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Nobutaka Tani - One of the best experts on this subject based on the ideXlab platform.

  • development of selective low density lipoprotein ldl apheresis system immobilized Polyanion as ldl specific adsorption for ldl apheresis system
    Therapeutic Apheresis, 2000
    Co-Authors: Nobutaka Tani
    Abstract:

    :Guest Editor's Introduction: The binding site of the human LDL receptor is rich in anionic amino acids, and interacts with apolipoprotein-B by the electrostatic force. Therefore, anionic ligands could be used for the selective adsorption of LDL without HDL adsorption. Based upon this concept, Kaneka Co. developed LDL adsorbent. The adsorbent named Loposorber consists of microporous cellulose beads which immobilized dextrane sulfate with a molecular weight of several thousands. This paper describes the basic study for the selection of Polyanions, in vitro adsorption characteristics, and the references of initial clinical applications. This paper was printed in Artificial Organs, vol. 20, page 922–929 (1996), and reprinted here with permission. Low-density lipoprotein (LDL) is widely recognized as one of the major risk factors for developing coronary heart diseases. Despite intensive development of LDL-lowering drugs, there still exist those patients with refractory hyperlipidemia whose plasma LDL levels are not sufficiently lowered by drugs. LDL apheresis, direct removal of plasma LDL from circulating blood, is thought to be the most promising treatment for such refractory patients. Various techniques, such as the use of an immunoadsorbent utilizing an anti-LDL antibody, have been used in an attempt to achieve the selective removal of LDL. However, none were widely used because of complications, poor selectivity, and so forth. To establish a safe and effective LDL apheresis system, we chose a synthetic affinity adsorbent as the LDL-removing device. Synthetic Polyanion compounds were used as the affinity ligands for LDL adsorbent to simulate the anion-rich sequence of LDL binding sites in the human LDL receptor. Among various Polyanion compounds, those Polyanions with sulfate or sulfonate groups and hydrophilic backbone were found to have a strong affinity for LDL. In contrast, Polyanions with carboxyl groups showed poor affinity. Dextran sulfate (DS) was selected as the affinity ligand of LDL adsorbent for its high affinity and low toxicity. The influence of its charge density and molecular weight on its affinity for LDL was suitable. The affinity rapidly increased as the charge density increased, then, reached a constant value. Little affinity was found for either the DS monomer (glucose sulfate) or DS with a molecular weight higher than 104 daltons whereas DS with molecular weights in the midrange showed strong affinity. DS with a midrange molecular weight was immobilized on cellulose hard gel to give LDL adsorbent clinical application. The adsorbent demonstrated an excellent selectivity for LDL and very low density lipoprotein (VLDL) in vitro. Adsorption of high-density lipoprotein and major plasma proteins was almost negligible. Additional study of the LDL-binding mechanism revealed that DS directly interacts with positively charged sites on LDL, which demonstrates that the nature of the interaction is the same as that of the LDL receptor. An LDL adsorption column (Liposorber) packed with an LDL adsorbent and polysulfone hollow-fiber plasma separator (Sulflux) was developed as an efficient LDL apheresis system. Clinical investigation proved that this system is capable of intensively lowering the plasma LDL level without affecting major plasma components.

  • development of selective low density lipoprotein ldl apheresis system immobilized Polyanion as ldl specific adsorption for ldl apheresis system
    Artificial Organs, 1996
    Co-Authors: Nobutaka Tani
    Abstract:

    : Low-density lipoprotein (LDL) is widely recognized as one of the major risk factors for developing coronary heart diseases. Despite intensive development of LDL-lowering drugs, there still exist those patients with refractory hyperlipidemia whose plasma LDL levels are not sufficiently lowered by drugs. LDL apheresis, direct removal of plasma LDL from circulating blood, is thought to be the most promising treatment for such refractory patients. Various techniques, such as the use of an im-munoadsorbent utilizing an anti-LDL antibody, have been used in an attempt to achieve the selective removal of LDL. However, none were widely used because of complications, poor selectivity, and so forth. To establish a safe and effective LDL apheresis system, we chose a synthetic affinity adsorbent as the LDL-removing device. Synthetic Polyanion compounds were used as the affinity ligands for LDL adsorbent to simulate the anion-rich sequence of LDL binding sites in the human LDL receptor. Among various Polyanion compounds, those Polyanions with sulfate or sulfonate groups and hydrophilic backbone were found to have strong affinity for LDL. In contrast, Polyanions with carboxyl groups showed poor affinity. Dextran sulfate (DS) was selected as the affinity ligand of LDL adsorbent for its high affinity and low toxicity. The influence of its charge density and molecular weight on its affinity for LDL was suitable. The affinity rapidly increased as the charge density increased, then, reached a constant value. Little affinity was found for either the DS monomer (glucose sulfate) or DS with a molecular weight higher than 104 daltons whereas DS with molecular weights in the midrange showed strong affinity. DS with a midrange molecular weight was immobilized on cellulose hard gel to give LDL adsorbent clinical application. The adsorbent demonstrated an excellent selectivity for LDL and very low density lipoprotein (VLDL) in vitro. Adsorption of high-density lipoprotein and major plasma proteins was almost negligible. Additional study of the LDL-binding mechanism revealed that DS directly interacts with positively charged sites on LDL, which demonstrates that the nature of the interaction is the same as that of LDL receptor. An LDL adsorption column (Liposorber) packed with an LDL adsorbent and polysulfone hollow-fiber plasma separator (Sulflux) was developed as an efficient LDL apheresis system. Clinical investigation proved that this system is capable of intensively lowering the plasma LDL level without affecting major plasma components.

