and Their Generalization

    Directory of Open Access Journals (Sweden)

    Mumtaz Ali

    2014-06-01

    Full Text Available Soft set theory is a general mathematical tool for dealing with uncertain, fuzzy, not clearly defined objects. In this paper we introduced soft neutrosophic loop,soft neutosophic biloop, soft neutrosophic N -loop with the discuission of some of their characteristics. We also introduced a new type of soft neutrophic loop, the so called soft strong neutrosophic loop which is of pure neutrosophic character. This notion also found in all the other corresponding notions of soft neutrosophic thoery. We also given some of their properties of this newly born soft structure related to the strong part of neutrosophic theory.

  7. UWB communication receiver feedback loop

    Science.gov (United States)

    Spiridon, Alex; Benzel, Dave; Dowla, Farid U.; Nekoogar, Faranak; Rosenbury, Erwin T.

    2007-12-04

    A novel technique and structure that maximizes the extraction of information from reference pulses for UWB-TR receivers is introduced. The scheme efficiently processes an incoming signal to suppress different types of UWB as well as non-UWB interference prior to signal detection. Such a method and system adds a feedback loop mechanism to enhance the signal-to-noise ratio of reference pulses in a conventional TR receiver. Moreover, sampling the second order statistical function such as, for example, the autocorrelation function (ACF) of the received signal and matching it to the ACF samples of the original pulses for each transmitted bit provides a more robust UWB communications method and system in the presence of channel distortions.

  8. Closed loop steam cooled airfoil

    Science.gov (United States)

    Widrig, Scott M.; Rudolph, Ronald J.; Wagner, Gregg P.

    2006-04-18

    An airfoil, a method of manufacturing an airfoil, and a system for cooling an airfoil is provided. The cooling system can be used with an airfoil located in the first stages of a combustion turbine within a combined cycle power generation plant and involves flowing closed loop steam through a pin array set within an airfoil. The airfoil can comprise a cavity having a cooling chamber bounded by an interior wall and an exterior wall so that steam can enter the cavity, pass through the pin array, and then return to the cavity to thereby cool the airfoil. The method of manufacturing an airfoil can include a type of lost wax investment casting process in which a pin array is cast into an airfoil to form a cooling chamber.

  9. Lose Your Loops with Numpy

    CERN Multimedia

    CERN. Geneva

    2016-01-01

    Developing in python is fast. Computation, however, can often be another story. Or at least that is how it may seem. When working with arrays and numerical datasets one can subvert many of python’s computational limitations by utilizing numpy. Numpy is python’s standard matrix computation library. Many python users only use numpy to store and generate arrays, failing to utilize one of python’s most powerful computational tools. By leveraging numpy’s ufuncs, aggregation, broadcasting and slicing/masking/indexing functionality one can cut back on slow python loops and increase the speed of their programs by as much as 100x. This talk aims at teaching attendees how to use these tools through toy examples.

  10. Fiber loop ringdown humidity sensor.

    Science.gov (United States)

    Alali, Haifa; Wang, Chuji

    2016-11-01

    An optical fiber relative humidity (RH) sensor based on the evanescent field-fiber loop ringdown (EF-FLRD) technique is demonstrated. The sensor was placed inside a chamber that provides a humidity reference and is monitored by a humidity meter. The presence of moisture in the chamber changes the refractive index of the medium; thus the ringdown time changes due to a change in the EF scattering loss induced in the sensor head. The sensor demonstrated a fast response (∼1  s), high sensitivity, and excellent reproducibility and reversibly. The EF-FLRD sensor can measure RH in a wide dynamic range of 4% to 100% at a constant temperature of 20±1°C.

  11. Introduction of a covalent histidine-heme linkage in a hemoglobin: a promising tool for heme protein engineering.

    Science.gov (United States)

    Rice, Selena L; Preimesberger, Matthew R; Johnson, Eric A; Lecomte, Juliette T J

    2014-12-01

    The hemoglobins of the cyanobacteria Synechococcus and Synechocystis (GlbNs) are capable of spontaneous and irreversible attachment of the b heme to the protein matrix. The reaction, which saturates the heme 2-vinyl by addition of a histidine residue, is reproduced in vitro by preparing the recombinant apoprotein, adding ferric heme, and reducing the iron to the ferrous state. Spontaneous covalent attachment of the heme is potentially useful for protein engineering purposes. Thus, to explore whether the histidine-heme linkage can serve in such applications, we attempted to introduce it in a test protein. We selected as our target the heme domain of Chlamydomonas eugametos LI637 (CtrHb), a eukaryotic globin that exhibits less than 50% sequence identity with the cyanobacterial GlbNs. We chose two positions, 75 in the FG corner and 111 in the H helix, to situate a histidine near a vinyl group. We characterized the proteins with gel electrophoresis, absorbance spectroscopy, and NMR analysis. Both T111H and L75H CtrHbs reacted upon reduction of the ferric starting material containing cyanide as the distal ligand to the iron. With L75H CtrHb, nearly complete (>90%) crosslinking was observed to the 4-vinyl as expected from the X-ray structure of wild-type CtrHb. Reaction of T111H CtrHb also occurred at the 4-vinyl, in a 60% yield indicating a preference for the flipped heme orientation in the starting material. The work suggests that the His-heme modification will be applicable to the design of proteins with a non-dissociable heme group. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Biofabrication of ZnS:Mn luminescent nanocrystals using histidine, hexahistidine, and His-tagged proteins: a comparison study.

    Science.gov (United States)

    Zhou, Weibin; Baneyx, François

    2014-08-15

    The ubiquitous hexahistidine purification tag has been used to conjugate proteins to the shell of CdSe:ZnS quantum dots (QDs) due to its affinity for surface-exposed Zn(2+) ions but little attention has been paid to the potential of His-tagged proteins for mineralizing luminescent ZnS nanocrystals. Here, we compare the ability of free histidine, a His tag peptide, His-tagged thioredoxin (TrxA, a monomeric protein), and N- and C-terminally His-tagged versions of Hsp31 (a homodimeric protein) to support the synthesis of Mn-doped ZnS nanocrystals from aqueous precursors under mild conditions of pH (8.2) and temperature (37°C). We find that: (1) it is possible to produce poor quality QDs when histidine is used at high (8 mM) concentration; (2) an increase in local histidine concentration through repetition of the amino acid as a His tag decreases the amount of needed reagent ≈10-fold and improves optical properties; (3) fusion of the same His tag to TrxA allows for ZnS:Mn QDs mineralization at micromolar concentrations; and (4) doubling the local hexahistidine concentration by exploiting Hsp31 dimerization further improves nanocrystal luminescence with the brightest particles obtained when His tags are spatially co-localized at the Hsp31 N-termini. Although hexahistidine tracts are not as efficient as combinatorially selected ZnS binding peptides at QD synthesis, it should be possible to use the large number of available His-tagged proteins and the synthesis approach described herein to produce luminescent nanoparticles whose protein shell carries a broad range of functions.

  13. Histidines in the octapeptide repeat of PrPC react with PrPSc at an acidic pH.

    Science.gov (United States)

    Cruite, Justin T; Abalos, Gil C; Bellon, Anne; Solforosi, Laura

    2011-03-15

    Cellular PrP is actively cycled between the cell surface and the endosomal pathway. The exact site and mechanism of conversion from PrP(C) to PrP(Sc) remain unknown. We have previously used recombinant antibodies containing grafts of PrP sequence to identify three regions of PrP(C) (aa23-27, 98-110, and 136-158) that react with PrP(Sc) at neutral pH. To determine if any regions of PrP(C) react with PrP(Sc) at an acidic pH similar to that of an endosomal compartment, we tested our panel of grafted antibodies for the ability to precipitate PrP(Sc) in a range of pH conditions. At pH near or lower than 6, PrP-grafted antibodies representing the octapeptide repeat react strongly with PrP(Sc) but not PrP(C). Modified grafts in which the histidines of the octarepeat were replaced with alanines did not react with PrP(Sc). PrP(Sc) precipitated by the octapeptide at pH 5.7 was able to seed conversion of normal PrP to PrP(Sc) in vitro. However, modified PrP containing histidine to alanine substitutions within the octapeptide repeats was still converted to PrP(Sc) in N2a cells. These results suggest that once PrP has entered the endosomal pathway, the acidic environment facilitates the binding of PrP(Sc) to the octarepeat of PrP(C) by the change in charge of the histidines within the octarepeat.

  14. Cloning and sequencing of the histidine decarboxylase gene from Photobacterium phosphoreum and its functional expression in Escherichia coli.

    Science.gov (United States)

    Morii, Hideaki; Kasama, Kentaro; Herrera-Espinoza, Raul

    2006-08-01

    The major causative agent of scombroid poisoning is histamine formed by bacterial decarboxylation of histidine. We reported previously that histamine was exclusively formed by the psychrotrophic halophilic bacteria Photobacterium phosphoreum in scombroid fish during storage at or below 10 degrees C. Moreover, histamine-forming ability was affected by two histidine decarboxylases (HDCs): constitutive and inducible enzymes. In this study, the gene encoding P. phosphoreum HDC was cloned into Escherichia coli and sequenced. A sequence analysis of the DNA corresponding to the hdc gene revealed an open reading frame of 1,140 bp coding for a pyridoxal-5'-phosphate-dependent HDC of 380 amino acid residues with a predicted molecular mass of 42.6 kDa. The HDC amino acid sequences formed a phylogenetic clade with strong bootstrap support and revealed high sequence similarities among the P. phosphoreum isolate and species of the family Enterobacteriaceae and a separate phylogenetic branch with the lowest sequence similarity between the isolate and the taxonomically closer Listonella anguillarum. The T7 promoter was used to overexpress the hdc gene in E. coli cells. The recombinant clone, E. coli BL21(DE3), displayed significant levels of HDC activity. The recombinant hdc gene was suggested to code the inducible HDC; therefore, the optimum reaction conditions of the recombinant HDC were similar to those of the inducible HDC in the P. phosphoreum isolate. In addition, a putative catabolite-repressor protein binding site, amino acid permease gene, and histidine-tRNA synthetase gene were found in flanking regions of the hdc gene.

  15. Improving the binding capacity of Ni2+ decorated porous magnetic silica spheres for histidine-rich protein separation.

    Science.gov (United States)

    Benelmekki, M; Caparros, C; Xuriguera, E; Lanceros-Mendez, S; Rodriguez-Carmona, E; Mendoza, R; Corchero, J L; Martinez, Ll M

    2013-01-01

    Biomagnetic immobilization of histidine-rich proteins based on the single-step affinity adsorption of transition metal ions continues to be a suitable practice as a cost effective and a up scaled alternative to the to multiple-step chromatographic separations. In our previous work, we synthesised Porous Magnetic silica (PMS) spheres by one-step hydrothermal-assisted modified-stöber method. The obtained spheres were decorated with Ni(2+) and Co(2+), and evaluated for the capture of a H6-Tagged green fluorescence protein (GFP-H6) protein. The binding capacity of the obtained spheres was found to be slightly higher in the case Ni(2+) decorated PMS spheres (PMSNi). However, comparing with commercial products, the binding capacity was found to be lower than the expected. In this way, the present work is an attempt to improve the binding capacity of PMSNi to histidine-rich proteins. We find that increasing the amount of Ni(2+) onto the surface of the PMS spheres leads to an increment of the binding capacity to GFP-H6 by a factor of two. On the other hand, we explore how the size of histidine-rich protein can affect the binding capacity comparing the results of the GFP-6H to those of the His-tagged α-galactosidase (α-GLA). Finally, we demonstrate that the optimization of the magnetophoresis parameters during washing and eluting steps can lead to an additional improvement of the binding capacity. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Evolution of Helicobacter: Acquisition by Gastric Species of Two Histidine-Rich Proteins Essential for Colonization

    Science.gov (United States)

    Vorontsov, Egor; Gallaud, Julien; Malosse, Christian; Michel, Valérie; Cavazza, Christine; Robbe-Saule, Marie; Richaud, Pierre; Chamot-Rooke, Julia; Brochier-Armanet, Céline; De Reuse, Hilde

    2015-01-01

    Metal acquisition and intracellular trafficking are crucial for all cells and metal ions have been recognized as virulence determinants in bacterial pathogens. Virulence of the human gastric pathogen Helicobacter pylori is dependent on nickel, cofactor of two enzymes essential for in vivo colonization, urease and [NiFe] hydrogenase. We found that two small paralogous nickel-binding proteins with high content in Histidine (Hpn and Hpn-2) play a central role in maintaining non-toxic intracellular nickel content and in controlling its intracellular trafficking. Measurements of metal resistance, intracellular nickel contents, urease activities and interactomic analysis were performed. We observed that Hpn acts as a nickel-sequestration protein, while Hpn-2 is not. In vivo, Hpn and Hpn-2 form homo-multimers, interact with each other, Hpn interacts with the UreA urease subunit while Hpn and Hpn-2 interact with the HypAB hydrogenase maturation proteins. In addition, Hpn-2 is directly or indirectly restricting urease activity while Hpn is required for full urease activation. Based on these data, we present a model where Hpn and Hpn-2 participate in a common pathway of controlled nickel transfer to urease. Using bioinformatics and top-down proteomics to identify the predicted proteins, we established that Hpn-2 is only expressed by H. pylori and its closely related species Helicobacter acinonychis. Hpn was detected in every gastric Helicobacter species tested and is absent from the enterohepatic Helicobacter species. Our phylogenomic analysis revealed that Hpn acquisition was concomitant with the specialization of Helicobacter to colonization of the gastric environment and the duplication at the origin of hpn-2 occurred in the common ancestor of H. pylori and H. acinonychis. Finally, Hpn and Hpn-2 were found to be required for colonization of the mouse model by H. pylori. Our data show that during evolution of the Helicobacter genus, acquisition of Hpn and Hpn-2 by gastric

  17. Thermochemistry of alkali metal cation interactions with histidine: influence of the side chain.

    Science.gov (United States)

    Armentrout, P B; Citir, Murat; Chen, Yu; Rodgers, M T

    2012-12-06

    The interactions of alkali metal cations (M(+) = Na(+), K(+), Rb(+), Cs(+)) with the amino acid histidine (His) are examined in detail. Experimentally, bond energies are determined using threshold collision-induced dissociation of the M(+)(His) complexes with xenon in a guided ion beam tandem mass spectrometer. Analyses of the energy dependent cross sections provide 0 K bond energies of 2.31 ± 0.11, 1.70 ± 0.08, 1.42 ± 0.06, and 1.22 ± 0.06 eV for complexes of His with Na(+), K(+), Rb(+), and Cs(+), respectively. All bond dissociation energy (BDE) determinations include consideration of unimolecular decay rates, internal energy of reactant ions, and multiple ion-neutral collisions. These experimental results are compared to values obtained from quantum chemical calculations conducted previously at the MP2(full)/6-311+G(2d,2p), B3LYP/6-311+G(2d,2p), and B3P86/6-311+G(2d,2p) levels with geometries and zero point energies calculated at the B3LYP/6-311+G(d,p) level where Rb and Cs use the Hay-Wadt effective core potential and basis set augmented with additional polarization functions (HW*). Additional calculations using the def2-TZVPPD basis set with B3LYP geometries were conducted here at all three levels of theory. Either basis set yields similar results for Na(+)(His) and K(+)(His), which are in reasonable agreement with the experimental BDEs. For Rb(+)(His) and Cs(+)(His), the HW* basis set and ECP underestimate the experimental BDEs, whereas the def2-TZVPPD basis set yields results in good agreement. The effect of the imidazole side chain on the BDEs is examined by comparing the present results with previous thermochemistry for other amino acids. Both polarizability and the local dipole moment of the side chain are influential in the energetics.

  18. The histidine kinase AHK5 integrates endogenous and environmental signals in Arabidopsis guard cells.

    Directory of Open Access Journals (Sweden)

    Radhika Desikan

    2008-06-01

    Full Text Available Stomatal guard cells monitor and respond to environmental and endogenous signals such that the stomatal aperture is continually optimised for water use efficiency. A key signalling molecule produced in guard cells in response to plant hormones, light, carbon dioxide and pathogen-derived signals is hydrogen peroxide (H(2O(2. The mechanisms by which H(2O(2 integrates multiple signals via specific signalling pathways leading to stomatal closure is not known.Here, we identify a pathway by which H(2O(2, derived from endogenous and environmental stimuli, is sensed and transduced to effect stomatal closure. Histidine kinases (HK are part of two-component signal transduction systems that act to integrate environmental stimuli into a cellular response via a phosphotransfer relay mechanism. There is little known about the function of the HK AHK5 in Arabidopsis thaliana. Here we report that in addition to the predicted cytoplasmic localisation of this protein, AHK5 also appears to co-localise to the plasma membrane. Although AHK5 is expressed at low levels in guard cells, we identify a unique role for AHK5 in stomatal signalling. Arabidopsis mutants lacking AHK5 show reduced stomatal closure in response to H(2O(2, which is reversed by complementation with the wild type gene. Over-expression of AHK5 results in constitutively less stomatal closure. Abiotic stimuli that generate endogenous H(2O(2, such as darkness, nitric oxide and the phytohormone ethylene, also show reduced stomatal closure in the ahk5 mutants. However, ABA caused closure, dark adaptation induced H(2O(2 production and H(2O(2 induced NO synthesis in mutants. Treatment with the bacterial pathogen associated molecular pattern (PAMP flagellin, but not elf peptide, also exhibited reduced stomatal closure and H(2O(2 generation in ahk5 mutants.Our findings identify an integral signalling function for AHK5 that acts to integrate multiple signals via H(2O(2 homeostasis and is independent of ABA

  19. Improving the binding capacity of Ni2+ decorated porous magnetic silica spheres for histidine-rich protein separation

    OpenAIRE

    Benelmekki, Maria; Caparrós Vázquez, Cristina Maria; Xuriguera, Elena; Lanceros Méndez, Senentxu; Rodriguez-Carmona, Escar; Mendoza, R; Corchero, Jose Luis; Martinez, lluis Maria

    2012-01-01

    Biomagnetic immobilization of histidine-rich proteins based on the single-step affinity adsorption of transition metal ions continues to be a suitable practice as a cost effective and a up scaled alternative to the to multiple-step chromatographic separations. In our previous work [12], we synthesised Porous Magnetic silica (PMS) spheres by one-step hydrothermal-assisted modified-stöber method. The obtained spheres were decorated with Ni2+ and Co2+, and evaluated for the capture of a H6-Tagge...

  20. Vacuum energy sequestering and graviton loops

    OpenAIRE

    Kaloper, Nemanja; Padilla, Antonio

    2017-01-01

    We recently formulated a local mechanism of vacuum energy sequester. This mechanism automatically removes all matter loop contributions to vacuum energy from the stress energy tensor which sources the curvature. Here we adapt the local vacuum energy sequestering mechanism to also cancel all the vacuum energy loops involving virtual gravitons, in addition to the vacuum energy generated by matter fields alone.

  1. Loop calculus for lattice gauge theories

    Energy Technology Data Exchange (ETDEWEB)

    Gambini, R.; Leal, L.; Trias, A.

    1989-05-15

    Hamiltonian calculations are performed using a loop-labeled basis where the full set of identities for the SU(/ital N/) gauge models has been incorporated. The loops are classified as clusterlike structures and the eigenvalue problem leads to a linear set of finite-difference equations easily amenable to numerical treatment. Encouraging results are reported for SU(2) at spatial dimension 2.

  2. Newtonian gravity in loop quantum gravity

    OpenAIRE

    Smolin, Lee

    2010-01-01

    We apply a recent argument of Verlinde to loop quantum gravity, to conclude that Newton's law of gravity emerges in an appropriate limit and setting. This is possible because the relationship between area and entropy is realized in loop quantum gravity when boundaries are imposed on a quantum spacetime.

  3. Design Principles for Closed Loop Supply Chains

    NARCIS (Netherlands)

    H.R. Krikke (Harold); C.P. Pappis (Costas); G.T. Tsoulfas; J.M. Bloemhof-Ruwaard (Jacqueline)

    2001-01-01

    textabstractIn this paper we study design principles for closed loop supply chains. Closed loop supply chains aim at closing material flows thereby limiting emission and residual waste, but also providing customer service at low cost. We study 'traditional' and 'new' design principles known in the

  4. Holonomy loops, spectral triples and quantum gravity

    DEFF Research Database (Denmark)

    Johannes, Aastrup; Grimstrup, Jesper Møller; Nest, Ryszard

    2009-01-01

    We review the motivation, construction and physical interpretation of a semi-finite spectral triple obtained through a rearrangement of central elements of loop quantum gravity. The triple is based on a countable set of oriented graphs and the algebra consists of generalized holonomy loops...

  5. Droplet flows through periodic loop networks

    Science.gov (United States)

    Jeanneret, Raphael; Schindler, Michael; Bartolo, Denis

    2010-11-01

    Numerous microfluidic experiments have revealed non-trivial traffic dynamics when droplets flow through a channel including a single loop. A complex encoding of the time intervals between the droplets is achieved by the binary choices they make as they enter the loop. Very surprisingly, another set of experiments has demonstrated that the addition of a second loop does not increase the complexity of the droplet pattern. Conversely, the second loop decodes the temporal signal encrypted by the first loop [1]. In this talk we show that no first principle argument based on symmetry or conservation laws can account for this unexpected decoding process. Then, to better understand how a loop maps time intervals between droplets, we consider a simplified model which has proven to describe accurately microfluidic droplet flows. Combining numerical simulations and analytical calculations for the dynamic of three droplets travelling through N loops: (i) We show that three different traffic regimes exist, yet none of them yields exact decoding. (ii) We uncover that for a wide class of loop geometry, the coding process is analogous to a Hamiltonian mapping: regular orbits are destabilized in island chains and separatrix. (iii) Eventually, we propose a simple explanation to solve the apparent paradox with the coding/decoding dynamics observed in experiments. [1] M.J. Fuerstman, P. Garstecki, and G.M. Whitesides, Science, 315:828, 2007.

  6. Iron (III) porphyrin bearing 2,6-di-tert-butylphenol pendants deposited onto gold electrodes for amperometric determination of L-histidine.

    Science.gov (United States)

    Kurzatkowska, Katarzyna; Shpakovsky, Dmitry; Radecki, Jerzy; Radecka, Hanna; Jingwei, Zhang; Milaeva, Elena

    2009-04-15

    A sensitive amperometric sensor for determination of L-histidine was developed using gold electrode modified with Fe(III)-porphyrin bearing three 2,6-di-tert-butylphenol groups and one palmitoyl chain. Two methods of electrode modification were applied: direct chemisorption and embedment into dodecanethiol monolayer. Both types of electrodes were used for detection of L-histidine using Osteryoung square-wave voltammetry. The sensitivity of sensors presented towards L-histidine depends on the method of electrode modification. The detection limits observed for the electrodes incorporating with Fe(III)-porphyrin host by embedment and chemisorption were in 1 and 100 nM ranges, respectively. In addition, the determination of L-histidine with electrode modified by embedment technique was more precise, in comparison to that obtained by the direct chemisorption. Applicability of gold electrodes modified with Fe(III)-porphyrin for the direct electrochemical determination of L-histidine was demonstrated using the artificial matrix mimicking human serum.

  7. Binding of the human "electron transferring flavoprotein" (ETF) to the medium chain acyl-CoA dehydrogenase (MCAD) involves an arginine and histidine residue.

    Science.gov (United States)

    Parker, Antony R

    2003-10-01

    The interaction between the "electron transferring flavoprotein" (ETF) and medium chain acyl-CoA dehydrogenase (MCAD) enables successful flavin to flavin electron transfer, crucial for the beta-oxidation of fatty acids. The exact biochemical determinants for ETF binding to MCAD are unknown. Here we show that binding of human ETF, to MCAD, was inhibited by 2,3-butanedione and diethylpyrocarbonate (DEPC) and reversed by incubation with free arginine and hydroxylamine respectively. Spectral analyses of native ETF vs modified ETF suggested that flavin binding was not affected and that the loss of ETF activity with MCAD involved modification of one ETF arginine residue and one ETF histidine residue respectively. MCAD and octanoyl-CoA protected ETF against inactivation by both 2,3-butanedione and DEPC indicating that the arginine and histidine residues are present in or around the MCAD binding site. Comparison of exposed arginine and histidine residues among different ETF species, however, indicates that arginine residues are highly conserved but that histidine residues are not. These results lead us to conclude that this single arginine residue is essential for the binding of ETF to MCAD, but that the single histidine residue, although involved, is not.

  8. Phytoremediation of mixed-contaminated soil using the hyperaccumulator plant Alyssum lesbiacum: Evidence of histidine as a measure of phytoextractable nickel

    Energy Technology Data Exchange (ETDEWEB)

    Singer, Andrew C. [Centre for Ecology and Hydrology-Oxford, Mansfield Road, Oxford OX1 3SR (United Kingdom)]. E-mail: acsi@ceh.ac.uk; Bell, Thomas [Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS (United Kingdom); Heywood, Chloe A. [Centre for Ecology and Hydrology-Oxford, Mansfield Road, Oxford OX1 3SR (United Kingdom); Smith, J.A.C. [Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB (United Kingdom); Thompson, Ian P. [Centre for Ecology and Hydrology-Oxford, Mansfield Road, Oxford OX1 3SR (United Kingdom)

    2007-05-15

    In this study we examine the effects of polycyclic aromatic hydrocarbons (PAHs) on the ability of the hyperaccumulator plant Alyssum lesbiacum to phytoextract nickel from co-contaminated soil. Planted and unplanted mesocosms containing the contaminated soils were repeatedly amended with sorbitan trioleate, salicylic acid and histidine in various combinations to enhance the degradation of two PAHs (phenanthrene and chrysene) and increase nickel phytoextraction. Plant growth was negatively affected by PAHs; however, there was no significant effect on the phytoextraction of Ni per unit biomass of shoot. Exogenous histidine did not increase nickel phytoextraction, but the histidine-extractable fraction of soil nickel showed a high correlation with phytoextractable nickel. These results indicate that Alyssum lesbiacum might be effective in phytoextracting nickel from marginally PAH-contaminated soils. In addition, we provide evidence for the broader applicability of histidine for quantifying and predicting Ni phytoavailability in soils. - Alyssum lesbiacum was shown to phytoextract nickel from PAH-contaminated soils from which the pool of nickel accessed for phytoextraction is closely modelled by a histidine-soil extract.

  9. Mass Inflation in the Loop Black Hole

    CERN Document Server

    Brown, Eric G; Modesto, Leonardo

    2011-01-01

    In classical general relativity the Cauchy horizon within a two-horizon black hole is unstable via a phenomenon known as mass inflation, in which the mass parameter (and the spacetime curvature) of the black hole diverges at the Cauchy horizon. Here we study this effect for loop black holes -- quantum gravitationally corrected black holes from loop quantum gravity -- whose construction alleviates the $r=0$ singularity present in their classical counterparts. We use a simplified model of mass inflation, which makes use of the generalized DTR relation, to conclude that the Cauchy horizon of loop black holes indeed results in a curvature singularity similar to that found in classical black holes. The DTR relation is of particular utility in the loop black hole because it does not directly rely upon Einstein's field equations. We elucidate some of the interesting and counterintuitive properties of the loop black hole, and corroborate our results using an alternate model of mass inflation due to Ori.

  10. Feedback Loop Gains and Feedback Behavior (1996)

    DEFF Research Database (Denmark)

    Kampmann, Christian Erik

    2012-01-01

    Linking feedback loops and system behavior is part of the foundation of system dynamics, yet the lack of formal tools has so far prevented a systematic application of the concept, except for very simple systems. Having such tools at their disposal would be a great help to analysts in understanding...... large, complicated simulation models. The paper applies tools from graph theory formally linking individual feedback loop strengths to the system eigenvalues. The significance of a link or a loop gain and an eigenvalue can be expressed in the eigenvalue elasticity, i.e., the relative change...... of an eigenvalue resulting from a relative change in the gain. The elasticities of individual links and loops may be found through simple matrix operations on the linearized system. Even though the number of feedback loops can grow rapidly with system size, reaching astronomical proportions even for modest systems...

  11. Osmotic mechanism of the loop extrusion process

    Science.gov (United States)

    Yamamoto, Tetsuya; Schiessel, Helmut

    2017-09-01

    The loop extrusion theory assumes that protein factors, such as cohesin rings, act as molecular motors that extrude chromatin loops. However, recent single molecule experiments have shown that cohesin does not show motor activity. To predict the physical mechanism involved in loop extrusion, we here theoretically analyze the dynamics of cohesin rings on a loop, where a cohesin loader is in the middle and unloaders at the ends. Cohesin monomers bind to the loader rather frequently and cohesin dimers bind to this site only occasionally. Our theory predicts that a cohesin dimer extrudes loops by the osmotic pressure of cohesin monomers on the chromatin fiber between the two connected rings. With this mechanism, the frequency of the interactions between chromatin segments depends on the loading and unloading rates of dimers at the corresponding sites.

  12. Carrier tracking algorithm based on joint acquisition of frequency locked loop and phase locked loop

    Directory of Open Access Journals (Sweden)

    Gao Kang

    2017-01-01

    Full Text Available Aiming at the problem of frequency step in the frequency lock loop (FLL - phase lock loop (PLL carrier tracking algorithm’s conversion state, presenting an improved algorithm: PLL and FLL joint acquisition to replace the single FLL acquires frequency, and deduce the loop state transition threshold. The simulation results show that the improved algorithm is more stable in the conversion process, and the loop performance is optimized. When the SNR is -10dB, and has the acceleration rate, the tracking loop does not have a frequency step at the time of conversion, achieving the design purpose.

  13. Development and validation of a combined temperature, water activity, pH model for bacterial growth rate Lactobacillus curvatus

    NARCIS (Netherlands)

    Wijtzes, T.; Rombouts, F.M.; Kant-Muermans, M.L.T.; Riet, K. van 't; Zwietering, M.H.

    2001-01-01

    A model was established to predict growth rate as a function of temperature, pH and water activity. The model is based on two, earlier developed models, one for growth rate as a function of temperature and water activity and the other for growth rate as a function of temperature and pH. Based on the

  14. Development and validation of a combined temperature, water activity, pH model for bacterial growth rate of Lactobacillus curvatus

    NARCIS (Netherlands)

    Wijtzes, T.; Rombouts, F.M.; Kant-Muermans, M.L.T.; Riet, van 't K.; Zwietering, M.H.

    2001-01-01

    A model was established to predict growth rate as a function of temperature, pH and water activity. The model is based on two, earlier developed models, one for growth rate as a function of temperature and water activity and the other for growth rate as a function of temperature and pH. Based on the

  15. Effect of the method of process on the control of microbial growth by water activity in foods

    Science.gov (United States)

    Labuzu, T. D.

    1972-01-01

    Two methods for preparation of intermediate moisture foods (IMF) were investigated; water absorption and water desorption technique. Results indicate that shelf stability of IMF systems might be enhanced by preparing foods by rehumidifying dehydrated foods to optimum water activity rather than drying food to reduce the water activity.

  16. Water activity of aqueous solutions of ethylene oxide-propylene oxide block copolymers and maltodextrins

    Directory of Open Access Journals (Sweden)

    N. D. D. Carareto

    2010-03-01

    Full Text Available The water activity of aqueous solutions of EO-PO block copolymers of six different molar masses and EO/PO ratios and of maltodextrins of three different molar masses was determined at 298.15 K. The results showed that these aqueous solutions present a negative deviation from Raoult's law. The Flory-Huggins and UNIFAC excess Gibbs energy models were employed to model the experimental data. While a good agreement was obtained with the Flory-Huggins equation, discrepancies were observed when predicting the experimental behavior with the UNIFAC model. The water activities of ternary systems formed by a synthetic polymer, maltodextrin and water were also measured and used to test the predictive capability of both models.

