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Sample records for cationic liposome-dna complexes

  1. Potent Adjuvant Activity of Cationic Liposome-DNA Complexes for Genital Herpes Vaccines▿

    PubMed Central

    Bernstein, David I.; Cardin, Rhonda D.; Bravo, Fernando J.; Strasser, Jane E.; Farley, Nicholas; Chalk, Claudia; Lay, Marla; Fairman, Jeff

    2009-01-01

    Development of a herpes simplex virus (HSV) vaccine is a priority because these infections are common. It appears that potent adjuvants will be required to augment the immune response to subunit HSV vaccines. Therefore, we evaluated cationic liposome-DNA complexes (CLDC) as an adjuvant in a mouse model of genital herpes. Using a whole-virus vaccine (HVAC), we showed that the addition of CLDC improved antibody responses compared to vaccine alone. Most important, CLDC increased survival, reduced symptoms, and decreased vaginal virus replication compared to vaccine alone or vaccine administered with monophosphoryl lipid A (MPL) plus trehalose dicorynomycolate (TDM) following intravaginal challenge of mice. When CLDC was added to an HSV gD2 vaccine, it increased the amount of gamma interferon that was produced from splenocytes stimulated with gD2 compared to the amount produced with gD2 alone or with MPL-alum. The addition of CLDC to the gD2 vaccine also improved the outcome following vaginal HSV type 2 challenge compared to vaccine alone and was equivalent to vaccination with an MPL-alum adjuvant. CLDC appears to be a potent adjuvant for HSV vaccines and should be evaluated further. PMID:19279167

  2. Gene transfection efficiency into dendritic cells is influenced by the size of cationic liposomes/DNA complexes.

    PubMed

    Inoh, Yoshikazu; Nagai, Mie; Matsushita, Kayo; Nakanishi, Mamoru; Furuno, Tadahide

    2017-05-01

    Cationic liposomes have attracted recent attention as DNA vaccine carriers that can target dendritic cells (DCs). In general, cationic liposome/DNA complexes (lipoplexes) are taken up by various cells via clathrin-mediated endocytosis, caveolae-mediated endocytosis, macropinocytosis, or phagocytosis, with the mode of endocytosis determining further intracellular trafficking pathways. Moreover, the physicochemical properties of cationic lipoplexes, including lipid composition, shape, size, and charge, influence transfection efficiency, affecting uptake and subsequent intracellular pathways. To develop cationic liposomes as potential DNA vaccine carriers, the objective of this study was to study the effect of lipoplex size on DNA transfection efficiency in DCs. We explored the size-dependent endocytosis pathway and the intracellular trafficking of cationic lipoplexes using bone marrow derived dendritic cells (BMDCs). Our results indicated that small-sized lipoplexes (approximately 270nm diameter) were taken up by BMDCs via caveolae-mediated endocytosis, which led to a non-degradative pathway, whereas larger-sized lipoplexes (approximately 500nm diameter) were taken up by BMDCs via clathrin-mediated endocytosis and micropinocytosis, which led to a lysosomal degradation pathway. These findings suggest that, by regulating the size of lipoplexes, it may be possible to develop cationic liposomes as DNA vaccine therapies for targeting DCs. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Synthesis of linear and cyclic peptide-PEG-lipids for stabilization and targeting of cationic liposome-DNA complexes.

    PubMed

    Ewert, Kai K; Kotamraju, Venkata Ramana; Majzoub, Ramsey N; Steffes, Victoria M; Wonder, Emily A; Teesalu, Tambet; Ruoslahti, Erkki; Safinya, Cyrus R

    2016-03-15

    Because nucleic acids (NAs) have immense potential value as therapeutics, the development of safe and effective synthetic NA vectors continues to attract much attention. In vivo applications of NA vectors require stabilized, nanometer-scale particles, but the commonly used approaches of steric stabilization with a polymer coat (e.g., PEGylation; PEG=poly(ethylene glycol)) interfere with attachment to cells, uptake, and endosomal escape. Conjugation of peptides to PEG-lipids can improve cell attachment and uptake for cationic liposome-DNA (CL-DNA) complexes. We present several synthetic approaches to peptide-PEG-lipids and discuss their merits and drawbacks. A lipid-PEG-amine building block served as the common key intermediate in all synthetic routes. Assembling the entire peptide-PEG-lipid by manual solid phase peptide synthesis (employing a lipid-PEG-carboxylic acid) allowed gram-scale synthesis but is mostly applicable to linear peptides connected via their N-terminus. Conjugation via thiol-maleimide or strain-promoted (copper-free) azide-alkyne cycloaddition chemistry is highly amenable to on-demand preparation of peptide-PEG-lipids, and the appropriate PEG-lipid precursors are available in a single chemical step from the lipid-PEG-amine building block. Azide-alkyne cycloaddition is especially suitable for disulfide-bridged peptides such as iRGD (cyclic CRGDKGPDC). Added at 10 mol% of a cationic/neutral lipid mixture, the peptide-PEG-lipids stabilize the size of CL-DNA complexes. They also affect cell attachment and uptake of nanoparticles in a peptide-dependent manner, thereby providing a platform for preparing stabilized, affinity-targeted CL-DNA nanoparticles. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Cationic Liposome-DNA Complexes: From supramolecular assembly toward gene delivery

    NASA Astrophysics Data System (ADS)

    Evans, Heather M.; Ahmad, A.; Ewert, K.; Martin, A.; Safinya, Cr

    2003-03-01

    Cationic liposomes (CL) present a viable alternative to viral delivery of therapeutic DNA and peptides to cells. We complex CL with DNA to deliver foreign DNA (genes) to cells. Typical self-assembly of CL-DNA shown by x-ray diffraction reveals multilamellar lipids with DNA intercalated between the lipid layers, having a DNA interaxial spacing d(DNA)[1]. The length d(DNA) can be tuned at the subnanometer level (from 35 down to 5 angstroms) by control of the membrane charge density and other parameters. Three distinct DNA-DNA interaction regimes were found due to repulsive long-range electrostatic forces, repulsive short-range hydration forces, and a polymer induced attractive depletion force [2-4]. We correlate d(DNA) to transfection in mammalian cells. These compact DNA structures suggest use for high density storage of genetic information, as well as for biological templates. Supported by NSF DMR-0203755, NIH GM59288. 1. J Radler et al, Science 275, 810 (1997). 2. AJ Lin et al, Biophys. J. (in press). 3. K Ewert, A Ahmad, H Evans et al, J. Med. Chem. 45, 5023 (2002). 4. A Martin et al, (submitted).

  5. Three-Dimensional Imaging of Lipid Gene-Carriers: Membrane Charge Density Controls Universal Transfection Behavior in Lamellar Cationic Liposome-DNA Complexes

    PubMed Central

    Lin, Alison J.; Slack, Nelle L.; Ahmad, Ayesha; George, Cyril X.; Samuel, Charles E.; Safinya, Cyrus R.

    2003-01-01

    Cationic liposomes (CLs) are used worldwide as gene vectors (carriers) in nonviral clinical applications of gene delivery, albeit with unacceptably low transfection efficiencies (TE). We present three-dimensional laser scanning confocal microscopy studies revealing distinct interactions between CL-DNA complexes, for both lamellar LαC and inverted hexagonal HIIC nanostructures, and mouse fibroblast cells. Confocal images of LαC complexes in cells identified two regimes. For low membrane charge density (σM), DNA remained trapped in CL-vectors. By contrast, for high σM, released DNA was observed in the cytoplasm, indicative of escape from endosomes through fusion. Remarkably, firefly luciferase reporter gene studies in the highly complex LαC-mammalian cell system revealed an unexpected simplicity where, at a constant cationic to anionic charge ratio, TE data for univalent and multivalent cationic lipids merged into a single curve as a function of σM, identifying it as a key universal parameter. The universal curve for transfection by LαC complexes climbs exponentially over ≈ four decades with increasing σM below an optimal charge density (σM*), and saturates for \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\sigma}_{{\\mathrm{M}}}>{\\sigma}_{M}^{{^\\ast}}\\end{equation*}\\end{document} at a value rivaling the high transfection efficiency of HIIC complexes. In contrast, the transfection efficiency of HIIC complexes is independent of σM. The exponential dependence of TE on σM for LαC complexes, suggests the existence of a kinetic barrier against endosomal fusion, where an increase in σM lowers the barrier. In the saturated TE regime, for both LαC complexes and HIIC, confocal microscopy reveals the dissociation of lipid and DNA. However, the lipid-released DNA is

  6. Cationic liposome-DNA complexes (CLDC) adjuvant enhances the immunogenicity and cross-protective efficacy of a pre-pandemic influenza A H5N1 vaccine in mice.

    PubMed

    Dong, Libo; Liu, Feng; Fairman, Jeffery; Hong, David K; Lewis, David B; Monath, Thomas; Warner, John F; Belser, Jessica A; Patel, Jenish; Hancock, Kathy; Katz, Jacqueline M; Lu, Xiuhua

    2012-01-05

    The development of pre-pandemic influenza A H5N1 vaccines that confer both antigen-sparing and cross-clade protection are a high priority given the limited worldwide capacity for influenza vaccine production, and the antigenic and genetic heterogeneity of circulating H5N1 viruses. The inclusion of potent adjuvants in vaccine formulations may achieve both of these aims. Here we show that the addition of JVRS-100, an adjuvant consisting of cationic liposome-DNA complexes (CLDC) to a clade 1-derived H5N1 split vaccine induced significantly higher virus-specific antibody than unadjuvanted formulations, with a >30-fold dose-sparing effect and induction of increased antigen-specific CD4(+) T-cell responses in mice. All mice that received one dose of adjuvanted vaccine and subsequent H5N1 viral challenges exhibited mild illness, lower lung viral titers, undetectable spleen and brain viral titers, and 100% survival after either homologous clade 1 or heterologous clade 2 H5N1 viral challenges, whereas unadjuvanted vaccine recipients showed significantly increased weight loss, viral titers, and mortality. The protective immunity induced by JVRS-100 adjuvanted H5N1 vaccine was shown to last for over one year without significant waning. Thus, JVRS-100 adjuvanted H5N1 vaccine elicited enhanced humoral and T-cell responses, dose-sparing, and cross-clade protection in mice. CLDC holds promise as an adjuvant for human pre-pandemic inactivated H5N1 vaccines.

  7. A cationic liposome-DNA complexes adjuvant (JVRS-100) enhances the immunogenicity and cross-protective efficacy of pre-pandemic influenza A (H5N1) vaccine in ferrets.

    PubMed

    Liu, Feng; Sun, Xiangjie; Fairman, Jeffery; Lewis, David B; Katz, Jacqueline M; Levine, Min; Tumpey, Terrence M; Lu, Xiuhua

    2016-05-01

    Influenza A (H5N1) viruses continue to pose a public health threat. As inactivated H5N1 vaccines are poorly immunogenic, adjuvants are needed to improve the immunogenicity of H5N1 vaccine in humans. Here, we investigated the immunogenicity and cross-protective efficacy in ferrets of a clade 2.2-derived vaccine with addition of JVRS-100, an adjuvant consisting of cationic liposome-DNA complexes (CLDC). After the first vaccination, significantly higher levels of hemagglutination-inhibition (HAI) and neutralizing antibody titers were detected in ferrets immunized with adjuvanted vaccine compared to unadjuvanted vaccine. Following a second dose of adjuvanted vaccine, HAI antibody titers of ≥ 40 were detected against viruses from multiple H5N1 clades. HAI antibodies against newly isolated H5N2 and H5N8 viruses were also augmented by JVRS-100. Ferrets were challenged with a heterologous H5N1 virus. All ferrets that received two doses of adjuvanted vaccine exhibited mild illness, significantly reduced nasal wash virus titers and protection from lethal challenge. In contrast, ferrets that received unadjuvanted vaccine showed greater weight loss, high viral titers and 3 of 6 animals succumbed to the lethal challenge. Our results indicate that the addition of JVRS-100 to H5N1 vaccine enhanced immunogenicity and cross-protection against lethal H5N1 virus disease in ferrets. JVRS-100 warrants further investigation as a potential adjuvant for influenza vaccines.

  8. Cell transfection in vitro and in vivo with nontoxic TAT peptide-liposome-DNA complexes

    NASA Astrophysics Data System (ADS)

    Torchilin, Vladimir P.; Levchenko, Tatyana S.; Rammohan, Ram; Volodina, Natalia; Papahadjopoulos-Sternberg, Brigitte; D'Souza, Gerard G. M.

    2003-02-01

    Liposomes modified with TAT peptide (TATp-liposomes) showed fast and efficient translocation into the cell cytoplasm with subsequent migration into the perinuclear zone. TATp-liposomes containing a small quantity (10 mol %) of a cationic lipid formed firm noncovalent complexes with DNA. Here, we present results demonstrating both in vitro and in vivo transfection with TATp-liposome-DNA complexes. Mouse NIH/3T3 fibroblasts and rat H9C2 cardiomyocytes were transfected with such complexes in vitro. The transfection with the TATp-liposome-associated pEGFP-N1 plasmid encoding for the green fluorescent protein (GFP) was high, whereas the cytotoxicity was lower than that of commonly used cationic lipid-based gene-delivery systems. Intratumoral injection of TATp-liposome-DNA complexes into the Lewis lung carcinoma tumor of mice also resulted in an expression of GFP in tumor cells. This transfection system should be useful for various protocols of cell treatment in vitro or ex vivo as well as for localized in vivo gene therapy.

  9. A review of scanning probe microscopy investigations of liposome-DNA complexes.

    PubMed

    Mozafari, M R; Reed, C J; Rostron, C; Hasirci, V

    2005-01-01

    Liposome-DNA complexes are one of the most promising systems for the protection and delivery of nucleic acids to combat neoplastic, viral, and genetic diseases. In addition, they are being used as models in the elucidation of many biological phenomena such as viral infection and transduction. In order to understand these phenomena and to realize the mechanism of nucleic acid transfer by liposome-DNA complexes, studies at the molecular level are required. To this end, scanning probe microscopy (SPM) is increasingly being used in the characterization of lipid layers, lipid aggregates, liposomes, and their complexes with nucleic acid molecules. The most attractive attributes of SPM are the potential to image samples with subnanometer spatial resolution under physiological conditions and provide information on their physical and mechanical properties. This review describes the application of scanning tunneling microscopy and atomic force microscopy, the two most commonly applied SPM techniques, in the characterisation of liposome-DNA complexes.

  10. Rab11 and Lysotracker Markers Reveal Correlation between Endosomal Pathways and Transfection Efficiency of Surface-Functionalized Cationic Liposome-DNA Nanoparticles.

    PubMed

    Majzoub, Ramsey N; Wonder, Emily; Ewert, Kai K; Kotamraju, Venkata Ramana; Teesalu, Tambet; Safinya, Cyrus R

    2016-07-07

    Cationic liposomes (CLs) are widely studied as carriers of DNA and short-interfering RNA for gene delivery and silencing, and related clinical trials are ongoing. Optimization of transfection efficiency (TE) requires understanding of CL-nucleic acid nanoparticle (NP) interactions with cells, NP endosomal pathways, endosomal escape, and events leading to release of active nucleic acid from the lipid carrier. Here, we studied endosomal pathways and TE of surface-functionalized CL-DNA NPs in PC-3 prostate cancer cells displaying overexpressed integrin and neuropilin-1 receptors. The NPs contained RGD-PEG-lipid or RPARPAR-PEG-lipid, targeting integrin, and neuropilin-1 receptors, respectively, or control PEG-lipid. Fluorescence colocalization using Rab11-GFP and Lysotracker enabled simultaneous colocalization of NPs with recycling endosome (Rab11) and late endosome/lysosome (Rab7/Lysotracker) pathways at increasing mole fractions of pentavalent MVL5 (+5 e) at low (10 mol %), high (50 mol %), and very high (70 mol %) membrane charge density (σM). For these cationic NPs (lipid/DNA molar charge ratio, ρchg = 5), the influence of membrane charge density on pathway selection and transfection efficiency is similar for both peptide-PEG NPs, although, quantitatively, the effect is larger for RGD-PEG compared to RPARPAR-PEG NPs. At low σM, peptide-PEG NPs show preference for the recycling endosome over the late endosome/lysosome pathway. Increases in σM, from low to high, lead to decreases in colocalization with recycling endosomes and simultaneous increases in colocalization with the late endosome/lysosome pathway. Combining colocalization and functional TE data at low and high σM shows that higher TE correlates with a larger fraction of NPs colocalized with the late endosome/lysosome pathway while lower TE correlates with a larger fraction of NPs colocalized with the Rab11 recycling pathway. The findings lead to a hypothesis that increases in σM, leading to enhanced

  11. Genetic Immunization With In Vivo Dendritic Cell-targeting Liposomal DNA Vaccine Carrier Induces Long-lasting Antitumor Immune Response

    PubMed Central

    Garu, Arup; Moku, Gopikrishna; Gulla, Suresh Kumar; Chaudhuri, Arabinda

    2016-01-01

    A major limiting factor retarding the clinical success of dendritic cell (DC)-based genetic immunizations (DNA vaccination) is the scarcity of biologically safe and effective carrier systems for targeting the antigen-encoded DNA vaccines to DCs under in vivo settings. Herein, we report on a potent, mannose receptor selective in vivo DC-targeting liposomes of a novel cationic amphiphile with mannose-mimicking shikimoyl head-group. Flow cytometric experiments with cells isolated from draining lymph nodes of mice s.c. immunized with lipoplexes of pGFP plasmid (model DNA vaccine) using anti-CD11c antibody-labeled magnetic beads revealed in vivo DC-targeting properties of the presently described liposomal DNA vaccine carrier. Importantly, s.c. immunizations of mice with electrostatic complex of the in vivo DC-targeting liposome and melanoma antigen-encoded DNA vaccine (p-CMV-MART1) induced long-lasting antimelanoma immune response (100 days post melanoma tumor challenge) with remarkable memory response (more than 6 months after the second tumor challenge). The presently described direct in vivo DC-targeting liposomal DNA vaccine carrier is expected to find future exploitations toward designing effective vaccines for various infectious diseases and cancers. PMID:26666450

  12. Electrostatics of DNA complexes with cationic lipids

    NASA Astrophysics Data System (ADS)

    Cherstvy, Andrey

    2007-03-01

    We present the exact solutions of the linear Poisson-Boltzmann theory for several problems relevant to electrostatics of DNA complexes with cationic lipids. We calculate the electrostatic potential and energy for lamellar and inverted hexagonal phases, concentrating on the effects of water-membrane dielectric boundaries. Our results for the complex energy agree qualitatively well with the known numerical solutions of the nonlinear Poisson-Boltzmann equation. Using the solution for the lamellar phase, we calculate its compressibility modulus and compare our findings with experimental data available suggesting a new scaling dependence on DNA-DNA separations in the complex. Also, we treat analytically charge-charge electrostatic interactions across, along, and in between two low-dielectric membranes. We obtain an estimate for the strength of electrostatic interactions of 1D DNA smectic layers across a lipid membrane. We discuss also some aspects of 2D DNA condensation and DNA-DNA attraction in DNA-lipid lamellar phase in the presence of di- and tri-valent cations and analyze the equilibrium intermolecular separations using the recently developed theory of electrostatic interactions of DNA helical charge motifs.

  13. A novel cationic liposome formulation for efficient gene delivery via a pulmonary route

    NASA Astrophysics Data System (ADS)

    Li, Peng; Liu, Donghua; Sun, Xiaoli; Liu, Chunxi; Liu, Yongjun; Zhang, Na

    2011-06-01

    The clinical success of gene therapy for lung cancer is not only dependent on efficient gene carriers but also on a suitable delivery route. A pulmonary delivery route can directly deliver gene vectors to the lung which is more efficient than a systemic delivery route. For gene carriers, cationic liposomes have recently emerged as leading non-viral vectors in worldwide gene therapy clinical trials. However, cytotoxic effects or apoptosis are often observed which is mostly dependent on the cationic lipid used. Therefore, an efficient and safe cationic lipid, 6-lauroxyhexyl lysinate (LHLN), previously synthesized by our group was first used to prepare cationic liposomes. Physicochemical and biological properties of LHLN-liposomes were investigated. LHLN-liposome/DNA complexes showed positive surface charge, spherical morphology, a relatively narrow particle size distribution and strong DNA binding capability. Compared with Lipofectamine2000, the new cationic liposome formulation using LHLN exhibited not only lower cytotoxicity (P < 0.05) but also similar transfection efficiency in A549 and HepG2 lung cancer cells for in vitro tests. When administered by intratracheal instillation into rat lungs for in vivo evaluation, LHLN-liposome/DNA complexes exhibited higher pulmonary gene transfection efficiency than Lipofectamine2000/DNA complexes (P < 0.05). These results suggested that LHLN-liposomes may have great potential for efficient pulmonary gene delivery.

  14. Cationic aluminum alkyl complexes incorporating aminotroponiminate ligands.

    PubMed

    Korolev, A V; Ihara, E; Guzei, I A; Young, V G; Jordan, R F

    2001-08-29

    The synthesis, structures, and reactivity of cationic aluminum complexes containing the N,N'-diisopropylaminotroponiminate ligand ((i)Pr(2)-ATI(-)) are described. The reaction of ((i)Pr(2)-ATI)AlR(2) (1a-e,g,h; R = H (a), Me (b), Et (c), Pr (d), (i)Bu (e), Cy (g), CH(2)Ph (h)) with [Ph(3)C][B(C(6)F(5))(4)] yields ((i)()Pr(2)-ATI)AlR(+) species whose fate depends on the properties of the R ligand. 1a and 1b react with 0.5 equiv of [Ph(3)C][B(C(6)F(5))(4)] to produce dinuclear monocationic complexes [([(i)Pr(2)-ATI] AlR)(2)(mu-R)][(C(6)F(5))(4)] (2a,b). The cation of 2b contains two ((i)()Pr(2)-ATI)AlMe(+) units linked by an almost linear Al-Me-Al bridge; 2a is presumed to have an analogous structure. 2b does not react further with [Ph(3)C][B(C(6)F(5))(4)]. However, 1a reacts with 1 equiv of [Ph(3)C][B(C(6)F(5))(4)] to afford ((i Pr(2)-ATI)Al(C(6)F(5))(mu-H)(2)B(C(6)F(5))(2) (3) and other products, presumably via C(6)F(5)(-) transfer and ligand redistribution of a [((i)()Pr(2)-ATI)AlH][(C(6)F(5))(4)] intermediate. 1c-e react with 1 equiv of [Ph(3)C][B(C(6)F(5))(4)] to yield stable base-free [((i)Pr(2)-ATI)AlR][B(C(6)F(5))(4)] complexes (4c-e). 4c crystallizes from chlorobenzene as 4c(ClPh).0.5PhCl, which has been characterized by X-ray crystallography. In the solid state the PhCl ligand of 4c(ClPh) is coordinated by a dative PhCl-Al bond and an ATI/Ph pi-stacking interaction. 1g,h react with [Ph(3)C][B(C(6)F(5))(4)] to yield ((i)Pr(2)-ATI)Al(R)(C(6)F(5)) (5g,h) via C(6)F(5)(-) transfer of [((i)Pr(2)-ATI)AlR][(BC(6)F(5))(4)] intermediates. 1c,h react with B(C(6)F(5))(3) to yield ((i)Pr(2)-ATI)Al(R)(C(6)F(5)) (5c,h) via C(6)F(5)(-) transfer of [((i)Pr(2)-ATI)AlR][RB(C(6)F(5))(3)] intermediates. The reaction of 4c-e with MeCN or acetone yields [((i)Pr(2)-ATI)Al(R)(L)][B(C(6)F(5))(4)] adducts (L = MeCN (8c-e), acetone (9c-e)), which undergo associative intermolecular L exchange. 9c-e undergo slow beta-H transfer to afford the dinuclear dicationic alkoxide complex [(((i

  15. Plant rhamnogalacturonan II complexation of heavy metal cations

    DOEpatents

    O'Neill, Malcolm A.; Pellerin, Patrice J. M.; Warrenfeltz, Dennis; Vidal, Stephane; Darvill, Alan G.; Albersheim, Peter

    1999-01-01

    The present invention provides rhamnogalacturonan-II (RG-II) and relates to its ability to complex specific multivalent heavy metal cations. In the presence of boric acid, RG-II monomers form dimers that are cross-linked by a borate ester. The yield of such borate ester cross-linked dimers of RG-II is enhanced in the presence of specific heavy metal cations. The present invention further relates to the utility of RG-II in assays for the detection of specific heavy metal contamination; as a reagent useful in the removal of specific heavy metal cations contaminating foods and liquids, for example, fish, wines, etc.; as a pharmaceutical composition useful as an antidote in specific heavy metal cation poisoning; as a treatment for the detoxification of specific heavy metal cations from blood and/or tissues; and in a method of remediation of waters and soils contaminated with specific heavy metal cations.

  16. Plant rhamnogalacturonan II complexation of heavy metal cations

    DOEpatents

    O`Neill, M.A.; Pellerin, P.J.M.; Warrenfeltz, D.; Vidal, S.; Darvill, A.G.; Albersheim, P.

    1999-03-02

    The present invention provides rhamnogalacturonan-II (RG-II) and relates to its ability to complex specific multivalent heavy metal cations. In the presence of boric acid, RG-II monomers form dimers that are cross-linked by a borate ester. The yield of such borate ester cross-linked dimers of RG-II is enhanced in the presence of specific heavy metal cations. The present invention further relates to the utility of RG-II in assays for the detection of specific heavy metal contamination; as a reagent useful in the removal of specific heavy metal cations contaminating foods and liquids, for example, fish, wines, etc.; as a pharmaceutical composition useful as an antidote in specific heavy metal cation poisoning; as a treatment for the detoxification of specific heavy metal cations from blood and/or tissues; and in a method of remediation of waters and soils contaminated with specific heavy metal cations. 15 figs.

  17. Immune complexes with cationic antibodies deposit in glomeruli more effectively than cationic antibodies alone.

    PubMed

    Mannik, M; Gauthier, V J; Stapleton, S A; Agodoa, L Y

    1987-06-15

    In previously published studies, highly cationized antibodies alone and in immune complexes bound to glomeruli by charge-charge interaction, but only immune complexes persisted in glomeruli. Because normal IgG does not deposit in glomeruli, studies were conducted to determine whether cationized antibodies can be prepared which deposit in glomeruli when bound to antigen but not when free in circulation. A series of cationized rabbit antiHSA was prepared with the number of added amino groups ranging from 13.3 to 60.2 per antibody molecule. Antibodies alone or in preformed soluble immune complexes, prepared at fivefold or 50-fold antigen excess, were administered to mice. With the injection of a fixed dose of 100 micrograms per mouse, antibodies alone did not deposit in glomeruli with less than 29.6 added amino groups by immunofluorescence microscopy. In contrast, 100 micrograms of antibodies with 23.5 added amino groups in immune complexes, made at fivefold antigen excess, formed immune deposits in glomeruli. With selected preparations of cationized, radiolabeled antibodies, deposition in glomeruli was quantified by isolation of mouse glomeruli. These quantitative data were in good agreement with the results of immunofluorescence microscopy. Immune complexes made at 50-fold antigen excess, containing only small-latticed immune complexes with no more than two antibody molecules per complex, deposited in glomeruli similar to antibodies alone. Selected cationized antibodies alone or in immune complexes were administered to mice in varying doses. In these experiments, glomerular deposition of immune complexes, made at fivefold antigen excess, was detected with five- to 10-fold smaller doses than the deposition of the same antibodies alone. These studies demonstrate that antibody molecules in immune complexes are more likely to deposit in glomeruli by charge-charge interactions than antibodies alone.

  18. Complexation Between Cationic Diblock Copolymers and Plasmid DNA

    NASA Astrophysics Data System (ADS)

    Jung, Seyoung; Reineke, Theresa; Lodge, Timothy

    Deoxyribonucleic acids (DNA), as polyanions, can spontaneously bind with polycations to form polyelectrolyte complexes. When the polycation is a diblock copolymer with one cationic block and one uncharged hydrophilic block, the polyelectrolyte complexes formed with plasmid DNA (pDNA) are often colloidally stable, and show great promise in the field of polymeric gene therapy. While the resulting properties (size, stability, and toxicity to biological systems) of the complexes have been studied for numerous cationic diblocks, the fundamentals of the pDNA-diblock binding process have not been extensively investigated. Herein, we report how the cationic block content of a diblock influences the pDNA-diblock interactions. pDNA with 7164 base pairs and poly(2-deoxy-2-methacrylamido glucopyranose)-block-poly(N-(2-aminoethyl) methacrylamide) (PMAG-b-PAEMA) are used as the model pDNA and cationic diblock, respectively. To vary the cationic block content, two PMAG-b-PAEMA copolymers with similar PMAG block lengths but distinct PAEMA block lengths and a PAEMA homopolymer are utilized. We show that the enthalpy change from pDNA-diblock interactions is dependent on the cationic diblock composition, and is closely associated with both the binding strength and the pDNA tertiary structure.

  19. [Synthesis of functionalized cyanines. Fluorescence properties following complexation of cations].

    PubMed

    Mazières, M R; Duprat, C; Sutra, E; Lamandé, L; Bergon, M; Bellan, J; Wolf, J G; Roques, C

    2003-01-01

    The ionophoric properties of podands containing dioxazaphosphocane moieties linked by inactive spacers were studied. To increase the detection sensibility of these compounds we introduced a cyanine as spacer. Fluorescence analysis demonstrated the interest of cyanines as active spacers since the complexation by cations as Ca2+ and Mg2+ gives an enhancement of the emission intensity.

  20. Complexes of Negatively Charged Polypeptides with Cationic Lipids

    NASA Astrophysics Data System (ADS)

    Subramanian, G.; Li, Youli; Safinya, Cyrus R.

    1997-03-01

    Complexes of cationic lipids with oppositely charged proteins are promising candidates for new biomolecular materials. In addition to being used as a direct vehicle for protein transfection, they also find applications as templates for synthesis of molecular sieves. In spite of these wide ranging applications, the structure and interactions in these complexes have largely remained unclear. Here we report on the study of complexes formed between the cationic lipid didodecyldimethylammonium bromide (DDAB) with negatively charged polypeptide poly glutamic acid (PGA) both in the presence and absence of the neutral lipid dilauroylglycerophosphocholine (DLPC). X-ray diffraction of the complexes indicates a condensed lamellar lipid structure with the polypeptide intercalated between the layers. We present a comprehensive phase diagram on this system based on X-ray diffraction data. This work is supported in part by grants NSF DMR-9624091, PRF-31352 AC7, and CU LAR STP/UC 96-118.

  1. Hydrogen bond vs. halogen bond in cation-cation complexes. The effect of the solvent.

    PubMed

    Chalanchi, Saber Mohammadi; Alkorta, Ibon; Elguero, Jose; Quiñonero, David

    2017-09-07

    In this manuscript we have explored the competition between hydrogen- (HB) and halogen-bonded (XB) 4-amonium pyridine and halogenamonium (NHnF3-nX+, n=0-3, X= F, Cl, Br and I) cation-cation complexes by means of DFT theoretical calculations. HB and XB minima structures are found for all systems in gas phase. As the number of fluorine atoms increases the HB complexes are more favored than the XB ones. Proton transfer is generally observed in the complexes with two or more halogen atoms. The XB complexes evolved from traditional ZB, to halogen shared, and to ionic complexes as the number of fluorine atoms increases. The dissociation transition states and their corresponding barriers have also been characterized, increasing as the number of fluorine atoms increases. The results when solvent effects are considered indicate that even in an apolar solvent as n-hexane most of the complexes have favorable binding energies. The ''atoms-in-molecules'' (AIM) theory was used to analyze the complexes, obtaining good correlations between electron density and total electron energy density () values with the intermolecular bond distance. According to the  values obtained, the covalency of these interactions would start manifesting at distances around 72%-74% the sum of the van der Waals radii of the interacting atoms. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Stable Complexes of Cationic Liposomes and Membrane Protein Bacteriorhodopsin

    NASA Astrophysics Data System (ADS)

    Kubo, I.; Koltover, I.; Safinya, C. R.; Israelachvili, J. N.

    1998-03-01

    Bacteriorhodposin (bR) is a light-driven proton pump which converts photoenergy to electro-chemical potential across cytoplasmic membrane of bacteria. It forms a self assembled two-dimensional crystal, purple membrane, in the bacterial membrane. Purple membrane has been used to construct photovoltaic cells, imaging devices and biosensors for pH measurement. In these devices, purple membrane was deposited on a solid metal substrate or a semiconductor electrode. However, puple membrane on solid surfaces is not stable in water. In our study, we propose a method for fabrication of stable complexes between cationic lipid and purple membrane. This complexes can be used to prepare robust bR multilayers for biosensors. We have caracterised the complex structure and photo-function at different bR/cationic lipid ratios. Supported by NSF DMR-9624091, Los Alamos CULAR grant No.STB/UC:95-146 and Soka University, foreign exchange program.

  3. High temperature stabilization of DNA in complexes with cationic lipids.

    PubMed Central

    Tarahovsky, Yury S; Rakhmanova, Vera A; Epand, Richard M; MacDonald, Robert C

    2002-01-01

    The influence on the melting of calf thymus and plasmid DNA of cationic lipids of the type used in gene therapy was studied by ultraviolet spectrophotometry and differential scanning calorimetry. It was found that various membrane-forming cationic lipids are able to protect calf thymus DNA against denaturation at 100 degrees C. After interaction with cationic lipids, the differential scanning calorimetry melting profile of both calf thymus and plasmid DNA revealed two major components, one corresponding to a thermolabile complex with transition temperature, T(m(labile)), close to that of free DNA and a second corresponding to a thermostable complex with a transition temperature, T(m(stable)), at 105 to 115 degrees C. The parameter T(m(stable)) did not depend on the charge ratio, R(+/-). Instead, the amount of thermostable DNA and the enthalpy ratio Delta H((stable))/Delta H((labile)) depended upon R(+/-) and conditions of complex formation. In the case of O-ethyldioleoylphosphatidylcholine, the cationic lipid that was the main subject of the investigation, the maximal stabilization of DNA exceeded 90% between R(+/-) = 1.5 and 3.0. Several other lipids gave at least 75% protection in the range R(+/-) = 1.5 to 2.0. Centrifugal separation of the thermostable and thermolabile fractions revealed that almost all the transfection activity was present at the thermostable fraction. Electron microscopy of the thermostable complex demonstrated the presence of multilamellar membranes with a periodicity 6.0 to 6.5 nm. This periodic multilamellar structure was retained at temperatures as high as 130 degrees C. It is concluded that constraint of the DNA molecules between oppositely charged membrane surfaces in the multilamellar complex is responsible for DNA stabilization. PMID:11751314

  4. DNA-Cationic Lipid Complexes: Lamellar and Inverted Hexagonal Phases

    NASA Astrophysics Data System (ADS)

    Koltover, I.; Salditt, T.; Raedler, J.; Safinya, C.

    1998-03-01

    Cationic lipid-DNA (CL-DNA) complexes can be efficient non-viral vectors for gene therapy. However, it is not known why transfection rates vary widely for complexes with different lipid compositions. We have discovered a transition between two distinct liquid crystalline (LC) structures of the complex by varying the lipid composition: a lamellar structure ( J. Raedler, I. Koltover, T. Salditt, C. Safinya, Science 275, 810 (1997)) and a novel LC phase with DNA double-strands surrounded by lipid monolayers arranged on a regular hexagonal lattice. The CL-DNA complexes with the two structures interact differently with giant negatively charged liposomes, which represent the simplest model of cellular membranes. We demonstrate the generality of the lamellar-hexagonal transformation by observing it in complexes of cationic lipid with two other negatively charged biopolymers - polyglutamic acid (PGA), a model polypeptide and poly-thymine (polyT), a model single-stranded oligo-nucleotide. We identify the interactions leading to the transformations between the two complex phases for the three different polyelectrolytes. Supported by NSF DMR-9624091 and a Los Alamos CULAR grant No.STB/UC:95-146.

  5. Computational and analytical modeling of cationic lipid-DNA complexes.

    PubMed

    Farago, Oded; Grønbech-Jensen, Niels

    2007-05-01

    We present a theoretical study of the physical properties of cationic lipid-DNA (CL-DNA) complexes--a promising synthetically based nonviral carrier of DNA for gene therapy. The study is based on a coarse-grained molecular model, which is used in Monte Carlo simulations of mesoscopically large systems over timescales long enough to address experimental reality. In the present work, we focus on the statistical-mechanical behavior of lamellar complexes, which in Monte Carlo simulations self-assemble spontaneously from a disordered random initial state. We measure the DNA-interaxial spacing, d(DNA), and the local cationic area charge density, sigma(M), for a wide range of values of the parameter (c) representing the fraction of cationic lipids. For weakly charged complexes (low values of (c)), we find that d(DNA) has a linear dependence on (c)(-1), which is in excellent agreement with x-ray diffraction experimental data. We also observe, in qualitative agreement with previous Poisson-Boltzmann calculations of the system, large fluctuations in the local area charge density with a pronounced minimum of sigma(M) halfway between adjacent DNA molecules. For highly-charged complexes (large (c)), we find moderate charge density fluctuations and observe deviations from linear dependence of d(DNA) on (c)(-1). This last result, together with other findings such as the decrease in the effective stretching modulus of the complex and the increased rate at which pores are formed in the complex membranes, are indicative of the gradual loss of mechanical stability of the complex, which occurs when (c) becomes large. We suggest that this may be the origin of the recently observed enhanced transfection efficiency of lamellar CL-DNA complexes at high charge densities, because the completion of the transfection process requires the disassembly of the complex and the release of the DNA into the cytoplasm. Some of the structural properties of the system are also predicted by a continuum

  6. Polysaccharide-polynucleotide complexes VIII. Cation-induced complex formation between polyuridylic acid and schizophyllan.

    PubMed

    Sakurai, Kazuo; Iguchi, Ritsuko; Koumoto, Kazuya; Kimura, Taro; Mizu, Masami; Hisaeda, Yoshio; Shinkai, Seiji

    2002-10-05

    Schizophyllan belongs to the beta-1,3-D-glucan family, and dissolves as a single chain in dimethyl sulfoxide (DMSO) and as a triple helix in water, respectively. It is already known that when we prepare a mixture of poly(C) and schizophyllan in DMSO and subsequently exchange the solvent to water, poly(C) and schizophyllan can form a complex. When we applied this procedure to the poly(U) system, we could not induce the complex formation between poly(U) and schizophyllan at all. However, we found that addition of some alkaline cations is necessary to induce the complexation between poly(U) and schizophyllan. The complex stability strongly depends on both the cation species and the salt concentration. The complexation is sensitively reflected in the CD spectrum. The magnitude of the spectral change is followed by the order; Rb(+) > K(+) > Na(+) ? Cs(+). This cation order in the stability is confirmed by the fluorescence polarization measurements. (23)Na-NMR spectroscopy reveals that the product system is stabilized by addition of the cations, suggesting that the OH group in schizophyllan and the phosphate anion in poly(U) synergistically form a specific ligand system for the cations. To the best of our knowledge, such a cation-induced specific interaction between saccharides and polynucleotides has not been reported, and may provide a new clue to understand the biological role of beta-1,3-D-glucans. Copyright 2002 Wiley Periodicals, Inc. Biopolymers 65: 1-9, 2002

  7. The phase behavior of cationic lipid-DNA complexes.

    PubMed Central

    May, S; Harries, D; Ben-Shaul, A

    2000-01-01

    We present a theoretical analysis of the phase behavior of solutions containing DNA, cationic lipids, and nonionic (helper) lipids. Our model allows for five possible structures, treated as incompressible macroscopic phases: two lipid-DNA composite (lipoplex) phases, namely, the lamellar (L(alpha)(C)) and hexagonal (H(II)(C)) complexes; two binary (cationic/neutral) lipid phases, that is, the bilayer (L(alpha)) and inverse-hexagonal (H(II)) structures, and uncomplexed DNA. The free energy of the four lipid-containing phases is expressed as a sum of composition-dependent electrostatic, elastic, and mixing terms. The electrostatic free energies of all phases are calculated based on Poisson-Boltzmann theory. The phase diagram of the system is evaluated by minimizing the total free energy of the three-component mixture with respect to all the compositional degrees of freedom. We show that the phase behavior, in particular the preferred lipid-DNA complex geometry, is governed by a subtle interplay between the electrostatic, elastic, and mixing terms, which depend, in turn, on the lipid composition and lipid/DNA ratio. Detailed calculations are presented for three prototypical systems, exhibiting markedly different phase behaviors. The simplest mixture corresponds to a rigid planar membrane as the lipid source, in which case, only lamellar complexes appear in solution. When the membranes are "soft" (i.e., low bending modulus) the system exhibits the formation of both lamellar and hexagonal complexes, sometimes coexisting with each other, and with pure lipid or DNA phases. The last system corresponds to a lipid mixture involving helper lipids with strong propensity toward the inverse-hexagonal phase. Here, again, the phase diagram is rather complex, revealing a multitude of phase transitions and coexistences. Lamellar and hexagonal complexes appear, sometimes together, in different regions of the phase diagram. PMID:10733951

  8. Structural analysis of DNA complexation with cationic lipids

    PubMed Central

    Marty, Regis; N'soukpoé-Kossi, Christophe N.; Charbonneau, David; Weinert, Carl Maximilian; Kreplak, Laurent; Tajmir-Riahi, Heidar-Ali

    2009-01-01

    Complexes of cationic liposomes with DNA are promising tools to deliver genetic information into cells for gene therapy and vaccines. Electrostatic interaction is thought to be the major force in lipid–DNA interaction, while lipid-base binding and the stability of cationic lipid–DNA complexes have been the subject of more debate in recent years. The aim of this study was to examine the complexation of calf-thymus DNA with cholesterol (Chol), 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), dioctadecyldimethylammoniumbromide (DDAB) and dioleoylphosphatidylethanolamine (DOPE), at physiological condition, using constant DNA concentration and various lipid contents. Fourier transform infrared (FTIR), UV-visible, circular dichroism spectroscopic methods and atomic force microscopy were used to analyse lipid-binding site, the binding constant and the effects of lipid interaction on DNA stability and conformation. Structural analysis showed a strong lipid–DNA interaction via major and minor grooves and the backbone phosphate group with overall binding constants of KChol = 1.4 (±0.5) × 104 M−1, KDDAB = 2.4 (±0.80) × 104 M−1, KDOTAP = 3.1 (±0.90) × 104 M−1 and KDOPE = 1.45 (± 0.60) × 104 M−1. The order of stability of lipid–DNA complexation is DOTAP>DDAB>DOPE>Chol. Hydrophobic interactions between lipid aliphatic tails and DNA were observed. Chol and DOPE induced a partial B to A-DNA conformational transition, while a partial B to C-DNA alteration occurred for DDAB and DOTAP at high lipid concentrations. DNA aggregation was observed at high lipid content. PMID:19103664

  9. Neisseria lactamica antigens complexed with a novel cationic adjuvant

    PubMed Central

    Gaspar, Emanuelle B.; Rosetti, Andreza S.; Lincopan, Nilton; De Gaspari, Elizabeth

    2013-01-01

    Colonization of the nasopharynx by non-pathogenic Neisseria species, including N. lactamica, has been suggested to lead to the acquisition of natural immunity against Neisseria meningitidis in young children. The aim of this study was to identify a model complex of antigens and adjuvant for immunological preparation against N. meningitidis B, based on cross reactivity with N. lactamica outer membrane vesicles (OMV) antigens and the (DDA-BF) adjuvant. Complexes of 25 µg of OMV in 0.1 mM of DDA-BF were colloidally stable, exhibiting a mean diameter and charge optimal for antigen presentation. Immunogenicity tests for these complexes were performed in mice. A single dose of OMV/DDA-BF was sufficient to induce a (DTH) response, while the same result was achieved only after two doses of OMV/alum. In addition, to achieve total IgG levels that are similar to a single immunization with OMV/DDA-BF, it was necessary to give the mice a second dose of OMV/alum. Moreover, the antibodies induced from a single immunization with OMV/DDA-BF had an intermediate avidity, but antibodies with a similar avidity were only induced by OMV/alum after two immunizations. The use of this novel cationic adjuvant for the first time with a N. lactamica OMV preparation revealed good potential for future vaccine design. PMID:23296384

  10. Neisseria lactamica antigens complexed with a novel cationic adjuvant.

    PubMed

    Gaspar, Emanuelle B; Rosetti, Andreza S; Lincopan, Nilton; De Gaspari, Elizabeth

    2013-03-01

    Colonization of the nasopharynx by non-pathogenic Neisseria species, including N. lactamica, has been suggested to lead to the acquisition of natural immunity against Neisseria meningitidis in young children. The aim of this study was to identify a model complex of antigens and adjuvant for immunological preparation against N. meningitidis B, based on cross reactivity with N. lactamica outer membrane vesicles (OMV) antigens and the (DDA-BF) adjuvant. Complexes of 25 µg of OMV in 0.1 mM of DDA-BF were colloidally stable, exhibiting a mean diameter and charge optimal for antigen presentation. Immunogenicity tests for these complexes were performed in mice. A single dose of OMV/DDA-BF was sufficient to induce a (DTH) response, while the same result was achieved only after two doses of OMV/alum. In addition, to achieve total IgG levels that are similar to a single immunization with OMV/DDA-BF, it was necessary to give the mice a second dose of OMV/alum. Moreover, the antibodies induced from a single immunization with OMV/DDA-BF had an intermediate avidity, but antibodies with a similar avidity were only induced by OMV/alum after two immunizations. The use of this novel cationic adjuvant for the first time with a N. lactamica OMV preparation revealed good potential for future vaccine design.

  11. Synthesis and structures of cationic aluminum and galllium amidinate complexes

    SciTech Connect

    Dagorne, S.; Guzei, I.A.; Coles, M.P.; Jordan, R.F.

    2000-01-19

    Aluminum and gallium amidinate complexes, {l{underscore}brace}RC(NR{prime}){sub 2}{r{underscore}brace}MMe{sub 2} (R, R{prime} = alkyl; M - Al, Ga), react with the ``cationic activators'' [Ph{sub 3}C][B(C{sub 6}F{sub 5}){sub 4}] and B(C{sub 6}F{sub 5}){sub 3} to yield cationic Al and Ga alkyl species whose structures are strongly influenced by the steric properties of the amidinate ligand. The reaction of acetamidinate Al complexes {l{underscore}brace}MeC(NR{prime}){sub 2}{r{underscore}brace}AlMe{sub 2}(R{prime} = {sup i}Pr, 1a; R{prime} = Cy, 3a) with 0.5 equiv of [Ph{sub 3}C][B(C{sub 6}F{sub 5}){sub 4}] or B(C{sub 6}F{sub 5}){sub 3} yields {l{underscore}brace}MeC(NR{prime}){sub 2}{r{underscore}brace}{sub 2}Al{sub 2}Me{sub 3}{sup +} (R{prime} - {sup i}Pr, 2a{sup +}; R{prime} = Cy, 4a{sup +}) as the B(C{sub 6}F{sub 5}){sub 4}{sup {minus}} or MeB(C{sub 6}F{sub 5}){sub 3}{sup {minus}} salts. X-ray crystallographic analyses establish that 2a{sup +} and 4a{sup +} are double-amidinate-bridged dinuclear cations, in which the two metal centers are linked by {mu}-{eta}{sup 1},{eta}{sup 1} and {mu}-{eta}{sup 1},{eta}{sup 2} amidinate bridges. NMR studies show that 2a{sup +} undergoes two dynamic processes in solution: (1) a {mu}-{eta}{sup 1},{eta}{sup 1}/{mu}-{eta}{sup 1},{eta}{sup 2} amidinate exchange and (2) Me exchange between the two metal centers. The reaction of {l{underscore}brace}MeC(N{sup i}Pr){sub 2}{r{underscore}brace} (1b) with 0.5 equiv of B(C{sub 6}F{sub 5}){sub 3} yields {l{underscore}brace}MeC(N{sup i}Pr){sub 2}{r{underscore}brace}{sub 2}Ga{sub 2}Me{sub 3}{sup +} (2b{sup +}), whose structure and dynamic properties are similar to those of 2a{sup +}. The reaction of the bulkier {sup t}Bu-substituted amidinate complexes {l{underscore}brace}{sup t}BuC(N{sup i}Pr){sub 2}{r{underscore}brace}MMe{sub 2} (M - Al, 6a; M - Ga, 6b) with 0.5 equiv of [Ph{sub 3}C][B(C{sub 6}F{sub 5}){sub 4}] yields {l{underscore}brace}{sup t}BuC(N{sup i}Pr){sub 2}{r

  12. Insights into dynamic processes of cations in pyrochlores and other complex oxides

    SciTech Connect

    Uberuaga, Blas Pedro; Perriot, Romain

    2015-08-26

    Complex oxides are critical components of many key technologies, from solid oxide fuel cells and superionics to inert matrix fuels and nuclear waste forms. In many cases, understanding mass transport is important for predicting performance and, thus, extensive effort has been devoted to understanding mass transport in these materials. However, most work has focused on the behavior of oxygen while cation transport has received relatively little attention, even though cation diffusion is responsible for many phenomena, including sintering, radiation damage evolution, and deformation processes. Here, we use accelerated molecular dynamics simulations to examine the kinetics of cation defects in one class of complex oxides, A₂B₂O₇ pyrochlore. In some pyrochlore chemistries, B cation defects are kinetically unstable, transforming to A cation defects and antisites at rates faster than they can diffuse. When this occurs, transport of B cations occurs through defect processes on the A sublattice. Further, these A cation defects, either interstitials or vacancies, can interact with antisite disorder, reordering the material locally, though this process is much more efficient for interstitials than vacancies. Whether this behavior occurs in a given pyrochlore depends on the A and B chemistry. Pyrochlores with a smaller ratio of cation radii exhibit this complex behavior, while those with larger ratios exhibit direct migration of B interstitials. Similar behavior has been reported in other complex oxides such as spinels and perovskites, suggesting that this coupling of transport between the A and B cation sublattices, while not universal, occurs in many complex oxide.

  13. A theoretical study of complexes formed between cations and curved aromatic systems: electrostatics does not always control cation-π interaction.

    PubMed

    Carrazana-García, Jorge A; Cabaleiro-Lago, Enrique M; Rodríguez-Otero, Jesús

    2017-04-10

    The present work studies the interaction of two extended curved π-systems (corannulene and sumanene) with various cations (sodium, potassium, ammonium, tetramethylammonium, guanidinium and imidazolium). Polyatomic cations are models of groups found in important biomolecules in which cation-π interaction plays a fundamental role. The results indicate an important size effect: with extended π systems and cations of the size of potassium and larger, dispersion is much more important than has been generally recognized for cation-π interactions. In most of the systems studied here, the stability of the cationcomplexes is the result of a balanced combination of electrostatic, induction and dispersion contributions. None of the systems studied here owes its stability to the electrostatic interaction more than 42%. Induction dominates stabilization in complexes with sodium, and in some of the potassium and ammonium complexes. In complexes with large cations and with flat cations dispersion is the major stabilizing contribution and can provide more than 50% of the stabilization energy. This implies that theoretical studies of the cation-π interaction involving large or even medium-size fragments require a level of calculation capable of properly modelling dispersion. The separation between the cation and the π system is another important factor to take into account, especially when the fragments of the cationcomplex are bound (for example, to a protein backbone) and cannot interact at the most favourable distance.

  14. Alkali metal cation-hexacyclen complexes: effects of alkali metal cation size on the structure and binding energy.

    PubMed

    Austin, C A; Rodgers, M T

    2014-07-24

    Threshold collision-induced dissociation (CID) of alkali metal cation-hexacyclen (ha18C6) complexes, M(+)(ha18C6), with xenon is studied using guided ion beam tandem mass spectrometry techniques. The alkali metal cations examined here include: Na(+), K(+), Rb(+), and Cs(+). In all cases, M(+) is the only product observed, corresponding to endothermic loss of the intact ha18C6 ligand. The cross-section thresholds are analyzed to extract zero and 298 K M(+)-ha18C6 bond dissociation energies (BDEs) after properly accounting for the effects of multiple M(+)(ha18C6)-Xe collisions, the kinetic and internal energy distributions of the M(+)(ha18C6) and Xe reactants, and the lifetimes for dissociation of the activated M(+)(ha18C6) complexes. Ab initio and density functional theory calculations are used to determine the structures of ha18C6 and the M(+)(ha18C6) complexes, provide molecular constants necessary for the thermodynamic analysis of the energy-resolved CID data, and theoretical estimates for the M(+)-ha18C6 BDEs. Calculations using a polarizable continuum model are also performed to examine solvent effects on the binding. In the absence of solvent, the M(+)-ha18C6 BDEs decrease as the size of the alkali metal cation increases, consistent with the noncovalent nature of the binding in these complexes. However, in the presence of solvent, the ha18C6 ligand exhibits selectivity for K(+) over the other alkali metal cations. The M(+)(ha18C6) structures and BDEs are compared to those previously reported for the analogous M(+)(18-crown-6) and M(+)(cyclen) complexes to examine the effects of the nature of the donor atom (N versus O) and the number donor atoms (six vs four) on the nature and strength of binding.

  15. Polycation-DNA complexes for gene delivery: a comparison of the biopharmaceutical properties of cationic polypeptides and cationic lipids.

    PubMed

    Pouton, C W; Lucas, P; Thomas, B J; Uduehi, A N; Milroy, D A; Moss, S H

    1998-04-30

    DNA plasmids formed particulate complexes with a variety of cationic polyamino acids and cationic lipids, which were used to transfect mammalian cells in culture. Complexation was studied by assaying for exclusion of ethidium using a fluorometric assay, which indicated that complexation with cationic polyamino acids took place with utilisation of the majority of charged functional groups. The particle sizes and zeta potentials of a range of complexes were determined. Generally polyamino acids formed uniform particles 80-120 nm in diameter in water, but their particle size increased on dilution of the particles in electrolytes or cell culture media. The efficiency of transfection was compared using complexes of pRSVlacZ, a reporter construct which expressed beta-galactosidase under the control of the Rous sarcoma virus promoter. Positively charged DNA/polyamino acid complexes were taken up by cells but required an endosomolytic agent, such as chloroquine, to facilitate transfection. Polyornithine complexes resulted in the highest levels of expression, in comparison with other homopolyamino acids (polyornithine>poly-L-lysine=poly-D-lysine>polyarginine). Copolyamino acids of lysine and alanine condensed DNA but were less active in transfection experiments. Copoly(L-Lys, L-Ala 1:1) was inactive even in the presence of chloroquine. In contrast DNA/cationic lipid complexes transfected cells spontaneously, and chloroquine did not improve the extent of expression, rather it usually reduced efficiency. There was little correlation between comparative efficiencies of lipid complexes between cell lines suggesting that the nature of the cell membrane and differences in mechanisms of internalisation were determinants of efficiency. In an effort to explore better cell culture models for gene delivery, monolayers of Caco-2 cells were transfected in filter culture. As the cells differentiated and formed a polarized monolayer, expression of beta-galactosidase was reduced until at

  16. Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations.

    PubMed

    Sato, T; Ramirez-Cuesta, A J; Daemen, L; Cheng, Y-Q; Tomiyasu, K; Takagi, S; Orimo, S

    2016-09-27

    Hydrogen release from Al-based complex hydrides composed of metal cation(s) and [AlH4](-) was investigated using inelastic neutron scattering viewed from vibrational dynamics. The hydrogen release followed the softening of translational and [AlH4](-) librational modes, which was enhanced by vibrational dynamics and the valence(s) of the metal cation(s).

  17. Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations

    DOE PAGES

    Sato, T.; Ramirez-Cuesta, Anibal J.; Daemen, Luke L.; ...

    2016-08-31

    Hydrogen release from Al-based complex hydrides composed of metal cation(s) and [AlH4]– was investigated using inelastic neutron scattering viewed from vibrational dynamics. Here, the hydrogen release followed the softening of translational and [AlH4]– librational modes, which was enhanced by vibrational dynamics and the valence(s) of the metal cation(s).

  18. The diastereoselective synthesis of octahedral cationic iridium hydride complexes with a stereogenic metal centre.

    PubMed

    Humbert, Nicolas; Mazet, Clément

    2016-08-23

    We report herein the highly diastereoselective synthesis of octahedral cationic Ir(iii) hydride complexes with a stereogenic metal centre following various strategies. The configurational stability of these compounds has also been investigated.

  19. Thermochromic and solvatochromic Nafion films incorporating cationic metal-chelate complexes.

    PubMed

    Funasako, Yusuke; Mochida, Tomoyuki

    2013-05-21

    Nafion films incorporating cationic nickel complexes [Ni(II)(acac)(R4en)](+) (acac = acetylacetonato, R4en = tetraalkylethylenediamine) that exhibit chromic behavior in response to temperature changes and solvent molecules in the vapor and liquid phases have been prepared.

  20. Iridium(III) soft salts from dinuclear cationic and mononuclear anionic complexes for OLED devices.

    PubMed

    Nasr, Gihane; Guerlin, Audrey; Dumur, Frédéric; Beouch, Layla; Dumas, Eddy; Clavier, Gilles; Miomandre, Fabien; Goubard, Fabrice; Gigmes, Didier; Bertin, Denis; Wantz, Guillaume; Mayer, Cédric R

    2011-10-14

    Two iridium(III) soft salts based on ion-paired dinuclear cationic and mononuclear anionic complexes were designed and investigated as phosphorescent emitters for solution processed OLEDs. New dinuclear cationic complexes were prepared with two different bridging ligands, a carbazole and a phenylene spacer. Best devices were designed with the soft salt bearing a carbazole moiety. This journal is © The Royal Society of Chemistry 2011

  1. Cationic Liposomes Modified with Polyallylamine as a Gene Carrier: Preparation, Characterization and Transfection Efficiency Evaluation

    PubMed Central

    Kazemi Oskuee, Reza; Mahmoudi, Asma; Gholami, Leila; Rahmatkhah, Alireza; Malaekeh-Nikouei, Bizhan

    2016-01-01

    Purpose: Cationic polymers and cationic liposomes have shown to be effective non-viral gene delivery vectors. In this study, we tried to improve the transfection efficiency by employing the advantages of both. Methods: For this purpose, modified polyallylamines (PAAs) were synthesized. These modifications were done through the reaction of PAA (15 KDa) with acrylate and 6-bromoalkanoic acid derivatives. Liposomes comprising of these cationic polymers and cationic lipid were prepared and extruded through polycarbonate filters to obtain desired size. Liposome-DNA nanocomplexes were prepared in three carrier to plasmid (C/P) ratios. Size, zeta potential and DNA condensation ability of each complex were characterized separately and finally transfection efficiency and cytotoxicity of prepared vectors were evaluated in Neuro2A cell line. Results: The results showed that mean particle size of all these nanocomplexes was lower than 266 nm with surface charge of 22.0 to 33.9 mV. Almost the same condensation pattern was observed in all vectors and complete condensation was occurred at C/P ratio of 1.5. The lipoplexes containing modified PAA 15 kDa with 10% hexyl acrylate showed the highest transfection efficacy and lowest cytotoxicity in C/P ratio of 0.5. Conclusion: In some cases nanocomplexes consisting of cationic liposome and modified PAA showed better transfection activity and lower cytotoxicity compared to PAA. PMID:28101458

  2. Insights into dynamic processes of cations in pyrochlores and other complex oxides

    DOE PAGES

    Uberuaga, Blas Pedro; Perriot, Romain

    2015-08-26

    Complex oxides are critical components of many key technologies, from solid oxide fuel cells and superionics to inert matrix fuels and nuclear waste forms. In many cases, understanding mass transport is important for predicting performance and, thus, extensive effort has been devoted to understanding mass transport in these materials. However, most work has focused on the behavior of oxygen while cation transport has received relatively little attention, even though cation diffusion is responsible for many phenomena, including sintering, radiation damage evolution, and deformation processes. Here, we use accelerated molecular dynamics simulations to examine the kinetics of cation defects in onemore » class of complex oxides, A₂B₂O₇ pyrochlore. In some pyrochlore chemistries, B cation defects are kinetically unstable, transforming to A cation defects and antisites at rates faster than they can diffuse. When this occurs, transport of B cations occurs through defect processes on the A sublattice. Further, these A cation defects, either interstitials or vacancies, can interact with antisite disorder, reordering the material locally, though this process is much more efficient for interstitials than vacancies. Whether this behavior occurs in a given pyrochlore depends on the A and B chemistry. Pyrochlores with a smaller ratio of cation radii exhibit this complex behavior, while those with larger ratios exhibit direct migration of B interstitials. Similar behavior has been reported in other complex oxides such as spinels and perovskites, suggesting that this coupling of transport between the A and B cation sublattices, while not universal, occurs in many complex oxide.« less

  3. In vitro biopharmaceutical evaluation of ciprofloxacin/metal cation complexes for pulmonary administration.

    PubMed

    Brillault, J; Tewes, F; Couet, W; Olivier, J C

    2017-01-15

    Pulmonary delivery of fluoroquinolones (FQs) is an interesting approach to treat lung infections as it may lead to high local concentrations while minimizing systemic exposure. However, FQs have a rapid diffusion through the lung epithelium giving the pulmonary route no advantage compared to the oral route. Interactions between FQs and metal cations form complexes which limit the diffusion through the epithelial barrier and would reduce the absorption of FQs and maintain high concentrations in the lung. The effects of this complexation depend on the FQ and the metal cations and optimum partners should be selected through in vitro experiments prior to aerosol drug formulation. In this study, CIP was chosen as a representative FQ and 5 cations (Ca(2+), Mg(2+), Zn(2+), Al(3+), Cu(2+)) were selected to study the complexation and its effects on permeability, antimicrobial efficacy and cell toxicity. The results showed that the apparent association constants between CIP and cations ranked with the descending order: Cu(2+)>Al(3+)>Zn(2+)>Mg(2+)>Ca(2+). When a target of 80% complexation was reached with the adequate concentrations of cations, the CIP permeability through the Calu-3 lung epithelial cells was decreased of 50%. Toxicity of the CIP on the Calu-3 cells, with an EC50 evaluated at 7μM, was not significantly affected by the presence of the cations. The minimum inhibitory concentration of CIP for Pseudomonas aeruginosa was not affected or slightly increased in the range of cation concentrations tested, except for Mg(2+). In conclusion, permeability was the main parameter that was affected by the metal cation complexation while cell toxicity and antimicrobial activity were not or slightly modified. Cu(2+), with the highest apparent constant of association and with no effect on cell toxicity and antimicrobial activity of the CIP, appeared as a promising cation for the development of a controlled-permeability formulation of CIP for lung treatment. Copyright © 2016

  4. Comparison of covalency in the complexes of trivalent actinide and lanthanide cations.

    PubMed

    Jensen, Mark P; Bond, Andrew H

    2002-08-21

    The complexes of trivalent actinide (Am(III) and Cm(III)) and lanthanide (Nd(III) and Sm(III)) cations with bis(2,4,4-trimethylpentyl)phosphinic acid, bis(2,4,4-trimethylpentyl)monothiophosphinic acid, and bis(2,4,4-trimethylpentyl)dithiophosphinic acid in n-dodecane have been studied by visible absorption spectroscopy and X-ray absorption fine structure (XAFS) measurements in order to understand the chemical interactions responsible for the great selectivity the dithiophosphinate ligand exhibits for trivalent actinide cations in liquid-liquid extraction. Under the conditions studied, each type of ligand displays a different coordination mode with trivalent f-element cations. The phosphinate ligand coordinates as hydrogen-bonded dimers, forming M(HL2)3. Both the oxygen and the sulfur donor of the monothiophosphinate ligand can bind the cations, affording both bidentate and monodentate ligands. The dithiophosphinate ligand forms neutral bidentate complexes, ML3, with no discernible nitrate or water molecules in the inner coordination sphere. Comparison of the Cm(III), Nd(III), and Sm(III) XAFS shows that the structure and metal-donor atom bond distances are indistinguishable within experimental error for similarly sized trivalent lanthanide and actinide cations, despite the selectivity of bis(2,4,4-trimethylpentyl)dithiophosphinic acid for trivalent actinide cations over trivalent lanthanide cations.

  5. Comparison of covalency in the complexes of trivalent actinide and lanthanide cations.

    SciTech Connect

    Jensen, M. P.; Bond, A. H.; Chemistry

    2002-08-21

    The complexes of trivalent actinide (Am(III) and Cm(III)) and lanthanide (Nd(III) and Sm(III)) cations with bis(2,4,4-trimethylpentyl)phosphinic acid, bis(2,4,4-trimethylpentyl)monothiophosphinic acid, and bis(2,4,4-trimethylpentyl)dithiophosphinic acid in n-dodecane have been studied by visible absorption spectroscopy and X-ray absorption fine structure (XAFS) measurements in order to understand the chemical interactions responsible for the great selectivity the dithiophosphinate ligand exhibits for trivalent actinide cations in liquid-liquid extraction. Under the conditions studied, each type of ligand displays a different coordination mode with trivalent f-element cations. The phosphinate ligand coordinates as hydrogen-bonded dimers, forming M(HL{sub 2}){sub 3}. Both the oxygen and the sulfur donor of the monothiophosphinate ligand can bind the cations, affording both bidentate and monodentate ligands. The dithiophosphinate ligand forms neutral bidentate complexes, ML{sub 3}, with no discernible nitrate or water molecules in the inner coordination sphere. Comparison of the Cm(III), Nd(III), and Sm(III) XAFS shows that the structure and metal-donor atom bond distances are indistinguishable within experimental error for similarly sized trivalent lanthanide and actinide cations, despite the selectivity of bis(2,4,4-trimethylpentyl)dithiophosphinic acid for trivalent actinide cations over trivalent lanthanide cations.

  6. Time-resolved fluorescence spectroscopic investigation of cationic polymer/DNA complex formation

    NASA Astrophysics Data System (ADS)

    D'Andrea, Cosimo; Bassi, Andrea; Taroni, Paola; Pezzoli, Daniele; Volonterio, Alessandro; Candiani, Gabriele

    2011-07-01

    Since DNA is not internalized efficiently by cells, the success of gene therapy depends on the availability of carriers to efficiently deliver genetic material into target cells. Gene delivery vectors can be broadly categorized into viral and non-viral ones. Non-viral gene delivery systems are represented by cationic lipids and polymers rely on the basics of supramolecular chemistry termed "self-assembling": at physiological pH, they are cations and spontaneously form lipoplexes (for lipids) and polyplexes (for polymers) complexing nucleic acids. In this scenario, cationic polymers are commonly used as non-viral vehicles. Their effectiveness is strongly related to key parameters including DNA binding ability and stability in different environments. Time-resolved fluorescence spectroscopy of SYBR Green I (DNA dye) was carried out to characterize cationic polymer/DNA complex (polyplex) formation dispersed in aqueous solution. Both fluorescence amplitude and lifetime proved to be very sensitive to the polymer/DNA ratio (N/P ratio, +/-).

  7. Enantioselective Cyclizations of Silyloxyenynes Catalyzed by Cationic Metal Phosphine Complexes

    PubMed Central

    Brazeau, Jean-François; Zhang, Suyan; Colomer, Ignacio; Corkey, Britton K.; Toste, F. Dean

    2012-01-01

    The discovery of complementary methods for enantioselective transition-metal-catalyzed cyclization with silyloxyenynes has been accomplished using chiral phosphine ligands. Under palladium catalysis, 1,6-silyloxyenynes bearing a terminal alkyne led to the desired 5-membered ring with high enantioselectivities (up to 91% ee). As for reactions under cationic gold catalysis, 1,6- and 1,5-silyloxyenynes bearing an internal alkyne furnished the chiral cyclopentane derivatives with excellent enantiomeric excess (up to 94% ee). Modification of the substrate by incorporating an α,β-unsaturation led to the discovery of a tandem cyclization. Remarkably, using silyloxy-1,3-dien-7-ynes under gold catalysis conditions provided the bicyclic derivatives with excellent diastereo- and enantioselectivities (up to >20:1 dr and 99% ee). PMID:22296571

  8. Neutral and Cationic Alkyl Tantalum Imido Complexes: Synthesis and Migratory Insertion Reactions

    PubMed Central

    Anderson, Laura L.; Schmidt, Joseph A. R.; Arnold, John; Bergman, Robert G.

    2008-01-01

    The synthesis and reactivity of dibenzyl cationic tantalum imido complexes is described. The trialkyl tantalum imido compounds Bn3Ta=NCMe3 (1) and Np3Ta=NCMe3 (2) were synthesized as starting materials for the study of dialkyl cationic tantalum imido complexes. Compound 1 undergoes insertion reactions with diisopropylcarbodiimide and 2,6-dimethylphenylisocyanide to give (bisamidinate)imido complex 5 and (bisimino-acyl)imido complex 6, respectively. Treatment of compound 1 with B(C6F5)3 gives the zwitterionic tantalum complex [Bn2Ta=NCMe3][BnB(C6F5)3] (7) which is stabilized by η6-coordination of the benzyl triaryl borate anion. Coordination of the aryl anion can be displaced by three equivalents of pyridine to give the Lewis base complex 8. Treatment of compound 1 with [Ph3C][B(C6F5)4] gives the cationic tantalum imido complex [Bn2Ta=NCMe3][B(C6F5)4] (3). This salt forms insoluble aggregates unless trapped by THF coordination or an insertion reaction with an alkyne or an alkene. Cation 3 undergoes migratory insertion reactions with diphenylacetylene, phenylacetylene, norbornene, and cis-cyclooctene to give the corresponding alkenyl or modified alkyl imido complexes. The characterization of these products and the significance of these insertion reactions with respect to Ziegler-Natta polymerizations and hydroamination reactions are described. PMID:19079787

  9. Enhancing electrocatalytic hydrogen evolution by nickel salicylaldimine complexes with alkali metal cations in aqueous media.

    PubMed

    Shao, Haiyan; Muduli, Subas K; Tran, Phong D; Soo, Han Sen

    2016-02-18

    New salicylaldimine nickel complexes, comprising only earth-abundant elements, have been developed for electrocatalytic hydrogen evolution in aqueous media. The second-sphere ether functionalities on the periphery of the complexes enhance the electrocatalytic activity in the presence of alkali metal cations. The electrocatalysts demonstrate improved performances especially in the economical and sustainable seawater reaction medium.

  10. Catalytic Hydroamination of Alkynes and Norbornene with Neutral and Cationic Tantalum Imido Complexes

    PubMed Central

    Anderson, Laura L.; Arnold, John; Bergman, Robert G.

    2005-01-01

    Several tantalum imido complexes have been synthesized and shown to efficiently catalyze the hydroamination of internal and terminal alkynes. An unusual hydroamination/hydroarylation reaction of norbornene catalyzed by a highly electrophilic cationic tantalum imido complex is also reported. Factors affecting catalyst activity and selectivity are discussed along with mechanistic insights gained from stoichiometric reactions. PMID:15255680

  11. Vanadyl cationic complexes as catalysts in olefin oxidation.

    PubMed

    Nunes, Carla D; Vaz, Pedro D; Félix, Vítor; Veiros, Luis F; Moniz, Tânia; Rangel, Maria; Realista, Sara; Mourato, Ana C; Calhorda, Maria José

    2015-03-21

    Three new mononuclear oxovanadium(IV) complexes [VO(acac)(R-BIAN)]Cl (BIAN = 1,2-bis{(R-phenyl)imino}acenaphthene, R = H, 1; CH3, 2; Cl, 3) were prepared and characterized. They promoted the catalytic oxidation of olefins such as cyclohexene, cis-cyclooctene, and styrene with both tbhp (tert-butylhydroperoxide) and H2O2, and of enantiopure olefins (S(-)- and R(+)-pinene, and S(-)- and R(+)-limonene) selectively to their epoxides, with tbhp as the oxidant. The TOFs for styrene epoxidation promoted by complex 3 with H2O2 (290 mol mol(-1)V h(-1)) and for cis-cyclooctene epoxidation by 2 with tbhp (248 mol mol(-1)V h(-1)) are particularly good. Conversions reached 90% for several systems with tbhp, and were lower with H2O2. A preference for the internal C=C bond, rather than the terminal one, was found for limonene. Kinetic data indicate an associative process as the first step of the reaction and complex [VO(acac)(H-BIAN)](+) (1(+)) was isolated in an FTICR cell after adding tbhp to 1. EPR studies provide evidence for the presence of a V(IV) species in solution, until at least 48 hours after the addition of tbhp and cis-cyclooctene, and cyclic voltammetry studies revealed an oxidation potential above 1 V for complex 1. DFT calculations suggest that a [VO(H-BIAN)(MeOO)](+) complex is the likely active V(IV) species in the catalytic cycle from which two competitive mechanisms for the reaction proceed, an outer sphere path with an external attack of the olefin at the coordinated peroxide, and an inner sphere mechanism starting with a complex with the olefin coordinated to vanadium.

  12. Ultrasonic Absorption Rate Studies of Crown Ether and 222 Cryptate Complexes of Alkali Metal Cations in Nonaqueous Solutions

    DTIC Science & Technology

    1988-06-30

    Studies of Crown Ether and 222 Cryptate Complexes of Alkali Metal Cations in Nonaqueous Solutions * by Sergio Petrucci and Edward M. Eyring Prepared...STUDIES OF CROWN ETHER AND 222 CRYPTATE COMPLEXES OF ALKALI METAL CATIONS IN NONAQUEOUS SOLUTIONS 12. PERSONAL AUTHOR(S) Sergio Petrucci and Edward M...of Crown Ether and 222 Cryptate Complexes of Alkali Metal Cations in Nonaqueous Solutions Sergio Petrucci and Edward M. Eyring Department of

  13. Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations

    SciTech Connect

    Sato, T.; Ramirez-Cuesta, Anibal J.; Daemen, Luke L.; Cheng, Yong -Qiang; Tomiyasu, Keisuke; Takagi, Shigeyuki; Orimo, Shin-ichi

    2016-08-31

    Hydrogen release from Al-based complex hydrides composed of metal cation(s) and [AlH4] was investigated using inelastic neutron scattering viewed from vibrational dynamics. Here, the hydrogen release followed the softening of translational and [AlH4] librational modes, which was enhanced by vibrational dynamics and the valence(s) of the metal cation(s).

  14. Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations

    SciTech Connect

    Sato, T.; Ramirez-Cuesta, Anibal J.; Daemen, Luke L.; Cheng, Yong -Qiang; Tomiyasu, Keisuke; Takagi, Shigeyuki; Orimo, Shin-ichi

    2016-08-31

    Hydrogen release from Al-based complex hydrides composed of metal cation(s) and [AlH4] was investigated using inelastic neutron scattering viewed from vibrational dynamics. Here, the hydrogen release followed the softening of translational and [AlH4] librational modes, which was enhanced by vibrational dynamics and the valence(s) of the metal cation(s).

  15. ESI MS, spectroscopic and semiempirical characterization of a macrobicyclic complex with Er (III) cation

    NASA Astrophysics Data System (ADS)

    Przybylski, Piotr; Kołodziej, Beata; Leniec, Grzegorz; Kaczmarek, Sławomir M.; Grech, Eugeniusz; Typek, Janusz; Brzezinski, Bogumil

    2008-04-01

    Erbium cryptate [(MSB-H+NO 3+H 2O) Er] NO 3 has been synthesized as a result of the Schiff base condensation and investigated by FT-IR, ESI MS and EPR methods. In the ESI MS spectrum of this complex [(MSB-H+NO 3+H 2O) Er] NO 3 in the range of cv = 10-30V two main signals at m/z = 422 and m/z = 842 were observed corresponding to the [(MSB-H) Er] 2+ and [(MSB-2H) Er] + fragmentary cations, respectively. Besides these main peaks, a low intensity signals at m/z = 903 and m/z = 921 assigned to the [(MSB-H+NO 3) Er] + and [(MSB-H+NO 3+H 2O) Er] + complexes were also found. FT-IR spectrum revealed a broad band at 3403 cm -1 assigned to the ν(OH) vibrations of hydrogen bonded water molecule within the 1:1 macrobicyclic Schiff base-Er 3+ complex as well as the bands at 1335 cm -1 and 1355 cm -1 assigned to the ν(NO3-) vibrations of both bonded and non-bonded with the metal cations nitrate groups, respectively. DTA-TG analysis confirmed the presence of one water molecule in the complex. Full geometry optimization and heat of formation calculations of macrobicyclic Schiff base ligand and its complexes including nitrate anion and one water molecule were carried out. A comparison of these data suggests that the complexation of Er 3+ cation by the macrobicyclic Schiff base molecule with the involvement of water molecule is less energetically favourable. EPR measurements confirmed the presence of one Er 3+ cation in the complex structure. Computer simulation of the recorded EPR spectra revealed the presence of low symmetry at the Er ion site. The semiempirical MM/AM1d calculations indicated an asymmetrical location of the Er 3+ cation within the complex structure.

  16. Selective complexation of divalent cations by a cyclic α,β-peptoid hexamer: a spectroscopic and computational study.

    PubMed

    De Santis, E; Edwards, A A; Alexander, B D; Holder, S J; Biesse-Martin, A-S; Nielsen, B V; Mistry, D; Waters, L; Siligardi, G; Hussain, R; Faure, S; Taillefumier, C

    2016-12-07

    We describe the qualitative and quantitative analysis of the complexation properties towards cations of a cyclic peptoid hexamer composed of alternating α- and β-peptoid monomers, which bear exclusively chiral (S)-phenylethyl side chains (spe) that have no noticeable chelating properties. The binding of a series of monovalent and divalent cations was assessed by (1)H NMR, circular dichroism, fluorescence and molecular modelling. In contrast to previous studies on cations binding by 18-membered α-cyclopeptoid hexamers, the 21-membered cyclopeptoid cP1 did not complex monovalent cations (Na(+), K(+), Ag(+)) but showed selectivity for divalent cations (Ca(2+), Ba(2+), Sr(2+) and Mg(2+)). Hexacoordinated C-3 symmetrical complexes were demonstrated for divalent cations with ionic radii around 1 Å (Ca(2+) and Ba(2+)), while 5-coordination is preferred for divalent cations with larger (Ba(2+)) or smaller ionic radii (Mg(2+)).

  17. Cationic PCP iridaepoxide and carbene complexes for facile water elimination and activation processes.

    PubMed

    Doyle, Lauren E; Piers, Warren E; Bi, David W

    2017-03-13

    Iridaepoxide dihydride complexes of a PCP ligand bearing benzo[b]thiophene linkers are synthesized through ligand coopertive N2O and H2 activations. These neutral complexes also eliminate water at elevated temperatures to form the corresponding PCcarbeneP complexes which results in the formal hydrogenation of N2O to water. The synthesis of cationic iridaepoxide dihydride complexes are reported herein where the room temperature elimination of water is observed when a donating solvent is used. This supports a previously proposed mechanism for this water elimination where hydrides cis to the epoxide are required. Ir(i) and Ir(iii) cationic PCcarbeneP complexes are also synthesized through protonation and through O-H oxidation additions of water and phenol.

  18. ESI MS, NMR and PM5 semiempirical studies of oligomycin A and its complexes with Li + and Na + cations

    NASA Astrophysics Data System (ADS)

    Gierczyk, Błażej; Schroeder, Grzegorz; Przybylski, Piotr; Brzezinski, Bogumil; Bartl, Franz; Zundel, Georg

    2005-03-01

    The ability to complex formation of oligomycin A (OLA) with monovalent cations was studied by the ESI mass spectrometry, 1H, 13C, 7Li and 23Na NMR spectroscopic and PM5 semiempirical methods. The ESI MS spectra indicated that OLA formed stable 1:1 complexes with all monovalent cations irrespective of the stoichiometry and cone voltage values used. With increasing cone voltages only the degradations of the OLA-Li + and OLA-Na + complexes with formation of fragmentary metal cation complexes were found. For OLA complexes with K +, Rb + and Cs + cations, with increasing cone voltage the fragmentation of these complexes occurred without the formation of fragmentary metal cation complexes. On the basis of the NMR studies the assignment of the signals of hydroxyl groups in the spectrum of OLA was made and the spectra of its complexes evidenced the involvement of certain oxygen atoms in the complexation process. The PM5 semiempirical calculations allowed visualizations of all structures of the OLA—monovalent cation complexes as well as the fragmentary cations. The most interesting structure was found for OLA-Li + complex, in which the Li + cation is fully isolated from the interactions with the environment.

  19. Acetohydroxamic Acid Complexes with Trivalent f-Block Metal Cations

    SciTech Connect

    Sinkov, Serguei I.; Choppin, Gregory

    2003-11-01

    Acetohydroxamic acid has been studied by optical absorbance spectroscopy as a complex forming reagent for the lighter trivalent lanthanides and actinides (Pu(III) and Am(III)) in aqueous solution at 2.0 M (NaClO4) ionic strength. The highest stoichiometry in all the cases studied has been found to be a 1:4 metal-to-ligand ratio; formation of tetrahydroxamato species requires a high excess of the ligand and alkaline pH, Spectrophotometric monitoring confirmed the presence of Pu(III) by electrochemical reduction of Pu(IV) in the course of the pH titration experiment. The formation constants can be used for optimization of processing flowsheets in the advanced PUREX process.

  20. [Sorption and desorption of phenanthrene by organo-mineral complexes with different bridge cations].

    PubMed

    Ni, Jin-zhi; Luo, Yong-ming; Wei, Ran; Li, Xiu-hua; Qian, Wei

    2008-12-01

    Sorption and desorption of phenanthrene by organo-mineral complexes with Ca2+, Fe3+ and Al3+ as bridge cations were studied according to the association type between organic matter and minerals in natural soils. The results showed that the data of phenanthrene sorption and desorption by different cation saturated montmorillonite and their corresponding humic acid and mineral complexes could be fitted with Freundlich model, and the order of the sorption capacities (Kf) were Ca-Mont (0.184) > Fe-Mont (0.028) > Al-Mont (0.015) and Fe-Mont-HA (2.341) > Ca-Mont-HA (1.557) > Al-Mont-HA (1.136), respectively. The Kf values of humic acid and mineral complexes were far greater than those of minerals, which demonstrated that humic acid made great contributions to the sorption of phenanthrene in the organo-mineral complexes. However, the Kf values of the organo-mineral complexes with different bridge cations were not consistent with their organic carbon content, which indicated that both the organic carbon content and the combined types between organic matter and mineral could affect the sorption capacity of phenanthrene by the organo-mineral complexes. The desorption hysteresis of phenanthrene was significant for Ca2+ and Al3+ bridged organo-mineral complexes. Desorption hysteresis of phenanthrene was mainly from the sorption of phenanthrene by organic matter, and the contributions of mineral to the desorption hysteresis were not significant.

  1. Chiroptical properties of cation complexes of chiral phenazino-18-crown-6 ether-type hosts.

    PubMed

    Szarvas, Szilvia; Szalay, Luca; Vass, Elemér; Hollósi, Miklós; Samu, Erika; Huszthy, Péter

    2005-06-01

    Herein we report CD spectroscopic studies on complexes of (R,R)-dimethyl-, (R,R)-diisobutyl-, and (S,S)-di-sec-butyl-phenazino-18-crown-6 ligands (Scheme 1) with selected alkali (Na+, K+), alkaline earth (Mg2+, Ca2+), and transition-metal (Ag+, Zn2+, Ni2+, Cd2+, Pb2+) cations. The complexation was monitored in the 300- to 240-nm region of the CD spectra comprising mainly the 1Bb band of the heteroaromatic subunit. The CD spectra of the complexes showed an unexpected diversity. In the most characteristic 1Bb spectral region, the number, position, and intensity of band(s) depend not only on the heteroaromatic subunit and the size of the substituents but also on the diameter, ion strength, and coordination geometry of the cation. The appearance of two weak 1Bb CD bands (type-I spectra) with the sign pattern of the host is an indication of two complexes of comparable stability. The "type-II" spectra differ from that of the host in the number, sign pattern, and intensity of the bands. Complexes of transition-metal cations generally show CD spectra with more intense bands. The CD spectra of complexes of (S,S)-di-sec-butyl-phenazino-18-crown-6 ligand with Na+, K+, and Pb2+ (type III) strongly suggest exciton coupling caused by the closeness of the heteroaromatic rings of two 1:1 complex molecules.

