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Sample records for ion binding properties

  1. Ion exchanger in the brain: Quantitative analysis of perineuronally fixed anionic binding sites suggests diffusion barriers with ion sorting properties

    Science.gov (United States)

    Morawski, Markus; Reinert, Tilo; Meyer-Klaucke, Wolfram; Wagner, Friedrich E.; Tröger, Wolfgang; Reinert, Anja; Jäger, Carsten; Brückner, Gert; Arendt, Thomas

    2015-12-01

    Perineuronal nets (PNs) are a specialized form of brain extracellular matrix, consisting of negatively charged glycosaminoglycans, glycoproteins and proteoglycans in the direct microenvironment of neurons. Still, locally immobilized charges in the tissue have not been accessible so far to direct observations and quantifications. Here, we present a new approach to visualize and quantify fixed charge-densities on brain slices using a focused proton-beam microprobe in combination with ionic metallic probes. For the first time, we can provide quantitative data on the distribution and net amount of pericellularly fixed charge-densities, which, determined at 0.4-0.5 M, is much higher than previously assumed. PNs, thus, represent an immobilized ion exchanger with ion sorting properties high enough to partition mobile ions in accord with Donnan-equilibrium. We propose that fixed charge-densities in the brain are involved in regulating ion mobility, the volume fraction of extracellular space and the viscosity of matrix components.

  2. Ion binding to biological macromolecules.

    Science.gov (United States)

    Petukh, Marharyta; Alexov, Emil

    2014-11-01

    Biological macromolecules carry out their functions in water and in the presence of ions. The ions can bind to the macromolecules either specifically or non-specifically, or can simply to be a part of the water phase providing physiological gradient across various membranes. This review outlines the differences between specific and non-specific ion binding in terms of the function and stability of the corresponding macromolecules. Furthermore, the experimental techniques to identify ion positions and computational methods to predict ion binding are reviewed and their advantages compared. It is indicated that specifically bound ions are relatively easier to be revealed while non-specifically associated ions are difficult to predict. In addition, the binding and the residential time of non-specifically bound ions are very much sensitive to the environmental factors in the cells, specifically to the local pH and ion concentration. Since these characteristics differ among the cellular compartments, the non-specific ion binding must be investigated with respect to the sub-cellular localization of the corresponding macromolecule.

  3. Cholesterol binding to ion channels

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    Irena eLevitan

    2014-02-01

    Full Text Available Numerous studies demonstrated that membrane cholesterol is a major regulator of ion channel function. The goal of this review is to discuss significant advances that have been recently achieved in elucidating the mechanisms responsible for cholesterol regulation of ion channels. The first major insight that comes from growing number of studies that based on the sterol specificity of cholesterol effects, show that several types of ion channels (nAChR, Kir, BK, TRPV are regulated by specific sterol-protein interactions. This conclusion is supported by demonstrating direct saturable binding of cholesterol to a bacterial Kir channel. The second major advance in the field is the identification of putative cholesterol binding sites in several types of ion channels. These include sites at locations associated with the well-known cholesterol binding motif CRAC and its reversed form CARC in nAChR, BK, and TRPV, as well as novel cholesterol binding regions in Kir channels. Notably, in the majority of these channels, cholesterol is suggested to interact mainly with hydrophobic residues in non-annular regions of the channels being embedded in between transmembrane protein helices. We also discuss how identification of putative cholesterol binding sites is an essential step to understand the mechanistic basis of cholesterol-induced channel regulation. Clearly, however, these are only the first few steps in obtaining a general understanding of cholesterol-ion channels interactions and their roles in cellular and organ functions.

  4. Insights into the binding properties of a cuprous ion embedded in the tren cap of a calix[6]arene and supramolecular trapping of an intermediate.

    Science.gov (United States)

    Izzet, Guillaume; Rager, Marie-Noëlle; Reinaud, Olivia

    2007-02-21

    Coordination of Cu(I) to a tren unit that is covalently linked to a calix[6]arene has been explored. The resulting complex revealed itself very stable in solution under an inert atmosphere, but extremely sensitive to O2 in solution as well as in the solid state. Therefore, its binding properties towards non-redox ligands have been studied in detail. The electron-rich metal center displays moderate affinity for nitrilo ligands compared to the calix[6]tris-pyridine ligand. Indeed, the binding enthalpy with acetonitrile is only -30 kJ mol(-1), whereas it is -72 kJ mol(-1) with the tris-pyridine system. In contrast, CO binding is relatively strong due to important pi-back donation from the metal center, as evidenced by the CO stretch, which was found to be less energetic (2075 cm(-1)) than that measured for ligands based on aromatic donors such as imidazole or pyridine. The conformational and dynamic properties of this calix-system have also been studied in detail. With an empty cavity or with the very small CO guest-ligand, the calix-core undergoes partial self-inclusion leading to dissymmetrical conformations. In contrast, nitrilo ligands act as "shoe-trees" that maintain the calix-core in a C(3v) symmetrical cone conformation. Very interestingly, the variable T study relative to the ligand exchange process highlighted a two-step dissociative pathway, where Cu-N bond cleavage/formation is differentiated from the nitrilo guest expulsion/inclusion from/into the calixarene cavity.

  5. Importance of diffuse metal ion binding to RNA.

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    Tan, Zhi-Jie; Chen, Shi-Jie

    2011-01-01

    RNAs are highly charged polyanionic molecules. RNA structure and function are strongly correlated with the ionic condition of the solution. The primary focus of this article is on the role of diffusive ions in RNA folding. Due to the long-range nature of electrostatic interactions, the diffuse ions can contribute significantly to RNA structural stability and folding kinetics. We present an overview of the experimental findings as well as the theoretical developments on the diffuse ion effects in RNA folding. This review places heavy emphasis on the effect of magnesium ions. Magnesium ions play a highly efficient role in stabilizing RNA tertiary structures and promoting tertiary structural folding. The highly efficient role goes beyond the mean-field effect such as the ionic strength. In addition to the effects of specific ion binding and ion dehydration, ion-ion correlation for the diffuse ions can contribute to the efficient role of the multivalent ions such as the magnesium ions in RNA folding.

  6. Conformational thermodynamics of metal-ion binding to a protein

    Science.gov (United States)

    Das, Amit; Chakrabarti, J.; Ghosh, Mahua

    2013-08-01

    Conformational changes in proteins induced by metal-ions play extremely important role in various cellular processes and technological applications. Dihedral angles are suitable conformational variables to describe microscopic conformations of a biomacromolecule. Here, we use the histograms of the dihedral angles to study the thermodynamics of conformational changes of a protein upon metal-ion binding. Our method applied to Ca2+ ion binding to an important metalloprotein, Calmodulin, reveals different thermodynamic changes in different metal-binding sites. The ligands coordinating to Ca2+ ions also play different roles in stabilizing the metal-ion coordinated protein-structure. Metal-ion binding induce remarkable thermodynamic changes in distant part of the protein via modification of secondary structural elements.

  7. Competing binding of metal ions with protein studied by microdialysis

    Institute of Scientific and Technical Information of China (English)

    GUO; Ming(郭明); KONG; Liang(孔亮); MAO; Xiqin(毛希琴); LI; Xin(历欣); ZOU; Hanfa(邹汉法)

    2002-01-01

    A method has been established to study the competing binding of metal ions with protein by a combined technique of microdialysis with high performance liquid chromatography (HPLC). Ni2+, Cd2+, Zn2+, Cu2+ and human serum albumin (HSA) were chosen as model metal ions and protein. The experimental results show that Ni2+ and Cu2+ share a common primary binding site on HSA, and Zn2+ and Cd2+ share a different common primary binding site from them, but there is a common multi-metal binding site for all of those four metal ions. This method show advantages of fast sampling, easily to be operated and especially to be useful when ideal spectroscopic probes are not available for the study of interaction between protein and metal ions.

  8. Influence of salt ions on binding to molecularly imprinted polymers.

    OpenAIRE

    Kempe, Henrik; Kempe, Maria

    2010-01-01

    Salt ions were found to have an influence on template binding to two model molecularly imprinted polymers (MIPs), targeted to penicillin G and propranolol, respectively, in water-acetonitrile mixtures. Water was detrimental to rebinding of penicillin G whereas propranolol bound in the entire water-acetonitrile range tested. In 100% aqueous solution, 3-M salt solutions augmented the binding of both templates. The effects followed the Hofmeister series with kosmotropic ions promoting the larges...

  9. Ion-binding of glycine zwitterion with inorganic ions in biologically relevant aqueous electrolyte solutions.

    Science.gov (United States)

    Fedotova, Marina V; Kruchinin, Sergey E

    2014-06-01

    The ion-binding between inorganic ions and charged functional groups of glycine zwitter-ion in NaCl(aq), KCl(aq), MgCl2(aq), and CaCl2(aq) has been investigated over a wide salt concentration range by using integral equation theory in the 3D-RISM approach. These systems mimic biological systems where binding of ions to charged residues at protein surfaces is relevant. It has been found that the stability of ion pairs formed by the carboxylate group and added inorganic cations decreases in the sequence Mg(2+)>Ca(2+)>Na(+)>K(+). However, all formed ion pairs are weak and decrease in stability with increasing salt concentration. On the other hand, at a given salt concentration the stability of (-NH3(+):Cl(-))aq ion pairs is similar in all studied systems. The features of ion-binding and the salt concentration effect on this process are discussed.

  10. An entropic mechanism of generating selective ion binding in macromolecules.

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    Michael Thomas

    Full Text Available Several mechanisms have been proposed to explain how ion channels and transporters distinguish between similar ions, a process crucial for maintaining proper cell function. Of these, three can be broadly classed as mechanisms involving specific positional constraints on the ion coordinating ligands which arise through: a "rigid cavity", a 'strained cavity' and 'reduced ligand fluctuations'. Each operates in subtly different ways yet can produce markedly different influences on ion selectivity. Here we expand upon preliminary investigations into the reduced ligand fluctuation mechanism of ion selectivity by simulating how a series of model systems respond to a decrease in ligand thermal fluctuations while simultaneously maintaining optimal ion-ligand binding distances. Simple abstract-ligand models, as well as simple models based upon the ion binding sites in two amino acid transporters, show that limiting ligand fluctuations can create ion selectivity between Li(+, Na(+ and K(+ even when there is no strain associated with the molecular framework accommodating the different ions. Reducing the fluctuations in the position of the coordinating ligands contributes to selectivity toward the smaller of two ions as a consequence of entropic differences.

  11. Production and Characterization of Desmalonichrome Relative Binding Affinity for Uranyl Ions in Relation to Other Siderophores

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Kai-For; Dai, Ziyu; Wunschel, David S.

    2016-06-24

    Siderophores are Fe binding secondary metabolites that have been investigated for their uranium binding properties. Much of the previous work has focused on characterizing hydroxamate types of siderophores, such as desferrioxamine B, for their uranyl binding affinity. Carboxylate forms of these metabolites hold potential to be more efficient chelators of uranyl, yet they have not been widely studied and are more difficult to obtain. Desmalonichrome is a carboxylate siderophore which is not commercially available and so was obtained from the ascomycete fungus Fusarium oxysporum cultivated under Fe depleted conditions. The relative affinity for uranyl binding of desmalonichrome was investigated using a competitive analysis of binding affinities between uranyl acetate and different concentrations of iron(III) chloride using electrospray ionization mass spectrometry (ESI-MS). In addition to desmalonichrome, three other siderophores, including two hydroxamates (desferrioxamine B and desferrichrome) and one carboxylate (desferrichrome A) were studied to understand their relative affinities for the uranyl ion at two pH values. The binding affinities of hydroxymate siderophores to uranyl ion were found to decrease to a greater degree at lower pH as the concentration of Fe (III) ion increases. On the other hand, lowering pH has little impact on the binding affinities between carboxylate siderophores and uranyl ion. Desmalonichrome was shown to have the greatest relative affinity for uranyl at any pH and Fe(III) concentration. These results suggest that acidic functional groups in the ligands are critical for strong chelation with uranium at lower pH.

  12. Isothermal Titration Calorimetry Measurements of Metal Ions Binding to Proteins.

    Science.gov (United States)

    Quinn, Colette F; Carpenter, Margaret C; Croteau, Molly L; Wilcox, Dean E

    2016-01-01

    ITC measurements involving metal ions are susceptible to a number of competing reactions (oxidation, precipitation, and hydrolysis) and coupled reactions involving the buffer and protons. Stabilization and delivery of the metal ion as a well-defined and well-characterized complex with the buffer, or a specific ligand, can suppress undesired solution chemistry and, depending on the stability of the metal complex, allow accurate measurements of higher affinity protein-binding sites. This requires, however, knowledge of the thermodynamics of formation of the metal complex and accounting for its contribution to the experimentally measured values (KITC and ΔHITC) through a post hoc analysis that provides the condition-independent binding thermodynamics (K, ΔG(o), ΔH, ΔS, and ΔCP). This analysis also quantifies the number of protons that are displaced when the metal ion binds to the protein. © 2016 Elsevier Inc. All rights reserved.

  13. Influence of salt ions on binding to molecularly imprinted polymers.

    Science.gov (United States)

    Kempe, Henrik; Kempe, Maria

    2010-02-01

    Salt ions were found to have an influence on template binding to two model molecularly imprinted polymers (MIPs), targeted to penicillin G and propranolol, respectively, in water-acetonitrile mixtures. Water was detrimental to rebinding of penicillin G whereas propranolol bound in the entire water-acetonitrile range tested. In 100% aqueous solution, 3-M salt solutions augmented the binding of both templates. The effects followed the Hofmeister series with kosmotropic ions promoting the largest increase. Binding was mainly of a non-specific nature under these conditions. In acetonitrile containing low amounts of water, the specific binding to the MIPs increased with the addition of salts. Binding of penicillin G followed the Hofmeister series while an ion-exchange mechanism was observed for propranolol. The results suggest that hydration of kosmotropic ions reduces the water activity in water-poor media providing a stabilizing effect on water-sensitive MIP-template interactions. The effects were utilized to develop a procedure for molecularly imprinted solid-phase extraction (MISPE) of penicillin G from milk with a recovery of 87%.

  14. High Affinity Binding of Indium and Ruthenium Ions by Gastrins.

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    Graham S Baldwin

    Full Text Available The peptide hormone gastrin binds two ferric ions with high affinity, and iron binding is essential for the biological activity of non-amidated forms of the hormone. Since gastrins act as growth factors in gastrointestinal cancers, and as peptides labelled with Ga and In isotopes are increasingly used for cancer diagnosis, the ability of gastrins to bind other metal ions was investigated systematically by absorption spectroscopy. The coordination structures of the complexes were characterized by extended X-ray absorption fine structure (EXAFS spectroscopy. Changes in the absorption of gastrin in the presence of increasing concentrations of Ga3+ were fitted by a 2 site model with dissociation constants (Kd of 3.3 x 10-7 and 1.1 x 10-6 M. Although the absorption of gastrin did not change upon the addition of In3+ ions, the changes in absorbance on Fe3+ ion binding in the presence of indium ions were fitted by a 2 site model with Kd values for In3+ of 6.5 x 10-15 and 1.7 x 10-7 M. Similar results were obtained with Ru3+ ions, although the Kd values for Ru3+ of 2.6 x 10-13 and 1.2 x 10-5 M were slightly larger than observed for In3+. The structures determined by EXAFS all had metal:gastrin stoichiometries of 2:1 but, while the metal ions in the Fe, Ga and In complexes were bridged by a carboxylate and an oxygen with a metal-metal separation of 3.0-3.3 Å, the Ru complex clearly demonstrated a short range Ru-Ru separation, which was significantly shorter, at 2.4 Å, indicative of a metal-metal bond. We conclude that gastrin selectively binds two In3+ or Ru3+ ions, and that the affinity of the first site for In3+ or Ru3+ ions is higher than for ferric ions. Some of the metal ion-gastrin complexes may be useful for cancer diagnosis and therapy.

  15. Ion exchange properties of humus acids

    Science.gov (United States)

    Shoba, V. N.; Chudnenko, K. V.

    2014-08-01

    Ion exchange equilibriums in a complex of brown humic acids (HAs) and related fulvic acids (FAs) with cations (H+, K+, Na+, Ca2+, Mg2+, Zn2+, Mn2+, Cu2+, Fe3+, and Al3+) have been studied, and the activity coefficients of the acid monoionic forms have been determined. The composition of the stoichiometric cell in the system of black and brown HAs and related FAs in a leached chernozem of the Ob' region has been calculated with consideration for the earlier studies of the ion exchange properties of black HAs and related FAs. It has been shown that hydrogen, calcium, magnesium, aluminum, and iron are the major components in the exchange complex of humus acids in the leached chernozem with the other cations being of subordinate importance. In spite of some differences between the analytical and calculated compositions of the humus acids, the results of the calculations can be considered satisfactory. They indicate that calculations are feasible for such complex objects as soils, and their accuracy will improve with the expansion of the experimental studies. The physicochemical simulation of the transformation of the humus acid composition under different acid-base conditions shows that the contents of most cations decrease under alkalization, and hydroxides or carbonates become the most stable forms of these cations. Under the acidification of solutions, the binding of alkaline and alkaline-earth elements by humus acids decreases and the adsorption of iron and aluminum by humus acids increases.

  16. Binding energy and fine structure of the He- ion

    Institute of Scientific and Technical Information of China (English)

    ZHUO; Lin; ZHU; Jing-jing; GOU; Bing-cong

    2007-01-01

    The variational method using a multiconfiguration wavefunction is carried out on the core-excited state 1s2s2p 4P0 for helium negative ion, including mass polarization and relativistic corrections. Binding energy and fine structure are reported. The results are compared with other theoretical and experimental date in the literature.

  17. Europium ion as a probe for binding sites to carrageenans

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, Ana P.; Goncalves, Rogeria R.; Serra, Osvaldo A. [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo 14040-901 (Brazil); Zaniquelli, Maria Elisabete D. [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo 14040-901 (Brazil)], E-mail: medzaniquelli@ffclrp.usp.br; Wong, Kenneth [Laboratorio de Fisico-Quimica, Centro de Pesquisas de Paulinia, Rhodia Brasil, Paulinia, Sao Paulo (Brazil)

    2007-12-15

    Carrageenans, sulfated polysaccharides extracted from red algae, present a coil-helix transition and helix aggregation dependence on the type and concentration of counterions. In this study, we focus attention on a mixed valence counterion system: Eu{sup 3+}/Na{sup +} or K{sup +} with different gel-forming carrageenans: kappa, iota, and kappa-2. Results of stationary and time-dependent luminescence showed to be a suitable tool to probe ion binding to both the negatively charged sulfate group and the hydroxyl groups present in the biopolymer. For lower europium ion concentrations, a single longer decay emission lifetime was detected, which was attributed to the binding of europium ion to the carrageenan sulfate groups. An additional decay ascribed to europium binding to hydroxyl groups was observed above a threshold concentration, and this decay was dependent on the carrageenan charge density. Symmetry of the europium ion microenvironment was estimated by the ratio between the intensities of its emission bands, which has been shown to depend on the concentration of europium ions and on the specificity of the monovalent counterion bound to the carrageenan.

  18. Binding of nickel and zinc ions to bacitracin A.

    Science.gov (United States)

    Scogin, D A; Mosberg, H I; Storm, D R; Gennis, R B

    1980-07-08

    Bacitracin A is a cyclic dodecapeptide antibiotic produced by Bacillus licheniformis. Bacteriocidal activity requires the presence of divalent cations such as Zn2+. The metal-bacitracin A complex binds to bactoprenyl pyrophosphate, a lipid intermediate required for cell wall biosynsthesis which is found within the bacterial membrane. In this paper, the pH dependence of the metal binding to bacitracin A is investigated in an effort to define the sites of metal coordination. Most of the studies described in this report were performed with Ni2+ and Zn2+. Metal binding was monitored by observing changes in the ultraviolet absorption spectrum of bacitracin A and by monitoring the proton release which is concomitant with metal binding to the peptide. It was determined that both Ni2+ and Zn2+ form 1:1 complexes with bacitracin A in solution. These complexes are soluble in acidic solutions, but above approximately pH 5.5 they become insoluble. On the basis of the data reported as well as results previously reported from other laboratories, a model for divalent metal ion binding to bacitracin is suggested. It is proposed that the metal coordinates directly to the glutamate carboxyl, the histidine imidazole, and the thiazoline ring. The aspartate carboxyl and N-terminal amino group are not directly involved in metal binding. It is further proposed that due to the proximity of the metab, the pK of the N-terminal amino is shifted from 7.7 to 5.7 upon metal binding. Deprotonation of this group is suggested to cause precipitation of the bacitracin A-metal complex. This model is consistent with all the metal binding data and, furthermore, is consistent with the 1H NMR data presented in the accompanying paper [Mosberg, H. I., Scogin, D. A., Storm, D. R., & Gennis, R. B. (1980) Biochemistry (following paper in this issue)].

  19. Hydration and Ion Binding of the Osmolyte Ectoine.

    Science.gov (United States)

    Eiberweiser, Andreas; Nazet, Andreas; Kruchinin, Sergey E; Fedotova, Marina V; Buchner, Richard

    2015-12-10

    Ectoine is a widespread osmolyte enabling halophilic bacteria to withstand high osmotic stress that has many potential applications ranging from cosmetics to its use as a therapeutic agent. In this contribution, combining experiment and theory, the hydration and ion-binding of this zwitterionic compound was studied to gain information on the functioning of ectoine in particular and of osmolytes in general. Dielectric relaxation spectroscopy was used to determine the effective hydration number of ectoine and its effective dipole moment in aqueous solutions with and without added NaCl. The obtained experimental data were compared with structural results from 1D-RISM and 3D-RISM calculations. It was found that ectoine is strongly hydrated, even in the presence of high salt concentrations. Upon addition of NaCl, ions are bound to ectoine but the formed complexes are not very stable. Interestingly, this osmolyte strongly rises the static relative permittivity of its solutions, shielding thus effectively long-range Coulomb interactions among ions in ectoine-containing solutions. We believe that via this effect, which should be common to all zwitterionic osmolytes, ectoine protects against excessive ions within the cell in addition to its strong osmotic activity protecting against ions outside.

  20. Metal ion enhanced binding of AMD3100 to Asp262 in the CXCR4 receptor

    DEFF Research Database (Denmark)

    Gerlach, Lars Ole; Jakobsen, Janus S; Jensen, Kasper P;

    2003-01-01

    +), Zn(2+), or Ni(2+) into the cyclam rings of the compound. The rank order of the transition metal ions correlated with the calculated binding energy between free acetate and the metal ions coordinated in a cyclam ring. Construction of AMD3100 substituted with only a single Cu(2+) or Ni(2+) ion...... demonstrated that the increase in binding affinity of the metal ion substituted bicyclam is achieved through an enhanced interaction of just one of the ring systems. Mutational analysis of potential metal ion binding residues in the main ligand binding crevice of the CXCR4 receptor showed that although binding...... of the bicyclam is dependent on both Asp(171) and Asp(262), the enhancing effect of the metal ion was selectively eliminated by substitution of Asp(262) located at the extracellular end of TM-VI. It is concluded that the increased binding affinity of the metal ion substituted AMD3100 is obtained through enhanced...

  1. The selectivity of different external binding sites for quaternary ammonium ions in cloned potassium channels.

    Science.gov (United States)

    Jarolimek, W; Soman, K V; Brown, A M; Alam, M

    1995-09-01

    Tetraethylammonium (TEA) is thought to be the most effective quaternary ammonium (QA) ion blocker at the external site of K+ channels, and small changes to the TEA ion reduce its potency. To examine the properties of the external QA receptor, we applied a variety of QA ions to excised patches from human embryonic kidney cells or Xenopus oocytes transfected with the delayed rectifying K+ channels Kv 2.1 and Kv 3.1. In outside-out patches of Kv 3.1, the relative potencies were TEA > tetrapropylammonium (TPA) > tetrabutylammonium (TBA). In contrast to Kv 3.1, the relative potencies in Kv 2.1 were TBA > TEA > TPA. In Kv 3.1 and Kv 2.1, external tetrapentylammonium (TPeA) blocked K+ currents in a fast, reversible and, in contrast to TEA, time-dependent manner. The external binding of TPeA appeared to be voltage independent, unlike the effects of TPeA applied to inside-out patches. External n-alkyl-triethylammonium compounds (C8, C10 chain length) had a lower affinity than TEA in Kv 3.1, but a higher affinity than TEA in Kv 2.1. In Kv 3.1, the decrease in QA affinity was large when one or two methyl groups were substituted for ethyl groups in TEA, but minor when propyl groups replaced ethyl groups. Changes in the free energy of binding could be correlated to changes in the free energy of hydration of TEA derivatives calculated by continuum methodology. These results reveal a substantial hydrophobic component of external QA ion binding to Kv 2.1, and to a lesser degree to Kv 3.1, in addition to the generally accepted electrostatic interactions. The chain length of hydrophobic TEA derivatives affects the affinity for the hydrophobic binding site, whereas the hydropathy of QA ions determines the electrostatic interaction energy.

  2. Carrageenans as a New Source of Drugs with Metal Binding Properties

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    Yuri S. Khotimchenko

    2010-04-01

    Full Text Available Carrageenans are abundant and safe non-starch polysaccharides exerting their biological effects in living organisms. Apart from their known pro-inflammation properties and some pharmacological activity, carrageenans can also strongly bind and hold metal ions. This property can be used for creation of the new drugs for elimination of metals from the body or targeted delivery of these metal ions for healing purposes. Metal binding activity of different carrageenans in aqueous solutions containing Y3+ or Pb2+ ions was studied in a batch sorption system. The metal uptake by carrageenans is not affected by the change of the pH within the range from 2.0 to 6.0. The rates and binding capacities of carrageenans regarding metal ions were evaluated. The Langmuir, Freundlich and BET sorption models were applied to describe the isotherms and constants, and the sorption isothermal data could be explained well by the Langmuir equation. The results obtained through the study suggest that κ-, ι-, and λ-carrageenans are favorable sorbents. The largest amount of Y3+ and Pb2+ ions are bound by i-carrageenan. Therefore, it can be concluded that this type of polysaccharide is the more appropriate substance for elaboration of the drugs with high selective metal binding properties.

  3. THE EFFECTS OF COPPER AND ZINC IONS DURING THEIR BINDING WITH HUMAN SERUM γ-GLOBULIN

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    S. B. Cheknev

    2006-01-01

    Full Text Available Abstract. Conformational changes of human serum γ-globulin were studied during and after its binding with copper and zinc ions, using molecular ultrafiltration and differential spectrophotometry. The contents of nonbound metals in the filtrate were evaluated, resp., with sodium diethyl thyocarbamate and o-phenanthroline. It has been shown that copper and zinc exhibited common biological properties during their interactions with protein, but the binding differed sufficiently under similar experimental conditions. E.g., it was confirmed that copper was more active at the external sites of γ-globulin molecule, whereas zinc demonstrated tropicity for the areas of protein intraglobular compartments. The metal-binding sites have been described that differ in their parameters of interactions with cations and their spatial location within globular domains. Approaches are suggested for dynamic analysis of saturation for these differently located sites by the metal ions. We discuss the issues of altered conformational state of the γ-globulin molecule during the binding of cations, as well as potential usage of these data in clinical immunology.

  4. Assessment Criteria of Bentonite Binding Properties

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    S. Żymankowska-Kumon

    2012-09-01

    Full Text Available The criteria, with which one should be guided at the assessment of the binding properties of bentonites used for moulding sands, areproposed in the paper. Apart from the standard parameter which is the active bentonite content, the unrestrained growth indicator should be taken into account since it seems to be more adequate in the estimation of the sand compression strength. The investigations performed for three kinds of bentonites, applied in the Polish foundry plants, subjected to a high temperature influences indicate, that the pathway of changes of the unrestrained growth indicator is very similar to the pathway of changes of the sand compression strength. Instead, the character of changes of the montmorillonite content in the sand in dependence of the temperature is quite different. The sand exhibits the significant active bentonite content, and the sand compression strength decreases rapidly. The montmorillonite content in bentonite samples was determined by the modern copper complex method of triethylenetetraamine (Cu(II-TET. Tests were performed for bentonites and for sands with those bentonites subjected to high temperatures influences in a range: 100-700ºC.

  5. Drug binding properties of neonatal albumin

    DEFF Research Database (Denmark)

    Brodersen, R; Honoré, B

    1989-01-01

    Neonatal and adult albumin was isolated by gel chromatography on Sephacryl S-300, from adult and umbilical cord serum, respectively. Binding of monoacetyl-diamino-diphenyl sulfone, warfarin, sulfamethizole, and diazepam was studied by means of equilibrium dialysis and the binding data were analyzed...... by the method of several acceptable fitted curves. It was found that the binding affinity to neonatal albumin is less than to adult albumin for monoacetyl-diamino-diphenyl sulfone and warfarin. Sulfamethizole binding to the neonatal protein is similarly reduced when more than one molecule of the drug is bound...

  6. Dissecting electrostatic screening, specific ion binding, and ligand binding in an energetic model for glycine riboswitch folding

    Energy Technology Data Exchange (ETDEWEB)

    Lipfert, Jan; Sim, Adelene Y.L.; Herschlag, Daniel; Doniach, Sebastian (Stanford)

    2010-09-17

    Riboswitches are gene-regulating RNAs that are usually found in the 5{prime}-untranslated regions of messenger RNA. As the sugar-phosphate backbone of RNA is highly negatively charged, the folding and ligand-binding interactions of riboswitches are strongly dependent on the presence of cations. Using small angle X-ray scattering (SAXS) and hydroxyl radical footprinting, we examined the cation dependence of the different folding stages of the glycine-binding riboswitch from Vibrio cholerae. We found that the partial folding of the tandem aptamer of this riboswitch in the absence of glycine is supported by all tested mono- and divalent ions, suggesting that this transition is mediated by nonspecific electrostatic screening. Poisson-Boltzmann calculations using SAXS-derived low-resolution structural models allowed us to perform an energetic dissection of this process. The results showed that a model with a constant favorable contribution to folding that is opposed by an unfavorable electrostatic term that varies with ion concentration and valency provides a reasonable quantitative description of the observed folding behavior. Glycine binding, on the other hand, requires specific divalent ions binding based on the observation that Mg{sup 2+}, Ca{sup 2+}, and Mn{sup 2+} facilitated glycine binding, whereas other divalent cations did not. The results provide a case study of how ion-dependent electrostatic relaxation, specific ion binding, and ligand binding can be coupled to shape the energetic landscape of a riboswitch and can begin to be quantitatively dissected.

  7. Selective Binding, Self-Assembly and Nanopatterning of the Creutz-Taube Ion on Surfaces

    Directory of Open Access Journals (Sweden)

    Qingling Hang

    2009-02-01

    Full Text Available The surface attachment properties of the Creutz-Taube ion, i.e., [(NH35Ru(pyrazineRu(NH35]5+, on both hydrophilic and hydrophobic types of surfaces were investigated using X-ray photoelectron spectroscopy (XPS. The results indicated that the Creutz-Taube ions only bound to hydrophilic surfaces, such as SiO2 and –OH terminated organic SAMs on gold substrates. No attachment of the ions on hydrophobic surfaces such as –CH3 terminated organic SAMs and poly(methylmethacrylate (PMMA thin films covered gold or SiO2 substrates was observed. Further ellipsometric, atomic force microscopy (AFM and time-dependent XPS studies suggested that the attached cations could form an inorganic analog of the self-assembled monolayer on SiO2 substrate with a “lying-down” orientation. The strong electrostatic interaction between the highly charged cations and the anionic SiO2 surface was believed to account for these observations. Based on its selective binding property, patterning of wide (~200 nm and narrow (~35 nm lines of the Creutz-Taube ions on SiO2 surface were demonstrated through PMMA electron resist masks written by electron beam lithography (EBL.

  8. Metal ion binding with carbon nanotubes and graphene: Effect of chirality and curvature

    Science.gov (United States)

    Umadevi, Deivasigamani; Sastry, G. Narahari

    2012-10-01

    First principles calculations have been used to comprehensively study the binding of a series alkali (Li+, Na+, K+) and alkaline earth (Be2+, Mg2+, Ca2+) metal ions with carbon nanotubes (CNTs) and graphene. It is interesting to note that the mono-cationic systems prefer binding to armchair CNTs over zigzag CNTs, while the preference for the di-cationic systems is exactly opposite. We have also observed significant changes in the HOMO-LUMO energy gap of the CNTs on metal ion binding and these results indicate that the fine tuning of energy gap of the CNTs can be effected through metal ion binding.

  9. Coupled ion Binding and Structural Transitions Along the Transport Cycle of Glutamate Transporters

    Energy Technology Data Exchange (ETDEWEB)

    Verdon, Gregory [Weill Cornell Medical College, New York, NY (United States); Oh, SeCheol [Weill Cornell Medical College, New York, NY (United States); Serio, Ryan N. [Weill Cornell Medical College, New York, NY (United States); Boudker, Olga [Weill Cornell Medical College, New York, NY (United States)

    2014-05-19

    Membrane transporters that clear the neurotransmitter glutamate from synapses are driven by symport of sodium ions and counter-transport of a potassium ion. Previous crystal structures of a homologous archaeal sodium and aspartate symporter showed that a dedicated transport domain carries the substrate and ions across the membrane. We report new crystal structures of this homologue in ligand-free and ions-only bound outward- and inward-facing conformations. We then show that after ligand release, the apo transport domain adopts a compact and occluded conformation that can traverse the membrane, completing the transport cycle. Sodium binding primes the transport domain to accept its substrate and triggers extracellular gate opening, which prevents inward domain translocation until substrate binding takes place. Moreover, we describe a new cation-binding site ideally suited to bind a counter-transported ion. We suggest that potassium binding at this site stabilizes the translocation-competent conformation of the unloaded transport domain in mammalian homologues.

  10. Characterization of the DNA binding properties of polyomavirus capsid protein

    Science.gov (United States)

    Chang, D.; Cai, X.; Consigli, R. A.; Spooner, B. S. (Principal Investigator)

    1993-01-01

    The DNA binding properties of the polyomavirus structural proteins VP1, VP2, and VP3 were studied by Southwestern analysis. The major viral structural protein VP1 and host-contributed histone proteins of polyomavirus virions were shown to exhibit DNA binding activity, but the minor capsid proteins VP2 and VP3 failed to bind DNA. The N-terminal first five amino acids (Ala-1 to Lys-5) were identified as the VP1 DNA binding domain by genetic and biochemical approaches. Wild-type VP1 expressed in Escherichia coli (RK1448) exhibited DNA binding activity, but the N-terminal truncated VP1 mutants (lacking Ala-1 to Lys-5 and Ala-1 to Cys-11) failed to bind DNA. The synthetic peptide (Ala-1 to Cys-11) was also shown to have an affinity for DNA binding. Site-directed mutagenesis of the VP1 gene showed that the point mutations at Pro-2, Lys-3, and Arg-4 on the VP1 molecule did not affect DNA binding properties but that the point mutation at Lys-5 drastically reduced DNA binding affinity. The N-terminal (Ala-1 to Lys-5) region of VP1 was found to be essential and specific for DNA binding, while the DNA appears to be non-sequence specific. The DNA binding domain and the nuclear localization signal are located in the same N-terminal region.

  11. Metal ion binding with dehydroannulenes - Plausible two-dimensional molecular sieves

    Indian Academy of Sciences (India)

    B Sateesh; Y Soujanya; G Narahari Sastry

    2007-09-01

    Theoretical investigations have been carried out at B3LYP/6-311++G∗∗ level of theory to study the binding interaction of various metal ions, Li+, Na+ and K+ with dehydroannulene systems. The present study reveals that alkali metal ions bind strongly to dehydroannulenes and the passage through the central cavity is controlled by the size of metal ion and dimension of dehydroannulene cavity.

  12. Chronic Beryllium Disease: revealing the role of beryllium ion and small peptides binding to HLA-DP2.

    Science.gov (United States)

    Petukh, Marharyta; Wu, Bohua; Stefl, Shannon; Smith, Nick; Hyde-Volpe, David; Wang, Li; Alexov, Emil

    2014-01-01

    Chronic Beryllium (Be) Disease (CBD) is a granulomatous disorder that predominantly affects the lung. The CBD is caused by Be exposure of individuals carrying the HLA-DP2 protein of the major histocompatibility complex class II (MHCII). While the involvement of Be in the development of CBD is obvious and the binding site and the sequence of Be and peptide binding were recently experimentally revealed [1], the interplay between induced conformational changes and the changes of the peptide binding affinity in presence of Be were not investigated. Here we carry out in silico modeling and predict the Be binding to be within the acidic pocket (Glu26, Glu68 and Glu69) present on the HLA-DP2 protein in accordance with the experimental work [1]. In addition, the modeling indicates that the Be ion binds to the HLA-DP2 before the corresponding peptide is able to bind to it. Further analysis of the MD generated trajectories reveals that in the presence of the Be ion in the binding pocket of HLA-DP2, all the different types of peptides induce very similar conformational changes, but their binding affinities are quite different. Since these conformational changes are distinctly different from the changes caused by peptides normally found in the cell in the absence of Be, it can be speculated that CBD can be caused by any peptide in presence of Be ion. However, the affinities of peptides for Be loaded HLA-DP2 were found to depend of their amino acid composition and the peptides carrying acidic group at positions 4 and 7 are among the strongest binders. Thus, it is proposed that CBD is caused by the exposure of Be of an individual carrying the HLA-DP2*0201 allele and that the binding of Be to HLA-DP2 protein alters the conformational and ionization properties of HLA-DP2 such that the binding of a peptide triggers a wrong signaling cascade.

  13. Characterization of the Binding Properties of Molecularly Imprinted Polymers.

    Science.gov (United States)

    Ansell, Richard J

    2015-01-01

    The defining characteristic of the binding sites of any particular molecularly imprinted material is heterogeneity: that is, they are not all identical. Nonetheless, it is useful to study their fundamental binding properties, and to obtain average properties. In particular, it has been instructive to compare the binding properties of imprinted and non-imprinted materials. This chapter begins by considering the origins of this site heterogeneity. Next, the properties of interest of imprinted binding sites are described in brief: affinity, selectivity, and kinetics. The binding/adsorption isotherm, the graph of concentration of analyte bound to a MIP versus concentration of free analyte at equilibrium, over a range of total concentrations, is described in some detail. Following this, the techniques for studying the imprinted sites are described (batch-binding assays, radioligand binding assays, zonal chromatography, frontal chromatography, calorimetry, and others). Thereafter, the parameters that influence affinity, selectivity and kinetics are discussed (solvent, modifiers of organic solvents, pH of aqueous solvents, temperature). Finally, mathematical attempts to fit the adsorption isotherms for imprinted materials, so as to obtain information about the range of binding affinities characterizing the imprinted sites, are summarized.

  14. Atmospheric Ion Clusters: Properties and Size Distributions

    Science.gov (United States)

    D'Auria, R.; Turco, R. P.

    2002-12-01

    Ions are continuously generated in the atmosphere by the action of galactic cosmic radiation. Measured charge concentrations are of the order of 103 ~ {cm-3} throughout the troposphere, increasing to about 5 x 103 ~ {cm-3} in the lower stratosphere [Cole and Pierce, 1965; Paltridge, 1965, 1966]. The lifetimes of these ions are sufficient to allow substantial clustering with common trace constituents in air, including water, nitric and sulfuric acids, ammonia, and a variety of organic compounds [e.g., D'Auria and Turco, 2001 and references cited therein]. The populations of the resulting charged molecular clusters represent a pre-nucleation phase of particle formation, and in this regard comprise a key segment of the over-all nucleation size spectrum [e.g., Castleman and Tang, 1972]. It has been suggested that these clusters may catalyze certain heterogeneous reactions, and given their characteristic crystal-like structures may act as freezing nuclei for supercooled droplets. To investigate these possibilities, basic information on cluster thermodynamic properties and chemical kinetics is needed. Here, we present new results for several relevant atmospheric ion cluster families. In particular, predictions based on quantum mechanical simulations of cluster structure, and related thermodynamic parameters, are compared against laboratory data. We also describe a hybrid approach for modeling cluster sequences that combines laboratory measurements and quantum predictions with the classical liquid droplet (Thomson) model to treat a wider range of cluster sizes. Calculations of cluster mass distributions based on this hybrid model are illustrated, and the advantages and limitations of such an analysis are summarized. References: Castelman, A. W., Jr., and I. N. Tang, Role of small clusters in nucleation about ions, J. Chem. Phys., 57, 3629-3638, 1972. Cole, R. K., and E. T. Pierce, Electrification in the Earth's atmosphere for altitudes between 0 and 100 kilometers, J

  15. Polypeptide binding properties of the chaperone calreticulin

    DEFF Research Database (Denmark)

    Jørgensen, C S; Heegaard, N H; Holm, A

    2000-01-01

    to be elucidated. We have investigated the interactions of human calreticulin with denatured ovalbumin, proteolytic digests of ovalbumin, and different available peptides by solid phase assays, size-exclusion chromatography, capillary electrophoresis, and MS. The results show that calreticulin interacts better...... with unfolded ovalbumin than with native ovalbumin, that calreticulin strongly binds components in proteolytic digests of denatured ovalbumin, and that calreticulin interacts strongly with certain synthetic peptides....

  16. Metal ion binding and function in natural and artificial small RNA enzymes from a structural perspective.

    Science.gov (United States)

    Wedekind, Joseph E

    2011-01-01

    Ribozymes are often perceived as part of an antiquated catalytic arsenal hearkening back to a pre-biotic RNA World that was eventually supplanted by proteins. However, recent genome-wide searches have revealed a plethora of new catalytic RNA motifs that appear to be variations on well-known themes. This suggests that ribozymes have continued to evolve in order to fulfill specific, RNA-essential biological niches. Although such ribozymes are small and catalyze one-step phosphodiester-bond scission reactions, ongoing structure and function analyses at the lab bench have demonstrated that RNA has the capacity for a diverse number of reactions such as carbon-carbon bond formation, and tRNA aminoacylation. Here we describe the fundamental structure and metal binding properties of four naturally occurring RNA enzymes: the hammerhead, hairpin, hepatitis delta virus, and glmS metabolite sensing ribozyme. In addition, we discuss the fold and ion coordination of three artificial ribozymes developed to probe the boundaries of RNA catalysis; these include the leadzyme, the flexizyme, and the Diels-Alder ribozyme. Our approach is to relate structure to function with the knowledge of ideal metal-ion coordination geometry that we have derived herein from surveys of high-resolution small molecule structures. An emergent theme is that natural and artificial ribozymes that catalyze single-step reactions often possess a pre-formed active site. Multivalent ions facilitate RNA active site formation, but can also provide Lewis acid functionality that is necessary for catalysis. When metal ion binding isn't possible, ribozymes make due by ionizing their bases, or by recruiting cofactors that augment their chemical functionality.

  17. Binding of Cu(II) ions to peptides studied by fluorescence spectroscopy and isothermal titration calorimetry.

    Science.gov (United States)

    Makowska, Joanna; Żamojć, Krzysztof; Wyrzykowski, Dariusz; Uber, Dorota; Wierzbicka, Małgorzata; Wiczk, Wiesław; Chmurzyński, Lech

    2016-01-15

    Steady-state and time-resolved fluorescence quenching measurements supported by Isothermal Titration Calorimetry (ITC) were used to study the interactions of Cu(2+) with four peptides. Two of them were taken from the N-terminal part of the FBP28 protein (formin binding protein) WW domain: Tyr-Lys-Thr-Ala-Asp-Gly-Lys-Thr-Tyr-NH2 (D9) and its mutant Tyr-Lys-Thr-Ala-Asn-Gly-Lys-Thr-Tyr-NH2 (D9_M) as well as two mutated peptides from the B3 domain of the immunoglobulin binding protein G derived from Streptococcus: Asp-Val-Ala-Thr-Tyr-Thr-NH2 (J1) and Glu-Val-Ala-Thr-Tyr-Thr-NH2 (J2). The measurements were carried out at 298.15K in 20mM 2-(N-morpholino)ethanesulfonic acid (MES) buffer solution with a pH of 6. The fluorescence of all peptides was quenched by Cu(2+) ions. The stoichiometry, conditional stability constants and thermodynamic parameters for the interactions of the Cu(2+) ions with D9 and D9_M were determined from the calorimetric data. The values of the conditional stability constants were additionally determined from fluorescence quenching measurements and compared with those obtained from calorimetric studies. There was a good correlation between data obtained from the two techniques. On the other hand, the studies revealed that J1 and J2 do not exhibit an affinity towards metal ions. The obtained results prove that fluorescence quenching experiments may be successfully used in order to determine stability constants of complexes with fluorescent ligands. Finally, based on the obtained results, the coordinating properties of the peptides towards the Cu(2+) ions are discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Electrical properties of ion irradiated polypropylene films

    Indian Academy of Sciences (India)

    N L Singh; Anita Sharma; V Shrinet; A K Rakshit; D K Avasthi

    2004-06-01

    The effect of high-energy (50 MeV) Li3+ ion beam irradiation on polypropylene (PP) film has been studied in the fluence range 2.4 × 1012-1.5 × 1014 ions/cm2. The a.c. electrical properties of PP films were measured in the frequency range from 0.05–100 kHz, and at temperature range between 30 and 140°C. This study indicates two peaks at 60°C and 120°C with comparatively high magnitudes. There is an exponential increase in conductivity with log of frequency and the effect is significant at higher fluences. The loss factor (tan ) vs frequency plot suggests that PP film based capacitors may be useful below 10 kHz. The capacitance is constant over a wide temperature range up to 130°C. FTIR spectra of the PP films before and after irradiation indicate that intensity of C–H stretching vibration at 2900 cm-1 is modified. The presence of many new peaks with the increase of fluence suggests the formation of alkanes and alkynes which might be responsible for the observed changes in the dielectric and electrical properties of PP films.

  19. Binding and removal of aluminum ions in water by an algal biomass

    Energy Technology Data Exchange (ETDEWEB)

    Zimnik, P.R.; Sneddon, J.

    1988-08-01

    A preliminary study on the binding and removal of trace concentrations of aluminum ions in waters by two species of algae, Chlorella Pyrenoidosa and Chlorella Vulgaris, were investigated. Binding by the former was minimal over all pH ranges, but binding by the latter was effective with a maximum binding of 68% occurring at pH 5. Binding was lowered drastically below pH 2, and this may be used to remove aluminum from the algae. Optimum binding occurred after 20 minutes exposure time of algae to aluminum solution and 450 mg algae mass to 100 mL solution. Binding was reproducible and more efficient in waters with low suspended solids. High salt concentrations interfere with binding, and the Chlorella Vulgaris could be reused 7 times with washings between each binding before a noticeable decrease in binding efficiency was found.

  20. Interacion of Heavy Metal Ions with C-Phycocyanin: Binding Isotherms and Cooperative Effects

    CERN Document Server

    Gelagutashvili, Eteri

    2007-01-01

    The binding constant of copper(II) ions to C-PC were determined at different ionic strengths from binding isotherms by equilibrium dialysis and flame atomic absorption spectroscopy. Fluorescence and absorbtion spectroscopy provides insight of metal-C-phycocyanin interactions. Fluorescence measurements demonstrate C-PC quenching of heavy metal ions emission intensities. Stern-Volmer quenching constants were obtained from the linear quenching plots. Blue shifts in the fluorescence spectra were observed during metal binding to C-PC. It was shown, that between bound metal ions in C-PC there exists positive cooperativity.

  1. Polypeptide binding properties of the chaperone calreticulin

    DEFF Research Database (Denmark)

    Jørgensen, C S; Heegaard, N H; Holm, A;

    2000-01-01

    Calreticulin is a highly conserved eukaryotic ubiquitious protein located mainly in the endoplasmic reticulum. Two major characteristics of calreticulin are its chaperone activity and its lectin properties, but its precise function in intracellular protein and peptide processing remains to be elu......Calreticulin is a highly conserved eukaryotic ubiquitious protein located mainly in the endoplasmic reticulum. Two major characteristics of calreticulin are its chaperone activity and its lectin properties, but its precise function in intracellular protein and peptide processing remains...

  2. Coupling Substrate and Ion Binding to Extracellular Gate of a Sodium-Dependent Aspartate Transporter

    Energy Technology Data Exchange (ETDEWEB)

    Boudker,O.; Ryan, R.; Yernool, D.; Shimamoto, K.; Gouaux, E.

    2007-01-01

    Secondary transporters are integral membrane proteins that catalyze the movement of substrate molecules across the lipid bilayer by coupling substrate transport to one or more ion gradients, thereby providing a mechanism for the concentrative uptake of substrates. Here we describe crystallographic and thermodynamic studies of Glt{sub Ph}, a sodium (Na{sup +})-coupled aspartate transporter, defining sites for aspartate, two sodium ions and D,L-threo-{beta}-benzyloxyaspartate, an inhibitor. We further show that helical hairpin 2 is the extracellular gate that controls access of substrate and ions to the internal binding sites. At least two sodium ions bind in close proximity to the substrate and these sodium-binding sites, together with the sodium-binding sites in another sodium-coupled transporter, LeuT, define an unwound {alpha}-helix as the central element of the ion-binding motif, a motif well suited to the binding of sodium and to participation in conformational changes that accompany ion binding and unbinding during the transport cycle.

  3. Metal-binding and redox properties of substituted linear and cyclic ATCUN motifs.

    Science.gov (United States)

    Neupane, Kosh P; Aldous, Amanda R; Kritzer, Joshua A

    2014-10-01

    The amino-terminal copper and nickel binding (ATCUN) motif is a short peptide sequence found in human serum albumin and other proteins. Synthetic ATCUN-metal complexes have been used to oxidatively cleave proteins and DNA, cross-link proteins, and damage cancer cells. The ATCUN motif consists of a tripeptide that coordinates Cu(II) and Ni(II) ions in a square planar geometry, anchored by chelation sites at the N-terminal amine, histidine imidazole and two backbone amides. Many studies have shown that the histidine is required for tight binding and square planar geometry. Previously, we showed that macrocyclization of the ATCUN motif can lead to high-affinity binding with altered metal ion selectivity and enhanced Cu(II)/Cu(III) redox cycling (Inorg. Chem. 2013, 52, 2729-2735). In this work, we synthesize and characterize several linear and cyclic ATCUN variants to explore how substitutions at the histidine alter the metal-binding and catalytic properties. UV-visible spectroscopy, EPR spectroscopy and mass spectrometry indicate that cyclization can promote the formation of ATCUN-like complexes even in the absence of imidazole. We also report several novel ATCUN-like complexes and quantify their redox properties. These findings further demonstrate the effects of conformational constraints on short, metal-binding peptides, and also provide novel redox-active metallopeptides suitable for testing as catalysts for stereoselective or regioselective oxidation reactions.

  4. Glutamate Water Gates in the Ion Binding Pocket of Na+ Bound Na+, K+-ATPase

    Science.gov (United States)

    Han, Minwoo; Kopec, Wojciech; Solov’yov, Ilia A.; Khandelia, Himanshu

    2017-01-01

    The dynamically changing protonation states of the six acidic amino acid residues in the ion binding pocket of the Na+, K+ -ATPase (NKA) during the ion transport cycle are proposed to drive ion binding, release and possibly determine Na+ or K+ selectivity. We use molecular dynamics (MD) and density functional theory (DFT) simulations to determine the protonation scheme of the Na+ bound conformation of NKA. MD simulations of all possible protonation schemes show that the bound Na+ ions are most stably bound when three or four protons reside in the binding sites, and that Glu954 in site III is always protonated. Glutamic acid residues in the three binding sites act as water gates, and their deprotonation triggers water entry to the binding sites. From DFT calculations of Na+ binding energies, we conclude that three protons in the binding site are needed to effectively bind Na+ from water and four are needed to release them in the next step. Protonation of Asp926 in site III will induce Na+ release, and Glu327, Glu954 and Glu779 are all likely to be protonated in the Na+ bound occluded conformation. Our data provides key insights into the role of protons in the Na+ binding and release mechanism of NKA. PMID:28084301

  5. A Manganese(V)-Oxo Complex: Synthesis by Dioxygen Activation and Enhancement of Its Oxidizing Power by Binding Scandium Ion.

    Science.gov (United States)

    Hong, Seungwoo; Lee, Yong-Min; Sankaralingam, Muniyandi; Vardhaman, Anil Kumar; Park, Young Jun; Cho, Kyung-Bin; Ogura, Takashi; Sarangi, Ritimukta; Fukuzumi, Shunichi; Nam, Wonwoo

    2016-07-13

    A mononuclear non-heme manganese(V)-oxo complex, [Mn(V)(O)(TAML)](-) (1), was synthesized by activating dioxygen in the presence of olefins with weak allylic C-H bonds and characterized structurally and spectroscopically. In mechanistic studies, the formation rate of 1 was found to depend on the allylic C-H bond dissociation energies (BDEs) of olefins, and a kinetic isotope effect (KIE) value of 16 was obtained in the reactions of cyclohexene and cyclohexene-d10. These results suggest that a hydrogen atom abstraction from the allylic C-H bonds of olefins by a putative Mn(IV)-superoxo species, which is formed by binding O2 by a high-spin (S = 2) [Mn(III)(TAML)](-) complex, is the rate-determining step. A Mn(V)-oxo complex binding Sc(3+) ion, [Mn(V)(O)(TAML)](-)-(Sc(3+)) (2), was also synthesized in the reaction of 1 with Sc(3+) ion and then characterized using various spectroscopic techniques. The binding site of the Sc(3+) ion was proposed to be the TAML ligand, not the Mn-O moiety, probably due to the low basicity of the oxo group compared to the basicity of the amide carbonyl group in the TAML ligand. Reactivity studies of the Mn(V)-oxo intermediates, 1 and 2, in oxygen atom transfer and electron-transfer reactions revealed that the binding of Sc(3+) ion at the TAML ligand of Mn(V)-oxo enhanced its oxidizing power with a positively shifted one-electron reduction potential (ΔEred = 0.70 V). This study reports the first example of tuning the second coordination sphere of high-valent metal-oxo species by binding a redox-inactive metal ion at the supporting ligand site, thereby modulating their electron-transfer properties as well as their reactivities in oxidation reactions.

  6. Metal ion binding to peptides: Oxygen or nitrogen sites?

    NARCIS (Netherlands)

    Dunbar, R. C.; Polfer, N. C.; G. Berden,; Oomens, J.

    2012-01-01

    Infrared multiple-photon dissociation (IRMPD) spectroscopy was used to probe the conformations of gas-phase metal-ion complexes between a series of five metal ions and six small peptide ligands. This report is presented in recognition and tribute for the Armentrout group's long and hugely produ

  7. Metal ion binding to peptides: oxygen or nitrogen sites?

    NARCIS (Netherlands)

    R.C. Dunbar; N.C. Polfer; G. Berden; J. Oomens

    2012-01-01

    Infrared multiple-photon dissociation (IRMPD) spectroscopy was used to probe the conformations of gas-phase metal-ion complexes between a series of five metal ions and six small peptide ligands. This report is presented in recognition and tribute for the Armentrout group's long and hugely productive

  8. Molecular mechanism of ATP binding and ion channel activation in P2X receptors

    Energy Technology Data Exchange (ETDEWEB)

    Hattori, Motoyuki; Gouaux, Eric (Oregon HSU)

    2012-10-24

    P2X receptors are trimeric ATP-activated ion channels permeable to Na{sup +}, K{sup +} and Ca{sup 2+}. The seven P2X receptor subtypes are implicated in physiological processes that include modulation of synaptic transmission, contraction of smooth muscle, secretion of chemical transmitters and regulation of immune responses. Despite the importance of P2X receptors in cellular physiology, the three-dimensional composition of the ATP-binding site, the structural mechanism of ATP-dependent ion channel gating and the architecture of the open ion channel pore are unknown. Here we report the crystal structure of the zebrafish P2X4 receptor in complex with ATP and a new structure of the apo receptor. The agonist-bound structure reveals a previously unseen ATP-binding motif and an open ion channel pore. ATP binding induces cleft closure of the nucleotide-binding pocket, flexing of the lower body {beta}-sheet and a radial expansion of the extracellular vestibule. The structural widening of the extracellular vestibule is directly coupled to the opening of the ion channel pore by way of an iris-like expansion of the transmembrane helices. The structural delineation of the ATP-binding site and the ion channel pore, together with the conformational changes associated with ion channel gating, will stimulate development of new pharmacological agents.

  9. Core-modified octaphyrins: Syntheses and anion-binding properties

    Indian Academy of Sciences (India)

    Rajneesh Misra; Venkataramanarao G Anand; Harapriya Rath; Tavarekere K Chandrashekar

    2005-03-01

    In this paper, a brief review of the syntheses, characterization and anion-binding properties of core-modified octaphyrins is presented. It has been shown that the core-modified octaphyrins exhibit aromaticity both in solution and in solid state, confirming the validity of the (4 + 2) Huckel rule for larger -electron systems. Solid-state binding characteristics of TFA anions of two core-modified octaphyrins are also described.

  10. Some properties of the central heavy ion collisions

    CERN Document Server

    Wazir, Z; Khan, E U; Haseeb, Mahnaz Q; Ajaz, M; Khan, K H

    2009-01-01

    Some experimental results are discussed in connection with the properties of the central heavy ion collisions. These experiments indicate the regime changes and saturation at some values of the centrality. This phenomenon is considered to be a signal of the percolation cluster formation in heavy ion collisions at high energies. Keywords: heavy ion collisions, theoretical models, centrality, phase transition.

  11. Biomolecular mode of action of metformin in relation to its copper binding properties.

    Science.gov (United States)

    Repiščák, Peter; Erhardt, Stefan; Rena, Graham; Paterson, Martin J

    2014-02-04

    Metformin (Metf), the most commonly used type 2 diabetes drug, is known to affect the cellular housekeeping of copper. Recently, we discovered that the structurally closely related propanediimidamide (PDI) shows a cellular behavior different from that of Metf. Here we investigate the binding of these compounds to copper, to compare their binding strength. Furthermore, we take a closer look at the electronic properties of these compounds and their copper complexes such as molecular orbital interactions and electrostatic potential surfaces. Our results clearly show that the copper binding energies cannot alone be the cause of the biochemical differentiation between Metf and PDI. We conclude that other factors such as pKa values and hydrophilicity of the compounds play a crucial role in their cellular activity. Metf in contrast to PDI can occur as an anion in aqueous medium at moderate pH, forming much stronger complexes particularly with Cu(II) ions, suggesting that biguanides but not PDI may induce easy oxidation of Cu(I) ions extracted from proteins. The higher hydrophobicity and the lack of planarity of PDI may further differentiate it from biguanides in terms of their molecular recognition characteristics. These different properties could hold the key to metformin's mitochondrial activity because they suggest that the drug could act at least in part as a pro-oxidant of accessible protein-bound Cu(I) ions.

  12. /sup 3/H-imipramine binding in aged mouse brain: regulation by ions and serotonin

    Energy Technology Data Exchange (ETDEWEB)

    Severson, J.A.

    1986-03-01

    The density of binding sites (Bmax) for /sup 3/H-imipramine was elevated in cerebral cortical, hypothalamic and hippocampal membranes from 24 month old male C57BL/6J mice. Cerebellar binding was constant with increasing age. There were no changes in the equilibrium dissociation constant (Kd) for /sup 3/H-imipramine in any brain region. The increase in the binding of /sup 3/H-imipramine induced by sodium and chloride ions in vitro was diminished in cerebral cortical homogenates from aged mice; both the sodium-sensitive and chloride-sensitive components of binding were about 50% less in aged mice. Dose-response curves indicated that the effectiveness with which chloride enhanced binding was similar with age, even though the absolute increase in binding was less. The rate of dissociation of /sup 3/H-imipramine from cerebral cortical homogenates was similar with age and serotonin slowed the rate of dissociation equally at all ages. Possible mechanisms for the age-related increase in brain /sup 3/H-imipramine binding are discussed. Ion-sensitive binding is discussed in relationship to the current controversy surrounding desipramine-sensitive versus ion-sensitive binding.

  13. Functional identification of catalytic metal ion binding sites within RNA.

    Directory of Open Access Journals (Sweden)

    James L Hougland

    2005-09-01

    Full Text Available The viability of living systems depends inextricably on enzymes that catalyze phosphoryl transfer reactions. For many enzymes in this class, including several ribozymes, divalent metal ions serve as obligate cofactors. Understanding how metal ions mediate catalysis requires elucidation of metal ion interactions with both the enzyme and the substrate(s. In the Tetrahymena group I intron, previous work using atomic mutagenesis and quantitative analysis of metal ion rescue behavior identified three metal ions (MA, MB, and MC that make five interactions with the ribozyme substrates in the reaction's transition state. Here, we combine substrate atomic mutagenesis with site-specific phosphorothioate substitutions in the ribozyme backbone to develop a powerful, general strategy for defining the ligands of catalytic metal ions within RNA. In applying this strategy to the Tetrahymena group I intron, we have identified the pro-SP phosphoryl oxygen at nucleotide C262 as a ribozyme ligand for MC. Our findings establish a direct connection between the ribozyme core and the functionally defined model of the chemical transition state, thereby extending the known set of transition-state interactions and providing information critical for the application of the recent group I intron crystallographic structures to the understanding of catalysis.

  14. Ionic force field optimization based on single-ion and ion-pair solvation properties

    CERN Document Server

    Fyta, Maria; Dzubiella, Joachim; Vrbka, Lubos; Netz, Roland R

    2009-01-01

    Molecular dynamics simulations of ionic solutions depend sensitively on the force fields employed for the ions. To resolve the fine differences between ions of the same valence and roughly similar size and in particular to correctly describe ion-specific effects, it is clear that accurate force fields are necessary. In the past, optimization strategies for ionic force fields either considered single-ion properties (such as the solvation free energy at infinite dilution or the ion-water structure) or ion-pair properties (in the form of ion-ion distribution functions). In this paper we investigate strategies to optimize ionic force fields based on single-ion and ion-pair properties simultaneously. To that end, we simulate five different salt solutions, namely CsCl, KCl, NaI, KF, and CsI, at finite ion concentration. The force fields of these ions are systematically varied under the constraint that the single-ion solvation free energy matches the experimental value, which reduces the two-dimensional $\\{\\sigma,\\e...

  15. Physicochemical Properties of Ion Pairs of Biological Macromolecules.

    Science.gov (United States)

    Iwahara, Junji; Esadze, Alexandre; Zandarashvili, Levani

    2015-09-30

    Ion pairs (also known as salt bridges) of electrostatically interacting cationic and anionic moieties are important for proteins and nucleic acids to perform their function. Although numerous three-dimensional structures show ion pairs at functionally important sites of biological macromolecules and their complexes, the physicochemical properties of the ion pairs are not well understood. Crystal structures typically show a single state for each ion pair. However, recent studies have revealed the dynamic nature of the ion pairs of the biological macromolecules. Biomolecular ion pairs undergo dynamic transitions between distinct states in which the charged moieties are either in direct contact or separated by water. This dynamic behavior is reasonable in light of the fundamental concepts that were established for small ions over the last century. In this review, we introduce the physicochemical concepts relevant to the ion pairs and provide an overview of the recent advancement in biophysical research on the ion pairs of biological macromolecules.

  16. Binding properties of SUMO-interacting motifs (SIMs) in yeast.

    Science.gov (United States)

    Jardin, Christophe; Horn, Anselm H C; Sticht, Heinrich

    2015-03-01

    Small ubiquitin-like modifier (SUMO) conjugation and interaction play an essential role in many cellular processes. A large number of yeast proteins is known to interact non-covalently with SUMO via short SUMO-interacting motifs (SIMs), but the structural details of this interaction are yet poorly characterized. In the present work, sequence analysis of a large dataset of 148 yeast SIMs revealed the existence of a hydrophobic core binding motif and a preference for acidic residues either within or adjacent to the core motif. Thus the sequence properties of yeast SIMs are highly similar to those described for human. Molecular dynamics simulations were performed to investigate the binding preferences for four representative SIM peptides differing in the number and distribution of acidic residues. Furthermore, the relative stability of two previously observed alternative binding orientations (parallel, antiparallel) was assessed. For all SIMs investigated, the antiparallel binding mode remained stable in the simulations and the SIMs were tightly bound via their hydrophobic core residues supplemented by polar interactions of the acidic residues. In contrary, the stability of the parallel binding mode is more dependent on the sequence features of the SIM motif like the number and position of acidic residues or the presence of additional adjacent interaction motifs. This information should be helpful to enhance the prediction of SIMs and their binding properties in different organisms to facilitate the reconstruction of the SUMO interactome.

  17. MeRNA: a Database of Metal Ion Binding Sites in RNAStructures

    Energy Technology Data Exchange (ETDEWEB)

    Stefan, Liliana R.; Zhang, Rui; Levitan, Aaron G.; Hendrix, DonnaF.; Brenner, Steven E.; Holbrook, Stephen R.

    2005-10-05

    Metal ions are essential for the folding of RNA into stable tertiary structures and for the catalytic activity of some RNA enzymes. To aid in the study of the roles of metal ions in RNA structural biology, we have created MeRNA (Metals in RNA), a comprehensive compilation of all metal binding sites identified in RNA three-dimensional structures available from the Protein Data Bank (PDB) and Nucleic Acid Database (NDB). Currently, our database contains information relating to binding of 9764 metal ions corresponding to 23 distinct elements; in 256 RNA structures. The metal ion locations were confirmed and ligands characterized using original literature references. MeRNA includes eight manually identified metal-ion binding motifs, which are described in the literature. MeRNA is searchable by PDB identifier, metal ion, method of structure determination, resolution and R-values for X-ray structure, and distance from metal to any RNA atom or to water. New structures with their respective binding motifs will be added to the database as they become available. The MeRNA database will further our understanding of the roles of metal ions in RNA folding and catalysis and have applications in structural and functional analysis, RNA design and engineering.

  18. Heterogeneous behavior of metalloproteins toward metal ion binding and selectivity: insights from molecular dynamics studies.

    Science.gov (United States)

    Gogoi, Prerana; Chandravanshi, Monika; Mandal, Suraj Kumar; Srivastava, Ambuj; Kanaujia, Shankar Prasad

    2016-07-01

    About one-third of the existing proteins require metal ions as cofactors for their catalytic activities and structural complexities. While many of them bind only to a specific metal, others bind to multiple (different) metal ions. However, the exact mechanism of their metal preference has not been deduced to clarity. In this study, we used molecular dynamics (MD) simulations to investigate whether a cognate metal (bound to the structure) can be replaced with other similar metal ions. We have chosen seven different proteins (phospholipase A2, sucrose phosphatase, pyrazinamidase, cysteine dioxygenase (CDO), plastocyanin, monoclonal anti-CD4 antibody Q425, and synaptotagmin 1 C2B domain) bound to seven different divalent metal ions (Ca(2+), Mg(2+), Zn(2+), Fe(2+), Cu(2+), Ba(2+), and Sr(2+), respectively). In total, 49 MD simulations each of 50 ns were performed and each trajectory was analyzed independently. Results demonstrate that in some cases, cognate metal ions can be exchanged with similar metal ions. On the contrary, some proteins show binding affinity specifically to their cognate metal ions. Surprisingly, two proteins CDO and plastocyanin which are known to bind Fe(2+) and Cu(2+), respectively, do not exhibit binding affinity to any metal ion. Furthermore, the study reveals that in some cases, the active site topology remains rigid even without cognate metals, whereas, some require them for their active site stability. Thus, it will be interesting to experimentally verify the accuracy of these observations obtained computationally. Moreover, the study can help in designing novel active sites for proteins to sequester metal ions particularly of toxic nature.

  19. A novel method for thermodynamic study on binding of copper ion with Alzheimer's amyliod β peptide

    Institute of Scientific and Technical Information of China (English)

    BEHBEHANI G. Rezaei

    2009-01-01

    The interaction of Cu2+ with the first 16 residues of the Alzheimer's amyliod β peptide, Afl(1-16), was studied by employing isothermal titration calorimetry at pH 7.2 and 37℃ in aqueous solution. The Gholamreza Rezaei Behbehani (GRB) solvation model was used to reproduce the enthalpies of Cu2++Aβ(1-16) interaction over the whole Cu++concentrations. The binding parameters recovered from the solvation model were attributed to the structural change of Aβ(1-16) due to the metal ion interaction. It was found that there is a set of two identical and non interacting binding sites for Cu2+ ions. The molar enthalpy of binding is △H=27.895 kJ/mol. The association binding constants are 1.895 μM-1 and 1.891 μM-1 for the first and second binding sites respectively.

  20. Water-soluble cavitands - synthesis, solubilities and binding properties

    NARCIS (Netherlands)

    Middel, Oskar; Verboom, Willem; Reinhoudt, David N.

    2002-01-01

    Water-soluble cavitand receptors have been obtained by the introduction of ionizable groups (5, 21-28, 39) and neutral hydrophilic tetraethylene glycol based dendritic wedges (19, 20). The synthesis of these cavitands and a study of their water solubilities and binding properties toward neutral orga

  1. Zinc ions bind to and inhibit activated protein C

    DEFF Research Database (Denmark)

    Zhu, Tianqing; Ubhayasekera, Wimal; Nickolaus, Noëlle

    2010-01-01

    Zn2+ ions were found to efficiently inhibit activated protein C (APC), suggesting a potential regulatory function for such inhibition. APC activity assays employing a chromogenic peptide substrate demonstrated that the inhibition was reversible and the apparent K I was 13 +/- 2 microM. k cat was ...

  2. Patchiness of ion-exchanged mica revealed by DNA binding dynamics at short length scales

    Science.gov (United States)

    Billingsley, D. J.; Lee, A. J.; Johansson, N. A. B.; Walton, A.; Stanger, L.; Crampton, N.; Bonass, W. A.; Thomson, N. H.

    2014-01-01

    The binding of double-stranded (ds) DNA to mica can be controlled through ion-exchanging the mica with divalent cations. Measurements of the end-to-end distance of linear DNA molecules discriminate whether the binding mechanism occurs through 2D surface equilibration or kinetic trapping. A range of linear dsDNA fragments have been used to investigate length dependences of binding. Mica, ion-exchanged with Ni(II) usually gives rise to kinetically trapped DNA molecules, however, short linear fragments (ion-exchanged mica is heterogeneous, and contains patches or domains, separating different ionic species. These results correlate with imaging of dsDNA under aqueous buffer on Ni(II)-mica and indicate that binding domains are of the order of 100 nm in diameter. Shorter DNA fragments behave intermediate to the two extreme cases of 2D equilibration and kinetic trapping. Increasing the incubation time of Ni(II) on mica, from minutes to hours, brings the conformations of the shorter DNA fragments closer to the theoretical value for kinetic trapping, indicating that long timescale kinetics play a role in ion-exchange. X-ray photoelectron spectroscopy (XPS) was used to confirm that the relative abundance of Ni(II) ions on the mica surface increases with time. These findings can be used to enhance spatial control of binding of DNA to inorganic surfaces with a view to patterning high densities arrays.

  3. Control of ion selectivity in LeuT: two Na+ binding sites with two different mechanisms.

    Science.gov (United States)

    Noskov, Sergei Y; Roux, Benoît

    2008-03-28

    The x-ray structure of LeuT, a bacterial homologue of Na(+)/Cl(-)-dependent neurotransmitter transporters, provides a great opportunity to better understand the molecular basis of monovalent cation selectivity in ion-coupled transporters. LeuT possesses two ion binding sites, NA1 and NA2, which are highly selective for Na(+). Extensive all-atom free-energy molecular dynamics simulations of LeuT embedded in an explicit membrane are performed at different temperatures and various occupancy states of the binding sites to dissect the molecular mechanism of ion selectivity. The results show that the two binding sites display robust selectivity for Na(+) over K(+) or Li(+), the competing ions of most similar radii. Of particular interest, the mechanism primarily responsible for selectivity for each of the two binding sites appears to be different. In NA1, selectivity for Na(+) over K(+) arises predominantly from the strong electrostatic field arising from the negatively charged carboxylate group of the leucine substrate coordinating the ion directly. In NA2, which comprises only neutral ligands, selectivity for Na(+) is enforced by the local structural restraints arising from the hydrogen-bonding network and the covalent connectivity of the polypeptide chain surrounding the ion according to a "snug-fit" mechanism.

  4. The two distinctive metal ion binding domains of the wheat metallothionein Ec-1.

    Science.gov (United States)

    Peroza, Estevão A; Kaabi, Ali Al; Meyer-Klaucke, Wolfram; Wellenreuther, Gerd; Freisinger, Eva

    2009-03-01

    Metallothioneins are small cysteine-rich proteins believed to play a role, among others, in the homeostasis of essential metal ions such as Zn(II) and Cu(I). Recently, we could show that wheat E(c)-1 is coordinating its six Zn(II) ions in form of metal-thiolate clusters analogously to the vertebrate metallothioneins. Specifically, two Zn(II) ions are bound in the N-terminal and four in the C-terminal domain. In the following, we will present evidence for the relative independence of the two domains from each other with respect to their metal ion binding abilities, and uncover three intriguing peculiarities of the protein. Firstly, one Zn(II) ion of the N-terminal domain is relative resistant to complete replacement with Cd(II) indicating the presence of a Zn(II)-binding site with increased stability. Secondly, the C-terminal domain is able to coordinate an additional fifth metal ion, though with reduced affinity, which went undetected so far. Finally, reconstitution of apoE(c)-1 with an excess of Zn(II) shows a certain amount of sub-stoichiometrically metal-loaded species. The possible relevance of these finding for the proposed biological functions of wheat E(c)-1 will be discussed. In addition, extended X-ray absorption fine structure (EXAFS) measurements on both, the full-length and the truncated protein, provide final evidence for His participation in metal ion binding.

  5. Trends for isolated amino acids and dipeptides: Conformation, divalent ion binding, and remarkable similarity of binding to calcium and lead

    Science.gov (United States)

    Ropo, M.; Blum, V.; Baldauf, C.

    2016-11-01

    We derive structural and binding energy trends for twenty amino acids, their dipeptides, and their interactions with the divalent cations Ca2+, Ba2+, Sr2+, Cd2+, Pb2+, and Hg2+. The underlying data set consists of more than 45,000 first-principles predicted conformers with relative energies up to ~4 eV (~400 kJ/mol). We show that only very few distinct backbone structures of isolated amino acids and their dipeptides emerge as lowest-energy conformers. The isolated amino acids predominantly adopt structures that involve an acidic proton shared between the carboxy and amino function. Dipeptides adopt one of two intramolecular-hydrogen bonded conformations C5 or . Upon complexation with a divalent cation, the accessible conformational space shrinks and intramolecular hydrogen bonding is prevented due to strong electrostatic interaction of backbone and side chain functional groups with cations. Clear correlations emerge from the binding energies of the six divalent ions with amino acids and dipeptides. Cd2+ and Hg2+ show the largest binding energies–a potential correlation with their known high acute toxicities. Ca2+ and Pb2+ reveal almost identical binding energies across the entire series of amino acids and dipeptides. This observation validates past indications that ion-mimicry of calcium and lead should play an important role in a toxicological context.