  17. Microbial Safety of Low Water Activity Foods: Study of Simulated and Durban Household Samples

    OpenAIRE

    Ijabadeniyi, O. A.; Pillay, Y.

    2017-01-01

    Sixty household low water activity foods were examined and a simulative study was conducted in a high sugar, low aw almond and macadamia butter to determine the survival of Bacillus cereus and Staphylococcus aureus ATCC 25923. Results obtained from 60 low aw samples collected at household level had some significant differences (P≤0,05) within food categories amongst the various tests. Spices had the highest number of aerobic bacteria, aerobic spore-formers, anaerobic spore-formers, and S. aur...

  18. Thermal properties of ration components as affected by moisture content and water activity during freezing.

    Science.gov (United States)

    Li, J; Chinachoti, P; Wang, D; Hallberg, L M; Sun, X S

    2008-11-01

    Beef roast with vegetables is an example of a meal, ready-to-eat (MRE) ration entrée. It is a mixture of meat, potato, mushroom, and carrot with a gravy sauce. The thermal properties of each component were characterized in terms of freezing point, latent heat, freezable and unfreezable water contents, and enthalpy during freezing using differential scanning calorimetry. Freezing and thawing curves and the effect of freezing and thawing cycles on thermal properties were also evaluated. The freezing points of beef, potato, mushroom, and sauce were all in the range of -5.1 to -5.6 degrees C, but moisture content, water activity, latent heat, freezable and unfreezable water contents, and enthalpy varied among these components. Freezing temperature greatly affected the unfrozen water fraction. The unfreezable water content (unfrozen water fraction at -50 degrees C) of ration components was in the range of 8.2% to 9.7%. The freezing and thawing curves of vegetables with sauce differed from those of beef but took similar time to freeze or thaw. Freezing and thawing cycles did not greatly affect the thermal properties of each component. Freezing point and latent heat were reduced by decreasing moisture content and water activity of each component. Water activity was proportionally linear to freezing point at a(w) > 0.88, and moisture content was proportionally linear to freezable water content in all ration components. Water was not available for freezing when moisture content was reduced to 28.8% or less. This study indicates that moisture content and water activity are critical factors affecting thermal behavior of ration components during freezing.

  19. Growth of Byssochlamys nivea in pineapple juice under the effect of water activity and ascospore age

    Directory of Open Access Journals (Sweden)

    M Zimmermann

    2011-03-01

    Full Text Available The study of thermal resistant mould, including Byssochlamys nivea, is of extreme importance since it has been associated with fruit and fruit products. The aim of this work is to analyze the influence of water activity (a w and ascospore age (I on the growth of Byssochlamys nivea in pineapple juice. Mold growth was carried out under different conditions of water activity (a w (0.99, 0.96, 0.95, 0.93, 0.90 and ascospore age (I (30, 51, 60, 69, 90 days. Growth parameters as length of adaptation phase (λ, maximum specific growth rate (µmax and maximum diameter reached by the colony (λ were obtained through the fit of the Modified Gompertz model to experimental data (measuring radial colony diameter. Statistica 6.0 was used for statistical analyses (significance level α = 0.05. The results obtained clearly showed that water activity is statistically significant and that it influences all growth parameters, while ascospore age does not have any statistically significant influence on growth parameters. Also, these data showed that by increasing a w from 0.90 to 0.99, the λ value substantially decreased, while µmax and λ values rose. The data contributed for the understanding of the behavior of B. nivea in pineapple juice. Therefore, it provided mathematical models that can well predict growth parameters, also helping on microbiological control and products' shelf life determination.

  20. Influence of water activity, temperature and time on mycotoxins production on barley rootlets.

    Science.gov (United States)

    Ribeiro, J M M; Cavaglieri, L R; Fraga, M E; Direito, G M; Dalcero, A M; Rosa, C A R

    2006-02-01

    The objective of this study was to determine the ochratoxin (OT) and aflatoxin (AF) production by three strains of Aspergillus spp. under different water activities, temperature and incubation time on barley rootlets (BR). Aspergillus ochraceus and Aspergillus flavus were able to produce mycotoxins on BR. Aspergillus ochraceus produced ochratoxin A (OTA) at 0.80 water activity (a(w)), at 25 and 30 degrees C as optimal environmental conditions. The OTA production varies at different incubation days depending on a(w). Aflatoxin B(1) (AFB1) accumulation was obtained at 25 degrees C, at 0.80 and 0.95 a(w), after 14 and 21 incubation days respectively. Temperature was a critical factor influencing OTA and AFB(1) production. This study demonstrates that BR support OTA and AFB(1) production at relatively low water activity (0.80 a(w)) and high temperatures (25-30 degrees C). The study of ecophysiological parameters and their interactions would determine the prevailing environmental factors, which enhance the mycotoxin production on BR used as animal feed.

  1. Water content or water activity: what rules crispy behavior in bread crust?

    Science.gov (United States)

    van Nieuwenhuijzen, N H; Primo-Martín, C; Meinders, M B J; Tromp, R H; Hamer, R J; van Vliet, T

    2008-08-13

    A dry crust loses its crispness when water migrates into the crust. It is not clear if it is the amount of water absorbed or the water activity ( a w) that leads to a loss of crispness. The hysteresis effect observed when recording a water sorption isotherm allowed us to study the effects of a w and moisture content separately. All experiments were carried out on model bread crusts made from Soissons bread flour. The effect of water content and water activity on the glass transition of model bread crusts was studied in detail using two complimentary techniques: phase transition analysis (PTA) and nuclear magnetic resonance (NMR). The results were compared with sensory data and results from a puncture test, which provided data on acoustic emission and fracture mechanics during breaking of the crusts. The water content of the crust was found to be decisive for the transition point as measured by PTA and NMR. However, both water content and water activity had an effect on perceived crispness and number of force and sound peaks. From this may be concluded that the distribution of the water in the samples with a history of high water content is more inhomogeneous, which results in crispy and less crispy regions, thus making them overall more crispy than samples with the same water content but higher a w.

  2. Diurnal fluctuation in histidine decarboxylase expression, the rate limiting enzyme for histamine production, and its disorder in neurodegenerative diseases.

    Science.gov (United States)

    Shan, Ling; Hofman, Michel A; van Wamelen, Daniel J; Van Someren, Eus J W; Bao, Ai-Min; Swaab Dick, F

    2012-05-01

    Neuronal histamine shows diurnal rhythms in rodents and plays a major role in the maintenance of vigilance. No data are available on its diurnal fluctuation in humans, either in health or in neurodegenerative disorders such as Parkinson disease (PD), Alzheimer disease (AD), or Huntington disease (HD), all of which are characterized by sleep-wake disturbances. Quantitative in situ hybridization was used to study the mRNA expression of histidine decarboxylase (HDC), the key enzyme of histamine production in the tuberomammillary nucleus (TMN) in postmortem human hypothalamic tissue, obtained from 33 controls and 31 patients with a neurodegenerative disease-PD (n = 15), AD (n = 9), and HD (n = 8)-and covering the full 24-h cycle with respect to clock time of death. HDC-mRNA levels in controls were found to be significantly higher during the daytime than at night (e.g., 08:01-20:00 versus 20:01-08:00, P = 0.004). This day-night fluctuation was markedly different in patients with neurodegenerative diseases. The diurnal fluctuation of HDC-mRNA expression in human TMN supports a role for neuronal histamine in regulating day-night rhythms. Future studies should investigate histamine rhythm abnormalities in neurodegenerative disorders. Shan L; Hofman MA; van Wamelen DJ; Van Someren EJW; Bao AM; Swaab DF. Diurnal fluctuation in histidine decarboxylase expression, the rate limiting enzyme for histamine production, and its disorder in neurodegenerative diseases.

  3. Mechanistic insights revealed by the crystal structure of a histidine kinase with signal transducer and sensor domains.

    Directory of Open Access Journals (Sweden)

    Chen Wang

    Full Text Available Two-component systems (TCSs are important for the adaptation and survival of bacteria and fungi under stress conditions. A TCS is often composed of a membrane-bound sensor histidine kinase (SK and a response regulator (RR, which are relayed through sequential phosphorylation steps. However, the mechanism for how an SK is switched on in response to environmental stimuli remains obscure. Here, we report the crystal structure of a complete cytoplasmic portion of an SK, VicK from Streptococcus mutans. The overall structure of VicK is a long-rod dimer that anchors four connected domains: HAMP, Per-ARNT-SIM (PAS, DHp, and catalytic and ATP binding domain (CA. The HAMP, a signal transducer, and the PAS domain, major sensor, adopt canonical folds with dyad symmetry. In contrast, the dimer of the DHp and CA domains is asymmetric because of different helical bends in the DHp domain and spatial positions of the CA domains. Moreover, a conserved proline, which is adjacent to the phosphoryl acceptor histidine, contributes to helical bending, which is essential for the autokinase and phosphatase activities. Together, the elegant architecture of VicK with a signal transducer and sensor domain suggests a model where DHp helical bending and a CA swing movement are likely coordinated for autokinase activation.

  4. Analysis of Mammalian Histidine Decarboxylase Dimerization Interface Reveals an Electrostatic Hotspot Important for Catalytic Site Topology and Function.

    Science.gov (United States)

    Moya-García, Aurelio A; Rodríguez-Agudo, Daniel; Hayashi, Hideyuki; Medina, Miguel Angel; Urdiales, José Luis; Sánchez-Jiménez, Francisca

    2011-06-14

    Selective intervention of mammalian histidine decarboxylase (EC 4.1.1.22) could provide a useful antihistaminic strategy against many different pathologies. It is known that global conformational changes must occur during reaction that involves the monomer-monomer interface of the enzyme. Thus, the dimerization surface is a promising target for histidine decarboxylase inhibition. In this work, a rat apoenzyme structural model is used to analyze the interface of the dimeric active HDC. The dimerization surface mainly involves the fragments 1-213 and 308-371 from both subunits. Part of the overlapping surfaces conforms each catalytic site entrance and the substrate-binding sites. In addition, a cluster of charged residues is located in each overlapping surface, so that both electrostatic hotspots mediate in the interaction between the catalytic sites of the dimeric enzyme. It is experimentally demonstrated that the carboxyl group of aspartate 315 is critical for the proper conformation of the holoenzyme and the progression of the reaction. Comparison to the available information on other evolutionary related enzymes also provides new insights for characterization and intervention of homologous l-amino acid decarboxylases.

  5. UmTco1, a Hybrid Histidine Kinase Gene, Is Essential for the Sexual Development and Virulence of Ustilago maydis.

    Science.gov (United States)

    Yun, Yeo Hong; Oh, Man Hwan; Kim, Jun Young; Kim, Seong Hwan

    2017-05-28

    Hybrid histidine kinase is part of a two-component system that is required for various stress responses and pathogenesis of pathogenic fungi. The Tco1 gene in human pathogen Cryptococcus neoformans encodes a hybrid histidine kinase and is important for pathogenesis. In this study, we identified a Tco1 homolog, UmTco1, in the maize pathogen Ustilago maydis by bioinformatics analysis. To explore the role of UmTco1 in the survival of U. maydis under environmental stresses and its pathogenesis, Δumtco1 mutants were constructed by allelic exchange. The growth of Δumtco1 mutants was significantly impaired when they were cultured under hyperosmotic stress. The Δumtco1 mutants exhibited increased resistance to antifungal agent fludioxonil. In particular, the Δumtco1 mutants were unable to produce cytokinesis or conjugation tubes, and to develop fuzzy filaments, resulting in impaired mating between compatible strains. The expression levels of Prf1, Pra1, and Mfa1, which are involved in the pheromone pathway, were significantly decreased in the Δumtco1 mutants. In inoculation tests to the host plant, the Δumtco1 mutants showed significantly reduced ability in the production of anthocyanin pigments and tumor development on maize leaves. Overall, the combined results indicated that UmTco1 plays important roles in the survival under hyperosmotic stress, and contributes to cytokinesis, sexual development, and virulence of U. maydis by regulating the expression of the genes involved in the pheromone pathway.

  6. The nonoxidative conversion of nitroethane to ethylnitronate in Neurospora crassa 2-nitropropane dioxygenase is catalyzed by histidine 196.

    Science.gov (United States)

    Francis, Kevin; Gadda, Giovanni

    2008-09-02

    The deprotonation of nitroethane catalyzed by Neurospora crassa 2-nitropropane dioxygenase was investigated by measuring the formation and release of ethylnitronate formed in turnover as a function of pH and through mutagenesis studies. Progress curves for the enzymatic reaction obtained by following the increase in absorbance at 228 nm over time were visibly nonlinear, requiring a logarithmic approximation of the initial reaction rates for the determination of the kinetic parameters of the enzyme. The pH dependence of the second-order rate constant k cat/ K m with nitroethane as substrate implicates the presence of a group with a p K a of 8.1 +/- 0.1 that must be unprotonated for nitronate formation. Mutagenesis studies suggest that this group is histidine 196 as evident from the inability of a H196N variant form of the enzyme to catalyze the formation of ethylnitronate from nitroethane. Replacement of histidine 196 with asparagine resulted in an approximately 15-fold increase in the k cat/ K m with ethylnitronate as compared to the wild-type, which results from the inability of the mutant enzyme to undergo nonoxidative turnover. The results presented herein are consistent with a branched catalytic mechanism for the enzyme in which the ethylnitronate intermediate formed from the H196-catalyzed deprotonation of nitroethane partitions between release from the active site and oxidative denitrification to yield acetaldehyde and nitrite.

  7. Antioxidation status and histidine dipeptides content in broiler blood and muscles depending on protein sources in feed.

    Science.gov (United States)

    Kopeć, W; Jamroz, D; Wiliczkiewicz, A; Biazik, E; Hikawczuk, T; Skiba, T; Pudło, A; Orda, J

    2013-06-01

    One-day-old chickens were fed mixtures containing different raw materials (fish by-products meal, porcine blood cells meal, blood meal, wheat gluten, fodder yeast), as a source of histidine and β-alanine - components of carnosine. Control birds were administered a feed mixture, in which soy bean meal was the main protein source. The bodyweight, feed consumption and conversion, antioxidant characteristics and histidine dipeptides content in blood and muscles, and also amino acid composition of chicken meat on day 34 post-hatch were recorded. The best (p chickens fed mixture containing porcine blood cells meal. In blood plasma of control chickens, a significantly (p chickens fed mixtures with blood by-products. Insignificant differences in both carnosine and anserine levels in plasma between treatments were noted. Breast muscles from control birds were characterized by lower activity of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) (p chickens fed blood by-products. Improved ability to reduce ferric ions (FRAP) (p content in meat from chickens fed blood cell meal were recorded. No direct relations between amino acids content in feed mixtures and in meat were observed. © 2012 Blackwell Verlag GmbH.

  8. Isolation and transcript analysis of two-component histidine kinase gene Le.nik1 in Shiitake mushroom, Lentinula edodes.

    Science.gov (United States)

    Szeto, Carol Y Y; Wong, Queenie W L; Leung, Grace S; Kwan, H S

    2008-01-01

    Le.nik1, a two-component histidine kinase gene of Lentinula edodes, the Shiitake mushroom, was identified. The relationship between this two-component signal transduction system and mushroom development was studied. We used a modified RNA arbitrarily-primed PCR (RAP-PCR) method to isolate Le.nik1 as a differentially expressed gene during L. edodes development. We determined the 6.29kb full-length cDNA sequence of Le.nik1. It had high sequence homology to Neurospora crassa nik1, which encoded a histidine kinase essential for development and osmotic response. In L. edodes, the expression level of Le.nik1 was highest during primordium formation and fruiting body maturation. The transcripts were localized predominantly in the developing hymenophores, or mushroom gills, which may indicate the role of a two-component signal transduction system in cell differentiation during mushroom development. Mannitol stress influenced transcript expression of Le.nik1, suggesting that it may be involved in osmo-sensing and regulation. To our knowledge, this is the first report on the two-component system in mushrooms and the first analysis on the distribution of Le.nik1 transcript in the course of fruiting body formation and in parts of fruiting bodies.

  9. Loops in exceptional field theory

    Energy Technology Data Exchange (ETDEWEB)

    Bossard, Guillaume [Centre de Physique Théorique, Ecole Polytechnique, CNRS, Université Paris-Saclay,91128 Palaiseau cedex (France); Kleinschmidt, Axel [Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut),Am Mühlenberg 1, DE-14476 Potsdam (Germany); International Solvay Institutes,ULB-Campus Plaine CP231, BE-1050 Brussels (Belgium)

    2016-01-27

    We study certain four-graviton amplitudes in exceptional field theory in dimensions D≥4 up to two loops. As the formulation is manifestly invariant under the U-duality group E{sub 11−D}(ℤ), our resulting expressions can be expressed in terms of automorphic forms. In the low energy expansion, we find terms in the M-theory effective action of type R{sup 4}, ∇{sup 4}R{sup 4} and ∇{sup 6}R{sup 4} with automorphic coefficient functions in agreement with independent derivations from string theory. This provides in particular an explicit integral formula for the exact string theory ∇{sup 6}R{sup 4} threshold function. We exhibit moreover that the usual supergravity logarithmic divergences cancel out in the full exceptional field theory amplitude, within an appropriately defined dimensional regularisation scheme. We also comment on terms of higher derivative order and the role of the section constraint for possible counterterms.

  10. Theory of loop flows and instability

    Science.gov (United States)

    Priest, E. R.

    A preliminary theory for the steady and transient coronal loop flows in solar active regions and their magnetohydrodynamic instability is presented. Siphon flow is shown to be possible in the loops if a pressure difference is maintained between the footpoints, and to account for the presence of cool cores and appearances of only half a loop. The evolution of active region magnetic loops is found to lead to the continual evaporation and draining of the plasma contained within them, particularly as a result of an increase in heating rate. Consideration of static models for thermally isolated loops reveals them to be thermally unstable, implying that in the absence of some atmospheric stabilizing mechanism, the loops must be in a dynamic state of thermal activity. It is shown that kilogauss photospheric fields may be formed by an intense magnetic field instability, with an associated transient downflow which may induce coronal flows at enhanced velocities. Magnetohydrodynamic stability analysis suggests that the major cause of magnetic stability may be line-tying of loop footpoints in the dense photosphere.

  11. Iterative structure of finite loop integrals

    Energy Technology Data Exchange (ETDEWEB)

    Caron-Huot, Simon [Institute for Advanced Study, Princeton, NJ 08540 (United States); Niels Bohr International Academy and Discovery Center, Blegdamsvej 17, Copenhagen 2100 (Denmark); Henn, Johannes M. [Institute for Advanced Study, Princeton, NJ 08540 (United States)

    2014-06-18

    In this paper we develop further and refine the method of differential equations for computing Feynman integrals. In particular, we show that an additional iterative structure emerges for finite loop integrals. As a concrete non-trivial example we study planar master integrals of light-by-light scattering to three loops, and derive analytic results for all values of the Mandelstam variables s and t and the mass m. We start with a recent proposal for defining a basis of loop integrals having uniform transcendental weight properties and use this approach to compute all planar two-loop master integrals in dimensional regularization. We then show how this approach can be further simplified when computing finite loop integrals. This allows us to discuss precisely the subset of integrals that are relevant to the problem. We find that this leads to a block triangular structure of the differential equations, where the blocks correspond to integrals of different weight. We explain how this block triangular form is found in an algorithmic way. Another advantage of working in four dimensions is that integrals of different loop orders are interconnected and can be seamlessly discussed within the same formalism. We use this method to compute all finite master integrals needed up to three loops. Finally, we remark that all integrals have simple Mandelstam representations.

  12. Hexagon Wilson Loop OPE and Harmonic Polylogarithms

    CERN Document Server

    Papathanasiou, Georgios

    2013-01-01

    A recent, integrability-based conjecture in the framework of the Wilson loop OPE for N=4 SYM theory, predicts the leading OPE contribution for the hexagon MHV remainder function and NMHV ratio function to all loops, in integral form. We prove that these integrals evaluate to a particular basis of harmonic polylogarithms, at any order in the weak coupling expansion. The proof constitutes an algorithm for the direct computation of the integrals, which we employ in order to obtain the full (N)MHV OPE contribution in question up to 6 loops, and certain parts of it up to 12 loops. We attach computer-readable files with our results, as well as an algorithm implementation which may be readily used to generate higher-loop corrections. The feasibility of obtaining the explicit kinematical dependence of the first term in the OPE in principle at arbitrary loop order, offers promise for the suitability of this approach as a non-perturbative description of Wilson loops/scattering amplitudes.

  13. Mitotic chromosome compaction via active loop extrusion

    Science.gov (United States)

    Goloborodko, Anton; Imakaev, Maxim; Marko, John; Mirny, Leonid; MIT-Northwestern Team

    During cell division, two copies of each chromosome are segregated from each other and compacted more than hundred-fold into the canonical X-shaped structures. According to earlier microscopic observations and the recent Hi-C study, chromosomes are compacted into arrays of consecutive loops of ~100 kilobases. Mechanisms that lead to formation of such loop arrays are largely unknown. Here we propose that, during cell division, chromosomes can be compacted by enzymes that extrude loops on chromatin fibers. First, we use computer simulations and analytical modeling to show that a system of loop-extruding enzymes on a chromatin fiber self-organizes into an array of consecutive dynamic loops. Second, we model the process of loop extrusion in 3D and show that, coupled with the topo II strand-passing activity, it leads to robust compaction and segregation of sister chromatids. This mechanism of chromosomal condensation and segregation does not require additional proteins or specific DNA markup and is robust against variations in the number and properties of such loop extruding enzymes. Work at NU was supported by the NSF through Grants DMR-1206868 and MCB-1022117, and by the NIH through Grants GM105847 and CA193419. Work at MIT was supported by the NIH through Grants GM114190 R01HG003143.

  14. Construction of the blowdown and condensation loop

    Energy Technology Data Exchange (ETDEWEB)

    Park, Choon Kyung; Song, Chul Kyung; Cho, Seok; Chun, S. Y.; Chung, Moon Ki

    1997-12-01

    The blowdown and condensation loop (B and C loop) has been constructed to get experimental data for designing the safety depressurization system (SDS) and steam sparger which are considered to implement in the Korea Next Generation Reactor (KNGR). In this report, system description on the B and C loop is given in detail, which includes the drawings and technical specification of each component, instrumentation and control system, and the operational procedures and the results of the performance testing. (author). 7 refs., 11 tabs., 48 figs.

  15. Polyakov loop correlator in perturbation theory

    Science.gov (United States)

    Berwein, Matthias; Brambilla, Nora; Petreczky, Péter; Vairo, Antonio

    2017-07-01

    We study the Polyakov loop correlator in the weak coupling expansion and show how the perturbative series reexponentiates into singlet and adjoint contributions. We calculate the order g7 correction to the Polyakov loop correlator in the short distance limit. We show how the singlet and adjoint free energies arising from the reexponentiation formula of the Polyakov loop correlator are related to the gauge invariant singlet and octet free energies that can be defined in pNRQCD, namely we find that the two definitions agree at leading order in the multipole expansion, but differ at first order in the quark-antiquark distance.

  16. Eigenvalue distributions of Wilson loops

    Energy Technology Data Exchange (ETDEWEB)

    Lohmayer, Robert

    2010-07-01

    In the first part of this thesis, we focus on the distribution of the eigenvalues of the unitary Wilson loop matrix in the two-dimensional case at arbitrary finite N. To characterize the distribution of the eigenvalues, we introduce three density functions (the ''symmetric'', the ''antisymmetric'', and the ''true'' eigenvalue density) which differ at finite N but possess the same infinite-N limit, exhibiting the Durhuus-Olesen phase transition. Using expansions of determinants and inverse determinants in characters of totally symmetric or totally antisymmetric representations of SU(N), the densities at finite N can be expressed in terms of simple sums involving only dimensions and quadratic Casimir invariants of certain irreducible representations of SU(N), allowing for a numerical computation of the densities at arbitrary N to any desired accuracy. We find that the true eigenvalue density, adding N oscillations to the monotonic symmetric density, is in some sense intermediate between the symmetric and the antisymmetric density, which in turn is given by a sum of N delta peaks located at the zeros of the average of the characteristic polynomial. Furthermore, we show that the dependence on N can be made explicit by deriving integral representations for the resolvents associated to the three eigenvalue densities. Using saddle-point approximations, we confirm that all three densities reduce to the Durhuus-Olesen result in the infinite-N limit. In the second part, we study an exponential form of the multiplicative random complex matrix model introduced by Gudowska-Nowak et al. Varying a parameter which can be identified with the area of the Wilson loop in the unitary case, the region of non-vanishing eigenvalue density of the N-dimensional complex product matrix undergoes a topological change at a transition point in the infinite-N limit. We study the transition by a detailed analysis of the average of the

  17. Loop Diuretics in the Treatment of Hypertension.

    Science.gov (United States)

    Malha, Line; Mann, Samuel J

    2016-04-01

    Loop diuretics are not recommended in current hypertension guidelines largely due to the lack of outcome data. Nevertheless, they have been shown to lower blood pressure and to offer potential advantages over thiazide-type diuretics. Torsemide offers advantages of longer duration of action and once daily dosing (vs. furosemide and bumetanide) and more reliable bioavailability (vs. furosemide). Studies show that the previously employed high doses of thiazide-type diuretics lower BP more than furosemide. Loop diuretics appear to have a preferable side effect profile (less hyponatremia, hypokalemia, and possibly less glucose intolerance). Studies comparing efficacy and side effect profiles of loop diuretics with the lower, currently widely prescribed, thiazide doses are needed. Research is needed to fill gaps in knowledge and common misconceptions about loop diuretic use in hypertension and to determine their rightful place in the antihypertensive arsenal.

  18. Force distribution in a semiflexible loop

    CERN Document Server

    Waters, James T

    2016-01-01

    Loops undergoing thermal fluctuations are prevalent in nature. Ring-like or cross-linked polymers, cyclic macromolecules, and protein-mediated DNA loops all belong to this category. Stability of these molecules are generally described in terms of free energy, an average quantity, but it may also be impacted by local fluctuating forces acting within these systems. The full distribution of these forces can thus give us insights into mechanochemistry beyond the predictive capability of thermodynamics. In this paper, we study the force exerted by an inextensible semiflexible polymer constrained in a looped state. By using a novel simulation method termed "phase-space sampling", we generate the equilibrium distribution of chain conformations in both position and momentum space. We compute the constraint forces between the two ends of the loop in this chain ensemble using Lagrangian mechanics, and show that the mean of these forces is equal to the thermodynamic force. By analyzing kinetic and potential contribution...

  19. A theory of desynchronisable closed loop system

    Directory of Open Access Journals (Sweden)

    Harsh Beohar

    2010-10-01

    Full Text Available The task of implementing a supervisory controller is non-trivial, even though different theories exist that allow automatic synthesis of these controllers in the form of automata. One of the reasons for this discord is due to the asynchronous interaction between a plant and its controller in implementations, whereas the existing supervisory control theories assume synchronous interaction. As a consequence the implementation suffer from the so-called inexact synchronisation problem. In this paper we address the issue of inexact synchronisation in a process algebraic setting, by solving a more general problem of refinement. We construct an asynchronous closed loop system by introducing a communication medium in a given synchronous closed loop system. Our goal is to find sufficient conditions under which a synchronous closed loop system is branching bisimilar to its corresponding asynchronous closed loop system.

  20. The Universal One-Loop Effective Action

    CERN Document Server

    Drozd, Aleksandra; Quevillon, Jérémie; You, Tevong

    2016-01-01

    We present the universal one-loop effective action for all operators of dimension up to six obtained by integrating out massive, non-degenerate multiplets. Our general expression may be applied to loops of heavy fermions or bosons, and has been checked against partial results available in the literature. The broad applicability of this approach simplifies one-loop matching from an ultraviolet model to a lower-energy effective field theory (EFT), a procedure which is now reduced to the evaluation of a combination of matrices in our universal expression, without any loop integrals to evaluate. We illustrate the relationship of our results to the Standard Model (SM) EFT, using as an example the supersymmetric stop and sbottom squark Lagrangian and extracting from our universal expression the Wilson coefficients of dimension-six operators composed of SM fields.

  1. Hardware-in-the-Loop Testing

    Data.gov (United States)

    Federal Laboratory Consortium — RTC has a suite of Hardware-in-the Loop facilities that include three operational facilities that provide performance assessment and production acceptance testing of...

  2. Mathematical Modeling of Loop Heat Pipes

    Science.gov (United States)

    Kaya, Tarik; Ku, Jentung; Hoang, Triem T.; Cheung, Mark L.

    1998-01-01

    The primary focus of this study is to model steady-state performance of a Loop Heat Pipe (LHP). The mathematical model is based on the steady-state energy balance equations at each component of the LHP. The heat exchange between each LHP component and the surrounding is taken into account. Both convection and radiation environments are modeled. The loop operating temperature is calculated as a function of the applied power at a given loop condition. Experimental validation of the model is attempted by using two different LHP designs. The mathematical model is tested at different sink temperatures and at different elevations of the loop. Tbc comparison of the calculations and experimental results showed very good agreement (within 3%). This method proved to be a useful tool in studying steady-state LHP performance characteristics.

  3. Nonequilibrium Chromosome Looping via Molecular Slip Links

    Science.gov (United States)

    Brackley, C. A.; Johnson, J.; Michieletto, D.; Morozov, A. N.; Nicodemi, M.; Cook, P. R.; Marenduzzo, D.

    2017-09-01

    We propose a model for the formation of chromatin loops based on the diffusive sliding of molecular slip links. These mimic the behavior of molecules like cohesin, which, along with the CTCF protein, stabilize loops which contribute to organizing the genome. By combining 3D Brownian dynamics simulations and 1D exactly solvable nonequilibrium models, we show that diffusive sliding is sufficient to account for the strong bias in favor of convergent CTCF-mediated chromosome loops observed experimentally. We also find that the diffusive motion of multiple slip links along chromatin is rectified by an intriguing ratchet effect that arises if slip links bind to the chromatin at a preferred "loading site." This emergent collective behavior favors the extrusion of loops which are much larger than the ones formed by single slip links.

  4. Modulation of DNA loop lifetimes by the free energy of loop formation

    CERN Document Server

    Chen, Yi-Ju; Mulligan, Peter; Spakowitz, Andrew J; Phillips, Rob

    2015-01-01

    Storage and retrieval of the genetic information in cells is a dynamic process that requires the DNA to undergo dramatic structural rearrangements. DNA looping is a prominent example of such a structural rearrangement that is essential for transcriptional regulation in both prokaryotes and eukaryotes, and the speed of such regulations affects the fitness of individuals. Here, we examine the in vitro looping dynamics of the classic Lac repressor gene-regulatory motif. We show that both loop association and loop dissociation at the DNA-repressor junctions depend on the elastic deformation of the DNA and protein, and that both looping and unlooping rates approximately scale with the looping J factor, which reflects the system's deformation free energy. We explain this observation by transition state theory and model the DNA-protein complex as an effective worm-like chain with twist. We introduce a finite protein-DNA binding interaction length, in competition with the characteristic DNA deformation length scale, ...

  5. Laser welding closed-loop power control

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    2003-01-01

    A closed-loop control system is developed to maintain an even seam width on the root side of a laser weld by continually controlling the output laser power of a 1500 W CO2 laser.......A closed-loop control system is developed to maintain an even seam width on the root side of a laser weld by continually controlling the output laser power of a 1500 W CO2 laser....

  6. Design configurations of the methanol synthesis loop

    OpenAIRE

    Bøhn, Kristian

    2011-01-01

    In recent years the chemical industry has undergone considerable changes due to increased environmental regulations and energy costs. This master thesis has evaluated three different design considerations of the methanol synthesis loop using Honeywell's general purpose process simulator UniSim Design (R380 Build 14027) combined with MathWorks programming language MATLAB. The three configurations are Lurgis methanol reactor loop as built on Tjeldbergodden, the use of interstage methanol remova...