  2. Cation transport by the respiratory NADH:quinone oxidoreductase (complex I): facts and hypotheses.

    PubMed

    Steffen, Wojtek; Steuber, Julia

    2013-10-01

    The respiratory complex I (electrogenic NADH:quinone oxidoreductase) has been considered to act exclusively as a H+ pump. This was questioned when the search for the NADH-driven respiratory Na+ pump in Klebsiella pneumoniae initiated by Peter Dimroth led to the discovery of a Na+-translocating complex in this enterobacterium. The 3D structures of complex I from different organisms support the idea that the mechanism of cation transport by complex I involves conformational changes of the membrane-bound NuoL, NuoM and NuoN subunits. In vitro methods to follow Na+ transport were compared with in vivo approaches to test whether complex I, or its individual NuoL, NuoM or NuoN subunits, extrude Na+ from the cytoplasm to the periplasm of bacterial host cells. The truncated NuoL subunit of the Escherichia coli complex I which comprises amino acids 1-369 exhibits Na+ transport activity in vitro. This observation, together with an analysis of putative cation channels in NuoL, suggests that there exists in NuoL at least one continuous pathway for cations lined by amino acid residues from transmembrane segments 3, 4, 5, 7 and 8. Finally, we discuss recent studies on Na+ transport by mitochondrial complex I with respect to its putative role in the cycling of Na+ ions across the inner mitochondrial membrane.

  3. Secondary hydrogen isotope effects on the structure and stability of cation-pi complexes (cation = Li(+), Na(+), K(+) and pi = acetylene, ethylene, benzene).

    PubMed

    Moreno, Diego V; González, Sergio A; Reyes, Andrés

    2010-09-02

    Secondary hydrogen isotope effects on the geometries, electronic wave functions and binding energies of cation-pi complexes (cation = Li(+), Na(+), K(+) and pi = acetylene, ethylene, benzene) are investigated with NEO/HF and NEO/MP2 methods. These methods determine both electronic and nuclear wave functions simultaneously. Our results show that an increase of the hydrogen nuclear mass leads to the elongation of the cation-pi bond distance and the decrease in its binding energy. An explanation to this behavior is given in terms of the changes in the pi-molecule electronic structure and electrostatic potential induced by isotopic substitutions.

  4. A porphyrin complex of Gold(I): (Phosphine)gold(I) azides as cation precursors

    PubMed Central

    Partyka, David V.; Robilotto, Thomas J.; Zeller, Matthias; Hunter, Allen D.; Gray, Thomas G.

    2008-01-01

    A silver- and Brönsted acid-free protocol for generating the (tricyclohexylphosphine)gold(I) cation from the corresponding azide complexes is disclosed. The gold(I) cations so liberated are trapped by complexation with octaethylporphyrin. The first structurally authenticated gold(I) porphyrin complex crystallizes with formula C72H112Au2F12N4P2Sb2, space group C2/c, a = 21.388 (4), b = 19.679 (4), c = 19.231 (3) Å; β = 111.030 (3)°. Solution spectroscopic studies indicate that the di-gold complex fragments on dissolution in organic solvents. Approximate density-functional theory calculations find an electrostatic origin for the binding of two gold(I) centers to the unprotonated nitrogen atoms, despite greater orbital density on the porphyrin meso carbons. PMID:18780788

  5. Investigation of the structural organization of cationic nanoemulsion/antisense oligonucleotide complexes.

    PubMed

    Bruxel, Fernanda; Vilela, José Mario Carneiro; Andrade, Margareth Spangler; Malachias, Ângelo; Perez, Carlos A; Magalhães-Paniago, Rogério; Oliveira, Mônica Cristina; Teixeira, Helder F

    2013-12-01

    Atomic force microscopy image analysis and energy dispersive X-ray diffraction experiments were used to investigate the structural organization of cationic nanoemulsion/oligonucleotide complexes. Oligonucleotides targeting topoisomerase II gene were adsorbed on cationic nanoemulsions obtained by means of spontaneous emulsification procedure. Topographical analysis by atomic force microscopy allowed the observation of the nanoemulsion/oligonucleotide complexes through three-dimensional high-resolution images. Flattening of the oil droplets was observed, which was reduced in the complexes obtained at high amount of adsorbed oligonucleotides. In such conditions, complexes exhibit droplet size in the 600nm range. The oligonucleotides molecules were detected on the surface of the droplets, preventing their fusion during aggregation. A lamellar structure organization was identified by energy dispersive X-ray diffraction experiments. The presence of the nucleic acid molecules led to a disorganization of the lipid arrangement and an expansion in the lattice spacing, which was proportional to the amount of oligonucleotides added.

  6. DFT and TDDFT study on cationcomplexes of diboryne (NHC → B ≡ B←NHC).

    PubMed

    Bania, Kusum K; Guha, Ankur Kanti; Bhattacharyya, Pradip K

    2016-11-14

    In this study, density functional theory calculation on mono-cationic cationcomplexes of diborynes has been made to understand the interaction in cationcomplexes of diboryne. Results suggest that apart from the smaller cations Li(+) and Na(+), larger cation like K(+) ion could also form complexes with diboryne compounds via cation-π interaction. From the calculated structural and spectroscopic analysis (11)B, (13)C NMR (Nuclear Magnetic Resonance), FTIR (Fourier Transform Infra red) (force constant, value), and UV-vis spectra, it is found that the interaction between the cations and π-electron cloud of the diboryne is purely electrostatic. It is also observed that smaller cation (Li(+)) with high electronegativity interacts more strongly compared to larger cation (K(+)). Calculated interaction energy advocates that the π-electron cloud of the B2 unit contributes more to the cation-π interaction than the two aromatic phenyl rings of the NHC (N-heterocyclic carbene) substituted with 2,6-diisopropylphenyl group. The aryl substituent at the NHC-ligands undergoes a change in spatial orientation with respect to the size of cations in order to provide suitable space to the cations for effective cation-π interaction. Quantum theory of atoms in molecules study clarifies further the nature and extent of B-B and B2-cation interactions.(11)B-NMR, (13)C-NMR, and time dependent density functional theory analysis indicate that cation-π interaction annihilates the B → C (NHC) π-back donation and favours the B≡B bond formation.

  7. DFT and TDDFT study on cationcomplexes of diboryne (NHC → B ≡ B←NHC)

    NASA Astrophysics Data System (ADS)

    Bania, Kusum K.; Guha, Ankur Kanti; Bhattacharyya, Pradip K.

    2016-11-01

    In this study, density functional theory calculation on mono-cationic cationcomplexes of diborynes has been made to understand the interaction in cationcomplexes of diboryne. Results suggest that apart from the smaller cations Li+ and Na+, larger cation like K+ ion could also form complexes with diboryne compounds via cation-π interaction. From the calculated structural and spectroscopic analysis 11B, 13C NMR (Nuclear Magnetic Resonance), FTIR (Fourier Transform Infra red) (force constant, value), and UV-vis spectra, it is found that the interaction between the cations and π-electron cloud of the diboryne is purely electrostatic. It is also observed that smaller cation (Li+) with high electronegativity interacts more strongly compared to larger cation (K+). Calculated interaction energy advocates that the π-electron cloud of the B2 unit contributes more to the cation-π interaction than the two aromatic phenyl rings of the NHC (N-heterocyclic carbene) substituted with 2,6-diisopropylphenyl group. The aryl substituent at the NHC-ligands undergoes a change in spatial orientation with respect to the size of cations in order to provide suitable space to the cations for effective cation-π interaction. Quantum theory of atoms in molecules study clarifies further the nature and extent of B-B and B2-cation interactions.11B-NMR, 13C-NMR, and time dependent density functional theory analysis indicate that cation-π interaction annihilates the B → C (NHC) π-back donation and favours the B≡B bond formation.

  8. Rates and Mechanisms of Complexation Reactions of Cations with Crown Ethers and Related Macrocycles

    DTIC Science & Technology

    1989-01-23

    as stability constants and entropies of solvation t, be of paramount importance. Complexation rate constants alone seldom disclose a great deal more...sample equilibrium to assure detectability of the reaction. Disadvantages include 1) the need for high solute concentrations in order to detect small...ultrasonic techniques. In principle, the stability constants of macrocycles complexing various cations can be deduced from the amplitudes of the experimental

  9. Complexation of Trivalent Metal Cations to Mannuronate Type Alginate Models from a Density Functional Study.

    PubMed

    Menakbi, Chemseddine; Quignard, Francoise; Mineva, Tzonka

    2016-04-21

    Complexation of alginate models, built of β-d-mannuronic units (M) linked by a 1-4 glycosidic bridge, to Al(3+), Sc(3+), Cr(3+), Fe(3+), Ga(3+), and La(3+) cations was studied by applying the quantum chemical density functional theory (DFT) based method. The binding modes and energies were obtained for complexes with one, two, and three truncated alginate chain(s). In all the hydrated structures a monodentate binding mode is established to be the energetically most favored with shorter M(3+)···O(COO(-)) bonds than M(3+)···O(OH) bonds. Coordination bond lengths are found to be specific to each cation and to depend very little on the water in the coordination sphere and on the number of saccharide units used to model an alginate chain. The binding energy tendency Fe(3+) ≈ Cr(3+) > Al(3+) ≈ Ga(3+) ≫ Sc(3+) ≥ La(3+) is not affected by the alginate models, the coordination to water molecules, and the number of chains. A significant covalent contribution that arises predominantly from a charge donation from the carboxylate oxygen to the metal cation was established from the orbital population analysis. An exothermic chain-chain association is predicted by the computed enthalpy variations. A comparison between the structural features of alginate complexation to trivalent and divalent cations is provided and discussed.

  10. Capillary electrophoretic and computational study of the complexation of valinomycin with rubidium cation.

    PubMed

    Ehala, Sille; Dybal, Jirí; Makrlík, Emanuel; Kasicka, Václav

    2009-03-01

    This study is focused on the characterization of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with rubidium cation, Rb(+). Capillary affinity electrophoresis was employed for the experimental evaluation of the strength of the Val-Rb(+) complex. The study involved the measurement of the change of effective electrophoretic mobility of Val at increasing concentration of Rb(+) cation in the BGE. From the dependence of Val effective electrophoretic mobility on the Rb(+) cation concentration in the BGE (methanolic solution of 100 mM Tris, 50 mM acetic acid, 0-1 mM RbCl), the apparent binding (stability) constant (K(b)) of the Val-Rb(+) complex in methanol was evaluated as log K(b)=4.63+/-0.27. According to the quantum mechanical density functional theory calculations employed to predict the most probable structure of Val-Rb(+) complex, Val is stabilized by strong non-covalent bond interactions of Rb(+) with six ester carbonyl oxygen atoms so that the position of the "central" Rb(+) cation in the Val cage is symmetric.

  11. Mode of formation and structural features of DNA-cationic liposome complexes used for transfection.

    PubMed

    Gershon, H; Ghirlando, R; Guttman, S B; Minsky, A

    1993-07-20

    Complexes formed between cationic liposomes and nucleic acids represent a highly efficient vehicle for delivery of DNA and RNA molecules into a large variety of eukaryotic cells. By using fluorescence, gel electrophoresis, and metal-shadowing electron microscopy techniques, the factors that affect the, yet unclear, interactions between DNA and cationic liposomes as well as the structural features of the resulting complexes have been elucidated. A model is suggested according to which cationic liposomes bind initially to DNA molecules to form clusters of aggregated vesicles along the nucleic acids. At a critical liposome density, two processes occur, namely, DNA-induced membrane fusion, indicated by lipid mixing studies, and liposome-induced DNA collapse, pointed out by the marked cooperativity of the encapsulation processes, by their modulations by DNA-condensing agents, and also by their conspicuous independence upon DNA length. The DNA collapse leads to the formation of condensed structures which can be completely encapsulated within the fused lipid bilayers in a fast, highly cooperative process since their exposed surface is substantially smaller than that of extended DNA molecules. The formation of the transfecting DNA-liposome complexes in which the nucleic acids are fully encapsulated within a positively-charged lipid bilayer is proposed, consequently, to be dominated by mutual effects exerted by the DNA and the cationic liposomes, leading to interrelated lipid fusion and DNA collapse.

  12. Complexation of the calcium cation with antamanide: an experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Makrlík, Emanuel; Böhm, Stanislav; Vaňura, Petr; Ruzza, Paolo

    2015-06-01

    By using extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Ca2+(aq) + 1 .Sr2+(nb) ? 1 .Ca2+(nb) + Sr2+(aq) occurring in the two-phase water-nitrobenzene system (1 = antamanide; aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex (Ca2+, 1 .Sr2+) = 1.6 ± 0.1. Further, the stability constant of the 1 .Ca2+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1 .Ca2+) = 10.9 ± 0.2. Finally, applying quantum mechanical density functional level of theory calculations, the most probable structure of the cationic complex species 1 .Ca2+ was derived. In the resulting complex, the 'central' cation Ca2+ is bound by six strong bonding interactions to the corresponding six carbonyl oxygen atoms of the parent ligand 1. Besides, the whole 1 .Ca2+ complex structure is stabilised by two intramolecular hydrogen bonds. The interaction energy of the considered 1 .Ca2+ complex, involving the Boys-Bernardi counterpoise corrections of the basis set superposition error, was found to be -1219.3 kJ/mol, confirming the formation of this cationic species.

  13. Effects of salt on intermolecular polyelectrolyte complexes formation between cationic microgel and polyanion.

    PubMed

    Ogawa, Kazuyoshi

    2015-12-01

    The study of interpolyelectrolyte complex (IPEC) formation between cationic microgel and polyanion was presented. The size and molecular weight of cationic microgel are much larger than those of linear anionic polyelectrolyte. The resulting IPEC was divided by dynamic light scattering (DLS), static light scattering (SLS), and turbidity or spectrometry; (i) water-soluble intra-particle complexes consisting of one microgel to which linear polyelectrolytes bind; (ii) complex coacervates (inter-particle complexes composed of aggregated intra-particle complexes); and (iii) insoluble amorphous precipitates. These types depended on not only the mixing ratio of polyanion to cationic microgel but also salt concentration. This trend was discussed from IPEC's composition, thermodynamics of IPEC formation and the salt effect on intermolecular interactions which were expected in IPEC formation. The results obtained from the use of microgel in IPEC's study suggested that not only electrostatic interaction but also hydrophobic interaction play an important role in the aggregation or association of IPEC. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Structure And Gene Silencing Activities of Monovalent And Pentavalent Cationic Lipid Vectors Complexed With Sirna

    SciTech Connect

    Bouxsein, N.F.; McAllister, C.S.; Ewert, K.K.; Samuel, C.E.; Safinya, C.R.; /UC, Santa Barbara

    2007-07-03

    Small interfering RNAs (siRNAs) of 19-25 bp mediate the cleavage of complementary mRNA, leading to post-transcriptional gene silencing. We examined cationic lipid (CL)-mediated delivery of siRNA into mammalian cells and made comparisons to CL-based DNA delivery. The effect of lipid composition and headgroup charge on the biophysical and biological properties of CL-siRNA vectors was determined. X-ray diffraction revealed that CL-siRNA complexes exhibited lamellar and inverted hexagonal phases, qualitatively similar to CL-DNA complexes, but also formed other nonlamellar structures. Surprisingly, optimally formulated inverted hexagonal 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)/1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE) CL-siRNA complexes exhibited high toxicity and much lower target-specific gene silencing than lamellar CL-siRNA complexes even though optimally formulated, inverted hexagonal CL-DNA complexes show high transfection efficiency in cell culture. We further found that efficient silencing required cationic lipid/nucleic acid molar charge ratios (chg) nearly an order of magnitude larger than those yielding efficiently transfecting CL-DNA complexes. This second unexpected finding has implications for cell toxicity. Multivalent lipids (MVLs) require a smaller number of cationic lipids at a given chg of the complex. Consistent with this observation, the pentavalent lipid MVL5 exhibited lower toxicity and superior silencing efficiency over a large range in both the lipid composition and chg when compared to monovalent DOTAP. Most importantly, MVL5 achieved much higher total knockdown of the target gene in CL-siRNA complex regimes where toxicity was low. This property of CL-siRNA complexes contrasts to CL-DNA complexes, where the optimized transfection efficiencies of multivalent and monovalent lipids are comparable.

  15. Extraction and DFT study on complexation of the barium cation with [Gly6]-antamanide

    NASA Astrophysics Data System (ADS)

    Makrlík, Emanuel; Böhm, Stanislav; Vaňura, Petr; Ruzza, Paolo

    2017-10-01

    On the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Ba2+(aq) + 1·Sr2+(nb) ⇄1·Ba2+ (nb) + Sr2+(aq) occurring in the two-phase water - nitrobenzene system (1 = [Gly6]-antamanide; aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex (Ba2+,1·Sr2+) = 0.6 ± 0.1. Further, the stability constant of the 1·Ba2+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1·Ba2+) = 9.5 ± 0.2. Finally, by using quantum chemical DFT calculations, the most probable structure of the cationic complex species 1·Ba2+ was derived. In the resulting complex, the ;central; cation Ba2+ is bound by six bonding interactions to the corresponding six carbonyl oxygen atoms of the parent ligand 1. The interaction energy of the considered 1·Ba2+ complex was found to be -943.5 kJ/mol, confirming the formation of this cationic species as well

  16. Synthesis and SMM behaviour of trinuclear versus dinuclear 3d-5f uranyl(v)-cobalt(ii) cation-cation complexes.

    PubMed

    Chatelain, Lucile; Tuna, Floriana; Pécaut, Jacques; Mazzanti, Marinella

    2017-01-17

    Trinuclear versus dinuclear heterodimetallic U(V)O2(+)Co(2+) complexes were selectively assembled via a cation-cation interaction by tuning the ligand. The trimeric complex 2, with a linear [Co-O[double bond, length as m-dash]U[double bond, length as m-dash]O-Co] core, exhibits magnetic exchange and slow relaxation with a reversal barrier of 30.5 ± 0.9 K providing the first example of a U-Co exchange-coupled SMM.

  17. Cationic schiff base amphiphiles and their metal complexes: Surface and biocidal activities against bacteria and fungi.

    PubMed

    Negm, N A; Zaki, M F; Salem, M A I

    2010-05-01

    A series of cationic surfactants containing schiff base groups was synthesized by condensation of four fatty amines namely: dodecyl, tetradecyl, hexadecyl and octadecyl amine and 4-diethyl aminobenzaldehyde (1-4), as well as their metal complexes with divalent transition metal ions including Co, Cu and Mn (5-16). The surface activities of the synthesized surfactants were influenced by their chemical structures and the type of the transition metals. The biological activity measurements of the parent cationic schiff bases showed high efficacy against Gram positive and Gram negative bacterial strains and fungi. While on complexation, the biocidal activity was increased remarkably. The biocidal activity of the tested compounds against sulfur reducing bacteria showed promising results in the field of biocide applications. 2010 Elsevier B.V. All rights reserved.

  18. Oligomycin A complex structures with some divalent metal cations studied by ESI MS and PM5 semiempirical methods

    NASA Astrophysics Data System (ADS)

    Przybylski, Piotr; Brzezinski, Bogumil; Bartl, Franz

    2007-03-01

    The ability of Oligomycin A (OLA) to form complexes with monovalent cations was studied by the ESI mass spectrometry and PM5 semiempirical method. At low cone voltage values the ESI MS spectra indicate that OLA formes stable 1:1 complexes with Mg 2+, Ca 2+, Sr 2+, Ba 2+, Zn 2+ divalent cations irrespective of the stoichiometry. With increasing cone voltages the formation of the [OLA + M + (ClO 4 or Cl)] + complexes was preferred. This process occurred simultaneously with the formation of fragmentary metal cation complexes with the exception of Pb 2+ ions which does not form complexes with OLA molecule. PM5 semiempirical calculations allowed the visualizations of all structures of (OLA + M) 2+ and [OLA + M + (ClO 4or Cl)] + complexes as well as the fragmentary cations.

  19. Emergent ion-gated binding of cationic host-guest complexes within cationic M12L24 molecular flasks.

    PubMed

    Bruns, Carson J; Fujita, Daishi; Hoshino, Manabu; Sato, Sota; Stoddart, J Fraser; Fujita, Makoto

    2014-08-27

    "Molecular flasks" are well-defined supramolecular cages that can encapsulate one or more molecular guests within their cavities and, in so doing, change the physical properties and reactivities of the guests. Although molecular flasks are powerful tools for manipulating matter on the nanoscale, most of them are limited in their scope because of size restrictions. Recently, however, increasingly large and diverse supramolecular cages have become available with enough space in their cavities for larger chemical systems such as polymers, nanoparticles, and biomolecules. Here we report how a class of metallosupramolecular cages known as M12L24 polyhedra have been adapted to serve as nanometer-scale containers for solutions of a pseudorotaxane host-guest complex based on a tetracationic cyclophane host, cyclobis(paraquat-p-phenylene) (CBPQT(4+)), and a 1,5-dioxynaphthalene (DNP) guest. Remarkably, the hierarchical integration of pseudorotaxanes and M12L24 superhosts causes the system to express stimulus-responsive behavior, a property which can be described as emergent because neither the DNP⊂CBPQT(4+) nor the M12L24 assemblies exhibit this behavior independently. The DNP-containing M12L24 molecular flasks are effectively "sealed off" to CBPQT(4+) until ions are added as a stimulus to "open" them. The electrolyte stimulus reduces the electrostatic screening distance in solution, allowing favorable DNP⊂CBPQT(4+) host-guest interactions to overcome repulsive Coulombic interactions between the cationic M12L24 cages and CBPQT(4+) rings. This unusual example of ion-gated transport into chemical nanocontainers is reminiscent of transmembrane ion channels which act as gates to the cell, with the important difference that this system is reversible and operates at equilibrium.

  20. Cationic lipophilic complexes of /sup 99/ /SUP m/ Tc and their use for myocardial and hepatobiliary imaging

    SciTech Connect

    Deutsch, E. A.; Glavan, K. A.

    1984-12-18

    A method of imaging organs with /sup 99/ /SUP m/ Tc radiopharmaceuticals, especially of hepatobiliary imaging and negative myocardial infarct imaging in a mammal which comprises administering to the mammal a hepatobiliary or myocardial imaging amount of a cationic lipophilic complex of Tc-99m and detecting the Tc-99m complex in the mammal. A method for the preparation of cationic lipophilic complexes of Tc-99m.

  1. Binding energies and dissociation pathways in the aniline-Ar2 cation complex.

    PubMed

    Gu, Quanli; Knee, J L

    2008-02-14

    Mass analyzed threshold ionization spectroscopy is used to measure the Ar binding energy for the cationic aniline-Ar (An(+)-Ar) and aniline-Ar(2) (An(+)-Ar(2)) complexes. Since the experiments begin with the neutral species, photoexcitation creates the cations in the pi-bonding configuration with the Ar located above the phenyl ring. The binding energy in this conformation of the An(+)-Ar complex is determined to be 495+/-15 cm(-1). Measurements of An(+)-Ar(2) revealed the production of a lower energy dissociation product which is assigned to the An(+)-Ar H-bonding configuration. Combinations of measurements allow determination of the dissociation energy of this complex to be 640+/-20 cm(-1). The observation of a more stable H-bonded conformer is consistent with recent infrared experiments on An(+)-Ar complexes created by complexing An(+) with Ar, rather than creation through the neutral complex. Calculations are presented which closely reproduce the binding energy of the pi bound Ar but underestimate the stability of the H-bonded species.

  2. Reversible mechanochromic luminescence at room temperature in cationic platinum(II) terpyridyl complexes.

    PubMed

    Han, Ali; Du, Pingwu; Sun, Zijun; Wu, Haotian; Jia, Hongxing; Zhang, Rui; Liang, Zhenning; Cao, Rui; Eisenberg, Richard

    2014-04-07

    Reversible mechanochromic luminescence in cationic platinum(II) terpyridyl complexes is described. The complexes [Pt(Nttpy)Cl]X2 (Nttpy = 4'-(p-nicotinamide-N-methylphenyl)-2,2':6',2″-terpyridine, X = PF6 (1), SbF6 (2), Cl (3), ClO4 (4), OTf (5), BF4 (6)) exhibit different colors under ambient light in the solid state, going from red to orange to yellow. All of these complexes are brightly luminescent at both room temperature and 77 K. Upon gentle grinding, the yellow complexes (4-6) turn orange and exhibit bright red luminescence. The red luminescence can be changed back to yellow by the addition of a few drops of acetonitrile to the sample. Crystallographic studies of the yellow and red forms of complex 5 suggest that the mechanochromic response is likely the result of a change in intermolecular Pt···Pt distances upon grinding.

  3. Isolation of homoleptic platinum oxyanionic complexes with doubly protonated diazacrown cation

    NASA Astrophysics Data System (ADS)

    Vasilchenko, Danila; Tkachev, Sergey; Baidina, Iraida; Romanenko, Galina; Korenev, Sergey

    2017-02-01

    Doubly protonated diazacrown ether cation (1,4,10,13-tetraoxa-7,16-diazoniacyclooctadecane DCH22+) was used for the efficient isolation of the homoleptic platinum complexes [Pt(NO3)6]2- and [Pt(C2O4)2]2- to crystalline solid phases from solutions containing mixtures of related platinum complexes. DCH22+ molecules in nitric acid solution were shown to prevent the condensation of mononuclear [Pt(H2O)n(NO3)6-n]n-2 species.

  4. Depassivation of aged Fe 0 by divalent cations: correlation between contaminant degradation and surface complexation constants.

    PubMed

    Liu, Tongxu; Li, Xiaomin; Waite, T David

    2014-12-16

    The dechlorination of trichloroethylene (TCE) by aged Fe(0) in the presence of a series of divalent cations was investigated with the result that while no significant degradation of TCE was observed in Milli-Q water or in solutions of Ba(2+), Sr(2+), or Ca(2+), very effective TCE removal was observed in solutions containing Mg(2+), Mn(2+), Co(2+), Fe(2+), Ni(2+), Zn(2+), Cu(2+), or Pb(2+). The rate constants of TCE removal in the presence of particular cations were positively correlated to the log K representing the affinity of the cations for hydrous ferric oxide (HFO) surface sites though the treatments with Co(2+) and Ni(2+) were found to provide particularly strong enhancement in TCE degradation rate. The extent of Fe(II) release to solution also increased with increase in log K, while the solution pH from both experimental measurement and thermodynamic calculation decreased with increasing log K. While the peak areas of Fe and O XPS spectra of the passivated ZVI in the presence of Ba(2+), Sr(2+), and Ca(2+) were very close to those in Milli-Q water, very significant increases in surface Fe and O (and OH) were observed in solutions of Mg(2+), Mn(2+), Co(2+), Fe(2+), Ni(2+), Zn(2+), Cu(2+) and Pb(2+), revealing that the surface oxide layer dissolution is consistent with the recovery of aged Fe(0) with respect to TCE degradation. The depassivation process is proposed to involve (i) surface complexation of cations on surface coatings of aged Fe(0), (ii) dissolution of the hydrated surface as a consequence of magnetite exposure, and (iii) transport of electrons from underlying Fe(0) via magnetite to TCE, resulting in TCE dechlorination and, for some cations (Co(2+), Ni(2+), Cu(2+), and Pb(2+)), reduction to their zero or +1 valence state (with potential for these reduced metals to enhance TCE degradation).

  5. Thermodynamics of cationic lipid-DNA complex formation as studied by isothermal titration calorimetry.

    PubMed

    Pozharski, Edwin; MacDonald, Robert C

    2002-07-01

    The detailed analysis of the cationic lipid-DNA complex formation by means of isothermal titration calorimetry is presented. Most experiments were done using 1,2-dioleyl-sn-glycero-3-ethylphosphocholine (EDOPC), but basic titrations were also done using DOTAP, DOTAP:DOPC, and DOTAP:DOPE mixtures. Complex formation was endothermic with less than 1 kcal absorbed per mole of lipid or DNA charge. This enthalpy change was attributed to DNA-DNA mutual repulsion within the lamellar complex. The exception was DOTAP:DOPE-containing lipoplex for which the enthalpy of formation was exothermic, presumably because of DOPE amine group protonation. Experimental conditions, namely, direction and titration increment as well as concentration of titrant, which dictate the structure of resulting lipoplex (whether lamellar complex or DNA-coated vesicle), were found to affect the apparent thermodynamics of complex formation. The structure, in turn, influences the biological properties of the lipoplex. If the titration of lipid into DNA was carried out in large increments, the DeltaH was larger than when the injection increments were smaller, a finding that is consistent with increased vesicle disruption under large increments and which is expected theoretically. Cationic lipid-DNA binding was weak in high ionic strength solutions, however, the effective binding constant is within micromolar range because of macromolecular nature of the interaction.

  6. Thermodynamics of cationic lipid-DNA complex formation as studied by isothermal titration calorimetry.

    PubMed Central

    Pozharski, Edwin; MacDonald, Robert C

    2002-01-01

    The detailed analysis of the cationic lipid-DNA complex formation by means of isothermal titration calorimetry is presented. Most experiments were done using 1,2-dioleyl-sn-glycero-3-ethylphosphocholine (EDOPC), but basic titrations were also done using DOTAP, DOTAP:DOPC, and DOTAP:DOPE mixtures. Complex formation was endothermic with less than 1 kcal absorbed per mole of lipid or DNA charge. This enthalpy change was attributed to DNA-DNA mutual repulsion within the lamellar complex. The exception was DOTAP:DOPE-containing lipoplex for which the enthalpy of formation was exothermic, presumably because of DOPE amine group protonation. Experimental conditions, namely, direction and titration increment as well as concentration of titrant, which dictate the structure of resulting lipoplex (whether lamellar complex or DNA-coated vesicle), were found to affect the apparent thermodynamics of complex formation. The structure, in turn, influences the biological properties of the lipoplex. If the titration of lipid into DNA was carried out in large increments, the DeltaH was larger than when the injection increments were smaller, a finding that is consistent with increased vesicle disruption under large increments and which is expected theoretically. Cationic lipid-DNA binding was weak in high ionic strength solutions, however, the effective binding constant is within micromolar range because of macromolecular nature of the interaction. PMID:12080142

  7. Fluctuation analysis of nonselective cation currents induced by AIF complex in guinea-pig chromaffin cells.

    PubMed

    Inoue, M; Imanaga, I

    1996-11-11

    Properties of aluminium fluoride (AIF) complex-activated nonselective cation (NS) channels in guinea-pig chromaffin cells were investigated using the patch clamp technique. As the membrane potential was hyperpolarized from the holding potential of -55 mV, the AIF-induced nonselective cation current (INS) diminished progressively. With hyperpolarizations to -100 mV or more negative potentials, the AIF.INS almost instantaneously disappeared. The apparent unit conductance of AIF INS was estimated to be 3 pS by fluctuation analysis. The open state probability of AIF-activated NS channels became large with a decrease in concentration of free Mg2+ ions inside the cell and was less than 0.5 at 12 microM Mg2+. It is concluded that NS channels in the chromaffin cell apparently differ from those in smooth muscle cells.

  8. Aza-crown ether complex cation ionic liquids: preparation and applications in organic reactions.

    PubMed

    Song, Yingying; Cheng, Chen; Jing, Huanwang

    2014-09-26

    Aza-crown ether complex cation ionic liquids (aCECILs) were devised, fabricated, and characterized by using NMR spectroscopy, MS, thermogravimetric differential thermal analysis (TG-DTA), elemental analysis and physical properties. These new and room-temperature ILs were utilized as catalysts in various organic reactions, such as the cycloaddition reaction of CO2 to epoxides, esterification of acetic acid and alcohols, the condensation reaction of aniline and propylene carbonate, and Friedel-Crafts alkylation of indole with aldehydes were investigated carefully. In these reactions, the ionic liquid exhibited cooperative catalytic activity between the anion and cation. In addition, the aza-[18-C-6HK][HSO4]2 was the best acidic catalyst in the reactions of esterification and Friedel-Crafts alkylation under mild reaction conditions.

  9. Cationic and anionic polyelectrolyte complexes of xylan and chitosan. Interaction with lignocellulosic surfaces.

    PubMed

    Mocchiutti, Paulina; Schnell, Carla N; Rossi, Gerardo D; Peresin, María S; Zanuttini, Miguel A; Galván, María V

    2016-10-05

    Cationic (CatPECs) and anionic (AnPECs) polyelectrolyte complexes from xylan and chitosan were formed, characterized and adsorbed onto unbleached fibers for improving the papermaking properties. They were prepared at a level of 30% of neutralization charge ratio by modifying the order of addition of polyelectrolytes and the ionic strength (0.01N and 0.1N NaCl). The charge density, colloidal stability and particle size of polyelectrolyte complexes (PECs) was measured using polyelectrolyte titration method, Turbiscan and Zetasizer Nano equipments, respectively. All the complexes were stable even after seven days from PEC formation. DRIFT spectra of complexes were also analyzed. The adsorption behavior of them onto cellulose nanofibrils model surfaces was studied using quartz crystal microbalance with dissipation monitoring, and surface plasmon resonance. It was found that the PEC layers were viscoelastic and highly hydrated. Finally, it is shown that the adsorbed PECs onto cellulosic fibers markedly improved the tensile and crushing strengths of paper.

  10. Synthesis and styrene polymerisation catalysis of eta5- and eta1-pyrrolyl-ligated cationic rare earth metal aminobenzyl complexes.

    PubMed

    Nishiura, Masayoshi; Mashiko, Tomohiro; Hou, Zhaomin

    2008-05-07

    The cationic rare earth metal aminobenzyl complexes bearing mono(pyrrolyl) ligands are synthesised and structurally characterised, and the coordination mode of the pyrrolyl ligands is found to show significant influence on the polymerisation of styrene.

  11. Comparing Gene Silencing and Physiochemical Properties in siRNA Bound Cationic Star-Polymer Complexes.

    PubMed

    Dearnley, Megan; Reynolds, Nicholas P; Cass, Peter; Wei, Xiaohu; Shi, Shuning; Mohammed, A Aalam; Le, Tam; Gunatillake, Pathiraja; Tizard, Mark L; Thang, San H; Hinton, Tracey M

    2016-11-14

    The translation of siRNA into clinical therapies has been significantly delayed by issues surrounding the delivery of naked siRNA to target cells. Here we investigate siRNA delivery by cationic acrylic polymers developed by Reversible Addition-Fragmentation chain Transfer (RAFT) mediated free radical polymerization. We investigated cell uptake and gene silencing of a series of siRNA-star polymer complexes both in the presence and absence of a protein "corona". Using a multidisciplinary approach including quantitative nanoscale mechanical-atomic force microscopy, dynamic light scattering and nanoparticle tracking analysis we have characterized the nanoscale morphology, stiffness, and surface charge of the complexes with and without the protein corona. This is one of the first examples of a comprehensive physiochemical analysis of siRNA-polymer complexes being performed alongside in vitro biological assays, allowing us to describe a set of desirable physical features of cationic polymer complexes that promote gene silencing. Multifaceted studies such as this will improve our understanding of structure-function relationships in nanotherapeutics, facilitating the rational design of polymer-mediated siRNA delivery systems for novel treatment strategies.

  12. Experimental and DFT study on complexation of the strontium cation with cyclosporin A

    NASA Astrophysics Data System (ADS)

    Makrlík, Emanuel; Böhm, Stanislav; Vaňura, Petr

    2015-11-01

    By using extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Sr2+(aq) + 2A-(aq) + 1(nb) ⇄ 1·Sr2+(nb) + 2A-(nb) occurring in the two-phase water-nitrobenzene system (A- = picrate, 1 = cyclosporin A; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (1·Sr2+,2A-) = 0.1 ± 0.1. Further, the stability constant of the 1·Sr2+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1·Sr2+) = 9.2 ± 0.1. Finally, applying quantum mechanical DFT calculations, the most probable structure of the proven 1·Sr2+ cationic complex was derived. In the resulting complex, the "central" cation Sr2+ is bound by five bonds to the corresponding five oxygen atoms of the parent cyclosporin A ligand. The interaction energy, E(int), of the investigated 1·Sr2+ complex, involving the 7-point correction for the basis set superposition error, was calculated as -894.5 kJ/mol.

  13. Zeaxanthin Radical Cation Formation in Minor Light-Harvesting Complexes of Higher Plant Antenna

    SciTech Connect

    Avenson, Thomas H.; Ahn, Tae Kyu; Zigmantas, Donatas; Niyogi, Krishna K.; Li, Zhirong; Ballottari, Matteo; Bassi, Roberto; Fleming, Graham R.

    2008-01-31

    Previous work on intact thylakoid membranes showed that transient formation of a zeaxanthin radical cation was correlated with regulation of photosynthetic light-harvesting via energy-dependent quenching. A molecular mechanism for such quenching was proposed to involve charge transfer within a chlorophyll-zeaxanthin heterodimer. Using near infrared (880-1100 nm) transient absorption spectroscopy, we demonstrate that carotenoid (mainly zeaxanthin) radical cation generation occurs solely in isolated minor light-harvesting complexes that bind zeaxanthin, consistent with the engagement of charge transfer quenching therein. We estimated that less than 0.5percent of the isolated minor complexes undergo charge transfer quenching in vitro, whereas the fraction of minor complexes estimated to be engaged in charge transfer quenching in isolated thylakoids was more than 80 times higher. We conclude that minor complexes which bind zeaxanthin are sites of charge transfer quenching in vivo and that they can assume Non-quenching and Quenching conformations, the equilibrium LHC(N)<--> LHC(Q) of which is modulated by the transthylakoid pH gradient, the PsbS protein, and protein-protein interactions.

  14. Cationic complexation with dissolved organic matter: Insights from molecular dynamics computer simulations and NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kalinichev, A. G.; Xu, X.; Kirkpatrick, R.

    2006-12-01

    Dissolved organic matter (DOM) is ubiquitous in soil and surface water and plays many important geochemical and environmental roles acting as a proton donor/acceptor and pH buffer and interacting with metal ions, minerals and organic species to form water-soluble and water-insoluble complexes of widely differing chemical and biological stabilities. There are strong correlations among the concentration of DOM and the speciation, solubility and toxicity of many trace metals in soil and water due to metal-DOM interaction. DOM can also significantly negatively affect the performance of nanofiltration and reverse osmosis membranes used industrially for water purification and desalination, being one of the major causes of a so-called `membrane bio- fouling'. The molecular scale mechanisms and dynamics of the DOM interactions with metals and membranes are, however, quite poorly understood. Methods of computational molecular modeling, combined with element- specific nuclear magnetic resonance (NMR) spectroscopy, can serve as highly effective tools to probe and quantify on a fundamental molecular level the DOM interactions with metal cations in aqueous solutions, and to develop predictive models of the molecular mechanisms responsible for the metal-DOM complexation in the environment. This paper presents the results of molecular dynamics (MD) computer simulations of the interaction of DOM with dissolved Na+, Cs+, Mg2+, and Ca2+. Na+ forms only very weak outer-sphere complexes with DOM. These results and the results of other recent molecular modeling efforts (e.g., Sutton et al., Environmental Toxicology and Chemistry, 24, 1902-1911, 2005), clearly indicate that both the structural and dynamic aspects of the cation-DOM complexation follow a simple trend in terms of the charge/size ratio for the ions. Due to the competition between ion hydration in bulk aqueous solution and adsorption of these cations by the negatively charged DOM functional groups (primarily carboxylate

  15. Density Functional Theory and Mass Spectrometry of Phthalate Fragmentations Mechanisms: Modeling Hyperconjugated Carbocation and Radical Cation Complexes with Neutral Molecules

    NASA Astrophysics Data System (ADS)

    Jeilani, Yassin A.; Cardelino, Beatriz H.; Ibeanusi, Victor M.

    2011-11-01

    This is the first ab initio study of the energetics of the fragmentation mechanisms of phthalate, by mass spectrometry, leading to protonated phthalic anhydride ( m/z 149). Phthalates fragment by two major pathways; namely, the McLafferty + 1 rearrangement and the loss of alkoxy. Both pathways involve a carbonyl oxygen attack to the ortho-carbonyl carbon leading to structures with tetrahedral carbon intermediates that eventually give m/z 149. These pathways were studied by collision induced dissociation (CID) using triple quadrupole mass spectrometry. The proposed McLafferty + 1 pathway proceeds through a distonic M•+, leading to the loss of an allylic-stabilized alkene radical. The McLafferty rearrangement step proceeds through a six-membered ring transition state with a small activation energy ranging 0.4-6.2 kcal/mol; the transfer of a second H from the distonic ion of the rearrangement step proceeds through a radical cation molecule complex. Based on quantum chemical modeling of the cation molecule complexes, two kinds of cation molecule complexes were identified as radical cation molecule complex and hyperconjugated cation molecule complex. This distinction is based on the cation and simplifies future modeling of similar complexes. Optimization of important fragments in these pathways showed cyclized and hydrogen-bonded structures to be favored. An exception was the optimized structure of the protonated phthalic anhydride ( m/z 149) that showed a structure with an open anhydride ring.

  16. Modulation of photo-oxidative DNA damage by cationic surfactant complexation.

    PubMed

    Rudiuk, Sergii; Franceschi-Messant, Sophie; Chouini-Lalanne, Nadia; Perez, Emile; Rico-Lattes, Isabelle

    2008-08-19

    The natural packaging of DNA in the cell by histones provides a particular environment affecting its sensitivity to oxidative damage. In this work, we used the complexation of DNA by cationic surfactants to modulate the conformation, the dynamics, and the environment of the double helix. Photo-oxidative damage initiated by benzophenone as the photosensitizer on a plasmid DNA complexed by dodecyltrimethylammonium chloride (DTAC), tetradecyltrimethylammonium chloride (TTAC), cetyltrimethyammonium chloride (CTAC) and bromide (CTAB) was detected by agarose gel electrophoresis. By fluorescent titration in the presence of ethidium bromide (EB) and agarose gel electrophoresis, we experimentally confirmed the complexation diagrams with a critical aggregation concentration on DNA matrix (CAC DNA) delimiting two regions of complexation, according to the DNA-phosphate concentration. The study of the photo-oxidative damage shows, for the first time, a direct correlation between the DNA complexation by these surfactants and the efficiency of DNA cleavage, with a maximum corresponding to the CAC DNA for DTAC and CTAC, and to DNA neutralization for CTAC and CTAB. The localization of a photosensitizer having low water solubility, such as benzophenone, inside the hydrophobic domains formed by the surfactant aggregated on DNA, locally increases the photoinduced cleavage by the free radical oxygen species generated. The inefficiency of a water-soluble quencher of hydroxyl radicals, such as mannitol, confirmed this phenomenon. The detection of photo-oxidative damage constitutes a new tool for investigating DNA complexation by cationic surfactants. Moreover, highlighting the drastically increased sensitivity of a complexed DNA to photo-oxidative damage is of crucial importance for the biological use of surfactants as nonviral gene delivery systems.

  17. Chapter 17 - Engineering cationic liposome siRNA complexes for in vitro and in vivo delivery.

    PubMed

    Podesta, Jennifer E; Kostarelos, Kostas

    2009-01-01

    RNA interference, the sequence-specific silencing of gene expression by introduction of short interfering RNA (siRNA) is a powerful tool that that the potential to act as a therapeutic agent and the advantage of decreasing toxic effects on normal tissue sometimes seen with conventional treatments i.e. small molecule inhibitors. Naked, unmodified siRNA is poorly taken up by cells and is subject to degradation when exposed to blood proteins during systemic administration. It has also been shown to produce non-specific immune response as well as having the potential to generate 'off-target' effects. Therefore there is a requirement for a delivery system to not only protect the siRNA and facilitate its uptake, but additionally to offer the potential for targeted delivery with an aim of exploiting the high specificity afforded by RNA interference. Cationic liposomes are the most studied, non-viral delivery system used for nucleic acid delivery. As such, the use of cationic liposomes is promising for siRNA for delivery. Furthermore, polyethylene glycol (PEG) can be incorporated into the liposome formulation to create sterically stabilized or 'stealth' liposomes. Addition of PEG can reduce recognition by the reticuloendothelial system (RES) thereby prolonging circulation time. Here we describe a methodology for the complexation of siRNA with cationic liposomes and PEGylated liposomes using two protocols: mixing and encapsulation. Moreover, the different formulations are compared head to head to demonstrate their efficacy for gene silencing.

  18. Quantum chemical insights in energy dissipation and carotenoid radical cation formation in light harvesting complexes.

    PubMed

    Wormit, Michael; Dreuw, Andreas

    2007-06-21

    Light harvesting complexes (LHCs) have been identified in all photosynthetic organisms. To understand their function in light harvesting and energy dissipation, detailed knowledge about possible excitation energy transfer (EET) and electron transfer (ET) processes in these pigment proteins is of prime importance. This again requires the study of electronically excited states of the involved pigment molecules, in LHCs of chlorophylls and carotenoids. This paper represents a critical review of recent quantum chemical calculations on EET and ET processes between pigment pairs relevant for the major LHCs of green plants (LHC-II) and of purple bacteria (LH2). The theoretical methodology for a meaningful investigation of such processes is described in detail, and benefits and limitations of standard methods are discussed. The current status of excited state calculations on chlorophylls and carotenoids is outlined. It is focused on the possibility of EET and ET in the context of chlorophyll fluorescence quenching in LHC-II and carotenoid radical cation formation in LH2. In the context of non-photochemical quenching of green plants, it is shown that replacement of the carotenoid violaxanthin by zeaxanthin in its binding pocket of LHC-II can not result in efficient quenching. In LH2, our computational results give strong evidence that the S(1) states of the carotenoids are involved in carotenoid cation formation. By comparison of theoretical findings with recent experimental data, a general mechanism for carotenoid radical cation formation is suggested.

  19. Effect of monovalent cations on the kinetics of hypoxic conformational change of mitochondrial complex I

    PubMed Central

    Stepanova, Anna; Valls, Alba; Galkin, Alexander

    2015-01-01

    Mitochondrial complex I is a large, membrane-bound enzyme central to energy metabolism, and its dysfunction is implicated in cardiovascular and neurodegenerative diseases. An interesting feature of mammalian complex I is the so-called A/D transition, when the idle enzyme spontaneously converts from the active (A) to the de-active, dormant (D) form. The A/D transition plays an important role in tissue response to ischemia and rate of the conversion can be a crucial factor determining outcome of ischemia/reperfusion. Here, we describe the effects of alkali cations on the rate of the D-to-A transition to define whether A/D conversion may be regulated by sodium. At neutral pH (7–7.5) sodium resulted in a clear increase of rates of activation (D-to-A conversion) while other cations had minor effects. The stimulating effect of sodium in this pH range was not caused by an increase in ionic strength. EIPA, an inhibitor of Na+/H+ antiporters, decreased the rate of D-to-A conversion and sodium partially eliminated this effect of EIPA. At higher pH (> 8.0), acceleration of the D-to-A conversion by sodium was abolished, and all tested cations decreased the rate of activation, probably due to the effect of ionic strength. The implications of this finding for the mechanism of complex I energy transduction and possible physiological importance of sodium stimulation of the D-to-A conversion at pathophysiological conditions in vivo are discussed. PMID:26009015

  20. Three-coordinate cationic aluminum alkyl complexes incorporating {Beta}-diketiminate ligands

    SciTech Connect

    Radzewich, C.E.; Guzei, I.A.; Jordan, R.F.

    1999-09-22

    Low-coordinate cationic aluminum complexes are expected to be highly electrophilic and therefore are of interest for Lewis acid catalysis, olefin polymerization, and other potential applications. The authors describe three-coordinate, base-free aluminum alkyl cations that incorporate {beta}-diketiminate ligands. The reaction of {l{underscore}brace}HC(CMeNAr){sub 2}{r{underscore}brace}AlMe{sub 2} (1, Ar = 2.6-{sup i}Pr{sub 2}-phenyl) with [PH{sub 3}C][B(C{sub 6}F{sub 5}){sub 4}] in C{sub 6}D{sub 6} or C{sub 6}D{sub 5}Cl proceeds by methyl abstraction and yields [{l{underscore}brace}HC(CMeNAr){sub 2}{r{underscore}brace}AlMe][B(C{sub 6}F{sub 5}){sub 4}] (2) and Ph{sub 3}CMe. Complex 2 is soluble in C{sub 6}D{sub 5}Cl, separates as a liquid clathrate (oil) from benzene, and was isolated as an off-white solid by the addition of hexanes to a liquid clathrate in benzene. The addition of benzene/hexanes (1:10 by volume) to the isolated powder of 2, gently heating to 50 C for 2 days, and slowly cooling the mixture yielded 2{center{underscore}dot}benzene as colorless crystals. Complex 2 crystallizes as an ion pair in which the B(C{sub 6}F{sub 5}){sub 4}{sup {minus}} anion binds weakly to the {l{underscore}brace}HC(CMeNAr){sub 2}{r{underscore}brace}AlMe{sup {plus}} cation through a meta fluorine.

  1. Cesium complexes of naphthalimide substituted carboxylate ligands: Unusual geometries and extensive cation-π interactions

    NASA Astrophysics Data System (ADS)

    Reger, Daniel L.; Leitner, Andrew; Smith, Mark D.

    2015-07-01

    The reactions of (1,8-naphthalimido)ethanoic acid (HLgly), and (S)-2-(1,8-naphthalimido)-3-hydroxypropanoic acid (HLser), protonated forms of ligands that contain a carboxylate donor group and a 1,8-naphthalimide π⋯π stacking supramolecular tecton, with cesium hydroxide followed by solvothermal treatment in ethanol led to the formation of crystalline Cs(Lgly) (1) and Cs(Lene) (2), where the Lene- ligand, 2-(1,8-naphthalimido)acrylate, is formed from the dehydration of the HLser starting material. The X-ray studies show that 1 crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 30.430(7) Å, b = 4.9820(12) Å, c = 16.566(4) Å, β = 101.951(4)° and 2 in the monoclinic space group P21/n with unit cell dimensions a = 13.6049(15) Å, b = 6.8100(8) Å, c = 14.4187(16) Å, β = 105.345(2)°. The solid state structure of 1 contains two types of 6-coordinate cesium cations linked into sheets by bridging carboxylate oxygen atoms. One cation has a distorted octahedral environment, while the other is in an unusual planar, hexagonal O6-coordination geometry. The latter geometry is stabilized on both sides of the plane by η2-coordination of naphthalimide rings. The 1,8-naphthalimide rings are involved in intra-sheet π⋯π stacking interactions. The O6 coordination sphere of complex 2 is distorted and only half-filled with the oxygen atoms, which link the cations into rods that are further linked into sheets by bridging interactions of naphthalimide carbonyls with cesium cations from adjacent rods. The open face on the cation has unique η2:η1 interactions with two methylene groups in the ligands. These sheets are linked into a 3D supramolecular structure by interdigitated 1,8-naphthalimide rings involved in strong π⋯π interactions. Both complexes show naphthalimide based fluorescence.

  2. Bell Curve for Transfection by Lamellar Cationic Lipid--DNA Complexes

    NASA Astrophysics Data System (ADS)

    Ahmad, A.; Evans, Heather M.; Ewert, K.; George, C. X.; Samuel, C. E.; Safinya, C. R.

    2004-03-01

    Cationic liposomes (CL) present a viable alternative to viral delivery of therapeutic DNA to cells. We combine CL with DNA in order to form complexes that can deliver foreign DNA (genes) to cells. In trying to improve the transfection efficiency (TE) of lamellar CL-DNA complexes, we have identified universal trends depending on the headgroup size and charge of the cationic lipid. By using new multivalent lipids ranging from 2+ to 16+ (e.g. Ewert et al, J. Med. Chem. 2002; 45: 5023) we are able to access a wide range of membrane charge density values, or σ _M. TE plots vs. σ M for multivalent lipids merge onto a universal curve with a Gaussian shape. The optimal σ M depends on the overall CL/DNA charge. The universal TE curve shows three regimes related to cellular obstacles: at low σ _M, TE is limited by endosomal escape of CL-DNA, while at high σ M TE is limited by complex dissociation and DNA release into the cytoplasm. Funded by NIH GM-59288 and NSF DMR-0203755.

  3. Characterization of the interaction between cationic Erbium (III)-porphyrin complex with bovine serum albumin

    NASA Astrophysics Data System (ADS)

    Lu, Xi-Liang; Fan, Jian-Jun; Liu, Yi; Hou, An-Xin

    2009-09-01

    The interaction of cationic Erbium (III)-porphyrin complex (Er-Porp) with bovine serum albumin (BSA) has been investigated by fluorescence quenching spectra, UV-vis absorbance, circular dichroism (CD) and three-dimensional (3D) fluorescence spectra. It is proved that the fluorescence quenching of BSA by Er-Porp was mainly for the formation of Er-Porp-BSA complex. The Stern-Volmer quenching constants KSV and corresponding thermodynamic parameters ΔH, ΔG and ΔS were estimated by fluorescence quenching method. The results indicated that the electrostatic and hydrophobic interactions were the predominant intermolecular forces in stabilizing the complex. The binding distance was obtained according to Förster's non-radiative energy transfer theory. Displacement experiment and the number of binding sites calculation show that the cationic Er-Porp ring can inset in site-I (in subdomain IIA) of BSA. The effect of Er-Porp on the conformation of BSA was observed using CD, UV and 3D fluorescence spectra methods. The results show that the conformation of BSA was changed dramatically in the presence of Er-Porp by binding to the Trp residues of BSA. The interaction between BSA and Er-Porp can be used as a model for drug design and pharmaceutical research.

  4. Zinc (II) complex with a cationic Schiff base ligand: Synthesis, characterization, and biological studies

    NASA Astrophysics Data System (ADS)

    Lee, Sze Koon; Tan, Kong Wai; Ng, Seik Weng; Ooi, Kah Kooi; Ang, Kok Pian; Abdah, Md Akim

    2014-03-01

    A cationic Schiff base ligand, TSB (L) and its Zn (II) complex (1) were synthesized and characterized by using CHN, 1H-NMR, FT-IR, UV, LC-MS, and X-ray methods. Their ability to inhibit topoisomerase I, DNA cleavage activities, and cytotoxicity were studied. X-ray diffraction study shows that the mononuclear complex 1 is four coordinated with distorted tetrahedral geometry. The singly deprotonated Schiff base ligand L acts as a bidentate ON-donor ligand. Complexation of L increases the inhibitory strength on topoisomerase I activity. Complex 1 could fully inhibit topoisomerase I activity at 250 μM, while L did not show any inhibitory effect on topoisomerase I activity. In addition, L and complex 1 could cleave pBR322 DNA in a concentration and time dependent profile. Surprisingly, L has better DNA cleavage activity than complex 1. The cleavage of DNA by complex 1 is altered in the presence of hydrogen peroxide. Furthermore, L and complex 1 are mildly cytotoxic towards human ovarian cancer A2780 and hepatocellular carcinoma HepG2.

  5. Cationic Group-IV pincer-type complexes for polymerization and hydroamination catalysis.

    PubMed

    Luconi, Lapo; Klosin, Jerzy; Smith, Austin J; Germain, Stéphane; Schulz, Emmanuelle; Hannedouche, Jérôme; Giambastiani, Giuliano

    2014-03-21

    Neutral Zr(IV) and Hf(IV) dimethyl complexes stabilized by unsymmetrical dianionic {N,C,N'} pincer ligands have been prepared from their corresponding bis-amido complexes upon treatment with AlMe₃. Their structure consists of a central ó-bonded aryl donor group (C) capable of forming robust M-C bonds with the metal center, enforced by the synergic effect of both the coordination of peripheral donor groups (N) and the chelating rigid structure of the {N,C,N} ligand framework. Such a combination translates into systems having a unique balance between stability and reactivity. These Zr(IV) and Hf(IV) dimethyl complexes were converted in situ into cationic species [M(IV){N⁻,C⁻,N}Me][B(C₆F₅)₄] which are active catalysts for the room temperature (r.t.) intramolecular hydroamination/cyclization of primary and secondary aminoalkenes as well as for the high temperature ethylene-1-octene copolymerizations.

  6. Cationic Platinum(II) σ-SiH Complexes in Carbon Dioxide Hydrosilation.

    PubMed

    Ríos, Pablo; Díez, Josefina; López-Serrano, Joaquín; Rodríguez, Amor; Conejero, Salvador

    2016-11-14

    The low-electron-count cationic platinum complex [Pt(ItBu')(ItBu)][BAr(F) ], 1, interacts with primary and secondary silanes to form the corresponding σ-SiH complexes. According to DFT calculations, the most stable coordination mode is the uncommon η(1) -SiH. The reaction of 1 with Et2 SiH2 leads to the X-ray structurally characterized 14-electron Pt(II) species [Pt(SiEt2 H)(ItBu)2 ][BAr(F) ], 2, which is stabilized by an agostic interaction. Complexes 1, 2, and the hydride [Pt(H)(ItBu)2 ][BAr(F) ], 3, catalyze the hydrosilation of CO2 , leading to the exclusive formation of the corresponding silyl formates at room temperature.

  7. Functional Mn–Mg{sub k} cation complexes in GaN featured by Raman spectroscopy

    SciTech Connect

    Devillers, T. Bonanni, A.; Leite, D. M. G.; Dias da Silva, J. H.

    2013-11-18

    The evolution of the optical branch in the Raman spectra of (Ga,Mn)N:Mg epitaxial layers as a function of the Mn and Mg concentrations, reveals the interplay between the two dopants. We demonstrate that the various Mn-Mg-induced vibrational modes can be understood in the picture of functional Mn–Mg{sub k} complexes formed when substitutional Mn cations are bound to k substitutional Mg through nitrogen atoms, the number of ligands k being driven by the ratio between the Mg and the Mn concentrations.

  8. Controlled Hydrosilylation of Carbonyls and Imines Catalyzed by a Cationic Alkyl Complex

    SciTech Connect

    Koller, Jurgen; Bergman, Robert G.

    2012-04-09

    The synthesis, characterization, and unprecedented catalytic activity of cationic aluminum alkyl complexes toward hydrosilylation are described. X-ray crystallographic analysis of Tp*AlMe₂ (1) and [Tp*AlMe][I₃] (3) revealed the preference of Al for a tetrahedral coordination environment and the versatility of the Tp* ligand in stabilizing Al in bi- and tridentate coordination modes. [Tp*AlMe][MeB(C₆F₅)₃] (2) is highly active toward the hydrosilylation of a wide variety of carbonyls and imines, thus providing an inexpensive and versatile alternative to late transition metal catalysts.

  9. Cationic Amphiphilic Tris-Cyclometalated Iridium(III) Complexes Induce Cancer Cell Death via Interaction with Ca(2+)-Calmodulin Complex.

    PubMed

    Hisamatsu, Yosuke; Suzuki, Nozomi; Masum, Abdullah-Al; Shibuya, Ai; Abe, Ryo; Sato, Akira; Tanuma, Sei-Ichi; Aoki, Shin

    2017-02-15

    In our previous paper, we reported on the preparation of some cationic amphiphilic Ir complexes (2c, 2d) containing KKGG peptides that induce and detect cell death of Jurkat cells. Mechanistic studies suggest that 2c interacts with anionic molecules and/or membrane receptors on the cell surface to trigger an intracellular Ca(2+) response, resulting in the induction of cell death, accompanied by membrane disruption. We have continued the studies of cell death of Jurkat cells induced by 2c and found that xestospongin C, a selective inhibitor of an inositol 1,4,5-trisphosphate receptor located on the endoplasmic reticulum (ER), reduces the cytotoxicity of 2c, suggesting that 2c triggers the release of Ca(2+) from the ER, leading to an increase in the concentration of cytosolic Ca(2+), thus inducing cell death. Moreover, we synthesized a series of new amphiphilic cationic Ir complexes 5a-c containing photoreactive 3-trifluoromethyl-3-phenyldiazirine (TFPD) groups, in an attempt to identify the target molecules of 2c. Interestingly, it was discovered that a TFPD group functions as a triplet quencher of Ir complexes. It was also found that 5b is useful as a turn-on phosphorescent probe of acidic proteins such as bovine serum albumin (BSA) (pI = 4.7) and their complexation was confirmed by luminescence titrations and SDS-PAGE of photochemical products between them. These successful results allowed us to carry out photoaffinity labeling of the target biomolecules of 5b (2c and analogues thereof) in Jurkat cells. A proteomic analysis of the products obtained by the photoirradiation of 5b with Jurkat cells suggests that the Ca(2+)-binding protein "calmodulin (CaM)" is one of target proteins of the Ir complexes. Indeed, 5b was found to interact with the Ca(2+)-CaM complex, as evidenced by luminescence titrations and the results of photochemical reactions of 5b with CaM in the presence of Ca(2+) (SDS-PAGE). A plausible mechanism for cell death induced by a cationic amphiphilic

  10. Structures and dynamic solution behavior of cationic, two-coordinate gold(I)-π-allene complexes.

    PubMed

    Brown, Timothy J; Sugie, Atsushi; Leed, Marina G D; Widenhoefer, Ross A

    2012-05-29

    A family of seven cationic gold complexes that contain both an alkyl substituted π-allene ligand and an electron-rich, sterically hindered supporting ligand was isolated in >90% yield and characterized by spectroscopy and, in three cases, by X-ray crystallography. Solution-phase and solid-state analysis of these complexes established preferential binding of gold to the less substituted C=C bond of the allene and to the allene π face trans to the substituent on the uncomplexed allenyl C=C bond. Kinetic analysis of intermolecular allene exchange established two-term rate laws of the form rate=k(1)[complex]+k(2)[complex][allene] consistent with allene-independent and allene-dependent exchange pathways with energy barriers of ΔG(≠)(1)=17.4-18.8 and ΔG(≠)(2)=15.2-17.6 kcal mol(-1), respectively. Variable temperature (VT) NMR analysis revealed fluxional behavior consistent with facile (ΔG(≠)=8.9-11.4 kcal mol(-1)) intramolecular exchange of the allene π faces through η(1)-allene transition states and/or intermediates that retain a staggered arrangement of the allene substituents. VT NMR/spin saturation transfer analysis of [{P(tBu)(2)o-binaphthyl}Au(η(2)-4,5-nonadiene)](+)SbF(6)(-) (5), which contains elements of chirality in both the phosphine and allene ligands, revealed no epimerization of the allene ligand below the threshold for intermolecular allene exchange (ΔG(≠)(298K)=17.4 kcal mol(-1)), which ruled out the participation of a η(1)-allylic cation species in the low-energy π-face exchange process for this complex. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Biocompatible Double-Membrane Hydrogels from Cationic Cellulose Nanocrystals and Anionic Alginate as Complexing Drugs Codelivery.

    PubMed

    Lin, Ning; Gèze, Annabelle; Wouessidjewe, Denis; Huang, Jin; Dufresne, Alain

    2016-03-23

    A biocompatible hydrogel with a double-membrane structure is developed from cationic cellulose nanocrystals (CNC) and anionic alginate. The architecture of the double-membrane hydrogel involves an external membrane composed of neat alginate, and an internal composite hydrogel consolidates by electrostatic interactions between cationic CNC and anionic alginate. The thickness of the outer layer can be regulated by the adsorption duration of neat alginate, and the shape of the inner layer can directly determine the morphology and dimensions of the double-membrane hydrogel (microsphere, capsule, and filmlike shapes). Two drugs are introduced into the different membranes of the hydrogel, which will ensure the complexing drugs codelivery and the varied drugs release behaviors from two membranes (rapid drug release of the outer hydrogel, and prolonged drug release of the inner hydrogel). The double-membrane hydrogel containing the chemically modified cellulose nanocrystals (CCNC) in the inner membrane hydrogel can provide the sustained drug release ascribed to the "nano-obstruction effect" and "nanolocking effect" induced by the presence of CCNC components in the hydrogels. Derived from natural polysaccharides (cellulose and alginate), the novel double-membrane structure hydrogel material developed in this study is biocompatible and can realize the complexing drugs release with the first quick release of one drug and the successively slow release of another drug, which is expected to achieve the synergistic release effects or potentially provide the solution to drug resistance in biomedical application.

  12. Emergence of symmetry and chirality in crown ether complexes with alkali metal cations.

    PubMed

    Martínez-Haya, Bruno; Hurtado, Paola; Hortal, Ana R; Hamad, Said; Steill, Jeffrey D; Oomens, Jos

    2010-07-08

    Crown ethers provide a valuable benchmark for the comprehension of molecular recognition mediated by inclusion complexes. One of the most relevant crown ethers, 18-crown-6 (18c6), features a flexible six-oxygen cyclic backbone that is well-known for its selective cation binding. This study employs infrared spectroscopy and quantum mechanical calculations to elucidate the structure of the gas-phase complexes formed by the 18c6 ether with the alkali metal cations. It is shown that symmetric and chiral arrangements play a dominant role in the conformational landscape of the 18c6-alkali system. Most stable 18c6-M(+) conformers are found to have symmetries C(3v) and C(2) for Cs(+), D(3d) for K(+), C(1) and D(3d) for Na(+), and D(2) for Li(+). Remarkably, whereas the bare 18c6 ether is achiral, chirality emerges in the C(2) and D(2) 18c6-M(+) conformations, both of which involve pairs of stable atropoisomers capable of acting as enantiomeric selective substrates.

  13. Cationic liposome–nucleic acid complexes for gene delivery and gene silencing

    PubMed Central

    Ewert, Kai K.; Majzoub, Ramsey N.; Leal, Cecília

    2014-01-01

    Cationic liposomes (CLs) are studied worldwide as carriers of DNA and short interfering RNA (siRNA) for gene delivery and gene silencing, and related clinical trials are ongoing. Optimization of transfection efficiency and silencing efficiency by cationic liposome carriers requires a comprehensive understanding of the structures of CL–nucleic acid complexes and the nature of their interactions with cell membranes as well as events leading to release of active nucleic acids within the cytoplasm. Synchrotron x-ray scattering has revealed that CL–nucleic acid complexes spontaneously assemble into distinct liquid crystalline phases including the lamellar, inverse hexagonal, hexagonal, and gyroid cubic phases, and fluorescence microscopy has revealed CL–DNA pathways and interactions with cells. The combining of custom synthesis with characterization techniques and gene expression and silencing assays has begun to unveil structure–function relations in vitro. As a recent example, this review will briefly describe experiments with surface-functionalized PEGylated CL–DNA nanoparticles. The functionalization, which is achieved through custom synthesis, is intended to address and overcome cell targeting and endosomal escape barriers to nucleic acid delivery faced by PEGylated nanoparticles designed for in vivo applications. PMID:25587216

  14. Synthesis and chemistry of cationic d sup 0 metal alkyl complexes

    SciTech Connect

    Jordan, R.F.

    1991-01-01

    The objective of this project is to develop new types of electrophilic metal alkyl complexes for catalytic C-H activation and olefin polymerization chemistry, and associated fundamental mechanistic studies. We have focused our efforts on four classes of early metal alkyl complexes: (1) cationic group 4 Cp{sub 2}M(R){sup +} complexes (1) which are active species in Cp{sub 2}MX{sub 2}-based Ziegler-Natta olefin polymerization catalyst systems and which catalyze productive C-H activation reactions of heterocycles, (2) neutral (dicarbollide)(Cp*)M(R) complexes (2) which are structurally are electronically very similar to 1, (3) half-sandwich complexes CpM(R){sub 2}(L){sub n}{sup +} which are highly coordinatively and electronically unsaturated, and (4) new group 5 (dicarbollide)(Cp)MR{sub 2} and (dicarbollide){sub 2} MR complexes which are more unsaturated than group 5 Cp{sub 2}M systems due to incorporation of the dicarbollide ligand.

  15. Green Phosphorescence and Electroluminescence of Sulfur Pentafluoride-Functionalized Cationic Iridium(III) Complexes.

    PubMed

    Shavaleev, Nail M; Xie, Guohua; Varghese, Shinto; Cordes, David B; Slawin, Alexandra M Z; Momblona, Cristina; Ortí, Enrique; Bolink, Henk J; Samuel, Ifor D W; Zysman-Colman, Eli

    2015-06-15

    We report on four cationic iridium(III) complexes [Ir(C^N)2(dtBubpy)](PF6) that have sulfur pentafluoride-modified 1-phenylpyrazole and 2-phenylpyridine cyclometalating (C^N) ligands (dtBubpy = 4,4'-di-tert-butyl-2,2'-bipyridyl). Three of the complexes were characterized by single-crystal X-ray structure analysis. In cyclic voltammetry, the complexes undergo reversible oxidation of iridium(III) and irreversible reduction of the SF5 group. They emit bright green phosphorescence in acetonitrile solution and in thin films at room temperature, with emission maxima in the range of 482-519 nm and photoluminescence quantum yields of up to 79%. The electron-withdrawing sulfur pentafluoride group on the cyclometalating ligands increases the oxidation potential and the redox gap and blue-shifts the phosphorescence of the iridium complexes more so than the commonly employed fluoro and trifluoromethyl groups. The irreversible reduction of the SF5 group may be a problem in organic electronics; for example, the complexes do not exhibit electroluminescence in light-emitting electrochemical cells (LEECs). Nevertheless, the complexes exhibit green to yellow-green electroluminescence in doped multilayer organic light-emitting diodes (OLEDs) with emission maxima ranging from 501 nm to 520 nm and with an external quantum efficiency (EQE) of up to 1.7% in solution-processed devices.

  16. A Study of Complexation-ability of Neutral Schiff Bases to Some Metal Cations

    PubMed Central

    Topal, Giray; Tümerdem, Recep; Basaran, Ismet; Gümüş, Arzu; Cakir, Umit

    2007-01-01

    The constants of the extraction equilibrium and the distribution for dichloromethane as an organic solvent having low dielectric constant of metal cations with chiral Schiff bases, benzaldehydene-(S)-2-amino-3-phenylpropanol (I), ohydroxybenzaldehydene-( S)-2-amino-3-phenyl-propanol (II), benzaldehydene-(S)-2- amino-3-methylbutanol (III) with anionic dyes [4-(2-pyridylazo)-resorcinol mono sodium monohydrate (NaPar), sodium picrat (NaPic) and potassium picrat (KPic)] and some heavy metal chlorides were determined at 25 ºC. All the ligands have given strongest complexation for NaPar. In contrast, similar behaviour for both alkali metal picrates is not apparent in the complexation of corresponding ligands.

  17. In vitro anticancer activity evaluation of new cationic platinum(II) complexes based on imidazole moiety.

    PubMed

    Rimoldi, Isabella; Facchetti, Giorgio; Lucchini, Giorgio; Castiglioni, Elisa; Marchianò, Silvia; Ferri, Nicola

    2017-03-15

    The development and the synthesis of cationic platinum(II) complexes were realized and their cytotoxic activity was tested on triple negative breast cancer MDA-MB-231 cell line and in two cell lines poorly responsive to cisplatin (DLD-1 and MCF-7). The complex 2c resulted the most potent cytotoxic agent in MDA-MB-231 (IC50=61.9µM) and more effective than cisplatin on both DLD-1 (IC50=57.4µM) and MCF-7 (IC50=79.9µM) cell lines. 2c showed different cellular uptake and pharmacodynamic properties than cisplatin, interfering with the progression of the M phase of the cell cycle. Thus, 2c represents a lead compound of a new class of cytotoxic agents with promising antitumor activity.

  18. Borinium cations as sigma-B-H ligands in osmium complexes.

    PubMed

    Esteruelas, Miguel A; Fernández-Alvarez, Francisco J; López, Ana M; Mora, Malka; Oñate, Enrique

    2010-04-28

    The complex OsH(2)Cl(2)(P(i)Pr(3))(2) reacts with pinacolborane, Me(2)NH-BH(3), and (t)BuNH(2)-BH(3) to give the complexes OsH(2)Cl{eta(2)-HBOC(CH(3))(2)C(CH(3))(2)OBpin}(P(i)Pr(3))(2) and OsH(2)Cl(eta(2)-HBNR(1)R(2))(P(i)Pr(3))(2) (R(1) = R(2) = Me; R(1) = H, R(2) = (t)Bu) containing monosubstituted alkoxy- and amidoborinium cations coordinated as sigma-B-H ligands. The process is proposed to take place via the electrophilic 14-valence-electron fragment OsHCl(P(i)Pr(3))(2), which promotes hydride transfer from the corresponding borane to the osmium atom.

  19. Polyanionic Biopolymers for the Delivery of Pt(II) Cationic Antiproliferative Complexes

    PubMed Central

    2016-01-01

    Phenanthriplatin, that is, (SP-4-3)-diamminechlorido(phenanthridine)platinum(II) nitrate, an effective antitumor cationic Pt(II) complex, was loaded on negatively charged dextran sulfate (DS) as a model vector for drug delivery via electrostatic interactions. The free complex and the corresponding conjugate with DS were tested on two standard human tumor cell lines, namely, ovarian A2780 and colon HCT 116, and on several malignant pleural mesothelioma cell lines (namely, epithelioid BR95, mixed/biphasic MG06, sarcomatoid MM98, and sarcomatoid cisplatin-resistant MM98R). The in vitro results suggest that the conjugate releases the active metabolite phenanthriplatin with a biphasic fashion. In these experimental conditions, the conjugate is slightly less active than free phenanthriplatin; but both exhibited antiproliferative potency higher than the reference metallodrug cisplatin and were able to overcome the acquired cisplatin chemoresistance in MM98R cells. PMID:27774043

  20. Cationic technetium-99m complexes of N-substituted pyridoxal derivatives as renal function agents

    SciTech Connect

    Karube, Yoshiharu; Iwamoto, Koji; Takata, Jiro

    1994-10-01

    New cationic technetium-chelating agents containing a pyridinium group have been synthesized and evaluated as potential renal radiopharmaceuticals. The pyridinium compounds used in the study are N-methyl pyridoxal chloride, N-ethyl pyridoxal chloride, N-propyl pyridoxal chloride, 1-methyl-3-hydroxy-4-formylpyridinium chloride, 1-methyl-2-formyl-3-hydroxpyridinium chloride and the Schiff`s bases of N-methyl pyridoxal chloride with amino acid, amino acid ester and amino acid amide. Complexes of these chelating agents with {sup 22m}Tc were prepared using a Na{sub 2}S{sub 2}O{sub 4} or a SnCl{sub 2} solution as a reducing agent. The purity of the {sup 99m}Tc complexes was determined by paper electrophoresis in 0.1 Mtris buffer. Electrophoresis indicates slightly positive-charged species. The log P values of these complexes showed a hydrophilic nature. Urinary excretion of the {sup 99m}Tc N-alkylated pyridoxal derivatives, {sup 99m}Tc-diethylenetriaminepentaacetic acid, {sup 99m}Tc-mercaptoacetylglycylglycylglycine (MAG3) and {sup 131}I-o-iodohippurate were determined in mice and rats at different time intervals. In a rat model, the pyridoxal-derived {sup 99m}Tc complexes are rapidly excreted in urine and provide clear renal scintigrams. Hepatobiliary excretion was negligible, reducing scan interference from the intestines. Total clearances were lower than that of {sup 131}I-hippurate and {sup 99m}Tc-MAG3. The rate of urinary clearance of the new tracers was not significantly faster than {sup 99m}Tc diethylenetriaminepentaacetic acid and the inhibitor N{sup 1}-methylnicotinamide had only a minimal effect on the renal behavior. Though the new tracers have cationic properties, the pyridinium group did not contribute largely to the excretion of active transport. 21 refs., 4 figs., 4 tabs.

  1. Covalent and Noncovalent Interactions Between Boron and Argon: AN Infrared Photodissociation Spectroscopic Study of Argon-Boron Oxide Cation Complexes

    NASA Astrophysics Data System (ADS)

    Jin, Jiaye; Li, Wei; Wang, Guanjun; Zhou, Mingfei

    2017-06-01

    Although a wide range of compounds of the heavy rare-gas elements are experimentally known, very few chemically bound molecules have been experimentally observed for the lighter noble gases. Here we report a combined infrared photodissociation spectroscopic and theoretical study on a series of argon-boron oxide cation complexes prepared via a laser vaporization supersonic ion source in the gas phase. Infrared spectroscopic combined with state-of-the-art quantum chemical calculations indicate that the [ArB_3O_{4,5}]^+, [ArB_4O_{5-7}]^+ and [ArB_5O_7]^+ cation complexes have planar structures each involving an aromatic boroxol ring and an argon-boron covalent bond formed between the in-plane 2p atomic orbitals of Ar and boron. In contrast, the [ArB_3O_4]^+ cation complex is characterized to be a weakly bound complex with a BO chain structure.

  2. Alkali Cation Chelation in Cold β-O-4 Tetralignol Complexes

    NASA Astrophysics Data System (ADS)

    DeBlase, Andrew F.; Dziekonski, Eric T.; Hopkins, John R.; Burke, Nicole L.; Kenttamaa, Hilkka I.; McLuckey, Scott A.; Zwier, Timothy S.

    2016-06-01

    Lignins are the second most abundant naturally occurring polymer class, contributing to about 30% of the organic carbon in the biosphere. Their primary function is to provide the structural integrity of plant cell walls and have recently come under consideration as a potential source of biofuels because they have an energy content similar to coal. Herein, we employ cold ion spectroscopy (UV action and IR-UV double resonance) to unravel the spectroscopic signatures of G-type alkali metal cationized (X = Li+, Na+, K+) lignin tetramers connected by β-O-4 linkages. The conformation-specific spectroscopy reveals a variety of conformers, each containing distinct infrared spectra in the OH stretching region building on recent studies on the neutral and alkali metal cationized β-O-4 dimers. Based on comparisons of our infrared spectra to density functional theory [M05-2X/6-31+G*] harmonic level calculations for structures derived from a Monte Carlo conformational search, the alkali metal ion is discovered to engage in M+-OH-O interactions as important motifs that determine the secondary structures of these complexes. This interaction disappears in the major conformer of the K+ adduct, suggesting a reemergence of a neutral dimer segment as the metal binding energy decreases. Chelation of the metal cation by oxygen lone pair(s) of nearby oxygens in the β-O-4 linkage is observed to be the predominant driving force for 3D structure around the charge site, relegating OH-O H-bonds as secondary stabilizing elements.

  3. Two dinuclear Ru(II) polypyridyl complexes with different photophysical and cation recognition properties

    NASA Astrophysics Data System (ADS)

    Cheng, Feixiang; He, Chixian; Ren, Mingli; Wang, Fan; Yang, Yuting

    2015-02-01

    Two dinuclear Ru(II) polypyridyl complexes functionalized with vacant coordination sites have been designed and synthesized. Their photophysical properties and interactions with various metal ions have been investigated at room temperature. The two complexes exhibit different UV/Vis absorption and emission intensities. When titrated with various metal ions, complex [{Ru(bpy)2}2(μ2-L1)]4+ exhibits a notable fluorescence quenching in the presence of Cu2+ in H2O-CH3CN media (1:1, v/v); its analogous complex [{Ru(bpy)2}2(μ2-L2)]4+ exhibits no cation selectivity, the fluorescence intensity of complex [{Ru(bpy)2}2(μ2-L2)]4+ has been enhanced by several transition metal ions due to prevention of the photo-induced electron transfer process. The fluorescence titration spectra and Benesi-Hildebrand expression reveal the formation of a 1:1 bonding mode between [{Ru(bpy)2}2(μ2-L1)]4+ and Cu2+ ion with the association constant of 5.50 × 104 M-1.

  4. Optical tweezers reveal a dynamic mechanical response of cationic peptide-DNA complexes

    NASA Astrophysics Data System (ADS)

    Lee, Amy; Zheng, Tai; Sucayan, Sarah; Chou, Szu-Ting; Tricoli, Lucas; Hustedt, Jason; Kahn, Jason; Mixson, A. James; Seog, Joonil

    2013-03-01

    Nonviral carriers have been developed to deliver nucleic acids by forming nanoscale complexes; however, there has been limited success in achieving high transfection efficiency. Our hypothesis is that a factor affecting gene delivery efficiency is the mechanical response of the condensed complex. To begin to test this hypothesis, we directly measured the mechanical properties of DNA-carrier complexes using optical tweezers. Histidine-lysine (HK) polymer, Asparagine-lysine (NK) polymer and poly-L-lysine were used to form complexes with a single DNA molecule. As carriers were introduced, a sudden decrease in DNA extension occurrs at a force level which is defined as critical force (Fc). Fc is carrier and concentration dependent. Pulling revealed reduction in DNA extension length for HK-DNA complexes. The characteristics of force profiles vary by agent and can be dynamically manipulated by changes in environmental conditions such as ionic strength of the buffer as well as pH. Heparin can remove cationic reagents which are otherwise irreversibly bound to DNA. The implications for optimizing molecular interactions to enhance transfection efficiency will be discussed.

  5. Circular Dichroism is Sensitive to Monovalent Cation Binding in Monensin Complexes.

    PubMed

    Nedzhib, Ahmed; Kessler, Jiří; Bouř, Petr; Gyurcsik, Béla; Pantcheva, Ivayla

    2016-05-01

    Monensin is a natural antibiotic that exhibits high affinity to certain metal ions. In order to explore its potential in coordination chemistry, circular dichroism (CD) spectra of monensic acid A (MonH) and its derivatives containing monovalent cations (Li(+) , Na(+) , K(+) , Rb(+) , Ag(+) , and Et4 N(+) ) in methanolic solutions were measured and compared to computational models. Whereas the conventional CD spectroscopy allowed recording of the transitions down to 192 nm, synchrotron radiation circular dichroism (SRCD) revealed other bands in the 178-192 nm wavelength range. CD signs and intensities significantly varied in the studied compounds, in spite of their similar crystal structure. Computational modeling based on the Density Functional Theory (DFT) and continuum solvent model suggests that the solid state monensin structure is largely conserved in the solutions as well. Time-dependent Density Functional Theory (TDDFT) simulations did not allow band-to-band comparison with experimental spectra due to their limited precision, but indicated that the spectral changes were caused by a combination of minor conformational changes upon the monovalent cation binding and a direct involvement of the metal electrons in monensin electronic transitions. Both the experiment and simulations thus show that the CD spectra of monensin complexes are very sensitive to the captured ions and can be used for their discrimination. Chirality 28:420-428, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  6. Modulation of pyridinium cationic lipid-DNA complex properties by pyridinium gemini surfactants and its impact on lipoplex transfection properties

    PubMed Central

    Sharma, Vishnu Dutt; Lees, Julia; Hoffman, Nicholas E.; Brailoiu, Eugen; Madesh, Muniswamy; Wunder, Stephanie L.; Ilies, Marc A.

    2014-01-01

    The study presents the effects of blending a cationic gemini surfactant into cationic lipid bilayers and its impact towards plasmid DNA compaction and delivery process. Using nanoDSC, dynamic light scattering, zeta potential and electrophoretic mobility measurements, together with transfection (2D- and 3D-) and viability assays, we identified the main physicochemical parameters of the lipid bilayers, liposomes and lipoplexes that are affected by the gemini surfactant addition. We also correlated the cationic bilayer composition with the dynamics of the DNA compaction process, and with transfection efficiency, cytotoxicity and internalization mechanism of the resultant nucleic acid complexes. We found that blending of gemini surfactant into the cationic bilayers fluidized the supramolecular assemblies, reduced the amount of positive charge required to fully compact the plasmid DNA and, in certain cases, changed the internalization mechanism of the lipoplexes. Transfection efficiency of select ternary lipoplexes derived from cationic gemini surfactants and lipids was several times superior to transfection efficiency of corresponding binary lipoplexes, also surpassing standard transfection systems. The overall impact of gemini surfactants into the formation and dynamic of cationic bilayers was found to depend heavily on the presence of co-lipids, their nature and amount present into lipoplexes. The study confirmed the possibility of combining the specific properties of pyridinium gemini surfactants and cationic lipids synergistically for obtaining efficient synthetic transfection systems with negligible cytotoxicity useful for therapeutic gene delivery. PMID:24377350

  7. Modulation of pyridinium cationic lipid-DNA complex properties by pyridinium gemini surfactants and its impact on lipoplex transfection properties.

    PubMed

    Sharma, Vishnu Dutt; Lees, Julia; Hoffman, Nicholas E; Brailoiu, Eugen; Madesh, Muniswamy; Wunder, Stephanie L; Ilies, Marc A

    2014-02-03

    The study presents the effects of blending a cationic gemini surfactant into cationic lipid bilayers and its impact on the plasmid DNA compaction and delivery process. Using nanoDSC, dynamic light scattering, zeta potential, and electrophoretic mobility measurements, together with transfection (2D- and 3D-) and viability assays, we identified the main physicochemical parameters of the lipid bilayers, liposomes, and lipoplexes that are affected by the gemini surfactant addition. We also correlated the cationic bilayer composition with the dynamics of the DNA compaction process and with transfection efficiency, cytotoxicity, and the internalization mechanism of the resultant nucleic acid complexes. We found that the blending of gemini surfactant into the cationic bilayers fluidized the supramolecular assemblies, reduced the amount of positive charge required to fully compact the plasmid DNA and, in certain cases, changed the internalization mechanism of the lipoplexes. The transfection efficiency of select ternary lipoplexes derived from cationic gemini surfactants and lipids was several times superior to the transfection efficiency of corresponding binary lipoplexes, also surpassing standard transfection systems. The overall impact of gemini surfactants into the formation and dynamic of cationic bilayers was found to depend heavily on the presence of colipids, their nature, and amount present in lipoplexes. The study confirmed the possibility of combining the specific properties of pyridinium gemini surfactants and cationic lipids synergistically to obtain efficient synthetic transfection systems with negligible cytotoxicity useful for therapeutic gene delivery.