  6. Fe binding properties of two soybean (Glycine max L.) LEA4 proteins associated with antioxidant activity.

    Science.gov (United States)

    Liu, Guobao; Xu, Hong; Zhang, Liao; Zheng, Yizhi

    2011-06-01

    Late embryogenesis abundant (LEA) group 4 (LEA4) proteins play an important role in the water stress tolerance of plants. Although they have been hypothesized to stabilize macromolecules in stressed cells, the protective functions and mechanisms of LEA4 proteins are still not clear. In this study, the metal binding properties of two related soybean LEA4 proteins, GmPM1 and GmPM9, were tested using immobilized metal ion affinity chromatography (IMAC). The metal ions Fe(3+), Ni(2+), Cu(2+) and Zn(2+) were observed to bind these two proteins, while Ca(2+), Mg(2+) or Mn(2+) did not. Results from isothermal titration calorimetry (ITC) indicated that the binding affinity of GmPM1 for Fe(3+) was stronger than that of GmPM9. Hydroxyl radicals generated by the Fe(3+)/H(2)O(2) system were scavenged by both GmPM1 and GmPM9 in the absence or the presence of high ionic conditions (100 mM NaCl), although the scavenging activity of GmPM1 was significantly greater than that of GmPM9. These results suggest that GmPM1 and GmPM9 are metal-binding proteins which may function in reducing oxidative damage induced by abiotic stress in plants.

  7. Production of a Purified Marine Neurotoxin and Demonstration of its Binding Affinity to Ion Channel Receptors

    Science.gov (United States)

    1989-06-10

    Saxitoxin Conotoxins 2 Batrachotoxin Persistent activation Veratrum alkaloids Grayanotoxins 3 a- scorpion toxins Inhibit inactivation sea anemone... toxins 4 b- scorpion toxins Shift activation 5 Brevetoxins Shift activation and Ciguatoxin Inhibit J.nactivation Baden 1989 5 The objectives of this study...includes 1) demonstration of dinoflagellate toxin binding to synaptosome ion ch nnels 2) investigation of the effects of maitotoxin on the binding of

  8. Characterization of parvalbumin and polcalcin divalent ion binding by isothermal titration calorimetry.

    Science.gov (United States)

    Henzl, Michael T

    2009-01-01

    The elucidation of structure-affinity relationships in EF-hand proteins requires a reliable assay of divalent ion affinity. In principle, isothermal titration calorimetry (ITC) should be capable of furnishing estimates for Ca2+- and Mg2+-binding constants in these systems. And because the method yields the binding enthalpy directly, ITC can provide a more detailed view of binding energetics than methods that rely on 45Ca2+ or fluorescent indicators. For several reasons, however, it is generally not possible to extract reliable binding parameters from single ITC experiments. Ca2+ affinity is often too high, and Mg2+ affinity is invariably too low. Moreover, least-squares minimization of multisite systems may not afford a unique fit because of strong parameter correlations. This chapter outlines a strategy for analyzing two-site systems that overcomes these obstacles. The method--which involves simultaneous, or global, least-squares analysis of direct and competitive ITC data--yields binding parameters for both Ca2+ and Mg2+. Application of the method is demonstrated for two systems. The S55D/E59D variant of rat alpha-parvalbumin, noteworthy for its elevated metal ion affinity, binds divalent ions noncooperatively and is amenable to analysis using an independent two-site model. On the other hand, Phl p 7, a pollen-specific EF-hand protein from timothy grass, binds Ca2+ with positive cooperativity. Divalent ion-binding data for the protein must be analyzed using a two-site Adair model.

  9. Cellular Responses to the Metal-Binding Properties of Metformin

    Science.gov (United States)

    Logie, Lisa; Harthill, Jean; Patel, Kashyap; Bacon, Sandra; Hamilton, D. Lee; Macrae, Katherine; McDougall, Gordon; Wang, Huan-Huan; Xue, Lin; Jiang, Hua; Sakamoto, Kei; Prescott, Alan R.; Rena, Graham

    2012-01-01

    In recent decades, the antihyperglycemic biguanide metformin has been used extensively in the treatment of type 2 diabetes, despite continuing uncertainty over its direct target. In this article, using two independent approaches, we demonstrate that cellular actions of metformin are disrupted by interference with its metal-binding properties, which have been known for over a century but little studied by biologists. We demonstrate that copper sequestration opposes known actions of metformin not only on AMP-activated protein kinase (AMPK)-dependent signaling, but also on S6 protein phosphorylation. Biguanide/metal interactions are stabilized by extensive π-electron delocalization and by investigating analogs of metformin; we provide evidence that this intrinsic property enables biguanides to regulate AMPK, glucose production, gluconeogenic gene expression, mitochondrial respiration, and mitochondrial copper binding. In contrast, regulation of S6 phosphorylation is prevented only by direct modification of the metal-liganding groups of the biguanide structure, supporting recent data that AMPK and S6 phosphorylation are regulated independently by biguanides. Additional studies with pioglitazone suggest that mitochondrial copper is targeted by both of these clinically important drugs. Together, these results suggest that cellular effects of biguanides depend on their metal-binding properties. This link may illuminate a better understanding of the molecular mechanisms enabling antihyperglycemic drug action. PMID:22492524

  10. Oligomerization of Mannan-binding Lectin Dictates Binding Properties and Complement Activation.

    Science.gov (United States)

    Kjaer, T R; Jensen, L; Hansen, A; Dani, R; Jensenius, J C; Dobó, J; Gál, P; Thiel, S

    2016-07-01

    The complement system is a part of the innate immune system and is involved in recognition and clearance of pathogens and altered-self structures. The lectin pathway of the complement system is initiated when soluble pattern recognition molecules (PRMs) with collagen-like regions bind to foreign or altered self-surfaces. Associated with the collagen-like stems of these PRMs are three mannan-binding lectin (MBL)-associated serine proteases (MASPs) and two MBL-associated proteins (MAps). The most studied of the PRMs, MBL, is present in serum mainly as trimeric and tetrameric oligomers of the structural subunit. We hypothesized that oligomerization of MBL may influence both the potential to bind to micro organisms and the interaction with the MASPs and MAps, thus influencing the ability to initiate complement activation. When testing binding at 37 °C, we found higher binding of tetrameric MBL to Staphylococcus aureus (S. aureus) than trimeric and dimeric MBL. In serum, we found that tetrameric MBL was the main oligomeric form present in complexes with the MASPs and MAp44. Such preference was confirmed using purified forms of recombinant MBL (rMBL) oligomers, where tetrameric rMBL interacted stronger with all of the MASPs and MAp44, compared to trimeric MBL. As a direct consequence of the weaker interaction with the MASPs, we found that trimeric rMBL was inferior to tetrameric rMBL in activating the complement system. Our data suggest that the oligomeric state of MBL is crucial both for the binding properties and the effector function of MBL.

  11. Binding of ArgTX-636 in the NMDA receptor ion channel

    DEFF Research Database (Denmark)

    Poulsen, Mette H; Andersen, Jacob; Christensen, Rune

    2015-01-01

    The N-methyl-d-aspartate receptors (NMDARs) constitute an important class of ligand-gated cation channels that are involved in the majority of excitatory neurotransmission in the human brain. Compounds that bind in the NMDAR ion channel and act as blockers are use- and voltage-dependent inhibitor...

  12. Binding of alkali metal ions by cyclic polyethers: significance in ion transport processes.

    Science.gov (United States)

    Izatt, R M; Rytting, J H; Nelson, D P; Haymore, B L; Christensen, J J

    1969-04-25

    Values for the formation constant (log K), the change in enthalpy (triangle upH degrees ), and the change in entropy (triangle upS degrees ) have been determined for the interaction of lithium, sodium, potassium, rubidium, and cesium ions with the two isomers of the cyclic polyether, 2,5,8,15,18,21-hexaoxatricyclo[20.4.0.0(9,14)] hexacosane. The stability order of these metal ions with either isomer is identical to the permeability order for these same metal ions with the structurally related antibiotics, valinomycin and monactin.

  13. Cu(I) binding properties of a designed metalloprotein.

    Science.gov (United States)

    Xie, Fei; Sutherland, Duncan E K; Stillman, Martin J; Ogawa, Michael Y

    2010-03-01

    The Cu(I) binding properties of the designed peptide C16C19-GGY are reported. This peptide was designed to form an alpha-helical coiled-coil but modified to incorporate a Cys-X-X-Cys metal-binding motif along its hydrophobic face. Absorption, emission, electrospray ionization mass spectrometry (ESI-MS), and circular dichroism (CD) experiments show that a 1:1 Cu-peptide complex is formed when Cu(I) is initially added to a solution of the monomeric peptide. This is consistent with our earlier study in which the emissive 1:1 complex was shown to exist as a peptide tetramer containing a tetranuclear copper cluster Kharenko et al. (2005) [11]. The presence of the tetranuclear copper center is now confirmed by ESI-MS which along with UV data show that this cluster is formed in a cooperative manner. However, spectroscopic titrations show that continued addition of Cu(I) results in the occupation of a second, lower affinity metal-binding site in the metallopeptide. This occupancy does not significantly affect the conformation of the metallopeptide but does result in a quenching of the 600nm emission. It was further found that the exogenous reductant tris(2-carboxyethyl)phosphine (TCEP) can competitively inhibit the binding of Cu(I) to the low affinity site of the peptide, but does not interact with Cu(I) clusters.

  14. Tetrameric ZBRK1 DNA binding domain has affinity towards cognate DNA in absence of zinc ions.

    Science.gov (United States)

    Yadav, Lumbini R; Biswal, Mahamaya N; Vikrant; Hosur, M V; Varma, Ashok K

    2014-07-18

    Zinc finger transcription regulatory proteins play crucial roles in cell-cycle regulation, DNA damage response and tumor genesis. Human ZBRK1 is a zinc-finger transcription repressor protein, which recognizes double helical DNA containing consensus sequences of 5'GGGXXXCAGXXXTTT3'. In the present study, we have purified recombinant DNA binding domain of ZBRK1, and studied binding with zinc ions and DNA, using biophysical techniques. The elution profile of the purified protein suggests that this ZBRK1 forms a homotetramer in solution. Dissociation and pull down assays also suggest that this domain forms a higher order oligomer. The ZBRK1-DNA binding domain acquires higher stability in the presence of zinc ions and DNA. The secondary structure of the ZBRK1-DNA complex is found to be significantly altered from the standard B-DNA conformation. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. Kinetic and thermodynamic evaluation of phosphate ions binding onto sevelamer hydrochloride.

    Science.gov (United States)

    Elsiddig, Reem; Hughes, Helen; Owens, Eleanor; O' Reilly, Niall J; O'Grady, David; McLoughlin, Peter

    2014-10-20

    Sevelamer hydrochloride is the first non-aluminium, non-calcium-based phosphate binder developed for the management of hyperphosphatemia in end stage renal diseases. It is a synthetic ion-exchange polymer which binds and removes phosphate ions due to the high content of cationic charge associated with protonated amine groups on the polymer matrix. This is the first in-depth study investigating phosphate removal in vitro from aqueous solutions using commercially available sevelamer hydrochloride at physiological conditions of phosphate level, pH and temperature. The kinetic and thermodynamic parameters of phosphate binding onto the sevelamer hydrochloride particles were evaluated in order to define the binding process. A series of kinetic studies were carried out in order to delineate the effect of initial phosphate concentration, absorbent dose and temperature on the rate of binding. The results were analysed using three kinetic models with the best-fit of the experimental data obtained using a pseudo-second order model. Thermodynamic parameters provide in-depth information on inherent energetic changes that are associated with binding. Free energy ΔG°, enthalpy ΔH°, and entropy ΔS° changes were calculated in this study in order to assess the relationship of these parameters to polymer morphology. The binding reaction was found to be a spontaneous endothermic process with increasing entropy at the solid-liquid interface.

  16. Initial binding of ions to the interhelical loops of divalent ion transporter CorA: replica exchange molecular dynamics simulation study.

    Directory of Open Access Journals (Sweden)

    Tong Zhang

    Full Text Available Crystal structures of Thermotoga maritima magnesium transporter CorA, reported in 2006, revealed its homo-pentameric constructions. However, the structure of the highly conserved extracellular interhelical loops remains unsolved, due to its high flexibility. We have explored the configurations of the loops through extensive replica exchange molecular dynamics simulations in explicit solvent model with the presence of either Co(III Hexamine ions or Mg(2+ ions. We found that there are multiple binding sites available on the interhelical loops in which the negatively charged residues, E316 and E320, are located notably close to the positively charged ions during the simulations. Our simulations resolved the distinct binding patterns of the two kinds of ions: Co(III Hexamine ions were found to bind stronger with the loop than Mg(2+ ions with binding free energy -7.3 kJ/mol lower, which is nicely consistent with the previous data. Our study provides an atomic basis description of the initial binding process of Mg(2+ ions on the extracellular interhelical loops of CorA and the detailed inhibition mechanism of Co(III Hexamine ions on CorA ions transportation.

  17. Initial binding of ions to the interhelical loops of divalent ion transporter CorA: replica exchange molecular dynamics simulation study.

    Science.gov (United States)

    Zhang, Tong; Mu, Yuguang

    2012-01-01

    Crystal structures of Thermotoga maritima magnesium transporter CorA, reported in 2006, revealed its homo-pentameric constructions. However, the structure of the highly conserved extracellular interhelical loops remains unsolved, due to its high flexibility. We have explored the configurations of the loops through extensive replica exchange molecular dynamics simulations in explicit solvent model with the presence of either Co(III) Hexamine ions or Mg(2+) ions. We found that there are multiple binding sites available on the interhelical loops in which the negatively charged residues, E316 and E320, are located notably close to the positively charged ions during the simulations. Our simulations resolved the distinct binding patterns of the two kinds of ions: Co(III) Hexamine ions were found to bind stronger with the loop than Mg(2+) ions with binding free energy -7.3 kJ/mol lower, which is nicely consistent with the previous data. Our study provides an atomic basis description of the initial binding process of Mg(2+) ions on the extracellular interhelical loops of CorA and the detailed inhibition mechanism of Co(III) Hexamine ions on CorA ions transportation.

  18. Induced binding of proteins by ammonium sulfate in affinity and ion-exchange column chromatography.

    Science.gov (United States)

    Arakawa, Tsutomu; Tsumoto, Kouhei; Ejima, Daisuke; Kita, Yoshiko; Yonezawa, Yasushi; Tokunaga, Masao

    2007-04-10

    In general, proteins bind to affinity or ion-exchange columns at low salt concentrations, and the bound proteins are eluted by raising the salt concentration, changing the solvent pH, or adding competing ligands. Blue-Sepharose is often used to remove bovine serum albumin (BSA) from samples, but when we applied BSA to Blue-Sepharose in 20 mM phosphate, pH 7.0, 50%-60% of the protein flowed through the column; however, complete binding of BSA was achieved by the addition of 2 M ammonium sulfate (AS) to the column equilibration buffer and the sample. The bound protein was eluted by decreasing the AS concentration or by adding 1 M NaCl or arginine. AS at high concentrations resulted in binding of BSA even to an ion-exchange column, Q-Sepharose, at pH 7.0. Thus, although moderate salt concentrations elute proteins from Blue-Sepharose or ion-exchange columns, proteins can be bound to these columns under extreme salting-out conditions. Similar enhanced binding of proteins by AS was observed with an ATP-affinity column.

  19. Identification of a chloride ion binding site in Na+/Cl -dependent transporters.

    Science.gov (United States)

    Forrest, Lucy R; Tavoulari, Sotiria; Zhang, Yuan-Wei; Rudnick, Gary; Honig, Barry

    2007-07-31

    The recent determination of the crystal structure of the leucine transporter from Aquifex aeolicus (aaLeuT) has provided significant insights into the function of neurotransmitter:sodium symporters. Transport by aaLeuT is Cl(-) independent, whereas many neurotransmitter:sodium symporters from higher organisms depend on Cl(-) ions. However, the only Cl(-) ion identified in the aaLeuT structure interacts with nonconserved residues in extracellular loops, and thus the relevance of this binding site is unclear. Here, we use calculations of pK(A)s and homology modeling to predict the location of a functionally important Cl(-) binding site in serotonin transporter and other Cl(-)-dependent transporters. We validate our model through the site-directed mutagenesis of residues predicted to coordinate the Cl(-) ion and through the observation of sequence conservation patterns in other Cl(-)-dependent transporters. The proposed site is located midway across the membrane and is formed by residues from transmembrane helices 2, 6, and 7. It is close to the Na1 sodium binding site, thus providing an explanation for the coupling of Cl(-) and Na(+) ions during transport. Other implications of the model are also discussed.

  20. The solvation and ion condensation properties for sulfonated polyelectrolytes in different solvents—a computational study

    Science.gov (United States)

    Smiatek, J.; Wohlfarth, A.; Holm, C.

    2014-02-01

    In contrast to the broad knowledge about aqueous polyelectrolyte solutions, less is known about the properties in aprotic and apolar solvents. We therefore investigate the behavior of sulfonated polyelectrolytes in sodium form in the presence of different solvents via all-atom molecular dynamics simulations. The results clearly reveal strong variations in ion condensation constants and polyelectrolyte conformations for different solvents like water, dimethyl sulfoxide (DMSO) and chloroform. The binding free energies of the solvent contacts with the polyelectrolyte groups validate the influence of different solvent qualities. With regard to the ion condensation behavior, the numerical findings show that the explicit values for the condensation constants depend on the preferential binding coefficient as derived by the evaluation of Kirkwood-Buff integrals. Surprisingly, the smallest ion condensation constant is observed for DMSO compared to water, whereas in the presence of chloroform, virtually no free ions are present, which is in good agreement to the donor number concept. In contrast to the results for the low condensation constants, the sodium conductivity in DMSO is smaller compared to water. We are able to relate this result to the observed smaller diffusion coefficient for the sodium ions in DMSO.

  1. Enhanced Physicochemical and Biological Properties of Ion-Implanted Titanium Using Electron Cyclotron Resonance Ion Sources

    Directory of Open Access Journals (Sweden)

    Csaba Hegedűs

    2016-01-01

    Full Text Available The surface properties of metallic implants play an important role in their clinical success. Improving upon the inherent shortcomings of Ti implants, such as poor bioactivity, is imperative for achieving clinical use. In this study, we have developed a Ti implant modified with Ca or dual Ca + Si ions on the surface using an electron cyclotron resonance ion source (ECRIS. The physicochemical and biological properties of ion-implanted Ti surfaces were analyzed using various analytical techniques, such as surface analyses, potentiodynamic polarization and cell culture. Experimental results indicated that a rough morphology was observed on the Ti substrate surface modified by ECRIS plasma ions. The in vitro electrochemical measurement results also indicated that the Ca + Si ion-implanted surface had a more beneficial and desired behavior than the pristine Ti substrate. Compared to the pristine Ti substrate, all ion-implanted samples had a lower hemolysis ratio. MG63 cells cultured on the high Ca and dual Ca + Si ion-implanted surfaces revealed significantly greater cell viability in comparison to the pristine Ti substrate. In conclusion, surface modification by electron cyclotron resonance Ca and Si ion sources could be an effective method for Ti implants.

  2. The influence of ion binding and ion specific potentials on the double layer pressure between charged bilayers at low salt concentrations

    Science.gov (United States)

    Bostrom, M.; Lima, E. R. A.; Tavares, F. W.; Ninham, B. W.

    2008-04-01

    Measurements of surface forces between double-chained cationic bilayers adsorbed onto molecularly smooth mica surfaces across different millimolar salt solutions have revealed a large degree of ion specificity [Pashley et al., J. Phys. Chem. 90, 1637 (1986)]. This has been interpreted in terms of highly specific anion binding to the adsorbed bilayers. We show here that inclusion in the double layer theory of nonspecific ion binding and ion specific nonelectrostatic potentials acting between ions and the two surfaces can account for the phenomenon. It also gives the right Hofmeister series for the double layer pressure.

  3. Anticoagulant and calcium-binding properties of high molecular weight derivatives of human fibrinogen, produced by plasmin (fragments X).

    Science.gov (United States)

    Nieuwenhuizen, W; Gravesen, M

    1981-03-27

    Early plasmin degradation products (X fragments) of human fibrinogen were prepared in the presence of calcium-ions or EGTA, and purified on Sepharose 6B-CL. X fragments were characterized with respect to amino-terminal amino acids, polypeptide-chain composition, anticlotting properties and calcium-binding. Amino-terminal amino acids were alanine and tyrosine. The molecular weights of the chains were about 26 000, 58 000 and 48 000 for A alpha-, B beta- and gamma-chains, respectively. X fragments were about 6-times as potent in anticlotting behaviour as D fragments prepared in the presence of calcium ions. Calcium-binding properties were essentially identical to those of fibrinogen. No differences were observed between X fragments prepared in the presence of calcium ions and those prepared in the presence of EGTA. This indicates that the carboxy-terminal parts of the A alpha-chains of fibrinogen are not involved in calcium-binding and that differences in chain-remnants as observed in late plasmic degradation products (which depend on the presence of calcium ions or EGTA [23] in the incubation medium) are introduced beyond the stage of fragment X formation.

  4. Mechanistic studies of metal ion binding to water-soluble polymers using potentiometry.

    Science.gov (United States)

    Jarvis, N V; Wagener, J M

    1995-02-01

    A method for elucidating metal ion binding mechanisms with water-soluble polymers has been developed in which the polymer is treated as a collection of monomeric units. Data obtained from potentiometric titrations are analysed by the ESTA library of programs and apparent formation constants may be calculated. From this information, predictions may be made as to metal ion separation using complexation-ultrafiltration techniques. The polymer used in this study was Polymin Water-Free and its complexation with Hg(II), Cd(II), Pb(II), Co(II) and Ni(II) was successfully modelled.

  5. Enhanced bilirubin binding to different mammalian erythrocytes in the presence of magnesium ions

    OpenAIRE

    M. K. Ali; Siddiqui, M. U.; Tayyab, S.

    2001-01-01

    Effect of magnesium ions on the binding of bilirubin to erythrocytes of different mammalian species, namely, human, buffalo, goat and sheep was studied. Increase in the concentration of magnesium ions led to a gradual increase in the erythrocyte-bound bilirubin in both human and buffalo erythrocytes whereas in sheep and goat erythrocytes, the pronounced increase was found beyond 2.0 and 2.7 mM MgCl2 concentrations respectively. Percentage increase in erythrocyte-bound bilirubin was found high...

  6. Carbohydrate Binding Modules: Biochemical Properties and Novel Applications

    Science.gov (United States)

    Shoseyov, Oded; Shani, Ziv; Levy, Ilan

    2006-01-01

    Polysaccharide-degrading microorganisms express a repertoire of hydrolytic enzymes that act in synergy on plant cell wall and other natural polysaccharides to elicit the degradation of often-recalcitrant substrates. These enzymes, particularly those that hydrolyze cellulose and hemicellulose, have a complex molecular architecture comprising discrete modules which are normally joined by relatively unstructured linker sequences. This structure is typically comprised of a catalytic module and one or more carbohydrate binding modules (CBMs) that bind to the polysaccharide. CBMs, by bringing the biocatalyst into intimate and prolonged association with its substrate, allow and promote catalysis. Based on their properties, CBMs are grouped into 43 families that display substantial variation in substrate specificity, along with other properties that make them a gold mine for biotechnologists who seek natural molecular “Velcro” for diverse and unusual applications. In this article, we review recent progress in the field of CBMs and provide an up-to-date summary of the latest developments in CBM applications. PMID:16760304

  7. A thermodynamic investigation on the binding of mercury ion with myelin basic protein at different temperatures

    Institute of Scientific and Technical Information of China (English)

    G. Rezaei Behbehani; L. Barzegar; A.A. Saboury; S. Ghammami

    2011-01-01

    A thermodynamic study on the interaction of myelin basic protein with mercury ion was studied by using isothermal titration calorimetry, ITC, at 300.15, 310.15 and 320.15 K in Tris buffer solution at pH 7. The enthalpies of MBP + Hg2+ interaction are reported and analysed in terms of the extended solvation model. It was found that MBP has two identical and non-cooperative binding sites for Hg2+ ions. The intrinsic dissociation equilibrium constants are 99.904,112.968 and 126.724 |μmol/L, and the molar enthalpy of binding are -11.634, -10.768 and -10.117 kJ mol 1 at 300.15, 310.15 and 320.15 K, respectively.

  8. Binding Interaction of Captopril with Metal Ions: A Fluorescence Quenching Study

    Institute of Scientific and Technical Information of China (English)

    SIDDIQI K.S.; BANO Shaista; MOHD Ayaz; KHAN Aslam Aftab Parwaz

    2009-01-01

    The binding interaction of captopril(CPL)with biologically active metal ions Mg2+,Ca2+,Mn2+,Co2+,Ni2+,Cu2+ and Zn2+ was investigated in an aqueous acidic medium by fluorescence spectroscopy.The experimental results showed that the metal ions quenched the intrinsic fluorescence of CPL by forming CPL-metal complexes.It was found that static quenching was the main reason for the fluorescence quenching.The quenching constant in the case of Cu2+ was highest among all quenchers,perhaps due to its high nuclear charge and small size.Quenching of CPL by metal ions follows the order Cu2+> Ni2+> Co2+> Ca2+>Zn2+ > Mn2+ > Mg2+.The quenching constant Ksv,bimolecular quenching constant Kq,binding constant K and the binding sites "n" were determined together with their thermodynamic parameters at 27 and 37℃.The positive entropy change indicated the gain in configurational entropy as a result of chelation.The process of interaction was spontaneous and mainly △S-driven.

  9. Characterization and antibacterial properties of porous fibers containing silver ions

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Zhaoyang; Fan, Chenxu; Tang, Xiaopeng; Zhao, Jianghui; Song, Yanhua; Shao, Zhongbiao [National Engineering Laboratory for Modern Silk, College of Textile and Engineering, Soochow University, 199 Ren-ai Road, Suzhou 215123 (China); Xu, Lan, E-mail: lanxu@suda.edu.cn [National Engineering Laboratory for Modern Silk, College of Textile and Engineering, Soochow University, 199 Ren-ai Road, Suzhou 215123 (China); Nantong Textile Institute of Soochow University, 58 Chong-chuan Road, Nantong 226018 (China)

    2016-11-30

    Highlights: • Antibacterial electrospun PLA porous fibers containing silver ions were prepared. • Porous structure and porosity of PLA/Ag{sup +} porous fibers were investigated. • The antibacterial effects of PLA/Ag{sup +} porous fibers were studied. • The released mechanism of silver ions in the porous fibers was illustrated. • The porous structure could improve the antibacterial properties. - Abstract: Materials prepared on the base of bioactive silver compounds have become more and more popular. In the present work, the surface morphology, structure and properties, of electrospun Polylactide Polylactic acid (PLA) porous fibers containing various ratios of silver ions were investigated by a combination of X-ray photoelectron spectroscopy (XPS), universal testing machine, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and et al. The biological activities of the proposed porous fibers were discussed in view of the released silver ions concentration. Antibacterial properties of these porous fibers were studied using two bacterial strains: Escherichia coli (E. coli) and Methicillin-resistant Staphylococcus aureus (MRSA). Results of the antibacterial testing suggested that PLA porous fibers containing silver ions could be used as potent antibacterial wound dressing materials in the biomedical field.

  10. Combined sodium ion sensitivity in agonist binding and internalization of vasopressin V1b receptors.

    Science.gov (United States)

    Koshimizu, Taka-Aki; Kashiwazaki, Aki; Taniguchi, Junichi

    2016-05-03

    Reducing Na(+) in the extracellular environment may lead to two beneficial effects for increasing agonist binding to cell surface G-protein coupled receptors (GPCRs): reduction of Na(+)-mediated binding block and reduce of receptor internalization. However, such combined effects have not been explored. We used Chinese Hamster Ovary cells expressing vasopressin V1b receptors as a model to explore Na(+) sensitivity in agonist binding and receptor internalization. Under basal conditions, a large fraction of V1b receptors is located intracellularly, and a small fraction is in the plasma membrane. Decreases in external Na(+) increased cell surface [(3)H]AVP binding and decreased receptor internalization. Substitution of Na(+) by Cs(+) or NH4(+) inhibited agonist binding. To suppress receptor internalization, the concentration of NaCl, but not of CsCl, had to be less than 50 mM, due to the high sensitivity of the internalization machinery to Na(+) over Cs(+). Iso-osmotic supplementation of glucose or NH4Cl maintained internalization of the V1b receptor, even in a low-NaCl environment. Moreover, iodide ions, which acted as a counter anion, inhibited V1b agonist binding. In summary, we found external ionic conditions that could increase the presence of high-affinity state receptors at the cell surface with minimum internalization during agonist stimulations.

  11. Understanding the interaction between trivalent lanthanide ions and stereoregular polymethacrylates through luminescence, binding isotherms, NMR, and interaction with cetylpyridinium chloride.

    Science.gov (United States)

    Kogej, Ksenija; Fonseca, Sofia M; Rovisco, José; Azenha, M Emília; Ramos, M Luísa; Seixas de Melo, J Sérgio; Burrows, Hugh D

    2013-11-26

    Complexation of isotactic, syndiotactic, and atactic poly(methacrylic acid), PMA, with trivalent lanthanide ions has been studied in water at a degree of neutralization 0.5. Metal ion binding is shown by quenching of cerium(III) fluorescence, enhancement of Tb(III) luminescence, and lanthanide-induced line broadening in the PMA (1)H NMR spectra. Comparison with lanthanide-acetate complexation suggests carboxylate binds in a bidentate fashion, while Ce(III) luminescence quenching suggests an ≈3:1 carboxylate:metal ion stoichiometry, corresponding to charge neutralization. The presence of both free and bound Ce(III) cations in PMA solutions is confirmed from luminescence decays. Studies of Tb(3+) luminescence lifetime in H2O and D2O solutions show complexation is accompanied by loss of 5-6 water molecules, indicating that each bidentate carboxylate replaces two coordinated water molecules. The behavior depends on pH and polyelectrolyte stereoregularity, and stronger binding is observed with isotactic polyelectrolyte. Binding of cetylpyridinium chloride, CPC, in these systems is studied by luminescence, NMR, and potentiometry. NMR and Tb(3+) luminescence lifetime studies show the strongest binding with the isotactic polymer. Binding of surfactant to poly(methacrylate) in the presence of lanthanides is noncooperative, i.e., it binds to the free sites; binding isotherms in the presence of lanthanides are shifted to higher free surfactant concentrations, compared with sodium ions, have lower slopes and show a clear two-step binding mechanism. While CPC readily replaces the Na(+) ions of poly(methacrylate) and binds very strongly (low critical association concentrations), exchange is much more difficult with the strongly bound trivalent lanthanide ions. Effects of tacticity are seen, with surfactant interacting most strongly with isotactic chains in the initial stages of binding, while in the final stages of binding the interaction is strongest with atactic poly(methacrylate).

  12. Spectral properties of oxide crystals free of iron ions

    Energy Technology Data Exchange (ETDEWEB)

    Kvapil, J.; Perner, B.; Kvapil, J.; Manek, B.; Kubelka, J.; Blazek, K. (Monokrystaly, Turnov (Czechoslovakia)); Austrata, R.; Schauer, P. (Czechoslovak Academy of Sciences, Brno. Inst. of Scientific Instruments); Vitamvas, Z. (Technical Univ., Liberec (Czechoslovakia))

    1982-07-01

    Al/sub 2/O/sub 3/ and YAG crystals were purified from traces of iron by the growth in reducing atmosphere. Luminescence output of such materials was substantially increased, but some undesirable properties as transient colour centre formation in YAG:Nd and low damage threshold of ruby laser rods were observed. Minimum concentration of iron ions which drastically change spectral properties of oxide crystals seems to be

  13. Ion plated gold films: Properties, tribological behavior and performance

    Science.gov (United States)

    Spalvins, Talivaldis

    1987-01-01

    The glow discharge energizing favorably modifies and controls the coating/substrate adherence and the nucleation and growth sequence of ion plated gold films. As a result the adherence, coherence, internal stresses, and morphology of the films are significantly improved. Gold ion plated films because of their graded coating/substrate interface and fine uniform densely packed microstructure not only improve the tribological properties but also induce a surface strengthening effect which improves the mechanical properties such as yield, tensile, and fatigue strength. Consequently significant improvements in the tribological performance of ion plated gold films as compared to vapor deposited gold films are shown in terms of decreased friction/wear and prolonged endurance life.

  14. Characterization and antibacterial properties of porous fibers containing silver ions

    Science.gov (United States)

    Sun, Zhaoyang; Fan, Chenxu; Tang, Xiaopeng; Zhao, Jianghui; Song, Yanhua; Shao, Zhongbiao; Xu, Lan

    2016-11-01

    Materials prepared on the base of bioactive silver compounds have become more and more popular. In the present work, the surface morphology, structure and properties, of electrospun Polylactide Polylactic acid (PLA) porous fibers containing various ratios of silver ions were investigated by a combination of X-ray photoelectron spectroscopy (XPS), universal testing machine, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and et al. The biological activities of the proposed porous fibers were discussed in view of the released silver ions concentration. Antibacterial properties of these porous fibers were studied using two bacterial strains: Escherichia coli (E. coli) and Methicillin-resistant Staphylococcus aureus (MRSA). Results of the antibacterial testing suggested that PLA porous fibers containing silver ions could be used as potent antibacterial wound dressing materials in the biomedical field.

  15. Towards a model of non-equilibrium binding of metal ions in biological systems.

    Science.gov (United States)

    Beardmore, James; Exley, Christopher

    2009-02-01

    We have used a systems biology approach to address the hitherto insoluble problem of the quantitative analysis of non-equilibrium binding of aqueous metal ions by competitive ligands in heterogeneous media. To-date, the relative proportions of different metal complexes in aqueous media has only been modelled at chemical equilibrium and there are no quantitative analyses of the approach to equilibrium. While these models have improved our understanding of how metals are used in biological systems they cannot account for the influence of kinetic factors in metal binding, transport and fate. Here we have modelled the binding of aluminium, Al(III), in blood serum by the iron transport protein transferrin (Tf) as it is widely accepted that the biological fate of this non-essential metal is not adequately described by experiments, invitro and insilico, which have consistently demonstrated that at equilibrium 90% of serum Al(III) is bound by Tf. We have coined this paradox 'the blood-aluminium problem' and herein applied a systems biology approach which utilised well-found assumptions to pare away the complexities of the problem such that it was defined by a comparatively simple set of computational rules and, importantly, its solution assumed significant predictive capabilities. Here we show that our novel computational model successfully described the binding of Al(III) by Tf both at equilibrium and as equilibrium for Al(Tf) was approached. The model predicted significant non-equilibrium binding of Al by ligands in competition with Tf and, thereby, provided an explanation of why the distribution of Al(III) in the body cannot be adequately described by its binding and transport by Tf alone. Generically the model highlighted the significance of kinetic in addition to thermodynamic constraints in defining the fate of metal ions in biological systems.

  16. Electronic properties of ion-implanted yttria-stabilized zirconia

    NARCIS (Netherlands)

    Vohrer, U.; Wiemhöfer, H.-D.; Göpel, W.; Hassel, van B.A.; Burggraaf, A.J.

    1993-01-01

    Ion implantation of iron and titanium has been applied to modify the surface properties of polycrystalline yttria-stabilized zirconia ((ZrO2)0.87(YO1.5)0.13 (YSZ)) discs in an attempt to prepare surfaces with a mixed conductivity and by this an enhanced surface oxygen exchange kinetics. Surface-sen

  17. Application of a simple calorimetric data analysis on the binding study of cyanide ions by Jack bean urease

    Institute of Scientific and Technical Information of China (English)

    G.Rezaei; Behbehani; A.A.Saboury; M.Mohebbian; S.Ghammamy

    2010-01-01

    Cyanide ion was studied as an effector of Jack bean urease(JBU) at 300 K in 30 mmol/LTris buffer,pH 7 by isothermal titration calorimetry(ITC).The simple novel model was used for CN~- + JBU interaction over the whole range of CN~- concentrations.The binding parameters recovered from the simple novel model were attributed to the cyanide ion interaction.It was found that cyanide ion acted as a noncooperative inhibitor of JBU,and there is a set of 12 identical and independent binding sites for CN~- ions.The...

  18. Ion Transport and Structural Properties of Polymeric Electrolytes and Ionic Liquids from Molecular Dynamics Simulations

    Science.gov (United States)

    Borodin, Oleg

    2010-03-01

    Molecular dynamics simulations are well suited for exploring electrolyte structure and ion transport mechanisms on the nanometer length scale and the nanosecond time scales. In this presentation we will describe how MD simulations assist in answering fundamental questions about the lithium transport mechanisms in polymeric electrolytes and ionic liquids. In particular, in the first part of the presentation the extent of ion aggregation, the structure of ion aggregates and the lithium cation diffusion in binary polymeric electrolytes will be compared with that of single-ion conducting polymers. In the second part of the talk, the lithium transport in polymeric electrolytes will be compared with that of three ionic liquids ( [emim][FSI] doped with LiFSI , [pyr13][FSI] doped with LiFSI, [emim][BF4] doped with LiBF4). The relation between ionic liquid self-diffusion, conductivity and thermodynamic properties will be discussed in details. A number of correlations between heat of vaporization Hvap, cation-anion binding energy (E+/-), molar volume (Vm), self-diffusion coefficient (D) and ionic conductivity for 29 ionic liquids have been investigated using MD simulations. A significant correlation between D and Hvap has been found, while best correlation was found for -log((D Vm)) vs. Hvap+0.28E+/-. A combination of enthalpy of vaporization and a fraction of the cation-anion binding energy was suggested as a measure of the effective cohesive energy for ionic liquids.

  19. Plant coilin: structural characteristics and RNA-binding properties.

    Directory of Open Access Journals (Sweden)

    Valentine Makarov

    Full Text Available Cajal bodies (CBs are dynamic subnuclear compartments involved in the biogenesis of ribonucleoproteins. Coilin is a major structural scaffolding protein necessary for CB formation, composition and activity. The predicted secondary structure of Arabidopsis thaliana coilin (Atcoilin suggests that the protein is composed of three main domains. Analysis of the physical properties of deletion mutants indicates that Atcoilin might consist of an N-terminal globular domain, a central highly disordered domain and a C-terminal domain containing a presumable Tudor-like structure adjacent to a disordered C terminus. Despite the low homology in amino acid sequences, a similar type of domain organization is likely shared by human and animal coilin proteins and coilin-like proteins of various plant species. Atcoilin is able to bind RNA effectively and in a non-specific manner. This activity is provided by three RNA-binding sites: two sets of basic amino acids in the N-terminal domain and one set in the central domain. Interaction with RNA induces the multimerization of the Atcoilin molecule, a consequence of the structural alterations in the N-terminal domain. The interaction with RNA and subsequent multimerization may facilitate coilin's function as a scaffolding protein. A model of the N-terminal domain is also proposed.

  20. Ca(II) Binding Regulates and Dominates the Reactivity of a Transition-Metal-Ion-Dependent Diesterase from Mycobacterium tuberculosis.

    Science.gov (United States)

    Pedroso, Marcelo M; Larrabee, James A; Ely, Fernanda; Gwee, Shuhui E; Mitić, Nataša; Ollis, David L; Gahan, Lawrence R; Schenk, Gerhard

    2016-01-18

    The diesterase Rv0805 from Mycobacterium tuberculosis is a dinuclear metallohydrolase that plays an important role in signal transduction by controlling the intracellular levels of cyclic nucleotides. As Rv0805 is essential for mycobacterial growth it is a promising new target for the development of chemotherapeutics to treat tuberculosis. The in vivo metal-ion composition of Rv0805 is subject to debate. Here, we demonstrate that the active site accommodates two divalent transition metal ions with binding affinities ranging from approximately 50 nm for Mn(II) to about 600 nm for Zn(II) . In contrast, the enzyme GpdQ from Enterobacter aerogenes, despite having a coordination sphere identical to that of Rv0805, binds only one metal ion in the absence of substrate, thus demonstrating the significance of the outer sphere to modulate metal-ion binding and enzymatic reactivity. Ca(II) also binds tightly to Rv0805 (Kd ≈40 nm), but kinetic, calorimetric, and spectroscopic data indicate that two Ca(II) ions bind at a site different from the dinuclear transition-metal-ion binding site. Ca(II) acts as an activator of the enzymatic activity but is able to promote the hydrolysis of substrates even in the absence of transition-metal ions, thus providing an effective strategy for the regulation of the enzymatic activity.

  1. Binding of transition metal ions [cobalt, copper, nickel and zinc] with furanyl-, thiophenyl-, pyrrolyl-, salicylyl- and pyridyl-derived cephalexins as potent antibacterial agents.

    Science.gov (United States)

    Chohan, Zahid H; Pervez, Humayun; Khan, Khalid Mohammed; Rauf, A; Supuran, Claudiu T

    2004-02-01

    A method is described for the preparation of novel cephalexin-derived furanyl-, thiophenyl-, pyrrolyl-, salicylyl- and pyridyl-containing compounds showing potent antibacterial activity. The binding of these newly synthesized antibacterial agents with metal ions such as cobalt(II), copper(II), nickel(II) and zinc(II) has been studied and their inhibitory properties against various bacterial species such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae are also reported. These results suggest that metal ions to possess an important role in the designing of metal-based antibacterials and that such complexes are more effective against infectious diseases compared to the uncomplexed drugs.

  2. New metal based drugs: Spectral, electrochemical, DNA-binding, surface morphology and anticancer activity properties

    Science.gov (United States)

    Çeşme, Mustafa; Gölcü, Aysegul; Demirtaş, Ibrahim

    2015-01-01

    The NSAID piroxicam (PRX) drug was used for complex formation reactions with Cu(II), Zn(II) and Pt(II) metal salts have been synthesized. Then, these complexes have been characterized by spectroscopic and analytical techniques. Thermal behavior of the complexes were also investigated. The electrochemical properties of all complexes have been investigated by cyclic voltammetry (CV) using glassy carbon electrode. The biological activity of the complexes has been evaluated by examining their ability to bind to fish sperm double strand DNA (FSFSdsDNA) with UV spectroscopy. UV studies of the interaction of the PRX and its complexes with FSdsDNA have shown that these compounds can bind to FSdsDNA. The binding constants of the compounds with FSdsDNA have also been calculated. The morphology of the FSdsDNA, PRX, metal ions and metal complexes has been investigated by scanning electron microscopy (SEM). To get the SEM images, the interaction of compounds with FSdsDNA has been studied by means of differential pulse voltammetry (DPV) at FSdsDNA modified pencil graphite electrode (PGE). The decrease in intensity of the guanine oxidation signals has been used as an indicator for the interaction mechanism. The effect of proliferation PRX and complexes were examined on the HeLA and C6 cells using real-time cell analyzer with four different concentrations.

  3. Dual ion beam deposition of carbon films with diamondlike properties

    Science.gov (United States)

    Mirtich, M. J.; Swec, D. M.; Angus, J. C.

    1984-01-01

    A single and dual ion beam system was used to generate amorphous carbon films with diamond like properties. A methane/argon mixture at a molar ratio of 0.28 was ionized in the low pressure discharge chamber of a 30-cm-diameter ion source. A second ion source, 8 cm in diameter was used to direct a beam of 600 eV Argon ions on the substrates (fused silica or silicon) while the deposition from the 30-cm ion source was taking place. Nuclear reaction and combustion analysis indicate H/C ratios for the films to be 1.00. This high value of H/C, it is felt, allowed the films to have good transmittance. The films were impervious to reagents which dissolve graphitic and polymeric carbon structures. Although the measured density of the films was approximately 1.8 gm/cu cm, a value lower than diamond, the films exhibited other properties that were relatively close to diamond. These films were compared with diamondlike films generated by sputtering a graphite target.

  4. Modification of polyvinyl alcohol surface properties by ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Pukhova, I.V., E-mail: ivpuhova@mail.ru [National Research Tomsk State University, 36 Lenin Ave, Tomsk 634050 (Russian Federation); Institute of High Current Electronics, 2/3 Akademichesky Ave, Tomsk 634055 (Russian Federation); Kurzina, I.A. [National Research Tomsk State University, 36 Lenin Ave, Tomsk 634050 (Russian Federation); Savkin, K.P. [Institute of High Current Electronics, 2/3 Akademichesky Ave, Tomsk 634055 (Russian Federation); Laput, O.A. [National Research Tomsk Polytechnic University, 30 Lenin Ave, Tomsk 634050 (Russian Federation); Oks, E.M. [Institute of High Current Electronics, 2/3 Akademichesky Ave, Tomsk 634055 (Russian Federation)

    2017-05-15

    We describe our investigations of the surface physicochemical properties of polyvinyl alcohol modified by silver, argon and carbon ion implantation to doses of 1 × 10{sup 14}, 1 × 10{sup 15} and 1 × 10{sup 16} ion/cm{sup 2} and energies of 20 keV (for C and Ar) and 40 keV (for Ag). Infrared spectroscopy (IRS) indicates that destructive processes accompanied by chemical bond (−C=O) generation are induced by implantation, and X-ray photoelectron spectroscopy (XPS) analysis indicates that the implanted silver is in a metallic Ag3d state without stable chemical bond formation with polymer chains. Ion implantation is found to affect the surface energy: the polar component increases while the dispersion part decreases with increasing implantation dose. Surface roughness is greater after ion implantation and the hydrophobicity increases with increasing dose, for all ion species. We find that ion implantation of Ag, Ar and C leads to a reduction in the polymer microhardness by a factor of five, while the surface electrical resistivity declines modestly.

  5. Transport properties of ion implanted poly (p-phenylene vinylene)

    Energy Technology Data Exchange (ETDEWEB)

    Lucas, B. (LEPOFI, Faculte des Sciences, 87 Limoges (France)); Ratier, B. (LEPOFI, Faculte des Sciences, 87 Limoges (France)); Moliton, A. (LEPOFI, Faculte des Sciences, 87 Limoges (France)); Moreau, C. (Cavendish Lab., Univ. of Cambridge, Cambridge (United Kingdom)); Friend, R.H. (Cavendish Lab., Univ. of Cambridge, Cambridge (United Kingdom))

    1993-04-19

    We have studied the effect of ion implantation on transport properties (thermopower S, dc conductivity [sigma], ac conductivity [sigma][sub T]) of poly (p-phenylene vinylene). We have noticed that the thermopower sign is characteristic of the implanted ion (S > 0 for halogen, S < 0 for alkali) at low implantation energy (E [<=] 50 keV). The slope of [sigma] = f (T[sup -1]) varies, with values for activation energy between 32 meV (D = 10[sup 16] ions/cm[sup 2]) and 57 meV (D = 10[sup 15] ions/cm[sup 2]): the activation energy falls as the fluence increases in the case of implantation at low energy (E [<=] 50 keV). AC conductivity has been studied as a function of frequency v (v = 20 Hz - 1 MHz) and of temperatures T (T = 100 K - 380 K). For lower fluences (D = 2.10[sup 15] ions/cm[sup 2]), at low temperatures the ac conductivity shows hopping behaviour, switching to activated behaviour at higher temperatures. For higher fluences (D = 2.10[sup 16] ions/cm[sup 2]) the main processes are thermally activated. Thus for a high implantation energy (E = 250 keV), the related conductivity is less thermally activated and the curve [sigma][sub T] = f (1/T) slightly depends on temperature (hopping mechanism). (orig.)

  6. Metal ion interaction of an oligopeptide fragment representing the regulatory metal binding site of a CueR protein

    DEFF Research Database (Denmark)

    Jancsó, Attila; Szokolai, Hajnalka; Roszahegyi, Livia;

    2013-01-01

    Metalloregulatory proteins of the MerR family are transcriptional activators that sense/control the concentration of various metal ions inside bacteria.1 The Cu+ efflux regulator CueR, similarly to other MerR proteins, possesses a short multiple Cys-containing metal binding loop close to the C......-terminus. CueR has a high selectivity for Cu+, Ag+ and Au+, but exhibits no transcriptional activity for the divalent ions Hg2+ and Zn2+.2 The two Cys- residues of the metal binding loop were shown to settle M+ ions into a linear coordination environment but other factors may also play a role in the recognition...... of cognate metal ions.2 Nevertheless, it is an interesting question whether the same sequence, when removed from the protein, shows a flexibility to adopt different coordination environments and may efficiently bind metal ions having preferences for larger coordination numbers....

  7. Mechanical properties of metallic nanowires using tight-binding model

    Science.gov (United States)

    Aish, Mohammed; Starostenkov, Mikhail

    2016-01-01

    The mechanical properties of Nickel nanowires have been studied at different temperatures using molecular dynamics simulations. Molecular Dynamics (MD) simulations have been carried out on pure Nickel (Ni) crystal with face-centered cubic (FCC) lattice upon application of uniaxial tension at nanolevel with a speed of 20 m/s. The deformation corresponds to the direction . To the calculated block of crystal, free boundary conditions are applied in the directions , . A many body interatomic potential for Ni within the second moment approximation of the tight binding model (the Cleri-Rosato potentials) was employed to carry out three dimensional molecular dynamics simulations. MD simulation used to investigate the effect of temperature of Ni nanowire on the nature of deformation and fracture. Temperature effect on the extension property of metal nanowire is discussed in detail. The mechanical strengths and the mechanical strain of the nanowires decrease linearly with the increasing temperature. The feature of deformation energy can be divided into four regions: quasi-elastic, plastic, flow and failure. Experiments have shown that when the temperature increases the yielding stress decreases, the first stage of deformation was narrowed, and the second stage was widened. The results showed that breaking position depended on temperature.

  8. Electron impact phenomena and the properties of gaseous ions

    CERN Document Server

    Field, F H; Massey, H S W; Brueckner, Keith A

    1970-01-01

    Electron Impact Phenomena and the Properties of Gaseous Ions, Revised Edition deals with data pertaining to electron impact and to molecular gaseous ionic phenomena. This book discusses electron impact phenomena in gases at low pressure that involve low-energy electrons, which result in ion formation. The text also describes the use of mass spectrometers in electron impact studies and the degree of accuracy obtained when measuring electron impact energies. This book also reviews relatively low speed electrons and the transitions that result in the ionization of the atomic system. This text the

  9. Optical properties of lead borate glasses containing Dy3+ ions

    Science.gov (United States)

    Pisarska, Joanna

    2009-07-01

    Optical properties of lead borate glasses containing Dy3+ ions were examined using absorption and luminescence measurements and theoretical calculations based on the Judd-Ofelt framework and the Inokuti-Hirayama model. The luminescence spectra show two characteristic bands at 480 and 573 nm, which are due to 4F9/2-6H15/2 (blue) and 4F9/2-6H13/2 (yellow) transitions of trivalent Dy3+ ions. The yellow/blue luminescence and its decay were analyzed as a function of activator concentration.

  10. A scale of metal ion binding strengths correlating with ionic charge, Pauling electronegativity, toxicity, and other physiological effects.

    Science.gov (United States)

    Kinraide, Thomas B; Yermiyahu, Uri

    2007-09-01

    Equilibrium constants for binding to plant plasma membranes have been reported for several metal ions, based upon adsorption studies and zeta-potential measurements. LogK values for the ions are these: Al(3+), 4.30; La(3+), 3.34; Cu(2+), 2.60; Ca(2+) and Mg(2+), 1.48; Na(+) and K(+), 0 M(-1). These values correlate well with logK values for ion binding to many organic and inorganic ligands. LogK values for metal ion binding to 12 ligands were normalized and averaged to produce a scale for the binding of 49 ions. The scale correlates well with the values presented above (R(2)=0.998) and with ion binding to cell walls and other biomass. The scale is closely related to the charge (Z) and Pauling electronegativity (PE) of 48 ions (all but Hg(2+)); R(2)=0.969 for the equation (Scale values)=-1.68+Z(1.22+0.444PE). Minimum rhizotoxicity of metal ions appears to be determined by binding strengths: log a(PM,M)=1.60-2.41exp[0.238(Scale values)] determines the value of ion activities at the plasma membrane surface (a(PM,M)) that will ensure inhibition of root elongation. Additional toxicity appears to be related to softness, accounting for the great toxicity of Ag(+), for example. These binding-strength values correlate with additional physiological effects and are suitable for the computation of cell-surface electrical potentials.

  11. Vanadyl ions binding to GroEL (HSP60) and inducing its depolymerization

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Several vanadium compounds have been known for the hypoglycemic and anticancer effects. However, the mechanisms of the pharmacological and toxicological effects were not clear. In this work, we investigated the potential targets of vanadium in mitochondria. Vanadyl ions were found to bind to mitochondria from rat liver with a stoichiometry of 244±58 nmol/mg protein and an apparent dissocia- tion constant (Kd) of (2.0±0.8)×10-16 mol/L. Using size exclusion chromatography, a vanadium-binding protein was isolated and identified to be the 60-kDa heat shock protein (HSP60) by mass spectrometry analysis and immunoassays. Additionally, binding of vanadyl ions was found to result in depolymerization of homo-oligomeric HSP60 (GroEL). HSP60 is an indispensable molecular chaperone and involved in many kinds of pathogenesis of inflammatory and autoimmune diseases, e.g. type 1 diabetes. Our results suggested that HSP60 could be a novel important target involved in the biological and/or toxicological effects of vanadium compounds.

  12. Selective binding of oligonucleotide on TiO{sub 2} surfaces modified by swift heavy ion beam lithography

    Energy Technology Data Exchange (ETDEWEB)

    Vicente Pérez-Girón, J. [Nanoate, S.L. C/Poeta Rafael Morales 2, San Sebastian de los Reyes, 28702 Madrid (Spain); Emerging Viruses Department Heinrich Pette Institute, Hamburg 20251 (Germany); Hirtz, M. [Institute of Nanotechnology (INT) and Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology - KIT, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); McAtamney, C.; Bell, A.P. [Advanced Microscopy Laboratory, CRANN, Trinity College Dublin, Dublin 2 (Ireland); Antonio Mas, J. [Laboratorio de Genómica del Centro de Apoyo Tecnológico, Universidad Rey Juan Carlos, Campus de Alcorcón 28922, Madrid (Spain); Jaafar, M. [Nanoate, S.L. C/Poeta Rafael Morales 2, San Sebastian de los Reyes, 28702 Madrid (Spain); Departamento de Física de la Materia Condensada, Facultad de Ciencias, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Luis, O. de [Nanoate, S.L. C/Poeta Rafael Morales 2, San Sebastian de los Reyes, 28702 Madrid (Spain); Departamento de Bioquímica, Fisiología y Genética Molecular, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Campus de Alcorcón, 28922 Madrid (Spain); Fuchs, H. [Institute of Nanotechnology (INT) and Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology - KIT, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Physical Institute and Center for Nanotechnology (CeNTech), Wilhelm-Klemm-Straße 10, University of Münster (Germany); and others

    2014-11-15

    We have used swift heavy-ion beam based lithography to create patterned bio-functional surfaces on rutile TiO{sub 2} single crystals. The applied lithography method generates a permanent and well defined periodic structure of micrometre sized square holes having nanostructured TiO{sub 2} surfaces, presenting different physical and chemical properties compared to the surrounding rutile single crystal surface. On the patterned substrates selective binding of oligonucleotides molecules is possible at the surfaces of the holes. This immobilisation process is only being controlled by UV light exposure. The patterned transparent substrates are compatible with fluorescence detection techniques, are mechanically robust, have a high tolerance to extreme chemical and temperature environments, and apparently do not degrade after ten cycles of use. These qualities make the patterned TiO{sub 2} substrates useful for potential biosensor applications.

  13. Structural and binding properties of two paralogous fatty acid binding proteins of Taenia solium metacestode.

    Directory of Open Access Journals (Sweden)

    Seon-Hee Kim

    Full Text Available BACKGROUND: Fatty acid (FA binding proteins (FABPs of helminths are implicated in acquisition and utilization of host-derived hydrophobic substances, as well as in signaling and cellular interactions. We previously demonstrated that secretory hydrophobic ligand binding proteins (HLBPs of Taenia solium metacestode (TsM, a causative agent of neurocysticercosis (NC, shuttle FAs in the surrounding host tissues and inwardly transport the FAs across the parasite syncytial membrane. However, the protein molecules responsible for the intracellular trafficking and assimilation of FAs have remained elusive. METHODOLOGY/PRINCIPAL FINDINGS: We isolated two novel TsMFABP genes (TsMFABP1 and TsMFABP2, which encoded 133- and 136-amino acid polypeptides with predicted molecular masses of 14.3 and 14.8 kDa, respectively. They shared 45% sequence identity with each other and 15-95% with other related-members. Homology modeling demonstrated a characteristic β-barrel composed of 10 anti-parallel β-strands and two α-helices. TsMFABP2 harbored two additional loops between β-strands two and three, and β-strands six and seven, respectively. TsMFABP1 was secreted into cyst fluid and surrounding environments, whereas TsMFABP2 was intracellularly confined. Partially purified native proteins migrated to 15 kDa with different isoelectric points of 9.2 (TsMFABP1 and 8.4 (TsMFABP2. Both native and recombinant proteins bound to 11-([5-dimethylaminonaphthalene-1-sulfonyl]aminoundecannoic acid, dansyl-DL-α-amino-caprylic acid, cis-parinaric acid and retinol, which were competitively inhibited by oleic acid. TsMFABP1 exhibited high affinity toward FA analogs. TsMFABPs showed weak binding activity to retinol, but TsMFABP2 showed relatively high affinity. Isolation of two distinct genes from an individual genome strongly suggested their paralogous nature. Abundant expression of TsMFABP1 and TsMFABP2 in the canal region of worm matched well with the histological distributions

  14. Structural and Binding Properties of Two Paralogous Fatty Acid Binding Proteins of Taenia solium Metacestode

    Science.gov (United States)

    Yang, Hyun-Jong; Shin, Joo-Ho; Diaz-Camacho, Sylvia Paz; Nawa, Yukifumi; Kang, Insug; Kong, Yoon

    2012-01-01

    Background Fatty acid (FA) binding proteins (FABPs) of helminths are implicated in acquisition and utilization of host-derived hydrophobic substances, as well as in signaling and cellular interactions. We previously demonstrated that secretory hydrophobic ligand binding proteins (HLBPs) of Taenia solium metacestode (TsM), a causative agent of neurocysticercosis (NC), shuttle FAs in the surrounding host tissues and inwardly transport the FAs across the parasite syncytial membrane. However, the protein molecules responsible for the intracellular trafficking and assimilation of FAs have remained elusive. Methodology/Principal Findings We isolated two novel TsMFABP genes (TsMFABP1 and TsMFABP2), which encoded 133- and 136-amino acid polypeptides with predicted molecular masses of 14.3 and 14.8 kDa, respectively. They shared 45% sequence identity with each other and 15–95% with other related-members. Homology modeling demonstrated a characteristic β-barrel composed of 10 anti-parallel β-strands and two α-helices. TsMFABP2 harbored two additional loops between β-strands two and three, and β-strands six and seven, respectively. TsMFABP1 was secreted into cyst fluid and surrounding environments, whereas TsMFABP2 was intracellularly confined. Partially purified native proteins migrated to 15 kDa with different isoelectric points of 9.2 (TsMFABP1) and 8.4 (TsMFABP2). Both native and recombinant proteins bound to 11-([5-dimethylaminonaphthalene-1-sulfonyl]amino)undecannoic acid, dansyl-DL-α-amino-caprylic acid, cis-parinaric acid and retinol, which were competitively inhibited by oleic acid. TsMFABP1 exhibited high affinity toward FA analogs. TsMFABPs showed weak binding activity to retinol, but TsMFABP2 showed relatively high affinity. Isolation of two distinct genes from an individual genome strongly suggested their paralogous nature. Abundant expression of TsMFABP1 and TsMFABP2 in the canal region of worm matched well with the histological distributions of lipids

  15. Heme binding properties of glyceraldehyde-3-phosphate dehydrogenase.

    Science.gov (United States)

    Hannibal, Luciana; Collins, Daniel; Brassard, Julie; Chakravarti, Ritu; Vempati, Rajesh; Dorlet, Pierre; Santolini, Jérôme; Dawson, John H; Stuehr, Dennis J

    2012-10-30

    Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a glycolytic enzyme that also functions in transcriptional regulation, oxidative stress, vesicular trafficking, and apoptosis. Because GAPDH is required for the insertion of cellular heme into inducible nitric oxide synthase [Chakravarti, R., et al. (2010) Proc. Natl. Acad. Sci. U.S.A. 107, 18004-18009], we extensively characterized the heme binding properties of GAPDH. Substoichiometric amounts of ferric heme bound to GAPDH (one heme per GAPDH tetramer) to form a low-spin complex with UV-visible maxima at 362, 418, and 537 nm and when reduced to ferrous gave maxima at 424, 527, and 559 nm. Ferric heme association and dissociation rate constants at 10 °C were as follows: k(on) = 17800 M(-1) s(-1), k(off1) = 7.0 × 10(-3) s(-1), and k(off2) = 3.3 × 10(-4) s(-1) (giving approximate affinities of 19-390 nM). Ferrous heme bound more poorly to GAPDH and dissociated with a k(off) of 4.2 × 10(-3) s(-1). Magnetic circular dichroism, resonance Raman, and electron paramagnetic resonance spectroscopic data on the ferric, ferrous, and ferrous-CO complexes of GAPDH showed that the heme is bis-ligated with His as the proximal ligand. The distal ligand in the ferric complex was not displaced by CN(-) or N(3)(-) but in the ferrous complex could be displaced by CO at a rate of 1.75 s(-1) (for >0.2 mM CO). Studies with heme analogues revealed selectivity toward the coordinating metal and porphyrin ring structure. The GAPDH-heme complex was isolated from bacteria induced to express rabbit GAPDH in the presence of δ-aminolevulinic acid. Our finding of heme binding to GAPDH expands the protein's potential roles. The strength, selectivity, reversibility, and redox sensitivity of heme binding to GAPDH are consistent with it performing heme sensing or heme chaperone-like functions in cells.

  16. Membrane Modulates Affinity for Calcium Ion to Create an Apparent Cooperative Binding Response by Annexin a5

    OpenAIRE

    Gauer, Jacob W.; Knutson, Kristofer J.; Jaworski, Samantha R.; Rice, Anne M.; Rannikko, Anika M.; Lentz, Barry R.; Hinderliter, Anne

    2013-01-01

    Isothermal titration calorimetry was used to characterize the binding of calcium ion (Ca2+) and phospholipid to the peripheral membrane-binding protein annexin a5. The phospholipid was a binary mixture of a neutral and an acidic phospholipid, specifically phosphatidylcholine and phosphatidylserine in the form of large unilamellar vesicles. To stringently define the mode of binding, a global fit of data collected in the presence and absence of membrane concentrations exceeding protein saturati...

  17. DFT Study of the effects of counter ions on bonding, molecular and spectral properties of pentaflourophenyl xenonium diflouride cation

    Indian Academy of Sciences (India)

    Hossein Tavakol; Neda Khedri

    2015-09-01

    The structures and properties of pentaflourophenyl xenonium diflouride cation (PFF) have been studied in their salts with 12 different counter ions using DFT calculations. The results demonstrated the huge effect of counter ion on all properties. The hybridization values, obtained from the NBO calculations, showed that xenon mostly used pure p orbital in their bonds, especially in Xe-F bond. Calculated binding energies (Hb) and (Gb) indicated that the best anions for PFF are OH-, F-, BH-4 and OAc-. Moreover, the variations of HOMO and LUMO energies and the reactivity parameters have been investigated for all structures. The results of QTAIM calculations confirmed the covalent nature of Xe-C bond and the electrostatic nature of other xenon bonds. Finally, IR frequencies, NMR chemical shifts and NMR coupling constants were calculated to examine the effect of counter ion on the spectral properties of studied structures.

  18. Cellulose Nanocrystals Obtained from Rice By-Products and Their Binding Potential to Metallic Ions

    Directory of Open Access Journals (Sweden)

    Vanessa L. Albernaz

    2015-01-01

    Full Text Available The present study aimed to develop and optimize a method to obtain cellulose nanocrystals from the agricultural by-products rice husk and straw and to evaluate their electrostructural modifications in the presence of metallic ions. First, different particle formation conditions and routes were tested and analyzed by spectrophotometry, dynamic light scattering (DLS, and Zeta potential measurements. Then, electrostructural effects of ions Na(I, Cd(II, and Al(III on the optimized nanoparticles were analyzed by atomic force microscopy (AFM, scanning electron microscopy (SEM, and electrical conductivity (EC assessments. The produced cellulose nanocrystals adopted a rod-like shape. AFM height distribution and EC data indicated that the nanocrystals have more affinity in binding with Na(I > Al(III > Cd(II. These data suggest that the use of these cellulose nanocrystals in the bioremediation field is promising, both in metal sorption from wastewater and as an alternative for water desalination.

  19. Data for β-lactoglobulin conformational analysis after (--epigallocatechin gallate and metal ions binding

    Directory of Open Access Journals (Sweden)

    Liangliang Zhang

    2017-02-01

    Full Text Available This data article contains complementary results related to the paper “Effect of metal ions on the binding reaction of (--epigallocatechin gallate to β-lactoglobulin” (Zhang et al., 2017 [1]. Data was obtained by circular dichroism (CD spectroscopy to investigate potential β-lactoglobulin (β-Lg conformational changes with different concentrations of EGCg and Cu2+ or Al3+ added to β-Lg. 500 µL of the 25 µM β-Lg solution containing EGCg (25 µM or metal ions (0–500 µM were measured, and the spectra were recorded. CD spectroscopy data present in this article indicated that the β-Lg-Cu, β-Lg-Al and β-Lg-EGCg interaction resulted in unfolding of the secondary structure of β-Lg.

  20. Copper(II) ions and the Alzheimer's amyloid-β peptide: Affinity and stoichiometry of binding

    Science.gov (United States)

    Tõugu, Vello; Friedemann, Merlin; Tiiman, Ann; Palumaa, Peep

    2014-10-01

    Deposition of amyloid beta (Aβ) peptides into amyloid plaques is the hallmark of Alzheimer's disease. According to the amyloid cascade hypothesis this deposition is an early event and primary cause of the disease, however, the mechanisms that cause this deposition remain elusive. An increasing amount of evidence shows that the interactions of biometals can contribute to the fibrillization and amyloid formation by amyloidogenic peptides. From different anions the copper ions deserve the most attention since it can contribute not only toamyloid formation but also to its toxicity due to the generation of ROS. In this thesis we focus on the affinity and stoichiometry of copper(II) binding to the Aβ molecule.

  1. Mechanical and tribological properties of ion beam-processed surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kodali, Padma [Univ. of Maryland, College Park, MD (United States)

    1998-01-01

    The intent of this work was to broaden the applications of well-established surface modification techniques and to elucidate the various wear mechanisms that occur in sliding contact of ion-beam processed surfaces. The investigation included characterization and evaluation of coatings and modified surfaces synthesized by three surface engineering methods; namely, beam-line ion implantation, plasma-source ion implantation, and DC magnetron sputtering. Correlation among measured properties such as surface hardness, fracture toughness, and wear behavior was also examined. This dissertation focused on the following areas of research: (1) investigating the mechanical and tribological properties of mixed implantation of carbon and nitrogen into single crystal silicon by beam-line implantation; (2) characterizing the mechanical and tribological properties of diamond-like carbon (DLC) coatings processed by plasma source ion implantation; and (3) developing and evaluating metastable boron-carbon-nitrogen (BCN) compound coatings for mechanical and tribological properties. The surface hardness of a mixed carbon-nitrogen implant sample improved significantly compared to the unimplanted sample. However, the enhancement in the wear factor of this sample was found to be less significant than carbon-implanted samples. The presence of nitrogen might be responsible for the degraded wear behavior since nitrogen-implantation alone resulted in no improvement in the wear factor. DLC coatings have low friction, low wear factor, and high hardness. The fracture toughness of DLC coatings has been estimated for the first time. The wear mechanism in DLC coatings investigated with a ruby slider under a contact stress of 1 GPa was determined to be plastic deformation. The preliminary data on metastable BCN compound coatings indicated high friction, low wear factor, and high hardness.

  2. Metal ion interaction of an oligopeptide fragment representing the regulatory metal binding site of a CueR protein

    DEFF Research Database (Denmark)

    Jancsó, Attila; Szokolai, Hajnalka; Roszahegyi, Livia

    2013-01-01

    Metalloregulatory proteins of the MerR family are transcriptional activators that sense/control the concentration of various metal ions inside bacteria.1 The Cu+ efflux regulator CueR, similarly to other MerR proteins, possesses a short multiple Cys-containing metal binding loop close to the C......-terminus. CueR has a high selectivity for Cu+, Ag+ and Au+, but exhibits no transcriptional activity for the divalent ions Hg2+ and Zn2+.2 The two Cys- residues of the metal binding loop were shown to settle M+ ions into a linear coordination environment but other factors may also play a role in the recognition...

  3. Characterization of ion-exchange membrane materials: properties vs structure.

    Science.gov (United States)

    Berezina, N P; Kononenko, N A; Dyomina, O A; Gnusin, N P

    2008-06-22

    This review focuses on the preparation, structure and applications of ion-exchange membranes formed from various materials and exhibiting various functions (electrodialytic, perfluorinated sulphocation-exchange and novel laboratory-tested membranes). A number of experimental techniques for measuring electrotransport properties as well as the general procedure for membrane testing are also described. The review emphasizes the relationships between membrane structures, physical and chemical properties and mechanisms of electrochemical processes that occur in charged membrane materials. The water content in membranes is considered to be a key factor in the ion and water transfer and in polarization processes in electromembrane systems. We suggest the theoretical approach, which makes it possible to model and characterize the electrochemical properties of heterogeneous membranes using several transport-structural parameters. These parameters are extracted from the experimental dependences of specific electroconductivity and diffusion permeability on concentration. The review covers the most significant experimental and theoretical research on ion-exchange membranes that have been carried out in the Membrane Materials Laboratory of the Kuban State University. These results have been discussed at the conferences "Membrane Electrochemistry", Krasnodar, Russia for many years and were published mainly in Russian scientific sources.

  4. LUMINESCENT PROPERTIES OF SILICATE GLASSES WITH CERIUM IONS AND ANTIMONY

    Directory of Open Access Journals (Sweden)

    A. M. Klykova

    2014-05-01

    Full Text Available The paper deals with the results of an experimental study of luminescence excitation spectra and luminescence of silicate glasses containing cerium ions and antimony. The aim of this work was to study the features of the luminescence and the effect of UV irradiation and heat treatment on luminescence and the state of cerium ions and antimony in glass. We investigated glass system Na2O-ZnO-Al2O3-SiO2-NaF-NaBr with additives CeO2 and Sb2O3. Synthesis was carried out in platinum crucibles in the air at 14500C. The samples were polished glass plates with a thickness of 0.5-1 mm. UV irradiation was carried out with a mercury lamp having a wide range of radiation in the spectral range 240-390 nm. It was conducted in a Nabertherm muffle furnaces. Luminescence spectra and excitation spectra were measured using a spectrofluorimeter MPF-44A (PerkinElmer at the room temperature. Measured luminescence spectra were corrected in view of the spectral sensitivity of the photodetector for spectrofluorimeter. Adjustment of the excitation spectra for the spectral dependence of the intensity of the excitation source was not carried out. During the experiments it was found that in silicate glasses Sb3+ ions can exist in two energy states, which corresponds to a different environment with oxygen ions. Heat treatment of these glasses in an oxidizing atmosphere leads to an increase in ion concentration of Sb3+ ions with a greater amount of oxygen in the environment. In glasses containing antimony and cerium ions, ultraviolet irradiation causes a change in the valence of cerium ions and antimony, which is accompanied by luminescence quenching. Subsequent heat treatment of glass leads to the inverse processes and restore luminescence excitation spectra. The study of fluorescent properties of silicate glasses with cerium and antimony ions led to the conclusion of the practical significance of this work. Promising multifunctional materials can be created on the basis of

  5. Distinct binding properties of TIAR RRMs and linker region.

    Science.gov (United States)

    Kim, Henry S; Headey, Stephen J; Yoga, Yano M K; Scanlon, Martin J; Gorospe, Myriam; Wilce, Matthew C J; Wilce, Jacqueline A

    2013-04-01

    The RNA-binding protein TIAR is an mRNA-binding protein that acts as a translational repressor, particularly important under conditions of cellular stress. It binds to target mRNA and DNA via its RNA recognition motif (RRM) domains and is involved in both splicing regulation and translational repression via the formation of "stress granules." TIAR has also been shown to bind ssDNA and play a role in the regulation of transcription. Here we show, using surface plasmon resonance and nuclear magnetic resonance spectroscopy, specific roles of individual TIAR domains for high-affinity binding to RNA and DNA targets. We confirm that RRM2 of TIAR is the major RNA- and DNA-binding domain. However, the strong nanomolar affinity binding to U-rich RNA and T-rich DNA depends on the presence of the six amino acid residues found in the linker region C-terminal to RRM2. On its own, RRM1 shows preferred binding to DNA over RNA. We further characterize the interaction between RRM2 with the C-terminal extension and an AU-rich target RNA sequence using NMR spectroscopy to identify the amino acid residues involved in binding. We demonstrate that TIAR RRM2, together with its C-terminal extension, is the major contributor for the high-affinity (nM) interactions of TIAR with target RNA sequences.

  6. Chelation gradients for investigation of metal ion binding at silica surfaces.

    Science.gov (United States)

    Kannan, Balamurali; Higgins, Daniel A; Collinson, Maryanne M

    2014-08-26

    Centimeter-long surface gradients in bi- and tridentate chelating agents have been formed via controlled rate infusion, and the coordination of Cu(2+) and Zn(2+) to these surfaces has been examined as a function of distance by X-ray photoelectron spectroscopy (XPS). 3-(Trimethoxysilylpropyl)ethylenediamine and 3-(trimethoxysilylpropyl)diethylenetriamine were used as precursor silanes to form the chelation gradients. When the gradients were exposed to a metal ion solution, a series of coordination complexes formed along the length of the substrate. For both chelating agents at the three different concentrations studied, the amine content gradually increased from top to bottom as expected for a surface chemical gradient. While the Cu 2p peak area had nearly the same profile as nitrogen, the Zn 2p peak area did not and exhibited a plateau along much of the gradient. The normalized nitrogen-to-metal peak area ratio (N/M) was found to be highly dependent on the type of ligand, its surface concentration, and the type of metal ion. For Cu(2+), the N/M ratio ranged from 8 to 11 on the diamine gradient and was ∼4 on the triamine gradient, while for Zn(2+), the N/M ratio was 4-8 on diamine and 5-7 on triamine gradients. The extent of protonation of amine groups was higher for the diamine gradients, which could lead to an increased N/M ratio. Both 1:1 and 1:2 ligand/metal complexes along with dinuclear complexes are proposed to form, with their relative amounts dependent on the ligand, ligand density, and metal ion. Collectively, the methods and results described herein represent a new approach to study metal ion binding and coordination on surfaces, which is especially important to the extraction, preconcentration, and separation of metal ions.

  7. Whether metal (Pb, Cd, Zn) binding property of natural organic matter is source-dependent-A study based on spectroscopy, potentiometry, and voltammetry

    Science.gov (United States)

    Chen, W.; Gueguen, C.; Smith, S.

