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Sample records for tridentate nitrogen-donor ligands

  1. Zinc acetylacetonate hydrate adducted with nitrogen donor ligands: Synthesis, spectroscopic characterization, and thermal analysis

    Science.gov (United States)

    Brahma, Sanjaya; Shivashankar, S. A.

    2015-12-01

    We report synthesis, spectroscopic characterization, and thermal analysis of zinc acetylacetonate complex adducted by nitrogen donor ligands, such as pyridine, bipyridine, and phenanthroline. The pyridine adducted complex crystallizes to monoclinic crystal structure, whereas other two adducted complexes have orthorhombic structure. Addition of nitrogen donor ligands enhances the thermal property of these complexes as that with parent metal-organic complex. Zinc acetylacetonate adducted with pyridine shows much higher volatility (106 °C), decomposition temperature (202 °C) as that with zinc acetylacetonate (136 °C, 220 °C), and other adducted complexes. All the adducted complexes are thermally stable, highly volatile and are considered to be suitable precursors for metal organic chemical vapor deposition. The formation of these complexes is confirmed by powder X-ray diffraction, Fourier transform infrared spectroscopy, mass spectroscopy, and elemental analysis. The complexes are widely used as starting precursor materials for the synthesis of ZnO nanostructures by microwave irradiation assisted coating process.

  2. Lanthanide(III) complexes with tridentate Schiff base ligand ...

    African Journals Online (AJOL)

    The X-ray study reveals isotopic Nd/Sm binuclear structures were each metal ion is nine-coordinated in the same fashion. Both metal centers have distorted tricapped trigonal prism geometry, with the Schiff base acting as tridentate ligand. The DPPH· radical scavenging effects of the Schiff base ligand and its Ln(III) ...

  3. Catalytic hydrogenation using complexes of base metals with tridentate ligands

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, Susan K.; Zhang, Guoqi; Vasudevan, Kalyan V.

    2017-02-14

    Complexes of cobalt and nickel with tridentate ligand PNHP.sup.R are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHP.sup.Cy)Co(CH.sub.2SiMe.sub.3)]BAr.sup.F.sub.4 (PNHP.sup.Cy=bis[2-(dicyclohexylphosphino)ethyl]amine, BAr.sup.F.sub.4=B(3,5-(CF.sub.3).sub.2C.sub.6H.sub.3).sub.4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60.degree. C., 1-4 atm H.sub.2). Nickel complex [(PNHP.sup.Cy)Ni(H)]BPh.sub.4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNP.sup.Cy)Ni(H) was used for hydrogenating alkenes.

  4. Catalytic hydrogenation using complexes of base metals with tridentate ligands

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Kalyan V.; Zhang, Guoqi; Hanson, Susan K.

    2016-09-06

    Complexes of cobalt and nickel with tridentate ligand PNHP.sup.R are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHP.sup.Cy)Co(CH.sub.2SiMe.sub.3)]BAr.sup.F.sub.4 (PNHP.sup.Cy=bis[2-(dicyclohexylphosphino)ethyl]amine, BAr.sup.F.sub.4=B(3,5-(CF.sub.3).sub.2C.sub.6H.sub.3).sub.4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60.degree. C., 1-4 atm H.sub.2). Nickel complex [(PNHP.sup.Cy)Ni(H)]BPh.sub.4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNP.sup.Cy)Ni(H) was used for hydrogenating alkenes.

  5. Cytotoxic, antibacterial, DNA interaction and superoxide dismutase like activities of sparfloxacin drug based copper(II) complexes with nitrogen donor ligands.

    Science.gov (United States)

    Patel, Mohan N; Joshi, Hardik N; Patel, Chintan R

    2013-03-01

    The novel neutral mononuclear copper(II) complexes with fluoroquinolone antibacterial drug, sparfloxacin and nitrogen donor heterocyclic ligand have been synthesized and characterized. An antimicrobial efficiency of the complexes has been tested against five different microorganisms and showed diverse biological activity. The interaction of complex with Herring sperm (HS) DNA was investigated using viscosity titration and absorption titration techniques. The results indicate that the complexes bind to DNA by intercalative mode and have rather high DNA-binding constants. DNA cleavage study showed better cleaving ability of the complexes compare to metal salt and standard drug. All the complexes showed good cytotoxic activity with LC(50) values ranging from 4.89 to 11.94 μg mL(-1). Complexes also exhibit SOD-like activity with their IC(50) values ranging from 0.717 to 1.848 μM. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. New Cu(II) coordination polymer by chiral tridentate Schiff base ligand

    Science.gov (United States)

    Messai, Amel; Bilge, Duygu; Bilge, Metin; Parlak, Cemal

    2017-06-01

    The present research reports the synthesis, X-ray, magnetic and electronic properties for novel coordination polymer based upon copper (II) with chiral tridentate Schiff base ligand synthesized at condensation of acetylacetone and L-leucine amino acid. The investigation was also conducted by quantum mechanical calculations. The large energy gap indicates a high kinetic stability. Magnetic measurement gives predominant antiferromagnetic interactions within the chain. Results reveals further insight into copper(II) chiral tridentate Schiff base complexes.

  7. Direct Hydrogenation of Biobased Carboxylic Acids Mediated by a Nitrogen-centered Tridentate Phosphine Ligand.

    Science.gov (United States)

    Deng, Li; Kang, Bin; Englert, Ulli; Klankermayer, Jürgen; Palkovits, Regina

    2016-01-01

    A novel nitrogen-centered tridentate ligand was identified from a series of multidentate ligands and applied for the direct hydrogenation of 9 biogenic acids into alcohols, lactones and esters with high yields. Comparison of substrates and ruthenium precursors suggested that the Ru(II) hydride cationic species was more active to transform acids than the corresponding lactone or esters. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Comparisons Between Tridentate Bis(benzazoles-pyridine and Bis(benzazolestriazine Ligands: a Theoretical Study

    Directory of Open Access Journals (Sweden)

    Mihaiela Andoni

    2015-12-01

    Full Text Available Twelve bis(benzazole structures with potential ligand character were investigated by means of computational chemistry. Global and local reactivity descriptors within DFT (Density Functional Theory theory (Fukui functions, chemical potential, hardness, electrophilicity index have been computed at B3LYP/6-31G(d,p level of theory. NICS(0 (Nucleus Independent Chemical Shift index computations were employed for the evaluation of the local aromatic character of each heterocyclic moiety. Best results have been reported for the bis(benzimidazole derivatives. Copper and zinc complexes of the investigated tridentate ligands have been proposed.

  9. Separation of lanthanides and actinides(III) using tridentate benzimidazole, benzoxazole and benzothiazole ligands

    Energy Technology Data Exchange (ETDEWEB)

    Drew, M.G.B.; Hudson, M.J.; Iveson, P.B.; Vaillant, L.; Youngs, T.G.A. [Reading Univ. (United Kingdom). Dept. of Chemistry; Hill, C.; Madic, Ch. [CEA Valrho, Dir. de l' Energie Nucleaire, Departement RadioChimie et Procedes, Service de Chimie des Procedes de Separation (DEN/DRCP/SCPS/LCSE), 30 - Marcoule (France)

    2004-04-01

    The ability of new hydrophobic tridentate ligands based on 2,6-bis(benzimidazole-2-yl)pyridine, 2,6-bis(benzoxazole-2-yl)pyridine and 2,6-bis(benzothiazole-2-yl)pyridine to selectively extract americium(III) from europium(III) was measured. The most promising ligand - 2,6-bis(benzoxazole-2-yl)-4-(2-decyl-1-tetra-decyl-oxy)pyridine L{sup 9} was found to give separation factors (SF{sub Am/Eu}) of up to 70 when used to extract cations from 0.02-0.10 M HNO{sub 3} into TPH in synergy with 2-bromo-decanoic acid. Six structures of lanthanide complexes with 2,6-bis(benzoxazole-2-yl)pyridine L{sup 6} were then determined to evaluate the types of species that are likely to be involved in the separation process. Three structural types were observed, namely [LnL{sup 6}(NO{sub 3}){sub 3}(H{sub 2}O){sub 2}), 11-coordinate only for La, [LnL{sup 6}(NO{sub 3})3 (CH{sub 3}CN)], 10-coordinate for Pr, Nd and Eu and [LnL{sup 6}(NO{sub 3}){sub 3}(H{sub 2}O)], L 10-coordinate for Eu and Gd. Quantum Mechanics calculations were carried out on the tridentate ligands to elucidate the conformational preferences of the ligands in the free state and protonated and di-protonated forms and to assess the electronic properties of the ligands for comparison with other ter-dentate ligands used in lanthanide/actinide separation processes. (authors)

  10. Synthesis, spectral, thermal, potentiometric and antimicrobial studies of transition metal complexes of tridentate ligand

    Directory of Open Access Journals (Sweden)

    Sarika M. Jadhav

    2014-01-01

    Full Text Available A series of metal complexes of Cu(II, Ni(II, Co(II, Fe(III and Mn(II have been synthesized with newly synthesized biologically active tridentate ligand. The ligand was synthesized by condensation of dehydroacetic acid (3-acetyl-6-methyl-(2H pyran-2,4(3H-dione or DHA, o-phenylene diamine and fluoro benzaldehyde and characterized by elemental analysis, molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, IR, 1H-NMR, UV–Vis spectroscopy and mass spectra. From the analytical data, the stoichiometry of the complexes was found to be 1:2 (metal:ligand with octahedral geometry. The molar conductance values suggest the non-electrolyte nature of metal complexes. The IR spectral data suggest that the ligand behaves as a dibasic tridentate ligand with ONN donor atoms sequence towards central metal ion. Thermal behaviour (TG/DTA and kinetic parameters calculated by the Coats–Redfern and Horowitz–Metzger method suggest more ordered activated state in complex formation. To investigate the relationship between stability constants of metal complexes and antimicrobial activity, the dissociation constants of Schiff bases and stability constants of their binary metal complexes have been determined potentiometrically in THF–water (60:40% solution at 25 ± 1 °C and at 0.1 M NaClO4 ionic strength. The potentiometric study suggests 1:1 and 1:2 complexation. Antibacterial and antifungal activities in vitro were performed against Staphylococcus aureus, Escherichia coli and Aspergillus niger, Trichoderma, respectively. The stability constants of the metal complexes were calculated by the Irving–Rosotti method. A relation between the stability constant and antimicrobial activity of complexes has been discussed. It is observed that the activity enhances upon complexation and the order of antifungal activity is in accordance with stability order of metal ions.

  11. New mixed ligand cobalt(II/III) complexes based on the drug sodium valproate and bioactive nitrogen-donor ligands. Synthesis, structure and biological properties

    Science.gov (United States)

    Abu Ali, Hijazi; Abu Shamma, Amani; Kamel, Shayma

    2017-08-01

    New cobalt valproate complexes with different nitrogen based ligands were synthesized and characterized using various techniques such as IR, UV-Vis, single crystal X-ray diffraction as well as other physical properties. The general formula of the prepared complexes is [Con(valp)m(L)z], (n = 1, 2 …; m = 1, 2, …; Z = 1, 2 …). The complexes [Co2(valp)4] (1), [Co(valp)2(2-ampy)2] (2) and [Co2(valp)4(quin)2] (3) showed different carboxylate coordination modes. The crystal structures of the complexes 2 and 3 were determined using single crystal X-ray diffraction. Kinetic studies of hydrolysis reactions of BNPP [bis-(p-nitrophenyl)phosphate] with complexes 2 and 3 were performed. The hydrolysis rate of BNPP was studied at different temperatures, pH and concentrations by UV-Vis spectrophotometric method. The results showed that the hydrolysis rate of BNPP was 7.70 × 102 L mol-1 s-1 for (3) and 2.60 × 10-1 L mol-1 s-1 for (2).

  12. Highly active chromium(III) complexes based on tridentate pyrazolyl pyridyl ligands for ethylene polymerization and oligomerization.

    Science.gov (United States)

    Park, Jong-Eun; Kang, Sung Kwon; Woo, Jeong Oh; Son, Kyung-sun

    2015-06-07

    A set of new chromium(III) [Cr(III)] complexes based on the tridentate ligand HC(Pz)2Py (Pz = pyrazole; Py = pyridine) and its derivatives were prepared, characterized, and evaluated for ethylene polymerization/oligomerization. X-ray single-crystal analyses of the Cr(III) complexes showed tridentate coordination on the fac-octahedral Cr sphere. Upon activation with methylaluminoxane (MAO), the precatalysts and the ligands L1-L3 mixed in situ with Cr(acac)3 were highly active and generally produced polyethylene as a major product. Their catalytic performances were markedly affected by the substituents on the methine carbon atom of the ligands and reaction conditions.

  13. Spectroscopic characterization of chromium(III), manganese(II) and nickel(II) complexes with a nitrogen donor tetradentate, 12-membered azamacrocyclic ligand

    Science.gov (United States)

    Chandra, Sulekh; Pundir, Meenakshi

    2008-01-01

    The complexes of Cr(III), Mn(II) and Ni(II) were synthesized with macrocyclic ligand i.e. 5,11-dimethyl-6,12-diethyl-dione-1,2,4,7,9,10-hexazacyclododeca -1,4,6,10-tetraene. The ligand (L) was prepared by [2 + 2] condensation reaction of 2,3-pentanedione and semicarbazide hydrochloride. These complexes were found to have the general composition [Cr(L)X 2]X and [M(L)X 2] (where M = Mn(II) and Ni(II); X = Cl -, NO 3-, (1/2)SO 42-, NCS - and L = ligand [N 6]). The ligand and its transition metal complexes were characterized by the elemental analysis, molar conductance, magnetic susceptibility, mass, IR, electronic and EPR spectral studies. On the basis of IR, electronic and EPR spectral studies, an octahedral geometry has been assigned for these complexes except sulphato complexes which are of five coordinated geometry.

  14. Spectroscopic approach in characterization of chromium(III), manganese(II), iron(III) and copper(II) complexes with a nitrogen donor tetradentate, 14-membered azamacrocyclic ligand

    Science.gov (United States)

    Chandra, Sulekh; Gupta, Lokesh Kumar

    2005-07-01

    The complexes of Cr(III), Mn(II), Fe(III) and Cu(II) were synthesized with the macrocyclic ligand i.e. 2,3,9,10-tetraketo-1,4,8,11-tetraazacyclotetradecane. The ligand was prepared by the [2 + 2] condensation reaction of diethyloxalate and 1,3-diamino propane. These complexes were found to have the general composition M(L)X 3 and M'(L)X 2 [where M = Mn(II) and Cu(II), M' = Cr(III) and Fe(III), L = ligand (N 4) and X = Cl -, NO 3-, 1/2SO 42- and [CH 3COO -]. The ligand and its transition metal complexes were characterized by the elemental analyses, molar conductance, magnetic susceptibility, mass, IR, electronic, and EPR spectral studies. On the basis of IR, electronic and EPR spectral studies an octahedral geometry has been assigned for Cr(III), Mn(II) and Fe(III) and a tetragonal geometry for Cu(II) complexes.

  15. Ethylene oligomerization promoted by chromium complexes bearing pyrrolide-imine-amine/ether tridentate ligands.

    Science.gov (United States)

    Pinheiro, A C; Roisnel, T; Kirillov, E; Carpentier, J-F; Casagrande, Osvaldo L

    2015-09-28

    Chromium(iii) complexes [CrCl2(L)(THF)] based on monoanionic tridentate ligands [, L = {2-(C4H3N-2'-CH[double bond, length as m-dash]N)C2H4NHPh}; , L = {5-tert-butyl-2-(C4H2N-2'-CH[double bond, length as m-dash]N)C2H3NHPh}; , L = {2-(C4H3N-2'-CH[double bond, length as m-dash]N)C2H4OPh}] have been prepared. Complexes and were converted into the monomeric acetonitrile adducts [CrCl2(L)(NCMe)] [, L = {2-(C4H3N-2'-CH[double bond, length as m-dash]N)C2H4NHPh}; , L = {5-tert-butyl-2-(C4H2N-2'-CH[double bond, length as m-dash]N)C2H3NHPh}] by reaction with acetonitrile at room temperature. All Cr complexes were characterized by IR spectroscopy, elemental analysis, magnetochemistry for , and by X-ray crystallography for and . Upon activation with methylaluminoxane (MAO), chromium precatalysts and showed good activity in ethylene oligomerization (TOF = 47.0-57.0 × 10(3) (mol ethylene)(mol Cr)(-1) h(-1) at 80 °C), producing mostly oligomers (93.0-95.6 wt% of total products). On the other hand, under identical oligomerization conditions, /MAO behaved as a polymerization catalyst generating predominantly polyethylene (73.0 wt%). However, the catalytic behavior of the precatalyst can be adjusted by varying the MAO-to-Cr ratio. Thus, the use of 500 equiv. causes a dramatic shift from polymerization to ethylene oligomerization, eventually producing mainly lighter α-olefin fractions [α-C4 (68.7 wt%) and α-C6 (19.2 wt%)]. A further increase in the amount of MAO (1000 equiv.) leads to a more balanced distribution of oligomers, with a drastic decrease in the α-C4 and increase in the α-C8 fractions.

  16. Organonickel(II) complexes with anionic tridentate 1, 3-bis(azolylmethyl)phenyl ligands. synthesis, structural characterization and catalytic behavior

    Energy Technology Data Exchange (ETDEWEB)

    Hurtado, John; Rojas, Rene; Valderrama, Mauricio, E-mail: jmvalder@puc.cl [Departamento de Quimica Inorganica, Facultad de Quimica, Pontificia Universidad Catolica de Chile, Santiago (Chile); Ibanez, Andres [Centro para la Investigacion Interdisciplinaria Avanzada en Ciencia de los Materiales (CIMAT), Santiago (Chile); Froehlich, Roland [Organisch Chemisches Institut der Universitaet Muenster, Muenster (Germany)

    2011-09-15

    The reaction of 2-bromo-1,3-bis(bromomethyl)benzene with 3,5-dimethylpyrazole and {sup 1}H-indazole yields the tridentate ligands 2-bromo-1,3-bis(3,5-dimethylpirazol-1-ylmethyl)benzene (1) and 2-bromo-1,3-bis(indazol-2-ylmethyl)benzene (2). These compounds react with [Ni(cod)2] in tetrahydrofuran (thf) to form the oxidative addition complexes [NiBr{l_brace}1,3-bis(azolylmethyl)phenyl-N,C,N{r_brace}], azol 3,5-dimethylpyrazol (3), indazol (4), which were isolated in good yields as stable yellow solids and characterized by elemental analysis, Fourier-transform infrared spectroscopy (FTIR), mass spectroscopy and nuclear magnetic resonance (NMR). In addition, the molecular structures of 2 and 4 were determined by single-crystal X-ray diffraction analysis. Complex 4 was tested as a catalyst in ethylene polymerization reaction. (author)

  17. Tuning facial-meridional isomerisation in monometallic nine-co-ordinate lanthanide complexes with unsymmetrical tridentate ligands.

    Science.gov (United States)

    Le Borgne, Thierry; Altmann, Peter; André, Nicolas; Bünzli, Jean-Claude G; Bernardinelli, Gérald; Morgantini, Pierre-Yves; Weber, Jacques; Piguet, Claude

    2004-03-07

    The unsymmetrical tridentate benzimidazole-pyridine-carboxamide units in ligands L1-L4 react with trivalent lanthanides, Ln(III), to give the nine-co-ordinate triple-helical complexes [Ln(Li)3]3+ (i = 1-4) existing as mixtures of C3-symmetrical facial and C1-symmetrical meridional isomers. Although the beta13 formation constants are 3-4 orders of magnitude smaller for these complexes than those found for the D3-symmetrical analogues [Ln(Li)3]3+ (i = 5-6) with symmetrical ligands, their formation at the millimolar scale is quantitative and the emission quantum yield of [Eu(L2)3]3+ is significantly larger. The fac-[Ln(Li)3]3+ mer-[Ln(Li)3]3+ (i = 1-4) isomerisation process in acetonitrile is slow enough for Ln = Lu(III) to be quantified by 1H NMR below room temperature. The separation of enthalpic and entropic contributions shows that the distribution of the facial and meridional isomers can be tuned by the judicious peripheral substitution of the ligands affecting the interstrand interactions. Molecular mechanics (MM) calculations suggest that one supplementary interstrand pi-stacking interaction stabilises the meridional isomers, while the facial isomers benefit from more favourable electrostatic contributions. As a result of the mixture of facial and meridional isomers in solution, we were unable to obtain single crystals of 1:3 complexes, but the X-ray crystal structures of their nine-co-ordinate precursors [Eu(L1)2(CF3SO3)2(H2O)](CF3SO3)(C3H5N)2(H2O) (6, C45H54EuF9N10O13S3, monoclinic, P2(1)/c, Z = 4) and [Eu(L4)2(CF3SO3)2(H2O)](CF3SO3)(C4H4O)(1.5) (7, C51H66EuF9N8O(15.5)S3, triclinic, P1, Z = 2) provide crucial structural information on the binding mode of the unsymmetrical tridentate ligands.

  18. copper(I) and copper(II) complexes with tridentate ligands

    Indian Academy of Sciences (India)

    Administrator

    Tridendate ligands with nitrogen centers, generally well-known as the tripod ligands, have been of considerable interest to inorganic chemists dealing with the preparation of model compounds for hemocyanin, tyrosinase etc. We have found that such ligands when complexed with iron(II) and copper(II) and copper(I) ions ...

  19. Nickel(II) and palladium(II) triphenylphosphine complexes incorporating tridentate Schiff base ligands: Synthesis, characterization and biocidal activities

    Science.gov (United States)

    Shabbir, Muhammad; Akhter, Zareen; Ashraf, Ahmad Raza; Ismail, Hammad; Habib, Anum; Mirza, Bushra

    2017-12-01

    Nickel(II) and palladium(II) triphenylphosphine complexes incorporating tridentate Schiff bases have been prepared and characterized by elemental analysis as well as by spectroscopic techniques (FTIR & NMR). The synthesized compounds were assessed to check their potential biocidal activity by using different biological assays (brine shrimp cytotoxicity, antimicrobial, antioxidant, antitumor and drug-DNA interaction). Results of brine shrimp cytotoxicity assay showed that ligand molecules are more bioactive than metal complexes with LD50 as low as 12.4 μg/mL. The prominent antitumor activity was shown by nickel complexes while the palladium complexes exhibited moderate activity. The synthesized compounds have shown high propensity for DNA binding either through intercalation or groove binding which represents the mechanism of antitumor effect of these compounds. Additionally, ligand molecules and nickel metal complexes showed significant antioxidant activity with IC50 values as low as 3.1 μg/mL and 18.9 μg/mL respectively while palladium complexes exhibited moderate activity. Moreover, in antimicrobial assays H2L1, Ni(L1)PPh3 and H2L3 showed dual inhibition against bacterial and fungal strains while for the rest of the compounds varying degree of activity was recorded against different strains. Overall comparison of results suggests that the synthesized compounds can be promising candidate for drug formulation and development.

  20. Ru alkylidene compounds bearing tridentate, dianionic ligands: Lewis acid activation and olefin metathesis.

    Science.gov (United States)

    McKinty, Adam M; Stephan, Douglas W

    2016-03-07

    The series of tridentate complexes of Ru-alkylidenes (L)Ru(CHPh)(SCH2CH2)2E (E = O, L = SIMes 1, PCy3 2, E = S, L = SIMes 3, PCy3 4; E = PPh 7, L = PCy3), (L)Ru(CHPh)(SC6H4)2S (L = SIMes 5, PCy3 6), (L)Ru(CHPh) (OCH2CH2)2O (L = SIMes 8, PCy3 9) were prepared and shown to react with one equivalent of BCl3 to give the complexes (L)Ru(CHPh)Cl[E(CH2CH2S)2BCl2] (E = O, L = SIMes 10, PCy3 11, E = S, L = SIMes 12a/b, PCy3 13, E = PPh, L = PCy3 16) and (L)Ru(CHPh)(SC6H4)2O (L = SIMes 14, PCy3 15). In the case of 1 and 2 reaction with two equivalents of BCl3 affording the corresponding cation via chloride abstraction. These cations coordinate MeCN to give the six coordinate Ru cation salts [(L)Ru(CHPh)- (NCMe)(O(CH2CH2S)2BCl2)][BCl4] L = SIMes 17, PCy3 18). The generated five coordinate cations derived from 2-9 via addition of two equivalents of BCl3 were evaluated in standard preliminary tests for olefin metathesis catalysis.

  1. Formation of a metal-to-nitrogen bond of normal length by a neutral sufonamide group within a tridentate ligand. A new approach to radiopharmaceutical bioconjugation.

    Science.gov (United States)

    Perera, Theshini; Abhayawardhana, Pramuditha; Marzilli, Patricia A; Fronczek, Frank R; Marzilli, Luigi G

    2013-03-04

    We demonstrate that a tertiary sulfonamide group, N(SO2R)R'2, can rehybridize to form a M-N bond of normal length even when the group is in a linear tridentate ligand, such as in the new tridentate N(SO2R)dpa ligands derived from di-(2-picolyl)amine (N(H)dpa). N(SO2R)dpa ligands were used to prepare fac-[Re(CO)3(N(SO2R)dpa)](PF6 or BF4) complexes. Structural characterization of the new complexes established that the tertiary sulfonamide nitrogen atom binds to Re with concomitant sp(2)-to-sp(3) rehybridization, facilitating facial coordination. The new fac-[Re(CO)3(N(SO2R)dpa)]X structures provide the only examples for any metal with the sulfonamide as part of a noncyclic linear tridentate ligand and with a normal metal-to-nitrogen(tertiary sulfonamide) bond length. Rare previous examples of such normal M-N bonds have been found only in more constrained situations, such as with tripodal tetradentate ligands. Our long-term objectives for the new tridentate N(SO2R)dpa ligands are to develop the fundamental chemistry relevant to the eventual use of the fac-[M(I)(CO)3](+) core (M = (99m)Tc, (186/188)Re) in imaging and therapy. The sulfonamide group uniquely contributes to two of our goals: expanding ways to conjugate the fac-[M(I)(CO)3](+) core to biological molecules and also developing new symmetrical tridentate ligands that can coordinate facially to this core. Tests of our conjugation method, conducted by linking the fac-[Re(I)(CO)3](+) core to a new tetraarylporphyrin (T(N(SO2C6H4)dpa)P) as well as to a dansyl (5-(dimethylamino)naphthalene-1-sulfonyl) group, demonstrate that large molecular fragments can be tethered via a coordinated tertiary sulfonamide linkage to this core.

  2. Neutral tridentate PNP ligands and their hybrid analogues: versatile non-innocent scaffolds for homogeneous catalysis.

    Science.gov (United States)

    van der Vlugt, Jarl Ivar; Reek, Joost N H

    2009-01-01

    Ligands in coordination chemistry and homogeneous catalysis are traditionally "static" spectators that do not actively participate in the catalytic cycle. However, such classic systems do not provide additional "handles" that could facilitate or trigger alternative productive reaction pathways. Recent advances in the use of novel nitrogen-centered pincer systems have unveiled interesting opportunities for cooperative catalysis. The chemistry of pyridine-derived, neutral ligands is discussed, with a specific focus on their non-innocent behavior and potential as facilitators for metal-mediated organic transformations. This overview should provide inspiration and an incentive to incorporate non-innocent ligands and their metal complexes within old and new homogeneously catalyzed reactions.

  3. Modelling thermodynamic properties of lanthanide (LnL)3+ and actinide (AnL)3+ complexes with tridentate planar nitrogen ligands (L)

    International Nuclear Information System (INIS)

    Ionova, G.; Rabbe, C.; Charbonnel, M.C.; Hill, C.; Guillaumont, D.; Guillaumont, R.; Ionov, S.; Madic, C.

    2004-01-01

    We report here the results obtained from a systematic theoretical study on the thermodynamic properties of trivalent lanthanide (Ln) and actinide (An) complexes with chelating nitrogen tridentate ligands. The mechanism of chelation has been investigated and the role of cation dissolution is investigated through a comparison of the thermodynamic properties of solvated cations and complexes. The difference in thermodynamic properties of LnL and AnL complexes is analyzed. (authors)

  4. Highly active ethylene polymerization and regioselective 1-hexene oligomerization using zirconium and titanium catalysts with tridentate [ONO] ligands.

    Science.gov (United States)

    Xu, Tieqi; Liu, Jie; Wu, Guang-Peng; Lu, Xiao-Bing

    2011-11-07

    A series of tridentate dianionic ligands [4-(t)Bu-6-R-2-(3-R'-5-(t)Bu-2-OC(6)H(2))N=CH C(6)H(2)O](2-) (L) [R = R' = (t)Bu (L1); R = CMe(2)Ph, R' = (t)Bu (L2); R = adamantyl, R' = (t)Bu (L3); R = R' = CMe(2)Ph (L4); R = SiMe(2)(t)Bu, R' = CMe(2)Ph (L5)] were synthesized. Reactions of TiCl(4) with 1 equiv of ligands L1-L5 in toluene afford five-coordinate titanium complexes with general formula LTiCl(2) [L = L1 (1); L2 (2); L3 (3); L4 (4); L5 (5)]. The addition of tetrahydrofuran (THF) to titanium complex 5 readily gives THF-solvated six-coordinate complex 6, which also was obtained by reaction of TiCl(4) with 1 equiv of ligand L5 in THF. Reactions of ZrCl(4) with 1 or 2 equiv of ligands L1-L5 afford six-coordinate zirconium mono(ligand) complexes LZrCl(2)(THF) [L = L2 (7); L4 (8); L5 (9)], and bis(ligand) complexes L(2)Zr [L = L1 (10); L4 (11)]. The molecular structures of complexes 2, 8, and 11 were established by single-crystal X-ray diffraction studies. Upon activation with methylaluminoxane, complexes 1-9 are active for ethylene polymerization. The activities and half-lifes of the catalyst systems based on zirconium complexes are more than 10(6) g of polyethylene (mol Zr)(-1) h(-1) and 6 h, respectively. Complex 9 is more active and long-lived, with a turnover frequency (TOF) of 2.6 × 10(5) (mol C(2)H(4)) (mol Zr)(-1) h(-1), a half-life of >16 h, and a total turnover number (TON) of more than 10(6) (mol C(2)H(4)) (mol Zr)(-1) at 20 °C and 0.5 MPa pressure. Even at 80 °C, complex 9/MAO catalyst system has a long lifetime (t(1/2) > 2 h), as well as high activity that is comparable with that at 20 °C. When activated with methylaluminoxane (MAO), complex 9 also show moderate catalytic activity and more than 99% 2,1-regioselectivity for 1-hexene oligomerization. © 2011 American Chemical Society

  5. Synthesis of electron-rich uranium(IV) complexes supported by tridentate Schiff base ligands and their multi-electron redox chemistry.

    Science.gov (United States)

    Camp, Clément; Andrez, Julie; Pécaut, Jacques; Mazzanti, Marinella

    2013-06-17

    The synthesis, structure, and reactivity of a new complex of U(IV) with the tridentate Schiff base ligand Menaphtquinolen are reported. The reduction of the bis-ligand complexes [UX2((Me)naphtquinolen)2] (X = Cl, (1-Cl) ; I (1-I)) with potassium metal affords the U(IV) complex of the new tetranionic hexadentate ligand μ-bis-(Me)naphtquinolen formed through the intramolecular reductive coupling of the imino groups of each (Me)naphtquinolen unit. The solid state structure of the [U(μ-bis-(Me)naphtquinolen)]2 dimer 2 isolated from toluene confirms the presence of a U(IV) complex of the reduced ligand. Reactivity studies with molecular oxygen and 9,10-phenanthrenequinone show that complex 2 can act as a multielectron reducing agent releasing two electrons through the cleavage of the C-C bond to restore the original imino function of the ligand. In the resulting U(IV) and U(VI) complexes [U(9,10-phenanthrenediol)((Me)naphtquinolen)2], 3, and [UO2((Me)naphtquinolen)2], 4, the restored tridentate Schiff base allows for the coordination of the reduced substrate to the metal. Electrochemical studies of complex 2 show the presence of irreversible ligand centered reduction processes and of a reversible U(IV)/U(III) couple.

  6. Substituted tridentate pyrazolyl ligands for chromium and nickel-catalyzed ethylene oligomerization reactions: effect of auxiliary ligand on activity and selectivity

    International Nuclear Information System (INIS)

    Oliveira, Lucilene L. de; Campedelli, Roberta R.; Bergamo, Adao L.; Santos, Ana H.D.P dos; Casagrande, Osvaldo L.

    2010-01-01

    Two new chromium(III) complexes [CrCl 3 (L)] based on tridentate ligands (1a, L = bis[2-(3-phenyl-1-pyrazolyl)ethyl)]amine; 2a, L bis[2-(3-methyl-5-phenyl-l-pyrazolyl)ethyl]sulfide) have been prepared and characterized by elemental analysis. Upon activation with methylaluminoxane (MAO), these pre-catalysts showed high turnover frequencies for ethylene oligomerization under optimized conditions (TOFs = 22.9-36.4 x 103 mol C 2 H 4 (mol Cr III ) -1 h -1 , [Cr] = 10.0 μmol, 80 deg C, 20 bar ethylene, MAO: Cr = 300, oligomerization time = 20 min), producing alpha-olefins in the range C 4 -C 14+ with high selectively (67.71-73.47%). The catalytic performances are substantially affected by the ligand environment, especially the substituents at the 3- and 5-positions of the pyrazolyl rings. In parallel, the use of nickel complexes such as NiCl 2 {bis[2-(3,5-dimethyl-1-pyrazolyl)methyl]benzylamine} (3) and NiCl 2 {bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl)]ether} (5) in oligomerization reactions carried out in the presence of triphenylphosphine (PPh 3 ) afforded highly active catalytic systems with turnover frequencies (TOFs) varying from 36.4 to 154.2 x 10 3 mol C 2 H 4 (mol Ni II ) -1 h -1 . The presence of this auxiliary ligand has a strong impact on the selectivity towards the production of a-olefins, decreasing substantially the amount of 1-butene with a concomitant increase of the 2-butene fractions. Attempts to crystallize the nickel complex 3 afforded the tetrametallic [{ (L)(μ 3 -Cl)NiCl} 4 ] (4, L 1-anilinomethyl-3,5-dimethylpyrazole) which was characterized by X-ray diffraction analysis. (author)

  7. Zn(II), Ni(II), Cu(II) and Pb(II) complexes of tridentate asymmetrical Schiff base ligands: Synthesis, characterization, properties and biological activity

    Science.gov (United States)

    Şahin, Mustafa; Koçak, Nuriye; Erdenay, Damla; Arslan, Uğur

    2013-02-01

    New asymmetrical tridentate Schiff base ligands were synthesized using 1,2-phenylenediamine, 4-methyl-1,2-phenylenediamine, 2-hydroxy-1-napthaldehyde, 9-anthracenecarboxaldehyde. Schiff base ligands and their metal complexes were synthesised and characterized by using FT-IR, 1H NMR, 13C NMR, UV-Vis, XRD, ESR, elemental analysis and fluorescence studies. The antimicrobial activity of the ligands and their metal complexes were studied against Staphylococcus aureus ATCC 29213, S. aureus ATCC 25923, Streptococcus mutans RSHM 676, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853. The determination of the antibacterial activity was done using the broth microdilution methods. In general, it has been determined that the studied compounds have MIC values similar to Gram-positive and Gram-negative bacteria. It has been found that Ni, Pb, Zn derivatives of HL1A and ZnL2A has lower MIC values than ampicillin for P. aeruginosa ATCC 27853 strain.

  8. Stability studies on 99mTechnetium(III) complexes with tridentate/monodentate thiol ligands and phosphine ('3+1+1' complexes)

    International Nuclear Information System (INIS)

    Seifert, Sepp; Drews, Antje; Gupta, Antje; Pietzsch, Hans-Juergen; Spies, Hartmut; Johannsen, Bernd

    2000-01-01

    The preparation and characterisation of 3+1+1 technetium complexes of the general formula [Tc(SES)(RS)(PMe 2 Ph)] (SES=tridentate dithiol ligand, E=S, O, NMe; RSH=monothiol ligand) at the n.c.a. level is described. The Tc(III) complexes are prepared in a one-step procedure starting from pertechnetate in yields of 85-95% of radiochemical purity. A comparison of their chromatographic data with the fully characterised 99 Tc complexes indicate the identity of the investigated compounds. Stability studies show that the 99m Tc complexes undergo some alteration in solution. They are oxidised to the 3+1 oxotechnetium (V) complexes and/or decompose in aqueous solution. In challenge experiments performed with glutathione, exchange of the monothiolato ligand occurs in the same manner as known for the 3+1 complexes

  9. Substituted tridentate pyrazolyl ligands for chromium and nickel-catalyzed ethylene oligomerization reactions: effect of auxiliary ligand on activity and selectivity

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Lucilene L. de; Campedelli, Roberta R.; Bergamo, Adao L.; Santos, Ana H.D.P dos; Casagrande, Osvaldo L., E-mail: osvaldo.casagrande@ufrgs.b [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Inst. de Quimica. Lab. de Catalise Molecular

    2010-07-01

    Two new chromium(III) complexes [CrCl{sub 3}(L)] based on tridentate ligands (1a, L = bis[2-(3-phenyl-1-pyrazolyl)ethyl)]amine; 2a, L bis[2-(3-methyl-5-phenyl-l-pyrazolyl)ethyl]sulfide) have been prepared and characterized by elemental analysis. Upon activation with methylaluminoxane (MAO), these pre-catalysts showed high turnover frequencies for ethylene oligomerization under optimized conditions (TOFs = 22.9-36.4 x 103 mol C{sub 2}H{sub 4} (mol Cr{sup III}){sup -1} h{sup -1}, [Cr] = 10.0 mumol, 80 deg C, 20 bar ethylene, MAO: Cr = 300, oligomerization time = 20 min), producing alpha-olefins in the range C{sub 4}-C{sub 14+} with high selectively (67.71-73.47%). The catalytic performances are substantially affected by the ligand environment, especially the substituents at the 3- and 5-positions of the pyrazolyl rings. In parallel, the use of nickel complexes such as NiCl{sub 2}{l_brace}bis[2-(3,5-dimethyl-1-pyrazolyl)methyl]benzylamine{r_brace} (3) and NiCl{sub 2}{l_brace}bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl)]ether{r_brace} (5) in oligomerization reactions carried out in the presence of triphenylphosphine (PPh{sub 3}) afforded highly active catalytic systems with turnover frequencies (TOFs) varying from 36.4 to 154.2 x 10{sup 3} mol C{sub 2}H{sub 4} (mol Ni{sup II}){sup -1} h{sup -1}. The presence of this auxiliary ligand has a strong impact on the selectivity towards the production of a-olefins, decreasing substantially the amount of 1-butene with a concomitant increase of the 2-butene fractions. Attempts to crystallize the nickel complex 3 afforded the tetrametallic [{l_brace} (L)(mu{sub 3}-Cl)NiCl{r_brace}{sub 4}] (4, L 1-anilinomethyl-3,5-dimethylpyrazole) which was characterized by X-ray diffraction analysis. (author)

  10. fac-Re(CO)3L complexes containing tridentate monoanionic ligands (L-) with a seldom-studied sulfonamido group as one terminal ligating group.

    Science.gov (United States)

    Christoforou, Anna Maria; Fronczek, Frank R; Marzilli, Patricia A; Marzilli, Luigi G

    2007-08-20

    To achieve a net-neutral coordination unit in radiopharmaceuticals with a fac-M(CO)3+ core (M = Tc, Re), facially coordinated monoanionic tridentate ligands are needed. New neutral fac-Re(CO)3L complexes were obtained by treating fac-[Re(CO)3(H2O)3]+ with unsymmetrical tridentate NNN donor ligands (LH) based primarily on a diethylenetriamine (dien) moiety with an aromatic group linked to a terminal nitrogen through a sulfonamide. LHs contain 2,4,6-trimethylbenzenesulfonyl (tmbSO2) and 5-(dimethylamino)naphthalene-1-sulfonyl (DNS) groups. X-ray crystallographic and NMR analyses confirm that in both the solid and the solution states all L- in fac-Re(CO)3L complexes are bound in a tridentate fashion with one donor being nitrogen from a deprotonated sulfonamido group. Another fundamental property that is important in radiopharmaceuticals is shape, which in turn depends on ring pucker. For L- = tmbSO2-dien-, tmbSO2-N'-Medien-, and tmbSO2-N,N-Me2dien-, the two chelate rings have a different pucker chirality, as is commonly found for a broad range of metal complexes. However, for fac-Re(CO)3(DNS-dien), both chelate rings have the same pucker chirality because the sulfonamido ring has an unusual pucker for the absolute configuration at Re; a finding that is attributable to intramolecular and intermolecular hydrogen bonds from the sulfonamido oxygens to the NH2 groups. Averaging of tmb NMR signals, even at -90 degrees C for Re(CO)3(tmbSO2-N,N-Me2dien), indicates rapid dynamic motion in the complexes with this group. However, examination of the structures suggests that free rotation about the S-C(tmb) bond is not possible but that concerted coupled rotations about the N-S and the S-C bonds can explain the NMR data.

  11. Ruthenium(II) bipyridine complexes bearing quinoline-azoimine (NN'N″) tridentate ligands: synthesis, spectral characterization, electrochemical properties and single-crystal X-ray structure analysis.

    Science.gov (United States)

    Al-Noaimi, Mousa; Abdel-Rahman, Obadah S; Fasfous, Ismail I; El-khateeb, Mohammad; Awwadi, Firas F; Warad, Ismail

    2014-05-05

    Four octahedral ruthenium(II) azoimine-quinoline complexes having the general molecular formula [Ru(II)(L-Y)(bpy)Cl](PF6) {L-Y=YC6H4N=NC(COCH3)=NC9H6N, Y=H (1), CH3 (2), Br (3), NO2 (4) and bpy=2,2'-bipyrdine} were synthesized. The azoimine-quinoline based ligands behave as NN'N″ tridentate donors and coordinated to ruthenium via azo-N', imine-N' and quinolone-N″ nitrogen atoms. The composition of the complexes has been established by elemental analysis, spectral methods (FT-IR, electronic, (1)H NMR, UV/Vis and electrochemical (cyclic voltammetry) techniques. The crystal structure of complex 1 is reported. The Ru(II) oxidation state is greatly stabilized by the novel tridentate ligands, showing Ru(III/II) couples ranging from 0.93-1.27 V vs. Cp2Fe/Cp2Fe(+). The absorption spectrum of 1 in dichloromethane was modeled by time-dependent density functional theory (TD-DFT). Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Binary and ternary copper(II) complexes of a tridentate ONS ligand derived from 2-aminochromone-3 carboxaldehyde and thiosemicarbazide: Synthesis, spectral studies and antimicrobial activity

    Science.gov (United States)

    Shebl, Magdy; Ibrahim, M. A.; Khalil, Saied M. E.; Stefan, S. L.; Habib, H.

    2013-11-01

    A tridentate ONS donor ligand, HL, was synthesized by the condensation of 2-aminochromone-3-carboxaldehyde with thiosemicarbazide. The structure of the ligand was elucidated by elemental analyses, IR, 1H and 13C NMR, electronic and mass spectra. Reaction of the ligand with several copper(II) salts, including AcO-, NO3-, SO42-, Cl-, Br- and ClO4- afforded different metal complexes that reflect the non-coordinating or weakly coordinating power of the ClO4- and Br- anions as compared to the strongly coordinating power of AcO-, SO42-, Cl- and NO3- anions. Also, the ligand was allowed to react with Cu(II) ion in the presence of a secondary ligand (L‧) [N,O-donor; 8-hydroxyquinoline or N,N-donor; 1,10-phenanthroline]. Characterization and structure elucidation of the prepared complexes were achieved by elemental and thermal analyses, IR, electronic, mass and EPR spectra as well as conductivity and magnetic susceptibility measurements. The EPR spin Hamiltonian parameters of some complexes were calculated. The metal complexes exhibited octahedral and square planar geometrical arrangements depending on the nature of the anion. The ligand and most of its metal complexes showed antibacterial activity towards Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Salmonella typhimurium and Escherichia coli), yeast (Candida albicans) and fungus (Aspergillus fumigatus).

  13. Synthesis, characterization, electrical conductivity and luminescence properties of two copper(II) complexes with tridentate N2O chelating ligands containing imine bond

    Science.gov (United States)

    Gönül, İlyas; Ay, Burak; Karaca, Serkan; Şahin, Onur; Serin, Selahattin

    2018-03-01

    In the present study, we describe the synthesis and characterization of two tridentate N2O donor ligands, namely, (E)-2-(((2-(diethylamino)ethyl)imino)methyl)-6-methoxyphenol (HL1) and (E)-2-(((2-(diethylamino)ethyl)imino)methyl)-6-ethoxyphenol (HL2), and their copper(II) complexes, [Cu(L1)(CH3COO)] (1), [Cu(L2)(CH3COO)] (2). They have been synthesized under conventional methods and characterized by elemental analysis, FTIR, 1H and 13C NMR, ICP-OES, TGA and GC/MS analysis. For the morphological analysis field emission scanning electron microscopy (FESEM) was used. The geometry of the copper(II) complexes was determined by single crystal X-ray diffraction analysis. The copper(II) ions are in distorted square-pyramidal coordination environments. Complexes crystallize in monoclinic space group, P21/c. The electrical conductivity and luminescence properties of 1-2 have been investigated.

  14. End-to-end single cyanato and thiocyanato bridged Cu(II) polymers with a new tridentate Schiff base ligand: crystal structure and magnetic properties.

    Science.gov (United States)

    Talukder, Pritha; Datta, Amitabha; Mitra, Samiran; Rosair, Georgina; El Fallah, M Salah; Ribas, Joan

    2004-12-21

    A new tridentate Schiff base ligand HL (L = C14H19N2O), derived from the condensation of benzoylacetone and 2-dimethylaminoethylamine in a 1:1 ratio, reacts with copper(ii) acetate and cyanate, thiocyanate or azide, to give rise to several end-to-end polymeric complexes of formulae [CuL(mu(1,3)-NCO)]n 1, [CuL(mu(1,3)-NCS)]n 2 and the complex 3 has two crystallographically independent units of formula [CuL(N3)] in the asymmetric unit cell. Complex 3 exists in dimeric form rather than as a polymeric chain. Compound 1 is the first report of a singly end-to-end cyanate bridged polymeric chain of Cu(II) with a Schiff base as a co-ligand. There are many examples of double NCS bridged polymeric chains, but fewer singly bridged ones such as compound 2. We have characterized these complexes by analytical, spectroscopic, structural and variable temperature magnetic susceptibility measurements. The coordination geometry around the Cu(II) centers is distorted square pyramidal for 1 and 2 and square planar for complex 3. The magnetic susceptibility data show slight antiferromagnetic coupling for the polymers having J values -0.19 and -0.57 cm(-1) for complexes 1 and 2 respectively. The low values of J are consistent with the equatorial-axial disposition of the bridges in the polymers.

  15. A P,O,P′-tridentate mixed-donor scorpionate ligand: 6-[4,6-bis(diphenylphosphino-10H-phenoxazin-10-yl]hexan-1-ol

    Directory of Open Access Journals (Sweden)

    Holger B. Friedrich

    2008-10-01

    Full Text Available The title compound, C42H39NO2P2, is a P,O,P′-tridentate scorpionate-type ligand and has one molecule in the asymmetric unit. The angles involving the P atoms range from 100.21 (7 to 104.89 (7°. The N-hexanol group was found to be disordered and was refined over two positions with final occupancies of 0.683 (3 and 0.317 (3 which affected the C—O and C—N bond lengths. The bond lengths for C—O range from 1.402 (2 to 1.415 (2 Å and for C—N from 1.410 (2 to 1.448 (3 Å for the major disorder component; the corresponding ranges for the minor disorder component are 1.429 (3–1.408 (3 and 1.474 (3–1.474 (4 Å.

  16. Antioxidant, electrochemical, thermal, antimicrobial and alkane oxidation properties of tridentate Schiff base ligands and their metal complexes

    Science.gov (United States)

    Ceyhan, Gökhan; Çelik, Cumali; Uruş, Serhan; Demirtaş, İbrahim; Elmastaş, Mahfuz; Tümer, Mehmet

    2011-10-01

    In this study, two Schiff base ligands (HL 1 and HL 2) and their Cu(II), Co(II), Ni(II), Pd(II) and Ru(III) metal complexes were synthesized and characterized by the analytical and spectroscopic methods. Alkane oxidation activities of the metal complexes were studied on cyclohexane as substrate. The ligands and their metal complexes were evaluated for their antimicrobial activity against Corynebacterium xerosis, Bacillus brevis, Bacillus megaterium, Bacillus cereus, Mycobacterium smegmatis, Staphylococcus aureus, Micrococcus luteus and Enterococcus faecalis (as Gram-positive bacteria) and Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Yersinia enterocolitica, Klebsiella fragilis, Saccharomyces cerevisiae, and Candida albicans (as Gram-negative bacteria). The antioxidant properties of the Schiff base ligands were evaluated in a series of in vitro tests: 1,1-diphenyl-2-picrylhydrazyl (DPPH rad ) free radical scavenging and reducing power activity of superoxide anion radical generated non-enzymatic systems. Electrochemical and thermal properties of the compounds were investigated.

  17. Nano structure zinc (II) Schiff base complexes of a N3-tridentate ligand as new biological active agents: spectral, thermal behaviors and crystal structure of zinc azide complex.

    Science.gov (United States)

    Montazerozohori, M; Mojahedi Jahromi, S; Masoudiasl, A; McArdle, P

    2015-03-05

    In this work, synthesis of some new five coordinated zinc halide/pseudo-halide complexes of a N3-tridentate ligand is presented. All complexes were subjected to spectroscopic and physical methods such as FT-IR, UV-visible, (1)H and (13)C NMR spectra, thermal analyses and conductivity measurements for identification. Based on spectral data, the general formula of ZnLX2 (X=Cl(-), Br(-), I(-), SCN(-) and N3(-)) was proposed for the zinc complexes. Zinc complexes have been also prepared in nano-structure sizes under ultrasonic irradiation. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for confirmation of nano-structure character for the complexes. Among the complexes, zinc azide complex structure was analyzed by X-ray crystallography. This complex crystallizes as a triplet in trigonal system with space group of P31. The coordination sphere around the zinc center is well shown as a distorted trigonal bipyramidal with three nitrogen atoms from Schiff base ligand and two terminal azide nitrogen atoms attached to zinc ion. Various intermolecular interactions such as NH⋯N, CH⋯N and CH⋯π hydrogen bonding interactions stabilize crystalline lattice so that they causes a three dimensional supramolecular structure for the complex. In vitro screening of the compounds for their antimicrobial activities showed that ZnLI2, ZnL(N3)2, ZnLCl2 and ZnL(NCS)2 were found as the most effective compound against bacteria of Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli respectively. Also ZnLI2 and ZnLCl2 complexes were found more effective against two selected fungi than others. Finally, thermal behaviors of the zinc complexes showed that they are decomposed via 2-4 thermal steps from room temperature up to 1000°C. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Complexation of actinides(III) and lanthanides(III) cations by tridentate nitrogen ligands; Complexation des cations actinides(III) et lanthanides(III) par des ligands azotes tridentates

    Energy Technology Data Exchange (ETDEWEB)

    Cordier, P.Y.; Francois, N.; Guillaneux, D.; Hill, C.; Madic, Ch. [CEA Valrho, (DCC/DRRV/SEMP), 30 - Marcoule (France); Illemassene, M. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire

    2000-07-01

    To understand the properties of some systems able to extract actinides (III) from lanthanides(III) selectively, the solution chemistry of lanthanide(III) and actinide(III) cations with poly-hetero-aromatic nitrogen-containing ligands was studied by Time-Resolved Laser Induced Fluorimetry (TRLIF) and UV-visible spectrophotometry, combined with chemo-metric methods. Three soft donor ligands (L) were selected for the study: 2,2':6;2{sup -}ter-pyridine (Tpy),4,6-tri-(pyridine-2-yl)-1,3,5-triazine (Tptz) and 2,6-bis-(5,6-dimethyl-1,2,4-triazine-3-yl)-pyridine (MeBtp). Tpy and Tptz exhibit moderate affinity (distribution ratio) and selectivity when used in the synergistic liquid-liquid extraction of americium(III) (with a lipophilic carboxylic acid). MeBtp is also very efficient, and extracts Am(III) with high selectivity; The TRLIF study analyzed the Eu(III) fluorescence emission spectrum. By analyzing the respective changes in the band intensities, and the lifetimes of the Eu(III) excited states, when the ligands were added in homogeneous phase, the following conclusions were drawn: - for Tpy and Tptz, only one EuL{sup 3+} complex species was detected, with a low symmetry in the first coordination sphere, and the Eu(III) hydration number (number of water molecules in the Eu(III) first sphere of coordination) in these complexes was found to be around 5-6; - for MeBtp, two species were detected, one with a low symmetry and a hydration number close to 5-6, the other with a high symmetry and almost completely dehydrated. This is indicative of the formation of the complexes: EuL{sup 3+} for L =Tpy and Tptz, and Eu(MeBtp){sup 3+} and Eu(MeBtp){sub 3}{sup 3+} in the case of MeBtp. The formation of these complexes, as well as the protonated ligands, was quantitatively studied using UV-visible spectrophotometry. In each case, the variation in the absorption spectrum of one species was monitored, while the concentration of the other was varied. The complex formation

  19. Synthesis, characterization and anti-proliferative activity of Cd(II) complexes with NNN type pyrazole-based ligand and pseudohalide ligands as coligand

    Science.gov (United States)

    Hopa, Cigdem; Yildirim, Hatice; Kara, Hulya; Kurtaran, Raif; Alkan, Mahir

    2014-03-01

    Cd(II) complexes of tridentate nitrogen donor ligand, 2,6-bis(3,4,5-trimethylpyrazolyl)pyridine (btmpp), Cd(btmpp)X2 (X:Cl, ONO or N(CN)2) have been synthesized and characterized by elemental and spectral (FT-IR, 1H NMR, 13C NMR, UV-Vis) analyses, differential thermal analysis and single crystal X-ray diffraction studies. The molecular structure of reported complex 1, revealed distorted square-pyramidal geometry around Cadmium. Complexes 1-3 and corresponding ligand were tested for cytotoxic activity against the human carcinoma cell lines HEP3B (hepatocellular carcinoma), PC3 (prostate adenocarcinoma), MCF7 (breast adenocarcinoma) and Saos2 (osteosarcoma). The results show that, complexes are more cytotoxic than the free ligand and complex 2 is the most cytotoxic complex for PC3.

  20. Studies on the mixed ligand complexes of copper(II involving a sulfa drug and some potentially bi or tridentate ligands under physiological conditions

    Directory of Open Access Journals (Sweden)

    S. Regupathy

    2014-12-01

    Full Text Available The stability constants of mixed ligand complexes formed in the Cu(II-sulfathiazole(stz(A-glycine(gly, dl-2-aminobutanoic acid(2aba, dl-3-aminobutanoic acid(3aba, 1,2-diaminopropane(dp, 1,3-diaminopropane(tp, dl-2,3-diaminopropanoic acid(dapa, dl-2,4-diaminobutanoic acid(daba, dl-2,5-diaminopentanoic acid(ornithine, orn(B systems have been determined pH-metrically at 37 °C and I = 0.15 mol dm−3 (NaClO4 using SCOGS program. Analysis of experimental data indicates the presence of CuABH, CuAB, CuAB2H2 or CuAB2 species. The Δlog K values demonstrate higher stabilities for the mixed ligand complexes compared to the binary analogues. The CuAB complexes with B = gly, 2aba, dapa & orn systems were isolated and characterized using micro analytical, magnetic moment, ESR, electrochemical studies, TG/DTA, power XRD and SEM analysis. Magnetic susceptibility and electronic spectral studies suggest square planar geometry for the CuAB complexes. The g values indicate that the unpaired electron lies in thedx2-y2 orbital. The TG/DTA studies reveal that the complexes are non hydrated and possesses high thermal stability. The powder XRD data suggest that the complex is microcrystalline. The antimicrobial activity and CT DNA cleavage studies of the complexes are also reported.

  1. A tetranuclear cubane-like nickel(II complex with a tridentate salicylideneimine Schiff base ligand: tetrakis[μ3-4-methyl-N-(2-oxidophenylsalicylideneiminato]tetrakis[methanolnickel(II] methanol 0.8-solvate

    Directory of Open Access Journals (Sweden)

    Gordana Pavlović

    2016-12-01

    Full Text Available The tetranuclear title complex, [Ni4(C14H11NO24(CH3OH4]·0.8CH3OH, has a distorted cubane topology shaped by four Schiff base ligands. The cubane [Ni4(μ3-O4] core is formed via the O atoms from the Schiff base ligands. The octahedrally coordinated NiII ions occupy alternating vertices of the cube. Each NiII ion is coordinated by one O,N,O′-tridentate dianionic ligand, two O atoms of oxidophenyl groups from adjacent ligands and the O atom of a coordinating methanol molecule. The cubane core is stabilized via an intramolecular O—H...O hydrogen bond between the hydroxy group of the coordinating methanol molecules and the phenolate O atom of the aldehyde Schiff base fragment. Additional stabilization is obtained via intramolecular C—H...O hydrogen bonds involving aromatic C—H groups and the oxygen atoms of adjacent methanol molecules. In the crystal, complex molecules are linked into chains parallel to the c axis via weak C—H...O hydrogen bonds. The partial-occupancy disordered methanol solvent molecule has a site occupancy of 0.8 and is linked to the tetranuclear unit via an intermolecular C—H...O hydrogen bond involving a phenolate O atom.

  2. Trident Web page

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Randall P. [Los Alamos National Laboratory; Fernandez, Juan C. [Los Alamos National Laboratory

    2012-06-25

    An Extensive Diagnostic Suite Enables Cutting-edge Research at Trident The Trident Laser Facility at Los Alamos National Laboratory is an extremely versatile Nd:glass laser system dedicated to high energy density physics research and fundamental laser-matter interactions. Trident's Unique Laser Capabilities Provide an Ideal Platform for Many Experiments. The laser system consists of three high energy beams which can be delivered into two independent target experimental areas. The target areas are equipped with an extensive suite of diagnostics for research in ultra-intense laser matter interactions, dynamic material properties, and laser-plasma instabilities. Several important discoveries and first observations have been made at Trident including laser-accelerated MeV mono-energetic ions, nonlinear kinetic plasma waves, transition between kinetic and fluid nonlinear behavior, as well as other fundamental laser-matter interaction processes. Trident's unique long-pulse capabilities have enabled state-of-the-art innovations in laser-launched flyer-plates, and other unique loading techniques for material dynamics research.

  3. The Trident Warrior Experimentation Process

    National Research Council Canada - National Science Library

    Barrett, Kevin

    2005-01-01

    ...." The Trident Warrior experiments are the Navy's premier FORCEnet Sea Trial experiments. The purpose of the Trident Warrior experiments is to provide "speed to capability" and to develop supporting tactics, techniques, and procedures...

  4. Low temperature X-ray structure analyses combined with NBO studies of a new heteroleptic octa-coordinated Holmium(III) complex with N,N,N-tridentate hydrazono-phthalazine-type ligand

    Science.gov (United States)

    Soliman, Saied M.; El-Faham, Ayman

    2018-04-01

    The new heteroleptic [HoL(H2O)5]Br3 complex, L is hydrazono-phthalazine ligand, is synthesized and its molecular structure aspects were analyzed using single crystal X-ray structure (SCXRD), Hirshfeld (HF) analysis, quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) method. The SCXRD showed that the Ho is octa-coordinated with one N,N,N-tridentate ligand L and five water molecules. The HF analysis is used to analyze the molecular packing in the [HoL(H2O)5]Br3crystal structure. The complex cations are connected via strong Osbnd H⋯Br and Nsbnd H⋯Br H-bonding interactions which have greater importance than the Csbnd H⋯Br contacts. Also, all the Hosbnd N and Hosbnd O bonds have the characteristics of closed shell interactions using QTAIM. The natural orbitals included in these interactions were analyzed using NBO method. The alpha LP*(8)Ho and beta LP*(4)Ho which have mainly s-orbital characters are the most important anti-bonding natural orbitals included in all Ho-N and Hosbnd O bonds. The rest of the Ho anti-bonding orbitals which have either p or d-orbital characters shared partially in the Ho-ligands interactions. Natural charges analysis revealed the presence of significant amount of electron density (0.9225-0.9300 e) transferred from the ligands to Ho (2.0700-2.0775 e). Spherical spin density with ∼4.0 e is predicted over the Ho atom.

  5. Ruthenium(II) carbonyl complexes bearing quinoline-based NNO tridentate ligands as catalyst for one-pot conversion of aldehydes to amides and o-allylation of phenols.

    Science.gov (United States)

    Manikandan, R; Prakash, G; Kathirvel, R; Viswanathamurthi, P

    2013-12-01

    Six new octahedral ruthenium(II) carbonyl complexes having the general molecular formula [RuCl(CO)(B)L(1-2)] (B = PPh3, AsPh3 or py; L(1-2) = quinoline based NNO ligand) were synthesized. The quinoline based ligands behave as monoanionic tridentate donor and coordinated to ruthenium via ketoenolate oxygen, azomethine nitrogen and quinoline nitrogen. The composition of the complexes has been established by elemental analysis and spectral methods (FT-IR, electronic, (1)H NMR, (13)C NMR, (31)P NMR and ESI-Mass). The complexes were used as efficient catalysts for one-pot conversion of various aldehydes to their corresponding primary amides in presence of NH2OH · HCl and NaHCO3. The effect of catalyst loading and reaction temperature on catalytic activity of the ruthenium(II) carbonyl complexes were also investigated. The synthesized complexes also possess good catalytic activity for the o-allylation of phenols in the presence of K2CO3 under mild conditions. The complexes afforded branched allyl aryl ethers according to a regioselective reaction. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Versatile Design Strategy for Highly Luminescent Vacuum-Evaporable and Solution-Processable Tridentate Gold(III) Complexes with Monoaryl Auxiliary Ligands and Their Applications for Phosphorescent Organic Light Emitting Devices.

    Science.gov (United States)

    Tang, Man-Chung; Lee, Chin-Ho; Lai, Shiu-Lun; Ng, Maggie; Chan, Mei-Yee; Yam, Vivian Wing-Wah

    2017-07-12

    A new class of brightly blue-green-emitting arylgold(III) complexes has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable and vacuum-deposited organic light-emitting devices (OLEDs). These arylgold(III) complexes can be readily synthesized by reacting the corresponding arylboronic acids with the gold(III) precursor complexes in a one-pot Suzuki-Miyaura coupling reaction. When compared to the structurally related alkynylgold(III) complex, arylgold(III) complexes 1 and 2 exhibit much higher photoluminescence quantum yields in solution state. High photoluminescence quantum yields are also observed in solid-state thin films. More importantly, the solid-state emission spectra show strong resemblance to those in solution, irrespective of the dopant concentration, leading to significant improvement in the color purity of the OLEDs by suppressing any excimer emission resulting from the π-stacking of the tridentate ligand. High performance solution-processable and vacuum-deposited blue-green-emitting OLEDs have also been realized, with maximum external quantum efficiencies of 7.3% and 14.7%, respectively, representing the first demonstration of efficient blue-green-emitting OLEDs based on cyclometalated arylgold(III) complexes.

  7. Syntheses, crystal structures and antimicrobial activities of 6-coordinate antimony(III) complexes with tridentate 2-acetylpyridine thiosemicarbazone, bis(thiosemicarbazone) and semicarbazone ligands.

    Science.gov (United States)

    Kasuga, Noriko Chikaraishi; Onodera, Kuniaki; Nakano, Saori; Hayashi, Kunihiko; Nomiya, Kenji

    2006-07-01

    Five novel antimony(III) complexes with the mono- and bis(thiosemicarbazone) ligands of 2N1S or 4N2S donor atoms, N'-[1-(2-pyridyl)ethylidene]morpholine-4-carbothiohydrazide (Hmtsc, L1) and bis[N'-[1-(2-pyridyl)ethylidene

  8. Synthesis, Spectral, Magnetic and Thermal Studies of the Complexes of CoII and NiII With Some Bidentate and Tridentate Hydrazone Ligands

    Directory of Open Access Journals (Sweden)

    Chetan K. Modi

    2005-01-01

    Full Text Available The reaction of Co(NO32.6H2O and Ni(NO32.6H2O with hydrazones derived from 1-phenyl-3-methyl-4-acyl-5-pyrazolone (where acyl = acetyl, propionyl, butyryl and benzoyl with 2-picolinic acid hydrazide have been studied and characterized on the basis of elemental analysis, magnetic moments, molar conductivity measurements, IR and electronic spectral studies and thermogravimetric analysis. Various ligand field parameters have been calculated. Electronic spectral data and the magnetic moment values suggest an octahedral structure for all cobalt(II and nickel(II complexes.

  9. An extremely bulky tris(pyrazolyl)methanide: a tridentate ligand for the synthesis of heteroleptic magnesium(II) and ytterbium(II) alkyl, hydride, and iodide complexes.

    Science.gov (United States)

    Lalrempuia, Ralte; Stasch, Andreas; Jones, Cameron

    2015-02-01

    The tris(pyrazolyl)methane compound HC(3-Ad-5-Mepz)3 [1, 3-Ad-5-Mepz=3-(1-adamantyl)-5-methylpyrazolyl] and its regioisomer, HC(3-Ad-5-Mepz)2 (3-Me-5-Adpz), were synthesized and crystallographically characterized. Deprotonation of 1 with MeLi afforded the lithium complex [{κ(3) -N-C(3-Ad-5-Mepz)3 }Li(thf)], which incorporates a tris(pyrazolyl)methanide ligand of unprecedented bulk. Reaction of 1 with MeMgI gave the ionic coordination complex [{κ(3) -N-HC(3-Ad-5-Mepz)3 }MgMe]I, which was readily deprotonated to afford the neutral compound [{κ(3) -N-C(3-Ad-5-Mepz)3 }MgMe]. The related magnesium butyl compound [{κ(3) -N-C(3-Ad-5-Mepz)3 }MgBu] was prepared from the reaction of 1 and MgBu2 . Treating this with LiAlH4 or LiAlD4 led to rare examples of terminal magnesium hydride/deuteride complexes, [{κ(3) -N-C(3-Ad-5-Mepz)3 }MgH/D]. All neutral magnesium alkyl and hydride compounds were crystallographically authenticated. Reaction of [{κ(3) κN-C(3-Ad-5-Mepz)3 }Li(thf)] with [YbI2 (thf)2 ] yielded the first structurally characterized f-block tris(pyrazolyl)methanide complex, [{κ(3) -N-C(3-Ad-5-Mepz)3 }YbI(thf)]. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Fission product interactions with nitrogen donor ligands used for spent nuclear fuel treatment

    Czech Academy of Sciences Publication Activity Database

    Aneheim, E.; Grüner, Bohumír; Ekberg, C.; Foreman, M.R.S.J.; Hájková, Zuzana; Löfström-Engdahl, E.; Drew, M. G. B.; Hudson, M.J.

