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Sample records for methyl methacrylate-styrene copolymeric

  1. Microgel formation in the free radical crosslinking copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethcrylate (EGDMA)

    SciTech Connect

    Xiudong Sung; Yuen-Yuen Chiu; Lee, L.J.

    1996-12-31

    The formation of heterogeneous structure through intramolecular reaction is an important feature in the free radical crosslinking copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA). Such structure formation affects not only the curing behavior but also the rheological changes of the resin. In this work, the effect of co-monomer composition on the reaction kinetics, rheological changes and microgel formation of MMA-EGDMA copolymerization was studied. A percolation model was adopted to simulate such monovinyl-divinyl reactions.

  2. Radiation induced graft copolymerization of methyl methacrylate onto chrome-tanned pig skins

    NASA Astrophysics Data System (ADS)

    Pietrucha, K.; Pȩkala, W.; Kroh, J.

    Graft copolymerization of methyl methacrylate (MMA) onto chrome-tanned pig skins was carried out by the irradiation with 60Co ?-rays. The grafted polymethyl methacrylate (PMMA) chains were isolated by acid hydrolysis of the collagen backbone in order to characterize the graft copolymers. Proof of grafting was obtained through the detection of amino acid endgroups in the isolated grafts by reaction with ninhydrin. The grafting yield of MMA in aqueous emulsion was found to be higher than that for pure MMA and MMA in acetone. The degree of grafting increases with increasing monomer concentration in emulsion and reaches maximum at radiation dose ca 15 kGy. The yield of grafting is very high - ca 90% of monomer converts into copolymer and only 10% is converted into homopolymer. The present paper reports the physical properties of chrome-tanned pig skins after graft polymerization with MMA in emulsion. Modified leathers are more resistant against water absorption and abrasion in comparison with unmodified ones. They have more uniform structure over the whole surface, greater thickness and stiffness. The results reported seem to indicate that MMA may be used in the production of shoe upper and sole leathers. The mechanism of some of the processes occuring during radiation grafting of MMA in water emulsion on tanned leathers has been also suggested and discussed.

  3. A methyl methacrylate-HEMA-CL(n) copolymerization investigation: from kinetics to bioapplications.

    PubMed

    Ferrari, Raffaele; Rooney, Thomas R; Lupi, Monica; Ubezio, Paolo; Hutchinson, Robin A; Moscatelli, Davide

    2013-10-01

    The radical copolymerization kinetics of methyl methacrylate (MMA) and poly-ϵ-caprolactone macromonomer functionalized with a vinyl end group (HEMA-CL(n)) is studied using a pulsed-laser technique. The reactivity ratios for this system are near unity, while a linear relationship between k(p,cop), the copolymer-averaged propagation rate coefficient, and the composition of macromonomer in the feed (0-80 wt% range) is determined. At 50 wt% macromonomer in the feed, a 1.67 ± 0.02 and 1.64 ± 0.06 increase in k(p,cop)/k(p,MMA) is determined for HEMA-CL3 and HEMA-CL2, respectively. These macromonomers are adopted to synthesize nanoparticles (NPs) in the range of 100-150 nm through batch emulsion free radical polymerization (BEP) to produce partially degradable drug delivery carriers. The produced NPs are tested in 4T1 cell line and show excellent characteristics as carriers: they do not affect cell proliferation, and a relevant number of NPs, thousands per cell, are internalized.

  4. Synthesis of cationic flocculant by radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide in aqueous solution. II. Copolymerization at higher monomer concentration

    SciTech Connect

    Ishigaki, I.; Fukuzaki, H.; Okada, T.; Okada, T.; Okamoto, J.; Machi, S.

    1981-05-01

    The radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide was studied to prepare a polymer flocculant that can be handled as a solid. The product obtained in the presence of 5 to 20% water was a solid and could be ground to a powder without drying. In order to obtain a water-soluble polymer at a higher concentration, the effect of various additives on the copolymerization was investigated and found that alcohols bearing a hydrogen atom attached to the tertiary carbon atom effectively inhibit intermolecular crosslinking to give water-soluble polymer. It is suggested that the formation of water-insoluble polymer is predominantly attributable to the crosslinking of polymer chains rather than to the imidation of amide groups. Copolymerization in the presence of isopropyl alcohol as inhibitor of the crosslinking was also studied and compared with that reported previously, which was carried out at a lower monomer concentration without additives.

  5. A Curtin-Hammett mechanism for the copolymerization of ethylene and methyl acrylate monomer using a PymNox nickel catalyst as revealed by DFT computational studies.

    PubMed

    Ramos, Javier; Martínez, Sonia; Cruz, Víctor L; Martínez-Salazar, Javier

    2012-02-01

    In this work, the copolymerization of ethylene and methyl acrylate (MA) as catalyzed by a new Ni-based PymNox organometallic compound was studied computationally. We recently tested the behavior of this type of catalyst in ethylene homopolymerization. Experimental results show that the unsubstituted catalyst Ni2 (aldimino PymNox catalyst) is unable to incorporate the MA monomer, whereas methyl-substituted Ni1 (acetaldimino PymNox catalyst) is able to achieve copolymerization. The reactivities of both catalysts were examined using density functional theory (DFT) models. Based on energy profiles calculated at the BP86 level, a Curtin-Hammett mechanism was proposed to explain the different reactivities of the catalysts in ethylene/MA copolymerization. Our results indicate that the methyl substituent Ni1 introduces additional steric hindrance that results in a catalyst conformation that is better suited to polar monomer incorporation. This model provides insights into the design of new catalysts to produce polar functionalized copolymers based on ethylene.

  6. Affinity chromatography of proteins on non-porous copolymerized particles of styrene, methyl methacrylate and glycidyl methacrylate.

    PubMed

    Chen, C H; Lee, W C

    2001-06-29

    Non-porous particles having an average diameter of 2.1 microm were prepared by co-polymerization of styrene, methyl methacrylate and glycidyl methacrylate, which was abbreviated as P(S-MMA-GMA). The particles were mechanically stable due to the presence of benzene rings in the backbone of polymer chains, and could withstand high pressures when a column packed with these particles was operated in the HPLC mode. The polymer particles were advantaged by immobilization of ligands via the epoxy groups on the particle surface that were introduced by one of the monomers, glycidyl methacrylate. As a model system, Cibacron Blue 3G-A was covalently immobilized onto the non-porous copolymer beads. The dye-immobilized P(S-MMA-GMA) particles were slurry packed into a 1.0 cm x 0.46 cm I.D. column. This affinity column was effective for the separation of turkey egg white lysozyme from a protein mixture. The bound lysozyme could be eluted to yield a sharp peak by using a phosphate buffer containing 1 M NaCl. For a sample containing up to 8 microg of lysozyme, the retained portion of proteins could be completely eluted without any slit peak. Due to the use of a shorter column, the analysis time was shorter in comparison with other affinity systems reported in the literature. The retention time could be reduced significantly by increasing the flow-rate, while the capacity factor remained at the same level.

  7. Organophosphazenes.22 Copolymerization of (Alpha-Methylethenylphenyl) Penta-fluorocyclotriphosphazenes with Styrene and Methyl Methacrylate.

    DTIC Science & Technology

    1988-03-15

    pennultimate effects , 19. BSTRACT (Continue on reverse it necessary and identify by block number) i ., i. Both 3- and 4- (l-Methylethenylphenyl...parameters for theA, styrene system show that the major perturbation produced by the phosphazene is a polar6 electron withdrawing effect . The methyl...methacrylate system was found to exhibit significant penultimate effects in its reactivity behavior. The copolymers were characteri-zed using elemental

  8. Highly Robust Palladium(II) α-Diimine Catalysts for Slow-Chain-Walking Polymerization of Ethylene and Copolymerization with Methyl Acrylate.

    PubMed

    Dai, Shengyu; Sui, Xuelin; Chen, Changle

    2015-08-17

    A series of sterically demanding α-diimine ligands bearing electron-donating and electron-withdrawing substituents were synthesized by an improved synthetic procedure in high yield. Subsequently, the corresponding Pd complexes were prepared and isolated by column chromatography. These Pd complexes demonstrated unique properties in ethylene polymerization, including high thermal stability and high activity, thus generating polyethylene with a high molecular weight and very low branching density. Similar properties were observed for ethylene/methyl acrylate copolymerization. Because of the high molecular weight and low branching density, the generated polyethylene and ethylene/methyl acrylate copolymer were semicrystalline solids. The (co)polymers had unique microstructures originating from the unique slow-chain-walking activity of these Pd complexes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Surface treatment of poly(ethylene terephthalate) by gamma-ray induced graft copolymerization of methyl acrylate and its toughening effect on poly(ethylene terephthalate)/elastomer blend

    NASA Astrophysics Data System (ADS)

    Ma, Liang; Wang, Mozhen; Ge, Xuewu

    2013-09-01

    To improve the compatibility between ethylene-methyl acrylate-glycidyl methacrylate random terpolymer (E-MA-GMA) elastomer and poly(ethylene terephthalate) (PET), thereby enhance the toughening effect of E-MA-GMA on PET, γ-radiation-induced graft copolymerization technique was used to graft methyl acrylate (MA) monomer onto PET. The produced PET-g-PMA copolymer can be used as a self-compatibilizer in PET/E-MA-GMA blend since the copolymer contains the same segments, respectively, with PET and E-MA-GMA. The impact strength of PET/E-MA-GMA blend increased nearly by 30% in the presence of less than 0.1 wt% PET-g-PMA compared with that of the neat PET/elastomer blend, without loss of the tensile strength of the blends. This work proposed a potential application of radiation-induced grafting copolymerization technique on the in-situ compatibilization of PET/elastomer blends so as to improve the integral mechanical properties of PET based engineering plastic.

  10. Porating anion-responsive copolymeric gels.

    PubMed

    England, Dustin; Yan, Feng; Texter, John

    2013-09-24

    A polymerizable ionic liquid surfactant, 1-(11-acryloyloxyundecyl)-3-methylimidiazolium bromide (ILBr), was copolymerized with methyl methacrylate (MMA) in aqueous microemulsions at 30% (ILBr w/w) and various water to MMA ratios. The ternary phase diagram of the ILBr/MMA/water system was constructed at 25 and 60 °C. Homopolymers and copolymers of ILBr and MMA were produced by thermally initiated chain radical microemulsion polymerization at various compositions in bicontinuous and reverse microemulsion subdomains. Microemulsion polymerization reaction products varied from being gel-like to solid, and these materials were analyzed by thermal and scanning electron microscopy methods. Microemulsion polymerized materials were insoluble in all solvents tested, consistent with light cross-linking. Ion exchange between Br(-) and PF6(-) in these copolymeric materials resulted in the formation of open-cell porous structures in some of these materials, as was confirmed by scanning electron microscopy (SEM). Several compositions illustrate the capture of prepolymerization nanoscale structure by thermally initiated polymerization, expanding the domain of compositions exhibiting this feat and yet to be demonstrated in any other system. Regular cylindrical pores in interpenetrating ILBr-co-MMA and PMMA networks are produced by anion exchange in the absence of templates. A percolating cluster/bicontinuous transition is "captured" by SEM after using anion exchange to visualize the mixed cluster/pore morphology. Some design principles for achieving this capture and for obtaining stimuli responsive solvogels are articulated, and the importance of producing solvogels in capturing the nanoscale is highlighted.

  11. Chain Transfer of Vegetable Oil Macromonomers in Acrylic Solution Copolymerization

    SciTech Connect

    Black, Micah; Messman, Jamie M; Rawlins, James

    2011-01-01

    Use of vegetable oil macromonomers (VOMMs) as comonomers in emulsion polymerization enables good film coalescence without the addition of solvents that constitute volatile organic compounds (VOCs). VOMMs are derived from renewable resources and offer the potential of post-application crosslinking via auto-oxidation. However, chain transfer reactions of VOMMs with initiator and/or polymer radicals during emulsion polymerization reduce the amount of allylic hydrogen atoms available for primary auto-oxidation during drying. Vegetable oils and derivatives were reacted in combination with butyl acrylate and methyl methacrylate via solution polymerization. The copolymerization was monitored using in situ infrared spectroscopy to determine the extent of chain transfer. 1H NMR spectroscopy was used to determine the loci of chain transfer and the molecular weight characteristics of the polymers were characterized by SEC. Solution polymerization was utilized to minimize temperature fluctuations and maintain polymer solubility during the initial characterization.

  12. Zirconium oxocluster/polymer hybrid nanoparticles prepared by photoactivated miniemulsion copolymerization

    NASA Astrophysics Data System (ADS)

    Benedetti, Cesare; Flouda, Paraskevi; Antonello, Alice; Rosenauer, Christine; Pérez-Pla, Francisco F.; Landfester, Katharina; Gross, Silvia; Muñoz-Espí, Rafael

    2017-09-01

    The photoactivated free radical miniemulsion copolymerization of methyl methacrylate (MMA) and the zirconium oxocluster Zr4O2(methacrylate)12 is used as an effective and fast preparation method for polymer/inorganic hybrid nanoparticles. The oxoclusters, covalently anchored to the polymer network, act as metal-organic cross-linkers, thus improving the thermomechanical properties of the resulting hybrid nanoparticles. Benzoin carbonyl organic compounds were used as photoinitiators. The obtained materials are compared in terms of cross-linking, effectiveness of cluster incorporation, and size distribution with the analogous nanoparticles produced by using conventional thermally induced free radical miniemulsion copolymerization. The kinetics of the polymerization process in the absence and in the presence of the oxocluster is also investigated.

  13. Equilibrium polymerization of acenaphthylene and its copolymerizations with electron-accepting vinyl monomers

    SciTech Connect

    Iwatsuki, Shouji; Kubo, Masataka; Iwayama, Hiroaki

    1993-12-20

    Radical polymerization kinetics of acenaphthylene in toluene using 2,2{prime}-azobis (isobutyronitrile) (AIBN) as an initiator was investigated revealing an equilibrium polymerization. The values of monomer concentration at equilibrium were determined to be between 1.3 and 3.3 mol/L for a temperature range of 50--70 C. The thermodynamics parameters were determined and showed an enthalpy change of {delta}H = {minus}43 kJ/mol and an entropy change of {delta}S ={minus}98J/K {center_dot} mol. Furthermore, copolymerization of acenaphthylene with electron-accepting vinyl monomers such as methyl methacrylate (MMA) and acrylonitrile (AN) were carried out and showed a change from random to alternating copolymerization as the acenaphthylene concentration decreased. This change in mechanism is rationally explained in terms of the equilibrium polymerization of acenaphthylene.

  14. Zirconium oxocluster/polymer hybrid nanoparticles prepared by photoactivated miniemulsion copolymerization.

    PubMed

    Benedetti, Cesare; Flouda, Paraskevi; Antonello, Alice; Rosenauer, Christine; Pérez-Pla, Francisco F; Landfester, Katharina; Gross, Silvia; Muñoz-Espí, Rafael

    2017-09-08

    The photoactivated free radical miniemulsion copolymerization of methyl methacrylate (MMA) and the zirconium oxocluster Zr4O2(methacrylate)12 is used as an effective and fast preparation method for polymer/inorganic hybrid nanoparticles. The oxoclusters, covalently anchored to the polymer network, act as metal-organic cross-linkers, thus improving the thermomechanical properties of the resulting hybrid nanoparticles. Benzoin carbonyl organic compounds were used as photoinitiators. The obtained materials are compared in terms of cross-linking, effectiveness of cluster incorporation, and size distribution with the analogous nanoparticles produced by using conventional thermally induced free radical miniemulsion copolymerization. The kinetics of the polymerization process in the absence and in the presence of the oxocluster is also investigated.

  15. SYNTHESIS AND INVESTIGATION OF HIGH-MOLECULAR-WEIGHT TERTIARY AMINES AND QUATERNARY AMMONIUM COMPOUNDS FROM COPOLYMERS OF 2-METHYL-5-VINYL-PYRIDINE AND VARIOUS CROSS-LINKING AGENTS

    DTIC Science & Technology

    AMIDES, *COPOLYMERIZATION, *ION EXCHANGE RESINS, *PYRIDINES, ACRYLIC RESINS, ALKYL RADICALS, BENZENE, CHEMICAL PROPERTIES, CHEMICAL REACTIONS ...ETHYLENES, GLYCOLS, METHYL RADICALS, PHYSICAL PROPERTIES, POLYMERIZATION, POLYMERS, SYNTHESIS, VINYL RADICALS.

  16. Direct Copolymerization of CO2 and Diols

    PubMed Central

    Tamura, Masazumi; Ito, Kazuki; Honda, Masayoshi; Nakagawa, Yoshinao; Sugimoto, Hiroshi; Tomishige, Keiichi

    2016-01-01

    Direct polymerization of CO2 and diols is promising as a simple and environmental-benign method in place of conventional processes using high-cost and/or hazardous reagents such as phosgene, carbon monoxide and epoxides, however, there are no reports on the direct method due to the inertness of CO2 and severe equilibrium limitation of the reaction. Herein, we firstly substantiate the direct copolymerization of CO2 and diols using CeO2 catalyst and 2-cyanopyridine promotor, providing the alternating cooligomers in high diol-based yield (up to 99%) and selectivity (up to >99%). This catalyst system is applicable to various diols including linear C4-C10 α,ω-diols to provide high yields of the corresponding cooligomers, which cannot be obtained by well-known methods such as copolymerization of CO2 and cyclic ethers and ring-opening polymerization of cyclic carbonates. This process provides us a facile synthesis method for versatile polycarbonates from various diols and CO2 owing to simplicity of diols modification. PMID:27075987

  17. Direct Copolymerization of CO2 and Diols

    NASA Astrophysics Data System (ADS)

    Tamura, Masazumi; Ito, Kazuki; Honda, Masayoshi; Nakagawa, Yoshinao; Sugimoto, Hiroshi; Tomishige, Keiichi

    2016-04-01

    Direct polymerization of CO2 and diols is promising as a simple and environmental-benign method in place of conventional processes using high-cost and/or hazardous reagents such as phosgene, carbon monoxide and epoxides, however, there are no reports on the direct method due to the inertness of CO2 and severe equilibrium limitation of the reaction. Herein, we firstly substantiate the direct copolymerization of CO2 and diols using CeO2 catalyst and 2-cyanopyridine promotor, providing the alternating cooligomers in high diol-based yield (up to 99%) and selectivity (up to >99%). This catalyst system is applicable to various diols including linear C4-C10 α,ω-diols to provide high yields of the corresponding cooligomers, which cannot be obtained by well-known methods such as copolymerization of CO2 and cyclic ethers and ring-opening polymerization of cyclic carbonates. This process provides us a facile synthesis method for versatile polycarbonates from various diols and CO2 owing to simplicity of diols modification.

  18. Graft copolymerization onto polybutadiene: Cross-linking and thermal degradation of vinyl polymers and copolymers

    NASA Astrophysics Data System (ADS)

    Jiang, Dayue (David)

    This work consists of three parts. In Part I, the graft copolymerization of methyl methacrylate, methyl acrylate, methacylic acid and acrylic acid onto polybutadiene and its copolymers by benzoyl peroxide, BPO, or 2, 2'azobis(2-methylpropionitrile), AIBN, initiation were explored. The results show that these monomers can be grafted onto butadiene region of butadiene-containing polymers. The extent of both graft copolymerization and homopolymerization are dependent on the time and temperature of the reaction and the concentration of all of the reactants. One must specify the monomer, initiator and solvent for the efficient graft copolymerization. The methyl methacrylate adds directly to the radical sites which are formed on the backbone by the interaction of the polymer and the primary radical form the initiator, while for the other three monomers, the graft copolymerization occurs by addition of macro-radical to the double bonds. In Part II, the cross-linking of polybutadiene, butadiene-styrene copolymers, and polystyrene by irradiation, thermal and chemical processes, and Friedel-Crafts chemistry and the effect of cross-linking on the thermal stability were investigated. The proof of cross-linking of the polymer comes from the insolubility of the product after the cross-linking reaction and is characterized by gel content and swelling ratio. The results show that the thermal stability of the polymer can be improved by cross-linking. In Part III, the thermal degradation of three vinyl polymers, poly(vinylsulfonic acid) and its sodium salt and poly(vinylphosphonic acid) were studied by combination technique: TGA/FTIR. The results show that TGA/FTIR combined with analysis of residues provides an excellent opportunity to understand the degradation pathway of the compounds. The observation of foaming indicates that the char which is formed contains carbon as well as the inorganic salts which have been observed. The carbon is in a partially graphitized form. The salts

  19. Logarithmic Exchange Kinetics in Monodisperse Copolymeric Micelles

    NASA Astrophysics Data System (ADS)

    García Daza, Fabián A.; Bonet Avalos, Josep; Mackie, Allan D.

    2017-06-01

    Experimental measurements of the relaxation kinetics of copolymeric surfactant exchange for micellar systems unexpectedly show a peculiar logarithmic decay. Several authors use polydispersity as an explanation for this behavior. However, in coarse-grained simulations that preserve microscopic details of the surfactants, we find evidence of the same logarithmic behavior. Since we use a strictly monodisperse distribution of chain lengths such a relaxation process cannot be attributed to polydispersity, but has to be caused by an inherent physical process characteristic of this type of system. This is supported by the fact that the decay is specifically logarithmic and not a power law with an exponent inherited from the particular polydispersity distribution of the sample. We suggest that the degeneracy of the energy states of the hydrophobic block in the core, which is broken on leaving the micelle, can qualitatively explain the broad distribution of energy barriers, which gives rise to the observed nonexponential relaxation.

  20. Kinetics and thermodynamics of living copolymerization processes.

    PubMed

    Gaspard, Pierre

    2016-11-13

    Theoretical advances are reported on the kinetics and thermodynamics of free and template-directed living copolymerizations. Until recently, the kinetic theory of these processes had only been established in the fully irreversible regime, in which the attachment rates are only considered. However, the entropy production is infinite in this regime and the approach to thermodynamic equilibrium cannot be investigated. For this purpose, the detachment rates should also be included. Inspite of this complication, the kinetics can be exactly solved in the regimes of steady growth and depolymerization. In this way, analytical expressions are obtained for the mean growth velocity, the statistical properties of the copolymer sequences, as well as the thermodynamic entropy production. The results apply to DNA replication, transcription and translation, allowing us to understand important aspects of molecular evolution.This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'. © 2016 The Author(s).

  1. Thermodynamics meets information in copolymerization processes

    NASA Astrophysics Data System (ADS)

    Gaspard, Pierre

    2014-03-01

    Copolymers are natural supports of information. This latter is contained in the sequence of monomeric units composing every copolymer. A well-known example is DNA in biology. At the molecular scale, the growth of a single copolymer is stochastic and proceeds by successive random attachments or detachments of monomers continuously supplied by the surrounding solution. The thermodynamics of copolymerization with or without a template shows that fundamental links exist between entropy production and the information content of the copolymer sequence. During depolymerization, this information is erased in a way compatible with Landauer's principle. These advances open new perspectives to understand information transmission during DNA replication and, more generally, information processing at the molecular scale in biology and polymer science.

  2. Kinetics and thermodynamics of living copolymerization processes

    NASA Astrophysics Data System (ADS)

    Gaspard, Pierre

    2016-11-01

    Theoretical advances are reported on the kinetics and thermodynamics of free and template-directed living copolymerizations. Until recently, the kinetic theory of these processes had only been established in the fully irreversible regime, in which the attachment rates are only considered. However, the entropy production is infinite in this regime and the approach to thermodynamic equilibrium cannot be investigated. For this purpose, the detachment rates should also be included. Inspite of this complication, the kinetics can be exactly solved in the regimes of steady growth and depolymerization. In this way, analytical expressions are obtained for the mean growth velocity, the statistical properties of the copolymer sequences, as well as the thermodynamic entropy production. The results apply to DNA replication, transcription and translation, allowing us to understand important aspects of molecular evolution. This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.

  3. Copolymerization on Selective Substrates: Experimental Test and Computer Simulations.

    PubMed

    Kozhunova, Elena Yu; Gavrilov, Alexey A; Zaremski, Mikhail Yu; Chertovich, Alexander V

    2017-04-11

    We explore the influence of a selective substrate on the composition and sequence statistics during the free radical copolymerization. In particular, we study the radical copolymerization of styrene and acrylic acid in bulk and in silica pores of different sizes. We show that the substrate affects both polymer composition and sequence statistics. We use dissipative particle dynamics simulations to study the polymerization process in detail, trying to pinpoint the parameters responsible for the observed differences in the polymer chain composition and sequences. The magnitude of the observed effect depends on the fraction of adsorbed monomer units, which cannot be described in the framework of the copolymerization theories based on the terminal unit model.

  4. UV-initiated template copolymerization of AM and MAPTAC: Microblock structure, copolymerization mechanism, and flocculation performance.

    PubMed

    Li, Xiang; Zheng, Huaili; Gao, Baoyu; Sun, Yongjun; Liu, Bingzhi; Zhao, Chuanliang

    2017-01-01

    Flocculation as the core technology of sludge pretreatment can improve the dewatering performance of sludge that enables to reduce the cost of sludge transportation and the subsequent disposal costs. Therefore, synthesis of high-efficiency and economic flocculant is remarkably desired in this field. This study presents a cationic polyacrylamide (CPAM) flocculant with microblock structure synthesized through ultraviolet (UV)-initiated template copolymerization by using acrylamide (AM) and methacrylamido propyl trimethyl ammonium chloride (MAPTAC) as monomers, sodium polyacrylate (PAAS) as template, and 2,2'-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (VA-044) as photoinitiator. The microblock structure of the CPAM was observed through nuclear magnetic resonance ((1)H NMR and (13)C NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) analyses. Furthermore, thermogravimetric/differential scanning calorimetry (TG/DSC) analysis was used to evaluate its thermal decomposition property. The copolymerization mechanism was investigated through the determination of the binding constant MK and study on polymerization kinetics. Results showed that the copolymerization was conducted in accordance with the I (ZIP) template polymerization mechanism, and revealed the coexistence of bimolecular termination free-radical reaction and mono-radical termination in the polymerization process. Results of sludge dewatering tests indicated the superior flocculation performance of microblock flocculant than random distributed CPAM. The residual turbidity, filter cake moisture content, and specific resistance to filtration reached 9.37 NTU, 68.01%, and 6.24 (10(12) m kg(-1)), respectively, at 40 mg L(-1) of template poly(AM-MAPTAC) and pH 6.0. Furthermore, all flocculant except commercial CPAM showed a wide scope of pH application. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Perfectly alternating copolymerization of CO2 and epichlorohydrin using cobalt(III)-based catalyst systems.

    PubMed

    Wu, Guang-Peng; Wei, Sheng-Hsuan; Ren, Wei-Min; Lu, Xiao-Bing; Xu, Tie-Qi; Darensbourg, Donald J

    2011-09-28

    Selective transformations of carbon dioxide and epoxides into biodegradable polycarbonates by the alternating copolymerization of the two monomers represent some of the most well-studied and innovative technologies for potential large-scale utilization of carbon dioxide in chemical synthesis. For the most part, previous studies of these processes have focused on the use of aliphatic terminal epoxides or cyclohexene oxide derivatives, with only rare reports concerning the synthesis of CO(2) copolymers from epoxides containing electron-withdrawing groups such as styrene oxide. Herein we report the production of the CO(2) copolymer with more than 99% carbonate linkages from the coupling of CO(2) with epichlorohydrin, employing binary and bifunctional (salen)cobalt(III)-based catalyst systems. Comparative kinetic studies were performed via in situ infrared measurements as a function of temperature to assess the activation barriers for the production of cyclic carbonate versus copolymer involving two electronically different epoxides: epichlorohydrin and propylene oxide. The relative small activation energy difference between copolymer versus cyclic carbonate formation for the epichlorohydrin/CO(2) process (45.4 kJ/mol) accounts in part for the selective synthesis of copolymer to be more difficult in comparison with the propylene oxide/CO(2) case (53.5 kJ/mol). Direct observation of the propagating polymer-chain species from the binary (salen)CoX/MTBD (X = 2,4-dinitrophenoxide and MTBD = 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene) catalyst system by means of electrospray ionization mass spectrometry confirmed the perfectly alternating nature of the copolymerization process. This observation in combination with control experiments suggests possible intermediates involving MTBD in the CO(2)/epichlorohydrin copolymerization process.

  6. Tuning the critical solution temperature of polymers by copolymerization

    SciTech Connect

    Schulz, Bernhard; Chudoba, Richard; Dzubiella, Joachim; Heyda, Jan

    2015-12-28

    We study statistical copolymerization effects on the upper critical solution temperature (CST) of generic homopolymers by means of coarse-grained Langevin dynamics computer simulations and mean-field theory. Our systematic investigation reveals that the CST can change monotonically or non-monotonically with copolymerization, as observed in experimental studies, depending on the degree of non-additivity of the monomer (A-B) cross-interactions. The simulation findings are confirmed and qualitatively explained by a combination of a two-component Flory-de Gennes model for polymer collapse and a simple thermodynamic expansion approach. Our findings provide some rationale behind the effects of copolymerization and may be helpful for tuning CST behavior of polymers in soft material design.

  7. Catalysts for CO2/epoxide ring-opening copolymerization

    PubMed Central

    Trott, G.; Saini, P. K.; Williams, C. K.

    2016-01-01

    This article summarizes and reviews recent progress in the development of catalysts for the ring-opening copolymerization of carbon dioxide and epoxides. The copolymerization is an interesting method to add value to carbon dioxide, including from waste sources, and to reduce pollution associated with commodity polymer manufacture. The selection of the catalyst is of critical importance to control the composition, properties and applications of the resultant polymers. This review highlights and exemplifies some key recent findings and hypotheses, in particular using examples drawn from our own research. PMID:26755758

  8. Grafting onto wool. XX. Graft copolymerization of vinyl monomers by use of redox initiators. Comparison of monomer reactivities

    SciTech Connect

    Misra, B.N.; Singha, A.S.; Sharma, R.K.

    1982-04-01

    Methyl methacrylate (MMA) and ethylacrylate (EA) have been graft copolymerized onto Himachali wool in aqueous medium by using a ferrous ammonium sulfate-hydrogen peroxide (FAS-H/sub 2/O/sub 2/) system as redox initiator. Percentage of grafting has been determined as functions of concentration of monomer, molar ratio of (FAS)/(H/sub 2/O/sub 2/), time, and temperature. Percentage of grafting is found to depend upon the molar ratio of (FAS)/(H/sub 2/O/sub 2/). An attempt has been made to compare the reactivities of the acceptor monomer (MMA and EA) with that of the donor monomer (VAc) toward grafting onto wool.

  9. A sterically expanded "constrained geometry catalyst" for highly active olefin polymerization and copolymerization: an unyielding comonomer effect.

    PubMed

    Irwin, Levi J; Reibenspies, Joseph H; Miller, Stephen A

    2004-12-29

    The 14 A octamethyloctahydrodibenzofluorene moiety has been incorporated into a sterically expanded constrained geometry catalyst, Me2Si(eta1-C29H36)(eta1-N-tBu)ZrCl2.OEt2 (1). The solid-state structure suggests that the activated olefin polymerization catalyst is quite spatially accessible, rationalizing its extraordinary reactivity toward alpha-olefins. 1/MAO (MAO = methylaluminoxane) can be more reactive toward alpha-olefins than toward ethylene and exhibit activities that are linearly and continuously proportional to 4-methyl-1-pentene or 1-octene concentration in their copolymerizations with ethylene.

  10. Copolymerization of carbon dioxide and butadiene via a lactone intermediate.

    PubMed

    Nakano, Ryo; Ito, Shingo; Nozaki, Kyoko

    2014-04-01

    Although carbon dioxide has attracted broad interest as a renewable carbon feedstock, its use as a monomer in copolymerization with olefins has long been an elusive endeavour. A major obstacle for this process is that the propagation step involving carbon dioxide is endothermic; typically, attempted reactions between carbon dioxide and an olefin preferentially yield olefin homopolymerization. Here we report a strategy to circumvent the thermodynamic and kinetic barriers for copolymerizations of carbon dioxide and olefins by using a metastable lactone intermediate, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one, which is formed by the palladium-catalysed condensation of carbon dioxide and 1,3-butadiene. Subsequent free-radical polymerization of the lactone intermediate afforded polymers of high molecular weight with a carbon dioxide content of 33 mol% (29 wt%). Furthermore, the protocol was applied successfully to a one-pot copolymerization of carbon dioxide and 1,3-butadiene, and one-pot terpolymerizations of carbon dioxide, butadiene and another 1,3-diene. This copolymerization technique provides access to a new class of polymeric materials made from carbon dioxide.

  11. Copolymerization of carbon dioxide and butadiene via a lactone intermediate

    NASA Astrophysics Data System (ADS)

    Nakano, Ryo; Ito, Shingo; Nozaki, Kyoko

    2014-04-01

    Although carbon dioxide has attracted broad interest as a renewable carbon feedstock, its use as a monomer in copolymerization with olefins has long been an elusive endeavour. A major obstacle for this process is that the propagation step involving carbon dioxide is endothermic; typically, attempted reactions between carbon dioxide and an olefin preferentially yield olefin homopolymerization. Here we report a strategy to circumvent the thermodynamic and kinetic barriers for copolymerizations of carbon dioxide and olefins by using a metastable lactone intermediate, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one, which is formed by the palladium-catalysed condensation of carbon dioxide and 1,3-butadiene. Subsequent free-radical polymerization of the lactone intermediate afforded polymers of high molecular weight with a carbon dioxide content of 33 mol% (29 wt%). Furthermore, the protocol was applied successfully to a one-pot copolymerization of carbon dioxide and 1,3-butadiene, and one-pot terpolymerizations of carbon dioxide, butadiene and another 1,3-diene. This copolymerization technique provides access to a new class of polymeric materials made from carbon dioxide.

  12. Copolymerization of Metal Nanoparticles: A Route to Colloidal Plasmonic Copolymers**

    PubMed Central

    Lukach, Ariella; Sugikawa, Kota; Chung, Siyon; Vickery, Jemma; Therien-Aubin, Heloise; Yang, Bai; Rubinstein, Michael

    2014-01-01

    The resemblance between colloidal and molecular polymerization reactions has been recognized as a powerful tool for the fundamental studies of polymerization reactions, as well as a platform for the development of new nanoscale systems with desired properties. Future applications of colloidal polymers will require nanoparticle (NP) ensembles with a high degree of complexity that can be realized by hetero-assembly of NPs with different dimensions, shapes and compositions. In the present work, we have developed a method to apply strategies from molecular copolymerization to the co-assembly of gold nanorods with different dimensions into random and block copolymer structures (plasmonic copolymers). The approach was extended to the co-assembly of random copolymers of gold and palladium nanorods. A kinetic model validated and further expanded the kinetic theories developed for molecular copolymerization reactions. PMID:24520012

  13. Polar-Nonpolar Radical Copolymerization under Li+ Catalysis

    DTIC Science & Technology

    2008-09-21

    description of our copolymerization results. The polyisobutylene (b- PIB ) that is produced by homopolymerization of IB in an inert solvent such as 1,2...the linear polyisobutylene (l- PIB ) produced under the usual cationic initiation. The difference is clear in spectral (NMR) and physical (DSC, TGA...HPLC) properties. A detailed 2D-NMR examination of b- PIB obtained from ordinary IB and several isotopically labeled versions of IB revealed that its

  14. Recent advances in photoinduced donor/acceptor copolymerization

    NASA Astrophysics Data System (ADS)

    Jönsson, S.; Viswanathan, K.; Hoyle, C. E.; Clark, S. C.; Miller, C.; Morel, F.; Decker, C.

    1999-05-01

    Photoinitiated free radical polymerization of donor (D)/acceptor (A) type monomers has gained considerable interest due to the possibility to efficiently photopolymerize non-acrylate based systems. Furthermore, this photoinduced alternating copolymerization can be accomplished without the presence of a conventional free radical generating photoinitiator. In the past, we have shown that the structural influences in the direct photolysis of N-Alkyl and N-Arylmaleimides as well as their corresponding ground state charge transfer complexes (CTC) with suitable donors have carefully been investigated. For certain combinations of A and D type monomers, a direct photolysis of the ground state complex or the excitation of the acceptor, followed by the formation of an exciplex, has been shown to initiate the copolymerization. Herein, we show that the main route of initiation is based on inter or intra molecular H-abstraction from an excited state maleimide, whereby no exciplex formation takes place. H-abstraction will predominantly take place in systems where easily abstractable hydrogens are present. Our laser flash photolysis investigation, ESR [1] (A. Hiroshi, I. Takasi, T. Nosi, Macromol. Chem. 190 (1989) 2821) and phosphorescence emissions [2,3] (K.S. Chen, T. Foster, J.K.S. Wan, J. Phys. Chem. 84 (1980) 2473; C.J. Seliskar, S.P. McGlynn, J. Chem. Phys. 55 (1971) 4337) studies show that triplet excited states of N-alkyl substituted maleimides (RMI), which are well known strong precursors for direct H-abstractions from aliphatic ethers and secondary alcohols, are formed upon excitation. Rates of copolymerization and degrees of conversion for copolymerization of maleimide/vinyl ether pairs in air and nitrogen have been measured as a function of hydrogen abstractability of the excited triplet state MI as well as the influence of concentration and hydrogen donating effect of the hydrogen donor.

  15. Ethylene Copolymerization with 1-Octene Using a 2-Methylbenz

    PubMed

    Xu; Ruckenstein

    1998-07-28

    A new effective constrained geometry catalyst precursor for the ethylene/1-octene copolymerization, namely 2-methylbenz[e]indenylamido complex [eta5:eta1-(2-MeBenzInd)SiMe2NtBu]TiCl2 (4), was synthesized. Activated with methylaluminoxane (MAO), the complex 4 showed (a) an improved copolymerization activity and stability, (b) an enhanced comonomer incorporation in the copolymer, and (c) most importantly, an increased copolymer molecular weight, when compared with the previously employed catalysts. The polymerization conditions were found to have a significant effect on the catalyst activity, 1-octene incorporation, molecular weight, and even copolymer microstructure. For the copolymerization parameters, the values rE approximately 2.20 for ethylene and rO approximately 0.55 for 1-octene with rE.rO approximately 1.21 were obtained, reflecting a pronounced tendency for the random distribution of the comonomers in the copolymer chain. The 13C NMR analysis revealed that the E-O copolymer generated by the MAO-activated complex 4 has a regioirregular arrangement of the 1-octene repeat units as a result of some tail-to-tail incorporation of the 1-octene comonomer.

  16. Reactivity ratios and sequence structures of the copolymers prepared using photo-induced copolymerization of MMA with MTMP.

    PubMed

    Liu, Xiaoxuan; Zhang, Yongtao; Cui, Yanyan; Dong, Zhixian

    2012-05-01

    4-Methacryloyl-2,2,6,6-tetramethyl-piperidine (MTMP) was applied as reactive hindered amine piperidine. Photo-induced copolymerization of methyl methacrylate (MMA, M(1)) with MTMP (M(2)) was carried out in benzene solution at ambient temperature. The reactivity ratios for these monomers were measured by running a series of reactions at various feed ratios of initial monomers, and the monomer incorporation into copolymer was determined using (1)H NMR. Reactivity ratios of the MMA/MTMP system were measured to be r(1)= 0.37 and r(2)= 1.14 from extended Kelen-Tüdos method. The results show that monomer MTMP prefers homopolymerization to copolymerization in the system, whereas monomer MMA prefers copolymerization to homopolymerization. Sequence structures of the MMA/MTMP copolymers were characterized using (1)H NMR. The results show that the sequence structure for the main chain of the MMA/MTMP copolymers is mainly composed of a syndiotactic configuration, only with a little heterotactic configuration. Three kinds of the sequences of rr, rr', and lr' in the syndiotactic configuration are found. The sequence-length distribution in the MMA/MTMP copolymers is also obtained. For f(1)= 0.2, the monomer unit of MMA is mostly separated by MTMP units, and for f(1)= 0.6, the alternating tendency prevails and a large number of mono-sequences are formed; further up to f(1)= 0.8, the monomer unit of MTMP with the sequence of one unit is interspersed among the chain of MMA.

  17. Chain Copolymerization Reactions: An Algorithm to Predict the Reaction Evolution with Conversion

    ERIC Educational Resources Information Center

    Gallardo, Alberto; Aguilar, Maria Rosa; Abraham, Gustavo A.; Roman, Julio San

    2004-01-01

    An algorithm is developed to study and understand the behavior of chain copolymerization reactions. When a binary copolymerization reaction follows the terminal model, Conversion is able to predict the evolution of different parameters, such as instantaneous and cumulative copolymer molar fractions, or molar fractions of any sequence with the…

  18. Chain Copolymerization Reactions: An Algorithm to Predict the Reaction Evolution with Conversion

    ERIC Educational Resources Information Center

    Gallardo, Alberto; Aguilar, Maria Rosa; Abraham, Gustavo A.; Roman, Julio San

    2004-01-01

    An algorithm is developed to study and understand the behavior of chain copolymerization reactions. When a binary copolymerization reaction follows the terminal model, Conversion is able to predict the evolution of different parameters, such as instantaneous and cumulative copolymer molar fractions, or molar fractions of any sequence with the…

  19. Metabolism of environmental chemicals by plants - copolymerization into lignin

    SciTech Connect

    Sandermann, H. Jr.; Scheel, D.; Trenck, T.v.d.

    1983-01-01

    Plants have frequently been found to incorporate xenobiotics into ill-defined ''insoluble'' metabolite fractions. Evidence for the lignin nature of such fractions and for the formation of ''insoluble'' metabolite fractions in sterile plant cell cultures is summarized. In several cases, total ''insoluble'' plant metabolite fractions of pesticides were found to be excreted undigested by rats and sheep. Conclusive evidence for covalent incorporation of chemicals into lignin has only recently been obtained. In the case of herbicide 2,4-dichlorophenoxyacetic acid and of the fungicide pentachlorophenol, the derived pesticide/lignin copolymers were characterized by gel permeation chromatography in dimethylformamide, spectral methods, and chemical degradation. In independent studies, artificial lignin was prepared from coniferyl alcohol with the aid of peroxidase/H/sub 2/O/sub 2/. Benzo(..cap alpha..)pyrene quinones and chlorinated anilines could be copolymerized, and the resulting copolymer species were characterized with regard to size distribution and spectral properties. Detailed /sup 1/H- and /sup 13/C-NMR spectroscopic studies showed that a major mechanism of copolymerization of the anilines consisted of a nucleophilic addition to the benzylic ..cap alpha..-carbon of lignol quinone-methide intermediates. In addition, covalent linkages involving the aromatic rings were also formed. 61 references, 3 figures, 4 tables.

  20. Film Formation from Nanosized Copolymeric Latex Particles: A Photon Transmission Study.

    PubMed

    Arda; Özer; Pişkin; Pekcan

    2001-01-15

    The photon transmission technique was used to monitor the evolution of transparency during film formation from nanosized copolymeric latex particles. The latex films were prepared from poly(methyl methacrylate-co-butyl methacrylate) (P(MMA-co-BMA)) particles which were produced by microemulsion polymerization. These films were annealed at elevated temperatures in various time intervals above the glass transition temperature (T(g)) of P(MMA-co-BMA). It is observed that the transmitted photon intensity (I(tr)) from these films increased as the annealing temperature increased. There are three different film formation stages. These stages are explained by the void closure, healing, and interdiffusion processes, respectively. The activation energies for viscous flow (DeltaH approximately 16 kcal/mol), minor chains (DeltaE(H) approximately 27 kcal/mol), and backbone motion (Delta E(b) approximately 132 kcal/mol) were obtained using various models. Void closure (tau(v), T(v)) and healing points (tau(H), T(H)) were determined. Using the time-temperature pairs, void closure and healing activation energies were measured and found to be 21 and 30 kcal/mol, respectively. Copyright 2001 Academic Press.

  1. Kinetics and thermodynamics of first-order Markov chain copolymerization

    NASA Astrophysics Data System (ADS)

    Gaspard, P.; Andrieux, D.

    2014-07-01

    We report a theoretical study of stochastic processes modeling the growth of first-order Markov copolymers, as well as the reversed reaction of depolymerization. These processes are ruled by kinetic equations describing both the attachment and detachment of monomers. Exact solutions are obtained for these kinetic equations in the steady regimes of multicomponent copolymerization and depolymerization. Thermodynamic equilibrium is identified as the state at which the growth velocity is vanishing on average and where detailed balance is satisfied. Away from equilibrium, the analytical expression of the thermodynamic entropy production is deduced in terms of the Shannon disorder per monomer in the copolymer sequence. The Mayo-Lewis equation is recovered in the fully irreversible growth regime. The theory also applies to Bernoullian chains in the case where the attachment and detachment rates only depend on the reacting monomer.

  2. Direct Synthesis of Imidazolium-Functional Polyethylene by Insertion Copolymerization.

    PubMed

    Jian, Zhongbao; Leicht, Hannes; Mecking, Stefan

    2016-06-01

    Cationic imidazolium-functionalized polyethylene is accessible by insertion copolymerization of ethylene and allyl imidazolium tetrafluoroborate (AIm-BF4 ) with phosphinesulfonato palladium(II) catalyst precursors. Imidazolium-substituted repeat units are incorporated into the main chain and the initiating saturated chain end of the linear polymers, rather than the terminating unsaturated chain end. The counterion of the allyl imidazolium monomer is decisive, with the chloride analogue (AIm-Cl) no polymerization is observed. Stoichiometric studies reveal the formation of an inactive chloride complex from the catalyst precursor. An effect of moderate densities (0.5 mol%) of ionic groups on the copolymers' physical properties is exemplified by an enhanced wetting by water.

  3. Invertase immobilization onto radiation-induced graft copolymerized polyethylene pellets

    NASA Astrophysics Data System (ADS)

    de Queiroz, Alvaro Antonio Alencar; Vitolo, Michele; de Oliveira, Rômulo Cesar; Higa, Olga Zazuco

    1996-06-01

    The graft copolymer poly(ethylene-g-acrylic acid) (LDPE-g-AA) was prepared by radiation-induced graft copolymerization of acrylic acid onto low density polyethylene (LDPE) pellets, and characterized by infrared photoacoustic spectroscopy and scanning electron microscopy (SEM). The presence of the grafted poly(acrylic acid) (PAA) was established. Invertase was immobilized onto the graft polymer and the thermodynamic parameters of the soluble and immobilized enzyme were determined. The Michaelis constant, Km, and the maximum reaction velocity, Vmax, were determined for the free and the immobilized invertase. The Michaelis constant, Km was larger for the immobilized invertase than for the free enzyme, whereas Vmax was smaller for the immobilized invertase. The thermal stability of the immobilized invertase was higher than that of the free enzyme.

  4. Kinetic theory and thermodynamics of template-directed copolymerization

    NASA Astrophysics Data System (ADS)

    Gaspard, Pierre

    2017-02-01

    Template-directed copolymerization is the fundamental process for the replication, transcription, and translation of genetic information. The copy of the template sequence is grown by the attachment of monomers with a molecular machine. The long-time kinetics of such processes is exactly solvable in terms of iterated function systems. This method determines the effects of sequence heterogeneity and replication errors on the growth of the copy and the statistical properties of its sequence. In particular, a transition can occur between linear and sublinear growth in time of the copy. In the linear regime, the local growth velocity along the template may have a fractal distribution. Furthermore, the growth can be driven around equilibrium by the entropic effect of replication errors in an adverse free-energy landscape.

  5. Free-radical copolymerization of fullerenes with styrene

    SciTech Connect

    Cao, T.; Webber, S.E.

    1995-05-08

    Various methods to chemically modify the fullerenes have been reported in the last few years since the production of large-scale amounts of fullerene soot that contains primarily C{sub 60}, a lesser amount of C{sub 70}, and traces of higher fullerenes. Fortunately, these components can be separated from each other by standard chromatographic methods, permitting convenient experimentation on relatively pure components. The authors have found that C{sub 60} and C{sub 70} copolymerize with styrene in a standard free-radical polymerization, either in the bulk or codissolved in an aromatic solvent. The resulting polymers are soluble in common solvents that dissolve polystyrene and possess a dark brown color. The absorption spectrum of the copolymer is strongly modified from that of the parent fullerene, and the fluorescence is blue-shifted and much stronger. The present paper describes a very simple method for direct incorporation of C{sub 60} or C{sub 70} into polystyrene by direct free-radical copolymerization under routine conditions. While a great deal remains to be done to characterize fullerenes as comonomers in free-radical polymerization, this method is so direct and simple that it may be of interest to a wide range of researchers working in the area of fullerene chemistry. The authors note a report by Gong et al. in which a polymerization of styrene and {alpha}-methylstyrene was carried out in the presence of C{sub 60} using benzoyl peroxide as an initiator. These authors explicitly state that the C{sub 60} retains its normal absorption spectrum and is dispersed within the resulting solid polymer matrix. No other characterization is presented to demonstrate if chemical attachment of the C{sub 60} to the polymer occurred.

  6. Synthesis evaluation and adsorption studies of anionic copolymeric surfactants based on fatty acrylate ester

    NASA Astrophysics Data System (ADS)

    El-Dougdoug, W. I. A.; El-Mossalamy, E. H.

    2006-12-01

    A series of anionic copolymeric surfactants based on n-dodecylacrylate ester (M 1) as hydrophobe, and oxypropylated acrylate ester (MA 4,6) as hydrophiles, were prepared by copolymerization of n-dodecylacrylate (M 1) and oxypropylated acrylate ester (MA 4,6) with molar ratio's (0.3:0.7, 0.4:0.6 and 0.5:0.5, respectively) in presence of benzoyl peroxide as initiator followed by sulfation and neutralization to afforded [(PAS 4), and (PAS 6)] a-c, as anionic copolymeric surfactant in suitable yield. These derivatives were purified and characterized by IR and 1H NMR spectral studies. Surface activity, and biodegradability were evaluated. Adsorption of some copolymeric surfactant on salary sand was investigated to assess possibility of treating waste water streams for removal of Pb 2+ and Hg 2+ toxic minerals. The effect of several factors governing the adsorption such as initial concentration, temperature, pH, have been studied.

  7. P-chiral phosphine-sulfonate/palladium-catalyzed asymmetric copolymerization of vinyl acetate with carbon monoxide.

    PubMed

    Nakamura, Akifumi; Kageyama, Takeharu; Goto, Hiroki; Carrow, Brad P; Ito, Shingo; Nozaki, Kyoko

    2012-08-01

    Utilization of palladium catalysts bearing a P-chiral phosphine-sulfonate ligand enabled asymmetric copolymerization of vinyl acetate with carbon monoxide. The obtained γ-polyketones have head-to-tail and isotactic polymer structures. The origin of the regio- and stereoregularities was elucidated by stoichiometric reactions of acylpalladium complexes with vinyl acetate. The present report for the first time demonstrates successful asymmetric coordination-insertion (co)polymerization of vinyl acetate.

  8. Aluminium coordination complexes in copolymerization reactions of carbon dioxide and epoxides.

    PubMed

    Ikpo, Nduka; Flogeras, Jenna C; Kerton, Francesca M

    2013-07-07

    Al complexes are widely used in a range of polymerization reactions (ROP of cyclic esters and cationic polymerization of alkenes). Since the discovery in 1978 that an Al porphyrin complex could copolymerize propylene oxide with carbon dioxide, Al coordination compounds have been studied extensively as catalysts for epoxide-carbon dioxide copolymerizations. The most widely studied catalysts are Al porphyrin and Al salen derivatives. This is partially due to their ability to act as mechanistic models for more reactive, paramagnetic Cr catalysts. However, this in depth mechanistic understanding could be employed to design more active Al catalysts themselves, which would be beneficial given the wide availability of this metal. Polymerization data (% CO3 linkages, M(n), M(w)/M(n) and TON) for these complexes are presented and mechanisms discussed. In most cases, especially those employing square-based pyramidal Al complexes, co-catalysts are required to obtain high levels of carbon dioxide incorporation. However, in some cases, the use of co-catalysts inhibits the copolymerization reaction. Lewis acidic Al phenolate complexes have been used as activators in CHO-carbon dioxide copolymerizations to increase TOF and this has recently led to the development of asymmetric copolymerization reactions. Given the ready availability of Al, the robustness of many complexes (e.g. use in immortal polymerizations) and opportunity to prepare block copolymers and other designer materials, Al complexes for copolymerization of carbon dioxide are surely worth a second look.

  9. Effects of stereochemistry and copolymerization on the LCST of PNIPAm

    NASA Astrophysics Data System (ADS)

    de Oliveira, Tiago E.; Mukherji, Debashish; Kremer, Kurt; Netz, Paulo A.

    2017-01-01

    Poly(N-isopropylacrylamide) (PNIPAm) is a smart polymer that presents a lower critical transition temperature (LCST) of 305 K. Interestingly, this transition point falls within the range of the human body temperature, making PNIPAm a highly suitable candidate for bio-medical applications. However, it is sometimes desirable to have a rather flexible tuning of the LCST of these polymers to further increase their range of applications. In this work, we use all-atom molecular dynamics simulations to study the LCST of PNIPAm-based (co-)polymers. We study different molecular architectures where the polymer sequences are tuned either by modifying its stereochemistry or by the co-polymerization of PNIPAm with acrylamide (Am) units. Our analysis connects global polymer conformations with the microscopic intermolecular interactions. These findings suggest that the collapse of a PNIPAm chain upon heating is dependent on the hydration structure around the monomers, which is strongly dependent on the tacticity and the presence of more hydrophilic acrylamide monomers. Our results are found to be in good agreement with the existing experimental data.

  10. Effects of stereochemistry and copolymerization on the LCST of PNIPAm.

    PubMed

    de Oliveira, Tiago E; Mukherji, Debashish; Kremer, Kurt; Netz, Paulo A

    2017-01-21

    Poly(N-isopropylacrylamide) (PNIPAm) is a smart polymer that presents a lower critical transition temperature (LCST) of 305 K. Interestingly, this transition point falls within the range of the human body temperature, making PNIPAm a highly suitable candidate for bio-medical applications. However, it is sometimes desirable to have a rather flexible tuning of the LCST of these polymers to further increase their range of applications. In this work, we use all-atom molecular dynamics simulations to study the LCST of PNIPAm-based (co-)polymers. We study different molecular architectures where the polymer sequences are tuned either by modifying its stereochemistry or by the co-polymerization of PNIPAm with acrylamide (Am) units. Our analysis connects global polymer conformations with the microscopic intermolecular interactions. These findings suggest that the collapse of a PNIPAm chain upon heating is dependent on the hydration structure around the monomers, which is strongly dependent on the tacticity and the presence of more hydrophilic acrylamide monomers. Our results are found to be in good agreement with the existing experimental data.

  11. Temperature-responsive copolymeric hydrogel systems synthetized by ionizing radiation

    NASA Astrophysics Data System (ADS)

    López-Barriguete, Jesús Eduardo; Bucio, Emilio

    2017-06-01

    Eight different systems of hydrogel copolymers with diverse temperature responsiveness were prepared to elaborate membranes for their biomedical application. The hydrogels were synthesized using poly(N-isopropylacrylamide) (PNIPAAm) and poly(N-vinylcaprolactam) (PNVCL), which have a low critical solution temperature (LCST) close to that of the human body temperature. The networks were synthesized using gamma radiation at a dose rate of 11.2 kGy h-1, and dose of 50 kGy. The LCST of each system was measured by differential scanning calorimetry (DSC). The effect of using hydrophilic monomers of acrylic acid (AAc), methacrylic acid (MAAc), dimethyl acrylamide (DMAAm), and hydroxyethyl methacrylate (HEMA) for the copolymerization on the critical point was evaluated. Five viable systems were obtained, with the best hydrogel being that of poly(NIPAAm-co-DMAAm), which an LCST at 39.8 °C. All the samples were characterized by FTIR-ATR, DSC, TGA, X-Ray Diffraction, and SEM. The proportion of monomers during the formation of the copolymers was decisive in the displacement of the LCST.

  12. Poly(monothiocarbonate)s from the Alternating and Regioselective Copolymerization of Carbonyl Sulfide with Epoxides.

    PubMed

    Luo, Ming; Zhang, Xing-Hong; Darensbourg, Donald J

    2016-10-18

    Carbonyl sulfide (COS) is an air pollutant that causes acid rain, ozonosphere damage, and carbon dioxide (CO2) generation. It is a heterocumulene and structural analogue of CO2. Relevant to organic synthesis, it is a source of C═O or C═S groups and thus an ideal one-carbon (C1) building block for synthesizing sulfur-containing polymers through the similar route of CO2 copolymerization. In contrast, traditional synthesis of sulfur-containing polymers often involves the condensation of thiols with phosgene and ring-opening polymerization of cyclic thiocarbonates that are generally derived from thiols and phosgene; thus, COS/epoxide copolymerization is a "greener" route to supplement or supplant current processes for the production of sulfur-containing polymers. This Accounts highlights our efforts on the discovery of the selective formation of poly(monothiocarbonate)s from COS with epoxides via heterogeneous zinc-cobalt double metal cyanide complex (Zn-Co(III) DMCC) and homogeneous (salen)CrX complexes. The catalytic activity and selectivity of Zn-Co(III) DMCC for COS/epoxide copolymerization are similar to those for CO2/epoxide copolymerization. (salen)CrX complexes accompanied by onium salts exhibited high activity and selectivity for COS/epoxide copolymerization under mild conditions, affording copolymers with >99% monothiocarbonate units and high tail-to-head content up to 99%. By way of contrast, these catalysts often show moderate or low activity for CO2/epoxide copolymerization. Of note, a specialty of COS/epoxide copolymerization is the occurrence of an oxygen-sulfur exchange reaction (O/S ER), which may produce carbonate and dithiocarbonate units. O/S ER, which are induced by the metal-OH bond regenerated by chain transfer reactions, can be kinetically inhibited by changing the reaction conditions. We provide a thorough mechanistic understanding of the electronic/steric effect of the catalysts on the regioselectivity of COS copolymerization. The

  13. Reactivity ratios, and mechanistic insight for anionic ring-opening copolymerization of epoxides

    PubMed Central

    Lee, Bongjae F.; Wolffs, Martin; Delaney, Kris T.; Sprafke, Johannes K.; Leibfarth, Frank A.; Hawker, Craig J.; Lynd, Nathaniel A.

    2012-01-01

    Reactivity ratios were evaluated for anionic ring-opening copolymerizations of ethylene oxide (EO) with either allyl glycidyl ether (AGE) or ethylene glycol vinyl glycidyl ether (EGVGE) using a benzyl alkoxide initiator. The chemical shift for the benzylic protons of the initiator, as measured by 1H NMR spectroscopy, were observed to be sensitive to the sequence of the first two monomers added to the initiator during polymer growth. Using a simple kinetic model for initiation and the first propagation step, reactivity ratios for the copolymerization of AGE and EGVGE with EO could be determined by analysis of the 1H NMR spectroscopy for the resulting copolymer. For the copolymerization between EO and AGE, the reactivity ratios were determined to be rAGE = 1.31 ± 0.26 and rEO = 0.54 ± 0.03, while for EO and EGVGE, the reactivity ratios were rEGVGE = 3.50 ± 0.90 and rEO = 0.32 ± 0.10. These ratios were consistent with the compositional drift observed in the copolymerization between EO and EGVGE, with EGVGE being consumed early in the copolymerization. These experimental results, combined with density functional calculations, allowed a mechanism for oxyanionic ring-opening polymerization that begins with coordination of the Lewis-basic epoxide to the cation to be proposed. The calculated transition-state energies agree qualitatively with the observed relative rates for polymerization. PMID:23226879

  14. Mechanistic Insights into the Carbon Dioxide/Cyclohexene Oxide Copolymerization Reaction: Is One Metal Center Enough?

    PubMed

    González-Fabra, Joan; Castro-Gómez, Fernando; Kleij, Arjan W; Bo, Carles

    2017-03-22

    A detailed study on the mechanism for the alternating copolymerization of cyclohexene oxide (CHO) and CO2 mediated by an [Al{amino-tri(phenolate)}]/NBu4 I binary catalyst system was performed by using DFT-based methods. Four potential mechanisms (one monometallic and three bimetallic) were considered for the first propagation cycle of the CHO/CO2 copolymerization. The obtained Gibbs free energies provided a rationale for the relative high activity of a non-covalent dimeric structure formed in situ and thus for the feasibility of a bimetallic mechanism to obtain polycarbonates quantitatively. Gibbs free energies also indicated that the alternating copolymerization was favored over the cyclic carbonate formation.

  15. Novel palladium(II)-catalyzed copolymerization of carbon monoxide with olefins

    SciTech Connect

    Sen, A.; Lai, T.W.

    1982-01-01

    The catalyst, (Pd(CH/sub 3/CN)/sub 4/)(BF/sub 4/)/sub 2/.n-triphenylphosphine n = (1-3), demonstrated the capacity to mediate the copolymerization of CO with ethylene and other alkenes under very mild conditions. The reaction of ethylene (350 psi), dissolved in acetonitrile, and CO(350 psi) was performed at 25/sup 0/C for 1 d. The copolymerizations of CO(800 psi) with norbornadiene and norbornylene were performed at 60/sup 0/C. The structures of the copolymers were studied by NMR. 9 references, 1 figure.

  16. Mechanical properties of products of thermocatalytic and radiolytic styrene - acrylonitrile copolymerization

    SciTech Connect

    Gadalla, A.M.; Derini, M.A.E.

    1983-12-01

    The mechanical properties of styrene (S)-acrylonitrile (AN) mixtures, ranging from 20 to 80 wt % S, polymerized by thermocatalytic and radiolytic techniques were studied. Maximum compressive and tensile strength was obtained for the mixture containing 60 wt % styrene. The hardness increased with styrene concentration up to 40 wt % and then remained nearly constant. Radiolytic copolymerization gave stronger copolymers than thermal copolymerization since irradiation enhances crosslinking. For the same composition, as the dose increases, the strength increases to a maximum and then decreases due to competing rates of crosslinking and degradation. 5 figures.

  17. The chemical modification and characterization of polypropylene membrane with environment response by in-situ chlorinating graft copolymerization

    NASA Astrophysics Data System (ADS)

    Zhang, Yue; Liu, Jiankai; Hu, Wenjie; Feng, Ying; Zhao, Jiruo

    2017-08-01

    In this study, a novel chemical surface modification method of polyolefin membranes is applied following the in-situ chlorinating graft copolymerization (ISCGC). Polypropylene (PP)/methyl methacrylate (MMA) system was used as an example. A unique structure was formed by the modification process on the original membrane surface and the product exhibited an environmental response. Chlorine free radicals were generated using ultraviolet and heat and were used to capture the hydrogen in the polymer chains on the substrate surface. The formed macromolecular radicals could react with MMA over 2 h to achieve a high coverage ratio polymer on the PP membrane surface. The graft copolymers were characterized using FTIR, 1H-NMR, DSC, and XPS, which all proved the feasibility of chemically modifying the PP membrane surface by ISCGC. The surface morphology of the grafted PP membrane was characterized using SEM and AFM. The results showed that the grafted product presents a uniform, neat, and dense mastoid structure with an average thickness of 4.44 μm, which was expected to be similar to the brush-like surface structure. The contact angle and AFM tests indicated that the product surface is responsive to solvent and pH. The experimental results showed that the PP membrane surface structure can be reconstructed using ISCGC, a method that can be used for environment-responsive polymer materials. Moreover, the product has the characteristics of polymer interfacial brush.

  18. o-Phenylene-bridged Cp/sulfonamido titanium complexes for ethylene/1-octene copolymerization.

    PubMed

    Joe, Dae June; Wu, Chun Ji; Bok, Taekki; Lee, Eun Jung; Lee, Choong Hoon; Han, Won-Sik; Kang, Sang Ook; Lee, Bun Yeoul

    2006-09-07

    The Suzuki-coupling reaction of 2-(dihydroxyboryl)-3,4-dimethyl-2-cyclopenten-1-one and 2-(dihydroxyboryl)-3-methyl-2-cyclopenten-1-one with 2-bromoaniline derivatives affords cyclopentenone compounds from which cyclopentadiene compounds, 4,6-R'(2)-2-(2,5-Me2C5H3)C6H2NH2 and 4,6-R'(2)-2-(2,3,5-Me3C5H2)C6H2NH2 are prepared. After sulfonation of the -NH2 group with p-TsCl, metallation is carried out by successive addition of Ti(NMe2)4 and Me2SiCl2 affording o-phenylene-bridged Cp/sulfonamido titanium dichloride complexes, [4,6-R'(2)-2-(2,5-Me2C5H2)C6H2NSO2C6H4CH3)]TiCl2 (R'=H, ; R'=Me, ; R'=F, ) and [4,6-R'(2)-2-(2,3,5-Me3C5H)C6H2NSO2C6H4CH3)]TiCl2 (R'=H, ; R'=Me, ; R'=F, ). The molecular structures of and [2-(2,5-Me2C5H2)C6H4NSO2C6H4CH3)]Ti(NMe2)2 are determined by X-ray crystallography. The Cp(centroid)-Ti-N angle in is smaller (100.90 degrees) than that observed for the CGC (constrained-geometry catalyst), [Me2Si(eta5-Me4Cp)(NtBu)]TiCl2 (107.6 degrees) indicating a more "constrained feature" in than in the CGC. Complex shows the highest activity among the newly prepared complexes in ethylene/1-octene copolymerization but it is slightly inferior to the CGC in terms of activity, comonomer-incorporation ability, and molecular weight of the obtained polymers.

  19. Synthesis and Characterization of Amphiphilic Graft Copolymers of Poly (1,3dioxolane) Macromonomers with Styrene and Methyl Methacrylate

    NASA Astrophysics Data System (ADS)

    Bendaikha, H.; Clisson, G.; Khoukh, A.; François, J.; Kada, S. Ould; Krallafa, A.

    2008-08-01

    Methacrylate-terminated Poly (1,3dioxolane) (PDXL) macromonomers were synthesized by cationic ring-opening polymerization in the presence of 2-hydroxypropyl methacrylate (2-HPMA) as transfer agent. Molecular weights and polydispersity index of the PDXL macromonomers were evaluated by size exclusion chromatography (SEC) and 1H-NMR. Copolymerizations of PDXL macromonomers with styrene (St) and methyl methacrylate (MMA) were carried out using various feed molar ratios. Monomer reactivity ratios between the macromonomers and the comonomers were estimated from the copolymerization results. Glass transition temperatures of the copolymers were found to decrease with an increase in the amount of PDXL in the copolymers.

  20. Methylation matters

    PubMed Central

    Costello, J.; Plass, C.

    2001-01-01

    DNA methylation is not just for basic scientists any more. There is a growing awareness in the medical field that having the correct pattern of genomic methylation is essential for healthy cells and organs. If methylation patterns are not properly established or maintained, disorders as diverse as mental retardation, immune deficiency, and sporadic or inherited cancers may follow. Through inappropriate silencing of growth regulating genes and simultaneous destabilisation of whole chromosomes, methylation defects help create a chaotic state from which cancer cells evolve. Methylation defects are present in cells before the onset of obvious malignancy and therefore cannot be explained simply as a consequence of a deregulated cancer cell. Researchers are now able to detect with exquisite sensitivity the cells harbouring methylation defects, sometimes months or years before the time when cancer is clinically detectable. Furthermore, aberrant methylation of specific genes has been directly linked with the tumour response to chemotherapy and patient survival. Advances in our ability to observe the methylation status of the entire cancer cell genome have led us to the unmistakable conclusion that methylation abnormalities are far more prevalent than expected. This methylomics approach permits the integration of an ever growing repertoire of methylation defects with the genetic alterations catalogued from tumours over the past two decades. Here we discuss the current knowledge of DNA methylation in normal cells and disease states, and how this relates directly to our current understanding of the mechanisms by which tumours arise.


Keywords: methylation; cancer PMID:11333864

  1. Improvement of holographic thermal stability in phenanthrenequinone-doped poly(methyl methacrylate-co-methacrylic acid) photopolymer

    NASA Astrophysics Data System (ADS)

    Yu, Dan; Liu, Hongpeng; Wang, Heng; Wang, Jian; Jiang, Yongyuan; Sun, Xiudong

    2011-08-01

    Experimental studies of holographic thermal stability in phenanthrenequinone (PQ)-doped poly(methyl methacrylate-co-methacrylic acid) [P(MMA-co-MAA)] photopolymers are presented. A possibility to improve the thermal stability of holograms is demonstrated by doping methacrylic acid (MAA) into the poly(methyl methacrylate) (PMMA) polymer matrix. MAA as a copolymerization monomer can form a more stable polymer matrix with methyl methacrylate (MMA) monomer and increase average molecular weight of photoproducts, which finally depress the diffusion of photoproduct. The optimized MAA concentration copolymerized into P(MMA-co-MAA) polymer matrix can bring nearly a month's lifetime of gratings, which is obviously an improvement over the usual PQ-PMMA material under thermal treatment.

  2. Copolymeric pour-point depressant for diesel fuel

    SciTech Connect

    Ivanov, V.I.; Dadyko, V.A.; Dushechkin, A.P.; Shapkina, L.N.

    1984-03-01

    This article considers the use of a pour-point depressant consisting of a mixture of ethylene with methyl methacrylate (EMMA) and ethylene with vinyl acetate (EVA) to improve the low-temperature indexes of diesel fuels. It is determined that the greatest effect with respect to limiting filterability temperature from the addition of EMMA is achieved with an EVA content of approximately 0.04%. The use of both a copolymer promoting the formation of a large number of crystallization centers (EMMA) and a copolymer that is a good modifier of the wax crystal surface (EVA) leads to a limitation of the crystal growth and preservation of the fine-crystal structure as the fuel temperature is lowered.

  3. Homo-polymerization of alpha-olefins and co-polymerization of higher alpha-olefins with ethylene in the presence of CpTiCl2(OC6H4X-p)/MAO catalysts (X = CH3, Cl).