    2016-02-01

    Natural organic matter (NOM) is a complex molecule of diverse ligands that essentially regulates metal speciation and toxicity. NOM source is heterogeneous, but can be operationally classified into allochthonous, autochthonous, and intermediate between these two groups. Whether the metal binding property (i.e. affinity and capacity) is NOM-source dependent however, remains unclear. The answer of this question is helpful for environmental modeling. If metal binding properties are sensitive to NOM source, then models used to determine metal speciation will need to be revised to take some measurement of NOM quality into consideration. In this study, different sources of NOM were collected for the study of Pb, Cd, and Zn binding. The NOM properties were characterized by different techniques from different chemistry indexes, including acidity chemistry, optical spectroscopy for component and structure, and cathodic stripping voltammetry for thiol determination. Absence of Gradient and Nernstian Equilibrium Stripping was used to selectively determine the concentration of free metal ion for binding isotherm. A model based on continuous site distribution was used to describe this binding isotherm. By best fitting the binding isotherm into the model using a regularized optimization, a conditional affinity spectrum was derived. Comparing binding isotherm and affinity spectrum between NOM samples showed that Pb binding was more dependent on NOM sources than Cd and Zn binding. Under the same binding condition (i.e. DOC, pH and ionic strength), allochthonous NOM mostly showed higher binding level (i.e. up to 3 log unit of bound species concentration) and stronger binding affinity for Pb than autochthonous NOM. This tendency however, was not obvious for Cd and Zn. Humic-like content probably contributed the most significant factor for Pb binding discrimination. Thiol content may be another important factor to differentiate metal binding affinity and capacity between NOM samples.

  8. Ion exchange properties of titanic fiber of layered structure

    Energy Technology Data Exchange (ETDEWEB)

    Fujiki, Yoshinori; Komatsu, Yu; Sasaki, Takayoshi

    1986-12-01

    Usually, titanic acid is produced by hydrolyzing titanium tetrachloride, titanium sulfate or titanium alkoxide and is obtained in the form of precipitate in an amorphous gel state. The present authors have synthesized two types of titanic fibers of a layered crystaline structure to provide new ion exchangers. Three synthetic techniques, namely, flux process, annealing baking process and melt process, have been developed. This report deals with the structure and properties of these materials. In the flux process, a mixture of TiO/sub 2/, K/sub 2/CO/sub 3/ and K/sub 2/MoO/sub 4/ (flux) is melted at 1150 deg C and annealed at about 950 deg C to provide a K/sub 2/Ti/sub 4/O/sub 3/ fiber of a layered structure, which is subsequently converted into H/sub 2/Ti/sub 4/O/sub 9/ center dot nH/sub 2/O fiber. In the melt process, a mixture of materials is heate up to 1100 deg C to produce molten K/sub 2/Ti/sub 2/O/sub 5/, which is quenched to form K/sub 2/Ti/sub 2/O/sub 5/ fiber of a layered structure. Then it is converted into H/sub 2/Ti/sub 2/O/sub 5/ center dot nH/sub 2/O fiber. The annealing baking process provides K/sub 2/Ti/sub 4/O/sub 9/, which is converted into K/sub 2/Ti/sub 2/O/sub 5/ fiber. In this report, the crystal structure of H/sub 2/Ti/sub 4/O/sub 9/ center dot nH/sub 2/O is discussed and the ion exchanging properties are analized. Examination is made on the ion exchanging reactions involving potassium, alkali metal ions, alkaline earth metal ions and divalent transition metal ions. Various ion exchangers, including the present ones, are compared in terms of the partition coefficient and separation factor. (Nogami, K.).

  9. Simulative Calculation of Mechanical Property, Binding Energy and Detonation Property of TATB/Fluorine-polymer PBX

    Institute of Scientific and Technical Information of China (English)

    MA, Xiu-Fang; XIAO, Ji-Jun; HUANG, Hui; JU, Xue-Hai; LI, Jin-Shan; XIAO, He-Ming

    2006-01-01

    Molecular dynamics (MD) method was used to simulate 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) coated with fluorine containing polymers. The mechanical properties and binding energies of PBXs were obtained. It was found that when the number of chain monomers of fluorine containing polymers was the same, the elasticity of TATB/F2314 was increased more greatly than others and the binding energy of TATB/F2311 was the largest among four PBXs. Detonation heat and velocity of such four PBXs were calculated according to theoretical and empirical formulas. The results show that the order of detonation heat is TATB>TATB/PVDF>TATB/F2311 >TATB/F2314>TATB/PCTFE while the order of detonation velocity is TATB/PVDF<TATB/F2311 <TATB/F2314<TATB/PCTFE<TATB.

  10. Structures and Metal-Binding Properties of Helicobacter pylori Neutrophil-Activating Protein with a Di-Nuclear Ferroxidase Center

    Directory of Open Access Journals (Sweden)

    Hideshi Yokoyama

    2014-06-01

    Full Text Available Helicobacter pylori causes severe diseases, such as chronic gastritis, peptic ulcers, and stomach cancers. H. pylori neutrophil-activating protein (HP-NAP is an iron storage protein that forms a dodecameric shell, promotes the adhesion of neutrophils to endothelial cells, and induces the production of reactive oxygen radicals. HP-NAP belongs to the DNA-protecting proteins under starved conditions (Dps family, which has significant structural similarities to the dodecameric ferritin family. The crystal structures of the apo form and metal-ion bound forms, such as iron, zinc, and cadmium, of HP-NAP have been determined. This review focused on the structures and metal-binding properties of HP-NAP. These metal ions bind at the di-nuclear ferroxidase center (FOC by different coordinating patterns. In comparison with the apo structure, metal loading causes a series of conformational changes in conserved residues among HP-NAP and Dps proteins (Trp26, Asp52, and Glu56 at the FOC. HP-NAP forms a spherical dodecamer with 23 symmetry including two kinds of pores. Metal ions have been identified around one of the pores; therefore, the negatively-charged pore is suitable for the passage of metal ions.

  11. Properties of tin oxides prepared by ion-beam-sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Becker, Martin; Hamann, Robert; Polity, Angelika; Feili, Davar; Meyer, Bruno K. [I. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 16, 35392 Giessen (Germany)

    2013-07-01

    The success of n-type oxide semiconductors and its application in oxide-based electronic devices has motivated the interest in p-type oxide based semiconductors. Therefore synthesis of tin monoxide (SnO) recently has received increasing attention. Another phase of this binary system, SnO{sub 2}, is of great technological interest in manifold applications, such as transparent electrodes, heat-reflecting filters and gas sensing. The preparation of tin oxide thin films has been performed by many different procedures such as sol/gel, epitaxial procedures or methods working under vacuum conditions like sputtering techniques. Radio-Frequency-Ion-Thrusters, as designed for propulsion applications, are also qualified for thin film deposition and surface etching if utilized as ion source. Tin oxide thin films were grown by ion-beam sputtering using a 3 inch metallic tin target. Different aspects of growth and properties of the tin oxide phases were investigated in relation to growth parameters such as substrate temperature or flux of oxygen. Structural, optical and electrical properties of the films are discussed.

  12. Native Mass Spectrometry, Ion mobility, and Collision-Induced Unfolding Categorize Malaria Antigen/Antibody Binding

    Science.gov (United States)

    Huang, Yining; Salinas, Nichole D.; Chen, Edwin; Tolia, Niraj H.; Gross, Michael L.

    2017-09-01

    Plasmodium vivax Duffy Binding Protein (PvDBP) is a promising vaccine candidate for P. vivax malaria. Recently, we reported the epitopes on PvDBP region II (PvDBP-II) for three inhibitory monoclonal antibodies (2D10, 2H2, and 2C6). In this communication, we describe the combination of native mass spectrometry and ion mobility (IM) with collision induced unfolding (CIU) to study the conformation and stabilities of three malarial antigen-antibody complexes. These complexes, when collisionally activated, undergo conformational changes that depend on the location of the epitope. CIU patterns for PvDBP-II in complex with antibody 2D10 and 2H2 are highly similar, indicating comparable binding topology and stability. A different CIU fingerprint is observed for PvDBP-II/2C6, indicating that 2C6 binds to PvDBP-II on an epitope different from 2D10 and 2H2. This work supports the use of CIU as a means of classifying antigen-antibody complexes by their epitope maps in a high throughput screening workflow. [Figure not available: see fulltext.

  13. Changes of conformation and aggregation state induced by binding of lanthanide ions to insulin

    Institute of Scientific and Technical Information of China (English)

    程驿; 李荣昌; 王夔

    2002-01-01

    To clarify the mechanism of lanthanide ions (Ln3+) on the across-membrane transport of insulin and subsequent reducing blood glucose, the interactions of Ln3+with Zn-insulin and Zn-free insulin are investigated by spectroscopic methods. The results reveal that the binding of Ln3+ to insulin can induce its structure changes from secondary to quaternary structure, depending on the Ln3+ concentration. In the lower concentration, it triggers the conformational changes of insulin monomer in the binding region with insulin receptor (B(24-30)). It would affect insulin-insulin receptor interaction. Moreover, Ln3+ binding promotes the assembly of insulin monomer from dimer to polymer. The potency of Ln3+ in inducing insulin’s aggregation is stronger than that of Zn2+. Furthermore, the aggregation can be reversed partly by EDTA-treatment, indicating that it is not due to denaturation. Similar to Zn2+ effect, Ln3+ can stabilize insulin hexamer in a certain range of concentration, but is stronger than the former.

  14. Changes of conformation and aggregation state induced by binding of lanthanide ions to insulin

    Institute of Scientific and Technical Information of China (English)

    程驿; 李荣昌; 王夔

    2002-01-01

    To clarify the mechanism of lanthanide ions (Ln3+) on the across-membrane transport of insulin and subsequent reducing blood glucose, the interactions of Ln3+ with Zn-insulin and Zn-free insulin are investigated by spectroscopic methods. The results reveal that the binding of Ln3+ to insulin can induce its structure changes from secondary to quaternary structure, depending on the Ln3+ concentration. In the lower concentration, it triggers the conformational changes of insulin monomer in the binding region with insulin receptor (B(24-30)). It would affect insulin-insulin receptor interaction. Moreover, Ln3+ binding promotes the assembly of insulin monomer from dimer to polymer. The potency of Ln3+ in inducing insulin's aggregation is stronger than that of Zn2+. Furthermore, the aggregation can be reversed partly by EDTA-treatment, indicating that it is not due to denaturation. Similar to Zn2+ effect, Ln3+ can stabilize insulin hexamer in a certain range of concentration, but is stronger than the former.

  15. Synthesis, metal ion binding, and biological evaluation of new anticancer 2-(2'-hydroxyphenyl)benzoxazole analogs of UK-1.

    Science.gov (United States)

    McKee, Mireya L; Kerwin, Sean M

    2008-02-15

    UK-1 is a bis(benzoxazole) natural product displaying activity against a wide range of human cancer cell lines. A simplified analog of UK-1, 4-carbomethoxy-2-(2'-hydroxyphenyl)benzoxazole, was previously found to be almost as active as UK-1 against cancer cell lines, and similar to the natural product, formed complexes with a variety of metal ions such as Mg2+ and Zn2+. A series of 4-substituted-2-(2'-hydroxyphenyl)benzoxazole analogs of this 'minimal pharmacophore' of UK-1 were prepared. The anti-cancer activity of these analogs was examined in breast and lung cancer cell lines. Spectrophotometric titrations in methanol were carried out in order to assess the ability of UK-1 and these analogs to coordinate with Mg2+ and Cu2+ ions. Although none of the new analogs were more cytotoxic than 4-carbomethoxy-2-(2'-hydroxyphenyl)benzoxazole, some analogs were identified that display similar cytotoxicity to this simplified UK-1 analog with improved water solubility. UK-1 and all of these new analogs bind Cu2+ ions better than Mg2+ ions, and the nature of the 4-substituent is important for the Mg2+ ion binding ability of these 2-(2'-hydroxyphenyl)benzoxazoles. Previous studies of a limited number of UK-1 analogs demonstrated a correlation between Mg2+ ion binding ability and cytotoxicity; however, within this series of 4-substituted-2-(2'-hydroxyphenyl)benzoxazoles the variations in cytotoxicity do not correlate with either Mg2+ or Cu2+ ion binding ability. These results, together with recent ESI-MS studies of Cu2+-mediated DNA binding by UK-1 and analogs, indicate that UK-1 and analogs may exert their cytotoxic effects by interaction with Cu2+ or other transition metal ions, rather than Mg2+, and that metal ion-mediated DNA binding, rather than metal ion binding affinity, is important for the cytotoxic effect of these compounds. The potential role of Cu2+ ions in the cytotoxic action of UK-1 is further supported by the observation that UK-1 in the presence of Cu2

  16. Effect of Cd ions on transport properties of orthomanganites

    CERN Document Server

    Troyanchuk, I O; Pastushonok, S N

    1998-01-01

    Magnetic and magnetotransport measurements have been used to study the compositional dependence of the electronic properties of the solid solutions La sub 0 sub . sub 7 (Pb sub 0 sub . sub 3 sub - sub x Cd sub x)MnO sub 3 and Nd sub 0 sub . sub 7 (Pb sub 0 sub . sub 3 sub - sub x Cd sub x)MnO sub 3. It was found that these compounds are ferromagnets and have the rhombohedrally or orthorhombically distorted perovskite structure. The substitution of Pb ions by Cd leads to the transition from the metallic to the insulating state. The intermediate compositions exhibit two peaks of the resistivity and magnetoresistance. The high-temperature peak is associated with the Curie temperature whereas there is no magnetic anomaly in the temperature interval of the second peak. We suppose that Cd ions participate in the formation of the narrow impurity band limiting the mobility of charge carriers. (author)

  17. Reconstruction of negative hydrogen ion beam properties from beamline diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Ruf, Benjamin

    2014-09-25

    For the experimental fusion reactor ITER, which should show the feasibility of sustaining a fusion plasma with a positive power balance, some technology still has to be developed, amongst others also the plasma heating system. One heating technique is the neutral beam injection (NBI). A beam of fast deuterium atoms is injected into the fusion plasma. By heavy particle collisions the beam particles give their energy to the plasma. A NBI system consists of three major components. First, deuterium ions are generated in a low temperature, low pressure plasma of an ion source. At ITER, the requirements on the beam energy of 1 MeV cause the necessity of negative charged deuterium ions. Secondly, the ions are accelerated within an acceleration system with several grids, where the plasma grid is the first grid. The grids are on different descending high voltage potentials. The source itself is on the highest negative potential. Thirdly, the fast deuterium ions have to be neutralised. This thesis deals with the second step in the mentioned beam system, the ion acceleration and beam formation. The underlying experiments and measurements were carried out at the testbeds BATMAN (BAvarianTest MAchine for Negative ions) and ELISE (Extraction from a Large Ion Source Experiment) at the Max-Planck-Institut fuer Plasmaphysik Garching (IPP Garching). The main goal of this thesis is to provide a tool which allows the determination of the beam properties. These are beam divergence, stripping losses and beam inhomogeneity. For this purpose a particle trajectory code has been developed from scratch, namely BBC-NI (Bavarian Beam Code for Negative Ions). The code is able to simulate the whole beam and the outcome of several beam diagnostic tools. The data obtained from the code together with the measurements of the beam diagnostic tools should allow the reconstruction of the beam properties. The major beam diagnostic tool, which is used in this thesis, is the beam emission spectroscopy

  18. Cucumber Metallothionein-Like 2 (CsMTL2) Exhibits Metal-Binding Properties

    Science.gov (United States)

    Pan, Yu; Pan, Yanglu; Zhai, Junpeng; Xiong, Yan; Li, Jinhua; Du, Xiaobing; Su, Chenggang; Zhang, Xingguo

    2016-01-01

    We identified a novel member of the metallothionein (MT) family, Cucumis sativus metallothionein-like 2 (CsMTL2), by screening a young cucumber fruit complementary DNA (cDNA) library. The CsMTL2 encodes a putative 77-amino acid Class II MT protein that contains two cysteine (Cys)-rich domains separated by a Cys-free spacer region. We found that CsMTL2 expression was regulated by metal stress and was specifically induced by Cd2+ treatment. We investigated the metal-binding characteristics of CsMTL2 and its possible role in the homeostasis and/or detoxification of metals by heterologous overexpression in Escherichia coli cells. Furthermore, we produced a deletion mutant form of the protein, CsMTL2m, that contained the two Cys-rich clusters but lacked the spacer region, in E. coli. We compared the metal-binding properties of CsMTL2 with those of CsMTL2m, the β domain of human metallothionein-like protein 1 (HsMTXb), and phytochelatin-like (PCL) heterologously expressed in E. coli using metal-binding assays. We found that E. coli cells expressing CsMTL2 accumulated the highest levels of Zn2+ and Cd2+ of the four transformed cell types, with levels being significantly higher than those of control cells containing empty vector. E. coli cells expressing CsMTL2 had a higher tolerance for cadmium than for zinc ions. These findings show that CsMTL2 improves metal tolerance when heterologously expressed in E. coli. Future studies should examine whether CsMTL2 improves metal tolerance in planta. PMID:27916887

  19. Cucumber Metallothionein-Like 2 (CsMTL2 Exhibits Metal-Binding Properties

    Directory of Open Access Journals (Sweden)

    Yu Pan

    2016-11-01

    Full Text Available We identified a novel member of the metallothionein (MT family, Cucumis sativus metallothionein-like 2 (CsMTL2, by screening a young cucumber fruit complementary DNA (cDNA library. The CsMTL2 encodes a putative 77-amino acid Class II MT protein that contains two cysteine (Cys-rich domains separated by a Cys-free spacer region. We found that CsMTL2 expression was regulated by metal stress and was specifically induced by Cd2+ treatment. We investigated the metal-binding characteristics of CsMTL2 and its possible role in the homeostasis and/or detoxification of metals by heterologous overexpression in Escherichia coli cells. Furthermore, we produced a deletion mutant form of the protein, CsMTL2m, that contained the two Cys-rich clusters but lacked the spacer region, in E. coli. We compared the metal-binding properties of CsMTL2 with those of CsMTL2m, the β domain of human metallothionein-like protein 1 (HsMTXb, and phytochelatin-like (PCL heterologously expressed in E. coli using metal-binding assays. We found that E. coli cells expressing CsMTL2 accumulated the highest levels of Zn2+ and Cd2+ of the four transformed cell types, with levels being significantly higher than those of control cells containing empty vector. E. coli cells expressing CsMTL2 had a higher tolerance for cadmium than for zinc ions. These findings show that CsMTL2 improves metal tolerance when heterologously expressed in E. coli. Future studies should examine whether CsMTL2 improves metal tolerance in planta.

  20. Peripheral benzodiazepine binding sites on striated muscles of the rat: Properties and effect of denervation

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, W.E.; Ickstadt, A. (Mainz Univ. (Germany, F.R.). Pharmakologisches Inst.); Hopf, H.Ch. (Mainz Univ. (Germany, F.R.))

    1985-01-01

    In order to test the hypothesis that peripheral benzodiazepine binding sites mediate some direct effects of benzodiazepines on striated muscles, the properties of specific /sup 3/H-Ro 5-4864 binding to rat biceps and rat diaphragm homogenates were investigated. In both tissues a single population of sites was found with a Ksub(D) value of 3 nmol/l. The density of these sites in both muscles was higher than the density in rat brain, but was considerably lower than in rat kidney. Competition experiments indicate a substrate specificity of specific /sup 3/H-Ro 5-4864 binding similar to the properties already demonstrated for the specific binding of this ligand to peripheral benzodiazepine binding sites in many other tissues. The properties of these sites in the rat diaphragm are not changed after motoric denervation by phrenicectomy. It is concluded that peripheral benzodiazepine binding sites are not involved in direct effects of benzodiazepines on striated muscles.

  1. Magnetic properties of Pr ions in perovskite-type oxides

    Science.gov (United States)

    Sekizawa, K.; Kitagawa, M.; Takano, Y.

    1998-01-01

    Magnetic properties of Pr ions with the controlled valence on the A and B sites of perovskite-type oxides (ABO 3) were investigated for two systems, PrSc 1 - xMg xO 3 and BaPr 1 - xBi xO 3. From the magnetic susceptibility χ versus temperature T curves of PrSc 1 - xMg xO 3, the χ-T curve for molar Pr 3+ ions on the A site and that of Pr 4+ ions were obtained. The 1/χ-T curves for both ions exhibit the crystalline electric field (CEF) effect and the effective magnetic moment μ eff above 100 K is 3.41 μ B for Pr 3+ and 2.58 μ B for Pr 4+, respectively. The χ-T curve of PrSc 0.8Mg 0.2O 3 is similar to that of PrBa 2Cu 3O y. In the BaPr 1 - xBi xO 3 system, only one intermediate phase BaPr 0.5Bi 0.5O 3 exists, in which Pr and Bi take an ordered arrangement on the B site. The magnetic susceptibility χ for Pr 4+ and that of Pr 3- in the ordered arrangement with Bi 5+ on the B site are much smaller than those for the A site, reflecting the strong CEF effect on the B site. Experimental χ-T curves can be well reproduced by the numerical calculation for Pr 3+ or Pr 4+ ions in the molecular field and the CEF with proper respective parameters.

  2. Properties of Opiate-Receptor Binding in Rat Brain

    Science.gov (United States)

    Pert, Candace B.; Snyder, Solomon H.

    1973-01-01

    [3H]Naloxone, a potent opiate antagonist, binds stereospecifically to opiate-receptor sites in rat-brain tissue. The binding is time, temperature, and pH dependent and saturable with respect to [3H]naloxone and tissue concentration. The [3H]naloxone-receptor complex formation is bimolecular with a dissociation constant of 20 nM. 15 Opiate agonists and antagonists compete for the same receptors, whose density is 30 pmol/g. Potencies of opiates and their antagonists in displacing [3H]naloxone binding parallel their pharmacological potencies. PMID:4525427

  3. Effects of urea, metal ions and surfactants on the binding of baicalein with bovine serum albumin

    Directory of Open Access Journals (Sweden)

    Atanu Singha Roy

    2016-08-01

    Full Text Available The interaction of baicalein with bovine serum albumin (BSA was investigated with the help of spectroscopic and molecular docking studies. The binding affinity of baicalein towards BSA was estimated to be in order of 105 M−1 from fluorescence quenching studies. Negative ΔH° (−5.66±0.14 kJ/mol and positive (ΔS° (+79.96±0.65 J/mol K indicate the presence of electrostatic interactions along with the hydrophobic forces that result in a positive ΔS°. The hydrophobic association of baicalein with BSA diminishes in the presence of sodium dodecyl sulfate (SDS due to probable hydrophobic association of baicalein with SDS, resulting in a negative ΔS° (−40.65±0.87 J/mol K. Matrix-assisted laser desorption ionization/time of flight (MALDI--TOF experiments indicate a 1:1 complexation between baicalein and BSA. The unfolding and refolding phenomena of BSA were investigated in the absence and presence of baicalein using steady-state and fluorescence lifetime measurements. It was observed that the presence of urea ruptured the non-covalent interaction between baicalein and BSA. The presence of metal ions (Ag+, Mg2+, Ni2+, Mn2+, Co2+and Zn2+ increased the binding affinity of ligand towards BSA. The changes in conformational aspects of BSA after ligand binding were also investigated using circular dichroism (CD and Fourier transform infrared (FT-IR spectroscopic techniques. Site selectivity studies following molecular docking analyses indicated the binding of baicalein to site 1 (subdomain IIA of BSA.

  4. Effects of urea, metal ions and surfactants on the binding of baicalein with bovine serum albumin$

    Institute of Scientific and Technical Information of China (English)

    Atanu Singha Roy n; Amit Kumar Dinda; Nitin Kumar Pandey; Swagata Dasgupta

    2016-01-01

    The interaction of baicalein with bovine serum albumin (BSA) was investigated with the help of spec-troscopic and molecular docking studies. The binding affinity of baicalein towards BSA was estimated to be in order of 105 M?1 from fluorescence quenching studies. NegativeΔH° (?5.6670.14 kJ/mol) and positive (ΔS°) ( þ 79.96 7 0.65 J/mol K) indicate the presence of electrostatic interactions along with the hydrophobic forces that result in a positiveΔS°. The hydrophobic association of baicalein with BSA di-minishes in the presence of sodium dodecyl sulfate (SDS) due to probable hydrophobic association of baicalein with SDS, resulting in a negativeΔS° ( ? 40.65 7 0.87 J/mol K). Matrix-assisted laser desorption ionization/time of flight (MALDI–TOF) experiments indicate a 1:1 complexation between baicalein and BSA. The unfolding and refolding phenomena of BSA were investigated in the absence and presence of baicalein using steady-state and fluorescence lifetime measurements. It was observed that the presence of urea ruptured the non-covalent interaction between baicalein and BSA. The presence of metal ions (Ag þ , Mg2 þ , Ni2 þ , Mn2 þ , Co2 þ and Zn2 þ ) increased the binding affinity of ligand towards BSA. The changes in conformational aspects of BSA after ligand binding were also investigated using circular di-chroism (CD) and Fourier transform infrared (FT-IR) spectroscopic techniques. Site selectivity studies following molecular docking analyses indicated the binding of baicalein to site 1 (subdomain IIA) of BSA.&2016 Xi'an Jiaotong University. Production and hosting by Elsevier B.V. This is an open access article.

  5. The NMDA receptor ion channel: a site for binding of Huperzine A.

    Science.gov (United States)

    Gordon, R K; Nigam, S V; Weitz, J A; Dave, J R; Doctor, B P; Ved, H S

    2001-12-01

    Huperzine A (HUP-A), first isolated from the Chinese club moss Huperzia serrata, is a potent, reversible and selective inhibitor of acetylcholinesterase (AChE) over butyrylcholinesterase (BChE) (Life Sci. 54: 991-997). Because HUP-A has been shown to penetrate the blood-brain barrier, is more stable than the carbamates used as pretreatments for organophosphate poisoning (OP) and the HUP-A:AChE complex has a longer half-life than other prophylactic sequestering agents, HUP-A has been proposed as a pretreatment drug for nerve agent toxicity by protecting AChE from irreversible OP-induced phosphonylation. More recently (NeuroReport 8: 963-968), pretreatment of embryonic neuronal cultures with HUP-A reduced glutamate-induced cell death and also decreased glutamate-induced calcium mobilization. These results suggest that HUP-A might interfere with and be beneficial for excitatory amino acid overstimulation, such as seen in ischemia, where persistent elevation of internal calcium levels by activation of the N-methyl-D-aspartate (NMDA) glutamate subtype receptor is found. We have now investigated the interaction of HUP-A with glutamate receptors. Freshly frozen cortex or synaptic plasma membranes were used, providing 60-90% specific radioligand binding. Huperzine A (< or =100 microM) had no effect on the binding of [3H]glutamate (low- and high-affinity glutamate sites), [3H]MDL 105,519 (NMDA glycine regulatory site), [3H]ifenprodil (NMDA polyamine site) or [3H]CGS 19755 (NMDA antagonist). In contrast with these results, HUP-A non-competitively (Hill slope < 1) inhibited [3H]MK-801 and [3H]TCP binding (co-located NMDA ion channel PCP site) with pseudo K(i) approximately 6 microM. Furthermore, when neuronal cultures were pretreated with HUP-A for 45 min prior to NMDA exposure, HUP-A dose-dependently inhibited the NMDA-induced toxicity. Although HUP-A has been implicated to interact with cholinergic receptors, it was without effect at 100 microM on muscarinic (measured by

  6. Binding Properties of General Odorant Binding Proteins from the Oriental Fruit Moth, Grapholita molesta (Busck (Lepidoptera: Tortricidae.

    Directory of Open Access Journals (Sweden)

    Guangwei Li

    Full Text Available The oriental fruit moth Grapholita molesta is a host-switching pest species. The adults highly depend on olfactory cues in locating optimal host plants and oviposition sites. Odorant binding proteins (OBPs are thought to be responsible for recognizing and transporting hydrophobic odorants across the aqueous sensillum lymph to stimulate the odorant receptors (ORs within the antennal sensilla and activate the olfactory signal transduction pathway. Exploring the physiological function of these OBPs could facilitate understanding insect chemical communications.Two antennae-specific general OBPs (GOBPs of G. molesta were expressed and purified in vitro. The binding affinities of G. molesta GOBP1 and 2 (GmolGOBP1 and 2 for sex pheromone components and host plant volatiles were measured by fluorescence ligand-binding assays. The distribution of GmolGOBP1 and 2 in the antennal sensillum were defined by whole mount fluorescence immunohistochemistry (WM-FIHC experiments. The binding sites of GmolGOBP2 were predicted using homology modeling, molecular docking and site-directed mutagenesis. Both GmolGOBP1 and 2 are housing in sensilla basiconica and with no differences in male and female antennae. Recombinant GmolGOBP1 (rGmolGOBP1 exhibited broad binding properties towards host plant volatiles and sex pheromone components; rGmolGOBP2 could not effectively bind host plant volatiles but showed specific binding affinity with a minor sex pheromone component dodecanol. We chose GmolGOBP2 and dodecanol for further homology modeling, molecular docking, and site-directed mutagenesis. Binding affinities of mutants demonstrated that Thr9 was the key binding site and confirmed dodecanol bonding to protein involves a hydrogen bond. Combined with the pH effect on binding affinities of rGmolGOBP2, ligand binding and release of GmolGOBP2 were related to a pH-dependent conformational transition.Two rGmolGOBPs exhibit different binding characteristics for tested ligands. r

  7. Substituent Effects on Cytotoxic Activity, Spectroscopic Property, and DNA Binding Property of Naphthalimide Derivatives.

    Science.gov (United States)

    Wang, Ke-Rang; Qian, Feng; Sun, Qian; Ma, Cui-Lan; Rong, Rui-Xue; Cao, Zhi-Ran; Wang, Xiao-Man; Li, Xiao-Liu

    2016-05-01

    A series of novel naphthalimide derivatives NI1-5 containing piperazine moieties (N-(2-hydroxyethyl)piperazine and 1-piperazinepropanol) and piperidine moieties (4-piperidinemethanol, 4-hydroxypiperidine and 4-piperidineethanol) have been synthesized and evaluated for their cytotoxic activity, spectroscopic property, and DNA binding behaviors. It was found that substituents at the 4-position remarkably influence the various activities of this series of compound. Compounds NI3-5 modified with piperidines exhibited potent cytotoxic activities against Hela, SGC-7901, and A549 cells with the IC50 values from 0.73 μm to 6.80 μm, which are better than NI1-2 functionalized with piperazines. Compounds NI1-2 showed higher binding capacity with Ct-DNA than compounds NI3-5 based on studies of UV-vis, fluorescence and CD spectra. Furthermore, compounds NI3-5, as DNA intercalators, showed fluorescence enhancement upon binding with Ct-DNA. More interestingly, fluorescence imaging studies of compound NI4 with A549 cells showed that the fluorescence predominantly appeared in the cytoplasm. These results provided a potential application of NI3-5 as anticancer therapeutic and cancer cell imaging agents.

  8. Luminescent Behavior of Ru(II) Polypyridyl Morpholine Complexes, Synthesis, Characterization, DNA, Protein Binding, Sensor Effect of Ions/Solvents and Docking Studies.

    Science.gov (United States)

    Vuradi, Ravi Kumar; Putta, Venkat Reddy; Nancherla, Deepika; Sirasani, Satyanarayana

    2016-03-01

    New three ruthenium (II) polypyridyl complexes [Ru(phen)2mpip](2+)(1) {mpip = 2-(4-morpholinophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline}, (phen = 1,10-Phenanthrolene), [Ru(bpy)2mpip](2+)(2) (bpy = 2,2'bipyridyl), [Ru(dmb)2mpip](2+)(3) (dmb = 4, 4-dimethyl 2, 2'-bipyridine) have been synthesized and characterized by spectral studies IR, UV-vis, (1)H, (13)C-NMR, mass and elemental analysis. The binding properties of these three complexes towards calf-thymus DNA (CT-DNA) have been investigated by UV-Vis spectroscopy, different fluorescence methods and viscosity measurements, indicating that all the complexes bind to CT-DNA by means of intercalation, but with different binding affinities. Sensor effect of ions/solvents and BSA (Bovine Serum Albumin) binding studies of these complexes were also studied. Docking studies also reveals that complexes will bind in between base pairs (Intercalate) of DNA and gives information about the binding strength.

  9. Changes in Storage Properties of Hydrides Induced by Ion Irradiation

    Directory of Open Access Journals (Sweden)

    Jasmina GRBOVIĆ NOVAKOVIĆ

    2013-05-01

    Full Text Available The influence of structural changes caused by irradiation with different ions, their energies and fluences on sorption properties has been investigated. Results suggest that there are several mechanisms of desorption depending on defect concentration, their interaction and ordering. It has been also demonstrated that the changes in near-surface area play the crucial role in hydrogen desorption kinetics. It is confirmed that there is possibility to control the thermodynamic parameters of these systems by controlling vacancies depth profile and concentration. DOI: http://dx.doi.org/10.5755/j01.ms.19.2.1579

  10. Changes in Storage Properties of Hydrides Induced by Ion Irradiation

    Directory of Open Access Journals (Sweden)

    Jasmina GRBOVIĆ NOVAKOVIĆ

    2013-05-01

    Full Text Available The influence of structural changes caused by irradiation with different ions, their energies and fluences on sorption properties has been investigated. Results suggest that there are several mechanisms of desorption depending on defect concentration, their interaction and ordering. It has been also demonstrated that the changes in near-surface area play the crucial role in hydrogen desorption kinetics. It is confirmed that there is possibility to control the thermodynamic parameters of these systems by controlling vacancies depth profile and concentration. DOI: http://dx.doi.org/10.5755/j01.ms.19.2.1579

  11. Properties of the ion-ion hybrid resonator in fusion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Morales, George J. [Univ. of California, Los Angeles, CA (United States)

    2015-10-06

    The project developed theoretical and numerical descriptions of the properties of ion-ion hybrid Alfvén resonators that are expected to arise in the operation of a fusion reactor. The methodology and theoretical concepts were successfully compared to observations made in basic experiments in the LAPD device at UCLA. An assessment was made of the excitation of resonator modes by energetic alpha particles for burning plasma conditions expected in the ITER device. The broader impacts included the generation of basic insight useful to magnetic fusion and space science researchers, defining new avenues for exploration in basic laboratory experiments, establishing broader contacts between experimentalists and theoreticians, completion of a Ph.D. dissertation, and promotion of interest in science through community outreach events and classroom instruction.

  12. Structure and Ca2+-binding Properties of the Tandem C2 domains of E-Syt2

    Science.gov (United States)

    Xu, Junjie; Bacaj, Taulant; Zhou, Amy; Tomchick, Diana R.; Südhof, Thomas C.; Rizo, Josep

    2014-01-01

    SUMMARY Contacts between the endoplasmic reticulum and the plasma membrane involve extended synaptotagmins (E-Syts) in mammals or tricalbins in yeast, proteins with multiple C2 domains. One of the tandem C2 domains of E-Syt2 is predicted to bind Ca2+, but no Ca2+-dependent function has been attributed to this protein. We have determined the crystal structures of the tandem C2 domains of E-Syt2 in the absence and presence of Ca2+, and analyzed their Ca2+-binding properties by NMR spectroscopy. Our data reveal an unexpected V-shaped structure with a rigid orientation between the two C2 domains that is not substantially altered by Ca2+. The E-Syt2 C2A domain binds up to four Ca2+ ions, whereas the C2B domain does not bind Ca2+. These results suggest that E-Syt2 performs an as yet unidentified Ca2+-dependent function through its C2A domain, and uncover fundamental differences between the properties of the tandem C2 domains of E-Syts and synaptotagmins. PMID:24373768

  13. The interaction of human serum albumin with selected lanthanide and actinide ions: Binding affinities, protein unfolding and conformational changes.

    Science.gov (United States)

    Ali, Manjoor; Kumar, Amit; Kumar, Mukesh; Pandey, Badri N

    2016-04-01

    Human serum albumin (HSA), the most abundant soluble protein in blood plays critical roles in transportation of biomolecules and maintenance of osmotic pressure. In view of increasing applications of lanthanides- and actinides-based materials in nuclear energy, space, industries and medical applications, the risk of exposure with these metal ions is a growing concern for human health. In present study, binding interaction of actinides/lanthanides [thorium: Th(IV), uranium: U(VI), lanthanum: La(III), cerium: Ce(III) and (IV)] with HSA and its structural consequences have been investigated. Ultraviolet-visible, Fourier transform-infrared, Raman, Fluorescence and Circular dichroism spectroscopic techniques were applied to study the site of metal ions interaction, binding affinity determination and the effect of metal ions on protein unfolding and HSA conformation. Results showed that these metal ions interacted with carbonyl (CO..:)/amide(N..-H) groups and induced exposure of aromatic residues of HSA. The fluorescence analysis indicated that the actinide binding altered the microenvironment around Trp214 in the subdomain IIA. Binding affinity of U(VI) to HSA was slightly higher than that of Th(IV). Actinides and Ce(IV) altered the secondary conformation of HSA with a significant decrease of α-helix and an increase of β-sheet, turn and random coil structures, indicating a partial unfolding of HSA. A correlation was observed between metal ion's ability to alter HSA conformation and protein unfolding. Both cationic effects and coordination ability of metal ions seemed to determine the consequences of their interaction with HSA. Present study improves our understanding about the protein interaction of these heavy ions and their impact on its secondary structure. In addition, binding characteristics may have important implications for the development of rational antidote for the medical management of health effects of actinides and lanthanides.

  14. Electrical properties of oxygen ion-implanted InP

    Science.gov (United States)

    He, L.; Anderson, W. A.

    1992-10-01

    The effect of oxygen ion implantation on defect levels and the electrical properties of undoped InP ( n-type) and Sn-doped InP have been investigated as a function of postimplant annealing at temperatures of 300 and 400° C. The surface interruption by ion bombardment was studied by a non-invasive optical technique—photoreflectance (PR) spectroscopy. Current-voltage (I-V) characterization and deep level transient spectros-copy (DLTS) were carried out. The free carrier compensation mechanism was studied from the microstructure behavior of defect levels associated with O+ implantation. Free carriers may be trapped in both residual and ion-bombardment-induced defect sites. Rapid thermal annealing (RTA) performed at different temperatures showed that if residual traps were removed by annealing, the compensation efficiency will be enhanced. Post-implant RTA treatment showed that at the higher temperature (400°C), trapped carriers may be re-excited, resulting in a weakened compensation. Comparing the results of undoped and Sn-doped InP indicated that the carrier compensation effect is substrate doping dependent.

  15. Expressing a bacterial mercuric ion binding protein in plant for phytoremediation of heavy metals.

    Science.gov (United States)

    Hsieh, Ju-Liang; Chen, Ching-Yi; Chiu, Meng-Hsuen; Chein, Mei-Fang; Chang, Jo-Shu; Endo, Ginro; Huang, Chieh-Chen

    2009-01-30

    A specific mercuric ion binding protein (MerP) originating from transposon TnMERI1 of Bacillus megaterium strain MB1 isolated from Minamata Bay displayed good adsorption capability for a variety of heavy metals. In this study, the Gram-positive MerP protein was expressed in transgenic Arabidopsis to create a model system for phytoremediation of heavy metals. Under control of an actin promoter, the transgenic Arabidpsis showed higher tolerance and accumulation capacity for mercury, cadium and lead when compared with the control plant. Results from confocal microscopy analysis also indicate that MerP was localized at the cell membrane and vesicles of plant cells. The developed transgenic plants possessing excellent metal-accumulative ability could have potential applications in decontamination of heavy metals.

  16. A highly Selective Fluorescent Sensor for Monitoring Cu(2+) Ion: Synthesis, Characterization and Photophysical Properties.

    Science.gov (United States)

    Aderinto, Stephen Opeyemi; Xu, Yuling; Peng, Hongping; Wang, Fei; Wu, Huilu; Fan, Xuyang

    2017-01-01

    A new fluorescent sensor, 4-allylamine-N-(N-salicylidene)-1,8-naphthalimide (1), anchoring a naphthalimide moiety as fluorophore and a Schiff base group as receptor, was synthesized and characterized. The photophysical properties of sensor 1 were conducted in organic solvents of different polarities. Our study revealed that, depending on the solvent polarity, the fluorescence quantum yields varied from 0.59 to 0.89. The fluorescent activity of the sensor was monitored and the sensor was consequently applied for the detection of Cu(2+) with high selectivity over various metal ions by fluorescence quenching in Tris-HCl (pH = 7.2) buffer/DMF (1:1, v/v) solution. From the binding stoichiometry, it was indicated that a 1:1 complex was formed between Cu(2+) and the sensor 1. The fluorescence intensity was linear with Cu(2+) in the concentration range 0.5-5 μM. Moreso, the detection limit was calculated to be 0.32 μM, which is sufficiently low for good sensitivity of Cu(2+) ion. The binding mode was due to the intramolecular charge transfer (ICT) and the coordination of Cu(2+) with C = N and hydroxyl oxygen groups of the sensor 1. The sensor proved effective for Cu(2+) monitoring in real water samples with recovery rates of 95-112.6 % obtained.

  17. Investigation of the binding of Salvianolic acid B to human serum albumin and the effect of metal ions on the binding

    Science.gov (United States)

    Chen, Tingting; Cao, Hui; Zhu, Shajun; Lu, Yapeng; Shang, Yanfang; Wang, Miao; Tang, Yanfeng; Zhu, Li

    2011-10-01

    The studies on the interaction between HSA and drugs have been an interesting research field in life science, chemistry and clinical medicine. There are also many metal ions present in blood plasma, thus the research about the effect of metal ions on the interaction between drugs and plasma proteins is crucial. In this study, the interaction of Salvianolic acid B (Sal B) with human serum albumin (HSA) was investigated by the steady-state, synchronous fluorescence and circular dichroism (CD) spectroscopies. The results showed that Sal B had a strong ability to quench the intrinsic fluorescence of HSA through a static quenching mechanism. Binding parameters calculated showed that Sal B was bound to HSA with the binding affinities of 10 5 L mol -1. The thermodynamic parameters studies revealed that the binding was characterized by positive enthalpy and positive entropy changes, and hydrophobic interactions were the predominant intermolecular forces to stabilize the complex. The specific binding distance r (2.93 nm) between donor (HSA) and acceptor (Sal B) was obtained according to Förster non-radiative resonance energy transfer theory. The synchronous fluorescence experiment revealed that Sal B cannot lead to the microenvironmental changes around the Tyr and Trp residues of HSA, and the binding site of Sal B on HSA is located in hydrophobic cavity of subdomain IIA. The CD spectroscopy indicated the secondary structure of HSA is not changed in the presence of Sal B. Furthermore, The effect of metal ions (e.g. Zn 2+, Cu 2+, Co 2+, Ni 2+, Fe 3+) on the binding constant of Sal B-HSA complex was also discussed.

  18. All Ca(2+)-binding loops of light-sensitive ctenophore photoprotein berovin bind magnesium ions: The spatial structure of Mg(2+)-loaded apo-berovin.

    Science.gov (United States)

    Burakova, Ludmila P; Natashin, Pavel V; Malikova, Natalia P; Niu, Fengfeng; Pu, Mengchen; Vysotski, Eugene S; Liu, Zhi-Jie

    2016-01-01

    Light-sensitive photoprotein berovin accounts for a bright bioluminescence of ctenophore Beroe abyssicola. Berovin is functionally identical to the well-studied Ca(2+)-regulated photoproteins of jellyfish, however in contrast to those it is extremely sensitive to the visible light. Berovin contains three EF-hand Ca(2+)-binding sites and consequently belongs to a large family of the EF-hand Ca(2+)-binding proteins. Here we report the spatial structure of apo-berovin with bound Mg(2+) determined at 1.75Å. The magnesium ion is found in each functional EF-hand loop of a photoprotein and coordinated by oxygen atoms donated by the side-chain groups of aspartate, carbonyl groups of the peptide backbone, or hydroxyl group of serine with characteristic oxygen-Mg(2+) distances. As oxygen supplied by the side-chain of the twelfth residue of all Ca(2+)-binding loops participates in the magnesium ion coordination, it was suggested that Ca(2+)-binding loops of berovin belong to the mixed Ca(2+)/Mg(2+) rather than Ca(2+)-specific type. In addition, we report an effect of physiological concentration of Mg(2+) on bioluminescence of berovin (sensitivity to Ca(2+), rapid-mixed kinetics, light-sensitivity, thermostability, and apo-berovin conversion into active protein). The different impact of physiological concentration of Mg(2+) on berovin bioluminescence as compared to hydromedusan photoproteins was attributed to different affinities of the Ca(2+)-binding sites of these photoproteins to Mg(2+).

  19. Allostery between two binding sites in the ion channel subunit TRIP8b confers binding specificity to HCN channels.

    Science.gov (United States)

    Lyman, Kyle A; Han, Ye; Heuermann, Robert J; Cheng, Xiangying; Kurz, Jonathan E; Lyman, Reagan E; Van Veldhoven, Paul P; Chetkovich, Dane M

    2017-09-08

    Tetratricopeptide repeat (TPR) domains are ubiquitous structural motifs that mediate protein-protein interactions. For example, the TPR domains in the peroxisomal import receptor PEX5 enable binding to a range of type 1 peroxisomal targeting signal (PTS1) motifs. A homolog of PEX5, tetratricopeptide repeat-containing Rab8b interacting protein (TRIP8b), binds to and functions as an auxiliary subunit of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Given the similarity between TRIP8b and PEX5, this difference in function raises the question of what mechanism accounts for their binding specificity. In this report, we found that the cyclic nucleotide-binding domain (CNBD) and the C-terminus of the HCN channel are critical for conferring specificity to TRIP8b binding. We show that TRIP8b binds the HCN CNBD through a 37-residue domain and the HCN C-terminus through the TPR domains. Using a combination of fluorescence polarization and co-immunoprecipitation based assays, we establish that binding at either site increases affinity at the other. Thus, allosteric coupling of the TRIP8b TPR domains both promotes binding to HCN channels and limits binding to PTS1 substrates. These results raise the possibility that other TPR domains may similarly be influenced by allosteric mechanisms as a general feature of protein-protein interactions. Copyright © 2017, The American Society for Biochemistry and Molecular Biology.

  20. Chemical Properties of Dipole-Bound Negative Ions

    Science.gov (United States)

    Liu, Y.

    2005-05-01

    In dipole bound negative ions the extra electron is weakly bound by the dipole potential of the neutral molecule in a diffuse orbital localized near the positive end of the dipole. In consequence, it is reasonable to expect that such species will be highly reactive and possess chemical properties similar to those of Rydberg atoms, which also contain a weakly-bound electron in a diffuse orbital. These properties are being examined using a negative ion Penning trap. Data for electron transfer in collisions with attaching targets such as SF6 show that the rate constants for this process are large, ˜ 10-7 cm^3 s-1, and similar to those for free electron attachment. This suggests that collisions can be described in terms of an essentially-free electron model. This is further reinforced by the observation that rotational energy transfer in collisions with polar molecules can lead to rapid electron detachment, again with large rate constants of ˜ 10 -7 cm^3 s-1. Results for several target species will be presented and discussed in light of a free electron model.

  1. The ion dependence of carbohydrate binding of CBM36: an MD and 3D-RISM study

    Science.gov (United States)

    Tanimoto, Shoichi; Higashi, Masahiro; Yoshida, Norio; Nakano, Haruyuki

    2016-09-01

    The molecular recognition process of the carbohydrate-binding module family 36 (CBM36) was examined theoretically. The mechanism of xylan binding by CBM36 and the role of Ca2+ were investigated by the combined use of molecular dynamics simulations and the 3D reference interaction site model method. The CBM36 showed affinity for xylan after Ca2+ binding, but not after Mg2+ binding. Free-energy component analysis of the xylan-binding process revealed that the major factor for xylan-binding affinity is the electrostatic interaction between the Ca2+ and the hydroxyl oxygens of xylan. The van der Waals interaction between the hydrophobic side chain of CBM36 and the glucopyranose ring of xylan also contributes to the stabilization of the xylan-binding state. Dehydration on the formation of the complex has the opposite effect on these interactions. The affinity of CBM36 for xylan results from a balance of the interactions between the binding ion and solvents, hydrophilic residues around xylan, and the hydroxyl oxygens of xylan. When CBM binds Ca2+, these interactions are well balanced; in contrast, when CBM binds Mg2+, the dehydration penalty is excessively large.

  2. Nucleic acid binding and other biomedical properties of artificial oligolysines

    Directory of Open Access Journals (Sweden)

    Roviello GN

    2016-11-01

    Full Text Available Giovanni N Roviello,1 Caterina Vicidomini,1 Vincenzo Costanzo,1 Valentina Roviello2 1CNR Istituto di Biostrutture e Bioimmagini, Via Mezzocannone site and Headquarters, 2Centro Regionale di Competenza (CRdC Tecnologie, Via Nuova Agnano, Napoli, Italy Abstract: In the present study, we report the interaction of an artificial oligolysine (referred to as AOL realized in our laboratory with targets of biomedical importance. These included polyinosinic acid (poly rI and its complex with polycytidylic acid (poly I:C, RNAs with well-known interferon-inducing ability, and double-stranded (ds DNA. The ability of the peptide to bind both single-stranded poly rI and ds poly I:C RNAs emerged from our circular dichroism (CD and ultraviolet (UV studies. In addition, we found that AOL forms complexes with dsDNA, as shown by spectroscopic binding assays and UV thermal denaturation experiments. These findings are encouraging for the possible use of AOL in biomedicine for nucleic acid targeting and oligonucleotide condensation, with the latter being a key step preceding their clinical application. Moreover, we tested the ability of AOL to bind to proteins, using serum albumin as a model protein. We demonstrated the oligolysine–protein binding by CD experiments which suggested that AOL, positively charged under physiological conditions, binds to the protein regions rich in anionic residues. Finally, the morphology characterization of the solid oligolysine, performed by scanning electron microscopy, showed different crystal forms including cubic-shaped crystals confirming the high purity of AOL. Keywords: nucleic acid binding, polyinosinic acid, double-stranded nucleic acids, oligolysine, circular dichroism

  3. Visualizing KcsA conformational changes upon ion binding by infrared spectroscopy and atomistic modeling.

    Science.gov (United States)

    Stevenson, Paul; Götz, Christoph; Baiz, Carlos R; Akerboom, Jasper; Tokmakoff, Andrei; Vaziri, Alipasha

    2015-05-07

    The effect of ion binding in the selectivity filter of the potassium channel KcsA is investigated by combining amide I Fourier-transform infrared spectroscopy with structure-based spectral modeling. Experimental difference IR spectra between K(+)-bound KcsA and Na(+)-bound KcsA are in good qualitative agreement with spectra modeled from structural ensembles generated from molecular dynamics simulations. The molecular origins of the vibrational modes contributing to differences in these spectra are determined not only from structural differences in the selectivity filter but also from the pore helices surrounding this region. Furthermore, the coordination of K(+) or Na(+) to carbonyls in the selectivity filter effectively decouples the vibrations of those carbonyls from the rest of the protein, creating local probes of the electrostatic environment. The results suggest that it is necessary to include the influence of the surrounding helices in discussing selectivity and transport in KcsA and, on a more general level, that IR spectroscopy offers a nonperturbative route to studying the structure and dynamics of ion channels.

  4. Semiconducting Properties of Swift Au Ion-Irradiated ZnO Thin Films at Room Temperature

    Science.gov (United States)

    Kwon, Sera; Park, Hyun-Woo; Chung, Kwun-Bum

    2017-02-01

    The semiconducting properties of Au ion-irradiated ZnO thin films were investigated as a function of ion irradiation dose at room temperature. The Au ion irradiation was conducted with acceleration energy of 130 MeV in the ion dose range from 1 × 1011 to 5 × 1012 ions/cm2. The physical properties showed no change regardless of the Au ion irradiation dose; however, the electrical properties of Au ion-irradiated ZnO thin films changed, depending on the Au ion irradiation dose. The electronic structure drastically changed with the evolution of hybridized molecular orbital structure for the conduction band and band edge states below the conduction band. These remarkable changes in electronic structure correlate with changes in electrical properties, such as carrier concentration and mobility.

  5. Calix[4]pyrrole derivative: recognition of fluoride and mercury ions and extracting properties of the receptor-based new material.

    Science.gov (United States)

    de Namor, Angela F Danil; Khalife, Rasha

    2008-12-11

    A calix[4]pyrrole derivative, namely, meso-tetramethyl tetrakis (4-phenoxy methyl ketone) calix[4]pyrrole, 1, was synthesized and structurally (1H NMR) and thermodynamically characterized. The complexing properties of this receptor with a wide variety of anions and cations in dipolar aprotic media (acetonitrile, propylene carbonate, and dimethyl sulfoxide) were investigated through 1H NMR and conductance studies. The former technique was used to assess whether or not complexation occurs and if so to identify the active sites of interaction of 1 with ions. The composition of the complexes was established by conductance measurements. It was found that in dipolar aprotic solvents, 1 interacts only with two polluting ions (fluoride and mercury). The complexation thermodynamics of 1 and these ions in these solvents is reported. The medium effect on the binding process involving the fluoride ion is discussed taking into account the solvation properties of reactants and the product. Complexes of moderate stability are found. Given that this is an important factor to consider for the recycling of the loaded material in extraction processes, 1 was treated with formaldehyde in basic medium leading to the production of a calix[4]pyrrole based material able to extract fluoride and mercury (II) ions from water. Thus the optimum conditions for the extraction of these ions from aqueous solutions were established. The material is easily recyclable using an organic acid. Final conclusions are given.

  6. Binding of antioxidant flavonol morin to the native state of bovine serum albumin: Effects of urea and metal ions on the binding

    Energy Technology Data Exchange (ETDEWEB)

    Singha Roy, Atanu; Dinda, Amit Kumar; Chaudhury, Susmitnarayan; Dasgupta, Swagata, E-mail: swagata@chem.iitkgp.ernet.in

    2014-01-15

    In consideration of the various medicinal aspects of the flavonoid polyphenols, the interaction of morin with bovine serum albumin (BSA) has been investigated using multi-spectroscopic approaches. The pKa{sub 1} of morin being 5.09, which is below physiological pH, binding studies provide important insights into its potential use as a biotherapeutic. The binding was performed under different pH (5, 7 and 9) conditions and in absence and presence of Cu(II) and Fe(III) ions. It is observed that the presence of metal ions affect the binding of morin towards BSA. The binding with BSA results in a motional restriction of morin in solution that causes an increase in anisotropy (r), rotational correlation time (t{sub r}) and steady-state lifetime (t{sub av}) of the ligand. Urea causes denaturation of BSA resulting in the release of morin from the protein core as determined from both the steady-state fluorescence and anisotropy (r) measurements. The possibility of non-radiative energy transfer from the donor tryptophan to the acceptor morin is detected following the Förster's theory. The site marker displacement studies along with the molecular docking results indicated that morin binds to the hydrophobic pocket of site 1 (subdomain IIA) near Trp 213 of BSA. -- Highlights: • Binding mainly occurs through the electrostatic forces with partial hydrophobic association. • Negative ΔG° indicates the spontaneity of the complexation between morin and BSA. • Morin binds near Trp 213 (site 1, subdomain IIA) of BSA only in its native state. • Lifetime of morin increases as a function of BSA. • Motional restriction of morin occurs in the presence of BSA.

  7. The binding of in vitro synthesized adenovirus DNA binding protein to single-stranded DNA is stimulated by zinc ions

    NARCIS (Netherlands)

    Vos, H.L.; Lee, F.M. van der; Sussenbach, J.S.

    1988-01-01

    We have synthesized wild type DNA binding protein (DBP) of adenovirus type 5 (Ad5) and several truncated forms of this protein by a combination of in vitro transcription and translation. The proteins obtained were tested for binding to a single-stranded DNA-cellulose column. It could be shown that f

  8. Analysis of the ligand binding properties of recombinant bovine liver-type fatty acid binding protein

    DEFF Research Database (Denmark)

    Rolf, B; Oudenampsen-Krüger, E; Börchers, T

    1995-01-01

    The coding part of the cDNA for bovine liver-type fatty acid binding protein (L-FABP) has been amplified by RT-PCR, cloned and used for the construction of an Escherichia coli (E. coli) expression system. The recombinant protein made up to 25% of the soluble E. coli proteins and could be isolated...

  9. Binding of scandium ions to metalloporphyrin-flavin complexes for long-lived charge separation.

    Science.gov (United States)

    Kojima, Takahiko; Kobayashi, Ryosuke; Ishizuka, Tomoya; Yamakawa, Shinya; Kotani, Hiroaki; Nakanishi, Tatsuaki; Ohkubo, Kei; Shiota, Yoshihito; Yoshizawa, Kazunari; Fukuzumi, Shunichi

    2014-11-17

    A porphyrin-flavin-linked dyad and its zinc and palladium complexes (MPor-Fl: 2-M, M=2 H, Zn, and Pd) were newly synthesized and the X-ray crystal structure of 2-Pd was determined. The photodynamics of 2-M were examined by femto- and nanosecond laser flash photolysis measurements. Photoinduced electron transfer (ET) in 2-H2 occurred from the singlet excited state of the porphyrin moiety (H2 Por) to the flavin (Fl) moiety to produce the singlet charge-separated (CS) state (1) (H2 Por(.+) -Fl(.-) ), which decayed through back ET (BET) to form (3) [H2 Por]*-Fl with rate constants of 1.2×10(10) and 1.2×10(9)  s(-1) , respectively. Similarly, photoinduced ET in 2-Pd afforded the singlet CS state, which decayed through BET to form (3) [PdPor]*Fl with rate constants of 2.1×10(11) and 6.0×10(10)  s(-1) , respectively. The rate constant of photoinduced ET and BET of 2-M were related to the ET and BET driving forces by using the Marcus theory of ET. One and two Sc(3+) ions bind to the flavin moiety to form the Fl-Sc(3+) and Fl-(Sc(3+) )2 complexes with binding constants of K1 =2.2×10(5)  M(-1) and K2 =1.8×10(3)  M(-1) , respectively. Other metal ions, such as Y(3+) , Zn(2+) , and Mg(2+) , form only 1:1 complexes with flavin. In contrast to 2-M and the 1:1 complexes with metal ions, which afforded the short-lived singlet CS state, photoinduced ET in 2-Pd⋅⋅⋅Sc(3+) complexes afforded the triplet CS state ((3) [PdPor(.+) -Fl(.-) (Sc(3+) )2 ]), which exhibited a remarkably long lifetime of τ=110 ms (kBET =9.1 s(-1) ).

  10. Thermodynamic study of the binding of calcium and magnesium ions with myelin basic protein using the extended solvation theory

    Institute of Scientific and Technical Information of China (English)

    G. Rezaei Behbehani; A.A. Saboury; A. Divsalar

    2008-01-01

    The interaction of myelin basic protein (MBP) from the bovine central nervous system with Ca2+ and Mg2+ ions, named as M2+, was studied by isothermal titration calorimetry at 27℃ in aqueous solution. The extended solvation model was used to reproduce the enthaipies of MBP+M2+ interactions.The solvation parameters recovered from the extended solvation model were attributed to the structural change of MBP due to the metal ion interaction. It was found that there is a set of two identical and noninteracting binding sites for Ca2+ and Mg2+ ions.

  11. Binding properties of beetal recombinant caprine growth hormone to ...

    African Journals Online (AJOL)

    SAM

    2014-07-23

    Jul 23, 2014 ... 2Institute of Molecular Biology and Biotechnology, the University of ... This study provides data for beetal rcGH .... obtained; big and small peak showing the purified tracer and free 125I, respectively. ... analysis of rcGH binding to Bovidae receptors was analyzed by ..... science to commercial application.

  12. spectral characterization and dna binding properties of lanthanide(iii)

    African Journals Online (AJOL)

    The complexes undergo quasi-reversible one electron reduction. The binding interaction ... cleavage activities of transition metal complex, herein we report synthesis, spectral ... instruments 660C Electrochemical analyzer and a conventional three electrode, Ag/AgCl reference ..... F.19-106/2013(BSR)] for financial support.

  13. Elucidating the structures and cooperative binding mechanism of cesium salts to the multitopic ion-pair receptor through density functional theory calculations.

    Science.gov (United States)

    Sadhu, Biswajit; Sundararajan, Mahesh; Velmurugan, Gunasekaran; Venuvanalingam, Ponnambalam

    2015-09-21

    Designing new and innovative receptors for the selective binding of radionuclides is central to nuclear waste management processes. Recently, a new multi-topic ion-pair receptor was reported which binds a variety of cesium salts. Due to the large size of the receptor, quantum chemical calculations on the full ion-pair receptors are restricted, thus the binding mechanisms are not well understood at the molecular level. We have assessed the binding strengths of various cesium salts to the recently synthesized multi-topic ion-pair receptor molecule using density functional theory based calculations. Our calculations predict that the binding of cesium salts to the receptor predominantly occurs via the cooperative binding mechanism. Cesium and the anion synergistically assist each other to bind favorably inside the receptor. Energy decomposition analysis on the ion-pair complexes shows that the Cs salts are bound to the receptor mainly through electrostatic interactions with small contribution from covalent interactions for large ionic radius anions. Further, QTAIM analysis characterizes the importance of different inter-molecular interactions between the ions and the receptor inside the ion-pair complexes. The role of the crystallographic solvent molecule contributes significantly by ~10 kcal mol(-1) to the overall binding affinities which is quite significant. Further, unlike the recent molecular mechanics (MM) calculations, our calculated binding affinity trends for various Cs ion-pair complexes (CsF, CsCl and CsNO3) are now in excellent agreement with the experimental binding affinity trends.

  14. Central Plasma Sheet Ion Properties as Inferred from Ionospheric Observations

    Science.gov (United States)

    Wing, Simon; Newell, Patrick T.

    1998-01-01

    A method of inferring central plasma sheet (CPS) temperature, density, and pressure from ionospheric observations is developed. The advantage of this method over in situ measurements is that the CPS can be studied in its entirely, rather than only in fragments. As a result, for the first time, comprehensive two-dimensional equatorial maps of CPS pressure, density, and temperature within the isotropic plasma sheet are produced. These particle properties are calculated from data taken by the Special Sensor for Precipitating Particles, version 4 (SSJ4) particle instruments onboard DMSP F8, F9, F10, and F11 satellites during the entire year of 1992. Ion spectra occurring in conjunction with electron acceleration events are specifically excluded. Because of the variability of magnetotail stretching, the mapping to the plasma sheet is done using a modified Tsyganenko [1989] magnetic field model (T89) adjusted to agree with the actual magnetotail stretch at observation time. The latter is inferred with a high degree of accuracy (correlation coefficient -0.9) from the latitude of the DMSP b2i boundary (equivalent to the ion isotropy boundary). The results show that temperature, pressure, and density all exhibit dawn-dusk asymmetries unresolved with previous measurements. The ion temperature peaks near the midnight meridian. This peak, which has been associated with bursty bulk flow events, widens in the Y direction with increased activity. The temperature is higher at dusk than at dawn, and this asymmetry increases with decreasing distance from the Earth. In contrast, the density is higher at dawn than at dusk, and there appears to be a density enhancement in the low-latitude boundary layer regions which increases with decreasing magnetic activity. In the near-Earth regions, the pressure is higher at dusk than at dawn, but this asymmetry weakens with increasing distance from the Earth and may even reverse so that at distances X less than approx. 10 to -12 R(sub E

  15. Dynamical Properties of Potassium Ion Channels with a Hierarchical Model

    Institute of Scientific and Technical Information of China (English)

    ZHAN Yong; AN Hai-Long; YU Hui; ZHANG Su-Hua; HAN Ying-Rong

    2006-01-01

    @@ It is well known that potassium ion channels have higher permeability than K ions, and the permeable rate of a single K ion channel is about 108 ions per second. We develop a hierarchical model of potassium ion channel permeation involving ab initio quantum calculations and Brownian dynamics simulations, which can consistently explain a range of channel dynamics. The results show that the average velocity of K ions, the mean permeable time of K ions and the permeable rate of single channel are about 0.92nm/ns, 4.35ns and 2.30×108 ions/s,respectively.

  16. A new bile acid-derived lariat-ether: Design, synthesis and cation binding properties

    Indian Academy of Sciences (India)

    P Babu; Uday Maitra

    2003-10-01

    A new chola lariat ether (1, a 21-crown-6) was constructed from readily available precursors. The association constant of compound 1 with alkali metal picrates was measured using Cram’s extraction protocol. Evidence is presented for the involvement of the 3-methoxy group for the complexation. Energy minimised structures show that the A-ring gets slightly distorted upon metal ion binding.

  17. Cortisol levels, binding, and properties of corticosteroid-binding globulin in the serum of primates.

    Science.gov (United States)

    Klosterman, L L; Murai, J T; Siiteri, P K

    1986-01-01

    New World primates have exceptionally high plasma levels of cortisol and other steroid hormones when compared with humans and other primates. It has been suggested that this difference can be explained by either low affinity or concentration of cellular steroid receptors. We have assessed cortisol availability in serum from several species of New and Old World primates under physiological conditions (whole serum at 37 degrees C). Measurements were made of total and free cortisol, corticosteroid-binding globulin (CBG) binding capacity and affinity for cortisol, distribution of cortisol in serum, and its binding to albumin. In agreement with earlier reports, plasma free cortisol levels in Old World primates, prosimians, and humans range from 10-300 nM. However, very high total plasma cortisol together with low CBG binding capacity and affinity result in free cortisol concentrations of 1-4 microM in some New World primates (squirrel monkey and marmosets) but not in others such as the titi and capuchin. In squirrel monkeys, free cortisol levels are far greater than might be predicted from the affinity of the glucocorticoid receptor estimated in cultured skin fibroblasts. In addition to low affinity, CBG from squirrel monkeys and other New World primates exhibits differences in electrophoretic mobility and sedimentation behavior in sucrose density ultracentrifugation, suggestive of a molecular weight that is approximately twice that of CBG from other species. Together with other data these results indicate that the apparent glucocorticoid resistance found in New World primates is a complex phenomenon that is not easily explained by present concepts of glucocorticoid action.

  18. Oxygen binding properties of non-mammalian nerve globins

    DEFF Research Database (Denmark)

    Hundahl, Christian; Fago, Angela; Dewilde, Sylvia

    2006-01-01

    Oxygen-binding globins occur in the nervous systems of both invertebrates and vertebrates. While the function of invertebrate nerve haemoglobins as oxygen stores that extend neural excitability under hypoxia has been convincingly demonstrated, the physiological role of vertebrate neuroglobins...... is less well understood. Here we provide a detailed analysis of the oxygenation characteristics of nerve haemoglobins from an annelid (Aphrodite aculeata), a nemertean (Cerebratulus lacteus) and a bivalve (Spisula solidissima) and of neuroglobin from zebrafish (Danio rerio). The functional differences...... temperatures investigated and exhibited large enthalpies of oxygenation, the hexacoordinate globins showed reverse Bohr effects (at least at low temperature) and approximately twofold lower oxygenation enthalpies. Only S. solidissima nerve haemoglobin showed apparent cooperativity in oxygen binding, suggesting...

  19. Integrative decomposition procedure and Kappa statistics set up ATF2 ion binding module in malignant pleural mesothelioma (MPM)

    Institute of Scientific and Technical Information of China (English)

    Ying SUN; Lin WANG; Lei LIU

    2008-01-01

    Activating transcription factor 2 (ATF2) is a member of the ATF/cyclic AMP-responsive element bind-ing protein family of transcription factors. However, the information concerning ATF2 ion-mediated DNA binding module and function of ATF2 in malignant pleural mesothelioma (MPM) has never been addressed. In this study, by using GRNInfer and GVedit based on linear pro-gramming and a decomposition procedure, with integrated analysis of the function cluster using Kappa statistics and fuzzy heuristic clustering in MPM, we identified one ATF2 ion-mediated DNA binding module involved in invasive function including ATF2 inhibition to target genes FALZ, C20orf31, NME2, PLOD2, RNF10, and RNASEH1, upstream RNF10 and PLOD2 activation to ATF2, upstream RNASEH1 and FALZ inhibition to ATF2 from 40 MPM tumors and 5 normal pleural tissues. Remarkably, our results showed that the predominant effect of ATF2 occupancy is to suppress the activation of target genes on MPM. Importantly, the ATF2 ion-mediated DNA binding module reflects 'mutual' positive and negative feedback regulation mechanism of ATF2 with up-and down-stream genes. It may be useful for developing novel prognostic markers and therapeutic targets in MPM.

  20. Synthesis and metal binding properties of N-alkylcarboxyspiropyrans

    OpenAIRE

    Perry, Alexis; Kousseff, Christina J

    2017-01-01

    Spiropyrans bearing an N-alkylcarboxylate tether are a common structure in dynamic, photoactive materials and serve as colourimetric/fluorimetric cation receptors. In this study, we describe an efficient synthesis of spiropyrans with 2–12 carbon atom alkylcarboxylate substituents, and a systematic analysis of their interactions with metal cations using 1H NMR and UV-visible spectroscopy. All N-alkylcarboxyspiropyrans in this study displayed a strong preference for binding divalent metal catio...

  1. Fluorescence properties of porcine odorant binding protein Trp 16 residue

    Energy Technology Data Exchange (ETDEWEB)

    Albani, Jihad Rene, E-mail: Jihad-Rene.Albani@univ-lille1.f [Laboratoire de Biophysique Moleculaire, Universite des Sciences et Technologies de Lille, F-59655 Villeneuve d' Ascq Cedex (France)

    2010-11-15

    Summary: The present work deals with fluorescence studies of adult porcine odorant binding protein at pH=7.5. At this pH, the protein is a dimer, each monomer contains one tryptophan residue. Our results show that tryptophan residue displays significant motions and emits with three fluorescence lifetimes. Decay associated spectra showed that the three lifetime's components emanate from sub-structures surrounded by the same microenvironment.

  2. Evidence for a metal-thiolate intermediate in alkyl group transfer from epoxypropane to coenzyme M and cooperative metal ion binding in epoxyalkane:CoM transferase.

    Science.gov (United States)

    Boyd, Jeffrey M; Ensign, Scott A

    2005-10-04

    Epoxyalkane:coenzyme M transferase (EaCoMT) catalyzes the nucleophilic addition of coenzyme M (CoM, 2-mercaptoethanesulfonic acid) to epoxypropane forming 2-hydroxypropyl-CoM. The biochemical properties of EaCoMT suggest that the enzyme belongs to the family of alkyltransferase enzymes for which Zn plays a role in activating an organic thiol substrate for nucleophilic attack on an alkyl-donating substrate. The enzyme has a hexameric (alpha(6)) structure with one zinc atom per subunit. In the present work M(2+) binding and the role of Zn(2+) in EaCoMT have been established through a combination of biochemical, calorimetric, and spectroscopic techniques. A variety of metal ions, including Zn(2+), Co(2+), Cd(2+), and Ni(2+), were capable of activating a Zn-deficient "apo" form of EaCoMT, affording enzymes with various levels of activity. Titration of Co(2+) into apo-EaCoMT resulted in UV-visible spectroscopic changes consistent with the formation of a tetrahedral Co(2+) binding site, with coordination of bound Co(2+) to two thiolate ligands. Quantification of UV-visible spectral changes upon Co(2+) titration into apo-EaCoMT demonstrated that EaCoMT binds Co(2+) cooperatively at six interacting sites. Isothermal titration calorimetric studies of Co(2+) and Zn(2+) binding to EaCoMT also showed cooperativity for metal ion binding among six sites. The addition of CoM to Co(2+)-substituted EaCoMT resulted in UV-visible spectral changes indicative of formation of a new thiol-Co(2+) bond. Co(2+)-substituted EaCoMT exhibited a unique Co(2+) EPR spectrum, and this spectrum was perturbed significantly upon addition of CoM. The presence of a divalent metal ion was required for the release of protons from CoM upon binding to EaCoMT, with Zn(2+), Co(2+), and Cd(2+) each facilitating proton release. The divalent metal ion of EaCoMT is proposed to play a key role in the coordination and deprotonation of CoM, possibly through formation of a metal-thiolate that is activated for attack

  3. Cassini CAPS Measurements of Thermal Ion Properties: An Update

    Science.gov (United States)

    Wilson, R. J.; Bagenal, F.; Delamere, P. A.

    2010-12-01

    Since the Wilson et al. [2008] paper on thermal ion properties in Saturn's inner equatorial magnetosphere there have been several advances in forward model techniques and instrument knowledge. These include: a) Improved CAPS (SNG) calibration values since 2008. While the previous fits to data are still valid, this efficiency adjustment has the effect of reducing the density values calculated from that fit. Compared to the previous calibration values, nOH+ and nH+ are ≈30% and ≈9% lower respectively. b) Robust error analysis on the forward model process to produce standard deviations for the fitted parameters. This also shows the expected dependences between various fitted parameters, such as Vφ and OH+ T⊥, inherent in the model. c) Utilization of real magnetic field data to forward model T⊥ and T\\par. Previously assumed magnetic field was in the -z direction. In addition, these improvements allow us to remove the constraint that Vz = 0, and the use of real magnetic field data allows us to analyze data farther from the equator. References Wilson, R. J., R. L. Tokar, M. G. Henderson, T. W. Hill, M. F. Thomsen, and D. H. Pontius (2008), Cassini plasma spectrometer thermal ion measurements in Saturn's inner magnetosphere,

  4. Heavy Ion Beams for Investigation of Thermophysical Properties

    CERN Document Server

    Iosilevskiy, Igor

    2010-01-01

    Perspectives for study of thermophysical properties via uniform quasi-stationary volumetric heating under Heavy Ion Beam (HIB) heating with moderate but realistic energy deposition (~ 1 kJ/g) are under discussion. New quasi-isobaric regime of heating is proposed as combination of the HIB energy deposition with the use of highly dispersed porous material as an irradiating sample. Regime of "tracing saturation curve" is proposed also when heating the evaporating porous materials. Consequent preferences and priorities are emphasized. In frames of this technique HIB could became an uncompetitive tool for study of phase transition phenomenon for a wide number of materials with high-temperature location of critical point. Two important thermophysical problems, which could approve using of HIB facility, are discussed as the first-row candidates. Evaporation in Uranium is one of the most tempting candidates to be studied under HIB heating in such manner. When being successful this experiment has a good chance to reso...

  5. Hydrogen storage in a potassium-ion-bound metal-organic framework incorporating crown ether struts as specific cation binding sites.

    Science.gov (United States)

    Lim, Dae-Woon; Chyun, Seung An; Suh, Myunghyun Paik

    2014-07-21

    To develop a metal-organic framework (MOF) for hydrogen storage, SNU-200 incorporating a 18-crown-6 ether moiety as a specific binding site for selected cations has been synthesized. SNU-200 binds K(+), NH4(+), and methyl viologen (MV(2+)) through single-crystal to single-crystal transformations. It exhibits characteristic gas-sorption properties depending on the bound cation. SNU-200 activated with supercritical CO2 shows a higher isosteric heat (Qst) of H2 adsorption (7.70 kJ mol(-1)) than other zinc-based MOFs. Among the cation inclusions, K(+) is the best for enhancing the isosteric heat of the H2 adsorption (9.92 kJ mol(-1)) as a result of the accessible open metal sites on the K(+) ion. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Influence of nanoparticle-ion and nanoparticle-polymer interactions on ion transport and viscoelastic properties of polymer electrolytes.