    2013-01-01

    Roč. 50, č. 1 (2013), s. 154-163 ISSN 0277-5387 R&D Projects: GA MŠk(CZ) 7G08073 Grant - others:ACSEPT(XE) FP7-CP-2007-211 267 Institutional support: RVO:61388980 Keywords : BTBP * palladium * complexation * water solubility Subject RIV: CA - Inorganic Chemistry Impact factor: 2.047, year: 2013

  11. Tridentate hydrazone metal complexes derived from cephalexin and 2-hydrazinopyridine: Synthesis, characterization and antibacterial activity

    Science.gov (United States)

    Anacona, J. R.; Rincones, Maria

    2015-04-01

    Metal(II) coordination compounds of a tridentate hydrazone ligand (HL) derived from the condensation of cephalexin antibiotic with 2-hydrazinopyridine were synthesized. The hydrazone ligand and mononuclear [ML(OAc)(H2O)] (M(II) = Mn, Co, Ni, Cu, Zn, Ag) complexes were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and 1H NMR spectral studies. The cephalexin 2-pyridinylhydrazone ligand HL behaves as a monoanionic tridentate NNO chelating agent. The biological applications of complexes have been studied on three bacteria strains (Escherichia coli, Acinetobacter baumannii and Enterococcus faecalis) by agar diffusion disc method.

  12. Synthesis and Characterization of 4-Benzyloxybenzaldehyde-4-methyl-3-thiosemicarbazone (Containing Sulphur and Nitrogen Donor Atoms and Its Cd(II Complex

    Directory of Open Access Journals (Sweden)

    Lakshmi Narayana Suvarapu

    2015-12-01

    Full Text Available A chelating agent, 4-benzyloxybenzaldehyde-4-methyl-3-thiosemicarbazone (BBMTSC, containing sulphur and nitrogen donor atoms was synthesized and applied as a ligand for the chelation of Cd(II. Both the BBMTSC and its Cd(II complex were characterized by elemental analysis, UV-Vis absorption spectra, Fourier transform infrared spectroscopy (FT-IR, mass spectra, nuclear magnetic resonance spectroscopy (NMR, X-ray powder diffraction (XRD, and field emission scanning electron microscopy (FESEM. The FTIR spectra confirmed the formation of both BBMTSC and its Cd(II complex. XRD revealed the polycrystalline nature of the synthesized compounds. BBMTSC exhibited a flake-like micro-rod morphology, whereas the Cd(II complex had a flower-like nanorod structure.

  13. Spectroscopic and biological studies of new binuclear metal complexes of a tridentate ONS hydrazone ligand derived from 4-amino-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one and 4,6-diacetylresorcinol

    Science.gov (United States)

    Adly, Omima M. I.; Emara, Adel A. A.

    2014-11-01

    The binuclear hydrazone, H2L, ligand derived from 4-amino-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one and 4,6-diacetylresorcinol, in the molar ratio 2:1, and its copper(II), nickel(II), cobalt(II), zinc(II), cadmium(II), cerium(III), iron(III), oxovanadium(IV) and dioxouranium(VI) complexes have been synthesized. Structures of the ligand and its metal complexes were characterized by elemental analyses, spectral (infrared, electronic, mass, 1H NMR and ESR) data, magnetic susceptibility, molar conductivity measurements and thermal gravimetric analysis (TGA). The ligand acts as dibasic with two ONS tridentate sites. The bonding sites are the azomethine nitrogen, phenolate oxygen and sulfur atoms. The metal complexes exhibit different geometrical arrangements such as square planer, tetrahedral and octahedral. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. The ligand and its metal complexes showed antimicrobial activity towards Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Salmonella typhimurium and Escherichia coli), yeast (Candida albicans) and fungus (Aspergillus fumigatus). Structural parameters of the ligand and its metal complexes were theoretically computed on the basis of semiempirical PM3 level, and the results were correlated with their experimental data.

  14. Aluminum complexes of the redox-active [ONO] pincer ligand.

    Science.gov (United States)

    Szigethy, Géza; Heyduk, Alan F

    2012-07-14

    A series of aluminum complexes containing the tridentate, redox-active ligand bis(3,5-di-tert-butyl-2-phenol)amine ([ONO]H(3)) in three different oxidation states were synthesized. The aluminum halide salts AlCl(3) and AlBr(3) were reacted with the doubly deprotonated form of the ligand to afford five-coordinate [ONHO(cat)]AlX(solv) complexes (1a, X = Cl, solv = OEt(2); 1b, X = Br, solv = THF), each having a trigonal bipyramidal coordination geometry at the aluminum and containing the [ONHO(cat)](2-) ligand with a protonated, sp(3)-hybridized nitrogen donor. The [ONO] ligand platform may also be added to aluminum through the use of the oxidized ligand salt [ONO(q)]K, which was reacted with AlCl(3) in the presence of either diphenylacetylacetonate (acacPh(2)(-)) or 8-oxyquinoline (quinO(-)) to afford [ONO(q)]Al(acacPh(2))Cl (2) or [ONO(q)]Al(quinO)Cl (3), respectively, with well-defined [ONO(q)](-) ligands. Quinonate complexes 2 and 3 were reduced by one electron to afford the corresponding complexes K{[ONO(sq)]Al(acacPh(2))(py)} (4) and K{[ONO(sq)]Al(quinO)(py)} (5), respectively, containing well-defined [ONO(sq)](2-) ligands. The addition of tetrachloro-1,2-quinone to 1a in the presence of pyridine resulted in the expulsion of HCl and the formation of an aluminum complex with two different redox active ligands, [ONO]Al(o-O(2)C(6)Cl(4))(py) (6). Similar results were obtained when 1a was reacted with 9,10-phenanthrenequinone to afford [ONO]Al(o-O(2)C(14)H(8))(py) (7) or with pyrene-4,5-dione to afford [ONO]Al(o-O(2)C(16)H(8))(py) (8). Structural, spectroscopic and preliminary magnetic measurements on 6-8 suggest ligand non-innocent redox behavior in these complexes.

  15. Trident II (D-5) Sea Launched Ballistic Missile UGM 133A (Trident II Missile)

    Science.gov (United States)

    2015-12-01

    TRIDENT II (D5) Sea-Launched Ballistic Missile UGM 133A (TRIDENT II (D5) missile) developed an improved Submarine Launched Ballistic Missile with...The TRIDENT II (D5) missile’s increased payload allows the deterrent mission to be achieved with fewer submarines . Trident II Missile December 2015...needed for the cable builds, which extended the overall time required for build/test, and b) unplanned work was required during the Burn-In Console

  16. fac-[Re(CO)(3)L](+) complexes with N-CH(2)-CH(2)-X-CH(2)-CH(2)-N tridentate ligands. synthetic, X-ray crystallographic, and NMR spectroscopic investigations.

    Science.gov (United States)

    Christoforou, Anna Maria; Marzilli, Patricia A; Fronczek, Frank R; Marzilli, Luigi G

    2007-12-24

    Polyamine ligands (L) have excellent binding characteristics for the formation of fac-99mTc(CO)3-based radiopharmaceuticals. Normally, these L are elaborated so as to leave pendant groups designed to impart useful biodistribution characteristics to the fac-[99mTc(CO)3L] imaging agent. Our goal is to lay a foundation for understanding the features of the bound elaborated ligands by using the fac-[Re(CO)3L]-analogue approach with the minimal prototypical ligands, diethylenetriamine (dien) or simple dien-related derivatives. Treatment of the fac-[Re(CO)3(H2O)3]+ cation with such triamine (NNN) ligands afforded fac-[Re(CO)3L]+ complexes. Ligand variations included having a central amine thioether donor, thus allowing X-ray crystallographic and NMR spectroscopic comparisons of fac-[Re(CO)3L]+ complexes with NNN and NSN ligands. fac-[Re(CO)3L]+ complexes with two terminal exo-NH groups exhibit unusually far upfield exo-NH NMR signals in DMSO-d6. Upon the addition of Cl-, these exo-NH signals move downfield, while the signals of any endo-NH or central NH groups move very little. This behavior is attributed to the formation of 1:1 ion pairs having selective Cl- hydrogen bonding to both exo-NH groups. Base addition to a DMSO-d6 solution of meso-exo-[Re(CO)3(N,N',N''-Me3dien)]PF6 led to isomerization of only one NHMe group, producing the chiral isomer. The meso isomer did not form. The [Re(CO)3(N,N,N',N'',N''-pentamethyldiethylenetriamine)]triflate.[Re(CO)3(mu3-OH)]4.3.35H2O crystal, the first structure with a fac-[Re(CO)3L] complex cocrystallized with this well-known cluster, provided parameters for a bulky NNN ligand and also reveals CO-CO interlocking intermolecular interactions that could stabilize the crystal.

  17. Silyl phosphorus and nitrogen donor chelates for homogeneous ortho borylation catalysis.

    Science.gov (United States)

    Ghaffari, Behnaz; Preshlock, Sean M; Plattner, Donald L; Staples, Richard J; Maligres, Peter E; Krska, Shane W; Maleczka, Robert E; Smith, Milton R

    2014-10-15

    Ir catalysts supported by bidentate silyl ligands that contain P- or N-donors are shown to effect ortho borylations for a range of substituted aromatics. The substrate scope is broad, and the modular ligand synthesis allows for flexible catalyst design.

  18. Synthesis, Characterization, Crystal Structure, and Biological Studies of a Cadmium(II) Complex with a Tridentate Ligand 4′-Chloro-2,2′:6′,2′′-Terpyridine

    Science.gov (United States)

    Saghatforoush, L. A.; Valencia, L.; Chalabian, F.; Ghammamy, Sh.

    2011-01-01

    A new Cd(II) complex with the ligand 4′-chloro-2,2′6′,2′′-terpyridine (Cltpy), [Cd(Cltpy)(I)2], has been synthesized and characterized by CHN elemental analysis, 1H-NMR, 13C-NMR, and IR spectroscopy and structurally analyzed by X-ray single-crystal diffraction. The single-crystal X-ray analyses show that the coordination number in complex is five with three terpyridine (Cltpy) N-donor atoms and two iodine atoms. The antibacterial activities of Cltpy and its Cd(II) complex are tested against different bacteria. PMID:21738495

  19. Accomplishments in the Trident Laser Facility

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, Juan Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-25

    Trident has been an extremely productive laser facility, despite its modest size and operating cost in the firmament of high-energy, high-power laser facilities worldwide. More than 150 peer-reviewed journal articles (in 39 different journals) have been published using Trident experimental data, many in high-impact journals such as Nature, Nature Physics, Nature Communications, and Physical Review Letters. More than 230 oral presentations involving research at Trident have been presented at national and international conferences. Trident publications have over 5000 citations in the literature with an h-index of 38. AT least 23 Los Alamos postdoctoral researchers have worked on Trident. In the period since its inception in 1992-2007, despite not issuing formal proposal calls for access nor functioning explicitly as a user facility until later, Trident has 170 unique users from more than 30 unique institutions, such as Los Alamos, Lawrence Livermore, and Sandia national laboratories, various University of California campuses, General Atomic, Imperial College, and Ecole Polytechnique. To reinforce its role as an important Los Alamos point of connection to the external research community, at least 20 PhD students did a significant fraction of their thesis work on Trident. Such PhD students include Mike Dunne (Imperial College, 1995) - now director of LCLS and professor at Stanford; David Hoarty (IC, 1997) - scientist at Atomic Weapons Establishment, UK; Dustin Froula (UC Davis, 2002) - Plasma and Ultrafast Physics Group leader at the Laboratory for Laser Energetics and assistant professor at the Physics and Astronomy Department at the University of Rochester; Tom Tierney (UC Irvine, 2002) - scientist at Los Alamos; Eric Loomis (Arizona State U., 2005) - scientist at Los Alamos; and Eliseo Gamboa (University of Michigan, 2013) - scientist at the Linac Coherent Light Source. The work performed on Trident, besides its scientific impact, has also supported the Inertial

  20. Atmospheric trident production for probing new physics

    Directory of Open Access Journals (Sweden)

    Shao-Feng Ge

    2017-09-01

    Full Text Available We propose to use atmospheric neutrinos as a powerful probe of new physics beyond the Standard Model via neutrino trident production. The final state with double muon tracks simultaneously produced from the same vertex is a distinctive signal at large Cherenkov detectors. We calculate the expected event numbers of trident production in the Standard Model. To illustrate the potential of this process to probe new physics we obtain the sensitivity on new vector/scalar bosons with coupling to muon and tau neutrinos.

  1. Several novel N-donor tridentate ligands formed in chemical studies of new fac-Re(CO)3 complexes relevant to fac-99mTc(CO)3 radiopharmaceuticals: attack of a terminal amine on coordinated acetonitrile.

    Science.gov (United States)

    Perera, Theshini; Marzilli, Patricia A; Fronczek, Frank R; Marzilli, Luigi G

    2010-03-01

    To evaluate syntheses of fac-[Re(CO)(3)L](+) complexes in organic solvents, we treated fac-[Re(CO)(3)(CH(3)CN)(3)]PF(6)/BF(4) in acetonitrile with triamine ligands (L). When L had two primary or two tertiary terminal amine groups, the expected fac-[Re(CO)(3)L](+) complexes formed. In contrast, N,N-dimethyldiethylenetriamine (N,N-Me(2)dien) formed an unusual compound, fac-[Re(CO)(3)(DAE)]BF(4) {DAE = (Z)-N'-(2-(2-(dimethylamino)ethylamino)ethyl)acetimidamide = (Me(2)NCH(2)CH(2))NH(CH(2)CH(2)N=C(NH(2))Me)}. DAE is formed by addition of acetonitrile to the N,N-Me(2)dien terminal primary amine, converting this sp(3) nitrogen to an sp(2) nitrogen with a double bond to the original acetonitrile sp carbon. The three Ns bound to Re derive from N,N-Me(2)dien. The pathway to fac-[Re(CO)(3)(DAE)]BF(4) is suggested by a second unusual compound, fac-[Re(CO)(3)(MAE)]PF(6) {MAE = N-methyl-N-(2-(methyl-(2-(methylamino)ethyl)amino)ethyl)acetimidamide = MeN(H)-CH(2)CH(2)-N(Me)-CH(2)CH(2)-N(Me)-C(Me)=NH}, isolated after treating fac-[Re(CO)(3)(CH(3)CN)(3)]PF(6) with N,N',N''-trimethyldiethylenetriamine (N,N',N''-Me(3)dien). MAE chelates via a terminal and a central sp(3) N from N,N',N''-Me(3)dien and via one sp(2) NH in a C(Me)=NH group. This group is derived from acetonitrile by addition of the other N,N',N''-Me(3)dien terminal amine to the nitrile carbon. This addition creates an endocyclic NMe group within a seven-membered chelate ring. The structure and other properties of fac-[Re(CO)(3)(MAE)]PF(6) allow us to propose a reaction scheme for the formation of the unprecedented DAE ligand. The new compounds advance our understanding of the spectral and structural properties of Re analogues of (99m)Tc radiopharmaceuticals.

  2. COMPLEXES WITH TRIDENTATE N2,O-DONOR LIGAND

    African Journals Online (AJOL)

    The molar conductance of 10-3 M solutions of the metal complexes ... conductivity cell. Room temperature magnetic susceptibilities of the powdered samples. {calibrant Hg[Co(SCN)4]} were measured using a Johnson Mattey scientific ..... 2 and 4) complexes and the dinuclear complex 3 are neutral and non-electrolyte [21].

  3. complexes of linear and tripodal tridentate ligands as functional ...

    Indian Academy of Sciences (India)

    fashion due to the sp3 hybridization of amine N-atom.27. Upon adding ..... iron(III) center along this series. This trend is in con- trast to that observed in electronic spectra, obviously because the coordinated chloride ions compensate for the increase .... appearance of the DBC2−-to-iron(III) charge-transfer band is monitored.

  4. Influence of a Heterocyclic Nitrogen-Donor Group on the Coordination of Trivalent Actinides and Lanthanides by Aminopolycarboxylate Complexants.

    Science.gov (United States)

    Grimes, Travis S; Heathman, Colt R; Jansone-Popova, Santa; Ivanov, Alexander S; Roy, Santanu; Bryantsev, Vyacheslav S; Zalupski, Peter R

    2018-02-05

    The novel metal chelator N-2-(pyridylmethyl)diethylenetriamine-N,N',N″,N″-tetraacetic acid (DTTA-PyM) was designed to replace a single oxygen-donor acetate group of the well-known aminopolycarboxylate complexant diethylenetriamine-N,N,N',N″,N″-pentaacetic acid (DTPA) with a nitrogen-donor 2-pyridylmethyl. Potentiometric, spectroscopic, computational, and radioisotope distribution methods show distinct differences for the 4f and 5f coordination environments and enhanced actinide binding due to the nitrogen-bearing heterocyclic moiety. The Am 3+ , Cm 3+ , and Ln 3+ complexation studies for DTTA-PyM reveal an enhanced preference, relative to DTPA, for trivalent actinide binding. Fluorescence studies indicate no changes to the octadentate coordination of trivalent curium, while evidence of heptadentate complexation of trivalent europium is found in mixtures containing EuHL (aq) complexes at the same aqueous acidity. The denticity change observed for Eu 3+ suggests that complex protonation occurs on the pyridyl nitrogen. Formation of the CmHL (aq) complex is likely due to the protonation of an available carboxylate group because the carbonyl oxygen can maintain octadentate coordination through a rotation. The observed suppressed protonation of the pyridyl nitrogen in the curium complexes may be attributed to stronger trivalent actinide binding by DTTA-PyM. Density functional theory calculations indicate that added stabilization of the actinide complexes with DTTA-PyM may originate from π-back-bonding interactions between singly occupied 5f orbitals of Am 3+ and the pyridyl nitrogen. The differences between the stabilities of trivalent actinide chelates (Am 3+ , Cm 3+ ) and trivalent lanthanide chelates (La 3+ -Lu 3+ ) are observed in liquid-liquid extraction systems, yielding unprecedented 4f/5f differentiation when using DTTA-PyM as an aqueous holdback reagent. In addition, the enhanced nitrogen-donor softness of the new DTTA-PyM chelator was perturbed by

  5. Influence of a Heterocyclic Nitrogen-Donor Group on the Coordination of Trivalent Actinides and Lanthanides by Aminopolycarboxylate Complexants

    Energy Technology Data Exchange (ETDEWEB)

    Grimes, Travis S. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Heathman, Colt R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Jansone-Popova, Santa [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ivanov, Alexander S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Roy, Santanu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Bryantsev, Vyacheslav S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Zalupski, Peter R. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2018-01-05

    Here, the novel metal chelator N-2-(pyridylmethyl)diethylenetriamine-N,N',N",N"-tetraacetic acid (DTTA-PyM) was designed to replace a single oxygen-donor acetate group of the well-known aminopolycarboxylate complexant diethylenetriamine-N,N,N',N",N"-pentaacetic acid (DTPA) with a nitrogen-donor 2-pyridylmethyl. Potentiometric, spectroscopic, computational, and radioisotope distribution methods show distinct differences for the 4f and 5f coordination environments and enhanced actinide binding due to the nitrogen-bearing heterocyclic moiety. The Am3+, Cm3+, and Ln3+ complexation studies for DTTA-PyM reveal an enhanced preference, relative to DTPA, for trivalent actinide binding. Fluorescence studies indicate no changes to the octadentate coordination of trivalent curium, while evidence of heptadentate complexation of trivalent europium is found in mixtures containing EuHL(aq) complexes at the same aqueous acidity. The denticity change observed for Eu3+ suggests that complex protonation occurs on the pyridyl nitrogen. Formation of the CmHL(aq) complex is likely due to the protonation of an available carboxylate group because the carbonyl oxygen can maintain octadentate coordination through a rotation. The observed suppressed protonation of the pyridyl nitrogen in the curium complexes may be attributed to stronger trivalent actinide binding by DTTA-PyM. Density functional theory calculations indicate that added stabilization of the actinide complexes with DTTA-PyM may originate from π-back-bonding interactions between singly occupied 5f orbitals of Am3+ and the pyridyl nitrogen. The differences between the stabilities of trivalent actinide chelates (Am3+, Cm3+) and trivalent lanthanide chelates (La3+–Lu3+) are observed in liquid–liquid extraction systems, yielding unprecedented 4f/5f differentiation when using DTTA

  6. Binuclear complexes of technetium. Evidence for bis(terdentate)bidentate coordination by the bridging ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine to technetium(V)

    International Nuclear Information System (INIS)

    Du Preez, J.G.H.; Gerber, T.I.A.; Gibson, M.L.; Geyser, R.

    1990-01-01

    The authors have used the potentially bis(terdentate) nitrogen aromatic heterocyclic ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) to prepare mono- and bimetallic technetium(V) complexes bound to tppz. The stimulus for the development of the coordination chemistry of the man-made element technetium is provided by the use of complexes of this element as anatomical imaging agents in nuclear medicine. Although the chemistry of technetium(V) with nitrogen donor ligands is well understood, no complexes have been prepared using potentially terdentate neutral nitrogen donor ligands of this metal in the +5 oxidation state

  7. Trident II (D-5) Sea-Launched Ballistic Missile UGM 133A (Trident II Missile)

    Science.gov (United States)

    2013-12-01

    unfavorable net change in the schedule variance is due to stopping Interferometric Fiber Optic Gyro assembly operations as a result of a technical problem...with oxygen depletion in the fill gas causing a frequency response problem with an optoelectrical gyro part. Trident II Missile December 2013 SAR

  8. Experimental investigation of strong field trident production

    CERN Document Server

    Esberg, J; Knudsen, H; Thomsen, H D; Uggerhøj, E; Uggerhøj, U I; Sona, P; Mangiarotti, A; Ketel, T J; Dizdar, A; Dalton, M M; Ballestrero, S; Connell, S H

    2010-01-01

    We show by experiment that an electron impinging on an electric field that is of critical magnitude in its rest frame, may produce an electron-positron pair. Our measurements address higher-order QED, using the strong electric fields obtainable along particular crystallographic directions in single crystals. For the amorphous material our data are in good agreement with theory, whereas a discrepancy with theory on the magnitude of the trident enhancement is found in the precisely aligned case where the strong electric field acts.

  9. EPR, ESE, and pulsed ENDOR study of the nitrogen donors in 15R SiC grown under carbon-rich conditions

    Czech Academy of Sciences Publication Activity Database

    Savchenko, Dariia; Kalabukhova, E.; Shanina, B.; Pöppl, A.; Yukhymchuk, V.; Lančok, Ján; Ubyivovk, E.; Mokhov, E.

    2014-01-01

    Roč. 252, č. 3 (2014), s. 566-572 ISSN 0370-1972 R&D Projects: GA ČR GP13-06697P; GA MŠk(CZ) LM2011029 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : ENDOR * nitrogen donors * 15R SiC * stoichiometry Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.489, year: 2014

  10. Electronic structure of the nitrogen donors in 6H SiC as studied by pulsed ENDOR and TRIPLE ENDOR spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Savchenko, Dariia; Kalabukhova, E.N.; Pöppl, A.; Shanina, B.D.

    2012-01-01

    Roč. 249, č. 11 (2012), s. 2167-2178 ISSN 0370-1972 R&D Projects: GA MŠk(CZ) LM2011029 Grant - others:The Center for Analysis of Functional Materials(CZ) CZ.2.16/3.1.00/22132 Institutional research plan: CEZ:AV0Z10100522 Keywords : 6H SiC * electronic structure * ENDOR * nitrogen donors Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.489, year: 2012

  11. Expanding the family of heteroleptic oxidovanadium(IV) compounds with salicylaldehyde semicarbazones and polypyridyl ligands showing anti-Trypanosoma cruzi activity.

    Science.gov (United States)

    Scalese, Gonzalo; Benítez, Julio; Rostán, Santiago; Correia, Isabel; Bradford, Lara; Vieites, Marisol; Minini, Lucía; Merlino, Alicia; Coitiño, E Laura; Birriel, Estefania; Varela, Javier; Cerecetto, Hugo; González, Mercedes; Pessoa, João Costa; Gambino, Dinorah

    2015-06-01

    Searching for prospective vanadium-based drugs for the treatment of Chagas disease, a new series of heteroleptic [V(IV)O(L-2H)(NN)] compounds was developed by including the lipophilic 3,4,7,8-tetramethyl-1,10-phenanthroline (tmp) NN ligand and seven tridentate salicylaldehyde semicarbazone derivatives (L1-L7). The compounds were characterized in the solid state and in solution. EPR spectroscopy suggests that the NN ligand is bidentate bound through both nitrogen donor atoms in an axial-equatorial mode. The EPR and (51)V-NMR spectra of aerated solutions at room temperature indicate that the compounds are stable to hydrolysis and that no significant oxidation of V(IV) to V(V) takes place at least in 24h. The complexes are more active in vitro against Trypanosoma cruzi, the parasite responsible for Chagas disease, than the reference drug Nifurtimox and most of them are more active than previously reported [V(IV)O(L-2H)(NN)] complexes of other NN co-ligands. Selectivity towards the parasite was analyzed using J-774 murine macrophages as mammalian cell model. Due to both, high activity and high selectivity, L2, L4, L5 and L7 complexes could be considered new hits for further drug development. Lipophilicity probably plays a relevant role in the bioactivity of the new compounds. The [V(IV)O(L-2H)(NN)] compounds were designed aiming DNA as potential molecular target. Therefore, the novel L1-L7 tmp complexes were screened by computational modeling, comparing their DNA-binding features with those of previously reported [V(IV)O(L-2H)(NN)] compounds with different NN co-ligands. Whereas all the complexes interact well with DNA, with binding modes and strength tuned in different extents by the NN and semicarbazone co-ligands, molecular docking suggests that the observed anti-T. cruzi activity cannot be explained upon DNA intercalation as the sole mechanism of action. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. The spin relaxation of nitrogen donors in 6H SiC crystals as studied by the electron spin echo method

    Czech Academy of Sciences Publication Activity Database

    Savchenko, Dariia; Shanina, B.; Kalabukhova, E.; Pöppl, A.; Lančok, Ján; Mokhov, E.

    2016-01-01

    Roč. 119, č. 13 (2016), 1-7, č. článku 135706. ISSN 0021-8979 R&D Projects: GA ČR GP13-06697P; GA MŠk LO1409; GA MŠk LM2015088 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : electron spin resonance * SiC * nitrogen donors * relaxation times Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.068, year: 2016

  13. Pincer ligands with an all-phosphorus donor set: subtle differences between rhodium and palladium

    NARCIS (Netherlands)

    Bauer, R.C.; Gloaguen, Y.; Lutz, M.; Reek, J.N.H.; de Bruin, B.; van der Vlugt, J.I.

    2011-01-01

    The synthesis of a new, all-phosphorus pincer PPNEt2P ligand L3NEt2, which is derived from 2-indolylphosphine and features a central N2P(NEt2) core, is described. This ‘PPP’ species shows coordination toward Rh as a neutral trisphosphine ligand. Tridentate diphenylphosphine-derived PPHP ligands L1H

  14. Probing new charged scalars with neutrino trident production

    Science.gov (United States)

    Magill, Gabriel; Plestid, Ryan

    2018-03-01

    We investigate the possibility of using neutrino trident production to probe leptophilic charged scalars at future high intensity neutrino experiments. We show that under specific assumptions, this production process can provide competitive sensitivity for generic charged scalars as compared to common existing bounds. We also investigate how the recently proposed mixed-flavor production—where the two oppositely charged leptons in the final state need not be muon flavored—can give a 20%-50% increase in sensitivity for certain configurations of new physics couplings as compared to traditional trident modes. We then categorize all renormalizable leptophilic scalar extensions based on their representation under SU (2 )×U (1 ), and discuss the Higgs triplet and Zee-Babu models as explicit UV realizations. We find that the inclusion of additional doubly charged scalars and the need to reproduce neutrino masses make trident production uncompetitive with current bounds for these specific UV completions. Our work represents the first application of neutrino trident production to study charged scalars. Additionally, it is the first application of mixed-flavor trident production to study physics beyond the standard model more generally.

  15. Ruthenium(III) Complexes of Heterocyclic Tridentate (ONN) Schiff Base: Synthesis, Characterization and its Biological Properties as an Antiradical and Antiproliferative Agent

    Science.gov (United States)

    Ejidike, Ikechukwu P.; Ajibade, Peter A.

    2016-01-01

    The current work reports the synthesis, spectroscopic studies, antiradical and antiproliferative properties of four ruthenium(III) complexes of heterocyclic tridentate Schiff base bearing a simple 2′,4′-dihydroxyacetophenone functionality and ethylenediamine as the bridging ligand with RCHO moiety. The reaction of the tridentate ligands with RuCl3·3H2O lead to the formation of neutral complexes of the type [Ru(L)Cl2(H2O)] (where L = tridentate NNO ligands). The compounds were characterized by elemental analysis, UV-vis, conductivity measurements, FTIR spectroscopy and confirmed the proposed octahedral geometry around the Ru ion. The Ru(III) compounds showed antiradical potentials against 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, with DPPH scavenging capability in the order: [(PAEBOD)RuCl2] > [(BZEBOD)RuCl2] > [(MOABOD)RuCl2] > [Vit. C] > [rutin] > [(METBOD)RuCl2], and ABTS radical in the order: [(PAEBOD)RuCl2] < [(MOABOD)RuCl2] < [(BZEBOD)RuCl2] < [(METBOD)RuCl2]. Furthermore, in vitro anti-proliferative activity was investigated against three human cancer cell lines: renal cancer cell (TK-10), melanoma cancer cell (UACC-62) and breast cancer cell (MCF-7) by SRB assay. PMID:26742030

  16. Ruthenium(III Complexes of Heterocyclic Tridentate (ONN Schiff Base: Synthesis, Characterization and its Biological Properties as an Antiradical and Antiproliferative Agent

    Directory of Open Access Journals (Sweden)

    Ikechukwu P. Ejidike

    2016-01-01

    Full Text Available The current work reports the synthesis, spectroscopic studies, antiradical and antiproliferative properties of four ruthenium(III complexes of heterocyclic tridentate Schiff base bearing a simple 2′,4′-dihydroxyacetophenone functionality and ethylenediamine as the bridging ligand with RCHO moiety. The reaction of the tridentate ligands with RuCl3·3H2O lead to the formation of neutral complexes of the type [Ru(LCl2(H2O] (where L = tridentate NNO ligands. The compounds were characterized by elemental analysis, UV-vis, conductivity measurements, FTIR spectroscopy and confirmed the proposed octahedral geometry around the Ru ion. The Ru(III compounds showed antiradical potentials against 2,2-Diphenyl-1-Picrylhydrazyl (DPPH and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS radicals, with DPPH scavenging capability in the order: [(PAEBODRuCl2] > [(BZEBODRuCl2] > [(MOABODRuCl2] > [Vit. C] > [rutin] > [(METBODRuCl2], and ABTS radical in the order: [(PAEBODRuCl2] < [(MOABODRuCl2] < [(BZEBODRuCl2] < [(METBODRuCl2]. Furthermore, in vitro anti-proliferative activity was investigated against three human cancer cell lines: renal cancer cell (TK-10, melanoma cancer cell (UACC-62 and breast cancer cell (MCF-7 by SRB assay.

  17. Tridentate Schiff base (ONO) transition metal complexes: Synthesis ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 128; Issue 7. Tridentate Schiff base (ONO) transition metal complexes: Synthesis, crystal structure, spectroscopic and larvicidal studies. SUNDARAMURTHY SANTHA LAKSHMI KANNAPPAN GEETHA P MAHADEVI. Regular Article Volume 128 Issue 7 July 2016 pp ...

  18. Coordination of Tridentate Schiff Base Derivatives of 4 ...

    African Journals Online (AJOL)

    NICO

    KEYWORDS. Tridentate, rhenium(V), imido, crystal structures. 1. Introduction. The research interest in pyrazolone (pz) and its derivatives is mainly due to their pharmaceutical properties. Pz is a five-membered lactam ring, containing two nitrogen atoms and a ketone, and it is an active moiety in pharmacology, such as for.

  19. Nickel (II) complexes containing ONS donor ligands: Synthesis ...

    Indian Academy of Sciences (India)

    The analysis revealed that the complexes possess a distorted octahedral geometry with the ligand coordinating in a uni-negative tridentate ONS fashion. The catalytic activity of complexes towards some C–C coupling reactions (viz., Kumada-Corriu, Suzuki-Miyaura and Sonogashira) has been examined. The complexes ...

  20. Synthesis, characterization and antibacterial activity of a tridentate Schiff base derived from cephalothin and sulfadiazine, and its transition metal complexes

    Science.gov (United States)

    Anacona, J. R.; Noriega, Natiana; Camus, Juan

    2015-02-01

    Metal(II) coordination compounds of a cephalothin Schiff base (H2L) derived from the condensation of cephalothin antibiotic with sulfadiazine were synthesized. The Schiff base ligand, mononuclear [ML(H2O)3] (M(II) = Mn, Co, Ni, Zn) complexes and magnetically diluted dinuclear copper(II) complex [CuL(H2O)3]2 were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and 1H NMR spectral studies. The cephalothin Schiff base ligand H2L behaves as a dianionic tridentate NOO chelating agent. The biological applications of complexes have been studied on two bacteria strains (Escherichia coli and Staphylococcus aureus) by agar diffusion disc method.

  1. Suitable ligands for homogeneous ruthenium-catalyzed hydrogenolysis of esters

    OpenAIRE

    Engelen, Marcel Chr. van; Teunissen, Herman T.; Vries, Johannes G. de; Elsevier, Cornelis J.

    2003-01-01

    Effective hydrogenolysis of dimethyl oxalate to ethylene glycol has been obtained using a catalyst prepared in situ from Ru(acac)3 with the facially coordinating tridentate phosphine ligand CH3C(CH2PPh2)3. This catalyst enabled full and selective conversion in 16 h at [S]/[Ru] = 500 at 80–100 bar hydrogen pressure at 120 °C. This catalyst is far more active than any known homogeneous catalyst able to hydrogenate dimethyl oxalate to ethylene glycol. Several mono-, di- and tridentate P- and N-l...

  2. Tracking Near-Earth Asteroids: A Trident Scholar Project

    Science.gov (United States)

    Campbell, D. T.; Katz-Stone, D. M.

    2000-05-01

    At the U. S. Naval Academy, the most elite students are given an opportunity to do a year-long research project. This "Trident Scholar" project teaches students about all aspects of research including writing and defending a research proposal as well as communicating results in a written paper, a poster display and an oral presentation. This Trident Scholar project employed the newly updated observatory at the U. S. Naval Academy. The scientific goal of this research focused upon tracking several near-earth asteroids (NEAs) in order to determine their orbits. In addition, lightcurves were observed for a subset of these NEAs in order to find their rotational periods and their general shapes. The poster presented here shows the scientific results of this project as well as the some of the insights this student has gained by doing his own research.

  3. Slow relaxation of magnetization in a bis-mer-tridentate octahedral Co(ii) complex.

    Science.gov (United States)

    Sertphon, Darunee; Murray, Keith S; Phonsri, Wasinee; Jover, Jesús; Ruiz, Eliseo; Telfer, Shane G; Alkaş, Adil; Harding, Phimphaka; Harding, David J

    2018-01-15

    Reaction of a rigid tridentate ligand o-[(1H-imidazol-2-yl)methylideneamino]phenol (2-H 2 imap) with Co(ClO 4 ) 2 in the presence of NaN 3 , or Co(NO 3 ) 2 without a base yields [Co II (2-Himap) 2 ] 1 and [Co III (2-Himap) 2 ]NO 3 ·MeOH 2, respectively. Both complexes exhibit a mer-octahedral geometry with the cobalt centre being distorted along an octahedral-trigonal prismatic pathway. The packing in 1 and 2 is dominated by H-bonding forming 2D sheets and 1D chains, respectively. Detailed dc and ac magnetic studies indicate that 1 is a field-induced single-ion magnet (SIM) with D = 36.7 cm -1 and E = 2.0 cm -1 . Extensive ab initio calculations support these conclusions and suggest that relaxation of the magnetization occurs principally through direct quantum tunnelling in the ground state, with the Raman process dominant in an applied field. This contrasts with the recently reported series of mer-[Co(L) 2 ] (L = monoanionic NNO donor ligand; Inorg. Chem., 2017, 56, 6056-6066) complexes where D is negative, as these compounds have a more ambiguous geometry, and highlights the importance of supramolecular interactions in subtly altering the coordination sphere thereby impacting the magnetic behaviour.

  4. A new donor atom system [(SNN)(S)] for the synthesis of neutral oxotechnetium(V) mixed ligand complexes

    International Nuclear Information System (INIS)

    Papadopoulos, M.S.; Pirmettis, I.C.; Spyriounis, D.M.

    1996-01-01

    Oxotechnetium complexes ligated in a 3 + 1 inch fashion yielding TcOL1L2 complexes were prepared. The L1 tridentate ligand binds with a SNN donor set of atoms. L2 corresponds to a monodentate thiol ligand. Representative members of this group of compounds were chemically characterized by NMR and X-ray diffraction

  5. On the structure of transition metals complexes with the new tridentate dye of thiazole series: Theoretical and experimental studies

    Science.gov (United States)

    Fizer, Maksym; Sidey, Vasyl; Tupys, Andrii; Ostapiuk, Yurii; Tymoshuk, Oleksandr; Bazel, Yaroslav

    2017-12-01

    The 1-[(5-Benzyl-1,3-thiazol-2-yl)diazenyl]naphthalene-2-ol (BnTAN) is a recently synthesized azo dye that can act as a tridentate ligand in complexes with transition metals. In a series of previous works, this analytical reagent was shown to be applicable for selective, reliable, express and relatively inexpensive determination of heavy metals in different objects through the spectrophotometric technique. Although the action of 1-(2-thiazolylazo)-2-naphthol (TAN) dyes as tridentate ligands has been suggested in the literature long time ago, due to the lack of experimental data, it was necessary to investigate the mechanism of formation and the structure of BnTAN complexes with the such transition metals as Cu(II), Zn(II) and Cd(II). Furthermore, the reactivity and properties of different acidity forms and conformers of BnTAN and related TAN dyes were not fully defined, so the determination of these properties by analysis of wavefunction was also necessary. Two standard spectrophotometric methods and voltammetric technique were used to determine the composition of complex of BnTAN with metals ions. All three experimental methods indicate that coordination ratio of metal:dye is equal to 1:2. Moreover, this study reports the stability and geometry of conformers of different forms (anionic/neutral/cationic) of BnTAN, along with a detailed analysis of electronic properties, reactivity and aromaticity of the most stable conformers of BnTAN forms. Each of the above forms has some difference in position of benzyl ring against the thiazole moiety, which is explained in terms of attraction and repulsion of these two fragments induced by partial atomic charges. The crucial influence of hydrogen bond and weak non-covalent interactions between naphthyl, aza- and thiazolyl fragments has been established. The quantum chemical calculations have shown that partial atomic charges of anionic, neutral and cationic forms can explain the reactivity of each BnTAN form, and have also

  6. Synthesis and characterization of novel M(II (M = Mn(II, Ni(II, Cu(II or Zn(II complexes with tridentate N2,O-donor ligand (E-2-amino-N’-[1-(pyridin-2-yl- ethylidene]benzohydrazide

    Directory of Open Access Journals (Sweden)

    C. H. Kane

    2016-02-01

    Full Text Available The coordination chemistry towards the M(II metal centre (M = Mn, Ni, Cu or Zn of the hydrazone ligand (E-2-amino-N’-[1-(pyridin-2-ylethylidene]benzohydrazide (H3L has been explored and complexes having formulae [Mn(H2L2] (1, {[Ni(H2L2].DMF.0.4H2O} (2, {[Cu2(H2L2(µ-Cl2].DMF} (3 and [Zn(H2L2] (4 have been isolated and characterized by IR, UV-Visible spectroscopy, elemental analysis and X-ray crystal diffraction. Structural studies reveal that the mononuclear complexes (1, (2 and (4 adopt highly distorted octahedral geometries while the dinuclear complex (3 adopts a square pyramidal geometry around each copper(II ion. DOI: http://dx.doi.org/10.4314/bcse.v30i1.9

  7. Trident: scalable compute archives: workflows, visualization, and analysis

    Science.gov (United States)

    Gopu, Arvind; Hayashi, Soichi; Young, Michael D.; Kotulla, Ralf; Henschel, Robert; Harbeck, Daniel

    2016-08-01

    The Astronomy scientific community has embraced Big Data processing challenges, e.g. associated with time-domain astronomy, and come up with a variety of novel and efficient data processing solutions. However, data processing is only a small part of the Big Data challenge. Efficient knowledge discovery and scientific advancement in the Big Data era requires new and equally efficient tools: modern user interfaces for searching, identifying and viewing data online without direct access to the data; tracking of data provenance; searching, plotting and analyzing metadata; interactive visual analysis, especially of (time-dependent) image data; and the ability to execute pipelines on supercomputing and cloud resources with minimal user overhead or expertise even to novice computing users. The Trident project at Indiana University offers a comprehensive web and cloud-based microservice software suite that enables the straight forward deployment of highly customized Scalable Compute Archive (SCA) systems; including extensive visualization and analysis capabilities, with minimal amount of additional coding. Trident seamlessly scales up or down in terms of data volumes and computational needs, and allows feature sets within a web user interface to be quickly adapted to meet individual project requirements. Domain experts only have to provide code or business logic about handling/visualizing their domain's data products and about executing their pipelines and application work flows. Trident's microservices architecture is made up of light-weight services connected by a REST API and/or a message bus; a web interface elements are built using NodeJS, AngularJS, and HighCharts JavaScript libraries among others while backend services are written in NodeJS, PHP/Zend, and Python. The software suite currently consists of (1) a simple work flow execution framework to integrate, deploy, and execute pipelines and applications (2) a progress service to monitor work flows and sub

  8. Studies on complexation of a tridentate ONS Schiff base with lighter and heavier metals ions, and investigation into their biological properties

    International Nuclear Information System (INIS)

    Tarafder, M.T.H.; Ali, A.M.; Juan, W.D.; Crouse, K.A.; Silong, S.

    1999-05-01

    Several new complexes of a tridentate ONS Schiff base derived from the condensation of S-benzyldithiocarbazate with salicylaldehyde have been characterised by elemental analyses, molar conductivity measurements, infrared, and electronic spectral studies. The tridentate Schiff base (HONSH) behaves as a dinegatively charged ligand coordinating through the thiolo sulphur, the azomethine nitrogen atom and the hydroxyl oxygen atom. It forms mono-ligand complexes of the general formula, [M(ONS)X], [M = Ni(II), Cu(II), Cr(III), Sb(III), Zn(II), Zr(IV) or U(VI) and X = H 2 O, Cl]. The ligand produced bis-chelated complex with Th(IV) of composition, [Th(ONS) 2 ]. Square-planar structures were proposed for the Ni(II) and Cu(II) complexes. Antimicrobial tests indicated that the Schiff base and five of the metal complexes of Cu(II), Ni(II), U(VI), Zn(II) and Sb(III) were found to be strongly active against bacteria. Ni(II) and Sb(III) complexes were the most effective against Pseudomonas aeruginosa (gram negative) while the Cu(II) complex proved to be the best against Bacillus cereus (gram positive bacteria). Antifungal activities were also noted with the Schiff base and the U(VI) complex. These compounds have shown results against Candida albicans fungi. But none of these compounds were effective against Aspergillus ochraceous fungi. (author)

  9. First light with Trident: multi-platform synthetic quasar spectra

    Science.gov (United States)

    Silvia, Devin W.; Hummels, Cameron B.; Smith, Britton

    2017-01-01

    Observational efforts to better understand the nature of the intergalactic and circumgalactic media have relied heavily on the information encoded in the absorption line systems of quasar spectra. Numerical simulations of large-scale structure and galaxy evolution are well-suited to explore the properties of those same media owing to the relative ease with which one can access physical quantities from complex, three-dimensional data. However, a difficulty arises when one tries to make direct “apple-to-apples” comparisons between observed spectra and simulated data. In an effort to provide a common language capable of linking theory and observation, we announce the release of Trident. Trident is a publicly available software tool that enables the creation of realistic synthetic absorption spectra from virtually all widely-used hydrodynamics simulation codes. Through user-controlled levels of spectral realism, direct comparisons between simulated and observed data become not only possible, but greatly simplified. We present the methods for extracting artificial quasar sightlines and generating spectra as well as early-stage applications of those spectra to intergalactic and circumgalactic absorption line studies.

  10. Group 4 Transition-Metal Complexes of an Aniline–Carbene–Phenol Ligand

    KAUST Repository

    Despagnet-Ayoub, Emmanuelle

    2013-05-24

    Attempts to install a tridentate aniline-NHC-phenol (NCO) ligand on titanium and zirconium led instead to complexes resulting from unexpected rearrangement pathways that illustrate common behavior in carbene-early- transition-metal chemistry. © 2013 American Chemical Society.

  11. Early-transition-metal catalysts with phenoxy-imine-type ligands for the oligomerization of ethylene.

    Science.gov (United States)

    Kinoshita, Shinsuke; Kawamura, Kazumori; Fujita, Terunori

    2011-02-01

    Early-transition-metal complexes incorporating phenoxy-imine-type bidentate and tridentate ligands, after activation, can achieve selective as well as nonselective ethylene oligomerization to produce 1-hexene, linear α-olefins, and vinyl-terminated low-molecular-weight polyethylenes, all with high efficiency. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. New mixed ligand palladium(II) complexes based on the antiepileptic drug sodium valproate and bioactive nitrogen-donor ligands: Synthesis, structural characterization, binding interactions with DNA and BSA, in vitro cytotoxicity studies and DFT calculations

    Science.gov (United States)

    Tabrizi, Leila; Chiniforoshan, Hossein; Tavakol, Hossein

    2015-04-01

    The complexes [Pd(valp)2(imidazole)2] (1), [Pd(valp)2(pyrazine)2] (2) (valp is sodium valproate) have been synthesized and characterized using IR, 1H NMR, 13C{1H} NMR and UV-Vis spectrometry. The interaction of complexes with CT-DNA has been investigated using spectroscopic tools and viscosity measurement. In each case, the association constant (Kb) was deduced from the absorption spectral study and the number of binding sites (n) and the binding constant (K) were calculated from relevant fluorescence quenching data. As a result, a non-covalent interaction between the metal complex and DNA was suggested, which could be assigned to an intercalative binding. In addition, the interaction of 1 and 2 was ventured with bovine serum albumin (BSA) with the help of absorption and fluorescence spectroscopy measurements. Through these techniques, the apparent association constant (Kapp) and the binding constant (K) could be calculated for each complex. Evaluation of cytotoxic activity of the complexes against four different cancer cell lines proved that the complexes exhibited cytotoxic specificity and significant cancer cell inhibitory rate. Moreover, density functional theory (DFT) calculations were employed to provide more evidence about the observed data. The majority of trans isomers were supported not only by energies, but also by the similarity of its calculated IR frequencies, UV adsorptions and NMR chemical shifts to the experimental values.

  13. Hexacoordinated mixed-ligand complexes of vanadium(IV) and copper(II)

    International Nuclear Information System (INIS)

    Islam, M.S.; Motahera Begum; Roy, H.N.; Haroon, S.A.Q.M.

    1996-01-01

    The literature reports simple complexes of metal ions with Schiff bases derived from amino acids. But their mixed-ligand complexes are very rare. Keeping this fact in mind, some new mixed ligand complexes of V IV and Cu II with tridentate Schiff bases derived from glycine, salicylaldehyde and amino bases, e.g. quinoline (Q), isoquinoline (IQ), 2-picoline (2-pic), 4-picoline (4-pic) and pyridine (Py) were prepared and studied. 6 refs., 1 tab

  14. Dual inhibition of topoisomerases I and IIα by ruthenium(II) complexes containing asymmetric tridentate ligands.

    Science.gov (United States)

    Du, Kejie; Liang, Jiewen; Wang, Yi; Kou, Junfeng; Qian, Chen; Ji, Liangnian; Chao, Hui

    2014-12-14

    Five novel ruthenium(II) complexes, [Ru(dtzp)(dppt)](2+) (1), [Ru(dtzp)(pti)](2+) (2), [Ru(dtzp)(ptn)](2+) (3), [Ru(dtzp)(pta)](2+) (4) and [Ru(dtzp)(ptp)](2+) (5) (where dtzp = 2,6-di(thiazol-2-yl)pyridine, dppt = 3-(1,10-phenanthroline-2-yl)-5,6-diphenyl-as-triazine), pti = 3-(1,10-phenanthroline-2-yl)-as-triazino-[5,6-f]isatin, ptn = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]naphthalene, pta = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]acenaphthylene, and ptp = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-phenanthrene), were synthesised and characterised. The structures of complexes 3-5 were determined by X-ray diffraction. The DNA binding behaviours of the complexes were studied by spectroscopic and viscosity measurements. The results suggested that the Ru(II) complexes, except for complex 1, bind to DNA in an intercalative mode. Topoisomerase inhibition and DNA strand passage assay confirmed that Ru(II) complexes 3, 4, and 5 acted as efficient dual inhibitors of topoisomerases I and IIα. In vitro cytotoxicity assays indicated that these complexes exhibited anticancer activity against various cancer cell lines. Ruthenium(ii) complexes were confirmed to preferentially accumulate in the nucleus of cancer cells and induced DNA damage. Flow cytometric analysis and AO/EB staining assays indicated that these complexes induced cell apoptosis. With the loss of the mitochondrial membrane potential, the Ru(ii) complexes induce apoptosis via the mitochondrial pathway.

  15. Rhenium(V) Complexes Containing Mono- and Tridentate Imido ...

    African Journals Online (AJOL)

    NICO

    rhenium dxy orbital. The HOMO and HOMO-16 are localized amongst the rhenium ion, phenoxide oxygen and pna–3 ligand. Accordingly, the transitions assigned to this experimental wave- length can be considered as mixed phenoxide/rhenium LMCT and d-d LF (ligand field) transitions. The experimental absorption band ...

  16. Strong metal-metal coupling in mixed-valent intermediates [Cl(L)Ru(mu-tppz)Ru(L)Cl](+), L = beta-diketonato ligands, tppz=2,3,5,6-tetrakis(2-pyridyl)pyrazine

    Czech Academy of Sciences Publication Activity Database

    Kundu, T.; Schweinfurth, D.; Sarkar, B.; Mondal, T. K.; Fiedler, Jan; Mobin, S. M.; Puranik, V. G.; Kaim, W.; Lahiri, G. K.

    2012-01-01

    Roč. 41, č. 43 (2012), s. 13429-13440 ISSN 1477-9226 R&D Projects: GA AV ČR IAA400400802 Institutional support: RVO:61388955 Keywords : TRIDENTATE BRIDGING LIGAND * DENSITY-FUNCTIONAL THEORY * HYDRAZONE-BASED LIGAND S Subject RIV: CG - Electrochemistry Impact factor: 3.806, year: 2012

  17. Studies on coordination chemistry and bioactivity of complexes of a tridentate ONS Schiff base with some heavier transition metal ions

    International Nuclear Information System (INIS)

    Tarafder, M.T.H.; Tan Mei Lin; Ali, A.M.

    2003-09-01

    A tridentate Schiff base, S-benzyl-β-N-(2-hydroxyphenyl)methylenedithiocarbazate, (HONSH), with a donor sequence of ONS, was synthesized from the condensation of S-benzyldithiocarbazate (SBDTC) with an equimolar amount of 2-hydroxybenzaldehyde in absolute ethanol. The reactions of HONSH with metal ions [La(III), Ce(IV) and Th(IV)] yielded complexes of compositions, [La(ONS)NO 3 .2H 2 O], [Ce(ONS)(NO 3 ) 2 ] and [Th(ONS) 2 ]. The ligands and the complexes were characterized from elemental analyses and spectroscopic measurements. The metal complexes were found to be active against colon cancer cell lines with the CD 50 values of 27.5, 28.4 and 19.3 μg/ml for the La(III), Ce(FV) and Th(IV) complexes, respectively. The La(IH) complex was found to be very active against leukemic cell lines with the CD 50 value of 6.8 μg/ml. (author)

  18. Utilization of LVO $^{-} _ {2} $ species (L 2-is a tridentate ONS donor ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 118; Issue 6. Utilization of LVO 2 − species (L2- is a tridentate ONS donor) as an inorganic analogue of carboxylate group: A journey to a new domain of coordination chemistry. Satyabrata Samanta Subodh Kanti Dutta Muktimoy Chaudhury. Volume 118 Issue 6 ...

  19. TRIDENT-CTR: a two-dimensional transport code for CTR applications

    International Nuclear Information System (INIS)

    Seed, T.J.

    1978-01-01

    TRIDENT-CTR is a two-dimensional x-y and r-z geometry multigroup neutral transport code developed at Los Alamos for toroidal calculations. The use of triangular finite elements gives it the geometric flexibility to cope with the nonorthogonal shapes of many toroidal designs of current interest in the CTR community

  20. Synthesis and Spectroscopic Studies of Axially Ligated Zn(II5,10,15,20-meso-tetra(p-chlorophenylporphyrin with Oxygen and Nitrogen Donors

    Directory of Open Access Journals (Sweden)

    Gauri D. Bajju

    2013-01-01

    Full Text Available Reaction of 5,10,15,20-meso-tetra(p-chlorophenylporphyrin[H2(p-Clpp] with zinc(IIacetate(Zn(OAc2 and phenols results in the formation of corresponding axially ligated zinc(II-meso-tetra(p-chlorophenylporphyrin (X-Zn-t(p-ClPP (X = phenolates and pyridinates. The four-coordinated zinc porphyrin accepts one axial ligand in 1 : 1 molar ratio to form five-coordinated complex, which is purified by column chromatography and characterized by IR spectra, 1H NMR, electronic absorption spectra, elemental analysis, mass spectroscopy, and TGA/DTA studies. IR spectra confirms the appearance of Zn– at 500–400 cm−1, Zn– at 650–570 cm−1 and Zn–O at 650–350 cm−1. 1H NMR spectra show that the protons of the Phenolic ring axially attached to the central metal ion are merged with the protons of the tetraphenyl rings of the porphyrin moiety. Absorption spectra reveal that complexes are accompanied by blue shift (hypsochromic shift for phenolates and red shift (bathchromic shift for pyridinates in comparison with the basic Zporphyrin emission bands. Mass Spectra determine the m/z ratio. The percentage of each element is confirmed by elemental analysis. According to the thermal studies, the complexes have a higher thermal stability and the decomposition temperature of these complexes depends on the axial ligation. The invitro antifungal activity of the complexes synthesized above had been done by disc diffusion method against the pathogen “Fusarium spp.,” which shows that with the increase in the concentration of the complexes, the colony diameter decreases and hence percent inhibition increases.

  1. Coordination chemistry of N-heterocyclic nitrenium-based ligands.

    Science.gov (United States)

    Tulchinsky, Yuri; Kozuch, Sebastian; Saha, Prasenjit; Mauda, Assaf; Nisnevich, Gennady; Botoshansky, Mark; Shimon, Linda J W; Gandelman, Mark

    2015-05-04

    Comprehensive studies on the coordination properties of tridentate nitrenium-based ligands are presented. N-heterocyclic nitrenium ions demonstrate general and versatile binding abilities to various transition metals, as exemplified by the synthesis and characterization of Rh(I) , Rh(III) , Mo(0) , Ru(0) , Ru(II) , Pd(II) , Pt(II) , Pt(IV) , and Ag(I) complexes based on these unusual ligands. Formation of nitrenium-metal bonds is unambiguously confirmed both in solution by selective (15) N-labeling experiments and in the solid state by X-ray crystallography. The generality of N-heterocyclic nitrenium as a ligand is also validated by a systematic DFT study of its affinity towards all second-row transition and post-transition metals (Y-Cd) in terms of the corresponding bond-dissociation energies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Open coordination sites-induced structural diversity of a new series of Cu(II) complexes with tridentate aroylhydrazone Schiff base

    Science.gov (United States)

    Xu, Guohong; Tang, Beibei; Gu, Leilei; Zhou, Pei; Li, Hui

    2016-09-01

    Six Cu(II) complexes containing the NO2 donor tridentate asymmetrical aroylhydrazone ligand (E)-4-hydroxy-N‧-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide (HL), namely, [Cu(L)Cl]·2H2O (1), [Cu(L)(CH3OH)2]·NO3 (2), [Cu(L)(NO3)(H2O)]·H2O (3), [Cu(L)(CH3OH)Cl]·CH3OH (4), [Cu(L)(SCN)(DMF)]·DMF (5) and {[Cu(L)(4,4‧-bipy)]ClO4·4DMF}n (6) have been synthesized and analysized by X-ray singal crystal diffraction. The structures of 1-6 are varied from zero-dimensional (0D) mononuclear complex to one-dimensional (1D) polymer based on the control of solvents, anions or auxiliary ligands, which can occupy the open coordination sites of Cu(II). Different hydrogen bonding interactions can also be observed in these complexes.

  3. Synthesis and characterization of two novel TcO and ReO mixed ligand complexes (3+1 combination, SNS/S) for hypoxia imaging

    International Nuclear Information System (INIS)

    Jaipetch, T.; Pirmettis, I.; Papadopoulos, M.; Nock, B.; Maina, T.; Raptopoulou, C.P.; Terzis, A.; Chiotellis, E.

    1998-01-01

    As part of our project to develop small-size, neutral, mixed ligand oxotechnetium and oxorhenium complexes of the general formula MOL 1 L 2 , we have synthesized and characterized two novel complexes of the general formula MO[EtN(CH 2 CH 2 S) 2 ][p-O 2 NC 6 H 4 S] where M=Re (complex 1) or M=Tc (complex 2) as a new approach for tissue hypoxia imaging. Complex 1 has been synthesized by exchange reaction in equimolar quantities of the tridentate and the monodentate ligand on ReOCl 3 (PPh 3 ) 2 . Only the syn isomer has been isolated and characterized by elemental analysis, IR, UV-vis, and 1 H NMR. Crystal data reveal a trigonal bipyramidal geometry around the metal. The basal plane is defined by the sulfur atoms of the tridentate ligand and the oxygen, while the two apical positions are occupied by the nitrogen of the tridentate ligand and the sulfur atom of the monodentate thiol. Complex 2 is prepared by exchange reaction using Tc-99m-glucoheptonate as precursor and equimolar quantities of the two ligands. Only one complex, the syn isomer, is formed. Its identity is confirmed by comparative HPLC studies with complex 1. (author)

  4. Pinhole aperture point backlighter development experiments on Trident, 9-13, 2001

    International Nuclear Information System (INIS)

    Lanier, N.E.; Murphy, Thomas J.

    2001-01-01

    Pinhole aperture point backlighter (PAPBL) imaging has been used on experiments on Omega, but results have been compromised by large backgrounds. This technique has advantages over traditional area backlighting/pinhole imaging, and the Omega experiments could benefit from this capability, but Omega time is expensive and not the place for developing diagnostic techniques if they can be developed on Trident instead. PAPBL, shot from Direct Drive Cylinder Mix experiments on Omega (DDCYLMIX 00-1, January 18 and 19, 2000). (See LA-UR-00-4187, Post-Shot Report, Direct Drive Cylinder Mix). In this campaign, they used Trident to obtain clean PAPBL images. Having accomplished that, they attempted to replicate the noise environment of Omega by producing hot electrons and having them impinge on material to produce high-energy x-rays similar to those that might be produced by hot electrons impinging on diagnostics or target positioner components on Omega. Backlighter target design was based, to some degree, on that shown by Bullock et al. at the 42nd Annual APS-DPP Meeting in Quebec City, Quebec, Canada, October 23-27, 2000. (A.B. Bullock et al., Bull. Am. Phys. Soc. 45,(7) 359 (2000); A.B. Bullock et al., Rev. Sci. Instrum. 72, 690 (2001).) We accomplished this to some degree and then attempted, with some success, to obtain a good PAPBL image in the presence of this noise. Results of this work suggest methods that might reduce the background noise in Omega PAPBL images. The goals are to obtain a pinhole aperture point backlighter (PAPBL) image on Trident and develop a method to simulate the high-energy background contribution to PAPBL imnages seen on Omega experients in order to allow future experiments to optimize signal-to-noise in PAPBL imaging.

  5. Highly active group 11 metal complexes with α-hydrazidophosphonate ligands.

    Science.gov (United States)

    Salvador-Gil, Daniel; Ortego, Lourdes; Herrera, Raquel P; Marzo, Isabel; Gimeno, M Concepción

    2017-10-17

    α-Hydrazidophosphonates are interesting scaffolds that could combine the biological properties of hydrazones and phosphonyl species, and their coordination properties remain unknown. The coordination chemistry of these ligands towards group 11 metals has been studied. A series of novel gold(i), silver(i) and copper(i) complexes with α-hydrazidophosphonate ligands have been prepared and characterised. The coordination geometries obtained vary from linear to trigonal planar for gold(i) to distorted trigonal planar or tetrahedral for silver(i) and copper(i). Structural characterisation of two silver derivatives shows the ligands in an O^N^O tridentate fashion, with dissimilar bond lengths. These compounds were screened for the in vitro cytotoxic activity against two tumour human cell lines such as HeLa (cervical carcinoma) and A549 (lung carcinoma). The IC 50 values reveal an excellent cytotoxic activity of the metal complexes compared with the α-hydrazidophosphonate ligands alone and cisplatin.

  6. Trident pair production in plane waves: Coherence, exchange, and spacetime inhomogeneity

    Science.gov (United States)

    Dinu, Victor; Torgrimsson, Greger

    2018-02-01

    We study the trident process in inhomogeneous plane-wave background fields. We obtain compact analytical expressions for all terms in the probability, including the exchange part, for an arbitrarily shaped plane wave. We evaluate the probability numerically using complex deformation of light-front time integrals and derive various analytical approximations. Our results provide insights into the importance of the one-step and exchange parts of the probability relative to the two-step process, and into the convergence to the locally constant field approximation.

  7. The Trident Scholar Program: Year-Long Undergraduate Research Projects at the United States Naval Academy

    Science.gov (United States)

    Katz-Stone, D. M.; Campbell, D. T.

    2000-05-01

    The Trident Scholar Program allows undergraduate students at the U.S. Naval Academy to carry out advanced-level research in their senior year. This program was begun in 1963 and has provided an important opportunity for the most elite students, with five to fifteen students out of a class of a thousand participating each year. The program gives students the opportunity to explore all aspects of scientific research. First, the prospective scholar must write a proposal for the project. The student defends the proposal in front of two committees: a division-level committee as well as an academy-wide committee. Finally, the project must gain approval from the Academic Dean and Provost. Once approved, the Trident Scholar may be awarded a small budget and is released from some course credits. In addition, the academy-wide committee makes on-sight inspections midyear. At the end of the year, each Trident Scholar must write a professional-quality paper, create a display presentation and give an oral presentation to the whole Academy. With these goals in mind, MIDN Campbell decided to pursue a hands-on project using the newly renovated observatory. He found a project that was both scientifically interesting and doable on a short timescale. An Earth impact with an asteroid has potentially devastating consequences. In order to avoid global destruction, astronomers have been attempting to map out the orbits of all possibly hazardous Near-Earth Asteroids (NEAs) for the past two decades. Although there are a number of astronomers devoted to discovering new NEAs, there are very few who are tracking these discoveries, therefore many recently identified NEAs are routinely lost. Therefore, a Trident Scholar Project tracking NEAs is both a service to the astronomy community as well as an important experience for the student. MIDN Campbell completed his scientific goals, and along the way he improved the observatory at the U. S. Naval Academy. Most importantly, this experience has

  8. Characterization and application of a laser-driven intense pulsed neutron source using Trident

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, Sven C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-25

    A team of Los Alamos researchers supported a final campaign to use the Trident laser to produce neutrons, contributed their multidisciplinary expertise to experimentally assess if laser-driven neutron sources can be useful for MaRIE. MaRIE is the Laboratory’s proposed experimental facility for the study of matter-radiation interactions in extremes. Neutrons provide a radiographic probe that is complementary to x-rays and protons, and can address imaging challenges not amenable to those beams. The team's efforts characterize the Laboratory’s responsiveness, flexibility, and ability to apply diverse expertise where needed to perform successful complex experiments.

  9. Unexpected rearrangements in the synthesis of an unsymmetrical tridentate dianionic N-heterocyclic carbene

    KAUST Repository

    Despagnet-Ayoub, Emmanuelle

    2013-01-01

    Starting from the same ethylenediamine species, three valuable carbene precursors were synthesized under differing conditions: a tridentate dianionic N-heterocyclic carbene bearing an aniline, a phenol and a central dihydroimidazolium salt, its benzimidazolium isomer by intramolecular rearrangement and a dicationic benzimidazolium-benzoxazolium salt by changing the Brønsted acid from HCl to HBF4. A DFT study was performed to understand the rearrangement pathway. The structure of a bis[(NCO)carbene] zirconium complex was determined. © 2013 The Royal Society of Chemistry.

  10. Synthesis, spectroscopic, coordination and biological activities of some transition metal complexes containing ONO tridentate Schiff base ligand.

    Science.gov (United States)

    Belal, A A M; El-Deen, I M; Farid, N Y; Zakaria, Rosan; Refat, Moamen S

    2015-01-01

    The main target of this paper is to get an interesting data for the preparation and characterizations of metal oxide (MO) nanoparticles using H2L Schiff base complexes as precursors through the thermal decomposition procedure. Five Schiff base complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions were synthesized from 2-[(2-hydroxy-naphthalen-1-ylmethylene)-amino]-benzoic acid new adduct (H2L). Theses complexes were characterized using infrared, electronic, mass and (1)H NMR spectroscopic techniques. The elemental analysis data was confirmed that the stoichiometry of (metal:H2L) is 1:1 molar ratio. The molar conductance indicates that all of complexes are non electrolytic. The general chemical formulas of these complexes is [M(L)(NH3)]·nH2O. All complexes are tetrahedral geometry. The thermal decomposition behavior of H2L hydrated and anhydrous complexes has been discussed using thermogravimetric analysis (TG/DTG) and differential thermal analyses (DTA) under nitrogen atmosphere. The crystalline phases of the reaction products were checked using X-ray diffractometer (XRD) and scanning electron microscopy (SEM). Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Re(VII) and Tc(VII) trioxo complexes stabilized by tridentate ligands and their potential use as radiopharmaceuticals

    NARCIS (Netherlands)

    Hahn, Eva M.; Casini, Angela; Kuehn, Fritz E.