  7. Loop residues and catalysis in OMP synthase

    DEFF Research Database (Denmark)

    Wang, Gary P.; Hansen, Michael Riis; Grubmeyer, Charles

    2012-01-01

    (preceding paper in this issue, DOI 10.1021/bi300083p)]. The full expression of KIEs by H105A and E107A may result from a less secure closure of the catalytic loop. The lower level of expression of the KIE by K103A suggests that in these mutant proteins the major barrier to catalysis is successful closure...... of the catalytic loop, which when closed, produces rapid and reversible catalysis....

  8. Mutations in the catalytic loop HRD motif alter the activity and function of Drosophila Src64.

    Directory of Open Access Journals (Sweden)

    Taylor C Strong

    Full Text Available The catalytic loop HRD motif is found in most protein kinases and these amino acids are predicted to perform functions in catalysis, transition to, and stabilization of the active conformation of the kinase domain. We have identified mutations in a Drosophila src gene, src64, that alter the three HRD amino acids. We have analyzed the mutants for both biochemical activity and biological function during development. Mutation of the aspartate to asparagine eliminates biological function in cytoskeletal processes and severely reduces fertility, supporting the amino acid's critical role in enzymatic activity. The arginine to cysteine mutation has little to no effect on kinase activity or cytoskeletal reorganization, suggesting that the HRD arginine may not be critical for coordinating phosphotyrosine in the active conformation. The histidine to leucine mutant retains some kinase activity and biological function, suggesting that this amino acid may have a biochemical function in the active kinase that is independent of its side chain hydrogen bonding interactions in the active site. We also describe the phenotypic effects of other mutations in the SH2 and tyrosine kinase domains of src64, and we compare them to the phenotypic effects of the src64 null allele.

  9. Functional analysis of the large periplasmic loop of the Escherichia coli K-12 WaaL O-antigen ligase.

    Science.gov (United States)

    Pérez, José M; McGarry, Megan A; Marolda, Cristina L; Valvano, Miguel A

    2008-12-01

    WaaL is a membrane enzyme implicated in ligating undecaprenyl-diphosphate (Und-PP)-linked O antigen to lipid A-core oligosaccharide. We determined the periplasmic location of a large (EL5) and small (EL4) adjacent loops in the Escherichia coli K-12 WaaL. Structural models of the EL5 from the K-12, R1 and R4 E. coli ligases were generated by molecular dynamics. Despite the poor amino acid sequence conservation among these proteins, the models afforded similar folds consisting of two pairs of almost perpendicular alpha-helices. One alpha-helix in each pair contributes a histidine and an arginine facing each other, which are highly conserved in WaaL homologues. Mutations in either residue rendered WaaL non-functional, since mutant proteins were unable to restore O antigen surface expression. Replacements of residues located away from the putative catalytic centre and non-conserved residues within the centre itself did not affect ligation. Furthermore, replacing a highly conserved arginine in EL4 with various amino acids inactivates WaaL function, but functionality reappears when the positive charge is restored by a replacement with lysine. These results lead us to propose that the conserved amino acids in the two adjacent periplasmic loops could interact with Und-PP, which is the common component in all WaaL substrates.

  10. Multiple Flow Loop SCADA System Implemented on the Production Prototype Loop

    Energy Technology Data Exchange (ETDEWEB)

    Baily, Scott A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dalmas, Dale Allen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wheat, Robert Mitchell [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Woloshun, Keith Albert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dale, Gregory E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-11-16

    The following report covers FY 15 activities to develop supervisory control and data acquisition (SCADA) system for the Northstar Moly99 production prototype gas flow loop. The goal of this effort is to expand the existing system to include a second flow loop with a larger production-sized blower. Besides testing the larger blower, this system will demonstrate the scalability of our solution to multiple flow loops.

  11. Space Station evolution study oxygen loop closure

    Science.gov (United States)

    Wood, M. G.; Delong, D.

    1993-01-01

    In the current Space Station Freedom (SSF) Permanently Manned Configuration (PMC), physical scars for closing the oxygen loop by the addition of oxygen generation and carbon dioxide reduction hardware are not included. During station restructuring, the capability for oxygen loop closure was deferred to the B-modules. As such, the ability to close the oxygen loop in the U.S. Laboratory module (LAB A) and the Habitation A module (HAB A) is contingent on the presence of the B modules. To base oxygen loop closure of SSF on the funding of the B-modules may not be desirable. Therefore, this study was requested to evaluate the necessary hooks and scars in the A-modules to facilitate closure of the oxygen loop at or subsequent to PMC. The study defines the scars for oxygen loop closure with impacts to cost, weight and volume and assesses the effects of byproduct venting. In addition, the recommended scenarios for closure with regard to topology and packaging are presented.

  12. A note on two-loop superloop

    Energy Technology Data Exchange (ETDEWEB)

    Belitsky, A.V., E-mail: Andrei.Belitsky@asu.edu [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States)

    2012-11-15

    We explore the duality between supersymmetric Wilson loop on null polygonal contours in maximally supersymmetric Yang-Mills theory and next-to-maximal helicity violating (NMHV) scattering amplitudes. Earlier analyses demonstrated that the use of a dimensional regulator for ultraviolet divergences, induced due to presence of the cusps on the loop, yields anomalies that break both conformal symmetry and supersymmetry. At one-loop order, these are present only in Grassmann components localized in the vicinity of a single cusp and result in a universal function for any number of sites of the polygon that can be subtracted away in a systematic manner leaving a well-defined supersymmetric remainder dual to corresponding components of the superamplitude. The question remains though whether components which were free from the aforementioned supersymmetric anomaly at leading order of perturbation theory remain so once computed at higher orders. Presently we verify this fact by calculating a particular component of the null polygonal super Wilson loop at two loops restricting the contour kinematics to a two-dimensional subspace. This allows one to perform all computations in a concise analytical form and trace the pattern of cancellations between individual Feynman graphs in a transparent fashion. As a consequence of our consideration we obtain a dual conformally invariant result for the remainder function in agreement with one-loop NMHV amplitudes.

  13. Hybrid Combustion-Gasification Chemical Looping

    Energy Technology Data Exchange (ETDEWEB)

    Herbert Andrus; Gregory Burns; John Chiu; Gregory Lijedahl; Peter Stromberg; Paul Thibeault

    2009-01-07

    For the past several years Alstom Power Inc. (Alstom), a leading world-wide power system manufacturer and supplier, has been in the initial stages of developing an entirely new, ultra-clean, low cost, high efficiency power plant for the global power market. This new power plant concept is based on a hybrid combustion-gasification process utilizing high temperature chemical and thermal looping technology The process consists of the oxidation, reduction, carbonation, and calcination of calcium-based compounds, which chemically react with coal, biomass, or opportunity fuels in two chemical loops and one thermal loop. The chemical and thermal looping technology can be alternatively configured as (i) a combustion-based steam power plant with CO{sub 2} capture, (ii) a hybrid combustion-gasification process producing a syngas for gas turbines or fuel cells, or (iii) an integrated hybrid combustion-gasification process producing hydrogen for gas turbines, fuel cells or other hydrogen based applications while also producing a separate stream of CO{sub 2} for use or sequestration. In its most advanced configuration, this new concept offers the promise to become the technology link from today's Rankine cycle steam power plants to tomorrow's advanced energy plants. The objective of this work is to develop and verify the high temperature chemical and thermal looping process concept at a small-scale pilot facility in order to enable AL to design, construct and demonstrate a pre-commercial, prototype version of this advanced system. In support of this objective, Alstom and DOE started a multi-year program, under this contract. Before the contract started, in a preliminary phase (Phase 0) Alstom funded and built the required small-scale pilot facility (Process Development Unit, PDU) at its Power Plant Laboratories in Windsor, Connecticut. Construction was completed in calendar year 2003. The objective for Phase I was to develop the indirect combustion loop with CO{sub 2

  14. Aspergillus penicillioides differentiation and cell division at 0.585 water activity.

    Science.gov (United States)

    Stevenson, Andrew; Hamill, Philip G; O'Kane, Callum J; Kminek, Gerhard; Rummel, John D; Voytek, Mary A; Dijksterhuis, Jan; Hallsworth, John E

    2017-02-01

    Water availability acts as the most stringent constraint for life on Earth. Thus, understanding the water relations of microbial extremophiles is imperative to our ability to increase agricultural productivity (e.g., by enhancing the processing and turnover of dead organic matter in soils of arid regions), reduce human exposure to mycotoxins in buildings and our food-supply chain, prevent the spoilage of foods/animal feeds, books, museum specimens and artworks and better control microbiology of industrial fermentations. Only a small number of microbial systems can retain activity at development of mycelium and/or sporulation; fifthly, assessments were carried out over a range of water-activity values and time points to obtain a complete profile of the germination process. Conidia swelled, formed differentiated germination-structures and then produced septate germlings at a water-activity of just 0.585 (≡58.5% relative humidity), outside the currently understood thermodynamic window for life. Furthermore, analyses of these data suggest a theoretical water-activity minimum of 0.565 for germination of A. penicilliodes. In relation to astrobiology, these findings have an application in understanding the limits to life in extraterrestrial environments. In light of current plans for exploration missions to Mars and other places, and the need to safeguard martian scientific sites and potential resources (including water) for future human habitation, a knowledge-based and effective policy for planetary protection is essential. As it is, Mars-bound spacecraft may frequently be contaminated with aspergilli (including A. penicillioides) and other organisms which, when transported to other planetary bodies, pose a contamination risk. In crafting countermeasures to offset this, it is important to know as precisely as possible the capabilities of these potential interplanetary visitors. © 2017 The Authors. Environmental Microbiology published by Society for Applied

  15. Heterogeneous ice nucleation in aqueous solutions: the role of water activity.

    Science.gov (United States)

    Zobrist, B; Marcolli, C; Peter, T; Koop, T

    2008-05-01

    Heterogeneous ice nucleation experiments have been performed with four different ice nuclei (IN), namely nonadecanol, silica, silver iodide and Arizona test dust. All IN are either immersed in the droplets or located at the droplets surface. The IN were exposed to various aqueous solutions, which consist of (NH4)2SO4, H2SO4, MgCl2, NaCl, LiCl, Ca(NO3)2, K2CO3, CH3COONa, ethylene glycol, glycerol, malonic acid, PEG300 or a NaCl/malonic acid mixture. Freezing was studied using a differential scanning calorimeter and a cold finger cell. The results show that the heterogeneous ice freezing temperatures decrease with increasing solute concentration; however, the magnitude of this effect is solute dependent. In contrast, when the results are analyzed in terms of the solution water activity a very consistent behavior emerges: heterogeneous ice nucleation temperatures for all four IN converge each onto a single line, irrespective of the nature of the solute. We find that a constant offset with respect to the ice melting point curve, Deltaaw,het, can describe the observed freezing temperatures for each IN. Such a behavior is well-known for homogeneous ice nucleation from supercooled liquid droplets and has led to the development of water-activity-based ice nucleation theory. The large variety of investigated solutes together with different general types of ice nuclei studied (monolayers, ionic crystals, covalently bound network-forming compounds, and a mixture of chemically different crystallites) underlines the general applicability of water-activity-based ice nucleation theory also for heterogeneous ice nucleation in the immersion mode. Finally, the ice nucleation efficiencies of the various IN, as well as the atmospheric implication of the developed parametrization are discussed.

  16. Use of histidine dipeptides and myoglobin to monitor adulteration of cooked beef with meat from other species.

    Science.gov (United States)

    Carnegie, P R; Ilic, M Z; Etheridge, M O; Stuart, S

    1985-08-01

    A new high performance liquid chromatography (HPLC) method was used to monitor the adulteration of cooked beef products with meat from other species. The ratio of the histidine dipeptides anserine and carnosine which are present in skeletal muscle, are so different between sheep, cattle, horse and kangaroo that detection of adulteration can be rapidly achieved by chromatography on a Partisil-10 SCX column with 0.2 M lithium formate, pH 2.9. To obtain a definitive identification of the adulterant it was necessary to also examine the electrophoretic mobility of myoglobin in sodium dodecylsulphate gels. One brand of "beefsteak" pie was found to actually be a mixture of mutton and beef.

  17. Potentiometric determination of the dissociation constants of L-histidine, proline and tryptophane in various hydroorganic media.

    Science.gov (United States)

    Azab, H A; El-Nady, A M; El-Shatoury, S A; Hassan, A

    1994-08-01

    The dissociation constant values of L-histidine, proline and tryptophane were determined at 25 +/- 0.1 degrees C by potentiometric pH titration in pure water and different hydroorganic solvent media. The organic solvents used were methanol, ethanol, N,N-dimethylformamide, dimethyl sulfoxide, acetone and dioxane. Initial estimates of the dissociation constant values of the different amino acids studied have been refined with ESAP2M computer program. It was observed that changing the medium permittivity as the solvent is enriched in methanol or ethanol has little influence on the pK*(a) values of the amino acids studied. The results obtained are discussed in terms of average macroscopic properties of the mixed solvents and the possible variation in microheterogeneity of the salvation shells around the solute.

  18. Plasmodium falciparum histidine-rich protein II causes vascular leakage and exacerbates experimental cerebral malaria in mice.

    Science.gov (United States)

    Pal, Priya; Balaban, Amanda E; Diamond, Michael S; Sinnis, Photini; Klein, Robyn S; Goldberg, Daniel E

    2017-01-01

    A devastating complication of Plasmodium falciparum infection is cerebral malaria, in which vascular leakage and cerebral swelling lead to coma and often death. P. falciparum produces a protein called histidine-rich protein II (HRPII) that accumulates to high levels in the bloodstream of patients and serves as a diagnostic and prognostic marker for falciparum malaria. Using a human cerebral microvascular endothelial barrier model, we previously found that HRPII activates the endothelial cell inflammasome, resulting in decreased integrity of tight junctions and increased endothelial barrier permeability. Here, we report that intravenous administration of HRPII induced blood-brain barrier leakage in uninfected mice. Furthermore, HRPII infusion in P. berghei-infected mice increased early mortality from experimental cerebral malaria. These data support the hypothesis that HRPII is a virulence factor that contributes to cerebral malaria by compromising the integrity of the blood-brain barrier.

  19. Synthesis of poly(methyl methacrylate)-block-poly(L-histidine) and its use as a hybrid silver nanoparticle conjugate.

    Science.gov (United States)

    Shin, Nam Ho; Lee, Jin Kyu; Li, Haiqing; Ha, Chang-Sik; Shchipunov, Yury A; Kim, Il

    2010-10-01

    Poly[(methyl methacrylate)-block-poly(L-histidine)] (PMMA-b-PHIS) was synthesized by combining atom transfer radical polymerization and living ring-opening polymerization of alpha-amino acid-N-carboxyanhydride. The resulting hybrid block copolymer forms reverse micelles in the mixture solution of water and N,N-dimethylformamide (DMF) and self-assembles into PHIS/PMMA core/shell spheres with controllable size in the range of 80 to 250 nm depending on the micellization temperature. The self-assembly of PMMA-b-PHIS was carried out in H2O/DMF (3/7) mixture in the presence of AgNO3. Reduction of the resulting Ag ions encapsulated inside of the reverse micelles yielded an attractive Ag nanoparticle core/polymer shell conjugate system.

  20. Assembly of the transmembrane domain of E. coli PhoQ histidine kinase: implications for signal transduction from molecular simulations.

    Directory of Open Access Journals (Sweden)

    Thomas Lemmin

    Full Text Available The PhoQP two-component system is a signaling complex essential for bacterial virulence and cationic antimicrobial peptide resistance. PhoQ is the histidine kinase chemoreceptor of this tandem machine and assembles in a homodimer conformation spanning the bacterial inner membrane. Currently, a full understanding of the PhoQ signal transduction is hindered by the lack of a complete atomistic structure. In this study, an atomistic model of the key transmembrane (TM domain is assembled by using molecular simulations, guided by experimental cross-linking data. The formation of a polar pocket involving Asn202 in the lumen of the tetrameric TM bundle is crucial for the assembly and solvation of the domain. Moreover, a concerted displacement of the TM helices at the periplasmic side is found to modulate a rotation at the cytoplasmic end, supporting the transduction of the chemical signal through a combination of scissoring and rotational movement of the TM helices.

  1. Arabidopsis histidine-containing phosphotransfer factor 4 (AHP4) negatively regulates secondary wall thickening of the anther endothecium during flowering.

    Science.gov (United States)

    Jung, Kwang Wook; Oh, Seung-Ick; Kim, Yun Young; Yoo, Kyoung Shin; Cui, Mei Hua; Shin, Jeong Sheop

    2008-04-30

    Cytokinins are essential hormones in plant development. Arabidopsis histidine-containing phosphotransfer proteins (AHPs) are mediators in a multistep phosphorelay pathway for cytokinin signaling. The exact role of AHP4 has not been elucidated. In this study, we demonstrated young flower-specific expression of AHP4, and compared AHP4-overexpressing (Ox) trangenic Arabidopsis lines and an ahp4 knock-out line. AHP4-Ox plants had reduced fertility due to a lack of secondary cell wall thickening in the anther endothecium and inhibition of IRREGURAR XYLEMs (IRXs) expression in young flowers. Conversely, ahp4 anthers had more lignified anther walls than the wild type, and increased IRXs expression. Our study indicates that AHP4 negatively regulates thickening of the secondary cell wall of the anther endothecium, and provides new insight into the role of cytokinins in formation of secondary cell walls via the action of AHP4.

  2. Growth, structural and optical characterization of L-histidine 4-nitrophenolate (LHPNP) single crystals for NLO applications

    Energy Technology Data Exchange (ETDEWEB)

    Mahadevan, M., E-mail: devanphysics@gmail.com [Department of Physics, Adhiparasakthi Engineering College, Melmaruvathur - 603319 (India); Ramachandran, K., E-mail: ramach76@yahoo.com [Department of Physics, SRM University - Vadapalani Campus, Chennai -600026 (India); Anandan, P., E-mail: anandantcet@gmail.com [Department of Physics, Thiruvalluvar College of Engineering and Technology, Vandavasi-604 505, India and Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-Ku, Hamamatsu 432-8011 (Japan); Arivanandhan, M., E-mail: arivucz@gmail.com, E-mail: royhaya@ipc.shizuoka.ac.jp; Hayakawa, Y., E-mail: arivucz@gmail.com, E-mail: royhaya@ipc.shizuoka.ac.jp [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-Ku, Hamamatsu 432-8011 (Japan)

    2014-10-15

    Using slow evaporation solution growth technique, single crystals of L-histidine-4-nitro phenolate has been grown from the solution. Structural analyses were carried out by powder x-ray diffraction, FT-Raman, Fourier Transform Infrared and Nuclear Magnetic Resonance spectral methods to conform the grown crystals. Thermal stability of the grown crystals was studied by thermo-gravimetric (TG) and differential thermal analyses (DTA). UV-Vis spectral analysis has been carried out to find the transparency of the grown crystal. Nonlinear optical property has been confirmed by Kurtz powder technique. The PL measurements were carried out in Perkin Elmer LS 55 Luminescence spectrometer using 410 nm as excitation wavelength. The observed properties have confirmed that the grown crystal is suitable for nonlinear optical applications.

  3. Syntheses of stable, synthetic diadenosine polyphosphate analogues using recombinant histidine-tagged lysyl tRNA synthetase (LysU).

    Science.gov (United States)

    Wright, Michael; Azhar, M Ameruddin; Kamal, Ahmed; Miller, Andrew D

    2014-05-15

    Recombinant Escherichia coli lysyl-tRNA synthase (LysU) has been previously utilised in the production of stabile, synthetic diadenosine polyphosphate (ApnA) analogues. Here we report on the extended use of a new recombinant histidine residue-tagged LysU as a tool for highly controlled phosphatephosphate bond formation between nucleotides, avoiding the need for complex protecting group chemistries. Resulting high yielding tandem LysU-based biosynthetic-synthetic/synthetic-biosynthetic strategies emerge for the preparation of varieties of ApnA analogues directly from inexpensive natural nucleotides and nucleosides. Analogues so formed make a useful small library with which to probe ApnA activities in vitro and in vivo leading to the discovery of new, potentially potent biopharmaceuticals active against chronic pain and other chronic, high-burden disease states. Copyright © 2014. Published by Elsevier Ltd.

  4. Structural and functional analogies and differences between histidine decarboxylase and aromatic l-amino acid decarboxylase molecular networks: Biomedical implications.

    Science.gov (United States)

    Sanchez-Jiménez, Francisca; Pino-Ángeles, Almudena; Rodríguez-López, Rocio; Morales, María; Urdiales, José Luis

    2016-12-01

    Human histidine decarboxylase (HDC) and dopa decarboxilase (DDC) are highly homologous enzymes responsible for the synthesis of biogenic amines (BA) like histamine, and serotonin and dopamine, respectively. The enzymes share many structural and functional analogies, while their product metabolisms also follow similar patterns that are confluent in some metabolic steps. They are involved in common physiological functions, such as neurotransmission, gastrointestinal track function, immunity, cell growth and cell differentiation. As a consequence, metabolic elements of both BA subfamilies are also co-participants in a long list of human diseases. This review summarizes the analogies and differences in their origin (HDC and DDC) as well as their common pathophysiological scenarios. The major gaps of information are also underlined, as they delay the possibility of holistic approaches that would help personalized medicine and pharmacological initiatives for prevalent and rare diseases. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Detection of Cu2+ in Water Based on Histidine-Gold Labeled Multiwalled Carbon Nanotube Electrochemical Sensor

    Directory of Open Access Journals (Sweden)

    Rilong Zhu

    2017-01-01

    Full Text Available Based on the strong interaction between histidine and copper ions and the signal enhancement effect of gold-labeling carbon nanotubes, an electrochemical sensor is established and used to measure copper ions in river water. In this study the results show that the concentrations of copper ion have well linear relationship with the peak current in the range of 10−11–10−7 mol/L, and the limit of detection is 10−12 mol/L. When using this method to detect copper ions in the Xiangjiang River, the test results are consistent with the atomic absorption method. This study shows that the sensor is convenient to be used in daily monitoring of copper ions in river water.

  6. Hg-coordination studies of oligopeptides containing cysteine, histidine and tyrosine by $^{199m}$Hg-TDPAC

    CERN Document Server

    Ctortecka, B; Mallion, S; Butz, T; Hoffmann, R

    1999-01-01

    In order to study the interaction of histidine- and tyrosine- containing peptide chains with Hg(II), the nuclear quadrupole interaction (NQI) of /sup 199m/Hg in the Hg complexes of the oligopeptides alanyl-alanyl-histidyl-alanyl-alanine-amid (AAHAA-NH /sub 2/) and alanyl-alanyl-tyrosyl-alanyl-alanine-amid (AAYAA-NH/sub 2/) was determined by time differential perturbed angular correlation and is compared with previous data on alanyl-alanyl-cysteyl-alanyl- alanyl (AACAA-OH). The /sup 199m/Hg-NQIs depend on the oligopeptide to Hg(II) stoichiometry and indicate that two-fold and four-fold coordinations occur for the bound Hg(II). (12 refs).

  7. DETERMINATION OF THE 3-DIMENSIONAL SOLUTION STRUCTURE OF THE HISTIDINE-CONTAINING PHOSPHOCARRIER PROTEIN HPR FROM ESCHERICHIA-COLI USING MULTIDIMENSIONAL NMR-SPECTROSCOPY

    NARCIS (Netherlands)

    VANNULAND, NAJ; GROTZINGER, J; DIJKSTRA, K; SCHEEK, RM; ROBILLARD, GT

    1992-01-01

    We recorded several types of heteronuclear three-dimensional (3D) NMR spectra on N-15-enriched and C-13/N-15-enriched histidine-containing phosphocarrier protein, HPr, to extend the backbone assignments [van Nuland, N. A. J., van Dijk, A. A., Dijkstra, K., van Hoesel, F. H. J., Scheek, R. M. &

  8. The Cell Lysis Activity of the Streptococcus agalactiae Bacteriophage B30 Endolysin Relies on the Cysteine, Histidine-Dependent Amidohydrolase/Peptidase Domain

    Science.gov (United States)

    Donovan, David M.; Foster-Frey, Juli; Dong, Shengli; Rousseau, Geneviève M.; Moineau, Sylvain; Pritchard, David G.

    2006-01-01

    The Streptococcus agalactiae bacteriophage B30 endolysin contains three domains: cysteine, histidine-dependent amidohydrolase/peptidase (CHAP), Acm glycosidase, and the SH3b cell wall binding domain. Truncations and point mutations indicated that the Acm domain requires the SH3b domain for activity, while the CHAP domain is responsible for nearly all the cell lysis activity. PMID:16820517

  9. Examination of Correlation between Histidine and Cadmium Absorption by Eleagnus angustifolia L., Vitis vinifera L. and Nerium oleander L. Using HPLC-MS and ICP-MS.

    Science.gov (United States)

    Ozen, Sukran Akkus; Yaman, Mehmet

    2016-02-01

    In this study, HPLC-MS and ICP-MS methods wereused for the determination of histidine and cadmium in Eleagnus angustifolia L., Vitis vinifera L. and Nerium oleander L. leaves taken from industrial area including Gaziantep and Bursa cities. To histidine determination by HPLC-MS, flow rate of mobile phase, fragmentor potential, injection volume and column temperature were optimized as 0.2 mL · min⁻¹, 70 V, 15 µL and 20 °C, respectively. For extraction of histidine from plants, distilled water was used by applying on 90 °C and 30 min. The concentrations (as mg · kg⁻¹) of histidine were found to be in range of 8~22 for Eleagnus angustifolia L., 10~33 for Vitis vinifera L. and 6~11 for Nerium oleander L. The concentrations of cadmium were found to be in ranges of 6~21 µg · kg⁻¹ for Vitis vinifera L. 15~110 µg · kg⁻¹ for Eleagnus angustifolia L. and 63~218 µg · kg⁻¹ for Nerium oleander L.

  10. Contribution of Histidine and Lysine to the Generation of Volatile Compounds in Jinhua Ham Exposed to Ripening Conditions Via Maillard Reaction.

    Science.gov (United States)

    Zhu, Chao-Zhi; Zhao, Jing-Li; Tian, Wei; Liu, Yan-Xia; Li, Miao-Yun; Zhao, Gai-Ming

    2017-12-01

    To evaluate the role of Maillard reactions in the generation of flavor compounds in Jinhua ham, the reactions of glucose and ethanal with histidine and lysine, respectively, were studied by simulating the ripening conditions of Jinhua ham. The volatile products produced were analyzed using solid phase microextraction-gas chromatography/mass spectrometry. The results showed that 8 volatile compounds were generated by the reaction of glucose and histidine and 10 volatile compounds were generated by the reaction of glucose and lysine. Reactions of ethanal with lysine and with histidine both generated 31 volatile compounds that contributed to the flavor of Jinhua ham. This indicates that histidine and lysine related to Maillard reactions possibly play important roles in the generation of the unique flavor compounds in Jinhua ham. This research demonstrates that free amino acids participate in the generation of volatile compounds from Jinhua ham via the Maillard reaction and provides a basic mechanism to explain flavor formation in Jinhua ham. Jinhua ham is a well-known traditional Chinese dry-cured meat product. However, the formation of the compounds comprising its special flavor is not well understood. Our results indicate that Maillard reactions occur in Jinhua ham under ripening conditions. This work illustrates the contribution of Maillard reactions to the flavor of Jinhua ham. © 2017 Institute of Food Technologists®.

  11. A Novel Secretory Poly-Cysteine and Histidine-Tailed Metalloprotein (Ts-PCHTP) from Trichinella spiralis (Nematoda)

    Science.gov (United States)

    Radoslavov, Georgi; Jordanova, Rositsa; Teofanova, Denitsa; Georgieva, Katya; Hristov, Petar; Salomone-Stagni, Marco; Liebau, Eva; Bankov, Ilia

    2010-01-01

    Background Trichinella spiralis is an unusual parasitic intracellular nematode causing dedifferentiation of the host myofiber. Trichinella proteomic analyses have identified proteins that act at the interface between the parasite and the host and are probably important for the infection and pathogenesis. Many parasitic proteins, including a number of metalloproteins are unique for the nematodes and trichinellids and therefore present good targets for future therapeutic developments. Furthermore, detailed information on such proteins and their function in the nematode organism would provide better understanding of the parasite - host interactions. Methodology/Principal Findings In this study we report the identification, biochemical characterization and localization of a novel poly-cysteine and histidine-tailed metalloprotein (Ts-PCHTP). The native Ts-PCHTP was purified from T. spiralis muscle larvae that were isolated from infected rats as a model system. The sequence analysis showed no homology with other proteins. Two unique poly-cysteine domains were found in the amino acid sequence of Ts-PCHTP. This protein is also the first reported natural histidine tailed protein. It was suggested that Ts-PCHTP has metal binding properties. Total Reflection X-ray Fluorescence (TXRF) assay revealed that it binds significant concentrations of iron, nickel and zinc at protein:metal ratio of about 1∶2. Immunohistochemical analysis showed that the Ts-PCHTP is localized in the cuticle and in all tissues of the larvae, but that it is not excreted outside the parasite. Conclusions/Significance Our data suggest that Ts-PCHTP is the first described member of a novel nematode poly-cysteine protein family and its function could be metal storage and/or transport. Since this protein family is unique for parasites from Superfamily Trichinelloidea its potential applications in diagnostics and treatment could be exploited in future. PMID:20967224

  12. A novel secretory poly-cysteine and histidine-tailed metalloprotein (Ts-PCHTP from Trichinella spiralis (Nematoda.

    Directory of Open Access Journals (Sweden)

    Georgi Radoslavov

    Full Text Available BACKGROUND: Trichinella spiralis is an unusual parasitic intracellular nematode causing dedifferentiation of the host myofiber. Trichinella proteomic analyses have identified proteins that act at the interface between the parasite and the host and are probably important for the infection and pathogenesis. Many parasitic proteins, including a number of metalloproteins are unique for the nematodes and trichinellids and therefore present good targets for future therapeutic developments. Furthermore, detailed information on such proteins and their function in the nematode organism would provide better understanding of the parasite-host interactions. METHODOLOGY/PRINCIPAL FINDINGS: In this study we report the identification, biochemical characterization and localization of a novel poly-cysteine and histidine-tailed metalloprotein (Ts-PCHTP. The native Ts-PCHTP was purified from T. spiralis muscle larvae that were isolated from infected rats as a model system. The sequence analysis showed no homology with other proteins. Two unique poly-cysteine domains were found in the amino acid sequence of Ts-PCHTP. This protein is also the first reported natural histidine tailed protein. It was suggested that Ts-PCHTP has metal binding properties. Total Reflection X-ray Fluorescence (TXRF assay revealed that it binds significant concentrations of iron, nickel and zinc at protein:metal ratio of about 1:2. Immunohistochemical analysis showed that the Ts-PCHTP is localized in the cuticle and in all tissues of the larvae, but that it is not excreted outside the parasite. CONCLUSIONS/SIGNIFICANCE: Our data suggest that Ts-PCHTP is the first described member of a novel nematode poly-cysteine protein family and its function could be metal storage and/or transport. Since this protein family is unique for parasites from Superfamily Trichinelloidea its potential applications in diagnostics and treatment could be exploited in future.