  8. Preparation, stability and antimicrobial activity of cationic cross-linked starch-iodine complexes.

    PubMed

    Klimaviciute, Rima; Bendoraitiene, Joana; Rutkaite, Ramune; Siugzdaite, Jurate; Zemaitaitis, Algirdas

    2012-12-01

    Cationic cross-linked starch (CCS)-iodine complexes containing different amounts of quaternary ammonium groups (different degrees of substitution (DS)) and iodine have been obtained by iodine adsorption on CCS from aqueous iodine potassium iodide solution. Equilibrium adsorption studies showed that with an increase of DS the amount of iodine adsorbed on CCS and the affinity of iodine to CCS increased linearly. The influences of the DS of CCS and the amount of adsorbed iodine on the stability of CCS-iodine complexes in a solution of 0.02M sodium acetate and reactivity toward l-tyrosine have been investigated. At the same DS, the stability of CCS-iodine complexes decreased with an increase of the amount of adsorbed iodine. With increasing the DS, the stability of CCS-iodine complexes increased. The iodine consumption in the reaction with l-tyrosine increased significantly with an increase of the amount of adsorbed iodine. The influence of DS on iodine consumption was lower and depended on the amount of adsorbed iodine. The antibacterial activity of CCS-iodine complexes against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli was determined by the broth-dilution and spread-plate methods. The obtained results have demonstrated that an appropriate selection of the CCS-iodine complex composition (the DS of CCS and the amount of adsorbed iodine) could ensure good antimicrobial properties by keeping a low concentration of free iodine in the system. The main advantage of using CCS-iodine complexes as antimicrobial agents is the biodegradability of the polymeric matrix.

  9. Structures of restriction endonuclease HindIII in complex with its cognate DNA and divalent cations.

    PubMed

    Watanabe, Nobuhisa; Takasaki, Yozo; Sato, Chika; Ando, Shoji; Tanaka, Isao

    2009-12-01

    The three-dimensional crystal structures of HindIII bound to its cognate DNA with and without divalent cations were solved at 2.17 and 2.00 A resolution, respectively. HindIII forms a dimer. The structures showed that HindIII belongs to the EcoRI-like (alpha-class) subfamily of type II restriction endonucleases. The cognate DNA-complex structures revealed the specific DNA-recognition mechanism of HindIII by which it recognizes the palindromic sequence A/AGCTT. In the Mg(2+) ion-soaked structure the DNA was cleaved and two ions were bound at each active site, corresponding to the two-metal-ion mechanism.

  10. A cationic Rh(III) complex that efficiently catalyzes hydrogen isotope exchange in hydrosilanes.

    PubMed

    Campos, Jesús; Esqueda, Ana C; López-Serrano, Joaquín; Sánchez, Luis; Cossio, Fernando P; de Cozar, Abel; Alvarez, Eleuterio; Maya, Celia; Carmona, Ernesto

    2010-12-01

    The synthesis and structural characterization of a mixed-sandwich (η(5)-C(5)Me(5))Rh(III) complex of the cyclometalated phosphine PMeXyl(2) (Xyl = 2,6-C(6)H(3)Me(2)) with unusual κ(4)-P,C,C',C'' coordination (compound 1-BAr(f); BAr(f) = B(3,5-C(6)H(3)(CF(3))(2))(4)) are reported. A reversible κ(4) to κ(2) change in the binding of the chelating phosphine in cation 1(+) induced by dihydrogen and hydrosilanes triggers a highly efficient Si-H/Si-D (or Si-T) exchange applicable to a wide range of hydrosilanes. Catalysis can be carried out in an organic solvent solution or without solvent, with catalyst loadings as low as 0.001 mol %, and the catalyst may be recycled a number of times.

  11. A square-planar hydrated cationic tetrakis(methimazole)gold(III) complex.

    PubMed

    Lynch, Will E; Padgett, Clifford W; Quillian, Brandon; Haddock, John

    2015-04-01

    The cationic pseudo-square-planar complex tetrakis(1-methyl-2,3-dihydro-1H-imidazole-2-thione-κS)gold(III) trichloride sesquihydrate, [Au(C4H6N2S)4]Cl3·1.5H2O, was isolated as dark-red crystals from the reaction of chloroauric acid trihydrate (HAuCl4·3H2O) with four equivalents of methimazole in methanol. The Au(III) atoms reside at the corners of the unit cell on an inversion center and are bound by the S atoms of four methimazole ligands in a planar arrangement, with S-Au-S bond angles of approximately 90°.

  12. Synthesis and reactivity of cationic niobium and tantalum methyl complexes supported by imido and β-diketiminato ligands.

    PubMed

    Tomson, Neil C; Arnold, John; Bergman, Robert G

    2011-08-14

    The synthesis and reactivity of the cationic niobium and tantalum monomethyl complexes [(BDI)MeM(N(t)Bu)][X] (BDI = [Ar]NC(CH(3))CHC(CH(3))N[Ar], Ar = 2,6-(i)Pr(2)C(6)H(3); M = Nb, Ta; X = MeB(C(6)F(5))(3), B(C(6)F(5))(4)] was investigated. The cationic alkyl complexes failed to irreversibly bind CO but formed phosphine-trapped acyl complexes [(BDI)(R(3)PC(O)Me)M(N(t)Bu)][B(C(6)F(5))(4)] (R = Et, Cy) in the presence of a combination of trialkylphosphines and CO. Treatment of the monoalkyl cationic Nb complex with XylNC (Xyl = 2,6-Me(2)-C(6)H(3)) resulted in irreversible formation of the iminoacyl complex [(BDI)(XylN[double bond, length as m-dash]C(Me))Nb(N(t)Bu)][B(C(6)F(5))(4)], which did not bind phosphines but would add a methide group to the iminoacyl carbon to provide the known ketimine complex (BDI)(XylNCMe(2))Nb(N(t)Bu). Further stoichiometric chemistry explored i) migratory insertion reactions to form new alkoxide, amidinate, and ketimide complexes; ii) protonolysis reactions with Ph(3)SiOH to form thermally robust cationic siloxide complexes; and iii) catalytic high-density polyethylene formation mediated by the cationic Nb methyl complex. This journal is © The Royal Society of Chemistry 2011

  13. Unexpected Actinyl Cation-Directed Structural Variation in Neptunyl(VI) A-Type Tri-lacunary Heteropolyoxotungstate Complexes

    DOE PAGES

    Berg, John M.; Gaunt, Andrew J.; May, Iain; ...

    2015-04-22

    A-type tri-lacunary heteropolyoxotungstate anions (e.g., [PW9O34]9-, [AsW9O34]9-, [SiW9O34]10- and [GeW9O34]10-) are multi-dentate oxygen donor ligands that readily form sandwich complexes with actinyl cations ({UO2}2+, {NpO2}+, {NpO2}2+ & {PuO2}2+) in near neutral/slightly alkaline aqueous solutions. Two or three actinyl cations are sandwiched between two trilacunary anions, with additional cations (Na+, K+ or NH4 +) also often held within the cluster. Studies thus far have indicated that it is these additional +I cations, rather than the specific actinyl cation, that direct the structural variation in the complexes formed. We now report the structural characterization of the neptunyl (VI) cluster complex (NH4)13 [Na(NpO2)2(A-α-more » PW9O34)2]·12H2O. The anion in this complex, [Na(NpO2)2(PW9O34)2]13-, contains one Na+ cation and two {NpO2}2+ cations held between two [PW9O34]9- anions – with an additional partial occupancy NH4 + or {NpO2}2+ cation also present. In the analogous uranium (VI) system, under similar reaction conditions that includes an excess of NH4Cl in the parent solution, it was previously shown that [(NH4)2(UVIO2)2(A-PW9O34)2]12- is the dominant species in both solution and the crystallized salt. Spectroscopic studies provide further proof of differences in the observed chemistry for the {NpO2}2+/[PW9O34]9- and {UO2}2+/[PW9O34]9- systems, both in solution and in solid state complexes crystallized from comparable salt solutions. The work revealed that varying the actinide element (Np vs. U) can indeed measurably impact structure and complex stability in the cluster chemistry of actinyl (VI) cations with A-type tri-lacunary heteropolyoxotungstate anions.« less

  14. Surface complexation of heavy metal cations on clay edges: insights from first principles molecular dynamics simulation of Ni(II)

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Liu, Xiandong; Lu, Xiancai; He, Mengjia; Jan Meijer, Evert; Wang, Rucheng

    2017-04-01

    Aiming at an atomistic mechanism of heavy metal cation complexing on clay surfaces, we carried out systematic first principles molecular dynamics (FPMD) simulations to investigate the structures, free energies and acidity constants of Ni(II) complexes formed on edge surfaces of 2:1 phyllosilicates. Three representative complexes were studied, including monodentate complex on the tbnd SiO site, bidentate complex on the tbnd Al(OH)2 site, and tetradentate complex on the octahedral vacancy where Ni(II) fits well into the lattice. The complexes structures were characterized in detail. Computed free energy values indicate that the tetradentate complex is significantly more stable than the other two. The calculated acidity constants indicate that the tetradentate complex can get deprotonated (pKa = 8.4) at the ambient conditions whereas the other two hardly deprotonate due to extremely high pKa values. By comparing with the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange (2SPNE SC/CE) model, the vacant site has been assigned to the strong site and the other two to the weak site, respectively. Thus a link has been built between atomistic simulations and macroscopic experiments and it is deduced that this should also apply to other heavy metal cations based on additional simulations of Co(II) and Cu(II) and previous simulations of Fe(II) and Cd(II)). This study forms a physical basis for understanding the transport and fixation of heavy metal elements in many geologic environments.

  15. Cationic bis-N-heterocyclic carbene (NHC) ruthenium complex: structure and application as latent catalyst in olefin metathesis.

    PubMed

    Rouen, Mathieu; Queval, Pierre; Falivene, Laura; Allard, Jessica; Toupet, Loïc; Crévisy, Christophe; Caijo, Frédéric; Baslé, Olivier; Cavallo, Luigi; Mauduit, Marc

    2014-10-13

    An unexpected cationic bis-N-heterocyclic carbene (NHC) benzylidene ether based ruthenium complex (2 a) was prepared through the double incorporation of an unsymmetrical unsaturated N-heterocyclic carbene (U2 -NHC) ligand that bore an N-substituted cyclododecyl side chain. The isolation and full characterization (including X-ray diffraction studies) of key synthetic intermediates along with theoretical calculations allowed us to understand the mechanism of the overall cationization process. Finally, the newly developed complex 2 a displayed interesting latent behavior during ring-closing metathesis, which could be "switched on" under acidic conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Cationic Group-IV pincer-type complexes for polymerization and hydroamination catalysis.

    PubMed

    Luconi, Lapo; Klosin, Jerzy; Smith, Austin J; Germain, Stéphane; Schulz, Emmanuelle; Hannedouche, Jérôme; Giambastiani, Giuliano

    2013-12-07

    Neutral Zr(IV) and Hf(IV) dimethyl complexes stabilized by unsymmetrical dianionic {N,C,N'} pincer ligands have been prepared from their corresponding bis-amido complexes upon treatment with AlMe3. Their structure consists of a central σ-bonded aryl donor group (C) capable of forming robust M-C bonds with the metal center, enforced by the synergic effect of both the coordination of peripheral donor groups (N) and the chelating rigid structure of the {N,C,N} ligand framework. Such a combination translates into systems having a unique balance between stability and reactivity. These Zr(IV) and Hf(IV) dimethyl complexes were converted in situ into cationic species [M(IV){N(-),C(-),N}Me][B(C6F5)4] which are active catalysts for the room temperature (r.t.) intramolecular hydroamination/cyclization of primary and secondary aminoalkenes as well as for the high temperature ethylene-1-octene copolymerizations.

  17. Computational study on the complexation behavior of tetrapropyl diglycolamide with Ln3+ (Ln = Nd, Pm, Sm, and Eu) cation series

    NASA Astrophysics Data System (ADS)

    Hosseinnejad, Tayebeh; Nikoo, Sepideh

    2015-09-01

    In the present study, we have focused mainly on the survey of interactions in Ln3+ (Ln = Nd, Pm, Sm, Eu) complexes with tetrapropyl diglycolamide (TPDGA) by means of density functional theory (DFT) methods. In the first step, the interaction of TPDGA ligand with Ln3+ cation series has been assessed thermodynamically in the gas phase and in presence of three solvents: n-hexane, chloroform and toluene, via polarized continuum model (PCM) calculations. The trend of metal-ligand interaction strength has been investigated and compared with the trend of ionic hardness within the series of lanthanide cations. Our results for the gas and solution phases demonstrate a consistency between the increasing trend in the hardness of Ln3+ cation series with the increasing in thermodynamical stability of [Ln(TPDGA)]3+ complex series. Moreover, our PCM calculations show that using n-hexane as a solvent is more favorable thermodynamically than chloroform and toluene for the complexation reaction of all [Ln(TPDGA)]3+ complex series. It should be stated that this issue has been observed in many experimental calculations. Finally the assessment of calculated deformation energies and also the variation in bond order of some selected key bonds in [Ln(TPDGA)]3+ complex series shows a similar trend with increasing in the hardness of Ln3+ cation series.

  18. Well-defined cationic alkyl- and alkoxide-aluminum complexes and their reactivity with epsilon-caprolactone and lactides.

    PubMed

    Dagorne, Samuel; Le Bideau, Franck; Welter, Richard; Bellemin-Laponnaz, Stéphane; Maisse-François, Aline

    2007-01-01

    We describe the synthesis, structure, and reactivity of low-coordinate Al-alkyl and -alkoxide cationic complexes incorporating the sterically bulky aminophenolate bidentate ligand 6-(CH(2)NMe(2))-2-CPh(3)-4-Me-C(6)H(2)O- (N,O). These complexes are derived from the ionization of neutral dialkyl Al complexes (N,O)Al2) (1 a, R=Me; 1 b, R=iBu), readily obtained by alkane elimination between AlR3 and the corresponding aminophenol ligand, with the alkyl abstracting reagents B(C(6)F(5))3 and [Ph(3)C][B(C(6)F(5))4]. The reactions of 1 a,b with B(C(6)F(5))3 yield complicated mixtures or decomposition products, however the ionization of the Al-diisobutyl derivative 1 b with [Ph(3)C][B(C(6)F(5))4] affords a stable four-coordinate Al-PhBr cationic adduct [(N,O)Al(iBu)(PhBr)]+ (3+), as deduced from elemental analysis data. Complex 3+ readily coordinates Lewis bases such as THF to form the corresponding adduct [(N,O)Al(iBu)(thf)]+ (4+), and also rapidly chain-transfers with 1-hexene to yield the three-coordinate Al-hexyl cation [(N,O)Al-hexyl]+ (5+). Both cations 3+ and 5+ slowly dimerize to form unprecedented organoaluminum dications [(N,O)AlR+]2 (3'++, R=iBu; 5'++, R=hexyl) as deduced from X-ray crystallographic analysis. Cation 3+ reacts quickly with iPrOH to form a stable Lewis acid/base adduct [(N,O)Al(iBu)(HOiPr)]+ (6+), which constitutes the first X-ray characterized adduct between an Al-alkyl complex and a simple ROH. The Al-ROH proton in 6+ is readily abstracted by NMe(2)Ph to form the neutral isopropoxide Al complex [(N,O)Al(iBu)(OiPr)] (7). Upon reaction with THF, cation 6+ undergoes an intramolecular proton transfer to yield the ammonium Al-THF complex [(eta1-HN,O)Al(iBu)(OiPr)(thf)] (8 b+), in which the aminophenolate is eta1-coordinated to the Al center. Cation 8 b+ can then be converted to the desired Al-alkoxide derivative [(N,O)Al(OiPr)(thf)](+) (10+), by an intramolecular protonolysis reaction, as confirmed by X-ray crystallography. The synthesized Al

  19. Methodology for the calculation of the potential of mean force for a cation-pi complex in water.

    PubMed

    Ghoufi, Aziz; Archirel, Pierre; Morel, Jean-Pierre; Morel-Desrosiers, Nicole; Boutin, Anne; Malfreyt, Patrice

    2007-08-06

    We report potential of mean force (PMF) calculations on the interaction between the p-sulfonatocalix[4]arene and a monovalent cation (Cs(+)). It has been recently shown from microcalorimetry and (133)Cs NMR experiments that the association with Cs(+) is governed by favourable cation-pi interactions and is characterized by the insertion of the cation into the cavity of the macrocycle. We show that the PMF calculation based upon a classical model is not able to reproduce both the thermodynamic properties of association and the insertion of the cation. In order to take into account the different contributions of the cation-pi interactions, we develop a new methodology consisting of changing the standard PMF by an additional contribution resulting from quantum calculations. The calculated thermodynamic properties of association are thus in line with the microcalorimetry and (133)Cs NMR experiments and the structure of the complex at the Gibbs free-energy minimum shows the insertion of the cation into the cavity of the calixarene.

  20. Halide, amide, cationic, manganese carbonylate, and oxide derivatives of triamidosilylamine uranium complexes.

    PubMed

    Gardner, Benedict M; Lewis, William; Blake, Alexander J; Liddle, Stephen T

    2011-10-03

    Treatment of the complex [U(Tren(TMS))(Cl)(THF)] [1, Tren(TMS) = N(CH(2)CH(2)NSiMe(3))(3)] with Me(3)SiI at room temperature afforded known crystalline [U(Tren(TMS))(I)(THF)] (2), which is reported as a new polymorph. Sublimation of 2 at 160 °C and 10(-6) mmHg afforded the solvent-free dimer complex [{U(Tren(TMS))(μ-I)}(2)] (3), which crystallizes in two polymorphic forms. During routine preparations of 1, an additional complex identified as [U(Cl)(5)(THF)][Li(THF)(4)] (4) was isolated in very low yield due to the presence of a slight excess of [U(Cl)(4)(THF)(3)] in one batch. Reaction of 1 with one equivalent of lithium dicyclohexylamide or bis(trimethylsilyl)amide gave the corresponding amide complexes [U(Tren(TMS))(NR(2))] (5, R = cyclohexyl; 6, R = trimethylsilyl), which both afforded the cationic, separated ion pair complex [U(Tren(TMS))(THF)(2)][BPh(4)] (7) following treatment of the respective amides with Et(3)NH·BPh(4). The analogous reaction of 5 with Et(3)NH·BAr(f)(4) [Ar(f) = C(6)H(3)-3,5-(CF(3))(2)] afforded, following addition of 1 to give a crystallizable compound, the cationic, separated ion pair complex [{U(Tren(TMS))(THF)}(2)(μ-Cl)][BAr(f)(4)] (8). Reaction of 7 with K[Mn(CO)(5)] or 5 or 6 with [HMn(CO)(5)] in THF afforded [U(Tren(TMS))(THF)(μ-OC)Mn(CO)(4)] (9); when these reactions were repeated in the presence of 1,2-dimethoxyethane (DME), the separated ion pair [U(Tren(TMS))(DME)][Mn(CO)(5)] (10) was isolated instead. Reaction of 5 with [HMn(CO)(5)] in toluene afforded [{U(Tren(TMS))(μ-OC)(2)Mn(CO)(3)}(2)] (11). Similarly, reaction of the cyclometalated complex [U{N(CH(2)CH(2)NSiMe(2)Bu(t))(2)(CH(2)CH(2)NSiMeBu(t)CH(2))}] with [HMn(CO)(5)] gave [{U(Tren(DMSB))(μ-OC)(2)Mn(CO)(3)}(2)] [12, Tren(DMSB) = N(CH(2)CH(2)NSiMe(2)Bu(t))(3)]. Attempts to prepare the manganocene derivative [U(Tren(TMS))MnCp(2)] from 7 and K[MnCp(2)] were unsuccessful and resulted in formation of [{U(Tren(TMS))}(2)(μ-O)] (13) and [MnCp(2)]. Complexes 3-13 have been

  1. Complexation as an approach to entrap cationic drugs into cationic nanoparticles administered intranasally for Alzheimer's disease management: preparation and detection in rat brain.

    PubMed

    Hanafy, Amira S; Farid, Ragwa M; ElGamal, Safaa S

    2015-01-01

    Complexation was investigated as an approach to enhance the entrapment of the cationic neurotherapeutic drug, galantamine hydrobromide (GH) into cationic chitosan nanoparticles (CS-NPs) for Alzheimer's disease management intranasally. Biodegradable CS-NPs were selected due to their low production cost and simple preparation. The effects of complexation on CS-NPs physicochemical properties and uptake in rat brain were examined. Placebo CS-NPs were prepared by ionic gelation, and the parameters affecting their physicochemical properties were screened. The complex formed between GH and chitosan was detected by the FT-IR study. GH/chitosan complex nanoparticles (GH-CX-NPs) were prepared by ionic gelation, and characterized in terms of particle size, zeta potential, entrapment efficiency, in vitro release and stability for 4 and 25 °C for 3 months. Both placebo CS-NPs and GH-CX-NPs were visualized by transmission electron microscopy. Rhodamine-labeled GH-CX-NPs were prepared, administered to male Wistar rats intranasally, and their delivery to different brain regions was detected 1 h after administration using fluorescence microscopy and software-aided image processing. Optimized placebo CS-NPs and GH-CX-NPs had a diameter 182 and 190 nm, and a zeta potential of +40.4 and +31.6 mV, respectively. GH encapsulation efficiency and loading capacity were 23.34 and 9.86%, respectively. GH/chitosan complexation prolonged GH release (58.07% ± 6.67 after 72 h), improved formulation stability at 4 °C in terms of drug leakage and particle size, and showed insignificant effects on the physicochemical properties of the optimized placebo CS-NPs (p > 0.05). Rhodamine-labeled GH-CX-NPs were detected in the olfactory bulb, hippocampus, orbitofrontal and parietal cortices. Complexation is a promising approach to enhance the entrapment of cationic GH into the CS-NPs. It has insignificant effect on the physicochemical properties of CS-NPs. GH-CX-NPs were successfully

  2. Influence of phospholipid composition on cationic emulsions/DNA complexes: physicochemical properties, cytotoxicity, and transfection on Hep G2 cells

    PubMed Central

    Fraga, Michelle; Bruxel, Fernanda; Lagranha, Valeska Lizzi; Teixeira, Helder Ferreira; Matte, Ursula

    2011-01-01

    Background Cationic nanoemulsions have been recently considered as potential delivery systems for nucleic acids. This study reports the influence of phospholipids on the properties of cationic nanoemulsions/DNA plasmid complexes. Methods Nanoemulsions composed of medium-chain triglycerides, stearylamine, egg lecithin or isolated phospholipids, ie, DSPC, DOPC, DSPE, or DOPE, glycerol, and water were prepared by spontaneous emulsification. Gene transfer to Hep G2 cells was analyzed using real-time polymerase chain reaction. Results The procedure resulted in monodispersed nanoemulsions with a droplet size and zeta potential of approximately 250 nm and +50 mV, respectively. The complexation of cationic nanoemulsions with DNA plasmid, analyzed by agarose gel retardation assay, was complete when the complex was obtained at a charge ratio of ≥1.0. In these conditions, the complexes were protected from enzymatic degradation by DNase I. The cytotoxicity of the complexes in Hep G2 cells, evaluated by MTT assay, showed that an increasing number of complexes led to progressive toxicity. Higher amounts of reporter DNA were detected for the formulation obtained with the DSPC phospholipid. Complexes containing DSPC and DSPE phospholipids, which have high phase transition temperatures, were less toxic in comparison with the formulations obtained with lecithin, DOPC, and DOPE. Conclusion The results show the effect of the DNA/nanoemulsion complexes composition on the toxicity and transfection results. PMID:22114484

  3. Spectrophotometric Study of the Complex Formation of Anionic Chelates of Cobalt(II) with Monotetrazolium Cations

    NASA Astrophysics Data System (ADS)

    Divarova, V. V.; Stojnova, K. T.; Racheva, P. V.; Lekova, V. D.

    2017-05-01

    The complex formation and extraction of anionic chelates of Co(II)-4-(2-thiazolylazo)resorcinol (TAR) with cations of monotetrazolium salts (TS) — (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and 3-(2-naphthyl)-2,5-diphenyl-2H-tetrazolium chloride (TV) — in the liquid-liquid extraction system Co(II)-TAR-TS-H2O-CHCl3 were studied by spectrophotometric methods. The optimum conditions for the extraction of Co(II) were found. The molar ratio of the components and the form of the anionic chelates of Co(II) in the extracted compounds were determined by independent methods. The association process in the aqueous phase and the extraction process were investigated and quantitatively characterized. The following key constants were calculated: association constant, distribution constant, extraction constant, and recovery factor. The validity of the Beer's law was checked, and some analytical characteristics were calculated. Based on the obtained results and the lower price of the monotetrazolium salt MTT compared with that of TV, the ion-associated complex of Co(II)-TAR-MTT can be implemented for determination of cobalt(II) traces in alloys and biological, medical, and pharmaceutical samples.

  4. Interaction and complex formation between catalase and cationic polyelectrolytes: chitosan and Eudragit E100.

    PubMed

    Boeris, Valeria; Romanini, Diana; Farruggia, Beatriz; Picó, Guillemo

    2009-08-01

    Interactions between catalase and the cationic polyelectrolytes: chitosan and Eudragit E100 have been investigated owing to their scientific and technological importance. These interactions have been characterized by turbidimetry, circular dichroism and fluorescence spectroscopy. It was found that the catalase conformation does not change significantly during the chain entanglements between the protein and the polyelectrolytes. The effects of pH, ionic strength and anions which modify the water structure were evaluated on the polymer-protein complex formation. A net coulombic interaction force between them was found since the insoluble complex formation decreased after the NaCl addition. Both polymers were found to precipitate around 80% of the protein in solution. No modification of the tertiary and secondary protein structure or the enzymatic activity was observed when the precipitate was dissolved by changing the pH of the medium. Chitosan and Eudragit E100 proved to be a useful framework to isolate catalase or proteins with a slightly acid isoelectrical pH by means of precipitation.

  5. Aminoclay as a highly effective cationic vehicle for enhancing adenovirus-mediated gene transfer through nanobiohybrid complex formation.

    PubMed

    Kim, Soo-Yeon; Lee, Sang-Jin; Han, Hyo-Kyung; Lim, Soo-Jeong

    2017-02-01

    Electrostatic complexation of adenovirus (Ad) with cationic lipids or polymers has been shown to be an effective means for overcoming the limitations of adenoviral vectors and enhancing gene-transfer efficacy. However, such complexation causes cytotoxicity, limiting the use of this strategy. The present study explored the potential of 3-aminopropyl functionalized magnesium phyllosilicate (aminoclay) as a cationic vehicle for improving Ad-mediated gene transfer without inducing cytotoxicity. Aminoclay complexation produced a dose-dependent increase in Ad-mediated transgene expression in both Ad infection-sensitive and -refractory cells, thereby greatly lowering the Ad dose required for transgene expression. Unlike the case for cationic lipids (Lipofectamine) or polymers (Polybrene), the enhancement effect of aminoclay was not accompanied by significant cytotoxicity regardless of cell lines and it was not observed for nonviral plasmid vectors. Physical characterization studies revealed that nanobiohybrid complexes formed between aminoclay and Ad particles through electrostatic interactions, creating aggregates of Ad particles whose surface was shielded with aminoclay nanosheet oligomers. It appears that aminoclay complexation changes the surface charge of Ad particles from a negative to a highly positive value and thus increases Ad binding to cellular membranes, thereby providing an additional cellular entry mechanism, namely caveolae-dependent endocytosis. Aminoclay-Ad nanobiohybrids may serve as a next-generation efficient, versatile and biocompatible gene-delivery carrier. Electrostatic complexation of adenovirus with cationic materials has been shown to be an effective means for enhancing gene-transfer efficacy in vitro. However, such complexation causes cytotoxicity, limiting the use of this strategy. The present study explored the potential of a synthesized organoclay 3-aminopropyl functionalized magnesium phyllosilicate (aminoclay) as a cationic vehicle for

  6. Adsorption behaviors of DNA/cation complexes on amino and silica chip surfaces: a dual polarization interferometry study.

    PubMed

    Huang, Fujian; Liang, Haojun

    2013-06-12

    The adsorption of DNA/Ca(2+), DNA/Cu(2+), and DNA/Co(NH3)6(3+) complexes on amino and silica chip surfaces were investigated using dual polarization interferometry. A more compact DNA/cation complex layer formed on the amino chip surface compared with that on the silica chip surface at the same cation condition. The real-time mass, thickness, and density changes were monitored during the adsorption process. The overall results show that the approaching complexes can cause the conformation rearrangement of the preadsorbed complexes and the preadsorbed complexes affect the deposition pattern of the approaching complexes during the adsorption of DNA/Ca(2+) and DNA/Cu(2+) complexes on both chip surfaces. The relatively strong electrostatic repulsion between the approaching and adsorbed complexes results in multiple mass loading rate changes and loose attachment of the approaching complexes. The weak repulsion between the DNA/Co(NH3)6(3+) complexes cannot induce this kind of conformation rearrangement. Thus, no multiple mass loading rate changes were observed. Meanwhile, the preadsorbed DNA/Co(NH3)6(3+) complex can also affect the deposition pattern of the approaching complex because of the geometric resistance. Therefore, this study will help better understand the conformation change and deposition pattern of complexes with different charge conditions during the adsorption process on the solid-liquid interface.

  7. Neutral and cationic palladium(II) bis(pyrazolyl)methane complexes

    SciTech Connect

    Tsuji, S.; Swenson, D.C.; Jordan, R.F.

    1999-11-08

    The synthesis, structures, and reactivity of neutral and cationic Pd(II) complexes incorporating bis(pyrazolyl)methane ligands are described. The reaction of (CH{sub 3}CN){sub 2}PdCl{sub 2} with the appropriate bis(pyrazoyl)methane in CH{sub 2}Cl{sub 2}yields {l{underscore}brace}Ph{sub 2}C(3-{sup t}Bu-pz){sub 2}{r{underscore}brace}PdCl{sub 2}(1) and {l{underscore}brace}Ph{sub 2}C(pz){sub 2}{r{underscore}brace}PdCl{sub 2} (2). Steric crowding associated with the {sup t}Bu groups of 1 increases the puckering of the chelate ring (boat conformation) and retards the chelate ring inversion relative to 2. The reaction of {l{underscore}brace}Me{sub 2}C(px){sub 2}{r{underscore}brace}PdMe{sub 2} (3) with p[HNMe{sub 2}Ph][B(C{sub 6}F{sub 5}){sub 4}] yields {l{underscore}brace}Me{sub 2}C(pz){sub 2}{r{underscore}brace}PdMe(NMe{sub 2}Ph){sup +} (4a, B(C{sub 6}F{sub 5}){sub 4}{sup {minus}} salt), while treatment of 3 with [H(OEt{sub 2}){sub 2}][B{l{underscore}brace}3,5(CF{sub 3}){sub 2}C{sub 6}H{sub 3}{r{underscore}brace}{sub 4}] yields {l{underscore}brace}Me{sub 2}C(pz){sub 2}{r{underscore}brace}PdMe(OEt{sub 2}){sup +} (4b, B{l{underscore}brace}3,5-(CF{sub 3}){sub 2}C{sub 6}H{sub 3}{l{underscore}brace}{sub 4}{sup {minus}} salt). Complex 4a reacts with ethylene at {minus}60 C (CD{sub 2}Cl{sub 2}) to yield {l{underscore}brace}Me{sub 2}C(pz){sub 2}{r{underscore}brace}PdMe(CH{sub 2}{double{underscore}bond}CH{sub 2}){sup +} (5, B(C{sub 6}F{sub 5}){sub 4}{sup {minus}}salt) and free NMe{sub 2}Ph. Cation 5 undergoes ethylene insertion at {minus}10 C and oligomerizes ethylene (1 atm) to predominantly linear internal C{sub 8} to C{sub 24} olefins (ca. 0.1 branches per 2 carbons) at 23 C.

  8. Mono- and dinuclear cationic iridium(III) complexes bearing a 2,5-dipyridylpyrazine (2,5-dpp) ligand.

    PubMed

    Donato, Loïc; McCusker, Catherine E; Castellano, Felix N; Zysman-Colman, Eli

    2013-08-05

    The synthesis, X-ray structures, photophysical, and electrochemical characterization of mono- (1) and dinuclear (2) cationic iridium(III) complexes bearing a 2,5-dipyridylpyrazine (2,5-dpp) ancillary ligand are reported. Upon the complexation of a first equivalent of iridium, the photoluminescence shifts markedly into the deep red (λem = 710 nm, ΦPL = 0.9%) compared to other cationic iridium complexes such as [Ir(ppy)2(bpy)]PF6. With the coordination of a second equivalent of iridium, room temperature luminescence is completely quenched. Both 1 and 2 are luminescent at low temperatures but with distinct excited state decay kinetics; the emission of 2 is significantly red-shifted compared to 1. Emission both at 298 and 77 K results from a mixed charge-transfer state. Density functional theory (DFT) calculations and electrochemical behavior point to an electronic communication between the two iridium complexes.

  9. Vanillic Acid Ameliorates Cationic Bovine Serum Albumin Induced Immune Complex Glomerulonephritis in BALB/c Mice.

    PubMed

    Motiram Kakalij, Rahul; Tejaswini, G; Patil, Madhoosudan A; Dinesh Kumar, B; Diwan, Prakash V

    2016-06-01

    Preclinical Research Vanillic acid (VA) is a dihydroxybenzoic acid derivative widely used as a flavoring agent. It has chemopreventive effects on experimentally-induced carcinogenesis and in ulcerative colitis. The object of the present study was to investigate the effects of VA, alone and in combination with methylprednisolone (MP), on cationic bovine serum albumin (cBSA induced immune-complex glomerulonephritis in female BALB/c mice. Pre-immunization was carried out with cBSA in BALB/c mice and repeated (cBSA, 13 mg/kg, 3 times/week, i.v.) for 6 weeks to induce glomerulonephritis which was confirmed by the presence of severe proteinuria. The effect of VA (50, 100, and 200 mg/kg, p.o.) and its combination with MP (12.5 mg/kg, p.o.) was assessed in the nephrotic disease model. Treatment with VA decreased inflammatory nephrotic injury as evidenced by decreased proteinuria, serum creatinine, blood urea nitrogen, serum IgG1 and TNF-α levels. Co-administration of VA with MP showed an improvement in the immunohistochemistry of glomerular nephrin and podocin. The present results indicate that VA has a nephroprotective effect in the management of autoimmune nephritis. Drug Dev Res 77 : 171-179, 2016.   © 2016 Wiley Periodicals, Inc.

  10. Thermochromic Magnetic Ionic Liquids from Cationic Nickel(II) Complexes Exhibiting Intramolecular Coordination Equilibrium.

    PubMed

    Lan, Xue; Mochida, Tomoyuki; Funasako, Yusuke; Takahashi, Kazuyuki; Sakurai, Takahiro; Ohta, Hitoshi

    2017-01-18

    Among the various thermochromic materials, liquid thermochromic materials are comparatively rare. To produce functional thermochromic liquids, we have designed ionic liquids based on cationic nickel complexes with ether side chains, [Ni(acac)(Me2 NC2 H4 NR(1) R(2) )]Tf2 N ([1]Tf2 N: R(1) =C3 H6 OEt, R(2) =Me; [2]Tf2 N: R(1) =C3 H6 OMe, R(2) =Me; [3]Tf2 N: R(1) =R(2) =C3 H6 OMe), where acac=acetylacetonate and Tf2 N=(F3 CSO2 )2 N(-) . The side chains (R(1) , R(2) ) can moderately coordinate to the metal center, enabling temperature-dependent coordination equilibria in the liquid state. [1]Tf2 N is a liquid at room temperature. [2]Tf2 N is obtained as a solid (Tm =352.7 K) but remains liquid at room temperature after melting. [3]Tf2 N is a solid with a high melting point (Tm =422.3 K). These salts display thermochromism in the liquid state, appearing red at high temperatures and orange, light-blue, or bluish-green at lower temperatures, and exhibiting concomitant changes in their magnetic properties. This phenomenon is based on temperature-dependent equilibrium between a square-planar diamagnetic species and a paramagnetic species with intramolecular ether coordination.

  11. Successful gene transfer into dendritic cells with cationized gelatin and plasmid DNA complexes via a phagocytosis-dependent mechanism.

    PubMed

    Inada, Satoshi; Fujiwara, Hitoshi; Atsuji, Kiyoto; Takashima, Kazuhiro; Araki, Yasunobu; Kubota, Takeshi; Tabata, Yasuhiko; Yamagishi, Hisakazu

    2006-01-01

    The use of gene-modified dendritic cells (DC) is a powerful tool to enhance antitumor immune responses stimulated by these cells in cancer immunotherapy. Cationized gelatin is preferably incorporated via phagocytosis and is gradually degraded by proteolysis while buffering lysosomal activity. This may be appropriate for gene transfer into phagocytic cells, such as immature DC. In the present study, successful transfection into monocyte-derived immature DC was demonstrated using cationized gelatin and plasmid DNA complexes. A high transfection efficiency, approaching 16%, was obtained upon transfection of the enhanced green fluorescent protein (EGFP) gene as evaluated by flow cytometry. Transgene expression of EGFP and murine interleukin 12 were also detected by RT-PCR. The antigen-presenting capacity of the transfected DC was equal to that of untransfected DC as evaluated by the allogeneic mixed lymphocyte reaction. Cationized gelatin has the potential to be a unique non-viral vector for gene transfer into DC.

  12. Influence of complexation phenomena with multivalent cations on the analysis of glyphosate and aminomethyl phosphonic acid in water.

    PubMed

    Freuze, Ingrid; Jadas-Hecart, Alain; Royer, Alain; Communal, Pierre-Yves

    2007-12-21

    Experimental and theoretical influence of multivalent cations on the analysis of glyphosate and aminomethyl phosphonic acid (AMPA) was studied in pure water and in one surface water. The procedure chosen, based on derivatization with FMOC-Cl, HPLC separation, and fluorescence detection, appears highly affected at cations concentrations current in natural waters. A detailed speciation study performed with the VMINTEQ software strongly suggests that the complexes formed between analytes and cations do not dissociate during the reaction and do not react with the derivatization agent, so that only the free forms are derivatized. These results point out the necessity of a pre-treatment to prevent these interferences, even in low salinity waters. The different ways conceivable are discussed in terms of kinetic and thermodynamic considerations.

  13. Conformation Transformation Determined by Different Self-Assembled Phases in a DNA Complex with Cationic Polyhedral Oligomeric Silsesquioxane Lipid

    SciTech Connect

    Cui,L.; Chen, D.; Zhu, L.

    2008-01-01

    In this work, a novel cube-shaped cationic lipid based on the imidazolium salt of polyhedral oligomeric silsesquioxane (POSS) was complexed with double-stranded DNA. Because of the negative spontaneous curvature of the cationic POSS imidazolium lipid, an inverted hexagonal phase resulted above the melting point of POSS crystals. Depending on the competition between the crystallization of POSS molecules and the negative spontaneous curvature of cationic POSS imidazolium lipids, different self-assembled phase morphologies were obtained. A lamellar phase was obtained when the POSS crystallization was relatively slow. When the POSS crystallization was fast, an inverted hexagonal phase was obtained with POSS lamellar crystals grown in the interstitials of DNA cylinders. On the basis of a circular dichroism study, double-stranded DNA adopted the B-form helical conformation in the inverted hexagonal phase, whereas the helical conformation was largely destroyed in the lamellar phase.

  14. Specific interaction between uranium anionic complexes and the cations of bis(trifluoromethylsulfonyl)imide based ionic liquids.

    PubMed

    Cannes, Céline; Le Naour, Claire; Moisy, Philippe; Guilbaud, Philippe

    2013-10-07

    The redox properties of uranium(IV) hexachloro complex have been investigated with a glassy carbon electrode in four bis(trifluoromethylsulfonyl)imide (Tf2N(-)) based ionic liquids (ILs): the 1-butyl-3-methylimidazolium ([BuMeIm](+)), the 1-butyl-2,3-dimethylimidazolium ([BuMe2Im](+)), the N-butylmethylpyrrolidinium ([BuMePyr](+)), and the tributyl-methylammonium ([MeBu3N](+)). The cyclic voltammetric analysis has revealed two main redox systems: U(V)Cl6(-)/U(IV)Cl6(2-) around 0.2 V and U(IV)Cl6(2-)/U(III)Cl6(3-) around -2 V. The formation of U(V)Cl6(-), a non-dioxo uranium(V) species, can then be observed at the electrode in [Tf2N](-) based ILs. This work also provides evidence of a specific interaction between the uranium anionic species and the IL cations because the standard potentials of both redox couples depend on the IL. The interaction extent has been evaluated by comparison of the IL cation number associated with the uranium anionic complex. For that purpose, the standard potentials of both systems have been measured in the less interacting medium [MeBu3N][Tf2N] as a function of the [BuMeIm](+), [BuMe2Im](+), and [BuMePyr](+) concentration. Predominance diagrams for uranium hexachloro complexes, analogous to the Pourbaix diagram, have then been built in [MeBu3N][Tf2N] depending on the IL cations concentration. The exploitation of these diagrams leads to the conclusion that the interaction is function of the charge of the uranium hexachloro complex (U(V)Cl6(-) < U(IV)Cl6(2-) < U(III)Cl6(3-)) and the IL cation ([BuMe2Im](+) < [BuMePyr](+) < [BuMeIm](+)). The influence of the IL cation could be correlated to the size and the electropositivity of the IL cation. The association would occur by H-bonding and electrostatic interaction. Ab initio calculations were also carried out to evaluate the strength of the interaction between the anionic uranium(IV) chloro complex and the IL cations. The results show that [BuMeIm](+) interacts the most and [MeBu3N](+) the

  15. Solvation of Ucl (6)**2- Anionic Complex By Mebu (3) N+, Bume (2) Im+, And Bumeim+ Cations

    SciTech Connect

    Bosse, E.; Auwer, C.Den; Berthon, C.; Guilbaud, P.; Grigoriev, M.S.; Nikitenko, S.; Naour, C.Le; Cannes, C.; Moisy, P.

    2009-05-11

    The complexes [MeBu{sub 3}N]{sub 2}[UCl{sub 6}] and [BuMe{sub 2}Im]{sub 2}[UCl{sub 6}] were characterized in the solid state and in solution of [MeBu{sub 3}N][Tf{sub 2}N], [BuMe{sub 2}Im][Tf{sub 2}N], and [BuMeIm][Tf{sub 2}N] room-temperature ionic liquids using single-crystal XRD, EXAFS, electrochemistry, UV-visible absorption spectroscopy, and NMR. In the solid state and in solution, the existence of hydrogen bonding between the UCl{sub 6}{sup 2-} complex and the ionic liquid cations was revealed by these techniques. The MeBu{sub 3}N{sup +} cation interacts with UCl{sub 6}{sup 2-} via the protons on the {alpha}-carbon atoms of nitrogen. The protons of the imidazolium ring account for the interaction between the BuMe{sub 2}Im{sup +} cation and the UCl{sub 6}{sup 2-} anion. For the BuMeIm{sup +} cation the major interaction was confirmed between the most acidic proton on C(2) and the chlorides of UCl{sub 6}{sup 2-}. The experimental results also show that the intensity of the interaction between the UCl{sub 6}{sup 2-} anion and the cation varies with the ionic liquid cation in the following order: MeBu{sub 3}N{sup +} {approx} BuMe{sub 2}Im{sup +} << BuMeIm{sup +}.

  16. Solid-State and Solution Metallophilic Aggregation of a Cationic [Pt(NCN)L](+) Cyclometalated Complex.

    PubMed

    Sivchik, Vasily V; Grachova, Elena V; Melnikov, Alexei S; Smirnov, Sergey N; Ivanov, Alexander Yu; Hirva, Pipsa; Tunik, Sergey P; Koshevoy, Igor O

    2016-04-04

    The noncovalent intermolecular interactions (π-π stacking, metallophilic bonding) of the cyclometalated complexes [Pt(NCN)L](+)X(-) (NCN = dipyridylbenzene, L = pyridine (1), acetonitrile (2)) are determined by the steric properties of the ancillary ligands L in the solid state and in solution, while the nature of the counterion X(-) (X(-) = PF6(-), ClO4(-), CF3SO3(-)) affects the molecular arrangement of 2·X in the crystal medium. According to the variable-temperature X-ray diffraction measurements, the extensive Pt···Pt interactions and π-stacking in 2·X are significantly temperature-dependent. The variable concentration (1)H and diffusion coefficients NMR measurements reveal that 2·X exists in the monomeric form in dilute solutions at 298 K, while upon increase in concentration [Pt(NCN)(NCMe)](+) cations undergo the formation of the ground-state oligomeric aggregates with an average aggregation number of ∼3. The photoluminescent characteristics of 1 and 2·X are largely determined by the intermolecular aggregation. For the discrete molecules the emission properties are assigned to metal perturbed IL charge transfer mixed with some MLCT contribution. In the case of oligomers 2·X the luminescence is significantly red-shifted with respect to 1 and originates mainly from the (3)MMLCT excited states. The emission energies depend on the structural arrangement in the crystal and on the complex concentration in solution, variation of which allows for the modulation of the emission color from greenish to deep red. In the solid state the lability of the ligands L leads to vapor-induced reversible transformation 1 ↔ 2 that is accompanied by the molecular reorganization and, consequently, dramatic change of the photophysical properties. Time-dependent density functional theory calculations adequately support the models proposed for the rationalization of the experimental observations.

  17. Superweak complexes of tetrahedral P4 molecules with the silver cation of weakly coordinating anions.

    PubMed

    Krossing, Ingo; van, Wüllen Leo

    2002-02-02

    The silver aluminates AgAl[OC(CF3)2(R)]4 (R = H, CH3, CF3) react with solutions of white phosphorus P4 to give complexes that bind one or two almost undistorted tetrahedral P4 molecules in an fashion: [Ag(P4)2]+[Al(OC(CF3)3)4]+ (1) containing the first homoleptic metal-phosphorus cation, the molecular species (P4)AgAl[OC(CH3)(CF3)2]4 (2), and the dimeric Ag(mu,eta2-P4)Ag bridged [(P4)AgAl[OC(H)(CF3)2]4]2 (3). Compounds 1-3 were characterized by variable-temperature (VT) 31P NMR spectroscopy (1 also by VT 32P MAS-NMR spectroscopy), Raman spectroscopy, and single-crystal X-ray crystallography. Other Ag:P4 ratios did not lead to new species, and this observation was rationalized on thermodynamic grounds. The Ag(P4)2+ ion has an almost planar coordination environment around the Ag+ ion due to d(x2 - y2)(Ag) --> sigma*(P-P) backbonding. Calculations (HF-DFT) on six Ag(P4)2+ isomers 4a-f showed that the planar eta2 form 4a is only slightly favored by 5.2 kJ mol(-1) over the tetrahedral eta2 species 4b; eta1-P4 and eta3-P4 complexes are less favorable (27-76 kJ mol(-1)). The bonding of the P4 moiety in [RhCl(eta2-P4)(PPh3)2], the only compound in which an eta2 bonding mode of a tetrahedral P4 molecule has been claimed, must be regarded as a tetraphosphabicyclobutane, and not as a tetrahedro-P4 complex, on the basis of the published NMR and vibrational spectra, the calculated geometry of [RhCl(P4)(PH3)2] (10), the highly endothermic (385 kJ mol(-1)) calculated dissociation enthalpy of 10 into P4 and RhCl(PH3)2 (11), as well as atoms in molecules (AIM) and natural bond orbital (NBO) population analyses of 10 and the Ag(P4)2+ ion. Therefore, 1-3 are the first examples of species containing eta2-coordinated tetrahedral P4 molecules.

  18. Influence of anion on the quadratic nonlinearity and depolarization ratios of scattered second harmonic light from cationcomplexes.

    PubMed

    Pandey, Ravindra; Mukhopadhyay, S; Ramasesha, S; Das, Puspendu K; Zyss, Joseph

    2012-05-21

    We have investigated quadratic nonlinearity (β(HRS)) and linear and circular depolarization ratios (D and D('), respectively) of a series of 1:1 complexes of tropyliumtetrafluoroborate as a cation and methyl-substituted benzenes as π-donors by making polarization resolved hyper-Rayleigh scattering measurements in solution. The measured D and D(') values are much lower than the values expected from a typical sandwich or a T-shaped geometry of a complex. In the cationcomplexes studied here, the D value varies from 1.36 to 1.46 and D(') from 1.62 to 1.72 depending on the number of methyl substitutions on the benzene ring. In order to probe it further, β, D and D(') were computed using the Zerner intermediate neglect of differential overlap-correction vector self-consistent reaction field technique including single and double configuration interactions in the absence and presence of BF(4) (-) anion. In the absence of the anion, the calculated value of D varies from 4.20 to 4.60 and that of D(') from 2.45 to 2.72 which disagree with experimental values. However, by arranging three cation-π BF(4)(-) complexes in a trigonal symmetry, the computed values are brought to agreement with experiments. When such an arrangement was not considered, the calculated β values were lower than the experimental values by more than a factor of two. This unprecedented influence of the otherwise "unimportant" anion in solution on the β value and depolarization ratios of these cationcomplexes is highlighted and emphasized in this paper.

  19. The electronic structure of vanadium monochloride cation (VCl(+)): tackling the complexities of transition metal species.

    PubMed

    DeYonker, Nathan J; Halfen, DeWayne T; Allen, Wesley D; Ziurys, Lucy M

    2014-11-28

    Six electronic states (X (4)Σ(-), A (4)Π, B (4)Δ, (2)Φ, (2)Δ, (2)Σ(+)) of the vanadium monochloride cation (VCl(+)) are described using large basis set coupled cluster theory. For the two lowest quartet states (X (4)Σ(-) and A (4)Π), a focal point analysis (FPA) approach was used that conjoined a correlation-consistent family of basis sets up to aug-cc-pwCV5Z-DK with high-order coupled cluster theory through pentuple (CCSDTQP) excitations. FPA adiabatic excitation energies (T0) and spectroscopic constants (re, r0, Be, B0, D¯e, He, ωe, v0, αe, ωexe) were extrapolated to the valence complete basis set Douglas-Kroll (DK) aug-cc-pV∞Z-DK CCSDT level of theory, and additional treatments accounted for higher-order valence electron correlation, core correlation, and spin-orbit coupling. Due to the delicate interplay between dynamical and static electronic correlation, single reference coupled cluster theory is able to provide the correct ground electronic state (X (4)Σ(-)), while multireference configuration interaction theory cannot. Perturbations from the first- and second-order spin orbit coupling of low-lying states with quartet spin multiplicity reveal an immensely complex rotational spectrum relative to the isovalent species VO, VS, and TiCl. Computational data on the doublet manifold suggest that the lowest-lying doublet state ((2)Γ) has a Te of ∼11 200 cm(-1). Overall, this study shows that laboratory and theoretical rotational spectroscopists must work more closely in tandem to better understand the bonding and structure of molecules containing transition metals.

  20. The electronic structure of vanadium monochloride cation (VCl+): Tackling the complexities of transition metal species

    NASA Astrophysics Data System (ADS)

    DeYonker, Nathan J.; Halfen, DeWayne T.; Allen, Wesley D.; Ziurys, Lucy M.

    2014-11-01

    Six electronic states (X 4Σ-, A 4Π, B 4Δ, 2Φ, 2Δ, 2Σ+) of the vanadium monochloride cation (VCl+) are described using large basis set coupled cluster theory. For the two lowest quartet states (X 4Σ- and A 4Π), a focal point analysis (FPA) approach was used that conjoined a correlation-consistent family of basis sets up to aug-cc-pwCV5Z-DK with high-order coupled cluster theory through pentuple (CCSDTQP) excitations. FPA adiabatic excitation energies (T0) and spectroscopic constants (re, r0, Be, B0, bar De, He, ωe, v0, αe, ωexe) were extrapolated to the valence complete basis set Douglas-Kroll (DK) aug-cc-pV∞Z-DK CCSDT level of theory, and additional treatments accounted for higher-order valence electron correlation, core correlation, and spin-orbit coupling. Due to the delicate interplay between dynamical and static electronic correlation, single reference coupled cluster theory is able to provide the correct ground electronic state (X 4Σ-), while multireference configuration interaction theory cannot. Perturbations from the first- and second-order spin orbit coupling of low-lying states with quartet spin multiplicity reveal an immensely complex rotational spectrum relative to the isovalent species VO, VS, and TiCl. Computational data on the doublet manifold suggest that the lowest-lying doublet state (2Γ) has a Te of ˜11 200 cm-1. Overall, this study shows that laboratory and theoretical rotational spectroscopists must work more closely in tandem to better understand the bonding and structure of molecules containing transition metals.

  1. Unexpected Actinyl Cation-Directed Structural Variation in Neptunyl(VI) A-Type Tri-lacunary Heteropolyoxotungstate Complexes

    SciTech Connect

    Berg, John M.; Gaunt, Andrew J.; May, Iain; Pugmire, Alison L.; Reilly, Sean D.; Scott, Brian L.; Wilkerson, Marianne P.

    2015-04-22

    A-type tri-lacunary heteropolyoxotungstate anions (e.g., [PW9O34]9-, [AsW9O34]9-, [SiW9O34]10- and [GeW9O34]10-) are multi-dentate oxygen donor ligands that readily form sandwich complexes with actinyl cations ({UO2}2+, {NpO2}+, {NpO2}2+ & {PuO2}2+) in near neutral/slightly alkaline aqueous solutions. Two or three actinyl cations are sandwiched between two trilacunary anions, with additional cations (Na+, K+ or NH4 +) also often held within the cluster. Studies thus far have indicated that it is these additional +I cations, rather than the specific actinyl cation, that direct the structural variation in the complexes formed. We now report the structural characterization of the neptunyl (VI) cluster complex (NH4)13 [Na(NpO2)2(A-α- PW9O34)2]·12H2O. The anion in this complex, [Na(NpO2)2(PW9O34)2]13-, contains one Na+ cation and two {NpO2}2+ cations held between two [PW9O34]9- anions – with an additional partial occupancy NH4 + or {NpO2}2+ cation also present. In the analogous uranium (VI) system, under similar reaction conditions that includes an excess of NH4Cl in the parent solution, it was previously shown that [(NH4)2(UVIO2)2(A-PW9O34)2]12- is the dominant species in both solution and the crystallized salt. Spectroscopic studies provide further proof of differences in the observed chemistry for the {NpO2}2+

  2. Effect of pendant group on pDNA delivery by cationic-β-cyclodextrin:alkyl-PVA-PEG pendant polymer complexes.

    PubMed

    Kulkarni, Aditya; Badwaik, Vivek; DeFrees, Kyle; Schuldt, Ryan A; Gunasekera, Dinara S; Powers, Cory; Vlahu, Alexander; VerHeul, Ross; Thompson, David H

    2014-01-13

    We have previously shown that cationic-β-cyclodextrin:R-poly(vinyl alcohol)-poly(ethylene glycol) (CD+:R-PVA-PEG) pendant polymer host:guest complexes are safe and efficient vehicles for nucleic acid delivery, where R = benzylidene-linked adamantyl or cholesteryl esters. Herein, we report the synthesis and biological performance of a family of PVA-PEG pendant polymers whose pendant groups have a wide range of different affinities for the β-CD cavity. Cytotoxicity studies revealed that all of the cationic-β-CD:pendant polymer host:guest complexes have 100-1000-fold lower toxicity than branched polyethylenimine (bPEI), with pDNA transfection efficiencies that are comparable to bPEI and Lipofectamine 2000. Complexes formed with pDNA at N/P ratios greater than 5 produced particles with diameters in the 100-170 nm range and ζ-potentials of 15-35 mV. Gel shift and heparin challenge experiments showed that the complexes are most stable at N/P ≥ 10, with adamantyl- and noradamantyl-modified complexes displaying the best resistance toward heparin-induced decomplexation. Disassembly rates of fluoresceinated-pDNA:CD(+):R-PVA-PEG-rhodamine complexes within HeLa cells showed a modest dependence on host:guest binding constant, with adamantyl-, noradamantyl-, and dodecyl-based complexes showing the highest loss in FRET efficiency 9 h after cellular exposure. These findings suggest that the host:guest binding constant has a significant impact on the colloidal stability in the presence of serum and cellular uptake efficiency, whereas endosomal disassembly and transfection performance of cationic-β-CD:R-poly(vinyl alcohol)-poly(ethylene glycol) pendant polymer complexes appears to be controlled by the hydrolysis rates of the acetal grafts onto the PVA main chain.

  3. Dehydrocoupling reactions of dimethylamine-borane by Pt(II) complexes: a new mechanism involving deprotonation of boronium cations.

    PubMed

    Roselló-Merino, Marta; López-Serrano, Joaquín; Conejero, Salvador

    2013-07-31

    Coordinatively unsaturated Pt(II) complex [Pt(I(t)Bu')(I(t)Bu)](+) stabilized by N-heterocyclic carbene (NHC) ligands dehydrogenates N,N-dimethylamineborane through a mechanism that involves hydride abstraction, assisted by an amine, to yield a platinum-hydride complex [PtH(I(t)Bu')(I(t)Bu)] with concomitant formation of the boronium cation [(NHMe2)2BH2](+). This latter species is very likely in equilibrium with the THF stabilized borenium cation [(NHMe2)(THF)BH2](+), bearing an acidic NH group that is able to protonate the platinum hydride [PtH(I(t)Bu')(I(t)Bu)] releasing H2, the amino borane H2B-NMe2 and regenerating the catalytic [Pt](+) species.

  4. Thermal treatment effects imposed on solid DNA cationic lipid complex with hexadecyltrimethylammonium chloride, observed by variable angle spectroscopic ellipsometry

    SciTech Connect

    Nizioł, Jacek

    2014-12-21

    DNA cationic lipid complexes are materials of properties required for applications in organic electronics and optoelectronics. Often, their thermal stability demonstrated by thermogravimetry is cited in the literature as important issue. However, little is known about processes occurring in heated solid DNA cationic lipid complexes. In frame of this work, thin films of Deoxyribonucleic acid-hexadecyltrimethylammonium chloride (DNA-CTMA) were deposited on silicon wafers. Samples were thermally annealed, and simultaneously, their optical functions were measured by spectroscopic ellipsometry. At lower temperatures, thermal expansion coefficient of solid DNA-CTMA was negative, but at higher temperatures positive. Thermally induced modification of absorption spectrum in UV-vis was observed. It occurred at a range of temperatures higher than this of DNA denaturation in solution. The observed phenomenon was irreversible, at least in time scale of the experiment (one day)

  5. Characterization of the nanostructure of complexes formed by single- or double-stranded oligonucleotides with a cationic surfactant.

    PubMed

    Liu, Xiaoyang; Abbott, Nicholas L

    2010-12-02

    We report the use of dynamic light scattering (DLS), small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS) to characterize the nanostructure of complexes formed by either single- or double-stranded oligonucleotides with a cationic surfactant (cetyltrimethylammonium bromide, CTAB) in aqueous solution (1 mM Li(2)SO(4)). For single-stranded oligonucleotides 5'-A(20)-3' and 5'-CCCCATTCTAGCAGCCCGGG-3', both the appearance of two Bragg peaks (at 0.14 and 0.28 Å(-1)) in SAXS spectra with a spacing of 1:2 and form factor fits to SANS spectra are consistent with the presence of multilamellar vesicles (with, on average, 6-9 layers with a periodicity of 45-48 Å). Some samples showed evidence of an additional Bragg peak (at 0.20 Å(-1)) associated with periodic packing (with a periodicity of 31 Å) of the oligonucleotides within the lamellae of the nanostructure. The nucleotide composition of the single-stranded oligonucleotides was also found to impact the number and size of the complexes formed with CTAB. In contrast to 5'-A(20)-3' and 5'-CCCCATTCTAGCAGCCCGGG-3', 5'-T(20)-3' did not change the state of aggregation of CTAB (globular micelles) over a wide range of oligonucleotide:CTAB charge ratios. These results support the proposition that hydrophobic interactions, as well as electrostatics, play a central role in the formation of complexes between cationic amphiphiles and single-stranded oligonucleotides and thus give rise to nanostructures that depend on nucleotide composition. In contrast to the single-stranded oligonucleotides, for double-stranded oligonucleotides mixed with CTAB, three Bragg peaks (0.13, 0.23, and 0.25 Å(-1)) in SAXS spectra with a spacing ratio of 1:√3:√4 and characteristic changes in SANS spectra indicate formation of a hexagonal nanostructure. Also, the composition of the double-stranded oligonucleotides did not measurably impact the nanostructure of complexes formed with CTAB, suggesting that electrostatic

  6. Probing the ubiquinone reduction site of mitochondrial complex I using novel cationic inhibitors.

    PubMed

    Miyoshi, H; Inoue, M; Okamoto, S; Ohshima, M; Sakamoto, K; Iwamura, H

    1997-06-27

    A wide variety of N-methylpyridinium and quinolinium cationic inhibitors of mitochondrial complex I was synthesized to develop potent and specific inhibitors acting selectively at one of the two proposed ubiquinone binding sites of this enzyme (Gluck, M. R., Krueger, M. J., Ramsay, R. R., Sablin, S. O., Singer, T. P., and Nicklas, W. J. (1994) J. Biol. Chem. 269, 3167-3174). N-Methyl-2-n-dodecyl-3-methylquinolinium (MQ18) inhibited electron transfer of complex I at under microM order regardless of whether exogenous or endogenous ubiquinone was used as an electron acceptor. The presence of tetraphenylboron (TPB-) potentiated the inhibition by MQ18 in a different way depending upon the molar ratio of TPB- to MQ18. In the presence of a catalytic amount of TPB-, the inhibitory potency of MQ18 was remarkably enhanced, and the extent of inhibition was almost complete. The presence of equimolar TPB- partially reactivated the enzyme activity, and the inhibition was saturated at an incomplete level (approximately 50%). These results are explained by the proposed dual binding sites model for ubiquinone (cited above). The inhibition behavior of MQ18 for proton pumping activity was similar to that for electron transfer activity. The good correlation of the inhibition behavior for the two activities indicates that both ubiquinone binding sites contribute to redox-driven proton pumping. On the other hand, N-methyl-4-[2-methyl-3-(p-tert-butylphenyl)]propylpyridinium (MP6) without TPB- brought about approximately 50% inhibition at 5 microM, but the inhibition reached a plateau at this level over a wide range of concentrations. Almost complete inhibition was readily obtained at low concentrations of MP6 in the presence of TPB-. Thus MP6 appears to be a selective inhibitor of one of the two ubiquinone binding sites. With a combined use of MP6 and 2,3-diethoxy-5-methyl-6-geranyl-1,4-benzoquinone, we also provided kinetic evidence for the existence of two ubiquinone binding sites.

  7. Variational first hyperpolarizabilities of 2,3-naphtho-15-crown-5 ether derivatives with cation-complexing: a potential and selective cation detector.

    PubMed

    Yu, Hai-Ling; Wang, Wen-Yong; Hong, Bo; Zong, Ying; Si, Yan-Ling; Hu, Zhong-Qiang

    2016-09-29

    Crown ethers, as a kind of heterocycle, have been the subject of great interest over recent decades due to their selective capability to bind to metal cations. The use of a constant crown ether, such as naphtho-15-crown-5 (N15C5), and varied metal cations (Li(+), Na(+), K(+), Be(2+), Mg(2+), Ca(2+), Co(2+), Ni(2+), Cu(2+)) makes it possible to determine the contributions of the metal cations to nonlinear optical (NLO) responses and to design an appropriate NLO-based cation detector. N15C5 and its metal cation derivatives have been systematically investigated by density functional theory. It is found that the dependency of the first hyperpolarizability relies on the metal cation, especially for transition metals. The decrease of the first hyperpolarizabilities for alkali metal cation derivatives is due to their relatively low oscillator strengths, whereas the significant increase of the first hyperpolarizabilities for transition metal cation derivatives can be further illustrated by their low transition energies, large amplitudes and separate distributions of first hyperpolarizability density. Thus, the alkali metal and transition metal cations are distinguishable and the transition metal cations are easier to detect by utilizing the variations in NLO responses.

  8. Cation-π and CH-π Interactions in the Coordination and Solvation of Cu(+)(acetylene)n Complexes.

    PubMed

    Brathwaite, Antonio D; Ward, Timothy B; Walters, Richard S; Duncan, Michael A

    2015-06-04

    Copper-acetylene cation complexes of the form Cu(C2H2)n(+) (n = 1-8) are produced by laser ablation in a supersonic expansion of acetylene/argon. The ions are mass selected and studied via infrared laser photodissociation spectroscopy in the C-H stretching region (3000-3500 cm(-1)). The structure and bonding of these complexes are investigated through the number of infrared active bands, their relative intensities and their frequency positions. Density functional theory calculations are carried out in support of the experimental data. The combined data show that cationcomplexes are formed for the n = 1-3 species, resulting in red-shifted C-H stretches on the acetylene ligands. The coordination of the copper cation is completed with three acetylene ligands, forming a "propeller" structure with D3 symmetry. Surprisingly, complexes with even greater numbers of acetylenes than this (4-6) have distinctive infrared band patterns quite different from those of the smaller complexes. Experiment combined with theory establishes that there is a fascinating pattern of second-sphere solvation involving the binding of acetylenes in bifurcated CH-π binding sites at the apex of two core ligands. This binding motif leads to three equivalent sites for second-sphere ligands, which when filled form a highly symmetrical Cu(+)(C2H2)6 complex. Solvent binding in this complex induces a structural change to planarity in the core, producing an appealing "core-shell" structure with D(3h) symmetry.

  9. The role of multivalent metal cations and organic complexing agents in bitumen-mineral interactions in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Gan, Weibing

    A systematic investigation was carried out to study the interactions between bitumen (or hexadecane) and minerals (quartz, kaolinite and illite) in aqueous solutions containing multivalent metal cations Ca2+, Mg2+ and Fe2+/Fe3+, in the absence and presence of organic complexing agents (oxalic acid, EDTA and citric acid). A range of experimental techniques, including coagulation measurement, visualization of bitumen-mineral attachment, metal ion adsorption measurement, zeta potential measurement, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopic analyses, were employed in the investigation. Free energy changes of adsorption of metal cations on the minerals and bitumen were evaluated using the James & Healy thermodynamic model. Total interaction energies between the minerals and bitumen were calculated using classical DLVO theory. It was observed that while the tested minerals showed varying degrees of mutual-coagulation with bitumen (or hexadecane), the presence of the multivalent metal cations could prominently increase the mutual coagulation. It was also found that such enhancement of the mutual coagulation was only significant when the metal cations formed first-order hydroxyl complexes (such as CaOH +, MgOH+, etc.) or metal hydroxides (such as Fe(OH) 3, Mg(OH)2, etc.). Therefore, the increase of the bitumen-mineral mutual coagulation by the metal cations was strongly pH dependent. Organic complexing agents (oxalic acid, citric acid and EDTA) used in this study, citric acid in particular, significantly reduced or virtually eliminated the mutual coagulation between bitumen (or hexadecane) and minerals caused by metal cations Ca2+, Mg2+, Fe 2+ and Fe3+. Due to its ability to substantially lower the mutual coagulation between bitumen and mineral particles, citric acid was found the most effective in improving bitumen-mineral liberation in solutions containing the multivalent metal cations at pH 8--10. In small scale flotation experiments

  10. Influence of the lipid environment on valinomycin structure and cation complex formation

    NASA Astrophysics Data System (ADS)

    Halsey, Christopher M.; Benham, Derek A.; JiJi, Renee D.; Cooley, Jason W.

    2012-10-01

    Carrier-type molecular ionophores, such as the cyclic dodecadepsipeptide valinomycin, often must undergo structural changes during the binding and transport of a cation across the lipid membrane. Observing the structural fluctuations that occur during this process experimentally has proven extremely difficult due to the complexities of spectroscopic analysis of protein structure/dynamics in native lipid bilayer environments. Currently, our understanding of how valinomycin selectively transports ions across membranes is derived from atomic structures solved of the cyclic macromolecule solvated in various organic solvents and complimentary in silico dynamics experiments. We have shown recently that deep-UV excited resonance Raman spectroscopy (DUVRR) has a unique ability to characterize secondary structure content and simultaneously provide information about the relative solvation of the probed peptide backbone C.M. Halsey, J. Xiong, O. Oshokoya, J.A. Johnson, S. Shinde, J.T. Beatty, G. Ghirlanda, R.D. JiJi, J.W. Cooley, Simultaneous observation of peptide backbone lipid solvation and a-helical structure by deep-UV resonance Raman spectroscopy, ChemBioChem 12 (2011) 2125-2128, [16]. Interpretation of DUVRR spectra of valinomycin in swelled lipid and unilamellar lipid bilayer environments indicate that the uncomplexed valinomycin molecule dynamically samples both the open and closed conformations as described for the structures derived from polar and non-polar organic solvents, respectively. Upon introduction of potassium, the structure of valinomycin in swelled lipid environments resembles more closely that of the open conformation. The shift in structure upon complexation is accompanied by a significant decrease in the valinomycin DUVRR spectral amide I intensity, indicating that the open conformation is more water solubilized and is seemingly "trapped" or predominantly located close to the lipid-water interface. The trapping of the valinomycin in the act of complex

  11. Promoted adipogenesis of rat mesenchymal stem cells by transfection of small interfering RNA complexed with a cationized dextran.

    PubMed

    Nagane, Kentaro; Jo, Jun-ichiro; Tabata, Yasuhiko

    2010-01-01

    The objective of this study is to investigate the possibility of small interfering RNA (siRNA) complexed with a cationized dextran of nonviral carrier to biologically modify the adipogenesis extent of bone marrow-derived mesenchymal stem cells (MSC). Spermine was chemically introduced to the hydroxyl groups of dextran to prepare the cationized dextran (spermine-dextran). The spermine-dextran could form a complex with siRNA, and the physicochemical properties were changed by the molecular weight of dextran, the molar percentage of spermine introduced to dextran, and the molar ratio of nitrogen molecule of spermine-dextran to the phosphorous ones of siRNA (N/P ratio). The gene expression level of luciferase or green fluorescence protein was significantly suppressed by transfection with the complex of spermine-dextran and siRNA. The gene expression level by the complex decreased with an increase in the extent of complex internalized. Biochemical experiments revealed that culture in an adipogenic differentiation medium allowed MSC to differentiate into adipogenic cells. However, upon culturing with siRNA of anti-transcription coactivator containing PDZ-binding motif (TAZ) for osteogenic differentiation complexed with the spermine-dextran, the adipogenesis of MSC was further promoted. It is concluded that the spemine-dextran was a promising nonviral carrier to suppress the expression level of differentiation gene, resulting in the modification of cell differentiation direction.

  12. Neutral and cationic aluminium complexes containing a chiral (OSSO)-type bis(phenolato) ligand: synthesis, structures and polymerization activity.

    PubMed

    Lian, Bing; Ma, Haiyan; Spaniol, Thomas P; Okuda, Jun

    2009-11-07

    Reaction of trimethylaluminium with the linked bis(phenol) trans-1,4-dithiocyclohexanediyl-2,2-bis(4,6-di-tert-butylphenol) (cydtbpH2, 1a) led to the chiral methyl aluminium complex [Al(cydtbp)Me] (2a) as both racemate and resolved enantiomers, which were characterized by multinuclear NMR spectroscopy and elemental analysis. Rac-{trans-1,2-dithiocyclohexanediyl-2,2-bis(6-tert-butyl-4-methylphenol)} (cytbmpH2, rac-1b) similarly gave rac-2b. Single-crystal X-ray diffraction of (S,S)-2a and rac-2b showed a strongly distorted trigonal bipyramidal geometry with significantly differing Al-S distances. Reaction of rac-2b with (-)-borneol gave the alkoxy complex 5 as a mixture of two diastereomers. Methyl abstraction from the neutral metal complex rac-2a using B(C6F5)3 gave the cationic complex [rac-Al(cydtbp)(THF)2]+[MeB(C6F5)3]- (rac-6 x (THF)2) that according to X-ray crystallography adopts an octahedral coordination geometry. Upon reacting trimethylaluminium with a bis(phenol) with a longer link, 3,4-trans-butanediyl-1,6-dithiahexanediyl)-2,2-bis(6-tert-butyl-4-methylphenol), (cmtbmpH2, 3, a dinuclear compound 4 was obtained that contains two square pyramidal aluminium centers with two "fly-over" bis(phenolate) ligands. The neutral methyl aluminium complexes are active in the polymerization of methyl methacrylate (MMA) and in the ring-polymerization of rac-lactide (LA), producing PMMAs and PLAs in a controlled fashion. The cationic aluminium complexes were active in the cationic polymerization of isoprene and benzofuran.

  13. Impact of bidentate chelators on lipophilicity, stability, and biodistribution characteristics of cationic 99mTc-nitrido complexes.

    PubMed

    Kim, Young-Seung; He, Zhengjie; Hsieh, Wen-Yuan; Liu, Shuang

    2007-01-01

    This report describes synthesis and evaluation of novel cationic 99mTc-nitrido complexes, [99mTcN(L)(PNP)](+) (L = ma, ema, tma, etma and mpo; PNP = PNP5, PNP6, and L6), as potential radiotracers for heart imaging. Cationic complexes [99mTcN(L)(PNP)](+) were prepared in two steps. For example, reaction of succinic dihydrazide with 99mTcO4(-) in the presence of excess stannous chloride and PDTA resulted in the [99mTcN(PDTA)n] intermediate, which then reacted Hmpo and PNP6 at 100 degrees C for 10-15 min to give [99mTcN(mpo)(PNP6)](+) in >90% yield. It was found that bidentate chelators have a significant impact on lipophilicity, solution stability, biodistribution, and metabolic stability of cationic 99mTc-nitrido complexes. The fact that [99mTcN(ema)(PNP6)](+) decomposes rapidly in the presence of cysteine (1 mg/mL) while [99mTcN(etma)(PNP6)](+) and [99mTcN(mpo)(PNP6)](+) remain stable for >6 h under the same conditions strongly suggests that thione-S donors in bidentate chelators increase the solution stability of their cationic 99mTc-nitrido complexes. Biodistribution studies were performed on four cationic 99mTc-nitrido complexes in Sprague-Dawley rats. [99mTcN(etma)(PNP5)](+) is of particular interest due to its high initial heart uptake (1.81 +/- 0.35 %ID/g at 5 min postinjection), and long myocardial retention (1.99 +/- 0.47 %ID/g at 120 min postinjection). The heart/liver ratio of [99mTcN(etma)(PNP5)](+) (6.06 +/- 1.48) at 30 min postinjection is almost identical that of 99mTcN-DBODC5 (6.01 +/- 1.45), and is >2 times better than that of 99mTc-sestamibi (2.90 +/- 0.22). Results from metabolism studies show that [99mTcN(etma)(PNP5)](+) has no significant metabolism in the urine, but it does show significant metabolism in feces samples at 120 min postinjection. Planar imaging studies suggest that [99mTcN(etma)(PNP5)](+) might be able to give clinically useful images of the heart as early as 30 min postinjection. [99mTcN(etma)(PNP5)](+) is a very promising

  14. Impact of Bidentate Chelators on Lipophilicity, Stability and Biodistribution Characteristics of Cationic 99mTc-Nitrido Complexes

    PubMed Central

    Liu, Shuang; He, Zhengjie; Hsieh, Wen-Yuan; Kim, Yong-Seung

    2008-01-01

    This report describes synthesis and evaluation of novel cationic 99mTc-nitrido complexes, [99mTcN(L)(PNP)]+ (L = ma, ema, tma, etma and mpo; PNP = PNP5, PNP6 and L6), as potential radiotracers for heart imaging. Cationic complexes [99mTcN(L)(PNP)]+ were prepared in two steps. For example, reaction of succinic dihydrazide with 99mTcO4− in the presence of excess stannous chloride and PDTA resulted in the [99mTcN(PDTA)n] intermediate, which then reacted Hmpo and PNP6 at 100 °C for 10 – 15 min to give [99mTcN(mpo)(PNP6)]+ in >90% yield. It was found that bidentate chelators have a significant impact on lipophilicity, solution stability, biodistribution and metabolic stability of cationic 99mTc-nitrido complexes. The fact that [99mTcN(ema)(PNP6)]+ decomposes rapidly in presence of cysteine (1 mg/mL) while [99mTcN(etma)(PNP6)]+ and [99mTcN(mpo)(PNP6)]+ remain stable for >6 h under the same conditions strongly suggests that thione-S donors in bidentate chelators increase the solution stability of their cationic 99mTc-nitrido complexes. Biodistribution studies were performed on four cationic 99mTc-nitrido complexes in Sprague-Dawley rats. [99mTcN(etma)(PNP5)]+ is of particular interest due to its high initial heart uptake (1.81±0.35 %ID/g at 5 min postinjection), and long myocardial retention (1.99±0.47 %ID/g at 120 min postinjection). The heart/liver ratio of [99mTcN(etma)(PNP5)]+ (6.06±1.48) at 30 min postinjection is almost identical that of 99mTcN-DBODC5 (6.01±1.45), and is >2 times better than that of 99mTc-sestamibi (2.90±0.22). Results from metabolism studies show that [99mTcN(etma)(PNP5)]+ has no significant metabolism in the urine; but it does show significant metabolism in feces samples at 120 min postinjection. Planar imaging studies suggest that [99mTcN(etma)(PNP5)]+ might be able to give clinically useful images of the heart as early as 30 min postinjection. [99mTcN(etma)(PNP5)]+ is a very promising candidate for more pre-clinical evaluations in

  15. Peptide-lanthanide cation equilibria in aqueous phase. I. Bound shifts for L-carnosine-praseodymium complexes

    NASA Astrophysics Data System (ADS)

    Mossoyan, J.; Asso, M.; Benlian, D.

    L-Carnosine complexes of Pr 3+ were characterized in aqueous solution by 1H NMR and potentiometric titration. A rigorous treatment of chemical shifts and pH variation data with lanthanide concentration is presented. Two different forms of the peptide ligand, forming simultaneously two complexes, were taken into account. At low pH values the cation is only coordinated at the carboxylate site of the ligand in a weak complex ( β2 = 6) whereas in neutral solution a stronger complex ( β1 = 37) is present as a consequence of the deprotonation of the imidazole ring. The computation of induced bound shifts † 2 and Δ1 for resonating nuclei of the peptide in both forms yields consistent figures. These provide the experimental basis for a conformational model which is usually not obtainable for labile complexes with low stability constants.

  16. Warm White Light-Emitting Diodes Based on a Novel Orange Cationic Iridium(III) Complex

    PubMed Central

    Tang, Huaijun; Meng, Guoyun; Chen, Zeyu; Wang, Kaimin; Zhou, Qiang; Wang, Zhengliang

    2017-01-01

    A novel orange cationic iridium(III) complex [(TPTA)2Ir(dPPOA)]PF6 (TPTA: 3,4,5-triphenyl-4H-1,2,4-triazole, dPPOA: N,N-diphenyl-4-(5-(pyridin-2-yl)-1,3,4-oxadiazol-2-yl)aniline) was synthesized and used as a phosphor in light-emitting diodes (LEDs). [(TPTA)2Ir(dPPOA)]PF6 has high thermal stability with a decomposition temperature (Td) of 375 °C, and its relative emission intensity at 100 °C is 88.8% of that at 25°C. When only [(TPTA)2Ir(dPPOA)]PF6 was used as a phosphor at 6.0 wt % in silicone and excited by a blue GaN (GaN: gallium nitride) chip (450 nm), an orange LED was obtained. A white LED fabricated by a blue GaN chip (450 nm) and only yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce) (1.0 wt % in silicone) emitted cold white light, its CIE (CIE: Commission International de I’Eclairage) value was (0.32, 0.33), color rendering index (CRI) was 72.2, correlated color temperature (CCT) was 6877 K, and luminous efficiency (ηL) was 128.5 lm∙W−1. Such a cold white LED became a neutral white LED when [(TPTA)2Ir(dPPOA)]PF6 was added at 0.5 wt %; its corresponding CIE value was (0.35, 0.33), CRI was 78.4, CCT was 4896 K, and ηL was 85.2 lm∙W−1. It further became a warm white LED when [(TPTA)2Ir(dPPOA)]PF6 was added at 1.0 wt %; its corresponding CIE value was (0.39, 0.36), CRI was 80.2, CCT was 3473 K, and ηL was 46.1 lm∙W−1. The results show that [(TPTA)2Ir(dPPOA)]PF6 is a promising phosphor candidate for fabricating warm white LEDs. PMID:28773020

  17. Photoluminescence of water-soluble CdSe/ZnS nanoparticles in complexes with cationic and anionic polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Strekal', N.; Kulakovich, O.; Belyaev, A.; Stsiapura, V.; Maskevich, S.

    2008-01-01

    The data on the influence of polyelectrolytes on the photon emission probability of water-soluble CdSe/ZnS nanoparticles are obtained. The decrease in the photoluminescence quantum yield of nanoparticles occurring upon their transfer to aqueous solutions from toluene (in the course of solubilization) depends on the ionic nature of an agent applied for the replacement of trioctylphosphine oxide residues on the surface of nanoparticles. It turns out that such a cationic modifying agent as cysteamine leads to an insignificant (˜10%) decrease in the photoluminescence quantum yield of nanoparticles. The use of such an anionic agent as mercaptoacetic acid causes a significant (˜80%) decrease in the quantum yield and the average decay time of photoluminescence. For nanoparticles modified by mercaptoacetic acid (anionic nanoparticles), this decrease is partially compensated if these particles interact with polyelectrolytes whose backbone is oppositely charged (cationic polyelectrolytes), such as polyallylamine and polydiallyldimethylammonium chloride. In this case, the photoluminescence quantum yield shows a reverse increase by 40%, remaining the same within a matter of months or longer. In contrast to this, cationic nanoparticles, only slightly quenched by cysteamine at the stage of solubilization, are appreciably degraded in complexes with anionic polyelectrolytes in solutions and upon immobilization of complexes on a substrate, so that their photoluminescence quantum yield irreversible decreases to zero within a few days. Possible mechanisms of the effects observed are discussed and their consideration in polyelectrolyte-based molecular lithography.

  18. Divalent cations and heparin/heparan sulfate cooperate to control assembly and activity of the fibroblast growth factor receptor complex.

    PubMed

    Kan, M; Wang, F; To, B; Gabriel, J L; McKeehan, W L

    1996-10-18

    Polypeptides of the fibroblast growth factor (FGF) family are ubiquitous bioregulators within tissues whose activity is controlled by heparan sulfates within the pericellular matrix. FGF and the ectodomain of their transmembrane tyrosine kinase receptors (FGFR) exhibit heparin-binding domains that when juxtaposed in a FGF middle dotFGFR complex can accommodate a single, potentially bivalent, decameric polysaccharide chain in a ternary complex. Here we show that the interaction of heparin with FGF ligands is not affected by divalent cations. In contrast, the high affinity interaction (apparent Kd = 10 nM) of heparin with FGFR requires Ca2+ or Mg2+ at physiological concentrations. Divalent cations maintain FGFR in a heparan sulfate-dependent state in respect to FGF binding and an FGF- and heparan sulfate-dependent state in respect to autophosphorylation. A model is proposed where divalent cations and heparan sulfate cooperate to maintain FGFR in a conformation that restricts trans-phosphorylation between intracellular kinase domains. The restriction is overcome by FGF or constitutively as a common consequence of diverse mutations in FGFR associated with skeletal and craniofacial abnormalities.

  19. Interactions and hybrid complex formation of anionic algal polysaccharides with a cationic glycine betaine-derived surfactant.