    2014-01-01

    Tc(VII) and Re(VII) trioxo complexes are currently arousing interest because of their potential use as radiopharmaceuticals due to their hydrophilic character and stability in a biological environment. The radioactive isotopes Tc-99m and Re-188 are readily obtained from commercially available

  12. A THIOLATO-BRIDGED OCTANUCLEAR COPPER(I,II MIXED- VALENCE COMPLEX WITH N,N,S-TRIDENTATE LIGAND

    Directory of Open Access Journals (Sweden)

    Takanori Kotera

    2007-06-01

    Full Text Available Thiolato-bridged complex [CuI4CuII4(peampt4Cl8]·2H2O (Hpeampt = 1-(2-pyridylethylamino methylpropane-2-thiol has been synthesized and characterized by the elemental analysis, IR and UV-vis spectroscopies and magnetic susceptibility measurement. The X-ray crystal structure analysis of this complex shows a localized mixed-valence octanuclear cage structure made up of four trigonal-bipyramidal CuIIN2SCl2, two trigonal CuIS2Cl, and two tetrahedral CuIS2Cl2 coordination sites. Temperature dependence of magnetic susceptibility (4.5— 300 K shows that a fairly strong antiferromagnetic interaction is operating between the four CuII ions.

  13. Synthesis, structures, and spectroscopic properties of Hg(II) complexes of bidentate NN and tridentate NNO Schiff-base ligands

    OpenAIRE

    Basu Baul, Tushar S; Kundu, Sajal; Höpfl, Herbert; Tiekink, Edward R T; Linden, Anthony

    2014-01-01

    Reactions of HgX2 (X = Cl, N3, NO3) with (E)-2-methoxy-N-(pyridin-2-ylmethylene)aniline (L1) and (E)-4-methoxy-N-(pyridin-2-ylmethylene)aniline (L2) in ethanol gave two monomers, [HgL1(Cl)2] (1) and [HgL2(NO3)2(DMSO)] (5), and three coordination polymers, {[HgL1(N3)2]2·Hg(N3)2}n (2), [HgL2(Cl)2]n (3), and [HgL2(NO3)2]n·nCH3CN (4). Compounds 1–5 were characterized by elemental analysis, IR, NMR spectroscopy, and single-crystal X-ray diffraction. The common feature of monomeric 1 and 5 is the p...

  14. A new tridentate Schiff base Cu(II) complex: synthesis, experimental and theoretical studies on its crystal structure, FT-IR and UV-Visible spectra.

    Science.gov (United States)

    Saheb, Vahid; Sheikhshoaie, Iran; Setoodeh, Nasim; Rudbari, Hadi Amiri; Bruno, Giuseppe

    2013-06-01

    A new Cu(II) complex [Cu(L)(NCS)] has been synthesized, using 1-(N-salicylideneimino)-2-(N,N-methyl)-aminoethane as tridentate ONN donor Schiff base ligand (HL). The dark green crystals of the compound are used for single-crystal X-ray analysis and measuring Fourier Transform Infrared (FT-IR) and UV-Visible spectra. Electronic structure calculations at the B3LYP and MP2 levels of theory are performed to optimize the molecular geometry and to calculate the UV-Visible and FT-IR spectra of the compound. Vibrational assignments and analysis of the fundamental modes of the compound are performed. Time-dependent density functional theory (TD-DFT) method is used to calculate the electronic transitions of the complex. A scaling factor of 1.015 is obtained for vibrational frequencies computed at the B3LYP level using basis sets 6-311G(d,p). It is found that solvent has a profound effect on the electronic absorption spectrum. The UV-Visible spectrum of the complex recorded in DMSO and DMF solution can be correctly predicted by a model in which DMSO and DMF molecules are coordinated to the central Cu atom via their oxygen atoms. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. Molybdenum complexes of biochemical interest. New coordination complexes of oxomolybdenum(V) with the tridentate ONO donor Schiff bases derived from salicylaldehydes and ethanolamine

    Energy Technology Data Exchange (ETDEWEB)

    Syamal, A.; Niazi, M.A.B.

    1985-02-01

    New oxomolybdenum(V) complexes MoOClL (where LH/sub 2/ = Schiff base) derived from ethanolamine and salicylaldehyde, 5-chlorosalicylaldehyde, 5-bromosalicylaldehyde, 5-nitrosalicylaldehyde, 3-ethoxysalicylaldehyde and 2-hydroxy-1-naphthaldehyde have been synthesized and characterised by elemental analyses, conductance, molecular weight, I.R. and electronic spectra and magnetic measurements. The Schiff bases behave as dibasic tridentate ONO donor ligands. The complexes are non-electrolytes and dimers. The complexes exhibit subnormal magnetic moments and are involved in antiferromagnetic exchange with S = 0 ground state. The complexes exhibit electronic spectral bands at ca. 13000 and ca. 17000 cm/sup -1/ due to the transitions dsub(xy)- > dsub(xz,yz) (/sup 2/B/sub 2/- > /sup 2/E) and dsub(xy)- > dsub(x2-y2) (/sup 2/B/sub 2/- > /sup 2/B/sub 1/), respectively. The ..nu..(Mo = O) frequency of the complexes is observed in the 900-970 cm/sup -1/ region. On the basis of the magnetic susceptibility, I.R. and molecular weight data a dimetallic structure with alcoholic oxygen atoms as the bridging atoms is suggested.

  16. Solvent extraction of Am(III) and Eu(III) from nitrate solution using synergistic mixtures of N-tridentate heterocycles and chlorinated cobalt dicarbollide

    International Nuclear Information System (INIS)

    Krejzler, J.; Narbutt, J.; Foreman, M.R.S.J.; Hudson, M.J.; Casensky, B.; Madic, C.

    2006-01-01

    The separation by solvent extraction of 241 Am(III) from 152 Eu(III), in 1 M NaNO 3 weakly acidic (pH 4) aqueous solutions, into dilute (ca. 10 -2 M) solutions of triazinyl bipyridine derivatives (diethylhemi-BTP or di(benzyloxyphenyl)hemi-BTP) and chlorinated cobalt dicarbollide (COSAN) in 1-octanol or nitrobenzene has been studied. The N-tridentate heterocyclic ligands, which are selective for Am(III) over Eu(III), secured efficient separation of the two metal ions, while COSAN, strongly hydrophobic and fully dissociated in polar diluents, enhanced the extraction of the metal ions by ion-pair formation. Molecular interactions between the two co-extractants, observed at higher concentrations, led to the precipitation of their 1:1 molecular adduct. In spite of that, efficient separations of Am and Eu ions were attained, with high separation factors, SF(Am/Eu) of 40 and even 60, provided the concentration of hemi-BTP was significantly greater than that of COSAN. Excess COSAN concentrations caused an antagonistic effect, decreasing both the distribution ratio of the metal ions and their separation factor. (author)

  17. Nanoscale control of competing interactions and geometrical frustration in a dipolar trident lattice.

    Science.gov (United States)

    Farhan, Alan; Petersen, Charlotte F; Dhuey, Scott; Anghinolfi, Luca; Qin, Qi Hang; Saccone, Michael; Velten, Sven; Wuth, Clemens; Gliga, Sebastian; Mellado, Paula; Alava, Mikko J; Scholl, Andreas; van Dijken, Sebastiaan

    2017-10-17

    Geometrical frustration occurs when entities in a system, subject to given lattice constraints, are hindered to simultaneously minimize their local interactions. In magnetism, systems incorporating geometrical frustration are fascinating, as their behavior is not only hard to predict, but also leads to the emergence of exotic states of matter. Here, we provide a first look into an artificial frustrated system, the dipolar trident lattice, where the balance of competing interactions between nearest-neighbor magnetic moments can be directly controlled, thus allowing versatile tuning of geometrical frustration and manipulation of ground state configurations. Our findings not only provide the basis for future studies on the low-temperature physics of the dipolar trident lattice, but also demonstrate how this frustration-by-design concept can deliver magnetically frustrated metamaterials.Artificial magnetic nanostructures enable the study of competing frustrated interactions with more control over the system parameters than is possible in magnetic materials. Farhan et al. present a two-dimensional lattice geometry where the frustration can be controlled by tuning the unit cell parameters.

  18. Synthesis and Characterization of a Triphos Ligand Derivative and the Corresponding Pd II Complexes: Triphos Ligand Derivative and Corresponding Pd II Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Deanna L.; Boro, Brian J.; Grubel, Katarzyna; Helm, Monte L.; Appel, Aaron M.

    2015-11-16

    The synthesis of the new bis(2-(diphenylphosphino)ethyl)methylhydroxyphosphine tridentate phosphine ligand, LCH2OH/Ph, is reported. The ligand reacts with [Pd(Cl)2(PhCN)2 to form [Pd(LCH2OH/Ph)Cl]Cl. Exchange of the chloride ions for triflate (OTf–) using AgOTf yielded pure [Pd(LCH2OH/Ph)OTf]OTf. In addition to spectral characterization the free ligand, LCH2OH/Ph, and Pd(II) complex, [Pd(LCH2OH/Ph)OTf]OTf, are structurally characterized. This research was supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences, and Geosciences. Pacific Northwest National Laboratory is a multiprogram national laboratory operated by Battelle for DOE.

  19. Nuclease Activity via Self-Activation and Anticancer Activity of Mononuclear Copper(II) Complex: Novel Role of Tertiary Butyl Group in the Ligand Frame

    OpenAIRE

    Ghosh, Kaushik; Kumar, Pramod; Mohan, Varun; Singh, Udai P.; Kasiri, Sahba; Mandal, Subhrangsu S.

    2012-01-01

    Copper complex [Cu(tBuPhimp)(Cl)] (1) derived from tridentate ligand tBuPhimpH having N2O donors was synthesized and molecular structure was determined. Phenoxyl radical complex was generated in solution at room temperature using Ce(IV) salt. Nuclease activity and anticancer activity of 1 was investigated. Roles of tert-butyl group and singlet oxygen in DNA cleavage activity were also discussed.

  20. Multipurpose 10 in. manipulator-based optical telescope for Omega and the Trident laser facilities

    International Nuclear Information System (INIS)

    Oertel, J.A.; Murphy, T.J.; Berggren, R.R.; Faulkner, J.; Schmell, R.; Little, D.; Archuleta, T.; Lopez, J.; Velarde, J.; Horton, R.F.

    1999-01-01

    We have recently designed and are building a telescope which acts as an imaging light collector relaying the image to an optical table for experiment dependent analysis and recording. The expected primary use of this instrument is a streaked optical pyrometer for witness plate measurements of the hohlraum drive temperature. The telescope is based on the University of Rochester close-quote s 10 in. manipulator (TIM) which allows compatibility between Omega, Trident, and the NIF lasers. The optics capture a f/7 cone of light, have a field of view of 6 mm, have a spatial resolution of 5 - 7 μm per line pair at the object plane, and are optimized for operation at 280 nm. The image is at a magnification of 11.7x, which is convenient for many experiments, but can be changed using additional optics that reside outside the TIM. copyright 1999 American Institute of Physics

  1. Selectivity in the aggregates of the chiral organolithium N-Boc-2-lithiopiperidine with a chiral ligand: a DFT study

    Science.gov (United States)

    Ince, Hasan H.; Dedeoglu, Burcu; Gul, Seref; Aviyente, Viktorya; Coldham, Iain

    2012-03-01

    In this paper the aggregates of the chiral organolithium N-Boc-2-lithiopiperidine [Boc=CO2C(CH3)3], which play an important role in the formation of chiral 2-substituted piperidines found in many alkaloid structures and medicinal compounds, have been investigated within the framework of Density Functional Theory (DFT) calculations. In the complex structures, the lithium atoms are tetra-coordinated, the diaminoalkoxide ligand is tridentate to one lithium atom and forms a chelate with the substrate which is stabilized by the solvent diethyl ether. The same type of bonding was observed for all the different ligand-bound structures; for ligands 6 and 7, which have bulky substituents, selectivity was in agreement with experiment. The results shed light on the microscopic structures of these species and suggest a potential ligand, 11, to yield high enantioselectivity.

  2. Sterically hindered complexes of platinum(II) with planar heterocyclic nitrogen donors. A novel complex with 1-methyl-cytosine has a spectrum of activity different from cisplatin and is able of overcoming acquired cisplatin resistance.

    Science.gov (United States)

    Margiotta, Nicola; Natile, Giovanni; Capitelli, Francesco; Fanizzi, Francesco P; Boccarelli, Angelina; De Rinaldis, Pietro; Giordano, Domenico; Coluccia, Mauro

    2006-11-01

    A very interesting series of water soluble platinum compounds violating some of the classical structure-activity relationships, but still showing antitumor activity, was reported by Hollis and collaborators some 25 years ago [L.S. Hollis, A.R. Amundsenm, E.W. Stern. J. Med. Chem. 32 (1989) 128-136]. The compounds, having formula [PtClA(2)L](+) (A(2)=two monodentate or a bidentate amine, L=a secondary or tertiary amine or a N-donor heterocycle), were characterized by a positive charge and three non-labile N-donor ligands. We have extended the investigation to analogous compounds in which 2,9-dimethyl-1,10-phenanthroline has taken the place of the A(2) ligand(s) and L is 2-picoline (1), 6-amino-2-picoline (2), or 1-methyl-cytosine (3). The X-ray analysis of 2 has revealed a bow-like distortion of the phenanthroline plane, a sloping of the phenanthroline plane with respect to the coordination plane, and an overall shielding of the metallic core by the ortho substituents of the phenanthroline and pyridine ligands. In vitro grow inhibition assays have been performed on the most water soluble complex 3. The results indicate that this complex is characterized by a potent growth inhibitory activity with mean IC(50) value (in a panel of 11 human tumor cell lines) of 1.1 microM to be compared with a mean value of 3.8 microM for cisplatin. The same compound also appears to completely overcome the acquired cisplatin resistance stemming from reduced uptake or a multifocal mechanism, thus pointing to a mechanism of action distinctly different from that of cisplatin.

  3. Characterization, molecular modeling and antimicrobial activity of metal complexes of tridentate Schiff base derived from 5-acetyl-4-hydroxy-2H-1,3-thiazine-2,6(3H)-dione and 2-aminophenol

    Science.gov (United States)

    Adly, Omima M. I.

    Metal complexes of Ni(II), Co(II), Cd(II), VO(IV) and UO2(VI) as well as several Cu(II) salts, including Cl,NO3-,AcO,ClO4- and SO4-2 with a tridentate O2N donor Schiff base ligand (H2L), synthesized by condensation of 5-acetyl-4-hydroxy-2H-1,3-thiazine-2,6(3H)-dione with 2-aminophenol, were prepared and characterized on the basis of elemental analyses, spectral, magnetic, molar conductance and thermal gravimetric analysis. Square planar, tetrahedral and octahedral geometries have been assigned to the prepared complexes. Molecular parameters of the ligand and its metal complexes have been calculated and correlated with the experimental data, and the changes of bond lengths are linearly correlated with IR data. The antimicrobial activities of the synthesized compounds were tested in vitro against the sensitive organisms Staphylococcus aureus as Gram positive bacteria, Proteus vulgaris as Gram negative bacteria and Candida albicans as fungus strain, and the results are discussed.

  4. Gamma radiolysis of the highly selective ligands CyMe{sub 4}BTBP and CyMe{sub 4}BTPhen: Qualitative and quantitative investigation of radiolysis product

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, H.; Wilden, A.; Modolo, G.; Bosbach, D. [Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research IEK-6: Nuclear Waste Management, 52425 Juelich (Germany); Santiago-Schuebel, B.; Hupert, M. [Forschungszentrum Juelich GmbH, Central Institute for Engineering, Analytics - ZEA-3, 52425 Juelich (Germany); Svehla, J.; Gruner, B. [Institute of Inorganic Chemistry, Academy of Sciences, Hlavni 1001, 25068 Husinec-Rez (Czech Republic); Ekberg, C. [Department of Chemical and Biochemical Engineering, Chalmers University of Technology, 41296 Gothenburg (Sweden)

    2016-07-01

    The highly selective nitrogen donor ligands CyMe{sub 4}BTBP and CyMe4{sub B}TPhen where γ-irradiated under identical experimental conditions in 1-octanol with and without contact to nitric acid solution. Subsequently, solvent extraction experiments were carried out to evaluate the stability of the extractants against γ-radiation monitoring Am(III) and Eu(III) distribution ratios. Generally, decreasing distribution ratios with increasing absorbed dose were detected for both molecules. Furthermore, qualitative mass spectrometric analyses were performed and ligand concentrations were determined by HPLC-DAD after irradiation to investigate the radiolysis mechanism. An exponential decrease with increasing absorbed dose was observed for both ligands with a faster rate for CyMe{sub 4}BTPhen. Main radiolysis products indicated the addition of one or more diluent molecules (1-octanol) to the ligand via prior production of α-hydroxy-octyl radicals from diluent radiolysis. The addition of nitric acid during the irradiation lead to a remarkable stabilization of the system, as the extraction of Am(III) and Eu(III) did not change significantly over the whole examined dose range. Quantification of the remaining ligand concentration on the other hand showed decreasing concentrations with increasing absorbed dose. The stabilization of D values is therefore explained by the formation of 1-octanol addition products which are also able to extract the studied metal ions. (authors)

  5. Gamma radiolysis of the highly selective ligands CyMe4BTBP and CyMe4BTPhen: Qualitative and quantitative investigation of radiolysis product

    International Nuclear Information System (INIS)

    Schmidt, H.; Wilden, A.; Modolo, G.; Bosbach, D.; Santiago-Schuebel, B.; Hupert, M.; Svehla, J.; Gruner, B.; Ekberg, C.

    2016-01-01

    The highly selective nitrogen donor ligands CyMe 4 BTBP and CyMe4 B TPhen where γ-irradiated under identical experimental conditions in 1-octanol with and without contact to nitric acid solution. Subsequently, solvent extraction experiments were carried out to evaluate the stability of the extractants against γ-radiation monitoring Am(III) and Eu(III) distribution ratios. Generally, decreasing distribution ratios with increasing absorbed dose were detected for both molecules. Furthermore, qualitative mass spectrometric analyses were performed and ligand concentrations were determined by HPLC-DAD after irradiation to investigate the radiolysis mechanism. An exponential decrease with increasing absorbed dose was observed for both ligands with a faster rate for CyMe 4 BTPhen. Main radiolysis products indicated the addition of one or more diluent molecules (1-octanol) to the ligand via prior production of α-hydroxy-octyl radicals from diluent radiolysis. The addition of nitric acid during the irradiation lead to a remarkable stabilization of the system, as the extraction of Am(III) and Eu(III) did not change significantly over the whole examined dose range. Quantification of the remaining ligand concentration on the other hand showed decreasing concentrations with increasing absorbed dose. The stabilization of D values is therefore explained by the formation of 1-octanol addition products which are also able to extract the studied metal ions. (authors)

  6. TRIDENT: a two-dimensional, multigroup, triangular mesh discrete ordinates, explicit neutron transport code

    International Nuclear Information System (INIS)

    Seed, T.J.; Miller, W.F. Jr.; Brinkley, F.W. Jr.

    1977-03-01

    TRIDENT solves the two-dimensional-multigroup-transport equations in rectangular (x-y) and cylindrical (r-z) geometries using a regular triangular mesh. Regular and adjoint, inhomogeneous and homogeneous (k/sub eff/ and eigenvalue searches) problems subject to vacuum, reflective, white, or source boundary conditions are solved. General anisotropic scattering is allowed and anisotropic-distributed sources are permitted. The discrete-ordinates approximation is used for the neutron directional variables. An option is included to append a fictitious source to the discrete-ordinates equations that is defined such that spherical-harmonics solutions (in x-y geometry) or spherical-harmonics-like solutions (in r-z geometry) are obtained. A spatial-finite-element method is used in which the angular flux is expressed as a linear polynomial in each triangle that is discontinous at triangle boundaries. Unusual Features of the program: Provision is made for creation of standard interface output files for S/sub N/ constants, angle-integrated (scalar) fluxes, and angular fluxes. Standard interface input files for S/sub N/ constants, inhomogeneous sources, cross sections, and the scalar flux may be read. Flexible edit options as well as a dump and restart capability are provided

  7. Results from colliding magnetized plasma jet experiments executed at the Trident laser facility

    Science.gov (United States)

    Manuel, M. J.-E.; Rasmus, A. M.; Kurnaz, C. C.; Klein, S. R.; Davis, J. S.; Drake, R. P.; Montgomery, D. S.; Hsu, S. C.; Adams, C. S.; Pollock, B. B.

    2015-11-01

    The interaction of high-velocity plasma flows in a background magnetic field has applications in pulsed-power and fusion schemes, as well as astrophysical environments, such as accretion systems and stellar mass ejections into the magnetosphere. Experiments recently executed at the Trident Laser Facility at the Los Alamos National Laboratory investigated the effects of an expanding aluminum plasma flow into a uniform 4.5-Tesla magnetic field created using a solenoid designed and manufactured at the University of Michigan. Opposing-target experiments demonstrate interesting collisional behavior between the two magnetized flows. Preliminary interferometry and Faraday rotation measurements will be presented and discussed. This work is funded by the U.S Department of Energy, through the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-NA0001840. Support for this work was provided by NASA through Einstein Postdoctoral Fellowship grant number PF3-140111 awarded by the Chandra X-ray Center, which is operated by the Astrophysical Observatory for NASA under contract NAS8-03060.

  8. Transition metal complexes with thiosemicarbazide-based ligands. Part46. Synthesis and physico-chemical characterization of mixed ligand cobalt(III-complexes with salicylaldehyde semi-, thiosemi- and isothiosemicarbazone and pyridine

    Directory of Open Access Journals (Sweden)

    VUKADIN M. LEOVAC

    2003-12-01

    Full Text Available Mixed ligand octahedral cobalt(III complexes with the tridentate salicylaldehyde semi-, thiosemi- and isothiosemicarbazone and pyridine of general formula [CoIII(L11-3(py3]X (H2L1 = salicylaldehyde semicarbazone, X = [CoIICl3(py]-, ClO4- . H2O, I- . 0.5 I2; H2L2 = salicylaldehyde thiosemicarbazone, X = [CoIICl3(py]-, [CoIIBr3(py]-, ClO4- . H2O, I3-; H2L3 = salicylaldehyde S-methylisothiosemicarbazone, X = [ CoIIBr3(py ]-, ClO4- . H2O, BF4- were synthesized. The tridentate coordination of all the three dianionic forms of the ligands involves the phenol oxygen, hydrazine nitrogen and the chalcogen (O or S in case of salicylaldehyde semi-, thiosemicarbazone and the terminal nitrogen atom in the case of isothiosemicarbazone. For all the complexes, a meridial octahedral arrangement is proposed, which is a consequence of the planarity of the chelate ligand. The compounds were characterized by elemental analysis, molar conductivity, magnetic susceptibility, IR and electronic absorption spectra. The thermal decomposition of the complexes was investigated by thermogravimetry, coupled TG-MS measurements and DSC.

  9. Syntheses and catalytic oxotransfer activities of oxo molybdenum(vi) complexes of a new aminoalcohol phenolate ligand.

    Science.gov (United States)

    Hossain, M K; Haukka, M; Sillanpää, R; Hrovat, D A; Richmond, M G; Nordlander, E; Lehtonen, A

    2017-05-30

    The new aminoalcohol phenol 2,4-di-tert-butyl-6-(((2-hydroxy-2-phenylethyl)amino)methyl)phenol (H2L) was prepared by a facile solvent-free synthesis and used as a tridentate ligand for new cis-dioxomolybdenum(vi)(L) complexes. In the presence of a coordinating solvent (DMSO, MeOH, pyridine), the complexes crystallise as monomeric solvent adducts while in the absence of such molecules, a trimer with asymmetric Mo[double bond, length as m-dash]O→Mo bridges crystallises. The complexes can catalyse epoxidation of cis-cyclooctene and sulfoxidation of methyl-p-tolylsulfide, using tert-butyl hydroperoxide as oxidant.

  10. Ruthenium(II) bipyridine complexes bearing new keto-enol azoimine ligands: synthesis, structure, electrochemistry and DFT calculations.

    Science.gov (United States)

    Al-Noaimi, Mousa; Awwadi, Firas F; Mansi, Ahmad; Abdel-Rahman, Obadah S; Hammoudeh, Ayman; Warad, Ismail

    2015-01-25

    The novel azoimine ligand, Ph-NH-N=C(COCH3)-NHPh(C≡CH) (H2L), was synthesized and its molecular structure was determined by X-ray crystallography. Catalytic hydration of the terminal acetylene of H2L in the presence of RuCl3·3H2O in ethanol at reflux temperature yielded a ketone (L1=Ph-N=N-C(COCH3)=N-Ph(COCH3) and an enol (L2=Ph-N=N-C(COCH3)=N-PhC(OH)=CH2) by Markovnikov addition of water. Two mixed-ligand ruthenium complexes having general formula, trans-[Ru(bpy)(Y)Cl2] (1-2) (where Y=L1 (1) and Y=L2 (2), bpy is 2.2'-bipyrdine) were achieved by the stepwise addition of equimolar amounts of (H2L) and bpy ligands to RuCl3·3H2O in absolute ethanol. Theses complexes were characterized by elemental analyses and spectroscopic (IR, UV-Vis, and NMR (1D (1)H NMR, (13)C NMR, (DEPT-135), (DEPT-90), 2D (1)H-(1)H and (13)C-(1)H correlation (HMQC) spectroscopy)). The two complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 604 mV vs. ferrocene/ferrocenium (Cp2Fe(0/+)) couple along with one electron ligand reduction at -1010 mV. The crystal structure of complex 1 showed that the bidentate ligand L1 coordinates to Ru(II) by the azo- and imine-nitrogen donor atoms. The complex adopts a distorted trans octahedral coordination geometry of chloride ligands. The electronic spectra of 1 and 1+ in dichloromethane have been modeled by time-dependent density functional theory (TD-DFT). Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Synthetic routes to mixed-ligand cobalt(III) dithiocarbamato complexes containing imidazole, amine and pyridine donors and the X-ray crystal structure of a cobalt(III) bis(dithiocarbamato) histamine complex.

    Science.gov (United States)

    Hodgson, Michael C; Brothers, Penelope J; Clark, George R; Ware, David C

    2008-04-01

    The binuclear cobalt complex [Co(2)(Me(2)dtc)(5)](+) reacts with a range of nitrogen donor ligands L' or L'' to form an equimolar mixture of Co(Me(2)dtc)(3) and the mixed-ligand complexes [Co(Me(2)dtc)(2)(L')(2)](+) or [Co(Me(2)dtc)(2)(L'')](+), where (L')(2) is two monodentate ligands and (L'') is one bidentate ligand. The complexes prepared by this route contain the monodentate ligands L'=1-methyl-imidazole, 1-methyl-5-nitro-imidazole and benzimidazole, all of which coordinate to cobalt through an imidazole nitrogen atom. Symmetrical bidentate ligand complexes contain the bisimidazole L''=2,2'-bis(4,5-dimethylimidazole), the diamine L''=1,2-diaminobenzene and the pyridine donors L''=2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine and 1,10-phenanthroline. Two examples of complexes with unsymmetrical bidentate imidazole-amine donors were prepared in which L''=4-(2-aminoethyl)imidazole (histamine) and 2-aminomethylbenzimidazole. All new complexes were fully characterised, and the X-ray crystal structure of the histamine complex [Co(Me(2)dtc)(2)(hist)]ClO(4) is also reported.

  12. Boosting Vis/NIR Charge-Transfer Absorptions of Iron(II) Complexes by N-Alkylation and N-Deprotonation in the Ligand Backbone.

    Science.gov (United States)

    Mengel, Andreas K C; Bissinger, Christian; Dorn, Matthias; Back, Oliver; Förster, Christoph; Heinze, Katja

    2017-06-12

    Reversing the metal-to-ligand charge transfer ( 3 MLCT)/metal-centered ( 3 MC) excited state order in iron(II) complexes is a challenging objective, yet would finally result in long-sought luminescent transition-metal complexes with an earth-abundant central ion. One approach to achieve this goal is based on low-energy charge-transfer absorptions in combination with a strong ligand field. Coordinating electron-rich and electron-poor tridentate oligopyridine ligands with large bite angles at iron(II) enables both low-energy MLCT absorption bands around 590 nm and a strong ligand field. Variations of the electron-rich ligand by introducing longer alkyl substituents destabilizes the iron(II) complex towards ligand substitution reactions while hardly affecting the optical properties. On the other hand, N-deprotonation of the ligand backbone is feasible and reversible, yielding deep-green complexes with charge-transfer bands extending into the near-IR region. Time-dependent density functional theory calculations assign these absorption bands to transitions with dipole-allowed ligand-to-ligand charge transfer character. This unique geometric and electronic situation establishes a further regulating screw to increase the energy gap between potentially emitting charge-transfer states and the non-radiative ligand field states of iron(II) dyes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Ruthenium(II) carbonyl compounds with the 4'-chloro-2,2':6',2''-terpyridine ligand.

    Science.gov (United States)

    Tatikonda, Rajendhraprasad; Haukka, Matti

    2017-04-01

    Two ruthenium carbonyl complexes with the 4'-chloro-2,2':6',2''-terpyridine ligand (tpy-Cl, C 15 H 10 ClN 3 ), i.e. [RuCl(tpy-Cl)(CO) 2 ][RuCl 3 (CO) 3 ] (I) [systematic name: cis -di-carbonyl-chlorido(4'-chloro-2,2':6',2''-terpyridine-κ 3 N )ruthenium(II) fac -tricarbonyltri-chlorido-ruthenate(II)], and [RuCl 2 (tpy-Cl)(CO) 2 ] (II) [ cis -dicarbonyl- trans -di-chlorido(4'-chloro-2,2':6',2''-terpyridine-κ 2 N 1 , N 1' )ruthenium(II)], were synthesized and characterized by single-crystal X-ray diffraction. The Ru II atoms in both centrosymmetric structures (I) and (II) display similar, slightly distorted octa-hedral coordination spheres. The coordination sphere in the complex cation in compound (I) is defined by three N atoms of the tridentate tpy-Cl ligand, two carbonyl carbon atoms and one chlorido ligand; the charge is balanced by an octa-hedral [Ru(CO) 3 Cl 3 ] - counter-anion. In the neutral compound (II), the tpy-Cl ligand coordinates to the metal only through two of its N atoms. The coordination sphere of the Ru II atom is completed by two carbonyl and two chlorido ligands. In the crystal structures of both (I) and (II), weak C-H⋯Cl inter-actions are observed.

  14. Ligands in PSI structures

    International Nuclear Information System (INIS)

    Kumar, Abhinav; Chiu, Hsiu-Ju; Axelrod, Herbert L.; Morse, Andrew; Elsliger, Marc-André; Wilson, Ian A.; Deacon, Ashley

    2010-01-01

    A survey of the types and frequency of ligands that are bound to PSI structures is analyzed as well as their utility in functional annotation of previously uncharacterized proteins. Approximately 65% of PSI structures report some type of ligand(s) that is bound in the crystal structure. Here, a description is given of how such ligands are handled and analyzed at the JCSG and a survey of the types, variety and frequency of ligands that are observed in the PSI structures is also compiled and analyzed, including illustrations of how these bound ligands have provided functional clues for annotation of proteins with little or no previous experimental characterization. Furthermore, a web server was developed as a tool to mine and analyze the PSI structures for bound ligands and other identifying features

  15. Preparation, characterization and cytotoxicity studies of some transition metal complexes with ofloxacin and 1,10-phenanthroline mixed ligand

    Science.gov (United States)

    Sadeek, S. A.; El-Hamid, S. M. Abd

    2016-10-01

    [Zn(Ofl)(Phen)(H2O)2](CH3COO)·2H2O (1), [ZrO(Ofl)(Phen)(H2O)]NO3·2H2O (2) and [UO2(Ofl)(Phen)(H2O)](CH3COO)·H2O (3) complexes of fluoroquinolone antibacterial agent ofloxacin (HOfl), containing a nitrogen donor heterocyclic ligand, 1,10-phenathroline monohydrate (Phen), were prepared and their structures were established with the help of elemental analysis, molar conductance, magnetic properties, thermal studies and different spectroscopic studies like IR, UV-Vis., 1H NMR and Mass. The IR data of HOfl and Phen ligands suggested the existing of a bidentate binding involving carboxylate O and pyridone O for HOfl ligand and two pyridine N atoms for Phen ligand. The coordination geometries and electronic structures are determined from electronic absorption spectra and magnetic moment measurements. From molar conductance studies reveals that metal complexes are electrolytes and of 1:1 type. The calculated bond length and force constant, F(Udbnd O), in the uranyl complex are 1.751 Å and 641.04 Nm-1. The thermal properties of the complexes were investigated by thermogravimetry (TGA) technique. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. Antimicrobial activity of the compounds was evaluated against some bacteria and fungi species. The activity data show that most metal complexes have antibacterial activity than that of the parent HOfl drug. The in vitro cytotoxicities of ligands and their complexes were also evaluated against human breast and colon carcinoma cells.

  16. Preparation and configurational analysis of the stereoisomers of β,γ-bidentate Rh(H2O)4ATP and α,β,γ-tridentate Rh(H2O)3ATP. A new class of enzyme active site probes

    International Nuclear Information System (INIS)

    Lu, Z.; Shorter, A.L.; Lin, I.; Dunaway-Mariano, D.

    1988-01-01

    Exchange-inert Co(III) and Cr(III) complexes of polyphosphates have proved to be useful probes of the structural and biochemical properties of naturally occurring Mg II (polyphosphate) complexes. However, applications of these complexes are not without limitations. The Cr III (polyphosphate) probes or their enzymatic products cannot be used in NMR methods because of the paramagnetic nature of the Cr(III) metal. The redox properties of the metal in the Co III (polyphosphate) complexes require that they also be coordinated to a nitrogen-containing ligand. This requirement is not always convenient. This work reported herein was undertaken to create a new class of exchange-inert metal polyphosphate complexes that contain a metal that is both diamagnetic and redox stable. The preparation, properties, and configurational analysis of the stereoisomers of β, γ-bidentate Rh(H 2 O) 4 ATP (ATP = adenosine 5'-triphosphate) and α,β,γ-tridentate Rh(H 2 O) 3 ATP are described. 12 refs., 5 figs

  17. Utilization of LVO 2 species (L is a tridentate ONS donor) as an ...

    Indian Academy of Sciences (India)

    2. Experimental. 2.1 Materials. Ligands H2L (L = L1 and L2) and [VO(acac)2] were synthesized as described elsewhere.8,9 Solvents were of reagent grade and were dried from appropriate re- agents10 and distilled under nitrogen prior to their use. All other chemicals were reagent grade, available commercially and used ...

  18. Los Alamos National Laboratory Request for Proposals: Trident Laser System (TLS) Redeployment and Life Extension, October 5, 2016

    Energy Technology Data Exchange (ETDEWEB)

    Stringer, Steven F. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-10-04

    In May 2016, LANS announced that the Trident Laser Facility would cease operating effective September 15, 2016. That date was subsequently extended. The current plan is to operate for an additional, limited period in early CY 2017, and to leverage that activity to provide a training opportunity to the party that will redeploy the TLS. The TLS will then be disassembled and packaged for shipping to the new site, where it may be reconstituted and continue to be used by the physics research community. It is LANS’ intent that Trident will be sited with an organization that will supply its own funding for TLS installation, calibration, and lifecycle operation. Ideally, the receiving party will plan to upgrade TLS with new capability. The equipment to be transferred includes the laser, its power supply, target station and chamber, and a suite of diagnostic instrumentation. Under a Joint Use Agreement it is anticipated that all equipment will remain property of the Laboratory and subject to on-site configuration verification.

  19. Zinc Bioavailability from Phytate-Rich Foods and Zinc Supplements. Modeling the Effects of Food Components with Oxygen, Nitrogen, and Sulfur Donor Ligands.

    Science.gov (United States)

    Tang, Ning; Skibsted, Leif H

    2017-10-04

    Aqueous solubility of zinc phytate (K sp = (2.6 ± 0.2) × 10 -47 mol 7 /L 7 ), essential for zinc bioavailability from plant foods, was found to decrease with increasing temperature corresponding to ΔH dis of -301 ± 22 kJ/mol and ΔS dis of -1901 ± 72 J/(mol K). Binding of zinc to phytate was found to be exothermic for the stronger binding site and endothermic for the weaker binding site. The solubility of the slightly soluble zinc citrate and insoluble zinc phytate was found to be considerably enhanced by the food components with oxygen donor, nitrogen donor, and sulfur donor ligands. The driving force for the enhanced solubility is mainly due to the complex formation between zinc and the investigated food components rather than ligand exchange and ternary complex formation as revealed by quantum mechanical calculations and isothermal titration calorimetry. Histidine and citrate are promising ligands for improving zinc absorption from phytate-rich foods.

  20. Synthesis and characterization of a tetraaza macrocyclic ligand and its cobalt(II, nickel(II and copper(II complexes

    Directory of Open Access Journals (Sweden)

    SULEKH CHANDR

    2010-07-01

    Full Text Available Co(II, Ni(II, and Cu(II complexes with a tetradentate nitrogen donor [N4] macrocyclic ligand, viz. 6,15-dimethyl-8,17diphenyl-7,16-dihydrodibenzo[b,i][1.4.8.11]tetraazacyclotetradecine, were synthesized. Their structures were determined based on elemental analyses, molar conductance and magnetic susceptibility measurements, and IR, 1H-NMR (ligand and electronic spectral studies. Based on analytical and molar conductance data, the complexes may be formulated as [M(LCl2] and [M’(L]Cl2 (where M = Co(II and Cu(II, and M’ = Ni(II due to their non-electrolytic and 1:2 electrolytic nature. Based on spectral studies, an octahedral geometry was assigned for the Co(II complex, whereas square-planar and tetragonal geometry were proposed for the Ni(II and Cu(II complexes, respectively. The synthesized ligand and its complexes were screened for fungicidal activity against two pathogenic fungi (i.e., Fusarium moniliformae and Rhizoctonia solani to assess their growth inhibiting potential.

  1. Synthesis of a new technetium radiotracer containing para-toluidine by tridentate chelation (N,N,O)

    International Nuclear Information System (INIS)

    Makhloufi, Amel

    2011-01-01

    Neuro degenerative diseases (Alzheimer, Parkinson, Creutzfeld-Jacob. and others) have an increasingly important impact as well on the economic plan as social. The diagnosis procedure and current therapies remain expensive and the assumption of responsibility of the patient is seldom assured. These last years, the development of new radiopharmaceuticals with aiming diagnosis procedure started again the interest for the search for new molecules. The asset of the synthesis of our technetium radiotracer, a tridentate chelate complex (N, N, O) resides in the facility of its obtaining; marking with the kit Alberto is done at a temperature about 90 degree approximately and this could consequently facilitate its implementation in the units of radiodiagnosis. Of lipophilic nature, neutral and of suitable molecular weight, the main challenge for this molecule would be to check its capacity to cross the blood-brain barrier by studying its cerebral extraction.

  2. Syntheses and study on nickel(II) complexes with thiodiglycolic acid and nitrogen-donor ligands. X-ray structures of [Ni(bpy)(tdga)(H2O)] . 4H2O and [(en)Ni(µ-tdga)2Ni(en)] . 4H2O (tdgaH2=thiodiglycolic acid)

    Czech Academy of Sciences Publication Activity Database

    Kopel, P.; Trávníček, Zdeněk; Marek, J.; Mrozinski, J.

    2004-01-01

    Roč. 23, č. 9 (2004), s. 1573-1578 ISSN 0277-5387 R&D Projects: GA ČR(CZ) GA203/02/0436 Grant - others:GA MŠk1(CZ) MSM 153100007; GA MŠK1(CZ) MSM 143100008; Polish State Committee for Scientific Research(PL) 4T09A 11523 Institutional research plan: CEZ:AV0Z5038910 Keywords : nickel(II) * thiodiglycolic acid complexes * X-ray structures Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.586, year: 2004

  3. Atmospheric pollutant and other data from the TRIDENT and tower as part of the International Decade of Ocean Exploration (IDOE) from 1972-02-01 to 1972-09-01 (NCEI Accession 7300574)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Atmospheric pollutant and other data were collected from the TRIDENT and tower from 01 February 1972 to 01 September 1972. Data include trace metals in the...

  4. Temperature profiles from expendable bathythermograph (XBT) casts from the R/V TRIDENT in the Caribbean Ocean in support of the Integrated Global Ocean Services System (IGOSS) project for 1971-01-28 (NODC Accession 7600706)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the R/V TRIDENT in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the University of...

  5. Temperature profiles from expendable bathythermograph (XBT) casts from the TRIDENT in the North Atlantic Ocean in support of the Integrated Global Ocean Services System (IGOSS) from 1972-12-15 to 1972-12-20 (NODC Accession 7600705)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the TRIDENT in support of the Integrated Global Ocean Services System (IGOSS). Data were collected by the the University of Rhode...

  6. Temperature profiles from expendable bathythermograph (XBT) casts from the R/V TRIDENT in the East Coast - US/Canada in support of the Integrated Global Ocean Services System (IGOSS) project for 1969-07-10 (NODC Accession 7600701)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the R/V TRIDENT in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the University of...

  7. New μ-OAC bridged dinuclear copper(II) complex with tridentate Schiff base ligand: synthesis, characterization, crystal structure, and CuO nano-particles formation

    Czech Academy of Sciences Publication Activity Database

    Grivani, G.; Eigner, Václav; Dušek, Michal; Sadeghi, B.; Khalaji, A.D.

    2015-01-01

    Roč. 41, č. 7 (2015), s. 456-461 ISSN 1070-3284 R&D Projects: GA ČR(CZ) GA14-03276S Institutional support: RVO:68378271 Keywords : Schiff base * complex structure * x-ray crystallography * Jana2006 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.516, year: 2015

  8. Synthesis, crystal structure and cytotoxic activity of ruthenium(II) piano-stool complex with N,N-chelating ligand

    Science.gov (United States)

    Rogala, Patrycja; Jabłońska-Wawrzycka, Agnieszka; Kazimierczuk, Katarzyna; Borek, Agnieszka; Błażejczyk, Agnieszka; Wietrzyk, Joanna; Barszcz, Barbara

    2016-12-01

    A mononuclear compound of the general formula [(η6-p-cymene)RuIICl(2,2‧-PyBIm)]PF6 has been synthesized from a bidentate N,N-donor ligand, viz. 2,-(2‧-pyridyl)benzimidazole (2,2‧-PyBIm) and the corresponding chloro-complex [(η6-p-cymene)Ru(μ-Cl)Cl]2 (precursor). The isolated coordination compound was characterized by IR, UV-vis and 1H, 13C NMR spectroscopies. The single crystal X-ray analysis of the complex reveals that the asymmetric part of the unit cell consists of two symmetrically independent, [(η6-p-cymene)RuCl(2,2‧-PyBIm)]+ cationic complexes. Each cation exhibits a pseudo-octahedral three-legged piano-stool geometry, in which three "legs" are occupied by one chloride ion and two nitrogen donor atoms of the chelating ligand 2,2‧-PyBIm. The Hirshfeld surface analysis of obtained complex was determined, too. The ionic nature of the compound is identified by a strong band at around 830 cm-1 due to the νP-F stretching mode of the PF6- counter ion. The electronic spectrum of this monomeric complex displays high intensity bands in the ultraviolet region assignable to π→π*/n→π* transitions, as well as a band attributable to the metal-to-ligand charge transfer (MLCT) dπ(Ru)→π*(L) transition. Additionally, the complex has been screened for its cytotoxicity against three human cancer lines: non-small cell lung carcinoma (A549), colon adenocarcinoma (HT29) and breast adenocarcinoma (MCF-7) as well as normal mice fibroblast cells (BALB/3T3). The complex demonstrated a moderate antiproliferative activity against the cell lines tested.

  9. A novel tridentate Schiff base dioxo-molybdenum(VI) complex: synthesis, experimental and theoretical studies on its crystal structure, FTIR, UV-visible, ¹H NMR and ¹³C NMR spectra.

    Science.gov (United States)

    Saheb, Vahid; Sheikhshoaie, Iran; Stoeckli-Evans, Helen

    2012-09-01

    A new dioxo-molybdenum(VI) complex [MoO(2)(L)(H(2)O)] has been synthesized, using 5-methoxy 2-[(2-hydroxypropylimino)methyl]phenol as tridentate ONO donor Schiff base ligand (H(2)L) and MoO(2)(acac)(2). The yellow crystals of the compound are used for single-crystal X-ray analysis and measuring Fourier Transform Infrared (FTIR), UV-visible, (1)H NMR and (13)C NMR spectra. Electronic structure calculations at the B3LYP and PW91PW91 levels of theory are performed to optimize the molecular geometry and to calculate the UV-visible, FTIR, (1)H NMR and (13)C NMR spectra of the compound. Vibrational assignments and analysis of the fundamental modes of the compound are performed. Time-dependent density functional theory (TDDFT) method is used to calculate the electronic transitions of the complex. All theoretical methods can well reproduce the structure of the compound. The (1)H NMR shielding tensors computed at the B3LYP/DGDZVP level of theory is in agreement with experimental (1)H NMR spectra. However, the (13)C NMR shielding tensors computed at the B3LYP level, employing a combined basis set of DGDZVP for Mo and 6-31+G(2df,p) for other atoms, are in better agreement with experimental (13)C NMR spectra. The electronic transitions calculated at the B3LYP/DGDZVP level by using TD-DFT method is in accordance with the observed UV-visible spectrum of the compound. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. The molecular genetics of clinal variation: a case study of ebony and thoracic trident pigmentation in Drosophila melanogaster from eastern Australia.

    Science.gov (United States)

    Telonis-Scott, Marina; Hoffmann, Ary A; Sgrò, Carla M

    2011-05-01

    Widespread pigmentation diversity coupled with a well-defined genetic system of melanin synthesis and patterning in Drosophila provides an excellent opportunity to study phenotypes undergoing evolutionary change. Pigmentation variation is highly correlated with different ecological variables and is thought to reflect adaptations to different environments. Several studies have linked candidate genes from Drosophila melanogaster to intra-population variation and interspecific morphological divergence, but less clearly to variation among populations forming pigmentation clines. We characterized a new thoracic trident pigmentation cline in D. melanogaster populations from eastern Australia, and applied a candidate gene approach to explain the majority of the geographically structured phenotypic variation. More melanized populations from higher latitudes tended to express less ebony than their tropical counterparts, and an independent artificial selection experiment confirmed this association. By partitioning temperature dependent effects, we showed that the genetic differences underlying clinal patterns for trident variation at 25 °C do not explain the patterns observed at 16 °C. Changes in thoracic trident pigmentation could be a common evolutionary response to climatically mediated environmental pressures. On the Australian east coast most of the changes appear to be associated with regulatory divergence of the ebony gene but this depends on temperature. © 2011 Blackwell Publishing Ltd.

  11. Synthesis, structure, DNA/BSA binding and antibacterial studies of NNO tridentate Schiff base metal complexes

    Science.gov (United States)

    Sakthi, Marimuthu; Ramu, Andy

    2017-12-01

    A new salicylaldehyde derived 2,4-diiodo-6-((2-phenylaminoethylimino)methyl)phenol Schiff base(L) and its transition metal complexes of the type MLCl where, M = Cu(II), Ni(II), Co(II), Mn(II) and Zn(II) have been synthesized. The coordination mode of Schiff base holding NNO donor atoms with metal ions was well investigated by elemental analysis, ESI-mass as well as IR, UV-vis, CV and NMR spectral studies. The binding efficiency and mode of these complexes with biological macromolecules viz., herring sperm DNA (HS- DNA) and bovine serum albumin (BSA) have been explored through various spectroscopic techniques. The characteristic changes in absorption, emission and, circular dichroism spectra of the complexes with DNA indicate the noticeable interaction between them. From the all spectral information complexes could interact with DNA via non-intercalation mode of binding. The hyperchromisim in absorption band and hypochromisim in emission intensity of BSA with different complex concentrations shown significant information, and the binding affinity value has been predicted from Stern-Volmer plots. Further, all the complexes could cleave the circular plasmid pUC19 DNA efficiently by using an activator H2O2. The ligand and all metal(II) complexes showed good antibacterial activities. The molecular docking studies of the complexes with DNA were performed in order to make a comparison and conclusion with spectral technic results.

  12. Some organodioxygen complexes of molybdenum(VI), tungsten(VI), zinc(II) and cadmium(II) containing some monodentate and multidentate ligands

    International Nuclear Information System (INIS)

    Tarafder, M.T.H.; Leo Man Lin; Grouse, Karen A.; Mariotto, Gino

    2003-08-01

    Several novel organodioxygen complexes of the type [M(O)(O 2 ) 2 L](MMo(VI), W(VI)) and [M'(O 2 )L](M'= Cd(II) and Zn(II)) have been synthesized using monodentate, bidentate and tridentate ligands, L pyridine, picolinic acid, diethylenetriamine, 1,2-phenylenediamine, triphenylphosphine oxide. These complexes were characterized by elemental analyses, conductivity measurements, infrared, Raman spectral studies. For dioxygen complexes, the v(O=O) stretches of the superoxo moities were only Raman active, because of apparent linearity of the M-O 2 moieties, giving peaks at 1020-1030 cm -1 . The complexes were all thermodynamically stable. The dioxygen complexes containing bidentate co-ligands were found to show oxygen transfer reactions to various organic and inorganic substrates. Mechanisms have been postulated. (author)

  13. Quantification of uncertainty in photon source spot size inference during laser-driven radiography experiments at TRIDENT

    Energy Technology Data Exchange (ETDEWEB)

    Tobias, Benjamin John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Palaniyappan, Sasikumar [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gautier, Donald Cort [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mendez, Jacob [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Burris-Mog, Trevor John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Huang, Chengkun K. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Favalli, Andrea [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hunter, James F. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Espy, Michelle E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Schmidt, Derek William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Nelson, Ronald Owen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sefkow, Adam [Univ. of Rochester, NY (United States); Shimada, Tsutomu [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Johnson, Randall Philip [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Fernandez, Juan Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-10-24

    Images of the R2DTO resolution target were obtained during laser-driven-radiography experiments performed at the TRIDENT laser facility, and analysis of these images using the Bayesian Inference Engine (BIE) determines a most probable full-width half maximum (FWHM) spot size of 78 μm. However, significant uncertainty prevails due to variation in the measured detector blur. Propagating this uncertainty in detector blur through the forward model results in an interval of probabilistic ambiguity spanning approximately 35-195 μm when the laser energy impinges on a thick (1 mm) tantalum target. In other phases of the experiment, laser energy is deposited on a thin (~100 nm) aluminum target placed 250 μm ahead of the tantalum converter. When the energetic electron beam is generated in this manner, upstream from the bremsstrahlung converter, the inferred spot size shifts to a range of much larger values, approximately 270-600 μm FWHM. This report discusses methods applied to obtain these intervals as well as concepts necessary for interpreting the result within a context of probabilistic quantitative inference.

  14. and Tetradentate N,O-donor Ligands

    African Journals Online (AJOL)

    NICO

    )], derived from the oxidation reactions (by O2) of trans-[ReCl3(MeCN)(PPh3)2] with the tridentate N2O-donor chelate 2-[((2-pyridinylmethyl)amino)methyl]phenol (Hham) and the N2O2-donor N,N-bis(2-hydroxybenzyl)-aminomethyl- pyridine ...

  15. Sterically demanding iminopyridine ligands

    NARCIS (Netherlands)

    Irrgang, Torsten; Keller, Sandra; Maisel, Heidi; Kretschmer, Winfried; Kempe, Rhett

    Two sterically demanding iminopyridine ligands, (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridin-2-ylmeth- ylene]amine and (2,6-diisopropylphenyl)]6-(2,6-dimethylphenyl)pyridin-2-ylmethylene]amine, were prepared by a two-step process: first, condensation of 6-bromopyridine-2-carbaldehyde

  16. Probing the difference in covalence by enthalpy measurements: a new heterocyclic N-donor ligand for actinide/lanthanide separation.

    Science.gov (United States)

    Yang, Yanqiu; Liu, Jun; Yang, Liang; Li, Kun; Zhang, Huabei; Luo, Shunzhong; Rao, Linfeng

    2015-05-21

    Complexation of Am(III), Nd(III), and Eu(III) with a new heterocyclic nitrogen-donor ligand, 2,9-di(quinazolin-2-yl)-1,10-phenanthroline (denoted as BQPhen in this paper), was studied by thermodynamic measurements and theoretical computations. The stability constants of two successive complexes in dimethylformamide, ML(3+) and ML2(3+) where M stands for Nd, Eu, or Am while L stands for the BQPhen ligand, were determined by absorption spectrophotometry. The enthalpy of complexation was determined by microcalorimetry. Results show that BQPhen forms ten times stronger complexes with Am(III) than Eu(III) or Nd(III) under identical conditions, suggesting that BQPhen could be used as an efficient extractant for the separations of trivalent actinides from lanthanides. The higher binding strength of BQPhen towards Am(III) than Nd(III) or Eu(III) is mainly due to the more favourable enthalpy of complexation for Am(III)/BQPhen complexes, implying a higher degree of covalence in the Am(III)/BQPhen complexes than the lanthanide(III)/BQPhen complexes. The thermodynamic trend was corroborated with computational results and validated by solvent extraction experiments that demonstrated BQPhen preferably extracted Am(III) more than Eu(III), with a separation factor of about 10. Discussions have been made to compare BQPhen with other phenanthroline derivatives such as CyMe4-BTPhen, a bis-triazine-phenanthroline derivative that was reported in the literature. Data suggest that, under identical conditions, BQPhen would form stronger complexes with Am(III), Eu(III), and Nd(III) than CyMe4-BTPhen.

  17. Complexation Studies of Bidentate Heterocyclic N-Donor Ligands with Nd(III) and Am(III)

    Energy Technology Data Exchange (ETDEWEB)

    Ogden, Mark; Hoch, Courtney L.; Sinkov, Sergey I.; Meier, Patrick; Lumetta, Gregg J.; Nash, Kenneth L.

    2011-11-28

    A new bidentate nitrogen donor complexing agent that combines pyridine and triazole functional groups, 2-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)pyridine (PTMP), has been synthesized. The strength of its complexes with trivalent americium (Am3+) and neodymium (Nd3+) in anhydrous methanol has been evaluated using spectrophotometric techniques. The purpose of this investigation is to assess this ligand (as representative of a class of similarly structured species) as a possible model compound for the challenging separation of trivalent actinides from lanthanides. This separation, important in the development of advanced nuclear fuel cycles, is best achieved through the agency of multidentate chelating agents containing some number of nitrogen or sulfur donor groups. To evaluate the relative strength of the bidentate complexes, the derived constants are compared to those of the same metal ions with 2,2*-bipyridyl (bipy), 1,10-phenanthroline (phen), and 2-pyridin-2-yl-1H-benzimidazole (PBIm). At issue is the relative affinity of the triazole moiety for trivalent f element ions. For all ligands, the derived stability constants are higher for Am3+ than Nd3+. In the case of Am3+ complexes with phen and PBIm, the presence of 1:2 (AmL2) species is indicated. Possible separations are suggested based on the relative stability and stoichiometry of the Am3+ and Nd3+ complexes. It can be noted that the 1,2,3-triazolyl group imparts a potentially useful selectivity for trivalent actinides (An(III)) over trivalent lanthanides (Ln(III)), though the attainment of higher complex stoichiometries in actinide compared with lanthanide complexes may be an important driver for developing successful separations.

  18. Complexation Studies of Bidentate Heterocyclic N-Donor Ligands with Nd(III) and Am(III)

    International Nuclear Information System (INIS)

    Ogden, Mark; Hoch, Courtney L.; Sinkov, Sergey I.; Meier, Patrick; Lumetta, Gregg J.; Nash, Kenneth L.

    2011-01-01

    A new bidentate nitrogen donor complexing agent that combines pyridine and triazole functional groups, 2-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)pyridine (PTMP), has been synthesized. The strength of its complexes with trivalent americium (Am3+) and neodymium (Nd3+) in anhydrous methanol has been evaluated using spectrophotometric techniques. The purpose of this investigation is to assess this ligand (as representative of a class of similarly structured species) as a possible model compound for the challenging separation of trivalent actinides from lanthanides. This separation, important in the development of advanced nuclear fuel cycles, is best achieved through the agency of multidentate chelating agents containing some number of nitrogen or sulfur donor groups. To evaluate the relative strength of the bidentate complexes, the derived constants are compared to those of the same metal ions with 2,2*-bipyridyl (bipy), 1,10-phenanthroline (phen), and 2-pyridin-2-yl-1H-benzimidazole (PBIm). At issue is the relative affinity of the triazole moiety for trivalent f element ions. For all ligands, the derived stability constants are higher for Am3+ than Nd3+. In the case of Am3+ complexes with phen and PBIm, the presence of 1:2 (AmL2) species is indicated. Possible separations are suggested based on the relative stability and stoichiometry of the Am3+ and Nd3+ complexes. It can be noted that the 1,2,3-triazolyl group imparts a potentially useful selectivity for trivalent actinides (An(III)) over trivalent lanthanides (Ln(III)), though the attainment of higher complex stoichiometries in actinide compared with lanthanide complexes may be an important driver for developing successful separations.

  19. Analysis of macromolecules, ligands and macromolecule-ligand complexes

    Science.gov (United States)

    Von Dreele, Robert B [Los Alamos, NM

    2008-12-23

    A method for determining atomic level structures of macromolecule-ligand complexes through high-resolution powder diffraction analysis and a method for providing suitable microcrystalline powder for diffraction analysis are provided. In one embodiment, powder diffraction data is collected from samples of polycrystalline macromolecule and macromolecule-ligand complex and the refined structure of the macromolecule is used as an approximate model for a combined Rietveld and stereochemical restraint refinement of the macromolecule-ligand complex. A difference Fourier map is calculated and the ligand position and points of interaction between the atoms of the macromolecule and the atoms of the ligand can be deduced and visualized. A suitable polycrystalline sample of macromolecule-ligand complex can be produced by physically agitating a mixture of lyophilized macromolecule, ligand and a solvent.

  20. Radiobiology with DNA ligands

    International Nuclear Information System (INIS)

    Weinreich, R.; Argentini, M.; Guenther, I.; Koziorowski, J.; Larsson, B.; Nievergelt-Egido, M.C.; Salt, C.; Wyer, L.; Dos Santos, D.F.; Hansen, H.J.

    1997-01-01

    The paper deals with the following topics: labelling of DNA ligands and other tumour-affinic compounds with 4.15-d 124 I, radiotoxicity of Hoechst 33258 and 33342 and of iodinated Hoechst 33258 in cell cultures, preparation of 76 Br-, 123 I-, and 221 At-labelled 5-halo-2'-deoxyuridine, chemical syntheses of boron derivatives of Hoechst 33258.III., Gadolinium neutron capture therapy

  1. Therapeutic androgen receptor ligands

    Science.gov (United States)

    Allan, George F.; Sui, Zhihua

    2003-01-01

    In the past several years, the concept of tissue-selective nuclear receptor ligands has emerged. This concept has come to fruition with estrogens, with the successful marketing of drugs such as raloxifene. The discovery of raloxifene and other selective estrogen receptor modulators (SERMs) has raised the possibility of generating selective compounds for other pathways, including androgens (that is, selective androgen receptor modulators, or SARMs). PMID:16604181

  2. Synthesis, characterization, biological activity and DNA cleavage studies of tridentate Schiff bases and their Co(II complexes

    Directory of Open Access Journals (Sweden)

    P. Kavitha

    2016-01-01

    Full Text Available In the present study a series of Co(II complexes of formyl chromone Schiff bases have been synthesized characterized by analytical, molar conductance, IR, electronic, magnetic susceptibility, thermal, fluorescence and powder XRD measurements and screened for various biological activities (antimicrobial, antioxidant, nematicidal, DNA cleavage and cytotoxicity. In all the Co(II complexes 1:2 metal to ligand molar ratio was obtained from analytical data. The molar conductance data confirm that all complexes are non-electrolytic in nature. Based on the electronic and magnetic data, an octahedral geometry is ascribed for all the Co(II complexes. Thermal behaviour of the synthesized complexes illustrates the general decomposition patterns of the complexes. The X-ray analysis data show that all the Co(II complexes have triclinic crystal system with different unit cell parameters. Metal complexes have greater antimicrobial activity than ligands. Antioxidant and nematicidal activities indicate that the ligands exhibit greater activity when compared to their respective Co(II complexes. All ligands and Co(II complexes of HL1 and HL2 showed considerable anticancer activity against Raw, MCF-7 and COLO 205 cell lines. All ligands and their Co(II complexes showed more pronounced DNA cleavage activity in the presence of H2O2.

  3. Key role of higher order symmetry and electrostatic ligand field design in the magnetic relaxation of low-coordinate Er(iii) complexes.

    Science.gov (United States)

    Singh, Saurabh Kumar; Pandey, Bhawana; Velmurugan, Gunasekaran; Rajaraman, Gopalan

    2017-09-12

    The conceptual framework of electrostatic ligand field modulation based on oblate/prolate type electron density of lanthanide ions is one of the most successful approaches to enhance barrier height in lanthanide-based single-ion magnets. Recently, a tetra coordinated [Er{N(SiMe 3 ) 2 }s 3 Cl]·2THF (1) complex with an unfavourable ligand field showed slow relaxation of magnetization in zero field and challenges the concept of electrostatic ligand field modulation. To unravel the magnetic relaxation in this complex, we carried out a detailed theoretical investigation on three Er(iii) complexes belonging to the same family of single-ion magnets. The CASSCF/PT2 + RASSI-SO approach highlights that the concept of electrostatic ligand field modulation based on oblate/prolate type is still valid in these complexes, and the relaxation dynamics observed can be rationalized by accounting for both the symmetry and geometrical distortions around the Er(iii) ion. Using ab initio computed blockade barriers and crystal field analysis, we analysed the key components of the magnetic relaxation. Our study suggests that in these structures, the Er(iii) ion shifted out of the triangular plane formed by the three nitrogen donor atoms and this out-of-plane shift (τ) significantly influences the slow-relaxation of magnetization. In order to gain deeper insights into the nature of metal-ligand bonding, and to predict quantitatively the strength of the axial and equatorial ligand field, ELF, QTAIM, and EDA analysis were carried out in these complexes. Our findings highlight that the molecules possessing large barrier height for magnetic relaxation are due to the combined effect of a favourable ligand field and the symmetry around the Er(iii) ion. To understand the intricate role of both effects, several robust magneto-structural correlations were developed. Besides, the lanthanide-halogen covalency was also found to play a vital role in controlling the magnetic anisotropy and thus the

  4. Effects of Ligands on a Ternary Hydroxo Complex Formation with Eu(III) in a Aqueous Solution: Comparison of a Pyridine-2,6-dicarboxylate with a Phthalate

    International Nuclear Information System (INIS)

    Park, K. K.; Cho, H. R.; Kim, W. H.; Jung, E. C.

    2008-01-01

    The interaction of a radionuclide with ligands in a groundwater influences its migration through a hydrogeological system due to a change in the characteristics of a dissolution and a sorption. Actinide ions are classified as a hard acid and strongly interact with ligands having an oxygen donor atom of a hard base such as a hydroxide, carbonate and carboxylate. These ligands reveal a large ionic bonding character. A number of experimental results on a binary complex formation of actinides have been reported. However, actinides may easily form a ternary complex by interacting simultaneously with two different ligands, since an ionic bonding does not restrict the spatial orientation of a ligand. In previous studies, a ternary hydroxo complex formation was investigated by using pyridine-2,6-dicarboxylate (PDA) or phthalate as an organic ligand and Eu(III) as an analogue of an actinide(III) ion. Although these organic ligands equally contain two carboxylate groups that interact with an Eu(III) ion, their stabilities reveal big differences. PDA is a tridentate ligand forming two 5-membered chelates, while phthalate is a bidentate ligand forming a 7-membered chelate. The latter reveals a lower stability than the former due to an angle strain. This is one of the reasons for the lower stability of the Eu(III)-phthalate than that of the Eu(III)- PDA. The difference in the stabilities of binary complexes, EuL + (L=organic ligand), influences the stabilities of the ternary hydroxo complexes, Eu(OH)L. The coordination of a phenylic or pyridine ligand can greatly enhance the fluorescence of an Eu(III) ion due to the high absorbance of a ligand by a π → π * transition and the transfer of this energy to an Eu(III) ion. These fluorescence characteristics in a binary complex system could be changed in a ternary complex. In this study, the effect of a ligand on the stability of a ternary hydroxo complex is reported by comparing the stabilities of Eu-PDA with Eu-phthalate systems

  5. Facile and Selective Synthetic Approach for Ruthenium Complexes Utilizing a Molecular Sieve Effect in the Supporting Ligand

    Directory of Open Access Journals (Sweden)

    Dai Oyama

    2013-12-01

    Full Text Available It is extremely important for synthetic chemists to control the structure of new compounds. We have constructed ruthenium-based mononuclear complexes with the tridentate 2,6-di(1,8-naphthyridin-2-ylpyridine (dnp ligand to investigate a new synthetic approach using a specific coordination space. The synthesis of a family of new ruthenium complexes containing both the dnp and triphenylphosphine (PPh3 ligands, [Ru(dnp(PPh3(X(L]n+ (X = PPh3, NO2−, Cl−, Br−; L = OH2, CH3CN, C6H5CN, SCN−, has been described. All complexes have been spectroscopically characterized in solution, and the nitrile complexes have also been characterized in the solid state through single-crystal X-ray diffraction analysis. Dnp in the present complex system behaves like a “molecular sieve” in ligand replacement reactions. Both experimental data and density functional theory (DFT calculations suggest that dnp plays a crucial role in the selectivity observed in this study. The results provide useful information toward elucidating this facile and selective synthetic approach to new transition metal complexes.

  6. Synthesis and spectral studies on metal complexes of s-triazine based ligand and non linear optical properties

    Science.gov (United States)

    Shanmugakala, R.; Tharmaraj, P.; Sheela, C. D.

    2014-11-01

    A series of transition metal complexes of type [ML] and [ML2]Cl2 (where M = Cu(II), Ni(II), Co(II) have synthesized from 2-phenylamino-4,6-dichloro-s-triazine and 3,5-dimethyl pyrazole; their characteristics have been investigated by means of elemental analyses, magnetic susceptibility, molar conductance, IR, UV-Vis, Mass, NMR and ESR spectra. The electrochemical behavior of copper(II) complexes we have studied, by using cyclic voltammetry. The ESR spectra of copper(II) complexes are recorded at 300 K and 77 K and their salient features are appropriately reported. Spectral datas, we found, show that the ligand acts as a neutral tridentate, and coordinates through the triazine ring nitrogen and pyrazolyl ring nitrogen atoms to the metal ion. Evident from our findings, the metal(II) complexes of [ML] type exhibit square pyramidal geometry, and that of [ML2]Cl2 exhibit octahedral geometry. The in vitro antimicrobial activities of the ligand and its complexes are evaluated against Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus mutans, Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, Proteus vulgaris, Cryptococcus neoformans, Pseudomonas aeruginosa, Salmonella typhi, Serratia marcescens, Shigella flexneri, Vibrio cholera, Vibris parahaemolyticus, Aspergillus niger, Candida albicans and Penicillium oxalicum by well-diffusion method. The second harmonic generation efficiency of the ligand and its complexes are determined and compared with urea and KDP.