    PubMed

    Skupinski, W; Nicinski, K; Jamanek, D; Wieczorek, Z

    2005-07-04

    Cyclopentadienyl-titanium complexes containing -OC6H4X ligands (X = Cl,CH3) activated with methylaluminoxane (MAO) were used in the homo-polymerization of ethylene, propylene, 1-butene, 1-pentene, 1-butene, and 1-hexene, and also in co-polymerization of ethylene with the alpha-olefins mentioned. The -X substituents exhibit different electron donor-acceptor properties, which is described by Hammett's factor (sigma). The chlorine atom is electron acceptor, while the methyl group is electron donor. These catalysts allow the preparation of polyethylene in a good yield. Propylene in the presence of the catalysts mentioned dimerizes and oligomerizes to trimers and tetramers at 25 degrees C under normal pressure. If the propylene pressure was increased to 7 atmospheres,CpTiCl2(OC6H4CH3)/MAO catalyst at 25 degrees gave mixtures with different contents of propylene dimers, trimers and tetramers. At 70 degrees C we obtained only propylene trimer. Using the catalysts with a -OC(6)H(4)Cl ligand we obtained atactic polymers with M(w) 182,000 g/mol (at 25 degrees C) and 100,000 g/mol (at 70 degrees C). The superior activity of the CpTiCl2(OC6H4Cl)/MAO catalyst used in polymerization of propylene prompted us to check its activity in polymerization of higher alpha-olefins (1-butene, 1-pentene, 1-hexene)and in co-polymerization of these olefins with ethylene. However, when homo-polymerization was carried out in the presence of this catalyst no polymers were obtained. Gas chromatography analysis revealed the presence of dimers. The activity of the CpTiCl2(OC6H4Cl)/MAO catalyst in the co-polymerization of ethylene with higher alpha-olefins is limited by the length of the co-monomer carbon chain. Hence, the highest catalyst activities were observed in co-polymerization of ethylene with propylene (here a lower pressure of the reagents and shorter reaction time were applied to obtain catalytic activity similar to that for other co-monomers). For other co-monomers the activity of the

  4. Copolymerized and bonded silica nanoparticles as labels and pseudostationary phase in bioanalytical applications (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Patonay, Gabor; Henary, Maged M.; Abdelwahab, Walid; Chapman, Gala

    2017-02-01

    Silica nanoparticles have been increasingly used in developing bioanalytical, biomedical and in many other applications. Silica nanoparticles can easily be synthesized and with the advent of wide availability of modified TEOS reactive analogues only the researcher imagination is the limit of preparing silica nanoparticles that contain different molecules that are either copolymerized inside of the silica nanoparticle or chemically attached (bonded) to the silica nanoparticle surface. Relatively non-porous silica nanoparticles can contain copolymerized dyes for the creation of bright fluorescence labels while the surface of these silica nanoparticles can be bonded with reactive moieties that are suitable for covalently labeling the molecule of interest. Also the surface bonded moieties can serve other purposes, e.g., molecular recognition either on a non-fluorescent or fluorescent silica nanoparticle. As far as the fluorescent nanoparticles development concerns near-infrared (NIR) absorbing carbocyanine dyes have been increasingly used as they can be useful for developing bioanalytical, biomedical methods and in many other applications. Carbocyanines are preferred as they are relatively easy to synthesize and can be designed to achieve particular spectroscopic properties. For example either copolymerized or surface bound dyes can contain appropriate functional moieties absorption and fluorescence properties change when it is complexed to metal ions, to detect pH changes, bind to biological molecules, etc. Fluorescence intensity of carbocyanines significantly increases by enclosing several dye molecules in a single silica nanoparticle due to shielding however self quenching may become a problem at high dye concentrations in confined spaces. Large Stokes' shift dyes can significantly decrease this problem. This can be achieved by substituting meso position halogens in the NIR fluorescent carbocyanines with a linker containing amino moiety which can also serve as

  5. Radiolysis of Resist Polymers. III. Copolymers of Methyl-Alpha-Chloroacrylate and Trihaloethylmethacrylates.

    DTIC Science & Technology

    1983-08-01

    copolymerization reactivity ratios crosslinking scission radiolysis product analysis e 20. ABSTRACT (Continue on reverse side if necessary and identify by block...8217-chloroacrylate (MCA) of a range of composition were synthesized. Radiolysis of copolymers are initiated by Li dissociative electron capture by the...773 TECHNICAL REPORT NO. 3 Radiolysis of Resist Polymers. Ill. Copolymers of Methyl-a-Chloroacrylate and Trihaloethylmethacrylates P. By G.N. Babu, P.H

  6. Sequential elution of multiply and singly phosphorylated peptides with polar-copolymerized mixed-mode RP18/SCX material.

    PubMed

    Li, Xiuling; Guo, Zhimou; Sheng, Qianying; Xue, Xingya; Liang, Xinmiao

    2012-06-21

    Novel polar-copolymerized mixed-mode RP18/SCX material was developed for feasible phosphopeptide enrichment, in which multiply and singly phosphorylated peptides could be sequentially eluted and separated with high selectivity.

  7. Antimicrobial cotton containing N-halamine and quaternary ammonium groups by grafting copolymerization

    NASA Astrophysics Data System (ADS)

    Liu, Ying; Liu, Yin; Ren, Xuehong; Huang, T. S.

    2014-03-01

    The monomer (3-acrylamidopropyl)trimethylammonium chloride (APTMAC) was used to treat cotton fibers by grafting copolymerization. The grafted cotton fabrics were characterized by SEM image and FTIR spectra. The treated samples with quaternary ammonium groups could decrease 96.08% of Staphylococcus aureus and 48.74% of Escherichia coli O157:H7 within 30 min. After chlorination with dilute sodium hypochlorite, the treated cotton fabrics containing both N-halamine and quaternary ammonium groups effectively inactivated 100% (log reduction 5.82) of S. aureus and 100% (log reduction 6.26) of E. coli O157:H7 within 5 min of contact time. The grafting process of cotton fabric has small effect on the thermal stability and tensile strength, which favors the practical application. Compared to the traditional pad-dry-cure method to produce antibacterial materials, the radical grafting copolymerization method occurred in water without any organic solvents involved in the whole treatment.

  8. Fabrication of microarray of gel-immobilized compounds on a chip by copolymerization.

    SciTech Connect

    Vasiliskov, A. V.; Timofeev, E. N.; Surzhikov, S. A.; Drobyshev, A. L.; Shick, V. V.; Mirzabekov, A. D.; Biochip Technology Center; Engelhardt Inst. of Molecular Biology; Moscow Inst. of Physics and Technology

    1999-09-01

    The manufacturing of microchips containing oligonucleotides and proteins immobilized within gel pads, ranging in size from 10 x 10 to 100 x 100 {mu}m, is described. The microchips are produced by photo- or persulfate-induced copolymerization of unsaturated derivatives of biomolecules with acrylamide-bisacrylamide mixture. Oligonucleotides containing 5'-allyl or 5'-butenediol units were synthesized using standard phosphoramidite chemistry. Acryloyl residues were attached to a protein by a twostep procedure. Photopolymerization was induced by illumination of the monomer solution containing initiator with UV light through the mask. The mask was applied directly over the monomer solution or projected through a microscope. Alternatively, copolymerization was carried out in drops of aqueous solution of monomers containing ammonium persulfate. Drops with different allyl-oligonucleotides were distributed on a glass slide, and the polymerization was induced by diffusion of N,N,N',N'-tetramethylethylenediamine (TEMED) from a hexane solution that covered the aqueous drops.

  9. Copolymerization of glycidyl ethers with CO/sub 2/ on a homogeneous catalyst

    SciTech Connect

    Kudashev, R.K.; Glukhov, E.A.; Kuramshina, E.A.; Monakov, Y.B.; Gailyunas, I.A.; Rafikov, S.R.

    1987-08-01

    The authors have investigated the relative reactivity of glycidyl ethers in copolymerization with CO/sub 2/ in the presence of the catalytic system Al(i-C/sub 4/H/sub 9/)/sub 3/-H/sub 2/O-epichlorohydrin. Solid CO/sub 2/ was introduced into the chilled autoclave, which contained toluene (the solvent), the epoxy compound, and epichlorohydrin. A relative reactivity series for glycidyl ethers in copolymerization with CO/sub 2/ in the presence of the system Al(i-C/sub 4/H/sub 9/)/sub 3/-H/sub 2/O-EPC has been established, which is connected with a dual type of the active centers present in the system. The viscous flow properties of the copolymers depend on the content of the CO/sub 2/-groups.

  10. Zwitterionic monomer graft copolymerization onto polyurethane surface through a PEG spacer

    NASA Astrophysics Data System (ADS)

    Huang, Jingjing; Xu, Weilin

    2010-04-01

    A new zwitterionic surface was obtained by a novel three-step grafting procedure. The zwitterionic monomer was introduced by cerium-induced graft copolymerization in the presence of N,N'-methylene bisacrylamide (MBAA) as cross-linking agent. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the MBAA could stimulate zwitterionic monomer grafting onto the membrane surface. Surface properties were also determined by atomic force microscope (AFM) and water contact angle. The hemocompatibility of the modified PU membranes was evaluated by the activated partial thromboplastin time (APTT), thrombin time (TT) and prothrombin time (PT). The TT and APTT of PU were significantly prolonged by the zwitterion of sulfobetaine monomer grafting copolymerization. The new polyurethane membrane could have a great potential in biomedical applications.

  11. Theoretical models of nonlinear effects in two-component cooperative supramolecular copolymerizations

    PubMed Central

    Markvoort, Albert J.; ten Eikelder, Huub M.M.; Hilbers, Peter A.J.; de Greef, Tom F.A.; Meijer, E.W.

    2011-01-01

    The understanding of multi-component mixtures of self-assembling molecules under thermodynamic equilibrium can only be advanced by a combined experimental and theoretical approach. In such systems, small differences in association energy between the various components can be significantly amplified at the supramolecular level via intricate nonlinear effects. Here we report a theoretical investigation of two-component, self-assembling systems in order to rationalize chiral amplification in cooperative supramolecular copolymerizations. Unlike previous models based on theories developed for covalent polymers, the models presented here take into account the equilibrium between the monomer pool and supramolecular polymers, and the cooperative growth of the latter. Using two distinct methodologies, that is, solving mass-balance equations and stochastic simulation, we show that monomer exchange accounts for numerous unexplained observations in chiral amplification in supramolecular copolymerization. In analogy with asymmetric catalysis, amplification of chirality in supramolecular polymers results in an asymmetric depletion of the enantiomerically related monomer pool. PMID:22027589

  12. EPR investigation on radiation-induced graft copolymerization of styrene onto polyethylene: Energy transfer effects

    NASA Astrophysics Data System (ADS)

    Salih, M. A.; Buttafava, A.; Ravasio, U.; Mariani, M.; Faucitano, A.

    2007-08-01

    In this paper, energy transfer phenomena concerning the in-source graft copolymerization of styrene onto LDPE were investigated through the EPR analysis of the radical intermediates. The model solution experiments have shown a substantial deviation of the experimental G (radicals) values with respect to the additivity law, which reflect the negative effect of the styrene monomer concentration on the initiation rate of the graft copolymerization. The EPR measurements performed on polyethylene- co-styrene graft copolymers of various composition following low-temperature vacuum gamma irradiation have confirmed the decrease of the total radical yields with increasing the styrene concentration. The effect was partly attributed to the heterogeneity of the graft copolymer matrix and to the lack of molecular mobility in the solid state at low temperature, which prevents the attainment of the favourable geometrical configurations in intermolecular energy and charge transfer events.

  13. A facile approach toward multifunctional polyethersulfone membranes via in situ cross-linked copolymerization.

    PubMed

    Sun, Chuangchao; Ji, Haifeng; Qin, Hui; Nie, Shengqiang; Zhao, Weifeng; Zhao, Changsheng

    2015-01-01

    In this study, multifunctional polyethersulfone (PES) membranes are prepared via in situ cross-linked copolymerization coupled with a liquid-liquid phase separation technique. Acrylic acid (AA) and N-vinylpyrrolidone (VP) are copolymerized in PES solution, and the solution is then directly used to prepare PES membranes. The infrared and X-ray photoelectron spectroscopy testing, scanning electron microscopy, and water contact angle measurements confirm the successful modification of pristine PES membrane. Protein adsorption, platelet adhesion, plasma recalcification time, and activated partial thromboplastin time assays convince that the modified PES membranes have a better biocompatibility than pristine PES membrane. In addition, the modified membranes showed good protein antifouling property and significant adsorption property of cationic dye. The loading of Ag nanoparticles into the modified membranes endows the composite membranes with antibacterial activity.

  14. Copolymerization of ethylene with polar monomer by α - diimine nickel complex

    NASA Astrophysics Data System (ADS)

    Han, Yiqin; Zhang, Danfeng

    2017-09-01

    Copolymerization of ethylene and ethyl acrylate was carried out by α-diimine nickel catalyst [ArN=CH-CH=NAr]NiBr2 (Ar = 2,6-C6H3(CH3)2) in the presence of methylaluminoxane (MAO). The effects of experimental conditions in which mole ratio of Al/Ni, concentration of polar monomer, polymerization temperature, ethylene pressure and polymerization time varied on ethylene-ethyl acrylate copolymerization were investigated. The structures of the obtained copolymers were characterized by high-temperature NMR and FT-IR. It was found that Al/Ni mole ratio was 1000, the concentration of ethyl acrylate was 10 mmol/L, the polymerization temperature was 30 °C, the ethylene pressure was 10 atm, the polymerization time was 4 h, the molecular weight of the polymer and the incorporation of ethyl acrylate in the copolymer reached the good result.

  15. RAFT Dispersion Alternating Copolymerization of Styrene with N-Phenylmaleimide: Morphology Control and Application as an Aqueous Foam Stabilizer

    PubMed Central

    2016-01-01

    We report a new nonaqueous polymerization-induced self-assembly (PISA) formulation based on the reversible addition–fragmentation chain transfer (RAFT) dispersion alternating copolymerization of styrene with N-phenylmaleimide using a nonionic poly(N,N-dimethylacrylamide) stabilizer in a 50/50 w/w ethanol/methyl ethyl ketone (MEK) mixture. The MEK cosolvent is significantly less toxic than the 1,4-dioxane cosolvent reported previously [YangP.; Macromolecules2013, 46, 8545−8556]. The core-forming alternating copolymer block has a relatively high glass transition temperature (Tg), which leads to vesicular morphologies being observed during PISA, as well as the more typical sphere and worm phases. Each of these copolymer morphologies has been characterized by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) studies. TEM studies reveal micrometer-sized elliptical particles with internal structure, with SAXS analysis suggesting an oligolamellar vesicle morphology. This structure differs from that previously reported for a closely related PISA formulation utilizing a poly(methacrylic acid) stabilizer block for which unilamellar platelet-like particles are observed by TEM and SAXS. This suggests that interlamellar interactions are governed by the nature of the steric stabilizer layer. Moreover, using the MEK cosolvent also enables access to a unilamellar vesicular morphology, despite the high Tg of the alternating copolymer core-forming block. This was achieved by simply conducting the PISA synthesis at a higher temperature for a longer reaction time (80 °C for 24 h). Presumably, MEK solvates the core-forming block more than the previously utilized 1,4-dioxane cosolvent, which leads to greater chain mobility. Finally, preliminary experiments indicate that the worms are much more efficient stabilizers for aqueous foams than either the spheres or the oligolamellar elliptical vesicles. PMID:27708458

  16. Oxidation-Responsive and "Clickable" Poly(ethylene glycol) via Copolymerization of 2-(Methylthio)ethyl Glycidyl Ether.

    PubMed

    Herzberger, Jana; Fischer, Karl; Leibig, Daniel; Bros, Matthias; Thiermann, Raphael; Frey, Holger

    2016-07-27

    Poly(ethylene glycol) (PEG) is a widely used biocompatible polymer. We describe a novel epoxide monomer with methyl-thioether moiety, 2-(methylthio)ethyl glycidyl ether (MTEGE), which enables the synthesis of well-defined thioether-functional poly(ethylene glycol). Random and block mPEG-b-PMTEGE copolymers (Mw/Mn = 1.05-1.17) were obtained via anionic ring opening polymerization (AROP) with molecular weights ranging from 5 600 to 12 000 g·mol(-1). The statistical copolymerization of MTEGE with ethylene oxide results in a random microstructure (rEO = 0.92 ± 0.02 and rMTEG E = 1.06 ± 0.02), which was confirmed by in situ (1)H NMR kinetic studies. The random copolymers are thermoresponsive in aqueous solution, with a wide range of tunable transition temperatures of 88 to 28 °C. In contrast, mPEG-b-PMTEGE block copolymers formed well-defined micelles (Rh ≈ 9-15 nm) in water, studied by detailed light scattering (DLS and SLS). Intriguingly, the thioether moieties of MTEGE can be selectively oxidized into sulfoxide units, leading to full disassembly of the micelles, as confirmed by detection of pure unimers (DLS and SLS). Oxidation-responsive release of encapsulated Nile Red demonstrates the potential of these micelles as redox-responsive nanocarriers. MTT assays showed only minor effects of the thioethers and their oxidized derivatives on the cellular metabolism of WEHI-164 and HEK-293T cell lines (1-1000 μg·mL(-1)). Further, sulfonium PEG polyelectrolytes can be obtained via alkylation or alkoxylation of MTEGE, providing access to a large variety of functional groups at the charged sulfur atom.

  17. Separation of actinide(III) from lanthanide(III) by thermo-sensitive gel co-polymerized with TPPEN derivatives

    SciTech Connect

    Takeshita, Kenji; Fugate, Glenn; Matsumura, Tatsuro; Nakano, Yoshio; Mori, Atsunori; Fukuoka, Sachio

    2007-07-01

    Extraction separation of Am(III) and Eu(III) was examined by the thermal-swing extraction technique using a thermo-sensitive gel, poly-N-isopropyl-acrylamide (NIPA) co-polymerized with a TPEN derivative, N,N,N',N'- tetrakis(4-propenyl-oxy-2-pyridyl-methyl)ethylenediamine (TPPEN). The separation of Am(III) from Eu(III) was observed in the swollen state of gel (5 deg. C) and the separation factor of Am(III) was evaluated as about 18 at pH 5.2. More than 90% of Am(III) extracted into the gel was released by the volume phase transition of gel from the swollen state (5 deg. C) to the shrunken one (40 deg. C). The repetition test for the thermal swing extraction of a soft metal ion, Cd(II), which was used as a substitute of Am(III), was carried out and the extraction and release of Cd(II) were repeated three times stably under the thermal-swing operation between 5 deg. C and 40 deg. C. The radiation effect of gel on the extraction of Am and Eu was tested by the irradiation of {gamma}-ray (10 kGy) and the long-term adsorption of {alpha}-emitter ({sup 244}Cm). The TPPEN-NIPA gel sustained no damage by these radiation tests. These results suggest that the thermal-swing extraction technique is applicable to the MA partitioning process indispensable for the establishment of P and T technology. (authors)

  18. Tailored Living Block Copolymerization: Multiblock Poly(cyclohexene carbonate)s with Sequence Control

    SciTech Connect

    Kim, Jeung Gon; Cowman, Christina D.; LaPointe, Anne M.; Wiesner, Ulrich; Coates, Geoffrey W.

    2011-03-08

    In this Communication, the living block copolymerization of functionalized cyclohexene oxides and CO{sub 2} is described, yielding multiblock poly(cyclohexene carbonate)s [p(CHC)s] with a diverse range of functionality on the side chains and good control of block sequence and length. Unlike prior systems that contain stable vinyl backbones, the carbonate backbones of polymers reported herein are degradable, allowing possible applications where removable templates are required.

  19. Methyl chloroform

    SciTech Connect

    Wray, T.K.

    1994-04-01

    Methyl chloroform is identified as a Class 1 ozone-depleting substance under Title VI of the CAA Amendments. On Nov. 30, 1993, EPA ordered the phaseout of Class 1 ozone-depleting substances -- chlorofluorocarbons (CFCs), halons, carbon tetrachloride and methyl chloroform -- by Jan. 1, 1996. Methyl chloroform and other Class 1 substances may be used after the dead-line if sources can be found through recycling or existing inventories. Methyl chloroform is listed as a hazardous air pollutant under CAA. It also is a SARA Title III, Sec. 313 compound with a reportable quantity of 1,000 pounds. OSHA and the American Conference of Government Industrial Hygienists have set 350 ppm as the time-weighted average airborne exposure level for methyl chloroform. NIOSH lists its immediately dangerous to life or health'' concentration as 1,000 parts per million. DOT identifies the substance as a hazardous material, Class 6.1 (poison).

  20. Nickel(0)-catalyzed cycloaddition copolymerization involving two diynes and carbon dioxide to poly(2-pyrone)

    SciTech Connect

    Tsuda, Tetsuo; Ooi, Osamu; Maruta, Ken-ichi )

    1993-08-01

    A copolymerizability order of five diynes, i.e., 3,11-tetradecadiyne (A), 2,6-octadiyne (B), 1,4-di(2-hexynyl)benzene (C), 1,3-di(2-hexynyl)benzene (D), and 1,7-cyclotridecadiyne (E), in the nickel(0)-catalyzed 1:1 cycloaddition copolymerization of the diyne with CO[sub 2] to the poly(2-pyrone) was determined by the nickel(0)-catalyzed copolymerization involving two diynes and CO[sub 2]. The copolymerizability order obtained by analyzing the copolymer composition using [sup 1]H NMR spectroscopy was A [gt] E [gt] B [gt] C [gt] D. This order was explained in terms of the steric hindrance exerted by the substituent on the terminal C[triple bond]C bond of the cooligomer or the copolymer to its cycloaddition along with mobility of its terminal C[triple bond]C bond moiety for the cycloaddition. An order of cycloaddition reactivity of the diyne, which is related to formation of the cooligomer, was determined by measuring the unreacted diyne in the copolymerization involving five diynes and CO[sub 2] using gas chromatography. The result was E [gt] B [gt] C [gt] D [gt] A. Thus high copolymerizability of diyne A is noteworthy.

  1. Tailored synthesis of amine N-halamine copolymerized polystyrene with capability of killing bacteria.

    PubMed

    Cai, Qian; Bao, Sarina; Zhao, Yue; Zhao, Tianyi; Xiao, Linghan; Gao, Ge; Chokto, Harnoode; Dong, Alideertu

    2015-04-15

    Novel amine N-halamine copolymerized polystyrene (ANHCPS) nanostructures were controllably fabricated as potent antibiotics by using the surfactant-free emulsion copolymerization for killing pathogenic bacteria. The morphology and size of the ANHCPS were well tailored by tuning reaction conditions such as monomer molar ratio, temperature, and copolymerization time. Effect of chlorination aging time on the oxidative chlorine content in the ANHCPS was established, and the oxidative chlorine content was determined by the modified iodometric/thiosulfate technique. Antibacterial behavior of the ANHCPS on bacterial strain was evaluated using Staphylococcus aureus and Escherichia coli as model pathogenic bacteria via the plate counting technique, inhibition zone study, and time-kill assay. Antimicrobial results illustrated that the ANHCPS possessed superior antibacterial capability of killing pathogenic bacteria. The destruction induced by the ANHCPS on bacterial surface structure was proven by using SEM technique. The effect of the oxidative chlorine content and morphology/size on the antimicrobial capability was constructed as well. This study provides us a novel approach for controllably synthesizing amine N-halamine polymers, and making them the potent candidates for killing bacteria or even the control of microorganism contamination.

  2. Methyl methacrylate

    Integrated Risk Information System (IRIS)

    TOXICOLOGICAL REVIEW of METHYL METHACRYLATE ( CAS No . 80 - 62 - 6 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) January 1998 U.S . Environmental Protection Agency Washington , DC TABLE OF CONTENTS DISCLAIMER . . . . . . . . . . . . . . . . . . . . . . . . .

  3. CG methylation.

    PubMed

    Vinson, Charles; Chatterjee, Raghunath

    2012-12-01

    A striking feature of mammalian genomes is the paucity of the CG dinucleotide. There are approximately 20,000 regions termed CpG islands where CGs cluster. This represents 5% of all CGs and 1% of the genome. CpG islands are typically unmethylated and are often promoters for housekeeping genes. The remaining 95% of CG dinucleotides are disposed throughout 99% of the genome and are typically methylated and found in half of all promoters. CG methylation facilitates binding of the C/EBP family of transcription factors, proteins critical for differentiation of many tissues. This allows these proteins to localize in the methylated CG poor regions of the genome where they may produce advantageous changes in gene expression at nearby or more distant regions of the genome. In this review, our growing understanding of the consequences of CG methylation will be surveyed.

  4. Development of Highly Active and Regioselective Catalysts for the Copolymerization of Epoxides with Cyclic Anhydrides: An Unanticipated Effect of Electronic Variation.

    PubMed

    DiCiccio, Angela M; Longo, Julie M; Rodríguez-Calero, Gabriel G; Coates, Geoffrey W

    2016-06-08

    Recent developments in polyester synthesis have established several systems based on zinc, chromium, cobalt, and aluminum catalysts for the ring-opening alternating copolymerization of epoxides with cyclic anhydrides. However, to date, regioselective processes for this copolymerization have remained relatively unexplored. Herein we report the development of a highly active, regioselective system for the copolymerization of a variety of terminal epoxides and cyclic anhydrides. Unexpectedly, electron withdrawing substituents on the salen framework resulted in a more redox stable Co(III) species and longer catalyst lifetime. Using enantiopure propylene oxide, we synthesized semicrystalline polyesters via the copolymerization of a range of epoxide/anhydride monomer pairs.

  5. Control of Grafting Density and Distribution in Graft Polymers by Living Ring-Opening Metathesis Copolymerization.

    PubMed

    Lin, Tzu-Pin; Chang, Alice B; Chen, Hsiang-Yun; Liberman-Martin, Allegra L; Bates, Christopher M; Voegtle, Matthew J; Bauer, Christina A; Grubbs, Robert H

    2017-03-15

    Control over polymer sequence and architecture is crucial to both understanding structure-property relationships and designing functional materials. In pursuit of these goals, we developed a new synthetic approach that enables facile manipulation of the density and distribution of grafts in polymers via living ring-opening metathesis polymerization (ROMP). Discrete endo,exo-norbornenyl dialkylesters (dimethyl DME, diethyl DEE, di-n-butyl DBE) were strategically designed to copolymerize with a norbornene-functionalized polystyrene (PS), polylactide (PLA), or polydimethylsiloxane (PDMS) macromonomer mediated by the third-generation metathesis catalyst (G3). The small-molecule diesters act as diluents that increase the average distance between grafted side chains, generating polymers with variable grafting density. The grafting density (number of side chains/number of norbornene backbone repeats) could be straightforwardly controlled by the macromonomer/diluent feed ratio. To gain insight into the copolymer sequence and architecture, self-propagation and cross-propagation rate constants were determined according to a terminal copolymerization model. These kinetic analyses suggest that copolymerizing a macromonomer/diluent pair with evenly matched self-propagation rate constants favors randomly distributed side chains. As the disparity between macromonomer and diluent homopolymerization rates increases, the reactivity ratios depart from unity, leading to an increase in gradient tendency. To demonstrate the effectiveness of our method, an array of monodisperse polymers (PLA(x)-ran-DME(1-x))n bearing variable grafting densities (x = 1.0, 0.75, 0.5, 0.25) and total backbone degrees of polymerization (n = 167, 133, 100, 67, 33) were synthesized. The approach disclosed in this work therefore constitutes a powerful strategy for the synthesis of polymers spanning the linear-to-bottlebrush regimes with controlled grafting density and side chain distribution, molecular

  6. Y-shaped Folic Acid-Conjugated PEG-PCL Copolymeric Micelles for Delivery of Curcumin.

    PubMed

    Feng, Runliang; Zhu, Wenxia; Chu, Wei; Teng, Fangfang; Meng, Ning; Deng, Peizong; Song, Zhimei

    2017-01-01

    Curcumin is a natural hydrophobic product showing anticancer activity. Many studies show its potential use in the field of cancer treatment due to its safety and efficiency. However, its application is limited due to its low water-solubility and poor selective delivery to cancer. A Y-shaped folic acid-modified poly (ethylene glycol)-b-poly (ε-caprolactone)2 copolymer was prepared to improve curcumin solubility and realize its selective delivery to cancer. The copolymer was synthesized through selective acylation reaction of folic acid with α- monoamino poly(ethylene glycol)-b-poly(ε-caprolactone)2. Curcumin was encapsulated into the copolymeric micelles with 93.71% of encapsulation efficiency and 11.94 % of loading capacity. The results from confocal microscopy and cellular uptake tests showed that folic acid-modified copolymeric micelles could improve cellular uptake of curcumin in Hela and HepG2 cells compared with folic acid-unmodified micelles. In vitro cytotoxicity assay showed that folic acid-modified micelles improved anticancer activity against Hela and HepG2 cells in comparison to folic acidunmodified micelles. Meanwhile, both drug-loaded micelles demonstrated higher activity against Hela cell lines than HepG2. The research results suggested that the folic acid-modified Y-shaped copolymeric micelles should be used to enhance hydrophobic anticancer drugs' solubility and their specific delivery to folic acid receptors-overexpressed cancer. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  7. DNA Methylation

    PubMed Central

    Marinus, M.G.; Løbner-Olesen, A.

    2014-01-01

    The DNA of E. coli contains 19,120 6-methyladenines and 12,045 5-methylcytosines in addition to the four regular bases and these are formed by the postreplicative action of three DNA methyltransferases. The majority of the methylated bases are formed by the Dam and Dcm methyltransferases encoded by the dam (DNA adenine methyltransferase) and dcm (DNA cytosine methyltransferase) genes. Although not essential, Dam methylation is important for strand discrimination during repair of replication errors, controlling the frequency of initiation of chromosome replication at oriC, and regulation of transcription initiation at promoters containing GATC sequences. In contrast, there is no known function for Dcm methylation although Dcm recognition sites constitute sequence motifs for Very Short Patch repair of T/G base mismatches. In certain bacteria (e.g., Vibrio cholerae, Caulobacter crescentus) adenine methylation is essential and in C. crescentus, it is important for temporal gene expression which, in turn, is required for coordinating chromosome initiation, replication and division. In practical terms, Dam and Dcm methylation can inhibit restriction enzyme cleavage; decrease transformation frequency in certain bacteria; decrease the stability of short direct repeats; are necessary for site-directed mutagenesis; and to probe eukaryotic structure and function. PMID:26442938

  8. Relative rates for plasma homo- and copolymerizations of olefins in a homologous series of fluorinated ethylenes

    NASA Technical Reports Server (NTRS)

    Golub, M. A.; Wydeven, T.

    1997-01-01

    It is well known that the rate of plasma polymerization, or deposition rate, of a given monomer depends on various plasma process parameters, e.g., monomer flow rate, pressure, power, frequency (DC, rf or microwave), location of the substrate in the reactor, reactor geometry or configuration, and temperature. In contrast, little work has been done to relate deposition rates to monomer structures for a homologous series of monomers where the rates are obtained under identical plasma process parameters. For the particular series of fluorinated ethylenes (C2HxF4-x; x = 0-4), deposition rates were reported for ethylene (ET), vinyl fluoride, vinylidene fluoride and tetrafluoroethylene (TFE), but for plasma polymerizations carried out under different discharge conditions, e.g., pressure, current density, and electrode temperature. Apparently, relative deposition rates were reported for only two members of that series (ET, x = 4, and TFE, x = 0) for which the plasma polymerizations were conducted under identical conditions. We now present relative deposition rates for both homopolymerizations and copolymerizations of the entire series of fluorinated ethylenes (x = 0-4). Our interest in such rates stems from prior work on the plasma copolymerization of ET and TFE in which it was found that the deposition rates for the plasma copolymers, when plotted versus mol % TFE in the ET/TFE feed stock, followed a concave-downward curve situated above the straight line joining the deposition rates for the plasma homopolymers. This type of plot (observed also for an argon-ET/TFE plasma copolymerization) indicated a positive interaction between ET and TFE such that each monomer apparently "sensitized" the plasma copolymerization of the other. Since the shape of that plot is not altered if mol % TFE is replaced by F/C, the fluorine-to-carbon ratio, this paper aims (1) to show how the relative deposition rates for plasma copolymers drawn from all pairs of monomers in the C2HxF4-x series

  9. Near-infrared luminescent copolymerized hybrid materials built from tin nanoclusters and PMMA.

    PubMed

    Fan, Weiqiang; Feng, Jing; Song, Shuyan; Lei, Yongqian; Zhou, Liang; Zheng, Guoli; Dang, Song; Wang, Song; Zhang, Hongjie

    2010-10-01

    Novel near-infrared (NIR) luminescent copolymerized hybrid materials were prepared by covalently grafting and physically doping Ln complexes (Ln = Er, Sm, Yb, and Nd) into a copolymer matrix built from nanobuilding blocks. The structures of the obtained hybrid materials were investigated by Fourier transform infrared (FTIR) spectra, nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). In the photoluminescence studies, the hybrid materials showed characteristic NIR luminescence of corresponding Ln(3+) ions through intramolecular energy transfer from ligands to Ln(3+) ions. Transparent films of these materials can be easily prepared through spin-coating on indium tin oxide (ITO) glasses taking advantage of the matrix nature.

  10. Mechanistic aspects of the alternating copolymerization of carbon monoxide with olefins catalyzed by cationic palladium complexes

    SciTech Connect

    Batistini, A.; Consiglio, G.

    1992-05-01

    The copolymerization of propylene with carbon monoxide using a catalytic system based on palladium acetate, modified with the atropisomeric chiral ligand (S)-(6,6{prime}-dimethylbiphenyl-2,2{prime}-diyl)bis(dicyclohexylphosphine), gives poly[spiro-2,5-(3-methyltetrahydrofuran)]. This material is transformed into the isomeric poly(1-oxo-2-methyltrimethylene) by dissolution in hexafluoro-2-propanol and precipitation with methanol. A mechanism based on a carbene intermediate is proposed in order to account for the formation of the polyketone material in the spiroketal form. 22 refs., 1 fig.

  11. Relative rates for plasma homo- and copolymerizations of olefins in a homologous series of fluorinated ethylenes

    NASA Technical Reports Server (NTRS)

    Golub, M. A.; Wydeven, T.

    1997-01-01

    It is well known that the rate of plasma polymerization, or deposition rate, of a given monomer depends on various plasma process parameters, e.g., monomer flow rate, pressure, power, frequency (DC, rf or microwave), location of the substrate in the reactor, reactor geometry or configuration, and temperature. In contrast, little work has been done to relate deposition rates to monomer structures for a homologous series of monomers where the rates are obtained under identical plasma process parameters. For the particular series of fluorinated ethylenes (C2HxF4-x; x = 0-4), deposition rates were reported for ethylene (ET), vinyl fluoride, vinylidene fluoride and tetrafluoroethylene (TFE), but for plasma polymerizations carried out under different discharge conditions, e.g., pressure, current density, and electrode temperature. Apparently, relative deposition rates were reported for only two members of that series (ET, x = 4, and TFE, x = 0) for which the plasma polymerizations were conducted under identical conditions. We now present relative deposition rates for both homopolymerizations and copolymerizations of the entire series of fluorinated ethylenes (x = 0-4). Our interest in such rates stems from prior work on the plasma copolymerization of ET and TFE in which it was found that the deposition rates for the plasma copolymers, when plotted versus mol % TFE in the ET/TFE feed stock, followed a concave-downward curve situated above the straight line joining the deposition rates for the plasma homopolymers. This type of plot (observed also for an argon-ET/TFE plasma copolymerization) indicated a positive interaction between ET and TFE such that each monomer apparently "sensitized" the plasma copolymerization of the other. Since the shape of that plot is not altered if mol % TFE is replaced by F/C, the fluorine-to-carbon ratio, this paper aims (1) to show how the relative deposition rates for plasma copolymers drawn from all pairs of monomers in the C2HxF4-x series

  12. Copper mediated controlled radical copolymerization of styrene and 2-ethylhexyl acrylate and determination of their reactivity ratios.

    NASA Astrophysics Data System (ADS)

    Koiry, Bishnu; Singha, Nikhil

    2014-10-01

    Copolymerization is an important synthetic tool to prepare polymers with desirable combination of properties which are difficult to achieve from the different homopolymers concerned. This investigation reports the copolymerization of 2-ethylhexyl acrylate (EHA) and styrene using copper bromide (CuBr) as catalyst in combination with N,N,N’,N”,N”- pentamethyldiethylenetriamine (PMDETA) as ligand and 1-phenylethyl bromide (PEBr) as initiator. Linear kinetic plot and linear increase in molecular weights versus conversion indicate that copolymerization reactions were controlled. The copolymer composition was calculated using 1H NMR studies. The reactivity ratio of styrene and EHA (r1 and r2) were determined using the Finemann-Ross (FR), inverted Finemann-Ross (FR) and Kelen-Tudos (KT) methods. Thermal properties of the copolymers were also studied by using TGA and DSC analysis.

  13. Characterization by Tin-Specific Size Exclusion Chromatography of the Free Radical Copolymerization of Tributyltin Methacrylate and Methyl Methacrylate,

    DTIC Science & Technology

    1980-12-11

    presence of a free radical initiator ( benzoyl peroxide ) at 80.1 OC. Aliquots, taken at preselected intervals from 0 to 1440 min, were fractionated by size...Commercial benzoyl peroxide was employed as the initiator. The THF employed as solvent and chromatographic eluent, containing butylated hydroxytoluene...liter, 3-neck flask equipped with a thermometer, septum, and condenser. To this mixture was added 4.29 g (.018 mole) of benzoyl peroxide . The flask and

  14. Copolymerization of Epichlorohydrin and CO2 Using Zinc Glutarate: An Additional Application of ZnGA in Polycarbonate Synthesis.

    PubMed

    Sudakar, Padmanaban; Sivanesan, Dharmalingam; Yoon, Sungho

    2016-05-01

    The use of zinc glutarate (ZnGA) as a heterogeneous catalyst for the copolymerization of epichlorohydrin, an epoxide with an electron-withdrawing substituent, and CO2 is reported. This catalyst shows the highest selectivity (98%) for polycarbonate over the cyclic carbonate in epichlorohydrin/CO2 copolymerization under mild conditions. The (epichlorohydrin-co-CO2 ) polymer exhibits a high glass transition temperature (Tg ), 44 °C, which is the maximum Tg value obtained for the (epichlorohydrin-co-CO2 ) polymer to date.

  15. In Situ Generation of Co(III) -Salen Complexes for Copolymerization of Propylene Oxide and CO2.

    PubMed

    Hatazawa, Masahiro; Nakabayashi, Koji; Ohkoshi, Shin-Ichi; Nozaki, Kyoko

    2016-09-12

    A simple admixture of Co(II) -salcy complexes with [Cp2 Fe(III) ]PF6 resulted in reproduction of the results with isolated Co(III) -salcy complexes in the copolymerization of epoxide and carbon dioxide. By using this in situ-generated active species with bis(triphenylphosphoranilydene)ammonium 2,4-dinitrophenolate, a para-methoxy-substituted Co-salcy complex was proven to be more active than the parent tert-butyl-substituted system. In contrast, the Co(II) -salcy complex substituted with the more strongly electron-donating NMe2 group did not show any activity for this copolymerization.

  16. Synthesis and characterization of membranes obtained by graft copolymerization of 2-hydroxyethyl methacrylate and acrylic acid onto chitosan.

    PubMed

    dos Santos, K S C R; Coelho, J F J; Ferreira, P; Pinto, I; Lorenzetti, S G; Ferreira, E I; Higa, O Z; Gil, M H

    2006-03-09

    Chitosan based membranes to be applied on wound healing as topical drug delivery systems were developed by graft copolymerization of acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) onto chitosan using cerium ammonium nitrate as chemical initiator. Evidence for graft copolymerization of the vinyl monomers onto chitosan was obtained by FTIR and DMTA. Swelling degree, cytotoxicity, thrombogenicity and haemolytic activity of these membranes were evaluated. Chitosan-graft-AA-graft-HEMA showed to be the best matrix for drug delivery systems than chitosan-graft-AA because it retains good swelling properties, but the content in HEMA has improved cytocompatibility, hemocompatibility and thrombogenic character.

  17. Discrete metal-based catalysts for the copolymerization of CO2 and epoxides: discovery, reactivity, optimization, and mechanism.

    PubMed

    Coates, Geoffrey W; Moore, David R

    2004-12-10

    Most synthetic polymers are made from petroleum feedstocks. Given the non-renewable nature of these materials, there is increasing interest in developing routes to polymeric materials from renewable resources. In addition, there is a growing demand for biodegradable polymeric materials. Polycarbonates made from CO(2) and epoxides have the potential to meet these goals. Since the discovery of catalysts for the copolymerization of CO(2) and epoxides in the late 1960's by Inoue, a significant amount of research has been directed toward the development of catalysts of improved activity and selectivity. Reviewed here are well-defined catalysts for epoxide-CO(2) copolymerization and related reactions.

  18. Methyl parathion

    Integrated Risk Information System (IRIS)

    Methyl parathion ; CASRN 298 - 00 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  19. Methyl chlorocarbonate

    Integrated Risk Information System (IRIS)

    Methyl chlorocarbonate ; CASRN 79 - 22 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinog

  20. Methyl chloride

    Integrated Risk Information System (IRIS)

    EPA / 635 / R01 / 003 TOXICOLOGICAL REVIEW OF METHYL CHLORIDE ( CAS No . 74 - 87 - 3 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) June 2001 U.S . Environmental Protection Agency Washington , DC DISCLAIMER This document has been reviewed in accordance with U.

  1. Methyl iodide

    Integrated Risk Information System (IRIS)

    Methyl iodide ; CASRN 74 - 88 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effe

  2. Methyl acrylate

    Integrated Risk Information System (IRIS)

    Methyl acrylate ; CASRN 96 - 33 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Ef

  3. Methyl isocyanate

    Integrated Risk Information System (IRIS)

    Methyl isocyanate ; CASRN 624 - 83 - 9 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  4. Copolymerization of Glycolide and ɛ-Caprolactone Using 12-Aminolauric Acid Modified Montmorillonite

    NASA Astrophysics Data System (ADS)

    Gallos, HAV; Reyes, LQ

    2017-09-01

    Poly(glycolide-co-ɛ-caprolactone) (PGLYCL) nanocomposites were prepared by copolymerization glycolide (GLY) and ɛ-caprolactone (ɛ-CL) in the presence of varying loadings 12-aminolauric acid (12-ALA)-modified montmorillonite. Copolymerization was successfully achieved based on the increase in polymer molecular weight after the reaction determined by gel permeation chromatography (GPC). The amount of the poly(glycolide) block and poly(ɛ-caprolactone) block units in the copolymer, identified by proton nuclear magnetic resonance (1H-NMR) spectroscopy, suggested that the increase in organo-clay loading cause a reduction GLYL: ɛ-CLL ratio. The arrangement of the monomers in the polymer products was elucidated to have an ABA triblock structure, where PCL block is the central block and the PGLY is found at both end of the copolymer. The presence of intercalated and exfoliated silicates in the nanocomposites were observed by x-ray diffraction (XRD) analysis. The biocompatibility of the nanocomposites with NCTC 292 mouse normal fibroblast was high relative to untreated cell cultures using tetrazolium bromide (MTT)-dye reduction assay.

  5. Relative Rates for Plasma Homo- and Copolymerizations of Olefins in a Homologous Series of Fluorinated Ethylenes

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Wydeven, Theodore; Kliss, Mark (Technical Monitor)

    1996-01-01

    The relative rates of plasma (co)polymerizations of ethylene, vinyl fluoride, vinylidene fluoride, trifluoroethylene and tetrafluoroethylene (VF(sub x); x = 0-4, respectively) were determined in an rf, capacitively coupled, tubular reactor with external electrodes using identical plasma parameters. The averages of deposition rates obtained by both microgravimetry and ellipsometry were plotted versus the F/C ratios of the monomers or monomer blends. The deposition rates for VF(sub x)(x = 1-3) and 20 monomer blends were all located above a straight line joining the rates for VF(sub 0) and VF(sub 4), following a concave-downward plot of deposition rate versus F/C ratio similar to that reported previously for VF(sub 0)/VF(sub 4) blends. The deposition rates for VF(sub m)/VF(sub n) blends (m = 3 or 4; n = 0-2) were all greater than expected for non-interacting monomers; those for VF(sub 0)/VF(sub 2) and VF(sub 1)/VF(sub 2) blends were all lower than expected; while those for VF(sub 0)/VF(sub 1) and VF(sub 3)/VF(sub 4) blends fen on a straightline plot versus F/C ratio, indicative of apparent non-interaction between monomers. The mechanisms for plasma (co)polymerizations of VF(sub x) monomers responsible for the wide range of relative deposition rates remain to be elucidated.

  6. Relative Rates for Plasma Homo- and Copolymerizations of Olefins in a Homologous Series of Fluorinated Ethylenes

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Wydeven, Theodore; Kliss, Mark (Technical Monitor)

    1996-01-01

    The relative rates of plasma (co)polymerizations of ethylene, vinyl fluoride, vinylidene fluoride, trifluoroethylene and tetrafluoroethylene (VF(sub x); x = 0-4, respectively) were determined in an rf, capacitively coupled, tubular reactor with external electrodes using identical plasma parameters. The averages of deposition rates obtained by both microgravimetry and ellipsometry were plotted versus the F/C ratios of the monomers or monomer blends. The deposition rates for VF(sub x)(x = 1-3) and 20 monomer blends were all located above a straight line joining the rates for VF(sub 0) and VF(sub 4), following a concave-downward plot of deposition rate versus F/C ratio similar to that reported previously for VF(sub 0)/VF(sub 4) blends. The deposition rates for VF(sub m)/VF(sub n) blends (m = 3 or 4; n = 0-2) were all greater than expected for non-interacting monomers; those for VF(sub 0)/VF(sub 2) and VF(sub 1)/VF(sub 2) blends were all lower than expected; while those for VF(sub 0)/VF(sub 1) and VF(sub 3)/VF(sub 4) blends fen on a straightline plot versus F/C ratio, indicative of apparent non-interaction between monomers. The mechanisms for plasma (co)polymerizations of VF(sub x) monomers responsible for the wide range of relative deposition rates remain to be elucidated.

  7. Synthesis of Vol. I. Improvers by copolymerization of decyl methacrylate with styrene

    SciTech Connect

    Akhmedov, A.I.; Levshina, A.M.

    1984-07-01

    This article demonstrates how copolymerization can be used to improve the quality of polyalkyl methacrylates. Benzoyl peroxide was used as an initiator for copolymerization performed in toluene solution. The influences of the concentrations of initiator and monomer mixture in toluene, the temperature, the length of the reaction period, and the quantity of styrene were investigated. The results indicate that as the reaction temperature was raised from 70/sup 0/ to 90/sup 0/C, the molecular weight of the copolymer decreased from 20,000 to 12,000 and the yield remained unchanged. An increase in the content of styrene from 10% to 40% led to an increase in the molecular weight of the copolymer from 10,000 to 17,000. When the volume ratio of toluene to monomer mixture was increased, the molecular weight of the copolymer decreased while the yield remained constant. It is determined that by varying the quantities of stryene and toluene, the molecular weight of the copolymer can be regulated without changing the temperature or the initiator concentration.

  8. Extraction of palm tree cellulose and its functionalization via graft copolymerization.

    PubMed

    Al-Hoqbani, Abdulmajeed A; Abdel-Halim, E S; Al-Deyab, Salem S

    2014-09-01

    The work in this paper was planned with the aim of extracting the cellulosic component of palm tree waste and functionalizing this cellulose through graft copolymerization with acrylic acid. The cellulose extraction included hot alkali treatment with aqueous sodium hydroxide to remove the non-cellulosic binding materials. The alkali treatment was followed by an oxidative bleaching using peracid/hydrogen peroxide mixture with the aim of removing the rest of non-cellulosic materials to improve the fiber hydrophilicity and accessibility towards further grafting reaction. Optimum conditions for cellulose extraction are boiling in 5% (W/V) NaOH in a material to liquor ratio of 1:20 for 1 h then bleaching with 60 ml/l bleaching mixture at initial pH value of 6.5 for 30 min. The pH of the bleaching medium is turned to the alkaline range 11 and bleaching continues for extra 30 min. Graft copolymerization reaction was initiated by potassium bromate/thiourea dioxide redox system. Optimum conditions for grafting are 30 mmol of potassium bromate, 30 mmol of thiourea dioxide and 150 g of acrylic acid (each per 100 g of cellulose). The polymerization reaction was carried out for 120 min at 50°C using a material to liquor ratio of 1:20.

  9. Plasma-induced graft copolymerization of HEMA onto silicone rubber and TPX film improving rabbit corneal epithelial cell attachment and growth.

    PubMed

    Hsiue, G H; Lee, S D; Wang, C C; Shiue, M H; Chang, P C

    1994-02-01

    A poly(2-hydroxyethyl methacrylate) (pHEMA)-grafted polymer film was prepared by plasma-induced graft copolymerization onto an elastic material, silicone rubber, and a plastic material, poly(4-methyl-1-pentene) (TPX). The control, Ar plasma-treated and pHEMA-grafted silicone rubber and TPX surfaces were characterized by ESCA, FTIR-ATR, SEM and contact angle techniques. ESCA verified the respective chemical shift of control and Ar plasma-treated films. The presence of the grafted pHEMA was also verified by ESCA. The introduction of pHEMA onto a hydrophobic support provided an adequate surface for rabbit corneal epithelium cell attachment and growth. Cell attachment and growth onto these surfaces were examined by light microscopy. Cell attachment onto the control and Ar plasma-treated surfaces was negligible, while improved attachment and growth of rabbit corneal epithelium cells was demonstrated on the pHEMA-grafted polymeric surface. At 72 h, the pHEMA-grafted silicone rubber surface attached and grew more cells as compared with those on a pHEMA-grafted TPX surface. The pHEMA-grafted silicone rubber surface demonstrated a confluent cell layer after 72 h.

  10. Preparation of half-metallocenes of thiophene-fused and tetrahydroquinoline-linked cyclopentadienyl ligands for ethylene/α-olefin copolymerization.

    PubMed

    Park, Ji Hae; Do, Seung Hyun; Cyriac, Anish; Yun, Hoseop; Lee, Bun Yeoul

    2010-11-07

    Directed ortho-lithiation of the lithium carbamates generated from tetrahydroquinoline or tetrahydroquinaldine enables one-step preparation of thiophene-fused and tetrahydroquinoline-linked cyclopentadienes [2-R(1)-3-R(2)-4,5-dimethyl-6-(2-R(3)-2,3,4,5-tetrahydroquinolin-8-yl)-4H-cyclopenta[b]thiophene (R(1), R(2), R(3) = H or methyl)], from which titanium(iv) and zirconium(iv) complexes are prepared. The molecular structures of Me(2)Ti-complexes (12, R(1) = R(2) = Me, R(3) = H; 14, R(1) = R(2) = R(3) = Me) and Cl(2)Zr-complex (17, R(1) = R(2) = Me, R(3) = H) are determined by X-ray crystallography. The Me(2)Ti-complexes, 14 and 15 (R(1) = R(3) = Me, R(2) = H) show excellent activities (62 and 54 × 10(6) g/molTi·h) in ethylene/1-octene copolymerization, even when activated with small amount of MAO (Al/Ti = 1000).

  11. Mechanistic aspects of the copolymerization reaction of carbon dioxide and epoxides, using a chiral salen chromium chloride catalyst.

    PubMed

    Darensbourg, Donald J; Yarbrough, Jason C

    2002-06-05

    The air-stable, chiral (salen)Cr(III)Cl complex (3), where H(2)salen = N,N'-bis(3,5-di-tert-butyl-salicylidene)-1,2-cyclohexene diamine, has been shown to be an effective catalyst for the coupling of cyclohexene oxide and carbon dioxide to afford poly(cyclohexenylene carbonate), along with a small quantity of its trans-cyclic carbonate. The thus produced polycarbonate contained >99% carbonate linkages and had a M(n) value of 8900 g/mol with a polydispersity index of 1.2 as determined by gel permeation chromatography. The turnover number (TON) and turnover frequency (TOF) values of 683 g of polym/g of Cr and 28.5 g of polym/g of Cr/h, respectively for reactions carried out at 80 degrees C and 58.5 bar pressure increased by over 3-fold upon addition of 5 equiv of the Lewis base cocatalyst, N-methyl imidazole. Although this chiral catalyst is well documented for the asymmetric ring-opening (ARO) of epoxides, in this instance the copolymer produced was completely atactic as illustrated by (13)C NMR spectroscopy. Whereas the mechanism for the (salen)Cr(III)-catalyzed ARO of epoxides displays a squared dependence on [catalyst], which presumably is true for the initiation step of the copolymerization reaction, the rate of carbonate chain growth leading to copolymer or cyclic carbonate formation is linearly dependent on [catalyst]. This was demonstrated herein by way of in situ measurements at 80 degrees C and 58.5 bar pressure. Hence, an alternative mechanism for copolymer production is operative, which is suggested to involve a concerted attack of epoxide at the axial site of the chromium(III) complex where the growing polymer chain for epoxide ring-opening resides. Preliminary investigations of this (salen)Cr(III)-catalyzed system for the coupling of propylene oxide and carbon dioxide reveal that although cyclic carbonate is the main product provided at elevated temperatures, at ambient temperature polycarbonate formation is dominant. A common reaction pathway for

  12. Thermo-sensitive polymer nanospheres as a smart plugging agent for shale gas drilling operations.

    PubMed

    Wang, Wei-Ji; Qiu, Zheng-Song; Zhong, Han-Yi; Huang, Wei-An; Dai, Wen-Hao

    2017-01-01

    Emulsifier-free poly(methyl methacrylate-styrene) [P(MMA-St)] nanospheres with an average particle size of 100 nm were synthesized in an isopropyl alcohol-water medium by a solvothermal method. Then, through radical graft copolymerization of thermo-sensitive monomer N-isopropylacrylamide (NIPAm) and hydrophilic monomer acrylic acid (AA) onto the surface of P(MMA-St) nanospheres at 80 °C, a series of thermo-sensitive polymer nanospheres, named SD-SEAL with different lower critical solution temperatures (LCST), were prepared by adjusting the mole ratio of NIPAm to AA. The products were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, particle size distribution, and specific surface area analysis. The temperature-sensitive behavior was studied by light transmittance tests, while the sealing performance was investigated by pressure transmission tests with Lungmachi Formation shales. The experimental results showed that the synthesized nanoparticles are sensitive to temperature and had apparent LCST values which increased with an increase in hydrophilic monomer AA. When the temperature was higher than its LCST value, SD-SEAL played a dual role of physical plugging and chemical inhibition, slowed down pressure transmission, and reduced shale permeability remarkably. The plugged layer of shale was changed to being hydrophobic, which greatly improved the shale stability.

  13. Characterization of methyl methacrylate grafting onto preirradiated biodegradable lignocellulose fiber by gamma-radiation.

    PubMed

    Khan, Ferdous

    2005-01-14

    Gamma-radiation-induced graft copolymerization of methyl methacrylate onto natural lignocellulose (jute) fiber was carried out by the preirradiation method in an aqueous medium by using octylphenoxy-polyethoxyethanol as an emulsifier. The different factors that influenced the graft copolymer reaction process were investigated. In the case of radiation-dose-dependent grafting, samples irradiated in the presence of air produced up to 73% graft weight compared to 53% obtained in the case of irradiation in a nitrogen environment. By assuming Arrhenius reaction kinetics, the activation energy (E(a)) of the grafting reaction process was evaluated for different reaction temperatures. Moreover, the graft copolymer reaction was controlled by incorporating a homopolymer-inhibiting agent and three different chain-transfer agents in the reaction medium. The mechanical and thermal properties of jute fiber 'as received' and jute-graft-poly(methyl methacrylate) were also investigated. The results showed that the percentage of grafting with jute fiber has a significant effect on the properties. The kinetic parameters were evaluated from TGA thermograms by using Broido's method in the temperature range 240-350 degrees C. Scanning electron micrographs show that the structural changes on the surface of jute fibers were induced by graft copolymerization of methyl methacrylate monomer. Fiber-fiber surface friction was measured in terms of the average maximum load and the kinetic friction. SEM of jute-graft-poly(methyl methacrylate).

  14. Methyl eucomate

    PubMed Central

    Li, Linglin; Zhou, Guang-Xiong; Jiang, Ren-Wang

    2008-01-01

    The crystal structure of the title compound [systematic name: methyl 3-carboxy-3-hydr­oxy-3-(4-hydroxy­benz­yl)propanoate], C12H14O6, is stabilized by inter­molecular O—H⋯O and C—H⋯O hydrogen bonds. The mol­ecules are arranged in layers, parallel to (001), which are inter­connected by the O—H⋯O hydrogen bonds. PMID:21202973

  15. RAFT copolymerization of itaconic anhydride and 2-methoxyethyl acrylate: a multifunctional scaffold for preparation of "clickable" gold nanoparticles.

    PubMed

    Javakhishvili, Irakli; Kasama, Takeshi; Jankova, Katja; Hvilsted, Søren

    2013-05-25

    RAFT copolymerization of 2-methoxyethyl acrylate and itaconic anhydride - a monomer derived from renewable resources - is carried out in a controlled fashion. The copolymer allows preparation of gold nanoparticles with abundant surficial carboxyl and alkyne functional groups that are dendronized via Cu(I)-mediated "click" reaction.

  16. Efficient catalyst removal and recycling in copolymerization of epoxides with carbon dioxide via simple liquid-liquid phase separation.

    PubMed

    Nakano, Koji; Fujie, Ryuhei; Shintani, Ryo; Nozaki, Kyoko

    2013-10-18

    A simple and efficient catalyst removal system has been developed in the cobalt-salen-catalyzed copolymerization of propylene oxide with carbon dioxide. The present system requires no prior modification of the catalyst, and the removal is achieved by simple addition of myristic acid, followed by organic liquid-liquid phase separation.

  17. Alternating copolymerization of dihydrocoumarin and epoxides catalyzed by chromium salen complexes: a new route to functional polyesters.

    PubMed

    Van Zee, Nathan J; Coates, Geoffrey W

    2014-06-18

    We report the alternating ring-opening copolymerization of dihydrocoumarin with epoxides catalyzed by chromium(III) salen complexes. This process provides access to a range of perfectly alternating polyesters with high molecular weights and narrow molecular weight distributions. Atactic poly(cyclohexene dihydrocoumarate) and poly(cyclopentene dihydrocoumarate) were found to be semi-crystalline by differential scanning calorimetry.

  18. Liquid marbles as a micro-reactor for efficient radical alternating copolymerization of diene monomer and oxygen.

    PubMed

    Sato, E; Yuri, M; Fujii, S; Nishiyama, T; Nakamura, Y; Horibe, H

    2015-12-18

    Liquid marbles have been shown to be a novel micro-reactor to synthesize polyperoxides by the radical alternating copolymerization of the 1,3-diene monomer with oxygen in a good yield. Oxygen gas is effectively absorbed as a comonomer by the large and permeable gas-liquid interface of the liquid marbles.

  19. Polymerization of olefins through heterogeneous catalysis: 14--The influence of temperature in the solution copolymerization of ethylene

    SciTech Connect

    Jaber, I.A.; Ray, W.H. . Chemical Engineering Dept.)

    1993-10-10

    The influence of temperature variation on the kinetics and the polymer properties in the homo- and copolymerization of ethylene in a solution reactor is discussed. The polymerization is conducted in a semibatch mode at 320 Psig total reactor pressure for 10 min polymerization time. Temperature variations in the range 145-200 C in both homo- and copolymerization of ethylene with 1-octene shows that the highest catalyst yield was obtained at temperature of 165--175 C. At the optimal temperature, a high initial maximum in the rate of ethylene consumption is attained in a few seconds followed by a relatively slow decay when compared with polymerization conducted a higher temperatures. Polymerization at temperatures [>=] 185 C resulted in a lower peak in the consumption rate of ethylene accompanied by a rapid decay with time. In the case of ethylene/1-octene copolymerization, a rather low comonomer incorporation level is obtained at the conditions employed; the 1-octene incorporated was only 0.2--0.7 mol%. Higher M[sub w] values, of about 350,000 at 145 C, are obtained in homopolymerization in comparison to M[sub w] values obtained in copolymerization, of about 195,000 at the same temperature. Over the temperature range of 145--200 C, both M[sub w] and M[sub n] values vary by about 40%.

  20. Histidine residues in the peptide D-Lys(6)-GnRH: potential for copolymerization in polymeric nanoparticles.

    PubMed

    Kafka, Alexandra P; Kleffmann, Torsten; Rades, Thomas; McDowell, Arlene

    2009-01-01

    Poly(ethylcyanoacrylate) (PECA) nanoparticles containing the bioactive d-Lys(6)-GnRH were manufactured by an in situ interfacial polymerization process using a w/o-microemulsion template containing the peptide in the dispersed aqueous pseudophase of the microemulsion. Polymeric nanoparticles were characterized using PCS, RP-HPLC (bulk level) and MALDI TOF mass spectrometry (molecular level). The peptide d-Lys(6)-GnRH was reactive with the alkylcyanoacrylate monomer, resulting in some of the peptide copolymerizing with the monomer. MALDI TOF/TOF (tandem) analysis revealed that the histidine residue in position 2 of d-Lys(6)-GnRH interacts covalently in the polymerization process. A reaction mechanism for this nucleophilic interference is suggested. The copolymerization reaction appeared to occur within seconds after the addition of the monomer to the microemulsion. The surface charge of resulting nanoparticles was less negative (-3 mV) compared with the zeta potential of empty nanoparticles (-27.5 mV). The copolymerization yielded high entrapment rates of 95 +/- 4% of peptide, but showed limited release ( approximately 11%) of free peptide over 5 days. A separate experiment demonstrated that the addition of d-Lys(6)-GnRH to preformed empty PECA nanoparticles (ex situ) also yielded fractions of copolymerized peptide suggesting a certain proportion of polymer remains available for copolymerization possibly through an unzipping depolymerization/repolymerization process. Therefore, the reactivity of histidine residues in bioactives needs to be considered whenever using the bioactive in situ or ex situ with polymeric PECA nanoparticles.

  1. Polylactide-based microspheres prepared using solid-state copolymerized chitosan and d,l-lactide.

    PubMed

    Demina, T S; Akopova, T A; Vladimirov, L V; Zelenetskii, A N; Markvicheva, E A; Grandfils, Ch

    2016-02-01

    Amphiphilic chitosan-g-poly(d,l-lactide) copolymers have been manufactured via solid-state mechanochemical copolymerization and tailored to design polyester-based microspheres for tissue engineering. A single-step solid-state reactive blending (SSRB) using low-temperature co-extrusion has been used to prepare these copolymers. These materials have been valorized to stabilize microspheres processed by an oil/water emulsion evaporation technique. Introduction of the copolymers either in water or in the oil phase of the emulsion allowed to replace a non-degradable emulsifier typically used for microparticle preparation. To enhance cell adhesion, these copolymers were also tailored to bring amino-saccharide positively charged segments to the microbead surface. Size distribution, surface morphology, and total microparticle yield have been studied and optimized as a function of the copolymer composition. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Improved detection of amylase activity by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with copolymerized starch.

    PubMed

    Martínez, T F; Alarcón, F J; Díaz-López, M; Moyano, F J

    2000-08-01

    An improved method, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for detection of amylase activity is described. This method will allow better characterization of certain amylases than that obtained by the Davis technique. The main features of the technique are: (i) identification of amylase bands and molecular mass determination are possible in the same gel; (ii) the hydrolysis of copolymerized substrate during electrophoretic separation is prevented using very low temperatures instead of inactivating agents such as chelating agents; and (iii) the technique is applicable to reveal amylase activity in a wide range of biological samples. The method is not useful for enzymes sensitive to SDS and for high molecular mass amylases.

  3. Block Copolymerization of Lactide and an Epoxide Facilitated by a Redox Switchable Iron-Based Catalyst.

    PubMed

    Biernesser, Ashley B; Delle Chiaie, Kayla R; Curley, Julia B; Byers, Jeffery A

    2016-04-18

    A cationic iron(III) complex was active for the polymerization of various epoxides, whereas the analogous neutral iron(II) complex was inactive. Cyclohexene oxide polymerization could be "switched off" upon in situ reduction of the iron(III) catalyst and "switched on" upon in situ oxidation, which is orthogonal to what was observed previously for lactide polymerization. Conducting copolymerization reactions in the presence of both monomers resulted in block copolymers whose identity can be controlled by the oxidation state of the catalyst: selective lactide polymerization was observed in the iron(II) oxidation state and selective epoxide polymerization was observed in the iron(III) oxidation state. Evidence for the formation of block copolymers was obtained from solubility differences, GPC, and DOSY-NMR studies.

  4. Radiation-induced graft copolymerization of binary monomer mixture containing acrylonitrile onto polyethylene films

    NASA Astrophysics Data System (ADS)

    Choi, Seong-Ho; Nho, Young Chang

    2000-04-01

    Graft copolymerization of acrylonitrile (AN)/acrylic acid (AA), acrylonitrile (AN)/methacrylic acid (MA), and acrylonitrile (AN)/glycidyl methacrylate (GMA) onto pre-irradiated polyethylene (PE) films were studied. The effect of reaction conditions such as solvents, additives, and monomer composition on the grafting yields was investigated. The extent of grafting was found to increase with increasing sulfuric acid concentration when sulfuric acid as an additive was added to the grafting solution. In AN/AA mixture, the proportion of acrylonitrile in the copolymer increased with an increasing AN component in feed monomers. On the other hand, in AN/MA mixture, acrylonitrile component in copolymer was very slight in spite of the increase AN component in feed monomers. In the AN/GMA mixture, the proportion of acrylonitrile in the copolymer increased with increasing acrylonitrile component in AN/GMA feed monomer.

  5. Surface Modification of PET Fabric by Graft Copolymerization with Acrylic Acid and Its Antibacterial Properties

    PubMed Central

    Abdolahifard, M.; Bahrami, S. Hajir; Malek, R. M. A.

    2011-01-01

    Graft copolymerization of acrylic acid (AA) onto Poly(ethylene terephthalate) (PET) fabrics with the aid of benzoyl peroxide was carried out. The effect of polymerization parameters on the graft yield was studied. Percent grafting was enhanced significantly by increasing benzoyl peroxide (BP) concentrations up to 3.84 g/lit and then decreased upon further increase in initiator concentration. Preswelling of PET leads to changes in its sorption-diffusion properties and favors an increase in the degree of grafting. The antibiotics treated grafted fabrics showed antibacterial properties towards gram-positive and gram-negative microorganisms. FTIR and SEM were used to characterize AA-grafted polyester fabrics. PMID:24052819

  6. Constrained Geometry Organotitanium Catalysts Supported on Nanosized Silica for Ethylene (co)Polymerization.

    PubMed

    Li, Kuo-Tseng; Wu, Ling-Huey

    2017-05-05

    Supported olefin polymerization catalysts can prevent reactor-fouling problems and produce uniform polymer particles. Constrained geometry complexes (CGCs) have less sterically hindered active sites than bis-cyclopentadienyl metallocene catalysts. In the literature, micrometer-sized silica particles were used for supporting CGC catalysts, which might have strong mass transfer limitations. This study aims to improve the activity of supported CGC catalysts by using nanometer-sized silica. Ti[(C₅Me₄)SiMe₂(N(t)Bu)]Cl₂, a "constrained-geometry" titanium catalyst, was supported on MAO-treated silicas (nano-sized and micro-sized) by an impregnation method. Ethylene homo-polymerization and co-polymerization with 1-octene were carried out in a temperature range of 80-120 °C using toluene as the solvent. Catalysts prepared and polymers produced were characterized. For both catalysts and for both reactions, the maximum activities occurred at 100 °C, which is significantly higher than that (60 °C) reported before for supported bis-cyclopentadienyl metallocene catalysts containing zirconium, and is lower than that (≥140 °C) used for unsupported Ti[(C₅Me₄)SiMe₂(N(t)Bu)]Me₂ catalyst. Activities of nano-sized catalyst were 2.6 and 1.6 times those of micro-sized catalyst for homopolymerization and copolymerization, respectively. The former produced polymers with higher crystallinity and melting point than the latter. In addition, copolymer produced with nanosized catalyst contained more 1-octene than that produced with microsized catalyst.

  7. Polar, non-coordinating ionic liquids as solvents for the alternating copolymerization of styrene and CO catalyzed by cationic palladium catalysts.

    PubMed

    Klingshirn, Marc A; Broker, Grant A; Holbrey, John D; Shaughnessy, Kevin H; Rogers, Robin D

    2002-07-07

    The palladium-catalyzed copolymerization of styrene and CO in an ionic liquid solvent, 1-hexylpyridinium bis(trifluoromethanesulfonyl)imide, gave improved yields and increased molecular weights compared to polymerizations run in methanol.

  8. Tunable mechano-responsive organogels by ring-opening copolymerizations of N-carboxyanhydrides.

    PubMed

    Fan, Jingwei; Zou, Jiong; He, Xun; Zhang, Fuwu; Zhang, Shiyi; Raymond, Jeffery E; Wooley, Karen L

    2014-01-01

    The simple copolymerization of N-carboxyanhydride (NCA) monomers is utilized to generate copolypeptides having a combination of α-helix and β-sheet sub-structures that, when grown from a solvophilic synthetic polymer block segment, are capable of driving mechano-responsive supramolecular sol-to-gel-to-sol and sol-to-gel-to-gel transitions reversibly, which allow also for injection-based processing and self-healing behaviors. A new type of polypeptide-based organogelator, methoxy poly(ethylene glycol)-block-poly(γ-benzyl-l-glutamate-co-glycine) (mPEG-b-P(BLG-co-Gly)), is facilely synthesized by statistical ring-opening copolymerizations (ROPs) of γ-benzyl-l-glutamate (BLG) and glycine (Gly) NCAs initiated by mPEG-amine. These systems exhibit tunable secondary structures and result in sonication stimulus responsiveness of the organogels with the polypeptide segment variation, controlled by varying the ratio of BLG NCA to Gly NCA during the copolymerizations. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) studies indicate the α-helical component decreases while the β-sheet content increases systematically with a higher mole fraction of Gly in the polypeptide segment. The supramolecular assembly of β-sheet nanofibrils, having a tunable width over the range of 10.4 - 14.5 nm with varied BLG to Gly ratio, are characterized by transmission electron microscopy (TEM). The further self-assembly of these nanostructures into 3-D gel networks within N,N-dimethylformamide (DMF) occurs at low critical gelation concentrations (CGC) (lowest ca. 0.6 wt %). Increased BLG to Gly ratios lead to an increase of the α-helical component in the secondary structures of the polypeptide segments, resulting in wider and more flexible nanofibrils. The presence of α-helical component in the polymers enhances the stability of the organogels against sonication, and instantaneous gel-to-gel transitions are observed as in situ reconstruction of networks

  9. Swelling and thermodynamic studies of temperature responsive 2-hydroxyethyl methacrylate/itaconic acid copolymeric hydrogels prepared via gamma radiation

    NASA Astrophysics Data System (ADS)

    Tomić, Simonida L. J.; Mićić, Maja M.; Filipović, Jovanka M.; Suljovrujić, Edin H.

    2007-08-01

    The copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were synthesized by gamma radiation induced radical polymerization. Swelling and thermodynamic properties of PHEMA and copolymeric P(HEMA/IA) hydrogels with different IA contents (2, 3.5 and 5 mol%) were studied in a wide pH and temperature range. Initial studies of so-prepared hydrogels show interesting pH and temperature sensitivity in swelling and drug release behavior. Special attention was devoted to temperature investigations around physiological temperature (37 °C), where small changes in temperature significantly influence swelling and drug release of these hydrogels. Due to maximum swelling of hydrogels around 40 °C, the P(HEMA/IA) hydrogel containing 5 mol% of IA without and with drug-antibiotic (gentamicin) were investigated at pH 7.40 and in the temperature range 25-42 °C, in order to evaluate their potential for medical applications.

  10. Synthesis, cyclopolymerization and cyclo-copolymerization of 9-(2-diallylaminoethyl)adenine and its hydrochloride salt.

    PubMed

    Bouhadir, Kamal H; Abramian, Lara; Ezzeddine, Alaa; Usher, Karyn; Vladimirov, Nikolay

    2012-11-08

    We report herein the synthesis and characterization of 9-(2-diallylaminoethyl) adenine. We evaluated two different synthetic routes starting with adenine where the optimal route was achieved through coupling of 9-(2-chloroethyl)adenine with diallylamine. The cyclopolymerization and cyclo-copolymerization of 9-(2-diallylaminoethyl)adenine hydrochloride salt resulted in low molecular weight oligomers in low yields. In contrast, 9-(2-diallylaminoethyl)adenine failed to cyclopolymerize, however, it formed a copolymer with SO₂ in relatively good yields. The molecular weights of the cyclopolymers were around 1,700-6,000 g/mol, as estimated by SEC. The cyclo-copolymer was stable up to 226 °C. To the best of our knowledge, this is the first example of a free-radical cyclo-copolymerization of a neutral alkyldiallylamine derivative with SO₂. These polymers represent a novel class of carbocyclic polynucleotides.