    PubMed

    Covis, Rudy; Vives, Thomas; Gaillard, Cédric; Benoit, Maud; Benvegnu, Thierry

    2015-05-05

    The interaction between anionic algal polysaccharides ((κ)-, (ι)-, (λ)-carrageenans, alginate and ulvan) and a cationic glycine betaine (GB) amide surfactant possessing a C18:1 alkyl chain has been studied using isothermal titration calorimetry (ITC), zeta-potential measurements, dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), and surface tension measurements. It was observed that this cationic surfactant derived from renewable raw materials induced cooperative binding with the anionic polymers at critical aggregation concentration (CAC) and the CAC values are significantly lower than the corresponding critical micelle concentration (CMC) for the surfactant. The CMC of cationic GB surfactant was obtained at higher surfactant concentration in polysaccharide solution than in pure water. More interestingly, the presence of original polysaccharide/surfactant hybrid complexes formed above the CMC value was evidenced from (κ)-carrageenan by microscopy (TEM and AFM). Preliminary investigations of the structure of these complexes revealed the existence of surfactant nanoparticles surrounded with polysaccharide matrix, probably resulting from electrostatic attraction. In addition, ITC measurements clearly showed that the interactions of the κ-carrageenan was stronger than for other polysaccharides ((ι)-, (λ)-carrageenans, alginate and ulvan). These results may have important impact on the use of the GB amide surfactant in formulations based on algal polysaccharides for several applications such as in food, cosmetics, and detergency fields.

  20. Broad Scope Aminocyclization of Enynes with Cationic JohnPhos-Gold(I) Complex as the Catalyst.

    PubMed

    Miller, Ricarda; Carreras, Javier; Muratore, Michael E; Gaydou, Morgane; Camponovo, Francesco; Echavarren, Antonio M

    2016-03-04

    A practical aminocyclization of 1,6-enynes with a wide variety of substituted anilines, including N-alkyl anilines, has been achived by using cationic [JohnPhosAu(MeCN)]SbF6 as a general purpose catalyst. The resulting adducts can be easily converted into polycyclic compounds by palladium- and gold-catalyzed reactions.

  1. Broad Scope Aminocyclization of Enynes with Cationic JohnPhos–Gold(I) Complex as the Catalyst

    PubMed Central

    2016-01-01

    A practical aminocyclization of 1,6-enynes with a wide variety of substituted anilines, including N-alkyl anilines, has been achived by using cationic [JohnPhosAu(MeCN)]SbF6 as a general purpose catalyst. The resulting adducts can be easily converted into polycyclic compounds by palladium- and gold-catalyzed reactions. PMID:26839084

  2. Polyampholyte nanoparticles prepared by self-complexation of cationized poly(γ-glutamic acid) for protein carriers.

    PubMed

    Shen, Heyun; Akagi, Takami; Akashi, Mitsuru

    2012-08-01

    A novel amphoteric poly(amino acid) is synthesized by grafting a cationic amino acid (L-Arg) to γ-PGA to prepare charged NPs. γ-PGA-Arg NPs can be prepared by the self-complexation of a single polymer by intra-/inter-molecular electrostatic interactions when the polymer is dispersed in water. The size and surface charge of the NPs can be regulated by the grafting degree of Arg (41, 56, and 83%). The smallest NPs are obtained at 56% grafting degree of the γ-PGA-Arg copolymer. The 56 and 83% grafting degree NPs are stable for at least 1 week. Depending on their surface charge, these NPs can selectively adsorb anionically or cationically charged proteins.

  3. Control of intramolecular π-π stacking interaction in cationic iridium complexes via fluorination of pendant phenyl rings.

    PubMed

    He, Lei; Ma, Dongxin; Duan, Lian; Wei, Yongge; Qiao, Juan; Zhang, Deqiang; Dong, Guifang; Wang, Liduo; Qiu, Yong

    2012-04-16

    Intramolecular π-π stacking interaction in one kind of phosphorescent cationic iridium complexes has been controlled through fluorination of the pendant phenyl rings on the ancillary ligands. Two blue-green-emitting cationic iridium complexes, [Ir(ppy)(2)(F2phpzpy)]PF(6) (2) and [Ir(ppy)(2)(F5phpzpy)]PF(6) (3), with the pendant phenyl rings on the ancillary ligands substituted with two and five fluorine atoms, respectively, have been synthesized and compared to the parent complex, [Ir(ppy)(2)(phpzpy)]PF(6) (1). Here Hppy is 2-phenylpyridine, F2phpzpy is 2-(1-(3,5-difluorophenyl)-1H-pyrazol-3-yl)pyridine, F5phpzpy is 2-(1-pentafluorophenyl-1H-pyrazol-3-yl)-pyridine, and phpzpy is 2-(1-phenyl-1H-pyrazol-3-yl)pyridine. Single crystal structures reveal that the pendant phenyl rings on the ancillary ligands stack to the phenyl rings of the ppy ligands, with dihedral angles of 21°, 18°, and 5.0° between least-squares planes for complexes 1, 2, and 3, respectively, and centroid-centroid distances of 3.75, 3.65, and 3.52 Å for complexes 1, 2, and 3, respectively, indicating progressively reinforced intramolecular π-π stacking interactions from complexes 1 to 2 and 3. Compared to complex 1, complex 3 with a significantly reinforced intramolecular face-to-face π-π stacking interaction exhibits a significantly enhanced (by 1 order of magnitude) photoluminescent efficiency in solution. Theoretical calculations reveal that in complex 3 it is unfavorable in energy for the pentafluorophenyl ring to swing by a large degree and the intramolecular π-π stacking interaction remains on the lowest triplet state. © 2012 American Chemical Society

  4. Cationic terminal gallylene complexes by halide abstraction: coordination chemistry of a valence isoelectronic analogue of CO and N2.

    PubMed

    Coombs, Natalie D; Vidovic, Dragoslav; Day, Joanna K; Thompson, Amber L; Le Pevelen, Delphine D; Stasch, Andreas; Clegg, William; Russo, Luca; Male, Louise; Hursthouse, Michael B; Willock, David J; Aldridge, Simon

    2008-11-26

    While N(2) and CO have played central roles in developing models of electronic structure, and their interactions with transition metals have been widely investigated, the valence isoelectronic diatomic molecules EX (E = group 13 element, X = group 17 element) have yet to be isolated under ambient conditions, either as the "free" molecule or as a ligand in a simple metal complex. As part of a program designed to address this deficiency, together with wider issues of the chemistry of cationic systems [L(n)M(ER)](+) (E = B, Al, Ga; R = aryl, amido, halide), we have targeted complexes of the type [L(n)M(GaX)](+). Halide abstraction is shown to be a viable method for the generation of mononuclear cationic complexes containing gallium donor ligands. The ability to isolate tractable two-coordinate products, however, is strongly dependent on the steric and electronic properties of the metal/ligand fragment. In the case of complexes containing ancillary pi-acceptor ligands such as CO, cationic complexes can only be isolated as base-trapped adducts, even with bulky aryl substituents at gallium. Base-free gallylene species such as [Cp*Fe(CO)(2)(GaMes)](+) can be identified only in the vapor phase by electrospray mass spectrometry experiments. With bis(phosphine) donor sets at the metal, the more favorable steric/electronic environment allows for the isolation of two-coordinate ligand systems, even with halide substituents at gallium. Thus, [Cp*Fe(dppe)(GaI)](+)[BAr(f)(4)](-) (9) can be synthesized and shown crystallographically to feature a terminally bound GaI ligand; 9 represents the first experimental realization of a complex containing a valence isoelectronic group 13/group 17 analogue of CO and N(2). DFT calculations reveal a relatively weakly bound GaI ligand, which is confirmed experimentally by the reaction of 9 with CO to give [Cp*Fe(dppe)(CO)](+)[BAr(f)(4)](-). In the absence of such reagents, 9 is stable for weeks in fluorobenzene solution, presumably reflecting (i

  5. Correction: A binary catalyst system of a cationic Ru-CNC pincer complex with an alkali metal salt for selective hydroboration of carbon dioxide.

    PubMed

    Ng, Chee Koon; Wu, Jie; Hor, T S Andy; Luo, He-Kuan

    2016-12-22

    Correction for 'A binary catalyst system of a cationic Ru-CNC pincer complex with an alkali metal salt for selective hydroboration of carbon dioxide' by Chee Koon Ng et al., Chem. Commun., 2016, 52, 11842-11845.

  6. Effects of crystal lattice and counterions on the geometries of metal complexes: Hexaaquomagnesium cation as a case study

    NASA Astrophysics Data System (ADS)

    Nascimento, Agrinaldo J.; Moura, Gustavo L. C.; Lima, Nathalia B. D.; Simas, Alfredo M.

    2017-04-01

    We address how diverse are crystallographic geometries of several compounds of the same metal complex cation, and also how they contrast from those resulting from quantum chemical calculations on isolated molecules. In a crystal, besides the desired molecule or molecular ion of interest, there are usually present co-crystallized molecules and/or counterions, that, together with the crystal lattice, perturb its geometry. In order to examine the nature and intensity of each of these effects, we present a novel methodology to separate and quantify them. Accordingly, we compared the crystallographic geometries of the hexaaquomagnesium cation in 45 different compounds, each one with different counter ions and other co-crystallized molecules. We show that the resulting perturbations of the counterions on the geometry of the complex behave as pseudorandom around a mean, and are subject to suitable probability distributions. Results indicate that the crystal lattice effect seems to compress the hexaaquomagnesium complex cation by a magnitude which we estimate to be 0.047 Å in its distances, and 6.6% in its volume. This crystal lattice effect is then superimposed to the effect of the counter ions and other molecules, which provokes a further ±0.035 Å variation on the geometries of the compounds. Consequently, perturbations of counterions and the lattice effect, together, amount to a statistical difference of ≈0.05 Å for distances, and ≈5° for the angles. As such, only within these boundaries, may quantum chemical calculations on isolated complexes be compared to crystallographic results.

  7. Time resolved SAXS to study the complexation of siRNA with cationic micelles of divalent surfactants.

    PubMed

    Falsini, Sara; Ristori, Sandra; Ciani, Laura; Di Cola, Emanuela; Supuran, Claudiu T; Arcangeli, Annarosa; In, Martin

    2014-04-07

    The complexation of siRNA (small interfering RNA) with cationic micelles was studied using time dependent synchrotron SAXS. Micelles were formed by two types of divalent cationic surfactants, i.e. Gemini bis(quaternary ammonium) bromide with variable spacer length (12-3-12, 12-6-12, 12-12-12) and a weak electrolyte surfactant (SH14) with triazine head. Immediately after mixing (t < 50 ms), new large aggregates appeared in solution and the scattering intensity at low q increased. Concomitantly, the presence of a quasi-Bragg peak at q ∼ 1.5 nm(-1) indicated core structuring within the complexes. We hypothesize that siRNA and micelles are alternately arranged into "sandwiches", forming domains with internal structural coherence. The process of complex reorganization followed a first-order kinetics and was completed in less than about 5 minutes, after which a steady state was reached. Aggregates containing Geminis were compact globular structures whose gyration radii Rg depended on the spacer length and were in the order of 7-27 nm. Complexes containing SH14 (Rg = 14-16 nm) were less ordered and possessed a looser internal arrangement. The obtained data, joint with previous structural investigation using Dynamic Light Scattering, Zeta Potential and Small Angle Neutron Scattering, are encouraging evidence for using these systems in biological trials. In fact we showed that transfection agents can be obtained by simply mixing a micelle solution of the cationic surfactant and a siRNA solution, both of which are easily prepared and stable.

  8. Effects of transition metal ion identity and π-cation interactions in metal-bis(peptide) complexes containing phenylalanine.

    PubMed

    Utley, Brandon; Angel, Laurence A

    2010-01-01

    Electrospray ionization-tandem mass spectrometry was used to study the effects of the metal ion identity and π-cation interactions on the dissociation pathways of metal-bis(peptide) complexes, where the metal is either Mn(2+), Co(2+), Ni(2+), Cu(2+), or Zn(2+); and the peptide is either FGGF, GGGG, GF, or GG, where G is glycine and F is phenylalanine. The [(FGGF)(FGGF-H) + M(2+)](+) and [(GGGG)(GGGG-H) + M(2+)](+) complexes dissociated by losing one FGGF or GGGG, respectively. Relative binding affinities were measured using the crossover points, where the parent and product ions were equal in ion abundance and a normalized-collision energy scale. The results indicate the relative binding affinities for FGGF and GGGG follow the same order with respect to the transition metal ion identity: Cu(2+) < Ni(2+) < Mn(2+) ≈ Zn(2+) < Co(2+), and the π-cation interactions in the FGGF complex have a measureable stabilizing effect. In contrast, the main fragmentation channels of [(GF)(GF-H) + M(2+)]+ and [(GG)(GG-H) + M(2+)](+) are loss of CO(2) and 2CO(2) with the [(GF)(GF-H) + M(2+)](+) complex also exhibiting cinnamic acid ,GF, residual glycine, cinnamate and styrene loss.

  9. Temperature-induced collapse of alkaline Earth cation-polyacrylate anion complexes.

    PubMed

    Lages, Sebastian; Schweins, Ralf; Huber, Klaus

    2007-09-06

    Polyacrylate anions are used to inhibit CaCO3 precipitation and may be a promising additive to control formation of inorganic nanoparticles. The origin of this applicability lies in specific interactions between the alkaline earth cations and the carboxylate functions along the polyacrylate chains. In the absence of CO32- anions, these interactions eventually cause precipitation of polyelectrolytes. Extended investigation of dilute sodium polyacrylate solutions approaching this precipitation threshold revealed a dramatic shrinking of the PA coil dimensions once the threshold is reached (Eur. Phys. J. E 2001, 5, 117). Recent isothermal calorimetric titration experiments by Antonietti et al. (Macromolecules 2004, 37, 3444) indicated that the driving force of this precipitation is entropic in nature. In the present work, we investigated the impact of temperature on the structural changes of dissolved polyacrylate chains decorated with alkaline earth cations. To this end, large polyacrylate chains were brought close to the precipitation threshold by the addition of distinct amounts of Ca2+ or Sr2+ cations. The resulting structural intermediates were then subjected to temperature variations in the range of 15 degrees C

  10. Photophysical and antibacterial properties of complex systems based on smectite, a cationic surfactant and methylene blue.

    PubMed

    Donauerová, Alena; Bujdák, Juraj; Smolinská, Miroslava; Bujdáková, Helena

    2015-10-01

    Solid or colloidal materials with embedded photosensitizers are promising agents from the medical or environmental perspective, where the direct use of photoactive solutions appears to be problematic. Colloids based on layered silicates of the saponite (Sap) and montmorillonite (Mon) type, including those modified with dodecylammonium cations (C12) and photosensitizer--methylene blue (MB) were studied. Two representatives of bacteria, namely Enterobacter cloacae and Escherichia coli, were selected for this work. A spectral study showed that MB solutions and also colloids with Sap including C12 exhibited the highest photoactivities. The antimicrobial properties of the smectite colloids were not directly linked to the photoactivity of the adsorbed MB cations. They were also influenced by other parameters, such as light vs. dark conditions, the spectrum, power and duration of the light used for the irradiation; growth phases, and the pre-treatment of microorganisms. Both the photoactivity and antimicrobial properties of the colloids were improved upon pre-modification with C12. Significantly higher antimicrobial properties were observed for the colloids based on Mon with MB in the form of molecular aggregates without significant photoactivities. The MB/Mon colloids, both modified and non-modified with C12 cations, exhibited higher antimicrobial effects than pure MB solution. Besides the direct effect of photosensitization, the surface properties of the silicate particles likely played a crucial role in the interactions with microorganisms. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Cation-limited kinetic model for microbial extracellular electron transport via an outer membrane cytochrome C complex

    PubMed Central

    Okamoto, Akihiro; Tokunou, Yoshihide; Saito, Junki

    2016-01-01

    Outer-membrane c-type cytochrome (OM c-Cyt) complexes in several genera of iron-reducing bacteria, such as Shewanella and Geobacter, are capable of transporting electrons from the cell interior to extracellular solids as a terminal step of anaerobic respiration. The kinetics of this electron transport has implications for controlling the rate of microbial electron transport during bioenergy or biochemical production, iron corrosion, and natural mineral cycling. Herein, we review the findings from in-vivo and in-vitro studies examining electron transport kinetics through single OM c-Cyt complexes in Shewanella oneidensis MR-1. In-vitro electron flux via a purified OM c-Cyt complex, comprised of MtrA, B, and C proteins from S. oneidensis MR-1, embedded in a proteoliposome system is reported to be 10- to 100-fold faster compared with in-vivo estimates based on measurements of electron flux per cell and OM c-Cyts density. As the proteoliposome system is estimated to have 10-fold higher cation flux via potassium channels than electrons, we speculate that the slower rate of electron-coupled cation transport across the OM is responsible for the significantly lower electron transport rate that is observed in-vivo. As most studies to date have primarily focused on the energetics or kinetics of interheme electron hopping in OM c-Cyts in this microbial electron transport mechanism, the proposed model involving cation transport provides new insight into the rate detemining step of EET, as well as the role of self-secreted flavin molecules bound to OM c-Cyt and proton management for energy conservation and production in S. oneidensis MR-1. PMID:27924259

  12. Long-lived phosphorescent iridium(III) complexes conjugated with cationic polyfluorenes for heparin sensing and cellular imaging.

    PubMed

    Jiang, Jiayang; Zhang, Chuanqi; Lin, Wenpeng; Liu, Yahong; Liu, Shujuan; Xu, Yunjian; Zhao, Qiang; Huang, Wei

    2015-04-01

    The applications of conjugated polyelectrolytes in biosensing and bioimaging have attracted more and more research interests due to their excellent photophysical properties. In this work, a new series of conjugated polyelectrolytes containing long-lived phosphorescent Ir(III) complexes is designed and synthesized, which can be used for ratiometric and lifetime-based sensing of heparin utilizing the electrostatic interaction between cationic polymers and anionic heparin. By changing the ligand structures of Ir(III) complexes, the sensing performances of phosphorescent-conjugated polyelectrolytes (PCPEs) are optimized. In addition, the application of PCPEs in cellular imaging is carried out. These polymers can be applied for specific staining of cell membrane. Importantly, utilizing the long emission lifetime of phosphorescent signal of Ir(III) complexes, time-gated luminescent imaging is carried out, which can eliminate the short-lived background fluorescence interferences from the environment or biological samples. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Is the formation of cationic lipid-DNA complexes a thermodynamically driven phenomenon? Structure and phase behavior of DC-Chol/DNA complexes say not

    NASA Astrophysics Data System (ADS)

    Caracciolo, Giulio; Pozzi, Daniela; Caminiti, Ruggero

    2006-07-01

    The currently accepted mechanism of formation of cationic lipid-DNA complexes (lipoplexes) relies on the basic assumption that equilibrium structure of lipoplexes is regulated by thermodynamics. The main consequence is that neutral lipoplexes are one phase whereas positively (or negatively) charged ones coexist with excess lipid (or excess DNA). The authors report a small angle x-ray diffraction study on the structure of lipoplexes made of the cationic lipid 3β-[N-(N ,N-dimethylaminoethane)-carbamoyl]cholesterol and calf thymus Na-DNA. Here the authors show that positively charged lipoplexes can coexist with unbound DNA and they claim that steric size effects are definitely important to determine the equilibrium structure of lipoplexes.

  14. Comparison of Strong Cation Exchange and SDS/PAGE Fractionation for Analysis of Multi-Protein Complexes

    PubMed Central

    Das, Sudipto; Bosley, Allen D.; Ye, Xiaoying; Chan, King C.; Chu, Isabel; Green, Jeffery E.; Issaq, Haleem J.; Veenstra, Timothy D.; Andresson, Thorkell

    2013-01-01

    Affinity purification of protein complexes followed by identification using liquid chromatography/mass spectrometry (LC-MS/MS) is a robust method to study the fundamental process of protein interaction. While affinity isolation reduces the complexity of the sample, fractionation prior to LC-MS/MS analysis is still necessary to maximize protein coverage. In this study, we compared the protein coverage obtained via LC-MS/MS analysis of protein complexes pre-fractionated using two commonly employed methods, SDS-PAGE and strong cation exchange chromatography (SCX). The two complexes analyzed focused on the nuclear proteins Bmi-1 and GATA3 that were expressed within the cells at low and high levels, respectively. Pre-fractionation of the complexes at the peptide level using SCX consistently resulted in the identification of approximately 3-fold more proteins compared to separation at the protein level using SDS-PAGE. The increase in the number of identified proteins was especially pronounced for the Bmi-1 complex, where the target protein was expressed at a low level. The data shows that pre-fractionation of affinity isolated protein complexes using SCX prior to LC-MS/MS analysis significantly increases the number of identified proteins and individual protein coverage, particularly for target proteins expressed at low levels. PMID:20968308

  15. Claudin-16 and claudin-19 interact and form a cation-selective tight junction complex.

    PubMed

    Hou, Jianghui; Renigunta, Aparna; Konrad, Martin; Gomes, Antonio S; Schneeberger, Eveline E; Paul, David L; Waldegger, Siegfried; Goodenough, Daniel A

    2008-02-01

    Tight junctions (TJs) play a key role in mediating paracellular ion reabsorption in the kidney. Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is an inherited disorder caused by mutations in the genes encoding the TJ proteins claudin-16 (CLDN16) and CLDN19; however, the mechanisms underlying the roles of these claudins in mediating paracellular ion reabsorption in the kidney are not understood. Here we showed that in pig kidney epithelial cells, CLDN19 functioned as a Cl(-) blocker, whereas CLDN16 functioned as a Na(+) channel. Mutant forms of CLDN19 that are associated with FHHNC were unable to block Cl(-) permeation. Coexpression of CLDN16 and CLDN19 generated cation selectivity of the TJ in a synergistic manner, and CLDN16 and CLDN19 were observed to interact using several criteria. In addition, disruption of this interaction by introduction of FHHNC-causing mutant forms of either CLDN16 or CLDN19 abolished their synergistic effect. Our data show that CLDN16 interacts with CLDN19 and that their association confers a TJ with cation selectivity, suggesting a mechanism for the role of mutant forms of CLDN16 and CLDN19 in the development of FHHNC.

  16. Al3Li4(BH4)13: a complex double-cation borohydride with a new structure.

    PubMed

    Lindemann, Inge; Domènech Ferrer, Roger; Dunsch, Lothar; Filinchuk, Yaroslav; Cerný, Radovan; Hagemann, Hans; D'Anna, Vincenza; Lawson Daku, Latévi Max; Schultz, Ludwig; Gutfleisch, Oliver

    2010-08-02

    The new double-cation Al-Li-borohydride is an attractive candidate material for hydrogen storage due to a very low hydrogen desorption temperature (approximately 70 degrees C) combined with a high hydrogen density (17.2 wt%). It was synthesised by high-energy ball milling of AlCl(3) and LiBH(4). The structure of the compound was determined from image-plate synchrotron powder diffraction supported by DFT calculations. The material shows a unique 3D framework structure within the borohydrides (space group=P-43n, a=11.3640(3) A). The unexpected composition Al(3)Li(4)(BH(4))(13) can be rationalized on the basis of a complex cation [(BH(4))Li(4)](3+) and a complex anion [Al(BH(4))(4)](-). The refinements from synchrotron powder diffraction of different samples revealed the presence of limited amounts of chloride ions replacing the borohydride on one site. In situ Raman spectroscopy, differential scanning calorimetry (DSC), thermogravimetry (TG) and thermal desorption measurements were used to study the decomposition pathway of the compound. Al-Li-borohydride decomposes at approximately 70 degrees C, forming LiBH(4). The high mass loss of about 20 % during the decomposition indicates the release of not only hydrogen but also diborane.

  17. Electron transfer from aromatic amino acids to guanine and adenine radical cations in pi stacked and T-shaped complexes.

    PubMed

    Butchosa, Cristina; Simon, Sílvia; Voityuk, Alexander A

    2010-04-21

    Similar redox properties of the natural nucleobases and aromatic amino acids make it possible for electron transfer (ET) to occur between these sites in protein-nucleic acid complexes. Using DFT calculations, we estimate the ET rate from aromatic amino acid X (X = Phe, His, Tyr and Trp) to radical cations of guanine (G) and adenine (A) in dimers G-X and A-X with different arrangement of the subunits. We show that irrespective of the mutual orientation of the aromatic rings, the electronic interaction in the systems is strong enough to ensure effective ET from X to G(+) or A(+). Surprisingly, relatively high ET rates are found in T-shaped dimers. This suggests that pi stacking of nucleobases and aromatic amino acids is not required for feasible ET. In most complexes [G-X](+) and [A-X](+), we find the excess charge to be confined to a single site, either the nucleobase or amino acid X. Then, conformational changes may initiate migration of the radical cation state from the nucleobase to X and back. The ET process from Trp and Tyr to G(+) is found to be faster than deprotonation of G(+). Because the last reaction may lead to the formation of highly mutagenic species, the efficient repair of G(+) may play an important role in the protection of genomic DNA from oxidative damage.

  18. Enhanced suppression of tumor growth using a combination of NK4 plasmid DNA-PEG engrafted cationized dextran complex and ultrasound irradiation.

    PubMed

    Hosseinkhani, H; Kushibiki, T; Matsumoto, K; Nakamura, T; Tabata, Y

    2006-05-01

    This investigation aims to determine experimentally whether or not ultrasound (US) irradiation is effective in enhancing the in vivo gene expression of NK4 plasmid DNA and suppressing tumor growth. NK4, composed of the NH2-terminal hairpin and subsequent four-kringle domains of hepatocyte growth factor (HGF), acts as an HGF-antagonist and angiogenesis inhibitor. Dextran was cationized by introducing spermine to the hydroxyl groups to allow for polyionic complexation with NK4 plasmid DNA. The cationized dextran was additionally modified with poly(ethylene glycol) (PEG) molecules giving PEG engrafted cationized dextran. Significant suppression of tumor growth was observed when PEG engrafted cationized dextran-NK4 plasmid DNA complexes were intravenously injected into mice carrying a subcutaneous Lewis lung carcinoma tumor mass with subsequent US irradiation when compared with the cationized dextran-NK4 plasmid DNA complex and naked NK4 plasmid DNA with or without US irradiation. We conclude that complexation with PEG-engrafted cationized dextran in combination with US irradiation is a promising way to target the NK4 plasmid DNA to the tumor for gene expression.

  19. Cationic lanthanide complexes of neutral tripodal N,O ligands: enthalpy versus entropy-driven podate formation in water.

    PubMed

    Bravard, Florence; Rosset, Caroline; Delangle, Pascale

    2004-07-07

    The cationic lanthanide complexes of two neutral tripodal N,O ligands, tpa (tris[(2-pyridyl)methyl]amine) and tpaam (tris[6-((2-N,N-diethylcarbamoyl)pyridyl)methyl]amine) are studied in water. The analysis of the proton lanthanide induced NMR shifts indicate that there is no abrupt structural change in the middle of the rare-earth series. Unexpectedly, the formation constant values of the lanthanide podates of tpaam and tpa in D2O at 298 K are similar, suggesting that the addition of the three amide groups to the ligand tpa does not lead to any increase in stability of the lanthanide complexes of tpaam in respect to tpa, even though the amide groups are coordinated to the metal in aqueous solution. The measurement of the enthalpy and entropy changes of the complexation reactions shows that the two similar ligands tpa and tpaam have different driving forces for lanthanide complexation. Indeed, the formation of tpa podates benefits from an exothermic enthalpy change associated with a small entropy change, whereas the complexation reaction with tpaam is clearly entropy-driven though opposed by a positive enthalpy change. The hydration states of the europium complexes were measured by luminescence and show the coordination of 4-5 water ligands in [Eu(tpa)]3+ whereas there are only 2 in [Eu(tpaam)]3+. Therefore the heptadentate ligand tpaam releases the translational entropy of more water molecules than does the tetradentate ligand tpa.

  20. Synthesis and chemistry of cationic d{sup 0} metal alkyl complexes. Progress report, July 1988--May 1991

    SciTech Connect

    Jordan, R.F.

    1991-12-31

    The objective of this project is to develop new types of electrophilic metal alkyl complexes for catalytic C-H activation and olefin polymerization chemistry, and associated fundamental mechanistic studies. We have focused our efforts on four classes of early metal alkyl complexes: (1) cationic group 4 Cp{sub 2}M(R){sup +} complexes (1) which are active species in Cp{sub 2}MX{sub 2}-based Ziegler-Natta olefin polymerization catalyst systems and which catalyze productive C-H activation reactions of heterocycles, (2) neutral (dicarbollide)(Cp*)M(R) complexes (2) which are structurally are electronically very similar to 1, (3) half-sandwich complexes CpM(R){sub 2}(L){sub n}{sup +} which are highly coordinatively and electronically unsaturated, and (4) new group 5 (dicarbollide)(Cp)MR{sub 2} and (dicarbollide){sub 2} MR complexes which are more unsaturated than group 5 Cp{sub 2}M systems due to incorporation of the dicarbollide ligand.

  1. Tuning the Emission of Cationic Iridium (III) Complexes Towards the Red Through Methoxy Substitution of the Cyclometalating Ligand

    PubMed Central

    Hasan, Kamrul; Bansal, Ashu K.; Samuel, Ifor D.W.; Roldán-Carmona, Cristina; Bolink, Henk J.; Zysman-Colman, Eli

    2015-01-01

    The synthesis, characterization and evaluation in solid-state devices of a series of 8 cationic iridium complexes bearing different numbers of methoxy groups on the cyclometallating ligands are reported. The optoelectronic characterization showed a dramatic red shift in the absorption and the emission and a reduction of the electrochemical gap of the complexes when a methoxy group was introduced para to the Ir-C bond. The addition of a second or third methoxy group did not lead to a significant further red shift in these spectra. Emission maxima over the series ranged from 595 to 730 nm. All complexes possessing a motif with a methoxy group at the 3-position of the cyclometalating ligands showed very short emission lifetimes and poor photoluminescence quantum yields whereas complexes having a methoxy group at the 4-position were slightly blue shifted compared to the unsubstituted parent complexes, resulting from the inductively electron withdrawing nature of this directing group on the Ir-C bond. Light-emitting electrochemical cells were fabricated and evaluated. These deep red emitters generally showed poor performance with electroluminescence mirroring photoluminescence. DFT calculations accurately modelled the observed photophysical and electrochemical behavior of the complexes and point to an emission from a mixed charge transfer state. PMID:26179641

  2. Tuning the Emission of Cationic Iridium (III) Complexes Towards the Red Through Methoxy Substitution of the Cyclometalating Ligand

    NASA Astrophysics Data System (ADS)

    Hasan, Kamrul; Bansal, Ashu K.; Samuel, Ifor D. W.; Roldán-Carmona, Cristina; Bolink, Henk J.; Zysman-Colman, Eli

    2015-07-01

    The synthesis, characterization and evaluation in solid-state devices of a series of 8 cationic iridium complexes bearing different numbers of methoxy groups on the cyclometallating ligands are reported. The optoelectronic characterization showed a dramatic red shift in the absorption and the emission and a reduction of the electrochemical gap of the complexes when a methoxy group was introduced para to the Ir-C bond. The addition of a second or third methoxy group did not lead to a significant further red shift in these spectra. Emission maxima over the series ranged from 595 to 730 nm. All complexes possessing a motif with a methoxy group at the 3-position of the cyclometalating ligands showed very short emission lifetimes and poor photoluminescence quantum yields whereas complexes having a methoxy group at the 4-position were slightly blue shifted compared to the unsubstituted parent complexes, resulting from the inductively electron withdrawing nature of this directing group on the Ir-C bond. Light-emitting electrochemical cells were fabricated and evaluated. These deep red emitters generally showed poor performance with electroluminescence mirroring photoluminescence. DFT calculations accurately modelled the observed photophysical and electrochemical behavior of the complexes and point to an emission from a mixed charge transfer state.

  3. Manipulating Mn-Mgk cation complexes to control the charge- and spin-state of Mn in GaN

    NASA Astrophysics Data System (ADS)

    Devillers, Thibaut; Rovezzi, Mauro; Szwacki, Nevill Gonzalez; Dobkowska, Sylwia; Stefanowicz, Wiktor; Sztenkiel, Dariusz; Grois, Andreas; Suffczyński, Jan; Navarro-Quezada, Andrea; Faina, Bogdan; Li, Tian; Glatzel, Pieter; D'Acapito, Francesco; Jakieła, Rafał; Sawicki, Maciej; Majewski, Jacek A.; Dietl, Tomasz; Bonanni, Alberta

    2012-10-01

    Owing to the variety of possible charge and spin states and to the different ways of coupling to the environment, paramagnetic centres in wide band-gap semiconductors and insulators exhibit a strikingly rich spectrum of properties and functionalities, exploited in commercial light emitters and proposed for applications in quantum information. Here we demonstrate, by combining synchrotron techniques with magnetic, optical and ab initio studies, that the codoping of GaN:Mn with Mg allows to control the Mnn+ charge and spin state in the range 3<=n<=5 and 2>=S>=1. According to our results, this outstanding degree of tunability arises from the formation of hitherto concealed cation complexes Mn-Mgk, where the number of ligands k is pre-defined by fabrication conditions. The properties of these complexes allow to extend towards the infrared the already remarkable optical capabilities of nitrides, open to solotronics functionalities, and generally represent a fresh perspective for magnetic semiconductors.

  4. Microcalorimetric and spectroscopic investigation of the antibacterial properties of cationic ytterbium(III)-porphyrin complexes lacking charged peripheral groups.

    PubMed

    Hou, An-Xin; Xue, Zhi; Liu, Yi; Qu, Song-Sheng; Wong, Wai-Kwok

    2007-12-01

    The antibacterial activities towards Escherichia coli of two cationic Yb(III)-monoporphyrin complexes, [Yb(III)(TMP)(H2O)3]Cl (1) and [Yb(III)(TTP)(H2O)3]Cl (2), were investigated at the cellular and sub-cellular levels. The biological effects of the complexes on the growth of E. coli were evaluated by microcalorimetry and by analysis of the resulting metabolic thermogenic curves, from which IC50 values and metabolic parameters such as growth rate and generation time were derived. At the subcellular level, DNA-binding experiments were performed by means of UV/VIS- and fluorescence-titration experiments, as well as by near-infrared (NIR) emission, which revealed that 1 and 2 strongly bind to herring-sperm DNA (HS-DNA), though by different binding modes.

  5. Aqueous complexation of trivalent lanthanide and actinide cations by N,N,N'{sub 2},N'-tetrakis(2-pyridylmethyl)ethylenediamine.

    SciTech Connect

    Beitz, J. V.; Ensor, D. D.; Jensen, M. P.; Morss, L. R.

    1999-06-16

    The aqueous complexation reactions of trivalent lanthanide and actinide cations with the hexadentate ligand N,N,N{prime},N{prime}-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), have been characterized using potentiometric and spectroscopic techniques in 0.1 M NaClO{sub 4} At 25 C, the stability constant of Am(TPEN){sup 3+} is two orders of magnitude larger than that of Sm(TPEN){sup 3+}, reflecting the stronger interactions of the trivalent actinide cations with softer ligands as compared to lanthanide cations.

  6. Role of cholesterol on the transfection barriers of cationic lipid/DNA complexes

    NASA Astrophysics Data System (ADS)

    Pozzi, Daniela; Cardarelli, Francesco; Salomone, Fabrizio; Marchini, Cristina; Amenitsch, Heinz; Barbera, Giorgia La; Caracciolo, Giulio

    2014-08-01

    Most lipid formulations need cholesterol for efficient transfection, but the precise motivation remains unclear. Here, we have investigated the effect of cholesterol on the transfection efficiency (TE) of cationic liposomes made of 1,2-dioleoyl-3-trimethylammonium-propane and dioleoylphosphocholine in Chinese hamster ovary cells. The transfection mechanisms of cholesterol-containing lipoplexes have been investigated by TE, synchrotron small angle X-ray scattering, and laser scanning confocal microscopy experiments. We prove that cholesterol-containing lipoplexes enter the cells using different endocytosis pathways. Formulations with high cholesterol content efficiently escape from endosomes and exhibit a lamellar-nonlamellar phase transition in mixture with biomembrane mimicking lipid formulations. This might explain both the DNA release ability and the high transfection efficiency. These studies highlight the enrichment in cholesterol as a decisive factor for transfection and will contribute to the rational design of lipid nanocarriers with superior TE.

  7. Solution-phase mechanistic study and solid-state structure of a tris(bipyridinium radical cation) inclusion complex.

    PubMed

    Fahrenbach, Albert C; Barnes, Jonathan C; Lanfranchi, Don Antoine; Li, Hao; Coskun, Ali; Gassensmith, Jeremiah J; Liu, Zhichang; Benítez, Diego; Trabolsi, Ali; Goddard, William A; Elhabiri, Mourad; Stoddart, J Fraser

    2012-02-15

    The ability of the diradical dicationic cyclobis(paraquat-p-phenylene) (CBPQT(2(•+))) ring to form inclusion complexes with 1,1'-dialkyl-4,4'-bipyridinium radical cationic (BIPY(•+)) guests has been investigated mechanistically and quantitatively. Two BIPY(•+) radical cations, methyl viologen (MV(•+)) and a dibutynyl derivative (V(•+)), were investigated as guests for the CBPQT(2(•+)) ring. Both guests form trisradical complexes, namely, CBPQT(2(•+))⊂MV(•+) and CBPQT(2(•+))⊂V(•+), respectively. The structural details of the CBPQT(2(•+))⊂MV(•+) complex, which were ascertained by single-crystal X-ray crystallography, reveal that MV(•+) is located inside the cavity of the ring in a centrosymmetric fashion: the 1:1 complexes pack in continuous radical cation stacks. A similar solid-state packing was observed in the case of CBPQT(2(•+)) by itself. Quantum mechanical calculations agree well with the superstructure revealed by X-ray crystallography for CBPQT(2(•+))⊂MV(•+) and further suggest an electronic asymmetry in the SOMO caused by radical-pairing interactions. The electronic asymmetry is maintained in solution. The thermodynamic stability of the CBPQT(2(•+))⊂MV(•+) complex was probed by both isothermal titration calorimetry (ITC) and UV/vis spectroscopy, leading to binding constants of (5.0 ± 0.6) × 10(4) M(-1) and (7.9 ± 5.5) × 10(4) M(-1), respectively. The kinetics of association and dissociation were determined by stopped-flow spectroscopy, yielding a k(f) and k(b) of (2.1 ± 0.3) × 10(6) M(-1) s(-1) and 250 ± 50 s(-1), respectively. The electrochemical mechanistic details were studied by variable scan rate cyclic voltammetry (CV), and the experimental data were compared digitally with simulated data, modeled on the proposed mechanism using the thermodynamic and kinetic parameters obtained from ITC, UV/vis, and stopped-flow spectroscopy. In particular, the electrochemical mechanism of association

  8. Long term stable deep red light-emitting electrochemical cells based on an emissive, rigid cationic Ir(iii) complex

    DOE PAGES

    Namanga, Jude E.; Gerlitzki, Niels; Mallick, Bert; ...

    2017-02-17

    Here, the new cationic iridium complex [Ir(bzq)2(biq)][PF6] (bzq = benzo[h]quinolinato and biq = 2,2'-biquinoline) has been synthesized for application as an emitter in light emitting electrochemical cells (LECs). The molecular structure and crystal packing of this complex were established by single X-ray diffraction (SXRD). The electrochemical and photophysical properties of the complex were examined to determine the frontier orbital energies as well as the optical transitions that led to photoemission. The complex was found to emit at 644 nm and 662 nm for powder and thin films, respectively. A high powder photoluminescence quantum yield of 25% was determined, which ismore » attributed to a reduction in vibrational modes of the complex due to the use of the rigid cyclometalated (C^N) bzq ligand. A LEC with [Ir(bzq)2(biq)][PF6] as the emitter was fabricated which showed a deep red emission (662 nm) with a luminance of 33.65 cd m–2, yielding a current efficiency of 0.33 cd A–1 and a power efficiency of 0.2 lm W–1. Most importantly, the LEC based on [Ir(bzq)2(biq)][PF6] demonstrated a lifetime of 280 hours which is among the longest device lifetimes reported for any deep red light emitting LEC.« less

  9. Efficient catalysis of Nazarov cyclization using a cationic iridium complex possessing adjacent labile coordination sites.

    PubMed

    Janka, Mesfin; He, Wei; Frontier, Alison J; Eisenberg, Richard

    2004-06-09

    The dicationic Ir(III) complex [IrMe(CO)(dppe)(DIB)](BARF)2 having adjacent labile sites has been found to be a very effective catalyst for promoting the Nazarov cyclization of aryl vinyl and divinyl ketones. Spectroscopic evidence for a substate-catalyst complex before cyclization is presented. The efficiency of the cyclization is attributed to the electrophilicity of the Ir(III) complex and substrate activation via chelation.

  10. DNA-METAFECTENE PRO complexation: a physical chemistry study.

    PubMed

    Alatorre-Meda, Manuel; González-Pérez, Alfredo; Rodríguez, Julio R

    2010-07-21

    Complexes formed between cationic liposomes and DNA (also known as lipoplexes or genosomes) have proven, for years now, to be a suitable option for gene delivery to cells, transfection, however, some aspects regarding the liposome-DNA interaction mechanism and complex stability remain still unclear. This work aims to improve the understanding of the poorly defined mechanisms and structural conformation associated with the interaction of METAFECTENE PRO (MEP), a commercial liposomal transfection reagent, with poly-anion DNA at mass ratios around the mass ratio recommended for transfection (L/D congruent with 700). A physical chemistry characterization was conducted at a pH of 6.5 and at a temperature of 25 degrees C by means of dynamic light scattering (DLS), electrophoretic mobility (zeta-potential), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Five parameters important for transfection were determined for the lipoplexes: (i) the hydrodynamic radius, R(H), (ii) the stability with time, (iii) the mass ratio of at which both moieties start to interact, (L/D)(i), (iv) the overall charge, and (v) the morphology. Results in ensemble point to a "beads on a string" conformation, with the lipoplex formation occurring well below isoneutrality from (L/D)(i) congruent with 600. The lipoplexes were found to be stable within at least seven days presenting an average R(H) of 135 nm.

  11. Alkali metal cation complexation by 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds

    DOE PAGES

    Surowiec, Malgorzata A.; Custelcean, Radu; Surowiec, Kazimierz; ...

    2014-04-23

    Alkali metal cation extraction behavior for two series of 1,3-alternate, mono-ionizable calix[4]arene-benzocrown-6 compounds is examined. In Series 1, the proton-ionizable group is a substituent on the benzo group of the polyether ring that directs it away from the crown ether cavity. In Series 2, the proton-ionizable group is attached to one para position in the calixarene framework, thus positioning it over the crown ether ring. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform shows high Cs+ efficiency and selectivity. Single-species extraction pH profiles of Cs+ for Series 1 and 2 ligands with the same proton-ionizable groupmore » are very similar. Thus, association of Cs+ with the calixcrown ring is more important than the the proton-ionizable group’s position in relation to the crown ether cavity. Solid-state structures are presented for two unionized ligands from Series 2, as is a crystal containing two different ionized ligand–Cs+ complexes.« less

  12. Alkali metal cation complexation by 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds

    SciTech Connect

    Surowiec, Malgorzata A.; Custelcean, Radu; Surowiec, Kazimierz; Bartsch, Richard A.

    2014-04-23

    Alkali metal cation extraction behavior for two series of 1,3-alternate, mono-ionizable calix[4]arene-benzocrown-6 compounds is examined. In Series 1, the proton-ionizable group is a substituent on the benzo group of the polyether ring that directs it away from the crown ether cavity. In Series 2, the proton-ionizable group is attached to one para position in the calixarene framework, thus positioning it over the crown ether ring. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform shows high Cs+ efficiency and selectivity. Single-species extraction pH profiles of Cs+ for Series 1 and 2 ligands with the same proton-ionizable group are very similar. Thus, association of Cs+ with the calixcrown ring is more important than the the proton-ionizable group’s position in relation to the crown ether cavity. Solid-state structures are presented for two unionized ligands from Series 2, as is a crystal containing two different ionized ligand–Cs+ complexes.

  13. Cationic cluster formation versus disproportionation of low-valent indium and gallium complexes of 2,2'-bipyridine

    PubMed Central

    Lichtenthaler, Martin R.; Stahl, Florian; Kratzert, Daniel; Heidinger, Lorenz; Schleicher, Erik; Hamann, Julian; Himmel, Daniel; Weber, Stefan; Krossing, Ingo

    2015-01-01

    Group 13 MI compounds often disproportionate into M0 and MIII. Here, however, we show that the reaction of the MI salt of the weakly coordinating alkoxyaluminate [GaI(C6H5F)2]+[Al(ORF)4]− (RF=C(CF3)3) with 2,2'-bipyridine (bipy) yields the paramagnetic and distorted octahedral [Ga(bipy)3]2+•{[Al(ORF)4]−}2 complex salt. While the latter appears to be a GaII compound, both, EPR and DFT investigations assign a ligand-centred [GaIII{(bipy)3}•]2+ radical dication. Surprisingly, the application of the heavier homologue [InI(C6H5F)2]+[Al(ORF)4]− leads to aggregation and formation of the homonuclear cationic triangular and rhombic [In3(bipy)6]3+, [In3(bipy)5]3+ and [In4(bipy)6]4+ metal atom clusters. Typically, such clusters are formed under strongly reductive conditions. Analysing the unexpected redox-neutral cationic cluster formation, DFT studies suggest a stepwise formation of the clusters, possibly via their triplet state and further investigations attribute the overall driving force of the reactions to the strong In−In bonds and the high lattice enthalpies of the resultant ligand stabilized [M3]3+{[Al(ORF)4]−}3 and [M4]4+{[Al(ORF)4]−}4 salts. PMID:26478464

  14. Lipid complexes with cationic peptides and OAKs; their role in antimicrobial action and in the delivery of antimicrobial agents.

    PubMed

    Epand, Raquel F; Mor, Amram; Epand, Richard M

    2011-07-01

    Antimicrobial agents are toxic to bacteria by a variety of mechanisms. One mechanism that is very dependent on the lipid composition of the bacterial membrane is the clustering of anionic lipid by cationic antimicrobial agents. Certain species of oligo-acyl-lysine (OAK) antimicrobial agents are particularly effective in clustering anionic lipids in mixtures mimicking the composition of bacterial membranes. The clustering of anionic lipids by certain cationic antimicrobial agents contributes to the anti-bacterial action of these agents. Bacterial membrane lipids are a determining factor, resulting in some species of bacteria being more susceptible than others. In addition, lipids can be used to increase the effectiveness of antimicrobial agents when administered in vivo. Therefore, we review some of the structures in which lipid mixtures can assemble, to more effectively be utilized as antimicrobial delivery systems. We describe in more detail the complexes formed between mixtures of lipids mimicking bacterial membranes and an OAK and their usefulness in synergizing with antibiotics to overcome bacterial multidrug resistance.

  15. Kinetic and Thermodynamic Studies of Gaseous Metallo-Organic Cationic Complexes

    NASA Astrophysics Data System (ADS)

    Dee, S. Jason; Castleberry, Vanessa A.; Villarroel, Otsmar J.; Laboren, Ivanna E.; Frey, Sarah E.; Bellert, Darrin J.

    2009-06-01

    The construction of a custom fabricated photodissociation spectrometer permits the determination of thermodynamic properties (activation energies), reaction rates, and mechanistic details of bare metal cation mediated σ -bond activation in the gas phase. Specifically, the products and rates resulting from the unimolecular decomposition of the Ni^+Acetaldehyde adduct are monitored after absorption of a known amount of energy. The two dissociative products which are observed in high yield are Ni^+ and Ni^+CO. The Ni^+CO fragment ion could result from the activation of a C-C σ-bond or from the activation of a C-H σ-bond. The rate constant for the decarbonylation of Ni^+Acetaldehyde was approximately 30 percent greater than that of the rate constant for the decarbonylation of Ni^+Acetone. For the decarbonylation of Ni^+Acetone, there needs to be a methide shift, whereas in the decarbonylation of Ni^+Acetaldehyde one could have C-C insertion followed by an aldhyde H-shift. The rate-limiting step of the decarbonylation process will be discussed.

  16. Organelle-specific expression of subunit ND5 of human complex I (NADH dehydrogenase) alters cation homeostasis in Saccharomyces cerevisiae.

    PubMed

    Steffen, Wojtek; Gemperli, Anja C; Cvetesic, Nevena; Steuber, Julia

    2010-09-01

    The ND5 component of the respiratory complex I is a large, hydrophobic subunit encoded by the mitochondrial genome. Its bacterial homologue, the NDH-1 subunit NuoL, acts as a cation transporter in the absence of other NDH-1 subunits. Mutations in human ND5 are frequently observed in neurodegenerative diseases. Wild type and mutant variants of ND5 fused to GFP or a FLAG peptide were targeted to the endoplasmatic reticulum (ER) or the inner mitochondrial membrane of Saccharomyces cerevisiae, which lacks an endogenous complex I. The localization of ND5 fusion proteins was confirmed by microscopic analyses of S. cerevisiae cells, followed by cellular fractionation and immunostaining. The impact of the expression of ND5 fusion proteins on the growth of S. cerevisiae in the presence and absence of added salts was studied. ER-resident ND5 conferred Li(+) sensitivity to S. cerevisiae, which was lost when the E145V variant of ND5 was expressed. All variants of ND5 tested led to increased resistance of S. cerevisiae at high external concentrations of Na(+) or K(+). The data seem to indicate that ND5 influences the salt homeostasis of S. cerevisiae independent of other complex I subunits, and paves the way for functional studies of mutations found in mitochondrially encoded complex I genes.

  17. Cationic Lipid-Nucleic Acid Complexes for Gene Delivery And Silencing: Pathways And Mechanisms for Plasmid Dna And Sirna

    SciTech Connect

    Ewert, K.K.; Zidovska, A.; Ahmad, A.; Bouxsein, N.F.; Evans, H.M.; McAllister, C.S.; Samuel, C.E.; Safinya, C.R.; /SLAC

    2012-07-17

    Motivated by the promises of gene therapy, there is great interest in developing non-viral lipid-based vectors for therapeutic applications due to their low immunogenicity, low toxicity, ease of production, and the potential of transferring large pieces of DNA into cells. In fact, cationic liposome (CL) based vectors are among the prevalent synthetic carriers of nucleic acids (NAs) currently used in gene therapy clinical trials worldwide. These vectors are studied both for gene delivery with CL-DNA complexes and gene silencing with CL-siRNA (short interfering RNA) complexes. However, their transfection efficiencies and silencing efficiencies remain low compared to those of engineered viral vectors. This reflects the currently poor understanding of transfection-related mechanisms at the molecular and self-assembled levels, including a lack of knowledge about interactions between membranes and double stranded NAs and between CL-NA complexes and cellular components. In this review we describe our recent efforts to improve the mechanistic understanding of transfection by CL-NA complexes, which will help to design optimal lipid-based carriers of DNA and siRNA for therapeutic gene delivery and gene silencing.

  18. Gel-derived cation-π stacking films of carbon nanotube-graphene complexes as oxygen cathodes.

    PubMed

    Zhang, Tao; Matsuda, Hirofumi; Zhou, Haoshen

    2014-10-01

    A key challenge in processing carbon nanotubes and their composites for large-scale applications is aggregation. Cation-π stacking interactions have been discovered to disperse heavily entangled single-walled carbon nanotube (SWNT) bundles in ionic liquids (ILs). In this work, we found that a dispersible, silky single-layer graphene (SLG) can be readily gathered together to form a crosslinked gel after entrapping sufficient IL molecular via the likely noncovalent interaction. By incorporating the dispersed SWNTs into the gathered SLG gel synchronously, we prepared solid, finely crosslinked SWNTs-SLG films, assisted by an avenue of 2-step extraction to remove the IL completely. The gel-derived SWNTs-SLG complex film was applied as a support material of oxygen cathodes for Li-O2 batteries. It exhibited a remarkable improved cycleability in comparison to made of SWNTs and SLG alone due to the finely crosslinked feature. Decorated SWNTs and SLG can also form gel-derived complexes via the same process to construct support-catalyst complexes. A SWNTs-SLG film loaded with Ru nanoparticles exhibited not only catalytic effects, but also the ability to suppress the side reactions, and hence stabilized the whole Li-O2 battery. Our research introduces a gel-derived, high-dispersed processing of carbon nanotube-graphene complexes and demonstrates their favorable applications on Li-O2 batteries.

  19. Stabilization of Curcumin by Complexation with Divalent Cations in Glycerol/Water System

    PubMed Central

    Zebib, Bachar; Mouloungui, Zéphirin; Noirot, Virginie

    2010-01-01

    The purpose of present study was to stabilize curcumin food pigment by its complexation with divalent ions like (Zn2+, Cu2+, Mg2+, Se2+), in “green media” and evaluate its stability in vitro compared to curcumin alone. The curcumin complexes were prepared by mechanical mixture of curcumin and sulfate salts of each metal (metal : curcumin 1/1mol) into unconventional and nontoxic glycerol/water solvent. Two stoichiometry of complex were obtained, 1 : 1 and 1 : 2 (metal/curcumin), respectively. On evaluation of in vitro stability, all complexes were found to provide a higher stability from curcumin alone. PMID:20634909

  20. Electronic structure and luminescence of tellurium (IV) halide complexes with guanidine and caesium cations

    NASA Astrophysics Data System (ADS)

    Dotsenko, A. A.; Shcheka, O. L.; Vovna, V. I.; Korochentsev, V. V.; Mirochnik, A. G.; Sedakova, T. V.

    2016-04-01

    The present paper continues a series of publications on the investigation of complex compounds of s2 ions and their properties. The structure of the valence levels of Cs2TeX6, (HGu)2TeCl6 complexes (where X = Cl, Br; HGu+ - guanidinium) is examined, the orbital nature of luminescence excitation is established, and the relationship of properties with the electronic structure is determined by means of X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT).

  1. Mercaptobenzoic acid-palladium(0) complexes as active catalysts for S-benzylation with benzylic alcohols via (η(3)-benzyl)palladium(II) cations in water.

    PubMed

    Hikawa, Hidemasa; Azumaya, Isao

    2014-08-21

    Mercaptobenzoic acid-palladium(0) complexes show high catalytic activity for S-benzylation with benzylic alcohols via the (η(3)-benzyl)palladium(II) cation in water. Notably, these palladium(0) complexes could play an important role in formation of active (η(3)-benzyl)palladium(II) cation complexes followed by S-benzylation. Hammett studies on the rate constants of S-benzylation by various substituted alcohols show good correlation between log(kX/kH) and the σ(+) value of the respective substituents. From the slope, negative ρ values are obtained, suggesting that there is a build-up of positive charge in the transition state. Water plays an important role in the catalytic system for sp(3) C-O bond activation and stabilization of the activated Pd(II) cation species. The catalytic system can be performed using only 2.5 mol% Pd2(dba)3 without the phosphine ligand or other additives.

  2. Cationized bovine serum albumin as gene carrier: Influence of specific secondary structure on DNA complexibility and gene transfection.

    PubMed

    Du, Jianwei; Li, Bangbang; Zhang, Peng; Wang, Youxiang

    2016-07-01

    In this research, BSA, one of the natural rigid globular proteins with ca. 51% of α-helix secondary structure, was utilized to prepare cationized BSA (cBSA) as gene carrier. Tetraethylenepentamine (TEPA) or polyethylenimine (PEI1800) was grafted to BSA with different grafting levels. Based on the circular dichoism (CD) spectra, all cBSA remained α-helical structure to some degree. This was exciting to endow cBSA with quite different DNA complexibility and cellular biology behavior from the random coiled and flexible polycations such as PEI and poly-l-lysine (PLL). Strangely, the DNA condensability decreased with the increment of TEPA or PEI1800 grafting level. Also, the cBSA could condense DNA effectively to form irregular nanoparticles around 50-200nm above N/P ratio of 10. On account of the excellent hydration of BSA, the cBSA/DNA complexes revealed good colloidal stability under physiological salt condition. Cell culture experiments indicated this BSA-based gene carrier possessed good cellular compatibility. Surprisingly, cBSA/DNA complexes could be uptaken excellently by up to 90% cells. This might be owing to the agitation effect of α-helical structure and the positive potential of these complexes. BSA-PEI1800/DNA complexes with quick endosome escape even had transfection efficiency as high as PEI25k/DNA complexes. Overall, this paper provided us the potential of cBSA as gene carrier and might have some instructions in the design of protein-based gene delivery system.

  3. Solid phase extraction of copper(II) by fixed bed procedure on cation exchange complexing resins.

    PubMed

    Pesavento, Maria; Sturini, Michela; D'Agostino, Girolamo; Biesuz, Raffaela

    2010-02-19

    The efficiency of the metal ion recovery by solid phase extraction (SPE) in complexing resins columns is predicted by a simple model based on two parameters reflecting the sorption equilibria and kinetics of the metal ion on the considered resin. The parameter related to the adsorption equilibria was evaluated by the Gibbs-Donnan model, and that related to the kinetics by assuming that the ion exchange is the adsorption rate determining step. The predicted parameters make it possible to evaluate the breakthrough volume of the considered metal ion, Cu(II), from different kinds of complexing resins, and at different conditions, such as acidity and ionic composition.

  4. Synthesis and antimicrobial activity of polysaccharide alginate derived cationic surfactant-metal(II) complexes.

    PubMed

    Tawfik, Salah M; Hefni, Hassan H

    2016-01-01

    New natural polysaccharide carbohydrate derivatives of sodium alginate surfactant and its cobalt, copper and zinc complexes were synthesized. Structures of the synthesized compounds are reported using FTIR, (1)H NMR and UV-vis. The critical micelle concentration (CMC) value of the alginate surfactant and its metal complexes in aqueous solution was found out from surface tension measurements. Surface tension data at different temperatures served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔGmic, ΔHmic, ΔSmic) and adsorption (ΔGads, ΔGads, ΔSads). The surface activities of the synthesized polymeric surfactant and its metal complexes were influenced by their chemical structures and the type of the transition metals. These compounds were evaluated against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and fungi (Candida albicans and Asperigllus niger). The antibacterial and antifungal screening tests of the alginate surfactant metal complexes have shown good results compared to its precursor alginate surfactant.

  5. Indium donor complexes with cation vacancies in CdTe and ZnSe

    SciTech Connect

    Griffith, J.W.; Lundquist, R.; Platzer, R.; Gardner, J.A.; Karczewski, G.; Furdyna, J.K.

    1993-11-01

    Very dilute (10{sub 12} cm{sup {minus}3}) indium donors in CdTe and ZnSe powders and in CdTe single crystals were investigated using {sup 111}In Perturbed angular correlation spectroscopy. Most indium atoms are in uncomplexed sites but can form weakly-bound complexes with native defects in very defective material. The only complex observed in CdTe is an indium-Cd vacancy pair. The CdTe in which these pairs occur is apparently n-type, most Cd vacancies are free and doubly-charged, and the binding energy with indium is 0.15 eV. In ZnSe, indium can pair with a Zn vacancy or with some other presently unidentified defect. These complexes form in ZnSe containing large concentrations of both free Zn vacancies and complexes of Zn vacancies with other defects. In CdTe, the pair formation equilibration time constant is two days at 15C,an implication that Cd vacancies are mobile at room temperature. Lattice relaxation around a Cd vacancy in CdTe was probed by single crystal PAC experiments.

  6. RgBF2(+) complexes (Rg = Ar, Kr, and Xe): the cations with large stabilities.

    PubMed

    Lv, Zhi; Chen, Guang-Hui; Li, Dan; Wu, Di; Huang, Xiao-Chun; Li, Zhi-Ru; Liu, Wen-Guang

    2011-04-21

    Rare gas containing cations with general formula [Rg, B, 2F](+) have been investigated theoretically by second-order Mo̸ller-Plesset perturbation, coupled cluster, and complete active space self-consistent field levels of theory with correlation-consistent basis sets. Totally two types of minima, i.e., boron centered C(2) (v) symmetried RgBF(2) (+) (Rg = Ar, Kr, and Xe) which can be viewed as loss of F(-) from FRgBF(2) and linear FRgBF(+) (Rg = Kr and Xe) are obtained at the CCSD(T)∕aug-cc-pVTZ∕SDD and CASSCF(10,8)∕aug-cc-pVTZ∕SDD levels, respectively. It is shown that the RgBF(2) (+) are global minima followed by FRgBF(+) at 170.9 and 142.2 kcal∕mol on the singlet potential-energy surfaces of [Rg, B, 2F](+) (Rg = Kr and Xe) at the CASPT2(10,8) ∕aug-cc-pVTZ∕SDD∕∕CASSCF(10,8)∕aug-cc-pVTZ∕SDD, respectively. The interconversion barrier heights between RgBF(2) (+) and FRgBF(+) (Rg = Kr and Xe) are at least 39 kcal∕mol. In addition, no dissociation transition state associated with RgBF(2) (+) and FRgBF(+) can be found. This suggests that RgBF(2) (+) (Rg = Ar, Kr, and Xe) can exist as both thermodynamically and kinetically stable species, while linear FRgBF(+) (Rg = Kr and Xe) can exist as metastable species compared with the lowest dissociation limit energies just like isoelectronic linear FRgBO and FRgBN(-). From natural bond orbital and atoms-in-molecules calculations, it is found that the positive charge is mainly located on Rg and boron atoms for both types of minima, the Rg-B bonds of ArBF(2) (+), KrBF(2) (+), and XeBF(2) (+) are mostly electrostatic, thus can be viewed as ion-induced dipole interaction; while that of linear FKrBF(+) and FXeBF(+) are covalent in nature. The previous experimental observation of ArBF(2) (+) by Pepi et al. [J. Phys. Chem. B. 110, 4492 (2006)] should correspond to C(2) (v) minimum. The presently predicted spectroscopies of KrBF(2) (+), XeBF(2) (+), FKrBF(+), and FXeBF(+) should be helpful for their experimental

  7. Correlation between pH dependence of O2 evolution and sensitivity of Mn cations in the oxygen-evolving complex to exogenous reductants.

    PubMed

    Semin, Boris K; Davletshina, Lira N; Rubin, Andrei B

    2015-08-01

    Effects of pH, Ca(2+), and Cl(-) ions on the extraction of Mn cations from oxygen-evolving complex (OEC) in Ca-depleted photosystem II (PSII(-Ca)) by exogenous reductants hydroquinone (H2Q) and H2O2 were studied. Two of 4 Mn cations are released by H2Q and H2O2 at pHs 5.7, 6.5, and 7.5, and their extraction does not depend on the presence of Ca(2+) and Cl(-) ions. One of Mn cations ("resistant" Mn cation) cannot be extracted by H2Q and H2O2 at any pH. Extraction of 4th Mn ion ("flexible" Mn cation) is sensitive to pH, Ca(2+), and Cl(-). This Mn cation is released by reductants at pH 6.5 but not at pHs 5.7 and 7.5. A pH dependence curve of the oxygen-evolving activity in PSII(-Ca) membranes (in the presence of exogenous Ca(2+)) has a bell-shaped form with the maximum at pH 6.5. Thus, the increase in the resistance of flexible Mn cation in OEC to the action of reductants at acidic and alkaline pHs coincides with the decrease in oxygen evolution activity at these pHs. Exogenous Ca(2+) protects the extraction of flexible Mn cation at pH 6.5. High concentration of Cl(-) anions (100 mM) shifts the pH optimum of oxygen evolution to alkaline region (around pH 7.5), while the pH of flexible Mn extraction is also shifted to alkaline pH. This result suggests that flexible Mn cation plays a key role in the water-splitting reaction. The obtained results also demonstrate that only one Mn cation in Mn4 cluster is under strong control of calcium. The change in the flexible Mn cation resistance to exogenous reductants in the presence of Ca(2+) suggests that Ca(2+) can control the redox potential of this cation.

  8. A Cationic Unsaturated Platinum(II) Complex that Promotes the Tautomerization of Acetylene to Vinylidene.

    PubMed

    Ortega-Moreno, Laura; Peloso, Riccardo; López-Serrano, Joaquín; Iglesias-Sigüenza, Javier; Maya, Celia; Carmona, Ernesto

    2017-03-01

    Complex [PtMe2 (PMe2 ArDipp2 )] (1), which contains a tethered terphenyl phosphine (ArDipp2 =2,6-(2,6-(i) Pr2 C6 H3 )2 C6 H3 ), reacts with [H(Et2 O)2 ]BArF (BArF(-) =B[3,5-(CF3 )2 C6 H3 ]4(-) ) to give the solvent (S) complex [PtMe(S)(PMe2 ArDipp2 )](+) (2⋅S). Although the solvent molecule is easily displaced by a Lewis base (e.g., CO or C2 H4 ) to afford the corresponding adducts, treatment of 2⋅S with C2 H2 yielded instead the allyl complex [Pt(η(3) -C3 H5 )(PMe2 ArDipp2 )](+) (6) via the alkyne intermediate [PtMe(η(2) -C2 H2 )(PMe2 ArDipp2 )](+) (5). Deuteration experiments with C2 D2 , and kinetic and theoretical investigations demonstrated that the conversion of 5 into 6 involves a Pt(II) -promoted HC≡CH to :C=CH2 tautomerization in preference over acetylene migratory insertion into the Pt-Me bond.

  9. Highly sensitive and selective difunctional ruthenium(II) complex-based chemosensor for dihydrogen phosphate anion and ferrous cation.

    PubMed

    Zheng, Ze-Bao; Duan, Zhi-Ming; Ma, Ying-Ying; Wang, Ke-Zhi

    2013-03-04

    The anion-interaction properties of a Ru(II) complex of [Ru(bpy)2(Htppip)](ClO4)2·H2O·DMF (RuL) {bpy =2,2'-bipyridine and Htppip =2-(4-(2,6-di(pyridin-2-yl)pyridin-4-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} were thoroughly investigated in CH3CN and CH3CN/H2O (50:1, v/v) solutions by UV-visible absorption, emission, and (1)H NMR spectra. These analyses revealed that RuL acts as an efficient "turn on" emission sensor for H2PO4(-), and a "turn off" sensor for F(-) and OAc(-); in addition, RuL exhibited slightly disturbed emission spectra in the presence of the other anions studied (Cl(-), Br(-), I(-), NO3(-), and ClO4(-)). The cation-sensing properties of RuL were also studied in both neat CH3CN and aqueous 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer (pH = 7.2)/CH3CN (71/1, v/v) solutions. RuL was found to exhibit a colorimetric sensing ability that was highly selective for Fe(2+), as evidenced by an obvious color change from pale yellow to light red-purple to the naked eye over the other cations studied (Na(+), Mg(2+), Ba(2+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), and Ag(+)). To obtain insights into the possible binding modes and the sensing mechanisms, (1)H NMR spectral analysis, luminescence lifetime measurements, and density functional theoretical calculations were also performed.

  10. Reversible dissociation and ligand-glutathione exchange reaction in binuclear cationic tetranitrosyl iron complex with penicillamine.

    PubMed

    Syrtsova, Lidia; Sanina, Natalia; Lyssenko, Konstantin; Kabachkov, Evgeniy; Psikha, Boris; Shkondina, Natal'ja; Pokidova, Olesia; Kotelnikov, Alexander; Aldoshin, Sergey

    2014-01-01

    This paper describes a comparative study of the decomposition of two nitrosyl iron complexes (NICs) with penicillamine thiolic ligands [Fe2(SC5H11NO2)2(NO)4]SO4 ·5H2O (I) and glutathione- (GSH-) ligands [Fe2(SC10H17N3O6)2(NO)4]SO4 ·2H2O (II), which spontaneously evolve to NO in aqueous medium. NO formation was measured by a sensor electrode and by spectrophotometric methods by measuring the formation of a hemoglobin- (Hb-) NO complex. The NO evolution reaction rate from (I)  k 1 = (4.6 ± 0.1)·10(-3) s(-1) and the elimination rate constant of the penicillamine ligand k 2 = (1.8 ± 0.2)·10(-3) s(-1) at 25°C in 0.05 M phosphate buffer,  pH 7.0, was calculated using kinetic modeling based on the experimental data. Both reactions are reversible. Spectrophotometry and mass-spectrometry methods have firmly shown that the penicillamine ligand is exchanged for GS(-) during decomposition of 1.5·10(-4) M (I) in the presence of 10(-3) M GSH, with 76% yield in 24 h. As has been established, such behaviour is caused by the resistance of (II) to decomposition due to the higher affinity of iron to GSH in the complex. The discovered reaction may impede S-glutathionylation of the essential enzyme systems in the presence of (I) and is important for metabolism of NIC, connected with its antitumor activity.

  11. Enhancing the luminescence properties and stability of cationic iridium(III) complexes based on phenylbenzoimidazole ligand: a combined experimental and theoretical study.

    PubMed

    Shan, Guo-Gang; Li, Hai-Bin; Sun, Hai-Zhu; Cao, Hong-Tao; Zhu, Dong-Xia; Su, Zhong-Min

    2013-08-21

    Herein we designed and synthesized a series of cationic iridium(III) complexes with a phenylbenzoimidazole-based cyclometalated ligand, containing different numbers of carbazole moieties from zero to three (complexes 1-4). The photophysical and electrochemical properties of this series have been systematically investigated. The complexes exhibit strong luminescence in both solution and in neat films, as well as excellent redox reversibility. Introducing carbazole groups into the complexes is found to lead to substantially enhanced photoluminescence quantum efficiency in the neat film, but has little effect on the emitting color and excited-state characteristics as supported by density functional theory (DFT) results. DFT calculations also suggest that functionalized complexes 2-4 reveal better hole-transporting properties than 1. More importantly, all complexes effectively reduce the degradation reaction to some extent in metal-centered (³MC) excited-states, demonstrating their stability. Further studies indicate that restriction of opening of the structures in the ³MC state is caused by the unique molecular conformation of the phenylbenzoimidazole ligand, which is first demonstrated here in cationic iridium(III) complexes without intramolecular π-π stacking. These results presented here would provide valuable information for designing and synthesizing highly efficient and stable cationic iridium(III) complexes suitable for the optical devices.

  12. Binding of cationic porphyrin to isolated DNA and nucleoprotein complex: quantitative analysis of binding forms under various experimental conditions.

    PubMed

    Zupán, Kristóf; Herényi, Levente; Tóth, Katalin; Egyeki, Marianna; Csík, Gabriella

    2005-11-15

    We studied the complex formation of tetrakis(4-N-methylpyridyl)porphyrin (TMPyP) with double stranded DNAs and T7 phage nucleoprotein complex. We analyzed the effect of base pair composition of DNA, the presence of capsid protein, and the composition of the microenvironment on the distribution of TMPyP between binding forms as determined by the decomposition of porphyrin absorption spectra. No difference was found in the amount of bound TMPyP between DNAs of various base compositions; however, the ratio of TMPyP binding forms depends on the AT/GC ratio. The presence of protein capsid opposes the binding of TMPyP to DNA. This behavior offers a possibility to investigate the protein capsid integrity due to the analysis of porphyrin binding. Increasing ionic strength of monovalent ions decreases the amount of bound porphyrin through the inhibition of intercalation, but does not influence the quantity of groove-binding forms when TMPyP interacts with isolated DNA. In the case of the nucleoprotein complex the groove-binding is also inhibited already at 140 mM ionic strength. The presence of 1 mM divalent cations (Mg(2+), Ca(2+), Cu(2+) and Ni(2+)) in a buffer solution of 70 mM ionic strength does not influence significantly the free to bound ration of TMPyP when it interacts with isolated DNA. The contribution of binding forms is remarkably different in Mg(2+)/Ca(2+) and Cu(2+)/Ni(2+) containing solutions. Transition metals significantly decrease the binding sites for intercalation in both DNA and nucleoprotein complex, but facilitate the groove-binding of TMPyP to isolated DNA.

  13. Large Size Color-tunable Electroluminescence from Cationic Iridium Complexes-based Light-emitting Electrochemical Cells

    PubMed Central

    Zeng, Qunying; Li, Fushan; Guo, Tailiang; Shan, Guogang; Su, Zhongmin

    2016-01-01

    Solution-processable light-emitting electrochemical cells (LECs) with simple device architecture have become an attractive candidate for application in next generation lighting and flat-panel displays. Herein, single layer LECs employing two cationic Ir(III) complexes showing highly efficient blue-green and yellow electroluminescence with peak current efficiency of 31.6 cd A−1 and 40.6 cd A−1, respectively, have been reported. By using both complexes in the device, color-tunable LECs with a single spectral peak in the wavelength range from 499 to 570 nm were obtained by varying their rations. In addition, the fabrication of efficient LECs was demonstrated based on low cost doctor-blade coating technique, which was compatible with the roll to roll fabrication process for the large size production. In this work, for the first time, 4 inch LEC devices by doctor-blade coating were fabricated, which exhibit the efficiencies of 23.4 cd A−1 and 25.4 cd A−1 for the blue-green and yellow emission, respectively. The exciting results indicated that highly efficient LECs with controllable color could be realized and find practical application in large size lighting and displays. PMID:27278527

  14. The Relation between the Physical Properties of Self-Assembling Cationic Lipid:DNA Complexes and Gene Delivery

    NASA Astrophysics Data System (ADS)

    Ahmad, A.; Slack, N. L.; Evans, Heather M.; Lin, Alison; Martin, A.; Safinya, C. R.

    2000-03-01

    The use of cationic lipids (CL) as carriers of genes (DNA sequences) for delivery in cells is a promising alternative to viral-carriers. Previous work on CL:DNA complexes has focused on binary mixtures of lipids and has shown that the optimal gene delivery vehicle may be mediated by physical properties of the lipid self-assembly(1). Using x-ray diffraction and biological assays, we show that membrane charge density and geometric shape may be universal parameters for successful gene delivery by binary CL mixtures in vitro. Preliminary results from complexes containing novel ternary CL mixtures further elucidate key parameters for gene delivery. Funded by NIH R01-GM59288-01 and R37-AI12520-24, UCBiotechnology Research and Education Program (97-02), NSF-DMR-9972246. 1. J. Raedler et al, Science 275, 810 (1997), Koltover et al Science 281, 78-81 (1998), Koltover et al, Biophysical Journal 77, 95 (1999), A. J. Lin, N. L. Slack, A. Ahmad, I. Koltover, C. X. George, C. E. Samuel, C. R. Safinya, Journal of Drug Targeting (to appear)

  15. Near-infrared spectroscopy and anharmonic theory of the H2O(+)Ar1,2 cation complexes.

    PubMed

    Wagner, J Philipp; McDonald, David C; Duncan, Michael A

    2017-09-14

    Weakly bound complexes of the water radical cation with argon (H2O(+)Arn, n = 1,2) were generated by an electrical discharge/supersonic expansion and probed with mid- and near-infrared photodissociation spectroscopy in the 2050-4550 and 4850-7350 cm(-1) regions. To elucidate these spectra, these complexes were studied computationally at the CCSD(T) level including anharmonicity with the VPT2 method. The comparison between experiment and predicted spectra demonstrates that the VPT2 method is adequate to capture most of the vibrational band positions and their intensities. In addition to the fundamentals, overtones of the symmetric and the asymmetric water stretches and their combination were detected. Additional bands were assigned to combinations of the overtone of the bound O-H stretch with multiple excitation levels of the intermolecular Ar-H stretch. H2O(+)Ar2 could not be dissociated in the higher frequency region (4850-7350 cm(-1)).

  16. Large Size Color-tunable Electroluminescence from Cationic Iridium Complexes-based Light-emitting Electrochemical Cells

    NASA Astrophysics Data System (ADS)

    Zeng, Qunying; Li, Fushan; Guo, Tailiang; Shan, Guogang; Su, Zhongmin

    2016-06-01

    Solution-processable light-emitting electrochemical cells (LECs) with simple device architecture have become an attractive candidate for application in next generation lighting and flat-panel displays. Herein, single layer LECs employing two cationic Ir(III) complexes showing highly efficient blue-green and yellow electroluminescence with peak current efficiency of 31.6 cd A‑1 and 40.6 cd A‑1, respectively, have been reported. By using both complexes in the device, color-tunable LECs with a single spectral peak in the wavelength range from 499 to 570 nm were obtained by varying their rations. In addition, the fabrication of efficient LECs was demonstrated based on low cost doctor-blade coating technique, which was compatible with the roll to roll fabrication process for the large size production. In this work, for the first time, 4 inch LEC devices by doctor-blade coating were fabricated, which exhibit the efficiencies of 23.4 cd A‑1 and 25.4 cd A‑1 for the blue-green and yellow emission, respectively. The exciting results indicated that highly efficient LECs with controllable color could be realized and find practical application in large size lighting and displays.

  17. Long-Residency Hydration, Cation Binding, and Dynamics of Loop E/Helix IV rRNA-L25 Protein Complex

    PubMed Central

    Réblová, Kamila; Špačková, Nad'a; Koča, Jaroslav; Leontis, Neocles B.; Šponer, Jiří

    2004-01-01

    Molecular dynamics simulations of RNA-protein complex between Escherichia coli loop E/helix IV (LE/HeIV) rRNA and L25 protein reveal a qualitative agreement between the experimental and simulated structures. The major groove of LE is a prominent rRNA cation-binding site. Divalent cations rigidify the LE major groove geometry whereas in the absence of divalent cations LE extensively interacts with monovalent cations via inner-shell binding. The HeIV region shows bistability of its major groove explaining the observed differences between x-ray and NMR structures. In agreement with the experiments, the simulations suggest that helix-α1 of L25 is the least stable part of the protein. Inclusion of Mg2+ cations into the simulations causes perturbation of basepairing at the LE/HeIV junction, which does not, however, affect the protein binding. The rRNA-protein complex is mediated by a number of highly specific hydration sites with long-residing water molecules and two of them are bound throughout the entire 24-ns simulation. Long-residing water molecules are seen also outside the RNA-protein contact areas with water-binding times substantially enhanced compared to simulations of free RNA. Long-residency hydration sites thus represent important elements of the three-dimensional structure of rRNA. PMID:15339800

  18. Lariat ethers with fluoroaryl side-arms: a study of CFmetal cation interaction in the complexes of N-(o-fluoroaryl)azacrown ethers.

    PubMed

    Sazonov, Petr K; Minacheva, Lidiya Kh; Churakov, Andrei V; Sergienko, Vladimir S; Artamkina, Galina A; Oprunenko, Yuri F; Beletskaya, Irina P

    2009-02-07

    New lariat ethers, N-(o-fluorophenyl)aza-15-crown-5 (F-A15C5) and N,N'-bis(o-fluorophenyl)diaza-18-crown-6 (F(2)-A(2)18C6), were prepared by the N-arylation of the corresponding azacrown ethers. The interaction of the ligands with metal cations was studied in solution by (1)H and (19)F NMR (in acetone-d(6)) and UV spectroscopy (MeOH) confirming the formation of complexes of F(2)-A(2)18C6 with K(+), Na(+), Ag(+), Ba(2+), Pb(2+) and of F-A15C5 with Na(+) and giving evidence of CFmetal cation interaction. Cation binding constants (beta, evaluated by UV titration method), demonstrate that F-A15C5 and F(2)-A(2)18C6 form more stable complexes than their fluorine-free analogs. The effect depends on the nature of the metal cation and is at a maximum for hard, singly charged cations (up to 3 logbeta units for K(+) complex of F(2)-A(2)18C6). The X-ray structures of complexes [Pb(F(2)-A(2)18C6)(H(2)O)](ClO(4))(2) () and [Ba(F(2)-A(2)18C6)(ClO(4))(2)] () reveal short Pb-F (2.805 A) and Ba-F (2.965 A) contacts. Complex is centrosymmetric (C(i)), while complex has C(2) symmetry with one-side coordination of o-fluorophenyl groups to Pb(2+). This "one-side" coordination mode of Pb(2+) is indicative of a partial localization of the Pb(2+) lone pair.

  19. Luminescent cyclometalated iridium(III) polypyridine di-2-picolylamine complexes: synthesis, photophysics, electrochemistry, cation binding, cellular internalization, and cytotoxic activity.

    PubMed

    Lee, Pui-Kei; Law, Wendell Ho-Tin; Liu, Hua-Wei; Lo, Kenneth Kam-Wing

    2011-09-05

    A series of luminescent cyclometalated iridium(III) polypyridine complexes containing a di-2-picolylamine (DPA) moiety [Ir(N^C)(2)(phen-DPA)](PF(6)) (phen-DPA = 5-(di-2-picolylamino)-1,10-phenanthroline) (HN^C = 2-phenylpyridine, Hppy (1a), 2-(4-methylphenyl)pyridine, Hmppy (2a), 2-phenylquinoline, Hpq (3a), 4-(2-pyridyl)benzaldehyde, Hpba (4a)) and their DPA-free counterparts [Ir(N^C)(2)(phen-DMA)](PF(6)) (phen-DMA = 5-(dimethylamino)-1,10-phenanthroline) (HN^C = Hppy (1b), Hmppy (2b), Hpq (3b), Hpba (4b)) have been synthesized and characterized, and their photophysical and electrochemical properties investigated. Photoexcitation of the complexes in fluid solutions at 298 K and in alcohol glass at 77 K resulted in intense and long-lived luminescence. The emission of the complexes has been assigned to a triplet metal-to-ligand charge-transfer ((3)MLCT) (dπ(Ir) → π*(N^N)) or triplet intraligand ((3)IL) (π → π*) (N^C) excited state and with substantial mixing of triplet amine-to-ligand charge-transfer ((3)NLCT) (n → π*) (N^N) character, depending on the identity of the cyclometalating and diimine ligands. Electrochemical measurements revealed an irreversible amine oxidation wave at ca. +1.1 to +1.2 V vs saturated calomel electrode, a quasi-reversible iridium(IV/III) couple at ca. +1.2 to +1.6 V, and a reversible diimine reduction couple at ca. -1.4 to -1.5 V. The cation-binding properties of these complexes have been studied by emission spectroscopy. Upon binding of zinc ion, the iridium(III) DPA complexes displayed 1.2- to 5.4-fold emission enhancement, and the K(d) values determined were on the order of 10(-5) M. Job's plot analysis confirmed that the binding stoichiometry was 1:1. Additionally, selectivity studies showed that the iridium(III) DPA complexes were more sensitive toward zinc ion among various transition metal ions examined. Furthermore, the cytotoxicity of these complexes toward human cervix epithelioid carcinoma cells have been studied by

  20. Infrared and electronic spectroscopy of benzene-ammonia cluster radical cations [C(6)H(6)(NH(3))(1,2)](+): observation of isolated and microsolvated σ-complexes.

    PubMed

    Mizuse, Kenta; Hasegawa, Hayato; Mikami, Naohiko; Fujii, Asuka

    2010-10-28

    We report infrared (IR) and electronic spectra of benzene-ammonia cluster radical cations [C(6)H(6)(NH(3))(n)](+) (n = 1 and 2) in the gas phase to explore cluster structures and chemical reactivity of the simplest aromatic radical cation with base (nucleophile) molecules. The electronic spectra in the visible region indicate that these cluster cations no longer have the benzene cation chromophore as a result of an intracluster reaction. Analyses of the IR spectra, on the basis quantum chemical calculations and the vibration-internal rotation analysis, reveal that both [C(6)H(6)(NH(3))(1,2)](+) form σ-complex structures, in which the ammonia moiety is covalently bonded to the benzene moiety due to the intracluster nucleophilic addition. For [C(6)H(6)(NH(3))(2)](+), it is also shown that the second ammonia molecule solvates the σ-complex core via a N-H···N hydrogen bond. Such σ-complex structures are generally supposed to be a key intermediate of aromatic substitution reactions. The observed mass spectra and energetics calculations, however, show that [C(6)H(6)(NH(3))(n)](+) systems are inert for aromatic substitutions. The present experimental observations indicate the inherent stability of these σ-complex structures, even though they do not show the aromatic substitution reactivity.

  1. Determination of the comparative complexing ability of cyclophosphate anions with respect to the yttrium cation

    SciTech Connect

    Lazarevski, E.V.; Chudinova, N.N.; Kubasova, L.V.

    1987-08-01

    On the basis of our study of the solubility of YPO/sub 4/ x 2H/sub 2/O in solutions of the cyclophosphates Na/sub 3/P/sub 3/O/sub 9/, Na/sub 4/P/sub 4/O/sub 12/, and Na/sub 8/P/sub 8/O/sub 24/ and the chain phosphates Na/sub 4/P/sub 2/O/sub 7/, Na/sub 5/P/sub 3/O/sub 10/, and Graham's salt we have established that according to effective complexing ability (per phosphorus atom) the indicated ligands form the series (PO/sub 3/)/sub x//sup x-/ > P/sub 8/O/sub 24//sup 8 -/ infinity P/sub 6/O/sub 18//sup 6 -/ > P/sub 3/O/sub 10//sup 5 -/ > P/sub 4/O/sub 12//sup 4 -/ > P/sub 2/O/sub 7//sup 4 -/ > P/sub 3/O/sub 9//sup 3 -/, which correlates with the anion charge. The authors have obtained estimated values of 2.5 x 10/sup -6/, 4.8 x 10/sup -7/, 2.5 x 10/sup -8/, and 1.4 x 10/sup -8/ for the instability constants of the complexes YP/sub 3/O/sub 9/, YP/sub 4/O/sub 12/-, YP/sub 6/O/sub 18//sup 3 -/, and YP/sub 8/O/sub 14//sup 5 -/, respectively.