  7. Bexarotene ligand pharmaceuticals.

    Science.gov (United States)

    Hurst, R E

    2000-12-01

    Bexarotene (LGD-1069), from Ligand, was the first retinoid X receptor (RXR)-selective, antitumor retinoid to enter clinical trials. The company launched the drug for the treatment of cutaneous T-cell lymphoma (CTCL), as Targretin capsules, in the US in January 2000 [359023]. The company filed an NDA for Targretin capsules in June 1999, and for topical gel in December 1999 [329011], [349982] specifically for once-daily oral administration for the treatment of patients with early-stage CTCL who have not tolerated other therapies, patients with refractory or persistent early stage CTCL and patients with refractory advanced stage CTCL. The FDA approved Targretin capsules at the end of December 1999 for once-daily oral treatment of all stages of CTCL in patients refractory to at least one prior systemic therapy, at an initial dose of 300 mg/m2/day. After an NDA was submitted in December 1999 for Targretin gel, the drug received Priority Review status for use as a treatment of cutaneous lesions in patients with stage IA, IB or IIA CTCL [354836]. The FDA issued an approvable letter in June 2000, and granted marketing clearance for CTCL in the same month [370687], [372768], [372769], [373279]. Ligand had received Orphan Drug designation for this indication [329011]. At the request of the FDA, Ligand agreed to carry out certain post-approval phase IV and pharmacokinetic studies [351604]. The company filed an MAA with the EMEA for Targretin Capsules to treat lymphoma in November 1999 [348944]. The NDA for Targretin gel is based on a multicenter phase III trial that was conducted in the US, Canada, Europe and Australia involving 50 patients and a multicenter phase I/II clinical program involving 67 patients. Targretin gel was evaluated for the treatment of patients with early stage CTCL (IA-IIA) who were refractory to, intolerant to, or reached a response plateau for at least 6 months on at least two prior therapies. Efficacy results exceeded the protocol-defined response

  8. Synthesis, Spectroscopic, and Electrochemical Studies on Some New Copper(II Complexes Containing 2-{[(Z-Phenyl (Pyridine-2-yl Methylidene] Amino}Benzenethiol and Monodentate Ligands

    Directory of Open Access Journals (Sweden)

    S. P. Rawat

    2014-01-01

    Full Text Available Five new mononuclear copper(II complexes, namely, [Cu(L(ImH]·ClO41; [Cu(L(Me-ImH]·ClO42; [Cu(L(Et-ImH]·ClO43; [Cu(L(2-benz-ImH]·ClO44; [Cu(L(benz-ImH]·ClO45, where HL = 2-{[(Z-phenyl (pyridine-2-yl methylidene] amino} benzenethiol; ImH = Imidazole; Me-ImH = Methy-limidazole; Et-ImH = Ethyl-imidazole; 2-benz-ImH = 2-methyl-benzimidazole; benz-ImH = benz-imidazole, have been synthesized and characterized by various physicochemical and spectroscopic techniques. Magnetic moments, electronic spectra, and EPR spectra of the complexes suggested a square planar geometry around Cu(II ion. The synthesized HL ligand behaves as monobasic tridentate Schiff base bound with the metal ion in a tridentate manner, with N2S donor sites of the pyridine-N, azomethine-N, and benzenethiol-S atoms. The redox behaviour of the copper complexes has been studied by cyclic voltammetry. Superoxide dismutase activity of these complexes has been revealed to catalyse the dismutation of superoxide (O2- and IC50 values were evaluated and discussed.

  9. Synthesis and evaluation of a tridentate Tc-99m labeled long chain fatty acid analog for myocardial imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B. C.; Kim, D. H.; Paik, J. Y.; Choi, J. S.; Lee, K. H.; Choi, Y.; Kim, B. T [Samsung Medical Center, Seoul (Korea, Republic of); Lee, J. H.; Ji, D. Y [Inha University, Incheon (Korea, Republic of)

    2004-07-01

    Long chain fatty acids serve as the main energy source for the myocardium. As an effort to develop Tc-99m labeled long chain fatty acid analogs due to ideal physical properties and ready availability of Tc-99m, we synthesized and evaluated a tridentate Tc-99m tricarbonyl-N{sub 2}O-pentadecanoic acid ([Tc-99m]) as a novel radiotracer for myocardial imaging. The pyridinyl precursor of methyl pentadecanoate was prepared in high yield and reacted with [Tc-99m(CO){sub 3}(H{sub 2}O){sub 3}]{sup +} at 75 .deg. for 30 min, followed by hydrolysis in 0.4 N NaOH-MeOH. The resulting [Tc-99m] was purified by HPLC and redissolved in 5% ethanol-saline containing 5% bovine serum albumin. In vitro stability of [Tc-99m] was measured in human serum at 37 .deg. for 12 h using radio-TLC. Dynamic images were obtained in SD rats using a gamma camera. Re standard was synthesized as the synthesis of [Tc-99m] using [(NEt{sub 4}){sub 2}[Re(CO){sub 3}CI{sub 3}]. [Tc-99m] was synthesized in 70-78% radiochemical yield and with radiochemical purity higher than 98%. Re counterpart was used to identify the Tc-99m labeled fatty acid analog. [Tc-99m] was shown to be stable (>98%) over 12 h when incubated in human serum. Dynamic images showed rapid accumulation of the radioactivity in the liver, the heart. and the kidneys. ROIs were drawn in the liver and the heart, and their count/pixel ratios were obtained as 2.2:1, 7.5:1, and 16.5:1 at 1, 2 and 5 min postinjection, respectively. There was no significant uptake in the thyroid or salivary gland, indicating that Tc-99m pertechnetate was not regenerated during the time of the study. The results demonstrated that [Tc-99m] may be useful for myocardial imaging. Further studies are warranted to perform tissue distribution of [Tc-99m] in mice.

  10. fac-Re(CO)3 complexes of 2,6-bis(4-substituted-1,2,3-triazol-1-ylmethyl)pyridine "click" ligands: synthesis, characterisation and photophysical properties.

    Science.gov (United States)

    Anderson, Christopher B; Elliott, Anastasia B S; Lewis, James E M; McAdam, C John; Gordon, Keith C; Crowley, James D

    2012-12-28

    The syntheses of the 4-n-propyl and 4-phenyl substituted fac-Re(CO)(3) complexes of the tridentate "click" ligand (2,6-bis(4-substituted-1,2,3-triazol-1-ylmethyl)pyridine) are described. The complexes were obtained by refluxing methanol solutions of [Re(CO)(5)Cl], AgPF(6) and either the 4-propyl or 4-phenyl substituted ligand for 16 h. The ligands and the two rhenium(I) complexes were characterised by elemental analysis, HR-ESMS, ATR-IR, (1)H and (13)C NMR spectroscopy and the molecular structures of both complexes were confirmed by X-ray crystallography. The electronic structure of the fac-Re(CO)(3) "click" complexes was probed using UV-Vis, Raman and emission spectroscopy, cyclic voltammetry and DFT calculations. Altering the electronic nature of the ligand's substituent, from aromatic to alkyl, had little effect on the absorption/emission maxima and electrochemical properties of the complexes indicating that the 1,2,3-triazole unit may insulate the metal centre from the electronic modification at the ligands' periphery. Both Re(I) complexes were found to be weakly emitting with short excited state lifetimes. The electrochemistry of the complexes is defined by quasi-reversible Re oxidation and irreversible triazole-based ligand reduction processes.

  11. Ligand Depot: a data warehouse for ligands bound to macromolecules.

    Science.gov (United States)

    Feng, Zukang; Chen, Li; Maddula, Himabindu; Akcan, Ozgur; Oughtred, Rose; Berman, Helen M; Westbrook, John

    2004-09-01

    Ligand Depot is an integrated data resource for finding information about small molecules bound to proteins and nucleic acids. The initial release (version 1.0, November, 2003) focuses on providing chemical and structural information for small molecules found as part of the structures deposited in the Protein Data Bank. Ligand Depot accepts keyword-based queries and also provides a graphical interface for performing chemical substructure searches. A wide variety of web resources that contain information on small molecules may also be accessed through Ligand Depot. Ligand Depot is available at http://ligand-depot.rutgers.edu/. Version 1.0 supports multiple operating systems including Windows, Unix, Linux and the Macintosh operating system. The current drawing tool works in Internet Explorer, Netscape and Mozilla on Windows, Unix and Linux.

  12. Coordination chemistry and reactivity of zinc complexes supported by a phosphido pincer ligand.

    Science.gov (United States)

    D'Auria, Ilaria; Lamberti, Marina; Mazzeo, Mina; Milione, Stefano; Roviello, Giuseppina; Pellecchia, Claudio

    2012-02-20

    The preparation and characterization of new Zn(II) complexes of the type [(PPP)ZnR] in which R = Et (1) or N(SiMe(3))(2) (2) and PPP is a tridentate monoanionic phosphido ligand (PPP-H = bis(2-diphenylphosphinophenyl)phosphine) are reported. Reaction of ZnEt(2) and Zn[N(SiMe(3))(2)](2) with one equivalent of proligand PPP-H produced the corresponding tetrahedral zinc ethyl (1) and zinc amido (2) complexes in high yield. Homoleptic (PPP)(2) Zn complex 3 was obtained by reaction of the precursors with two equivalents of the proligand. Structural characterization of 1-3 was achieved by multinuclear NMR spectroscopy ((1)H, (13)C, and (31)P) and X-ray crystallography (3). Variable-temperature (1)H and (31)P NMR studies highlighted marked flexibility of the phosphido pincer ligand in coordination at the metal center. A DFT calculation on the compounds provided theoretical support for this behavior. The activities of 1 and 2 toward the ring-opening polymerization of ε-caprolactone and of L- and rac-lactide were investigated, also in combination with an alcohol as external chain-transfer agent. Polyesters with controlled molecular parameters (M(n), end groups) and low polydispersities were obtained. A DFT study on ring-opening polymerization promoted by these complexes highlighted the importance of the coordinative flexibility of the ancillary ligand to promote monomer coordination at the reactive zinc center. Preliminary investigations showed the ability of these complexes to promote copolymerization of L-lactide and ε-caprolactone to achieve random copolymers whose microstructure reproduces the composition of the monomer feed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Melatonin: functions and ligands.

    Science.gov (United States)

    Singh, Mahaveer; Jadhav, Hemant R

    2014-09-01

    Melatonin is a chronobiotic substance that acts as synchronizer by stabilizing bodily rhythms. Its synthesis occurs in various locations throughout the body, including the pineal gland, skin, lymphocytes and gastrointestinal tract (GIT). Its synthesis and secretion is controlled by light and dark conditions, whereby light decreases and darkness increases its production. Thus, melatonin is also known as the 'hormone of darkness'. Melatonin and analogs that bind to the melatonin receptors are important because of their role in the management of depression, insomnia, epilepsy, Alzheimer's disease (AD), diabetes, obesity, alopecia, migraine, cancer, and immune and cardiac disorders. In this review, we discuss the mechanism of action of melatonin in these disorders, which could aid in the design of novel melatonin receptor ligands. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Silver(I) nitrate complexes of three tetra-kis-thio-ether-substituted pyrazine ligands: metal-organic chain, network and framework structures.

    Science.gov (United States)

    Assoumatine, Tokouré; Stoeckli-Evans, Helen

    2017-03-01

    The reaction of the ligand 2,3,5,6-tetra-kis-[(methyl-sulfanyl)-meth-yl]pyrazine ( L1 ) with silver(I) nitrate led to {[Ag(C 12 H 20 N 2 S 4 )](NO 3 )} n , (I), catena -poly[[silver(I)- μ -2,3,5,6-tetra-kis-[(methyl-sulfan-yl)meth-yl]pyrazine] nitrate], a compound with a metal-organic chain structure. The asymmetric unit is composed of two half ligands, located about inversion centres, with one ligand coordinating to the silver atoms in a bis-tridentate manner and the other in a bis-bidentate manner. The charge on the metal atom is compensated for by a free nitrate anion. Hence, the silver atom has a fivefold S 3 N 2 coordination sphere. The reaction of the ligand 2,3,5,6-tetra-kis-[(phenyl-sulfanyl)-meth-yl]pyrazine ( L2 ) with silver(I) nitrate, led to [Ag 2 (NO 3 ) 2 (C 32 H 28 N 2 S 4 )] n , (II), poly[di- μ -nitrato-bis-{ μ -2,3,5,6-tetra-kis-[(phenyl-sulfan-yl)meth-yl]pyrazine}disilver], a compound with a metal-organic network structure. The asymmetric unit is composed of half a ligand, located about an inversion centre, that coordinates to the silver atoms in a bis-tridentate manner. The nitrate anion coordinates to the silver atom in a bidentate/monodentate manner, bridging the silver atoms, which therefore have a sixfold S 2 NO 3 coordination sphere. The reaction of the ligand 2,3,5,6-tetra-kis-[(pyridin-2-yl-sulfanyl)-meth-yl]pyrazine ( L3 ) with silver(I) nitrate led to [Ag 3 (NO 3 ) 3 (C 28 H 24 N 6 S 4 )] n , (III), poly[trinitrato{ μ 6 -2,3,5,6-tetra-kis[(pyri-din-2-ylsulfan-yl)meth-yl]pyrazine}-trisilver(I)], a compound with a metal-organic framework structure. The asymmetric unit is composed of half a ligand, located about an inversion centre, that coordinates to the silver atoms in a bis-tridentate manner. One pyridine N atom bridges the monomeric units, so forming a chain structure. Two nitrate O atoms also coordinate to this silver atom, hence it has a sixfold S 2 N 2 O 2 coordination sphere. The chains are linked via a second silver atom

  15. Unusual saccharin-N,O (carbonyl) coordination in mixed-ligand copper(II) complexes: Synthesis, X-ray crystallography and biological activity

    Science.gov (United States)

    Mokhtaruddin, Nur Shuhada Mohd; Yusof, Enis Nadia Md; Ravoof, Thahira B. S. A.; Tiekink, Edward R. T.; Veerakumarasivam, Abhi; Tahir, Mohamed Ibrahim Mohamed

    2017-07-01

    Three tridentate Schiff bases containing N and S donor atoms were synthesized via the condensation reaction between S-2-methylbenzyldithiocarbazate with 2-acetyl-4-methylpyridine (S2APH); 4-methyl-3-thiosemicarbazide with 2-acetylpyridine (MT2APH) and 4-ethyl-3-thiosemicarbazide with 2-acetylpyridine (ET2APH). Three new, binuclear and mixed-ligand copper(II) complexes with the general formula, [Cu(sac)(L)]2 (sac = saccharinate anion; L = anion of the Schiff base) were then synthesized, and subsequently characterized by IR and UV/Vis spectroscopy as well as by molar conductivity and magnetic susceptibility measurements. The Schiff bases were also spectroscopically characterized using NMR and MS to further confirm their structures. The spectroscopic data indicated that the Schiff bases behaved as a tridentate NNS donor ligands coordinating via the pyridyl-nitrogen, azomethine-nitrogen and thiolate-sulphur atoms. Magnetic data indicated a square pyramidal environment for the complexes and the conductivity values showed that the complexes were essentially non-electrolytes in DMSO. The X-ray crystallographic analysis of one complex, [Cu(sac)(S2AP)]2 showed that the Cu(II) atom was coordinated to the thiolate-S, azomethine-N and pyridyl-N donors of the S2AP Schiff base and to the saccharinate-N from one anion, as well as to the carbonyl-O atom from a symmetry related saccharinate anion yielding a centrosymmetric binuclear complex with a penta-coordinate, square pyramidal geometry. All the copper(II) saccharinate complexes were found to display strong cytotoxic activity against the MCF-7 and MDA-MB-231 human breast cancer cell lines.

  16. Glutamate receptor ligands

    DEFF Research Database (Denmark)

    Guldbrandt, Mette; Johansen, Tommy N; Frydenvang, Karla Andrea

    2002-01-01

    Homologation and substitution on the carbon backbone of (S)-glutamic acid [(S)-Glu, 1], as well as absolute stereochemistry, are structural parameters of key importance for the pharmacological profile of (S)-Glu receptor ligands. We describe a series of methyl-substituted 2-aminoadipic acid (AA...... or slightly lower potencies than (S)-AA [e.g., EC(50) = 76 microM for (2S,4S)-4-methyl-AA (5a) as compared to EC(50) = 35 microM for (S)-AA]. The position of the methyl substituent had a profound effect on the observed pharmacology, whereas the absolute stereochemistry at the methylated carbon atom had a very......) analogs, and the synthesis, stereochemistry, and enantiopharmacology of 3-methyl-AA (4a-d), 4-methyl-AA (5a-d), 5-methyl-AA (6a-d), and (E)-Delta(4)-5-methyl-AA (7a and 7b) are reported. The compounds were resolved using chiral HPLC and the configurational assignments of the enantiomers were based on X...

  17. Synthesis, spectral characterization, computational calculations and biological activity of complexes designed from NNO donor Schiff-base ligand

    Science.gov (United States)

    El-Gammal, Ola A.; El-Reash, G. M. Abu; Yousef, T. A.; Mefreh, M.

    2015-07-01

    A new series of Co(II), Ni(II) and Cu(II) complexes of (Z)-2-oxo-2-(phenylamino)-N‧-(1-(pyridin-2-yl)ethylidene)acetohydrazide (H2OPPAH) have been prepared and characterized by conventional techniques. The spectral data indicated that the ligand acts as neutral or mononegative NNO tridentate. On the basis of magnetic and electronic spectral data an octahedral geometry for Ni(II) and Cu(II) complexes and a tetrahedral geometry for Co(II) complex have been proposed. The molecular modeling using DFT method are drawn showing the bond length, bond angle, chemical reactivity, energy components (kcal/mol) and binding energy (kcal/mol) for all title compounds. The Kinetic parameters were determined for each thermal degradation stages of the ligand and its complexes using Coats-Redfern and Horowitz-Metzger methods. Also, the compounds were screened for antioxidant activity using ABTS free radical, anti-hemolytic, and in vitro cytotoxic assay. H2OPPAH showed the potent antioxidant activity followed by Co(II) and Cu(II) complexes. On the other hand Ni(II) complex exhibited weak antioxidant activity using ABTS free radical and Erlich and strong erythrocyte hemolysis activity.

  18. New complexes of Cu(II) with dipicolinate and pyridyl-based ligands: An experimental and DFT approach.

    Science.gov (United States)

    Luzardo, Florencia; Álvarez, Natalia; Kremer, Carlos; de Camargo, Andrea S S; Gancheff, Jorge S

    2017-08-05

    The three novel mononuclear copper(II) complexes with dipicolinate and pyridyl-based ligands [Cu(dipic)(L)(OH 2 )] (L=4-picoline, vinylpyridine, 4-styrylpyridine; dipic 2- =dipicolinate) were afforded and structurally characterized. X-ray diffraction studies accounted for slight distorted square-pyramidal structures in which the dianion dipic 2- acts as a tridentate ligand in a mer-fashion, the N-donor species occupy an in-plane position, and a water molecule was detected apically coordinated. To assess the effect of the nature of the pyridyl-substituent (para position) on electronic properties, other complexes were also synthesized: [Cu(dipic)(py)(OH 2 )], [{Cu(dipic)(OH 2 )} 2 (μ-pyz)] and [{Cu(dipic)(OH 2 )}(μ-pypy){Cu(dipic)}] (py=pyridine, pyz=pyrazine, pypy=(E)-1,2-bis(pyridine-4-yl)ethane). Absorptive behavior in the UV-VIS region was studied in solution and in the solid state (reflectance measurements). Additionally, geometry and population analyses were conducted by means of DFT calculations. Electronic UV-VIS spectra were simulated for both dinuclear complexes in the framework of the TD-DFT methodology to assign the origin of the absorption bands. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Ligand-guided receptor optimization.

    Science.gov (United States)

    Katritch, Vsevolod; Rueda, Manuel; Abagyan, Ruben

    2012-01-01

    Receptor models generated by homology or even obtained by crystallography often have their binding pockets suboptimal for ligand docking and virtual screening applications due to insufficient accuracy or induced fit bias. Knowledge of previously discovered receptor ligands provides key information that can be used for improving docking and screening performance of the receptor. Here, we present a comprehensive ligand-guided receptor optimization (LiBERO) algorithm that exploits ligand information for selecting the best performing protein models from an ensemble. The energetically feasible protein conformers are generated through normal mode analysis and Monte Carlo conformational sampling. The algorithm allows iteration of the conformer generation and selection steps until convergence of a specially developed fitness function which quantifies the conformer's ability to select known ligands from decoys in a small-scale virtual screening test. Because of the requirement for a large number of computationally intensive docking calculations, the automated algorithm has been implemented to use Linux clusters allowing easy parallel scaling. Here, we will discuss the setup of LiBERO calculations, selection of parameters, and a range of possible uses of the algorithm which has already proven itself in several practical applications to binding pocket optimization and prospective virtual ligand screening.

  20. Temperature profiles from expendable bathythermograph (XBT) casts from the R/V TRIDENT in the North Atlantic Ocean in support of the Integrated Global Ocean Services System (IGOSS) project from 1971-01-04 to 18 January 197104 January (NODC Accession 7600707)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the R/V TRIDENT in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the University of...

  1. Temperature profiles from expendable bathythermograph (XBT) casts from the R/V TRIDENT in the Caribbean Sea in support of the Integrated Global Ocean Services System (IGOSS) project from 1975-04-28 to 1975-05-08 (NODC Accession 7600704)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the R/V TRIDENT in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the University of...

  2. Temperature profiles from expendable bathythermograph (XBT) casts from the R/V TRIDENT in the North/South Atlantic Ocean in support of the Integrated Global Ocean Services System (IGOSS) project from 1972-03-11 to 1974-12-02 (NODC Accession 7500273)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the R/V TRIDENT in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the University of...

  3. Temperature profiles from expendable bathythermograph (XBT) casts from the R/V TRIDENT in the North Atlantic Ocean in support of the Integrated Global Ocean Services System (IGOSS) project from 1975-11-20 to 1975-12-09 (NODC Accession 7600702)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the R/V TRIDENT in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the University of...

  4. Temperature profiles from expendable bathythermograph (XBT) casts from the R/V TRIDENT in the North Atlantic Ocean in support of the Integrated Global Ocean Services System (IGOSS) project from 1970-07-12 to 1972-11-04 (NODC Accession 7500783)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the R/V TRIDENT in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the University of...

  5. Temperature profiles from expendable bathythermograph (XBT) casts from the R/V TRIDENT in the North Atlantic Ocean in support of the Integrated Global Ocean Services System (IGOSS) project from 1975-07-27 to 1975-09-05 (NODC Accession 7501077)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the R/V TRIDENT in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the University of...

  6. Temperature profiles from expendable bathythermograph (XBT) casts from the R/V TRIDENT in the South Pacific Ocean in support of the Integrated Global Ocean Services System (IGOSS) project from 1975-04-07 to 1975-04-19 (NODC Accession 7600703)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the R/V TRIDENT in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the University of...

  7. Temperature profiles from expendable bathythermograph (XBT) casts from the R/V TRIDENT in the East Coast - US/Canada in support of the Integrated Global Ocean Services System (IGOSS) project from 1975-05-25 to 1975-07-10 (NODC Accession 7500782)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — XBT data were collected from the R/V TRIDENT in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the University of...

  8. Novel olfactory ligands via terpene synthases.

    Science.gov (United States)

    Touchet, Sabrina; Chamberlain, Keith; Woodcock, Christine M; Miller, David J; Birkett, Michael A; Pickett, John A; Allemann, Rudolf K

    2015-05-01

    A synthetic biology approach to the rational design of analogues of olfactory ligands by providing unnatural substrates for the enzyme synthesising (S)-germacrene D, an olfactory ligand acting as a plant derived insect repellent, to produce novel ligands is described as a viable alternative to largely unsuccessful ligand docking studies. (S)-14,15-Dimethylgermacrene D shows an unexpected reversal in behavioural activity.

  9. Synthesis, crystal structures, and thermal and spectroscopic properties of two Cd(II) metal-organic frameworks with a versatile ligand

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jia-Ming; He, Kun-Huan; Shi, Zhong-Feng [Qinzhou Univ. (China). Guangxi Colleges and Univs. Key Lab. of Beibu Gulf Oil and Natural Gas Resource Effective Utilization; Gao, Hui-Yuan; Jiang, Yi-Min [Guangxi Normal Univ., Guilin (China). Key Lab. for the Chemistry and Molecular Engineering of Medicinal Resources

    2016-11-01

    Two new metal-organic frameworks, namely, [Cd(L)(H{sub 2}O)]{sub n} (1) and {[Cd_0_._5(L)(4,4"'-bipy)_0_._5][Cd_0_._5(H_2O)(4,4"'-bipy)_0_._5].H_2O}{sub n} (2), where H{sub 2}L = N-pyrazinesulfonyl-glycine and 4,4{sup '}-bipy = 4,4{sup '}-bipyridine, have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental, thermogravimetric, and photoluminescent analysis. X-ray diffraction crystallographic analyses indicate that 1 displays a distorted octahedral metal coordination in a 3-connected (4, 8{sup 2}) topology, while the molecular structure of 2 has a 4-connected (4, 4) topology with two perfectly octahedrally coordinated Cd centers. The L{sup 2-} ligand serves as a N,N,O-tridentate, μ{sub 2}-pyrazine-bridging, and μ{sub 2}-carboxylate-bridging ligand in 1, and as a N,O-bidentate and μ{sub 2}-carboxylate-bridging ligand in 2. In the crystal, a 3D supramolecular architecture is formed by O-H..O hydrogen bond interactions in 1, but through O-H..O as well as π..π stacking in 2. The two compounds show intense fluorescence in the solid state at room temperature.

  10. Two mixed-ligand lanthanide-hydrazone complexes: [Pr(NCS)3(pbh)2]·H2O and [Nd(NCS)(NO3)(pbh)2(H2O)]NO3·2.33H2O [pbh is N'-(pyridin-2-ylmethylidene)benzo-hydrazide, C13H11N3O].

    Science.gov (United States)

    Paschalidis, Damianos G; Harrison, William T A

    2016-02-01

    The gel-mediated syntheses and crystal structures of [N'-(pyridin-2-ylmethylidene-κN)benzohydrazide-κ(2) N',O]tris(thiocyanato-κN)praseodymium(III) mono-hydrate, [Pr(NCS)3(C13H11N3O)2]·H2O, (I), and aqua(nitrato-κ(2) O,O')[N'-(pyri-din-2-ylmethylidene-κN)benzohydrazide-κ(2) N',O](thiocyanato-κN)neo-dym-ium(III) nitrate 2.33-hydrate, [Nd(NCS)(NO3)(C13H11N3O)2(H2O)]NO3·2.33H2O, (II), are reported. The Pr(3+) ion in (I) is coordinated by two N,N,O-tridentate N'-(pyridin-2-ylmethylidene)benzohydrazide (pbh) ligands and three N-bonded thio-cyanate ions to generate an irregular PrN7O2 coordination polyhedron. The Nd(3+) ion in (II) is coordinated by two N,N,O-tridentate pbh ligands, an N-bonded thio-cyanate ion, a bidentate nitrate ion and a water mol-ecule to generate a distorted NdN5O5 bicapped square anti-prism. The crystal structures of (I) and (II) feature numerous hydrogen bonds, which lead to the formation of three-dimensional networks in each case.

  11. Two mixed-ligand lanthanide–hydrazone complexes: [Pr(NCS3(pbh2]·H2O and [Nd(NCS(NO3(pbh2(H2O]NO3·2.33H2O [pbh is N′-(pyridin-2-ylmethylidenebenzohydrazide, C13H11N3O

    Directory of Open Access Journals (Sweden)

    Damianos G. Paschalidis

    2016-02-01

    Full Text Available The gel-mediated syntheses and crystal structures of [N′-(pyridin-2-ylmethylidene-κNbenzohydrazide-κ2N′,O]tris(thiocyanato-κNpraseodymium(III monohydrate, [Pr(NCS3(C13H11N3O2]·H2O, (I, and aqua(nitrato-κ2O,O′[N′-(pyridin-2-ylmethylidene-κNbenzohydrazide-κ2N′,O](thiocyanato-κNneodymium(III nitrate 2.33-hydrate, [Nd(NCS(NO3(C13H11N3O2(H2O]NO3·2.33H2O, (II, are reported. The Pr3+ ion in (I is coordinated by two N,N,O-tridentate N′-(pyridin-2-ylmethylidenebenzohydrazide (pbh ligands and three N-bonded thiocyanate ions to generate an irregular PrN7O2 coordination polyhedron. The Nd3+ ion in (II is coordinated by two N,N,O-tridentate pbh ligands, an N-bonded thiocyanate ion, a bidentate nitrate ion and a water molecule to generate a distorted NdN5O5 bicapped square antiprism. The crystal structures of (I and (II feature numerous hydrogen bonds, which lead to the formation of three-dimensional networks in each case.

  12. Synthesis of a Bis(thiophenolate)pyridine Ligand and Its Titanium, Zirconium, and Tantalum Complexes

    KAUST Repository

    Lenton, Taylor N.

    2012-11-12

    A precursor to a new tridentate LX 2 type ligand, bis(thiophenol)pyridine ((SNS)H 2 = (2-C 6H 4SH) 2-2,6-C 5H 3N), was prepared. Bis(thiophenolate)pyridine complexes of Ti, Zr, and Ta having dialkylamido coligands were synthesized and structurally characterized. The zirconium complex (SNS)Zr(NMe 2) 2 (4) displays C 2 symmetry in the solid state, unlike a related bis(phenolate)pyridine compound, C s-symmetric (ONO)Ti(NMe 2) 2. This change is likely the result of strain about the sulfur atom in the six-membered chelate with longer metal-sulfur and carbon-sulfur bonds. Solid-state structures of tantalum complexes (SNS)Ta(NMe 2) 3 (5) and (SNS)TaCl(NEt 2) 2 (6) also display pronounced C 2 twisting of the SNS ligand. 1D and 2D NMR experiments show that 5 is fluxional, with rotation about the Ta-N(amide) bonds occurring on the NMR time scale that interchange the equatorial amide methyl groups (ΔG ‡ 393 = 25.0(3) kcal/mol). The fluxional behavior of 6 in solution was also studied by variable-temperature 1H NMR. Observation of separate signals for the diastereotopic protons of the methylene unit of the diethylamide indicates that the complex remains locked on the NMR time scale in one diastereomeric conformation at temperatures below -50 °C, fast rotation about the equatorial amide Ta-N bonds occurs at higher temperature (ΔG ‡ 393 = 13.4(3) kcal/mol), and exchange of diastereomeric methylene protons occurs via inversion at Ta that interconverts antipodes (ΔG ‡ 393 ≈ 14(1) kcal/mol). © 2012 American Chemical Society.

  13. Peroxo complexes of molybdenum(VI), tungsten(VI), uranium(VI), zirconium(IV) and thorium(IV) ions containing tridentate Schiff bases derived from salicylaldehyde and amino acids

    International Nuclear Information System (INIS)

    Tarafder, M.T.H.; Khan, A.R.

    1997-01-01

    The synthesis of peroxo complexes of molybdenum(VI), tungsten(VI), uranium(VI), zirconium(IV), thorium(IV) and their possible oxygen transfer reactions is presented. An attempt has also been made to study the size of the metal ions and the electronic effect derived from the tridentate Schiff bases on the v 1 (O-O) mode of the complexes in their IR spectra

  14. Ruthenium(II carbonyl compounds with the 4′-chloro-2,2′:6′,2′′-terpyridine ligand

    Directory of Open Access Journals (Sweden)

    Rajendhraprasad Tatikonda

    2017-04-01

    Full Text Available Two ruthenium carbonyl complexes with the 4′-chloro-2,2′:6′,2′′-terpyridine ligand (tpy-Cl, C15H10ClN3, i.e. [RuCl(tpy-Cl(CO2][RuCl3(CO3] (I [systematic name: cis-dicarbonylchlorido(4′-chloro-2,2′:6′,2′′-terpyridine-κ3Nruthenium(II fac-tricarbonyltrichloridoruthenate(II], and [RuCl2(tpy-Cl(CO2] (II [cis-dicarbonyl-trans-dichlorido(4′-chloro-2,2′:6′,2′′-terpyridine-κ2N1,N1′ruthenium(II], were synthesized and characterized by single-crystal X-ray diffraction. The RuII atoms in both centrosymmetric structures (I and (II display similar, slightly distorted octahedral coordination spheres. The coordination sphere in the complex cation in compound (I is defined by three N atoms of the tridentate tpy-Cl ligand, two carbonyl carbon atoms and one chlorido ligand; the charge is balanced by an octahedral [Ru(CO3Cl3]− counter-anion. In the neutral compound (II, the tpy-Cl ligand coordinates to the metal only through two of its N atoms. The coordination sphere of the RuII atom is completed by two carbonyl and two chlorido ligands. In the crystal structures of both (I and (II, weak C—H...Cl interactions are observed.

  15. Synthesis, characterization and biological relevance of some metal (II) complexes with oxygen, nitrogen and oxygen (ONO) donor Schiff base ligand derived from thiazole and 2-hydroxy-1-naphthaldehyde

    Science.gov (United States)

    Nagesh, G. Y.; Mruthyunjayaswamy, B. H. M.

    2015-04-01

    The novel Schiff base ligand 2-((2-hydroxynaphthalen-1-yl)methylene)-N-(4-phenylthiazol-2-yl)hydrazinecarboxamide (L) obtained by the condensation of N-(4-phenylthiazol-2-yl)hydrazinecarboxamide with 2-hydroxy-1-naphthaldehyde and its newly synthesized Cu(II), Co(II), Ni(II), Zn(II) and Cd(II) complexes have been characterized by microanalysis, molar conductance, IR, 1H NMR, ESI-mass, UV-Visible, TGA/DTA, ESR and powder X-ray diffraction data to explicate their structures. The IR results confirmed the tridentate binding of the ligand involving oxygen atom of amide carbonyl, azomethine nitrogen and naphthol oxygen. 1H NMR spectral data of the ligand (L) and its Zn(II) complex agreed well with the proposed structures. Thermogravimetric studies for Cu(II) and Ni(II) complexes indicated the presence of coordinated water molecules and the final product is the metal oxide. In order to appraise the effect of antimicrobial activity of metal ions upon chelation, the newly synthesized ligand and its metal complexes were screened for their antimicrobial activity by minimum inhibitory concentration (MIC) method. The DNA cleavage activities were studied using plasmid DNA pBR322 (Bangal re Genei, Bengaluru, Cat. No 105850) as a target molecule by agarose gel electrophoresis method. The brine shrimp bioassay was also carried out to study the in vitro cytotoxicity properties against Artemia salina. Furthermore, the antioxidant activity were determined in vitro by reduction of 1,1-diphenyl-2-picryl hydrazyl (DPPH). The ligand exhibited better in vitro-antioxidant activity than its metal complexes.

  16. Rosetta Ligand docking with flexible XML protocols.

    Science.gov (United States)

    Lemmon, Gordon; Meiler, Jens

    2012-01-01

    RosettaLigand is premiere software for predicting how a protein and a small molecule interact. Benchmark studies demonstrate that 70% of the top scoring RosettaLigand predicted interfaces are within 2Å RMSD from the crystal structure [1]. The latest release of Rosetta ligand software includes many new features, such as (1) docking of multiple ligands simultaneously, (2) representing ligands as fragments for greater flexibility, (3) redesign of the interface during docking, and (4) an XML script based interface that gives the user full control of the ligand docking protocol.

  17. THERMODYNAMIC ASSESSMENT OF ANIONIC LIGANDS ...

    African Journals Online (AJOL)

    DJFLEX

    2010-06-30

    Jun 30, 2010 ... The presence of the ligands (ethylenediaminettraacetic acid, EDTA, enthylenediamine, en,and chloride ion, Cl-) generally improved the sorption capacity for the adsorbent, the best being. Cl- at optimum pH of 2.0 (for Co2+) and 5.0 (for Ni2+ and Cd2+). The thermodynamic studies reveal that the adsorption.

  18. Selective lanthanide sorption and mechanism using novel hybrid Lewis base (N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide) ligand modified adsorbent

    International Nuclear Information System (INIS)

    Awual, Md. Rabiul; Kobayashi, Tohru; Miyazaki, Yuji; Motokawa, Ryuhei; Shiwaku, Hideaki; Suzuki, Shinichi; Okamoto, Yoshihiro; Yaita, Tsuyoshi

    2013-01-01

    Highlights: •Hybrid Lewis base adsorbent was prepared for selective lanthanide (Eu, Sm) removal. •Common ions did not interfere due to strong interactions between Eu/Sm and adsorbent. •The adsorbent has good sorption and kinetic performances for potential applications. •The adsorption is reversible and adsorbent reusable in many cycles without any deterioration. -- Abstract: This study aims to develop a highly selective Lewis base adsorbent to investigate the selective sorption and recovery of Eu(III) and Sm(III) from wastewater. The oxygen and nitrogen donor atoms containing Lewis base N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide (MePhPTA) ligand was synthesized and subsequently an adsorbent was prepared by direct immobilization onto mesoporous silica. Determined maximum adsorption capacities were 125.63 and 124.38 mg/g for Eu(III) and Sm(III), respectively. Experiments with mixed-cations solutions showed that the sequence of preferential adsorption was Eu(III) > Sm(III). The lanthanide sorption by hybrid Lewis base adsorbent (HyLBA) was not adversely affected by the presence of sodium, potassium, calcium, magnesium, chloride, sulfate and nitrate ions due to strong affinity between hard Lewis acid lanthanide and hard Lewis base adsorbent. The crystallography for the Sm-MePhPTA complex suggested that MePhPTA was strongly coordinated to Sm(III) with oxygen and nitrogen by forming a stable complex with two 5-membered rings. The data clarified that bond lengths between Sm(III) and amide oxygen (2.475 Å) were shorter than Sm-N (2.662 Å) in phenanthroline moiety indicating strong oxygen driven HyLBA. The results suggested that HyLBA has a good prospect of promising applications for separation/sorption of lanthanide ions from effluents

  19. Crystallization of protein–ligand complexes

    International Nuclear Information System (INIS)

    Hassell, Anne M.; An, Gang; Bledsoe, Randy K.; Bynum, Jane M.; Carter, H. Luke III; Deng, Su-Jun J.; Gampe, Robert T.; Grisard, Tamara E.; Madauss, Kevin P.; Nolte, Robert T.; Rocque, Warren J.; Wang, Liping; Weaver, Kurt L.; Williams, Shawn P.; Wisely, G. Bruce; Xu, Robert; Shewchuk, Lisa M.

    2007-01-01

    Methods presented for growing protein–ligand complexes fall into the categories of co-expression of the protein with the ligands of interest, use of the ligands during protein purification, cocrystallization and soaking the ligands into existing crystals. Obtaining diffraction-quality crystals has long been a bottleneck in solving the three-dimensional structures of proteins. Often proteins may be stabilized when they are complexed with a substrate, nucleic acid, cofactor or small molecule. These ligands, on the other hand, have the potential to induce significant conformational changes to the protein and ab initio screening may be required to find a new crystal form. This paper presents an overview of strategies in the following areas for obtaining crystals of protein–ligand complexes: (i) co-expression of the protein with the ligands of interest, (ii) use of the ligands during protein purification, (iii) cocrystallization and (iv) soaks

  20. Spectroscopic and biological approach in the characterization of a novel 14-membered [N4] macrocyclic ligand and its palladium(II), platinum(II), ruthenium(III) and iridium(III) complexes.

    Science.gov (United States)

    Rani, Soni; Kumar, Sumit; Chandra, Sulekh

    2014-01-24

    A novel, tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 3,5,14,16-tetramethyl-2,6,13,17-tetraazatricyclo[12,0,0(7-12)] cosa-1(22),2,5,7,9,11,13,16,18,20-decaene(L), has been synthesized and characterized by elemental analyses, IR, Mass, and (1)H NMR spectral studies. Complexes of Pd(II), Pt(II), Ru(III) and Ir(III) have been prepared and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, Mass, electronic spectral and thermal studies. On the basis of molar conductance the complexes may be formulated as [PdL]Cl2, [PtL]Cl2, [Ru(L)Cl2]Cl and [Ir(L)Cl2]Cl. The complexes are insoluble in most common solvents, including water, ethanol, carbon tetrachloride and acetonitrile, but soluble in DMF/DMSO. The value of magnetic moment indicates that all the complexes are diamagnetic except Ru(III) complex which shows magnetic moment corresponding to one unpaired electron. The magnetic moment of Ru(III) complex is 1.73 B.M. at room temperature. The antimicrobial activities of ligand and its complexes have been screened in vitro, as growth inhibiting agents. The antifungal and antibacterial screening were carried out using Food Poison and Disc Diffusion Method against plant pathogenic fungi and bacteria Alternaria porri, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa respectively. The compounds were dissolved in DMSO to get the required solutions. The required medium used for these activities was PDA and nutrient agar. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. -Pincer Ligand Family through Ligand Post-Modification

    KAUST Repository

    Huang, Mei-Hui

    2017-10-02

    A series of air-stable nickel complexes containing triazine-based PN3P-pincer ligands were synthesized and fully characterized. Complex 3 contains a de-aromatized central triazine ring from the deprotonation of one of the N–H arms. With a post-modification strategy, the Me-PN3P*NiCl complex (3) could be converted into a new class of diimine–traizine PN3P-pincer nickel complexes.

  2. Chelating ligands for nanocrystals' surface functionalization

    NARCIS (Netherlands)

    Querner, Claudia; Reiss, Peter; Bleuse, Joël; Pron, Adam

    2004-01-01

    A new family of ligands for the surface functionalization of CdSe nanocrystals is proposed, namely alkyl or aryl derivatives of carbodithioic acids (R-C(S)SH). The main advantages of these new ligands are as follows: they nearly quantitatively exchange the initial surface ligands (TOPO) in very mild

  3. Alternative Affinity Ligands for Immunoglobulins.

    Science.gov (United States)

    Kruljec, Nika; Bratkovič, Tomaž

    2017-08-16

    The demand for recombinant therapeutic antibodies and Fc-fusion proteins is expected to increase in the years to come. Hence, extensive efforts are concentrated on improving the downstream processing. In particular, the development of better-affinity chromatography matrices, supporting robust time- and cost-effective antibody purification, is warranted. With the advances in molecular design and high-throughput screening approaches from chemical and biological combinatorial libraries, novel affinity ligands representing alternatives to bacterial immunoglobulin (Ig)-binding proteins have entered the scene. Here, we review the design, development, and properties of diverse classes of alternative antibody-binding ligands, ranging from engineered versions of Ig-binding proteins, to artificial binding proteins, peptides, aptamers, and synthetic small-molecular-weight compounds. We also provide examples of applications for the novel affinity matrices in chromatography and beyond.

  4. Ligand binding by PDZ domains

    DEFF Research Database (Denmark)

    Chi, Celestine N.; Bach, Anders; Strømgaard, Kristian

    2012-01-01

    The postsynaptic density protein-95/disks large/zonula occludens-1 (PDZ) protein domain family is one of the most common protein-protein interaction modules in mammalian cells, with paralogs present in several hundred human proteins. PDZ domains are found in most cell types, but neuronal proteins...... as pathological conditions have been reviewed recently. In this review, we focus on the molecular details of how PDZ domains bind their protein ligands and their potential as drug targets in this context....

  5. Bitopic Ligands and Metastable Binding Sites

    DEFF Research Database (Denmark)

    Fronik, Philipp; Gaiser, Birgit I; Sejer Pedersen, Daniel

    2017-01-01

    of orthosteric binding sites. Bitopic ligands have been employed to address the selectivity problem by combining (linking) an orthosteric ligand with an allosteric modulator, theoretically leading to high-affinity subtype selective ligands. However, it remains a challenge to identify suitable allosteric binding...... that have been reported to date, this type of bitopic ligands would be composed of two identical pharmacophores. Herein, we outline the concept of bitopic ligands, review metastable binding sites, and discuss their potential as a new source of allosteric binding sites....

  6. Radioiodinated ligands for dopamine receptors

    International Nuclear Information System (INIS)

    Kung, H.F.

    1994-01-01

    The dopamine receptor system is important for normal brain function; it is also the apparent action site for various neuroleptic drugs for the treatment of schizophrenia and other metal disorders. In the past few years radioiodinated ligands for single photon emission tomography (SPECT) have been successfully developed and tested in humans: [ 123 I]TISCH for D1 dopamine receptors; [ 123 I]IBZM, epidepride, IBF and FIDA2, four iodobenzamide derivatives, for D2/D3 dopamine receptors. In addition, [ 123 I]β-CIT (RTI-55) and IPT, cocaine derivatives, for the dopamine reuptake site are potentially useful for diagnosis of loss of dopamine neurons. The first iodinated ligand, (R)trans-7-OH-PIPAT, for D3 dopamine receptors, was synthesized and characterized with cloned cell lines (Spodoptera frugiperda, Sf9) expressing the D2 and D3 dopamine receptors and with rat basal forebrain membrane preparations. Most of the known iodobenzamides displayed similar potency in binding to both D2 and D3 dopamine receptors expressed in the cell lines. Initial studies appear to suggest that by fine tuning the structures it may be possible to develop agents specific for D2 and D3 dopamine receptors. It is important to investigate D2/D3 selectivity for this series of potent ligands

  7. Tumor targeting via integrin ligands

    Directory of Open Access Journals (Sweden)

    Udaya Kiran eMarelli

    2013-08-01

    Full Text Available Selective and targeted delivery of drugs to tumors is a major challenge for an effective cancer therapy and also to overcome the side effects associated with current treatments. Overexpression of various receptors on tumor cells is a characteristic structural and biochemical aspect of tumors and distinguishes them from physiologically normal cells. This abnormal feature is therefore suitable for selectively directing anticancer molecules to tumors by using ligands that can preferentially recognize such receptors. Several subtypes of integrin receptors that are crucial for cell adhesion, cell signaling, cell viability and motility have been shown to have an upregulated expression on cancer cells. Thus, ligands that recognize specific integrin subtypes represent excellent candidates to be conjugated to drugs or drug carrier systems and be targeted to tumors. In this regard, integrins recognizing the RGD cell adhesive sequence have been extensively targeted for tumor specific drug delivery. Here we review key recent examples on the presentation of RGD-based integrin ligands by means of distinct drug delivery systems, and discuss the prospects of such therapies to specifically target tumor cells.

  8. Solvation effects on isomeric preferences of curium(iii) complexes with multidentate phosphonopropionic acid ligands: CmH(2)PPA(2+) and CmHPPA(+) complexes.

    Science.gov (United States)

    Cao, Zhiji; Balasubramanian, K; Calvert, Michael G; Nitsche, Heino

    2009-10-19

    We have carried out both time-resolved laser fluorescence spectroscopic and computational studies on the complexes of curium(III) with multidentate Phosphonopropionic (PPA) acid ligands. A number of complexes of Cm(III) with these ligands, such as CmH(2)PPA(2+), CmHPPA(+), Cm[H(2)PPA](2)(+), and Cm[HPPA](2)(-) have been studied. Our computational studies focused on all possible isomers in the gas phase and aqueous solution so that the relative binding strengths of carboxylic versus phosphoric groups can be assessed in these multidentate systems. The solvation effects play an important role in the determination of the preferred configurations and binding propensities of carboxylate versus phosphate sites of the ligands. Our computations assess the relative strengths of single and multidentate complexes in solutions for these systems. The computed free energies of solvation explain the experimentally observed fluorescence spectra and the lifetimes of these complexes in that as more water molecules are displaced from the first hydration sphere by the ligands that bind to Cm(III), the fluorescence lifetime increases. We have found that the most stable complex for CmH(2)PPA(2+) in the aqueous phase exhibits a monodentate complex where the curium(III) is bound to the deprotonated phosphate oxygen atom. Our computations support the observed longer fluorescence lifetime of CmH(2)PPA(2+) (112 mus) compared to the free Cm(III) aquo ion (65 mus), suggesting a greater degree of H(2)O displacement from the hydration sphere. For the Cm-HPPA(+) complex, we find a tridentate form as the most stable structure which supports the observed fluorescence lifetime for the CmHPPA(+) complex (172 mus), confirming the removal of up to six water molecules from the inner hydration sphere. The relative stabilities of the complexes are found to vary substantially between the gas phase and solution, indicating a major role of solvation in the relative stabilities of these complexes.

  9. Molecular structure and biological studies on Cr(III), Mn(II) and Fe(III) complexes of heterocyclic carbohydrazone ligand

    Science.gov (United States)

    Abu El-Reash, G. M.; El-Gammal, O. A.; Radwan, A. H.

    2014-03-01

    The chelating behavior of the ligand (H2APC) based on carbohydrazone core modified with pyridine end towards Cr(III), Mn(II) and Fe(III) ions have been examined. The 1H NMR and IR data for H2APC revealed the presence of two stereoisomers syn and anti in both solid state and in solution in addition to the tautomeric versatility based on the flexible nature of the hydrazone linkage leading to varied coordination modes. The spectroscopic data confirmed that the ligand behaves as a monobasic tridentate in Cr(III) and Fe(III) complexes and as neutral tetradentate in Mn(II) complex. The electronic spectra as well as the magnetic measurements confirmed the octahedral geometry for all complexes. The bond length and angles were evaluated by DFT method using material studio program for all complexes. The thermal behavior and the kinetic parameters of degradation were determined using Coats-Redfern and Horowitz-Metzger methods. The antioxidant (DDPH and ABTS methods), anti-hemolytic and cytotoxic activities of the compounds have been screened. Cr(III) complex and H2APC showed the highest antioxidant activity using ABTS and DPPH methods. With respect to in vitro Ehrlich ascites assay, H2APC exhibited the potent activity followed by Fe(III) and Cr(III)complexes.

  10. Synthesis, Photochemical, and Redox Properties of Gold(I) and Gold(III) Pincer Complexes Incorporating a 2,2':6',2"-Terpyridine Ligand Framework.

    Science.gov (United States)

    Gimeno, M Concepción; López-de-Luzuriaga, José M; Manso, Elena; Monge, Miguel; Olmos, M Elena; Rodríguez-Castillo, María; Tena, María-Teresa; Day, David P; Lawrence, Elliot J; Wildgoose, Gregory G

    2015-11-16

    Reaction of [Au(C6F5)(tht)] (tht = tetrahydrothiophene) with 2,2':6',2"-terpyridine (terpy) leads to complex [Au(C6F5)(η(1)-terpy)] (1). The chemical oxidation of complex (1) with 2 equiv of [N(C6H4Br-4)3](PF6) or using electrosynthetic techniques affords the Au(III) complex [Au(C6F5)(η(3)-terpy)](PF6)2 (2). The X-ray diffraction study of complex 2 reveals that the terpyridine acts as tridentate chelate ligand, which leads to a slightly distorted square-planar geometry. Complex 1 displays fluorescence in the solid state at 77 K due to a metal (gold) to ligand (terpy) charge transfer transition, whereas complex 2 displays fluorescence in acetonitrile due to excimer or exciplex formation. Time-dependent density functional theory calculations match the experimental absorption spectra of the synthesized complexes. In order to further probe the frontier orbitals of both complexes and study their redox behavior, each compound was separately characterized using cyclic voltammetry. The bulk electrolysis of a solution of complex 1 was analyzed by spectroscopic methods confirming the electrochemical synthesis of complex 2.

  11. A new copper(II) chelate complex with tridentate ligand: Synthesis, crystal and molecular electronic structure of aqua-(diethylenetriamine-N, N‧, N‧‧)-copper(II) sulfate monohydrate and its fire retardant properties

    Science.gov (United States)

    Lavrenyuk, H.; Mykhalichko, O.; Zarychta, B.; Olijnyk, V.; Mykhalichko, B.

    2015-09-01

    The crystals of a new aqua-(diethylenetriamine-N, N‧, N‧‧)-copper(II) sulfate monohydrate have been synthesized by direct interaction of solid copper(II) sulfate pentahydrate with diethylenetriamine (deta). The crystal structure of [Cu(deta)H2O]SO4ṡH2O (1) has been determined by X-ray diffraction methods at 100 K and characterized using X-ray powder diffraction pattern: space group P 1 bar, a = 7.2819(4), b = 8.4669(4), c = 8.7020(3) Å, α = 83.590(3), β = 89.620(4), γ = 84.946(4)°, Z = 2. The environment of the Cu(II) atom is a distorted, elongated square pyramid which consists of three nitrogen atoms of the deta molecule and oxygen atom of the water molecule in the basal plane of the square pyramid (the average lengths of the in-plane Cu-N and Cu-O bonds are 2.00 Å). The apical position of the coordination polyhedron is occupied by complementary oxygen atom of the sulfate anion (the length of the axial Cu-O bond is 2.421(1) Å). The crystal packing is governed by strong hydrogen bonds of O-H⋯O and N-H⋯O types. The ab initio quantum-chemical calculations have been performed by the restricted Hartree-Fock method with a basis set 6-31∗G using the structural data of [Cu(deta)H2O]SO4ṡH2O. It has been ascertained that the degenerate d-orbitals of the Cu2+ ion split under the co-action of both the square-pyramidal coordination and the chelation. It is significant that visually observed crystals color (blue-violet) of the [Cu(deta)H2O]SO4ṡH2O complex is in good agreement with the calculated value of wavelength of visible light (λ = 5735 Å) which is closely related to the energy of the absorbed photon (Δ = 2.161 eV). Furthermore, the stereo-chemical aspect of influence of the CuSO4 upon combustibility of modified epoxy-amine polymers has been scrutinized.

  12. Ligand photo-isomerization triggers conformational changes in iGluR2 ligand binding domain.

    Directory of Open Access Journals (Sweden)

    Tino Wolter

    Full Text Available Neurological glutamate receptors bind a variety of artificial ligands, both agonistic and antagonistic, in addition to glutamate. Studying their small molecule binding properties increases our understanding of the central nervous system and a variety of associated pathologies. The large, oligomeric multidomain membrane protein contains a large and flexible ligand binding domains which undergoes large conformational changes upon binding different ligands. A recent application of glutamate receptors is their activation or inhibition via photo-switchable ligands, making them key systems in the emerging field of optochemical genetics. In this work, we present a theoretical study on the binding mode and complex stability of a novel photo-switchable ligand, ATA-3, which reversibly binds to glutamate receptors ligand binding domains (LBDs. We propose two possible binding modes for this ligand based on flexible ligand docking calculations and show one of them to be analogues to the binding mode of a similar ligand, 2-BnTetAMPA. In long MD simulations, it was observed that transitions between both binding poses involve breaking and reforming the T686-E402 protein hydrogen bond. Simulating the ligand photo-isomerization process shows that the two possible configurations of the ligand azo-group have markedly different complex stabilities and equilibrium binding modes. A strong but slow protein response is observed after ligand configuration changes. This provides a microscopic foundation for the observed difference in ligand activity upon light-switching.

  13. Ruthenium Cumulenylidene Complexes Bearing Heteroscorpionate Ligands

    OpenAIRE

    Strinitz, Frank

    2014-01-01

    In previous work of the BURZLAFF group, the design of suitable N,N,O ligands for a wide variety of applications ranging from catalysis to bioinorganic model compounds has been extensively investigated. Especially the methyl substituted bis(3,5-dimethylpyrazol-1-yl) acetate (bdmpza) ligand has shown manifold chemistry, comparable to the anionic cyclopentadienyl (Cp) and hydridotris(pyrazol-1-yl)borato (Tp) ligand. In the first part of this thesis the new tricarbonylmanganese(I) complexes be...

  14. Development of immobilized ligands for actinide separations

    International Nuclear Information System (INIS)

    Paine, R.T.

    1994-01-01

    Primary goals during this grant period were to (1) synthesize new bifunctional chelating ligands, (2) characterize the structural features of the Ln and An coordination complexes formed by these ligands, (3) use structural data to iteratively design new classes of multifunctional ligands, and (4) explore additional routes for attachment of key ligands to solid supports that could be useful for chromatographic separations. Some highlights of recently published work as well as a summary of submitted, unpublished and/or still in progress research are outlined

  15. Macrocyclic ligands for uranium complexation

    Energy Technology Data Exchange (ETDEWEB)

    Potts, K.T.

    1991-04-01

    A highly preorganized 24-macrocycle containing biuret, thiobiuret and pyridine subunits has been prepared by high dilution ring-closure procedures. Intermediate products to this macrocycle have been utilized to extend this synthetic route to include further representatives where solubility and stability will be influenced by substituent variation. A 1:1 complex has been formed from uranyl acetate and a quinquepyridine derivative, this representing a new type of ligand for the uranyl ion. A very convenient synthetic procedure that will allow the incorporation of these macrocycles into polymeric systems has been developed for the introduction of a vinyl substituent into the 4-position of the pyridine ring. Using triflate, vinyltributyltin and Pd{sup 0} chemistry, this procedure should make a variety of substituted 4-vinylpyridines available for the first time. 3 refs.

  16. Macrocyclic ligands for uranium complexation

    International Nuclear Information System (INIS)

    Potts, K.T.

    1991-04-01

    A highly preorganized 24-macrocycle containing biuret, thiobiuret and pyridine subunits has been prepared by high dilution ring-closure procedures. Intermediate products to this macrocycle have been utilized to extend this synthetic route to include further representatives where solubility and stability will be influenced by substituent variation. A 1:1 complex has been formed from uranyl acetate and a quinquepyridine derivative, this representing a new type of ligand for the uranyl ion. A very convenient synthetic procedure that will allow the incorporation of these macrocycles into polymeric systems has been developed for the introduction of a vinyl substituent into the 4-position of the pyridine ring. Using triflate, vinyltributyltin and Pd 0 chemistry, this procedure should make a variety of substituted 4-vinylpyridines available for the first time. 3 refs

  17. Ligand based pharmacophore modelling of anticancer histone ...

    African Journals Online (AJOL)

    USER

    2010-06-21

    Jun 21, 2010 ... HDAC ligands (Chen et al., 2008b). The knowledge of common properties of the binding group is essential for the determination of the type of inhibitor binding the target. Major goal of modern drug design is identification and development of new ligands with high affinity of binding toward a given protein.

  18. Organometallic chemistry of chiral diphosphazane ligands ...

    Indian Academy of Sciences (India)

    Unknown

    1. Introduction. Diphosphazanes constitute a class of versatile short-bite bidentate P-donor ligands that have given rise to a varied and extensive transition metal organometallic chemistry. The organometallic chemistry of diphosphazane ligands with almost every transition metal in the periodic table is well documented1–3.

  19. Cofactor-Controlled Chirality of Tropoisomeric Ligand

    NARCIS (Netherlands)

    Théveau, L.; Bellini, R.; Dydio, P.; Szabo, Z.; van der Werf, A.; Sander, R.A.; Reek, J.N.H.; Moberg, C.

    2016-01-01

    A new tropos ligand with an integrated anion receptor receptor site has been prepared. Chiral carboxylate and phosphate anions that bind in the anion receptor unit proved capable of stabilizing chiral conformations of the achiral flexible bidentate biaryl phosphite ligand, as shown by variable

  20. Ligand modification for mono- and biphasic oxosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Haerter, P.; Herrmann, W.A.; Baskakov, D. [Technische Univ. Muenchen (Germany). Dept. Chemie

    2006-07-01

    The use of aqueous/organic biphasic systems has attracted huge interest in catalytic reactions by transition metal complexes. [1,2,3] The biphasic systems have benefits in catalyst separation and recycling, and the reduction or elimination of organic solvents is also advantageous for the development of economical and environmentally friendly processes. The key for such biphasic catalysis is the use of water soluble phosphines as ligands. Since the launch of the commercial propylene hydroformylation process by Ruhrchemie/Rhone-Poulenc, sulfonated ligands such as TPPTS (1), and BINAS (2) have been widely used as ligands in hydroformylation, hydrogenation and related reactions catalyzed by transition metals. One of the draw backs of ligands 1 and 2 are corrosive production conditions and therefore unfavorable costs. With the synthesis of aminoacid based trishydroxymethylphosphine derivatives (THMP-aminoacid) we introduce to our knowledge a new group of water soluble and cheap to produce ligands [8]. The properties of catalysts based on these compounds in the hydroformylation reaction of propene are discussed in comparison to normally used catalyst systems. In a second part the performance of catalysts containing NHC-ligands in the hydroformylation of 1-octene is discussed [9]. These investigations show, that the activity can be influenced by the electron donating ability of the NHC ligand. Sterical variations on the NHC ligands have no effect on the selectivity performance of the the catalysts. (orig.)

  1. Organometallic chemistry of chiral diphosphazane ligands ...

    Indian Academy of Sciences (India)

    Unknown

    organometallic chemistry of diphosphazane ligands with almost every transition metal in the periodic table is well documented1–3. A very attractive feature of diphosphazane ligands is that 'chirality' can be incorporated at the phosphorus centres as well as at the substituents attached to the nitrogen and the two phosphorus ...

  2. Ligand sphere conversions in terminal carbide complexes

    DEFF Research Database (Denmark)

    Morsing, Thorbjørn Juul; Reinholdt, Anders; Sauer, Stephan P. A.

    2016-01-01

    Metathesis is introduced as a preparative route to terminal carbide complexes. The chloride ligands of the terminal carbide complex [RuC(Cl)2(PCy3)2] (RuC) can be exchanged, paving the way for a systematic variation of the ligand sphere. A series of substituted complexes, including the first exam...

  3. Biomimetic affinity ligands for protein purification.

    Science.gov (United States)

    Sousa, Isabel T; Taipa, M Angela

    2014-01-01

    The development of sophisticated molecular modeling software and new bioinformatic tools, as well as the emergence of data banks containing detailed information about a huge number of proteins, enabled the de novo intelligent design of synthetic affinity ligands. Such synthetic compounds can be tailored to mimic natural biological recognition motifs or to interact with key surface-exposed residues on target proteins and are designated as "biomimetic ligands." A well-established methodology for generating biomimetic or synthetic affinity ligands integrates rational design with combinatorial solid-phase synthesis and screening, using the triazine scaffold and analogues of amino acids side chains to create molecular diversity.Triazine-based synthetic ligands are nontoxic, low-cost, highly stable compounds that can replace advantageously natural biological ligands in the purification of proteins by affinity-based methodologies.

  4. Correcting ligands, metabolites, and pathways

    Directory of Open Access Journals (Sweden)

    Vriend Gert

    2006-11-01

    Full Text Available Abstract Background A wide range of research areas in bioinformatics, molecular biology and medicinal chemistry require precise chemical structure information about molecules and reactions, e.g. drug design, ligand docking, metabolic network reconstruction, and systems biology. Most available databases, however, treat chemical structures more as illustrations than as a datafield in its own right. Lack of chemical accuracy impedes progress in the areas mentioned above. We present a database of metabolites called BioMeta that augments the existing pathway databases by explicitly assessing the validity, correctness, and completeness of chemical structure and reaction information. Description The main bulk of the data in BioMeta were obtained from the KEGG Ligand database. We developed a tool for chemical structure validation which assesses the chemical validity and stereochemical completeness of a molecule description. The validation tool was used to examine the compounds in BioMeta, showing that a relatively small number of compounds had an incorrect constitution (connectivity only, not considering stereochemistry and that a considerable number (about one third had incomplete or even incorrect stereochemistry. We made a large effort to correct the errors and to complete the structural descriptions. A total of 1468 structures were corrected and/or completed. We also established the reaction balance of the reactions in BioMeta and corrected 55% of the unbalanced (stoichiometrically incorrect reactions in an automatic procedure. The BioMeta database was implemented in PostgreSQL and provided with a web-based interface. Conclusion We demonstrate that the validation of metabolite structures and reactions is a feasible and worthwhile undertaking, and that the validation results can be used to trigger corrections and improvements to BioMeta, our metabolite database. BioMeta provides some tools for rational drug design, reaction searches, and

  5. Autocrine signal transmission with extracellular ligand degradation

    International Nuclear Information System (INIS)

    Muratov, C B; Posta, F; Shvartsman, S Y

    2009-01-01

    Traveling waves of cell signaling in epithelial layers orchestrate a number of important processes in developing and adult tissues. These waves can be mediated by positive feedback autocrine loops, a mode of cell signaling where binding of a diffusible extracellular ligand to a cell surface receptor can lead to further ligand release. We formulate and analyze a biophysical model that accounts for ligand-induced ligand release, extracellular ligand diffusion and ligand–receptor interaction. We focus on the case when the main mode for ligand degradation is extracellular and analyze the problem with the sharp threshold positive feedback nonlinearity. We derive expressions that link the speed of propagation and other characteristics of traveling waves to the parameters of the biophysical processes, such as diffusion rates, receptor expression level, etc. Analyzing the derived expressions we found that traveling waves in such systems can exhibit a number of unusual properties, e.g. non-monotonic dependence of the speed of propagation on ligand diffusivity. Our results for the fully developed traveling fronts can be used to analyze wave initiation from localized perturbations, a scenario that frequently arises in the in vitro models of epithelial wound healing, and guide future modeling studies of cell communication in epithelial layers

  6. Chemistry of marine ligands and siderophores.

    Science.gov (United States)

    Vraspir, Julia M; Butler, Alison

    2009-01-01

    Marine microorganisms are presented with unique challenges to obtain essential metal ions required to survive and thrive in the ocean. The production of organic ligands to complex transition metal ions is one strategy to both facilitate uptake of specific metals, such as iron, and to mitigate the potential toxic effects of other metal ions, such as copper. A number of important trace metal ions are complexed by organic ligands in seawater, including iron, cobalt, nickel, copper, zinc, and cadmium, thus defining the speciation of these metal ions in the ocean. In the case of iron, siderophores have been identified and structurally characterized. Siderophores are low molecular weight iron-binding ligands produced by marine bacteria. Although progress has been made toward the identity of in situ iron-binding ligands, few compounds have been identified that coordinate the other trace metals. Deciphering the chemical structures and production stimuli of naturally produced organic ligands and the organisms they come from is fundamental to understanding metal speciation and bioavailability. The current evidence for marine ligands, with an emphasis on siderophores, and discussion of the importance and implications of metal-binding ligands in controlling metal speciation and cycling within the world's oceans are presented.

  7. Directed synthesis of a heterobimetallic complex based on a novel unsymmetric double-Schiff-base ligand: preparation, characterization, reactivity and structures of hetero- and homobimetallic nickel(II) and zinc(II) complexes.