    Science.gov (United States)

    Mogurampelly, Santosh; Sethuraman, Vaidyanathan; Pryamitsyn, Victor; Ganesan, Venkat

    2016-04-21

    We use atomistic simulations to probe the ion conductivities and mechanical properties of polyethylene oxide electrolytes containing Al2O3nanoparticles. We specifically study the influence of repulsive polymer-nanoparticle and ion-nanoparticle interactions and compare the results with those reported for electrolytes containing the polymorph β-Al2O3nanoparticles. We observe that incorporating repulsive nanoparticle interactions generally results in increased ionic mobilities and decreased elastic moduli for the electrolyte. Our results indicate that both ion transport and mechanical properties are influenced by the polymer segmental dynamics in the interfacial zones of the nanoparticle in the ion-doped systems. Such effects were seen to be determined by an interplay between the nanoparticle-polymer,nanoparticle-ion, and ion-polymer interactions. In addition, such interactions were also observed to influence the number of dissociated ions and the resulting conductivities. Within the perspective of the influence of nanoparticles on the polymer relaxation times in ion-doped systems, our results in the context of viscoelastic properties were consistent with the ionic mobilities. Overall, our results serve to highlight some issues that confront the efforts to use nanoparticle dispersions to simultaneously enhance the conductivity and the mechanical strength of polymer electrolyte.

  7. Ion-specific thermodynamical properties of aqueous proteins

    Directory of Open Access Journals (Sweden)

    Eduardo R.A. Lima

    2010-03-01

    Full Text Available Ion-specific interactions between two colloidal particles are calculated using a modified Poisson-Boltzmann (PBequationandMonteCarlo(MCsimulations. PBequationspresentgoodresultsofionicconcentration profiles around a macroion, especially for salt solutions containing monovalent ions. These equations include not only electrostatic interactions, but also dispersion potentials originated from polarizabilities of ions and proteins. This enables us to predict ion-specific properties of colloidal systems. We compared results obtained from the modified PB equation with those from MC simulations and integral equations. Phase diagrams and osmotic second virial coefficients are also presented for different salt solutions at different pH and ionic strengths, in agreement with the experimental results observed Hofmeister effects. In order to include the water structure and hydration effect, we have used an effective interaction obtained from molecular dynamics of each ion and a hydrophobic surface combined with PB equation. The method has been proved to be efficient and suitable for describing phenomena where the water structure close to the interface plays an essential role. Important thermodynamic properties related to protein aggregation, essential in biotechnology and pharmaceutical industries, can be obtained from the method shown here.Interações íon-específicas (dependentes do tipo de íon presente em solução entre duas partículas coloidais são calculadas usando a equação de Poisson-Boltzmann (PB modificada e simulações de Monte Carlo (MC. As equações de PB apresentam bons resultados de perfis de concentração nas proximidades de um macro-íon, principalmente para soluções salinas contendo íons monovalentes. Estas equações incluem não só interações eletrostáticas, mas também potenciais de dispersão, que têm origem nas polarizabilidades de íons e proteínas, permitindo a predição de propriedades íon-específicas de

  8. Enhanced AC conductivity and dielectric relaxation properties of polypyrrole nanoparticles irradiated with Ni{sup 12+} swift heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Hazarika, J.; Kumar, A., E-mail: ask@tezu.ernet.in

    2014-08-15

    In this paper, we report the 160 MeV Ni{sup 12+} swift heavy ions (SHIs) irradiation effects on AC conductivity and dielectric relaxation properties of polypyrrole (PPy) nanoparticles in the frequency range of 42 Hz–5 MHz. Four ion fluences of 5 × 10{sup 10}, 1 × 10{sup 11}, 5 × 10{sup 11} and 1 × 10{sup 12} ions/cm{sup 2} have been used for the irradiation purpose. Transport properties in the pristine and irradiated PPy nanoparticles have been investigated with permittivity and modulus formalisms to study the polarization effects and conductivity relaxation. With increasing ion fluence, the relaxation peak in imaginary modulus (M{sup ″}) plots shifts toward high frequency suggesting long range motion of the charge carriers. The AC conductivity studies suggest correlated barrier hopping as the dominant transport mechanism. The hopping distance (R{sub ω}) of the charge carriers decreases with increasing the ion fluence. Binding energy (W{sub m}) calculations depict that polarons are the dominant charge carriers.

  9. Structural Analysis Uncovers Lipid-Binding Properties of Notch Ligands

    Directory of Open Access Journals (Sweden)

    Chandramouli R. Chillakuri

    2013-11-01

    Full Text Available The Notch pathway is a core cell-cell signaling system in metazoan organisms with key roles in cell-fate determination, stem cell maintenance, immune system activation, and angiogenesis. Signals are initiated by extracellular interactions of the Notch receptor with Delta/Serrate/Lag-2 (DSL ligands, whose structure is highly conserved throughout evolution. To date, no structure or activity has been associated with the extreme N termini of the ligands, even though numerous mutations in this region of Jagged-1 ligand lead to human disease. Here, we demonstrate that the N terminus of human Jagged-1 is a C2 phospholipid recognition domain that binds phospholipid bilayers in a calcium-dependent fashion. Furthermore, we show that this activity is shared by a member of the other class of Notch ligands, human Delta-like-1, and the evolutionary distant Drosophila Serrate. Targeted mutagenesis of Jagged-1 C2 domain residues implicated in calcium-dependent phospholipid binding leaves Notch interactions intact but can reduce Notch activation. These results reveal an important and previously unsuspected role for phospholipid recognition in control of this key signaling system.

  10. DNA binding properties of the small cascade subunit Csa5.

    Directory of Open Access Journals (Sweden)

    Michael Daume

    Full Text Available CRISPR-Cas systems provide immunity against viral attacks in archaeal and bacterial cells. Type I systems employ a Cas protein complex termed Cascade, which utilizes small CRISPR RNAs to detect and degrade the exogenic DNA. A small sequence motif, the PAM, marks the foreign substrates. Previously, a recombinant type I-A Cascade complex from the archaeon Thermoproteus tenax was shown to target and degrade DNA in vitro, dependent on a native PAM sequence. Here, we present the biochemical analysis of the small subunit, Csa5, of this Cascade complex. T. tenax Csa5 preferentially bound ssDNA and mutants that showed decreased ssDNA-binding and reduced Cascade-mediated DNA cleavage were identified. Csa5 oligomerization prevented DNA binding. Specific recognition of the PAM sequence was not observed. Phylogenetic analyses identified Csa5 as a universal member of type I-A systems and revealed three distinct groups. A potential role of Csa5 in R-loop stabilization is discussed.

  11. Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

    Science.gov (United States)

    Sengwa, R. J.; Dhatarwal, Priyanka; Choudhary, Shobhna

    2016-05-01

    Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF4) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governed by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10-6 S cm-1 which suggests the suitability of the SPE film for rechargeable lithium batteries.

  12. Acid-base characterization, coordination properties towards copper(II) ions and DNA interaction studies of ribavirin, an antiviral drug.

    Science.gov (United States)

    Nagaj, Justyna; Starosta, Radosław; Jeżowska-Bojczuk, Małgorzata

    2015-01-01

    We have studied processes of copper(II) ion binding by ribavirin, an antiviral agent used in treating hepatitis C, which is accompanied usually by an increased copper level in the serum and liver tissue. Protonation equilibria and Cu(II) binding were investigated using the UV-visible, EPR and NMR spectroscopic techniques as well as the DFT (density functional theory) calculations. The spectroscopic data suggest that the first complex is formed in the water solution at pH as low as 0.5. In this compound Cu(II) ion is bound to one of the nitrogen atoms from the triazole ring. Above pH6.0, the metal ion is surrounded by two nitrogen and two oxygen atoms from two ligand molecules. The DFT calculations allowed to determine the exact structure of this complex. We found that in the lowest energy isomer two molecules of the ligand coordinate via O and N4 atoms in trans positions. The hypothetical oxidative properties of the investigated system were also examined. It proved not to generate plasmid DNA scission products. However, the calf thymus (CT)-DNA binding studies showed that it reacts with ribavirin and its cupric complex. Moreover, the interaction with the complex is much more efficient.

  13. Characterization of uranium binding to Diphonix{sup TM} and Duolite{sup TM} ion-exchange resins

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, J.G.; Shrinsky, A.J.; Sommerville, L.E. [Fort Lewis College, Durango, CO (United States)]|[Los Alamos National Lab., NM (United States)] [and others

    1995-12-01

    We initiated a series of experiments to characterize uranium binding to two commercially available ion-exchange resins, Diphonix{trademark} and Duolite{trademark}. These experiments were done to determine the most efficient means of recycling an organic chelator, tiron, in a process used to wash soil contaminated with uranium. The binding capacity and pH dependence were determined for uranium binding to Diphonix{trademark} and Duolite{trademark}. Also competition studies with aluminum, iron, and uranium were done to determine the optimum conditions for uranium binding in the presence of these other metals. Both resins were shown to effectively separate uranium from tiron allowing almost quantitative recovery of uranium-free tiron. Furthermore, these resins may serve as a suitable place to concentrate and store uranium.

  14. Structural Studies of the Alzheimer's Amyloid Precursor Protein Copper-Binding Domain Reveal How It Binds Copper Ions

    Energy Technology Data Exchange (ETDEWEB)

    Kong, G.K.-W.; Adams, J.J.; Harris, H.H.; Boas, J.F.; Curtain, C.C.; Galatis, D.; Master, C.L.; Barnham, K.J.; McKinstry, W.J.; Cappai, R.; Parker, M.W.; /Sydney U.

    2007-07-09

    Alzheimer's disease (AD) is the major cause of dementia. Amyloid {beta} peptide (A {beta}), generated by proteolytic cleavage of the amyloid precursor protein (APP), is central to AD pathogenesis. APP can function as a metalloprotein and modulate copper (Cu) transport, presumably via its extracellular Cu-binding domain (CuBD). Cu binding to the CuBD reduces A{beta} levels, suggesting that a Cu mimetic may have therapeutic potential. We describe here the atomic structures of apo CuBD from three crystal forms and found they have identical Cu-binding sites despite the different crystal lattices. The structure of Cu[2+]-bound CuBD reveals that the metal ligands are His147, His151, Tyrl68 and two water molecules, which are arranged in a square pyramidal geometry. The site resembles a Type 2 non-blue Cu center and is supported by electron paramagnetic resonance and extended X-ray absorption fine structure studies. A previous study suggested that Met170 might be a ligand but we suggest that this residue plays a critical role as an electron donor in CuBDs ability to reduce Cu ions. The structure of Cu[+]-bound CuBD is almost identical to the Cu[2+]-bound structure except for the loss of one of the water ligands. The geometry of the site is unfavorable for Cu[+], thus providing a mechanism by which CuBD could readily transfer Cu ions to other proteins.

  15. Iron-binding properties of sugar cane yeast peptides.

    Science.gov (United States)

    de la Hoz, Lucia; Ponezi, Alexandre N; Milani, Raquel F; Nunes da Silva, Vera S; Sonia de Souza, A; Bertoldo-Pacheco, Maria Teresa

    2014-01-01

    The extract of sugar-cane yeast (Saccharomyces cerevisiae) was enzymatically hydrolysed by Alcalase, Protex or Viscozyme. Hydrolysates were fractionated using a membrane ultrafiltration system and peptides smaller than 5kDa were evaluated for iron chelating ability through measurements of iron solubility, binding capacity and dialyzability. Iron-chelating peptides were isolated using immobilized metal affinity chromatography (IMAC). They showed higher content of His, Lys, and Arg than the original hydrolysates. In spite of poor iron solubility, hydrolysates of Viscozyme provided higher iron dialyzability than those of other enzymes. This means that more chelates of iron or complexes were formed and these kept the iron stable during simulated gastro-intestinal digestion in vitro, improving its dialyzability.

  16. Synthesis and anion binding properties of porphyrins and related compounds

    KAUST Repository

    Figueira, Flávio

    2016-12-02

    Over the last two decades the preparation of pyrrole-based receptors for anion recognition has attracted considerable attention. In this regard porphyrins, phthalocyanines and expanded porphyrins have been used as strong and selective receptors while the combination of those with different techniques and materials can boost their applicability in different applications as chemosensors and extracting systems. Improvements in the field, including the synthesis of this kind of compounds, can contribute to the development of efficient, cheap, and easy-to-prepare anion receptors. Extensive efforts have been made to improve the affinity and selectivity of these compounds and the continuous expansion of related research makes this chemistry even more promising. In this review, we summarize the most recent developments in anion binding studies while outlining the strategies that may be used to synthesize and functionalize these type of macrocycles. © 2016 World Scientific Publishing Company.

  17. SISGR: Linking Ion Solvation and Lithium Battery Electrolyte Properties

    Energy Technology Data Exchange (ETDEWEB)

    Trulove, Paul C. [U.S. Naval Academy, Annapolis, MD (United States); Foley, Matthew P. [U.S. Naval Academy, Annapolis, MD (United States)

    2012-09-30

    The solvation and phase behavior of the model battery electrolyte salt lithium trifluoromethanesulfonate (LiCF3SO3) in commonly used organic solvents; ethylene carbonate (EC), gamma-butyrolactone (GBL), and propylene carbonate (PC) was explored. Data from differential scanning calorimetry (DSC), Raman spectroscopy, and X-ray diffraction were correlated to provide insight into the solvation states present within a sample mixture. Data from DSC analyses allowed the construction of phase diagrams for each solvent system. Raman spectroscopy enabled the determination of specific solvation states present within a solvent-salt mixture, and X-ray diffraction data provided exact information concerning the structure of a solvates that could be isolated Thermal analysis of the various solvent-salt mixtures revealed the phase behavior of the model electrolytes was strongly dependent on solvent symmetry. The point groups of the solvents were (in order from high to low symmetry): C2V for EC, CS for GBL, and C1 for PC(R). The low symmetry solvents exhibited a crystallinity gap that increased as solvent symmetry decreased; no gap was observed for EC-LiTf, while a crystallinity gap was observed spanning 0.15 to 0.3 mole fraction for GBL-LiTf, and 0.1 to 0.33 mole fraction for PC(R)-LiTf mixtures. Raman analysis demonstrated the dominance of aggregated species in almost all solvent compositions. The AGG and CIP solvates represent the majority of the species in solutions for the more concentrated mixtures, and only in very dilute compositions does the SSIP solvate exist in significant amounts. Thus, the poor charge transport characteristics of CIP and AGG account for the low conductivity and transport properties of LiTf and explain why is a poor choice as a source of Li+ ions in a Li-ion battery.

  18. Understanding Ion Binding Affinity and Selectivity in β-Parvalbumin Using Molecular Dynamics and Mean Spherical Approximation Theory.

    Science.gov (United States)

    Kucharski, Amir N; Scott, Caitlin E; Davis, Jonathan P; Kekenes-Huskey, Peter M

    2016-08-25

    Parvalbumin (PV) is a globular calcium (Ca(2+))-selective protein expressed in a variety of biological tissues. Our computational studies of the rat β-parvalbumin (β-PV) isoform seek to elucidate the molecular thermodynamics of Ca(2+) versus magnesium (Mg(2+)) binding at the protein's two EF-hand motifs. Specifically, we have utilized molecular dynamics (MD) simulations and a mean-field electrolyte model (mean spherical approximation (MSA) theory) to delineate how the EF-hand scaffold controls the "local" thermodynamics of Ca(2+) binding selectivity over Mg(2+). Our MD simulations provide the probability density of metal-chelating oxygens within the EF-hand scaffolds for both Ca(2+) and Mg(2+), as well the conformational strain induced by Mg(2+) relative to Ca(2+) binding. MSA theory utilizes the binding domain oxygen and charge distributions to predict the chemical potential of ion binding, as well as their corresponding concentrations within the binding domain. We find that the electrostatic and steric contributions toward ion binding were similar for Mg(2+) and Ca(2+), yet the latter was 5.5 kcal/mol lower in enthalpy when internal strain within the EF hand was considered. We therefore speculate that beyond differences in dehydration energies for the Ca(2+) versus Mg(2+), strain induced in the β-PV EF hand by cation binding significantly contributes to the nearly 10,000-fold difference in binding affinity reported in the literature. We further complemented our analyses of local factors governing cation binding selectivity with whole-protein (global) contributions, such as interhelical residue-residue contacts and solvent exposure of hydrophobic surface. These contributions were found to be comparable for both Ca(2+)- and Mg(2+)-bound β-PV, which may implicate local factors, EF-hand strain, and dehydration, in providing the primary means of selectivity. We anticipate these methods could be used to estimate metal binding thermodynamics across a broad range of

  19. Membrane Modulates Affinity for Calcium Ion to Create an Apparent Cooperative Binding Response by Annexin a5

    Science.gov (United States)

    Gauer, Jacob W.; Knutson, Kristofer J.; Jaworski, Samantha R.; Rice, Anne M.; Rannikko, Anika M.; Lentz, Barry R.; Hinderliter, Anne

    2013-01-01

    Isothermal titration calorimetry was used to characterize the binding of calcium ion (Ca2+) and phospholipid to the peripheral membrane-binding protein annexin a5. The phospholipid was a binary mixture of a neutral and an acidic phospholipid, specifically phosphatidylcholine and phosphatidylserine in the form of large unilamellar vesicles. To stringently define the mode of binding, a global fit of data collected in the presence and absence of membrane concentrations exceeding protein saturation was performed. A partition function defined the contribution of all heat-evolving or heat-absorbing binding states. We find that annexin a5 binds Ca2+ in solution according to a simple independent-site model (solution-state affinity). In the presence of phosphatidylserine-containing liposomes, binding of Ca2+ differentiates into two classes of sites, both of which have higher affinity compared with the solution-state affinity. As in the solution-state scenario, the sites within each class were described with an independent-site model. Transitioning from a solution state with lower Ca2+ affinity to a membrane-associated, higher Ca2+ affinity state, results in cooperative binding. We discuss how weak membrane association of annexin a5 prior to Ca2+ influx is the basis for the cooperative response of annexin a5 toward Ca2+, and the role of membrane organization in this response. PMID:23746516

  20. Properties of Hydrated Alkali Metals Aimed at the Ion Channel Selectivity

    Institute of Scientific and Technical Information of China (English)

    AN Hai-Long; LIU Yu-Zhi; ZHANG Su-Hua; ZHAN Yong; ZHANG Hai-Lin

    2008-01-01

    The hydration structure properties of different alkali metal ions with eight water molecules and potassium ions with different numbers of water molecules are studied using the mixed density functional theory, B3LYP, with 6-311G basis set. The hydration structures are obtained from structure optimization and the optimum numbers of water molecules in the innermost hydration shell for the alkali metal ions are found. Some useful information about the ion channel selectivity is presented.

  1. A recombinant triblock protein polymer with dispersant and binding properties for digital printing.

    Science.gov (United States)

    Qi, Min; O'Brien, John P; Yang, Jianjun

    2008-01-01

    A structured triblock protein was designed to explore the potential of engineered peptides to function as high-performance ink dispersants and binders. The protein consists of three functional elements, including a pigment binding domain, a hydrophilic linker, and a printing surface binding domain. To construct such a chimeric protein, a carbon black binding peptide, FHENWPS, and a cellulose binding peptide, THKTSTQRLLAA, were identified from phage display libraries through biopanning, based on their strong and specific binding affinities to carbon black and cellulose. They were used as carbon black and cellulose binding domains, respectively, in a recombinant triblock protein. A linker sequence, PTPTPTPTPTPTPTPTPTPTPTP, was adapted from endoglucanase A of the bacterium Cellulomonas fimi, as a small, rigid, and hydrophilic interdomain linker. When incorporated into the triblock structure between the carbon black and cellulose binding sequences, the linker sufficiently isolates these two elements and allows dual binding activity. The structured triblock protein was shown to disperse carbon black particles and attach it to paper surfaces. Thus, the utility of structured proteins having useful dispersant and binding properties for digital printing inks was demonstrated.

  2. Structure and Property Changes in Self-Assembled Lubricin Layers Induced by Calcium Ion Interactions.

    Science.gov (United States)

    Greene, George W; Thapa, Rajiv; Holt, Stephen A; Wang, Xiaoen; Garvey, Christopher J; Tabor, Rico F

    2017-03-14

    Lubricin (LUB) is a "mucin-like" glycoprotein found in synovial fluids and coating the cartilage surfaces of articular joints, which is now generally accepted as one of the body's primary boundary lubricants and antiadhesive agents. LUB's superior lubrication and antiadhesion are believed to derive from its unique interfacial properties by which LUB molecules adhere to surfaces (and biomolecules, such as hyaluronic acid and collagen) through discrete interactions localized to its two terminal end domains. These regionally specific interactions lead to self-assembly behavior and the formation of a well-ordered "telechelic" polymer brush structure on most substrates. Despite its importance to biological lubrication, detailed knowledge on the LUB's self-assembled brush structure is insufficient and derived mostly from indirect and circumstantial evidence. Neutron reflectometry (NR) was used to directly probe the self-assembled LUB layers, confirming the polymer brush architecture and resolving the degree of hydration and level of surface coverage. While attempting to improve the LUB contrast in the NR measurements, the LUB layers were exposed to a 20 mM solution of CaCl2, which resulted in a significant change in the polymer brush structural parameters consisting of a partial denaturation of the surface-binding end-domain regions, partial dehydration of the internal mucin-domain "loop", and collapse of the outer mucin-domain surface region. A series of atomic force microscopy measurements investigating the LUB layer surface morphology, mechanical properties, and adhesion forces in phosphate-buffered saline and CaCl2 solutions reveal that the structural changes induced by calcium ion interactions also significantly alter key properties, which may have implications to LUB's efficacy as a boundary lubricant and wear protector in the presence of elevated calcium ion concentrations.

  3. NANOMECHANICAL AND CORROSION PROPERTIES OF ZK60 MAGNESIUM ALLOY IMPROVED BY GD ION IMPLANTATION

    OpenAIRE

    XUE WEI TAO; ZHANG ZHONG WANG; XIAO BO ZHANG; ZHI XIN BA; YA MEI WANG

    2014-01-01

    Gadolinium (Gd) ion implantation with doses from 2.5 × 1016 to 1 × 1017 ions/cm2 into ZK60 magnesium alloy was carried out to improve its surface properties. X-ray photoelectron spectroscopy (XPS), nanoindenter, electrochemical workstation and scanning electron microscope (SEM) were applied to analyze the chemical composition, nanomechanical properties and corrosion characteristics of the implanted layer. The results indicate that Gd ion implantation produces a hybrid-structure protective lay...

  4. Substrate binding properties of potato tuber ADP-glucose pyrophosphorylase as determined by isothermal titration calorimetry.

    Science.gov (United States)

    Cakir, Bilal; Tuncel, Aytug; Green, Abigail R; Koper, Kaan; Hwang, Seon-Kap; Okita, Thomas W; Kang, ChulHee

    2015-06-04

    Substrate binding properties of the large (LS) and small (SS) subunits of potato tuber ADP-glucose pyrophosphorylase were investigated by using isothermal titration calorimetry. Our results clearly show that the wild type heterotetramer (S(WT)L(WT)) possesses two distinct types of ATP binding sites, whereas the homotetrameric LS and SS variant forms only exhibited properties of one of the two binding sites. The wild type enzyme also exhibited significantly increased affinity to this substrate compared to the homotetrameric enzyme forms. No stable binding was evident for the second substrate, glucose-1-phosphate, in the presence or absence of ATPγS suggesting that interaction of glucose-1-phosphate is dependent on hydrolysis of ATP and supports the Theorell-Chance bi bi reaction mechanism. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  5. Ca2+ does not affect the binding properties of ITSN1 EH domains

    Directory of Open Access Journals (Sweden)

    Morderer D. Ye.

    2014-11-01

    Full Text Available ITSN1 is an endocytic scaffold protein implicated in synaptic functioning. Ca2+ is known to be important for endo- cytosis in both pre- and post-synaptic terminals. ITSN1 contains two EH (Eps15 homology domains which possess putative Ca2+-binding EF-hand motifs. Aim. To test the effect of Ca2+ on the EH domain binding properties. Methods. His-tag pulldown, Western blotting. Results. Addition of 1.5 mM Ca2+ does not affect the binding of the ITSN1 EH domains to the C-terminal fragment of the endocytic protein Epsin 1. Conclusions. The data obtained indicate that Ca2+ has no effect on the binding properties of the ITSN1 EH domains.

  6. Modification of anti-bacterial surface properties of textile polymers by vacuum arc ion source implantation

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaev, A.G., E-mail: nik@opee.hcei.tsc.ru [High Current Electronics Institute, Siberian Branch of the Russian Academy of Sciences, Tomsk 634055 (Russian Federation); Yushkov, G.Yu.; Oks, E.M. [High Current Electronics Institute, Siberian Branch of the Russian Academy of Sciences, Tomsk 634055 (Russian Federation); Oztarhan, A. [Izmir University, Izmir 35140 (Turkey); Akpek, A.; Hames-Kocabas, E.; Urkac, E.S. [Bioengineering Department, Ege University, Bornova 35100, Izmir (Turkey); Brown, I.G. [Lawrence Berkeley National Laboratory, Berkeley, CA 94708 (United States)

    2014-08-15

    Highlights: • Ion implantation. • Anti-bacterial properties. • Textile polymer. • Vacuum arc ion source. - Abstract: Ion implantation provides an important technology for the modification of material surface properties. The vacuum arc ion source is a unique instrument for the generation of intense beams of metal ions as well as gaseous ions, including mixed metal–gas beams with controllable metal:gas ion ratio. Here we describe our exploratory work on the application of vacuum arc ion source-generated ion beams for ion implantation into polymer textile materials for modification of their biological cell compatibility surface properties. We have investigated two specific aspects of cell compatibility: (i) enhancement of the antibacterial characteristics (we chose to use Staphylococcus aureus bacteria) of ion implanted polymer textile fabric, and (ii) the “inverse” concern of enhancement of neural cell growth rate (we chose Rat B-35 neuroblastoma cells) on ion implanted polymer textile. The results of both investigations were positive, with implantation-generated antibacterial efficiency factor up to about 90%, fully comparable to alternative conventional (non-implantation) approaches and with some potentially important advantages over the conventional approach; and with enhancement of neural cell growth rate of up to a factor of 3.5 when grown on suitably implanted polymer textile material.

  7. Morphology Control and Optical Absorption Properties of Ag Nanoparticles by Ion Implantation

    Institute of Scientific and Technical Information of China (English)

    G.X. Cai; F. Ren; X.H. Xiao; L.X. Fan; X.D. Zhou; C.Z. Jiang

    2009-01-01

    Ion implantation is a powerful method for fabricating nanoparticles in dielectric. For the actual application of nanoparticle composites, a careful control of nanoparticles has to be achieved. In this letter, the size, distribution and morphology of Ag nanoparticles are controlled by controlling the ion current density, ion implantation sequence and ion irradiation dose. Single layer Ag nanoparticles are formed by Ag~+ ion implantation at current density of 2.5 μA/cm~2. By Ag and Cu ions sequential implantation, the size of single layer Ag nanoparticles increases. While, by Cu and Ag ions sequential implantation, uniform Ag nanoparticles with wide distribution are formed. The morphology of Ag nanoparticles changes to hollow and sandwiched nanoparticles by Cu~+ ion irradiation to doses of 3×10~(16) and 5×10~(16) ions/cm~2. The optical absorption properties of Ag nanoparticles are also tailored by these ways.

  8. Trends for isolated amino acids and dipeptides: Conformation, divalent ion binding, and remarkable similarity of binding to calcium and lead

    CERN Document Server

    Ropo, Matti; Baldauf, Carsten

    2016-01-01

    We derive structural and binding energy trends for twenty amino acids, their dipeptides, and their interactions with the divalent cations Ca$^{2+}$, Ba$^{2+}$, Sr$^{2+}$, Cd$^{2+}$, Pb$^{2+}$, and Hg$^{2+}$. The underlying data set consists of 45,892 first-principles predicted conformers with relative energies up to about 4 eV (about 400kJ/mol). We show that only very few distinct backbone structures of isolated amino acids and their dipeptides emerge as lowest-energy conformers. The isolated amino acids predominantly adopt structures that involve an acidic proton shared between the carboxy and amino function. Dipeptides adopt one of two intramolecular-hydrogen bonded conformations C$_5$ or equatorial C$_7$. Upon complexation with a divalent cation, the accessible conformational space shrinks and intramolecular hydrogen bonding is prevented due to strong electrostatic interaction of backbone and side chain functional groups with cations. Clear correlations emerge from the binding energies of the six divalent ...

  9. Structure and Metal Binding Properties of ZnuA, a Periplasmic Zinc Transporter from Escherichia coli

    Energy Technology Data Exchange (ETDEWEB)

    Yatsunyk,L.; Easton, J.; Kim, L.; Sugarbaker, S.; Bennett, B.; Breece, R.; Vorontsov, I.; Tierney, D.; Crowder, M.; Rosenzweig, A.

    2008-01-01

    ZnuA is the periplasmic Zn(2+)-binding protein associated with the high-affinity ATP-binding cassette ZnuABC transporter from Escherichia coli. Although several structures of ZnuA and its homologs have been determined, details regarding metal ion stoichiometry, affinity, and specificity as well as the mechanism of metal uptake and transfer remain unclear. The crystal structures of E. coli ZnuA (Eco-ZnuA) in the apo, Zn(2+)-bound, and Co(2+)-bound forms have been determined. ZnZnuA binds at least two metal ions. The first, observed previously in other structures, is coordinated tetrahedrally by Glu59, His60, His143, and His207. Replacement of Zn(2+) with Co(2+) results in almost identical coordination geometry at this site. The second metal binding site involves His224 and several yet to be identified residues from the His-rich loop that is unique to Zn(2+) periplasmic metal binding receptors. Electron paramagnetic resonance and X-ray absorption spectroscopic data on CoZnuA provide additional insight into possible residues involved in this second site. The second site is also detected by metal analysis and circular dichroism (CD) titrations. Eco-ZnuA binds Zn(2+) (estimated K (d) < 20 nM), Co(2+), Ni(2+), Cu(2+), Cu(+), and Cd(2+), but not Mn(2+). Finally, conformational changes upon metal binding observed in the crystal structures together with fluorescence and CD data indicate that only Zn(2+) substantially stabilizes ZnuA and might facilitate recognition of ZnuB and subsequent metal transfer.

  10. Binding of kinetically inert metal ions to RNA: the case of platinum(II).

    Science.gov (United States)

    Chapman, Erich G; Hostetter, Alethia A; Osborn, Maire F; Miller, Amanda L; DeRose, Victoria J

    2011-01-01

    In this chapter several aspects of Pt(II) are highlighted that focus on the properties of Pt(II)-RNA adducts and the possibility that they influence RNA-based processes in cells. Cellular distribution of Pt(II) complexes results in significant platination of RNA, and localization studies find Pt(II) in the nucleus, nucleolus, and a distribution of other sites in cells. Treatment with Pt(II) compounds disrupts RNA-based processes including enzymatic processing, splicing, and translation, and this disruption may be indicative of structural changes to RNA or RNA-protein complexes. Several RNA-Pt(II) adducts have been characterized in vitro by biochemical and other methods. Evidence for Pt(II) binding in non-helical regions and for Pt(II) cross-linking of internal loops has been found. Although platinated sites have been identified, there currently exists very little in the way of detailed structural characterization of RNA-Pt(II) adducts. Some insight into the details of Pt(II) coordination to RNA, especially RNA helices, can be gained from DNA model systems. Many RNA structures, however, contain complex tertiary folds and common, purine-rich structural elements that present suitable Pt(II) nucleophiles in unique arrangements which may hold the potential for novel types of platinum-RNA adducts. Future research aimed at structural characterization of platinum-RNA adducts may provide further insights into platinum-nucleic acid binding motifs, and perhaps provide a rationale for the observed inhibition by Pt(II) complexes of splicing, translation, and enzymatic processing.

  11. Different antagonist binding properties of rat pancreatic and cardiac muscarinic receptors

    Energy Technology Data Exchange (ETDEWEB)

    Waelbroeck, M.; Camus, J.; Winand, J.; Christophe, J.

    1987-11-09

    The antagonist binding properties of rat pancreatic and cardiac muscarinic receptors were compared. In both tissues pirenzepine (PZ) had a low affinity for muscarinic receptors labelled by (/sup 3/H)N-methylscopolamine ((/sup 3/)NMS) (K/sub D/ values of 140 and 280nM, respectively, in pancreatic and cardiac homogenates). The binding properties of pancreatic and cardiac receptors were, however, markedly different. This was indicated by different affinities for dicyclomine, (11-(/(2-((diethylamino)-methyl)-1-piperidinyl/acetyl)-5, 11-dihydro-6H-pyrido(2,3-b)(1,4) benzodiazepin-6-on)(AFDX-116), 4-diphenylacetoxy-N-methyl-piperidine methobromide (4-DAMP) and hexahydrosiladifenidol (HHSiD). Pancreatic and cardiac muscarinic receptros also showed different (/sup 3/H)NMS association and dissociation rates. These results support the concept of M2 receptor subtypes have different binding kinetic properties. 20 references, 3 figures, 1 table.

  12. Binding and Adsorption Energies of Heavy Metal Ions with Hapli-Udic Argosol and Ferri-Udic Argosol Particles

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Gibbs free binding energy and adsorption energy between cations and charged soil particles were used to evaluate the interactions between ions and soil particles. The distribution of Gibbs free adsorption energies could not be determined experimentally before the development of Wien effect measurements in dilute soil suspensions. In the current study, energy relationships between heavy metal ions and particles of Hapli-Udic Argosol (Alfisol) and Ferri-Udic Argosol were inferred from Wien effect measurements in dilute suspensions of homoionic soil particles (< 2 μm) of the two soils, which were saturated with ions of five heavy metals, in deionized water. The mean Gibbs free binding energies of the heavy metal ions with Hapli-Udic Argosol and Ferri-Udic Argosol particles diminished in the order of Pb2+>Cd2+>Cu2+> Zn2+ >Cr3+, where the range of binding energies for Hapli-Udic Argosol (7.25-9.32 kJ mol-1) was similar to that for Ferri-Udic Argosol (7.43-9.35 kJ mol-1). The electrical field-dependent mean Gibbs free adsorption energies of these heavy metal ions for Hapli-Udic Argosol and for Ferri-Udic Argosol descended in the order: Cu2+≥ Cd2+≥ Pb2+ > Zn2+>Cr3+,and Cd2+ >Cu2+>Pb2+>Zn2+>Cr3+, respectively. The mean Gibbs free adsorption energies of Cu2+, Zn2+, Cd2+,Pb2+, and Cr3+ at a field strength of 200 kV cm-1, for example, were in the range of 0.8-3.2 kJ mol-1 for the two soils.

  13. Binding selectivity of vitamin K3 based chemosensors towards nickel(II) and copper(II) metal ions

    Science.gov (United States)

    Patil, Amit; Lande, Dipali N.; Nalkar, Archana; Gejji, Shridhar P.; Chakrovorty, Debamitra; Gonnade, Rajesh; Moniz, Tânia; Rangel, Maria; Pereira, Eulália; Salunke-Gawali, Sunita

    2017-09-01

    The vitamin K3 derivatives 2-methyl-3-[(pyridin-2-ylmethyl)-amino]-1,4-naphthoquinone (M-1), 2-methyl-3-[(pyridin-2-ylethyl)-amino]-1,4-naphthoquinone (M-2), 2-methyl-3-((2-(thiophen-2-yl)methyl)amino)naphthalene-1,4-dione (M-3) and 2-methyl-3-((2-(thiophen-2-yl)ethyl)amino)naphthalene-1,4-dione (M-4) have been synthesized, characterized and studied for their chemosensor abilities towards transition metal ions. Crystal structures of M-1 to M-4 revealed a variety of Nsbnd H⋯O, Csbnd H⋯O, Csbnd H⋯π and π⋯π interactions. Minor variations in such interactions by chemical stimuli such as metal ions, results in change in color that can be visualized by naked eyes. It has been shown that electronic structure and 1H NMR, vibrational as well as electronic spectra from the density functional theory agree well with the experiments. The metal ion binding in ethanol, ethanol-water and in mild base triethylamine brings forth recognizing ability of M-1 toward Ni2+ whereas M-2 exhibits large sensing ability for Cu2+ ion. Interestingly M-1 display varying metal ion binding specificity in different solvents with the association constant in ethanol being 11,786 M-1 for Ni2+ compared to 9462 M-1 for the Cu2+. A reversal in preferential binding of M-2 with the respective association constants being 4190 M-1 and 6370 M-1 is discernible.

  14. Synthesis, Characterization and Ion Exchange Properties of a New Composite of Inorganic Ion Exchanger: Polyacrylonitrile Cerium(IV) Molybdophosphate%Synthesis, Characterization and Ion Exchange Properties of a New Composite of Inorganic Ion Exchanger: Polyacrylonitrile Cerium(IV) Molybdophosphate

    Institute of Scientific and Technical Information of China (English)

    Ahmadi, Seyed Javad; Yavari, Ramin; Ashtari, Parviz'; Gholipour, Vanik; Kamel, Leila; Rakhshandehru, Farokh

    2012-01-01

    In this work, the synthesis of the composite of cerium(IV) molybdophosphate (CMP) and polyacrylonitrile (PAN) was reported (CMP-PAN). The material has been characterized by elemental and spectral (FT-IR), X-ray and thermal (TGA) analysis. Also the size analysis of the composite was done by scanning electron microscopy (SEM). Its chemical stability in acidic, basic and saline solutions and radiation stability up to 100 kGy total expose dose were assessed. Whereas the synthesized composite has ion exchange properties, its ion exchange capacity and behavior toward several metal ions were also investigated. Further, the distribution coefficients of the metal ions were calculated. Finally, the ability of the synthesized CMP-PAN composite for the decontamination of low level liquid waste (LLLW) was investigated.

  15. SERCA mutant E309Q binds two Ca ions but adopts a catalytically incompetent conformation

    DEFF Research Database (Denmark)

    Clausen, Johannes D.; Bublitz, Maike; Arnou, Bertrand;

    2013-01-01

    The sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) couples ATP hydrolysis to transport of Ca2+. This directed energy transfer requires cross-talk between the two Ca2+ sites and the phosphorylation site over 50 Å distance. We have addressed the mechano-structural basis for this intramolecular...... signal by analysing the structure and the functional properties of SERCA mutant E309Q. Glu309 contributes to Ca2+ coordination at site II, and a consensus has been that E309Q only binds Ca2+ at site I. The crystal structure of E309Q in the presence of Ca2+ and an ATP analogue, however, reveals two...... occupied Ca2+ sites of a non-catalytic Ca2E1 state. Ca2+ is bound with micromolar affinity by both Ca2+ sites in E309Q, but without cooperativity. The Ca2+-bound mutant does phosphorylate from ATP, but at a very low maximal rate. Phosphorylation depends on the correct positioning of the A-domain, requiring...

  16. Polyhydroxyfullerene binds cadmium ions and alleviates metal-induced oxidative stress in Saccharomyces cerevisiae.

    Science.gov (United States)

    Pradhan, Arunava; Pinheiro, José Paulo; Seena, Sahadevan; Pascoal, Cláudia; Cássio, Fernanda

    2014-09-01

    The water-soluble polyhydroxyfullerene (PHF) is a functionalized carbon nanomaterial with several industrial and commercial applications. There have been controversial reports on the toxicity and/or antioxidant properties of fullerenes and their derivatives. Conversely, metals have been recognized as toxic mainly due to their ability to induce oxidative stress in living organisms. We investigated the interactive effects of PHF and cadmium ions (Cd) on the model yeast Saccharomyces cerevisiae by exposing cells to Cd (≤5 mg liter(-1)) in the absence or presence of PHF (≤500 mg liter(-1)) at different pHs (5.8 to 6.8). In the absence of Cd, PHF stimulated yeast growth up to 10.4%. Cd inhibited growth up to 79.7%, induced intracellular accumulation of reactive oxygen species (ROS), and promoted plasma membrane disruption in a dose- and pH-dependent manner. The negative effects of Cd on growth were attenuated by the presence of PHF, and maximum growth recovery (53.8%) was obtained at the highest PHF concentration and pH. The coexposure to Cd and PHF decreased ROS accumulation up to 36.7% and membrane disruption up to 30.7% in a dose- and pH-dependent manner. Two mechanisms helped to explain the role of PHF in alleviating Cd toxicity to yeasts: PHF decreased Cd-induced oxidative stress and bound significant amounts of Cd in the extracellular medium, reducing its bioavailability to the cells.

  17. Ionic force field optimization based on single-ion and ion-pair solvation properties: going beyond standard mixing rules.

    Science.gov (United States)

    Fyta, Maria; Netz, Roland R

    2012-03-28

    Using molecular dynamics (MD) simulations in conjunction with the SPC/E water model, we optimize ionic force-field parameters for seven different halide and alkali ions, considering a total of eight ion-pairs. Our strategy is based on simultaneous optimizing single-ion and ion-pair properties, i.e., we first fix ion-water parameters based on single-ion solvation free energies, and in a second step determine the cation-anion interaction parameters (traditionally given by mixing or combination rules) based on the Kirkwood-Buff theory without modification of the ion-water interaction parameters. In doing so, we have introduced scaling factors for the cation-anion Lennard-Jones (LJ) interaction that quantify deviations from the standard mixing rules. For the rather size-symmetric salt solutions involving bromide and chloride ions, the standard mixing rules work fine. On the other hand, for the iodide and fluoride solutions, corresponding to the largest and smallest anion considered in this work, a rescaling of the mixing rules was necessary. For iodide, the experimental activities suggest more tightly bound ion pairing than given by the standard mixing rules, which is achieved in simulations by reducing the scaling factor of the cation-anion LJ energy. For fluoride, the situation is different and the simulations show too large attraction between fluoride and cations when compared with experimental data. For NaF, the situation can be rectified by increasing the cation-anion LJ energy. For KF, it proves necessary to increase the effective cation-anion Lennard-Jones diameter. The optimization strategy outlined in this work can be easily adapted to different kinds of ions.

  18. Effect of ion irradiation on the surface, structural and mechanical properties of brass

    Science.gov (United States)

    Ahmad, Shahbaz; Bashir, Shazia; Ali, Nisar; Umm-i-Kalsoom; Yousaf, Daniel; Faizan-ul-Haq; Naeem, Athar; Ahmad, Riaz; Khlaeeq-ur-Rahman, M.

    2014-04-01

    Modifications to the surface, structural and mechanical properties of brass after ion irradiation have been investigated. Brass targets were bombarded by carbon ions of 2 MeV energy from a Pelletron linear accelerator for various fluences ranging from 56 × 1012 to 26 × 1013 ions/cm2. A scanning electron microscope and X-ray diffractometer were utilized to analyze the surface morphology and crystallographic structure respectively. To explore the mechanical properties e.g., yield stress, ultimate tensile strength and microhardness of irradiated brass, an universal tensile testing machine and Vickers microhardness tester were used. Scanning electron microscopy results revealed an irregular and randomly distributed sputter morphology for a lower ion fluence. With increasing ion fluence, the incoherently shaped structures were transformed into dendritic structures. Nano/micro sized craters and voids, along with the appearance of pits, were observed at the maximum ion fluence. From X-ray diffraction results, no new phases were observed to be formed in the brass upon irradiation. However, a change in the peak intensity and higher and lower angle shifting were observed, which represents the generation of ion-induced defects and stresses. Analyses confirmed modifications in the mechanical properties of irradiated brass. The yield stress, ultimate tensile strength and hardness initially decreased and then increased with increasing ion fluence. The changes in the mechanical properties of irradiated brass are well correlated with surface and crystallographic modifications and are attributed to the generation, augmentation, recombination and annihilation of the ion-induced defects.

  19. The effect of metal ion implantation on the surface mechanical properties of Mylar (PET)

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, W.; Sood, D.K. [Royal Melbourne Inst. of Tech., VIC (Australia); Yao, X.; Brown, I.G. [California Univ., Berkeley, CA (United States). Lawrence Berkeley Lab.

    1993-12-31

    Ion implantation of polymers leads to the formation of new carbonaceous materials, the revolution during implantation of various species consists of (1) ion beam induced damage: chain scission, crosslinking, molecular emission of volatile elements and compounds, stoichiometric change in the surface layer of pristine polymers; and (2) chemical effect between ion and target materials: microalloying and precipitation. Literature regarding ion implanted polymers shows that the reorganisation of the carbon network after implantation can dramatically modify several properties of pristine polymers solubility, molecular weight, and electrical, optical and mechanical properties. However, ion implantation of polymers is actually a very complex interaction which depends on not only ion species, implantation condition, but also polymer type and specific structure. In this paper the effect of Ag or Ti ions implantation on surface mechanical properties of PET (polyethylenne terephthalate) polymer is reported. There was a clear deterioration in wear resistance after implantation of both Ag and Ti ions. It is suggested that the increment of wear after implantation may result from not only ion damage but also chemical effect between ion and target material. 3 refs., 1 tab., 2 figs.

  20. Binding properties of HABA-type azo derivatives to avidin and avidin-related protein 4.

    Science.gov (United States)

    Repo, Susanna; Paldanius, Tiina A; Hytönen, Vesa P; Nyholm, Thomas K M; Halling, Katrin K; Huuskonen, Juhani; Pentikäinen, Olli T; Rissanen, Kari; Slotte, J Peter; Airenne, Tomi T; Salminen, Tiina A; Kulomaa, Markku S; Johnson, Mark S

    2006-10-01

    The chicken genome encodes several biotin-binding proteins, including avidin and avidin-related protein 4 (AVR4). In addition to D-biotin, avidin binds an azo dye compound, 4-hydroxyazobenzene-2-carboxylic acid (HABA), but the HABA-binding properties of AVR4 are not yet known. Differential scanning calorimetry, UV/visible spectroscopy, and molecular modeling were used to analyze the binding of 15 azo molecules to avidin and AVR4. Significant differences are seen in azo compound preferences for the two proteins, emphasizing the importance of the loop between strands beta3 and beta4 for azo ligand recognition; information on these loops is provided by the high-resolution (1.5 A) X-ray structure for avidin reported here. These results may be valuable in designing improved tools for avidin-based life science and nanobiotechnology applications.

  1. Identification of fluorescent compounds with non-specific binding property via high throughput live cell microscopy.

    Directory of Open Access Journals (Sweden)

    Sangeeta Nath

    Full Text Available INTRODUCTION: Compounds exhibiting low non-specific intracellular binding or non-stickiness are concomitant with rapid clearing and in high demand for live-cell imaging assays because they allow for intracellular receptor localization with a high signal/noise ratio. The non-stickiness property is particularly important for imaging intracellular receptors due to the equilibria involved. METHOD: Three mammalian cell lines with diverse genetic backgrounds were used to screen a combinatorial fluorescence library via high throughput live cell microscopy for potential ligands with high in- and out-flux properties. The binding properties of ligands identified from the first screen were subsequently validated on plant root hair. A correlative analysis was then performed between each ligand and its corresponding physiochemical and structural properties. RESULTS: The non-stickiness property of each ligand was quantified as a function of the temporal uptake and retention on a cell-by-cell basis. Our data shows that (i mammalian systems can serve as a pre-screening tool for complex plant species that are not amenable to high-throughput imaging; (ii retention and spatial localization of chemical compounds vary within and between each cell line; and (iii the structural similarities of compounds can infer their non-specific binding properties. CONCLUSION: We have validated a protocol for identifying chemical compounds with non-specific binding properties that is testable across diverse species. Further analysis reveals an overlap between the non-stickiness property and the structural similarity of compounds. The net result is a more robust screening assay for identifying desirable ligands that can be used to monitor intracellular localization. Several new applications of the screening protocol and results are also presented.

  2. Characterisation of the Rab binding properties of Rab coupling protein (RCP) by site-directed mutagenesis.

    Science.gov (United States)

    Lindsay, Andrew J; McCaffrey, Mary W

    2004-07-30

    Rab coupling protein (RCP) is a member of the Rab11-family of interacting proteins (Rab11-FIPs). Family members are characterised by their ability to interact with Rab11. This property is mediated by a conserved Rab binding domain (RBD) located at their carboxy-termini. Several Rab11-FIPs can also interact with other small GTPases. RCP interacts with Rab4 in addition to Rab11. To dissect out the individual properties of the Rab4 and Rab11 interactions with RCP, conserved amino acids within the RBD of RCP were mutated by site-directed mutagenesis. The effect of these mutations on Rab4 and Rab11 binding, and the intracellular localisation of RCP, was examined. Our results indicate that Rab11, rather than Rab4, mediates the intracellular localisation of RCP, and that the class I Rab11-FIPs compete for binding to Rab11.

  3. Molecular Properties of Globin Channels and Pores: Role of Cholesterol in Ligand Binding and Movement

    Directory of Open Access Journals (Sweden)

    Gene A Morrill

    2016-09-01

    Full Text Available ABSTRACT: Globins contain one or more cavities that control or affect such functions as ligand movement and ligand binding. Here we report that the extended globin family [cytoglobin (Cygb; neuroglobin (Ngb; myoglobin (Mb; hemoglobin (Hb subunits Hba(α and Hbb(β] contain either a transmembrane (TM helix or pore-lining region as well as internal cavities. Protein motif/domain analyses indicate that Ngb and Hbb each contain 5 cholesterol-binding (CRAC/CARC domains and 1 caveolin binding motif, whereas the Cygb dimer has 6 cholesterol-binding domains but lacks caveolin-binding motifs. Mb and Hba each exhibit 2 cholesterol-binding domains and also lack caveolin-binding motifs. The Hb αβ-tetramer contains 14 cholesterol-binding domains. Computer algorithms indicate that Cygb and Ngb cavities display multiple partitions and C-terminal pore-lining regions, whereas Mb has three major cavities plus a C-terminal pore-lining region. The Hb tetramer exhibits a large internal cavity but the subunits differ in that they contain a C-terminal TM helix (Hba and pore-lining region (Hbb. The cavities include 43 of 190 Cygb residues, 38 of 151 of Ngb residues, 55 of 154 Mb residues and 137 of 688 residues in the Hb tetramer. Each cavity complex includes 6 to 8 residues of the TM helix or pore-lining region and CRAC/CARC domains exist within all cavities. Erythrocyte Hb αβ-tetramers are largely cytosolic but also bind to a membrane anion exchange protein, band 3, which contains a large internal cavity and 12 TM helices (5 being pore-lining regions. The Hba TM helix may be the erythrocyte membrane band 3 attachment site. Band 3 contributes 4 caveolin binding motifs and 10 CRAC/CARC domains. Cholesterol binding may create lipid-disordered phases that alter globin cavities and facilitate ligand movement, permitting ion channel formation and conformational changes that orchestrate anion and ligand (O2, CO2, NO movement within the large internal cavities and

  4. Molecular Properties of Globin Channels and Pores: Role of Cholesterol in Ligand Binding and Movement.

    Science.gov (United States)

    Morrill, Gene A; Kostellow, Adele B

    2016-01-01

    Globins contain one or more cavities that control or affect such functions as ligand movement and ligand binding. Here we report that the extended globin family [cytoglobin (Cygb); neuroglobin (Ngb); myoglobin (Mb); hemoglobin (Hb) subunits Hba(α); and Hbb(β)] contain either a transmembrane (TM) helix or pore-lining region as well as internal cavities. Protein motif/domain analyses indicate that Ngb and Hbb each contain 5 cholesterol- binding (CRAC/CARC) domains and 1 caveolin binding motif, whereas the Cygb dimer has 6 cholesterol-binding domains but lacks caveolin-binding motifs. Mb and Hba each exhibit 2 cholesterol-binding domains and also lack caveolin-binding motifs. The Hb αβ-tetramer contains 14 cholesterol-binding domains. Computer algorithms indicate that Cygb and Ngb cavities display multiple partitions and C-terminal pore-lining regions, whereas Mb has three major cavities plus a C-terminal pore-lining region. The Hb tetramer exhibits a large internal cavity but the subunits differ in that they contain a C-terminal TM helix (Hba) and pore-lining region (Hbb). The cavities include 43 of 190 Cygb residues, 38 of 151 of Ngb residues, 55 of 154 Mb residues, and 137 of 688 residues in the Hb tetramer. Each cavity complex includes 6 to 8 residues of the TM helix or pore-lining region and CRAC/CARC domains exist within all cavities. Erythrocyte Hb αβ-tetramers are largely cytosolic but also bind to a membrane anion exchange protein, "band 3," which contains a large internal cavity and 12 TM helices (5 being pore-lining regions). The Hba TM helix may be the erythrocyte membrane "band 3" attachment site. "Band 3" contributes 4 caveolin binding motifs and 10 CRAC/CARC domains. Cholesterol binding may create lipid-disordered phases that alter globin cavities and facilitate ligand movement, permitting ion channel formation and conformational changes that orchestrate anion and ligand (O2, CO2, NO) movement within the large internal cavities and channels of the

  5. Properties of Folate Binding Protein Purified from Cow’s Milk

    Directory of Open Access Journals (Sweden)

    SUBANDRATE

    2012-09-01

    Full Text Available Folic acid played an important role in the metabolism of the body. To measure the serum folic acid levels could use the folate binding protein (FBP from cow’s milk with a technique analogous to ELISA. The aims of this study were to identify characteristics of FBP from cow’s milk and binding capacity of FBP to folic acid and to purify FBP from other whey protein passed through DEAE-cellulose chromatography column. Each of DEAE-cellulose peaks was passed in affinity chromatography column. FBP was released from affinity column with sodium acetate buffer pH 3.5. The purity of obtained FBP was demonstrated by a single spot in SDS-PAGE analysis and the estimated molecular weight of FBP was around 31 kDa. Our study indicated that 1 mol FBP bound 1 mol folic acid. Alkylation with iodoacetic acid decreased the binding capacity of FBP which suggested the presence of a–SH or imidazol group in its active site. The importance of disulfide bridge was proven by decreasing of folate binding capacity of FBP after -mercaptoethanol treatment. In contrary, the folate binding didn need Ca2+ ion, as indicated by EDTA test which gave the same result as control.

  6. Structure and binding properties of a cameloid nanobody raised against KDM5B

    DEFF Research Database (Denmark)

    Wiuf, Anders; Kristensen, Line Hyltoft; Kristensen, Ole

    2015-01-01

    The histone demethylase KDM5B is considered to be a promising target for anticancer therapy. Single-chain antibodies from llama (nanobodies) have been raised to aid in crystallization and structure determination of this enzyme. The antigen-binding properties of 15 of these nanobodies have been...

  7. The copper binding properties of metformin - QCM-D, XPS and nanobead agglomeration

    DEFF Research Database (Denmark)

    Quan, Xueling; Uddin, Rokon; Heiskanen, Arto

    2015-01-01

    Study of the copper binding properties of metformin is important for revealing its mechanism of action as a first-line type-2 diabetes drug. A quantitative investigation of interactions between metformin and l-cysteine-copper complexes was performed. The results suggest that metformin could inter...

  8. The copper binding properties of metformin--QCM-D, XPS and nanobead agglomeration.

    Science.gov (United States)

    Quan, Xueling; Uddin, Rokon; Heiskanen, Arto; Parmvi, Mattias; Nilson, Katharina; Donolato, Marco; Hansen, Mikkel F; Rena, Graham; Boisen, Anja

    2015-12-18

    Study of the copper binding properties of metformin is important for revealing its mechanism of action as a first-line type-2 diabetes drug. A quantitative investigation of interactions between metformin and L-cysteine-copper complexes was performed. The results suggest that metformin could interact with biological copper, which plays a key role in mitochondrial function.

  9. The copper binding properties of metformin - QCM-D, XPS and nanobead agglomeration

    DEFF Research Database (Denmark)

    Quan, Xueling; Uddin, Rokon; Heiskanen, Arto;

    2015-01-01

    Study of the copper binding properties of metformin is important for revealing its mechanism of action as a first-line type-2 diabetes drug. A quantitative investigation of interactions between metformin and l-cysteine-copper complexes was performed. The results suggest that metformin could...

  10. Properties of planetward ion flows in Venus' magnetotail

    Science.gov (United States)

    Kollmann, P.; Brandt, P. C.; Collinson, G.; Rong, Z. J.; Futaana, Y.; Zhang, T. L.

    2016-08-01

    Venus is gradually losing some of its atmosphere in the form of ions through its induced magnetotail. Some of these ions have been reported previously to flow back to the planet. Proposed drivers are magnetic reconnection and deflection of pickup ions in the magnetic field. We analyze protons and oxygen ions with eV to keV energies acquired by the ASPERA-4/IMA instrument throughout the entire Venus Express mission. We find that venusward flowing ions are important in the sense that their density and deposition rate into the atmosphere is of the same order of magnitude as the density and escape rate of downtail flowing ions. Our analysis shows that during strong EUV irradiance, which occurs during solar maximum, the flux of venusward flowing protons is weaker and of oxygen ions is stronger than during weak irradiance. Since such a behavior was observed when tracing oxygen ions through a MHD model, the ultimate driver of the venusward flowing ions may simply be the magnetic field configuration around Venus. Although the pure downtail oxygen flux stays mostly unchanged for all observed EUV conditions, the increase in venusward oxygen flux for high irradiance results in a lower net atmospheric escape rate. Venusward bulk flows are mostly found in locations where the magnetic field is weak relative to the interplanetary conditions. Although a weak field is generally an indicator of proximity to the magnetotail current sheet, these flows do not cluster around current sheet crossings, as one may expect if they would be driven by magnetic reconnection.

  11. Benchmarking a computational design method for the incorporation of metal ion-binding sites at symmetric protein interfaces.

    Science.gov (United States)

    Hansen, William A; Khare, Sagar D

    2017-08-01

    The design of novel metal-ion binding sites along symmetric axes in protein oligomers could provide new avenues for metalloenzyme design, construction of protein-based nanomaterials and novel ion transport systems. Here, we describe a computational design method, symmetric protein recursive ion-cofactor sampling (SyPRIS), for locating constellations of backbone positions within oligomeric protein structures that are capable of supporting desired symmetrically coordinated metal ion(s) chelated by sidechains (chelant model). Using SyPRIS on a curated benchmark set of protein structures with symmetric metal binding sites, we found high recovery of native metal coordinating rotamers: in 65 of the 67 (97.0%) cases, native rotamers featured in the best scoring model while in the remaining cases native rotamers were found within the top three scoring models. In a second test, chelant models were crossmatched against protein structures with identical cyclic symmetry. In addition to recovering all native placements, 10.4% (8939/86013) of the non-native placements, had acceptable geometric compatibility scores. Discrimination between native and non-native metal site placements was further enhanced upon constrained energy minimization using the Rosetta energy function. Upon sequence design of the surrounding first-shell residues, we found further stabilization of native placements and a small but significant (1.7%) number of non-native placement-based sites with favorable Rosetta energies, indicating their designability in existing protein interfaces. The generality of the SyPRIS approach allows design of novel symmetric metal sites including with non-natural amino acid sidechains, and should enable the predictive incorporation of a variety of metal-containing cofactors at symmetric protein interfaces. © 2017 The Protein Society.

  12. Direct Fluorescent Detection of Blood Potassium by Ion-Selective Formation of Intermolecular G-Quadruplex and Ligand Binding.

    Science.gov (United States)

    Yang, Le; Qing, Zhihe; Liu, Changhui; Tang, Qiao; Li, Jishan; Yang, Sheng; Zheng, Jing; Yang, Ronghua; Tan, Weihong

    2016-09-20

    G-quadruplex analogues have been widely used as molecular tools for detection of potassium ion (K(+)). However, interference from a higher concentration of sodium ion (Na(+)), enzymatic degradation of the oligonucleotide, and background absorption and fluorescence of blood samples have all limited the use of G-quadruplex for direct detection of K(+) in blood samples. Here, we reported, for the first time, an intermolecular G-quadruplex-based assay capable of direct fluorescent detection of blood K(+). Increased stringency of intermolecular G-quadruplex formation based on our screened G-rich oligonucleotide (5'-TGAGGGA GGGG-3') provided the necessary selectivity for K(+) against Na(+) at physiological ion level. To increase long-term stability of oligonucleotide in blood, the screened oligonucleotide was modified with an inverted thymine nucleotide whose 3'-terminus was connected to the 3'-terminus of the upstream nucleotide, acting as a blocking group to greatly improve antinuclease stability. Lastly, to avoid interference from background absorption and autofluorescence of blood, a G-quadruplex-binding, two-photon-excited ligand, EBMVC-B, was synthesized and chosen as the fluorescence reporter. Thus, based on selective K(+) ion-induced formation of intermolecular G-quadruplex and EBMVC-B binding, this approach could linearly respond to K(+) from 0.5 to 10 mM, which matches quite well with the physiologically relevant concentration of blood K(+). Moreover, the system was highly selective for K(+) against other metal ions, including Na(+), Ca(2+), Mg(2+), Zn(2+) common in blood. The practical application was demonstrated by direct detection of K(+) from real blood samples by two-photon fluorescence technology. To the best of our knowledge, this is the first attempt to exploit molecular G-quadruplex-based fluorescent sensing for direct assay of blood target. As such, we expect that it will promote the design and practical application of similar DNA-based sensors in

  13. Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

    Directory of Open Access Journals (Sweden)

    Harald Schmaderer

    2009-05-01

    Full Text Available Flavin chromophores can mediate redox reactions upon irradiation by blue light. In an attempt to increase their catalytic efficacy, flavin derivatives bearing a guanidinium ion as oxoanion binding site were prepared. Chromophore and substrate binding site are linked by a rigid Kemp’s acid structure. The molecular structure of the new flavins was confirmed by an X-ray structure analysis and their photocatalytic activity was investigated in benzyl ester cleavage, nitroarene reduction and a Diels–Alder reaction. The modified flavins photocatalyze the reactions, but the introduced substrate binding site does not enhance their performance.

  14. Effect of ion irradiation on the surface, structural and mechanical properties of brass

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Shahbaz; Bashir, Shazia, E-mail: shaziabashir@gcu.edu.pk; Ali, Nisar; Umm-i-Kalsoom,; Yousaf, Daniel; Faizan-ul-Haq,; Naeem, Athar; Ahmad, Riaz; Khlaeeq-ur-Rahman, M.

    2014-04-01

    Highlights: • Brass targets were exposed to carbon ions of energy 2 MeV. • The effect of ion dose has been investigated. • The surface morphology is investigated by SEM analysis. • XRD analysis is performed to reveal structural modification. • Mechanical properties were investigated by tensile testing and microhardness testing. - Abstract: Modifications to the surface, structural and mechanical properties of brass after ion irradiation have been investigated. Brass targets were bombarded by carbon ions of 2 MeV energy from a Pelletron linear accelerator for various fluences ranging from 56 × 10{sup 12} to 26 × 10{sup 13} ions/cm{sup 2}. A scanning electron microscope and X-ray diffractometer were utilized to analyze the surface morphology and crystallographic structure respectively. To explore the mechanical properties e.g., yield stress, ultimate tensile strength and microhardness of irradiated brass, an universal tensile testing machine and Vickers microhardness tester were used. Scanning electron microscopy results revealed an irregular and randomly distributed sputter morphology for a lower ion fluence. With increasing ion fluence, the incoherently shaped structures were transformed into dendritic structures. Nano/micro sized craters and voids, along with the appearance of pits, were observed at the maximum ion fluence. From X-ray diffraction results, no new phases were observed to be formed in the brass upon irradiation. However, a change in the peak intensity and higher and lower angle shifting were observed, which represents the generation of ion-induced defects and stresses. Analyses confirmed modifications in the mechanical properties of irradiated brass. The yield stress, ultimate tensile strength and hardness initially decreased and then increased with increasing ion fluence. The changes in the mechanical properties of irradiated brass are well correlated with surface and crystallographic modifications and are attributed to the generation

  15. Ion binding to natural organic matter : General considerations and the NICA-Donnan model

    NARCIS (Netherlands)

    Koopal, L.K.; Saito, T.; Pinheiro, J.P.; Riemsdijk, van W.H.

    2005-01-01

    The general principles of cation binding to humic matter and the various aspects of modeling used in general-purpose speciation programs are discussed. The discussion will focus on (1) the discrimination between chemical and electrostatic interactions, (2) the binding site heterogeneity, (3) the mod

  16. Metal Cation Binding to Gas-Phase Pentaalanine: Divalent Ions Restructure the Complex

    NARCIS (Netherlands)

    Dunbar, R. C.; Steill, J. D.; Polfer, N. C.; Oomens, J.

    2013-01-01

    Ion-neutral complexes of pentaalalanine with several singly- and doubly charged metal ions are examined using conformation analysis by infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) computations. The infrared spectroscopy in the 1500-1800 cm(-1) region

  17. Metal Cation Binding to Gas-Phase Pentaalanine: Divalent Ions Restructure the Complex

    NARCIS (Netherlands)

    Dunbar, R.C.; Steill, J.D.; Polfer, N.C.; Oomens, J.

    2013-01-01

    Ion-neutral complexes of pentaalalanine with several singly- and doubly charged metal ions are examined using conformation analysis by infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) computations. The infrared spectroscopy in the 1500-1800 cm(-1) region

  18. A novel mode of ferric ion coordination by the periplasmic ferric ion-binding subunit FbpA of an ABC-type iron transporter from Thermus thermophilus HB8.

    Science.gov (United States)

    Wang, Shipeng; Ogata, Misaki; Horita, Shoichiro; Ohtsuka, Jun; Nagata, Koji; Tanokura, Masaru

    2014-01-01

    Crystal structures of FbpA, the periplasmic ferric ion-binding protein of an iron-uptake ABC transporter, from Thermus thermophilus HB8 (TtFbpA) have been solved in apo and ferric ion-bound forms at 1.8 and 1.7 Å resolution, respectively. The latter crystal structure shows that the bound ferric ion forms a novel six-coordinated complex with three tyrosine side chains, two bicarbonates and a water molecule in the metal-binding site. The results of gel-filtration chromatography and dynamic light scattering show that TtFbpA exists as a monomer in solution regardless of ferric ion binding and that TtFbpA adopts a more compact conformation in the ferric ion-bound state than in the apo state in solution.

  19. Mechanical and structural properties of fluorine-ion-implanted boron suboxide

    CSIR Research Space (South Africa)

    Machaka, R

    2011-09-01

    Full Text Available Results on a systematic study on the effects of ion implantation on the near-surface mechanical and structural properties of boron suboxide (B6 O) prepared by uniaxial hot pressing are reviewed. 150 keV fluorine ions at fluences of up to 5.0 × 1016...

  20. SQUEEZING PROPERTIES OF A TRAPPED ION IN THE STANDING-WAVE LASER

    Institute of Scientific and Technical Information of China (English)

    FANG MAO-FA; LIU XIANG

    2001-01-01

    We investigate the squeezing properties of a trapped ion in a standing-wave laser. Our results show that the squeezing of a trapped ion in the standing-wave laser is dependent on its position in the latter, the detuning parameter and the initial average phonon number.

  1. A machine learning approach for the identification of odorant binding proteins from sequence-derived properties

    Directory of Open Access Journals (Sweden)

    Suganthan PN

    2007-09-01

    Full Text Available Abstract Background Odorant binding proteins (OBPs are believed to shuttle odorants from the environment to the underlying odorant receptors, for which they could potentially serve as odorant presenters. Although several sequence based search methods have been exploited for protein family prediction, less effort has been devoted to the prediction of OBPs from sequence data and this area is more challenging due to poor sequence identity between these proteins. Results In this paper, we propose a new algorithm that uses Regularized Least Squares Classifier (RLSC in conjunction with multiple physicochemical properties of amino acids to predict odorant-binding proteins. The algorithm was applied to the dataset derived from Pfam and GenDiS database and we obtained overall prediction accuracy of 97.7% (94.5% and 98.4% for positive and negative classes respectively. Conclusion Our study suggests that RLSC is potentially useful for predicting the odorant binding proteins from sequence-derived properties irrespective of sequence similarity. Our method predicts 92.8% of 56 odorant binding proteins non-homologous to any protein in the swissprot database and 97.1% of the 414 independent dataset proteins, suggesting the usefulness of RLSC method for facilitating the prediction of odorant binding proteins from sequence information.

  2. Modification of anti-bacterial surface properties of textile polymers by vacuum arc ion source implantation

    Science.gov (United States)

    Nikolaev, A. G.; Yushkov, G. Yu.; Oks, E. M.; Oztarhan, A.; Akpek, A.; Hames-Kocabas, E.; Urkac, E. S.; Brown, I. G.

    2014-08-01

    Ion implantation provides an important technology for the modification of material surface properties. The vacuum arc ion source is a unique instrument for the generation of intense beams of metal ions as well as gaseous ions, including mixed metal-gas beams with controllable metal:gas ion ratio. Here we describe our exploratory work on the application of vacuum arc ion source-generated ion beams for ion implantation into polymer textile materials for modification of their biological cell compatibility surface properties. We have investigated two specific aspects of cell compatibility: (i) enhancement of the antibacterial characteristics (we chose to use Staphylococcus aureus bacteria) of ion implanted polymer textile fabric, and (ii) the "inverse" concern of enhancement of neural cell growth rate (we chose Rat B-35 neuroblastoma cells) on ion implanted polymer textile. The results of both investigations were positive, with implantation-generated antibacterial efficiency factor up to about 90%, fully comparable to alternative conventional (non-implantation) approaches and with some potentially important advantages over the conventional approach; and with enhancement of neural cell growth rate of up to a factor of 3.5 when grown on suitably implanted polymer textile material.

  3. Electronic transport properties of fullerene functionalized carbon nanotubes: Ab initio and tight-binding calculations

    DEFF Research Database (Denmark)

    Fürst, Joachim Alexander; Hashemi, J.; Markussen, Troels

    2009-01-01

    techniques and tight-binding calculations to illustrate these materials' transmission properties and give physical arguments to interpret the numerical results. Specifically, above the Fermi energy we find a strong reduction in electron transmission due to localized states in certain regions of the structure......Fullerene functionalized carbon nanotubes-NanoBuds-form a novel class of hybrid carbon materials, which possesses many advantageous properties as compared to the pristine components. Here, we report a theoretical study of the electronic transport properties of these compounds. We use both ab initio...

  4. Description of the binding of chitosan to DNA at different ionic strengths in terms of the theories of ion condensation and adsorption

    NARCIS (Netherlands)

    Vorob'ev, E. A.; Nechipurenko, Yu. D.; Salyanov, V. I.; Evdokimov, Yu. M.

    2007-01-01

    The binding of chitosan molecules to DNA in solutions of different ionic strength has been studied. The data were analyzed in terms of the model of ion condensation and the thermodynamic theory of the binding of protracted ligands to DNA. Combining these approaches made it possible to estimate the s

  5. Zn(II) ions bind very efficiently to tandem repeat region of "prion related protein" (PrP-rel-2) of zebra-fish. MS and potentiometric evidence.

    Science.gov (United States)

    Szyrwiel, Lukasz; Jankowska, Elzbieta; Janicka-Klos, Anna; Szewczuk, Zbigniew; Valensin, Daniela; Kozlowski, Henryk

    2008-11-28

    Multi-histidine peptide fragments of zebra-fish prion protein are effective ligands for Zn(II) ions. Moreover the formation of a dinuclear complex species with a longer peptide can suggest the existence of the cooperative effect in the metal ion binding.

  6. Multiply associating electrolytes in the binding mean spherical approximation: Thermodynamic properties and speciation

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, O., E-mail: olivier.bernard@upmc.fr; Simonin, J.-P. [Laboratoire Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques, PECSA (UMR CNRS 7195), Université P. M. Curie, Case 51, 4 Place Jussieu, 75252 Paris Cedex 05 (France); Torres-Arenas, J. [División de Ciencias e Ingenierías, Universidad de Guanajuato, Loma del Bosque 103, Colonia Lomas del Campestre, León, Guanajuato, CP 37150 (Mexico)

    2014-01-21

    Ionic solutions exhibiting multiple association are described within the binding mean spherical approximation (BiMSA). This model is based on the Wertheim formalism, in the framework of the primitive model at the McMillan-Mayer level. The cation and the anion form the various complexes according to stepwise complexation-equilibria. Analytic expressions for the Helmholtz energy, the internal energy, the speciation, and for the osmotic and activity coefficients are given considering a binary solution with an arbitrary number of association sites on one type of ion (polyion) and one site on the ions of opposite sign (counterions). As an alternative, mean field expressions, as developed in SAFT-type theories, are also presented. The result obtained from the latter approximate method exhibits a reasonable agreement with those from BiMSA for the speciation, and a remarkable one for the osmotic coefficient.

  7. Multiply associating electrolytes in the binding mean spherical approximation: Thermodynamic properties and speciation

    Science.gov (United States)

    Bernard, O.; Torres-Arenas, J.; Simonin, J.-P.

    2014-01-01

    Ionic solutions exhibiting multiple association are described within the binding mean spherical approximation (BiMSA). This model is based on the Wertheim formalism, in the framework of the primitive model at the McMillan-Mayer level. The cation and the anion form the various complexes according to stepwise complexation-equilibria. Analytic expressions for the Helmholtz energy, the internal energy, the speciation, and for the osmotic and activity coefficients are given considering a binary solution with an arbitrary number of association sites on one type of ion (polyion) and one site on the ions of opposite sign (counterions). As an alternative, mean field expressions, as developed in SAFT-type theories, are also presented. The result obtained from the latter approximate method exhibits a reasonable agreement with those from BiMSA for the speciation, and a remarkable one for the osmotic coefficient.

  8. Multiply associating electrolytes in the binding mean spherical approximation: thermodynamic properties and speciation.

    Science.gov (United States)

    Bernard, O; Torres-Arenas, J; Simonin, J-P

    2014-01-21

    Ionic solutions exhibiting multiple association are described within the binding mean spherical approximation (BiMSA). This model is based on the Wertheim formalism, in the framework of the primitive model at the McMillan-Mayer level. The cation and the anion form the various complexes according to stepwise complexation-equilibria. Analytic expressions for the Helmholtz energy, the internal energy, the speciation, and for the osmotic and activity coefficients are given considering a binary solution with an arbitrary number of association sites on one type of ion (polyion) and one site on the ions of opposite sign (counterions). As an alternative, mean field expressions, as developed in SAFT-type theories, are also presented. The result obtained from the latter approximate method exhibits a reasonable agreement with those from BiMSA for the speciation, and a remarkable one for the osmotic coefficient.

  9. Zinc complexes of the antibacterial drug oxolinic acid: structure and DNA-binding properties.

    Science.gov (United States)

    Tarushi, Alketa; Psomas, George; Raptopoulou, Catherine P; Kessissoglou, Dimitris P

    2009-06-01

    The neutral mononuclear zinc complexes with the quinolone antibacterial drug oxolinic acid in the absence or presence of a nitrogen donor heterocyclic ligand 2,2'-bipyridine or 1,10-phenanthroline have been synthesized and characterized. The experimental data suggest that oxolinic acid is on deprotonated mode acting as a bidentate ligand coordinated to the metal ion through the ketone and one carboxylato oxygen atoms. The crystal structures of (chloro)(oxolinato)(2,2'-bipyridine)zinc(II), 2, and bis(oxolinato)(1,10-phenanthroline)zinc(II), 3, have been determined with X-ray crystallography. The biological activity of the complexes has been evaluated by examining their ability to bind to calf-thymus DNA (CT DNA) with UV and fluorescence spectroscopies. UV studies of the interaction of the complexes with DNA have shown that they can bind to CT DNA and the DNA-binding constants have been calculated. Competitive studies with ethidium bromide (EB) have shown that complex 3 exhibits the ability to displace the DNA-bound EB indicating that it binds to DNA in strong competition with EB.

