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Sample records for cationically polymerizable monomers

  1. Cationically polymerizable monomers derived from renewable sources

    Energy Technology Data Exchange (ETDEWEB)

    Crivello, J.V.

    1992-10-01

    The objectives of this project are to design and synthesize novel monomers which orginate from renewable biological sources and to carry out their rapid, efficient, pollution-free and energy efficient cationic polymerization to useful products under the influence of ultraviolet light or heat. A summary of the results of the past year's research on cationically polymerizable monomers derived from renewable sources is presented. Three major areas of investigation corresponding to the different classes of naturally occurring starting materials were investigated; epoxidized terpenes and natural rubber and vinyl ethers from alcohols and carbohydrates.

  2. Cationically polymerizable monomers derived from renewable sources. Annual performance report

    Energy Technology Data Exchange (ETDEWEB)

    Crivello, J.V.

    1992-10-01

    The objectives of this project are to design and synthesize novel monomers which orginate from renewable biological sources and to carry out their rapid, efficient, pollution-free and energy efficient cationic polymerization to useful products under the influence of ultraviolet light or heat. A summary of the results of the past year`s research on cationically polymerizable monomers derived from renewable sources is presented. Three major areas of investigation corresponding to the different classes of naturally occurring starting materials were investigated; epoxidized terpenes and natural rubber and vinyl ethers from alcohols and carbohydrates.

  3. Synthesis of Polymerizable Cyclodextrin Derivatives for Use in Adhesion-Promoting Monomer Formulations

    Directory of Open Access Journals (Sweden)

    Bowen, Rafael L.

    2009-01-01

    Full Text Available The synthesis of the cyclodextrin derivatives reported herein was assisted by extensive literature research together with structure-property relationships derived from three-dimensional molecular modeling. These studies led to the hypothesis that many of the 21 hydroxyl groups on beta-cyclodextrin molecules could be derivatized to form a closely related family of analogous chemical compounds containing both polymerizable groups and hydrophilic ionizable ligand (substrate-binding groups, each attached via hydrolytically-stable ether-linkages. The vinylbenzylether polymerizable groups should readily homopolymerize and also copolymerize with methacrylates. This could be highly useful for dental applications because substantially all contemporary dental resins and composites are based on methacrylate monomers. Due to hydrophilic ligands and residual hydroxyl groups, these cyclodextrin derivatives should penetrate hydrated layers of dentin and enamel to interact with collagen and tooth mineral. Analyses indicated that the diverse reaction products resulting from the method of synthesis reported herein should comprise a family of copolymerizable molecules that collectively contain about 30 different combinations of vinylbenzyl and hexanoate groups on the various molecules, with up to approximately seven of such groups combined on some of the molecules. Although the hypothesis was supported, and adhesive bonding to dentin is expected to be significantly improved by the use of these polymerizable cyclodextrin derivatives, other efforts are planned for improved synthetic methods to ensure that each of the reaction-product molecules will contain at least one copolymerizable moiety. The long-term objective is to enable stronger and more durable attachments of densely cross-linked polymers to hydrated hydrophilic substrates. Capabilities for bonding of hydrolytically stable polymers to dental and perhaps other hydrous biological tissues could provide

  4. Photorheologically reversible micelle composed of polymerizable cationic surfactant and 4-phenylazo benzoic acid☆

    Institute of Scientific and Technical Information of China (English)

    Jie Chen; Bo Fang; Hao Jin; Licheng Yu; Meng Tian; Kejing Li; Leiping Jin; Mo Yang

    2016-01-01

    A photorheologically reversible micelle composed of polymerizable cationic surfactant n-cetyl dimethylallyl am-monium chloride (CDAAC) and trans-4-phenylazo benzoic acid (trans-ACA) was prepared. The effects of molar ratio of CDAAC/trans-ACA, time of UV and visible light irradiation and temperature on the rheological properties of micellar system were investigated. The results show that before UV irradiation the system with an optimum CDAAC/trans-ACA molar ratio of 1.4 forms viscoelastic micelles at 45 °C. After 365 nm UV irradiation, the viscos-ities of micel e systems with different concentrations at fixed molar ratio of 1.4 are decreased by 85%–95%. The CDAAC/trans-ACA (14 mmol·L−1/10 mmol·L−1) micel e system exhibits shear thinning property and its viscos-ity is decreased obviously with the increases of UV irradiation time less than 1 h. The rheological process during UV irradiation for CDAAC/trans-ACA (14 mmol·L−1/10 mmol·L−1) micelle proves that viscosity, elastic modulus G′and viscous modulus G″will reduce quickly with the UV light. Furthermore, the micelle system after 1 h UV-irradiation is able to revert to its initial high viscosity with 460 nm visible light irradiation for 4 h, and the micelle can be cycled between low and high viscosity states by repetitive UV and visible light irradiations. The UV–Vis spectra of CDAAC/trans-ACA micelle indicate that its photosensitive rheological properties are related closely to photoisomerization of trans-ACA to cis-ACA.

  5. Effect of cationic monomer on properties of fluorinated acrylate latex

    Institute of Scientific and Technical Information of China (English)

    Li Jun Chen

    2012-01-01

    Cationic fluorinated acrylate latex was prepared via semi-continuous emulsion copolymerization of cationic monomer and other monomers.The resultant latex and its film were characterized with dynamic light scattering detector and contact angle meter.Influences of amount of DMDAAC on the properties of resultant latex and its film were investigated in detail.Results show that the particle size of the latex has the minimum value and the zeta potential of the latex is increased when the amount of DMDAAC is increased.In addition,the particle size of the latex is unimodal distribution when the amount of DMDAAC is not more than 2.5%.However,the particle size of the latex is bimodal distribution when the amount of DMDAAC is more than 2.5%.The contact angle is varied slightly with the increase of amount of DMDAAC when it is not more than 2.5%.Nevertheless,the contact angle is decreased with the increase of the amount of DMDAAC when it is more than 25%.

  6. Crystal structure of channelrhodopsin, a light-gated cation channel - all cations lead through the monomer.

    Science.gov (United States)

    Kato, Hideaki E; Nureki, Osamu

    2013-01-01

    Channelrhodopsin (ChR) is a light-gated cation channel derived from green algae. Since the inward flow of cations triggers the neuron firing, neurons expressing ChRs can be optically controlled even within freely moving mammals. Although ChR has been broadly applied to neuro-science research, little is known about its molecular mechanisms. We determined the crystal structure of chimeric ChR at 2.3 Å resolution and revealed its molecular architecture. The integration of structural, electrophysio-logical, and computational analyses provided insight into the molecular basis for the channel function of ChR, and paved the way for the principled design of ChR variants with novel properties. PMID:27493541

  7. Novolacs With Alternating P-Cresol & Polyhydroxyphenyl Monomer Units: Developer Cationic Effects And Thermal Properties

    Science.gov (United States)

    Blakeney, Andrew J.; Jeffries, Alfred T.; Wehrle, John J.; Gardner, Wesley M.

    1988-01-01

    Novolacs which alternate p-cresol monomer units with polyhydroxyphenyl monomer units have been synthesized by acid catalyzed condensation of 2,6-bis(hydroxymethyl)-p-cresol with polyhydroxybenzenes such as resorcinol or 4-chlororesorcinol. These novolacs are highly alkaline soluble and exhibit improved glass transition temperatures relative to conventional novolacs. Unexpected developer cation effects have been observed on the dissolution times of some of these novolacs. The effect of molecular weight on these effects will be discussed for one system. The dissolution discrimination and inhibition of a 4- chlororesorcinol containing novolac was examined relative to a standard m-,p-cresol novolac and polyvinyl phenol. Images produced from a resist using a p-cresol/ 4-chlororesorcinol novolac showed no significant image degradation at 200 degrees C.

  8. Photoionization of cold gas phase coronene and its clusters: Autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation

    International Nuclear Information System (INIS)

    Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory

  9. Photoionization of cold gas phase coronene and its clusters: autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation.

    Science.gov (United States)

    Bréchignac, Philippe; Garcia, Gustavo A; Falvo, Cyril; Joblin, Christine; Kokkin, Damian; Bonnamy, Anthony; Parneix, Pascal; Pino, Thomas; Pirali, Olivier; Mulas, Giacomo; Nahon, Laurent

    2014-10-28

    Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory. PMID:25362317

  10. Photoionization of cold gas phase coronene and its clusters: Autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation

    Energy Technology Data Exchange (ETDEWEB)

    Bréchignac, Philippe, E-mail: philippe.brechignac@u-psud.fr; Falvo, Cyril; Parneix, Pascal; Pino, Thomas; Pirali, Olivier [Institut des Sciences Moléculaires d’Orsay, CNRS UMR8214, Univ Paris-Sud, F-91405 Orsay (France); Garcia, Gustavo A.; Nahon, Laurent [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, B.P. 48, F-91192 Gif-sur-Yvette (France); Joblin, Christine; Kokkin, Damian; Bonnamy, Anthony [IRAP, Université de Toulouse 3 - CNRS, 9 Av. Colonel Roche, B.P. 44346, F-31028 Toulouse Cedex 4 (France); Mulas, Giacomo [INAF - Osservatorio Astronomico di Cagliari, via della scienza 5, I-09047 Selargius (Italy)

    2014-10-28

    Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory.

  11. Relative activities of siloxane monomers toward the cation exchange resin-catalyst in the equilibration reactions

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    M. N. GOVEDARICA

    2001-07-01

    Full Text Available The relative activities of a number of siloxane monomers, both cyclic and linear, toward the cation exchange resin-equilibration catalyst were determined. The determination was based on the fact that when a particular siloxane compound is added to an arbitrarily chosen equilibrate, it takes part in the equilibration process, provoking certain viscosity changes of the reaction mixture. Taking these viscosity changes as a measure of activities, the following order was obtained: hexamethylcyclotrisiloxane > hexamethyldisiloxane > octamethylcyclotetrasiloxane > one linear all-methyl oligosiloxane of number average molecular weight of approximately 800 > decamethylcyclopentasiloxane. The results obtained by using the described viscosimetrical determination method were controlled by measuring the number average molecular weights of the reaction mixtures at the beginning and at the end of the equilibration process. The deviations of the experimentally measured from the calculated values were less than 20 %, as was found in one equilibration system. In most other systems the deviations were about 10 % which is a very good result which strengthens the validity of the applied determination method.

  12. Effect of Very High Charge Density and Monomer Constitution on the Synthesis and Properties of Cationic Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Hamideh Ahmadloo

    2016-06-01

    Full Text Available The free-radical homopolymerization of 1,3-bis(N,N,N-trimethylammonium-2-propylmethacrylate dichloride (di-M and 1,3-bis(N,N,N-trimethylammonium-2-propylacrylate dichloride (di-A in aqueous solution yields cationic polyelectrolytes (PEL with theoretical/structural charge spacing of only ≈0.12 nm. The high charge density causes condensation of ≈82% of the chloride counterions. The high level of counterion condensation reduces the ionic strength in the polymerizing batch when the monomer molecules connect to PEL chains. This has the consequence that the hydrodynamic and excluded volume of the PEL molecules will change. Studies of the free radical polymerization revealed non-ideal polymerization kinetics already at low conversion and additionally autoacceleration above a certain monomer concentration and conversion. Similar autoacceleration was not observed for monomers yielding PEL with charge spacing of 0.25 or 0.5 nm. Coulomb interactions, monomer association, steric effects, and specific features of the monomer constitution have been evaluated concerning their contributions to the concentration dependence and conversion dependence of kinetic parameters. The different backbone constitutions of di-M and di-A not only influence the polymerization kinetics but also equip poly(di-M with higher hydrolytic stability. The experimental results confirm the impact of electrochemical parameters and the necessity to reconsider their inclusion in kinetic models.

  13. Crystal structure of channelrhodopsin, a light-gated cation channel – all cations lead through the monomer

    OpenAIRE

    Kato, Hideaki E.; Nureki, Osamu

    2013-01-01

    Channelrhodopsin (ChR) is a light-gated cation channel derived from green algae. Since the inward flow of cations triggers the neuron firing, neurons expressing ChRs can be optically controlled even within freely moving mammals. Although ChR has been broadly applied to neuro-science research, little is known about its molecular mechanisms. We determined the crystal structure of chimeric ChR at 2.3 Å resolution and revealed its molecular architecture. The integration of structural, electrophys...

  14. INFLUENCES OF WATER-SOLUBLE CATIONIC MONOMERS ON THE POLYMERIZATION RATE IN THE INVERSE EMULSION

    Institute of Scientific and Technical Information of China (English)

    HOU Sijian; HA Runhua

    1996-01-01

    This investigation deals with the free radical polymerization both of (2-methacryloyloxyethyl) trimethyl ammonium chloride (QACEMA) and of diallyldimethyl ammonium chloride (DADMAC) in inverse emulsion. The influences of some factors, such as the concentration of monomers, initiator and emulsifier are discussed. The polymerization rate equations of above two monomers can be written as follows:Rp = k[M]1.21[I]0.82[E]0.57 (for QACEMA)Rp = k′[M]1.34[I]0.90[E]0.62 (for DADMAC)

  15. Crystal structure of channelrhodopsin, a light-gated cation channel – all cations lead through the monomer

    Science.gov (United States)

    Kato, Hideaki E.; Nureki, Osamu

    2013-01-01

    Channelrhodopsin (ChR) is a light-gated cation channel derived from green algae. Since the inward flow of cations triggers the neuron firing, neurons expressing ChRs can be optically controlled even within freely moving mammals. Although ChR has been broadly applied to neuro-science research, little is known about its molecular mechanisms. We determined the crystal structure of chimeric ChR at 2.3 Å resolution and revealed its molecular architecture. The integration of structural, electrophysio-logical, and computational analyses provided insight into the molecular basis for the channel function of ChR, and paved the way for the principled design of ChR variants with novel properties. PMID:27493541

  16. DFT studies of all fluorothiophenes and their cations as candidate monomers for conductive polymers

    International Nuclear Information System (INIS)

    In this paper, electronic, structural, and properties of mono-, di-, tri-, and tetrafluorothiophenes and their radical cations are studied using the density functional theory and B3LYP method with 6-311++G** basis set. Also, the effects of the number and position of the substituent of fluorine atoms on the properties of the thiophene ring have been studied using optimized structures obtained for these molecules and their radical cations; vibrational frequencies, spin-density distribution, size and direction of the dipole moment vector, ionization potential, electric Polarizabilities, HOMO–LUMO gaps and NICS values of these compounds have been calculated and analyzed

  17. Interaction of Refractory Dibenzothiophenes and Polymerizable Structures

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    Jose L. Rivera

    2014-01-01

    Full Text Available We carried out first principles calculations to show that polymerizable structures containing hydroxyl (alcoholic chain and amino groups are suitable to form stable complexes with dibenzothiophene (DBT and its alkyl derivates. These sulfur pollutants are very difficult to eliminate through traditional catalytic processes. Spontaneous and exothermic interactions at 0 K primarily occur through the formation of stable complexes of organosulfur molecules with monomeric structures by hydrogen bonds. The bonds are formed between the sulfur atom and the hydrogen of the hydroxyl group; additional hydrogen bonds are formed between the hydrogen atoms of the organosulfur molecule and the nitrogen atoms of the monomers. We vary the number of methylene groups in the alcoholic chain containing the hydroxyl group of the monomer and find that the monomeric structure with four methylene groups has the best selectivity towards the interaction with the methyl derivates with reference to the interaction with DBT. Even this study does not consider solvent and competitive adsorption effects; our results show that monomeric structures containing amino and hydroxyl groups can be used to develop adsorbents to eliminate organosulfur pollutants from oil and its derivates.

  18. Thermodynamic and stereochemical aspects of the polymerizability of glycolide and lactide

    OpenAIRE

    Alemán Llansó, Carlos; Bertran Cànovas, Òscar; Houk, K. N.; Padias, Anne Buyle; Hall, H K

    2012-01-01

    The ring-opening polymerizations of the dilactones glycolide and the S,S- and S,R-stereoisomers of lactide were studied using quantum mechanical methods. The ring strain and the conformational distribution of these cyclic monomers and of the polymers were calculated, and the effect of the medium on the polymerization was predicted, for both bulk and solution. The polymerizability of the three monomers in the gas phase, that is, nonpolar medium, is much greater than tha...

  19. Development of novel self-healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer%含聚合单体微胶囊的牙科新型自修复抗菌复合树脂合成初探

    Institute of Scientific and Technical Information of China (English)

    吴峻岭; 张强; 朱婷; 葛建华; 周传健

    2015-01-01

    Objective To develop novel self-healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer,and to measure its properties for further clinical application.Methods Microcapsules filled with healing monomer of triethylene glycol dimethacrylate were synthesized according to methods introduced in the previous research.Microcapsules were added into novel resin composite containing nano-antibacterial silica fillers grafted with long chain alkyl quaternary ammonium at mass fractions of 0,2.5%,5.0%,7.5% or 10.0%.A commercial resin composite(Tetric N-Ceram) was used as control.Flexural test was used to measure resin composite flexural strength and elastic modulus.The single edge Ⅴ-notched beam method was used to measure fracture toughness and self-healing efficiency.Scanning electron microscope(SEM) was used to examine the fractured surface of selected specimen for investigation of fracture mechanisms.Results The flexural strength and elastic modulus of the resin composite were (96.4 ± 14.3) MPa and (6.2 ± 1.1) GPa respectively after incorporation of microcapsules up to 7.5%,and no significant difference was found between the experimental group and the control group[(99.1±1 1.9) MPa and (6.1±1.1) GPa] (P>0.05).The self-healing efficiency of (66.8±7.0)% and (79.3±9.7)% were achieved for resin composite with microcapsule mass fractions at 7.5% and 10.0%.SEM image showed that irregular films covered the fractured surface.Conclusions This novel self-healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer exhibited a promising self-healing ability,which enabled itself well up for combating bulk fracture and secondary caries in clinical application.%目的 合成含聚合单体微胶囊的牙科新型自修复抗菌复合树脂,并探讨相关性能,为其进一步临床应用提供参考.方法 制备含聚合单体三乙二醇二甲基丙

  20. Ionic Liquid Epoxy Resin Monomers

    Science.gov (United States)

    Paley, Mark S. (Inventor)

    2013-01-01

    Ionic liquid epoxide monomers capable of reacting with cross-linking agents to form polymers with high tensile and adhesive strengths. Ionic liquid epoxide monomers comprising at least one bis(glycidyl) N-substituted nitrogen heterocyclic cation are made from nitrogen heterocycles corresponding to the bis(glycidyl) N-substituted nitrogen heterocyclic cations by a method involving a non-nucleophilic anion, an alkali metal cation, epichlorohydrin, and a strong base.

  1. Advanced clay nanocomposites based on in situ photopolymerization utilizing novel polymerizable organoclays

    Science.gov (United States)

    Kim, Soon Ki

    Polymer nanocomposite technology has had significant impact on material design. With the environmental advantages of photopolymerization, a research has recently focused on producing nanocomposites utilizing inexpensive clay particles based on in situ photopolymerization. In this research, novel polymerizable organoclays and thiol-ene photopolymerization have been utilized to develop advanced photopolymer clay nanocomposites and to overcome several limitations in conventional free radical photopolymers. To this end, factors important in nanocomposite processes such as monomer composition, clay dispersion, and photopolymerization behavior in combination with the evolution of ultimate nanocomposite properties have been investigated. For monomer-organoclay compositions, higher chemical compatibility of components induces enhanced clay exfoliation, resulting in photopolymerization rate increases due to an amplified clay template effect. Additionally, by affecting the stoichiometric ratio between thiol and acrylate double bond in the clay gallery, thiolated organoclays enhance thiol-ene copolymerization with increased final thiol conversion while acrylated organoclays encourage acrylate homopolymerization. In accordance with the reaction behavior, incorporation of thiolated organoclays makes polymer chains more flexible with decreased glass transition temperature due to higher formation of thio-ether linkages while adding acrylated organoclays significantly increases the modulus. Photopolymer nanocomposites also help overcome two major drawbacks in conventional free radical photopolymerization, namely severe polymerization shrinkage and oxygen inhibition during polymerization. With addition of a low level of thiol monomers, the oxygen inhibition in various acrylate systems can be overcome by addition of only 5wt% thiolated organoclay. The same amount of polymerizable organoclay also induces up to 90% decreases in the shrinkage stress for acrylate or thiol

  2. Preparation of highly monodisperse fluorescent polymer particles by miniemulsion polymerization of styrene with a polymerizable surfactant.

    Science.gov (United States)

    Taniguchi, Tatsuo; Takeuchi, Naoki; Kobaru, Shotaro; Nakahira, Takayuki

    2008-11-01

    Miniemulsion polymerization of styrene (St) in the presence of a hydrophobe (hexadecane:HD) using a cationic polymerizable surfactant (N,N-dimethyl-N-n-dodecyl-N-2-methacryloyloxyethylammonium bromide:C(12)Br) and a cationic initiator (2,2'-azobis(2-amidinopropane) dihydrochloride:V50), called St/C(12)Br/V50 hereafter, proceeded efficiently compared with that using sodium dodecyl sulfate (SDS) and potassium persulfate (KPS), i.e., St/SDS/KPS, providing monodisperse polystyrene latex particles with a narrower particle size distribution. In St/C(12)Br/AIBN, where an oil-soluble initiator, i.e., 2,2'-azobisisobutyronitrile (AIBN), was used in place of V50, little changes in polymerization kinetics or in particle size distribution were observed, while a significant drop in polymerization rate and a broad particle size distribution were observed with St/SDS/AIBN. A polymerizable pyrene derivative (1-pyrenylmethyl methacrylate: PyMMA) was quantitatively incorporated into monodisperse latex particles in St/PyMMA/C(12)Br/V50 compared to pyrene (Py) in St/Py/C(12)Br/V50. Contrary to our expectation, however, increased excimer emission was observed with St/PyMMA/C(12)Br/V50 particles, indicating less evenly distributed pyrene chromophores in the particles. The fluorescence lifetime of pyrene chromophores in St/Py/C(12)Br/V50 particles was determined to be 286 ns, which was 17 times longer than that of pyrene in THF solution.

  3. Synthesis and studies of novel high metal content organic aerogels obtained from a polymerizable titanium complex

    International Nuclear Information System (INIS)

    Inertial Confinement Fusion (ICF) is a technique widely studied by the French atomic commission (CEA). Experiments will be performed within the Laser Megajoule (LMJ). They require innovative materials like organic aerogels that constitute laser targets. Such polymeric material must provide both a high porosity and a significant titanium percentage (1 atom %). Moreover, the monomers developed must be compatible with the synthesis procedure already in use. According to these specifications, a new polymerizable titanium complex was synthesized and fully characterized. This air and moisture-stable monomer provides a high metal percentage. Its free-radical cross-linked copolymerization affords several titanium-containing polymers. These gels were dried under supercritical conditions and organic aerogels were obtained. The chemical compositions of these materials were investigated by NMR, IR and elemental analysis while their structure was characterized by MEB-EDS, MET, N2 adsorption/desorption isotherms measurements and SAXS. The data collected fit the specification requirements. Moreover, the mechanisms responsible of the foam nano-structure formation were discussed. (author)

  4. New polymerizable luminescence probe for detection of Chlorfenvinphos and Dichlorvos pesticides

    Energy Technology Data Exchange (ETDEWEB)

    Azab, Hassn A.; Orabi, Adel S.; Abbas, Abbas M., E-mail: abbasmamdoh@science.suez.edu.eg

    2015-11-15

    Luminescence quenching probe ratio Tb(III):(L) in 1:3 stoichiometric has been studied in methanol in the bearing of the pesticides Chlorfenvinphos and Dichlorvos. The luminescence intensity of Tb(III)–(L){sub 3} probe decreases as the concentrations of the pesticide increases. Direct methods for the determination of the pesticides under investigation have been developed using the luminescence quenching of Tb(III)–(L){sub 3} probe in the solution. The detection limits were 1.9 and 1.96 µM for Chlorfenvinphos and Dichlorvos, respectively. Stern–Volmer studies at different temperatures, indicating that collisional quenching dominates for the pesticides. The binding constants (K) and thermodynamic parameters (∆S°, ∆H° and ∆G°) of the interaction of pesticides with the complex were evaluated. A polymer containing Tb(III)–(L){sub 3} complex and the polymerizable ligand (L; as monomer) was prepared. The polymer was characterized using EDAX, FT-IR and thermal analysis (TGA and DTA). The interaction of the polymer with Chlorfenvinphos and Dichlorvos was investigated, which gave different behavior from Tb(III)–(L){sub 3} complex with limit of detection of 0.43 and 0.32 µM for pesticides Chlorfenvinphos and Dichlorvos, respectively. - Highlights: • Luminescence quenching probe of 1:3 stoichiometric ratio Tb(III)-(L) has been studied in methanol in the presence of the pesticides Chlorfenvinphos and Dichlorvos. The luminescence intensity of Tb(III)-(L)3 probe decreases as the concentration of the pesticide increases. • Direct methods for the determination of the pesticides under investigation have been developed using the luminescence quenching probe in solution. The detection limits were 1.9 and 1.96 µM for pesticides Chlorfenvinphos and Dichlorvos, respectively. • The binding constants (K) and thermodynamic parameters (∆Sº, ∆Hº and ∆Gº) of the interaction of pesticides with the complex were evaluated. • A polymer containing Tb

  5. New polymerizable luminescence probe for detection of Chlorfenvinphos and Dichlorvos pesticides

    International Nuclear Information System (INIS)

    Luminescence quenching probe ratio Tb(III):(L) in 1:3 stoichiometric has been studied in methanol in the bearing of the pesticides Chlorfenvinphos and Dichlorvos. The luminescence intensity of Tb(III)–(L)3 probe decreases as the concentrations of the pesticide increases. Direct methods for the determination of the pesticides under investigation have been developed using the luminescence quenching of Tb(III)–(L)3 probe in the solution. The detection limits were 1.9 and 1.96 µM for Chlorfenvinphos and Dichlorvos, respectively. Stern–Volmer studies at different temperatures, indicating that collisional quenching dominates for the pesticides. The binding constants (K) and thermodynamic parameters (∆S°, ∆H° and ∆G°) of the interaction of pesticides with the complex were evaluated. A polymer containing Tb(III)–(L)3 complex and the polymerizable ligand (L; as monomer) was prepared. The polymer was characterized using EDAX, FT-IR and thermal analysis (TGA and DTA). The interaction of the polymer with Chlorfenvinphos and Dichlorvos was investigated, which gave different behavior from Tb(III)–(L)3 complex with limit of detection of 0.43 and 0.32 µM for pesticides Chlorfenvinphos and Dichlorvos, respectively. - Highlights: • Luminescence quenching probe of 1:3 stoichiometric ratio Tb(III)-(L) has been studied in methanol in the presence of the pesticides Chlorfenvinphos and Dichlorvos. The luminescence intensity of Tb(III)-(L)3 probe decreases as the concentration of the pesticide increases. • Direct methods for the determination of the pesticides under investigation have been developed using the luminescence quenching probe in solution. The detection limits were 1.9 and 1.96 µM for pesticides Chlorfenvinphos and Dichlorvos, respectively. • The binding constants (K) and thermodynamic parameters (∆Sº, ∆Hº and ∆Gº) of the interaction of pesticides with the complex were evaluated. • A polymer containing Tb(III)-(L) complex and the

  6. Polymerization of organized monomers

    Directory of Open Access Journals (Sweden)

    Stoiljković Dragoslav M.

    2004-01-01

    Full Text Available The current explanations of olefin and vinyl monomer polymerization propose that monomer molecules are successively added one by one to the growing polymer chain. This may be true if the monomer molecules exist as individual species in a polymerizing system, e.g. in dilute solutions of monomer. There are cases, however, in which monomer molecules are organized: bulk liquid monomer, solid monomer, a monomer monolayer adsorbed on a support, etc. Various supra-molecular species and particles of monomer exist in such cases. In the 1960-ties, Semenov, Kargin and Kabanov proposed a theory of organized monomer polymerization. In the last 25 years, our research group has further developed and applied that theory to various polymerizing systems: the radical polymerization of compressed ethene gas, the radical polymerization of liquid methyl methacrylate, olefin polymerization by transition metals and by Al-based catalysts. An outline of the main achievements are presented in this article.

  7. Effect of cationic surfactants on characteristics and colorimetric behavior of polydiacetylene/silica nanocomposite as time-temperature indicator

    Science.gov (United States)

    Nopwinyuwong, Atchareeya; Kitaoka, Takuya; Boonsupthip, Waraporn; Pechyen, Chiravoot; Suppakul, Panuwat

    2014-09-01

    Polydiacetylene (PDA)/silica nanocomposites were synthesized by self-assembly method using polymerizable amphiphilic diacetylene monomers, 10,12-pentacosadiynoic acid (PCDA). Addition of cationic surfactants (PDADMAC and CTAB) to PDA/SiO2 nanocomposites induced higher intermolecular force which affected their size, shape and color transition. Pure PDA, PDA/SiO2, PDA/SiO2/PDADMAC and PDA/SiO2/CTAB were investigated by particle size analysis, TEM, SEM, UV-vis spectroscopy and FT-IR. It was found that the PDA/SiO2 nanocomposites exhibited slightly larger particle sizes than those of other samples. The PDA/SiO2 nanocomposites with a core-shell structure were almost regarded as spherical-shaped particles. Cationic surfactants, especially CTAB, presumably affected the particle size and shape of PDA/SiO2 nanocomposites due to the disruption of hydrogen bonding between PDA head group and ammonium group. The colorimetric response of both PDA/SiO2/surfactant and surfactant-free PDA/SiO2 aqueous solutions directly changed in relation to time and temperature; thus they were expected to be applied as a new polymer-based time-temperature indicator (TTI).

  8. Recovery of olefin monomers

    Science.gov (United States)

    Golden, Timothy Christoph; Weist, Jr., Edward Landis; Johnson, Charles Henry

    2004-03-16

    In a process for the production of a polyolefin, an olefin monomer is polymerised said polyolefin and residual monomer is recovered. A gas stream comprising the monomer and nitrogen is subjected to a PSA process in which said monomer is adsorbed on a periodically regenerated silica gel or alumina adsorbent to recover a purified gas stream containing said olefin and a nitrogen rich stream containing no less than 99% nitrogen and containing no less than 50% of the nitrogen content of the gas feed to the PSA process.

  9. Nonionic Polymerizable Emulsifier in High-Solids-Content Acrylate Emulsion Polymerization

    Institute of Scientific and Technical Information of China (English)

    LU Deping; HUANG Hongzhi; SHEN Ling; XIE Jin; GUAN Rong

    2012-01-01

    Stable high-solids-content acrylate emulsion were obtained with a nonionic polymerizable emulsifier allyloxy nonylphenoxy poly (ethyleneoxy) (10) ether (ANPEO10),and a conventional emulsifier OP-10 as a reference sample.1H NMR proves that the polymerizable emulsifier ANPEO10 has been incorporated into the resulted acrylate polymers.TEM demonstrates that there are some differences in the particle morphologies.AFM proves that the polymerizable emulsifier ANPEO10 migrating to the surface of the emulsion film was much less than the conventional emulsifier OP-10.The polymerizable emulsifier ANPEO10 can enhance the adhesion with glass plate compared to the conventional emulsifier.Furthermore,with increasing amount of emulsifier,the surface free energy of the films first decreased and then increased,and the adhesion with glass plate is initially enhanced and then attenuated.The water-resistance and solvent-resistance of the films prepared by the polymerizable emulsifier ANPEO10 are superior to those prepared by the conventional emulsifier OP-10.

  10. Radical Cations of the Monomer and van der Waals Dimer of a Methionine Residue as Prototypes of (2 Center-3 Electron) SN and SS Bonds. Molecular Simulations of Their Absorption Spectra in Water.

    Science.gov (United States)

    Archirel, Pierre; Bergès, Jacqueline; Houée-Lévin, Chantal

    2016-09-22

    Oxidation of peptides or proteins by the OH(•) radicals produced by pulse radiolysis yields species identified by their absorption spectra in the UV-visible domain. However, the case of methionine (Met) in peptides is complex because its oxidation can lead to various free radicals with 2 center-3 electron (2c-3e) bonds. We have performed Monte Carlo/density functional theory molecular simulations of the radical cation of the methylated methionine aminoacid, Met(•+), taken as a model of the methonine residue of peptides, and of the radical cation of its van der Waals dimer, Met2(•+). The cation of the methionine residue displays a 2c-3e SN bond. The cation of dimer Met2(•+) displays three quasidegenerate conformers, one stabilized by a 2c-3e SS bond and the other two stabilized by ion-molecule interactions and made up of a neutral and a cationic unit. These conformers are characterized by their charge and spin density localization and their UV-visible absorption spectra. These spectra enable a discussion of the absorption spectra of the literature; in particular, we emphasize the role of dimers before and after the oxidation process. PMID:27564585

  11. Regioselective Synthesis of Polymerizable Vinyl Guaifenesin Esters Catalyzed by an Alkaline Protease of Bacillus subtilis

    Institute of Scientific and Technical Information of China (English)

    Na WANG; Qi WU; Jian Ming XU; Xiu Ming JIANG; Xian Fu LIN

    2004-01-01

    Three polymerizable vinyl guaifenesin esters with different acyl donor carbon chain lengths (C4,C6,C10) were regioselectivly synthesized by an alkaline protease from Bacillus subtilis in pyridine at 50°C for 1, 3, 5 days respectively.

  12. Characterization of the phase behaviour of a novel polymerizable lyotropic ionic liquid crystal.

    Science.gov (United States)

    Goujon, Nicolas; Forsyth, Maria; Dumée, Ludovic F; Bryant, Gary; Byrne, Nolene

    2015-09-21

    The development of new polymerizable lyotropic liquid crystals (LLCs) utilizing charged amphiphilic molecules such as those based on long chain imidazolium compounds, is a relatively new design direction for producing robust membranes with controllable nano-structures. Here we have developed a novel polymerizable ionic liquid based LLC, 1-hexadecyl-3-methylimidazolium acrylate (C16mimAcr), where the acrylate anion acts as the polymerizable moiety. The phase behaviour of the C16mimAcr upon the addition of water was characterized using small and wide angle X-ray scatterings, differential scanning calorimetry and polarized optical microscopy. We compare the phase behaviour of this new polymerizable LLC to that of the well known LLC chloride analogue, 1-hexadecyl-3-methylimidazolium chloride (C16mimCl). We find that the C16mimAcr system has a more complex phase behaviour compared to the C16mimCl system. Additional lyotropic liquid crystalline mesophases such as hexagonal phase (H1) and discontinuous cubic phase (I1) are observed at 20 °C for the acrylate system at 50 and 65 wt% water respectively. The appearance of the hexagonal phase (H1) and discontinuous cubic phase (I1) for the acrylate system is likely due to the strong hydrating nature of the acrylate anion, which increases the head group area. The formation of these additional mesophases seen for the acrylate system, especially the hexagonal phase (H1), coupled with the polymerization functionality offers great potential in the design of advanced membrane materials with selective and anisotropic transport properties. PMID:26271610

  13. Xylene as a New Polymerizable Additive for Overcharge Protection of Lithium Ion Batteries

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qianyu; QIU Chenchen; FU Yanbao; MA Xiaohua

    2009-01-01

    The electrochemical properties and overcharge protection mechanism of xylene as a new polymerizable electrolyte additive for overcharge protection of lithium ion batteries were studied by cyclic voltammetry tests,chargedischarge performance and battery power capacity measurements.It was found that when the battery was overcharged,xylene could electrochemically polymerize at the overcharge potential of 4.3-4.7 V (vs.Li/Li+) to form a thin polymer film on the surface of the cathode,thus preventing voltage runaway.On the other hand,the use of xylene as an overcharge protection electrolyte additive did not influence the normal performance of lithium ion batteries.

  14. Di(hydroxyphenyl)- benzimidazole monomers

    Science.gov (United States)

    Connell, John W. (Inventor); Hergenrother, Paul M. (Inventor); Smith, Joseph G. (Inventor)

    1993-01-01

    Di(hydroxyphenyl)benzimidazole monomers were prepared from phenyl-hydroxybenzoate and aromatic bis(o-diamine)s. These monomers were used in the synthesis of soluble polybenzimidazoles. The reaction involved the aromatic nucleophilic displacement of various di(hydroxyphenyl)benzimidazole monomers with activated aromatic dihalides or activated aromatic dinitro compounds in the presence of an alkali metal base. These polymers exhibited lower glass transition temperatures, improved solubility, and better compression moldability over their commercial counterparts.

  15. 丙烯酰胺与季铵类阳离子单体双水相共聚的二次相分离%DOUBLE PHASE SEPARATION OF AQUEOUS TWO-PHASE COPOLYMERIZATION OF ACRYLAMIDE WITH QUATERNARY AMMONIUM CATIONIC MONOMERS

    Institute of Scientific and Technical Information of China (English)

    商宽祥; 单国荣

    2012-01-01

    以(2-甲基丙烯酰氧乙基)三甲基氯化铵(DMC)为例,用分光光度法研究了丙烯酰胺(AM)与季铵类阳离子单体在聚乙二醇(PEG)水溶液中双水相共聚的二次相分离.提出了二次相分离的机理,认为是阳离子单体单元的电离使得聚合物带上了正电荷,大分子间的静电排斥作用增加了其在PEG相中的溶解性(增容作用).讨论了反应条件对体系二次相分离的影响,发现二次相分离在一定的单体浓度和PEG浓度、以及适当的单体比例和PEG分子量条件下才能发生.总单体用量或PEG用量增加,第二次分相先出现后消失;PEG分子量增大,第二次分相逐渐明显;反应温度升高,两次分相更快完成.DMC摩尔分率为0.25~ 0.60时,第一次分相的临界转化率很小,第二次分相的临界转化率则随DMC摩尔分率的增加而增大;DMC摩尔分率超过0.60后,聚合反应主要在过渡区完成,第二次分相难以发生.%In the aqueous two-phase copolymerization of acrylamide ( AM ) with quaternary ammonium cationic monomers, such as 2-methylacryloylxyethyl trimethyl ammonium chloride (DMC),in aqueous poly-(ethylene glycol) (PEG) solution a double phase separation process was observed. In order to fix the critical points,the spectrophotometer was employed to detect the transmittance of the copolymerization system on-line. The transmittance curves showed three intervals. At the first interval, the transmittance keeps constant at the beginning,and then drops off quickly. At the second interval, the transmittance stops dropping and begins to increase. And at the last interval,the transmittance stops to keep constant for a moment,and then drops rapidly to nearly zero. When acrylamide was copolymerized with different monomers, the double phase separation process can be observed only for DMC and acryloylxyethyl trimethyl ammonium chloride ( DAC ) . It confirms that the double phase separation is attributed to the cationic nature of

  16. Copolymerization of Carbon–carbon Double-bond Monomer (Styrene with Cyclic Monomer (Tetrahydrofuran

    Directory of Open Access Journals (Sweden)

    Sari Fouad

    2012-12-01

    Full Text Available We reported in this work that the cationic copolymerization in one step takes place between carbon–carbon double-bond monomer styrene with cyclic monomer tetrahydrofuran. The comonomers studied belong to different families: vinylic and cyclic ether. The reaction is initiated with maghnite-H+ an acid exchanged montmorillonite as acid solid ecocatalyst. Maghnite-H+ is already used as catalyst for polymerization of many vinylic and heterocyclic monomers. The oxonium ion of tetrahydrofuran and carbonium ion of styrene propagated the reaction of copolymerization. The acetic anhydride is essential for the maintenance of the ring opening of tetrahydrofuran and the entry in copolymerization. The temperature was kept constant at 40°C in oil bath heating for 6 hours. A typical reaction product was analyzed by 1H-NMR, 13C-NMR and IR and the formation of the copolymer was confirmed. The reaction was proved by matched with analysis. The maghnite-H+ allowed us to obtain extremely pure copolymer in good yield by following a simples operational conditions. Copyright © 2012 by BCREC UNDIP. All rights reservedReceived: 29th October 2012; Revised: 29th November 2012; Accepted: 29th November 2012[How to Cite: S. Fouad, M.I. Ferrahi, M. Belbachir. (2012. Copolymerization of Carbon–carbon Double-bond Monomer (Styrene with Cyclic Monomer (Tetrahydrofuran. Bulletin of Chemical Reaction Engineering & Catalysis, 7(2: 165-171. (doi:10.9767/bcrec.7.2.4074.165-171][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.2.4074.165-171 ] | View in 

  17. Synthesis and characterization of polymerizable one-component photoinitiator based on sesamol.

    Science.gov (United States)

    Yang, Jinliang; Tang, Ruifen; Shi, Suqing; Nie, Jun

    2013-05-01

    Migration stability and biocompatibility are the crucial features for a photoinitiator or coinitiator used in UV curable formulations, especially when the cured product is in direct contact with food or human skin. To reduce the migration issues and increase the biocompatibility, a polymerizable one-component photoinitiator, 1-(1,3-benzodioxol-5-yloxy)-3-(4-benzoylphenoxy)propan-2-yl acrylate (BDOBPAc), based on sesamol and benzophenone has been synthesized. The photopolymerization induced by BDOBPAc was monitored by real-time infrared spectroscopy. The rate of decomposition and the migration stability of photoinitiators were studied by UV-Vis spectroscopy. The results showed that BDOBPAc is an effective free radical photoinitiator with good migration stability, which has great potential to be widely used in the food packing or biomedical fields. PMID:23479096

  18. Interactions of univalent counterions with headgroups of monomers and dimers of an anionic surfactant.

    Science.gov (United States)

    Jakubowska, Anna

    2015-03-24

    Specific ion effects in solution are related to the hydrated ion size and ion hydration, electrostatic interactions, dispersion forces, ion effects on water structure, and ion modification of surface tension. In this study, we tried to identify which factor determines the ion specificity observed. The preference and energy of metal cations binding with the headgroups of dodecylsulfate (DS) monomers and dimers were determined by mass spectrometry. In the gas phase, cation binding to DS dimer headgroups depends strongly on the cation radius. On the other hand, the interactions between DS monomer headgroups and chaotropic ions depend on the cation polarizability, and the binding of kosmotropic cations to DS monomer headgroups strongly depends on the Gibbs free energies of ion hydration. DS dimers are related to surfactants having doubly charged headgroups, and DS monomers are related to surfactants with singly charged headgroups. Our spectrometric study of the strength of counterion binding to free monomers of a surfactant provides insight into surfactant-counterion interactions at micellar interfaces in bulk solution.

  19. Monomer Migration and Annihilation Processes

    Institute of Scientific and Technical Information of China (English)

    KE Jian-Hong; LIN Zhen-Quan; ZHUANG You-Yi

    2005-01-01

    We propose a two-species monomer migration-annihilation model, in which monomer migration reactions occur between any two aggregates of the same species and monomer annihilation reactions occur between two different species. Based on the mean-field rate equations, we investigate the evolution behaviors of the processes. For the case with an annihilation rate kernel proportional to the sizes of the reactants, the aggregation size distribution of either species approaches the modified scaling form in the symmetrical initial case, while for the asymmetrical initial case the heavy species with a large initial data scales according to the conventional form and the light one does not scale. Moreover,at most one species can survive finally. For the case with aconstant annihilation rate kernel, both species may scale according to the conventional scaling law in the symmetrical case and survive together at the end.

  20. Monomers of cutin biopolymer: sorption and esterification on montmorillonite surfaces

    Science.gov (United States)

    Olshansky, Yaniv; Polubesova, Tamara; Chefetz, Benny

    2013-04-01

    One of the important precursors for soil organic matter is plant cuticle, a thin layer of predominantly lipids that cover all primary aerial surfaces of vascular plants. In most plant species cutin biopolymer is the major component of the cuticle (30-85% weight). Therefore cutin is the third most abundant plant biopolymer (after lignin and cellulose). Cutin is an insoluble, high molecular weight bio-polyester, which is constructed of inter-esterified cross linked hydroxy-fatty acids and hydroxyepoxy-fatty acids. The most common building blocks of the cutin are derivatives of palmitic acid, among them 9(10),16 dihydroxy palmitic acid (diHPA) is the main component. These fatty acids and their esters are commonly found in major organo-mineral soil fraction-humin. Hence, the complexes of cutin monomers with minerals may serve as model of humin. Both cutin and humin act as adsorption efficient domains for organic contaminants. However, only scarce information is available about the interactions of cutin with soil mineral surfaces, in particular with common soil mineral montmorillonite. The main hypothesize of the study is that adsorbed cutin monomers will be reconstituted on montmorillonite surface due to esterification and oligomerization, and that interactions of cutin monomers with montmorillonite will be affected by the type of exchangeable cation. Cutin monomers were obtained from the fruits of tomato (Lycopersicon esculentum). Adsorption of monomers was measured for crude Wyoming montmorillonites and montmorillonites saturated with Fe3+ and Ca2+. To understand the mechanism of monomer-clay interactions and to evaluate esterification on the clay surface, XRD and FTIR analyses of the montmorillonite-monomers complexes were performed. Our results demonstrated that the interactions of cutin monomers with montmorillonite are affected by the type of exchangeable cation. Isotherms of adsorption of cutin monomers on montmorillonites were fitted by a dual mode model of

  1. Comparison of Facially Amphiphilic versus Segregated Monomers in the Design of Antibacterial Copolymers

    OpenAIRE

    Gabriel, Gregory J.; Maegerlein, Janet A.; Nelson, Christopher F.; Dabkowski, Jeffrey M.; Eren, Tarik; Nüsslein, Klaus; Tew, Gregory N.

    2009-01-01

    A direct comparison of two strategies for designing antimicrobial polymers is presented. Previously, we published several reports on the use of facially amphiphilic (FA) monomers which led to polynorbornenes with excellent antimicrobial activities and selectivities. Our polymers obtained by copolymerization of structurally similar segregated monomers, in which cationic and non-polar moieties reside on separate repeat units, led to polymers with less pronounced activities. A wide range of poly...