    Science.gov (United States)

    Roth, Arne; Buchholz, Axel; Rudolph, Manfred; Schütze, Eileen; Kothe, Erika; Plass, Winfried

    2008-01-01

    A series of bimetallic zinc(II) and nickel(II) complexes based on the novel dinucleating unsymmetric double-Schiff-base ligand benzoic acid [1-(3-{[2-(bispyridin-2-ylmethylamino)ethylimino]methyl}-2-hydroxy-5-methylphenyl)methylidene]hydrazide (H(2)bpampbh) has been synthesized and structurally characterized. The metal centers reside in two entirely different binding pockets provided by the ligand H(2)bpampbh, a planar tridentate [ONO] and a pentadentate [ON(4)] compartment. The utilized ligand H(2)bpampbh has been synthesized by condensation of the single-Schiff-base proligand Hbpahmb with benzoic acid hydrazide. The reaction of H(2)bpampbh with two equivalents of either zinc(II) or nickel(II) acetate yields the homobimetallic complexes [Zn(2)(bpampbh)(mu,eta(1)-OAc)(eta(1)-OAc)] (ZnZn) and [Ni(2)(bpampbh)(mu-H(2)O)(eta(1)-OAc)(H(2)O)](OAc) (NiNi), respectively. Simultaneous presence of one equivalent zinc(II) and one equivalent nickel(II) acetate results in the directed formation of the heterobimetallic complex [NiZn(bpampbh)(mu,eta(1)-OAc)(eta(1)-OAc)] (NiZn) with a selective binding of the nickel ions in the pentadentate ligand compartment. In addition, two homobimetallic azide-bridged complexes [Ni(2)(bpampbh)(mu,eta(1)-N(3))]ClO(4) (NiNi(N(3))) and [Ni(2)(bpampbh)(mu,eta(1)-N(3))(MeOH)(2)](ClO(4))(0.5)(N(3))(0.5) (NiNi(N(3))(MeOH)(2)) were synthesized. In all complexes, the metal ions residing in the pentadentate compartment adopt a distorted octahedral coordination geometry, whereas the metal centers placed in the tridentate compartment vary in coordination number and geometry from square-planar (NiNi(N(3))) and square-pyramidal (ZnZn and NiZn), to octahedral (NiNi and NiNi(N(3))(MeOH)(2)). In the case of complex NiNi(N(3)) this leads to a mixed-spin homodinuclear nickel(II) complex. All compounds have been characterized by means of mass spectrometry as well as IR and UV/Vis spectroscopies. Magnetic susceptibility measurements show significant zero

  8. Radiation induced ligand loss from cobalt complexes

    International Nuclear Information System (INIS)

    Funston, A. M.; McFadyen, W.D.; Tregloan, P.A.

    2000-01-01

    Full text: Due to the rapid nature of ligand dissociation from cobalt(II) complexes the study of the rate of ligand dissociation necessitates the use of a technique such as pulse radiolysis. This allows the rapid reduction of the corresponding cobalt(III) complex by a reducing radical, such as the aquated electron, to form the cobalt(II) complex. However, to date, no systematic study of either the mechanism of reduction or the influence of the electronic structure on the rate of ligand dissociation has been carried out. In order to understand these processes more fully the mechanism of reduction of a range of related cobalt(III) complexes by the aquated electron and the subsequent rate of ligand dissociation from the resulting cobalt(II) complexes is being investigated. It has been found that a number of processes are observed following the initial rapid reaction of the cobalt(III) complex with the aquated electron. Ultimately ligand loss is observed. Depending upon the complex, the initial processes observed may include the formation of coordinated radicals and electron transfer within the complex. For complexes containing aromatic ligands such as 2,2'-bipyridine, 1,10-phenanthroline and dipyrido[3,2-a:2',3'-c]phenazine the formation of a coordinated radical is observed as the initial reduction step. The kinetics of ligand dissociation of these complexes has been determined. The loss of monodentate ligands is fast and has been indistinguishable from the reduction processes when aromatic ligands are also present in the complex. However, for diamine chelates and diimine chelates spectra of the transient species can be resolved

  9. Final Technical Report [Development of Catalytic Alkylation and Fluoroalkylation Methods

    Energy Technology Data Exchange (ETDEWEB)

    Vicic, David A.

    2014-05-01

    In the early stages of this DOE-funded research project, we sought to prepare and study a well-defined nickel-alkyl complex containing tridentate nitrogen donor ligands. We found that reaction of (TMEDA)NiMe2 (1) with terpyridine ligand cleanly led to the formation of (terpyridyl)NiMe (2), which we also determined to be an active alkylation catalyst. The thermal stability of 2 was unlike that seen for any of the active pybox ligands, and enabled a number of key studies on alkyl transfer reactions to be performed, providing new insights into the mechanism of nickel-mediated alkyl-alkyl cross-coupling reactions. In addition to the mechanistic studies, we showed that the terpyridyl nickel compounds can catalytically cross-couple alkyl iodides in yields up to 98% and bromides in yields up to 46 %. The yields for the bromides can be increased up to 67 % when the new palladium catalyst [(tpy’)Pd-Ph]I is used. The best route to the targeted [(tpy)NiBr] (1) was found to involve the comproportionation reaction of [(dme)NiBr{sub 2}] and [Ni(COD){sub 2}] in the presence of two equivalents of terpyridine. This reaction was driven to high yields of product formation (72 % isolated) by the precipitation of 1 from THF solvent.

  10. Stabilization of enzyme by using hydrophobic ligands

    Energy Technology Data Exchange (ETDEWEB)

    Ota, H.; Yamahara, K.; Kuboi, R. [Osaka University, Osaka (Japan)

    1998-02-01

    The protection (stabilization) effect of various hydrophobic ligands on the denaturation and aggregation of carbonic anhydrase from bovine (CAB) has been quantitatively investigated under various heat stress conditions. In a limited temperature range (40-60degC), where the protein was only partially denatured and the local hydrophobicities (LH) of CAB were positive effective stabilization of the protein is achieved by the addition of various ligands. The importance of balance between hydrophobic head and hydrophilic tail of the ligands is hypothesized. 18 refs., 5 figs.

  11. A versatile dinucleating ligand containing sulfonamide groups

    DEFF Research Database (Denmark)

    Sundberg, Jonas; Witt, Hannes; Cameron, Lisa

    2014-01-01

    ligand can be prepared in aqueous solutions using only divalent metal ions. Two of the copper(II) complexes, [Cu2(psmp)(OH)] and [Cu2(psmp)(OAc)2]-, demonstrate the anticipated 1:2 ligand/metal stoichiometry and show that the dimetallic binding site created for exogenous ligands possesses high inherent...... of antiferromagnetic coupling. This is corroborated computationally by broken-symmetry density functional theory, which for isotropic modeling of the coupling predicts an antiferromagnetic coupling strength of J = 70.5 cm-1....

  12. Coordination of bis(pyrazol-1-ylamine to palladium(II: influence of the co-ligands and counter-ions on the molecular and crystal structures

    Directory of Open Access Journals (Sweden)

    María de los Angeles Mendoza

    2015-01-01

    Full Text Available The structures of a series of complexes with general formula n[Pd(pzaX]Y·mH2O (n = 1, 2; X = Cl, Br, I, N3, NCS; Y = NO3, I, N3, [Pd(SCN4]; m = 0, 0.5, 1 have been determined, where pza is the tridentate ligand bis[2-(3,5-dimethylpyrazol-1-ylethyl]amine, C14H23N5. In all complexes, {bis[2-(3,5-dimethylpyrazol-1-yl-κN2ethyl]amine-κN}chloridopalladium nitrate, [Pd(pzaCl]NO3, (1, {bis[2-(3,5-dimethylpyrazol-1-yl-κN2ethyl]amine-κN}bromidopalladium nitrate, [Pd(pzaBr]NO3, (2, {bis[2-(3,5-dimethylpyrazol-1-yl-κN2ethyl]amine-κN}iodidopalladium iodide hemihydrate, [Pd(pzaI]I·0.5H2O, (3, azido{bis[2-(3,5-dimethylpyrazol-1-yl-κN2ethyl]amine-κN}palladium azide monohydrate, [Pd(pzaN3]N3·H2O, (4, and bis[{bis[2-(3,5-dimethylpyrazol-1-yl-κN2ethyl]amine-κN}(thiocyanato-κNpalladium] tetrakis(thiocyanato-κSpalladate, [Pd(pzaNCS]2[Pd(SCN4], (5, the [Pd(pzaX]+ complex cation displays a square-planar coordination geometry, and the pza ligand is twisted, approximating twofold rotation symmetry. Although the pza ligand is found with the same conformation along the series, the dihedral angle between pyrazole rings depends on the co-ligand X. This angle span the range 79.0 (3–88.6 (1° for the studied complexes. In (3, two complex cations, two I− anions and one water molecule of crystallization are present in the asymmetric unit. In (5, the central amine group of pza is disordered over two positions [occupancy ratio 0.770 (18:0.230 (18]. The complex [Pd(SCN4]2− anion of this compound exhibits inversion symmetry and shows the Pd2+ transition metal cation likewise in a square-planar coordination environment. Compound (5 is also a rare occurrence of a non-polymeric compound in which the pseudohalide ligand NCS− behaves both as thiocyanate and isothiocyanate, i.e. is coordinating either through the N atom (in the cation or the S atom (in the anion.

  13. Novel bis(5-methyltetrazolium)amine ligand-bonded stationary phase with reduced leakage of metal ions in immobilized metal affinity chromatography of proteins.

    Science.gov (United States)

    Bo, Chunmiao; Wang, Chaozhan; Wei, Yinmao

    2016-11-01

    Immobilized metal affinity chromatography (IMAC) has been widely used for the specific separation of biopolymers. However, leakage of metal ions from IMAC adsorbents is of concern in IMAC. In this study, we designed a novel tridenate bis(5-methyltetrazolium)amine (BMTA) to reduce the leakage of metal ions by improving the affinity to immobilized metal ions. The ligand was bonded onto silica via three-step reaction to prepare a high-performance IMAC stationary phase. The chromatographic behaviors of ribonuclease A, cytochrome c, and lysozyme on the Cu(II)-, Ni(II)-, and Zn(II)-chelated stationary phase were investigated with respect to pH effect and elution with an imidazole gradient. The retention times of these three proteins increased by increasing the pH of the mobile phase but decreased by increasing the concentration of the competitive displacer. The retaining strength of the three proteins on the chelated stationary phase were in the order Cu(II) > Ni(II) > Zn(II). The behavior of these three proteins was consistent with the properties of a typical IMAC. The BMTA ligand exhibited a much stronger affinity for Cu(II) and Ni(II) than iminodiacetic acid (IDA), which is often regarded as a standard tridentate IMAC ligand. Quantum mechanical calculations at the B3LYP/6-31G level were used to image the coordination mode of the protein-metal ions-BMTA complex. In addition, a fused histidine-tagged cecropin b-human epidermal growth factor (CB-EGF) from Escherichia coli crude extract was purified by the Ni(II)-chelated stationary phase, and the purity of the CB-EGF was determined to be at least 90 %. These results suggest that the BMTA ligand may have potential applications in the preparation of therapeutics. Graphical Abstract A novel ligand of tridenate bis(5-methyltetrazolium)amine (BMTA) was designed to reduce the leakage of metal ions from the column in immobolized metal affinity chromatography (IMAC).

  14. Novel CoIII complexes containing fluorescent coumarin-N-acylhydrazone hybrid ligands: Synthesis, crystal structures, solution studies and DFT calculations

    Science.gov (United States)

    Areas, Esther S.; Bronsato, Bruna Juliana da S.; Pereira, Thiago M.; Guedes, Guilherme P.; Miranda, Fábio da S.; Kümmerle, Arthur E.; da Cruz, Antônio G. B.; Neves, Amanda P.

    2017-12-01

    A series of new CoIII complexes of the type [Co(dien)(L1 -L3)]ClO4 (1-3), containing fluorescent coumarin-N-acylhydrazonate hybrid ligands, (E)-N‧-(1-(7-oxido-2-oxo-2H-chromen-3-yl)ethylidene)-4-R-benzohydrazonate [where R = H (L12 -), OCH3 (L22 -) or Cl (L32 -)], were obtained and isolated in the low spin CoIII configuration. Single-crystal X-ray diffraction showed that the coumarin-N-acylhydrazones act as tridentate ligands in their deprotonated form (L2 -). The cation (+ 1) complexes contain a diethylenetriamine (dien) as auxiliary ligand and their structures were calculated by DFT studies which were also performed for the CoII (S = 1/2 and S = 3/2) configurations. The LS CoII (S = 1/2) concentrated the spin density on the O-Co-O axis while the HS CoII (S = 3/2) exhibited a broad spin density distribution around the metallic center. Cyclic voltammetry studies showed that structural modifications made in the L2 - ligands caused a slight influence on the electronic density of the metal center, and the E1/2 values for the CoIII/CoII redox couple increased following the electronic effect of the R-substituent, in the order: 2 (R = OCH3) experimental values vs SHE (E°calc = - 0.37, - 0.36 and - 0.32 V vs E°exp. = - 0.371, - 0.406 and - 0.358 V, for 1-3 respectively). Complexes 1-3 exhibited a very intense absorption band around 470 nm, assigned by DFT calculations as π-π* transitions from the delocalized coumarin-N-acylhydrazone system. 1-3 were very stable in MeOH for several days. Likewise, 1-3 were stable in phosphate buffer containing sodium ascorbate after 15 h, which was attributed to the high chelate effect and σ-donor ability of the L2 - and dien ligands.

  15. Schiff base ligand derived from (±trans-1,2-cyclohexanediamine and its Cu(II, Co(II, Zn(II and Mn(II complexes: Synthesis, characterization, styrene oxidation and hydrolysis study of the imine bond in Cu(II Schiff base complex

    Directory of Open Access Journals (Sweden)

    Sarkheil Marzieh

    2016-01-01

    Full Text Available A Schiff base ligand (H2L derived from 2´-hydroxypropiophenone and (±trans-1,2-cyclohexanediamine was synthesized. The reactions of MCl2.xH2O (M =Cu(II, Co(II, Zn(II and Mn(IIwith the di-Schiff base ligand (H2L were studied. This ligand when stirred with 1 equivalent of CuCl2.2H2O in the solution of ethanol and chloroform undergoes partial hydrolysis of the imino bond and the resultant tridentate ligand (HL′immediately forms complex[CuL´Cl]∙3/2CHCl3(1with N2O coordination sphere. Under the same condition, the reaction of H2L with MCl2.xH2O (M = Co(II (3, Zn(II (4 and Mn(II (5 gave complexes[ML]•1/2CHCl3∙3/2H2O (3-5with N2O2 coordination sphere and no hydrolytic cleavage was occurred. Also, the reaction of H2L with CuCl2.2H2O in THF gave the complex CuL (2with N2O2 coordination sphere. The ligand and complexes were characterized by FTIR, UV-Vis, 1H NMRand elemental analysis. The homogeneous catalytic activity of the complexes1, 3 and 5wasevaluated for the oxidation of styrene using tert-butyl hydroperoxide (TBHP as oxidant. Finally, the copper(II complex(1encapsulated in the nanopores of zeolite-Y by flexible ligand method (CuL´-Yand its encapsulation was ensured by different studies. The catalytic performance of heterogeneous catalyst in the styrene oxidation with TBHP was investigated. The catalytic tests showed that the homogenous and heterogeneous catalysts were active in the oxidation of styrene.

  16. Controlling Signal Transduction with Synthetic Ligands

    Science.gov (United States)

    Spencer, David M.; Wandless, Thomas J.; Schreiber, Stuart L.; Crabtree, Gerald R.

    1993-11-01

    Dimerization and oligomerization are general biological control mechanisms contributing to the activation of cell membrane receptors, transcription factors, vesicle fusion proteins, and other classes of intra- and extracellular proteins. Cell permeable, synthetic ligands were devised that can be used to control the intracellular oligomerization of specific proteins. To demonstrate their utility, these ligands were used to reduce intracellular oligomerization of cell surface receptors that lacked their transmembrane and extracellular regions but contained intracellular signaling domains. Addition of these ligands to cells in culture resulted in signal transmission and specific target gene activation. Monomeric forms of the ligands blocked the pathway. This method of ligandregulated activation and termination of signaling pathways has the potential to be applied wherever precise control of a signal transduction pathway is desired.

  17. Allyl functionalized phosphinite and phosphonite ligands: Synthesis ...

    Indian Academy of Sciences (India)

    Allyl functionalized phosphinite and phosphonite ligands: Synthesis, transition metal chemistry and orthopalladation reactions. SINGAPPAGUDEM GOVINDARAJUa, GUDDEKOPPA S ANANTHNAGa, SUSMITA NAIKa,. SHAIKH M MOBINb and MARAVANJI S BALAKRISHNAa,∗. aPhosphorus Laboratory, Department of ...

  18. Organometallic chemistry of chiral diphosphazane ligands ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 114; Issue 4. Organometallic chemistry of chiral diphosphazane ligands: Synthesis and structural characterisation. Kannan Raghuraman Swadhin K Mandal T S Venkatakrishnan Setharampattu S Krishnamurthy Munirathinam Nethaji. Volume 114 Issue 4 August 2002 ...

  19. EGFR Activation by Spatially Restricted Ligands

    National Research Council Canada - National Science Library

    Clouse, Katherine N; Goodrich, Jennifer S

    2006-01-01

    ...) activity has been associated with an increased prognosis of breast cancer. During cogenesis in Drosophila melanogaster local Egfr activation by the spatially-restricted TGFalpha-like ligand Gurken (Grk...

  20. EGFR Activation by Spatially Restricted Ligands

    National Research Council Canada - National Science Library

    Goodrich, Jennifer S

    2005-01-01

    ...) activity has been associated with an increased prognosis of breast cancer. During oogenesis in Drosophila melanogaster, local EGFR activation by the spatially restricted TGF alpha-like ligand, Gurken (Grk...

  1. Dicynamide bridged two new zig-zag 1-D Zn(II) coordination polymers of pyrimidine derived Schiff base ligands: Synthesis, crystal structures and fluorescence studies

    Science.gov (United States)

    Konar, Saugata

    2015-07-01

    Two new zigzag 1-D polymeric Zn(II) coordination polymers {[Zn(L1)(μ1,5-dca)](H2O)}n (1), {[Zn(L2)(μ1,5-dca)](ClO4)}n (2) of two potentially tridentate NNO-, NNN-, donor Schiff base ligands [2-(2-(4,6-dimethylpyrimidin-2-yl)hydrazono)methyl)phenol] (L1), [1-(4,6-dimethylpyrimidin-2-yl)-2-(dipyridin-2ylmethylene)hydrazine] (L2) have been synthesized and characterized by elemental analyses, IR and 1H NMR, fluorescence spectroscopy and single crystal X-ray crystallography. The dicyanamide ions act as linkers (μ1,5 mode) in the formation of these coordination polymers. Both the complexes 1 and 2 have same distorted square pyramidal geometry around the Zn(II) centres. The weak forces like π⋯π, Csbnd H⋯π, anion⋯π interactions lead to various supramolecular architectures. Complex 1 shows high chelation enhanced fluorescence compared to that of 2. The fluorescence spectral changes observed high selectivity towards Zn(II) over other metal ions such as Mn(II), Co(II), Ni(II), Cu(II).

  2. Chemistry of Marine Ligands and Siderophores

    OpenAIRE

    Vraspir, Julia M.; Butler, Alison

    2009-01-01

    Marine microorganisms are presented with unique challenges to obtain essential metal ions required to survive and thrive in the ocean. The production of organic ligands to complex transition metal ions is one strategy to both facilitate uptake of specific metals, such as iron, and to mitigate the potential toxic effects of other metal ions, such as copper. A number of important trace metal ions are complexed by organic ligands in seawater, including iron, cobalt, nickel, copper, zinc, and cad...

  3. Designer TGFβ superfamily ligands with diversified functionality.

    Directory of Open Access Journals (Sweden)

    George P Allendorph

    Full Text Available Transforming Growth Factor--beta (TGFβ superfamily ligands, including Activins, Growth and Differentiation Factors (GDFs, and Bone Morphogenetic Proteins (BMPs, are excellent targets for protein-based therapeutics because of their pervasiveness in numerous developmental and cellular processes. We developed a strategy termed RASCH (Random Assembly of Segmental Chimera and Heteromer, to engineer chemically-refoldable TGFβ superfamily ligands with unique signaling properties. One of these engineered ligands, AB208, created from Activin-βA and BMP-2 sequences, exhibits the refolding characteristics of BMP-2 while possessing Activin-like signaling attributes. Further, we find several additional ligands, AB204, AB211, and AB215, which initiate the intracellular Smad1-mediated signaling pathways more strongly than BMP-2 but show no sensitivity to the natural BMP antagonist Noggin unlike natural BMP-2. In another design, incorporation of a short N-terminal segment from BMP-2 was sufficient to enable chemical refolding of BMP-9, without which was never produced nor refolded. Our studies show that the RASCH strategy enables us to expand the functional repertoire of TGFβ superfamily ligands through development of novel chimeric TGFβ ligands with diverse biological and clinical values.

  4. Exploiting ligand-protein conjugates to monitor ligand-receptor interactions.

    Directory of Open Access Journals (Sweden)

    Hirohito Haruki

    Full Text Available We introduce three assays for analyzing ligand-receptor interactions based on the specific conjugation of ligands to SNAP-tag fusion proteins. Conjugation of ligands to different SNAP-tag fusions permits the validation of suspected interactions in cell extracts and fixed cells as well as the establishment of high-throughput assays. The different assays allow the analysis of strong and weak interactions. Conversion of ligands into SNAP-tag substrates thus provides access to a powerful toolbox for the analysis of their interactions with proteins.

  5. Li+-ligand binding energies and the effect of ligand fluorination on the binding energies

    Science.gov (United States)

    Bauschlicher, Charles W.

    2018-02-01

    The Li+-ligand binding energies are computed for seven ligands and their perfluoro analogs using Density Functional Theory. The bonding is mostly electrostatic in origin. Thus the size of the binding energy tends to correlate with the ligand dipole moment, however, the charge-induced dipole contribution can be sufficiently large to affect the dipole-binding energy correlation. The perfluoro species are significantly less strongly bound than their parents, because the electron withdrawing power of the fluorine reduces the ligand dipole moment.

  6. LigandRFs: random forest ensemble to identify ligand-binding residues from sequence information alone

    KAUST Repository

    Chen, Peng

    2014-12-03

    Background Protein-ligand binding is important for some proteins to perform their functions. Protein-ligand binding sites are the residues of proteins that physically bind to ligands. Despite of the recent advances in computational prediction for protein-ligand binding sites, the state-of-the-art methods search for similar, known structures of the query and predict the binding sites based on the solved structures. However, such structural information is not commonly available. Results In this paper, we propose a sequence-based approach to identify protein-ligand binding residues. We propose a combination technique to reduce the effects of different sliding residue windows in the process of encoding input feature vectors. Moreover, due to the highly imbalanced samples between the ligand-binding sites and non ligand-binding sites, we construct several balanced data sets, for each of which a random forest (RF)-based classifier is trained. The ensemble of these RF classifiers forms a sequence-based protein-ligand binding site predictor. Conclusions Experimental results on CASP9 and CASP8 data sets demonstrate that our method compares favorably with the state-of-the-art protein-ligand binding site prediction methods.

  7. Synthesis and characterization of mixed ligand chiral nanoclusters

    KAUST Repository

    Guven, Zekiye P.

    2016-06-22

    Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. While the chiral ligand led mostly to the formation of nanoparticles, the presence of the achiral ligand drastically increased the yield of nanoclusters with enhanced chiral properties. © 2016 The Royal Society of Chemistry.

  8. The Connection between NHC Ligand Count and Photophysical Properties in Fe(II) Photosensitizers: An Experimental Study.

    Science.gov (United States)

    Zimmer, Peter; Burkhardt, Lukas; Friedrich, Aleksej; Steube, Jakob; Neuba, Adam; Schepper, Rahel; Müller, Patrick; Flörke, Ulrich; Huber, Marina; Lochbrunner, Stefan; Bauer, Matthias

    2018-01-02

    Four homo- and heteroleptic complexes bearing both polypyridyl units and N-heterocyclic carbene (NHC) donor functions are studied as potential noble metal-free photosensitizers. The complexes [Fe II (L1)(terpy)][PF 6 ] 2 , [Fe II (L2) 2 ][PF 6 ] 2 , [Fe II (L1)(L3)][PF 6 ] 2 , and [Fe II (L3) 2 ][PF 6 ] 2 (terpy = 2,2':6',2″ terpyridine, L1 = 2,6-bis[3-(2,6-diisopropylphenyl)imidazol-2-ylidene]pyridine, L2 = 2,6-bis[3-isopropylimidazol-2-ylidene]pyridine, L3 = 1-(2,2'-bipyridyl)-3-methylimidazol-2-ylidene) contain tridentate ligands of the C^N^C and N^N^C type, respectively, resulting in a Fe-NHC number between two and four. Thorough ground state characterization by single crystal diffraction, electrochemistry, valence-to-core X-ray emission spectroscopy (VtC-XES), and high energy resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) in combination with ab initio calculations show a correlation between the geometric and electronic structure of these new compounds and the number of the NHC donor functions. These results serve as a basis for the investigation of the excited states by ultrafast transient absorption spectroscopy, where the lifetime of the 3 MLCT states is found to increase with the NHC donor count. The results demonstrate for the first time the close interplay between the number of NHC functionalities in Fe(II) complexes and their photochemical properties, as revealed in a comparison of the activity as photosensitizers in photocatalytic proton reduction.

  9. Impact of protein and ligand impurities on ITC-derived protein-ligand thermodynamics.

    Science.gov (United States)

    Grüner, Stefan; Neeb, Manuel; Barandun, Luzi Jakob; Sielaff, Frank; Hohn, Christoph; Kojima, Shun; Steinmetzer, Torsten; Diederich, François; Klebe, Gerhard

    2014-09-01

    The thermodynamic characterization of protein-ligand interactions by isothermal titration calorimetry (ITC) is a powerful tool in drug design, giving valuable insight into the interaction driving forces. ITC is thought to require protein and ligand solutions of high quality, meaning both the absence of contaminants as well as accurately determined concentrations. Ligands synthesized to deviating purity and protein of different pureness were titrated by ITC. Data curation was attempted also considering information from analytical techniques to correct stoichiometry. We used trypsin and tRNA-guanine transglycosylase (TGT), together with high affinity ligands to investigate the effect of errors in protein concentration as well as the impact of ligand impurities on the apparent thermodynamics. We found that errors in protein concentration did not change the thermodynamic properties obtained significantly. However, most ligand impurities led to pronounced changes in binding enthalpy. If protein binding of the respective impurity is not expected, the actual ligand concentration was corrected for and the thus revised data compared to thermodynamic properties obtained with the respective pure ligand. Even in these cases, we observed differences in binding enthalpy of about 4kJ⋅mol(-1), which is considered significant. Our results indicate that ligand purity is the critical parameter to monitor if accurate thermodynamic data of a protein-ligand complex are to be recorded. Furthermore, artificially changing fitting parameters to obtain a sound interaction stoichiometry in the presence of uncharacterized ligand impurities may lead to thermodynamic parameters significantly deviating from the accurate thermodynamic signature. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Immobilisation of ligands by radio-derivatized polymers; Immobilisering av ligander med radioderiverte polymerer

    Energy Technology Data Exchange (ETDEWEB)

    Varga, J.M.; Fritsch, P.

    1995-01-30

    The invention relates to radio-derivatized polymers and a method of producing them by contacting non-polymerizable conjugands with radiolysable polymers in the presence of irradiation. The resulting radio-derivatized polymers can be further linked with ligand of organic or inorganic nature to immobilize such ligands. 2 figs., 5 tabs.

  11. A General Ligand Design for Gold Catalysis allowing Ligand-Directed Anti Nucleophilic Attack of Alkynes

    Science.gov (United States)

    Wang, Yanzhao; Wang, Zhixun; Li, Yuxue; Wu, Gongde; Cao, Zheng; Zhang, Liming

    2014-01-01

    Most homogenous gold catalyses demand ≥0.5 mol % catalyst loading. Due to the high cost of gold, these reactions are unlikely to be applicable in medium or large scale applications. Here we disclose a novel ligand design based on the privileged biphenyl-2-phosphine framework that offers a potentially general approach to dramatically lowering catalyst loading. In this design, an amide group at the 3’ position of the ligand framework directs and promotes nucleophilic attack at the ligand gold complex-activated alkyne, which is unprecedented in homogeneous gold catalysis considering the spatial challenge of using ligand to reach antiapproaching nucleophile in a linear P-Au-alkyne centroid structure. With such a ligand, the gold(I) complex becomes highly efficient in catalyzing acid addition to alkynes, with a turnover number up to 99,000. Density functional theory calculations support the role of the amide moiety in directing the attack of carboxylic acid via hydrogen bonding. PMID:24704803

  12. A new class of PN3-pincer ligands for metal–ligand cooperative catalysis

    KAUST Repository

    Li, Huaifeng

    2014-12-01

    Work on a new class of PN3-pincer ligands for metal-ligand cooperative catalysis is reviewed. While the field of the pyridine-based PN3-transition metal pincer complexes is still relatively young, many important applications of these complexes have already emerged. In several cases, the PN3-pincer complexes for metal-ligand cooperative catalysis result in significantly improved or unprecedented activities. The synthesis and coordination chemistry of PN3-pincer ligands are briefly summarized first to cover the synthetic routes for their preparation, followed by a focus review on their applications in catalysis. A specific emphasis is placed on the later section about the role of PN3-pincer ligands\\' dearomatization-rearomatization steps during the catalytic cycles. The mechanistic insights from density functional theory (DFT) calculations are also discussed.

  13. Effects of PPARγ ligands on vascular tone.

    Science.gov (United States)

    Salomone, Salvatore; Drago, Filippo

    2012-06-01

    Peroxisome Proliferator-Activated Receptor γ (PPARγ), originally described as a transcription factor for genes of carbohydrate and lipid metabolism, has been more recently studied in the context of cardiovascular pathophysiology. Here, we review the available data on PPARγ ligands as modulator of vascular tone. PPARγ ligands include: thiazolidinediones (used in the treatment of type 2 diabetes mellitus), glitazars (bind and activate both PPARγ and PPARα), and other experimental drugs (still in development) that exploit the chemistry of thiazolidinediones as a scaffold for PPARγ-independent pharmacological properties. In this review, we examine both short (mostly from in vitro data)- and long (mostly from in vivo data)-term effects of PPARγ ligands that extend from PPARγ-independent vascular effects to PPARγ-dependent gene expression. Because endothelium is a master regulator of vascular tone, we have attempted to differentiate between endothelium-dependent and endothelium-independent effects of PPARγ ligands. Based on available data, we conclude that PPARγ ligands appear to influence vascular tone in different experimental paradigms, most often in terms of vasodilatation (potentially increasing blood flow to some tissues). These effects on vascular tone, although potentially beneficial, must be weighed against specific cardiovascular warnings that may apply to some drugs, such as rosiglitazone.

  14. LIBRA: LIgand Binding site Recognition Application.

    Science.gov (United States)

    Hung, Le Viet; Caprari, Silvia; Bizai, Massimiliano; Toti, Daniele; Polticelli, Fabio

    2015-12-15

    In recent years, structural genomics and ab initio molecular modeling activities are leading to the availability of a large number of structural models of proteins whose biochemical function is not known. The aim of this study was the development of a novel software tool that, given a protein's structural model, predicts the presence and identity of active sites and/or ligand binding sites. The algorithm implemented by ligand binding site recognition application (LIBRA) is based on a graph theory approach to find the largest subset of similar residues between an input protein and a collection of known functional sites. The algorithm makes use of two predefined databases for active sites and ligand binding sites, respectively, derived from the Catalytic Site Atlas and the Protein Data Bank. Tests indicate that LIBRA is able to identify the correct binding/active site in 90% of the cases analyzed, 90% of which feature the identified site as ranking first. As far as ligand binding site recognition is concerned, LIBRA outperforms other structure-based ligand binding sites detection tools with which it has been compared. The application, developed in Java SE 7 with a Swing GUI embedding a JMol applet, can be run on any OS equipped with a suitable Java Virtual Machine (JVM), and is available at the following URL: http://www.computationalbiology.it/software/LIBRAv1.zip. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  15. Dockomatic - automated ligand creation and docking.

    Science.gov (United States)

    Bullock, Casey W; Jacob, Reed B; McDougal, Owen M; Hampikian, Greg; Andersen, Tim

    2010-11-08

    The application of computational modeling to rationally design drugs and characterize macro biomolecular receptors has proven increasingly useful due to the accessibility of computing clusters and clouds. AutoDock is a well-known and powerful software program used to model ligand to receptor binding interactions. In its current version, AutoDock requires significant amounts of user time to setup and run jobs, and collect results. This paper presents DockoMatic, a user friendly Graphical User Interface (GUI) application that eases and automates the creation and management of AutoDock jobs for high throughput screening of ligand to receptor interactions. DockoMatic allows the user to invoke and manage AutoDock jobs on a single computer or cluster, including jobs for evaluating secondary ligand interactions. It also automates the process of collecting, summarizing, and viewing results. In addition, DockoMatic automates creation of peptide ligand .pdb files from strings of single-letter amino acid abbreviations. DockoMatic significantly reduces the complexity of managing multiple AutoDock jobs by facilitating ligand and AutoDock job creation and management.

  16. Dockomatic - automated ligand creation and docking

    Directory of Open Access Journals (Sweden)

    Hampikian Greg

    2010-11-01

    Full Text Available Abstract Background The application of computational modeling to rationally design drugs and characterize macro biomolecular receptors has proven increasingly useful due to the accessibility of computing clusters and clouds. AutoDock is a well-known and powerful software program used to model ligand to receptor binding interactions. In its current version, AutoDock requires significant amounts of user time to setup and run jobs, and collect results. This paper presents DockoMatic, a user friendly Graphical User Interface (GUI application that eases and automates the creation and management of AutoDock jobs for high throughput screening of ligand to receptor interactions. Results DockoMatic allows the user to invoke and manage AutoDock jobs on a single computer or cluster, including jobs for evaluating secondary ligand interactions. It also automates the process of collecting, summarizing, and viewing results. In addition, DockoMatic automates creation of peptide ligand .pdb files from strings of single-letter amino acid abbreviations. Conclusions DockoMatic significantly reduces the complexity of managing multiple AutoDock jobs by facilitating ligand and AutoDock job creation and management.

  17. Chelating ligands for nanocrystals' surface functionalization.

    Science.gov (United States)

    Querner, Claudia; Reiss, Peter; Bleuse, Joël; Pron, Adam

    2004-09-22

    A new family of ligands for the surface functionalization of CdSe nanocrystals is proposed, namely alkyl or aryl derivatives of carbodithioic acids (R-C(S)SH). The main advantages of these new ligands are as follows: they nearly quantitatively exchange the initial surface ligands (TOPO) in very mild conditions; they significantly improve the resistance of nanocrystals against photooxidation because of their ability of strong chelate-type binding to metal atoms; their relatively simple preparation via Grignard intermediates facilitates the development of new bifunctional ligands containing, in addition to the anchoring carbodithioate group, a second function, which enables the grafting of molecules or macromolecules of interest on the nanocrystal surface. To give an example of this approach, we report, for the first time, the grafting of an electroactive oligomer from the polyaniline family-aniline tetramer-on CdSe nanocrystals after their functionalization with 4-formyldithiobenzoic acid. The grafting proceeds via a condensation reaction between the aldehyde group of the ligand and the terminal primary amine group of the tetramer. The resulting organic/inorganic hybrid exhibits complete extinction of the fluorescence of its constituents, indicating efficient charge or energy transfer between the organic and the inorganic semiconductors.

  18. Ligand identification using electron-density map correlations

    International Nuclear Information System (INIS)

    Terwilliger, Thomas C.; Adams, Paul D.; Moriarty, Nigel W.; Cohn, Judith D.

    2007-01-01

    An automated ligand-fitting procedure is applied to (F o − F c )exp(iϕ c ) difference density for 200 commonly found ligands from macromolecular structures in the Protein Data Bank to identify ligands from density maps. A procedure for the identification of ligands bound in crystal structures of macromolecules is described. Two characteristics of the density corresponding to a ligand are used in the identification procedure. One is the correlation of the ligand density with each of a set of test ligands after optimization of the fit of that ligand to the density. The other is the correlation of a fingerprint of the density with the fingerprint of model density for each possible ligand. The fingerprints consist of an ordered list of correlations of each the test ligands with the density. The two characteristics are scored using a Z-score approach in which the correlations are normalized to the mean and standard deviation of correlations found for a variety of mismatched ligand-density pairs, so that the Z scores are related to the probability of observing a particular value of the correlation by chance. The procedure was tested with a set of 200 of the most commonly found ligands in the Protein Data Bank, collectively representing 57% of all ligands in the Protein Data Bank. Using a combination of these two characteristics of ligand density, ranked lists of ligand identifications were made for representative (F o − F c )exp(iϕ c ) difference density from entries in the Protein Data Bank. In 48% of the 200 cases, the correct ligand was at the top of the ranked list of ligands. This approach may be useful in identification of unknown ligands in new macromolecular structures as well as in the identification of which ligands in a mixture have bound to a macromolecule

  19. Characteristic molecular vibrations of adenosine receptor ligands.

    Science.gov (United States)

    Chee, Hyun Keun; Yang, Jin-San; Joung, Je-Gun; Zhang, Byoung-Tak; Oh, S June

    2015-02-13

    Although the regulation of membrane receptor activation is known to be crucial for molecular signal transduction, the molecular mechanism underlying receptor activation is not fully elucidated. Here we study the physicochemical nature of membrane receptor behavior by investigating the characteristic molecular vibrations of receptor ligands using computational chemistry and informatics methods. By using information gain, t-tests, and support vector machines, we have identified highly informative features of adenosine receptor (AdoR) ligand and corresponding functional amino acid residues such as Asn (6.55) of AdoR that has informative significance and is indispensable for ligand recognition of AdoRs. These findings may provide new perspectives and insights into the fundamental mechanism of class A G protein-coupled receptor activation. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  20. Effects of PPARγ Ligands on Leukemia

    Directory of Open Access Journals (Sweden)

    Yoko Tabe

    2012-01-01

    Full Text Available Peroxisome proliferator-activated receptors (PPARs and retinoic acid receptors (RARs, members of the nuclear receptor superfamily, are transcription factors that regulate a variety of important cellular functions. PPARs form heterodimers retinoid X receptor (RXR, an obligate heterodimeric partner for other nuclear receptors. Several novel links between retinoid metabolism and PPAR responses have been identified, and activation of PPAR/RXR expression has been shown to increase response to retinoids. PPARγ has emerged as a key regulator of cell growth and survival, whose activity is modulated by a number of synthetic and natural ligands. While clinical trials in cancer patients with thiazolidinediones (TZD have been disappointing, novel structurally different PPARγ ligands, including triterpenoids, have entered clinical arena as therapeutic agents for epithelial and hematopoietic malignancies. Here we shall review the antitumor advances of PPARγ, alone and in combination with RARα ligands in control of cell proliferation, differentiation, and apoptosis and their potential therapeutic applications in hematological malignancies.

  1. Thermodynamic study on the complexation of Trivalent actinide and lanthanide cation by N-donor ligands in homogeneous conditions; Etude thermodynamique de la complexation des ions actinide (III) et lanthanide (III) par des ligands polyazotes en milieu homogene

    Energy Technology Data Exchange (ETDEWEB)

    Miguirditchian, M

    2004-07-01

    Polydentate N-donor ligands, alone or combined with a synergic acid, may selectively extract minor actinides(III) from lanthanide(III) ions, allowing to develop separation processes of long-live radioelements. The aim of the researches carried out during this thesis was to better understand the chemical mechanisms of the complexation of f-elements by Adptz, a tridentate N-donor ligand, in homogeneous conditions. A thermodynamic approach was retained in order to estimate, from an energetic point of view, the influence of the different contributions to the reaction, and to acquire a complete set of thermodynamic data on this reaction. First, the influence of the nature of the cation on the thermodynamics was considered. The stability constants of the 1/1 complexes were systematically determined by UV-visible spectrophotometry for every lanthanide ion (except promethium) and for yttrium in a mixed solvent methanol/water in volume proportions 75/25%. The thermodynamic parameters ({delta}H{sup 0} {delta}{sup S}) of complexation were estimated by the van't Hoff method and by micro-calorimetry. The trends of the variations across the lanthanide series are compared with similar studies. The same methods were applied to the study of three actinide(III) cations: plutonium, americium and curium. The comparison of these values with those obtained for the lanthanides highlights the increase of stability of these complexes by a factor of 20 in favor of the actinide cations. This gap is explained by a more exothermic reaction and is associated, in the data interpretation, to a higher covalency of the actinide(III)-nitrogen bond. Then, the influence of the change of solvent composition on the thermodynamic of complexation was studied. The thermodynamic parameters of the complexation of europium(III) by Adptz were determined for several fractions of methanol. The stability of the complex formed increases with the percentage of methanol in the mixed solvent, owing to an

  2. Ligand Exchange and 1H NMR Quantification of Single- and Mixed-Moiety Thiolated Ligand Shells on Gold Nanoparticles.

    Science.gov (United States)

    Smith, Ashley M; Millstone, Jill E

    2017-01-01

    The use of nanoparticles in biomedicine critically depends on their surface chemistry. For metal nanoparticles, a common way to tune this surface chemistry is through mass action ligand exchange, where ligand exchange can be used to expand the functionality of the resulting nanoparticle conjugates. Specifically, the quantity, identity, and arrangement of the molecules in the resulting ligand shell each can be tuned significantly. Here, we describe methods to exchange and quantify thiolated and non-thiolated ligands on gold nanoparticle surfaces. Importantly, these strategies allow the quantification of multiple ligand types within a single ligand shell, simultaneously providing ligand composition and ligand density information. These results are crucial for both designing and assigning structure-function relationships in bio-functionalized nanoparticles, and these methods can be applied to a broad range of nanoparticle cores and ligand types including peptides, small molecule drugs, and oligonucleotides.

  3. Spectroscopic studies and biological evaluation of some transition metal complexes of azo Schiff-base ligand derived from (1-phenyl-2,3-dimethyl-4-aminopyrazol-5-one) and 5-((4-chlorophenyl)diazenyl)-2-hydroxybenzaldehyde.

    Science.gov (United States)

    Anitha, C; Sheela, C D; Tharmaraj, P; Sumathi, S

    2012-10-01

    A series of metal(II) complexes of VO(II), Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized from the azo Schiff base ligand 4-((E)-4-((E)-(4-chlorophenyl)diazenyl)-2-hydroxybenzylideneamino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (CDHBAP) and characterized by elemental analysis, spectral (IR, UV-Vis, (1)H NMR, ESR and EI-mass), magnetic moment measurements, molar conductance, DNA, SEM, X-ray crystallography and fluorescence studies. The electronic absorption spectra and magnetic susceptibility measurements of the complexes indicate square pyramidal geometry for VO(II) and octahedral geometry for all the other complexes. The important infrared (IR) spectral bands corresponding to the active groups in the ligand and the solid complexes under investigation were studied and implies that CDHBAP is coordinated to the metal ions in a neutral tridentate manner. The redox behavior of copper(II) and vanadyl(II) complexes have been studied by cyclic voltammetry. The nuclease activity of the above metal(II) complexes shows that the complexes cleave DNA. All the synthesized complexes can serve as potential photoactive materials as indicated from their characteristic fluorescence properties. The antibacterial and antifungal activities of the synthesized ligand and its metal complexes were screened against bacterial species (Staphylococcus aureus, Salmonella typhi, Escherichia coli, Bacillus subtilis, Shigella sonnie) and fungi (Candida albicans, Aspergillus niger, Rhizoctonia bataicola). Amikacin and Ketoconozole were used as references for antibacterial and antifungal studies. The activity data show that the metal complexes have a promising biological activity comparable with the parent Schiff base ligand against bacterial and fungal species. The second harmonic generation (SHG) efficiency of the ligand was measured and the NLO (non-linear optical) properties of the ligand are expected to result in the realization of advanced optical devices in optical fiber

  4. A2AR Binding Kinetics in the Ligand Depletion Regime.

    Science.gov (United States)

    McNeely, Patrick M; Naranjo, Andrea N; Forsten-Williams, Kimberly; Robinson, Anne Skaja

    2017-02-01

    Ligand binding plays a fundamental role in stimulating the downstream signaling of membrane receptors. Here, ligand-binding kinetics of the full-length human adenosine A 2A receptor (A 2A R) reconstituted in detergent micelles were measured using a fluorescently labeled ligand via fluorescence anisotropy. Importantly, to optimize the signal-to-noise ratio, these experiments were conducted in the ligand depletion regime. In the ligand depletion regime, the assumptions used to determine analytical solutions for one-site binding models for either one or two ligands in competition are no longer valid. We therefore implemented a numerical solution approach to analyze kinetic binding data as experimental conditions approach the ligand depletion regime. By comparing the results from the numerical and the analytical solutions, we highlight the ligand-receptor ratios at which the analytical solution begins to lose predictive accuracy. Using the numerical solution approach, we determined the kinetic rate constants of the fluorescent ligand, FITC-APEC, and those for three unlabeled ligands using competitive association experiments. The association and dissociation rate constants of the unlabeled ligands determined from the competitive association experiments were then independently validated using competitive dissociation data. Based on this study, a numerical solution is recommended to determine kinetic ligand-binding parameters for experiments conducted in the ligand-depletion regime.

  5. CHELATING LIGANDS: ENHANCERS OF QUALITY AND PURITY ...

    African Journals Online (AJOL)

    Nwokem et al.

    ABSTRACT. The quality of biogas depends largely on the percentage of methane and hydrogen sulphide gas present. High concentration of hydrogen sulphide results in low quality biogas. This work employed the use of chelating ligands in scrubbing hydrogen sulphide gas while improving the yield of methane gas.

  6. Ligand iron catalysts for selective hydrogenation

    Science.gov (United States)

    Casey, Charles P.; Guan, Hairong

    2010-11-16

    Disclosed are iron ligand catalysts for selective hydrogenation of aldehydes, ketones and imines. A catalyst such as dicarbonyl iron hydride hydroxycyclopentadiene) complex uses the OH on the five member ring and hydrogen linked to the iron to facilitate hydrogenation reactions, particularly in the presence of hydrogen gas.

  7. Versatile phosphite ligands based on silsesquioxane backbones

    NARCIS (Netherlands)

    van der Vlugt, JI; Ackerstaff, J; Dijkstra, TW; Mills, AM; Kooijman, H; Spek, AL; Meetsma, A; Abbenhuis, HCL; Vogt, D

    Silsesquioxanes are employed as ligand backbones for the synthesis of novel phosphite compounds with 3,3'-5,5'-tetrakis(tert-butyl)-2,2'-di-oxa-1,1'-biphenyl substituents. Both mono- and bidentate phosphites are prepared in good yields. Two types of silsesquioxanes are employed as starting

  8. Constitutive and ligand-induced TCR degradation

    DEFF Research Database (Denmark)

    von Essen, Marina; Bonefeld, Charlotte Menné; Siersma, Volkert

    2004-01-01

    divergent models for TCR down-regulation and degradation have been suggested. The aims of this study were to determine the rate constants for constitutive and ligand-induced TCR degradation and to determine whether the TCR subunits segregate or are processed as an intact unit during TCR down...

  9. Ligand based pharmacophore modelling of anticancer histone ...

    African Journals Online (AJOL)

    like myocardium damage and bone marrow depression even leading to cell death have been observed in the treatment of caner cells using HDAC inhibitors. The discovery and development of type-specific HDAC inhibitors is of both research and clinical interests. Ligand based pharmacophore modelling is playing a key ...

  10. Ligand Exchange Kinetics of Environmentally Relevant Metals

    Energy Technology Data Exchange (ETDEWEB)

    Panasci, Adele Frances [Univ. of California, Davis, CA (United States)

    2014-07-15

    The interactions of ground water with minerals and contaminants are of broad interest for geochemists but are not well understood. Experiments on the molecular scale can determine reaction parameters (i.e. rates of ligand exchange, activation entropy, activation entropy, and activation volume) that can be used in computations to gain insight into reactions that occur in natural groundwaters. Experiments to determine the rate of isotopic ligand exchange for three environmentally relevant metals, rhodium (Rh), iron (Fe), and neptunium (Np), are described. Many environmental transformations of metals (e.g. reduction) in soil occur at trivalent centers, Fe(III) in particular. Contaminant ions absorb to mineral surfaces via ligand exchange, and the reversal of this reaction can be dangerous, releasing contaminants into the environment. Ferric iron is difficult to study spectroscopically because most of its complexes are paramagnetic and are generally reactive toward ligand exchange; therefore, Rh(III), which is diamagnetic and less reactive, was used to study substitution reactions that are analogous to those that occur on mineral oxide surfaces. Studies on both Np(V) and Np(VI) are important in their own right, as 237Np is a radioactive transuranic element with a half-life of 2 million years.

  11. Dynamic Ligand Based Pharmacophore Modeling and Virtual ...

    Indian Academy of Sciences (India)

    user

    ChEMBL-HIV https://www.ebi.ac.uk/chembl/index.php/assay/results (ChEMBL Bioassay was searched with the key word “Human. Immunodefficiency virus”, display bioactivity option was chosen and then “Download All Bioactivity Data” was ... Ligand based pharmacophore models generated from the crystal structure and.

  12. Mixed-ligand binuclear copper(II)

    Indian Academy of Sciences (India)

    A new mixed-ligand binuclear copper(II) complex [Cu(MS)(bpy)]2.(ClO4)2, built of 5-methylsalicylaldehyde and 2,2'-bipyridyl has been synthesized and characterized by using elemental analysis, IR and UV-Vis spectroscopy. Crystal structure of the complex shows that copper(II) ion lies in a square pyramidal coordination ...

  13. A versatile dinucleating ligand containing sulfonamide groups

    DEFF Research Database (Denmark)

    Sundberg, Jonas; Witt, Hannes; Cameron, Lisa

    2014-01-01

    Copper, iron, and gallium coordination chemistries of the new pentadentate bis-sulfonamide ligand 2,6-bis(N-2-pyridylmethylsulfonamido)-4-methylphenol (psmpH3) were investigated. PsmpH3 is capable of varying degrees of deprotonation, and notably, complexes containing the fully trideprotonated...

  14. Amidinate Ligands in Zinc coordination sphere

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 128; Issue 6. Amidinate Ligands in Zinc coordination sphere: Synthesis and structural diversity. SRINIVAS ANGA INDRANI BANERJEE TARUN K PANDA. Regular Article Volume 128 Issue 6 June 2016 pp ... Keywords. Zinc; carbodiimides; amidinate; alkyl migration.

  15. Simple tertiary phosphines to hexaphosphane ligands: Syntheses ...

    Indian Academy of Sciences (India)

    In this context, we have developed new synthetic methodologies for making unusual inorganic ring systems containing trivalent phosphorus centres, novel phosphorus-based multidentate and hybrid ligands and explored their rich transition metal chemistry and catalytic applications. We have also fine tuned a few existing ...

  16. Ammonia formation by metal-ligand cooperative hydrogenolysis of a nitrido ligand

    Science.gov (United States)

    Askevold, Bjorn; Nieto, Jorge Torres; Tussupbayev, Samat; Diefenbach, Martin; Herdtweck, Eberhardt; Holthausen, Max C.; Schneider, Sven

    2011-07-01

    Bioinspired hydrogenation of N2 to ammonia at ambient conditions by stepwise nitrogen protonation/reduction with metal complexes in solution has experienced remarkable progress. In contrast, the highly desirable direct hydrogenation with H2 remains difficult. In analogy to the heterogeneously catalysed Haber-Bosch process, such a reaction is conceivable via metal-centred N2 splitting and unprecedented hydrogenolysis of the nitrido ligands to ammonia. We report the synthesis of a ruthenium(IV) nitrido complex. The high nucleophilicity of the nitrido ligand is demonstrated by unusual N-C coupling with π-acidic CO. Furthermore, the terminal nitrido ligand undergoes facile hydrogenolysis with H2 at ambient conditions to produce ammonia in high yield. Kinetic and quantum chemical examinations of this reaction suggest cooperative behaviour of a phosphorus-nitrogen-phosphorus pincer ligand in rate-determining heterolytic hydrogen splitting.

  17. Role of Lanthanide-Ligand bonding in the magnetization relaxation ...

    Indian Academy of Sciences (India)

    Ligand bonding. Our calculations transpire comparatively improved Single-Ion Magnet (SIM) behaviour for carbene analogues due to the more axially compressed trigonal prismatic ligand environment. Furthermore, our detailed Mulliken charge, ...

  18. Substrate coated with receptor and labelled ligand for assays

    International Nuclear Information System (INIS)

    1980-01-01

    Improvements in the procedures for assaying ligands are described. The assay consists of a polystyrene tube on which receptors are present for both the ligand to be assayed and a radioactively labelled form of the ligand. The receptors on the bottom portion of the tube are also coated with labelled ligands, thus eliminating the necessity for separate addition of the labelled ligand and sample during an assay. Examples of ligands to which this method is applicable include polypeptides, nucleotides, nucleosides and proteins. Specific examples are given in which the ligand to be assayed is digoxin, the labelled form of the ligand is 3-0-succinyl digoxyigenin tyrosine ( 125 I) and the receptor is digoxin antibody. (U.K.)

  19. Ligand-Mediated Coating of Liposomes with Human Serum Albumin.

    Science.gov (United States)

    Sato, Hikari; Nakhaei, Elnaz; Kawano, Takahito; Murata, Masaharu; Kishimura, Akihiro; Mori, Takeshi; Katayama, Yoshiki

    2018-02-13

    Coating liposome surfaces with human serum albumin (HSA) can improve the colloidal stability and prevent opsonization. HSA coating via specific binding with alkyl ligands is promising because although the ligand-mediated coating is relatively stable it can spontaneously exchange with fresh HSA. However, to achieve surface coating with HSA, multiple hydrophobic ligands must be exposed to an aqueous medium prior to binding with HSA. This presents a challenge, as hydrophobic ligands tend to be buried in the liposomal membrane. Here we present the first HSA modification of liposome surfaces via alkyl ligands. We found that a relatively short alkyl ligand, or a long alkyl ligand with a terminal carboxylate, could be exposed on the liposome surface without causing aggregation of the liposomes and these ligands could subsequently bind HSA. The resulting HSA-coated liposomes were as inert as conventional PEGylated liposomes in terms of macrophage recognition.

  20. Quantum.Ligand.Dock: protein-ligand docking with quantum entanglement refinement on a GPU system.

    Science.gov (United States)

    Kantardjiev, Alexander A

    2012-07-01

    Quantum.Ligand.Dock (protein-ligand docking with graphic processing unit (GPU) quantum entanglement refinement on a GPU system) is an original modern method for in silico prediction of protein-ligand interactions via high-performance docking code. The main flavour of our approach is a combination of fast search with a special account for overlooked physical interactions. On the one hand, we take care of self-consistency and proton equilibria mutual effects of docking partners. On the other hand, Quantum.Ligand.Dock is the the only docking server offering such a subtle supplement to protein docking algorithms as quantum entanglement contributions. The motivation for development and proposition of the method to the community hinges upon two arguments-the fundamental importance of quantum entanglement contribution in molecular interaction and the realistic possibility to implement it by the availability of supercomputing power. The implementation of sophisticated quantum methods is made possible by parallelization at several bottlenecks on a GPU supercomputer. The high-performance implementation will be of use for large-scale virtual screening projects, structural bioinformatics, systems biology and fundamental research in understanding protein-ligand recognition. The design of the interface is focused on feasibility and ease of use. Protein and ligand molecule structures are supposed to be submitted as atomic coordinate files in PDB format. A customization section is offered for addition of user-specified charges, extra ionogenic groups with intrinsic pK(a) values or fixed ions. Final predicted complexes are ranked according to obtained scores and provided in PDB format as well as interactive visualization in a molecular viewer. Quantum.Ligand.Dock server can be accessed at http://87.116.85.141/LigandDock.html.

  1. Quantum.Ligand.Dock: protein–ligand docking with quantum entanglement refinement on a GPU system

    Science.gov (United States)

    Kantardjiev, Alexander A.

    2012-01-01

    Quantum.Ligand.Dock (protein–ligand docking with graphic processing unit (GPU) quantum entanglement refinement on a GPU system) is an original modern method for in silico prediction of protein–ligand interactions via high-performance docking code. The main flavour of our approach is a combination of fast search with a special account for overlooked physical interactions. On the one hand, we take care of self-consistency and proton equilibria mutual effects of docking partners. On the other hand, Quantum.Ligand.Dock is the the only docking server offering such a subtle supplement to protein docking algorithms as quantum entanglement contributions. The motivation for development and proposition of the method to the community hinges upon two arguments—the fundamental importance of quantum entanglement contribution in molecular interaction and the realistic possibility to implement it by the availability of supercomputing power. The implementation of sophisticated quantum methods is made possible by parallelization at several bottlenecks on a GPU supercomputer. The high-performance implementation will be of use for large-scale virtual screening projects, structural bioinformatics, systems biology and fundamental research in understanding protein–ligand recognition. The design of the interface is focused on feasibility and ease of use. Protein and ligand molecule structures are supposed to be submitted as atomic coordinate files in PDB format. A customization section is offered for addition of user-specified charges, extra ionogenic groups with intrinsic pKa values or fixed ions. Final predicted complexes are ranked according to obtained scores and provided in PDB format as well as interactive visualization in a molecular viewer. Quantum.Ligand.Dock server can be accessed at http://87.116.85.141/LigandDock.html. PMID:22669908

  2. Characterization of Ligand Shell for Mixed-Ligand Coated Gold Nanoparticles.

    Science.gov (United States)

    Ong, Quy; Luo, Zhi; Stellacci, Francesco

    2017-08-15

    Gold nanoparticles owe a large number of their properties to their ligand shell. Indeed, many researchers routinely use mixtures of ligand molecules for their nanoparticles to impart complex property sets. It has been shown that the morphology of ligand shells (e.g., Janus, random, stripelike) leads to specific properties. Examples include wettability, solubility, protein nonspecific adsorption, cell penetration, catalysis, and cation-capturing abilities. Yet, it remains a great challenge to evaluate such morphologies in even the most fundamental terms such as dimension and shape. In this Account, we review recent progress in characterization techniques applicable to gold nanoparticles with ligand shells composed of mixed ligands. We divide the characterization into three major categories, namely, microscopy, spectroscopy, and simulation. In microscopy, we review progresses in scanning tunneling microscopy (STM), atomic force microscopy (AFM), and scanning/transmission electron microscopy. In spectroscopy, we mainly highlight recent achievements in nuclear magnetic resonance (NMR), mass spectrometry (MS), small angle neutron scattering (SANS), electron spin resonance (EPR), and adsorption based spectroscopies. In simulation, we point out the latest results in understanding thermodynamic stability of ligand shell morphology and emphasize the role of computer simulation for helping interpretation of experimental data. We conclude with a perspective of future development.

  3. GLIDA: GPCR-ligand database for chemical genomic drug discovery

    OpenAIRE

    Okuno, Yasushi; Yang, Jiyoon; Taneishi, Kei; Yabuuchi, Hiroaki; Tsujimoto, Gozoh

    2005-01-01

    G-protein coupled receptors (GPCRs) represent one of the most important families of drug targets in pharmaceutical development. GPCR-LIgand DAtabase (GLIDA) is a novel public GPCR-related chemical genomic database that is primarily focused on the correlation of information between GPCRs and their ligands. It provides correlation data between GPCRs and their ligands, along with chemical information on the ligands, as well as access information to the various web databases regarding GPCRs. Thes...

  4. AutoSite: an automated approach for pseudo-ligands prediction—from ligand-binding sites identification to predicting key ligand atoms

    Science.gov (United States)

    Ravindranath, Pradeep Anand; Sanner, Michel F.

    2016-01-01

    Motivation: The identification of ligand-binding sites from a protein structure facilitates computational drug design and optimization, and protein function assignment. We introduce AutoSite: an efficient software tool for identifying ligand-binding sites and predicting pseudo ligand corresponding to each binding site identified. Binding sites are reported as clusters of 3D points called fills in which every point is labelled as hydrophobic or as hydrogen bond donor or acceptor. From these fills AutoSite derives feature points: a set of putative positions of hydrophobic-, and hydrogen-bond forming ligand atoms. Results: We show that AutoSite identifies ligand-binding sites with higher accuracy than other leading methods, and produces fills that better matches the ligand shape and properties, than the fills obtained with a software program with similar capabilities, AutoLigand. In addition, we demonstrate that for the Astex Diverse Set, the feature points identify 79% of hydrophobic ligand atoms, and 81% and 62% of the hydrogen acceptor and donor hydrogen ligand atoms interacting with the receptor, and predict 81.2% of water molecules mediating interactions between ligand and receptor. Finally, we illustrate potential uses of the predicted feature points in the context of lead optimization in drug discovery projects. Availability and Implementation: http://adfr.scripps.edu/AutoDockFR/autosite.html Contact: sanner@scripps.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27354702

  5. Integrating structural and mutagenesis data to elucidate GPCR ligand binding

    DEFF Research Database (Denmark)

    Munk, Christian; Harpsøe, Kasper; Hauser, Alexander S

    2016-01-01

    G protein-coupled receptors (GPCRs) represent the largest family of human membrane proteins, as well as drug targets. A recent boom in GPCR structural biology has provided detailed images of receptor ligand binding sites and interactions on the molecular level. An ever-increasing number of ligands...... elucidate new GPCR ligand binding sites, and ultimately design drugs with tailored pharmacological activity....

  6. New pinene-derived pyridines as bidentate chiral ligands

    Czech Academy of Sciences Publication Activity Database

    Malkov, A. V.; Stewart-Liddon, A.; Teplý, Filip; Kobr, L.; Muir, K. W.; Haigh, D.; Kočovský, P.

    2008-01-01

    Roč. 64, č. 18 (2008), s. 4011-4025 ISSN 0040-4020 Institutional research plan: CEZ:AV0Z40550506 Keywords : chiral ligands * transition metal catalysis * asymmetric catalysis * pyridine ligands * oxazoline ligands Subject RIV: CC - Organic Chemistry Impact factor: 2.897, year: 2008

  7. Study of the spectroscopic characteristics of methyl (ligand ...

    Indian Academy of Sciences (India)

    TECS

    Abstract. Spectroscopic characterization (IR, NMR and electronic spectra) of methyl (ligand) coba- loxime was done, where ligand = pyrazole, dimethyl pyrazole, alanine and alanine methyl ester. The fre- quency changes in the IR spectra and shifts in the NMR were explained on the basis of basicity of the ligand, steric ...

  8. Equilibrium and kinetic studies on ligand substitution reactions of ...

    Indian Academy of Sciences (India)

    Unknown

    The rate constants and equilibrium constants are correlated to the hardness and softness of the ligands and the Co(III) of cobaloxime. Keywords. Alkylcobaloximes; ligand substitution reactions; hard and soft ligands. 1. Introduction. B12-based enzymes are among the few cofactors known till now contain a metal–carbon.

  9. Design and use of conditional MHC class I ligands

    NARCIS (Netherlands)

    Toebes, Mireille; Coccoris, Miriam; Bins, Adriaan; Rodenko, Boris; Gomez, Raquel; Nieuwkoop, Nella J.; van de Kasteele, Willeke; Rimmelzwaan, Guus F.; Haanen, John B. A. G.; Ovaa, Huib; Schumacher, Ton N. M.

    2006-01-01

    Major histocompatibility complex (MHC) class I molecules associate with a variety of peptide ligands during biosynthesis and present these ligands on the cell surface for recognition by cytotoxic T cells. We have designed conditional MHC ligands that form stable complexes with MHC molecules but

  10. Hydrogen exchange and ligand binding: Ligand-dependent and ligand-independent protection in the Src SH3 domain

    OpenAIRE

    Wildes, David; Marqusee, Susan

    2005-01-01

    Amide hydrogen-deuterium exchange has proven to be a powerful tool for detecting and characterizing high-energy conformations in protein ensembles. Since interactions with ligands can modulate these high-energy conformations, hydrogen exchange appears to be an ideal experimental probe of the physical mechanisms underlying processes like allosteric regulation. The chemical mechanism of hydrogen exchange, however, can complicate such studies. Here, we examine hydrogen exchange rates in a simple...

  11. A ligand's view of target similarity

    DEFF Research Database (Denmark)

    Garland, Stephen L; Gloriam, David E

    2011-01-01

    -finding and, potentially, to produce ligands for previously intractable receptors. Sequence motifs correlated with ligands can be applied in the design of target-specific focused libraries that are both efficient and cost-effective and should provide increased hit-rates over diversity screening. Furthermore...... shows with several examples how focusing on the binding site(s) has a clear advantage when it comes to establishing sequence-correlated pharmacological profiles. By organizing and comparing sequence and structural data it is possible to "borrow" SAR from similar targets to increase the speed of lead......, in the optimization phase, the binding motif approach offers the possibility to identify quickly the most likely off-target candidates to be chosen for selectivity screening, as well as potentially characterizing those pockets which may best be exploited for improved selectivity....

  12. Coordination modes of multidentate ligands in fac-[Re(CO)(3)(polyaminocarboxylate)] analogues of (99m)Tc radiopharmaceuticals. dependence on aqueous solution reaction conditions.