  10. Computational methods of studying the binding of toxins from venomous animals to biological ion channels: theory and applications.

    Science.gov (United States)

    Gordon, Dan; Chen, Rong; Chung, Shin-Ho

    2013-04-01

    The discovery of new drugs that selectively block or modulate ion channels has great potential to provide new treatments for a host of conditions. One promising avenue revolves around modifying or mimicking certain naturally occurring ion channel modulator toxins. This strategy appears to offer the prospect of designing drugs that are both potent and specific. The use of computational modeling is crucial to this endeavor, as it has the potential to provide lower cost alternatives for exploring the effects of new compounds on ion channels. In addition, computational modeling can provide structural information and theoretical understanding that is not easily derivable from experimental results. In this review, we look at the theory and computational methods that are applicable to the study of ion channel modulators. The first section provides an introduction to various theoretical concepts, including force-fields and the statistical mechanics of binding. We then look at various computational techniques available to the researcher, including molecular dynamics, brownian dynamics, and molecular docking systems. The latter section of the review explores applications of these techniques, concentrating on pore blocker and gating modifier toxins of potassium and sodium channels. After first discussing the structural features of these channels, and their modes of block, we provide an in-depth review of past computational work that has been carried out. Finally, we discuss prospects for future developments in the field.

  11. Laser-induced lanthanide luminescence as a probe of metal ion-binding sites of human Factor Xa.

    Science.gov (United States)

    Rhee, M J; Horrocks, W D; Kosow, D P

    1984-06-25

    7F0 ---- 5D0 excitation spectroscopy of Eu(III) has shown that human Factor Xa has two high affinity lanthanide ion-binding sites. The deuterium isotope effect on the reciprocal lifetime (tau-1) of excited Eu(III) in human Factor Xa has indicated that 2 to 3 water molecules remain on Eu(III) after being complexed by Factor Xa, suggesting that 3-6 ligand atoms are provided by the protein, probably through two or three gamma-carboxyglutamic acids (GLA). F orster -type interlanthanide energy transfer has been utilized to measure the distance between the high affinity metal ion-binding sites of human Factor Xa using Tb(III) as an energy donor and Nd(III), Ho(III), or Er(III) as energy acceptors. Tau-1 values of Tb(III) in the presence of the acceptor ions Nd(III), Ho(III), and Er(III) were 1.90, 1.66, and 1.76 ms-1, respectively, which compared to 1.31 ms-1 in the presence of the nonacceptor ion Gd(III), yield energy transfer efficiencies of 0.29, 0.20, and 0.24, respectively. From these efficiencies and published critical distances (R0) ( Horrocks , W. DeW ., Jr., Rhee , M-J., Snyder, A. P., and Sudnick , D. R. (1980) J. Am. Chem. Soc. 102, 3650-3652), the distance between two high affinity sites is estimated to be 10.7 A. Based on these data, we propose that the two high affinity sites of human Factor Xa consist of two paired GLA residues; GLA-19, GLA-20 and GLA-25, GLA-26 together with one of the remaining single GLA residues for each site.

  12. The influence of metal ions on the substrate binding pocket of human alcohol dehydrogenase β 2β 2 by molecular modeling

    Science.gov (United States)

    Liu, Hsuan-Liang; Ho, Yih; Hsu, Chia-Ming

    2003-04-01

    Based on theoretical molecular modeling performed in this study, both structural and catalytic zinc ions, Zn s and Zn a, respectively, were shown to influence the structural integrity of the substrate binding pocket of human alcohol dehydrogenase β 2β 2 in the middle and outer regions. The replacement of both Zn s and Zn a with different metal ions restricts the access of bulky substrates to the bottom of the active site by narrowing the bottleneck formed between L116 and V294, whereas it does not affect substrate binding affinity since the accessible surface area of the substrate binding pocket remains more than 80% of the wild-type.

  13. Tribological Properties of DLC Film Prepared by C + Ion Beam-assisted Deposition (IBAD)

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    C + ion beam-assisted deposition was utilized to prepare deposit diamond-like carbon (DLC) film.With the help of a series of experiments such as Raman spectroscopy, FT- IR spectroscopy, AFM and nanoindentation, the DLC film has been recognized as hydrogenated DLC film and its tribological properties have been evaluated.The ball-on-disc testing results show that the hardness and the tribological properties of the DLC film produced by C + ion beam-assisted deposition are improved significandy.DLC film produced by C+ ion beam-assisted deposition is positive to have a prosperous tribological application in the near future.

  14. Researches on the Growth Habit and Optical Properties of Fe3+ Ion Doped KDP Crystal

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    During the process of KDP crystal growth, metal ions strongly affect the growth habit and optical properties of KDP single crystal. In this paper, KDP crystals were grown from an aqueous solution doped with different concentration of Fe3+ dopant by traditional temperaturereduction method and "point-seed" rapid growth method. Furthermore, we examined the light scatter and measured the transmission of these KDP crystals. It is found that the dopant of Fe3+ ion can improve the stability of the KDP growth solution when its concentration is less than 30 ppm.The effects of Fe3+ ion on the growth habit and optical properties of KDP crystal are also obvious.

  15. Investigation of the lithium ion mobility in cyclic model compounds and their ion conduction properties

    Energy Technology Data Exchange (ETDEWEB)

    Thielen, Joerg

    2011-07-27

    In view of both, energy density and energy drain, rechargeable lithium ion batteries outperform other present accumulator systems. However, despite great efforts over the last decades, the ideal electrolyte in terms of key characteristics such as capacity, cycle life, and most important reliable safety, has not yet been identified. Steps ahead in lithium ion battery technology require a fundamental understanding of lithium ion transport, salt association, and ion solvation within the electrolyte. Indeed, well defined model compounds allow for systematic studies of molecular ion transport. Thus, in the present work, based on the concept of immobilizing ion solvents, three main series with a cyclotriphosphazene (CTP), hexaphenylbenzene (HBP), and tetramethylcyclotetrasiloxane (TMS) scaffold were prepared. Lithium ion solvents, among others ethylene carbonate (EC), which has proven to fulfill together with propylene carbonate safety and market concerns in commercial lithium ion batteries, were attached to the different cores via alkyl spacers of variable length. All model compounds were fully characterized, pure and thermally stable up to at least 235 C, covering the requested broad range of glass transition temperatures from -78.1 C up to +6.2 C. While the CTP models tend to rearrange at elevated temperatures over time, which questions the general stability of alkoxide related (poly)phosphazenes, both, the HPB and CTP based models show no evidence of core stacking. In particular the CTP derivatives represent good solvents for various lithium salts, exhibiting no significant differences in the ionic conductivity {sigma}{sub dc} and thus indicating comparable salt dissociation and rather independent motion of cations and ions. In general, temperature-dependent bulk ionic conductivities investigated via impedance spectroscopy follow a William-Landel-Ferry (WLF) type behavior. Modifications of the alkyl spacer length were shown to influence ionic conductivities only in

  16. Nanomechanical and Corrosion Properties of ZK60 Magnesium Alloy Improved by GD Ion Implantation

    Science.gov (United States)

    Tao, Xue Wei; Wang, Zhang Zhong; Zhang, Xiao Bo; Ba, Zhi Xin; Wang, Ya Mei

    2014-09-01

    Gadolinium (Gd) ion implantation with doses from 2.5 × 1016 to 1 × 1017 ions/cm2 into ZK60 magnesium alloy was carried out to improve its surface properties. X-ray photoelectron spectroscopy (XPS), nanoindenter, electrochemical workstation and scanning electron microscope (SEM) were applied to analyze the chemical composition, nanomechanical properties and corrosion characteristics of the implanted layer. The results indicate that Gd ion implantation produces a hybrid-structure protective layer composed of MgO, Gd2O3 and metallic Gd in ZK60 magnesium alloy. The surface hardness and modulus of the Gd implanted magnesium alloy are improved by about 300% and 100%, respectively with the dose of 1 × 1017 ions/cm2, while the slowest corrosion rate of the magnesium alloy in 3.5 wt.% NaCl solution is obtained with the dose of 5 × 1016 ions/cm2.

  17. Modeling the microscopic electrical properties of thrombin binding aptamer (TBA) for label-free biosensors

    CERN Document Server

    Alfinito, Eleonora; Cataldo, Rosella; De Nunzio, Giorgio; Giotta, Livia; Guascito, Maria Rachele

    2016-01-01

    Aptamers are chemically produced oligonucleotides, able to bind a variety of targets such as drugs, proteins and pathogens with high sensitivity and selectivity. Therefore, aptamers are largely employed for producing label-free biosensors, with significant applications in diagnostics and drug delivery. In particular, the anti-thrombin aptamers are biomolecules of high interest for clinical use, because of their ability to recognize and bind the thrombin enzyme. Among them, the DNA 15-mer thrombin-binding aptamer (TBA), has been widely explored concerning both its structure, which was resolved with different techniques, and its function, especially about the possibility of using it as the active part of biosensors. This paper proposes a microscopic model of the electrical properties of TBA and the aptamer-thrombin complex, combining information from both structure and function. The novelty consists in describing both the aptamer alone and the complex as an impedance network, thus going deeper inside the issues...

  18. Novel molecular-level evidence of iodine binding to natural organic matter from Fourier transform ion cyclotron resonance mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Chen, E-mail: xuchen66@tamu.edu [Laboratory for Environmental and Oceanographic Research, Department of Marine Sciences, Texas A and M University, Building 3029, Galveston, TX 77551 (United States); Chen, Hongmei [Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529 (United States); Sugiyama, Yuko [Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529 (United States); University of Hyogo, 1-1-12, Shinzaike-honcho, Himeji, Hyogo 670-0092 (Japan); Zhang, Saijin; Li, Hsiu-Ping; Ho, Yi-Fang; Chuang, Chia-ying; Schwehr, Kathleen A. [Laboratory for Environmental and Oceanographic Research, Department of Marine Sciences, Texas A and M University, Building 3029, Galveston, TX 77551 (United States); Kaplan, Daniel I. [Savannah River National Laboratory, Aiken, SC 29808 (United States); Yeager, Chris [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Roberts, Kimberly A. [Savannah River National Laboratory, Aiken, SC 29808 (United States); Hatcher, Patrick G. [Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529 (United States); Santschi, Peter H. [Laboratory for Environmental and Oceanographic Research, Department of Marine Sciences, Texas A and M University, Building 3029, Galveston, TX 77551 (United States)

    2013-04-01

    Major fractions of radioiodine ({sup 129}I) are associated with natural organic matter (NOM) in the groundwater and surface soils of the Savannah River Site (SRS). Electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) was applied to elucidate the interactions between inorganic iodine species (iodide and iodate) and a fulvic acid (FA) extracted from a SRS surface soil. Iodate is likely reduced to reactive iodine species by the lignin- and tannin-like compounds or the carboxylic-rich alicyclic molecules (CRAM), during which condensed aromatics and lignin-like compounds were generated. Iodide is catalytically oxidized into reactive iodine species by peroxides, while FA is oxidized by peroxides into more aliphatic and less aromatic compounds. Only 9% of the total identified organo-iodine compounds derived from molecules originally present in the FA, whereas most were iodine binding to newly-produced compounds. The resulting iodinated molecules were distributed in three regions in the van Krevelen diagrams, denoting unsaturated hydrocarbons, lignin and protein. Moreover, characteristics of these organo-iodine compounds, such as their relatively low O/C ratios (< 0.2 or < 0.4) and yet some degree of un-saturation close to that of lignin, have multiple important environmental implications concerning possibly less sterically-hindered aromatic ring system for iodine to get access to and a lower hydrophilicity of the molecules thus to retard their migration in the natural aquatic systems. Lastly, ∼ 69% of the identified organo-iodine species contains nitrogen, which is presumably present as -NH{sub 2} or -HNCOR groups and a ring-activating functionality to favor the electrophilic substitution. The ESI-FTICR-MS technique provides novel evidence to better understand the reactivity and scavenging properties of NOM towards radioiodine and possible influence of NOM on {sup 129}I migration. Highlights: ► IO{sub 3}{sup

  19. Conservation of DNA-binding specificity and oligomerisation properties within the p53 family

    Directory of Open Access Journals (Sweden)

    Joerger Andreas C

    2009-12-01

    Full Text Available Abstract Background Transcription factors activate their target genes by binding to specific response elements. Many transcription factor families evolved from a common ancestor by gene duplication and subsequent divergent evolution. Members of the p53 family, which play key roles in cell-cycle control and development, share conserved DNA binding and oligomerisation domains but exhibit distinct functions. In this study, the molecular basis of the functional divergence of related transcription factors was investigated. Results We characterised the DNA-binding specificity and oligomerisation properties of human p53, p63 and p73, as well as p53 from other organisms using novel biophysical approaches. All p53 family members bound DNA cooperatively as tetramers with high affinity. Despite structural differences in the oligomerisation domain, the dissociation constants of the tetramers was in the low nanomolar range for all family members, indicating that the strength of tetramerisation was evolutionarily conserved. However, small differences in the oligomerisation properties were observed, which may play a regulatory role. Intriguingly, the DNA-binding specificity of p53 family members was highly conserved even for evolutionarily distant species. Additionally, DNA recognition was only weakly affected by CpG methylation. Prediction of p53/p63/p73 binding sites in the genome showed almost complete overlap between the different homologs. Conclusion Diversity of biological function of p53 family members is not reflected in differences in sequence-specific DNA binding. Hence, additional specificity factors must exist, which allowed the acquisition of novel functions during evolution while preserving original roles.

  20. Interface transport properties in ion-gated nano-sheets

    NARCIS (Netherlands)

    Ye, J. T.; Zhang, Y. J.; Kasahara, Y.; Iwasa, Y.

    Recent advances in atomic-scale preparation of ultrathin nano-sheets and efficient field-effect gating mediated by movement of ions have provided a prolific paradigm for creating exotic states at interfaces of a new-type of device called electric-double layer transistors (EDLTs). We present a short

  1. Ion-Implanted Diamond Films and Their Tribological Properties

    Science.gov (United States)

    Wu, Richard L. C.; Miyoshi, Kazuhisa; Korenyi-Both, Andras L.; Garscadden, Alan; Barnes, Paul N.

    1993-01-01

    This paper reports the physical characterization and tribological evaluation of ion-implanted diamond films. Diamond films were produced by microwave plasma, chemical vapor deposition technique. Diamond films with various grain sizes (0.3 and 3 microns) and roughness (9.1 and 92.1 nm r.m.s. respectively) were implanted with C(+) (m/e = 12) at an ion energy of 160 eV and a fluence of 6.72 x 10(exp 17) ions/sq cm. Unidirectional sliding friction experiments were conducted in ultrahigh vacuum (6.6 x 10(exp -7)Pa), dry nitrogen and humid air (40% RH) environments. The effects of C(+) ion bombardment on fine and coarse-grained diamond films are as follows: the surface morphology of the diamond films did not change; the surface roughness increased (16.3 and 135.3 nm r.m.s.); the diamond structures were damaged and formed a thin layer of amorphous non-diamond carbon; the friction coefficients dramatically decreased in the ultrahigh vacuum (0.1 and 0.4); the friction coefficients decreased slightly in the dry nitrogen and humid air environments.

  2. Study of the electrochemical properties of magnetite, maghemite and hematite nanoparticles for their applications in lithium ion batteries

    Science.gov (United States)

    Chen, Linfeng; Wang, Gaojun; Xie, Jining; Rai, Pratyush; Lee, Jungmin; Mathur, Gyanesh N.; Varadan, Vijay K.

    2013-04-01

    Iron oxide nanoparticles, including magnetite, maghemite and hematite, are promising electrode active materials for lithium ion batteries due to their low cost, high capacity and environmental friendliness. Though the electrochemical properties of each kind of iron oxide nanoparticles have been intensively studied, systematic comparison of the three kinds of iron oxides is hardly reported. This paper reports the study and comparison of the electrochemical properties of magnetite, maghemite and hematite nanoparticles with the same shape and size. In this work, hematite and maghemite nanoparticles were obtained from commercial magnetite nanoparticles by thermal treatments at different conditions. Their crystalline structures were characterized by X-ray diffraction (XRD), their magnetic properties were measured by a vibration sample magnetometer (VSM), and their particle morphologies were analyzed by scanning electron microscopy (SEM). Composite electrodes were made from iron oxide nanoparticles with carbon black as the conducting material and PVDF as the binding material (iron oxide : carbon black : PVDF = 70 : 15 : 15). Prototype lithium ion batteries (CR2032 button cells) were assembled with iron oxide composite electrodes as cathodes, metal lithium as anodes, and Celgard 2400 porous membrane as separators. The impedance and discharge-charge behaviors were characterized by a Solartron electrochemical workstation and an Arbin battery tester, respectively. It was found that at the same shape and size, hematite nanoparticles has higher specific discharge and charge capacities than magnetite and maghemite nanoparticles.

  3. Binding properties of ferrocene-glutathione conjugates as inhibitors and sensors for glutathione S-transferases.

    Science.gov (United States)

    Martos-Maldonado, Manuel C; Casas-Solvas, Juan M; Téllez-Sanz, Ramiro; Mesa-Valle, Concepción; Quesada-Soriano, Indalecio; García-Maroto, Federico; Vargas-Berenguel, Antonio; García-Fuentes, Luís

    2012-02-01

    The binding properties of two electroactive glutathione-ferrocene conjugates that consist in glutathione attached to one or both of the cyclopentadienyl rings of ferrocene (GSFc and GSFcSG), to Schistosoma japonica glutathione S-transferase (SjGST) were studied by spectroscopy fluorescence, isothermal titration calorimetry (ITC) and differential pulse voltammetry (DPV). Such ferrocene conjugates resulted to be competitive inhibitors of glutathione S-transferase with an increased binding affinity relative to the natural substrate glutathione (GSH). We found that the conjugate having two glutathione units (GSFcSG) exhibits an affinity for SjGST approximately two orders of magnitude higher than GSH. Furthermore, it shows negative cooperativity with the affinity for the second binding site two orders of magnitude lower than that for the first one. We propose that the reason for such negative cooperativity is steric since, i) the obtained thermodynamic parameters do not indicate profound conformational changes upon GSFcSG binding and ii) docking studies have shown that, when bound, part of the first bound ligand invades the second site due to its large size. In addition, voltammetric measurements show a strong decrease of the peak current upon binding of ferrocene-glutathione conjugates to SjGST and provide very similar K values than those obtained by ITC. Moreover, the sensing ability, expressed by the sensitivity parameter shows that GSFcSG is much more sensitive than GSFc, for the detection of SjGST.

  4. Effects of ligand binding on the mechanical properties of ankyrin repeat protein gankyrin.

    Directory of Open Access Journals (Sweden)

    Giovanni Settanni

    Full Text Available Ankyrin repeat proteins are elastic materials that unfold and refold sequentially, repeat by repeat, under force. Herein we use atomistic molecular dynamics to compare the mechanical properties of the 7-ankyrin-repeat oncoprotein Gankyrin in isolation and in complex with its binding partner S6-C. We show that the bound S6-C greatly increases the resistance of Gankyrin to mechanical stress. The effect is specific to those repeats of Gankyrin directly in contact with S6-C, and the mechanical 'hot spots' of the interaction map to the same repeats as the thermodynamic hot spots. A consequence of stepwise nature of unfolding and the localized nature of ligand binding is that it impacts on all aspects of the protein's mechanical behavior, including the order of repeat unfolding, the diversity of unfolding pathways accessed, the nature of partially unfolded intermediates, the forces required and the work transferred to the system to unfold the whole protein and its parts. Stepwise unfolding thus provides the means to buffer repeat proteins and their binding partners from mechanical stress in the cell. Our results illustrate how ligand binding can control the mechanical response of proteins. The data also point to a cellular mechano-switching mechanism whereby binding between two partner macromolecules is regulated by mechanical stress.

  5. DNA binding properties and biological evaluation of dihydropyrimidinones derivatives as potential antitumor agents

    Science.gov (United States)

    Wang, Gongke; Li, Xiangrong; Gou, Yaping; Chen, Yuhan; Yan, Changling; Lu, Yan

    2013-10-01

    The binding properties of two medicinally important dihydropyrimidinones derivatives 5-(Ethoxycarbonyl)-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (EMPD) and 5-(Ethoxycarbonyl)-6-methyl-4-(4-chlorophenyl)-3,4-dihydropyrimidin-2(1H)-one (EMCD) with calf-thymus DNA (ctDNA) were investigated by spectroscopy, viscosity, isothermal titration calorimetry (ITC) and molecular modeling techniques. Simultaneously, their biological activities were evaluated with MTT assay method. The binding constants determined with spectroscopic titration and ITC were found to be in the same order of 104 M-1. According to the results of viscosity studies, fluorescence competitive binding experiment and ITC investigations, intercalative binding was evaluated as the dominant binding modes between the two compounds and ctDNA. Furthermore, the results of molecular modeling corroborated those obtained from spectroscopic, viscosimetric and ITC investigations. Evaluation of the antitumor activities of the two derivatives against different tumor cell lines proved that they exhibited significant tumor cell inhibition rate, accordingly blocking DNA transcription and replication. The present results favor the development of potential drugs related with dihydropyrimidinones derivatives in the treatment of some diseases.

  6. A minimal model of peptide binding predicts ensemble properties of serum antibodies

    Directory of Open Access Journals (Sweden)

    Greiff Victor

    2012-02-01

    Full Text Available Background The importance of peptide microarrays as a tool for serological diagnostics has strongly increased over the last decade. However, interpretation of the binding signals is still hampered by our limited understanding of the technology. This is in particular true for arrays probed with antibody mixtures of unknown complexity, such as sera. To gain insight into how signals depend on peptide amino acid sequences, we probed random-sequence peptide microarrays with sera of healthy and infected mice. We analyzed the resulting antibody binding profiles with regression methods and formulated a minimal model to explain our findings. Results Multivariate regression analysis relating peptide sequence to measured signals led to the definition of amino acid-associated weights. Although these weights do not contain information on amino acid position, they predict up to 40-50% of the binding profiles' variation. Mathematical modeling shows that this position-independent ansatz is only adequate for highly diverse random antibody mixtures which are not dominated by a few antibodies. Experimental results suggest that sera from healthy individuals correspond to that case, in contrast to sera of infected ones. Conclusions Our results indicate that position-independent amino acid-associated weights predict linear epitope binding of antibody mixtures only if the mixture is random, highly diverse, and contains no dominant antibodies. The discovered ensemble property is an important step towards an understanding of peptide-array serum-antibody binding profiles. It has implications for both serological diagnostics and B cell epitope mapping.

  7. Detection of oral streptococci with collagen-binding properties in saliva specimens from mothers and their children.

    Science.gov (United States)

    Nomura, Ryota; Naka, Shuhei; Nakano, Kazuhiko; Taniguchi, Naho; Matsumoto, Michiyo; Ooshima, Takashi

    2010-07-01

    Approximately 10-20% of Streptococcus mutans strains have been reported to possess collagen-binding properties, whereas other species in the oral cavity with those properties remain to be elucidated. Aim. To identify strains with collagen-binding properties and analyse their characteristics in comparison with S. mutans. A total of 110 expectorated saliva specimens were collected from 55 pairs of mothers and their children. Bacterial strains with collagen-binding properties were isolated and the species specified. In addition, strains with collagen-binding properties isolated from mother-child pairs were analysed using molecular biological approaches. The detection frequency of strains with collagen-binding properties was shown to be 40.9%, among which S. salivarius was the most frequently detected, followed by S. mutans. The collagen-binding activity of the S. mutans group was the highest, followed by S. salivarius. In addition, S. mutans and S. salivarius strains from 3 and 1 mother-child pairs, respectively, were shown to be the same clones. Our results indicate that S. mutans and S. salivarius are major species with collagen-binding properties in the oral cavity, and that strains with such properties may be related to mother-child transmission.

  8. FcRn expression, ligands binding properties and its regulation in human immune cells and hepatocytes

    OpenAIRE

    2007-01-01

    ABSTRACT Expression and diverse functions of MHC class I related neonatal Fc receptor in different tissues is continually reported. To contribute to the understanding of how the receptor functions according to cell type, we investigated the expression and ligands binding properties of FcRn in human immune cells and hepatocytes. Here, we report that heterodimeric FcRn is expressed in these cells as evidenced by RT-PCR, Western immunoblottting and flow cytometry. The receptor expression i...

  9. Relationships of ligand binding, redox properties, and protonation in Coprinus cinereus peroxidase.

    Science.gov (United States)

    Ciaccio, Chiara; Rosati, Antonella; De Sanctis, Giampiero; Sinibaldi, Federica; Marini, Stefano; Santucci, Roberto; Ascenzi, Paolo; Welinder, Karen G; Coletta, Massimo

    2003-05-23

    The pH dependence of the redox potentials and kinetics for CO association and dissociation was determined between pH 3.0 and 13.0 at 25 degrees C for the wild-type Coprinus cinereus fungal peroxidase and for a site-directed mutant in which Asp245, which is H-bonded to N delta of the imidazole of the proximal His183, was substituted with Asn. The determination of these functional properties allowed this information to be merged in a self-consistent fashion and to formulate for the first time a complete scheme employing the minimum number of groups required to describe the whole proton-linked behavior of both redox and ligand binding properties. The overall pH dependence can be accounted for by four redox- and ligand-linked groups. The proximal H-bond, which is strictly conserved in all peroxidases, will still be present in the site-specific mutant, but will no longer have an ionic character, and this event will bring about an alteration of redox equilibria and CO binding kinetics, envisaging a relevant role played by this H-bond also in modulating redox properties and ligand binding equilibria.

  10. Variation in the electrical properties of ion beam irradiated cadmium selenate nanowires

    Science.gov (United States)

    Chauhan, R. P.; Narula, Chetna; Panchal, Suresh

    2016-05-01

    The key feature of nanowires consists in the pronounced change in properties induced by the low dimensionality and high surface to volume ratio. The study of electrical transport properties of nanowires is important for electronic device applications. Energetic ions create changes, which may be structural or chemical, in a material along their track and these changes might alter the material's properties. The demand of the modern technology is to understand the effect of radiation on the different properties of the material for its further applications. The present study is on the high-energy Nickel ion beam (160 MeV Ni+12) induced modifications in the electrical and structural properties of the cadmium selenate nanowires. An enhancement in the electrical conductivity of irradiated wires was observed as the ion fluence was increased especially in the forward I-V characteristics. The creation of defects by ion irradiation and the synergy of the ions during their passage in the sample with the intrinsic charge carriers may be responsible for the variation in the transport properties of the irradiated nanowires.

  11. The magnetic properties of the spin-1 Heisenberg antiferromagnetic chain with single-ion anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Gangsan; Zhu, Rengui, E-mail: rgzhu@mail.ahnu.edu.cn

    2015-02-15

    The magnetic properties of the spin-1 Heisenberg antiferromagnetic chain with exchange anisotropy and single-ion anisotropy are studied by the double-time Green's function method. The determinative equations for the critical temperature, the magnetization, and the zero-field susceptibility are derived analytically. The effects of the anisotropies on the magnetic properties are presented.

  12. Molecular dynamics simulations of the dynamic and energetic properties of alkali and halide ions using water-model-specific ion parameters.

    Science.gov (United States)

    Joung, In Suk; Cheatham, Thomas E

    2009-10-01

    The dynamic and energetic properties of the alkali and halide ions were calculated using molecular dynamics (MD) and free energy simulations with various different water and ion force fields including our recently developed water-model-specific ion parameters. The properties calculated were activity coefficients, diffusion coefficients, residence times of atomic pairs, association constants, and solubility. Through calculation of these properties, we can assess the validity and range of applicability of the simple pair potential models and better understand their limitations. Due to extreme computational demands, the activity coefficients were only calculated for a subset of the models. The results qualitatively agree with experiment. Calculated diffusion coefficients and residence times between cation-anion, water-cation, and water-anion showed differences depending on the choice of water and ion force field used. The calculated solubilities of the alkali-halide salts were generally lower than the true solubility of the salts. However, for both the TIP4P(EW) and SPC/E water-model-specific ion parameters, solubility was reasonably well-reproduced. Finally, the correlations among the various properties led to the following conclusions: (1) The reliability of the ion force fields is significantly affected by the specific choice of water model. (2) Ion-ion interactions are very important to accurately simulate the properties, especially solubility. (3) The SPC/E and TIP4P(EW) water-model-specific ion force fields are preferred for simulation in high salt environments compared to the other ion force fields.

  13. Friction and wear properties of N+ ion implanted nylon 1010

    Institute of Scientific and Technical Information of China (English)

    XIONG Dang-sheng

    2004-01-01

    The PA1010 was implanted with 450 keV N+ ions to three doses of 5× 1014 cm-2 , 2.5× 1015 cm-2 and 1.25 × 1016 cm-2. The friction and wear behaviors of the ion implanted PA1010 disks rubbing with two ceramic (ZrO2 and Si3N4) balls were studied using a pin-on-disk tribometer under dry friction. The results shows that the wear resistance of PA1010 is increased with the increasing implantation doses. The adhesion, plastic deformation and plow groove are wearing mechanisms for un-implanted PA1010, while abrasive wear for implanted PA1010.

  14. Optical properties of Yb ions in GaN epilayer

    Science.gov (United States)

    Jadwisienczak, W. M.; Lozykowski, H. J.

    2003-07-01

    In recent years, an important effort in semiconductor materials research has been devoted to III-nitrides semiconductors doped with rare earth ions due to the high potential of these materials in light-emitting device applications. Ytterbium (Yb 3+) is one of a few lanthanide ions which have not been investigated as an optically active center in these materials yet. In this paper we report the observation of luminescence from GaN films grown on sapphire (0 0 0 1) substrate by metal organic chemical vapor deposition and doped by implantation with Yb 3+ ions. The high resolution photo- and cathodoluminescence spectra of GaN:Yb 3+ were studied at different excitation conditions in temperatures ranging from 8 to 330 K and revealed weak thermal quenching. The luminescence emission lines are assigned to transitions between the spin-orbit levels 2F 5/2 → 2F 7/2 of Yb 3+ (4f 13). The analysis of the Yb luminescence spectra allowed us to suggest the energy level diagram of the crystal-field-split 4f 13 levels for the Yb ion center. The most probable lattice location of Yb in GaN is the substitutional Ga site. Furthermore, the luminescence kinetics of internal transitions of Yb 3+ incorporated in GaN was investigated by means of decay and time-resolved luminescence measurements. It was found that the ytterbium decay is non-exponential with dominant exponential term of ˜100 μs with little dependence on the ambient temperature. The results indicate that Yb-doped GaN epilayer may be suitable as a material for near infrared optoelectronic devices.

  15. Critical properties of the transverse ferromagnetic spin system with random single-ion anisotropy

    Institute of Scientific and Technical Information of China (English)

    邓玲玲; 晏世雷

    2002-01-01

    A transverse ferromagnetic spin-1 system with a random single-ion anisotropy is considered in the framework of an Ising model. The effective field theory and decoupling approximation are applied to the derivation of the expressions of magnetizations for a honeycomb lattice. Special emphasis is placed on the critical properties of the system. New critical properties are obtained in a certain range of single-ion anisotropy, random concentration, and transverse field.We discuss in detail the influence of the random concentration and transverse field on the critical properties. Some phenomena have not been discovered in previous reports. Detailed descriptions of the phase transition and magnetization curves are presented.

  16. Structural and binding properties of the PASTA domain of PonA2, a key penicillin binding protein from Mycobacterium tuberculosis.

    Science.gov (United States)

    Calvanese, Luisa; Falcigno, Lucia; Maglione, Cira; Marasco, Daniela; Ruggiero, Alessia; Squeglia, Flavia; Berisio, Rita; D'Auria, Gabriella

    2014-07-01

    PonA2 is one of the two class A penicillin binding proteins of Mycobacterium tuberculosis, the etiologic agent of tuberculosis. It plays a complex role in mycobacterial physiology and is spotted as a promising target for inhibitors. PonA2 is involved in adaptation of M. tuberculosis to dormancy, an ability which has been attributed to the presence in its sequence of a C-terminal PASTA domain. Since PASTA modules are typically considered as β-lactam antibiotic binding domains, we determined the solution structure of the PASTA domain from PonA2 and analyzed its binding properties versus a plethora of potential binders, including the β-lactam antibiotics, two typical muropeptide mimics, and polymeric peptidoglycan. We show that, despite a high structural similarity with other PASTA domains, the PASTA domain of PonA2 displays different binding properties, as it is not able to bind muropeptides, or β-lactams, or polymeric peptidoglycan. These results indicate that the role of PASTA domains cannot be generalized, as their specific binding properties strongly depend on surface residues, which are widely variable.

  17. Chemically synthesized glycosides of hydroxylated flavylium ions as suitable models of anthocyanins: binding to iron ions and human serum albumin, antioxidant activity in model gastric conditions.

    Science.gov (United States)

    Al Bittar, Sheiraz; Mora, Nathalie; Loonis, Michèle; Dangles, Olivier

    2014-12-11

    Polyhydroxylated flavylium ions, such as 3',4',7-trihydroxyflavylium chloride (P1) and its more water-soluble 7-O-β-d-glucopyranoside (P2), are readily accessible by chemical synthesis and suitable models of natural anthocyanins in terms of color and species distribution in aqueous solution. Owing to their catechol B-ring, they rapidly bind FeIII, weakly interact with FeII and promote its autoxidation to FeIII. Both pigments inhibit heme-induced lipid peroxidation in mildly acidic conditions (a model of postprandial oxidative stress in the stomach), the colorless (chalcone) forms being more potent than the colored forms. Finally, P1 and P2 are moderate ligands of human serum albumin (HSA), their likely carrier in the blood circulation, with chalcones having a higher affinity for HSA than the corresponding colored forms.

  18. Chemically Synthesized Glycosides of Hydroxylated Flavylium Ions as Suitable Models of Anthocyanins: Binding to Iron Ions and Human Serum Albumin, Antioxidant Activity in Model Gastric Conditions

    Directory of Open Access Journals (Sweden)

    Sheiraz Al Bittar

    2014-12-01

    Full Text Available Polyhydroxylated flavylium ions, such as 3',4',7-trihydroxyflavylium chloride (P1 and its more water-soluble 7-O-β-d-glucopyranoside (P2, are readily accessible by chemical synthesis and suitable models of natural anthocyanins in terms of color and species distribution in aqueous solution. Owing to their catechol B-ring, they rapidly bind FeIII, weakly interact with FeII and promote its autoxidation to FeIII. Both pigments inhibit heme-induced lipid peroxidation in mildly acidic conditions (a model of postprandial oxidative stress in the stomach, the colorless (chalcone forms being more potent than the colored forms. Finally, P1 and P2 are moderate ligands of human serum albumin (HSA, their likely carrier in the blood circulation, with chalcones having a higher affinity for HSA than the corresponding colored forms.

  19. Ion-beam-induced modifications in the structural and electrical properties of copper oxide selenite nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Rana, Pallavi, E-mail: prana.phy@gmail.com; Chauhan, R.P.

    2015-04-15

    Highlights: •Nanowires were synthesized via template-assisted electrodeposition method. •Copper oxide selenite nanowires were irradiated with 160 MeV, Ni{sup +12} ion beam. •XRD confirmed no change in phase of irradiated nanowires. •Electrical resistivity of nanowires was found to decrease with the ion fluence. -- Abstract: Irradiation with swift heavy ions (SHIs) with energy in the MeV range is a unique tool for engineering the properties of materials. In this context, the objective of the present work is to study the conduction of charge carriers in pre- and post-ion-irradiated semiconducting nanowires. Copper oxide selenite nanowires were synthesized using a template-assisted electrodeposition technique from an aqueous solution of 0.8 M CuSO{sub 4}·5H{sub 2}O and 8 mM SeO{sub 2}. The synthesized nanowires were observed to have a monoclinic structure with linear I–V characteristics (IVC). The effect of irradiation with 160 MeV Ni{sup +12} ions on the properties of the copper oxide selenite nanowires was investigated for fluences varying from 10{sup 11} to 10{sup 13} ions/cm{sup 2}. XRD spectra confirmed no change in the phase of the swift-heavy-ion-irradiated nanowires, but a modification in the orientation of the planes was observed that depended on the ion fluence. The electrical resistivity of the semiconducting nanowires also varied with the ion fluence. Simultaneous irradiation-induced modifications to the electro-chemical potential gradient and the granular properties of the material may have been the origin of the alteration in the structural and electrical properties of the nanowires.

  20. Ion beam sputter deposition of Ge films: Influence of process parameters on film properties

    Energy Technology Data Exchange (ETDEWEB)

    Bundesmann, C., E-mail: carsten.bundesmann@iom-leipzig.de [Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstrasse 15, 04318 Leipzig (Germany); Feder, R. [Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstrasse 15, 04318 Leipzig (Germany); Wunderlich, R.; Teschner, U.; Grundmann, M. [Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig (Germany); Neumann, H. [Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstrasse 15, 04318 Leipzig (Germany)

    2015-08-31

    Several sets of Ge films were grown by ion beam sputter deposition under systematic variation of ion beam parameters (ion species and ion energy) and geometrical parameters (ion incidence angle and polar emission angle). The films were characterized concerning thickness, growth rate, mass density, structural properties and composition. The film thicknesses show a cosine-like angular distribution, and the growth rates were found to increase with increasing ion incidence angle and ion energy. All films are amorphous and the average mass density was found to be (4.3 ± 0.2) g/cm{sup 3}, without a systematic relation to ion energy and geometrical parameters. Slightly higher mass densities were found for Ge films grown by sputtering with Xe than for sputtering with Ar. The Ge films contain a fraction of inert gas atoms from backscattered primary particles. This fraction is found to be higher for sputtering with Ar than for sputtering with Xe. The fraction of inert gas atoms increases with increasing polar emission angle and increasing ion incidence angle. Raman scattering experiments revealed also systematic shifts of the characteristic Raman mode. The shifts are tentatively assigned to the change of the Ge particle densities caused by the incorporation of inert gas particles. There seem to be also slight changes in short range ordering. The experimental data are discussed with respect to the known energy and angular distributions of the sputtered and backscattered particles. - Highlights: • Ion beam sputter deposition under systematic variation of process parameters • Thickness, growth rate, mass density, composition, structure, phonon properties • All germanium films are amorphous with small variations in mass density. • Incorporation of considerable amount of inert process gas • Vibrational properties correlate with composition.

  1. Electrical properties of irradiated PVA film by using ion/electron beam

    Science.gov (United States)

    Abdelrahman, M. M.; Osman, M.; Hashhash, A.

    2016-02-01

    Ion/electron beam bombardment has shown great potential for improving the surface properties of polymers. Low-energy charged (ion/electron) beam irradiation of polymers is a good technique to modify properties such as electrical conductivity, structural behavior, and their mechanical properties. This paper reports on the effect of nitrogen and electron beam irradiation on the electrical properties of polyvinyl alcohol (PVA) films. PVA films of 4 mm were exposed to a charged (ion/electron) beam for different treatment times (15, 30, and 60 minutes); the beam was produced from a dual beam source using nitrogen gas with the other ion/electron source parameters optimized. The dielectric loss tangent tan δ , electrical conductivity σ , and dielectric constant ɛ ^' } in the frequency range 100 Hz-100 kHz were measured at room temperature. The variation of dielectric constant and loss tangent as a function of frequency was also studied at room temperature. The dielectric constant was found to be strongly dependent on frequency for both ion and electron beam irradiation doses. The real (ɛ ^' }) and imaginary (ɛ ^' ' }) parts of the dielectric constant decreased with frequency for all irradiated and non-irradiated samples. The AC conductivity showed an increase with frequency for all samples under the influence of both ion and electron irradiation for different times. Photoluminescence (PL) spectral changes were also studied. The formation of clusters and defects (which serve as non-radiative centers on the polymer surface) is confirmed by the decrease in the PL intensity.

  2. Synthesis and ion-binding studies of platinum(Ⅱ) phenanthroline complexes containing crown ether moiety

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Two new benzo-[15]-crown-5 attached phenanthroline platinum(Ⅱ) complexes with the general formula Pt(phen)X2, where X = Cl (1), C≡CC6H5 (2) have been synthesized, and their absorption and luminescence response towards metal ions have been studied.

  3. Size and shape dependence of the electrochemical properties of hematite nanoparticles and their applications in lithium ion batteries

    Science.gov (United States)

    Chen, Linfeng; Wang, Gaojun; Mathur, Gyanesh N.; Varadan, Vijay K.

    2012-04-01

    Hematite nanoparticles are a type of promising electrode active materials for lithium ion batteries due to their low cost and high specific capacity. However, the cycling performances of hematite nanoparticles are not as good as those of the conventional electrode active materials for lithium ion batteries. This paper reports the study on the relationship between the electrochemical properties and the particle sizes and shapes, aiming to optimize the electrochemical properties of hematite nanoparticles for their applications in lithium ion batteries. Three types of hematite nanoparticles were compared, including hematite nanospheres with an average diameter of 200 nm, hematite nanoflakes with an average maximum dimension of 200 nm, and hematite nanospheres with an average diameter of 30 nm. Their crystalline structures were characterized by X-ray diffraction (XRD) and their particle morphologies were analyzed by scanning electron microscopy (SEM). Composite electrode materials were made from hematite nanoparticles with carbon black as the conducting material and PVDF as the binding material (hematite : carbon black : PVDF = 70 : 15 : 15). Prototype lithium ion batteries (CR2032 button cells) were assembled with the composite electrodes as cathodes, metal lithium as anodes, and Celgard 2400 porous membrane as separators. It was found that in the first few cycles, the specific discharge capacity of hematite nanospheres with an average diameter of 30 nm is higher than those of the other two, while after first seven cycles, the specific discharge capacity of hematite nanospheres with an average diameter of 30 nm is lower than those of the other two. Possible approaches for improving the cycling performance and rate capacity of hematite nanoparticles are discussed at the end of this paper.

  4. Searching the conformational complexity and binding properties of HDAC6 through docking and molecular dynamic simulations.

    Science.gov (United States)

    Sixto-López, Yudibeth; Bello, Martiniano; Rodríguez-Fonseca, Rolando Alberto; Rosales-Hernández, Martha Cecilia; Martínez-Archundia, Marlet; Gómez-Vidal, José Antonio; Correa-Basurto, José

    2017-10-01

    Histone deacetylases (HDACs) are a family of proteins involved in the deacetylation of histones and other non-histones substrates. HDAC6 belongs to class II and shares similar biological functions with others of its class. Nevertheless, its three-dimensional structure that involves the catalytic site remains unknown for exploring the ligand recognition properties. Therefore, in this contribution, homology modeling, 100-ns-long Molecular Dynamics (MD) simulation and docking calculations were combined to explore the conformational complexity and binding properties of the catalytic domain 2 from HDAC6 (DD2-HDAC6), for which activity and affinity toward five different ligands have been reported. Clustering analysis allowed identifying the most populated conformers present during the MD simulation, which were used as starting models to perform docking calculations with five DD2-HDAC6 inhibitors: Cay10603 (CAY), Rocilinostat (RCT), Tubastatin A (TBA), Tubacin (TBC), and Nexturastat (NXT), and then were also submitted to 100-ns-long MD simulations. Docking calculations revealed that the five inhibitors bind at the DD2-HDAC6 binding site with the lowest binding free energy, the same binding mode is maintained along the 100-ns-long MD simulations. Overall, our results provide structural information about the molecular flexibility of apo and holo DD2-HDAC6 states as well as insight of the map of interactions between DD2-HDAC6 and five well-known DD2-HDAC6 inhibitors allowing structural details to guide the drug design. Finally, we highlight the importance of combining different theoretical approaches to provide suitable structural models for structure-based drug design.

  5. Ion-ion correlation, solvent excluded volume and pH effects on physicochemical properties of spherical oxide nanoparticles.

    Science.gov (United States)

    Ovanesyan, Zaven; Aljzmi, Amal; Almusaynid, Manal; Khan, Asrar; Valderrama, Esteban; Nash, Kelly L; Marucho, Marcelo

    2016-01-15

    One major source of complexity in the implementation of nanoparticles in aqueous electrolytes arises from the strong influence that biological environments has on their physicochemical properties. A key parameter for understanding the molecular mechanisms governing the physicochemical properties of nanoparticles is the formation of the surface charge density. In this article, we present an efficient and accurate approach that combines a recently introduced classical solvation density functional theory for spherical electrical double layers with a surface complexation model to account for ion-ion correlation and excluded volume effects on the surface titration of spherical nanoparticles. We apply the proposed computational approach to account for the charge-regulated mechanisms on the surface chemistry of spherical silica (SiO2) nanoparticles. We analyze the effects of the nanoparticle size, as well as pH level and electrolyte concentration of the aqueous solution on the nanoparticle's surface charge density and Zeta potential. We validate our predictions for 580Å and 200Å nanoparticles immersed in acid, neutral and alkaline mono-valent aqueous electrolyte solutions against experimental data. Our results on mono-valent electrolyte show that the excluded volume and ion-ion correlations contribute significantly to the surface charge density and Zeta potential of the nanoparticle at high electrolyte concentration and pH levels, where the solvent crowding effects and electrostatic screening have shown a profound influence on the protonation/deprotonation reactions at the liquid/solute interface. The success of this approach in describing physicochemical properties of silica nanoparticles supports its broader application to study other spherical metal oxide nanoparticles.

  6. Using engineered single-chain antibodies to correlate molecular binding properties and nanoparticle adhesion dynamics.

    Science.gov (United States)

    Haun, Jered B; Pepper, Lauren R; Boder, Eric T; Hammer, Daniel A

    2011-11-15

    Elucidation of the relationship between targeting molecule binding properties and the adhesive behavior of therapeutic or diagnostic nanocarriers would aid in the design of optimized vectors and lead to improved efficacy. We measured the adhesion of 200-nm-diameter particles under fluid flow that was mediated by a diverse array of molecular interactions, including recombinant single-chain antibodies (scFvs), full antibodies, and the avidin/biotin interaction. Within the panel of scFvs, we used a family of mutants that display a spectrum of binding kinetics, allowing us to compare nanoparticle adhesion to bond chemistry. In addition, we explored the effect of molecular size by inserting a protein linker into the scFv fusion construct and by employing scFvs that are specific for targets with vastly different sizes. Using computational models, we extracted multivalent kinetic rate constants for particle attachment and detachment from the adhesion data and correlated the results to molecular binding properties. Our results indicate that the factors that increase encounter probability, such as adhesion molecule valency and size, directly enhance the rate of nanoparticle attachment. Bond kinetics had no influence on scFv-mediated nanoparticle attachment within the kinetic range tested, however, but did appear to affect antibody/antigen and avidin/biotin mediated adhesion. We attribute this finding to a combination of multivalent binding and differences in bond mechanical strength between recombinant scFvs and the other adhesion molecules. Nanoparticle detachment probability correlated directly with adhesion molecule valency and size, as well as the logarithm of the affinity for all molecules tested. On the basis of this work, scFvs can serve as viable targeting receptors for nanoparticles, but improvements to their bond mechanical strength would likely be required to fully exploit their tunable kinetic properties and maximize the adhesion efficiency of nanoparticles that

  7. SURFACE MODIFICATION OF TITANIUM FILMS WITH SODIUM ION IMPLANTATION: SURFACE PROPERTIES AND PROTEIN ADSORPTION

    Institute of Scientific and Technical Information of China (English)

    K. Y. Cai

    2007-01-01

    Sodium implanted titanium films with different ion doses were characterized to correlate their ion implantation parameters. Native titanium films and ion implanted titanium films were characterized with combined techniques of X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and light microscopy (LM). The surface presented increased sodium concentration on treated titanium films with ion dose increasing, except for the group with the highest ion dose of 4× 1017 ions/cm2. XPS depth profiling displayed that sodium entered titanium film around 25-50 nm depth depending on its implantation ion dose. AFM characterization showed that sodium ion implantation treatment changed the surface morphology from a relatively smooth titanium film to rough surfaces corresponding to different implantation doses.After sodium implantation, implanted titanium films presented big particles with island structure morphology. The surface morphology and particle growth displayed the corresponding trend.Fibrinogen adsorption on these titanium films was performed to correlate with the surface properties of treated titanium films. The results show that protein adsorption on ion-implanted samples with dose of 2 × 1017 and 4 × 1017 are statistically higher (p < 0. 01) than samples treated with dose of 5×1016 and 1 ×1017, as well as the control samples.

  8. Modified ion exchange resins - synthesis and properties. Pt. 1

    Energy Technology Data Exchange (ETDEWEB)

    Doescher, F.; Klein, J.; Pohl, F.; Widdecke, H.

    1982-01-22

    Sulfomethylated resins are prepared by polymer analogous reactions, starting from macroporous poly(styrene-co-divinylbenzene) matrices. Different reaction paths are discussed and used in the synthesis. Sulfomethylation can be achieved by reaction of a chloromethylated resin with dimethyl sulfide and sodium sulfonate or alternatively by oxidation of polymer-bound thiol groups. Both methods give high conversions as shown by IR spectra and titration of the sulfonic acid groups. Poly(1-(4-hydroxysulfomethylphenyl)ethylene) (3) is obtained by reaction of poly(1-(4-hydroxyphenyl)ethylene) (2) resin with formaldehyde/sodium sulfonate. The thermal stability, catalytic activity, and ion exchange equilibria of the sulfomethylated resin are investigated.

  9. Properties of the Excited States of Molecular Ions.

    Science.gov (United States)

    1981-04-13

    photafragmem spmuum for 0; obtained for seperatkon enrgy W =0 from 5770 to 5860 A. The noted tranisition wavelength@ are for the 0;(b, v1 =4-a. v" 411 had...rotational levels. We shall discuss this point in more detail In a following section. 8 B. Dissociation enrgies of he N levels 7 Before attempting to...NO, molecules, and should the mystem have turl Idth, sufficient (-0.5 oV) vibrational enrgy , the ,O will Wt Is 1.0 Tor 11,0, ions of mass 60 were

  10. Crystal lattice properties fully determine short-range interaction parameters for alkali and halide ions

    CERN Document Server

    Mao, Albert H; 10.1063/1.4742068

    2012-01-01

    Accurate models of alkali and halide ions in aqueous solution are necessary for computer simulations of a broad variety of systems. Previous efforts to develop ion force fields have generally focused on reproducing experimental measurements of aqueous solution properties such as hydration free energies and ion-water distribution functions. This dependency limits transferability of the resulting parameters because of the variety and known limitations of water models. We present a solvent-independent approach to calibrating ion parameters based exclusively on crystal lattice properties. Our procedure relies on minimization of lattice sums to calculate lattice energies and interionic distances instead of equilibrium ensemble simulations of dense fluids. The gain in computational efficiency enables simultaneous optimization of all parameters for Li+, Na+, K+, Rb+, Cs+, F-, Cl-, Br-, and I- subject to constraints that enforce consistency with periodic table trends. We demonstrate the method by presenting lattice-d...

  11. Heavy metal ion uptake properties of polystyrene-supported chelating polymer resins

    Indian Academy of Sciences (India)

    A Ravikumar Reddy; K Hussain Reddy

    2003-06-01

    Metal ion uptake properties of polystyrene-supported chelating polymer resins functionalized with (i) glycine, (ii) hydroxy benzoic acid, (iii) Schiff base and (iv) diethanol amine have been investigated. The effects of pH, time and initial concentration on the uptake of metal ions have been studied. The uptake of metal ion depends on pH. The resins are more selective at pH 10 for Pb(II) and Hg(II), whereas at pH 6 they are found to be Cd(II) and Cr(VI) selective. Metal ion uptake properties of resins follow Freundlich’s equation. The resins are recyclable and are therefore employed for the removal of heavy metal pollutants from industrial waste water.

  12. The influence of silver ion exchange on the luminescence properties of Er-Yb silicate glasses

    Science.gov (United States)

    Stanek, S.; Nekvindova, P.; Svecova, B.; Vytykacova, S.; Mika, M.; Oswald, J.; Barkman, O.; Spirkova, J.

    2017-10-01

    A set of zinc-silicate glasses with different ratios of Er-Yb as well amount of Zn was fabricated. The preparation of silver doped glasses was carried out using the Ag-Na ion-exchange method to enhance Er-Yb luminescence properties of the material. The samples were also annealed for 1-5 h to further support the creation of silver nanoparticles. Intensive absorption at 980 nm was observed in absorption spectra after ion exchange and annealing as well. Also luminescence spectra in the near-infrared range were measured and results showed positive effect of ion exchange process on luminescence properties. Luminescence intensity at 1530 nm was increased almost three times. Possible mechanisms responsible for the increase of the luminescence intensity are also discussed in this paper. We suggest that the enhancement of erbium luminescence intensity is caused by the energy transfer from isolated Ag+ ions to Er.

  13. Synthesis, characterization, thermal and DNA-binding properties of new zinc complexes with 2-hydroxyphenones.

    Science.gov (United States)

    Mrkalić, Emina; Zianna, Ariadni; Psomas, George; Gdaniec, Maria; Czapik, Agnieszka; Coutouli-Argyropoulou, Evdoxia; Lalia-Kantouri, Maria

    2014-05-01

    The neutral mononuclear zinc complexes with 2-hydroxyphenones (ketoH) having the formula [Zn(keto)2(H2O)2] and [Zn(keto)2(enR)], where enR stands for a N,N'-donor heterocyclic ligand such as 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen) or 2,2'-dipyridylamine (dpamH), have been synthesized and characterized by IR, UV and (1)H NMR spectroscopies. The 2-hydroxyphenones are chelated to the metal ion through the phenolate and carbonyl oxygen atoms. The crystal structures of [bis(2-hydroxy-4-methoxy-benzophenone)(2,2'-bipyridine)zinc(II)] dimethanol solvate and [bis(2-hydroxy-benzophenone)(2,2'-bipyridine)zinc(II)] dimethanol solvate have been determined by X-ray crystallography. The thermal stability of the zinc complexes has been investigated by simultaneous TG/DTG-DTA technique. The ability of the complexes to bind to calf-thymus DNA (CT DNA) has been studied by UV-absorption and fluorescence emission spectroscopy as well as viscosity measurements. UV studies of the interaction of the complexes with DNA have shown that they can bind to CT DNA and the corresponding binding constants to DNA have been calculated and evaluated. The complexes most probably bind to CT DNA via intercalation as concluded by studying the viscosity of a DNA solution in the presence of the complexes. Competitive studies with ethidium bromide (EB) have shown that the reported complexes can displace the DNA-bound EB, suggesting strong competition with EB for the intercalation site.

  14. Effect of nitrogen ion implantation on the structural and optical properties of indium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sethi, Riti; Aziz, Anver; Siddiqui, Azher M., E-mail: amsiddiqui@jmi.ac.in [Department of Physics, Jamia Millia Islamia, New Delhi-110025 (India); Kumar, Pravin [Inter University Accelerator Center, Aruna Asaf Ali Marg, New Delhi-110067 (India); Khan, Sameen Ahmed [Department of Mathematics and Sciences, College of Arts and Applied Sciences (CAAS) Dhofar University, Salalah, Sultanate of Oman (Oman)

    2016-06-10

    : We report here synthesis and subsequent nitrogen ion implantation of indium oxide (In{sub 2}O{sub 3}) thin films. The films were implanted with 25 keV N{sup +} beam for different ion doses between 3E15 to 1E16 ions/cm{sup 2}. The resulting changes in structural and optical properties were investigated using XRD, SEM-EDAX and UV-Vis Spectrometry. XRD studies reveal decrease in crystallite size from 20.06 to 12.42 nm with increase in ion dose. SEM micrographs show an increase in the grain size from 0.8 to 1.35 µm with increase in ion dose because of the agglomeration of the grains. Also, from EDAX data on pristine and N-implanted thin films the presence of indium and oxygen without any traces of impurity elements could be seen. However, at lower ion doses such as 3E15 and 5E15 ions/cm{sup 2}, no evidence of the presence of nitrogen ion was seen. However, for the ion dose of 1E16 ions/cm{sup 2}, evidence of presence of nitrogen can be seen in the EDAX data. Band gap calculations reveal a decrease in band gap from 3.54 to 3.38 eV with increasing ion dose. However, the band gap was found to again show an increase to 3.58 eV at the highest ion dose owing to quantum confinement effect.

  15. Properties of Laser-Produced Highly Charged Heavy Ions for Direct Injection Scheme

    CERN Document Server

    Sakakibara, Kazuhiko; Hayashizaki, Noriyosu; Ito, Taku; Kashiwagi, Hirotsugu; Okamura, Masahiro

    2005-01-01

    To accelerate highly charged intense ion beam, we have developed the Direct Plasma Injection Scheme (DPIS) with laser ion source. In this scheme an ion beam from a laser ion source is injected directly to a RFQ linac without a low energy beam transport (LEBT) and the beam loss in the LEBT can be avoided. We achieved high current acceleration of carbon ions (60mA) by DPIS with the high current optimized RFQ. As the next setp we will use heavier elements like Ag, Pb, Al and Cu as target in LIS (using CO2, Nd-YAG or other laser) for DPIS and will examine properties of laser-produced plasma (the relationship of between charge state and laser power density, the current dependence of the distance from the target, etc).

  16. DNA binding property and antitumor evaluation of xanthone with dimethylamine side chain.

    Science.gov (United States)

    Shen, Rui; Wang, Weihua; Yang, Gengliang

    2014-05-01

    In this work, a xanthone derivative was obtained by cationic modification of the free hydroxyl group of xanthone with dimethylamine group of high pKa value. The interactions of xanthones with DNA were investigated by spectroscopic methods, electrophoretic migration assay and polymerase chain reaction test. Results indicate that xanthones can intercalate into the DNA base pairs by the hydrophobic plane and the xanthone with dimethylamine side chain may also bind the DNA phosphate framework by the basic amine alkyl chain, thus showing a better DNA binding ability than the xanthone. Furthermore, inhibition on tumor cells (ECA109, SGC7901, GLC-82) proliferation of xanthones were evaluated by MTT method. Analysis results show that the xanthone with dimethylamine side chain exhibits more effective inhibition activity against three cancer cells than the xanthone. The effects on the inhibition of tumor cells in vitro agree with the studies of DNA binding. It means that the amine alkyl chain would play an important role in its antitumor activity and DNA binding property.

  17. Effect of Aging on the Mechanical Properties of Li-Ion Cell Components - A Preliminary Look

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Lei; Zhang, Chao; Santhanagopalan, Shriram; Pesaran, Ahmad

    2016-05-03

    DOE/VTO/ES initiated the Computer Aided Engineering for Batteries (CAEBAT) in 2010. CAEBAT had a strong focus on building electrochemical-thermal models that simulate the performance of lithium-ion batteries. Since the start of CAEBAT-2 projects in FY14, our emphasis has been on safety aspects -- mechanical deformation in particular. This presentation gives a preliminary look at the effect of aging on the mechanical properties of lithium-ion cell components.

  18. Polarizabilities and Other Properties of the td Muons Molecular Ion

    Science.gov (United States)

    Bhatia, A. K.; Drachman, Richard J.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Wavefunctions of Hylleraas type were used earlier to calculate energy levels of muonic systems. Recently, we found in the case of the molecular ions H2+, D2+ and HD+ that it was necessary to include high powers of the internuclear distance in the Hylleraas functions to localize the nuclear motion when treating the ions as three-body systems without invoking the Born-Oppenheimer approximation. We try the same approach in a muonic system, td(mu-). Improved convergence is obtained for J = 0 and 1 states for shorter expansions when we use this type of generalized Hylleraas function, but as the expansion length increases the high powers are no longer useful. We obtain good energy values for the two lowest J = 0 and J = 1 states and compare them with the best earlier calculations. Expectation values are obtained for various operators, the Fermi contact parameters, and the permanent quadrupole moment. The cusp conditions are also calculated. The polarizability of the ground state is then calculated using second-order perturbation theory with intermediate J = 1 pseudostates. It should be possible to measure the polarizability by observing Rydberg states of atoms with td(mu-) acting as the nucleus.

  19. Luminescent Properties of Samarium Ion in Calcium Molybdate

    Institute of Scientific and Technical Information of China (English)

    胡运生; 庄卫东; 叶红齐

    2004-01-01

    Trivalent samarium ion (Sm3+) activated calcium molybdate (CaMoO4) phosphor was prepared by solid-state reaction in air. The XRD pattern of the powder CaMoO4∶ Sm shows that the CaMoO4∶ Sm single phase is developed fully through our preparation procedure. The excitation spectrum of CaMoO4∶ Sm is composed of a broad absorption of host and some sharp lines of the f-f transition absorption of Sm3+. Illustrated in photoluminescence spectrum, CaMoO4 doped with Sm3+ displays orange red emission that is ascribed to the inner 4f5 electron transitions 6H7/2(orange)and 6H9/2(red)of Sm3+. Different from the sites of Sm3+ in CdWO4, the Sm3+ ions substitute for the Ca2+ and form only one type emission center in the CaMoO4 crystal lattice.

  20. Similarities between N-acetylcysteine and Glutathione in Binding to Lead(II) Ions

    OpenAIRE

    Sisombath, Natalie S.; Jalilehvand, Farideh

    2015-01-01

    N -acetylcysteine is a natural thiol-containing antioxidant, a precursor for cysteine and glutathione, and a potential detoxifying agent for heavy metal ions. However, previous accounts of the efficiency of N-acetylcysteine (H2NAC) in excretion of lead are few and contradicting. Here we report results on the nature of lead(II) complexes formed with N-acetylcysteine in aqueous solution, which were obtained by combining information from several spectroscopic methods, including 207Pb, 13C and 1H...

  1. Ion adsorption on oxides. Surface charge formation and cadmium binding on rutile and hematite.

    NARCIS (Netherlands)

    Fokkink, L.G.J.

    1987-01-01

    The adsorption of charge-determining (H +and OH -) and cadmium ions on rutile (TiO 2 ) and hematite (α-Fe 2 O 3 ) has been studied

  2. Tubulin Binding and Polymerization Promoting Properties of Tubulin Polymerization Promoting Proteins Are Evolutionarily Conserved.

    Science.gov (United States)

    Oláh, Judit; Szénási, Tibor; Szabó, Adél; Kovács, Kinga; Lőw, Péter; Štifanić, Mauro; Orosz, Ferenc

    2017-02-21

    Tubulin polymerization promoting proteins (TPPPs) constitute a eukaryotic protein family. There are three TPPP paralogs in the human genome, denoted as TPPP1-TPPP3. TPPP1 and TPPP3 are intrinsically unstructured proteins (IUPs) that bind and polymerize tubulin and stabilize microtubules, but TPPP2 does not. Vertebrate TPPPs originated from the ancient invertebrate TPPP by two-round whole-genome duplication; thus, whether the tubulin/microtubule binding function of TPPP1 and TPPP3 is a newly acquired property or was present in the invertebrate orthologs (generally one TPPP per species) has been an open question. To answer this question, we investigated a TPPP from a simple and early branching animal, the sponge Suberites domuncula. Bioinformatics, biochemical, immunochemical, spectroscopic, and electron microscopic data showed that the properties of the sponge protein correspond to those of TPPP1; namely, it is an IUP that strongly binds tubulin and induces its polymerization, proving that these features of animal TPPPs have been evolutionarily conserved.

  3. Tuning riboswitch-mediated gene regulation by rational control of aptamer ligand binding properties.

    Science.gov (United States)

    Rode, Ambadas B; Endoh, Tamaki; Sugimoto, Naoki

    2015-01-12

    Riboswitch-mediated control of gene expression depends on ligand binding properties (kinetics and affinity) of its aptamer domain. A detailed analysis of interior regions of the aptamer, which affect the ligand binding properties, is important for both understanding natural riboswitch functions and for enabling rational design of tuneable artificial riboswitches. Kinetic analyses of binding reaction between flavin mononucleotide (FMN) and several natural and mutant aptamer domains of FMN-specific riboswitches were performed. The strong dependence of the dissociation rate (52.6-fold) and affinity (100-fold) on the identities of base pairs in the aptamer stem suggested that the stem region, which is conserved in length but variable in base-pair composition and context, is the tuning region of the FMN-specific aptamer. Synthetic riboswitches were constructed based on the same aptamer domain by rationally modifying the tuning regions. The observed 9.31-fold difference in the half-maximal effective concentration (EC50) corresponded to a 11.6-fold difference in the dissociation constant (K(D)) of the aptamer domains and suggested that the gene expression can be controlled by rationally adjusting the tuning regions.

  4. Assessment of Density Functional Methods for Exciton Binding Energies and Related Optoelectronic Properties

    CERN Document Server

    Lee, Jui-Che; Lin, Shiang-Tai

    2015-01-01

    The exciton binding energy, the energy required to dissociate an excited electron-hole pair into free charge carriers, is one of the key factors to the optoelectronic performance of organic materials. However, it remains unclear whether modern quantum-mechanical calculations, mostly based on Kohn-Sham density functional theory (KS-DFT) and time-dependent density functional theory (TDDFT), are reliably accurate for exciton binding energies. In this study, the exciton binding energies and related optoelectronic properties (e.g., the ionization potentials, electron affinities, fundamental gaps, and optical gaps) of 121 small- to medium-sized molecules are calculated using KS-DFT and TDDFT with various density functionals. Our KS-DFT and TDDFT results are compared with those calculated using highly accurate CCSD and EOM-CCSD methods, respectively. The omegaB97, omegaB97X, and omegaB97X-D functionals are shown to generally outperform (with a mean absolute error of 0.36 eV) other functionals for the properties inve...

  5. Measurement of Cadmium Ion in the Presence of Metal-Binding Biopolymers in Aqueous Sample

    Science.gov (United States)

    Pu, Jian; Fukushi, Kensuke

    2013-01-01

    In aqueous environment, water-soluble polymers are effectively used to separate free metal ions from metal-polymer complexes. The feasibilities of four different analytical techniques, cadmium ion-selective electrode, dialysis sack, chelate disk cartridge, and ultrafiltration, in distinguishing biopolymer-bound and nonbound cadmium in aqueous samples were investigated. And two different biopolymers were used, including bovine serum albumin (BSA) and biopolymer solution extracted from cultivated activated sludge (ASBP). The ISE method requires relatively large amount of sample and contaminates sample during the pretreatment. After the long reaction time of dialysis, the equilibrium of cadmium in the dialysis sack would be shifted. Due to the sample nature, chelate disk cartridge could not filter within recommended time, which makes it unavailable for biopolymer use. Ultrafiltration method would not experience the difficulties mentioned above. Ultrafiltration method measuring both weakly and strongly bound cadmium was included in nominally biopolymer-cadmium complex. It had significant correlation with the Ion-selective electrode (ISE) method (R2 = 0.989 for BSA, 0.985 for ASBP). PMID:24194678

  6. Measurement of Cadmium Ion in the Presence of Metal-Binding Biopolymers in Aqueous Sample

    Directory of Open Access Journals (Sweden)

    Jian Pu

    2013-01-01

    Full Text Available In aqueous environment, water-soluble polymers are effectively used to separate free metal ions from metal-polymer complexes. The feasibilities of four different analytical techniques, cadmium ion-selective electrode, dialysis sack, chelate disk cartridge, and ultrafiltration, in distinguishing biopolymer-bound and nonbound cadmium in aqueous samples were investigated. And two different biopolymers were used, including bovine serum albumin (BSA and biopolymer solution extracted from cultivated activated sludge (ASBP. The ISE method requires relatively large amount of sample and contaminates sample during the pretreatment. After the long reaction time of dialysis, the equilibrium of cadmium in the dialysis sack would be shifted. Due to the sample nature, chelate disk cartridge could not filter within recommended time, which makes it unavailable for biopolymer use. Ultrafiltration method would not experience the difficulties mentioned above. Ultrafiltration method measuring both weakly and strongly bound cadmium was included in nominally biopolymer-cadmium complex. It had significant correlation with the Ion-selective electrode (ISE method (R2=0.989 for BSA, 0.985 for ASBP.

  7. Effect of Specific Adsorption of Ions on Electrokinetic Properties of Variable Charge Soils

    Institute of Scientific and Technical Information of China (English)

    ZHANGHONG; ZHANGXIAO-NIAN

    1991-01-01

    Studies were carried out by using electrophoretic method on the effects of the specific adsorption of the anions,such as SO42-,PO43-,and F- ions,the cations,such as Ca2+,Mn2+,Zn2+,and Cu2+,ions,and the anions and cations coexisting,such as Zn2+ and SO42= ions,on electrokinetic properties of the red soils as typical variable charge soils in China concerning variation in the specific ion species and concentrations,with an emphasis on the interaction between soil colloid surfaces and the ions in soil solutions.The results showed that the adsorption of specific ions led to a very pronounced decrease in zeta potentials of the soil colloids and a shift of the IEPs to lower values for specific anions,and an obvious increase in zeta potentials of the soil colloids and a shift of the IEPs to higher values for specific cations.Under circumstances of the specific anions and cations coexisting,for instance,Zn2+ and SO42- ions,the zeta potentials changed with values higher than the value for SO42- alone and lower than that for Zn2+ alone,and the IEP was between that for Zn2+ and that for SO42-.The adsorption of Zn2+ and Cu2+ ions resulted in a reversal of the zeta potentials,and appearance of two IEPs for Zn2+ and no IEP for Cu2+,exhibiting interesting special effects of these kinds of metal ions.The higher the concentrations of the ions,the greater the change of the electrokinetic properties.

  8. Direct hydrothermal synthesis and magnetic property of titanate nanotubes doped magnetic metal ions

    Institute of Scientific and Technical Information of China (English)

    Meili Wang; Gongbao Song; Jian Li; Landong Miao; Baoshu Zhang

    2008-01-01

    Pure titanate nanotubes and titanate nanotubes doped with Fe3+/Ni2+/Mn2+ ions were synthesized by the hydrothermal method. In this process, titanate nanotubes were first prepared synchronously with doping Fe3+/Ni2+/Mn2+ ions. The morphology,structure, thermal stability and magnetic property of titanate nanotubes were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), and magnetic measurement. The titanate nanotubes transformed into the anatase titania nanocrystals,and further the mixture of anatase and rutile titania along with increasing temperature. The results indicate that the titanate nanotubes doped with Fe3+/Ni2+/Mn2+ ions are paramagnetic behaviors.

  9. Ion beam sputter deposition of Ag films: Influence of process parameters on electrical and optical properties, and average grain sizes

    Energy Technology Data Exchange (ETDEWEB)

    Bundesmann, C., E-mail: carsten.bundesmann@iom-leipzig.de; Feder, R.; Gerlach, J.W.; Neumann, H.

    2014-01-31

    Ion beam sputter deposition is used to grow several sets of Ag films under systematic variation of ion beam parameters, such as ion species and ion energy, and geometrical parameters, such as ion incidence angle and polar emission angle. The films are characterized concerning their thickness by profilometry, their electrical properties by 4-point-probe-measurements, their optical properties by spectroscopic ellipsometry, and their average grain sizes by X-ray diffraction. Systematic influences of the growth parameters on film properties are revealed. The film thicknesses show a cosine-like angular distribution. The electrical resistivity increases for all sets with increasing emission angle and is found to be considerably smaller for Ag films grown by sputtering with Xe ions than for the Ag films grown by sputtering with Ar ions. Increasing the ion energy or the ion incidence angle also increases the electrical resistivity. The optical properties, which are the result of free charge carrier absorption, follow the same trends. The observed trends can be partly assigned to changes in the average grain size, which are tentatively attributed to different energetic and angular distributions of the sputtered and back-scattered particles. - Highlights: • Ion beam sputter deposition under systematic variation of process parameters. • Film characterization: thickness, electrical, optical and structural properties. • Electrical resistivity changes considerably with ion species and polar emission angle. • Electrical and optical data reveal a strong correlation with grain sizes. • Change of film properties related to changing properties of film-forming particles.

  10. Regulating rheological properties of binding medium for additive technologies using polyvinylpyrrolidone

    Science.gov (United States)

    Zemtsov, A. E.; Golunov, A. V.; Golunova, A. S.

    2017-08-01

    The paper considers the process of discreet element (droplet) formation in additive manufacturing. The urgency of the research is proved by using the inkjet method while forming fine powders in additive technologies. The binder rheological properties determine the formation accuracy for a discrete element of a three-dimensional part. The article suggests indicators that allow an operative assessment of a binder suitability for usage in the fine powder formation process. As a result of the research, the geometric parameters of the jetting apparatus forming the powder according to the Binder Jetting technology were aligned with the compositions studied. A comparative analysis of the known binders rheological properties with the prepared ones is carried out. The use of polyvinylpyrrolidone is proposed to regulate the rheological properties of binding materials used in additive technologies.

  11. High affinity binding of /sup 125/I-labeled mouse interferon to a specific cell surface receptor. II. Analysis of binding properties

    Energy Technology Data Exchange (ETDEWEB)

    Aguet, M.; Blanchard, B.

    1981-12-01

    Direct ligand-binding studies with highly purified /sup 125/I-labeled virus-induced mouse interferon on mouse lymphoma L 1210 cells revealed a direct correlation of specific high-affinity binding with the biologic response to interferon. Neutralization of the antiviral effect by anti-interferon gamma globulin occurred at the same antibody concentration as the inhibition of specific binding. These results suggest that specific high-affinity binding of /sup 125/I-interferon occurred at a biologically functional interferon receptor. Competitive inhibition experiments using /sup 125/I- and /sup 127/I-labeled interferon provided strong evidence that the fraction of /sup 125/I-interferon inactivated upon labeling did not bind specifically. Scatchard analysis of the binding data yielded linear plots and thus suggested that interferon binds to homogeneous noncooperative receptor sites. In contrast to a characteristic property of several peptide hormone systems, binding of /sup 125/I-interferon to its specific receptor did not induce subsequent ligand degradation. At 37/sup o/ bound interferon was rapidly released in a biologically active form without evidence for molecular degradation. The expression of interferon receptors was not modified by treatment with interferon. Trypsin treatment of target cells and inhibition of protein synthesis abolished the specific binding of /sup 125/I-interferon. Three major molecular weight species of Newcastle disease virus-induced mouse C 243 cell interferon were isolated, separated, and identified as mouse ..cap alpha.. and ..beta.. interferons. These interferons were shown to inhibit competitively the specific binding of the highly purified labeled starting material thus providing evidence for a common receptor site for mouse interferon.

  12. All three Ca[superscript 2+]-binding loops of photoproteins bind calcium ions: The crystal structures of calcium-loaded apo-aequorin and apo-obelin

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Lu; Vysotski, Eugene S.; Markova, Svetlana V.; Liu, Zhi-Jie; Lee, John; Rose, John; Wang, Bi-Cheng (Georgia)

    2010-07-13

    The crystal structures of calcium-loaded apoaequorin and apo-obelin have been determined at resolutions 1.7 {angstrom} and 2.2 {angstrom}, respectively. A calcium ion is observed in each of the three EF-hand loops that have the canonical calcium-binding sequence, and each is coordinated in the characteristic pentagonal bipyramidal configuration. The calcium-loaded apo-proteins retain the same compact scaffold and overall fold as the unreacted photoproteins containing the bound substrate, 2-hydroperoxycoelenterazine, and also the same as the Ca{sup 2+}-discharged obelin bound with the product, coelenteramide. Nevertheless, there are easily discerned shifts in both helix and loop regions, and the shifts are not the same between the two proteins. It is suggested that these subtle shifts are the basis of the ability of these photoproteins to sense Ca{sup 2+} concentration transients and to produce their bioluminescence response on the millisecond timescale. A mechanism of intrastructural transmission of the calcium signal is proposed.