  2. Comparison of facially amphiphilic versus segregated monomers in the design of antibacterial copolymers.

    Science.gov (United States)

    Gabriel, Gregory J; Maegerlein, Janet A; Nelson, Christopher F; Dabkowski, Jeffrey M; Eren, Tarik; Nüsslein, Klaus; Tew, Gregory N

    2009-01-01

    A direct comparison of two strategies for designing antimicrobial polymers is presented. Previously, we published several reports on the use of facially amphiphilic (FA) monomers which led to polynorbornenes with excellent antimicrobial activities and selectivities. Our polymers obtained by copolymerization of structurally similar segregated monomers, in which cationic and non-polar moieties reside on separate repeat units, led to polymers with less pronounced activities. A wide range of polymer amphiphilicities was surveyed by pairing a cationic oxanorbornene with eleven different non-polar monomers and varying the comonomer feed ratios. Their properties were tested using antimicrobial assays and copolymers possessing intermediate hydrophobicities were the most active. Polymer-induced leakage of dye-filled liposomes and microscopy of polymer-treated bacteria support a membrane-based mode of action. From these results there appears to be profound differences in how a polymer made from FA monomers interacts with the phospholipid bilayer compared with copolymers from segregated monomers. We conclude that a well-defined spatial relationship of the whole polymer is crucial to obtain synthetic mimics of antimicrobial peptides (SMAMPs): charged and non-polar moieties need to be balanced locally, for example, at the monomer level, and not just globally. We advocate the use of FA monomers for better control of biological properties. It is expected that this principle will be usefully applied to other backbones such as the polyacrylates, polystyrenes, and non-natural polyamides. PMID:19021176

  3. Synthesis of Polymerizable Amphiphiles with Systematic Variation of Critical Packing Parameters

    Institute of Scientific and Technical Information of China (English)

    M. H. Li; W. L. Yang; J. Qian; C. C. Wang; S. K. Fu

    2005-01-01

    @@ 1Introduction An amphiphile is a molecule composed of hydrophilic part and hydrophobic part, which are incompatible and tend to separate from each other. The tendency of separation is often promoted by addition of water and sometimes also oil. Under balanced conditions the mixtures form macroscopically homogeneous phases, including isotropic solution phases and liquid crystalline phases. Correlation of the amphiphile structure with its preferred phases could be understood with a simple geometric model[1], which defines a dimensionless Critical Packing Parameter (CPP) to describe the relative bulkiness of the hydrophobic part and the hydrophilic part in an amphiphile. With CPP increasing from a small value to a high value the amphiphile changes from hydrophilic to hydrophobic, its preferred phase structure from direct structures via lamellar structure to reverse structures. This model provides a basis for the molecular design of amphiphiles. To immobilize the microstructure of the phases formed by amphiphiles is a challenge for current material chemists. Techniques of both inorganic polymerization[2] and organic polymerization[3] have been developed. With organic polymerization the molecular design of polymerizable amphiphiles is critical for the successful immobilization of the vulnerable precursor microstructures.

  4. Synthesis of Thermal Polymerizable Alginate-GMA Hydrogel for Cell Encapsulation

    Directory of Open Access Journals (Sweden)

    Xiaokun Wang

    2015-01-01

    Full Text Available Alginate is a negative ionic polysaccharide that is found abundantly in nature. Calcium is usually used as a cross-linker for alginate. However, calcium cross-linked alginate is used only for in vitro culture. In the present work, alginate was modified with glycidyl methacrylate (GMA to produce a thermal polymerizable alginate-GMA (AA-GMA macromonomer. The molecular structure and methacrylation (%DM of the macromonomer were determined by 1H NMR. After mixing with the correct amount of initiator, the AA-GMA aqueous solution can be polymerized at physiological temperature. The AA-GMA hydrogels exhibited a three-dimensional porous structure with an average pore size ranging from 50 to 200 μm, directly depending on the macromonomer concentration. Biocompatibility of the AA-GMA hydrogel was determined by in vivo muscle injection and cell encapsulation. Muscle injection in vivo showed that the AA-GMA solution mixed with initiator could form a hydrogel in situ and had a mild inflammatory effect. Human umbilical vein endothelial cells (HUVECs were encapsulated in the AA-GMA hydrogels in situ at 37°C. Cell viability and proliferation were unaffected by macromonomer concentrations, which suggests that AA-GMA has a potential application in the field of tissue engineering, especially for myocardial repair.

  5. 两性聚羧酸类高聚物阳离子丙烯酸酯单体 DAC 的制备及其性能%Preparation and performance of cationic acrylate monomer (DAC) for amphoteric carboxylic acid polymer

    Institute of Scientific and Technical Information of China (English)

    陈宝璠

    2015-01-01

    以丙烯酸甲酯(MA)与2氯乙醇(CE)为反应原料,通过酯交换反应制备了丙烯酸氯乙醇酯(CA)中间体,再将 CA 与三甲胺(TMA)水溶液反应,合成了一种用于制备两性聚羧酸类高聚物的阳离子丙烯酸酯单体(丙烯酰氧乙基三甲基氯化铵,DAC).采用 FTIR 和1 HNMR 对 DAC 结构进行了表征,并考察了 n(TMA)/n (CA)、催化剂用量、阻聚剂用量、反应温度和反应时间对 CA 转化率和 DAC 质量分数的影响.结果显示:最佳制备工艺条件为 n(TMA)/n(CA)=1.2,催化剂用量为 CA 中间体质量的4.5%,阻聚剂用量为 CA 中间体质量的0.6%,反应温度为50℃,反应时间为3 h.以 DAC 为阳离子单体,与丙烯酸(AA)、聚乙二醇单甲醚丙烯酸酯(MPEGAA)通过反相乳液共聚合制得两性聚羧酸类高聚物,该高聚物具有优异的保坍性和较高的早期抗压强度.%A cationic acrylate monomer,[2-(acryloyloxy)ethyl]trimethyl ammonium chloride,DAC),used for synthetizing amphoteric carboxylic acid polymer was prepared by reaction of 2-chloroethyl acrylate (CA)inter-mediate and trimethylamine (TMA)aqueous solution.The 2-chloroethyl acrylate (CA)intermediate was pre-pared by transesterification of methyl acrylate and 2-chloroethanol.The DAC structure was identified by means of FTIR and 1 HNMR.The influences of n (TMA)/n (CA),dosages of catalyst and polymerization inhibitor,reaction temperature and reaction time were investigated with the conversion rate of CA and mass fraction of DAC.The results show that the optimal technological conditions for the preparation includes:n(TMA)/n(CA)is 1.2,the dosage of catalyst is 4.5% and the dosage of polymerization inhibitor is 0.6%according to the mass of CA,the reaction temperature is 50 ℃ and the reaction time is 3 h.And the amphoter-ic carboxylic acid polymer was prepared by means of inverse emulsion copolymerization of DAC

  6. GENERAL: Cluster Growth Through Monomer Adsorption Processes

    Science.gov (United States)

    Ke, Jian-Hong; Lin, Zhen-Quan; Chen, Xiao-Shuang

    2010-02-01

    We propose a monomer adsorption model, in which only the monomers are allowed to diffuse and adsorb onto other clusters. By means of the generalized rate equation we investigate the kinetic behavior of the system with a special rate kernel. For the system without monomer input, the concentration aj(t) of the Aj clusters (j > 1) asymptotically retains a nonzero quantity, while for the system with monomer input, it decays with time and vanishes finally. We also investigate the kinetics of an interesting model with fixed-rate monomer adsorption. For the case without monomer source, the evolution of the system will halt at a finite time; while the system evolves infinitely in time in the case with monomer source. Finally, we also suggest a connection between the fixed-rate monomer adsorption systems and growing networks.

  7. Monomer Fraction in Real Gases

    Directory of Open Access Journals (Sweden)

    Boris Sedunov

    2008-03-01

    Full Text Available This work is aimed to attract attention to monomer fraction density (MFD, the variable that has not yet taken its place in the theory of real gases. The work shows that this variable can be calculated for monocomponent real gases from experimental isothermal dependences of their density on pressure and can be used for calculations of Gibbs energy, entropy and clusters equilibrium constants in real gases. The MFD-based joint series expansions method for density and pressure is suggested as an alternative to virial expansions. This method corresponds to the chemical equilibrium theory and provides new non-obvious results.

  8. Optimum Conditions for Introducing Free Radical Polymerizable Methacrylate Groups on the MWCNT Surface by Michael Addition Reaction

    International Nuclear Information System (INIS)

    In this study, we investigated optimum conditions for the introduction of a lot of free radical polymerizable methacrylate groups on the multi-walled carbon nanotube (MWCNT) surface. Carboxyl groups were introduced first on MWCNT surfaces by treating with a mixture of sulfuric acid and nitric acid with ultrasonic bath for 2 hours, and oxidized MWCNTs were reacted further with thionyl chloride followed by triethylenetetramine (TETA) to introduce amino groups on the oxidized MWCNT surface, to make MWCNT-NH2. To introduce free radical polymerizable methacrylate groups on the MWCNT-NH2, MWCNT-NH2 was reacted with 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM) by Michael addition reaction. We investigated progress of modification reactions for MWCNT by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and elemental analysis (EA). We found maximum degree of Michael addition reactions between AHM and TETA grafted on MWCNT-NH2 for 10:1 mol ratio and 8 hour reaction time in our reaction conditions

  9. Monomer-dimer problem on some networks

    Science.gov (United States)

    Wu, Ruijuan; Yan, Weigen

    2016-09-01

    Zhang et al. (2012) obtained the exact formula for the number of all possible monomer-dimer arrangements and the asymptotic growth constant on a scale-free small-world network. In this note, we generalize this result and obtain the exact solution on the monomer-dimer model on many networks. Particularly, we prove that these networks have the same asymptotic growth constant of the number of monomer-dimer arrangements.

  10. Radiation-induced cationic curing of vinyl ethers

    International Nuclear Information System (INIS)

    Recently there has been an increasing interest in nonacrylate radiation-curable coatings. Vinyl ethers are particularly reactive under cationic polymerization reaction conditions. The high efficiency of the photoacid initiators combined with the high reactivity of vinyl ether monomers makes this a potentially very useful system. This chapter discusses the preparation of vinyl ethers, introduces vinyl ether-functional monomers and oligomers, describes radiation-induced cationic polymerization of vinyl ethers, and discusses various coating systems. Throughout the chapter, an emphasis is placed on radiation-curable coating applications. 64 refs., 5 figs., 11 tabs

  11. Visible Light Curable Restorative Composites for Dental Applications Based on Epoxy Monomer

    Directory of Open Access Journals (Sweden)

    Alessandra Vitale

    2014-01-01

    Full Text Available A cationic photo-curable cycloaliphatic epoxy resin has been investigated as reactive monomer in blue light crosslinking process. We have demonstrated that camphorquinone is able to abstract labile hydrogen from the epoxy monomer, giving rise to the formation of carbon-centered radicals that are oxidized by the onium salt; a complete epoxy group conversion was reached after 50 s of irradiation. The presence of water up to 1 wt% was tolerated without any important detrimental effect on the kinetics of light-curing. The presence of the inorganic filler up to 65 wt% did not significantly influence the curing process.

  12. Sulfometuron incorporation in cationic micelles adsorbed on montmorillonite

    OpenAIRE

    Mishael, Y. G.; Undabeytia López, Tomás; Rytwo, Giora; Papahadjopoulos Sternberg, B.; Rubin, Baruch; Nir, Shlomo

    2002-01-01

    The aim of this study was to understand the interactions between alkylammonium cations present as monomers and micelles and a clay mineral, montmorillonite, to develop slow release formulations of anionic herbicides, such as sulfometuron (SFM) whose leaching in soils is an environmental and economic problem. In the proposed formulation the herbicide is incorporated in positively charged micelles of quaternary amine cations, which in turn adsorb on the negatively charged clay. The adsorption o...

  13. Synthesis and characterisation of cationically modified phospholipid polymers.

    Science.gov (United States)

    Lewis, Andrew L; Berwick, James; Davies, Martyn C; Roberts, Clive J; Wang, Jin-Hai; Small, Sharon; Dunn, Anthony; O'Byrne, Vincent; Redman, Richard P; Jones, Stephen A

    2004-07-01

    Phospholipid-like copolymers based on 2-(methacryloyloxyethyl) phosphorylcholine were synthesised using monomer-starved free radical polymerisation methods and incorporating cationic charge in the form of the choline methacrylate monomer in amounts varying from 0 to 30 wt%, together with a 5 wt% silyl cross-linking agent in order to render them water-insoluble once thermally cured. Characterisation using a variety of techniques including nuclear magnetic resonance spectroscopy, high-pressure liquid chromatography and gel permeation chromatography showed the cationic monomer did not interfere with the polymerisation and that the desired amount of charge had been incorporated. Gravimetric and differential scanning calorimetry methods were used to evaluate the water contents of polymer membranes cured at 70 degrees C, which was seen to increase with increasing cation content, producing materials with water contents ranging from 50% to 98%. Surface plasmon resonance indicated that the coatings swelled rapidly in water, the rate and extent of swelling increasing with increasing cation level. Dynamic contact angle showed that coatings of all the polymers possessed a hydrophobic surface when dry in air, characteristic of the alkyl chains expressed at the surface (>100 degrees advancing angle). Rearrangement of the hydrophilic groups to the surface occurred once wet, to produce highly wettable surfaces with a decrease in advancing angle with increasing cation content. Atomic force microscopy showed all polymer films to be smooth with no features in topographical or phase imaging. Mechanical properties of the dry films were also unaffected by the increase in cation content.

  14. Cyclic Polymer with Alternating Monomer Sequence.

    Science.gov (United States)

    Zhu, Wen; Li, Zi; Zhao, Youliang; Zhang, Ke

    2015-11-01

    Cyclic polymers with alternating monomer sequence are synthesized for the first time based on the ring-closure strategy. Well-defined telechelic alternating polymers are synthesized by reversible addition-fragmentation chain transfer polymerization by copolymerizing the electron acceptor monomer of N-benzylmaleimide and donor monomer of styrene with a feed ratio of 1 between them. The corresponding cyclic alternating polymers are then produced by the UV-induced Diels-Alder click reaction to ring-close the linear alternating polymer precursors under highly diluted reaction solution.

  15. Characterization of Interactions of Hydroxyethylcellulose Derivatives in the Presence of Ionic Surfactants or with Cyclodextrin Monomers

    OpenAIRE

    2006-01-01

    In this work, Structural, dynamical, and rheological properties of aqueous solutions of hydroxyethylcellulose (HEC) derivatives in the presence of ionic surfactants or with cyclodextrin monomers have been investigated. The discussion about these systems has been divided into three parts. In the first part anionic hydroxyethylcellulose (HEC(-)) or its unmodified analogue in the presence of an anionic surfactant (SDS) or a cationic surfactant (CTAB or Gemini) is considered. Weak interactions be...

  16. Softening and elution of monomers in ethanol

    DEFF Research Database (Denmark)

    Benetti, Ana Raquel; Asmussen, Erik; Munksgaard, E Christian;

    2009-01-01

    The purpose of this study was to investigate the effect of light-curing protocol on softening and elution of monomers in ethanol as measured on a model polymer. It was a further aim to correlate the measured values with previously reported data on degree of conversion and glass transition tempera...

  17. Nonfouling hydrogels formed from charged monomer subunits.

    Science.gov (United States)

    Dobbins, Sean C; McGrath, Daniel E; Bernards, Matthew T

    2012-12-13

    A critical challenge in the field of biomaterials is the often undesirable, but immediate, coating of implants with nonspecifically adsorbed proteins upon contact with bodily fluids. Prior research has shown that overall neutral materials containing a homologous arrangement of mixed charges exhibit nonfouling properties. This has been widely demonstrated for zwitterionic materials and more recently for coatings containing an equimolar mixture of positively and negatively charged monomer subunits. In this investigation it is demonstrated that nonfouling hydrogels can be formed through this approach, and the physical properties of the resulting materials are thoroughly characterized. In particular, hydrogels were formed from mixtures of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TM) and 3-sulfopropyl methacrylate potassium salt (SA) monomers with varying concentrations of a triethylene glycol dimethacrylate (TEGDMA) cross-linker. The swelling, weight percentage water, surface zeta potential, and compressional properties of the gels were characterized, and the nonfouling properties were demonstrated using enzyme-linked immunosorbant assays for both negatively charged fibrinogen and positively charged lysozyme. The results confirm that the TM:SA hydrogel systems have nonfouling properties that are equivalent to established nonfouling controls. Additionally, even though the gels were resistant to nonspecific protein adsorption, a composition analysis suggests that there is room to further improve the nonfouling performance because there is a slight enrichment of the SA monomer relative to the TM monomer. PMID:23189949

  18. Monomers, Dimers, and Helices: Complexities of Cerium and Plutonium Phenanthrolinecarboxylates.

    Science.gov (United States)

    Cary, Samantha K; Ferrier, Maryline G; Baumbach, Ryan E; Silver, Mark A; Lezama Pacheco, Juan; Kozimor, Stosh A; La Pierre, Henry S; Stein, Benjamin W; Arico, Alexandra A; Gray, Danielle L; Albrecht-Schmitt, Thomas E

    2016-05-01

    The reaction of Ce(III) or Pu(III) with 1,10-phenanthroline-2,9-dicarboxylic acid (PDAH2) results in the formation of new f-element coordination complexes. In the case of cerium, Ce(PDA)(H2O)2Cl·H2O (1) or [Ce(PDAH)(PDA)]2[Ce(PDAH)(PDA)] (2) was isolated depending on the Ce/ligand ratio in the reaction. The structure of 2 is composed of two distinct substructures that are constructed from the same monomer. This monomer is composed of a Ce(III) cation bound by one PDA(2-) dianionic ligand and one PDAH(-) monoanionic ligand, both of which are tetradentate. Bridging by the carboxylate moieties leads to either [Ce(PDAH)(PDA)]2 dimers or [Ce(PDAH)(PDA)]1∞ helical chains. For plutonium, Pu(PDA)2 (3) was the only product isolated regardless of the Pu/ligand ratio employed in the reaction. During the reaction of plutonium with PDAH2, Pu(III) is oxidized to Pu(IV), generating 3. This assignment is consistent with structural metrics and the optical absorption spectrum. Ambiguity in the assignment of the oxidation state of cerium in 1 and 2 from UV-vis-near-IR spectra invoked the use of Ce L3,2-edge X-ray absorption near-edge spectroscopy, magnetic susceptibility, and heat capacity measurements. These experiments support the assignment of Ce(III) in both compounds. The bond distances and coordination numbers are also consistent with these assignments. 3 contains 8-coordinate Pu(IV), whereas the cerium centers in 1 and 2 are 9- and/or 10-coordinate, which correlates with the increased size of Ce(III) versus Pu(IV). Taken together, these data provide an example of a system where the differences in the redox behavior between these f elements creates more complex chemistry with cerium than with plutonium. PMID:27070401

  19. Polymerizable gemini surfactants at solid/solution interfaces: adsorption and polymerization on melamine formaldehyde particles and capsule fabrication.

    Science.gov (United States)

    Sakai, Kenichi; Izumi, Keiko; Sakai, Hideki; Abe, Masahiko

    2010-03-15

    Organic capsules have been fabricated via three steps, by using the polymerizable gemini surfactant (1,2-bis(dimethyl(11-methacryloyloxy)undecylammonio) hexane dibromide, PC11-6-11) as a single wall component. In the first fabrication step, the surfactant spontaneously adsorbs on acid-dissolvable melamine formaldehyde (MF) particles in aqueous media. The adsorption isotherm data reveal that the adsorbed amount of PC11-6-11 (per chain) is greater than that of the corresponding monomeric surfactant ((11-methacryloyloxy)undecyltrimethylammonium bromide, PC11), resulting from the greater intermolecular association of PC11-6-11 at the solid/solution interface. The closely packed adsorbed layer of PC11-6-11 provides an opportunity to give a polymer thin film, as a result of in situ photo-polymerization on MF particles (in the second fabrication step) and subsequent acid dissolution of the core MF particles (in the third fabrication step). The dynamic light scattering (DLS) measurements have shown that the apparent hydrodynamic diameter of PC11-6-11 capsules is reversibly changed in response to a change in ionic strength: the increased background electrolyte concentration results in deswelling of the capsules, and vice versa. It seems likely that this swelling/deswelling behavior is primarily driven by the electrostatic interaction between quaternary ammonium groups within the polymerized film. We have also studied the capture and release capabilities of glucose into/from the capsule core and found that (i) glucose is encapsulated into the capsule core at high electrolyte concentrations and (ii) the glucose molecules encapsulated into the core are gradually released when the outer electrolyte solution is replaced by pure water. We believe, therefore, that the PC11-6-11 capsules fabricated here are useful as stimulus-responsive smart vehicles.

  20. Functionalization of nanodiamond with epoxy monomer

    Institute of Scientific and Technical Information of China (English)

    Huan Huan Zhang; Ya Ting Liu; Rong Wang; Xiao Yan Yu; Xiong Wei Qu; Qing Xin Zhang

    2011-01-01

    A novel nanodiamond-epoxy derivative (ND-EP) was synthesized by grafting epoxy monomers onto the surface of nanodiamond (ND), and characterized by FTIR and TGA. The ratio of grafted epoxy groups was determined to be 32.5 wt% by TGA. The developed methodology provides an efficient method for the functionalization of nanodiamond material, which enables a variety of advanced engineering and biomedical applications of ND.

  1. Elution of Monomers from Provisional Composite Materials

    Directory of Open Access Journals (Sweden)

    Simon Daniel Schulz

    2015-01-01

    Full Text Available The aim of this study was to evaluate the elution of substances from different materials used for the manufacturing of temporary indirect restorations, after storage in saliva and ethanol 75%. 10 samples of three chemically cured materials (Protemp 3 Garant, Systemp.c&b, and Trim and one light-cured material (Clip F were stored in saliva and ethanol 75% for 24 h, 7, and days 28 days. From the storage media at each time period, samples were prepared and analysed by LC-MS/MS, in order to access the elution of monomers. The results differed among the materials (P ≤ 0.05. No monomers were detected in the samples of Protemp 3 Garant and Clip F. Substances were detected only in ethanol samples of Systemp.c&b and Trim. The amount of BisGMA, TEGDMA, and UDMA 2 released from Systemp.c&b was higher compared to Trim. Storage time affected the release of substances (P ≤ 0.05. The highest release was observed within the first 24 h. It can be concluded that provisional resin composite materials do not show high release of monomers and this release is material dependent. However, the detection of additional peaks during the analysis, suggesting the formation of by-products of the eluted substances, may not be in favour of these materials with respect to their toxicity.

  2. 21 CFR 888.4220 - Cement monomer vapor evacuator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement monomer vapor evacuator. 888.4220 Section... (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4220 Cement monomer vapor evacuator. (a) Identification. A cement monomer vapor evacuator is a device intended for use during surgery to contain or...

  3. Static and dynamical critical behavior of the monomer-monomer reaction model with desorption

    Science.gov (United States)

    da Costa, E. C.; Rusch, Flávio Roberto

    2016-06-01

    We studied in this work the monomer-monomer reaction model on a linear chain. The model is described by the following reaction: A + B → AB, where A and B are two monomers that arrive at the surface with probabilities yA and yB, respectively, and we have considered desorption of the monomer B with probability α. The model is studied in the adsorption controlled limit where the reaction rate is infinitely larger than the adsorption rate. We employ site and pair mean-field approximations as well as static and dynamical Monte Carlo simulations. We show that the model exhibits a continuous phase transition between an active steady state and an A-absorbing state, when the parameter yA is varied through a critical value, which depends on the value of α. Monte Carlo simulations and finite-size scaling analysis near the critical point are used to determine the static critical exponents β and ν⊥ and the dynamical critical exponents ν∥ and z. The results found for the monomer-monomer reaction model with B desorption, in the linear chain, are different from those found by E. V. Albano (Albano, 1992) and are in accordance with the values obtained by Jun Zhuo and Sidney Redner (Zhuo and Redner, 1993), and endorse the conjecture of Grassberger, which states that any system undergoing a continuous phase transition from an active steady state to a single absorbing state, exhibits the same critical behavior of the directed percolation universality class.

  4. Binding of alkaline cations to the double-helical form of gramicidin.

    OpenAIRE

    Chen, Y; Wallace, B.A.

    1996-01-01

    Gramicidin is a polypeptide antibiotic that forms monovalent cation-specific channels in membrane environments. In organic solvents and in lipids containing unsaturated fatty acid chains, it forms a double-helical "pore" structure, in which two monomers are intertwined. This form of gramicidin can bind two cations inside its lumen, and the crystal structures of both an ion complex and an ion-free form have been determined. In this study, we have used circular dichroism (CD) spectroscopy to ex...

  5. Synthesis and photoactivity of phenylazonaphthalene peptide nucleic acid monomers

    Institute of Scientific and Technical Information of China (English)

    Jin Du Li; Miao Chen; Sheng Liu; Hao Bo Zhang; Zhi Lu Liu

    2008-01-01

    Phenylazonaphthalene peptide nucleic acid (PNA) monomers were successfully synthesized,and their photoisomerization was examined.The new PNA monomers showed reversible trans-cis isomerization with UV and visible light irradiation,which might be the foundation of photo-regulating the hybridization between PNA containing phenylazonaphthalene unit and DNA.Simultaneously,the fluorescence of the new PNA monomers might make them especially useful as structural probes.

  6. Can the hydrophilicity of functional monomers affect chemical interaction?

    Science.gov (United States)

    Feitosa, V P; Ogliari, F A; Van Meerbeek, B; Watson, T F; Yoshihara, K; Ogliari, A O; Sinhoreti, M A; Correr, A B; Cama, G; Sauro, S

    2014-02-01

    The number of carbon atoms and/or ester/polyether groups in spacer chains may influence the interaction of functional monomers with calcium and dentin. The present study assessed the chemical interaction and bond strength of 5 standard-synthesized phosphoric-acid ester functional monomers with different spacer chain characteristics, by atomic absorption spectroscopy (AAS), ATR-FTIR, thin-film x-ray diffraction (TF-XRD), scanning electron microscopy (SEM), and microtensile bond strength (μTBS). The tested functional monomers were 2-MEP (two-carbon spacer chain), 10-MDP (10-carbon), 12-MDDP (12-carbon), MTEP (more hydrophilic polyether spacer chain), and CAP-P (intermediate hydrophilicity ester spacer). The intensity of monomer-calcium salt formation measured by AAS differed in the order of 12-MDDP=10-MDP>CAP-P>MTEP>2-MEP. FTIR and SEM analyses of monomer-treated dentin surfaces showed resistance to rinsing for all monomer-dentin bonds, except with 2-MEP. TF-XRD confirmed the weaker interaction of 2-MEP. Highest µTBS was observed for 12-MDDP and 10-MDP. A shorter spacer chain (2-MEP) of phosphate functional monomers induced formation of unstable monomer-calcium salts, and lower chemical interaction and dentin bond strength. The presence of ester or ether groups within longer spacer carbon chains (CAP-P and MTEP) may affect the hydrophilicity, μTBS, and also the formation of monomer-calcium salts. PMID:24284259

  7. Synthesis of Methacrylate Monomers with Antibacterial Effects Against S. Mutans

    Directory of Open Access Journals (Sweden)

    Jingwei He

    2011-11-01

    Full Text Available A series of polymerizable quaternary ammonium compounds were synthesized with the aim of using them as immobilized antibacterial agents in methacrylate dental composites, and their structures were characterized by FT-IR, 1H-NMR, and 13C-NMR analysis. Their antibacterial activities against the oral bacterium Streptococcus mutans were evaluated in vitro by a Minimum Inhibitory Concentration test, and the results showed that 2-dimethyl-2-hexadecyl-1-methacryloxyethyl ammonium iodide (C16 had the highest antibacterial activity against S. mutans, and 2-dimethyl-2-pentyl-1-methacryloxyethyl ammonium iodide (C5 and 2-dimethyl-2-octyl-1-methacryloxyethyl ammonium iodide (C8 did not show any inhibition.

  8. A review of the developments of multi-purpose primers and adhesives comprising novel dithiooctanoate monomers and phosphonic acid monomers.

    Science.gov (United States)

    Ikemura, Kunio; Endo, Takeshi; Kadoma, Yoshinori

    2012-02-01

    This paper reviews the developments of dithiooctanoate monomers and acidic adhesive monomers, and their roles in multi-purpose primers and adhesives in promoting adhesion to multiple substrate materials. Novel dithiooctanoate monomers exhibited excellent bonding to precious metals and alloys when compared against conventional sulfur-containing monomers. Newly developed phosphonic acid monomers, endowed with a water-soluble nature, enabled sufficient demineralization of dental hard tissues and thus improved bonding to both ground enamel and dentin. The optimal combination for bonding to dental hard tissues and precious and non-precious metals and alloys was 5.0 wt% 10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT) and 1.0 wt% 6-methacryloyloxyhexyl phosphonoacetate (6-MHPA). For bonding to dental porcelain, alumina, zirconia, and gold (Au) alloy, a ternary combination of silane coupling agent, acidic adhesive monomers, and dithiooctanoate monomers seemed promising. The latest development was a single-bottle, multi-purpose, self-etching adhesive which contained only acidic adhesive monomers and dithiooctanoate monomers but which produced strong adhesion to ground enamel and dentin, sandblasted zirconia, and Au alloy.

  9. Reaction kinetics and modeling of photoinitiated cationic polymerization of an alicyclic based diglycidyl ether

    Energy Technology Data Exchange (ETDEWEB)

    Harikrishna, R., E-mail: r.harikrishna@ncl.res.in [Polymer Science and Engineering Division, National Chemical Laboratory, Pune 411008 (India); Ponrathnam, S. [Polymer Science and Engineering Division, National Chemical Laboratory, Pune 411008 (India); Tambe, S.S. [Chemical Engineering and Process Development Division, National Chemical Laboratory, Pune 411008 (India)

    2014-01-01

    Highlights: • Photocationic polymerization of alicyclic based diglycidyl ether was carried out. • Kinetic parameters were influenced by gelation and diffusional restrictions. • Applicability of autocatalytic model was established by nonlinear regression. • System showed higher activation energy than cycloaliphatic and aromatic diepoxides. -- Abstract: Photoinitiated cationic polymerization of cycloaliphatic diepoxides had received tremendous attention, while studies with lesser polymerizable diglycidyl ethers are comparatively less reported. The present work deals with the photoinitiated cationic polymerization of cyclohexane dimethanol diglycidyl ether followed by estimation of kinetic parameters. The effects of concentration of photoinitiator and temperature on curing performance were studied using photo differential scanning calorimeter or photo DSC with polychromatic radiation. It was observed that the rate of polymerization as well as ultimate conversion increased with increasing concentration of photoinitiator and temperature. The influences of gelation as well as diffusional restrictions have remarkable effect on cure performance. The kinetic parameters as per autocatalytic kinetic model were studied by Levenberg–Marquardt nonlinear regression method instead of conventional linear method for obtaining more accurate values of apparent rate constant. It was observed that the model fits with data from initial stages to almost towards the end of the reaction. The activation energy was found to be higher than the values reported for more reactive cycloaliphatic diepoxides. The value of pre-exponential factor increased with increase in activation energy showing influence of gelation at early stages of reaction.

  10. Degradable Polymer Composites Fabricated from Starch and Alkyl Cyanoacrylate Monomer

    Science.gov (United States)

    Degradable polymer composites are fabricated from alkyl cyanoacrylate monomer and starch without special equipment. Alkyl cyanoacrylate, which is a major component of “super glue”, is a monomer that polymerizes at room temperature in the presence of initiators. During the fabrication of polymer com...

  11. Monomer-dimer tatami tilings of square regions

    CERN Document Server

    Erickson, Alejandro

    2011-01-01

    We prove that the number of monomer-dimer tilings of an $n\\times n$ square grid, with $mmonomers in which no four tiles meet at any point is $m2^m+(m+1)2^{m+1}$, when $m$ and $n$ have the same parity. In addition, we present a new proof of the result that there are $n2^{n-1}$ such tilings with $n$ monomers, which divides the tilings into $n$ classes of size $2^{n-1}$. The sum of these tilings over all monomer counts has the closed form $2^{n-1}(3n-4)+2$ and, curiously, this is equal to the sum of the squares of all parts in all compositions of $n$. We also describe two algorithms and a Gray code ordering for generating the $n2^{n-1}$ tilings with $n$ monomers, which are both based on our new proof.

  12. Green Synthesis of Cationic Polyacrylamide Composite Catalyzed by An Ecologically Catalyst Clay Called Maghnite-H+ (Algerian MMT) Under Microwave Irradiation.

    OpenAIRE

    Rahmouni Abdelkader; Belbachir Mohammed

    2016-01-01

    In this study, a novel green cationic hydrogel of cationic polyacrylamide composite have been prepared and investigated. The synthesis of green cationic polyacrylamide composite was evaluated for its solubility in water. The reactions were performed using acrylamide monomer, solvent, catalyst (clay fin called maghnite) and solution of  H2SO4 (0.25 M), with the system under microwave irradiation (160 ºC) for 4 min. Major factors affecting the polymerization reaction were studied with a view to...

  13. Study on the preirradiation polymerization of vinyl monomers

    Science.gov (United States)

    Yu-Ming, Liu; Yue-Qi, Yang; Zue-Teh, Ma

    This paper presents mainly the polymerization, copolymerization and crosslinking of monomers off-source induced by peroxides which are formed by high energy irradiation of vinyl monomers such as styrene (St), acrylonitrile (AN), methylmethacrylate (MMA), vinyl acetate (VAc) and 2-hydroxyethyl methacrylate (HEMA). The peroxides produced by irradiation of the above-mentioned monomers can not only induce the monomers themselves, but also another non-irradiated monomer to carry out copolymerization efficiently. The activation energy of peroxide formation, the apparent activation energy of polymerization and the activation energy of peroxide initiation by irradiation of vinyl monomers are: Ef(MMA) = 11, Ef(St) = 9.6, Ef(AN) = 8.5, EMMA = EVA = 11.4, Ei(MMA) = Ei(VA) = 13 kcal/mol. The rate of decomposition of monomer peroxides is smoother than that of BPO during the polymerization and so a smooth kinetic progress is obtained. The initiating ability of forming peroxides by irradiation of the vinyl monomers depends mainly on the chemical structure of the monomers. For instance, the main structure of peroxides formed during preirradiation MMA are: alternating peroxy-copolymer ? and random peroxy-copolymer ? Owing to the peroxy-bond which is unstable and in which homolytic breakage easily occurs to yield a pair of radicals, RO . is formed within the above-mentioned structural compounds, so that they possess stronger initiating reactivity. It is quite evident that the initiating reactivity of AN peroxide will be greatly reduced because of the conjugate double bond. In other words, the initiating ability of AN peroxide is lower than MMA peroxide and St peroxide.

  14. PREPARATION AND SURFACE PROPERTIES OF ACRYLIC COPOLYMERS CONTAINING FLUORINATED MONOMERS

    Institute of Scientific and Technical Information of China (English)

    Tai-jiang Gui; Hao Wei; Ying Zhao; Xiu-lin Wang; Du-jin Wang; Duan-fu Xu

    2006-01-01

    A series of copolymers comprising butylmethacrylate, styrene, butylacrylate, hydroxypropyl acrylate and perfluoroalkyl methacrylate were synthesized by the free radical polymerization using BPO as an initiator. The surface property of the copolymer films was subsequently characterized. The contact angle measurements and energy dispersive analysis of X-ray (EDAX) show that the length and content ofperfluoroalkyl side chains in the copolymers are crucial for the preparation of the film with low surface energy. At a given content of fluorinated monomers in the copolymers, the longer the perfluoroalkyl side chain, the larger the water contact angle of the copolymer films will be. On the other hand, the higher the content of fluorinated monomers, the lower the surface energy is. The water contact angle increases with the increase of the fluorinated monomer content and reaches a plateau at 3 wt% of fluorinated monomer content.

  15. 21 CFR 864.7300 - Fibrin monomer paracoagulation test.

    Science.gov (United States)

    2010-04-01

    ... to detect fibrin monomer in the diagnosis of disseminated intravascular coagulation (nonlocalized clotting within a blood vessel) or in the differential diagnosis between disseminated intravascular coagulation and primary fibrinolysis (dissolution of the fibrin in a blood clot). (b) Classification. Class...

  16. Pulse shape discrimination properties of plastic scintillators incorporating a rationally designed highly soluble and polymerizable derivative of 9,10-diphenylanthracene

    Science.gov (United States)

    Hajagos, Tibor Jacob; Kishpaugh, David; Pei, Qibing

    2016-07-01

    A highly soluble and polymerizable derivative of 9,10-diphenylanthracene was designed and synthesized specifically to be capable of achieving very high loadings (at least 50 wt.%) when copolymerized with a polyvinyltoluene (PVT) matrix. The resulting heavily crosslinked plastics are mechanically hard and robust, and were found to have exceptional clarity with no sign of dye precipitation. Samples of these plastics both with and without added wavelength shifter were characterized for light yield, scintillation decay, and pulse shape discrimination (PSD) performance for α / γ discrimination, and the results were compared to that of a commercially available PSD plastic, EJ-299-34. The best performing formulation, with a primary dye loading of 50 wt.%, had a measured light yield of 9950 photons/MeV, and achieved a PSD figure-of-merit (FOM) of 1.05, the latter indicating that while the present material is not suited for practical applications, the overall approach demonstrates a proof-of-concept of PSD in highly loaded plastics stabilized through copolymerization of the primary dye, and suggests that further improvements through better dye choice/design may yet be achievable.

  17. Perturbation of the Monomer-Monomer Interfaces of the Benzoylformate Decarboxylase Tetramer

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, Forest H.; Rogers, Megan P.; Paul, Lake N.; McLeish, Michael J. [IUPUI; (Purdue)

    2014-08-14

    The X-ray structure of benzoylformate decarboxylase (BFDC) from Pseudomonas putida ATCC 12633 shows it to be a tetramer. This was believed to be typical of all thiamin diphosphate-dependent decarboxylases until recently when the structure of KdcA, a branched-chain 2-keto acid decarboxylase from Lactococcus lactis, showed it to be a homodimer. This lent credence to earlier unfolding experiments on pyruvate decarboxylase from Saccharomyces cerevisiae that indicated that it might be active as a dimer. To investigate this possibility in BFDC, we sought to shift the equilibrium toward dimer formation. Point mutations were made in the noncatalytic monomer–monomer interfaces, but these had a minimal effect on both tetramer formation and catalytic activity. Subsequently, the R141E/Y288A/A306F variant was shown by analytical ultracentrifugation to be partially dimeric. It was also found to be catalytically inactive. Further experiments revealed that just two mutations, R141E and A306F, were sufficient to markedly alter the dimer–tetramer equilibrium and to provide an ~450-fold decrease in kcat. Equilibrium denaturation studies suggested that the residual activity was possibly due to the presence of residual tetramer. The structures of the R141E and A306F variants, determined to <1.5 Å resolution, hinted that disruption of the monomer interfaces will be accompanied by movement of a loop containing Leu109 and Leu110. As these residues contribute to the hydrophobicity of the active site and the correct positioning of the substrate, it seems that tetramer formation may well be critical to the catalytic activity of BFDC.

  18. Radiation Copolymerization of Styrene Monomer Onto Natural Rubber Film

    International Nuclear Information System (INIS)

    Studies on the effect of radiation copolymerization of styrene monomer onto natural rubber film on physical and chemical properties of natural rubber-polystyrene copolymer (NPC) have been done. Natural rubber film firstly immersed in styrene monomer in certain time, then it was wrapped with Mylar film, and then it was irradiated with gamma rays in various doses from 10,25, 50 up to 100 kGy. The styrene monomer content was also varying from 25, 50 and 100 phr (part per hundred part of rubber). Using tensile tester and hardness tester carried out physical characterization of NPC such as modulus-30G, modulus-600, elongation at break, permanent set and hardness. While chemical characterization was carried out by extraction method. The solvent used was acetone and tetrahydrofuran. The experimental results showed that by increasing the styrene monomer at the same irradiation dose, the molecule crosslinked fraction of NPC decreased, while the molecule grafted fraction was increased. But at the saine styrene monomer content, increasing irradiation dose was increasing the molecule crosslinked fraction and decreasing the molecule grafted fraction of NPC. The increasing of molecule crosslinked fraction was effected on the increasing of tensile strength, modulus, hardness, and decreasing of elongation at break of NPC. The tensile strength, modulus, aJId baldness ofNPC were achieved 195 kg/cm2, 108 kg/cm2 and 63 shore respectively at monomer content I00 phr and irradiation dose was 100 kGy

  19. Complex Macromolecular Architectures by Living Cationic Polymerization

    KAUST Repository

    Alghamdi, Reem D.

    2015-05-01

    Poly (vinyl ether)-based graft polymers have been synthesized by the combination of living cationic polymerization of vinyl ethers with other living or controlled/ living polymerization techniques (anionic and ATRP). The process involves the synthesis of well-defined homopolymers (PnBVE) and co/terpolymers [PnBVE-b-PCEVE-b-PSiDEGVE (ABC type) and PSiDEGVE-b-PnBVE-b-PSiDEGVE (CAC type)] by sequential living cationic polymerization of n-butyl vinyl ether (nBVE), 2-chloroethyl vinyl ether (CEVE) and tert-butyldimethylsilyl ethylene glycol vinyl ether (SiDEGVE), using mono-functional {[n-butoxyethyl acetate (nBEA)], [1-(2-chloroethoxy) ethyl acetate (CEEA)], [1-(2-(2-(t-butyldimethylsilyloxy)ethoxy) ethoxy) ethyl acetate (SiDEGEA)]} or di-functional [1,4-cyclohexanedimethanol di(1-ethyl acetate) (cHMDEA), (VEMOA)] initiators. The living cationic polymerizations of those monomers were conducted in hexane at -20 0C using Et3Al2Cl3 (catalyst) in the presence of 1 M AcOEt base.[1] The PCEVE segments of the synthesized block terpolymers were then used to react with living macroanions (PS-DPE-Li; poly styrene diphenyl ethylene lithium) to afford graft polymers. The quantitative desilylation of PSiDEGVE segments by n-Bu4N+F- in THF at 0 °C led to graft co- and terpolymers in which the polyalcohol is the outer block. These co-/terpolymers were subsequently subjected to “grafting-from” reactions by atom transfer radical polymerization (ATRP) of styrene to afford more complex macromolecular architectures. The base assisted living cationic polymerization of vinyl ethers were also used to synthesize well-defined α-hydroxyl polyvinylether (PnBVE-OH). The resulting polymers were then modified into an ATRP macro-initiator for the synthesis of well-defined block copolymers (PnBVE-b-PS). Bifunctional PnBVE with terminal malonate groups was also synthesized and used as a precursor for more complex architectures such as H-shaped block copolymer by “grafting-from” or

  20. Removal of monomer delignification products by laccase from Trametes versicolor.

    Science.gov (United States)

    Kolb, Michaela; Sieber, Volker; Amann, Manfred; Faulstich, Martin; Schieder, Doris

    2012-01-01

    The influence of a laccase from Trametes versicolor on the removal of phenolic monomers in liquid hot water pretreated wheat straw supernatants (LHW-S) was examined. Beside the total phenol content derived by Folin-Ciocalteu (FC-) assay, phenolic monomers were measured via headspace-solid phase micro-extraction (HS-SPME)/GC-MS. A notable decrease of the phenols was achieved using 0.2 and 0.5 U/mL laccase whilst higher dosage showed no improvement. Nearly all kind of monomer phenolic compounds identified in the LHW-S were found to be removed after 24h. However, acetophenone and 4-hydroxybenzaldehyde (HBA) were obviously not affected by laccase. Summarizing, three laccase reaction groups (LRG) of phenolic monomers could be classified: immediate removal (LRG-A), degradation after 1 day (LRG-B), no effect of laccase (LRG-C). Additionally, HS-SPME/GC was found to be a powerful tool to study the reaction of laccase and phenolic monomers in complex lignocellulose derived solutions.

  1. In situ polymerization of vinyl monomers in polyester yarns

    International Nuclear Information System (INIS)

    The effects of a pretreatment of polyester (PET) yarns with a strongly interacting solvent such as dimethylformamide (DMF) on vinyl monomer incorporation were investigated. When the DMF pretreatment is carried out at high temperatures (above 1200C), the swollen PET structure is stabilized by solvent-induced secondary crystallization. This substrate is highly suitable for the incorporation of vinyl monomers. In situ polymerization of vinyl monomers in DMF-treated PET was investigated using chemical and γ-irradiation polymerization techniques, both in the presence and in the absence of excess monomer outside the PET fibers. When polymerization was carried out in a system in which a constant supply of free radicals was available from the outside of the PET fibers, lower initiator concentrations and smaller γ-irradiation doses were necessary. These results are attributed to a low efficiency of the initiator inside the PET fiber due to mobility restrictions. Water uptake and moisture regain of PET yarns containing poly(hydroxyethyl methacrylate) and poly(acrylic acid) were also investigated. When most of the vinyl polymer was inside the PET fiber, water absorption was limited. The changes in mechanical properties of the PET yarns resulting from the DMF pretreatment were partially reversed by in situ polymerization of vinyl monomers

  2. The limits of precision monomer placement in chain growth polymerization

    Science.gov (United States)

    Gody, Guillaume; Zetterlund, Per B.; Perrier, Sébastien; Harrisson, Simon

    2016-02-01

    Precise control over the location of monomers in a polymer chain has been described as the `Holy Grail' of polymer synthesis. Controlled chain growth polymerization techniques have brought this goal closer, allowing the preparation of multiblock copolymers with ordered sequences of functional monomers. Such structures have promising applications ranging from medicine to materials engineering. Here we show, however, that the statistical nature of chain growth polymerization places strong limits on the control that can be obtained. We demonstrate that monomer locations are distributed according to surprisingly simple laws related to the Poisson or beta distributions. The degree of control is quantified in terms of the yield of the desired structure and the standard deviation of the appropriate distribution, allowing comparison between different synthetic techniques. This analysis establishes experimental requirements for the design of polymeric chains with controlled sequence of functionalities, which balance precise control of structure with simplicity of synthesis.

  3. Dimer-monomer model on the Towers of Hanoi graphs

    Science.gov (United States)

    Chen, Hanlin; Wu, Renfang; Huang, Guihua; Deng, Hanyuan

    2015-07-01

    The number of dimer-monomers (matchings) of a graph G is an important graph parameter in statistical physics. Following recent research, we study the asymptotic behavior of the number of dimer-monomers m(G) on the Towers of Hanoi graphs and another variation of the Sierpiński graphs which is similar to the Towers of Hanoi graphs, and derive the recursion relations for the numbers of dimer-monomers. Upper and lower bounds for the entropy per site, defined as μG = limv(G)→∞(lnm(G)/v(G)), where v(G) is the number of vertices in a graph G, on these Sierpiński graphs are derived in terms of the numbers at a certain stage. As the difference between these bounds converges quickly to zero as the calculated stage increases, the numerical value of the entropy can be evaluated with more than a hundred significant figures accuracy.