    Science.gov (United States)

    Lipowska, Malgorzata; He, Haiyang; Xu, Xiaolong; Taylor, Andrew T; Marzilli, Patricia A; Marzilli, Luigi G

    2010-04-05

    We study Re analogues of (99m)Tc renal agents to interpret previous results at the (99m)Tc tracer level. The relative propensities of amine donors versus carboxylate oxygen donors of four L = polyaminocarboxylate ligands to coordinate in fac-[Re(I)(CO)(3)L](n) complexes were assessed by examining the reaction of fac-[Re(I)(CO)(3)(H(2)O)(3)](+) under conditions differing in acidity and temperature. All four L [N,N-bis-(2-aminoethyl)glycine (DTGH), N,N-ethylenediaminediacetic acid, diethylenetriamine-N-malonic acid, and diethylenetriamine-N-acetic acid] can coordinate as tridentate ligands while creating a dangling chain terminated in a carboxyl group. Dangling carboxyl groups facilitate renal clearance in fac-[(99m)Tc(I)(CO)(3)L](n) agents. Under neutral conditions, the four ligands each gave two fac-[Re(I)(CO)(3)L](n) products with HPLC traces correlating well with known traces of the fac-[(99m)Tc(I)(CO)(3)L](n) mixtures. Such mixtures are common in renal agents because the needed dangling carboxyl group can compete for a coordination site. However, the HPLC separations needed to assess the biodistribution of a single tracer are impractical in a clinical setting. One goal in investigating this Re chemistry is to identify conditions for avoiding this problem of mixtures in preparations of fac-[(99m)Tc(I)(CO)(3)L](n) renal tracers. After separation and isolation of the fac-[Re(I)(CO)(3)L](n) products, NMR analysis of all products and single crystal X-ray crystallographic analysis of both DTGH products, as well as one product each from the other L, allowed us to establish coordination mode unambiguously. The product favored in acidic conditions has a dangling amine chain and more bound oxygen. The product favored in basic conditions has a dangling carboxyl chain and more bound nitrogen. At the elevated temperatures used for simulating tracer preparation, equilibration was facile (ca. 1 h or less), allowing selective formation of one product by utilizing acidic or

  13. Targeting Selectins and Their Ligands in Cancer

    Directory of Open Access Journals (Sweden)

    Alessandro eNatoni

    2016-04-01

    Full Text Available Aberrant glycosylation is a hallmark of cancer cells with increased evidence pointing to a role in tumor progression. In particular, aberrant sialylation of glycoproteins and glycolipids have been linked to increased immune cell evasion, drug evasion, drug resistance, tumor invasiveness, and vascular dissemination leading to metastases. Hypersialylation of cancer cells is largely the result of overexpression of sialyltransferases. Humans differentially express twenty different sialyltransferases in a tissue-specific manner, each of which catalyze the attachment of sialic acids via different glycosidic linkages (2-3; 2-6 or 2-8 to the underlying glycan chain. One important mechanism whereby overexpression of sialyltransferases contributes to an enhanced metastatic phenotype is via the generation of selectin ligands. Selectin ligand function requires the expression of sialyl-Lewis X and its structural-isomer sialyl-Lewis A, which are synthesized by the combined action of alpha 1-3-fucosyltransferases, 2-3-sialyltransferases, 1-4-galactosyltranferases, and N-acetyl--glucosaminyltransferases. The α2-3-sialyltransferases ST3Gal4 and ST3Gal6 are critical to the generation of functional E- and P-selectin ligands and overexpression of these sialyltransferases have been linked to increased risk of metastatic disease in solid tumors and poor outcome in multiple myeloma. Thus, targeting selectins and their ligands as well as the enzymes involved in their generation, in particular sialyltransferases, could be beneficial to many cancer patients. Potential strategies include sialyltransferase inhibition and the use of selectin antagonists, such as glycomimetic drugs and antibodies. Here, we review ongoing efforts to optimize the potency and selectivity of sialyltransferase inhibitors, including the potential for targeted delivery approaches, as well as evaluate the potential utility of selectin inhibitors, which are now in early clinical

  14. Complexes of .beta.-galactosidase with ligands

    Czech Academy of Sciences Publication Activity Database

    Štěpánková, Andrea; Skálová, Tereza; Dohnálek, Jan; Dušková, Jarmila; Koval, Tomáš; Hašek, Jindřich; Lipovová, P.

    2010-01-01

    Roč. 17, 1a (2010), b54 ISSN 1211-5894. [Discussions in Structural Molecular Biology /8./. 18.03.2010-20.03.2010, Nové Hrady] R&D Projects: GA ČR GA305/07/1073 Institutional research plan: CEZ:AV0Z40500505; CEZ:AV0Z10100521 Keywords : ligands * enzyme * galactosidase Subject RIV: CD - Macromolecular Chemistry

  15. Polyfluoroalkylated tripyrazolylmethane ligands: Synthesis and complexes

    Czech Academy of Sciences Publication Activity Database

    Skalická, V.; Rybáčková, M.; Skalický, M.; Kvíčalová, Magdalena; Cvačka, Josef; Březinová, Anna; Čejka, J.; Kvíčala, J.

    2011-01-01

    Roč. 132, č. 7 (2011), s. 434-440 ISSN 0022-1139 R&D Projects: GA MŠk ME 857; GA MŠk ME09114 Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z40550506 Keywords : tripyrazolylmethane * Tpm * tripyrazolylethanol * fluorinated * perfluoroalkylation * ligand Subject RIV: CC - Organic Chemistry Impact factor: 2.033, year: 2011

  16. Organotellurium ligands – designing and complexation reactions

    Indian Academy of Sciences (India)

    Unknown

    which can be compared to the values of 82⋅0(3) and 79⋅6(3)° for Te–Pd–Te angles in the complexes 9 and 10. However in the complex 11 the ditelluroether ligand is not in meso form. The distortions from all 90° angles in the octahedron about ruthenium are apparently not equally shared between the two tellurium atoms.

  17. Displacement of aqua ligands from the hydroxopentaaquarhodium ...

    Indian Academy of Sciences (India)

    cis-Pt(NH3)2Cl2 (cisplatin) is well-known as an anti- tumour drug.1,2 However, there are still difficulties related to its use, ... Cisplatin is not very soluble in water and tends to hydrolyse at neutral pH. Replacement ... cancer agents, but some of them exhibited marked toxic effects.17,18 For certain ligands, the anation reaction.

  18. Synthesis and Crystal Structures of Copper(II) Complexes with Schiff Base Ligands: [Cu2(acpy-mdtc)2(HBA)(ClO4)]·H2O and [Cu2(acpy-phtsc)2(HBA)]·ClO4

    International Nuclear Information System (INIS)

    Koo, Bon Kweon

    2013-01-01

    Two new Cu(II) complexes, [Cu 2 (acpy-mdtc) 2 (HBA)(ClO 4 )]·H 2 O (1) (acpy-mdtc - = 2-acetylpyridine S-methyldithiocarbamate and HBA - = benzilic acid anion) and [Cu 2 (acpy-phtsc) 2 (HBA)]·ClO 4 (2) (acpy-phtsc - = 2-acetylpyridine 4-phenyl-3-thiosemicarbazate) have been synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. The X-ray analysis reveals that the structures of 1 and 2 are dinuclear copper(II) complexes bridged by two thiolate sulfur atoms of Schiff base ligand and bidentate bridging HBA - anion. For 1, each of the two copper atoms has different coordination environments. Cu1 adopts a five-coordinate square-pyramidal with a N 2 OS 2 donor, while Cu 2 exhibits a distorted octahedral geometry in a N 2 O 2 S 2 manner. For 2, two Cu(II) ions all have a five-coordinate square-pyramidal with a N 2 OS 2 donor. In each complex, the Schiff base ligand is coordinated to copper ions as a tridentate thiol mode

  19. ProBiS-ligands: a web server for prediction of ligands by examination of protein binding sites.

    Science.gov (United States)

    Konc, Janez; Janežič, Dušanka

    2014-07-01

    The ProBiS-ligands web server predicts binding of ligands to a protein structure. Starting with a protein structure or binding site, ProBiS-ligands first identifies template proteins in the Protein Data Bank that share similar binding sites. Based on the superimpositions of the query protein and the similar binding sites found, the server then transposes the ligand structures from those sites to the query protein. Such ligand prediction supports many activities, e.g. drug repurposing. The ProBiS-ligands web server, an extension of the ProBiS web server, is open and free to all users at http://probis.cmm.ki.si/ligands. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

  20. Ligand activation of the prokaryotic pentameric ligand-gated ion channel ELIC.

    Directory of Open Access Journals (Sweden)

    Iwan Zimmermann

    2011-06-01

    Full Text Available While the pentameric ligand-gated ion channel ELIC has recently provided first insight into the architecture of the family at high resolution, its detailed investigation was so far prevented by the fact that activating ligands were unknown. Here we describe a study on the functional characterization of ELIC by electrophysiology and X-ray crystallography. ELIC is activated by a class of primary amines that include the neurotransmitter GABA at high micro- to millimolar concentrations. The ligands bind to a conserved site and evoke currents that slowly desensitize over time. The protein forms cation selective channels with properties that resemble the nicotinic acetylcholine receptor. The high single channel conductance and the comparably simple functional behavior make ELIC an attractive model system to study general mechanisms of ion conduction and gating in this important family of neurotransmitter receptors.

  1. Spectrophotometric method for determination of bifunctional macrocyclic ligands in macrocyclic ligand-protein conjugates

    International Nuclear Information System (INIS)

    Dadachova, E.; Chappell, L.L.; Brechbiel, M.W.

    1999-01-01

    A simple spectrophotometric assay for determination of bifunctional polyazacarboxylate-macrocyclic ligands of different sizes that are conjugated to proteins has been developed for: 12-membered macrocycle DOTA (2-[4-nitrobenzyl]-1, 4, 7, 10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid) and analogs, the 15-membered PEPA macrocycle (2-[4-nitrobenzyl]-1,4,7,10,13-pentaazacyclopentadecane-N,N',N'',N''',N'''' -pentaacetic acid), and the large 18-membered macrocycle HEHA (1,4,7,10,13,16-hexaazacyclooctadecane-N,N',N'',N''',N''''-hexaacetic acid). The method is based on titration of the blue-colored 1:1 Pb(II)-Arsenazo III (AAIII) complex with the polyazacarboxylate macrocyclic ligand in the concentration range of 0-2.5 μM, wherein color change occurring upon transchelation of the Pb(II) from the AAIII to the polyazamacrocyclic ligand is monitored at 656 nm. The assay is performed at ambient temperature within 20 min without any interfering interaction between the protein and Pb(II)-AA(III) complex. Thus, this method also provides a ligand-to-protein ratio (L/P ratio) that reflects the effective number of ligands per protein molecule available to radiolabeling. The method is not suitable for 14-membered TETA macrocycle (2-[4-nitrobenzyl]-1, 4, 8, 11-tetraazacyclotetradecane N,N',N'',N'''-tetraacetic acid) because of low stability constant of Pb(II)-TETA complex. The method is rapid, simple and may be customized for other polyazacarboxylate macrocyclic ligands

  2. Heteroleptic and Homoleptic Iron(III Spin-Crossover Complexes; Effects of Ligand Substituents and Intermolecular Interactions between Co-Cation/Anion and the Complex

    Directory of Open Access Journals (Sweden)

    Wasinee Phonsri

    2017-08-01

    Full Text Available The structural and magnetic properties of a range of new iron(III bis-tridentate Schiff base complexes are described with emphasis on how intermolecular structural interactions influence spin states and spin crossover (SCO in these d5 materials. Three pairs of complexes were investigated. The first pair are the neutral, heteroleptic complexes [Fe(3-OMe-SalEen(thsa] 1 and [Fe(3-MeOSalEen(3-EtOthsa] 2, where 3-R-HSalEen = (E-2-(((2-(ethylaminoethyliminomethyl-6-R-phenol and 3-R-H2thsa = thiosemicarbazone-3-R-salicylaldimine. They display spin transitions above room temperature. However, 2 shows incomplete and gradual change, while SCO in 1 is complete and more abrupt. Lower cooperativity in 2 is ascribed to the lack of π–π interactions, compared to 1. The second pair, cationic species [Fe(3-EtOSalEen2]NO3 3 and [Fe(3-EtOSalEen2]Cl 4 differ only in the counter-anion. They show partial SCO above room temperature with 3 displaying a sharp transition at 343 K. Weak hydrogen bonds from cation to Cl− probably lead to weaker cooperativity in 4. The last pair, CsH2O[Fe(3-MeO-thsa2] 5 and Cs(H2O2[Fe(5-NO2-thsa2] 6, are anionic homoleptic chelates that have different substituents on the salicylaldiminate rings of thsa2−. The Cs cations bond to O atoms of water and the ligands, in unusual ways thus forming attractive 1D and 3D networks in 5 and 6, respectively, and 5 remains HS (high spin at all temperatures while 6 remains LS (low spin. Comparisons are made to other literature examples of Cs salts of [Fe(5-R-thsa2]− (R = H and Br.

  3. Characterizing common substructures of ligands for GPCR protein subfamilies.

    Science.gov (United States)

    Erguner, Bekir; Hattori, Masahiro; Goto, Susumu; Kanehisa, Minoru

    2010-01-01

    The G-protein coupled receptor (GPCR) superfamily is the largest class of proteins with therapeutic value. More than 40% of present prescription drugs are GPCR ligands. The high therapeutic value of GPCR proteins and recent advancements in virtual screening methods gave rise to many virtual screening studies for GPCR ligands. However, in spite of vast amounts of research studying their functions and characteristics, 3D structures of most GPCRs are still unknown. This makes target-based virtual screenings of GPCR ligands extremely difficult, and successful virtual screening techniques rely heavily on ligand information. These virtual screening methods focus on specific features of ligands on GPCR protein level, and common features of ligands on higher levels of GPCR classification are yet to be studied. Here we extracted common substructures of GPCR ligands of GPCR protein subfamilies. We used the SIMCOMP, a graph-based chemical structure comparison program, and hierarchical clustering to reveal common substructures. We applied our method to 850 GPCR ligands and we found 53 common substructures covering 439 ligands. These substructures contribute to deeper understanding of structural features of GPCR ligands which can be used in new drug discovery methods.

  4. A new strategy for the preparation of peptide-targeted technetium and rhenium radiopharmaceuticals. The automated solid-phase synthesis, characterization, labeling, and screening of a peptide-ligand library targeted at the formyl peptide receptor.

    Science.gov (United States)

    Stephenson, Karin A; Banerjee, Sangeeta Ray; Sogbein, Oyebola O; Levadala, Murali K; McFarlane, Nicole; Boreham, Douglas R; Maresca, Kevin P; Babich, John W; Zubieta, Jon; Valliant, John F

    2005-01-01

    A new solid-phase synthetic methodology was developed that enables libraries of peptide-based Tc(I)/Re(I) radiopharmaceuticals to be prepared using a conventional automated peptide synthesizer. Through the use of a tridentate ligand derived from N-alpha-Fmoc-l-lysine, which we refer to as a single amino acid chelate (SAAC), a series of 12 novel bioconjugates [R-NH(CO)ZLF(SAAC)G, R = ethyl, isopropyl, n-propyl, tert-butyl, n-butyl, benzyl; Z = Met, Nle] that are designed to target the formyl peptide receptor (FPR) were prepared. Construction of the library was carried out in a multiwell format on an Advanced ChemTech 348 peptide synthesizer where multi-milligram quantities of each peptide were isolated in high purity without HPLC purification. After characterization, the library components were screened for their affinity for the FPR receptor using flow cytometry where the K(d) values were found to be in the low micromolar range (0.5-3.0 microM). Compound 5j was subsequently labeled with (99m)Tc(I) and the product isolated in high radiochemical yield using a simple Sep-Pak purification procedure. The retention time of the labeled compound matched that of the fully characterized Re-analogue which was prepared through the use of the same solid-phase synthesis methodology that was used to construct the library. The work reported here is a rare example of a method by which libraries of peptide-ligand conjugates and their rhenium complexes can be prepared.

  5. Nickel and iron complexes with N,P,N-type ligands: synthesis, structure and catalytic oligomerization of ethylene.

    Science.gov (United States)

    Kermagoret, Anthony; Tomicki, Falk; Braunstein, Pierre

    2008-06-14

    The N,P,N-type ligands bis(2-picolyl)phenylphosphine (), bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine (), bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine () and bis(2-picolyloxy)phenylphosphine () were used to synthesize the corresponding pentacoordinated Ni(ii) complexes [Ni{bis(2-picolyl)phenylphosphine}Cl(2)] (), [Ni{bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine}Cl(2)] (), [Ni{bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine}Cl(2)] () and [Ni{bis(2-picolyloxy)phenylphosphine}Cl(2)] (), respectively. The hexacoordinated iron complexes [Fe{bis(2-picolyl)phenylphosphine}(2)][Cl(3)FeOFeCl(3)] (), [Fe{bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine}(2)][Cl(3)FeOFeCl(3)] () and the tetracoordinated complex [Fe{bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine}Cl(2)] (abbreviated [FeCl(2)(NPN(Me2)-N,N)]) were prepared by reaction of FeCl(2).4H(2)O with ligands , respectively. The crystal structures of the octahedral complexes and , determined by X-ray diffraction, showed that two tridentate ligands are facially coordinated to the metal centre with a cis-arrangement of the P atoms and the dianion (mu-oxo)bis[trichloroferrate(iii)] compensates the doubly positive charge of the complex. The cyclic voltammograms of and showed two reversible redox couples attributed to the reduction of the dianion (Fe(2)OCl(6))(2-) (-0.24 V for and -0.20 V for vs. SCE) and to the oxidation of the Fe(ii) ion of the complex (0.67 V for and 0.52 V for vs. SCE). The cyclic voltammogram of [FeCl(2)(NPN(Me2)-N,N)] showed a reversible redox couple at -0.17 V vs. SCE assigned to the oxidation of the Fe(ii) atom and an irreversible process at 0.65 V. The complexes , and [FeCl(2)(NPN(Me2)-N,N)] have been evaluated in the catalytic oligomerization of ethylene with AlEtCl(2) or MAO as cocatalyst. The nickel complex proved to be the most active precatalyst in the series, with a turnover frequency (TOF) of 61 800 mol(C(2)H(4)) mol(Ni)(-1) h(-1) with 10 equiv. of AlEtCl(2) and 12 200 mol(C(2)H

  6. Field-Induced Co(II) Single-Ion Magnets with mer-Directing Ligands but Ambiguous Coordination Geometry.

    Science.gov (United States)

    Peng, Yan; Mereacre, Valeriu; Anson, Christopher E; Zhang, Yiquan; Bodenstein, Tilmann; Fink, Karin; Powell, Annie K

    2017-06-05

    Three air-stable Co(II) mononuclear complexes with different aromatic substituents have been prepared and structurally characterized by single-crystal X-ray diffraction. The mononuclear complexes [Co(H 2 L1) 2 ]·2THF (1), [Co(HL2) 2 ] (2), and [Co(H 2 L3) 2 ]·CH 2 Cl 2 (3) (where H 3 L1, H 2 L2, and H 3 L3 represent 3-hydroxy-naphthalene-2-carboxylic acid (6-hydroxymethyl-pyridin-2-ylmethylene) hydrazide, nicotinic acid (6-hydroxymethyl-pyridin-2-ylmethylene) hydrazide, and 2-hydroxy-benzoic acid (6-hydroxymethyl-pyridin-2-ylmethylene) hydrazide, respectively) feature a distorted mer octahedral coordination geometry. Detailed magnetic studies of 1-3 have been conducted using direct and alternating current magnetic susceptibility data. Field-induced slow magnetic relaxation was observed for these three complexes. There are few examples of such behavior in (distorted) octahedral coordination geometry (OC) Co(II) mononuclear complexes with uniaxial anisotropy. Analysis of the six-coordinate Co(II) mononuclear single-ion magnets (SIMs) in the literature using the SHAPE program revealed that they all show what is best described as distorted trigonal prismatic (TRP) coordination geometry, and in general, these show negative D zero-field splitting (ZFS) values. On the other hand, all the Co(II) mononuclear complexes displaying what is best approximated as distorted octahedral (OC) coordination geometry show positive D values. In the new Co(II) mononuclear complexes we describe here, there is an ambiguity, since the rigid tridentate ligands confer what is best described for an octahedral complex as a mer coordination geometry, but the actual shape of the first coordination sphere is between octahedral and trigonal prismatic. The negative D values observed experimentally and supported by high-level electronic structure calculations are thus in line with a trigonal prismatic geometry. However, a consideration of the rhombicity as indicated by the E value of the ZFS in

  7. Prediction of GPCR-Ligand Binding Using Machine Learning Algorithms

    Directory of Open Access Journals (Sweden)

    Sangmin Seo

    2018-01-01

    Full Text Available We propose a novel method that predicts binding of G-protein coupled receptors (GPCRs and ligands. The proposed method uses hub and cycle structures of ligands and amino acid motif sequences of GPCRs, rather than the 3D structure of a receptor or similarity of receptors or ligands. The experimental results show that these new features can be effective in predicting GPCR-ligand binding (average area under the curve [AUC] of 0.944, because they are thought to include hidden properties of good ligand-receptor binding. Using the proposed method, we were able to identify novel ligand-GPCR bindings, some of which are supported by several studies.

  8. Predicting Nanocrystal Shape through Consideration of Surface-Ligand Interactions

    KAUST Repository

    Bealing, Clive R.

    2012-03-27

    Density functional calculations for the binding energy of oleic acid-based ligands on Pb-rich {100} and {111} facets of PbSe nanocrystals determine the surface energies as a function of ligand coverage. Oleic acid is expected to bind to the nanocrystal surface in the form of lead oleate. The Wulff construction predicts the thermodynamic equilibrium shape of the PbSe nanocrystals. The equilibrium shape is a function of the ligand surface coverage, which can be controlled by changing the concentration of oleic acid during synthesis. The different binding energy of the ligand on the {100} and {111} facets results in different equilibrium ligand coverages on the facets, and a transition in the equilibrium shape from octahedral to cubic is predicted when increasing the ligand concentration during synthesis. © 2012 American Chemical Society.

  9. The autoxidation activity of new mixed-ligand manganese and iron complexes with tripodal ligands

    NARCIS (Netherlands)

    van Gorkum, R.; Berding, J.; Tooke, D.M.; Spek, A.L.|info:eu-repo/dai/nl/156517566; Reedijk, J.; Bouwman, E.

    2007-01-01

    The activity of new manganese and iron complexes of dianionic tripodal ligands in the autoxidation of ethyl linoleate (EL) is reported. EL consumption rates were monitored using time-resolved FTIR and the degree of oligomerisation was determined by SEC. Almost all complexes showed the same trend in

  10. LASSO-ligand activity by surface similarity order: a new tool for ligand based virtual screening.

    Science.gov (United States)

    Reid, Darryl; Sadjad, Bashir S; Zsoldos, Zsolt; Simon, Aniko

    2008-01-01

    Virtual Ligand Screening (VLS) has become an integral part of the drug discovery process for many pharmaceutical companies. Ligand similarity searches provide a very powerful method of screening large databases of ligands to identify possible hits. If these hits belong to new chemotypes the method is deemed even more successful. eHiTS LASSO uses a new interacting surface point types (ISPT) molecular descriptor that is generated from the 3D structure of the ligand, but unlike most 3D descriptors it is conformation independent. Combined with a neural network machine learning technique, LASSO screens molecular databases at an ultra fast speed of 1 million structures in under 1 min on a standard PC. The results obtained from eHiTS LASSO trained on relatively small training sets of just 2, 4 or 8 actives are presented using the diverse directory of useful decoys (DUD) dataset. It is shown that over a wide range of receptor families, eHiTS LASSO is consistently able to enrich screened databases and provides scaffold hopping ability.

  11. LASSO—ligand activity by surface similarity order: a new tool for ligand based virtual screening

    Science.gov (United States)

    Reid, Darryl; Sadjad, Bashir S.; Zsoldos, Zsolt; Simon, Aniko

    2008-06-01

    Virtual Ligand Screening (VLS) has become an integral part of the drug discovery process for many pharmaceutical companies. Ligand similarity searches provide a very powerful method of screening large databases of ligands to identify possible hits. If these hits belong to new chemotypes the method is deemed even more successful. eHiTS LASSO uses a new interacting surface point types (ISPT) molecular descriptor that is generated from the 3D structure of the ligand, but unlike most 3D descriptors it is conformation independent. Combined with a neural network machine learning technique, LASSO screens molecular databases at an ultra fast speed of 1 million structures in under 1 min on a standard PC. The results obtained from eHiTS LASSO trained on relatively small training sets of just 2, 4 or 8 actives are presented using the diverse directory of useful decoys (DUD) dataset. It is shown that over a wide range of receptor families, eHiTS LASSO is consistently able to enrich screened databases and provides scaffold hopping ability.

  12. Ligands hybrides : synthèse et chimie de coordination

    OpenAIRE

    Massard, Alexandre

    2011-01-01

    This manuscript deals with the synthesis of hybrids ligands and their coordination ability. The first part is dedicated to Cp-imidazole, Cp-imidazolium and Cp-phosphine ligands. Several synthetic routes have been developed to reach these mixed ligands and their coordination chemistry has been studied with titanium. In a second part, a method developed in our laboratory to synthesize phosphine-olefines was applied to obtain a phosphino-diene bearing three potential coordination sites. We have ...

  13. Functionalization of new PN ligands with steroids

    International Nuclear Information System (INIS)

    Jimenez, H.; Volkert, W.A.; Singh, P.R.; Ketring, A.R.; Katti, K.V.

    1993-01-01

    Efforts are currently underway to radiolabel steroids for possible imaging and treatment of breast cancer. The authors are exploring the ligating properties of phosphorus hydrazides to anchor radionuclides of diagnostic and therapeutic use (e.g. 99m Tc or 186 Re/ 188 Re) to estrogen and progesterone steroids which abound around breast tumor cells. The phenolic ring of estrone undergoes nucleophilic reaction with the pentavalent trichloro phosphorus sulfide (or oxide) in the presence of a weak base such as Et 3 N or pyridine. The chlorines were then substituted with hydrazine to produce the phosphorus attached steroid ligands in excellent yields. These ligands formed stable complexes with the metals at the open-quotes non-tracerclose quotes (Pd(II) and Re) and open-quotes tracerclose quotes ( 99m Tc and 109 Pd) levels. The alcohol functionalities as in 11-hydroxy progesterone and protected estradiol were also utilized with the use of a strong base LiN(SiMe 3 ) 2 and KH. Carbonyl containing steroid such as pregnenolone was directly added to a bishydrazido phosphine chelate by Schiff base coupling in a dean stark set-up. For estrone, which contains a hindered ketone, one hydrazone unit was first formed before the phosphorus chloride was introduced. C-O-P bond formation was also achieved from enolates of these ketones. By applying 2 eq of LDA or BuLi, α C-P bonding was accomplished. Structures and reactivities of these phosphorus hydrazide bound steroids are discussed

  14. Novel Somatostatin Receptor Ligands Therapies for Acromegaly

    Directory of Open Access Journals (Sweden)

    Rosa Maria Paragliola

    2018-03-01

    Full Text Available Surgery is considered the treatment of choice in acromegaly, but patients with persistent disease after surgery or in whom surgery cannot be considered require medical therapy. Somatostatin receptor ligands (SRLs octreotide (OCT, lanreotide, and the more recently approved pasireotide, characterized by a broader receptor ligand binding profile, are considered the mainstay in the medical management of acromegaly. However, in the attempt to offer a more efficacious and better tolerated medical approach, recent research has been aimed to override some limitations related to the use of currently approved drugs and novel SRLs therapies, with potential attractive features, have been proposed. These include both new formulation of older molecules and new molecules. Novel OCT formulations are aimed in particular to improve patients’ compliance and to reduce injection discomfort. They include an investigational ready-to-use subcutaneous depot OCT formulation (CAM2029, delivered via prefilled syringes and oral OCT that uses a “transient permeability enhancer” technology, which allows for OCT oral absorption. Another new delivery system is a long-lasting OCT implant (VP-003, which provide stable doses of OCT throughout a period of several months. Finally, a new SRL DG3173 (somatoprim seems to be more selective for GH secretion, suggesting possible advantages in the presence of hyperglycemia or diabetes. How much these innovations will actually be beneficial to acromegaly patients in real clinical practice remains to be seen.

  15. Design of targeting ligands in medicinal inorganic chemistry.

    Science.gov (United States)

    Storr, Tim; Thompson, Katherine H; Orvig, Chris

    2006-06-01

    This tutorial review will highlight recent advances in medicinal inorganic chemistry pertaining to the use of multifunctional ligands for enhanced effect. Ligands that adequately bind metal ions and also include specific targeting features are gaining in popularity due to their ability to enhance the efficacy of less complicated metal-based agents. Moving beyond the traditional view of ligands modifying reactivity, stabilizing specific oxidation states, and contributing to substitution inertness, we will discuss recent work involving metal complexes with multifunctional ligands that target specific tissues, membrane receptors, or endogenous molecules, including enzymes.

  16. Competitive antagonism of AMPA receptors by ligands of different classes

    DEFF Research Database (Denmark)

    Hogner, Anders; Greenwood, Jeremy R; Liljefors, Tommy

    2003-01-01

    that ATPO and DNQX stabilize an open form of the ligand-binding core by different sets of interactions. Computational techniques are used to quantify the differences between these two ligands and to map the binding site. The isoxazole moiety of ATPO acts primarily as a spacer, and other scaffolds could......-(phosphonomethoxy)-4-isoxazolyl]propionic acid (ATPO) in complex with the ligand-binding core of the receptor. Comparison with the only previous structure of the ligand-binding core in complex with an antagonist, 6,7-dinitro-2,3-quinoxalinedione (DNQX) (Armstrong, N.; Gouaux, E. Neuron 2000, 28, 165-181), reveals...

  17. Biased ligands: pathway validation for novel GPCR therapeutics.

    Science.gov (United States)

    Rominger, David H; Cowan, Conrad L; Gowen-MacDonald, William; Violin, Jonathan D

    2014-06-01

    G protein-coupled receptors (GPCRs), in recent years, have been shown to signal via multiple distinct pathways. Furthermore, biased ligands for some receptors can differentially stimulate or inhibit these pathways versus unbiased endogenous ligands or drugs. Biased ligands can be used to gain a deeper understanding of the molecular targets and cellular responses associated with a GPCR, and may be developed into therapeutics with improved efficacy, safety and/or tolerability. Here we review examples and approaches to pathway validation that establish the relevance and therapeutic potential of distinct pathways that can be selectively activated or blocked by biased ligands. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Comparing and combining implicit ligand sampling with multiple steered molecular dynamics to study ligand migration processes in heme proteins.

    Science.gov (United States)

    Forti, Flavio; Boechi, Leonardo; Estrin, Dario A; Marti, Marcelo A

    2011-07-30

    The ubiquitous heme proteins perform a wide variety of tasks that rely on the subtle regulation of their affinity for small ligands like O2, CO, and NO. Ligand affinity is characterized by kinetic association and dissociation rate constants, that partially depend on ligand migration between the solvent and active site, mediated by the presence of internal cavities or tunnels. Different computational methods have been developed to study these processes which can be roughly divided in two strategies: those costly methods in which the ligand is treated explicitly during the simulations, and the free energy landscape of the process is computed; and those faster methods that use prior computed Molecular Dynamics simulation without the ligand, and incorporate it afterwards, called implicit ligand sampling (ILS) methods. To compare both approaches performance and to provide a combined protocol to study ligand migration in heme proteins, we performed ILS and multiple steered molecular dynamics (MSMD) free energy calculations of the ligand migration process in three representative and well theoretically and experimentally studied cases that cover a wide range of complex situations presenting a challenging benchmark for the aim of the present work. Our results show that ILS provides a good description of the tunnel topology and a reasonable approximation to the free energy landscape, while MSMD provides more accurate and detailed free energy profile description of each tunnel. Based on these results, a combined strategy is presented for the study of internal ligand migration in heme proteins. Copyright © 2011 Wiley Periodicals, Inc.

  19. Calculating the mean time to capture for tethered ligands and its effect on the chemical equilibrium of bound ligand pairs.

    Science.gov (United States)

    Shen, Lu; Decker, Caitlin G; Maynard, Heather D; Levine, Alex J

    2016-09-01

    We present here the calculation of the mean time to capture of a tethered ligand to the receptor. This calculation is then used to determine the shift in the partitioning between (1) free, (2) singly bound, and (3) doubly bound ligands in chemical equilibrium as a function of the length of the tether. These calculations are used in the research article Fibroblast Growth Factor 2 Dimer with Superagonist in vitro Activity Improves Granulation Tissue Formation During Wound Healing (Decker et al., in press [1]) to explain quantitatively how changes in polymeric linker length in the ligand dimers modifies the efficacy of these molecules relative to that of free ligands.

  20. Programmed Death-Ligand 1 Immunohistochemistry Testing

    DEFF Research Database (Denmark)

    Büttner, Reinhard; Gosney, John R; Skov, Birgit Guldhammer

    2017-01-01

    Purpose Three programmed death-1/programmed death-ligand 1 (PD-L1) inhibitors are currently approved for treatment of non-small-cell lung cancer (NSCLC). Treatment with pembrolizumab in NSCLC requires PD-L1 immunohistochemistry (IHC) testing. Nivolumab and atezolizumab are approved without PD-L1...... testing, though US Food and Drug Administration-cleared complementary PD-L1 tests are available for both. PD-L1 IHC assays used to assess PD-L1 expression in patients treated with programmed death-1/PD-L1 inhibitors in clinical trials include PD-L1 IHC 28-8 pharmDx (28-8), PD-L1 IHC 22C3 pharmDx (22C3...

  1. Ligand-directed trafficking of receptor stimulus.

    Science.gov (United States)

    Chilmonczyk, Zdzisław; Bojarski, Andrzej J; Sylte, Ingebrigt

    2014-12-01

    GPCRs are seven transmembrane-spanning receptors that convey specific extracellular stimuli to intracellular signalling. They represent the largest family of cell surface proteins that are therapeutically targeted. According to the traditional two-state model of receptor theory, GPCRs were considered as operating in equilibrium between two functional conformations, an active (R*) and inactive (R) state. Thus, it was assumed that a GPCR can exist either in an "off" or "on" conformation causing either no activation or equal activation of all its signalling pathways. Over the past several years it has become evident that this model is too simple and that GPCR signalling is far more complex. Different studies have presented a multistate model of receptor activation in which ligand-specific receptor conformations are able to differentiate between distinct signalling partners. Recent data show that beside G proteins numerous other proteins, such as β-arrestins and kinases, may interact with GPCRs and activate intracellular signalling pathways. GPCR activation may therefore involve receptor desensitization, coupling to multiple G proteins, Gα or Gβγ signalling, and pathway activation that is independent of G proteins. This latter effect leads to agonist "functional selectivity" (also called ligand-directed receptor trafficking, stimulus trafficking, biased agonism, biased signalling), and agonist intervention with functional selectivity may improve the therapy. Many commercially available drugs with beneficial efficacy also show various undesirable side effects. Further studies of biased signalling might facilitate our understanding of the side effects of current drugs and take us to new avenues to efficiently design pathway-specific medications. Copyright © 2014 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

  2. From three-dimensional GPCR structure to rational ligand discovery

    NARCIS (Netherlands)

    Kooistra, A.J.; Leurs, R.; de Esch, I.J.P.; de Graaf, C.

    2014-01-01

    This chapter will focus on G protein-coupled receptor structure-based virtual screening and ligand design. A generic virtual screening workflow and its individual elements will be introduced, covering amongst others the use of experimental data to steer the virtual screening process, ligand binding

  3. GLIDA: GPCR-ligand database for chemical genomic drug discovery.

    Science.gov (United States)

    Okuno, Yasushi; Yang, Jiyoon; Taneishi, Kei; Yabuuchi, Hiroaki; Tsujimoto, Gozoh

    2006-01-01

    G-protein coupled receptors (GPCRs) represent one of the most important families of drug targets in pharmaceutical development. GPCR-LIgand DAtabase (GLIDA) is a novel public GPCR-related chemical genomic database that is primarily focused on the correlation of information between GPCRs and their ligands. It provides correlation data between GPCRs and their ligands, along with chemical information on the ligands, as well as access information to the various web databases regarding GPCRs. These data are connected with each other in a relational database, allowing users in the field of GPCR-related drug discovery to easily retrieve such information from either biological or chemical starting points. GLIDA includes structure similarity search functions for the GPCRs and for their ligands. Thus, GLIDA can provide correlation maps linking the searched homologous GPCRs (or ligands) with their ligands (or GPCRs). By analyzing the correlation patterns between GPCRs and ligands, we can gain more detailed knowledge about their interactions and improve drug design efforts by focusing on inferred candidates for GPCR-specific drugs. GLIDA is publicly available at http://gdds.pharm.kyoto-u.ac.jp:8081/glida. We hope that it will prove very useful for chemical genomic research and GPCR-related drug discovery.

  4. Immobilisation of ligands by radio-derivatized polymers

    International Nuclear Information System (INIS)

    Varga, J.M.; Fritsch, P.

    1995-01-01

    The invention relates to radio-derivatized polymers and a method of producing them by contacting non-polymerizable conjugands with radiolysable polymers in the presence of irradiation. The resulting radio-derivatized polymers can be further linked with ligand of organic or inorganic nature to immobilize such ligands. 2 figs., 5 tabs

  5. The Evaluation of Novel Camphor-derived Pyridyl Ligands as ...

    African Journals Online (AJOL)

    NJD

    2009-03-03

    Mar 3, 2009 ... group in the field of chiral synthesis and catalytic applications. The first paper involved the synthesis of pentacycloundecane oxazolines and the application of the ligands in an asymmetric. Diels-Alder reaction.1 The second paper made use of camphor- derived ligands in the chiral alkylation of aldehydes ...

  6. Synthesis of meta-substituted monodentate phosphinite ligands and ...

    Indian Academy of Sciences (India)

    SATEJ S DESHMUKH

    and a variety of ligands have been employed to tame the metal.1 Among the wide array of ligands, applica- ... cations in a variety of metal catalyzed transformations as depicted in Figure 1. Notable among these are .... was quenched with water, and organic layer was extracted with ethyl acetate (three times). The combined ...

  7. Mixed-Ligand Complexes Of Nickel (II) With 2-Acetylpyridine ...

    African Journals Online (AJOL)

    The preparation and spectral properties of five nickel (II) mixed-ligands complexes (Ni [2-Actsc.Y]CI2), derived from 2-acetylpyridinethiosermicarbazones and some nitrogen/sulphur monodentate ligands such as thiophene, ammonia, picoline, pyridine and aniline are described. The complexes have been characterized on ...

  8. Kinetics and mechanism of interaction of some bioactive ligands ...

    Indian Academy of Sciences (India)

    The rate constants increase with increasing ligand concentration and the evaluated activation parameters for all reactions suggest an associative substitution mechanism for both the aqua ligand substitution processes. The product of the reaction has been characterized by IR, NMR and ESI-MS spectral analysis; which ...

  9. a review of cyclopentadienyl type ligands in group 4 metallocene

    African Journals Online (AJOL)

    Neil Grimmer

    4. TiCl. Cl. 3. M. M=Ti 1. =Zr 2. Cl. Cl. 2. The Nature of Metallocene Catalysts. Before we commence the discussion of how metallocene ligand design has evolved, .... The use of kinetic isotope effects to probe the polymerisation mechanism, first ...... Here the size of a ligand is measured as a function of distance from the point.

  10. Partial association of restriction polymorphism of the ligand binding ...

    African Journals Online (AJOL)

    Partial association of restriction polymorphism of the ligand binding domain of human androgen receptor in prostate cancer. ... Background: Human androgen receptor (AR) functions as a steroid-hormone activated transcription factor. The receptor binds to its ligand (testosterone or dihydrotestosterone) and is translocated to ...

  11. Kinetics and Mechanism of the Ligand Exchange Reaction Between ...

    African Journals Online (AJOL)

    NICO

    Visible spectrophotometry is used to study the kinetics of ligand exchange in the system Ni(salpn)/H2salen with or without triethylamine ... rate of the ligand exchange reaction was accelerated by adding NEt3 to the reaction mixture. However, the ..... 0.05 M. The increase of the reaction rate at low [H2O] could be due to the ...

  12. Synthesis of meta-substituted monodentate phosphinite ligands and ...

    Indian Academy of Sciences (India)

    To demonstrate the synthetic usefulness of 4a and 4b, these ligands were tested in the rhodium catalyzed hydroformylation of 1-octene. The diethylamine substituted ligand 4a was found to be highly active, whereas4bwas less reactive but revealed slightly better regioselectivity of 62% under optimized conditions.

  13. The Evaluation of Novel Camphor-derived Pyridyl Ligands as ...

    African Journals Online (AJOL)

    A series of camphor-derived pyridyl ligands were evaluated in the Diels-Alder reaction of 3-acryloyl-2-oxazolidinone 1 with cyclopentadiene 2. High yields with good endo:exo selectivity, but only moderate enantioselectivities (43 % ee), were obtained. The structures of the copper (II) complexes of the ligands were ...

  14. THERMODYNAMICS OF PROTEIN-LIGAND INTERACTIONS AND THEIR ANALYSIS

    Directory of Open Access Journals (Sweden)

    Rummi Devi Saini

    2017-11-01

    Full Text Available Physiological processes are controlled mainly by intermolecular recognition mechanisms which involve protein–protein and protein–ligand interactions with a high specificity and affinity to form a specific complex. Proteins being an important class of macromolecules in biological systems, it is important to understand their actions through binding to other molecules of proteins or ligands. In fact, the binding of low molecular weight ligands to proteins plays a significant role in regulating biological processes such as cellular metabolism and signal transmission. Therefore knowledge of the protein–ligand interactions and the knowledge of the mechanisms involved in the protein-ligand recognition and binding are key in understanding biology at molecular level which will facilitate the discovery, design, and development of drugs. In this review, the mechanisms involved in protein–ligand binding, the binding kinetics, thermodynamic concepts and binding driving forces are discussed. Thermodynamic mechanisms involved in a few important protein-ligand binding are described. Various spectroscopic, non-spectroscopic and computational method for analysis of protein–ligand binding are also discussed.

  15. Models of protein-ligand crystal structures: trust, but verify

    Science.gov (United States)

    Deller, Marc C.; Rupp, Bernhard

    2015-09-01

    X-ray crystallography provides the most accurate models of protein-ligand structures. These models serve as the foundation of many computational methods including structure prediction, molecular modelling, and structure-based drug design. The success of these computational methods ultimately depends on the quality of the underlying protein-ligand models. X-ray crystallography offers the unparalleled advantage of a clear mathematical formalism relating the experimental data to the protein-ligand model. In the case of X-ray crystallography, the primary experimental evidence is the electron density of the molecules forming the crystal. The first step in the generation of an accurate and precise crystallographic model is the interpretation of the electron density of the crystal, typically carried out by construction of an atomic model. The atomic model must then be validated for fit to the experimental electron density and also for agreement with prior expectations of stereochemistry. Stringent validation of protein-ligand models has become possible as a result of the mandatory deposition of primary diffraction data, and many computational tools are now available to aid in the validation process. Validation of protein-ligand complexes has revealed some instances of overenthusiastic interpretation of ligand density. Fundamental concepts and metrics of protein-ligand quality validation are discussed and we highlight software tools to assist in this process. It is essential that end users select high quality protein-ligand models for their computational and biological studies, and we provide an overview of how this can be achieved.

  16. Ligand Binding Domain Protein in Tetracycline-Inducible Expression

    African Journals Online (AJOL)

    Purpose: To investigate tetracycline-inducible expression system for producing clinically usable, highquality liver X receptor ligand-binding domain recombinant protein. Methods: In this study, we have expressed and purified the recombinant liver X receptor β-ligand binding domain proteins in E. coli using a tetracycline ...

  17. Transient ligand docking sites in Cerebratulus lacteus mini-hemoglobin.

    Science.gov (United States)

    Deng, Pengchi; Nienhaus, Karin; Palladino, Pasquale; Olson, John S; Blouin, George; Moens, Luc; Dewilde, Sylvia; Geuens, Eva; Nienhaus, G Ulrich

    2007-08-15

    The monomeric hemoglobin of the nemertean worm Cerebratulus lacteus functions as an oxygen storage protein to maintain neural activity under hypoxic conditions. It shares a large, apolar matrix tunnel with other small hemoglobins, which has been implicated as a potential ligand migration pathway. Here we explore ligand migration and binding within the distal heme pocket, to which the tunnel provides access to ligands from the outside. FTIR/TDS experiments performed at cryogenic temperatures reveal the presence of three transient ligand docking sites within the distal pocket, the primary docking site B on top of pyrrole C and secondary sites C and D. Site C is assigned to a cavity adjacent to the distal portion of the heme pocket, surrounded by the B and E helices. It has an opening to the apolar tunnel and is expected to be on the pathway for ligand entry and exit, whereas site D, circumscribed by TyrB10, GlnE7, and the CD corner, most likely is located on a side pathway of ligand migration. Flash photolysis experiments at ambient temperatures indicate that the rate-limiting step for ligand binding to CerHb is migration through the apolar channel to site C. Movement from C to B and iron-ligand bond formation involve low energy barriers and thus are very rapid processes in the wt protein.

  18. The autoxidation activity of new mixed-ligand manganese and iron complexes with tripodal ligands

    OpenAIRE

    van Gorkum, R.; Berding, J.; Tooke, D.M.; Spek, A.L.; Reedijk, J.; Bouwman, E.

    2007-01-01

    The activity of new manganese and iron complexes of dianionic tripodal ligands in the autoxidation of ethyl linoleate (EL) is reported. EL consumption rates were monitored using time-resolved FTIR and the degree of oligomerisation was determined by SEC. Almost all complexes showed the same trend in the autoxidation of EL. After a short induction time, the reaction started at a relatively high constant rate; later, this rate changes to a lower rate, which was again constant and on average was ...

  19. Luminescence study of praseodymium complexes with selected phosphonate ligands

    Science.gov (United States)

    Pawlicki, G.; Lis, S.

    2011-08-01

    Spectroscopic properties of Pr(III) complexes with diethyl(phthalimidomethyl)phosphonate (DPIP) and diethyl(2-oxo-2phenylethyl)phosphonate (DEPP) ligands were studied using absorption and luminescence spectroscopy. Absorption spectra of praseodymium nitrate hexahydrate complexes with phosphonate ligands in acetonitrile solutions were measured and used to calculate oscillator strength values. Luminescence (excitation and emission) spectra of the Pr(III) complexes with DPIP and DEPP were measured in CH 3CN, DMSO, methanol and toluene solutions. The sensitized emission of Pr(III), observed from different excited states ( 3P 0 or 1D 2), resulted from the intramolecular energy transfer from the ligands to the emissive levels of Pr(III). The Pr(III) complexes with studied ligands were synthesized and their compositions, as Pr(DEPP) 2(NO 3) 3 and Pr(DPIP) 3(NO 3) 3, were confirmed by elemental analyses. Using IR and 31P NMR spectroscopy coordination mode of the ligands were described.

  20. Ligand specificity of nuclear hormone receptors: sifting through promiscuity.

    Science.gov (United States)

    Noy, Noa

    2007-11-27

    The superfamily of nuclear hormone receptors includes transcription factors that play key roles in regulating multiple biological functions during embryonic development and in adult tissues, as well as in many disease states. The quintessential characteristic of nuclear receptors, and the basis for the name of the family, is that their transcriptional activities can be regulated by small molecules, usually comprised of hydrophobic compounds. However, the endogenous ligands for approximately half of the members of the nuclear receptor family are unknown, and these receptors are thus designated as "orphan receptors". One class of orphan receptors encompasses receptors that display a broad ligand selectivity; i.e., they can promiscuously bind to and may be activated by multiple ligands. This characteristic complicates the identification of physiologically meaningful ligands that activate these receptors in vivo. Here, we discuss a few examples of promiscuous receptors and outline strategies that may be employed in shedding light on the nature of bona fide ligands for such receptors.

  1. Mathematical model for determining the binding constants between immunoglobulins, bivalent ligands, and monovalent ligands.

    Science.gov (United States)

    Mack, Eric T; Cummings, Linda; Perez-Castillejos, Raquel

    2011-02-01

    This paper analyzes the equilibria between immunoglobulins (R(2)), homo-bifunctional ligands (L(2)), monovalent ligands (I), and their complexes. We present a mathematical model that can be used to estimate the concentration of each species present in a mixture of R(2), L(2), and I, given the initial conditions defining the total concentration of R(2), L(2), I, and four dissociation constants (K(d)(inter), K(d)(intra), K(d)(mono), and α). This model is based on fewer assumptions than previous models and can be used to describe exactly a broad range of experimental conditions. A series of curves illustrates the dependence of the equilibria upon the total concentrations of receptors and ligands, and the dissociation constants. We provide a set of guidelines for the design and analysis of experiments with a focus on estimating the binding constants from experimental binding isotherms. Two analytical equations relate the conditions for maximum aggregation in this system to the binding constants. This model is a tool to quantify the binding of immunoglobulins to antigens and a guide to understanding and predicting the experimental data of assays and techniques that employ immunoglobulins.

  2. Regulation mechanisms of the FLT3-ligand after irradiation

    International Nuclear Information System (INIS)

    Prat-Lepesant, M.

    2005-06-01

    The hematopoietic compartment is one of the most severely damaged after chemotherapy, radiotherapy or accidental irradiations. Whatever its origin, the resulting damage to the bone marrow remains difficult to evaluate. Thus, it would be of great interest to get a biological indicator of residual hematopoiesis in order to adapt the treatment to each clinical situation. Recent results indicated that the plasma Flt3 ligand concentration was increased in patients suffering from either acquired or induced aplasia, suggesting that Flt3 ligand might be useful as a biological indicator of bone marrow status. We thus followed in a mouse model as well as in several clinical situations the variations in plasma Flt3 ligand concentration, after either homogeneous or heterogeneous irradiations. These variations were correlated to the number of hematopoietic progenitors and to other parameters such as duration and depth of pancytopenia. The results indicated that the concentration of Flt3 ligand in the blood reflects the bone marrow status, and that the follow-up of plasma Flt3 ligand concentration could give predictive information about the bone marrow function and the duration and severity of pancytopenia and thrombocytopenia. Nevertheless, the clinical use of Flt3 ligand as a biological indicator of bone marrow damage require the knowledge of the mechanisms regulating the variations in plasma Flt3 ligand concentration. We thus developed a study in the mouse model. The results indicated that the variations in plasma Flt3 ligand variations were not solely due to a balance between its production by lymphoid cells and its consumption by hematopoietic cells. Moreover, we showed that T lymphocytes are not the main regulator of plasma Flt3 ligand concentration as previously suggested, and that other cell types, possibly including bone marrow stromal cells, might be strongly implicated. These results also suggest that the Flt3 ligand is a main systemic regulator of hematopoiesis

  3. Developing Ligands for Palladium(II)-Catalyzed C–H Functionalization: Intimate Dialogue between Ligand and Substrate

    Science.gov (United States)

    Engle, Keary M.; Yu, Jin-Quan

    2013-01-01

    Homogeneous transition metal–catalyzed reactions are indispensable to all facets of modern chemical synthesis. It is thus difficult to imagine that for much of the early 20th century, the reactivity and selectivity of all known homogeneous metal catalysts paled in comparison to their heterogeneous and biological counterparts. In the intervening decades, advances in ligand design bridged this divide, such that today some of the most demanding bond-forming events are mediated by ligand-supported homogeneous metal species. While ligand design has propelled many areas of homogeneous catalysis, in the field of Pd(II)-catalyzed C–H functionalization, suitable ligand scaffolds are lacking, which has hampered the development of broadly practical transformations based on C–H functionalization logic. In this review, we offer an account of our research employing three ligand scaffolds, mono-N-protected amino acids, 2,6-disubstituted pyridines, and 2,2′-bipyridines, to address challenges posed by several synthetically versatile substrate classes. Drawing on this work, we discuss principles of ligand design, such as the need to match a ligand to a particular substrate class, and how ligand traits such as tunability and modularity can be advantageous in reaction discovery. PMID:23565982

  4. Gas adsorption and gas mixture separations using mixed-ligand MOF material

    Science.gov (United States)

    Hupp, Joseph T [Northfield, IL; Mulfort, Karen L [Chicago, IL; Snurr, Randall Q [Evanston, IL; Bae, Youn-Sang [Evanston, IL

    2011-01-04

    A method of separating a mixture of carbon dioxiode and hydrocarbon gas using a mixed-ligand, metal-organic framework (MOF) material having metal ions coordinated to carboxylate ligands and pyridyl ligands.

  5. Substituted biurets as uranophilic ligands: A facile DMSO-induced conversion of a 1:1 into a 2:1 uranyl-ligand complex

    Energy Technology Data Exchange (ETDEWEB)

    Potts, K.T.; O' Brien, J.J.; Tham, F.S. (Rensselaer Polytechnic Inst., Troy, NY (United States))

    1990-01-01

    1,5-Bis(6-(1-ethoxycarbonyl-3-thioureido)-2-pyridindiyl)biuret and uranyl acetate gave a crystalline 1:1 uranyl-ligand complex which, on crystallization from DMSO, underwent rearrangement to a crystalline 2:1 uranyl-ligand complex and a stoichiometric amount of the uncomplexed ligand. Spectral characteristics of these ligands and their uranyl complexes together with single crystal x-ray data for the uranyl-ligand complexes are described.

  6. Charged dopants in neutral supercells through substitutional donor (acceptor): nitrogen donor charging of the nitrogen-vacancy center in diamond

    Science.gov (United States)

    Löfgren, Robin; Pawar, Ravinder; Öberg, Sven; Larsson, J. Andreas

    2018-02-01

    Charged defects are traditionally computed by adding (subtracting) electrons for negative (positive) impurities. When using periodic boundary conditions this results in artificially charged supercells that also require a compensating background charge of the opposite sign, which makes slab supercells problematic because of an arbitrary dependence on the vacuum thickness. In this work, we test the method of using neutral supercells through the use of a substitutional electron donor (acceptor) to describe charged systems. We use density functional theory (DFT) to compare the effects of charging the well-studied NV-center in diamond by a substitutional donor nitrogen. We investigate the influence of the donor-N on the NV-center properties as a function of the distance between them, and find that they converge toward those obtained when adding an electron. We analyze the spin density and conclude that the donor-N has a zero magnetic moment, and thus, will not be seen in electron spin resonance. We validate our DFT energies through comparison to GW simulations. Charging the NV-center with a substitutional donor-N enables accurate calculations of slabs, without the ambiguity of using charged supercells. Implantation of donor-N atoms opens up the possibility to engineer NV-centers with the desired charge state for future ICT and sensor applications.

  7. Regulation mechanisms of the FLT3-ligand after irradiation; Mecanismes de regulation du FLT3-ligand apres irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Prat-Lepesant, M

    2005-06-15

    The hematopoietic compartment is one of the most severely damaged after chemotherapy, radiotherapy or accidental irradiations. Whatever its origin, the resulting damage to the bone marrow remains difficult to evaluate. Thus, it would be of great interest to get a biological indicator of residual hematopoiesis in order to adapt the treatment to each clinical situation. Recent results indicated that the plasma Flt3 ligand concentration was increased in patients suffering from either acquired or induced aplasia, suggesting that Flt3 ligand might be useful as a biological indicator of bone marrow status. We thus followed in a mouse model as well as in several clinical situations the variations in plasma Flt3 ligand concentration, after either homogeneous or heterogeneous irradiations. These variations were correlated to the number of hematopoietic progenitors and to other parameters such as duration and depth of pancytopenia. The results indicated that the concentration of Flt3 ligand in the blood reflects the bone marrow status, and that the follow-up of plasma Flt3 ligand concentration could give predictive information about the bone marrow function and the duration and severity of pancytopenia and thrombocytopenia. Nevertheless, the clinical use of Flt3 ligand as a biological indicator of bone marrow damage require the knowledge of the mechanisms regulating the variations in plasma Flt3 ligand concentration. We thus developed a study in the mouse model. The results indicated that the variations in plasma Flt3 ligand variations were not solely due to a balance between its production by lymphoid cells and its consumption by hematopoietic cells. Moreover, we showed that T lymphocytes are not the main regulator of plasma Flt3 ligand concentration as previously suggested, and that other cell types, possibly including bone marrow stromal cells, might be strongly implicated. These results also suggest that the Flt3 ligand is a main systemic regulator of hematopoiesis

  8. Identification of Soft Matter Binding Peptide Ligands Using Phage Display.

    Science.gov (United States)

    Günay, Kemal Arda; Klok, Harm-Anton

    2015-10-21

    Phage display is a powerful tool for the selection of highly affine, short peptide ligands. While originally primarily used for the identification of ligands to proteins, the scope of this technique has significantly expanded over the past two decades. Phage display nowadays is also increasingly applied to identify ligands that selectively bind with high affinity to a broad range of other substrates including natural and biological polymers as well as a variety of low-molecular-weight organic molecules. Such peptides are of interest for various reasons. The ability to selectively and with high affinity bind to the substrate of interest allows the conjugation or immobilization of, e.g., nanoparticles or biomolecules, or generally, facilitates interactions at materials interfaces. On the other hand, presentation of peptide ligands that selectively bind to low-molecular-weight organic materials is of interest for the development of sensor surfaces. The aim of this article is to highlight the opportunities provided by phage display for the identification of peptide ligands that bind to synthetic or natural polymer substrates or to small organic molecules. The article will first provide an overview of the different peptide ligands that have been identified by phage display that bind to these "soft matter" targets. The second part of the article will discuss the different characterization techniques that allow the determination of the affinity of the identified ligands to the respective substrates.

  9. Folding energetics of ligand binding proteins. I. Theoretical model.

    Science.gov (United States)

    Rösgen, J; Hinz, H J

    2001-03-02

    Heat capacity curves as obtained from differential scanning calorimetry are an outstanding source for molecular information on protein folding and ligand-binding energetics. However, deconvolution of C(p) data of proteins in the presence of ligands can be compromised by indeterminacies concerning the correct choice of the statistical thermodynamic ensemble. By convent, the assumption of constant free ligand concentration has been used to derive formulae for the enthalpy. Unless the ligand occurs at large excess, this assumption is incorrect. Still the relevant ensemble is the grand canonical ensemble. We derive formulae for both constraints, constancy of total or free ligand concentration and illustrate the equations by application to the typical equilibrium Nx N + x D + x. It is demonstrated that as long as the thermodynamic properties of the ligand can be completely corrected for by performing a reference measurement, the grand canonical approach provides the proper and mathematically significantly simpler choice. We demonstrate on the two cases of sequential or independent ligand-binding the fact, that similar binding mechanisms result in different and distinguishable heat capacity equations. Finally, we propose adequate strategies for DSC experiments as well as for obtaining first estimates of the characteristic thermodynamic parameters, which can be used as starting values in a global fit of DSC data. Copyright 2001 Academic Press.

  10. Effects of electrostatic interactions on ligand dissociation kinetics

    Science.gov (United States)

    Erbaş, Aykut; de la Cruz, Monica Olvera; Marko, John F.

    2018-02-01

    We study unbinding of multivalent cationic ligands from oppositely charged polymeric binding sites sparsely grafted on a flat neutral substrate. Our molecular dynamics simulations are suggested by single-molecule studies of protein-DNA interactions. We consider univalent salt concentrations spanning roughly a 1000-fold range, together with various concentrations of excess ligands in solution. To reveal the ionic effects on unbinding kinetics of spontaneous and facilitated dissociation mechanisms, we treat electrostatic interactions both at a Debye-Hückel (DH) (or implicit ions, i.e., use of an electrostatic potential with a prescribed decay length) level and by the more precise approach of considering all ionic species explicitly in the simulations. We find that the DH approach systematically overestimates unbinding rates, relative to the calculations where all ion pairs are present explicitly in solution, although many aspects of the two types of calculation are qualitatively similar. For facilitated dissociation (FD) (acceleration of unbinding by free ligands in solution) explicit-ion simulations lead to unbinding at lower free-ligand concentrations. Our simulations predict a variety of FD regimes as a function of free-ligand and ion concentrations; a particularly interesting regime is at intermediate concentrations of ligands where nonelectrostatic binding strength controls FD. We conclude that explicit-ion electrostatic modeling is an essential component to quantitatively tackle problems in molecular ligand dissociation, including nucleic-acid-binding proteins.

  11. Database of ligand-induced domain movements in enzymes

    Directory of Open Access Journals (Sweden)

    Hayward Steven

    2009-03-01

    Full Text Available Abstract Background Conformational change induced by the binding of a substrate or coenzyme is a poorly understood stage in the process of enzyme catalysed reactions. For enzymes that exhibit a domain movement, the conformational change can be clearly characterized and therefore the opportunity exists to gain an understanding of the mechanisms involved. The development of the non-redundant database of protein domain movements contains examples of ligand-induced domain movements in enzymes, but this valuable data has remained unexploited. Description The domain movements in the non-redundant database of protein domain movements are those found by applying the DynDom program to pairs of crystallographic structures contained in Protein Data Bank files. For each pair of structures cross-checking ligands in their Protein Data Bank files with the KEGG-LIGAND database and using methods that search for ligands that contact the enzyme in one conformation but not the other, the non-redundant database of protein domain movements was refined down to a set of 203 enzymes where a domain movement is apparently triggered by the binding of a functional ligand. For these cases, ligand binding information, including hydrogen bonds and salt-bridges between the ligand and specific residues on the enzyme is presented in the context of dynamical information such as the regions that form the dynamic domains, the hinge bending residues, and the hinge axes. Conclusion The presentation at a single website of data on interactions between a ligand and specific residues on the enzyme alongside data on the movement that these interactions induce, should lead to new insights into the mechanisms of these enzymes in particular, and help in trying to understand the general process of ligand-induced domain closure in enzymes. The website can be found at: http://www.cmp.uea.ac.uk/dyndom/enzymeList.do

  12. Ligand and structure-based methodologies for the prediction of the activity of G protein-coupled receptor ligands

    Science.gov (United States)

    Costanzi, Stefano; Tikhonova, Irina G.; Harden, T. Kendall; Jacobson, Kenneth A.

    2009-11-01

    Accurate in silico models for the quantitative prediction of the activity of G protein-coupled receptor (GPCR) ligands would greatly facilitate the process of drug discovery and development. Several methodologies have been developed based on the properties of the ligands, the direct study of the receptor-ligand interactions, or a combination of both approaches. Ligand-based three-dimensional quantitative structure-activity relationships (3D-QSAR) techniques, not requiring knowledge of the receptor structure, have been historically the first to be applied to the prediction of the activity of GPCR ligands. They are generally endowed with robustness and good ranking ability; however they are highly dependent on training sets. Structure-based techniques generally do not provide the level of accuracy necessary to yield meaningful rankings when applied to GPCR homology models. However, they are essentially independent from training sets and have a sufficient level of accuracy to allow an effective discrimination between binders and nonbinders, thus qualifying as viable lead discovery tools. The combination of ligand and structure-based methodologies in the form of receptor-based 3D-QSAR and ligand and structure-based consensus models results in robust and accurate quantitative predictions. The contribution of the structure-based component to these combined approaches is expected to become more substantial and effective in the future, as more sophisticated scoring functions are developed and more detailed structural information on GPCRs is gathered.

  13. Entangled zinc-ditetrazolate frameworks involving in situ ligand synthesis and topological modulation by various secondary N-donor ligands

    International Nuclear Information System (INIS)

    Li Yunwu; Chen Weilin; Wang Yonghui; Li Yangguang; Wang Enbo

    2009-01-01

    The introduction of various secondary N-donor ligands into an in situ ditetrazolate-ligand synthesis system of terephthalonitrile, NaN 3 and ZnCl 2 led to the formation of three new entangled frameworks Zn(pdtz)(4,4'-bipy).3H 2 O (1), [Zn(pdtz)(bpp)] 2 .3H 2 O (2) and Zn(pdtz) 0.5 (N 3 )(2,2'-bipy) (3) (4,4'-bipy=4,4'-bipyridine; bpp=1,3-bis(4-pyridyl)propane; 2,2'-bipy=2,2'-bipyridine; H 2 pdtz=5,5'-1,4-phenylene-ditetrazole). The formation of pdtz 2- ligand involves the Sharpless [2+3] cycloaddition reaction between terephthalonitrile and NaN 3 in the presence of Zn 2+ ion as a Lewis-acid catalyst under hydrothermal conditions. Compound 1 exhibits a fivefold interpenetrating 3D framework based on the diamondoid topology. Compound 2 displays a twofold parallel interpenetrating framework based on the wavelike individual network. Compound 3 possesses a 2D puckered network. These new Zn-ditetrazolate frameworks are highly dependent on the modulation of different secondary N-donor ligands. Their luminescent properties were investigated. - Graphical abstract: Three new entangled frameworks were prepared by an in situ ditetrazolate-ligand synthesis system assisted with various auxiliary N-donor ligands. The entangled structures can be modulated by different secondary ligands.

  14. Ligand-biased ensemble receptor docking (LigBEnD): a hybrid ligand/receptor structure-based approach

    Science.gov (United States)

    Lam, Polo C.-H.; Abagyan, Ruben; Totrov, Maxim

    2018-01-01

    Ligand docking to flexible protein molecules can be efficiently carried out through ensemble docking to multiple protein conformations, either from experimental X-ray structures or from in silico simulations. The success of ensemble docking often requires the careful selection of complementary protein conformations, through docking and scoring of known co-crystallized ligands. False positives, in which a ligand in a wrong pose achieves a better docking score than that of native pose, arise as additional protein conformations are added. In the current study, we developed a new ligand-biased ensemble receptor docking method and composite scoring function which combine the use of ligand-based atomic property field (APF) method with receptor structure-based docking. This method helps us to correctly dock 30 out of 36 ligands presented by the D3R docking challenge. For the six mis-docked ligands, the cognate receptor structures prove to be too different from the 40 available experimental Pocketome conformations used for docking and could be identified only by receptor sampling beyond experimentally explored conformational subspace.

  15. Formation of mixed ligand complexes of UO22+ involving some nitrogen and oxygen donor ligands

    International Nuclear Information System (INIS)

    Singh, Mamta; Ram Nayan

    1996-01-01

    The complexation reactions of UO 2 2+ ion with nitrogen and oxygen donor ligands, 1-amino-2-naphthol-4-sulphonic acid, o-aminophenol (ap), 2-hydroxybenzoic acid (sa), 3-carboxy-4-hydroxybenzenesulphonic acid (ss) and 1,2-dihydroxybenzene (ca) have been investigated in aqueous solution employing the pH-titration technique. Analysis of the experimental data recorded at 25 degC and at an ionic strength of 0.10 M KNO 3 indicates formation of binary, hydroxo and ternary complexes of uranium. Formation constant values of the existing species have been evaluated and the results have been discussed. (author). 21 refs., 2 figs., 2 tabs

  16. Experimental investigation of strong field trident production

    NARCIS (Netherlands)

    Esberg, J.; Kirsebom, K.; Knudsen, H.; Thomsen, H.D.; Uggerhøj, E.; Uggerhøj, U.I.; Sona, P.; Mangiarotti, A.; Ketel, T.J.; Ditzdar, A.; Dalton, M.M.; Ballestrero, S.; Connell, S.H.

    2010-01-01

    We show by experiment that an electron impinging on an electric field that is of critical magnitude in its rest frame, may produce an electron-positron pair. Our measurements address higher-order QED, using the strong electric fields obtainable along particular crystallographic directions in single

  17. PET and Hormone Receptor Ligands in Breast Cancer

    National Research Council Canada - National Science Library

    Gemignani, Mary

    2006-01-01

    .... To investigate this further, this project's objectives are: To evaluate the use of estrogen-like ligands labeled with positron emitters in preoperatively determining the ER status of breast cancer using PET...

  18. Linkable thiocarbamoylbenzamidines as ligands for bioconjugation of Rhenium and Technetium

    International Nuclear Information System (INIS)

    Castillo Gomez, Juan Daniel

    2015-01-01

    Bioconjugation reactions with Rhenium and Technetium are of high importance for the development of novel radiopharmaceuticals for nuclear medicine. In this thesis the possibilities for bioconjugation using linkable Thiocarmbamoylbenzamidines as ligands for the complexation of Rhenium and Technetium were examined.

  19. Unique advantages of organometallic supporting ligands for uranium complexes

    International Nuclear Information System (INIS)

    Diaconescu, Paula L.; Garcia, Evan

    2014-01-01

    The objective of our research project was to study the reactivity of uranium complexes supported by ferrocene-based ligands. In addition, this research provides training of graduate students as the next generation of actinide scientists.