Andreas Greinacher - One of the best experts on this subject based on the ideXlab platform.

  • platelets kill bacteria by bridging innate and adaptive immunity via platelet factor 4 and fcγriia
    Journal of Thrombosis and Haemostasis, 2018
    Co-Authors: Raghavendra Palankar, Krystin Krauel, Thomas P Kohler, Jan Wesche, Sven Hammerschmidt, Andreas Greinacher
    Abstract:

    Essentials Human platelets specifically interact with IgG opsonized bacteria through FcγRIIA. Platelet factor 4 (PF4) binds to Polyanions (P) and undergoes a conformational change. Anti-PF4/P IgG opsonizes PF4-coated Gram-positive and Gram-negative bacteria. Platelets specifically kill E.coli opsonized with PF4 and human anti-PF4/P IgG. SUMMARY Background Activated platelets release the chemokine platelet factor 4 (PF4) stored in their granules. PF4 binds to Polyanions (P) on bacteria, undergoes a conformational change and exposes neoepitopes. These neoepitopes induce production of anti-PF4/P antibodies. As PF4 binds to a variety of bacteria, anti-PF4/P IgG can bind and opsonize several bacterial species. Objective Here we investigated whether platelets are able to kill bacteria directly after recognizing anti-PF4/P IgG opsonized bacteria in the presence of PF4 via their FcγRIIA. Methods Using platelet-bacteria suspension co-culture experiments and micropatterns with immobilized viable bacteria, in combination with pharmacological inhibitors and human anti- PF4/P IgG we analyzed the role of platelet-mediated killing of bacteria. Results In the presence of PF4, human anti-PF4/P IgG and platelets, E. coli killing (> 50%) with colony forming units (CFU mL-1 ) 0.71 × 104 ± 0.19 was observed compared with controls incubated only with anti-PF4/P IgG (CFU mL-1 3.4 × 104 ± 0.38). Blocking of platelet FcγRIIA using mAb IV.3 (CFU mL-1 2.5 × 104 ± 0.45), or integrin αIIbβ3 (CFU mL-1 2.26 × 104 ± 0.31), or disruption of cytoskeletal functions (CFU mL-1 2.7 × 104 ± 0.4) markedly reduced E. coli killing by this mechanism. Our observation of E. coli killing by platelets on micropatterned arrays is compatible with the model that platelets kill bacteria by covering them, actively concentrating them into the area under their granulomere and then releasing antimicrobial substances of platelet α-granules site directed towards bacteria. Conclusion These findings collectively indicate that by bridging of innate and adaptive immune mechanisms, platelets and anti-PF4/Polyanion antibodies cooperate in an antibacterial host response.

  • anti platelet factor 4 Polyanion antibodies mediate a new mechanism of autoimmunity
    Nature Communications, 2017
    Co-Authors: Thihuong Nguyen, Mihaela Delcea, Nikolay Medvedev, Andreas Greinacher
    Abstract:

    Antibodies recognizing complexes of the chemokine platelet factor 4 (PF4/CXCL4) and Polyanions (P) opsonize PF4-coated bacteria hereby mediating bacterial host defense. A subset of these antibodies may activate platelets after binding to PF4/heparin complexes, causing the prothrombotic adverse drug reaction heparin-induced thrombocytopenia (HIT). In autoimmune-HIT, anti-PF4/P-antibodies activate platelets in the absence of heparin. Here we show that antibodies with binding forces of approximately 60-100 pN activate platelets in the presence of Polyanions, while a subset of antibodies from autoimmune-HIT patients with binding forces ≥100 pN binds to PF4 alone in the absence of Polyanions. These antibodies with high binding forces cluster PF4-molecules forming antigenic complexes which allow binding of Polyanion-dependent anti-PF4/P-antibodies. The resulting immunocomplexes induce massive platelet activation in the absence of heparin. Antibody-mediated changes in endogenous proteins that trigger binding of otherwise non-pathogenic (or cofactor-dependent) antibodies may also be relevant in other antibody-mediated autoimmune disorders.