  4. Monomer release from nanofilled and microhybrid dental composites after bleaching.

    Directory of Open Access Journals (Sweden)

    Masumeh Hasani Tabatabaee

    2014-02-01

    Full Text Available The aim of this study was to assess the effect of bleaching on elution of monomers from nanofilled and microhybrid composites.80 samples (5mm diameter and 3mm thickness of each composite were prepared. After curing, half of them were randomly polished. Each group was divided into 8 subgroups and immersed in water or 10%, 20% and 30% H2O2 for 3 or 8 hours. Eluted Bis-GMA (Bis-phenol A Glycidyl Dimethacrylate, TEGDMA (Triethyleneglycol Dimethacrylate, UDMA (Urethane Dimethacrylate and BisEMA (Bis-phenol A ethoxylate Dimethacrylate were quantified by high performance liquid chromatography and the results were analyzed by univariate ANOVA and t-test (P<0.05.Bleach significantly increased the overall release of monomers (P<0.001; TEGDMA was released more than Bis-GMA (P<0.001. Supreme released more TEGDMA compared to Z250 (P<0.001. Bleaching increased the release of this monomer (P<0.001. Increasing both the concentration of H2O2, and the immersion time, increased the release of TEGDMA (P<0.001. Polishing had no effect on release of this monomer (P=0.952. Supreme released more Bis-GMA than Z250 (P=0.000. The more concentrated H2O2 caused more elution of Bis-GMA (P= 0.003; while the effect of immersion time was not significant (P=0.824. Polishing increased the release of Bis-GMA (P=0.001. Neither the type of composite nor Bleaching had any effect on release of UDMA (P=0.972 and (P=0.811 respectively. Immersion duration increased the release of UDMA (P=0.002, as well as polishing (P=0.024.Bleaching increased the release of monomers. Nanofilled composites released more monomer than the microfilled.

  5. Biosynthesis of Polyhydroxyalkanoates Consisting of Short-chain-length Monomers and Medium-chain-length Monomers by Pseudomonas YS1

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A strain capable of producing polyhydroxyalkanoates (PHAs) consisting of short- and medium-chain-length monomers was identified as Pseudomonas sp.coded as YS1.The strain synthesized PHAs containing monomers of hydroxybutyrate(HB or C4) and/or hydroxyoctanoate (HO or C8) and/or hydroxydecanoate (HD or C10) when grown in various substrates including glucose, raw sugar, molasses and various fatty acids.It was found that growth temperature affected the HB and HO monomer contents in the PHA.HB content in PHA increased from mole fraction 69% at 26℃ to mole fraction 85% at 37℃ while HO content decreased from mole fraction 29% at 26℃ to mole fraction 12% at 37℃.The temperature effect provides a simple and effective way to control the PHA composition and hence control the PHA mechanical and other physical properties.Also, the fermentor experiment indicated that PHB formation was growth associated and HO monomer production was in fact promoted by N-limitation.This conclusion was further supported by the fact that the formation of PHB only polyester was observed only when C/N molar ratio was smaller than 20.Higher C/N ratio led to the formation of HO monomers in the polyesters.

  6. Evaluation of level of impregnation monomers in hydrotalcite

    International Nuclear Information System (INIS)

    To evaluate the impregnation degree of 1,6-hexamethylene diisocyanate and 1,4-butanediol monomers in hydrotalcite clays it was prepared dispersions with mixing ratio 1:100 (clay/monomer), using the Ultraturrax and Ultrasound. Subsequently the samples were characterized by Fourier Transform Infrared Spectroscopy and X-ray Diffraction. Swelling tests and Tyndall effect were used to illustrate the different dispersions. The results indicated a strong interaction between the hydrotalcite with 1,6-hexamethylene diisocyanate, favoring the formation of intercalated structures. (author)

  7. [Influence Factors on Monomer Conversion of Dental Composite Resin].

    Science.gov (United States)

    Wang, Shuang; Gao, Yan; Wang, Jing; Zhang, Yan; Zhang, Yuntao; Wang, Fanghui; Wang, Qingshan

    2015-04-01

    Dental composite resin is a kind of material which has been widely used in dental restoration. Research has found that the influence of residual monomer on the material mechanical, chemical and biological properties cannot be ignored. This paper elaborates these harms of residual monomers. The effects of resin matrix, inorganic filler and initiating system, illumination, secondarily treatment on the degree of conversion were also analyzed. The paper also discusses the effective measures to increase the conversion, and offers theoretical basis for the clinical application and development of composite resin.

  8. Photoinitiated Polymerization of Cationic Acrylamide in Aqueous Solution: Synthesis, Characterization, and Sludge Dewatering Performance

    Directory of Open Access Journals (Sweden)

    Huaili Zheng

    2014-01-01

    Full Text Available A copolymer of acrylamide (AM with acryloyloxyethyl trimethyl ammonium chloride (DAC as the cationic monomer was synthesized under the irradiation of high-pressure mercury lamp with 2,2-azobis(2-amidinopropane dihydrochloride (V-50 as the photoinitiator. The compositions of the photoinduced copolymer were characterized by Fourier transform infrared spectra (FTIR, ultraviolet spectra (UV, and scanning electron microscope (SEM. The effects of 6 important factors, that is, photo-initiators concentration, monomers concentration, CO(NH22 (urea concentrations, pH value, mass ratio of AM to DAC, and irradiation time on the molecular weight and dissolving time, were investigated. The optimal reaction conditions were that the photo-initiators concentration was 0.3%, monomers concentration was 30 wt.%, irradiation time was 60 min, urea concentration was 0.4%, pH value was 5.0, and mass ratio of AM to DAC was 6 : 4. Its flocculation properties were evaluated with activated sludge using jar test. The zeta potential of supernatant at different cationic monomer contents was simultaneously measured. The results demonstrated the superiority of the copolymer over the commercial polyacrylamide as a flocculant.

  9. 可聚合表面活性剂在磁性纳米材料制备中的应用%Application of polymerizable surfactant in the preparation of magnetic nano composite

    Institute of Scientific and Technical Information of China (English)

    李瑞雪; 王文志; 刘宝玉; 徐美芸; 章水化

    2009-01-01

    Surfactants play a crucial role in preparation of organic/inorganic nano composites through surface modification of inorganic nano parti-cles. Recently, polymerizable surfactants which contain reactive doub-le bonds are attracting more and more scientific and industrial attention for their application in the fields of emulsion polymerization, nano ma-terials preparation, etc. In this communication, monooctadecyl mal-eate as polymerizable surfactant synthesized by esterification of maleic anhydride and octadecanol was used to surface-modify Fe3O4 nano particles. A polymerizable magnetic fluid was obtained by directly dis-persing modified F3O4 nano particles into styrene and magnetic nano composite was prepared through free radical polymerization of polymer-izable magnetic fluid.%以马来酸酐和正十八醇为原料合成了可聚合表面活性剂马来酸单十八酯,并用其改性Fe3O4纳米磁粉.用改性纳米磁粉制备了苯乙烯基可聚合磁流体,并通过本体聚合获得了磁性纳米复合材料.透射电镜分析结果表明,直径约7 nm的Fe3O4纳米颗粒在磁流体和复合材料中分散均匀,无明显团聚现象;红外光谱分析结果表明,磁粉表面包覆的马来酸单十八酯和苯乙烯基质发生了共聚.差示扫描量热、热重及凝胶渗透色谱分析结果表明,与相间条件聚合的聚苯乙烯(PS)相比,复合材料的玻璃化转变温度和去除磁粉后的相对分子质量明显降低,但热稳定性比相同条件下聚合的PS有明显提高,这说明可聚合表面活性剂和活性PS链之间形成了共价键,从而增强了Fe3O4纳米颗粒与基质的相互作用.

  10. Oligonucleotides with 1,4-dioxane-based nucleotide monomers

    DEFF Research Database (Denmark)

    Madsen, Andreas S; Wengel, Jesper

    2012-01-01

    An epimeric mixture of H-phosphonates 5R and 5S has been synthesized in three steps from known secouridine 1. Separation of the epimers has been accomplished by RP-HPLC, allowing full characterization and incorporation of monomers X and Y into 9-mer oligonucleotides using H-phosphonates building ...

  11. Base-catalyzed depolymerization of lignin : separation of monomers

    Energy Technology Data Exchange (ETDEWEB)

    Vigneault, A. [Sherbrooke Univ., PQ (Canada). Dept. of Chemical Engineering; Johnson, D.K. [National Renewable Energy Laboratory, Golden, CO (United States); Chornet, E. [Sherbrooke Univ., PQ (Canada). Dept. of Chemical Engineering; National Renewable Energy Laboratory, Golden, CO (United States)

    2007-12-15

    Biofuels produced from residual lignocellulosic biomass range from ethanol to biodiesel. The use of lignin for the production of alternate biofuels and green chemicals has been studied with particular emphasis on the structure of lignin and its oxyaromatic nature. In an effort to fractionate lignocellulosic biomass and valorize specific constitutive fractions, the authors developed a strategy for the separation of 12 added value monomers produced during the hydrolytic base catalyzed depolymerization (BCD) of a Steam Exploded Aspen Lignin. The separation strategy was similar to vanillin purification to obtain pure monomers, but combining more steps after the lignin depolymerization such as acidification, batch liquid-liquid-extraction (LLE), followed by vacuum distillation, liquid chromatography (LC) and crystallization. The purpose was to develop basic data for an industrial size process flow diagram, and to evaluate both the monomer losses during the separation and the energy requirements. Experimentally testing of LLE, vacuum distillation and flash LC in the laboratory showed that batch vacuum distillation produced up to 4 fractions. Process simulation revealed that a series of 4 vacuum distillation columns could produce 5 distinct monomer streams, of which 3 require further chromatography and crystallization operations for purification. 22 refs., 4 tabs., 8 figs.

  12. Aggregation processes with catalysis-driven monomer birth/death

    Institute of Scientific and Technical Information of China (English)

    Chen Yu; Han An-Jia; Ke Jian-Hong; Lin Zhen-Quan

    2006-01-01

    We propose two solvable cluster growth models, in which an irreversible aggregation spontaneously occurs between any two clusters of the same species; meanwhile, monomer birth or death of species A occurs with the help of species B. The system with the size-dependent monomer birth/death rate kernel K(i,j) = Jijv is then investigated by means of the mean-field rate equation. The results show that the kinetic scaling behaviour of species A depends crucially on the value of the index v. For the model with catalysis-driven monomer birth, the cluster-mass distribution of species A obeys the conventional scaling law in the v ≤ 0 case, while it satisfies a generalized scaling form in the v>0 case; moreover, the total mass of species A is a nonzero value in the v< 0 case while it grows continuously with time in the v>0 case. For the model with catalysis-driven monomer death, the cluster-mass distribution also approaches the conventional scaling form in the v < 0 case, while the conventional scaling description of the system breaks down in the v ≥ 0 case. Additionally, the total mass of species A retains a nonzero quantity in the v <0 case, but it decreases to zero with time in the v ≥ 0 case.

  13. Synthesis of a benzoxazine monomer containing maleimide and allyloxy groups

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A novel benzoxazine monomer 3-(4-allyloxy)phenyl-3,4-dihydro-2H-6-(N-maleimido)-1,3-benzoxazine (AMB) was synthesized and structure was confirmed by FT-IR, 1H NMR. Thermal analysis (DSC) of AMB showed the introduction of allyloxy group decreased melting point and exhibited a narrow and symmetric curing exothermic window.

  14. Influence of the diene monomer on devulcanization of EPDM rubber

    NARCIS (Netherlands)

    Verbruggen, M.; Does, van der L.; Noordermeer, J.W.M.; Duin, van M.

    2008-01-01

    Ethylene–propylene–diene rubbers (EPDM) with 2-ethylidene-5-norbornene (ENB), dicyclopentadiene (DCPD), and 1,4-hexadiene (HD) as third monomers have been vulcanized with peroxide and with a conventional sulfur vulcanization recipe, and their devulcanization was subsequently investigated for recycli

  15. Ion exchange behaviour of polymeric zirconium cations

    International Nuclear Information System (INIS)

    Polymeric zirconium cations formed in weakly acid solutions (pH2) are taken up strongly into macroporous cation exchange resins, while uptake into normal cation exchange resins (pore diameter about 1 nm) is low. Macroporous cation exchange resins loaded with polymeric Zr cations are shown to function as ligand exchange sorbents. (Authors)

  16. Binding interactions between suberin monomer components and pesticides

    Energy Technology Data Exchange (ETDEWEB)

    Olivella, M.À., E-mail: angels.olivella@udg.edu [Department of Chemical Engineering, Escola Politècnica Superior, Universitat de Girona, Maria Aurèlia Capmany, 61, 17071 Girona (Spain); Bazzicalupi, C.; Bianchi, A. [Department of Chemistry “Ugo Schiff”, University of Florence, Via della Lastruccia, 3, 50019 Sesto Fiorentino (Italy); Río, J.C. del [Instituto de Recursos Naturales y Agrobiología de Sevilla, Consejo Superior de Investigaciones Científicas, P.O. Box 1052, 41080 Seville (Spain); Fiol, N.; Villaescusa, I. [Department of Chemical Engineering, Escola Politècnica Superior, Universitat de Girona, Maria Aurèlia Capmany, 61, 17071 Girona (Spain)

    2015-09-15

    Understanding the role of biomacromolecules and their interactions with pollutants is a key for elucidating the sorption mechanisms and making an accurate assessment of the environmental fate of pollutants. The knowledge of the sorption properties of the different constituents of these biomacromolecules may furnish a significant contribution to this purpose. Suberin is a very abundant biopolymer in higher plants. In this study, suberin monomers isolated from cork were analyzed by thermally-assisted methylation with tetramethylammonium hydroxide (TMAH) in a pyrolysis unit coupled to gas chromatography–mass spectrometry (GC/MS). The isolated monomer mixture was used to study the sorption of three pesticides (isoproturon, methomyl and oxamyl). The modes of pesticide–sorbent interactions were analyzed by means of two modeling calculations, the first one representing only the mixture of suberin monomers used in the sorption study, and the second one including glycerol to the mixture of suberin monomers, as a building block of the suberin molecule. The results indicated that the highest sorption capacity exhibited by the sorbent was for isoproturon (33%) being methomyl and oxamyl sorbed by the main suberin components to a lesser extent (3% and < 1%, respectively). In addition to van der Waals interactions with the apolar region of sorbent and isoproturon, modeling calculations evidenced the formation of a hydrogen bond between the isoproturon NH group and a carboxylic oxygen atom of a suberin monomer. In the case of methomyl and oxamyl only weak van der Waals interactions stabilize the pesticide–sorbent adducts. The presence of glycerol in the model provoked significant changes in the interactions with isoproturon and methomyl. - Highlights: • Suberin has low affinity to retain pesticides of aliphatic character. • Suberin has a moderate affinity to adsorb isoproturon. • Modeling calculations show that apolar portion of suberin interacts with isoproturon.

  17. Binding interactions between suberin monomer components and pesticides

    International Nuclear Information System (INIS)

    Understanding the role of biomacromolecules and their interactions with pollutants is a key for elucidating the sorption mechanisms and making an accurate assessment of the environmental fate of pollutants. The knowledge of the sorption properties of the different constituents of these biomacromolecules may furnish a significant contribution to this purpose. Suberin is a very abundant biopolymer in higher plants. In this study, suberin monomers isolated from cork were analyzed by thermally-assisted methylation with tetramethylammonium hydroxide (TMAH) in a pyrolysis unit coupled to gas chromatography–mass spectrometry (GC/MS). The isolated monomer mixture was used to study the sorption of three pesticides (isoproturon, methomyl and oxamyl). The modes of pesticide–sorbent interactions were analyzed by means of two modeling calculations, the first one representing only the mixture of suberin monomers used in the sorption study, and the second one including glycerol to the mixture of suberin monomers, as a building block of the suberin molecule. The results indicated that the highest sorption capacity exhibited by the sorbent was for isoproturon (33%) being methomyl and oxamyl sorbed by the main suberin components to a lesser extent (3% and < 1%, respectively). In addition to van der Waals interactions with the apolar region of sorbent and isoproturon, modeling calculations evidenced the formation of a hydrogen bond between the isoproturon NH group and a carboxylic oxygen atom of a suberin monomer. In the case of methomyl and oxamyl only weak van der Waals interactions stabilize the pesticide–sorbent adducts. The presence of glycerol in the model provoked significant changes in the interactions with isoproturon and methomyl. - Highlights: • Suberin has low affinity to retain pesticides of aliphatic character. • Suberin has a moderate affinity to adsorb isoproturon. • Modeling calculations show that apolar portion of suberin interacts with isoproturon.

  18. Naphthoxy Bounded Ferrocenium Salts as Cationic Photoinitiators for Epoxy Photopolymerization

    Directory of Open Access Journals (Sweden)

    Zh. Q. Li

    2009-01-01

    Full Text Available To improve the absorption and the bulk of arene ligands, two naphthoxy bounded ferrocenium salts as new cationic photoinitiators, (η6-α-naphthoxybenzene (η5-cyclopentadienyl iron hexafluorophosphate (NOFC-1 and (η6-β-naphthoxybenzene (η5-cyclopentadienyl iron hexafluorophosphate (NOFC-2, were synthesized, characterized, and studied. NOFC-1 and NOFC-2 were prepared by the reaction of nucleophilic substitution (SNAr with naphthol and chlorobenzene-cyclopentadienyliron salt. Their activity as cationic photoinitiators was studied using real-time infrared spectroscopy. The results obtained showed that NOFC-1 and NOFC-2 are capable of photoinitiating the cationic polymerization of epoxy monomer directly on irradiation with long-wavelength UV light (365 nm. Comparative studies also demonstrated that they exhibited better efficiency than cyclopentadienyl-Fe-cymene hexafluorophosphate (I-261. When NOFC-1 and NOFC-2 were used to efficiently initiate polymerization of epoxide, both rate of polymerization and final conversion increased using benzoyl peroxide (BPO as sensitizer. DSC studies showed that NOFC-1 and NOFC-2 photoinitiators in epoxides possess good thermal stability in the absence of light.

  19. Breathing zone concentrations of methylmethacrylate monomer during joint replacement operations

    DEFF Research Database (Denmark)

    Darre, E; Jørgensen, L G; Vedel, P;

    1992-01-01

    By use of a methylmethacrylate (MMA) Dräger tube and bellow bump, the breathing zone concentrations of MMA monomer were measured for the operating surgeon during cementation of the components of hip and knee joint prostheses. The highest recordings (50-100 p.p.m.) were encountered during cementat......By use of a methylmethacrylate (MMA) Dräger tube and bellow bump, the breathing zone concentrations of MMA monomer were measured for the operating surgeon during cementation of the components of hip and knee joint prostheses. The highest recordings (50-100 p.p.m.) were encountered during...... cementation of the acetabular cups with conventional polymethylmethacrylate cement. Such exposure could be eliminated by the use of personal protection equipment, local punctual field suction or change to a MMA/n-decylmethacrylate/isobornylmethacrylate bone cement....

  20. Polymer as a function of monomer: Analytical quantum modeling

    CERN Document Server

    Nakhaee, Mohammad

    2016-01-01

    To identify an analytical relation between the properties of polymers and their's monomer a Metal-Molecule-Metal (MMM) junction has been presented as an interesting and widely used object of research in which the molecule is a polymer which is able to conduct charge. The method used in this study is based on the Green's function approach in the tight-binding approximation using basic properties of matrices. For a polymer base MMM system, transmission, density of states (DOS) and local density of states (LDOS) have been calculated as a function of the hamiltonian of the monomer. After that, we have obtained a frequency for LDOS variations in pass from a subunit to the next one which is a function of energy.

  1. Dynamics of Aggregate Growth Through Monomer Birth and Death

    Institute of Scientific and Technical Information of China (English)

    KE Jian-Hong; LIN Zhen-Quan

    2004-01-01

    @@ We investigate the kinetic behaviour of the growth of aggregates through monomer birth and death and propose a simple model with the rate kernels K(k) ∝ ku and K′(k) ∝ kv at which the aggregate Ak of size k respectively yields and loses a monomer. For the symmetrical system with K(k) = K′(k), the aggregate size distribution approaches the conventional scaling form in the case of u < 2, while the system may undergo a gelation-like transition in the u > 2 case. Moreover, the typical aggregate size S(t) grows as t1/(2-u) in the u < 2 case and increases exponentially with time in the u = 2 case. We also investigate several solvable systems with asymmetrical rate kernels and find that the scaling of the aggregate size distribution may break down in most cases.

  2. Total sulphate vs. sulphuric acid monomer in nucleation studies

    OpenAIRE

    K. Neitola; Brus, D.; Makkonen, U.; Sipilä, M.; R. L. Mauldin III; N. Sarnela; Jokinen, T; Lihavainen, H.; M. Kulmala

    2014-01-01

    Sulphuric acid is known to be a key component for atmospheric nucleation. Precise determination of sulphuric acid concentration is crucial factor for prediction of nucleation rates and subsequent growth. In our study, we have noticed a substantial discrepancy between sulphuric acid monomer and total sulphate concentrations measured from the same source of sulphuric acid vapour. The discrepancy of about one to two orders of magnitude was found with similar formation rates. To...

  3. Structure of human insulin monomer in water/acetonitrile solution

    Energy Technology Data Exchange (ETDEWEB)

    Bocian, Wojciech; Sitkowski, Jerzy; Bednarek, Elzbieta [National Medicines Institute (Poland); Tarnowska, Anna; Kawecki, Robert [Institute of Organic Chemistry Polish Academy of Sciences (Poland); Kozerski, Lech [National Medicines Institute (Poland)], E-mail: lkoz@icho.edu.pl

    2008-01-15

    Here we present evidence that in water/acetonitrile solvent detailed structural and dynamic information can be obtained for important proteins that are naturally present as oligomers under native conditions. An NMR-derived human insulin monomer structure in H{sub 2}O/CD{sub 3}CN, 65/35 vol%, pH 3.6 is presented and compared with the available X-ray structure of a monomer that forms part of a hexamer (Acta Crystallogr. 2003 Sec. D59, 474) and with NMR structures in water and organic cosolvent. Detailed analysis using PFGSE NMR, temperature-dependent NMR, dilution experiments and CSI proves that the structure is monomeric in the concentration and temperature ranges 0.1-3 mM and 10-30 deg. C, respectively. The presence of long-range interstrand NOEs, as found in the crystal structure of the monomer, provides the evidence for conservation of the tertiary structure. Starting from structures calculated by the program CYANA, two different molecular dynamics simulated annealing refinement protocols were applied, either using the program AMBER in vacuum (AMBER{sub V}C), or including a generalized Born solvent model (AMBER{sub G}B)

  4. Structure of human insulin monomer in water/acetonitrile solution

    International Nuclear Information System (INIS)

    Here we present evidence that in water/acetonitrile solvent detailed structural and dynamic information can be obtained for important proteins that are naturally present as oligomers under native conditions. An NMR-derived human insulin monomer structure in H2O/CD3CN, 65/35 vol%, pH 3.6 is presented and compared with the available X-ray structure of a monomer that forms part of a hexamer (Acta Crystallogr. 2003 Sec. D59, 474) and with NMR structures in water and organic cosolvent. Detailed analysis using PFGSE NMR, temperature-dependent NMR, dilution experiments and CSI proves that the structure is monomeric in the concentration and temperature ranges 0.1-3 mM and 10-30 deg. C, respectively. The presence of long-range interstrand NOEs, as found in the crystal structure of the monomer, provides the evidence for conservation of the tertiary structure. Starting from structures calculated by the program CYANA, two different molecular dynamics simulated annealing refinement protocols were applied, either using the program AMBER in vacuum (AMBERVC), or including a generalized Born solvent model (AMBERGB)

  5. Electron-flux infrared response to varying π-bond topology in charged aromatic monomers.

    Science.gov (United States)

    Álvaro Galué, Héctor; Oomens, Jos; Buma, Wybren Jan; Redlich, Britta

    2016-01-01

    The interaction of delocalized π-electrons with molecular vibrations is key to charge transport processes in π-conjugated organic materials based on aromatic monomers. Yet the role that specific aromatic motifs play on charge transfer is poorly understood. Here we show that the molecular edge topology in charged catacondensed aromatic hydrocarbons influences the Herzberg-Teller coupling of π-electrons with molecular vibrations. To this end, we probe the radical cations of picene and pentacene with benchmark armchair- and zigzag-edges using infrared multiple-photon dissociation action spectroscopy and interpret the recorded spectra via quantum-chemical calculations. We demonstrate that infrared bands preserve information on the dipolar π-electron-flux mode enhancement, which is governed by the dynamical evolution of vibronically mixed and correlated one-electron configuration states. Our results reveal that in picene a stronger charge π-flux is generated than in pentacene, which could justify the differences of electronic properties of armchair- versus zigzag-type families of technologically relevant organic molecules. PMID:27577323

  6. Electron-flux infrared response to varying π-bond topology in charged aromatic monomers

    Science.gov (United States)

    Álvaro Galué, Héctor; Oomens, Jos; Buma, Wybren Jan; Redlich, Britta

    2016-08-01

    The interaction of delocalized π-electrons with molecular vibrations is key to charge transport processes in π-conjugated organic materials based on aromatic monomers. Yet the role that specific aromatic motifs play on charge transfer is poorly understood. Here we show that the molecular edge topology in charged catacondensed aromatic hydrocarbons influences the Herzberg-Teller coupling of π-electrons with molecular vibrations. To this end, we probe the radical cations of picene and pentacene with benchmark armchair- and zigzag-edges using infrared multiple-photon dissociation action spectroscopy and interpret the recorded spectra via quantum-chemical calculations. We demonstrate that infrared bands preserve information on the dipolar π-electron-flux mode enhancement, which is governed by the dynamical evolution of vibronically mixed and correlated one-electron configuration states. Our results reveal that in picene a stronger charge π-flux is generated than in pentacene, which could justify the differences of electronic properties of armchair- versus zigzag-type families of technologically relevant organic molecules.

  7. Electron-flux infrared response to varying π-bond topology in charged aromatic monomers

    Science.gov (United States)

    Álvaro Galué, Héctor; Oomens, Jos; Buma, Wybren Jan; Redlich, Britta

    2016-01-01

    The interaction of delocalized π-electrons with molecular vibrations is key to charge transport processes in π-conjugated organic materials based on aromatic monomers. Yet the role that specific aromatic motifs play on charge transfer is poorly understood. Here we show that the molecular edge topology in charged catacondensed aromatic hydrocarbons influences the Herzberg-Teller coupling of π-electrons with molecular vibrations. To this end, we probe the radical cations of picene and pentacene with benchmark armchair- and zigzag-edges using infrared multiple-photon dissociation action spectroscopy and interpret the recorded spectra via quantum-chemical calculations. We demonstrate that infrared bands preserve information on the dipolar π-electron-flux mode enhancement, which is governed by the dynamical evolution of vibronically mixed and correlated one-electron configuration states. Our results reveal that in picene a stronger charge π-flux is generated than in pentacene, which could justify the differences of electronic properties of armchair- versus zigzag-type families of technologically relevant organic molecules. PMID:27577323

  8. 新型抗菌型丙烯酸单体的合成及在牙科修复树脂中的应用%Synthesis of New Antibacterial Acrylic Monomer and Its Application in Dental Restoration Resin-based

    Institute of Scientific and Technical Information of China (English)

    赵中令; 连彦青

    2013-01-01

    Two acrylic monomers 2-(methacryloyloxy) ethyl 6-bromohexanoate pyridinium (MEBH-Py) and 2-(methacryloyloxy) ethyl 11-bromoundecanoate pyridinium(MEBU-Py) with antibacterial property were synthesized and copolymerized with the commercial dental restorative resin Single Bond Ⅱ adhesive (3 M ESPE dental products) to prepare modified binding agent with antibacterial activity to prevent second caries. The two monomers had good solubility in common solvents such as water, methanol. They could be dissolved in methyl methacrylate, hydroxyethyl methacrylate and other common dental resin. The results showed the two monomers could be copolymerized with commercial resin based restoratives. The monomers MEBH-Py and MEBU-Py got decomposed at 267. 6 and 247. 9℃ respectively and the minimal inhibitory concentration (MIC) of MEBH-Py and MEBU-Py were 6 and 1 mg/mL for E. coli JM05, respectively. The surface antibacterial efficiency for E. coli JM05 of the modified cured systems containing 1. 49%-5. 58% monomers were all up to 98%. The residual unpolymerized MEBH-Py or MEBU-Py were detected scarcely in the solution dipped out of the modified binder by UV-Vis analysis. The pyridinium salt groups were enriched on the surface of the modified binder by X-ray photoelectron spectroscopy ( XPS) which could be the reason of high antibacterial efficiency while low content of MEBH-Py or MEBU-Py. Thus, the two monomers have good thermal stability, good bactericidal activity and polymerizable property; they may be used in many other fields to achieve antibacterial materials.%制备了2种具有抗菌活性的丙烯酸酯类单体6-溴己酸-2-(2-甲基丙烯酰氧)乙基酯吡啶盐(MEBH-Py)和11-溴十一酸-2-(2-甲基丙烯酰氧)乙基酯吡啶盐(MEBU-Py),分别将其添加到牙科修复树脂Single BondⅡ纳米黏结剂中共聚,得到具有抗菌活性的改性黏结剂.MEBH-Py和MEBU-Py具有较好的热稳定性;以大肠杆菌JM05 (E.coli JM05)为受试菌,MEBH-Py和MEBU-Py

  9. Investigation on the aggregation properties of cationic [60]fullerene derivative

    Institute of Scientific and Technical Information of China (English)

    WANG Guanwu; ZHAO Guoxia; YAN Lifeng

    2004-01-01

    The UV-Vis spectra, HRTEM and AFM images of cationic fullerene derivative 1 with ammonium head group directly connected to C60 skeleton in tetrahydrofuran (THF)-water (H2O) binary mixtures and in pure H2O were investigated. It was found that the UV-Vis spectra of ammonium 1 in the THF-H2O mixtures with THF% ≥ 20% were nearly overlapped, while those with THF% < 20% showed broadened and red-shifted peaks, indicating the formation of aggregates. Corresponding to the UV-Vis spectral changes,the solvatochromism of ammonium 1 in THF-H2O mixtures was observed. Ammonium 1 in binary THF-H2O mixtures existing as the monomer state could aggregate upon prolonged standing. Higher temperature and lower concentration speeded up the aggregation process.

  10. SYNTHESIS AND CHARACTERIZATION OF A NOVEL STYRYLTHIOPHENE MONOMER AND CORRESPONDING POLYURETHANE FOR NLO MATERIALS

    Institute of Scientific and Technical Information of China (English)

    Jiang-hong Wang; Jian-feng Zhai; Jia-yun Zhou; Yu-xia Zhao; Yu-quan Shen

    1999-01-01

    A novel monomer,(trans)-7-[4-N,N-(di-β-hydroxyethyl) amino-benzene]-ethenyl-3,5-dinitro-thiophene (HBDT), was synthesized and characterized. The details of synthesizing the monomer and prepolymer, polyurethane with the monomer covalently incorporated are presented. The prepolymer and polyurethane exhibited good solubility in common organic solvents. Molecular nonlinear optical properties of the monomer (HBDT) substituted thiophene based stilbenes is presented.

  11. Liquid-solid extraction of cationic metals by cationic amphiphiles

    International Nuclear Information System (INIS)

    In the field of selective separation for recycling of spent nuclear fuel, liquid-liquid extraction processes are widely used (PUREX, DIAMEX..) in industrial scale. In order to guarantee a sustainable nuclear energy for the forthcoming generations, alternative reprocessing techniques are under development. One of them bases on the studies from Heckmann et al in the 80's and consists in selectively precipitating actinides from aqueous waste solutions by cationic surfactants (liquid-solid extraction). This technique has some interesting advantages over liquid-liquid extraction techniques, because several steps are omitted like stripping or solvent washing. Moreover, the amount of waste is decreased considerably, since no contaminated organic solvent is produced. In this thesis, we have carried out a physico-chemical study to understand the specific interactions between the metallic cations with the cationic surfactant. First, we have analysed the specific effect of the different counter-ions (Cl-, NO3-, C2O42-) and then the effect of alkaline cations on the structural properties of the surfactant aggregation in varying thermodynamical conditions. Finally, different multivalent cations (Cu2+, Zn2+, UO22+, Fe3+, Nd3+, Eu3+, Th4+) were considered; we have concluded that depending on the anionic complex of these metals formed in acidic media, we can observe either an adsorption at the micellar interface or not. This adsorption has a large influence of the surfactant aggregation properties and determines the limits of the application in term of ionic strength, temperature and surfactant concentration. (author)

  12. Limit Theorems for Monomer-Dimer Mean-Field Models with Attractive Potential

    Science.gov (United States)

    Alberici, Diego; Contucci, Pierluigi; Fedele, Micaela; Mingione, Emanuele

    2016-09-01

    The number of monomers in a monomer-dimer mean-field model with an attractive potential fluctuates according to the central limit theorem when the parameters are outside the critical curve. At the critical point the model belongs to the same universality class of the mean-field ferromagnet. Along the critical curve the monomer and dimer phases coexist.

  13. Effect of monomer-monomer interactions on the phase diagrams of the S = 1/2 distorted diamond type quantum spin chain

    Science.gov (United States)

    Okamoto, Kiyomi; Tonegawa, Takashi; Sakai, Tôru

    2016-02-01

    By use of mainly the exact diagonalization and the level spectroscopy method, we investigate the ground-state phase diagrams of the S = 1/2 distorted diamond type quantum spin chain with the monomer-monomer interactions and/or ferromagnetic interactions for the zero magnetic field case, as well as the M = Ms/3 case and the M = (2/3)Ms case, where M is the total magnetization and Ms is the saturation magnetization. The magnetization plateau at M = Ms/3 vanishes in the region where the ferromagnetic interaction is rather strong. The monomer-monomer interaction remarkably stabilizes the magnetization plateau at M = (2/3)Ms.

  14. Regioregular electrochromic polymers based on thienyl derivatives of fluorescent pyrene monomers: Optical properties, spectroelectrochemistry and quantum chemical study

    International Nuclear Information System (INIS)

    Graphical abstract: - Abstract: A detailed spectroelectrochemical and theoretical study of thienyl derivatives based on pyrene, namely 1-(2-thienyl)-pyrene (1), 1,6-bis(2-thienyl)-pyrene (2), 1,4-bis(2-thienyl)-pyrene (3), 1,3,6-tris(2-thienyl)-pyrene (4) and 1,3,6,8-tetra(2-thienyl)-pyrene (5), and their oxidation products with focus on the formation of their corresponding cationic states are presented. Regioregular polymeric systems were prepared by means of electrochemical polymerization from monomers 2–4. The redox behavior of the corresponding polymers was studied by cyclic voltammetry and in situ EPR/UV–vis–NIR spectroelectrochemistry with the aim of obtaining details on the type of charge carriers within the polymer film. Quantum chemical calculations of the optimal geometries and optical transitions for the neutral and charged forms were performed in order to reveal the influence of electrochemical oxidation on the molecular structure of the monomers and corresponding dimers and/or polymers

  15. Cationic Polymerization of 1,2-Epoxypropane by an Acid Exchanged Montmorillonite Clay in the Presence of Ethylene Glycol

    Directory of Open Access Journals (Sweden)

    Aïcha Hachemaoui

    2003-10-01

    Full Text Available Abstract: The polymerization of propylene oxide (PO catalysed by maghnite-H+ (mag-H+ in the presence of ethylene glycol was investigated. Mag-H+ is a montmorillonite silicate sheet clay was prepared through a straight forward proton exchange process. It was found that the cationic polymerization of PO was initiated by mag-H+ at 20 °C both in bulk and in solution. The effect of the amount of mag-H+ and solvent was studied. These results indicated the cationic nature of the polymerization A possible initiation pathway, via the transfer of protons from mag-H+ to the monomer, is proposed.

  16. Preparation of Eu2+ and Ce3+ co-activated phosphors with optimal composition in (Ba,Sr)2ZnS3 solid solution series by polymerizable complex method

    International Nuclear Information System (INIS)

    The series of Ba2-xSrxZnS3:Eu2+,Ce3+ (x = 0.3, 0.4, 0.5) red emission phosphors was synthesized by a solution based technique employing polymerizable complex method. The prepared materials conformed to Ba2MnS3 type crystal structure. Red fluorescence could be efficiently exited by the blue light of 445nm; thus these phosphors are prospective in white LED lighting application. The emission intensity vs. Sr concentration showed a distinct maximum at x = 0.4, while co-doping with Eu2+ and Ce3+ allowed for enhancement of emission intensity by 5-15% compared to the Ce free samples. The maximum emission intensity at 670nm exhibited by the material with optimal Sr concentration approached 80% compared to one of the best commercially available YAG:Ce3+.

  17. Recovery of Monomer from Nylon waste powder for its Recycling

    Directory of Open Access Journals (Sweden)

    Dilip B.Patil

    2014-03-01

    Full Text Available Recovery of monomer hexamethylene diamine(HMD in the form of dibenzoyl derivative of hexamethylene diamine (DBHMD from Nylon waste rope powder was carried out by degradation of Nylon waste powder of nylon rope waste.The molecular weight of nylon waste powder was found to be 26582.The minimum amount of nylon waste powder and hydrochloric acid required for maximum recovery of HMD and DBHMD was found to be 5g and 5N,50ml hydrochloric acid respectively. Further it was observed that the maximum time and temperature required for getting maximum yield of DBHMD was 120 minutes and 800C respectively.

  18. Cationic speciation in nonaqueous media

    International Nuclear Information System (INIS)

    Electronic spectra of solutions of d transition elements in the superacids HF, H2SO4, HSO3F, and CF3SO3H and in chloroaluminate melts indicate that in acidic monaqueous media the elements are present as solvated cations, whereas in basic media the speciation is anionic, the same situation as in aqueous solutions. Further, in very highly acidic media, cations in very low oxidation states are stable (e.g., Ti2+), but these disproportionate on addition of base to the system. In this paper spectra, where available, of U, Np, and Pu in oxidation states III and IV in aqueous media, in protonic superacids, and in chloroaluminates are presented to postulate cationic speciation of these early actinides in highly acidic media

  19. Synthesis of acrylic and allylic bifunctional cross-linking monomers derived from PET waste

    Science.gov (United States)

    Cruz-Aguilar, A.; Herrera-González, A. M.; Vázquez-García, R. A.; Navarro-Rodríguez, D.; Coreño, J.

    2013-06-01

    An acrylic and two novel allylic monomers synthesized from bis (hydroxyethyl) terephthalate, BHET, are reported. This was obtained by glycolysis of post-consumer PET with boiling ethylene glycol. The bifunctional monomer bis(2-(acryloyloxy)ethyl) terephthalate was obtained from acryloyl chloride, while the allylic monomers 2-(((allyloxi)carbonyl)oxy) ethyl (2-hydroxyethyl) terephthalate and bis(2-(((allyloxi)carbonyl)oxy)ethyl) terephthalate, from allyl chloroformate. Cross-linking was studied in bulk polymerization using two different thermal initiators. Monomers were analyzed by means of 1H NMR and the cross-linked polymers by infrared spectroscopy. Gel content higher than 90% was obtained for the acrylic monomer. In the case of the mixture of the allylic monomers, the cross-linked polymer was 80 % using BPO initiator, being this mixture 24 times less reactive than the acrylic monomer.

  20. Effects of acrylic resin monomers on porcine coronary artery reactivity.

    Science.gov (United States)

    Abebe, Worku; West, Daniel; Rueggeberg, Frederick A; Pashley, David; Mozaffari, Mahmood S

    2016-07-01

    The purpose of the present investigation was to assess the reactivity of porcine coronary arteries under in vitro conditions following their exposure to methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA) monomers. Confirming previous studies using rat aortas, both MMA and HEMA induced acute/direct relaxation of coronary ring preparations, which was partly dependent on the endothelium. With prolonged tissue exposure, both monomers caused time- and concentration-dependent inhibition of receptor-mediated contraction of the vascular smooth muscle caused by prostaglandin F2∝ (PGF2∝), with HEMA causing more inhibition than MMA. Hydroxyethyl methacrylate, but not MMA, also produced impairment of non-receptor-mediated contraction of the coronary smooth muscle induced by KCl. On the other hand, neither HEMA nor MMA altered relaxation of the smooth muscle produced by the direct-acting pharmacological agent, sodium nitroprusside (SNP). While exposure to HEMA impaired endothelium-dependent vasorelaxation caused by bradykinin (BK), MMA markedly enhanced this endothelial-mediated response of the arteries. The enhanced endothelial response produced by MMA was linked to nitric oxide (NO) release. In conclusion, with prolonged tissue exposure, MMA causes less pronounced effects/adverse consequences on coronary smooth muscle function relative to the effect of HEMA, while enhancing vasorelaxation associated with release of NO from the endothelium. Accordingly, MMA-containing resin materials appear to be safer for human applications than materials containing HEMA. PMID:27132475

  1. Shelf Life of PMR Polyimide Monomer Solutions and Prepregs Extended

    Science.gov (United States)

    Alston, William B.; Scheiman, Daniel A.

    2000-01-01

    PMR (Polymerization of Monomeric Reactants) technology was developed in the mid-1970's at the NASA Glenn Research Center at Lewis Field for fabricating high-temperature stable polyimide composites. This technology allowed a solution of polyimide monomers or prepreg (a fiber, such as glass or graphite, impregnated with PMR polyimide monomers) to be thermally cured without the release of volatiles that cause the formation of voids unlike the non-PMR technology used for polyimide condensation type resins. The initial PMR resin introduced as PMR 15 is still commercially available and is used worldwide by aerospace industries as the state-of-the-art resin for high-temperature polyimide composite applications. PMR 15 offers easy composite processing, excellent composite mechanical property retention, a long lifetime at use temperatures of 500 to 550 F, and relatively low cost. Later, second-generation PMR resin versions, such as PMR II 50 and VCAP 75, offer improvements in the upper-use temperature (to 700 F) and in the useful life at temperature without major compromises in processing and property retention but with significant increases in resin cost. Newer versions of nontoxic (non-methylene dianiline) PMR resins, such as BAX PMR 15, offer similar advantages as originally found for PMR 15 but also with significant increases in resin cost. Thus, the current scope of the entire PMR technology available meets a wide range of aeronautical requirements for polymer composite applications.

  2. Effects of acrylic resin monomers on porcine coronary artery reactivity.

    Science.gov (United States)

    Abebe, Worku; West, Daniel; Rueggeberg, Frederick A; Pashley, David; Mozaffari, Mahmood S

    2016-07-01

    The purpose of the present investigation was to assess the reactivity of porcine coronary arteries under in vitro conditions following their exposure to methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA) monomers. Confirming previous studies using rat aortas, both MMA and HEMA induced acute/direct relaxation of coronary ring preparations, which was partly dependent on the endothelium. With prolonged tissue exposure, both monomers caused time- and concentration-dependent inhibition of receptor-mediated contraction of the vascular smooth muscle caused by prostaglandin F2∝ (PGF2∝), with HEMA causing more inhibition than MMA. Hydroxyethyl methacrylate, but not MMA, also produced impairment of non-receptor-mediated contraction of the coronary smooth muscle induced by KCl. On the other hand, neither HEMA nor MMA altered relaxation of the smooth muscle produced by the direct-acting pharmacological agent, sodium nitroprusside (SNP). While exposure to HEMA impaired endothelium-dependent vasorelaxation caused by bradykinin (BK), MMA markedly enhanced this endothelial-mediated response of the arteries. The enhanced endothelial response produced by MMA was linked to nitric oxide (NO) release. In conclusion, with prolonged tissue exposure, MMA causes less pronounced effects/adverse consequences on coronary smooth muscle function relative to the effect of HEMA, while enhancing vasorelaxation associated with release of NO from the endothelium. Accordingly, MMA-containing resin materials appear to be safer for human applications than materials containing HEMA.

  3. Induced DNA damage by dental resin monomers in somatic cells.

    Science.gov (United States)

    Arossi, Guilherme Anziliero; Lehmann, Mauricio; Dihl, Rafael Rodrigues; Reguly, Maria Luiza; de Andrade, Heloisa Helena Rodrigues

    2010-02-01

    The present in vivo study investigated the genotoxicity of four dental resin monomers: triethyleneglycoldimethacrylate (TEGDMA), hydroxyethylmethacrylate (HEMA), urethanedimethacrylate (UDMA) and bisphenol A-glycidylmethacrylate (BisGMA). The Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster was applied to analyse their genotoxicity expressed as homologous mitotic recombination, point and chromosomal mutation. SMART detects the loss of heterozygosity of marker genes expressed phenotypically on the fly's wings. This fruit fly has an extensive genetic homology to mammalians, which makes it a suitable model organism for genotoxic investigations. The present findings provide evidence that the mechanistic basis underlying the genotoxicity of UDMA and TEGDMA is related to homologous recombination and gene/chromosomal mutation. A genotoxic pattern can correspondingly be discerned for both UDMA and TEGDMA: their genotoxicity is attributed respectively to 49% and 44% of mitotic recombination, as well as 51% and 56% of mutational events, including point and chromosomal alterations. The monomer UDMA is 1.6 times more active than TEGDMA to induce mutant clones per treatment unit. BisGMA and HEMA had no statistically significant effect on total spot frequencies - suggesting no genotoxic action in the SMART assay. The clinical significance of these observations has to be interpreted for data obtained in other bioassays.

  4. Structural Insights into Mitochondrial Calcium Uniporter Regulation by Divalent Cations.

    Science.gov (United States)

    Lee, Samuel K; Shanmughapriya, Santhanam; Mok, Mac C Y; Dong, Zhiwei; Tomar, Dhanendra; Carvalho, Edmund; Rajan, Sudarsan; Junop, Murray S; Madesh, Muniswamy; Stathopulos, Peter B

    2016-09-22

    Calcium (Ca(2+)) flux into the matrix is tightly controlled by the mitochondrial Ca(2+) uniporter (MCU) due to vital roles in cell death and bioenergetics. However, the precise atomic mechanisms of MCU regulation remain unclear. Here, we solved the crystal structure of the N-terminal matrix domain of human MCU, revealing a β-grasp-like fold with a cluster of negatively charged residues that interacts with divalent cations. Binding of Ca(2+) or Mg(2+) destabilizes and shifts the self-association equilibrium of the domain toward monomer. Mutational disruption of the acidic face weakens oligomerization of the isolated matrix domain and full-length human protein similar to cation binding and markedly decreases MCU activity. Moreover, mitochondrial Mg(2+) loading or blockade of mitochondrial Ca(2+) extrusion suppresses MCU Ca(2+)-uptake rates. Collectively, our data reveal that the β-grasp-like matrix region harbors an MCU-regulating acidic patch that inhibits human MCU activity in response to Mg(2+) and Ca(2+) binding.