  11. CAMELOT: A machine learning approach for coarse-grained simulations of aggregation of block-copolymeric protein sequences

    SciTech Connect

    Ruff, Kiersten M.; Harmon, Tyler S.; Pappu, Rohit V.

    2015-12-28

    We report the development and deployment of a coarse-graining method that is well suited for computer simulations of aggregation and phase separation of protein sequences with block-copolymeric architectures. Our algorithm, named CAMELOT for Coarse-grained simulations Aided by MachinE Learning Optimization and Training, leverages information from converged all atom simulations that is used to determine a suitable resolution and parameterize the coarse-grained model. To parameterize a system-specific coarse-grained model, we use a combination of Boltzmann inversion, non-linear regression, and a Gaussian process Bayesian optimization approach. The accuracy of the coarse-grained model is demonstrated through direct comparisons to results from all atom simulations. We demonstrate the utility of our coarse-graining approach using the block-copolymeric sequence from the exon 1 encoded sequence of the huntingtin protein. This sequence comprises of 17 residues from the N-terminal end of huntingtin (N17) followed by a polyglutamine (polyQ) tract. Simulations based on the CAMELOT approach are used to show that the adsorption and unfolding of the wild type N17 and its sequence variants on the surface of polyQ tracts engender a patchy colloid like architecture that promotes the formation of linear aggregates. These results provide a plausible explanation for experimental observations, which show that N17 accelerates the formation of linear aggregates in block-copolymeric N17-polyQ sequences. The CAMELOT approach is versatile and is generalizable for simulating the aggregation and phase behavior of a range of block-copolymeric protein sequences.

  12. Synthesis of copolymerized porous organic frameworks with high gas storage capabilities at both high and low pressures.

    PubMed

    Pei, Cuiying; Ben, Teng; Li, Yanqiang; Qiu, Shilun

    2014-06-11

    A series of copolymerized porous organic frameworks (C-POFs) were synthesized with monomers of tetrakis(4-bromophenyl)methane and tris(4-bromophenyl)amine in different ratios by a Yamamoto-type Ullmann cross-coupling reaction. These C-POFs exhibit high physicochemical stability, large surface areas and excellent H2, CH4 and CO2 adsorption properties both at low and high pressures.

  13. Ring-opening copolymerization of maleic anhydride with epoxides: a chain-growth approach to unsaturated polyesters.

    PubMed

    DiCiccio, Angela M; Coates, Geoffrey W

    2011-07-20

    We report the ring-opening copolymerization of maleic anhydride with a variety of epoxides catalyzed by a chromium(III) salen complex. Quantitative isomerization of the cis-maleate form of all polymers affords the trans-fumarate analogues. Addition of chain transfer reagents yields low M(n), narrow PDI polymer samples. This method provides access to a range of new unsaturated polyesters with versatile functionality, as well as the first synthesis of high molecular weight poly(propylene fumarate).

  14. CAMELOT: A machine learning approach for coarse-grained simulations of aggregation of block-copolymeric protein sequences

    PubMed Central

    Ruff, Kiersten M.; Harmon, Tyler S.; Pappu, Rohit V.

    2015-01-01

    We report the development and deployment of a coarse-graining method that is well suited for computer simulations of aggregation and phase separation of protein sequences with block-copolymeric architectures. Our algorithm, named CAMELOT for Coarse-grained simulations Aided by MachinE Learning Optimization and Training, leverages information from converged all atom simulations that is used to determine a suitable resolution and parameterize the coarse-grained model. To parameterize a system-specific coarse-grained model, we use a combination of Boltzmann inversion, non-linear regression, and a Gaussian process Bayesian optimization approach. The accuracy of the coarse-grained model is demonstrated through direct comparisons to results from all atom simulations. We demonstrate the utility of our coarse-graining approach using the block-copolymeric sequence from the exon 1 encoded sequence of the huntingtin protein. This sequence comprises of 17 residues from the N-terminal end of huntingtin (N17) followed by a polyglutamine (polyQ) tract. Simulations based on the CAMELOT approach are used to show that the adsorption and unfolding of the wild type N17 and its sequence variants on the surface of polyQ tracts engender a patchy colloid like architecture that promotes the formation of linear aggregates. These results provide a plausible explanation for experimental observations, which show that N17 accelerates the formation of linear aggregates in block-copolymeric N17-polyQ sequences. The CAMELOT approach is versatile and is generalizable for simulating the aggregation and phase behavior of a range of block-copolymeric protein sequences. PMID:26723608

  15. CAMELOT: A machine learning approach for coarse-grained simulations of aggregation of block-copolymeric protein sequences

    NASA Astrophysics Data System (ADS)

    Ruff, Kiersten M.; Harmon, Tyler S.; Pappu, Rohit V.

    2015-12-01

    We report the development and deployment of a coarse-graining method that is well suited for computer simulations of aggregation and phase separation of protein sequences with block-copolymeric architectures. Our algorithm, named CAMELOT for Coarse-grained simulations Aided by MachinE Learning Optimization and Training, leverages information from converged all atom simulations that is used to determine a suitable resolution and parameterize the coarse-grained model. To parameterize a system-specific coarse-grained model, we use a combination of Boltzmann inversion, non-linear regression, and a Gaussian process Bayesian optimization approach. The accuracy of the coarse-grained model is demonstrated through direct comparisons to results from all atom simulations. We demonstrate the utility of our coarse-graining approach using the block-copolymeric sequence from the exon 1 encoded sequence of the huntingtin protein. This sequence comprises of 17 residues from the N-terminal end of huntingtin (N17) followed by a polyglutamine (polyQ) tract. Simulations based on the CAMELOT approach are used to show that the adsorption and unfolding of the wild type N17 and its sequence variants on the surface of polyQ tracts engender a patchy colloid like architecture that promotes the formation of linear aggregates. These results provide a plausible explanation for experimental observations, which show that N17 accelerates the formation of linear aggregates in block-copolymeric N17-polyQ sequences. The CAMELOT approach is versatile and is generalizable for simulating the aggregation and phase behavior of a range of block-copolymeric protein sequences.

  16. Interaction between N-vinylpyrrolidone and methyl methacrylate

    NASA Astrophysics Data System (ADS)

    Zaitseva, V. V.; Shtonda, A. V.; Tyurina, T. G.; Bagdasarova, A. R.; Zaitsev, S. Yu.

    2014-04-01

    It is established that the interaction of the isomers of N-vinylpyrrolidone (NVP) and methyl methacrylate (MMA) leads to the formation of molecular π-H- and H-complexes with energies within the limits of 10.2-13.6 (AM1) or 18.2-24.0 (B3LYP/6-311++G( d)) kJ/mol. The structures of complex-bound molecules are examined with respect to changes in the charges on terminal -C1=C2- groups, the distance between them and atoms in an H-bond, and the presence of combined overlapping molecular orbitals (MOs). The presence of an averaged complex that includes presumably all possible structures and allows us to perform the copolymerization of specified monomers in the absence of an initiator is confirmed by means of UV and NMR spectroscopy.

  17. Swelling and drug release behavior of poly(2-hydroxyethyl methacrylate/itaconic acid) copolymeric hydrogels obtained by gamma irradiation

    NASA Astrophysics Data System (ADS)

    Tomić, S. Lj.; Mićić, M. M.; Filipović, J. M.; Suljovrujić, E. H.

    2007-05-01

    The new copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were prepared by gamma irradiation, in order to examine the potential use of these hydrogels in controlled drug release systems. The influence of IA content in the gel on the swelling characteristics and the releasing behavior of hydrogels, and the effect of different drugs, theophylline (TPH) and fenethylline hydrochloride (FE), on the releasing behavior of P(HEMA/IA) matrix were investigated in vitro. The diffusion exponents for swelling and drug release indicate that the mechanisms of buffer uptake and drug release are governed by Fickian diffusion. The swelling kinetics and, therefore, the release rate depends on the matrix swelling degree. The drug release was faster for copolymeric hydrogels with a higher content of itaconic acid. Furthermore, the drug release for TPH as model drug was faster due to a smaller molecular size and a weaker interaction of the TPH molecules with(in) the P(HEMA/IA) copolymeric networks.

  18. Nanospace-confinement copolymerization strategy for encapsulating polymeric sulfur into porous carbon for lithium-sulfur batteries.

    PubMed

    Ding, Bing; Chang, Zhi; Xu, Guiyin; Nie, Ping; Wang, Jie; Pan, Jin; Dou, Hui; Zhang, Xiaogang

    2015-06-03

    Given their high theoretical energy density, lithium-sulfur (Li-S) batteries have recently attracted ever-increasing research interest. However, the dissolution of polysulfides and uncontrolled deposition of insoluble discharge product significantly hinder the cycling stability. Herein, a nanospace-confinement copolymerization strategy for encapsulating polymeric sulfur into porous carbon matrix is presented. The morphologies and sulfur contents of carbon/polymeric sulfur (C/PS) composites could be readily tailored by controlling the copolymerization time. Confining polymeric sulfur in the porous carbon with abundant interparticle pores facilitates rapid electronic/ionic transport and mitigates dissolution of polysulfides intermediates. More importantly, the organic sulfur units dispersed in the insoluble/insulating Li2S2/Li2S phase could prevent its irreversible deposition. Such nanostructure with tailored chemistry property permits the C/PS electrodes to exhibit enhanced cycling stability and high rate capability. The nanospace-confinement copolymerization strategy features general and facial advantages, which may provide new opportunities for the future development of advanced sulfur cathodes.

  19. Modification of flax fibres by radiation induced emulsion graft copolymerization of glycidyl methacrylate

    NASA Astrophysics Data System (ADS)

    Moawia, Rihab Musaad; Nasef, Mohamed Mahmoud; Mohamed, Nor Hasimah; Ripin, Adnan

    2016-05-01

    Flax fibres were modified by radiation induced graft copolymerization of glycidyl methacrylate (GMA) by pre-irradiation method in an emulsion medium. The effect of reaction parameters on the degree of grafting (DOG) such as concentration of bleaching agent, absorbed dose, monomer concentration, temperature and reaction time were investigated. The DOG was found to be dependent on the investigated parameters. The incorporation of poly(GMA) grafts in the bleached flax fibres was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The structural and mechanical changes were evaluated by X-ray diffraction (XRD) and mechanical tester, respectively. The results revealed that reacting bleached flax fibres irradiated with 20 kGy with 5% GMA emulsion containing 0.5% polyoxyethylene-sorbitan monolaurate (Tween 20) surfactant at 40 °C for 1 h led to a maximum DOG of 148%. The grafted fibres showed sufficient mechanical strength and hydrophobicity which make them promising precursors for development of adsorbents after appropriate chemical treatments.

  20. Template-Directed Copolymerization, Random Walks along Disordered Tracks, and Fractals.

    PubMed

    Gaspard, Pierre

    2016-12-02

    In biology, template-directed copolymerization is the fundamental mechanism responsible for the synthesis of DNA, RNA, and proteins. More than 50 years have passed since the discovery of DNA structure and its role in coding genetic information. Yet, the kinetics and thermodynamics of information processing in DNA replication, transcription, and translation remain poorly understood. Challenging issues are the facts that DNA or RNA sequences constitute disordered media for the motion of polymerases or ribosomes while errors occur in copying the template. Here, it is shown that these issues can be addressed and sequence heterogeneity effects can be quantitatively understood within a framework revealing universal aspects of information processing at the molecular scale. In steady growth regimes, the local velocities of polymerases or ribosomes along the template are distributed as the continuous or fractal invariant set of a so-called iterated function system, which determines the copying error probabilities. The growth may become sublinear in time with a scaling exponent that can also be deduced from the iterated function system.

  1. Fluorinated polymides for interlayer dielectric applications: Tailoring of properties via copolymerization

    SciTech Connect

    Auman, B.C.; McKerrow, A.J.; Ho, P.S.

    1996-10-01

    Over the past several years DuPont has been exploring new, rod-like fluorinated polyimides for interlayer dielectric (ILD) applications. It has been shown that copolymerization is a versatile method for tailoring properties of these rigid polyimides. Initial product offerings from DuPont showed an excellent balance of properties for ILD applications. These materials, however, due to their highly rod-like structure and very low in-plane coefficient of thermal expansion (CTE), actually yielded negative thermal stresses on silicon at the 1 {mu}m thicknesses typical of interlayer dielectrics. More flexible materials with higher CTE typically yield positive stress values which can be undesirably quite high. The dielectric constant of these highly rod-like fluorinated polyimides was also somewhat anisotropic, again due to the rod-like nature and resulting high in-plane orientation of these polyimides. Since a thermal stress on silicon near zero and a more isotropic dielectric constant are likely the most desirable states for an ILD, the highly rod-like polyimide was further optimized by incorporation of a more flexible fluorinated comonomer, 6FDA, at various levels to increase CTE and balance dielectric constant. The various properties of this series of fluorinated polyimides were investigated. The results have shown that it is indeed possible to obtain near zero stress on silicon while attaining more isotropic dielectric constant via structure optimization.

  2. Arabidopsis peroxidase-catalyzed copolymerization of coniferyl and sinapyl alcohols: kinetics of an endwise process.

    PubMed

    Demont-Caulet, Nathalie; Lapierre, Catherine; Jouanin, Lise; Baumberger, Stéphanie; Méchin, Valérie

    2010-10-01

    In order to determine the mechanism of the earlier copolymerization steps of two main lignin precursors, sinapyl (S) alcohol and coniferyl (G) alcohol, microscale in vitro oxidations were carried out with a PRX34 Arabidopsis thaliana peroxidase in the presence of H(2)O(2). This plant peroxidase was found to have an in vitro polymerization activity similar to the commonly used horseradish peroxidase. The selected polymerization conditions lead to a bulk polymerization mechanism when G alcohol was the only phenolic substrate available. In the same conditions, the presence of S alcohol at a 50/50 S/G molar ratio turned this bulk mechanism into an endwise one. A kinetics monitoring (size-exclusion chromatography and liquid chromatography-mass spectrometry) of the different species formed during the first 24h oxidation of the S/G mixture allowed sequencing the bondings responsible for oligomerization. Whereas G homodimers and GS heterodimers exhibit low reactivity, the SS pinoresinol structure act as a nucleating site of the polymerization through an endwise process. This study is particularly relevant to understand the impact of S units on lignin structure in plants and to identify the key step at which this structure is programmed. Copyright © 2010 Elsevier Ltd. All rights reserved.

  3. Dinuclear Zinc Salen Catalysts for the Ring Opening Copolymerization of Epoxides and Carbon Dioxide or Anhydrides.

    PubMed

    Thevenon, Arnaud; Garden, Jennifer A; White, Andrew J P; Williams, Charlotte K

    2015-12-21

    A series of four dizinc complexes coordinated by salen or salan ligands, derived from ortho-vanillin and bearing (±)-trans-1,2-diaminocyclohexane (L1) or 2,2-dimethyl-1,3-propanediamine (L2) backbones, is reported. The complexes are characterized using a combination of X-ray crystallography, multinuclear NMR, DOSY, and MALDI-TOF spectroscopies, and elemental analysis. The stability of the dinuclear complexes depends on the ligand structure, with the most stable complexes having imine substituents. The complexes are tested as catalysts for the ring-opening copolymerization (ROCOP) of CO2/cyclohexene oxide (CHO) and phthalic anhydride (PA)/CHO. All complexes are active, and the structure/activity relationships reveal that the complex having both L2 and imine substituents displays the highest activity. In the ROCOP of CO2/CHO its activity is equivalent to other metal salen catalysts (TOF = 44 h(-1) at a catalyst loading of 0.1 mol %, 30 bar of CO2, and 80 °C), while for the ROCOP of PA/CHO, its activity is slightly higher than other metal salen catalysts (TOF = 198 h(-1) at a catalyst loading of 1 mol % and 100 °C). Poly(ester-block-carbonate) polymers are also afforded using the most active catalyst by the one-pot terpolymerization of PA/CHO/CO2.

  4. Preparation of hydrophilic and antifouling polysulfone ultrafiltration membrane derived from phenolphthalin by copolymerization method

    NASA Astrophysics Data System (ADS)

    Liu, Zhixiao; Mi, Zhiming; Chen, Chunhai; Zhou, Hongwei; Zhao, Xiaogang; Wang, Daming

    2017-04-01

    In this task, carboxylated polysulfone (PSF-COOH) was achieved by introducing the monomer of phenolphthalin (PPL) containing carboxyl to the molecule backbone of polysulfone (PSF). And a series of PSF-COOH copolymers with different carboxylation degree was synthesized by adjusting the molar (%) of bisphenol A (BPA) and PPL in direct copolymerization method and was prepared as PSF-COOH ultrafiltration membranes via phase separation method. The effect of PPL molar (%) in copolymers on the morphology, hydrophilicity, permeation flux, antifouling and mechanical properties of membranes was investigated by scanning electron microscope (SEM), atomic force microscope (AFM), water contact angle, ultrafiltration experiments and universal testing machine, respectively. The results showed that with the increased carboxyl content in membranes, the hydrophilicity, permeation fluxes and antifouling properties of membranes gradually increased. When the molar (%) of PPL to BPA was 100:0, the membrane exhibited the highest pure water flux (329.6 L/m2 h) and the maximum flux recovery rate (92.5%). When the content of carboxyl in the membrane was 80% or more, after three cycles of BSA solution (1 g/L) filtration, the flux recovery rate was basically constant or showed a slightly increase. Thus, it can achieve the goal of long term usage without compromising flux.

  5. MinCD cell division proteins form alternating co-polymeric cytomotive filaments

    PubMed Central

    Ghosal, Debnath; Trambaiolo, Daniel; Amos, Linda A.; Löwe, Jan

    2014-01-01

    Summary During bacterial cell division, filaments of the tubulin-like protein FtsZ assemble at midcell to form the cytokinetic Z-ring. Its positioning is regulated by the oscillation of MinCDE proteins. MinC is activated by MinD through an unknown mechanism and prevents Z-ring assembly anywhere but midcell. Here, using X-ray crystallography, electron microscopy and in vivo analyses we show that MinD activates MinC by forming a new class of alternating copolymeric filaments that show similarity to eukaryotic septin filaments A non-polymerising mutation in MinD causes aberrant cell division in E. coli. MinCD copolymers bind to membrane, interact with FtsZ, and are disassembled by MinE. Imaging a functional msfGFP-MinC fusion protein in MinE deleted cells reveals filamentous structures. EM imaging of our reconstitution of the MinCD-FtsZ interaction on liposome surfaces reveals a plausible mechanism for regulation of FtsZ ring assembly by MinCD copolymers. PMID:25500731

  6. Controlled graft copolymerization of lactic acid onto starch in a supercritical carbon dioxide medium.

    PubMed

    Salimi, Kouroush; Yilmaz, Mehmet; Rzayev, Zakir M O; Piskin, Erhan

    2014-12-19

    This work presents a new approach for the synthesis of a starch-g-poly L-lactic acid (St-g-PLA) copolymer via the graft copolymerization of LA onto starch using stannous 2-ethyl hexanoate (Sn(Oct)2) as a catalyst in a supercritical carbon dioxide (scCO2) medium. The effects of several process parameters, including the pressure, temperature, scCO2 flow rate and reaction time, on the polymerization yield and grafting degree were studied. Amorphous graft St-g-PLA copolymers with increased thermal stability and processability were produced with a high efficiency. The maximum grafting degree (i.e., 52% PLA) was achieved with the following reaction conditions: 6h, 100°C, 200 bar and a 1:3 (w/w) ratio of St/LA. It was concluded that these low cost biobased graft biopolymers are potential candidates for several environment-friendly applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. In vivo non-invasive optical imaging of temperature-sensitive co-polymeric nanohydrogel

    NASA Astrophysics Data System (ADS)

    Chen, Haiyan; Zhang, Jian; Qian, Zhiyu; Liu, Fei; Chen, Xinyang; Hu, Yuzhu; Gu, Yueqing

    2008-05-01

    Assessment of hyperthermia in pathological tissue is a promising strategy for earlier diagnosis of malignant tumors. In this study, temperature-sensitive co-polymeric nanohydrogel poly(N-isopropylacrylamide-co-acrylic acid) (PNIPA-co-AA) was successfully synthesized by the precipitation polymerization method. The diameters of nanohydrogels were controlled to be less than 100 nm. Also the lower critical solution temperature (LCST, 40 °C) was manipulated above physiological temperature after integration of near-infrared (NIR) organic dye (heptamethine cyanine dye, HMCD) within its interior cores. NIR laser light (765 nm), together with sensitive charge coupled device (CCD) cameras, were designed to construct an NIR imaging system. The dynamic behaviors of PNIPA-co-AA-HMCD composites in denuded mice with or without local hyperthermia treatment were real-time monitored by an NIR imager. The results showed that the PNIPA-co-AA-HMCD composites accumulated in the leg treated with local heating and diffused much slower than that in the other leg without heating. The results demonstrated that the temperature-responsive PNIPA-co-AA-HMCD composites combining with an NIR imaging system could be an effective temperature mapping technique, which provides a promising prospect for earlier tumor diagnosis and thermally related therapeutic assessment.

  8. Chemically induced graft copolymerization of 2-hydroxyethyl methacrylate onto polyurethane surface for improving blood compatibility

    NASA Astrophysics Data System (ADS)

    He, Chunli; Wang, Miao; Cai, Xianmei; Huang, Xiaobo; Li, Li; Zhu, Haomiao; Shen, Jian; Yuan, Jiang

    2011-11-01

    To improve hydrophilicity and blood compatibility properties of polyurethane (PU) film, we chemically induced graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto the surface of polyurethane film using benzoyl peroxide as an initiator. The effects of grafting temperature, grafting time, monomer and initiator concentrations on the grafting yields were studied. The maximum grafting yield value was obtained 0.0275 g/cm2 for HEMA. Characterization of the films was carried out by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements. ATR-FTIR data showed that HEMA was successfully grafted onto the PU films surface. Water contact angle measurement demonstrated the grafted films possessed a relatively hydrophilic surface. The blood compatibility of the grafted films was preliminarily evaluated by a platelet-rich plasma adhesion test and hemolysis test. The results of platelet adhesion experiment showed that polyurethane grafted polymerization with monomer of 2-hydroxyethyl methacrylate had good blood compatibility featured by the low platelet adhesion. Hemolysis rate of the PU-g-PHEMA films was dramatically decreased than the ungrafted PU films. This kind of new biomaterials grafted with HEMA monomers might have a potential usage for biomedical applications.

  9. Template-Directed Copolymerization, Random Walks along Disordered Tracks, and Fractals

    NASA Astrophysics Data System (ADS)

    Gaspard, Pierre

    2016-12-01

    In biology, template-directed copolymerization is the fundamental mechanism responsible for the synthesis of DNA, RNA, and proteins. More than 50 years have passed since the discovery of DNA structure and its role in coding genetic information. Yet, the kinetics and thermodynamics of information processing in DNA replication, transcription, and translation remain poorly understood. Challenging issues are the facts that DNA or RNA sequences constitute disordered media for the motion of polymerases or ribosomes while errors occur in copying the template. Here, it is shown that these issues can be addressed and sequence heterogeneity effects can be quantitatively understood within a framework revealing universal aspects of information processing at the molecular scale. In steady growth regimes, the local velocities of polymerases or ribosomes along the template are distributed as the continuous or fractal invariant set of a so-called iterated function system, which determines the copying error probabilities. The growth may become sublinear in time with a scaling exponent that can also be deduced from the iterated function system.

  10. Studies on graft copolymerization of gellan gum with N,N-dimethylacrylamide by the redox system.

    PubMed

    Pandey, Vijay Shankar; Verma, Shiv Kumar; Yadav, Mithilesh; Behari, Kunj

    2014-09-01

    The present paper reports the graft copolymerization of N,N-dimethylacrylamide onto gellan gumby free radical polymerization using potassium peroxymonosulphate/sarbose redox system in an inert atmosphere. The reaction conditions for maximum grafting have been optimized by varying the reaction variables, including the concentration of N,N-dimethylacrylamide(4.0×10(-2)-20×10(-2) mol dm(-3)), potassium peroxymonosulphate (0.6×10(-2)-1.4×10(-2)mol dm(-3)), sarbose (0.4×10(-3)-3.6×10(-3) mol dm(-3)), sulphuric acid (2.0×10(-3)-10×10(-3) mol dm(-3)), gellan gum (0.6-1.4 g dm(-3)) along with time duration (60-180 min) and temperature (25-45°C).Water-swelling capacity, metal ion sorption and flocculation studies of synthesized graft copolymer have been performed with respect to the parent polymer. The graft copolymer has been characterized by FTIR spectroscopy and thermogravimetric analysis. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Solid phase graft copolymerization of acrylic monomers onto thermoplastics and their use as blend compatibilizers

    NASA Astrophysics Data System (ADS)

    Subramanian, Srinivas

    This research work is an extension of some of the earlier work done on the development of solid phase grafting technique to graft various monomers onto polymers as well as postulation of the usefulness of the graft copolymers thus synthesized. Polystyrene grafted with acrylic acid, previously developed in bench scale, was synthesized in pilot-plant scale batches. Process parameter studies on the grafting of acrylic acid onto polypropylene and developmental studies on the grafting of maleic anhydride onto polystyrene were also done. Polymers grafted with polar molecules such as maleic anhydride and acrylic acid have been used to compatibilize immiscible blends of polar and non-polar polymers. On the same note, the applicability of the solid phase graft copolymers as blend compatibilizers were investigated and their performance was compared to commercially available compatibilizers. Solid phase graft copolymerization process is a technique to synthesize graft copolymers. Some of its salient features are use of minimal solvent to conduct the reaction and easy equipment modification. It is a low pressure and low temperature process. This technique provides a viable alternative to the environmentally hazardous, and time consuming conventional process currently in use. Hence, development of this technique could be beneficial not only to the plastics industry, but also to mankind. Also, this technique provides a low-cost and extremely easy method to develop graft copolymers such as acrylic acid functionalized polymers that are rapidly gaining popularity as blend compatibilizers and polymer reinforcing agents. A study that proves the potential of these solid phase graft copolymers as good blend compatibilizers for industrially important immiscible polymers will develop interest in the industries about this grafting process. The free radical solid phase graft copolymerization process was carried in a modified Brabender-type mixer fitted with specially designed blades to

  12. Clickable degradable aliphatic polyesters via copolymerization with alkyne epoxy esters: synthesis and postfunctionalization with organic dyes.

    PubMed

    Teske, Nele S; Voigt, Julia; Shastri, V Prasad

    2014-07-23

    Degradable aliphatic polyesters are the cornerstones of nanoparticle (NP)-based therapeutics. In this paradigm, covalent modification of the NP with cell-targeting motifs and dyes can aid in guiding the NP to its destination and gaining visual confirmation. Therefore, strategies to impart chemistries along the polymer backbone that are amenable to easy modification, such as 1,3-dipolar cycloaddition of an azide to an alkyne (the "click reaction"), could be significant. Here we present a simple and efficient way to introduce alkyne groups at high density in aliphatic polyesters without compromising their crystallinity via the copolymerization of cyclic lactones with propargyl 3-methylpentenoate oxide (PMPO). Copolymers of lactic acid and ε-caprolactone with PMPO were synthesized with up to 9 mol % alkyne content, and accessibility of the alkyne groups to the click reaction was demonstrated using several dyes commonly employed in fluorescence microscopy and imaging (Cy3, ATTO-740, and coumarin 343). In order to establish the suitability of these copolymers as nanocarriers, copolymers were formulated into NPs, and cytocompatibility, cellular uptake, and visualization studies undertaken in HeLa cells. Dye-modified NPs exhibited no quenching, remained stable in solution for at least 10 days, showed no cytotoxicity, and were readily taken up by HeLa cells. Furthermore, in addition to enabling the incorporation of multiple fluorophores within the same NP through blending of individual dye-modified copolymers, dye-modified polyesters offer advantages over physical entrapment of dye, including improved signal to noise ratio and localization of the fluorescence signal within cells, and possess the necessary prerequisites for drug delivery and imaging.

  13. Quantitative determination of insulin entrapment efficiency in triblock copolymeric nanoparticles by high-performance liquid chromatography.

    PubMed

    Xu, Xiongliang; Fu, Yao; Hu, Haiyan; Duan, Yourong; Zhang, Zhirong

    2006-04-11

    A rapid and effective isocratic chromatographic procedure was described in this paper for the determination of insulin entrapment efficiency (EE) in triblock copolymeric nanoparticles using reversed-phase high-performance liquid chromatography (RP-HPLC) with an ultraviolet/visible detector at low flow rate. The method has been developed on a Shimadzu Shim-pack VP-ODS column (150 mm x 4.6 mm, 5 microm, Chiyoda-Ku, Tokyo, Japan) using a mixture of 0.2 M sodium sulfate anhydrous solution adjusted to pH 2.3 with phosphoric acid and acetonitrile (73:27, v/v) as mobile phase at the flow rate of 0.8 ml min(-1) and a 214 nm detection. The method was validated in terms of selectivity, linearity, precision, accuracy, solution stability, limit of detection (LOD) and limit of quantification (LOQ). The calibration curve was linear in the concentration range of 2.0-500.0 microg ml(-1), and the limits of detection and quantitation were 8 and 20 ng, respectively. The mean recovery of insulin from spiked samples, in a concentration range of 8-100 microg ml(-1), was 98.96% (R.S.D.= 2.51%, n = 9). The intra- and inter-assay coefficients of variation were less than 2.24%. The proposed method has the advantages of simple pretreatment, rapid isolation, high specificity and precision, which can be used for direct analysis of insulin in commercially available raw materials, formulations of nanoparticles, and drug release as well as stability studies.

  14. Manganese(III) Schiff base complexes: chemistry relevant to the copolymerization of epoxides and carbon dioxide.

    PubMed

    Darensbourg, Donald J; Frantz, Eric B

    2007-07-23

    Schiff base complexes of the form (acacen)Mn(III)X (acacen = N,N'-bis(acetylacetone)-1,2-ethylenediimine), where X = OAc, Cl, or N(3), have been evaluated for their ability to couple CO(2) and cyclohexene oxide in the presence of a variety of cocatalysts to provide cyclic or polycarbonates. These complexes proved to be ineffective at catalyzing this process; however, valuable information related to the coordination chemistry of these manganese Schiff bases was elucidated. Of importance, mechanistic findings as revealed by comprehensive studies involving structurally related (salen)CrX and (salen)CoX complexes strongly support the requirement of six-coordinate metal species for the effective copolymerization of CO(2) and epoxides. In the case of these Mn(III) complexes, it was determined that in chloroform or toluene solution a five-coordinate species was greatly favored over a six-coordinate species even in the presence of 20 equiv or more of various Lewis bases. Significantly epoxide monomers such as propylene oxide and cyclohexene oxide displayed no tendency to bind to these (acacen)MnX derivatives, even when used as solvents. Only in the case of excessive quantities of heterocyclic amines such as pyridine, DMAP, and DBU was spectral evidence of a six-coordinate Mn derivative observed in solution. X-ray crystal structures are provided for many of the complexes involved in this study, including the one-dimensional polymeric structures of [(acacen)MnOAc x 2H(2)O](n), [(acacen)MnN(3)](n) (mu(1,3)-N(3)), and a rare mixed bridging species [(acacen)MnN(3)](n) (mu(1,3)-N(3)/mu(1,1)-N(3)). In addition, a structure was obtained in which the unit cell contains both a (acacen)MnN(3)(DMAP) and a (acacen)MnN(3) species.

  15. Two-dimensional Raman correlation spectroscopy study of an emulsion copolymerization reaction process.

    PubMed

    Noda, Isao; Allen, William M; Lindberg, Seth E

    2009-02-01

    The emulsion copolymerization of styrene and 1,3-butadiene using an oligomeric nonionic surfactant as an emulsifier to make a styrene-butadiene rubber (SBR) copolymer latex was monitored by real-time in situ Raman spectroscopy. Time-resolved Raman spectra collected during the early stage of the polymerization reaction were subjected to a series of data analysis techniques, including two-dimensional (2D) correlation spectroscopy, multivariate self-modeling curve resolution (SMCR), and kernel analysis, to elucidate the fine details of the complex reaction process. Generalized 2D correlation analysis of time-resolved Raman spectra readily identified the characteristic Raman scattering bands for the monomers and copolymer. Cross-peaks appearing in 2D Raman correlation spectra showed that the decrease in the spectral intensity of Raman bands assignable to 1,3-butadiene occurs before the band intensity changes for styrene or SBR copolymer. The positions of asynchronous cross-peaks were used to identify a spectral region with the most distinct pattern of intensity variations, which in turn could be used as the starting point for the alternating least squares iteration of the SMCR analysis. SMCR analysis of the time-resolved Raman spectra generated a set of estimated pure component spectra and concentration profiles of styrene, 1,3-butadiene, and SBR copolymer without requiring independently measured calibration data. The estimated concentration profiles of monomers and copolymer indicated that the reaction of 1,3-butadiene started before the consumption of styrene and production of SBR copolymer. Kernel analysis of the estimated concentration profiles provided a succinct measure of the similarity and dissimilarity of the concentration changes of monomers and copolymer.

  16. Novel rubbers from cationic copolymerization of soybean oils and dicyclopentadiene. 1. Synthesis and characterization.

    PubMed

    Andjelkovic, Dejan D; Larock, Richard C

    2006-03-01

    Novel thermosetting copolymers, ranging from tough and ductile to very soft rubbers, have been prepared by the cationic copolymerization of regular (SOY) and 100% conjugated soybean oils (C(100)SOY) with dicyclopentadiene (DCP) catalyzed by Norway fish oil (NFO)-modified and SOY- and C(100)SOY-diluted boron trifluoride diethyl etherate (BFE). The gelation time of the reactions varies from 4 to 991 min at 110 degrees C. The yields of the bulk copolymers are essentially quantitative, while the yields of the cross-linked copolymers remaining after Soxhlet extraction with methylene chloride range from 69% to 88%, depending on the monomer stoichiometry and the catalyst used. (1)H NMR spectroscopy and Soxhlet extraction data indicate that these copolymers consist of a cross-linked soybean oil-DCP network plasticized by certain amounts of methylene chloride-soluble linear or less cross-linked soybean oil-DCP copolymers, unreacted oil, and some low molecular weight hydrolyzed oil. The molecular weights of these soluble fractions are in the range from 400 to 10,000 g/mol based on polystyrene standards. The bulk copolymers have glass transition temperatures ranging from -22.6 to 56.6 degrees C, while their tan delta peak values range from 0.7 to 1.2. Thermogravimetric analysis (TGA) indicates that these soybean oil-DCP copolymers are thermally stable below 200 degrees C, with 10% and 50% weight loss temperatures ranging from 280 to 372 degrees C and 470-554 degrees C, respectively. These properties suggest that these biobased thermosets may prove useful alternatives to current petroleum-based plastics and find widespread utility.

  17. A DFT Study on the Co-polymerization of CO2 and Ethylene: Feasibility Analysis for the Direct Synthesis of Polyethylene Esters.

    PubMed

    Moha, Verena; Cozzula, Daniela; Hölscher, Markus; Leitner, Walter; Müller, Thomas E

    2016-07-07

    The co-polymerization of CO2 with the non-polar monomer ethylene, though highly desirable, still presents a challenge whereas the palladium-catalyzed CO/C2 H4 co-polymerization is well understood. Building on this analogy, the goal of this study was to elucidate the feasibility of developing suitable catalysts for co-polymerizing CO2 with ethylene to polyethylene esters. Computational methods based on density functional theory were hereby employed. In the search for new catalyst lead structures, a closed catalytic cycle was identified for the palladium-catalyzed CO2 /C2 H4 co-polymerization reaction. The computational study on palladium complexes with a substituted anionic 2-[bis(2,4-dimethoxyphenyl)-phosphine]-benzene-2-hydroxo ligand revealed key aspects that need to be considered when designing ligand sets for potential catalysts for the non-alternating co-polymerization of CO2 and ethylene. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Development of microporous drug-releasing films cast from artificial nanosized latexes of poly(styrene-co-methyl methacrylate) or poly(styrene-co-ethyl methacrylate).

    PubMed

    Otto, Daniel P; Vosloo, Hermanus C M; Liebenberg, Wilna; de Villiers, Melgardt M

    2008-08-01

    Two sets of copolymers comprising of styrene and either methyl or ethyl methacrylate as comonomer were conveniently synthesized by microemulsion copolymerization. The purified materials were characterized by GPC-MALLS and were shown to form artificial nanolatexes in THF. ATR-FTIR analysis revealed differences in copolymer composition and based on the copolymer properties, a selection of copolymers was chosen to cast drug-loaded, microporous films that exhibit microencapsulation of drug agglomerates. The contact angles of the copolymers suggested potential applications in medical devices to prevent the formation of bacterial biofilms that commonly result in infections. Additionally, the different copolymeric films showed two phases of drug release characterized by a rapid initial drug release followed by a zero-order phase. Depending on the application, one could select the copolymer films that best suited the application i.e. for short-term drug release applications such as urinary catheters or long-term applications such as artificial implants.

  19. Thermally reversible gels based on acryloyl- L-proline methyl ester as drug delivery systems

    NASA Astrophysics Data System (ADS)

    Martellini, Flavia; Higa, Olga Z.; Takacs, Erzsebet; Safranj, Agneza; Yoshida, Masaru; Katakai, Ryoichi; Carenza, Mario

    1999-06-01

    Thermally reversible hydrogels were synthesized by radiation-induced copolymerization of acryloyl- L-proline methyl ester with hydrophilic or hydrophobic monomers. The swelling behaviour was found to be affected by a proper balance of the latter. In particular, the transition temperature of the different hydrogels shifted to higher or lower values depending on the presence of hydrophilic or hydrophobic moieties in the polymer chain, respectively. Acetaminophen, an analgesic and antipyretic drug, was entrapped into some hydrogels and a wide range of release rates was obtained according to the nature of the comonomers. A novel thermoresponsive hydrogel was also prepared by radiation polymerization of acryloyl- L-proline methyl ester in the presence of 4-acryloyloxy acetanilide, an acrylic derivative of acetaminophen. Again, the swelling curves showed an inverse function of temperature. It was shown that with this hydrogel bearing the drug covalently attached to the polymer backbone, the hydrolysis process was the rate-determining process of the drug release.

  20. Preparation of metal adsorbent from poly(methyl acrylate)-grafted-cassava starch via gamma irradiation

    NASA Astrophysics Data System (ADS)

    Suwanmala, Phiriyatorn; Hemvichian, Kasinee; Hoshina, Hiroyuki; Srinuttrakul, Wannee; Seko, Noriaki

    2012-08-01

    Metal adsorbent containing hydroxamic acid groups was successfully synthesized by radiation-induced graft copolymerization of methyl acrylate (MA) onto cassava starch. The optimum conditions for grafting were studied in terms of % degree of grafting (Dg). Conversion of the ester groups present in poly(methyl acrylate)-grafted-cassava starch copolymer into hydroxamic acid was carried out by treatment with hydroxylamine (HA) in the presence of alkaline solution. The maximum percentage conversion of the ester groups of the grafted copolymer, % Dg=191 (7.63 mmol/g of MA), into the hydroxamic groups was 70% (5.35 mmol/g of MA) at the optimum condition. The adsorbent of 191%Dg had total adsorption capacities of 2.6, 1.46, 1.36, 1.15 and 1.6 mmol/g-adsorbent for Cd2+, Al3+, UO22+, V5+ and Pb2+, respectively, in the batch mode adsorption.

  1. Modifying graphite oxide with grafted methyl acrylate brushes for the attachment of magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Xiang; Cheng, Heming; Liu, Yan

    2013-09-01

    Surface-grafted polymer brushes of methyl acrylate of graphite oxide (GO) have been constructed to anchor poly(amidoamine) 2.0G (PAMAM 2.0G) dendrites for the attachment of magnetite nanoparticles. Monomers of methyl acrylate were copolymerized on the GO sheets by atom transfer radical polymerization. Then the PAMAM 2.0G was attached via covalent bond at the end of the grafted chains. Thus the inexpensive Fe(III) of ferric trichloride could coordinate with the remaining amino groups of PAMAM 2.0G and were reduced by the added sodium borohydrite at appropriate pH value to obtain nano magnetite-decorated GO hybrid materials. The hybrids exhibited a powerful catalysis on the degradation of aqueous solutions of hydroquinone.

  2. Methyl nutrients, DNA methylation, and cardiovascular disease.

    PubMed

    Glier, Melissa B; Green, Timothy J; Devlin, Angela M

    2014-01-01

    Diet plays an important role in the development and prevention of cardiovascular disease (CVD), but the molecular mechanisms are not fully understood. DNA methylation has been implicated as an underlying molecular mechanism that may account for the effect of dietary factors on the development and prevention of CVD. DNA methylation is an epigenetic process that provides "marks" in the genome by which genes are set to be transcriptionally activated or silenced. Epigenomic marks are heritable but are also responsive to environmental shifts, such as changes in nutritional status, and are especially vulnerable during development. S-adenosylmethionine is the methyl group donor for DNA methylation and several nutrients are required for the production of S-adenosylmethionine. These methyl nutrients include vitamins (folate, riboflavin, vitamin B12, vitamin B6, choline) and amino acids (methionine, cysteine, serine, glycine). As such, imbalances in the metabolism of these nutrients have the potential to affect DNA methylation. The focus of this review is to provide an overview on the current understanding of the relationship between methyl nutrient status and DNA methylation patterns and the potential role of this interaction in CVD pathology. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Surface modification of copolymerized films from three-armed biodegradable macromers - An analytical platform for modified tissue engineering scaffolds.

    PubMed

    Müller, Benno M; Loth, Rudi; Hoffmeister, Peter-Georg; Zühl, Friederike; Kalbitzer, Liv; Hacker, Michael C; Schulz-Siegmund, Michaela

    2017-03-15

    The concept of macromers allows for a broad adjustment of biomaterial properties by macromer chemistry or copolymerization. Copolymerization strategies can also be used to introduce reactive sites for subsequent surface modification. Control over surface features enables adjustment of cellular reactions with regard to site and object of implantation. We designed macromer-derived polymer films which function as non-implantable analytical substrates for the investigation of surface properties of equally composed scaffolds for bone tissue engineering. To this end, a toolbox of nine different biodegradable, three-armed macromers was thermally cross-copolymerized with poly(ethylene glycol)-methacrylate (PEG-MA) to films. Subsequent activation of PEG-hydroxyl groups with succinic anhydride and N-hydroxysuccinimid allowed for covalent surface modification. We quantified the capacity to immobilize analytes of low (amino-functionalized fluorescent dye, Fcad, and RGD-peptides) and high (alkaline phosphatase, ALP) molecular weight. Fcad grafting level was controlled by macromer chemistry, content and molecular weight of PEG-MA, but also the solvent used for film synthesis. Fcad molar amount per surface area was twentyfive times higher on high-swelling compared to low-swelling films, but differences became smaller when large ALP (appr. 2:1) were employed. Similarly, small differences were observed on RGD peptide functionalized films that were investigated by cell adhesion studies. Presentation of PEG-derivatives on surfaces was visualized by atomic force microscopy (AFM) which unraveled composition-dependent domain formation influencing fluorescent dye immobilization. Surface wetting characteristics were investigated via static water contact angle. We conclude that macromer ethoxylation and lactic acid content determined film swelling, PEG domain formation and eventually efficiency of surface decoration. Surfaces of implantable biomaterials are the site of interaction with a

  4. Methyl salicylate overdose

    MedlinePlus

    Methyl salicylate (oil of wintergreen) is a chemical that smells like wintergreen. It is used in many over- ... muscle ache creams. It is related to aspirin. Methyl salicylate overdose occurs when someone swallows a dangerous amount ...

  5. Synergistic effect on corrosion resistance of Phynox substrates grafted with surface-initiated ATRP (co)polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-hydroxyethyl methacrylate (HEMA).

    PubMed

    Barthélémy, Bastien; Maheux, Simon; Devillers, Sébastien; Kanoufi, Frédéric; Combellas, Catherine; Delhalle, Joseph; Mekhalif, Zineb

    2014-07-09

    Phynox is of high interest for biomedical applications due to its biocompatibility and corrosion resistance. However, some Phynox applications require specific surface properties. These can be imparted with suitable surface functionalizations of its oxide layer. The present work investigates the surface-initiated atom transfer radical polymerization (ATRP) of 2-methacryloyoxyethyl phosphorylcholine (MPC), 2-hydroxyethyl methacrylate (HEMA), and ATRP copolymerization of (HEMA-co-MPC) (block and statistic copolymerization with different molar ratios) on grafted Phynox substrates modified with 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid (BUPA) as initiator. It is found that ATRP (co)polymerization of these monomers is feasible and forms hydrophilic layers, while improving the corrosion resistance of the system.

  6. Octadecyl maleamic acid salt as a microreactor for its copolymerization reaction with butyl acrylate in aqueous medium.

    PubMed

    Milton Gaspar, L J; Baskar, Geetha

    2006-03-14

    The hydrogelator, octadecyl maleamic acid salt (ODMAS), has been shown to perform as a microreactor in copolymerization reaction with butyl acrylate in aqueous medium thereby providing functionalized latex. The evidence for occurrence of controlled polymerization reaction inside the microreactor is drawn from the composition and the polydispersity index of the copolymers. The copolymers generated under microreactor conditions or in other words, from emulsion phase provided by the hydrogelator exhibit significant incorporation of ODMAS with narrow polydispersity index. For example, a copolymer with ODMAS as high as 0.62 m and polydispersity index at 1.39 could be achieved. On the contrary, the solution copolymerization reactions in THF resulted in low yield of polymers with molecular weight at 10(3) order and polydispersity index in range of 2.53-2.91. The particle size distribution of the latexes remains almost invariant at 74 +/- 4 nm, over the concentration range of 0.12-0.62m with standard deviation (sigma) of 0.12-0.22. The surface area/molecule of ODMAS on the latex particle has been estimated to be 0.21 nm(2)/molecule. The polymerized latexes exhibit zeta potential at 64 +/- 3 mV and surface tension in range of 42.8-47.9 mN m(-)(1) respectively. This is indicative of coverage of latex with ODMAS.

  7. Concerning the deactivation of cobalt(III)-based porphyrin and salen catalysts in epoxide/CO2 copolymerization.

    PubMed

    Xia, Wei; Salmeia, Khalifah A; Vagin, Sergei I; Rieger, Bernhard

    2015-03-09

    Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)-based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)-salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X-ray crystallography (for cobalt(II)-salen). Further investigations on a TPPCoCl (TPP = tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo-first order in cobalt(III)-porphyrin. The addition of a co-catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)-salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO2 copolymerization by cobalt(III)-salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO-ring-opening intermediates, cobalt(III)-salen/porphyrin alkoxides.

  8. Mussel-inspired one-step copolymerization to engineer hierarchically structured surface with superhydrophobic properties for removing oil from water.

    PubMed

    Huang, Shouying

    2014-10-08

    In the present study, a superhydrophobic polyurethane (PU) sponge with hierarchically structured surface, which exhibits excellent performance in absorbing oils/organic solvents, was fabricated for the first time through mussel-inspired one-step copolymerization approach. Specifically, dopamine (a small molecular bioadhesive) and n-dodecylthiol were copolymerized in an alkaline aqueous solution to generate polydopamine (PDA) nanoaggregates with n-dodecylthiol motifs on the surface of the PU sponge skeletons. Then, the superhydrophobic sponge that comprised a hierarchical structured surface similar to the chemical/topological structures of lotus leaf was fabricated. The topological structures, surface wettability, and mechanical property of the sponge were characterized by scanning electron microscopy, contact angle experiments, and compression test. Just as a result of the highly porous structure, superhydrophobic property and strong mechanical stability, this sponge exhibited desirable absorption capability of oils/organic solvents (weight gains ranging from 2494% to 8670%), suggesting a promising sorbents for the removal of oily pollutants from water. Furthermore, thanks to the nonutilization of the complicated processes or sophisticated equipment, the fabrication of the superhydrophobic sponge seemed to be quite easy to scale up. All these merits make the sponge a competitive candidate when compared to the conventional absorbents, for example, nonwoven polypropylene fabric.

  9. Enrichment of methylated DNA by methyl-CpG immunoprecipitation.

    PubMed

    Sonnet, Miriam; Baer, Constance; Rehli, Michael; Weichenhan, Dieter; Plass, Christoph

    2013-01-01

    Normal DNA methylation is an epigenetic modification required for proper development. Aberrant DNA methylation, in contrast, is frequently observed in many different malignancies including leukemias and lymphomas. Global DNA methylation profiling addresses the methylated sequences (methylome) of patient genomes to identify disease-specific methylation patterns. Workload in methylome analyses can be considerably reduced by methylome enrichment using proteins or antibodies with high affinity to methylated DNA. Methyl-CpG Immunoprecipitation (MCIp) employs an immobilized recombinant human methyl-CpG binding domain protein 2, MBD2, which binds methylated CpGs in double-stranded DNA. Elution with increasing salt concentrations allows the fractionated enrichment of different degrees of methylation.

  10. Nitroxide-mediated radical ring-opening copolymerization: chain-end investigation and block copolymer synthesis.

    PubMed

    Delplace, Vianney; Harrisson, Simon; Tardy, Antoine; Gigmes, Didier; Guillaneuf, Yohann; Nicolas, Julien

    2014-02-01

    Well-defined, degradable copolymers are successfully prepared by nitroxide-mediated radical ring opening polymerization (NMrROP) of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) or methyl methacrylate (MMA), a small amount of acrylonitrile (AN) and cyclic ketene acetals (CKAs) of different structures. Phosphorous nuclear magnetic resonance allows in-depth chain-end characterization and gives crucial insights into the nature of the copoly-mer terminal sequences and the living chain fractions. By using a small library of P(OEGMA-co-AN-co-CKA) and P(MMA-co-AN-co-CKA) as macroinitiators, chain extensions with styrene are performed to furnish (amphiphilic) block copolymers comprising a degradable segment.

  11. Enhanced cellular uptake of nanoparticles by increasing the hydrophobicity of poly(lactic acid) through copolymerization with cell-membrane-lipid components.

    PubMed

    Samadi Moghaddam, Mariam; Heiny, Markus; Shastri, V Prasad

    2015-10-07

    The influence of hydrophobicity on the internalization of polymeric nanoparticles (NPs) remains poorly investigated. The hydrophobicity of poly(L-lactide) was increased by copolymerization with cell-membrane-lipid components, and this significantly enhanced the uptake of NPs up to 60% in the human cervical cancer cell line in comparison to unmodified poly(L-lactide) NPs.

  12. Comparative biomechanical and radiological characterization of osseointegration of a biodegradable magnesium alloy pin and a copolymeric control for osteosynthesis.

    PubMed

    Lindtner, Richard A; Castellani, Christoph; Tangl, Stefan; Zanoni, Gerald; Hausbrandt, Peter; Tschegg, Elmar K; Stanzl-Tschegg, Stefanie E; Weinberg, Annelie-Martina

    2013-12-01

    Magnesium alloys offer great advantages as degradable implant material for pediatric fracture fixation and hold the potential to overcome certain critical shortcomings inherent to currently used degradable (co)polymers. Besides good biocompatibility and appropriate degradation kinetics, sufficient implant anchorage in host bone is critical to prevent implant failure. Bone-implant anchorage of biodegradable magnesium alloys, however, has not yet been related and compared to that of copolymers, their degradable counterparts currently in clinical use. The aim of this study, therefore, was to comparatively assess bone-implant interface strength and the amount of peri-implant bone of a biodegradable magnesium alloy pin (Mg-Y-Nd-HRE) and a self-reinforced copolymeric control (85/15 poly(l-lactic-co-glycolic acid)). To this purpose, push-out testing, microfocus computed tomography (μCT), histological and scanning electron microscopic examination was performed after 4, 12 and 24 weeks of transcortical implantation in 72 rats. Biomechanical testing revealed significantly higher ultimate shear strength for the magnesium alloy pins than for the copolymeric controls at all 3 timepoints (P≤0.001 for all comparisons). As evaluated by μCT, the amount of bone present near the interface and in a wider radius (up to 0.5mm) around it was higher in the magnesium alloy implants at 4 weeks, without significant differences at 12 and 24 weeks. Histological examination confirmed direct bone-to-implant contact for both implant types. In vivo degradation of implants did not induce any noticeable local or systemic inflammation. This data suggests that the investigated degradable magnesium alloy rod exhibits markedly superior bone-implant interface strength and a greater amount of peri-implant bone than a self-reinforced copolymeric control currently in use; thus it fulfills a crucial prerequisite for its successful clinical deployment as an alternative degradable orthopedic implant

  13. Increasing entrapment of peptides within poly(alkyl cyanoacrylate) nanoparticles prepared from water-in-oil microemulsions by copolymerization.

    PubMed

    Liang, Mingtao; Davies, Nigel M; Toth, Istvan

    2008-10-01

    Low molecular hydrophilic actives such as peptides are typically poorly encapsulated within poly(alkyl cyanoacrylate) nanoparticles when prepared from micellar or microemulsion templates. The aim of the present study was to investigate whether the entrapment of peptides within poly(alkyl cyanoacrylate) nanoparticles could be increased by functionalizing the peptide so that it could copolymerize with the alkyl cyanoacrylate monomer. Peptide and acryloyl functionalized peptide representing the antigenic epitope of the lymphocytic choriomeningitis virus glycoprotein (LCMV(33-41)) were synthesized using solid-phase peptide synthesis. Poly(alkyl cyanoacrylate) nanoparticles were prepared to encapsulate either peptide or functionalized peptide using both an aqueous micellar and a water-in-oil microemulsion polymerization template. Using the micellar template, nanoparticles could not be produced in the presence of acryloyl peptide. Rather an agglomerated mass formed on the stirrer. In contrast, nanoparticles could be prepared using both acryloyl and parent peptide using the water-in-oil microemulsion template. Encapsulation efficiency was more than twofold greater for functionalized peptide, being greater than 90%. Encapsulation efficiency of functionalized peptide was also observed to increase with increasing the amount of alkyl cyanoacrylate monomer used for polymerization. A biphasic release profile was observed for the nanoparticles entrapping the non-functionalized peptide with greater than 50% of peptide being released during the first 10 min and with around 90% being released at 6h. In contrast, less than 10% of the total amount of acryloyl LCMV(33-41) entrapped within the nanoparticles was detected in the release media following the initial 10 min, and no further release of peptide was observed up to the termination of the release study at 360 min. The difference in entrapment and release kinetics between the parent and functionalized peptide strongly supports the

  14. Enhancing biosensor properties of conducting polymers via copolymerization: Synthesis of EDOT-substituted bis(2-pyridylimino)isoindolato-palladium complex and electrochemical sensing of glucose by its copolymerized film.

    PubMed

    Tekbaşoğlu, Tuğçe Yazıcı; Soganci, Tugba; Ak, Metin; Koca, Atıf; Şener, M Kasım

    2017-01-15

    1,3-Bis(2-pyridylimino)isoindoline derivative bearing 3,4-ethylenedioxythiophene (EDOT-BPI) and its palladium complex (EDOT-PdBPI) were synthesized and characterized by FT-IR, (1)H NMR, (13)C NMR, UV-Vis spectroscopies and via mass spectrometric analysis. Polymerization of EDOT-PdBPI and copolymerization with 4-amino-N-(2,5-di(thiophene-2-yl)-1H-pyrrol-1-yl)benzamide (HKCN) were carried out by an electrochemical method. In addition, P(EDOT-PdBPI-co-HKCN) modified graphite rod electrode was improved for amperometric glucose sensor based on glucose oxidase (GOx). In this novel biosensor matrix, amino groups in HKCN were used for the enzyme immobilization. On the other hand, EDOT-PdBPI used to mediate the bioelectrocatalytic reaction. Amperometric detection was carried out following oxygen consumption at -0.7V vs. the Ag reference electrode in phosphate buffer (50mM, pH 6.0). The novel biosensor showed a linear amperometric response for glucose within a concentration range of 0.25mM to 2.5mM (LOD: 0.176mM). Amperometric signals at 1mM of glucose were 17.9μA under anaerobic conditions. Amperometric response of the P(EDOT-PdBPI-co-HKCN)/GOx electrode decreased only by 13% within eight weeks. The P(EDOT-PdBPI-co-HKCN)/GOx electrode showed good selectivity in the presence of ethanol and phenol. This result shows that, modification of the proposed biosensor by copolymerization of amine functionalized monomer, which is indispensable to the enzyme immobilization, with palladium complex bearing monomer, which is mediate the bioelectrocatalytic reaction, have provided to give perfect response to different glucose concentrations.

  15. [DNA methylation and epigenetics].

    PubMed

    Vaniushin, B F

    2006-09-01

    In eukaryotic cells, nuclear DNA is subject to enzymatic methylation with the formation of 5-methylcytosine residues, mostly within the CG and CNG sequences. In plants and animals this DNA methylation is species-, tissue-, and organelle-specific. It changes (decreases) with age and is regulated by hormones. On the other hand, genome methylation can control hormonal signal. Replicative and post-replicative DNA methylation types are distinguished. They are mediated by multiple DNA methyltransferases with different site-specificity. Replication is accompanied by the appearance of hemimethylated DNA sites. Pronounced asymmetry of the DNA strand methylation disappears to the end of the cell cycle. A model of methylation-regulated DNA replication is proposed. DNA methylation controls all genetic processes in the cell (replication, transcription, DNA repair, recombination, and gene transposition). It is the mechanism of cell differentiation, gene discrimination and silencing. In animals, suppression of DNA methylation stops development (embryogenesis), switches on apoptosis, and is usually lethal. Disruption of DNA methylation pattern results in the malignant cell transformation and serves as one of the early diagnostic features of carcinogenesis. In malignant cell the pattern of DNA methylation, as well as the set of DNA methyltransferase activities, differs from that in normal cell. In plants inhibition of DNA methylation is accompanied by the induction of seed storage and florescence genes. In eukaryotes one and the same gene can be simultaneously methylated both at cytosine and adenine residues. It can be thus suggested, that the plant cell contains at least two different, and probably, interdependent systems of DNA methylation. The first eukaryotic adenine DNA methyltransferase was isolated from plants. This enzyme methylates DNA with the formation of N6-methyladenine residues in the sequence TGATCA (TGATCA-->TGm6ATCA). Plants possess AdoMet-dependent endonucleases

  16. Histone Arginine Methylation

    PubMed Central

    Lorenzo, Alessandra Di; Bedford, Mark T.

    2012-01-01

    Arginine methylation is a common posttranslational modification (PTM). This type of PTM occurs on both nuclear and cytoplasmic proteins, and is particularly abundant on shuttling proteins. In this review, we will focus on one aspect of this PTM: the diverse roles that arginine methylation of the core histone tails play in regulating chromatin function. A family of nine protein arginine methyltransferases (PRMTs) catalyze methylation reactions, and a subset target histones. Importantly, arginine methylation of histone tails can promote or prevent the docking of key transcriptional effector molecules, thus playing a central role in the orchestration of the histone code. PMID:21074527

  17. Enhanced electromagnetic loss of polybenzoxazole copolymerized with etched multiwalled carbon nanotube via direct Friedel-Crafts acylation

    NASA Astrophysics Data System (ADS)

    Chen, Yong; Qian, Jun; Teng, Xin; Zhang, Kan; Zhuang, Qixin; Han, Zhewen

    2014-04-01

    Etched multiwalled carbon nanotube (EMCNT) was prepared via an in situ reaction between Si and MCNT induced by the reaction between Na and I2. Subsequently, EMCNTs was subjected to a copolymerization reaction with 4,6-diaminoresorcinol salt (DAR·2HCl) and terephthalic acid (TA) in polyphosphoric acid (PPA) by Friedel-Crafts acylation reaction without any acid treatment or modification. The structure and morphology of the as-prepared poly(p-phenylene benzobisoxazole) (PBO)/EMCNT nanocomposites were characterized by x-ray diffraction (XRD), Raman spectra, and transmission electron microscopy (TEM). The scanning electronic microscope (SEM) images indicated that the EMCNTs can disperse in PBO matrix uniformly without agglomeration. And the electromagnetic properties of the obtained PBO/EMCNT nanocomposites characterized by vector network analyzer (VNA) showed that the introduced PBO/EMCNT composites exhibited a greater enhancement in dielectric loss and magnetic loss than PBO.

  18. (Salen)CrIIIX catalysts for the copolymerization of carbon dioxide and epoxides: role of the initiator and cocatalyst.

    PubMed

    Darensbourg, Donald J; Mackiewicz, Ryan M; Rodgers, Jody L; Phelps, Andrea L

    2004-03-22

    The copolymerization of CO(2) and cyclohexene or propylene oxide has been examined employing (salen)Cr(III)Nu complexes (Nu = Cl or N(3)) as catalysts. The addition of various cocatalysts, including phosphines and PPN+ or Bu4N+ Cl- salts serves to greatly enhance the rate of copolymer production. In these instances, the mechanism of the initiation step appears to be unimolecular in catalyst concentration, unlike the bimolecular process cocatalyzed by N-methylimidazole. The copolymers were produced with >95% carbonate linkages with TOFs in the range 39-494 mol epoxide consumed/mol Cr.h. In the presence of phosphine cocatalysts, no cyclic carbonate was produced as a byproduct.

  19. Preparation of hybrid thiol-acrylate emulsion-templated porous polymers by interfacial copolymerization of high internal phase emulsions.

    PubMed

    Langford, Caitlin R; Johnson, David W; Cameron, Neil R

    2015-05-01

    Emulsion-templated highly porous polymers (polyHIPEs), containing distinct regions differing in composition, morphology, and/or properties, are prepared by the simultaneous polymerization of two high internal phase emulsions (HIPEs) contained within the same mould. The HIPEs are placed together in the mould and subjected to thiol-acrylate photopolymerization. The resulting polyHIPE material is found to contain two distinct semicircular regions, reflecting the composition of each HIPE. The original interface between the two emulsions becomes a copolymerized band between 100 and 300 μm wide, which is found to be mechanically robust. The separate polyHIPE layers are distinguished from one another by their differing average void diameter, chemical composition, and extent of contraction upon drying. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Metal-Organic Framework Supported on Processable Polymer Matrix by In Situ Copolymerization for Enhanced Iron(III) Detection.

    PubMed

    Liu, Chun-Sen; Chen, Min; Tian, Jia-Yue; Wang, Lei; Li, Min; Fang, Shao-Ming; Wang, Xi; Zhou, Li-Ming; Wang, Zhuo-Wei; Du, Miao

    2017-03-17

    Metal-organic frameworks (MOFs) represent a promising class of porous materials. However, MOFs show poor processability that impedes their full potential in applications. This work develops a composite strategy to skillfully load MOFs on a polymer plate to afford processability for these powder materials. A predesigned mesoporous MOF with active -NH2 groups around the pore walls was prepared and its copolymerization with the -NCO groups of macromonomers (polyurethane acrylate) could be facilely induced by an initiator under mild conditions. Notably, the target MOF-polymer composite is transparent, elastic, and shows enhanced Fe(3+) detection compared with that of the individual MOF functional component. This result can be ascribed to the synergistic effect of the composite with newly formed chemical bonds between the MOF particle and polymer matrix. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Plasma-induced graft copolymerization of poly(methacrylic acid) on electrospun poly(vinylidene fluoride) nanofiber membrane.

    PubMed

    Kaur, Satinderpal; Ma, Zuwei; Gopal, Renuga; Singh, Gurdev; Ramakrishna, Seeram; Matsuura, Takeshi

    2007-12-18

    Electrospun nanofibrous membranes (ENM) which have a porous structure have a huge potential for various liquid filtration applications. In this paper, we explore the viability of using plasma-induced graft copolymerization to reduce the pore sizes of ENMs. Poly(vinylidene) fluoride (PVDF) was electrospun to produce a nonwoven membrane, comprised of nanofibers with diameters in the range of 200-600 nm. The surface of the ENM was exposed to argon plasma and subsequently graft-copolymerized with methacrylic acid. The effect of plasma exposure time on grafting was studied for both the ENM and a commercial hydrophobic PVDF (HVHP) membrane. The grafting density was quantitatively measured with toluidine blue-O. The degree of grafting increased steeply with an increase in plasma exposure time for the ENM, attaining a maximum of 180 nmol/mg after 120 s of plasma treatment. However, the increase in the grafting density on the surface of the HVHP membrane was not as drastic, reaching a plateau of 65 nmol/mg after 60 s. The liquid entry permeation of water dropped extensively for both membranes, indicating a change in surface properties. Field emission scanning electron microscopy micrographs revealed an alteration in the surface pore structure for both membranes after grafting. Bubble point measurements of the ENM reduced from 3.6 to 0.9 um after grafting. The pore-size distribution obtained using the capillary flow porometer for the grafted ENM revealed that it had a similar profile to that of a commercial hydrophilic commercial PVDF (HVLP) membrane. More significantly, water filtration studies revealed that the grafted ENM had a better flux throughput than the HVLP membrane. This suggests that ENMs can be successfully engineered through surface modification to achieve smaller pores while retaining their high flux performance.

  2. Synthesis and properties of poly(methyl methacrylate-2-acrylamido-2-methylpropane sulfonic acid)/PbS hybrid composite

    SciTech Connect

    Preda, N.; Rusen, E.; Musuc, A.; Enculescu, M.; Matei, E.; Marculescu, B.; Fruth, V.; Enculescu, I.

    2010-08-15

    The synthesis of a new hybrid composite based on PbS nanoparticles and poly(methyl methacrylate-2-acrylamido-2-methylpropane sulfonic acid) [P(MMA-AMPSA)] copolymer is reported. The chemical synthesis consists in two steps: (i) a surfactant-free emulsion copolymerization between methyl methacrylate and 2-acrylamido-2-methylpropane sulfonic acid and (ii) the generation of PbS particles in the presence of the P(MMA-AMPSA) latex, from the reaction between lead nitrate and thiourea. The composite was studied by scanning electron microscopy (SEM), X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The microstructure observed using SEM proves that the PbS nanoparticles are well dispersed in the copolymer matrix. The X-ray diffraction measurements demonstrate that the PbS nanoparticles have a cubic rock salt structure. It was also found that the inorganic semiconductor nanoparticles improve the thermal stability of the copolymer matrix.

  3. Copolymerization of Propylene and Polar Monomers Using Pd/IzQO Catalysts.

    PubMed

    Nakano, Ryo; Nozaki, Kyoko

    2015-09-02

    Palladium catalysts bearing imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) ligands polymerize α-olefins while incorporating polar monomers. The steric environment provided by N-heterocyclic-carbene (NHC) enables regioselective insertion of α-olefins and polar monomers, yielding polypropylene, propylene/allyl carboxylate copolymers, and propylene/methyl acrylate copolymer. Known polymerization catalysts bearing NHC-based ligands decompose rapidly, whereas the present catalyst is durable because of structural confinement, wherein the NHC-plane is coplanar to the metal square plane. The present catalyst system enables facile access to a new class of functionalized polyolefins and helps conceive a new fundamental principle for designing NHC-based ligands.

  4. Poly(1-adamantyl acrylate): Living Anionic Polymerization, Block Copolymerization, and Thermal Properties

    SciTech Connect

    Lu, Wei; Huang, Caili; Hong, Kunlun; Kang, Nam-Goo; Mays, Jimmy W.

    2016-12-06

    Living anionic polymerization of acrylates is challenging due to intrinsic side reactions including backbiting reactions of propagating enolate anions and aggregation of active chain ends. In this study, the controlled synthesis of poly(1-adamatyl acrylate) (PAdA) was performed successfully for the first time via living anionic polymerization through investigation of the initiation systems of sec-butyllithium/diphenylethylene/lithium chloride (sec-BuLi/DPE/LiCl), diphenylmethylpotassium/diethylzinc (DPMK/Et2Zn), and sodium naphthalenide/dipenylethylene/diethylzinc (Na-Naph/DPE/Et2Zn) in tetrahydrofuran at -78 °C using custom glass-blowing and high-vacuum techniques. PAdA synthesized via anionic polymerization using DPMK with a large excess (more than 40-fold to DPMK) of Et2Zn as the ligand exhibited predicted molecular weights from 4.3 to 71.8 kg/mol and polydispersity indices of around 1.10. In addition, the produced PAdAs exhibit a low level of isotactic content (mm triads of 2.1%). The block copolymers of AdA and methyl methacrylate (MMA) were obtained by sequential anionic polymerization, and the distinct living property of PAdA over other acrylates was demonstrated based on the observation that the resulting PAdA-b-PMMA block copolymers were formed with no residual PAdA homopolymer. The PAdA homopolymers exhibit a very high glass transition temperature (133 °C) and outstanding thermal stability (Td: 376 °C) as compared to other acrylic polymers such as poly(tert-butyl acrylate) and poly(methyl acrylate). These merits make PAdA a promising candidate for acrylic-based thermoplastic elastomers with high upper service temperature and enhanced mechanical strength.

  5. Poly(1-adamantyl acrylate): Living Anionic Polymerization, Block Copolymerization, and Thermal Properties

    DOE PAGES

    Lu, Wei; Huang, Caili; Hong, Kunlun; ...

    2016-12-06

    Living anionic polymerization of acrylates is challenging due to intrinsic side reactions including backbiting reactions of propagating enolate anions and aggregation of active chain ends. In this study, the controlled synthesis of poly(1-adamatyl acrylate) (PAdA) was performed successfully for the first time via living anionic polymerization through investigation of the initiation systems of sec-butyllithium/diphenylethylene/lithium chloride (sec-BuLi/DPE/LiCl), diphenylmethylpotassium/diethylzinc (DPMK/Et2Zn), and sodium naphthalenide/dipenylethylene/diethylzinc (Na-Naph/DPE/Et2Zn) in tetrahydrofuran at -78 °C using custom glass-blowing and high-vacuum techniques. PAdA synthesized via anionic polymerization using DPMK with a large excess (more than 40-fold to DPMK) of Et2Zn as the ligand exhibited predicted molecular weights from 4.3more » to 71.8 kg/mol and polydispersity indices of around 1.10. In addition, the produced PAdAs exhibit a low level of isotactic content (mm triads of 2.1%). The block copolymers of AdA and methyl methacrylate (MMA) were obtained by sequential anionic polymerization, and the distinct living property of PAdA over other acrylates was demonstrated based on the observation that the resulting PAdA-b-PMMA block copolymers were formed with no residual PAdA homopolymer. The PAdA homopolymers exhibit a very high glass transition temperature (133 °C) and outstanding thermal stability (Td: 376 °C) as compared to other acrylic polymers such as poly(tert-butyl acrylate) and poly(methyl acrylate). These merits make PAdA a promising candidate for acrylic-based thermoplastic elastomers with high upper service temperature and enhanced mechanical strength.« less

  6. Anti-fouling ultrafiltration membrane prepared from polysulfone-graft-methyl acrylate copolymers by UV-induced grafting method.