  13. Sensor histidine kinase is a β-lactam receptor and induces resistance to β-lactam antibiotics.

    Science.gov (United States)

    Li, Lu; Wang, Qiyao; Zhang, Hui; Yang, Minjun; Khan, Mazhar I; Zhou, Xiaohui

    2016-02-09

    β-Lactams disrupt bacterial cell wall synthesis, and these agents are the most widely used antibiotics. One of the principle mechanisms by which bacteria resist the action of β-lactams is by producing β-lactamases, enzymes that degrade β-lactams. In Gram-negative bacteria, production of β-lactamases is often induced in response to the antibiotic-associated damage to the cell wall. Here, we have identified a previously unidentified mechanism that governs β-lactamase production. In the Gram-negative enteric pathogen Vibrio parahaemolyticus, we found a histidine kinase/response regulator pair (VbrK/VbrR) that controls expression of a β-lactamase. Mutants lacking either VbrK or VbrR do not produce the β-lactamase and are no longer resistant to β-lactam antibiotics. Notably, VbrK autophosphorylation is activated by β-lactam antibiotics, but not by other lactams. However, single amino acid substitutions in the putative periplasmic binding pocket of VbrK leads its phosphorylation in response to both β-lactam and other lactams, suggesting that this kinase is a β-lactam receptor that can directly detect β-lactam antibiotics instead of detecting the damage to cell wall resulting from β-lactams. In strong support of this idea, we found that purified periplasmic sensor domain of VbrK binds penicillin, and that such binding is critical for VbrK autophosphorylation and β-lactamase production. Direct recognition of β-lactam antibiotics by a histidine kinase receptor may represent an evolutionarily favorable mechanism to defend against β-lactam antibiotics.

  14. Substitutions of PrP N-terminal histidine residues modulate scrapie disease pathogenesis and incubation time in transgenic mice.

    Directory of Open Access Journals (Sweden)

    Sabina Eigenbrod

    Full Text Available Prion diseases have been linked to impaired copper homeostasis and copper induced-oxidative damage to the brain. Divalent metal ions, such as Cu2+ and Zn2+, bind to cellular prion protein (PrPC at octapeptide repeat (OR and non-OR sites within the N-terminal half of the protein but information on the impact of such binding on conversion to the misfolded isoform often derives from studies using either OR and non-OR peptides or bacterially-expressed recombinant PrP. Here we created new transgenic mouse lines expressing PrP with disrupted copper binding sites within all four histidine-containing OR's (sites 1-4, H60G, H68G, H76G, H84G, "TetraH>G" allele or at site 5 (composed of residues His-95 and His-110; "H95G" allele and monitored the formation of misfolded PrP in vivo. Novel transgenic mice expressing PrP(TetraH>G at levels comparable to wild-type (wt controls were susceptible to mouse-adapted scrapie strain RML but showed significantly prolonged incubation times. In contrast, amino acid replacement at residue 95 accelerated disease progression in corresponding PrP(H95G mice. Neuropathological lesions in terminally ill transgenic mice were similar to scrapie-infected wt controls, but less severe. The pattern of PrPSc deposition, however, was not synaptic as seen in wt animals, but instead dense globular plaque-like accumulations of PrPSc in TgPrP(TetraH>G mice and diffuse PrPSc deposition in (TgPrP(H95G mice, were observed throughout all brain sections. We conclude that OR and site 5 histidine substitutions have divergent phenotypic impacts and that cis interactions between the OR region and the site 5 region modulate pathogenic outcomes by affecting the PrP globular domain.

  15. The effect of an adding histidine on biological activity and stability of Pc-pis from Pseudosciaena crocea.

    Science.gov (United States)

    Mao, Yong; Niu, Sufang; Xu, Xin; Wang, Jun; Su, Yongquan; Wu, Yang; Zhong, Shengping

    2013-01-01

    Pc-pis is a novel piscidin-like antimicrobial polypeptide that was identified in Pseudosciaena crocea. Although active against most bacteria tested, Pc-pis was inactive against Aeromonas hydrophila and Pseudomonas aeruginosa. The Pc-pis analogue Pc-pis-His was designed by adding a histidine residue at the carboxyl terminal. Pc-pis-His demonstrated a more broad-spectrum and stronger antimicrobial activity against a representative set of microorganisms and more potent antiparasitic activity against Cryptocaryon irritans trophonts than Pc-pis. The stability assay revealed that Pc-pis-His was active against Staphylococcus aureus not only in acidic (pH 5.5-7.3) and relatively low concentration monovalent cation (0-160 mM NaCl) environments but also in alkaline (pH 7.5-9.5), divalent cation (1.25-160 mM MgCl2 and 1.25-40 mM CaCl2) and high concentration monovalent cation (320-2560 mM NaCl) environments, which indicates that the added histidine residue conferred better salt-, acid- and alkali-tolerance to Pc-pis-His. Pc-pis-His also possessed the desired heat-tolerance, which was reflected by the antimicrobial activity of the peptide after being boiled for 10-60 minutes. Hemolytic activity analysis revealed that Pc-pis-His at concentrations up to 6 µM exhibited no hemolysis against human erythrocytes, with 6 µM being a concentration that is highly active against most of the microorganisms tested, although the hemolytic activity of Pc-pis-His was enhanced compared to Pc-pis. These results provide a unique, reasonable basis for designing novel piscidins with potent, broad-spectrum and stable antimicrobial activity and new insight into the future development of piscidins as potential therapeutic agents against microbial and external protozoan parasite infections.

  16. The effect of an adding histidine on biological activity and stability of Pc-pis from Pseudosciaena crocea.

    Directory of Open Access Journals (Sweden)

    Yong Mao

    Full Text Available Pc-pis is a novel piscidin-like antimicrobial polypeptide that was identified in Pseudosciaena crocea. Although active against most bacteria tested, Pc-pis was inactive against Aeromonas hydrophila and Pseudomonas aeruginosa. The Pc-pis analogue Pc-pis-His was designed by adding a histidine residue at the carboxyl terminal. Pc-pis-His demonstrated a more broad-spectrum and stronger antimicrobial activity against a representative set of microorganisms and more potent antiparasitic activity against Cryptocaryon irritans trophonts than Pc-pis. The stability assay revealed that Pc-pis-His was active against Staphylococcus aureus not only in acidic (pH 5.5-7.3 and relatively low concentration monovalent cation (0-160 mM NaCl environments but also in alkaline (pH 7.5-9.5, divalent cation (1.25-160 mM MgCl2 and 1.25-40 mM CaCl2 and high concentration monovalent cation (320-2560 mM NaCl environments, which indicates that the added histidine residue conferred better salt-, acid- and alkali-tolerance to Pc-pis-His. Pc-pis-His also possessed the desired heat-tolerance, which was reflected by the antimicrobial activity of the peptide after being boiled for 10-60 minutes. Hemolytic activity analysis revealed that Pc-pis-His at concentrations up to 6 µM exhibited no hemolysis against human erythrocytes, with 6 µM being a concentration that is highly active against most of the microorganisms tested, although the hemolytic activity of Pc-pis-His was enhanced compared to Pc-pis. These results provide a unique, reasonable basis for designing novel piscidins with potent, broad-spectrum and stable antimicrobial activity and new insight into the future development of piscidins as potential therapeutic agents against microbial and external protozoan parasite infections.

  17. A CHASE3/GAF sensor hybrid histidine kinase BmsA modulates biofilm formation and motility in Pseudomonas alkylphenolica.

    Science.gov (United States)

    Lee, Kyoung; Ha, Gwang Su; Veeranagouda, Yaligara; Seo, Young-Su; Hwang, Ingyu

    2016-11-01

    Pseudomonas alkylphenolica is an important strain in the biodegradation of toxic alkylphenols and mass production of bioactive polymannuronate polymers. This strain forms a diverse, 3D biofilm architecture, including mushroom-like aerial structures, circular pellicles and surface spreading, depending on culture conditions. A mutagenesis and complementation study showed that a predicted transmembrane kinase, PSAKL28_21690 (1164 aa), harbouring a periplasmic CHASE3 domain flanked by two transmembrane helices in addition to its cytoplasmic GAF, histidine kinase and three CheY-like response regulator domains, plays a positive role in the formation of the special biofilm architecture and a negative role in swimming activity. In addition, the gene, named here as bmsA, is co-transcribed with three genes encoding proteins with CheR (PSAKL28_21700) and CheB (PSAKL28_21710) domains and response regulator and histidine kinase domains (PSAKL28_21720). This gene cluster is thus named bmsABCD and is found widely distributed in pseudomonads and other bacteria. Deletion of the genes in the cluster, except forbmsA, did not result in changes in biofilm-related phenotypes. The RNA-seq analysis showed that the expression of genes coding for flagellar synthesis was increased when bmsA was mutated. In addition, the expression of rsmZ, which is one of final targets of the Gac regulon, was not significantly altered in the bmsA mutant, and overexpression of bmsA in the gacA mutant did not produce the WT phenotype. These results indicate that the sensory Bms regulon does not affect the upper cascade of the Gac signal transduction pathway for the biofilm-related phenotypes in P. alkylphenolica.

  18. Role of Conserved Histidine Residues in the Low-pH Dependence of the Semliki Forest Virus Fusion Protein▿

    Science.gov (United States)

    Qin, Zhao-ling; Zheng, Yan; Kielian, Margaret

    2009-01-01

    A wide variety of enveloped viruses infects cells by taking advantage of the low pH in the endocytic pathway to trigger virus-membrane fusion. For alphaviruses such as Semliki Forest virus (SFV), acidic pH initiates a series of conformational changes in the heterodimeric virus envelope proteins E1 and E2. Low pH dissociates the E2/E1 dimer, releasing the membrane fusion protein E1. E1 inserts into the target membrane and refolds to a trimeric hairpin conformation, thus driving the fusion reaction. The means by which E1 senses and responds to low pH is unclear, and protonation of conserved E1 histidine residues has been proposed as a possible mechanism. We tested the role of four conserved histidines by mutagenesis of the wild-type (wt) SFV infectious clone to create virus mutants with E1 H3A, H125A, H331A, and H331A/H333A mutations. The H125A, H331A, and H331A/H333A mutants had growth properties similar to those of wt SFV and showed modest change or no change in the pH dependence of virus-membrane fusion. By contrast, the E1 H3A mutation produced impaired virus growth and a markedly more acidic pH requirement for virus-membrane fusion. The dissociation of the H3A heterodimer and the membrane insertion of the mutant E1 protein were comparable to those of the wt in efficiency and pH dependence. However, the formation of the H3A homotrimer required a much lower pH and showed reduced efficiency. Together, these results and the location of H3 suggest that this residue acts to regulate the low-pH-dependent refolding of E1 during membrane fusion. PMID:19244325

  19. Role of conserved histidine residues in the low-pH dependence of the Semliki Forest virus fusion protein.

    Science.gov (United States)

    Qin, Zhao-Ling; Zheng, Yan; Kielian, Margaret

    2009-05-01

    A wide variety of enveloped viruses infects cells by taking advantage of the low pH in the endocytic pathway to trigger virus-membrane fusion. For alphaviruses such as Semliki Forest virus (SFV), acidic pH initiates a series of conformational changes in the heterodimeric virus envelope proteins E1 and E2. Low pH dissociates the E2/E1 dimer, releasing the membrane fusion protein E1. E1 inserts into the target membrane and refolds to a trimeric hairpin conformation, thus driving the fusion reaction. The means by which E1 senses and responds to low pH is unclear, and protonation of conserved E1 histidine residues has been proposed as a possible mechanism. We tested the role of four conserved histidines by mutagenesis of the wild-type (wt) SFV infectious clone to create virus mutants with E1 H3A, H125A, H331A, and H331A/H333A mutations. The H125A, H331A, and H331A/H333A mutants had growth properties similar to those of wt SFV and showed modest change or no change in the pH dependence of virus-membrane fusion. By contrast, the E1 H3A mutation produced impaired virus growth and a markedly more acidic pH requirement for virus-membrane fusion. The dissociation of the H3A heterodimer and the membrane insertion of the mutant E1 protein were comparable to those of the wt in efficiency and pH dependence. However, the formation of the H3A homotrimer required a much lower pH and showed reduced efficiency. Together, these results and the location of H3 suggest that this residue acts to regulate the low-pH-dependent refolding of E1 during membrane fusion.

  20. Predicting survival of Salmonella in low-water activity foods: an analysis of literature data.

    Science.gov (United States)

    Santillana Farakos, Sofia M; Schaffner, Donald W; Frank, Joseph F

    2014-09-01

    Factors such as temperature, water activity (aw), substrate, culture media, serotype, and strain influence the survival of Salmonella in low-aw foods. Predictive models for Salmonella survival in low-aw foods at temperatures ranging from 21 to 80(u) C and water activities below 0.6 were previously developed. Literature data on survival of Salmonella in low-aw foods were analyzed in the present study to validate these predictive models and to determine global influencing factors. The results showed the Weibull model provided suitable fits to the data in 75% of the curves as compared with the log-linear model. The secondary models predicting the time required for log-decimal reduction (log δ) and shape factor (log β) values were useful in predicting the survival of Salmonella in low-aw foods. Statistical analysis indicated overall fail-safe secondary models, with 88% of the residuals in the acceptable and safe zones (survival kinetics of Salmonella in low-aw foods and its influencing factors.

  1. PREDICTING WATER ACTIVITY IN ELECTROLYTE SOLUTIONS WITH THE CISTERNAS-LAM MODEL

    Energy Technology Data Exchange (ETDEWEB)

    REYNOLDS JG; GREER DA; DISSELKAMP RL

    2011-03-01

    Water activity is an important parameter needed to predict the solubility of hydrated salts in Hanford nuclear waste supernatants. A number of models available in the scientific literature predict water activity from electrolyte solution composition. The Cisternas-Lam model is one of those models and has several advantages for nuclear waste application. One advantage is that it has a single electrolyte specific parameter that is temperature independent. Thus, this parameter can be determined from very limited data and extrapolated widely. The Cisternas-Lam model has five coefficients that are used for all aqueous electrolytes. The present study aims to determine if there is a substantial improvement in making all six coefficients electrolyte specific. The Cisternas-Lam model was fit to data for six major electrolytes in Hanford nuclear waste supernatants. The model was first fit to all data to determine the five global coefficients, when they were held constant for all electrolytes it yielded a substantially better fit. Subsequently, the model was fit to each electrolyte dataset separately, where all six coefficients were allowed to be electrolyte specific. Treating all six coefficients as electrolyte specific did not make sufficient difference, given the complexity of applying the electrolyte specific parameters to multi-solute systems. Revised water specific parameters, optimized to the electrolytes relevant to Hanford waste, are also reported.

  2. Examination of correlation between histidine and nickel absorption by Morus L., Robinia pseudoacacia L. and Populus nigra L. using HPLC-MS and ICP-MS.

    Science.gov (United States)

    Ozen, Sukran Akkus; Yaman, Mehmet

    2016-08-02

    In this study, HPLC-MS and ICP-MS methods were used for the determination of histidine and nickel in Morus L., Robinia pseudoacacia L., and Populus nigra L. leaves taken from industrial areas including Gaziantep and Bursa cities. In the determination of histidine by HPLC-MS, all of the system parameters such as flow rate of mobile phase, fragmentor potential, injection volume and column temperature were optimized and found to be 0.2 mL min(-1), 70 V, 15 µL, and 20°C, respectively. Under the optimum conditions, histidine was extracted from plant sample by distilled water at 90°C for 30 min. Concentrations of histidine as mg kg(-1) were found to be between 2-9 for Morus L., 6-13 for Robinia pseudoacacia L., and 2-10 for Populus nigra L. Concentrations of nickel were in the ranges of 5-10 mg kg(-1) for Morus L., 3-10 mg kg(-1) for Robinia pseudoacacia L., and 0.6-4 mg kg(-1) for Populus nigra L. A significant linear correlation (r = 0.78) between histidine and Ni was observed for Populus nigra L., whereas insignificant linear correlation for Robinia pseudoacacia L. (r = 0.22) were seen. Limits of detection (LOD) and quantitation (LOQ) were found to be 0.025 mg Ni L(-1) and 0.075 mg Ni L(-1), respectively.

  3. Students' Understanding of Loops and Nested Loops in Computer Programming: An APOS Theory Perspective

    Science.gov (United States)

    Cetin, Ibrahim

    2015-01-01

    The purpose of this study is to explore students' understanding of loops and nested loops concepts. Sixty-three mechanical engineering students attending an introductory programming course participated in the study. APOS (Action, Process, Object, Schema) is a constructivist theory developed originally for mathematics education. This study is the…

  4. Open-loop versus closed-loop control of MEMS devices: choices and issues

    Science.gov (United States)

    Borovic, B.; Liu, A. Q.; Popa, D.; Cai, H.; Lewis, F. L.

    2005-10-01

    From a controls point of view, micro electromechanical systems (MEMS) can be driven in an open-loop and closed-loop fashion. Commonly, these devices are driven open-loop by applying simple input signals. If these input signals become more complex by being derived from the system dynamics, we call such control techniques pre-shaped open-loop driving. The ultimate step for improving precision and speed of response is the introduction of feedback, e.g. closed-loop control. Unlike macro mechanical systems, where the implementation of the feedback is relatively simple, in the MEMS case the feedback design is quite problematic, due to the limited availability of sensor data, the presence of sensor dynamics and noise, and the typically fast actuator dynamics. Furthermore, a performance comparison between open-loop and closed-loop control strategies has not been properly explored for MEMS devices. The purpose of this paper is to present experimental results obtained using both open- and closed-loop strategies and to address the comparative issues of driving and control for MEMS devices. An optical MEMS switching device is used for this study. Based on these experimental results, as well as computer simulations, we point out advantages and disadvantages of the different control strategies, address the problems that distinguish MEMS driving systems from their macro counterparts, and discuss criteria to choose a suitable control driving strategy.

  5. Quantum hysteresis loops in microscopic system: The loop area as a ...

    Indian Academy of Sciences (India)

    Effects of non-zero temperatures are explored with reference to a symmetric double well potential. The barrier crossing or, relaxation rates are shown to correlate systematically with the area of the loop. The possible use of hysteresis loop area in designing field parameters for optimal control is suggested.

  6. Parameterizing loop fusion for automated empirical tuning

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Y; Yi, Q; Kennedy, K; Quinlan, D; Vuduc, R

    2005-12-15

    Traditional compilers are limited in their ability to optimize applications for different architectures because statically modeling the effect of specific optimizations on different hardware implementations is difficult. Recent research has been addressing this issue through the use of empirical tuning, which uses trial executions to determine the optimization parameters that are most effective on a particular hardware platform. In this paper, we investigate empirical tuning of loop fusion, an important transformation for optimizing a significant class of real-world applications. In spite of its usefulness, fusion has attracted little attention from previous empirical tuning research, partially because it is much harder to configure than transformations like loop blocking and unrolling. This paper presents novel compiler techniques that extend conventional fusion algorithms to parameterize their output when optimizing a computation, thus allowing the compiler to formulate the entire configuration space for loop fusion using a sequence of integer parameters. The compiler can then employ an external empirical search engine to find the optimal operating point within the space of legal fusion configurations and generate the final optimized code using a simple code transformation system. We have implemented our approach within our compiler infrastructure and conducted preliminary experiments using a simple empirical search strategy. Our results convey new insights on the interaction of loop fusion with limited hardware resources, such as available registers, while confirming conventional wisdom about the effectiveness of loop fusion in improving application performance.

  7. Logical inference techniques for loop parallelization

    KAUST Repository

    Oancea, Cosmin E.

    2012-01-01

    This paper presents a fully automatic approach to loop parallelization that integrates the use of static and run-time analysis and thus overcomes many known difficulties such as nonlinear and indirect array indexing and complex control flow. Our hybrid analysis framework validates the parallelization transformation by verifying the independence of the loop\\'s memory references. To this end it represents array references using the USR (uniform set representation) language and expresses the independence condition as an equation, S = Ø, where S is a set expression representing array indexes. Using a language instead of an array-abstraction representation for S results in a smaller number of conservative approximations but exhibits a potentially-high runtime cost. To alleviate this cost we introduce a language translation F from the USR set-expression language to an equally rich language of predicates (F(S) ⇒ S = Ø). Loop parallelization is then validated using a novel logic inference algorithm that factorizes the obtained complex predicates (F(S)) into a sequence of sufficient-independence conditions that are evaluated first statically and, when needed, dynamically, in increasing order of their estimated complexities. We evaluate our automated solution on 26 benchmarks from PERFECTCLUB and SPEC suites and show that our approach is effective in parallelizing large, complex loops and obtains much better full program speedups than the Intel and IBM Fortran compilers. Copyright © 2012 ACM.

  8. Numerical simulation of a natural circulation loop

    Energy Technology Data Exchange (ETDEWEB)

    Verissimo, Gabriel L.; Moreira, Maria de Lourdes; Faccini, Jose Luiz H., E-mail: gabrielverissimo@poli.ufrj.b, E-mail: malu@ien.gov.b, E-mail: faccini@ien.gov.b [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2011-07-01

    This work presents a numerical simulation of a natural circulation loop using computational fluid dynamics. The simulated loop is an experimental model in a reduced scale of 1:10 of a passive heat removal system typical of advanced PWR reactors. The loop is composed of a heating vessel containing 52 electric heaters, a vertical shell-tube heat exchanger and a column of expansion. The working fluid is distilled water. Initially it was created a tridimensional geometric model of the loop components. After that, it was generated a tridimensional mesh of finite elements in order to calculate the variables of the problem. The boundaries of the numerical simulation were the power of the electric resistances and the cooling flow in the secondary side of the heat exchanger. The initial conditions were the temperature, the pressure and the fluid velocity at the time just before the power has been switched on. The results of this simulation were compared with the experimental data, in terms of the evolution of the temperatures in different locations of the loop, and of the average natural circulation flow as a function of time for a given power. (author)

  9. Coronal Loops: Observations and Modeling of Confined Plasma

    Directory of Open Access Journals (Sweden)

    Fabio Reale

    2010-11-01

    Full Text Available Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the review is divided into two separate but not independent parts: the first illustrates the observational framework, the second reviews the theoretical knowledge. Quiescent loops and their confined plasma are considered, and therefore topics such as loop oscillations and flaring loops (except for non-solar ones which provide information on stellar loops are not specifically addressed here. The observational section discusses loop classification and populations, and then describes the morphology of coronal loops, its relationship with the magnetic field, and the concept of loops as multi-stranded structures. The following part of this section is devoted to the characteristics of the loop plasma and of its thermal structure in particular, according to the classification into hot, warm, and cool loops. Then, temporal analyses of loops and the observations of plasma dynamics and flows are illustrated. In the modeling section some basics of loop physics are provided, supplying some fundamental scaling laws and timescales, a useful tool for consultation. The concept of loop modeling is introduced and models are distinguished between those treating loops as monolithic and static, and those resolving loops into thin and dynamic strands. Then, more specific discussions address modeling the loop fine structure and the plasma flowing along the loops. Special attention is devoted to the question of loop heating, with separate discussion of wave (AC and impulsive (DC heating. Finally, a brief discussion about stellar X-ray emitting structures related to coronal loops is included and followed by conclusions and open questions.

  10. BPS Wilson loops and Bremsstrahlung function in ABJ(M): a two loop analysis

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, Marco S. [Institut für Physik, Humboldt-Universität zu Berlin,Newtonstraße 15, 12489 Berlin (Germany); Griguolo, Luca [Dipartimento di Fisica e Scienze della Terra, Università di Parmaand INFN Gruppo Collegato di Parma,Viale G.P. Usberti 7/A, 43100 Parma (Italy); Leoni, Matias [Physics Department, FCEyN-UBA & IFIBA-CONICETCiudad Universitaria, Pabellón I, 1428, Buenos Aires (Argentina); Penati, Silvia [Dipartimento di Fisica, Università di Milano-Bicoccaand INFN, Sezione di Milano-Bicocca,Piazza della Scienza 3, I-20126 Milano (Italy); Seminara, Domenico [Dipartimento di Fisica, Università di Firenzeand INFN Sezione di Firenze,via G. Sansone 1, 50019 Sesto Fiorentino (Italy)

    2014-06-19

    We study a family of circular BPS Wilson loops in N=6 super Chern-Simons-matter theories, generalizing the usual 1/2-BPS circle. The scalar and fermionic couplings depend on two deformation parameters and these operators can be considered as the ABJ(M) counterpart of the DGRT latitudes defined in N=4 SYM. We perform a complete two-loop analysis of their vacuum expectation value, discuss the appearance of framing-like phases and propose a general relation with cohomologically equivalent bosonic operators. We make an all-loop proposal for computing the Bremsstrahlung function associated to the 1/2-BPS cusp in terms of these generalized Wilson loops. When applied to our two-loop result it reproduces the known expression. Finally, we comment on the generalization of this proposal to the bosonic 1/6-BPS case.

  11. Covariant diagrams for one-loop matching

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhengkang [Michigan Univ., Ann Arbor, MI (United States). Michigan Center for Theoretical Physics; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2016-10-15

    We present a diagrammatic formulation of recently-revived covariant functional approaches to one-loop matching from an ultraviolet (UV) theory to a low-energy effective field theory. Various terms following from a covariant derivative expansion (CDE) are represented by diagrams which, unlike conventional Feynman diagrams, involve gaugecovariant quantities and are thus dubbed ''covariant diagrams.'' The use of covariant diagrams helps organize and simplify one-loop matching calculations, which we illustrate with examples. Of particular interest is the derivation of UV model-independent universal results, which reduce matching calculations of specific UV models to applications of master formulas. We show how such derivation can be done in a more concise manner than the previous literature, and discuss how additional structures that are not directly captured by existing universal results, including mixed heavy-light loops, open covariant derivatives, and mixed statistics, can be easily accounted for.

  12. Solar flare loops observations and interpretations

    CERN Document Server

    Huang, Guangli; Ji, Haisheng; Ning, Zongjun

    2018-01-01

    This book provides results of analysis of typical solar events, statistical analysis, the diagnostics of energetic electrons and magnetic field, as well as the global behavior of solar flaring loops such as their contraction and expansion. It pays particular attention to analyzing solar flare loops with microwave, hard X-ray, optical and EUV emissions, as well as the theories of their radiation, and electron acceleration/transport. The results concerning influence of the pitch-angle anisotropy of non-thermal electrons on their microwave and hard X-ray emissions, new spectral behaviors in X-ray and microwave bands, and results related to the contraction of flaring loops, are widely discussed in the literature of solar physics. The book is useful for graduate students and researchers in solar and space physics.

  13. Automated one-loop calculations with GOSAM

    Energy Technology Data Exchange (ETDEWEB)

    Cullen, Gavin [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Greiner, Nicolas [Illinois Univ., Urbana-Champaign, IL (United States). Dept. of Physics; Max-Planck-Institut fuer Physik, Muenchen (Germany); Heinrich, Gudrun; Reiter, Thomas [Max-Planck-Institut fuer Physik, Muenchen (Germany); Luisoni, Gionata [Durham Univ. (United Kingdom). Inst. for Particle Physics Phenomenology; Mastrolia, Pierpaolo [Max-Planck-Institut fuer Physik, Muenchen (Germany); Padua Univ. (Italy). Dipt. di Fisica; Ossola, Giovanni [New York City Univ., NY (United States). New York City College of Technology; New York City Univ., NY (United States). The Graduate School and University Center; Tramontano, Francesco [European Organization for Nuclear Research (CERN), Geneva (Switzerland)

    2011-11-15

    We present the program package GoSam which is designed for the automated calculation of one-loop amplitudes for multi-particle processes in renormalisable quantum field theories. The amplitudes, which are generated in terms of Feynman diagrams, can be reduced using either D-dimensional integrand-level decomposition or tensor reduction. GoSam can be used to calculate one-loop QCD and/or electroweak corrections to Standard Model processes and offers the flexibility to link model files for theories Beyond the Standard Model. A standard interface to programs calculating real radiation is also implemented. We demonstrate the flexibility of the program by presenting examples of processes with up to six external legs attached to the loop. (orig.)

  14. Hybrid Models in Loop Quantum Cosmology

    CERN Document Server

    Navascués, B Elizaga; Marugán, G A Mena

    2016-01-01

    In the framework of Loop Quantum Cosmology, inhomogeneous models are usually quantized by means of a hybrid approach that combines loop quantization techniques with standard quantum field theory methods. This approach is based on a splitting of the phase space in a homogeneous sector, formed by global, zero-modes, and an inhomogeneous sector, formed by the remaining, infinite number of modes, that describe the local degrees of freedom. Then, the hybrid quantization is attained by adopting a loop representation for the homogeneous gravitational sector, while a Fock representation is used for the inhomogeneities. The zero-mode of the Hamiltonian constraint operator couples the homogeneous and inhomogeneous sectors. The hybrid approach, therefore, is expected to provide a suitable quantum theory in regimes where the main quantum effects of the geometry are those affecting the zero-modes, while the inhomogeneities, still being quantum, can be treated in a more conventional way. This hybrid strategy was first prop...

  15. All Digital Phase-Locked Loop

    Directory of Open Access Journals (Sweden)

    Marijan Jurgo

    2013-05-01

    Full Text Available The paper reviews working principles of phase-locked loop and drawbacks of classical PLL structure in nanometric technologies. It is proposed to replace the classical structure by all-digital phase-locked loop structure. Authors described the main blocks of all-digital phase-locked loop (time to digital converter and digitally controlled oscillator and overviewed the quantization noise arising in these blocks as well as its minimization strategies. The calculated inverter delay in 65 nm CMOS technology was from 8.64 to 27.71 ps and time to digital converter quantization noise was from −104.33 to −82.17 dBc/Hz, with tres = 8.64–27.71 ps, TSVG = 143–333 ps, FREF = 20–60 MHz.Article in Lithuanian

  16. Coronal Loops: Evolving Beyond the Isothermal Approximation

    Science.gov (United States)

    Schmelz, J. T.; Cirtain, J. W.; Allen, J. D.

    2002-05-01

    Are coronal loops isothermal? A controversy over this question has arisen recently because different investigators using different techniques have obtained very different answers. Analysis of SOHO-EIT and TRACE data using narrowband filter ratios to obtain temperature maps has produced several key publications that suggest that coronal loops may be isothermal. We have constructed a multi-thermal distribution for several pixels along a relatively isolated coronal loop on the southwest limb of the solar disk using spectral line data from SOHO-CDS taken on 1998 Apr 20. These distributions are clearly inconsistent with isothermal plasma along either the line of sight or the length of the loop, and suggested rather that the temperature increases from the footpoints to the loop top. We speculated originally that these differences could be attributed to pixel size -- CDS pixels are larger, and more `contaminating' material would be expected along the line of sight. To test this idea, we used CDS iron line ratios from our data set to mimic the isothermal results from the narrowband filter instruments. These ratios indicated that the temperature gradient along the loop was flat, despite the fact that a more complete analysis of the same data showed this result to be false! The CDS pixel size was not the cause of the discrepancy; rather, the problem lies with the isothermal approximation used in EIT and TRACE analysis. These results should serve as a strong warning to anyone using this simplistic method to obtain temperature. This warning is echoed on the EIT web page: ``Danger! Enter at your own risk!'' In other words, values for temperature may be found, but they may have nothing to do with physical reality. Solar physics research at the University of Memphis is supported by NASA grant NAG5-9783. This research was funded in part by the NASA/TRACE MODA grant for Montana State University.

  17. Coronal Loops: Observations and Modeling of Confined Plasma

    Directory of Open Access Journals (Sweden)

    Fabio Reale

    2014-07-01

    Full Text Available Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the review is divided into two separate but not independent parts: the first illustrates the observational framework, the second reviews the theoretical knowledge. Quiescent loops and their confined plasma are considered and, therefore, topics such as loop oscillations and flaring loops (except for non-solar ones, which provide information on stellar loops are not specifically addressed here. The observational section discusses the classification, populations, and the morphology of coronal loops, its relationship with the magnetic field, and the loop stranded structure. The section continues with the thermal properties and diagnostics of the loop plasma, according to the classification into hot, warm, and cool loops. Then, temporal analyses of loops and the observations of plasma dynamics, hot and cool flows, and waves are illustrated. In the modeling section, some basics of loop physics are provided, supplying fundamental scaling laws and timescales, a useful tool for consultation. The concept of loop modeling is introduced and models are divided into those treating loops as monolithic and static, and those resolving loops into thin and dynamic strands. More specific discussions address modeling the loop fine structure and the plasma flowing along the loops. Special attention is devoted to the question of loop heating, with separate discussion of wave (AC and impulsive (DC heating. Large-scale models including atmosphere boxes and the magnetic field are also discussed. Finally, a brief discussion about stellar coronal loops is followed by highlights and open questions.