  5. Cationic quaternization of cellulose with methacryloyloxy ethyl trimethyl ammonium chloride via ATRP method

    Energy Technology Data Exchange (ETDEWEB)

    Supeno [Cenderawasih University, Jayapura, Papua, Indonesia and School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Daik, Rusli, E-mail: rusli@ukm.edu.my [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); El-Sheikh, Said M. [Nano-Structured Materials Division, Advanced Materials Department, Central Metallurgical Research and Development Institute, Cairo (Egypt)

    2014-09-03

    The synthesis of a cationic cellulose copolymer from cellulose macro-initiator (MCC-BiB) and quaternary compound monomer (METMA) via atom transfer radical polymerization (ATRP) was studied. By using dimethylformamide (DMF), the optimum condition for successful synthesis was at the mole ratio of MCC-BIB:Catalyst:METMA = 1:1:26. The highest copolymer recovery was 93.2 % for 6 h and at 40°C. The copolymer was insoluble in weak polar solvents such as THF and DMF but soluble in methanol and water. The chemistry of cellulose copolymer was confirmed by the FTIR and TGA in which the METMA monomer was used as a reference. The absence of CC bond in the CiB-g-METMA spectrum indicated that graft copolymerization occurred.

  6. Research progress in cation-π interactions

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Cation-π interaction is a potent intermolecular interaction between a cation and an aromatic system,which has been viewed as a new kind of binding force,as being compared with the classical interactions(e.g. hydrogen bonding,electrostatic and hydrophobic interactions). Cation-π interactions have been observed in a wide range of biological contexts. In this paper,we present an overview of the typical cation-π interactions in biological systems,the experimental and theoretical investigations on cation-π interactions,as well as the research results on cation-π interactions in our group.

  7. Research progress in cation-π interactions

    Institute of Scientific and Technical Information of China (English)

    CHENG JiaGao; LUO XiaoMin; YAN XiuHua; LI Zhong; TANG Yun; JIANG HuaLiang; ZHU WeiLiang

    2008-01-01

    Cation-π interaction is a potent intermolecular interaction between a cation and an aromatic system, which has been viewed as a new kind of binding force, as being compared with the classical interac-tions (e.g. hydrogen bonding, electrostatic and hydrophobic interactions). Cation-π interactions have been observed in a wide range of biological contexts. In this paper, we present an overview of the typi-cal cation-π interactions in biological systems, the experimental and theoretical investigations on cation-π interactions, as well as the research results on cation-π interactions in our group.

  8. Polymerization of Polar Monomers from a Theoretical Perspective

    KAUST Repository

    Alghamdi, Miasser

    2016-10-11

    Density functional theory calculations have been used to investigate catalytic mechanism of polymer formation containing polar groups, from the synthesis of the monomer to the synthesis of the macromolecule. In the spirit of a sustainable and green chemistry, we initially focused attention on the coupling of CO2 as economically convenient and recyclable C1 source with C2H4 to form acrylate and/or butirro-lactone, two important polar monomers. In this process formation of a mettallolactone via oxidative coupling of CO2 and C2H4 is an important intermediate. Given this background, we explored in detail (chapter-3) several Ni based catalysts for CO2 coupling with C2H4 to form acrylate. In this thesis we report on the competitive reaction mechanisms (inner vs outer sphere) for the oxidative coupling of CO2 and ethylene for a set of 11 Ni-based complexes containing bisphosphine ligands. In another effort, considering incorporation of a C=C bond into a metal-oxygen-Functional-Group moiety is a challenging step in several polymerization reactions, we explored the details of this reaction (chapter4) using two different catalysts that are capable to perform this reaction in the synthesis of heterocycles. Specifically, the [Rh]-catalyzed intramolecular alkoxyacylation ([Rh] = [RhI(dppp)+] (dppp, 1,3-Bis-diphenylphosphino-propane), and the [Pd]/BPh3 intramolecular alkoxyfunctionalizations. Rest of the thesis we worked on understanding the details of the polymerization of polar monomers using organocatalysts based on N-heterocyclic carbenes (NHC) or N-heterocyclic olefins (NHO). In particular (chapter-5) we studied the polymerization of N-methyl N-carboxy- anhydrides, towards cyclic poly(N-substituted glycine)s, promoted by NHC catalysts. In good agreement with the experimental findings, we demonstrated that NHC promoted ring opening polymerization of N-Me N-Carboxyanhydrides may proceed via two different catalytic pathways. In a similar effort we studied polymerization of

  9. Polymerization of nonfood biomass-derived monomers to sustainable polymers.

    Science.gov (United States)

    Zhang, Yuetao; Chen, Eugene Y-X

    2014-01-01

    The development of sustainable routes to fine chemicals, liquid fuels, and polymeric materials from natural resources has attracted significant attention from academia, industry, the general public, and governments owing to dwindling fossil resources, surging energy demand, global warming concerns, and other environmental problems. Cellulosic material, such as grasses, trees, corn stover, or wheat straw, is the most abundant nonfood renewable biomass resources on earth. Such annually renewable material can potentially meet our future needs with a low carbon footprint if it can be efficiently converted into fuels, value added chemicals, or polymeric materials. This chapter focuses on various renewable monomers derived directly from cellulose or cellulose platforms and corresponding sustainable polymers or copolymers produced therefrom. Recent advances related to the polymerization processes and the properties of novel biomass-derived polymers are also reviewed and discussed. PMID:24699900

  10. Biobased Epoxy Nanocomposites Derived from Lignin-Based Monomers.

    Science.gov (United States)

    Zhao, Shou; Abu-Omar, Mahdi M

    2015-07-13

    Biobased epoxy nanocomposites were synthesized based on 2-methoxy-4-propylphenol (dihydroeugenol, DHE), a molecule that has been obtained from the lignin component of biomass. To increase the content of hydroxyl groups, DHE was o-demethylated using aqueous HBr to yield propylcatechol (DHEO), which was subsequently glycidylated to epoxy monomer. Optimal conditions in terms of yield and epoxy equivalent weight were found to be 60 °C with equal NaOH/phenolic hydroxyl molar ratio. The structural evolution from DHE to cured epoxy was followed by (1)H NMR and Fourier transform infrared spectroscopy. The nano-montmorillonite modified DHEO epoxy exhibited improved storage modulus and thermal stability as determined from dynamic mechanical analysis and thermogravimetric analysis. This study widens the synthesis routes of biobased epoxy thermosets from lignin-based molecules. PMID:26135389

  11. Graft-copolymerization of hydrophilic monomers onto irradiated polypropylene fibers

    International Nuclear Information System (INIS)

    A method of graft-copolymerization of hydrophilic monomers such as 1-vinyl-2 pyrolidone, acrylonitrile, acrylic acid and acrylamide onto irradiated polypropylene fibers has been studied. Gamma ray as well as electron beam were employed for the irradiation processes. Graft copolymerization kinetics and the properties of grafted fibers have been investigated. Moisture regain, dyes absorption and the melting point of the grafted fibers increased with the increase of the degree of grafting. Polypropilen 1-vinyl-2 pyrrolidone grafted fibers showed excellent dyes absorption of almost all kinds of dyes such as direct, basic, acid, reactive, dispers, and naphtol. However for polypropylene acrylic acid grafted fibers, the colour fastness to washing was found to be unsatisfactory. The colourfastness to washing for polypropylene grafted fibers was found to be fairly good for certain dyes such as v and naphtol dyes

  12. Synthesis of Bis(hydroxylmethylfurfuryl)amine Monomers from 5-Hydroxymethylfurfural.

    Science.gov (United States)

    Xu, Zhanwei; Yan, Peifang; Liu, Kairui; Wan, Lu; Xu, Wenjuan; Li, Huixiang; Liu, Xiumei; Zhang, Z Conrad

    2016-06-01

    We report the synthesis of bis(hydroxylmethylfurfuryl)amine (BHMFA) from 5-hydroxymethylfurfural (5-HMF) by reacting 5-HMF with primary amines in the presence of homogeneous Ru(II) catalysts having sterically strained ligands. BHMFA is a group of furan-based monomers that offer great potential to form functional biopolymers with tunable properties. A range of primary amines, such as aliphatic and benzyl amines, are readily converted with 5-HMF to form the corresponding BHMFA in good yields. The reaction proceeds through reductive amination of 5-HMF with primary amine to form secondary amine, followed by reductive amination of 5-HMF with in situ generated secondary amine to produce BHMFA. PMID:27151257

  13. Tripodal Receptors for Cation and Anion Sensors

    NARCIS (Netherlands)

    Kuswandi, Bambang; Nuriman,; Verboom, Willem; Reinhoudt, David N.

    2006-01-01

    This review discusses different types of artificial tripodal receptors for the selectiverecognition and sensing of cations and anions. Examples on the relationship between structure andselectivity towards cations and anions are described. Furthermore, their applications as potentiometricion sensing

  14. Features definition exchange cations in sedimentary rocks.

    OpenAIRE

    Bilec'ka V.A.

    2008-01-01

    The research method of determination of exchange cations in calcareous sedimentary rocks of different extractants, the influence of the ratio between the solid and liquid phases on extrusion exchange cations.

  15. Features definition exchange cations in sedimentary rocks.

    Directory of Open Access Journals (Sweden)

    Bilec'ka V.A.

    2008-05-01

    Full Text Available The research method of determination of exchange cations in calcareous sedimentary rocks of different extractants, the influence of the ratio between the solid and liquid phases on extrusion exchange cations.

  16. Sodium dodecyl sulfate monomers induce XAO peptide polyproline II to α-helix transition.

    Science.gov (United States)

    Hong, Zhenmin; Damodaran, Krishnan; Asher, Sanford A

    2014-09-11

    XAO peptide (Ac-X2A7O2-NH2; X: diaminobutyric acid side chain, -CH2CH2NH3(+); O: ornithine side chain, -CH2CH2CH2NH3(+)) in aqueous solution shows a predominantly polyproline II (PPII) conformation without any detectable α-helix-like conformations. Here we demonstrate by using circular dichroism (CD), ultraviolet resonance Raman (UVRR) and nuclear magnetic resonance (NMR) spectroscopy that sodium dodecyl sulfate (SDS) monomers bind to XAO and induce formation of α-helix-like conformations. The stoichiometry and the association constants of SDS and XAO were determined from the XAO-SDS diffusion coefficients measured by pulsed field gradient NMR. We developed a model for the formation of XAO-SDS aggregate α-helix-like conformations. Using UVRR spectroscopy, we calculated the Ramachandran ψ angle distributions of aggregated XAO peptides. We resolved α-, π- and 3(10)-helical conformations and a turn conformation. XAO nucleates SDS aggregation at SDS concentrations below the SDS critical micelle concentration. The XAO4-SDS16 aggregates have four SDS molecules bound to each XAO to neutralize the four side chain cationic charges. We propose that the SDS alkyl chains partition into a hydrophobic core to minimize the hydrophobic area exposed to water. Neutralization of the flanking XAO charges enables α-helix formation. Four XAO-SDS4 aggregates form a complex with an SDS alkyl chain-dominated hydrophobic core and a more hydrophilic shell where one face of the α-helix peptide contacts the water environment. PMID:25121643

  17. Cationic modified nucleic acids for use in DNA hairpins and parallel triplexes

    DEFF Research Database (Denmark)

    Bomholt, Niels; Filichev, Vyacheslav V; Pedersen, Erik Bjerregaard

    2011-01-01

    Non-nucleosidic DNA monomers comprising partially protonated amines at low pH have been designed and synthesized. The modifications were incorporated into DNA oligonucleotides via standard DNA phosphoramidite synthesis. The ability of cationic modifications to stabilize palindromic DNA hairpins and...... parallel triplexes were evaluated using gel electrophoresis, circular dichroism and thermal denaturation measurements. The non-nucleosidic modifications were found to increase the thermal stability of palindromic hairpins at pH 8.0 as compared with a nucleosidic tetraloop (TCTC). Incorporation of...

  18. Water-soluble cationic conjugated polymers: response to electron-rich bioanalytes.

    Science.gov (United States)

    Rochat, Sébastien; Swager, Timothy M

    2013-11-27

    We report the concise synthesis of a symmetrical monomer that provides a head-to-head pyridine building block for the preparation of cationic conjugated polymers. The obtained poly(pyridinium-phenylene) polymers display appealing properties such as high electron affinity, charge-transport upon n-doping, and optical response to electron-donating analytes. A simple assay for the optical detection of low micromolar amounts of a variety of analytes in aqueous solution was developed. In particular, caffeine could be measured at a 25 μM detection limit. The reported polymers are also suitable for layer-by-layer film formation.

  19. Small angle neutron scattering studies on the interaction of cationic surfactants with bovine serum albumin

    Indian Academy of Sciences (India)

    Nuzhat Gull; S Chodankar; V K Aswal; Kabir-Ud-Din

    2008-11-01

    The structure of the protein–surfactant complex of bovine serum albumin (BSA) and cationic surfactants has been studied by small angle neutron scattering. At low concentrations, the CTAB monomers are observed to bind to the protein leading to an increase in its size. On the other hand at high concentrations, surfactant molecules aggregate along the unfolded polypeptide chain of the protein resulting in the formation of a fractal structure representing a necklace model of micelle-like clusters randomly distributed along the polypeptide chain. The fractal dimension as well as the size and number of micelles attached to the complex have been determined.

  20. Islet amyloid polypeptide inserts into phospholipid monolayers as monomer.

    Science.gov (United States)

    Engel, Maarten F M; Yigittop, HaciAli; Elgersma, Ronald C; Rijkers, Dirk T S; Liskamp, Rob M J; de Kruijff, Ben; Höppener, Jo W M; Antoinette Killian, J

    2006-02-24

    Amyloid deposits in the pancreatic islets of Langerhans are thought to be a main factor responsible for death of the insulin-producing islet beta-cells in type 2 diabetes. It is hypothesized that beta-cell death is related to interaction of the 37 amino acid residue human islet amyloid polypeptide (hIAPP), the major constituent of islet amyloid, with cellular membranes. However, the mechanism of hIAPP-membrane interactions is largely unknown. Here, we study the nature and the molecular details of the initial step of hIAPP-membrane interactions by using the monolayer technique. It is shown that both freshly dissolved hIAPP and the non-amyloidogenic mouse IAPP (mIAPP) have a pronounced ability to insert into phospholipid monolayers, even at lipid packing conditions that exceed the conditions that occur in biological membranes. In contrast, the fibrillar form of hIAPP has lost the ability to insert. These results, combined with the observations that both the insertion kinetics and the dependence of insertion on the initial surface pressure are similar for freshly dissolved hIAPP and mIAPP, indicate that hIAPP inserts into phospholipid monolayers most likely as a monomer. In addition, our results suggest that the N-terminal part of hIAPP, which is nearly identical with that of mIAPP, is largely responsible for insertion. This is supported by experiments with hIAPP fragments, which show that a peptide consisting of the 19 N-terminal residues of hIAPP efficiently inserts into phospholipid monolayers, whereas an amyloidogenic decapeptide, consisting of residues 20-29 of hIAPP, inserts much less efficiently. The results obtained here suggest that hIAPP monomers might insert with high efficiency in biological membranes in vivo. This process could play an important role as a first step in hIAPP-induced membrane damage in type 2 diabetes. PMID:16403520

  1. Highly Efficient Synthesis of Allopurinol Locked Nucleic Acid Monomer by C6 Deamination of 8-Aza-7-bromo-7-deazaadenine Locked Nucleic Acid Monomer

    DEFF Research Database (Denmark)

    Kosbar, Tamer Reda El-Saeed; Sofan, M.; Abou-Zeid, L.;

    2013-01-01

    pathway. N-Glycosylation at the 8-position was prevented by steric hindrance from the 7-bromo atom in the starting material 8-aza-7-bromo-7-deazaadenine. In the final step of the synthesis, the bromine was removed together with a benzyl protecting group by catalytic reduction with ammonium formate to give......An allopurinol locked nucleic acid (LNA) monomer was prepared by a novel strategy through C6 deamination of the corresponding 8-aza-7-bromo-7-deazaadenine LNA monomer with aqueous sodium hydroxide. An 8-aza-7-deazaadenine LNA monomer was also synthesized by a modification of the new synthetic...

  2. Cationic electrodepositable coating composition comprising lignin

    Science.gov (United States)

    Fenn, David; Bowman, Mark P; Zawacky, Steven R; Van Buskirk, Ellor J; Kamarchik, Peter

    2013-07-30

    A cationic electrodepositable coating composition is disclosed. The present invention in directed to a cationic electrodepositable coating composition comprising a lignin-containing cationic salt resin, that comprises (A) the reaction product of: lignin, an amine, and a carbonyl compound; (B) the reaction product of lignin, epichlorohydrin, and an amine; or (C) combinations thereof.

  3. Organometallic cation-exchanged phyllosilicates

    OpenAIRE

    Fleming, Shay

    1991-01-01

    Organotin (IV) complexes formed between 0 01 M dimethyltin dichloride solutions prepared at pH 2 6 and 4 0, and trimethyltin chloride prepared at pH 3 4, with Na- 119 montmori 1lonite clay have been characterised using Sn Mflssbauer spectroscopy, X-ray diffraction, thermogravimetric analysis and water sorption isotherms Following cation exchange, Mttssbauer spectroscopy identified two tin species in the dimethyltin (IV)-exchanged clay prepared at pH 2 6 A cis specie...

  4. Glassy dynamics of model colloidal polymers: The effect of "monomer" size

    Science.gov (United States)

    Li, Jian; Zhang, Bo-kai; Li, Hui-shu; Chen, Kang; Tian, Wen-de; Tong, Pei-qing

    2016-05-01

    In recent years, attempts have been made to assemble colloidal particles into chains, which are termed "colloidal polymers." An apparent difference between molecular and colloidal polymers is the "monomer" size. Here, we propose a model to represent the variation from molecular polymer to colloidal polymer and study the quantitative differences in their glassy dynamics. For chains, two incompatible local length scales, i.e., monomer size and bond length, are manifested in the radial distribution function and intramolecular correlation function. The mean square displacement of monomers exhibits Rouse-like sub-diffusion at intermediate time/length scale and the corresponding exponent depends on the volume fraction and the monomer size. We find that the threshold volume fraction at which the caging regime emerges can be used as a rescaling unit so that the data of localization length versus volume fraction for different monomer sizes can gather close to an exponential curve. The increase of monomer size effectively increases the hardness of monomers and thus makes the colloidal polymers vitrify at lower volume fraction. Static and dynamic equivalences between colloidal polymers of different monomer sizes have been discussed. In the case of having the same peak time of the non-Gaussian parameter, the motion of monomers of larger size is much less non-Gaussian. The mode-coupling critical exponents for colloidal polymers are in agreement with that of flexible bead-spring chains.

  5. PREAPARATION OF CATIONIC LATEXES OF POLY(STYRENE-CO-BUTYL ACRYLATE) AND THEIR PROPERTIES EVOLUTION IN LATEX DILUTION

    Institute of Scientific and Technical Information of China (English)

    Dong Zou; Xiu-fen Li; Xiao-li Zhu; Xiang-zheng Kong

    2012-01-01

    Cationic latexes were prepared through emulsion copolymerization of styrene (St) and butyl acrylate (BA) with a cationic surfactant,cetyl trimethyl ammonium bromide (CTAB).Latex properties,including particle size,size distribution,ζ potential,surface tension and monomer conversion,were determined for latexes prepared with different CTAB amounts.Evolution of these properties during emulsion polymerization was followed in order to understand the mechanism of the particles formation.Results showed that both particle size and ζpotential were function of polymerization time and latex solids.Parallel emulsion polymerizations with cationic,anionic charged initiator and charge-free initiators were also carried out,the latex properties were determined at different polymerization time.All these results were attentively interpreted based on the mechanisms of emulsion polymerization,surfactant adsorption and latex particle stabilization.

  6. Computational screening of oxetane monomers for novel hydroxy terminated polyethers.

    Science.gov (United States)

    Sarangapani, Radhakrishnan; Ghule, Vikas D; Sikder, Arun K

    2014-06-01

    Energetic hydroxy terminated polyether prepolymers find paramount importance in search of energetic binders for propellant applications. In the present study, density functional theory (DFT) has been employed to screen the various novel energetic oxetane derivatives, which usually construct the backbone for these energetic polymers. Molecular structures were investigated at the B3LYP/6-31G* level, and isodesmic reactions were designed for calculating the gas phase heats of formation. The condensed phase heats of formation for designed compounds were calculated by the Politzer approach using heats of sublimation. Among the designed oxetane derivatives, T4 and T5 possess condensed phase heat of formation above 210 kJ mol(-1). The crystal packing density of the designed oxetane derivatives varied from 1.2 to 1.6 g/cm(3). The detonation velocities and pressures were evaluated using the Kamlet-Jacobs equations, utilizing the predicted densities and HOFCond. It was found that most of the designed oxetane derivatives have detonation performance comparable to the monomers of benchmark energetic polymers viz., NIMMO, AMMO, and BAMO. The strain energy (SE) for the oxetane derivatives were calculated using homodesmotic reactions, while intramolecular group interactions were predicted through the disproportionation energies. The concept of chemical hardness is used to analyze the susceptibility of designed compounds to reactivity and chemical transformations. The heats of formation, density, and predicted performance imply that the designed molecules are expected to be candidates for polymer synthesis and potential molecules for energetic binders. PMID:24863529

  7. Ligustrazine monomer against cerebral ischemia-reperfusion injury

    Directory of Open Access Journals (Sweden)

    Hai-jun Gao

    2015-01-01

    Full Text Available Ligustrazine (2,3,5,6-tetramethylpyrazine is a major active ingredient of the Szechwan lovage rhizome and is extensively used in treatment of ischemic cerebrovascular disease. The mechanism of action of ligustrazine use against ischemic cerebrovascular diseases remains unclear at present. This study summarizes its protective effect, the optimum time window of administration, and the most effective mode of administration for clinical treatment of cerebral ischemia/reperfusion injury. We examine the effects of ligustrazine on suppressing excitatory amino acid release, promoting migration, differentiation and proliferation of endogenous neural stem cells. We also looked at its effects on angiogenesis and how it inhibits thrombosis, the inflammatory response, and apoptosis after cerebral ischemia. We consider that ligustrazine gives noticeable protection from cerebral ischemia/reperfusion injury. The time window of ligustrazine administration is limited. The protective effect and time window of a series of derivative monomers of ligustrazine such as 2-[(1,1-dimethylethyloxidoimino]methyl]-3,5,6-trimethylpyrazine, CXC137 and CXC195 after cerebral ischemia were better than ligustrazine.

  8. Mechanisms of Activation of Receptor Tyrosine Kinases: Monomers or Dimers

    Directory of Open Access Journals (Sweden)

    Ichiro N. Maruyama

    2014-04-01

    Full Text Available Receptor tyrosine kinases (RTKs play essential roles in cellular processes, including metabolism, cell-cycle control, survival, proliferation, motility and differentiation. RTKs are all synthesized as single-pass transmembrane proteins and bind polypeptide ligands, mainly growth factors. It has long been thought that all RTKs, except for the insulin receptor (IR family, are activated by ligand-induced dimerization of the receptors. An increasing number of diverse studies, however, indicate that RTKs, previously thought to exist as monomers, are present as pre-formed, yet inactive, dimers prior to ligand binding. The non-covalently associated dimeric structures are reminiscent of those of the IR family, which has a disulfide-linked dimeric structure. Furthermore, recent progress in structural studies has provided insight into the underpinnings of conformational changes during the activation of RTKs. In this review, I discuss two mutually exclusive models for the mechanisms of activation of the epidermal growth factor receptor, the neurotrophin receptor and IR families, based on these new insights.

  9. Blood compatibility of polyurethane surface grafted copolymerization with sulfobetaine monomer.

    Science.gov (United States)

    Jiang, Yuan; Rongbing, Bian; Ling, Tong; Jian, Shen; Sicong, Lin

    2004-07-01

    Surface modification is an effective way to improve the hemocompatibility and remain bulk properties of biomaterials. Recently, polymer tailed with zwitterions was found having good blood compatibility. In this study, the grafting copolymerization of sulfobetaine onto polyurethane surface was obtained through two steps. In the first step, polyurethane film coupled with vinyl groups was obtained through the reaction between the carboxyl group of acrylic acid (AA) and the NH-urethane group of polyurethane by dicyclohexylcarbodiimide (DCC). In the second step, sulfobetaine was grafted copolymerization on the surface using AIBN as an initiator. The reaction process was monitored with ATR-IR spectra and X-ray photoelectron spectroscopy (XPS) spectra. The wettability of films was investigated by water contact angle measurement. The blood compatibility of the grafted films was evaluated by platelet adhesion in platelet rich plasma (PRP) and protein absorption in bovine fibrinogen (BFG). Low platelet adhesion was observed on the grafted films incubated in PRP for 1 and 3 h, respectively. The protein absorption was reduced on the grafted films after incubated in bovine fibrinogen for 2 h. All of these results revealed that the improved blood compatibility was obtained by grafting copolymerization with zwitterionic monomer of sulfobetaine onto polyurethane film. In addition, introducing vinyl groups onto surface through DCC and AA is a novel method to functionalize polyurethane for further modification.

  10. Conformational study of neutral histamine monomer and their vibrational spectra.

    Science.gov (United States)

    Mukherjee, V; Yadav, T

    2016-08-01

    Molecular modeling and potential energy scanning of histamine molecule, which is an important neurotransmitter, with respect to the dihedral angle of methylamine side chain have done which prefer three different conformers of histamine monomer. We have calculated molecular structures and vibrational spectra with IR and Raman intensities of these conformers using Density Functional Theory (DFT) with the exchange functional B3LYP incorporated with the basis set 6-31++G(d,p) and Hartree-Fock (HF) with the same basis set. We have also employed normal coordinate analysis (NCA) to scale the theoretical frequencies and to calculate potential energy distributions (PEDs) for the conspicuous assignments. Normal modes assignments of some of the vibrational frequencies of all the three conformers are in good agreement with the earlier reported experimental frequencies of histamine whereas others have modified. The standard deviations between the theoretical and experimental frequencies fall in the region 13-20cm(-1) for the three conformers. NBO analyses of histamine conformers were also performed. The net charge transfers from ethylamine side chain to the imidazole ring. The intensive interactions between bonding and anti-bonding orbitals are found in imidazole ring. The HOMO-LUMO energy gap is nearly 5.50eV. PMID:27155558

  11. Conformational study of neutral histamine monomer and their vibrational spectra

    Science.gov (United States)

    Mukherjee, V.; Yadav, T.

    2016-08-01

    Molecular modeling and potential energy scanning of histamine molecule, which is an important neurotransmitter, with respect to the dihedral angle of methylamine side chain have done which prefer three different conformers of histamine monomer. We have calculated molecular structures and vibrational spectra with IR and Raman intensities of these conformers using Density Functional Theory (DFT) with the exchange functional B3LYP incorporated with the basis set 6-31 ++G(d,p) and Hartree-Fock (HF) with the same basis set. We have also employed normal coordinate analysis (NCA) to scale the theoretical frequencies and to calculate potential energy distributions (PEDs) for the conspicuous assignments. Normal modes assignments of some of the vibrational frequencies of all the three conformers are in good agreement with the earlier reported experimental frequencies of histamine whereas others have modified. The standard deviations between the theoretical and experimental frequencies fall in the region 13-20 cm- 1 for the three conformers. NBO analyses of histamine conformers were also performed. The net charge transfers from ethylamine side chain to the imidazole ring. The intensive interactions between bonding and anti-bonding orbitals are found in imidazole ring. The HOMO-LUMO energy gap is nearly 5.50 eV.

  12. Superhydrophocity via gas-phase monomers grafting onto carbon nanotubes

    Science.gov (United States)

    Zha, Jinlong; Batisse, Nicolas; Claves, Daniel; Dubois, Marc; Frezet, Lawrence; Kharitonov, Alexander P.; Alekseiko, Leonid N.

    2016-05-01

    Superhydrophobic films were prepared using dispersions of fluorinated multi-walled carbon nanotubes (MWCNTs) or nanofibers (CNFs) in toluene. The grafting of polystyrene allowed stable dispersions to be obtained. The grafting of polystyrene (PS), polyacrylic acid (PAA) and polyaniline (PANI) onto nanofibers and MWCNTs was first evidenced by solid state NMR and Infrared Spectroscopy. The graft polymerization of styrene, acrylic acid and aniline monomers was initiated by radicals (dangling bonds) formed due to the initial fluorination. The process appeared as highly versatile and efficient for different polymers. The consumption of those radicals in the course of grafting was evidenced by EPR, through decrease of the spin density. The hydrophobic/hydrophilic character was tuned according to the grafted polymer nature, i.e. hydrophobic with PS or hydrophilic with PAA. Finally, in order to reach superhydrophobicity, films were prepared from CNFs or MWCNTs, irrespective of their average diameter, that allowed adequate structuring of the surface. The presence of fluorine atoms on their surface also favors superhydrophobicity. Water contact angles of 155 ± 2° and 159 ± 2° were measured for the films casted from fluorinated CNFs or MWCNTs with grafted polystyrene, respectively.

  13. Delamination of layered double hydroxides in polar monomers: new LDH-acrylate nanocomposites.

    Science.gov (United States)

    O'Leary, Shane; O'Hare, Dermot; Seeley, Gordon

    2002-07-21

    The layered double hydroxide Mg2Al(OH)6(C12H25SO4) was delaminated to give high levels of inclusion in acrylate monomers; subsequent polymerisation of the monomers containing the LDH dispersion gave polyacrylates with the inorganic component still in the delaminated form. PMID:12189866

  14. Synthesis and ATRP of novel fluorinated aromatic monomer with pendant sulfonate group

    DEFF Research Database (Denmark)

    Dimitrov, Ivaylo; Jankova Atanasova, Katja; Hvilsted, Søren

    2013-01-01

    Novel, fluorinated monomer with pendant sulfonate group was synthesized utilizing a two-step derivatization of 2,3,4,5,6-pentafluorostyrene (FS). The first step was a nucleophilic substitution of the fluorine atom in para position by hydroxyl group followed by sulfopropylation. The monomer was po...

  15. A comment on water’s structure using monomer fraction data and theories

    DEFF Research Database (Denmark)

    Liang, Xiaodong; Maribo-Mogensen, Bjørn; Tsivintzelis, Ioannis;

    2016-01-01

    Monomer fraction data for water (and other compounds) can provide useful information about their structure and can be used in “advanced” equations of state, which account explicitly for association phenomena. Recent findings about the performance of association theories in representing the monome...

  16. Modulation of i-motif thermodynamic stability by the introduction of UNA (unlocked nucleic acid) monomers

    DEFF Research Database (Denmark)

    Pasternak, Anna; Wengel, Jesper

    2011-01-01

    The influence of acyclic RNA derivatives, UNA (unlocked nucleic acid) monomers, on i-DNA thermodynamic stability has been investigated. The 22 nt human telomeric fragment was chosen as the model sequence for stability studies. UNA monomers modulate i-motif stability in a position-depending manner...

  17. Use of laser induced photoacoustic spectroscopy (LIPAS) to determine equilibrium constants of cation-cation complexes

    International Nuclear Information System (INIS)

    Laser Induced PhotoAcoustic Spectroscopy (LIPAS) is a relatively new, photothermal technique to examine solutions. Studies in the past have shown it to be more sensitive than conventional absorption spectroscopy, while, yielding the same information thus allowing lower concentrations to be used. This study is using LIPAS to examine solutions to determine the equilibrium constants of cation-cation complexes. It has been found that actinyl(V) cations form cation-cation complexes with a variety of cations, including actinyl(VI) cations. The radioactive nature of the actinide elements requires special handling techniques and also require limits be placed on the amount of material that can be used. The sensitivity of some oxidation states of the actinides to oxygen also presents a problem. Preliminary results will be presented for actinyl(V)-actinyl(VI) cation-cation complexes that were studied using a remote LIPAS system incorporating fiber optics for transmission of laser signals

  18. The Free Tricoordinated Silyl Cation Problem

    Directory of Open Access Journals (Sweden)

    Čičak, H.

    2010-03-01

    Full Text Available As the importance and abundance of silicon in our environment is large, it has been thought that silicon might take the place of carbon in forming a host of similar compounds and silicon-based life. However, until today there is no experimental evidence for such a hypothesis and carbon is still unique among the elements in the vast number and variety of compounds it can form. Also, the corresponding derivatives of the two elements show considerable differences in their chemical properties.The essential debate concerning organosilicon chemistry relates to the existence of the free planar tricoordinated silyl cations in condensed phase (R3Si+, in analogy to carbocations (R3C+ which have been known and characterized as free species. Although silyl cations are thermodynamically more stable than their carbon analogs, they are very reactive due to their high inherent electrophilicity and the ability of hypervalent coordination. On the other hand, stabilization by inductive and hyperconjugative effects and larger steric effects of carbocations make them less sensitive to solvation or other environmental effects than silyl cations. Hence, observation of free silyl cations in the condensed phase proved extremely difficult and the actual problem is the question of the degree of the (remaining silyl cation character.The first free silyl cation, trimesitylsilyl cation, and in analogy with it tridurylsilyl cation, were synthesized by Lambert et al. Free silyl cations based on analogy to aromatic ions (homocyclopropenylium and tropylium have also been prepared. However, in these silyl cations the cationic character is reduced by internal π -conjugation. Čičak et al. prepared some silyl-cationic intermediates (Me3Si--CH≡CR+in solid state. With the help of quantum-mechanical calculations it was concluded that these adducts have much more silyl cation than carbocation character.

  19. A mean-field monomer-dimer model with attractive interaction: Exact solution and rigorous results

    Energy Technology Data Exchange (ETDEWEB)

    Alberici, D., E-mail: diego.alberici2@unibo.it; Contucci, P., E-mail: pierluigi.contucci@unibo.it; Mingione, E., E-mail: emanuele.mingione2@unibo.it [Department of Mathematics, University of Bologna, Piazza di Porta San Donato 5, Bologna 40126 (Italy)

    2014-06-15

    A mean-field monomer-dimer model which includes an attractive interaction among both monomers and dimers is introduced and its exact solution rigorously derived. The Heilmann-Lieb method for the pure hard-core interacting case is used to compute upper and lower bounds for the pressure. The bounds are shown to coincide in the thermodynamic limit for a suitable choice of the monomer density m. The computation of the monomer density is achieved by solving a consistency equation in the phase space (h, J), where h tunes the monomer potential and J the attractive potential. The critical point and exponents are computed and show that the model is in the mean-field ferromagnetic universality class.

  20. Impact of cationic surfactant on the self-assembly of sodium caseinate.

    Science.gov (United States)

    Vinceković, Marko; Curlin, Marija; Jurašin, Darija

    2014-08-27

    The impact of a cationic surfactant, dodecylammonium chloride (DDACl), on the self-assembly of sodium caseinate (SC) has been investigated by light scattering, zeta potential, and rheological measurements as well as by microscopy (transmission electron and confocal laser scanning microscopy). In SC dilute solutions concentration-dependent self-assembly proceeds through the formation of spherical associates and their aggregation into elongated structures composed of connected spheres. DDACl interacts with SC via its hydrophilic and hydrophobic groups, inducing changes in SC self-assembled structures. These changes strongly depend on the surfactant aggregation states (monomeric or micellar) as well as concentration ratio of both components, leading to the formation of soluble and insoluble complexes of nano- to microdimensions. DDACl monomers interact with SC self-assembled entities in a different way compared to their micelles. Surfactant monomers form soluble complexes (similar to surfactant mixed micelles) at lower SC concentration but insoluble gelatinous complexes at higher SC concentration. At surfactant micellar concentration soluble complexes with casein chains wrapped around surfactant micelles are formed. This study suggests that the use of proper cationic surfactant concentration will allow modification and control of structural changes of SC self-assembled entities.

  1. Effect of the intercalated cation-exchanged on the properties of nanocomposites prepared by 2-aminobenzene sulfonic acid with aniline and montmorillonite

    Energy Technology Data Exchange (ETDEWEB)

    Toumi, I. [Laboratoire de Chimie Organique, Macromoleculaire et des Materiaux, Universite de Mascara, Bp 763 Mascara 29000 (Algeria); Benyoucef, A., E-mail: ghani29000@yahoo.fr [Laboratoire de Chimie Organique, Macromoleculaire et des Materiaux, Universite de Mascara, Bp 763 Mascara 29000 (Algeria); Yahiaoui, A. [Laboratoire de Chimie Organique, Macromoleculaire et des Materiaux, Universite de Mascara, Bp 763 Mascara 29000 (Algeria); Quijada, C. [Departamento de Ingenieria Textil y Papelera, Universidad Politecnica de Valencia, Pza Ferrandiz i Carbonel, E-03801 Alcoy, Alicante (Spain); Morallon, E. [Departamento de Quimica Fisica e Instituto Universitario de Materiales, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)

    2013-02-25

    Polymer/montmorillonite nanocomposites were prepared. Intercalation of 2-aminobenzene sulfonic acid with aniline monomers into montmorillonite modified by cation was followed by subsequent oxidative polymerization of monomers in the interlayer spacing. The clay was prepared by cation exchange process between sodium cation in (M-Na) and copper cation (M-Cu). XRD analyses show the manifestation of a basal spacing (d-spacing) for M-Cu changes depending on the inorganic cation and the polymer intercalated in the M-Cu structure. TGA analyses reveal that polymer/M-Cu composites is less stable than M-Cu. The conductivity of the composites is found to be 10{sup 3} times higher than that for M-Cu. The microscopic examinations including TEM picture of the nanocomposite demonstrated an entirely different and more compatible morphology. Remarkable differences in the properties of the polymers have also been observed by UV-Vis and FTIR, suggesting that the polymer produced with presence of aniline has a higher degree of branching. The electrochemical behavior of the polymers extracted from the nanocomposites has been studied by cyclic voltammetry which indicates the electroactive effect of nanocomposite gradually increased with aniline in the polymer chain.

  2. Organic-Inorganic Thermoelectrics from Single Monomers to Polymer Devices

    Science.gov (United States)

    Chang, William Bee

    Waste heat recovery from the human body provides opportunities to power electronics with a source that is cheap and readily available. Thermoelectrics utilize the Seebeck effect to recover useable electrical energy from this waste heat, but are limited due to material parameters being inversely coupled in the bulk. We investigate the role of novel physics at interfaces in order to develop new fundamental understanding of thermoelectrics. The goal is to discover systems where the Seebeck coefficient and the electrical conductivity are not inversely correlated. We investigate thermoelectric transport in organic-organic systems such as scanning tunneling microscope molecular break junctions on the nanoscale, gold nanocrystal arrays on the mesoscale and polymeric ion and mixed conductors at the macroscale. The STM molecular junctions studied in this work can provide design rules to positively couple the Seebeck coefficient and the electrical conductance. Since STM molecular junctions are one-dimensional systems, by minimizing the gap between the molecular orbital energy level and the electrode Fermi energy, the power factor S2? can be optimized. I built a toolbox of chemical structures by first understanding the role of the interface coupling to alkylthiol binding groups of thiophene-based molecules. With this understanding, I designed small molecules based on the monomer unit of donor-acceptor polymers and other conductive polymers. Molecules with very high HOMO levels or low LUMO levels were studied, and the corresponding energy levels were examined using spectroscopic techniques. I then present our work on scaling these molecular junctions to the macroscale using ligand-exchanged gold nanocrystal arrays. Beginning with a model system of alkanethiols and alkanedithiols, I show that the electrical conductivity scales with ligand length exactly as observed in single molecule junctions, and the Seebeck coefficient follows a similar trend. By showing that gold

  3. Cation-inverting-injection: a novel method for synthesis of aqueous ZnSe quantum dots with bright excitionic emission and suppressed trap emission

    International Nuclear Information System (INIS)

    In the conventional synthesis of aqueous ZnSe quantum dots (QDs), highly reactive Se monomers are rapidly injected into a Zn-thiol complexes solution at room temperature, resulting in a poor excitionic luminescence and a serious trap emission of as-prepared ZnSe QDs. In this paper, we develop a novel cation-inverting-injection method to prepare aqueous ZnSe QDs with a bright excitionic luminescence. In this method, highly reactive Se monomers are first diluted in the reaction solution, followed by low-reaction Zn-thiol complexes slowly dropped at a high reaction temperature (90 °C). The inverting monomer injection order, the suppressed monomer reactivity and the high nucleation temperature in the cation-inverting-injection method can contribute to low-concentration but high-quality ZnSe nuclei, thereby promoting the formation of ZnSe QDs with large-sized particles, a high excitionic emission and a weak trap emission. As-prepared ZnSe QDs exhibit an intense deep-blue excitionic emission, which is the first reported case of a visible excitionic emission instead of a trap emission resulting from ZnSe QDs that are directly synthesized in an aqueous media. Using three types of dyes, via two measuring methods, the accurate photoluminescence quantum yield of the as-prepared ZnSe QDs is measured as 15%, which is a new record for mercaptocarboxylic acid stabilized ZnSe QDs synthesized in an aqueous media. (paper)

  4. Afrikaans Syllabification Patterns

    Directory of Open Access Journals (Sweden)

    Tilla Fick

    2010-01-01

    Full Text Available In contrast to English, automatic hyphenation by computer of Afrikaans words is a problem that still needs to be addressed, since errors are still often encountered in printed text. An initial step in this task is the ability to automatically syllabify words. Since new words are created continuously by joining words, it is necessary to develop an “intelligent” technique for syllabification. As a first phase of the research, we consider only the orthographic information of words, and disregard both syntactic and morphological information. This approach allows us to use machine-learning techniques such as artificial neural networks and decision trees that are known for their pattern recognition abilities. Both these techniques are trained with isolated patterns consisting of input patterns and corresponding outputs (or targets that indicate whether the input pattern should be split at a certain position, or not. In the process of compiling a list of syllabified words from which to generate training data for the  syllabification problem, irregular patterns were identified. The same letter patterns are split differently in different words and complete words that are spelled identically are split differently due to meaning. We also identified irregularities in and between  the different dictionaries that we used. We examined the influence range of letters that are involved in irregularities. For example, for their in agter-ente and vaste-rente we have to consider three letters to the left of r to be certain where the hyphen should be inserted. The influence range of the k in verstek-waarde and kleinste-kwadrate is four to the left and three to the right. In an analysis of letter patterns in Afrikaans words we found that the letter e has the highest frequency overall (16,2% of all letters in the word list. The frequency of words starting with s is the highest, while the frequency of words ending with e is the highest. It is important to

  5. Influence of Monomer Types on the Designability of a Protein-Model Chain

    Institute of Scientific and Technical Information of China (English)

    梁好均; 王元元

    2002-01-01

    In a three-dimensional off-lattice model, the method of Shakhnovich and Gutin for minimizing the Hamiltonian is applied to the design of a protein-model chain. The effect of the number of hydrophobic and hydrophilic monomer types on the designability ora protein-model chain is investigated. The simulation results reveal that the number of hydrophobic monomer types is a much more important factor than that of the polar monomer types in the design of a protein-model chain.

  6. Investigation of hydrogen atom addition to vinyl monomers by time resolved ESR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Beckert, D.; Mehler, K.

    1983-07-01

    By means of time resolved ESR spectroscopy in the microsecond time scale the H atom addition to different vinyl monomers was investigated. The H atoms produced by pulse radiolysis of aqueous solutions show a strong recombination CIDEP effect which also allows the recombination rate constant of H atoms to be determined. By analysis of ESR time profiles with the modified Bloch equations the relaxation times T/sub 1/, T/sub 2/, the polarization factors and the chemical rate constants with scavengers were obtained. Besides the H atom addition rate constants to different vinyl monomers the structure of the monomer radical was determined for acrylic acid.

  7. A review of adaptive mechanisms in cell responses towards oxidative stress caused by dental resin monomers.

    Science.gov (United States)

    Krifka, Stephanie; Spagnuolo, Gianrico; Schmalz, Gottfried; Schweikl, Helmut

    2013-06-01

    Dental composite resins are biomaterials commonly used to aesthetically restore the structure and function of teeth impaired by caries, erosion, or fracture. Residual monomers released from resin restorations as a result of incomplete polymerization processes interact with living oral tissues. Monomers like triethylene glycol dimethacrylate (TEGDMA) or 2-hydroxylethyl methacrylate (HEMA) are cytotoxic via apoptosis, induce genotoxic effects, and delay the cell cycle. Monomers also influence the response of cells of the innate immune system, inhibit specific odontoblast cell functions, or delay the odontogenic differentiation and mineralization processes in pulp-derived cells including stem cells. These observations indicate that resin monomers act as environmental stressors which inevitably disturb regulatory cellular networks through interference with signal transduction pathways. We hypothesize that an understanding of the cellular mechanisms underlying these phenomena will provide a better estimation of the consequences associated with dental therapy using composite materials, and lead to innovative therapeutic strategies and improved materials being used at tissue interfaces within the oral cavity. Current findings strongly suggest that monomers enhance the formation of reactive oxygen species (ROS), which is most likely the cause of biological reactions activated by dental composites and resin monomers. The aim of the present review manuscript is to discuss adaptive cell responses to oxidative stress caused by monomers. The particular significance of a tightly controlled network of non-enzymatic as well as enzymatic antioxidants for the regulation of cellular redox homeostasis and antioxidant defense in monomer-exposed cells will be addressed. The expression of ROS-metabolizing antioxidant enzymes like superoxide dismutase (SOD1), glutathione peroxidase (GPx1/2), and catalase in cells exposed to monomers will be discussed with particular emphasis on the role

  8. Dynamic conformations of nucleophosmin (NPM1 at a key monomer-monomer interface affect oligomer stability and interactions with granzyme B.

    Directory of Open Access Journals (Sweden)

    Wei D Duan-Porter

    Full Text Available Nucleophosmin (NPM1 is an abundant, nucleolar tumor antigen with important roles in cell proliferation and putative contributions to oncogenesis. Wild-type NPM1 forms pentameric oligomers through interactions at the amino-terminal core domain. A truncated form of NPM1 found in some hepatocellular carcinoma tissue formed an unusually stable oligomer and showed increased susceptibility to cleavage by granzyme B. Initiation of translation at the seventh methionine generated a protein (M7-NPM that shared all these properties. We used deuterium exchange mass spectrometry (DXMS to perform a detailed structural analysis of wild-type NPM1 and M7-NPM, and found dynamic conformational shifts or local "unfolding" at a specific monomer-monomer interface which included the β-hairpin "latch." We tested the importance of interactions at the β-hairpin "latch" by replacing a conserved tyrosine in the middle of the β-hairpin loop with glutamic acid, generating Y67E-NPM. Y67E-NPM did not form stable oligomers and further, prevented wild-type NPM1 oligomerization in a dominant-negative fashion, supporting the critical role of the β-hairpin "latch" in monomer-monomer interactions. Also, we show preferential cleavage by granzyme B at one of two available aspartates (either D161 or D122 in M7-NPM and Y67E-NPM, whereas wild-type NPM1 was cleaved at both sites. Thus, we observed a correlation between the propensity to form oligomers and granzyme B cleavage site selection in nucleophosmin proteins, suggesting that a small change at an important monomer-monomer interface can affect conformational shifts and impact protein-protein interactions.