  2. Cationic boranes for the complexation of fluoride ions in water below the 4 ppm maximum contaminant level.

    PubMed

    Kim, Youngmin; Gabbaï, François P

    2009-03-11

    In search of a molecular receptor that could bind fluoride ions in water below the maximum contaminant level of 4 ppm set by the Environmental Protection Agency (EPA), we have investigated the water stability and fluoride binding properties of a series of phosphonium boranes of general formula [p-(Mes(2)B)C(6)H(4)(PPh(2)R)](+) with R = Me ([1](+)), Et ([2](+)), n-Pr ([3](+)), and Ph ([4](+)). These phosphonium boranes are water stable and react reversibly with water to form the corresponding zwitterionic hydroxide complexes of general formula p-(Mes(2)(HO)B)C(6)H(4)(PPh(2)R). They also react with fluoride ions to form the corresponding zwitterionic fluoride complexes of general formula p-(Mes(2)(F)B)C(6)H(4)(PPh(2)R). Spectrophotometric acid-base titrations carried out in H(2)O/MeOH (9:1 vol.) afford pK(R+) values of 7.3(+/-0.07) for [1](+), 6.92(+/-0.1) for [2](+), 6.59(+/-0.08) for [3](+), and 6.08(+/-0.09) for [4](+), thereby indicating that the Lewis acidity of the cationic boranes increases in following order: [1](+) < [2](+) < [3](+) < [4](+). In agreement with this observation, fluoride titration experiments in H(2)O/MeOH (9:1 vol.) show that the fluoride binding constants (K = 840(+/-50) M(-1) for [1](+), 2500(+/-200) M(-1) for [2](+), 4000(+/-300) M(-1) for [3](+), and 10 500(+/-1000) M(-1) for [4](+)) increase in the same order. These results show that the Lewis acidity of the cationic boranes increases with their hydrophobicity. The resulting Lewis acidity increase is substantial and exceeds 1 order of magnitude on going from [1](+) to [4](+). In turn, [4](+) is sufficiently fluorophilic to bind fluoride ions below the EPA contaminant level in pure water. These results indicate that phosphonium boranes related to [4](+) could be used as molecular recognition units in chemosensors for drinking water analysis.

  3. Protection against tuberculosis by a single intranasal administration of DNA-hsp65 vaccine complexed with cationic liposomes

    PubMed Central

    Rosada, Rogério S; Torre, Lucimara Gaziola de la; Frantz, Fabiani G; Trombone, Ana PF; Zárate-Bladés, Carlos R; Fonseca, Denise M; Souza, Patrícia RM; Brandão, Izaíra T; Masson, Ana P; Soares, Édson G; Ramos, Simone G; Faccioli, Lúcia H; Silva, Célio L; Santana, Maria HA; Coelho-Castelo, Arlete AM

    2008-01-01

    Background The greatest challenges in vaccine development include optimization of DNA vaccines for use in humans, creation of effective single-dose vaccines, development of delivery systems that do not involve live viruses, and the identification of effective new adjuvants. Herein, we describe a novel, simple technique for efficiently vaccinating mice against tuberculosis (TB). Our technique consists of a single-dose, genetic vaccine formulation of DNA-hsp65 complexed with cationic liposomes and administered intranasally. Results We developed a novel and non-toxic formulation of cationic liposomes, in which the DNA-hsp65 vaccine was entrapped (ENTR-hsp65) or complexed (COMP-hsp65), and used to immunize mice by intramuscular or intranasal routes. Although both liposome formulations induced a typical Th1 pattern of immune response, the intramuscular route of delivery did not reduce the number of bacilli. However, a single intranasal immunization with COMP-hsp65, carrying as few as 25 μg of plasmid DNA, leads to a remarkable reduction of the amount of bacilli in lungs. These effects were accompanied by increasing levels of IFN-γ and lung parenchyma preservation, results similar to those found in mice vaccinated intramuscularly four times with naked DNA-hsp65 (total of 400 μg). Conclusion Our objective was to overcome the significant obstacles currently facing DNA vaccine development. Our results in the mouse TB model showed that a single intranasal dose of COMP-hsp65 elicited a cellular immune response that was as strong as that induced by four intramuscular doses of naked-DNA. This formulation allowed a 16-fold reduction in the amount of DNA administered. Moreover, we demonstrated that this vaccine is safe, biocompatible, stable, and easily manufactured at a low cost. We believe that this strategy can be applied to human vaccines to TB in a single dose or in prime-boost protocols, leading to a tremendous impact on the control of this infectious disease. PMID

  4. Infrared spectra of the Li+-(H2)n (n=1-3) cation complexes

    NASA Astrophysics Data System (ADS)

    Emmeluth, C.; Poad, B. L. J.; Thompson, C. D.; Weddle, G. H.; Bieske, E. J.

    2007-05-01

    The Li+-(H2)n n =1-3 complexes are investigated through infrared spectra recorded in the H-H stretch region (3980-4120cm-1) and through ab initio calculations at the MP2/aug-cc-pVQZ level. The rotationally resolved H-H stretch band of Li+-H2 is centered at 4053.4cm-1 [a -108cm-1 shift from the Q1(0) transition of H2]. The spectrum exhibits rotational substructure consistent with the complex possessing a T-shaped equilibrium geometry, with the Li+ ion attached to a slightly perturbed H2 molecule. Around 100 rovibrational transitions belonging to parallel Ka=0-0, 1-1, 2-2, and 3-3 subbands are observed. The Ka=0-0 and 1-1 transitions are fitted by a Watson A-reduced Hamiltonian yielding effective molecular parameters. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 2.056Å increasing by 0.004Å when the H2 subunit is vibrationally excited. The spectroscopic data are compared to results from rovibrational calculations using recent three dimensional Li+-H2 potential energy surfaces [Martinazzo et al., J. Chem. Phys. 119, 11241 (2003); Kraemer and Špirko, Chem. Phys. 330, 190 (2006)]. The H-H stretch band of Li+-(H2)2, which is centered at 4055.5cm-1 also exhibits resolved rovibrational structure. The spectroscopic data along with ab initio calculations support a H2-Li+-H2 geometry, in which the two H2 molecules are disposed on opposite sides of the central Li+ ion. The two equivalent Li+⋯H2 bonds have approximately the same length as the intermolecular bond in Li+-H2. The Li+-(H2)3 cluster is predicted to possess a trigonal structure in which a central Li+ ion is surrounded by three equivalent H2 molecules. Its infrared spectrum features a broad unresolved band centered at 4060cm-1.

  5. Infrared consequence spectroscopy of gaseous protonated and metal ion cationized complexes.

    PubMed

    Fridgen, Travis D

    2009-01-01

    In this article, the new and exciting techniques of infrared consequence spectroscopy (sometimes called action spectroscopy) of gaseous ions are reviewed. These techniques include vibrational predissociation spectroscopy and infrared multiple photon dissociation spectroscopy and they typically complement one another in the systems studied and the information gained. In recent years infrared consequence spectroscopy has provided long-awaited direct evidence into the structures of gaseous ions from organometallic species to strong ionic hydrogen bonded structures to large biomolecules. Much is being learned with respect to the structures of ions without their stabilizing solvent which can be used to better understand the effect of solvent on their structures. This review mainly covers the topics with which the author has been directly involved in research: structures of proton-bound dimers, protonated amino acids and DNA bases, amino acid and DNA bases bound to metal ions and, more recently, solvated ionic complexes. It is hoped that this review reveals the impact that infrared consequence spectroscopy has had on the field of gaseous ion chemistry.

  6. On the stability of cationic complexes of neon with helium--solving an experimental discrepancy.

    PubMed

    Bartl, Peter; Denifl, Stephan; Scheier, Paul; Echt, Olof

    2013-10-21

    Helium nanodroplets are doped with neon and ionized by electrons. The size-dependence of the ion abundance of HenNex(+), identified in high-resolution mass spectra, is deduced for complexes containing up to seven neon atoms and dozens of helium atoms. Particularly stable ions are inferred from anomalies in the abundance distributions. Two pronounced anomalies at n = 11 and 13 in the HenNe(+) series confirm drift-tube data reported by Kojima et al. [T. M. Kojima et al., Z. Phys. D, 1992, 22, 645]. The discrepancy with previously published spectra of neon-doped helium droplets, which did not reveal any abundance anomalies [T. Ruchti et al., J. Chem. Phys., 1998, 109, 10679-10687; C. A. Brindle et al., J. Chem. Phys., 2005, 123, 064312], is most likely due to limited mass resolution, which precluded unambiguous analysis of contributions from different ions with identical nominal mass. However, calculated dissociation energies of HenNe(+) reported so far do not correlate with the present data, possibly because of challenges in correctly treating the linear, asymmetric [He-Ne-He](+) ionic core in HenNe(+). Anomalies identified in the distributions of HenNex(+) for x > 1, including prominent ones at He12Ne2(+) and He14Ne2(+), may help to better understand solvation of Ne(+) and Nex(+) in helium.

  7. Pyridyne radical cations produced by photodissociation of Mg*+ (multifluoro-pyridine) complexes: a combined experimental and theoretical study.

    PubMed

    Liu, Hai-Chuan; Zhang, Xin-Hao; Wang, Changsheng; Wu, Yun-Dong; Yang, Shihe

    2007-02-07

    Gas phase complexes Mg*+ (2,6-difluoropyridine) (1) and Mg*+ (pentafluoropyridine) (2) have been subjected to photodissociation in the spectral range of approximately 230-440 nm. Except for the evaporative photofragment Mg*+ , the primary photoproduct for is C(5)H(3)N*(+), which is associated with the rupture of two C-F bonds by the photoexcited Mg*+ , forming very stable MgF(2). In contrast, the direct loss of MgF(+) is more favorable for due to fluorine substitution. Given enough energy, C(5)H(3)N*(+) can undergo decomposition to form C(4)H(2)*(+) and HCN. These results are very different from those for Mg*+ (2-fluoropyridine), highlighting the significance of the additional F at C6 of and . Density functional theory (DFT) calculations have been employed to examine the geometries and energetics of the complexes as well as relevant reaction mechanisms. All of the complexes feature the direct attachment of Mg*+ to the N atom. The key intermediate is found to be FMg(+) (C(5)H(x)F(4-x)N) (x = 3 or 0), which can lead to the formation of MgF(+) directly or MgF(2) through activation of another C-F bond adjacent to N, producing the pyridyne radical cations. However, hydrogen-transfer prior to the rupture of the second C-F bond followed by ring-opening of C(5)H(3)N*(+) may result in the formation of chain forms of C(5)H(3)N*(+). The influence of the fluorine substitution on the competition of the two routes have been demonstrated.

  8. Highly luminescent and stable lyotropic liquid crystals based on a europium β-diketonate complex bridged by an ethylammonium cation.

    PubMed

    Yi, Sijing; Yao, Meihuan; Wang, Jiao; Chen, Xiao

    2016-10-05

    Soft lanthanide luminescent materials are impressive because of their tunable and self-assembling characteristics, which make them an attractive emerging materials field of research. In this report, novel luminescent lyotropic liquid crystals (LLCs) with four different mesophases have been fabricated by a protic ionic liquid (IL) based europium β-diketonate complex EA[Eu(TTA)4] (EA = ethylammonium, TTA = 2-thenoyltrifluoro-acetone) and an amphiphilic block copolymer (Pluronic P123). The protic IL, ethylammonium nitrate (EAN), was used as both the solvent and linkage to stabilize the doped complexes. Analyses by single-crystal X-ray diffraction for EA[Eu(TTA)4] and Fourier transform infrared spectroscopy for the LLC materials reveal convincingly that the ethylammonium cations establish an effective connection with both the carbonyl group of the β-diketonate ligand and the EO blocks of the amphiphilic block copolymer P123 via strong hydrogen bonding interactions. Due to this, an extremely long decay time of the excited state is obtained in EA[Eu(TTA)4] and excellent photostability of the luminescent LLCs could be achieved. The long-period ordered structures of the luminescent LLCs have been investigated by small-angle X-ray scattering measurements and the best luminescence performance was found in the most organized mesophase. Noteworthy, the LLCs could yield an effective confining effect on the europium complex accompanied by a sizeable elongation of the excited-state lifetime and an enhancement of the energy transfer efficiency, which reaches a remarkably high value of 52.6%. More importantly, the modulated luminescence properties observed in the four mesophase structures offer the potential and powerful possibility for these unique composite LLCs to be used in the fabrication of soft luminescent materials with tunable functions.

  9. Ternary complexes between cationic GdIII chelates and anionic metabolites in aqueous solution: an NMR relaxometric study.

    PubMed

    Botta, Mauro; Aime, Silvio; Barge, Alessandro; Bobba, Gabriella; Dickins, Rachel S; Parker, David; Terreno, Enzo

    2003-05-09

    The (1)H and (17)O NMR relaxometric properties of two cationic complexes formed by Gd(III) with a macrocyclic heptadentate triamide ligand, L(1), and its Nmethylated analogue, L(2), have been investigated in aqueous media as a function of pH, temperature and magnetic field strength. The complexes possess two water molecules in their inner coordination sphere for which the rate of exchange has been found to be sensibly faster for the Nmethylated derivative and explained in terms of electronic effects (decrease of the charge density at the metal center) and perturbation of the network of hydrogen-bonded water molecules in the outer hydration sphere. The proton relaxivity shows a marked dependence from pH and decreases of about six units in the pH range 6.5 to 9.0. This has been accounted for by the displacement of the two water molecules by dissolved carbonate which acts as a chelating anion. The formation of ternary complexes with lactate, malonate, citrate, acetate, fluoride and hydrogenphosphate has been monitored by (1)H NMR relaxometric titrations at 20 MHz and pH 6.3 and the value of the affinity constant, K, and of the relaxivity of the adducts could be obtained. Lactate, malonate and citrate interact strongly with the complexes (log K > or =3.7) and coordinate in a bidendate mode by displacing both water molecules. Larger affinity constants have been measured for GdL(2). Acetate, fluoride and hydrogenphosphate form monoaqua ternary complexes which were investigated in detail with regard to their relaxometric properties. The NMR dispersion (NMRD) profiles indicate a large contribution to the relaxivity of the adducts from water molecules belonging to the second hydration shell of the complexes and hydrogen-bonded to the anion. A VT (17)O NMR study has shown a marked increase of the rate of water exchange upon binding which is explained by coordination of the anion in an equatorial site, thus leaving the water molecule in an apical position, more accessible for

  10. Complex formation between cationic beta-1,3-glucan and hetero-sequence oligodeoxynucleotide and its delivery into macrophage-like cells to induce cytokine secretion.

    PubMed

    Ikeda, Masato; Minari, Jusaku; Shimada, Naohiko; Numata, Munenori; Sakurai, Kazuo; Shinkai, Seiji

    2007-07-21

    A cationic polysaccharide bearing a beta-1,3-glucan main-chain structure (CUR-N(+)) forms a complex with a hetero-sequence oligonucleotide, that is, a CpG ODN, and facilitates the transportation of the resultant complex into a murine macrophage-like cell J774.A1, which induces an efficient secretion of a cytokine (IL-12) as compared with that induced by conventional carriers such as poly(ethyleneimine) (PEI) and poly(L-lysine) (PLL).

  11. Submicellar complexes may initiate the fungicidal effects of cationic amphiphilic compounds on Candida albicans.

    PubMed Central

    Ahlström, B; Chelminska-Bertilsson, M; Thompson, R A; Edebo, L

    1997-01-01

    The killing of Candida albicans by a series of amphiphilic quaternary ammonium compounds (QACs) with different hydrocarbon chain lengths was closely related to the binding of the compounds to the cells and damage of the cell membranes. The membrane damage was measured as the level of release of the UV-absorbing material into the medium in which the cells were suspended and as the level of uptake of propidium iodide in individual cells by flow cytometry. It was shown that of the compounds tested, hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide [CTAB]) bound most efficiently. Tetradecyl betainate chloride (B14), tetradecanoylcholine bromide (C14), tetradecyltrimethylammonium bromide (TTAB), and dodecyltrimethylammonium bromide (DTAB) followed and had declining degrees of binding efficiency. The proportion of CTAB bound was almost total at concentrations up to the critical micelle concentration (CMC) of the compound, whereas that of B14 was somewhat smaller. For the two remaining tetradecyl compounds (C14 and TTAB), still smaller proportions were bound at low concentrations, but the proportions rose disproportionally at increasing concentrations to a distinct maximum at concentrations of 0.2 to 0.5 times the CMC. We propose that interfacial micelle-like aggregates are formed at the cell surface as a step in the binding process. An analogous, but less conspicuous, maximum was seen for DTAB. Thus, great differences in the binding affinity of QACs with different hydrocarbon chains at different concentrations to C. albicans were observed. These differences were related to the CMC of the compound. In contrast, the binding of TTAB to Salmonella typhimurium 395 MS was almost total at low as well as high concentrations until saturation was attained, indicating fundamental differences between binding to the yeast and binding to gram-negative bacteria. The importance of lipid-type complexes or aggregates to the antifungal effect of membrane-active substances

  12. Neutral and cationic aluminium complexes of a sterically demanding N-imidoylamidine ligand.

    PubMed

    Masuda, Jason D; Stephan, Douglas W

    2006-05-07

    The N-imidoylamidine ligand i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2 2 was prepared. Direct reactions with AlI3 or AlMe3 afforded [(i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2)AlI2][AlI4] 3 and [i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2)AlMe2][AlMe4].AlMe3, 4 respectively. Thermolysis of 4 gave (i-Pr2C6H3NC(=CH2)(NC6H3i-Pr2)(C(Me)NC6H3i-Pr2)AlMe2 6. Subsequent reaction with B(C6F5)3 gave the zwitterionic species [(i-Pr2C6H3)N(C(=CH2)NC6H3i-Pr2)(C(Me)NC6H3i-Pr2)AlMe(mu-MeB(C6F5)3)] 7. In a related reactions of 2, [Ph3C][B(C6F5)4] and AlMe3, AlH3.NEtMe2 or AlD3.NMe3, the complexes [(i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2)AlR2][B(C6F5)4] (R = Me 5, H 8, D 9) and [(i-Pr2C6H3)N(C(=CH2)NC6H3i-Pr2)(C(Me)NC6H3i-Pr2)AlH][B(C6F5)4] 10 are formed. Single-crystal X-ray data for 2, 3, 5 and 10 are reported.

  13. Infrared Multiple Photon Dissociation Action Spectroscopy and Theoretical Studies of Triethyl Phosphate Complexes: Effects of Protonation and Sodium Cationization on Structure

    NASA Astrophysics Data System (ADS)

    Fales, B. S.; Fujamade, N. O.; Oomens, J.; Rodgers, M. T.

    2011-10-01

    The gas-phase structures of protonated and sodium cationized complexes of triethyl phosphate, [TEP + H]+ and [TEP + Na]+, are examined via infrared multiple photon dissociation (IRMPD) action spectroscopy using tunable IR radiation generated by a free electron laser, a Fourier transform ion cyclotron resonance mass spectrometer with an electrospray ionization source, and theoretical electronic structure calculations. Measured IRMPD action spectra are compared to linear IR spectra calculated at the B3LYP/6-31 G(d,p) level of theory to identify the structures accessed in the experimental studies. For comparison, theoretical studies of neutral TEP are also performed. Sodium cationization and protonation produce changes in the central phosphate geometry, including an increase in the alkoxy ∠OPO bond angle and shortening of the alkoxy P-O bond. Changes associated with protonation are more pronounced than those produced by sodium cationization.

  14. Effect of cation species on surface-induced phase transition observed for platinum complex anions in platinum electrodeposition using nanoporous silicon

    NASA Astrophysics Data System (ADS)

    Koda, Ryo; Koyama, Akira; Fukami, Kazuhiro; Nishi, Naoya; Sakka, Tetsuo; Abe, Takeshi; Kitada, Atsushi; Murase, Kuniaki; Kinoshita, Masahiro

    2014-08-01

    In an earlier work [K. Fukami et al., J. Chem. Phys. 138, 094702 (2013)], we reported a transition phenomenon observed for platinum complex anions in our platinum electrodeposition experiment using nanoporous silicon. The pore wall surface of the silicon electrode was made hydrophobic by covering it with organic molecules. The anions are only weakly hydrated due to their large size and excluded from the bulk aqueous solution to the hydrophobic surface. When the anion concentration in the bulk was gradually increased, at a threshold the deposition behavior exhibited a sudden change, leading to drastic acceleration of the electrochemical deposition. It was shown that this change originates from a surface-induced phase transition: The space within a nanopore is abruptly filled with the second phase in which the anion concentration is orders of magnitude higher than that in the bulk. Here we examine how the platinum electrodeposition behavior is affected by the cation species coexisting with the anions. We compare the experimental results obtained using three different cation species: K+, (CH3)4N+, and (C2H5)4N+. One of the cation species coexists with platinum complex anions [PtCl4]2-. It is shown that the threshold concentration, beyond which the electrochemical deposition within nanopores is drastically accelerated, is considerably dependent on the cation species. The threshold concentration becomes lower as the cation size increases. Our theoretical analysis suggests that not only the anions but also the cations are remarkably enriched in the second phase. The remarkable enrichment of the anions alone would give rise to the energetic instability due to electrostatic repulsive interactions among the anions. We argue that the result obtained cannot be elucidated by the prevailing view based on classical electrochemistry. It is necessitated to consult a statistical-mechanical theory of confined aqueous solutions using a molecular model for water.

  15. Cationic Lipid/DNA Complex-Adjuvanted Influenza A Virus Vaccination Induces Robust Cross-Protective Immunity▿

    PubMed Central

    Hong, David K.; Chang, Stella; Botham, Crystal M.; Giffon, Thierry D.; Fairman, Jeffery; Lewis, David B.

    2010-01-01

    Influenza A virus is a negative-strand segmented RNA virus in which antigenically distinct viral subtypes are defined by the hemagglutinin (HA) and neuraminidase (NA) major viral surface proteins. An ideal inactivated vaccine for influenza A virus would induce not only highly robust strain-specific humoral and T-cell immune responses but also cross-protective immunity in which an immune response to antigens from a particular viral subtype (e.g., H3N2) would protect against other viral subtypes (e.g., H1N1). Cross-protective immunity would help limit outbreaks from newly emerging antigenically novel strains. Here, we show in mice that the addition of cationic lipid/noncoding DNA complexes (CLDC) as adjuvant to whole inactivated influenza A virus vaccine induces significantly more robust adaptive immune responses both in quantity and quality than aluminum hydroxide (alum), which is currently the most widely used adjuvant in clinical human vaccination. CLDC-adjuvanted vaccine induced higher total influenza virus-specific IgG, particularly for the IgG2a/c subclass. Higher levels of multicytokine-producing influenza virus-specific CD4 and CD8 T cells were induced by CLDC-adjuvanted vaccine than with alum-adjuvanted vaccine. Importantly, CLDC-adjuvanted vaccine provided significant cross-protection from either a sublethal or lethal influenza A viral challenge with a different subtype than that used for vaccination. This superior cross-protection afforded by the CLDC adjuvant required CD8 T-cell recognition of viral peptides presented by classical major histocompatibility complex class I proteins. Together, these results suggest that CLDC has particular promise for vaccine strategies in which T cells play an important role and may offer new opportunities for more effective control of human influenza epidemics and pandemics by inactivated influenza virus vaccine. PMID:20943978

  16. Factors affecting hydrogen-tunneling contribution in hydroxylation reactions promoted by oxoiron(IV) porphyrin π-cation radical complexes.

    PubMed

    Cong, Zhiqi; Kinemuchi, Haruki; Kurahashi, Takuya; Fujii, Hiroshi

    2014-10-06

    Hydrogen atom transfer with a tunneling effect (H-tunneling) has been proposed to be involved in aliphatic hydroxylation reactions catalyzed by cytochrome P450 and synthetic heme complexes as a result of the observation of large hydrogen/deuterium kinetic isotope effects (KIEs). In the present work, we investigate the factors controlling the H-tunneling contribution to the H-transfer process in hydroxylation reaction by examining the kinetics of hydroxylation reactions at the benzylic positions of xanthene and 1,2,3,4-tetrahydronaphthalene by oxoiron(IV) 5,10,15,20-tetramesitylporphyrin π-cation radical complexes ((TMP(+•))Fe(IV)O(L)) under single-turnover conditions. The Arrhenius plots for these hydroxylation reactions of H-isotopomers have upwardly concave profiles. The Arrhenius plots of D-isotopomers, clear isosbestic points, and product analysis rule out the participation of thermally dependent other reaction processes in the concave profiles. These results provide evidence for the involvement of H-tunneling in the rate-limiting H-transfer process. These profiles are simulated using an equation derived from Bell's tunneling model. The temperature dependence of the KIE values (k(H)/k(D)) determined for these reactions indicates that the KIE value increases as the reaction temperature becomes lower, the bond dissociation energy (BDE) of the C-H bond of a substrate becomes higher, and the reactivity of (TMP(+•))Fe(IV)O(L) decreases. In addition, we found correlation of the slope of the ln(k(H)/k(D)) - 1/T plot and the bond strengths of the Fe═O bond of (TMP(+•))Fe(IV)O(L) estimated from resonance Raman spectroscopy. These observations indicate that these factors modulate the extent of the H-tunneling contribution by modulating the ratio of the height and thickness of the reaction barrier.

  17. Phosphorus dendrimers and photodynamic therapy. Spectroscopic studies on two dendrimer-photosensitizer complexes: Cationic phosphorus dendrimer with rose bengal and anionic phosphorus dendrimer with methylene blue.

    PubMed

    Dabrzalska, Monika; Zablocka, Maria; Mignani, Serge; Majoral, Jean Pierre; Klajnert-Maculewicz, Barbara

    2015-08-15

    Dendrimers due to their unique architecture may play an important role in drug delivery systems including chemotherapy, gene therapy and recently, photodynamic therapy as well. We investigated two dendrimer-photosensitizer systems in context of potential use of these systems in photodynamic therapy. The mixtures of an anionic phosphorus dendrimer of the second generation and methylene blue were studied by UV-vis spectroscopy while that of a cationic phosphorus dendrimer (third generation) and rose bengal were investigated by spectrofluorimetric methods. Spectroscopic analysis of these two systems revealed the formation of dendrimer-photosensitizer complexes via electrostatic interactions as well as π stacking. The stoichiometry of the rose bengal-cationic dendrimer complex was estimated to be 7:1 and 9:1 for the methylene blue-anionic dendrimer complex. The results suggest that these polyanionic or polycationic phosphorus dendrimers can be promising candidates as carriers in photodynamic therapy.

  18. Asymmetric Hydrogenation of Quinoline Derivatives Catalyzed by Cationic Transition Metal Complexes of Chiral Diamine Ligands: Scope, Mechanism and Catalyst Recycling.

    PubMed

    Luo, Yi-Er; He, Yan-Mei; Fan, Qing-Hua

    2016-12-01

    This personal account is focused on the asymmetric hydrogenation of quinolines and their analogues recently developed by using phosphorus-free chiral cationic ruthenium(II)/η(6) -arene-N-monosulfonylated diamine complexes. In our initial study, the chiral Ru-diamine complexes were found to be highly effective catalysts for the asymmetric hydrogenation of difficult quinoline substrates in room temperature ionic liquids (RTILs) with unprecedentedly excellent enantioselectivity. Our further systematic study revealed that a wide range of quinoline derivatives could be efficiently hydrogenated in alcoholic solvents, or under solvent-free and concentrated conditions with good to excellent stereoselectivity. Complexes of iridium analogues could also efficiently catalyze the asymmetric hydrogenation of quinolines in undegassed solvent. Asymmetric tandem reduction of various 2-(aroylmethyl)quinolines was achieved in high yield with excellent enantioselectivity and good diastereoselectivity. More challenging substrates, alkyl- and aryl-substituted 1,5- and 1,8-naphthyridine derivatives were successfully hydrogenated with these chiral ruthenium catalysts to give 1,2,3,4-tetrahydronaphthyridines with good to excellent enantioselectivity. Unlike the asymmetric hydrogenation of ketones, quinoline is reduced via a stepwise H(+) /H(-) transfer process outside the coordination sphere rather than a concerted mechanism. The enantioselectivity originates from the CH/π attraction between the η(6) -arene ligand in the Ru-complex and the fused phenyl ring of dihydroquinoline via a 10-membered ring transition state with the participation of TfO(-) anion. In addition, the Ru-catalyzed asymmetric hydrogenation of quinolines could be carried out in some environmentally benign reaction media, such as undegassed water, RTILs and oligo(ethylene glycol)s (OEGs). In the latter two cases, unique chemoselectivity and/or reactivity were observed. Catalyst recycling could also be realized by using

  19. Cholesterol derived cationic lipids as potential non-viral gene delivery vectors and their serum compatibility.

    PubMed

    Ju, Jia; Huan, Meng-Lei; Wan, Ning; Hou, Yi-Lin; Ma, Xi-Xi; Jia, Yi-Yang; Li, Chen; Zhou, Si-Yuan; Zhang, Bang-Le

    2016-05-15

    Cholesterol derivatives M1-M6 as synthetic cationic lipids were designed and the biological evaluation of the cationic liposomes based on them as non-viral gene delivery vectors were described. Plasmid pEGFP-N1, used as model gene, was transferred into 293T cells by cationic liposomes formed with M1-M6 and transfection efficiency and GFP expression were tested. Cationic liposomes prepared with cationic lipids M1-M6 exhibited good transfection activity, and the transfection activity was parallel (M2 and M4) or superior (M1 and M6) to that of DC-Chol derived from the same backbone. Among them, the transfection efficiency of cationic lipid M6 was parallel to that of the commercially available Lipofectamine2000. The optimal formulation of M1 and M6 were found to be at a mol ratio of 1:0.5 for cationic lipid/DOPE, and at a N/P charge mol ratio of 3:1 for liposome/DNA. Under optimized conditions, the efficiency of M1 and M6 is greater than that of all the tested commercial liposomes DC-Chol and Lipofectamine2000, even in the presence of serum. The results indicated that M1 and M6 exhibited low cytotoxicity, good serum compatibility and efficient transfection performance, having the potential of being excellent non-viral vectors for gene delivery. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Formation of Stable and Metastable Porphyrin- and Corrole-Iron(IV) Complexes and Isomerizations to Iron(III) Macrocycle Radical Cations

    PubMed Central

    Pan, Zhengzheng; Harischandra, Dilusha N.; Newcomb, Martin

    2009-01-01

    Oxidations of three porphyrin-iron(III) complexes (1) with ferric perchlorate, Fe(ClO4)3, in acetonitrile solutions at −40 °C gave metastable porphyrin-iron(IV) diperchlorate complexes (2) that isomerized to known iron(III) diperchlorate porphyrin radical cations (3) when the solutions were warmed to room temperature. The 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetramesitylporphyrin (TMP), and 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) systems were studied by UV-visible spectroscopy. Low temperature NMR spectroscopy and effective magnetic moment measurements were possible with the TPP and TMP iron(IV) complexes. Reactions of two corrole systems, 5,10,15-tris(pentafluorophenyl)corrole (TPFC) and 5,15-bis(pentafluorophenyl)-10-p-methoxyphenylcorrole (BPFMC), also were studied. The corrole-iron(IV) chlorides reacted with silver salts to give corrole-iron(IV) complexes. The corrole-iron(IV) nitrate complexes were stable at room temperature. (TPFC)-iron(IV) toslyate, (TPFC)-iron(IV) chlorate, and (BPFMC)-iron(IV) chlorate were metastable and rearranged to their electronic isomers iron(III) corrole radical cations at room temperature. (TPFC)-iron(III) perchlorate corrole radical cation was the only product observed from reaction of the corrole-iron(IV) chloride with silver perchlorate. For the metastable iron(IV) species, the rates of isomerizations to the iron(III) macrocycle radical cation electronic isomers in dilute acetonitrile solutions were relatively insensitive to electron demands of the macrocyclic ligand but reflected the binding strength of the ligand to iron. Kinetic studies at varying temperatures and concentrations indicated that the mechanisms of the isomerization reactions are complex, involving mixed order reactivity. PMID:19013647

  1. Uranyl and uranyl-3d block cation complexes with 1,3-adamantanedicarboxylate: crystal structures, luminescence, and magnetic properties.

    PubMed

    Thuéry, Pierre; Rivière, Eric; Harrowfield, Jack

    2015-03-16

    The reaction of 1,3-adamantanedicarboxylic acid (LH2) with uranyl nitrate under solvo-hydrothermal conditions, either alone or in the presence of additional metal cations (Co(2+), Ni(2+), or Cu(2+)) gives a series of nine complexes displaying a wide range of architectures. While [UO2(L)(H2O)]·1.25CH3CN (1) and [UO2(L)(DMF)] (2) are one-dimensional (1D) species analogous to that previously known, [H2NMe2]2[(UO2)2(L)3]·1.5H2O (3), which includes dimethylammonium counterions generated in situ, is a three-dimensional (3D) framework, and [UO2(L)(NMP)] (4) (NMP = N-methyl-2-pyrrolidone) is a braid-shaped 1D polymer. When 3d block metal ions are present and bound to 2,2'-bipyridine (bipy) coligands, their role is reduced to that of decorating species attached to uranyl-containing 1D polymers, as in [UO2M(L)2(bipy)2]·0.5H2O with M = Co (5) or Ni (6), and [(UO2)2Cu2(L)3(NO3)2(bipy)2]·0.5H2O (9), or of counterions, as in [Ni(bipy)3][(UO2)4(O)2(L)3]·3H2O (7), in which a two-dimensional (2D) assembly is built from tetranuclear uranyl-containing building units. In contrast, the heterometallic 3D framework [UO2Cu(L)2] (8) can be isolated in the absence of bipy. The emission spectra measured in the solid state display the usual uranyl vibronic fine structure, with various degrees of resolution and quenching, except for that of complex 7, which shows emission from the nickel(II) centers. The magnetic properties of complexes 5, 6, 8, and 9 were investigated, showing, in particular, the presence of zero-field splitting effects in 6 and weak antiferromagnetic interactions in 9.

  2. A novel ternary ligand system useful for preparation of cationic (99m)Tc-diazenido complexes and (99m)Tc-labeling of small biomolecules.

    PubMed

    Kim, Young-Seung; He, Zhengjie; Hsieh, Wen-Yuan; Liu, Shuang

    2006-01-01

    This report describes a novel ternary ligand system composed of a phenylhydrazine, a crown ether-containing dithiocarbamate (DTC), and a PNP-type bisphosphine (PNP). The combination of three different ligands with (99m)Tc results in cationic (99m)Tc-diazenido complexes, [(99m)Tc(NNAr)(DTC)(PNP)]+, with potential radiopharmaceuticals for heart imaging. Synthesis of cationic (99m)Tc-diazenido complexes can be accomplished in two steps. For example, the reaction of phenylhydrazine with (99m)TcO4- at 100 degrees C in the presence of excess stannous chloride and 1,2-diaminopropane-N,N,N',N'-tetraacetic acid (PDTA) results in the [(99m)Tc(NNPh)(PDTA)n] intermediate, which then reacts with sodium N-(dithiocarbamato)-2-aminomethyl-15-Crown-5 (L4) and N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]ethoxyethylamine (PNP6) at 100 degrees C for 15 min to give the complex, [(99m)Tc(NNPh)(L4)(PNP6)]+ in high yield (>90%). Cationic complexes [(99m)Tc(NNPh)(DTC)(PNP)]+ are stable for > or = 6 h. Their composition was determined to be 1:1:1:1 for Tc:NNPh:DTC:PNP using the mixed-ligand experiments on the tracer ((99m)Tc) level and was further confirmed by the ESI-MS spectral data of a model compound [Re(NNPh)(L4)(L6)]+. It was found that both DTCs and bisphosphines have a significant impact on the lipophilicity of their cationic (99m)Tc-diazenido complexes. Results from a (99m)Tc-labeling efficiency experiment showed that 4-hydrazinobenzoic acid (HYBA) might be useful as a bifunctional coupling agent for (99m)Tc-labeling of small biomolecules. However, the (99m)Tc-labeling efficiency of HYBA is much lower than that of 6-hydrazinonicotinic acid (HYNIC) with tricine and trisodium triphenylphosphine-3,3',3''-trisulfonate (TPPTS) as coligands.

  3. Anchoring a cationic ligand: the structure of the Fab fragment of the anti-morphine antibody 9B1 and its complex with morphine.

    PubMed

    Pozharski, Edwin; Wilson, Mark A; Hewagama, Anura; Shanafelt, Armen B; Petsko, Gregory; Ringe, Dagmar

    2004-03-26

    The crystal structures of an anti-morphine antibody 9B1 (to 1.6A resolution) and its complex with morphine (to 2.0 A resolution) are reported. The morphine-binding site is described as a shallow depression on the protein surface, an unusual topology for a high-affinity ( Ka approximately 10(9) M(-1)) antibody against a small antigen. The polar part of the ligand is exposed to solvent, and the cationic nitrogen atom of the morphine molecule is anchored at the bottom of the binding site by a salt-bridge to a glutamate side-chain. Additional affinity is provided by a double cation-pi interaction with two tryptophan residues. Comparison of the morphine complex with the structure of the free Fab shows that a domain closure occurs upon binding of the ligand.

  4. Cationic rare-earth metal trimethylsilylmethyl complexes supported by THF and 12-crown-4 ligands: synthesis and structural characterization.

    PubMed

    Elvidge, Benjamin R; Arndt, Stefan; Zeimentz, Peter M; Spaniol, Thomas P; Okuda, Jun

    2005-09-19

    To expand the limited range of rare-earth metal cationic alkyl complexes known, a series of mono- and dicationic trimethylsilylmethyl complexes supported by THF and 12-crown-4 ligands with [BPh4]-, [BPh3(CH2SiMe3)]-, [B(C6F5)4]-, [B(C6F5)3(CH2SiMe3)]-, and [Al(CH2SiMe3)4]- anions were prepared from corresponding neutral precursors [Ln(CH2SiMe3)3Ln] (Ln = Sc, Y, Lu; L = THF, n = 2 or 3; L = 12-crown-4, n = 1) as solvent-separated ion pairs. The syntheses of the monocationic derivatives [Ln(CH2SiMe3)2(12-crown-4)n(THF)m]+[A]- are all high yielding and proceed rapidly in THF solution at room temperature. A "one pot" procedure using the neutral species directly for the syntheses of a number of lutetium and yttrium dicationic derivatives [Ln(CH2SiMe3)(12-crown-4)n(THF)m]2+[A]-2 with a variety of different anions, a class of compounds previously limited to just a few examples, is presented. When BPh3 is used to generate the ion triple, the presence of 12-crown-4 is required for complete conversion. Addition of a second equiv of 12-crown-4 and a third equiv of [NMe2PhH]+[B(C6F5)4]- abstracts a third alkyl group from [Ln(CH2SiMe3)(12-crown-4)2(THF)x]2+[B(C6F5)4]-2 (Ln = Y, Lu). X-ray crystallography and variable-temperature (VT) NMR spectroscopy reveal a structural diversity within the known series of neutral 12-crown-4 supported tris(trimethylsilylmethyl) complexes [Ln(CH2SiMe3)3(12-crown-4)] (Ln = Sc, Y, Sm, Gd-Lu) in the solid and solution states. The X-ray structure of [Sc(CH2SiMe3)3(12-crown-4)] exhibits incomplete 12-crown-4 coordination. VT NMR spectroscopy indicates fluxional 12-crown-4 coordination on the NMR time scale. X-ray crystallography of only the second structurally characterized dicationic rare-earth metal alkyl complex [Y(CH2SiMe3)(12-crown-4)(THF)3]2+[BPh4]-2 shows exocyclic 12-crown-4 coordination at the 8-coordinate metal center with well separated counteranions. 11B and 19F NMR spectroscopy of all mono- and dicationic rare-earth metal complexes

  5. A binary catalyst system of a cationic Ru-CNC pincer complex with an alkali metal salt for selective hydroboration of carbon dioxide.

    PubMed

    Ng, Chee Koon; Wu, Jie; Hor, T S Andy; Luo, He-Kuan

    2016-09-27

    Binary catalyst systems comprising a cationic Ru-CNC pincer complex and an alkali metal salt were developed for selective hydroboration of CO2 utilizing pinacolborane at r.t. and 1 atm CO2, with the combination of [Ru(CNCBn)(CO)2(H)][PF6] and KOCO2(t)Bu producing formoxyborane in 76% yield. A bicyclic catalytic mechanism was proposed and discussed.

  6. The energetic and structural effects of steric crowding in phosphate and dithiophosphinate complexes of lanthanide cations M3+: a computational study.

    PubMed

    Boehme, C; Wipff, G

    2001-04-01

    Metal-ligand binding strength and selectivity result from antagonistic metal-ligand M-L attractions and ligand-ligand L-L repulsions. On the basis of quantum-mechanical (QM) calculations on lanthanide complexes, we show that this interplay determines the binding affinities in the gas phase. In the series of [ML3] complexes (M = La, Eu, and Yb) with negatively charged phosphoryl ligands L- = (MeO)2PO2- and Me2PS2-, the binding energies follow the order Yb3+ > Eu3+ > La3- for a given ligand, and (MeO)2PO2- > Me2PS2- for a given cation. However, adding a neutral LH ligand to [ML3] changes the order to Eu3+ > Yb3+ > La3+ for the oxygen ligand and La3+ > Eu3- > Yb3+ for the sulfur ligand, indicating that steric strain in the first coordination sphere is largest for the smallest cation and for sulfur binding sites. We investigated the question of additional hydration of the [ML3LH] complexes in aqueous solution by molecular dynamics (MD) simulations, using two sets of atomic charges. It was found that pairwise additive potentials overestimate the coordination and hydration numbers of the cations, while adding polarization energy terms for the ligands yields better agreement between QM and MD results and supports the concept of steric strain in the first coordination sphere.

  7. Highly luminescent yellow and yellowish-green light-emitting electrochemical cells based on cationic iridium complexes with phenanthroline based ancillary ligands

    NASA Astrophysics Data System (ADS)

    Sunesh, Chozhidakath Damodharan; Chandran, Midhun; Mathai, George; Choe, Youngson

    2013-01-01

    Highly luminescent light-emitting electrochemical cells (LECs) based on cationic iridium complexes [Ir(ppz)2(dpphen)]PF6 (1) and [Ir(ppz)2(tmphen)]PF6 (2) (ppz is 1-phenylpyrazole, dpphen is 4,7-diphenyl-1,10-phenanthroline and tmphen is 3,4,7,8-tetramethyl-1,10-phenanthroline) with phenanthroline based ancillary ligands were fabricated using air stable electrodes and their electroluminescent properties were investigated. LECs based on complex 1 emitted yellow electroluminescence (λmax 574 nm) with Commission Internationale de L'Eclairage (CIE) coordinates of (0.49, 0.50) while the complex 2 gave yellowish-green electroluminescence (λmax 537 nm) with CIE coordinates of (0.35, 0.58). The work done here reveals that the alkyl substituted phenanthroline ancillary ligand, tmphen shifts the light emission to the shorter wavelength region than the phenyl substituted dpphen ligand, resulting in the color tuning of the light-emitting devices. Density functional theory (DFT) calculations were performed to gain insight into the molecular surfaces of cationic iridium complexes and their electrochemical behaviors. Single layer LECs based on these complexes exhibited a high luminescence of 5199 and 4751 cd/m2 for complexes 1 and 2 respectively. The ionic liquid, 1-ethyl-3-methylimidazolium hexafluorophosphate (EMIMPF6) was added to the light emitting layer and hence higher luminances were obtained than the pristine device.

  8. The electronic structure of vanadium monochloride cation (VCl{sup +}): Tackling the complexities of transition metal species

    SciTech Connect

    DeYonker, Nathan J.; Halfen, DeWayne T.; Ziurys, Lucy M.; Allen, Wesley D.

    2014-11-28

    Six electronic states (X {sup 4}Σ{sup −}, A {sup 4}Π, B {sup 4}Δ, {sup 2}Φ, {sup 2}Δ, {sup 2}Σ{sup +}) of the vanadium monochloride cation (VCl{sup +}) are described using large basis set coupled cluster theory. For the two lowest quartet states (X {sup 4}Σ{sup −} and A {sup 4}Π), a focal point analysis (FPA) approach was used that conjoined a correlation-consistent family of basis sets up to aug-cc-pwCV5Z-DK with high-order coupled cluster theory through pentuple (CCSDTQP) excitations. FPA adiabatic excitation energies (T{sub 0}) and spectroscopic constants (r{sub e}, r{sub 0}, B{sub e}, B{sub 0}, D{sup ¯}{sub e}, H{sub e}, ω{sub e}, v{sub 0}, α{sub e}, ω{sub e}x{sub e}) were extrapolated to the valence complete basis set Douglas-Kroll (DK) aug-cc-pV∞Z-DK CCSDT level of theory, and additional treatments accounted for higher-order valence electron correlation, core correlation, and spin-orbit coupling. Due to the delicate interplay between dynamical and static electronic correlation, single reference coupled cluster theory is able to provide the correct ground electronic state (X {sup 4}Σ{sup −}), while multireference configuration interaction theory cannot. Perturbations from the first- and second-order spin orbit coupling of low-lying states with quartet spin multiplicity reveal an immensely complex rotational spectrum relative to the isovalent species VO, VS, and TiCl. Computational data on the doublet manifold suggest that the lowest-lying doublet state ({sup 2}Γ) has a T{sub e} of ∼11 200 cm{sup −1}. Overall, this study shows that laboratory and theoretical rotational spectroscopists must work more closely in tandem to better understand the bonding and structure of molecules containing transition metals.

  9. Blue-green emitting cationic iridium complexes with 1,3,4-oxadiazole cyclometallating ligands: synthesis, photophysical and electrochemical properties, theoretical investigation and electroluminescent devices.

    PubMed

    Wang, Zhen; He, Lei; Duan, Lian; Yan, Jun; Tang, Ruiren; Pan, Chunyue; Song, Xiangzhi

    2015-09-28

    Two cationic iridium complexes, namely [Ir(dph-oxd)2(bpy)]PF6 (1) and [Ir(dph-oxd)2(pzpy)]PF6 (2), using 2,5-diphenyl-1,3,4-oxadiazole (dph-oxd) as the cyclometallating ligand and 2,2'-bipyridine (bpy) or 2-(1H-pyrazol-1-yl)pyridine (pzpy) as the ancillary ligands, have been synthesized, and their photophysical and electrochemical properties have been comprehensively investigated. In solution, both complexes emit efficient blue-green light. For complex 1, the light emission in a neat film is remarkably red-shifted; in solid state, it gives an intriguing piezochromic phenomenon. Compared with archetype [Ir(ppy)2(bpy)]PF6 (ppy is 2-phenylpyridine), complex 1 shows a largely stabilized HOMO (highest occupied molecular orbital) level, induced by the electron-deficient 1,3,4-oxadiazole (oxd) heterocycle of dph-oxd, which results in an enlarged energy gap and blue-shifted emission. Compared with complex 1, complex 2 shows an enhanced LUMO (lowest unoccupied molecular orbital) level, caused by the electron-rich pzpy ancillary ligand, but they exhibit similar emission energy in solution. For both complexes, theoretical calculations reveal that their blue-green emission in solution arises primarily from the (3)π-π* states centered on dph-oxd; moreover, complex 1 bears close-lying (3)π-π* and (3)CT (charge-transfer) states, underlying its remarkably red-shifted emission in the neat film and unique piezochromic behavior in the solid state. Solid state light emitting electrochemical cells (LECs) based on complexes 1 and 2 give efficient yellow and green-blue light, with peak current efficiencies of 18.3 and 5.2 cd A(-1), respectively. It is demonstrated that oxd-type cyclometallating ligands are promising as an avenue to stabilize the HOMOs and tune emission properties of cationic iridium complexes to a large extent.

  10. CATION-π and CH-π Interactions in the Coordination and Solvation of Cu+ (ACETYLENE)n (n=1-6) Complexes Investigated via Infrared Photodissociation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Brathwaite, Antonio David; Walters, Richard S.; Ward, Timothy B.; Duncan, Michael A.

    2015-06-01

    Mass-selected copper-acetylene cation complexes of the form Cu(C2H2)n+ are produced by laser ablation and studied via infrared laser photodissociation spectroscopy in the C-H stretching region (3000-3500 wn). Spectra for larger species are measured via ligand elimination, whereas argon tagging is employed to enhance dissociation yields in smaller complexes. The number of infrared active bands, their frequency positions and their relative intensities provide insight into the structure and bonding of these ions. Density functional theory calculations are carried out in support of this work. The combined data show that cation-π bonds are formed for the n=1-3 species, resulting in red-shifted C-H stretches on the acetylene ligands. Three acetylene ligands complete the coordination of the copper cation. Additional ligands (n=4-6) solvate the n=3 core by forming CH-pi bonds. Distinctive vibrational patterns are exhibited for coordinated vs. solvent ligands. Theory reproduces these results.

  11. Delivery of siRNA using ternary complexes containing branched cationic peptides: the role of peptide sequence, branching and targeting.

    PubMed

    Kudsiova, Laila; Welser, Katharina; Campbell, Frederick; Mohammadi, Atefeh; Dawson, Natalie; Cui, Lili; Hailes, Helen C; Lawrence, M Jayne; Tabor, Alethea B

    2016-03-01

    Ternary nanocomplexes, composed of bifunctional cationic peptides, lipids and siRNA, as delivery vehicles for siRNA have been investigated. The study is the first to determine the optimal sequence and architecture of the bifunctional cationic peptide used for siRNA packaging and delivery using lipopolyplexes. Specifically three series of cationic peptides of differing sequence, degrees of branching and cell-targeting sequences were co-formulated with siRNA and vesicles prepared from a 1 : 1 molar ratio of the cationic lipid DOTMA and the helper lipid, DOPE. The level of siRNA knockdown achieved in the human alveolar cell line, A549-luc cells, in both reduced serum and in serum supplemented media was evaluated, and the results correlated to the nanocomplex structure (established using a range of physico-chemical tools, namely small angle neutron scattering, transmission electron microscopy, dynamic light scattering and zeta potential measurement); the conformational properties of each component (circular dichroism); the degree of protection of the siRNA in the lipopolyplex (using gel shift assays) and to the cellular uptake, localisation and toxicity of the nanocomplexes (confocal microscopy). Although the size, charge, structure and stability of the various lipopolyplexes were broadly similar, it was clear that lipopolyplexes formulated from branched peptides containing His-Lys sequences perform best as siRNA delivery agents in serum, with protection of the siRNA in serum balanced against efficient release of the siRNA into the cytoplasm of the cell.

  12. Cu(II) and Cu(I) coordination complexes involving two tetrathiafulvalene-1,3-benzothiazole hybrid ligands and their radical cation salts.

    PubMed

    Yokota, Sayo; Tsujimoto, Keijiro; Hayashi, Sadayoshi; Pointillart, Fabrice; Ouahab, Lahcène; Fujiwara, Hideki

    2013-06-03

    Preparations, crystal structure analyses, and magnetic property investigations on a new Cu(II)(hfac)2 complex coordinated with two TTF-CH═CH-BTA ligands, where hfac is hexafluoroacetylacetonate, TTF is tetrathiafulvalene, and BTA is 1,3-benzothiazole, are reported together with those of its dicationic AsF6(-) salt, [Cu(hfac)2(TTF-CH═CH-BTA)2](AsF6)2, in which each TTF part is in a radical cation state. In these Cu(II)(hfac)2 complexes, two ligands are bonded to the central Cu atom of the Cu(hfac)2 part through the nitrogen atom of the 1,3-benzothiazole ring and occupy the two apical positions of the Cu(hfac)2 complex with an elongated octahedral geometry. These two ligands are located parallelly in a transverse head-to-tail manner, and the Cu(hfac)2 moiety is closely sandwiched by these two ligands. In the AsF6(-) salt of the Cu(hfac)2 complex, each TTF dimer is separated by the AsF6(-) anions and has no overlap with each other within the one-dimensional arrays, resulting in an insulating behavior. Both Cu(hfac)2 complexes showed the simple Curie-like temperature dependence of paramagnetic susceptibilities (χM), indicating that no interaction exists between the paramagnetic Cu(II) d spins. Furthermore, crystal structure analysis and magnetic/conducting properties of a radical cation ReO4(-) salt of the Cu(I) complex with two TTF-CH═CH-BTA ligands, [Cu(TTF-CH═CH-BTA)2](ReO4)2, are also described. Two nitrogen atoms of the ligands are connected to the central Cu(I) in a linear dicoordination with a Cu-N bond length of 1.879(9) Å. Two TTF parts of the neighboring complexes form a dimerized structure, and such a TTF dimer forms a one-dimensional uniform array along the a direction with a short S-S contact of 3.88 Å. Magnetic property measurement suggested the existence of a strongly antiferromagnetic one-dimensional uniform chain of S = 1/2 spins that originate from the radical cation states of the TTF dimers. Due to the construction of the one

  13. A Combined Density Functional Theory and Spectrophotometry Study of the Bonding Interactions of [NpO2·M]4+ Cation–Cation Complexes

    DOE PAGES

    Freiderich, John W.; Burn, Adam G.; Martin, Leigh R.; ...

    2017-04-14

    The equilibrium constants for [NpO2M∙]4+ (M = Al3+, In3+, Sc3+, Fe3+) in μ = 10 M nitric acid and [NpO2∙Ga]4+ in μ = 10 M hydrochloric acid media have been determined. The trend in the interaction strength follows: Fe3+ > Sc3+ In3+ > Ga3+ Al3+. These equilibrium constants are compared to those of previously reported values for NpO2+ complexes with Cr3+ and Rh3+ within the literature. Thermodynamic parameters and bonding modes are discussed, with density functional theory and natural bond orbital analysis indicating that the NpO2+ dioxocation acts as a -donor with transition-metal cations and a sigma donor with groupmore » 13 cations. The small changes in electron-donating ability is modulated by the overlap with the coordinating metal ion's valence atomic orbitals.« less

  14. Inner-sphere complexes of divalent cations with single-stranded poly(rA) and poly(rU).

    PubMed

    Kankia, Besik I

    2004-06-15

    A combination of ultrasound velocimetry, density, and UV spectroscopy has been employed to study the hydration effects of binding of Mn(2+) and alkaline-earth cations to poly(rA) and poly(rU) single strands. The hydration effects, obtained from volume and compressibility measurements, are positive due to overlapping the hydration shells of interacting molecules and consequently releasing the water molecules to bulk state. The volume effects of the binding to poly(rA), calculated per mole of cations, range from 30.6 to 40.6 cm(3) mol(-1) and the compressibility effects range from 59.2 x 10(-4) to 73.6 x 10(-4) cm(3) mol(-1) bar(-1). The volume and compressibility effects for poly(rU) are approximately 17 cm(3) mol(-1) and approximately 50 x 10(-4) cm(3) mol(-1) bar(-1), respectively. The comparative analysis of the dehydration effects suggests that the divalent cations bind to the polynucleotides in inner-sphere manner. In the case of poly(rU) the dehydration effects correspond to two direct coordination, probably between adjacent phosphate groups. The optical study did not reveal any effects of cation on the secondary structure or aggregation of poly(rU). In the case of single-helical poly(rA) binding is more specific: dehydration effects correspond to three to five direct contacts and must involve atomic groups of adenines, and the divalent cations stabilize and aggregate the polynucleotide. Copyright 2004 Wiley Periodicals, Inc. Biopolymers, 2004

  15. Ortho-para interconversion in cation-water complexes: The case of V+(H2O) and Nb+(H2O) clusters

    NASA Astrophysics Data System (ADS)

    Ward, T. B.; Miliordos, E.; Carnegie, P. D.; Xantheas, S. S.; Duncan, M. A.

    2017-06-01

    Vanadium and niobium cation-water complexes, V+(H2O) and Nb+(H2O), are produced by laser vaporization in a pulsed supersonic expansion, mass selected in a time-of-flight spectrometer, and studied with infrared photodissociation spectroscopy using rare gas atom (Ar, Ne) complex predissociation. The vibrational bands measured in the O-H stretching region contain K-type rotational sub-band structure, which provides insight into the structures of these complexes. However, rotational sub-bands do not exhibit the simple patterns seen previously for other metal ion-water complexes. The A rotational constants are smaller than expected and the normal 3:1 intensity ratios for K = odd:even levels for independent ortho:para nuclear spin states are missing for some complexes. We relied on highly correlated internally contracted multi-reference configuration interaction and Coupled Cluster [CCSD(T)] electronic structure calculations of those complexes with and without the rare gas atoms to investigate these anomalies. Rare gas atoms were found to bind via asymmetric motifs to the hydrated complexes undergoing large amplitude motions that vibrationally average to the quasi-C2v symmetry with a significant probability off the C2 axis, thus explaining the reduced A values. Both vanadium and niobium cations exhibit unusually strong nuclear spin coupling to the hydrogen atoms of water, the values of which vary with their electronic state. This catalyzes ortho-para interconversion in some complexes and explains the rotational patterns. The rate of ortho-para relaxation in the equilibrated complexes must therefore be greater than the collisional cooling rate in the supersonic expansion (about 106 s-1).

  16. One-dimensional polymers based on silver(I) cations and organometallic cyclo-P3 ligand complexes.

    PubMed

    Gregoriades, Laurence J; Wegley, Brian K; Sierka, Marek; Brunner, Eike; Gröger, Christian; Peresypkina, Eugenia V; Virovets, Alexander V; Zabel, Manfred; Scheer, Manfred

    2009-10-05

    The synthesis and characterization of the first supramolecular aggregates incorporating the organometallic cyclo-P3 ligand complexes [CpRMo(CO)2(eta3-P3)] (CpR=Cp (C5H5; 1a), Cp* (C5(CH3)5; 1b)) as linking units is described. The reaction of the Cp derivative 1a with AgX (X=CF3SO3, Al{OC(CF3)3}4) yields the one-dimensional (1D) coordination polymers [Ag{CpMo(CO)2(mu,eta3:eta1:eta1-P3)}2]n[Al{OC(CF3)3}4]n (2) and [Ag{CpMo(CO)2(mu,eta3:eta1:eta1-P3)}3]n[X]n (X=CF3SO3 (3a), Al{OC(CF3)3}4 (3b)). The solid-state structures of these polymers were revealed by X-ray crystallography and shown to comprise polycationic chains well-separated from the weakly coordinating anions. If AgCF3SO3 is used, polymer 3a is obtained regardless of reactant stoichiometry whereas in the case of Ag[Al{OC(CF3)3}4], reactant stoichiometry plays a decisive role in determining the structure and composition of the resulting product. Moreover, polymers 3a, b are the first examples of homoleptic silver complexes in which Ag(I) centers are found octahedrally coordinated to six phosphorus atoms. The Cp* derivative 1b reacts with Ag[Al{OC(CF3)3}4] to yield the 1D polymer [Ag{Cp*Mo(CO)2(mu,eta3:eta2:eta1-P3)}2]n[Al{OC(CF3)3}4]n (4), the crystal structure of which differs from that of polymer 2 in the coordination mode of the cyclo-P3 ligands: in 2, the Ag+ cations are bridged by the cyclo-P3 ligands in a eta1:eta1 (edge bridging) fashion whereas in 4, they are bridged exclusively in a eta2:eta1 mode (face bridging). Thus, one third of the phosphorus atoms in 2 are not coordinated to silver while in 4, all phosphorus atoms are engaged in coordination with silver. Comprehensive spectroscopic and analytical measurements revealed that the polymers 2, 3a, b, and 4 depolymerize extensively upon dissolution and display dynamic behavior in solution, as evidenced in particular by variable temperature 31P NMR spectroscopy. Solid-state 31P magic angle spinning (MAS) NMR measurements, performed on the polymers 2, 3

  17. Colloid, adhesive and release properties of nanoparticular ternary complexes between cationic and anionic polysaccharides and basic proteins like bone morphogenetic protein BMP-2.

    PubMed

    Petzold, R; Vehlow, D; Urban, B; Grab, A L; Cavalcanti-Adam, E A; Alt, V; Müller, M

    2017-03-01

    Herein we describe an interfacial local drug delivery system for bone morphogenetic protein 2 (BMP-2) based on coatings of polyelectrolyte complex (PEC) nanoparticles (NP). The application horizon is the functionalization of bone substituting materials (BSM) used for the therapy of systemic bone diseases. Nanoparticular ternary complexes of cationic and anionic polysaccharides and BMP-2 or two further model proteins, respectively, were prepared in dependence of the molar mixing ratio, pH value and of the cationic polysaccharide. As further proteins chymotrypsin (CHY) and papain (PAP) were selected, which served as model proteins for BMP-2 due to similar isoelectric points and molecular weights. As charged polysaccharides ethylenediamine modified cellulose (EDAC) and trimethylammonium modified cellulose (PQ10) were combined with cellulose sulphatesulfate (CS). Mixing diluted cationic and anionic polysaccharide and protein solutions according to a slight either anionic or cationic excess charge colloidal ternary dispersions formed, which were cast onto germanium model substrates by water evaporation. Dynamic light scattering (DLS) demonstrated, that these dispersions were colloidally stable for at least one week. Fourier Transform Infrared (FTIR) showed, that the cast protein loaded PEC NP coatings were irreversibly adhesive at the model substrate in contact to HEPES buffer and solely CHY, PAP and BMP-2 were released within long-term time scale. Advantageously, out of the three proteins BMP-2 showed the smallest initial burst and the slowest release kinetics and around 25% of the initial BMP-2 content were released within 14days. Released BMP-2 showed significant activity in the myoblast cells indicating the ability to regulate the formation of new bone. Therefore, BMP-2 loaded PEC NP are suggested as novel promising tool for the functionalization of BSM used for the therapy of systemic bone diseases. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Controlling the excited state and photosensitizing property of a 2-(2-pyridyl)benzo[b]thiophene-based cationic iridium complex through simple chemical modification.

    PubMed

    Takizawa, Shin-ya; Shimada, Kengo; Sato, Yoichi; Murata, Shigeru

    2014-03-17

    Bis-cyclometalated cationic iridium (Ir) complexes 1-4 comprising two 2-(2-pyridyl)benzo[b]thiophene (btp) ligands and one 2,2'-bipyridyl (bpy) ancillary ligand with different substituents were prepared as new visible light-absorbing sensitizers and examined for their photophysical and electrochemical properties. Complex 1 was prepared as a parent complex without any substituents. Complexes 2-4 contained methyl-, methoxy-, and trifluoromethyl groups at 4,4'-positions on the bpy ancillary ligand. Systematic investigation of these complexes revealed that such a simple chemical modification selectively controls the excited-state lifetime, while the absorption and emission spectral features remain unchanged. Specifically, the phosphorescence lifetimes of complexes 2 and 3 with electron-donating groups (τ = 3.50 μs, 3.90 μs) were found to be much longer than that of complex 1 (τ = 0.273 μs), and complex 4, possessing strong electron-withdrawing trifluoromethyl groups, did not exhibit detectable phosphorescence at room temperature. The large differences in excited-state lifetimes of complexes 1-3, as well as the nonemissive character of complex 4, are attributed to a strong influence of the substituents on the ligand field strength. The increased σ-donating ability of the ancillary ligand in complexes 2 and 3 destabilizes a short-lived, nonemissive triplet metal-centered ((3)MC) state and increases the energy separation between the (3)MC state and emissive triplet ligand-centered ((3)LC) state based on the btp ligand. For complex 4, however, the (3)MC state is close in energy to the (3)LC state because of the decreased σ-donating ability of the ancillary ligand. Additional evidence of the (3)MC state associated with the changeable excited state was also provided via low-temperature phosphorescence measurements and density functional theory calculations. Ir complexes 1-4 were tested as sensitizers in photoinduced electron-transfer reaction of triethanolamine and

  19. Analysis of self-assembled cationic lipid-DNA gene carrier complexes using flow field-flow fractionation and light scattering.

    PubMed

    Lee, H; Williams, S K; Allison, S D; Anchordoquy, T J

    2001-02-15

    Self-assembled cationic lipid-DNA complexes have shown an ability to facilitate the delivery of heterologous DNA across outer cell membranes and nuclear membranes (transfection) for gene therapy applications. While the size of the complex and the surface charge (which is a function of the lipid-to-DNA mass ratio) are important factors that determine transfection efficiency, lipid-DNA complex preparations are heterogeneous with respect to particle size and net charge. This heterogeneity contributes to the low transfection efficiency and instability of cationic lipid-DNA vectors. Efforts to define structure-activity relations and stable vector populations have been hampered by the lack of analytical techniques that can separate this type of particle and analyze both the physical characteristics and biological activity of the resulting fractions. In this study, we investigated the feasibility of flow field-flow fractionation (flow FFF) to separate cationic lipid-DNA complexes prepared at various lipid-DNA ratios. The compatibility of the lipid-DNA particles with several combinations of FFF carrier liquids and channel membranes was assessed. In addition, changes in elution profiles (or size distributions) were monitored as a function of time using on-line ultraviolet, multiangle light scattering, and refractive index detectors. Multiangle light scattering detected the formation of particle aggregates during storage, which were not observed with the other detectors. In comparison to population-averaged techniques, such as photon correlation spectroscopy, flow FFF allows a detailed examination of subtle changes in the physical properties of nonviral vectors and provides a basis for the definition of structure-activity relations for this novel class of pharmaceutical agents.

  20. Study of complexation process between 4'-nitrobenzo-15-crown-5 and yttrium(III) cation in binary mixed non-aqueous solvents using conductometric method

    NASA Astrophysics Data System (ADS)

    Habibi, N.; Rounaghi, G. H.; Mohajeri, M.

    2012-12-01

    The complexation reaction of macrocyclic ligand (4'-nitrobenzo-15C5) with Y3+ cation was studied in acetonitrile-methanol (AN-MeOH), acetonitrile-ethanol (AN-EtOH), acetonitrile-dimethylformamide (AN-DMF) and ethylacetate-methanol (EtOAc-MeOH) binary mixtures at different temperatures using conductometry method. The conductivity data show that in all solvent systems, the stoichiometry of the complex formed between 4'-nitrobenzo-15C5 and Y3+ cation is 1: 1 (ML). The stability order of (4'-nitrobenzo-15C5). Y3+ complex in pure non-aqueous solvents at 25°C was found to be: EtOAc > EtOH > AN ≈ DMF > MeOH, and in the case of most compositions of the binary mixed solvents at 25°C it was: AN≈MeOH ≈ AN-EtOH > AN-DMF > EtOAc-MeOH. But the results indicate that the sequence of the stability of the complex in the binary mixed solutions changes with temperature. A non-linear behavior was observed for changes of log K f of (4'-nitrobenzo-15C5 · Y3+) complex versus the composition of the binary mixed solvents, which was explained in terms of solvent-solvent interactions and also the hetero-selective solvation of the species involved in the complexation reaction. The values of thermodynamic parameters (Δ H {c/ℴ} and Δ S {c/ℴ}) for formation of the complex were obtained from temperature dependent of the stability constant using the van't Hoff plots. The results represent that in most cases, the complex is both enthalpy and entropy stabilized and the values and also the sign of thermodynamic parameters are influenced by the nature and composition of the mixed solvents.

  1. Ratiometric Molecular Probes Based on Dual Emission of a Blue Fluorescent Coumarin and a Red Phosphorescent Cationic Iridium(III) Complex for Intracellular Oxygen Sensing

    PubMed Central

    Yoshihara, Toshitada; Murayama, Saori; Tobita, Seiji

    2015-01-01

    Ratiometric molecular probes RP1 and RP2 consisting of a blue fluorescent coumarin and a red phosphorescent cationic iridium complex connected by a tetra- or octaproline linker, respectively, were designed and synthesized for sensing oxygen levels in living cells. These probes exhibited dual emission with good spectral separation in acetonitrile. The photorelaxation processes, including intramolecular energy transfer, were revealed by emission quantum yield and lifetime measurements. The ratios (RI=(Ip/If)) between the phosphorescence (Ip) and fluorescence (If) intensities showed excellent oxygen responses; the ratio of RI under degassed and aerated conditions (RI0/RI) was 20.3 and 19.6 for RP1 and RP2. The introduction of the cationic Ir (III) complex improved the cellular uptake efficiency compared to that of a neutral analogue with a tetraproline linker. The emission spectra of the ratiometric probes internalized into living HeLa or MCF-7 cells could be obtained using a conventional microplate reader. The complex RP2 with an octaproline linker provided ratios comparable to the ratiometric measurements obtained using a microplate reader: the ratio of the RI value of RP2 under hypoxia (2.5% O2) to that under normoxia (21% O2) was 1.5 and 1.7 for HeLa and MCF-7 cells, respectively. Thus, the intracellular oxygen levels of MCF-7 cells could be imaged by ratiometric emission measurements using the complex RP2. PMID:26066988

  2. Strong ionic interactions in noncovalent complexes between poly(ethylene imine), a cationic electrolyte, and Cibacron Blue, a nucleotide mimic--implications for oligonucleotide vectors.

    PubMed

    Çelikbıçak, Ömür; Salih, Bekir; Wesdemiotis, Chrys

    2014-07-01

    Cationic polymers can bind DNA to form polyplexes, which are noncovalent complexes used for gene delivery into the targeted cells. For more insight on such biologically relevant systems, the noncovalent complexes between the cationic polymer poly(ethylene imine) (PEI) and the nucleotide mimicking dye Cibacron Blue F3G-A (CB) were investigated using mass spectrometry methods. Two PEIs of low molecular weight were utilized (Mn  ≈ 423 and 600 Da). The different types of CB anions produced by Na(+)/H(+) exchanges on the three sulfonic acid groups of CB and their dehydrated counterparts were responsible for complex formation with PEI. The CB anions underwent noncovalent complex formation with protonated, but not with sodiated PEI. A higher proportion of cyclic oligomers were detected in PEI423 than PEI600, but both architectures formed association products with CB. Tandem mass spectrometry studies revealed a significantly stronger noncovalent interaction between PEI and dehydrated CB than between PEI and intact CB.

  3. Ratiometric Molecular Probes Based on Dual Emission of a Blue Fluorescent Coumarin and a Red Phosphorescent Cationic Iridium(III) Complex for Intracellular Oxygen Sensing.

    PubMed

    Yoshihara, Toshitada; Murayama, Saori; Tobita, Seiji

    2015-06-09

    Ratiometric molecular probes RP1 and RP2 consisting of a blue fluorescent coumarin and a red phosphorescent cationic iridium complex connected by a tetra- or octaproline linker, respectively, were designed and synthesized for sensing oxygen levels in living cells. These probes exhibited dual emission with good spectral separation in acetonitrile. The photorelaxation processes, including intramolecular energy transfer, were revealed by emission quantum yield and lifetime measurements. The ratios (R(I) = (I(p)/I(f))) between the phosphorescence (I(p)) and fluorescence (I(f)) intensities showed excellent oxygen responses; the ratio of R(I) under degassed and aerated conditions ( R(I)(0) was 20.3 and 19.6 for RP1 and RP2. The introduction of the cationic Ir (III) complex improved the cellular uptake efficiency compared to that of a neutral analogue with a tetraproline linker. The emission spectra of the ratiometric probes internalized into living HeLa or MCF-7 cells could be obtained using a conventional microplate reader. The complex RP2 with an octaproline linker provided ratios comparable to the ratiometric measurements obtained using a microplate reader: the ratio of the R(I)) value of RP2 under hypoxia (2.5% O2) to that under normoxia (21% O2) was 1.5 and 1.7 for HeLa and MCF-7 cells, respectively. Thus, the intracellular oxygen levels of MCF-7 cells could be imaged by ratiometric emission measurements using the complex RP2.

  4. A Highly Effective Strategy for Encapsulating Potassium Cations in Small Crown Ether Rings on a Dinuclear Palladium Complex.

    PubMed

    Lucio-Martínez, Fátima; Bermúdez, Brais; Ortigueira, Juan M; Adams, Harry; Fernández, Alberto; Pereira, M Teresa; Vila, José M

    2017-03-16

    The potential of 15-crown-5 ethers to link large cations, such as potassium, is limited by the quasi-parallel arrangement of two oxygen donor moieties upon appropriate orientation of the corresponding ether-ring-containing molecules. Substrates bearing the two crown ethers that are capable of achieving such coordination are hitherto unknown. The synthesis and isolation of a tailor-made dinuclear palladacycle bearing 15-crown-5 ether rings on the metallated phenyls offers such a possibility, providing the adequate environment for the formation of the sandwiched [K(metallacycle-15-crown-5)2 ] moiety. This synthetic strategy also culminates in the isolation of the first palladacycle able to entrap a potassium cation through bonding to two 15-crown-5 ether rings in a single molecule.

  5. A Novel Ternary Ligand System Useful for Preparation of Cationic 99mTc-Diazenido Complexes and 99mTc-Labeling of Small Biomolecules

    PubMed Central

    Kim, Young-Seung; He, Zhengjie; Hsieh, Wen-Yuan; Liu, Shuang

    2008-01-01

    This report describes a novel ternary ligand system composed of a phenylhydrazine, a crown ether-containing dithiocarbamate (DTC) and a PNP-type bisphosphine (PNP). The combination of three different ligands with 99mTc results in cationic 99mTc-diazenido complexes,[99mTc(NNAr)(DTC)(PNP)]+, with potential radiopharmaceuticals for heart imaging. Synthesis of cationic 99mTc-diazenido complexes can be accomplished in two steps with high yield. For example, the reaction of phenylhydrazine with 99mTcO4− at 100 °C in the presence of excess stannous chloride and 1,2-diaminopropane-N,N,N’,N’-tetraacetic acid (PDTA) results in the [99mTc(NNPh)(PDTA)n] intermediate, which then reacts with sodium N-(dithiocarbamato)-2-aminimethyl-15-Crown-5 (L4) and N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]ethoxy-ethylamine (PNP6) at 100 °C for 15 min to give the complex, [99mTc(NNPh)(L4)(PNP6)]+ in high yield (> 90%). Cationic complexes [99mTc(NNPh)(DTC)(PNP)]+ are stable for ≥6 h. Their composition was determined to be 1:1:1:1 for Tc:NNPh:DTC:PNP using the mixed-ligand experiments on the tracer (99mTc) level, and was further confirmed by the ESI-MS spectral data of a model compound [Re(NNPh)(L4)(L6)]+. It was found that both DTCs and bisphosphines have a significant impact on the lipophilicity of their cationic 99mTc-diazenido complexes. Results from a 99mTc-labeling efficiency experiment showed that 4-hydrazinobenzoic acid (HYBA) might be useful as a bifunctional coupling agent for 99mTc-labeling of small biomolecules. However, the 99mTc-labeling efficiency of HYBA is much lower than that of 6-hydrazinonicotinic acid (HYNIC) with tricine and trisodium triphenylphosphine-3,3’,3”-trisulfonate (TPPTS) as coligands. PMID:16536480

  6. Light-emitting properties of cationic iridium complexes containing phenanthroline based ancillary ligand with blue-green and green emission colors

    NASA Astrophysics Data System (ADS)

    Kwon, Yiseul; Sunesh, Chozhidakath Damodharan; Choe, Youngson

    2015-01-01

    We report here two new cationic iridium(III) complexes with phenanthroline-based ancillary ligands, [Ir(dfppy)2(dibutyl-phen)]PF6 (Complex 1) and [Ir(ppz)2(dibutyl-phen)]PF6 (Complex 2) and their uses in light-emitting electrochemical cells (LECs). The design is based on 2-(2,4-difluorophenyl)pyridine (dfppy) and 1-phenylpyrazole (ppz) as the cyclometalating ligands and 2,9-dibutyl-1,10-phenanthroline (dibutyl-phen) as the ancillary ligand. The photophysical and electrochemical properties of the complexes were studied and the results obtained were corroborated with theoretical density functional theory (DFT) calculations. LECs were fabricated incorporating each complexes which resulted in blue-green light emission (502 nm) with Commission Internationale de l'Eclairage (CIE) coordinates of (0.26, 0.49) for Complex 1 and green (530 nm) electroluminescence with CIE coordinates of (0.33, 0.54) for Complex 2. The luminance and the current efficiency of the LECs based on Complex 1 are 947 cd m-2 and 0.25 cd A-1, respectively, which are relatively higher than that of Complex 2 with a maximum luminance of 773 cd m-2 and an efficiency of 0.16 cd A-1.

  7. Possible conformational change within the desolvated and cationized sBBI/trypsin non-covalent complex during the collision-induced dissociation process.

    PubMed

    Darii, Ekaterina; Saravanamuthu, Gunalini; Afonso, Carlos; Alves, Sandra; Gut, Ivo; Tabet, Jean-Claude

    2011-06-30

    Electrospray ionization mass spectrometry (ESI-MS) has become an analytical technique widely used for the investigation of non-covalent protein-protein and protein-ligand complexes due to the soft desolvation conditions that preserve the stoichiometry of the interacting partners. Dissociation studies of solvated or desolvated complexes (in the source and in the collision cell, respectively) allow access to information on protein conformation and localization of the metal ions involved in protein structure stabilization and biological activity. The complex of bovine trypsin and small soybean Bowman-Birk inhibitor (sBBI) was studied by ESI-MS to determine changes occurring within the complex during its transfer from droplets to the gas phase independently of the ion polarity. Under collision-induced dissociation (CID) conditions, unexpected binding of the Ca(2+) ion (cofactor of native trypsin) to the inhibitor molecule was observed within the desolvated sBBI/trypsin/Ca(2+) complex (with a 1:1:1 stoichiometry). This formal gas-phase migration of the calcium ion from trypsin to the inhibitor may be related to conformational rearrangements in the solvent-free and likely collapsed complex. However, under conditions leading to the increase in complex charge state, the appearance of the cationized trypsin molecule was detected during complex dissociation, thus reflecting different pathways of the evolution of complex conformation.

  8. Sorption of aromatic compounds to clay mineral and model humic substance-clay complex: effects of solute structure and exchangeable cation.

    PubMed

    Zhang, Yingjie; Zhu, Dongqiang; Yu, Hongxia

    2008-01-01

    Clay minerals and humic substance (HS)-clay complexes are widely distributed in soil environments. Improved predictions on the uptake of organic pollutants by soil require a better understanding of fundamental mechanisms that control the relative contribution from organic and inorganic constituents. Five selected aromatic compounds varying in electronic structure, including nonpolar phenanthrene (PHEN), 1,2,4,5-tetrachlorobenzene (TeCB), polar 1,3-dinitrobenzene (DNB), 2,6-dichlorobenzonitrile (dichlobenil [DNL]), and 1-naphthalenyl methylcarbamate (carbaryl [CBL]), were sorbed separately from aqueous solution to Na(+)-, K(+)-, Cs(+)-, and Ca(2+)-saturated montmorillonites with and without the presence of dissolved HS at pH about 6. Upon normalizing for hydrophobic effects by solute aqueous solubility, the overall trend of sorptive affinity to HS-free K(+)-clay is DNB > DNL, CBL > PHEN, TeCB, indicating preferential adsorption of the polar solutes. With the presence of HS, sorption of PHEN, TeCB, and CBL increases by several times compared with the pure clay, attributed to HS-facilitated hydrophobic partition (PHEN and TeCB) or H-bonding (CBL). The enhanced sorption of PHEN by HS is cation dependent, where Cs(+) shows the strongest facilitative effect. Coadsorption of HS does not affect sorption of DNB and DNL to clays except that of DNB to Ca(2+)-clay because cation-dipole interactions between the polar group (NO(2) or CN) of solute and weakly hydrated exchangeable cations dominate the overall sorption.

  9. Influence of cations on the complexation yield of DOTATATE with yttrium and lutetium: a perspective study for enhancing the 90Y and 177Lu labeling conditions.

    PubMed

    Asti, Mattia; Tegoni, Matteo; Farioli, Daniela; Iori, Michele; Guidotti, Claudio; Cutler, Cathy S; Mayer, Pat; Versari, Annibale; Salvo, Diana

    2012-05-01

    The DOTA macrocyclic ligand can form stable complexes with many cations besides yttrium and lutetium. For this reason, the presence of competing cationic metals in yttrium-90 and lutetium-177 chloride solutions can dramatically influence the radiolabeling yield. The aim of this study was to evaluate the coordination yield of yttrium- and lutetium-DOTATATE complexes when the reaction is performed in the presence of varying amounts of competing cationic impurities. In the first set of experiments, the preparation of the samples was performed by using natural yttrium and lutetium (20.4 nmol). The molar ratio between DOTATATE and these metals was 1 to 1. Metal competitors (Pb(2+), Zn(2+), Cu(2+), Fe(3+), Al(3+), Ni(2+), Co(2+), Cr(3+)) were added separately to obtain samples with varying molar ratio with respect to yttrium or lutetium (0.1, 0.5, 1, 2 and 10). The final solutions were analyzed through ultra high-performance liquid chromatography with an UV detector. In the second set of experiments, an amount of (90)Y or (177)Lu chloride (6 MBq corresponding to 3.3 and 45 pmol, respectively) was added to the samples, and a radio-thin layer chromatography analysis was carried out. The coordination of Y(3+) and Lu(3+) was dramatically influenced by low levels of Zn(2+), Cu(2+) and Co(2+). Pb(2+) and Ni(2+) were also shown to be strong competitors at higher concentrations. Fe(3+) was expected to be a strong competitor, but the effect on the incorporation was only partly dependent on its concentration. Al(3+) and Cr(3+) did not compete with Y(3+) and Lu(3+) in the formation of DOTATATE complexes. Copyright © 2012 Elsevier Inc. All rights reserved.

  10. Influences of the propyl group on the van der Waals structures of 4-propylaniline complexes with one and two argon atoms studied by electronic and cationic spectroscopy.

    PubMed

    Yang, Zhijun; Gu, Quanli; Trindle, Carl O; Knee, J L

    2015-07-21

    4-propylaniline complexes with one and two argon atoms formed in the molecular beam were studied in the first excited electronic state, S1, using resonance enhanced two-photon ionization spectroscopy and in the cation ground state, D0, using mass analyzed threshold ionization spectroscopy. The combination of electronic and cationic spectra of the clusters allows two conformations to be identified in both aniline-Ar1 and aniline-Ar2, which are assigned to either the gauche configuration or anti-configuration of 4-propylaniline. The gauche isomer exhibits complex bands shifted 29 cm(-1) and 89 cm(-1) from the S1 origin bands and 83 cm(-1) and 148 cm(-1) from the ionization potential assigned to the Ar1 and Ar2 complexes, respectively. For the anti-rotamer, the corresponding shifts actually become nearly additive, 53 cm(-1) and 109 cm(-1) for the S1 origin bands, and 61 cm(-1) and 125 cm(-1) for the ionization potentials. Ab initio calculations provide insights into the influences of the propyl and amino groups on the positions of the argon atoms within the clusters. In addition, the binding energy of one argon with the gauche isomer of 4-propylaniline has been measured to be 550 ± 5 cm(-1) in the D0 state, 496 ± 5 cm(-1) in the S1 state, and 467 ± 5 cm(-1) in the neutral ground state, S0.

  11. Infrared Multiple Photon Dissociation Action Spectroscopy and Theoretical Studies of Diethyl Phosphate Complexes: Effects of Protonation and Sodium Cationization on Structure

    NASA Astrophysics Data System (ADS)

    Fales, B. S.; Fujamade, N. O.; Nei, Y.-W.; Oomens, J.; Rodgers, M. T.

    2011-01-01

    The gas-phase structures of deprotonated, protonated, and sodium-cationized complexes of diethyl phosphate (DEP) including [DEP - H]-, [DEP + H]+, [DEP + Na]+, and [DEP - H + 2Na]+ are examined via infrared multiple photon dissociation (IRMPD) action spectroscopy using tunable IR radiation generated by a free electron laser, a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) with an electrospray ionization (ESI) source, and theoretical electronic structure calculations. Measured IRMPD spectra are compared to linear IR spectra calculated at the B3LYP/6-31G(d,p) level of theory to identify the structures accessed in the experimental studies. For comparison, theoretical studies of neutral complexes are also performed. These experiments and calculations suggest that specific geometric changes occur upon the binding of protons and/or sodium cations, including changes correlating to nucleic acid backbone geometry, specifically P-O bond lengths and ∠OPO bond angles. Information from these observations may be used to gain insight into the structures of more complex systems, such as nucleotides and solvated nucleic acids.