  18. Rational Design of Nanobody80 Loop Peptidomimetics

    DEFF Research Database (Denmark)

    Martin, Charlotte; Moors, Samuel L C; Danielsen, Mia

    2017-01-01

    G protein-coupled receptors (GPCRs) play an important role in many cellular responses; as such, their mechanism of action is of utmost interest. To gain insight into the active conformation of GPCRs, the X-ray crystal structures of nanobody (Nb)-stabilized β2 -adrenergic receptor (β2 AR) have been...... that peptidomimetics of the CDR3 loop might be sufficient for binding to the receptor, inhibiting the interaction of β2 AR with intracellular GPCR interacting proteins (e.g., G proteins). Based on previous crystallographic data, a set of peptidomimetics were synthesized that, similar to the Nb80 CDR3 loop, adopt a β...

  19. On closed loop transient response system identification

    Directory of Open Access Journals (Sweden)

    Christer Dalen

    2016-10-01

    Full Text Available Some methods for transient closed loop step response system identification presented in the literature are reviewed. Interestingly some errors in a method published in the early 80's where propagated into a recently published method. These methods are reviewed and some improved methods are suggested and presented. The methods are compared against each other on some closed loop system examples, e.g. a well pipeline-riser severe-slugging flow regime example, using Monte Carlo simulations for comparison of the methods.

  20. Thermal coupling within LTP dynamics control loop

    Energy Technology Data Exchange (ETDEWEB)

    Nofrarias, M; Garcia Marin, A F; Heinzel, G; Hewitson, M; Danzmann, K [Max-Planck-Institut fuer Gravitationsphysik, Albert Einstein Institut (AEI), Callinstrasse 38, 30167 Hannover (Germany); Lobo, A; Sanjuan, J [Institut de Ciencies de l' Espai (ICE-CSIC), Facultat de Ciencies, Torre C5, 08193 Bellaterra (Spain); Ramos-Castro, J, E-mail: miquel.nofrarias@aei.mpg.d [Departament d' Enginyeria Electronica, UPC, Campus Nord, Edifici C4, Jordi Girona 1-3, 08034 Barcelona (Spain)

    2009-03-01

    The Diagnostic Subsytem in the LISA Technology Package (LTP) on board the LISA Pathfinder mission (LPF) will characterise those external disturbances with a potential impact on the performance of the experiment coming from either thermal, magnetic or charged particles perturbations. A correct design of the experiments to measure these effects in flight requires a closed loop analysis that takes into account the dynamics of the test masses, the force applied by the controllers and those noisy terms (coming from sensing or force noise) that enters into the loop. We describe this analysis in the thermal case and we give a first numerical example of the instrument response to controlled thermal inputs.

  1. Automation of one-loop QCD corrections

    CERN Document Server

    Hirschi, Valentin; Frixione, Stefano; Garzelli, Maria Vittoria; Maltoni, Fabio; Pittau, Roberto

    2011-01-01

    We present the complete automation of the computation of one-loop QCD corrections, including UV renormalization, to an arbitrary scattering process in the Standard Model. This is achieved by embedding the OPP integrand reduction technique, as implemented in CutTools, into the MadGraph framework. By interfacing the tool so constructed, which we dub MadLoop, with MadFKS, the fully automatic computation of any infrared-safe observable at the next-to-leading order in QCD is attained. We demonstrate the flexibility and the reach of our method by calculating the production rates for a variety of processes at the 7 TeV LHC.

  2. Magic spinor product methods in loop integrals

    CERN Document Server

    Ward, B F L

    2011-01-01

    We present an approach to higher point loop integrals using Chinese magic in the virtual loop integration variable. We show, using the five point function in the important e^+e^-\\to f\\bar{f}+\\gamma process for ISR as a pedagogical vehicle, that we get an expression for it directly reduced to one scalar 5-point function and 4-, 3-, and 2- point integrals, thereby avoiding the computation of the usual three tensor 5-pt Passarino-Veltman reduction. We argue that this offers potential for greater numerical stability.

  3. Magic spinor product methods in loop integrals

    Science.gov (United States)

    Ward, B. F. L.

    2011-06-01

    We present an approach to higher point loop integrals using Chinese magic in the virtual loop integration variable. We show, using the five point function in the important e+e-→ff¯+γ process for initial state radiation as a pedagogical vehicle, that we get an expression for it directly reduced to one scalar 5-point function and 4-, 3-, and 2- point integrals, thereby avoiding the computation of the usual three tensor 5-pt Passarino-Veltman reduction. We argue that this offers potential for greater numerical stability.

  4. Tuning OpenACC loop execution

    KAUST Repository

    Feki, Saber

    2017-01-07

    The purpose of this chapter is to help OpenACC developer who is already familiar with the basic and essential directives to further improve his code performance by adding more descriptive clauses to OpenACC loop constructs. At the end of this chapter the reader will: • Have a better understanding of the purpose of the OpenACC loop construct and its associated clauses illustrated with use cases • Use the acquired knowledge in practice to further improve the performance of OpenACC accelerated codes

  5. Minimally doubled fermions at one loop

    Science.gov (United States)

    Capitani, Stefano; Weber, Johannes; Wittig, Hartmut

    2009-10-01

    Minimally doubled fermions have been proposed as a cost-effective realization of chiral symmetry at non-zero lattice spacing. Using lattice perturbation theory at one loop, we study their renormalization properties. Specifically, we investigate the consequences of the breaking of hyper-cubic symmetry, which is a typical feature of this class of fermionic discretizations. Our results for the quark self-energy indicate that the four-momentum undergoes a renormalization which is linearly divergent. We also compute renormalization factors for quark bilinears, construct the conserved vector and axial-vector currents and verify that at one loop the renormalization factors of the latter are equal to one.

  6. High-Order Frequency-Locked Loops

    DEFF Research Database (Denmark)

    Golestan, Saeed; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez

    2017-01-01

    In very recent years, some attempts for designing high-order frequency-locked loops (FLLs) have been made. Nevertheless, the advantages and disadvantages of these structures, particularly in comparison with a standard FLL and high-order phase-locked loops (PLLs), are rather unclear. This lack...... study, and its small-signal modeling, stability analysis, and parameter tuning are presented. Finally, to gain insight about advantages and disadvantages of high-order FLLs, a theoretical and experimental performance comparison between the designed second-order FLL and a standard FLL (first-order FLL...

  7. Geometric structures on loop and path spaces

    Indian Academy of Sciences (India)

    in M. This is naturally a Fréchet manifold. The tangent space to L(M) at a loop γ is. Tγ L(M) ∼= (S1,γ∗TM). The loop space L(M) is equipped with a natural section of its tangent bundle defined as ξ: L(M) → T L(M) γ ↦→ γ . Whenever we fix a Riemannian metric g on M, we can define an associated weak metric on the space of ...

  8. A keyboard control method for loop measurement

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Z.W. [Universita Degli Studi di Roma La Sapienza (Italy)

    1994-12-31

    This paper describes a keyboard control mode based on the DEC VAX computer. The VAX Keyboard code can be found under running of a program was developed. During the loop measurement or multitask operation, it ables to be distinguished from a keyboard code to stop current operation or transfer to another operation while previous information can be held. The combining of this mode, the author successfully used one key control loop measurement for test Dual Input Memory module which is used in a rearrange Energy Trigger system for LEP 8 Bunch operation.

  9. [Effect of water activity on the growth of the xerophilic mold Eurotium herbariorum].

    Science.gov (United States)

    Vaamonde, G; Fernández Pinto, V E

    1993-01-01

    The influence of water activity (aw) on growth of a xerophilic mold isolated from dried figs and identified as Eurotium herbariorum was studied on culture media of aw adjusted with sucrose or glycerol. Rate of radial growth (kr) and lag period were the kinetic parameters analyzed. Fungal growth was inhibited at aw > 0.97. In the presence of sucrose, optimum growth was found in M6OY agar (malt agar with yeast extract and 60% W/V of sucrose, aw = 0.95). On glycerol (aw ranging from 0.65 to 0.90) the fungus did not grow at aw < 0.80. Sucrose supported better growth than glycerol at aw 0.90.

  10. Effect of water activity on the growth of fungi isolated from „muesli“ components

    Directory of Open Access Journals (Sweden)

    Dimić Gordana R.

    2013-01-01

    Full Text Available The effect of water activity (aw (0.85-0.97 on the growth of Aspergillus niger, A. flavus, Penicillium chrysogenum, P. brevicompactum and Eurotium herbariorum was examined. The growth of A. niger was lower than that of A. flavus at aw of 0.89 and 0.85. A. niger was the least tolerant of reduced moisture, and low aw (0.85 could prevent colony formation in 5 days. P. brevicompactum was less sensitive to reduced moisture conditions than P. chrysogenum. The maximal growth of E. herbariorum was observed at the level of 0.89 aw. Among the tested fungi, E. herbariorum appeared to be best adapted to the conditions of low aw. [Projekat Ministarstva nauke Republike Srbije, br. TR - 31017

  11. Effect of water activity and heating rate on Staphylococcus aureus heat resistance in walnut shells.

    Science.gov (United States)

    Zhang, Lihui; Kou, Xiaoxi; Zhang, Shuang; Cheng, Teng; Wang, Shaojin

    2018-02-02

    Water activity (a w ) and heating rate have shown important effects on the thermo-tolerance of pathogens in low moisture foods during thermal treatments. In this study, three strains were selected to compare the heat resistance in walnut shell powder and finally the most heat resistant S. aureus ATCC 25923 was chosen to investigate the influence of a w and heating rate using a heating block system (HBS). The results showed that S. aureus ATCC 25923 became more thermo-tolerant at lower a w . The D-values of S. aureus ATCC 25923 increased with decreasing water activity and heating rates (<1°C/min). A significant increase in heat resistance of S. aureus ATCC 25923 in walnut shell powder was observed only for the heating rates of 0.2 and 0.5°C/min but not at 1, 5 and 10°C/min. There was a rapid reduction of S. aureus ATCC 25923 at elevated temperatures from 26 to 56°C at a heating rate of 0.1°C/min. The inactivation under non-isothermal conditions was better fitted by Weibull distribution (R 2 =0.97 to 0.99) than first-order kinetics (R 2 =0.88 to 0.98). These results suggest that an appropriate increase in moisture content of in-shell walnuts and heating rate during thermal process can improve the inactivation efficiency of pathogens in low moisture foods. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Influence of water activity and anti-fungal compounds on development and competitiveness of Fusarium verticillioides

    Directory of Open Access Journals (Sweden)

    Paola GIORNI

    2015-01-01

    Full Text Available This investigated the roles of water activity (aw and fungicides on the competitiveness of two Fusarium verticillioides strains against other spoilage fungi commonly present in maize (F. proliferatum, Aspergillus niger, A. flavus, A. ochraceus and Penicillium verrucosum. Fungal strains were inoculated on artificial media containing maize flour. The effects were determined of three aw levels (0.99, 0.98 and 0.95 and three fungicides (tebuconazole, procloraz and prothioconazole on fungal interactions, the Index of Dominance (ID of isolates and fumonisin B1+B2 (FBs production. The two strains of F. verticillioides showed similar behaviour in conditions where water was freely available (0.99 aw; at 0.98 and 0.95 aw both F. verticilliodes strains had the lowest total ID scores (8–6 and 10–12, respectively. They showed the same ability to compete against other fungi having the highest ID scores against P. verrucosum and A. ochraceus and the lowest against A. niger and A. flavus. The lowest water activity gave (0.95 aw was the most conducive for fumonisin production with significant differences to 0.98 and 0.99 aw. In a co-inoculation experiment, only FBs production from P. verrucosum was greater in the presence of the F. verticilliodes strains other fungi. The use of fungicides reduced Indices of Dominancy (ID for both F. verticilliodes strains. A significant reduction in F. verticilloides growth was observed when combining water stress and fungicide treatments. This information provides increased understanding of the colonisation patterns of F. verticillioides in relation to other mycobiota and to both environmental and chemical stresses, and has implications in relation to future climate change scenarios.

  13. Fundamental and Harmonic Oscillations in Neighboring Coronal Loops

    Science.gov (United States)

    Li, Hongbo; Liu, Yu; Vai Tam, Kuan

    2017-06-01

    We present observations of multimode (fundamental and harmonic) oscillations in a loop system, which appear to be simultaneously excited by a GOES C-class flare. Analysis of the periodic oscillations reveals that (1) the primary loop with a period of P a ≈ 4 minutes and a secondary loop with two periods of P a ≈ 4 minutes and P b ≈ 2 minutes are detected simultaneously in closely spaced loop strands; (2) both oscillation components have their peak amplitudes near the loop apex, while in the second loop the low-frequency component P a dominates in a loop segment that is two times larger than the high-frequency component P b ; (3) the harmonic mode P b shows the largest deviation from a sinusoidal loop shape at the loop apex. We conclude that multiple harmonic modes with different displacement profiles can be excited simultaneously even in closely spaced strands, similar to the overtones of a violin string.

  14. NMR spectroscopic characterization of the sialyltransferase CstII from Campylobacter jejuni: histidine 188 is the general base.

    Science.gov (United States)

    Chan, Patrick H W; Lairson, Luke L; Lee, Ho Jun; Wakarchuk, Warren W; Strynadka, Natalie C J; Withers, Stephen G; McIntosh, Lawrence P

    2009-12-01

    Cell surface glycans are often terminated by sialic acid, which is incorporated onto sugar acceptors by sialyltransferases. The crystal structure of the GT family 42 Campylobacter jejuni alpha-2,3/2,8-sialyltransferase (CstII) provides key insights into the sialyl-transfer mechanism, including tentative identification of His188 as the catalytic base. In support of this hypothesis, the CstII-H188A mutant is able to catalyze sialyl transfer from CMP-Neu5Ac to added anions such as azide and formate but not to its natural sugar acceptor lactose. Complementing this work, NMR spectroscopy was used to investigate the structure and dynamics of CstII and to measure the intrinsic pK(a) value of His188 for comparison with the pK(a) determined from the pH-dependent k(cat)/K(M) of the enzyme. By systematically introducing point mutations at the subunit interfaces, two active monomeric variants, CstII-F121D and CstII-Y125Q, were obtained and characterized. In contrast to the wild-type tetramer, the monomeric CstII variants yielded good quality (1)H/(15)N-HSQC and (1)H/(13)C-methyl-TROSY NMR spectra. However, the absence of signals from approximately one-half of the amides in the (1)H/(15)N-HSQC spectra of both monomeric forms suggests that the enzyme undergoes substantial conformational exchange on a millisecond to microsecond time scale. The histidine pK(a) values of CstII-F121D in its apo form were measured by monitoring the pH-dependent chemical shifts of [(13)C(epsilon1)]histidine, biosynthetically incorporated into the otherwise uniformly deuterated protein. Consistent with its proposed catalytic role, the site-specific pK(a) value approximately 6.6 of His188 matches the apparent pK(a) value approximately 6.5 governing the pH dependence of k(cat)/K(M) for CstII toward CMP-Neu5Ac in the presence of saturating acceptor substrate.

  15. Resonance Raman investigation of the effects of copper binding to iron-mesoporphyrin.histidine-rich glycoprotein complexes.

    Science.gov (United States)

    Larsen, R W; Nunez, D J; Morgan, W T; Muhoberac, B B; Ondrias, M R

    1992-04-01

    Histidine-rich glycoprotein (HRG) binds both hemes and metal ions simultaneously with evidence for interaction between the two. This study uses resonance Raman and optical absorption spectroscopies to examine the heme environment of the 1:1 iron-mesoporphyrin.HRG complex in its oxidized, reduced and CO-bound forms in the absence and presence of copper. Significant perturbation of Fe(3+)-mesoporphyrin.HRG is induced by Cu2+ binding to the protein. Specifically, high frequency heme resonance Raman bands indicative of low-spin, six-coordinate iron before Cu2+ binding exhibit monotonic intensity shifts to bands representing high-spin, five-coordinate iron. The latter coordination is in contrast to that found in hemoglobin and myoglobin, and explains the Cu(2+)-induced decrease and broadening of the Fe(3+)-mesoporphyrin.HRG Soret band concomitant with the increase in the high-spin marker band at 620 nm. After dithionite reduction, the Fe(2+)-mesoporphyrin.HRG complex displays high frequency resonance Raman bands characteristic of low-spin heme and no iron-histidine stretch, which together suggest six-coordinate iron. Furthermore, the local heme environment of the complex is not altered by the binding of Cu1+. CO-bound Fe(2+)-mesoporphyrin.HRG exhibits bands in the high and low frequency regions similar to those of other CO-bound heme proteins except that the iron-CO stretch at 505 cm-1 is unusually broad with delta nu approximately 30 cm-1. The dynamics of CO photolysis and rebinding to Fe(2+)-mesoporphyrin.HRG are also distinctive. The net quantum yield for photolysis at 10 ns is low relative to most heme proteins, which may be attributed to very rapid geminate recombination. A similar low net quantum yield and broad iron-CO stretch have so far only been observed in a dimeric cytochrome c' from Chromatium vinosum. Furthermore, the photolytic transient of Fe(2+)-mesoporphyrin.HRG lacks bands corresponding to high-spin, five-coordinate iron as is found in hemoglobin and

  16. Evaluation and Comparison of Biomechanical Properties of Snail Loop with that of Opus Loop and Teardrop Loop for en masse Retraction of Anterior Teeth: FEM Study

    Directory of Open Access Journals (Sweden)

    Parikshit Rajkumar Rao

    2013-01-01

    Results: Inherently the M/F ratio produced was higher and F/D rate produced was least for opus loop compared to snail loop and teardrop loop. Conclusion: With incorporation of 20°gable bends snail loop prepared in 0.017 × 0.025 inch and 0.019 × 0.025 inch TMA wire is very efficient to deliver M/F ratio required for translatory tooth movement with acceptable F/D rate. Snail loop is easy to fabricate and finer shape morphology prevents tissue impingement.

  17. Logical inference techniques for loop parallelization

    DEFF Research Database (Denmark)

    Oancea, Cosmin Eugen; Rauchwerger, Lawrence

    2012-01-01

    of their estimated complexities. We evaluate our automated solution on 26 benchmarks from PERFECT-CLUB and SPEC suites and show that our approach is effective in parallelizing large, complex loops and obtains much better full program speedups than the Intel and IBM Fortran compilers....

  18. Loop quantum gravity; Gravedad cuantica de lazos

    Energy Technology Data Exchange (ETDEWEB)

    Pullin, J.

    2015-07-01

    Loop quantum gravity is one of the approaches that are being studied to apply the rules of quantum mechanics to the gravitational field described by the theory of General Relativity . We present an introductory summary of the main ideas and recent results. (Author)

  19. Phase locked loops design, simulation, and applications

    CERN Document Server

    Best, Roland E

    2007-01-01

    The Definitive Introduction to Phase-Locked Loops, Complete with Software for Designing Wireless Circuits! The Sixth Edition of Roland Best's classic Phase-Locked Loops has been updated to equip you with today's definitive introduction to PLL design, complete with powerful PLL design and simulation software written by the author. Filled with all the latest PLL advances, this celebrated sourcebook now includes new chapters on frequency synthesis…CAD for PLLs…mixed-signal PLLs…all-digital PLLs…and software PLLs_plus a new collection of sample communications applications. An essential tool for achieving cutting-edge PLL design, the Sixth Edition of Phase-Locked Loops features: A wealth of easy-to-use methods for designing phase-locked loops Over 200 detailed illustrations New to this edition: new chapters on frequency synthesis, including fractional-N PLL frequency synthesizers using sigma-delta modulators; CAD for PLLs, mixed-signal PLLs, all-digital PLLs, and software PLLs; new PLL communications ap...

  20. Closed Loop System Identification with Genetic Algorithms

    Science.gov (United States)

    Whorton, Mark S.

    2004-01-01

    High performance control design for a flexible space structure is challenging since high fidelity plant models are di.cult to obtain a priori. Uncertainty in the control design models typically require a very robust, low performance control design which must be tuned on-orbit to achieve the required performance. Closed loop system identi.cation is often required to obtain a multivariable open loop plant model based on closed-loop response data. In order to provide an accurate initial plant model to guarantee convergence for standard local optimization methods, this paper presents a global parameter optimization method using genetic algorithms. A minimal representation of the state space dynamics is employed to mitigate the non-uniqueness and over-parameterization of general state space realizations. This control-relevant system identi.cation procedure stresses the joint nature of the system identi.cation and control design problem by seeking to obtain a model that minimizes the di.erence between the predicted and actual closed-loop performance.

  1. Aesthetic rehabilitation with multiple loop connectors

    Directory of Open Access Journals (Sweden)

    Ashish Kalra

    2013-01-01

    Full Text Available Patients with a missing tooth along with diastema have limited treatment options to restore the edentulous space. The use of a conventional fixed partial denture (FPD to replace the missing tooth may result in too wide anterior teeth leading to poor esthetics. The diastema resulting from the missing central incisors can be managed with implant-supported prosthesis or FPD with loop connectors. An old lady reported with chief complaints of missing upper anterior teeth due to trauma. Her past dental history revealed that she was having generalized spacing between her upper anterior teeth. Considering her esthetic requirement of maintaining the diastema between 12, 11, 22, and 21, the treatment option of 06 units porcelain fused to metal FPD from canine to canine with intermittent loop connectors between 21, 22, 11, 12 was planned. Connectors basically link different parts of FPDs. The modified FPD with loop connectors enhanced the natural appearance of the restoration, maintained the diastemas and the proper emergence profile, and preserve the remaining tooth structure of abutment teeth. This clinical report discussed a method for fabrication of a modified FPD with loop connectors to restore the wide span created by missing central incisors.

  2. String loop corrected hypermultiplet moduli spaces

    NARCIS (Netherlands)

    Robles-Llana, D.; Saueressig, Frank; Vandoren, S.

    2006-01-01

    Using constraints from supersymmetry and string perturbation theory, we determine the string loop corrections to the hypermultiplet moduli space of type II strings compactified on a generic Calabi-Yau threefold. The corresponding quaternion-Kähler manifolds are completely encoded in terms of a

  3. Semiclassical analysis of loop quantum gravity

    Energy Technology Data Exchange (ETDEWEB)

    Conrady, F.

    2005-10-17

    In this Ph.D. thesis, we explore and develop new methods that should help in determining an effective semiclassical description of canonical loop quantum gravity and spin foam gravity. A brief introduction to loop quantum gravity is followed by three research papers that present the results of the Ph.D. project. In the first article, we deal with the problem of time and a new proposal for implementing proper time as boundary conditions in a sum over histories: we investigate a concrete realization of this formalism for free scalar field theory. In the second article, we translate semiclassical states of linearized gravity into states of loop quantum gravity. The properties of the latter indicate how semiclassicality manifests itself in the loop framework, and how this may be exploited for doing semiclassical expansions. In the third part, we propose a new formulation of spin foam models that is fully triangulation- and background-independent: by means of a symmetry condition, we identify spin foam models whose triangulation-dependence can be naturally removed. (orig.)

  4. Introduction to Loop Quantum Gravity and Cosmology

    Science.gov (United States)

    Ashtekar, Abhay

    The goal of the lecture is to present a broad perspective on loop quantum gravity and cosmology for young researchers which would serve as an introduction to lectures by Rovelli and Bojowald. The first part is addressed to beginning students and the second to young researchers who are already working in quantum gravity.

  5. Closing the loop: towards strategic defence management

    NARCIS (Netherlands)

    de Spiegeleire, S.; van Hooft, P.; Culpepper, C.; Willems, R.

    2009-01-01

    How do defence-organisations (or organisations with comparable profiles) of other countries map out policy goals and how are policy goals related to activities and capabilities and the required financial means, and finally how does the feedback loop on the performance in all these areas take place?

  6. Closed-loop control of magnetotactic bacteria

    NARCIS (Netherlands)

    Khalil, I.S.M.; Pichel, Marc Philippe; Pichel, M.P.; Abelmann, Leon; Misra, Sarthak

    Realization of point-to-point positioning of a magnetotactic bacterium (MTB) necessitates the application of a relatively large magnetic field gradients to decrease its velocity in the vicinity of a reference position. We investigate an alternative closed-loop control approach to position the MTB.

  7. Geometry of the analytic loop group

    NARCIS (Netherlands)

    De Concini, C.; Hernandez, D.; Reshetikhin, N.

    2013-01-01

    We introduce and study a notion of analytic loop group with a Riemann-Hilbert factorization relevant for the representation theory of quantum affine algebras at roots of unity View the MathML source with non-trivial central charge. We introduce a Poisson structure and study properties of its Poisson

  8. Selective purge for hydrogenation reactor recycle loop

    Science.gov (United States)

    Baker, Richard W.; Lokhandwala, Kaaeid A.

    2001-01-01

    Processes and apparatus for providing improved contaminant removal and hydrogen recovery in hydrogenation reactors, particularly in refineries and petrochemical plants. The improved contaminant removal is achieved by selective purging, by passing gases in the hydrogenation reactor recycle loop or purge stream across membranes selective in favor of the contaminant over hydrogen.

  9. Thermal instabilities in magnetically confined plasmas - Solar coronal loops

    Science.gov (United States)

    Habbal, S. R.; Rosner, R.

    1979-01-01

    The thermal stability of confined solar coronal structures ('loops') is investigated, following both normal mode and a new, global instability analysis. It is demonstrated that: (1) normal mode analysis shows modes with size scales comparable to that of loops to be unstable, but to be strongly affected by the loop boundary conditions; (2) a global analysis, based upon variation of the total loop energy losses and gains, yields loop stability conditions for global modes dependent upon the coronal loop heating process, with magnetically coupled heating processes giving marginal stability. The connection between the present analysis and the minimum flux corona of Hearn is also discussed.

  10. Loop Evolution Observed with AIA and Hi-C

    Science.gov (United States)

    Mulu-Moore, Fana; Winebarger, Amy R.; Cirtain, Jonathan W.; Kobayashi, Ken; Korreck, Kelly E.; Golub, Leon; Kuzin, Sergei; Walsh, Robert William; DeForest, Craig E.; De Pontieu, Bart; hide

    2012-01-01

    In the past decade, the evolution of EUV loops has been used to infer the loop substructure. With the recent launch of High Resolution Coronal Imager (Hi-C), this inference can be validated. In this presentation we discuss the first results of loop analysis comparing AIA and Hi-C data. In the past decade, the evolution of EUV loops has been used to infer the loop substructure. With the recent launch of High Resolution Coronal Imager (Hi-C), this inference can be validated. In this presentation we discuss the first results of loop analysis comparing AIA and Hi-C data.

  11. The importance of the non-active site and non-periodical structure located histidine residue respect to the structure and function of exo-inulinase.

    Science.gov (United States)

    Arjomand, Maryam Rezaei; Ahmadian, Gholamreza; Habibi-Rezaei, Mehran; Hassanzadeh, Malihe; Karkhane, Ali Asghar; Moosavi-Movahedi, Ali Akbar; Amanlou, Massoud

    2017-05-01

    Here, we have studied the role of a histidine residue with the lowest solvent accessibility among other histidine residues at the end of a short connecting structure ( 189 AELH 192 ) of the catalytic domain of the exo-inulinase through creation of H192A mutant. Site-directed mutagenesis method was applied to create the mutant enzyme. Molecular dynamics (MD) simulations, spectroscopic, calorimetric and kinetics analysis were used to study the structural and functional consequences of His192 substitution. Accordingly, the thermo-stabilities and catalytic performance were decreased upon H192A mutation. In silico and experimental approaches evidently confirm that His192 residue of exo-inulinase possesses structural and functional importance regardless of the lack of direct interaction with the substrate or involvement in the catalytic activity of exo-inulinase. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Comparative survival analysis of 12 histidine kinase mutants of Deinococcus radiodurans after exposure to DNA-damaging agents.

    Science.gov (United States)

    Im, Seonghun; Song, Dusup; Joe, Minho; Kim, Dongho; Park, Don-Hee; Lim, Sangyong

    2013-06-01

    Bacteria are able to adapt to changes in the environment using two-component signal transduction systems (TCSs) composed of a histidine kinase (HK) and a response regulator (RR). Deinococcus radiodurans, one of the most resistant organisms to ionizing radiation, has 20 putative HKs and 25 putative RRs. In this study, we constructed 12 D. radiodurans mutant strains lacking a gene encoding a HK and surveyed their resistance to γ-radiation, UV-B radiation (302 nm), mitomycin C (MMC), and H(2)O(2). Five (dr0860 (-), dr1174 (-), dr1556 (-), dr2244 (-), and dr2419 (-)) of the 12 mutant strains showed at least a one-log cycle reduction in γ-radiation resistance. The mutations (1) dr1174, dr1227, and dr2244 and (2) dr0860, dr2416, and dr2419 caused decreases in resistance to UV radiation and MMC, respectively. Only the dr2416 and dr2419 mutant strains showed higher sensitivity to H(2)O(2) than the wild-type. Reductions in the resistance to γ-radiation and H(2)O(2), but not to UV and MMC, were observed in the absence of DR2415, which seems to be a cognate RR of DR2416. This result suggests that DR2415/DR2416 (DrtR/S: DNA damage response TCS) may be another TCS responsible for the extreme resistance of D. radiodurans to DNA-damaging agents.

  13. A two-component histidine kinase Shk1 controls stress response, sclerotial formation and fungicide resistance in Sclerotinia sclerotiorum.

    Science.gov (United States)

    Duan, Yabing; Ge, Changyan; Liu, Shengming; Wang, Jianxin; Zhou, Mingguo

    2013-09-01

    Fungal histidine kinases (HKs) are involved in osmotic and oxidative stress responses, hyphal development, fungicide sensitivity and virulence. Members of HK class III are known to signal through the high-osmolarity glycerol mitogen-activated protein kinase (HOG MAPK). In this study, we characterized the Shk1 gene (SS1G_12694.3), which encodes a putative class III HK, from the plant pathogen Sclerotinia sclerotiorum. Disruption of Shk1 resulted in resistance to phenylpyrrole and dicarboximide fungicides and increased sensitivity to hyperosmotic stress and H2 O2 -induced oxidative stress. The Shk1 mutant showed a significant reduction in vegetative hyphal growth and was unable to produce sclerotia. Quantitative real-time polymerase chain reaction (qRT-PCR and glycerol determination assays showed that the expression of SsHOG1 (the last kinase of the Hog pathway) and glycerol accumulation were regulated by the Shk1 gene, but PAK (p21-activated kinase) was not. In addition, the Shk1 mutant showed no change in virulence. All the defects were restored by genetic complementation of the Shk1 deletion mutant with the wild-type Shk1 gene. These findings indicate that Shk1 is involved in vegetative differentiation, sclerotial formation, glycerol accumulation and adaption to hyperosmotic and oxidative stresses, and to fungicides, in S. sclerotiorum. Taken together, our results demonstrate, for the first time, the role of two-component HKs in Sclerotinia. © 2013 BSPP AND JOHN WILEY & SONS LTD.