  9. Localization versus delocalization in diamine radical cations

    DEFF Research Database (Denmark)

    Brouwer, A.M.; Wiering, P.G.; Zwier, J.M.;

    1997-01-01

    The optical absorption spectrum of the radical cation of 1,4-diphenylpiperazine 2a shows a strong transition in the near-IR, and only a weak band at 445 nm, in the region where aniline radical cations normally absorb strongly. This indicates that the charge and spin are delocalized over the two...

  10. Tripodal Receptors for Cation and Anion Sensors

    Directory of Open Access Journals (Sweden)

    David N. Reinhoudt

    2006-08-01

    Full Text Available This review discusses different types of artificial tripodal receptors for the selectiverecognition and sensing of cations and anions. Examples on the relationship between structure andselectivity towards cations and anions are described. Furthermore, their applications as potentiometricion sensing are emphasised, along with their potential applications in optical sensors or optodes.

  11. Radiation induced redox reactions and fragmentation of constituent ions in ionic liquids. 2. Imidazolium cations.

    Science.gov (United States)

    Shkrob, Ilya A; Marin, Timothy W; Chemerisov, Sergey D; Hatcher, Jasmine L; Wishart, James F

    2011-04-14

    In part 1 of this study, radiolytic degradation of constituent anions in ionic liquids (ILs) was examined. The present study continues the themes addressed in part 1 and examines the radiation chemistry of 1,3-dialkyl substituted imidazolium cations, which currently comprise the most practically important and versatile class of ionic liquid cations. For comparison, we also examined 1,3-dimethoxy- and 2-methyl-substituted imidazolium and 1-butyl-4-methylpyridinium cations. In addition to identification of radicals using electron paramagnetic resonance spectroscopy (EPR) and selective deuterium substitution, we analyzed stable radiolytic products using (1)H and (13)C nuclear magnetic resonance (NMR) and tandem electrospray ionization mass spectrometry (ESMS). Our EPR studies reveal rich chemistry initiated through "ionization of the ions": oxidation and the formation of radical dications in the aliphatic arms of the parent cations (leading to deprotonation and the formation of alkyl radicals in these arms) and reduction of the parent cation, yielding 2-imidazolyl radicals. The subsequent reactions of these radicals depend on the nature of the IL. If the cation is 2-substituted, the resulting 2-imidazolyl radical is relatively stable. If there is no substitution at C(2), the radical then either is protonated or reacts with the parent cation forming a C(2)-C(2) σσ*-bound dimer radical cation. In addition to these reactions, when methoxy or C(α)-substituted alkyl groups occupy the N(1,3) positions, their elimination is observed. The elimination of methyl groups from N(1,3) was not observed. Product analyses of imidazolium liquids irradiated in the very-high-dose regime (6.7 MGy) reveal several detrimental processes, including volatilization, acidification, and oligomerization. The latter yields a polymer with m/z of 650 ± 300 whose radiolytic yield increases with dose (~0.23 monomer units per 100 eV for 1-methyl-3-butylimidazolium trifluorosulfonate). Gradual

  12. A novel quinoxaline bearing electroactive monomer: Pyrrole as the donor moiety

    Energy Technology Data Exchange (ETDEWEB)

    Taskin, Asli Tuba; Balan, Abidin; Epik, Bugra; Yildiz, Ersin [Middle East Technical University, Department of Chemistry, 06531, Ankara (Turkey); Udum, Yasemin Arslan [Gazi University, Institute of Science and Technology, Department of Advanced Technologies, 06570, Ankara (Turkey); Toppare, Levent [Middle East Technical University, Department of Chemistry, 06531, Ankara (Turkey)], E-mail: toppare@metu.edu.tr

    2009-09-30

    A novel electroactive monomer 5,8-di(1H-pyrrol-2-yl)-2,3-di(thiophen-2-yl)quinoxaline (PTQ) was successfully synthesized and its electrochromic properties were reported. Nuclear magnetic resonance ({sup 1}H NMR-{sup 13}C NMR) and mass spectroscopy were used to characterize the monomer. The monomer was electrochemically polymerized in the presence of tetrabutylammonium perchlorate (TBAP) as supporting electrolyte in dichloromethane. Monomer reveals relatively low oxidation potential at +0.70 V. Spectroelectrochemical behaviors and switching ability of homopolymer were investigated by UV-vis spectroscopy and cyclic voltammetry. Two {pi}-{pi}* transitions were observed at 400 and 815 nm with a low band gap, 1.0 eV. Polymer possesses 66% optical contrast in the Near IR region, which may be promising in NIR electrochromic device applications.

  13. Facile synthesis of allyl resinate monomer in an aqueous solution under microwave irradiation

    Indian Academy of Sciences (India)

    Yanju Lu; Mixia Wang; Zhendong Zhao; Yuxiang Chen; Shichao Xu; Jing Wang; Liangwu Bi

    2015-07-01

    We have developed a facile method for production of allyl resinate monomer (allyl rosin ester) via a phase transfer reaction under microwave irradiation. The synthesis of allyl resinate was conducted using allyl chloride and sodium resinate as starting materials in aqueous solution at 50°C for 30 min with a yield of 94.7%, which is 20% higher than conventional heating method. The products precipitated spontaneously from the aqueous phase after reaction, which significantly facilitated the subsequent separation of monomer products. The synthesized monomer product appeared as a viscous liquid, with a viscosity of 460 mPa·s at 25°C and a density of 1.0469 g/cm3. The physical and chemical properties suggested that the synthesized monomer has great potential for free radical polymerization.

  14. A novel quinoxaline bearing electroactive monomer: Pyrrole as the donor moiety

    International Nuclear Information System (INIS)

    A novel electroactive monomer 5,8-di(1H-pyrrol-2-yl)-2,3-di(thiophen-2-yl)quinoxaline (PTQ) was successfully synthesized and its electrochromic properties were reported. Nuclear magnetic resonance (1H NMR-13C NMR) and mass spectroscopy were used to characterize the monomer. The monomer was electrochemically polymerized in the presence of tetrabutylammonium perchlorate (TBAP) as supporting electrolyte in dichloromethane. Monomer reveals relatively low oxidation potential at +0.70 V. Spectroelectrochemical behaviors and switching ability of homopolymer were investigated by UV-vis spectroscopy and cyclic voltammetry. Two π-π* transitions were observed at 400 and 815 nm with a low band gap, 1.0 eV. Polymer possesses 66% optical contrast in the Near IR region, which may be promising in NIR electrochromic device applications.

  15. [MORPHOLOGICAL FEATURES OF RAT MUCOUS MEMBRANE OF THE TONGUE EARLY AFFECTED BY ACRYLIC RESIN MONOMER].

    Science.gov (United States)

    Davydenko, V; Nidzelskiy, M; Starchenko, I; Davydenko, A; Kuznetsov, V

    2016-03-01

    Base materials, made on the basis of various derivatives of acrylic and methacrylic acids, have been widely used in prosthetic dentistry. Free monomer, affecting the tissues of prosthetic bed and the whole body, is always found in dentures. Therefore, study of the effect of acrylic resins' monomer on mucous membrane of the tongue is crucial. Rat tongue is very similar to human tongue, and this fact has become the basis for selecting these animals to be involved into the experiment. The paper presents the findings related to the effect of "Ftoraks" base acrylic resin monomer on the state of rat mucous membrane of the tongue and its regeneration. The microscopy has found that the greatest changes in the mucous membrane of the tongue occur on day 3 and 7 day after applying the monomer and are of erosive and inflammatory nature. Regeneration of tongue epithelium slows down. PMID:27119844

  16. A novel antibacterial orthodontic cement containing a quaternary ammonium monomer dimethylaminododecyl methacrylate

    OpenAIRE

    Melo, Mary A. S.; Wu, Junling; Weir, Michael D; Xu, Hockin H. K.

    2014-01-01

    Demineralized lesions in tooth enamel around orthodontic brackets are caused by acids from cariogenic biofilm. This study aimed to develop a novel antibacterial orthodontic cement by incorporating a quaternary ammonium monomer dimethylaminododecyl methacrylate (DMADDM) into a commercial orthodontic cement, and to investigate the effects on microcosm biofilm response and enamel bond strength. DMADDM, a recently-synthetized antibacterial monomer, was incorporated into orthodontic cement at 0%, ...

  17. Triptycene-based ladder monomers and polymers, methods of making each, and methods of use

    KAUST Repository

    Pinnau, Ingo

    2015-02-05

    Embodiments of the present disclosure provide for a triptycene-based A-B monomer, a method of making a triptycene-based A-B monomer, a triptycene-based ladder polymer, a method of making a triptycene-based ladder polymers, a method of using triptycene-based ladder polymers, a structure incorporating triptycene-based ladder polymers, a method of gas separation, and the like.

  18. Bacterial decomposition of synthetic 14C-labeled lignin and lignin monomer derivatives

    International Nuclear Information System (INIS)

    Nocardia sp. which was isolated from soil is capable of degrading synthetic lignin and utilizing its monomer derivatives. Decomposition was monitored by measuring the 14CO2 evolved and O2 consumed, when the bacterium was grown on a medium containing specifically 14C-labeled lignins or monomer phenolic compounds as major carbon source. The time course of the 14CO2 release and O2 uptake indicates a significant depolymerization and utilization of lignin by the Nocardia sp. (author)

  19. Syringyl Methacrylate, a Hardwood Lignin-Based Monomer for High-T g Polymeric Materials

    OpenAIRE

    Holmberg, Angela L.; Reno, Kaleigh H.; Nguyen, Ngoc A.; Wool, Richard P.; Epps, Thomas H.

    2016-01-01

    As viable precursors to a diverse array of macromolecules, biomass-derived compounds must impart wide-ranging and precisely controllable properties to polymers. Herein, we report the synthesis and subsequent reversible addition–fragmentation chain-transfer polymerization of a new monomer, syringyl methacrylate (SM, 2,6-dimethoxyphenyl methacrylate), that can facilitate widespread property manipulations in macromolecules. Homopolymers and heteropolymers synthesized from SM and related monomers...

  20. Effect of food simulating liquids on release of monomers from two dental resin composites

    Directory of Open Access Journals (Sweden)

    Ghavam M

    2010-06-01

    Full Text Available "nBackground and Aims: The elution of residual monomers from cured dental composites to oral cavity has a harmful effect on human health and can affect their clinical durability. The purpose of this study was to evaluate the amount of eluted monomers (Bis-GMA, TEGDMA, UDMA from two types of composites (Gradia and P60 after exposure to food simulating liquids such as ethanol (25, 50, 75 % and heptane 50 % for 24 hours and 7 days. "nMaterials and Methods: Forty specimens of each composite were prepared. Equal numbers of each composite were immersed in tubes containing 2cc volumes of 25, 50, 75 % ethanole and 50 % heptane. The amount of eluted monomers in standard condition such as Bis-GMA, TEGDMA and UDMA was measured by GC/MS (Gas Chromatography/Mass Spectroscopy and results were statistically analysed by three way and one way ANOVA. P<0.05 was considered as the level of significancy. "nResults: The results showed that Gradia released more TEGDMA than P60. In assessing the effect of environment, the result showed that ethanol caused releasing monomers more than heptane and the concentration rate of 75 % ethanole resulted in most releasing of monomers. In assessing the effect of time, the observation showed that more monomers were released 7 days compared to 24 hours. Bis-GMA and UDMA were not detected in any solutions in these conditions. "nConclusion: Ethanole caused more release of monomers than heptane and 75 % ethanole released the most amount of monomers. Gradia released more amount of TEGDMA than P60.

  1. Cationic Bolaamphiphiles for Gene Delivery

    Science.gov (United States)

    Tan, Amelia Li Min; Lim, Alisa Xue Ling; Zhu, Yiting; Yang, Yi Yan; Khan, Majad

    2014-05-01

    Advances in medical research have shed light on the genetic cause of many human diseases. Gene therapy is a promising approach which can be used to deliver therapeutic genes to treat genetic diseases at its most fundamental level. In general, nonviral vectors are preferred due to reduced risk of immune response, but they are also commonly associated with low transfection efficiency and high cytotoxicity. In contrast to viral vectors, nonviral vectors do not have a natural mechanism to overcome extra- and intracellular barriers when delivering the therapeutic gene into cell. Hence, its design has been increasingly complex to meet challenges faced in targeting of, penetration of and expression in a specific host cell in achieving more satisfactory transfection efficiency. Flexibility in design of the vector is desirable, to enable a careful and controlled manipulation of its properties and functions. This can be met by the use of bolaamphiphile, a special class of lipid. Unlike conventional lipids, bolaamphiphiles can form asymmetric complexes with the therapeutic gene. The advantage of having an asymmetric complex lies in the different purposes served by the interior and exterior of the complex. More effective gene encapsulation within the interior of the complex can be achieved without triggering greater aggregation of serum proteins with the exterior, potentially overcoming one of the great hurdles faced by conventional single-head cationic lipids. In this review, we will look into the physiochemical considerations as well as the biological aspects of a bolaamphiphile-based gene delivery system.

  2. Tandem ring-opening/ring-closing metathesis polymerization: relationship between monomer structure and reactivity.

    Science.gov (United States)

    Park, Hyeon; Lee, Ho-Keun; Choi, Tae-Lim

    2013-07-24

    Monomers containing either cycloalkenes with low ring strain or 1-alkynes are poor monomers for olefin metathesis polymerization. Ironically, keeping two inactive functional groups in proximity within one molecule can make it an excellent monomer for metathesis polymerization. Recently, we demonstrated that monomer 1 having cyclohexene and propargyl moieties underwent rapid tandem ring-opening/ring-closing metathesis (RO/RCM) polymerization via relay-type mechanism. Furthermore, living polymerization was achieved when a third-generation Grubbs catalyst was used. Here, we present a full account on this tandem polymerization by investigating how various structural modifications of the monomers affected the reactivity of the tandem polymerization. We observed that changing the ring size of the cycloalkene moieties, the length of the alkynes, and linker units influenced not only the polymerization rates but also the reactivities of Diels-Alder reaction, which is a post-modification reaction of the resulting polymers. Also, the mechanism of tandem polymerization was studied by conducting end-group analysis using (1)H NMR analysis, thereby concluding that the polymerization occurred by the alkyne-first pathway. With this mechanistic conclusion, factors responsible for the dramatic structure-reactivity relationship were proposed. Lastly, tandem RO/RCM polymerization of monomers containing sterically challenging trisubstituted cycloalkenes was successfully carried out to give polymer repeat units having tetrasubstituted cycloalkenes.

  3. Occupational asthma caused by a prepolymer but not the monomer of toluene diisocyanate (TDI).

    Science.gov (United States)

    Vandenplas, O; Cartier, A; Lesage, J; Perrault, G; Grammer, L C; Malo, J L

    1992-06-01

    Isocyanates are the most common cause of occupational asthma. Isocyanate monomers and prepolymers are widely used in the manufacture of polyurethane compounds. However, prepolymers are generating increasing interest because of their lower volatility. No distinction has yet been made between asthmatic reactions caused by the monomers and the prepolymers of isocyanates, and asthmatic reactions caused by one type of isocyanate but not the other type have not been reported. We describe two wood-roof maintenance workers who developed asthma after being exposed to a varnish containing a prepolymer of toluene diisocyanate (TDI) with only small amounts of the monomer. Specific inhalation-challenge tests with the TDI monomer did not elicit significant airway obstruction, whereas exposure to the varnish and to the purified TDI prepolymer induced late asthmatic reactions. Specific antibodies against TDI monomer human serum albumin and TDI prepolymer human serum albumin conjugates could not be demonstrated. These observations demonstrate that isocyanate prepolymers can cause occupational asthma and that asthmatic reactions caused by isocyanate prepolymers, but not to the corresponding monomer, can occur in some exposed workers. PMID:1318888

  4. Residual monomer content determination in some acrylic denture base materials and possibilities of its reduction

    Directory of Open Access Journals (Sweden)

    Kostić Milena

    2009-01-01

    Full Text Available Background/Aim. Polymethyl methacrylate is used for producing a denture basis. It is a material made by the polymerization process of methyl methacrylate. Despite of the polymerization type, there is a certain amount of free methyl methacrylate (residual monomer incorporated in the denture, which can cause irritation of the oral mucosa. The aim of this study was to determine the amount of residual monomer in four different denture base acrylic resins by liquid chromatography and the possibility of its reduction. Methods. After the polymerization, a postpolymerization treatment was performed in three different ways: in boiling water for thirty minutes, with 500 W microwaves for three minutes and in steam bath at 22º C for one to thirty days. Results. The obtained results showed that the amount of residual monomer is significantly higher in cold polymerizing acrylates (9.1-11%. The amount of residual monomer after hot polymerization was in the tolerance range (0.59- 0.86%. Conclusion. The obtained results denote a low content of residual monomer in the samples which have undergone postpolymerization treatment. A lower percent of residual monomer is established in samples undergone a hot polymerization.

  5. Cationic ruthenium alkylidene catalysts bearing phosphine ligands

    OpenAIRE

    Endo, Koji; Grubbs, Robert H.

    2016-01-01

    The discovery of highly active catalysts and the success of ionic liquid immobilized systems have accelerated attention to a new class of cationic metathesis catalysts. We herein report the facile syntheses of cationic ruthenium catalysts bear-ing bulky phosphine ligands. Simple ligand exchange using silver(I) salts of non-coordinating or weakly coordinating anions pro-vided either PPh3 or chelating Ph2P(CH2)nPPh2 (n = 2 or 3) ligated cationic catalysts. The structures of these newly reported...

  6. Thermodynamically stable amyloid-β monomers have much lower membrane affinity than the small oligomers

    Directory of Open Access Journals (Sweden)

    Bidyut eSarkar

    2013-04-01

    Full Text Available Amyloid beta (Aβ is an extracellular 39-43 residue long peptide present in the mammalian cerebrospinal fluid, whose aggregation is associated with Alzheimer’s disease. Small oligomers of Aβ are currently thought to be the key to toxicity. However, it is not clear why the monomers of Aβ are non-toxic, and at what stage of aggregation toxicity emerges. Interactions of Aβ with cell membranes is thought to be the initiator of toxicity, but membrane-binding studies with different preparations of monomers and oligomers have not settled this issue. We have earlier found that thermodynamically stable Aβ monomers emerge spontaneously from oligomeric mixtures upon long term incubation in physiological solutions (Nag et al, JBC, 2011. Here we show that the membrane-affinity of these stable Aβ monomers is much lower than that of a mixture of small oligomers (containing dimers to decamers, providing a clue to the emergence of toxicity. Fluorescently labeled Aβ40 monomers show negligible binding to cell membranes of a neuronal cell line (RN46A at physiological concentrations (250 nM, while oligomers at the same concentrations show strong binding within 30 minutes of incubation. The increased affinity most likely does not require any specific neuronal receptor, since this difference in membrane-affinity was also observed in a somatic cell-line (HEK 293T. Similar results are also obtained for Aβ42 monomers and oligomers. Minimal amount of cell death is observed at these concentrations even after 36 hours of incubation. It is likely that membrane binding precedes subsequent slower toxic events induced by Aβ. Our results a provide an explanation for the non-toxic nature of Aβ monomers, b suggest that Aβ toxicity emerges at the initial oligomeric phase, and c provide a quick assay for monitoring the benign-to-toxic transformation of Aβ.

  7. Beyond interfacial anion/cation pairing: The role of Cu(I) coordination chemistry in additive-controlled copper plating

    International Nuclear Information System (INIS)

    Highlights: ► We study synergistic and antagonistic ensemble effects of various polymeric suppressor additives and MPS relevant for copper electroplating. ► Type-I suppressors (e.g. PEGs) show a purely antagonistic interaction with MPS. ► Type-II suppressors (e.g. PEIs) show a purely synergistic interaction with MPS. ► Hybrid suppressors (e.g. Imep) reveal both synergistic and antagonistic effects depending on the MPS concentration. ► We identify a combination of Cu(I) coordination chemistry and an inner salt formation as key to the understanding of the suppressing mode of polymeric leveler additives. - Abstract: This study reinvestigates the electrochemical characteristics of three different suppressor additives that are used in context of industrial copper plating (Damascene, Through-Silicon-Via). It is the particular aim of this contribution to further substantiate our recently introduced classification scheme of suppressor chemistries that relies on their antagonistic and synergistic interplay with MPS (mercaptopropane sulfonic acid/sulfonate). The latter appears as intermediate species in the course of copper electrodeposition in the presence of SPS (bis-(sodium-sulfopropyl)-disulfide). Both the linear sweep voltammetry and potential transient experiments reveal a purely antagonistic interaction between PAG (polyalkylene glycol) based suppressor ensembles and the SPS (MPS precursor) which is rationalized in terms of the coordinative dissolution of a hyper-branched PAG-Cu(I)-Cl coordination network by the MPS. Such purely antagonistic suppressor/MPS interplay is our criterion for a so-called type-I suppressor. A purely synergistic suppressor/MPS interaction is observed for the PEI (polyethylene-imine) which can be considered as a prototypical type-II suppressor. Beyond classical interfacial anion/cation pairing the partly protonated, poly-cationic PEI is capable to form MPS-stabilized Cu(I) adducts. Their suppressing effect relies on an in situ hyper

  8. Cation locations and dislocations in zeolites

    Science.gov (United States)

    Smith, Luis James

    The focus of this dissertation is the extra-framework cation sites in a particular structural family of zeolites, chabazite. Cation sites play a particularly important role in the application of these sieves for ion exchange, gas separation, catalysis, and, when the cation is a proton, acid catalysis. Structural characterization is commonly performed through the use of powder diffraction and Rietveld analysis of powder diffraction data. Use of high-resolution nuclear magnetic resonance, in the study of the local order of the various constituent nuclei of zeolites, complements well the long-range order information produced by diffraction. Recent developments in solid state NMR techniques allow for increased study of disorder in zeolites particularly when such phenomena test the detection limits of diffraction. These two powerful characterization techniques, powder diffraction and NMR, offer many insights into the complex interaction of cations with the zeolite framework. The acids site locations in SSZ-13, a high silica chabazite, and SAPO-34, a silicoaluminophosphate with the chabazite structure, were determined. The structure of SAPO-34 upon selective hydration was also determined. The insensitivity of X-rays to hydrogen was avoided through deuteration of the acid zeolites and neutron powder diffraction methods. Protons at inequivalent positions were found to have different acid strengths in both SSZ-13 and SAPO-34. Other light elements are incorporated into zeolites in the form of extra-framework cations, among these are lithium, sodium, and calcium. Not amenable by X-ray powder diffraction methods, the positions of such light cations in fully ion-exchanged versions of synthetic chabazite were determined through neutron powder diffraction methods. The study of more complex binary cation systems were conducted. Powder diffraction and solid state NMR methods (MAS, MQMAS) were used to examine cation site preferences and dislocations in these mixed-akali chabazites

  9. Cycloaliphatic epoxide resins for cationic UV - cure

    International Nuclear Information System (INIS)

    This paper introduces the cyclo - aliphatic epoxide resins used for the various applications of radiation curing and their comparison with acrylate chemistry. Radiation curable coatings and inks are pre - dominantly based on acrylate chemistry but over the last few years, cationic chemistry has emerged successfully with the unique properties inherent with cyclo - aliphatic epoxide ring structures. Wide variety of cationic resins and diluents, the formulation techniques to achieve the desired properties greatly contributes to the advancement of UV - curing technology

  10. Cations and activated sludge floc structure

    OpenAIRE

    Park, Chul

    2002-01-01

    This research was designed to investigate the effect of cations on activated sludge characteristics and also to determine their influence on digestion performance. For this purpose, cations in solution and in floc were evaluated along with various activated sludge characteristics and the collected waste activated sludge underwent both anaerobic and aerobic digestion. It was found that large amounts of biopolymer (protein + polysaccharide) remained in the effluent of WWTP that received high in...

  11. Test procedure for cation exchange chromatography

    International Nuclear Information System (INIS)

    The purpose of this test plan is to demonstrate the synthesis of inorganic antimonate ion exchangers and compare their performance against the standard organic cation exchangers. Of particular interest is the degradation rate of both inorganic and organic cation exchangers. This degradation rate will be tracked by determining the ion exchange capacity and thermal stability as a function of time, radiation dose, and chemical reaction

  12. Silica-based cationic bilayers as immunoadjuvants

    OpenAIRE

    Carmona-Ribeiro Ana M; da Costa Maria; Faquim-Mauro Eliana; Santana Mariana RA; Lincopan Nilton

    2009-01-01

    Abstract Background Silica particles cationized by dioctadecyldimethylammonium bromide (DODAB) bilayer were previously described. This work shows the efficiency of these particulates for antigen adsorption and presentation to the immune system and proves the concept that silica-based cationic bilayers exhibit better performance than alum regarding colloid stability and cellular immune responses for vaccine design. Results Firstly, the silica/DODAB assembly was characterized at 1 mM NaCl, pH 6...

  13. Photopolymerizable phosphate acrylates as comonomers in dental adhesives with or without triclosan monomer units

    Energy Technology Data Exchange (ETDEWEB)

    Melinte, Violeta [Petru Poni Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487 Iasi (Romania); Buruiana, Tinca, E-mail: tbur@icmpp.ro [Petru Poni Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487 Iasi (Romania); Aldea, Horia [Gr. T. Popa University of Medicine and Pharmacy, Faculty of Dentistry, Iasi (Romania); Matiut, Simona [Praxis Medical Investigations, 33 Independence, 700102 Iasi (Romania); Silion, Mihaela; Buruiana, Emil C. [Petru Poni Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487 Iasi (Romania)

    2014-01-01

    Phosphate diacrylates (CO-DAP, TMP-DAP) based on castor oil or trimethylolpropane were synthesized and evaluated in dental adhesive formulations in comparison with 3-acryloyloxy-2-hydroxypropyl methacrylate phosphate (AMP-P). In an attempt to promote antibacterial activity, another photopolymerizable monomer (TCS-UMA) containing 5-chloro-2-(2,4-dichlorophenoxy)phenol moiety (triclosan) was prepared and incorporated in adhesive resins. Each of these monomers had a molecular structure confirmed by spectral methods. The photopolymerization rates for monomers (0.063–0.088 s{sup −1}) were lower than those determined in the monomer combinations (0.116–0.158 s{sup −1}) incorporating phosphate diacrylate (11 wt.%), BisGMA (33 wt.%), TEGDMA (10 wt.%), UDMA (10 wt.%) and HEMA (15 wt.%), the degree of conversion varying between 63.4 and 74.5%. The formed copolymers showed high values for water sorption (18.65–57.02 μg/mm{sup 3}) and water solubility (3.51–13.38 μg/mm{sup 3}), and the contact angle was dependent on the presence of CO-DAP (θ{sub F1}: 66.67°), TMP-DAP (θ{sub F2}: 55.05°) or AMP-P (θ{sub F3}: 52.90°) in the photocrosslinked specimens compared to the sample without phosphate monomer (θ{sub F4}: 82.14°). The scanning electron microscopy image of the dentin–resin composite interface after applying our F1 formulation (pH: 4.1) and its light-curing for 20 s supports the evidence of the formation of the hybrid layer with the tooth structure created by self-etching approach, with no gaps or cracks in the adhesive. A comparative analysis of the adhesion achieved with commercial adhesive systems (Single Bond Universal, C-Bond) rather indicates similarities than differences between them. The addition of triclosan methacrylate (1 wt.%) into the formulation inhibited the bacterial growth of the Streptococcus mutans and Escherichia coli in the direct contact area due to the covalently linked antibacterial monomer. - Highlights: • Synthesis of

  14. Design and Applications of Biodegradable Polyester Tissue Scaffolds Based on Endogenous Monomers Found in Human Metabolism

    Directory of Open Access Journals (Sweden)

    Devin G. Barrett

    2009-10-01

    Full Text Available Synthetic polyesters have deeply impacted various biomedical and engineering fields, such as tissue scaffolding and therapeutic delivery. Currently, many applications involving polyesters are being explored with polymers derived from monomers that are endogenous to the human metabolism. Examples of these monomers include glycerol, xylitol, sorbitol, and lactic, sebacic, citric, succinic, α-ketoglutaric, and fumaric acids. In terms of mechanical versatility, crystallinity, hydrophobicity, and biocompatibility, polyesters synthesized partially or completely from these monomers can display a wide range of properties. The flexibility in these macromolecular properties allows for materials to be tailored according to the needs of a particular application. Along with the presence of natural monomers that allows for a high probability of biocompatibility, there is also an added benefit that this class of polyesters is more environmentally friendly than many other materials used in biomedical engineering. While the selection of monomers may be limited by nature, these polymers have produced or have the potential to produce an enormous number of successes in vitro and in vivo.

  15. Determination of residual monomers resulting from the chemical polymerization process of dental materials

    Energy Technology Data Exchange (ETDEWEB)

    Boboia, S. [Babes Bolyai University, Raluca Ripan Chemistry Research Institute, Department of Polymer Composites, 400294 Cluj-Napoca, Romania and Technical University of Cluj-Napoca, Physics and Chemistry Department, 400114 Cluj-Napoca (Romania); Moldovan, M. [Babes Bolyai University, Raluca Ripan Chemistry Research Institute, Department of Polymer Composites, 400294 Cluj-Napoca (Romania); Ardelean, I. [Technical University of Cluj-Napoca, Physics and Chemistry Department, 400114 Cluj-Napoca (Romania)

    2013-11-13

    The residual monomer present in post-polymerized dental materials encourages premature degradation of the reconstructed tooth. That is why the residual monomer should be quantified in a simple, fast, accurate and reproducible manner. In our work we propose such an approach for accurate determination of the residual monomer in dental materials which is based on low-field nuclear magnetic resonance (NMR) relaxometry. The results of the NMR approach are compared with those of the high performance liquid chromatography (HPLC) technique. The samples under study contain the main monomers (2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane and triethylene glycol dimethacrylate) constituting the liquid phase of most dental materials and an initiator. Two samples were analyzed with different ratios of chemical initiation systems: N,N-dimethyl-p-toluide: benzoyl peroxide (1:2 and 0.7:1.2). The results obtained by both techniques highlight that by reducing the initiator the polymerization process slows down and the amount of residual monomer reduces. This prevents the premature degradation of the dental fillings and consequently the reduction of the biomaterial resistance.

  16. Limit theorems in the imitative monomer-dimer mean-field model via Stein's method

    Science.gov (United States)

    Chen, Wei-Kuo

    2016-08-01

    We consider the imitative monomer-dimer model on the complete graph introduced in the work of Alberici et al. [J. Math. Phys. 55, 063301-1-063301-27 (2014)]. It was shown that this model is described by the monomer density and has a phase transition along certain coexistence curve, where the monomer and dimer phases coexist. More recently, it was understood [D. Alberici et al., Commun. Math. Phys. (published online, 2016)] that the monomer density exhibits the central limit theorem away from the coexistence curve and enjoys a non-normal limit theorem at criticality with normalized exponent 3/4. By reverting the model to a weighted Curie-Weiss model with hard core interaction, we establish the complete description of the fluctuation properties of the monomer density on the full parameter space via Stein's method of exchangeable pairs. Our approach recovers what were established in the work of Alberici et al. [Commun. Math. Phys. (published online, 2016)] and furthermore allows to obtain the conditional central limit theorems along the coexistence curve. In all these results, the Berry-Esseen inequalities for the Kolmogorov-Smirnov distance are given.

  17. Radiation-induced graft polymerization of amphiphilic monomers with different polymerization characteristics onto hydrophobic polysilane

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Hidenori; Iwasaki, Isao; Kunai, Yuichiro [Research Reactor Institute, Kyoto University, Asashironishi 2-1010, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan); Sato, Nobuhiro, E-mail: sato-n@rri.kyoto-u.ac.j [Research Reactor Institute, Kyoto University, Asashironishi 2-1010, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan); Matsuyama, Tomochika [Research Reactor Institute, Kyoto University, Asashironishi 2-1010, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan)

    2011-08-15

    The structures of poly(methyl-n-propylsilane) (PMPrS) amphiphilically modified through {gamma}-ray-induced graft polymerization were investigated with {sup 1}H NMR measurement. By the use of methyl methacrylate (MMA) or diethyl fumarate (DEF) as monomers for the graft polymerization, grafting yield rose with increasing total absorption dose and monomer concentrations, but decreased with increasing dose rate. This result means that grafting yield of modified PMPrS can be controlled by changing irradiation conditions. However, the number of PMMA or PDEF graft chains per PMPrS chain was estimated to be less than 1.0 by analysis of {sup 1}H NMR spectra, and this value was lower than that we had expected. To improve graft density, maleic anhydride (MAH), which is known as a non-homopolymerizable monomer in radical polymerization, was used as a monomer for grafting. As a result, high density grafting (one MAH unit for 4.2 silicon atoms) was attained. It demonstrates that the structure of {gamma}-ray-modified polysilane strongly depends on the polymerization characteristics of grafted monomers.

  18. Aβ1-42 monomers or oligomers have different effects on autophagy and apoptosis.

    Science.gov (United States)

    Guglielmotto, Michela; Monteleone, Debora; Piras, Antonio; Valsecchi, Valeria; Tropiano, Marta; Ariano, Stefania; Fornaro, Michele; Vercelli, Alessandro; Puyal, Julien; Arancio, Ottavio; Tabaton, Massimo; Tamagno, Elena

    2014-10-01

    The role of autophagy and its relationship with apoptosis in Alzheimer disease (AD) pathogenesis is poorly understood. Disruption of autophagy leads to buildup of incompletely digested substrates, amyloid-β (Aβ) peptide accumulation in vacuoles and cell death. Aβ, in turn, has been found to affect autophagy. Thus, Aβ might be part of a loop in which it is both the substrate of altered autophagy and its cause. Given the relevance of different soluble forms of Aβ1-42 in AD, we have investigated whether monomers and oligomers of the peptide have a differential role in causing altered autophagy and cell death. Using differentiated SK-N-BE neuroblastoma cells, we found that monomers hamper the formation of the autophagic BCL2-BECN1/Beclin 1 complex and activate the MAPK8/JNK1-MAPK9/JNK2 pathway phosphorylating BCL2. Monomers also inhibit apoptosis and allow autophagy with intracellular accumulation of autophagosomes and elevation of levels of BECN1 and LC3-II, resulting in an inhibition of substrate degradation due to an inhibitory action on lysosomal activity. Oligomers, in turn, favor the formation of the BCL2-BECN1 complex favoring apoptosis. In addition, they cause a less profound increase in BECN1 and LC3-II levels than monomers without affecting the autophagic flux. Thus, data presented in this work show a link for autophagy and apoptosis with monomers and oligomers, respectively. These studies are likely to help the design of novel disease modifying therapies.

  19. The binding of glucose to yeast hexokinase monomers is independent of ionic strength.

    Science.gov (United States)

    Mayes, E L; Hoggett, J G; Kellett, G L

    1982-05-01

    Hoggett & Kellett [Eur. J. Biochem. 66, 65-77 (1976)] have reported that the binding of glucose to the monomer of hexokinase PII isoenzyme is independent of ionic strength, in contrast to the subsequent claim of Feldman & Kramp [Biochemistry 17, 1541-1547 (1978)] that the binding is strongly dependent on ionic strength. Since measurements with native hexokinase P forms are complicated by the fact that the enzyme exists in a monomer-dimer association-dissociation equilibrium, we have now studied the binding of glucose to the proteolytically-modified S forms which are monomeric. At pH 8.5, the affinity of glucose for both SI and SII monomers is independent of salt concentration over the range of KCl concentrations 0-1.0 mol . dm-3 and is in good agreement with that of the corresponding P forms in both low and high salt. These observations confirm that the binding of glucose to hexokinase P monomers is independent of ionic strength and that the affinity of glucose for the hexokinase PII monomer is about an order of magnitude greater than that for the dimer. PMID:7052060

  20. Water sorption and solubility of dental composites and identification of monomers released in an aqueous environment.

    Science.gov (United States)

    Ortengren, U; Wellendorf, H; Karlsson, S; Ruyter, I E

    2001-12-01

    Water sorption and solubility of six proprietary composite resin materials were assessed, and monomers eluted from the organic matrix during water storage identified. Water sorption and solubility tests were carried out with the following storage times: 4 h, 24 h and 7, 60 and 180 days. After storage, water sorption and solubility were determined. Eluted monomers were analysed by high performance liquid chromatography (HPLC). Correlation between the retention time of the registered peak and the reference peak was observed, and UV-spectra confirmed the identity. The results showed an increase in water sorption until equilibrium for all materials with one exception. The solubility behaviour of the composite resin materials tested revealed variations, with both mass decrease and increase. The resin composition influences the water sorption and solubility behaviour of composite resin materials. The HPLC analysis of eluted components revealed that triethyleneglycol dimethacrylate (TEGDMA) was the main monomer released. Maximal monomer concentration in the eluate was observed after 7 days. During the test period, quantifiable quantities of urethanedimethacrylate (UEDMA) monomer were observed, whereas 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)-phenyl]propane (Bis-GMA) was only found in detectable quantities. No detectable quantities of bisphenol-A were observed during the test period.

  1. Epigallocatechin-3-Gallate Reduces Cytotoxic Effects Caused by Dental Monomers: A Hypothesis

    Science.gov (United States)

    Jiao, Yang; Ma, Sai; Wang, Yirong; Li, Jing; Shan, Lequn; Chen, Jihua

    2015-01-01

    Resin monomers from dental composite materials leached due to incomplete polymerization or biodegradation may cause contact allergies and damage dental pulp. The cytotoxicity of dental resin monomers is due to a disturbance of intracellular redox equilibrium, characterized by an overproduction of reactive oxygen species (ROS) and depletion of reduced glutathione (GSH). Oxidative stress caused by dental resin monomers leads to the disturbance of vital cell functions and induction of cell apoptosis in affected cells. The nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway plays a key role in the cellular defense system against oxidative and electrophilic stress. Epigallocatechin-3-gallate (EGCG) can activate the Nrf2 pathway and induce expression of a multitude of antioxidants and phase II enzymes that can restore redox homeostasis. Therefore, here, we tested the hypothesis that EGCG-mediated protection against resin monomer cytotoxicity is mediated by activation of the Nrf2 pathway. This study will help to elucidate the mechanism of resin monomer cytotoxicity and provide information that will be helpful in improving the biocompatibility of dental resin materials. PMID:26489899

  2. Pathway and mechanism of pH dependent human hemoglobin tetramer-dimer-monomer dissociations.

    Directory of Open Access Journals (Sweden)

    Yao-Xiong Huang

    Full Text Available Hemoglobin dissociation is of great interest in protein process and clinical medicine as well as in artificial blood research. However, the pathway and mechanisms of pH-dependent human Hb dissociation are not clear, whether Hb would really dissociate into monomers is still a question. Therefore, we have conducted a multi-technique investigation on the structure and function of human Hb versus pH. Here we demonstrate that tetramer hemoglobin can easily dissociate into dimer in abnormal pH and the tetramer → dimer dissociation is reversible if pH returns to normal physiological value. When the environmental pH becomes more acidic (8.0, Hb can further dissociate from dimer to monomer. The proportion of monomers increases while the fraction of dimers decreases as pH declines from 6.2 to 5.4. The dimer → monomer dissociation is accompanied with series changes of protein structure thus it is an irreversible process. The structural changes in the dissociated Hbs result in some loss of their functions. Both the Hb dimer and monomer cannot adequately carry and release oxygen to the tissues in circulation. These findings provide a comprehensive understanding on the pH-dependent protein transitions of human Hb, give guideline to explain complex protein processes and the means to control protein dissociation or re-association reaction. They are also of practical value in clinical medicine, blood preservation and blood substitute development.

  3. [Use of immobilization in the study of glyceraldehyde 3-phosphate dehydrogenase. Immobilized monomers].

    Science.gov (United States)

    Muronets, V I; Ashmarina, L I; Asriiants, R A; Nagradova, N K

    1982-06-01

    Active immobilized monomers of glyceraldehyde 3-phosphate dehydrogenase were prepared by means of dissociation of the tetrameric enzyme molecule covalently bound to Sepharose via a single subunit. The conditions were elaborated to achieve the inactivation and solubilization of the non-covalently bound subunits leaving the monomer coupled to the matrix intact. This procedure differs from the previously developed method of matrix-bound oligomeric enzymes dissociation in a detail which was found to be essentially important. The widely used method includes complete denaturation of all subunits during treatment with urea followed by reactivation of the immobilized one, whereas only the non-covalently bound subunits suffer denaturation under the conditions developed in the present work. The immobilized monomers of glyceraldehyde 3-phosphate dehydrogenase exhibit Vmax and Km (for NAD and substrate) values similar to those found for the immobilized tetramer. Reassociation of the immobilized monomers with soluble enzyme subunits obtained in the presence of urea produces matrix-bound tetrameric species. Immobilized trimers ae formed upon incubation of matrix-bound monomers in a diluted apoenzyme solution. The immobilized monomeric, trimeric and tetrameric enzyme species were used to study the role of subunit interactions in cooperative phenomena exhibited by the dehydrogenase. PMID:7115810

  4. Cu K-edge X-ray Absorption Spectroscopy Reveals Differential Copper Coordimation Within Amyloid-beta Oligomers Compared to Amyloid-beta Monomers

    Energy Technology Data Exchange (ETDEWEB)

    J Shearer; P Callan; T Tran; V Szalai

    2011-12-31

    The fatal neurodegenerative disorder Alzheimer's disease (AD) has been linked to the formation of soluble neurotoxic oligomers of amyloid-{beta} (A{beta}) peptides. These peptides have high affinities for copper cations. Despite their potential importance in AD neurodegeneration few studies have focused on probing the Cu{sup 2+/1+} coordination environment within A{beta} oligomers. Herein we present a Cu K-edge X-ray absorption spectroscopic study probing the copper-coordination environment within oligomers of A{beta}(42) (sequence: DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA). We find that the Cu{sup 2+} cation is contained within a square planar mixed N/O ligand environment within A{beta}(42) oligomers, which is similar to the copper coordination environment of the monomeric forms of {l_brace}Cu{sup II}A{beta}(40){r_brace} and {l_brace}Cu{sup II}A{beta}(16){r_brace}. Reduction of the Cu{sup 2+} cation within the A{beta}(42) oligomers to Cu{sup 1+} yields a highly dioxygen sensitive copper-species that contains Cu{sup 1+} in a tetrahedral coordination geometry. This can be contrasted with monomers of {l_brace}Cu{sup I}A{beta}(40){r_brace} and {l_brace}Cu{sup I}A{beta}(16){r_brace}, which contain copper in a dioxygen inert linear bis-histidine ligand environment [Shearer and Szalai, J. Am. Chem. Soc., 2008, 130, 17826]. The biological implications of these findings are discussed.

  5. Radical cations of aromatic selenium compounds: role of Se···X nonbonding interactions.

    Science.gov (United States)

    Singh, Beena G; Thomas, Elizabeth; Sawant, Shilpa N; Takahashi, Kohei; Dedachi, Kenchi; Iwaoka, Michio; Priyadarsini, K Indira

    2013-09-26

    Selenium centered radical cations in aliphatic selenium compounds are stabilized by formation of two-center-three electron (2c-3e) hemi bonds either with nearby heteroatoms forming monomer radicals or with selenium atoms of the parent molecules forming dimer radicals. Such radicals in aromatic selenium compounds would generally be stabilized as monomers by the delocalization of the spin density along the aromatic ring. To test the assumption if aromatic selenides having Se···X nonbonding interactions can show different types of radical cations, we have performed pulse radiolysis studies of three structurally related aromatic selenium compounds and the results have been substantiated with cyclic voltammetry and quantum chemical calculations. The three aromatic selenium compounds have functional groups like -CH2N(CH3)2 (1), -CH2OH (2), and -CH3 (3) at ortho position to the -SeCH3 moiety. The energy of Se···X nonbonding interactions (E(nb)) for these compounds is in the order 1 (Se···N) > 2 (Se···O) > 3 (Se···H). Radical cations, 1(•+), 2(•+) and 3(•+) were produced by the one-electron oxidation of 1, 2 and 3 by radiolytically generated (•)OH and Br2(•-) radicals. Results on transient spectra, lifetime, and secondary reactions of 1(•+), 2(•+), and 3(•+) indicated that 1(•+) shows a significantly different absorption spectrum, longer lifetime, and less oxidizing power compared to those of 2(•+) or 3(•+). Quantum chemical calculations suggested that 1(•+) is stabilized by the formation of a 2c-3e bond between Se and N atoms, whereas 2(•+) and 3(•+) acquire stability through the delocalization of the spin density on the aromatic ring. These results provide evidence for the first time that stronger nonbonding interactions between Se···N in the ground state, facilitate the formation of stabilized radical cations, which can significantly influence the redox chemistry and the biological activity of aromatic selenium compounds.

  6. Gamma-rays initiated cationic polymerization of epoxy resins and their carbon nanotubes composites

    Science.gov (United States)

    Przybytniak, Grażyna; Nowicki, Andrzej; Mirkowski, Krzysztof; Stobiński, Leszek

    2016-04-01

    Epoxy resins based on diglycidyl ether of bisphenol A (DGEBA) in the presence cationic initiator in the form of iodonium salt were exposed to gamma-rays in order to initiate curing process. The influence of the initiator concentration, dose rate, chemical structure of monomers and the presence of carbon nanotubes were determined on the basis of the recorded on-line thermal effects. The induction time of radiation curing increased with lowering concentration of the initiator and oxirane groups as well as with decreasing dose rates. As was confirmed by SEM images, carbon nanotubes were uniformly distributed over the matrix and closely surrounded by the macromolecules. Such a structure resulted from adsorption of the initiator on the filler surface what allowed to begin polymerization around nanoparticles and facilitated their incorporation into the matrix. As a consequence, the mechanical properties of the nanocomposites were improved.