  13. The effect of ion implantation on the tribomechanical properties of carbon fibre reinforced polymers

    Energy Technology Data Exchange (ETDEWEB)

    Mistica, R.; Sood, D.K. [Royal Melbourne Inst. of Tech., VIC (Australia); Janardhana, M.N. [Deakin University, Geelong, VIC (Australia). School of Engineering and Technology

    1993-12-31

    Graphite fibre reinforced epoxy composite material (GFRP) is used extensively in the aerospace and other industries for structural application. The trend is to address the 20 to 30 year life endurance of this material in service. Mechanical joints in air crafts are exposed to dynamic loads during service and wear may be experienced by the composite material joint. Generally it has been shown that graphite fibre reinforced polymers have superior wear and friction properties as compared with the unfilled polymers. In the described experiment, ion implantation was used as a novel surface treatment. Wear and friction of a polymer composite material (GFRP) was studied and ion implantation was used in order to observe the effect on the tribomechanical properties of the material. It was found that ion implantation of C on GFRP sliding against Ti changes the tribological properties of the system, and in particular decreases the coefficient of friction and wear. 4 refs., 2 figs.

  14. Investigating change of properties in gallium ion irradiation patterned single-layer graphene

    Science.gov (United States)

    Wang, Quan; Dong, Jinyao; Bai, Bing; Xie, Guoxin

    2016-10-01

    Besides its excellent physical properties, graphene promises to play a significant role in electronics with superior properties, which requires patterning of graphene for device integration. Here, we presented the changes in properties of single-layer graphene before and after patterning using gallium ion beam. Combined with Raman spectra of graphene, the scanning capacitance microscopy (SCM) image confirmed that a metal-insulator transition occurred after large doses of gallium ion irradiation. The changes in work function and Raman spectra of graphene indicated that the defect density increased as increasing the dose and a structural transition occurred during gallium ion irradiation. The patterning width of graphene presented an increasing trend due to the scattering influence of the impurities and the substrate.

  15. Modeling the microscopic electrical properties of thrombin binding aptamer (TBA) for label-free biosensors

    Science.gov (United States)

    Alfinito, Eleonora; Reggiani, Lino; Cataldo, Rosella; De Nunzio, Giorgio; Giotta, Livia; Guascito, Maria Rachele

    2017-02-01

    Aptamers are chemically produced oligonucleotides, able to bind a variety of targets such as drugs, proteins and pathogens with high sensitivity and selectivity. Therefore, aptamers are largely employed for producing label-free biosensors (aptasensors), with significant applications in diagnostics and drug delivery. In particular, the anti-thrombin aptamers are biomolecules of high interest for clinical use, because of their ability to recognize and bind the thrombin enzyme. Among them, the DNA 15-mer aptamer (TBA), has been widely explored around the possibility of using it in aptasensors. This paper proposes a microscopic model of the electrical properties of TBA and of the aptamer-thrombin complex, combining information from both structure and function, following the issues addressed in an emerging branch of electronics known as proteotronics. The theoretical results are compared and validated with measurements reported in the literature. Finally, the model suggests resistance measurements as a novel tool for testing aptamer-target affinity.

  16. Theoretical and Experimental: The Synthetic and Anion-Binding Properties of Tripodal Salicylaldehyde Derivatives

    Directory of Open Access Journals (Sweden)

    Zhong-Jie Xu

    2016-05-01

    Full Text Available A series of colorimetric anion probes 1–6 containing OH and NO2 groups were synthesized, and their recognition properties toward various anions were investigated by visual observation, ultraviolet–visible spectroscopy, fluorescence, 1H nuclear magnetic resonance titration spectra and theoretical investigation. Nanomaterials of three compounds 2–4 were prepared successfully. Four compounds 3–6 that contain electron-withdrawing substituents showed a high binding ability for AcO−. The host–guest complex formed through a 1:1 binding ratio, and color changes were detectable during the recognition process. Theoretical investigation analysis revealed that an intramolecular hydrogen bond existed in the structures of compounds and the roles of molecular frontier orbitals in molecular interplay. These studies suggested that this series of compounds could be used as colorimetric probes to detect of AcO−.

  17. Rat neuronal nicotinic acetylcholine receptors containing a7 subunit: pharmacological properties of ligand binding and function

    Institute of Scientific and Technical Information of China (English)

    Yingxian XIAO; Galya R ABDRAKHMANOVA; Maryna BAYDYUK; Susan HERNANDEZ; Kenneth J KELLAR

    2009-01-01

    Aim: To compare pharmacological properties of heterologously expressed homomeric a7 nicotinic acetylcholine receptors (a.7 nAChRs) with those of native nAChRs containing a.7 subunit (a.7* nAChRs) in rat hippocampus and cerebral cortex. Methods: We established a stably transfected HEK-293 cell line that expresses homomeric rat a7 nAChRs. We studies ligand binding profiles and functional properties of nAChRs expressed in this cell line and native rat a.7* nAChRs in rat hippocampus and cerebral cortex. We used [125IJ-a-bungarotoxin to compare ligand binding profiles in these cells with those in rat hippocampus and cerebral cortex. The functional properties of the a.7 nAChRs expressed in this cell line were studied using whole-cell current recording.Results: The newly established cell line, KXa7Rl, expresses homomeric a7 nAChRs that bind [125I]-a-bungarotoxin with a Kd value of 0.38±0.06 nmol/L, similar to Kj values of native rat a.7* nAChRs from hippocampus (Kd=0.28±0.03 nmol/L) and cerebral cortex (Kd=0.33±0.05 nmol/L). Using whole-cell current recording, the homomeric a7 nAChRs expressed in the cells were activated by acetylcholine and (-)-nicotine with EC50 values of 280±19 nmol/L and 180±40 nmol/L, respectively. The acetylcholine activated currents were potently blocked by two selective antagonists of a.7 nAChRs, a-bungarotoxin (IC5o=19±2 nmol/L) and methyllycaconitine (IC50=100±10 pmol/L). A comparative study of ligand binding profiles, using 13 nicotinic ligands, showed many similarities between the homomeric a.7 nAChRs and native a.7* receptors in rat brain, but it also revealed several notable differences.Conclusion: This newly established stable cell line should be very useful for studying the properties of homomeric a7 nAChRs and comparing these properties to native a.7* nAChRs.

  18. Discovery of a novel selective PPARγ ligand with partial agonist binding properties by integrated in silico / in vitro work flow

    DEFF Research Database (Denmark)

    Kouskoumvekaki, Irene; Petersen, Rasmus K.; Fratev, Filip Filipov

    2013-01-01

    agonist binding properties. Toward this end we applied an integrated in silico/in vitro workflow, based on pharmacophore-and structure-based virtual screening of the ZINC library, coupled with competitive binding and transactivation assays, and adipocyte differentiation and gene expression studies. Hit...

  19. Effects of extraction procedures on metal binding properties of extracellular polymeric substances (EPS) from anaerobic granular sludges

    NARCIS (Netherlands)

    Abzac, D' P.; Bordas, F.; Hullebusch, E.; Lens, P.N.L.; Guibaud, G.

    2010-01-01

    The effects of the extraction procedure of extracellular polymeric substances (EPS) on their proton/metal binding properties were studied. Nine extraction procedures (one control, four physical and four chemical procedures) were applied to four types of anaerobic granular sludges. The binding capaci

  20. Optical and dielectric properties of ion beam irradiated Ag/polymethyl methacrylate nanocomposites.

    Science.gov (United States)

    Gavade, Chaitali; Singh, N L; Khanna, P K

    2014-08-01

    Changes in the dielectric, optical, structural and thermal properties of PMMA/silver nanocomposites of different concentrations of silver nanoparticles (5%, 10%, 15%) due to swift heavy ion irradiation were studied by means of impedance gain phase analyzer, UV-visible spectroscopy, X-ray diffraction and differential scanning calorimetry. Samples were irradiated with 120 MeV Si-ions at fluences of 1 x 10(11), 1 x 10(12) ions/cm2. Dependence of dielectric properties on frequency, ion beam fluence and filler concentration was studied. The results revealed the enhancement in dielectric properties after dopping nanoparticles and also upon irradiation. Optical properties like band gap was estimated for pure polymer and nanocomposite films from their optical absorption spectra in the wavelength region 200-800 nm. It was found that the band gap value shifted to lower energy (from 4.58 eV to 3.21 eV) on doping with silver nanoparticles. Differential scanning calorimetry analysis revealed a decrease in the glass transition temperature upon irradiation, which may be attributed to scissioning of polymer chain due to ion beam irradiation which is also confirmed with XRD analysis.

  1. Molecular biology and biophysical properties of ion channel gating pores.

    Science.gov (United States)

    Moreau, Adrien; Gosselin-Badaroudine, Pascal; Chahine, Mohamed

    2014-11-01

    The voltage sensitive domain (VSD) is a pivotal structure of voltage-gated ion channels (VGICs) and plays an essential role in the generation of electrochemical signals by neurons, striated muscle cells, and endocrine cells. The VSD is not unique to VGICs. Recent studies have shown that a VSD regulates a phosphatase. Similarly, Hv1, a voltage-sensitive protein that lacks an apparent pore domain, is a self-contained voltage sensor that operates as an H⁺ channel. VSDs are formed by four transmembrane helices (S1-S4). The S4 helix is positively charged due to the presence of arginine and lysine residues. It is surrounded by two water crevices that extend into the membrane from both the extracellular and intracellular milieus. A hydrophobic septum disrupts communication between these water crevices thus preventing the permeation of ions. The septum is maintained by interactions between the charged residues of the S4 segment and the gating charge transfer center. Mutating the charged residue of the S4 segment allows the water crevices to communicate and generate gating pore or omega pore. Gating pore currents have been reported to underlie several neuronal and striated muscle channelopathies. Depending on which charged residue on the S4 segment is mutated, gating pores are permeant either at depolarized or hyperpolarized voltages. Gating pores are cation selective and seem to converge toward Eisenmann's first or second selectivity sequences. Most gating pores are blocked by guanidine derivatives as well as trivalent and quadrivalent cations. Gating pores can be used to study the movement of the voltage sensor and could serve as targets for novel small therapeutic molecules.

  2. Tailoring surface properties of polymeric blend material by ion beam bombardment

    Science.gov (United States)

    Ali, Z. I.; Abdul-Kader, A. M.; Rizk, R. A. M.; Ali, M.

    2013-10-01

    In this work, LDPE/SBR polymer blend samples were bombarded with 130 keV He and 320 keV Ar ions at different fluencies ranging from 1×1013 to 2×1016 ions cm-2. The changes in surface properties of the ion-bombarded polymers were investigated with ultraviolet-visible (UV-vis) spectroscopy, Photoluminescence (PL) and energy dispersive X-ray (EDX) techniques. The variations in the wettability, surface free energy and spreading coefficient of ion beam bombarded LDPE polymer blend samples have been studied. The UV-vis analysis revealed that the transmission spectra shifted towards lower energy region after bombardment with increasing ion fluence. This shift clearly reflects decrease in optical band gap. A remarkable decrease in the PL intensity with increasing ion beam fluence was observed. The EDX study indicates the oxygen uptake increases with increasing ion fluence. Contact angle measurements showed that wettability, surface free energy and spreading coefficient of LDPE blends samples have increased with increasing ion fluence. This increase in the wettability and surface free energy of the bombarded samples are attributed to formation of oxidized layer on the polymer surface, which apparently occurs after exposure of bombarded samples to the air.

  3. A study on biocompatibility and bactericidal properties of pyrolytic carbon by silver ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Tang, H.Q. [College of Physics and Electronic Information Science, Tianjin Normal University, Tianjin 300074 (China); Liu, T. [College of Physics and Electronic Information Science, Tianjin Normal University, Tianjin 300074 (China); Liu, X. [Tianjin Urinary Surgery Institute, Tianjin 300211 (China); Gu, H.Q. [Tianjin Urinary Surgery Institute, Tianjin 300211 (China); Zhao, J. [College of Physics and Electronic Information Science, Tianjin Normal University, Tianjin 300074 (China)]. E-mail: jiezhao1943@126.com

    2007-02-15

    The biocompatibility and bactericidal properties of Ag{sup +}-implanted pyrolytic carbon were investigated by means of Staphylococcus aureus and Escherichia coli bacteria and some biocompatible experiments. The pyrolytic carbon samples were implanted by silver ions with the dose ranging from 5 x 10{sup 14} to 5 x 10{sup 18} ions/cm{sup 2} at an energy of 70 keV. The silver distribution in pyrolytic carbon was characterized by Rutherford Backscattering Spectrometry (RBS). The results show that the bactericidal rate for both S. aureus and E. coli increase with the ion dose when the silver ion dose is under the saturated dose of 5 x 10{sup 17} ions/cm{sup 2}. The bactericidal rate is over 97% when the ion dose exceeds that value. In comparison with the reference sample, Ag{sup +}-implanted pyrolytic carbon shows a good biocompatibility and without biotoxication by means of cytotoxicity, hemolysis and platelet tests. RBS analyses show that silver atoms penetrate into the sample surface and form a silver-rich surface region which plays an important role in killing bacteria. When the ion dose is not exceed 1 x 10{sup 16} ions/cm{sup 2}, the structure of Ag{sup +}-implanted pyrolytic carbon is kept unchanged maintaining the original biocompatibility.

  4. Structural basis for distinct binding properties of the human galectins to Thomsen-Friedenreich antigen.

    Directory of Open Access Journals (Sweden)

    Cheng-Feng Bian

    Full Text Available The Thomsen-Friedenreich (TF or T antigen, Galβ1-3GalNAcα1-O-Ser/Thr, is the core 1 structure of O-linked mucin type glycans appearing in tumor-associated glycosylation. The TF antigen occurs in about 90% of human cancer cells and is a potential ligand for the human endogenous galectins. It has been reported that human galectin-1 (Gal-1 and galectin-3 (Gal-3 can perform their cancer-related functions via specifically recognizing TF antigen. However, the detailed binding properties have not been clarified and structurally characterized. In this work, first we identified the distinct TF-binding abilities of Gal-1 and Gal-3. The affinity to TF antigen for Gal-3 is two orders of magnitude higher than that for Gal-1. The structures of Gal-3 carbohydrate recognition domain (CRD complexed with TF antigen and derivatives, TFN and GM1, were then determined. These structures show a unique Glu-water-Arg-water motif-based mode as previously observed in the mushroom galectin AAL. The observation demonstrates that this recognition mode is commonly adopted by TF-binding galectins, either as endogenous or exogenous ones. The detailed structural comparisons between Gal-1 and Gal-3 CRD and mutagenesis experiments reveal that a pentad residue motif ((51AHGDA(55 at the loop (g1-L4 connecting β-strands 4 and 5 of Gal-1 produces a serious steric hindrance for TF binding. This motif is the main structural basis for Gal-1 with the low affinity to TF antigen. These findings provide the intrinsic structural elements for regulating the TF-binding activity of Gal-1 in some special conditions and also show certain target and approach for mediating some tumor-related bioactivities of human galectins.

  5. Modifying the morphology and magnetic properties of magnetite nanoparticles using swift heavy ion irradiation

    Science.gov (United States)

    Gokhale, Shubha; Lamba, Subhalakshmi; Kumari, Neha; Singh, Bhupendra; Avasthi, D. K.; Kulkarni, S. K.

    2014-08-01

    Magnetite (Fe3O4) nanospheres of ˜8-11 nm diameter synthesized using a chemical co-precipitation method were deposited as thin films on different substrates using spin coating. The thin films were irradiated with Ag ions at 100 MeV energy. Comparison of unirradiated, as synthesized Fe3O4 nanoparticulate thin film and ion irradiated film shows that irradiation causes dramatic changes in the morphology, structure and magnetic properties. Monte Carlo simulations carried out on this system indicate that the origin of the changes in the magnetic properties lies in the enhanced magnetic anisotropy energy density and reorientation of magnetic easy axis.

  6. Exposure to positively- and negatively-charged plasma cluster ions impairs IgE-binding capacity of indoor cat and fungal allergens

    OpenAIRE

    NISHIKAWA, Kazuo; Fujimura, Takashi; Ota, Yasuhiro; Abe, Takuya; ElRamlawy, Kareem Gamal; Nakano, Miyako; Takado, Tomoaki; Uenishi, Akira; Kawazoe, Hidechika; Sekoguchi, Yoshinori; Tanaka, Akihiko; Ono, Kazuhisa; Kawamoto, Seiji

    2016-01-01

    Background Environmental control to reduce the amount of allergens in a living place is thought to be important to avoid sensitization to airborne allergens. However, efficacy of environmental control on inactivation of airborne allergens is not fully investigated. We have previously reported that positively- and negatively-charged plasma cluster ions (PC-ions) reduce the IgE-binding capacity of crude allergens from Japanese cedar pollen as important seasonal airborne allergens. Cat (Felis do...

  7. Structural and optical properties of vanadium ion-implanted GaN

    Science.gov (United States)

    Macková, A.; Malinský, P.; Jagerová, A.; Sofer, Z.; Klímová, K.; Sedmidubský, D.; Mikulics, M.; Lorinčík, J.; Veselá, D.; Böttger, R.; Akhmadaliev, S.

    2017-09-01

    The field of advanced electronic and optical devices searches for a new generation of transistors and lasers. The practical development of these novel devices depends on the availability of materials with the appropriate magnetic and optical properties, which is strongly connected to the internal morphology and the structural properties of the prepared doped structures. In this contribution, we present the characterisation of V ion-doped GaN epitaxial layers. GaN layers, oriented along the (0 0 0 1) crystallographic direction, grown by low-pressure metal-organic vapour-phase epitaxy (MOVPE) on c-plane sapphire substrates were implanted with 400 keV V+ ions at fluences of 5 × 1015 and 5 × 1016 cm-2. Elemental depth profiling was accomplished by Rutherford Backscattering Spectrometry (RBS) and Secondary Ion Mass Spectrometry (SIMS) to obtain precise information about the dopant distribution. Structural investigations are needed to understand the influence of defect distribution on the crystal-matrix recovery and the desired structural and optical properties. The structural properties of the ion-implanted layers were characterised by RBS-channelling and Raman spectroscopy to get a comprehensive insight into the structural modification of implanted GaN and to study the influence of subsequent annealing on the crystalline matrix reconstruction. Photoluminescence measurement was carried out to check the optical properties of the prepared structures.

  8.  De novo isolation of antibodies with pH-dependent binding properties

    OpenAIRE

    Bonvin, Pauline; Venet, Sophie; Fontaine, Gaëlle; Ravn, Ulla; Gueneau, Franck; Kosco-Vilbois, Marie; Proudfoot, Amanda; Fischer, Nicolas

    2015-01-01

    pH-dependent antibodies are engineered to release their target at a slightly acidic pH, a property making them suitable for clinical as well as biotechnological applications. Such antibodies were previously obtained by histidine scanning of pre-existing antibodies, a labor-intensive strategy resulting in antibodies that displayed residual binding to their target at pH 6.0. We report here the de novo isolation of pH-dependent antibodies selected by phage display from libraries enriched in hist...

  9. Evolution of the receptor binding properties of the influenza A(H3N2) hemagglutinin

    OpenAIRE

    Lin, Yi Pu; Xiong, Xiaoli; Wharton, Stephen A.; Martin, Stephen R.; Coombs, Peter J.; Vachieri, Sebastien G.; Christodoulou, Evangelos; Walker, Philip A.; Liu, Junfeng; John J Skehel; Gamblin, Steven J.; Hay, Alan J.; Daniels, Rodney S; McCauley, John W.

    2012-01-01

    The hemagglutinin (HA) of influenza A(H3N2) virus responsible for the 1968 influenza pandemic derived from an avian virus. On introduction into humans, its receptor binding properties had changed from a preference for avian receptors (α2,3-linked sialic acid) to a preference for human receptors (α2,6-linked sialic acid). By 2001, the avidity of human H3 viruses for avian receptors had declined, and since then the affinity for human receptors has also decreased significantly. These changes in ...

  10. Defect induced modification of structural, topographical and magnetic properties of zinc ferrite thin films by swift heavy ion irradiation

    Science.gov (United States)

    Raghavan, Lisha; Joy, P. A.; Vijaykumar, B. Varma; Ramanujan, R. V.; Anantharaman, M. R.

    2017-04-01

    Swift heavy ion irradiation provides unique ways to modify physical and chemical properties of materials. In ferrites, the magnetic properties can change significantly as a result of swift heavy ion irradiation. Zinc ferrite is an antiferromagnet with a Neel temperature of 10 K and exhibits anomalous magnetic properties in the nano regime. Ion irradiation can cause amorphisation of zinc ferrite thin films; thus the role of crystallinity on magnetic properties can be examined. The influence of surface topography in these thin films can also be studied. Zinc ferrite thin films, of thickness 320 nm, prepared by RF sputtering were irradiated with 100 MeV Ag ions. Structural characterization showed amorphisation and subsequent reduction in particle size. The change in magnetic properties due to irradiation was correlated with structural and topographical effects of ion irradiation. A rough estimation of ion track radius is done from the magnetic studies.

  11. Immunological properties of prolactin and studies on a gonadotropin binding inhibitor

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Y.S.

    1985-01-01

    The physiological role of prolactin in horses has not yet been well defined. With the availability of highly purified ePRL for inducing antibody formation in rabbits and for radiolabeling with Na/sup 125/I, a very sensitive (0.4-0.6 ng/ml) and highly specific homologous RIA for ePRL was developed. A heterologous RIA using /sup 125/I-labeled ovine PRL and anti-ePRL antiserum was also developed and compared to the homologous RIA for ePRL. Of the two systems, it is concluded that this homologous RIA system is more suitable and more reliable for measuring prolactin concentration in horse serum samples. Until now, biochemical information on PRL has not been available for reptilian species. Sea turtle (Chelonia mydas) prolactin was purified from pituitary extracts by selective precipitation, DEAE-cellulose chromatography and gel filtration. Similar to other species of PRL, sea turtle PRL is a 22,000-24,000 daltons protein and contains a high content of glutamic acid, aspartic acid, serine and leucine, the N-terminal amino acid residue. Gonadotropin (FSH) binding inhibitor was partially purified from sheep testes by ammonium sulfate fractionation and ion exchange chromatography. The FSH-BI (molecular weight: 50,000 daltons, estimated by gel filtration) contains a protein moiety necessary for binding inhibitory activity. The inhibition of the binding of /sup 125/I-labeled ovine FSH to its receptor by the FSH-BI is not competitive. Both in vivo and in vitro biological studies of FSH-BI preparations in rats indicated various effects on FSH and LH activities at the gonadal level. These findings suggest a physiological role for FSH-BI in the regulation of reproduction.

  12. Tribological properties of boron nitride synthesized by ion beam deposition

    Science.gov (United States)

    Miyoshi, K.; Buckley, D. H.; Spalvins, T.

    1985-01-01

    The adhesion and friction behavior of boron nitride films on 440 C bearing stainless steel substrates was examined. The thin films containing the boron nitride were synthesized using an ion beam extracted from a borazine plasma. Sliding friction experiments were conducted with BN in sliding contact with itself and various transition metals. It is indicated that the surfaces of atomically cleaned BN coating film contain a small amount of oxides and carbides, in addition to boron nitride. The coefficients of friction for the BN in contact with metals are related to the relative chemical activity of the metals. The more active the metal, the higher is the coefficient of friction. The adsorption of oxygen on clean metal and BN increases the shear strength of the metal - BN contact and increases the friction. The friction for BN-BN contact is a function of the shear strength of the elastic contacts. Clean BN surfaces exhibit relatively strong interfacial adhesion and high friction. The presence of adsorbates such as adventitious carbon contaminants on the BN surfaces reduces the shear strength of the contact area. In contrast, chemically adsorbed oxygen enhances the shear strength of the BN-BN contact and increases the friction.

  13. Protein-ion binding process on finite macromolecular concentration. A Poisson-Boltzmann and Monte Carlo study.

    Science.gov (United States)

    de Carvalho, Sidney Jurado; Fenley, Márcia O; da Silva, Fernando Luís Barroso

    2008-12-25

    Electrostatic interactions are one of the key driving forces for protein-ligands complexation. Different levels for the theoretical modeling of such processes are available on the literature. Most of the studies on the Molecular Biology field are performed within numerical solutions of the Poisson-Boltzmann Equation and the dielectric continuum models framework. In such dielectric continuum models, there are two pivotal questions: (a) how the protein dielectric medium should be modeled, and (b) what protocol should be used when solving this effective Hamiltonian. By means of Monte Carlo (MC) and Poisson-Boltzmann (PB) calculations, we define the applicability of the PB approach with linear and nonlinear responses for macromolecular electrostatic interactions in electrolyte solution, revealing some physical mechanisms and limitations behind it especially due the raise of both macromolecular charge and concentration out of the strong coupling regime. A discrepancy between PB and MC for binding constant shifts is shown and explained in terms of the manner PB approximates the excess chemical potentials of the ligand, and not as a consequence of the nonlinear thermal treatment and/or explicit ion-ion interactions as it could be argued. Our findings also show that the nonlinear PB predictions with a low dielectric response well reproduce the pK shifts calculations carried out with an uniform dielectric model. This confirms and completes previous results obtained by both MC and linear PB calculations.

  14. Identification of a binding motif in the S5 helix that confers cholesterol sensitivity to the TRPV1 ion channel.

    Science.gov (United States)

    Picazo-Juárez, Giovanni; Romero-Suárez, Silvina; Nieto-Posadas, Andrés; Llorente, Itzel; Jara-Oseguera, Andrés; Briggs, Margaret; McIntosh, Thomas J; Simon, Sidney A; Ladrón-de-Guevara, Ernesto; Islas, León D; Rosenbaum, Tamara

    2011-07-15

    The TRPV1 ion channel serves as an integrator of noxious stimuli with its activation linked to pain and neurogenic inflammation. Cholesterol, a major component of cell membranes, modifies the function of several types of ion channels. Here, using measurements of capsaicin-activated currents in excised patches from TRPV1-expressing HEK cells, we show that enrichment with cholesterol, but not its diastereoisomer epicholesterol, markedly decreased wild-type rat TRPV1 currents. Substitutions in the S5 helix, rTRPV1-R579D, and rTRPV1-F582Q, decreased this cholesterol response and rTRPV1-L585I was insensitive to cholesterol addition. Two human TRPV1 variants, with different amino acids at position 585, had different responses to cholesterol with hTRPV1-Ile(585) being insensitive to this molecule. However, hTRPV1-I585L was inhibited by cholesterol addition similar to rTRPV1 with the same S5 sequence. In the absence of capsaicin, cholesterol enrichment also inhibited TRPV1 currents induced by elevated temperature and voltage. These data suggest that there is a cholesterol-binding site in TRPV1 and that the functions of TRPV1 depend on the genetic variant and membrane cholesterol content.

  15. Green synthesis of magnesium ion incorporated nanocrystalline hydroxyapatite and their mechanical, dielectric and photoluminescence properties

    Energy Technology Data Exchange (ETDEWEB)

    Arul, K. Thanigai; Kolanthai, Elayaraja [Crystal Growth Centre, Anna University, Chennai 600 025 (India); Manikandan, E. [Nanosciences African Network (NANO-AFNET), iThemba LABS-National Research Foundation (NRF), Materials Research Department, Cape Town, South Africa. (South Africa); Bhalerao, G.M. [University Grants Commission – Department of Atomic Energy, Consortium for Scientific Research, Kalpakkam 603 104 (India); Chandra, V. Sarath; Ramya, J. Ramana [Crystal Growth Centre, Anna University, Chennai 600 025 (India); Mudali, U. Kamachi [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Nair, K.G.M. [Accelerator Material Science Section, Material Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kalkura, S.Narayana, E-mail: kalkurasn@annauniv.edu [Crystal Growth Centre, Anna University, Chennai 600 025 (India)

    2015-07-15

    Highlights: • Rapid technique to synthesize nanorods of magnesium ion incorporated hydroxyapatite. • Enhanced electrical and mechanical properties. • Improved photoluminescence and wettability on magnesium incorporation. • Increased in vitro bioactivity. - Abstract: Nanocrystalline hydroxyapatite (HAp-Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2,} 35 nm) and magnesium (Mg{sup 2+}) ion incorporated HAp were synthesized by microwave technique. XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy), FE-HRTEM (Field emission high resolution transmission electron microscopy), DLS (dynamic light scattering), EDXRF (energy dispersive X-ray fluorescence spectrometry), microhardness, permittivity and alternating current (ac) conductivity, besides the PL (photoluminescence), wettability and in vitro bioactivity of the samples were analysed. EDXRF revealed the Mg{sup 2+} ion incorporation in HAp. The Mg{sup 2+} ion incorporation did not alter the phase but drastically reduced the crystallite size and particle size respectively by 48% and 32%. There was enhanced microhardness (24%) at low level (<13%) and decreased zeta potential of Mg{sup 2+} ion incorporation. The permittivity, ac conductivity, PL, wettability and in vitro bioactivity were enhanced on Mg{sup 2+} ion incorporation. These properties enable them to be a promising candidate for wound healing, bone replacement applications and also as a biosensor.

  16. Superoleophobic polymers with metal ion affinity toward materials with both oleophobic and hydrophilic properties.

    Science.gov (United States)

    Darmanin, Thierry; Guittard, Frédéric

    2013-10-15

    Bis(trifluoromethane)sulfonimide salts are used as electrolyte for the elaboration of superoleophobic properties by electrodeposition using a monomer containing a short perfluorobutyl (C4F9), separated from the polymer backbone by a long alkyl spacer, to reduce the mobility of these chains, and an amido connector to form complexes with ions. The electrodeposition in some of these electrolytes induces the formation of microstructures composed of nanosheets able to reach superoleophobic properties. When complexant ions (Na(+), Mg(2+), Ca(2+), Ba(2+)) are used as cation of the electrolyte, these ions are incorporated in the polymer leading to a material with higher oleophobicity than hydrophobicity. Indeed, when a water droplet is deposited on the surface, the migration of the ions induces a decrease in the surface hydrophobicity, while the deposition of an oil droplet (diiodomethane or hexadecane) does not induce this migration. If the incorporation of these ions is not sufficiently stable for applications in oil/water separation, this work opens new strategies in the elaboration of both superoleophobic/oleophobic and superhydrophilic/hydrophilic materials. Such materials can also be used for the ion capture and release.

  17. On the Relation between Electrical and Acoustical Properties of ION Conductivite Glasses

    Directory of Open Access Journals (Sweden)

    Igor Jamnicky

    2003-01-01

    Full Text Available The technological interest in fast ionic conductivity in glassy materials is increased in last years for various solid state electrochemical devices such as solid-state batteries, electrochronic displays, and sensors. The ion conductive glasses have several advantages comparing with crystalline materials because of their easy preparation, their stability, the large available compositionranges and reasonable cost. It is known that the investigation of conductivity spectra of ionic glasses can reflect the basic features ofthe relaxation and transport mechanisms of the mobile ions and the high ion conductivity at room temperature is the most important criterion which should be meet the fast ion conductive glasses. However, the relaxation and transport mechanisms can be investigated also by acoustic methods, that can have some advantages comparing to electrical ones as the high sensitivity, absence of contact phenomena and so on.In the contribution we present some electrical and acoustical properties of glasses prepared in the system CuI-CuBr-Cu20-(P20j+Mo03. The main purpose of the contribution is to contribute to the investigation of ion transport mechanisms in these fast ion conductive glasses and to determine the relation between electrical and acoustical properties considering the various glass compositions.

  18. Apo, Zn2+-bound and Mn2+-bound structures reveal ligand-binding properties of SitA from the pathogen Staphylococcus pseudintermedius.

    Science.gov (United States)

    Abate, Francesca; Malito, Enrico; Cozzi, Roberta; Lo Surdo, Paola; Maione, Domenico; Bottomley, Matthew J

    2014-11-24

    The Gram-positive bacterium Staphylococcus pseudintermedius is a leading cause of canine bacterial pyoderma, resulting in worldwide morbidity in dogs. S. pseudintermedius also causes life-threatening human infections. Furthermore, methicillin-resistant S. pseudintermedius is emerging, resembling the human health threat of methicillin-resistant Staphylococcus aureus. Therefore it is increasingly important to characterize targets for intervention strategies to counteract S. pseudintermedius infections. Here we used biophysical methods, mutagenesis, and X-ray crystallography, to define the ligand-binding properties and structure of SitA, an S. pseudintermedius surface lipoprotein. SitA was strongly and specifically stabilized by Mn2+ and Zn2+ ions. Crystal structures of SitA complexed with Mn2+ and Zn2+ revealed a canonical class III solute-binding protein with the metal cation bound in a cavity between N- and C-terminal lobes. Unexpectedly, one crystal contained both apo- and holo-forms of SitA, revealing a large side-chain reorientation of His64, and associated structural differences accompanying ligand binding. Such conformational changes may regulate fruitful engagement of the cognate ABC (ATP-binding cassette) transporter system (SitBC) required for metal uptake. These results provide the first detailed characterization and mechanistic insights for a potential therapeutic target of the major canine pathogen S. pseudintermedius, and also shed light on homologous structures in related staphylococcal pathogens afflicting humans.

  19. Competitive binding exchange between alkali metal ions (K+, Rb+, and Cs+) and Na+ ions bound to the dimeric quadruplex [d(G4T4G4)]2: a 23Na and 1H NMR study.

    Science.gov (United States)

    Cesare Marincola, Flaminia; Virno, Ada; Randazzo, Antonio; Mocci, Francesca; Saba, Giuseppe; Lai, Adolfo

    2009-12-01

    A comparative study of the competitive cation exchange between the alkali metal ions K+, Rb+, and Cs+ and the Na+ ions bound to the dimeric quadruplex [d(G4T4G4)]2 was performed in aqueous solution by a combined use of the 23Na and 1H NMR spectroscopy. The titration data confirm the different binding affinities of these ions for the G-quadruplex and, in particular, major differences in the behavior of Cs+ as compared to the other ions were found. Accordingly, Cs+ competes with Na+ only for the binding sites at the quadruplex surface (primarily phosphate groups), while K+ and Rb+ are also able to replace sodium ions located inside the quadruplex. Furthermore, the 1H NMR results relative to the CsCl titration evidence a close approach of Cs+ ions to the phosphate groups in the narrow groove of [d(G4T4G4)]2. Based on a three-site exchange model, the 23Na NMR relaxation data lead to an estimate of the relative binding affinity of Cs+ versus Na+ for the quadruplex surface of 0.5 at 298 K. Comparing this value to those reported in the literature for the surface of the G-quadruplex formed by 5'-guanosinemonophosphate and for the surface of double-helical DNA suggests that topology factors may have an important influence on the cation affinity for the phosphate groups on DNA.

  20. Tuning silver ion release properties in reactively sputtered Ag/TiOx nanocomposites

    Science.gov (United States)

    Xiong, J.; Ghori, M. Z.; Henkel, B.; Strunskus, T.; Schürmann, U.; Deng, M.; Kienle, L.; Faupel, F.

    2017-07-01

    Silver/titania nanocomposites with strong bactericidal effects and good biocompatibility/environmental safety show a high potential for antibacterial applications. Tailoring the silver ion release is thus highly promising to optimize the antibacterial properties of such coatings and to preserve biocompatibility. Reactive sputtering is a fast and versatile method for the preparation of such Ag/TiOx nanocomposites coatings. The present work is concerned with the influence of sputter parameters on the surface morphology and silver ion release properties of reactively sputtered Ag/TiOx nanocomposites coatings showing a silver nanoparticle size distribution in the range from 1 to 20 nm. It is shown that the silver ion release rate strongly depends on the total pressure: the coatings prepared at lower pressure present a lower but long-lasting release behavior. The much denser structure produced under these conditions reduces the transport of water molecules into the coating. In addition, the influence of microstructure and thickness of titanium oxide barriers on the silver ion release were investigated intensively. Moreover, for the coatings prepared at high total pressure, it was demonstrated that stable and long-lasting silver release can be achieved by depositing a barrier with a high rate. Nanocomposites produced under these conditions show well controllable silver ion release properties for applications as antibacterial coatings.

  1. Using Electronic Properties of Adamantane Derivatives to Analyze their Ion Channel Interactions: Implications for Alzheimer's Disease

    Science.gov (United States)

    Bonacum, Jason

    2013-03-01

    The derivatives of adamantane, which is a cage-like diamondoid structure, can be used as pharmaceuticals for the treatment of various diseases and disorders such as Alzheimer's disease. These drugs interact with ion channels, and they act by electronically and physically hindering the ion transport. The electronic properties of each compound influence the location and level of ion channel hindrance, and the specific use of each compound depends on the functional groups that are attached to the adamantane base chain. Computational analysis and molecular simulations of these different derivatives and the ion channels can provide useful insight into the effect that the functional groups have on the properties of the compounds. Using this information, conclusions can be made about the pharmaceutical mechanisms, as well as how to improve them or create new beneficial compounds. Focusing on the electronic properties, such as the dipole moments of the derivatives and amino acids in the ion channels, can provide more efficient predictions of how these drugs work and how they can be enhanced. Department of Energy Grant DE-FG02-06ER46304

  2. Effect of enzymatic protein deamidation on protein solubility and flavor binding properties of soymilk.

    Science.gov (United States)

    Suppavorasatit, Inthawoot; Lee, Soo-Yeun; Cadwallader, Keith R

    2013-01-01

    The effect of enzymatic deamidation by protein-glutaminase (PG) on protein solubility and flavor binding potential of soymilk was studied. Treatment of soymilk with PG for 2 h (temperature of 44 °C and enzyme:substrate ratio (E/S) of 40 U/g protein) resulted in high degree of protein deamidation (66.4% DD) and relatively low degree of protein hydrolysis (4.25% DH). Deamidated (DSM) and control soymilks (CSM) did not differ with respect to aroma, but differed in taste characteristics by sensory evaluation. Protein solubility in DSM was enhanced at weakly acidic conditions (pH 5.0), but did not differ from non-deamidated soymilk at pH values of 3.0 and 7.0. Odor detection thresholds for the flavor compounds vanillin and maltol were approximately 5 and 3 fold lower, respectively, in DSM than in CSM. Dose-response curves (Fechner's law plots and n exponents from Stevens's power law) further demonstrated that DSM had a lower flavor binding potential than CSM. PG deamidation has the potential to reduce flavor binding problems encountered in high protein-containing foods and beverages. The findings of this study can help lead to the development of technology to produce protein-containing foods with improved functional properties, especially protein solubility, and potentially decreased flavor fade problems associated with flavor-protein interactions, especially with carbonyl containing flavor compounds. © 2012 Institute of Food Technologists®

  3. Fluorescence Spectral Properties of All4261 Binding with Phycocyanobilin in E.Coli

    Science.gov (United States)

    Ma, Q.; Zheng, X. J.; Zhou, Z.; Zhou, N.; Zhao, K. H.; Zhou, M.

    2014-07-01

    Cyanobacteriochromes (CBCRs) are chromophorylated proteins that acting as sensory photoreceptors in cyanobacteria. Based on the bioinformatics of All4261 in Nostoc sp. PCC7120, All4261 is a CBCR apoprotein composed of GAF domains in the N-terminal region. Via polymerase chain reaction with specific primers, All4261 was amplified with genome DNA of Nostoc sp. PCC7120 as template and then subcloned into the expression vector pET30(a+). To survey the fluorescence spectral properties, All4261 was coexpressed with the plasmid that catalyzes phycocyanobilin (PCB) biosynthesis, pACYC-ho1-pcyA, in E.coli BL21. Fluorescence emission spectra and excitation spectra showed that chromophorylated cells containing All4261-PCB had a fluorescence emission peak at 645 nm and a fluorescence excitation peak at 550 nm, but no reversible photoconversion. In order to identify the binding site of PCB in All4261, we obtained three variants All4261(C296L), All4261(C328A), and All4261(C339L), via sitedirected mutagenesis. The binding site was identified as C339 based on the lack of PCB binding of All4261(C339L).

  4. The new generation drug candidate molecules: Spectral, electrochemical, DNA-binding and anticancer activity properties

    Science.gov (United States)

    Gölcü, Ayşegül; Muslu, Harun; Kılıçaslan, Derya; Çeşme, Mustafa; Eren, Özge; Ataş, Fatma; Demirtaş, İbrahim

    2016-09-01

    The new generation drug candidate molecules [Cu(5-Fu)2Cl2H2O] (NGDCM1) and [Zn(5-Fu)2(CH3COO)2] (NGDCM2) were obtained from the reaction of copper(II) and zinc(II) salts with the anticancer drug 5-fluoracil (5-Fu). These compounds have been characterized by spectroscopic and analytical techniques. Thermal behavior of the compounds were also investigated. The electrochemical properties of the compounds have been investigated by cyclic voltammetry (CV) using glassy carbon electrode. The biological activity of the NGDCM1 and NGDCM2 has been evaluated by examining their ability to bind to fish sperm double strand DNA (FSdsDNA) with UV spectroscopy. UV studies of the interaction of the 5-Fu and metal derivatives with FSdsDNA have shown that these compounds can bind to FSdsDNA. The binding constants of the compounds with FSdsDNA have also been calculated. Thermal decomposition of the compounds lead to the formation of CuO and ZnO as final products. The effect of proliferation 5-Fu, NGDCM1 and NGDCM2 were examined on the HeLa cells using real-time cell analyzer with three different concentrations.

  5. Identification and properties of very high affinity brain membrane-binding sites for a neurotoxic phospholipase from the taipan venom

    Energy Technology Data Exchange (ETDEWEB)

    Lambeau, G.; Barhanin, J.; Schweitz, H.; Qar, J.; Lazdunski, M. (Centre de Biochimie, Nice (France))

    1989-07-05

    Four new monochain phospholipases were purified from the Oxyuranus scutellatus (taipan) venom. Three of them were highly toxic when injected into mice brain. One of these neurotoxic phospholipases, OS2, was iodinated and used in binding experiments to demonstrate the presence of two families of specific binding sites in rat brain synaptic membranes. The affinities were exceptionally high, Kd1 = 1.5 +/- 0.5 pM and Kd2 = 45 +/- 10 pM, and the maximal binding capacities were Bmax 1 = 1 +/- 0.4 and Bmax 2 = 3 +/- 0.5 pmol/mg of protein. Both binding sites were sensitive to proteolysis and demonstrated to be located on proteins of Mr 85,000-88,000 and 36,000-51,000 by cross-linking and photoaffinity labeling techniques. The binding of {sup 125}I-OS2 to synaptic membranes was dependent on Ca2+ ions and enhanced by Zn2+ ions which inhibit phospholipase activity. Competition experiments have shown that, except for beta-bungarotoxin, a number of known toxic snake or bee phospholipases have very high affinities for the newly identified binding sites. A good correlation (r = 0.80) was observed between toxicity and affinity but not between phospholipase activity and affinity.

  6. Reactive Ar ion beam sputter deposition of TiO{sub 2} films: Influence of process parameters on film properties

    Energy Technology Data Exchange (ETDEWEB)

    Bundesmann, C., E-mail: carsten.bundesmann@iom-leipzig.de [Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstrasse 15, 04318 Leipzig (Germany); Lautenschläger, T.; Thelander, E. [Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstrasse 15, 04318 Leipzig (Germany); Spemann, D. [Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstrasse 15, 04318 Leipzig (Germany); Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig (Germany)

    2017-03-15

    Highlights: • Ion beam sputter deposition under systematic variation of process parameters. • Thickness, growth rate, structure, mass density, composition, optical properties. • All TiO{sub 2} films are amorphous with systematic variations in mass density. • Considerable amount of inert process gas correlated with scattering angle. • Correlation of mass density and index of refraction. - Abstract: Several sets of TiO{sub 2} films were grown by Ar ion beam sputter deposition under systematic variation of ion energy and geometrical parameters (ion incidence angle and polar emission angle). The films were characterized concerning thickness, growth rate, structural properties, composition, mass density, and optical properties. The film thicknesses show a cosine-like angular distribution, and the growth rates were found to increase with increasing ion incidence angle and ion energy. All films are amorphous and stoichiometric, but can contain a considerable amount of backscattered primary particles. The atomic fraction of Ar particles decreases systematically with increasing scattering angle, independent from ion energy and ion incidence angle. Mass density and index of refraction show similar systematic variations with ion energy and geometrical parameters. The film properties are mainly influenced by the scattering geometry, and only slightly by ion energy and ion incidence angle. The variations in the film properties are tentatively assigned to changes in the angular and energy distribution of the sputtered target particles and back-scattered primary particles.

  7. Optical properties of swift ion beam irradiated CdTe thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chandramohan, S. [PG and Research Department of Physics, Kongunadu Arts and Science College, Coimbatore, Tamilnadu 641029 (India); Sathyamoorthy, R. [PG and Research Department of Physics, Kongunadu Arts and Science College, Coimbatore, Tamilnadu 641029 (India)], E-mail: rsathya59@yahoo.co.in; Sudhagar, P. [PG and Research Department of Physics, Kongunadu Arts and Science College, Coimbatore, Tamilnadu 641029 (India); Kanjilal, D.; Kabiraj, D.; Asokan, K. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2008-06-30

    This paper reports the effect of swift (80 MeV) oxygen (O{sup +6}) ion irradiation on the optical properties of CdTe thin films grown by conventional thermal evaporation on glass substrates. The films are found to be slightly Te-rich in composition and irradiation results no change in the elemental composition. The optical constants such as refractive index (n), absorption coefficient ({alpha}) and the optical band gap energy show significant variation in their values with increase in ion fluence. Upon irradiation the band gap energy decreased from a value of 1.53 eV to 1.46 eV whereas the refractive index (n) increased from 2.38 to 3.12 at {lambda} = 850 nm. The photoluminescence spectrum shows high density of native defects whose density strongly depends on the ion fluence. Both analyses indicate considerable defect production after swift ion beam irradiation.

  8. Optical and magnetic properties of nitrogen ion implanted MgO single crystal

    Institute of Scientific and Technical Information of China (English)

    Liu Chun-Ming; Gu Hai-Quan; Xiang Xia; Zhang Yan; Jiang Yong; Chen Meng; Zu Xiao-Tao

    2011-01-01

    The microstructure, optical property and magnetism of nitrogen ion implanted single MgO crystals are studied.A parallel investigation is also performed in an iron ion implanted single MgO sample as a reference. Large structural,optical and magnetic differences are obtained between the nitrogen and iron implanted samples. Room temperature ferromagnetism with a fairly large coercivity field of 300 Oe (1 Oe=79.5775 A/m), a remanence of 38% and a slightly changed optical absorption is obtained in the sample implanted using nitrogen with a dose of 1×1018 ions/cm2. Transition metal contamination and defects induced magnetism can be excluded when compared with those of the iron ion implanted sample, and the nitrogen doping is considered to be the main origin of ferromagnetism.

  9. Surface properties of nitrogen-ion-implanted TiNi shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    X-ray diffraction (XRD), auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface properties of the N+-ion-implanted TiNi alloy.There is a high nitrogen content region at the outermost surface of the N+-ion-implanted TiNi alloy.The detected nitrogen exists mainly in the form of TiN.Small amounts of Ti3O5 and TiO2 also exist on the surface of the N+-ion-implanted TiNi sample.The modified layer of the N+-ion-implanted sample can work as an obstacle layer of the nickel's dissolution, which obstructs Ni dissolving from the TiNi surface effectively.

  10. Effect of calcium/sodium ion exchange on the osmotic properties and structure of polyelectrolyte gels.

    Science.gov (United States)

    Horkay, Ferenc; Basser, Peter J; Hecht, Anne-Marie; Geissler, Erik

    2015-12-01

    We discuss the main findings of a long-term research program exploring the consequences of sodium/calcium ion exchange on the macroscopic osmotic and elastic properties, and the microscopic structure of representative synthetic polyelectrolyte (sodium polyacrylate, (polyacrylic acid)) and biopolymer gels (DNA). A common feature of these gels is that above a threshold calcium ion concentration, they exhibit a reversible volume phase transition. At the macroscopic level, the concentration dependence of the osmotic pressure shows that calcium ions influence primarily the third-order interaction term in the Flory-Huggins model of polymer solutions. Mechanical tests reveal that the elastic modulus is practically unaffected by the presence of calcium ions, indicating that ion bridging does not create permanent cross-links. At the microscopic level, small-angle neutron scattering shows that polyacrylic acid and DNA gels exhibit qualitatively similar structural features in spite of important differences (e.g. chain flexibility and chemical composition) between the two polymers. The main effect of calcium ions is that the neutron scattering intensity increases due to the decrease in the osmotic modulus. At the level of the counterion cloud around dissolved macroions, anomalous small-angle X-ray scattering measurements made on DNA indicate that divalent ions form a cylindrical sheath enveloping the chain, but they are not localized. Small-angle neutron scattering and small-angle X-ray scattering provide complementary information on the structure and interactions in polymer solutions and gels.

  11. Can the Transport Properties of Molten Salts and Ionic Liquids Be Used To Determine Ion Association?

    Science.gov (United States)

    Harris, Kenneth R

    2016-12-01

    There have long been arguments supporting the concept of ion association in molten salts and ionic liquids, largely based on differences between the conductivity and that predicted from self-diffusion coefficients by the Nernst-Einstein equation for noninteracting ions. It is known from molecular dynamics simulations that even simple models based on charged hard spheres show such a difference due to the (anti)-correlation of ion motions. Formally this is expressed as a difference between the velocity cross-correlation coefficient of the oppositely charged ions and the mean of those for the two like-charged ions. This article examines molten salt and ionic liquid transport property data, comparing simple and model associated salts (ZnCl2, PbCl2, and TlCl) including weakly dissociated molecular liquids (H2O, HCOOH, H2SO4). Analysis employing Laity resistance coefficients (rij) shows that the common ion-association rationalization is flawed, consistent with recent direct measurements of the degree of ionicity in ionic liquid chlorides and with theoretical studies. However, the protic ionic liquids [PyrOMe][BF4] and [DBUH][CH3SO3] have larger than usual NE deviation parameters (>0.5), and large negative like-ion rii, analogous to those of ZnCl2. Structural, spectroscopic, and theoretical studies are suggested to determine whether these are indeed genuine examples of association.

  12. Tailoring the structural and optical properties of TiN thin films by Ag ion implantation

    Science.gov (United States)

    Popović, M.; Novaković, M.; Rakočević, Z.; Bibić, N.

    2016-12-01

    Titanium nitride (TiN) thin films thickness of ∼260 nm prepared by dc reactive sputtering were irradiated with 200 keV silver (Ag) ions to the fluences ranging from 5 × 1015 ions/cm2 to 20 × 1015 ions/cm2. After implantation TiN layers were annealed 2 h at 700 °C in a vacuum. Ion irradiation-induced microstructural changes were examined by using Rutherford backscattering spectrometry, X-ray diffraction and transmission electron microscopy, while the surface topography was observed using atomic force microscopy. Spectroscopic ellipsometry was employed to get insights on the optical and electronic properties of TiN films with respect to their microstructure. The results showed that the irradiations lead to deformation of the lattice, increasing disorder and formation of new Ag phase. The optical results demonstrate the contribution of surface plasmon resonace (SPR) of Ag particles. SPR position shifted in the range of 354.3-476.9 nm when Ag ion fluence varied from 5 × 1015 ions/cm2 to 20 × 1015 ions/cm2. Shift in peak wavelength shows dependence on Ag particles concentration, suggesting that interaction between Ag particles dominate the surface plasmon resonance effect. Presence of Ag as second metal in the layer leads to overall decrease of optical resistivity of TiN.

  13. Ion beam properties after mass filtering with a linear radiofrequency quadrupole

    Energy Technology Data Exchange (ETDEWEB)

    Ferrer, R., E-mail: Rafael.Ferrer@fys.kuleuven.be [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Kwiatkowski, A.A.; Bollen, G.; Lincoln, D.L. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, East Lansing, MI 48824 (United States); Morrissey, D.J.; Pang, G.K. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Chemistry, East Lansing, MI 48824 (United States); Ringle, R. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Savory, J. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, East Lansing, MI 48824 (United States); Schwarz, S. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States)

    2014-01-21

    The properties of ion beams passing through a linear radiofrequency quadrupole mass filter were investigated with special attention to their dependence on the mass resolving power. Experimentally, an increase of the transverse emittance was observed as the mass-to-charge selectivity of the mass filter was raised. The experimental behavior was confirmed by beam transport simulations. -- Highlights: • The ion-optical properties of a Quadrupole Mass Filter (QMF) are presented. • Measured beam emittances follow a trend to larger values for smaller A/Q ratios and increasing mass resolution. • The experimental behavior was confirmed by beam transport simulations. • The use of a QMF for mass filtering comes at the cost of emittance growth of the ion beam.

  14. Hydrodynamic and Membrane Binding Properties of Purified Rous Sarcoma Virus Gag Protein

    Energy Technology Data Exchange (ETDEWEB)

    Dick, Robert A.; Datta, Siddhartha A.K.; Nanda, Hirsh; Fang, Xianyang; Wen, Yi; Barros, Marilia; Wang, Yun-Xing; Rein, Alan; Vogt, Volker M. (NCI); (Cornell); (CM); (NIST)

    2016-05-06

    Previously, no retroviral Gag protein has been highly purified in milligram quantities and in a biologically relevant and active form. We have purified Rous sarcoma virus (RSV) Gag protein and in parallel several truncation mutants of Gag and have studied their biophysical properties and membrane interactionsin vitro. RSV Gag is unusual in that it is not naturally myristoylated. From its ability to assemble into virus-like particlesin vitro, we infer that RSV Gag is biologically active. By size exclusion chromatography and small-angle X-ray scattering, Gag in solution appears extended and flexible, in contrast to previous reports on unmyristoylated HIV-1 Gag, which is compact. However, by neutron reflectometry measurements of RSV Gag bound to a supported bilayer, the protein appears to adopt a more compact, folded-over conformation. At physiological ionic strength, purified Gag binds strongly to liposomes containing acidic lipids. This interaction is stimulated by physiological levels of phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2] and by cholesterol. However, unlike HIV-1 Gag, RSV Gag shows no sensitivity to acyl chain saturation. In contrast with full-length RSV Gag, the purified MA domain of Gag binds to liposomes only weakly. Similarly, both an N-terminally truncated version of Gag that is missing the MA domain and a C-terminally truncated version that is missing the NC domain bind only weakly. These results imply that NC contributes to membrane interactionin vitro, either by directly contacting acidic lipids or by promoting Gag multimerization.

    Retroviruses like HIV assemble at and bud from the plasma membrane of cells. Assembly requires the interaction between thousands of Gag molecules to form a lattice. Previous work indicated that lattice formation at the plasma membrane is influenced by the conformation of monomeric HIV. We have extended this work to the more tractable RSV Gag. Our

  15. Application of differential scanning calorimetry to measure the differential binding of ions, water and protons in the unfolding of DNA molecules.

    Science.gov (United States)

    Olsen, Chris M; Shikiya, Ronald; Ganugula, Rajkumar; Reiling-Steffensmeier, Calliste; Khutsishvili, Irine; Johnson, Sarah E; Marky, Luis A

    2016-05-01

    The overall stability of DNA molecules globally depends on base-pair stacking, base-pairing, polyelectrolyte effect and hydration contributions. In order to understand how they carry out their biological roles, it is essential to have a complete physical description of how the folding of nucleic acids takes place, including their ion and water binding. To investigate the role of ions, water and protons in the stability and melting behavior of DNA structures, we report here an experimental approach i.e., mainly differential scanning calorimetry (DSC), to determine linking numbers: the differential binding of ions (Δnion), water (ΔnW) and protons (ΔnH(+)) in the helix-coil transition of DNA molecules. We use DSC and temperature-dependent UV spectroscopic techniques to measure the differential binding of ions, water, and protons for the unfolding of a variety of DNA molecules: salmon testes DNA (ST-DNA), one dodecamer, one undecamer and one decamer duplexes, nine hairpin loops, and two triplexes. These methods can be applied to any conformational transition of a biomolecule. We determined complete thermodynamic profiles, including all three linking numbers, for the unfolding of each molecule. The favorable folding of a DNA helix results from a favorable enthalpy-unfavorable entropy compensation. DSC thermograms and UV melts as a function of salt, osmolyte and proton concentrations yielded releases of ions and water. Therefore, the favorable folding of each DNA molecule results from the formation of base-pair stacks and uptake of both counterions and water molecules. In addition, the triplex with C(+)GC base triplets yielded an uptake of protons. Furthermore, the folding of a DNA duplex is accompanied by a lower uptake of ions and a similar uptake of four water molecules as the DNA helix gets shorter. In addition, the oligomer duplexes and hairpin thermodynamic data suggest ion and water binding depends on the DNA sequence rather than DNA composition. Copyright

  16. Properties of the periplasmic ModA molybdate-binding protein of Escherichia coli.

    Science.gov (United States)

    Rech, S; Wolin, C; Gunsalus, R P

    1996-02-02

    The modABCD operon, located at 17 min on the Escherichia coli chromosome, encodes the protein components of a high affinity molybdate uptake system. Sequence analysis of the modA gene (GenBank L34009) predicts that it encodes a periplasmic binding protein based on the presence of a leader-like sequence at its N terminus. To examine the properties of the ModA protein, the modA structural gene was overexpressed, and its product was purified. The ModA protein was localized to the periplasmic space of the cell, and it was released following a gentle osmotic shock. The N-terminal sequence of ModA confirmed that a leader region of 24 amino acids was removed upon export from the cell. The apparent size of ModA is 31.6 kDa as determined by gel sieve chromatography, whereas it is 22.5 kDa when examined by SDS-polyacrylamide gel electrophoresis. A ligand-dependent protein mobility shift assay was devised using a native polyacrylamide gel electrophoresis protocol to examine binding of molybdate and other anions to the ModA periplasmic protein. Whereas molybdate and tungstate were bound with high affinity (approximately 5 microM), sulfate, chromate, selenate, phosphate, and chlorate did not bind even when tested at 2 mM. A UV spectral assay revealed apparent Kd values of binding for molybdate and tungstate of 3 and 7 microM, respectively. Strains defective in the modA gene were unable to transport molybdate unless high levels of the anion were supplied in the medium. Therefore the modA gene product is essential for high affinity molybdate uptake by the cell. Tungstate interference of molybdate acquisition by the cell is apparently due in part to the high affinity of the ModA protein for this anion.

  17. Exploration of DAPI analogues: Synthesis, antitrypanosomal activity, DNA binding and fluorescence properties.

    Science.gov (United States)

    Farahat, Abdelbasset A; Kumar, Arvind; Say, Martial; Wenzler, Tanja; Brun, Reto; Paul, Ananya; Wilson, W David; Boykin, David W

    2017-03-10

    The DAPI structure has been modified by replacing the phenyl group with substituted phenyl or heteroaryl rings. Twelve amidines were synthesized and their DNA binding, fluorescence properties, in vitro and in vivo activities were evaluated. These compounds are shown to bind in the DNA minor groove with high affinity, and exhibit superior in vitro antitrypanosomal activity to that of DAPI. Six new diamidines (5b, 5c, 5d, 5e, 5f and 5j) exhibit superior in vivo activity to that of DAPI and four of these compounds provide 100% animal cure at a low dose of 4 × 5 mg/kg i.p. in T. b. rhodesiense infected mice. Generally, the fluorescence properties of the new analogues are inferior to that of DAPI with the exception of compound 5i which shows a moderate increase in efficacy while compound 5k is comparable to DAPI.

  18. Modifying the properties of 4f single-ion magnets by peripheral ligand functionalisation

    DEFF Research Database (Denmark)

    Pedersen, Kasper Steen; Ungur, Liviu; Sigrist, Marc;

    2014-01-01

    We study the ligand-field splittings and magnetic properties of three ErIII single-ion magnets which differ in the peripheral ligand sphere but exhibit similar first coordination spheres by inelastic neutron scattering (INS) and SQUID magnetometry. The INS spectra of the three compounds are profo...

  19. Probing anharmonic properties of nuclear surface vibration by heavy-ion fusion reactions

    CERN Document Server

    Takigawa, N; Kuyucak, S

    1997-01-01

    Describing fusion reactions between ^{16}O and ^{154}Dy and, between ^{16}O and ^{144}Sm by the $sd-$ and $sdf-$ interacting boson model, we show that heavy-ion fusion reactions are strongly affected by anharmonic properties of nuclear surface vibrations and nuclear shape, and thus provide a powerful method to study details of nuclear structure and dynamics.

  20. Effect of Disaccharides on Ion Properties in Milk-Based Systems

    NARCIS (Netherlands)

    Gao, R.; Leeuwen, van H.P.; Temminghoff, E.J.M.; Valenberg, van H.J.F.; Eisner, M.D.; Boekel, van M.A.J.S.

    2010-01-01

    The mean spherical approximation (MSA) theory is used to explain the impact of sugars on ion properties in milk-based systems by taking into account electrostatic interactions and volume exclusion effects. This study first focuses on the changes in Ca2+ activity and pH in a solution consisting of Ca

  1. Crystal structure and RNA-binding properties of an Hfq homolog from the deep-branching Aquificae: conservation of the lateral RNA-binding mode.

    Science.gov (United States)

    Stanek, Kimberly A; Patterson-West, Jennifer; Randolph, Peter S; Mura, Cameron

    2017-04-01

    The host factor Hfq, as the bacterial branch of the Sm family, is an RNA-binding protein involved in the post-transcriptional regulation of mRNA expression and turnover. Hfq facilitates pairing between small regulatory RNAs (sRNAs) and their corresponding mRNA targets by binding both RNAs and bringing them into close proximity. Hfq homologs self-assemble into homo-hexameric rings with at least two distinct surfaces that bind RNA. Recently, another binding site, dubbed the `lateral rim', has been implicated in sRNA·mRNA annealing; the RNA-binding properties of this site appear to be rather subtle, and its degree of evolutionary conservation is unknown. An Hfq homolog has been identified in the phylogenetically deep-branching thermophile Aquifex aeolicus (Aae), but little is known about the structure and function of Hfq from basal bacterial lineages such as the Aquificae. Therefore, Aae Hfq was cloned, overexpressed, purified, crystallized and biochemically characterized. Structures of Aae Hfq were determined in space groups P1 and P6, both to 1.5 Å resolution, and nanomolar-scale binding affinities for uridine- and adenosine-rich RNAs were discovered. Co-crystallization with U6 RNA reveals that the outer rim of the Aae Hfq hexamer features a well defined binding pocket that is selective for uracil. This Aae Hfq structure, combined with biochemical and biophysical characterization of the homolog, reveals deep evolutionary conservation of the lateral RNA-binding mode, and lays a foundation for further studies of Hfq-associated RNA biology in ancient bacterial phyla.

  2. Probing the influence of solvent effect on the lithium ion binding affinity of 12-crown-O3N derivatives with unsaturated side arms: a computational study.

    Science.gov (United States)

    Patidar, Rajesh; Paul, Parimal; Ganguly, Bishwajit

    2013-11-01

    Molecular structures of crown ether derivatives play a crucial role in complexing and transporting alkali metal ions such as lithium ion. The complexation of such ions take place in solution, hence it is important to examine the complexation behavior of host systems in solution. We have investigated employing quantum chemical calculations the stable conformations of 12-crown-O3N derivatives with unsaturated side-arms and its corresponding Li(+) ion complexation in low polar to high polar solvent medium. The General Gradient Approximation (GGA) using PW91 functional with DNP basis set calculated results show that the side-arms contribute via cation-π interaction in the complexation of lithium ion with the receptor molecules 2 and 3 quite effectively in the gas phase and in low polar solvent medium (CHCl3). The vinyl and acetylene groups attached to the receptor molecules are away from the cavity of the crown ether, however, orients toward the cavity while complexing with the lithium ion. The auxiliary effect of such side-arms to augment the binding affinity of Li(+) ion is reduced in the high polar solvent medium. The side-arms also orient away from the complexed Li(+) ion in relatively more polar solvents. These calculated results indicate that the complexing ability of aza-crowns toward the Li(+) ion can be enhanced with the unsaturated side-arms in low polar solvent medium, which however, is less effective in more polar mediums.

  3. Electron-Ion Collider: The next QCD frontier. Understanding the glue that binds us all

    Energy Technology Data Exchange (ETDEWEB)

    Accardi, A. [Hampton University, Hampton, VA (United States); Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Albacete, J.L. [Universite Paris-Sud 11, CNRS/IN2P3, IPNO, Orsay (France); Anselmino, M. [Torino University (Italy); INFN, Torino (Italy); Armesto, N. [University of Santiago de Campostela, Santiago de Compostela (Spain); Aschenauer, E.C.; Burton, T.; Fazio, S.; Hao, Y.; Lamont, M.A.C.; Lee, J.H.; Lee, Y.; Litvinenko, V.; Ludlam, T.W.; Ptitsyn, V.; Qiu, J.W.; Roser, T.; Toll, T.; Trbojevic, D.; Ullrich, T.; Venugopalan, R.; Vigdor, S. [Brookhaven National Laboratory, Upton, NY (United States); Bacchetta, A. [University of Pavia, Pavia (Italy); Boer, D. [University of Groningen, Groningen (Netherlands); Brooks, W.K.; Hakobyan, H.; Kopeliovich, B. [Universidad Tecnica Federico Santa Maria, Valparaiso (Chile); Chang, N.B.; Huang, M. [Shandong University, Shandong (China); Deng, W.T. [Frankfurt University, FIAS, Frankfurt (Germany); Shandong University, Shandong (China); Deshpande, A.; Kumar, K. [Stony Brook University, Stony Brook, NY (United States); Diehl, M. [DESY, Hamburg (Germany); Dumitru, A.; Jalilian-Marian, J. [Baruch College, CUNY, New York, NY (United States); Dupre, R.; Sabatie, F. [Centre de Saclay, CEA, Gif-sur-Yvette (France); Ent, R.; Guzey, V.; Hutton, A.; Lin, F.L.; McKeown, R.; Morozov, V.S.; Nadel-Turonski, P.; Prokudin, A.; Weiss, C.; Zhang, Y.H. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Gao, H. [Duke University, Durham, NC (United States); Hasch, D. [INFN, LNF, Frascati (Italy); Holt, R. [Argonne National Laboratory, Argonne, IL (United States); Horn, T. [The Catholic University of America, N.E. Washington, DC (United States); Hyde, C. [Old Dominion University, Norfolk, VA (United States); Klein, S.; Sichtermann, E.; Yuan, F. [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Kovchegov, Y. [The Ohio State University, Columbus, OH (United States); Kumericki, K. [University of Zagreb, Zagreb (Croatia); Lappi, T.; Paukkunen, H. [University of Jyvaskyla, Jyvaskyla (Finland); Levin, E.M. [Tel Aviv University, Tel Aviv (Israel); Universidad Tecnica Federico Santa Maria, Valparaiso (Chile); Marquet, C. [CERN, Geneva (Switzerland); Meziani, Z.E.; Metz, A. [Temple University, Philadelphia, PA (United States); Milner, R. [Massachusetts Institute of Technology, Cambridge, MA (United States); Mueller, A.H. [Columbia University, New York, NY (US); Mueller, B. [Brookhaven National Laboratory, Upton, NY (US); Duke University, Durham, NC (US); Mueller, D. [Ruhr-University Bochum, Bochum (DE); Qian, X. [California Institute of Technology, Pasadena, CA (US); Ramsey-Musolf, M. [University of Massachusetts at Amherst, Amherst, MA (US); Sassot, R. [University of Buenos Aires, Buenos Aires (AR); Schnell, G. [University of Basque Country, Bilbao (ES); Schweitzer, P. [University of Connecticut, Storrs, CT (US); Stratmann, M.; Vogelsang, W. [University of Tuebingen, Tuebingen (DE); Strikman, M. [Pennsylvania State University, Philadelphia, PA (US); Sullivan, M. [Stanford Linear Accelerator Center, Menlo Park, CA (US); Taneja, S. [Dalhousie University, Halifax, Nova Scotia (CA); Stony Brook University, Stony Brook, NY (US); Xiao, B.W. [Central China Normal University, Wuhan, Hubei (CN); Zheng, L. [Brookhaven National Laboratory, Upton, NY (US); Central China Normal University, Wuhan, Hubei (CN)

    2016-09-15

    This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on ''Gluons and quark sea at high energies'' at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users' communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier. (orig.)

  4. Electron-Ion Collider: The next QCD frontier. Understanding the glue that binds us all

    Science.gov (United States)

    Accardi, A.; Albacete, J. L.; Anselmino, M.; Armesto, N.; Aschenauer, E. C.; Bacchetta, A.; Boer, D.; Brooks, W. K.; Burton, T.; Chang, N.-B.; Deng, W.-T.; Deshpande, A.; Diehl, M.; Dumitru, A.; Dupré, R.; Ent, R.; Fazio, S.; Gao, H.; Guzey, V.; Hakobyan, H.; Hao, Y.; Hasch, D.; Holt, R.; Horn, T.; Huang, M.; Hutton, A.; Hyde, C.; Jalilian-Marian, J.; Klein, S.; Kopeliovich, B.; Kovchegov, Y.; Kumar, K.; Kumerički, K.; Lamont, M. A. C.; Lappi, T.; Lee, J.-H.; Lee, Y.; Levin, E. M.; Lin, F.-L.; Litvinenko, V.; Ludlam, T. W.; Marquet, C.; Meziani, Z.-E.; McKeown, R.; Metz, A.; Milner, R.; Morozov, V. S.; Mueller, A. H.; Müller, B.; Müller, D.; Nadel-Turonski, P.; Paukkunen, H.; Prokudin, A.; Ptitsyn, V.; Qian, X.; Qiu, J.-W.; Ramsey-Musolf, M.; Roser, T.; Sabatié, F.; Sassot, R.; Schnell, G.; Schweitzer, P.; Sichtermann, E.; Stratmann, M.; Strikman, M.; Sullivan, M.; Taneja, S.; Toll, T.; Trbojevic, D.; Ullrich, T.; Venugopalan, R.; Vigdor, S.; Vogelsang, W.; Weiss, C.; Xiao, B.-W.; Yuan, F.; Zhang, Y.-H.; Zheng, L.

    2016-09-01

    This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on "Gluons and quark sea at high energies" at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users' communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier.

  5. Vanadyl ion (VO sup 2+ ) as a spectroscopic probe of metal binding to nitrohumic acid

    Energy Technology Data Exchange (ETDEWEB)

    Mangrich, A.S.; Vugman, N.V. (Universidad Federal do Parana, Parana (Brazil). Dept. de Quimica)

    1990-07-01

    A coal nitrohumic acid (CNHA) of high nitrogen content (compared with natural humic acid) was obtained by extraction from nitric acid oxidation products of a mineral coal. It was studied by e.s.r. and i.r. spectroscopies, using VO{sup 2+} as a probe of metal ion complexation sites. Spectroscopic data and a LCAO-MO ligand field calculation were used to evaluate the bond parameters of vanadyl-coal nitrohumic acid complex (VO-CNHA). In spite of the high nitrogen content of CNHA, plots of hyperfine coupling constants {lt}A{gt} versus isotropic {lt}g{gt} values indicate that nitrogen is not a donor atom in the complexation sites of these materials. The bond parameter values, {lt}A{gt} and {lt}g{gt}, and i.r. data suggest that VO{sup 2+} groups (in the CNHA molecules) are at sites with C{sub 4}{sub V}, symmetry having o-hydroxycarboxylic aromatic (salicylic) acids as equatorial ligands. 21 refs., 2 figs.

  6. Electron Ion Collider: The Next QCD Frontier - Understanding the glue that binds us all

    CERN Document Server

    Deshpande, Abhay; Anselmino, M.; Armesto, N.; Aschenauer, E.C.; Bacchetta, A.; Boer, D.; Brooks, W.; Burton, T.; Chang, N.B.; Deng, W.T.; Deshpande, A.; Diehl, M.; Dumitru, A.; Dupre, R.; Ent, R.; Fazio, S.; Gao, H.; Guzey, V.; Hakobyan, H.; Hao, Y.; Hasch, D.; Holt, R.; Horn, T.; Huang, M.; Hutton, A.; Hyde, C.; Jalilian-Marian, J.; Klein, S.; Kopeliovich, B.; Kovchegov, Y.; Kumar, K.; Kumericki, K.; Lamont, M.A.C.; Lappi, T.; Lee, J.H.; Lee, Y.; Levin, E.M.; Lin, F.L.; Litvinenko, V.; Ludlam, T.W.; Marquet, C.; Meziani, Z.E.; McKeown, R.; Metz, A.; Milner, R.; Morozov, V.S.; Mueller, A.H.; Muller, B.; Mueller, Dieter; Nadel-Turonski, P.; Prokudin, A.; Ptitsyn, V.; Qian, X.; Qiu, J.W.; Ramsey-Musolf, M.; Roser, T.; Sabatie, F.; Sassot, R.; Schnell, G.; Schweitzer, P.; Sichtermann, E.; Stratmann, M.; Strikman, M.; Sullivan, M.; Taneja, S.; Toll, T.; Trbojevic, D.; Ullrich, T.; Venugopalan, R.; Vigdor, S.; Vogelsang, W.; Weiss, C.; Xiao, B.W.; Yuan, F.; Zhang, Y.H.; Zheng, L.

    2012-01-01

    This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics and, in particular, the focused ten-week program on "Gluons and quark sea at high energies" at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them, and it benefited from inputs from the users' communities of BNL and JLab. This White Paper offers the promise to prope...

  7. Controlling the Charge State and Redox Properties of Supported Polyoxometalates via Soft Landing of Mass Selected Ions

    Energy Technology Data Exchange (ETDEWEB)

    Gunaratne, Kalupathirannehelage Don D.; Johnson, Grant E.; Andersen, Amity; Du, Dan; Zhang, Weiying; Prabhakaran, Venkateshkumar; Lin, Yuehe; Laskin, Julia

    2014-12-04

    We investigate the controlled deposition of Keggin polyoxometalate (POM) anions, PMo12O403- and PMo12O402-, onto different self-assembled monolayer (SAM) surfaces via soft landing of mass-selected ions. Utilizing in situ infrared reflection absorption spectroscopy (IRRAS), ex situ cyclic voltammetry (CV) and electronic structure calculations, we examine the structure and charge retention of supported multiply-charged POM anions and characterize the redox properties of the modified surfaces. SAMs of alkylthiol (HSAM), perfluorinated alkylthiol (FSAM), and alkylthiol terminated with NH3+ functional groups (NH3+SAM) are chosen as model substrates for soft landing to examine the factors which influence the immobilization and charge retention of multiply charged anionic molecules. The distribution of charge states of POMs on different SAM surfaces are determined by comparing the IRRAS spectra with vibrational spectra calculated using density functional theory (DFT). In contrast to the results obtained previously for multiply charged cations, soft landed anions are found to retain charge on all three SAM surfaces. This charge retention is attributed to the substantial electron binding energy of the POM anions. Investigation of redox properties by CV reveals that, while surfaces prepared by soft landing exhibit similar features to those prepared by adsorption of POM from solution, the soft landed POM2- has a pronounced shift in oxidation potential compared to POM3- for one of the redox couples. These results demonstrate that ion soft landing is uniquely suited for precisely controlled preparation of substrates with specific electronic and chemical properties that cannot be achieved using conventional deposition techniques.