  • characterisation of the conformational changes in platelet factor 4 induced by Polyanions towards in vitro prediction of antigenicity
    Thrombosis and Haemostasis, 2014
    Co-Authors: Sven Brandt, Andreas Greinacher, Krystin Krauel, Christiane A Helm, Kay E Gottschalk, Thomas Renne, Stephan Block
    Abstract:

    Heparin-induced thrombocytopenia (HIT) is the most frequent drug-induced immune reaction affecting blood cells. Its antigen is formed when the chemokine platelet factor 4 (PF4) complexes with Polyanions. By assessing Polyanions of varying length and degree of sulfation using immunoassay and circular dichroism (CD)-spectroscopy, we show that PF4 structural changes resulting in antiparallel β-sheet content >30% make PF4/Polyanion complexes antigenic. Further, we found that polyphosphates (polyP-55) induce antigenic changes on PF4, whereas fondaparinux does not. We provide a model suggesting that conformational changes exposing antigens on PF4/Polyanion complexes occur in the hairpin involving AA 32–38, which form together with C-terminal AA (66–70) of the adjacent PF4 monomer a continuous patch on the PF4 tetramer surface, explaining why only tetrameric PF4 molecules express “HIT antigens”. The correlation of antibody binding in immunoassays with PF4 structural changes provides the intriguing possibility that CD-spectroscopy could become the first antibody-independent, in vitro method to predict potential immunogenicity of drugs. CD-spectroscopy could identify compounds during preclinical drug development that induce PF4 structural changes correlated with antigenicity. The clinical relevance can then be specifically addressed during clinical trials. Whether these findings can be transferred to other endogenous proteins requires further studies.

  • platelet factor 4 binding to lipid a of gram negative bacteria exposes pf4 heparin like epitopes
    Blood, 2012
    Co-Authors: Krystin Krauel, Sven Brandt, Andreas Greinacher, Claudia Weber, Ulrich Zahringer, Uwe Mamat, Sven Hammerschmidt
    Abstract:

    The positively charged chemokine platelet factor 4 (PF4) forms immunogenic complexes with heparin and other Polyanions. Resulting antibodies can induce the adverse drug effect heparin-induced thrombocytopenia. PF4 also binds to bacteria, thereby exposing the same neoantigen(s) as with heparin. In this study, we identified the negatively charged lipopolysaccharide (LPS) as the PF4 binding structure on Gram-negative bacteria. We demonstrate by flow cytometry that mutant bacteria with progressively truncated LPS structures show increasingly enhanced PF4 binding activity. PF4 bound strongest to mutants lacking the O-antigen and core structure of LPS, but still exposing lipid A on their surfaces. Strikingly, PF4 bound more efficiently to bisphosphorylated lipid A than to monophosphorylated lipid A, suggesting that phosphate residues of lipid A mediate PF4 binding. Interactions of PF4 with Gram-negative bacteria, where only the lipid A part of LPS is exposed, induce epitopes on PF4 resembling those on PF4/heparin complexes as shown by binding of human anti-PF4/heparin antibodies. As both the lipid A on the surface of Gram-negative bacteria and the amino acids of PF4 contributing to Polyanion binding are highly conserved, our results further support the hypothesis that neoepitope formation on PF4 after binding to bacteria is an ancient host defense mechanism.

  • close approximation of two platelet factor 4 tetramers by charge neutralization forms the antigens recognized by hit antibodies
    Arteriosclerosis Thrombosis and Vascular Biology, 2006
    Co-Authors: Andreas Greinacher, Manesh Gopinadhan, Jensuwe Gunther, Mahmoud A Omeradam, Ulrike Strobel, Theodore E Warkentin, Georg Papastavrou, Werner Weitschies, Christiane A Helm
    Abstract:

    Objective— Heparin-induced thrombocytopenia (HIT) is a prothrombotic drug reaction caused by antibodies that recognize positively charged platelet factor 4 (PF4), bound to the Polyanion, heparin. The resulting immune complexes activate platelets. Unfractionated heparin (UFH) causes HIT more frequently than low-molecular-weight heparin (LMWH), whereas the smallest heparin-like molecule (the pentasaccharide, fondaparinux), induces anti-PF4/heparin antibodies as frequently as LMWH, but without exhibiting cross-reactivity with these antibodies. To better understand these findings, we analyzed the molecular structure of the complexes formed between PF4 and UFH, LMWH, or fondaparinux. Methods and Results— By atomic force microscopy and photon correlation spectroscopy, we show that with any of the 3 Polyanions, but in the order, UFH>LMWH≫fondaparinux—PF4 forms clusters in which PF4 tetramers become closely apposed, and to which anti-PF4/heparin antibodies bind. By immunoassay, HIT antibodies bind strongly to PF4/H/PF4 complexes, but only weakly to single PF4/heparin molecules. Conclusion— HIT antigens are formed when charge neutralization by Polyanion allows positively charged PF4 tetramers to undergo close approximation. Whereas such a model could explain why all 3 Polyanions form antibodies with similar specificities, the striking differences in the relative size and amount of complexes formed likely correspond to the observed differences in immunogenicity (UFH>LMWH≈fondaparinux) and clinically relevant cross-reactivity (UFH>LMWH≫fondaparinux).

Ulrich Kortz - One of the best experts on this subject based on the ideXlab platform.

  • incorporation of transition metal ion guests co2 ni2 cu2 zn2 into the ti2 containing 18 tungsto 2 arsenate iii monolacunary host
    European Journal of Inorganic Chemistry, 2016
    Co-Authors: Kaiyao Wang, Bassem S. Bassil, Xiaolin Xing, Bineta Keita, Jasleen K Bindra, Kariem Diefenbach, Naresh S Dalal, Ulrich Kortz
    Abstract:

    The four 18-tungsto-2-arsenates(III) [MII(H2O)(TiIVO)2(α-AsIIIW9O33)2]12– [M = Co (CoTi2), Ni (NiTi2), Cu (CuTi2), Zn (ZnTi2)] were rationally synthesized by treating the respective divalent metal ions with the monolacunary, dititanium(IV)-containing Polyanion precursor [(TiIVO)2(α-AsIIIW9O33)2]14– (Ti2) in aqueous solution. All four Polyanions are isostructural and correspond to dimers with two Ti4+ and one M2+ ion sandwiched between two [α-AsIIIW9O33]9– units. The compounds were characterized in the solid state by single-crystal XRD, infrared spectroscopy, thermogravimetric analysis, and elemental analysis and in solution by UV/Vis and NMR spectroscopy as well as electrochemistry. Variable-temperature magnetic susceptibility and variable-field magnetization characterization of the paramagnetic derivatives indicate antiferromagnetic interactions between nearest neighbors in the solid state. The resolved hyperfine structure obtained from multifrequency EPR measurements on CuTi2 (which exhibits a Jahn–Teller effect) in the solid state lead us to assign the ground state mainly to the Cu dx²–y² orbital. Despite the fact that the four Polyanions are isostructural and have the same overall negative charge, the cyclic voltammetric patterns featuring their chemically reversible reduction waves display distinct features. Electrocatalytic studies demonstrate that the activities of the Polyanions towards nitrate reduction are strikingly influenced by the nature of the substituent metal ion.

  • Polyoxomolybdodiphosphonates: Examples Incorporating Ethylidenepyridines
    2016
    Co-Authors: Abhishek Banerjee, Farah S. Raad, Nina Vankova, Bassem S. Bassil, Thomas Heine, Ulrich Kortz
    Abstract:

    We have synthesized and structurally characterized three pyridylethylidene-functionalized diphosphonate-containing polyoxomolybdates, [{MoVIO3}2{MoV2O4}{HO3PC(O)(CH2-3-C5NH4)PO3}2]6– (1), [{MoVI2O6}2{MoV2O4}{O3PC(O)(CH2-3-C5NH4)PO3}2]8– (2), and [{MoV2O4(H2O)}4{O3PC(O)(CH2-3-C5NH4)PO3}4]12– (3). Polyanions 1–3 were prepared in a one-pot reaction of the dinuclear, dicationic {MoV2O4(H2O)6}2+ with 1-hydroxo-2-(3-pyridyl)ethylidenediphosphonate (Risedronic acid) in aqueous solution. Polyanions 1 and 2 are mixed-valent MoVI/V species with open tetranuclear and hexanuclear structures, respectively, containing two diphosphonate groups. Polyanion 3 is a cyclic octanuclear structure based on four {MoV2O4(H2O)} units and four diphosphonates. Polyanions 1 and 2 crystallized as guanidinium salts [C(NH2)3]5H[{MoVIO3}2{MoV2O4}{HO3PC(O)(CH2-3-C5NH4)PO3}2]·13H2O (1a) and [C(NH2)3]6H2[{MoVI2O6}2{MoV2O4}{O3PC(O)(CH2-3-C5NH4)PO3}2]·10H2O (2a), whereas Polyanion 3 crystallized as a mixed sodium–guanidinium salt, Na8[C(NH2)3]4[{MoV2O4(H2O)}4{O3PC(O)(CH2-3-C5NH4)PO3}4]·8H2O (3a). The compounds were characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, and thermogravimetric and elemental analyses. The formation of Polyanions 1 and 3 is very sensitive to the pH value of the reaction solution, with exclusive formation of 1 above pH 7.4 and 3 below pH 6.6. Detailed solution studies by multinuclear NMR spectrometry were performed to study the equilibrium between these two compounds. Polyanion 2 was insoluble in all common solvents. Detailed computational studies on the solution phases of 1 and 3 indicated the stability of these Polyanions in solution, in complete agreement with the experimental findings

  • Gallium(III)-Containing, Sandwich-Type Heteropolytungstates: Synthesis, Solution Characterization, and Hydrolytic Studies toward Phosphoester and Phosphoanhydride Bond Cleavage
    2016
    Co-Authors: Balamurugan Kandasamy, Bassem S. Bassil, Stef Vanhaecht, Fiona Marylyn Nkala, Tessa Beelen, Tatjana N. Parac-vogt, Ulrich Kortz
    Abstract:

    The gallium­(III)-containing heteropolytungstates [Ga4(H2O)10(β-XW9O33)2]6– (X = AsIII, 1; SbIII, 2) were synthesized in aqueous acidic medium by reaction of Ga3+ ions with the trilacunary, lone-pair-containing [XW9O33]9–. Polyanions 1 and 2 are isostructural and crystallized as the hydrated sodium salts Na6[Ga4(H2O)10­(β-AsW9O33)2]·28H2O (Na-1) and Na6[Ga4(H2O)10­(β-SbW9O33)2]·30H2O (Na-2) in the monoclinic space group P21/c, with unit cell parameters a = 16.0218(12) Å, b = 15.2044(10) Å, c = 20.0821(12) Å, and β = 95.82(0)°, as well as a = 16.0912(5) Å, b = 15.2178(5) Å, c = 20.1047(5) Å, and β = 96.2(0)°, respectively. The corresponding tellurium­(IV) derivative [Ga4(H2O)10­(β-TeW9O33)2]4– (3) was also prepared, by direct reaction of sodium tungstate, tellurium­(IV) oxide, and gallium nitrate. Polyanion 3 crystallized as the mixed rubidium/sodium salt Rb2Na2[Ga4(H2O)10­(β-TeW9O33)2]·28H2O (RbNa-3) in the triclinic space group P1̅ with unit cell parameters a = 12.5629(15) Å, b = 13.2208(18) Å, c = 15.474(2) Å, α = 80.52(1)°, β = 84.37(1)°, and γ = 65.83(1)°. All Polyanions 1–3 were characterized in the solid state by single-crystal XRD, FT-IR, TGA, and elemental analysis, and Polyanion 2 was also characterized in solution by 183W NMR and UV–vis spectroscopy. Polyanion 2 was used as a homogeneous catalyst toward adenosine triphosphate (ATP) and the DNA model substrate 4-nitrophenylphosphate, monitored by 1H and 31P NMR spectroscopy. The encapsulated gallium­(III) centers in 2 promote the Lewis acidic synergistic activation of the hydrolysis of ATP and DNA model substrates at a higher rate in near-physiological conditions. A strong interaction of 2 with the P–O bond of ATP was evidenced by changes in chemical shift values and line broadening of the 31P nucleus in ATP upon addition of the Polyanion

  • ti2 containing 18 tungsto 2 arsenate iii monolacunary host and the incorporation of a phenylantimony iii guest
    Inorganic Chemistry, 2015
    Co-Authors: Kaiyao Wang, Bassem S. Bassil, Xiaolin Xing, Ali Haider, Bineta Keita, Guangjin Zhang, Cristian Silvestru, Ulrich Kortz
    Abstract:

    The novel Ti-2-containing, sandwich-type 18-tungsto-2-arsenate(III) [ ((TiO)-O-IV)(2) (alpha-(AsW9O33)-W-III)(2)](14-) (1) was successfully synthesized by the reaction of [TiO](2+) species with [alpha-(AsW9O33)-W-III](9-). The monolacunary Polyanion 1 is solution-stable, and a further reaction with 1 equiv of phenylantimony(III) dichloride resulted in [C6H5SbIII((TiO)-O-IV)(2)(alpha-(AsW9O33)-W-III)(2)](12-) (2). Both Polyanions 1 and 2 were structurally characterized in the solid state and solution. Electrochemical studies were also performed on both Polyanions.