  12. The role of different network modifying cations on the speciation of the Co(2+) complex in silicates and implication in the investigation of historical glasses.

    PubMed

    Fornacelli, Cristina; Ceglia, Andrea; Bracci, Susanna; Vilarigues, Marcia

    2018-01-05

    In the last decades the speciation of the cobalt complex in a glass matrix has been extensively studied. Bivalent cobalt ions in glasses of different composition commonly adopt a tetrahedral coordination, though hexa- or penta-coordinated species are also possible. Changes in the absorbance spectrum of Co-doped glasses were attested in previous studies according to the introduction of different modifying cations. A shifting of the first sub-band characterizing the typical triplets of tetrahedral Co(2+) ions in both the visible and near infrared regions was observed, but discrepancies in literature suggested a relevant role of glass composition on the definition of the optical signature of cobalt. Co-doped glasses with different composition (soda-lime, potash-lime, mixed alkali and ZnO-Na2O-CaO-SiO2) were studied via Fiber Optic Reflectance Spectroscopy (FORS). Pseudo-Voigt functions were used for the deconvolution of the absorbance spectra and the features of the bands characteristic of each cobalt complex were investigated. The structural role played by each modifying cation and the fundamental implications of glass basicity on the speciation of different Co-complexes were stressed. Changes in glass structure resulted in different equilibria between the three absorbing species whose specific optical signatures in the 480-530nm region interact to determine the resulting absorbance spectrum. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Thermochemistry and infrared spectroscopy of neutral and cationic iron-polycyclic aromatic hydrocarbon complexes of astrophysical interest: fundamental density functional theory studies.

    PubMed

    Simon, Aude; Joblin, Christine

    2007-10-04

    This paper reports extensive calculations on the structural, thermodynamic, and mid-infrared spectroscopic properties of neutral and cationic model iron-polycyclic aromatic hydrocarbon (PAH) complexes of astrophysical interest for three PAHs of increasing size, namely, naphthalene (C10H8), pyrene (C16H10), and coronene (C24H12). Geometry optimizations and frequency calculations were performed using hybrid Hartree-Fock/density functional theory (DFT) methods. The use of DFT methods is mandatory in terms of computational cost and efficiency to describe the electronic and vibrational structures of such large organometallic unsaturated species that present several low-energy isomers of different structures and electronic and spin states. The calculated structures for the low-energy isomers of the model Fe-PAH and Fe-PAH+ complexes are presented and discussed. Iron-PAH binding energies are extracted, and the consequences of the coordination of iron on the infrared spectra of neutral and cationic PAHs are shown with systematic effects on band intensities and positions being demonstrated. The first results are discussed in terms of astrophysical implications. This work is the first step of an ongoing effort in our group to understand the photophysics and spectroscopy of iron-PAH complexes in the conditions of the interstellar medium using a synergy between observations, laboratory experiments, and theory.

  14. Influences of the propyl group on the van der Waals structures of 4-propylaniline complexes with one and two argon atoms studied by electronic and cationic spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, Zhijun; Gu, Quanli; Trindle, Carl O.; Knee, J. L.

    2015-07-01

    4-propylaniline complexes with one and two argon atoms formed in the molecular beam were studied in the first excited electronic state, S1, using resonance enhanced two-photon ionization spectroscopy and in the cation ground state, D0, using mass analyzed threshold ionization spectroscopy. The combination of electronic and cationic spectra of the clusters allows two conformations to be identified in both aniline-Ar1 and aniline-Ar2, which are assigned to either the gauche configuration or anti-configuration of 4-propylaniline. The gauche isomer exhibits complex bands shifted 29 cm-1 and 89 cm-1 from the S1 origin bands and 83 cm-1 and 148 cm-1 from the ionization potential assigned to the Ar1 and Ar2 complexes, respectively. For the anti-rotamer, the corresponding shifts actually become nearly additive, 53 cm-1 and 109 cm-1 for the S1 origin bands, and 61 cm-1 and 125 cm-1 for the ionization potentials. Ab initio calculations provide insights into the influences of the propyl and amino groups on the positions of the argon atoms within the clusters. In addition, the binding energy of one argon with the gauche isomer of 4-propylaniline has been measured to be 550 ± 5 cm-1 in the D0 state, 496 ± 5 cm-1 in the S1 state, and 467 ± 5 cm-1 in the neutral ground state, S0.

  15. A cationic iridium(III) complex showing aggregation-induced phosphorescent emission (AIPE) in the solid state: synthesis, characterization and properties.

    PubMed

    Shan, Guo-Gang; Zhang, Ling-Yu; Li, Hai-Bin; Wang, Shuang; Zhu, Dong-Xia; Li, Peng; Wang, Chun-Gang; Su, Zhong-Min; Liao, Yi

    2012-01-14

    We report the synthesis and characterization of two cationic iridium(III) complexes with dendritic carbazole ligands as ancillary ligands, namely, [Ir(ppy)(2)L3]PF(6) (1) and [Ir(ppy)(2)L4]PF(6) (2), where L3 and L4 represent 3,8-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)-1,10-phenanthroline and 3,8-bis(3',6'-di-tert-butyl-6-(3,6-di-tert-butyl-9H-carbazol-9-yl)-3,9'-bi(9H-carbazol)-9-yl)-1,10-phenanthroline, respectively. Their photophysical properties have been investigated and compared. The results have shown that complex 2 is aggregation-induced phosphorescent emission (AIPE) active and exhibits the highest photoluminescent quantum yield (PLQY) of 16.2% in neat film among the reported cationic Ir(III) complexes with AIPE activity. In addition, it also enjoys redox reversibility, good film-forming ability, excellent thermal stability as well as off/on luminescence switching properties, revealing its potential application as a candidate for light-emitting electrochemical cells and organic vapor sensing. To explore applications in biology, 2 was used to image cells.

  16. Blue-green emissive cationic iridium(III) complexes using partially saturated strongly-donating guanidyl-pyridine/-pyrazine ancillary ligands.

    PubMed

    Hasan, Kamrul; Pal, Amlan K; Auvray, Thomas; Zysman-Colman, Eli; Hanan, Garry S

    2015-09-25

    A new class of cationic iridium(III) complexes of the form [(C(∧)N)2Ir(N(∧)N)][PF6] is reported, where C(∧)N = cyclometallating 2-phenylpyridinato, ppy, or 2-(2,4-difluorophenyl)-5'-methylpyridinato, dFMeppy, and N(∧)N = guanidyl-pyridine, gpy, or -pyrazine, gpz, as the ancillary ligand. A large blue-shift in the emission coupled with a 7-to-9 fold enhancement in photoluminescence quantum yield and microsecond emission lifetimes were observed for the complexes containing the partially saturated gpy ligand as compared to the benchmark complex [(ppy)2Ir(bpy)][PF6], C1, where bpy is 2,2'-bipyridine.

  17. Luminescence Quenching of the Tris(2,2’-bipyrazine) Ruthenium(II) Cation, and Its Monoprotonated Complex.

    DTIC Science & Technology

    1984-01-01

    rates corrected for ionic strength (I14 KCl) using Debye - Huckel expressions in the literature. 2 0 ,21 The lowest excited state of Ru(bpz)4 2 lies at...Ru(bpz) 3 2+ cation with amines and methoxybenzenes is reductive quenching. The theory of electron transfer quenching 13 , is based on the...R.A., and Sutin, N., 1975, 14, 213 and refs. therein. 20. (a) Debye , P., Trans. Electrochem. Soc., 1942, 82, 265. (b) Noyes, R.M., Prog. React. Kinet

  18. Human 17β-hydroxysteroid dehydrogenase-ligand complexes: crystals of different space groups with various cations and combined seeding and co-crystallization

    NASA Astrophysics Data System (ADS)

    Zhu, D.-W.; Han, Q.; Qiu, W.; Campbell, R. L.; Xie, B.-X.; Azzi, A.; Lin, S.-X.

    1999-01-01

    Human estrogenic 17β-hydroxysteroid dehydrogenase (17β-HSD1) is responsible for the synthesis of active estrogens that stimulate the proliferation of breast cancer cells. The enzyme has been crystallized using a Mg 2+/PEG (3500)/β-octyl glucoside system [Zhu et al., J. Mol. Biol. 234 (1993) 242]. The space group of these crystals is C2. Here we report that cations can affect 17β-HSD1 crystallization significantly. In the presence of Mn 2+ instead of Mg 2+, crystals have been obtained in the same space group with similar unit cell dimensions. In the presence of Li + and Na + instead of Mg 2+, the space group has been changed to P2 12 12 1. A whole data set for a crystal of 17ß-HSD1 complex with progesterone grown in the presence of Li + has been collected to 1.95 Å resolution with a synchrotron source. The cell dimensions are a=41.91 Å, b=108.21 Å, c=117.00 Å. The structure has been preliminarily determined by molecular replacement, yielding important information on crystal packing in the presence of different cations. In order to further understand the structure-function relationship of 17β-HSD1, enzyme complexes with several ligands have been crystallized. As the steroids have very low aqueous solubility, we used a combined method of seeding and co-crystallization to obtain crystals of 17β-HSD1 complexed with various ligands. This method provides ideal conditions for growing complex crystals, with ligands such as 20α-hydroxysteroid progesterone, testosterone and 17β-methyl-estradiol-NADP +. Several complex structures have been determined with reliable electronic density of the bound ligands.

  19. Role of organic cation/carnitine transporter 1 in uptake of phenformin and inhibitory effect on complex I respiration in mitochondria.

    PubMed

    Shitara, Yoshihisa; Nakamichi, Noritaka; Norioka, Misaki; Shima, Hiroyo; Kato, Yukio; Horie, Toshiharu

    2013-03-01

    Phenformin causes lactic acidosis in clinical situations due to inhibition of mitochondrial respiratory chain complex I. It is reportedly taken up by hepatocytes and exhibits mitochondrial toxicity in the liver. In this study, uptake of phenformin and [(14)C]tetraethylammonium (TEA) and complex I inhibition by phenformin were examined in isolated liver and heart mitochondria. Uptake of phenformin into isolated rat liver mitochondria was higher than that into heart mitochondria. It was inhibited by several cat ionic compounds, which suggests the involvement of multispecific transport system(s). Similar characteristics were also observed for uptake of TEA; however, uptake of phenformin into mitochondria of organic cation/carnitine transporter 1 (OCTN1) knockout mice was lower than that in wild-type mice, whereas uptake of TEA was comparable between the two strains, suggesting the involvement of distinct transport mechanisms for these two cations in mitochondria. Inhibition by phenformin of oxygen consumption via complex I respiration in isolated rat liver mitochondria was greater than that in heart mitochondria, whereas inhibitory effect of phenformin on complex I respiration was similar in inside-out structured submitochondrial particles prepared from rat livers and hearts. Lactic acidosis provoked by iv infusion of phenformin was weaker in octn1(-/-) mice than that in wild-type mice. These observations suggest that uptake of phenformin into liver mitochondria is at least partly mediated by OCTN1 and functionally relevant to its inhibition potential of complex I respiration. This study was, thus, the first to demonstrate OCTN1-mediated mitochondrial transport and toxicity of biguanide in vivo in rodents.

  20. Endosomal Escape and Transfection Efficiency of PEGylated Cationic Lipid–DNA Complexes Prepared with an Acid-Labile PEG-Lipid

    PubMed Central

    Chan, Chia-Ling; Majzoub, Ramsey N.; Shirazi, Rahau S.; Ewert, Kai K.; Chen, Yen-Ju; Liang, Keng S.

    2012-01-01

    Cationic liposome–DNA (CL–DNA) complexes are being pursued as nonviral gene delivery systems for use in applications that include clinic trials. However, to compete with viral vectors for systemic delivery in vivo, their efficiencies and pharmacokinetics need to be improved. The addition of poly (ethylene glycol)-lipids (PEGylation) prolongs circulation lifetimes of liposomes, but inhibits cellular uptake and endosomal escape of CL–DNA complexes. We show that this limits their transfection efficiency (TE) in a manner dependent on the amount of PEG-lipid, the lipid/DNA charge ratio, and the lipid membrane charge density. To improve endosomal escape of PEGylated CL–DNA complexes, we prepared an acid-labile PEG-lipid (HPEG2K-lipid, PEG MW 2000) which is designed to lose its PEG chains at the pH of late endosomes. The HPEG2K-lipid and a similar but acid-stable PEG-lipid were used to prepare PEGylated CL–DNA complexes. TLC and dynamic light scattering showed that HPEG2K-CL–DNA complexes are stable at pH 7.4 for more than 24 hours, but the PEG chains are cleaved at pH 5 within one hour, leading to complex aggregation. The acid-labile HPEG2K-CL–DNA complexes showed enhanced TE over complexes stabilized with the acid-stable PEG-lipid. Live-cell imaging showed that both types of complexes were internalized to quantitatively similar particle distributions within the first 2 hours of incubation with cells. Thus, we attribute the increased TE of the HPEG2K-CL–DNA complexes to efficient endosomal escape, enabled by the acid-labile HPEG2K-lipid which sheds its PEG chains in the low-pH environment of late endosomes, effectively switching on the electrostatic interactions that promote fusion of the membranes of complex and endosome. PMID:22469293

  1. Self-Assembly of Nanostructured, Complex, Multi-cation Films via Spontaneous Phase Separation and Strain-driven Ordering

    SciTech Connect

    Goyal, Amit; Wee, Sung Hun; Stocks, George Malcolm; Zuev, Yuri L; More, Karren Leslie; Meng, Jianyong; Zhong, Jianxin

    2013-01-01

    Spontaneous self-assembly of a multi-cation nanophase in another multi-cation matrix phase is a promising bottom-up approach to fabricate novel, nanocomposite structures for a range of applications. In an effort to understand the mechanisms for such self-assembly, we report on complimentary experimental and theoretical studies to first understand and then control or guide the self-assembly of insulating BaZrO3 (BZO) nanodots within REBa2Cu3O7- (RE=rare earth elements including Y, REBCO) superconducting films. It was determined that the strain field developed around BZO nanodots embedded in REBCO matrix is a key driving force dictating the self-assembly of BZO nanodots along REBCO c-axis. The size selection and spatial ordering of BZO self-assembly were simulated using thermodynamic and kinetic models. The BZO self-assembly was controllable by tuning the interphase strain field. REBCO superconducting films with BZO defects arrays self-assembled to align in both vertical (REBCO c-axis) and horizontal (REBCO ab-planes) directions, resulted in the maximized pinning and Jc performance for all field angles with smaller angular Jc anisotropy. The work has broad implications for fabrication of controlled self-assembled nanostructures for a range of applications via strain-tuning.

  2. Highly Active Electrolytes for Rechargeable Mg Batteries Based on [Mg2(μ-Cl)2]2+ Cation Complex in Dimethoxyethane

    SciTech Connect

    Cheng, Yingwen; Stolley, Ryan M.; Han, Kee Sung; Shao, Yuyan; Arey, Bruce W.; Washton, Nancy M.; Mueller, Karl T.; Helm, Monte L.; Sprenkle, Vincent L.; Liu, Jun; Li, Guosheng

    2015-01-01

    Highly active electrolytes based on a novel [Mg2(μ-Cl)2]2+ cation complex for reversible Mg deposition were developed and analyzed in this work. These electrolytes were formulated in dimethoxyethane through dehalodimerization of non-nucleophilic MgCl2 by reacting with either Mg salts (such as Mg(TFSI)2, TFSI= bis(trifluoromethane)sulfonylimide) or Lewis acid salts (such as AlEtCl2 or AlCl3). The cation complex was identified for the first time as [Mg2(μ-Cl)2(DME)4]2+ (DME=dimethoxyethane) and its molecular structure was characterized by single crystal X-ray diffraction, Raman spectroscopy and NMR. The electrolyte synthesis process was studied and rational approaches for formulating highly active electrolytes were proposed. Through control of the anions, electrolytes with efficiency close to 100%, wide electrochemical window (up to 3.5V) and high ionic conductivity (> 6 mS/cm) were obtained. The electrolyte synthesis and understandings developed in this work could bring significant opportunities for rational formulation of electrolytes with the general formula [Mg2(μ-Cl)2(DME)4][anion]x for practical Mg batteries.

  3. Superparamagnetic Iron Oxide Nanoparticles-Complexed Cationic Amylose for In Vivo Magnetic Resonance Imaging Tracking of Transplanted Stem Cells in Stroke.

    PubMed

    Lin, Bing-Ling; Zhang, Jun-Zhao; Lu, Lie-Jing; Mao, Jia-Ji; Cao, Ming-Hui; Mao, Xu-Hong; Zhang, Fang; Duan, Xiao-Hui; Zheng, Chu-Shan; Zhang, Li-Ming; Shen, Jun

    2017-05-10

    Cell-based therapy with mesenchymal stem cells (MSCs) is a promising strategy for acute ischemic stroke. In vivo tracking of therapeutic stem cells with magnetic resonance imaging (MRI) is imperative for better understanding cellular survival and migrational dynamics over time. In this study, we develop a novel biocompatible nanocomplex (ASP-SPIONs) based on cationic amylose, by introducing spermine and the image label, ultrasmall superparamagnetic iron oxide nanoparticles (SPIONs), to label MSCs. The capacity, efficiency, and cytotoxicity of the nanocomplex in transferring SPIONs into green fluorescence protein-modified MSCs were tested; and the performance of in vivo MRI tracking of the transplanted cells in acute ischemic stroke was determined. The results demonstrated that the new class of SPIONs-complexed nanoparticles based on biodegradable amylose can serve as a highly effective and safe carrier to transfer magnetic label into stem cells. A reliable tracking of transplanted stem cells in stroke was achieved by MRI up to 6 weeks, with the desirable therapeutic benefit of stem cells on stroke retained. With the advantages of a relatively low SPIONs concentration and a short labeling period, the biocompatible complex of cationic amylose with SPIONs is highly translatable for clinical application. It holds great promise in efficient, rapid, and safe labeling of stem cells for subsequent cellular MRI tracking in regenerative medicine.

  4. Intracellular siRNA delivery system using polyelectrolyte complex micelles prepared from VEGF siRNA-PEG conjugate and cationic fusogenic peptide.

    PubMed

    Lee, Soo Hyeon; Kim, Sun Hwa; Park, Tae Gwan

    2007-06-01

    To develop a small interfering RNA (siRNA) delivery system with low cytotoxicity and high transfection efficiency, siRNA was conjugated to poly(ethylene glycol) via a disulfide linkage (siRNA-PEG) to prepare polyelectrolyte complex micelles (PECMs) by condensing with a cationic fusogenic peptide (KALA). The siRNA-PEG conjugate exhibited enhanced resistance to degradation from nucleases. Anionic siRNA-PEG conjugate and cationic KALA, when mixed in an aqueous phase, spontaneously formed nano-sized PECMs (<200nm) that have an inner core of charge neutralized siRNA/KALA complex surrounded by a PEG corona. Vascular endothelial growth factor (VEGF) siRNA was used to demonstrate VEGF sequence-specific gene inhibition in prostate carcinoma cells (PC-3 cells). The extent of gene silencing was gradually increased with increasing nitrogen to phosphate (N/P) ratio and the concentration of siRNA-PEG/KALA PECMs. These results suggest that the formulation of siRNA-PEG/KALA PECMs could be widely applied for intracellular delivery of various therapeutic siRNAs.

  5. Implementation of the GAUSSIAN 78 programs on the NYU VAX/11-780: a probe into basis set and correlation effects on the structure of molecular complexes. [Complexes of p- and m-hydroxylaniline with formamidinium cation

    SciTech Connect

    Topiol, S; Moskowitz, J W; Osman, R; Weinstein, H

    1980-04-01

    The program package is used in a theoretical study of molecular complexes that serve as models of drug receptor interactions. The complexes are of para-hydroxyaniline and meta-hydroxyaniline with formamidinium cation. Results indicate that the description of the nature of interaction obtained at the STO-3G SCF level does not change when the basis set is extended to the 4-31G level or when correlation effects are included to second order in a Moeller-Plesset formulation. 5 figures, 4 tables. (DLC)

  6. A manganese(V)-oxo π-cation radical complex: influence of one-electron oxidation on oxygen-atom transfer.

    PubMed

    Prokop, Katharine A; Neu, Heather M; de Visser, Sam P; Goldberg, David P

    2011-10-12

    One-electron oxidation of Mn(V)-oxo corrolazine 2 affords 2(+), the first example of a Mn(V)(O) π-cation radical porphyrinoid complex, which was characterized by UV-vis, EPR, LDI-MS, and DFT methods. Access to 2 and 2(+) allowed for a direct comparison of their reactivities in oxygen-atom transfer (OAT) reactions. Both complexes are capable of OAT to PPh(3) and RSR substrates, and 2(+) was found to be a more potent oxidant than 2. Analysis of rate constants and activation parameters, together with DFT calculations, points to a concerted OAT mechanism for 2(+) and 2 and indicates that the greater electrophilicity of 2(+) likely plays a dominant role in enhancing its reactivity. These results are relevant to comparisons between Compound I and Compound II in heme enzymes.

  7. Inclusion complexes of trivalent lutetium cations with an acidic derivative of per(3,6-anhydro)-alpha-cyclodextrin.

    PubMed

    Bonnet, Célia; Gadelle, Andrée; Pécaut, Jacques; Fries, Pascal H; Delangle, Pascale

    2005-02-07

    The cyclodextrin derivative (hexakis (2-O-carboxymethyl-3,6-anhydro)-alpha-cyclodextrin) forms mono- and bimetallic complexes with lutetium(III) in aqueous solution; the X-ray structure of the binuclear complex [Lu2(ACX)(H2O)2] is the first example of a lanthanide-cyclodextrin inclusion complex.

  8. Multistate λ-local-elevation umbrella-sampling (MS-λ-LEUS): method and application to the complexation of cations by crown ethers.

    PubMed

    Bieler, Noah S; Tschopp, Jan P; Hünenberger, Philippe H

    2015-06-09

    An extension of the λ-local-elevation umbrella-sampling (λ-LEUS) scheme [ Bieler et al. J. Chem. Theory Comput. 2014 , 10 , 3006 ] is proposed to handle the multistate (MS) situation, i.e. the calculation of the relative free energies of multiple physical states based on a single simulation. The key element of the MS-λ-LEUS approach is to use a single coupling variable Λ controlling successive pairwise mutations between the states of interest in a cyclic fashion. The Λ variable is propagated dynamically as an extended-system variable, using a coordinate transformation with plateaus and a memory-based biasing potential as in λ-LEUS. Compared to other available MS schemes (one-step perturbation, enveloping distribution sampling and conventional λ-dynamics) the proposed method presents a number of important advantages, namely: (i) the physical states are visited explicitly and over finite time periods; (ii) the extent of unphysical space required to ensure transitions is kept minimal and, in particular, one-dimensional; (iii) the setup protocol solely requires the topologies of the physical states; and (iv) the method only requires limited modifications in a simulation code capable of handling two-state mutations. As an initial application, the absolute binding free energies of five alkali cations to three crown ethers in three different solvents are calculated. The results are found to reproduce qualitatively the main experimental trends and, in particular, the experimental selectivity of 18C6 for K(+) in water and methanol, which is interpreted in terms of opposing trends along the cation series between the solvation free energy of the cation and the direct electrostatic interactions within the complex.

  9. Influences of the propyl group on the van der Waals structures of 4-propylaniline complexes with one and two argon atoms studied by electronic and cationic spectroscopy

    SciTech Connect

    Yang, Zhijun; Gu, Quanli; Trindle, Carl O.; Knee, J. L.

    2015-07-21

    4-propylaniline complexes with one and two argon atoms formed in the molecular beam were studied in the first excited electronic state, S{sub 1}, using resonance enhanced two-photon ionization spectroscopy and in the cation ground state, D{sub 0}, using mass analyzed threshold ionization spectroscopy. The combination of electronic and cationic spectra of the clusters allows two conformations to be identified in both aniline-Ar{sub 1} and aniline-Ar{sub 2}, which are assigned to either the gauche configuration or anti-configuration of 4-propylaniline. The gauche isomer exhibits complex bands shifted 29 cm{sup −1} and 89 cm{sup −1} from the S{sub 1} origin bands and 83 cm{sup −1} and 148 cm{sup −1} from the ionization potential assigned to the Ar{sub 1} and Ar{sub 2} complexes, respectively. For the anti-rotamer, the corresponding shifts actually become nearly additive, 53 cm{sup −1} and 109 cm{sup −1} for the S{sub 1} origin bands, and 61 cm{sup −1} and 125 cm{sup −1} for the ionization potentials. Ab initio calculations provide insights into the influences of the propyl and amino groups on the positions of the argon atoms within the clusters. In addition, the binding energy of one argon with the gauche isomer of 4-propylaniline has been measured to be 550 ± 5 cm{sup −1} in the D{sub 0} state, 496 ± 5 cm{sup −1} in the S{sub 1} state, and 467 ± 5 cm{sup −1} in the neutral ground state, S{sub 0}.

  10. Influence of biological media on the structure and behavior of ferrocene-containing cationic lipid/DNA complexes used for DNA delivery.

    PubMed

    Golan, Sharon; Aytar, Burcu S; Muller, John P E; Kondo, Yukishige; Lynn, David M; Abbott, Nicholas L; Talmon, Yeshayahu

    2011-06-07

    Biological media affect the physicochemical properties of cationic lipid-DNA complexes (lipoplexes) and can influence their ability to transfect cells. To develop new lipids for efficient DNA delivery, the influence of serum-containing media on the structures and properties of the resulting lipoplexes must be understood. To date, however, a clear and general picture of how serum-containing media influences the structures of lipoplexes has not been established. Some studies suggest that serum can disintegrate lipoplexes formed using certain types of cationic lipids, resulting in the inhibition of transfection. Other studies have demonstrated that lipoplexes formulated from other lipids are stable in the presence of serum and are able to transfect cells efficiently. In this article, we describe the influence of serum-containing media on lipoplexes formed using the redox-active cationic lipid bis(n-ferrocenylundecyl)dimethylammonium bromide (BFDMA). This lipoplex system promotes markedly decreased levels of transgene expression in COS-7 cells as serum concentrations are increased from 0 to 2, 5, 10, and 50% (v/v). To understand the cause of this decrease in transfection efficiency, we used cryogenic transmission electron microscopy (cryo-TEM) and measurements of zeta potential to characterize lipoplexes in cell culture media supplemented with 0, 2, 5, 10, and 50% serum. Cryo-TEM revealed that in serum-free media BFDMA lipoplexes form onionlike, multilamellar nanostructures. However, the presence of serum in the media caused disassociation of the intact multilamellar lipoplexes. At low serum concentrations (2 and 5%), DNA threads appeared to separate from the complex, leaving the nanostructure of the lipoplexes disrupted. At higher serum concentration (10%), disassociation increased and bundles of multilamellae were discharged from the main multilamellar complex. In contrast, lipoplexes characterized in serum-free aqueous salt (Li(2)SO(4)) medium and in OptiMEM cell

  11. Unexpected anion effect in the alkoxylation of alkynes catalyzed by N-heterocyclic carbene (NHC) cationic gold complexes.

    PubMed

    Biasiolo, Luca; Trinchillo, Marina; Belanzoni, Paola; Belpassi, Leonardo; Busico, Vincenzo; Ciancaleoni, Gianluca; D'Amora, Angela; Macchioni, Alceo; Tarantelli, Francesco; Zuccaccia, Daniele

    2014-11-03

    The intermolecular alkoxylation of alkynes is the oldest application of cationic gold(I) catalysts; however, no systematic experimental data about the role of the anion are available. In this contribution, the role of the anion in this catalytic reaction as promoted by a N-heterocyclic carbene-based gold catalyst, [(NHC)AuX] (X=BARF(-) , BF4 (-) , OTf(-) , OTs(-) , TFA(-) , or OAc(-) ) is analyzed, through a combined experimental (NMR spectroscopy) and theoretical (DFT calculation) approach. The most important factor seems to be the ability to abstract the proton from the methanol during the nucleophilic attack, and such ability is related to the anion basicity. On the other hand, too high coordination power or basicity of the anion worsens the catalytic performance by preventing alkyne coordination or by forming too much free methoxide in solution, which poisons the catalyst. The intermediate coordinating power and basicity of the OTs(-) anion provides the best compromise to achieve efficient catalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Crystal structure, spectroscopy, DFT studies and thermal characterization of Cobalt(II) complex with 2-protonated aminopyridinium cation as ligand

    NASA Astrophysics Data System (ADS)

    Mhadhbi, Noureddine; Saïd, Salem; Elleuch, Slim; Naïli, Houcine

    2016-03-01

    Single crystals of a new organic-inorganic hybrid compound (2-HAMP)2[CoBr4], (2-HAMP = 2-protonated aminopyridinium cation) was synthesized and characterized by X-Ray diffraction at room temperature, DTA-TG measurement, FT-IR and FT-Raman spectroscopies and optical absorption. Its crystal structure is a packing of alternated organic and inorganic layers parallel to (a, b) plane. The different components are connected by a network of N/C-H⋯Br hydrogen bonds and halogen⋯halogen interactions. These hydrogen bonds give notable vibrational effects. Theoretical calculations were performed using density functional theory (DFT) for studying the molecular structure, vibrational spectra and optical properties of the investigated molecule in the ground state. The optimized geometrical parameters obtained by DFT calculations are in good agreement with single crystal XRD data. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complements with the experimental findings. The simulated spectra satisfactorily coincide with the experimental UV-Visible spectrum. The results show good consistent with the experiment and confirm the contribution of metal orbital to the HOMO-LUMO boundary. Thermal analysis studies indicate the presence of three phase transitions at 68, 125 and 172 °C, which are confirmed by X-ray powder diffraction as a function of temperature.

  13. Quantitative investigations of cation complexation of photochromic 8-benzothiazole-substituted benzopyran: towards metal-ion sensors.

    PubMed

    Zakharova, Marianna I; Coudret, Christophe; Pimienta, Véronique; Micheau, Jean Claude; Delbaere, Stéphanie; Vermeersch, Gaston; Metelitsa, Anatoly V; Voloshin, Nikolai; Minkin, Vladimir I

    2010-02-01

    The photochromic, thermochromic and metallochromic behaviour of a series of three spiro[indoline-8-(benzothiazol-2-yl)-benzopyrans] has been investigated. The thermodynamic and kinetic parameters of their thermal equilibrium between the ring-closed (spiro) and ring-opened (merocyanine) isomeric forms have been determined using UV-Vis absorption and (1)H NMR spectroscopies. By adding Co(ii) and Ni(ii) ions in acetonitrile solution, 1 : 1 and 1 : 2 metal : merocyanine complexes are formed simultaneously. Using appropriate numerical methods, the kinetic analysis of the complexation allowed us to determine accurately key thermodynamic and spectroscopic parameters of the metal complexes. Results showed that the complexation strength is very sensitive to the size of the indoline nitrogen substituent. Complexation can be reversed by shining white light on the coloured complexes which regenerates the inactive spiropyran form, and releases the metallic ion; hence, these systems display fully reversible negative photochromism. The Zn(ii) complexes exhibit intense fluorescence in the 600-800 nm wavelength range. All these behaviours make these spiropyrans bearing benzothiazole heterocycles promising building blocks for the future construction of photodynamic chemosensors for transition metal ions.

  14. DNA-binding and oxidative properties of cationic phthalocyanines and their dimeric complexes with anionic phthalocyanines covalently linked to oligonucleotides.

    PubMed

    Kuznetsova, A A; Lukyanets, E A; Solovyeva, L I; Knorre, D G; Fedorova, O S

    2008-12-01

    Design of chemically modified oligonucleotides for regulation of gene expression has attracted considerable attention over the past decades. One actively pursued approach involves antisense or antigene oligonucleotide constructs carrying reactive groups, many of these based on transition metal complexes. The complexes of Fe(II) and Co(II) with phthalocyanines are extremely good catalysts of oxidation of organic compounds with molecular oxygen and hydrogen peroxide. The binding of positively charged Fe(II) and Co(II) phthalocyanines with single- and double-stranded DNA was investigated. It was shown that these phthalocyanines interact with nucleic acids through an outside binding mode. The site-directed modification of single-stranded DNA by O2 and H2O2 in the presence of dimeric complexes of negatively and positively charged Fe(II) and Co(II) phthalocyanines was investigated. These complexes were formed directly on single-stranded DNA through interaction between negatively charged phthalocyanine in conjugate and positively charged phthalocyanine in solution. The resulting oppositely charged phthalocyanine complexes showed significant increase of catalytic activity compared with monomeric forms of phthalocyanines Fe(II) and Co(II). These complexes catalyzed the DNA oxidation with high efficacy and led to direct DNA strand cleavage. It was determined that oxidation of DNA by molecular oxygen catalyzed by complex of Fe(II)-phthalocyanines proceeds with higher rate than in the case of Co(II)-phthalocyanines but the latter led to a greater extent of target DNA modification.

  15. The Photoluminescent Properties of New Cationic Iridium(III) Complexes Using Different Anions and Their Applications in White Light-Emitting Diodes.

    PubMed

    Yang, Hui; Meng, Guoyun; Zhou, Yayun; Tang, Huaijun; Zhao, Jishou; Wang, Zhengliang

    2015-09-14

    Three cationic iridium(III) complexes [Ir(ppy)₂(phen)][PF₆] (C1), [Ir(ppy)₂(phen)]₂SiF₆ (C2) and [Ir(ppy)₂(phen)]₂TiF₆ (C3) (ppy: 2-phenylpyridine, phen: 1, 10-phenanthroline) using different anions were synthesized and characterized by ¹H Nuclear magnetic resonance (¹HNMR), mass spectra (MS), Fourier transform infrared (FTIR) spectra and element analysis (EA). After the ultraviolet visible (UV-vis) absorption spectra, photoluminescent (PL) properties and thermal properties of the complexes were investigated, complex C1 and C3 with good optical properties and high thermal stability were used in white light-emitting diodes (WLEDs) as luminescence conversion materials by incorporation with 460 nm-emitting blue GaN chips. The integrative performances of the WLEDs fabricated with complex C1 and C3 are better than those fabricated with the widely used yellow phosphor Y₃Al₅O12:Ce(3+) (YAG). The color rendering indexes of the WLEDs with C1 and C3 are 82.0 and 82.6, the color temperatures of them are 5912 K and 3717 K, and the maximum power efficiencies of them are 10.61 Lm·W(-1) and 11.41 Lm·W(-1), respectively.

  16. Self-assembled ternary complexes of neutral liposomes, deoxyribonucleic acid, and bivalent metal cations. Promising vectors for gene transfer?

    NASA Astrophysics Data System (ADS)

    Bruni, P.; Pisani, M.; Amici, A.; Marchini, C.; Montani, M.; Francescangeli, O.

    2006-02-01

    By means of synchrotron x-ray diffraction we demonstrate the self-assembled formation of the neutral ternary dioleoyl-phosphatidylcholine-deoxyribonucleic acid (plasmid)-Me2+ (Me=Ca and Mn) complexes in the liquid-crystalline Lα phase. We also report an attempt of an in vitro transfection on mouse fibroplast NIH 3T3 cell lines, which shows the capability of these complexes to transfect DNA. Based on the reported results, efficient encapsulation of DNA plasmids in these ternary neutral complexes may represent an important alternative to current systemic gene approaches.

  17. Simultaneous detection of [metal(II)-tpen]2+ as kinetically inert cationic complexes using pre-capillary derivatization electrophoresis: an application to biological samples.

    PubMed

    Saito, Shingo; Sasamura, Satoru; Hoshi, Suwaru

    2005-05-01

    A high resolution of doubly charged first row transition (Fe, Cu, Zn, Ni, Co, Mn) and heavy metal (Pb, Cd, Hg) ions was achieved in capillary electrophoresis (CE) with high sensitivity (sub-micromol dm(-3) level), using NN,N'N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) as a pre-capillary derivatizing agent. The non-charged reagent, TPEN, was applied to capillary zone electrophoresis (CZE) for the first time. Since complete spatial separation between the complexes and the ligand was carried out in a carrier buffer, which was free of TPEN, kinetic inertness of metal complexes was necessary for the detection in this pre-capillary method. All the nine listed metal complexes were detected: Ca(2+), Mg(2+), Al(3+), Fe(3+), and Co(3+) complexes were undetectable. This, interestingly, suggests that those nine cations form kinetically inert tpen complexes without strong charge-charge interactions between the metal ion and the ligand. It is expected that the hard-soft-acid-base (HSAB) principle governed the kinetics selectivity. With respect to the electrophoretic behavior, the addition of chloride ion and methanol to the carrier significantly improved the resolution. This is due to the formation of ternary complexes or ion aggregates and the solvation effect, respectively. These effects provided a satisfactory baseline resolution among the nine metal ions. An application to biological samples was demonstrated. Some metal ions in human serum and urine were successfully detected in a simple process without the need for deproteinization using a non-coated fused-silica capillary because of the differenciation in the direction of migration between organic matter and complexes.

  18. Molecular complexation of curcumin with pH sensitive cationic copolymer enhances the aqueous solubility, stability and bioavailability of curcumin.

    PubMed

    Kumar, Sunny; Kesharwani, Siddharth S; Mathur, Himanshi; Tyagi, Mohit; Bhat, G Jayarama; Tummala, Hemachand

    2016-01-20

    Curcumin is a natural dietary compound with demonstrated potential in preventing/treating several chronic diseases in animal models. However, this success is yet to be translated to humans mainly because of its poor oral bioavailability caused by extremely low water solubility. This manuscript demonstrates that water insoluble curcumin (~1μg/ml) forms highly aqueous soluble complexes (>2mg/ml) with a safe pH sensitive polymer, poly(butyl-methacrylate-co-(2-dimethylaminoethyl) methacrylate-co-methyl-methacrylate) when precipitated together in water. The complexation process was optimized to enhance curcumin loading by varying several formulation factors. Acetone as a solvent and polyvinyl alcohol as a stabilizer with 1:2 ratio of drug to polymer yielded complexes with relatively high loading (~280μg/ml) and enhanced solubility (>2mg/ml). The complexes were amorphous in solid and were soluble only in buffers with pHs less than 5.0. Hydrogen bond formation and hydrophobic interactions between curcumin and the polymer were recorded by infrared spectroscopy and nuclear magnetic resonance spectroscopy, respectively. Molecular complexes of curcumin were more stable at various pHs compared to unformulated curcumin. In mice, these complexes increased peak plasma concentration of curcumin by 6 times and oral bioavailability by ~20 times. This is a simple, economic and safer strategy of enhancing the oral bioavailability of curcumin.

  19. Binding of cationic bis-porphyrins linked with p- or m-xylylenediamine and their zinc(II) complexes to duplex DNA.

    PubMed

    Ishikawa, Yoshinobu; Yamakawa, Naoki; Uno, Tadayuki

    2008-12-15

    Spectroscopic, viscometric, and molecular docking analysis of binding of cationic bis-porphyrins linked with p- or m-xylylenediamine (H(2)pXy and H(2)mXy) and their zinc(II) complexes (ZnpXy and ZnmXy) to duplex DNA are described. H(2)pXy and H(2)mXy bound to calf thymus DNA (CTDNA) stronger than unichromophoric H(2)TMPyP, and showed exciton-type induced circular dichroism spectra of their Soret bands. The H(2)TMPyP-like units of the metal-free bis-porphyrins did not intercalate into CTDNA, and thus the binding mode is outside binding with intramolecular stacking. ZnpXy showed favorable binding to A.T over G.C region, and should lie in the major groove of A.T region.

  20. Preoperative scintigraphic and intraoperative scintimetric localization of parathyroid adenoma with cationic Tc-99m complexes and a hand-held gamma-probe.

    PubMed

    Gallowitsch, H J; Fellinger, J; Kresnik, E; Mikosch, P; Pipam, W; Lind, P

    1997-01-01

    The aim of our study was to evaluate the possibility of intraoperative scintimetric detection of parathyroid adenomas with Tc-99m labelled tracers for its usefulness in dystropic or ectopic adenomas. 12 women with biochemically confirmed hyperparathyroidism were included in our study. After injection of 370 MBq Tc-99m tetrofosmin e.g. sestamibi, preoperative scintigraphy (double phase study and SPECT) was performed and T/NT ratios were evaluated for early, delayed and SPECT images. Surgery was performed using a hand-held gamma-probe after preoperative injection of 555-925 MBq Tc-99m tetrofosmin e.g. sestamibi. Count rates (cts/10 sec) were measured and used for calculating in situ- and ex situ-T/NT ratios. In 9 out of 12 patients, adenoma could be detected on static images. Mean T/NT ratios for Tc-99m tetrofosmin were 1.29 for early and 1.23 for delayed images, respectively 1.39 and 1.23 for early and delayed Tc-99m sestamibi scan. Three cases could only be detected with SPECT reconstruction, 11 of 12 parathyroid adenomas could be confirmed intra-operatively. SPECT with Tc-99m labelled cationic complexes showed advantages in detection, precise localization and contrast over static scintigraphy and should therefore be performed at least in cases with poor or no uptake on static images to avoid failures in detection of deeply sited, dislocated glands or adenomas with low uptake. Intraoperative localization and confirmation of parathyroid adenoma with Tc-99m labelled cationic complexes and a gamma probe is possible an 1 may be useful in case of dys- or ectopic adenoma by influencing surgical approach and operating time.

  1. Nucleophilic Aromatic Addition in Ionizing Environments: Observation and Analysis of New C-N Valence Bonds in Complexes between Naphthalene Radical Cation and Pyridine.

    PubMed

    Peverati, Roberto; Platt, Sean P; Attah, Isaac K; Aziz, Saaudallah G; El-Shall, M Samy; Head-Gordon, Martin

    2017-08-30

    Radical organic ions can be stabilized by complexation with neutral organics via interactions that can resemble chemical bonds, but with much diminished bond energies. Those interactions are a key factor in cluster growth and polymerization reactions in ionizing environments such as regions of the interstellar medium and solar nebulae. Such radical cation complexes between naphthalene (Naph) and pyridine (Pyr) are characterized using mass-selected ion mobility experiments. The measured enthalpy of binding of the Naph(+•)(Pyr) heterodimer (20.9 kcal/mol) exceeds that of the Naph(+•)(Naph) homodimer (17.8 kcal/mol). The addition of 1-3 more pyridine molecules to the Naph(+•)(Pyr) heterodimer gives 10-11 kcal/mol increments in binding enthalpy. A rich array of Naph(+•)(Pyr) isomers are characterized by electronic structure calculations. The calculated Boltzmann distribution at 400 K yields an enthalpy of binding in reasonable agreement with experiment. The global minimum is a distonic cation formed by Pyr attack on Naph(+•) at the α-carbon, changing its hybridization from sp(2) to distorted sp(3). The measured collision cross section in helium for the Naph(+•)(Pyr) heterodimer of 84.9 ± 2.5 Å(2) at 302 K agrees well with calculated angle-averaged cross sections (83.9-85.1 Å(2) at 302 K) of the lowest energy distonic structures. A remarkable 16 kcal/mol increase in the binding energy between Naph(+•)(Pyr) and Bz(+•)(Pyr) (Bz is benzene) is understood by energy decomposition analysis. A similar increase in binding from Naph(+•)(NH3) to Naph(+•)(Pyr) (as well as between Bz(+•)(NH3) and Bz(+•)(Pyr)) is likewise rationalized.

  2. Iminothiol/thiourea tautomeric equilibrium in thiourea lipids impacts DNA compaction by inducing a cationic nucleation for complex assembly.

    PubMed

    Breton, Marie; Bessodes, Michel; Bouaziz, Serge; Herscovici, Jean; Scherman, Daniel; Mignet, Nathalie

    2009-11-01

    Our research on lipidic vectors for transfection led us to develop thiourea lipids able to interact with DNA. Hence, we developed a series of lipopolythioureas based on the strong hydrogen bond donor ability of thiourea. More recently we have reported a branched hydroxylated bis-thiourea derivative with interesting transfecting properties. The last step of the syntheses involved a strong acidic condition, leading to an unstable product upon storage. Therefore we designed a new synthesis in mild acidic conditions. Though they exhibit the same mass, the lipids obtained in the two different conditions differ by their interaction with DNA. We therefore explored the physicochemical properties of these two lipids by different means that we describe in this article. In order to insure easier and reliable (13)C-NMR studies of the thiourea group we have designed the synthesis of the corresponding (13)C-labeled thiourea lipids. We have thus shown that when the lipid was submitted to mildly acidic medium; only the thiourea group was observed; while a thiourea/charged and/or uncharged iminothiol tautomeric equilibrium formed when the last step of the synthesis was submitted to low pH. NMR experiments showed that this tautomeric equilibrium could not form in polar solvents. However, UV experiments on the liposomal form of the lipopolythiourea showed the presence of the tautomers. Lipid/DNA interaction consequently differed according to the acidic treatment applied. Eventually, these results revealed that on this particular thiourea lipid, electrostatic interactions due to cationic thioureas are likely to be responsible for DNA compaction and that this tautomeric form of the thiourea could be stabilised by hydrogen bonds in a supramolecular assembly. Nevertheless, this does not reflect a general thiourea lipid/DNA interaction as other thiourea lipids that are able to compact DNA do not undergo an acidic treatment during the final stage of their synthesis.

  3. Synthesis, Properties, and Light-Emitting Electrochemical Cell (LEEC) Device Fabrication of Cationic Ir(III) Complexes Bearing Electron-Withdrawing Groups on the Cyclometallating Ligands.

    PubMed

    Pal, Amlan K; Cordes, David B; Slawin, Alexandra M Z; Momblona, Cristina; Ortı, Enrique; Samuel, Ifor D W; Bolink, Henk J; Zysman-Colman, Eli

    2016-10-17

    The structure-property relationship study of a series of cationic Ir(III) complexes in the form of [Ir(C^N)2(dtBubpy)]PF6 [where dtBubpy = 4,4'-di-tert-butyl-2,2'-bipyridine and C^N = cyclometallating ligand bearing an electron-withdrawing group (EWG) at C4 of the phenyl substituent, i.e., -CF3 (1), -OCF3 (2), -SCF3 (3), -SO2CF3 (4)] has been investigated. The physical and optoelectronic properties of the four complexes were comprehensively characterized, including by X-ray diffraction analysis. All the complexes exhibit quasireversible dtBubpy-based reductions from -1.29 to -1.34 V (vs SCE). The oxidation processes are likewise quasireversible (metal + C^N ligand) and are between 1.54 and 1.72 V (vs SCE). The relative oxidation potentials follow a general trend associated with the Hammett parameter (σ) of the EWGs. Surprisingly, complex 4 bearing the strongest EWG does not adhere to the expected Hammett behavior and was found to exhibit red-shifted absorption and emission maxima. Nevertheless, the concept of introducing EWGs was found to be generally useful in blue-shifting the emission maxima of the complexes (λem = 484-545 nm) compared to that of the prototype complex [Ir(ppy)2(dtBubpy)]PF6 (where ppy = 2-phenylpyridinato) (λem = 591 nm). The complexes were found to be bright emitters in solution at room temperature (ΦPL = 45-66%) with microsecond excited-state lifetimes (τe = 1.14-4.28 μs). The photophysical properties along with density functional theory (DFT) calculations suggest that the emission of these complexes originates from mixed contributions from ligand-centered (LC) transitions and mixed metal-to-ligand and ligand-to-ligand charge transfer (LLCT/MLCT) transitions, depending on the EWG. In complexes 1, 3, and 4 the (3)LC character is prominent over the mixed (3)CT character, while in complex 2, the mixed (3)CT character is much more pronounced, as demonstrated by DFT calculations and the observed positive solvatochromism effect. Due to the

  4. Synthesis, Properties, and Light-Emitting Electrochemical Cell (LEEC) Device Fabrication of Cationic Ir(III) Complexes Bearing Electron-Withdrawing Groups on the Cyclometallating Ligands

    PubMed Central

    2016-01-01

    The structure–property relationship study of a series of cationic Ir(III) complexes in the form of [Ir(C^N)2(dtBubpy)]PF6 [where dtBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine and C^N = cyclometallating ligand bearing an electron-withdrawing group (EWG) at C4 of the phenyl substituent, i.e., −CF3 (1), −OCF3 (2), −SCF3 (3), −SO2CF3 (4)] has been investigated. The physical and optoelectronic properties of the four complexes were comprehensively characterized, including by X-ray diffraction analysis. All the complexes exhibit quasireversible dtBubpy-based reductions from −1.29 to −1.34 V (vs SCE). The oxidation processes are likewise quasireversible (metal + C^N ligand) and are between 1.54 and 1.72 V (vs SCE). The relative oxidation potentials follow a general trend associated with the Hammett parameter (σ) of the EWGs. Surprisingly, complex 4 bearing the strongest EWG does not adhere to the expected Hammett behavior and was found to exhibit red-shifted absorption and emission maxima. Nevertheless, the concept of introducing EWGs was found to be generally useful in blue-shifting the emission maxima of the complexes (λem = 484–545 nm) compared to that of the prototype complex [Ir(ppy)2(dtBubpy)]PF6 (where ppy = 2-phenylpyridinato) (λem = 591 nm). The complexes were found to be bright emitters in solution at room temperature (ΦPL = 45–66%) with microsecond excited-state lifetimes (τe = 1.14–4.28 μs). The photophysical properties along with density functional theory (DFT) calculations suggest that the emission of these complexes originates from mixed contributions from ligand-centered (LC) transitions and mixed metal-to-ligand and ligand-to-ligand charge transfer (LLCT/MLCT) transitions, depending on the EWG. In complexes 1, 3, and 4 the 3LC character is prominent over the mixed 3CT character, while in complex 2, the mixed 3CT character is much more pronounced, as demonstrated by DFT calculations and the observed positive solvatochromism

  5. SO2-Binding Properties of Cationic η6,η1-NCN-Pincer Arene Ruthenium Platinum Complexes: Spectroscopic and Theoretical Studies

    SciTech Connect

    Bonnet, Sylvestre A.; Van Lenthe, Joop H.; van Dam, Hubertus JJ; van Koten, Gerard; Klein Gebbink, Robertus J M

    2011-03-01

    The SO2-binding properties of a series of η6,η1-NCN-pincer ruthenium platinum complexes have been studied by both UV-visible spectroscopy, and theoretical calculations. When an electronwithdrawing [Ru(C5R5)]+ fragment (R = H or Me) is η6-coordinated to the phenyl ring of the NCNpincer platinum fragment (cf. [2]+ and [3]+, see scheme 1), the characteristic orange coloration (pointing to η1- SO2 binding to Pt) of a solution of the parent NCN-pincer platinum complex 1 in dichloromethane upon SO2-bubbling is not observed. However, when the ruthenium center is η6- coordinated to a phenyl substituent linked in para-position to the carbon-to-platinum bond, i.e. complex [4]+, the SO2-binding property of the NCN-platinum center seems to be retained, as bubbling SO2 into a solution of the latter complex produces the characteristic orange color. We performed theoretical calculations at the MP2 level of approximation and TD-DFT studies, which enabled us to interpret the absence of color change in the case of [2]+ as an absence of coordination of SO2 to platinum. We analyze this absence or weaker SO2-coordination in dichloromethane to be a consequence of the relative electron-poorness of the platinum center in the respective η6- ruthenium coordinated NCN-pincer platinum complexes, that leads to a lower binding energy and an elongated calculated Pt-S bond distance. We also discuss the effects of electrostatic interactions in these cationic systems, which also seems to play a destabilizing role for complex [2(SO2)]+.

  6. Chelate bis(imino)pyridine cobalt complexes: synthesis, reduction, and evidence for the generation of ethene polymerization catalysts by Li+ cation activation.

    PubMed

    Kleigrewe, Nina; Steffen, Winfried; Blömker, Tobias; Kehr, Gerald; Fröhlich, Roland; Wibbeling, Birgit; Erker, Gerhard; Wasilke, Julia-Christina; Wu, Guang; Bazan, Guillermo C

    2005-10-12

    Treatment of the bis(iminobenzyl)pyridine chelate Schiff-base ligand 8 (ligPh) with FeCl2 or CoCl2 yielded the corresponding (ligPh)MCl2 complexes 9 (Fe) and 10 (Co). The reaction of 10 with methyllithium or "butadiene-magnesium" resulted in reduction to give the corresponding (ligPh)Co(I)Cl product 11. Similarly, the bis(aryliminoethyl)pyridine ligand (ligMe) was reacted with CoCl2 to yield (ligMe)CoCl2 (12). Reduction to (ligMe)CoCl (13) was effected by treatment with "butadiene-magnesium". Complex 13 reacted with Li[B(C6F5)4] in toluene followed by treatment with pyridine to yield [(ligMe)Co+-pyridine] (15). The reaction of the Co(II) complexes 10 or 12 with ca. 3 molar equiv of methyllithium gave the cobalt(I) complexes 16 and 17, respectively. Treatment of the (ligMe)CoCH3 (17) with Li[B(C6F5)4] gave a low activity ethene polymerization catalyst. Likewise, complex 16 produced polyethylene (activity = 33 g(PE) mmol(cat)(-1) h(-1) bar(-1) at room temperature) upon treatment with a stoichiometric amount of Li[B(C6F5)4]. A third ligand (lig(OMe)) was synthesized featuring methoxy groups in the ligand backbone (22). Coordination to FeCl2 and CoCl2 yielded the desired compounds 23 and 24. Reaction with MeLi gave (ligOMe)CoMe (25/26). Treatment of 25/26 with excess B(C6F5)3 gave the eta6-arene cation complex 27, where one Co-N linkage was cleaved. Activation of 25/26 with Li[B(C6F5)4] again gave a catalytically active species.

  7. Zn(2+) and Cd(2+) cationized serine complexes: infrared multiple photon dissociation spectroscopy and density functional theory investigations.

    PubMed

    Coates, Rebecca A; Boles, Georgia C; McNary, Christopher P; Berden, Giel; Oomens, Jos; Armentrout, P B

    2016-08-10

    The gas-phase structures of zinc and cadmium dications bound to serine (Ser) are investigated by infrared multiple photon dissociation (IRMPD) action spectroscopy using the free electron laser FELIX, in combination with ab initio calculations. To identify the structures of the experimentally observed species, [Zn(Ser-H)CH3CN](+) and CdCl(+)(Ser), the measured action spectra are compared to linear absorption spectra calculated at the B3LYP/6-311+G(d,p) level for Zn(2+) containing complexes and B3LYP/def2-TZVP levels for Cd(2+) containing complexes. Good agreement between the observed IRMPD spectra and the predicted spectra allows identification of the isomers present. The intact amino acid interacting with cadmium chloride adopts a tridentate chelation involving the amino acid backbone amine and carbonyl groups as well as the hydroxyl group of the side-chain, [N,CO,OH]. The presence of two low-energy conformers is observed for the deprotonated serine-zinc complex, with the same tridentate coordination as for the cadmium complex but proton loss occurs at both the hydroxyl side-chain, [N,CO,O(-)], and the carboxylic acid of the amino acid backbone, [N,CO(-),OH]. These results are profitably compared with the analogous results previously obtained for comparable complexes with cysteine.

  8. Calculation of structural parameters of a Van Der Waals complex of the CO molecule with a Li+ cation

    NASA Astrophysics Data System (ADS)

    Bulanin, K. M.; Bulychev, V. P.; Buturlimova, M. V.

    2015-12-01

    The equilibrium nuclear configuration and the potential energy and dipole moment component surfaces of an isolated Li+-CO complex are calculated quantum-mechanically in the MP4(SDQ)/6-311++G(3df) approximation. The geometrical parameters and the binding energy of the complex are determined. The frequencies and intensities for the fundamental transitions are calculated in the harmonic approximation. The one-, two-, and three-dimensional anharmonic vibrational Schrödinger equations are solved using the variational method. The energies of states of a three-dimensional vibrational system, anharmonic constants, and the frequencies and intensities of fundamental transitions are determined with the anharmonic interactions taken into account. The changes in the frequency and intensity of the C-O stretching vibration upon the formation of the complex are predicted.

  9. Chemiluminescence reactions with cationic, neutral, and anionic ruthenium(II) complexes containing 2,2'-bipyridine and bathophenanthroline disulfonate ligands.

    PubMed

    Francis, Paul S; Papettas, Dimitra; Zammit, Elizabeth M; Barnett, Neil W

    2010-07-15

    Ruthenium complexes containing 4,7-diphenyl-1,10-phenanthroline disulfonate (bathophenanthroline disulfonate; BPS) ligands, Ru(BPS)(3)(4-), Ru(BPS)(2)(bipy)(2-) and Ru(BPS)(bipy)(2), were compared to tris(2,2'-bipyridine)ruthenium(II) (Ru(bipy)(3)(2+)), including examination of the wavelengths of maximum absorption and corrected emission intensity, photoluminescence quantum yield, stability of their oxidised ruthenium(III) form, and relative chemiluminescence intensities and signal-to-blank ratios with cerium(IV) sulfate and six analytes (codeine, morphine cocaine, potassium oxalate, furosemide and hydrochlorothiazide) in acidic aqueous solution. The presence of BPS ligands in the complex increased the photoluminescence quantum yield, but decreased the stability of the oxidised form of the reagent. In contrast to previous evidence showing much greater electrochemiluminescence intensities using Ru(BPS)(2)(bipy)(2-) and Ru(BPS)(bipy)(2), these complexes did not provide superior chemiluminescence signals than their homoleptic analogues.

  10. Synthesis and X-ray crystal structures of amine bis(phenolate) lanthanide complexes containing alkali metal cation

    NASA Astrophysics Data System (ADS)

    Ma, Mengtao; Xu, Xiaoping; Yao, Yingming; Zhang, Yong; Shen, Qi

    2005-04-01

    Three lanthanide "ate" complexes L 2YbM(THF) n supported by amine bis(phenolate) ligand [L=Me 2NCH 2CH 2N{CH 2-(2-O-C 6H 2-Bu t2-2,4)} 2; M=Li, n=2 ( 1); M=Na, n=2 ( 2); M=K, n=3 ( 3)] were synthesized by the metathesis reactions of LM 2 with anhydrous YbCl 3 in 2:1 molar ratio in high yield. All the complexes were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. The influence of the alkali metal ions on the molecular structure of these lanthanide complexes has been elucidated.

  11. Spectral and electrochemical studies of bis(diimine)copper(II) complexes in anionic, cationic and nonionic micelles.

    PubMed

    Anitha, N; Balamurugan, R; Palaniandavar, M

    2011-10-15

    The spectral and redox behavior of bis(diimine)copper(II) complexes, where diimine is bipyridine, 1,10-phenanthroline, 4-methyl-1,10-phenanthroline, 5-methyl-1,10-phenanthroline, 5-nitro-1,10-phenanthroline, 4,7-dimethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline and dipyrido-[3,2-d:2',3'-f]-quinoxaline, are significantly different in aqueous and in aqueous SDS, CTAB and Triton X-100 micellar solutions. The (1)H NMR spectral study in aqueous (D(2)O) and aqueous micelles reveals that the Cu(II) complexes interact more strongly with SDS than with CTAB and Triton X-100 micelles and at sites on SDS micelles different from those on the latter. Ligand Field spectral studies reveal that the complexes exist as the dicationic aquated species [Cu(diimine)(2)(H(2)O)(2)](2+), which interacts strongly with the anionic SDS micelles through columbic forces. However, they exist as [Cu(diimine)(2)(H(2)O)Cl](+) and/or [Cu(diimine)(2)H(2)] located in the hydrophobic microenvironments in Triton X-100 and CTAB micelles. The attainment of reversibility of the redox systems in the micellar microenvironments is remarkable and this illustrates that the Cu(II) and Cu(I) species undergo stereochemical changes suitable for reversible electron-transfer. The remarkable differences in spectral and electrochemical properties of Cu(II) complexes in aqueous and aqueous micellar solutions illustrate that the complexes are nestled largely within the micellar environments and imply that the accessibilities of the complexes to electron-transfer are different and are dependent on the nature of micelles as well as the nature and hydrophobicity of the diimine ligands. Copyright © 2011 Elsevier Inc. All rights reserved.

  12. Ligand-Controlled CO2 Activation Mediated by Cationic Titanium Hydride Complexes, [LTiH](+) (L=Cp2 , O).

    PubMed

    Tang, Shi-Ya; Rijs, Nicole J; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2015-06-01

    CO2 activation mediated by [LTiH](+) (L=Cp2 , O) is observed in the gas phase at room temperature using electrospray-ionization mass spectrometry, and reaction details are derived from traveling wave ion-mobility mass spectrometry. Wheresas oxygen-atom transfer prevails in the reaction of the oxide complex [OTiH](+) with CO2 , generating [OTi(OH)](+) under the elimination of CO, insertion of CO2 into the metal-hydrogen bond of the cyclopentadienyl complex, [Cp2 TiH](+) , gives rise to the formate complex [Cp2 Ti(O2 CH)](+) . DFT-based methods were employed to understand how the ligand controls the observed variation in reactivity toward CO2 . Insertion of CO2 into the Ti-H bond constitutes the initial step for the reaction of both [Cp2 TiH](+) and [OTiH](+) , thus generating formate complexes as intermediates. In contrast to [Cp2 Ti(O2 CH)](+) which is kinetically stable, facile decarbonylation of [OTi(O2 CH)](+) results in the hydroxo complex [OTi(OH)](+) . The longer lifetime of [Cp2 Ti(O2 CH)](+) allows for secondary reactions with background water, as a result of which, [Cp2 Ti(OH)](+) is formed. Further, computational studies reveal a good linear correlation between the hydride affinity of [LTi](2+) and the barrier for CO2 insertion into various [LTiH](+) complexes. Understanding the intrinsic ligand effects may provide insight into the selective activation of CO2 .

  13. Synthesis, one- and two-photon photophysical and excited-state properties, and sensing application of a new phosphorescent dinuclear cationic iridium(III) complex.

    PubMed

    Xu, Wen-Juan; Liu, Shu-Juan; Zhao, Xin; Zhao, Ning; Liu, Zhi-Qiang; Xu, Hang; Liang, Hua; Zhao, Qiang; Yu, Xiao-Qiang; Huang, Wei

    2013-01-07

    A new phosphorescent dinuclear cationic iridium(III) complex (Ir1) with a donor-acceptor-π-bridge-acceptor-donor (D-A-π-A-D)-conjugated oligomer (L1) as a N^N ligand and a triarylboron compound as a C^N ligand has been synthesized. The photophysical and excited-state properties of Ir1 and L1 were investigated by UV/Vis absorption spectroscopy, photoluminescence spectroscopy, and molecular-orbital calculations, and they were compared with those of the mononuclear iridium(III) complex [Ir(Bpq)(2)(bpy)](+)PF(6)(-) (Ir0). Compared with Ir0, complex Ir1 shows a more-intense optical-absorption capability, especially in the visible-light region. For example, complex Ir1 shows an intense absorption band that is centered at λ=448 nm with a molar extinction coefficient (ε) of about 10(4) , which is rarely observed for iridium(III) complexes. Complex Ir1 displays highly efficient orange-red phosphorescent emission with an emission wavelength of 606 nm and a quantum efficiency of 0.13 at room temperature. We also investigated the two-photon-absorption properties of complexes Ir0, Ir1, and L1. The free ligand (L1) has a relatively small two-photon absorption cross-section (δ(max) =195 GM), but, when complexed with iridium(III) to afford dinuclear complex Ir1, it exhibits a higher two-photon-absorption cross-section than ligand L1 in the near-infrared region and an intense two-photon-excited phosphorescent emission. The maximum two-photon-absorption cross-section of Ir1 is 481 GM, which is also significantly larger than that of Ir0. In addition, because the strong B-F interaction between the dimesitylboryl groups and F(-) ions interrupts the extended π-conjugation, complex Ir1 can be used as an excellent one- and two-photon-excited "ON-OFF" phosphorescent probe for F(-) ions.

  14. Inner-sphere complexation of cations at the rutile-water interface: A concise surface structural interpretation with the CD and MUSIC model

    NASA Astrophysics Data System (ADS)

    Ridley, Moira K.; Hiemstra, Tjisse; van Riemsdijk, Willem H.; Machesky, Michael L.

    2009-04-01

    Acid-base reactivity and ion-interaction between mineral surfaces and aqueous solutions is most frequently investigated at the macroscopic scale as a function of pH. Experimental data are then rationalized by a variety of surface complexation models. These models are thermodynamically based which in principle does not require a molecular picture. The models are typically calibrated to relatively simple solid-electrolyte solution pairs and may provide poor descriptions of complex multi-component mineral-aqueous solutions, including those found in natural environments. Surface complexation models may be improved by incorporating molecular-scale surface structural information to constrain the modeling efforts. Here, we apply a concise, molecularly-constrained surface complexation model to a diverse suite of surface titration data for rutile and thereby begin to address the complexity of multi-component systems. Primary surface charging curves in NaCl, KCl, and RbCl electrolyte media were fit simultaneously using a charge distribution (CD) and multisite complexation (MUSIC) model [Hiemstra T. and Van Riemsdijk W. H. (1996) A surface structural approach to ion adsorption: the charge distribution (CD) model. J. Colloid Interf. Sci. 179, 488-508], coupled with a Basic Stern layer description of the electric double layer. In addition, data for the specific interaction of Ca 2+ and Sr 2+ with rutile, in NaCl and RbCl media, were modeled. In recent developments, spectroscopy, quantum calculations, and molecular simulations have shown that electrolyte and divalent cations are principally adsorbed in various inner-sphere configurations on the rutile 1 1 0 surface [Zhang Z., Fenter P., Cheng L., Sturchio N. C., Bedzyk M. J., Předota M., Bandura A., Kubicki J., Lvov S. N., Cummings P. T., Chialvo A. A., Ridley M. K., Bénézeth P., Anovitz L., Palmer D. A., Machesky M. L. and Wesolowski D. J. (2004) Ion adsorption at the rutile-water interface: linking molecular and macroscopic

  15. inner-sphere complexation of cations at the rutile-water interface: A concise surface structural interpretation with the CD and MUSIC model

    SciTech Connect

    Ridley, Mora K.; Hiemstra, T; Van Riemsdijk, Willem H.; Machesky, Michael L.

    2009-01-01

    Acid base reactivity and ion-interaction between mineral surfaces and aqueous solutions is most frequently investigated at the macroscopic scale as a function of pH. Experimental data are then rationalized by a variety of surface complexation models. These models are thermodynamically based which in principle does not require a molecular picture. The models are typically calibrated to relatively simple solid-electrolyte solution pairs and may provide poor descriptions of complex multicomponent mineral aqueous solutions, including those found in natural environments. Surface complexation models may be improved by incorporating molecular-scale surface structural information to constrain the modeling efforts. Here, we apply a concise, molecularly-constrained surface complexation model to a diverse suite of surface titration data for rutile and thereby begin to address the complexity of multi-component systems. Primary surface charging curves in NaCl, KCl, and RbCl electrolyte media were fit simultaneously using a charge distribution (CD) and multisite complexation (MUSIC) model [Hiemstra T. and Van Riemsdijk W. H. (1996) A surface structural approach to ion adsorption: the charge distribution (CD) model. J. Colloid Interf. Sci. 179, 488 508], coupled with a Basic Stern layer description of the electric double layer. In addition, data for the specific interaction of Ca2+ and Sr2+ with rutile, in NaCl and RbCl media, were modeled. In recent developments, spectroscopy, quantum calculations, and molecular simulations have shown that electrolyte and divalent cations are principally adsorbed in various inner-sphere configurations on the rutile 110 surface [Zhang Z., Fenter P., Cheng L., Sturchio N. C., Bedzyk M. J., Pr edota M., Bandura A., Kubicki J., Lvov S. N., Cummings P. T., Chialvo A. A., Ridley M. K., Be ne zeth P., Anovitz L., Palmer D. A., Machesky M. L. and Wesolowski D. J. (2004) Ion adsorption at the rutile water interface: linking molecular and macroscopic

  16. Strong Lewis acid air-stable cationic titanocene perfluoroalkyl(aryl)sulfonate complexes as highly efficient and recyclable catalysts for C-C bond forming reactions.

    PubMed

    Li, Ningbo; Wang, Jinying; Zhang, Xiaohong; Qiu, Renhua; Wang, Xie; Chen, Jinyang; Yin, Shuang-Feng; Xu, Xinhua

    2014-08-14

    A series of strong Lewis acid air-stable titanocene perfluoroalkyl(aryl)sulfonate complexes Cp2Ti(OH2)2(OSO2X)2·THF (X = C8F17, 1·THF; X = C4F9, 2·H2O·THF; X = C6F5, 3) were successfully synthesized by the treatment of Cp2TiCl2 with C8F17SO3Ag, C4F9SO3Ag and C6F5SO3Ag, respectively. In contrast to well-known titanocene bis(triflate), these complexes showed no change in open air over three months. TG-DSC analysis showed that 1·THF, 2·H2O·THF and 3 were thermally stable at 230 °C, 220 °C and 280 °C, respectively. Conductivity measurements showed that these complexes underwent ionic dissociation in CH3CN solution. X-ray analysis results confirmed that 2·H2O·THF and 3 were cationic. ESR spectra showed that the Lewis acidity of 1·THF (1.06 eV) was higher than that of Sc(3+) (1.00 eV) and Y(3+) (0.85 eV). UV/Vis spectra showed a significant red shift due to the strong complex formation between 10-methylacridone and 2·H2O·THF. Fluorescence spectra showed that the Lewis acidity of 2 (λ(em) = 477 nm) was higher than that of Sc(3+) (λ(em) = 474 nm). These complexes showed high catalytic ability in various carbon-carbon bond forming reactions. Moreover, they show good reusability. Compared with 1·THF, 2·H2O·THF and 3 exhibit higher solubility and better catalytic activity, and will find broad applications in organic synthesis.

  17. Cationic allyl complexes of the rare-earth metals: synthesis, structural characterization, and 1,3-butadiene polymerization catalysis.

    PubMed

    Robert, Dominique; Abinet, Elise; Spaniol, Thomas P; Okuda, Jun

    2009-11-09

    Monocationic bis-allyl complexes [Ln(eta(3)-C(3)H(5))(2)(thf)(3)](+)[B(C(6)X(5))(4)](-) (Ln = Y, La, Nd; X = H, F) and dicationic mono-allyl complexes of yttrium and the early lanthanides [Ln(eta(3)-C(3)H(5))(thf)(6)](2+)[BPh(4)](2)(-) (Ln = La, Nd) were prepared by protonolysis of the tris-allyl complexes [Ln(eta(3)-C(3)H(5))(3)(diox)] (Ln = Y, La, Ce, Pr, Nd, Sm; diox = 1,4-dioxane) isolated as a 1,4-dioxane-bridged dimer (Ln = Ce) or THF adducts [Ln(eta(3)-C(3)H(5))(3)(thf)(2)] (Ln = Ce, Pr). Allyl abstraction from the neutral tris-allyl complex by a Lewis acid, ER(3) (Al(CH(2)SiMe(3))(3), BPh(3)) gave the ion pair [Ln(eta(3)-C(3)H(5))(2)(thf)(3)](+)[ER(3)(eta(1)-CH(2)CH=CH(2))](-) (Ln = Y, La; ER(3) = Al(CH(2)SiMe(3))(3), BPh(3)). Benzophenone inserts into the La-C(allyl) bond of [La(eta(3)-C(3)H(5))(2)(thf)(3)](+)[BPh(4)](-) to form the alkoxy complex [La{OCPh(2)(CH(2)CH=CH(2))}(2)(thf)(3)](+)[BPh(4)](-). The monocationic half-sandwich complexes [Ln(eta(5)-C(5)Me(4)SiMe(3))(eta(3)-C(3)H(5))(thf)(2)](+)[B(C(6)X(5))(4)](-) (Ln = Y, La; X = H, F) were synthesized from the neutral precursors [Ln(eta(5)-C(5)Me(4)SiMe(3))(eta(3)-C(3)H(5))(2)(thf)] by protonolysis. For 1,3-butadiene polymerization catalysis, the yttrium-based systems were more active than the corresponding lanthanum or neodymium homologues, giving polybutadiene with approximately 90% 1,4-cis stereoselectivity.

  18. Catalysis of the carbonylation of olefins by the cationic chromium complexes allyl(arene)dicarbonylchromium(I) tetrafluoroborates

    SciTech Connect

    Magomedov, G.K.I.; Morozova, L.V.; Sigachev, S.A.; Krivykh, V.V.; Taits, E.S.; Rybinskaya, M.I.

    1986-11-10

    A qualitative comparison of the catalytic activities of the title complexes and cobalt carbonyl showed that (arene)allyldicarbonylchromium(I) tetrafluoroborates are more active than cobalt carbonyl, and this applies particularly to (C/sub 6/H/sub 6/Cr(CO)/sub 2/..pi..-C/sub 3/H/sub 5/)/sup +/BF/sub 4/. The possibility is not ruled out that in the course of the synthesis the acid HBF/sub 4/ is generated, and this is known to be a catalyst for the Koch reaction, but in this reaction only secondary and tertiary carboxy derivatives, i.e., only products of addition in accordance with the Markovnikov rule, are formed. In view of these results the authors investigated the activity of the title complexes in the hydroformylation process, an important industrial method for the preparation of aldehydes and alcohols.

  19. Reaction of the coordinate complexes of inositol hexaphosphate with first row transition series cations and Cd(II) with calf intestinal alkaline phosphatase.

    PubMed

    Martin, C J

    1995-05-01

    The reaction of alkaline phosphatase (APase) with the complexes of myo-inositol hexakisphosphate (IHP) and various cations at pH 7.2 results in a decrease in activity. Singly, neither IHP nor metal ions induce such changes. IHP-Mn(II) complexes were the least effective. Using the ions of nickel or cadmium, activity was reduced by > 95%. A similar large decrease (> 99%) was seen previously in the reaction of APase with IHP-Cu(II) complexes. With Co(II) and IHP as reactants, the activity was reduced to 10-12% of that of the native enzyme. When the apoprotein, prepared by reaction of the enzyme with either EDTA or 1,10-phenanthroline, was titrated with Co(II), the activity was equal to that resulting from the reaction of the enzyme with IHP-Co(II) complexes. Titration with zinc restored 95% of the original activity. The products are metal-substituted derivatives in which the resident catalytic (A-site) zinc ions, at least, are replaced by the cation of the IHP complex that was used. The rates of such reactions were fastest with the complexes of Cu(II) and Cd(II) (0.12 min-1), less so with Co(II) as the ion (0.056 min-1), and slowest with complexes of nickel and manganese (0.01 min-1). In every case, the rate of reaction, but not its extent of change, was inhibited by zinc ions that reduced rate constants to 0.0014-0.0054 min-1. Magnesium ions had no effect. Likewise, Mn(II), with but one exception, did not affect the reactions. When present along with IHP-Ni(II) complexes, the rate was increased and the enzyme activity further decreased. If Zn(II) was also present, this enhancement was eliminated. All changes in enzyme activity were reversible by treatment with EDTA followed by reconstitution with zinc. Approximately 95% conversion to the original activity could be attained. Reactivation of modified APase preparation also could be attained, in some cases, by pre-incubation with Zn(II) at pH 8. For example, conversion of the Cd(II)-substituted APase to the zinc enzyme

  20. Catalytic ability of a cationic Ru(II) monochloro complex for the asymmetric hydrogenation of dimethyl itaconate and enamides.

    PubMed

    Serrano, Isabel; Rodríguez, Montserrat; Romero, Isabel; Llobet, Antoni; Parella, Teodor; Campelo, Juan M; Luna, Diego; Marinas, José M; Benet-Buchholz, Jordi

    2006-03-20

    The synthesis of two Ru chloro complexes, Ru(III)Cl(3)(bpea), 1, and cis-fac-Delta-[Ru(II)Cl{(R)-(bpea)}{(S)-(BINAP)}](BF(4)), cis-fac-Delta-(R)-(S)-2, (bpea = N,N-bis(2-pyridylmethyl)ethylamine; (S)-BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl), is described. Complex 2 is characterized in solution through UV-vis, cyclic voltammetry (CV), and 1D and 2D NMR spectroscopy. X-ray diffraction analysis indicates that in the solid state it possesses the same structure as in solution, as expected for a low-spin d(6) Ru(II)-type complex. The molecular structure of cis-fac-Delta-(R)-(S)-2, consists of a nonsymmetric complex, where the Ru metal center has a significantly distorted octahedral-type coordination because of the bulkiness of the (S)-BINAP ligand. cis-fac-Delta-(R)-(S)-2 has a remarkable catalytic performance at P = 6.8 atm of H2 and T = 70 degrees C toward the hydrogenation of prochiral double bonds both from efficiency and from stereoselectivity viewpoints. As an example, prochiral olefins of technological interest such as dimethyl itaconate, methyl 2-acetamidoacrylate or methyl 2-acetamidocinnamate are catalytically hydrogenated by cis-fac-Delta-(R)-(S)-2, with conversions higher than 99.9% and ee > 99. Furthermore, cis-fac-Delta-(R)-(S)-2, also catalyzes the selective hydrogenation of beta-keto esters, although the reaction rates are lower than those found with the former substrates.

  1. Highly Stable and Efficient Light-Emitting Electrochemical Cells Based on Cationic Iridium Complexes Bearing Arylazole Ancillary Ligands.

    PubMed

    Martínez-Alonso, Marta; Cerdá, Jesús; Momblona, Cristina; Pertegás, Antonio; Junquera-Hernández, José M; Heras, Aránzazu; Rodríguez, Ana M; Espino, Gustavo; Bolink, Henk; Ortí, Enrique

    2017-09-05

    A series of bis-cyclometalated iridium(III) complexes of general formula [Ir(ppy)2(N(∧)N)][PF6] (ppy(-) = 2-phenylpyridinate; N(∧)N = 2-(1H-imidazol-2-yl)pyridine (1), 2-(2-pyridyl)benzimidazole (2), 1-methyl-2-pyridin-2-yl-1H-benzimidazole (3), 2-(4'-thiazolyl)benzimidazole (4), 1-methyl-2-(4'-thiazolyl)benzimidazole (5)) is reported, and their use as electroluminescent materials in light-emitting electrochemical cell (LEC) devices is investigated. [2][PF6] and [3][PF6] are orange emitters with intense unstructured emission around 590 nm in acetonitrile solution. [1][PF6], [4][PF6], and [5][PF6] are green weak emitters with structured emission bands peaking around 500 nm. The different photophysical properties are due to the effect that the chemical structure of the ancillary ligand has on the nature of the emitting triplet state. Whereas the benzimidazole unit stabilizes the LUMO and gives rise to a (3)MLCT/(3)LLCT emitting triplet in [2][PF6] and [3][PF6], the presence of the thiazolyl ring produces the opposite effect in [4][PF6] and [5][PF6] and the emitting state has a predominant (3)LC character. Complexes with (3)MLCT/(3)LLCT emitting triplets give rise to LEC devices with luminance values 1 order higher than those of complexes with (3)LC emitting states. Protecting the imidazole N-H bond with a methyl group, as in complexes [3][PF6] and [5][PF6], shows that the emissive properties become more stable. [3][PF6] leads to outstanding LECs with simultaneously high luminance (904 cd m(-2)), efficiency (9.15 cd A(-1)), and stability (lifetime over 2500 h).

  2. Structures of complexes of benzyl and allyl esters of monensin A with Mg 2+, Ca 2+, Sr 2+, Ba 2+ cations studied by ESI-MS and PM5 methods

    NASA Astrophysics Data System (ADS)

    Huczyński, Adam; Brzezinski, Bogumil; Bartl, Franz

    2008-08-01

    Benzyl ester of monensin A (MON3) and allyl ester of monensin A (MON4) were synthesized and their ability of forming complexes with divalent cations was studied by ESI mass spectrometry and by PM5 semi empirical calculations. The ESI-MS spectra indicate that MON3 as well as MON4 form stable 1:1 complexes with the divalent cations used in this study. The complexes of MON3 are stable to cv = 50 V and after this cv value no m/ z signals are more observed in the spectra. In contrast, with increasing cone voltage values, a fragmentation process of the MON4 complexes is simultaneously observed, where dehydration processes are the main events. The structures of the complexes are discussed in detail on the basis of conformational analysis together with the PM5 semiempirical calculations.

  3. The phosphate clamp: sequence selective nucleic acid binding profiles and conformational induction of endonuclease inhibition by cationic Triplatin complexes

    PubMed Central

    Prisecaru, Andreea; Molphy, Zara; Kipping, Ralph G.; Peterson, Erica J.; Qu, Yun; Kellett, Andrew; Farrell, Nicholas P.

    2014-01-01

    The substitution-inert polynuclear platinum(II) complex (PPC) series, [{trans-Pt(NH3)2(NH2(CH2)nNH3)}2-μ-(trans-Pt(NH3)2(NH2(CH2)nNH2)2}](NO3)8, where n = 5 (AH78P), 6 (AH78 TriplatinNC) and 7 (AH78H), are potent non-covalent DNA binding agents where nucleic acid recognition is achieved through use of the ‘phosphate clamp' where the square-planar tetra-am(m)ine Pt(II) coordination units all form bidentate N–O–N complexes through hydrogen bonding with phosphate oxygens. The modular nature of PPC–DNA interactions results in high affinity for calf thymus DNA (Kapp ∼5 × 107 M−1). The phosphate clamp–DNA interactions result in condensation of superhelical and B-DNA, displacement of intercalated ethidium bromide and facilitate cooperative binding of Hoechst 33258 at the minor groove. The effect of linker chain length on DNA conformational changes was examined and the pentane-bridged complex, AH78P, was optimal for condensing DNA with results in the nanomolar region. Analysis of binding affinity and conformational changes for sequence-specific oligonucleotides by ITC, dialysis, ICP-MS, CD and 2D-1H NMR experiments indicate that two limiting modes of phosphate clamp binding can be distinguished through their conformational changes and strongly suggest that DNA condensation is driven by minor-groove spanning. Triplatin-DNA binding prevents endonuclease activity by type II restriction enzymes BamHI, EcoRI and SalI, and inhibition was confirmed through the development of an on-chip microfluidic protocol. PMID:25414347

  4. Stoichiometric and catalytic deuterium and tritium labeling of "unactivated" organic substrates with cationic Ir(III) complexes.

    PubMed

    Skaddan, Marc B; Yung, Cathleen M; Bergman, Robert G

    2004-01-08

    [reaction: see text] Ir(III) complex [Cp(PMe(3))IrMe(CH(2)Cl(2))][BAr(f)] (1) was used to introduce deuterium stoichiometrically into substituted naphthalene/benzene templates and several "drug-like" entities. The exchange process is tolerant of a wide array of functional groups. Labeling of warfarin using subatmospheric pressures of T(2) led to specific activities and total activities rivaling current functional group directed tritium labeling methods. When paired with the appropriate deuterium donor, Cp(PMe(3))Ir(H(3))OTf (4) was found to deuterate a number of organic compounds catalytically.

  5. Use of dipicolinate-based complexes for producing ion-imprinted polystyrene resins for the extraction of yttrium-90 and heavy lanthanide cations.

    PubMed

    Chauvin, Anne-Sophie; Bünzli, Jean-Claude G; Bochud, François; Scopelliti, Rosario; Froidevaux, Pascal

    2006-09-06

    Highly selective separation of yttrium (and lanthanides) is of interest for the design of radiopharmaceuticals, and an efficient method based on the ion-imprinting concept is proposed here. The synthesis and structural, thermodynamic and photophysical characterization of complexes of trivalent yttrium and lanthanides with two new vinyl derivatives of dipicolinic acid, HL1 and L2, are described. The feasibility of using ion-imprinted resins for yttrium and lanthanide separation is demonstrated. The resins were obtained by copolymerization with styrene and divinylbenzene and subsequent acid treatment to remove the metal ion. High-resolution Eu luminescence experiments revealed that the geometry of the complexation sites is well preserved in the imprinted polymers. The ion-imprinted polymer based on HL1 proved to be particularly well adapted for yttrium extraction, having a sizeable capacity (8.9+/-0.2 mg g(-1) resin) and a fast rate of extraction (t(1/2)=1.7 min). In addition, lighter and heavier lanthanide ions are separated. Finally, the resin displays high selectivity for yttrium and lanthanide cations against alkali and alkaline earth metals. For instance, in a typical experiment, 10 mg of yttrium was extracted from 5 g of milk ash sample by 2 g of the resin. The good separation properties displayed by the resin based on HL1 open interesting perspectives for the production of highly pure (90)Y and radiolanthanides for medical applications, and for trace analysis of these radiochemicals in food and in the environment.