    PubMed

    Hua, Helin; Li, Na; Wu, Linlin; Zhong, Hui; Wu, Guangxial; Yuan, Zonghuan; Lin, Xiangwei; Tang, Lianyi

    2008-01-01

    Membrane fouling is one of the most important challenges faced in membrane ultrafiltration operations. The copolymers of polysulfone-graft-methyl acrylate were synthesized by homogeneous photo-initiated graft copolymerization. The variables affecting the degree of grafting, such as the time of UV (Ultraviolet-visible) irradiation and the concentrations of the methyl acrylate and photoinitiator, were investigated. The graft copolymer membranes were prepared by the phase inversion method. The chemical and morphological changes were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), scanning electron microscopy, and water contact angles measurements. Results revealed that methyl acrylate groups were present on the membranes and the graft degree of methyl acrylate had remarkable effect on the performance of membranes. Pure water contact angle on the membrane surface decreases with the increase of methyl acrylate graft degree, which indicated that the hydrophilicity of graft copolymer membranes was improved. The permeation fluxes of pure water and bovine serum albumin solution were measured to evaluate the antifouling property of graft copolymer membranes, the results of which have shown an enhancement of antifouling property for graft copolymer membranes.

  7. ENZYMOLOGY OF ARSENIC METHYLATION

    EPA Science Inventory

    Enzymology of Arsenic Methylation

    David J. Thomas, Pharmacokinetics Branch, Experimental Toxicology Division, National
    Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park...

  8. Thiophanate-methyl

    Integrated Risk Information System (IRIS)

    Integrated Risk Information System ( IRIS ) Chemical Assessment Summary U.S . Environmental Protection Agency National Center for Environmental Assessment This IRIS Summary has been removed from the IRIS database and is available for historical reference purposes . ( July 2016 ) Thiophanate - methyl

  9. ENZYMOLOGY OF ARSENIC METHYLATION

    EPA Science Inventory

    Enzymology of Arsenic Methylation

    David J. Thomas, Pharmacokinetics Branch, Experimental Toxicology Division, National
    Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park...

  10. Graft copolymerization onto cellulose-based filter paper and its further development as silver nanoparticles loaded antibacterial food-packaging material.

    PubMed

    Tankhiwale, Rasika; Bajpai, S K

    2009-03-01

    The present work describes ceric ammonium nitrate (CAN) initiated graft copolymerization of acrylamide onto cellulose-based filter paper followed by entrapment of silver nanoparticles. The copolymerization was carried out in aqueous solution, containing 2M acrylamide monomer and 16mM N,N'-methylene bisacrylamide (MB) crosslinker. The optimum initiation time and grafting reaction temperature were found to be 15min and 30 degrees C, respectively. The silver nanoparticles were loaded into grafted filter paper by equilibration in silver nitrate solution followed by citrate reduction. The formation of silver nanoparticles has been confirmed by TEM and SAED analysis. The novel nano silver loaded filter paper has been investigated for its antimicrobial properties against E.coli. This newly developed material shows strong antibacterial property and thus offers its candidature for possible use as antibacterial food-packaging material.

  11. Alternating copolymerization of propylene oxide with biorenewable terpene-based cyclic anhydrides: a sustainable route to aliphatic polyesters with high glass transition temperatures.

    PubMed

    Van Zee, Nathan J; Coates, Geoffrey W

    2015-02-23

    The alternating copolymerization of propylene oxide with terpene-based cyclic anhydrides catalyzed by chromium, cobalt, and aluminum salen complexes is reported. The use of the Diels-Alder adduct of α-terpinene and maleic anhydride as the cyclic anhydride comonomer results in amorphous polyesters that exhibit glass transition temperatures (Tg ) of up to 109 °C. The polymerization conditions and choice of catalyst have a dramatic impact on the molecular weight distribution, the relative stereochemistry of the diester units along the polymer chain, and ultimately the Tg of the resulting polymer. The aluminum salen complex exhibits exceptional selectivity for copolymerization without transesterification or epimerization side reactions. The resulting polyesters are highly alternating and have high molecular weights and narrow polydispersities.

  12. Copolymerization as a Strategy to Combine Epoxidized Linseed Oil and Furfuryl Alcohol: The Design of a Fully Bio-Based Thermoset.

    PubMed

    Pin, Jean-Mathieu; Guigo, Nathanaël; Vincent, Luc; Sbirrazzuoli, Nicolas; Mija, Alice

    2015-12-21

    Epoxidized linseed oil and furfuryl alcohol are bio-sourced monomers known for their high-potential applications in materials science. In this work, we propose the association of these monomers through copolymerization reactions with the target to design fully bio-based thermosets. Herein, investigations on cationic polymerization reactivity have been explored using differential scanning calorimetry. The obtained structures have been confirmed by IR spectroscopy and 2 D NMR spectroscopy, which revealed the principal chain connections. In spite of the multiple capabilities of chemical connections, which include copolymerization and cross-linking, the obtained networks are homogeneous as confirmed by dynamic mechanical analysis and SEM. Furthermore, the copolymer demonstrates a semiductile behavior if subjected to tensile measurements (tensile strain at break ≈40 %), which is a significant advance in terms of its applications as a furanic bio-based thermoset material.

  13. Copolymerizations of epsilon-caprolactone and glycolide-a comparison of tin(II)octanoate and bismuth(III)subsalicylate as initiators.

    PubMed

    Kricheldorf, Hans R; Rost, Simon

    2005-01-01

    Copolymerizations of epsilon-caprolactone (epsilonCL) and glycolide (GL) were conducted in bulk at 120 degrees C with variation of the reaction time. Either Sn(II) 2-ethylhexanoate (SnOct(2)) or bismuth(III)subsalicylate (BiSS) were used as initiators combined with tetra(ethylene glycol) as co-initiator. The resulting copolyesters were analyzed by (1)H and (13)C NMR spectroscopy with regard to the total molar composition and to the sequence of the comonomers. Furthermore, two series of copolymerizations (either Sn- or Bi-initiated) were performed at constant time with variation of the temperature. It was found that BiSS favors alternating sequences more than SnOct(2). Time-conversion curves and MALDI-TOF mass spectrometry of homopolymerization suggest that SnOct(2) is the more efficient transesterification catalyst. A hypothetical reaction mechanism is discussed.

  14. METHYL GREEN-PYRONIN

    PubMed Central

    Kurnick, N. B.

    1950-01-01

    1. Methyl green stains selectively highly polymerized desoxyribonucleic acid, and fails to stain, to any significant extent, depolymerized desoxyribonucleic acid and ribonucleic acid. 2. Pyronin stains preferentially low polymers of nucleic acid. 3. Triphenylmethane dyes with two amino groups appear to share the selectivity of methyl green. Those with three amino groups are not selective. 4. A stereochemical hypothesis is offered to account for these observations. PMID:15402708

  15. Effects of agitation in emulsion polymerization of n-butyl methacrylate and its copolymerization with N-methylol acrylamide

    NASA Astrophysics Data System (ADS)

    Krishnan, Sitaraman

    Effects of agitation in emulsion polymerization were investigated using a 2 dm3 stirred reactor and Rushton turbine agitators and a semi-batch mode of reaction. High-solids recipes giving monodisperse polymer particles with core-shell morphology were developed for monomer-starved, semi-batch emulsion copolymerization of n-butyl methacrylate (BMA) and N-methylol acrylamide (NMA). A larger agitator, or a higher agitation speed, resulted in higher particle concentration, more viscous latex, less water-soluble polymer, and higher mass of coagulum. Better incorporation of NMA in the polymer particles was because of greater particle-water interfacial area and more efficient macromixing in the reactor. A mechanism where the surface of the polymer particles is the most favorable site for copolymerization, is proposed for the incorporation of NMA. Nucleation of a greater number of particles at higher agitation intensity was a general observation for recipes with surfactant concentrations below the critical micelle concentration (cmc). Effects of agitation on the kinetics of emulsion polymerization of BMA were studied using reaction calorimetry. At a reaction temperature of 70°C, the molecular weight was higher at higher agitation speed, while at 50°C, the converse was true. The order of dependence of the mass of coagulum on the agitation speed depended on the surfactant coverage of the polymer particles: the variation was almost two-fold (1.2 to 2.3). The coagulum mass was related to surfactant coverage using results from the DLVO theory. The volume-surface average diameter of the monomer droplets in the emulsion scaled to the 1.6 power of agitation speed, and the droplet size distribution was log-normal. Thermal crosslinking of the copolymer particles and films was investigated, and the effect of carbon tetrabromide on the gel content of the copolymer films was studied experimentally and theoretically. The increase in the gel content as a function of time during thermal

  16. Template copolymerization to control site structure around metal ions: Applications towards sensing and gas storage and release

    NASA Astrophysics Data System (ADS)

    Mitchell-Koch, Jeremy T.

    The development of functional materials for sensing and gas storage and release is useful in a number of chemical and biological applications. Investigating function of molecularly imprinted polymers (MIP), often used for these purposes, has relied on circumstantial evidence because direct examination of immobilized sites is not possible. Described in this dissertation is the design, synthesis, characterization and function studies of materials synthesized by template copolymerization methods. Metal ions exhibit unique spectroscopic properties and their utilization makes site examination more feasible. Ligand binding modulates these properties such that the event can be measured by spectroscopy. The metal ion's secondary coordination environment can also be tuned to increase or decrease function of the material. In Chapter Two the utilization of template copolymerization to immobilize a europium-containing compound for the detection of volatile organic compounds is described. Luminescence of the immobilized complex is quenched in the presence of volatile organic compounds (VOC). The quenching effect is dependent on concentration of VOC and the nature of polymeric host. Chapters Three and Four describe the development of materials for the photolytic release of nitric oxide (NO). In Chapter Three, a novel manipulation of the immobilized complex is employed to produce binding sites that contain ligands covalently embedded into the host in a position to bind the metal ion upon NO release in order to block rebinding. Incompatible binding affinities of the iron-containing templates made it impossible to study NO photo-release from this material. Second-row transition metals are more compatible with NO binding, and Chapter Four describes a ruthenium salen-containing polymer that releases NO in response to light. Additionally, transfer of NO to a metalloporphyrin and myoglobin has been achieved. This is the first report of photolytic heterogeneous NO transfer by a material

  17. DNA methylation and differentiation.

    PubMed Central

    Michalowsky, L A; Jones, P A

    1989-01-01

    The methylation of specific cytosine residues in DNA has been implicated in regulating gene expression and facilitating functional specialization of cellular phenotypes. Generally, the demethylation of certain CpG sites correlates with transcriptional activation of genes. 5-Azacytidine is an inhibitor of DNA methylation and has been widely used as a potent activator of suppressed genetic information. Treatment of cells with 5-azacytidine results in profound phenotypic alterations. The drug-induced hypomethylation of DNA apparently perturbs DNA-protein interactions that may consequently alter transcriptional activity and cell determination. The inhibitory effect of cytosine methylation may be exerted via altered DNA-protein interactions specifically or may be transduced by a change in the conformation of chromatin. Recent studies have demonstrated that cytosine methylation also plays a central role in parental imprinting, which in turn determines the differential expression of maternal and paternal genomes during embryogenesis. In other words, methylation is the mechanism whereby the embryo retains memory of the gametic origin of each component of genetic information. A memory of this type would probably persist during DNA replication and cell division as methylation patterns are stable and heritable. PMID:2466640

  18. Isoselective 3,4-(co)polymerization of bio-renewable myrcene using NSN-ligated rare-earth metal precursor: an approach to a new elastomer.

    PubMed

    Liu, Bo; Li, Lei; Sun, Guangping; Liu, Dongtao; Li, Shihui; Cui, Dongmei

    2015-01-21

    The polymerization of bio-renewable myrcene (MY), using a cationic β-diimidosulfonate lutetium catalyst in high activity, afforded an unprecedented isotactic 3,4-polymyrcene (PMY) with a low Tg (-42 °C). Based on this result, the random and block copolymerization of myrcene and isoprene (IP) resulted in novel elastomers that comprise the amorphous iso-3,4-PMY and iso-3,4-PIP sequences.

  19. Preparation of Syndiotactic Poly(vinyl alcohol)/Poly(vinyl pivalate/vinyl acetate) Microspheres with Radiopacity Using Suspension Copolymerization and Saponification

    NASA Astrophysics Data System (ADS)

    Seok Lyoo, Won; Wook Cha, Jin; Young Kwak, Kun; Jae Lee, Young; Yong Jeon, Han; Sik Chung, Yong; Kyun Noh, Seok

    2010-06-01

    To prepare Poly(vinyl pivalate/vinyl acetate) [P(VPi/VAc)] microspheres with radiopacity, the suspension copolymerization approach in the presence of aqueous radiopaque nanoparticles was used. After, The P(VPi/VAc) microspheres with radiopacity were saponified in heterogeneous system, and then P(VPi/VAc) microspheres without aggregates were converted to s-PVA/P(VPi/VAc) microspheres of skin/core structure through the heterogeneous surface saponification. Radiopacity of microspheres was confirmed with Computed tomography (CT).

  20. Copolymerization and terpolymerization of carbon dioxide/propylene oxide/phthalic anhydride using a (salen)Co(III) complex tethering four quaternary ammonium salts

    PubMed Central

    Jeon, Jong Yeob; Eo, Seong Chan; Varghese, Jobi Kodiyan

    2014-01-01

    Summary The (salen)Co(III) complex 1 tethering four quaternary ammonium salts, which is a highly active catalyst in CO2/epoxide copolymerizations, shows high activity for propylene oxide/phthalic anhydride (PO/PA) copolymerizations and PO/CO2/PA terpolymerizations. In the PO/PA copolymerizations, full conversion of PA was achieved within 5 h, and strictly alternating copolymers of poly(1,2-propylene phthalate)s were afforded without any formation of ether linkages. In the PO/CO2/PA terpolymerizations, full conversion of PA was also achieved within 4 h. The resulting polymers were gradient poly(1,2-propylene carbonate-co-phthalate)s because of the drift in the PA concentration during the terpolymerization. Both polymerizations showed immortal polymerization character; therefore, the molecular weights were determined by the activity (g/mol-1) and the number of chain-growing sites per 1 [anions in 1 (5) + water (present as impurity) + ethanol (deliberately fed)], and the molecular weight distributions were narrow (M w/M n, 1.05–1.5). Because of the extremely high activity of 1, high-molecular-weight polymers were generated (M n up to 170,000 and 350,000 for the PO/PA copolymerization and PO/CO2/PA terpolymerization, respectively). The terpolymers bearing a substantial number of PA units (f PA, 0.23) showed a higher glass-transition temperature (48 °C) than the CO2/PO alternating copolymer (40 °C). PMID:25161738

  1. Cyclohexene oxide/CO2 copolymerization catalyzed by chromium(III) salen complexes and N-methylimidazole: effects of varying salen ligand substituents and relative cocatalyst loading.

    PubMed

    Darensbourg, Donald J; Mackiewicz, Ryan M; Rodgers, Jody L; Fang, Cindy C; Billodeaux, Damon R; Reibenspies, Joseph H

    2004-09-20

    A detailed mechanistic study into the copolymerization of CO2 and cyclohexene oxide utilizing CrIII(salen)X complexes and N-methylimidazole, where H2salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediimine and other salen derivatives and X = Cl or N3, has been conducted. By studying salen ligands with various groups on the diimine backbone, we have observed that bulky groups oriented perpendicular to the salen plane reduce the activity of the catalyst significantly, while such groups oriented parallel to the salen plane do not retard copolymer formation. This is not surprising in that the mechanism for asymmetric ring opening of epoxides was found to occur in a bimetallic fashion, whereas these perpendicularly oriented groups along with the tert-butyl groups on the phenolate rings produce considerable steric requirements for the two metal centers to communicate and thus initiate the copolymerization process. It was also observed that altering the substituents on the phenolate rings of the salen ligand had a 2-fold effect, controlling both catalyst solubility as well as electron density around the metal center, producing significant effects on the rate of copolymer formation. This and other data discussed herein have led us to propose a more detailed mechanistic delineation, wherein the rate of copolymerization is dictated by two separate equilibria. The first equilibrium involves the initial second-order epoxide ring opening and is inhibited by excess amounts of cocatalyst. The second equilibrium involves the propagation step and is enhanced by excess cocatalyst. This gives the [cocatalyst] both a positive and negative effect on the overall rate of copolymerization.

  2. In vitro drug release behavior, mechanism and antimicrobial activity of rifampicin loaded low molecular weight PLGA-PEG-PLGA triblock copolymeric nanospheres.

    PubMed

    Gajendiran, M; Divakar, S; Raaman, N; Balasubramanian, S

    2013-12-01

    Poly (lactic-co-glycolic acid) (PLGA (92:8)) and a series of PLGA-PEG-PLGA tri block copolymers were synthesized by direct melt polycondensation. The copolymers were characterized by FTIR, and 1HNMR spectroscopic techniques, viscosity, gel permeation chromatography (GPC) and powder x-ray diffraction (XRD). The rifampicin (RIF) loaded polymeric nanospheres (NPs) were prepared by ultrasonication-W/O emulsification technique. The NPs have been characterized by field emission scanning electron microscopy (FESEM), TEM, powder X-ray diffraction (XRD), UVvisible spectroscopy and DLS measurements. The drug loaded triblock copolymeric NPs have five folds higher drug content and drug loading efficiency than that of PLGA microspheres (MPs). The in vitro drug release study shows that the drug loaded NPs showed an initial burst release after that sustained release up to 72 h. All the triblock copolymeric NPs follow anomalous drug diffusion mechanism while the PLGA MPs follow non-Fickian super case-II mechanism up to 12 h. The overall in-vitro release follows second order polynomial kinetics up to 72 h. The antimicrobial activity of the RIF loaded polymer NPs was compared with that of pure RIF and tetracycline (TA). The RIF loaded triblock copolymeric NPs inhibited the bacterial growth more effectively than the pure RIF and TA.

  3. Influence of nanopores of MCM-41 and SBA-15 confining (n-BuCp)2ZrCl2 on copolymerization of ethylene-alpha-olefin.

    PubMed

    Ko, Young Soo; Lee, Jeong Suk; Yim, Jin-Heong; Jeon, Jong-Ki; Jung, Kyeong Youl

    2010-01-01

    The effect of nanopore in mesoporous materials confining (n-BuCp),ZrCl2 and methylaluminoxane (MAO) on ethylene-1-hexene and ethylene-1-octene copolymerization was investigated on the basis of the copolymerization results, and the analysis of the supported catalyst and the copolymers. SBA-15 and MCM-41 together with amorphous silica were employed as supports, which are capable of confining (n-BuCp)2ZrCl2 and MAO in the nanopore. The copolymerization activities of MCM-41-supported (n-BuCp)2ZrCl2 were higher than those of SBA-15 and SiO2 although that its Zr content was quite lower than those of SBA-15 and SiO2. SBA-15 and MCM-41 showed a remarkable decrease in BET surface area after confining MAO and (n-BuCp)2ZrCl2 compared to SiO2, explaining an even adsorption of MAO and (n-BuCp)2ZrCl2 complexes on the nanopore surface. Temperature rising elution fractionation (TREF) results showed bimodal curves of MCM-41-supported (n-BuCp)2ZrCl2 at the C6/C2 and C8/C2 molar ratios of 0.6 and 0.5, respectively, which was attributed to the differences in ethylene and alpha-olefin concentrations along with the cylindrical nanopore of MCM-41 due to the narrow nanospace.

  4. Preparation and characterization of pH-sensitive methyl methacrylate-g-starch/hydroxypropylated starch hydrogels: in vitro and in vivo study on release of esomeprazole magnesium.

    PubMed

    Kumar, Pankaj; Ganure, Ashok Laxmanrao; Subudhi, Bharat Bhushan; Shukla, Shubhanjali

    2015-06-01

    In the present study, novel hydrogels were prepared through graft copolymerization of methyl methacrylate onto starch and hydroxypropylated starch for intestinal drug delivery. The successful grafting has been confirmed by FTIR, NMR spectroscopy, and elemental analysis. Morphological examination of copolymeric hydrogels by scanning electron microscopy (SEM) confirms the macroporous nature of the copolymers. The high decomposition temperature was observed in thermograms indicating the thermal stability of the hydrogels. To attain a hydrogel with maximum percent graft yield, the impact of reaction variables like concentration of ceric ammonium nitrate as initiator and methyl methacrylate as monomer were consistently optimized. X-ray powder diffraction and differential scanning calorimetric analysis supported the successful entrapment of the drug moiety (esomeprazole magnesium; proton pump inhibitor) within the hydrogel network. Drug encapsulation efficiency of optimized hydrogels was found to be >78%. Furthermore, swelling capacity of copolymeric hydrogels exhibited a pH-responsive behavior which makes the synthesized hydrogels potential candidates for controlled delivery of medicinal agents. In vitro drug release was found to be sustained up to 14 h with 80-90% drug release in pH 6.8 solution; however, the cumulative release was 40-45% in pH 1.2. The gastrointestinal transit behavior of optimized hydrogel was determined by gamma scintigraphy, using (99m)Tc as marker. The amount of radioactive tracer released from the labeled hydrogel was minimal when the hydrogel was in the stomach, whereas it increased as hydrogel reached in intestine. Well-correlated results of in vitro and in vivo analysis proved their controlled release behavior with preferential delivery into alkaline pH environment.

  5. DNA methylation profiling identifies CG methylation clusters in Arabidopsis genes.

    PubMed

    Tran, Robert K; Henikoff, Jorja G; Zilberman, Daniel; Ditt, Renata F; Jacobsen, Steven E; Henikoff, Steven

    2005-01-26

    Cytosine DNA methylation in vertebrates is widespread, but methylation in plants is found almost exclusively at transposable elements and repetitive DNA. Within regions of methylation, methylcytosines are typically found in CG, CNG, and asymmetric contexts. CG sites are maintained by a plant homolog of mammalian Dnmt1 acting on hemi-methylated DNA after replication. Methylation of CNG and asymmetric sites appears to be maintained at each cell cycle by other mechanisms. We report a new type of DNA methylation in Arabidopsis, dense CG methylation clusters found at scattered sites throughout the genome. These clusters lack non-CG methylation and are preferentially found in genes, although they are relatively deficient toward the 5' end. CG methylation clusters are present in lines derived from different accessions and in mutants that eliminate de novo methylation, indicating that CG methylation clusters are stably maintained at specific sites. Because 5-methylcytosine is mutagenic, the appearance of CG methylation clusters over evolutionary time predicts a genome-wide deficiency of CG dinucleotides and an excess of C(A/T)G trinucleotides within transcribed regions. This is exactly what we find, implying that CG methylation clusters have contributed profoundly to plant gene evolution. We suggest that CG methylation clusters silence cryptic promoters that arise sporadically within transcription units.

  6. 49 CFR 173.193 - Bromoacetone, methyl bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... methyl bromide or methyl chloride mixtures, etc. 173.193 Section 173.193 Transportation Other Regulations... bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc. (a) Bromoacetone must be...) Bromoacetone, methyl bromide, chloropicrin and methyl bromide mixtures, chloropicrin and methyl...

  7. 49 CFR 173.193 - Bromoacetone, methyl bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... methyl bromide or methyl chloride mixtures, etc. 173.193 Section 173.193 Transportation Other Regulations... bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc. (a) Bromoacetone must be...) Bromoacetone, methyl bromide, chloropicrin and methyl bromide mixtures, chloropicrin and methyl...

  8. Effects of heat pretreatment of starch on graft copolymerization reaction and performance of resulting starch-based wood adhesive.

    PubMed

    Zheng, Xianyu; Cheng, Li; Gu, Zhengbiao; Hong, Yan; Li, Zhaofeng; Li, Caiming

    2017-03-01

    In this study, effects of starch heat pretreatment at 70, 80 and 90°C on graft copolymerization reaction with vinyl acetate (VAc) and the performance of the resulting starch-based wood adhesive (SWA) were investigated. It was shown that SWA pretreated at 90°C achieved the best performance. At this temperature, the bonding capacity improved by 17.84% compared to the adhesive synthesized without heat pretreatment and the viscosity increased by 18.16% after 7 free-thaw cycles, much better than other samples. Scanning electron microscopy (SEM) and polarizing microscopy demonstrated that structures of starch granules were fully damaged after heat pretreatment at 90°C. The reaction took place not only on the surface of starch granules, but also internally, leading to improvement in the grafting amounts and grafting efficiency by 42.86% and 39.03%, respectively. This was further confirmed by Fourier transform infrared spectroscopy (FT-IR), Confocal Raman microscopy (CRM) and X-ray photoelectron spectroscopy (XPS), which also showed better reaction homogeneity both between different starch granules and from granule surface to its internal structure. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Homogeneous graft copolymerization of styrene onto cellulose in a sulfur dioxide-diethylamine-dimethyl sulfoxide cellulose solvent

    SciTech Connect

    Tsuzuki, M.; Hagiwara, I.; Shiraishi, N.; Yokota, T.

    1980-12-01

    Graft copolymerization of styrene onto cellulose was studied in a homogeneous system (SO/sub 2/(liquid)- diethylamine (DEA)-dimethyl sulfoxide (DMSO) medium)) by ..gamma..-ray mutual irradiation technique. At the same time, homopolymerization of styrene was also examined separately in DMSO, SO/sub 2/-DMSO, DEA-DMSO, and SO/sub 2/-DEA-DMSO media by the same technique. Polymerization of styrene hardly occurs on concentrations above 10 mole SO/sub 2/-DEA complex per mole glucose unit. Maximum percent grafting was obtained in concentrations of 4 mole, after which it decreased rapidly. Total conversion and percent grafting increased with the irradiation time. The value (=0.55) of the slope of the total conversion rate plotted against the dose was only a little higher than the 1/2 which was expected from normal kinetics. No retardation in homopolymerization of styrene in DMSO, SO/sub 2/-DMSO, and DEA-DMSO was evident, while the retardation of homopolymerization in the SO/sub 2/-DEA-DMSO medium was measurable. Sulfur atoms were detected in the polymers obtained in both of SO/sub 2/-DMSO and SO/sub 2/-DEA-DMSO solutions. All of the molecular weights of polymers obtained in the present experiment were very low (3.9 x 10/sup 3/-1.75 x 10/sup 4/).

  10. Preparation and characterization of PVDF-glass fiber composite membrane reinforced by interfacial UV-grafting copolymerization.

    PubMed

    Luo, Nan; Xu, Rongle; Yang, Min; Yuan, Xing; Zhong, Hui; Fan, Yaobo

    2015-12-01

    A novel inorganic-organic composite membrane, namely poly(vinylidene fluoride) PVDF-glass fiber (PGF) composite membrane, was prepared and reinforced by interfacial ultraviolet (UV)-grafting copolymerization to improve the interfacial bonding strength between the membrane layer and the glass fiber. The interfacial polymerization between inorganic-organic interfaces is a chemical cross-linking reaction that depends on the functionalized glass fiber with silane coupling (KH570) as the initiator and the polymer solution with acrylamide monomer (AM) as the grafting block. The Fourier transform infrared spectrometer-attenuated total reflectance (FTIR-ATR) spectra and the energy dispersive X-ray (EDX) pictures of the interface between the glass fiber and polymer matrix confirmed that the AM was grafted to the surface of the glass fiber fabric and that the grafting polymer was successfully embedded in the membrane matrix. The formation mechanisms, permeation, and anti-fouling performance of the PGF composite membrane were measured with different amounts of AM in the doping solutions. The results showed that the grafting composite membrane improved the interfacial bonding strength and permeability, and the peeling strength was improved by 32.6% for PGF composite membranes with an AM concentration at 2wt.%.

  11. Characterization of polyethyleneterephthalate (PET) based proton exchange membranes prepared by UV-radiation-induced graft copolymerization of styrene

    NASA Astrophysics Data System (ADS)

    Ahmed, Mostak; Khan, Mohammad B.; Khan, Mubarak A.; Alam, S. Shamsul; Halim, Md. Abdul; Khan, M. Anwar H.

    Polymer electrolyte membranes (PEMs) were successfully prepared by simultaneous ultraviolet (UV) radiation-induced graft copolymerization of styrene (35 vol.% concentration) onto poly(ethyleneterephthalate) (PET) film, followed by sulfonation on the styrene monomer units in the grafting chain using 0.05 M chlorosulfonic acid (ClSO 3H). The radiation grafting and the sulfonation have been confirmed by titrimetric and gravimetric analyses as well as Fourier Transform Infrared (FTIR) spectroscopy. The maximum ion-exchange capacity (IEC) of the PEM was measured to be 0.04385 mmol g -1 at its highest level of grafting and sulfonation. They exhibited high thermal and mechanical properties as well as oxidative stability. They are highly stable in H 2SO 4 solutions and can be used in the acidic fuel cells. The membranes showed low water uptake as well as low proton conductivity than Nafion. In this study, the preparation of PEMs from commodity-type polymers is found to be very inexpensive and is a suitable candidate for applications in fuel cells.

  12. Synthesis, copolymerization and peptide-modification of carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) for neural electrode interfaces.

    PubMed

    Povlich, Laura K; Cho, Jae Cheol; Leach, Michelle K; Corey, Joseph M; Kim, Jinsang; Martin, David C

    2013-09-01

    Conjugated polymers have been developed as effective materials for interfacing prosthetic device electrodes with neural tissue. Recent focus has been on the development of conjugated polymers that contain biological components in order to improve the tissue response upon implantation of these electrodes. Carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) monomer was synthesized in order to covalently bind peptides to the surface of conjugated polymer films. EDOTacid was copolymerized with EDOT monomer to form stable, electrically conductive copolymer films referred to as PEDOT-PEDOTacid. The peptide GGGGRGDS was bound to PEDOT-PEDOTacid to create peptide functionalized PEDOT films. The PEDOT-PEDOTacid-peptide films increased the adhesion of primary rat motor neurons between 3 and 9 times higher than controls, thus demonstrating that the peptide maintained its biological activity. The EDOT-acid monomer can be used to create functionalized PEDOT-PEDOTacid copolymer films that can have controlled bioactivity. PEDOT-PEDOTacid-peptide films have the potential to control the behavior of neurons and vastly improve the performance of implanted electrodes. This article is part of a Special Issue entitled Organic Bioelectronics-Novel Applications in Biomedicine. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Monodispersepoly[BMA-co-(COPS-I)] Particles by Soap-Free Emulsion Copolymerization and Its Optical Properties as Photonic Crystals.

    PubMed

    Lee, Ki Chang; Choo, Hun Seung

    2015-10-01

    In order to study the surfactant-free emulsion copolymerization of benzyl methacrylate (BMA) with sodium 1-allyloxy-2-hydroxypropane sulfonate (COPS-I) and the resulting optical properties, a series of experiments was carried out at various reaction conditions such as the changes of BMA concentration, COPS-I concentration, BMA concentration under a fixed COPS-I amount, initiator and divinyl benzene (DVB) concentration. All the latices showed highly monodispersed spherical particles in the size range of 144~435 nm and the respective shiny structural colors from their colloidal photonic crystals. It is found that the changes in such polymerization factors greatly affect the number of particles and particle diameter, polymerization rate, molecular weight, zeta-potential, and refractive indices. The increase of number of particles led to the increased rate of polymerization and zeta-potential of the latices, on the other hand, to the decreased molecular weight. Refractive indices and the reflectivity increased with COPS-I concentration, on the other hand, and decreased with DVB concentration. Especially, refractive indices of the resulting poly[BMA-co-(COPS-I)] colloidal photonic crystals showed much higher values of 1.65~2.21 than that of polystyrene, due to the formation of core-shell shaped morphology. Monodisperse and high refractive index of poly[BMA-co-(COPS-I)] particles prepared in this work could be used for the study in photonic crystals and electrophoretic display.

  14. Radiation-induced graft copolymerization of poly(ethylene glycol) monomethacrylate onto deoxycholate-chitosan nanoparticles as a drug carrier

    NASA Astrophysics Data System (ADS)

    Pasanphan, Wanvimol; Rattanawongwiboon, Thitirat; Rimdusit, Pakjira; Piroonpan, Thananchai

    2014-01-01

    Poly(ethylene glycol) monomethacrylate-grafted-deoxycholate chitosan nanoparticles (PEGMA-g-DCCSNPs) were successfully prepared by radiation-induced graft copolymerization. The hydrophilic poly(ethylene glycol) monomethacrylate was grafted onto deoxycholate-chitosan in an aqueous system. The radiation-absorbed dose is an important parameter on degree of grafting, shell thickness and particle size of PEGMA-g-DCCSNPs. Owing to their amphiphilic architecture, PEGMA-g-DCCSNPs self-assembled into spherical core-shell nanoparticles in aqueous media. The particle size of PEGMA-g-DCCSNPs measured by TEM varied in the range of 70-130 nm depending on the degree of grafting as well as the irradiation dose. Berberine (BBR) as a model drug was encapsulated into the PEGMA-g-DCCSNPs. Drug release study revealed that the BBR drug was slowly released from PEGMA-g-DCCSNPs at a mostly constant rate of 10-20% in PBS buffer (pH 7.4) at 37 °C over a period of 23 days.

  15. Synthesis of high-molecular-weight polymer of methyl chloride salt of N,N-dimethylaminoethyl methacrylate by radiation-induced polymerization at high pressure. [Gamma radiation

    SciTech Connect

    Ishigaki, I.; Okada, T.; Sasuga, T.; Takehisa, M.; Machi, S.

    1981-02-01

    Polymer of the methyl chloride salt of N,N-dimethylaminoethyl methacrylate and its copolymer with acrylamide are used as cationic flocculants for the treatment of waste water containing organic suspensions. As reported, radiation-induced polymerization is one of the most convenient methods because of its temperature independence of initiation and extremely large G-value. In general, a flocculant with higher molecular weight has larger flocculation effects. The high-molecular-weight products were prepared in high monomer concentration and a low dose rate. This paper concerns the polymerization and copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate at high pressure, up to 7000 kg/cm/sup 2/, providing high-molecular-weight cationic flocculants.

  16. Facile Synthesis of Novel Polyethylene-Based A-B-C Block Copolymers Containing Poly(methyl methacrylate) Using a Living Polymerization System.

    PubMed

    Song, Xiangyang; Ma, Qiong; Cai, Zhengguo; Tanaka, Ryo; Shiono, Takeshi; Grubbs, Robert B

    2016-02-01

    Ethylene-propylene-methyl methacrylate (MMA) and ethylene-hexene-MMA A-B-C block copolymers with high molecular weight (>100,000) are synthesized using fluorenylamide-ligated titanium complex activated by modified methylaluminoxane and 2,6-di-tert-butyl-4-methylphenol for the first time. After diblock copolymerization of olefin is conducted completely, MMA is added and activated by aluminum Lewis acid to promote anionic polymerization. The length of polyolefin and poly (methyl methacrylate) (PMMA) is controllable precisely by the change of the additive amount of olefin and polymerization time, respectively. A soft amorphous polypropylene or polyhexene segment is located between two hard segments of semicrystalline polyethylene and glassy PMMA blocks.

  17. Pirimiphos-methyl

    Integrated Risk Information System (IRIS)

    Pirimiphos - methyl ; CASRN 29232 - 93 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinog

  18. Kapok oil methyl esters

    USDA-ARS?s Scientific Manuscript database

    The increased need for biodiesel feedstocks has caused various vegetable oils to be examined for this purpose. In the present work, the methyl esters of kapok (Ceiba pentandra) oil were prepared. The essential fuel properties were comprehensively determined and evaluated in comparison to specificati...

  19. Methyl ethyl ketone (MEK)

    Integrated Risk Information System (IRIS)

    Methyl ethyl ketone ( MEK ) ( CASRN 78 - 93 - 3 ) Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Nonc

  20. Haloxyfop-methyl

    Integrated Risk Information System (IRIS)

    Haloxyfop - methyl ; CASRN 69806 - 40 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinoge

  1. Nutrients and DNA Methylation

    USDA-ARS?s Scientific Manuscript database

    Epigenetics is a new mechanism responsible for development, aging, and disease process such as cancer development. One major epigenetic phenomenon is DNA methylation, which attributes to gene expression and integrity. Deepening the knowledge on one-carbon metabolism is very important to understandin...

  2. Methyl isobutyl ketone (MIBK)

    Integrated Risk Information System (IRIS)

    EPA / 635 / R - 03 / 002 TOXICOLOGICAL REVIEW OF METHYL ISOBUTYL KETONE ( CAS No . 108 - 10 - 1 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) March 2003 U.S . Environmental Protection Agency Washington DC DISCLAIMER This document has been reviewed in accordan

  3. Chloromethyl methyl ether (CMME)

    Integrated Risk Information System (IRIS)

    Chloromethyl methyl ether ( CMME ) ; CASRN 107 - 30 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments fo

  4. Kenaf methyl esters

    USDA-ARS?s Scientific Manuscript database

    Additional or alternative feedstocks are one of the major areas of interest regarding biodiesel. In this paper, for the first time, the fuel properties of kenaf (Hibiscus cannabinus L.) seed oil methyl esters are comprehensively reported. This biodiesel is also relatively unique by containing small ...

  5. DNA Methylation and Cancer Diagnosis

    PubMed Central

    Delpu, Yannick; Cordelier, Pierre; Cho, William C.; Torrisani, Jérôme

    2013-01-01

    DNA methylation is a major epigenetic modification that is strongly involved in the physiological control of genome expression. DNA methylation patterns are largely modified in cancer cells and can therefore be used to distinguish cancer cells from normal tissues. This review describes the main technologies available for the detection and the discovery of aberrantly methylated DNA patterns. It also presents the different sources of biological samples suitable for DNA methylation studies. We discuss the interest and perspectives on the use of DNA methylation measurements for cancer diagnosis through examples of methylated genes commonly documented in the literature. The discussion leads to our consideration for why DNA methylation is not commonly used in clinical practice through an examination of the main requirements that constitute a reliable biomarker. Finally, we describe the main DNA methylation inhibitors currently used in clinical trials and those that exhibit promising results. PMID:23873296

  6. DNA Methylation within Transcribed Regions

    PubMed Central

    To, Taiko K.; Saze, Hidetoshi; Kakutani, Tetsuji

    2015-01-01

    DNA methylation within transcribed genes is commonly found in diverse animals and plants. Here, we provide an overview of recent advances and the remaining mystery regarding intragenic DNA methylation. PMID:26143255

  7. Observation of different catalytic activity of various 1-olefins during ethylene/1-olefin copolymerization with homogeneous metallocene catalysts.

    PubMed

    Wannaborworn, Mingkwan; Praserthdam, Piyasan; Jongsomjit, Bunjerd

    2011-01-07

    This research aimed to investigate the copolymerization of ethylene and various 1-olefins. The comonomer lengths were varied from 1-hexene (1-C₆) up to 1-octadecene (1-C₁₈) in order to study the effect of comonomer chain length on the activity and properties of the polymer in the metallocene/MAO catalyst system. The results indicated that two distinct cases can be described for the effect of 1-olefin chain length on the activity. Considering the short chain length comonomers, such as 1-hexene, 1-octene and 1-decene, it is obvious that the polymerization activity decreased when the length of comonomer was higher, which is probably due to increased steric hindrance at the catalytic center hindering the insertion of ethylene monomer to the active sites, hence, the polymerization rate decreased. On the contrary, for the longer chain 1-olefins, namely 1-dodecene, 1-tetradecene and 1-octadecene, an increase in the comonomer chain length resulted in better activity due to the opening of the gap aperture between C(p)(centroid)-M-C(p)-(centroid), which forced the coordination site to open more. This effect facilitated the polymerization of the ethylene monomer at the catalytic sites, and thus, the activity increased. The copolymers obtained were further characterized using thermal analysis, X-ray diffraction spectroscopy and ¹³C-NMR techniques. It could be seen that the melting temperature and comonomer distribution were not affected by the 1-olefin chain length. The polymer crystallinity decreased slightly with increasing comonomer chain length. Moreover, all the synthesized polymers were typical LLDPE having random comonomer distribution.

  8. Molecular-shape selective high-performance liquid chromatography: stabilization effect of polymer main chain by alternating copolymerization.

    PubMed

    Mallik, Abul K; Qiu, Hongdeng; Sawada, Tsuyoshi; Takafuji, Makoto; Ihara, Hirotaka

    2012-04-06

    This work aims to clarify that stabilization or increased rigidity of polymer main chains as an organic stationary phase can lead the selectivity enhancement in high-performance liquid chromatography (HPLC). For this purpose, the alternating copolymer of octadecyl acrylate (ODA) with a cyclic monomer (N-octadecylmaleimide, OMI) as a rigid segment was synthesized and compared with the ODA homopolymer. Both of the polymer-grafted silicas (Sil-poly(ODA-alt-OMI) and Sil-poly(ODA), respectively) were prepared by radical polymerization on 3-mercaptopropyltrimethoxysilane-modified silica. The characterizations were carried out by elemental analyses, diffuse reflectance infrared Fourier transform (DRIFT), and solid-state (13)C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS-NMR) spectroscopies. Chromatographic behaviors were evaluated by the retention studies of shape-constrained isomers of polycyclic aromatic hydrocarbons (PAHs), isomers of tocopherol and carotenoids. Higher molecular-linearity selectivity toward PAHs was obtained on Sil-poy(ODA-alt-OMI) regardless of temperature changes but at temperature below 40 °C, Sil-poly(ODA) showed better planarity selectivity than that of Sil-poy(ODA-alt-OMI). As a result, the higher separation ability toward tocopherols and carotenoids was obtained on Sil-poy(ODA-alt-OMI). These results indicate that the stabilization in the polymer main chain by alternating copolymerization and the stabilization in the side chains by a disordered-to-ordered phase transition were effective to enhance the molecular-shape selectivity. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. 49 CFR 173.193 - Bromoacetone, methyl bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... methyl bromide or methyl chloride mixtures, etc. 173.193 Section 173.193 Transportation Other Regulations... bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc. (a) Bromoacetone must be... Group I performance level. (b) Bromoacetone, methyl bromide, chloropicrin and methyl bromide...

  10. 49 CFR 173.193 - Bromoacetone, methyl bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... methyl bromide or methyl chloride mixtures, etc. 173.193 Section 173.193 Transportation Other Regulations... bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc. (a) Bromoacetone must be... Group I performance level. (b) Bromoacetone, methyl bromide, chloropicrin and methyl bromide...

  11. PCR-less DNA co-polymerization detection of Shiga like toxin 1 (stx1) in Escherichia coli O157:H7.

    PubMed

    Anderson, Michael J; Miller, Hanna R; Alocilja, Evangelyn C

    2013-04-15

    There is a great need for rapid identification of bacterial agents, specifically pathogenic species such as Escherichia coli O157:H7, which is a highly infectious and lethal member of the Shigatoxigenic group of E. coli. In this study, the Shiga like toxin gene (stx1) responsible for the pathogenicity of E. coli was recovered from live samples and detected with a two particle DNA assay from genomic DNA. The two particle system consisted of a magnetic microparticle for separation/recovery and a DNA linked gold nanoparticle (AuNP) for reporting. Oligonucleotide reporters on the AuNP were used for fluorescent readout and the gold nanoparticle was used for direct electrochemical readout. Electrochemical detection successfully detected stx1 gene at 5 CFU/mL. Signal amplification via self assembling co-polymerization fluorescent readout was accomplished using the oligonucleotide linked AuNP. The two co-polymerization methods and electrochemical detection were compared against standard end-labeled DNA fluorescence detection of the gold nanoparticles in the system. The self assembling reporter consisted of two oligonucleotide sequences that repeatedly hybridized to each other to form large double stranded structures. Tethered co-polymerization amplification was able to detect the stx1 gene at 10⁵ CFU/mL (p=0.03) of E. coli in a total assay time of 7 h, including DNA extraction. The self assembling nature of the amplification system provides an enzyme free means of rapid signal amplification using inexpensive materials. Amplification can be accomplished with most any small single stranded DNA species providing an amplified readout method to a large number of other DNA based technologies. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. CO2/ethylene oxide copolymerization and ligand variation for a highly active salen-cobalt(III) complex tethering 4 quaternary ammonium salts.

    PubMed

    Jeon, Jong Yeob; Lee, Jung Jae; Varghese, Jobi Kodiyan; Na, Sung Jae; Sujith, S; Go, Min Jeong; Lee, Junseong; Ok, Myung-Ahn; Lee, Bun Yeoul

    2013-07-07

    A cobalt(III) complex (1) of a salcy-type ligand tethering 4 quaternary ammonium salts, which is thought to act as a highly active catalyst for CO2/propylene oxide (PO) copolymerization, also shows high activity (TOF, 25,900 h(-1); TON, 518,000; 2.72 kg polymer per g cat) and selectivity (>98%) for CO2/ethylene oxide (EO) copolymerization that results in high-molecular-weight polymers (M(n), 200,000-300,000) that have strictly alternating repeating units. The related cobalt(III) complexes 11-14 were prepared through variations of the ligand framework of 1 by replacing the trans-1,2-diaminocyclohexane unit with 2,2-dimethyl-1,3-propanediamine, trans-1,2-diaminocyclopentane, or 1,1'-binaphthyl-2,2'-diamine or by replacing the aldimine bond with ketimine. These ligand frameworks are thought to favour the formation of the cis-β configuration in complexation, and the formation of the cis-β configuration in 11-14 was confirmed through NMR studies or X-ray crystallographic studies of model complexes not bearing the quaternary ammonium salts. Complexes 11, 13, and 14, which adopt the cis-β configuration even in DMSO did not show any activity for CO2/PO copolymerization. Complex 12, which was constructed with trans-1,2-diaminocyclopentane and fluctuated in DMSO between the coordination and de-coordination of the acetate ligand as observed for 1, showed fairly high activity (TOF, 12,400 h(-1)). This fluctuating behaviour may play a role in polymerization. However, complex 12 did not compete with 1 in terms of activity, selectivity, and the catalyst cost.

  13. Mechanistic aspects of the copolymerization of CO2 with epoxides using a thermally stable single-site cobalt(III) catalyst.

    PubMed

    Ren, Wei-Min; Liu, Zhong-Wen; Wen, Ye-Qian; Zhang, Rong; Lu, Xiao-Bing

    2009-08-19

    The mechanism of the copolymerization of CO(2) and epoxides to afford the corresponding polycarbonates catalyzed by a highly active and thermally stable cobalt(III) complex with 1,5,7-triabicyclo[4,4,0] dec-5-ene (designated as TBD, a sterically hindered organic base) anchored on the ligand framework has been studied by means of electrospray ionization mass spectrometry (ESI-MS) and Fourier transform infrared spectroscopy (FTIR). The single-site, cobalt-based catalyst exhibited excellent activity and selectivity for polymer formation during CO(2)/propylene oxide (PO) copolymerization even at temperatures up to 100 degrees C and high [epoxide]/[catalyst] ratios, and/or low CO(2) pressures. The anchored TBD on the ligand framework plays an important role in maintaining thermal stability and high activity of the catalyst. ESI-MS and FTIR studies, in combination with some control experiments, confirmed the formation of the carboxylate intermediate with regard to the anchored TBD on the catalyst ligand framework. This analysis demonstrated that the formed carboxylate intermediate helped to stabilize the active Co(III) species against decomposition to inactive Co(II) by reversibly intramolecular Co-O bond formation and dissociation. Previous studies of binary catalyst systems based on Co(III)-Salen complexes did not address the role of these nucleophilic cocatalysts in stabilizing active Co(III) species during the copolymerization. The present study provides a new mechanistic understanding of these binary catalyst systems in which alternating chain-growth and dissociation of propagating carboxylate species derived from the nucleophilic axial anion and the nucleophilic cocatalyst take turns at both sides of the Co(III)-Salen center. This significantly increases the reaction rate and also helps to stabilize the active SalenCo(III) against decomposition to inactive SalenCo(II) even at low CO(2) pressures and/or relatively high temperatures.

  14. Thermal and Mechanical Properties of Poly(methyl methacrylate)/Poly(vinylidene fluoride-r-hexafluoro propylene) Blends

    NASA Astrophysics Data System (ADS)

    Lee, Steven; Conway, Maeve; Rende, Deniz; Ozisik, Rahmi

    Poly(vinylidene fluoride), PVDF, is a highly crystalline and rigid polymer, and is used in many applications where chemical inertness, resistance to various solvents and environmental degradation are required. Copolymerization of PVDF with hexafluoropropylene (HFP) tends to decrease the amount of crystallinity, thereby, resulting in a more flexible polymer, which provides new applications for PVDF. Various studies were undertaken to investigate the structure and properties of miscible blends of PVDF and poly(methyl methacrylate), PMMA; however, no studies were performed on the blends of P(VDF-HFP) random copolymers and PMMA. In the current study, we investigate the miscibility, and thermal and mechanical properties of P(VDF-HFP)/PMMA blends via differential scanning calorimetry, thermogravimetric analysis, and nanoindentation. Results indicate that increasing PMMA concentration leads to decreased crystallinity and shifting of the crystallization onset temperature during cooling to lower values. This material is based upon work supported by the National Science Foundation under Grant No. CMMI-1538730.

  15. Mechanism of the alternating copolymerization of epoxides and CO2 using beta-diiminate zinc catalysts: evidence for a bimetallic epoxide enchainment.

    PubMed

    Moore, David R; Cheng, Ming; Lobkovsky, Emil B; Coates, Geoffrey W

    2003-10-01

    A series of zinc beta-diiminate (BDI) complexes and their solid-state structures, solution dynamics, and copolymerization behavior with CO(2) and cyclohexene oxide (CHO) are reported. Stoichiometric reactions of the copolymerization initiation steps show that zinc alkoxide and bis(trimethylsilyl)amido complexes insert CO(2), whereas zinc acetates react with CHO. [(BDI-2)ZnOMe](2) [(BDI-2) = 2-((2,6-diethylphenyl)amido)-4-((2,6-diethylphenyl)imino)-2-pentene] and (BDI-1)ZnO(i)Pr [(BDI-1) = 2-((2,6-diisopropylphenyl)amido)-4-((2,6-diisopropylphenyl)imino)-2-pentene] react with CO(2) to form [(BDI-2)Zn(mu-OMe)(mu,eta(2)-O(2)COMe)Zn(BDI-2)] and [(BDI-1)Zn(mu,eta(2)-O(2)CO(i)Pr)](2), respectively. (BDI-2)ZnN(SiMe(3))(2) inserts CO(2) and eliminates trimethylsilyl isocyanate to give [(BDI-2)Zn(mu-OSiMe(3))](2). [(BDI-7)Zn(mu-OAc)](2) [(BDI-7) = 3-cyano-2-((2,6-diethylphenyl)amido)-4-((2,6-diethylphenyl)imino)-2-pentene] reacts with 1.0 equiv of CHO to yield [(BDI-7)Zn(mu,eta(2)-OAc)(mu,eta(1)-OCyOAc)Zn(BDI-7)]. Under typical polymerization conditions, rate studies on the copolymerization exhibit no dependence in [CO(2)], a first-order dependence in [CHO], and orders in [Zn](tot) ranging from 1.0 to 1.8 for [(BDI)ZnOAc] complexes. The copolymerizations of CHO (1.98 M in toluene) and 300 psi CO(2) at 50 degrees C using [(BDI-1)ZnOAc] and [(BDI-2)ZnOAc] show orders in [Zn](tot) of 1.73 +/- 0.06 and 1.02 +/- 0.03, respectively. We propose that two zinc complexes are involved in the transition state of the epoxide ring-opening event.

  16. DNA methylation dynamics in neurogenesis.

    PubMed

    Wang, Zhiqin; Tang, Beisha; He, Yuquan; Jin, Peng

    2016-03-01

    Neurogenesis is not limited to the embryonic stage, but continually proceeds in the adult brain throughout life. Epigenetic mechanisms, including DNA methylation, histone modification and noncoding RNA, play important roles in neurogenesis. For decades, DNA methylation was thought to be a stable modification, except for demethylation in the early embryo. In recent years, DNA methylation has proved to be dynamic during development. In this review, we summarize the latest understanding about DNA methylation dynamics in neurogenesis, including the roles of different methylation forms (5-methylcytosine, 5-hydroxymethylcytosine, 5-formylcytosine and 5-carboxylcytosine), as well as their 'writers', 'readers' and interactions with histone modifications.

  17. DNA Methylation in Mammals

    PubMed Central

    Li, En; Zhang, Yi

    2014-01-01

    DNA methylation is one of the best characterized epigenetic modifications. In mammals it is involved in various biological processes including the silencing of transposable elements, regulation of gene expression, genomic imprinting, and X-chromosome inactivation. This article describes how DNA methylation serves as a cellular memory system and how it is dynamically regulated through the action of the DNA methyltransferase (DNMT) and ten eleven translocation (TET) enzymes. Its role in the regulation of gene expression, through its interplay with histone modifications, is also described, and its implication in human diseases discussed. The exciting areas of investigation that will likely become the focus of research in the coming years are outlined in the summary. PMID:24789823

  18. Radiation degradation of methyl. cap alpha. -chloroacrylate-methacrylonitrile copolymers. [Gamma rays

    SciTech Connect

    Chen, C.Y.; Pittman, C.U. Jr.; Helbert, J.N.

    1980-01-01

    The radiation degradation behavior of methyl ..cap alpha..-chloroacrylate (MCA) and methacrylonitrile (MCN) copolymers has been investigated as part of a program to develop high-sensitivity polymeric resists for integrated circuit manufacture. High-molecular-weight copolymers were prepared by emulsion techniques. Several different copolymer compositions were prepared varying from 19 to 68 mol % MCA. These copolymers were fractionated and then subjected to ..gamma.. irradiation from a /sup 60/Co source. The G/sub s/ - G/sub x/, G/sub s/ - 4G/sub x/ values were determined from anti M/sub n//sup -1/ and anti M/sub w//sup -1/ versus dose plots, and the G/sub s/ and G/sub x/ values were then calculated. Molecular weights of both unirradiated and irradiated polymers were analyzed by membrane osmometry and gel permeation chromatography. All copolymers exhibited higher degradation susceptibilities than that of poly(methyl methacrylate), which has G/sub s/ = 1.3. The individual G/sub s/ and G/sub x/ values of the copolymers were found to fall between those of the two homopolymers, poly(methyl ..cap alpha..-chloracrylate) (G/sub s/ = 6.0) and polymethacrylonitrile (G/sub s/ = 3.1). The dependence of G/sub s/ and G/sub x/ values on molecular weight was minor. The crosslinking susceptibility of the poly(methyl ..cap alpha..-chloroacrylate) (G/sub x/ = 0.8) was greatly decreased by copolymerization with MCN. Relatively small amounts of MCN caused alarge drop in G/sub x/, i.e., G/sub x/ = 0.15 at 32% MCN and G/sub x/ = 0.03 at 51% MCN. The observation could be attributed to the decreasing probability that crosslinking sites, in the MCA monomer units on adjacent chains, would lie in close proximity. 3 figures, 8 tables.

  19. Preparation, structure, and ethylene (co)polymerization behavior of Group IV metal complexes with an [OSSO]-carborane ligand.

    PubMed

    Hu, Ping; Wang, Jian-Qiang; Wang, Fosong; Jin, Guo-Xin

    2011-07-25

    The synthesis of Group IV metal complexes that contain a tetradentate dianionic [OSSO]-carborane ligand [(HOC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2 (B(10)H(10))] (1a) is described. Reactions of TiCl(4) and Ti(OiPr)(4) with the [OSSO]-type ligand 1a afford six-coordinated titanium complex [Ti(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))Cl(2)] (2a) and four-coordinated titanium complex [Ti(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))(OiPr)(2)] (2b), respectively. ZrCl(4) and HfCl(4) were treated with 1a to give six-coordinated zirconium complex [Zr(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))Cl(2) (thf)(2)] (2c) and six-coordinated hafnium complex [Hf(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))Cl(2)] (2d). All the complexes were fully characterized by IR, NMR spectroscopy, and elemental analysis. In addition, X-ray structure analyses were performed on complexes 2a and 2b and reveal the expected different coordination geometry due to steric hindrance effects. Extended X-ray absorption fine structure (EXAFS) spectroscopy was performed on complexes 2c and 2d to describe the coordination chemistry of this ligand around Zr and Hf. Six-coordinated titanium complex 2a showed good activity toward ethylene polymerization as well as toward copolymerization of ethylene with 1-hexene in the presence of methylaluminoxane (MAO) as cocatalyst (up to 1060 kg[mol(Ti)](-1) h(-1) in the case of 10 atm of ethylene pressure).

  20. Alkylation of Methyl Linoleate with Propene in Ionic Liquids in the Presence of Metal Salts.

    PubMed

    Pomelli, Christian Silvio; Ghilardi, Tiziana; Chiappe, Cinzia; de Angelis, Alberto Renato; Calemma, Vincenzo

    2015-12-07

    Vegetable oils and fatty acid esters are suitable precursor molecules for the production of a variety of bio-based products and materials, such as paints and coatings, plastics, soaps, lubricants, cosmetics, pharmaceuticals, printing inks, surfactants, and biofuels. Here, we report the possibility of using Lewis acidic ionic liquids (ILs) to obtain polyunsaturated ester dimerization-oligomerization and/or, in the presence of another terminal alkene (propene), co-polymerization. In particular, we have tested the Lewis acidic mixtures arising from the addition of a proper amount of GaCl₃ (Χ > 0.5) to two chloride-based (1-butyl-3-methylimidazolium chloride, [bmim]Cl, and 1-butylisoquinolium chloride, [BuIsoq]Cl) or by dissolution of a smaller amount of Al(Tf₂N)₃ (Χ = 0.1) in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][Tf₂N]. On the basis of product distribution studies, [bmim][Tf₂N]/Al(Tf₂N)₃ appears the most suitable medium in which methyl linoleate alkylation with propene can compete with methyl linoleate or propene oligomerization.

  1. Methylation profiling using methylated DNA immunoprecipitation and tiling array hybridization.

    PubMed

    Cheung, Hoi-Hung; Lee, Tin-Lap; Rennert, Owen M; Chan, Wai-Yee

    2012-01-01

    DNA methylation is an important epigenetic modification that regulates development and plays a role in the pathophysiology of many diseases. It is dynamically changed during germline development. Methylated DNA immunoprecipitation (MeDIP) is an efficient, cost-effective method for locus-specific and genome-wide analysis. Methylated DNA fragments are enriched by a 5-methylcytidine-recognizing antibody, therefore allowing the analysis of both CpG and non-CpG methylation. The enriched DNA fragments can be amplified and hybridized to tiling arrays covering CpG islands, promoters, or the entire genome. Comparison of different methylomes permits the discovery of differentially methylated regions that might be important in disease- or tissue-specific expression. Here, we describe an established MeDIP protocol and tiling array hybridization method for profiling methylation of testicular germ cells.

  2. Event extraction for DNA methylation.

    PubMed

    Ohta, Tomoko; Pyysalo, Sampo; Miwa, Makoto; Tsujii, Jun'ichi

    2011-10-06

    We consider the task of automatically extracting DNA methylation events from the biomedical domain literature. DNA methylation is a key mechanism of epigenetic control of gene expression and implicated in many cancers, but there has been little study of automatic information extraction for DNA methylation. We present an annotation scheme for DNA methylation following the representation of the BioNLP shared task on event extraction, select a set of 200 abstracts including a representative sample of all PubMed citations relevant to DNA methylation, and introduce manual annotation for this corpus marking nearly 3000 gene/protein mentions and 1500 DNA methylation and demethylation events. We retrain a state-of-the-art event extraction system on the corpus and find that automatic extraction of DNA methylation events, the methylated genes, and their methylation sites can be performed at 78% precision and 76% recall. Our results demonstrate that reliable extraction methods for DNA methylation events can be created through corpus annotation and straightforward retraining of a general event extraction system. The introduced resources are freely available for use in research from the GENIA project homepage http://www-tsujii.is.s.u-tokyo.ac.jp/GENIA.

  3. Preparation of Thermo-Responsive Poly(ionic liquid)s-Based Nanogels via One-Step Cross-Linking Copolymerization.

    PubMed

    Zhang, Jing; Liu, Jingjiang; Zuo, Yong; Wang, Rongmin; Xiong, Yubing

    2015-09-18

    In this study, thermo-responsive polymeric nanogels were facilely prepared via one-step cross-linking copolymerization of ethylene glycol dimethacrylate/divinylbenzene and ionic liquid (IL)-based monomers, 1,n-dialkyl-3,3'-bis-1-vinyl imidazolium bromides ([CnVIm]Br; n = 6, 8, 12) in selective solvents. The results revealed that stable and blue opalescent biimidazolium (BIm)-based nanogel solutions could be obtained without any precipitation when the copolymerizations were conducted in methanol. Most importantly, these novel nanogels were thermo-response, and could reversibly transform to precipitation in methanol with temperature changes. Turbidity analysis and dynamic light scatting (DLS) measurement illustrated that PIL-based nanogel solutions presented the phase transform with upper critical solution temperature (UCST) in the range of 5-25 °C. The nanogels were characterized using Fourier transform infrared (FTIR), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM). In addition, BIm-based nanogels could also be used as highly active catalysts in the cycloaddition reaction of CO₂ and epoxides. As a result, our attributes build a robust platform suitable for the preparation of polymeric nanomaterials, as well as CO₂ conversion.

  4. Lipase-catalyzed copolymerization of dialkyl carbonate with 1,4-butanediol and ω-pentadecalactone: synthesis of poly(ω-pentadecalactone-co-butylene-co-carbonate).

    PubMed

    Jiang, Zhaozhong

    2011-05-09

    Candida antarctica lipase B (CALB) was successfully used to promote synthesis of aliphatic poly(carbonate-co-ester) copolymers from dialkyl carbonate, diol, and lactone monomers. The polymerization reactions were carried out in two stages: first-stage oligomerization under low vacuum, followed by second-stage polymerization under high vacuum. Therefore, copolymerization of ω-pentadecalactone (PDL), diethyl carbonate (DEC), and 1,4-butanediol (BD) yielded PDL-DEC-BD copolymers with a M(w) of whole product (nonfractionated) up to 33 000 and M(w)/M(n) between 1.2 and 2.3. Desirable reaction temperature for the copolymerization was found to be ∼80 °C. The copolymer compositions, in the range from 10 to 80 mol % PDL unit content versus total (PDL + carbonate) units, were effectively controlled by adjusting the monomer feed ratio. Reprecipitation in chloroform/methanol mixture allowed isolation of the purified copolymers in up to 92% yield. (1)H and (13)C NMR analyses, including statistical analysis on repeat unit sequence distribution, were used to determine the polymer microstructures. The synthesized PDL-DEC-BD copolymers possessed near random structures with all possible combinations of PDL, carbonate, and butylene units via either ester or carbonate linkages in the polymer chains and are more appropriately named as poly(PDL-co-butylene-co-carbonate).

  5. Zwitterionic sulfobetaine-grafted poly(vinylidene fluoride) membrane with highly effective blood compatibility via atmospheric plasma-induced surface copolymerization.

    PubMed

    Chang, Yung; Chang, Wan-Ju; Shih, Yu-Ju; Wei, Ta-Chin; Hsiue, Ging-Ho

    2011-04-01

    Development of nonfouling membranes to prevent nonspecific protein adsorption and platelet adhesion is critical for many biomedical applications. It is always a challenge to control the surface graft copolymerization of a highly polar monomer from the highly hydrophobic surface of a fluoropolymer membrane. In this work, the blood compatibility of poly(vinylidene fluoride) (PVDF) membranes with surface-grafted electrically neutral zwitterionic poly(sulfobetaine methacrylate) (PSBMA), from atmospheric plasma-induced surface copolymerization, was studied. The effect of surface composition and graft morphology, electrical neutrality, hydrophilicity and hydration capability on blood compatibility of the membranes were determined. Blood compatibility of the zwitterionic PVDF membranes was systematically evaluated by plasma protein adsorption, platelet adhesion, plasma-clotting time, and blood cell hemolysis. It was found that the nonfouling nature and hydration capability of grafted PSBMA polymers can be effectively controlled by regulating the grafting coverage and charge balance of the PSBMA layer on the PVDF membrane surface. Even a slight charge bias in the grafted zwitterionic PSBMA layer can induce electrostatic interactions between proteins and the membrane surfaces, leading to surface protein adsorption, platelet activation, plasma clotting and blood cell hemolysis. Thus, the optimized PSBMA surface graft layer in overall charge neutrality has a high hydration capability and the best antifouling, anticoagulant, and antihemolytic activities when comes into contact with human blood.

  6. Novel star-type methoxy-poly(ethylene glycol) (PEG)-poly(ɛ-caprolactone) (PCL) copolymeric nanoparticles for controlled release of curcumin

    NASA Astrophysics Data System (ADS)

    Feng, Runliang; Zhu, Wenxia; Song, Zhimei; Zhao, Liyan; Zhai, Guangxi

    2013-06-01

    To improve curcumin's (CURs) water solubility and release property, a novel star methoxy poly(ethylene glycol)-poly(ɛ-caprolactone) (MPEG-PCL) copolymer was synthesized through O-alkylation, basic hydrolysis and ring-opening polymerization reaction with MPEG, epichlorohydrin, and ɛ-caprolactone as raw materials. The structure of the novel copolymer was characterized by 1H NMR, FT-IR, and GPC. The results of FT-IR and differential scanning calorimeter of CUR-loaded nanoparticles (NPs) prepared by dialysis method showed that CUR was successfully encapsulated into the SMP12 copolymeric NPs with 98.2 % of entrapment efficiency, 10.91 % of drug loading, and 88.4 ± 11.2 nm of mean particle diameter in amorphous forms. The dissolubility of nanoparticulate CUR was increased by 1.38 × 105 times over CUR in water. The obtained blank copolymer showed no hemolysis. A sustained CUR release to a total of approximately 56.13 % was discovered from CUR-NPs in 40 % of ethanol saline solution within 72 h on the use of dialysis method. The release behavior fitted the ambiexponent and biphasic kinetics equation. In conclusion, the copolymeric NPs loading CUR might serve as a potential nanocarrier to improve the solubility and release property of CUR.

  7. Synthesis of organoplatinum poly(dendrimer)s: pronounced effect of size and geometry of small organoplatinum linkers on the copolymerization efficiency with bifunctional dendritic macromonomers.

    PubMed

    Cheung, Siu-Yin; Chow, Hak-Fun

    2009-09-07

    The copolymerizations of two series of surface functionalized bis(acetylene) G1-G3 dendrimers, one (S-Gn) having a structural rigid skeleton and the other (L-Gn) a relatively more flexible architecture, with two platinum linkers, cis-[(Et(2)PCH(2)CH(2)PEt(2))PtCl(2)] (2) and [Cl(Et(3)P)(2)Pt-C[triple bond]C-p-C(6)H(4)-](2) (3) were investigated. For both series of dendrimers, only linear and/or cyclic oligomers were formed when the cis-platinum linker 2 was used. However, high molecular weight (100-200 kD) organoplatinum poly(dendrimer)s were obtained from both series when the elongated linear rod-liked platinum linker 3 was employed and the formation of cyclic oligomers was greatly suppressed for both the structural rigid S-Gn and the structural flexible L-Gn series. These results are in sharp contrast to our earlier findings (S.-Y. Cheung, H.-F. Chow, T. Ngai, X. Wei, Chem. Eur. J. 2009, 15, 2278-2288) obtained by using a shorter linear platinum linker trans-[Pt(PEt(3))(2)Cl(2)] (1), where a larger amount of cyclic oligomers was formed from the structural flexible L-Gn dendrimers. A model was proposed to rationalize how the geometry and size of the platinum linker could control the copolymerization behaviours of these dendritic macromonomers.

  8. Precise synthesis of thermoreversible block copolymers containing reactive furfuryl groups via living anionic polymerization: the countercation effect on block copolymerization behavior

    SciTech Connect

    Kang, Beom-Goo; Pramanik, Nabendu B.; Singha, Nikhil K.; Lee, Jae-Suk; Mays, Jimmy

    2015-08-07

    The anionic block copolymerization of 4,4' -vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine (A) with furfuryl isocyanate (B) was carried out using potassium naphthalenide (K-Naph) in tetrahydrofuran at -78 and -98 °C to prepare well-defined block copolymers containing furan groups for the formation of thermoreversible networks via a Diels Alder (DA) reaction. While no block copolymerization was observed in the absence of sodium tetraphenylborate (NaBPh4) due to side reactions, well-defined poly-(B-b-A-b-B) (PBAB) copolymers with controlled molecular weights (Mn = 18 700 19 500 g mol -1) and narrow molecular weight distributions (Mw/Mn = 1.08 -1.17) were successfully synthesized in the presence of excess NaBPh4. We prevented the occurrence of the undesirable side reactions during polymerization of B of NaBPh4, which results in the change in the countercation from K+ to Na+ for further polymerization of B. Moreover, the cross-linking via the DA reaction between the furan groups of PBAB and bismaleimide was proved by FT-IR and differential scanning calorimetry (DSC), and the thermoreversible properties of the cross-linked polymer were subsequently investigated using DSC and solubility testing.

  9. Bovine serum albumin surface imprinted polymer fabricated by surface grafting copolymerization on zinc oxide rods and its application for protein recognition.

    PubMed

    Li, Xiangjie; Zhou, Jingjing; Tian, Lei; Li, Wei; Zhang, Baoliang; Zhang, Hepeng; Zhang, Qiuyu

    2015-10-01

    A novel bovine serum albumin (BSA) surface imprinted polymer based on ZnO rods was synthesized by surface grafting copolymerization. It exhibited an excellent recognition performance to bovine serum albumin. The adsorption capacity and imprinting factor of bovine serum albumin could reach 89.27 mg/g and 2.35, respectively. Furthermore, the fluorescence property of ZnO was used for tracing the process of protein imprinting and it implied the excellent optical sensing property of this material. More importantly, the hypothesis that the surface charge of carrier could affect the imprinting process was confirmed. That is, ZnO with positive surface charge could not only improve the recognition specificity of binding sites to template proteins (pI < 7), but also deteriorate the bindings between sites and non-template proteins (pI > 7). It was also important that the reusability of ZnO@BSA molecularly imprinted polymers was satisfactory. This implied that the poor mechanical/chemical stability of traditional zinc oxide sensors could be solved by the introduction of surface grafting copolymerization. These results revealed that the ZnO@BSA molecularly imprinted polymers are a promising optical/electrochemical sensor element.

  10. Genetic effects of methylation diets.

    PubMed

    Van den Veyver, Ignatia B

    2002-01-01

    DNA methylation at cytosines in CpG dinucleotides can lead to changes in gene expression and function without altering the primary sequence of the DNA. Methylation can be affected by dietary levels of methyl-donor components, such as folic acid. This may be an important mechanism for environmentally induced changes in gene expression. Recent literature supports a role for DNA-methylation changes in a number of adult-onset disorders and during development. These changes may be significant for better understanding certain birth defects (e.g., neural tube defects) and the long-term consequences of early environmental influences on gene expression (metabolic programming). Optimal "methylation diets" should be investigated as part of the prevention and treatment of all these conditions, as well as in disorders such as Rett syndrome, whose primary defects may lie in DNA methylation-dependent gene regulation.

  11. 49 CFR 173.193 - Bromoacetone, methyl bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Bromoacetone, methyl bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc. 173.193 Section 173.193 Transportation Other Regulations... bromide, chloropicrin and methyl bromide or methyl chloride mixtures, etc. (a) Bromoacetone must be...