  7. STUDIES ON SELF-ASSOCIATIVE BEHAVIOR OF A NOVEL CATION AMPHIPHILIC POLYMER

    Institute of Scientific and Technical Information of China (English)

    Jing Li; Fei-peng Wu; Er-jian Wang

    2009-01-01

    A novel associating polymer P(AEBA) was synthesized by radical polymerization of the cationic amphiphilic monomer, 4-(2-(acryloyloxy)ethoxy)benzyl tri-ethyl ammonium bromide (AEBA), in aqueous solutions. P(AEBA) displays a strong tendency for self-association in aqueous solutions and is sensitive to the external stimulation such as added salt. The associative properties and morphologies of P(AEBA) were studied by fluorescnece probe technique, viscometry and TEM. In dilute salt-free solutions P(AEBA) behaves as polyelectrolyte, while its behavior is similar to that of the polysoap as salt added. Accompanying increasing polymer concentration, polymer aggregation conformation changes from an extended necklace-like structure to a compact globular aggregate corresponding to the viscosity reduction.

  8. Arsenite and arsenate removal from wastewater using cationic polymer-modified waste tyre rubber.

    Science.gov (United States)

    Imyim, Apichat; Sirithaweesit, Thitayati; Ruangpornvisuti, Vithaya

    2016-01-15

    Waste tyre rubber (WTR) granulate was modified with a cationic polymer, poly(3-acrylamidopropyl)trimethylammonium chloride (p(APTMACl)). The resulting WTR/p(APTMACl) was utilized for the adsorption of arsenite, As(III) and arsenate, As(V) from aqueous medium in both batch and column methods. The level of adsorption increased gradually with increasing monomer concentration and contact time. The adsorption behavior obeyed the Freundlich model, and the rate of adsorption could be predicted by employing the pseudo-second order model. In the column method, As(V) could be adsorbed onto the sorbent more effectively than As(III). Remarkable desorption of As(III) and As(V) (99 and 92%, respectively) from the adsorbent was achieved using 0.10 M HCl as eluent. An approach of evaluation of adsorption capacity uncertainty is proposed. PMID:26607568

  9. Photochemical Production of Interpenetrating Polymer Networks; Simultaneous Initiation of Radical and Cationic Polymerization Reactions

    Directory of Open Access Journals (Sweden)

    Jean Pierre Fouassier

    2014-10-01

    Full Text Available In this paper, we propose to review the ways to produce, through photopolymerization, interpenetrating polymer networks (IPN based, e.g., on acrylate/epoxide or acrylate/vinylether blends and to outline the recent developments that allows a one-step procedure (concomitant radical/cationic polymerization, under air or in laminate, under various irradiation conditions (UV/visible/near IR; high/low intensity sources; monochromatic/polychromatic sources; household lamps/laser diodes/Light Emitting Diodes (LEDs. The paper illustrates the encountered mechanisms and the polymerization profiles. A short survey on the available monomer systems and some brief examples of the attained final properties of the IPNs is also provided.

  10. Synthesis of crosslinked polystyrene particles by seeded batch polymerization with monomer absorption

    Institute of Scientific and Technical Information of China (English)

    Ki-Chang LEE; Han-Ah WI

    2011-01-01

    A highly crosslinked. monodispersed polystyrene(PS) particle was prepared by a seeded batch dispersion polymerization with a monomer absorption method. Prior to polymerization, 1.9 μm monodispersed PS seed particles were treated under an optimum condition of monomer absorption. The effects of divinylbenzebe(DVB) concentration and polymerization temperature were examined for styrene(in PS seed)/styrene(in the second stage) mass ratio of 1:1 in the medium range of EtOH/water mass ratio of 100/0-80/20 and 2.3 μm uniform crosslinked PS particles containing 15%-20% (mass frtction) DVB were prepared at 60-70 ℃. The results show that monomer absorption before the second stage of polymerization is more effective to prepare highly crosslinked monodispersed PS particles.

  11. Close-packed polymer crystals from two-monomer-connected precursors

    Science.gov (United States)

    Lee, Hong-Joon; Jo, Yong-Ryun; Kumar, Santosh; Yoo, Seung Jo; Kim, Jin-Gyu; Kim, Youn-Joong; Kim, Bong-Joong; Lee, Jae-Suk

    2016-09-01

    The design of crystalline polymers is intellectually stimulating and synthetically challenging, especially when the polymerization of any monomer occurs in a linear dimension. Such linear growth often leads to entropically driven chain entanglements and thus is detrimental to attempts to realize the full potential of conjugated molecular structures. Here we report the polymerization of two-monomer-connected precursors (TMCPs) in which two pyrrole units are linked through a connector, yielding highly crystalline polymers. The simultaneous growth of the TMCP results in a close-packed crystal in polypyrrole (PPy) at the molecular scale with either a hexagonal close-packed or face-centred cubic structure, as confirmed by high-voltage electron microscopy, and the structure that formed could be controlled by simply changing the connector. The electrical conductivity of the TMCP-based PPy is almost 35 times that of single-monomer-based PPy, demonstrating its promise for application in diverse fields.

  12. Theoretical Researches on the Recognizing Characteristics of Atrazine Imprinted Polymers with Different Functional Monomers

    Institute of Scientific and Technical Information of China (English)

    LIU Jun-Bo; SUN Jia-Ni; TANG Shan-Shan; CHEN Kai-Yin; JIN Rui-Fa

    2012-01-01

    As a widely used herbicide, the threat of atrazine to both environment and health of people has become the focus. Therefore, the research and analysis of atrazine are getting more important. In this work, the MIT was used to detect atrazine theoretically. Atrazine was taken as a template molecule. MAA, MMA and TFMAA were taken as the functional monomers, respectively. The geometry optimization, the nature of hydrogen bonds, the NBO charge, and the binding energies of the imprinted molecule with the functional monomers were investigated at the B3LYP/6-31g(d,p) level. Results indicated that atrazine had the strongest interaction with TFMAA. When the ratio of atrazine and TFMAA was 1:6, the amount of H-bond formed from atrazine and TFMAA was the largest. Moreover, TFMAA owned the largest binding energy with atrazine while MMA owned the smallest. The study is helpful to interpret experiment phenomena of molecular imprinting and select better functional monomers.

  13. Bio-based production of monomers and polymers by metabolically engineered microorganisms.

    Science.gov (United States)

    Chung, Hannah; Yang, Jung Eun; Ha, Ji Yeon; Chae, Tong Un; Shin, Jae Ho; Gustavsson, Martin; Lee, Sang Yup

    2015-12-01

    Recent metabolic engineering strategies for bio-based production of monomers and polymers are reviewed. In the case of monomers, we describe strategies for producing polyamide precursors, namely diamines (putrescine, cadaverine, 1,6-diaminohexane), dicarboxylic acids (succinic, glutaric, adipic, and sebacic acids), and ω-amino acids (γ-aminobutyric, 5-aminovaleric, and 6-aminocaproic acids). Also, strategies for producing diols (monoethylene glycol, 1,3-propanediol, and 1,4-butanediol) and hydroxy acids (3-hydroxypropionic and 4-hydroxybutyric acids) used for polyesters are reviewed. Furthermore, we review strategies for producing aromatic monomers, including styrene, p-hydroxystyrene, p-hydroxybenzoic acid, and phenol, and propose pathways to aromatic polyurethane precursors. Finally, in vivo production of polyhydroxyalkanoates and recombinant structural proteins having interesting applications are showcased. PMID:26318077

  14. Testing of residual monomer content reduction possibility on acrilic resins quality

    Directory of Open Access Journals (Sweden)

    Kostić Milena

    2011-01-01

    Full Text Available Poly (methyl methacrylate (PMMA is material widely used in dentistry. Despite the various methods used to initiate the polymerization of acrylic resins, the conversion of monomer to polymer is not complete thus leaving some unreacted methyl methacrylate (MMA, known as residual monomer (RM, in denture structure. RM in dental acrylic resins has deleterious effects on their mechanical properties and their biocompatibility. The objective of the work was to test the residual monomer reduction possibility by applying the appropriate postpolymerization treatment as well as to determine the effects of this reduction on pressure yields stress and surface structure characteristics of the acrylic resins. Postpolymerization treatments and water storage induced reduction of RM amount in cold-polymerized acrylic resins improved their mechanical properties and the homogenized surface structure. After the polymerization of heat-polymerized acrylic resins the post-polymerization treatments for improving the quality of this material type are not necessary.

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

    International Nuclear Information System (INIS)

    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.

  16. Close-packed polymer crystals from two-monomer-connected precursors.

    Science.gov (United States)

    Lee, Hong-Joon; Jo, Yong-Ryun; Kumar, Santosh; Yoo, Seung Jo; Kim, Jin-Gyu; Kim, Youn-Joong; Kim, Bong-Joong; Lee, Jae-Suk

    2016-01-01

    The design of crystalline polymers is intellectually stimulating and synthetically challenging, especially when the polymerization of any monomer occurs in a linear dimension. Such linear growth often leads to entropically driven chain entanglements and thus is detrimental to attempts to realize the full potential of conjugated molecular structures. Here we report the polymerization of two-monomer-connected precursors (TMCPs) in which two pyrrole units are linked through a connector, yielding highly crystalline polymers. The simultaneous growth of the TMCP results in a close-packed crystal in polypyrrole (PPy) at the molecular scale with either a hexagonal close-packed or face-centred cubic structure, as confirmed by high-voltage electron microscopy, and the structure that formed could be controlled by simply changing the connector. The electrical conductivity of the TMCP-based PPy is almost 35 times that of single-monomer-based PPy, demonstrating its promise for application in diverse fields. PMID:27640812

  17. Preparation of cationic chitosan-polyacrylamide flocculant and its properties in wastewater treatment

    Science.gov (United States)

    Wang, Ben; Zhang, Yulian; Miao, Chunbao

    2011-03-01

    Chitosan derived from crab shells, was used to prepare the graft polymer in aqueous solution with acrylamide (AM) and methacrylatoethyl trimethyl ammonium chloride (DMC) as raw materials and ceric ammonium nitrate (CAN) as initiator. The flocculation ability of the resulting polymer (PCAD) was studied in waste water treatment experiments. Its properties were determined on the basis of the transmittance of waste water after flocculation. The effects of chitosan and DMC content on PCAD's flocculation ability were studied. Flocculation experiments were also undertaken under various pH conditions. According to the experimental data, the flocculation ability could be improved when chitosan content decreased in the raw material, but the monomer conversion would decrease obviously. When the chitosan's content was more than 65%, AM and DMC groups were less on each chitosan molecule. So PCAD's flocculation ability was poor. Similarly, high content of DMC would result in low monomer conversion and high flocculation ability. PCAD molecules with more DMC group had more positive charges. It was favorable to flocculation. However, monomer conversion would decrease with the increase of DMC content. The suitable conditions were that chitosan and DMC contents were 65% and 15-20%, respectively. The experiment data showed that PCAD had good flocculation ability under weak acidic condition. Its ability would be weakened by strong acidic or alkaline condition. The flocculation efficiency was the best at pH of 5.5 when PCAD's dosage was 8mg·L-1. Compared with cationic polymer (the copolymer of AM and DMC, PAD), PCAD showed better flocculation ability under acid and neutral conditions, but worse ability under alkaline condition.

  18. Preparation of Cationic Chitosan-Polyacrylamide Flocculant and Its Properties in Wastewater Treatment

    Institute of Scientific and Technical Information of China (English)

    WANG Ben; ZHANG Yulian; MIAO Chunbao

    2011-01-01

    Chitosan derived from crab shells, was used to prepare the graft polymer in aqueous solution with acrylamide (AM) and methacrylatoethyl trimethyl ammonium chloride (DMC) as raw materials and eerie ammonium nitrate (CAN) as initiator. The flocculation ability of the resulting polymer (PCAD) was studied in waste water treatment experiments. Its properties were determined on the basis of the transmittance of waste water after flocculation. The effects of chitosan and DMC content on PCAD's flocculation ability were studied. Flocculation experiments were also undertaken under various pH conditions. According to the experimental data, the flocculation ability could be improved when chitosan content decreased in the raw material, but the monomer conversion would decrease obviously. When the chitosan's content was more than 65%, AM and DMC groups were less on each chitosan molecule. So PCAD's flocculation ability was poor. Similarly, high content of DMC would result in low monomer conversion and high flocculation ability. PCAD molecules with more DMC group had more positive charges. It was favorable to flocculation. However, monomer conversion would decrease with the increase of DMC content. The suitable conditions were that chitosan and DMC contents were 65% and 15-20%, respectively. The experiment data showed that PCAD had good flocculation ability under weak acidic condition. Its ability would be weakened by strong acidic or alkaline condition. The flocculation efficiency was the best at pH of 5.5 when PCAD's dosage was 8mg·L-1. Compared with cationic polymer (the copolymer of AM and DMC, PAD), PCAD showed better flocculation ability under acid and neutral conditions, but worse ability under alkaline condition.

  19. Cationic Ring Opening polymerization of ε-caprolactam by a Montmorillonite Clay Catalyst

    Directory of Open Access Journals (Sweden)

    Djamal Eddine Kherroub

    2014-03-01

    Full Text Available The ring opening bulk polymerization of ε-caprolactam catalyzed by Maghnite-H+ was reported. Maghnite-H+ is a montmorillonite silicate sheet clay was prepared through a straight forward proton exchange process. The effect of the amount of catalyst, and temperature was studied. Increasing Maghnite-H+ proportion and temperature produced the increase in ε-caprolactam conversion. The kinetics indicated that the polymerization rate is first order with respect to monomer concentration. Mechanism studies showed that monomer inserted into the growing chains with the acyl–oxygen bond scission rather than the break of alkyl–oxygen bond. © 2014 BCREC UNDIP. All rights reservedSubmitted: 3rd October 2013; Revised: 28th February 2014; Accepted: 1st March 2014[How to Cite: Kherroub, D.E., Belbachir, M., Lamouri, S. (2014. Cationic Ring Opening Polymeriza-tion of ε-caprolactam by a Montmorillonite Clay Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 9 (1: 74-79. (doi:10.9767/bcrec.9.1.5555.74-80][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.1.5555.74-80

  20. Kinetics of the monomer-dimer reaction of yeast hexokinase PI.

    Science.gov (United States)

    Hoggett, J G; Kellett, G L

    1992-10-15

    Kinetic studies of the glucose-dependent monomer-dimer reaction of yeast hexokinase PI at pH 8.0 in the presence of 0.1 M-KCl have been carried out using the fluorescence temperature-jump technique. A slow-relaxation effect was observed which was attributed from its dependence on enzyme concentration to the monomer-dimer reaction; the reciprocal relaxation times tau-1 varied from 3 s-1 at low concentrations of glucose to 42 s-1 at saturating concentrations. Rate constants for association (kass.) and dissociation (kdiss.) were determined as a function of glucose concentration using values of the equilibrium association constant of the monomer-dimer reaction derived from sedimentation ultracentrifugation studies under similar conditions, and also from the dependence of tau-2 on enzyme concentration. kass. was almost independent of glucose concentration and its value (2 x 10(5) M-1.s-1) was close to that expected for a diffusion-controlled process. The influence of glucose on the monomer-dimer reaction is entirely due to effects on kdiss., which increases from 0.21 s-1 in the absence of glucose to 25 s-1 at saturating concentrations. The monomer and dimer forms of hexokinase have different affinities and Km values for glucose, and the results reported here imply that there may be a significant lag in the response of the monomer-dimer reaction to changes in glucose concentrations in vivo with consequent hysteretic effects on the hexokinase activity. PMID:1445216

  1. A Relativistic Density Functional Study on the Uranium Hexafluoride and Plutonium Hexafluoride Monomer and Dimer Species

    OpenAIRE

    Gagliardi, Laura; Willetts, Andrew; Skylaris, Chris-Kriton; Handy, Nicholas C.; Spencer, Steven; Ioannou, Andrew G.; Simper, Adrian M.

    1998-01-01

    A study on the UF6 monomer and dimer was carried out within the density functional method. The U−F distance in the UF6 monomer was optimized at different levels of theory, pointwise, assuming octahedral geometry, (1) by using an all-electron basis for both U and F in a nonrelativistic calculation; (2) by using a relativistic effective core potential (RECP) on U and nonrelativistic effective core potential (ECP) on the fluorines; and (3) by using RECP on the U atom and an all-electron basis on...

  2. New aromatic activated dihalides and bisphenol monomers for the preparation of novel poly(arylene ethers)

    Science.gov (United States)

    Wolfe, James F.

    1993-01-01

    The goal of this research program was to synthesize a series of unique monomers of type I to be utilized at NASA-Langley in the preparation of new poly(arylene ether ketones), poly(arylene ether ketosulfones), and poly(arylene ether ketophosphine oxides). These A-A and A-B monomer systems, which possess activated aryl halide and/or phenolic end groups, are accessible via condensation reactions of appropriately substituted aryl acetonitrile carbanions with activated aryl dihalides followed by oxidative decyanation.

  3. Improved thrombin binding aptamer by incorporation of a single unlocked nucleic acid monomer

    DEFF Research Database (Denmark)

    Pasternak, Anna; Hernandez, Frank J; Rasmussen, Lars Melholt;

    2011-01-01

    A 15-mer DNA aptamer (named TBA) adopts a G-quadruplex structure that strongly inhibits fibrin-clot formation by binding to thrombin. We have performed thermodynamic analysis, binding affinity and biological activity studies of TBA variants modified by unlocked nucleic acid (UNA) monomers. UNA...... that a UNA monomer is allowed in many positions of the aptamer without significantly changing the thrombin-binding properties. The biological effect of a selection of the modified aptamers was tested by a thrombin time assay and showed that most of the UNA-modified TBAs possess anticoagulant properties...

  4. Monomer Basis Representation Method For Calculating The Spectra Of Molecular Clusters II. Application To Water Dimer

    CERN Document Server

    Ocak, Mahir E

    2012-01-01

    The Monomer Basis Representation (MBR) method developed in the first paper is applied to water dimer in order to illustrate its application and to show its validity. The calculations are done by using the SAPT-5st potential surface. Monomers are treated as rigid bodies. Radial coordinate is separated from the angular coordinates adiabatically. MBR method is used for solving the five dimensional angular problem. Then, the results of the angular calculations are fit to a Morse function to find the potential surface for the radial motion. The results show that the method works efficiently and accurately.

  5. pH driven conformational dynamics and dimer-to-monomer transition in DLC8

    OpenAIRE

    Mohan, P.M. Krishna; Barve, Maneesha; Chatterjee, Amarnath; Hosur, Ramakrishna V.

    2006-01-01

    Dynein light chain protein, a part of the cytoplasmic motor assembly, is a homodimer at physiological pH and dissociates below pH 4.5 to a monomer. The dimer binds to a variety of cargo, whereas the monomer does not bind any of the target proteins. We report here the pH induced stepwise structural and motional changes in the protein, as derived from line broadening and 15N transverse relaxation measurements. At pH 7 and below until 5, partial protonation and consequent interconversion between...

  6. One-pot synthesis of cyclic triamides with a triangular cavity from trans-stilbene and diphenylacetylene monomers.

    Science.gov (United States)

    Yokoyama, Akihiro; Maruyama, Takurou; Tagami, Kei; Masu, Hyuma; Katagiri, Kosuke; Azumaya, Isao; Yokozawa, Tsutomu

    2008-08-01

    Base-promoted self-condensation reactions of trans-stilbene and diphenylacetylene monomers bearing 4-alkylamino and 4'-methoxycarbonyl groups were investigated. Reactions of N-propyl monomers under pseudohigh-dilution conditions (a THF solution of monomer was added dropwise to a THF solution of LiHMDS) afforded the corresponding cyclic triamides in good yields. X-ray crystallographic analysis showed that these cyclic triamides possessed an almost equilateral triangle structure with a cavity surrounded by tilted benzene rings.

  7. Innate cation sensitivity in a semiconducting polymer.

    Science.gov (United States)

    Althagafi, Talal M; Algarni, Saud A; Grell, Martin

    2016-09-01

    Water-gated organic thin film transistors (OTFTs) using the hole transporting semiconducting polymer, poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT), show an innate response of their threshold voltage to the addition of divalent metal cations to the gating water, without deliberately introducing an ion-sensitive component. A similar threshold response is shown for several divalent cations, but is absent for monovalent cations. Response is absent for transistors using the inorganic semiconductor ZnO, or the similar organic semiconductor poly(3-hexylthiophene) (rrP3HT), instead of PBTTT. We assign innate cation sensitivity to residues of the organometallic Pd(0) complex used as catalyst in PBTTT synthesis which bears strong resemblance to typical metal chelating agents. Organometallic Pd(0) residues are absent from ZnO, and also from rrP3HT which is polymerised with a different type of catalyst. However, when Pd(0) complex is deliberately added to rrP3HT casting solutions, resulting OTFTs also display threshold response to a divalent cation. PMID:27343580

  8. Effect of the Surface Affinity of Liquid Crystals and Monomers on the Orientation of Polymer-Dispersed Liquid Crystal

    Science.gov (United States)

    Lee, Ji-Hoon; Yoon, Tae-Hoon

    2013-09-01

    We investigated the effect of the surface affinity of liquid crystals and reactive monomers on liquid crystal orientation. Liquid crystals and monomers having different contact angles with the vertical alignment polyimide were mixed and photo-polymerized using a UV light. Liquid crystals with smaller contact angles and reactive monomers with greater contact angles promoted a uniform vertical orientation of liquid crystals with a vertical polymer morphology. On the other hand, liquid crystals with greater contact angles and monomers with smaller contact angles resulted in a deformed liquid crystal orientation with an elliptical polymer structure.

  9. Forging Colloidal Nanostructures via Cation Exchange Reactions

    Science.gov (United States)

    2016-01-01

    Among the various postsynthesis treatments of colloidal nanocrystals that have been developed to date, transformations by cation exchange have recently emerged as an extremely versatile tool that has given access to a wide variety of materials and nanostructures. One notable example in this direction is represented by partial cation exchange, by which preformed nanocrystals can be either transformed to alloy nanocrystals or to various types of nanoheterostructures possessing core/shell, segmented, or striped architectures. In this review, we provide an up to date overview of the complex colloidal nanostructures that could be prepared so far by cation exchange. At the same time, the review gives an account of the fundamental thermodynamic and kinetic parameters governing these types of reactions, as they are currently understood, and outlines the main open issues and possible future developments in the field. PMID:26891471

  10. Synthesis of Cationic PEM Emulsion and Application in Waste Water Treatment

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-bin; LI Min; FANG Yi; SONG Hong; LUO Juan; XU Cheng-yin; WAN Chang-xiu

    2004-01-01

    Cationic polymer as a kind of flocculant is widely applied in purification treatment of waste water. Because it has positive charge group, it is able to connect strongly the suspended matters, short cellulose and other microparticles. The research on synthesis of cationic polymer and application in treatment of waste water is very universal abroad. But domestic research on those is not general. The technology of synthesis of PEM is simple, and the production cost is low. It is easy to apply in treatment of waste water.Synthesis of PEM Emulsion FlocculantSome distilled water, PVA(poly(vinyl alcohol)), EA(ethyl acrylate), and K2S2O8(potassium persulfate) were put into reaction vessel. Kept stirring up under nitrogen. When heated the solution to 40℃, dropped the water solution of MTA[(2-methacryloxylethyl)trimethyl ammonium].Maintained the temperature at 70℃, reacted about 7-8 hours. Then got the PEM emulsion. Changed the ratio of EA and MTA. Obtained a series of PEM emulsions.Stability and Convertibility of PEM EmulsionThe test results showed that when the EA/MTA was 85/15, the PEM emulsion was most stable.When the total monomer quantity was 35%, the convertibility of PEM emulsion was the highest,i.e.98.6%.The MTA Copolymerization Ratio and Morphology of PEM EmulsionWhen the monomers EA/MTA=85/15 and total monomer quantity was 35%, the MTA copolymerization ratio of PEM emulsion was 95.15%(the highest), and the PEM emulsion was some microspheres with 100-180nm of diameter.The Test Results of PEM Emulsion in Treatment of Waste Water The PEM emulsion flocculant was applied in treatment of waste water of paper mill, and measured the precipitation time(t) and transmittancy(T). The test results were showed in table 1. The optimum value of PEM which was able to make the waste water of paper mill into clear water was 0.008%.

  11. Mixed cation effect in sodium aluminosilicate glasses

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Smedskjær, Morten Mattrup; Mauro, John C.;

    , network structure, and the resistances associated with the deformation processes in mixed cation glasses by partially substituting magnesium for calcium and calcium for lithium in sodium aluminosilicate glasses. We use Raman and 27Al NMR spectroscopies to obtain insights into the structural...... and topological features of these glasses and we use AFM to quantify the resistances associated with each deformation process under Vickers indentation. We demonstrate that the mixed cation effect manifests itself as a maximum in the amount of bonded tetrahedral units and as a minimum in liquid fragility index...

  12. Cation Effect on Copper Chemical Mechanical Polishing

    Institute of Scientific and Technical Information of China (English)

    WANG Liang-Yong; LIU Bo; SONG Zhi-Tang; FENG Song-Lin

    2009-01-01

    We examine the effect of cations in solutions containing benzotriazole (BTA) and H2O2 on copper chemical mechanical polishing (CMP). On the base of atomic force microscopy (AFM) and material removal rate (MRR) results, it is found that ammonia shows the highest MRR as well as good surface after CMP, while KOH demon-strates the worst performance. These results reveal a mechanism that sma//molecules with lone-pairs rather than molecules with steric effect and common inorganic cations are better for copper CMP process, which is indirectly confirmed by open circuit potential (OCP).

  13. Trimer-Monomer Mixture Problem on (111) $1 \\times 1$ Surface of Diamond Structure

    OpenAIRE

    Akutsu, Noriko; Akutsu, Yasuhiro

    2000-01-01

    We consider a system of trimers and monomers on the triangular lattice, which describes the adsorption problem on (111) $1 \\times 1$ surface of diamond structure. We give a mapping to a 3-state vertex model on the square lattice. We treat the problem by the transfer-matrix method combined with the density-matrix algorithm, to obtain thermodynamic quantities.

  14. Determination of acrylamide monomer in polyacrylamide degradation studies by high-performance liquid chromatography.

    Science.gov (United States)

    Ver Vers, L M

    1999-12-01

    A high-performance liquid chromatography method using C18 and ion-exchange columns in series is developed for the determination of acrylamide and acrylic acid monomers in polymeric samples. The C18 column acts as a guard column, trapping surfactants and impurities and retaining the nonionic species. The ion-exchange column then separates the monomers according to their respective ionic strengths. This method has been proven in the laboratory to work successfully for all types of acrylamide/acrylic acid polymers and matrices. Detection limits for both monomers can be achieved in the parts-per-billion range. The method is used to study the possible degradation of polyacrylamide to acrylamide monomer in the presence of glyphosate (a herbicide) and sunlight. Polyacrylamide is used as a spray drift reduction aid in combination with glyphosate. In normal applications, the polymer and herbicide are in contact with each other in the presence of sunlight. The results show that the polymer does not degrade to acrylamide in the presence of glyphosate or sunlight or any combination of the two. It is also observed that glyphosate influences the solubility of polyacrylamide, and care must be used when combining the two.

  15. Influencing solvent miscibility and aqueous stability of aluminum nanoparticles through surface functionalization with acrylic monomers.

    Science.gov (United States)

    Crouse, Christopher A; Pierce, Christian J; Spowart, Jonathan E

    2010-09-01

    With growing interest in the development of new composite systems for a variety of applications that require easily processable materials and adequate structural properties with high energy densities, we have pursued the chemical functionalization of oxide-passivated aluminum nanoparticles (nAl) using three acrylic monomers, 3-methacryloxypropyltrimethoxysilane (MPS), 2-carboxyethyl acrylate (CEA), and phosphonic acid 2-hydroxyethyl methacrylate ester (PAM), to provide chemical compatibility within various solvent and polymeric systems. Fourier transform infrared and X-ray photoelectron spectroscopy suggest that attachment of MPS and PAM monomers occurs through the formation of bonds directly to the passivated oxide surface upon reaction with surface hydroxyls, whereas CEA monomers interact through the formation of ionic carboxylate binding to aluminum atoms within the oxide. The coated particles demonstrate enhanced miscibility in common organic solvents and monomers; MPS and PAM coatings are additionally shown to inhibit oxidation of the aluminum particles when exposed to aqueous environments at room temperature, and PAM coatings are stable at even elevated temperatures. PMID:20795650

  16. Augmentation of NKT and NK cell-mediated cytotoxicity by peptidoglycan monomer linked with zinc

    Directory of Open Access Journals (Sweden)

    Ines Mrakovcic-Šutic

    2002-01-01

    Full Text Available Background: Peptidoglycan monomer (PGM, which was originally prepared by biosynthesis from culture fluids of penicillin-treated Brevibacterium divaricatum, is an immunostimulator, the activities of which might be improved by addition of zinc (Zn to the basic molecule.

  17. Development of ionic gels using thiol-based monomers in ionic liquid

    Science.gov (United States)

    Ahmed, Kumkum; Naga, Naofumi; Kawakami, Masaru; Furukawa, Hidemitsu

    2016-04-01

    Ionic gels (IGs) using ionic liquids (ILs) can propose diverse applications in the field of optics, sensors and separation have opened wide prospects in materials science. ILs have attracted remarkable interest for gel polymer electrolytes and batteries based on their useful properties such as non-volatility, non-flammability, a wide electrochemical window, high thermal stability and a high ionic conductivity. The formation of gel in IL media makes it possible to immobilize ILs within organic or inorganic matrices and to take advantage of their unique properties in the solid state, thus eliminating some shortcomings related to shaping and risk of leakage. In this work for the first time we used multifunctional thiol monomers having uniform structure and good compatibility with the IL of our interest. Therefore we focused on developing thiol monomer-based IGs using multifunctional thiol monomers and acrylate crosslinkers utilizing thiol-ene reaction between monomer and crosslinking molecules in an IL medium and characterize their physico-chemical properties like thermal, conductive, mechanical properties etc.. This work has been focused mainly to improve the mechanical strength of IGs and make prospects of IGs in tribology and lubricants.

  18. Radiation Induced Crosslinking of Polyethylene in the Presence of Bifunctional Vinyl Monomers

    DEFF Research Database (Denmark)

    Joshi, M. S.; Singer, Klaus Albert Julius; Silverman, J.

    1977-01-01

    Several reports have been published showing that the radiation induced grafting of bifunctional vinyl monomers to low density polyethylene results in a product with an unusually high density of crosslinks. The same grafting reactions are shown to reduce the incipient gel dose by more than a facto...

  19. Pseudomonas syringae evades host immunity by degrading flagellin monomers with alkaline protease AprA

    NARCIS (Netherlands)

    Pel, Michiel J C; van Dijken, Anja J H; Bardoel, Bart W; Seidl, Michael F; van der Ent, Sjoerd; van Strijp, Jos A G; Pieterse, Corné M J

    2014-01-01

    Bacterial flagellin molecules are strong inducers of innate immune responses in both mammals and plants. The opportunistic pathogen Pseudomonas aeruginosa secretes an alkaline protease called AprA that degrades flagellin monomers. Here, we show that AprA is widespread among a wide variety of bacteri

  20. Pseudomonas syringae evades host Immunity by degrading flagellin monomers with alkaline protease AprA

    NARCIS (Netherlands)

    Pel, M.J.C.; Van Dijken, A.J.H.; Bardoel, B.W.; Seidl, M.F; Van der Ent, S.; Van Strijp, J.A.G.

    2014-01-01

    Bacterial flagellin molecules are strong inducers of innate immune responses in both mammals and plants. The opportunistic pathogen Pseudomonas aeruginosa secretes an alkaline protease called AprA that degrades flagellin monomers. Here, we show that AprA is widespread among a wide variety of bacteri

  1. General low-temperature reaction pathway from precursors to monomers before nucleation of compound semiconductor nanocrystals

    Science.gov (United States)

    Yu, Kui; Liu, Xiangyang; Qi, Ting; Yang, Huaqing; Whitfield, Dennis M.; Y. Chen, Queena; Huisman, Erik J. C.; Hu, Changwei

    2016-08-01

    Little is known about the molecular pathway to monomers of semiconductor nanocrystals. Here we report a general reaction pathway, which is based on hydrogen-mediated ligand loss for the precursor conversion to `monomers' at low temperature before nucleation. We apply 31P nuclear magnetic resonance spectroscopy to monitor the key phosphorous-containing products that evolve from MXn+E=PPh2H+HY mixtures, where MXn, E=PPh2H, and HY are metal precursors, chalcogenide precursors, and additives, respectively. Surprisingly, the phosphorous-containing products detected can be categorized into two groups, Ph2P-Y and Ph2P(E)-Y. On the basis of our experimental and theoretical results, we propose two competing pathways to the formation of M2En monomers, each of which is accompanied by one of the two products. Our study unravels the pathway of precursor evolution into M2En monomers, the stoichiometry of which directly correlates with the atomic composition of the final compound nanocrystals.

  2. Unbiased charge oscillations in DNA monomer-polymers and dimer-polymers

    CERN Document Server

    Lambropoulos, Konstantinos; Morphis, Andreas; Kaklamanis, Konstantinos; Theodorakou, Marina; Simserides, Constantinos

    2015-01-01

    We call {\\it monomer} a B-DNA base-pair and examine, analytically and numerically, electron or hole oscillations in monomer- and dimer-polymers, i.e., periodic sequences with repetition unit made of one or two monomers. We employ a tight-binding (TB) approach at the base-pair level to readily determine the spatiotemporal evolution of a single extra carrier along a $N$ base-pair polymer. We study HOMO and LUMO eigenspectra as well as the mean over time probabilities to find the carrier at a particular monomer. We use the pure mean transfer rate $k$ to evaluate the easiness of charge transfer. The inverse decay length $\\beta$ for exponential fits $k(d)$, where $d$ is the charge transfer distance, and the exponent $\\eta$ for power law fits $k(N)$ are computed; generally power law fits are better. We illustrate that increasing the number of different parameters involved in the TB description, the fall of $k(d)$ or $k(N)$ becomes steeper and show the range covered by $\\beta$ and $\\eta$. Finally, both for the time-...

  3. The monomer-dimer problem and moment Lyapunov exponents of homogeneous Gaussian random fields

    CERN Document Server

    Vladimirov, Igor G

    2012-01-01

    We consider an "elastic" version of the statistical mechanical monomer-dimer problem on the n-dimensional integer lattice. Our setting includes the classical "rigid" formulation as a special case and extends it by allowing each dimer to consist of particles at arbitrarily distant sites of the lattice, with the energy of interaction between the particles in a dimer depending on their relative position. We reduce the free energy of the elastic dimer-monomer (EDM) system per lattice site in the thermodynamic limit to the moment Lyapunov exponent (MLE) of a homogeneous Gaussian random field (GRF) whose mean value and covariance function are the Boltzmann factors associated with the monomer energy and dimer potential. In particular, the classical monomer-dimer problem becomes related to the MLE of a moving average GRF. We outline an approach to recursive computation of the partition function for "Manhattan" EDM systems where the dimer potential is a weighted l1-distance and the auxiliary GRF is a Markov random fie...

  4. PLASMA POLYMERIZATION OF HYDROPHILIC AND HYDROPHOBIC MONOMERS FOR SURFACE MODIFICATION OF NUCLE-MICROPOROUS MEMBRANE

    Institute of Scientific and Technical Information of China (English)

    LI Xuefen; LI Zhifen; CHEN Chuanfu; WU Wenhui

    1990-01-01

    Surface modification of nucle-microporous membrane by plasma polymerization of HEMA, NVP and D4 has been studied. The hydrophilicity of membranes was increased with increasing of plasma polymerization time of hydrophilic monomers HEMA and NVP. The flow rate of water through the membrane was increased remarkably after plasma polymerization of HEMA on it.

  5. ENZYMATIC COUPLING OF THE HERBICIDE BENTAZON WITH HUMUS MONOMERS AND CHARACTERIZATION OF REACTION PRODUCTS (R823847)

    Science.gov (United States)

    To elucidate the binding mechanism of the herbicide bentazon (3-isopropyl-1H-2,1,3-benzothiadiazine-4(3H)-one 2,2-dioxide) with humic monomers in the presence of an oxidative enzyme, the reaction of bentazon with catechol, caffeic acid, protocatechuic...

  6. Synthesis and characterization of nitroaromatic peptoids: fine tuning peptoid secondary structure through monomer position and functionality.

    Science.gov (United States)

    Fowler, Sarah A; Luechapanichkul, Rinrada; Blackwell, Helen E

    2009-02-20

    N-substituted glycine oligomers, or peptoids, have emerged as an important class of foldamers for the study of biomolecular interactions and for potential use as therapeutic agents. However, the design of peptoids with well-defined conformations a priori remains a formidable challenge. New approaches are required to address this problem, and the systematic study of the role of individual monomer units in the global peptoid folding process represents one strategy. Here, we report our efforts toward this approach through the design, synthesis, and characterization of peptoids containing nitroaromatic monomer units. This work required the synthesis of a new chiral amine building block, (S)-1-(2-nitrophenyl)ethanamine (s2ne), which could be readily installed into peptoids using standard solid-phase peptoid synthesis techniques. We designed a series of peptoid nonamers that allowed us to probe the effects of this relatively electron-deficient and sterically encumbered alpha-chiral side chain on peptoid structure, namely, the peptoid threaded loop and helix. Circular dichroism spectroscopy of the peptoids revealed that the nitroaromatic monomer has a significant effect on peptoid secondary structure. Specifically, the threaded loop structure was disrupted in a nonamer containing alternating N-(S)-1-phenylethylglycine (Nspe) and Ns2ne monomers, and the major conformation was helical instead. Indeed, placement of a single Ns2ne at the N-terminal position of (Nspe)(9) resulted in a destabilized form of the threaded loop structure relative to the homononamer (Nspe)(9). Conversely, we observed that incorporation of N-(S)-1-(4-nitrophenyl)ethylglycine (Nsnp, a p-nitro monomer) at the N-terminal position stabilized the threaded loop structure relative to (Nspe)(9). Additional experiments revealed that nitroaromatic side chains can influence peptoid nonamer folding by modulating the strength of key intramolecular hydrogen bonds in the peptoid threaded loop structure. Steric

  7. The properties of polymerizable luting cements.

    Science.gov (United States)

    Nicholson, J W; McKenzie, M A

    1999-10-01

    The properties of a polyacid-modified composite resin and two resin-modified luting cements have been studied. The polyacid-modified composite resin had the slowest setting reaction and, in this respect, it did not conform to the current international standard for luting cements. The compressive strength of all of the materials was studied after varying periods of storage from 24 h to 1 year. The polyacid-modified composite resin showed a distinct dip in strength at 1 month in all of the storage media, but otherwise it showed no significant variation with either age or storage medium. The resin-modified glass-ionomers showed variation at 24 h with storage medium (deionized water, 0.9% NaCl or 20 mmol dm(-3) lactic acid), but thereafter they showed little variation, until 1 year, when Vitremer luting showed a significant decline in strength in pure water. However, at 24 h and when stored in water, all of the materials had strengths that easily exceeded the minimum requirement of the current standard (70 MPa). They all took up water on storage, with diffusion coefficients ranging from 1.32 to 17. 19x10(-7) cm2 s(-1). These values were found to depend on whether the specimens were stored in pure water or in physiological saline. However, equilibrium water contents varied only slightly between water and saline. The polyacid-modified composite resin, Dyract-Cem, took up the least water, as well as showing the smallest variation in strength with age. By contrast, it was more difficult to mix than the other materials and the high viscosity of the paste led to the formation of voids and other imperfections in the specimens. PMID:10564431

  8. An investigation of agitation speed as a factor affecting the quantity and monomer distribution of alginate from Azotobacter vinelandii ATCC(®) 9046.

    Science.gov (United States)

    Kıvılcımdan Moral, C; Sanin, F D

    2012-03-01

    Alginate is a copolymer of β-D: -mannuronic and α-L: -guluronic acids. Distribution of these monomers in the alginate structure is one of the important characteristics that affect the commercial value of the polymer. In the present work, the effect of agitation speed in the range of 200-700 rpm on alginate production by Azotobacter vinelandii ATCC(®) 9046 was investigated at a dissolved oxygen tension of 5% of air saturation. Experiments were conducted in a fermentor operated in batch mode for 72 h while the production of biomass and alginate, the consumption of substrate and the change in culture broth viscosity and monomer distribution of the polymer were monitored. Results showed that the growth rate of the bacteria increased from 0.165 to 0.239 h(-1) by the increase of mixing speed from 200 to 400 rpm. On the other hand, alginate production was found to be the most efficient at 400 rpm with the highest value of 4.51 g/l achieved at the end of fermentation. The viscosity of culture broth showed similar trends to alginate production. Viscosity was recorded as 24.61 cP at 400 rpm while it was only 4.26 cP at 700 rpm. The MM- and GG-block contents were almost equal in most of the culture times at 400 rpm. On the other hand, GG-blocks dominated at both low and high mixing speeds. Knowing that GG-blocks make rigid and protective gels with divalent cations, due to the higher GG-block content, the gel formation potential is higher at 200 rpm as well at 700 rpm, which might originate from the unfavorable environmental conditions that the bacteria were exposed to. PMID:22009058

  9. Synthesis and Physicochemical Properties of Cationic Microgels Based on Poly(N-isopropylmethacrylamide).

    Science.gov (United States)

    Hu, Xiaobo; Tong, Zhen; Lyon, L Andrew

    2010-12-01

    Surfactant-free, radical precipitation co-polymerization of N-isopropylmethacrylamide (NIPMAm) and the cationic co-monomer N-(3-aminopropyl) methacrylamide hydrochloride (APMH) was carried out to prepare microgels functionalized with primary amines. The morphology and hydrodynamic diameter of the microgels were characterized by atomic force microscopy (AFM) and photon correlation spectroscopy (PCS), with the effect of NaCl concentration and initiator type on the microgel size and yield being investigated. When a V50-initiated reaction was carried out in pure water, relatively small microgels (~160 nm diameter) were obtained in low yield (~20%). However, both the yield and size increased if the reaction was carried out in saline or by using APS as initiator instead of V50. Stable amine-laden microgels in the range from 160 nm to 950 nm in diameter with narrow size distributions were thus produced using reaction media with controlled salinity. Microgel swelling and electrophoretic mobility values as a function of pH, ionic strength and temperature were also studied, illustrating the presence of cationic sidechains and their influence on microgel properties. Finally, the availability of the primary amine groups for post-polymerization modification was confirmed via modification with fluorescein-NHS.

  10. Effect of cationic side-chains on intracellular delivery and cytotoxicity of pH sensitive polymer-doxorubicin nanocarriers

    Science.gov (United States)

    Fang, Chen; Kievit, Forrest M.; Cho, Yong-Chan; Mok, Hyejung; Press, Oliver W.; Zhang, Miqin

    2012-10-01

    Fine-tuning the design of polymer-doxorubicin conjugates permits optimization of an efficient nanocarrier to greatly increase intracellular uptake and cytotoxicity. Here, we report synthesis of a family of self-assembled polymer-doxorubicin nanoparticles and an evaluation of the effects of various types of side-chains on intracellular uptake and cytotoxicity of the nanocarriers for lymphoma cells. Monomers with three different cationic side-chains (CA) and pKa's, i.e., a guanidinium group (Ag), an imidazole group (Im), and a tertiary amine group (Dm), were comparatively investigated. The cationic monomer, poly(ethylene glycol) (PEG), and doxorubicin (Dox) were reacted with 1,4-(butanediol) diacrylate (BUDA) to prepare a poly(β-amino ester) (PBAE) polymer via Michael addition. All three polymer-Dox conjugates spontaneously formed nanoparticles (NP) through hydrophobic interactions between doxorubicin in aqueous solution, resulting in NP-Im/Dox, NP-Ag/Dox, and NP-Dm/Dox, with hydrodynamic sizes below 80 nm. Doxorubicin was linked to all 3 types of NPs with a hydrazone bond to assure selective release of doxorubicin only at acidic pH, as it occurs in the tumor microenvironment. Both NP-Im/Dox and NP-Ag/Dox exhibited much higher intracellular uptake by Ramos cells (Burkitt's lymphoma) than NP-Dm/Dox, suggesting that the type of side chain in the NPs determines the extent of intracellular uptake. As a result, NP-Im/Dox and NP-Ag/Dox showed cytotoxicity that was comparable to free Dox in vitro. Our findings suggest that the nature of surface cationic group on nanocarriers may profoundly influence their intracellular trafficking and resulting therapeutic efficacy. Thus, it is a crucial factor to be considered in the design of novel carriers for intracellular drug delivery.

  11. Cation Selectivity in Biological Cation Channels Using Experimental Structural Information and Statistical Mechanical Simulation.

    Directory of Open Access Journals (Sweden)

    Justin John Finnerty

    Full Text Available Cation selective channels constitute the gate for ion currents through the cell membrane. Here we present an improved statistical mechanical model based on atomistic structural information, cation hydration state and without tuned parameters that reproduces the selectivity of biological Na+ and Ca2+ ion channels. The importance of the inclusion of step-wise cation hydration in these results confirms the essential role partial dehydration plays in the bacterial Na+ channels. The model, proven reliable against experimental data, could be straightforwardly used for designing Na+ and Ca2+ selective nanopores.

  12. Green Synthesis of Cationic Polyacrylamide Composite Catalyzed by An Ecologically Catalyst Clay Called Maghnite-H+ (Algerian MMT Under Microwave Irradiation.

    Directory of Open Access Journals (Sweden)

    Rahmouni Abdelkader

    2016-08-01

    Full Text Available In this study, a novel green cationic hydrogel of cationic polyacrylamide composite have been prepared and investigated. The synthesis of green cationic polyacrylamide composite was evaluated for its solubility in water. The reactions were performed using acrylamide monomer, solvent, catalyst (clay fin called maghnite and solution of  H2SO4 (0.25 M, with the system under microwave irradiation (160 ºC for 4 min. Major factors affecting the polymerization reaction were studied with a view to discover appropriate conditions for preparation of the composite. The cationic polyacrylamide obtained is the subject of future studies of modification and transformation. The resulting polymer has been characterized by a variety of characterization techniques, such as: Fourier Transform Infrared Spectra and 1H NMR spectra.  Copyright © 2016 BCREC GROUP. All rights reserved Received: 10th June 2015; Revised: 2nd September 2015; Accepted: 5th January 2016 How to Cite: Abdelkader, R., Mohammed, B. (2016. Green Synthesis of Cationic Polyacrylamide Composite Catalyzed by An Ecologically  Catalyst Clay Called Maghnite-H+ (Algerian MMT Under Microwave Irradiation. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (2: 170-175 (doi:10.9767/bcrec.11.2.543.170-175 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.2.543.170-175

  13. Water adsorption on free cobalt cluster cations

    NARCIS (Netherlands)

    D.M. Kiawi; J.M. Bakker; J. Oomens; W.J. Buma; Z. Jamshidi; L. Visscher; L.B.F.M. Waters

    2015-01-01

    Cationic cobalt clusters complexed with water Con+-​H2O (n = 6-​20) are produced through laser ablation and investigated via IR multiple photon dissocn. (IR-​MPD) spectroscopy in the 200-​1700 cm-​1 spectral range. All spectra exhibit a resonance close to the 1595 cm-​1 frequency of the free water b

  14. Simultaneous anion and cation mobility in polypyrrole

    DEFF Research Database (Denmark)

    Skaarup, Steen; Bay, Lasse; Vidanapathirana, K.;

    2003-01-01

    Polypyrrole (PPy) polymer films permanently doped with large, immobile anion dodecyl benzene sulfonate (DBS) have been characterized by cyclic voltammetry in order to clarify the roles of cations and anions in the aqueous electrolyte as mobile ions in the film. Aqueous solutions of 0.05-0.1 M alk...