Bassem S. Bassil - One of the best experts on this subject based on the ideXlab platform.

  • incorporation of transition metal ion guests co2 ni2 cu2 zn2 into the ti2 containing 18 tungsto 2 arsenate iii monolacunary host
    European Journal of Inorganic Chemistry, 2016
    Co-Authors: Kaiyao Wang, Bassem S. Bassil, Xiaolin Xing, Bineta Keita, Jasleen K Bindra, Kariem Diefenbach, Naresh S Dalal, Ulrich Kortz
    Abstract:

    The four 18-tungsto-2-arsenates(III) [MII(H2O)(TiIVO)2(α-AsIIIW9O33)2]12– [M = Co (CoTi2), Ni (NiTi2), Cu (CuTi2), Zn (ZnTi2)] were rationally synthesized by treating the respective divalent metal ions with the monolacunary, dititanium(IV)-containing Polyanion precursor [(TiIVO)2(α-AsIIIW9O33)2]14– (Ti2) in aqueous solution. All four Polyanions are isostructural and correspond to dimers with two Ti4+ and one M2+ ion sandwiched between two [α-AsIIIW9O33]9– units. The compounds were characterized in the solid state by single-crystal XRD, infrared spectroscopy, thermogravimetric analysis, and elemental analysis and in solution by UV/Vis and NMR spectroscopy as well as electrochemistry. Variable-temperature magnetic susceptibility and variable-field magnetization characterization of the paramagnetic derivatives indicate antiferromagnetic interactions between nearest neighbors in the solid state. The resolved hyperfine structure obtained from multifrequency EPR measurements on CuTi2 (which exhibits a Jahn–Teller effect) in the solid state lead us to assign the ground state mainly to the Cu dx²–y² orbital. Despite the fact that the four Polyanions are isostructural and have the same overall negative charge, the cyclic voltammetric patterns featuring their chemically reversible reduction waves display distinct features. Electrocatalytic studies demonstrate that the activities of the Polyanions towards nitrate reduction are strikingly influenced by the nature of the substituent metal ion.

  • Polyoxomolybdodiphosphonates: Examples Incorporating Ethylidenepyridines
    2016
    Co-Authors: Abhishek Banerjee, Farah S. Raad, Nina Vankova, Bassem S. Bassil, Thomas Heine, Ulrich Kortz
    Abstract:

    We have synthesized and structurally characterized three pyridylethylidene-functionalized diphosphonate-containing polyoxomolybdates, [{MoVIO3}2{MoV2O4}{HO3PC(O)(CH2-3-C5NH4)PO3}2]6– (1), [{MoVI2O6}2{MoV2O4}{O3PC(O)(CH2-3-C5NH4)PO3}2]8– (2), and [{MoV2O4(H2O)}4{O3PC(O)(CH2-3-C5NH4)PO3}4]12– (3). Polyanions 1–3 were prepared in a one-pot reaction of the dinuclear, dicationic {MoV2O4(H2O)6}2+ with 1-hydroxo-2-(3-pyridyl)ethylidenediphosphonate (Risedronic acid) in aqueous solution. Polyanions 1 and 2 are mixed-valent MoVI/V species with open tetranuclear and hexanuclear structures, respectively, containing two diphosphonate groups. Polyanion 3 is a cyclic octanuclear structure based on four {MoV2O4(H2O)} units and four diphosphonates. Polyanions 1 and 2 crystallized as guanidinium salts [C(NH2)3]5H[{MoVIO3}2{MoV2O4}{HO3PC(O)(CH2-3-C5NH4)PO3}2]·13H2O (1a) and [C(NH2)3]6H2[{MoVI2O6}2{MoV2O4}{O3PC(O)(CH2-3-C5NH4)PO3}2]·10H2O (2a), whereas Polyanion 3 crystallized as a mixed sodium–guanidinium salt, Na8[C(NH2)3]4[{MoV2O4(H2O)}4{O3PC(O)(CH2-3-C5NH4)PO3}4]·8H2O (3a). The compounds were characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, and thermogravimetric and elemental analyses. The formation of Polyanions 1 and 3 is very sensitive to the pH value of the reaction solution, with exclusive formation of 1 above pH 7.4 and 3 below pH 6.6. Detailed solution studies by multinuclear NMR spectrometry were performed to study the equilibrium between these two compounds. Polyanion 2 was insoluble in all common solvents. Detailed computational studies on the solution phases of 1 and 3 indicated the stability of these Polyanions in solution, in complete agreement with the experimental findings