  12. Chromatin methylation and cardiovascular aging.

    PubMed

    Illi, Barbara; Ciarapica, Roberta; Capogrossi, Maurizio C

    2015-06-01

    DNA and histone methylation are well characterized epigenetic marks that are altered during the aging process. In aged cells and tissues, DNA cytosine tagging by methylation undergoes the so-called "epigenetic drift", in parallel with a change in the methylated histone profile. Despite the large body of knowledge regarding age-dependent epigenetic changes, there are few reports related to this topic in the cardiovascular field. This review summarizes age-dependent changes in DNA and histone methylation with a specific focus on age-related cardiovascular diseases (CVDs). Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Methyl and skeletal torsion interaction in methyl thiolfluoroformate

    NASA Astrophysics Data System (ADS)

    Caminati, Walther; Meyer, Rolf

    1981-12-01

    The microwave spectrum of methyl thiolfluoroformate (FCOSCH 3) is reported for the ground state and seven vibrational satellites. The methyl group is in the syn conformation to the carbonyl group. The dipole moment components are μa = 2.89(2) D, μb = 0.30(8) D, and μc = 0. Spacings of A and E levels due to methyl internal rotation are analyzed for the ground state, the first excited methyl torsional state, and the first excited skeletal torsional state. An anomalous sequence of A and E levels occurring in the latter satellite arises from torsional interaction, according to two-dimensional model calculations. Potential parameters consistent with the three observed level separations are V3 = 304(5) cm -1, V6 = 23(1) cm -1 for the methyl torsion and either k = 1.912 or k = 2.936 cm -1 deg -2 for the skeletal torsional force constant.

  14. Living/controlled free radical copolymerization of chlorotrifluoroethene and butyl vinyl ether under 60Co γ-ray irradiation in the presence of S-benzyl O-ethyl dithiocarbonate.

    PubMed

    Liu, Lei; Lu, Dan; Wang, Hu; Dong, Qibao; Wang, Pucheng; Bai, Ruke

    2011-07-21

    Living/controlled free radical copolymerization of chlorotrifluoroethene and butyl vinyl ether has been successfully achieved at room temperature under (60)Co γ-ray irradiation in the presence of S-benzyl O-ethyl dithiocarbonate. The alternating and block copolymers have been obtained with well-defined molecular weights and narrow molecular weight distributions.

  15. Copolymerization of isoprene and nonconjugated α,ω-dienes by half-sandwich scandium catalysts with and without a coordinative side arm.

    PubMed

    Guo, Fang; Nishiura, Masayoshi; Li, Yang; Hou, Zhaomin

    2013-10-01

    A series of half-sandwich scandium-dialkyl complexes that bear various auxiliary ligands have been examined for the copolymerization of isoprene (IP) with nonconjugated α,ω-dienes such as 1,5-hexadiene (HD) and 1,6-heptadiene (HPD). Significant ligand influence on the catalytic activity and selectivity has been observed. The thf-coordinated complex [(C5Me4SiMe3)Sc(CH2SiMe3)2(thf)] (2) and the methoxy side arm containing the half-sandwich complex [(C5Me4C6H4OMe-o)Sc(CH2SiMe3)2] (3), in combination with an equivalent of [Ph3C][B(C6F5)4], can serve as excellent catalysts for the random cyclocopolymerizations of IP with HD and HPD. The resulting random HD-IP copolymers contain five-membered-ring methylene-1,3-cyclopentane (MCP), 3,4-polyisoprene (3,4-IP), and 1,4-polyisoprene (1,4-IP) units with controllable HD incorporation in a range of 17-82 mol%. The random HPD-IP copolymers possess six-membered-ring methylene-1,3-cyclohexane (MCH), 1,4-IP, and 3,4-IP units with HPD incorporation in a range of 11-55 mol%. By use of a catalyst that bears a phosphine oxide group [{C5Me4SiMe2CH2P(O)Ph2}Sc(CH2SiMe3)2] (5), the alternating copolymerizations of IP with HD and HPD have been achieved for the first time in which HD and HPD are completely cyclized to the MCP and MCH units, respectively. More remarkably, in the alternating copolymerization of HPD and IP by 5, the regio- and stereospecific cis-MCH selectivity reached as high as 99%. The microstructures and compositions of these copolymers showed significant influences on their mechanical properties.

  16. Development of surface imprinted core-shell nanoparticles and their application in a solid-phase dispersion extraction matrix for methyl parathion.

    PubMed

    Tan, Lei; Li, Weiming; Li, He; Tang, Youwen

    2014-04-04

    Applying molecular imprinting techniques to the surface of functionalized SiO2 allows the preparation of molecularly imprinted polymers (MIPs) with accessible, high affinity and surface exposed binding sites. This paper demonstrates a new strategy for producing such hybrid organic-inorganic surface imprinted silica nanoparticles for specific recognition of methyl parathion. The technique provides surface grafting imprinting in chloroform using amino modified silica nanoparticles as supports, acrylamide as the functional monomer, γ-methacryloxypropyl trimethoxy silane as the grafting agent, and methyl parathion as a template. The amino propyl functional monomer layer directs the selective occurrence of imprinting polymerization at the silica surface through copolymerization of grafting agents with functional monomers, but also acts as an assistive monomer to drive the template into the formed polymer shells to create effective recognition sites. The resulting MIPs-SiO2 nanoparticles display three-dimensional core-shell architectures and large surface areas. The molecularly imprinted shell provides recognition sites for methyl parathion, with the materials exhibiting excellent performance for selecting the template. Using MIPs-SiO2 nanoparticles as a matrix of solid-phase dispersion extraction sorbents, trace amounts of methyl parathion are selectivity extracted from pear and green vegetable samples while simultaneously eliminating matrix interferences, attaining recoveries of 84.7-94.4% for the samples.

  17. Contact dermatitis to methyl methacrylate.

    PubMed

    Kassis, V; Vedel, P; Darre, E

    1984-07-01

    2 cases of contact dermatitis to methyl methacrylate monomer are presented. The patients are nurses who mixed bone cement at orthopedic operations. During the procedure, they used 2 pairs of gloves (latex). Butyl rubber gloves are recommended for methyl methacrylate monomer to avoid sensitization and/or cumulative irritant contact dermatitis on the hands.

  18. Managing Nematodes without Methyl Bromide

    USDA-ARS?s Scientific Manuscript database

    Methyl bromide is an effective pre-plant soil fumigant used to control nematodes in many high-input, high-value production systems including vegetables, nurseries, ornamentals, tree fruits, strawberries, and grapes. Because methyl bromide has provided a reliable return on investment for nematode c...

  19. Methods of DNA methylation detection

    NASA Technical Reports Server (NTRS)

    Maki, Wusi Chen (Inventor); Filanoski, Brian John (Inventor); Mishra, Nirankar (Inventor); Rastogi, Shiva (Inventor)

    2010-01-01

    The present invention provides for methods of DNA methylation detection. The present invention provides for methods of generating and detecting specific electronic signals that report the methylation status of targeted DNA molecules in biological samples.Two methods are described, direct and indirect detection of methylated DNA molecules in a nano transistor based device. In the direct detection, methylated target DNA molecules are captured on the sensing surface resulting in changes in the electrical properties of a nano transistor. These changes generate detectable electronic signals. In the indirect detection, antibody-DNA conjugates are used to identify methylated DNA molecules. RNA signal molecules are generated through an in vitro transcription process. These RNA molecules are captured on the sensing surface change the electrical properties of nano transistor thereby generating detectable electronic signals.

  20. Programming of DNA methylation patterns.

    PubMed

    Cedar, Howard; Bergman, Yehudit

    2012-01-01

    DNA methylation represents a form of genome annotation that mediates gene repression by serving as a maintainable mark that can be used to reconstruct silent chromatin following each round of replication. During development, germline DNA methylation is erased in the blastocyst, and a bimodal pattern is established anew at the time of implantation when the entire genome gets methylated while CpG islands are protected. This brings about global repression and allows housekeeping genes to be expressed in all cells of the body. Postimplantation development is characterized by stage- and tissue-specific changes in methylation that ultimately mold the epigenetic patterns that define each individual cell type. This is directed by sequence information in DNA and represents a secondary event that provides long-term expression stability. Abnormal methylation changes play a role in diseases, such as cancer or fragile X syndrome, and may also occur as a function of aging or as a result of environmental influences.

  1. DNA Methylation in Schizophrenia.

    PubMed

    Pries, Lotta-Katrin; Gülöksüz, Sinan; Kenis, Gunter

    2017-01-01

    Schizophrenia is a highly heritable psychiatric condition that displays a complex phenotype. A multitude of genetic susceptibility loci have now been identified, but these fail to explain the high heritability estimates of schizophrenia. In addition, epidemiologically relevant environmental risk factors for schizophrenia may lead to permanent changes in brain function. In conjunction with genetic liability, these environmental risk factors-likely through epigenetic mechanisms-may give rise to schizophrenia, a clinical syndrome characterized by florid psychotic symptoms and moderate to severe cognitive impairment. These pathophysiological features point to the involvement of epigenetic processes. Recently, a wave of studies examining aberrant DNA modifications in schizophrenia was published. This chapter aims to comprehensively review the current findings, from both candidate gene studies and genome-wide approaches, on DNA methylation changes in schizophrenia.

  2. Methyl Halide Production by Fungi

    NASA Astrophysics Data System (ADS)

    Dailey, G. D.; Varner, R. K.; Blanchard, R. O.; Sive, B. C.; Crill, P. M.

    2005-12-01

    Methyl chloride (CH3Cl), methyl bromide (CH3Br) and methyl iodide (CH3I) are methyl halide gases that contribute significant amounts of halogen radicals to the atmosphere. In an effort to better understand the global budget of methyl halides and their impact on the atmosphere, we need to identify the natural sources in addition to the known anthropogenic sources of these compounds. We are investigating the role of fungi in the production of methyl halides in the soils and wetlands in southern New Hampshire, USA. Previous research has shown that wood decay fungi and ectomycorrhizal fungi, which are within a group of fungi called basidiomycetes, emit methyl halides. In our study, measurements of headspace gas extracted from flasks containing fungi grown in culture demonstrate that a variety of fungi, including basidiomycetes and non-basidiomycetes, emit methyl halides. Our research sites include four ecosystems: an agricultural field, a temperate forest, a fresh water wetland, and coastal salt marshes. We have collected and isolated fungi at each site by culturing tissue samples of fruiting bodies and plant material, by using wood baits, and from the direct culture of soil. We compared the rates of methyl halide emissions from the fungi in the four ecosystems. In addition, we measured emissions from previously assayed fungal isolates after reintroducing them to sterilized soils that were collected from their original environments. Fungal biomass was determined by substrate-induced respiration (SIR). The emission rate by the fungus was determined by a linear regression of the concentration of methyl halide in the sample headspace over time divided by the fungal biomass.

  3. AAB-sequence living radical chain copolymerization of naturally occurring limonene with maleimide: an end-to-end sequence-regulated copolymer.

    PubMed

    Satoh, Kotaro; Matsuda, Masaru; Nagai, Kanji; Kamigaito, Masami

    2010-07-28

    Sequence control in chain-growth polymerization is still one of the most challenging topics in synthetic polymer chemistry in contrast to natural macromolecules with completely sequence-regulated structures like proteins and DNA. Here, we report the quantitative and highly selective 1:2 sequence-regulated radical copolymerization of naturally occurring (+)-d-limonene (L) and a maleimide (M) in fluoroalcohol giving chiral copolymers with high glass transition temperatures (220-250 degrees C) originating from the specific rigid cyclic structures of the monomers. Furthermore, the combination with a reversible addition-fragmentation chain transfer (RAFT) agent (C-S) via the controlled/living radical polymerization resulted in end-to-end sequence-regulated copolymers [C-(M-M-L)(n)-M-S] with both highly sequenced chain ends and main-chain repeating units as well as controlled molecular weights.

  4. Possibility of Solid-State Graft Copolymerization on Poly(ethylene terephthalate) Films by Plasma Irradiation and Effects of Surface Modification

    NASA Astrophysics Data System (ADS)

    Narushima, Kazuo; Matsuda, Noriko; Mizutani, Chie; Yamashita, Nanami; Inagaki, Norihiro; Iio, Kokoro; Isono, Yoshihiro; Islam, Mohammed Rafiqul

    2007-07-01

    A solid-state graft copolymerization for poly(ethylene terephthalate) (PET) films was proposed for a new surface modification technique. The functional groups included in graft monomers can be introduced on a PET surface. Allylbiguanide hydrochloric acid salt (ABG), N-methylol acrylamide (NM-AAm), and N-isopropyl acrylamide (NIP-AAm) were used as graft monomers. This technique led to a large change in the N/C atomic ratio on the PET film surfaces, which shows that nitrogen functional groups were introduced on PET surfaces. On the grafted PET films, a new N 1s spectrum appeared. This N 1s spectrum contained two components, namely, amino and amido groups, which suggests that the two groups were introduced onto the PET surfaces. In particular, isopropyl groups were introduced on the PET surface in the case of NIP-AAm. The formation of these functional groups demonstrated changes in the surface properties of PET, such as improved wettability.

  5. Solid contact ion sensor with conducting polymer layer copolymerized with the ion-selective membrane for determination of calcium in blood serum.

    PubMed

    Abramova, Natalia; Moral-Vico, Javier; Soley, Jordi; Ocaña, Cristina; Bratov, Andrey

    2016-11-02

    A new solid contact ion selective electrode with intermediate conducting polymer (CP) layer formed by electropolymerization on a gold electrode of a bifunctional monomer, n-phenyl-ethylenediamine-methacrylamide (NPEDMA), which contains a methacrylamide group attached to aniline, is presented. The conducting polymer was studied by means of optical spectroscopy, cyclic voltammetry and potentiometric measurements. Ca(2+)-ion-selective membrane based on acrylated urethane polymer was shown to co-polymerize with the CP forming highly adhesive boundary that prevents formation of water layers between the CP and membrane, thus enhancing the stability and life-time of the sensor. The designed ion-selective electrode was successfully used for determination of total calcium ion concentration in blood serum samples.

  6. Electronic Effects of Aluminum Complexes in the Copolymerization of Propylene Oxide with Tricyclic Anhydrides: Access to Well-Defined, Functionalizable Aliphatic Polyesters.

    PubMed

    Van Zee, Nathan J; Sanford, Maria J; Coates, Geoffrey W

    2016-03-02

    The synthesis of well-defined and functionalizable aliphatic polyesters remains a key challenge in the advancement of emerging drug delivery and self-assembly technologies. Herein, we investigate the factors that influence the rates of undesirable transesterification and epimerization side reactions at high conversion in the copolymerization of tricyclic anhydrides with excess propylene oxide using aluminum salen catalysts. The structure of the tricyclic anhydride, the molar ratio of the aluminum catalyst to the nucleophilic cocatalyst, and the Lewis acidity of the aluminum catalyst all influence the rates of these side reactions. Optimal catalytic activity and selectivity against these side reactions requires a careful balance of all these factors. Effective suppression of undesirable transesterification and epimerization was achieved even with sterically unhindered monomers using a fluorinated aluminum salph complex with a substoichiometric amount of a nucleophilic cocatalyst. This process can be used to synthesize well-defined block copolymers via a sequential addition strategy.

  7. The synthesis of surface-glycosylated porous monolithic column via aqueous two-phase graft copolymerization and its application in capillary-liquid chromatography.

    PubMed

    Xiong, Xiyue; He, Haiqin; Shu, Yan; Li, Yuxin; Yang, Zihui; Chen, Yingzhuang; Ma, Ming; Chen, Bo

    2016-12-01

    A facile, flexible process was developed for the preparation of surface-glycosylated porous monolithic columns via aqueous two-phase graft copolymerization of polyethylene glycol diacrylate (PEGDA) and water-soluble dextran (dextran sulfate). The formation of poly(PEGDA) porous skeletons and surface glycosylation were achieved via a one-step process without pre-modification of the dextran. The synthesis conditions were thoroughly optimized. The optimal monolithic column exhibited a large dry state surface area (greater than 400m(2)/g), and it was evaluated as a hydrophilic liquid chromatography (HILIC) stationary phase. A typical HILIC mechanism was observed at high organic solvent content (≥65% acetonitrile). In addition, the resulting monolithic column demonstrated the potential use in analysis of complex biological sample and enviroment water. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Photodissociation of methyl chloride and methyl bromide in the atmosphere

    NASA Technical Reports Server (NTRS)

    Robbins, D. E.

    1976-01-01

    Methyl chloride (CH3Cl) and methyl bromide (CH3Br) have been suggested to be significant sources of the stratospheric halogens. The breakup of these compounds in the stratosphere by photodissociation or reaction with OH releases halogen atoms which catalytically destroy ozone. Experimental results are presented for ultraviolet photoabsorption cross sections of CH3Cl and CH3Br. Calculations are presented of loss rates for the methyl halides due to photodissociation and reaction with OH and of mixing ratios of these species in the stratosphere.

  9. DNA methylation pathways and their crosstalk with histone methylation

    PubMed Central

    Du, Jiamu; Johnson, Lianna M.; Jacobsen, Steven E.; Patel, Dinshaw J.

    2015-01-01

    Methylation of DNA and of histone 3 at Lys 9 (H3K9) are highly correlated with gene silencing in eukaryotes from fungi to humans. Both of these epigenetic marks need to be established at specific regions of the genome and then maintained at these sites through cell division. Protein structural domains that specifically recognize methylated DNA and methylated histones are key for targeting enzymes that catalyse these marks to appropriate genome sites. Genetic, genomic, structural and biochemical data reveal connections between these two epigenetic marks, and these domains mediate much of the crosstalk. PMID:26296162

  10. Conducting polymer films fabricated by oxidative graft copolymerization of aniline on poly(acrylic acid) grafted poly(ethylene terephthalate) surfaces.

    PubMed

    Wang, Jiku; Liu, Xuyan; Choi, Ho-Suk; Kim, Jong-Hoon

    2008-11-27

    A conductive polyaniline/poly(ethylene terephthalate) (PANI/PET) composite film was fabricated via the oxidative graft copolymerization of aniline (ANI) onto the plasma-induced poly(acrylic acid) (PAAc) grafted PET surface. The attenuated total reflectance Fourier transform infrared spectroscopy spectra (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) results confirmed that PANI was successfully grafted onto the surface of the PAAc-g-PET films. The effects of the experimental conditions on the percentage of PANI grafted onto the PAAc-g-PET films were extensively investigated. A very high grafting percentage of ANI can be obtained through the acid-base reaction between the aniline monomer and PAAc on the PAAc-g-PET surface at high temperature. As a result, the grafting percentage of PANI can be increased to as high as 12.18 wt %, which causes the surface resistance of the PANI-g-PAAc-g-PET film to be reduced to about 1000 Omega/sq. We predicted that this is because of the high flexibility of the PAAc molecular chains and high solubility of aniline, both of which facilitate the binding of aniline to PAAc during this high temperature acid-base reaction. It was observed by atomic force microscopy (AFM) that the PANI-modified PET surface exhibits higher size irregularity and surface roughness, which further indicated that a much greater number of aniline molecules can be reactively bonded to and distributed along the grafted AAc chains and that the PANI-g-PAAc-g-PET surface resulting from the sequential oxidative graft copolymerization can possess higher electrical conductivity.

  11. Electrostatic self-assembly of multilayer copolymeric membranes on the surface of porous tantalum implants for sustained release of doxorubicin

    PubMed Central

    Guo, Xinming; Chen, Muwan; Feng, Wenzhou; Liang, Jiabi; Zhao, Huibin; Tian, Lin; Chao, Hui; Zou, Xuenong

    2011-01-01

    Many studies in recent years have focused on surface engineering of implant materials in order to improve their biocompatibility and other performance. Porous tantalum implants have increasingly been used in implant surgeries, due to their biocompatibility, physical stability, and good mechanical strength. In this study we functionalized the porous tantalum implant for sustained drug delivery capability via electrostatic self-assembly of polyelectrolytes of hyaluronic acid, methylated collagen, and terpolymer on the surface of a porous tantalum implant. The anticancer drug doxorubicin was encapsulated into the multilayer copolymer membranes on the porous tantalum implants. Results showed the sustained released of doxorubicin from the functionalized porous tantalum implants for up to 1 month. The drug release solutions in 1 month all had inhibitory effects on the proliferation of chondrosarcoma cell line SW1353. These results suggest that this functionalized implant could be used in reconstructive surgery for the treatment of bone tumor as a local, sustained drug delivery system. PMID:22162662

  12. Electrostatic self-assembly of multilayer copolymeric membranes on the surface of porous tantalum implants for sustained release of doxorubicin.

    PubMed

    Guo, Xinming; Chen, Muwan; Feng, Wenzhou; Liang, Jiabi; Zhao, Huibin; Tian, Lin; Chao, Hui; Zou, Xuenong

    2011-01-01

    Many studies in recent years have focused on surface engineering of implant materials in order to improve their biocompatibility and other performance. Porous tantalum implants have increasingly been used in implant surgeries, due to their biocompatibility, physical stability, and good mechanical strength. In this study we functionalized the porous tantalum implant for sustained drug delivery capability via electrostatic self-assembly of polyelectrolytes of hyaluronic acid, methylated collagen, and terpolymer on the surface of a porous tantalum implant. The anticancer drug doxorubicin was encapsulated into the multilayer copolymer membranes on the porous tantalum implants. Results showed the sustained released of doxorubicin from the functionalized porous tantalum implants for up to 1 month. The drug release solutions in 1 month all had inhibitory effects on the proliferation of chondrosarcoma cell line SW1353. These results suggest that this functionalized implant could be used in reconstructive surgery for the treatment of bone tumor as a local, sustained drug delivery system.

  13. Methylation of cysteine in hemoglobin following exposure to methylating agents

    SciTech Connect

    Bailey, E.; Connors, T.A.; Farmer, P.B.; Gorf, S.M.; Rickard, J.

    1981-06-01

    In addition to reacting with biologically important nucleophilic sites in DNA, alkylating agents also interact with amino acids in proteins. Measurements of the extent of formation of these alkyl amino acids may be used as a means of determining exposure to these compounds. The degree of S-methylation of cysteine in hemoglobin was studied following in vivo exposure of rats to methyl methanesulfonate, dimethylnitrosamine, and 5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide. A linear dose-response curve was observed for methyl methanesulfonate over a 100-fold dose range. For dimethylnitrosamine, there was a threshold of doses where no methylation could be detected, and a curved dose-response curve was obtained. At high doses, the degree of methylation of hemoglobin cysteine was 7-fold lower than that with methyl methanesulfonate. In vivo, no alkylation could be observed with 5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide; however, the existence of naturally occurring S-methylcysteine in the rat hemoglobin may have overshadowed small increases in alkylation arising from exposure to this compound. The natural occurrence of S-methylcysteine was studied in 13 species, and amounts ranging from 5.6 nmol/g globin (hamster) to 481 nmol/g globin (partridge) were observed. The reason for its occurrence is unknown but is under investigation.

  14. Geometry Constrained N-(5,6,7-Trihydroquinolin-8-ylidene)arylaminopalladium Dichloride Complexes: Catalytic Behavior toward Methyl Acrylate (MA), Methyl Acrylate-co-Norbornene (MA-co-NB) Polymerization and Heck Coupling.

    PubMed

    Zeng, Yanning; Mahmood, Qaiser; Liang, Tongling; Sun, Wen-Hua

    2016-12-07

    A new pair of plladium complexes (Pd4 and Pd5) ligated with constrained N-(5,6,7-trihydroquinolin-8-ylidene)arylamine ligands have been prepared and well characterized by ¹H-, (13)C-NMR and FTIR spectroscopies as well as elemental analysis. The molecular structure of Pd4 and Pd5 in solid state have also been determined by X-ray diffraction, showing slightly distorted square planar geometry around the palladium metal center. All complexes Pd1-Pd5 are revealed highly efficient catalyst in methyl acrylate (MA) polymerization as well as methyl acrylate/norbornene (MA/NB) copolymerization. In the case of MA polymerization, as high as 98.4% conversion with high molecular weight up to 6282 kg·mol(-1) was achieved. Likewise, Pd3 complex has good capability to incorporate about 18% NB content into MA polymer chains. Furthermore, low catalyst loadings (0.002 mol %) of Pd4 or Pd5 are able to efficiently mediate the coupling of haloarenes with styrene affording up to 98% conversion.

  15. Stringent programming of DNA methylation in humans.

    PubMed

    Aung, Hnin T; Harrison, Dion K; Findlay, Ian; Mattick, John S; Martin, Nicholas G; Carroll, Bernard J

    2010-10-01

    We describe a PCR-based method called Amplified Methylation Polymorphism (AMP) for scanning genomes for DNA methylation changes. AMP detects tissue-specific DNA methylation signatures often representing junctions between methylated and unmethylated DNA close to intronexon junctions and/or associated with CpG islands. Identical AMP profiles are detected for healthy, young, monozygotic twins.

  16. Cigarette smoking and DNA methylation

    PubMed Central

    Lee, Ken W. K.; Pausova, Zdenka

    2013-01-01

    DNA methylation is the most studied epigenetic modification, capable of controlling gene expression in the contexts of normal traits or diseases. It is highly dynamic during early embryogenesis and remains relatively stable throughout life, and such patterns are intricately related to human development. DNA methylation is a quantitative trait determined by a complex interplay of genetic and environmental factors. Genetic variants at a specific locus can influence both regional and distant DNA methylation. The environment can have varying effects on DNA methylation depending on when the exposure occurs, such as during prenatal life or during adulthood. In particular, cigarette smoking in the context of both current smoking and prenatal exposure is a strong modifier of DNA methylation. Epigenome-wide association studies have uncovered candidate genes associated with cigarette smoking that have biologically relevant functions in the etiology of smoking-related diseases. As such, DNA methylation is a potential mechanistic link between current smoking and cancer, as well as prenatal cigarette-smoke exposure and the development of adult chronic diseases. PMID:23882278

  17. Modulating fibroblast cell proliferation with functionalized poly(methyl methacrylate) based copolymers: chemical composition and monomer distribution effect.

    PubMed

    El Khadali, Fatima; Hélary, Gérard; Pavon-Djavid, Graciela; Migonney, Véronique

    2002-01-01

    Poly(methyl methacrylate)-based terpolymers bearing sulfonate and carboxylate groups have been synthesized by radical copolymerization leading to polymers with random distributions of ionic monomer units. Fibroblast cells were seeded on terpolymers of various molar compositions of ionic groups. Kinetics of the cell proliferation were examined and systematically compared to the nonfunctionalized control polymer, poly(methyl methacrylate). Modulation of cell proliferation was observed on 15% ionic monomer content copolymers of various compositions (R = COO(-)/(COO(-) + SO(3)(-)) and varies from 0 to 1). The inhibition percentage of cell proliferation calculated for each polymer by comparison to the cell proliferation on the control was plotted against R and gave a maximum value for R close to 0.55. Copolymers with ionic group contents higher or lower than 15% exhibit inhibition percentages fitting with those previously observed for the same R values, showing that the hydrophilic properties are not sufficient to explain the modulation effect of this material toward cells. Moreover, for each polymer tested, cells, even if inhibited in growth, were shown to be viable, indicating that the synthesized terpolymers exhibit cytostatic properties excluding any cytotoxic effect. Such polymers may be used for the fabrication of biocompatible intraocular lenses and prevent secondary cataract.

  18. Calibration and application of a passive air sampler (XAD-PAS) for volatile methyl siloxanes.

    PubMed

    Krogseth, Ingjerd S; Zhang, Xianming; Lei, Ying D; Wania, Frank; Breivik, Knut

    2013-05-07

    Because the atmosphere is key to understanding the environmental behavior of volatile methyl siloxanes (VMS), a variety of reliable air sampling methods are needed. The purpose of this study was to calibrate and evaluate an existing, polystyrene-divinylbenzene copolymeric resin-based passive air sampler (XAD-PAS) for VMS. Sixteen XAD-PAS were deployed for 7-98 days at a suburban site in Toronto, Canada, while the VMS concentration in air was monitored by an active sampling method. This calibration and a subsequent field test further allowed for investigation of the temporal and spatial variability of VMS in the region. Uptake in the XAD-PAS of octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and three linear VMS was linear throughout the whole deployment period. Sampling rates were between 0.4 and 0.5 m(3)/day. The XAD-PAS measured ∑VMS concentrations ranged from nondetects in rural areas (n = 3), to 169 ± 49 ng/m(3) in the urban region (n = 21), to levels above 600 ng/m(3) at sewage treatment plants (n = 2). Levels and composition of VMS within the urban area were remarkably uniform in space. Levels, but not composition, were highly variable in time and weakly correlated with temperature, wind speed, and wind direction.

  19. Genome-wide methylation study on depression: differential methylation and variable methylation in monozygotic twins

    PubMed Central

    Córdova-Palomera, A; Fatjó-Vilas, M; Gastó, C; Navarro, V; Krebs, M-O; Fañanás, L

    2015-01-01

    Depressive disorders have been shown to be highly influenced by environmental pathogenic factors, some of which are believed to exert stress on human brain functioning via epigenetic modifications. Previous genome-wide methylomic studies on depression have suggested that, along with differential DNA methylation, affected co-twins of monozygotic (MZ) pairs have increased DNA methylation variability, probably in line with theories of epigenetic stochasticity. Nevertheless, the potential biological roots of this variability remain largely unexplored. The current study aimed to evaluate whether DNA methylation differences within MZ twin pairs were related to differences in their psychopathological status. Data from the Illumina Infinium HumanMethylation450 Beadchip was used to evaluate peripheral blood DNA methylation of 34 twins (17 MZ pairs). Two analytical strategies were used to identify (a) differentially methylated probes (DMPs) and (b) variably methylated probes (VMPs). Most DMPs were located in genes previously related to neuropsychiatric phenotypes. Remarkably, one of these DMPs (cg01122889) was located in the WDR26 gene, the DNA sequence of which has been implicated in major depressive disorder from genome-wide association studies. Expression of WDR26 has also been proposed as a biomarker of depression in human blood. Complementarily, VMPs were located in genes such as CACNA1C, IGF2 and the p38 MAP kinase MAPK11, showing enrichment for biological processes such as glucocorticoid signaling. These results expand on previous research to indicate that both differential methylation and differential variability have a role in the etiology and clinical manifestation of depression, and provide clues on specific genomic loci of potential interest in the epigenetics of depression. PMID:25918994

  20. Whole genome methylation profiling by immunoprecipitation of methylated DNA.

    PubMed

    Sharp, Andrew J

    2012-01-01

    I provide a protocol for DNA methylation profiling based on immunoprecipitation of methylated DNA using commercially available monoclonal antibodies that specifically recognize 5-methylcytosine. Quantification of the level of enrichment of the resulting DNA enables DNA methylation to be assayed for any genomic locus, including entire chromosomes or genomes if appropriate microarray or high-throughput sequencing platforms are used. In previous studies (1, 2), I have used hybridization to oligonucleotide arrays from Roche Nimblegen Inc, which allow any genomic region of interest to be interrogated, dependent on the array design. For example, using modern tiling arrays comprising millions of oligonucleotide probes, several complete human chromosomes can be assayed at densities of one probe per 100 bp or greater, sufficient to yield high-quality data. However, other methods such as quantitative real-time PCR or high-throughput sequencing can be used, giving either measurement of methylation at a single locus or across the entire genome, respectively. While the data produced by single locus assays is relatively simple to analyze and interpret, global assays such as microarrays or high-throughput sequencing require more complex statistical approaches in order to effectively identify regions of differential methylation, and a brief outline of some approaches is given.

  1. Miniemulsion copolymerization of (meth)acrylates in the presence of functionalized multiwalled carbon nanotubes for reinforced coating applications.

    PubMed

    Pérez-Martínez, Bertha T; Farías-Cepeda, Lorena; Ovando-Medina, Víctor M; Asua, José M; Rosales-Marines, Lucero; Tomovska, Radmila

    2017-01-01

    Film forming, stable hybrid latexes made of methyl metacrylate (MMA), butyl acrylate (BA) and 2-hydroxyethyl methacrylate (HEMA) copolymer reinforced with modified multiwalled carbon nanotubes (MWCNTs) were synthesized by in situ miniemulsion polymerization. The MWCNTs were pretreated by an air sonication process and stabilized by polyvinylpyrrolidone. The presence of the MWCNTs had no significant effect on the polymerization kinetics, but strongly affected the polymer characteristics (Tg and insoluble polymer fraction). The performance of the in situ composites was compared with that of the neat polymer dispersion as well as with those of the polymer/MWCNT physical blends. The in situ composites showed the presence of an additional phase likely due to the strong interaction between the polymer and MWNCTs (including grafting) that reduced the mobility of the polymer chains. As a result, a substantial increase of both the storage and the loss moduli was achieved. At 60 °C, which is above the main transition region of the polymer, the in situ composites maintained the reinforcement, whereas the blends behaved as a liquid-like material. This suggests the formation of a 3D network, in good agreement with the high content of insoluble polymer in the in situ composites.

  2. Miniemulsion copolymerization of (meth)acrylates in the presence of functionalized multiwalled carbon nanotubes for reinforced coating applications

    PubMed Central

    Pérez-Martínez, Bertha T; Ovando-Medina, Víctor M; Asua, José M; Rosales-Marines, Lucero

    2017-01-01

    Film forming, stable hybrid latexes made of methyl metacrylate (MMA), butyl acrylate (BA) and 2-hydroxyethyl methacrylate (HEMA) copolymer reinforced with modified multiwalled carbon nanotubes (MWCNTs) were synthesized by in situ miniemulsion polymerization. The MWCNTs were pretreated by an air sonication process and stabilized by polyvinylpyrrolidone. The presence of the MWCNTs had no significant effect on the polymerization kinetics, but strongly affected the polymer characteristics (T g and insoluble polymer fraction). The performance of the in situ composites was compared with that of the neat polymer dispersion as well as with those of the polymer/MWCNT physical blends. The in situ composites showed the presence of an additional phase likely due to the strong interaction between the polymer and MWNCTs (including grafting) that reduced the mobility of the polymer chains. As a result, a substantial increase of both the storage and the loss moduli was achieved. At 60 °C, which is above the main transition region of the polymer, the in situ composites maintained the reinforcement, whereas the blends behaved as a liquid-like material. This suggests the formation of a 3D network, in good agreement with the high content of insoluble polymer in the in situ composites. PMID:28690968

  3. Functional copolymer/organo-MMT nanoarchitectures. VI. Synthesis and characterization of novel nanocomposites by interlamellar controlled/living radical copolymerization via preintercalated RAFT-agent/organoclay complexes.

    PubMed

    Rzayev, Zakir M O; Söylemez, A Ernur

    2011-04-01

    We have developed a new approach for the synthesis of polymer nanocomposites using a bifunctional reversible addition-fragmentation chain transfer (RAFT) agent, two types of organo-montmorillonites, such as a non-reactive dimethyldodecyl ammonium (DMDA)-MMT and a reactive octadecylamine (ODA)-MMT organoclays, and a radical initiator. The method includes the following stages: (1) synthesis of RAFT intercalated O-MMTs by a physical or chemical interaction of the RAFT agent having two pendant carboxylic groups [S,S-bis(alpha,alpha'-dimethyl-alpha"-acetic acid)trithiocarbonate] with surface alkyl amines of O-MMT containing tertiary ammonium cation or primary amine groups through strong H-bonding and complexing/amidization reactions, respectively, and (2) utilization of these well-dispersed and intercalated RAFT ... O-MMT complexes and their amide derivatives as new modified RAFT agents in radical-initiated interlamellar controlled/living copolymerization of itaconic acid (IA)-n-butylmethacrylate (BMA) monomer pair. The structure and compositions of the synthesized RAFT ... O-MMT complexes and functional copolymer/O-MMT hybrids were confirmed by FTIR, XRD, thermal (DSC-TGA), SEM and TEM morphology analyses. It was demonstrated that the degree of interaction/exfoliation, morphology and thermal behavior of nanocomposites significantly depended on the type of organoclay and in situ interaction, as well as on the content of flexible butyl-ester linkages as a internal plasticizer. The results of the comparative analysis of the nanocomposites structure-composition-property relations show that the functional copolymer-organoclay hybrids prepared with reactive RAFT ... ODA-MMT complex and containing a combination of partially intercalated and predominantly exfoliated nano-structures exhibit relatively higher thermal stability and fine dispersed morphology. These effects were explained by in situ interfacial chemical reactions through amidization of RAFT with surface alkyl amine

  4. Design of a single-step immunoassay principle based on the combination of an enzyme-labeled antibody release coating and a hydrogel copolymerized with a fluorescent enzyme substrate in a microfluidic capillary device.

    PubMed

    Wakayama, Hideki; Henares, Terence G; Jigawa, Kaede; Funano, Shun-ichi; Sueyoshi, Kenji; Endo, Tatsuro; Hisamoto, Hideaki

    2013-11-21

    A combination of an enzyme-labeled antibody release coating and a novel fluorescent enzyme substrate-copolymerized hydrogel in a microchannel for a single-step, no-wash microfluidic immunoassay is demonstrated. This hydrogel discriminates the free enzyme-conjugated antibody from an antigen-enzyme-conjugated antibody immunocomplex based on the difference in molecular size. A selective and sensitive immunoassay, with 10-1000 ng mL(-1) linear range, is reported.

  5. Alcohol, DNA Methylation, and Cancer

    PubMed Central

    Varela-Rey, Marta; Woodhoo, Ashwin; Martinez-Chantar, Maria-Luz; Mato, José M.; Lu, Shelly C.

    2013-01-01

    Cancer is one of the most significant diseases associated with chronic alcohol consumption, and chronic drinking is a strong risk factor for cancer, particularly of the upper aerodigestive tract, liver, colorectum, and breast. Several factors contribute to alcohol-induced cancer development (i.e., carcinogenesis), including the actions of acetaldehyde, the first and primary metabolite of ethanol, and oxidative stress. However, increasing evidence suggests that aberrant patterns of DNA methylation, an important epigenetic mechanism of transcriptional control, also could be part of the pathogenetic mechanisms that lead to alcohol-induced cancer development. The effects of alcohol on global and local DNA methylation patterns likely are mediated by its ability to interfere with the availability of the principal biological methyl donor, S-adenosylmethionine (SAMe), as well as pathways related to it. Several mechanisms may mediate the effects of alcohol on DNA methylation, including reduced folate levels and inhibition of key enzymes in one-carbon metabolism that ultimately lead to lower SAMe levels, as well as inhibition of activity and expression of enzymes involved in DNA methylation (i.e., DNA methyltransferases). Finally, variations (i.e., polymorphisms) of several genes involved in one-carbon metabolism also modulate the risk of alcohol-associated carcinogenesis. PMID:24313162

  6. Alcohol, DNA methylation, and cancer.

    PubMed

    Varela-Rey, Marta; Woodhoo, Ashwin; Martinez-Chantar, Maria-Luz; Mato, José M; Lu, Shelly C

    2013-01-01

    Cancer is one of the most significant diseases associated with chronic alcohol consumption, and chronic drinking is a strong risk factor for cancer, particularly of the upper aerodigestive tract, liver, colorectum, and breast. Several factors contribute to alcohol-induced cancer development (i.e., carcinogenesis), including the actions of acetaldehyde, the first and primary metabolite of ethanol, and oxidative stress. However, increasing evidence suggests that aberrant patterns of DNA methylation, an important epigenetic mechanism of transcriptional control, also could be part of the pathogenetic mechanisms that lead to alcohol-induced cancer development. The effects of alcohol on global and local DNA methylation patterns likely are mediated by its ability to interfere with the availability of the principal biological methyl donor, S-adenosylmethionine (SAMe), as well as pathways related to it. Several mechanisms may mediate the effects of alcohol on DNA methylation, including reduced folate levels and inhibition of key enzymes in one-carbon metabolism that ultimately lead to lower SAMe levels, as well as inhibition of activity and expression of enzymes involved in DNA methylation (i.e., DNA methyltransferases). Finally, variations (i.e., polymorphisms) of several genes involved in one-carbon metabolism also modulate the risk of alcohol-associated carcinogenesis.

  7. Histone methylation during neural development.

    PubMed

    Roidl, Deborah; Hacker, Christine

    2014-06-01

    Post-translational modification of histone proteins, such as the methylation of lysine and arginine residues, influences the higher order of chromatin and leads to gene activation or silencing. Histone methyltransferases or demethylases actively add or remove various methylation marks in a cell-type-specific and context-dependent way. They are therefore important players in regulating the transcriptional program of a cell. Some control of the various cellular programs is necessary during the differentiation of stem cells along a specific lineage, when differentiation to alternative lineages needs to be suppressed. One example is the development of neurons from neural stem cells during neurogenesis. Neurogenesis is a highly organized process that requires the proper coordination of survival, proliferation, differentiation and migration signals. This holds true for both embryonic and neural stem cells that give rise to the various cell types of the central nervous system. The control of embryonic and neural stem cell self-renewal and differentiation is achieved by both extrinsic and intrinsic signals that regulate gene expression precisely. Recent advances in neuroscience support the importance of epigenetic modifications, such as the methylation and acetylation of histones, as an important intrinsic mechanism for the regulation of central nervous system development. This review summarizes our current knowledge of histone methylation processes during neural development and provides insights into the function of histone methylation enzymes and their role during central nervous system development.

  8. PCMdb: Pancreatic Cancer Methylation Database

    NASA Astrophysics Data System (ADS)

    Nagpal, Gandharva; Sharma, Minakshi; Kumar, Shailesh; Chaudhary, Kumardeep; Gupta, Sudheer; Gautam, Ankur; Raghava, Gajendra P. S.

    2014-02-01

    Pancreatic cancer is the fifth most aggressive malignancy and urgently requires new biomarkers to facilitate early detection. For providing impetus to the biomarker discovery, we have developed Pancreatic Cancer Methylation Database (PCMDB, http://crdd.osdd.net/raghava/pcmdb/), a comprehensive resource dedicated to methylation of genes in pancreatic cancer. Data was collected and compiled manually from published literature. PCMdb has 65907 entries for methylation status of 4342 unique genes. In PCMdb, data was compiled for both cancer cell lines (53565 entries for 88 cell lines) and cancer tissues (12342 entries for 3078 tissue samples). Among these entries, 47.22% entries reported a high level of methylation for the corresponding genes while 10.87% entries reported low level of methylation. PCMdb covers five major subtypes of pancreatic cancer; however, most of the entries were compiled for adenocarcinomas (88.38%) and mucinous neoplasms (5.76%). A user-friendly interface has been developed for data browsing, searching and analysis. We anticipate that PCMdb will be helpful for pancreatic cancer biomarker discovery.

  9. Red-NIR luminescent hybrid poly(methyl methacrylate) containing covalently linked octahedral rhenium metallic clusters.

    PubMed

    Molard, Yann; Dorson, Frederick; Brylev, Konstantin A; Shestopalov, Michael A; Le Gal, Yann; Cordier, Stéphane; Mironov, Yuri V; Kitamura, Noboru; Perrin, Christiane

    2010-05-17

    The embedding of functional inorganic entities into polymer matrices has become an intense field of investigation in which the main challenges are to keep the added value of the inorganic entities while preventing their self-aggregation within the organic matrix. We present a simple way to obtain a homogeneous highly red-NIR luminescent hybrid copolymer that contains covalently bonded nanometric-sized {Re(6)} octahedral clusters. The [Re(6)Se(i)(8)(OH)(a)(6)](4-) cluster complexes are primarily functionalized in two steps with tert-butylpyridine (TBP) and methacrylic acid (MAC) to give neutral [Re(6)Se(8)(TBP)(4)(MAC)(2)] building blocks that are copolymerized with methyl methacrylate (MMA) either in solution or in bulk in the presence of azobisisobutyronitrile as an initiator. Several samples containing 0, 0.025, 0.05, and 0.1 wt % of functionalized {Re(6)} clusters were prepared. As the {Re(6)} cluster/MMA ratio is very low, the obtained copolymers keep the entire processability of pure poly(methyl methacrylate) (PMMA), as demonstrated by differential scanning calorimetry and thermogravimetric analysis. Voltammetric and luminescence studies also indicate that the intrinsic properties of the clusters are preserved within the polymer matrix. All the samples show a bright (emission quantum yield=0.07), broad, and structureless emission band, which extends from lambda=600 nm to more than lambda=950 nm, with the maximum wavelength centered around lambda(em)=710 nm either in solution or in the solid state. Moreover, the high stability of the incorporated inorganic phosphors prevents the material from photobleaching, and thus the luminescence properties are kept entirely even after nine months of ageing.

  10. Characterization of tailor-made copolymers of oligo(ethylene glycol) methyl ether methacrylate and N,N-dimethylaminoethyl methacrylate as nonviral gene transfer agents: influence of macromolecular structure on gene vector particle properties and transfection efficiency.

    PubMed

    Uzgün, Senta; Akdemir, Ozgür; Hasenpusch, Günther; Maucksch, Christof; Golas, Monika M; Sander, Bjoern; Stark, Holger; Imker, Rabea; Lutz, Jean-François; Rudolph, Carsten

    2010-01-11

    Oligo(ethylene glycol) methyl ether methacrylates (OEGMA) of various chain lengths (i.e., 9, 23, or 45 EG units) and N,N-dimethylaminoethyl methacrylate (DMAEMA) were copolymerized by atom transfer radical polymerization (ATRP), yielding well-defined P(DMAEMA-co-OEGMA) copolymers with increasing OEGMA molar fractions (F(OEGMA)) but a comparable degree of polymerization (DP approximately 120). Increase of both F(OEGMA) and OEGMA chain lengths correlated inversely with gene vector size, morphology, and zeta potential. P(DMAEMA-co-OEGMA) copolymers prevented gene vector aggregation at high plasmid DNA (pDNA) concentrations in isotonic solution and did not induce cytotoxicity even at high concentrations. Transfection efficiency of the most efficient P(DMAEMA-co-OEGMA) copolymers was found to be >10-fold lower compared with branched polyethylenimine (PEI) 25 kDa. Although OEGMA copolymerization largely reduced gene vector binding with the cell surface, cellular internalization of the bound complexes was less affected. These observations suggest that inefficient endolysosomal escape limits transfection efficiency of P(DMAEMA-co-OEGMA) copolymer gene vectors. Despite this observation, optimized p(DMAEMA-co-OEGMA) gene vectors remained stable under conditions for in vivo application leading to 7-fold greater gene expression in the lungs compared with PEI. Tailor-made P(DMAEMA-co-OEGMA) copolymers are promising nonviral gene transfer agents that fulfill the requirements for successful in vivo gene delivery.

  11. Methyl chloroform and the atmosphere

    SciTech Connect

    Ravishankara, A.R.; Albritton, D.L.

    1995-07-14

    The atmospheric abundance of methyl chloroform, CH{sub 3}CCl{sub 3}, a compound of only anthropogenic origin, is actually decreasing because of emission reductions in compliance with the United Nations Montreal Protocol and its subsequent amendments. This observation, reported by Prinn and co-workers elsewhere in this issue, is based on data from surface-level monitoring stations. The observed trends in methyl chloroform abundance have a few straightforward scientific consequences and substantial policy relevance as discussed in this article. 6 refs., 1 fig.

  12. 40 CFR 180.437 - Methyl 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate and methyl 6-(4-isopropyl-4...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-imidazolin-2-yl)-p-toluate and methyl 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluate; tolerances... Tolerances § 180.437 Methyl 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate and methyl 6-(4... for the combined residues of the herbicide methyl...

  13. Histone Methylation by Temozolomide; A Classic DNA Methylating Anticancer Drug.

    PubMed

    Wang, Tieli; Pickard, Amanda J; Gallo, James M

    2016-07-01

    The alkylating agent, temozolomide (TMZ), is considered the standard-of-care for high-grade astrocytomas -known as glioblastoma multiforme (GBM)- an aggressive type of tumor with poor prognosis. The therapeutic benefit of TMZ is attributed to formation of DNA adducts involving the methylation of purine bases in DNA. We investigated the effects of TMZ on arginine and lysine amino acids, histone H3 peptides and histone H3 proteins. Chemical modification of amino acids, histone H3 peptide and protein by TMZ was performed in phosphate buffer at physiological pH. The reaction products were examined by mass spectrometry and western blot analysis. Our results showed that TMZ following conversion to a methylating cation, can methylate histone H3 peptide and histone H3 protein, suggesting that TMZ exerts its anticancer activity not only through its interaction with DNA, but also through alterations of protein post-translational modifications. The possibility that TMZ can methylate histones involved with epigenetic regulation of protein indicates a potentially unique mechanism of action. The study will contribute to the understanding the anticancer activity of TMZ in order to develop novel targeted molecular strategies to advance the cancer treatment. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  14. Histone Methylation by Temozolomide; A Classic DNA Methylating Anticancer Drug

    PubMed Central

    Pickard, Amanda J.; Diaz, Anthony Joseph; Mura, Hugo; Nyuwen, Lila; Coello, Daniel; Sheva, Saif; Maria, Nava; Gallo, James M.; Wang, Tieli

    2017-01-01

    Background/Aim The alkylating agent, temozolomide (TMZ), is considered the standard-of-care for high-grade astrocytomas –known as glioblastoma multiforme (GBM)– an aggressive type of tumor with poor prognosis. The therapeutic benefit of TMZ is attributed to formation of DNA adducts involving the methylation of purine bases in DNA. We investigated the effects of TMZ on arginine and lysine amino acids, histone H3 peptides and histone H3 proteins. Materials and Methods Chemical modification of amino acids, histone H3 peptide and protein by TMZ was performed in phosphate buffer at physiological pH. The reaction products were examined by mass spectrometry and western blot analysis. Results Our results showed that TMZ following conversion to a methylating cation, can methylate histone H3 peptide and histone H3 protein, suggesting that TMZ exerts its anticancer activity not only through its interaction with DNA, but also through alterations of protein post-translational modifications. Conclusion The possibility that TMZ can methylate histones involved with epigenetic regulation of protein indicates a potentially unique mechanism of action. The study will contribute to the understanding the anticancer activity of TMZ in order to develop novel targeted molecular strategies to advance the cancer treatment. PMID:27354585

  15. Spontaneously Healable Thermoplastic Elastomers Achieved through One-Pot Living Ring-Opening Metathesis Copolymerization of Well-Designed Bulky Monomers.

    PubMed

    Yang, Ji-Xing; Long, Ying-Yun; Pan, Li; Men, Yong-Feng; Li, Yue-Sheng

    2016-05-18

    We report here a series of novel spontaneously healable thermoplastic elastomers (TPEs) with a combination of improved mechanical and good autonomic self-healing performances. Hard-soft diblock and hard-soft-hard triblock copolymers with poly[exo-1,4,4a,9,9a,10-hexahydro-9,10(1',2')-benzeno-l,4-methanoanthracene] (PHBM) as the hard block and secondary amide group containing norbornene derivative polymer as the soft block were synthesized via living ring-opening metathesis copolymerization by use of Grubbs third-generation catalyst through sequential monomer addition. The microstructure, mechanical, self-healing, and surface morphologies of the block copolymers were thoroughly studied. Both excellent mechanical performance and self-healing capability were achieved for the block copolymers because of the interplayed physical cross-link of hard block and dynamic interaction formed by soft block in the self-assembled network. Under an optimized hard block (PHBM) weight ratio of 5%, a significant recovery of tensile strength (up to 100%) and strain at break (ca. 85%) was achieved at ambient temperature without any treatment even after complete rupture. Moreover, the simple reaction operations and well-designed monomers offer versatility in tuning the architectures and properties of the resulting block copolymers.

  16. Functional Degradable Polymers by Radical Ring-Opening Copolymerization of MDO and Vinyl Bromobutanoate: Synthesis, Degradability and Post-Polymerization Modification.

    PubMed

    Hedir, Guillaume G; Bell, Craig A; O'Reilly, Rachel K; Dove, Andrew P

    2015-07-13

    The synthesis of vinyl bromobutanoate (VBr), a new vinyl acetate monomer derivative obtained by the palladium-catalyzed vinyl exchange reaction between vinyl acetate (VAc) and 4-bromobutyric acid is reported. The homopolymerization of this new monomer using the RAFT/MADIX polymerization technique leads to the formation of novel well-defined and controlled polymers containing pendent bromine functional groups able to be modified via postpolymerization modification. Furthermore, the copolymerization of vinyl bromobutanoate with 2-methylene-1,3-dioxepane (MDO) was also performed to deliver a range of novel functional degradable copolymers, poly(MDO-co-VBr). The copolymer composition was shown to be able to be tuned to vary the amount of ester repeat units in the polymer backbone, and hence determine the degradability, while maintaining a control of the final copolymers' molar masses. The addition of functionalities via simple postpolymerization modifications such as azidation and the 1,3-dipolar cycloaddition of a PEG alkyne to an azide is also reported and proven by (1)H NMR spectroscopy, FTIR spectroscopy, and SEC analyses. These studies enable the formation of a novel class of hydrophilic functional degradable copolymers using versatile radical polymerization methods.

  17. Synthesis of a novel supermagnetic iron oxide nanocomposite hydrogel based on graft copolymerization of poly((2-dimethylamino)ethyl methacrylate) onto salep for controlled release of drug.

    PubMed

    Bardajee, Ghasem Rezanejade; Hooshyar, Zari; Asli, Maryam Jahanbakhsh; Shahidi, Fatemeh Emamjome; Dianatnejad, Nastaran

    2014-03-01

    In this research, a novel supermagnetic iron oxide nanocomposite hydrogel was prepared using simultaneous in situ formation of iron oxide nanoparticles (IONs) and three-dimensional cross-linked polymer networks based on graft copolymerization of poly((2-dimethylamino)ethyl methacrylate) (PDMA) onto salep (PDMA-g-salep). The prepared ION-PDMA-g-salep hydrogel was systematically characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDAX), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). In addition, the ION-PDMA-g-salep hydrogel exhibits favorable swelling properties that are sensitive to temperature, pH, and external magnetic field (EMF). The drug release behavior of the prepared hydrogel under EMF, different temperatures and pHs was also studied for the evaluation of the release mechanism and determination of diffusion coefficients. Finally, the antibacterial activity and cytotoxicity studies of the prepared hydrogel were examined. These results suggested that the ION-PDMA-g-salep hydrogel could be a promising candidate for biological dressing applications. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Copolymerization with 2,4,6-triaminopyrimidine for the rolling-up the layer structure, tunable electronic properties, and photocatalysis of g-C3N4.

    PubMed

    Ho, Wingkei; Zhang, Zizhong; Lin, Wei; Huang, Shuping; Zhang, Xianwen; Wang, Xuxu; Huang, Yu

    2015-03-11

    Copolymerization with 2,4,6-triaminopyrimidine (TAP) is developed for precise substitution of one nitrogen with carbon atom in the triazine ring of polymeric g-C3N4. Direct incorporation of C4N2 ring from TAP into the network retains the structural features of g-C3N4, but induces the rolling-up of g-C3N4 sheets into tubular configuration. The band gap energy is narrowed from 2.7 to 2.4 eV by a negative shift of valence band of the g-C3N4 photocatalyst, which enhances charge-carrier migration and separation, leading to higher photocatalytic activity for NO gas pollutant removal. It is attributed to the decrease of the π-deficiency and the generation of imbalanced electron density in π-electron conjugated units of g-C3N4 by TAP incorporation. This work provides a significant technique for precise control of heteroatom in the framework of g-C3N4 to finely adjust its intrinsic electronic properties and its photocatalytic properties.

  19. Radiation graft copolymerization of butyl methacrylate and acrylamide onto low density polyethylene and polypropylene films, and its application in wastewater treatment

    NASA Astrophysics Data System (ADS)

    Abdel Ghaffar, A. M.; El-Arnaouty, M. B.; Aboulfotouh, Maysara E.; Taher, N. H.; Taha, Ahmed A.

    2014-09-01

    Butyl methacrylate and acrylamide (BMA/AAm) comonomers were grafted onto low-density polyethylene (LDPE) and polypropylene (PP) films using the mutual gamma radiation grafting technique. The influences of grafting conditions such as solvent, monomer concentration, monomer composition, and irradiation dose on the grafting yield were determined. It was found that using dimethyl formamide as a solvent enhanced the copolymerization process. The grafting yield increases as the comonomer concentration increases up to 60%. Also it was found that the degree of grafting of BMA/AAm onto both LDPE and PP films increases as the AAm content increases till an optimum value at 50:50 wt%. The grafting yield of the comonomers was found to increase with increase in the radiation dose. It was observed that the degree of grafting of polyethylene films is higher than that of polypropylene (PP) films at the same conditions. Some selected properties of the graft copolymers, such as water uptake and thermal properties, were determined using thermogravimetric analysis. The morphology and structure of the grafted films were investigated using scanning electron microscopy, infra-red, and X-ray diffraction. Improvement in such properties of the prepared copolymers was observed which offers possible uses in some practical applications such as the removal of some heavy metals from wastewater. It was found that the maximum metal uptake by the copolymer followed the order Cu2+>Co2+>Ni2+ ions.

  20. Radiation induced graft copolymerization of n-butyl acrylate onto poly(ethylene terephthalate) (PET) films and thermal properties of the obtained graft copolymer

    NASA Astrophysics Data System (ADS)

    Ping, Xiang; Wang, Mozhen; Ge, Xuewu

    2011-05-01

    n-Butyl acrylate (BA) was successfully grafted onto poly(ethylene terephthalate) (PET) film using simultaneous radiation induced graft copolymerization with gamma rays. When BA concentration ranges from 20% to 30%, the Degree of Grafting (DG), measured by gravimetry and 1H NMR, increases with the monomer concentration and absorbed dose, but decreases with dose rate from 0.83 to 2.53 kGy/h. The maximum DG can reach up to 22.1%. The thermal transition temperatures such as glass-transition temperature ( Tg) and cold-crystallization temperature ( Tcc) of PET in grafted films were little different from those in original PET film, indicating that microphase separation occurred between PBA side chains and PET backbone. This work implied that if PET/elastomers (e.g., acrylate rubber) blends are radiated by high energy gamma rays under a certain condition, PET-g-polyacrylate copolymer may be produced in-situ, which will improve the compatibility between PET and the elastomers so as to improve the integral mechanical properties of PET based engineering plastic.

  1. 2-(1-(Arylimino)propyl)quinolin-8-olate half-titanocene dichlorides: synthesis, characterization and ethylene (co-)polymerization behaviour.

    PubMed

    Huang, Wei; Sun, Wen-Hua; Redshaw, Carl

    2011-07-07

    A series of 2-(1-(arylimino)propyl)quinolin-8-olate half-titanocene dichlorides, Cp'TiCl(2)L (Cp' = η(5)-C(5)H(5) or η(5)-C(5)Me(5), L = 2-(1-(2,6-R(1)-4-R(2)-phenylimino)propyl)quinolin-8-olate), was synthesized via the stoichiometric reaction of Cp'TiCl(3) with the corresponding potassium 2-(1-(2,6-R(1)-4-R(2)-phenylimino)propyl)quinolin-8-olate salt. All titanium compounds were characterized by elemental analysis, (1)H NMR and (13)C NMR spectroscopy; the molecular structures of two representative compounds were determined by single crystal X-ray diffraction. On activation with methylaluminoxane (MAO), all half-titanocene compounds showed high activity in ethylene polymerization, and furthermore, performed with good to high activities in the co-polymerization of ethylene with either 1-hexene or 1-octene affording polyethylenes with high co-monomer incorporation. Less bulky ortho-substituents (R(1)) on the phenylimino groups were found to enhance the catalytic activities of their titanium compounds. In general, the titanium pro-catalysts containing η(5)-C(5)Me(5) (C7-C12) exhibited higher activities than did their analogues bearing η(5)-C(5)H(5) (C1-C6). Some of the resultant polyolefins were ultrahigh molecular weight polyethylene.

  2. Electrophoretic analysis of proteinases in sodium dodecyl sulfate-polyacrylamide gels containing copolymerized radiolabeled protein substrates: Application to proenkephalin processing enzymes

    SciTech Connect

    Irvine, J.W.; Roberts, S.F.; Lindberg, I. )

    1990-10-01

    A novel method is described for the zymographic analysis of proteinases in sodium dodecyl sulfate-polyacrylamide gels containing copolymerized radiolabeled protein substrates such as ({sup 35}S)methionine-labeled proenkephalin or {sup 125}I-labeled proinsulin. After electrophoresis the enzyme is reactivated and cleaves the radiolabeled in situ substrate into smaller peptides. These small peptides are able to diffuse out of the gel, leaving clear areas against a dark background when visualized by autoradiography. The technique can be used to detect as little as 200 fg of trypsin using only 50 ng (1.25 microCi) of ({sup 35}S)proenkephalin. Soluble- and membrane-bound adrenal trypsin-like enzyme were isolated from bovine adrenal chromaffin granules. Both proteinases cleaved ({sup 35}S)methionine-labeled proenkephalin but not {sup 125}I-labeled proinsulin. Moreover, both had a Mr of approximately 30,000. The potential of this technique for general use is discussed. An additional method using the synthetic fluorogenic substrate t-butoxycarbonyl Glu-Lys-Lys aminomethylcoumarin is also described.

  3. Preparation of "Constrained Geometry" Titanium Complexes of [1,2]Azasilinane Framework for Ethylene/1-Octene Copolymerization.

    PubMed

    Lee, Seul; Park, Seung Soo; Kim, Jin Gu; Kim, Chung Sol; Lee, Bun Yeoul

    2017-02-09

    The Me₂Si-bridged ansa-Cp/amido half-metallocene, [Me₂Si(η⁵-Me₄C₅)(N(t)Bu)]TiCl₂, termed a "constrained-geometry catalyst (CGC)", is a representative homogeneous Ziegler catalyst. CGC derivatives with the [1,2]azasilinane framework, in which the amide alkyl substituent is joined by the Si-bridge, were prepared, and the catalytic performances of these species was studied. Me₄C₅HSi(Me)(CH₂CH=CH₂)-NH(C(R)(R')CH=CH₂) (R, R' = H or methyl; Me₄C₅H = tetramethylcyclopentadienyl) was susceptible to ring closure metathesis (RCM) when treated with Schrock's Mo-catalyst to afford -Si(Me₄C₅H)(Me)CH₂CH=CHC(R)(R')NH- containing a six-membered ring framework. Using the precursors and the products of RCM, various CGC derivatives, i.e., [-Si(η⁵-Me₄C₅)(Me)CH₂CH=CHC(R)(H)N-]TiMe₂ (13, R = H; 15, R = Me), [-Si(η⁵-Me₄C₅)(Me)CH₂CH₂CH₂CH₂N]TiMe₂ (14), [(η⁵-Me₄C₅)Si(Me)(CH₂CH=CH₂)NCH₂CH=CH₂]TiMe₂ (16), [(η⁵-Me₄C₅)Si (Me)(CH=CH₂)NCH₂CH=CH₂]TiMe₂ (17), and [(η⁵-Me₄C₅)Si(Me)(CH₂CH₃)NCH₂CH₂CH₃]TiMe₂ (18), were prepared. The catalytic activity of the newly prepared complexes was lower than that of CGC when activated with [Ph₃C][B(C₆F₅)₄]/iBu₃Al. However, the catalytic activity of these species was improved by using tetrabutylaluminoxane ([iBu₂Al]₂O) instead of iBu₃Al and the activity of 14/[Ph₃C][B(C₆F₅)₄]/[iBu₂Al]₂O was comparable to that of CGC/[Ph₃C][B(C₆F₅)₄]/iBu₃Al (4.7 and 5.0 × 10⁶ g/mol-Ti, respectively). Advantageously, the newly prepared complexes produced higher molecular weight poly(ethylene-co-1-octene)s than CGC.

  4. Evolution of DNA Methylation across Insects

    PubMed Central

    Vogel, Kevin J.; Moore, Allen J.; Schmitz, Robert J.

    2017-01-01

    DNA methylation contributes to gene and transcriptional regulation in eukaryotes, and therefore has been hypothesized to facilitate the evolution of plastic traits such as sociality in insects. However, DNA methylation is sparsely studied in insects. Therefore, we documented patterns of DNA methylation across a wide diversity of insects. We predicted that underlying enzymatic machinery is concordant with patterns of DNA methylation. Finally, given the suggestion that DNA methylation facilitated social evolution in Hymenoptera, we tested the hypothesis that the DNA methylation system will be associated with presence/absence of sociality among other insect orders. We found DNA methylation to be widespread, detected in all orders examined except Diptera (flies). Whole genome bisulfite sequencing showed that orders differed in levels of DNA methylation. Hymenopteran (ants, bees, wasps and sawflies) had some of the lowest levels, including several potential losses. Blattodea (cockroaches and termites) show all possible patterns, including a potential loss of DNA methylation in a eusocial species whereas solitary species had the highest levels. Species with DNA methylation do not always possess the typical enzymatic machinery. We identified a gene duplication event in the maintenance DNA methyltransferase 1 (DNMT1) that is shared by some Hymenoptera, and paralogs have experienced divergent, nonneutral evolution. This diversity and nonneutral evolution of underlying machinery suggests alternative DNA methylation pathways may exist. Phylogenetically corrected comparisons revealed no evidence that supports evolutionary association between sociality and DNA methylation. Future functional studies will be required to advance our understanding of DNA methylation in insects. PMID:28025279

  5. Water Column Methylation in Estuaries

    NASA Astrophysics Data System (ADS)

    Schartup, A. T.; Calder, R.; Soerensen, A. L.; Mason, R. P.; Balcom, P. H.; Sunderland, E. M.

    2014-12-01

    Methylmercury (MeHg) is a neurotoxin that bioaccumulates in aquatic food webs and affects humans and wildlife through fish consumption. Many studies have measured active methylation/demethylation in ocean margin sediments but few have reported similar rates for the marine water column. This presentation will review available evidence for water column methylation in estuaries, including new experimental measurements of methylation/demethylation rates from a deep subarctic fjord in Labrador Canada collected in Spring and Fall of 2012-2013. We used these and other data to construct a mass budget for MeHg in the estuary and show that water column methylation (with rates ranging from 1.5 to 2.8 % day-1), is the largest contributor, followed by inputs from rivers (4.9 mol year-1), to the in situ pool of MeHg available for uptake by biota. By contrast, the sediment in this system is a net sink for MeHg (-1.5 mol year-1). We discuss the relationship between observed MeHg and other ancillary environmental factors (organic carbon, sulfur and nutrients) as well as implications for the response time of fish to future changes in mercury inputs.

  6. RNA Methylation Clears the Way.

    PubMed

    Kontur, Cassandra; Giraldez, Antonio

    2017-03-13

    During the maternal-to-zygotic transition, maternal mRNAs are cleared by multiple distinct but interrelated pathways. A recent study in Nature by Zhao et al. (2017) finds that YTHDF2, a reader of N(6)- methylation, facilitates maternal mRNA decay, introducing an additional facet of control over transcript fate and developmental reprogramming.

  7. Methods of DNA methylation analysis.

    USDA-ARS?s Scientific Manuscript database

    The purpose of this review was to provide guidance for investigators who are new to the field of DNA methylation analysis. Epigenetics is the study of mitotically heritable alterations in gene expression potential that are not mediated by changes in DNA sequence. Recently, it has become clear that n...

  8. Desoxyhemigossypol-6-methyl-ether

    USDA-ARS?s Scientific Manuscript database

    Desoxyhemigossypol-6-methyl ether is an antimicrobial compound produced by the cotton plant in response to attack by pathogens. For the first time, we now report the crystal structure of this compound. This may prove useful in studies on the interaction of the compound with pathogenic fungal cells...

  9. Lacinilene C 7-methyl ether

    USDA-ARS?s Scientific Manuscript database

    Lacinilene C 7-methyl ether is an antimicrobial compound produced by the cotton plant in response to attack by pathogens. For the first time, we now report the crystal structure of this compound. This may prove useful in studies on the interaction of the compound with pathogenic fungal cells....

  10. p-Chlorophenyl methyl sulfide

    Integrated Risk Information System (IRIS)

    p - Chlorophenyl methyl sulfide ; CASRN 123 - 09 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for N

  11. p-Chlorophenyl methyl sulfoxide

    Integrated Risk Information System (IRIS)

    p - Chlorophenyl methyl sulfoxide ; CASRN 934 - 73 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for

  12. p-Chlorophenyl methyl sulfone

    Integrated Risk Information System (IRIS)

    p - Chlorophenyl methyl sulfone ; CASRN 98 - 57 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for No

  13. Isopropyl methyl phosphonic acid (IMPA)

    Integrated Risk Information System (IRIS)

    Isopropyl methyl phosphonic acid ( IMPA ) ; CASRN 1832 - 54 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assess

  14. DNA methylation in endometriosis (Review)

    PubMed Central

    KOUKOURA, OURANIA; SIFAKIS, STAVROS; SPANDIDOS, DEMETRIOS A.

    2016-01-01

    Endometriosis is defined by the presence and growth of functional endometrial tissue, outside the uterine cavity, primarily in the ovaries, pelvic peritoneum and rectovaginal septum. Although it is a benign disease, it presents with malignant characteristics, such as invasion to surrounding tissues, metastasis to distant locations and recurrence following treatment. Accumulating evidence suggests that various epigenetic aberrations may play an essential role in the pathogenesis of endometriosis. Aberrant DNA methylation represents a possible mechanism repsonsible for this disease, linking gene expression alterations observed in endometriosis with hormonal and environmental factors. Several lines of evidence indicate that endometriosis may partially be due to selective epigenetic deregulations influenced by extrinsic factors. Previous studies have shed light into the epigenetic component of endometriosis, reporting variations in the epigenetic patterns of genes known to be involved in the aberrant hormonal, immunologic and inflammatory status of endometriosis. Although recent studies, utilizing advanced molecular techniques, have allowed us to further elucidate the possible association of DNA methylation with altered gene expression, whether these molecular changes represent the cause or merely the consequence of the disease is a question which remains to be answered. This review provides an overview of the current literature on the role of DNA methylation in the pathophysiology and malignant evolution of endometriosis. We also provide insight into the mechanisms through which DNA methylation-modifying agents may be the next step in the research of the pharmaceutical treatment of endometriosis. PMID:26934855

  15. Bacterial production of methyl ketones

    DOEpatents

    Beller, Harry R.; Goh, Ee-Been

    2017-01-31

    The present invention relates to methods and compositions for increasing production of methyl ketones in a genetically modified host cell that overproduces .beta.-ketoacyl-CoAs through a re-engineered .beta.-oxidation pathway and overexpresses FadM.