  20. Synthesis of symmetrical and non-symmetrical bivalent neurotransmitter ligands

    DEFF Research Database (Denmark)

    Stuhr-Hansen, Nicolai; Andersen, Jacob; Thygesen, Mikkel Boas

    2016-01-01

    A novel procedure for synthesis of bivalent neurotransmitter ligands was developed by reacting O-benzyl protected N-nosylated dopamine and serotonin with alkyl- or PEG-linked diols under Fukuyama-Mitsunobu conditions in the presence of DIAD/PPh3 generating three different bivalent neurotransmitter...... ligands in a one-pot reaction. The methodol. establishes a facile route towards bivalent neurotransmitter ligands, and libraries of in total 40 sym. and non-sym. bivalent and monovalent dopamine and serotonin compds. linked through alkyl or PEG spacers of varying length were prepd. Interestingly......, attempted synthesis of an O-tert-Bu analog of the N-nosylated serotonin precursor resulted in unexpected tert-butylations at the 1-, 2- and 6-positions of the indole skeleton. We found that upscaling of selected bivalent serotonin ligands was most efficiently performed via N,O-bis-nosyl-serotonin since...

  1. Mixed-ligand binuclear copper(II) complex of 5 ...

    Indian Academy of Sciences (India)

    ligand binuclear copper(II) complex of 5-methylsalicylaldehyde and 2,2 -bipyridyl: Synthesis, crystal structure, DNA binding and nuclease activity. PERUMAL GURUMOORTHYa, JAYARAM RAVICHANDRANa,b and AZIZ KALILUR RAHIMANa,∗.

  2. Identification of RNA-ligand interactions by affinity electrophoresis.

    Science.gov (United States)

    Boodram, Sherry N; Cho, Chul M; Tavares, Tony J; Johnson, Philip E

    2011-02-01

    We have developed an affinity electrophoresis method to screen for RNA-ligand interactions. Native polyacrylamide gels were polymerized in the absence and presence of different RNA binding molecules. Binding is indicated by a difference in mobility between the gel with ligand present and the gel with no ligand present. The utility of this method was demonstrated using the known interaction between the Escherichia coli ribosomal A-site RNA and different aminoglycoside ligands. The RNA-aminoglycoside interaction observed is dose dependent, and the affinity mirrors what is observed in solution. In addition, we used this method to gauge the affinity to different aminoglycoside molecules of an RNA molecule derived from the thymidylate synthase mRNA construct that contains a CC mismatch. Copyright © 2010 Elsevier Inc. All rights reserved.

  3. Synthesis and Catalytic Activity of Two New Cyclic Tetraaza Ligands

    Directory of Open Access Journals (Sweden)

    Burkhard König

    2003-05-01

    Full Text Available Two new chiral cyclic tetraaza ligands were synthesized and characterized. Their catalytic activity was tested in the asymmetric addition of diethylzinc to benzaldehyde. The expected secondary alcohol was obtained in moderate yields, but with very low enantioselectivity.

  4. Specific activity of radioiodine-labelled human chorionic gonadotropin ligand

    International Nuclear Information System (INIS)

    Crespi, M.; Kay, G.W.; Van der Walt, L.A.

    1983-01-01

    The article deals with the determination of the specific activity of radioiodine-labbelled human chorionic gonadotropin ligand. The iodiation of human chorionic gonadotropin and the counting efficiency of 125 I are discussed

  5. related apoptosis-inducing ligand in transplastomic tobacco

    African Journals Online (AJOL)

    -inducing ligand (sTRAIL) can, as the whole length TRAIL protein, bind with its receptors and specifically induce the apoptosis of cancer cells; therefore, it has been developed as a potential therapeutic agent for various cancer treatments.

  6. Epibatidine-derivatives: ligands for the neuronal nicotinic acetylcholine receptor

    International Nuclear Information System (INIS)

    Westera, G.; Patt, J.T.; Jankowski, K.; Bertrand, D.; Spang, J.; Schubiger, P.A.

    1997-01-01

    Epibatidine, isolated from the Ecuadorian frog Epipedobates tricolar, has been synthesized. 11 C-N-methyl derivate is investigated as useful nicotinergic receptor ligand by electrophysiological methods and in vivo mice experiments. (author) 2 figs., 7 refs

  7. Unique advantages of organometallic supporting ligands for uranium complexes

    Energy Technology Data Exchange (ETDEWEB)

    Diaconescu, Paula L. [Univ. of California, Los Angeles, CA (United States); Garcia, Evan [Univ. of California, Los Angeles, CA (United States)

    2014-05-31

    The objective of our research project was to study the reactivity of uranium complexes supported by ferrocene-based ligands. In addition, this research provides training of graduate students as the next generation of actinide scientists.

  8. The Foundations of Protein-Ligand Interaction

    Science.gov (United States)

    Klebe, Gerhard

    For the specific design of a drug we must first answer the question: How does a drug achieve its activity? An active ingredient must, in order to develop its action, bind to a particular target molecule in the body. Usually this is a protein, but also nucleic acids in the form of RNA and DNA can be target structures for active agents. The most important condition for binding is at first that the active agent exhibits the correct size and shape in order to optimally fit into a cavity exposed to the surface of the protein, the "bindingpocket". It is further necessary for the surface properties of the ligand and protein to be mutually compatible to form specific interactions. In 1894 Emil Fischer compared the exact fit of a substrate for the catalytic centre of an enzyme with the picture of a "lock-and-key". Paul Ehrlich coined in 1913 "Corpora non agunt nisi fixata", literally "bodies do not work when they are not bound". He wanted to imply that active agents that are meant to kill bacteria or parasites must be "fixed" by them, i.e. linked to their structures. Both concepts form the starting point for any rational concept in the development of active pharmaceutical ingredients. In many respects they still apply today. A drug must, after being administered, reach its target and interact with a biological macromolecule. Specific agents have a large affinity and sufficient selectivity to bind to the macromolecule's active site. This is the only way they can develop the desired biological activity without side-effects.

  9. Dysprosium complexes with the tetraphenylporphyrin macrocyclic ligand

    International Nuclear Information System (INIS)

    Martinez M, V.; Padilla, J.; Ramirez, F.M.

    1992-04-01

    In this report, the results obtained on the synthesis, characterization and study of the chemical behavior of dysprosium complex with the acetylacetone chelating agent (Hacac) and the tetraphenylporphyrin macrocyclic ligand (H 2 TFP) are given. Based on the literature but according to our necessities and interest, the appropriate methodology settled down from the synthesis of prime matters until the obtaining and characterization of the products. The acetyl acetonate complex was obtained of mono hydrated dysprosium [Dy(acac) 3 . H 2 0] and trihydrated [Dy(acac) 3 .3 H 2 0], the mono tetra phenyl porphyrinate [Dy(TFP)(acac). 2 ac] the double sandwich of the dysprosium porphyrinate [Dy(TFP) 2 ] and the triple sandwich of the dysprosium porphyrinate [Dy(TFP) 3 . 2 TCB] (TCB = trichlorobenzene). Its were characterized by their melting points, solubility, IR, UV, TGA and DTA both first and besides the techniques already mentioned for NMR'H, RPE and Magnetic susceptibility the three last complexes. From the spectroscopic point of view, IR and RPE its suggested the existence of a complex of inverse mixed valence [Dy(TFP) 2- (TFP) 1- ] for the Dy(TFP) 2 as a result of the existence of the free radical (TFP' 1- and that it was not in none of the other porphyrin compounds. In the NMR'H spectra of the compounds were not observed signals in the region from 0 to 10 ppm that which shows that the dysprosium complexes in special those of the porphyrin type are highly paramagnetic and its could be used as displacement reagents, creators of images and contrast agents of great utility in these days in studies of NMR, technique today by today used in medical diagnoses. (Author)

  10. Metallogel formation in aqueous DMSO by perfluoroalkyl decorated terpyridine ligands.

    Science.gov (United States)

    Tatikonda, Rajendhraprasad; Bhowmik, Sandip; Rissanen, Kari; Haukka, Matti; Cametti, Massimo

    2016-08-09

    Terpyridine based ligands 1 and 2, decorated with a C8F17 perfluorinated tag, are able to form stable thermoreversible gels in the presence of several d-block metal chloride salts. The gel systems obtained have been characterized by NMR, X-ray diffraction, electron microscopies and Tgel experiments in order to gain insights into the observed different behaviour of the two similar ligands, also in terms of the effect of additional common anionic species.

  11. Reversible Size Control of Silver Nanoclusters via Ligand-exchange

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa

    2015-05-21

    The properties of atomically monodisperse noble metal nanoclusters (NCs) are intricately intertwined with their precise molecular formula. The vast majority of size-specific NC syntheses start from the reduction of the metal salt and thiol ligand mixture. Only in gold was it recently shown that ligand-exchange could induce the growth of NCs from one atomically precise species to another; a process of yet unknown reversibility. Here, we present a process for the ligand-exchange-induced growth of atomically precise silver NCs, in a biphasic liquid-liquid system, which is particularly of interest because of its complete reversibility and ability to occur at room temperature. We explore this phenomenon in-depth using Ag35(SG)18 [SG= glutathionate] and Ag44(4-FTP)30 [4-FTP= 4-fluorothiophenol] as model systems. We show that the ligand-exchange conversion of Ag35(SG)18 into Ag44(4-FTP)30 is rapid (< 5 min) and direct, while the reverse process proceeds slowly through intermediate cluster sizes. We adapt a recently developed theory of reverse Ostwald ripening to model the NCs’ interconvertibility. The model’s predictions are in good agreement with the experimental observations, and they highlight the importance of small changes in the ligand-metal binding energy in determining the final equilibrium NC size. Based on the insight provided by this model, we demonstrated experimentally that by varying the choice of ligands, ligand-exchange can be used to obtain different sized NCs. The findings in this work establish ligand-exchange as a versatile tool for tuning cluster sizes.

  12. Reaction chemistry and ligand exchange at cadmium selenide nanocrystal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Owen, Jonathan; Park, Jungwon; Trudeau, Paul-Emile; Alivisatos, A. Paul

    2008-12-02

    Chemical modification of nanocrystal surfaces is fundamentally important to their assembly, their implementation in biology and medicine, and greatly impacts their electrical and optical properties. However, it remains a major challenge owing to a lack of analytical tools to directly determine nanoparticle surface structure. Early nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) studies of CdSe nanocrystals prepared in tri-n-octylphosphine oxide (1) and tri-n-octylphosphine (2), suggested these coordinating solvents are datively bound to the particle surface. However, assigning the broad NMR resonances of surface-bound ligands is complicated by significant concentrations of phosphorus-containing impurities in commercial sources of 1, and XPS provides only limited information about the nature of the phosphorus containing molecules in the sample. More recent reports have shown the surface ligands of CdSe nanocrystals prepared in technical grade 1, and in the presence of alkylphosphonic acids, include phosphonic and phosphinic acids. These studies do not, however, distinguish whether these ligands are bound datively, as neutral, L-type ligands, or by X-type interaction of an anionic phosphonate/phosphinate moiety with a surface Cd{sup 2+} ion. Answering this question would help clarify why ligand exchange with such particles does not proceed generally as expected based on a L-type ligand model. By using reagents with reactive silicon-chalcogen and silicon-chlorine bonds to cleave the ligands from the nanocrystal surface, we show that our CdSe and CdSe/ZnS core-shell nanocrystal surfaces are likely terminated by X-type binding of alkylphosphonate ligands to a layer of Cd{sup 2+}/Zn{sup 2+} ions, rather than by dative interactions. Further, we provide spectroscopic evidence that 1 and 2 are not coordinated to our purified nanocrystals.

  13. Tetrapyrroles as Endogenous TSPO Ligands in Eukaryotes and Prokaryotes: Comparisons with Synthetic Ligands

    Directory of Open Access Journals (Sweden)

    Leo Veenman

    2016-06-01

    Full Text Available The 18 kDa translocator protein (TSPO is highly 0conserved in eukaryotes and prokaryotes. Since its discovery in 1977, numerous studies established the TSPO’s importance for life essential functions. For these studies, synthetic TSPO ligands typically are applied. Tetrapyrroles present endogenous ligands for the TSPO. Tetrapyrroles are also evolutionarily conserved and regulate multiple functions. TSPO and tetrapyrroles regulate each other. In animals TSPO-tetrapyrrole interactions range from effects on embryonic development to metabolism, programmed cell death, response to stress, injury and disease, and even to life span extension. In animals TSPOs are primarily located in mitochondria. In plants TSPOs are also present in plastids, the nuclear fraction, the endoplasmic reticulum, and Golgi stacks. This may contribute to translocation of tetrapyrrole intermediates across organelles’ membranes. As in animals, plant TSPO binds heme and protoporphyrin IX. TSPO-tetrapyrrole interactions in plants appear to relate to development as well as stress conditions, including salt tolerance, abscisic acid-induced stress, reactive oxygen species homeostasis, and finally cell death regulation. In bacteria, TSPO is important for switching from aerobic to anaerobic metabolism, including the regulation of photosynthesis. As in mitochondria, in bacteria TSPO is located in the outer membrane. TSPO-tetrapyrrole interactions may be part of the establishment of the bacterial-eukaryote relationships, i.e., mitochondrial-eukaryote and plastid-plant endosymbiotic relationships.

  14. Discovery of GPCR ligands for probing signal transduction pathways.

    Science.gov (United States)

    Brogi, Simone; Tafi, Andrea; Désaubry, Laurent; Nebigil, Canan G

    2014-01-01

    G protein-coupled receptors (GPCRs) are seven integral transmembrane proteins that are the primary targets of almost 30% of approved drugs and continue to represent a major focus of pharmaceutical research. All of GPCR targeted medicines were discovered by classical medicinal chemistry approaches. After the first GPCR crystal structures were determined, the docking screens using these structures lead to discovery of more novel and potent ligands. There are over 360 pharmaceutically relevant GPCRs in the human genome and to date about only 30 of structures have been determined. For these reasons, computational techniques such as homology modeling and molecular dynamics simulations have proven their usefulness to explore the structure and function of GPCRs. Furthermore, structure-based drug design and in silico screening (High Throughput Docking) are still the most common computational procedures in GPCRs drug discovery. Moreover, ligand-based methods such as three-dimensional quantitative structure-selectivity relationships, are the ideal molecular modeling approaches to rationalize the activity of tested GPCR ligands and identify novel GPCR ligands. In this review, we discuss the most recent advances for the computational approaches to effectively guide selectivity and affinity of ligands. We also describe novel approaches in medicinal chemistry, such as the development of biased agonists, allosteric modulators, and bivalent ligands for class A GPCRs. Furthermore, we highlight some knockout mice models in discovering biased signaling selectivity.

  15. Discovery of GPCR ligands for probing signal transduction pathways

    Science.gov (United States)

    Brogi, Simone; Tafi, Andrea; Désaubry, Laurent; Nebigil, Canan G.

    2014-01-01

    G protein-coupled receptors (GPCRs) are seven integral transmembrane proteins that are the primary targets of almost 30% of approved drugs and continue to represent a major focus of pharmaceutical research. All of GPCR targeted medicines were discovered by classical medicinal chemistry approaches. After the first GPCR crystal structures were determined, the docking screens using these structures lead to discovery of more novel and potent ligands. There are over 360 pharmaceutically relevant GPCRs in the human genome and to date about only 30 of structures have been determined. For these reasons, computational techniques such as homology modeling and molecular dynamics simulations have proven their usefulness to explore the structure and function of GPCRs. Furthermore, structure-based drug design and in silico screening (High Throughput Docking) are still the most common computational procedures in GPCRs drug discovery. Moreover, ligand-based methods such as three-dimensional quantitative structure–selectivity relationships, are the ideal molecular modeling approaches to rationalize the activity of tested GPCR ligands and identify novel GPCR ligands. In this review, we discuss the most recent advances for the computational approaches to effectively guide selectivity and affinity of ligands. We also describe novel approaches in medicinal chemistry, such as the development of biased agonists, allosteric modulators, and bivalent ligands for class A GPCRs. Furthermore, we highlight some knockout mice models in discovering biased signaling selectivity. PMID:25506327

  16. Predicting Efficient Antenna Ligands for Tb(III) Emission

    Energy Technology Data Exchange (ETDEWEB)

    Samuel, Amanda P.S.; Xu, Jide; Raymond, Kenneth

    2008-10-06

    A series of highly luminescent Tb(III) complexes of para-substituted 2-hydroxyisophthalamide ligands (5LI-IAM-X) has been prepared (X = H, CH{sub 3}, (C=O)NHCH{sub 3}, SO{sub 3}{sup -}, NO{sub 2}, OCH{sub 3}, F, Cl, Br) to probe the effect of substituting the isophthalamide ring on ligand and Tb(III) emission in order to establish a method for predicting the effects of chromophore modification on Tb(III) luminescence. The energies of the ligand singlet and triplet excited states are found to increase linearly with the {pi}-withdrawing ability of the substituent. The experimental results are supported by time-dependent density functional theory (TD-DFT) calculations performed on model systems, which predict ligand singlet and triplet energies within {approx}5% of the experimental values. The quantum yield ({Phi}) values of the Tb(III) complex increases with the triplet energy of the ligand, which is in part due to the decreased non-radiative deactivation caused by thermal repopulation of the triplet. Together, the experimental and theoretical results serve as a predictive tool that can be used to guide the synthesis of ligands used to sensitize lanthanide luminescence.

  17. Ligand exchange in quaternary alloyed nanocrystals--a spectroscopic study.

    Science.gov (United States)

    Gabka, Grzegorz; Bujak, Piotr; Giedyk, Kamila; Kotwica, Kamil; Ostrowski, Andrzej; Malinowska, Karolina; Lisowski, Wojciech; Sobczak, Janusz W; Pron, Adam

    2014-11-14

    Exchange of initial, predominantly stearate ligands for pyridine in the first step and butylamine (BA) or 11-mercaptoundecanoic acid (MUA) in the second one was studied for alloyed quaternary Cu-In-Zn-S nanocrystals. The NMR results enabled us to demonstrate, for the first time, direct binding of the pyridine labile ligand to the nanocrystal surface as evidenced by paramagnetic shifts of the three signals attributed to its protons to 7.58, 7.95 and 8.75 ppm. XPS investigations indicated, in turn, a significant change in the composition of the nanocrystal surface upon the exchange of initial ligands for pyridine, which being enriched in indium in the 'as prepared' form became enriched in zinc after pyridine binding. This finding indicated that the first step of ligand exchange had to involve the removal of the surface layer enriched in indium with simultaneous exposure of a new, zinc-enriched layer. In the second ligand exchange step (replacement of pyridine with BA or MUA) the changes in the nanocrystal surface compositions were much less significant. The presence of zinc in the nanocrystal surface layer turned out necessary for effective binding of pyridine as shown by a comparative study of ligand exchange in Cu-In-Zn-S, Ag-In-Zn-S and CuInS2, carried out by complementary XPS and NMR investigations.

  18. A Ferrocene-Based Catecholamide Ligand: the Consequences of Ligand Swivel for Directed Supramolecular Self-Assembly

    Energy Technology Data Exchange (ETDEWEB)

    Mugridge, Jeffrey; Fiedler, Dorothea; Raymond, Kenneth

    2010-02-04

    A ferrocene-based biscatecholamide ligand was prepared and investigated for the formation of metal-ligand supramolecular assemblies with different metals. Reaction with Ge(IV) resulted in the formation of a variety of Ge{sub n}L{sub m} coordination complexes, including [Ge{sub 2}L{sub 3}]{sup 4-} and [Ge{sub 2}L{sub 2}({mu}-OMe){sub 2}]{sup 2-}. The ligand's ability to swivel about the ferrocenyl linker and adopt different conformations accounts for formation of many different Ge{sub n}L{sub m} species. This study demonstrates why conformational ligand rigidity is essential in the rational design and directed self-assembly of supramolecular complexes.

  19. Secondary ligand-directed assembly of Co(II) coordination polymers based on a pyridine carboxylate ligand

    International Nuclear Information System (INIS)

    Cao, Ke-Li; Zhang, Yi-Ping; Cai, Yi-Ni; Xu, Xiao-Wei; Feng, Yun-Long

    2014-01-01

    To investigate the influence of hydrogen bonds and secondary ligands on the structures and properties of the resulting frameworks, five new Co(II) compounds have been synthesized by the reactions of Co(II) salts and 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL) with four rationally selected dicarboxylic acid ligands. Without secondary ligand, we got one compound [CoL 2 (H 2 O) 2 ] n ·2nH 2 O (1), which possesses a 1D chain structure. In the presence of ancillary ligands, namely, 1,3-adamantanedicarboxylic acid (H 2 adbc), terephthalic acid (H 2 tpa), thiophene-2,5-dicarboxylic acid (H 2 tdc) and 1,4-benzenedithioacetic acid (H 2 bdtc), four 3D structures [Co 2 L 2 (adbc)] n ·nH 2 O (2), [Co 2 L 2 (tpa)] n (3), [Co 2 L 2 (tdc)] n (4), [Co 2 L 2 (bdtc)(H 2 O)] n (5) were obtained, respectively. It can be observed from the architectures of 1–5 that hydrogen bonds and secondary ligands both have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. The XRPD, TGA data of title polymers and the magnetic properties for 2 and 5 have also been investigated. - Graphical abstract: The structural differences show that the ancillary ligands have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. - Highlights: • Five new Co(II) coordination polymers have been synthesized by solvothermal reactions based on 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL). • The long-flexible ligand (HL) is a good candidate to produce interpenetrating architectures. • The secondary dicarboxylic acid ligands play important roles in the spatial connective fashions and the formation of various dimensional compounds. • The magnetism studies show that both 2 and 5 exhibit antiferromagnetic interactions

  20. Integration of screening and identifying ligand(s) from medicinal plant extracts based on target recognition by using NMR spectroscopy

    OpenAIRE

    sprotocols

    2015-01-01

    Authors: Yalin Tang, Qian Shang, Junfeng Xiang, Qianfan Yang, Qiuju Zhou, Lin Li, Hong Zhang, Qian Li, Hongxia Sun, Aijiao Guan, Wei Jiang & Wei Gai ### Abstract This protocol presents the screening of ligand(s) from medicinal plant extracts based on target recognition by using NMR spectroscopy. A detailed description of sample preparation and analysis process is provided. NMR spectroscopies described here are 1H NMR, diffusion-ordered spectroscopy (DOSY), relaxation-edited NMR, 1H–1...

  1. An Analysis of Central Residues Between Ligand-Bound and Ligand-Free Protein Structures Based on Network Approach.

    Science.gov (United States)

    Amala, Arumugam; Emerson, Isacc Arnold

    2017-08-01

    Depiction of protein structures as networks of interacting residues has enabled us to understand the structure and function of the protein. Previous investigations on closeness centrality have identified protein functional sites from three- dimensional structures. It is well recognized that ligand binding to a receptor protein induces a wide range of structural changes. An interesting question is how central residues function during conformational changes triggered during ligand binding? The aim of this study is to comprehend at what extent central residues change during ligand binding to receptor proteins. To determine this, we examined 37 pairs of protein structures consisting of ligand-bound and ligand-free forms. These protein structures were modelled as an undirected network and significant central residues were obtained using residue centrality measures. In addition to these, the basic network parameters were also analysed. On analysing the residue centrality measures, we observed that 60% of central residues were common in both the ligand-bound and ligand-free states. The geometry of the central residues revealed that they were situated closer to the protein center of the mass. Finally, we demonstrated the effectiveness of central residues in amino acids substitutions and in the evolution itself. The closeness centrality was also analyzed among different protein domain sizes and the values gradually declined from single-domains to multi-domain proteins suggesting that the network has potential for hierarchical organization. Betweenness centrality measure was also used to determine the central residues and 31% of these residues were common between the holo/apo states. Findings reveal that central residues play a significant role in determining the functional properties of proteins. These results have implications in predicting binding/active site residues, specifically in the context of drug designing, if additional information concerning ligand binding is

  2. A thermal responsive affinity ligand for precipitation of sialylated proteins

    Directory of Open Access Journals (Sweden)

    Lindsay Arnold

    2016-01-01

    Full Text Available We report here the development of a thermal responsive affinity ligand specific to sialic acid, sialic acid containing oligosaccharides, glycoproteins, and other sialylated glycoconjugates. The ligand is a fusion protein of 40 repeats of pentapeptide of an elastin like polymer (ELP and the 21 kD sialic acid binding domain of a Vibrio cholera neuraminidase (VCNA. For cost-effective synthesis, the fusion protein was targeted to the periplasmic space of an E. coli lpp deletion mutant, resulting in its secretion to the growth medium. A pre-induction heat-shock step at 42 ˚C for 20 minutes was necessary to achieve high level expression of the ligand. Under optimized induction condition (18 ˚C, 0.1 mM IPTG and 48 hours of post-induction cultivation, the ligand was produced to about 100 mg/L. The ligand exhibited a transition temperature of 52 ˚C, which could be depressed to 37 ˚C with the addition of 0.5 M NaCl. Using fetuin as a model sialylated protein, the ligand was applied in an affinity precipitation process to illustrate its potential application in glycoprotein isolation. The ligand captured 100% fetuin from an aqueous solution when the molar ratio of ligand to fetuin was 10 to 1, which was lower than the expected for full titration of sialic acid on the glycoprotein by the lectin. Elution of fetuin from ligand was achieved with PBS buffer containing 2 mM sialic acid. To evaluate how protein and other contaminants influence the recovery of sialylated proteins, CHO medium was spiked into the fetuin solution. The predominant protein species in CHO medium was found to be albumin. Although its removal of over 94% was evident, purified fetuin contained some albumin due to its over-abundance. Additional experiments with albumin contaminant of varying concentrations showed that below 1 mg/L, albumin had no impact on the affinity precipitation, whereas above 10 mg/L, some albumin was co-purified with fetuin. However, even at 50 mg/ml, fetuin

  3. Designer ligands. Part 14. Novel Mn(lI), Ni(II) and Zn(II) complexes of benzamide- and biphenyl-derived ligands

    CSIR Research Space (South Africa)

    Wellington, Kevin W

    2009-01-01

    Full Text Available Manganese (II), nickel (II) and zinc (II) complexes have been prepared using various benzamideand biphenyl-derived ligands; their structures have been investigated using infrared spectroscopy and it is apparent that, depending on the ligand...

  4. Ligand-based virtual screening under partial shape constraints

    Science.gov (United States)

    von Behren, Mathias M.; Rarey, Matthias

    2017-04-01

    Ligand-based virtual screening has proven to be a viable technology during the search for new lead structures in drug discovery. Despite the rapidly increasing number of published methods, meaningful shape matching as well as ligand and target flexibility still remain open challenges. In this work, we analyze the influence of knowledge-based sterical constraints on the performance of the recently published ligand-based virtual screening method mRAISE. We introduce the concept of partial shape matching enabling a more differentiated view on chemical structure. The new method is integrated into the LBVS tool mRAISE providing multiple options for such constraints. The applied constraints can either be derived automatically from a protein-ligand complex structure or by manual selection of ligand atoms. In this way, the descriptor directly encodes the fit of a ligand into the binding site. Furthermore, the conservation of close contacts between the binding site surface and the query ligand can be enforced. We validated our new method on the DUD and DUD-E datasets. Although the statistical performance remains on the same level, detailed analysis reveal that for certain and especially very flexible targets a significant improvement can be achieved. This is further highlighted looking at the quality of calculated molecular alignments using the recently introduced mRAISE dataset. The new partial shape constraints improved the overall quality of molecular alignments especially for difficult targets with highly flexible or different sized molecules. The software tool mRAISE is freely available on Linux operating systems for evaluation purposes and academic use (see http://www.zbh.uni-hamburg.de/raise).

  5. 2 : 2 Fe(III): ligand and "adamantane core" 4 : 2 Fe(III): ligand (hydr)oxo complexes of an acyclic ditopic ligand

    DEFF Research Database (Denmark)

    Ghiladi, Morten; Larsen, Frank B.; McKenzie, Christine J.

    2005-01-01

    bond lengths of the two different octahedral iron sites: Fe -mu-OH, 1.953( 5), 2.013( 5) angstrom and Fe-mu-O, 1.803( 5), 1.802( 5) angstrom. The difference in ligand environment is too small for allowing Mossbauer spectroscopy to distinguish between the two crystallographically independent Fe sites...

  6. Microassay for measurement of binding of radiolabelled ligands to cell surface molecules

    International Nuclear Information System (INIS)

    Woof, J.M.; Burton, D.R.

    1988-01-01

    An improved technique for measuring the binding of radiolabelled ligands to cell surface molecules has been developed by modification of a procedure using centrifugation through a water-immiscible oil to separate free and cell-bound ligand. It maximises the percentage of ligand bound since cell-bound and free ligand can be separated easily and reproducibly even when very small reaction volumes are used. This permits low levels of ligand radiolabelling and relatively low numbers of cells to be used

  7. Ligand-specific conformational changes in the alpha1 glycine receptor ligand-binding domain

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Lynch, Joseph W

    2009-01-01

    , and by the antagonist, strychnine. Voltage-clamp fluorometry involves labeling introduced cysteines with environmentally sensitive fluorophores and inferring structural rearrangements from ligand-induced fluorescence changes. In the inner beta-sheet, we labeled residues in loop 2 and in binding domain loops D and E....... At each position, strychnine and glycine induced distinct maximal fluorescence responses. The pre-M1 domain responded similarly; at each of four labeled positions glycine produced a strong fluorescence signal, whereas strychnine did not. This suggests that glycine induces conformational changes...... in the inner beta-sheet and pre-M1 domain that may be important for activation, desensitization, or both. In contrast, most labeled residues in loops C and F yielded fluorescence changes identical in magnitude for glycine and strychnine. A notable exception was H201C in loop C. This labeled residue responded...

  8. Zirconium and hafnium complexes containing N-alkyl substituted amine biphenolate ligands: coordination chemistry and living ring-opening polymerization catalysis.

    Science.gov (United States)

    Liang, Lan-Chang; Lin, Sheng-Ta; Chien, Chia-Cheng; Chen, Ming-Tsz

    2013-07-07

    The coordination chemistry of zirconium and hafnium complexes containing the tridentate amine biphenolate ligands [RN(CH2-2-O-3,5-C6H2(tBu)2)2](2-) ([R-ONO](2-); R = tBu (1a), iPr (1b), nPr (1c)) featuring distinct N-alkyl substituents is described. Alcoholysis of Zr(OiPr)4(HOiPr) or Hf(OiPr)4(HOiPr) with H2[1a] in diethyl ether solutions at -35 °C generates the corresponding five-coordinate [1a]M(OiPr)2 (M = Zr (2a), Hf (3a)) in high isolated yield. Similar reactions employing H2[1b] produce six-coordinate [1b]M(OiPr)2(HOiPr) (M = Zr (2b·HOiPr), Hf (3b·HOiPr)) as an isopropanol adduct. Repetitive trituration of 2b·HOiPr and 3b·HOiPr with diethyl ether gives five-coordinate 2b and 3b, respectively. Treatment of M(OiPr)4(HOiPr) with H2[1c] under similar conditions affords six-coordinate [1c]M(OiPr)2(HOiPr) (M = Zr (2c·HOiPr), Hf (3c·HOiPr)), subsequent recrystallization of which from acetonitrile-diethyl ether solutions leads to acetonitrile adducts 2c·MeCN and 3c·MeCN. Reactivity studies of these zirconium and hafnium complexes revealed that they are all active catalysts for ring-opening polymerization of ε-caprolactone. Among them, the N-isopropyl derived complexes are most reactive. Polymerizations catalyzed by 2b, 3b and 3c·MeCN were proved to be living. The X-ray structures of 2a·HOiPr, 2a·MeCN, 2c·HOiPr, 2c·MeCN, and 3c·MeCN are presented.

  9. Using chemical shift perturbation to characterise ligand binding.

    Science.gov (United States)

    Williamson, Mike P

    2013-08-01

    Chemical shift perturbation (CSP, chemical shift mapping or complexation-induced changes in chemical shift, CIS) follows changes in the chemical shifts of a protein when a ligand is added, and uses these to determine the location of the binding site, the affinity of the ligand, and/or possibly the structure of the complex. A key factor in determining the appearance of spectra during a titration is the exchange rate between free and bound, or more specifically the off-rate koff. When koff is greater than the chemical shift difference between free and bound, which typically equates to an affinity Kd weaker than about 3μM, then exchange is fast on the chemical shift timescale. Under these circumstances, the observed shift is the population-weighted average of free and bound, which allows Kd to be determined from measurement of peak positions, provided the measurements are made appropriately. (1)H shifts are influenced to a large extent by through-space interactions, whereas (13)Cα and (13)Cβ shifts are influenced more by through-bond effects. (15)N and (13)C' shifts are influenced both by through-bond and by through-space (hydrogen bonding) interactions. For determining the location of a bound ligand on the basis of shift change, the most appropriate method is therefore usually to measure (15)N HSQC spectra, calculate the geometrical distance moved by the peak, weighting (15)N shifts by a factor of about 0.14 compared to (1)H shifts, and select those residues for which the weighted shift change is larger than the standard deviation of the shift for all residues. Other methods are discussed, in particular the measurement of (13)CH3 signals. Slow to intermediate exchange rates lead to line broadening, and make Kd values very difficult to obtain. There is no good way to distinguish changes in chemical shift due to direct binding of the ligand from changes in chemical shift due to allosteric change. Ligand binding at multiple sites can often be characterised, by

  10. Cloud computing for protein-ligand binding site comparison.

    Science.gov (United States)

    Hung, Che-Lun; Hua, Guan-Jie

    2013-01-01

    The proteome-wide analysis of protein-ligand binding sites and their interactions with ligands is important in structure-based drug design and in understanding ligand cross reactivity and toxicity. The well-known and commonly used software, SMAP, has been designed for 3D ligand binding site comparison and similarity searching of a structural proteome. SMAP can also predict drug side effects and reassign existing drugs to new indications. However, the computing scale of SMAP is limited. We have developed a high availability, high performance system that expands the comparison scale of SMAP. This cloud computing service, called Cloud-PLBS, combines the SMAP and Hadoop frameworks and is deployed on a virtual cloud computing platform. To handle the vast amount of experimental data on protein-ligand binding site pairs, Cloud-PLBS exploits the MapReduce paradigm as a management and parallelizing tool. Cloud-PLBS provides a web portal and scalability through which biologists can address a wide range of computer-intensive questions in biology and drug discovery.

  11. Sensitive and specific detection of ligands using engineered riboswitches.

    Science.gov (United States)

    Morse, Daniel P; Nevins, Colin E; Aggrey-Fynn, Joana; Bravo, Rick J; Pfaeffle, Herman O I; Laney, Jess E

    2018-03-05

    Riboswitches are RNA elements found in non-coding regions of messenger RNAs that regulate gene expression through a ligand-triggered conformational change. Riboswitches typically bind tightly and specifically to their ligands, so they have the potential to serve as highly effective sensors in vitro. In B. subtilis and other gram-positive bacteria, purine nucleotide synthesis is regulated by riboswitches that bind to guanine. We modified the xpt-pbuX guanine riboswitch for use in a fluorescence quenching assay that allowed us to specifically detect and quantify guanine in vitro. Using this assay, we reproducibly detected as little as 5 nM guanine. We then produced sensors for 2'-deoxyguanosine and cyclic diguanylate (c-diGMP) by appending the P1 stem of the guanine riboswitch to the ligand-binding domains of a 2'-deoxyguanosine riboswitch and a c-diGMP riboswitch. These hybrid sensors could detect 15 nM 2'-deoxyguanosine and 3 nM c-diGMP, respectively. Each sensor retained the ligand specificity of its corresponding natural riboswitch. In order to extend the utility of our approach, we developed a strategy for the in vitro selection of sensors with novel ligand specificity. Here we report a proof-of-principle experiment that demonstrated the feasibility of our selection strategy. Published by Elsevier B.V.

  12. Structural basis for EGFR ligand sequestration by Argos.

    Science.gov (United States)

    Klein, Daryl E; Stayrook, Steven E; Shi, Fumin; Narayan, Kartik; Lemmon, Mark A

    2008-06-26

    Members of the epidermal growth factor receptor (EGFR) or ErbB/HER family and their activating ligands are essential regulators of diverse developmental processes. Inappropriate activation of these receptors is a key feature of many human cancers, and its reversal is an important clinical goal. A natural secreted antagonist of EGFR signalling, called Argos, was identified in Drosophila. We showed previously that Argos functions by directly binding (and sequestering) growth factor ligands that activate EGFR. Here we describe the 1.6-A resolution crystal structure of Argos bound to an EGFR ligand. Contrary to expectations, Argos contains no EGF-like domain. Instead, a trio of closely related domains (resembling a three-finger toxin fold) form a clamp-like structure around the bound EGF ligand. Although structurally unrelated to the receptor, Argos mimics EGFR by using a bipartite binding surface to entrap EGF. The individual Argos domains share unexpected structural similarities with the extracellular ligand-binding regions of transforming growth factor-beta family receptors. The three-domain clamp of Argos also resembles the urokinase-type plasminogen activator (uPA) receptor, which uses a similar mechanism to engulf the EGF-like module of uPA. Our results indicate that undiscovered mammalian counterparts of Argos may exist among other poorly characterized structural homologues. In addition, the structures presented here define requirements for the design of artificial EGF-sequestering proteins that would be valuable anti-cancer therapeutics.

  13. Chiral ligand exchange countercurrent chromatography: Enantioseparation of amino acids.

    Science.gov (United States)

    Xiong, Qing; Jin, Jing; Lv, Liqiong; Bu, Zhisi; Tong, Shengqiang

    2018-03-01

    This work deals with the enantioseparation of α-amino acids by chiral ligand exchange high-speed countercurrent chromatography using N-n-dodecyl-l-hydroxyproline as a chiral ligand and copper(II) as a transition metal ion. A biphasic solvent system composed of n-hexane/n-butanol/aqueous phase with different volume ratios was selected for each α-amino acid. The enantioseparation conditions were optimized by enantioselective liquid-liquid extractions, in which the main influence factors, including type of chiral ligand, concentration of chiral ligand and transition metal ion, separation temperature, and pH of the aqueous phase, were investigated for racemic phenylalanine. Altogether, we tried to enantioseparate 15 racemic α-amino acids by the analytical countercurrent chromatography, of which only five of them could be successfully enantioseparated. Different elution sequence for phenylalanine enantiomer was observed compared with traditional liquid chromatography and the proposed interactions between chiral ligand, transition metal ion (Cu 2+ ), and enantiomer are discussed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. The chemistry of separations ligand degradation by organic radical cations

    International Nuclear Information System (INIS)

    Mezyk, S.P.; Horne, G.P.; Mincher, B.J.; Zalupski, P.R.; Cook, A.R.; Wishart, J.F.

    2016-01-01

    Solvent based extractions of used nuclear fuel use designer ligands in an organic phase extracting ligand complexed metal ions from an acidic aqueous phase. These extractions will be performed in highly radioactive environments, and the radiation chemistry of all these complexing agents and their diluents will play a major role in determining extraction efficiency, separation factors, and solvent-recycle longevity. Although there has been considerable effort in investigating ligand damage occurring in acidic water radiolysis conditions, only minimal fundamental kinetic and mechanistic data has been reported for the degradation of extraction ligands in the organic phase. Extraction solvent phases typically use normal alkanes such as dodecane, TPH, and kerosene as diluents. The radiolysis of such diluents produce a mixture of radical cations (R .+ ), carbon-centered radicals (R . ), solvated electrons, and molecular products such as hydrogen. Typically, the radical species will preferentially react with the dissolved oxygen present to produce relatively inert peroxyl radicals. This isolates the alkane radical cation species, R .+ as the major radiolytically-induced organic species that can react with, and degrade, extraction agents in this phase. Here we report on our recent studies of organic radical cation reactions with 2 ligands: CMPO and TODGA. Elucidating these parameters, and combining them with the known acidic aqueous phase chemistry, will allow a full, fundamental, understanding of the impact of radiation on solvent extraction based separation processes to be achieved. (authors)

  15. Mixed Valence Aspects of Diruthenium Complexes [{(L)ClRu}2(.mu.-tppz)]n+ Incorporating 2-(2-Pyridyl)azoles (L) as Ancillary Functions and 2,3,5,6-Tetrakis(2-pyridyl)pyrazine (Tppz) as Bis-Tridentate Bridging Ligand

    Czech Academy of Sciences Publication Activity Database

    Chanda, N.; Sarkar, B.; Kar, S.; Fiedler, Jan; Kaim, W.; Lahiri, G. K.

    2004-01-01

    Roč. 43, č. 16 (2004), s. 5128-5133 ISSN 0020-1669 R&D Projects: GA MŠk OC D15.10; GA MŠk OC D14.20 Institutional research plan: CEZ:AV0Z4040901 Keywords : electron-transfer * ruthenium complexes * spectroelectrochemical properties Subject RIV: CG - Electrochemistry Impact factor: 3.454, year: 2004

  16. Ligands of histamine receptors modulate acid-sensing ion channels.

    Science.gov (United States)

    Shteinikov, V Y; Korosteleva, A S; Tikhonova, T B; Potapieva, N N; Tikhonov, D B

    2017-09-02

    Recently we found that synthetic compounds containing amino group linked to hydrophobic or aromatic moiety are potent modulators of the proton-gated channels (ASICs). These structures have clear similarity with ligands of histamine receptors. We have also demonstrated that histamine potentiates homomeric ASIC1a by shifting its activation dependence to less acidic conditions. In the present work the action of a series of histamine receptors ligands on recombinant ASIC1a and ASIC2a was characterized. Two types of action were found for ASIC1a. 1-methylhistamine, N-alpha-methylhistamine, dimaprit and thioperamide caused significant potentiation, which was pH-dependent and voltage-independent. The H4R antagonist A943931 caused inhibition, which is likely due to voltage-dependent pore block. ASIC2a were virtually insensitive to the drugs tested. We conclude that ligands of histamine receptors should also be considered as ASIC modulators. Copyright © 2017. Published by Elsevier Inc.

  17. Novel peptide ligand with high binding capacity for antibody purification

    DEFF Research Database (Denmark)

    Lund, L. N.; Gustavsson, P. E.; Michael, R.

    2012-01-01

    commonly used capture step in mAb down stream processing; however, the use of Protein A chromatography is less attractive due to toxic ligand leakage as well as high cost. Whether used as an alternative to the Protein A chromatographic media or as a subsequent polishing step, small synthetic peptide...... ligand for purification of human IgG. Immobilized on WorkBeads, an agarose-based base matrix from Bio-Works, the ligand has a dynamic binding capacity of up to 48 mg/mL and purifies IgG from harvest cell culture fluid with purities and recovery of >93%. The binding affinity is similar to 10(5) M-1...

  18. Memetic algorithms for ligand expulsion from protein cavities

    Science.gov (United States)

    Rydzewski, J.; Nowak, W.

    2015-09-01

    Ligand diffusion through a protein interior is a fundamental process governing biological signaling and enzymatic catalysis. A complex topology of channels in proteins leads often to difficulties in modeling ligand escape pathways by classical molecular dynamics simulations. In this paper, two novel memetic methods for searching the exit paths and cavity space exploration are proposed: Memory Enhanced Random Acceleration (MERA) Molecular Dynamics (MD) and Immune Algorithm (IA). In MERA, a pheromone concept is introduced to optimize an expulsion force. In IA, hybrid learning protocols are exploited to predict ligand exit paths. They are tested on three protein channels with increasing complexity: M2 muscarinic G-protein-coupled receptor, enzyme nitrile hydratase, and heme-protein cytochrome P450cam. In these cases, the memetic methods outperform simulated annealing and random acceleration molecular dynamics. The proposed algorithms are general and appropriate in all problems where an accelerated transport of an object through a network of channels is studied.

  19. Synthesis and characterization of highly conjugated, chiral bridging ligands.

    Science.gov (United States)

    Sauers, Angela L; Ho, Douglas M; Bernhard, Stefan

    2004-12-10

    This paper describes the synthesis of four chiral derivatives of the electronically highly conjugated tetra-2-pyridylpyrazine (TPPZ) bridging ligand, which are denoted (R)- and (S)-4,5- and 5,6-pineno-tetra-2-pyridylpyrazine (PTPPZ). Preparation of these ligands was undertaken through the use of commercially available, enantiomerically pure (1R)- and (1S)-alpha-pinene, which was functionalized and subsequently employed in a Krohnke pyridine synthesis involving a furan-substituted pyridinium salt to yield a chiral, furan-substituted pyridyl intermediate. Oxidative degradation and subsequent reduction of this furan led to a chiral, substituted 2-pyridylaldehyde, which underwent a pyridoin condensation followed by cyclization to produce the final PTPPZ ligands.

  20. Analytical developments for screening of lanthanides/ligands interactions

    International Nuclear Information System (INIS)

    Varenne, F.

    2012-01-01

    This work investigates the potential of hyphenated capillary electrophoresis and inductively coupled mass spectrometry to classify different ligands according to their europium binding affinity in a hydro-organic medium. On the one hand, this method enables to evaluate the affinity of phosphorus-containing ligands in less than two hours and using less than 15 ng of ligand. On the other hand, complexation constants could be determined. The results are in excellent agreement with the values obtained by spectrophotometric titrations.Moreover, a library of copolymers for solid/liquid extraction of europium is investigated. The extraction protocol enables to classify copolymers according to their europium affinity in a hydro-organic medium. This screening requires 60 mg of copolymers. For the most promising recognition properties and selectivity La 3+ /Eu 3+ /Lu 3+ are evaluated. (author)

  1. Ligand screening by saturation-transfer difference (STD) NMR spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, V V

    2005-04-26

    NMR based methods to screen for high-affinity ligands have become an indispensable tool for designing rationalized drugs, as these offer a combination of good experimental design of the screening process and data interpretation methods, which together provide unprecedented information on the complex nature of protein-ligand interactions. These methods rely on measuring direct changes in the spectral parameters, that are often simpler than the complex experimental procedures used to study structure and dynamics of proteins. The goal of this review article is to provide the basic details of NMR based ligand-screening methods, with particular focus on the saturation transfer difference (STD) experiment. In addition, we provide an overview of other NMR experimental methods and a practical guide on how to go about designing and implementing them.

  2. Heterobifunctional PEG Ligands for Bioconjugation Reactions on Iron Oxide Nanoparticles

    Science.gov (United States)

    Bloemen, Maarten; Van Stappen, Thomas; Willot, Pieter; Lammertyn, Jeroen; Koeckelberghs, Guy; Geukens, Nick; Gils, Ann; Verbiest, Thierry

    2014-01-01

    Ever since iron oxide nanoparticles have been recognized as promising scaffolds for biomedical applications, their surface functionalization has become even more important. We report the synthesis of a novel polyethylene glycol-based ligand that combines multiple advantageous properties for these applications. The ligand is covalently bound to the surface via a siloxane group, while its polyethylene glycol backbone significantly improves the colloidal stability of the particle in complex environments. End-capping the molecule with a carboxylic acid introduces a variety of coupling chemistry possibilities. In this study an antibody targeting plasminogen activator inhibitor-1 was coupled to the surface and its presence and binding activity was assessed by enzyme-linked immunosorbent assay and surface plasmon resonance experiments. The results indicate that the ligand has high potential towards biomedical applications where colloidal stability and advanced functionality is crucial. PMID:25275378

  3. Xanthene and Xanthone Derivatives as G-Quadruplex Stabilizing Ligands

    Directory of Open Access Journals (Sweden)

    Alessandro Altieri

    2013-10-01

    Full Text Available Following previous studies on anthraquinone and acridine-based G-quadruplex ligands, here we present a study of similar aromatic cores, with the specific aim of increasing G-quadruplex binding and selectivity with respect to duplex DNA. Synthesized compounds include two and three-side chain xanthone and xanthene derivatives, as well as a dimeric “bridged” form. ESI and FRET measurements suggest that all the studied molecules are good G-quadruplex ligands, both at telomeres and on G-quadruplex forming sequences of oncogene promoters. The dimeric compound and the three-side chain xanthone derivative have been shown to represent the best compounds emerging from the different series of ligands presented here, having also high selectivity for G-quadruplex structures with respect to duplex DNA. Molecular modeling simulations are in broad agreement with the experimental data.

  4. The Parathyroid Hormone Family of Ligands and Receptors

    Directory of Open Access Journals (Sweden)

    Damian G. D'Souza

    2015-07-01

    Full Text Available The PTH family of ligands and receptors have a wide range of vital functions from calcium homeostasis to tissue and bone development from the embryo to adult. This family has undergone whole genome duplication events predating vertebrate evolution, indicating more primitive and ancient functions other than skeletal development. The N-terminal region of the ligands, have been widely studied by biophysical and functional analysis, resulting in the discovery of key characteristics essential for ligand-receptor activation being elucidated. Multi-substituted amino acid analogs with differential binding affinities and either antagonistic or agonistic signalling potencies have been created based on these findings allowing for improvement on potential therapies affected by the PTH system in skeletal and embryonic development. The PTH family has diversely evolved to cover a wide range of pivotal pathways crucial to growth and development throughout all animal life.

  5. GPCR biased ligands as novel heart failure therapeutics.

    Science.gov (United States)

    Violin, Jonathan D; Soergel, David G; Boerrigter, Guido; Burnett, John C; Lark, Michael W

    2013-10-01

    G protein-coupled receptors have been successfully targeted by numerous therapeutics including drugs that have transformed the management of cardiovascular disease. However, many GPCRs, when activated or blocked by drugs, elicit both beneficial and adverse pharmacology. Recent work has demonstrated that in some cases, the salutary and deleterious signals linked to a specific GPCR can be selectively targeted by "biased ligands" that entrain subsets of a receptor's normal pharmacology. This review briefly summarizes the advances and current state of the biased ligand field, focusing on an example: biased ligands targeting the angiotensin II type 1 receptor. These compounds exhibit unique pharmacology, distinct from classic agonists or antagonists, and one such molecule is now in clinical development for the treatment of acute heart failure. Copyright © 2013 Elsevier Inc. All rights reserved.

  6. Control of Energy Flow Dynamics between Tetracene Ligands and PbS Quantum Dots by Size Tuning and Ligand Coverage

    Energy Technology Data Exchange (ETDEWEB)

    Kroupa, Daniel M. [National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States; Arias, Dylan H. [National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States; Blackburn, Jeffrey L. [National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States; Carroll, Gerard M. [National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States; Granger, Devin B. [Department; Anthony, John E. [Department; Beard, Matthew C. [National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States; Johnson, Justin C. [National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States

    2018-01-08

    We have prepared a series of samples with the ligand 6,13-bistri(iso-propyl)silylethynyl tetracene 2-carboxylic acid (TIPS-Tc-COOH) attached to PbS quantum dot (QD) samples of three different sizes in order to monitor and control the extent and time scales of energy flow after photoexcitation. Fast energy transfer (~1 ps) to the PbS QD occurs upon direct excitation of the ligand for all samples. The largest size QD maintains the microsecond exciton lifetime characteristic of the as-prepared oleate terminated PbS QDs. However, two smaller QD sizes with lowest exciton energies similar to or larger than the TIPS-Tc-COO- triplet energy undergo energy transfer between QD core and ligand triplet on nanosecond to microsecond timescales. For the intermediate size QDs in particular, energy can be recycled many times between ligand and core, but the triplet remains the dominant excited species at long times, living for ~3 us for fully exchanged QDs and up to 30 us for partial ligand exchange, which is revealed as a method for controlling the triplet lifetime. A unique upconverted luminescence spectrum is observed that results from annihilation of triplets after exclusive excitation of the QD core.

  7. Use of protein-engineered fabrics to identify design rules for integrin ligand clustering in biomaterials.

    Science.gov (United States)

    Benitez, Patrick L; Mascharak, Shamik; Proctor, Amy C; Heilshorn, Sarah C

    2016-01-01

    While ligand clustering is known to enhance integrin activation, this insight has been difficult to apply to the design of implantable biomaterials because the local and global ligand densities that enable clustering-enhanced integrin signaling were unpredictable. Here, two general design principles for biomaterial ligand clustering are elucidated. First, clustering ligands enhances integrin-dependent signals when the global ligand density, i.e., the ligand density across the cellular length scale, is near the ligand's effective dissociation constant (KD,eff). Second, clustering ligands enhances integrin activation when the local ligand density, i.e., the ligand density across the length scale of individual focal adhesions, is less than an overcrowding threshold. To identify these principles, we fabricated a series of elastin-like, electrospun fabrics with independent control over the local (0 to 122 000 ligands μm(-2)) and global (0 to 71 000 ligand μm(-2)) densities of an arginine-glycine-aspartate (RGD) ligand. Antibody blocking studies confirmed that human umbilical vein endothelial cell adhesion to these protein-engineered biomaterials was primarily due to αVβ3 integrin binding. Clustering ligands enhanced cell proliferation, focal adhesion number, and focal adhesion kinase expression near the ligand's KD,eff of 12 000 RGD μm(-2). Near this global ligand density, cells on ligand-clustered fabrics behaved similarly to cells grown on fabrics with significantly larger global ligand densities but without clustering. However, this enhanced ligand-clustering effect was not observed above a threshold cut-off concentration. At a local ligand density of 122 000 RGD μm(-2), cell division, focal adhesion number, and focal adhesion kinase expression were significantly reduced relative to fabrics with identical global ligand density and lesser local ligand densities. Thus, when clustering results in overcrowding of ligands, integrin receptors are no longer

  8. Systematic study of ligand structures of metal oxide EUV nanoparticle photoresists

    KAUST Repository

    Jiang, Jing

    2015-03-19

    Ligand stabilized metal oxide nanoparticle resists are promising candidates for EUV lithography due to their high sensitivity for high-resolution patterning and high etching resistance. As ligand exchange is responsible for the patterning mechanism, we systematically studied the influence of ligand structures of metal oxide EUV nanoparticles on their sensitivity and dissolution behavior. ZrO2 nanoparticles were protected with various aromatic ligands with electron withdrawing and electron donating groups. These nanoparticles have lower sensitivity compared to those with aliphatic ligands suggesting the structures of these ligands is more important than their pka on resist sensitivity. The influence of ligand structure was further studied by comparing the nanoparticles’ solubility for a single type ligand to mixtures of ligands. The mixture of nanoparticles showed improved pattern quality. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  9. Selection of ligands for affinity chromatography using quartz crystal biosensor.

    Science.gov (United States)

    Liu, Yang; Tang, Xiaoling; Liu, Feng; Li, Ke'an

    2005-07-01

    This paper described a new strategy for rapid selecting ligands for application in affinity chromatography using a quartz crystal microbalance (QCM) biosensor. An aminoglycoside antibiotic drug, kanamycin (KM), was immobilized on the gold electrodes of the QCM sensor chip. The binding interactions of the immobilized KM with various proteins in solution were monitored as the variations of the resonant frequency of the modified sensor. Such a rapid screen analysis of interactions indicated clearly that KM-immobilized sensor showed strong specific interaction only with lysozyme (LZM). The resultant sensorgrams were rapidly analyzed by using a kinetic analysis software based on a genetic algorithm to derive both the kinetic rate constants (k(ass) and k(diss)) and equilibrium dissociation constants (K(D)) for LZM-KM interactions. The immobilized KM showed higher affinity to LZM with a dissociation constant on the order of 10(-5) M, which is within the range of 10(-4)-10(-8) M and suitable for an affinity ligand. Therefore, KM was demonstrated for the first time as a novel affinity ligand for purification of LZM and immobilized onto the epoxy-activated silica in the presence of a high potassium phosphate concentration. The KM immobilized affinity column has proved useful for a very convenient purification of LZM from chicken egg white. The purity of LZM obtained was higher than 90%, as determined by densitometric scanning of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified fraction. These results confirmed that the selected KM ligand is indeed a valuable affinity ligand for purification of LZM. The new screening strategy based on a QCM biosensor is expected to be a promising way for rapid selecting specific ligands for purifying other valuable proteins.

  10. Structural parameterization of the binding enthalpy of small ligands.

    Science.gov (United States)

    Luque, Irene; Freire, Ernesto

    2002-11-01

    A major goal in ligand and drug design is the optimization of the binding affinity of selected lead molecules. However, the binding affinity is defined by the free energy of binding, which, in turn, is determined by the enthalpy and entropy changes. Because the binding enthalpy is the term that predominantly reflects the strength of the interactions of the ligand with its target relative to those with the solvent, it is desirable to develop ways of predicting enthalpy changes from structural considerations. The application of structure/enthalpy correlations derived from protein stability data has yielded inconsistent results when applied to small ligands of pharmaceutical interest (MW the enthalpy associated with any possible conformational change in the protein or ligand upon binding; and, (3) the enthalpy associated with protonation/deprotonation events, if present. As in the case of protein stability, the intrinsic binding enthalpy scales with changes in solvent accessible surface areas. However, an accurate estimation of the intrinsic binding enthalpy requires explicit consideration of long-lived water molecules at the binding interface. The best statistical structure/enthalpy correlation is obtained when buried water molecules within 5-7 A of the ligand are included in the calculations. For all seven protein systems considered (HIV-1 protease, dihydrodipicolinate reductase, Rnase T1, streptavidin, pp60c-Src SH2 domain, Hsp90 molecular chaperone, and bovine beta-trypsin) the binding enthalpy of 25 small molecular weight peptide and nonpeptide ligands can be accounted for with a standard error of +/-0.3 kcal x mol(-1). Copyright 2002 Wiley-Liss, Inc.

  11. Structural studies of Ca2+-ATPase ligand and regulatory complexes

    DEFF Research Database (Denmark)

    Drachmann, Nikolaj Düring

    2015-01-01

    to explore the possibilities for an efficient screening of ligand-bound SERCA structures, serial femtosecond crystallography experiments of microcrystals of SERCA1a in the Ca2+ bound state and in a vanadate stabilised E2 state was conducted. A structure obtained at 2.8 Å maximum resolution of the proof......-of-concept Ca2+ bound crystal form, indicated that the information content of SFX data is higher than synchrotron data, and ligands and ions can be detected with low redundant data. The data of the E2 stabilised form was processed to 5 Å resolution, and it was possible to extract useful anomalous data showing...

  12. Force loading explains spatial sensing of ligands by cells

    Science.gov (United States)

    Oria, Roger; Wiegand, Tina; Escribano, Jorge; Elosegui-Artola, Alberto; Uriarte, Juan Jose; Moreno-Pulido, Cristian; Platzman, Ilia; Delcanale, Pietro; Albertazzi, Lorenzo; Navajas, Daniel; Trepat, Xavier; García-Aznar, José Manuel; Cavalcanti-Adam, Elisabetta Ada; Roca-Cusachs, Pere

    2017-12-01

    Cells can sense the density and distribution of extracellular matrix (ECM) molecules by means of individual integrin proteins and larger, integrin-containing adhesion complexes within the cell membrane. This spatial sensing drives cellular activity in a variety of normal and pathological contexts. Previous studies of cells on rigid glass surfaces have shown that spatial sensing of ECM ligands takes place at the nanometre scale, with integrin clustering and subsequent formation of focal adhesions impaired when single integrin-ligand bonds are separated by more than a few tens of nanometres. It has thus been suggested that a crosslinking ‘adaptor’ protein of this size might connect integrins to the actin cytoskeleton, acting as a molecular ruler that senses ligand spacing directly. Here, we develop gels whose rigidity and nanometre-scale distribution of ECM ligands can be controlled and altered. We find that increasing the spacing between ligands promotes the growth of focal adhesions on low-rigidity substrates, but leads to adhesion collapse on more-rigid substrates. Furthermore, disordering the ligand distribution drastically increases adhesion growth, but reduces the rigidity threshold for adhesion collapse. The growth and collapse of focal adhesions are mirrored by, respectively, the nuclear or cytosolic localization of the transcriptional regulator protein YAP. We explain these findings not through direct sensing of ligand spacing, but by using an expanded computational molecular-clutch model, in which individual integrin-ECM bonds—the molecular clutches—respond to force loading by recruiting extra integrins, up to a maximum value. This generates more clutches, redistributing the overall force among them, and reducing the force loading per clutch. At high rigidity and high ligand spacing, maximum recruitment is reached, preventing further force redistribution and leading to adhesion collapse. Measurements of cellular traction forces and actin flow speeds

  13. Contrasting roles for TLR ligands in HIV-1 pathogenesis.

    Directory of Open Access Journals (Sweden)

    Beda Brichacek

    2010-09-01

    Full Text Available The first line of a host's response to various pathogens is triggered by their engagement of cellular pattern recognition receptors (PRRs. Binding of microbial ligands to these receptors leads to the induction of a variety of cellular factors that alter intracellular and extracellular environment and interfere directly or indirectly with the life cycle of the triggering pathogen. Such changes may also affect any coinfecting microbe. Using ligands to Toll-like receptors (TLRs 5 and 9, we examined their effect on human immunodeficiency virus (HIV-1 replication in lymphoid tissue ex vivo. We found marked differences in the outcomes of such treatment. While flagellin (TLR5 agonist treatment enhanced replication of CC chemokine receptor 5 (CCR 5-tropic and CXC chemokine receptor 4 (CXCR4-tropic HIV-1, treatment with oligodeoxynucleotide (ODN M362 (TLR9 agonist suppressed both viral variants. The differential effects of these TLR ligands on HIV-1 replication correlated with changes in production of CC chemokines CCL3, CCL4, CCL5, and of CXC chemokines CXCL10, and CXCL12 in the ligand-treated HIV-1-infected tissues. The nature and/or magnitude of these changes were dependent on the ligand as well as on the HIV-1 viral strain. Moreover, the tested ligands differed in their ability to induce cellular activation as evaluated by the expression of the cluster of differentiation markers (CD 25, CD38, CD39, CD69, CD154, and human leukocyte antigen D related (HLA-DR as well as of a cell proliferation marker, Ki67, and of CCR5. No significant effect of the ligand treatment was observed on apoptosis and cell death/loss in the treated lymphoid tissue ex vivo. Our results suggest that binding of microbial ligands to TLRs is one of the mechanisms that mediate interactions between coinfected microbes and HIV-1 in human tissues. Thus, the engagement of appropriate TLRs by microbial molecules or their mimetic might become a new strategy for HIV therapy or prevention.

  14. Development of catalysts and ligands for enantioselective gold catalysis.

    Science.gov (United States)

    Wang, Yi-Ming; Lackner, Aaron D; Toste, F Dean

    2014-03-18

    During the past decade, the use of Au(I) complexes for the catalytic activation of C-C π-bonds has been investigated intensely. Over this time period, the development of homogeneous gold catalysis has been extraordinarily rapid and has yielded a host of mild and selective methods for the formation of carbon-carbon and carbon-heteroatom bonds. The facile formation of new bonds facilitated by gold naturally led to efforts toward rendering these transformations enantioselective. In this Account, we survey the development of catalysts and ligands for enantioselective gold catalysis by our research group as well as related work by others. We also discuss some of our strategies to address the challenges of enantioselective gold(I) catalysis. Early on, our work with enantioselective gold-catalyzed transformations focused on bis(phosphinegold) complexes derived from axially chiral scaffolds. Although these complexes were highly successful in some reactions like cyclopropanation, the careful choice of the weakly coordinating ligand (or counterion) was necessary to obtain high levels of enantioselectivity for the case of allene hydroamination. These counterion effects led us to use the anion itself as a source of chirality, which was successful in the case of allene hydroalkoxylation. In general, these tactics enhance the steric influence around the reactive gold center beyond the two-coordinate ligand environment. The use of binuclear complexes allowed us to use the second gold center and its associated ligand (or counterion) to exert a further steric influence. In a similar vein, we employed a chiral anion (in place of or in addition to a chiral ligand) to move the chiral information closer to the reactive center. In order to expand the scope of reactions amenable to enantioselective gold catalysis to cycloadditions and other carbocyclization processes, we also developed a new class of mononuclear phosphite and phosphoramidite ligands to supplement the previously widely

  15. Coordination chemistry of poly(thioether)borate ligands

    Science.gov (United States)

    Riordan, Charles G.

    2010-01-01

    This review traces the development and application of the tris(thioether)borate ligands, tripodal ligands with highly polarizable thioether donors. Areas of emphasis include the basic coordination chemistry of the mid-to-late first row transition metals (Fe, Ni, Co, Cu), and the role of the thioether substituent in directing complex formation, the modeling of zinc thiolate protein active sites, high-spin organo-iron and organo-cobalt chemistry, the preparation of monovalent complexes of Fe, Co and Ni, and dioxygen and sulfur activation by monovalent nickel complexes. PMID:20607091

  16. Luminescent cyclometallated iridium(III) complexes having acetylide ligands

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Mark E.; Bossi, Alberto; Djurovich, Peter Ivan

    2014-09-02

    The present invention relates to phosphorescent (triplet-emitting) organometallic materials. The phosphorescent materials of the present invention comprise Ir(III)cyclometallated alkynyl complexes for use as triplet light-emitting materials. The Ir(III)cyclometallated alkynyl complexes comprise at least one cyclometallating ligand and at least one alkynyl ligand bonded to the iridium. Also provided is an organic light emitting device comprising an anode, a cathode and an emissive layer between the anode and the cathode, wherein the emissive layer comprises a Ir(III)cyclometallated alkynyl complex as a triplet emitting material.

  17. Aluminum Dimer Containing Bulky 1,2,3-Triazolate Ligand

    Directory of Open Access Journals (Sweden)

    Issam Kobrsi

    2014-01-01

    Full Text Available The first molecular aluminum 1,2,3-triazolato complex was synthesized bearing a bulky 1,2,3-triazolate ligand. Oligomers and polymers were avoided due to the bulkiness and noncoordinating nature of the substituents. The novel Al2N4 ring formed contains symmetrical Al-N bond distances unexpectedly having asymmetric Al-N-N angles of 144.55(15° and 115.83(14°. This asymmetry demonstrates the effect of the steric hindrance of the ligand.

  18. Designer ligands: The search for metal ion selectivity

    Directory of Open Access Journals (Sweden)

    Perry T. Kaye

    2011-03-01

    Full Text Available The paper reviews research conducted at Rhodes University towards the development of metal-selective ligands. The research has focused on the rational design, synthesis and evaluation of novel ligands for use in the formation of copper complexes as biomimetic models of the metalloenzyme, tyrosinase, and for the selective extraction of silver, nickel and platinum group metal ions in the presence of contaminating metal ions. Attention has also been given to the development of efficient, metal-selective molecular imprinted polymers.

  19. Structural Basis of Cooperative Ligand Binding by the Glycine Riboswitch

    Energy Technology Data Exchange (ETDEWEB)

    E Butler; J Wang; Y Xiong; S Strobel

    2011-12-31

    The glycine riboswitch regulates gene expression through the cooperative recognition of its amino acid ligand by a tandem pair of aptamers. A 3.6 {angstrom} crystal structure of the tandem riboswitch from the glycine permease operon of Fusobacterium nucleatum reveals the glycine binding sites and an extensive network of interactions, largely mediated by asymmetric A-minor contacts, that serve to communicate ligand binding status between the aptamers. These interactions provide a structural basis for how the glycine riboswitch cooperatively regulates gene expression.