  6. Effect of water coordination on competition between π and non-π cation binding sites in aromatic amino acids: L-phenylalanine, L-tyrosine, and L-tryptophan Li+, Na +, and K+ complexes.

    PubMed

    Remko, Milan; Šoralová, Stanislava

    2012-04-01

    Quantum chemistry methods have been applied to charged complexes of the alkali metals Li(+), Na(+), and K(+) with the aromatic amino acids (AAAs) phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp). The geometries of 72 different complexes (Phe·M, Tyr·M, Trp·M, M is Li(+), Na(+), or K(+)) were completely optimized at the B3LYP/6-311+G(d,p) level of density functional theory. The solvent effect on the geometry and stability of individual complexes was studied by making use of a microsolvation model. The interaction enthalpies, entropies, and Gibbs energies of nine different complexes of the systems Phe·M, Tyr·M, and Trp·M (M is Li(+), Na(+), or K(+)) were also determined at the B3LYP density functional level of theory. The calculated Gibbs binding energies of the M(+)-AAA complexes follow the order Phe < Tyr < Trp for all three metal cations studied. Among the three AAAs studied, the indole ring of Trp is the best π donor for alkali metal cations. Our calculations demonstrated the existence of strong cation-π interactions between the alkali metals and the aromatic side chains of the three AAAs. These AAAs comprise about 8% of all known protein sequences. Thus, besides the potential for hydrogen-bond interaction, aromatic residues of Phe, Tyr, and Trp show great potential for π-donor interactions. The existence of cation-π interaction in proteins has also been demonstrated experimentally. However, more complex experimental studies of metal cation-π interaction in diverse biological systems will no doubt lead to more exact validation of these investigations. © SBIC 2012

  7. Succinate, iron chelation, and monovalent cations affect the transformation efficiency of Acinetobacter baylyi ATCC 33305 during growth in complex media.

    PubMed

    Leong, Colleen G; Boyd, Caroline M; Roush, Kaleb S; Tenente, Ricardo; Lang, Kristine M; Lostroh, C Phoebe

    2017-10-01

    Natural transformation is the acquisition of new genetic material via the uptake of exogenous DNA by competent bacteria. Acinetobacter baylyi is model for natural transformation. Here we focus on the natural transformation of A. baylyi ATCC 33305 grown in complex media and seek environmental conditions that appreciably affect transformation efficiency. We find that the transformation efficiency for A. baylyi is a resilient characteristic that remains high under most conditions tested. We do find several distinct conditions that alter natural transformation efficiency including addition of succinate, Fe(2+) (ferrous) iron chelation, and substitution of sodium ions with potassium ones. These distinct conditions could be useful to fine tune transformation efficiency for researchers using A. baylyi as a model organism to study natural transformation.

  8. Raman spectroscopic studies of dimyristoylphosphatidic acid and its interactions with ferricytochrome c in cationic binary and ternary lipid-protein complexes.

    PubMed Central

    Vincent, J. S.; Levin, I. W.

    1991-01-01

    stretching modes at 2,103 cm-1 provide a sensitive measure of the conformational and dynamic properties of the perdeuterated lipid component, while the 3,000 cm-1 C-H spectral region reflects the bilayer characteristics of the DMPA species in the complex. Although calcium clearly induces a lateral phase separation in the DMPA/DMPC-d54 system at pH 7.5 (Kouaouci, R., J.R. Silvius, I. Grah, and M. Pezolet. 1985. Biochemistry. 24:7132-7140), no distinct lateral segregation of the lipid components is observed in the mixed DMPA/DMPC-d54 lipid system in the presence of either ferricytochrome c or the sodium and calcium cations at pH 4.0. However, domain formation, consisting of regions rich in DMPA and DMPC-d54, respectively, is suggested for the calcium binary lipid mixture at pH 4.0 by the different values for Tm and AT characterizing the DMPA and DMPC-d54 species.Spectral evidence strongly suggests that ferricytochrome c also induces domain formation in the ternary lipid-protein mixtures at pH 7.0, but only for the sodium cation. PMID:1651120

  9. Lipophilic Cationic Cyanines Are Potent Complex I Inhibitors and Specific in Vitro Dopaminergic Toxins with Mechanistic Similarities to Both Rotenone and MPP(.).

    PubMed

    Kadigamuwa, Chamila C; Mapa, Mapa S T; Wimalasena, Kandatege

    2016-09-19

    We have recently reported that simple lipophilic cationic cyanines are specific and potent dopaminergic toxins with a mechanism of toxicity similar to that of the Parkinsonian toxin MPP(+). In the present study, a group of fluorescent lipophilic cyanines have been used to further exploit the structure-activity relationship of the specific dopaminergic toxicity of cyanines. Here, we report that all cyanines tested were highly toxic to dopaminergic MN9D cells with IC50s in the range of 60-100 nM and not toxic to non-neuronal HepG2 cells parallel to that previously reported for 2,2'- and 4,4'-cyanines. All cyanines nonspecifically accumulate in the mitochondria of both MN9D and HepG2 cells at high concentrations, inhibit the mitochondrial complex I with the inhibition potencies similar to the potent complex I inhibitor, rotenone. They increase the reactive oxygen species (ROS) production specifically in dopaminergic cells causing apoptotic cell death. These and other findings suggest that the complex I inhibition, the expression of low levels of antioxidant enzymes, and presence of high levels of oxidatively labile radical propagator, dopamine, could be responsible for the specific increase in ROS production in dopaminergic cells. Thus, the predisposition of dopaminergic cells to produce high levels of ROS in response to mitochondrial toxins together with their inherent greater demand for energy may contribute to their specific vulnerability toward these toxins. The novel findings that cyanines are an unusual class of potent mitochondrial toxins with specific dopaminergic toxicity suggest that their presence in the environment could contribute to the etiology of PD similar to that of MPP(+) and rotenone.

  10. A combined experimental and quantum mechanical investigation on some selected metal complexes of L-serine with first row transition metal cations

    NASA Astrophysics Data System (ADS)

    Mandal, Shilpi; Das, Gunajyoti; Askari, Hassan

    2015-02-01

    In the current study a joint solvent-free synthetic and computational approach has been adopted to explore the coordination properties of L-serine with the doubly charged cations of nickel, copper and zinc. The reaction products were characterized by elemental analyses, molar conductance, EDAX-SEM, TEM, TG/DTA, infrared, electronic absorption and fluorescence spectroscopy. Quantum chemical calculations, carried out in gas and aqueous phase using the BHandHLYP and MP2 methods in conjunction with 6-311++G(d,p) basis set, provide valuable insights concerning the interaction enthalpies and free energies; vibrational and absorption spectra along with various other molecular and electronic properties of the metal complexes. This study reveals that L-serine binds to the metal ions in a bi-dentate manner through its amino and carboxylate groups exhibiting highest binding affinity towards Cu(II) among the three metal ions considered here. As compared to the MP2 method, the spin-delocalized situations of the open-shell Cu(II) complex of L-serine have been better described at the BHandHLYP level. The physical origin of the molecular interactions of L-serine with the metal ions has also been examined by performing energy decomposition analysis (EDA). Effects of the aqueous environment are evident on the structure and stability of the metal complexes. The vibrational spectroscopic data furnished at MP2/6-311++G(d,p) level, which provide a good account of the structural changes inflicted in the molecular geometry of L-serine as a result of metal coordination, are in better agreement with our experimental observations as compared to those produced at the BHandHLYP/6-311++G(d,p) level.

  11. Clarifying the mechanism of cation exchange in Ca(II)[15-MC(Cu(II)ligand)-5] complexes.

    PubMed

    Lim, Choong-Sun; Tegoni, Matteo; Jakusch, Tamás; Kampf, Jeff W; Pecoraro, Vincent L

    2012-11-05

    The calcium metallacrown Ca(II)[15-MC(Cu(II)N(Trpha))-5](2+) was obtained by self-assembly of Ca(II), Cu(II), and tryptophanhydroxamic acid. Its X-ray structure shows that the core calcium ion is well-encapsulated in the five oxygen cavity of the metallacrown scaffold. The kinetics of Ca-Ln core metal substitution was studied by visible spectrophotometry by addition of Ln(III) nitrate to solutions of Ca(II)[15-MC(Cu(II)N(Trpha))-5](2+) in methanol solution at pH 6.2 (Ln(III) = La(III), Nd(III), Gd(III), Dy(III), Er(III)) to obtain the corresponding Ln(III)[15-MC(Cu(II)N(Trpha))-5](3+) complexes on the hours time scale. The reaction is first order in the two reactants (second order overall) with different rate constants across the lanthanide series. In particular, the rate for the Ca-Ln substitution decreases from La(III) to Gd(III) and then increases slightly from Gd(III) to Er(III). This substitution reaction occurs with second order rate constants ranging from 0.1543(3) M(-1) min(-1) for La(III) to 0.0720(6) M(-1) min(-1) for Gd(III). By means of the thermodynamic log K constants for the same reaction previously reported, the rate constants for the inverse Ln-Ca substitution were also determined. In this study, we demonstrated that the substitution reaction proceeds through a direct metal substitution and does not involve the disassembly of the MC scaffold. These observations in concert allow the proposition of a hypothesis that the dimension of the core metals play the major role in determining the rate constants of the substitution reaction. In particular, the largest lanthanides, which do not require complete encapsulation in the MC cavity, displace the Ca(II) ion faster, whereas in the back reaction Ca(II) displaces the smaller lanthanides faster as they interact relatively weakly with the metallacrown oxygen cavity.

  12. Luminescence dynamics and {sup 13}C NMR characteristics of dinuclear complexes exhibiting coupled lanthanide(III) cation pairs

    SciTech Connect

    Matthews, K.D.; Bailey-Folkes, S.A.; Kahwa, I.A.

    1992-08-20

    Luminescence and cross-polarization magic angle spinning (CP-MAS) {sup 13}C NMR properties of lanthanide dinuclear macrocyclic complexes of a compartmental Schiff base chelate (1) derived from the condensation of 2,6-diformyl-p-cresol and 3,6-dioxa-1,8-octanediamine are reported. The Schiff base chromophore in 1 is a strong light absorber and an efficient sensitizer for intense Tb{sup 3+}({sup 5}D{sub 4}) and Eu{sup 3+}({sup 5}D{sub 0})(T < 110 K ) emission which does not exhibit self-quenching effects. Emission from Tb{sup 3+} is sensitized by the ligand singlet state; in striking contrast, Eu{sup 3+} emission is sensitized by the triplet state and reveals an unusual nonradiative quenching process at T > 110 K with a thermal barrier of {approx} 2300 cm{sup {minus}1}. Weak emission is observed from Dy{sup 3+}({sup 4}F{sub 9/2}), Sm{sup 3+}({sup 4}G{sub 5/2}), and Pr{sup 3+}({sup 1}D{sub 2}) diluted in Gd{sup 3+} (i.e., from Gd{sup 3+}-Ln{sup 3+} heteropairs, Ln = Pr, Sm, Dy). Intramolecular metal-metal (Ln-Ln = 4 {Angstrom}) interactions account for the greatly quenched emission from Sm{sup 3+}-Sm{sup 3+} and Dy{sup 3+}-Dy{sup 3+} homopairs compared to Gd{sup 3+}-Ln heteropairs (Ln = Sm, Dy). Gd{sup 3+}-Ln{sup 3+} emission lifetimes at 77 K are 1610 (Tb{sup 3+}), 890 (Eu{sup 3+}), 14 (Dy{sup 3+}) and {approx} 13 {mu}s (Sm{sup 3+}). Nonradiative relaxation processes at 77 K in dilute Ln{sup 3+}:Gd{sub 2}1(NO{sub 3}){sub 4}{center_dot}H{sub 2}O, being temperature independent for Sm{sup 3+} and Eu{sup 3+} but temperature dependent for Tb{sup 3+}, follow the energy gap law with {alpha} {approx} - 10{sup {minus}3} cm and B {approx} 2 x 10{sup 8} s{sup {minus}1}. CP-MAS data show paramagnetic broadening of {sup 13}C resonances which increases with the magnetic moment of Ln{sup 3+}. Surprisingly, no significant shifts in resonance positions corresponding to the changing nature of paramagnetic Ln{sup 3+} ions are observed. 43 refs., 8 figs., 2 tabs.

  13. Cyclometalated Iminophosphorane Gold(III) and Platinum(II) Complexes. A Highly Permeable Cationic Platinum(II) Compound with Promising Anticancer Properties

    PubMed Central

    2015-01-01

    New organometallic gold(III) and platinum(II) complexes containing iminophosphorane ligands are described. Most of them are more cytotoxic to a number of human cancer cell lines than cisplatin. Cationic Pt(II) derivatives 4 and 5, which differ only in the anion, Hg2Cl62– or PF6– respectively, display almost identical IC50 values in the sub-micromolar range (25–335-fold more active than cisplatin on these cell lines). The gold compounds induced mainly caspase-independent cell death, as previously reported for related cycloaurated compounds containing IM ligands. Cycloplatinated compounds 3, 4, and 5 can also activate alternative caspase-independent mechanisms of death. However, at short incubation times cell death seems to be mainly caspase dependent, suggesting that the main mechanism of cell death for these compounds is apoptosis. Mercury-free compound 5 does not interact with plasmid (pBR322) DNA or with calf thymus DNA. Permeability studies of 5 by two different assays, in vitro Caco-2 monolayers and a rat perfusion model, have revealed a high permeability profile for this compound (comparable to that of metoprolol or caffeine) and an estimated oral fraction absorbed of 100%, which potentially makes it a good candidate for oral administration. PMID:26147404

  14. Human granulocyte-macrophage colony-stimulating factor DNA cationic-lipid complexed autologous tumour cell vaccination in the treatment of canine B-cell multicentric lymphoma.

    PubMed

    Turek, M M; Thamm, D H; Mitzey, A; Kurzman, I D; Huelsmeyer, M K; Dubielzig, R R; Vail, D M

    2007-12-01

    This study describes the development of an human granulocyte-macrophage colony-stimulating factor DNA cationic-lipid complexed autologous tumour cell vaccine (hGM-CSF CLDC ATCV) and its implementation, following a chemotherapy treatment protocol, in a randomized, placebo-controlled, double-blinded clinical trial in pet dogs with naturally occurring lymphoma. We hypothesized that the use of this vaccine would result in an antitumour immune response leading to improved first remission duration and overall survival in dogs with B-cell lymphoma when compared with chemotherapy alone. Immune stimulation generated by hGM-CSF CLDC ATCV was assessed by means of surrogate in vivo analysis (delayed-type hypersensitivity [DTH]) as well as an ex vivo cellular assay (lymphocyte proliferation assay). The vaccine approach considered in the current report did not result in clinically improved outcomes. A small measure of immunomodulation was documented by DTH and several modifications to the approach are suggested. This report illustrates the feasibility of clinical trials with vaccine strategies using companion animals with non-Hodgkin's lymphoma.

  15. Formation of Polyion Complex (PIC) Micelles and Vesicles with Anionic pH-Responsive Unimer Micelles and Cationic Diblock Copolymers in Water.

    PubMed

    Ohno, Sayaka; Ishihara, Kazuhiko; Yusa, Shin-Ichi

    2016-04-26

    A random copolymer (p(A/MaU)) of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS) and sodium 11-methacrylamidoundecanate (MaU) was prepared via conventional radical polymerization, which formed a unimer micelle under acidic conditions due to intramolecular hydrophobic interactions between the pendant undecanoic acid groups. Under basic conditions, unimer micelles were opened up to an expanded chain conformation by electrostatic repulsion between the pendant sulfonate and undecanoate anions. A cationic diblock copolymer (P163M99) consisting of poly(3-(methacrylamido)propyl)trimethylammonium chloride (PMAPTAC) and hydrophilic polybetaine, 2-(methacryloyloxy)ethylphosphorylcholine (MPC), blocks was prepared via controlled radical polymerization. Mixing of p(A/MaU) and P163M99 in 0.1 M aqueous NaCl under acidic conditions resulted in the formation of spherical polyion complex (PIC) micelles and vesicles, depending on polymer concentration before mixing. Shapes of the PIC micelles and vesicles changed under basic conditions due to collapse of the charge balance between p(A/MaU) and P163M99. The PIC vesicles can incorporate nonionic hydrophilic guest molecules, and the PIC micelles and vesicles can accept hydrophobic guest molecules in the hydrophobic core formed from p(A/MaU).

  16. Cellular Uptake of Cationic Polymer-DNA Complexes Via Caveolae Plays a Pivotal Role in Gene Transfection in COS-7 Cells

    PubMed Central

    van der Aa, M. A. E. M.; Huth, U. S.; Häfele, S. Y.; Schubert, R.; Oosting, R. S.; Hennink, W. E.; Peschka-Süss, R.; Koning, G. A.; Crommelin, D. J. A.

    2007-01-01

    Purpose Knowledge about the uptake mechanism and subsequent intracellular routing of non-viral gene delivery systems is important for the development of more efficient carriers. In this study we compared two established cationic polymers pDMAEMA and PEI with regard to their transfection efficiency and mechanism of cellular uptake. Materials and Methods The effects of several inhibitors of particular cellular uptake routes on the uptake of polyplexes and subsequent gene expression in COS-7 cells were investigated using FACS and transfection. Moreover, cellular localization of fluorescently labeled polyplexes was assessed by spectral fluorescence microscopy. Results Both pDMAEMA- and PEI-complexed DNA showed colocalization with fluorescently-labeled transferrin and cholera toxin after internalization by COS-7 cells, which indicates uptake via the clathrin- and caveolae-dependent pathways. Blocking either routes of uptake with specific inhibitors only resulted in a marginal decrease in polyplex uptake, which may suggest that uptake routes of polyplexes are interchangeable. Despite the marginal effect of inhibitors on polyplex internalization, blocking the caveolae-mediated uptake route resulted in an almost complete loss of polyplex-mediated gene expression, whereas gene expression was not negatively affected by blocking the clathrin-dependent route of uptake. Conclusions These results show the importance of caveolae-mediated uptake for successful gene expression and have implications for the rational design of non-viral gene delivery systems. PMID:17385010

  17. Cellular uptake of cationic polymer-DNA complexes via caveolae plays a pivotal role in gene transfection in COS-7 cells.

    PubMed

    van der Aa, M A E M; Huth, U S; Häfele, S Y; Schubert, R; Oosting, R S; Mastrobattista, E; Hennink, W E; Peschka-Süss, R; Koning, G A; Crommelin, D J A

    2007-08-01

    Knowledge about the uptake mechanism and subsequent intracellular routing of non-viral gene delivery systems is important for the development of more efficient carriers. In this study we compared two established cationic polymers pDMAEMA and PEI with regard to their transfection efficiency and mechanism of cellular uptake. The effects of several inhibitors of particular cellular uptake routes on the uptake of polyplexes and subsequent gene expression in COS-7 cells were investigated using FACS and transfection. Moreover, cellular localization of fluorescently labeled polyplexes was assessed by spectral fluorescence microscopy. Both pDMAEMA- and PEI-complexed DNA showed colocalization with fluorescently-labeled transferrin and cholera toxin after internalization by COS-7 cells, which indicates uptake via the clathrin- and caveolae-dependent pathways. Blocking either routes of uptake with specific inhibitors only resulted in a marginal decrease in polyplex uptake, which may suggest that uptake routes of polyplexes are interchangeable. Despite the marginal effect of inhibitors on polyplex internalization, blocking the caveolae-mediated uptake route resulted in an almost complete loss of polyplex-mediated gene expression, whereas gene expression was not negatively affected by blocking the clathrin-dependent route of uptake. These results show the importance of caveolae-mediated uptake for successful gene expression and have implications for the rational design of non-viral gene delivery systems.

  18. Cyclometalated Iminophosphorane Gold(III) and Platinum(II) Complexes. A Highly Permeable Cationic Platinum(II) Compound with Promising Anticancer Properties.

    PubMed

    Frik, Malgorzata; Fernández-Gallardo, Jacob; Gonzalo, Oscar; Mangas-Sanjuan, Víctor; González-Alvarez, Marta; Serrano del Valle, Alfonso; Hu, Chunhua; González-Alvarez, Isabel; Bermejo, Marival; Marzo, Isabel; Contel, María

    2015-08-13

    New organometallic gold(III) and platinum(II) complexes containing iminophosphorane ligands are described. Most of them are more cytotoxic to a number of human cancer cell lines than cisplatin. Cationic Pt(II) derivatives 4 and 5, which differ only in the anion, Hg2Cl6(2-) or PF6(-) respectively, display almost identical IC50 values in the sub-micromolar range (25-335-fold more active than cisplatin on these cell lines). The gold compounds induced mainly caspase-independent cell death, as previously reported for related cycloaurated compounds containing IM ligands. Cycloplatinated compounds 3, 4, and 5 can also activate alternative caspase-independent mechanisms of death. However, at short incubation times cell death seems to be mainly caspase dependent, suggesting that the main mechanism of cell death for these compounds is apoptosis. Mercury-free compound 5 does not interact with plasmid (pBR322) DNA or with calf thymus DNA. Permeability studies of 5 by two different assays, in vitro Caco-2 monolayers and a rat perfusion model, have revealed a high permeability profile for this compound (comparable to that of metoprolol or caffeine) and an estimated oral fraction absorbed of 100%, which potentially makes it a good candidate for oral administration.

  19. Synthesis and application of hypercrosslinked polymers with weak cation-exchange character for the selective extraction of basic pharmaceuticals from complex environmental water samples.

    PubMed

    Bratkowska, D; Marcé, R M; Cormack, P A G; Sherrington, D C; Borrull, F; Fontanals, N

    2010-03-05

    The synthesis of high specific surface area sorbents (HXLPP-WCX) in the form of hypercrosslinked polymer microspheres with narrow particle size distributions, average particle diameters around 6 microm, and weak cation-exchange (WCX) character, is described. The WCX character arises from carboxylic acid moieties in the polymers, derived from the comonomer methacrylic acid. A novel HXLPP-WCX sorbent with an attractive set of chemical and physical properties was then used in an off-line solid-phase extraction (SPE) protocol for the selective extraction of a group of basic compounds from complex environmental samples, a priority being the clean separation of the basic compounds of interest from acidic compounds and interferences. The separation power of the new sorbent for basic pharmaceuticals was compared to two commercially available, mixed-mode sorbents, namely Oasis WCX and Strata-X-CW. Under identical experimental conditions, HXLPP-WCX was found to deliver both higher capacity and better selectivity in SPE than either of the two commercially available materials. In an optimised SPE protocol, the HXLPP-WCX sorbent gave rise to quantitative and selective extractions of low microg l(-1) levels of basic pharmaceuticals present in 500 ml of river water and 250 ml of effluent waste water.

  20. Energy-resolved collision-induced dissociation studies of 1,10-phenanthroline complexes of the late first-row divalent transition metal cations: determination of the third sequential binding energies.

    PubMed

    Nose, Holliness; Chen, Yu; Rodgers, M T

    2013-05-23

    The third sequential binding energies of the late first-row divalent transition metal cations to 1,10-phenanthroline (Phen) are determined by energy-resolved collision-induced dissociation (CID) techniques using a guided ion beam tandem mass spectrometer. Five late first-row transition metal cations in their +2 oxidation states are examined including: Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+). The kinetic energy dependent CID cross sections for loss of an intact Phen ligand from the M(2+)(Phen)3 complexes are modeled to obtain 0 and 298 K bond dissociation energies (BDEs) after accounting for the effects of the internal energy of the complexes, multiple ion-neutral collisions, and unimolecular decay rates. Electronic structure theory calculations at the B3LYP, BHandHLYP, and M06 levels of theory are employed to determine the structures and theoretical estimates for the first, second, and third sequential BDEs of the M(2+)(Phen)x complexes. B3LYP was found to deliver results that are most consistent with the measured values. Periodic trends in the binding of these complexes are examined and compared to the analogous complexes to the late first-row monovalent transition metal cations, Co(+), Ni(+), Cu(+), and Zn(+), previously investigated.

  1. Design and Synthesis of Amphiphilic and Luminescent Tris-Cyclometalated Iridium(III) Complexes Containing Cationic Peptides as Inducers and Detectors of Cell Death via a Calcium-Dependent Pathway.

    PubMed

    Hisamatsu, Yosuke; Shibuya, Ai; Suzuki, Nozomi; Suzuki, Toshihiro; Abe, Ryo; Aoki, Shin

    2015-05-20

    Cationic amphiphilic peptides have the potential to function as agents for the treatment of microbial infections and cancer therapy. The cationic and hydrophobic parts of these molecules allow them to associate strongly with negatively charged bacterial or cancer cell membranes, thus exerting antimicrobial and anticancer activities through membrane disruption. Meanwhile, cyclometalated iridium(III) complexes such as fac-Ir(ppy)3 (ppy = 2-phenylpyridine) and fac-Ir(tpy)3 (tpy = 2-(4'-tolyl)pyridine) possess C3-symmetric structures and excellent photophysical properties as phosphorescence materials, which make them important candidates for use in biological applications such as chemosensors, biolabeling, living cell staining, in vivo tumor imaging, and anticancer agents. We recently reported on some regioselective substitution reactions of Ir(tpy)3 and Ir(ppy)3 at the 5'-position (p-position with respect to the C-Ir bond) on the 2-phenylpyridine ligands and their subsequent conversions to a variety of functional groups. We report here on the design and synthesis of amphiphilic and luminescent tris-cyclometalated Ir complexes in which cationic peptides are attached through alkyl chain linkers that work as inducers and detectors of cell death. Ir complexes containing cationic peptides such as a KKGG sequence and alkyl chain linkers of adequate length (C6 and C8) exhibit considerable cytotoxicity against cancer cells such as Jurkat, Molt-4, HeLa-S3, and A549 cells, and that dead cells are well stained with these Ir complexes. Furthermore, an Ir complex in which the KKGG peptide is attached through a C6 linker displayed lower cytotoxicity against normal mouse lymphocytes. Mechanistic studies suggest that Ir complexes containing the KKGG peptide interact with anionic molecules on the cell surface and/or membrane receptors to trigger the Ca(2+) dependent pathway and intracellular Ca(2+) response, resulting in necrosis accompanied by membrane disruption.

  2. Effect of water vapors on the luminescence of cation-exchange membranes modified by Pt(II) and Ru(II) complexes and Nile blue

    NASA Astrophysics Data System (ADS)

    Khakhalina, M. S.; Musaeva, D. N.; Tikhomirova, I. Yu.; Puzyk, M. V.

    2010-04-01

    The surface of a cation-exchange membrane was modified by the [PtEnPpy]+, [PtEnBt]+, [PtEnTpy]+, [RuBpy3]+2, and NB+, (En is ethylenediamine; Ppy, Bt, Tpy are α-deprotonated forms of 2-phenylpyridine, 2-phenylbenzothiazole, and 2-(2'-thienyl)pyridine, respectively; Bpy is 2,2'-bipyridyl, and NB+ is Nile blue) ions, which exhibit intense luminescence. It is found that the quenching of the luminescence of the modified cation-exchange membrane by water vapors depends on the nature of the excited electronic state of the immobilized cation.

  3. Addition, cycloaddition, and metathesis reactions of the cationic carbyne complexes [Cp(CO)[sub 2]Mn[triple bond]CCH[sub 2]R][sup +] and neutral vinylidene complexes Cp(CO)[sub 2]M=C=C(H)R (M = Mn, Re)

    SciTech Connect

    Terry, M.R.; Mercando, L.A.; Kelley, C.; Geoffroy, G.L. ); Nombel, P.; Lugan, N.; Mathieu, R. ); Ostrander, R.L.; Owens-Waltermire, B.E.; Rheingold, A.L. )

    1994-03-01

    The cationic alkylidyne complexes [Cp(CO)[sub 2]M=VCCH[sub 2]R][sup +] (M = Re, R = H; M = Mn, R = H, Me, Ph) undergo facile deprotonation to give the corresponding neutral vinylidene complexes Cp(CO)[sub 2]M=C=C(H)R. For [Cp(CO)[sub 2]Re=VCCH[sub 3

  4. Dehydrogenation of ammonia-borane by cationic Pd(II) and Ni(II) complexes in a nitromethane medium: hydrogen release and spent fuel characterization.

    PubMed

    Kim, Sung-Kwan; Hong, Sung-Ahn; Son, Ho-Jin; Han, Won-Sik; Michalak, Artur; Hwang, Son-Jong; Kang, Sang Ook

    2015-04-28

    A highly electrophilic cationic Pd(II) complex, [Pd(MeCN)4][BF4]2 (1), brings about the preferential activation of the B-H bond in ammonia-borane (NH3·BH3, AB). At room temperature, the reaction between 1 in CH3NO2 and AB in tetraglyme leads to Pd nanoparticles and formation of spent fuels of the general formula MeNHxBOy as reaction byproducts, while 2 equiv. of H2 is efficiently released per AB equiv. at room temperature within 60 seconds. For a mechanistic understanding of dehydrogenation by 1, the chemical structures of spent fuels were intensely characterized by a series of analyses such as elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), solid state magic-angle-spinning (MAS) NMR spectra ((2)H, (13)C, (15)N, and (11)B), and cross polarization (CP) MAS methods. During AB dehydrogenation, the involvement of MeNO2 in the spent fuels showed that the mechanism of dehydrogenation catalyzed by 1 is different from that found in the previously reported results. This AB dehydrogenation derived from MeNO2 is supported by a subsequent digestion experiment of the AB spent fuel: B(OMe)3 and N-methylhydroxylamine ([Me(OH)N]2CH2), which are formed by the methanolysis of the AB spent fuel (MeNHxBOy), were identified by means of (11)B NMR and single crystal structural analysis, respectively. A similar catalytic behavior was also observed in the AB dehydrogenation catalyzed by a nickel catalyst, [Ni(MeCN)6][BF4]2 (2).

  5. Interaction between anions and cationic metal complexes containing tridentate ligands with exo-C-H groups: complex stability and hydrogen bonding.

    PubMed

    Martínez-García, Héctor; Morales, Dolores; Pérez, Julio; Puerto, Marcos; del Río, Ignacio

    2014-05-05

    [Re(CO)3 ([9]aneS3 )][BAr'4 ] (1), prepared by reaction of ReBr(CO)5 , 1,4,7-trithiacyclononane ([9]aneS3 ) and NaBAr'4 , forms stable, soluble supramolecular adducts with chloride (2), bromide, methanosulfonate (3) and fluoride (4) anions. These new species were characterized by IR, NMR spectroscopy and, for 2 and 3, also by X-ray diffraction. The results of the solid state structure determinations indicate the formation of CH⋅⋅⋅X hydrogen bonds between the anion (X) and the exo-CH groups of the [9]aneS3 ligand, in accord with the relatively large shifts found by (1) H NMR spectroscopy in dichloromethane solution for those hydrogens. The stability of the chloride adduct contrasts with the lability of the [9]aneS3 ligand in allyldicarbonyl molybdenum complexes recently studied by us. With fluoride, in dichloromethane solution, a second, minor neutral dimeric species 5 is formed in addition to 4. In 4, the deprotonation of a CH group of the [9]aneS3 ligand, accompanied by CS bond cleavage and dimerization, afforded 5, featuring bridging thiolates. Compounds [Mo(η(3) -methallyl)(CO)2 (TpyN)][BAr'4 ] (6) and [Mo(η(3) -methallyl)(CO)2 (TpyCH)][BAr'4 ] (7) were synthesized by the reactions of [MoCl(η(3) -methallyl)(CO)2 (NCMe)2 ], NaBAr'4 and tris(2-pyridyl)amine (TpyN) or tris(2-pyridyl)methane (TpyCH) respectively, and characterized by IR and (1) H and (13) C NMR spectroscopy in solution, and by X-ray diffraction in the solid state. Compound 6 undergoes facile substitution of one of the 2-pyridyl groups by chloride, bromide, and methanosulfonate anions. Stable supramolecular adducts were formed between 7 and chloride, bromide, iodide, nitrate, and perrhenate anions. The solid state structures of these adducts (12-16) were determined by X-ray diffraction. Binding constants in dichloromethane were calculated from (1) H NMR titration data for all the new supramolecular adducts. The signal of the bridgehead CH group is the one that undergoes a

  6. Cationic Conjugated Polymer/Hyaluronan-Doxorubicin Complex for Sensitive Fluorescence Detection of Hyaluronidase and Tumor-Targeting Drug Delivery and Imaging.

    PubMed

    Huang, Yanqin; Song, Caixia; Li, Huichang; Zhang, Rui; Jiang, Rongcui; Liu, Xingfen; Zhang, Guangwei; Fan, Quli; Wang, Lianhui; Huang, Wei

    2015-09-30

    Hyaluronidase (HAase) is becoming a new type of tumor marker since it has been demonstrated to be overexpressed in various kinds of cancer cells. In this study, we described a novel fluorescence method for sensitive, rapid, and convenient HAase detection and tumor-targeting drug delivery and imaging, using a probe prepared by electrostatic assembly of a cationic conjugated polymer (CCP) and anionic hyaluronan (HA) conjugated with the anticancer drug doxorubicin (Dox). The CCP we used was poly{[9,9-bis(6'-(N,N,N-diethylmethylammonium)hexyl)-2,7-fluorenylene ethynylene]-alt-co-[2,5-bis(3'-(N,N,N-diethylmethylammonium)-1'-oxapropyl)-1,4-phenylene]} tetraiodide (PFEP). HA is a natural mucopolysaccharide that can be hydrolyzed by HAase into fragments with low molecular weights. In the PFEP/HA-Dox complex, the fluorescence of PFEP was efficiently quenched due to electron transfer from PFEP to Dox. After the PFEP/HA-Dox complex was exposed to HAase or was taken up by cancer cells through the specific binding between HA and CD44 receptor, HA was degraded by HAase to release the Dox, leading to the recovery of PFEP fluorescence to the "turn-on" state. Moreover, the degree of fluorescence recovery was quantitatively correlated with the concentrations of HAase. Compared with many previously reported methods, our work did not require laborious multiple modifications of HA that may affect the activity of HAase. This point, combined with the excellent optoelectronic property of conjugated polymer, endowed this method with high sensitivity (detection limit: 0.075 U/mL), high specificity, and rapid response, making it applicable for reliable and routine detection of HAase. This fluorescent probe was successfully utilized to detect HAase levels in human urine samples; furthermore, it can also be employed as a multifunctional system by realizing tumor-targeting drug delivery and cell imaging simultaneously. The development of this fluorescence method showed promising potential for

  7. Strong Inhibition of O-Atom Transfer Reactivity for Mn(IV)(O)(π-Radical-Cation)(Lewis Acid) versus Mn(V)(O) Porphyrinoid Complexes.

    PubMed

    Zaragoza, Jan Paulo T; Baglia, Regina A; Siegler, Maxime A; Goldberg, David P

    2015-05-27

    The oxygen atom transfer (OAT) reactivity of two valence tautomers of a Mn(V)(O) porphyrinoid complex was compared. The OAT kinetics of Mn(V)(O)(TBP8Cz) (TBP8Cz = octakis(p-tert-butylphenyl)corrolazinato(3-)) reacting with a series of triarylphosphine (PAr3) substrates were monitored by stopped-flow UV-vis spectroscopy, and revealed second-order rate constants ranging from 16(1) to 1.43(6) × 10(4) M(-1) s(-1). Characterization of the OAT transition state analogues Mn(III)(OPPh3)(TBP8Cz) and Mn(III)(OP(o-tolyl)3)(TBP8Cz) was carried out by single-crystal X-ray diffraction (XRD). A valence tautomer of the closed-shell Mn(V)(O)(TBP8Cz) can be stabilized by the addition of Lewis and Brønsted acids, resulting in the open-shell Mn(IV)(O)(TBP8Cz(•+)):LA (LA = Zn(II), B(C6F5)3, H(+)) complexes. These Mn(IV)(O)(π-radical-cation) derivatives exhibit dramatically inhibited rates of OAT with the PAr3 substrates (k = 8.5(2) × 10(-3) - 8.7 M(-1) s(-1)), contrasting the previously observed rate increase of H-atom transfer (HAT) for Mn(IV)(O)(TBP8Cz(•+)):LA with phenols. A Hammett analysis showed that the OAT reactivity for Mn(IV)(O)(TBP8Cz(•+)):LA is influenced by the Lewis acid strength. Spectral redox titration of Mn(IV)(O)(TBP8Cz(•+)):Zn(II) gives Ered = 0.69 V vs SCE, which is nearly +700 mV above its valence tautomer Mn(V)(O)(TBP8Cz) (Ered = -0.05 V). These data suggest that the two-electron electrophilicity of the Mn(O) valence tautomers dominate OAT reactivity and do not follow the trend in one-electron redox potentials, which appear to dominate HAT reactivity. This study provides new fundamental insights regarding the relative OAT and HAT reactivity of valence tautomers such as M(V)(O)(porph) versus M(IV)(O)(porph(•+)) (M = Mn or Fe) found in heme enzymes.

  8. The Cation-π Interaction

    PubMed Central

    DOUGHERTY, DENNIS A.

    2014-01-01

    CONSPECTUS The chemistry community now recognizes the cation-π interaction as a major force for molecular recognition, joining the hydrophobic effect, the hydrogen bond, and the ion pair in determining macromolecular structure and drug-receptor interactions. This Account provides the author’s perspective on the intellectual origins and fundamental nature of the cation-π interaction. Early studies on cyclophanes established that water-soluble, cationic molecules would forgo aqueous solvation to enter a hydrophobic cavity if that cavity was lined with π systems. Important gas phase studies established the fundamental nature of the cation-π interaction. The strength of the cation-π interaction – Li+ binds to benzene with 38 kcal/mol of binding energy; NH4+ with 19 kcal/mol– distinguishes it from the weaker polar-π interactions observed in the benzene dimer or water-benzene complexes. In addition to the substantial intrinsic strength of the cation-π interaction in gas phase studies, the cation-π interaction remains energetically significant in aqueous media and under biological conditions. Many studies have shown that cation-π interactions can enhance binding energies by 2 – 5 kcal/mol, making them competitive with hydrogen bonds and ion pairs in drug-receptor and protein-protein interactions. As with other noncovalent interactions involving aromatic systems, the cation-π interaction includes a substantial electrostatic component. The six (four) Cδ−–Hδ+ bond dipoles of a molecule like benzene (ethylene) combine to produce a region of negative electrostatic potential on the face of the π system. Simple electrostatics facilitate a natural attraction of cations to the surface. The trend for (gas phase) binding energies is Li+>Na+>K+>Rb+: as the ion gets larger the charge is dispersed over a larger sphere and binding interactions weaken, a classical electrostatic effect. On other hand, polarizability does not define these interactions. Cyclohexane

  9. Foundations of chemical microscopy. 1. Solid-state characterization of 5-nitrobarbituric acid (dilituric acid) and its complexes with group IA and group IIA cations.

    PubMed

    Brittain, H G

    1997-05-01

    5-Nitrobarbituric acid (dilituric acid) has been used as a chemical microscopic reagent for the qualitative identification of alkali metal (Group IA) and alkaline earth (Group IIA) cations. This methodology was based on the characterization of observed crystal morphologies, since a unique crystal habit could be associated with each adduct product. To understand the scientific foundations which permitted chemical microscopy to function as a useful analytical technique, the products formed between dilituric acid and the Group IA and IIA cations were characterized using polarizing optical microscopy, powder X-ray diffraction, thermal analysis and solid-state nuclear magnetic resonance. It was found that the origins of the different crystal morphologies associated with each of the adduct arose from the ability of the systems to form various hydrate species, which could also contain structural variations due to cation/diliturate packing patterns.

  10. Low-dimensional compounds containing bioactive ligands. Part VIII: DNA interaction, antimicrobial and antitumor activities of ionic 5,7-dihalo-8-quinolinolato palladium(II) complexes with K(+) and Cs(+) cations.

    PubMed

    Farkasová, Veronika; Drweesh, Sayed Ali; Lüköová, Andrea; Sabolová, Danica; Radojević, Ivana D; Čomić, Ljiljana R; Vasić, Sava M; Paulíková, Helena; Fečko, Stanislav; Balašková, Tatiana; Vilková, Mária; Imrich, Ján; Potočňák, Ivan

    2017-02-01

    Starting from well-defined NH2(CH3)2[PdCl2(XQ)] complexes, coordination compounds of general formula Cat[PdCl2(XQ)] have been prepared by cationic exchange of NH2(CH3)2(+) and Cat cations, where XQ are biologically active halogen derivatives of quinolin-8-ol (5-chloro-7-iodo-quinolin-8-ol (CQ), 5,7-dibromo-quinolin-8-ol (dBrQ) and 5,7-dichloro-quinolin-8-ol (dClQ)) and Cat is K(+) or Cs(+). The cation exchange of all prepared complexes, K[PdCl2(CQ)] (1), K[PdCl2(dClQ)] (2), K[PdCl2(dBrQ)] (3), Cs[PdCl2(CQ)] (4), Cs[PdCl2(dClQ)] (5) and Cs[PdCl2(dBrQ)] (6) was approved using IR spectroscopy, their structures in DMSO solution were elucidated by one- and two-dimensional NMR experiments, whereas their stability in solution was verified by UV-VIS spectroscopy. Interaction of complexes to ctDNA was investigated using UV-VIS and fluorescence emission spectroscopy. The minimum inhibitory concentration and the minimum microbicidal concentration values were detected against 15 bacterial strains and 4 yeast strains to examine the antimicrobial activity for the complexes. The in vitro antitumor properties of the complexes were studied by testing the complexes on leukemic cell line L1210, ovarian cancer cell line A2780 and non-cancerous cell line HEK293. The majority of the prepared compounds exhibited moderate antimicrobial and very high cytotoxic activity.

  11. Structural and energetic study of cation-π-cation interactions in proteins.

    PubMed

    Pinheiro, Silvana; Soteras, Ignacio; Gelpí, Josep Lluis; Dehez, François; Chipot, Christophe; Luque, F Javier; Curutchet, Carles

    2017-04-12

    Cation-π interactions of aromatic rings and positively charged groups are among the most important interactions in structural biology. The role and energetic characteristics of these interactions are well established. However, the occurrence of cation-π-cation interactions is an unexpected motif, which raises intriguing questions about its functional role in proteins. We present a statistical analysis of the occurrence, composition and geometrical preferences of cation-π-cation interactions identified in a set of non-redundant protein structures taken from the Protein Data Bank. Our results demonstrate that this structural motif is observed at a small, albeit non-negligible frequency in proteins, and suggest a preference to establish cation-π-cation motifs with Trp, followed by Tyr and Phe. Furthermore, we have found that cation-π-cation interactions tend to be highly conserved, which supports their structural or functional role. Finally, we have performed an energetic analysis of a representative subset of cation-π-cation complexes combining quantum-chemical and continuum solvation calculations. Our results point out that the protein environment can strongly screen the cation-cation repulsion, leading to an attractive interaction in 64% of the complexes analyzed. Together with the high degree of conservation observed, these results suggest a potential stabilizing role in the protein fold, as demonstrated recently for a miniature protein (Craven et al., J. Am. Chem. Soc. 2016, 138, 1543). From a computational point of view, the significant contribution of non-additive three-body terms challenges the suitability of standard additive force fields for describing cation-π-cation motifs in molecular simulations.

  12. FIA potentiometric and solvent extraction studies of alkali metal and alkaline earth cation complexation by bis(tert-butylbenzo)-21-crown-7

    SciTech Connect

    Attiyat, A.S. ); Christian, G.D. ); McDonough, J.A.; Strzelbicka, B.; Goo, M.J.; Yu, Z.Y.; Bartsch, R.A. )

    1993-07-01

    A flow injection analysis study of the potentiometric selectivity of bis[4(5)-tert-butylbenzo]-21-crown-7 (D(tBB)21C7) for cesium over the other alkali metal cations and three alkaline earth cations has been conducted. A PVC matrix membrane containing D(tBB)21C7 as an ionophore was coated on the tip of a silver wire incorporated in a flow cell. No selectivity for cesium over rubidium and only low selectivity over potassium were noted. However, very high selectivities for cesium over sodium, lithium, strontium, calcium, and magnesium were observed. Selectivity of D(tBB)21C7 in the solvent extraction of alkali metal cations was determined by the picrate extraction method. The percent extraction into deuteriochloroform decreased in the order cesium, rubidium > potassium >> sodium >> lithium. Thus good agreement was observed between the responses of D(tBB)21C7 towards alkali metal cations in polymeric membrane electrodes and in solvent extraction. 19 refs., 1 fig., 3 tabs.

  13. Biological activity of neutral and cationic iridium(III) complexes with κP and κP,κS coordinated Ph₂PCH₂S(O)xPh (x = 0-2) ligands.

    PubMed

    Ludwig, Gerd; Mijatović, Sanja; Ranđelović, Ivan; Bulatović, Mirna; Miljković, Djordje; Maksimović-Ivanić, Danijela; Korb, Marcus; Lang, Heinrich; Steinborn, Dirk; Kaluđerović, Goran N

    2013-11-01

    Neutral iridium(III) complexes of the type [Ir(η(5)-C₅Me₅)Cl₂{Ph₂PCH₂S(O)xPh-κP}] (1-3) with diphenylphosphino-functionalized methyl phenyl sulfides, sulfoxides, and sulfones Ph₂PCH₂S(O)xPh (x = 0, L1; 1, L2; 2, L3) and the cationic complex [Ir(η(5)-C₅Me₅)Cl{Ph₂PCH₂SPh-κP,κS}][PF6] (4) were synthesized and fully characterized analytically and spectroscopically. Furthermore, the structure of 2 was determined by X-ray diffraction analysis. The biological potential of the neutral and cationic iridium(III) complexes was tested in vitro against the cell lines 8505C, A253, MCF-7, SW480 and 518A2. Complex [Ir(η(5)-C₅Me₅)Cl₂{Ph₂PCH₂S(O)Ph-κP}] (2), with ligand L2 κP coordinated containing a pendent sulfinyl group, is the most active one (IC₅₀ values of about 3 μM), thus, with activities comparable to cisplatin. Complex 2 proved to have an even a higher antiproliferative activity than cisplatin against 8505C and SW480 cell lines, used as a model system of highly anaplastic cancers with low sensitivity to conventional chemotherapeutics such as cisplatin. Additional experiments demonstrated that apoptosis and autophagic cell death contribute to the drug's tumoricidal action. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  14. The Stepwise Reaction of Rhodium and Iridium Complexes of Formula [MCl2 (κ(4) C,N,N',P-L)] with Silver Cations: A Case of trans-Influence and Chiral Self-Recognition.

    PubMed

    Carmona, María; Tejedor, Leyre; Rodríguez, Ricardo; Passarelli, Vincenzo; Lahoz, Fernando J; García-Orduña, Pilar; Carmona, Daniel

    2017-07-27

    Acetonitrile suspensions of the dichlorido complexes [MCl2 (κ(4) C,N,N',P-L)] [M=Rh (1), Ir (2)] react with AgSbF6 in a 1:2 molar ratio affording the bis-acetonitrile complexes [M(κ(4) C,N,N',P-L)(NCMe)2 ][SbF6 ]2 (3 and 4). The reaction takes place in a sequential manner and the intermediates can be isolated varying the M:Ag molar ratio. In a 2:1 molar ratio, it affords the dimetallic monochlorido-bridged compounds [{MCl(κ(4) C,N,N',P-L)}2 (μ-Cl)][SbF6 ] (5 and 6). In a 1:1 molar ratio, the monosubstituted solvato-complexes [MCl(κ(4) C,N,N',P-L)(Solv)][SbF6 ] (Solv=H2 O, MeCN, 7-10) were obtained. Finally, in a 2:3 molar ratio, it gives complexes 11 and 12 of formula [{M(κ(4) C,N,N',P-L)(NCMe)(μ-Cl)}2 Ag][SbF6 ]3 in which a silver cation joints two cationic monosubstituted acetonitrile-complexes [MCl(κ(4) C,N,N',P-L)(NCMe)](+) through the remaining chlorido ligands and two Ag⋅⋅⋅C interactions with one of the phenyl rings of each PPh2 group. In all the complexes, the aminic nitrogen and the central metal atom are stereogenic centers. In the trimetallic complexes 11 and 12, the silver atom is also a stereogenic center. The formation of the cation of the dimetallic complexes 5 and 6, as well as that of the trimetallic complexes 11 and 12, takes place with chiral molecular self-recognition. Experimental data and DFT calculations provide plausible explanations for the observed molecular recognition. The new complexes have been characterized by analytical, spectroscopic means and by X-ray diffraction methods. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Synthesis, characterization, and PGSE (1H and 19F) NMR diffusion studies on cationic (eta6- arene)Mn(CO)3+ complexes: boron counterion, ion pairing, and solvent dependences.

    PubMed

    Schott, Daniele; Pregosin, Paul S; Jacques, Béatrice; Chavarot, Murielle; Rose-Munch, Françoise; Rose, Eric

    2005-08-08

    The synthesis, characterization, and PGSE ((1)H and (19)F) NMR diffusion studies on the cationic [(eta(6)-arene)Mn(CO)(3)][X] (arene = anisole, 4-chloroanisole, and 1,3,5-trimethoxybenzene; X = BPh(4) and BArF) are reported. The tetraphenyl borate complexes of anisole and 4-chloroanisole show surprisingly strong ion pairing in dichloromethane solution, whereas the BArF salts do not. (1)H,(1)H-NOESY data support this anion selectivity. In chloroform solution one finds the usual strong ion pairing for both anions. The solid-state structure of [(eta(6)-1,3,5-trimethoxybenzene)Mn(CO)(3)][BPh(4)] has been determined. (13)C NMR and IR data for the new complexes are reported. The observed IR frequencies are higher for the BArF complexes than for the BPh(4) complexes.

  16. Hybrid organic-inorganic chlorozincate and a molecular zinc complex involving the in situ formed imidazo[1,5-a]pyridinium cation: serendipitous oxidative cyclization, structures and photophysical properties.

    PubMed

    Buvaylo, Elena A; Kokozay, Vladimir N; Linnik, Rostyslav P; Vassilyeva, Olga Yu; Skelton, Brian W

    2015-08-14

    Two novel compounds, the organic-inorganic hybrid [L](2)[ZnCl(4)] (1) and the coordination complex LZnCl(3) (2), where L is the 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, were prepared using the oxidative condensation-cyclization of 2-pyridinecarbaldehyde and CH(3)NH(2)·HCl in methanol in the presence of Zn(2+) cations. The metal-free interaction of the organic components afforded the salt [L][Cl]·1.5H(2)O (3). The use of methylamine hydrochloride instead of its aqueous solution is believed to be responsible for the cyclocondensation with the formation of L instead of the expected Schiff base ligand. Compounds 1-3 have been obtained as single crystals and characterized by elemental analysis, IR, NMR spectroscopy, and single-crystal X-ray diffraction techniques. The structure of 1 is described as layers of cations and anions stacked along the c-axis, with the minimum ZnZn distance being 8.435 Å inside a layer. In the crystal lattice of 3, the cations are arranged in stacks propagating along the a-axis; the 1D H-bonding polymer built of chloride ions and water molecules runs parallel to a column of stacked cations. The organic cations in salts 1 and 3 show various patterns of π-π stacking. The discrete molecular structure of 2 shows coordination of a Zn atom to the N(pyridyl) atom, which enables one of the chloride atoms attached to the metal centre to interact with a π-system of the positively charged imidazolium ring. Numerous C-HCl contacts in a 1-3 are seen as space-filling van der Waals interactions of minor importance in determining crystal packing. The (1)H NMR studies suggest that the Zn-N coordination found in the solid-state structure of 2 is not retained in dmso, and 1, 2 and 3 are completely dissociated in solution. The emission spectra of 1 and 2 (λ(max) = 455 and 445 nm, respectively) exhibit red-shifts of fluorescence wavelength when compared to 3 and differ in the shapes and maxima of the emission as well as in relative

  17. Cationic Pd(II)/Pt(II) 5,5-diethylbarbiturate complexes with bis(2-pyridylmethyl)amine and terpyridine: Synthesis, structures,DNA/BSA interactions, intracellular distribution, cytotoxic activity and induction of apoptosis.

    PubMed

    Icsel, Ceyda; Yilmaz, Veysel T; Kaya, Yunus; Durmus, Selvi; Sarimahmut, Mehmet; Buyukgungor, Orhan; Ulukaya, Engin

    2015-11-01

    Four new cationic Pd(II) and Pt(II) 5,5-diethylbarbiturate (barb) complexes, [M(barb)(bpma)]X·H2O [M = Pd(II), X = Cl (1); M = Pt(II), X = NO3(-) (2)] and [M(barb)(terpy)]NO3·0.5H2O [M = Pd(II) (3); M = Pt(II) (4)], where bpma = bis(2-pyridylmethyl)amine and terpy = terpyridine, were synthesized and characterized by elemental analysis, IR, UV–vis, NMR, ESI-MS and X-ray crystallography. The DNA binding properties of the cationic complexes were investigated by spectroscopic titrations, displacement experiments, viscosity, DNA melting and electrophoresis measurements. The results revealed that the complexes effectively bind to FS-DNA (fish sperm DNA) via intercalative/minor groove binding modes with intrinsic binding constants (Kb) in the range of 0.50 × 10(4)–1.67 × 10(5) M(-1). Absorption, emission and synchronous fluorescence measurements showed strong association of the complexes with protein (BSA) through a static mechanism. The mode of interaction of complexes towards DNA and protein was also supported by molecular docking. Complexes 1 and 3 showed significant nuclear uptake in HT-29 cells. In addition, 1 and 3 showed higher inhibition than cisplatin on the growth of MCF-7 and HT-29 cells and induced apoptosis on these cells much more effectively than the rest of the complexes as evidenced by pyknotic nuclear morphology. The levels of caspase-cleaved cytokeratin 18 (M30 antigen) in HT-29 cells treated with 1 and 3 increased in a dose-dependent manner, suggesting apoptosis. Moreover, qRT-PCR experiments showed that 1 and 3 caused significant increases in the expression of TNFRSF10B in HT-29 cells, indicating the initiation of apoptosis via cell surface death receptors.

  18. A complete map of the ion chemistry of the naphthalene radical cation? DFT and RRKM modeling of a complex potential energy surface

    NASA Astrophysics Data System (ADS)

    Solano, Eduardo A.; Mayer, Paul M.

    2015-09-01

    The fragmentation mechanisms of the naphthalene molecular ion to [M-C4H2]+•, [M-C2H2]+•, [M-H2]+•, and [M-H•]+ were obtained at the UB3LYP/6-311+G(3df,2p)//UB3LYP/6-31G(d) level of theory and were subsequently used to calculate the microcanonical rate constants, k(E)'s, for all the steps by the Rice-Ramsperger-Kassel-Marcus formalism. The pre-equilibrium and steady state approximations were applied on different regions of the potential energy profiles to obtain the fragmentation k(E)'s and calculate the relative abundances of the ions as a function of energy. These results reproduce acceptably well the imaging photoelectron-photoion coincidence spectra of naphthalene, in the photon-energy range 14.0-18.8 eV that was previously reported by our group. Prior to dissociation, the molecular ion rapidly equilibrates with a set of isomers that includes the Z- and E-phenylvinylacetylene (PVA) radical cations. The naphthalene ion is the predominant isomer below 10 eV internal energy, with the other isomers remaining at steady state concentrations. Later on, new steady-state intermediates are formed, such as the azulene and 1-phenyl-butatriene radical cations. The naphthalene ion does not eject an H atom directly but eliminates an H2 molecule in a two-step fragmentation. H• loss occurs instead from the 1-phenyl-butatriene ion. The PVA ions initiate the ejection of diacetylene (C4H2) to yield the benzene radical cation. Acetylene elimination yields the pentalene cation at low energies (where it can account for 45.9%-100.0% of the rate constant of this channel), in a three-step mechanism starting from the azulene ion. However, above 7.6 eV, the major [M-C2H2]+• structure is the phenylacetylene cation.

  19. A complete map of the ion chemistry of the naphthalene radical cation? DFT and RRKM modeling of a complex potential energy surface

    SciTech Connect

    Solano, Eduardo A.; Mayer, Paul M.

    2015-09-14

    The fragmentation mechanisms of the naphthalene molecular ion to [M–C{sub 4}H{sub 2}]{sup +•}, [M–C{sub 2}H{sub 2}]{sup +•}, [M–H{sub 2}]{sup +•}, and [M–H{sup •}]{sup +} were obtained at the UB3LYP/6-311+G(3df,2p)//UB3LYP/6-31G(d) level of theory and were subsequently used to calculate the microcanonical rate constants, k(E)’s, for all the steps by the Rice-Ramsperger-Kassel-Marcus formalism. The pre-equilibrium and steady state approximations were applied on different regions of the potential energy profiles to obtain the fragmentation k(E)’s and calculate the relative abundances of the ions as a function of energy. These results reproduce acceptably well the imaging photoelectron-photoion coincidence spectra of naphthalene, in the photon-energy range 14.0–18.8 eV that was previously reported by our group. Prior to dissociation, the molecular ion rapidly equilibrates with a set of isomers that includes the Z- and E-phenylvinylacetylene (PVA) radical cations. The naphthalene ion is the predominant isomer below 10 eV internal energy, with the other isomers remaining at steady state concentrations. Later on, new steady-state intermediates are formed, such as the azulene and 1-phenyl-butatriene radical cations. The naphthalene ion does not eject an H atom directly but eliminates an H{sub 2} molecule in a two-step fragmentation. H{sup •} loss occurs instead from the 1-phenyl-butatriene ion. The PVA ions initiate the ejection of diacetylene (C{sub 4}H{sub 2}) to yield the benzene radical cation. Acetylene elimination yields the pentalene cation at low energies (where it can account for 45.9%–100.0% of the rate constant of this channel), in a three-step mechanism starting from the azulene ion. However, above 7.6 eV, the major [M–C{sub 2}H{sub 2}]{sup +•} structure is the phenylacetylene cation.

  20. A complete map of the ion chemistry of the naphthalene radical cation? DFT and RRKM modeling of a complex potential energy surface.

    PubMed

    Solano, Eduardo A; Mayer, Paul M

    2015-09-14

    The fragmentation mechanisms of the naphthalene molecular ion to [M-C4H2](+•), [M-C2H2](+•), [M-H2](+•), and [M-H(•)](+) were obtained at the UB3LYP/6-311+G(3df,2p)//UB3LYP/6-31G(d) level of theory and were subsequently used to calculate the microcanonical rate constants, k(E)'s, for all the steps by the Rice-Ramsperger-Kassel-Marcus formalism. The pre-equilibrium and steady state approximations were applied on different regions of the potential energy profiles to obtain the fragmentation k(E)'s and calculate the relative abundances of the ions as a function of energy. These results reproduce acceptably well the imaging photoelectron-photoion coincidence spectra of naphthalene, in the photon-energy range 14.0-18.8 eV that was previously reported by our group. Prior to dissociation, the molecular ion rapidly equilibrates with a set of isomers that includes the Z- and E-phenylvinylacetylene (PVA) radical cations. The naphthalene ion is the predominant isomer below 10 eV internal energy, with the other isomers remaining at steady state concentrations. Later on, new steady-state intermediates are formed, such as the azulene and 1-phenyl-butatriene radical cations. The naphthalene ion does not eject an H atom directly but eliminates an H2 molecule in a two-step fragmentation. H(•) loss occurs instead from the 1-phenyl-butatriene ion. The PVA ions initiate the ejection of diacetylene (C4H2) to yield the benzene radical cation. Acetylene elimination yields the pentalene cation at low energies (where it can account for 45.9%-100.0% of the rate constant of this channel), in a three-step mechanism starting from the azulene ion. However, above 7.6 eV, the major [M-C2H2](+•) structure is the phenylacetylene cation.

  1. Photochemistry of framework-supported M(diimine)(CO)3X complexes in three-dimensional lithium carboxylate metal-organic frameworks: monitoring the effect of framework cations.

    PubMed

    Reade, Thomas J; Murphy, Thomas S; Calladine, James A; Horvath, Raphael; Clark, Ian P; Greetham, Gregory M; Towrie, Michael; Lewis, William; George, Michael W; Champness, Neil R

    2017-01-13

    The structures and photochemical behaviour of two new metal-organic frameworks (MOFs) are reported. Reaction of Re(2,2'-bipy-5,5'-dicarboxylic acid)(CO)3Cl or Mn(2,2'-bipy-5,5'-dicarboxylic acid)(CO)3Br with LiCl or LiBr, respectively, produces single crystals of {Li2(DMF)2 [(2,2'-bipy-5,5'-dicarboxylate)Re(CO)3Cl]}n ( RELI: ) or {Li2(DMF)2[(2,2'-bipy-5,5'-dicarboxylate)Mn(CO)3Br]}n ( MNLI: ). The structures formed by the two MOFs comprise one-dimensional chains of carboxylate-bridged Li(I) cations that are cross-linked by units of Re(2,2'-bipy-5,5'-dicarboxylate)(CO)3Cl ( RELI: ) or Mn(2,2'-bipy-5,5'- dicarboxylate)(CO)3Br ( MNLI: ). The photophysical and photochemical behaviour of both RELI: and MNLI: are probed. The rhenium-containing MOF, RELI: , exhibits luminescence and the excited state behaviour, as established by time-resolved infrared measurements, is closer in behaviour to that of unsubstituted [Re(bipy)(CO)3Cl] rather than a related MOF where the Li(I) cations are replaced by Mn(II) cations. These observations are further supported by density functional theory calculations. Upon excitation MNLI: forms a dicarbonyl species which rapidly recombines with the dissociated CO, in a fashion consistent with the majority of the photoejected CO not escaping the MOF channels.This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.

  2. Ion recognition: application of symmetric and asymmetric schiff bases and their complexes for the fabrication of cationic and anionic membrane sensors to determine ions in real samples.

    PubMed

    Faridbod, Farnoush; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Norouzi, Parviz

    2007-08-01

    Schiff base compounds refer to the branch of supra-molecules and can be used as sensing material in the construction of potentiometric ion selective electrodes (ISEs). This relatively modern field has been subject to extensive research in the period of 1999-2007 when more than 100 ISEs employing Schiff bases were constructed. The quantitative high-throughput detection of 29 cations and 7 anions has been demonstrated in various scientific branches, such as biomedicine, pharmacy, biochemistry, pharmacology, environmental chemistry, food technology, and agriculture. This review discusses Schiff base compounds and their applications in the design and development of ion selective sensors and microsensors.

  3. Cationic iridium(III) complexes bearing ancillary 2,5-dipyridyl(pyrazine) (2,5-dpp) and 2,2':5',2''-terpyridine (2,5-tpy) ligands: synthesis, optoelectronic characterization and light-emitting electrochemical cells.

    PubMed

    Hasan, Kamrul; Donato, Loïc; Shen, Yulong; Slinker, Jason D; Zysman-Colman, Eli

    2014-09-28

    Four cationic iridium(III) complexes of the form [Ir(C^N)2(N^N)](+) bearing either a 2,5-dipyridylpyrazine (2,5-dpp) or a 2,2':5',2''-terpyridine (2,5-tpy) ancillary ligand and either 2-phenylpyridine (ppy) or a 2-(2,4-difluorophenyl)-5-methylpyridine (dFMeppy) cyclometalating ligands were synthesized. The optoelectronic properties of all complexes have been fully characterized by UV-visible absorption, cyclic voltammetry and emission spectroscopy. The conclusions drawn from these studies have been corroborated by DFT and TDDFT calculations. The four complexes were assessed as emitters in light-emitting electrochemical cells. Complex 1a, [Ir(ppy)2(2,5-dpp)]PF6, was found to be a deep red emitter (666 nm) both in acetonitrile solution and in the electroluminescent device. Complex 2a, [Ir(ppy)2(2,5-tpy)]PF6 was found to be an orange emitter (604 nm) both in solution and in the LEEC. LEECs incorporating both of these complexes were stable over the course of around 4-6 hours. Complex 1b, [Ir(dFMeppy)2(2,5-dpp)]PF6, was also determined to emit in the orange (605 nm) but with a photoluminescent quantum yield (ΦPL) double that of 2a. Complex 2b, [Ir(dFMeppy)2(2,5-tpy)]PF6 is an extremely bright green emitter (544 nm, 93%). All four complexes exhibited quasireversible electrochemistry and all four complexes phosphoresce from a mixed charge-transfer excited state.

  4. Halogen contacts-induced unusual coloring in Bi(III) bromide complex: anion-to-cation charge transfer via Br···Br interactions.

    PubMed

    Adonin, Sergey A; Gorokh, Igor D; Novikov, Alexander S; Abramov, Pavel A; Sokolov, Maxim N; Fedin, Vladimir P

    2017-09-21

    A yellow bromobismuthate {(2-BrPy)2H}[BiBr4] (1) transforms into unusually deeply colored cherry-red (2-BrPyH)2[BiBr5] (2). Combination of structural studies and theoretical calculations confirms that appearance of short non-covalent Br···Br interactions (≈ 3.3 Å) in 2 is responsible for the anion-to-cation charge transfer (LP(Brligand) → σ*(Br-C)), yielding in dramatic changes in optical behavior. This effect opens the way towards novel halogen bonding-templated halometalate-based hybrid materials with enhanced optical properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Theoretical study of alkali cation-benzene complexes: potential energy surfaces and binding energies with improved results for rubidium and cesium.

    PubMed

    Coletti, Cecilia; Re, Nazzareno

    2006-05-25

    High level ab initio quantum chemical calculations have been carried out on the binding of alkali metal to benzene with special attention to heavier metals for which the agreement between the most recent theoretical investigations and the experimental bond dissociation energies (BDEs) is not very good. We performed BSSE-corrected geometry optimizations employing the MP2 level of theory with large basis sets and a modified Stuttgart RSC 1997 basis set for rubidium and cesium and carried out single point energy calculations at the MP4 level, obtaining, also for the latter metals, BDE values in good agreement with the experimental results. Furthermore, in view of the development of empirical correction terms to force fields to describe cation-pi interactions, we evaluated the potential energy surface along the benzene symmetry axis and discussed the role of the BSSE correction on the accuracy of our results.

  6. The cubyl cation rearrangements.

    PubMed

    Jalife, Said; Mondal, Sukanta; Cabellos, Jose Luis; Martinez-Guajardo, Gerardo; Fernandez-Herrera, Maria A; Merino, Gabriel

    2016-02-25

    Born-Oppenheimer molecular dynamics simulations and high-level ab initio computations predict that the cage-opening rearrangement of the cubyl cation to the 7H(+)-pentalenyl cation is feasible in the gas phase. The rate-determining step is the formation of the cuneyl cation with an activation barrier of 25.3 kcal mol(-1) at the CCSD(T)/def2-TZVP//MP2/def2-TZVP level. Thus, the cubyl cation is kinetically stable enough to be formed and trapped at moderate temperatures, but it may be rearranged at higher temperatures.

  7. Charge transfer complexes of fullerenes containing C₆₀˙⁻ and C₇₀˙⁻ radical anions with paramagnetic Co(II)(dppe)₂Cl⁺ cations (dppe: 1,2-bis(diphenylphosphino)ethane).

    PubMed

    Konarev, Dmitri V; Troyanov, Sergey I; Otsuka, Akihiro; Yamochi, Hideki; Saito, Gunzi; Lyubovskaya, Rimma N

    2016-04-21

    The reduction of Co(II)(dppe)Cl2 with sodium fluorenone ketyl produces a red solution containing the Co(I) species. The dissolution of C60 in the obtained solution followed by the precipitation of crystals with hexane yields a salt {Co(I)(dppe)2(+)}(C60˙(-))·2C6H4Cl2 and a novel complex {Co(dppe)2Cl}(C60) (). With C70, only the crystals of {Co(dppe)2Cl}(C70)·0.5C6H4Cl2 () are formed. Complex contains zig-zag fullerene chains whereas closely packed double chains are formed from fullerenes in . According to the optical spectra and magnetic data charge transfer occurs in both and with the formation of the Co(II)(dppe)2Cl(+) cations and the C60˙(-) or C70˙(-) radical anions. In spite of the close packing in crystals, C60˙(-) or C70˙(-) retain their monomeric form at least down to 100 K. The effective magnetic moments of and of 1.98 and 2.27μB at 300 K, respectively, do not attain the value of 2.45μB expected for the system with two non-interacting S = 1/2 spins at full charge transfer to fullerenes. Most probably diamagnetic {Co(I)(dppe)2Cl}(0) and neutral fullerenes are partially preserved in the samples which can explain the weak magnetic coupling of spins and the absence of fullerene dimerization in both complexes. The EPR spectra of and show asymmetric signals approximated by several lines with g-factors ranging from 2.0009 to 2.3325. These signals originate from the exchange interaction between the paramagnetic Co(II)(dppe)2Cl(+) cations and the fullerene˙(-) radical anions.

  8. Cation-π interaction of the univalent silver cation with meso-octamethylcalix[4]pyrrole: Experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Polášek, Miroslav; Kvíčala, Jaroslav; Makrlík, Emanuel; Křížová, Věra; Vaňura, Petr

    2017-02-01

    By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent silver cation Ag+ forms with meso-octamethylcalix[4]pyrrole (abbrev. 1) the cationic complex species 1·Ag+. Further, applying quantum chemical DFT calculations, four different conformations of the resulting complex 1·Ag+ were derived. It means that under the present experimental conditions, this ligand 1 can be considered as a macrocyclic receptor for the silver cation.

  9. Incorporation of transition metals into Mg-Al layered double hydroxides: Coprecipitation of cations vs. their pre-complexation with an anionic chelator

    SciTech Connect

    Tsyganok, Andrey; Sayari, Abdelhamid . E-mail: Abdel.Sayari@science.uottawa.ca

    2006-06-15

    A comparative study on two different methods for preparing Mg-Al layered double hydroxides (LDH) containing various divalent transition metals M (M=Co, Ni, Cu) has been carried out. The first (conventional) method involved coprecipitation of divalent metals M(II) with Mg(II) and Al(III) cations using carbonate under basic conditions. The second approach was based on the ability of transition metals to form stable anionic chelates with edta{sup 4-} (edta{sup 4-}=ethylenediaminetetraacetate) that were synthesized and further introduced into LDH by coprecipitation with Mg and Al. The synthesized LDHs were characterized by X-ray diffraction (XRD) and X-ray fluorescence (XRF) methods, thermogravimetry with mass-selective detection of decomposition products (TG-MSD), Fourier transform infrared (FTIR) and Raman spectroscopy techniques. The results obtained were discussed in terms of efficiency of transition metal incorporation into the LDH structure, thermal stability of materials and the ability of metal chelates to intercalate the interlayer space of Mg-Al LDH. Vibrational spectroscopy studies confirmed that the integrity of the metal chelates was preserved upon incorporation into the LDH. - Graphical abstract: Two ways for introducing transition metals M(II) into Mg-Al layered double hydroxides (MY{sup 2-} denotes the edta chelate of transition metal M(II)).0.

  10. Notable effects of the metal salts on the formation and decay reactions of α-tocopheroxyl radical in acetonitrile solution. The complex formation between α-tocopheroxyl and metal cations.

    PubMed

    Kohno, Yutaro; Fujii, Miyabi; Matsuoka, Chihiro; Hashimoto, Haruka; Ouchi, Aya; Nagaoka, Shin-ichi; Mukai, Kazuo

    2011-08-18

    The measurement of the UV-vis absorption spectrum of α-tocopheroxyl (α-Toc(•)) radical was performed by reacting aroxyl (ArO(•)) radical with α-tocopherol (α-TocH) in acetonitrile solution including four kinds of alkali and alkaline earth metal salts (MX or MX(2)) (LiClO(4), LiI, NaClO(4), and Mg(ClO(4))(2)), using stopped-flow spectrophotometry. The maximum wavelength (λ(max)) of the absorption spectrum of the α-Toc(•) at 425.0 nm increased with increasing concentration of metal salts (0-0.500 M) in acetonitrile, and it approached constant values, suggesting an [α-Toc(•)-M(+) (or M(2+))] complex formation. The stability constants (K) were determined to be 9.2, 2.8, and 45 M(-1) for LiClO(4), NaClO(4), and Mg(ClO(4))(2), respectively. By reacting ArO(•) with α-TocH in acetonitrile, the absorption of ArO(•) disappeared rapidly, while that of α-Toc(•) appeared and then decreased gradually as a result of the bimolecular self-reaction of α-Toc(•) after passing through the maximum. The second-order rate constants (k(s)) obtained for the reaction of α-TocH with ArO(•) increased linearly with an increasing concentration of metal salts. The results indicate that the hydrogen transfer reaction of α-TocH proceeds via an electron transfer intermediate from α-TocH to ArO(•) radicals followed by proton transfer. Both the coordination of metal cations to the one-electron reduced anions of ArO(•) (ArO:(-)) and the coordination of counteranions to the one-electron oxidized cations of α-TocH (α-TocH(•)(+)) may stabilize the intermediate, resulting in the acceleration of electron transfer. A remarkable effect of metal salts on the rate of bimolecular self-reaction (2k(d)) of the α-Toc(•) radical was also observed. The rate constant (2k(d)) decreased rapidly with increasing concentrations of the metal salts. The 2k(d) value decreased at the same concentration of the metal salts in the following order: no metal salt > NaClO(4) > LiClO(4) > Mg

  11. Gas-phase and solution-phase polymerization of epoxides by Cr(salen) complexes: evidence for a dinuclear cationic mechanism.

    PubMed

    Schön, Eva; Zhang, Xiangyang; Zhou, Zhiping; Chisholm, Malcolm H; Chen, Peter

    2004-11-15

    The gas-phase reactions of a series of mass-selected mononuclear and dinuclear Cr(salen) complexes with propylene oxide suggest that the enhanced reactivity of the dinuclear complexes in gas-phase and in solution may derive from a dicationic mechanism in which the alkoxide chain is mu(2)-coordinated to two Lewis acidic metal centers. The double coordination is proposed to suppress backbiting, and hence chain-transfer in the gas-phase homopolymerization of epoxides.

  12. A band Lanczos approach for calculation of vibrational coupled cluster response functions: simultaneous calculation of IR and Raman anharmonic spectra for the complex of pyridine and a silver cation.

    PubMed

    Godtliebsen, Ian H; Christiansen, Ove

    2013-07-07

    We describe new methods for the calculation of IR and Raman spectra using vibrational response theory. Using damped linear response functions that incorporate a Lorentzian line-shape function from the outset, it is shown how the calculation of Raman spectra can be carried out through the calculation of a set of vibrational response functions in the same manner as described previously for IR spectra. The necessary set of response functions can be calculated for both vibrational coupled cluster (VCC) and vibrational configuration interaction (VCI) anharmonic vibrational wave-functions. For the efficient and simultaneous calculation of the full set of necessary response functions, a non-hermitian band Lanczos algorithm is implemented for VCC, and a hermitian band Lanczos algorithm is implemented for VCI. It is shown that the simultaneous calculation of several response functions is often advantageous. Sample calculations are presented for pyridine and the complex between pyridine and the silver cation.

  13. Cation recognition of thiacalix[2]thianthrene and p-tert-butylthiacalix[2]thianthrene and their conformers and complexes with Zn(II), Cd(II) and Hg(II): a theoretical investigation.

    PubMed

    Kaenkaew, Saowapak; Sae-Khow, Ornchuree; Ruangpornvisuti, Vithaya

    2010-02-01

    The structures of thiacalix[2]thianthrene, p-tert-butylthiacalix[2]thianthrene and their complexes with Zn(2+), Cd(2+) and Hg(2+) were obtained using B3LYP/LanL2DZ and HF/LanL2DZ calculations. The structures of the most stable conformers of thiacalix[2]thianthrene and p-tert-butylthiacalix[2]thianthrene optimized at either the B3LYP/LanL2DZ or HF/LanL2DZ level are in good agreement with their corresponding X-ray crystallographic structures. The binding energies of cations, Zn(2+), Cd(2+) and Hg(2+) to thiacalix[2]thianthrene and to p-tert-butylthiacalix[2]thianthrene conformers, and the thermodynamic properties of their associations were obtained. The relative selectivities of both thiacalix[2]thianthrene and thiacalix[2]thianthrene conformer are in same order: Zn(2+) > Hg(2+) > Cd(2+).

  14. Cation binding by bacteriorhodopsin

    SciTech Connect

    Chang, C.H.; Chen, J.G.; Govindjee, R.; Ebrey, T.

    1984-01-01

    It was found that extensively washed purple membrane has about 1 calcium and 3-4 magnesium ions bound per bacteriorhodopsin molecule. When these divalent cations are removed by any of a variety of means, the pigment changes its color from purple to blue (lambda/sub max/ approx. = 600 nm). This blue pigment, which can be formed at near neutral pH, is probably very similar to blue species formed when the pH of a purple membrane sample is lowered to approx. = 2. When any of a wide variety of cations are added to a blue membrane preparation, the characteristic purple color of bacteriorhodopsin returns. Divalent and trivalent cations are much more efficient than monovalent cations in restoring the purple color and are effective at a ratio approaching one cation per pigment molecule. Besides shifting the absorption spectrum, removal of the divalent cations drastically alters the photochemical cycle of bacteriorhodopsin, including abolishing the unprotonated Schiff base (M-type) intermediate. Finally, lanthanum not only displaces the divalent cations normally bound to the purple membrane but also greatly reduces both the rate of decay of the M412 intermediate and proton uptake.

  15. The renaissance of high-energy CID for structural elucidation of complex lipids: MALDI-TOF/RTOF-MS of alkali cationized triacylglycerols.

    PubMed

    Pittenauer, Ernst; Allmaier, Günter

    2009-06-01

    Triacylglycerols were analyzed as cationized species (Li(+), Na(+), K(+)) by high-energy CID at 20 keV collisions utilizing MALDI-TOF/RTOF mass spectrometry. Precursor ions, based on [M + Li](+)-adduct ions exhibited incomplete fragmentation in the high and low m/z region whereas [M + K](+)-adducts did not show useful fragmentation. Only sodiated precursor ions yielded product ion spectra with structurally diagnostic product ions across the whole m/z range. The high m/z region of the CID spectra is dominated by abundant charge-remote fragmentation of the fatty acid substituents. In favorable cases also positions of double bonds or of hydroxy groups of the fatty acid alkyl chains could be determined. A-type product ions represent the end products of these charge-remote fragmentations. B- and C-type product ions yield the fatty acid composition of individual triacylglycerol species based on loss of either one neutral fatty acid or one sodium carboxylate residue, respectively. Product ions allowing fatty acid substituent positional determination were present in the low m/z range enabling identification of either the sn-1/sn-3 substituents (E-, F-, and G-type ions) or the sn-2 substituent (J-type ion). These findings were demonstrated with synthetic triacylglycerols and plant oils such as cocoa butter, olive oil, and castor bean oil. Typical features of 20 keV CID spectra of sodiated triacylglycerols obtained by MALDI-TOF/RTOF MS were an even distribution of product ions over the entire m/z range and a mass accuracy of +/-0.1 to 0.2 u. One limitation of the application of this technique is mainly the insufficient precursor ion gating after MS1 (gating window at 4 u) of species separated by 2 u.

  16. Experimental and theoretical studies on the DNA-binding of cationic yttrium(III) complex containing 2,2‧-bipyridine

    NASA Astrophysics Data System (ADS)

    Khorasani-Motlagh, Mozhgan; Noroozifar, Meissam; Akbari, Alireza; Mirkazehi-Rigi, Sohaila

    2015-03-01

    The interaction of DNA with [Y(bpy)(OH2)6]+3, where bpy is 2,2‧-bipyridine has been studied at physiological pH in Tris-HCl buffer. Fluorescence and absorption spectroscopy, agarose gel electrophoresis as well as EB quenching experiments are used to study DNA binding of the complex. The results reveal that DNA have the strong ability to bind with Y(III) complex. The binding constant, Kb and the Stern-Volmer quenching constant, KSV are determined. For characterization of the binding mode between the Y(III) complex and DNA various procedures such as: iodide quenching assay, salt effect and thermodynamical investigation are used. The results suggest that minor groove binding should be the interaction mode of complex to DNA. A gel electrophoresis assay demonstrates the ability of the complex to cleave the DNA via oxidative pathway. Electronic structure of [Y(bpy)(OH2)6]+3 was also carried out applying the density functional theory (DFT) method and applied to explain some obtained experimental observations.

  17. Cationic copper (I) complexes with bulky 1,4-diaza-1,3-butadiene ligands - Synthesis, solid state structure and catalysis

    NASA Astrophysics Data System (ADS)

    Anga, Srinivas; Kottalanka, Ravi K.; Pal, Tigmansu; Panda, Tarun K.

    2013-05-01

    We report the full characterization of two glyoxal-based ligands N,N bis(diphenylmethyl)-1,4-diaza-1,3-butadiene ligand (DADPh2, 1) and more bulky N,N bis(triphenylmethyl)-1,4-diaza-1,3-butadiene ligand (DADPh3, 2) by the condensation reaction of glyoxal and diphenylmethanamine and triphenyl-methanamine respectively. The copper (I) complex of composition [Cu(DADPh2)2]PF6 (3) having two neutral bidentate N,N bis(diphenyl-methyl)-1,4-diaza-1,3-butadiene ligand was prepared by the reaction of [Cu(CH3CN)4]PF6 and 1 in 1:2 ratio in dichloromethane. In a similar reaction with N,N bis(triphenylmethyl)-1,4-diaza-1,3-butadiene ligand (2) and [Cu(CH3CN)4]PF6 in dichloromethane yielded corresponding heteroleptic copper (I) complex [Cu(DADPh3)(CH3CN)2]PF6 (4). Another copper (I) complex [Cu(DADPh2)(PPh3)]PF6 (5) can also be obtained by the one pot reaction involving ligand 1, [Cu(CH3CN)4]PF6 and triphenylphosphine. Solid state structures of all the five compounds were established by single crystal X-ray diffraction analysis. The solid state structures of the copper complexes 3-5 reveal a distorted tetrahedral geometry around the copper (I) centers. The copper complexes 3-5 were tested as catalysts for the coupling reaction of o-iodophenol and phenyl acetylene and it was observed that complex 4 exhibits the highest catalytic activity.

  18. Variable magnetic interactions between S = 1/2 cation radical salts of functionalizable electron-rich dithiolene and diselenolene Cp2Mo complexes.

    PubMed

    Bsaibess, Talia; Guerro, Michel; Le Gal, Yann; Sarraf, Daad; Bellec, Nathalie; Fourmigué, Marc; Barrière, Frédéric; Dorcet, Vincent; Guizouarn, Thierry; Roisnel, Thierry; Lorcy, Dominique

    2013-02-18

    A series of Cp(2)Mo(dithiolene) and Cp(2)Mo(diselenolene) complexes containing N-alkyl-1,3-thiazoline-2-thione-4,5-dithiolate ligand (R-thiazdt, R = Me, Et, CH(2)CH(2)OH) and N-alkyl-1,3-thiazoline-2-thione-4,5-diselenolate ligand (R-thiazds, R = Me, Et) have been synthesized. These heteroleptic molybdenum complexes have been characterized by electrochemistry, spectroelectrochemistry, and single crystal X-ray diffraction. They act as very good electron donor complexes with a first oxidation potential 200 mV lower than in the prototypical Cp(2)Mo(dmit) complex and exhibit almost planar MoS(2)C(2) (or MoSe(2)C(2)) metallacycles. All five complexes formed charge transfer salts with a weak (TCNQ) and a strong acceptor (TCNQF(4)), affording ten different charge-transfer salts, all with 1:1 stoichiometry. Crystal structure determinations show that the S/Se substitution in the metallacycle systematically affords isostructural salts, while the Cp(2)Mo(R-thiazdt) complexes with R equals ethyl or CH(2)CH(2)OH can adopt different structures, depending on the involvement of the hydroxyl group into intra- or intermolecular hydrogen bonding interactions. Magnetic susceptibility data of the salts are correlated with their structural organization, demonstrating that a face-to-face organization of the Me-thiazdt (or Me-thiazds) ligand favors a strong antiferromagnetic interaction, while the bulkier R = Et or R = CH(2)CH(2)OH substituents can completely suppress such intermolecular interactions, with the added contribution of hydrogen bonding to the solid state organization.