  14. Phosphorylation of Spo0A by the Histidine Kinase KinD Requires the Lipoprotein Med in Bacillus subtilis ▿

    Science.gov (United States)

    Banse, Allison V.; Hobbs, Errett C.; Losick, Richard

    2011-01-01

    The response regulatory protein Spo0A of Bacillus subtilis is activated by phosphorylation by multiple histidine kinases via a multicomponent phosphorelay. Here we present evidence that the activity of one of the kinases, KinD, depends on the lipoprotein Med, a mutant of which has been known to cause a cannibalism phenotype. We show that the absence of Med impaired and the overproduction of Med stimulated the transcription of two operons (sdp and skf) involved in cannibalism whose transcription is known to depend on Spo0A in its phosphorylated state (Spo0A∼P). Further, these effects of Med were dependent on KinD but not on kinases KinA, KinB, and KinC. Additionally, we show that deletion or overproduction of Med impaired or enhanced, respectively, biofilm formation and that these effects, too, depended specifically on KinD. Finally, we report that overproduction of Med bypassed the dominant negative effect on transcription of sdp of a truncated KinD retaining the transmembrane segments but lacking the kinase domain. We propose that Med directly or indirectly interacts with KinD in the cytoplasmic membrane and that this interaction is required for KinD-dependent phosphorylation of Spo0A. PMID:21622736

  15. Phosphorylation of Spo0A by the histidine kinase KinD requires the lipoprotein med in Bacillus subtilis.

    Science.gov (United States)

    Banse, Allison V; Hobbs, Errett C; Losick, Richard

    2011-08-01

    The response regulatory protein Spo0A of Bacillus subtilis is activated by phosphorylation by multiple histidine kinases via a multicomponent phosphorelay. Here we present evidence that the activity of one of the kinases, KinD, depends on the lipoprotein Med, a mutant of which has been known to cause a cannibalism phenotype. We show that the absence of Med impaired and the overproduction of Med stimulated the transcription of two operons (sdp and skf) involved in cannibalism whose transcription is known to depend on Spo0A in its phosphorylated state (Spo0A∼P). Further, these effects of Med were dependent on KinD but not on kinases KinA, KinB, and KinC. Additionally, we show that deletion or overproduction of Med impaired or enhanced, respectively, biofilm formation and that these effects, too, depended specifically on KinD. Finally, we report that overproduction of Med bypassed the dominant negative effect on transcription of sdp of a truncated KinD retaining the transmembrane segments but lacking the kinase domain. We propose that Med directly or indirectly interacts with KinD in the cytoplasmic membrane and that this interaction is required for KinD-dependent phosphorylation of Spo0A.

  16. Functional Regulation of the Plasma Protein Histidine-Rich Glycoprotein by Zn2+ in Settings of Tissue Injury

    Directory of Open Access Journals (Sweden)

    Kristin M. Priebatsch

    2017-03-01

    Full Text Available Divalent metal ions are essential nutrients for all living organisms and are commonly protein-bound where they perform important roles in protein structure and function. This regulatory control from metals is observed in the relatively abundant plasma protein histidine-rich glycoprotein (HRG, which displays preferential binding to the second most abundant transition element in human systems, Zinc (Zn2+. HRG has been proposed to interact with a large number of protein ligands and has been implicated in the regulation of various physiological and pathological processes including the formation of immune complexes, apoptotic/necrotic and pathogen clearance, cell adhesion, antimicrobial activity, angiogenesis, coagulation and fibrinolysis. Interestingly, these processes are often associated with sites of tissue injury or tumour growth, where the concentration and distribution of Zn2+ is known to vary. Changes in Zn2+ levels have been shown to modify HRG function by altering its affinity for certain ligands and/or providing protection against proteolytic disassembly by serine proteases. This review focuses on the molecular interplay between HRG and Zn2+, and how Zn2+ binding modifies HRG-ligand interactions to regulate function in different settings of tissue injury.

  17. LOV Histidine Kinase Modulates the General Stress Response System and Affects the virB Operon Expression in Brucella abortus.

    Directory of Open Access Journals (Sweden)

    Gabriela Sycz

    Full Text Available Brucella is the causative agent of the zoonotic disease brucellosis, and its success as an intracellular pathogen relies on its ability to adapt to the harsh environmental conditions that it encounters inside the host. The Brucella genome encodes a sensor histidine kinase containing a LOV domain upstream from the kinase, LOVHK, which plays an important role in light-regulated Brucella virulence. In this report we study the intracellular signaling pathway initiated by the light sensor LOVHK using an integrated biochemical and genetic approach. From results of bacterial two-hybrid assays and phosphotransfer experiments we demonstrate that LOVHK functionally interacts with two response regulators: PhyR and LovR, constituting a functional two-component signal-transduction system. LOVHK contributes to the activation of the General Stress Response (GSR system in Brucella via PhyR, while LovR is proposed to be a phosphate-sink for LOVHK, decreasing its phosphorylation state. We also show that in the absence of LOVHK the expression of the virB operon is down-regulated. In conclusion, our results suggest that LOVHK positively regulates the GSR system in vivo, and has an effect on the expression of the virB operon. The proposed regulatory network suggests a similar role for LOVHK in other microorganisms.

  18. Bromobenzene 3,4-oxide alkylates histidine and lysine side chains of rat liver proteins in vivo.

    Science.gov (United States)

    Bambal, R B; Hanzlik, R P

    1995-01-01

    The hepatotoxic effects of bromobenzene (BB) are correlated with and generally ascribed to the covalent modification of cellular proteins by chemically reactive metabolites, particularly BB-3,4-oxide. Previous studies revealed that quinone as well as epoxide metabolites of BB form adducts to protein sulfur nucleophiles, that the quinone-derived adducts are more abundant by a factor of ca. 7, and that collectively these sulfur adducts account for only about 10% of the total protein covalent binding [Slaughter, D. E., and Hanzlik, R. P. (1991) Chem. Res. Toxicol. 4, 349-359]. To examine the possibility that metabolically-formed BB-3,4-oxide alkylates nitrogen nucleophiles on proteins under toxicologically relevant conditions in vivo, we synthesized standards of N tau-(p-bromophenyl)histidine (7) and N epsilon-(p-bromophenyl)lysine (8) as anticipated adduct structures and used them to guide a chromatographic search for their presence in hydrolysates of liver protein from BB-treated rats. While radio-LC chromatography and GC/MS provide unequivocal evidence for their presence, the amounts of 7 and 8 observed are very low ( covalent binding). The apparently small net contribution of epoxide metabolites to covalent binding of BB in vivo suggests the majority of binding may arise via quinone metabolites, but this should not be construed to imply that quinone adducts are necessarily more important toxicologically than epoxide adducts; in this context the identity of the protein targets is probably at least as important as the type of electrophilic metabolite involved.

  19. Effect of Ni2+ Doping on the Growth and Properties of Mn-L-Histidine Hydrochloride Monohydrate Crystals

    Directory of Open Access Journals (Sweden)

    J. Sai Chandra

    2013-01-01

    Full Text Available The main focus of this work had been to grow good quality crystals from amino acids and amino acid-based materials for nonlinear optics (NLO applications. For the first time, a series of amino acid complexes doped with transition metal ions were grown in our laboratory from aqueous solutions by slow evaporation technique. Ni(II ion doped Manganese L-Histidine hydrochloride monohydrate (Ni(II-MnLHICl crystals were grown on the same lines and were characterized by powder X-ray diffraction (XRD, optical absorption, electron paramagnetic resonance, and infrared absorption studies. From Powder XRD, the unit cell lattice parameters were calculated as a=1.5301 nm, b=0.8928 nm and c=0.6851 nm. From electron paramagnetic resonance (EPR spectra, isotropic “g” factor and spin hamiltonian parameter A all were calculated as 2.0439 and 20×10−4, respectively. From optical absorption studies, crystal field splitting value (Dq and the interelectron repulsion parameters B and C were calculated for Ni2+ and Mn2+ as Dq=850 cm−1, B=725 cm−1, C=2640 cm−1 and Dq=915 cm−1, B=810 cm−1, C=2780 cm−1, respectively. The presence of various functional groups and the modes of vibrations were confirmed by FTIR studies.

  20. Multiple genetic origins of histidine-rich protein 2 gene deletion in Plasmodium falciparum parasites from Peru

    Science.gov (United States)

    Akinyi, Sheila; Hayden, Tonya; Gamboa, Dionicia; Torres, Katherine; Bendezu, Jorge; Abdallah, Joseph F.; Griffing, Sean M.; Quezada, Wilmer Marquiño; Arrospide, Nancy; De Oliveira, Alexandre Macedo; Lucas, Carmen; Magill, Alan J.; Bacon, David J.; Barnwell, John W.; Udhayakumar, Venkatachalam

    2013-01-01

    The majority of malaria rapid diagnostic tests (RDTs) detect Plasmodium falciparum histidine-rich protein 2 (PfHRP2), encoded by the pfhrp2 gene. Recently, P. falciparum isolates from Peru were found to lack pfhrp2 leading to false-negative RDT results. We hypothesized that pfhrp2-deleted parasites in Peru derived from a single genetic event. We evaluated the parasite population structure and pfhrp2 haplotype of samples collected between 1998 and 2005 using seven neutral and seven chromosome 8 microsatellite markers, respectively. Five distinct pfhrp2 haplotypes, corresponding to five neutral microsatellite-based clonal lineages, were detected in 1998-2001; pfhrp2 deletions occurred within four haplotypes. In 2003-2005, outcrossing among the parasite lineages resulted in eight population clusters that inherited the five pfhrp2 haplotypes seen previously and a new haplotype; pfhrp2 deletions occurred within four of these haplotypes. These findings indicate that the genetic origin of pfhrp2 deletion in Peru was not a single event, but likely occurred multiple times. PMID:24077522

  1. [Interaction between folate deficiency and aberrant expression related to fragile histidine triad gene in the progression of cervical cancerization].

    Science.gov (United States)

    Chen, Xiao; Wang, Jintao; Bai, Lixia; Ding, Ling; Wu, Tingting; Bai, Lan; Xu, Juan; Sun, Xuesong

    2015-04-01

    To explore the interaction between folate deficiency and aberrant expression related to fragile histidine triad (FHIT) gene in the progression of cervical cancerization. A total number of 80 patients with histological diagnosis of cervix inflammation (CI), 55 cervical intraepithelial neoplasm I (CIN I), 55 cervical intraepithelial neoplasm II/III (CIN II/III) and 64 cervical squamous cell carcinoma (SCC) were included in this study. Levels of serum folate were detected by microbiological assay method and the methylation status of FHIT gene CpG islands was tested by methylation-specific PCR (MSP). FHIT protein levels were measured by Western blot. In vitro, cervical cancer cell lines CaSki (HPV16-positive) was treated with different concentrations of folate. Proliferation and apoptosis of cells, methylation of FHIT gene and the levels of FHIT protein expression were measured in each group. All analyses were performed with SPSS (version 17.0) statistical software. Differences among groups were assessed by chi-square test, Kruskal-Wallis test. Spearman correlation, and the interaction effects were evaluated by additive model. The levels of serum folate (H = 59.08, P cancer and cervix precancerous lesions, and thus play a synergistic action in the progression of cervical cancerization.

  2. Novel sigmaB regulation modules of Gram-positive bacteria involve the use of complex hybrid histidine kinases.

    Science.gov (United States)

    de Been, Mark; Francke, Christof; Siezen, Roland J; Abee, Tjakko

    2011-01-01

    A common bacterial strategy to cope with stressful conditions is the activation of alternative sigma factors that control specific regulons enabling targeted responses. In the human pathogen Bacillus cereus, activation of the major stress-responsive sigma factor σ(B) is controlled by a signalling route that involves the multi-sensor hybrid histidine kinase RsbK. RsbK-type kinases are not restricted to the B. cereus group, but occur in a wide variety of other bacterial species, including members of the the low-GC Gram-positive genera Geobacillus and Paenibacillus as well as the high-GC actinobacteria. Genome context and protein sequence analyses of 118 RsbK homologues revealed extreme variability in N-terminal sensory as well as C-terminal regulatory domains and suggested that RsbK-type kinases are subject to complex fine-tuning systems, including sensitization and desensitization via methylation and demethylation within the helical domain preceding the H-box. The RsbK-mediated stress-responsive sigma factor activation mechanism that has evolved in B. cereus and the other species differs markedly from the extensively studied and highly conserved RsbRST-mediated σ(B) activation route found in Bacillus subtilis and other low-GC Gram-positive bacteria. Implications for future research on sigma factor control mechanisms are presented and current knowledge gaps are briefly discussed.

  3. Synthesis and biology of ring-modified l-Histidine containing thyrotropin-releasing hormone (TRH) analogues.

    Science.gov (United States)

    Meena, Chhuttan L; Thakur, Avinash; Nandekar, Prajwal P; Sharma, Shyam S; Sangamwar, Abhay T; Jain, Rahul

    2016-03-23

    Thyrotropin-releasing hormone (TRH) analogues bearing halogen groups (Cl, Br and I) at the C-2 and/or C-5 position, and the alkyl group (CH3, C2H5, C3H7, CH2C6H5) at the N-1 position of the imidazole ring of the central histidine residue were synthesized and evaluated for the receptor binding, calcium mobilization (FLIPR), and IP-1 assay at the HEK mTRHR1 and HEK mTRHR2 expressing cell lines. The most promising analogue 7k showed 925-fold selectivity for HEK mTRH-R2 receptor subtype in the IP-1 assay, 272-fold selectivity for HEK mTRH-R2 receptor subtype in the FLIPR assay, and 21-fold receptor binding specificity at HEK TRH-R2 receptor subtype. The peptide 7k was evaluated in vitro in a brain membrane competitive binding assay, and for stability analysis in the presence of TRH-DE, in vivo. The analogue 7k showed decrease in the sleeping time by more than 76% in a pentobarbital-induced sleeping assay, and showed comparatively less elevation in the TSH level in the blood, in vivo. The computational homology modeling of TRH-R1 and TRH-R2 and docking study with the most potent peptide 7k provide impetus to design CNS specific TRH analogues. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  4. Screening for Methylated Poly(⌊-histidine with Various Dimethylimidazolium/Methylimidazole/Imidazole Contents as DNA Carrier

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    Shoichiro Asayama

    2015-08-01

    Full Text Available Methylated poly(l-histidine (PLH-Me, our original polypeptide, has controlled the contents of dimethylimidazolium, τ/π-methylimidazole and imidazole groups for efficient gene delivery. The screening for the PLH-Me as DNA carrier has been carried out by use of the PLH with 25 mol% (τ-methyl, 16 mol%; π-methyl, 17 mol%; deprotonated imidazole, 41 mol%, 68 mol% (τ-methyl, 16 mol%; π-methyl, 8 mol%; deprotonated imidazole, 8 mol% and 87 mol% (τ-methyl, 7 mol%; π-methyl, 4 mol%; deprotonated imidazole, 2 mol% dimethylimidazolium groups, that is, PLH-Me(25, PLH-Me(68 and PLH-Me(87, respectively. The screening of the chemical structure of PLH-Me has been carried out for DNA carrier properties, which are the stability of its DNA polyion complexes and gene expression. The DNA complexes with the 25 mol% and 68 mol% dimethylated PLH-Me possessed almost same ability to retain DNA, as compared with the 87 mol% dimethylated PLH-Me, which was examined by competitive exchange with dextran sulfate. From the gene transfection experiment against HepG2 cells, human hepatoma cell line, the PLH-Me(25/DNA complex was revealed to mediate highest gene expression. These results suggest that the dimethyl-imidazolium/methylimidazole/imidazole balance of the PLH-Me is important for DNA carrier design.

  5. The histidine-phosphocarrier protein of the phosphoenolpyruvate: sugar phosphotransferase system of Bacillus sphaericus self-associates.

    Directory of Open Access Journals (Sweden)

    Rosa Doménech

    Full Text Available The phosphotransferase system (PTS is involved in the use of carbon sources in bacteria. Bacillus sphaericus, a bacterium with the ability to produce insecticidal proteins, is unable to use hexoses and pentoses as the sole carbon source, but it has ptsHI genes encoding the two general proteins of the PTS: enzyme I (EI and the histidine phosphocarrier (HPr. In this work, we describe the biophysical and structural properties of HPr from B. sphaericus, HPr(bs, and its affinity towards EI of other species to find out whether there is inter-species binding. Conversely to what happens to other members of the HPr family, HPr(bs forms several self-associated species. The conformational stability of the protein is low, and it unfolds irreversibly during heating. The protein binds to the N-terminal domain of EI from Streptomyces coelicolor, EIN(sc, with a higher affinity than that of the natural partner of EIN(sc, HPr(sc. Modelling of the complex between EIN(sc and HPr(bs suggests that binding occurs similarly to that observed in other HPr species. We discuss the functional implications of the oligomeric states of HPr(bs for the glycolytic activity of B. sphaericus, as well as a strategy to inhibit binding between HPr(sc and EIN(sc.

  6. The histidine-phosphocarrier protein of the phosphoenolpyruvate: sugar phosphotransferase system of Bacillus sphaericus self-associates.

    Science.gov (United States)

    Doménech, Rosa; Hernández-Cifre, José G; Bacarizo, Julio; Díez-Peña, Ana I; Martínez-Rodríguez, Sergio; Cavasotto, Claudio N; de la Torre, José García; Cámara-Artigás, Ana; Velázquez-Campoy, Adrián; Neira, José L

    2013-01-01

    The phosphotransferase system (PTS) is involved in the use of carbon sources in bacteria. Bacillus sphaericus, a bacterium with the ability to produce insecticidal proteins, is unable to use hexoses and pentoses as the sole carbon source, but it has ptsHI genes encoding the two general proteins of the PTS: enzyme I (EI) and the histidine phosphocarrier (HPr). In this work, we describe the biophysical and structural properties of HPr from B. sphaericus, HPr(bs), and its affinity towards EI of other species to find out whether there is inter-species binding. Conversely to what happens to other members of the HPr family, HPr(bs) forms several self-associated species. The conformational stability of the protein is low, and it unfolds irreversibly during heating. The protein binds to the N-terminal domain of EI from Streptomyces coelicolor, EIN(sc), with a higher affinity than that of the natural partner of EIN(sc), HPr(sc). Modelling of the complex between EIN(sc) and HPr(bs) suggests that binding occurs similarly to that observed in other HPr species. We discuss the functional implications of the oligomeric states of HPr(bs) for the glycolytic activity of B. sphaericus, as well as a strategy to inhibit binding between HPr(sc) and EIN(sc).

  7. Characterization of singlet oxygen production and its involvement in photodamage of Photosystem II in the cyanobacterium Synechocystis PCC 6803 by histidine-mediated chemical trapping.

    Science.gov (United States)

    Rehman, Ateeq Ur; Cser, Krisztián; Sass, László; Vass, Imre

    2013-06-01

    Singlet oxygen production in intact cells of the cynobacterium Synechocystis 6803 was studied using chemical trapping by histidine, which leads to O2 uptake during illumination. The rate of O2 uptake, measured by a standard Clark-type electrode, is enhanced in the presence of D2O, which increases the lifetime of (1)O2, and suppressed by the (1)O2 quencher NaN3. Due to the limited mobility of (1)O2 these data demonstrate that exogenous histidine reaches close vicinity of (1)O2 production sites inside the cells. Flash induced chlorophyll fluorescence measurements showed that histidine does not inhibit Photosystem II activity up to 5mM concentration. By applying the histidine-mediated O2 uptake method we showed that (1)O2 production linearly increases with light intensity even above the saturation of photosynthesis. We also studied (1)O2 production in site directed mutants in which the Gln residue at the 130th position of the D1 reaction center subunit was changed to either Glu or Leu, which affect the efficiency of nonradiative charge recombination from the primary radical pair (Rappaport et al. 2002, Biochemistry 41: 8518-8527; Cser and Vass 2007, BBA 1767:233-243). We found that the D1-Gln130Glu mutant showed decreased (1)O2 production concomitant with decreased rate of photodamage relative to the WT, whereas both (1)O2 production and photodamage were enhanced in the D1-Gln130Leu mutant. The data are discussed in the framework of the model of photoinhibition in which (3)P680 mediated (1)O2 production plays a key role in PSII photodamage, and nonradiative charge recombination of the primary charge separated state provides a photoprotective pathway. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Detection of histidine rich protein & lactate dehydrogenase of Plasmodium falciparum in malaria patients by sandwich ELISA using in-house reagents

    OpenAIRE

    Verma, Priyanka; Biswas, Sukla; Mohan, Teena; Ali, Shakir; Rao, D.N.

    2013-01-01

    Background & objectives: Despite major control efforts, malaria remains a major public health problem that still causes high mortality rate worldwide especially in Africa and Asia. Accurate and confirmatory diagnosis before treatment initiation is the only way to control the disease. The present study was undertaken to develop reagents using sandwich ELISA for simultaneous detection of PfHRP2 (Plasmodium falciparum histidine rich protein) and PfLDH (P. falciparum lactate dehydrogenase) antige...

  9. NikA/TcsC histidine kinase is involved in conidiation, hyphal morphology, and responses to osmotic stress and antifungal chemicals in Aspergillus fumigatus.

    Directory of Open Access Journals (Sweden)

    Daisuke Hagiwara

    Full Text Available The fungal high osmolarity glycerol (HOG pathway is composed of a two-component system (TCS and Hog1-type mitogen-activated protein kinase (MAPK cascade. A group III (Nik1-type histidine kinase plays a major role in the HOG pathway of several filamentous fungi. In this study, we characterized a group III histidine kinase, NikA/TcsC, in the life-threatening pathogenic fungus, Aspergillus fumigatus. A deletion mutant of nikA showed low conidia production, abnormal hyphae, marked sensitivity to high osmolarity stresses, and resistance to cell wall perturbing reagents such as congo red and calcofluor white, as well as to fungicides such as fludioxonil, iprodione, and pyrrolnitrin. None of these phenotypes were observed in mutants of the SskA response regulator and SakA MAPK, which were thought to be downstream components of NikA. In contrast, in response to fludioxonil treatment, NikA was implicated in the phosphorylation of SakA MAPK and the transcriptional upregulation of catA, dprA, and dprB, which are regulated under the control of SakA. We then tested the idea that not only NikA, but also the other 13 histidine kinases play certain roles in the regulation of the HOG pathway. Interestingly, the expression of fos1, phkA, phkB, fhk5, and fhk6 increased by osmotic shock or fludioxonil treatment in a SakA-dependent manner. However, deletion mutants of the histidine kinases showed no significant defects in growth under the tested conditions. Collectively, although the signal transduction network related to NikA seems complicated, NikA plays a crucial role in several aspects of A. fumigatus physiology and, to a certain extent, modulates the HOG pathway.

  10. Neighbor-Directed Histidine N (s)–Alkylation: A Route to Imidazolium-Containing Phosphopeptide Macrocycles-Biopolymers | Center for Cancer Research

    Science.gov (United States)

    Our recently discovered, selective, on-resin route to N(s)-alkylated imidazolium-containing histidine residues affords new strategies for peptide mimetic design. In this, we demonstrate the use of this chemistry to prepare a series of macrocyclic phosphopeptides, in which imidazolium groups serve as ring-forming junctions. Interestingly, these cationic moieties subsequently serve to charge-mask the phosphoamino acid group that directed their formation.

  11. Determination of the three-dimensional solution structure of the histidine-containing phosphocarrier protein HPr from Escherichia coli using multidimensional NMR spectroscopy

    NARCIS (Netherlands)

    Nuland, Nico A.J. van; Grötzinger, Joachim; Dijkstra, Klaas; Scheek, Ruud M.; Robillard, George T.

    1992-01-01

    We recorded several types of heteronuclear three-dimensional (3D) NMR spectra on 15N-enriched and 13C/15N-enriched histidine-containing phosphocarrier protein, HPr, to extend the backbone assignments to the side-chain 1H, 15N and 13C resonances. From both 3D heteronuclear 1H-NOE 1H-13C and 1H-NOE

  12. Modification of photosynthetic electron transport and amino acid levels by overexpression of a circadian-related histidine kinase hik8 in Synechocystis sp. PCC 6803

    OpenAIRE

    Kuwahara, Ayuko; Arisaka, Satomi; Takeya, Masahiro; Iijima, Hiroko; Hirai, Masami Yokota; Osanai, Takashi

    2015-01-01

    Cyanobacteria perform oxygenic photosynthesis, and the maintenance of photosynthetic electron transport chains is indispensable to their survival in various environmental conditions. Photosynthetic electron transport in cyanobacteria can be studied through genetic analysis because of the natural competence of cyanobacteria. We here show that a strain overexpressing hik8, a histidine kinase gene related to the circadian clock, exhibits an altered photosynthetic electron transport chain in the ...

  13. EFFECT OF Β-ALANINE AND L-HISTIDINE ON CONCENTRATION OF CARNOSINE IN MUSCLE TISSUE AND OXIDATIVE STABILITY OF CHICKEN MEAT

    Directory of Open Access Journals (Sweden)

    Gordana Kralik

    2015-09-01

    Full Text Available This paper presents the results of two separate experiments, each involving 75 chickens of Cobb 500 provenience, divided into three experimental groups. During the last three weeks of fattening, chickens were fed finisher diets supplemented with amino acids β-alanine (0%, 0.5% and 1% and L-histidine (0%, 0.3% and 0.5% in different portions. After chickens have been slaughtered, 10 samples of breast tissue were taken from each group for carnosine content determination in muscle tissue and lipid oxidation expressed as TBARS. Analysis of THE results referring to carnosine concentration in breast muscle proved that supplementation of 0.5% L-histidine affected the carnosine concentration increase in breast muscles from 941.58 µg/g of tissue (H1 to 1186.06 µg/g of tissue (H3, while supplementation of 1% β-alanine influenced the increase in carnosine concentration from 756.15 µg/g of tissue (A1 to 911.01 µg/g of tissue (A3. Supplementation of amino acids did not have effects on TBARS values, but oxidation values decreased along with the supplementation of higher amounts of amino acids to diets, which was particularly expressed in samples stored for 60 days at -20°C. The experimental group H3 (0.5% L-histidine exhibited 30.54% lower value of lipid oxidation than the control one H1 (0% L-histidine, while the group with 1% β-alanine (A3 had lipid oxidation value by 17.65% lower than the control group A1 (0% β-alanine.

  14. Supercritical water loop for in-pile materials testing

    Energy Technology Data Exchange (ETDEWEB)

    Ruzickova, M.; Vsolak, R.; Hajek, P.; Zychova, M.; Fukac, R. [Research Centre Rez Ltd., Husinec-Rez (Czech Republic)

    2011-07-01

    The Supercritical Water Loop (SCWL) has been designed and built within the HPLWR Phase 2 project, with the objective of testing materials under supercritical water conditions and radiation. The design parameters are set to 25MPa and 600{sup o}C in the testing area, where material samples shall be located. The loop has recently undergone pressure and leakage tests, during which the strength and tightness of the loop were proved. The loop has been also subjected to the first trial operation at nearly maximum operating parameters (temperature 550 {sup o}C was reached); loop operation was steady during several days. Presently, loop operation is envisaged in order to test the loop's long term operation ability. Samples of a material that needs further testing under out- of-pile conditions shall be exposed in the loop; the choice shall be made in agreement with the results of the WP4 - Materials of the HPLWR Phase 2 project. (author)

  15. Vapor Compressor Driven Hybrid Two-Phase Loop Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project will demonstrate a vapor compressor driven hybrid two-phase loop technology. The hybrid two-phase loop...

  16. Multi-loop calculations: numerical methods and applications

    Science.gov (United States)

    Borowka, S.; Heinrich, G.; Jahn, S.; Jones, S. P.; Kerner, M.; Schlenk, J.

    2017-11-01

    We briefly review numerical methods for calculations beyond one loop and then describe new developments within the method of sector decomposition in more detail. We also discuss applications to two-loop integrals involving several mass scales.

  17. Stability in Real Food Webs: Weak Links in Long Loops

    National Research Council Canada - National Science Library

    Anje-Margriet Neutel; Johan A. P. Heesterbeek; Peter C. de Ruiter

    2002-01-01

    ... of these patterns, how they come about, and why they influence stability. We show that in real food webs, interaction strengths are organized in trophic loops in such a way that long loops contain relatively many weak links...

  18. Real-time RT-PCR analysis of human histidine decarboxylase, a new marker for several types of leukemia and cancer.

    Science.gov (United States)

    Melgarejo, Esther; Medina, Miguel Angel; Paz, José Carlos; Sánchez-Jiménez, Francisca; Urdiales, José Luis

    2006-01-01

    Histamine is involved in different physiological and pathological responses, such as immune response, gastric acid secretion or neurotransmission, as either angiogenesis or cancer. Histidine decarboxylase (HDC) catalyzes the formation of histamine from histidine. HDC has been suggested as a new marker for neuroendocrine differentiation, inflammatory pathologies and several leukemia and highly malignant forms of cancer, such as melanoma and small cell lung carcinoma. In the present work, we describe the use of Syber Green-based quantitative real-time RT-PCR to determine the expression of histidine decarboxylase in human cells and tissue. As an internal control, glyceraldehyde 3-phosphate dehydrogenase was also amplified. The linear dynamic range of the assay covered 4 orders of magnitude for HDC amplification. The detection limit was 0.1 ng of total RNA extracted from HMC-1 cells. This method is simple, rapid, sensitive, and quantitative, and allows for the specific identification of cells and tissue expressing HDC, stressing its potential diagnostic usefulness in malignancies in which HDC is described as a new marker.

  19. Two Independent Histidines One in Human Prolactin and One in Its Receptor Are Critical for pH-dependent Receptor Recognition and Activation

    Energy Technology Data Exchange (ETDEWEB)

    M Kulkarni; M Tettamanzi; J Murphy; C Keeler; D Myszka; N Chayen; E Lolis; M Hodsdon

    2011-12-31

    Human prolactin (hPRL), a member of the family of hematopoietic cytokines, functions as both an endocrine hormone and autocrine/paracrine growth factor. We have previously demonstrated that recognition of the hPRL-receptor depends strongly on solution acidity over the physiologic range from pH 6 to pH 8. The hPRL-receptor binding interface contains four histidines whose protonation is hypothesized to regulate pH-dependent receptor recognition. Here, we systematically dissect its molecular origin by characterizing the consequences of His to Ala mutations on pH-dependent receptor binding kinetics, site-specific histidine protonation, and high resolution structures of the intermolecular interface. Thermodynamic modeling of the pH dependence to receptor binding affinity reveals large changes in site-specific protonation constants for a majority of interface histidines upon complexation. Removal of individual His imidazoles reduces these perturbations in protonation constants, which is most likely explained by the introduction of solvent-filled, buried cavities in the crystallographic structures without inducing significant conformational rearrangements.

  20. Integrated logic gate for fluorescence turn-on detection of histidine and cysteine based on Ag/Au bimetallic nanoclusters-Cu²⁺ ensemble.

    Science.gov (United States)

    Sun, Jian; Yang, Fan; Zhao, Dan; Chen, Chuanxia; Yang, Xiurong

    2015-04-01

    By means of employing 11-mercaptoundecanoic acid (11-MUA) as a reducing agent and protecting ligand, we present straightforward one-pot preparation of fluorescent Ag/Au bimetallic nanoclusters (namely AgAuNCs@11-MUA) from AgNO3 and HAuCl4 in alkaline aqueous solution at room temperature. It is found that the fluorescence of AgAuNCs@11-MUA has been selectively quenched by Cu(2+) ions, and the nonfluorescence off-state of the as-prepared AgAuNCs@11-MUA-Cu(2+) ensemble can be effectively switched on upon the addition of histidine and cysteine. By incorporating Ni(2+) ions and N-ethylmaleimide, this phenomenon is further exploited as an integrated logic gate and a specific fluorescence turn-on assay for selectively and sensitively sensing histidine and cysteine has been designed and established based on the original noncovalent AgAuNCs@11-MUA-Cu(2+) ensemble. Under the optimal conditions, histidine and cysteine can be detected in the concentration ranges of 0.25-9 and 0.25-7 μM; besides, the detection limits are found to be 87 and 111 nM (S/N = 3), respectively. Furthermore, we demonstrate that the proposed AgAuNCs@11-MUA-based fluorescent assay can be successfully utilized for biological fluids sample analysis.

  1. Investigations on the growth aspects and characterization of semiorganic nonlinear optical single crystals of L-histidine and its hydrochloride derivative.