  15. Resonance raman studies of phenylcyclopropane radical cations

    NARCIS (Netherlands)

    Godbout, J.T.; Zuilhof, H.; Heim, G.; Gould, I.R.; Goodman, J.L.; Dinnocenzo, J.P.; Myers Kelley, A.

    2000-01-01

    Resonance Raman spectra of the radical cations of phenylcyclopropane and trans-1-phenyl-2-methylcyclopropane are reported. A near-UV pump pulse excites a photosensitizer which oxidizes the species of interest, and a visible probe pulse delayed by 35 ns obtains the spectrum of the radical ion. The tr

  16. Anionic/cationic complexes in hair care.

    Science.gov (United States)

    O'Lenick, Tony

    2011-01-01

    The formulation of cosmetic products is always more complicated than studying the individual components in aqueous solution. This is because there are numerous interactions between the components, which make the formulation truly more than the sum of the parts. This article will look at interactions between anionic and cationic surfactants and offer insights into how to use these interactions advantageously in making formulations.

  17. FLUORESCENT OLIGONUCLEOTIDES CONTAINING A NOVEL PERYLENE 2 '-AMINO-alpha-L-LNA MONOMER: SYNTHESIS AND ANALYTICAL POTENTIAL

    DEFF Research Database (Denmark)

    Astakhova, I. V.; Kumar, T. S.; Wengel, J.

    2011-01-01

    efficiency of the resulting perylene-2'-amino-alpha-L-LNA monomer (T*) into synthetic oligonucleotides was significantly improved by replacement of the typically used 1H-tetrazole activator with pyridine hydrochloride. Generally, oligonucleotides containing monomer T* showed high binding affinity towards...

  18. Cationic lipids and cationic ligands induce DNA helix denaturation: detection of single stranded regions by KMnO4 probing.

    Science.gov (United States)

    Prasad, T K; Gopal, Vijaya; Rao, N Madhusudhana

    2003-09-25

    Cationic lipids and cationic polymers are widely used in gene delivery. Using 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) as a cationic lipid, we have investigated the stability of the DNA in DOTAP:DNA complexes by probing with potassium permanganate (KMnO4). Interestingly, thymidines followed by a purine showed higher susceptibility to cationic ligand-mediated melting. Similar studies performed with other water-soluble cationic ligands such as polylysine, protamine sulfate and polyethyleneimine also demonstrated melting of the DNA but with variations. Small cations such as spermine and spermidine and a cationic detergent, cetyl trimethylammonium bromide, also rendered the DNA susceptible to modification by KMnO4. The data presented here provide direct proof for melting of DNA upon interaction with cationic lipids. Structural changes subsequent to binding of cationic lipids/ligands to DNA may lead to instability and formation of DNA bubbles in double-stranded DNA.

  19. NMR chemical shift analysis of the conformational transition between the monomer and tetramer of melittin in an aqueous solution.

    Science.gov (United States)

    Miura, Yoshinori

    2016-05-01

    It is known that melittin in an aqueous solution undergoes a conformational transition between the monomer and tetramer by variation in temperature. The transition correlates closely with isomers of the proline residue; monomeric melittin including a trans proline peptide bond (trans-monomer) is involved directly in the transition, whereas monomeric melittin having a cis proline peptide bond (cis-monomer) is virtually not. The transition has been explored by using nuclear magnetic resonance spectroscopy in order to clarify the stability of the tetrameric conformation and the cooperativity of the transition. In the light of temperature dependence of chemical shifts of resonances from the isomeric monomers, we qualitatively estimate the temperature-, salt-, and concentration-dependence of the relative equilibrium populations of the trans-monomer and tetramer, and show that the tetramer has a maximum conformational stability at 30-45 °C and that the transition cooperativity is very low. PMID:26658745

  20. Cation-cation interactions, magnetic communication and reactivity of the pentavalent uraniumion [U(NR)2]+

    Energy Technology Data Exchange (ETDEWEB)

    Spencer, Liam P [Los Alamos National Laboratory; Schelter, Eric J [Los Alamos National Laboratory; Boncella, James M [Los Alamos National Laboratory; Yang, Ping [Los Alamos National Laboratory; Gsula, Robyn L [NON LANL; Scott, Brian L [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Kiplinger, Jacqueline L [Los Alamos National Laboratory; Batista, Enrique R [Los Alamos National Laboratory

    2009-01-01

    The dimeric bis(imido) uranium complex [{l_brace}U(NtBu)2(I)(tBu2bpy){r_brace}2] (see picture; U green, N blue, I red) has cation-cation interactions between [U(NR)2]+ ions. This f1-f1 system also displays f orbital communication between uranium(V) centers at low temperatures, and can be oxidized to generate uranium(VI) bis(imido) complexes.

  1. Synthesis of hydrophobic association cationic starch and its flocculation application on containing algae water of Dianchi Lake

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The hydrophobic formation cationic starch (PSOAMDA) was prepared from starch (St),octadecyl acrylate (OA),acrylamide (AM) and dimethyl diallyl ammonium chloride (DMDAAC) by means of inverse suspension polymerization with redox initiator.Water with algae from Dianchi Lake was tested with PSOAMDA.Results show that when the molar ratio of St:perature is 40℃ with a reaction time of 3 h,the monomer conversion yield,graft percentage and cationic degree is 92.4%,63.8% and 7.3%,respectively,and Mη=3.26 × 106 g/vmol.It had been found from the flocculation of disposed water with algae from Dianchi Lake that the transparency and COD elimination reach to 93.5%and 70.3%,respectively,with 15 mg/L PSOAMDA and at pH 6,vs.91.3% and 69.2% obtained with the commercial cationic polyacrylamide (PAM-C).When PSOAMDA dosage is 10-25 mg/L and the pH of aqueous solution is 6-10,the flocculation performance is well capable of dealing with the water with algae from Dianchi Lake.

  2. Printing continuously graded interpenetrating polymer networks of acrylate/epoxy by manipulating cationic network formation during stereolithography

    Directory of Open Access Journals (Sweden)

    W. Li

    2016-12-01

    Full Text Available Ultra-violet (UV laser assisted stereolithography is used to print graded interpenetrating polymer networks (IPNs by controlling network formation. Unlike the traditional process where structural change in IPNs is achieved by varying the feeding ratio of monomers or polymer precursors, in this demonstration property is changed by controlled termination of network formation. A photo-initiated process is used to construct IPNs by a combination of radical and cationic network formation in an acrylate/epoxy system. The extent of the cationic network formation is used to control the final properties of the system. Rapid-Scan Fourier Transformation Infrared Spectroscopy (RS-FTIR is used to track the curing kinetics of the two networks and identify key parameters to control the final properties. Atomic force microscopy (AFM and differential scanning calorimetry (DSC confirm the formation of homogenous IPNs, whereas nano-indentation indicates that properties vary with the extent of cationic network formation. The curing characteristics are used to design and demonstrate printing of graded IPNs that show two orders of magnitude variation in mechanical properties in the millimeter scale.

  3. Preparation of unsaturated acrylic prepolymer and electron beam curing of its mixture with vinyl monomers

    International Nuclear Information System (INIS)

    Electron beam curable prepolymers were prepared by the addition reaction of methyl methacrylate-glycidyl methacrylate copolymer with methacrylic acid, and electron beam curing was studied for the prepolymer and their mixtures of several kind of vinyl monomers. When the reaction was carried out in the presence of triethylbenzyl ammonium chloride in N,N-dimethyl formamide solution, the rate of addition reaction obeyed first-order kinetics. In the electron beam curing, the rate of gel formation of the prepolymer was slower than that of the mixtures of prepolymer and monomers. In the curing of mixtures of prepolymer with polyethyleneglycol dimethacrylates, the rate of gel formation increased with the increase in the degree of polymerization of polyethylene oxide fraction of polyethyleneglycol dimethacrylate, and decreased with the increase the polyethyleneglycol dimethacrylate content. The properties of cured coatings were also examined. (author)

  4. Mangrove tannins and their flavanoid monomers as alternative steel corrosion inhibitors in acidic medium

    International Nuclear Information System (INIS)

    The inhibitive behaviour on steel of flavanoid monomers that constitute mangrove tannins namely catechin, epicatechin, epigallocatechin and epicatechingallate was investigated in an aerated HCl solution via electrochemical methods. The monomers were found to be mainly cathodic inhibitors and the inhibition efficiency was dependent on concentration. To explain the adsorptive behaviour of the molecules on the steel surface, a semiempirical approach involving quantum chemical calculations using HyperChem 6.0 was undertaken. The HOMO electronic density of the molecule was used to explain the inhibiting mechanism. The most probable adsorption centers were found in the vicinity of the phenolic groups. In a second part, the use of mangrove tannin, extracted from the mangrove barks as steel corrosion inhibitors in acidic media was investigated and its inhibitive efficiency was compared with that of commercial mimosa, quebracho and chestnut tannins. The inhibitive performance of mangrove tannins was comparable to the other tannins investigated, indicating their potential in corrosion protection

  5. Investigation on Vibrational Spectra and Structures of 4-Mercaptopyridine Monomer and Its Dihydrate

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The optimized molecular structures and vibrational frequencies of 4-mercaptopyridine(4MPY) monomer and its dihydrate were studied by means of the density functional theory(DFT), viz. B3LYP method with the 6-311++G(d,p) basis set. On the basis of the calculations, the assignments of the vibrational spectra of the monomer and the dihydrate were performed, and so were investigated the changes in the structure and the vibrational spectrum of the dihydrate as well as the intermolecular force resulting in the formation of the dihydrate. The calculated results show that each of the water molecule planes is vertical to the pyridine ring plane in the dihydrate that is formed via the H-bonds between 4MPY and water molecules. Furthermore, the structure and the vibrational spectrum of 4MPY can be consi-derably affected by the water molecules.

  6. Water adsorption on the Be(0001) surface:from monomer to trimer adsorption

    Institute of Scientific and Technical Information of China (English)

    Ning Hua; Tao Xiang-Ming; Tan Ming-Qiu

    2012-01-01

    In this paper,the density functional theory has been used to perform a comparative theoretical study of water monomer,dimer,trimer,and bilayer adsorptions on the Be(0001) surface. In our calculations,the adsorbed water molecules are energetically favoured adsorbed on the atop sites,and the dimer adsorption is found to be the most stable with a peak adsorption energy of ~ 437 meV.Further analyses have revealed that the essential bonding interaction between the water monomer and the metal substrate is the hybridization of the water 3a1-like molecular orbital with the (s,pz) orbitals of the surface beryllium atoms.While in the case of the water dimer adsorption,the lb1-like orbital of the H2O molecule plays a dominant role.

  7. Gelcasting of Alumina with Application of New Monomer Synthesised from Xylitol

    Directory of Open Access Journals (Sweden)

    Szudarska A.

    2013-12-01

    Full Text Available Podążając za trendem „zielonej chemii", zakładającym m.in. wykorzystywanie nietoksycznych i odnawialnych surowców w technologii, zaprojektowano i zsyntezowano nowy monomer przeznaczony do zastosowania w procesie odlewania żelowego. Wyjściowym substratem trójetapowej syntezy był ksyłitol, a finalnym produktem 1-O-akryloiloksylitol. Otrzymana pochodna została sprawdzona pod względem efektywności polimeryzacji in situ w ceramicznej masie lejnej na bazie tlenku glinu. Zbadano jej wpływ na właściwości neologiczne stosowanych zawiesin. Odlano serie kształtek, dla których wyznaczono podstawowe parametry w stanie surowym oraz p|j spiekaniu. Wyniki porównano stosując równolegle komercyjnie dostępny monomer akrylan 2-hydroksyetylu.

  8. A cleaner two-step synthesis of high purity diallyldimethylammonium chloride monomers for flocculant preparation

    Institute of Scientific and Technical Information of China (English)

    TIAN Bing-hui; FAN Bin; PENG Xian-jia; LUAN Zhao-kun

    2005-01-01

    In order to improve the flocculation efficiency of polydiallyldimethylammonium chloride (PDADMAC), high molecular weight PDADMAC should be prepared from high purity diallyldimethylammonium chloride(DADMAC) monomers. In this paper, a cleaner method with microwave irradiation and alkali solidification was proposed for preparing high pure DADMAC by selective heating under low temperature, and the prepared high purity DADMAC is characterized using FTIR and atomic absorption spectrometry. The new method provides a solution to the key technical problem of PDADMAC synthesis. Comparing with the conventional methods, the results showed that the advantages of the novel synthesis include: (a) high purity DADMAC is improved from 57% to 71%; (b) reaction time of tertiary amine preparation is shortened from 6 h to 7 min; (c) water instead of acetone was used as reaction medium; (d) toxic by-products,wastewater and waste gas are eliminated. Flocculant made from the synthesized high purity DADMAC monomers was proved more efficient in flocculation tests.

  9. NGAL (Lcn2) monomer is associated with tubulointerstitial damage in chronic kidney disease.

    Science.gov (United States)

    Nickolas, Thomas L; Forster, Catherine S; Sise, Meghan E; Barasch, Nicholas; Solá-Del Valle, David; Viltard, Melanie; Buchen, Charles; Kupferman, Shlomo; Carnevali, Maria Luisa; Bennett, Michael; Mattei, Silvia; Bovino, Achiropita; Argentiero, Lucia; Magnano, Andrea; Devarajan, Prasad; Mori, Kiyoshi; Erdjument-Bromage, Hediye; Tempst, Paul; Allegri, Landino; Barasch, Jonathan

    2012-09-01

    The type and the extent of tissue damage inform the prognosis of chronic kidney disease (CKD), but kidney biopsy is not a routine test. Urinary tests that correlate with specific histological findings might serve as surrogates for the kidney biopsy. We used immunoblots and ARCHITECT-NGAL assays to define the immunoreactivity of urinary neutrophil gelatinase-associated lipocalin (NGAL) in CKD, and we used mass spectroscopy to identify associated proteins. We analyzed kidney biopsies to determine whether specific pathological characteristics associated with the monomeric NGAL species. Advanced CKD urine contained the NGAL monomer as well as novel complexes of NGAL. When these species were separated, we found a significant correlation between the NGAL monomer and glomerular filtration rate (r=-0.53, Phistology that typifies progressive, severe CKD.

  10. Mangrove tannins and their flavanoid monomers as alternative steel corrosion inhibitors in acidic medium

    Energy Technology Data Exchange (ETDEWEB)

    Rahim, Afidah A. [School of Chemical Sciences, University Sains Malaysia, 11800 Penang (Malaysia)]. E-mail: afidah@usm.my; Rocca, E. [Laboratoire de Chimie du Solide Mineral, Universite Henri Poincare, Nancy I BP 239, 54506 Vandoeuvre Les Nancy (France); Steinmetz, J. [Laboratoire de Chimie du Solide Mineral, Universite Henri Poincare, Nancy I BP 239, 54506 Vandoeuvre Les Nancy (France); Kassim, M.J. [School of Chemical Sciences, University Sains Malaysia, 11800 Penang (Malaysia); Adnan, R. [School of Chemical Sciences, University Sains Malaysia, 11800 Penang (Malaysia); Sani Ibrahim, M. [School of Chemical Sciences, University Sains Malaysia, 11800 Penang (Malaysia)

    2007-02-15

    The inhibitive behaviour on steel of flavanoid monomers that constitute mangrove tannins namely catechin, epicatechin, epigallocatechin and epicatechingallate was investigated in an aerated HCl solution via electrochemical methods. The monomers were found to be mainly cathodic inhibitors and the inhibition efficiency was dependent on concentration. To explain the adsorptive behaviour of the molecules on the steel surface, a semiempirical approach involving quantum chemical calculations using HyperChem 6.0 was undertaken. The HOMO electronic density of the molecule was used to explain the inhibiting mechanism. The most probable adsorption centers were found in the vicinity of the phenolic groups. In a second part, the use of mangrove tannin, extracted from the mangrove barks as steel corrosion inhibitors in acidic media was investigated and its inhibitive efficiency was compared with that of commercial mimosa, quebracho and chestnut tannins. The inhibitive performance of mangrove tannins was comparable to the other tannins investigated, indicating their potential in corrosion protection.

  11. A cleaner two-step synthesis of high purity diallyldimethylammonium chloride monomers for flocculant preparation.

    Science.gov (United States)

    Tian, Bing-hui; Fan, Bin; Peng, Xian-jia; Luan, Zhao-kun

    2005-01-01

    In order to improve the flocculation efficiency of polydiallyldimethylammonium chloride (PDADMAC), high molecular weight PDADMAC should be prepared from high purity diallyldimethylammonium chloride(DADMAC) monomers. In this paper, a cleaner method with microwave irradiation and alkali solidification was proposed for preparing high pure DADMAC by selective heating under low temperature, and the prepared high purity DADMAC is characterized using FTIR and atomic absorption spectrometry. The new method provides a solution to the key technical problem of PDADMAC synthesis. Comparing with the conventional methods, the results showed that the advantages of the novel synthesis include: (a) high purity DADMAC is improved from 57% to 71%; (b) reaction time of tertiary amine preparation is shortened from 6 h to 7 min; (c) water instead of acetone was used as reaction medium; (d) toxic by-products, wastewater and waste gas are eliminated. Flocculant made from the synthesized high purity DADMAC monomers was proved more efficient in flocculation tests. PMID:16313006

  12. Ferroelectric liquid-crystalline side group polymers - spacer length variation and comparison with the monomers

    OpenAIRE

    Kühnpast, Kurt; Springer, Jürgen; Scherowsky, Günter; Gießelmann, Frank; Zugenmaier, Peter

    1993-01-01

    The phase behaviour and the ferroelectric properties of liquid-crystalline side group polyacrylates containing an (R)-4''(1-methylheptyloxy)-4'-biphenylyloxycarbonyl-4-phenoxy moiety are compared with the properties of their monomers. A S*C phase polymorphism including monolayer and bilayer structures was found for the polymers. Some of the S*C subphases, consisting of smectic mono- or bi-layers, do not exhibit ferroelectric properties. These unusual properties do not exist for the correspond...

  13. Vegetable oil-derived epoxy monomers and polymer blends: A comparative study with review

    OpenAIRE

    T. P. Schuman; Wang, R.

    2013-01-01

    Glycidyl esters of epoxidized fatty acids derived from soybean oil (EGS) and linseed oil (EGL) have been synthesized to have higher oxirane content, more reactivity and lower viscosity than epoxidized soybean oil (ESO) or epoxidized linseed oil (ELO). The EGS and ESO, for comparison, were used neat and in blends with diglycidyl ether of bisphenol A (DGEBA). Thermosetting resins were fabricated with the epoxy monomers and either BF3 catalyst or anhydride. The curing behaviors, glass transition...

  14. Inclusion polymerization of vinyl chloride monomer in deoxycholic acid host via {gamma}-ray irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Chirachanchai, S.; Kumkrong, A. [The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok (Thailand); Ishida, Hatsuo [Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH (United States)

    2000-03-01

    Inclusion polymerization of vinyl chloride monomer (VCM) was studied in the system of 3{alpha}, 12{alpha} -dihydroxy-5{beta}-cholan-24-oic acid (deoxycholic acid, DCA). DCA-VCM inclusion compound system was originally prepared by guest intercalation technique in DCA guest free crystal. The inclusion polymerization of DCA-VCM by {gamma}-irradiation at total dose 2 Mrad, gives a syndiotactic rich polyvinyl chloride (PVC) as can be confirmed by FT-IR and FT-NMR. (author)

  15. Total sulphate vs. sulphuric acid monomer in nucleation studies: which represents the "true" concentration?

    OpenAIRE

    K. Neitola; Brus, D.; Makkonen, U.; Sipilä, M.; R. L. Mauldin III; K. Kyllönen; Lihavainen, H.; M. Kulmala

    2013-01-01

    Sulphuric acid is known to be a key component for atmospheric nucleation. Precise determination of sulphuric acid concentration is crucial factor for prediction of nucleation rates and subsequent growth. In our study, we have noticed a substantial discrepancy between sulphuric acid monomer and total sulphate concentrations measured from the same source of sulphuric acid vapour. The discrepancy of about one to two orders of magnitude was found with similar formation rates....

  16. A clue for unusual metallic aggregates with monomers in the nanometer scale

    Energy Technology Data Exchange (ETDEWEB)

    Laliberte, Maryse; Boisjoli, Andreanne; Rioux, Claude; Leclerc, Jean-Claude; Piche, Michel; Slobodrian, R.J. E-mail: rjslobod@phy.ulaval.ca

    2004-11-01

    Laser evaporation of metals followed by condensation within an inert gas has yielded monomers in the nanometer range aggregated in a complex cobweb like pattern, quite unusual when compared with the results obtained via ohmic heating. The latter correspond to isolated fractal structures well reproduced by diffusion limited aggregation models. A multiple aggregation model appears to provide a clue to the understanding of the observations reported here.

  17. An ionic force-field study of monomers, dimers and higher polymers in pentafluoride vapors

    Energy Technology Data Exchange (ETDEWEB)

    Cicek Onem, Z. [Department of Physics, Istanbul University, Istanbul (Turkey); Akdeniz, Z. [Department of Physics, Istanbul University, Istanbul (Turkey); Classe di Scienze, Scuola Normale Superiore, I-56126 Pisa (Italy)], E-mail: zakdeniz@istanbul.edu.tr; Tosi, M.P. [Classe di Scienze, Scuola Normale Superiore, I-56126 Pisa (Italy)], E-mail: tosim@sns.it

    2008-08-01

    Pentafluoride compounds such as NbF{sub 5} and TaF{sub 5} have been reported in the literature to admit various states of polymerization coexisting with monomers in their vapor phase, in relative concentrations that vary with temperature and pressure. We construct a microscopic interionic force-field model for the molecular monomer of these compounds (including VF{sub 5}, SbF{sub 5} and MoF{sub 5} in addition to NbF{sub 5} and TaF{sub 5}), the stable form of the monomer being in the shape of a D{sub 3h} trigonal bipyramid in all cases. The model emulates chemical bonds by allowing for electrical and short-range overlap polarizabilities of the fluorines, and is used to evaluate the structure and the stability of (MF{sub 5}){sub n} molecules with n running from 2 to 6. The dimer is formed by two distorted edge-sharing octahedral, while the trimer and the higher polymers can form rings of distorted corner-sharing octahedra. A chain-like configuration is also found for the trimer of NbF{sub 5}, which consists of a seven-fold coordinated Nb bonded to two distorted octahedra via edge sharing. Comparison of calculated vibrational frequencies and bond lengths with experimental data is made whenever possible. We find that there is a small net gain of energy in the formation of a dimer, while otherwise the static energy of the n-mer is very close to that of n separated monomers. High sensitivity of the state of molecular aggregation to the thermodynamic conditions of the vapor is clearly indicated by our calculations.

  18. Hemoglobin-imprinted polymer gel prepared using modified glucosamine as functional monomer

    Institute of Scientific and Technical Information of China (English)

    Hai Li Zhao; Tian Ying Guo; Yong Qing Xia; Mou Dao Song

    2008-01-01

    A new functional glycomonomer was obtained from modified glucosamine.Hemoglobin-imprinted polymer gel was prepared with allyl-bromide modified glucosamine as functional monomer,poly(ethylene-glycol)diaorylate(PEGDA)as cross-linker and ammonium persulfate[(NH4)2S2O8]/sodium hydrogen sulfite(NaHSO3)as initiators in a phosphate buffer.The adsorption capacity and selective adsorption of the molecular imprinting polymer(MIP)were also discussed.

  19. Papain-Catalyzed Synthesis of Polyglutamate Containing a Nylon Monomer Unit

    OpenAIRE

    Kenjiro Yazawa; Keiji Numata

    2016-01-01

    Peptides have the potential to serve as an alternative for petroleum-based polymers to support a sustainable society. However, they lack thermoplasticity, owing to their strong intermolecular interactions. In contrast, nylon is famous for its thermoplasticity and chemical resistance. Here, we synthesized peptides containing a nylon unit to modify their thermal properties by using papain-catalyzed chemoenzymatic polymerization. We used l-glutamic acid alkyl ester as the amino acid monomer and ...

  20. Enhanced lignin monomer production caused by cinnamic Acid and its hydroxylated derivatives inhibits soybean root growth.

    Directory of Open Access Journals (Sweden)

    Rogério Barbosa Lima

    Full Text Available Cinnamic acid and its hydroxylated derivatives (p-coumaric, caffeic, ferulic and sinapic acids are known allelochemicals that affect the seed germination and root growth of many plant species. Recent studies have indicated that the reduction of root growth by these allelochemicals is associated with premature cell wall lignification. We hypothesized that an influx of these compounds into the phenylpropanoid pathway increases the lignin monomer content and reduces the root growth. To confirm this hypothesis, we evaluated the effects of cinnamic, p-coumaric, caffeic, ferulic and sinapic acids on soybean root growth, lignin and the composition of p-hydroxyphenyl (H, guaiacyl (G and syringyl (S monomers. To this end, three-day-old seedlings were cultivated in nutrient solution with or without allelochemical (or selective enzymatic inhibitors of the phenylpropanoid pathway in a growth chamber for 24 h. In general, the results showed that 1 cinnamic, p-coumaric, caffeic and ferulic acids reduced root growth and increased lignin content; 2 cinnamic and p-coumaric acids increased p-hydroxyphenyl (H monomer content, whereas p-coumaric, caffeic and ferulic acids increased guaiacyl (G content, and sinapic acid increased sinapyl (S content; 3 when applied in conjunction with piperonylic acid (PIP, an inhibitor of the cinnamate 4-hydroxylase, C4H, cinnamic acid reduced H, G and S contents; and 4 when applied in conjunction with 3,4-(methylenedioxycinnamic acid (MDCA, an inhibitor of the 4-coumarate:CoA ligase, 4CL, p-coumaric acid reduced H, G and S contents, whereas caffeic, ferulic and sinapic acids reduced G and S contents. These results confirm our hypothesis that exogenously applied allelochemicals are channeled into the phenylpropanoid pathway causing excessive production of lignin and its main monomers. By consequence, an enhanced stiffening of the cell wall restricts soybean root growth.

  1. Structurally Distinct Cation Channelrhodopsins from Cryptophyte Algae.

    Science.gov (United States)

    Govorunova, Elena G; Sineshchekov, Oleg A; Spudich, John L

    2016-06-01

    Microbial rhodopsins are remarkable for the diversity of their functional mechanisms based on the same protein scaffold. A class of rhodopsins from cryptophyte algae show close sequence homology with haloarchaeal rhodopsin proton pumps rather than with previously known channelrhodopsins from chlorophyte (green) algae. In particular, both aspartate residues that occupy the positions of the chromophore Schiff base proton acceptor and donor, a hallmark of rhodopsin proton pumps, are conserved in these cryptophyte proteins. We expressed the corresponding polynucleotides in human embryonic kidney (HEK293) cells and studied electrogenic properties of the encoded proteins with whole-cell patch-clamp recording. Despite their lack of residues characteristic of the chlorophyte cation channels, these proteins are cation-conducting channelrhodopsins that carry out light-gated passive transport of Na(+) and H(+). These findings show that channel function in rhodopsins has evolved via multiple routes. PMID:27233115

  2. Radiation chemistry of aromatic dimer radical cations

    International Nuclear Information System (INIS)

    π-π Interactions of aromatic molecules are paid attention much in many fields, especially biology, chemistry, and applied physics, represented as protein, DNA, electron donor-accepter complexes, charge transfers, and self assembly molecules. Aromatic molecules including benzene rings are the simplest case to study the π-π interactions. To interpret the charge resonance (CR) structure in the dimer radical cations, spectroscopic and ESR methods have been carried out. The spectroscopic study on the dimer radical ion of molecules with two chromophores would be profitable to identify the electronic and configurational properties. In this article, dynamics of the dimer radical cation of benzenes, polystyrenes, and resist polymers is described on the basis of direct observation of CR band by the nanosecond pulse radiolysis and low temperature γ-radiolysis methods. (author)

  3. Poly-amido-saccharides: synthesis via anionic polymerization of a β-lactam sugar monomer.

    Science.gov (United States)

    Dane, Eric L; Grinstaff, Mark W

    2012-10-01

    Enantiopure poly-amido-saccharides (PASs) with a defined molecular weight and narrow dispersity are synthesized using an anionic ring-opening polymerization of a β-lactam sugar monomer. The PASs have a previously unreported main chain structure that is composed of pyranose rings linked through the 1- and 2-positions by an amide with α-stereochemistry. The monomer is synthesized in one-step from benzyl-protected D-glucal and polymerized using mild reaction conditions to give degrees of polymerization ranging from 25 to >120 in high yield. Computational modeling reveals how the monomer's structure and steric bulk affect the thermodynamics and kinetics of polymerization. Protected and deprotected polymers and model compounds are characterized using a variety of methods (NMR, GPC, IR, DLS, etc.). On the basis of circular dichroism, the deprotected polymer possesses a regular secondary structure in aqueous solution, which agrees favorably with the prediction of a helical structure using molecular modeling. Furthermore, we provide evidence suggesting that the polymers bind the lectin concanavalin A at the same site as natural carbohydrates, showing the potential of these polymers to mimic natural polysaccharides. PASs offer the advantages associated with synthetic polymers, such as greater control over structure and derivitization. At the same time, they preserve many of the structural features of natural polysaccharides, such as a stereochemically regular, rigid pyranose backbone, that make natural carbohydrate polymers important materials both for their unique properties and useful applications.

  4. Enzymatic aryl-O-methyl-14C labeling of model lignin monomers

    International Nuclear Information System (INIS)

    Aryl-O-methyl ethers are abundant in aerobic and anaerobic environments. In particular, lignin is composed of units of this type. Lignin monomers specifically radiolabeled in methoxy, side chain, and ring carbons have been synthesized by chemical procedures and are important in studies of lignin synthesis and degradation, humus formation, and microbial O-demethylation. In this paper attention is drawn to an enzymatic procedure for preparing O-methyl-14C-labeled aromatic lignin monomers which has not previously been exploited in microbial ecology and physiology studies and which has several advantages compared with chemical synthesis procedures. O-[methyl-14C]vanillic and O-[methyl-14C]ferulic acids were prepared with S-[methyl-14C]adenosyl-L-methionine as the methyl donor, using commercially obtained porcine liver catechol-O-methyltransferase (EC 2.1.1.6). The specific activity of the methylated products was the same as that of the methyl donor, a maximum of about 58 μCi/μmol, and the yields were 42% (vanillate) and 35% (ferulate). Thus lignin monomers are readily prepared as O-methylated products of the catechol-O-methyltransferase reaction and, with this enzyme method of preparation, would be more widely available than labeled compounds which require chemical synthesis

  5. Permeability of different types of medical protective gloves to acrylic monomers.

    Science.gov (United States)

    Lönnroth, Emma-Christin; Wellendorf, Hanne; Ruyter, Eystein

    2003-10-01

    Dental personnel and orthopedic surgeons are at risk when manually handling products containing methyl methacrylate (MMA). Dental products may also contain cross-linking agents such as ethylene glycol dimethacrylate (EGDMA) or 1,4-butanediol dimethacrylate (1,4-BDMA). Skin contact with monomers can cause hand eczema, and the protection given by gloves manufactured from different types of material is not well known. The aim of this study was to determine the breakthrough time (BTT, min) as a measure of protection (according to the EU standard EN-374-3) for a mixture consisting of MMA, EGDMA and 1,4-BDMA. Fifteen different gloves representing natural rubber latex material, synthetic rubber material (e.g. nitrile rubbers), and synthetic polymer material were tested. The smallest monomer MMA permeated within 3 min through all glove materials. A polyethylene examination glove provided the longest protection period to EGDMA and 1, 4-BDMA (> 120 min and 25.0 min), followed by the surgical glove Tactylon (6.0 min and 8.7 min) and the nitrile glove Nitra Touch (5.0 min and 8.7 min). This study showed that the breakthrough time (based on permeation rate) cannot be regarded as a 'safe limit'. When the permeation rate is low, monomers may have permeated before BTT can be determined. Using double gloves with a synthetic rubber inner glove and a natural rubber outer glove provided longer protection when the inner glove was rinsed in water before placing the outer glove on top.

  6. Modification of polyethersulfone films by grafting hydrophilic monomers with 60Co γ-rays

    International Nuclear Information System (INIS)

    Polyethersulfone (PES), with its high strength, high temperature resistance, corrosion- resistance, oxidation resistance and applicability under wide pH range, is used extensively as ultrafiltration and nanofiltration membrane. However, PES membranes foul easily in such an application because of hydrophobic nature of PES raw materials. Improving the hydrophilicity of PES by grafting hydrophilic monomers onto it is of potential to solve the problem. At present, common approaches to improve hydrophilicity of PES membranes are UV grafting modification, plasma modification, and chemical modification, whereas grafting and modifying PES films by 60Co γ-rays has rarely been reported. Studies have been carried out in our laboratory to graft hydrophilic monomers onto PES membranes directly or PES powders via simultaneous radiation grafting with the rays. Acrylic acid, methyl acrylic acid or acrylamide was used to study effects of the monomer concentration, irradiation dose and dose rate, solvent, inhibitor and pH of the grafting solution on the degree of grafting. The results showed that hydrophilicity of all the PES membranes could be improved, with the extent of improvement being dependent on the grafting conditions. (authors)

  7. Sequence Analysis of Trimer Isomers Formed by Montmorillonite Catalysis in the Reaction of Binary Monomer Mixtures

    Science.gov (United States)

    Ertem, Gözen; Hazen, Robert M.; Dworkin, Jason P.

    2007-10-01

    Oligonucleotides are structurally similar to short RNA strands. Therefore, their formation via non-enzymatic reactions is highly relevant to Gilbert's RNA world scenario (1986) and the origin of life. In laboratory synthesis of oligonucleotides from monomers, it is necessary to remove the water molecules from the reaction medium to shift the equilibrium in favor of oligonucleotide formation, which would have been impossible for reactions that took place in dilute solutions on the early Earth. Model studies designed to address this problem demonstrate that montmorillonite, a phyllosilicate common on Earth and identified on Mars, efficiently catalyzes phosphodiester-bond formation between activated mononucleotides in dilute solutions and produces RNA-like oligomers. The purpose of this study was to examine the sequences and regiospecificity of trimer isomers formed in the reaction of 5'-phosphorimidazolides of adenosine and uridine. Results demonstrated that regiospecificity and sequence specificity observed in the dimer fractions are conserved in their elongation products. With regard to regiospecificity, 61% of the linkages were found to be RNA-like 3',5'-phosphodiester bonds. With regard to sequence specificity, we found that 88% of the linear trimers were hetero-isomers with 61% A-monomer and 39% U-monomer incorporation. These results lend support to Bernal's hypothesis that minerals may have played a significant role in the chemical processes that led to the origin of life by catalyzing the formation of phosphodiester bonds in RNA-like oligomers.

  8. Synthesis and characterization of copolymers from hindered amines and vinyl monomers

    Directory of Open Access Journals (Sweden)

    Marcelo Aparecido Chinelatto

    2014-01-01

    Full Text Available New copolymers from hindered amines and vinyl monomers were synthesized by radical chain polymerization. To obtain polymeric HALS, acrylamide-(1ATP and acrylate-(4ATP monomers, derivatives from 2,2,6,6-tetramethylpiperidine and 2,2,6,6-tetramethyl-4-piperidinol were synthesized. The radical chain polymerization of 1ATP with styrene (Sty using 1-butanethiol (BTN resulted in a copolymer with 95 units of Sty and 15 units of 1ATP. The radical chain polymerization of 1ATP and vinyl acetate (VAc has produced only 1ATP homopolymer. In the chain polymerization of 4ATP with Sty or VAc, the hydrogen atom bonded to the nitrogen of 4ATP is labile enough to originate another radical at this site. The steric hindrance imposed by methyl groups on this bonding site hampers its reaction with other propagating species and the formation of a copolymer or network structure will be dependent on the size of the pendent group in the vinyl monomer.

  9. Wire and extended ladder model predict THz oscillations in DNA monomers, dimers and trimers

    CERN Document Server

    Lambropoulos, K; Morphis, A; Tassi, M; Lopp, R; Georgiadis, G; Theodorakou, M; Chatzieleftheriou, M; Simserides, C

    2016-01-01

    We call \\textit{monomer} a B-DNA base pair and study, analytically and numerically, electron or hole oscillations in \\textit{monomers}, \\textit{dimers} and \\textit{trimers}. We employ two Tight Binding (TB) approaches: (I) at the base-pair level, using the on-site energies of the base pairs and the hopping parameters between successive base pairs i.e. \\textit{a wire model}, and (II) at the single-base level, using the on-site energies of the bases and the hopping parameters between neighbouring bases, specifically between (a) two successive bases in the same strand, (b) complementary bases that define a base pair, and (c) diagonally located bases of successive base pairs, i.e. \\textit{an extended ladder model} since it also includes the diagonal hoppings (c). For \\textit{monomers}, with TB II, we predict periodic carrier oscillations with frequency $f \\approx$ 50-550 THz. For \\textit{dimers}, with TB I, we predict periodic carrier oscillations with $f \\approx$ 0.25-100 THz. For \\textit{trimers made of identic...

  10. Alkaline earth cation extraction from acid solution

    Science.gov (United States)

    Dietz, Mark; Horwitz, E. Philip

    2003-01-01

    An extractant medium for extracting alkaline earth cations from an aqueous acidic sample solution is described as are a method and apparatus for using the same. The separation medium is free of diluent, free-flowing and particulate, and comprises a Crown ether that is a 4,4'(5')[C.sub.4 -C.sub.8 -alkylcyclohexano]18-Crown-6 dispersed on an inert substrate material.

  11. Cation Permeability in Soybean Aleurone Layer

    OpenAIRE

    Noda, Hiroko; Fukuda, Mitsuru

    1998-01-01

    The permeation of water and ions into bean seeds is essential for processing and cooking of beans. The permeability of cations, K, Na, Ca, and Mg ions, into soybean seed tissue, especially aleurone layer, during water uptake was investigated to characterize the ion permeation into soybeans. Aleurone layers and seed coats contained relatively high concentration of endogenous K and Ca ions, and endogenous Ca ion, respectively. The amounts of Ca ion entered seed coats and aleurone layers were gr...

  12. Low cation coordination in oxide melts

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, Lawrie [State University of New York, Stony Brook; Benmore, Chris J [Argonne National Laboratory (ANL); Du, Jincheng [University of North Texas; Weber, Richard [Argonne National Laboratory (ANL); Neuefeind, Joerg C [ORNL; Tumber, Sonia [Materials Development, Inc., Evanston, IL; Parise, John B [Stony Brook University (SUNY)

    2014-01-01

    The complete set of Faber-Ziman partial pair distribution functions for a rare earth oxide liquid were measured for the first time by combining aerodynamic levitation, neutron diffraction, high energy x-ray diffraction and isomorphic substitution using Y2 O3 and Ho2 O3 melts. The average Y- O coordination is measured to be 5.5(2), which is significantly less than the octahedral coordination of crystalline Y2 O3 (or Ho2 O3 ). Investigation of high temperature La2 O3 , ZrO2 , SiO2 , and Al2 O3 melts by x-ray diffraction and molecular dynamics simulations also show lower-than-crystal cation- oxygen coordination. These measurements suggest a general trend towards lower M-O coordination compared to their crystalline counterparts. It is found that this coordination number drop is larger for lower field strength, larger radius cations and is negligible for high field strength (network forming) cations. These findings have broad implications for predicting the local structure and related physical properties of metal-oxide melts and oxide glasses.

  13. Low Cation Coordination in Oxide Melts

    Science.gov (United States)

    Skinner, L. B.; Benmore, C. J.; Weber, J. K. R.; Du, J.; Neuefeind, J.; Tumber, S. K.; Parise, J. B.

    2014-04-01

    The complete set of partial pair distribution functions for a rare earth oxide liquid are measured by combining aerodynamic levitation, neutron and x-ray diffraction on Y2O3, and Ho2O3 melts at 2870 K. The average Y-O (or Ho-O) coordination of these isomorphic melts is measured to be 5.5(2), which is significantly less than the octahedral coordination of crystalline Y2O3 (or Ho2O3). Investigation of La2O3, ZrO2, and Al2O3 melts by x-ray diffraction and molecular dynamics simulations also show lower-than-crystal cation-oxygen coordination. These measurements suggest a general trend towards lower coordination compared to their crystalline counterparts. It is found that the coordination drop is larger for lower field strength, larger radius cations and is negligible for high field strength (network forming) cations, such as SiO2. These findings have broad implications for predicting the local structure and related physical properties of metal-oxide melts and oxide glasses.

  14. Limited data speaker identification

    Indian Academy of Sciences (India)

    H S Jayanna; S R Mahadeva Prasanna

    2010-10-01

    In this paper, the task of identifying the speaker using limited training and testing data is addressed. Speaker identification system is viewed as four stages namely, analysis, feature extraction, modelling and testing. The speaker identification performance depends on the techniques employed in these stages. As demonstrated by different experiments, in case of limited training and testing data condition, owing to less data, existing techniques in each stage will not provide good performance. This work demonstrates the following: multiple frame size and rate (MFSR) analysis provides improvement in the analysis stage, combination of mel frequency cepstral coefficients (MFCC), its temporal derivatives $(\\Delta,\\Delta \\Delta)$, linear prediction residual (LPR) and linear prediction residual phase (LPRP) features provides improvement in the feature extraction stage and combination of learning vector quantization (LVQ) and gaussian mixture model – universal background model (GMM–UBM) provides improvement in the modelling stage. The performance is further improved by integrating the proposed techniques at the respective stages and combining the evidences from them at the testing stage. To achieve this, we propose strength voting (SV), weighted borda count (WBC) and supporting systems (SS) as combining methods at the abstract, rank and measurement levels, respectively. Finally, the proposed hierarchical combination (HC) method integrating these three methods provides significant improvement in the performance. Based on these explorations, this work proposes a scheme for speaker identification under limited training and testing data.

  15. A Protons Exchanged Montmorillonite Clay as an Efficient Catalyst for the Reaction of Isobutylene Polymerization

    OpenAIRE

    Mohammed Belbachir; Rachid Meghabar; Amine Harrane

    2002-01-01

    Abstract: “Maghnite†a montmorillonite sheet silicate clay, exchanged with protons to produce “H-Maghnite†is an efficient catalyst for cationic polymerization of many vinylic and heterocyclic monomers (Belbachir, M. U.S. Patent. 066969.0101 –2001). The structure compositions of both “Maghnite†and “H-Maghnite†have been developed. Isobutylene monomer, wich is polymerizable only by cationic process (Odian,G. La Polymerisation :principes et Applications...

  16. An Acid Exchanged Montmorillonite Clay-Catalyzed Synthesis of Polyepichlorhydrin

    OpenAIRE

    Ahmed Yahiaoui; Mohammed Belbachir; Aïcha Hachemaoui

    2003-01-01

    “Maghniteâ€Â, a montmorillonite sheet silicate clay, exchanged with protons to produce “H-Maghnite†is an efficient catalyst for cationic polymerisation of many heterocyclic and vinylic monomers (Belbachir, M. U.S. Patent. 066969.0101 –2001). The structural compositions of both “Maghnite†and “H-Maghnite†have already been determined. Epichlorhydrin monomer, which is polymerizable by a cationic process (Odian,G. La Polymerisation: Principes et Applicatio...

  17. Solution NMR characterization of WT CXCL8 monomer and dimer binding to CXCR1 N-terminal domain

    OpenAIRE

    Joseph, Prem Raj B.; Rajarathnam, Krishna

    2014-01-01

    Chemokine CXCL8 and its receptor CXCR1 are key mediators in combating infection and have also been implicated in the pathophysiology of various diseases including chronic obstructive pulmonary disease (COPD) and cancer. CXCL8 exists as monomers and dimers but monomer alone binds CXCR1 with high affinity. CXCL8 function involves binding two distinct CXCR1 sites – the N-terminal domain (Site-I) and the extracellular/transmembrane domain (Site-II). Therefore, higher monomer affinity could be due...

  18. Alkali cation specific adsorption onto fcc(111) transition metal electrodes.

    Science.gov (United States)

    Mills, J N; McCrum, I T; Janik, M J

    2014-07-21

    The presence of alkali cations in electrolyte solutions is known to impact the rate of electrocatalytic reactions, though the mechanism of such impact is not conclusively determined. We use density functional theory (DFT) to examine the specific adsorption of alkali cations to fcc(111) electrode surfaces, as specific adsorption may block catalyst sites or otherwise impact surface catalytic chemistry. Solvation of the cation-metal surface structure was investigated using explicit water models. Computed equilibrium potentials for alkali cation adsorption suggest that alkali and alkaline earth cations will specifically adsorb onto Pt(111) and Pd(111) surfaces in the potential range of hydrogen oxidation and hydrogen evolution catalysis in alkaline solutions.

  19. Studies on a Cationically Modified Quaternary Ammonium Salt of Lignin

    Institute of Scientific and Technical Information of China (English)

    YANG Ai-li; JIANG Wen-ju

    2007-01-01

    A new quaternary ammonium salt monomer was synthesized and a quaternary amination of lignin( noted as QL),with the monomer was carried out by grafting copolymerization. The products were characterized by Fourier Transform Infrared spectroscopy(FTIR). The experimental results indicate that the yield of the monomer was 99.06%, and the conversion of the monomer and the grafting yield of QL were 93.69% and 185.78%, respectively. The feasibility of QL as the fiocculant to be applied in color removal of five artificial dyes, eriochrome black T( dye A), gongo red( dye B), direct fast black G (dye C), cuprofix blue green B (dye D), and acid black ATT (dye E) was examined.Results show that QL exhibits the favorable flocculation performance and high stability.