  19. Halogenated silanes, radicals, and cations

    NASA Astrophysics Data System (ADS)

    Wang, Liming; He, Yi-Liang

    2008-09-01

    Quantum chemistry study has been carried out on the structure and energetics of halogenated silanes, radicals, and cations (SiHxXy0,+1, X = F, Cl, Br; x + y = 1-4). The geometries are optimized at B3LYP/6-31+G(2df,p) level. The adiabatic ionization energiess (IEas), relative energetics of cations, proton affinities (PAs) of silanes, and the enthalpies of formation are predicted using G3(CC) model chemistry. Non-classical ion complex structures are found for hydrogenated cations and transition states connecting classical and non-classical structures are also located. The most stable cations for silylene and silyl radicals have their classical divalent and trivalent structures, and those for silanes have non-classical structures except for SiH3Br+ and SiH2Br2+. The non-classical structures for halosilane cations imply difficulty in experimentally measurement of the adiabatic ionization energies using photoionization or photoelectron studies. For SiH3X, SiH2X2, and SiHX3, the G3(CC) adiabatic IEas to classical ionic structures closest to their neutrals agree better with the photoelectron spectroscopic measurements. The transition states between classical and non-classical structures also hamper the photoionization determination of the appearance energies for silylene cations from silanes. The G3(CC) results for SiHx0,+1 agree excellently with the photoionization mass spectrometric study, and the results for fluorinated and chlorinated species also agree with the previous theoretical predictions at correlation levels from BAC-MP4 to CCSD(T)/CBS. The predicted enthalpy differences between SiH2Cl+, SiHCl2+, and SiCl3+ are also in accordance with previous kinetics study. The G3(CC) results show large discrepancies to the collision-induced charge transfer and/or dissociation reactions involving SiFx+ and SiClx+ ions, for which the G3(CC) enthalpies of formation are also significantly differed from the previous theoretical predictions, especially on SiFx+ (x = 2-4). The G3

  20. Polymer light-emitting diodes based on cationic iridium(III) complexes with a 1,10-phenanthroline derivative containing a bipolar carbazole-oxadiazole unit as the auxiliary ligand

    NASA Astrophysics Data System (ADS)

    Tang, Huaijun; Wei, Liying; Meng, Guoyun; Li, Yanhu; Wang, Guanze; Yang, Furui; Wu, Hongbin; Yang, Wei; Cao, Yong

    2014-11-01

    A 1,10-phenanthroline derivative (co-phen) containing a bipolar carbazole-oxadiazole unit was synthesized and used as the auxiliary ligand in cationic iridium(III) complexes [(ppy)2Ir(co-phen)]PF6 (ppy: 2-phenylpyridine) and [(npy)2Ir(co-phen)]PF6 (npy: 2-(naphthalen-1-yl)pyridine). Two complexes have high thermal stability with the glass-transition temperatures (Tg) of 207 °C and 241 °C, and the same 5% weight-reduction temperatures (ΔT5%) of 402 °C. Both of them were used as phosphorescent dopants in solution-processed polymer light-emitting diodes (PLEDs): ITO/PEDOT: PSS/PVK: PBD: complex (mass ratios 100: 40: x, x = 1.0, 2.0, and 4.0)/CsF/Al. The maximum luminances of the PLEDs using [(ppy)2Ir(co-phen)]PF6 and [(npy)2Ir(co-phen)]PF6 were 12567 cd m-2 and 11032 cd m-2, the maximum luminance efficiencies were 17.3 cd A-1 and 20.4 cd A-1, the maximum power efficiencies were 9.8 lm W-1 and 10.3 lm W-1, and the maximum external quantum efficiencies were 9.3% and 11.4% respectively. The CIE color coordinates were around (0.37, 0.57) and (0.44, 0.54) respectively, corresponding to the yellow green region.

  1. A series of three-dimensional architectures constructed from lanthanide-substituted polyoxometalosilicates and lanthanide cations or lanthanide-organic complexes as linkers.

    PubMed

    An, Haiyan; Zhang, Hua; Chen, Zhaofei; Li, Yangguang; Liu, Xuan; Chen, Hao

    2012-07-21

    Six 3D architectures based on lanthanide-substituted polyoxometalosilicates, KLn[(H(2)O)(6)Ln](2)[(H(2)O)(4)LnSiW(11)O(39)](2)·nH(2)O (Ln = La 1, n = 42; Ce 2, n = 40), H[(H(2)O)(6)Nd](2)[(H(2)O)(7)Nd][(H(2)O)(4)NdSiW(11)O(39)][(H(2)O)(3)NdSiW(11)O(39)]·13H(2)O (3), H(2)K(2)[(Hpic)(H(2)O)(5)Ln](2)[(H(2)O)(4)LnSiW(11)O(39)](2)·nH(2)O (Ln = La 4, n = 18.5; Ce 5, n = 35; Nd 6, n = 36; Hpic = 4-picolinic acid), have been synthesized and characterized by elemental analysis, IR and UV-vis spectroscopy, TG analysis, powder X-ray diffraction and single crystal X-ray diffraction. Compounds 1 and 2 are isostructural, built up of lanthanide-substituted polyoxoanions [{(H(2)O)(4)Ln(SiW(11)O(39))}(2)](10-) linked by Ln(3+) cations to form a 3D open framework with 1D channels. The polyoxoanion [{(H(2)O)(4)Ln(SiW(11)O(39))}(2)](10-) consists of two α(1)-type mono-Ln-substituted Keggin anions. When Nd(3+) ion was used instead of La(3+) or Ce(3+) ions, compound 3 with a different structure was obtained, containing two kinds of polyoxoanions [{(H(2)O)(4)Nd(SiW(11)O(39))}(2)](10-) and [{(H(2)O)(3)Nd(SiW(11)O(39))}(2)](10-) which are connected together by Nd(3+) ions to yield a 3D framework. When 4-picolinic acid was added to the reaction system of 1-3, isostructural compounds 4-6 were obtained, constructed from the polyoxoanions [{(H(2)O)(4)Ln(SiW(11)O(39))}(2)](10-) linked by picolinate-chelated lanthanide centers to form a 3D channel framework. From a topological viewpoint, the 3D nets of 1, 2, 4, 5 and 6 exhibit a (3,6)-connected rutile topology, whereas the 3D structure of 3 possesses a rare (3,3,6,10)-connected topology. The magnetic properties of 2, 3, 5 and 6 have been studied by measuring their magnetic susceptibilities in the temperature range 2-300 K.

  2. Quantitative analysis of free and bonded forms of volatile sulfur compouds in wine. Basic methodologies and evidences showing the existence of reversible cation-complexed forms.

    PubMed

    Franco-Luesma, Ernesto; Ferreira, Vicente

    2014-09-12

    This paper examines first some basic aspects critical to the analysis of Volatile Sulfur Compounds (VSCs), such as the analytical characteristics of the GC-pFPD system and the stability of the different standard solutions required for a proper calibration. Following, a direct static headspace analytical method for the determination of exclusively free forms of VSCs has been developed. Method repeatability is better than 4%, detection limits for main analytes are below 0.5μgL(-1), and the method dynamic linear range (r(2)>0.99) is expanded by controlling the split ratio in the chromatographic inlet to cover the natural range of occurrence of these compounds in wines. The method gives reliable estimates of headspace concentrations but, as expected, suffers from strong matrix effects with recoveries ranging from 0 to 100% or from 60 to 100 in the cases of H2S and the other mercaptans, respectively. This demonstrates the existence of strong interactions of these compounds with different matrix components. The complexing ability of Cu(2+) and to a lower extent Fe(2+) and Zn(2+) has been experimentally checked. A previously developed method in which the wine is strongly diluted with brine and the volatiles are preconcentrated by HS-SPME, was found to give a reliable estimation of the total amount (free+complexed) of mercaptans, demonstrating that metal-mercaptan complexes are reversible. The comparative analysis of different wines by the two procedures reveals that in normal wines H2S and methanethiol can be complexed at levels above 99%, with averages around 97% for H2S and 75% for methanethiol, while thioethers such as dimethyl sulfide (DMS) are not complexed. Overall, the proposed strategy may be generalized to understand problems caused by VSCs in different matrices. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Cation disorder in shocked orthopyroxene.

    NASA Technical Reports Server (NTRS)

    Dundon, R. W.; Hafner, S. S.

    1971-01-01

    The study of cation distributions over nonequivalent lattice sites in minerals may reveal information on the history of temperature and pressure in rocks. Chemically homogeneous orthopyroxene specimens were shocked under well-controlled conditions in the laboratory in order to provide a basis for the interpretation of more complex natural materials. As a result of the investigation it is concluded that the distribution of magnesium and iron over the M1 and M2 positions in Bamle enstatite shocked at 1 megabar is highly disordered. It corresponds to an equilibrium distribution of at least 1000 C.

  4. Cation locations and dislocations in zeolites

    NASA Astrophysics Data System (ADS)

    Smith, Luis James

    The focus of this dissertation is the extra-framework cation sites in a particular structural family of zeolites, chabazite. Cation sites play a particularly important role in the application of these sieves for ion exchange, gas separation, catalysis, and, when the cation is a proton, acid catalysis. Structural characterization is commonly performed through the use of powder diffraction and Rietveld analysis of powder diffraction data. Use of high-resolution nuclear magnetic resonance, in the study of the local order of the various constituent nuclei of zeolites, complements well the long-range order information produced by diffraction. Recent developments in solid state NMR techniques allow for increased study of disorder in zeolites particularly when such phenomena test the detection limits of diffraction. These two powerful characterization techniques, powder diffraction and NMR, offer many insights into the complex interaction of cations with the zeolite framework. The acids site locations in SSZ-13, a high silica chabazite, and SAPO-34, a silicoaluminophosphate with the chabazite structure, were determined. The structure of SAPO-34 upon selective hydration was also determined. The insensitivity of X-rays to hydrogen was avoided through deuteration of the acid zeolites and neutron powder diffraction methods. Protons at inequivalent positions were found to have different acid strengths in both SSZ-13 and SAPO-34. Other light elements are incorporated into zeolites in the form of extra-framework cations, among these are lithium, sodium, and calcium. Not amenable by X-ray powder diffraction methods, the positions of such light cations in fully ion-exchanged versions of synthetic chabazite were determined through neutron powder diffraction methods. The study of more complex binary cation systems were conducted. Powder diffraction and solid state NMR methods (MAS, MQMAS) were used to examine cation site preferences and dislocations in these mixed-akali chabazites

  5. Cationic half-sandwich Ru(II) complexes containing (N,N)-bound Schiff-base ligands: Synthesis, crystal structure analysis and spectroscopic studies

    NASA Astrophysics Data System (ADS)

    Tao, Li; Miao, Qian; Tehrani, Alireza Azhdari; Hajiashrafi, Taraneh; Hu, Mao-Lin; Morsali, Ali

    2016-08-01

    Three Ru(II) half-sandwich complexes containing (N,N)-bound Schiff-base ligands, [(η6-C6H6) RuCl(L1)]PF6 (1) L1 = (E)-1-(6-methylpyridin-2-yl)-N-(p-tolyl)methanimine, [(η6-p-cymene)RuCl(L1)]PF6 (2) and [(η6-p-cymene)RuCl(L2)]PF6(3) L2 = (E)-1-(6-bromopyridin-2-yl)-N-(p-tolyl)methanimine, were synthesized, characterized and their supramolecular structures were analyzed. The crystal packing of these compounds was studied using geometrical analysis and Hirshfeld surface analysis. The fluorescence behavior of these compounds was also studied. TD-DFT calculations were carried out to better understand the fluorescence properties of complexes 1-3. These compounds could be promising for the design of organometallic dye systems.

  6. High-resolution structures of two complexes between thrombin and thrombin-binding aptamer shed light on the role of cations in the aptamer inhibitory activity

    PubMed Central

    Russo Krauss, Irene; Merlino, Antonello; Randazzo, Antonio; Novellino, Ettore; Mazzarella, Lelio; Sica, Filomena

    2012-01-01

    The G-quadruplex architecture is a peculiar structure adopted by guanine-rich oligonucleotidic sequences, and, in particular, by several aptamers, including the thrombin-binding aptamer (TBA) that has the highest inhibitory activity against human α-thrombin. A crucial role in determining structure, stability and biological properties of G-quadruplexes is played by ions. In the case of TBA, K+ ions cause an enhancement of the aptamer clotting inhibitory activity. A detailed picture of the interactions of TBA with the protein and with the ions is still lacking, despite the importance of this aptamer in biomedical field for detection and inhibition of α-thrombin. Here, we fill this gap by presenting a high-resolution crystallographic structural characterization of the thrombin–TBA complex formed in the presence of Na+ or K+ and a circular dichroism study of the structural stability of the aptamer both free and complexed with α-thrombin, in the presence of the two ionic species. The results indicate that the different effects exerted by Na+ and K+ on the inhibitory activity of TBA are related to a subtle perturbation of a few key interactions at the protein–aptamer interface. The present data, in combination with those previously obtained on the complex between α-thrombin and a modified aptamer, may allow the design of new TBA variants with a pharmacological performance enhancement. PMID:22669903

  7. Baeyer-Villiger oxidation of cyclic ketones with hydrogen peroxide catalyzed by cationic complexes of platinum(II): Selectivity properties and mechanistic studies

    SciTech Connect

    Del Todesco Frisone, M.; Pinna, F.; Strukul, G. )

    1993-01-01

    The catalytic oxidation of simple cyclic ketones with hydrogen peroxide to give the corresponding lactones is reported. The reaction is catalyzed by complexes of Pt(II) of the type [(P-P)Pt(CF[sub 3])(solv)][sup +] (P-P = diphosphine) that may be deactivated by the hydroxy acids formed by hydrolysis of the lactones. The selectivity of the catalyst is studied in the oxidation of substrates like camphor, 2-cyclohexene-1-one, menthone, carvone, and indanones. Cyclobutanone is used to determine the mechanism of the reaction from initial rates studies. The reaction scheme proposed, which accounts for the observed effects of the various reactants, involves the coordination of the ketone on the vacant coordination site of the complex followed by nucleophilic attack of free hydrogen peroxide on the carbonyl carbon. The involvement of a quasi-peroxymetallacyclic intermediate is suggested which rearranges to give the lactone and the starting complex. A comparison with the mechanistic behavior of organic peroxy acids is given. 24 refs., 10 figs., 3 tabs.

  8. Synthesis, Characterization, Cytotoxic Activity, and Interactions with CT-DNA and BSA of Cationic Ruthenium(II) Complexes Containing Dppm and Quinoline Carboxylates

    PubMed Central

    da Silva, Edinaldo N.; da Silva, Paulo A. B.; Graminha, Angélica E.; de Oliveira, Pollyanna F.; Damasceno, Jaqueline L.; Tavares, Denise C.; Batista, Alzir A.

    2017-01-01

    The complexes cis-[Ru(quin)(dppm)2]PF6 and cis-[Ru(kynu)(dppm)2]PF6 (quin = quinaldate; kynu = kynurenate; dppm = bis(diphenylphosphino)methane) were prepared and characterized by elemental analysis, electronic, FTIR, 1H, and 31P{1H} NMR spectroscopies. Characterization data were consistent with a cis arrangement for the dppm ligands and a bidentate coordination through carboxylate oxygens of the quin and kynu anions. These complexes were not able to intercalate CT-DNA as shown by circular dichroism spectroscopy. On the other hand, bovine serum albumin (BSA) binding constants and thermodynamic parameters suggest spontaneous interactions with this protein by hydrogen bonds and van der Waals forces. Cytotoxicity assays were carried out on a panel of human cancer cell lines including HepG2, MCF-7, and MO59J and one normal cell line GM07492A. In general, the new ruthenium(II) complexes displayed a moderate to high cytotoxicity in all the assayed cell lines with IC50 ranging from 10.1 to 36 µM and were more cytotoxic than the precursor cis-[RuCl2(dppm)2]. The cis-[Ru(quin)(dppm)2]PF6 were two to three times more active than the reference metallodrug cisplatin in the MCF-7 and MO59J cell lines. PMID:28814948

  9. Detachable strong cation exchange monolith, integrated with capillary zone electrophoresis and coupled with pH gradient elution, produces improved sensitivity and numbers of peptide identifications during bottom-up analysis of complex proteomes.

    PubMed

    Zhang, Zhenbin; Yan, Xiaojing; Sun, Liangliang; Zhu, Guijie; Dovichi, Norman J

    2015-04-21

    A detachable sulfonate-silica hybrid strong cation-exchange monolith was synthesized in a fused silica capillary, and used for solid phase extraction with online pH gradient elution during capillary zone electrophoresis-tandem mass spectrometry (CZE-MS/MS) proteomic analysis. Tryptic digests were prepared in 50 mM formic acid and loaded onto the strong cation-exchange monolith. Fractions were eluted using a series of buffers with lower concentration but higher pH values than the 50 mM formic acid background electrolyte. This combination of elution and background electrolytes results in both sample stacking and formation of a dynamic pH junction and allows use of relatively large elution buffer volumes while maintaining reasonable peak efficiency and resolution. A series of five pH bumps were applied to elute E. coli tryptic peptides from the monolith, followed by analysis using CZE coupled to an LTQ-Orbitrap Velos mass spectrometer; 799 protein groups and 3381 peptides were identified from 50 ng of the digest in a 2.5 h analysis, which approaches the identification rate for this organism that was obtained with an Orbitrap Fusion. We attribute the improved numbers of peptide and protein identifications to the efficient fractionation by the online pH gradient elution, which decreased the complexity of the sample in each elution step and improved the signal intensity of low abundance peptides. We also performed a comparative analysis using a nanoACQUITY UltraPerformance LCH system. Similar numbers of protein and peptide identifications were produced by the two methods. Protein identifications showed significant overlap between the two methods, whereas peptide identifications were complementary.

  10. (N-pyrrolyl)B(C6F5)2--a new organometallic Lewis acid for the generation of group 4 metallocene cation complexes.

    PubMed

    Kehr, G; Fröhlich, R; Wibbeling, B; Erker, G

    2000-01-01

    Treatment of the (C6F5)2BF x OEt2 (3) complex with N-pyrrolyl lithium gives bis(pentafluorophenyl)(N-pyrrolyl)borane (2), a strong organometallic Lewis acid, which was characterized by X-ray diffraction (B-N bond length: 1.401(5) A). It exhibits a columnar superstructure in the crystal and contains pi-stacks of pyrrolyl units. Compound 2 readily abstracts alkyl anions from a variety of alkyl Group 4 metallocene-type complexes and leads to the clean formation of the respective metallocene ions or ion pairs. For example, the treatment of Cp3ZrCH3 (9) with 2 transfers a methyl anion to yield the ion pair [Cp3Zr]+[(C4H4N)B(CH3)(C6F5)2]- (12). The X-ray crystal structure analysis of 12 shows a close contact between zirconium and the pyrrolyl-beta-carbon (2.641(2) A). The borane 2 adds to (butadiene)zirconocene (13) to yield the betaine system [Cp2Zr]+[(C4H6)B- (NC4H4)(C6F)2]- (15). Complex 15 contains a distorted eta3-allyl moiety inside the metallacyclic framework and it features an internal Zr+...(pyrrolyl)B- ion pair interaction with a Zr...pyrrolyl-alphacarbon separation of 2.723(3) A (determined by X-ray diffraction). From the dynamic NMR spectra of 15 the bond strength of the internal ion pair interaction was estimated to be deltaGdiss (223 K) approximately = to15 kcalmol(-1). Treatment of dimethylzirconocene (16) with 2 yields the metallocene borate salt [Cp2ZrCH3]+[(C4H4N)B(CH3)(C6F5)2]- (17), which is an active catalyst for the polymerization of ethene.

  11. Neutral, cationic, and anionic low-spin iron(III) complexes stabilized by amidophenolate and iminobenzosemiquinonate radical in N,N,O ligands.

    PubMed

    Rajput, Amit; Sharma, Anuj K; Barman, Suman K; Koley, Debasis; Steinert, Markus; Mukherjee, Rabindranath

    2014-01-06

    A brownish-black complex [Fe(III)(L)2] (1) (S = 0), supported by two tridentate redox-active azo-appended o-amidophenolates [H2L = 2-(2-phenylazo)-anilino-4,6-di-tert-butylphenol], has been synthesized and structurally characterized. In CH2Cl2 1 displays two oxidative and two reductive 1e(-) redox processes at E1/2 values of 0.48 and 1.06 V and -0.42 and -1.48 V vs SCE, respectively. The one-electron oxidized form [1](+) isolated as a green solid [Fe(III)(L)2][BF4] (2) (S = 1/2) has been structurally characterized. Isolation of a dark ink-blue one-electron reduced form [1](-) has also been achieved [Co(III)(η(5)-C10H15)2][Fe(III)(L)2] (3) (S = 1/2). Mössbauer spectral parameters unequivocally establish that 1 is a low-spin (LS) Fe(III) complex. Careful analysis of Mössbauer spectral data of 2 and 3 at 200 and 80 K reveal that each complex has a major LS Fe(III) and a minor LS Fe(II) component (redox isomers): [Fe(III){(L(ISQ))(-•)}2](+) and [Fe(II){(L(IBQ))(0)}{(L(ISQ))(-•)}](+) (2) and [Fe(III){(L(AP))(2-)}2](-) and [Fe(II){(L(ISQ))(-•)}{(L(AP))(2-)}](-) (3). Notably, for both at 8 K mainly the major component exists. Broken-Symmetry (BS) Density Functional Theory (DFT) calculations at the B3LYP level reveals that in 1 the unpaired electron of LS Fe(III) is strongly antiferromagnetically coupled with a π-radical of o-iminobenzosemiquinonate(1-) (L(ISQ))(-•) form of the ligand, delocalized over two ligands providing 3- charge (X-ray structure). DFT calculations reveal that the unpaired electron in 2 is due to (L(ISQ))(-•) [LS Fe(III) (SFe = 1/2) is strongly antiferromagnetically coupled to one of the (L(ISQ))(-•) radicals (Srad = 1/2)] and 3 is primarily a LS Fe(III) complex, supported by two o-amidophenolate(2-) ligands. Time-Dependent-DFT calculations shed light on the origin of UV-vis-NIR spectral absorptions for 1-3. The collective consideration of Mössbauer, variable-temperature (77-298 K) electron paramagnetic resonance (EPR), and absorption

  12. A divalent cation stabilizes the active conformation of the B. subtilis RNase P x pre-tRNA complex: a role for an inner-sphere metal ion in RNase P.

    PubMed

    Hsieh, John; Koutmou, Kristin S; Rueda, David; Koutmos, Markos; Walter, Nils G; Fierke, Carol A

    2010-07-02

    Metal ions interact with RNA to enhance folding, stabilize structure, and, in some cases, facilitate catalysis. Assigning functional roles to specifically bound metal ions presents a major challenge in analyzing the catalytic mechanisms of ribozymes. Bacillus subtilis ribonuclease P (RNase P), composed of a catalytically active RNA subunit (PRNA) and a small protein subunit (P protein), catalyzes the 5'-end maturation of precursor tRNAs (pre-tRNAs). Inner-sphere coordination of divalent metal ions to PRNA is essential for catalytic activity but not for the formation of the RNase P x pre-tRNA (enzyme-substrate, ES) complex. Previous studies have demonstrated that this ES complex undergoes an essential conformational change (to the ES* conformer) before the cleavage step. Here, we show that the ES* conformer is stabilized by a high-affinity divalent cation capable of inner-sphere coordination, such as Ca(II) or Mg(II). Additionally, a second, lower-affinity Mg(II) activates cleavage catalyzed by RNase P. Structural changes that occur upon binding Ca(II) to the ES complex were determined by time-resolved Förster resonance energy transfer measurements of the distances between donor-acceptor fluorophores introduced at specific locations on the P protein and pre-tRNA 5' leader. These data demonstrate that the 5' leader of pre-tRNA moves 4 to 6 A closer to the PRNA x P protein interface during the ES-to-ES* transition and suggest that the metal-dependent conformational change reorganizes the bound substrate in the active site to form a catalytically competent ES* complex.

  13. Electric field effects on nuclear magnetic shielding of the 1:1 and 2:1 (homo and heterochiral) complexes of XOOX' (X, X' = H, CH3) with lithium cation and their chiral discrimination.

    PubMed

    Alkorta, Ibon; Elguero, José; Provasi, Patricio F; Pagola, Gabriel I; Ferraro, Marta B

    2011-09-14

    The set of 1:1 and 2:1 complexes of XOOX' (X, X' = H, CH(3)) with lithium cation has been studied to determine if they are suitable candidates for chiral discrimination in an isotropic medium via nuclear magnetic resonance spectroscopy. Conventional nuclear magnetic resonance is unable to distinguish between enantiomers in the absence of a chiral solvent. The criterion for experimental detection is valuated by the isotropic part of nuclear shielding polarisability tensors, related to a pseudoscalar of opposite sign for two enantiomers. The study includes calculations at coupled Hartree-Fock and density functional theory schemes for (17)O nucleus in each compound. Additional calculations for (1)H are also included for some compounds. A huge static homogeneous electric field, perpendicular to the magnetic field of the spectromer, as big as ≈1.7 × 10(8) V m(-1) should be applied to observe a shift of ≈1 ppm for (17)O magnetic shielding in the proposed set of complexes. © 2011 American Institute of Physics

  14. Cation-ether complexes in the gas phase: Bond dissociation energies and equilibrium structures of Li{sup +}[O(CH{sub 3}){sub 2}]{sub x}, x=1-4

    SciTech Connect

    More, M.B.; Armentrout, P.B.; Glendening, E.D.; Ray, D.; Feller, D.

    1996-02-01

    Bond dissociation energies, equilibrium structures, and harmonic vibrational frequencies of Li{sup +}[O(CH{sub 3}){sub 2}]{sub x}, x=1-4, are reported. The bond dissociation energies are determined experimentally by analysis of the thresholds for collision-induced dissociation of the cation-ether complexes by xenon (measured using guided ion beam mass spectrometry) and computationally by ab initio electronic structure calculation at the RHF and MP2 levels of theory. In all cases, the primary and lowest energy dissociation channel observed experimentally is endothermic loss of one ether molecule. The cross-section thresholds are interpreted to yield 0 and 298 K bond energies after accounting for the effects of multiple ion-molecule collisions, internal energy of the complexes, and unimolecular decay rates. The experimental and theoretical bond energies are in good agreement with previous experimental results. Some of the discrepancies disappear at the complete basis set limit. The equilibrium structures are determined primarily by strong electrostatic and polarization interactions. Charge transfer interactions are also important, as indicated by natural energy decomposition analysis of the calculated wave functions. 59 refs., 6 figs., 5 tabs.

  15. Glycosylated Platinum(IV) Complexes as Substrates for Glucose Transporters (GLUTs) and Organic Cation Transporters (OCTs) Exhibited Cancer Targeting and Human Serum Albumin Binding Properties for Drug Delivery.

    PubMed

    Ma, Jing; Wang, Qingpeng; Huang, Zhonglv; Yang, Xiande; Nie, Quandeng; Hao, Wenpei; Wang, Peng George; Wang, Xin

    2017-07-13

    Glycosylated platinum(IV) complexes were synthesized as substrates for GLUTs and OCTs for the first time, and the cytotoxicity and detailed mechanism were determined in vitro and in vivo. Galactoside Pt(IV), glucoside Pt(IV), and mannoside Pt(IV) were highly cytotoxic and showed specific cancer-targeting properties in vitro and in vivo. Glycosylated platinum(IV) complexes 5, 6, 7, and 8 (IC50 0.24-3.97 μM) had better antitumor activity of nearly 166-fold higher than the positive controls cisplatin (1a), oxaliplatin (3a), and satraplatin (5a). The presence of a hexadecanoic chain allowed binding with human serum albumin (HSA) for drug delivery, which not only enhanced the stability of the inert platinum(IV) prodrugs but also decreased their reduction by reductants present in human whole blood. Their preferential accumulation in cancer cells compared to noncancerous cells (293T and 3T3 cells) suggested that they were potentially safe for clinical therapeutic use.

  16. A theoretical survey of substituent effects on the properties of pnicogen and hydrogen bonds in cationic complexes of PH4(+) with substituted benzonitrile.

    PubMed

    Bagheri, Sotoodeh; Masoodi, Hamid Reza; Akrami-Mohajeri, Ali Reza

    2017-08-12

    In this paper, we analyze the substituent effects on the nature and characteristics of P⋯N and H⋯N interactions in X-PhCN:PH4(+) complexes (X=H, F, Cl, Br, CN, NH2, NO2, CH3 and N(CH3)2) as a working model at MP2(FC)/6-311++G(d,p) level of theory. The natural bond orbital (NBO) method as well as the quantum theory of atoms in molecules (AIM) is applied to characterize interactions in the studied complexes. In general, the pnicogen bonded systems are more stable than the corresponding hydrogen bonded cases. The strength of the interactions generally correlates well with the magnitudes of the negative electrostatic potentials of the nitrogen atom of isolated substituted benzonitrile (Vs,min(N)). The results indicate that increase in the electron withdrawing power of substituents is accompanied by decrease in the absolute value of Vs,min(N). Also, there are meaningful relationships between Vs,min(N) values and the results of AIM and NBO analyses in studied systems. Moreover, it is found that substituent effects on characteristics of P⋯N pnicogen and H⋯N hydrogen bonds can be expressed by Hammett constants. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. A comparative mechanistic study of the reversible binding of NO to a water-soluble octa-cationic Fe(III) porphyrin complex.

    PubMed

    Jee, Joo-Eun; Wolak, Maria; Balbinot, Domenico; Jux, Norbert; Zahl, Achim; van Eldik, Rudi

    2006-02-06

    The water-soluble, non-mu-oxo dimer-forming porphyrin, [5,10,15,20-tetrakis-4'-t-butylphenyl-2',6'-bis-(N-methylene-(4''-t-butylpyridinium))porphyrinato]iron(III) octabromide, (P(8+))Fe(III), with eight positively charged substituents in the ortho positions of the phenyl rings, was characterized by UV-vis and 1H NMR spectroscopy and 17O NMR water-exchange studies in aqueous solution. Spectrophotometric titrations of (P(8+))Fe(III) indicated a pKa1 value of 5.0 for coordinated water in (P(8+))Fe(III)(H2O)2. The monohydroxo-ligated (P(8+))Fe(III)(OH)(H2O) formed at 5 < pH < 12 has a weakly bound water molecule that undergoes an exchange reaction, k(ex) = 2.4 x 10(6) s(-1), significantly faster than water exchange on (P(8+))Fe(III)(H2O)2, viz. k(ex) = 5.5 x 10(4) s(-1) at 25 degrees C. The porphyrin complex reacts with nitric oxide to yield the nitrosyl adduct, (P(8+))Fe(II)(NO+)(L) (L = H2O or OH-). The diaqua-ligated (P(8+))Fe(III)(H2O)2 binds and releases NO according to a dissociatively activated mechanism, analogous to that reported earlier for other (P)Fe(III)(H2O)2 complexes. Coordination of NO to (P(8+))Fe(III)(OH)(H2O) at high pH follows an associative mode, as evidenced by negative deltaS(double dagger)(on) and deltaV(double dagger)(on) values measured for this reaction. The observed ca. 10-fold decrease in the NO binding rate on going from six-coordinate (P(8+))Fe(III)(H2O)2 (k(on) = 15.1 x 10(3) M(-1) s(-1)) to (P(8+))Fe(III)(OH)(H2O) (k(on) = 1.56 x 10(3) M(-1) s(-1) at 25 degrees C) is ascribed to the different nature of the rate-limiting step for NO binding at low and high pH, respectively. The results are compared with data reported for other water-soluble iron(III) porphyrins with positively and negatively charged meso substituents. Influence of the porphyrin periphery on the dynamics of reversible NO binding to these (P)Fe(III) complexes as a function of pH is discussed on the basis of available experimental data.

  18. Protein quantitation by complexation of fluorescent tetraphenylthiophene cation to anion-terminated poly(N-isopropylacrylamide): aggregation-enhanced emission and electrostatic interaction.

    PubMed

    Deng, Shiang-Lin; Hsiao, Tai-Shen; Shih, Ke-Ying; Hong, Jin-Long

    2014-09-05

    A fluorescent biological sensor utilizing aggregation-enhanced emission (AEE) property was developed in our laboratory. First, the AEE-active fluorescent tetraphenylthiophene (TP) unit was synthetically connected to poly(N-isopropylacrylamide) by covalent and ionic bonds, resulting in the respective c- and i-TP-PNIPAM for the detection and quantification of the bovine serum albumin (BSA) model protein. When bind to BSA, the ionic i-TP-PNIPAM shows much better fluorescence (FL) sensitivity compared to c-PNIPAM. The fluorescence (FL) intensity of i-TP-PNIAPM displays a good linear dependence on concentration of BSA (0-1 mg/mL), indicating quantitative fluorimetric protein detection can be achieved. Further addition of anionic surfactant of sodium dodecylsulfate (SDS) considerably raised the FL intensity of the complex solution. All the FL response was discussed in term of conformational freedom of the TP unit under different environmental constraints.

  19. Binding of fluoroanions by a cationic cobalt(III) complex: Syntheses, characterization and single crystal X-ray structure determination of [Co(phen) 2CO 3]BF 4 and [Co(phen) 2CO 3]PF 6·3H 2O

    NASA Astrophysics Data System (ADS)

    Sharma, Raj Pal; Singh, Ajnesh; Venugopalan, Paloth; Harrison, William T. A.

    2011-05-01

    In an effort to utilize the cationic cobalt(III) complex as a binding agent for fluoroanions, the reaction of carbonatobis(1,10-phenanthroline)cobalt(III) chloride with sodium tetrafluoroborate and sodium hexafluorophosphate in water (1:1 M ratio) leads to the formation of [Co(phen) 2CO 3]BF 4 ( 1) and [Co(phen) 2CO 3]PF 6·3H 2O ( 2). These cobalt(III) complex salts have been characterized by elemental analyses, spectroscopic techniques (multinuclear NMR, UV/Visible and FT-IR), solubility product and conductance measurements. X-ray structure determination of these complex salts revealed the presence of ionic structures i.e., one complex cation [Co(phen) 2CO 3] + and one BF4- anion in 1 and one complex cation [Co(phen) 2CO 3] +, one PF6- anion and three water molecules of crystallisation in 2. The packings in both complex salts are stabilized by C sbnd H⋯F, C sbnd H⋯O(carbonato) hydrogen bonds and anion⋯π interactions beside electrostatic forces of attraction. In addition to these non-covalent interactions, O sbnd H⋯O(water) and π-π stacking interactions are also observed in 2. The formation of complex salts of definite composition with tetrafluoroborate and hexafluorophosphate ions suggest that [Co(phen) 2CO 3] + may be used as binding agent for weakly coordinating fluoroanions i.e. BF4- and PF6-.

  20. Predictive complexation models of the impact of natural organic matter and cations on scaling in cooling water pipes: A case study of power generation plants in South Africa

    NASA Astrophysics Data System (ADS)

    Bosire, G. O.; Ngila, J. C.; Mbugua, J. M.

    This work discusses simulative models of Ca and Mg complexation with natural organic matter (NOM), in order to control the incidence of scaling in pipes carrying cooling water at the Eskom power generating stations in South Africa. In particular, the paper reports how parameters such as pH and trace element levels influence the distribution of scaling species and their interactions, over and above mineral phase saturation indices. In order to generate modelling inputs, two experimental scenarios were created in the model solutions: Firstly, the trace metals Cu, Pb and Zn were used as markers for Ca and Mg complexation to humic acid and secondly the effect of natural organic matter in cooling water was determined by spiking model solutions. Labile metal ions and total elements in model solutions and water samples were analysed by square wave anodic stripping voltammetry and inductively coupled plasma optical emission spectrometry (ICP-OES), respectively. ICP-OES results revealed high levels of K, Na, S, Mg and Ca and low levels of trace elements (Cd, Se, Pb, Cu, Mn, Mo, Ni, Al and Zn) in the cooling water samples. Using the Tipping and Hurley's database WHAM in PHREEQC format (T_H.DAT), the total elemental concentrations were run as inputs on a PHREEQC code, at pH 6.8 and defined charge as alkalinity (as HCO3-) For model solutions, PHREEQC inputs were based on (i) free metal differences attributed to competitive effect of Ca and the effect of Ca + Mg, respectively; (ii) total Ca and Mg used in the model solutions and (iii) alkalinity described as hydrogen carbonate. Anodic stripping peak heights were used to calculate the concentration of the free/uncomplexed/labile metal ions (used as tracers) in the model solutions. The objective of modelling was to describe scaling in terms of saturation indices of mineral phases. Accordingly, the minerals most likely to generate scale were further simulated (over a range of pH (3-10) to yield results that mimicked changing p

  1. Molecular structure and vibrational properties of pyramidal MPc+ phthalocyanine cation in InPcI and LuPc(OAc) complexes

    NASA Astrophysics Data System (ADS)

    Hanuza, J.; Godlewska, P.; Kadłubański, P.; Ptak, M.; Mączka, M.; Gerasymchuk, Y. S.; Legendziewicz, J.

    2017-02-01

    Room temperature FT-IR spectra in the range 30-4000 cm-1 and FT-Raman spectra in the range 80-4000 cm-1 of indium and lutetium MPX-type phthalocyanines have been compared. The assignment of the observed bands has been accomplished on the basis of DFT chemical calculations using the B3LYP functional and its long range corrected version - CAM-B3LYP. The calculations were carried out for the indium derivative using the LANL2DZ, CC-PVDZ basis sets, i.e. the following approximations were used: B3LYP/CC-PVDZ, B3LYP/CC-PVTZ, B3LYP/LANL2DZ, CAM-B3LYP/CC-PVDZ and CAM-B3LYP/LANL2DZ. The molecular structures of these derivatives have been discussed in terms of group theory and geometry optimisation taking into account the shape and number of the bands corresponding to the stretching and bending vibrations of MN4 coordination polyhedron as well as the whole studied complex. The calculated structural parameters have been related to those from XRD studies. The usefulness of the proposed theoretical approaches in the prediction of the structural and vibrational data were analysed.

  2. The formation of singly and doubly cationized oligomers in SIMS

    NASA Astrophysics Data System (ADS)

    Delcorte, A.; Wojciechowski, I.; Gonze, X.; Garrison, B. J.; Bertrand, P.

    2003-01-01

    The cationization of sputtered organic species via metal particle adduction is investigated using poly-4-methylstyrene molecules in combination with Cu, Pd, Ag and Au substrates. Metal-cationization occurs for these four substrates. The cationized molecule yields vary with the considered substrate and they are not correlated with the metal ion yields. In addition, double cationization with two metal particles is observed with a very significant intensity for Cu, Ag and Au supports. We interpret the results with an emission scheme in which excited molecules and metal atoms recombine above the surface and decay via electron emission, thereby locking the complex in the ionic state.

  3. Reducible cationic lipids for gene transfer.

    PubMed Central

    Wetzer, B; Byk, G; Frederic, M; Airiau, M; Blanche, F; Pitard, B; Scherman, D

    2001-01-01

    One of the main challenges of gene therapy remains the increase of gene delivery into eukaryotic cells. We tested whether intracellular DNA release, an essential step for gene transfer, could be facilitated by using reducible cationic DNA-delivery vectors. For this purpose, plasmid DNA was complexed with cationic lipids bearing a disulphide bond. This reduction-sensitive linker is expected to be reduced and cleaved in the reducing milieu of the cytoplasm, thus potentially improving DNA release and consequently transfection. The DNA--disulphide-lipid complexation was monitored by ethidium bromide exclusion, and the size of complexes was determined by dynamic light scattering. It was found that the reduction kinetics of disulphide groups in DNA--lipid complexes depended on the position of the disulphide linker within the lipid molecule. Furthermore, the internal structure of DNA--lipid particles was examined by small-angle X-ray scattering before and after lipid reduction. DNA release from lipid complexes was observed after the reduction of disulphide bonds of several lipids. Cell-transfection experiments suggested that complexes formed with selected reducible lipids resulted in up to 1000-fold higher reporter-gene activity, when compared with their analogues without disulphide bonds. In conclusion, reduction-sensitive groups introduced into cationic lipid backbones potentially allow enhanced DNA release from DNA--lipid complexes after intracellular reduction and represent a tool for improved vectorization. PMID:11389682

  4. Reducible cationic lipids for gene transfer.

    PubMed

    Wetzer, B; Byk, G; Frederic, M; Airiau, M; Blanche, F; Pitard, B; Scherman, D

    2001-06-15

    One of the main challenges of gene therapy remains the increase of gene delivery into eukaryotic cells. We tested whether intracellular DNA release, an essential step for gene transfer, could be facilitated by using reducible cationic DNA-delivery vectors. For this purpose, plasmid DNA was complexed with cationic lipids bearing a disulphide bond. This reduction-sensitive linker is expected to be reduced and cleaved in the reducing milieu of the cytoplasm, thus potentially improving DNA release and consequently transfection. The DNA--disulphide-lipid complexation was monitored by ethidium bromide exclusion, and the size of complexes was determined by dynamic light scattering. It was found that the reduction kinetics of disulphide groups in DNA--lipid complexes depended on the position of the disulphide linker within the lipid molecule. Furthermore, the internal structure of DNA--lipid particles was examined by small-angle X-ray scattering before and after lipid reduction. DNA release from lipid complexes was observed after the reduction of disulphide bonds of several lipids. Cell-transfection experiments suggested that complexes formed with selected reducible lipids resulted in up to 1000-fold higher reporter-gene activity, when compared with their analogues without disulphide bonds. In conclusion, reduction-sensitive groups introduced into cationic lipid backbones potentially allow enhanced DNA release from DNA--lipid complexes after intracellular reduction and represent a tool for improved vectorization.

  5. Novel biscapped and monocapped tris(dioxime) Mn(II) complexes: x-ray crystal structure of the first cationic tris(dioxime) Mn(II) complex [Mn(CDOH)3BPh]OH (CDOH2= 1,2-cyclohexanedione dioxime).

    PubMed

    Hsieh, Wen-Yuan; Liu, Shuang

    2006-06-26

    This report describes the synthesis and characterization of a series of novel biscapped and monocapped tris(dioxime) Mn(II) complexes [Mn(dioxime)3(BR)2] and [Mn(dioxime)3BR]+ (dioxime = cyclohexanedione dioxime (CDOH2) and 1,2-dimethylglyoxyl dioxime (DMGH(2)); R = Me, n-Bu, and Ph). All tris(dioxime) Mn(II) complexes have been characterized by elemental analysis, IR, UV/vis, cyclic voltammetry, ESI-MS, and, in the cases of [Mn(CDOH)3BPh]OH.CHCl3 and [Mn(CDO)(CDOH)2(BBu(OC2H5))2], X-ray crystallography. It was found that biscapped Mn(II) complexes [Mn(dioxime)3(BR)2] are not stable in the presence of water and readily hydrolyze to form monocapped cationic complexes [M(dioxime)3BR]+. This instability is most likely caused by mismatch between the size of Mn(II) and the coordination cavity of the biscapped tris(dioxime) ligands. In contrast, monocapped cationic complexes [M(dioxime)3BR]+ are very stable in aqueous solution even in the presence of PDTA (1,2-diaminopropane-N,N,N',N'-tetraacetic acid) because of the kinetic inertness imposed by the monocapped tris(dioxime) chelators that are able to completely "wrap" Mn(II) into their N6 coordination cavity. [Mn(CDO)3BPh]OH has a distorted trigonal prismatic coordination geometry, with the Mn(II) being bonded by six imine-N donors. The hydroxyl groups from three dioxime chelating arms form very strong intramolecular hydrogen bonds with the hydroxide counterion so that the structure of [Mn(CDOH)3BPh]OH can be considered as being the clathrochelate with the hydroxide counterion as a "cap".

  6. Cation-Poor Complex Metallic Alloys in Ba(Eu)-Au-Al(Ga) Systems: Identifying the Keys that Control Structural Arrangements and Atom Distributions at the Atomic Level.

    PubMed

    Smetana, Volodymyr; Steinberg, Simon; Mudryk, Yaroslav; Pecharsky, Vitalij; Miller, Gordon J; Mudring, Anja-Verena

    2015-11-02

    Four complex intermetallic compounds BaAu(6±x)Ga(6±y) (x = 1, y = 0.9) (I), BaAu(6±x)Al(6±y) (x = 0.9, y = 0.6) (II), EuAu6.2Ga5.8 (III), and EuAu6.1Al5.9 (IV) have been synthesized, and their structures and homogeneity ranges have been determined by single crystal and powder X-ray diffraction. Whereas I and II originate from the NaZn13-type structure (cF104-112, Fm3̅c), III (tP52, P4/nbm) is derived from the tetragonal Ce2Ni17Si9-type, and IV (oP104, Pbcm) crystallizes in a new orthorhombic structure type. Both I and II feature formally anionic networks with completely mixed site occupation by Au and triel (Tr = Al, Ga) atoms, while a successive decrease of local symmetry from the parental structures of I and II to III and, ultimately, to IV correlates with increasing separation of Au and Tr on individual crystallographic sites. Density functional theory-based calculations were employed to determine the crystallographic site preferences of Au and the respective triel element to elucidate reasons for the atom distribution ("coloring scheme"). Chemical bonding analyses for two different "EuAu6Tr6" models reveal maximization of the number of heteroatomic Au-Tr bonds as the driving force for atom organization. The Fermi levels fall in broad pseudogaps for both models allowing some electronic flexibility. Spin-polarized band structure calculations on the "EuAu6Tr6" models hint to singlet ground states for europium and long-range magnetic coupling for both EuAu6.2Ga5.8 (III) and EuAu6.1Al5.9 (IV). This is substantiated by experimental evidence because both compounds show nearly identical magnetic behavior with ferromagnetic transitions at TC = 6 K and net magnetic moments of 7.35 μB/f.u. at 2 K. The effective moments of 8.3 μB/f.u., determined from Curie-Weiss fits, point to divalent oxidation states for europium in both III and IV.

  7. Interactions of Verkade's Superbase with Strong Lewis Acids: From Labile Mono- and Binuclear Lewis Acid-Base Complexes to Phosphenium Cations.

    PubMed

    Mummadi, Suresh; Kenefake, Dustin; Diaz, Rony; Unruh, Daniel K; Krempner, Clemens

    2017-09-05

    A series of mono- and binuclear Lewis acid-base complexes of the formulas N[CH2CH2N(Pr(i))]3P→LA [LA = BH3 (8), Ga(C6F5)3 (10), GaCl3 (11)], LA←N[CH2CH2N(Pr(i))]3P [LA = Al(C6F5)3 (6a), AlMe3 (6b), AlEt3 (6c), AlBu(i)3 (6d), BF3 (13)], and LA←N[CH2CH2N(Pr(i))]3P→LA [Lewis acid (LA) = Al(C6F5)3 (7a), AlMe3 (7b), AlEt3 (7c), AlBu(i)3 (7d), AlCl3 (7e), BH3 (9)] were generated from reactions of Verkade's base, N[CH2CH2N(Pr(i))]3P (1), with various boron-, aluminum-, and gallium-containing Lewis acids, and characterized by multinuclear NMR spectroscopy. {N[CH2CH2N(Pr(i))]3P→C7H7}[BF4] (5) was synthesized via the treatment of 1 with [C7H7][BF4]. The reaction of 1 with B(C6F5)3, followed by the addition of [Ph3C]2[B12Cl12], gave rise to the rearranged borate salt [PN4C9H17(Pr(i))2][B12Cl12] (3), while treating 1 with [Ph3C]2[B12Cl12] exclusively afforded {N[CH2CH2N(Pr(i))]3PH}2[B12Cl12] (4). Reactions of 1 with 2 equiv of GaCl3 and BF3, respectively, afforded the novel phosphenium gallate and borate salts 12a, 12b, and 15. The solid-state structures of 1, 3-5, 6b, 7a, 7b, 7e, 8, 10, 11, 12b, 13, and 15 were determined by X-ray crystallography.

  8. Cationic Bolaamphiphiles for Gene Delivery

    NASA Astrophysics Data System (ADS)

    Tan, Amelia Li Min; Lim, Alisa Xue Ling; Zhu, Yiting; Yang, Yi Yan; Khan, Majad

    2014-05-01

    Advances in medical research have shed light on the genetic cause of many human diseases. Gene therapy is a promising approach which can be used to deliver therapeutic genes to treat genetic diseases at its most fundamental level. In general, nonviral vectors are preferred due to reduced risk of immune response, but they are also commonly associated with low transfection efficiency and high cytotoxicity. In contrast to viral vectors, nonviral vectors do not have a natural mechanism to overcome extra- and intracellular barriers when delivering the therapeutic gene into cell. Hence, its design has been increasingly complex to meet challenges faced in targeting of, penetration of and expression in a specific host cell in achieving more satisfactory transfection efficiency. Flexibility in design of the vector is desirable, to enable a careful and controlled manipulation of its properties and functions. This can be met by the use of bolaamphiphile, a special class of lipid. Unlike conventional lipids, bolaamphiphiles can form asymmetric complexes with the therapeutic gene. The advantage of having an asymmetric complex lies in the different purposes served by the interior and exterior of the complex. More effective gene encapsulation within the interior of the complex can be achieved without triggering greater aggregation of serum proteins with the exterior, potentially overcoming one of the great hurdles faced by conventional single-head cationic lipids. In this review, we will look into the physiochemical considerations as well as the biological aspects of a bolaamphiphile-based gene delivery system.

  9. A new nanohybrid material constructed from Keggin-type polyoxometalate and Cd(II) semicarbazone Schiff base complex with excellent adsorption properties for the removal of cationic dye pollutants

    NASA Astrophysics Data System (ADS)

    Farhadi, Saeed; Amini, Mostafa M.; Dusek, Michal; Kucerakova, Monika; Mahmoudi, Farzaneh

    2017-02-01

    A novel nanohybrid material containing a Cd(II) semicarbazone Schiff base complex and phosphomolybdic acid, [Cd(H2L+)6][H2L]+4[PMo12O40]4·18CH3OH·4H2O (1), [HL = pyridine-2-carbaldehyde semicarbazone] was prepared by a simple sonochemical route and characterized by 1HNMR, 13CNMR, FT-IR, UV-vis, PXRD, FESEM, TG-DTA and BET-BJH surface area analysis. Also the single crystal 1, was characterized by single-crystal X-ray diffraction analysis. It crystallizes in the triclinic system with space group P-1 and is assembled into 3D supramolecular structure via hydrogen intermolecular interactions. The nanohybrid 1 was tested for the adsorption and removal of organic dyes such as methylene blue (MB), Rhodamine B (RhB) and methyl orange (MO) from aqueous solutions. The effects of parameters such as the dosage of adsorbent, the initial concentration and pH of dye solution were investigated on the removal efficiency of methylene blue. The nanohybrid 1 exhibited excellent adsorption ability towards cationic dyes. Moreover, it could be easily separated from the reaction solution and recycled up to three times without significant loss of adsorption activity.

  10. INORGANIC CATIONS IN THE CELL NUCLEUS

    PubMed Central

    Tres, Laura L.; Kierszenbaum, A. L.; Tandler, C. J.

    1972-01-01

    Earlier reports indicated the presence of significant amounts of inorganic salts in the nucleus. In the present study the possibility that this might be related to the transcription process was tested on seminiferous epithelium of the adult mouse, using potassium pyroantimonate as a fixative. The results indicated that a correlation exists between the inorganic cations comprising the pyroantimonate-precipitable fraction and the RNA synthetic activity. During meiotic prophase an accumulation of cation-antimonate precipitates occurs dispersed through the middle pachytene nuclei, the stage in which RNA synthesis reaches a maximum. At other stages (zygotene to diplotene), where RNA synthesis falls to a low level, that pattern is not seen; cation-antimonate deposits are restricted to a few masses in areas apparently free of chromatin. The condensed sex chromosomes, the heterochromatin of the "basal knobs," the axial elements, and the synaptonemal complexes are devoid of antimonate deposits during the meiotic prophase. The Sertoli cells, active in RNA synthesis in both nucleoplasm and nucleolus, show cation-antimonate deposits at these sites. In the nucleoplasm some "patches" of precipitates appear coincident with clusters of interchromatin granules; in the nucleolus the inorganic cations are mainly located in the fibrillar and/or amorphous areas, whereas relatively few are shown by the granular component. The condensed chromatin bodies associated with the nucleolus were always free of antimonate precipitates. It is suggested that the observed sites of inorganic cation accumulation within the nucleus may at least partially indicate the presence of RNA polymerases, the activity of which is dependent on divalent cations. PMID:4112542

  11. Forging Colloidal Nanostructures via Cation Exchange Reactions

    PubMed Central

    2016-01-01

    Among the various postsynthesis treatments of colloidal nanocrystals that have been developed to date, transformations by cation exchange have recently emerged as an extremely versatile tool that has given access to a wide variety of materials and nanostructures. One notable example in this direction is represented by partial cation exchange, by which preformed nanocrystals can be either transformed to alloy nanocrystals or to various types of nanoheterostructures possessing core/shell, segmented, or striped architectures. In this review, we provide an up to date overview of the complex colloidal nanostructures that could be prepared so far by cation exchange. At the same time, the review gives an account of the fundamental thermodynamic and kinetic parameters governing these types of reactions, as they are currently understood, and outlines the main open issues and possible future developments in the field. PMID:26891471

  12. Organic cation transporter 3 (OCT3) is localized to intracellular and surface membranes in select glial and neuronal cells within the basolateral amygdaloid complex of both rats and mice.

    PubMed

    Gasser, Paul J; Hurley, Matthew M; Chan, June; Pickel, Virginia M

    2016-09-22

    Organic cation transporter 3 (OCT3) is a high-capacity, low-affinity transporter that mediates corticosterone-sensitive uptake of monoamines including norepinephrine, epinephrine, dopamine, histamine and serotonin. OCT3 is expressed widely throughout the amygdaloid complex and other brain regions where monoamines are key regulators of emotional behaviors affected by stress. However, assessing the contribution of OCT3 to the regulation of monoaminergic neurotransmission and monoamine-dependent regulation of behavior requires fundamental information about the subcellular distribution of OCT3 expression. We used immunofluorescence and immuno-electron microscopy to examine the cellular and subcellular distribution of the transporter in the basolateral amygdaloid complex of the rat and mouse brain. OCT3-immunoreactivity was observed in both glial and neuronal perikarya in both rat and mouse amygdala. Electron microscopic immunolabeling revealed plasma membrane-associated OCT3 immunoreactivity on axonal, dendritic, and astrocytic processes adjacent to a variety of synapses, as well as on neuronal somata. In addition to plasma membrane sites, OCT3 immunolabeling was also observed associated with neuronal and glial endomembranes, including Golgi, mitochondrial and nuclear membranes. Particularly prominent labeling of the outer nuclear membrane was observed in neuronal, astrocytic, microglial and endothelial perikarya. The localization of OCT3 to neuronal and glial plasma membranes adjacent to synaptic sites is consistent with an important role for this transporter in regulating the amplitude, duration, and physical spread of released monoamines, while its localization to mitochondrial and outer nuclear membranes suggests previously undescribed roles for the transporter in the intracellular disposition of monoamines.

  13. Synthesis, FT-IR, ¹H, ¹³CNMR, ESI MS and PM5 studies of a new Mannich base of polyether antibiotic - Lasalocid acid and its complexes with Li⁺, Na⁺ and K⁺ cations.

    PubMed

    Huczyński, Adam; Rutkowski, Jacek; Brzezinski, Bogumil; Bartl, Franz

    2013-03-01

    The polyether antibiotic Lasalocid acid has been converted to its Mannich base derivative by a chemoselective one-pot reaction with formaldehyde and morpholine through the decarboxylation process. Spectroscopic studies of the structure of this new derivative have shown that in this ortho-phenol Mannich base the O-H⋯N intarmolecular hydrogen bond is present. The compound forms complexes with Li(+), Na(+) and K(+) cations of exclusively 1:1 stoichiometry. The structures of these complexes have been studied and visualized by semi-empirical calculation based on results of spectrometric and spectroscopic investigation. It is demonstrated that in contrast to Lasalocid acid the novel Mannich type derivative forms preferential complexes with Li(+) cation. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Diaryldichalcogenide radical cations.

    PubMed

    Mallow, Ole; Khanfar, Monther A; Malischewski, Moritz; Finke, Pamela; Hesse, Malte; Lork, Enno; Augenstein, Timo; Breher, Frank; Harmer, Jeffrey R; Vasilieva, Nadezhda V; Zibarev, Andrey; Bogomyakov, Artem S; Seppelt, Konrad; Beckmann, Jens

    2015-01-01

    One-electron oxidation of two series of diaryldichalcogenides (C6F5E)2 (13a-c) and (2,6-Mes2C6H3E)2 (16a-c) was studied (E = S, Se, Te). The reaction of 13a and 13b with AsF5 and SbF5 gave rise to the formation of thermally unstable radical cations [(C6F5S)2]˙(+) (14a) and [(C6F5Se)2]˙(+) (14b) that were isolated as [Sb2F11](-) and [As2F11](-) salts, respectively. The reaction of 13c with AsF5 afforded only the product of a Te-C bond cleavage, namely the previously known dication [Te4](2+) that was isolated as [AsF6](-) salt. The reaction of (2,6-Mes2C6H3E)2 (16a-c) with [NO][SbF6] provided the corresponding radical cations [(2,6-Mes2C6H3E)2]˙(+) (17a-c; E = S, Se, Te) in the form of thermally stable [SbF6](-) salts in nearly quantitative yields. The electronic and structural properties of these radical cations were probed by X-ray diffraction analysis, EPR spectroscopy, and density functional theory calculations and other methods.

  15. Cationic derivatives of dextran and hydroxypropylcellulose as novel potential heparin antagonists.

    PubMed

    Kamiński, Kamil; Płonka, Monika; Ciejka, Justyna; Szczubiałka, Krzysztof; Nowakowska, Maria; Lorkowska, Barbara; Korbut, Ryszard; Lach, Radosław

    2011-10-13

    Cationic derivatives of dextran (Dex) and hydroxypropylcellulose (HPC) were studied as potential alternatives of protamine sulfate (PS) used in the reversal of anticoagulant activity of heparin. The modification was performed by the attachment of cationic groups to the Dex main chain or by grafting short side chains of a polycation onto HPC. The cationic derivatives of these polysaccharides were found to bind heparin with the efficiency increasing with growing degree of cationic modification. The degree of cationic modification and consequently the ζ potential of the polymers do not have to be high to achieve effective heparin binding. The size of the complexes of cationic Dex with unfractionated heparin (UFH) is a few micrometers. For complexes of cationic HPC and UFH the size is much below 1 μm, both below and above the lower critical solution temperature of HPC. None of the cationic polysaccharides studied caused hemolysis. The concentrations of the polymers inducing the aggregation of human erythrocytes in vitro were determined.

  16. Preparation of poly(ethylene glycol)-introduced cationized gelatin as a non-viral gene carrier.

    PubMed

    Kushibiki, Toshihiro; Tabata, Yasuhiko

    2005-01-01

    The objective of this study was to prepare cationized gelatins grafted with poly(ethylene glycol) (PEG) (PEG-cationized gelatin) and evaluate the in vivo efficiency as a non-viral gene carrier. Cationized gelatin was prepared by chemical introduction of ethylenediamine to the carboxyl groups of gelatin. PEG with one terminal of active ester group was coupled to the amino groups of cationized gelatin to prepare PEG-cationized gelatins. Electrophoretic experiments revealed that the PEG-cationized gelatin with low PEGylation degrees was complexed with a plasmid DNA of luciferase, in remarked contrast to that with high PEGylation degrees. When the plasmid DNA complexed with the cationized gelatin or PEG-cationized gelatin was mixed with deoxyribonuclease I (DNase I) in solution to evaluate the resistance to enzymatic degradation, stronger protection effect of the PEG-cationized gelatin was observed than that of the cationized gelatin. The complex of plasmid DNA and PEG-cationized gelatin had an apparent molecular size of about 300 nm and almost zero surface charge. These findings indicate that the PEG-cationized gelatin-plasmid DNA complex has a nano-order structure where the plasmid DNA is covered with PEG molecules. When the PEG-cationized gelatin-plasmid DNA complex was intramuscularly injected, the level of gene expression was significantly increased compared with the injection of plasmid DNA solution. It is concluded that the PEG-cationized gelatin was a promising non-viral gene carrier to enhance gene expression in vivo.

  17. Efficacy of HGF carried by ultrasound microbubble-cationic nano-liposomes complex for treating hepatic fibrosis in a bile duct ligation rat model, and its relationship with the diffusion-weighted MRI parameters.

    PubMed

    Zhang, Shou-hong; Wen, Kun-ming; Wu, Wei; Li, Wen-yan; Zhao, Jian-nong

    2013-12-01

    Hepatic fibrosis is a major consequence of liver aggression. Finding novel ways for counteracting this damaging process, and for evaluating fibrosis with a non-invasive imaging approach, represent important therapeutic and diagnostic challenges. Hepatocyte growth factor (HGF) is an anti-fibrosis cell growth factor that induces apoptosis in activated hepatic stellate cells, reduces excessive collagen deposition, and stimulates hepatocyte regeneration. Thus, using HGF in gene therapy against liver fibrosis is an attractive approach. The aims of the present study were: (i) to explore the efficacy of treating liver fibrosis using HGF expression vector carried by a novel ultrasound microbubble delivery system; (ii) to explore the diagnostic interest of diffusion-weighted MRI (DWI-MRI) in evaluating liver fibrosis. We established a rat model of hepatic fibrosis. The rats were administered HGF linked to novel ultrasound micro-bubbles. Progression of hepatic fibrosis was evaluated by histopathology, hydroxyproline content, and DWI-MRI to determine the apparent diffusion coefficient (ADC). Our targeted gene therapy produced a significant anti-fibrosis effect, as shown by liver histology and significant reduction of hydroxyproline content. Moreover, using DWI-MRI, the b value (diffusion gradient factor) was equal to 300s/mm(2), and the ADC values significantly decreased as the severity of hepatic fibrosis increased. Using this methodology, F0-F2 could be distinguished from F3 and F4 (P<0.01). This is the first in vivo report of using an ultrasound microbubble-cationic nano-liposome complex for gene delivery. The data indicate that, this approach is efficient to counteract the fibrosis process. DWI-MRI appears a promising imaging technique for evaluating liver fibrosis.

  18. Controlled formation of optically reflective and electrically conductive silvered surfaces on polyimide film via a direct ion-exchange self-metallization technique using silver ammonia complex cation as the precursor.

    PubMed

    Qi, Shengli; Wu, Zhanpeng; Wu, Dezhen; Jin, Riguang

    2008-05-08

    Double-surface-silvered polyimide films have been successfully fabricated using silver ammonia complex cation ([Ag(NH3)2]+) as the silver precursor and 3,3',4,4'-benzophenonetetracarboxylic dianhydride/4,4'-oxidianile- (BTDA/ODA-) based poly(amic acid) (PAA) as the polyimide precursor via a direct ion-exchange self-metallization technique. The process has been clarified to involve the loading of silver(I) into PAA via ion exchange, the thermally induced reduction of silver(I) to silver(0) and the concomitant imidization of PAA to polyimide upon thermal treatment, the subsequent silver-catalyzed and oxygen-assisted decomposition of the polyimide overlayer, and the self-accelerated aggregation of silver clusters on the film surface to produce well-defined surface silver layers. By employing [Ag(NH3)2]+ solution with a concentration of only 0.01 M and an ion-exchange time of no more than 10 min, the controlled formation of highly reflective and conductive silver surfaces upon thermal treatment at 300 degrees C for less than 4.5 h indicates that the present work provides an efficient route and an effacious silver species for polyimide surface metallization. Although the alkaline characteristics of [Ag(NH3)2]+ have a strong hydrolysis effect on the polyimide precursor chains, the final metallized films retain the key mechanical and thermal properties of the pure polyimide. Films were characterized by ATR-FTIR, XPS, ICP-AES, SEM, TEM, DSC, TGA, reflectivity, conductivity, and mechanical measurements.

  19. Comproportionation of Cationic and Anionic Tungsten Complexes Having an N -Heterocyclic Carbene Ligand To Give the Isolable 17-Electron Tungsten Radical CpW(CO) 2 (IMes)

    SciTech Connect

    Roberts, John A. S.; Franz, James A.; van der Eide, Edwin F.; Walter, Eric D.; Petersen, Jeffrey L.; DuBois, Daniel L.; Bullock, R. Morris

    2011-09-21

    A series consisting of a tungsten anion, radical and cation, supported by the N-heterocyclic carbene IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) and spanning formal oxidation states W(0), W(I) and W(II), has been synthesized, isolated, and characterized. Reaction of the hydride CpW(CO)2(IMes)H with KH and 18 crown 6 gives the tungsten anion [CpW(CO)2(IMes)]-[K(18 crown 6)]+. The crystal structure of this complex shows that the K+ interacts not only with the oxygen atoms in the crown ether, but also with the carbonyl oxygens. The electrochemical oxidation of [CpW(CO)2(IMes)]- in acetonitrile is fully reversible (E½ = -1.65 V vs Cp2Fe+•/0) at all scan rates, indicating that CpW(CO)2(IMes)• is a persistent radical. Hydride transfer from CpW(CO)2(IMes)H to Ph3C+PF6 affords [cis-CpW(CO)2(IMes)(MeCN)]+PF6 . Comproportionation of [CpW(CO)2(IMes)]- with [CpW(CO)2(IMes)(MeCN)]+ gives the 17-electron tungsten radical CpW(CO)2(IMes)•. This complex shows paramagnetically shifted resonances in 1H NMR spectra and has been characterized by IR spectroscopy, low-temperature EPR spectroscopy, and X-ray diffraction. CpW(CO)2(IMes)• is very stable with respect to disproportionation and dimerization. NMR studies of degenerate electron transfer between CpW(CO)2(IMes)• and [CpW(CO)2(IMes)]- are reported. DFT calculations were carried out on CpW(CO)2(IMes)H, as well as on related complexes bearing NHC ligands with N,N´ substituents Me [CpW(CO)2(IMe)H] or H [CpW(CO)2(IH)H] to compare to the experimentally studied IMes complexes with mesityl substituents. These calculations reveal W H homolytic bond dissociation energies (BDEs) to decrease with increasing steric bulk of the NHC ligand, from 67 for CpW(CO)2(IH)H to 64 for CpW(CO)2(IMe)H to 63 kcal/mol for CpW(CO)2(IMes)H. The calculated spin density at W for CpW(CO)2(IMes)• is 0.63. The W radicals CpW(CO)2(IMe)• and CpW(CO)2(IH)• are calculated to form weak W W bonds. The weakly bonded complexes [CpW(CO)2(IMe)]2

  20. Complexity.

    PubMed

    Gómez-Hernández, J Jaime

    2006-01-01

    It is difficult to define complexity in modeling. Complexity is often associated with uncertainty since modeling uncertainty is an intrinsically difficult task. However, modeling uncertainty does not require, necessarily, complex models, in the sense of a model requiring an unmanageable number of degrees of freedom to characterize the aquifer. The relationship between complexity, uncertainty, heterogeneity, and stochastic modeling is not simple. Aquifer models should be able to quantify the uncertainty of their predictions, which can be done using stochastic models that produce heterogeneous realizations of aquifer parameters. This is the type of complexity addressed in this article.

  1. Cation diffusion in titanomagnetites

    NASA Astrophysics Data System (ADS)

    Aragon, R.; McCallister, R. H.; Harrison, H. R.

    1984-02-01

    Interdiffusion couple experiments were performed with titanomagnetite single crystals at 1,000°C, 1,100° C and 1,200° C in various buffered atmospheres. The dependence of the interdiffusion coefficient on oxygen fugacity, composition and temperature was interpreted in terms of point defect structure. Estimates of the cation tracer diffusivities indicate that Fe migrates via a point defect mechanism, involving mixed tetrahedral-octahedral site jumps, with an activation energy of 33 Kcal/mole; whereas Ti migration is one to two orders of magnitude slower, is restricted to octahedral sites and has an activation energy of 60 Kcal/mole.

  2. Predicting Organic Cation Sorption Coefficients: Accounting for Competition from Sorbed Inorganic Cations Using a Simple Probe Molecule.

    PubMed

    Jolin, William C; Goyetche, Reaha; Carter, Katherine; Medina, John; Vasudevan, Dharni; MacKay, Allison A

    2017-06-06

    estimation of Kd values for more structurally complex organic cations to homoionic montmorillonites and to heteroionic soils (mean absolute error of 0.27 log unit). Accordingly, we concluded that the use of phenyltrimethylammonium as a probe compound was a promising means to account for the identity, affinity, and abundance of natural exchange ions in the prediction of organic cation sorption coefficients for environmental solids.

  3. Generation of oxoiron (IV) tetramesitylporphyrin pi-cation radical complexes by m-CPBA oxidation of ferric tetramesitylporphyrin derivatives in butyronitrile at - 78 degrees C. Evidence for the formation of six-coordinate oxoiron (IV) tetramesitylporphyrin pi-cation radical complexes FeIV = O(tmp*)X (X = Cl-, Br-), by Mössbauer and X-ray absorption spectroscopy.

    PubMed

    Wolter, T; Meyer-Klaucke, W; Müther, M; Mandon, D; Winkler, H; Trautwein, A X; Weiss, R

    2000-01-30

    The generation of six-coordinate oxoiron (IV) tetramesitylporphyrin pi-caption radical complexes by m-CPBA (meta-chloroperbenzoic acid) oxidation of ferric tetramesitylporphyrin derivatives in butyronitrile at - 78 degrees C was investigated. UV-Vis and EPR spectroscopies indicate that the axial ligand present in the ferric starting derivatives is retained in the high-valent iron complexes. Indirect evidence for the formation of six-coordinate oxoiron (IV) tetramesitylporphyrin complexes FeIV = O(tmp*)X (X=Cl-, Br-) by m-CPBA oxidation of FeX(tmp) (X=Cl-, Br-) in butyronitrile at - 78 degrees C was also obtained by Mössbauer spectroscopy. Direct confirmation of the presence of a halide ion as second axial ligand of iron in these high-valent iron species was obtained by X-ray absorption spectroscopy. The EXAFS spectra of the samples obtained by m-CPBA oxidation of FeX(tmp) (X=Cl-, Br-) were refined using two different coordination models including both four porphyrinato-nitrogens and the axial oxo group. The two models include (model I) or exclude (model II) the axial halogen. The statistical tests indicate the presence of a halide ion as second axial ligand of iron in both derivatives. The refinements led to the following bond distances: FeIV=O(tmp*)Cl(3):Fe-O=1.66(1),Fe-Cl=2.39(2) and Fe-Np=1.99(1) A;FeIV=O(tmp*)Br(4):Fe-O=1.65(1),Fe-Br=2.93(2), Fe-Np=2.02(1) A. The lengthening of the Fe-X(X=Cl-, Br-) distances relative to those occurring in the ferric precursor porphyrins is, most probably, related to the strong trans influence of the oxoiron(IV) fragment present in 3 or 4.

  4. Dissecting the cation-cation interaction between two uranyl units.

    PubMed

    Tecmer, Paweł; Hong, Sung W; Boguslawski, Katharina

    2016-07-21

    We present a state-of-the-art computational study of the uranyl(vi) and uranyl(v) cation-cation interactions (dications) in aqueous solution. Reliable electronic structures of two interacting uranyl(vi) and uranyl(v) subunits as well as those of the uranyl(vi) and uranyl(v) clusters are presented for the first time. Our theoretical study elucidates the impact of cation-cation interactions on changes in the molecular structure as well as changes in vibrational and UV-Vis spectra of the bare uranyl(vi) and uranyl(v) moieties for different total spin-states and total charges of the dications.

  5. Tubular cationized pullulan hydrogels as local reservoirs for plasmid DNA.

    PubMed

    San Juan, Aurélie; Ducrocq, Grégory; Hlawaty, Hanna; Bataille, Isabelle; Guénin, Erwann; Letourneur, Didier; Feldman, Laurent J

    2007-12-01

    In the present study, we measured the ability of various cationized pullulan tubular hydrogels to retain plasmid DNA, and tested the ability of retained plasmid DNA to transfect vascular smooth muscle cells (VSMCs). Cationized pullulans were obtained by grafting at different charge densities ethylamine (EA) or diethylaminoethylamine (DEAE) on the pullulan backbone. Polymers were characterized by elemental analysis, acid-base titration, size exclusion chromatography, Fourier-transform infrared spectroscopy, and proton nuclear magnetic resonance. The complexation of cationized pullulans in solution with plasmid DNA was evidenced by fluorescence quenching with PicoGreen. Cationized pullulans were then chemically crosslinked with phosphorus oxychloride to obtain tubular cationized pullulan hydrogels. Native pullulan tubes did not retain loaded plasmid DNA. In contrast, the ability of cationized pullulan tubes to retain plasmid DNA was dependent on both the amine content and the type of amine. The functional integrity of plasmid DNA in cationized pullulan tubes was demonstrated by in vitro transfection of VSMCs. Hence, cationized pullulan hydrogels can be designed as tubular structures with high affinity for plasmid DNA, which may provide new biomaterials to enhance the efficiency of local arterial gene transfer strategies.

  6. Binding of monovalent metal cations by the p-sulfonatocalix[4]arene: experimental evidence for cation-pi interactions in water.

    PubMed

    Morel, Jean-Pierre; Morel-Desrosiers, Nicole

    2006-02-07

    Gibbs free energies, enthalpies and entropies for the binding of Na+, K+, Rb+, Cs+, Ag+, Tl+ and NH4+ by the p-sulfonatocalix[4]arene in water are determined by microcalorimetry. Whereas no significant heat effect is detected with Na+ or Ag+, suggesting that these cations are not complexed, weak but selective binding is observed with the other cations. The whole set of thermodynamic parameters, which demonstrate that the cations bind inside the cavity of the calixarene, evidence the importance of the cation-pi interactions for these complexes in water.

  7. Controlling Cesium Cation Recognition via Cation Metathesis within and Ion Pair Receptor

    SciTech Connect

    Kim, Sung Kuk; Vargas-Zuniga, Gabriela; Hay, Benjamin; Young, Neil J; Delmau, Laetitia Helene; Lee, Prof. Chang-Hee; Kim, Jong Seung; Lynch, Vincent M.; Sessler, Jonathan L.

    2012-01-01

    Ion pair receptor 3 bearing an anion binding site and multiple cation binding sites has been synthesized and shown to function in a novel binding-release cycle that does not necessarily require displacement to effect release. The receptor forms stable complexes with the test cesium salts, CsCl and CsNO{sub 3}, in solution (10% methanol-d{sub 4} in chloroform-d) as inferred from {sup 1}H NMR spectroscopic analyses. The addition of KClO{sub 4} to these cesium salt complexes leads to a novel type of cation metathesis in which the 'exchanged' cations occupy different binding sites. Specifically, K{sup +} becomes bound at the expense of the Cs{sup +} cation initially present in the complex. Under liquid-liquid conditions, receptor 3 is able to extract CsNO{sub 3} and CsCl from an aqueous D{sub 2}O layer into nitrobenzene-d{sub 5} as inferred from {sup 1}H NMR spectroscopic analyses and radiotracer measurements. The Cs{sup +} cation of the CsNO{sub 3} extracted into the nitrobenzene phase by receptor 3 may be released into the aqueous phase by contacting the loaded nitrobenzene phase with an aqueous KClO{sub 4} solution. Additional exposure of the nitrobenzene layer to chloroform and water gives 3 in its uncomplexed, ion-free form. This allows receptor 3 to be recovered for subsequent use. Support for the underlying complexation chemistry came from single-crystal X-ray diffraction analyses and gas-phase energy-minimization studies.

  8. Cationic Polymerization of Vinyl Ethers Controlled by Visible Light.

    PubMed

    Kottisch, Veronika; Michaudel, Quentin; Fors, Brett P

    2016-12-07

    Photoinitiated cationic polymerizations are widely used in industrial processes; however, gaining photocontrol over chain growth would expand the utility of these methods and facilitate the design of novel complex architectures. We report herein a cationic polymerization regulated by visible light. This polymerization proceeds under mild conditions: a combination of a metal-free photocatalyst, a chain-transfer agent, and light irradiation enables the synthesis of various poly(vinyl ether)s with good control over molecular weight and dispersity as well as excellent chain-end fidelity. Significantly, photoreversible cation formation in this system enables efficient control over polymer chain growth with light.

  9. Combined delivery of the adiponectin gene and rosiglitazone using cationic lipid emulsions.

    PubMed

    Davaa, Enkhzaya; Kang, Bong-Seok; Han, Joo-Hui; Lee, Sang-Eun; Ng, Choon Lian; Myung, Chang-Seon; Park, Jeong-Sook

    2015-04-10

    For the combined delivery of an insulin-sensitizing adipokine; i.e., the ADN gene, and the potent PPARγ agonist rosiglitazone, cationic lipid emulsions were formulated using the cationic lipid DOTAP, helper lipid DOPE, castor oil, Tween 20 and Tween 80. The effect of drug loading on the physicochemical characteristics of the cationic emulsion/DNA complexes was investigated. Complex formation between the cationic emulsion and negatively charged plasmid DNA was confirmed and protection from DNase was observed. The in vitro transfection efficiency and cytotoxicity were evaluated in HepG2 cells. The particle sizes of the cationic emulsion/DNA complex were in the range 230-540 nm and those of the rosiglitazone-loaded cationic emulsion/DNA complex were in the range 220-340 nm. Gel retardation of the complexes was observed when the complexation weight ratios of the cationic lipid to plasmid DNA exceeded 4:1 for both the drug-free and rosiglitazone-loaded complexes. Both complexes stabilized plasmid DNA against DNase. The ADN expression level increased dose-dependently when cells were transfected with the cationic emulsion/DNA complexes. The rosiglitazone-loaded cationic emulsion/DNA complexes showed higher cellular uptake in HepG2 cells depending on the rosiglitazone loading, but not depending on the type of plasmid DNA type such as pVAX/ADN, pCAG/ADN, or pVAX. The drug-loaded cationic emulsion/plasmid DNA complexes were less cytotoxic than free rosiglitazone. Therefore, a cationic emulsion could potentially serve as a co-delivery system for rosiglitazone and the adiponectin gene. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Infrared multiple photon dissociation spectroscopy of cationized asparagine: effects of metal cation size on gas-phase conformation.

    PubMed

    Heaton, A L; Bowman, V N; Oomens, J; Steill, J D; Armentrout, P B

    2009-05-14

    Gas-phase structures of cationized asparagine (Asn) including complexes with Li(+), Na(+), K(+), Rb(+), Cs(+), and Ba(2+), as well as protonated Asn, are examined by infrared multiple photon dissociation (IRMPD) action spectroscopy utilizing light generated by a free electron laser. Experimental spectra for the alkali metal cation complexes exhibit systematic trends, whereas spectra for Ba(2+)(Asn) and H(+)(Asn) are more distinct. To identify the structures formed experimentally, measured IRMPD spectra are compared to spectra calculated at a B3LYP/6-311+G(d,p) level with several effective core potentials and basis sets evaluated for the heavy metal systems. The dominant conformation ascertained for complexes with the smaller metal cations, Li(+)(Asn) and Na(+)(Asn), is a charge-solvated, tridentate [N,CO,CO] structure that binds the metal cation with the amine group of the amino acid backbone and to the carbonyl oxygen atoms of the backbone and amino acid side chain. For the larger alkali metal cation complexes, K(+)(Asn), Rb(+)(Asn), and Cs(+)(Asn), an additional charge-solvated, tridentate [COOH,CO] structure that binds the metal cation with the two oxygen atoms of the backbone carboxylic acid group and the carbonyl oxygen atom of the Asn side chain may also be present. The Ba(2+)(Asn) spectrum is characteristic of a single charge-solvated [N,CO,CO] conformation, in contrast to Gly, Trp, Arg, Gln, Pro, Ser, Val, and Glu, which all take on a zwitterionic structure when complexed to Ba(2+). In no case do the cationized Asn complexes show definitive evidence of forming a zwitterionic structure in the complexes studied here. For H(+)(Asn), a mixture of two [N,CO] structures, which differ only in the orientation the side chain and are calculated to be nearly identical in energy, explains the experimental spectrum well.

  11. Focused fluorescent probe library for metal cations and biological anions.

    PubMed

    Rhee, Hyun-Woo; Lee, Sang Wook; Lee, Jun-Seok; Chang, Young-Tae; Hong, Jong-In

    2013-09-09

    A focused fluorescent probe library for metal cations was developed by combining metal chelators and picolinium/quinolinium moieties as combinatorial blocks connected through a styryl group. Furthermore, metal complexes derived from metal chelators having high binding affinities for metal cations were used to construct a focused probe library for phosphorylated biomolecules. More than 250 fluorescent probes were screened for identifying an ultraselective probe for dTTP.

  12. Interaction of the cesium cation with meso-octamethylcalix[4]pyrrole: Experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Polášek, Miroslav; Makrlík, Emanuel; Kvíčala, Jaroslav; Křížová, Věra; Petr Vaňura

    2017-02-01

    By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent cesium cation (Cs+) forms with meso-octamethylcalix[4]pyrrole (abbrev. 1) the cationic complex species 1.Cs+. Further, applying quantum chemical DFT calculations, four different conformations of the resulting complex 1.Cs+ were derived. It means that under the present experimental conditions, this ligand 1 can be considered as a macrocyclic receptor for the cesium cation.

  13. Biophysical characterization of complexes of DNA with mixtures of the neutral lipids 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-hexanoylamine or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-dodecanoylamine and 1,2-dioleoyl-sn-glycero-3-phosphocholine in the presence of bivalent metal cations for DNA transfection.

    PubMed

    Pisani, Michela; Mobbili, Giovanna; Placentino, Immacolata F; Smorlesi, Arianna; Bruni, Paolo

    2011-09-01

    Neutral lipids have received up to now a little attention as genetic material carriers, despite some valuable features, such as the absence of toxicity and the high stability in serum of their complexes with DNA. We have prepared two quaternary complexes of DNA and mixtures of 1, 2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-hexanoylamine (6PE) or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-dodecanoylamine (12PE) with DOPC in aqueous dispersions of bivalent metal cations (PE/DOPC-DNA-M(2+)). The aim was to evaluate the effect of the amide moiety on the transfection efficiency. These complexes form in a self-assembled manner, the DNA condensation being promoted by the metal cations. Synchrotron X-ray diffraction analysis was used to determine the structure of the complexes, which exhibit the lamellar symmetry of the L(α)(c) phase. The size and surface charge of the complexes have also been measured, and promising results of DNA transfections in vitro have been reported. © 2011 American Chemical Society

  14. In vitro transfection of plasmid DNA by cationized gelatin prepared from different amine compounds.

    PubMed

    Kushibiki, Toshihiro; Tomoshige, Ryuji; Iwanaga, Kazunori; Kakemi, Masawo; Tabata, Yasuhiko

    2006-01-01

    The objective of this paper is to compare the in vitro transfection efficiency of a luciferase plasmid DNA using cationized gelatin prepared from different amine compounds. The compounds used here were ethylenediamine, putrescine, spermidine and spermine, chemically introduced to the carboxyl group of gelatin for the cationization. Complexation of the cationized gelatin with the plasmid DNA was performed by simply mixing the two materials at various N+/P- mixing ratios (the molar number ratio of amino groups of gelatin to the phosphate groups of DNA) in aqueous solution. Gel retardation studies revealed that the formation of cationized-gelatin-plasmid DNA complexes depended on the N+/P- mixing ratio. The stronger interaction of plasmid DNA with the cationized gelatin of spermine compared to the other cationized gelatins was observed by an ethidium bromide intercalation assay and Scatchard binding analysis. When the transfection efficiency of plasmid DNA complexed with the various cationized gelatins at different N+/P- mixing ratios was evaluated for mouse L929 fibroblasts, the highest transfection efficiency was observed for the complex prepared from the cationized gelatin of spermine at a N+/P- mixing ratio of 2. The present study indicates that there is an optimal N+/P- mixing ratio and a type of amine compound or cationization extent of cationized gelatin to enhance the transfection efficiency of plasmid DNA.

  15. Nanoheterostructure cation exchange: anionic framework conservation.

    PubMed

    Jain, Prashant K; Amirav, Lilac; Aloni, Shaul; Alivisatos, A Paul

    2010-07-28

    In ionic nanocrystals the cationic sublattice can be replaced with a different metal ion via a fast, simple, and reversible place exchange, allowing postsynthetic modification of the composition of the nanocrystal, while preserving its size and shape. Here, we demonstrate that, during such an exchange, the anionic framework of the crystal is preserved. When applied to nanoheterostructures, this phenomenon ensures that compositional interfaces within the heterostructure are conserved throughout the transformation. For instance, a morphology composed of a CdSe nanocrystal embedded in a CdS rod (CdSe/CdS) was exchanged to a PbSe/PbS nanorod via a Cu(2)Se/Cu(2)S structure. During every exch