  8. Squeezing properties of a trapped ion in the running-wave laser beyond the Lamb-Dicke limit

    Institute of Scientific and Technical Information of China (English)

    Pan Chang-Ning; Fang Mao-Fa; Zheng Xiao-Juan; Hu Yao-Hua

    2007-01-01

    Beyond the Lamb-Dicke limit, this paper investigates the squeezing properties of the trapped ion in the travelling-wave laser. It shows that the squeezing properties of the trapped ion in the travelling-wave laser are strongly affected by the sideband number k, the Lamb- Dicke parameterηand the initial average phonon number.

  9. Influence of Lanthanum Ion-Implantation on Adhesive Property of Oxide Film Formed on Co-40Cr Alloy

    Institute of Scientific and Technical Information of China (English)

    JIN Hui-ming; ZHANG Lin-nan; LIU Xiao-jun

    2008-01-01

    The isothermal and cyclic oxidizing kinetics of Co-40Cr alloy and its lanthanum ion-implanted samples were studied at 1 000 ℃ in air by thermal gravimetric analysis (TGA). Scanning electron microscopy (SEM) was used to examine the Cr2O3 oxide film's morphology after oxidation. Secondary ion mass spectrum (SIMS) method was used to examine the binding energy change of chromium caused by La-doping and its influence on the formation of Cr2O3 film. Acoustic emission (AE) method was used in situ to monitor the cracking and spalling of oxide films during oxidizing and subsequent air-cooling stages. Laser Raman spectrum was used to examine the stress changes within oxide films. A theoretical model was proposed relating to the film fracture process and was used to analyze the AE spectrum both on time domain and AE-event number domain. It was found that lanthanum implantation remarkably reduced the isothermal oxidizing rate of Co-40Cr and improved the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement were mainly that the implanted lanthanum reduced the grain size and internal stress of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr2O3/Co-40Cr interfacial defects.

  10. DFT/TDDFT investigation of the modulation of photochromic properties in an organoboron-based diarylethene by fluoride ions.

    Science.gov (United States)

    Liu, Shujuan; Sun, Shi; Wang, Chuanming; Zhao, Qiang; Sun, Huibin; Li, Fuyou; Fan, Quli; Huang, Wei

    2011-02-07

    The diarylethene derivative 1,2-bis-(5'-dimesitylboryl-2'-methylthieny-3'-yl)-cyclopentene (1) containing dimesitylboryl groups is an interesting photochromic material. The dimesitylboryl groups can bind to F(-), which tunes the optical and electronic properties of the diarylethene compound. Hence, the diarylethene derivative 1 containing dimesitylboryl groups is sensitive to both light and F(-), and its photochromic properties can be tuned by a fluoride ion. Herein, we studied the substituent effect of dimesitylboron groups on the optical properties of both the closed-ring and open-ring isomers of the diarylethene molecule by DFT/TDDFT calculations and found that these methods are reliable for the determination of the lowest singlet excitation energies of diarylethene compounds. The introduction of dimesitylboron groups to the diarylethene compound can elongate its conjugation length and change the excited-state properties from π→π* transition to a charge-transfer state. This explains the modulation of photochromic properties through the introduction of dimesitylboron groups. Furthermore, the photochromic properties can be tuned through the binding of F(-) to a boron center and the excited state of the diarylethene compound is changed from a charge-transfer state to a π→π* transition. Hence, a subtle control of the photochromic spectroscopic properties was realized. In addition, the changes of electronic characteristics by the isomerization reaction of diarylethene compounds were also investigated with theoretical calculations. For the model compound 2 without dimesitylboryl groups, the closed-ring isomer has better hole- and electron-injection abilities, as well as higher charge-transport rates, than the open-ring isomer. The introduction of dimesitylboron groups to diarylethene can dramatically improve the charge-injection and -transport abilities. The closed isomer of compound 1 (1 C) has the best hole- and electron-injection abilities, whereas the

  11. The Solution Structure, Binding Properties, and Dynamics of the Bacterial Siderophore-binding Protein FepB

    NARCIS (Netherlands)

    Chu, Byron C. H.; Otten, Renee; Krewulak, Karla D.; Mulder, Frans A.A.; Vogel, Hans J.

    2014-01-01

    The periplasmic binding protein (PBP) FepB plays a key role in transporting the catecholate siderophore ferric enterobactin from the outer to the inner membrane in Gram-negative bacteria. The solution structures of the 34-kDa apo- and holo-FepB from Escherichia coli, solved by NMR, represent the fir

  12. Efficient synthesis of metallated thioporphyrazines in task specific ionic liquids and their spectroscopic investigation of binding with selected transition metal ions

    Indian Academy of Sciences (India)

    POONAM; RITIKA NAGPAL; SMRITI ARORA; SHIVE M S CHAUHAN

    2016-09-01

    Tetramerization of substituted maleonitriles in task specific 2-hydroxylethyl based imidazolium ionic liquids at 120◦C gave corresponding electron rich peripheral substituted thioporphyrazines in moderate yield. The 2-hydroxylethyl imidazolium ionic liquids gave better yields of peripheral substituted thioporphyrazinesin comparison with non-hydroxyl functionalized ionic liquids. Further, these peripherally functionalized porphyrazines containing sulphur are used to investigate spectroscopically the binding studies with palladium(II) and mercury(II) ions. These metal ions are toxic in nature and deserve serious attention in the areaof design of effective separation and efficient micro-sensing techniques. The UV–Vis absorption spectroscopy and fluorescence signalling are mainly used to study peripheral binding of transition metal ions.

  13. Modifications in surface, structural and mechanical properties of brass using laser induced Ni plasma as an ion source

    Directory of Open Access Journals (Sweden)

    Shahbaz Ahmad

    2016-03-01

    Full Text Available Laser induced Ni plasma has been employed as source of ion implantation for surface, structural and mechanical properties of brass. Excimer laser (248 nm, 20 ns, 120mJ and 30 Hz was used for the generation of Ni plasma. Thomson parabola technique was employed to estimate the energy of generated ions using CR39 as a detector. In response to stepwise increase in number of laser pulses from 3000 to 12000, the ion dose varies from 60 × 1013 to 84 × 1016 ions/cm2 with constant energy of 138 KeV. SEM analysis reveals the growth of nano/micro sized cavities, pores, pits, voids and cracks for the ion dose ranging from 60 × 1013 to 70 × 1015 ions/cm2. However, at maximum ion dose of 84 × 1016 ions/cm2 the granular morphology is observed. XRD analysis reveals that new phase of CuZnNi (200 is formed in the brass substrate after ion implantation. However, an anomalous trend in peak intensity, crystallite size, dislocation line density and induced stresses is observed in response to the implantation with various doses. The increase in ion dose causes to decrease the Yield Stress (YS, Ultimate Tensile Strength (UTS and hardness. However, for the maximum ion dose the highest values of these mechanical properties are achieved. The variations in the mechanical properties are correlated with surface and crystallographical changes of ion implanted brass.

  14. Dual-ion-beam deposition of carbon films with diamond-like properties

    Science.gov (United States)

    Mirtich, M. J.; Swec, D. M.; Angus, J. C.

    1985-01-01

    A single and dual ion beam system was used to generate amorphous carbon films with diamond like properties. A methane/argon mixture at a molar ratio of 0.28 was ionized in the low pressure discharge chamber of a 30-cm-diameter ion source. A second ion source, 8 cm in diameter was used to direct a beam of 600 eV Argon ions on the substrates (fused silica or silicon) while the deposition from the 30-cm ion source was taking place. Nuclear reaction and combustion analysis indicate H/C ratios for the films to be 1.00. This high value of H/C, it is felt, allowed the films to have good transmittance. The films were impervious to reagents which dissolve graphitic and polymeric carbon structures. Although the measured density of the films was approximately 1.8 gm/cu cm, a value lower than diamond, the films exhibited other properties that were relatively close to diamond. These films were compared with diamond like films generated by sputtering a graphite target.

  15. Selective detection of mercury (II) ion using nonlinear optical properties of gold nanoparticles.

    Science.gov (United States)

    Darbha, Gopala Krishna; Singh, Anant Kumar; Rai, Uma Shanker; Yu, Eugene; Yu, Hongtao; Chandra Ray, Paresh

    2008-06-25

    Contamination of the environment with heavy metal ions has been an important concern throughout the world for decades. Driven by the need to detect trace amounts of mercury in environmental samples, this article demonstrates for the first time that nonlinear optical (NLO) properties of MPA-HCys-PDCA-modified gold nanoparticles can be used for rapid, easy and reliable screening of Hg(II) ions in aqueous solution, with high sensitivity (5 ppb) and selectivity over competing analytes. The hyper Rayleigh scattering (HRS) intensity increases 10 times after the addition of 20 ppm Hg(2+) ions to modified gold nanoparticle solution. The mechanism for HRS intensity change has been discussed in detail using particle size-dependent NLO properties as well as a two-state model. Our results show that the HRS assay for monitoring Hg(II) ions using MPA-HCys-PDCA-modified gold nanoparticles has excellent selectivity over alkali, alkaline earth (Li(+), Na(+), K(+), Mg(2+), Ca(2+)), and transition heavy metal ions (Pb(2+), Pb(+), Mn(2+), Fe(2+), Cu(2+), Ni(2+), Zn(2+), Cd(2+)).

  16. Assessment of CpTi Surface Properties after Nitrogen Ion Implantation with Various Doses and Energies

    Science.gov (United States)

    Fulazzaky, Mohamad Ali; Ali, Nurdin; Samekto, Haryanti; Ghazali, Mohd Imran

    2012-11-01

    Nitrogen ion implantation is one of the surface modification techniques used for increasing corrosion resistance of commercially pure titanium (CpTi). The nitrogen ion implanted CpTi in various doses markedly changes the corrosion resistance. Still the effect of nitrogen ion implantation on the CpTi at different energies needs to be verified. This study uses different methods to assess the CpTi surface properties after nitrogen ion implantation in various doses and energy. Surface hardness of the CpTi increases with an increase of the dose and decreases with an increase of the energy. The precipitation of the TiN increases with an increase of the nitrogen dose, and no formation of the Ti2N phase clearly appears. Corrosion resistance of the CpTi specimens can be upgraded to some extent after their surfaces are modified, implanting nitrogen ions at 100 keV by increasing dose. The optimum surface properties of the implanted CpTi are analyzed to contribute to materials science technology.

  17. Layer compression and enhanced optical properties of few-layer graphene nanosheets induced by ion irradiation

    CERN Document Server

    Tan, Yang; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng

    2016-01-01

    Graphene has been recognized as an attractive two-dimensional material for fundamental research and wide applications in electronic and photonic devices owing to its unique properties. The technologies to modulate the properties of graphene are of continuous interest to researchers in multidisciplinary areas. Herein, we report on the first experimental observation of the layer-to-layer compression and enhanced optical properties of few-layer graphene nanosheets by applying the irradiation of energetic ion beams. After the irradiation, the space between the graphene layers was reduced, resulting in a tighter contact between the few-layer graphene nanosheet and the surface of the substrate. This processing also enhanced the interaction between the graphene nanosheets and the evanescent-field wave near the surface, thus reinforcing the polarization-dependent light absorption of the graphene layers (with 3-fold polarization extinction ratio increment). Utilizing the ion-irradiated graphene nanosheets as saturable...

  18. Construction and Ion Exchange Properties of Supramolecular Complexes with Organic Ligands and Metal Ions

    Institute of Scientific and Technical Information of China (English)

    SUN; WeiYin

    2001-01-01

    Supramolecular architectures with specific topologies such as closed threedimensional molecular cages present a large range of applications in material science, medicine and chemical technology.1,2 In the past decades, a number of such frameworks, e.g. M6L4, M12L8 and M18L6, have been synthesized by assembly of organic ligands with transitional metal salts.3-5 However, the M3L2 type cage-like complexes are not well known up to now.6,7 We report herein the generation of M3L2 type cages by tripodal ligands and various metal salts, and the anion exchange, molecular recognition properties of these metallosupramolecular cages.  ……

  19. Construction and Ion Exchange Properties of Supramolecular Complexes with Organic Ligands and Metal Ions

    Institute of Scientific and Technical Information of China (English)

    SUN WeiYin; FAN Jian

    2001-01-01

    @@ Supramolecular architectures with specific topologies such as closed threedimensional molecular cages present a large range of applications in material science, medicine and chemical technology.1,2 In the past decades, a number of such frameworks, e.g. M6L4, M12L8 and M18L6, have been synthesized by assembly of organic ligands with transitional metal salts.3-5 However, the M3L2 type cage-like complexes are not well known up to now.6,7 We report herein the generation of M3L2 type cages by tripodal ligands and various metal salts, and the anion exchange, molecular recognition properties of these metallosupramolecular cages.

  20. Effect of Ion Bombardment on the Growth and Properties of Hydrogenated Amorphous Silicon-Germanium Alloys

    Science.gov (United States)

    Perrin, Jérôme; Takeda, Yoshihiko; Hirano, Naoto; Matsuura, Hideharu; Matsuda, Akihisa

    1989-01-01

    We report a systematic investigation of the effect of ion bombardment during the growth of amorphous silicon-germanium alloy films from silane and germane rf-glow discharge. Independent control of the plasma and the ion flux and energy is obtained by using a triode configuration. The ion contribution to the total deposition rate can reach 20% on negatively biased substrates. Although the Si and Ge composition of the film does not depend on the ion flux and energy, the optical, structural and electronic properties are drastically modified at low deposition temperatures when the maximum ion energy increases up to 50 eV, and remain constant above 50 eV. For a Ge atomic concentration of 37% and a temperature of 135°C, the optical gap decreases from 1.67 to 1.45 eV. This is correlated with a modification of hydrogen bonding configurations. Silicon dihydride sites disappear and preferential attachment of hydrogen to silicon is reduced in favour of germanium. Moreover the photoconductivity increases which shows that ion bombardment is a key parameter to optimize the quality of low band gap amorphous silicon-germanium alloys.

  1. Ion Transport Properties of Mechanically Stable symmetric ABCBA Pentablock Copolymers with Quaternary Ammonium Functionalized Midblock

    Energy Technology Data Exchange (ETDEWEB)

    Ertem, S. Piril; Caire, Benjamin R.; Tsai, Tsung-Han; Zeng, Di; Vandiver, Melissa A.; Kusoglu, Ahmet; Seifert, Soenke; Hayward, Ryan C.; Weber, Adam Z.; Herring , Andrew M.; Coughlin, E. Bryan; Liberatore, Matthew W.

    2017-01-01

    Anion exchange membranes (AEMs) are a promising class of materials for applications that require selective ion transport, such as fuel cells, water purification, and electrolysis devices. Studies of structure–morphology–property relationships of ion-exchange membranes revealed that block copolymers exhibit improved ion conductivity and mechanical properties due to their microphase-separated morphologies with well-defined ionic domains. While most studies focused on symmetric diblock or triblock copolymers, here, the first example of a midblock quaternized pentablock AEM is presented. A symmetric ABCBA pentablock copolymer was functionalized to obtain a midblock brominated polymer. Solution cast films were then quaternized to obtain AEMs with resulting ion exchange capacities (IEC) ranging from 0.4 to 0.9 mmol/g. Despite the relatively low IEC, the polymers were highly conductive (up to 60 mS/cm Br2 at 90 8C and 95%RH) with low water absorption (<25 wt %) and maintained adequate mechanical properties in both dry and hydrated conditions. Xray scattering and transmission electron microscopy (TEM) revealed formation of cylindrical non-ionic domains in a connected ionic phase.

  2. Experimental control of the beam properties of laser-accelerated protons and carbon ions

    Energy Technology Data Exchange (ETDEWEB)

    Amin, Munib

    2008-12-15

    The laser generation of energetic high quality beams of protons and heavier ions has opened up the door to a plethora of applications. These beams are usually generated by the interaction of a short pulse high power laser with a thin metal foil target. They could already be applied to probe transient phenomena in plasmas and to produce warm dense matter by isochoric heating. Other applications such as the production of radioisotopes and tumour radiotherapy need further research to be put into practice. To meet the requirements of each application, the properties of the laser-accelerated particle beams have to be controlled precisely. In this thesis, experimental means to control the beam properties of laser-accelerated protons and carbon ions are investigated. The production and control of proton and carbon ion beams is studied using advanced ion source designs: Experiments concerning mass-limited (i.e. small and isolated) targets are conducted. These targets have the potential to increase both the number and the energy of laser-accelerated protons. Therefore, the influence of the size of a plane foil target on proton beam properties is measured. Furthermore, carbon ion sources are investigated. Carbon ions are of particular interest in the production of warm dense matter and in cancer radiotherapy. The possibility to focus carbon ion beams is investigated and a simple method for the production of quasi-monoenergetic carbon ion beams is presented. This thesis also provides an insight into the physical processes connected to the production and the control of laser-accelerated ions. For this purpose, laser-accelerated protons are employed to probe plasma phenomena on laser-irradiated targets. Electric fields evolving on the surface of laser-irradiated metal foils and hollow metal foil cylinders are investigated. Since these fields can be used to displace, collimate or focus proton beams, understanding their temporal and spatial evolution is crucial for the design of

  3. Variation in one residue associated with the metal ion-dependent adhesion site regulates αIIbβ3 integrin ligand binding affinity.

    Directory of Open Access Journals (Sweden)

    Joel Raborn

    Full Text Available The Asp of the RGD motif of the ligand coordinates with the β I domain metal ion dependent adhesion site (MIDAS divalent cation, emphasizing the importance of the MIDAS in ligand binding. There appears to be two distinct groups of integrins that differ in their ligand binding affinity and adhesion ability. These differences may be due to a specific residue associated with the MIDAS, particularly the β3 residue Ala(252 and corresponding Ala in the β1 integrin compared to the analogous Asp residue in the β2 and β7 integrins. Interestingly, mutations in the adjacent to MIDAS (ADMIDAS of integrins α4β7 and αLβ2 increased the binding and adhesion abilities compared to the wild-type, while the same mutations in the α2β1, α5β1, αVβ3, and αIIbβ3 integrins demonstrated decreased ligand binding and adhesion. We introduced a mutation in the αIIbβ3 to convert this MIDAS associated Ala(252 to Asp. By combination of this mutant with mutations of one or two ADMIDAS residues, we studied the effects of this residue on ligand binding and adhesion. Then, we performed molecular dynamics simulations on the wild-type and mutant αIIbβ3 integrin β I domains, and investigated the dynamics of metal ion binding sites in different integrin-RGD complexes. We found that the tendency of calculated binding free energies was in excellent agreement with the experimental results, suggesting that the variation in this MIDAS associated residue accounts for the differences in ligand binding and adhesion among different integrins, and it accounts for the conflicting results of ADMIDAS mutations within different integrins. This study sheds more light on the role of the MIDAS associated residue pertaining to ligand binding and adhesion and suggests that this residue may play a pivotal role in integrin-mediated cell rolling and firm adhesion.

  4. Recent trends in precision measurements of atomic and nuclear properties with lasers and ion traps

    Energy Technology Data Exchange (ETDEWEB)

    Block, Michael, E-mail: m.block@gsi.de [GSI Helmholtzzentrum für Schwerionenforschung GmbH (Germany)

    2017-11-15

    The X. international workshop on “Application of Lasers and Storage Devices in Atomic Nuclei Research” took place in Poznan in May 2016. It addressed the latest experimental and theoretical achievements in laser and ion trap-based investigations of radionuclides, highly charged ions and antiprotons. The precise determination of atomic and nuclear properties provides a stringent benchmark for theoretical models and eventually leads to a better understanding of the underlying fundamental interactions and symmetries. This article addresses some general trends in this field and highlights select recent achievements presented at the workshop. Many of these are covered in more detail within the individual contributions to this special issue of Hyperfine Interactions.

  5. Optical properties of lead borate glasses containing Dy{sup 3+} ions

    Energy Technology Data Exchange (ETDEWEB)

    Pisarska, Joanna [Department of Materials Science, Silesian University of Technology, Krasinskiego 8, 40-019 Katowice (Poland)], E-mail: Joanna.Pisarska@polsl.pl

    2009-07-15

    Optical properties of lead borate glasses containing Dy{sup 3+} ions were examined using absorption and luminescence measurements and theoretical calculations based on the Judd-Ofelt framework and the Inokuti-Hirayama model. The luminescence spectra show two characteristic bands at 480 and 573 nm, which are due to {sup 4}F{sub 9/2}-{sup 6}H{sub 15/2} (blue) and {sup 4}F{sub 9/2}-{sup 6}H{sub 13/2} (yellow) transitions of trivalent Dy{sup 3+} ions. The yellow/blue luminescence and its decay were analyzed as a function of activator concentration.

  6. Multiple Metal Binding Domains Enhance the Zn(II) Selectivity of the Divalent Metal Ion Transporter AztA

    Energy Technology Data Exchange (ETDEWEB)

    Liu, T.; Reyes-Caballero, H.; Li, C.; Scott, R.A.; Giedroc, D.P.

    2009-06-03

    Transition metal-transporting P{sub 1B}-type CPx ATPases play crucial roles in mediating metal homeostasis and resistance in all cells. The degree to which N-terminal metal binding domains (MBDs) confer metal specificity to the transporter is unclear. We show that the two MBDs of the Zn/Cd/Pb effluxing pump Anabaena AztA are functionally nonequivalent, but only with respect to zinc resistance. Inactivation of the a-MBD largely abrogates resistance to high intracellular Zn(II) levels, whereas inactivation of the b-MBD is not as deleterious. In contrast, inactivation of either the a- or b-MBD has little measurable impact on Cd(II) and Pb(II) resistance. The membrane proximal b-MBD binds Zn(II) with a higher affinity than the distal N-terminal a-MBD. Facile Zn(II)-specific intermolecular transfer from the a-MBD to the higher-affinity b-MBD is readily observed by {sup 1}H-{sup 15}N HSQC spectroscopy. Unlike Zn(II), Cd(II) and Pb(II) form saturated 1:1 S{sub 4} or S{sub 3}(O/N) complexes with AztA{sup aHbH}, where a single metal ion bridges the two MBDs. We propose that the tandem MBDs enhance Zn(II)-specific transport, while stabilizing a non-native inter-MBD Cd/Pb cross-linked structure that is a poor substrate and/or regulator for the transporter.

  7. Comparative study of glycated hemoglobin by ion exchange chromatography and affinity binding nycocard reader in type 2 diabetes mellitus.

    Science.gov (United States)

    Gautam, N; Dubey, R K; Jayan, A; Nepaune, Y; Padmavathi, P; Chaudhary, S; Jha, S K; Sinha, A K

    2014-12-01

    The aim of this study was to compare the level of glycated hemoglobin (HbA1c) in type 2 Diabetes Mellitus (DM) patients by two different methods namely Ion Exchange Chromatography and Affinity Binding Nycocard Reader. This is a cross-sectional study conducted on confirmed type 2 diabetes mellitus patients (n = 100) who visited Out Patients Department of the Universal College of Medical Sciences Teaching hospital, Bhairahawa, Nepal from November 2012 to March 2013. The diagnosis of diabetes mellitus was done on the basis of their fasting (164.46 ± 45.33 mg/dl) and random (187.93 ± 78.02 mg/dl) serum glucose level along with clinical history highly suggestive of type 2 DM. The HbA1c values of (7.8 ± 1.9%) and (8.0 ± 2.2%) were found in DM patients as estimated by those two different methods respectively. The highest frequency was observed in HbA1c > 8.0% indicating maximum cases were under very poor glycemic control. However, there were no significant differences observed in HbA1c value showing both methods are comparable in nature and can be used in lab for ease of estimation. The significant raised in HbA1c indicates complications associated with DM and monitoring of therapy become hard for those patients. Despite having standard reference method for HbA1c determination, the availability of report at the time of the patient visit can be made easy by using Nycocard Reader and Ion Exchange Chromatography techniques without any delay in communicating glycemic control, clinical decision-making and changes in treatment regimen.

  8. Computational studies of ion pairing. 8. Ion pairing of tetraalkylammonium ions to nitrosobenzene and benzaldehyde redox species. A general binding motif for the interaction of tetraalkylammonium ions with benzenoid species.

    Science.gov (United States)

    Fry, Albert J

    2013-06-01

    Very little data is available on the detailed structures of ion pairs in solution, since few general experimental methods are available for obtaining such information. For this reason, computational methods have emerged as the method of choice for determining the structures of organic ion pairs in solution. The present study examines the ion pairs between a series of tetraalkylammonium ions and several redox forms of nitrosobenzene and a series of substituted benzaldehydes. The structures, though previously unexpected, are chemically reasonable and fit into a previous pattern of ion pairing described in previous publications in this series. To date in these studies, a total of 73 ion pairs and related species have in fact been identified having exactly the same unusual orientation of the tetraalkylammonium component with respect to the donor species. The results are pertinent to topics of general current interest, including self-assembly, molecular recognition, and supramolecular assembly.

  9. Cell Surface Properties of Lactococcus lactis Reveal Milk Protein Binding Specifically Evolved in Dairy Isolates

    Directory of Open Access Journals (Sweden)

    Mariya Tarazanova

    2017-09-01

    Full Text Available Surface properties of bacteria are determined by the molecular composition of the cell wall and they are important for interactions of cells with their environment. Well-known examples of bacterial interactions with surfaces are biofilm formation and the fermentation of solid materials like food and feed. Lactococcus lactis is broadly used for the fermentation of cheese and buttermilk and it is primarily isolated from either plant material or the dairy environment. In this study, we characterized surface hydrophobicity, charge, emulsification properties, and the attachment to milk proteins of 55 L. lactis strains in stationary and exponential growth phases. The attachment to milk protein was assessed through a newly developed flow cytometry-based protocol. Besides finding a high degree of biodiversity, phenotype-genotype matching allowed the identification of candidate genes involved in the modification of the cell surface. Overexpression and gene deletion analysis allowed to verify the predictions for three identified proteins that altered surface hydrophobicity and attachment of milk proteins. The data also showed that lactococci isolated from a dairy environment bind higher amounts of milk proteins when compared to plant isolates. It remains to be determined whether the alteration of surface properties also has potential to alter starter culture functionalities.

  10. Cell Surface Properties of Lactococcus lactis Reveal Milk Protein Binding Specifically Evolved in Dairy Isolates.

    Science.gov (United States)

    Tarazanova, Mariya; Huppertz, Thom; Beerthuyzen, Marke; van Schalkwijk, Saskia; Janssen, Patrick; Wels, Michiel; Kok, Jan; Bachmann, Herwig

    2017-01-01

    Surface properties of bacteria are determined by the molecular composition of the cell wall and they are important for interactions of cells with their environment. Well-known examples of bacterial interactions with surfaces are biofilm formation and the fermentation of solid materials like food and feed. Lactococcus lactis is broadly used for the fermentation of cheese and buttermilk and it is primarily isolated from either plant material or the dairy environment. In this study, we characterized surface hydrophobicity, charge, emulsification properties, and the attachment to milk proteins of 55 L. lactis strains in stationary and exponential growth phases. The attachment to milk protein was assessed through a newly developed flow cytometry-based protocol. Besides finding a high degree of biodiversity, phenotype-genotype matching allowed the identification of candidate genes involved in the modification of the cell surface. Overexpression and gene deletion analysis allowed to verify the predictions for three identified proteins that altered surface hydrophobicity and attachment of milk proteins. The data also showed that lactococci isolated from a dairy environment bind higher amounts of milk proteins when compared to plant isolates. It remains to be determined whether the alteration of surface properties also has potential to alter starter culture functionalities.

  11. Bovine peptidoglycan recognition protein-S: antimicrobial activity, localization, secretion, and binding properties.

    Science.gov (United States)

    Tydell, C Chace; Yuan, Jun; Tran, Patti; Selsted, Michael E

    2006-01-15

    Peptidoglycan (PGN) recognition proteins (PGRPs) are pattern recognition molecules of innate immunity that are conserved from insects to humans. Various PGRPs are reported to have diverse functions: they bind bacterial molecules, digest PGN, and are essential to the Toll pathway in Drosophila. One family member, bovine PGN recognition protein-S (bPGRP-S), has been found to bind and kill microorganisms in a PGN-independent manner, raising questions about the identity of the bPGRP-S ligand. Addressing this, we have determined the binding and microbicidal properties of bPGRP-S in a range of solutions approximating physiologic conditions. In this study we show that bPGRP-S interacts with other bacterial components, including LPS and lipoteichoic acid, with higher affinities than for PCP, as determined by their abilities to inhibit bPGRP-S-mediated killing of bacteria. Where and how PGRPs act in vivo is not yet clear. Using Immunogold electron microscopy, PGRP-S was localized to the dense/large granules of naive neutrophils, which contain the oxygen-independent bactericidal proteins of these cells, and to the neutrophil phagolysosome. In addition, Immunogold staining and secretion studies demonstrate that neutrophils secrete PGRP-S when exposed to bacteria. Bovine PGRP-S can mediate direct lysis of heat-killed bacteria; however, PGRP-S-mediated killing of bacteria is independent of this activity. Evidence that bPGRP-S has multiple activities and affinity to several bacterial molecules challenges the assumption that the PGRP family of proteins recapitulates the evolution of TLRs. Mammalian PGRPs do not have a single antimicrobial activity against a narrow range of target organisms; rather, they are generalists in their affinity and activity.

  12. RNA-binding properties and RNA chaperone activity of human peroxiredoxin 1

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ji-Hee; Lee, Jeong-Mi; Lee, Hae Na; Kim, Eun-Kyung; Ha, Bin [Lee Gil Ya Cancer and Diabetes Institute, Gachon University (Korea, Republic of); Ahn, Sung-Min, E-mail: smahn@gachon.ac.kr [Lee Gil Ya Cancer and Diabetes Institute, Gachon University (Korea, Republic of); Department of Translational Medicine, Gachon University Gil Hospital, Incheon (Korea, Republic of); Jang, Ho Hee, E-mail: hhjang@gachon.ac.kr [Lee Gil Ya Cancer and Diabetes Institute, Gachon University (Korea, Republic of); Lee, Sang Yeol [Division of Applied Life Sciences (Brain Korea 21 program), Gyeongsang National University, Jinju 660-701 (Korea, Republic of)

    2012-09-07

    Highlights: Black-Right-Pointing-Pointer hPrx1 has RNA-binding properties. Black-Right-Pointing-Pointer hPrx1 exhibits helix-destabilizing activity. Black-Right-Pointing-Pointer Cold stress increases hPrx1 level in the nuclear fraction. Black-Right-Pointing-Pointer hPrx1 enhances the viability of cells exposed to cold stress. -- Abstract: Human peroxiredoxin 1 (hPrx1), a member of the peroxiredoxin family, detoxifies peroxide substrates and has been implicated in numerous biological processes, including cell growth, proliferation, differentiation, apoptosis, and redox signaling. To date, Prx1 has not been implicated in RNA metabolism. Here, we investigated the ability of hPrx1 to bind RNA and act as an RNA chaperone. In vitro, hPrx1 bound to RNA and DNA, and unwound nucleic acid duplexes. hPrx1 also acted as a transcription anti-terminator in an assay using an Escherichia coli strain containing a stem-loop structure upstream of the chloramphenicol resistance gene. The overall cellular level of hPrx1 expression was not increased at low temperatures, but the nuclear level of hPrx1 was increased. In addition, hPrx1 overexpression enhanced the survival of cells exposed to cold stress, whereas hPrx1 knockdown significantly reduced cell survival under the same conditions. These findings suggest that hPrx1 may perform biological functions as a RNA-binding protein, which are distinctive from known functions of hPrx1 as a reactive oxygen species scavenger.

  13. FAD binding properties of a cytosolic version of Escherichia coli NADH dehydrogenase-2.

    Science.gov (United States)

    Villegas, Josefina M; Valle, Lorena; Morán Vieyra, Faustino E; Rintoul, María R; Borsarelli, Claudio D; Rapisarda, Viviana A

    2014-03-01

    Respiratory NADH dehydrogenase-2 (NDH-2) of Escherichia coli is a peripheral membrane-bound flavoprotein. By eliminating its C-terminal region, a water soluble truncated version was obtained in our laboratory. Overall conformation of the mutant version resembles the wild-type protein. Considering these data and the fact that the mutant was obtained as an apo-protein, the truncated version is an ideal model to study the interaction between the enzyme and its cofactor. Here, the FAD binding properties of this version were characterized using far-UV circular dichroism (CD), differential scanning calorimetry (DSC), limited proteolysis, and steady-state and dynamic fluorescence spectroscopy. CD spectra, thermal unfolding and DSC profiles did not reveal any major difference in secondary structure between apo- and holo-protein. In addition, digestion site accessibility and tertiary conformation were similar for both proteins, as seen by comparable chymotryptic cleavage patterns. FAD binding to the apo-protein produced a parallel increment of both FAD fluorescence quantum yield and steady-state emission anisotropy. On the other hand, addition of FAD quenched the intrinsic fluorescence emission of the truncated protein, indicating that the flavin cofactor should be closely located to the protein Trp residues. Analysis of the steady-state and dynamic fluorescence data confirms the formation of the holo-protein with a 1:1 binding stoichiometry and an association constant KA=7.0(±0.8)×10(4)M(-1). Taken together, the FAD-protein interaction is energetically favorable and the addition of FAD is not necessary to induce the enzyme folded state. For the first time, a detailed characterization of the flavin:protein interaction was performed among alternative NADH dehydrogenases.

  14. Effect of temperature, chloride ions and sulfide ions on the electrochemical properties of 316L stainless steel in simulated cooling water

    Institute of Scientific and Technical Information of China (English)

    Li Jinbo; Zhai Wen; Zheng Maosheng; Zhu Jiewu

    2008-01-01

    The influence of temperature, chloride ions and sulfide ions on the anticorrosion behavior of 316L stainless steel in simulated cooling water was studied by electrochemical impedance spectroscopy and anodic polarization curves. The results show that the film resistance increases with the solution temperature but decreases after 8 days' immersion, which indicates that the film formed at higher temperature has inferior anticorrosion behavior; Chloride ions and sulfide ions have remarkable effects on the electrochemical property of 316L stainless steel in simulated cooling water and the pitting potential declines with the concentration of chloride ions; the passivation current has no obvious effect; the rise of the concentration of sulfide ions obviously increases the passivation current, but the pitting potential changes little, which indicates that the two types of ions may have different effects on destructing passive film of stainless steel. The critical concentration of chloride ions causing anodic potential curve's change in simulated cooling water is 250 mg/L for 316 L stainless. The effect of sulfide ions on the corrosion resistance behavior of stainless steel is increasing the passivation current density Ip. The addition of 6mg/L sulfide ions to the solution makes Ip of 316 L increase by 0.5 times.

  15. Binding properties of a mannose-specific lectin from the snowdrop (Galanthus nivalis) bulb.

    Science.gov (United States)

    Shibuya, N; Goldstein, I J; Van Damme, E J; Peumans, W J

    1988-01-15

    Carbohydrate binding properties of a new plant lectin (GNA) isolated from snowdrop bulbs were studied using the technique of quantitative precipitation, hapten inhibition, and affinity chromatography on immobilized lectin. Purified GNA precipitated highly branched yeast mannans but did not react with most glucans. Hapten inhibition experiments showed that D-mannose is an inhibitor of GNA-mannan interaction but neither N-acetyl-D-mannosamine nor D-glucose is an inhibitor. Hapten inhibition with various sugars showed that GNA requires the presence of equatorial hydroxyl groups at the C-3 and C-4 positions and an axial group at the C-2 position of the D-pyranose ring. A nonreducing terminal D-mannose residue is necessary for the interaction of oligosaccharides, and oligosaccharides with terminal Man(alpha-1-3)Man units showed the highest inhibitory potency (10-30 times greater than D-mannose) among the manno-oligosaccharides tested. The presence of the hydrophobic p-nitrophenyl aglycone increased the affinity of D-mannose only slightly. Immobilized GNA bound yeast mannan but did not bind glycogen. The behavior of glycoproteins with high mannose type glycan chains depended on the density and the structure of their glycan chains. Glycopeptides which carry Man(alpha 1-3)Man units were retarded on the immobilized GNA column whereas those lacking this unit or with hybrid type glycan chains were not retarded on the column.

  16. Decoding Structural Properties of a Partially Unfolded Protein Substrate: En Route to Chaperone Binding.

    Science.gov (United States)

    Nagpal, Suhani; Tiwari, Satyam; Mapa, Koyeli; Thukral, Lipi

    2015-01-01

    Many proteins comprising of complex topologies require molecular chaperones to achieve their unique three-dimensional folded structure. The E.coli chaperone, GroEL binds with a large number of unfolded and partially folded proteins, to facilitate proper folding and prevent misfolding and aggregation. Although the major structural components of GroEL are well defined, scaffolds of the non-native substrates that determine chaperone-mediated folding have been difficult to recognize. Here we performed all-atomistic and replica-exchange molecular dynamics simulations to dissect non-native ensemble of an obligate GroEL folder, DapA. Thermodynamics analyses of unfolding simulations revealed populated intermediates with distinct structural characteristics. We found that surface exposed hydrophobic patches are significantly increased, primarily contributed from native and non-native β-sheet elements. We validate the structural properties of these conformers using experimental data, including circular dichroism (CD), 1-anilinonaphthalene-8-sulfonic acid (ANS) binding measurements and previously reported hydrogen-deutrium exchange coupled to mass spectrometry (HDX-MS). Further, we constructed network graphs to elucidate long-range intra-protein connectivity of native and intermediate topologies, demonstrating regions that serve as central "hubs". Overall, our results implicate that genomic variations (or mutations) in the distinct regions of protein structures might disrupt these topological signatures disabling chaperone-mediated folding, leading to formation of aggregates.

  17. Decoding Structural Properties of a Partially Unfolded Protein Substrate: En Route to Chaperone Binding.

    Directory of Open Access Journals (Sweden)

    Suhani Nagpal

    Full Text Available Many proteins comprising of complex topologies require molecular chaperones to achieve their unique three-dimensional folded structure. The E.coli chaperone, GroEL binds with a large number of unfolded and partially folded proteins, to facilitate proper folding and prevent misfolding and aggregation. Although the major structural components of GroEL are well defined, scaffolds of the non-native substrates that determine chaperone-mediated folding have been difficult to recognize. Here we performed all-atomistic and replica-exchange molecular dynamics simulations to dissect non-native ensemble of an obligate GroEL folder, DapA. Thermodynamics analyses of unfolding simulations revealed populated intermediates with distinct structural characteristics. We found that surface exposed hydrophobic patches are significantly increased, primarily contributed from native and non-native β-sheet elements. We validate the structural properties of these conformers using experimental data, including circular dichroism (CD, 1-anilinonaphthalene-8-sulfonic acid (ANS binding measurements and previously reported hydrogen-deutrium exchange coupled to mass spectrometry (HDX-MS. Further, we constructed network graphs to elucidate long-range intra-protein connectivity of native and intermediate topologies, demonstrating regions that serve as central "hubs". Overall, our results implicate that genomic variations (or mutations in the distinct regions of protein structures might disrupt these topological signatures disabling chaperone-mediated folding, leading to formation of aggregates.

  18. Reactive Ar ion beam sputter deposition of TiO2 films: Influence of process parameters on film properties

    Science.gov (United States)

    Bundesmann, C.; Lautenschläger, T.; Thelander, E.; Spemann, D.

    2017-03-01

    Several sets of TiO2 films were grown by Ar ion beam sputter deposition under systematic variation of ion energy and geometrical parameters (ion incidence angle and polar emission angle). The films were characterized concerning thickness, growth rate, structural properties, composition, mass density, and optical properties. The film thicknesses show a cosine-like angular distribution, and the growth rates were found to increase with increasing ion incidence angle and ion energy. All films are amorphous and stoichiometric, but can contain a considerable amount of backscattered primary particles. The atomic fraction of Ar particles decreases systematically with increasing scattering angle, independent from ion energy and ion incidence angle. Mass density and index of refraction show similar systematic variations with ion energy and geometrical parameters. The film properties are mainly influenced by the scattering geometry, and only slightly by ion energy and ion incidence angle. The variations in the film properties are tentatively assigned to changes in the angular and energy distribution of the sputtered target particles and back-scattered primary particles.

  19. Synthesis, photochemistry, DNA cleavage/binding and cytotoxic properties of fluorescent quinoxaline and quinoline hydroperoxides.

    Science.gov (United States)

    Chowdhury, Nilanjana; Gangopadhyay, Moumita; Karthik, S; Pradeep Singh, N D; Baidya, Mithu; Ghosh, S K

    2014-01-01

    Novel fluorescent quinoxaline and quinoline hydroperoxides were shown to perform dual role as both fluorophores for cell imaging and photoinduced DNA cleaving agents. Photophysical studies of newly synthesized quinoxaline and quinoline hydroperoxides showed that they all exhibited moderate to good fluorescence. Photolysis of quinoxaline and quinoline hydroperoxides in acetonitrile using UV light above 350nm resulted in the formation of corresponding ester compounds via γ-hydrogen abstraction by excited carbonyl chromophore. Single strand DNA cleavage was achieved on irradiation of newly synthesized hydroperoxides by UV light (⩾350nm). Both hydroxyl radicals and singlet oxygen were identified as reactive oxygen species (ROS) responsible for the DNA cleavage. Further, we showed quinoline hydroperoxide binds to ct-DNA via intercalative mode. In vitro biological studies revealed that quinoline hydroperoxide has good biocompatibility, cellular uptake property and cell imaging ability. Finally, we showed that quinoline hydroperoxide can permeate into cells efficiently and may cause cytotoxicity upon irradiation by UV light.

  20. Effects of carbon doping on the electronic properties of boron nitride nanotubes: Tight binding calculation

    Science.gov (United States)

    Chegel, Raad

    2016-10-01

    The electronic properties of pure and carbon doped zigzag and armchair Boron Nitride Nanotubes (BNNTs) have been investigated based on tight binding formalism. It was found that the band gap is reduced due to substitution of Boron or Nitrogen atoms by carbon atoms and the doping effects of B- and N-substituted BNNTs are different. The applied electric field converts the carbon doped BNNTs from semiconductor to metal. The gap energy reduction shows an identical dependence to electric field and doping for both armchair and zigzag carbon doped BNNTs. Our results indicate that the band gap of carbon doped BNNTs is a function of the Impurity concentration, electric field strength and the direction between the electric field and dopant location. The band gap for C-doped BNNTs with four carbon atoms decreases linearly but for two carbon atoms, it is constant at first then decreases linearly.

  1. The structural and optical properties of metal ion-implanted GaN

    Science.gov (United States)

    Macková, A.; Malinský, P.; Sofer, Z.; Šimek, P.; Sedmidubský, D.; Veselý, M.; Böttger, R.

    2016-03-01

    The practical development of novel optoelectronic materials with appropriate optical properties is strongly connected to the structural properties of the prepared doped structures. We present GaN layers oriented along the (0 0 0 1) crystallographic direction that have been grown by low-pressure metal-organic vapour-phase epitaxy (MOVPE) on sapphire substrates implanted with 200 keV Co+, Fe+ and Ni+ ions. The structural properties of the ion-implanted layers have been characterised by RBS-channelling and Raman spectroscopy to obtain a comprehensive insight into the structural modification of implanted GaN layers and to study the subsequent influence of annealing on crystalline-matrix recovery. Photoluminescence was measured to control the desired optical properties. The post-implantation annealing induced the structural recovery of the modified GaN layer depending on the introduced disorder level, e.g. depending on the ion implantation fluence, which was followed by structural characterisation and by the study of the surface morphology by AFM.

  2. Surface insulating properties of titanium implanted alumina ceramics by plasma immersion ion implantation

    Science.gov (United States)

    Zhu, Mingdong; Song, Falun; Li, Fei; Jin, Xiao; Wang, Xiaofeng; Wang, Langping

    2017-09-01

    The insulating property of the alumina ceramic in vacuum under high voltage is mainly limited by its surface properties. Plasma immersion ion implantation (PIII) is an effective method to modify the surface chemical and physical properties of the alumina ceramic. In order to improve the surface flashover voltage of the alumina ceramic in vacuum, titanium ions with an energy of about 20 keV were implanted into the surface of the alumina ceramic using the PIII method. The surface properties of the as-implanted samples, such as the chemical states of the titanium, morphology and surface resistivity, were characterized by X-ray photoelectron spectroscopy, scanning electron microscope and electrometer, respectively. The surface flashover voltages of the as-implanted alumina samples were measured by a vacuum surface flashover experimental system. The XPS spectra revealed that a compound of Ti, TiO2 and Al2O3 was formed in the inner surface of the alumina sample. The electrometer results showed that the surface resistivity of the implanted alumina decreased with increased implantation time. In addition, after the titanium ion implantation, the maximum hold-off voltage of alumina was increased to 38.4 kV, which was 21.5% higher than that of the unimplanted alumina ceramic.

  3. Correlation between the structural and optical properties of ion-assisted hafnia thin films

    Science.gov (United States)

    Scaglione, Salvatore; Sarto, Francesca; Alvisi, Marco; Rizzo, Antonella; Perrone, Maria R.; Protopapa, Maria L.

    2000-03-01

    The ion beam assistance during the film growth is one of the most useful method to obtain dense film along with improved optical and structural properties. Afnia material is widely used in optical coating operating in the UV region of the spectrum and its optical properties depend on the production method and the physical parameters of the species involved in the deposition process. In this work afnia thin films were evaporated by an e-gun and assisted during the growth process. The deposition parameters, ion beam energy, density of ions impinging on the growing film and the number of arrival atoms from the crucible, have been related to the optical and structural properties of the film itself. The absorption coefficient and the refractive index were measured by spectrophotometric technique while the microstructure has been studied by means of x-ray diffraction. A strictly correlation between the grain size, the optical properties and the laser damage threshold measurements at 248 nm was found for the samples deposited at different deposition parameters.

  4. MECHANICAL PROPERTIES OF PVA NANOFIBER TEXTILES WITH INCORPORATED NANODIAMONDS, COPPER AND SILVER IONS

    Directory of Open Access Journals (Sweden)

    Kateřina Indrová

    2015-02-01

    Full Text Available The unique properties of nanotextiles based on poly(vinyl-alcohol (PVA manufactured using electrospinning method have been known and exploited for many years. Recently, the enrichment of nanofiber textiles with nanoparticles, such as ions or nanodiamond particles (NDP, has become a popular way to modify the textile mechanical, chemical and physical properties. The aim of our study is to investigate the macromechanical properties of PVA nanotextiles enriched with NDP, silver (Ag and copper (Cu ions. The nanofiber textiles of a various surface weight were prepared from 16% PVA solution, while glyoxal and phosphoric acid were used as cross-linking agents. The copper and silver ions were diluted in aqueous solution and NDP were dispersed into the fibers by ultrasound homogenization. All but one set of samples were exposed to the temperature of 140 °C for 10 minutes. The samples without thermal stabilization exhibited significantly lower elastic stiffness and tensile strength. Moreover, the results of tensile testing indicate that the addition of dispersed nanoparticles has a minor effect on the mechanical properties of textiles and contributes rather to their reinforcement. On the other hand, the lack of thermal stabilization results in a poor interconnection of individual nanofiber layers and the non-stabilized textiles exhibit a lower elastic stiffness and reduced tensile strength.

  5. Preparation and biological properties of a melibiose binding lectin from Bauhinia variegata seeds.

    Science.gov (United States)

    Lin, Peng; Ng, Tzi Bun

    2008-11-26

    A dimeric 64-kDa melibiose-binding lectin was isolated from the seeds of Bauhinia variegata. The isolation procedure comprised affinity chromatography on Affi-gel blue gel, ion exchange chromatography on Mono Q, and gel filtration on Superdex 75. The lectin was adsorbed on the first two chromatographic media. Its hemagglutinating activity was stable after 30-min exposure to temperatures up to 70 degrees C. Since lectins may demonstrate biological activities such as antiproliferative, immunomodulatory, antifungal, antiviral, and HIV-1 reverse transcriptase inhibitory activities, the isolated lectin was tested for these activities. It was found that the lectin inhibited proliferation in hepatoma HepG2 cells and breast cancer MCF7 cells with an IC(50) of 1.4 microM and 0.18 microM, respectively. HIV-1 reverse transcriptase activity was inhibited with an IC(50) of 1.02 microM. The lectin and concanavalin A (Con A) evoked maximal mitogenic response from mouse splenocytes at similar concentrations, but the maximal response to B. variegata lectin was only 1/5 of that induced by Con A in magnitude. B. variegata lectin was devoid of antifungal activity.

  6. The luminescence properties of rare-earth ions in natural fluorite

    Science.gov (United States)

    Czaja, M.; Bodył-Gajowska, S.; Lisiecki, R.; Meijerink, A.; Mazurak, Z.

    2012-09-01

    For the first time, the luminescence properties of Pr3+, Nd3+ and Tm3+ and Yb3+ ions in fluorite crystal have been obtained by steady-state measurements. In addition, the luminescence spectra of Ce3+, Sm2+, Sm3+, Dy3+, Er3+ and Yb3+ were measured. It was pointed out that λexc. = 415 nm is most suitable for measuring the Ho3+ emission beside the Er3+. The emission of trivalent holmium and erbium ions was measured independently using time-resolved measurements and tentative assignment of luminescence lines to C 3v and C 4v symmetry sites was proposed. Besides for natural fluorite crystal, the transitions between Stark energy levels of lanthanide ions were presented.

  7. Electrochemically Controlled Ion-exchange Property of Carbon Nanotubes/Polypyrrole Nanocomposite in Various Electrolyte Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Daiwon [Pacific Northwest National Laboratory, 902 Battelle Boulevard P.O. Box 999 Richland WA 99352 USA; Zhu, Chengzhou [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 United States; Fu, Shaofang [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 United States; Du, Dan [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 United States; Engelhard, Mark H. [Pacific Northwest National Laboratory, 902 Battelle Boulevard P.O. Box 999 Richland WA 99352 USA; Lin, Yuehe [Pacific Northwest National Laboratory, 902 Battelle Boulevard P.O. Box 999 Richland WA 99352 USA; School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 United States

    2016-09-15

    The electrochemically controlled ion-exchange properties of multi-wall carbon nanotube (MWNT)/electronically conductive polypyrrole (PPy) polymer composite in the various electrolyte solutions have been investigated. The ion-exchange behavior, rate and capacity of the electrochemically deposited polypyrrole with and without carbon nanotube (CNT) were compared and characterized using cyclic voltammetry (CV), chronoamperometry (CA), electrochemical quartz crystal microbalance (EQCM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It has been found that the presence of carbon nanotube backbone resulted in improvement in ion-exchange rate, stability of polypyrrole, and higher anion loading capacity per PPy due to higher surface area, electronic conductivity, porous structure of thin film, and thinner film thickness providing shorter diffusion path. Chronoamperometric studies show that electrically switched anion exchange could be completed more than 10 times faster than pure PPy thin film. The anion selectivity of CNT/PPy film is demonstrated using X-ray photoelectron spectroscopy (XPS).

  8. Correlation, Breit and Quantum Electrodynamics effects on energy level and transition properties of W54+ ion

    Science.gov (United States)

    Ding, Xiaobin; Sun, Rui; Koike, Fumihiro; Kato, Daiji; Murakami, Izumi; Sakaue, Hiroyuki A.; Dong, Chenzhong

    2017-03-01

    The electron correlation effects and Breit interaction as well as Quantum Electro-Dynamics (QED) effects were expected to have important contribution to the energy level and transition properties of heavy highly charged ions. The ground states [Ne]3 s 23 p 63 d 2 and first excited states [Ne]3 s 23 p 53 d 3 of W54+ ion have been studied by using Multi-Configuration Dirac-Fock method with the implementation of Grasp2K package. A restricted active space method was employed to investigate the correlation contribution from different models. The Breit interaction and QED effects were taken into account in the relativistic configuration interaction calculation with the converged wavefunction. It is found that the correlation contribution from 3 s and 3 p orbital have important contribution to the energy level, transition wavelength and probability of the ground and the first excited state of W54+ ion.

  9. Influence of implantation of three metallic ions on the mechanical properties of two polymers

    Energy Technology Data Exchange (ETDEWEB)

    Swain, M.V. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Lindfield, NSW (Australia). Div. of Applied Physics; Perry, A.J. [Australian National Univ., Canberra, ACT (Australia); Treglio, J.R.

    1996-12-31

    Ion implantation of poly ethylene terephthalate (PET) and polystyrene (PS) with various high energy metallic ions at 70 kV to dose of 3 x 10{sup 16} ions/cm 2 have been made. Measurements of the mechanical properties of the polymers before and after implantation have been made with an ultra microindentation system using both pointed and a small (2 nm) radiused spherical tipped indenter. Significant differences have been observed between the Ti-B dual implanted surfaces and those of the Au and W implanted surfaces. For both the PET and PS the resistance to indenter penetration at very low loads was much greater for the Ti-B dual implanted surfaces. The estimated hardness and modulus versus depth of penetration for both indenters shows that the spherical indenter produces more consistent and less controversial values that are somewhat lower than the optimistic estimates from pointed indenters. 8 refs., 2 fig.

  10. pH-dependence of the specific binding of Cu(II) and Zn(II) ions to the amyloid-{beta} peptide

    Energy Technology Data Exchange (ETDEWEB)

    Ghalebani, Leila, E-mail: leila.ghalebani@ki.se [Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm (Sweden); Wahlstroem, Anna, E-mail: anna.wahlstrom@dbb.su.se [Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm (Sweden); Danielsson, Jens, E-mail: jensd@dbb.su.se [Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm (Sweden); Waermlaender, Sebastian K.T.S., E-mail: seb@dbb.su.se [Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm (Sweden); Graeslund, Astrid, E-mail: astrid@dbb.su.se [Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm (Sweden)

    2012-05-11

    Highlights: Black-Right-Pointing-Pointer Cu(II) and Zn(II) display pH-dependent binding to the A{beta}(1-40) peptide. Black-Right-Pointing-Pointer At pH 7.4 both metal ions display residue-specific binding to the A{beta} peptide. Black-Right-Pointing-Pointer At pH 5.5 the binding specificity is lost for Zn(II). Black-Right-Pointing-Pointer Differential Cu(II) and Zn(II) binding may help explain metal-induced AD toxicity. -- Abstract: Metal ions like Cu(II) and Zn(II) are accumulated in Alzheimer's disease amyloid plaques. The amyloid-{beta} (A{beta}) peptide involved in the disease interacts with these metal ions at neutral pH via ligands provided by the N-terminal histidines and the N-terminus. The present study uses high-resolution NMR spectroscopy to monitor the residue-specific interactions of Cu(II) and Zn(II) with {sup 15}N- and {sup 13}C,{sup 15}N-labeled A{beta}(1-40) peptides at varying pH levels. At pH 7.4 both ions bind to the specific ligands, competing with one another. At pH 5.5 Cu(II) retains its specific histidine ligands, while Zn(II) seems to lack residue-specific interactions. The low pH mimics acidosis which is linked to inflammatory processes in vivo. The results suggest that the cell toxic effects of redox active Cu(II) binding to A{beta} may be reversed by the protective activity of non-redox active Zn(II) binding to the same major binding site under non-acidic conditions. Under acidic conditions, the protective effect of Zn(II) may be decreased or changed, since Zn(II) is less able to compete with Cu(II) for the specific binding site on the A{beta} peptide under these conditions.

  11. Probing kinetic drug binding mechanism in voltage-gated sodium ion channel: open state versus inactive state blockers.

    Science.gov (United States)

    Pal, Krishnendu; Gangopadhyay, Gautam

    2015-01-01

    The kinetics and nonequilibrium thermodynamics of open state and inactive state drug binding mechanisms have been studied here using different voltage protocols in sodium ion channel. We have found that for constant voltage protocol, open state block is more efficient in blocking ionic current than inactive state block. Kinetic effect comes through peak current for mexiletine as an open state blocker and in the tail part for lidocaine as an inactive state blocker. Although the inactivation of sodium channel is a free energy driven process, however, the two different kinds of drug affect the inactivation process in a different way as seen from thermodynamic analysis. In presence of open state drug block, the process initially for a long time remains entropy driven and then becomes free energy driven. However in presence of inactive state block, the process remains entirely entropy driven until the equilibrium is attained. For oscillating voltage protocol, the inactive state blocking is more efficient in damping the oscillation of ionic current. From the pulse train analysis it is found that inactive state blocking is less effective in restoring normal repolarisation and blocks peak ionic current. Pulse train protocol also shows that all the inactive states behave differently as one inactive state responds instantly to the test pulse in an opposite manner from the other two states.

  12. Synthesis and Structure of a Ternary Copper(II) Complex with Mixed Ligands of Diethylenetriamine and Picrate: DNA/Protein-Binding Property and In Vitro Anticancer Activity Studies.

    Science.gov (United States)

    Shi, Ya-Ning; Zheng, Kang; Zhu, Ling; Li, Yan-Tuan; Wu, Zhi-Yong; Yan, Cui-Wei

    2015-05-01

    Based on the importance of the design and synthesis of transition metal complexes with noncovalent DNA/protein-binding abilities in the field of metallo pharmaceuticals, a new mononuclear ternary copper(II) complex with mixed ligands of diethylenetriamine (dien) and picrate anion (pic), identified as [Cu(dien)(pic)](pic), was synthesized and characterized by elemental analysis, molar conductivity measurement, infrared spectrum, electronic spectral studies, and single-crystal X-ray diffractometry. The structure analysis reveals that the copper(II) complex crystallizes in the monoclinic space group P21 /c, and the copper(II) ion has a distorted square pyramidal coordination geometry. A two-dimensional supramolecular structure is formed through hydrogen bonds. The DNA/bovine serum albumin (BSA)-binding properties of the complex are explored, indicating that the complex can interact with herring sperm DNA via intercalation mode and bind to BSA responsible for quenching of tryptophan fluorescence by static quenching mechanism. The in vitro anticancer activity shows that the copper(II) complex is active against the selected tumor cell lines.

  13. Specific /sup 3/H-DMCM binding to a non-benzodiazepine binding site after silver ion treatment of rat brain membranes

    Energy Technology Data Exchange (ETDEWEB)

    Honore, T.; Nielsen, M.; Braestrup, C.

    1984-11-26

    Specific binding of the BZ-receptor ligand /sup 3/H-DMCM to rat cortical membranes was dramatically enhanced by preincubation of the homogenate with 0.1 mM silver (Ag/sup +/) nitrate. The binding was completely inhibited by midazolam. Nevertheless, the pharmacological specificity of the Ag/sup +/-enhanced /sup 3/H-DMCM binding was different from that of BZ-receptors. Furthermore, the B/sub max/ value, the regional distribution and the molecular target size determined by radiation inactivation analysis of the Ag/sup +/-enhanced binding site were different from those of BZ-receptors. The results indicate that Ag/sup +/-enhanced /sup 3/H-DMCM binding represent a high affinity metal complex formation between /sup 3/H-DMCM and an unknown brain specific protein of approximately 100,000 daltons molecular weight. 11 references, 3 figures, 4 tables.

  14. Influence of Kilo-Electron Oxygen Ion Irradiation on Structural, Electrical and Optical Properties of CdTe Thin Films

    Science.gov (United States)

    Honey, Shehla; Thema, F. T.; Bhatti, M. T.; Ishaq, A.; Naseem, Shahzad; Maaza, M.

    2016-09-01

    In this paper, effect of oxygen (O+) ion irradiation on the properties of polycrystalline cubic structure CdTe thin films has been investigated. CdTe thin films were irradiated with O+ ions of energy 80keV at different fluence ranging from 1×1015 to 5×1016 ion/cm2 at room temperature. At 1×1015 ion/cm2 O+ ions fluence, the CdTe structure was maintained while XRD peaks of cubic phase were shifted toward lower angles. At 5×1016 ion/cm2 O+ ions fluence, cubic structure of CdTe thin films was transformed into hexagonal structure. In addition, electrical resistivity and optical bandgap were decreased with increasing O+ ion beam irradiation.

  15. Effect of metal-ion doping on the optical properties of nanocrystalline ZnO thin films

    Science.gov (United States)

    Mendoza-Galván, A.; Trejo-Cruz, C.; Lee, J.; Bhattacharyya, D.; Metson, J.; Evans, P. J.; Pal, U.

    2006-01-01

    Optical properties of metal (Al, Ag, Sb, and Sn)-ion-implanted ZnO films have been studied by ultraviolet-visible spectroscopy and spectroscopic ellipsometric techniques. The effects of metal-ion doping on the optical band gap (Eg), refractive index (n), and extinction coefficient (k) of nanocrystalline ZnO films have been studied for the similar implantation dose of all the metal ions. The ellipsometric spectra of the ion-implanted samples could be well described by considering an air/roughness/ZnO-M (layer 1)/ZnO (layer 2)/glass model. The band gap of ZnO films increases with Al ion doping and decreases with doping of Ag, Sb, and Sn ions. The refractive index of ZnO films in the visible spectral region increases substantially on Sb and Sn ion doping, while it decreases to some extent with Al ion doping.

  16. Examination of the Addictive and Behavioral Properties of Fatty Acid Binding Protein Inhibitor SBFI26

    Directory of Open Access Journals (Sweden)

    Panayotis eThanos

    2016-04-01

    Full Text Available Abstract:The therapeutic properties of cannabinoids have been well demonstrated but are overshadowed by such adverse effects as cognitive and motor dysfunction, as well as their potential for addiction. Recent research on the natural lipid ligands of cannabinoid receptors, also known as endocannabinoids, have shed light on the mechanisms of intracellular transport of the endocannabinoid anandamide by fatty acid binding proteins (FABPs and subsequent catabolism by fatty acid amide hydrolase (FAAH. These findings facilitated the recent development of SBFI26, a pharmacological inhibitor of epidermal- and brain-specific FABP5 and FABP7, which effectively increases anandamide signaling. The goal of this study was to examine this compound for any possible rewarding and addictive properties as well as effects on locomotor activity, working / recognition memory, and propensity for sociability and preference for social novelty given its recently reported anti-inflammatory and analgesic properties. Male C57BL mice were split into four treatment groups and conditioned with 5.0 mg/kg, 20.0 mg/kg, 40.0 mg/kg SBFI26 or vehicle during a conditioned placed preference (CPP paradigm. Following CPP, mice underwent a battery of behavioral tests (open field, novel object recognition (NOR, and social interaction (SI and novelty (SN paired with acute SBFI26 administration. Results showed that SBFI26 did not produce conditioned placed preference or conditioned place aversion regardless of dose, and did not induce any differences in locomotor and exploratory activity during CPP or SBFI26-paired open field activity. We also observed no differences between treatment groups in NOR, SI, and SN. In conclusion, as SBFI26 was shown previously by our group to have significant analgesic and anti-inflammatory properties, here we show that it does not pose a risk of dependence or motor and cognitive impairment under the conditions tested.

  17. Alternative binding modes of l-histidine guided by metal ions for the activation of the antiterminator protein HutP of Bacillus subtilis.

    Science.gov (United States)

    Dhakshnamoorthy, Balasundaresan; Mizuno, Hiroshi; Kumar, Penmetcha K R

    2013-09-01

    Anti-terminator proteins control gene expression by recognizing control signals within cognate transcripts and then preventing transcription termination. HutP is such a regulatory protein that regulates the expression of the histidine utilization (hut) operon in Bacillus subtilis by binding to cis-acting regulatory sequences in hut mRNAs. During the anti-termination process, l-histidine and a divalent ion are required for hutP to bind to the specific sequence within the hut mRNA. Our previous crystal structure of the HutP-l-histidine-Mg(2+)-RNA ternary complex demonstrated that the l-histidine ligand and Mg(2+) bind together such that the backbone nitrogen and carboxyl oxygen of l-histidine coordinate with Mg(2+). In addition to the Mg(2+), other divalent ions are also known to efficiently support the l-histidine-dependent anti-termination of the hut operon, and the best divalent ion is Zn(2+). In this study, we determined the crystal structure of the HutP-l-histidine-Zn(2+) complex and found that the orientation of l-histidine coordinated to Zn(2+) is reversed relative to that of l-histidine coordinated to Mg(2+), i.e., the imidazole side chain nitrogen of l-histidine coordinates to Zn(2+). This alternative binding mode of the l-histidine ligand to a divalent ion provides further insight into the mechanisms responsible for the activation of RNA binding during the hut anti-termination process.

  18. A Specific Peptide with Calcium-Binding Capacity from Defatted Schizochytrium sp. Protein Hydrolysates and the Molecular Properties

    Directory of Open Access Journals (Sweden)

    Xixi Cai

    2017-03-01

    Full Text Available Marine microorganisms have been proposed as a new kind of protein source. Efforts are needed in order to transform the protein-rich biological wastes left after lipid extraction into value-added bio-products. Thus, the utilization of protein recovered from defatted Schizochytrium sp. by-products presents an opportunity. A specific peptide Tyr-Leu (YL with calcium-binding capacity was purified from defatted Schizochytrium sp. protein hydrolysates through gel filtration chromatography and RP-HPLC. The calcium-binding activity of YL reached 126.34 ± 3.40 μg/mg. The calcium-binding mechanism was investigated through ultraviolet, fluorescence and infrared spectroscopy. The results showed that calcium ions could form dative bonds with carboxyl oxygen atoms and amino nitrogen atoms as well as the nitrogen and oxygen atoms of amide bonds. YL-Ca exhibited excellent thermal stability and solubility, which was beneficial for its absorption and transport in the basic intestinal tract of the human body. Moreover, the cellular uptake of calcium in Caco-2 cells showed that YL-Ca could enhance calcium uptake efficiency and protect calcium ions against precipitation caused by dietary inhibitors such as tannic acid, oxalate, phytate and metal ions. The findings indicate that the by-product of Schizochytrium sp. is a promising source for making peptide-calcium bio-products as algae-based functional supplements for human beings.

  19. A Specific Peptide with Calcium-Binding Capacity from Defatted Schizochytrium sp. Protein Hydrolysates and the Molecular Properties.

    Science.gov (United States)

    Cai, Xixi; Yang, Qian; Lin, Jiaping; Fu, Nanyan; Wang, Shaoyun

    2017-03-29

    Marine microorganisms have been proposed as a new kind of protein source. Efforts are needed in order to transform the protein-rich biological wastes left after lipid extraction into value-added bio-products. Thus, the utilization of protein recovered from defatted Schizochytrium sp. by-products presents an opportunity. A specific peptide Tyr-Leu (YL) with calcium-binding capacity was purified from defatted Schizochytrium sp. protein hydrolysates through gel filtration chromatography and RP-HPLC. The calcium-binding activity of YL reached 126.34 ± 3.40 μg/mg. The calcium-binding mechanism was investigated through ultraviolet, fluorescence and infrared spectroscopy. The results showed that calcium ions could form dative bonds with carboxyl oxygen atoms and amino nitrogen atoms as well as the nitrogen and oxygen atoms of amide bonds. YL-Ca exhibited excellent thermal stability and solubility, which was beneficial for its absorption and transport in the basic intestinal tract of the human body. Moreover, the cellular uptake of calcium in Caco-2 cells showed that YL-Ca could enhance calcium uptake efficiency and protect calcium ions against precipitation caused by dietary inhibitors such as tannic acid, oxalate, phytate and metal ions. The findings indicate that the by-product of Schizochytrium sp. is a promising source for making peptide-calcium bio-products as algae-based functional supplements for human beings.

  20. The biomedical properties of polyethylene terephthalate surface modified by silver ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jin [Key Laboratory for Advanced Technologies of Materials of Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Li Jianxin [Key Laboratory for Advanced Technologies of Materials of Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Shen Liru [Southwestern Institute of Physics, Chengdu, Sichuan 610041 (China); Ling Ren [Key Laboratory for Advanced Technologies of Materials of Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Xu Zejin [Southwestern Institute of Physics, Chengdu, Sichuan 610041 (China); Zhao Ansha [Key Laboratory for Advanced Technologies of Materials of Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Leng Yongxiang [Key Laboratory for Advanced Technologies of Materials of Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Huang Nan [Key Laboratory for Advanced Technologies of Materials of Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)]. E-mail: nhuang@263.net

    2007-04-15

    Polyethylene terephthalate (PET) film is modified by Ag ion implantation with a fluence 1 x 10{sup 16} ions/cm{sup 2}. The results of X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicate that silver has been successfully implanted into the surface of PET. The PET samples modified by silver ion implantation have significantly bactericidal property. The capacity of the staphylococcus epidermidis (SE) adhered on the Ag{sup +} implanted PET surface is 5.3 x 10{sup 6} CFU/ml, but the capacity of the SE adhered on the untreated PET film is 2.23 x 10{sup 7} CFU/ml. The thromboembolic property is evaluated by in vitro platelet adhesion test, and there is not statistically difference between the untreated PET and the Ag{sup +} implanted PET for the number of adhered and activated platelets. The PET implanted by silver ion has not acute toxicity to endothelial cell (EC) which was evaluated by the release of lactate dehydrogenase (LDH) test.

  1. Optical properties of K9 glass waveguides fabricated by using carbon-ion implantation

    Science.gov (United States)

    Liu, Chun-Xiao; Wei, Wei; Fu, Li-Li; Zhu, Xu-Feng; Guo, Hai-Tao; Li, Wei-Nan; Lin, She-Bao

    2016-07-01

    K9 glass is a material with promising properties that make it attractive for optical devices. Ion implantation is a powerful technique to form waveguides with controllable depth and refractive index profile. In this work, optical planar waveguide structures were fabricated in K9 glasses by using 6.0-MeV C3+-ion implantation with a fluence of 1.0 × 1015 ions/cm2. The effective refractive indices of the guided modes were measured by using a prism-coupling system. The refractive index change in the ion-irradiated region was simulated by using the intensity calculation method. The modal intensity profile of the waveguide was calculated and measured by using the finite difference beam propagation method and the end-face coupling technique, respectively. The transmission spectra before and after the implantation showed that the main absorption band was not influenced by the low fluence dopants. The optical properties of the carbon-implanted K9 glass waveguides show promise for use as integrated photonic devices.

  2. Properties of large Li ion cells using a nickel based mixed oxide

    Science.gov (United States)

    Broussely, M.; Blanchard, Ph; Biensan, Ph; Planchat, J. P.; Nechev, K.; Staniewicz, R. J.

    The possible use of LiNiO 2 similar to LiCoO 2, as a positive material in rechargeable lithium batteries was recognized 20 years ago and starting 10 years later, many research studies led to material improvement through substitution of some of the nickel ions by other metallic ions. These modifications improve the thermal stability at high charge level or overcharge, as well as cycling and storage properties. Commercial material is now available at large industrial scale, which allows its use in big "industrial" Li ion batteries. Using low cost raw material (Ni), it is expected to be cost competitive with the manganese based systems usually mentioned as low cost on the total cell $/Wh basis. Providing higher energy density, and demonstrating excellent behavior on storage and extended cycle life, LiNiO 2 has definite advantages over the manganese system. Thanks to their properties, these batteries have demonstrated their ability to be used in lot of applications, either for transportation or standby. Their light weight makes them attractive for powering satellites. Although safety improvements are always desirable for all non-aqueous batteries using flammable organic electrolytes, suitable battery designs allow the systems to reach the acceptable level of safety required by many users. Beside the largely distributed lead acid and nickel cadmium batteries, Li ion will found its place in the "industrial batteries" market, in a proportion directly linked to its future cost reduction.

  3. Structural and fast ion transport properties of glassy and amorphous materials

    Energy Technology Data Exchange (ETDEWEB)

    Whitmore, D.H.; Georgopoulos, P.

    1989-11-01

    This research has dealt with ionic conductivity in two classes of electrolytes. Solid inorganic, as well as polymer. In the former case, a structural characterization study of the fast Ag{sup +} ion conducting glassy electrolyte Ag{sub 0.25}Ge{sub 0.19}Se{sub 0.56} was undertaken by means of differential anomalous x-ray scattering techniques. The Ag{sup +} ion transport behavior was probed with the aid of complex impedance spectroscopy and pulsed field gradient NMR measurements of the Ag{sup +} ion diffusivity. We found evidence suggesting that short (3.1--3.5 A) Ag-Ag distances are present. The observed prefactor for conductivity suggests that the number of mobile Ag{sup +} ions in this glass is significantly less than expected from its stoichiometry. The transport property results were examined in the light of our structural findings and analyses were attempted in terms of some reasonable microscopic models. The other major aspect of this research, dealing with amorphous poly(ethylene glycol)-LiCF{sub 3}SO{sub 3} electrolytes, involved measurements, via the pulsed field gradient NMR method, of the diffusivity of the polymer host, the cation (Li{sup +}) and the anion (CF{sub 3}SO{sub 3}{sup -}) in these complexes and the ionic conductivity, via complex impedance spectroscopy. Based on the conductivity prefactors, it appears that these amorphous polymer electrolytes exhibit classical Meyer-Nelder behavior; moreover, our ion transport results could be rationalized in terms of an ion association model (involving ion pairs and higher order aggregates).

  4. Changes of structural and hydrogen desorption properties of MgH2 indused by ion irradiation

    Directory of Open Access Journals (Sweden)

    Kurko Sandra V.

    2010-01-01

    Full Text Available Changes in structural and hydrogen desorption properties of MgH2 induced by ion irradiation have been investigated. MgH2 powder samples have been irradiated with 45 keV B3+ and 120 keV Ar8+ions, with ion fluence of 1015 ions/cm2. The effects of ion irradiation are estimated by numerical calculations using SRIM package. The induced material modifications and their consequences on hydrogen dynamics in the system are investigated by XRD, particle size distribution and TPD techniques. Changes of TPD spectra with irradiation conditions suggest that there are several mechanisms involved in desorption process which depend on defect concentration and their interaction and ordering. The results confirmed that the near-surface area of MgH2 and formation of a substoichiometric MgHx (x<2 play a crucial role in hydrogen kinetics and that various concentrations of induced defects substantially influence H diffusion and desorption kinetics in MgH2. The results also confirm that there is possibility to control the thermodynamic parameters by controlling vacancies concentration in the system.

  5. Antibacterial properties of metal and metalloid ions in chronic periodontitis and peri-implantitis therapy.

    Science.gov (United States)

    Goudouri, Ourania-Menti; Kontonasaki, Eleana; Lohbauer, Ulrich; Boccaccini, Aldo R

    2014-08-01

    Periodontal diseases like periodontitis and peri-implantitis have been linked with Gram-negative anaerobes. The incorporation of various chemotherapeutic agents, including metal ions, into several materials and devices has been extensively studied against periodontal bacteria, and materials doped with metal ions have been proposed for the treatment of periodontal and peri-implant diseases. The aim of this review is to discuss the effectiveness of materials doped with metal and metalloid ions already used in the treatment of periodontal diseases, as well as the potential use of alternative materials that are currently available for other applications but have been proved to be cytotoxic to the specific periodontal pathogens. The sources of this review included English articles using Google Scholar™, ScienceDirect, Scopus and PubMed. Search terms included the combinations of the descriptors "disease", "ionic species" and "bacterium". Articles that discuss the biocidal properties of materials doped with metal and metalloid ions against the specific periodontal bacteria were included. The articles were independently extracted by two authors using predefined data fields. The evaluation of resources was based on the quality of the content and the relevance to the topic, which was evaluated by the ionic species and the bacteria used in the study, while the final application was not considered as relevant. The present review summarizes the extensive previous and current research efforts concerning the use of metal ions in periodontal diseases therapy, while it points out the challenges and opportunities lying ahead.