    Science.gov (United States)

    Anandan, P; Arivanandhan, M; Hayakawa, Y; Babu, D Rajan; Jayavel, R; Ravi, G; Bhagavannarayana, G

    2014-01-01

    Semiorganic single crystals of l-histidine and l-histidine hydrochloride monohydrate have been obtained in a single solution prepared from the mixture of l-histidine and hydrochloric acid in 1:2M ratio. Growth aspects of the single crystals have been discussed along with characterization studies. Crystal system and lattice parameters have been identified by X-ray diffraction analyses. It has been observed that the grown crystals possess orthorhombic system but with different set of lattice parameters. Presence of various functional groups has been identified and formation of two different crystals has been confirmed by Fourier transform infrared spectral analyses and FT-Raman studies. Linear and nonlinear optical properties have been studied by UV-Vis spectral analyses and Kurtz-Perry powder technique respectively. The thermal stability of the grown crystals was determined by thermal analyses. From the characterization studies it is found that both the crystals are useful for second harmonic generation applications. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Single-step synthesis and characterization of biotinylated nitrilotriacetic acid, a unique reagent for the detection of histidine-tagged proteins immobilized on nitrocellulose.

    Science.gov (United States)

    McMahan, S A; Burgess, R R

    1996-04-05

    Using a one-step reaction, a bifunctional compound was synthesized for detecting histidine-tagged proteins immobilized on nitrocellulose. This compound has a biotin as one functional group and a nitrilotriacetic acid as the other. The nitrilotriacetic acid is used to chelate a Ni(II) ion at four of its six coordination sites. The remaining two sites are available for binding to a histidine tag. The biotin functional group can then be detected using a streptavidin-horseradish peroxidase conjugate and chemiluminescence. Using this biotinylated nitrilotriacetic acid, it is possible to detect less than 0.11 pmol of histidine-tagged Escherichia coli RNA polymerase sigma70 subunit. This reagent is also able to specifically detect His-tagged sigma70 from a whole cell lysate following SDS-PAGE and transfer to nitrocellulose. The reagent can be dissociated from the His-tagged protein at pH 4.8 and the blot can be reprobed with a monoclonal antibody for detection of different proteins on the same blot.

  3. Molecular characterization of flavanone 3 beta-hydroxylases. Consensus sequence, comparison with related enzymes and the role of conserved histidine residues.

    Science.gov (United States)

    Britsch, L; Dedio, J; Saedler, H; Forkmann, G

    1993-10-15

    A heterologous cDNA probe from Petunia hybrida was used to isolate flavanone-3 beta-hydroxylase-encoding cDNA clones from carnation (Dianthus caryophyllus), china aster (Callistephus chinensis) and stock (Matthiola incana). The deduced protein sequences together with the known sequences of the enzyme from P. hybrida, barley (Hordeum vulgare) and snapdragon (Antirrhinum majus) enabled the determination of a consensus sequence which revealed an overall 84% similarity (53% identity) of flavanone 3 beta-hydroxylases from the different sources. Alignment with the sequences of other known enzymes of the same class and to related non-heme iron-(II) enzymes demonstrated the strict genetic conservation of 14 amino acids, in particular, of three histidines and an aspartic acid. The conservation of the histidine motifs provides strong support for the possible conservation of structurally similar iron-binding sites in these enzymes. The putative role of histidines as chelators of ferrous ions in the active site of flavanone 3 beta-hydroxylases was corroborated by diethyl-pyrocarbonate modification of the partially purified recombinant Petunia enzyme.

  4. Amino acid-mediated 'turn-off/turn-on' nanozyme activity of gold nanoclusters for sensitive and selective detection of copper ions and histidine.

    Science.gov (United States)

    Liu, Yan; Ding, Ding; Zhen, Yuanlin; Guo, Rong

    2017-06-15

    Herein, we presented a facile strategy for highly sensitive and selective detection of both Cu2+ and histidine (His) by combining the peroxidase-like nanozyme activity of gold nanoclusters with amino acid's ambidentate nature. The peroxidase-like catalytic ability of histidine-Au nanoclusters (His-AuNCs) can be inhibited by the addition of Cu2+. The sensitivity of this probe to Cu2+ is significant with a linear range of 1-100nM, and a low detection limit of 0.1nM. More interestingly, His-AuNC/Cu2+ undergoes recovery of the activity upon exposure to free His, because His/Cu2+ complex is more stable due to the participation of the imidazole ring of His. The method displays a good selectivity toward histidine over all the other amino acids, with a wide linear relationship in the range of 20nM-2μM, and a low detection limit of 20nM. The feasibility of the probe for the rapid analysis of copper ion and His in human serum has been demonstrated with satisfactory results. With the merits of high sensitivity and selectivity, simplification, low cost, and visual readout with the naked eye, this novel 'turn-off/turn-on' sensing approach based on the amino acid's ambidentate nature is potentially applicable to metal ions, amino acids and peptides in biological and environmental areas. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. The Seasonality Of The Loop Current

    Science.gov (United States)

    Hall, Cody Alan

    A total of 20 Loop Current eddy separation event dates were derived from Seasat and ERS-1 satellite altimetry, Coastal Zone Color Scanner chlorophyll-a images, Advanced Very High Resolution Radiometer sea surface temperature images, Horizon Marine, Inc. EddyWatch(TM) reports, and Climatology and Simulation of Eddies Eddy Joint Industry Project Gulf Eddy Model analyses spanning mid-1978 - 1992. There were many inconsistencies between the new "pre-altimetry" reanalysis dates derived from mostly non-altimeter data and dates published in past literature based on earlier versions of the pre-altimetry record. The reanalysis dates were derived from a larger compilation of data types and, consequently, were not as affected by intermittent and seasonal data outages common with past records. Therefore, the reanalysis dates are likely more accurate. About 30 Loop Current eddy separation dates were derived from altimetry data spanning 1993 -- 2012. The pre-altimetry and altimetry reanalysis dates along with similar altimetry dates published in other literature exhibit statistically significant seasonality. Eddy separation events are more likely in the months March, August, and September, and less likely in December. Reanalysis event dates were objectively divided into "spring" and "fall" seasons using a k-means clustering algorithm. The estimated spring and fall season centers are March 2nd and August 23 rd, respectively, with seasonal boundaries on May 22nd and December 3rd. The altimetry data suggest that Loop Current intrusion/retreat is dominantly an annual process. Loop Current metrics such as maximum northern boundary latitude and area are relatively high from January through about July and low in September and October. February metrics are statistically different than metrics in either October or November or both. This annual process is primarily driven by and dynamically linked to geostrophic currents seaward of the Campeche Bank shelf break forced by Kelvin waves

  6. Magnetic Monopoles and the Loop Group.

    Science.gov (United States)

    Norbury, Paul Timothy

    My thesis relates three major works in gauge theory and geometry. I use a technique involving jumping lines in the study of holomorphic bundles over the projective plane to gain information about the loop group and hyperbolic monopoles. I also turn this around and get some information on the jumping lines of a holomorphic bundle. Hurtubise studied the local geometry of a holomorphic bundle on the projective plane around a jumping line, encoding this information into the Toeplitz space. Milgram identified a stratum of the projectivized Toeplitz space with a quotient of the space of rational maps from the two-sphere to itself. I associate the Toeplitz space to the loop group and use Milgram's result to get a description of a stratum of the loop group. By studying their jumping lines I construct those holomorphic bundles on the projective plane which are invariant under a circle action so in particular correspond to hyperbolic monopoles. Again I use Milgram's result to get a new proof of the theorem of Atiyah where he obtains a homeomorphism between the space of hyperbolic monopoles and the space of rational maps from the two-sphere to itself that fix infinity. Conversely using Atiyah's theorem I get a new proof of Milgram's result. This equivalence between the theorems of Milgram and Atiyah generalises to the case of higher rank so I get new results on the local geometry of jumping lines of a holomorphic bundle over the projective plane. There are two main ways to describe holomorphic bundles over the projective plane. Using the loop group I produce a third way to describe such bundles. With this description I show that there is a deeper equivalence between the theorems of Milgram and Atiyah. This work originated from questions about the relationship between the instantons of two dynamical theories --gauge theory over the four-sphere and holomorphic curves in the loop group. I study the gradient flows of the energy functional on the loop group and show how they

  7. Closed-loop fiber optic gyroscope with homodyne detection

    Science.gov (United States)

    Zhu, Yong; Qin, BingKun; Chen, Shufen

    1996-09-01

    Interferometric fiber optic gyroscope (IFOG) has been analyzed with autocontrol theory in this paper. An open-loop IFOG system is not able to restrain the bias drift, but a closed-loop IFOG system can do it very well using negative feedback in order to suppress zero drift. The result of our theoretic analysis and computer simulation indicate that the bias drift of a closed-loop system is smaller than an open- loop one.

  8. Polyakov loops, Gross-Witten like point and Hagedorn states

    OpenAIRE

    Zakout, I.; Greiner, C.

    2011-01-01

    The phase transition for a finite volume system that incorporates the Polyakov loops and maintains the colorless state is explored using the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model. The order parameter for Polyakov loops is demonstrated to signal the appearance of a transition for $SU(3)_{c}$ analogous to Gross-Witten (GW-) phase transition instead of the deconfinement phase transition to quark-gluon plasma. The asymptotic restoration of Polyakov loops is conjectured to be a th...

  9. Loop-loop interactions govern multiple steps in indole-3-glycerol phosphate synthase catalysis.

    Science.gov (United States)

    Zaccardi, Margot J; O'Rourke, Kathleen F; Yezdimer, Eric M; Loggia, Laura J; Woldt, Svenja; Boehr, David D

    2014-03-01

    Substrate binding, product release, and likely chemical catalysis in the tryptophan biosynthetic enzyme indole-3-glycerol phosphate synthase (IGPS) are dependent on the structural dynamics of the β1α1 active-site loop. Statistical coupling analysis and molecular dynamic simulations had previously indicated that covarying residues in the β1α1 and β2α2 loops, corresponding to Arg54 and Asn90, respectively, in the Sulfolobus sulfataricus enzyme (ssIGPS), are likely important for coordinating functional motions of these loops. To test this hypothesis, we characterized site mutants at these positions for changes in catalytic function, protein stability and structural dynamics for the thermophilic ssIGPS enzyme. Although there were only modest changes in the overall steady-state kinetic parameters, solvent viscosity and solvent deuterium kinetic isotope effects indicated that these amino acid substitutions change the identity of the rate-determining step across multiple temperatures. Surprisingly, the N90A substitution had a dramatic effect on the general acid/base catalysis of the dehydration step, as indicated by the loss of the descending limb in the pH rate profile, which we had previously assigned to Lys53 on the β1α1 loop. These changes in enzyme function are accompanied with a quenching of ps-ns and µs-ms timescale motions in the β1α1 loop as measured by nuclear magnetic resonance studies. Altogether, our studies provide structural, dynamic and functional rationales for the coevolution of residues on the β1α1 and β2α2 loops, and highlight the multiple roles that the β1α1 loop plays in IGPS catalysis. Thus, substitution of covarying residues in the active-site β1α1 and β2α2 loops of indole-3-glycerol phosphate synthase results in functional, structural, and dynamic changes, highlighting the multiple roles that the β1α1 loop plays in enzyme catalysis and the importance of regulating the structural dynamics of this loop through noncovalent

  10. Solutions of selected pseudo loop equations in water distribution ...

    African Journals Online (AJOL)

    This paper demonstrated the use of Microsoft Excel Solver (a computer package) in solving selected pseudo loop equations in pipe network analysis problems. Two pipe networks with pumps and overhead tanks were used to demonstrate the use of Microsoft Excel Solver in solving pseudo loops (open loops; networks with ...

  11. The autoregulatory loop: A common mechanism of regulation of key ...

    Indian Academy of Sciences (India)

    ... an autoregulatory positive feedback loop. In this review, by taking examples from various insects, we propose the hypothesis that autoregulatory loop mechanisms of sex determination might be a general strategy. We also discuss the possible reasons for the evolution of autoregulatory loops in sex determination cascades ...

  12. Rare Case of Double Looped Ansa Cervicalis Associated with its ...

    African Journals Online (AJOL)

    fibers of C1‑C3 nerves arose from this loop and ran obliquely downwards superficial to CCA and branched out to supply the infrahyoid muscles. Rare Case of Double Looped Ansa ... Keywords: Ansa cervicalis, Double loop, Nerve muscle transplant, Variation ... categorized as type 3 with the prevalence of 4% and double.

  13. Closed-Loop Optimal Control Implementations for Space Applications

    Science.gov (United States)

    2016-12-01

    COVERED Master’s thesis , Jan-Dec 2016 4. TITLE AND SUBTITLE CLOSED-LOOP OPTIMAL CONTROL IMPLEMENTATIONS FOR SPACE APPLICATIONS 5. FUNDING NUMBERS... Mechanical and Aerospace Engineering iv THIS PAGE INTENTIONALLY LEFT BLANK v ABSTRACT This thesis explores concepts for a closed-loop optimal...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release. Distribution is unlimited. CLOSED-LOOP

  14. Modulation of RNA polymerase activity through trigger loop folding

    OpenAIRE

    Miropolskaya, Nataliya; Nikiforov, Vadim; Klimašauskas, Saulius; Artsimovitch, Irina; Kulbachinskiy, Andrey

    2010-01-01

    Folding of the trigger loop of RNA polymerase promotes nucleotide addition through creating a closed, catalytically competent conformation of the active center. Here, we discuss the impact of adjacent RNA polymerase elements, including the F loop and the jaw domain, as well as external regulatory factors on the trigger loop folding and catalysis.

  15. Low Water Activity Induces the Production of Bioactive Metabolites in Halophilic and Halotolerant Fungi

    Directory of Open Access Journals (Sweden)

    Nina Gunde-Cimerman

    2010-12-01

    Full Text Available The aim of the present study was to investigate indigenous fungal communities isolated from extreme environments (hypersaline waters of solar salterns and subglacial ice, for the production of metabolic compounds with selected biological activities: hemolysis, antibacterial, and acetylcholinesterase inhibition. In their natural habitats, the selected fungi are exposed to environmental extremes, and therefore the production of bioactive metabolites was tested under both standard growth conditions for mesophilic microorganisms, and at high NaCl and sugar concentrations and low growth temperatures. The results indicate that selected halotolerant and halophilic species synthesize specific bioactive metabolites under conditions that represent stress for non-adapted species. Furthermore, adaptation at the level of the chemical nature of the solute lowering the water activity of the medium was observed. Increased salt concentrations resulted in higher hemolytic activity, particularly within species dominating the salterns. The appearance of antibacterial potential under stress conditions was seen in the similar pattern of fungal species as for hemolysis. The active extracts exclusively affected the growth of the Gram-positive bacterium tested, Bacillus subtilis. None of the extracts tested showed inhibition of acetylcholinesterase activity.

  16. Effect of water activity and temperature on competing abilities of common postharvest citrus fungi.

    Science.gov (United States)

    Plaza, Pilar; Usall, Josep; Teixidó, Neus; Viñas, Immaculada

    2004-01-01

    The effect of temperature (4-30 degrees C) and water activity (a(w), 0.995-0.90) on the 'in vitro' interactions between Penicillium digitatum, Penicillium italicum and Geotrichum candidum were evaluated. The effect of temperature on growth of green and blue mould decays and their interactions on wounded oranges was also studied. The major competing abilities were observed at optimal conditions of temperature and a(w) for growth (25 degrees C and 0.995 a(w)), and no differences between growth rates when the fungi were growing alone or paired were observed in the other studied conditions. P. italicum and G. candidum were able to reduce the growth rate of P. digitatum when it was growing paired 'in vitro', suggesting that inhibitory metabolites were produced. In the 'in vivo' assays, growth rates of green mould were higher than those of blue mould at any temperature studied. However, at 4 degrees C, P. italicum began its rot development 1 week before P. digitatum. When these two pathogens were inoculated into the same wound at 25 degrees C, blue mould was practically inhibited. The difference between the results obtained in 'in vitro' and 'in vivo' assays suggests that other factors could interact with fungi, favoring the development of one pathogen to the detriment of the others.

  17. Microbial Safety of Low Water Activity Foods: Study of Simulated and Durban Household Samples

    Directory of Open Access Journals (Sweden)

    O. A. Ijabadeniyi

    2017-01-01

    Full Text Available Sixty household low water activity foods were examined and a simulative study was conducted in a high sugar, low aw almond and macadamia butter to determine the survival of Bacillus cereus and Staphylococcus aureus ATCC 25923. Results obtained from 60 low aw samples collected at household level had some significant differences (P≤0,05 within food categories amongst the various tests. Spices had the highest number of aerobic bacteria, aerobic spore-formers, anaerobic spore-formers, and S. aureus. Mean aerobic colony counts for nuts and spices were 2.30 log CFU/g and 4.40 log CFU/g, respectively. Pathogens such as Escherichia coli and Cronobacter sakazakii were present in nuts, whilst Salmonella spp. was present in chocolates. This implies that certain low aw foods may present a public health risk. In the simulative study, temperature and high sucrose concentrations played a significant role in the survival of B. cereus and S. aureus ATCC 25923. B. cereus was found to be more osmotolerant at both reduced and elevated temperatures (18°C and 25°C in the 12% sucrose sample in both butters, whilst S. aureus ATCC 25923 seemed to grow better in sucrose-free samples at both temperatures in both butters. This implies that certain low aw foods may present a public health risk. Also, B. cereus, being a spore-forming bacterium, can be osmotolerant at both reduced and elevated temperatures.

  18. Antiaflatoxigenic property of food grade antioxidants under different conditions of water activity in peanut grains.

    Science.gov (United States)

    Passone, María A; Resnik, Silvia; Etcheverry, Miriam G

    2007-08-15

    Analytical grade (AG) and industrial grade (IG) of three-food grade antioxidants butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl paraben (PP) were analyzed to prove their fungitoxic effect on Aspergillus section Flavi strains. The effect of interactions among 10 antioxidant treatments at water activity levels (0.982, 0.955, 0.937 a(W)) for 11 and 35 days of incubation and at 25 degrees C in peanut grains on mycelial growth (CFU g(-1)) and aflatoxin B(1) (AFB(1)) accumulation were evaluated. Both antioxidant grade treatments had a significant effect (PM2 (10+20 mM), M3 (20+10 mM), M4 (20+20 mM) and ternary mixtures M5 (10+10+10 mM), M6 (10+20+10 mM), M7 (20+10+10 mM) and M8 (20+20+10 mM) completely inhibited AFB(1) production. The studied results suggest that IG antioxidant mixtures have potential for controlling growth of these mycotoxigenic species and prevent aflatoxin accumulation at the peanut storage system.

  19. Sorption characteristics of Amaranthus stems under storage conditions and water activity prediction.

    Science.gov (United States)

    Stencl, Jiri; Fajman, Martin; Sedlak, Pavel; Janstova, Bohumira; Kleparnik, Jan; Stencl, Jiri

    2010-12-01

    Stems of amaranthus are considered as prospective biofuel in the Czech Republic. The study presents results of water sorption tests of this biomass in the range of 10-30 degrees C and water activity (a(w)) ranging from 0.4 to 0.99. The experimental procedure used was a gravimetric dynamic method. Four sorption models (Chung-Pfost, Halsey, Henderson, Oswin) were evaluated. The modified Henderson's equation was the best model for moisture adsorption and desorption of amaranthus stems. Critical values of equilibrium moisture content, corresponding to the a(w)=0.6, were 11.45% and 13.28%(wb) for water adsorption and desorption respectively, at the temperature of 20 degrees C. Heat of sorption (q(st)) was calculated using the chosen sorption model and Clausius-Clapeyron equation. An exponential function was found to fit the experimental q(st) values of amaranthus stems at moisture contents ranging from 7% to 40%(wb) for adsorption and desorption. 2010 Elsevier Ltd. All rights reserved.

  20. Water activity of poultry litter: Relationship to moisture content during a grow-out.

    Science.gov (United States)

    Dunlop, Mark W; McAuley, Jim; Blackall, Patrick J; Stuetz, Richard M

    2016-05-01

    Poultry grown on litter floors are in contact with their own waste products. The waste material needs to be carefully managed to reduce food safety risks and to provide conditions that are comfortable and safe for the birds. Water activity (Aw) is an important thermodynamic property that has been shown to be more closely related to microbial, chemical and physical properties of natural products than moisture content. In poultry litter, Aw is relevant for understanding microbial activity; litter handling and rheological properties; and relationships between in-shed relative humidity and litter moisture content. We measured the Aw of poultry litter collected throughout a meat chicken grow-out (from fresh pine shavings bedding material to day 52) and over a range of litter moisture content (10-60%). The Aw increased non-linearly from 0.71 to 1.0, and reached a value of 0.95 when litter moisture content was only 22-33%. Accumulation of manure during the grow-out reduced Aw for the same moisture content. These results are relevant for making decisions regarding litter re-use in multiple grow-outs as well as setting targets for litter moisture content to minimise odour, microbial risks and to ensure necessary litter physical conditions are maintained during a grow-out. Methods to predict Aw in poultry litter from moisture content are proposed. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

  1. Infrared decontamination of oregano: effects on Bacillus cereus spores, water activity, color, and volatile compounds.

    Science.gov (United States)

    Eliasson, Lovisa; Libander, Patrik; Lövenklev, Maria; Isaksson, Sven; Ahrné, Lilia

    2014-12-01

    Infrared (IR) heating, a novel technology for decontaminating oregano, was evaluated by investigating the reduction of inoculated Bacillus cereus spores and the effect on water activity (a(w)), color, and headspace volatile compounds after exposure to IR treatment. Conditioned oregano (a(w) 0.88) was IR-treated in a closed heating unit at 90 and 100 °C for holding times of 2 and 10 min, respectively. The most successful reduction in B. cereus spore numbers (5.6 log units) was achieved after a holding time of 10 min at 90 °C, while treatment at 100 °C for the same time resulted in a lower reduction efficiency (4.7 log units). The lower reduction at 100 °C was probably due to a reduced aw (aw 0.76) during IR treatment or possibly to the alteration or loss of volatile compounds possessing antimicrobial properties. The green color of oregano was only slightly affected, while the composition of volatile compounds was clearly altered by IR heating. However, two of the key aroma compounds, carvacrol and thymol, were only slightly affected, compared to the effect on the other studied compounds, indicating that the typical oregano aroma can likely be preserved. In conclusion, IR heating shows potential for the successful decontamination of oregano without severe alteration of its color or the key aroma compounds, carvacrol and thymol. © 2014 Institute of Food Technologists®

  2. Modeling the effect of water activity and storage temperature on chemical stability of coffee brews.

    Science.gov (United States)

    Manzocco, Lara; Nicoli, Maria Cristina

    2007-08-08

    This work was addressed to study the chemical stability of coffee brew derivatives as a function of water activity (aw) and storage temperature. To this purpose, coffee brew was freeze-dried, equilibrated at increasing aw values, and stored for up to 10 months at different temperatures from -30 to 60 degrees C. The chemical stability of the samples was assessed by measuring H3O+ formation during storage. Independently of storage temperature, the rate of H3O+ formation was considerably low only when aw was reduced below 0.5 (94% w/w). Beyond this critical boundary, the rate increased, reaching a maximum value at ca. 0.8 aw (78% w/w). Further hydration up to the aw of the freshly prepared beverage significantly increased chemical stability. It was suggested that mechanisms other than lactones' hydrolysis, probably related to nonenzymatic browning pathways, could contribute to the observed increase in acidity during coffee staling. The temperature dependence of H3O+ formation was well-described by the Arrhenius equation in the entire aw range considered. However, aw affected the apparent activation energy and frequency factor. These effects were described by simple equations that were used to set up a modified Arrhenius equation. This model was validated by comparing experimental values, not used to generate the model, with those estimated by the model itself. The model allowed efficient prediction of the chemical stability of coffee derivatives on the basis of only the aw value and storage temperature.

  3. Effect of water activity and temperature on the stability of creatine during storage.

    Science.gov (United States)

    Uzzan, Michael; Nechrebeki, Jacob; Zhou, Peng; Labuza, Theodore P

    2009-08-01

    Creatine degradation to creatinine, which has no biological activity, in combinations of glycerol and pH 4.0 buffer solutions followed first-order kinetics up to a point where degradation started to level off, generally beyond the first half-life. Practical data are reported for a wide range of water activity (a(w)) values (0.31-0.983) at 4 degrees C, 23 degrees C, and 35 degrees C. Creatine degradation did not exhibit a dilution effect, that is a decrease in rate about an a(w) of 0.7, as is found for both microbiological growth and chemical reactions in semisolid food matrix systems. The temperature dependence obeyed the Arrhenius relationship with an energy of activation of about 20 kcal/mol at a(w) >or= 0.68 increasing to 23 kcal/mole below that a(w). In addition, a semilog plot of half-life as a function of a(w) at each temperature follows a predicted straight line. The pH and assumed liquid viscosity increase through increased glycerol concentration were not able to completely explain the decrease in rate of degradation as a function of a(w). Furthermore, we confirmed that creatine stability in the crystal form is very high as long as it does not reach the deliquescence state.

  4. Capillary pumped loop body heat exchanger

    Science.gov (United States)

    Swanson, Theodore D. (Inventor); Wren, deceased, Paul (Inventor)

    1998-01-01

    A capillary pumped loop for transferring heat from one body part to another body part, the capillary pumped loop comprising a capillary evaporator for vaporizing a liquid refrigerant by absorbing heat from a warm body part, a condenser for turning a vaporized refrigerant into a liquid by transferring heat from the vaporized liquid to a cool body part, a first tube section connecting an output port of the capillary evaporator to an input of the condenser, and a second tube section connecting an output of the condenser to an input port of the capillary evaporator. A wick may be provided within the condenser. A pump may be provided between the second tube section and the input port of the capillary evaporator. Additionally, an esternal heat source or heat sink may be utilized.

  5. A new vacuum for Loop Quantum Gravity

    CERN Document Server

    Dittrich, Bianca

    2014-01-01

    We construct a new vacuum for loop quantum gravity, which is dual to the Ashtekar-Lewandowski vacuum. Because it is based on BF theory, this new vacuum is physical for $(2+1)$-dimensional gravity, and much closer to the spirit of spin foam quantization in general. To construct this new vacuum and the associated representation of quantum observables, we introduce a modified holonomy-flux algebra which is cylindrically consistent with respect to the notion of refinement by time evolution suggested in [1]. This supports the proposal for a construction of a physical vacuum made in [1,2], also for $(3+1)$-dimensional gravity. We expect that the vacuum introduced here will facilitate the extraction of large scale physics and cosmological predictions from loop quantum gravity.

  6. Loop transfer recovery for general observer architecture

    DEFF Research Database (Denmark)

    Niemann, Hans Henrik; Søgaard-Andersen, Per; Stoustrup, Jakob

    1991-01-01

    A general and concise formulation is given of the loop transfer recovery (LTR) design problem based on recovery errors. Three types of recovery errors are treated: open loop recovery, sensitivity recovery and input-output recovery errors. The three corresponding versions of the asymptotic recovery...... recovery cases. This general recovery formulation covers all known observer based compensator types as special cases. The conditions given in this setting are effectively the aim of all known LTR design methods. The recovery formulation is interpreted in terms of a modelmatching problem as well, which...... is examined by means of the Q-parametrization. It is shown how the general controller obtained by the Q-parametrization can be written as a Luenberger observer based controller. In all cases, n controller states suffice to achieve recovery. The compensators are characterized for errors both on the input...

  7. Loop quantization of the Schwarzschild black hole.

    Science.gov (United States)

    Gambini, Rodolfo; Pullin, Jorge

    2013-05-24

    We quantize spherically symmetric vacuum gravity without gauge fixing the diffeomorphism constraint. Through a rescaling, we make the algebra of Hamiltonian constraints Abelian, and therefore the constraint algebra is a true Lie algebra. This allows the completion of the Dirac quantization procedure using loop quantum gravity techniques. We can construct explicitly the exact solutions of the physical Hilbert space annihilated by all constraints. New observables living in the bulk appear at the quantum level (analogous to spin in quantum mechanics) that are not present at the classical level and are associated with the discrete nature of the spin network states of loop quantum gravity. The resulting quantum space-times resolve the singularity present in the classical theory inside black holes.

  8. MBNL expression in autoregulatory feedback loops.

    Science.gov (United States)

    Konieczny, Patryk; Stepniak-Konieczna, Ewa; Sobczak, Krzysztof

    2017-09-26

    Muscleblind-like (MBNL) proteins bind to hundreds of pre- and mature mRNAs to regulate their alternative splicing, alternative polyadenylation, stability and subcellular localization. Once MBNLs are withheld from transcript regulation, cellular machineries generate products inapt for precise embryonal/adult developmental tasks and myotonic dystrophy, a devastating multi-systemic genetic disorder, develops. We have recently demonstrated that all three MBNL paralogs are capable of fine-tuning cellular content of one of the three MBNL paralogs, MBNL1, by binding to the first coding exon (e1) of its pre-mRNA. Intriguingly, this autoregulatory feedback loop grounded on alternative splicing of e1 appears to play a crucial role in delaying the onset of myotonic dystrophy. Here, we describe this process in the context of other autoregulatory and regulatory loops that maintain the content and diverse functions of MBNL proteins at optimal level in health and disease, thus supporting the overall cellular homeostasis.

  9. Dynamical Casimir effect and loop corrections

    Science.gov (United States)

    Akhmedov, E. T.; Alexeev, S. O.

    2017-09-01

    We calculate quantum loop corrections to the stress-energy flux caused by moving mirrors. We consider massless, self-interacting, ϕ4, real scalar theory. In these calculations we encounter new and quite unexpected subtleties due to the absence of global hyperbolicity in the presence of mirrors. We attempt to clearly phrase as many hidden assumptions and complications as possible that appear while solving the problem in question. On top of that, we find that quantum loop corrections to the stress-energy flux grow with time and are not suppressed in comparison with the semiclassical contributions. Thus, we observe the breakdown of the perturbation theory, and we discuss its physical origin and ways to deal with such a situation. As a byproduct, we observe a similarity of the problem in question with that for the minimally coupled, massless scalar field in de Sitter space.

  10. The gluon beam function at two loops

    Science.gov (United States)

    Gaunt, Jonathan R.; Stahlhofen, Maximilian; Tackmann, Frank J.

    2014-08-01

    The virtuality-dependent beam function is a universal ingredient in the resummation for observables probing the virtuality of incoming partons, including N -jettiness and beam thrust. We compute the gluon beam function at two-loop order. Together with our previous results for the two-loop quark beam function, this completes the full set of virtuality-dependent beam functions at next-to-next-to-leading order (NNLO). Our results are required to account for all collinear initial-state radiation effects on the N -jettiness event shape through N3LL order. We present numerical results for both the quark and gluon beam functions up to NNLO and N3LL order. Numerically, the NNLO matching corrections are important. They reduce the residual matching scale dependence in the resummed beam function by about a factor of two.

  11. The gluon beam function at two loops

    Energy Technology Data Exchange (ETDEWEB)

    Gaunt, Jonathan R.; Stahlhofen, Maximilian; Tackmann, Frank J. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Theory Group

    2014-05-15

    The virtuality-dependent beam function is a universal ingredient in the resummation for observables probing the virtuality of incoming partons, including N-jettiness and beam thrust. We compute the gluon beam function at two-loop order. Together with our previous results for the two-loop quark beam function, this completes the full set of virtuality-dependent beam functions at next-to-next-to-leading order (NNLO). Our results are required to account for all collinear ISR effects to the N-jettiness event shape through N{sup 3}LL order. We present numerical results for both the quark and gluon beam functions up to NNLO and N{sup 3}LL order. Numerically, the NNLO matching corrections are important. They reduce the residual matching scale dependence in the resummed beam function by about a factor of two.