  • Gallium(III)-Containing, Sandwich-Type Heteropolytungstates: Synthesis, Solution Characterization, and Hydrolytic Studies toward Phosphoester and Phosphoanhydride Bond Cleavage
    2016
    Co-Authors: Balamurugan Kandasamy, Bassem S. Bassil, Stef Vanhaecht, Fiona Marylyn Nkala, Tessa Beelen, Tatjana N. Parac-vogt, Ulrich Kortz
    Abstract:

    The gallium­(III)-containing heteropolytungstates [Ga4(H2O)10(β-XW9O33)2]6– (X = AsIII, 1; SbIII, 2) were synthesized in aqueous acidic medium by reaction of Ga3+ ions with the trilacunary, lone-pair-containing [XW9O33]9–. Polyanions 1 and 2 are isostructural and crystallized as the hydrated sodium salts Na6[Ga4(H2O)10­(β-AsW9O33)2]·28H2O (Na-1) and Na6[Ga4(H2O)10­(β-SbW9O33)2]·30H2O (Na-2) in the monoclinic space group P21/c, with unit cell parameters a = 16.0218(12) Å, b = 15.2044(10) Å, c = 20.0821(12) Å, and β = 95.82(0)°, as well as a = 16.0912(5) Å, b = 15.2178(5) Å, c = 20.1047(5) Å, and β = 96.2(0)°, respectively. The corresponding tellurium­(IV) derivative [Ga4(H2O)10­(β-TeW9O33)2]4– (3) was also prepared, by direct reaction of sodium tungstate, tellurium­(IV) oxide, and gallium nitrate. Polyanion 3 crystallized as the mixed rubidium/sodium salt Rb2Na2[Ga4(H2O)10­(β-TeW9O33)2]·28H2O (RbNa-3) in the triclinic space group P1̅ with unit cell parameters a = 12.5629(15) Å, b = 13.2208(18) Å, c = 15.474(2) Å, α = 80.52(1)°, β = 84.37(1)°, and γ = 65.83(1)°. All Polyanions 1–3 were characterized in the solid state by single-crystal XRD, FT-IR, TGA, and elemental analysis, and Polyanion 2 was also characterized in solution by 183W NMR and UV–vis spectroscopy. Polyanion 2 was used as a homogeneous catalyst toward adenosine triphosphate (ATP) and the DNA model substrate 4-nitrophenylphosphate, monitored by 1H and 31P NMR spectroscopy. The encapsulated gallium­(III) centers in 2 promote the Lewis acidic synergistic activation of the hydrolysis of ATP and DNA model substrates at a higher rate in near-physiological conditions. A strong interaction of 2 with the P–O bond of ATP was evidenced by changes in chemical shift values and line broadening of the 31P nucleus in ATP upon addition of the Polyanion

  • ti2 containing 18 tungsto 2 arsenate iii monolacunary host and the incorporation of a phenylantimony iii guest
    Inorganic Chemistry, 2015
    Co-Authors: Kaiyao Wang, Bassem S. Bassil, Xiaolin Xing, Ali Haider, Bineta Keita, Guangjin Zhang, Cristian Silvestru, Ulrich Kortz
    Abstract:

    The novel Ti-2-containing, sandwich-type 18-tungsto-2-arsenate(III) [ ((TiO)-O-IV)(2) (alpha-(AsW9O33)-W-III)(2)](14-) (1) was successfully synthesized by the reaction of [TiO](2+) species with [alpha-(AsW9O33)-W-III](9-). The monolacunary Polyanion 1 is solution-stable, and a further reaction with 1 equiv of phenylantimony(III) dichloride resulted in [C6H5SbIII((TiO)-O-IV)(2)(alpha-(AsW9O33)-W-III)(2)](12-) (2). Both Polyanions 1 and 2 were structurally characterized in the solid state and solution. Electrochemical studies were also performed on both Polyanions.