  16. Gene methylation in gastric cancer.

    PubMed

    Qu, Yiping; Dang, Siwen; Hou, Peng

    2013-09-23

    Gastric cancer is one of the most common malignancies and remains the second leading cause of cancer-related death worldwide. Over 70% of new cases and deaths occur in developing countries. In the early years of the molecular biology revolution, cancer research mainly focuses on genetic alterations, including gastric cancer. Epigenetic mechanisms are essential for normal development and maintenance of tissue-specific gene expression patterns in mammals. Disruption of epigenetic processes can lead to altered gene function and malignant cellular transformation. Recent advancements in the rapidly evolving field of cancer epigenetics have shown extensive reprogramming of every component of the epigenetic machinery in cancer, including DNA methylation, histone modifications, nucleosome positioning, noncoding RNAs, and microRNAs. Aberrant DNA methylation in the promoter regions of gene, which leads to inactivation of tumor suppressor and other cancer-related genes in cancer cells, is the most well-defined epigenetic hallmark in gastric cancer. The advantages of gene methylation as a target for detection and diagnosis of cancer in biopsy specimens and non-invasive body fluids such as serum and gastric washes have led to many studies of application in gastric cancer. This review focuses on the most common and important phenomenon of epigenetics, DNA methylation, in gastric cancer and illustrates the impact epigenetics has had on this field. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

  17. Methylation analyses in liquid biopsy

    PubMed Central

    Lissa, Delphine

    2016-01-01

    Lung cancer is the leading cause of cancer-related deaths worldwide. Recent implementation of low-dose computed tomography (LDCT) screening is predicted to lead to diagnosis of lung cancer at an earlier stage, with survival benefit. However, there is still a pressing need for biomarkers that will identify individuals eligible for screening, as well as improve the diagnostic accuracy of LDCT. In addition, biomarkers for prognostic stratification of patients with early stage disease, and those that can be used as surrogates to monitor tumor evolution, will greatly improve clinical management. Molecular alterations found in the DNA of tumor cells, such as mutations, translocations and methylation, are reflected in DNA that is released from the tumor into the bloodstream. Thus, in recent years, circulating tumor DNA (ctDNA) has gained increasing attention as a noninvasive alternative to tissue biopsies and potential surrogate for the entire tumor genome. Activating gene mutations found in ctDNA have been proven effective in predicting response to targeted therapy. Analysis of ctDNA is also a valuable tool for longitudinal follow-up of cancer patients that does not require serial biopsies and may anticipate the acquisition of resistance. DNA methylation has also emerged as a promising marker for early detection, prognosis and real-time follow-up of tumor dynamics that is independent of the genomic composition of the primary tumor. This review summarizes the various investigational applications of methylated ctDNA in lung cancer reported to date. It also provides a brief overview of the technologies for analysis of DNA methylation in liquid biopsies, and the challenges that befall the implementation of methylated ctDNA into routine clinical practice. PMID:27826530

  18. Electronic transport in methylated fragments of DNA

    SciTech Connect

    Almeida, M. L. de; Oliveira, J. I. N.; Lima Neto, J. X.; Gomes, C. E. M.; Fulco, U. L. Albuquerque, E. L.; Freire, V. N.; Caetano, E. W. S.; Moura, F. A. B. F. de; Lyra, M. L.

    2015-11-16

    We investigate the electronic transport properties of methylated deoxyribonucleic-acid (DNA) strands, a biological system in which methyl groups are added to DNA (a major epigenetic modification in gene expression), sandwiched between two metallic platinum electrodes. Our theoretical simulations apply an effective Hamiltonian based on a tight-binding model to obtain current-voltage curves related to the non-methylated/methylated DNA strands. The results suggest potential applications in the development of novel biosensors for molecular diagnostics.

  19. Electronic transport in methylated fragments of DNA

    NASA Astrophysics Data System (ADS)

    de Almeida, M. L.; Oliveira, J. I. N.; Lima Neto, J. X.; Gomes, C. E. M.; Fulco, U. L.; Albuquerque, E. L.; Freire, V. N.; Caetano, E. W. S.; de Moura, F. A. B. F.; Lyra, M. L.

    2015-11-01

    We investigate the electronic transport properties of methylated deoxyribonucleic-acid (DNA) strands, a biological system in which methyl groups are added to DNA (a major epigenetic modification in gene expression), sandwiched between two metallic platinum electrodes. Our theoretical simulations apply an effective Hamiltonian based on a tight-binding model to obtain current-voltage curves related to the non-methylated/methylated DNA strands. The results suggest potential applications in the development of novel biosensors for molecular diagnostics.

  20. Adenine N6-methylation in diverse fungi.

    PubMed

    Seidl, Michael F

    2017-05-26

    A DNA modification-methylation of cytosines and adenines-has important roles in diverse processes such as regulation of gene expression and genome stability, yet until recently adenine methylation had been considered to be only a hallmark of prokaryotes. A new study identifies abundant adenine methylation of transcriptionally active genes in early-diverging fungi that, together with recent other work, emphasizes the importance of adenine methylation in eukaryotes.

  1. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Butyl acrylate, polymer with... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

  2. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Butyl acrylate, polymer with... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

  3. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Butyl acrylate, polymer with... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane...

  4. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Butyl acrylate, polymer with... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane...

  5. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Butyl acrylate, polymer with... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane...

  6. 77 FR 35295 - Methyl Bromide; Pesticide Tolerances

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-13

    ... AGENCY 40 CFR Part 180 RIN 2070-ZA16 Methyl Bromide; Pesticide Tolerances AGENCY: Environmental... methyl bromide in or on cotton, undelinted seed under the Federal Food, Drug, and Cosmetic Act (FFDCA... to establish a tolerance for residues of methyl bromide, including metabolites and degradates in or...

  7. ELUCIDATING THE PATHWAY FOR ARSENIC METHYLATION

    EPA Science Inventory

    Enzymatically-catalyzed methylation of arsenic is part of a metabolic pathway that converts inorganic arsenic into methylated products. Hence, in humans chronically exposed to inorganic arsenic, methyl and dimethyl arsenic account for most of the arsenic that is excreted in the ...

  8. DNA methylation and its basic function.

    PubMed

    Moore, Lisa D; Le, Thuc; Fan, Guoping

    2013-01-01

    In the mammalian genome, DNA methylation is an epigenetic mechanism involving the transfer of a methyl group onto the C5 position of the cytosine to form 5-methylcytosine. DNA methylation regulates gene expression by recruiting proteins involved in gene repression or by inhibiting the binding of transcription factor(s) to DNA. During development, the pattern of DNA methylation in the genome changes as a result of a dynamic process involving both de novo DNA methylation and demethylation. As a consequence, differentiated cells develop a stable and unique DNA methylation pattern that regulates tissue-specific gene transcription. In this chapter, we will review the process of DNA methylation and demethylation in the nervous system. We will describe the DNA (de)methylation machinery and its association with other epigenetic mechanisms such as histone modifications and noncoding RNAs. Intriguingly, postmitotic neurons still express DNA methyltransferases and components involved in DNA demethylation. Moreover, neuronal activity can modulate their pattern of DNA methylation in response to physiological and environmental stimuli. The precise regulation of DNA methylation is essential for normal cognitive function. Indeed, when DNA methylation is altered as a result of developmental mutations or environmental risk factors, such as drug exposure and neural injury, mental impairment is a common side effect. The investigation into DNA methylation continues to show a rich and complex picture about epigenetic gene regulation in the central nervous system and provides possible therapeutic targets for the treatment of neuropsychiatric disorders.

  9. Protein methylation in pea chloroplasts. [Pisum sativum

    SciTech Connect

    Niemi, K.J.; Adler, J.; Selman, B.R. )

    1990-07-01

    The methylation of chloroplast proteins has been investigated by incubating intact pea (Pisum sativum) chloroplasts with ({sup 3}H-methyl)-S-adenosylmethionine. Incubation in the light increases the amount of methylation in both the thylakoid and stromal fractions. Numerous thylakoid proteins serve as substrates for the methyltransfer reactions. Three of these thylakoid proteins are methylated to a significantly greater extent in the light than in the dark. The primary stromal polypeptide methylated is the large subunit of ribulose bisphosphate carboxylase/oxygenase. One other stromal polypeptide is also methylated much more in the light than in the dark. Two distinct types of protein methylation occur. One methylinkage is stable to basic conditions whereas a second type is base labile. The base-stable linkage is indicative of N-methylation of amino acid residues while base-lability is suggestive of carboxymethylation of amino acid residues. Labeling in the light increases the percentage of methylation that is base labile in the thylakoid fraction while no difference is observed in the amount of base-labile methylations in light-labeled and dark-labeled stromal proteins. Also suggestive of carboxymethylation is the detection of volatile ({sup 3}H)methyl radioactivity which increases during the labeling period and is greater in chloroplasts labeled in the light as opposed to being labeled in the dark; this implies in vivo turnover of the ({sup 3}H)methyl group.

  10. Quantitative DNA Methylation Profiling in Cancer.

    PubMed

    Ammerpohl, Ole; Haake, Andrea; Kolarova, Julia; Siebert, Reiner

    2016-01-01

    Epigenetic mechanisms including DNA methylation are fundamental for the regulation of gene expression. Epigenetic alterations can lead to the development and the evolution of malignant tumors as well as the emergence of phenotypically different cancer cells or metastasis from one single tumor cell. Here we describe bisulfite pyrosequencing, a technology to perform quantitative DNA methylation analyses, to detect aberrant DNA methylation in malignant tumors.

  11. Methyl rotational barriers in the E-forms of methyl esters

    NASA Astrophysics Data System (ADS)

    Wiberg, K. B.; Bohn, R. K.; Jimenez-Vazquez, H.

    1999-08-01

    Methyl nitrite has a normal 2.09 kcal/mol methyl rotation barrier in the Z-conformer, but only a small 0.03-0.06 kcal/mol barrier in the E-conformer as determined from microwave spectra (Turner et al., J. Phys. Chem., 83 (1979) 1473). Using dependable calculational methods, we show that this is a general result which carries over to another E-methyl ester, E-methyl formate, which does not have a sterically large substituent on the acid group, and is not specific to methyl nitrite alone. The small methyl barriers in E-methyl nitrite and E-methyl formate result from the absence of large steric interactions. Replacing H in the formyl group by sterically larger F, results in a normal O-methyl torsional barrier calculated to be 1.8 kcal/mol in the E-methyl fluoroformate.

  12. Identification of endometrial cancer methylation features using combined methylation analysis methods

    PubMed Central

    Trimarchi, Michael P.; Yan, Pearlly; Groden, Joanna; Bundschuh, Ralf; Goodfellow, Paul J.

    2017-01-01

    Background DNA methylation is a stable epigenetic mark that is frequently altered in tumors. DNA methylation features are attractive biomarkers for disease states given the stability of DNA methylation in living cells and in biologic specimens typically available for analysis. Widespread accumulation of methylation in regulatory elements in some cancers (specifically the CpG island methylator phenotype, CIMP) can play an important role in tumorigenesis. High resolution assessment of CIMP for the entire genome, however, remains cost prohibitive and requires quantities of DNA not available for many tissue samples of interest. Genome-wide scans of methylation have been undertaken for large numbers of tumors, and higher resolution analyses for a limited number of cancer specimens. Methods for analyzing such large datasets and integrating findings from different studies continue to evolve. An approach for comparison of findings from a genome-wide assessment of the methylated component of tumor DNA and more widely applied methylation scans was developed. Methods Methylomes for 76 primary endometrial cancer and 12 normal endometrial samples were generated using methylated fragment capture and second generation sequencing, MethylCap-seq. Publically available Infinium HumanMethylation 450 data from The Cancer Genome Atlas (TCGA) were compared to MethylCap-seq data. Results Analysis of methylation in promoter CpG islands (CGIs) identified a subset of tumors with a methylator phenotype. We used a two-stage approach to develop a 13-region methylation signature associated with a “hypermethylator state.” High level methylation for the 13-region methylation signatures was associated with mismatch repair deficiency, high mutation rate, and low somatic copy number alteration in the TCGA test set. In addition, the signature devised showed good agreement with previously described methylation clusters devised by TCGA. Conclusion We identified a methylation signature for a

  13. Transgene-induced CCWGG methylation does not alter CG methylation patterning in human kidney cells.

    PubMed

    Shevchuk, Taras; Kretzner, Leo; Munson, Kristofer; Axume, John; Clark, Jarrod; Dyachenko, Olga V; Caudill, Marie; Buryanov, Yaroslav; Smith, Steven S

    2005-01-01

    Several reports suggest that C(m)CWGG methylation tends not to co-exist with (m)CG methylation in human cells. We have asked whether or not methylation at CCWGG sites can influence CG methylation. DNA from cells expressing an M.EcoRII-GFP fusion was actively methylated at CCWGG sites. CG methylation as measured by R.HpaII/R.MspI ratios was unchanged in cells expressing the transgene. Cloned representatives of C(m)CWGG methylated DNA often contained, or were adjacent to an ALU repeat, suggesting that M.EcoRII-GFP actively methylated gene-rich R-band DNA. The transgenic methyltransferase applied C(m)CWGG methylation to a representative human promoter that was heavily methylated at CG dinucleotides (the SERPINB5 promoter) and to a representative promoter that was essentially unmethylated at CG dinucleotides (the APC promoter). In each case, the CG methylation pattern remained in its original state, unchanged by the presence of neighboring C(m)CWGG sites. Q-PCR measurements showed that RNA expression from the APC gene was not significantly altered by the presence of C(m)CWGG in its promoter. Kinetic studies suggested that an adjacent C(m)CWGG methylation site influences neither the maintenance nor the de novo methylation activities of purified human Dnmt1. We conclude that C(m)CWGG methylation does not exert a significant effect on CG methylation in human kidney cells.

  14. Preparation and characterization of protein-resistant hydrogels for soft contact lens applications via radical copolymerization involving a zwitterionic sulfobetaine comonomer.

    PubMed

    Zhang, Wanlu; Li, Guangji; Lin, Yinlei; Wang, Liying; Wu, Shuqing

    2017-11-01

    We aimed to introduce hydrophilic sulfobetaine-type zwitterionic groups to macromolecular chains of copolymers to construct novel copolymer hydrogels with anti-protein-fouling performance that could be used as soft contact lens (SCL) materials. Using hydroxyethyl methacrylate (HEMA), N-vinyl pyrrolidinone (NVP) and sulfobetaine methacrylate (SBMA) as comonomers, several copolymer hydrogels with different SBMA contents, poly(HEMA-NVP-SBMA), are synthesized via radical copolymerization in an aqueous phase. Surface chemistry, structural morphologies, water contact angle (WCA), equilibrium water content (EWC), visible light transmittance and tensile mechanical properties are investigated. The prepared hydrogels exhibit a closed-type porous structure. With increasing SBMA content in the comonomer mixture, the prepared copolymer hydrogel pore size gradually increases up to the micron level, WCA tends to decrease, EWC tends to increase, and visible light transmittance slightly increases, but their tensile mechanical properties decline. The amounts of protein Lyz and BSA adsorbed on the copolymer hydrogels and on commercially available EASY DAY(®) SCLs as a control are also determined by protein adsorption tests. The amount of protein adsorbed on the copolymer hydrogel decreases with increasing SBMA content. For the hydrogel prepared using the comonomer mixture with 5.0 wt % SBMA, the amount of adsorbed Lyz is 0.91 μg/cm(2), which corresponds to only 56.8% of the amount adsorbed on EASY DAY(®) SCLs. Thus, novel SCL materials with high water content and excellent anti-protein-fouling performance were efficiently constructed by introducing sulfobetaine-type zwitterionic groups into a traditional polymer hydrogel system.

  15. Nanoporous array anodic titanium-supported co-polymeric ionic liquids as high performance solid-phase microextraction sorbents for hydrogen bonding compounds.

    PubMed

    Jia, Jing; Liang, Xiaojing; Wang, Licheng; Guo, Yong; Liu, Xia; Jiang, Shengxiang

    2013-12-13

    A nanoporous array anodic titanium-supported co-polymeric ionic liquids (NAAT/PILs) solid-phase microextraction (SPME) fiber was prepared in situ on the titanium wire. NAAT was selected as the substrate, in view of its high surface-to-volume ratio, easy preparation, mechanical stability, and rich titanol groups on its surface which can anchor silica coupling agent containing vinyl and then introduce ionic liquid copolymers as sorbents. In this work, 1-vinyl-3-nonanol imidazolium bromide ([C9OHVIm]Br) and 1,4-di(3-vinylimidazolium) butane dibromide ([(VIM)2C4]2[Br]) were synthesized and used as monomer and crosslinker, respectively. Extraction properties of the NAAT/PILs fiber for polar alcohols and volatile fatty acids (VFAs) in aqueous matrix were examined using gaseous sampling-SPME (GS-SPME) and headspace SPME (HS-SPME) mode, respectively. Combining the superior properties of NAAT substrate and the strong hydrogen bond interaction of PILs to polar compounds, the NAAT/PILs SPME fiber showed much higher adsorption affinity to aliphatic alcohols than bare NAAT and pure PILs fibers. The detection limits (LOD) of established GS-SPME-GC-FID method are in the range of 0.35-17.30ngL(-1) with a linear range from 0.01 to 500ngmL(-1). Also, it showed high extraction performance toward volatile fatty acids (VFAs) compounds from aqueous matrix. Under the optimized SPME conditions, wide linear ranges were obtained with correlation coefficients (R(2)) greater than 0.99 and limits of detection were in the range of 0.85-8.74ngL(-1). Moreover, real-world samples were analyzed and good results were obtained.

  16. Etoposide-loaded biodegradable amphiphilic methoxy (poly ethylene glycol) and poly (epsilon caprolactone) copolymeric micelles as drug delivery vehicle for cancer therapy.

    PubMed

    Mohanty, Anjan K; Dilnawaz, Fahima; Mohanty, Chandana; Sahoo, Sanjeeb K

    2010-07-01

    Amphiphilic diblock copolymers composed of methoxy poly ethylene glycol (MePEG) and poly epsilon caprolactone (PCL) were synthesized for the formation of micelles by ring opening mechanism using stannous octoate as a catalyst. The effects of the molecular weight of MePEG and the copolymer ratio on the properties of micelles were investigated by Nuclear Magnetic Resonance ((1)H-NMR), Fourier Transform Infrared Spectroscopy (FT-IR), and Gel Permeation Chromatography (GPC). The diblock copolymers were self-assembled to form micelles and their hydrophobic core was used for the encapsulation of the anti-cancer drug (etoposide) in aqueous solution. The sizes of micelles were less than 250 nm with a narrow size distribution with monodispersed unimodal pattern. Differential Scanning Calorimetric (DSC) thermogram was done for etoposide-loaded micelles to understand the crystalline nature of the drug after entrapment. A drug loading capacity up to 60% (w/w) with an entrapment efficiency of 68% was achieved as determined by reverse phase high performance liquid chromatography (RP-HPLC). In vitro release kinetics showed a biphasic release pattern of etoposide for 2 weeks. The cytotoxic efficacy of the etoposide-loaded micelles demonstrated greater anti-proliferative activity (IC(50) = 1.1 microg/ml) as compared to native drug (IC(50) = 6.3 microg/ml) in pancreatic cancer cell line MIA-PaCa-2. Thus, etoposide-loaded MePEG/PCL block copolymeric micelles can be used as an efficient drug delivery vehicle for pancreatic cancer therapy.

  17. A Strategy for Control of “Random” Copolymerization of Lactide and Glycolide: Application to Synthesis of PEG-b-PLGA Block Polymers Having Narrow Dispersity

    PubMed Central

    Qian, Haitao; Wohl, Adam R.; Crow, Jordan T.; Macosko, Christopher W.; Hoye, Thomas R.

    2011-01-01

    Poly(lactic-co-glycolic acid) (PLGA) is a biodegradable copolymer that is also acceptable for use in a variety of biomedical applications. Typically, a random PLGA polymer is synthesized in a bulk batch polymerization using a tin-based catalyst at high temperatures. This methodology results in relatively broad polydispersity indexes (PDIs) due to transesterification, and the polymer product is often discolored. We report here the use of 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU), a known, effective, and convenient organocatalyst for the ring-opening polymerization of cyclic esters, to synthesize random copolymers of lactide and glycolide. The polymerization kinetics of the homo- and copolymerizations of lactide and glycolide were explored via NMR spectroscopy. A novel strategy that employs a controlled addition of the more reactive glycolide monomer to a solution containing the lactide monomer, the poly(ethylene glycol) (PEG) macroinitiator, and DBU catalyst was developed. Using this tactic (semi-batch polymerization), we synthesized a series of block copolymers that exhibited excellent correlation of the expected and observed molecular weights and possessed narrow PDIs. We also measured the thermal properties of these block copolymers and observed trends based on the composition of the block copolymer. We also explored the need for experimental rigor in several aspects of the preparations and have identified a set of convenient reaction conditions that provide polymer products that retain the aforementioned desirable characteristics. These polymerizations proceed rapidly at room temperature and without the need for tin-based catalysts to provide PEG-b-PLGAs suitable for use in biomedical investigations. PMID:22287809

  18. Altered DNA methylation in PAH deficient phenylketonuria.

    PubMed

    Dobrowolski, Steven F; Lyons-Weiler, James; Spridik, Kayla; Biery, Amy; Breck, Jane; Vockley, Jerry; Yatsenko, Svetlana; Sultana, Tamanna

    2015-01-01

    While phenylalanine (PHE) is the toxic insult in phenylketonuria (PKU), mechanisms underlying PHE toxicity remain ill-defined. Altered DNA methylation in response to toxic exposures is well-recognized. DNA methylation patterns were assessed in blood and brain from PKU patients to determine if PHE toxicity impacts methylation. Methylome assessment, utilizing methylated DNA immunoprecipitation and paired-end sequencing, was performed in DNA obtained from brain tissue of classical PKU patients, leukocytes from poorly controlled PKU patients, leukocytes from well controlled PKU patients, and appropriate control tissues. In PKU brain tissue, expression analysis determined the impact of methylation on gene function. Differential methylation was observed in brain tissue of PKU patients and expression studies identified downstream impact on gene expression. Altered patterns of methylation were observed in leukocytes of well controlled and poorly controlled patients with more extensive methylation in patients with high PHE exposure. Differential methylation of noncoding RNA genes was extensive in patients with high PHE exposure but minimal in well controlled patients. Methylome repatterning leading to altered gene expression was present in brain tissue of PKU patients, suggesting a role in neuropathology. Aberrant methylation is observed in leukocytes of PKU patients and is influenced by PHE exposure. DNA methylation may provide a biomarker relating to historic PHE exposure. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Methods in DNA methylation profiling

    PubMed Central

    Zuo, Tao; Tycko, Benjamin; Liu, Ta-Ming; Lin, Huey-Jen L; Huang, Tim H-M

    2010-01-01

    Metastable and somatically heritable patterns of DNA methylation provide an important level of genomic regulation. In this article, we review methods for analyzing these genome-wide epigenetic patterns and offer a perspective on the ever-expanding literature, which we hope will be useful for investigators who are new to this area. The historical aspects that we cover will be helpful in interpreting this literature and we hope that our discussion of the newest analytical methods will stimulate future progress. We emphasize that no single approach can provide a complete view of the overall methylome, and that combinations of several modalities applied to the same sample set will give the clearest picture. Given the unexpected epigenomic patterns and new biological principles, as well as new disease markers, that have been uncovered in recent studies, it is likely that important discoveries will continue to be made using genome-wide DNA methylation profiling. PMID:20526417

  20. Methods in DNA methylation profiling.

    PubMed

    Zuo, Tao; Tycko, Benjamin; Liu, Ta-Ming; Lin, Juey-Jen L; Huang, Tim H-M

    2009-12-01

    Metastable and somatically heritable patterns of DNA methylation provide an important level of genomic regulation. In this article, we review methods for analyzing these genome-wide epigenetic patterns and offer a perspective on the ever-expanding literature, which we hope will be useful for investigators who are new to this area. The historical aspects that we cover will be helpful in interpreting this literature and we hope that our discussion of the newest analytical methods will stimulate future progress. We emphasize that no single approach can provide a complete view of the overall methylome, and that combinations of several modalities applied to the same sample set will give the clearest picture. Given the unexpected epigenomic patterns and new biological principles, as well as new disease markers, that have been uncovered in recent studies, it is likely that important discoveries will continue to be made using genome-wide DNA methylation profiling.

  1. Microbial mercury methylation in Antarctic sea ice.

    PubMed

    Gionfriddo, Caitlin M; Tate, Michael T; Wick, Ryan R; Schultz, Mark B; Zemla, Adam; Thelen, Michael P; Schofield, Robyn; Krabbenhoft, David P; Holt, Kathryn E; Moreau, John W

    2016-08-01

    Atmospheric deposition of mercury onto sea ice and circumpolar sea water provides mercury for microbial methylation, and contributes to the bioaccumulation of the potent neurotoxin methylmercury in the marine food web. Little is known about the abiotic and biotic controls on microbial mercury methylation in polar marine systems. However, mercury methylation is known to occur alongside photochemical and microbial mercury reduction and subsequent volatilization. Here, we combine mercury speciation measurements of total and methylated mercury with metagenomic analysis of whole-community microbial DNA from Antarctic snow, brine, sea ice and sea water to elucidate potential microbially mediated mercury methylation and volatilization pathways in polar marine environments. Our results identify the marine microaerophilic bacterium Nitrospina as a potential mercury methylator within sea ice. Anaerobic bacteria known to methylate mercury were notably absent from sea-ice metagenomes. We propose that Antarctic sea ice can harbour a microbial source of methylmercury in the Southern Ocean.

  2. Increased DNA methylation in the suicide brain.

    PubMed

    Haghighi, Fatemeh; Xin, Yurong; Chanrion, Benjamin; O'Donnell, Anne H; Ge, Yongchao; Dwork, Andrew J; Arango, Victoria; Mann, J John

    2014-09-01

    Clinical studies find that childhood adversity and stressful life events in adulthood increase the risk for major depression and for suicide. The predispositions to either major depression or suicide are thought to depend on genetic risk factors or epigenetic effects. We investigated DNA methylation signatures postmortem in brains of suicides with diagnosis of major depressive disorder. DNA methylation levels were determined at single C-phosphate-G (CpG) resolution sites within ventral prefrontal cortex of 53 suicides and nonpsychiatric controls, aged 16 to 89 years. We found that DNA methylation increases throughout the lifespan. Suicides showed an 8-fold greater number of methylated CpG sites relative to controls (P < 2.2 x 10(-16)), with greater DNA methylation changes over and above the increased methylation observed in normal aging. This increased DNA methylation may be a significant contributor to the neuropathology and psychopathology underlying the risk of suicide in depression.

  3. DNA methylation profiling of hematopoietic stem cells.

    PubMed

    Begtrup, Amber Hogart

    2014-01-01

    DNA methylation is a key epigenetic mark that is essential for properly functioning hematopoietic stem cells. Determining where functionally relevant DNA methylation marks exist in the genome is crucial to understanding the role that methylation plays in hematopoiesis. This chapter describes a method to profile DNA methylation by selectively enriching methylated DNA sequences that are bound in vitro by methyl-binding domain (MBD) proteins. The MBD-pulldown approach selects for DNA sequences that have the potential to be "read" by the endogenous machinery involved in epigenetic regulation. Furthermore, this approach is feasible with very small quantities of DNA, and is compatible with the use of any downstream high-throughput sequencing approach. This technique offers a reliable, simple, and powerful tool for exploration of the role of DNA methylation in hematopoietic stem cells.

  4. Conventional and nanotechniques for DNA methylation profiling.

    PubMed

    Shanmuganathan, Rajasree; Basheer, Nazeema B; Amirthalingam, Laxmi; Muthukumar, Harshiny; Kaliaperumal, Rajendran; Shanmugam, Kumaran

    2013-01-01

    DNA methylation is critical for gene silencing and is associated with the incidence of many diseases, including cancer. Underlying molecular mechanisms of human diseases and tissue-specific gene expression have been elucidated based on DNA methylation studies. This review highlights the advantages and drawbacks of various methylation screening techniques: blotting, genomic sequencing, bisulfite sequencing, methylation-specific PCR, methylated DNA immunoprecipitation, microarray analysis, matrix-assisted laser desorption ionization time-of-flight mass spectroscopy, nanowire transistor detection procedure, quantum dot-based nanoassay, single-molecule real-time detection, fluorimetric assay, electrochemical detection, and atomic force spectroscopy. The review provides insight for selecting a method or a combination of methods for DNA methylation analysis. Convergence of conventional and contemporary nanotechniques to enumerate methylation at specific CpG sites of oncogene would fill the gap in diagnosis of cancer.

  5. First evidence of DNA methylation in insect Tribolium castaneum: environmental regulation of DNA methylation within heterochromatin.

    PubMed

    Feliciello, Isidoro; Parazajder, Josip; Akrap, Ivana; Ugarković, Durđica

    2013-05-01

    DNA methylation has been studied in many eukaryotic organisms, in particular vertebrates, and was implicated in developmental and phenotypic variations. Little is known about the role of DNA methylation in invertebrates, although insects are considered as excellent models for studying the evolution of DNA methylation. In the red flour beetle, Tribolium castaneum (Tenebrionidae, Coleoptera), no evidence of DNA methylation has been found till now. In this paper, a cytosine methylation in Tribolium castaneum embryos was detected by methylation sensitive restriction endonucleases and immuno-dot blot assay. DNA methylation in embryos is followed by a global demethylation in larvae, pupae and adults. DNA demethylation seems to proceed actively through 5-hydroxymethylcytosine, most probably by the action of TET enzyme. Bisulfite sequencing of a highly abundant satellite DNA located in pericentromeric heterochromatin revealed similar profile of cytosine methylation in adults and embryos. Cytosine methylation was not only restricted to CpG sites but was found at CpA, CpT and CpC sites. In addition, complete cytosine demethylation of heterochromatic satellite DNA was induced by heat stress. The results reveal existence of DNA methylation cycling in T. castaneum ranging from strong overall cytosine methylation in embryos to a weak DNA methylation in other developmental stages. Nevertheless, DNA methylation is preserved within heterochromatin during development, indicating its role in heterochromatin formation and maintenance. It is, however, strongly affected by heat stress, suggesting a role for DNA methylation in heterochromatin structure modulation during heat stress response.

  6. Protein Methylation in Full Length Chlamydomonas Flagella

    PubMed Central

    Sloboda, Roger D.; Howard, Louisa

    2010-01-01

    Post-translational protein modification occurs extensively in eukaryotic flagella. Here we examine protein methylation, a protein modification that has only recently been reported to occur in flagella (Schneider et al. 2008). The cobalamin (vitamin B12) independent form of the enzyme methionine synthase (MetE), which catalyzes the final step in methionine production, is localized to flagella. Here we demonstrate, using immunogold scanning electron microscopy, that MetE is bound to the outer doublets of the flagellum. Methionine can be converted to S-adenosyl methionine, which then serves as the methyl donor for protein methylation reactions. Using antibodies that recognize symmetrically or asymmetrically methylated arginine residues, we identify three highly methylated proteins in intact flagella: two symmetrically methylated proteins of about 30 and 40 kDa, and one asymmetrically methylated protein of about 75 kDa. Several other relatively less methylated proteins could also be detected. Fractionation and immunoblot analysis shows that these proteins are components of the flagellar axoneme. Immunogold thin section electron microscopy indicates that the symmetrically methylated proteins are located in the central region of the axoneme, perhaps as components of the central pair complex and the radial spokes, while the asymmetrically methylated proteins are associated with the outer doublets. PMID:19472373

  7. Surface Molecularly Imprinted Polymer of Chitosan Grafted Poly(methyl methacrylate) for 5-Fluorouracil and Controlled Release

    PubMed Central

    Zheng, Xue-Fang; Lian, Qi; Yang, Hua; Wang, Xiuping

    2016-01-01

    The molecular surface imprinted graft copolymer of chitosan with methyl methacrylate (MIP-CS-g-PMMA) were prepared by free radical polymerization with 5-fluorouracil (5-FU) as the template molecule using initiator of ammonium persulfate as adsorption system. MIPs were characterized by FTIR, X-ray diffraction, thermo-gravimetric analysis, 1H NMR and SEM. The mechanism of graft copolymerization and factors affected graft reaction were studied in details, and the optimum reaction conditions (to the highest %G and %E as the standard) were obtained at [MMA] 1.2 mol/L, [Chitosan] 16.67 mol/L, [initiator] 0.0062 mol/L, temperature 60 °C and reaction time 7 h. MIPs exhibited high recognition selectivity and excellent combining affinity to template molecular. The in vitro release of the 5-FU was highly pH-dependent and time delayed. The release behavior showed that the drugs did not release in simulated gastric fluid (pH = 1.0), and the drug release was small in the simulated small intestinal fluid (pH = 6.8), and drug abrupt release will be produced in the simulated colon fluid (pH = 7.4), indicating excellent colon-specific drug delivery behavior. PMID:26892676

  8. Surface Molecularly Imprinted Polymer of Chitosan Grafted Poly(methyl methacrylate) for 5-Fluorouracil and Controlled Release.

    PubMed

    Zheng, Xue-Fang; Lian, Qi; Yang, Hua; Wang, Xiuping

    2016-02-19

    The molecular surface imprinted graft copolymer of chitosan with methyl methacrylate (MIP-CS-g-PMMA) were prepared by free radical polymerization with 5-fluorouracil (5-FU) as the template molecule using initiator of ammonium persulfate as adsorption system. MIPs were characterized by FTIR, X-ray diffraction, thermo-gravimetric analysis, (1)H NMR and SEM. The mechanism of graft copolymerization and factors affected graft reaction were studied in details, and the optimum reaction conditions (to the highest %G and %E as the standard) were obtained at [MMA] 1.2 mol/L, [Chitosan] 16.67 mol/L, [initiator] 0.0062 mol/L, temperature 60 °C and reaction time 7 h. MIPs exhibited high recognition selectivity and excellent combining affinity to template molecular. The in vitro release of the 5-FU was highly pH-dependent and time delayed. The release behavior showed that the drugs did not release in simulated gastric fluid (pH = 1.0), and the drug release was small in the simulated small intestinal fluid (pH = 6.8), and drug abrupt release will be produced in the simulated colon fluid (pH = 7.4), indicating excellent colon-specific drug delivery behavior.

  9. Synthesis and swelling property of superabsorbent starch grafted with acrylic acid/2-acrylamido-2-methyl-1-propanesulfonic acid.

    PubMed

    Meng, Yeqiao; Ye, Lin

    2017-08-01

    In order to develop starch-based superabsorbent polymers (SAPs) with high water absorbency, both acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were graft copolymerized onto cassava starch, and St-g-AA-AMPS SAP was successfully synthesized. The effect of AA/AMPS molar ratio on the structure and swelling property of SAP was investigated. Introduction of AMPS units improved the storage modulus and crosslinking density of St-g-AA-AMPS SAP, and was beneficial in forming a perfect network structure. With increasing AMPS content, the equilibrium swelling ratio and swelling rate constant (k) of the SAP first increased and then decreased, and the maximum swelling ratio reached 1200.0 and 90.0 g/g in distilled water and brine respectively, resulting from the high ionization constant and hydrophilic ability of AMPS, and improved tolerance to brine. By introducing AMPS units, the re-swelling capability of SAP was improved, and more hydrogen bonds could form between molecules of water and SAP, leading to an increase in non-freezing bound water and freezing bound water, and the water retention of SAP was enhanced. Introduction of AMPS units improved the water absorption capacity, swelling rate, and water retention ability of St-g-AA-AMPS SAP, presenting wide application potential in agriculture and horticulture of desert regions. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  10. Evolution of DNA Methylation across Insects.

    PubMed

    Bewick, Adam J; Vogel, Kevin J; Moore, Allen J; Schmitz, Robert J

    2017-03-01

    DNA methylation contributes to gene and transcriptional regulation in eukaryotes, and therefore has been hypothesized to facilitate the evolution of plastic traits such as sociality in insects. However, DNA methylation is sparsely studied in insects. Therefore, we documented patterns of DNA methylation across a wide diversity of insects. We predicted that underlying enzymatic machinery is concordant with patterns of DNA methylation. Finally, given the suggestion that DNA methylation facilitated social evolution in Hymenoptera, we tested the hypothesis that the DNA methylation system will be associated with presence/absence of sociality among other insect orders. We found DNA methylation to be widespread, detected in all orders examined except Diptera (flies). Whole genome bisulfite sequencing showed that orders differed in levels of DNA methylation. Hymenopteran (ants, bees, wasps and sawflies) had some of the lowest levels, including several potential losses. Blattodea (cockroaches and termites) show all possible patterns, including a potential loss of DNA methylation in a eusocial species whereas solitary species had the highest levels. Species with DNA methylation do not always possess the typical enzymatic machinery. We identified a gene duplication event in the maintenance DNA methyltransferase 1 (DNMT1) that is shared by some Hymenoptera, and paralogs have experienced divergent, nonneutral evolution. This diversity and nonneutral evolution of underlying machinery suggests alternative DNA methylation pathways may exist. Phylogenetically corrected comparisons revealed no evidence that supports evolutionary association between sociality and DNA methylation. Future functional studies will be required to advance our understanding of DNA methylation in insects. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  11. The vegetarian lifestyle and DNA methylation.

    PubMed

    Geisel, Jürgen; Schorr, Heike; Bodis, Marion; Isber, Sonia; Hübner, Ulrich; Knapp, Jean-Pierre; Obeid, Rima; Herrmann, Wolfgang

    2005-01-01

    Vegetarians have a lower intake of vitamin B12 than omnivores do. Vitamin B12 deficiency (holotranscobalamin II <35 pmol/L or methylmalonic acid >271 nmol/L) was found in 58% of 71 vegetarians studied. Higher homocysteine levels (>12 micromol/L) found in 45% indicate disturbed remethylation of homocysteine to methionine. The methylation of DNA is strongly linked to homocysteine metabolism. Since DNA methylation is an important epigenetic factor in the regulation of gene expression, alteration of the methylation pattern has been associated with aging, cancer, atherosclerosis and other diseases. Three observations indicate that DNA methylation could be diminished by a vegetarian lifestyle. The vegetarian diet has a low content of methionine, remethylation of homocysteine is reduced by vitamin B12 deficiency and elevated homocysteine levels can induce the generation of S-adenosylhomocysteine (SAH), a potent inhibitor of methyltransferases. In our study we observed a significant correlation between SAH and whole-genome methylation (r=-0.36, p<0.01). This observation underlines the role of SAH as a potent inhibitor of methyltransferases. The methylation status was not correlated with homocysteine or S-adenosylemethionine (SAM). These results indicate that the degree of methylation does not depend on the supply of methyl groups and that the reverse generation of SAH has no influence. In addition to whole-genome methylation, the specific promoter methylation of the p66Shc gene was studied. However, the latter did not correlate with SAH, SAM or homocysteine. Obviously, the promoter methylation of the p66Shc gene is controlled in a specific way, without following the general regulating influence of SAH. In conclusion, an inhibitory effect of SAH on whole-genome methylation was found, but from our data no interaction between vegetarian lifestyle and DNA methylation could be determined.

  12. Rotational spectra of methyl ethyl and methyl propyl nitrosamines. Conformational assignment, internal rotation and quadrupole coupling

    NASA Astrophysics Data System (ADS)

    Walker, A. R. Hight; Lou, Qi; Bohn, Robert K.; Novick, Stewart E.

    1995-02-01

    A structural determination of two carcinogenic nitrosamines, methyl ethyl and methyl propyl nitrosamine, was performed. Microwave spectra were gathered from both a Stark cell spectrometer and a pulsed jet Fabry-Perot Fourier transform microwave spectrometer. Each rotational transition is split into quadrupole hyperfine components by two nitrogen nuclei. This quadrupole pattern is doubled by a low barrier methyl rotor which produces resolvable A and E states. Rotational spectra were assigned for one conformer of methyl ethyl nitrosamine and two conformers of methyl propyl nitrosamine. The lowest energy conformers of each compound, according to empirical force field calculations, were assigned. The structure found for methyl ethyl nitrosamine has the nitrosyl oxygen on the methyl side with the terminal methyl group of the ethyl chain in the gauche position (OMG). Both conformers of methyl propyl nitrosamine have the same skeletal structure as the methyl ethyl compound; one conformer has the terminal methyl of the propyl group in the anti position (OMGA) while the other conformer has this methyl in the gauche position (OMGG -). Rotational constants and quadrupole coupling constants are reported for each assigned species. A barrier to internal rotation of the N-methyl group in each compound is also reported.

  13. Wp specific methylation of highly proliferated LCLs

    SciTech Connect

    Park, Jung-Hoon; Jeon, Jae-Pil; Shim, Sung-Mi; Nam, Hye-Young; Kim, Joon-Woo; Han, Bok-Ghee; Lee, Suman . E-mail: suman@cha.ac.kr

    2007-06-29

    The epigenetic regulation of viral genes may be important for the life cycle of EBV. We determined the methylation status of three viral promoters (Wp, Cp, Qp) from EBV B-lymphoblastoid cell lines (LCLs) by pyrosequencing. Our pyrosequencing data showed that the CpG region of Wp was methylated, but the others were not. Interestingly, Wp methylation was increased with proliferation of LCLs. Wp methylation was as high as 74.9% in late-passage LCLs, but 25.6% in early-passage LCLs. From two Burkitt's lymphoma cell lines, Wp specific hypermethylation was also found (>80%). Interestingly, the expression of EBNA2 gene which located directly next to Wp was associated with its methylation. Our data suggested that Wp specific methylation may be important for the indicator of the proliferation status of LCLs, and the epigenetic viral gene regulation of EBNA2 gene by Wp should be further defined possibly with other biological processes.

  14. In vitro Assays of Inorganic Arsenic Methylation

    PubMed Central

    Drobna, Zuzana; Styblo, Miroslav; Thomas, David J.

    2009-01-01

    Inorganic arsenic is extensively metabolized to produce mono-, di-, and trimethylated products. The formation of these metabolites produces a variety of intermediates that differ from inorganic arsenic in terms of patterns of distribution and retention and in toxic effects. In order to elucidate the pathway for arsenic methylation, it was necessary to develop a reliable in vitro assay system in which the formation of methylated metabolites could be monitored. Here, in vitro assay system that uses the postmicrosomal supernate from rat liver is used as the source of the enzymatic activity that catalyzes methylation reactions. This system can be used to study the requirements for methylation reactions (e.g., identifying the donor of methyl groups) and for screening of compounds as potential activators or inhibitors of arsenic methylation. PMID:20440380

  15. Direct synthesis of methyl phosphoramidates in carbohydrates.

    PubMed

    Dhurandhare, Vijay M; Mishra, Girija Prasad; Lam, Sarah; Wang, Cheng-Chung

    2015-09-28

    A direct installation of a methyl phosphoramidate group by using methyl benzylphosphoramidochloridate into carbohydrates and amino acid is described. This one-step synthesis is efficient for both primary and secondary alcohols and exhibited excellent regioselectivity and functional group compatibility. Formation of a single diastereomer is observed in certain cases. The N-benzyl protecting group on methyl phosphoramidates is easily removed under mild conditions.

  16. MAGI: Methylation analysis using genome information.

    PubMed

    Baumann, Douglas D; Doerge, R W

    2014-05-01

    By incorporating annotation information into the analysis of next-generation sequencing DNA methylation data, we provide an improvement in performance over current testing procedures. Methylation analysis using genome information (MAGI) is applicable for both unreplicated and replicated data, and provides an effective analysis for studies with low sequencing depth. When compared with current tests, the annotation-informed tests provide an increase in statistical power and offer a significance-based interpretation of differential methylation.

  17. DNA Methylation of BDNF Gene in Schizophrenia

    PubMed Central

    Çöpoğlu, Ümit Sertan; İğci, Mehri; Bozgeyik, Esra; Kokaçya, M. Hanifi; İğci, Yusuf Ziya; Dokuyucu, Recep; Arı, Mustafa; Savaş, Haluk A.

    2016-01-01

    Background Although genetic factors are risk factors for schizophrenia, some environmental factors are thought to be required for the manifestation of disease. Epigenetic mechanisms regulate gene functions without causing a change in the nucleotide sequence of DNA. Brain-derived neurotrophic factor (BDNF) is a neurotrophin that regulates synaptic transmission and plasticity. It has been suggested that BDNF may play a role in the pathophysiology of schizophrenia. It is established that methylation status of the BDNF gene is associated with fear learning, memory, and stressful social interactions. In this study, we aimed to investigate the DNA methylation status of BDNF gene in patients with schizophrenia. Material/Methods The study included 49 patients (33 male and 16 female) with schizophrenia and 65 unrelated healthy controls (46 male and 19 female). Determination of methylation pattern of CpG islands was based on the principle that bisulfite treatment of DNA results in conversion of unmethylated cytosine residues into uracil, whereas methylated cytosine residues remain unmodified. Methylation-specific PCR was performed with primers specific for either methylated or unmethylated DNA. Results There was no significant difference in methylated or un-methylated status for BDNF promoters between schizophrenia patients and controls. The mean duration of illness was significantly lower in the hemi-methylated group compared to the non-methylated group for BDNF gene CpG island-1 in schizophrenia patients. Conclusions Although there were no differences in BDNF gene methylation status between schizophrenia patients and healthy controls, there was an association between duration of illness and DNA methylation. PMID:26851233

  18. DNA Methylation of BDNF Gene in Schizophrenia.

    PubMed

    Çöpoğlu, Ümit Sertan; Igci, Mehri; Bozgeyik, Esra; Kokaçya, M Hanifi; İğci, Yusuf Ziya; Dokuyucu, Recep; Ari, Mustafa; Savaş, Haluk A

    2016-02-06

    BACKGROUND Although genetic factors are risk factors for schizophrenia, some environmental factors are thought to be required for the manifestation of disease. Epigenetic mechanisms regulate gene functions without causing a change in the nucleotide sequence of DNA. Brain-derived neurotrophic factor (BDNF) is a neurotrophin that regulates synaptic transmission and plasticity. It has been suggested that BDNF may play a role in the pathophysiology of schizophrenia. It is established that methylation status of the BDNF gene is associated with fear learning, memory, and stressful social interactions. In this study, we aimed to investigate the DNA methylation status of BDNF gene in patients with schizophrenia. MATERIAL AND METHODS The study included 49 patients (33 male and 16 female) with schizophrenia and 65 unrelated healthy controls (46 male and 19 female). Determination of methylation pattern of CpG islands was based on the principle that bisulfite treatment of DNA results in conversion of unmethylated cytosine residues into uracil, whereas methylated cytosine residues remain unmodified. Methylation-specific PCR was performed with primers specific for either methylated or unmethylated DNA. RESULTS There was no significant difference in methylated or un-methylated status for BDNF promoters between schizophrenia patients and controls. The mean duration of illness was significantly lower in the hemi-methylated group compared to the non-methylated group for BDNF gene CpG island-1 in schizophrenia patients. CONCLUSIONS Although there were no differences in BDNF gene methylation status between schizophrenia patients and healthy controls, there was an association between duration of illness and DNA methylation.

  19. Detailed Chemical Kinetic Reaction Mechanism for Biodiesel Components Methyl Stearate and Methyl Oleate

    SciTech Connect

    Naik, C; Westbrook, C K; Herbinet, O; Pitz, W J; Mehl, M

    2010-01-22

    New chemical kinetic reaction mechanisms are developed for two of the five major components of biodiesel fuel, methyl stearate and methyl oleate. The mechanisms are produced using existing reaction classes and rules for reaction rates, with additional reaction classes to describe other reactions unique to methyl ester species. Mechanism capabilities were examined by computing fuel/air autoignition delay times and comparing the results with more conventional hydrocarbon fuels for which experimental results are available. Additional comparisons were carried out with measured results taken from jet-stirred reactor experiments for rapeseed methyl ester fuels. In both sets of computational tests, methyl oleate was found to be slightly less reactive than methyl stearate, and an explanation of this observation is made showing that the double bond in methyl oleate inhibits certain low temperature chain branching reaction pathways important in methyl stearate. The resulting detailed chemical kinetic reaction mechanism includes more approximately 3500 chemical species and more than 17,000 chemical reactions.

  20. EXTRACTION OF TETRAVALENT PLUTONIUM VALUES WITH METHYL ETHYL KETONE, METHYL ISOBUTYL KETONE ACETOPHENONE OR MENTHONE

    DOEpatents

    Seaborg, G.T.

    1961-08-01

    A process is described for extracting tetravalent plutonium from an aqueous acid solution with methyl ethyl ketone, methyl isobutyl ketone, or acetophenone and with the extraction of either tetravalent or hexavalent plutonium into menthone. (AEC)

  1. Methylation – an uncommon modification of glycans*

    PubMed Central

    Staudacher, Erika

    2013-01-01

    A methyl group on a sugar residue is a rarely reported event. Until now this kind of modification has been found in the kingdom of animals only in worms and molluscs, whereas it is more frequently present in some species of bacteria, fungi, algae and plants, but not in mammals. The monosaccharides involved as well as the positions of the methyl groups on the sugar vary with the species. Methylation seems to play a role in some recognition events but details are still unknown. This review summarises the current knowledge on methylation of sugars in all kinds of organism. PMID:22944672

  2. Flocculation of diatomite by methylated egg albumin.

    PubMed

    Seki, Hideshi; Suzuki, Akira

    2003-07-01

    A common and inexpensive protein, egg albumin, was applied to the solid-liquid separation or flocculation of diatomite. Egg albumin was methylated in a 0.05 M HCl methyl alcohol solution at room temperature. About 90% of the carboxylic groups of egg albumin could be methylated within 24 h. The adsorption of egg albumin onto diatomite at pH 6.8 was remarkably enhanced by methylation. The adsorption constant of methylated egg albumin to diatomite at 30 degrees C was about 100-fold larger than that of native egg albumin; however, the adsorption constant of methylated egg albumin decreased to about 1/100 with temperature decreasing from 30 to 6 degrees C. The saturated adsorption amount of egg albumin was also increased by the methylation. The flocculating ability of methylated egg albumin was examined with a diatomite suspension at 6 and 30 degrees C in the pH range from pH 2 to 11. The diatomite suspension was effectively flocculated by the addition of small amounts of methylated egg albumin (only 0.5-1 wt% against diatomite) over a wide pH range from pH 3 to 10.

  3. Druggability of methyl-lysine binding sites

    NASA Astrophysics Data System (ADS)

    Santiago, C.; Nguyen, K.; Schapira, M.

    2011-12-01

    Structural modules that specifically recognize—or read—methylated or acetylated lysine residues on histone peptides are important components of chromatin-mediated signaling and epigenetic regulation of gene expression. Deregulation of epigenetic mechanisms is associated with disease conditions, and antagonists of acetyl-lysine binding bromodomains are efficacious in animal models of cancer and inflammation, but little is known regarding the druggability of methyl-lysine binding modules. We conducted a systematic structural analysis of readers of methyl marks and derived a predictive druggability landscape of methyl-lysine binding modules. We show that these target classes are generally less druggable than bromodomains, but that some proteins stand as notable exceptions.

  4. Genistein alters methylation patterns in mice.

    PubMed

    Day, J Kevin; Bauer, Andrew M; DesBordes, Charles; Zhuang, Yi; Kim, Byung-Eun; Newton, Leslie G; Nehra, Vedika; Forsee, Kara M; MacDonald, Ruth S; Besch-Williford, Cynthia; Huang, Tim Hui-Ming; Lubahn, Dennis B

    2002-08-01

    In this study we examine the effect of the phytoestrogen genistein on DNA methylation. DNA methylation is thought to inhibit transcription of genes by regulating alterations in chromatin structure. Estrogenic compounds have been reported to regulate DNA methylation in a small number of studies. Additionally, phytoestrogens are believed to affect progression of some human diseases, such as estrogen-dependent cancers, osteoporosis and cardiovascular disease. Specifically, our working hypothesis is that certain soy phytoestrogens, such as genistein, may be involved in preventing the development of certain prostate and mammary cancers by maintaining a protective DNA methylation profile. The objective of the present study is to use mouse differential methylation hybridization (DMH) arrays to test for changes in the methylation status of the cytosine guanine dinucleotide (CpG) islands in the mouse genome by examining how these methylation patterns are affected by genistein. Male mice were fed a casein-based diet (control) or the same diet containing 300 mg genistein/kg according to one of four regimens: control diet for 4 wk, genistein diet for 4 wk, control diet for 2 wk followed by genistein diet for 2 wk and genistein diet for 2 wk followed by control diet for 2 wk. DNA from liver, brain and prostate were then screened with DMH arrays. Clones with methylation differences were sequenced and compared with known sequences. In conclusion, consumption of genistein diet was positively correlated with changes in prostate DNA methylation at CpG islands of specific mouse genes.

  5. RNA-directed DNA methylation in Arabidopsis

    PubMed Central

    Aufsatz, Werner; Mette, M. Florian; van der Winden, Johannes; Matzke, Antonius J. M.; Matzke, Marjori

    2002-01-01

    In plants, double-stranded RNA that is processed to short RNAs ≈21–24 nt in length can trigger two types of epigenetic gene silencing. Posttranscriptional gene silencing, which is related to RNA interference in animals and quelling in fungi, involves targeted elimination of homologous mRNA in the cytoplasm. RNA-directed DNA methylation involves de novo methylation of almost all cytosine residues within a region of RNA–DNA sequence identity. RNA-directed DNA methylation is presumed to be responsible for the methylation observed in protein coding regions of posttranscriptionally silenced genes. Moreover, a type of transcriptional gene silencing and de novo methylation of homologous promoters in trans can occur if a double-stranded RNA contains promoter sequences. Although RNA-directed DNA methylation has been described so far only in plants, there is increasing evidence that RNA can also target genome modifications in other organisms. To understand how RNA directs methylation to identical DNA sequences and how changes in chromatin configuration contribute to initiating or maintaining DNA methylation induced by RNA, a promoter double-stranded RNA-mediated transcriptional gene silencing system has been established in Arabidopsis. A genetic analysis of this system is helping to unravel the relationships among RNA signals, DNA methylation, and chromatin structure. PMID:12169664

  6. Aberrant DNA methylation patterns in diabetic nephropathy

    PubMed Central

    2014-01-01

    Background The aim of this study was to evaluate whether global levels of DNA methylation status were associated with albuminuria and progression of diabetic nephropathy in a case-control study of 123 patients with type 2 diabetes- 53 patients with albuminuria and 70 patients without albuminuria. Methods The 5-methyl cytosine content was assessed by reverse phase high pressure liquid chromatography (RP-HPLC) of peripheral blood mononuclear cells to determine individual global DNA methylation status in two groups. Results Global DNA methylation levels were significantly higher in patients with albuminuria compared with those in normal range of albuminuria (p = 0.01). There were significant differences in global levels of DNA methylation in relation to albuminuria (p = 0.028) and an interesting pattern of increasing global levels of DNA methylation in terms of albuminuria severity. In patients with micro- and macro albuminuria, we found no significant correlations between global DNA methylation levels and duration of diabetes (p > 0.05). In both sub groups, there were not significant differences between global DNA methylation levels with good and poor glycaemic control (p > 0.05). In addition, in patients with albuminuria, no differences in DNA methylation levels were observed between patients with and without other risk factors including age, gender, hypertension, dyslipidaemia and obesity. Conclusions These data may be helpful in further studies to develop novel biomarkers and new strategies for clinical care of patients at risk of diabetic nephropathy. PMID:25028646

  7. DNA Methylation Landscapes of Human Fetal Development.

    PubMed

    Slieker, Roderick C; Roost, Matthias S; van Iperen, Liesbeth; Suchiman, H Eka D; Tobi, Elmar W; Carlotti, Françoise; de Koning, Eelco J P; Slagboom, P Eline; Heijmans, Bastiaan T; Chuva de Sousa Lopes, Susana M

    2015-10-01

    Remodelling the methylome is a hallmark of mammalian development and cell differentiation. However, current knowledge of DNA methylation dynamics in human tissue specification and organ development largely stems from the extrapolation of studies in vitro and animal models. Here, we report on the DNA methylation landscape using the 450k array of four human tissues (amnion, muscle, adrenal and pancreas) during the first and second trimester of gestation (9,18 and 22 weeks). We show that a tissue-specific signature, constituted by tissue-specific hypomethylated CpG sites, was already present at 9 weeks of gestation (W9). Furthermore, we report large-scale remodelling of DNA methylation from W9 to W22. Gain of DNA methylation preferentially occurred near genes involved in general developmental processes, whereas loss of DNA methylation mapped to genes with tissue-specific functions. Dynamic DNA methylation was associated with enhancers, but not promoters. Comparison of our data with external fetal adrenal, brain and liver revealed striking similarities in the trajectory of DNA methylation during fetal development. The analysis of gene expression data indicated that dynamic DNA methylation was associated with the progressive repression of developmental programs and the activation of genes involved in tissue-specific processes. The DNA methylation landscape of human fetal development provides insight into regulatory elements that guide tissue specification and lead to organ functionality.

  8. Microwave-accelerated methylation of starch.

    PubMed

    Singh, Vandana; Tiwari, Ashutosh

    2008-01-14

    A novel microwave-accelerated method for methylating soluble starch is described. Soluble starch could be fully methylated in 72% yield within 4.66 min using iodomethane and 30% potassium hydroxide under microwave irradiation. The completely methylated starch thus obtained was hydrolyzed with 60% HCO(2)H for 1.5 min under 80% MW power, followed by 0.05 M H(2)SO(4) for 2.0 min under 100% MW power. The partially methylated monosaccharides were separated by preparative paper chromatography and identified by their melting points and optical rotations.

  9. Chiral methyl-branched pheromones.

    PubMed

    Ando, Tetsu; Yamakawa, Rei

    2015-07-01

    Insect pheromones are some of the most interesting natural products because they are utilized for interspecific communication between various insects, such as beetles, moths, ants, and cockroaches. A large number of compounds of many kinds have been identified as pheromone components, reflecting the diversity of insect species. While this review deals only with chiral methyl-branched pheromones, the chemical structures of more than one hundred non-terpene compounds have been determined by applying excellent analytical techniques. Furthermore, their stereoselective syntheses have been achieved by employing trustworthy chiral sources and ingenious enantioselective reactions. The information has been reviewed here not only to make them available for new research but also to understand the characteristic chemical structures of the chiral pheromones. Since biosynthetic studies are still limited, it might be meaningful to examine whether the structures, particularly the positions and configurations of the branched methyl groups, are correlated with the taxonomy of the pheromone producers and also with the function of the pheromones in communication systems.

  10. A fully integrated high-throughput screening methodology for the discovery of new polyolefin catalysts: discovery of a new class of high temperature single-site group (IV) copolymerization catalysts.

    PubMed

    Boussie, Thomas R; Diamond, Gary M; Goh, Christopher; Hall, Keith A; LaPointe, Anne M; Leclerc, Margarete; Lund, Cheryl; Murphy, Vince; Shoemaker, James A W; Tracht, Ursula; Turner, Howard; Zhang, Jessica; Uno, Tetsuo; Rosen, Robert K; Stevens, James C

    2003-04-09

    For the first time, new catalysts for olefin polymerization have been discovered through the application of fully integrated high-throughput primary and secondary screening techniques supported by rapid polymer characterization methods. Microscale 1-octene primary screening polymerization experiments combining arrays of ligands with reactive metal complexes M(CH(2)Ph)(4) (M = Zr, Hf) and multiple activation conditions represent a new high-throughput technique for discovering novel group (IV) polymerization catalysts. The primary screening methods described here have been validated using a commercially relevant polyolefin catalyst, and implemented rapidly to discover the new amide-ether based hafnium catalyst [eta(2)-(N,O)[bond](2-MeO[bond]C(6)H(4))(2,4,6-Me(3)C(6)H(2))N]Hf(CH(2)Ph)(3) (1), which is capable of polymerizing 1-octene to high conversion. The molecular structure of 1 has been determined by X-ray diffraction. Larger scale secondary screening experiments performed on a focused 96-member amine-ether library demonstrated the versatile high temperature ethylene-1-octene copolymerization capabilities of this catalyst class, and led to significant performance improvements over the initial primary screening discovery. Conventional one gallon batch reactor copolymerizations performed using selected amide-ether hafnium compounds confirmed the performance features of this new catalyst class, serving to fully validate the experimental results from the high-throughput approaches described herein.

  11. 21 CFR 177.2000 - Vinylidene chloride/methyl acrylate/methyl methacrylate polymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... methacrylate polymers. 177.2000 Section 177.2000 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF...: POLYMERS Substances for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.2000 Vinylidene chloride/methyl acrylate/methyl methacrylate polymers. The vinylidene chloride/methyl...

  12. 21 CFR 177.2000 - Vinylidene chloride/methyl acrylate/methyl methacrylate polymers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... methacrylate polymers. 177.2000 Section 177.2000 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances for Use as Basic.../methyl methacrylate polymers. The vinylidene chloride/methyl acrylate/methyl methacrylate polymers (CAS...

  13. Copolymerization of dibenzofuran and dichloromethane

    SciTech Connect

    Rao, S.P.; Jones, M.B.; Baltisberger, R.J.; Brown, C.E.; Burger, V.T.

    1983-01-01

    As part of a project involving synthesis of model oligomers of coal derived asphaltenes and preasphaltenes, we required bis(2-dibenzofuranyl)methane (1). The successful preparation of 1 was carried out via coupling of 2-lithio-dibenzofuran with 2-formyldibenzofuran, followed by reduction of the resulting diaryl substituted methanol. Attempts to prepare 1 by Friedel-Crafts alkylation of dibenzofuran (DBF) with stoichiometric amounts of CH/sub 2/Cl/sub 2/ failed. However, when CH/sub 2/Cl/sub 2/ was present in excess (as solvent), alkylation of DBF proceeded smoothly at ambient temperature to yield an insoluble, infusible, yellow powder. We report herein preliminary observations on the characteristics and structural features of this new copolymer.

  14. Methylation Linear Discriminant Analysis (MLDA) for identifying differentially methylated CpG islands

    PubMed Central

    Dai, Wei; Teodoridis, Jens M; Graham, Janet; Zeller, Constanze; Huang, Tim HM; Yan, Pearlly; Vass, J Keith; Brown, Robert; Paul, Jim

    2008-01-01

    Background Hypermethylation of promoter CpG islands is strongly correlated to transcriptional gene silencing and epigenetic maintenance of the silenced state. As well as its role in tumor development, CpG island methylation contributes to the acquisition of resistance to chemotherapy. Differential Methylation Hybridisation (DMH) is one technique used for genome-wide DNA methylation analysis. The study of such microarray data sets should ideally account for the specific biological features of DNA methylation and the non-symmetrical distribution of the ratios of unmethylated and methylated sequences hybridised on the array. We have therefore developed a novel algorithm tailored to this type of data, Methylation Linear Discriminant Analysis (MLDA). Results MLDA was programmed in R (version 2.7.0) and the package is available at CRAN [1]. This approach utilizes linear regression models of non-normalised hybridisation data to define methylation status. Log-transformed signal intensities of unmethylated controls on the microarray are used as a reference. The signal intensities of DNA samples digested with methylation sensitive restriction enzymes and mock digested are then transformed to the likelihood of a locus being methylated using this reference. We tested the ability of MLDA to identify loci differentially methylated as analysed by DMH between cisplatin sensitive and resistant ovarian cancer cell lines. MLDA identified 115 differentially methylated loci and 23 out of 26 of these loci have been independently validated by Methylation Specific PCR and/or bisulphite pyrosequencing. Conclusion MLDA has advantages for analyzing methylation data from CpG island microarrays, since there is a clear rational for the definition of methylation status, it uses DMH data without between-group normalisation and is less influenced by cross-hybridisation of loci. The MLDA algorithm successfully identified differentially methylated loci between two classes of samples analysed by DMH

  15. DNA methylation in demyelinated multiple sclerosis hippocampus.

    PubMed

    Chomyk, Anthony M; Volsko, Christina; Tripathi, Ajai; Deckard, Sadie A; Trapp, Bruce D; Fox, Robert J; Dutta, Ranjan

    2017-08-18

    Multiple Sclerosis (MS) is an immune-mediated demyelinating disease of the human central nervous system (CNS). Memory impairments and hippocampal demyelination are common features in MS patients. Our previous data have shown that demyelination alters neuronal gene expression in the hippocampus. DNA methylation is a common epigenetic modifier of gene expression. In this study, we investigated whether DNA methylation is altered in MS hippocampus following demyelination. Our results show that mRNA levels of DNA methyltransferase were increased in demyelinated MS hippocampus, while de-methylation enzymes were decreased. Comparative methylation profiling identify hypo-methylation within upstream sequences of 6 genes and hyper-methylation of 10 genes in demyelinated MS hippocampus. Genes identified in the current study were also validated in an independent microarray dataset generated from MS hippocampus. Independent validation using RT-PCR revealed that DNA methylation inversely correlated with mRNA levels of the candidate genes. Queries across cell-specific databases revealed that a majority of the candidate genes are expressed by astrocytes and neurons in mouse and human CNS. Taken together, our results expands the list of genes previously identified in MS hippocampus and establish DNA methylation as a mechanism of altered gene expression in MS hippocampus.

  16. mCCG methylation in angiosperms.

    PubMed

    Jeddeloh, J A; Richards, E J

    1996-05-01

    Two different methods were used to investigate the abundance of cytosine methylation at the outer (5') position in 5'-CCG-3' trinucleotides in angiosperm genomes. Mspl is unable to cut its target site if the outer cytosine is methylated (5'-mCCGG-3'). Using Mspl restriction analysis, it was shown that 5'-mCCG-3' is present in all angiosperm genomes examined, and that the amount of cytosine methylation at this site varies between species. Subsequently, direct measurements were made of the amount of methylation at both cytosines in a subset of 5'-CCG-3' trinucleotides in the Arabidopsis thaliana genome. Based upon these analyses, it was estimated that approximately 20-30% of 5'-CCG-3' trinucleotides in A. thaliana are methylated at the outer cytosine. Approximately 20% of the 5'-CCG-3' trinucleotides contain 5-methyl-cytosine at the inner cytosine position, which corresponds to a previous determination of 5'-mCG-3' methylation in A. thaliana. The implications of 5'-mCCG-3' methylation are discussed.

  17. The origins of atmospheric methyl mercury

    SciTech Connect

    Prestbo, E.M.; Bloom, N.S.

    1995-12-31

    Methyl Hg in precipitation shows strong regional patterns, with highest volume weighted mean values (0.4 ng/L) in the Pacific Northwest and lowest values in Florida (<0.01 ng/l). Over most of the North Central region, average values range from 0.05 to 0.2 ng/L. Several potential sources of methyl Hg to the atmosphere have been investigated, including direct anthropogenic emissions, atmospheric methylation of Hg{sup o} or Hg(II), and emissions of methyl or dimethyl Hg from natural surfaces (oceans, bogs, or forests). Direct measurements of major total Hg sources such as coal and waste combustors, and sewage treatment facilities suggest that direct anthropogenic emissions are an insignificant source of methyl Hg to the atmosphere. The gas phase reaction of methyl halides with Hg{sup o} also appears to be an insignificant source of methyl Hg to the atmosphere. Recent laboratory experiments have provided a likely mechanism for atmospheric Hg methylation via a complex reaction involving acetate, sulfite, and iron. From a series of field measurements, another source appears to be the degradation of dimethyl mercury emitted by the upwelling of deep ocean water.

  18. Implications of DNA Methylation in Parkinson's Disease.

    PubMed

    Miranda-Morales, Ernesto; Meier, Karin; Sandoval-Carrillo, Ada; Salas-Pacheco, José; Vázquez-Cárdenas, Paola; Arias-Carrión, Oscar

    2017-01-01

    It has been 200 years since Parkinson's disease (PD) was first described, yet many aspects of its etiopathogenesis remain unclear. PD is a progressive and complex neurodegenerative disorder caused by genetic and environmental factors including aging, nutrition, pesticides and exposure to heavy metals. DNA methylation may be altered in response to some of these factors; therefore, it is proposed that epigenetic mechanisms, particularly DNA methylation, can have a fundamental role in gene-environment interactions that are related with PD. Epigenetic changes in PD-associated genes are now widely studied in different populations, to discover the mechanisms that contribute to disease development and identify novel biomarkers for early diagnosis and future pharmacological treatment. While initial studies sought to find associations between promoter DNA methylation and the regulation of associated genes in PD brain tissue, more recent studies have described concordant DNA methylation patterns between blood and brain tissue DNA. These data justify the use of peripheral blood samples instead of brain tissue for epigenetic studies. Here, we summarize the current data about DNA methylation changes in PD and discuss the potential of DNA methylation as a potential biomarker for PD. Additionally, we discuss environmental and nutritional factors that have been implicated in DNA methylation. Although the search for significant DNA methylation changes and gene expression analyses of PD-associated genes have yielded inconsistent and contradictory results, epigenetic modifications remain under investigation for their potential to reveal the link between environmental risk factors and the development of PD.

  19. Effects of DNA methylation on nucleosome stability.

    PubMed

    Collings, Clayton K; Waddell, Peter J; Anderson, John N

    2013-03-01

    Methylation of DNA at CpG dinucleotides represents one of the most important epigenetic mechanisms involved in the control of gene expression in vertebrate cells. In this report, we conducted nucleosome reconstitution experiments in conjunction with high-throughput sequencing on 572 KB of human DNA and 668 KB of mouse DNA that was unmethylated or methylated in order to investigate the effects of this epigenetic modification on the positioning and stability of nucleosomes. The results demonstrated that a subset of nucleosomes positioned by nucleotide sequence was sensitive to methylation where the modification increased the affinity of these sequences for the histone octamer. The features that distinguished these nucleosomes from the bulk of the methylation-insensitive nucleosomes were an increase in the frequency of CpG dinucleotides and a unique rotational orientation of CpGs such that their minor grooves tended to face toward the histones in the nucleosome rather than away. These methylation-sensitive nucleosomes were preferentially associated with exons as compared to introns while unmethylated CpG islands near transcription start sites became enriched in nucleosomes upon methylation. The results of this study suggest that the effects of DNA methylation on nucleosome stability in vitro can recapitulate what has been observed in the cell and provide a direct link between DNA methylation and the structure and function of chromatin.

  20. Global DNA methylation in neonatal sepsis.

    PubMed

    Dhas, Benet Bosco; Antony, Hiasindh Ashmi; Bhat, Vishnu; Newton, Banupriya; Parija, Subhash Chandra

    2015-04-01

    To find out whether gDNA methylation can be used as a diagnostic/prognostic method for neonatal sepsis. The study was conducted in the neonatal division of a tertiary care referral hospital. Fifty one newborns as cases and thirty seven newborns as controls were enrolled in the study. Using 5-mC DNA ELISA method, the percentage of genomic DNA methylated in these newborns was established. Highly significant difference in percentage of gDNA methylated was found between the cases and controls (Cases: 2.4 ± 0.39; 2.07 ± 0.35; P < 0.0001). Culture proven and possible cases were also significantly distinguishable (P < 0.05). No significant differences in methylation were observed in terms of gestational age, birth weight and outcomes such shock, thrombocytopenia, except for renal failure. The index results showed that genomic DNA methylation varies significantly among newborns with sepsis (clinical, probable and culture positive) and without sepsis. Although the global DNA methylation was not a highly sensitive diagnostic method, this study reveals that DNA methylation might play a vital role in neonatal sepsis susceptibility. Identification of the specific differentially methylated genes might serve as a promising future diagnostic/prognostic marker for neonatal sepsis.