  20. Synthesis, structure and reactivity of rare-earth metal complexes containing anionic phosphorus ligands.

    Science.gov (United States)

    Li, Tianshu; Kaercher, Sabrina; Roesky, Peter W

    2014-01-07

    A comprehensive review of structurally characterized rare-earth metal complexes containing anionic phosphorus ligands is presented. Since rare-earth elements form hard ions and phosphorus is considered as a soft ligand, the rare-earth metal phosphorus coordination is regarded as a less favorite combination. Three classes of phosphorus ligands, (1) the monoanionic organophosphide ligands (PR2(-)) bearing one negative charge on the phosphorus atom; (2) the dianionic phosphinidene (PR(2-)) and P(3-) ligands; and (3) the pure inorganic polyphosphide ligands (Pn(x-)), are included here. Particular attention has been paid to the synthesis, structure, and reactivity of the rare-earth metal phosphides.

  1. A liposomal drug platform overrides peptide ligand targeting to a cancer biomarker, irrespective of ligand affinity or density.

    Directory of Open Access Journals (Sweden)

    Bethany Powell Gray

    Full Text Available One method for improving cancer treatment is the use of nanoparticle drugs functionalized with targeting ligands that recognize receptors expressed selectively by tumor cells. In theory such targeting ligands should specifically deliver the nanoparticle drug to the tumor, increasing drug concentration in the tumor and delivering the drug to its site of action within the tumor tissue. However, the leaky vasculature of tumors combined with a poor lymphatic system allows the passive accumulation, and subsequent retention, of nanosized materials in tumors. Furthermore, a large nanoparticle size may impede tumor penetration. As such, the role of active targeting in nanoparticle delivery is controversial, and it is difficult to predict how a targeted nanoparticle drug will behave in vivo. Here we report in vivo studies for αvβ6-specific H2009.1 peptide targeted liposomal doxorubicin, which increased liposomal delivery and toxicity to lung cancer cells in vitro. We systematically varied ligand affinity, ligand density, ligand stability, liposome dosage, and tumor models to assess the role of active targeting of liposomes to αvβ6. In direct contrast to the in vitro results, we demonstrate no difference in in vivo targeting or efficacy for H2009.1 tetrameric peptide liposomal doxorubicin, compared to control peptide and no peptide liposomes. Examining liposome accumulation and distribution within the tumor demonstrates that the liposome, and not the H2009.1 peptide, drives tumor accumulation, and that both targeted H2009.1 and untargeted liposomes remain in perivascular regions, with little tumor penetration. Thus H2009.1 targeted liposomes fail to improve drug efficacy because the liposome drug platform prevents the H2009.1 peptide from both actively targeting the tumor and binding to tumor cells throughout the tumor tissue. Therefore, using a high affinity and high specificity ligand targeting an over-expressed tumor biomarker does not guarantee

  2. Glucagon-like peptide-1 receptor ligand interactions: structural cross talk between ligands and the extracellular domain.

    Directory of Open Access Journals (Sweden)

    Graham M West

    Full Text Available Activation of the glucagon-like peptide-1 receptor (GLP-1R in pancreatic β-cells potentiates insulin production and is a current therapeutic target for the treatment of type 2 diabetes mellitus (T2DM. Like other class B G protein-coupled receptors (GPCRs, the GLP-1R contains an N-terminal extracellular ligand binding domain. N-terminal truncations on the peptide agonist generate antagonists capable of binding to the extracellular domain, but not capable of activating full length receptor. The main objective of this study was to use Hydrogen/deuterium exchange (HDX to identify how the amide hydrogen bonding network of peptide ligands and the extracellular domain of GLP-1R (nGLP-1R were altered by binding interactions and to then use this platform to validate direct binding events for putative GLP-1R small molecule ligands. The HDX studies presented here for two glucagon-like peptide-1 receptor (GLP-1R peptide ligands indicates that the antagonist exendin-4[9-39] is significantly destabilized in the presence of nonionic detergents as compared to the agonist exendin-4. Furthermore, HDX can detect stabilization of exendin-4 and exendin-4[9-39] hydrogen bonding networks at the N-terminal helix [Val19 to Lys27] upon binding to the N-terminal extracellular domain of GLP-1R (nGLP-1R. In addition we show hydrogen bonding network stabilization on nGLP-1R in response to ligand binding, and validate direct binding events with the extracellular domain of the receptor for putative GLP-1R small molecule ligands.

  3. 2 : 2 Fe(III): ligand and "adamantane core" 4 : 2 Fe(III): ligand (hydr)oxo complexes of an acyclic ditopic ligand

    DEFF Research Database (Denmark)

    Ghiladi, Morten; Larsen, Frank B.; McKenzie, Christine J.

    2005-01-01

    crystalline platelets. The Fe4O6 core of 2 shows an adamantane-like structure: The six bridging oxygen atoms are provided by the two phenolato groups of the two bpbp(-) ligands, two bridging oxo groups and two bridging hydroxo groups. The hydroxo and oxo ligands could be distinguished on the basis of Fe - O......-ray structure of the dinuclear complex [{( Hbpbp) Fe(mu-OH)}(2)](ClO4)(4) center dot 2C(3)H(6)O ( 1 center dot 2C(3)H(6)O) shows that only one of the metal-binding cavities of each ligand is occupied by an iron( III) atom and two [Fe(Hbpbp)](3+) units are linked together by two hydroxo bridging groups to form...... a [ Fe(III) -(mu-OH)](2) rhomb structure with Fe center dot center dot center dot Fe = 3.109(1) angstrom. The non-coordinated tertiary amine of Hbpbp is protonated. Magnetic susceptibility measurements show a well-behaved weak antiferromagnetic coupling between the two Fe( III) atoms, J =- 8 cm(-1...

  4. Identification of VDR Antagonists among Nuclear Receptor Ligands Using Virtual Screening

    Directory of Open Access Journals (Sweden)

    Kelly Teske

    2014-04-01

    Full Text Available Herein, we described the development of two virtual screens to identify new vitamin D receptor (VDR antagonists among nuclear receptor (NR ligands. Therefore, a database of 14330 nuclear receptor ligands and their NR affinities was assembled using the online available “Binding Database.” Two different virtual screens were carried out in conjunction with a reported VDR crystal structure applying a stringent and less stringent pharmacophore model to filter docked NR ligand conformations. The pharmacophore models were based on the spatial orientation of the hydroxyl functionalities of VDR's natural ligands 1,25(OH2D3 and 25(OH2D3. The first virtual screen identified 32 NR ligands with a calculated free energy of VDR binding of more than -6.0 kJ/mol. All but nordihydroguaiaretic acid (NDGA are VDR ligands, which inhibited the interaction between VDR and coactivator peptide SRC2-3 with an IC50 value of 15.8 μM. The second screen identified 162 NR ligands with a calculated free energy of VDR binding of more than -6.0 kJ/mol. More than half of these ligands were developed to bind VDR followed by ERα/β ligands (26%, TRα/β ligands (7%, and LxRα/β ligands (7%. The binding between VDR and ERα ligand H6036 as well as TRα/β ligand triiodothyronine and a homoserine analog thereof was confirmed by fluorescence polarization.

  5. Molecular dynamics simulations suggest ligand's binding to nicotinamidase/pyrazinamidase.

    Science.gov (United States)

    Zhang, Ji-Long; Zheng, Qing-Chuan; Li, Zheng-Qiang; Zhang, Hong-Xing

    2012-01-01

    The research on the binding process of ligand to pyrazinamidase (PncA) is crucial for elucidating the inherent relationship between resistance of Mycobacterium tuberculosis and PncA's activity. In the present study, molecular dynamics (MD) simulation methods were performed to investigate the unbinding process of nicotinamide (NAM) from two PncA enzymes, which is the reverse of the corresponding binding process. The calculated potential of mean force (PMF) based on the steered molecular dynamics (SMD) simulations sheds light on an optimal binding/unbinding pathway of the ligand. The comparative analyses between two PncAs clearly exhibit the consistency of the binding/unbinding pathway in the two enzymes, implying the universality of the pathway in all kinds of PncAs. Several important residues dominating the pathway were also determined by the calculation of interaction energies. The structural change of the proteins induced by NAM's unbinding or binding shows the great extent interior motion in some homologous region adjacent to the active sites of the two PncAs. The structure comparison substantiates that this region should be very important for the ligand's binding in all PncAs. Additionally, MD simulations also show that the coordination position of the ligand is displaced by one water molecule in the unliganded enzymes. These results could provide the more penetrating understanding of drug resistance of M. tuberculosis and be helpful for the development of new antituberculosis drugs.

  6. Molecular dynamics simulations suggest ligand's binding to nicotinamidase/pyrazinamidase.

    Directory of Open Access Journals (Sweden)

    Ji-Long Zhang

    Full Text Available The research on the binding process of ligand to pyrazinamidase (PncA is crucial for elucidating the inherent relationship between resistance of Mycobacterium tuberculosis and PncA's activity. In the present study, molecular dynamics (MD simulation methods were performed to investigate the unbinding process of nicotinamide (NAM from two PncA enzymes, which is the reverse of the corresponding binding process. The calculated potential of mean force (PMF based on the steered molecular dynamics (SMD simulations sheds light on an optimal binding/unbinding pathway of the ligand. The comparative analyses between two PncAs clearly exhibit the consistency of the binding/unbinding pathway in the two enzymes, implying the universality of the pathway in all kinds of PncAs. Several important residues dominating the pathway were also determined by the calculation of interaction energies. The structural change of the proteins induced by NAM's unbinding or binding shows the great extent interior motion in some homologous region adjacent to the active sites of the two PncAs. The structure comparison substantiates that this region should be very important for the ligand's binding in all PncAs. Additionally, MD simulations also show that the coordination position of the ligand is displaced by one water molecule in the unliganded enzymes. These results could provide the more penetrating understanding of drug resistance of M. tuberculosis and be helpful for the development of new antituberculosis drugs.

  7. Synthesis and evaluation of potential ligands for nuclear waste processing

    NARCIS (Netherlands)

    Iqbal, M.

    2012-01-01

    The research presented in this thesis deals with the synthesis and evaluation of new potential ligands for the complexation of actinide and lanthanide ions either for their extraction from bulk radioactive waste or their stripping from an extracted organic phase for final processing of the waste. In

  8. NMR-based screening of membrane protein ligands

    NARCIS (Netherlands)

    Yanamala, Naveena; Dutta, Arpana; Beck, Barbara; Van Fleet, Bart; Hay, Kelly; Yazbak, Ahmad; Ishima, Rieko; Doemling, Alexander; Klein-Seetharaman, Judith

    2010-01-01

    Membrane proteins pose problems for the application of NMR-based ligand-screening methods because of the need to maintain the proteins in a membrane mimetic environment such as detergent micelles: they add to the molecular weight of the protein, increase the viscosity of the solution, interact with

  9. Synthesis and Characterization of Metal Complexes with Schiff Base Ligands

    Science.gov (United States)

    Wilkinson, Shane M.; Sheedy, Timothy M.; New, Elizabeth J.

    2016-01-01

    In order for undergraduate laboratory experiments to reflect modern research practice, it is essential that they include a range of elements, and that synthetic tasks are accompanied by characterization and analysis. This intermediate general chemistry laboratory exercise runs over 2 weeks, and involves the preparation of a Schiff base ligand and…

  10. synthesis and spectra characterization of mixed- ligand complexes

    African Journals Online (AJOL)

    BARTH EKWUEME

    bipyridine(bpy) has been announced to be “the most used ligand in coordination chemistry” (Humphries, et al., 2005), 2,2':6',2''-terpyridine (tpy) also has a rich chemistry. Almost 70 years ago, Burstall and Morgan reported the first synthesis of 2, 2':6', 2''-terpyridine. (Bermejo, et al., 1999). The kinetics and mechanism of ...

  11. Development and Application of Ligand-Exchange Reaction Method ...

    African Journals Online (AJOL)

    Purpose: This paper presents an improved kinetic-spectrophotometric procedure for determining clonazepam (CZP) in pharmaceutical formulations and human serum. Methods: The method is based on ligand-exchange reaction. The reaction was followed spectrophotometrically by measuring the rate of change of ...

  12. Mixed-ligand binuclear copper(II) complex of 5 ...

    Indian Academy of Sciences (India)

    carbon, saturated Ag/AgCl and platinum wire are used as the working, reference and auxiliary electrodes, ... was mounted on a glass fibre for diffraction experiment. X-ray single crystal data were collected on a Kappa ..... with the covalent nature of the metal–ligand bond. 3.4 DNA binding studies. 3.4a Absorption spectral ...

  13. A Simple Ligand for Lanthanide Energy Transfer Luminescence in ...

    African Journals Online (AJOL)

    NJD

    induced electron transfer (P.E.T.) fluorescent-based sensor that responds to the presence of Mg2+ ions by ... phenol tetraacetic acid (bapta).12,13 Owing to the similarity of the structures of bapta and apta, we decided to .... The protonation state can have a profound effect on the ability of the ligand to facilitate the formation of ...

  14. Dynamic ligand-based pharmacophore modeling and virtual ...

    Indian Academy of Sciences (India)

    1398 non-inhibitors of CmaA1. A VS protocol was designed with four levels of screening i.e., ligand-based pharmacophore screening, structure-based pharmacophore screening, docking and absorption, distribution, metabolism, excretion and the toxicity (ADMET) filters. In an attempt towards repurposing the existing drugs.

  15. contribution to study the glycoprotein ligands of the cerebellar ...

    African Journals Online (AJOL)

    H. Rechreche and J.P. Zanetta

    2016-09-01

    Sep 1, 2016 ... SDS-PAGE and revelation with CBB or silver nitrate. Finally, the Bio-CSL activity was ... vacuum centrifuge, the pellets thus obtained were included in 20 µl H2O and aliquots (1 µl) were deposited onto a .... SDS-PAGE (silver staining); B: Western blot (CSL ligands revealed with Bio-CSL and avidin-AKP). a) ...

  16. complexes of histamine Schiff base and pyridyl ligands

    Indian Academy of Sciences (India)

    ARC

    histamine Schiff base and pyridyl ligands. SAMYA BANERJEE a. , AKANKSHA DIXIT b. , K. SESHA MAHESWARAMMA a. ,. BASUDEV MAITY a. , SANJOY MUKHERJEE a. , ARUN KUMAR a. , ANJALI A. KARANDE*. ,b. AND AKHIL R. CHAKRAVARTY*. ,a a. Department of Inorganic and Physical Chemistry, Indian Institute ...

  17. Chemokine-Ligands/Receptors: Multiplayers in Traumatic Spinal Cord Injury

    Directory of Open Access Journals (Sweden)

    Friederike Knerlich-Lukoschus

    2015-01-01

    Full Text Available Spinal cord injury (SCI results in complex posttraumatic sequelae affecting the whole neuraxis. Due to its involvement in varied neuromodulatory processes, the chemokine-ligand/receptor-network is a key element of secondary lesion cascades induced by SCI. This review will provide a synopsis of chemokine-ligand/receptor-expression along the whole neuraxis after traumatic spinal cord (sc insults on basis of recent in vivo and in vitro findings in a SCI paradigm of thoracic force-defined impact lesions (Infinite Horizon Impactor in adult rats. Analyses of chemokine-ligand/receptor-expression at defined time points after sc lesion of different severity grades or sham operation revealed that these inflammatory mediators are induced in distinct anatomical sc regions and in thalamic nuclei, periaqueductal grey, and hippocampal structures in the brain. Cellular and anatomical expression profiles together with colocalization/expression of neural stem/progenitor cell markers in adult sc stem cells niches or with pain-related receptors and mediators in dorsal horns, dorsal columns, and pain-processing brain areas support the notion that chemokines are involved in distinct cascades underlying clinical posttraumatic impairments and syndromes. These aspects and their implication in concepts of tailored SCI treatment are reviewed in the context of the recent literature on chemokine-ligand/receptor involvement in complex secondary lesion cascades.

  18. Mixed-ligand binuclear copper (II) complex of 5 ...

    Indian Academy of Sciences (India)

    A new mixed-ligand binuclear copper(II) complex [Cu(MS)(bpy)]2.(ClO4)2, built of 5-methylsalicylaldehyde and 2,2'-bipyridyl has been synthesized and characterized by using elemental analysis, IR and UV-Vis spectroscopy. Crystal structure of the complex shows that copper(II) ion lies in a square pyramidal coordination ...

  19. Ruthenium, osmium and rhodium complexes of polypyridyl ligands ...

    Indian Academy of Sciences (India)

    Unknown

    Molecular structures of some of the complexes, especially stereoisomers of the hydroxylated products ... developed by covalent linking of building blocks with spacers which, therefore, is the key component because the .... the metal ion has the ability to form π-back-bonding with unsaturated ligands compensating partially ...

  20. Amidinate Ligands in Zinc coordination sphere: Synthesis and ...

    Indian Academy of Sciences (India)

    ... Refresher Courses · Symposia · Live Streaming. Home; Journals; Journal of Chemical Sciences; Volume 128; Issue 6. Amidinate Ligands in Zinc coordination sphere: Synthesis and structural diversity. SRINIVAS ANGA INDRANI BANERJEE TARUN K PANDA. Regular Article Volume 128 Issue 6 June 2016 pp 867-873 ...

  1. Selective Electrocatalytic Activity of Ligand Stabilized Copper Oxide Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kauffman, Douglas R; Ohodnicki, Paul R; Kail, Brian W; Matranga, Christopher

    2011-01-01

    Ligand stabilization can influence the surface chemistry of Cu oxide nanoparticles (NPs) and provide unique product distributions for electrocatalytic methanol (MeOH) oxidation and CO{sub 2} reduction reactions. Oleic acid (OA) stabilized Cu{sub 2}O and CuO NPs promote the MeOH oxidation reaction with 88% and 99.97% selective HCOH formation, respectively. Alternatively, CO{sub 2} is the only reaction product detected for bulk Cu oxides and Cu oxide NPs with no ligands or weakly interacting ligands. We also demonstrate that OA stabilized Cu oxide NPs can reduce CO{sub 2} into CO with a {approx}1.7-fold increase in CO/H{sub 2} production ratios compared to bulk Cu oxides. The OA stabilized Cu oxide NPs also show 7.6 and 9.1-fold increases in CO/H{sub 2} production ratios compared to weakly stabilized and non-stabilized Cu oxide NPs, respectively. Our data illustrates that the presence and type of surface ligand can substantially influence the catalytic product selectivity of Cu oxide NPs.

  2. Ligand-mediated adhesive mechanics of two static, deformed spheres.

    Science.gov (United States)

    Sircar, Sarthok; Nguyen, Giang; Kotousov, Andrei; Roberts, Anthony J

    2016-10-01

    A self-consistent model is developed to investigate attachment/detachment kinetics of two static, deformable microspheres with irregular surface and coated with flexible binding ligands. The model highlights how the microscale binding kinetics of these ligands as well as the attractive/repulsive potential of the charged surface affects the macroscale static deformed configuration of the spheres. It is shown that in the limit of smooth, neutrally charged surface (i.e., the dimensionless inverse Debye length, [Formula: see text]), interacting via elastic binders (i.e., the dimensionless stiffness coefficient, [Formula: see text]) the adhesion mechanics approaches the regime of application of the JKR theory, and in this particular limit, the contact radius, R c , scales with the particle radius, R, according to the scaling law, [Formula: see text]. We show that static, deformed, highly charged, ligand-coated surface of micro-spheres exhibit strong adhesion. Normal stress distribution within the contact area adjusts with the binder stiffness coefficient, from a maximum at the center to a maximum at the periphery of the region. Although reported in some in vitro experiments involving particle adhesion, until now a physical interpretation for this variation of the stress distribution for deformable, charged, ligand-coated microspheres is missing. Surface roughness results in a diminished adhesion with a distinct reduction in the pull-off force, larger separation gap, weaker normal stress and limited area of adhesion. These results are in agreement with the published experimental findings.

  3. Programmed death ligand 2 in cancer-induced immune suppression

    NARCIS (Netherlands)

    Rozali, Esdy N.; Hato, Stanleyson V.; Robinson, Bruce W.; Lake, Richard A.; Lesterhuis, W. Joost

    2012-01-01

    Inhibitory molecules of the B7/CD28 family play a key role in the induction of immune tolerance in the tumor microenvironment. The programmed death-1 receptor (PD-1), with its ligands PD-L1 and PD-L2, constitutes an important member of these inhibitory pathways. The relevance of the PD-1/PD-L1

  4. GluR2 ligand-binding core complexes

    DEFF Research Database (Denmark)

    Kasper, C; Lunn, M-L; Liljefors, T

    2002-01-01

    X-ray structures of the GluR2 ligand-binding core in complex with (S)-Des-Me-AMPA and in the presence and absence of zinc ions have been determined. (S)-Des-Me-AMPA, which is devoid of a substituent in the 5-position of the isoxazolol ring, only has limited interactions with the partly hydrophobic...

  5. [Mechanisms of action of voltage-gated sodium channel ligands].

    Science.gov (United States)

    Tikhonov, D B

    2007-05-01

    The voltage-gated sodium channels play a key role in the generation of action potential in excitable cells. Sodium channels are targeted by a number of modulating ligands. Despite numerous studies, the mechanisms of action of many ligands are still unknown. The main cause of the problem is the absence of the channel structure. Sodium channels belong to the superfamily of P-loop channels that also the data abowt includes potassium and calcium channels and the channels of ionotropic glutamate receptors. Crystallization of several potassium channels has opened a possibility to analyze the structure of other members of the superfamily using the homology modeling approach. The present study summarizes the results of several recent modelling studies of such sodium channel ligands as tetrodotoxin, batrachotoxin and local anesthetics. Comparison of available experimental data with X-ray structures of potassium channels has provided a new level of understanding of the mechanisms of action of sodium channel ligands and has allowed proposing several testable hypotheses.

  6. : Recyclable, ligand free palladium(II) catalyst for Heck reaction

    Indian Academy of Sciences (India)

    acetate or chloride salts.6 Several ligands such as phosphines, phoshites, carbenes, thioethers have been successfully employed for this reaction.7 However, ... carbon9, magnesium oxide10, silica, alumina or tita- nia11, palladium/Nb-MCM-4112, polymers13, zeo- lites14, polyionic resins.15 Basic supports such as.

  7. Are 90Y metal ligand complexes possible antineoplastics?

    International Nuclear Information System (INIS)

    Schomaecker, K.; Franke, W.G.; Muenze, R.; Medizinische Akademie, Dresden

    1989-01-01

    Treatment of tumor-bearing mice with 90 Y-citrate revealed a significant influence on tumor growth and survival time. The radiotherapeutic effect depended on the kind of tumor as well as on the form of application. Promising results were gained with 90 Y metal ligand complexes both in pelliative treatment of skeletal metastases and in soft tissue tumor therapy

  8. Colloidal-quantum-dot photovoltaics using atomic-ligand passivation

    KAUST Repository

    Tang, Jiang

    2011-09-18

    Colloidal-quantum-dot (CQD) optoelectronics offer a compelling combination of solution processing and spectral tunability through quantum size effects. So far, CQD solar cells have relied on the use of organic ligands to passivate the surface of the semiconductor nanoparticles. Although inorganic metal chalcogenide ligands have led to record electronic transport parameters in CQD films, no photovoltaic device has been reported based on such compounds. Here we establish an atomic ligand strategy that makes use of monovalent halide anions to enhance electronic transport and successfully passivate surface defects in PbS CQD films. Both time-resolved infrared spectroscopy and transient device characterization indicate that the scheme leads to a shallower trap state distribution than the best organic ligands. Solar cells fabricated following this strategy show up to 6% solar AM1.5G power-conversion efficiency. The CQD films are deposited at room temperature and under ambient atmosphere, rendering the process amenable to low-cost, roll-by-roll fabrication. © 2011 Macmillan Publishers Limited. All rights reserved.

  9. Group 4 Metal Complexes of Chelating Cyclopentadienyl-ketimide Ligands

    Czech Academy of Sciences Publication Activity Database

    Večeřa, M.; Varga, Vojtěch; Císařová, I.; Pinkas, Jiří; Kucharczyk, P.; Sedlařík, V.; Lamač, Martin

    2016-01-01

    Roč. 35, č. 5 (2016), s. 785-798 ISSN 0276-7333 R&D Projects: GA ČR(CZ) GA14-08531S; GA MŠk(CZ) LO1504 Institutional support: RVO:61388955 Keywords : group 4 metal complexes * cyclopentadienyl-ketimide ligands * metallocenes Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.862, year: 2016

  10. Chelating ligands: enhancers of quality and purity of biogas ...

    African Journals Online (AJOL)

    The quality of biogas depends largely on the percentage of methane and hydrogen sulphide gas present. High concentration of hydrogen sulphide results in low quality biogas. This work employed the use of chelating ligands in scrubbing hydrogen sulphide gas while improving the yield of methane gas. Experimental ...

  11. The thermodynamic principles of ligand binding in chromatography and biology

    DEFF Research Database (Denmark)

    Mollerup, Jørgen

    2007-01-01

    the general thermodynamic principles of ligand binding. Models of the multi-component adsorption in ion-exchange and hydrophobic chromatography, HIC and RPLC, are developed. The parameters in the models have a well-defined physical significance. The models are compared to the Langmuir model...

  12. Asymmetric borane reduction using mixtures of homochiral amino alcohol ligands

    NARCIS (Netherlands)

    Kaptein, Bernard; Elsenberg, Henk; Minnaard, Adriaan J.; Broxterman, Quirinus B.; Hulshof, Lumbertus A.; Vries, Ton R.

    1999-01-01

    The asymmetric borane reduction of acetophenone is investigated using mixtures of homochiral β-amino alcohol ligands. With stoichiometric amounts of a mixture of two- or three-amino alcohols, the e.e. remains at the level of the best amino alcohol for a wide composition range. A small but

  13. Synergistic Effects of PPARγ Ligands and Retinoids in Cancer Treatment

    Directory of Open Access Journals (Sweden)

    Masahito Shimizu

    2008-01-01

    Full Text Available Peroxisome proliferator-activated receptors (PPARs are members of the nuclear receptor superfamily. The activation of PPARs by their specific ligands is regarded as one of the promising strategies to inhibit cancer cell growth. However, recent clinical trials targeting several common cancers showed no beneficial effect when PPAR ligands are used as a monotherapy. Retinoid X receptors (RXRs, which play a critical role in normal cell proliferation as a master regulator for nuclear receptors, preferentially form heterodimers with PPARs. A malfunction of RXRα due to phosphorylation by the Ras/MAPK signaling pathway is associated with the development of certain types of human malignancies. The activation of PPARγ/RXR heterodimer by their respective ligands synergistically inhibits cell growth, while inducing apoptosis in human colon cancer cells when the phosphorylation of RXRα was inhibited. We herein review the synergistic antitumor effects produced by the combination of the PPAR, especially PPARγ, ligands plus other agents, especially retinoids, in a variety of human cancers. We also focus on the phosphorylation of RXRα because the inhibition of RXRα phosphorylation and the restoration of its physiological function may activate PPAR/RXR heterodimer and, therefore, be a potentially effective and critical strategy for the inhibition of cancer cell growth.

  14. Optimal Overlay of Ligands with Flexible Bonds Using Differential Evolution

    DEFF Research Database (Denmark)

    Kristensen, Thomas Greve; Pedersen, Christian Storm

    2009-01-01

    spatial alignment of a set of active ligands taking the flexibility of chemical bonds into account. We present two implementations of our method. One using Differential Evolution (DE) for numerical optimization, and one using the Nelder-Mead method for numerical optimization. We investigate the quality...

  15. Biosensors engineered from conditionally stable ligand-binding domains

    Energy Technology Data Exchange (ETDEWEB)

    Church, George M.; Feng, Justin; Mandell, Daniel J.; Baker, David; Fields, Stanley; Jester, Benjamin Ward; Tinberg, Christine Elaine

    2017-09-19

    Disclosed is a biosensor engineered to conditionally respond to the presence of specific small molecules, the biosensors including conditionally stable ligand-binding domains (LBDs) which respond to the presence of specific small molecules, wherein readout of binding is provided by reporter genes or transcription factors (TFs) fused to the LBDs.

  16. A response calculus for immobilized T cell receptor ligands

    DEFF Research Database (Denmark)

    Andersen, P S; Menné, C; Mariuzza, R A

    2001-01-01

    To address the molecular mechanism of T cell receptor (TCR) signaling, we have formulated a model for T cell activation, termed the 2D-affinity model, in which the density of TCR on the T cell surface, the density of ligand on the presenting surface, and their corresponding two-dimensional affini...

  17. Designer Ligands. Part 13. Synthesis and Catalytic Activity of ...

    African Journals Online (AJOL)

    Copper(I), copper(II), cobalt(II) and zinc(II) complexes of a macrocyclic, multidentate Schiff-base ligand have been prepared and, with the exception of the zinc(II) complex, have been shown to exhibit biomimetic catecholase activity. Keywords: Copper(II);Cobalt(II); Zinc(II); Biomimetic complexes; Catecholase activity

  18. Phenalenyl-based ligand for transition metal chemistry: Application ...

    Indian Academy of Sciences (India)

    mandal@iiserkol.ac.in. Abstract. We report the synthesis and characterization of the first transition metal complex of a phenalenyl- based ligand. The reaction of Cu(OAc)2.H2O with 9-N-methylamino-1-N -methylimino-phenalene (LH) in 1:1.

  19. Topological estimation of proton–ligand formation constants of ...

    Indian Academy of Sciences (India)

    Proton-ligand formation constants of salicylhydroxamic acids (SHA) and their nuclear substituted derivatives have been estimated topologically using the normalized Wiener index, referred to as mean square Wiener index (Wms). Regression analysis of the data indicates that Wms can be used successfully for estimating ...

  20. Development and Application of Ligand-Exchange Reaction Method ...

    African Journals Online (AJOL)

    Erah

    clonazepam (CZP) in pharmaceutical formulations and human serum. Methods: The method is based on ligand-exchange reaction. The reaction was followed spectrophotometrically by measuring the rate of change of absorbance at 425 nm in ethanolic sodium hydroxide solution. Results: The optimum operating conditions ...

  1. Optimal Overlay of Ligands with Flexible Bonds Using Differential Evolution

    DEFF Research Database (Denmark)

    Pedersen, Christian Storm; Kristensen, Thomas Greve

    When designing novel drugs, the need arise to screen databases for structures resembling active ligands, e.g. by generating a query meta-structure which summarizes these. We propose a flexible bond method for making a meta-structure and present Monte Carlo, Nelder-Mead and Differential Evolution...

  2. Synthesis and characterization of mixed ligand complexes of Zn (II ...

    Indian Academy of Sciences (India)

    Mixed ligand complexes of Zn(II) and Co(II) with cysteine, histidine, cysteinemethylester, and histidinemethylester have been synthesized and characterized by elemental analysis, conductivity, magnetic susceptibility measurements, and infrared, 1H NMR, TGA and FAB mass spectra. In these complexes, histidine, and ...

  3. Dependence of the cone angles of phosphorus-containing ligands ...

    Indian Academy of Sciences (India)

    Administrator

    )(L)][BF4], dppe = Ph2CH2CH2Ph2, L = P(OMe)3, P(OEt)3, PMe2Ph,. P(OiPr)3 have been prepared and characterized using a procedure similar to the one reported earlier. It was found that the binding ability of the ligand decreases in the order.

  4. Oxahelicene NHC ligands in the asymmetric synthesis of nonracemic helicenes

    Czech Academy of Sciences Publication Activity Database

    Gay Sánchez, Isabel; Šámal, Michal; Nejedlý, Jindřich; Karras, Manfred; Klívar, Jiří; Rybáček, Jiří; Buděšínský, Miloš; Bednárová, Lucie; Seidlerová, Beata; Stará, Irena G.; Starý, Ivo

    2017-01-01

    Roč. 53, č. 31 (2017), s. 4370-4373 ISSN 1359-7345 R&D Projects: GA ČR(CZ) GA14-29667S Institutional support: RVO:61388963 Keywords : helicene-based NHC ligands * enantioselective [2+2+2] cycloisomerisation Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 6.319, year: 2016

  5. Hybrid diphosphorus ligands in rhodium catalysed asymmetric hydroformylation

    NARCIS (Netherlands)

    Chikkali, S.H.; van der Vlugt, J.I.; Reek, J.N.H.

    2014-01-01

    This review aims to illustrate recent advances in the application of hybrid diphosphorus ligands for the Rh catalysed hydroformylation of alkenes, discussing the most prevalent classes of hybrid systems, i.e. phosphine-phosphinite, phosphine-phosphonite, phosphine-phosphite,

  6. Reactivity descriptors and electron density analysis for ligand ...

    Indian Academy of Sciences (India)

    We discuss evaluation of local descriptors using relaxed as well as frozen approximation and characterize the / acceptance/donor characteristics of the above ligands. The intermolecular reactivity sequence for the same systems is examined by the global and local philicity index. In addition, electron density analysis has ...

  7. A Guided Inquiry Activity for Teaching Ligand Field Theory

    Science.gov (United States)

    Johnson, Brian J.; Graham, Kate J.

    2015-01-01

    This paper will describe a guided inquiry activity for teaching ligand field theory. Previous research suggests the guided inquiry approach is highly effective for student learning. This activity familiarizes students with the key concepts of molecular orbital theory applied to coordination complexes. Students will learn to identify factors that…

  8. The Effect of Solvent on the Ligand Substitution Reactions of ...

    African Journals Online (AJOL)

    NJD

    A2 and kobs as variables. At least six half-lives were monitored and fitted for each ligand concentration and these recorded traces were averaged to obtain the final kobs value. Since hydroxo- cobalamin is inert to substitution,1,5 values of kobs were converted into a pH-independent value, k, using Equation 2, where KCo is.

  9. Amidinate Ligands in Zinc coordination sphere: Synthesis and ...

    Indian Academy of Sciences (India)

    Amidinate Ligands in Zinc coordination sphere: Synthesis and structural diversity. SRINIVAS ANGA, INDRANI BANERJEE and TARUN K PANDA. ∗. Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi 502 285,. Sangareddy, Telangana, India e-mail: tpanda@iith.ac.in. MS received 25 February 2016; ...

  10. Water-soluble diphosphadiazacyclooctanes as ligands for aqueous organometallic catalysis

    KAUST Repository

    Boulanger, Jérôme

    2012-12-01

    Two new water-soluble diphosphacyclooctanes been synthesized and characterized by NMR and surface tension measurements. Both phosphanes proved to coordinate rhodium in a very selective way as well-defined bidentates were obtained. When used in Rh-catalyzed hydroformylation of terminal alkenes, both ligands positively impacted the reaction chemoselectivity. © 2012 Elsevier B.V.

  11. Supramolecular coordination and antimicrobial activities of constructed mixed ligand complexes

    Science.gov (United States)

    El-Sonbati, A. Z.; Diab, M. A.; El-Bindary, A. A.; Abou-Dobara, M. I.; Seyam, H. A.

    2013-03-01

    A novel series of copper(II) and palladium(II) with 4-derivatives benzaldehyde pyrazolone (Ln) were synthesized. The mixed ligand complexes were prepared by using 1,10-phenanthroline (Phen) as second ligand. The structure of these complexes was identified and confirm by elemental analysis, molar conductivity, UV-Vis, IR and 1H NMR spectroscopy and magnetic moment measurements as well as thermal analysis. The ligand behaves as a neutral bidentate ligand through ON donor sites. ESR spectra show the simultaneous presence of a planar trans and a nearly planar cis isomers in the 1:2 ratio for all N,O complexes [Cu(Ln)2]Cl2ṡ2H2O. Schiff bases (Ln) were tested against bacterial species; namely two Gram positive bacteria (Staphylococcus aureus and Bacillus cereus) and two Gram negative bacteria (Escherichia coli and Klebsiella pneumoniae) and fungal species (Aspergillus niger, Fusarium oxysporium, Penicillium italicum and Alternaria alternata). The tested compounds have antibacterial activity against S. aureus, B. cereus and K. pneumoniae.

  12. Some new IIB group complexes of an imidazolidine ligand ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 1. Some new IIB group complexes of an imidazolidine ligand: Synthesis, spectral characterization, electrochemical, thermal and antimicrobial propert. Morteza Montazerozohori Sayed Alireza Musavi Asghar Naghiha Somayeh Veyseh. Volume 126 Issue 1 ...

  13. Docking Validation Resources: Protein Family and Ligand Flexibility Experiments

    Science.gov (United States)

    Mukherjee, Sudipto; Balius, Trent E.; Rizzo, Robert C.

    2010-01-01

    A database consisting of 780 ligand-receptor complexes, termed SB2010, has been derived from the Protein Databank to evaluate the accuracy of docking protocols for regenerating bound ligand conformations. The goal is to provide easily accessible community resources for development of improved procedures to aid virtual screening for ligands with a wide range of flexibilities. Three core experiments using the program DOCK, which employ rigid (RGD), fixed anchor (FAD), and flexible (FLX) protocols, were used to gauge performance by several different metrics: (1) global results, (2) ligand flexibility, (3) protein family, and (4) crossdocking. Global spectrum plots of successes and failures vs rmsd reveal well-defined inflection regions, which suggest the commonly used 2 Å criteria is a reasonable choice for defining success. Across all 780 systems, success tracks with the relative difficulty of the calculations: RGD (82.3%) > FAD (78.1%) > FLX (63.8%). In general, failures due to scoring strongly outweigh those due to sampling. Subsets of SB2010 grouped by ligand flexibility (7-or-less, 8-to-15, and 15-plus rotatable bonds) reveal success degrades linearly for FAD and FLX protocols, in contrast to RGD which remains constant. Despite the challenges associated with FLX anchor orientation and on-the-fly flexible growth, success rates for the 7-or-less (74.5%), and in particular the 8-to-15 (55.2%) subset, are encouraging. Poorer results for the very flexible 15-plus set (39.3%) indicate substantial room for improvement. Family-based success appears largely independent of ligand flexibility suggesting a strong dependence on the binding site environment. For example, zinc-containing proteins are generally problematic despite moderately flexible ligands. Finally, representative crossdocking examples, for carbonic anhydrase, thermolysin, and neuraminidase families, show the utility of family-based analysis for rapid identification of particularly good or bad docking trends

  14. Heterobifunctional crosslinkers for tethering single ligand molecules to scanning probes

    International Nuclear Information System (INIS)

    Riener, Christian K.; Kienberger, Ferry; Hahn, Christoph D.; Buchinger, Gerhard M.; Egwim, Innocent O.C.; Haselgruebler, Thomas; Ebner, Andreas; Romanin, Christoph; Klampfl, Christian; Lackner, Bernd; Prinz, Heino; Blaas, Dieter; Hinterdorfer, Peter; Gruber, Hermann J.

    2003-01-01

    Single molecule recognition force microscopy (SMRFM) is a versatile atomic force microscopy (AFM) method to probe specific interactions of cognitive molecules on the single molecule level. It allows insights to be gained into interaction potentials and kinetic barriers and is capable of mapping interaction sites with nm positional accuracy. These applications require a ligand to be attached to the AFM tip, preferably by a distensible poly(ethylene glycol) (PEG) chain between the measuring tip and the ligand molecule. The PEG chain greatly facilitates specific binding of the ligand to immobile receptor sites on the sample surface. The present study contributes to tip-PEG-ligand tethering in three ways: (i) a convenient synthetic route was found to prepare NH 2 -PEG-COOH which is the key intermediate for long heterobifunctional crosslinkers; (ii) a variety of heterobifunctional PEG derivatives for tip-PEG-ligand linking were prepared from NH 2 -PEG-COOH; (iii) in particular, a new PEG crosslinker with one thiol-reactive end and one terminal nitrilotriacetic acid (NTA) group was synthesized and successfully used to tether His 6 -tagged protein molecules to AFM tips via noncovalent NTA-Ni 2+ -His 6 bridges. The new crosslinker was applied to link a recombinant His 6 -tagged fragment of the very-low density lipoprotein receptor to the AFM tip whereupon specific docking to the capsid of human rhinovirus particles was observed by force microscopy. In a parallel study, the specific interaction of the small GTPase Ran with the nuclear import receptor importin β1 was studied in detail by SMRFM, using the new crosslinker to link His 6 -tagged Ran to the measuring tip [Nat. Struct. Biol. (2003), 10, 553-557

  15. Structural and Electrochemical Consequences of [Cp*] Ligand Protonation.

    Science.gov (United States)

    Peng, Yun; Ramos-Garcés, Mario V; Lionetti, Davide; Blakemore, James D

    2017-09-05

    There are few examples of the isolation of analogous metal complexes bearing [η 5 -Cp*] and [η 4 -Cp*H] (Cp* = pentamethylcyclopentadienyl) complexes within the same metal/ligand framework, despite the relevance of such structures to catalytic applications. Recently, protonation of Cp*Rh(bpy) (bpy = 2,2'-bipyridyl) has been shown to yield a complex bearing the uncommon [η 4 -Cp*H] ligand, rather than generating a [Rh III -H] complex. We now report the purification and isolation of this protonated species, as well as characterization of analogous complexes of 1,10-phenanthroline (phen). Specifically, reaction of Cp*Rh(bpy) or Cp*Rh(phen) with 1 equiv of Et 3 NH + Br - affords rhodium compounds bearing endo-η 4 -pentamethylcyclopentadiene (η 4 -Cp*H) as a ligand. NMR spectroscopy and single-crystal X-ray diffraction studies confirm protonation of the Cp* ligand, rather than formation of metal hydride complexes. Analysis of new structural data and electronic spectra suggests that phen is significantly reduced in Cp*Rh(phen), similar to the case of Cp*Rh(bpy). Backbonding interactions with olefinic motifs are activated by formation of [η 4 -Cp*H]; protonation of [Cp*] stabilizes the low-valent metal center and results in loss of reduced character on the diimine ligands. In accord with these changes in electronic structure, electrochemical studies reveal a distinct manifold of redox processes that are accessible in the [Cp*H] complexes in comparison with their [Cp*] analogues; these processes suggest new applications in catalysis for the complexes bearing endo-η 4 -Cp*H.

  16. Specific ability of sulfur-ligands on removal of 203Hg-labeled organomercury from hemoglobin in comparison with nitrogen-ligands

    International Nuclear Information System (INIS)

    Hojo, Yasuji; Sugiura, Yukio; Tanaka, Hisashi

    1975-01-01

    Removal of 203 Hg-labeled organomercurials, bound to sulfhydryl groups of hemoglobin, by various chelating agents was investigated by the use of equilibrium dialysis. Organomercurials employed were chlormerodrin, methylmercury, ethylmercury and phenylmercury compounds. Higher and more specific effects of the sulfur-ligands, such as penicillamine and glutathione, on removal of organomercurial were found as compared with those of the nitrogen-ligands such as EDTA, glycine and polymethylenediamines. Linear correlation was observed between the degree of organomercury elimination from hemoglobin and the stability constant (log K 1 ) of 1:1 organomercury complex in both the sulfur- and nitrogen-ligand systems and at the same value of log K 1 , the elimination-effect of sulfur-ligands was extremely greater than that of the nitrogen-ligands. The relationship between the average percentage of removal and the Taft's polar substituent constant of organic moiety of the metal was also linear among the organomercury compounds other than chlormerodrin. The average removal percentage by sulfur-ligands increased in the order, ethylmercury>methylmercury>phenylmercury, while that of the nitrogen-ligands was not different among the organomercurials investigated. In addition, direct ligand-exchange reaction between hemoglobin-SH and the ligand coordinating-atom (S or N) against organomercurials rather than Ssub(N2) reaction via the ternary complex, hemoglobin-S-RHg-ligand, is postulated. (auth.)

  17. Switching of bacterial adhesion to a glycosylated surface by reversible reorientation of the carbohydrate ligand

    DEFF Research Database (Denmark)

    Weber, Theresa; Chrasekaran, Vijayan; Stamer, Insa

    2014-01-01

    The surface recognition in many biological systems is guided by the interaction of carbohydrate-specific proteins (lectins) with carbohydrate epitopes (ligands) located within the unordered glycoconjugate layer (glycocalyx) of cells. Thus, for recognition, the respective ligand has to reorient...

  18. Ligand flexibility and framework rearrangement in a new family of porous metal-organic frameworks

    DEFF Research Database (Denmark)

    Hawxwell, Samuel M; Espallargas, Guillermo Mínguez; Bradshaw, Darren

    2007-01-01

    Ligand flexibility permits framework rearrangement upon evacuation and gas uptake in a new family of porous MOFs.......Ligand flexibility permits framework rearrangement upon evacuation and gas uptake in a new family of porous MOFs....

  19. Changes in electrostatic surface potential of Na+/K+-ATPase cytoplasmic headpiece induced by cytoplasmic ligand(s) binding.

    Science.gov (United States)

    Kubala, Martin; Grycova, Lenka; Lansky, Zdenek; Sklenovsky, Petr; Janovska, Marika; Otyepka, Michal; Teisinger, Jan

    2009-09-16

    A set of single-tryptophan mutants of the Na(+)/K(+)-ATPase isolated, large cytoplasmic loop connecting transmembrane helices M4 and M5 (C45) was prepared to monitor effects of the natural cytoplasmic ligands (i.e., Mg(2+) and/or ATP) binding. We introduced a novel method for the monitoring of the changes in the electrostatic surface potential (ESP) induced by ligand binding, using the quenching of the intrinsic tryptophan fluorescence by acrylamide or iodide. This approach opens a new way to understanding the interactions within the proteins. Our experiments revealed that the C45 conformation in the presence of the ATP (without magnesium) substantially differed from the conformation in the presence of Mg(2+) or MgATP or in the absence of any ligand not only in the sense of geometry but also in the sense of the ESP. Notably, the set of ESP-sensitive residues was different from the set of geometry-sensitive residues. Moreover, our data indicate that the effect of the ligand binding is not restricted only to the close environment of the binding site and that the information is in fact transmitted also to the distal parts of the molecule. This property could be important for the communication between the cytoplasmic headpiece and the cation binding sites located within the transmembrane domain.

  20. Effects of size and ligand density on the chirality transfer from chiral-ligand-capped nanoparticles to nematic liquid crystals

    Science.gov (United States)

    Mori, Taizo; Sharma, Anshul; Nemati, Ahlam; Bergquist, Leah; Hegmann, Torsten

    2017-08-01

    Studies of chiroptical effects of chiral ligand-capped gold nanoparticles (Au NPs) are a fascinating and rapidly evolving field in nanomaterial research with promising applications of such chiral metal NPs in catalysis and metamaterials as well as chiral sensing and separation. The aim of our studies was to seek out a system that not only allows the detection and understanding of Au NP chirality but also permits visualization and ranking — considering size, shape and nature as well as density of the ligand shell — of the extent of chirality transfer to a surrounding medium. Nematic liquid crystal (N-LC) phases are an ideal platform to examine these effects, exhibiting characteristic defect textures upon doping with a chiral additive. To test this, we synthesized series of Au NPs capped with two structurally different chiral ligands and studied well-dispersed mixtures in two nematic liquid crystal hosts. Induced circular dichroism (ICD) spectropolarimetry and polarized light optical microscopy (POM) confirmed that all Au NPs induce chiral nematic (N*-LC) phases, and measurements of the helical pitch as well as calculation of the helical twisting power (HTP) in various cell geometries allowed for an insightful ranking of the efficiency of chirality transfer of all Au NPs as well as their free ligands.

  1. Synthesis of novel '4+1' Tc(III)/Re(III) mixed-ligand complexes with dendritically modified ligands

    International Nuclear Information System (INIS)

    Gniazdowska, E.; Kuenstler, J.U.; Stephan, H.; Pietzsch, H.J.

    2006-01-01

    Coordination chemistry of technetium and rhenium attracts a considerable interest due to the nuclear medicine applications of their radionuclides. Inert, so-called '3+1' or '4+1' technetium/rhenium mixed-ligand complexes open a new way to application of 99 mTc/ 188 Re labeled compounds in tumor diagnosis and therapy. In the presented paper, authors describe the synthesis and study of novel 99 mTc/ 188 Re complexes with dendritically functionalized tetradentate (tripodal chelator 2,2',2''-nitrilotris(ethanethiol), NS 3 and carboxyl group-bearing ligand, NS 3 (COOH) 3 ) and monodentate (dendritically modified isocyanide, CN-R(COOMe) 3 and isocyanide-modified peptide, CN-GGY) ligands. To verify the identity of the prepared n.c.a. complexes, non-radioactive analogous '4+1' Re compounds were synthesized. The experimental data show that a dendritic modification of the tetradentate/monodentate ligands changes the complex lipophilicity and does not influence its stability

  2. The synthesis, structures and characterisation of new mixed-ligand manganese and iron complexes with tripodal, tetradentate ligands

    NARCIS (Netherlands)

    van Gorkum, R.; Berding, J.; Mills, A.M.; Kooijman, H.; Tooke, D.M.; Spek, A.L.; Mutikainen, I.; Turpeinen, U.; Reedijk, J.; Bouwman, E.

    2008-01-01

    The preparation of new manganese and iron complexes with the general formula [M(tripod)(anion)] is described, where M = FeIII or MnIII, “tripod” is a dianionic tetradentate tripodal ligand and the anion is a chelating β-diketonate, 8-oxyquinoline or acetate. The synthesis of this type of complexes

  3. Synthesis and ligand-based reduction chemistry of boron difluoride complexes with redox-active formazanate ligands

    NARCIS (Netherlands)

    Chang, M. -C.; Otten, E.

    2014-01-01

    Mono(formazanate) boron difluoride complexes (LBF2), which show remarkably facile and reversible ligand-based redox-chemistry, were synthesized by transmetallation of bis(formazanate) zinc complexes with boron trifluoride. The one-electron reduction product [LBF2](-)[Cp2Co](+) and a key intermediate

  4. Redesigning an FKBP–ligand interface to generate chemical dimerizers with novel specificity

    OpenAIRE

    Clackson, Tim; Yang, Wu; Rozamus, Leonard W.; Hatada, Marcos; Amara, Jane F.; Rollins, Carl T.; Stevenson, Lauren F.; Magari, Shannon R.; Wood, Susan A.; Courage, Nancy L.; Lu, Xiaode; Cerasoli, Franklin; Gilman, Michael; Holt, Dennis A.

    1998-01-01

    FKBP ligand homodimers can be used to activate signaling events inside cells and animals that have been engineered to express fusions between appropriate signaling domains and FKBP. However, use of these dimerizers in vivo is potentially limited by ligand binding to endogenous FKBP. We have designed ligands that bind specifically to a mutated FKBP over the wild-type protein by remodeling an FKBP-ligand interface to introduce a specificity binding pocket. A compound bearing an ethyl substituen...

  5. Gene Duplication of the zebrafish kit ligand and partitioning of melanocyte development functions to kit ligand a.

    Directory of Open Access Journals (Sweden)

    Keith A Hultman

    2007-01-01

    Full Text Available The retention of particular genes after the whole genome duplication in zebrafish has given insights into how genes may evolve through partitioning of ancestral functions. We examine the partitioning of expression patterns and functions of two zebrafish kit ligands, kit ligand a (kitla and kit ligand b (kitlb, and discuss their possible coevolution with the duplicated zebrafish kit receptors (kita and kitb. In situ hybridizations show that kitla mRNA is expressed in the trunk adjacent to the notochord in the middle of each somite during stages of melanocyte migration and later expressed in the skin, when the receptor is required for melanocyte survival. kitla is also expressed in other regions complementary to kita receptor expression, including the pineal gland, tail bud, and ear. In contrast, kitlb mRNA is expressed in brain ventricles, ear, and cardinal vein plexus, in regions generally not complementary to either zebrafish kit receptor ortholog. However, like kitla, kitlb is expressed in the skin during stages consistent with melanocyte survival. Thus, it appears that kita and kitla have maintained congruent expression patterns, while kitb and kitlb have evolved divergent expression patterns. We demonstrate the interaction of kita and kitla by morpholino knockdown analysis. kitla morphants, but not kitlb morphants, phenocopy the null allele of kita, with defects for both melanocyte migration and survival. Furthermore, kitla morpholino, but not kitlb morpholino, interacts genetically with a sensitized allele of kita, confirming that kitla is the functional ligand to kita. Last, we examine kitla overexpression in embryos, which results in hyperpigmentation caused by an increase in the number and size of melanocytes. This hyperpigmentation is dependent on kita function. We conclude that following genome duplication, kita and kitla have maintained their receptor-ligand relationship, coevolved complementary expression patterns, and that

  6. A Langmuir study of novel Schiff Base ligand for ion sensor application

    African Journals Online (AJOL)

    Two novel Schiff Base ligands are used in this work. These amphiphilic ligands were being chosen because of the suitability in forming Langmuir film by using Langmuir-Blodgett (LB) technique. Characterizations of these ligands were carried out through LB technique to obtain the surface pressure-mean molecular area ...

  7. Design, Testing and Kinetic Analysis of Bulky Monodentate Phosphorus Ligands in the Mizoroki-Heck Reaction

    NARCIS (Netherlands)

    Dodds, Deborah L.; Boele, Maarten D. K.; van Strijdonck, Gino P. F.; de Vries, Johannes G.; van Leeuwen, Piet W. N. M.; Kamer, Paul C. J.

    A series of new monodentate phosphane ligands 2 have been evaluated in the MizorokiHeck arylation reaction of iodobenzene and styrene and compared with our previously reported ligands, 1, 3 and 4. The concept of rational ligand design is discussed, and we describe how the performance of this new

  8. Phosphorus ligand imaging with two-photon fluorescence spectroscopy: towards rational catalyst immobilization

    NARCIS (Netherlands)

    Marras, F.; Kluwer, A.M.; Siekierzycka, J.R.; Vozza, A.; Brouwer, A.M.; Reek, J.N.H.

    2010-01-01

    Spotless catalysts: Ligand immobilization was studied by two-photon fluorescence microscopy with a fluorescent nixantphos ligand as probe (see picture). In the immobilization process ligand aggregates form in solution and are deposited on the support, where they appear as bright spots in

  9. Flow Cytometry-Based Bead-Binding Assay for Measuring Receptor Ligand Specificity

    NARCIS (Netherlands)

    Sprokholt, Joris K.; Hertoghs, Nina; Geijtenbeek, Teunis B. H.

    2016-01-01

    In this chapter we describe a fluorescent bead-binding assay, which is an efficient and feasible method to measure interaction between ligands and receptors on cells. In principle, any ligand can be coated on fluorescent beads either directly or via antibodies. Binding between ligand-coated beads

  10. Olefin Metathesis Mediated By: - Schiff Base Ru-Alkylidenes -Ru-Alkylidenes Bearing Unsymmetrical NH Ligands

    Science.gov (United States)

    Monsaert, Stijn; Voort, Pascal Van Der; Ledoux, Nele; Allaert, Bart; Drozdzak, Renata; Verpoort, Francis

    The classic Grubbs second-generation complex 2 was modified through 1. The introduction of a bidentate Schiff base ligand 2. Changes in the amino side groups of the NHC ligand Representative olefin metathesis test reactions show the effects induced by the ligand modifications and demonstrate some interesting new properties of the described catalysts. catalysts.

  11. Amino acids as chiral anionic ligands for ruthenium based asymmetric olefin metathesis.

    Science.gov (United States)

    Ivry, Elisa; Ben-Asuly, Amos; Goldberg, Israel; Lemcoff, N Gabriel

    2015-03-04

    Several amino acid ligands were introduced into the Hoveyda-Grubbs 2nd generation complex by a facile anionic ligand exchange. The chiral pre-catalysts obtained displayed enantioselectivity in asymmetric ring-closing and ring-opening cross-metathesis reactions. Reduction of the lability of the carboxylate ligands was found to be cardinal for improving the observed enantiomeric product enrichment.

  12. Computational approaches to modeling receptor flexibility upon ligand binding: Application to interfacially activated enzymes

    DEFF Research Database (Denmark)

    Wade, R.C.; Sobolev, V.; Ortiz, A.R. .

    1998-01-01

    Receptors generally undergo conformational change upon ligand binding. We describe how fairly simple techniques may be used in docking and design studies to account for some of the changes in the conformations of proteins on ligand binding. Simulations of protein-ligand interactions that give...

  13. DMPD: Endogenous ligands of Toll-like receptors. [Dynamic Macrophage Pathway CSML Database

    Lifescience Database Archive (English)

    Full Text Available 15178705 Endogenous ligands of Toll-like receptors. Tsan MF, Gao B. J Leukoc Biol. ...2004 Sep;76(3):514-9. Epub 2004 Jun 3. (.png) (.svg) (.html) (.csml) Show Endogenous ligands of Toll-like re...ceptors. PubmedID 15178705 Title Endogenous ligands of Toll-like receptors. Authors Tsan MF, Gao B. Publicat

  14. Comprehensive assessment of flexible-ligand docking algorithms: current effectiveness and challenges.

    Science.gov (United States)

    Huang, Sheng-You

    2017-03-14

    Protein-ligand docking has been playing an important role in modern drug discovery. To model drug-target binding in real systems, a number of flexible-ligand docking algorithms with different sampling strategies and scoring methods have been subsequently developed over the past three decades, while rigid-ligand docking is still being used because of its compelling computational efficiency. Here, a comprehensive assessment has been conducted to investigate the effectiveness of flexible-ligand docking versus rigid-ligand docking for three representative docking algorithms (global optimization, incremental construction and multi-conformer docking) in virtual screening and pose prediction on the Directory of Useful Decoys. It was found that overall flexible-ligand docking did not achieve a statistically significant improvement in enrichments over rigid-ligand docking in virtual screening, but all docking programs significantly improved the success rates when considering ligand flexibility in pose prediction. The worse effectiveness of flexible-ligand docking in virtual screening than in pose prediction suggests that the challenges of current docking algorithms exist in ranking more than docking, although the use of flexible-ligand docking in virtual screening was justified by its better effectiveness for more flexible ligand in virtual screening. Challenges for scoring, including internal energy, charge polarization, entropy and flexibility, were investigated and discussed. An empirical way was also proposed to consider loss of ligand conformational entropy for virtual screening. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  15. Understanding ligand effects in gold clusters using mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Grant E.; Laskin, Julia

    2016-01-01

    This review summarizes recent research on the influence of phosphine ligands on the size, stability, and reactivity of gold clusters synthesized in solution. Sub-nanometer clusters exhibit size- and composition-dependent properties that are unique from those of larger nanoparticles. The highly tunable properties of clusters and their high surface-to-volume ratio make them promising candidates for a variety of technological applications. However, because “each-atom-counts” toward defining cluster properties it is critically important to develop robust synthesis methods to efficiently prepare clusters of predetermined size. For decades phosphines have been known to direct the size-selected synthesis of gold clusters. Despite the preparation of numerous species it is still not understood how different functional groups at phosphine centers affect the size and properties of gold clusters. Using electrospray ionization mass spectrometry (ESI-MS) it is possible to characterize the effect of ligand substitution on the distribution of clusters formed in solution at defined reaction conditions. In addition, ligand exchange reactions on preformed clusters may be monitored using ESI-MS. Collision induced dissociation (CID) may also be employed to obtain qualitative insight into the fragmentation of mixed ligand clusters and the relative binding energies of differently substituted phosphines. Quantitative ligand binding energies and cluster stability may be determined employing surface induced dissociation (SID) in a custom-built Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR-MS). Rice-Ramsperger-Kassel-Marcus (RRKM) based modeling of the SID data allows dissociation energies and entropy values to be extracted that may be compared with the results of high-level theoretical calculations. The charge reduction and reactivity of atomically precise gold clusters, including partially ligated species generated in the gas-phase by in source CID, on well

  16. Understanding ligand effects in gold clusters using mass spectrometry.

    Science.gov (United States)

    Johnson, Grant E; Laskin, Julia

    2016-06-21

    This review summarizes recent research on the influence of phosphine ligands on the size, stability, and reactivity of gold clusters synthesized in solution. Sub-nanometer clusters exhibit size- and composition-dependent properties that are unique from those of larger nanoparticles. The highly tunable properties of clusters and their high surface-to-volume ratio make them promising candidates for a variety of technological applications. However, because "each-atom-counts" toward defining cluster properties it is critically important to develop robust synthesis methods to efficiently prepare clusters of predetermined size. For decades phosphines have been known to direct the size-selected synthesis of gold clusters. Despite the preparation of numerous species it is still not understood how different functional groups at phosphine centers affect the size and properties of gold clusters. Using electrospray ionization mass spectrometry (ESI-MS) it is possible to characterize the effect of ligand substitution on the distribution of clusters formed in solution at defined reaction conditions. In addition, ligand exchange reactions on preformed clusters may be monitored using ESI-MS. Collision induced dissociation (CID) may also be employed to obtain qualitative insight into the fragmentation of mixed ligand clusters and the relative binding energies of differently substituted phosphines. Quantitative ligand binding energies and cluster stability may be determined employing surface induced dissociation (SID) in a custom-built Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR-MS). Rice-Ramsperger-Kassel-Marcus (RRKM) based modeling of the SID data allows dissociation energies and entropy values to be extracted. The charge reduction and reactivity of atomically precise gold clusters, including partially ligated species generated in the gas-phase by in source CID, on well-defined surfaces may be explored using ion soft landing (SL) in a custom

  17. I. The synthesis and coordination chemistry of novel 6pi-electron ligands. II. Improvement of student writing skills in general chemistry lab reports through the use of Calibrated Peer Review

    Science.gov (United States)

    William, Wilson Ngambeki

    Abstract I. The goal of this study was to synthesize and characterize a set of coordination complexes containing 6pi-cationic ligands. These compounds could be extremely useful as catalysts for the polymerization of olefins that are widely used in the synthetic polymer industry. The original strategy was to synthesize the 6pi-cationic ligands using (Ph2P) 3CH (1) and (Me2P)3CH (10) as precursors; however, both precursors 1 and 10 were found to be highly reactive leading to the fragmentation products (Ph 2P)2CH2 and (Me2P)2CH 2 respectively. In trying to control the reactivity, precursor 1 was coordinated to the group 6B metal carbonyl in two modes, Mo(CO)3(C 2H5CN)(Ph2P)2CHPPh2 and W(CO) 3(C2H5CN)(Ph2P)2CHPPh 2. In these novel compounds, two of the three phosphorus atoms are chelated to the metal. These complexes were isolated and characterized by X-ray analysis, elemental analysis, NMR and infrared spectroscopy. When these metal complexes were reacted with B(C6F5)3, the complexes were stabilized, and no molecular fragmentation was observed. Instead, a second mode of coordination was observed by 31P{1H} NMR spectroscopy, where all three phosphorus atoms are bonded to the metal in a tridentate fashion, yielding the novel product EtCNB(C6F 5)3, which was characterized by X-ray analysis. However, because there was no hydride abstraction from the tertiary carbon in either compound, further studies will be required to develop a strategy for hydride abstraction to produce a cationic ligand. Another strategy for the synthesis of 6pi-cationic ligands was to directly synthesize the halogenated version of the tertiary carbon atom of compound 10. Fractional recrystallization of the crude product yielded two compounds of 2,4,6-trimethypyridinium bromide and (PMe2)3CBr. (PMe2)3CBr was determined to be pure as revealed by 31P{1H} NMR. It is expected that oxidation of the bromide should yield the 6pi-cationic ligand. In the next strategy, density function theory calculations (DFT

  18. Age dependent accumulation patterns of advanced glycation end product receptor (RAGE) ligands and binding intensities between RAGE and its ligands differ in the liver, kidney, and skeletal muscle.

    Science.gov (United States)

    Son, Myeongjoo; Chung, Wook-Jin; Oh, Seyeon; Ahn, Hyosang; Choi, Chang Hu; Hong, Suntaek; Park, Kook Yang; Son, Kuk Hui; Byun, Kyunghee

    2017-01-01

    Much evidence indicates receptor for advanced glycation end products (RAGE) related inflammation play essential roles during aging. However, the majority of studies have focused on advanced glycation end products (AGEs) and not on other RAGE ligands. In the present study, the authors evaluated whether the accumulation of RAGE ligands and binding intensities between RAGE and its ligands differ in kidney, liver, and skeletal muscle during aging. In C57BL/6 N mice aged 12 weeks, 12 months, and 22 months, ligands accumulation, binding intensities between RAGE and its ligands, activated macrophage infiltration, M1/M2 macrophage expression, glyoxalase-1expression, and signal pathways related to inflammation were evaluated. The RAGE ligands age-associated accumulation patterns were found to be organ dependent. Binding intensities between RAGE and its ligands in kidney and liver increased with age, but those in skeletal muscle were unchanged. Infiltration of activated macrophages in kidney and liver increased with age, but infiltration in the skeletal muscle was unchanged. M1 expression increased and M2 and glyoxalase-1 expression decreased with age in kidney and liver, but their expressions in skeletal muscle were not changed. These findings indicate patterns of RAGE ligands accumulation, RAGE/ligands binding intensities, or inflammation markers changes during aging are organs dependent.

  19. A Structural Switch between Agonist and Antagonist Bound Conformations for a Ligand-Optimized Model of the Human Aryl Hydrocarbon Receptor Ligand Binding Domain

    Directory of Open Access Journals (Sweden)

    Arden Perkins

    2014-10-01

    Full Text Available The aryl hydrocarbon receptor (AHR is a ligand-activated transcription factor that regulates the expression of a diverse group of genes. Exogenous AHR ligands include the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, which is a potent agonist, and the synthetic AHR antagonist N-2-(1H-indol-3ylethyl-9-isopropyl-2- (5-methylpyridin-3-yl-9H-purin-6-amine (GNF351. As no experimentally determined structure of the ligand binding domain exists, homology models have been utilized for virtual ligand screening (VLS to search for novel ligands. Here, we have developed an “agonist-optimized” homology model of the human AHR ligand binding domain, and this model aided in the discovery of two human AHR agonists by VLS. In addition, we performed molecular dynamics simulations of an agonist TCDD-bound and antagonist GNF351-bound version of this model in order to gain insights into the mechanics of the AHR ligand-binding pocket. These simulations identified residues 307–329 as a flexible segment of the AHR ligand pocket that adopts discrete conformations upon agonist or antagonist binding. This flexible segment of the AHR may act as a structural switch that determines the agonist or antagonist activity of a given AHR ligand.

  20. Mesoporous organosilica nanotubes containing a chelating ligand in their walls

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    Xiao Liu

    2014-11-01

    Full Text Available We report the synthesis of organosilica nanotubes containing 2,2′-bipyridine chelating ligands within their walls, employing a single-micelle-templating method. These nanotubes have an average pore diameter of 7.8 nm and lengths of several hundred nanometers. UV-vis absorption spectra and scanning transmission electron microscopy observations of immobilized nanotubes with an iridium complex on the bipyridine ligands showed that the 2,2′-bipyridine groups were homogeneously distributed in the benzene-silica walls. The iridium complex, thus, immobilized on the nanotubes exhibited efficient catalytic activity for water oxidation using Ce4+, due to the ready access of reactants to the active sites in the nanotubes.