  • cobalt manganese nickel and vanadium derivatives of the cyclic 48 tungsto 8 phosphate h7p8w48o184 33
    Inorganic Chemistry, 2010
    Co-Authors: Bassem S. Bassil, Bineta Keita, Masooma Ibrahim, Sib Sankar Mal, Andreas Suchopar, Rosa Ngo Biboum, Louis Nadjo, Saritha Nellutla, Johan Van Tol, N S Dalal
    Abstract:

    The cobalt(II) containing tungstophosphate [Co4(H2O)16P8W48O184]32− (1) has been synthesized by addition of Co2+ ions to an aqueous solution of [H7P8W48O184]33− (P8W48) and characterized by single-crystal XRD, IR, and UV−vis spectroscopy, elemental analysis, electrochemistry, and magnetochemistry. The novel Polyanion 1 is a derivative of the superlacunary P8W48 with four cobalt(II) ions coordinated to the rim of the central cavity and two additional cobalt(II) ions linked on the outside bridging neighboring Polyanions. Using similar synthetic procedures, but adding a few drops of H2O2, we isolated the manganese(II) derivative [Mn4(H2O)16(P8W48O184)(WO2(H2O)2)2]28− (2) and its nickel(II) analogue [Ni4(H2O)16(P8W48O184)(WO2(H2O)2)2]28− (3). Both Polyanions have picked up two equivalents of tungsten resulting in the unprecedented {P8W50} host framework. We also made the vanadium(V) derivative [(VO2)4(P8W48O184)]36− (4), with four tetrahedral vanadate groups grafted to the P8W48 host. The voltammetric pattern...

Kenneth R. Poeppelmeier - One of the best experts on this subject based on the ideXlab platform.

  • assisting the effective design of polar iodates with early transition metal oxide fluoride anions
    Journal of the American Chemical Society, 2018
    Co-Authors: Matthew L. Nisbet, Kenneth R. Poeppelmeier
    Abstract:

    Polar materials are of great technical interest but challenging to effectively synthesize. That is especially true for iodates, an important class of visible and mid-IR transparent nonlinear optical (NLO) materials. Aiming at developing a new design strategy for polar iodates, we successfully synthesized two sets of polymorphic early transition-metal (ETM) oxide-fluoride iodates, α- and β-Ba[VFO2(IO3)2] and α- and β-Ba2[VO2F2(IO3)2]IO3, based on the distinct structure-directing properties of oxide-fluoride anions. α- and β-Ba[VFO2(IO3)2] contain the trans-[VFO2(IO3)2]2– Polyanion and crystallize in the nonpolar space groups Pbcn and P212121. In contrast, α- and β-Ba2[VO2F2(IO3)2]IO3 contain the cis-[VO2F2(IO3)2]3– Λ-shaped Polyanion and crystallize in the polar space groups Pna21 and P21, respectively. Detailed structural analyses show that the variable polar orientation of trans-[VFO2(IO3)2]2– Polyanions is the main cause of the nonpolar structures in α- and β-Ba[VFO2(IO3)2]. However, the Λ-shaped config...

  • Assisting the Effective Design of Polar Iodates with Early Transition-Metal Oxide Fluoride Anions
    2018
    Co-Authors: Matthew L. Nisbet, Kenneth R. Poeppelmeier
    Abstract:

    Polar materials are of great technical interest but challenging to effectively synthesize. That is especially true for iodates, an important class of visible and mid-IR transparent nonlinear optical (NLO) materials. Aiming at developing a new design strategy for polar iodates, we successfully synthesized two sets of polymorphic early transition-metal (ETM) oxide-fluoride iodates, α- and β-Ba­[VFO2(IO3)2] and α- and β-Ba2[VO2F2(IO3)2]­IO3, based on the distinct structure-directing properties of oxide-fluoride anions. α- and β-Ba­[VFO2(IO3)2] contain the trans-[VFO2(IO3)2]2– Polyanion and crystallize in the nonpolar space groups Pbcn and P212121. In contrast, α- and β-Ba2[VO2F2(IO3)2]­IO3 contain the cis-[VO2F2(IO3)2]3– Λ-shaped Polyanion and crystallize in the polar space groups Pna21 and P21, respectively. Detailed structural analyses show that the variable polar orientation of trans-[VFO2(IO3)2]2– Polyanions is the main cause of the nonpolar structures in α- and β-Ba­[VFO2(IO3)2]. However, the Λ-shaped configuration of cis-[VO2F2(IO3)2]3– Polyanions can effectively guarantee the polar structures. Further property measurements show that polar α- and β-Ba2[VO2F2(IO3)2]­IO3 possess excellent NLO properties, including the large SHG responses (∼9 × KDP), wide visible and mid-IR transparent region (∼0.5–10.5 μm), and high thermal stability (up to 470 °C). Therefore, combining cis-directing oxide-fluoride anions and iodates is a viable strategy for the effective design of polar iodates