  12. Harmonic Oscillator SUSY Partners and Evolution Loops

    Directory of Open Access Journals (Sweden)

    David J. Fernández

    2012-07-01

    Full Text Available Supersymmetric quantum mechanics is a powerful tool for generating exactly solvable potentials departing from a given initial one. If applied to the harmonic oscillator, a family of Hamiltonians ruled by polynomial Heisenberg algebras is obtained. In this paper it will be shown that the SUSY partner Hamiltonians of the harmonic oscillator can produce evolution loops. The corresponding geometric phases will be as well studied.

  13. Two-loop statsum of superstrings

    Science.gov (United States)

    Morozov, A.

    1988-06-01

    We discuss, whether there is a choice of odd moduli on super-Riemann surfaces of genus p≳2, which leads to the vanishing of statistical sums of superstrings before integration over the space of even moduli. The answer is shown to be positive at least for p=2, when odd moduli are localized at ramification points. The relation between various definitions of many-loop statistical sums in superstring theory is discussed.

  14. Activation of Bvg-Repressed Genes in Bordetella pertussis by RisA Requires Cross Talk from Noncooperonic Histidine Kinase RisK.

    Science.gov (United States)

    Chen, Qing; Ng, Victoria; Warfel, Jason M; Merkel, Tod J; Stibitz, Scott

    2017-11-15

    The two-component response regulator RisA, encoded by open reading frame BP3554 in the Bordetella pertussis Tohama I genomic sequence, is a known activator of vrg genes, a set of genes whose expression is increased under the same environmental conditions (known as modulation) that result in repression of the bvgAS virulence regulon. Here we demonstrate that RisA is phosphorylated in vivo and that RisA phosphorylation is required for activation of vrg genes. An adjacent histidine kinase gene, risS , is truncated by frameshift mutation in B. pertussis but not in Bordetella bronchiseptica or Bordetella parapertussis Neither deletion of risS ' or bvgAS nor phenotypic modulation with MgSO 4 affected levels of phosphorylated RisA (RisA∼P) in B. pertussis However, RisA phosphorylation did require the histidine kinase encoded by BP3223, here named RisK (cognate histidine kinase of RisA). RisK was also required for expression of the vrg genes. This requirement could be obviated by the introduction of the phosphorylation-mimicking RisA D60E mutant, indicating that an active conformation of RisA, but not phosphorylation per se , is crucial for vrg activation. Interestingly, expression of vrg genes is still modulated by MgSO 4 in cells harboring the RisA D60E mutation, suggesting that the activated RisA senses additional signals to control vrg expression in response to environmental stimuli. IMPORTANCE In B. pertussis , the BvgAS two-component system activates the expression of virulence genes by binding of BvgA∼P to their promoters. Expression of the reciprocally regulated vrg genes requires RisA and is also repressed by the Bvg-activated BvgR. RisA is an OmpR-like response regulator, but RisA phosphorylation was not expected because the gene for its presumed, cooperonic, histidine kinase is inactivated by mutation. In this study, we demonstrate phosphorylation of RisA in vivo by a noncooperonic histidine kinase. We also show that RisA phosphorylation is necessary but not

  15. Transverse loop colostomy and colonic motility.

    Science.gov (United States)

    Pucciani, F; Ringressi, M N; Maltinti, G; Bechi, P

    2014-11-01

    The motility of the defunctionalized colon, distal to transverse loop colostomy, has never been studied "in vivo." The aim of our study was to evaluate the influence of transverse loop colostomy on colonic motility. Thirteen patients were examined before stoma closure by means of clinical evaluation and colonic manometry; we studied both the right and distal colon in both fasting and fed patients in order to detect motor activity. Quantitative and qualitative manometric analyses showed that the diverted colon had motor activity even if no regular colonic motor pattern was observed. The spreading of aboral propagated contractions (PCs) was sometimes recorded from the right colon to the distal colon. The response of the proximal and distal colon to a standard meal, when compared to fasting values, increased more than 40 and 35 %, respectively. Stool and gas ejections from the colostomy were never related to a particular type of colonic motility: Motor quiescence such as PCs was chaotically related to stool escape. In conclusion, motility of the defunctionalized colon is preserved in patients with transverse loop colostomy.

  16. Leptogenesis from loop effects in curved spacetime

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, Jamie I.; Shore, Graham M. [Department of Physics, Swansea University,Singleton Park, Swansea, SA2 8PP (United Kingdom)

    2016-04-05

    We describe a new mechanism — radiatively-induced gravitational leptogenesis — for generating the matter-antimatter asymmetry of the Universe. We show how quantum loop effects in C and CP violating theories cause matter and antimatter to propagate differently in the presence of gravity, and prove this is forbidden in flat space by CPT and translation symmetry. This generates a curvature-dependent chemical potential for leptons, allowing a matter-antimatter asymmetry to be generated in thermal equilibrium in the early Universe. The time-dependent dynamics necessary for leptogenesis is provided by the interaction of the virtual self-energy cloud of the leptons with the expanding curved spacetime background, which violates the strong equivalence principle and allows a distinction between matter and antimatter. We show here how this mechanism is realised in a particular BSM theory, the see-saw model, where the quantum loops involve the heavy sterile neutrinos responsible for light neutrino masses. We demonstrate by explicit computation of the relevant two-loop Feynman diagrams how the size of the radiative corrections relevant for leptogenesis becomes enhanced by increasing the mass hierarchy of the sterile neutrinos, and show how the induced lepton asymmetry may be sufficiently large to play an important rôle in determining the baryon-to-photon ratio of the Universe.

  17. Quantum Loop Topography for Machine Learning

    Science.gov (United States)

    Zhang, Yi; Kim, Eun-Ah

    2017-05-01

    Despite rapidly growing interest in harnessing machine learning in the study of quantum many-body systems, training neural networks to identify quantum phases is a nontrivial challenge. The key challenge is in efficiently extracting essential information from the many-body Hamiltonian or wave function and turning the information into an image that can be fed into a neural network. When targeting topological phases, this task becomes particularly challenging as topological phases are defined in terms of nonlocal properties. Here, we introduce quantum loop topography (QLT): a procedure of constructing a multidimensional image from the "sample" Hamiltonian or wave function by evaluating two-point operators that form loops at independent Monte Carlo steps. The loop configuration is guided by the characteristic response for defining the phase, which is Hall conductivity for the cases at hand. Feeding QLT to a fully connected neural network with a single hidden layer, we demonstrate that the architecture can be effectively trained to distinguish the Chern insulator and the fractional Chern insulator from trivial insulators with high fidelity. In addition to establishing the first case of obtaining a phase diagram with a topological quantum phase transition with machine learning, the perspective of bridging traditional condensed matter theory with machine learning will be broadly valuable.

  18. Leptogenesis from loop effects in curved spacetime

    Science.gov (United States)

    McDonald, Jamie I.; Shore, Graham M.

    2016-04-01

    We describe a new mechanism — radiatively-induced gravitational leptogenesis — for generating the matter-antimatter asymmetry of the Universe. We show how quantum loop effects in C and CP violating theories cause matter and antimatter to propagate differently in the presence of gravity, and prove this is forbidden in flat space by CPT and translation symmetry. This generates a curvature-dependent chemical potential for leptons, allowing a matter-antimatter asymmetry to be generated in thermal equilibrium in the early Universe. The time-dependent dynamics necessary for leptogenesis is provided by the interaction of the virtual self-energy cloud of the leptons with the expanding curved spacetime background, which violates the strong equivalence principle and allows a distinction between matter and antimatter. We show here how this mechanism is realised in a particular BSM theory, the see-saw model, where the quantum loops involve the heavy sterile neutrinos responsible for light neutrino masses. We demonstrate by explicit computation of the relevant two-loop Feynman diagrams how the size of the radiative corrections relevant for leptogenesis becomes enhanced by increasing the mass hierarchy of the sterile neutrinos, and show how the induced lepton asymmetry may be sufficiently large to play an important rôle in determining the baryon-to-photon ratio of the Universe.

  19. The quark beam function at two loops

    Science.gov (United States)

    Gaunt, Jonathan R.; Stahlhofen, Maximilian; Tackmann, Frank J.

    2014-04-01

    In differential measurements at a hadron collider, collinear initial-state radiation is described by process-independent beam functions. They are the field-theoretic analog of initial-state parton showers. Depending on the measured observable they are differential in the virtuality and/or transverse momentum of the colliding partons in addition to the usual longitudinal momentum fraction. Perturbatively, the beam functions can be calculated by matching them onto standard quark and gluon parton distribution functions. We calculate the inclusive virtuality-dependent quark beam function at NNLO, which is relevant for any observables probing the virtuality of the incoming partons, including N -jettiness and beam thrust. For such observables, our results are an important ingredient in the resummation of large logarithms at N3LL order, and provide all contributions enhanced by collinear t-channel singularities at NNLO for quark-initiated processes in analytic form. We perform the calculation in both Feynman and axial gauge and use two different methods to evaluate the discontinuity of the two-loop Feynman diagrams, providing nontrivial checks of the calculation. As part of our results we reproduce the known two-loop QCD splitting functions and confirm at two loops that the virtuality-dependent beam and final-state jet functions have the same anomalous dimension.

  20. The quark beam function at two loops

    Energy Technology Data Exchange (ETDEWEB)

    Gaunt, Jonathan R.; Stahlhofen, Maximilian; Tackmann, Frank J.

    2014-01-15

    In differential measurements at a hadron collider, collinear initial-state radiation is described by process-independent beam functions. They are the field-theoretic analog of initial-state parton showers. Depending on the measured observable they are differential in the virtuality and/or transverse momentum of the colliding partons in addition to their usual longitudinal momentum fractions. Perturbatively, the beam functions can be calculated by matching them onto standard quark and gluon parton distribution functions. We calculate the inclusive virtuality-dependent quark beam function at NNLO, which is relevant for any observables probing the virtuality of the incoming partons, including N-jettiness and beam thrust. For such observables, our results are an important ingredient in the resummation of large logarithms at N{sup 3}LL order, and provide all contributions enhanced by collinear t-channel singularities at NNLO for quark-initiated processes in analytic form. We perform the calculation in both Feynman and axial gauge and use two different methods to evaluate the discontinuity in the two-loop Feynman diagrams, providing nontrivial checks of the calculation. As part of our results we reproduce the known two-loop QCD splitting functions and confirm at two loops that the virtuality-dependent beam and final-state jet functions have the same anomalous dimension.

  1. The quark beam function at two loops

    Energy Technology Data Exchange (ETDEWEB)

    Gaunt, Jonathan R.; Stahlhofen, Maximilian; Tackmann, Frank J. [Theory Group, Deutsches Elektronen-Synchrotron (DESY),D-22607 Hamburg (Germany)

    2014-04-16

    In differential measurements at a hadron collider, collinear initial-state radiation is described by process-independent beam functions. They are the field-theoretic analog of initial-state parton showers. Depending on the measured observable they are differential in the virtuality and/or transverse momentum of the colliding partons in addition to the usual longitudinal momentum fraction. Perturbatively, the beam functions can be calculated by matching them onto standard quark and gluon parton distribution functions. We calculate the inclusive virtuality-dependent quark beam function at NNLO, which is relevant for any observables probing the virtuality of the incoming partons, including N-jettiness and beam thrust. For such observables, our results are an important ingredient in the resummation of large logarithms at N{sup 3}LL order, and provide all contributions enhanced by collinear t-channel singularities at NNLO for quark-initiated processes in analytic form. We perform the calculation in both Feynman and axial gauge and use two different methods to evaluate the discontinuity of the two-loop Feynman diagrams, providing nontrivial checks of the calculation. As part of our results we reproduce the known two-loop QCD splitting functions and confirm at two loops that the virtuality-dependent beam and final-state jet functions have the same anomalous dimension.

  2. Immobilization of Yarrowia lipolytica lipase Ylip2 for the biocatalytic synthesis of phytosterol ester in a water activity controlled reactor.

    Science.gov (United States)

    Cui, Caixia; Guan, Nan; Xing, Chen; Chen, Biqiang; Tan, Tianwei

    2016-10-01

    In this work, phytosterol ester was synthesized using Yarrowia lipolytica lipase Ylip2 that had been immobilized on inorganic support in a solvent-free system and reacted in a computer-aided water activity controlled bioreactor. The immobilization of Ylip2 on celite led to a remarkable increase in the phytosterol conversion compared to that of free lipase. An investigation of the reaction conditions were oleic acid as the fatty acid variety, 10,000U/g substrate, and a temperature of 50°C for phytosterol ester synthesis. Controlling of the water activity at a set point was accomplished by the introduction of dry air through the reaction medium at a digital feedback controlled flow rate. For the esterification of phytosterol ester, a low (15%) water activity resulted in a considerable improvement in phytosterol conversion (91.1%) as well as a decreased reaction time (78h). Furthermore, Ylip2 lipase immobilized on celite retained 90% esterification activity for the synthesis of phytosterol oleate after reused 8 cycles, while free lipase was only viable for 5 batches with 90% esterification activity remained. Finally, the phytosterol oleate space time yield increased from 1.65g/L/h with free lipase to 2.53g/L/h with immobilized lipase. These results illustrate that the immobilized Yarrowia lipolytica lipase Ylip2 in a water activity controlled reactor has great potential for the application in phytosterol esters synthesis. Copyright © 2016. Published by Elsevier B.V.

  3. Changes in Upper Extremity Range of Motion and Efficiency in Multiple Sclerosis Patients Due to Water Activity.

    Science.gov (United States)

    Duthie, Pamela Rae

    To determine the effects of water exercise on the movements of multiple sclerosis patients, this study utilized tests to determine changes in the linear range of motion of the shoulder, elbow, and wrist after a 45-minute period of water activities and to determine if the movement became more effective. The test used was an overhead throw with a…

  4. Gravitational smoothing of kinks on cosmic string loops

    CERN Document Server

    Wachter, Jeremy M

    2016-01-01

    We analyze the effect of gravitational back reaction on cosmic string loops with kinks, which is an important determinant of the shape, and thus the potential observability, of string loops which may exist in the universe today. Kinks are not rounded off, but may be straightened out. In some loops, symmetries prevent even this process, so that the loop evaporates in a self-similar fashion and the kinks are unchanged. As an example, we give results for the rectangular Garfinkle-Vachaspati loop.

  5. On Vanishing Two Loop Cosmological Constants in Nonsupersymmetric Strings

    Energy Technology Data Exchange (ETDEWEB)

    Kachru, S

    1998-10-22

    It has recently been suggested that in certain special nonsupersymmetric type II string compactifications, at least the first two perturbative contributions to the cosmological constant Lambda vanish. Support for perturbative vanishing beyond 1-loop (as well as evidence for the absence of some nonperturbative contributions) has come from duality arguments. There was also a direct 2-loop computation which was incomplete; in this note we explain the deficiency of the previous 2-loop calculation and discuss the complete 2-loop computation in two different models. The corrected analysis yields a vanishing 2-loop contribution to Lambda in these models.

  6. Simulaciones numéricas en modelos de loops

    OpenAIRE

    Serna Martínez, Pablo

    2014-01-01

    El objetivo de esta tesis consiste en el estudio de varias familias de modelos de loops en dos y tres dimensiones, donde se encuentran dos fases diferentes: una con loops finitos y otra donde hay al menos uno infinito. En concreto, se han estudiado tres clases de modelos de loops. El primero, un modelo de loops tridimensionales con orientación y color, definidos en redes con número de coordinación cuatro. El segundo, una modificación de estos modelos de loops que es un firme candidato ...

  7. On the loop-loop scattering amplitudes in Abelian and non-Abelian gauge theories

    Energy Technology Data Exchange (ETDEWEB)

    Meggiolaro, Enrico [Dipartimento di Fisica, Universita di Pisa, Largo Pontecorvo 3, I-56127 Pisa (Italy)]. E-mail: enrico.meggiolaro@df.unipi.it

    2005-02-14

    The high-energy elastic scattering amplitude of two colour-singlet qq-bar pairs is governed by the correlation function of two Wilson loops, which follow the classical straight lines for quark (antiquark) trajectories. This quantity is expected to be free of IR divergences, differently from what happens for the parton-parton elastic scattering amplitude, described, in the high-energy limit, by the expectation value of two Wilson lines. We shall explicitly test this IR finiteness by a direct non-perturbative computation of the loop-loop scattering amplitudes in the (pedagogic, but surely physically interesting) case of quenched QED. The results obtained for the Abelian case will be generalized to the case of a non-Abelian gauge theory with Nc colours, but stopping to the order O(g4) in perturbation theory. In connection with the above-mentioned IR finiteness, we shall also discuss some analytic properties of the loop-loop scattering amplitudes in both Abelian and non-Abelian gauge theories, when going from Minkowskian to Euclidean theory, which can be relevant to the still unsolved problem of the s-dependence of hadron-hadron total cross-sections.

  8. In Vivo Neuroprotective Effect of Histidine-Tryptophan-Ketoglutarate Solution in an Ischemia/Reperfusion Spinal Cord Injury Animal Model

    Directory of Open Access Journals (Sweden)

    Shin Kwang Kang

    2016-08-01

    Full Text Available Background: Paraplegia is a devastating complication following operations on the thoracoabdominal aorta. We investigated whether histidine-tryptophan-ketoglutarate (HTK solution could reduce the extent of ischemia/reperfusion (IR spinal cord injuries in a rat model using a direct delivery method. Methods: Twenty-four Sprague-Dawley male rats were randomly divided into four groups. The sham group (n=6 underwent a sham operation, the IR group (n=6 underwent only an aortic occlusion, the saline infusion group (saline group, n=6 underwent an aortic occlusion and direct infusion of cold saline into the occluded aortic segment, and the HTK infusion group (HTK group, n=6 underwent an aortic occlusion and direct infusion of cold HTK solution into the occluded aortic segment. An IR spinal cord injury was induced by transabdominal clamping of the aorta distally to the left renal artery and proximally to the aortic bifurcation for 60 minutes. A neurological evaluation of locomotor function was performed using the modified Tarlov score after 48 hours of reperfusion. The spinal cord was harvested for histopathological and immunohistochemical examinations. Results: The spinal cord IR model using direct drug delivery in rats was highly reproducible. The Tarlov score was 4.0 in the sham group, 1.17±0.75 in the IR group, 1.33±1.03 in the saline group, and 2.67±0.81 in the HTK group (p=0.04. The histopathological analysis of the HTK group showed reduced neuronal cell death. Conclusion: Direct infusion of cold HTK solution into the occluded aortic segment may reduce the extent of spinal cord injuries in an IR model in rats.

  9. Sensitive detection of biothiols and histidine based on the recovered fluorescence of the carbon quantum dots–Hg(II) system

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Juan; Zhang, Fengshuang; Yan, Xu; Wang, Long; Yan, Jin [College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Ding, Hong [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Ding, Lan, E-mail: dinglan@jlu.edu.cn [College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012 (China)

    2015-02-15

    Highlights: • Carbon quantum dots-based probe was used for detection of GSH, Cys or His. • The fluorescence of CQDs was quenched by Hg(II) and then recovered by GSH, Cys or His. • No further surface modification or purification of CQDs was required. • This sensor exhibits superior accuracy and sensitivity. • The proposed method was simple in design, fast in operation. - Abstract: In this paper, we presented a novel, rapid and highly sensitive sensor for glutathione (GSH), cysteine (Cys) and histidine (His) based on the recovered fluorescence of the carbon quantum dots (CQDs)–Hg(II) system. The CQDs were synthesized by microwave-assisted approach in one pot according to our previous report. The fluorescence of CQDs could be quenched in the presence of Hg(II) due to the coordination occurring between Hg(II) and functional groups on the surface of CQDs. Subsequently, the fluorescence of the CQDs–Hg(II) system was recovered gradually with the addition of GSH, Cys or His due to their stronger affinity with Hg(II). A good linear relationship was obtained from 0.10 to 20 μmol L{sup −1} for GSH, from 0.20 to 45 μmol L{sup −1} for Cys and from 0.50 to 60 μmol L{sup −1} for His, respectively. This method has been successfully applied to the trace detection of GSH, Cys or His in human serum samples with satisfactory results. The proposed method was simple in design and fast in operation, which demonstrated great potential in bio-sensing fields.

  10. The peripheral binding of 14-3-3γ to membranes involves isoform-specific histidine residues.

    Directory of Open Access Journals (Sweden)

    Helene J Bustad

    Full Text Available Mammalian 14-3-3 protein scaffolds include seven conserved isoforms that bind numerous phosphorylated protein partners and regulate many cellular processes. Some 14-3-3-isoforms, notably γ, have elevated affinity for membranes, which might contribute to modulate the subcellular localization of the partners and substantiate the importance of investigating molecular mechanisms of membrane interaction. By applying surface plasmon resonance we here show that the binding to phospholipid bilayers is stimulated when 14-3-3γ is complexed with its partner, a peptide corresponding to the Ser19-phosphorylated N-terminal region of tyrosine hydroxylase. Moreover, membrane interaction is dependent on salts of kosmotropic ions, which also stabilize 14-3-3γ. Electrostatic analysis of available crystal structures of γ and of the non-membrane-binding ζ-isoform, complemented with molecular dynamics simulations, indicate that the electrostatic potential distribution of phosphopeptide-bound 14-3-3γ is optimal for interaction with the membrane through amphipathic helices at the N-terminal dimerization region. In addition, His158, and especially His195, both specific to 14-3-3γ and located at the convex lateral side, appeared to be pivotal for the ligand induced membrane interaction, as corroborated by site-directed mutagenesis. The participation of these histidine residues might be associated to their increased protonation upon membrane binding. Overall, these results reveal membrane-targeting motifs and give insights on mechanisms that furnish the 14-3-3γ scaffold with the capacity for tuned shuffling from soluble to membrane-bound states.

  11. Expression and functional analysis of genes encoding cytokinin receptor-like histidine kinase in maize (Zea mays L.).

    Science.gov (United States)

    Wang, Bo; Chen, Yanhong; Guo, Baojian; Kabir, Muhammad Rezaul; Yao, Yingyin; Peng, Huiru; Xie, Chaojie; Zhang, Yirong; Sun, Qixin; Ni, Zhongfu

    2014-08-01

    Cytokinin signaling is vital for plant growth and development which function via the two-component system (TCS). As one of the key component of TCS, transmembrane histidine kinases (HK) are encoded by a small gene family in plants. In this study, we focused on expression and functional analysis of cytokinin receptor-like HK genes (ZmHK) in maize. Firstly, bioinformatics analysis revealed that seven cloned ZmHK genes have different expression patterns during maize development. Secondly, ectopic expression by CaMV35S promoter in Arabidopsis further revealed that functional differentiation exists among these seven members. Among them, the ZmHK1a2-OX transgenic line has the lowest germination rate in the dark, ZmHK1-OX and ZmHK2a2-OX can delay leaf senescence, and seed size of ZmHK1-OX, ZmHK1a2-OX, ZmHK2-OX, ZmHK3b-OX and ZmHK2a2-OX was obviously reduced as compared to wild type. Additionally, ZmHK genes play opposite roles in shoot and root development; all ZmHK-OX transgenic lines display obvious shorter root length and reduced number of lateral roots, but enhanced shoot development compared with the wild type. Most notably, Arabidopsis response regulator ARR5 gene was up-regulated in ZmHK1-OX, ZmHK1a2-OX, ZmHK2-OX, ZmHK3b-OX and ZmHK2a2-OX as compared to wild type. Although the causal link between ZmHK genes and cytokinin signaling pathway is still an area to be further elucidated, these findings reflected that the diversification of ZmHK genes expression patterns and functions occurred in the course of maize evolution, indicating that some ZmHK genes might play different roles during maize development.

  12. Gauge and Gravity Amplitudes from Trees to Loops

    DEFF Research Database (Denmark)

    Huang, Rijun

    This thesis describes two subjects that I mainly work on during my PhD study. They are both about scattering amplitudes, covering gravity and gauge theories, tree and loop level, with or without supersymmetry. The rst subject is Kawai-Lewellen-Tye(KLT) relation in field theory, which mysteriously...... a special type of two-loop and three-loop diagrams where equations of maximal unitarity cut de ne complex curve. Geometry genus of complex curve is a topological invariant, and characterizes the property of curve. We compute the genus of complex curve for some two-loop and three-loop diagrams from...... for vanishing identities of Yang-Mills amplitudes as violation of linear symmetry groups based on KLT relation argument. The second subject is integrand reduction of multi-loop amplitude. The recent methods based on computational algebraic geometry make it possible to systematically study multi-loop amplitude...

  13. Optimatization of loop heat pipe for cooling of electrotechnical box

    Science.gov (United States)

    Roman, Banovcan; Tomas, Puchor; Andrej, Kapjor; Milan, Malcho

    2017-09-01

    The paper deals with use of LOOP thermosyphon heat pipe to transfer heat from electrotechnical box and describe of construction individual types of LOOP heat pipes. The LOOP heat pipe is very good cooling device which requires no mechanical parts in their design. LOOP heat pipe use only phase change during heat transfer, without a compressor, fan or pump. LOOP heat pipe is more energy saving compared to conventional cooling systems with forced convection. The main advantage of cooling by heat pipe is that electrotechnical box can be hermetically closed (dust -free construction), because dust reduces the lifetime of electrotechnical elements in box. Lifetime of LOOP heat pipe equals to the lifetime of construction material. The paper describes mathematical model of LOOP thermosyphon heat pipe (condenser). Compares selected types of working fluids which are filled with a heat pipe and construction materials of heat pipe.

  14. Modelling thermal inactivation of Listeria monocytogenes in sucrose solutions of various water activities.

    Science.gov (United States)

    Fernández, A; López, M; Bernardo, A; Condón, S; Raso, J

    2007-06-01

    The heat resistance of Listeria monocytogenes was determined in sucrose solutions with water activity (a(w)) ranging from 0.99 to 0.90. At all temperatures investigated shape of the survival curves depended on the a(w) of the treatment medium. The survival curves for a(w)=0.99 appeared to be linear, for a(w)=0.96 were slightly upwardly concaved and for a(w)=0.93 and 0.90 were markedly concave upward. A mathematical model based on the Weibull distribution provided a good fit for all the survival curves obtained in this investigation. The effect of the temperature and a(w) on the Weibull model parameters was also studied. The shape parameter (p) depended on the a(w) of the treatment medium but in each medium of different a(w) the temperature did not have a significant effect on this parameter. The p parameter followed a linear relationship with a(w). The scale parameter (delta) decreased with the temperature following an exponential relationship and increased by decreasing the a(w) in the range from 0.99 to 0.93. However the delta parameter of survival curves obtained at a(w)=0.90 were lower than those obtained at a(w)=0.93. A mathematical model based on the Weibull parameters was built to describe the joint effect of temperature and a(w) on thermal inactivation of L. monocytogenes. This model provides a more complete information on the influence of the a(w) on the L. monocytogenes than the data initially generated. The model developed indicated that the effect of the a(w) on the thermal resistance of L. monocytogenes varied depending upon the temperature of treatment.

  15. Analytical on shell QED results 3-loop vacuum polarization, 4-loop $\\beta$-function and the muon anomaly

    CERN Document Server

    Broadhurst, D J; Tarasov, O V

    1993-01-01

    We present the results of analytical calculations of the 3-loop contributions to the asymptotic photon vacuum polarization function, in the on shell scheme, and of the 4-loop contributions to the on shell QED beta-function. These are used to evaluate various 4-loop and 5-loop contributions to the muon anomaly. Our analytical contributions to (g-2)_\\mu differ significantly from previous numerical results. A very recent numerical re-evaluation of 4-loop muon-anomaly contributions has yielded results much closer to ours.

  16. Current systems of coronal loops in 3D MHD simulations

    Science.gov (United States)

    Warnecke, J.; Chen, F.; Bingert, S.; Peter, H.

    2017-11-01

    Aims: We study the magnetic field and current structure associated with a coronal loop. Through this we investigate to what extent the assumptions of a force-free magnetic field break down and where they might be justified. Methods: We analyze a three-dimensional (3D) magnetohydrodynamic (MHD) model of the solar corona in an emerging active region with the focus on the structure of the forming coronal loops. The lower boundary of this simulation is taken from a model of an emerging active region. As a consequence of the emerging magnetic flux and the horizontal motions at the surface a coronal loop forms self-consistently. We investigate the current density along magnetic field lines inside (and outside) this loop and study the magnetic and plasma properties in and around this loop. The loop is defined as the bundle of field lines that coincides with enhanced emission in extreme UV. Results: We find that the total current along the emerging loop changes its sign from being antiparallel to parallel to the magnetic field. This is caused by the inclination of the loop together with the footpoint motion. Around the loop, the currents form a complex non-force-free helical structure. This is directly related to a bipolar current structure at the loop footpoints at the base of the corona and a local reduction of the background magnetic field (I.e., outside the loop) caused by the plasma flow into and along the loop. Furthermore, the locally reduced magnetic pressure in the loop allows the loop to sustain a higher density, which is crucial for the emission in extreme UV. The action of the flow on the magnetic field hosting the loop turns out to also be responsible for the observed squashing of the loop. Conclusions: The complex magnetic field and current system surrounding it can only be modeled in 3D MHD models where the magnetic field has to balance the plasma pressure. A one-dimensional coronal loop model or a force-free extrapolation cannot capture the current system

  17. Pemakaian Crown Loop dan Band Loop di Rahang Bawah Anak Usia Enam Tahun (Laporan Kasus

    Directory of Open Access Journals (Sweden)

    Rivi Isabela

    2015-11-01

    Full Text Available The function of space maintainer is to preserve arch length following the premature loss of a primary teeth. Early loss of primary tooth may compromise the eruption of succedaneous teeth if there is a reduction in the arch length. The Band and Crown Loop are used to maintain the loss of primary molar. The report describe a 6 year old girl who has premature loss of second left mandibular primary molar and first right mandibular primary molar treated using crown and band loop space maintainer. The patient still has mastication function from other posterior primary teeth.

  18. The 1/2 BPS Wilson loop in ABJM theory at two loops

    OpenAIRE

    Bianchi, Marco S.; Giribet, Gaston Enrique; Leoni Olivera, Matías; Penati, Silvia

    2013-01-01

    We compute the expectation value of the 1/2 BPS circular Wilson loop in ABJM theory at two loops in perturbation theory. The result shows perfect agreement with the prediction from localization and the proposed framing factor. Fil: Bianchi, Marco S.. Institut für Physik. Humboldt-Universität zu Berlin; Alemania; Fil: Giribet, Gaston Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Bue...

  19. LISA Pathfinder closed-loop analysis: a model breakdown of the in-loop observables

    Science.gov (United States)

    LISA Pathfinder Collaboration

    2017-05-01

    This paper describes a methodology to analyze, in the frequency domain, the steady-state control performances of the LISA Pathfinder mission. In particular, it provides a technical framework to give a comprehensive understanding of the spectra of all the degrees of freedom by breaking them down into their various physical origins, hence bringing out the major contributions of the control residuals. A reconstruction of the measured in-loop output, extracted from a model of the closed-loop system, is shown as an instance to illustrate the potential of such a model breakdown of the data.

  20. Open-loop and closed-loop control of flying qubits

    Energy Technology Data Exchange (ETDEWEB)

    Lucamarini, M; Di Giuseppe, G; Vitali, D; Tombesi, P, E-mail: marco.lucamarini@unicam.it [School of Science and Technology, Physics Division, University of Camerino, I-62032 Camerino (Italy)

    2011-08-14

    We describe two recent techniques, along with related experiments, to control and reduce the noise affecting a photon polarization qubit. The first is based on the open-loop 'bang-bang' method, where suitably tailored pulses are implemented on the system to prevent polarization decoherence. This requires only passive elements when the physical system is a photon and the operation is performed in space rather than in time. The second technique is based on closed-loop 'asymmetric feedback', where some quantities are measured and used for a real-time correction of the system dynamics. This technique necessarily requires active electronics to work.