  1. Electrochemical biosensing strategies for DNA methylation analysis.

    PubMed

    Hossain, Tanvir; Mahmudunnabi, Golam; Masud, Mostafa Kamal; Islam, Md Nazmul; Ooi, Lezanne; Konstantinov, Konstantin; Hossain, Md Shahriar Al; Martinac, Boris; Alici, Gursel; Nguyen, Nam-Trung; Shiddiky, Muhammad J A

    2017-02-17

    DNA methylation is one of the key epigenetic modifications of DNA that results from the enzymatic addition of a methyl group at the fifth carbon of the cytosine base. It plays a crucial role in cellular development, genomic stability and gene expression. Aberrant DNA methylation is responsible for the pathogenesis of many diseases including cancers. Over the past several decades, many methodologies have been developed to detect DNA methylation. These methodologies range from classical molecular biology and optical approaches, such as bisulfite sequencing, microarrays, quantitative real-time PCR, colorimetry, Raman spectroscopy to the more recent electrochemical approaches. Among these, electrochemical approaches offer sensitive, simple, specific, rapid, and cost-effective analysis of DNA methylation. Additionally, electrochemical methods are highly amenable to miniaturization and possess the potential to be multiplexed. In recent years, several reviews have provided information on the detection strategies of DNA methylation. However, to date, there is no comprehensive evaluation of electrochemical DNA methylation detection strategies. Herein, we address the recent developments of electrochemical DNA methylation detection approaches. Furthermore, we highlight the major technical and biological challenges involved in these strategies and provide suggestions for the future direction of this important field.

  2. The Synthesis of Methyl Salicylate: Amine Diazotization.

    ERIC Educational Resources Information Center

    Zanger, Murray; McKee, James R.

    1988-01-01

    Notes that this experiment takes safety and noncarcinogenic reactants into account. Demonstrates the use of diazonium salts for the replacement of an aromatic amine group by a phenolic hydroxyl. Involves two pleasant-smelling organic compounds, methyl anthranilate (grape) and methyl salicylate (oil of wintergreen). (MVL)

  3. The Synthesis of Methyl Salicylate: Amine Diazotization.

    ERIC Educational Resources Information Center

    Zanger, Murray; McKee, James R.

    1988-01-01

    Notes that this experiment takes safety and noncarcinogenic reactants into account. Demonstrates the use of diazonium salts for the replacement of an aromatic amine group by a phenolic hydroxyl. Involves two pleasant-smelling organic compounds, methyl anthranilate (grape) and methyl salicylate (oil of wintergreen). (MVL)

  4. Optical biosensing strategies for DNA methylation analysis.

    PubMed

    Nazmul Islam, Md; Yadav, Sharda; Hakimul Haque, Md; Munaz, Ahmed; Islam, Farhadul; Al Hossain, Md Shahriar; Gopalan, Vinod; Lam, Alfred K; Nguyen, Nam-Trung; Shiddiky, Muhammad J A

    2017-06-15

    DNA methylation is an epigenetic modification of DNA, where a methyl group is added at the fifth carbon of the cytosine base to form 5 methyl cytosine (5mC) without altering the DNA sequences. It plays important roles in regulating many cellular processes by modulating key genes expression. Alteration in DNA methylation patterns becomes particularly important in the aetiology of different diseases including cancers. Abnormal methylation pattern could contribute to the pathogenesis of cancer either by silencing key tumor suppressor genes or by activating oncogenes. Thus, DNA methylation biosensing can help in the better understanding of cancer prognosis and diagnosis and aid the development of therapies. Over the last few decades, a plethora of optical detection techniques have been developed for analyzing DNA methylation using fluorescence, Raman spectroscopy, surface plasmon resonance (SPR), electrochemiluminescence and colorimetric readouts. This paper aims to comprehensively review the optical strategies for DNA methylation detection. We also present an overview of the remaining challenges of optical strategies that still need to be focused along with the lesson learnt while working with these techniques. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Maternal DNA Methylation Regulates Early Trophoblast Development

    PubMed Central

    Branco, Miguel R.; King, Michelle; Perez-Garcia, Vicente; Bogutz, Aaron B.; Caley, Matthew; Fineberg, Elena; Lefebvre, Louis; Cook, Simon J.; Dean, Wendy; Hemberger, Myriam; Reik, Wolf

    2016-01-01

    Summary Critical roles for DNA methylation in embryonic development are well established, but less is known about its roles during trophoblast development, the extraembryonic lineage that gives rise to the placenta. We dissected the role of DNA methylation in trophoblast development by performing mRNA and DNA methylation profiling of Dnmt3a/3b mutants. We find that oocyte-derived methylation plays a major role in regulating trophoblast development but that imprinting of the key placental regulator Ascl2 is only partially responsible for these effects. We have identified several methylation-regulated genes associated with trophoblast differentiation that are involved in cell adhesion and migration, potentially affecting trophoblast invasion. Specifically, trophoblast-specific DNA methylation is linked to the silencing of Scml2, a Polycomb Repressive Complex 1 protein that drives loss of cell adhesion in methylation-deficient trophoblast. Our results reveal that maternal DNA methylation controls multiple differentiation-related and physiological processes in trophoblast via both imprinting-dependent and -independent mechanisms. PMID:26812015

  6. Identifying DNA methylation in a nanochannel

    PubMed Central

    Sun, Xiaoyin; Yasui, Takao; Yanagida, Takeshi; Kaji, Noritada; Rahong, Sakon; Kanai, Masaki; Nagashima, Kazuki; Kawai, Tomoji; Baba, Yoshinobu

    2016-01-01

    Abstract DNA methylation is a stable epigenetic modification, which is well known to be involved in gene expression regulation. In general, however, analyzing DNA methylation requires rather time consuming processes (24–96 h) via DNA replication and protein modification. Here we demonstrate a methodology to analyze DNA methylation at a single DNA molecule level without any protein modifications by measuring the contracted length and relaxation time of DNA within a nanochannel. Our methodology is based on the fact that methylation makes DNA molecules stiffer, resulting in a longer contracted length and a longer relaxation time (a slower contraction rate). The present methodology offers a promising way to identify DNA methylation without any protein modification at a single DNA molecule level within 2 h. PMID:27877910

  7. Global Proteomics Analysis of Protein Lysine Methylation.

    PubMed

    Cao, Xing-Jun; Garcia, Benjamin A

    2016-11-01

    Lysine methylation is a common protein post-translational modification dynamically mediated by protein lysine methyltransferases (PKMTs) and protein lysine demethylases (PKDMs). Beyond histone proteins, lysine methylation on non-histone proteins plays a substantial role in a variety of functions in cells and is closely associated with diseases such as cancer. A large body of evidence indicates that the dysregulation of some PKMTs leads to tumorigenesis via their non-histone substrates. However, most studies on other PKMTs have made slow progress owing to the lack of approaches for extensive screening of lysine methylation sites. However, recently, there has been a series of publications to perform large-scale analysis of protein lysine methylation. In this unit, we introduce a protocol for the global analysis of protein lysine methylation in cells by means of immunoaffinity enrichment and mass spectrometry. © 2016 by John Wiley & Sons, Inc. Copyright © 2016 John Wiley & Sons, Inc.

  8. Whole genome DNA methylation: beyond genes silencing

    PubMed Central

    Tirado-Magallanes, Roberto; Rebbani, Khadija; Lim, Ricky; Pradhan, Sriharsa; Benoukraf, Touati

    2017-01-01

    The combination of DNA bisulfite treatment with high-throughput sequencing technologies has enabled investigation of genome-wide DNA methylation at near base pair level resolution, far beyond that of the kilobase-long canonical CpG islands that initially revealed the biological relevance of this covalent DNA modification. The latest high-resolution studies have revealed a role for very punctual DNA methylation in chromatin plasticity, gene regulation and splicing. Here, we aim to outline the major biological consequences of DNA methylation recently discovered. We also discuss the necessity of tuning DNA methylation resolution into an adequate scale to ease the integration of the methylome information with other chromatin features and transcription events such as gene expression, nucleosome positioning, transcription factors binding dynamic, gene splicing and genomic imprinting. Finally, our review sheds light on DNA methylation heterogeneity in cell population and the different approaches used for its assessment, including the contribution of single cell DNA analysis technology. PMID:27895318

  9. DNA methylation as a universal biomarker

    PubMed Central

    Levenson, Victor V

    2010-01-01

    Cell-free circulating DNA carries not only tumor-specific changes in its sequence but also distinctive epigenetic marks, namely DNA methylation, in certain GC-rich fragments. These fragments are usually located within the promoters and first exons of many genes, comprising CpG islands. Analysis of DNA methylation using cell-free circulating DNA can facilitate development of very accurate biomarkers for detection, diagnosis, prediction of response to therapy and prognosis of outcomes. Recent data suggest that benign and inflammatory diseases have very specific methylation patterns within cell-free circulating DNA, which are different from the pattern of a malignant tumor of the same organ. In addition, specific methylation patterns have been detected for cancers of different organs, so a differential diagnosis of site-specific cancer appears feasible. Currently, cancer-related applications dominate the field, although methylation-based biomarkers may also be possible for other diseases, including neurodegenerative and psychiatric disorders. PMID:20465502

  10. Protein methylation reactions in intact pea chloroplasts

    SciTech Connect

    Niemi, K.J. )

    1989-04-01

    Post-translational protein methylation was investigated in Pisum sativum chloroplasts. Intact pea chloroplasts were incubated with ({sup 3}H-methyl)-S-adenosylmethionine under various conditions. The chloroplasts were then separated into stromal and thylakoid fractions and analyzed for radioactivity transferred to protein. Light enhanced the magnitude of labeling in both fractions. One thylakoid polypeptide with an apparent molecular mass of 43 kDa was labeled only in the light. Several other thylakoid and stromal proteins were labeled in both light and dark-labeling conditions. Both base-labile methylation, carboxy-methylesters and base-stable groups, N-methylations were found. Further characterization of the methyl-transfer reactions will be presented.

  11. Mercury methylation by fish intestinal contents.

    PubMed Central

    Rudd, J W; Furutani, A; Turner, M A

    1980-01-01

    A new radiochemical method has been applied to the examination of mercury methylation in fish intestinal contents. Intestinal contents of six freshwater fish species were found capable of converting 203Hg2+ to CH3203Hg+. This activity was observed in fish from five of six lakes tested whether or not there was mercury pollution. Bacterial activity in the intestinal contents is most likely responsible for this methylation. Methylating activity of piscivors increased with decreasing quantity of intestinal contents. Generally, pike and walleye intestinal contents methylated a larger fraction of 203Hg2+ than those of whitefish and suckers. These data contradict the previous general conclusion that there is no mercury methylation in fish. PMID:7425625

  12. Global Proteomics Analysis of Protein Lysine Methylation

    PubMed Central

    Cao, Xing-Jun; Garcia, Benjamin A.

    2017-01-01

    Lysine methylation is a common protein post-translational modification dynamically mediated by protein lysine methyltransferases (PKMTs) and demethylases (PKDMs). Beyond histone proteins, lysine methylation on non-histone proteins play substantial roles in a variety of functions in cells, and is closely associated with diseases such as cancer. A large body of evidence indicates that the dysregulation of some PKMTs lead to tumorigenesis via their non-histone substrates. However, more studies on other PKMTs have made slow progress owing to the lack of the approaches for extensive screening of lysine methylation sites. Recently a series of publications to perform large-scale analysis of protein lysine methylation have emerged. In this unit, we introduce a protocol for the global analysis of protein lysine methylation in cells by means of immunoaffinity enrichment and mass spectrometry. PMID:27801517

  13. CG methylation in DNA transcription

    NASA Astrophysics Data System (ADS)

    Chela-Flores, J.; Migoni, R. L.

    1990-08-01

    A simple model of DNA is considered in which the nucleotides cytosine (C) and guanine (G) are not assumed to be identical, and in which macroscopic thermodynamic quantities may be calculated exactly. The H bonds between the C and G nucleotides are assumed to be Morse potentials. We discuss the statistical mechanics of the DNA molecule in the configuration (5'...GGG ...3'; 3'...CCC ...5'), which may be copied by RNA polymerase into a messenger RNA (mRNA) strand (5'...CCC ...3'). This model suggests that replacements of C by 5-methylcytosine (5mC) may be a secondary effect in the inhibition of genetic expression, not interfering directly with the formation of an open state. An experimental test is suggested. The implications of this result are discussed for a related system, in which the enzyme methylase is known to methylate almost exclusively those Cs that are followed by Gs as a regulatory strategy employed by some eukaryotes.

  14. Whole-genome DNA methylation profiling using MethylCap-seq.

    PubMed

    Brinkman, Arie B; Simmer, Femke; Ma, Kelong; Kaan, Anita; Zhu, Jingde; Stunnenberg, Hendrik G

    2010-11-01

    MethylCap-seq is a robust procedure for genome-wide profiling of DNA methylation. The approach consists of the capture of methylated DNA using the MBD domain of MeCP2, and subsequent next-generation sequencing of eluted DNA. Elution of the captured methylated DNA is done in steps using a salt gradient, which stratifies the genome into fractions with different CpG density. The enrichment reached within the individual eluates allows for cost-effective deep sequence coverage. The profiles together yield a detailed genome-wide map of methylated regions and readily allows detection of DNA methylation in known and novel regions. Here, we describe principles and details of the MethylCap-seq procedure using different sources of starting material.

  15. DNA methylation profiling using the methylated-CpG island recovery assay (MIRA).

    PubMed

    Rauch, Tibor A; Pfeifer, Gerd P

    2010-11-01

    The methylated-CpG island recovery assay (MIRA) exploits the intrinsic specificity and the high affinity of a methylated-CpG-binding protein complex (MBD2B and MBD3L1) to methylated CpG dinucleotides in genomic DNA. The MIRA approach works on double-stranded DNA and does not depend on the application of methylation-sensitive restriction enzymes. It can be performed on a few hundred nanograms of genomic DNA. Recently, the MIRA technique has been used to profile DNA methylation patterns at a resolution of 100 base pairs along the entire genome of normal human B-lymphocytes. The MIRA method is compatible with microarray and next generation DNA sequencing approaches. We describe the principles and details of this method applied for methylation profiling of genomes containing methylated CpG sequences.

  16. Installation of site-specific methylation into histones using methyl lysine analogs.

    PubMed

    Simon, Matthew D

    2010-04-01

    Chromatin structure is influenced by post-translational modifications on histones, the principal basic protein component of chromatin. In order to study one of these modifications, lysine methylation, in the context of reconstituted chromatin, this unit describes the installation of analogs of methyl lysine residues into recombinant histones. The modification site is specified by mutating the lysine of interest to cysteine. The mutant histones are expressed and purified, and the cysteine residue alkylated to produce N-methyl aminoethylcysteine, an isosteric analog of methyl lysine. Using different alkylating reagents, it is possible to install analogs of mono-, di-, or trimethyl lysine. While these analogs are not identical to methyl lysine residues, they show similar biochemical properties to their natural counterparts. The ease of synthesis of methyl lysine analog (MLA) histones, especially on a large scale, makes them particularly useful reagents for studying the effects of histone lysine methylation on chromatin structure, biophysics and biochemistry. (c) 2010 by John Wiley & Sons, Inc.

  17. Methylation-Sensitive Melt Curve Analysis of the Reprimo Gene Methylation in Gastric Cancer

    PubMed Central

    Lai, Junzhong; Luo, Qianping; Ke, Huican; Chen, Qi

    2016-01-01

    Reprimo (RPRM) is a p53-induced tumor suppressor gene. Its aberrant DNA methylation is correlated with carcinogenesis and may be used as a surrogate marker for the early detection of gastric cancer. However, the detail information regarding its DNA methylation has not been revealed. Here, we investigated the RPRM gene methylation in gastric cancer tumor and plasma samples by methylation-sensitive melt curve analysis (MS-MCA) and bisulfite sequencing in depth. We developed a semi-quantitative method based on MS-MCA for detecting DNA methylation and unraveled the RPRM gene methylation pattern in gastric cancer. This study provides a solid foundation for the future application of detecting RPRM gene methylation in human plasma or serum samples to help diagnose gastric cancer or for prognosis evaluation. PMID:27992600

  18. DNA methylation profiling using the methylated-CpG island recovery assay (MIRA)

    PubMed Central

    Rauch, Tibor A.; Pfeifer, Gerd P.

    2010-01-01

    The methylated-CpG island recovery assay (MIRA) exploits the intrinsic specificity and the high affinity of a methylated CpG-binding protein complex (MBD2B and MBD3L1) to methylated CpG dinucleotides in genomic DNA. The MIRA approach works on double-stranded DNA and does not depend on the application of methylation-sensitive restriction enzymes. It can be performed on a few hundred nanograms of genomic DNA. Recently, the MIRA technique has been used to profile DNA methylation patterns at a resolution of 100 base pairs along the entire genome of normal human B-lymphocytes. The MIRA method is compatible with microarray and next generation DNA sequencing approaches. We describe the principles and details of this method applied for methylation profiling of genomes containing methylated CpG sequences. PMID:20304072

  19. Is the Fungus Magnaporthe Losing DNA Methylation?

    PubMed Central

    Ikeda, Ken-ichi; Van Vu, Ba; Kadotani, Naoki; Tanaka, Masaki; Murata, Toshiki; Shiina, Kohta; Chuma, Izumi; Tosa, Yukio; Nakayashiki, Hitoshi

    2013-01-01

    The long terminal repeat retrotransposon, Magnaporthe gypsy-like element (MAGGY), has been shown to be targeted for cytosine methylation in a subset of Magnaporthe oryzae field isolates. Analysis of the F1 progeny from a genetic cross between methylation-proficient (Br48) and methylation-deficient (GFSI1-7-2) isolates revealed that methylation of the MAGGY element was governed by a single dominant gene. Positional cloning followed by gene disruption and complementation experiments revealed that the responsible gene was the DNA methyltransferase, MoDMT1, an ortholog of Neurospora crassa Dim-2. A survey of MAGGY methylation in 60 Magnaporthe field isolates revealed that 42 isolates from rice, common millet, wheat, finger millet, and buffelgrass were methylation proficient while 18 isolates from foxtail millet, green bristlegrass, Japanese panicgrass, torpedo grass, Guinea grass, and crabgrass were methylation deficient. Phenotypic analyses showed that MoDMT1 plays no major role in development and pathogenicity of the fungus. Quantitative polymerase chain reaction analysis showed that the average copy number of genomic MAGGY elements was not significantly different between methylation-deficient and -proficient field isolates even though the levels of MAGGY transcript were generally higher in the former group. MoDMT1 gene sequences in the methylation-deficient isolates suggested that at least three independent mutations were responsible for the loss of MoDMT1 function. Overall, our data suggest that MoDMT1 is not essential for the natural life cycle of the fungus and raise the possibility that the genus Magnaporthe may be losing the mechanism of DNA methylation on the evolutionary time scale. PMID:23979580

  20. Profiling genome-wide DNA methylation.

    PubMed

    Yong, Wai-Shin; Hsu, Fei-Man; Chen, Pao-Yang

    2016-01-01

    DNA methylation is an epigenetic modification that plays an important role in regulating gene expression and therefore a broad range of biological processes and diseases. DNA methylation is tissue-specific, dynamic, sequence-context-dependent and trans-generationally heritable, and these complex patterns of methylation highlight the significance of profiling DNA methylation to answer biological questions. In this review, we surveyed major methylation assays, along with comparisons and biological examples, to provide an overview of DNA methylation profiling techniques. The advances in microarray and sequencing technologies make genome-wide profiling possible at a single-nucleotide or even a single-cell resolution. These profiling approaches vary in many aspects, such as DNA input, resolution, genomic region coverage, and bioinformatics analysis, and selecting a feasible method requires knowledge of these methods. We first introduce the biological background of DNA methylation and its pattern in plants, animals and fungi. We present an overview of major experimental approaches to profiling genome-wide DNA methylation and hydroxymethylation and then extend to the single-cell methylome. To evaluate these methods, we outline their strengths and weaknesses and perform comparisons across the different platforms. Due to the increasing need to compute high-throughput epigenomic data, we interrogate the computational pipeline for bisulfite sequencing data and also discuss the concept of identifying differentially methylated regions (DMRs). This review summarizes the experimental and computational concepts for profiling genome-wide DNA methylation, followed by biological examples. Overall, this review provides researchers useful guidance for the selection of a profiling method suited to specific research questions.

  1. Copper-catalyzed N-methylation of amides and O-methylation of carboxylic acids by using peroxides as the methylating reagents.

    PubMed

    Xia, Qinqin; Liu, Xiaolong; Zhang, Yuejiao; Chen, Chao; Chen, Wanzhi

    2013-07-05

    The copper-catalyzed N-methylation of amides and O-methylation of carboxylic acids by using peroxides as the methylating reagent are described. Various amides and carboxylic acids were methylated affording N-substituted amides and esters. Tentative mechanistic studies suggest that this reaction is likely to involve a radical process.

  2. Maternal Methyl-Group Donor Intake and Global DNA (Hydroxy)Methylation before and during Pregnancy

    PubMed Central

    Pauwels, Sara; Duca, Radu Corneliu; Devlieger, Roland; Freson, Kathleen; Straetmans, Dany; Van Herck, Erik; Huybrechts, Inge; Koppen, Gurdun; Godderis, Lode

    2016-01-01

    It is still unclear to which extent methyl-group intake during pregnancy can affect maternal global DNA (hydroxyl)methylation. Pregnancy methylation profiling and its link with methyl-group intake in a healthy population could enhance our understanding of the development of pregnancy related disorders. One hundred forty-eight women were enrolled in the MANOE (MAternal Nutrition and Offspring’s Epigenome) study. Thiry-four women were enrolled before pregnancy and 116 during the first trimester of pregnancy. Global DNA (hydroxy)methylation in blood using LC-MS/MS and dietary methyl-group intake (methionine, folate, betaine, and choline) using a food-frequency questionnaire were estimated pre-pregnancy, during each trimester, and at delivery. Global DNA (hydroxy)methylation levels were highest pre-pregnancy and at weeks 18–22 of pregnancy. We observed a positive relation between folic acid and global DNA methylation (p = 0.04) and hydroxymethylation (p = 0.04). A high intake of methionine pre-pregnancy and in the first trimester showed lower (hydroxy)methylation percentage in weeks 11–13 and weeks 18–22, respectively. Choline and betaine intake in the first weeks was negatively associated with hydroxymethylation. Women with a high intake of these three methyl groups in the second and third trimester showed higher hyrdoxymethylation/methylation levels in the third trimester. To conclude, a time trend in DNA (hydroxy)methylation was found and women with higher methyl-group intake showed higher methylation in the third trimester, and not in earlier phases of pregnancy. PMID:27509522

  3. Rice allelopathy induced by methyl jasmonate and methyl salicylate.

    PubMed

    Bi, Hai Hong; Zeng, Ren Sen; Su, Li Ming; An, Min; Luo, Shi Ming

    2007-05-01

    Methyl jasmonate (MeJA) and methyl salicylate (MeSA) are important signaling molecules that induce plant defense against insect herbivores and microbial pathogens. We tested the hypothesis that allelopathy is an inducible defense mechanism, and that the JA and SA signaling pathways may activate allelochemicals release. Exogenous application of MeJA and MeSA to rice (Oryza sativa L.) enhanced rice allelopathic potential and led to accumulation of phenolics, an increase in enzymatic activities, and gene transcription of phenylalanine ammonia-lyase (PAL) and cinnamate 4-hydroxylase (C4H), two key enzymes in the phenylpropanoid pathway. Aqueous extracts of the leaves of rice IAC165, a putative allelopathic variety, treated with MeSA (5 mM) or MeJA (0.05 mM), showed increased inhibitory effects (25 and 21%, respectively) on root growth of barnyardgrass (Echinochloa crus-galli L.), and increased inhibitory effects (18 and 23%, respectively) on shoot growth. Aqueous extracts from leaves of Huajingxian 1 rice, a putative nonallelopathic variety treated with MeJA and MeSA, caused 63 and 24% inhibition of root growth in barnyardgrass seedlings. The root exudates of both IAC165 and Huajingxian 1 plants treated with MeJA and MeSA for 48 hr also showed significant increases in their inhibitory effects on root growth of barnyardgrass seedlings. At the four-leaf stage, levels of 3,4-hydroxybenzoic acid, vanillic acid, coumaric acid, and ferulic acid that accumulated in the leaves were 5.3-, 31.3-, 2.2-, and 1.7-fold higher in response to MeJA exposure, and 3.3-, 13.1-, 2.0-, and 2.2-fold higher in response to MeSA. Treatments of MeSA and MeJA enhanced the PAL activity in the rice leaves up to 52.3 and 80.1%, respectively, whereas C4H activity was increased by 40.2 and 67%. Gene transcription of PAL and C4H in rice leaves significantly increased after the plants were subjected to treatment with MeJA and MeSA. These results suggest that allelopathy may be an active defense

  4. 40 CFR 180.439 - Thifensulfuron methyl; tolerances for residues.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... residues of thifensulfuron methyl, including its metabolites and degradates, in or on the commodities... established for residues of thifensulfuron methyl, including its metabolites and degradates, in or on...

  5. DNA Methylation Signatures of the Plant Chromomethyltransferases

    PubMed Central

    Baulcombe, David C.

    2016-01-01

    DNA methylation in plants is traditionally partitioned into CG, CHG and CHH contexts (with H any nucleotide but G). By investigating DNA methylation patterns in trinucleotide contexts in four angiosperm species, we show that such a representation hides spatial and functional partitioning of different methylation pathways and is incomplete. CG methylation (mCG) is largely context-independent whereas, at CHG motifs, there is under-representation of mCCG in pericentric regions of A. thaliana and tomato and throughout the chromosomes of maize and rice. In A. thaliana the biased representation of mCCG in heterochromatin is related to specificities of H3K9 methyltransferase SUVH family members. At CHH motifs there is an over-representation of different variant forms of mCHH that, similarly to mCCG hypomethylation, is partitioned into the pericentric regions of the two dicots but dispersed in the monocot chromosomes. The over-represented mCHH motifs in A. thaliana associate with specific types of transposon including both class I and II elements. At mCHH the contextual bias is due to the involvement of various chromomethyltransferases whereas the context-independent CHH methylation in A. thaliana and tomato is mediated by the RNA-directed DNA methylation process that is most active in the gene-rich euchromatin. This analysis therefore reveals that the sequence context of the methylome of plant genomes is informative about the mechanisms associated with maintenance of methylation and the overlying chromatin structure. PMID:27997534

  6. DNA Methylation Signatures of the Plant Chromomethyltransferases.

    PubMed

    Gouil, Quentin; Baulcombe, David C

    2016-12-01

    DNA methylation in plants is traditionally partitioned into CG, CHG and CHH contexts (with H any nucleotide but G). By investigating DNA methylation patterns in trinucleotide contexts in four angiosperm species, we show that such a representation hides spatial and functional partitioning of different methylation pathways and is incomplete. CG methylation (mCG) is largely context-independent whereas, at CHG motifs, there is under-representation of mCCG in pericentric regions of A. thaliana and tomato and throughout the chromosomes of maize and rice. In A. thaliana the biased representation of mCCG in heterochromatin is related to specificities of H3K9 methyltransferase SUVH family members. At CHH motifs there is an over-representation of different variant forms of mCHH that, similarly to mCCG hypomethylation, is partitioned into the pericentric regions of the two dicots but dispersed in the monocot chromosomes. The over-represented mCHH motifs in A. thaliana associate with specific types of transposon including both class I and II elements. At mCHH the contextual bias is due to the involvement of various chromomethyltransferases whereas the context-independent CHH methylation in A. thaliana and tomato is mediated by the RNA-directed DNA methylation process that is most active in the gene-rich euchromatin. This analysis therefore reveals that the sequence context of the methylome of plant genomes is informative about the mechanisms associated with maintenance of methylation and the overlying chromatin structure.

  7. Targeting DNA methylation with green tea catechins.

    PubMed

    Yiannakopoulou, Eugenia C

    2015-01-01

    Aberrant epigenetic alterations in the genome such as DNA methylation play a significant role in cancer development. Green tea catechins have been reported to modulate epigenetic processes. This review aims to synthesize evidence on the modulation of DNA methylation by green tea catechins. Green tea catechins have been reported to reverse DNA methylation of tumor suppressor genes and increase transcription of these genes. Green tea catechins and especially epigallocatechin gallate modulate DNA methylation by attenuating the effect of DNA methyltransferase 1 (DNMT1). However, the exact mechanism of DNMT1 inhibition is not delineated. Suggested mechanisms include direct enzymatic inhibition, indirect enzymatic inhibition, reduced DNMT1 expression and translation. The possible effect of green tea catechins on other pathways of DNA methylation, i.e. methyl-CpG binding domain proteins, has not been investigated. Furthermore, the link between redox properties and epigenetic modulation by green tea catechins has not been defined either. Since green tea catechins are natural compounds with a rather acceptable safety profile, further research on their action as inhibitors of DNA methylation seems worthwhile. © 2015 S. Karger AG, Basel

  8. Mercury Methylation by the Methanogen Methanospirillum hungatei

    PubMed Central

    Reinfelder, John R.; Hines, Mark E.

    2013-01-01

    Methylmercury (MeHg), a neurotoxic substance that accumulates in aquatic food chains and poses a risk to human health, is synthesized by anaerobic microorganisms in the environment. To date, mercury (Hg) methylation has been attributed to sulfate- and iron-reducing bacteria (SRB and IRB, respectively). Here we report that a methanogen, Methanospirillum hungatei JF-1, methylated Hg in a sulfide-free medium at comparable rates, but with higher yields, than those observed for some SRB and IRB. Phylogenetic analyses showed that the concatenated orthologs of the Hg methylation proteins HgcA and HgcB from M. hungatei are closely related to those from known SRB and IRB methylators and that they cluster together with proteins from eight other methanogens, suggesting that these methanogens may also methylate Hg. Because all nine methanogens with HgcA and HgcB orthologs belong to the class Methanomicrobia, constituting the late-evolving methanogenic lineage, methanogenic Hg methylation could not be considered an ancient metabolic trait. Our results identify methanogens as a new guild of Hg-methylating microbes with a potentially important role in mineral-poor (sulfate- and iron-limited) anoxic freshwater environments. PMID:23934484

  9. Neurological manifestation of methyl bromide intoxication.

    PubMed

    Suwanlaong, Kanokrat; Phanthumchinda, Kammant

    2008-03-01

    Methyl bromide is a highly toxic gas with poor olfactory warning properties. It is widely used as insecticidal fumigant for dry foodstuffs and can be toxic to central and peripheral nervous systems. Most neurological manifestations of methyl bromide intoxication occur from inhalation. Acute toxicity characterized by headache, dizziness, abdominal pain, nausea, vomiting and visual disturbances. Tremor, convulsion, unconsciousness and permanent brain damage may occur in severe poisoning. Chronic exposure can cause neuropathy, pyramidal and cerebellar dysfunction, as well as neuropsychiatric disturbances. The first case of methyl bromide intoxication in Thailand has been described. The patient was a 24-year-old man who worked in a warehouse of imported vegetables fumigated with methyl bromide. He presented with unstable gait, vertigo and paresthesia of both feet, for two weeks. He had a history of chronic exposure to methyl bromide for three years. His fourteen co-workers also developed the same symptoms but less in severity. Neurological examination revealed ataxic gait, decreased pain and vibratory sense on both feet, impaired cerebellar signs and hyperactive reflex in all extremities. The serum concentration of methyl bromide was 8.18 mg/dl. Electrophysilogical study was normal. Magnetic resonance imaging of the brain (MRI) revealed bilateral symmetrical lesion of abnormal hypersignal intensity on T2 and fluid-attenuation inversion recovery (FLAIR) sequences at bilateral dentate nuclei of cerebellum and periventricular area of the fourth ventricle. This incident stresses the need for improvement of worker education and safety precautions during all stages of methyl bromide fumigation.

  10. DNA methylation in white blood cells

    PubMed Central

    Delgado-Cruzata, Lissette; Vin-Raviv, Neomi; Wu, Hui Chen; Santella, Regina M

    2011-01-01

    Alterations in DNA methylation patterns, both at specific loci and overall in the genome, have been associated with many different health outcomes. In cancer and other diseases, most of these changes have been observed at the tissue level. Data on whether DNA methylation changes in white blood cells (WBC) can serve as a useful biomarker for different health outcomes are much more limited, but rapidly emerging. Epidemiologic studies have reported associations between global WBC methylation and several different cancers including cancers of the colon, bladder, stomach, breast, and head and neck, as well as schizophrenia and myelodysplastic syndrome. Evidence for WBC methylation at specific loci and disease risk is more limited, but increasing. Differences in WBC DNA methylation by selected risk factors including demographic (age, gender, race), environmental exposures (benzene, persistent organic pollutants, lead, arsenic and air pollution), and other risk factors (cigarette smoke, alcohol drinking, body size, physical activity and diet) have been observed in epidemiologic studies though the patterns are far from consistent. Challenges in inferences from the existing data are primarily due to the cross-sectional fashion and small size of most studies performed to date, as well as to the differences in results across assay type and source of DNA. Large, prospective studies will be needed to understand whether changes in risk factors are associated with changes in DNA methylation patterns, and if changes in DNA methylation patterns are associated with changes in disease endpoints. PMID:21636973

  11. Relationship between nucleosome positioning and DNA methylation

    PubMed Central

    Chodavarapu, Ramakrishna K.; Feng, Suhua; Bernatavichute, Yana V.; Chen, Pao-Yang; Stroud, Hume; Yu, Yanchun; Hetzel, Jonathan; Kuo, Frank; Kim, Jin; Cokus, Shawn J.; Casero, David; Bernal, Maria; Huijser, Peter; Clark, Amander T.; Krämer, Ute; Merchant, Sabeeha S.; Zhang, Xiaoyu; Jacobsen, Steven E.; Pellegrini, Matteo

    2010-01-01

    Nucleosomes compact and regulate access to DNA in the nucleus, and are composed of approximately 147 bases of DNA wrapped around a histone octamer1, 2. Here we report a genome-wide nucleosome positioning analysis of Arabidopsis thaliana utilizing massively parallel sequencing of mononucleosomes. By combining this data with profiles of DNA methylation at single base resolution, we identified ten base periodicities in the DNA methylation status of nucleosome-bound DNA and found that nucleosomal DNA was more highly methylated than flanking DNA. These results suggest that nucleosome positioning strongly influences DNA methylation patterning throughout the genome and that DNA methyltransferases preferentially target nucleosome-bound DNA. We also observed similar trends in human nucleosomal DNA suggesting that the relationships between nucleosomes and DNA methyltransferases are conserved. Finally, as has been observed in animals, nucleosomes were highly enriched on exons, and preferentially positioned at intron-exon and exon-intron boundaries. RNA Pol II was also enriched on exons relative to introns, consistent with the hypothesis that nucleosome positioning regulates Pol II processivity. DNA methylation is enriched on exons, consistent with the targeting of DNA methylation to nucleosomes, and suggesting a role for DNA methylation in exon definition. PMID:20512117

  12. Exercise effects on methylation of ASC gene.

    PubMed

    Nakajima, K; Takeoka, M; Mori, M; Hashimoto, S; Sakurai, A; Nose, H; Higuchi, K; Itano, N; Shiohara, M; Oh, T; Taniguchi, S

    2010-09-01

    Chronic moderate exercise has been reported to reduce pro-inflammatory cytokines. To analyze the molecular mechanisms by which training exerts these effects, the epigenetic influences of age and exercise on the ASC gene, which is responsible for IL-1beta and IL-18 secretion, were investigated by ASC gene methylation. Further, the relationship between carcinogenesis and exercise, and methylation of the P15 tumor suppressive gene was also analyzed. High-intensity interval walking exercise, consisting of 3 min low-intensity walking at 40% of peak aerobic capacity followed by a 3 min high-intensity walking period above 70% of peak aerobic capacity, was continued for 6 months. Peripheral blood DNA extracts from young control (n=34), older control (n=153), and older exercise (n=230) groups were then analyzed by pyrosequencing for DNA methylation. Methylation of ASC decreased significantly with age (young control vs. older control, p<0.01), which is indicative of an age-dependent increase in ASC expression. Compared to the older control group, the degree of ASC methylation was higher in the older exercise group (older control vs. older exercise: p<0.01), and presumably lower ASC expression. Neither exercise nor age affected the methylation of the P15. In summary, chronic moderate exercise appears to attenuate the age-dependent decrease in ASC methylation, implying suppression of excess pro-inflammatory cytokines through reduction of ASC expression.

  13. Targeting histone methylation for colorectal cancer

    PubMed Central

    Huang, Tao; Lin, Chengyuan; Zhong, Linda L. D.; Zhao, Ling; Zhang, Ge; Lu, Aiping; Wu, Jiang; Bian, Zhaoxiang

    2016-01-01

    As a leading cause of cancer deaths worldwide, colorectal cancer (CRC) results from accumulation of both genetic and epigenetic alterations. Disruption of epigenetic regulation in CRC, particularly aberrant histone methylation mediated by histone methyltransferases (HMTs) and demethylases (HDMs), have drawn increasing interest in recent years. In this paper, we aim to review the roles of histone methylation and associated enzymes in the pathogenesis of CRC, and the development of small-molecule modulators to regulate histone methylation for treating CRC. Multiple levels of evidence suggest that aberrant histone methylations play important roles in CRC. More than 20 histone-methylation enzymes are found to be clinically relevant to CRC, including 17 oncoproteins and 8 tumor suppressors. Inhibitors of EZH2 and DOT1L have demonstrated promising therapeutic effects in preclinical CRC treatment. Potent and selective chemical probes of histone-methylation enzymes are required for validation of their functional roles in carcinogenesis and clinical translations as CRC therapies. With EZH2 inhibitor EPZ-6438 entering into phase I/II trials for advanced solid tumors, histone methylation is emerging as a promising target for CRC. PMID:28286564

  14. A Feature Selection Algorithm to Compute Gene Centric Methylation from Probe Level Methylation Data

    PubMed Central

    Baur, Brittany; Bozdag, Serdar

    2016-01-01

    DNA methylation is an important epigenetic event that effects gene expression during development and various diseases such as cancer. Understanding the mechanism of action of DNA methylation is important for downstream analysis. In the Illumina Infinium HumanMethylation 450K array, there are tens of probes associated with each gene. Given methylation intensities of all these probes, it is necessary to compute which of these probes are most representative of the gene centric methylation level. In this study, we developed a feature selection algorithm based on sequential forward selection that utilized different classification methods to compute gene centric DNA methylation using probe level DNA methylation data. We compared our algorithm to other feature selection algorithms such as support vector machines with recursive feature elimination, genetic algorithms and ReliefF. We evaluated all methods based on the predictive power of selected probes on their mRNA expression levels and found that a K-Nearest Neighbors classification using the sequential forward selection algorithm performed better than other algorithms based on all metrics. We also observed that transcriptional activities of certain genes were more sensitive to DNA methylation changes than transcriptional activities of other genes. Our algorithm was able to predict the expression of those genes with high accuracy using only DNA methylation data. Our results also showed that those DNA methylation-sensitive genes were enriched in Gene Ontology terms related to the regulation of various biological processes. PMID:26872146

  15. A Feature Selection Algorithm to Compute Gene Centric Methylation from Probe Level Methylation Data.

    PubMed

    Baur, Brittany; Bozdag, Serdar

    2016-01-01

    DNA methylation is an important epigenetic event that effects gene expression during development and various diseases such as cancer. Understanding the mechanism of action of DNA methylation is important for downstream analysis. In the Illumina Infinium HumanMethylation 450K array, there are tens of probes associated with each gene. Given methylation intensities of all these probes, it is necessary to compute which of these probes are most representative of the gene centric methylation level. In this study, we developed a feature selection algorithm based on sequential forward selection that utilized different classification methods to compute gene centric DNA methylation using probe level DNA methylation data. We compared our algorithm to other feature selection algorithms such as support vector machines with recursive feature elimination, genetic algorithms and ReliefF. We evaluated all methods based on the predictive power of selected probes on their mRNA expression levels and found that a K-Nearest Neighbors classification using the sequential forward selection algorithm performed better than other algorithms based on all metrics. We also observed that transcriptional activities of certain genes were more sensitive to DNA methylation changes than transcriptional activities of other genes. Our algorithm was able to predict the expression of those genes with high accuracy using only DNA methylation data. Our results also showed that those DNA methylation-sensitive genes were enriched in Gene Ontology terms related to the regulation of various biological processes.

  16. The MBD7 complex promotes expression of methylated transgenes without significantly altering their methylation status.

    PubMed

    Li, Dongming; Palanca, Ana Marie S; Won, So Youn; Gao, Lei; Feng, Ying; Vashisht, Ajay A; Liu, Li; Zhao, Yuanyuan; Liu, Xigang; Wu, Xiuyun; Li, Shaofang; Le, Brandon; Kim, Yun Ju; Yang, Guodong; Li, Shengben; Liu, Jinyuan; Wohlschlegel, James A; Guo, Hongwei; Mo, Beixin; Chen, Xuemei; Law, Julie A

    2017-04-28

    DNA methylation is associated with gene silencing in eukaryotic organisms. Although pathways controlling the establishment, maintenance and removal of DNA methylation are known, relatively little is understood about how DNA methylation influences gene expression. Here we identified a METHYL-CpG-BINDING DOMAIN 7 (MBD7) complex in Arabidopsis thaliana that suppresses the transcriptional silencing of two LUCIFERASE (LUC) reporters via a mechanism that is largely downstream of DNA methylation. Although mutations in components of the MBD7 complex resulted in modest increases in DNA methylation concomitant with decreased LUC expression, we found that these hyper-methylation and gene expression phenotypes can be genetically uncoupled. This finding, along with genome-wide profiling experiments showing minimal changes in DNA methylation upon disruption of the MBD7 complex, places the MBD7 complex amongst a small number of factors acting downstream of DNA methylation. This complex, however, is unique as it functions to suppress, rather than enforce, DNA methylation-mediated gene silencing.

  17. A genetic sensor for strong methylating compounds

    PubMed Central

    Moser, Felix; Horwitz, Andrew; Chen, Jacinto; Lim, Wendell A.; Voigt, Christopher A.

    2013-01-01

    Methylating chemicals are common in industry and agriculture and are often toxic, partly due to their propensity to methylate DNA. The Escherichia coli Ada protein detects methylating compounds by sensing aberrant methyl adducts on the phosphoester backbone of DNA. We characterize this system as a genetic sensor and engineer it to lower the detection threshold. By overexpressing Ada from a plasmid, we improve the sensor’s dynamic range to 350-fold induction and lower its detection threshold to 40 µM for methyl iodide. In eukaryotes, there is no known sensor of methyl adducts on the phosphoester backbone of DNA. By fusing the N-terminal domain of Ada to the Gal4 transcriptional activation domain, we built a functional sensor for methyl phosphotriester adducts in Saccharomyces cerevisiae. This sensor can be tuned to variable specifications by altering the expression level of the chimeric sensor and changing the number of Ada operators upstream of the Gal4-sensitive reporter promoter. These changes result in a detection threshold of 28 µM and 5.2-fold induction in response to methyl iodide. When the yeast sensor is exposed to different SN1 and SN2 alkylating compounds, its response profile is similar to that observed for the native Ada protein in E. coli, indicating that its native function is retained in yeast. Finally, we demonstrate that the specifications achieved for the yeast sensor are suitable for detecting methylating compounds at relevant concentrations in environmental samples. This work demonstrates the movement of a sensor from a prokaryotic to eukaryotic system and its rational tuning to achieve desired specifications. PMID:24032656

  18. Cellular uptake, subcellular distribution and toxicity of arsenic compounds in methylating and non-methylating cells.

    PubMed

    Dopp, E; von Recklinghausen, U; Diaz-Bone, R; Hirner, A V; Rettenmeier, A W

    2010-07-01

    Arsenic is a known human carcinogen, inducing tumors of the skin, urinary bladder, liver and lung. Inorganic arsenic, existing in highly toxic trivalent and significantly less toxic pentavalent forms, is methylated to mono- and di-methylated species mainly in the liver. Due to the low toxicity of pentavalent methylated species, methylation has been regarded as a detoxification process for many years; however, recent findings of a high toxicity of trivalent methylated species have indicated the contrary. In order to elucidate the role of speciation and methylation for the toxicity and carcinogenicity of arsenic, systematic studies were conducted comparing cellular uptake, subcellular distribution as well as toxic and genotoxic effects of organic and inorganic pentavalent and trivalent arsenic species in both non-methylating (urothelial cells and fibroblasts) and methylating cells (hepatocytes). The membrane permeability was found to be dependent upon both the arsenic species and the cell type. Uptake rates of trivalent methylated species were highest and exceeded those of their pentavalent counterparts by several orders of magnitude. Non-methylating cells (urothelial cells and fibroblasts) seem to accumulate higher amounts of arsenic within the cell than the methylating hepatocytes. Cellular uptake and extrusion seem to be faster in hepatocytes than in urothelial cells. The correlation of uptake with toxicity indicates a significant role of membrane permeability towards toxicity. Furthermore, cytotoxic effects are more distinct in hepatocytes. Differential centrifugation studies revealed that elevated concentrations of arsenic are present in the ribosomal fraction of urothelial cells and in nucleic and mitochondrial fractions of hepatic cells. Further studies are needed to define the implications of the observed enrichment of arsenic in specific cellular organelles for its carcinogenic activity. This review summarizes our recent research on cellular uptake

  19. Sunflower oil methyl ester as diesel fuel

    SciTech Connect

    Hassett, D.J.; Hasan, R.A.

    1982-01-01

    Methyl ester formation represents one approach to overcome the problems associated with the relatively high viscosity of sunflower oil when used as a diesel fuel replacement. Sunflower oil methyl ester is being prepared at the University of North Dakota Engieering Experiment Station. Physical and chemical properties of this material at varying levels of refinement and purity will be used to define fuel properties. Engine testing is being carried out to determine if the fouling characteristics of methyl ester are significantly less than those of sunflower oil. 1 figure, 1 table.

  20. Conformations and Barriers to Methyl Group Internal Rotation in Two Asymmetric Ethers: Propyl Methyl Ether and Butyl Methyl Ether

    NASA Astrophysics Data System (ADS)

    Long, B. E.; Dechirico, F.; Cooke, S. A.

    2012-06-01

    The conformational preferences of the O-C-C-C unit are important in many biological systems with the unit generally preferring a gauche configuration compared to an anti configuration. Butyl methyl ether and propyl methyl ether provide very simple systems for this phenomenom to manifest. Pure rotational spectra of the title molecules have been recorded using chirped pulse Fourier transform microwave spectroscopy (CP-FTMW). In the case of butyl methyl ether, only one conformer has been observed. This conformer has torsional angles of COCC = 180°, OCCC = 62° and CCCC = 180° (anti-gauche-anti) and rotational constants of A = 10259.4591(33) MHz, B = 1445.6470(13) MHz, and C = 1356.2944(14) MHz. The rotational spectrum was doubled and has been analyzed to produce an effective barrier to methyl group internal rotation of 780(35) cm-1. A prior rotational spectroscopic study on propyl methyl ether had focused only on the high energy anti-anti conformer. We have analyzed spectra from the lowest energy anti-gauche conformer and the spectroscopic constants will be presented. A summary of the differences in conformational energies and methyl group internal rotation barriers for the class of aliphatic asymmetric ethers will be presented. K. N. Houk, J. E. Eksterowicz, Y.-D. Wu, C. D. Fuglesang, D. B. Mitchell. J. Am. Chem. Soc. 115 (4170), 1993. Hiroshi Kato, Jun Nakagawa, Michiro Hayashi. J. Mol. Spectrosc. 80 (272), 1980.

  1. Method of uranium reclamation from aqueous systems by reactive ion exchange. [US DOE patent application; anion exchange resin of copolymerized divinyl-benzene and styrene having quarternary ammonium groups and bicarbonate ligands

    DOEpatents

    Maya, L.

    1981-11-05

    A reactive ion exchange method for separation and recovery of values of uranium, neptunium, plutonium, or americium from substantially neutral aqueous systems of said metals comprises contacting said system with an effective amount of a basic anion exchange resin of copolymerized divinyl-benzene and styrene having quarternary ammonium groups and bicarbonate ligands to achieve nearly 100% sorption of said actinyl ion onto said resin and an aqueous system practically free of said actinyl ions. The method is operational over an extensive range of concentrations from about 10/sup -6/ M to 1.0 M actinyl ion and a pH range of about 4 to 7. The method has particulr application to treatment of waste streams from Purex-type nuclear fuel reprocessing facilities and hydrometallurgical processes involving U, Np, P, or Am.

  2. Bis(imino)diphenylamido rare-earth metal dialkyl complexes: synthesis, structure, and catalytic activity in living ring-opening ε-caprolactone polymerization and copolymerization with γ-butyrolactone.

    PubMed

    Du, Gaixia; Wei, Yanling; Zhang, Wei; Dong, Yuping; Lin, Zhengguo; He, Huan; Zhang, Shaowen; Li, Xiaofang

    2013-01-28

    Bis(imino)diphenylamido rare-earth metal dialkyl complexes [o-(2,6-(i)Pr(2)-C(6)H(3)-N=C-C(6)H(4))(2)-N]Ln(CH(2)SiMe(3))(2) (1: Ln = Sc; 2: Ln = Lu; 3: Ln = Y) have been synthesized in good yields and structurally characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray diffraction studies. They serve as highly efficient single-component catalysts both for the living ring-opening ε-caprolactone polymerization and random copolymerization with γ-butyrolactone, with the activity being dependent on the steric hindrance around the metal center, yielding high molecular weight PCLs or P(CL-co-BL)s with narrow molecular weight distributions.

  3. A new statistical approach to detecting differentially methylated loci for case control Illumina array methylation data.

    PubMed

    Chen, Zhongxue; Liu, Qingzhong; Nadarajah, Saralees

    2012-04-15

    As an epigenetic alteration, DNA methylation plays an important role in epigenetic controls of gene transcription. Recent advances in genome-wide scan of DNA methylation provide great opportunities in studying the impact of DNA methylation on many human diseases including various types of cancer. Due to the unique feature of this type of data, applicable statistical methods are limited and new sophisticated approaches are desirable. In this article, we propose a new statistical test to detect differentially methylated loci for case control methylation data generated by Illumina arrays. This new method utilizes the important finding that DNA methylation is highly correlated with age. The proposed method estimates the overall P-value by combining the P-values from independent individual tests each for one age group. Through real data application and simulation study, we show that the proposed test is robust and usually more powerful than other methods.

  4. Studies on in vitro S-methylation of naturally occurring thiol compounds with N-methyl-N-nitrosourea and methyl methanesulfonate

    SciTech Connect

    Trezl, L.; Park, K.S.; Kim, S.; Paik, W.K.

    1987-08-01

    N-Methyl-N-nitrosourea (MNU) and methyl methanesulfonate (MMS) were found to rapidly methylate glutathione (GSH) in vitro yielding S-methyl glutathione, as verified and quantitated by high-performance liquid chromatography and thin-layer chromatography. Formation of S-methylcysteine in the acid-hydrolyzate of the methylated GSH further confirmed the formation of S-methyl glutathione. Other naturally occurring thiol compounds such as cystein and homocysteine were also methylated by MNU. The observed pH dependency of GSH methylation by MNU suggests that the sulfide anion form of the thiol may represent the favored methyl acceptor. The high reactivity of GSH toward MNU and MMS may be of biological significance in that it could compete with macromolecular cellular components as a target for alkylation.

  5. 21 CFR 175.360 - Vinylidene chloride copolymer coatings for nylon film.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... vinylidene chloride copolymers produced by copolymerizing vinylidene chloride with methyl methacrylate and/or 2-sulfoethyl methacrylate, or with methyl methacrylate and/or 2-sulfoethyl methacrylate...

  6. 21 CFR 175.360 - Vinylidene chloride copolymer coatings for nylon film.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... vinylidene chloride copolymers produced by copolymerizing vinylidene chloride with methyl methacrylate and/or 2-sulfoethyl methacrylate, or with methyl methacrylate and/or 2-sulfoethyl methacrylate...

  7. Evaluating genome-wide DNA methylation changes in mice by Methylation Specific Digital Karyotyping

    PubMed Central

    Boon, Kathy; Tomfohr, John K; Bailey, Nathaniel W; Garantziotis, Stavros; Li, Zhuowei; Brass, David M; Maruoka, Shuichiro; Hollingsworth, John W; Schwartz, David A

    2008-01-01

    Background The study of genome-wide DNA methylation changes has become more accessible with the development of various array-based technologies though when studying species other than human the choice of applications are limited and not always within reach. In this study, we adapted and tested the applicability of Methylation Specific Digital Karyotyping (MSDK), a non-array based method, for the prospective analysis of epigenetic changes after perinatal nutritional modifications in a mouse model of allergic airway disease. MSDK is a sequenced based method that allows a comprehensive and unbiased methylation profiling. The method generates 21 base pairs long sequence tags derived from specific locations in the genome. The resulting tag frequencies determine in a quantitative manner the methylation level of the corresponding loci. Results Genomic DNA from whole lung was isolated and subjected to MSDK analysis using the methylation-sensitive enzyme Not I as the mapping enzyme and Nla III as the fragmenting enzyme. In a pair wise comparison of the generated mouse MSDK libraries we identified 158 loci that are significantly differentially methylated (P-value = 0.05) after perinatal dietary changes in our mouse model. Quantitative methylation specific PCR and sequence analysis of bisulfate modified genomic DNA confirmed changes in methylation at specific loci. Differences in genomic MSDK tag counts for a selected set of genes, correlated well with changes in transcription levels as measured by real-time PCR. Furthermore serial analysis of gene expression profiling demonstrated a dramatic difference in expressed transcripts in mice exposed to perinatal nutritional changes. Conclusion The genome-wide methylation survey applied in this study allowed for an unbiased methylation profiling revealing subtle changes in DNA methylation in mice maternally exposed to dietary changes in methyl-donor content. The MSDK method is applicable for mouse models of complex human diseases in

  8. A systematic comparison of quantitative high-resolution DNA methylation analysis and methylation-specific PCR

    PubMed Central

    Claus, Rainer; Wilop, Stefan; Hielscher, Thomas; Sonnet, Miriam; Dahl, Edgar; Galm, Oliver; Jost, Edgar; Plass, Christoph

    2012-01-01

    Assessment of DNA methylation has become a critical factor for the identification, development and application of methylation based biomarkers. Here we describe a systematic comparison of a quantitative high-resolution mass spectrometry-based approach (MassARRAY), pyrosequencing and the broadly used methylation-specific PCR (MSP) technique analyzing clinically relevant epigenetically silenced genes in acute myeloid leukemia (AML). By MassARRAY and pyrosequencing, we identified significant DNA methylation differences at the ID4 gene promoter and in the 5′ region of members of the SFRP gene family in 62 AML patients compared with healthy controls. We found a good correlation between data obtained by MassARRAY and pyrosequencing (correlation coefficient R2 = 0.88). MSP-based assessment of the identical samples showed less pronounced differences between AML patients and controls. By direct comparison of MSP-derived and MassARRAY-based methylation data as well as pyrosequencing, we could determine overestimation of DNA methylation data by MSP. We found sequence-context dependent highly variable cut-off values of quantitative DNA methylation values serving as discriminator for the two MSP methylation categories. Moreover, good agreements between quantitative methods and MSP could not be achieved for all investigated loci. Significant correlation of the quantitative assessment but not of MSP-derived methylation data with clinically important characteristics in our patient cohort demonstrated clinical relevance of quantitative DNA methylation assessment. Taken together, while MSP is still the most commonly applied technique for DNA methylation assessment, our data highlight advantages of quantitative approaches for precise characterization and reliable biomarker use of aberrant DNA methylation in primary patient samples, particularly. PMID:22647397

  9. Differential methylation of chloroplast DNA regulates maternal inheritance in a methylated mutant of Chlamydomonas

    PubMed Central

    Sager, Ruth; Grabowy, Constance

    1983-01-01

    In Chlamydomonas, the maternal inheritance of chloroplast genes correlates with the differential methylation of chloroplast DNA (chlDNA) in females (mt+) but not in males (mt-). Our previous studies have supported our methylation-restriction model in which the maternal transmission is accounted for by the differential methylation in gametes which protects female but not male chlDNA from degradation during zygote formation. In the mutant me-1 [Bolen, P. L., Grant, D. M., Swinton, D., Boynton, J. E. & Gillham, N. W. (1982) Cell 28, 335-343], chlDNA of vegetative cells of both mating types is heavily methylated even before gametogenesis; nonetheless, maternal inheritance occurs in mutants as in wild type. To investigate the mechanism of maternal inheritance in the me-1 mutant, we have compared restriction fragment patterns after agarose gel electrophoresis of chlDNAs from mutant vegetative cells and gametes with those from wild type, by using a set of 32 restriction enzymes of which 17 were methylation-sensitive in this system. We find that additional methylation occurs during gametogenesis in the mutant female (mt+) but not in the corresponding male (mt-). Thus, gamete-specific, mating-type-specific methylation occurs in the me-1 mutant as in the wild type, consistent with our methylation-restriction model. In the me-1 mutant, gametic methylation occurs on a background of vegetative cell methylation not present in wild-type cells and irrelevant to the regulation of chloroplast inheritance. Comparison of the me-1 mutation with the mat-1 mutation [Sager, R., Grabowy, C. & Sano, H. (1981) Cell 24, 41-47] provides evidence for the existence of two different chlDNA methylation control systems: mat-1, linked to the mating type locus and regulating the mating-type-specific methylation that correlates with maternal inheritance, and me-1, unlinked to the mating type locus and unrelated to the regulation of maternal inheritance. Images PMID:16593314

  10. Methylation of hemoglobin to enhance flocculant performance

    USDA-ARS?s Scientific Manuscript database

    An inexpensive bioflocculant, bovine hemoglobin (Hb), has been covalently modified through methylation of the side chain carboxyl groups of aspartic and glutamic acid residues to improve its flocculation activity. Potentiometric titration of the recovered products showed approximately 28% degree of ...

  11. Methyl Ethyl Ketoxime; Final Test Rule

    EPA Pesticide Factsheets

    EPA is issuing this final test rule under section 4 of the Toxic Substances Control Act (TSCA), requiring manufacturers and processors of methyl ethyl ketoxime (MEKO, CAS No. 96-29-7) to perform testing for health effects.

  12. Histone lysine methylation and chromatin replication.

    PubMed

    Rivera, Carlos; Gurard-Levin, Zachary A; Almouzni, Geneviève; Loyola, Alejandra

    2014-12-01

    In eukaryotic organisms, the replication of the DNA sequence and its organization into chromatin are critical to maintain genome integrity. Chromatin components, such as histone variants and histone post-translational modifications, along with the higher-order chromatin structure, impact several DNA metabolic processes, including replication, transcription, and repair. In this review we focus on lysine methylation and the relationships between this histone mark and chromatin replication. We first describe studies implicating lysine methylation in regulating early steps in the replication process. We then discuss chromatin reassembly following replication fork passage, where the incorporation of a combination of newly synthesized histones and parental histones can impact the inheritance of lysine methylation marks on the daughter strands. Finally, we elaborate on how the inheritance of lysine methylation can impact maintenance of the chromatin landscape, using heterochromatin as a model chromatin domain, and we discuss the potential mechanisms involved in this process.

  13. Emission of methyl bromide from biomass burning

    SciTech Connect

    Manoe, S.; Andreae, M.O. )

    1994-03-04

    Bromine is, per atom, far more efficient than chlorine in destroying stratospheric ozone, and methyl bromide is the single largest source of stratospheric bromine. The two main previously known sources of this compound are emissions from the ocean and from the compound's use as an agricultural pesticide. Laboratory biomass combustion experiments showed that methyl bromide was emitted in the smoke from various fuels tested. Methyl bromide was also found in smoke plumes from wildfires in savannas, chaparral, and boreal forest. Global emissions of methyl bromide from biomass burning are estimated to be in the range of 10 to 50 gigagrams per year, which is comparable to the amount produced by ocean emission and pesticide use and represents a major contribution ([approximately]30 percent) to the stratospheric bromine budget.

  14. Incorporating DNA Methylation Dynamics Into Epigenetic Codes

    PubMed Central

    Szulwach, Keith E.; Jin, Peng

    2014-01-01

    Summary Genomic function is dictated by a combination of DNA sequence and the molecular mechanisms controlling access to genetic information. Access to DNA can be determined by the interpretation of covalent modifications that influence the packaging of DNA into chromatin, including DNA methylation and histone modifications. These modifications are believed to be forms of “epigenetic codes” that exist in discernable combinations that reflect cellular phenotype. Although DNA methylation is known to play important roles in gene regulation and genomic function, its contribution to the encoding of epigenetic information is just beginning to emerge. Here we discuss paradigms associated with the various components of DNA methylation/demethylation and recent advances in the understanding of its dynamic regulation in the genome, integrating these mechanisms into a framework to explain how DNA methylation could contribute to epigenetic codes. PMID:24242211

  15. Chirped Pulse Microwave Spectroscopy on Methyl Butanoate

    NASA Astrophysics Data System (ADS)

    Hernandez-Castillo, Alicia O.; Hays, Brian M.; Abeysekera, Chamara; Zwier, Timothy S.

    2016-06-01

    The microwave spectrum of methyl butanoate has been taken from 8-18 GHz using a chirped pulse spectrometer. This molecule is a model biofuel, and its thermal decomposition products are of interest due to its many dissociation channels. As a preliminary step before such pyrolysis studies, we have examined the jet cooled spectrum of methyl butanoate in a chirped pulse spectrometer, which shows a very rich spectrum. Several conformers have been identified, each with tunneling splittings in the methyl ester group due to internal rotation. These spectra have been fit to obtain rotational constants, relative populations, and methyl rotor barriers for each conformational isomer. The results of these studies are compared to high level calculations.

  16. Degradation of methyl bromide in anaerobic sediments

    USGS Publications Warehouse

    Oremland, R.S.; Miller, L.G.; Strohmaler, F.E.

    1994-01-01

    Methyl bromide (MeBr) was anaerobically degraded in saltmarsh sediments after reaction with sulfide. The product of this nucleophilic substitution reaction was methanethiol, which underwent further chemical and bacterial reactions to form dimethyl sulfide. These two gases appeared transiently during sediment incubations because they were metabolized by methanogenic and sulfate-reducing bacteria. A second, less significant reaction of MeBr was the exchange with chloride, forming methyl chloride, which was also susceptible to attack by sulfide. Incubation of 14C-labeled methyl iodide as an analogue of MeBr resulted in the formation of 14CH4 and 14CO2 and also indicated that sulfate-reducing bacteria as well as methanogens metabolized the methylated sulfur intermediates. These results suggest that exposed sediments with abundant free sulfide, such as coastal salt-marshes, may constitute a sink for atmospheric MeBr.

  17. Genomic targeting of methylated DNA: influence of methylation on transcription, replication, chromatin structure, and histone acetylation.

    PubMed

    Schübeler, D; Lorincz, M C; Cimbora, D M; Telling, A; Feng, Y Q; Bouhassira, E E; Groudine, M

    2000-12-01

    We have developed a strategy to introduce in vitro-methylated DNA into defined chromosomal locations. Using this system, we examined the effects of methylation on transcription, chromatin structure, histone acetylation, and replication timing by targeting methylated and unmethylated constructs to marked genomic sites. At two sites, which support stable expression from an unmethylated enhancer-reporter construct, introduction of an in vitro-methylated but otherwise identical construct results in specific changes in transgene conformation and activity, including loss of the promoter DNase I-hypersensitive site, localized hypoacetylation of histones H3 and H4 within the reporter gene, and a block to transcriptional initiation. Insertion of methylated constructs does not alter the early replication timing of the loci and does not result in de novo methylation of flanking genomic sequences. Methylation at the promoter and gene is stable over time, as is the repression of transcription. Surprisingly, sequences within the enhancer are demethylated, the hypersensitive site forms, and the enhancer is hyperacetylated. Nevertheless, the enhancer is unable to activate the methylated and hypoacetylated reporter. Our findings suggest that CpG methylation represses transcription by interfering with RNA polymerase initiation via a mechanism that involves localized histone deacetylation. This repression is dominant over a remodeled enhancer but neither results in nor requires region-wide changes in DNA replication or chromatin structure.

  18. Genomic Targeting of Methylated DNA: Influence of Methylation on Transcription, Replication, Chromatin Structure, and Histone Acetylation

    PubMed Central

    Schübeler, Dirk; Lorincz, Matthew C.; Cimbora, Daniel M.; Telling, Agnes; Feng, Yong-Quing; Bouhassira, Eric E.; Groudine, Mark

    2000-01-01

    We have developed a strategy to introduce in vitro-methylated DNA into defined chromosomal locations. Using this system, we examined the effects of methylation on transcription, chromatin structure, histone acetylation, and replication timing by targeting methylated and unmethylated constructs to marked genomic sites. At two sites, which support stable expression from an unmethylated enhancer-reporter construct, introduction of an in vitro-methylated but otherwise identical construct results in specific changes in transgene conformation and activity, including loss of the promoter DNase I-hypersensitive site, localized hypoacetylation of histones H3 and H4 within the reporter gene, and a block to transcriptional initiation. Insertion of methylated constructs does not alter the early replication timing of the loci and does not result in de novo methylation of flanking genomic sequences. Methylation at the promoter and gene is stable over time, as is the repression of transcription. Surprisingly, sequences within the enhancer are demethylated, the hypersensitive site forms, and the enhancer is hyperacetylated. Nevertheless, the enhancer is unable to activate the methylated and hypoacetylated reporter. Our findings suggest that CpG methylation represses transcription by interfering with RNA polymerase initiation via a mechanism that involves localized histone deacetylation. This repression is dominant over a remodeled enhancer but neither results in nor requires region-wide changes in DNA replication or chromatin structure. PMID:11094062

  19. DNA Methylation and BMI: Investigating Identified Methylation Sites at HIF3A in a Causal Framework

    PubMed Central

    Richmond, Rebecca C.; Ward, Mary E.; Fraser, Abigail; Lyttleton, Oliver; McArdle, Wendy L.; Ring, Susan M.; Gaunt, Tom R.; Lawlor, Debbie A.; Davey Smith, George; Relton, Caroline L.

    2016-01-01

    Multiple differentially methylated sites and regions associated with adiposity have now been identified in large-scale cross-sectional studies. We tested for replication of associations between previously identified CpG sites at HIF3A and adiposity in ∼1,000 mother-offspring pairs from the Avon Longitudinal Study of Parents and Children (ALSPAC). Availability of methylation and adiposity measures at multiple time points, as well as genetic data, allowed us to assess the temporal associations between adiposity and methylation and to make inferences regarding causality and directionality. Overall, our results were discordant with those expected if HIF3A methylation has a causal effect on BMI and provided more evidence for causality in the reverse direction (i.e., an effect of BMI on HIF3A methylation). These results are based on robust evidence from longitudinal analyses and were also partially supported by Mendelian randomization analysis, although this latter analysis was underpowered to detect a causal effect of BMI on HIF3A methylation. Our results also highlight an apparent long-lasting intergenerational influence of maternal BMI on offspring methylation at this locus, which may confound associations between own adiposity and HIF3A methylation. Further work is required to replicate and uncover the mechanisms underlying the direct and intergenerational effect of adiposity on DNA methylation. PMID:26861784

  20. DNA Methylation Profiling Reveals Correlation of Differential Methylation Patterns with Gene Expression in Human Epilepsy.

    PubMed

    Wang, Liang; Fu, Xinwei; Peng, Xi; Xiao, Zheng; Li, Zhonggui; Chen, Guojun; Wang, Xuefeng

    2016-05-01

    DNA methylation plays important roles in regulating gene expression and has been reported to be related with epilepsy. This study aimed to define differential DNA methylation patterns in drug-refractory epilepsy patients and to investigate the role of DNA methylation in human epilepsy. We performed DNA methylation profiling in brain tissues from epileptic and control patients via methylated-cytosine DNA immunoprecipitation microarray chip. Differentially methylated loci were validated by bisulfite sequencing PCR, and the messenger RNA (mRNA) levels of candidate genes were evaluated by reverse transcriptase PCR. We found 224 genes that showed differential DNA methylation between epileptic patients and controls. Among the seven candidate genes, three genes (TUBB2B, ATPGD1, and HTR6) showed relative transcriptional regulation by DNA methylation. TUBB2B and ATPGD1 exhibited hypermethylation and decreased mRNA levels, whereas HTR6 displayed hypomethylation and increased mRNA levels in the epileptic samples. Our findings suggest that certain genes become differentially regulated by DNA methylation in human epilepsy.

  1. Function and Evolution of DNA Methylation in Nasonia vitripennis

    PubMed Central

    Wang, Xu; Wheeler, David; Avery, Amanda; Rago, Alfredo; Choi, Jeong-Hyeon; Colbourne, John K.; Clark, Andrew G.; Werren, John H.

    2013-01-01

    The parasitoid wasp Nasonia vitripennis is an emerging genetic model for functional analysis of DNA methylation. Here, we characterize genome-wide methylation at a base-pair resolution, and compare these results to gene expression across five developmental stages and to methylation patterns reported in other insects. An accurate assessment of DNA methylation across the genome is accomplished using bisulfite sequencing of adult females from a highly inbred line. One-third of genes show extensive methylation over the gene body, yet methylated DNA is not found in non-coding regions and rarely in transposons. Methylated genes occur in small clusters across the genome. Methylation demarcates exon-intron boundaries, with elevated levels over exons, primarily in the 5′ regions of genes. It is also elevated near the sites of translational initiation and termination, with reduced levels in 5′ and 3′ UTRs. Methylated genes have higher median expression levels and lower expression variation across development stages than non-methylated genes. There is no difference in frequency of differential splicing between methylated and non-methylated genes, and as yet no established role for methylation in regulating alternative splicing in Nasonia. Phylogenetic comparisons indicate that many genes maintain methylation status across long evolutionary time scales. Nasonia methylated genes are more likely to be conserved in insects, but even those that are not conserved show broader expression across development than comparable non-methylated genes. Finally, examination of duplicated genes shows that those paralogs that have lost methylation in the Nasonia lineage following gene duplication evolve more rapidly, show decreased median expression levels, and increased specialization in expression across development. Methylation of Nasonia genes signals constitutive transcription across developmental stages, whereas non-methylated genes show more dynamic developmental expression

  2. 21 CFR 173.385 - Sodium methyl sulfate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... pectin by sulfuric acid and methyl alcohol and subsequent treatment with sodium bicarbonate. (b) It does... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium methyl sulfate. 173.385 Section 173.385... CONSUMPTION Specific Usage Additives § 173.385 Sodium methyl sulfate. Sodium methyl sulfate may be present in...

  3. 21 CFR 173.250 - Methyl alcohol residues.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Methyl alcohol residues. 173.250 Section 173.250... and Related Substances § 173.250 Methyl alcohol residues. Methyl alcohol may be present in the... specifies the presence of methyl alcohol and provides for the use of the hops extract only as prescribed...

  4. 21 CFR 173.385 - Sodium methyl sulfate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... pectin by sulfuric acid and methyl alcohol and subsequent treatment with sodium bicarbonate. (b) It does... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium methyl sulfate. 173.385 Section 173.385... CONSUMPTION Specific Usage Additives § 173.385 Sodium methyl sulfate. Sodium methyl sulfate may be present...

  5. 21 CFR 173.385 - Sodium methyl sulfate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... pectin by sulfuric acid and methyl alcohol and subsequent treatment with sodium bicarbonate. (b) It does... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium methyl sulfate. 173.385 Section 173.385... CONSUMPTION Specific Usage Additives § 173.385 Sodium methyl sulfate. Sodium methyl sulfate may be present...

  6. 21 CFR 173.385 - Sodium methyl sulfate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... sulfuric acid and methyl alcohol and subsequent treatment with sodium bicarbonate. (b) It does not exceed 0... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium methyl sulfate. 173.385 Section 173.385 Food... Specific Usage Additives § 173.385 Sodium methyl sulfate. Sodium methyl sulfate may be present in pectin...