  6. The Spectr-W3 database on the spectroscopic properties of atoms and ions

    Science.gov (United States)

    Skobelev, I. Yu.; Loboda, P. A.; Gagarin, S. V.; Ivliev, S. V.; Kozlov, A. I.; Morozov, S. V.; Pikuz, S. A.; Pikuz, T. A.; Popova, V. V.; Faenov, A. Ya.

    2016-04-01

    The Spectr-W3 database was developed in 2001-2013 and is available online (http://spectrw3. snz.ru). The database contains information on various spectroscopic constants of atoms and ions such as the wavelengths and probabilities of radiative transitions, energy levels of atoms and ions, ionization potentials, autoionization rates, and the parameters of analytical approximation of cross sections and rates of collisional transitions in atoms and ions. Spectr-W3 presently contains around 450 thousand records and is the world's largest factual database on spectral properties of multicharged ions. A new stage of development of Spectr-W3, which involves adding a new section titled "Emission Spectrograms" to the database, commenced in 2014. In contrast to the already existing sections that contain tabulated data, this new section provides graphical data (with necessary explanatory notes) on the spectrograms of emission of atoms and ions excited in various plasma sources. The structure of sections of the Spectr-W3 database is characterized, and examples of queries and the corresponding search results are given.

  7. Transport properties and electroanalytical response characteristics of drotaverine ion-selective sensors.

    Science.gov (United States)

    Kharitonov, Sergey V

    2005-08-01

    The construction and electroanalytical response characteristics of poly(vinyl chloride) matrix ion-selective sensors (ISSs) for drotaverine hydrochloride are described. The membranes incorporate ion-association complexes of drotaverine with tetraphenylborate, picrate, tetraiodomercurate, tetraiodobismuthate, Reinecke salt, and heteropolycompounds of Keggin structure-molybdophosphoric acid, tungstophosphoric acid, molybdosiliconic acid and tungstosiliconic acid as electroactive materials for ionometric sensor controls. These ISSs have a linear response to drotaverine hydrochloride over the range 8 x 10(-6) to 5 x 10(-2) mol L(-1) with cationic slopes from 51 to 58 mV per concentration decade. These ISSs have a fast response time (up to 1 min), a low determination limit (down to 4.3 x 10(-6) mol L(-1)), good stability (3-5 weeks), and reasonable selectivity. Permeabilities and ion fluxes through a membrane were calculated for major and interfering ions. Dependences of the transport properties of the membranes on the concentrations of the ion exchanger and near-membrane solution and their electrochemical characteristics are presented. The ISSs were used for direct potentiometry and potentiometric titration (sodium tetraphenylborate) of drotaverine hydrochloride. Results with mean accuracy of 99.1+/-1.0% of nominal were obtained which corresponded well to data obtained by use of high-performance liquid chromatography.

  8. Optical properties of 3d-ions in crystals spectroscopy and crystal field analysis

    CERN Document Server

    Brik, Mikhail

    2013-01-01

    "Optical Properties of 3d-Ions in Crystals: Spectroscopy and Crystal Field Analysis" discusses spectral, vibronic and magnetic properties of 3d-ions in a wide range of crystals, used as active media for solid state lasers and potential candidates for this role. Crystal field calculations (including first-principles calculations of energy levels and absorption spectra) and their comparison with experimental spectra, the Jahn-Teller effect, analysis of vibronic spectra, materials science applications are systematically presented. The book is intended for researchers and graduate students in crystal spectroscopy, materials science and optical applications. Dr. N.M. Avram is an Emeritus Professor at the Physics Department, West University of Timisoara, Romania; Dr. M.G. Brik is a Professor at the Institute of Physics, University of Tartu, Estonia.

  9. Nano-sized Thin Films Fabricated by Ion Beam Sputtering and Its Properties

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Nanoscale thick amorphous Ni-Cr alloy thin films were fabricated by low-energy ion beam sputtering technology; then the as-deposited samples experienced rapid thermal process to realize the transformation from amorphous to crystalline state. The film thickness was measured with α-stylus surface profiler, the structure and the compositions of the films were confirmed by low angle X-ray diffraction and scanning auger electron microprobe respectively, and the surface topography was characterized by scanning electron microscope and scanning probe microscope. Electrical property of the films was measured by fourpoint probe. The experimental results illustrate that the combined processes of ion beam sputtering and rapid thermal process are effective for fabrication nanoscale Ni-Cr alloy thin film with good properties.

  10. Modifying the morphology and magnetic properties of magnetite nanoparticles using swift heavy ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Gokhale, Shubha, E-mail: sgokhale@ignou.ac.in [School of Sciences, Indira Gandhi National Open University, New Delhi 110068 (India); Lamba, Subhalakshmi; Kumari, Neha; Singh, Bhupendra [School of Sciences, Indira Gandhi National Open University, New Delhi 110068 (India); Avasthi, D.K. [Inter University Accelerator Centre, P.O. Box 10502, New Delhi 110067 (India); Kulkarni, S.K. [Indian Institute of Science Education Research, Dr. Homi Bhabha Road, Pune 411008 (India)

    2014-08-15

    Magnetite (Fe{sub 3}O{sub 4}) nanospheres of ∼8–11 nm diameter synthesized using a chemical co-precipitation method were deposited as thin films on different substrates using spin coating. The thin films were irradiated with Ag ions at 100 MeV energy. Comparison of unirradiated, as synthesized Fe{sub 3}O{sub 4} nanoparticulate thin film and ion irradiated film shows that irradiation causes dramatic changes in the morphology, structure and magnetic properties. Monte Carlo simulations carried out on this system indicate that the origin of the changes in the magnetic properties lies in the enhanced magnetic anisotropy energy density and reorientation of magnetic easy axis.

  11. Interrelationships among biological activity, disulfide bonds, secondary structure, and metal ion binding for a chemically synthesized 34-amino-acid peptide derived from alpha-fetoprotein.

    Science.gov (United States)

    MacColl, R; Eisele, L E; Stack, R F; Hauer, C; Vakharia, D D; Benno, A; Kelly, W C; Mizejewski, G J

    2001-10-01

    A 34-amino-acid peptide has been chemically synthesized based on a sequence from human alpha-fetoprotein. The purified peptide is active in anti-growth assays when freshly prepared in pH 7.4 buffer at 0.20 g/l, but this peptide slowly becomes inactive. This functional change is proven by mass spectrometry to be triggered by the formation of an intrapeptide disulfide bond between the two cysteine residues on the peptide. Interpeptide cross-linking does not occur. The active and inactive forms of the peptide have almost identical secondary structures as shown by circular dichroism (CD). Zinc ions bind to the active peptide and completely prevents formation of the inactive form. Cobalt(II) ions also bind to the peptide, and the UV-Vis absorption spectrum of the cobalt-peptide complex shows that: (1) a near-UV sulfur-to-metal-ion charge-transfer band had a molar extinction coefficient consistent with two thiolate bonds to Co(II); (2) the lowest-energy visible d-d transition maximum at 659 nm, also, demonstrated that the two cysteine residues are ligands for the metal ion; (3) the d-d molar extinction coefficient showed that the metal ion-ligand complex was in a distorted tetrahedral symmetry. The peptide has two cysteines, and it is speculated that the other two metal ion ligands might be the two histidines. The Zn(II)- and Co(II)-peptide complexes had similar peptide conformations as indicated by their ultraviolet CD spectra, which differed very slightly from that of the free peptide. Surprisingly, the cobalt ions acted in the reverse of the zinc ions in that, instead of stabilizing anti-growth form of the peptide, they catalyzed its loss. Metal ion control of peptide function is a saliently interesting concept. Calcium ions, in the conditions studied, apparently do not bind to the peptide. Trifluoroethanol and temperature (60 degrees C) affected the secondary structure of the peptide, and the peptide was found capable of assuming various conformations in solution

  12. Principles and properties of ion flow in P2X receptors

    Directory of Open Access Journals (Sweden)

    Damien Stephen Kenneth Samways

    2014-02-01

    Full Text Available P2X receptors are a family of trimeric ion channels that are gated by extracellular adenosine 5’-triphosphate (ATP. These receptors have long been a subject of intense research interest by virtue of their vital role in mediating the rapid and direct effects of extracellular ATP on membrane potential and intracellular Ca2+ concentration, which in turn underpin the ability of ATP to regulate a diverse range of clinically significant physiological functions, including cardiovascular function, pain, and the immune response. An important aspect of an ion channel’s function is, of course, the means by which it transports ions across the biological membrane. A concerted effort by investigators over the last two decades has culminated in significant advances in our understanding of how P2X receptors conduct the inward flux of Na+ and Ca2+ in response to binding by ATP. However, this work has relied heavily on results from current recordings of P2X receptors altered by site-directed mutagenesis. In the absence of a 3-dimensional channel structure, this prior work provided only a vague and indirect appreciation of the relationship between structure, ion selectivity and flux. The recent publication of the crystal structures for both the closed and open channel conformations of the zebrafish P2X4 receptor has thus proved a significant boon, and has provided an important opportunity to overview the amassed functional data in the context of a working 3-dimensional model of a P2X receptor. In this paper, we will attempt to reconcile the existing functional data regarding ion permeation through P2X receptors with the available crystal structure data, highlighting areas of concordance and discordance as appropriate.

  13. Binding properties of oxacalix[4]arenes derivatives toward metal cations; Interactions entre cations metalliques et derives des oxacalix[4]arenes

    Energy Technology Data Exchange (ETDEWEB)

    Mellah, B

    2006-11-15

    The objective of this work was to establish the binding properties of oxacalix[4]arene derivatives with different numbers of the oxa bridges, functional groups (ketones, pyridine, ester, amide and methoxy) and conformations. Their interactions with alkali and alkaline-earth, heavy and transition metal cations have been evaluated according to different approaches: (i) extraction of corresponding picrates from an aqueous phase into dichloromethane; (ii) determination of the thermodynamic parameters of complexation in methanol and/or acetonitrile by UV-spectrophotometry and micro-calorimetry; (iii) determination of the stoichiometry of the complexes by ESI-MS; (iv) {sup 1}H-NMR titrations allowing to localize the metal ions in the ligand cavity. In a first part dealing on homo-oxacalix[4]arenes, selectivities for Na{sup +}, K{sup +}, Ca{sup 2+}, Pb{sup 2+} and Mn{sup 2+} of ketones derivatives was shown. The presence of oxa bridge in these derivatives increases their efficiency while decreasing their selectivity with respect to related calixarenes. The pyridine derivative prefers transition and heavy metal cations, in agreement with the presence of the soft nitrogen atoms. In the second part, di-oxacalix[4]arene ester and secondary amide derivatives were shown to be less effective than tertiary amide counterparts but to present high selectivities for Li{sup +}, Ba{sup 2+}, Zn{sup 2+} and Hg{sup 2+}. A third part devoted to the octa-homo-tetra-oxacalix[4]arene tetra-methoxy shows that the 1:1 metal complexes formed are generally more stable than those of calixarenes, suggesting the participation of the oxygen atoms of the bridge in the complexation. Selectivity for Cs{sup +}, Ba{sup 2+}, Cu{sup 2+} and Hg{sup 2+} were noted. (author)

  14. Process for improving mechanical properties of epoxy resins by addition of cobalt ions

    Science.gov (United States)

    Stoakley, D. M.; St.clair, A. K. (Inventor)

    1984-01-01

    A resin product useful as an adhesive, composite or casting resin is described as well as the process used in its preparation to improve its flexural strength mechanical property characteristics. Improved flexural strength is attained with little or no change in density, thermal stability or moisture resistance by chemically incorporating 1.2% to 10.6% by weight Co(3) ions in an epoxidized resin system.

  15. Probing the acidic residue within the integrin binding site of laminin-511 that interacts with the metal ion-dependent adhesion site of α6β1 integrin.

    Science.gov (United States)

    Taniguchi, Yukimasa; Li, Shaoliang; Takizawa, Mamoru; Oonishi, Eriko; Toga, Junko; Yagi, Emiko; Sekiguchi, Kiyotoshi

    2017-06-03

    Laminins are major cell-adhesive proteins of basement membranes that interact with integrins in a divalent cation-dependent manner. Laminin-511 consists of α5, β1, and γ1 chains, of which three laminin globular domains of the α5 chain (α5/LG1-3) and a Glu residue in the C-terminal tail of chain γ1 (γ1-Glu1607) are required for binding to integrins. However, it remains unsettled whether the Glu residue in the γ1 tail is involved in integrin binding by coordinating the metal ion in the metal ion-dependent adhesion site of β1 integrin (β1-MIDAS), or by stabilizing the conformation of α5/LG1-3. To address this issue, we examined whether α5/LG1-3 contain an acidic residue required for integrin binding that is as critical as the Glu residue in the γ1 tail; to achieve this, we undertook exhaustive alanine substitutions of the 54 acidic residues present in α5/LG1-3 of the E8 fragment of laminin-511 (LM511E8). Most of the alanine mutants possessed α6β1 integrin binding activities comparable with wild-type LM511E8. Alanine substitution for α5-Asp3198 and Asp3219 caused mild reduction in integrin binding activity, and that for α5-Asp3218 caused severe reduction, possibly resulting from conformational perturbation of α5/LG1-3. When α5-Asp3218 was substituted with asparagine, the resulting mutant possessed significant binding activity to α6β1 integrin, indicating that α5-Asp3218 is not directly involved in integrin binding through coordination with the metal ion in β1-MIDAS. Given that substitution of γ1-Glu1607 with glutamine nullified the binding activity to α6β1 integrin, these results, taken together, support the possibility that the critical acidic residue coordinating the metal ion in β1-MIDAS is Glu1607 in the γ1 tail, but no such residue is present in α5/LG1-3. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Separated effects of ions, metastables and photons on the properties of barrier layers on polymers

    Science.gov (United States)

    Biskup, Beatrix; Boeke, Marc; Benedikt, Jan; von Keudell, Achim

    2016-09-01

    Analyses of a-C:H /a-Si:H multilayers on polymer substrates indicated that prolonged ion bombardment influences negatively the properties of the barrier layer, while a short plasma pretreatment can improve the barrier effect. This work is motivated by these results and investigates the influence of different reactive plasma components, namely ions, metastables and VUV-photons, on the properties of the grown barrier layer. To separate the different species and their influence on plasma pretreatment and film growth, we build a grid system, which repels the ions from the substrate, so that only metastables and VUV-photons have an effect on the layer. An integral part of this investigation is, to measure the photon fluxes to the substrate by an intensity calibrated VUV monochromator. For that, a differentially pumped monochromator with a spectral range 30 - 300 nm is used, where the two most prominent argon lines at 104.9 and 106.8 nm can be measured. In this approach we are able to study the different effects of the plasma species and also possible synergy effects, to improve the properties of the barrier layer. This work is supported by the DFG within the SFB-TR 87.

  17. Soluble M3 proteins of murine gammaherpesviruses 68 and 72 expressed in Escherichia coli: analysis of chemokine-binding properties.

    Science.gov (United States)

    Matúšková, R; Pančík, P; Štibrániová, I; Belvončíková, P; Režuchová, I; Kúdelová, M

    2015-12-01

    M3 protein of murine gammaherpesvirus 68 (MHV-68) was identified as a viral chemokine-binding protein 3 (vCKBP-3) capable to bind a broad spectrum of chemokines and their receptors. During both acute and latent infection MHV-68 M3 protein provides a selective advantage for the virus by inhibiting the antiviral and inflammatory response. A unique mutation Asp307Gly was identified in the M3 protein of murine gammaherpesvirus 72 (MHV-72), localized near chemokine-binding domain. Study on chemokine-binding properties of MHV-72 M3 protein purified from medium of infected cells implied reduced binding to some chemokines when compared to MHV-68 M3 protein. It was suggested that the mutation in the M3 protein might be involved in the attenuation of immune response to infection with MHV-72. Recently, Escherichia coli cells were used to prepare native recombinant M3 proteins of murine gammaherpesviruses 68 and 72 (Pančík et al., 2013). In this study, we assessed the chemokine-binding properties of three M3 proteins prepared in E. coli Rosetta-gami 2 (DE3) cells, the full length M3 protein of both MHV-68 and MHV-72 and MHV-68 M3 protein truncated in the signal sequence (the first 24 aa). They all displayed binding activity to human chemokines CCL5 (RANTES), CXCL8 (IL-8), and CCL3 (MIP-1α). The truncated MHV-68 M3 protein had more than twenty times reduced binding activity to CCL5, but only about five and three times reduced binding to CXCL8 and CCL3 when compared to its full length counterpart. Binding of the full length MHV-72 M3 protein to all chemokines was reduced when compared to MHV-68 M3 protein. Its binding to CCL5 and CCL3 was reduced over ten and seven times. However, its binding to CXCL8 was only slightly reduced (64.8 vs 91.8%). These data implied the significance of the signal sequence and also of a single mutation (at aa 307) for efficient M3 protein binding to some chemokines.

  18. Electronic transport properties of molecular junctions based on the direct binding of aromatic ring to electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Tran Nguyen, E-mail: lantran@ims.ac.jp

    2014-01-15

    Highlights: • Transport properties of molecular junction having direct binding of aromatic ring to electrode have been investigated. • The conductance of junction with sp-type electrode is higher than that of junction with sd-type electrode. • The rectifying mechanism critically depends on the nature of benzene–electrode coupling. • The p–n junction-like can be obtained even without heteroatom doping. • The negative differential resistance effect was observed for the case of sp-type electrode. - Abstract: We have used the non-equilibrium Green’s function in combination with the density functional theory to investigate the quantum transport properties of the molecular junctions including a terminated benzene ring directly coupled to surface of metal electrodes (physisorption). The other side of molecule was connected to electrode via thiolate bond (chemisorption). Two different electrodes have been studied, namely Cu and Al. Rectification and negative differential resistance behavior have been observed. We found that the electron transport mechanism is affected by the nature of benzene–electrode coupling. In other words, the transport mechanism depends on the nature of metallic electrode. Changing from sp- to sd-metallic electrode, the molecular junction changes from the Schottky to p–n junction-like diode. The transmission spectra, projected density of state, molecular projected self-consistent Hamiltonian, transmission eigenchannel, and Muliken population have been analyzed for explanation of electronic transport properties. Understanding the transport mechanism in junction having direct coupling of π-conjugate to electrode will be useful to design the future molecular devices.

  19. Scaling properties of the radius of gyration and surface area for EF-hand calcium binding proteins

    Energy Technology Data Exchange (ETDEWEB)

    Pitulice, L. [West University of Timisoara, Department of Chemistry, Pestalozzi 16, 300115 Timisoara (Romania); Isvoran, A. [West University of Timisoara, Department of Chemistry, Pestalozzi 16, 300115 Timisoara (Romania)], E-mail: aisvoran@cbg.uvt.ro; Craescu, C.T. [INSERM U759/Institute Curie-Recherche, Centre Universitaire Paris-Sud, Batiment 112, 91405 Orsay (France); Chiriac, A. [West University of Timisoara, Department of Chemistry, Pestalozzi 16, 300115 Timisoara (Romania)

    2009-04-30

    In this paper, we analyze the scaling properties of both the radius of gyration and the surface area for EF-hand calcium binding proteins. These properties are different for two conformational subfamilies: proteins with extended and compact structures, respectively. The radius of gyration is a measure of the shape of protein, whereas its surface fractal dimension is a measure of its interatomic packing. Different scaling properties for the radius of gyration underline that these two subfamilies present different shapes whilst different scaling properties for the surface area reveal different strengths of their intermolecular forces. All these data suggest different mechanisms responsible for the global folding of proteins belonging to these two subfamilies.

  20. Brush border membrane binding properties of Bacillus thuringiensis Vip3A toxin to Heliothis virescens and Helicoverpa zea midguts.

    Science.gov (United States)

    Lee, Mi Kyong; Miles, Paul; Chen, Jeng-Shong

    2006-01-27

    The binding properties of Vip3A, a new family of Bacillus thuringiensis insecticidal toxins, have been examined in the major cotton pests, Heliothis virescens and Helicoverpa zea. Vip3A bound specifically to brush border membrane vesicles (BBMV) prepared from both insect larval midguts. In order to examine the cross-resistance potential of Vip3A to the commercially available Cry1Ac and Cry2Ab2 toxins, the membrane binding site relationship among these toxins was investigated. Competition binding assays demonstrated that Vip3A does not inhibit the binding of either Cry1Ac or Cry2Ab2 and vice versa. BBMV protein blotting experiments showed that Vip3A does not bind to the known Cry1Ac receptors. These distinct binding properties and the unique protein sequence of Vip3A support its use as a novel insecticidal agent. This study indicates a very low cross-resistance potential between Vip3A and currently deployed Cry toxins and hence supports its use in an effective resistance management strategy in cotton.

  1. Modifications in physico-chemical properties of 100 MeV oxygen ions irradiated polyimide Kapton-H polymer

    Science.gov (United States)

    Gupta, Sanjeev Kumar; Gupta, Rashi; Singh, Paramjit; Kumar, Vikas; Jaiswal, Manoj Kumar; Chakarvarti, S. K.; Kumar, Rajesh

    2017-09-01

    The optical, structural and chemical properties of polyimide Kapton-H polymer thin film samples were modified by irradiation with 100 MeV O7+ ions (in the fluence range of 1 × 1011 to 5 × 1012 ions/cm2) and the modifications of these properties were observed by UV-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy respectively. The band gap energy of the polymer decreased considerably with discrete increment of the ion fluence (different fluence for each sample) and effective change for the sample irradiated at a fluence of 5 × 1012 ions/cm2 was observed from that of pristine sample. The amorphous nature of the polymer was observed to be decreased with increase of ion fluence. The vibrations of Ctbnd C appeared at mid fluences but the stretching vibrations of Osbnd H bond disappeared at these fluences due to the high LET of the oxygen ions.

  2. Globin-like proteins in Caenorhabditis elegans: in vivo localization, ligand binding and structural properties

    Directory of Open Access Journals (Sweden)

    Van Doorslaer Sabine

    2010-04-01

    Full Text Available Abstract Background The genome of the nematode Caenorhabditis elegans contains more than 30 putative globin genes that all are transcribed. Although their translated amino acid sequences fit the globin fold, a variety of amino-acid substitutions and extensions generate a wide structural diversity among the putative globins. No information is available on the physicochemical properties and the in vivo expression. Results We expressed the globins in a bacterial system, characterized the purified proteins by optical and resonance Raman spectroscopy, measured the kinetics and equilibria of O2 binding and determined the crystal structure of GLB-1* (CysGH2 → Ser mutant. Furthermore, we studied the expression patterns of glb-1 (ZK637.13 and glb-26 (T22C1.2 in the worms using green fluorescent protein technology and measured alterations of their transcript abundances under hypoxic conditions.GLB-1* displays the classical three-over-three α-helical sandwich of vertebrate globins, assembled in a homodimer associated through facing E- and F-helices. Within the heme pocket the dioxygen molecule is stabilized by a hydrogen bonded network including TyrB10 and GlnE7.GLB-1 exhibits high ligand affinity, which is, however, lower than in other globins with the same distal TyrB10-GlnE7 amino-acid pair. In the absence of external ligands, the heme ferrous iron of GLB-26 is strongly hexacoordinated with HisE7, which could explain its extremely low affinity for CO. This globin oxidizes instantly to the ferric form in the presence of oxygen and is therefore incapable of reversible oxygen binding. Conclusion The presented data indicate that GLB-1 and GLB-26 belong to two functionally-different globin classes.

  3. Globin-like proteins in Caenorhabditis elegans: in vivo localization, ligand binding and structural properties.

    Science.gov (United States)

    Geuens, Eva; Hoogewijs, David; Nardini, Marco; Vinck, Evi; Pesce, Alessandra; Kiger, Laurent; Fago, Angela; Tilleman, Lesley; De Henau, Sasha; Marden, Michael C; Weber, Roy E; Van Doorslaer, Sabine; Vanfleteren, Jacques; Moens, Luc; Bolognesi, Martino; Dewilde, Sylvia

    2010-04-02

    The genome of the nematode Caenorhabditis elegans contains more than 30 putative globin genes that all are transcribed. Although their translated amino acid sequences fit the globin fold, a variety of amino-acid substitutions and extensions generate a wide structural diversity among the putative globins. No information is available on the physicochemical properties and the in vivo expression. We expressed the globins in a bacterial system, characterized the purified proteins by optical and resonance Raman spectroscopy, measured the kinetics and equilibria of O2 binding and determined the crystal structure of GLB-1* (CysGH2 --> Ser mutant). Furthermore, we studied the expression patterns of glb-1 (ZK637.13) and glb-26 (T22C1.2) in the worms using green fluorescent protein technology and measured alterations of their transcript abundances under hypoxic conditions.GLB-1* displays the classical three-over-three alpha-helical sandwich of vertebrate globins, assembled in a homodimer associated through facing E- and F-helices. Within the heme pocket the dioxygen molecule is stabilized by a hydrogen bonded network including TyrB10 and GlnE7.GLB-1 exhibits high ligand affinity, which is, however, lower than in other globins with the same distal TyrB10-GlnE7 amino-acid pair. In the absence of external ligands, the heme ferrous iron of GLB-26 is strongly hexacoordinated with HisE7, which could explain its extremely low affinity for CO. This globin oxidizes instantly to the ferric form in the presence of oxygen and is therefore incapable of reversible oxygen binding. The presented data indicate that GLB-1 and GLB-26 belong to two functionally-different globin classes.

  4. Characterisation of Conformational and Ligand Binding Properties of Membrane Proteins Using Synchrotron Radiation Circular Dichroism (SRCD).

    Science.gov (United States)

    Hussain, Rohanah; Siligardi, Giuliano

    Membrane proteins are notoriously difficult to crystallise for use in X-ray crystallographic structural determination, or too complex for NMR structural studies. Circular dichroism (CD) is a fast and relatively easy spectroscopic technique to study protein conformational behaviour in solution. The advantage of synchrotron radiation circular dichroism (SRCD) measured with synchrotron beamlines compared to the CD from benchtop instruments is the extended spectral far-UV region that increases the accuracy of secondary structure estimations, in particular under high ionic strength conditions. Membrane proteins are often available in small quantities, and for this SRCD measured at the Diamond B23 beamline has successfully facilitated molecular recognition studies. This was done by probing the local tertiary structure of aromatic amino acid residues upon addition of chiral or non-chiral ligands using long pathlength cells (1-5 cm) of small volume capacity (70 μl-350 μl). In this chapter we describe the use of SRCD to qualitatively and quantitatively screen ligand binding interactions (exemplified by Sbma, Ace1 and FsrC proteins); to distinguish between functionally similar drugs that exhibit different mechanisms of action towards membrane proteins (exemplified by FsrC); and to identify suitable detergent conditions to observe membrane protein-ligand interactions using stabilised proteins (exemplified by inositol transporters) as well as the stability of membrane proteins (exemplified by GalP, Ace1). The importance of the in solution characterisation of the conformational behaviour and ligand binding properties of proteins in both far- andnear-UV regions and the use of high-throughput CD (HT-CD) using 96- and 384-well multiplates to study the folding effects in various protein crystallisation buffers are also discussed.

  5. Adiponectin Receptors Form Homomers and Heteromers Exhibiting Distinct Ligand Binding and Intracellular Signaling Properties*

    Science.gov (United States)

    Almabouada, Farid; Diaz-Ruiz, Alberto; Rabanal-Ruiz, Yoana; Peinado, Juan R.; Vazquez-Martinez, Rafael; Malagon, Maria M.

    2013-01-01

    Adiponectin binds to two widely expressed receptors (AdipoR1 and AdipoR2) that contain seven transmembrane domains but, unlike G-protein coupled receptors, present an extracellular C terminus and a cytosolic N terminus. Recently, AdipoR1 was found to associate in high order complexes. However, it is still unknown whether AdipoR2 may also form homomers or heteromers with AdipoR1 or if such interactions may be functionally relevant. Herein, we have analyzed the oligomerization pattern of AdipoRs by FRET and immunoprecipitation and evaluated both the internalization of AdipoRs in response to various adiponectin isoforms and the effect of adiponectin binding to different AdipoR combinations on AMP-activated protein kinase phosphorylation and peroxisome proliferator-activated receptor α activation. Transfection of HEK293AD cells with AdipoR1 and AdipoR2 showed that both receptors colocalize at both the plasma membrane and the endoplasmic reticulum. Co-transfection with the different AdipoR pairs yielded high FRET efficiencies in non-stimulated cells, which indicates that AdipoR1 and AdipoR2 form homo- and heteromeric complexes under resting conditions. Live FRET imaging suggested that both homo- and heteromeric AdipoR complexes dissociate in response to adiponectin, but heteromers separate faster than homomers. Finally, phosphorylation of AMP-activated protein kinase in response to adiponectin was delayed in cells wherein heteromer formation was favored. In sum, our findings indicate that AdipoR1 and AdipoR2 form homo- and heteromers that present unique interaction behaviors and signaling properties. This raises the possibility that the pleiotropic, tissue-dependent functions of adiponectin depend on the expression levels of AdipoR1 and AdipoR2 and, therefore, on the steady-state proportion of homo- and heteromeric complexes. PMID:23255609

  6. Adiponectin receptors form homomers and heteromers exhibiting distinct ligand binding and intracellular signaling properties.

    Science.gov (United States)

    Almabouada, Farid; Diaz-Ruiz, Alberto; Rabanal-Ruiz, Yoana; Peinado, Juan R; Vazquez-Martinez, Rafael; Malagon, Maria M

    2013-02-01

    Adiponectin binds to two widely expressed receptors (AdipoR1 and AdipoR2) that contain seven transmembrane domains but, unlike G-protein coupled receptors, present an extracellular C terminus and a cytosolic N terminus. Recently, AdipoR1 was found to associate in high order complexes. However, it is still unknown whether AdipoR2 may also form homomers or heteromers with AdipoR1 or if such interactions may be functionally relevant. Herein, we have analyzed the oligomerization pattern of AdipoRs by FRET and immunoprecipitation and evaluated both the internalization of AdipoRs in response to various adiponectin isoforms and the effect of adiponectin binding to different AdipoR combinations on AMP-activated protein kinase phosphorylation and peroxisome proliferator-activated receptor α activation. Transfection of HEK293AD cells with AdipoR1 and AdipoR2 showed that both receptors colocalize at both the plasma membrane and the endoplasmic reticulum. Co-transfection with the different AdipoR pairs yielded high FRET efficiencies in non-stimulated cells, which indicates that AdipoR1 and AdipoR2 form homo- and heteromeric complexes under resting conditions. Live FRET imaging suggested that both homo- and heteromeric AdipoR complexes dissociate in response to adiponectin, but heteromers separate faster than homomers. Finally, phosphorylation of AMP-activated protein kinase in response to adiponectin was delayed in cells wherein heteromer formation was favored. In sum, our findings indicate that AdipoR1 and AdipoR2 form homo- and heteromers that present unique interaction behaviors and signaling properties. This raises the possibility that the pleiotropic, tissue-dependent functions of adiponectin depend on the expression levels of AdipoR1 and AdipoR2 and, therefore, on the steady-state proportion of homo- and heteromeric complexes.

  7. Removing adsorbed heavy metal ions from sand surfaces via applying interfacial properties of rhamnolipid.

    Science.gov (United States)

    Haryanto, Bode; Chang, Chien-Hsiang

    2015-01-01

    In this study, the interfacial properties of biosurfactant rhamnolipid were investigated and were applied to remove adsorbed heavy metal ions from sand surfaces with flushing operations. The surface tension-lowering activity, micelle charge characteristic, and foaming ability of rhamnolipid were identified first. For rhamnolipid in water, the negatively charged characteristic of micelles or aggregates was confirmed and the foaming ability at concentrations higher than 40 mg/L was evaluated. By using the rhamnolipid solutions in a batch washing approach, the potential of applying the interfacial properties of rhamnolipid to remove adsorbed copper ions from sand surfaces was then demonstrated. In rhamnolipid solution flushing operations for sand-packed medium, higher efficiency was found for the removal of adsorbed copper ions with residual type than with inner-sphere interaction type, implying the important role of interaction type between the copper ion and the sand surface in the removal efficiency. In addition, the channeling effect of rhamnolipid solution flow in the sand-packed medium was clearly observed in the solution flushing operations and was responsible for the low removal efficiency with low contact areas between solution and sand. By using rhamnolipid solution with foam to flush the sand-packed medium, one could find that the channeling effect of the solution flow was reduced and became less pronounced with the increase in the rhamnolipid concentration, or with the enhanced foaming ability. With the reduced channeling effect in the flushing operations, the removal efficiency for adsorbed copper ions was significantly improved. The results suggested that the foam-enhanced rhamnolipid solution flushing operation was efficient in terms of surfactant usage and operation time.

  8. Rational design of ion force fields based on thermodynamic solvation properties.

    Science.gov (United States)

    Horinek, Dominik; Mamatkulov, Shavkat I; Netz, Roland R

    2009-03-28

    Most aqueous biological and technological systems contain solvated ions. Atomistic explicit-water simulations of ionic solutions rely crucially on accurate ionic force fields, which contain most commonly two adjustable parameters: the Lennard-Jones diameter and the interaction strength. Assuming these parameters to be properly optimized, the plethora of parameters one finds in the literature for one and the same ion is surprising. In principle, the two parameters should be uniquely determined by matching two ionic properties obtained for a particular water model and within a given simulation protocol with the corresponding experimental observables. Traditionally, ion parameters were chosen in a somewhat unsystematic way to reproduce the solvation free energy and to give the correct ion size when compared with scattering results. Which experimental observable one chooses to reproduce should in principle depend on the context within which the ionic force field is going to be used. In the present work we suggest to use the solvation free energy in conjunction with the solvation entropy to construct thermodynamically sound force fields for the alkali and halide ions for the simulation of ion-specific effects in aqueous environment. To that end we determine the solvation free energy and entropy of both cations and anions in the entire relevant parameter space. As an independent check on the quality of the resulting force fields we also determine the effective ionic radius from the first peak of the radial ion-water distribution function. Several difficulties during parameter optimization are discussed in detail. (i) Single-ion solvation depends decisively on water-air surface properties, which experimentally becomes relevant when introducing extrathermodynamic assumptions on the hydronium (H(3)O(+)) solvation energy. Fitting ion pairs circumvents this problem but leaves the parameters of one reference ion (here we choose chloride) undetermined. (ii) For the halides the

  9. Ion Exchange Equilibrium and Kinetic Properties of Polyacrylate Films and Applications to Chemical Analysis and Environmental Decontamination

    Science.gov (United States)

    Tanner, Stephen P.

    1997-01-01

    One of the goals of the original proposal was to study how cross-linking affects the properties of an ion exchange material(IEM) developed at Lewis Research Center. However, prior to the start of this work, other workers at LERC investigated the effect of cross-linking on the properties of this material. Other than variation in the ion exchange capacity, the chemical characteristics were shown to be independent of the cross-linking agent, and the degree of cross-linking. New physical forms of the film were developed (film, supported film, various sizes of beads, and powder). All showed similar properties with respect to ion exchange equilibria but the kinetics of ion exchange depended on the surface area per unit mass; the powder form of the IEM exchanging much more rapidly than the other forms. The research performed under this grant was directed towards the application of the IEM to the analysis of metal ions at environmental concentrations.

  10. Investigation of trace metal binding properties of lignin by diffusive gradients in thin films.

    Science.gov (United States)

    Hojaji, Elahe

    2012-09-01

    The binding behavior of lignin for Pb, Cu, Co, Mn, Cd and Ni was studied using the diffusive gradients in thin films technique (DGT). Samplers with different structures of diffusive gel were used in the well-stirred systems containing known concentrations of metals along with (a) 10, 20 and 40 μM lignin and; (b) 0.64 and 6.47 μM Suwannee river fulvic acid+40 μM lignin at an ionic strength of 0.01 M (NaNO(3)) and pH=7. Diffusion coefficients of lignin complexes in acrylamide gels were estimated and found to be less than 5% of the equivalent coefficients for the uncomplexed metal ions. These values were used to calculate concentrations of labile metals from DGT measurements in solutions, where lignin could discriminate metals in the order of Pb(+2)>Cu(+2)>Cd(+2)>Ni(+2)>Co(+2)>Mn(+2). Stability constants (LogK) were calculated using Visual MINTEQ II and WHAM V software. The K values were compared with the stability constants from titration of Pb and Cd with 10 μM lignin aqueous samples and with those of humic substances in natural waters. The constants obtained from measurement of complexing capacities might bias the real corresponding values unless two line regression analyses on titration data are considered. The DGT study of fractionation of metal species at varying ratios indicated that the proportion of organic complexes decreased with increasing ratios and gradually more metals were exchanged with inorganic phases. Speciation of Pb and Cd is affected by the concentrations of FA, Cd is dominantly bound with FA while Pb is evenly partitioned between the ligands. The comprehensive knowledge of metal-lignin complexes sheds some light on in situ operational speciation information that can be achieved by DGT.

  11. Structural and dynamical properties of ionic liquids: the influence of ion size disparity.

    Science.gov (United States)

    Spohr, H V; Patey, G N

    2008-08-14

    The influence of ion size disparity on structural and dynamical properties of ionic liquids is systematically investigated employing molecular dynamics simulations. Ion size ratios are varied over a realistic range (from 1:1 to 5:1) while holding other important molecular and system parameters fixed. In this way we isolate and identify effects that stem from size disparity alone. In strongly size disparate systems the larger species (cations in our model) tend to dominate the structure; the anion-anion distribution is largely determined by anion-cation correlations. The diffusion coefficients of both species increase, and the shear viscosity decreases with increasing size disparity. The influence of size disparity is strongest up to a size ratio of 3:1, then decreases, and by 5:1 both the diffusion coefficients and viscosity appear to be approaching limiting values. The conventional Stokes-Einstein expression for diffusion coefficients holds reasonably well for the cations but fails for the smaller anions as size disparity increases likely due to the neglect of strong anion-cation correlations. The electrical conductivity is not a simple monotonic function of size disparity; it first increases up to size ratios of 2:1, remains nearly constant until 3:1, then decreases such that the conductivities of the 1:1 and 5:1 systems are similar. This behavior is traced to the competing influences of ion diffusion (enhancing) and ion densities (reducing) on conductivities at constant packing fraction. The temperature dependence of the transport properties is examined for the 1:1 and 3:1 systems. In accord with experiment, the temperature dependence of all transport properties is well represented by the Vogel-Fulcher-Tammann equation. The dependence of the diffusion coefficients on the temperature/viscosity ratio is well described by the fractional Stokes-Einstein relation D proportional to (T/eta)(beta) with beta approximately = 0.8, consistent with the exponent observed for

  12. A c subunit with four transmembrane helices and one ion (Na+)-binding site in an archaeal ATP synthase: implications for c ring function and structure.

    Science.gov (United States)

    Mayer, Florian; Leone, Vanessa; Langer, Julian D; Faraldo-Gómez, José D; Müller, Volker

    2012-11-16

    The ion-driven membrane rotors of ATP synthases consist of multiple copies of subunit c, forming a closed ring. Subunit c typically comprises two transmembrane helices, and the c ring features an ion-binding site in between each pair of adjacent subunits. Here, we use experimental and computational methods to study the structure and specificity of an archaeal c subunit more akin to those of V-type ATPases, namely that from Pyrococcus furiosus. The c subunit was purified by chloroform/methanol extraction and determined to be 15.8 kDa with four predicted transmembrane helices. However, labeling with DCCD as well as Na(+)-DCCD competition experiments revealed only one binding site for DCCD and Na(+), indicating that the mature c subunit of this A(1)A(O) ATP synthase is indeed of the V-type. A structural model generated computationally revealed one Na(+)-binding site within each of the c subunits, mediated by a conserved glutamate side chain alongside other coordinating groups. An intriguing second glutamate located in-between adjacent c subunits was ruled out as a functional Na(+)-binding site. Molecular dynamics simulations indicate that the c ring of P. furiosus is highly Na(+)-specific under in vivo conditions, comparable with the Na(+)-dependent V(1)V(O) ATPase from Enterococcus hirae. Interestingly, the same holds true for the c ring from the methanogenic archaeon Methanobrevibacter ruminantium, whose c subunits also feature a V-type architecture but carry two Na(+)-binding sites instead. These findings are discussed in light of their physiological relevance and with respect to the mode of ion coupling in A(1)A(O) ATP synthases.

  13. Coupling and binding-saturation effects in L -subshell ionization of heavy atoms by 0.3-1.3-MeV/amu Si ions

    Science.gov (United States)

    Fijał-Kirejczyk, I.; Jaskóła, M.; Czarnacki, W.; Korman, A.; Banaś, D.; Braziewicz, J.; Majewska, U.; Semaniak, J.; Pajek, M.; Kretschmer, W.; Mukoyama, T.; Trautmann, D.; Lapicki, G.

    2008-03-01

    The coupling and binding effects have been studied in L -subshell ionization of heavy Au, Bi, Th, and U atoms by an impact of S28iq+ ions in the energy range of 8.5-36.0 MeV. The measured L x-ray spectra were analyzed taking into account the multiple ionization effects in outer M and N shells. The L -subshell ionization cross sections have been obtained from measured x-ray production cross sections using the L -shell fluorescence and Coster-Kronig yields which were modified for a reduced number of electrons and closed Coster-Kronig transitions in the multiply ionized atoms. The results are compared with the available calculations, which are based on the semiclassical approximation (SCA) as well as the plane-wave Born approximation (PWBA). We demonstrate that for silicon ion impact these theoretical approaches have to be modified to include the L -subshell coupling effect using the “coupled subshell model” (CSM) as well as the saturation of the binding effect at the united atom limit. The calculations modified for both effects are in much better agreement with the data. In particular, an order-of-magnitude improvement of agreement between the data and the SCA-CSM calculations including the binding-saturation effect is reported for low-energy Si ions for the L2 -subshell. The results are also compared with the predictions of the PWBA based ECPSSR and ECUSAR theories accounting for the energy-loss (E), Coulomb-deflection (C), and relativistic (R) effects treating the binding effect within the perturbed stationary state (PSS) approximation with correction for the binding-saturation effect introduced to describe the united-atom and separated-atom (USA) limits.

  14. Influence of ion/atom arrival ratio on structure and optical properties of AlN films by ion beam assisted deposition

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Jian-ping [Department of Energy Material and Technology, General Research Institute for Nonferrous Metals, Beijing 100088 (China); School of Engineering and Technology, China University of Geosciences, Beijing 100083 (China); Fu, Zhi-qiang, E-mail: fuzq@cugb.edu.cn [School of Engineering and Technology, China University of Geosciences, Beijing 100083 (China); Liu, Xiao-peng [Department of Energy Material and Technology, General Research Institute for Nonferrous Metals, Beijing 100088 (China); Yue, Wen; Wang, Cheng-biao [School of Engineering and Technology, China University of Geosciences, Beijing 100083 (China)

    2014-10-30

    Highlights: • AlN films were fabricated by dual ion beam sputtering. • Chemical bond status and phase composition of the films were studied by XPS and XRD. • Optical constants were measured by spectroscopic ellipsometry. • Influence of ion/atom arrival ratio on the films was studied. - Abstract: In order to improve the optical properties of AlN films, the influence of the ion/atom arrival ratio on the structure and optical characteristics of AlN films deposited by dual ion beam sputtering was studied by using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, spectroscopic ellipsometry and UV–vis spectroscopy. The films prepared at the ion/atom arrival ratio of 1.4 are amorphous while the crystalline quality is improved with the increase of the ion/atom arrival ratio. The films deposited at the ion/atom arrival ratio of no less than 1.8 have an approximately stoichiometric ratio and mainly consist of aluminum nitride with little aluminum oxynitride, while metallic aluminum component appears in the films deposited at the ion/atom arrival ratio of 1.4. When the ion/atom arrival ratio is not less than 1.8, films are smooth, high transmitting and dense. The films prepared with high ion/atom arrival ratio (≥1.8) display the characteristic of a dielectric. The films deposited at the ion/atom arrival ratio of 1.4 are coarse, opaque and show characteristic of cermet.

  15. Inorganic Solid-State Electrolytes for Lithium Batteries: Mechanisms and Properties Governing Ion Conduction.

    Science.gov (United States)

    Bachman, John Christopher; Muy, Sokseiha; Grimaud, Alexis; Chang, Hao-Hsun; Pour, Nir; Lux, Simon F; Paschos, Odysseas; Maglia, Filippo; Lupart, Saskia; Lamp, Peter; Giordano, Livia; Shao-Horn, Yang

    2016-01-13

    This Review is focused on ion-transport mechanisms and fundamental properties of solid-state electrolytes to be used in electrochemical energy-storage systems. Properties of the migrating species significantly affecting diffusion, including the valency and ionic radius, are discussed. The natures of the ligand and metal composing the skeleton of the host framework are analyzed and shown to have large impacts on the performance of solid-state electrolytes. A comprehensive identification of the candidate migrating species and structures is carried out. Not only the bulk properties of the conductors are explored, but the concept of tuning the conductivity through interfacial effects-specifically controlling grain boundaries and strain at the interfaces-is introduced. High-frequency dielectric constants and frequencies of low-energy optical phonons are shown as examples of properties that correlate with activation energy across many classes of ionic conductors. Experimental studies and theoretical results are discussed in parallel to give a pathway for further improvement of solid-state electrolytes. Through this discussion, the present Review aims to provide insight into the physical parameters affecting the diffusion process, to allow for more efficient and target-oriented research on improving solid-state ion conductors.

  16. Leaching and antimicrobial properties of silver nanoparticles loaded onto natural zeolite clinoptilolite by ion exchange and wet impregnation

    CSIR Research Space (South Africa)

    Missengue, RNM

    2015-11-01

    Full Text Available This study aimed to compare the leaching and antimicrobial properties of silver that was loaded onto the natural zeolite clinoptilolite by ion exchange and wet impregnation. Silver ions were reduced using sodium borohydride (NaBH(sub4...

  17. A cDNA encoding a pRB-binding protein with properties of the transcription factor E2F

    DEFF Research Database (Denmark)

    Helin, K; Lees, J A; Vidal, M

    1992-01-01

    The retinoblastoma protein (pRB) plays an important role in the control of cell proliferation, apparently by binding to and regulating cellular transcription factors such as E2F. Here we describe the characterization of a cDNA clone that encodes a protein with properties of E2F. This clone, RBP3...

  18. Catalytic properties of two Rhizopus oryzae 99-880 glucoamylase enzymes without starch binding domains expressed in Pichia pastoris

    Science.gov (United States)

    Catalytic properties of the two glucoamylases, AmyC and AmyD, without starch binding domains from Rhizopus oryzae strain 99-880 were heterologously expressed and purified to homogeneity. AmyC and AmyD demonstrate pH optima of 5.5 and 6.0, respectively, nearly 1 unit higher than most fungal glucoamy...

  19. Ionic strength-dependent changes in tentacular ion exchangers with variable ligand density. II. Functional properties.

    Science.gov (United States)

    Bhambure, Rahul; Angelo, James M; Gillespie, Christopher M; Phillips, Michael; Graalfs, Heiner; Lenhoff, Abraham M

    2017-07-14

    The effect of ligand density was studied on protein adsorption and transport behavior in tentacular cation-exchange sorbents at different ionic strengths. Results were obtained for lysozyme, lactoferrin and a monoclonal antibody (mAb) in order to examine the effects of protein size and charge. The combination of ligand density and ionic strength results in extensive variability of the static and dynamic binding capacities, transport rate and binding affinity of the proteins. Uptake and elution experiments were performed to quantify the transport behavior of selected proteins, specifically to estimate intraparticle protein diffusivities. The observed trend of decreasing uptake diffusivities with an increase in ligand density was correlated to structural properties of the ligand-density variants, particularly the accessible porosity. Increasing the ionic strength of the equilibration buffer led to enhanced mass transfer during uptake, independent of the transport model used, and specifically for larger proteins like lactoferrin and mAb, the most significant effects were evident in the sorbent of the highest ligand density. For lysozyme, higher ligand density leads to higher static and dynamic binding capacities whereas for lactoferrin and the mAb, the binding capacity is a complex function of accessible porosity due to ionic strength-dependent changes. Ligand density has a less pronounced effect on the elution rate, presumably due to ionic strength-dependent changes in the pore architecture of the sorbents. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Structural and magnetic properties of Gd{sup 3+} ion substituted magnesium ferrite nanopowders

    Energy Technology Data Exchange (ETDEWEB)

    Elkady, Ashraf S. [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Department of Reactor Physics, NRC, Atomic Energy Authority, Cairo (Egypt); Hussein, Shaban I. [Department of Reactor Physics, NRC, Atomic Energy Authority, Cairo (Egypt); Rashad, Mohamed M., E-mail: rashad133@yahoo.com [Central Metallurgical Research and Development Institute, Helwan, Cairo 11421 (Egypt)

    2015-07-01

    Nanocrystalline MgGd{sub x}Fe{sub 2−x}O{sub 4} powders (where x=0, 0.05, 0.1, 0.2, 0.25, 0.3) have been synthesized by the ethylene diamine tetraacetic acid (EDTA)-based sol–gel combustion method. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM) were applied in order to study the effect of variation of Gd{sup 3+} ion substitution and its impact on crystal structure, crystallite size, lattice parameters, nanostructure and magnetic properties of the formed powders. XRD indicated that, after doping and calcination at 400 °C for 2 h, all samples have two spinel ferrite structures namely cubic and tetragonal phases, which are dependent on Gd{sup 3+} ion concentration. The cubic phase is found to increase with increasing the Gd{sup 3+} ion molar ratio up to 0.1, compared to pure MgFe{sub 2}O{sub 4} and higher Gd{sup 3+} content samples. Indeed, with increasing Gd{sup 3+} ion, the crystallite size was almost unchanged whereas the lattice parameter was found to increase. FT-IR spectrum showed broadening of the ν{sub 2} band and the presence of another band in the range (465–470 cm{sup −1}) upon adding Gd{sup 3+} ion, which confirm the presence of Gd{sup 3+} ion in addition to Fe{sup 3+} ion at octahedral site. Besides, these bands were assigned to the formation of (Gd{sup 3+}–O{sup 2−}) complexes at B-sites. HRTEM images showed that the studied samples consist of nanocrystallites having average particle sizes around 9 nm for pure MgFe{sub 2}O{sub 4} up to 27 and 42 nm for the Gd{sup 3+} ion substituted MgFe{sub 2}O{sub 4} of molar ratio 0.05 and 0.30, respectively. An examination of the magnetic properties revealed an increase in saturation magnetization with increasing Gd concentration incorporation up to x=0.1, as a result of the change of cubic and tetragonal spinel ratio and lattice parameters. Meanwhile, the formed powders exhibited

  1. Magnetic properties of manganites doped with gallium, iron, and chromium ions

    Energy Technology Data Exchange (ETDEWEB)

    Troyanchuk, I. O., E-mail: troyan@physics.by; Bushinsky, M. V.; Tereshko, N. V. [National Academy of Sciences of Belarus, Scientific and Practical Materials Research Center (Belarus); Dobryanskii, V. M. [Belarussian State Agrarian Technical University (Belarus); Sikolenko, V. [Joint Institute for Nuclear Research (Russian Federation); Többens, D. M. [Helmholtz Center (Germany)

    2015-05-15

    The magnetization and the crystal structure of the La{sub 0.7}Sr{sub 0.3}Mn{sub 1−x}M{sub x}O{sub 3} (M = Ga, Fe, Cr; x ≤ 0.3) systems are studied. The substitution of gallium and chromium is shown to cause phase separation into antiferromagnetic and ferromagnetic phases, whereas the substitution of iron for manganese stabilizes a spinglass state. The ferromagnetic phase in the chromium-substituted compositions is much more stable than that in the case of substitution by iron ions or diamagnetic gallium ions. The magnetic properties are explained in terms of the model of superexchange interactions and the localization of most e{sub g} electrons of manganese. The stabilization of ferromagnetism in the chromium-substituted compositions can be caused by the fact that the positive and negative contributions to the superexchange interaction between Mn{sup 3+} and Cr{sup 3+} ions are close to each other but the antiferromagnetic part of the exchange is predominant. Moreover, some chromium ions are in the tetravalent state, which maintains the optimum doping conditions.

  2. Effect of F ions on physical and optical properties of fluorine substituted zinc arsenic tellurite glasses

    Science.gov (United States)

    Kareem Ahmmad, Shaik; kondaul, Edu; Rahman, Syed

    2015-02-01

    The effect of substitution of fluoride ions for oxide ions on the physical and optical properties of glass system (20-x) ZnO-xZnF2-40As2O3-40TeO2 where x = 0, 4, 8,12,16,20 mole % were investigated. The samples prepared by melt quenching method under controlled condition. The amorphous nature of these glasses was checked by X-ray diffraction technique. The density was measured according to Archimedes principle. The room temperature absorption spectra of all glass samples were determined using UV-Vis-NIR spectrometer. The thermal behaviour, glass transition temperature and stability of glass samples were studied by a differential scanning calorimetric (DSC). The density reduction of present glasses with ZnF2 concentrations may be due to the low density of ZnF2 compared with that of ZnO. Breaking the oxide network, the cross linking degree of the glass former could be reduced which results in decrease of both Tg and Tx. In the present glass system when F ions replaced by oxygen ions UV-Vis absorption cut-off wavelength decreases. This resulted form the conversion of structural unit in the glass from TeO4 to Te(O,F)4 and then to Te(O, F)3.

  3. Modification of thermal and electronic properties of bilayer graphene by using slow Na+ ions

    Science.gov (United States)

    Ryu, Mintae; Lee, Paengro; Kim, Jingul; Park, Heemin; Chung, Jinwook

    2016-12-01

    Bilayer graphene (BLG) has an extensive list of industrial applications in graphene-based nanodevices such as energy storage devices, flexible displays, and thermoelectric devices. By doping slow Na+ ions on Li-intercalated BLG, we find significantly improved thermal and electronic properties of BLG by using angle-resolved photoemission and high-resolution core level spectroscopy (HRCLS) with synchrotron photons. Our HRCLS data reveal that the adsorbed Na+ ions on a BLG produced by Li-intercalation through single layer graphene (SLG) spontaneously intercalate below the BLG, and substitute Li atoms to form Na-Si bonds at the SiC interface while preserving the same phase of BLG. This is in sharp contrast with no intercalation of Na+ ions on SLG though neutral Na atoms intercalate. The Na+-induced BLG is found to be stable upon heating up to T = 400 °C, but returns to SLG when heated at T d = 500 °C. The evolution of the π-bands upon doping the Na+ ions followed by thermal annealing shows that the carrier concentration of the π-band may be artificially controlled without damaging the Dirac nature of the π-electrons. The doubled desorption temperature from that (T d = 250 °C) of the Na-intercalated SLG together with the electronic stability of the Na+-intercalated BLG may find more practical and effective applications in advancing graphene-based thermoelectric devices and anode materials for rechargeable batteries.

  4. Absorption and luminescence properties of terbium ions in heavy metal glasses

    Energy Technology Data Exchange (ETDEWEB)

    Żur, Lidia, E-mail: lzur@us.edu.pl; Sołtys, Marta; Pisarska, Joanna; Pisarski, Wojciech A.

    2013-11-25

    Highlights: •Tb-doped heavy metal glasses were studied as a function of glass composition. •Excitation and luminescence spectra of Tb ions in heavy metal glasses were examined. •Luminescence intensity ratios (G/B) and measured lifetimes of Tb were determined. •Correlation between G/B factor, measured lifetimes and energy phonon was proposed. -- Abstract: Heavy metal glasses doped with Tb{sup 3+} ions have been investigated. Influence of glass-former oxides on the absorption and luminescence properties of terbium ions in inorganic glasses containing lead are discussed. Green emission line located at 543 nm due to {sup 5}D{sub 4} → {sup 7}F{sub 5} transition of Tb{sup 3+} was observed as a most intensive line. Green-to-blue luminescence ratio related to the integrated emission intensity of the {sup 5}D{sub 4} → {sup 7}F{sub 5} transition to that of the {sup 5}D{sub 4} → {sup 7}F{sub 6} transition was calculated and examined as a function of glass composition. Luminescence lifetimes for the {sup 5}D{sub 4} excited state of Tb{sup 3+} ions in heavy metal glasses were also determined. Correlation between green-to-blue luminescence ratios, measured lifetimes and the energy phonon of the glass hosts was proposed.

  5. Physical and biological properties of the ion beam irradiated PMMA-based composite films

    Energy Technology Data Exchange (ETDEWEB)

    Shanthini, G.M.; Martin, Catherine Ann; Sakthivel, N.; Veerla, Sarath Chandra; Elayaraja, K. [Crystal Growth Centre, Anna University, Chennai 600025 (India); Lakshmi, B.S. [Department of Biotechnology, Anna University, Chennai 600025 (India); Asokan, K.; Kanjilal, D. [Materials Science Group, Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Kalkura, S. Narayana, E-mail: kalkurasn@annauniv.edu [Crystal Growth Centre, Anna University, Chennai 600025 (India)

    2015-02-28

    Highlights: • First report of swift heavy ion irradiation on PMMA-HAp as bioceramic composite. • Augmented protein adsorption of about 400% was attained due to irradiation. • Tailored surface morphology, topography, roughness, wettability and crystallinity. • Irradiation transformed the hydrophobic surface into hydrophilic surface. • Better blood and cell–material interaction leading to improved biocompatibility. - Abstract: Polymethyl methacrylate (PMMA) and PMMA-hydroxyapatite (PMMA-HAp) composite films, prepared by the solvent evaporation method were irradiated with 100 MeV Si{sup 7+} ions. Crystallographic, morphological and the functional groups of the pristine and irradiated samples were studied using glancing incident X-ray diffraction (GIXRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) respectively. SEM reveals the creation of pores, along with an increase in porosity and cluster size on irradiation. Decrease in crystalline nature and crystallite size with an increase in ion fluence was observed from GIXRD patterns. The surface roughness and the wettability of the material were also enhanced, which could favour the cell–material interaction. The irradiated samples adsorbed significantly greater amount of proteins than pristine. Also, irradiation does not produce any toxic byproducts or leachants, and maintains the viability of 3T3 cells. The response of the irradiated samples towards biomedical applications was demonstrated by the improved antimicrobial activity, haemocompatibility and cytocompatibility. Swift heavy ion irradiation (SHI) could be an effective tool to modify and engineer the surface properties of the polymers to enhance the biocompatibility.

  6. Modification in surface properties of poly-allyl-diglycol-carbonate (CR-39 implanted by Au+ ions at different fluences

    Directory of Open Access Journals (Sweden)

    Sagheer Riffat

    2016-06-01

    Full Text Available Ion implantation has a potential to modify the surface properties and to produce thin conductive layers in insulating polymers. For this purpose, poly-allyl-diglycol-carbonate (CR-39 was implanted by 400 keV Au+ ions with ion fluences ranging from 5 × 1013 ions/cm2 to 5 × 1015 ions/cm2. The chemical, morphological and optical properties of implanted CR-39 were analyzed using Raman, Fourier transform infrared (FT-IR spectroscopy, atomic force microscopy (AFM and UV-Vis spectroscopy. The electrical conductivity of implanted samples was determined through four-point probe technique. Raman spectroscopy revealed the formation of carbonaceous structures in the implanted layer of CR-39. From FT-IR spectroscopy analysis, changes in functional groups of CR-39 after ion implantation were observed. AFM studies revealed that morphology and surface roughness of implanted samples depend on the fluence of Au ions. The optical band gap of implanted samples decreased from 3.15 eV (for pristine to 1.05 eV (for sample implanted at 5 × 1015 ions/cm2. The electrical conductivity was observed to increase with the ion fluence. It is suggested that due to an increase in ion fluence, the carbonaceous structures formed in the implanted region are responsible for the increase in electrical conductivity.

  7. Influence of different ions doping on the antibacterial properties of MgO nanopowders

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Yuanyuan; Wang, Wei, E-mail: weiwang@hust.edu.cn; Tan, Fatang; Cai, Yuncheng; Lu, Junwen; Qiao, Xueliang

    2013-11-01

    Compared with other inorganic antibacterial agents, magnesium oxide (MgO) nanopowders exhibit a unique antibacterial mechanism and various advantages in applications, having attracted extensive attention. In this study, MgO nanopowders doped with different ions (Li{sup +}, Zn{sup 2+} and Ti{sup 4+}) were synthesized by a sol–gel method, respectively. The structures and morphologies of the as-obtained precursors and nanopowders were characterized and confirmed by X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) analysis. The influence of three metal ions doping on the antibacterial properties of MgO nanopowders was also investigated by their bactericidal activity against Escherichia coli (E. coli, ATCC 25922) using the broth microdilution method and the agar method. The results show that Li-doped MgO exhibits better antibacterial activity, Zn-doped and Ti-doped MgO display poorer antibacterial activity than pure MgO. It can be concluded that the influence of different ions doping on the antibacterial properties of MgO mainly lies on oxygen vacancies and basicity of nanopowders.

  8. Influence of different ions doping on the antibacterial properties of MgO nanopowders

    Science.gov (United States)

    Rao, Yuanyuan; Wang, Wei; Tan, Fatang; Cai, Yuncheng; Lu, Junwen; Qiao, Xueliang

    2013-11-01

    Compared with other inorganic antibacterial agents, magnesium oxide (MgO) nanopowders exhibit a unique antibacterial mechanism and various advantages in applications, having attracted extensive attention. In this study, MgO nanopowders doped with different ions (Li+, Zn2+ and Ti4+) were synthesized by a sol-gel method, respectively. The structures and morphologies of the as-obtained precursors and nanopowders were characterized and confirmed by X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) analysis. The influence of three metal ions doping on the antibacterial properties of MgO nanopowders was also investigated by their bactericidal activity against Escherichia coli (E. coli, ATCC 25922) using the broth microdilution method and the agar method. The results show that Li-doped MgO exhibits better antibacterial activity, Zn-doped and Ti-doped MgO display poorer antibacterial activity than pure MgO. It can be concluded that the influence of different ions doping on the antibacterial properties of MgO mainly lies on oxygen vacancies and basicity of nanopowders.

  9. Effect of argon ion implantation on the electrical and dielectric properties of CR-39

    Energy Technology Data Exchange (ETDEWEB)

    Chawla, Mahak, E-mail: mahak.chawla@gmail.com; Shekhawat, Nidhi; Goyal, Meetika; Gupta, Divya; Sharma, Annu; Aggarwal, Sanjeev [Department of Physics, Kurukshetra University, Kurukshetra - 136119 (India)

    2016-05-23

    The objective of the present work is to study the effect of 130 keV Ar{sup +} ions on the electrical and dielectric properties of CR-39 samples at various doses 5×10{sup 14}, 1×10{sup 15} and 1×10{sup 16} Ar{sup +} cm{sup −2}. Current-Voltage (I-V characteristics) measurements have been used to study the electrical properties of virgin and Ar{sup +} implanted CR-39 specimens. The current has been found to be increased with increasing voltage as well as with increasing ion dose. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. The dielectric constant has been found to be decreasing whereas dielectric loss factor increases with increasing ion fluence. These kind of behavior observed in the implanted specimens indicate towards the formation of carbonaceous clusters due to the cross linking, chemical bond cleavage, formation of free radicals. The changes observed in the dielectric behavior have been further correlated with the structural changes observed through I-V characteristics.

  10. Effect of argon ion implantation on the electrical and dielectric properties of CR-39

    Science.gov (United States)

    Chawla, Mahak; Shekhawat, Nidhi; Goyal, Meetika; Gupta, Divya; Sharma, Annu; Aggarwal, Sanjeev

    2016-05-01

    The objective of the present work is to study the effect of 130 keV Ar+ ions on the electrical and dielectric properties of CR-39 samples at various doses 5×1014, 1×1015 and 1×1016 Ar+ cm-2. Current-Voltage (I-V characteristics) measurements have been used to study the electrical properties of virgin and Ar+ implanted CR-39 specimens. The current has been found to be increased with increasing voltage as well as with increasing ion dose. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. The dielectric constant has been found to be decreasing whereas dielectric loss factor increases with increasing ion fluence. These kind of behavior observed in the implanted specimens indicate towards the formation of carbonaceous clusters due to the cross linking, chemical bond cleavage, formation of free radicals. The changes observed in the dielectric behavior have been further correlated with the structural changes observed through I-V characteristics.

  11. Effects of mutagenesis of aspartic acid residues in the putative phosphoribosyl diphosphate binding site of Escherichia coli phosphoribosyl diphosphate synthetase on metal ion specificity and ribose 5-phosphate binding

    DEFF Research Database (Denmark)

    Willemoës, Martin; Nilsson, Dan; Hove-Jensen, Bjarne

    1996-01-01

    an increase in KM for ribose 5-phosphate in the presence of at least one of the divalent metal ions Mg2+, Mn2+, Co2+, or Cd2+, with the most dramatic changes revealed by the D220E and D220F enzymes in the presence of Co2+ and the D221A enzyme in the presence of Mn2+ or Co2+. The D220F and D221A enzymes both...... showed large decreases in Vapp in the presence of the various divalent metal ions, except for the D221A enzyme in the presence of Co2+. Vapp of the D220E enzyme was similar to that of the wild-type enzyme in the presence of Mg2+, Mn2+, or Cd2+, whereas the Vapp was increased in the presence of Co2+. Vapp...... enzymes were dependent on the metal ion present, suggesting a function of the investigated aspartic acid residues both in the binding of ribose 5-phosphate, possibly via a divalent metal ion, and in the interaction with a divalent metal ion during catalysis...

  12. Interpretation with a Donnan-based concept of the influence of simple salt concentration on the apparent binding of divalent ions to the polyelectrolytes polystyrenesulfonate and dextran sulfate

    Science.gov (United States)

    Marinsky, J.A.; Baldwin, Robert F.; Reddy, M.M.

    1985-01-01

    It has been shown that the apparent enhancement of divalent metal ion binding to polyions such as polystyrenesulfonate (PSS) and dextran sulfate (DS) by decreasing the ionic strength of these mixed counterion systems (M2+, M+, X-, polyion) can be anticipated with the Donnan-based model developed by one of us (J.A.M.). Ion-exchange distribution methods have been employed to measure the removal by the polyion of trace divalent metal ion from simple salt (NaClO4)-polyion (NaPSS) mixtures. These data and polyion interaction data published earlier by Mattai and Kwak for the mixed counterion systems MgCl2-LiCl-DS and MgCl2-CsCl-DS have been shown to be amenable to rather precise analysis by this model. ?? 1985 American Chemical Society.

  13. Influence of binding material of PZT coating on microresonator's electrical and mechanical properties

    Science.gov (United States)

    Janusas, Giedrius; Guobiene, Asta; Palevicius, Arvydas; Brunius, Alfredas; Cekas, Elingas; Baltrusaitis, Valentinas; Sakalys, Rokas

    2017-06-01

    Microresonators are fundamental components integrated in hosts of MEMS applications: covering the automotive sector, the telecommunication industry, electronic equipment for surface/material characterization and motion sensing, and etc. The aim of this paper is to investigate the mechanical and electrical properties of PZT film fabricated with three binding materials: polyvinyl butyral (PVB), polymethyl methacrylate (PMMA) and polystyrene (PS) and to evaluate applicability in control of microresonators Q factor. Micro particles of PZT powder were mixed with 20% solution of PVB, PMMA and PS in benzyl alcohol. For investigation of mechanical and electrical properties multilayer cantilevers were made. Obtained PZT and polymer paste was screen printed on copper (thickness 40 μm) using polyester monofilament screen meshes (layer thickness 50 μm) and dried for 30 min at 100°C. Electric dipoles of the PZT particles in composite material were aligned using high voltage generator (5 kV) and a custom-made holder. Electric field was held for 30 min. Surfaces of the applied films were investigated by Atomic Force Microscope NanoWizard(R)3 NanoScience. Dynamic and electrical characteristics of the multilayer were investigated using laser triangular displacement sensor LK-G3000. The measured vibration amplitude and generated electrical potential was collected with USB oscilloscope PicoScope 3424. As the results showed, these cantilevers were able to transform mechanical strain energy into electric potential and, v.v. However, roughness of PZT coatings with PMMA and PS were higher, what could be the reason of the worse quality of the top electrode. However, the main advantage of the created composite piezoelectric material is the possibility to apply it on any uniform or non-uniform vibrating surface and to transform low frequency vibrations into electricity.

  14. Constraining properties of rapidly rotating neutron stars using data from heavy-ion collisions

    CERN Document Server

    Krastev, Plamen G; Worley, Aaron

    2007-01-01

    Aims.- Properties, structure, and thermal evolution of neutron stars are determined by the equation of state of stellar matter. Recent data on isospin-diffusion in heavy-ion collisions at intermediate energies and the size of neutron skin in $^{208}Pb$ have constrained considerably the density dependence of the nuclear symmetry energy and, in turn, the equation of state of neutron-rich nucleonic matter. These constraints could provide useful information about the global properties of rapidly rotating neutron stars. Methods.- Models of rapidly rotating neutron stars are constructed applying several nucleonic equations of state. Particular emphasis is placed on configurations rotating rigidly at 716 and 1122Hz. The range of allowed hydrostatic equilibrium solutions is determined and tested for stability. The effect of rotation on the internal composition and thermal properties of neutron stars is also examined. Results.- At a given rotational frequency, each equation of state yields a range of possible neutron ...

  15. Heavy metal binding properties of Pinus sylvestris mycorrhizas from industrial wastes

    Directory of Open Access Journals (Sweden)

    Katarzyna Turnau

    2014-01-01

    Full Text Available Mycorrhizas of Pinus sylvestris, collected from zinc wastes in Poland and France were investigated using transmission electron microscope (TEM and scanning electron microscope (SEM equipped with energy dispersion spectroscopy (EDS and electron energy loss spectroscopy (EELS. At both sites, mycorrhizas of Hebeloma were the most frequent, however, they were often characterised by a sparse or only locally developed fungal mantle. Mycorrhizas formed by suilloid fungi were much less frequent, and usually produced a clearly defined fungal mantle characterised by abundant formation of pigments and crystals covering the hyphae of the outer mantle. These two groups of mycorrhizas differed in their heavy metal binding properties. A biofiltering effect of Pb and Zn by the fungal mantle was observed only in the case of suilloid mycorrhizas, which represented up to 10% of the total number of mycorrhizas. No statistical differences between the mantle, the cortical cell walls and the vascular tissue were demonstrated in mycorrhizas formed by other fungi dominating on industrial wastes. In the case of Hebeloma and Inocybe, however, elements such as Cu and Cd were present in higher amounts in the extra-matrical mycelium, whereas no or only low amounts of these elements were detected within fungal mantles, mainly in mycorrhizas from the French waste. Analysis of the root systems has shown relatively high percentage of nonmycorrhizal short roots, suggesting the inhibition of mycorrhiza formation or a decreased number of mycorrhizal propagules. The role of dead roots and mycorrhizas in biosorption and immobilization of heavy metals was discussed.

  16. ANION-BINDING AND SENSING PROPERTIES OF NOVEL RECEPTORS BASED ON N-(INDOL-3-YLGLYOXYLYLBENZYLAMINE

    Directory of Open Access Journals (Sweden)

    Wei Wei

    2015-12-01

    Full Text Available Indole-based receptors such as biindole, carbazole, and indolocarbazole are regarded as some of the most favorable anion receptors in molecular recognition. This is because indole groups possess N–H groups as hydrogen-bonding donors. The introduction of amide groups in the indole framework can induce strong binding properties and good water solubility. In this study, we designed and synthesized a series of N-(indol-3-ylglyoxylylbenzylamine derivatives as novel and simple anion receptors. The receptors derived by aryl and aliphatic amines can selectively recognize F– based on a color change from colorless-to-yellow in DMSO. The receptors derived by hydrazine hydrate can recognize F–, AcO–, and H2PO4– by similar color changes in DMSO and can even enable the selective recognition of F– in a DMSO–H2O binary solution by the naked eye. Spectrographic data indicate that complexes are formed between receptors and anions through multiple hydrogen-bonding interactions in dual solutions.

  17. The energy levels and transition properties of In-like ions

    Science.gov (United States)

    Wang, H.-W.; Zhang, L.; Jiang, G.; Li, X.-F.; Wang, H.-B.

    2017-08-01

    The energy levels and transition properties of In-like ions are investigated by using the multi-configuration Dirac-Hartree-Fock method. The results for the energy levels, transition probabilities, wavelengths, line strengths and lifetimes of In-like Cs VII—Pm XIII are reported. Relativistic effects and electron correlation are included. Our calculations agree well with the experimental and other theoretical values. The new data of energy levels and transition parameters are predicted. The level crossing happens between the configurations 5s 24f and 5s 25p with increasing nuclear charge. The transition frequencies are within the range of usual lasers because of the level crossing. In-like ions may be developed into atomic clock.

  18. Hydrothermally Processed Oxide Nanostructures and Their Lithium–ion Storage Properties

    Directory of Open Access Journals (Sweden)

    Kim Yong-Jin

    2010-01-01

    Full Text Available Abstract Y- and Si-based oxide nanopowders were synthesized by a hydrothermal reaction of Y or Si powders with NaOH or LiOH aqueous solution. Nanoparticles with different morphology such as elongated nanospheres, flower-like nanoparticles and nanowires were produced by a control of processing parameters, in particular, the starting composition of solution. The preliminary result of electrochemical examination showed that the hydrothermally processed nanowires exhibit high initial capacities of Li-ion storage: 653 mAh/g for Y2O3 nanowires as anode materials and 186 mAh/g for Li2Si2O5 nanowires as cathode materials in a Li secondary cell. Compared to the powder with elongated sphere or flower-like shapes, the nanowires showed a higher Li-ion capacity and a better cycle property.

  19. Radiation properties and hydrodynamics evolution of highly charged ions in laser-produced silicon plasma.

    Science.gov (United States)

    Min, Qi; Su, Maogen; Cao, Shiquan; Sun, Duixiong; O'Sullivan, Gerry; Dong, Chenzhong

    2016-11-15

    We present a simplified radiation hydrodynamic model based on the fluid dynamic equations and the radiative transfer equation, which can be used to investigate the radiation properties and dynamics evolution of highly charged ions in a laser-produced plasma in vacuum. The outputs of the model consist of the evolution of the electron temperature, atom, and ion density, and the temporal and spatial evolution of various transient particles in plasma, as well as the simulated spectrum related to certain experimental conditions in a specified spectral window. In order to test the model and provide valuable experimental feedback, a series of EUV emission spectra of silicon plasmas have been measured using the spatio-temporally resolved laser produced plasma technique. The temporal and spatial evolution of the plasma is reliably reconstructed by using this model.

  20. RETRACTED: Effect of F- ions on spectroscopic properties of Yb3+-doped zinc tellurite glasses

    Science.gov (United States)

    Wang, Guonian; Zhang, Junjie; Dai, Shixun; Yang, Jianhu; Jiang, Zhonghong

    2005-06-01

    This article has been retracted at the request of the Editors, after a reader brought the following to their attention. Reason: The article substantially reproduces parts of articles published by the same authors in the Journal of Luminescence (“Effect of F- ions on physical and spectroscopic properties of Yb3+-doped TeO2 glasses”, Volume 113, Issues 1-2, Pages 27-32) and the Journal of Alloys and Compounds (“Fluorescence lifetime increase by introduction of F- ions in ytterbium-doped TeO2-based glasses”, Volume 393, Issues 1-2, Pages 279-282). There was also a failure to cite either of these articles. These other articles have also been retracted. This action has been agreed by the Editors of the three journals.