  7. DNA methylation abnormalities in congenital heart disease.

    PubMed

    Serra-Juhé, Clara; Cuscó, Ivon; Homs, Aïda; Flores, Raquel; Torán, Núria; Pérez-Jurado, Luis A

    2015-01-01

    Congenital heart defects represent the most common malformation at birth, occurring also in ∼50% of individuals with Down syndrome. Congenital heart defects are thought to have multifactorial etiology, but the main causes are largely unknown. We have explored the global methylation profile of fetal heart DNA in comparison to blood DNA from control subjects: an absolute correlation with the type of tissue was detected. Pathway analysis revealed a significant enrichment of differential methylation at genes related to muscle contraction and cardiomyopathies in the developing heart DNA. We have also searched for abnormal methylation profiles on developing heart-tissue DNA of syndromic and non-syndromic congenital heart defects. On average, 3 regions with aberrant methylation were detected per sample and 18 regions were found differentially methylated between groups. Several epimutations were detected in candidate genes involved in growth regulation, apoptosis and folate pathway. A likely pathogenic hypermethylation of several intragenic sites at the MSX1 gene, involved in outflow tract morphogenesis, was found in a fetus with isolated heart malformation. In addition, hypermethylation of the GATA4 gene was present in fetuses with Down syndrome with or without congenital heart defects, as well as in fetuses with isolated heart malformations. Expression deregulation of the abnormally methylated genes was detected. Our data indicate that epigenetic alterations of relevant genes are present in developing heart DNA in fetuses with both isolated and syndromic heart malformations. These epimutations likely contribute to the pathogenesis of the malformation by cis-acting effects on gene expression.

  8. DNA methylation and application in forensic sciences.

    PubMed

    Kader, Farzeen; Ghai, Meenu

    2015-04-01

    DNA methylation of cytosine residues is a stable epigenetic alteration, beginning as early as foetal development in the uterus and continuously evolving throughout life. DNA methylation as well as other epigenetic modifications such as chromatin remodelling and histone modifications are indispensable in mammalian development. Methylation is to a large extent influenced by the ageing process, diets and lifestyle choices. Our understanding of this crucial modification may even contribute to the treatment and prevention of age-related illnesses in the very near future. Genome-wide methylation analysis using high throughput DNA technologies has discovered numerous differentially methylated regions (tDMRs) which differ in levels of methylation in various cell types and tissues. TDMRs have been useful in various applications, particularly medicine and forensic sciences. Forensic scientists are constantly seeking exciting and novel methods to aid in the reconstruction of crime scenes, and the analysis of tDMRs represents a new and reliable technique to identify biological fluids and tissues found at the scene of a violent act. Not only has research been able to unequivocally identify various fluids and tissues, but methods to determine the sex, age and phenotype of donors has been developed. New tDMRs in genes are being searched for consistently to serve as novel markers in forensic DNA analysis.

  9. DNA Methylation Biomarkers: Cancer and Beyond

    PubMed Central

    Mikeska, Thomas; Craig, Jeffrey M.

    2014-01-01

    Biomarkers are naturally-occurring characteristics by which a particular pathological process or disease can be identified or monitored. They can reflect past environmental exposures, predict disease onset or course, or determine a patient’s response to therapy. Epigenetic changes are such characteristics, with most epigenetic biomarkers discovered to date based on the epigenetic mark of DNA methylation. Many tissue types are suitable for the discovery of DNA methylation biomarkers including cell-based samples such as blood and tumor material and cell-free DNA samples such as plasma. DNA methylation biomarkers with diagnostic, prognostic and predictive power are already in clinical trials or in a clinical setting for cancer. Outside cancer, strong evidence that complex disease originates in early life is opening up exciting new avenues for the detection of DNA methylation biomarkers for adverse early life environment and for estimation of future disease risk. However, there are a number of limitations to overcome before such biomarkers reach the clinic. Nevertheless, DNA methylation biomarkers have great potential to contribute to personalized medicine throughout life. We review the current state of play for DNA methylation biomarkers, discuss the barriers that must be crossed on the way to implementation in a clinical setting, and predict their future use for human disease. PMID:25229548

  10. Aberrant DNA Methylation and Prostate Cancer

    PubMed Central

    Majumdar, Sunipa; Buckles, Eric; Estrada, John; Koochekpour, Shahriar

    2011-01-01

    Prostate cancer (PCa) is the most prevalent cancer, a significant contributor to morbidity and a leading cause of cancer-related death in men in Western industrialized countries. In contrast to genetic changes that vary among individual cases, somatic epigenetic alterations are early and highly consistent events. Epigenetics encompasses several different phenomena, such as DNA methylation, histone modifications, RNA interference, and genomic imprinting. Epigenetic processes regulate gene expression and can change malignancy-associated phenotypes such as growth, migration, invasion, or angiogenesis. Methylations of certain genes are associated with PCa progression. Compared to normal prostate tissues, several hypermethylated genes have also been identified in benign prostate hyperplasia, which suggests a role for aberrant methylation in this growth dysfunction. Global and gene-specific DNA methylation could be affected by environmental and dietary factors. Among other epigenetic changes, aberrant DNA methylation might have a great potential as diagnostic or prognostic marker for PCa and could be tested in tumor tissues and various body fluids (e.g., serum, urine). The DNA methylation markers are simple in nature, have high sensitivity, and could be detected either quantitatively or qualitatively. Availability of genome-wide screening methodologies also allows the identification of epigenetic signatures in high throughput population studies. Unlike irreversible genetic changes, epigenetic alterations are reversible and could be used for PCa targeted therapies. PMID:22547956

  11. DNA methylation biomarkers: cancer and beyond.

    PubMed

    Mikeska, Thomas; Craig, Jeffrey M

    2014-09-16

    Biomarkers are naturally-occurring characteristics by which a particular pathological process or disease can be identified or monitored. They can reflect past environmental exposures, predict disease onset or course, or determine a patient's response to therapy. Epigenetic changes are such characteristics, with most epigenetic biomarkers discovered to date based on the epigenetic mark of DNA methylation. Many tissue types are suitable for the discovery of DNA methylation biomarkers including cell-based samples such as blood and tumor material and cell-free DNA samples such as plasma. DNA methylation biomarkers with diagnostic, prognostic and predictive power are already in clinical trials or in a clinical setting for cancer. Outside cancer, strong evidence that complex disease originates in early life is opening up exciting new avenues for the detection of DNA methylation biomarkers for adverse early life environment and for estimation of future disease risk. However, there are a number of limitations to overcome before such biomarkers reach the clinic. Nevertheless, DNA methylation biomarkers have great potential to contribute to personalized medicine throughout life. We review the current state of play for DNA methylation biomarkers, discuss the barriers that must be crossed on the way to implementation in a clinical setting, and predict their future use for human disease.

  12. Methylated spirit burns: an ongoing problem.

    PubMed

    Jansbeken, J R H; Vloemans, A F P M; Tempelman, F R H; Breederveld, R S

    2012-09-01

    Despite many educational campaigns we still see burns caused by methylated spirit every year. We undertook a retrospective study to analyse the impact of this problem. We retrospectively collected data of all patients with burns caused by methylated spirit over twelve years from 1996 to 2008. Our main endpoints were: incidence, age, mechanism of injury, total body surface area (TBSA) burned, burn depth, need for surgery and length of hospital stay. Ninety-seven patients with methylated spirit burns were included. During the study period there was no decrease in the number of patients annually admitted to the burn unit with methylated spirit burns. 28% of the patients (n=27) were younger than eighteen years old, 15% (n=15) were ten years old or younger. The most common cause of burns was carelessness in activities involving barbecues, campfires and fondues. Mean TBSA burned was 16% (SD 12.4). 70% (n=68) had full thickness burns. 66% (n=64) needed grafting. Mean length of hospital stay was 23 days (SD 24.7). The use of methylated spirit is an ongoing problem, which continues to cause severe burns in adults and children. Therefore methylated spirit should be banned in households. We suggest sale only in specialised shops, clear labelling and mandatory warnings. Copyright © 2012 Elsevier Ltd and ISBI. All rights reserved.

  13. Poly(butyl methacrylate-g-methoxypoly(ethylene glycol)) and poly(methyl methacrylate-g-methoxypoly(ethylene glycol)) graft copolymers: preparation and aqueous solution properties.

    PubMed

    Horgan, Adrian; Saunders, Brian; Vincent, Brian; Heenan, Richard K

    2003-06-15

    A series of water-soluble, amphiphilic graft copolymers has been prepared by free-radical copolymerization of methoxypoly(ethylene glycol) macromonomers, with either methyl methacrylate or butyl methacrylate as the comonomers, in water/ethanol solvent mixtures. Lower molecular weight copolymers were obtained by increasing the concentration of the initiator, azobisisobutyronitrile (AIBN), used in the polymerization reaction. However, the route used also led to the formation of significant quantities of tetramethylsuccinodinitrile, a toxic byproduct resulting from the cage reaction of AIBN. Static fluorescence measurements using pyrene as a probe, along with 1H NMR experiments, showed that the graft copolymers form aggregates in water at very low concentrations (approximately 0.01 g l(-1)) with the pendant hydrophilic graft chains forming a stabilizing shell around the hydrophobic backbone. An increase in the hydrophile-lipophile balance of the graft copolymers was found to lead to smaller aggregates with lower aggregation numbers and highly swollen hydrophilic shells, as revealed by small angle neutron scattering (SANS).

  14. 40 CFR 721.10326 - 2-Propenoic acid, 2-methyl-, methyl ester, polymer with butyl 2-propenoate, ethyl 2-propenoate...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... ester, polymer with butyl 2-propenoate, ethyl 2-propenoate, zinc 2-methyl-2-propenoate (1:2) and zinc 2... 2-Propenoic acid, 2-methyl-, methyl ester, polymer with butyl 2-propenoate, ethyl 2-propenoate, zinc 2-methyl-2-propenoate (1:2) and zinc 2-propenoate (1:2), 2,2'-(1,2-diazenediyl)bis - and 2,2'-(1,2...

  15. Cytosine methylation at CpCpG sites triggers accumulation of non-CpG methylation in gene bodies

    PubMed Central

    Prischi, Filippo

    2017-01-01

    Abstract Methylation of cytosine is an epigenetic mark involved in the regulation of transcription, usually associated with transcriptional repression. In mammals, methylated cytosines are found predominantly in CpGs but in plants non-CpG methylation (in the CpHpG or CpHpH contexts, where H is A, C or T) is also present and is associated with the transcriptional silencing of transposable elements. In addition, CpG methylation is found in coding regions of active genes. In the absence of the demethylase of lysine 9 of histone 3 (IBM1), a subset of body-methylated genes acquires non-CpG methylation. This was shown to alter their expression and affect plant development. It is not clear why only certain body-methylated genes gain non-CpG methylation in the absence of IBM1 and others do not. Here we describe a link between CpG methylation and the establishment of methylation in the CpHpG context that explains the two classes of body-methylated genes. We provide evidence that external cytosines of CpCpG sites can only be methylated when internal cytosines are methylated. CpCpG sites methylated in both cytosines promote spreading of methylation in the CpHpG context in genes protected by IBM1. In contrast, CpCpG sites remain unmethylated in IBM1-independent genes and do not promote spread of CpHpG methylation. PMID:28053115

  16. Efficient acquisition of high-resolution 4-D diagonal-suppressed methyl-methyl NOESY for large proteins

    NASA Astrophysics Data System (ADS)

    Wen, Jie; Zhou, Pei; Wu, Jihui

    2012-05-01

    The methyl-methyl NOESY experiment plays an important role in determining the global folds of large proteins. Despite the high sensitivity of this experiment, the analysis of methyl-methyl NOEs is frequently hindered by the limited chemical shift dispersion of methyl groups, particularly methyl protons. This makes it difficult to unambiguously assign all of the methyl-methyl NOE crosspeaks using 3-D spectroscopy. The recent development of sparse sampling methods enables highly efficient acquisition of high-resolution 4-D spectra, which provides an excellent solution to resolving the degeneracy of methyl signals. However, many reconstruction algorithms for processing sparsely-sampled NMR data do not provide adequate suppression of aliasing artifacts in the presence of strong NOE diagonal signals. In order to overcome this limitation, we present a 4-D diagonal-suppressed methyl-methyl NOESY experiment specifically optimized for ultrasparse sampling and evaluate it using a deuterated, ILV methyl-protonated sample of the 42 kDa Escherichia coli maltose binding protein (MBP). Suppression of diagonal signals removes the dynamic range barrier of the methyl-methyl NOESY experiment such that residual aliasing artifacts in the CLEAN-reconstructed high-resolution 4-D spectrum can be further reduced. At an ultrasparse sampling rate of less than 1%, we were able to identify and unambiguously assign the vast majority of expected NOE crosspeaks between methyl groups separated by less than 5 Å and to detect very weak NOE crosspeaks from methyl groups that are over 7 Å apart.

  17. Methylating agents and DNA repair responses: methylated bases and sources of strand breaks

    PubMed Central

    Wyatt, Michael D.; Pittman, Douglas L.

    2008-01-01

    The chemical methylating agents methylmethane sulfonate (MMS) and N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) have been used for decades as classical DNA damaging agents. These agents have been utilized to uncover and explore pathways of DNA repair, DNA damage response, and mutagenesis. MMS and MNNG modify DNA by adding methyl groups to a number of nucleophilic sites on the DNA bases, although MNNG produces a greater percentage of O-methyl adducts. There has been substantial progress elucidating direct reversal proteins that remove methyl groups and base excision repair (BER), which removes and replaces methylated bases. Direct reversal proteins and BER thus counteract the toxic, mutagenic and clastogenic effects of methylating agents. Despite recent progress, the complexity of DNA damage responses to methylating agents is still being discovered. In particular, there is growing understanding of pathways such as homologous recombination, lesion bypass, and mismatch repair that react when the response of direct reversal proteins and BER is insufficient. Furthermore, the importance of proper balance within the steps in BER has been uncovered with the knowledge that DNA structural intermediates during BER are deleterious. A number of issues complicate elucidating the downstream responses when direct reversal is insufficient or BER is imbalanced. These include inter-species differences, cell-type specific differences within mammals and between cancer cell lines, and the type of methyl damage or BER intermediate encountered. MMS also carries a misleading reputation of being a ‘radiomimetic,’ i.e., capable of directly producing strand breaks. This review focuses on the DNA methyl damage caused by MMS and MNNG for each site of potential methylation to summarize what is known about the repair of such damage and the downstream responses and consequences if not repaired. PMID:17173371

  18. Methyl-CpG-binding domain sequencing reveals a prognostic methylation signature in neuroblastoma.

    PubMed

    Decock, Anneleen; Ongenaert, Maté; Cannoodt, Robrecht; Verniers, Kimberly; De Wilde, Bram; Laureys, Geneviève; Van Roy, Nadine; Berbegall, Ana P; Bienertova-Vasku, Julie; Bown, Nick; Clément, Nathalie; Combaret, Valérie; Haber, Michelle; Hoyoux, Claire; Murray, Jayne; Noguera, Rosa; Pierron, Gaelle; Schleiermacher, Gudrun; Schulte, Johannes H; Stallings, Ray L; Tweddle, Deborah A; De Preter, Katleen; Speleman, Frank; Vandesompele, Jo

    2016-01-12

    Accurate assessment of neuroblastoma outcome prediction remains challenging. Therefore, this study aims at establishing novel prognostic tumor DNA methylation biomarkers. In total, 396 low- and high-risk primary tumors were analyzed, of which 87 were profiled using methyl-CpG-binding domain (MBD) sequencing for differential methylation analysis between prognostic patient groups. Subsequently, methylation-specific PCR (MSP) assays were developed for 78 top-ranking differentially methylated regions and tested on two independent cohorts of 132 and 177 samples, respectively. Further, a new statistical framework was used to identify a robust set of MSP assays of which the methylation score (i.e. the percentage of methylated assays) allows accurate outcome prediction. Survival analyses were performed on the individual target level, as well as on the combined multimarker signature. As a result of the differential DNA methylation assessment by MBD sequencing, 58 of the 78 MSP assays were designed in regions previously unexplored in neuroblastoma, and 36 are located in non-promoter or non-coding regions. In total, 5 individual MSP assays (located in CCDC177, NXPH1, lnc-MRPL3-2, lnc-TREX1-1 and one on a region from chromosome 8 with no further annotation) predict event-free survival and 4 additional assays (located in SPRED3, TNFAIP2, NPM2 and CYYR1) also predict overall survival. Furthermore, a robust 58-marker methylation signature predicting overall and event-free survival was established. In conclusion, this study encompasses the largest DNA methylation biomarker study in neuroblastoma so far. We identified and independently validated several novel prognostic biomarkers, as well as a prognostic 58-marker methylation signature.

  19. Methyl-CpG-binding domain sequencing reveals a prognostic methylation signature in neuroblastoma

    PubMed Central

    Decock, Anneleen; Ongenaert, Maté; Cannoodt, Robrecht; Verniers, Kimberly; De Wilde, Bram; Laureys, Geneviève; Van Roy, Nadine; Berbegall, Ana P.; Bienertova-Vasku, Julie; Bown, Nick; Clément, Nathalie; Combaret, Valérie; Haber, Michelle; Hoyoux, Claire; Murray, Jayne; Noguera, Rosa; Pierron, Gaelle; Schleiermacher, Gudrun; Schulte, Johannes H.; Stallings, Ray L.; Tweddle, Deborah A.; De Preter, Katleen; Speleman, Frank; Vandesompele, Jo

    2016-01-01

    Accurate assessment of neuroblastoma outcome prediction remains challenging. Therefore, this study aims at establishing novel prognostic tumor DNA methylation biomarkers. In total, 396 low- and high-risk primary tumors were analyzed, of which 87 were profiled using methyl-CpG-binding domain (MBD) sequencing for differential methylation analysis between prognostic patient groups. Subsequently, methylation-specific PCR (MSP) assays were developed for 78 top-ranking differentially methylated regions and tested on two independent cohorts of 132 and 177 samples, respectively. Further, a new statistical framework was used to identify a robust set of MSP assays of which the methylation score (i.e. the percentage of methylated assays) allows accurate outcome prediction. Survival analyses were performed on the individual target level, as well as on the combined multimarker signature. As a result of the differential DNA methylation assessment by MBD sequencing, 58 of the 78 MSP assays were designed in regions previously unexplored in neuroblastoma, and 36 are located in non-promoter or non-coding regions. In total, 5 individual MSP assays (located in CCDC177, NXPH1, lnc-MRPL3-2, lnc-TREX1-1 and one on a region from chromosome 8 with no further annotation) predict event-free survival and 4 additional assays (located in SPRED3, TNFAIP2, NPM2 and CYYR1) also predict overall survival. Furthermore, a robust 58-marker methylation signature predicting overall and event-free survival was established. In conclusion, this study encompasses the largest DNA methylation biomarker study in neuroblastoma so far. We identified and independently validated several novel prognostic biomarkers, as well as a prognostic 58-marker methylation signature. PMID:26646589

  20. Site-specific methylated reporter constructs for functional analysis of DNA methylation.

    PubMed

    Han, Weiguo; Shi, Miao; Spivack, Simon D

    2013-11-01

    Methods to experimentally alter and functionally evaluate cytosine methylation in a site-specific manner have proven elusive. We describe a site-specific DNA methylation method, using synthetically methylated primers and high fidelity PCR coupled with ligation of reporter constructs. We applied this method to introduce methylated cytosines into fragments of the respective DAPK and RASSF1A promoters that had been cloned into luciferase reporters. We found that methylation of 3-7 residue CpG clusters that were 5' adjacent to the transcription start site (TSS) of the DAPK gene produced up to a 54% decrease in promoter activity (p<0.01). Similarly, for RASSF1A promoter reporter constructs, the methylation of either of two clusters of four CpGs each, but not an intervening cluster, produced a 63% decrease in promoter activity (p<0.01), suggesting that precise mCpG position is crucial, and factors other than simple proximity to the TSS are at play. Chromatin immunoprecipitation analysis of these reporter constructs demonstrated that transcription factor Oct-1 and Sp1 preferentially bound the unmethylated vs. methylated DAPK or RASSF1A promoter reporter constructs at the functional CpG sites. Histone H1, hnRNP1, and MeCP2 showed preferential binding to methylated sequence at functional sites in these reporter constructs, as well as highly preferential (> 8-80-fold) binding to native methylated vs. unmethylated chromatin. These results suggest that: (1) site-specific, precision DNA methylation of a reporter construct can be used for functional analysis of commonly observed gene promoter methylation patterns; (2) the reporter system contains key elements of the endogenous chromatin machinery.

  1. DNA methylation profiling of esophageal adenocarcinoma using Methylation Ligation-dependent Macroarray (MLM).

    PubMed

    Guilleret, Isabelle; Losi, Lorena; Chelbi, Sonia T; Fonda, Sergio; Bougel, Stéphanie; Saponaro, Sara; Gozzi, Gaia; Alberti, Loredana; Braunschweig, Richard; Benhattar, Jean

    2016-10-14

    Most types of cancer cells are characterized by aberrant methylation of promoter genes. In this study, we described a rapid, reproducible, and relatively inexpensive approach allowing the detection of multiple human methylated promoter genes from many tissue samples, without the need of bisulfite conversion. The Methylation Ligation-dependent Macroarray (MLM), an array-based analysis, was designed in order to measure methylation levels of 58 genes previously described as putative biomarkers of cancer. The performance of the design was proven by screening the methylation profile of DNA from esophageal cell lines, as well as microdissected formalin-fixed and paraffin-embedded (FFPE) tissues from esophageal adenocarcinoma (EAC). Using the MLM approach, we identified 32 (55%) hypermethylated promoters in EAC, and not or rarely methylated in normal tissues. Among them, 21promoters were found aberrantly methylated in more than half of tumors. Moreover, seven of them (ADAMTS18, APC, DKK2, FOXL2, GPX3, TIMP3 and WIF1) were found aberrantly methylated in all or almost all the tumor samples, suggesting an important role for these genes in EAC. In addition, dysregulation of the Wnt pathway with hypermethylation of several Wnt antagonist genes was frequently observed. MLM revealed a homogeneous pattern of methylation for a majority of tumors which were associated with an advanced stage at presentation and a poor prognosis. Interestingly, the few tumors presenting less methylation changes had a lower pathological stage. In conclusion, this study demonstrated the feasibility and accuracy of MLM for DNA methylation profiling of FFPE tissue samples. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. DNA methylation during differentiation of a lower eukaryote, Physarum polycephalum.

    PubMed

    Fronk, J; Magiera, R

    1994-11-15

    Starvation-induced differentiation of the slime mould Physarum polycephalum is accompanied by continuous methylation of DNA. No stable changes in the overall level of DNA methylation are evident, but a gene known to be transcribed specifically during differentiation is subject to increased methylation. Inhibitors of DNA methylation preclude differentiation of P. polycephalum, although they are only marginally inhibitory to normal growth. Taken together these results indicate that methylation of DNA is involved in differentiation of this lower eukaryote.

  3. Measurement of Mercury Methylation in Lake Water and Sediment Samples

    PubMed Central

    Furutani, Akira; Rudd, John W. M.

    1980-01-01

    Biological mercury methylation was assayed by a new radiochemical technique in the water column and sediments of a mercury-contaminated lake. In 24 weeks during 1979, there were three episodes of methylating activity in surface floc and in water, each lasting 3 to 5 weeks. Periods of methylation in the water column coincided with surface sediment methylation and appeared to be related to overall microbial activity. Mercury was actively methylated in the presence of bound sulfide. PMID:16345649

  4. Methylation interactions in Arabidopsis hybrids require RNA-directed DNA methylation and are influenced by genetic variation

    PubMed Central

    Zhang, Qingzhu; Wang, Dong; Lang, Zhaobo; He, Li; Yang, Lan; Zeng, Liang; Li, Yanqiang; Zhao, Cheng; Huang, Huan; Zhang, Heng; Zhang, Huiming; Zhu, Jian-Kang

    2016-01-01

    DNA methylation is a conserved epigenetic mark in plants and many animals. How parental alleles interact in progeny to influence the epigenome is poorly understood. We analyzed the DNA methylomes of Arabidopsis Col and C24 ecotypes, and their hybrid progeny. Hybrids displayed nonadditive DNA methylation levels, termed methylation interactions, throughout the genome. Approximately 2,500 methylation interactions occurred at regions where parental DNA methylation levels are similar, whereas almost 1,000 were at differentially methylated regions in parents. Methylation interactions were characterized by an abundance of 24-nt small interfering RNAs. Furthermore, dysfunction of the RNA-directed DNA methylation pathway abolished methylation interactions but did not affect the increased biomass observed in hybrid progeny. Methylation interactions correlated with altered genetic variation within the genome, suggesting that they may play a role in genome evolution. PMID:27382183

  5. Elucidating the pathway for arsenic methylation.

    PubMed

    Thomas, David J; Waters, Stephen B; Styblo, Miroslav

    2004-08-01

    Although biomethylation of arsenic has been studied for more than a century, unequivocal demonstration of the methylation of inorganic arsenic by humans occurred only about 30 years ago. Because methylation of inorganic arsenic activates it to more reactive and toxic forms, elucidating the pathway for the methylation of this metalloid is a topic of considerable importance. Understanding arsenic metabolism is of public health concern as millions of people chronically consume drinking water that contains high concentrations of inorganic arsenic. Hence, the focus of our research has been to elucidate the molecular basis of the steps in the pathway that leads from inorganic arsenic to methylated and dimethylated arsenicals. Here we describe a new S-adenosylmethionine (AdoMet)-dependent methyltransferase from rat liver cytosol that catalyzes the conversion of arsenite to methylated and dimethylated species. This 42-kDa protein has sequence motifs common to many non-nucleic acid methyltransferases and is closely related to methyltransferases of previously unknown function that have been identified by conceptual translations of cyt19 genes of mouse and human genomes. Hence, we designate rat liver arsenic methyltransferase as cyt19 and suggest that orthologous cyt19 genes encode an arsenic methyltransferase in the mouse and human genomes. Our studies with recombinant rat cyt19 find that, in the presence of an exogenous or a physiological reductant, this protein can catalyze the entire sequence of reactions that convert arsenite to methylated metabolites. A scheme linking cyt19 and thioredoxin-thioredoxin reductase in the methylation and reduction of arsenicals is proposed.

  6. High-Throughput Analysis of Global DNA Methylation Using Methyl-Sensitive Digestion

    PubMed Central

    Feinweber, Carmen; Knothe, Claudia; Lötsch, Jörn; Thomas, Dominique; Geisslinger, Gerd; Parnham, Michael J.; Resch, Eduard

    2016-01-01

    DNA methylation is a major regulatory process of gene transcription, and aberrant DNA methylation is associated with various diseases including cancer. Many compounds have been reported to modify DNA methylation states. Despite increasing interest in the clinical application of drugs with epigenetic effects, and the use of diagnostic markers for genome-wide hypomethylation in cancer, large-scale screening systems to measure the effects of drugs on DNA methylation are limited. In this study, we improved the previously established fluorescence polarization-based global DNA methylation assay so that it is more suitable for application to human genomic DNA. Our methyl-sensitive fluorescence polarization (MSFP) assay was highly repeatable (inter-assay coefficient of variation = 1.5%) and accurate (r2 = 0.99). According to signal linearity, only 50–80 ng human genomic DNA per reaction was necessary for the 384-well format. MSFP is a simple, rapid approach as all biochemical reactions and final detection can be performed in one well in a 384-well plate without purification steps in less than 3.5 hours. Furthermore, we demonstrated a significant correlation between MSFP and the LINE-1 pyrosequencing assay, a widely used global DNA methylation assay. MSFP can be applied for the pre-screening of compounds that influence global DNA methylation states and also for the diagnosis of certain types of cancer. PMID:27749902

  7. Methyl N-phenyl carbamate synthesis from aniline and methyl formate: carbon recycling to chemical products.

    PubMed

    Yalfani, Mohammad S; Lolli, Giulio; Müller, Thomas E; Wolf, Aurel; Mleczko, Leslaw

    2015-02-01

    Methyl N-phenyl carbamate was synthesized from aniline by using methyl formate as a green and efficient carbonylating agent. High yields were obtained at milder reaction conditions compared to the conventional CO/CH3 OH route. Studies on the reaction sequence led to suggest an alternative and more efficient route to the carbamate via formanilide as intermediate.

  8. Evidence for methyl group transfer between the methyl-accepting chemotaxis proteins in Bacillus subtilis

    SciTech Connect

    Bedale, W.A.; Nettleton, D.O.; Sopata, C.S.; Thoelke, M.S.; Ordal, G.W.

    1988-01-01

    The authors present evidence for methyl (as methyl or methoxy) transfer from the methyl-accepting chemotaxis proteins H1 and possibly H3 of Bacillus subtilis to the methyl-accepting chemotaxis protein H2. This methyl transfer, which has been observed in vitro was strongly stimulated by the chemoattractant aspartate and thus may plan an important role in the sensory processing system of this organism. Although radiolabeling of H1 and H3 began at once after the addition of (/sup 3/H) methionine, radiolabeling of H2 showed a lag. Furthermore, the addition of excess nonradioactive methionine caused immediate exponential delabeling of H1 and H3 while labeling of H2 continued to increase. Methylation of H2 required the chemotactic methyltransferase, probably to first methylate H1 and H3. Aspartate caused increased labeling of H2 and strongly decreased labeling of H1 and H3 after the addition of nonradioactive methionine. Without the addition of nonradioactive methionine, aspartate caused demethylation of H1 and to a lesser extent H3, with an approximately equal increase of methylation of H2.

  9. GSH2 promoter methylation in pancreatic cancer analyzed by quantitative methylation-specific polymerase chain reaction

    PubMed Central

    GAO, FEI; HUANG, HAO-JIE; GAO, JUN; LI, ZHAO-SHEN; MA, SHU-REN

    2015-01-01

    Tumor suppressor gene silencing via promoter hypermethylation is an important event in pancreatic cancer pathogenesis. Aberrant DNA hypermethylation events are highly tumor specific, and may provide a diagnostic tool for pancreatic cancer patients. The objective of the current study was to identify novel methylation-related genes that may potentially be used to establish novel therapeutic and diagnostic strategies against pancreatic cancer. The methylation status of the GS homeobox 2 (GSH2) gene was analyzed using the sodium bisulfite sequencing method. The GSH2 methylation ratio was examined in primary carcinomas and corresponding normal tissues derived from 47 patients with pancreatic cancer, using quantitative methylation-specific polymerase chain reaction. Methylation ratios were found to be associated with the patient's clinicopathological features. GSH2 gene methylation was detected in 26 (55.3%) of the 47 pancreatic cancer patients, indicating that it occurs frequently in pancreatic cancer. A significant association with methylation was observed for tumor-node-metastasis stage (P=0.031). GSH2 may be a novel methylation-sensitive tumor suppressor gene in pancreatic cancer and may be a tumor-specific biomarker of the disease. PMID:26171036

  10. High-Throughput Analysis of Global DNA Methylation Using Methyl-Sensitive Digestion.

    PubMed

    Shiratori, Hiromi; Feinweber, Carmen; Knothe, Claudia; Lötsch, Jörn; Thomas, Dominique; Geisslinger, Gerd; Parnham, Michael J; Resch, Eduard

    2016-01-01

    DNA methylation is a major regulatory process of gene transcription, and aberrant DNA methylation is associated with various diseases including cancer. Many compounds have been reported to modify DNA methylation states. Despite increasing interest in the clinical application of drugs with epigenetic effects, and the use of diagnostic markers for genome-wide hypomethylation in cancer, large-scale screening systems to measure the effects of drugs on DNA methylation are limited. In this study, we improved the previously established fluorescence polarization-based global DNA methylation assay so that it is more suitable for application to human genomic DNA. Our methyl-sensitive fluorescence polarization (MSFP) assay was highly repeatable (inter-assay coefficient of variation = 1.5%) and accurate (r2 = 0.99). According to signal linearity, only 50-80 ng human genomic DNA per reaction was necessary for the 384-well format. MSFP is a simple, rapid approach as all biochemical reactions and final detection can be performed in one well in a 384-well plate without purification steps in less than 3.5 hours. Furthermore, we demonstrated a significant correlation between MSFP and the LINE-1 pyrosequencing assay, a widely used global DNA methylation assay. MSFP can be applied for the pre-screening of compounds that influence global DNA methylation states and also for the diagnosis of certain types of cancer.

  11. Methyl esters from vegetable oils with hydroxy fatty acids: Comparison of lesquerella and castor methyl esters

    USDA-ARS?s Scientific Manuscript database

    The search for alternative feedstocks for biodiesel as partial replacement for petrodiesel has recently extended to castor oil. In this work, the castor oil methyl esters were prepared and their properties determined in comparison to the methyl esters of lesquerella oil, which in turn is seen as alt...

  12. Evidence for methyl group transfer between the methyl-accepting chemotaxis proteins in Bacillus subtilis.

    PubMed Central

    Bedale, W A; Nettleton, D O; Sopata, C S; Thoelke, M S; Ordal, G W

    1988-01-01

    We present evidence for methyl (as methyl or methoxy) transfer from the methyl-accepting chemotaxis proteins H1 and possibly H3 of Bacillus subtilis to the methyl-accepting chemotaxis protein H2. This methyl transfer, which has been observed in vitro (D. J. Goldman and G. W. Ordal, Biochemistry 23:2600-2606, 1984), was strongly stimulated by the chemoattractant aspartate and thus may play an important role in the sensory processing system of this organism. Although radiolabeling of H1 and H3 began at once after the addition of [3H]methionine, radiolabeling of H2 showed a lag. Furthermore, the addition of excess nonradioactive methionine caused immediate exponential delabeling of H1 and H3 while labeling of H2 continued to increase. Methylation of H2 required the chemotactic methyltransferase, probably to first methylate H1 and H3. Aspartate caused increased labeling of H2 and strongly decreased labeling of H1 and H3 after the addition of nonradioactive methionine. Without the addition of nonradioactive methionine, aspartate caused demethylation of H1 and to a lesser extent H3, with an approximately equal increase of methylation of H2. Images PMID:3121584

  13. Properties of radiation cured vinyl-divinyl copolymers. Part I. Thermomechanical properties of crosslinked methyl methacrylate polymers

    SciTech Connect

    Micko, M.M.; Paszner, L.

    1980-01-01

    Radiation copolymerization (crosslinking) of methyl methacrylate (MMA) with a series of divinyl monomers containing 1 to 4 ethyleneglycol connecting units between the terminal reactive divinyl units was found to provide numerous improvements in the thermomechanical properties of the copolymers. Thermoplastic poly-MMA was converted to a thermoset copolymer with only small additions (2 to 5%) of the divinyl crosslinking agent. When the measured thermomechanical properties (glass transition temperature, Tg, thermal distortion temperature, TDT; and thermomechanical deformation degree, TDD) of the above crosslinked copolymers were related to the respective crosslink densities (expressed by the copolymer connection number, CN/sub co/) the crosslink efficiency increased in terms of the above parameters in a reverse order as observed for acceleration, i.e., TEGDMA < TrEGDMA < DEGDMA < EGDMA. This observation is readily explained by the relation between segmental mobility of the respective macromolecules of the copolymers formed and the critical thermomechanical parameters which can be determined for such solid copolymers. Segmental mobility of the crosslinking agent increases with increasing molecular bridge length and hence the increased temperature sensitivity of the copolymers to thermal softening and distortion as the bridge length increases from a single ethyleneglycol (EGDMA) to four ethyleneglycol (TEGDMA) units in the bridge connecting the vinyl functions of the divinyl monomers. For all copolymers of this study, the linear thermomechanical deformation coefficient, representing thermal deformation between the plastic and rubbery states, remained relatively constant across a broad temperature interval until the respective TDT temperatures are reached, and decreased exponentially with the divinyl monomer concentration in the copolymer regardless of the connecting bridge length.

  14. Methylation matters? Decreased methylation status of genomic DNA in the blood of schizophrenic twins.

    PubMed

    Bönsch, Dominikus; Wunschel, Michael; Lenz, Bernd; Janssen, Gesa; Weisbrod, Matthias; Sauer, Heinrich

    2012-08-15

    Studies of schizophrenia inheritance in identical twins show a concordance of about 50%, which supports an epigenetic model. In our present study we investigated methylation of genomic DNA and promoter methylation of Reelin and SOX10 genes in peripheral blood of twins suffering from schizophrenia. Global DNA methylation was reduced (52.3%) in schizophrenic twins if compared with healthy control twins (65.7%). The reduced methylation was significant in males only. We also found a similar hypomethylation in the non-affected twins of discordant pairs and a mixed group of psychiatric controls. In discordant twins there was a relative hypermethylation of the SOX10 promoter. Within-pair-difference of methylation of Reelin promoter was significantly lower in monozygotic twins than in dizygotic twins.

  15. The effect of paternal methyl-group donor intake on offspring DNA methylation and birth weight.

    PubMed

    Pauwels, S; Truijen, I; Ghosh, M; Duca, R C; Langie, S A S; Bekaert, B; Freson, K; Huybrechts, I; Koppen, G; Devlieger, R; Godderis, L

    2017-03-06

    Most nutritional studies on the development of children focus on mother-infant interactions. Maternal nutrition is critically involved in the growth and development of the fetus, but what about the father? The aim is to investigate the effects of paternal methyl-group donor intake (methionine, folate, betaine, choline) on paternal and offspring global DNA (hydroxy)methylation, offspring IGF2 DMR DNA methylation, and birth weight. Questionnaires, 7-day estimated dietary records, whole blood samples, and anthropometric measurements from 74 fathers were obtained. A total of 51 cord blood samples were collected and birth weight was obtained. DNA methylation status was measured using liquid chromatography-tandem mass spectrometry (global DNA (hydroxy)methylation) and pyrosequencing (IGF2 DMR methylation). Paternal betaine intake was positively associated with paternal global DNA hydroxymethylation (0.028% per 100 mg betaine increase, 95% CI: 0.003, 0.053, P=0.03) and cord blood global DNA methylation (0.679% per 100 mg betaine increase, 95% CI: 0.057, 1.302, P=0.03). Paternal methionine intake was positively associated with CpG1 (0.336% per 100 mg methionine increase, 95% CI: 0.103, 0.569, P=0.006), and mean CpG (0.201% per 100 mg methionine increase, 95% CI: 0.001, 0.402, P=0.049) methylation of the IGF2 DMR in cord blood. Further, a negative association between birth weight/birth weight-for-gestational age z-score and paternal betaine/methionine intake was found. In addition, a positive association between choline and birth weight/birth weight-for-gestational age z-score was also observed. Our data indicate a potential impact of paternal methyl-group donor intake on paternal global DNA hydroxymethylation, offspring global and IGF2 DMR DNA methylation, and prenatal growth.

  16. Genome-wide methylation profiling identifies novel methylated genes in neuroblastoma tumors

    PubMed Central

    Olsson, Maja; Beck, Stephan; Kogner, Per; Martinsson, Tommy; Carén, Helena

    2016-01-01

    ABSTRACT Neuroblastoma is a very heterogeneous tumor of childhood. The clinical spectra range from very aggressive metastatic disease to spontaneous regression, even without therapy. Aberrant DNA methylation pattern is a common feature of most cancers. For neuroblastoma, it has been demonstrated both for single genes as well as genome-wide, where a so-called methylator phenotype has been described. Here, we present a study using Illumina 450K methylation arrays on 60 neuroblastoma tumors. We show that aggressive tumors, characterized by International Neuroblastoma Risk Group (INRG) as stage M, are hypermethylated compared to low-grade tumors. On the contrary, INRG stage L tumors display more non-CpG methylation. The genes with the highest number of hypermethylated CpG sites in INRG M tumors are TERT, PCDHGA4, DLX5, and DLX6-AS1. Gene ontology analysis showed a representation of neuronal tumor relevant gene functions among the differentially methylated genes. For validation, we used a set of independent tumors previously analyzed with the Illumina 27K methylation arrays, which confirmed the differentially methylated sites. Top candidate genes with aberrant methylation were analyzed for altered gene expression through the R2 platform (http://r2.amc.nl), and for correlations between methylation and gene expression in a public dataset. Altered expression in nonsurvivors was found for the genes B3GALT4 and KIAA1949, CLIC5, DLX6-AS, TERT, and PIRT, and strongest correlations were found for TRIM36, KIAA0513, and PIRT. Our data indicate that methylation profiling can be used for patient stratification and informs on epigenetically deregulated genes with the potential of increasing our knowledge about the underlying mechanisms of tumor development. PMID:26786290

  17. DNA methylation array analyses identified breast cancer-associated HYAL2 methylation in peripheral blood.

    PubMed

    Yang, Rongxi; Pfütze, Katrin; Zucknick, Manuela; Sutter, Christian; Wappenschmidt, Barbara; Marme, Frederik; Qu, Bin; Cuk, Katarina; Engel, Christoph; Schott, Sarah; Schneeweiss, Andreas; Brenner, Hermann; Claus, Rainer; Plass, Christoph; Bugert, Peter; Hoth, Markus; Sohn, Christof; Schmutzler, Rita; Bartram, Claus R; Burwinkel, Barbara

    2015-04-15

    Breast cancer (BC) is the leading cause of cancer-related mortality in women worldwide. Changes in DNA methylation in peripheral blood could be associated with malignancy at early stage. However, the BC-associated DNA methylation signatures in peripheral blood were largely unknown. Here, we performed a genome-wide methylation screening and identified a BC-associated differentially methylated CpG site cg27091787 in the hyaluronoglucosaminidase 2 gene (HYAL2) (discovery round with 72 BC case and 24 controls: p = 2.61 × 10(-9) adjusted for cell-type proportions). The substantially decreased methylation of cg27091787 in BC cases was confirmed in two validation rounds (first validation round with 338 BC case and 507 controls: p < 0.0001; second validation round with 189 BC case and 189 controls: p < 0.0001). In addition to cg27091787, the decreased methylation of a 650-bp CpG island shore of HYAL2 was also associated with increased risk of BC. Moreover, the expression and methylation of HYAL2 were inversely correlated with a p-value of 0.006. To note, the BC-associated decreased HYAL2 methylation was replicated in the T-cell fraction (p = 0.034). The cg27091787 methylation level enabled a powerful discrimination of early-stage BC cases (stages 0 and I) from healthy controls [area under curve (AUC) = 0.89], and was robust for the detection of BC in younger women as well (age < 50, AUC = 0.87). Our study reveals a strong association between decreased HYAL2 methylation in peripheral blood and BC, and provides a promising blood-based marker for the detection of early BC. © 2014 UICC.

  18. Genome-wide methylation profiling identifies novel methylated genes in neuroblastoma tumors.

    PubMed

    Olsson, Maja; Beck, Stephan; Kogner, Per; Martinsson, Tommy; Carén, Helena

    2016-01-01

    Neuroblastoma is a very heterogeneous tumor of childhood. The clinical spectra range from very aggressive metastatic disease to spontaneous regression, even without therapy. Aberrant DNA methylation pattern is a common feature of most cancers. For neuroblastoma, it has been demonstrated both for single genes as well as genome-wide, where a so-called methylator phenotype has been described. Here, we present a study using Illumina 450K methylation arrays on 60 neuroblastoma tumors. We show that aggressive tumors, characterized by International Neuroblastoma Risk Group (INRG) as stage M, are hypermethylated compared to low-grade tumors. On the contrary, INRG stage L tumors display more non-CpG methylation. The genes with the highest number of hypermethylated CpG sites in INRG M tumors are TERT, PCDHGA4, DLX5, and DLX6-AS1. Gene ontology analysis showed a representation of neuronal tumor relevant gene functions among the differentially methylated genes. For validation, we used a set of independent tumors previously analyzed with the Illumina 27K methylation arrays, which confirmed the differentially methylated sites. Top candidate genes with aberrant methylation were analyzed for altered gene expression through the R2 platform ( http://r2.amc.nl), and for correlations between methylation and gene expression in a public dataset. Altered expression in nonsurvivors was found for the genes B3GALT4 and KIAA1949, CLIC5, DLX6-AS, TERT, and PIRT, and strongest correlations were found for TRIM36, KIAA0513, and PIRT. Our data indicate that methylation profiling can be used for patient stratification and informs on epigenetically deregulated genes with the potential of increasing our knowledge about the underlying mechanisms of tumor development.

  19. Methylation plotter: a web tool for dynamic visualization of DNA methylation data.

    PubMed

    Mallona, Izaskun; Díez-Villanueva, Anna; Peinado, Miguel A

    2014-01-01

    Methylation plotter is a Web tool that allows the visualization of methylation data in a user-friendly manner and with publication-ready quality. The user is asked to introduce a file containing the methylation status of a genomic region. This file can contain up to 100 samples and 100 CpGs. Optionally, the user can assign a group for each sample (i.e. whether a sample is a tumoral or normal tissue). After the data upload, the tool produces different graphical representations of the results following the most commonly used styles to display this type of data. They include an interactive plot that summarizes the status of every CpG site and for every sample in lollipop or grid styles. Methylation values ranging from 0 (unmethylated) to 1 (fully methylated) are represented using a gray color gradient. A practical feature of the tool allows the user to choose from different types of arrangement of the samples in the display: for instance, sorting by overall methylation level, by group, by unsupervised clustering or just following the order in which data were entered. In addition to the detailed plot, Methylation plotter produces a methylation profile plot that summarizes the status of the scrutinized region, a boxplot that sums up the differences between groups (if any) and a dendrogram that classifies the data by unsupervised clustering. Coupled with this analysis, descriptive statistics and testing for differences at both CpG and group levels are provided. The implementation is based in R/shiny, providing a highly dynamic user interface that generates quality graphics without the need of writing R code. Methylation plotter is freely available at http://gattaca.imppc.org:3838/methylation_plotter/.

  20. Methylation plotter: a web tool for dynamic visualization of DNA methylation data

    PubMed Central

    2014-01-01

    Methylation plotter is a Web tool that allows the visualization of methylation data in a user-friendly manner and with publication-ready quality. The user is asked to introduce a file containing the methylation status of a genomic region. This file can contain up to 100 samples and 100 CpGs. Optionally, the user can assign a group for each sample (i.e. whether a sample is a tumoral or normal tissue). After the data upload, the tool produces different graphical representations of the results following the most commonly used styles to display this type of data. They include an interactive plot that summarizes the status of every CpG site and for every sample in lollipop or grid styles. Methylation values ranging from 0 (unmethylated) to 1 (fully methylated) are represented using a gray color gradient. A practical feature of the tool allows the user to choose from different types of arrangement of the samples in the display: for instance, sorting by overall methylation level, by group, by unsupervised clustering or just following the order in which data were entered. In addition to the detailed plot, Methylation plotter produces a methylation profile plot that summarizes the status of the scrutinized region, a boxplot that sums up the differences between groups (if any) and a dendrogram that classifies the data by unsupervised clustering. Coupled with this analysis, descriptive statistics and testing for differences at both CpG and group levels are provided. The implementation is based in R/shiny, providing a highly dynamic user interface that generates quality graphics without the need of writing R code. Methylation plotter is freely available at http://gattaca.imppc.org:3838/methylation_plotter/. PMID:25260021

  1. Methyl Iodide Fumigation of Bacillus anthracis Spores.

    PubMed

    Sutton, Mark; Kane, Staci R; Wollard, Jessica R

    2015-09-01

    Fumigation techniques such as chlorine dioxide, vaporous hydrogen peroxide, and paraformaldehyde previously used to decontaminate items, rooms, and buildings following contamination with Bacillus anthracis spores are often incompatible with materials (e.g., porous surfaces, organics, and metals), causing damage or residue. Alternative fumigation with methyl bromide is subject to U.S. and international restrictions due to its ozone-depleting properties. Methyl iodide, however, does not pose a risk to the ozone layer and has previously been demonstrated as a fumigant for fungi, insects, and nematodes. Until now, methyl iodide has not been evaluated against Bacillus anthracis. Sterne strain Bacillus anthracis spores were subjected to methyl iodide fumigation at room temperature and at 550C. Efficacy was measured on a log-scale with a 6-log reduction in CFUs being considered successful compared to the U.S. Environmental Protection Agency biocide standard. Such efficacies were obtained after just one hour at 55 °C and after 12 hours at room temperature. No detrimental effects were observed on glassware, PTFE O-rings, or stainless steel. This is the first reported efficacy of methyl iodide in the reduction of Bacillus anthracis spore contamination at ambient and elevated temperatures.

  2. Modeling of the oxidation of methyl esters - Validation for methyl hexanoate, methyl heptanoate, and methyl decanoate in a jet-stirred reactor

    SciTech Connect

    Glaude, Pierre Alexandre; Herbinet, Olivier; Bax, Sarah; Biet, Joffrey; Warth, Valerie; Battin-Leclerc, Frederique

    2010-11-15

    The modeling of the oxidation of methyl esters was investigated and the specific chemistry, which is due to the presence of the ester group in this class of molecules, is described. New reactions and rate parameters were defined and included in the software EXGAS for the automatic generation of kinetic mechanisms. Models generated with EXGAS were successfully validated against data from the literature (oxidation of methyl hexanoate and methyl heptanoate in a jet-stirred reactor) and a new set of experimental results for methyl decanoate. The oxidation of this last species was investigated in a jet-stirred reactor at temperatures from 500 to 1100 K, including the negative temperature coefficient region, under stoichiometric conditions, at a pressure of 1.06 bar and for a residence time of 1.5 s: more than 30 reaction products, including olefins, unsaturated esters, and cyclic ethers, were quantified and successfully simulated. Flow rate analysis showed that reactions pathways for the oxidation of methyl esters in the low-temperature range are similar to that of alkanes. (author)

  3. Histone Lysine Methylation in Diabetic Nephropathy

    PubMed Central

    Sun, Guang-dong; Cui, Wen-peng; Guo, Qiao-yan; Miao, Li-ning

    2014-01-01

    Diabetic nephropathy (DN) belongs to debilitating microvascular complications of diabetes and is the leading cause of end-stage renal diseases worldwide. Furthermore, outcomes from the DCCT/EDIC study showed that DN often persists and progresses despite intensive glucose control in many diabetes patients, possibly as a result of prior episode of hyperglycemia, which is called “metabolic memory.” The underlying mechanisms responsible for the development and progression of DN remain poorly understood. Activation of multiple signaling pathways and key transcription factors can lead to aberrant expression of DN-related pathologic genes in target renal cells. Increasing evidence suggests that epigenetic mechanisms in chromatin such as DNA methylation, histone acetylation, and methylation can influence the pathophysiology of DN and metabolic memory. Exciting researches from cell culture and experimental animals have shown that key histone methylation patterns and the related histone methyltransferases and histone demethylases can play important roles in the regulation of inflammatory and profibrotic genes in renal cells under diabetic conditions. Because histone methylation is dynamic and potentially reversible, it can provide a window of opportunity for the development of much-needed novel therapeutic potential for DN in the future. In this minireview, we discuss recent advances in the field of histone methylation and its roles in the pathogenesis and progression of DN. PMID:25215303

  4. DNA methylation in memory formation: Emerging insights

    PubMed Central

    Heyward, Frankie D.; Sweatt, J. David

    2016-01-01

    The establishment of synaptic plasticity and long-term memory requires lasting cellular and molecular modifications that, as a whole, must endure despite the rapid turnover of their constituent parts. Such a molecular feat must be mediated by a stable, self-perpetuating, cellular information storage mechanism. DNA methylation, being the archetypal cellular information storage mechanism, has been heavily implicated as being necessary for stable activity-dependent transcriptional alterations within the central nervous system (CNS). This review details the foundational discoveries from both gene-targeted, as well as whole-genome sequencing, studies that have successfully brought DNA methylation to our attention as a chief regulator of activity- and experience-dependent transcriptional alterations within the CNS. We present a hypothetical framework with which the disparate experimental findings dealing with distinct manipulations of the DNA methylation, and their effect on memory, might be resolved while taking into account the unique impact activity-dependent alterations in DNA methylation potentially have on both memory promoting and memory-suppressing gene expression. And last, we discuss potential avenues for future inquiry into the role of DNA methylation during remote memory formation. PMID:25832671

  5. Methyl-DEAE-dextran: a candidate biomaterial.

    PubMed

    Zambito, Ylenia; Baggiani, Andrea; Carelli, Vera; Serafini, Maria Francesca; Di Colo, Giacomo

    2004-01-01

    The full quaternisation of DEAE-dextran was successfully attempted and an application of the quaternised product was suggested. Commercial DEAE-dextran was reacted with iodomethane at 60 degrees C in the presence of NaOH. The raw product was purified by dialysis, during which the iodide ion was replaced by chloride. N-methylation and O-methylation resulted from the reaction. A second methylation step produced no further changes in the molecule. Alkalimetry indicated the absence of amino groups in the methylated polymer molecule, thus testifying to a complete quaternisation. N-acetylcysteine (AcCy) was neutralised with the polymer in the hydroxide form, thus obtaining the methyl DEAE-dextran salt of AcCy (Me-DEAE-dextran/AcCy), whereby an ophthalmic formulation for the treatment of the dry eye syndrome was prepared. For comparison, the neutral AcCy salt of commercial DEAE-dextran (DEAE-dextran/AcCy) was prepared. The AcCy content in Me-DEAE-dextran/AcCy was higher than in DEAE-dextran/AcCy (23 vs 13%), while the viscosity of a solution containing the salt concentration corresponding to the therapeutic AcCy concentration (4%w/v) was lower with the former compared to the latter salt (20.5 vs 23.9 mPa s). Both solutions were ipotonic (245 mOsm/kg), whereas the commercial Tirocular is strongly hypertonic (900 mOsm/kg) and irritant.

  6. DNA methylation, a hand behind neurodegenerative diseases

    PubMed Central

    Lu, Haoyang; Liu, Xinzhou; Deng, Yulin; Qing, Hong

    2013-01-01

    Epigenetic alterations represent a sort of functional modifications related to the genome that are not responsible for changes in the nucleotide sequence. DNA methylation is one of such epigenetic modifications that have been studied intensively for the past several decades. The transfer of a methyl group to the 5 position of a cytosine is the key feature of DNA methylation. A simple change as such can be caused by a variety of factors, which can be the cause of many serious diseases including several neurodegenerative diseases. In this review, we have reviewed and summarized recent progress regarding DNA methylation in four major neurodegenerative diseases: Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). The studies of these four major neurodegenerative diseases conclude the strong suggestion of the important role DNA methylation plays in these diseases. However, each of these diseases has not yet been understood completely as details in some areas remain unclear, and will be investigated in future studies. We hope this review can provide new insights into the understanding of neurodegenerative diseases from the epigenetic perspective. PMID:24367332

  7. Distinct methylation profiles of glioma subtypes.

    PubMed

    Uhlmann, Karen; Rohde, Klaus; Zeller, Constanze; Szymas, Janusz; Vogel, Siegfried; Marczinek, Karola; Thiel, Gundula; Nürnberg, Peter; Laird, Peter W

    2003-08-10

    Gliomas are tumors of the central nervous system with a wide spectrum of different tumor types. They range from pilocytic astrocytoma, with a generally good prognosis, to the extremely aggressive malignant glioblastoma. In addition to these 2 types of contrasting neoplasms, several other subtypes can be distinguished, each characterized by specific phenotypic, as well as genotypic features. Recently, the epigenotype, as evident from differentially methylated DNA loci, has been proposed to be useful as a further criterion to distinguish between tumor types. In our study, we screened 139 tissue samples, including 33 pilocytic astrocytomas, 46 astrocytomas of different grades, 7 oligoastrocytomas, 10 oligodendrogliomas, 10 glioblastoma multiforme samples and 33 control tissues, for methylation at CpG islands of 15 different gene loci. We used the semiquantitative high throughput method MethyLight to analyze a gene panel comprising ARF, CDKN2B, RB1, APC, CDH1, ESR1, GSTP1, TGFBR2, THBS1, TIMP3, PTGS2, CTNNB1, CALCA, MYOD1 and HIC1. Seven of these loci showed tumor specific methylation changes. We found tissue as well as grade specific methylation profiles. Interestingly, pilocytic astrocytomas showed no evidence of CpG island hypermethylation, but were significantly hypomethylated, relative to control tissues, at MYOD1. Our results show that glioma subtypes have characteristic methylation profiles and, with the exception of pilocytic astrocytomas, show both locus specific hyper- as well as hypomethylation. Copyright 2003 Wiley-Liss, Inc.

  8. Prognostic DNA Methylation Markers for Prostate Cancer

    PubMed Central

    Strand, Siri H.; Orntoft, Torben F.; Sorensen, Karina D.

    2014-01-01

    Prostate cancer (PC) is the most commonly diagnosed neoplasm and the third most common cause of cancer-related death amongst men in the Western world. PC is a clinically highly heterogeneous disease, and distinction between aggressive and indolent disease is a major challenge for the management of PC. Currently, no biomarkers or prognostic tools are able to accurately predict tumor progression at the time of diagnosis. Thus, improved biomarkers for PC prognosis are urgently needed. This review focuses on the prognostic potential of DNA methylation biomarkers for PC. Epigenetic changes are hallmarks of PC and associated with malignant initiation as well as tumor progression. Moreover, DNA methylation is the most frequently studied epigenetic alteration in PC, and the prognostic potential of DNA methylation markers for PC has been demonstrated in multiple studies. The most promising methylation marker candidates identified so far include PITX2, C1orf114 (CCDC181) and the GABRE~miR-452~miR-224 locus, in addition to the three-gene signature AOX1/C1orf114/HAPLN3. Several other biomarker candidates have also been investigated, but with less stringent clinical validation and/or conflicting evidence regarding their possible prognostic value available at this time. Here, we review the current evidence for the prognostic potential of DNA methylation markers in PC. PMID:25238417

  9. Femtosecond dissociation dynamics of methyl iodide clusters

    NASA Astrophysics Data System (ADS)

    Poth, L.; Zhong, Q.; Ford, J. V.; Castleman, A. W.

    1998-09-01

    The photodissociation dynamics of methyl iodide clusters using λ=270 nm as pump and λ=405 nm as probe are studied using a femtosecond two color pump-probe laser arrangement combined with a reflectron time-of-flight (RTOF) mass spectrometer. This enables the à state and 10s Rydberg state of methyl iodide to be accessed with the pump beam. Of particular interest is a comparison of the femtosecond dynamics of the methyl iodide monomer with the clustered species. Clocking of the monomer dissociation shows a transient which is indicative of a fast C-I bond breakage as is to be expected upon excitation of methyl iodide into the fast dissociating à state, or into the predissociative 10s Rydberg state. Clusters, however, show a very different pump-probe transient composed of a fast decay and a subsequent dip in ion signal followed by a rise for pump-probe delay times greater than 2 ps. The cluster ion signal shows an enhancement for pump probe delay times up to 70 ps. The results are interpreted in terms of the electronic state diagram of the methyl iodide monomer and effects resulting from clustering of these species, shifts of electronic energy levels and caging of excited species in the cluster.

  10. Intragenic DNA methylation prevents spurious transcription initiation.

    PubMed

    Neri, Francesco; Rapelli, Stefania; Krepelova, Anna; Incarnato, Danny; Parlato, Caterina; Basile, Giulia; Maldotti, Mara; Anselmi, Francesca; Oliviero, Salvatore

    2017-03-02

    In mammals, DNA methylation occurs mainly at CpG dinucleotides. Methylation of the promoter suppresses gene expression, but the functional role of gene-body DNA methylation in highly expressed genes has yet to be clarified. Here we show that, in mouse embryonic stem cells, Dnmt3b-dependent intragenic DNA methylation protects the gene body from spurious RNA polymerase II entry and cryptic transcription initiation. Using different genome-wide approaches, we demonstrate that this Dnmt3b function is dependent on its enzymatic activity and recruitment to the gene body by H3K36me3. Furthermore, the spurious transcripts can either be degraded by the RNA exosome complex or capped, polyadenylated, and delivered to the ribosome to produce aberrant proteins. Elongating RNA polymerase II therefore triggers an epigenetic crosstalk mechanism that involves SetD2, H3K36me3, Dnmt3b and DNA methylation to ensure the fidelity of gene transcription initiation, with implications for intragenic hypomethylation in cancer.

  11. DNA methylation detection: bisulfite genomic sequencing analysis.

    PubMed

    Li, Yuanyuan; Tollefsbol, Trygve O

    2011-01-01

    DNA methylation, which most commonly occurs at the C5 position of cytosines within CpG dinucleotides, plays a pivotal role in many biological procedures such as gene expression, embryonic development, cellular proliferation, differentiation, and chromosome stability. Aberrant DNA methylation is often associated with loss of DNA homeostasis and genomic instability leading to the development of human diseases such as cancer. The importance of DNA methylation creates an urgent demand for effective methods with high sensitivity and reliability to explore innovative diagnostic and therapeutic strategies. Bisulfite genomic sequencing developed by Frommer and colleagues was recognized as a revolution in DNA methylation analysis based on conversion of genomic DNA by using sodium bisulfite. Besides various merits of the bisulfite genomic sequencing method such as being highly qualitative and quantitative, it serves as a fundamental principle to many derived methods to better interpret the mystery of DNA methylation. Here, we present a protocol currently frequently used in our laboratory that has proven to yield optimal outcomes. We also discuss the potential technical problems and troubleshooting notes for a variety of applications in this field.

  12. DNA Methylation in Memory Formation: Emerging Insights.

    PubMed

    Heyward, Frankie D; Sweatt, J David

    2015-10-01

    The establishment of synaptic plasticity and long-term memory requires lasting cellular and molecular modifications that, as a whole, must endure despite the rapid turnover of their constituent parts. Such a molecular feat must be mediated by a stable, self-perpetuating, cellular information storage mechanism. DNA methylation, being the archetypal cellular information storage mechanism, has been heavily implicated as being necessary for stable activity-dependent transcriptional alterations within the CNS. This review details the foundational discoveries from both gene-targeted and whole-genome sequencing studies that have brought DNA methylation to our attention as a chief regulator of activity- and experience-dependent transcriptional alterations within the CNS. We present a hypothetical framework to resolve disparate experimental findings regarding distinct manipulations of DNA methylation and their effect on memory, taking into account the unique impact activity-dependent alterations in DNA methylation potentially have on both memory-promoting and memory-suppressing gene expression. And last, we discuss potential avenues for future inquiry into the role of DNA methylation during remote memory formation. © The Author(s) 2015.

  13. Water-soluble antioxidant derivative poly(triethylene glycol methyl acrylate-co-α-tocopheryl acrylate) as a potential prodrug to enable localized neuroprotection.

    PubMed

    Cao, Y; He, W

    2013-01-01

    Implantable microelectrode arrays (MEA) hold enormous hope for individuals with sensory or motor deficits. However, long-term function of MEA remains a critical hurdle. The objective of this study was to synthesize an antioxidant prodrug that can be delivered to the neural tissue around the implant and present a pharmacological depot to combat the injurious oxidative stress around the MEA. In this report, monomers of triethylene glycol methyl acrylate and α-tocopheryl acrylate, a synthetic derivative of the antioxidant α-tocopherol (vitamin E, Ve), were copolymerized to obtain poly(triethylene glycol methyl acrylate-co-α-tocopheryl acrylate) (PVT) with different compositions. In contrast to the poor water solubility of Ve, solubility of the PVT prodrug in water can reach as high as 3.1 mg ml(-1) (equivalent to 500 μM Ve) by tuning the copolymer composition. To demonstrate the applicability of the prodrug for MEA implants, PVT was successfully deposited on silicon substrates with poly(acrylic acid) (PAA) or tannic acid (TA) using the layer-by-layer technique mediated by hydrogen bonding. Ellipsometry and quartz crystal microbalance data showed that the multilayers of PAA/PVT were destructible at physiological pH. In contrast, multilayers of TA/PVT were stable. The PVT prodrug was non-cytotoxic toward A172 human astrocytes. Furthermore, PVT was able to protect astrocytes against oxidative stress exerted by H(2)O(2) in vitro. Using a free radical scavenging assay, the protection mechanism was attributed to the hydrolysis of the labile ester linkage and release of the active Ve. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  14. Developmental differences in posttranslational calmodulin methylation in pea plants

    SciTech Connect

    Oh, Sukheung; Roberts, D.M. )

    1990-05-01

    A calmodulin-N-methyltransferase was used to analyze the degree of lysine-115 methylation of pea calmodulin. Calmodulin was isolated from segments of developing roots of young etiolated and green pea plants and was tested for its ability to be methylated by the calmodulin methyltransferase in the presence of {sup 3}H-methyl-S-adenosylmethionine. Calmodulin methylation levels were lower in apical root segments and in the young lateral roots compared with the mature, differentiated root tissues. The methylation of these calmodulin samples occurs specifically at lysine 115 since site-directed mutants of calmodulin with substitutions at this position were not methylated and competitively inhibited methylation. The present findings, combined with previous data showing differences in NAD kinase activation by methylated and unmethylated calmodulins, raise the possibility that posttranslational methylation could affect calmodulin action.

  15. Decreased LINE-1 methylation levels in aldosterone-producing adenoma.

    PubMed

    Chen, Chen; Zhou, Xiaoyu; Jing, Jing; Cheng, Jing; Luo, Yu; Chen, Jiachao; Xu, Xi; Leng, Fei; Li, Xiaomu; Lu, Zhiqiang

    2014-01-01

    Abnormal global DNA methylation levels are associated with many diseases. In this study, we examined long interspersed nuclear elements-1 (LINE-1) methylation as a biomarker for abnormal global DNA methylation and aldosterone-producing adenoma (APA). Tissues from 25 APA and 6 normal adrenal glands (NAs) were analyzed for LINE-1 methylation by real-time methylation-specific polymerase chain reaction. The estimated LINE-1 methylation level was then tested for correlation with the clinicopathologic parameters of APA patients. The methylation index (MI) level for LINE-1 was 0.91 in NA samples and 0.77 in APA samples (P < 0.001). For the APA samples, there were no statistical correlations between the MI level and various clinicopathologic parameters such as gender (P = 0.07). LINE-1 methylation is significantly lower in APA samples than in NA samples. LINE-1 methylation is not correlated with the clinical characteristics of APA.

  16. DNA methylation of the LIN28 pseudogene family.

    PubMed

    Davis, Aaron P; Benninghoff, Abby D; Thomas, Aaron J; Sessions, Benjamin R; White, Kenneth L

    2015-04-11

    DNA methylation directs the epigenetic silencing of selected regions of DNA, including the regulation of pseudogenes, and is widespread throughout the genome. Pseudogenes are decayed copies of duplicated genes that have spread throughout the genome by transposition. Pseudogenes are transcriptionally silenced by DNA methylation, but little is known about how pseudogenes are targeted for methylation or how methylation levels are maintained in different tissues. We employed bisulfite next generation sequencing to examine the methylation status of the LIN28 gene and four processed pseudogenes derived from LIN28. The objective was to determine whether LIN28 pseudogenes maintain the same pattern of methylation as the parental gene or acquire a methylation pattern independent of the gene of origin. In this study, we determined that the methylation status of LIN28 pseudogenes does not resemble the pattern evident for the LIN28 gene, but rather these pseudogenes appear to acquire methylation patterns independent of the parental gene. Furthermore, we observed that methylation levels of the examined pseudogenes correlate to the location of insertion within the genome. LIN28 pseudogenes inserted into gene bodies were highly methylated in all tissues examined. In contrast, pseudogenes inserted into genomic regions that are not proximal to genes were differentially methylated in various tissue types. Our analysis suggests that Lin28 pseudogenes do not acquire patterns of tissue-specific methylation as for the parental gene, but rather are methylated in patterns specific to the local genomic environment into which they were inserted.

  17. Magnetic Trapping of Cold Methyl Radicals

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Vashishta, Manish; Djuricanin, Pavle; Zhou, Sida; Zhong, Wei; Mittertreiner, Tony; Carty, David; Momose, Takamasa

    2017-03-01

    We have demonstrated that a supersonic beam of methyl radicals (CH3 ) in the ground rotational state of both para and ortho species has been slowed down to standstill with a magnetic molecular decelerator, and successfully captured spatially in an anti-Helmholtz magnetic trap for >1 s . The trapped CH3 radicals have a mean translational temperature of about 200 mK with an estimated density of >5.0 ×1 07 cm-3 . The methyl radical is an ideal system for the study of cold molecules not only because of its high reactivities at low temperatures, but also because further cooling below 1 mK is plausible via sympathetic cooling with ultracold atoms. The demonstrated trapping capability of methyl radicals opens up various possibilities for realizing ultracold ensembles of molecules towards Bose-Einstein condensation of polyatomic molecules and investigations of reactions governed by quantum statistics.

  18. Effect of salinity on methylation of mercury

    SciTech Connect

    Blum, J.E.; Bartha, R.

    1980-09-01

    Monomethyl and dimethylmercury are potent neurotoxins subject to biomagnification in food webs. This fact was tragically demonstrated by the Minamata and Niigata poisoning incidents in Japan in which 168 persons who ate seafood from mercury polluted waters were poisoned, 52 fatally. Shortly after these two incidents, work conducted in freshwater environments demonstrated the microbial conversion of inorganic and phenylmercury compounds to mono- and di-methylmercury. Consideration of some fragmentary evidence from the literature, however, indicates that the rate and the significance of microbial methylation of mercury in freshwater and saltwater environments may not be the same. A demonstrated relationship between mercury methylation rates and water salinity would greatly influence our thinking about mercury pollution effects in marine versus freshwater environments. Since we were unable to locate published reports on this subject, we are investigating the influence of salinity on the rate of mercury methylation in an estuarine sediment.

  19. Metabolic control of methylation and acetylation.

    PubMed

    Su, Xiaoyang; Wellen, Kathryn E; Rabinowitz, Joshua D

    2016-02-01

    Methylation and acetylation of DNA and histone proteins are the chemical basis for epigenetics. From bacteria to humans, methylation and acetylation are sensitive to cellular metabolic status. Modification rates depend on the availability of one-carbon and two-carbon substrates (S-adenosylmethionine, acetyl-CoA, and in bacteria also acetyl-phosphate). In addition, they are sensitive to demodification enzyme cofactors (α-ketoglutarate, NAD(+)) and structural analog metabolites that function as epigenetic enzyme inhibitors (e.g., S-adenosylhomocysteine, 2-hydroxyglutarate). Methylation and acetylation likely initially evolved to tailor protein activities in microbes to their metabolic milieu. While the extracellular environment of mammals is more tightly controlled, the combined impact of nutrient abundance and metabolic enzyme expression impacts epigenetics in mammals sufficiently to drive important biological outcomes such as stem cell fate and cancer.

  20. Maternal Regulation of Estrogen Receptor α Methylation

    PubMed Central

    Champagne, Frances A.; Curley, James P.

    2008-01-01

    Summary Advances in molecular biology have provided tools for studying the epigenetic factors which modulate gene expression. DNA methylation is an epigenetic modification which can have sustained effects on transcription and is associated with long-term gene silencing. In this review, we focus on the regulation of estrogen receptor alpha (ERα) expression by hormonal and environmental cues, the consequences of these cues for female maternal and sexual behavior and recent studies which explore the role of DNA methylation in mediating these developmental effects, with particular focus on the mediating role of maternal care. The methylation status of ERα has implications for reproductive behavior, cancer susceptibility and recovery from ischemic injury suggesting an epigenetic basis for risk and resilience across the life span. PMID:18644464