  20. Synthesis and Characterization of Poly(α-Methylstyrene by Cationic Polymerization Using a New Solid Ecological Catalyst

    Directory of Open Access Journals (Sweden)

    Moulkheir Ayat

    2015-12-01

    Full Text Available The cationic polymerization of α-methylstyrene (AMS is examined at 0°C in bulk and in solution in heterogenous phase using Maghnite-Na as a new solid ecological and efficient catalyst. Maghnite-Na is Algerian Montmorillonite sheet silicate clay, exchanged with sodium. Poly (α-methylstyrene (PAMS have been successfully prepared and characterized by differents techniques, such as, 1H NMR, 13C NMR, IR and DSC. The structural characteristics and thermal properties of the resulting polymers are elucidated. The influences of reaction temperature, initiator/monomer weight ratio and reaction time on the yields and the molecular weights are investigated. A mechanism for the reaction was proposed.

  1. Pseudomonas putida KT2442 cultivated on glucose accumulates poly(3-hydroxyalkanoates) consisting of saturated and unsaturated monomers.

    OpenAIRE

    Huijberts, G N; Eggink, G.; Waard, P. de; Huisman, G W; Witholt, B

    1992-01-01

    The biosynthesis of poly(3-hydroxyalkanoates) (PHAs) by Pseudomonas putida KT2442 during growth on carbohydrates was studied. PHAs isolated from P. putida cultivated on glucose, fructose, and glycerol were found to have a very similar monomer composition. In addition to the major constituent 3-hydroxydecanoate, six other monomers were found to be present: 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydodecanoate, 3-hydroxydodecenoate, 3-hydroxytetradecanoate, and 3-hydroxytetradecenoate. T...

  2. Aggregate Formed by a Cationic Fluorescence Probe

    Institute of Scientific and Technical Information of China (English)

    TIAN, Juan; SANG, Da-Yong; JI, Guo-Zhen

    2007-01-01

    The aggregation behavior of a cationic fluorescence probe 10-(4,7,10,13,16-pentaoxa-1-azacyclooctadecyl-methyl)anthracen-9-ylmethyl dodecanoate (1) was observed and studied by a fluorescence methodology in acidic and neutral conditions. By using the Py scale, differences between simple aggregates and micelles have been discussed. The stability of simple aggregates was discussed in terms of hydrophobic interaction and electrostatic repulsion. The absence of excimer emission of the anthrancene moiety of probe 1 in neutral condition was attributed to the photoinduced electron transfer mechanism instead of photodimerization.

  3. Regulation of UVR8 photoreceptor dimer/monomer photo-equilibrium in Arabidopsis plants grown under photoperiodic conditions.

    Science.gov (United States)

    Findlay, Kirsten M W; Jenkins, Gareth I

    2016-08-01

    The UV RESISTANCE LOCUS 8 (UVR8) photoreceptor specifically mediates photomorphogenic responses to UV-B. Photoreception induces dissociation of dimeric UVR8 into monomers to initiate responses. However, the regulation of dimer/monomer status in plants growing under photoperiodic conditions has not been examined. Here we show that UVR8 establishes a dimer/monomer photo-equilibrium in plants growing in diurnal photoperiods in both controlled environments and natural daylight. The photo-equilibrium is determined by the relative rates of photoreception and dark-reversion to the dimer. Experiments with mutants in REPRESSOR OF UV-B PHOTOMORPHOGENESIS 1 (RUP1) and RUP2 show that these proteins are crucial in regulating the photo-equilibrium because they promote reversion to the dimer. In plants growing in daylight, the UVR8 photo-equilibrium is most strongly correlated with low ambient fluence rates of UV-B (up to 1.5 μmol m(-2) s(-1) ), rather than higher fluence rates or the amount of photosynthetically active radiation. In addition, the rate of reversion of monomer to dimer is reduced at lower temperatures, promoting an increase in the relative level of monomer at approximately 8-10 °C. Thus, UVR8 does not behave like a simple UV-B switch under photoperiodic growth conditions but establishes a dimer/monomer photo-equilibrium that is regulated by UV-B and also influenced by temperature. PMID:26864532

  4. Computational Modeling and Theoretical Calculations on the Interactions between Spermidine and Functional Monomer (Methacrylic Acid in a Molecularly Imprinted Polymer

    Directory of Open Access Journals (Sweden)

    Yujie Huang

    2015-01-01

    Full Text Available This paper theoretically investigates interactions between a template and functional monomer required for synthesizing an efficient molecularly imprinted polymer (MIP. We employed density functional theory (DFT to compute geometry, single-point energy, and binding energy (ΔE of an MIP system, where spermidine (SPD and methacrylic acid (MAA were selected as template and functional monomer, respectively. The geometry was calculated by using B3LYP method with 6-31+(d basis set. Furthermore, 6-311++(d, p basis set was used to compute the single-point energy of the above geometry. The optimized geometries at different template to functional monomer molar ratios, mode of bonding between template and functional monomer, changes in charge on natural bond orbital (NBO, and binding energy were analyzed. The simulation results show that SPD and MAA form a stable complex via hydrogen bonding. At 1 : 5 SPD to MAA ratio, the binding energy is minimum, while the amount of transferred charge between the molecules is maximum; SPD and MAA form a stable complex at 1 : 5 molar ratio through six hydrogen bonds. Optimizing structure of template-functional monomer complex, through computational modeling prior synthesis, significantly contributes towards choosing a suitable pair of template-functional monomer that yields an efficient MIP with high specificity and selectivity.

  5. High-resolution structure of a retroviral protease folded as a monomer

    Energy Technology Data Exchange (ETDEWEB)

    Gilski, Miroslaw [A. Mickiewicz University, 60-780 Poznan (Poland); Polish Academy of Sciences, 61-704 Poznan (Poland); Kazmierczyk, Maciej; Krzywda, Szymon [A. Mickiewicz University, 60-780 Poznan (Poland); Zábranská, Helena [Academy of Sciences of the Czech Republic, 166 10 Prague (Czech Republic); Cooper, Seth; Popović, Zoran [University of Washington, Box 352350, Seattle, WA 98195 (United States); Khatib, Firas; DiMaio, Frank; Thompson, James; Baker, David [University of Washington, Box 357350, Seattle, WA 98195 (United States); Pichová, Iva [Academy of Sciences of the Czech Republic, 166 10 Prague (Czech Republic); Jaskolski, Mariusz, E-mail: mariuszj@amu.edu.pl [A. Mickiewicz University, 60-780 Poznan (Poland); Polish Academy of Sciences, 61-704 Poznan (Poland)

    2011-11-01

    The crystal structure of Mason–Pfizer monkey virus protease folded as a monomer has been solved by molecular replacement using a model generated by players of the online game Foldit. The structure shows at high resolution the details of a retroviral protease folded as a monomer which can guide rational design of protease dimerization inhibitors as retroviral drugs. Mason–Pfizer monkey virus (M-PMV), a D-type retrovirus assembling in the cytoplasm, causes simian acquired immunodeficiency syndrome (SAIDS) in rhesus monkeys. Its pepsin-like aspartic protease (retropepsin) is an integral part of the expressed retroviral polyproteins. As in all retroviral life cycles, release and dimerization of the protease (PR) is strictly required for polyprotein processing and virion maturation. Biophysical and NMR studies have indicated that in the absence of substrates or inhibitors M-PMV PR should fold into a stable monomer, but the crystal structure of this protein could not be solved by molecular replacement despite countless attempts. Ultimately, a solution was obtained in mr-rosetta using a model constructed by players of the online protein-folding game Foldit. The structure indeed shows a monomeric protein, with the N- and C-termini completely disordered. On the other hand, the flap loop, which normally gates access to the active site of homodimeric retropepsins, is clearly traceable in the electron density. The flap has an unusual curled shape and a different orientation from both the open and closed states known from dimeric retropepsins. The overall fold of the protein follows the retropepsin canon, but the C{sup α} deviations are large and the active-site ‘DTG’ loop (here NTG) deviates up to 2.7 Å from the standard conformation. This structure of a monomeric retropepsin determined at high resolution (1.6 Å) provides important extra information for the design of dimerization inhibitors that might be developed as drugs for the treatment of retroviral infections

  6. Heterologous production and functional and thermodynamic characterization of cation diffusion facilitator (CDF) transporters of mesophilic and hyperthermophilic origin.

    Science.gov (United States)

    Goswami, Devrishi; Kaur, Jagdeep; Surade, Sachin; Grell, Ernst; Michel, Hartmut

    2012-07-01

    The members of the cation diffusion facilitator (CDF) family transport heavy metal ions and play an important function in zinc ion homeostasis of the cell. A recent structure of an Escherichia coli CDF transporter protein YiiP has revealed its dimeric nature and autoregulatory zinc transport mechanism. Here, we report the cloning and heterologous production of four different CDF transporters, two each from the pathogenic mesophilic bacterium Salmonella typhimurium and from the hyperthermophilic bacterium Aquifex aeolicus, in E. coli host cells. STM0758 of S. typhimurium was able to restore resistance to zinc ions when tested by complementation assays in the zinc-sensitive GG48 strain. Furthermore, copurification of bicistronically produced STM0758 and cross-linking experiments with the purified protein have revealed its possible oligomeric nature. The interaction between heavy metal ions and Aq_2073 of A. aeolicus was investigated by titration calorimetry. The entropy-driven, high-affinity binding of two Cd2+ and two Zn2+ per protein monomer with Kd values of around 100 nm and 1 μm, respectively, was observed. In addition, at least one more Zn2+ can be bound per monomer with low affinity. This low-affinity site is likely to possess a functional role contributing to Zn2+ transport across membranes. PMID:22944666

  7. In Vivo Simulations of the Intravenous Dynamics of Submicron Particles of pH-Responsive Cationic Hydrogels in Diabetic Patients.

    Science.gov (United States)

    Farmer, Terry G; Edgar, Thomas F; Peppas, Nicholas A

    2008-12-17

    A mathematical model describing glucose-dependent pH swelling and insulin release is developed for pH-sensitive cationic hydrogels in which glucose oxidase and catalase have been immobilized and insulin imbibed. Glucose based swelling and insulin release are simulated for intravenously injected particles at various design conditions. The effects of particle size, the number of injected particles, insulin loading, enzyme loading, monomer functional group loading and pK(a), and hydrogel crosslinking ratio on insulin release and glucose sensitivity are investigated in order to optimally design the device for use. Increased insulin infusion is shown to result from increasing the number of circulating gels, increasing the collapsed particle size, or by decreasing the crosslinking ratio of the system. Release duration is shown to be dependent only upon the particle size and the achievable diffusion coefficient of the system. Glucose sensitivity, as measured by gluconic acid production and by the system pH, are functions of glucose oxidase loading and the concentration and pK(a) of the monomer used in the hydrogel.The necessarily submicron particle size results in very rapid device insulin depletion. When the device is designed without considering constraints, the resulting release profile resembles that of an on/off switching mechanism. Future work will focus on simulations of swelling and release when the device is implanted in an alternative administration site. PMID:20428328

  8. Self-assembly of actin monomers into long filaments: Brownian Dynamics simulations

    DEFF Research Database (Denmark)

    Shillcock, Julian C.

    2009-01-01

    Brownian dynamics simulations are used to study the dynamical process of self-assembly of actin monomers into long filaments containing up to 1000 actin protomers. In order to overcome the large separation of time scales between the diffusive motion of the freemonomers and the relatively slow...... to unravel certain relations between thefilament's physical properties and the model parameters such as the attachment rate constant and the size of the capture zone, the detachment rate and the probability of the detached event, as well as the growth rate and waiting times between two successive attachment...

  9. Condensation monomers and polymers based on 2,4,6-trinitrotoluene

    International Nuclear Information System (INIS)

    The feasibility of conversion of 2,4,6-trinitrotoluene into condensation monomers (nitro compounds, diamines, etc.) and their applications in the synthesis of aromatic polymers has been analysed within the framework of a general problem of 2,4,6-trinitroluene conversion. The use of aromatic dinitro compounds and diamines for the preparation of oligomeric polyethers and polyamides (or polyimides), respectively, is considered. The possibility of the synthesis of polyamides and polyimides containing side aliphatic and aromatic groups and possessing better (in comparison with the corresponding unsubstituted polymers) characteristics is demonstrated.

  10. Glucagon stop-go kinetics supports a monomer-trimer fibrillation model

    CERN Document Server

    Kosmrlj, Andrej; Kyrsting, Anders; Otzen, Daniel E; Oddershede, Lene B; Jensen, Mogens H

    2014-01-01

    We investigate in vitro fibrillation kinetics of the hormone peptide glucagon at various concentrations using confocal microscopy and determine the glucagon fibril persistence length $60 \\mu\\textrm{m}$. At all concentrations we observe that periods of individual fibril growth are interrupted by periods of stasis. The growth probability is large at high and low concentrations and is reduced for intermediate glucagon concentrations. To explain this behavior we propose a simple model, where fibrils come in two forms, one built entirely from glucagon monomers and one entirely from glucagon trimers. The opposite building blocks act as fibril growth blockers, and this generic model reproduces experimental behavior well.

  11. Construction of Multi-Chromophoric Spectra from Monomer Data: Applications to Resonant Energy Transfer

    CERN Document Server

    Chenu, Aurélia

    2016-01-01

    We develop a model that establishes a quantitative link between the physical properties of molecular aggregates and their constituent building blocks. The relation is built on the coherent potential approximation, calibrated against exact results, and proven reliable for a wide range of parameters. It provides a practical method to compute spectra and transfer rates in multi-chromophoric systems from experimentally accessible monomer data. Applications to F\\"orster energy transfer reveal optimal transfer rates as functions of both the system-bath coupling and intra-aggregate coherence.

  12. Migration of formaldehyde and melamine monomers from kitchen- and tableware made of melamine plastic

    DEFF Research Database (Denmark)

    Lund, K.H.; Petersen, J.H.

    2006-01-01

    Migration of one or both formaldehyde and/or melamine monomers was found in seven of ten tested melamine samples bought on the Danish market. The samples were a bowl, a jug, a mug, a ladle, and different cups and plates. No violation of the European Union-specific migration limits for melamine (30...... mg kg(-1)) and formaldehyde (15 mg kg(-1)) was found after three successive exposures to the food stimulant 3% acetic acid after 2 h at 70 degrees C. To investigate the effects of long-term use, migration tests were performed with two types of cups from a day nursery. Furthermore, medium-term use...

  13. Ground State Properties of Ising Chain with Random Monomer-Dimer Couplings

    Science.gov (United States)

    Ardebili, S. Bahareh Seyedein; Sepehrinia, Reza

    2016-05-01

    We study analytically the one-dimensional Ising model with a random binary distribution of ferromagnetic and antiferromagnetic exchange couplings at zero temperature. We introduce correlations in the disorder by assigning a dimer of one type of coupling with probability x, and a monomer of the other type with probability 1-x. We find that the magnetization behaves differently from the original binary model. In particular, depending on which type of coupling comes in dimers, magnetization jumps vanish at a certain set of critical fields. We explain the results based on the structure of ground state spin configuration.

  14. INS as a probe of inter-monomer angles in polymers

    CERN Document Server

    Eijck, L V; Grozema, F C; Schepper, I M D; Kearley, G J

    2002-01-01

    The angle between monomers in conjugated polymers plays an important role in their conductivity. The vibrational spectrum is sensitive to this angle and can be used to probe the distribution of angles in poorly crystalline systems. We show that the INS spectrum is correctly calculated for bithiophene and shows the molecule to be planar in the solid - in agreement with crystallographic measurements. Poor agreement between observed and calculated spectra in the 700-cm sup - sup 1 region may be due to dynamic coupling, but this does not detract from the angle-sensitivity of the spectra. (orig.)

  15. Gelcasting of Alumina with Application of New Monomer Synthesised from Xylitol

    OpenAIRE

    Szudarska A.; Guryniuk D.; Mizerski T.; Szafran M.

    2013-01-01

    Podążając za trendem „zielonej chemii", zakładającym m.in. wykorzystywanie nietoksycznych i odnawialnych surowców w technologii, zaprojektowano i zsyntezowano nowy monomer przeznaczony do zastosowania w procesie odlewania żelowego. Wyjściowym substratem trójetapowej syntezy był ksyłitol, a finalnym produktem 1-O-akryloiloksylitol. Otrzymana pochodna została sprawdzona pod względem efektywności polimeryzacji in situ w ceramicznej masie lejnej na bazie tlenku glinu. Zbadano jej wpływ na właściw...

  16. Lurgi megamethanol technology - delivering the building blocks for the future fuel and monomer demand

    Energy Technology Data Exchange (ETDEWEB)

    Wurzel, T. [Lurgi AG, Frankfurt am Main (Germany)

    2007-06-15

    The article describes the central role of methanol within a changing environment with respect to feedstock availability as well as steadily growing fuel and monomer demand. The current large-scale production facilities are described with respect to the technological challenges in order to ensure the availability of sufficient methanol for downstream applications. Different downstream applications are described which clearly confirm that methanol is the dominant CI-building block due to its chemical flexibility. It is concluded that by means of the implementation of two MTP (Methanol to Propylene) projects in China the era of ''down-stream methanol'' has begun in the industry. (orig.)

  17. 1,3-Diphenylethenylcarbazolyl-Based Monomer for Cross-Linked Hole Transporting Layers

    Directory of Open Access Journals (Sweden)

    Maryte Daskeviciene

    2015-05-01

    Full Text Available A new cross-linkable monomer containing 1,3-diphenylethenylcarbazolyl-based hole-transporting moieties and four reactive epoxy groups, was prepared by a multistep synthesis route from 1,3-bis(2,2-diphenylethenyl-9H-carbazol-2-ol and its application for the in situ formation of cross-linked hole transporting layers was investigated. A high concentration of flexible aliphatic epoxy chains ensures good solubility and makes this compound an attractive cross-linking agent. The synthesized compounds were characterized by various techniques, including differential scanning calorimetry, xerographic time of flight, and electron photoemission in air methods.

  18. Pseudomonas syringae evades host Immunity by degrading flagellin monomers with alkaline protease AprA

    OpenAIRE

    Pel, M.J.C.; Van Dijken, A.J.H.; Bardoel, B.W.; Seidl, M. F.; Van der Ent, S.; van Strijp, J. A. G.

    2014-01-01

    Bacterial flagellin molecules are strong inducers of innate immune responses in both mammals and plants. The opportunistic pathogen Pseudomonas aeruginosa secretes an alkaline protease called AprA that degrades flagellin monomers. Here, we show that AprA is widespread among a wide variety of bacterial species. In addition, we investigated the role of AprA in virulence of the bacterial plant athogen P. syringae pv. tomato DC3000. The AprA-deficient DC3000 ΔaprA knockout mutant was significantl...

  19. Cationic Antimicrobial Polymers and Their Assemblies

    Directory of Open Access Journals (Sweden)

    Ana Maria Carmona-Ribeiro

    2013-05-01

    Full Text Available Cationic compounds are promising candidates for development of antimicrobial agents. Positive charges attached to surfaces, particles, polymers, peptides or bilayers have been used as antimicrobial agents by themselves or in sophisticated formulations. The main positively charged moieties in these natural or synthetic structures are quaternary ammonium groups, resulting in quaternary ammonium compounds (QACs. The advantage of amphiphilic cationic polymers when compared to small amphiphilic molecules is their enhanced microbicidal activity. Besides, many of these polymeric structures also show low toxicity to human cells; a major requirement for biomedical applications. Determination of the specific elements in polymers, which affect their antimicrobial activity, has been previously difficult due to broad molecular weight distributions and random sequences characteristic of radical polymerization. With the advances in polymerization control, selection of well defined polymers and structures are allowing greater insight into their structure-antimicrobial activity relationship. On the other hand, antimicrobial polymers grafted or self-assembled to inert or non inert vehicles can yield hybrid antimicrobial nanostructures or films, which can act as antimicrobials by themselves or deliver bioactive molecules for a variety of applications, such as wound dressing, photodynamic antimicrobial therapy, food packing and preservation and antifouling applications.

  20. Cobalt 60 cation exchange with mexican clays

    International Nuclear Information System (INIS)

    Mexican clays can be used to remove radioactive elements from contaminated aqueous solutions. Cation exchange experiments were performed with 60 Co radioactive solution. In the present work the effect of contact time on the sorption of Co 2+ was studied. The contact time in hydrated montmorillonite was from 5 to 120 minutes and in dehydrated montmorillonite 5 to 1400 minutes. The Co 2+ uptake value was, in hydrated montmorillonite, between 0.3 to 0.85 m eq/g and in dehydrated montmorillonite, between 0.6 to 1.40 m eq/g. The experiments were done in a pH 5.1 to 5.7 and normal conditions. XRD patterns were used to characterize the samples. The crystallinity was determined by X-ray Diffraction and it was maintained before and after the cation exchange. DTA thermo grams showed the temperatures of the lost humidity and crystallization water. Finally, was observed that dehydrated montmorillonite adsorb more cobalt than hydrated montmorillonite. (Author)

  1. Photodissociation of Cerium Oxide Nanocluster Cations.

    Science.gov (United States)

    Akin, S T; Ard, S G; Dye, B E; Schaefer, H F; Duncan, M A

    2016-04-21

    Cerium oxide cluster cations, CexOy(+), are produced via laser vaporization in a pulsed nozzle source and detected with time-of-flight mass spectrometry. The mass spectrum displays a strongly preferred oxide stoichiometry for each cluster with a specific number of metal atoms x, with x ≤ y. Specifically, the most prominent clusters correspond to the formula CeO(CeO2)n(+). The cluster cations are mass selected and photodissociated with a Nd:YAG laser at either 532 or 355 nm. The prominent clusters dissociate to produce smaller species also having a similar CeO(CeO2)n(+) formula, always with apparent leaving groups of (CeO2). The production of CeO(CeO2)n(+) from the dissociation of many cluster sizes establishes the relative stability of these clusters. Furthermore, the consistent loss of neutral CeO2 shows that the smallest neutral clusters adopt the same oxidation state (IV) as the most common form of bulk cerium oxide. Clusters with higher oxygen content than the CeO(CeO2)n(+) masses are present with much lower abundance. These species dissociate by the loss of O2, leaving surviving clusters with the CeO(CeO2)n(+) formula. Density functional theory calculations on these clusters suggest structures composed of stable CeO(CeO2)n(+) cores with excess oxygen bound to the surface as a superoxide unit (O2(-)). PMID:27035210

  2. Graft copolymers of polyurethane with various vinyl monomers via radiation-induced miniemulsion polymerization: Influential factors to grafting efficiency and particle morphology

    Energy Technology Data Exchange (ETDEWEB)

    Wang Hua [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China (USTC), Hefei, Anhui 230026 (China); Wang Mozhen [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China (USTC), Hefei, Anhui 230026 (China)], E-mail: pstwmz@ustc.edu.cn; Ge Xuewu [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China (USTC), Hefei, Anhui 230026 (China)], E-mail: xwge@ustc.edu.cn

    2009-02-15

    Graft copolymers of polyurethane (PU) with various vinyl monomers were synthesized through a one-pot but two-step miniemulsion polymerization process. Firstly, the polycondensation of isophorone diisocyanate (IPDI) with hydroxyl-terminated polybutadiene (HTPB) had been performed in aqueous miniemulsion at 40 deg. C in order to obtain PU dispersions. Consecutively, an in-situ graft copolymerization of the vinyl monomers with the synthesized PU was initiated by {gamma}-ray radiation at room temperature. The grafting efficiency of PU with vinyl monomer (G{sub PU/monomer}) was calculated from {sup 1}H NMR spectra and the particle morphology of the final hybrid latex was observed by transmission electron microscopy (TEM). As there was no monomer transferring in miniemulsion system, homogenous hybrid particles would be synthesized provided that the monomer was miscible with PU, such as styrene. With the increase of the polarity of the monomer, the compatibility of PU with monomer decreased. G{sub PU/monomer} varied as G{sub PU/styrene}(37%)>G{sub PU/butyl} {sub acrylate} {sub (BA)}(21%)>G{sub PU/methyl} {sub methacrylate} {sub (MMA)}(12%). The proportion of homogeneous nucleation would increase as the hydrophilicity of the monomer increased. High temperature would destabilize the miniemulsion so as to result in a less grafting efficiency. Compared to the phase separation during the seeded emulsion polymerization, the miniemulsion polymerization method facilitated the preparation of homogeneous materials owing to its monomer droplet nucleation mechanism.

  3. Graft copolymers of polyurethane with various vinyl monomers via radiation-induced miniemulsion polymerization: Influential factors to grafting efficiency and particle morphology

    Science.gov (United States)

    Wang, Hua; Wang, Mozhen; Ge, Xuewu

    2009-02-01

    Graft copolymers of polyurethane (PU) with various vinyl monomers were synthesized through a one-pot but two-step miniemulsion polymerization process. Firstly, the polycondensation of isophorone diisocyanate (IPDI) with hydroxyl-terminated polybutadiene (HTPB) had been performed in aqueous miniemulsion at 40 °C in order to obtain PU dispersions. Consecutively, an in-situ graft copolymerization of the vinyl monomers with the synthesized PU was initiated by γ-ray radiation at room temperature. The grafting efficiency of PU with vinyl monomer ( GPU/monomer) was calculated from 1H NMR spectra and the particle morphology of the final hybrid latex was observed by transmission electron microscopy (TEM). As there was no monomer transferring in miniemulsion system, homogenous hybrid particles would be synthesized provided that the monomer was miscible with PU, such as styrene. With the increase of the polarity of the monomer, the compatibility of PU with monomer decreased. GPU/monomer varied as GPU/styrene(37%)> GPU/butyl acrylate (BA)(21%)> GPU/methyl methacrylate (MMA)(12%). The proportion of homogeneous nucleation would increase as the hydrophilicity of the monomer increased. High temperature would destabilize the miniemulsion so as to result in a less grafting efficiency. Compared to the phase separation during the seeded emulsion polymerization, the miniemulsion polymerization method facilitated the preparation of homogeneous materials owing to its monomer droplet nucleation mechanism.

  4. Cationic polymethacrylates with covalently linked membrane destabilizing peptides as gene delivery vectors.

    Science.gov (United States)

    Funhoff, Arjen M; van Nostrum, Cornelus F; Lok, Martin C; Kruijtzer, John A W; Crommelin, Daan J A; Hennink, Wim E

    2005-01-01

    A membrane-disrupting peptide derived from the influenza virus was covalently linked to different polymethacrylates (pDMAEMA, pDAMA and the degradable pHPMA-DMAE, monomers depicted in Fig. 1) using N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP) as coupling agent to increase the transfection efficiency of polyplexes based on these polymers. It was shown by circular dichroism (CD) measurements that the polymer-conjugated peptide was, as the free peptide, able to undergo a conformational change of a random coil to an alpha helix upon lowering the pH to 5.0. This indicates that the property of the peptide to destabilize the endosomal membrane was preserved after its conjugation to the cationic polymers. In line herewith, a liposome leakage assay revealed that the polymer-bound peptide has comparable activity as the free peptide. The DNA condensing properties of the synthesized polymer-peptide conjugates were studied with dynamic light scattering and zeta-potential measurements, and it was shown that small (100 to 250 nm), positively charged (+15 to +20 mV) particles were formed. In vitro transfection and toxicity was tested in COS-7 cells, and these experiments showed that the polyplexes with grafted peptide had a substantially higher transfection activity than the control polyplexes, while the toxicity remained unchanged. Cellular uptake of the polyplexes was visualized with confocal laser scanning microscopy, and no differences in cellular uptake could be determined between the peptide containing systems and the control formulation. This shows that the increased transfection activity is indeed due to a better endosomal escape of the peptide grafted polyplexes. This study demonstrates that it is possible to covalently conjugate an endosome disruptive peptide to cationic gene delivery polymers with preservation of its membrane destabilization activity, making these conjugates suitable for in vivo DNA delivery. PMID:15588908

  5. Ground state of naphthyl cation: Singlet or triplet?

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Achintya Kumar; Vaval, Nayana, E-mail: np.vaval@ncl.res.in; Pal, Sourav, E-mail: s.pal@ncl.res.in [Physical Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008 (India); Manohar, Prashant U. [Department of Chemistry, BITS Pilani, Pilani Campus (India)

    2014-03-21

    We present a benchmark theoretical investigation on the electronic structure and singlet-triplet(S-T) gap of 1- and 2-naphthyl cations using the CCSD(T) method. Our calculations reveal that the ground states of both the naphthyl cations are singlet, contrary to the results obtained by DFT/B3LYP calculations reported in previous theoretical studies. However, the triplet states obtained in the two structural isomers of naphthyl cation are completely different. The triplet state in 1-naphthyl cation is (π,σ) type, whereas in 2-naphthyl cation it is (σ,σ{sup ′}) type. The S-T gaps in naphthyl cations and the relative stability ordering of the singlet and the triplet states are highly sensitive to the basis-set quality as well as level of correlation, and demand for inclusion of perturbative triples in the coupled-cluster ansatz.

  6. Influence of interlayer cations on organic intercalation of montmorillonite.

    Science.gov (United States)

    Wu, Limei; Liao, Libing; Lv, Guocheng

    2015-09-15

    The influence of the types of interlayer cations on organic intercalation of montmorillonite (Mt) was studied in this paper. The distribution of Na(+), K(+), Mg(2+), Ca(2+) and Fe(3+) in montmorillonite interlayer, their interaction with structure layers and the effect of interlayer cations on the basal spacing of Mt, the amount of binding water for different interlayer cations and the binding force between them were investigated systematically. 1-Hexadecy1-3-methylimidazolium chloride monohydrate (C16mimCl) was intercalated into montmorillonites with different interlayer cations. The influence of interlayer cations on organic intercalation was investigated. Molecular dynamics (MD) modeling was used to speculate the interlayer microstructures of the organically intercalated Mt with different interlayer cations. These simulations help to predict the microstructure of organo-Mt and guide their relevant engineering applications. PMID:26001131

  7. Reversible energy transfer between monomers and fluorescent dimers of rhodamine S in polyvinyl alcohol films

    International Nuclear Information System (INIS)

    Research highlights: → Contrary to liquid solutions rhodamine S aggregates in PVA are fluorescent. → Overlap between aggregate fluorescence and monomer absorption leads to reverse energy transfer. → This effect influences strongly quantum yield and emission anisotropy concentration courses. → Monte-Carlo simulation enables estimation of dimer quantum yield and describes well experiments. - Abstract: Nonradiative energy transfer and excitation trapping are studied for rhodamine S in polyvinyl alcohol (PVA) films. It occurs that fluorescent dimers of rhodamine S can play a role of imperfect traps for the excitation energy. At highest dye concentrations experimental data of fluorescence quantum yield and emission anisotropy cannot be described by the model of energy transfer neglecting the possibility of excitation return to the monomers. However, the agreement between experimental data and the results of computations can be much improved, if the reverse energy transfer is taken into account. Based on the quantitative analysis it is possible to estimate selected characteristics of rhodamine S dimer in polyvinyl alcohol matrix. The experiments and corresponding analysis are made both at room and elevated temperature.

  8. Analysis of lignocellulose derived phenolic monomers by headspace solid-phase microextraction and gas chromatography.

    Science.gov (United States)

    Kolb, Michaela; Schieder, Doris; Faulstich, Martin; Sieber, Volker

    2013-09-13

    A headspace solid-phase microextraction method with subsequent GC-MS (HS-SPME/GC-MS) was established for the quantitative analysis of volatile lignin derived phenolic monomers in complex aqueous solutions. Extraction was done using a polyacrylate fiber. The optimization of HS-SPME - parameters was performed using a multi component model solution of six representative phenolic monomers identified in liquid hot water (LHW) supernatants of hydrothermally treated lignocellulosic biomass: p-coumaric acid, guaiacol, vanillin, acetosyringone, 4-hydroxy-3-methoxyphenylacetone, and acetophenone. Plackett-Burman design was applied for pre-evaluation and 2(3) central composite designs with star points for parameter optimization. LOQ (S/N>10) and LOD (S/N>3) were determined for 12 phenols yielding LOQ of <0.005-618nM and LOD of <0.005-412nM. Within-day and between-day tests (n=6) showed different results for the tested phenols. RSD ranged from 2% to 30% and recovery rates from 99% to 160% in LHW matrix. Tests on storage of LHW supernatants for several weeks indicated a considerable influence of temperature on the stability of the solutions which may even have to be taken into account for auto sampler handling. All in all the method allows a fast and solvent free analysis requiring low sample volumes making it a powerful tool for screening or high-throughput analysis of aqueous solutions of lignin derived aromatics.

  9. Therapeutic TNF Inhibitors can Differentially Stabilize Trimeric TNF by Inhibiting Monomer Exchange

    Science.gov (United States)

    van Schie, Karin A.; Ooijevaar-de Heer, Pleuni; Dijk, Lisanne; Kruithof, Simone; Wolbink, Gertjan; Rispens, Theo

    2016-01-01

    Tumor necrosis factor (TNF) is a homotrimeric cytokine that is a key mediator of inflammation. It is unstable at physiological concentrations and slowly converts into an inactive form. Here, we investigated the mechanism of this process by using a Förster resonance energy transfer (FRET) assay that allowed monitoring of monomeric subunit exchange in time. We observed continuous exchange of monomeric subunits even at concentrations of TNF high enough to maintain its bioactivity. The kinetics of this process closely corresponds with the appearance of monomeric subunits and disappearance of trimeric TNF in time at ng/ml concentrations as monitored by high-performance size-exclusion chromatography (HP-SEC). Furthermore, of the five therapeutic TNF inhibitors that are currently used in the clinic, three (adalimumab, infliximab, etanercept) were found to completely inhibit the monomer exchange reaction and stabilize TNF trimers, whereas golimumab and certolizumab could not prevent monomer exchange, but did slow down the exchange process. These differences were not correlated with the affinities of the TNF inhibitors, measured with both surface plasmon resonance (SPR) and in fluid phase using fluorescence-assisted HP-SEC. The stabilizing effect of these TNF inhibitors might result in prolonged residual TNF bioactivity under conditions of incomplete blocking, as observed in vitro for adalimumab. PMID:27605058

  10. A conserved cysteine residue is involved in disulfide bond formation between plant plasma membrane aquaporin monomers.

    Science.gov (United States)

    Bienert, Gerd P; Cavez, Damien; Besserer, Arnaud; Berny, Marie C; Gilis, Dimitri; Rooman, Marianne; Chaumont, François

    2012-07-01

    AQPs (aquaporins) are conserved in all kingdoms of life and facilitate the rapid diffusion of water and/or other small solutes across cell membranes. Among the different plant AQPs, PIPs (plasma membrane intrinsic proteins), which fall into two phylogenetic groups, PIP1 and PIP2, play key roles in plant water transport processes. PIPs form tetramers in which each monomer acts as a functional channel. The intermolecular interactions that stabilize PIP oligomer complexes and are responsible for the resistance of PIP dimers to denaturating conditions are not well characterized. In the present study, we identified a highly conserved cysteine residue in loop A of PIP1 and PIP2 proteins and demonstrated by mutagenesis that it is involved in the formation of a disulfide bond between two monomers. Although this cysteine seems not to be involved in regulation of trafficking to the plasma membrane, activity, substrate selectivity or oxidative gating of ZmPIP1s (Zm is Zea mays), ZmPIP2s and hetero-oligomers, it increases oligomer stability under denaturating conditions. In addition, when PIP1 and PIP2 are co-expressed, the loop A cysteine of ZmPIP1;2, but not that of ZmPIP2;5, is involved in the mercury sensitivity of the channels.

  11. Estimation of the lag time in a subsequent monomer addition model for fibril elongation.

    Science.gov (United States)

    Shoffner, Suzanne K; Schnell, Santiago

    2016-08-01

    Fibrillogenesis, the production or development of protein fibers, has been linked to protein folding diseases. The progress curve of fibrils or aggregates typically takes on a sigmoidal shape with a lag phase, a rapid growth phase, and a final plateau regime. The study of the lag phase and the estimation of its critical timescale provide insight into the factors regulating the fibrillation process. However, methods to estimate a quantitative expression for the lag time rely on empirical expressions, which cannot connect the lag time to kinetic parameters associated with the reaction mechanisms of protein fibrillation. Here we introduce an approach for the estimation of the lag time using the governing rate equations of the elementary reactions of a subsequent monomer addition model for protein fibrillation as a case study. We show that the lag time is given by the sum of the critical timescales for each fibril intermediate in the subsequent monomer addition mechanism and therefore reveals causal connectivity between intermediate species. Furthermore, we find that single-molecule assays of protein fibrillation can exhibit a lag phase without a nucleation process, while dyes and extrinsic fluorescent probe bulk assays of protein fibrillation do not exhibit an observable lag phase during template-dependent elongation. Our approach could be valuable for investigating the effects of intrinsic and extrinsic factors to the protein fibrillation reaction mechanism and provides physicochemical insights into parameters regulating the lag phase. PMID:27250246

  12. A thioacidolysis method tailored for higher-throughput quantitative analysis of lignin monomers

    Energy Technology Data Exchange (ETDEWEB)

    Harman-Ware, Anne E. [Bioenergy Science Center, Golden CO USA; National Bioenergy Center, National Renewable Energy Laboratory, Golden CO USA; Foster, Cliff [Great Lakes BioEnergy Research Center, Michigan State University, East Lansing MI USA; Happs, Renee M. [Bioenergy Science Center, Golden CO USA; National Bioenergy Center, National Renewable Energy Laboratory, Golden CO USA; Doeppke, Crissa [Bioenergy Science Center, Golden CO USA; National Bioenergy Center, National Renewable Energy Laboratory, Golden CO USA; Meunier, Kristoffer [Great Lakes BioEnergy Research Center, Michigan State University, East Lansing MI USA; Gehan, Jackson [Great Lakes BioEnergy Research Center, Michigan State University, East Lansing MI USA; Yue, Fengxia [Wisconsin Bioenergy Initiative, University of Wisconsin, Madison WI USA; Lu, Fachuang [Wisconsin Bioenergy Initiative, University of Wisconsin, Madison WI USA; Davis, Mark F. [Bioenergy Science Center, Golden CO USA; National Bioenergy Center, National Renewable Energy Laboratory, Golden CO USA

    2016-09-14

    Thioacidolysis is a method used to measure the relative content of lignin monomers bound by SS-O-4 linkages. Current thioacidolysis methods are low-throughput as they require tedious steps for reaction product concentration prior to analysis using standard GC methods. A quantitative thioacidolysis method that is accessible with general laboratory equipment and uses a non-chlorinated organic solvent and is tailored for higher-throughput analysis is reported. The method utilizes lignin arylglycerol monomer standards for calibration, requires 1-2 mg of biomass per assay and has been quantified using fast-GC techniques including a Low Thermal Mass Modular Accelerated Column Heater (LTM MACH). Cumbersome steps, including standard purification, sample concentrating and drying have been eliminated to help aid in consecutive day-to-day analyses needed to sustain a high sample throughput for large screening experiments without the loss of quantitation accuracy. The method reported in this manuscript has been quantitatively validated against a commonly used thioacidolysis method and across two different research sites with three common biomass varieties to represent hardwoods, softwoods, and grasses.

  13. Structural and Vibrational Study on Monomer and Dimer Forms and Water Clusters of Acetazolamide

    Directory of Open Access Journals (Sweden)

    Aysen E. Ozel

    2013-01-01

    Full Text Available Experimental IR and Raman spectra of solid acetazolamide have been analysed by computing the molecular structures and vibrational spectra of monomer and dimer forms and water clusters of acetazolamide. The possible stable conformers of free acetazolamide molecule in the ground state were obtained by scanning the potential energy surface through the dihedral angles, D1 (1S-2C-6S-9N, D2 (4N-5C-12N-14C, and D3 (5C-12N-14C-16C. The final geometry parameters for the obtained stable conformers were determined by means of geometry optimization, carried out at DFT/B3LYP/6-31G++(d,p theory level. Afterwards the possible dimer forms of the molecule and acetazolamide-H2O clusters were formed and their energetically preferred conformations were investigated using the same method and the same level of theory. The effect of BSSE on the structure and energy of acetazolamide dimer has been investigated. The assignment of the vibrational modes was performed based on the potential energy distribution of the vibrational modes, calculated by using GAR2PED program. The experimental vibrational wavenumbers of solid acetazolamide are found to be in better agreement with the calculated wavenumbers of dimer form of acetazolamide than those of its monomeric form. NBO analysis has been performed on both monomer and dimer geometries.

  14. Evidences of monomer, dimer and trimer of recombinant human cyclophilin A.

    Science.gov (United States)

    Zhang, Xin-Chao; Wang, Wei-Dong; Wang, Jin-Song; Pan, Ji-Cheng; Zou, Guo-Lin

    2011-12-01

    Cyclophilin A (CyPA) is a cytosolic receptor of immunosuppressive drug cyclosporin A (CsA) which possesses peptidyl-prodyl cis/trans isomerase (PPIase) activity. The recombinant human CyPA (rhCyPA) gene has been expressed in E. coli M15. Purification was performed using salting-out, as well as Sephacryl S-100 and DEAE-Sepharose CL-6B column chromatography. The molecular weight is about 18 kDa, confirmed by SDS-PAGE and mass spectrum. The results of Native-PAGE and immunoblotting showed the existence of three bands, which agreed well with the gel filtration results. The molecular mass of the three bands determined via CTAB gel electrophoresis and SDS-PAGE (rhCyPA cross-linked with glutaraldehyde) was 18 kDa, 36 kDa and 54 kDa respectively. Further more, the native rhCyPA and the cross-linked rhCyPA had the similar chromatographic behavior in gel filtration. All of the evidences above suggest that rhCyPA exists in forms of monomer, dimer and trimer. Moreover, we observed that even at low protein concentrations CyPA largely occurs as a dimer in solution, and enzyme kinetic parameters showed that activity of dimer was much higher than monomer or trimer, which probably have some biological significances. PMID:21728990

  15. The Optimization of Synthesizing Graft Copolymer of Starch with Vinyl Monomers

    Institute of Scientific and Technical Information of China (English)

    WANG Zhiyu; LIU Zuoxin

    2006-01-01

    The graft copolymerization of acrylamide (AM)/acrylic acid (AA) onto starch (St-g-pAA and St-g-p(AA-co-AM)) was carried out using an orthogonal test method. The combined effects of different reaction conditions on the water absorbency of the graft copolymers were optimized through mathematical statistical methods of range and square variance analysis. The maximum water absorbency was obtained when the ratio of dried starch to distilled water was 1∶8 (w/w), the ratio of starch to monomer 1∶6 (w/w), the initiator concentration 4.40×10-3 mol/L, the crosslinker concentration 10.86×10-2 mol/L, and the basicity to AA 0.70(mol/mol). Both the graft copolymers have an excellent water absorption capacity in distilled water and in 0.9wt% NaCl solution. It was also found that in distilled water the water absorbency of St-g-pAA was higher than that of St-g-p(AA-co-AM), while in 0.9wt% NaCl solution, the situation was just the reverse. The correlation between the water absorbency and the nature of the solution and the properties of the copolymers, which is related to the properties of the monomers, was discussed. The grafting of AA and AM onto starch was confirmed by the IR spectra of St-g-pAA and St-g-p(AA-co-AM).

  16. Short-time dynamics of monomers and dimers in quasi-two-dimensional colloidal mixtures

    Science.gov (United States)

    Sarmiento-Gómez, Erick; Villanueva-Valencia, José Ramón; Herrera-Velarde, Salvador; Ruiz-Santoyo, José Arturo; Santana-Solano, Jesús; Arauz-Lara, José Luis; Castañeda-Priego, Ramón

    2016-07-01

    We report on the short-time dynamics in colloidal mixtures made up of monomers and dimers highly confined between two glass plates. At low concentrations, the experimental measurements of colloidal motion agree well with the solution of the Navier-Stokes equation at low Reynolds numbers; the latter takes into account the increase in the drag force on a colloidal particle due to wall-particle hydrodynamic forces. More importantly, we find that the ratio of the short-time diffusion coefficient of the monomer and that of the center of mass of the dimmer is almost independent of both the dimer molar fraction, xd, and the total packing fraction, ϕ , up to ϕ ≈0.5 . At higher concentrations, this ratio displays a small but systematic increase. A similar physical scenario is observed for the ratio between the parallel and the perpendicular components of the short-time diffusion coefficients of the dimer. This dynamical behavior is corroborated by means of molecular dynamics computer simulations that include explicitly the particle-particle hydrodynamic forces induced by the solvent. Our results suggest that the effects of colloid-colloid hydrodynamic interactions on the short-time diffusion coefficients are almost identical and factorable in both species.

  17. Characterization of cluster/monomer ratio in pulsed supersonic gas jets

    Science.gov (United States)

    Gao, Xiaohui; Shim, Bonggu; Wang, Xiaoming; Downer, Mike

    2008-11-01

    While Rayleigh scatter and interferometry are standard methods for determining average cluster size and total atomic density, respectively, in cluster gas jets, determination of cluster mass fraction has required additional input from gasdynamic simulations. Here we determine cluster mass fraction experimentally with fs-time-resolved measurement of refractive index using frequency domain interferometery (FDI) after ionization and heating by a pump pulse. The essence of this method is that the negative index contribution of monomer plasma appears immediately after ionization by the pump, whereas the positive contribution of clustered plasma becomes significant only after clusters expand to a Mie resonance condition, enabling separation of monomer and cluster densities in the time domain. This method allows us to investigate various influences (nozzle geometry, temperature, etc.) on cluster fraction, which varies widely in nominally identical gas jets, and is a critical parameter in realizing phase-matched harmonic generation at high laser intensity, which would lead to an efficient table-top soft X-ray source.

  18. Antifungal Effect of Streptomyces 702 Antifungal Monomer Component DZP8 on Rhizoctonia solani and Magnaporthe grisea

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    The aim of this study was to investigate the in vitro antifungal effects of antifungal monomer component DZP8 isolated from Streptomyces 702 on the mycelium growth, sclerotium formation and germination of Rhizoctonia solani and on the mycelium growth, conidial formation, germination, appressorium formation of Magnaporthe grisea. The results showed that the antifungal monomer component DZP8 has strong antifungal effect on both the R. solani and M. grisea. The EC50 and EC90 of DZP8 were 1.81 and 3.35 μg/ml on Ft. solani respectively, and 37.01 and 136.21 μg/ml on M. grisea respectively. Under the treatment of 48.01 μg/ml DZP8, the sclerotium formation rate of R. solani was just 39.21%, the formation time delayed by 216 h and the dry weight decreased by 81.37% in comparison the con- trol; and 33.51 μg/ml DZP8 significantly inhibited the sclerotium germination. In the presence of 160.08 μg/ml DZP8, the sporulation of M. grisea was just 9.29% of control sample; 20.14 μg/ml DZP8 inhibited the conidial germination suppression rate by 95.16%, and the appressorium formation by 100%.

  19. EFFECT OF GAMMA RAYS IN THE PREPARATION OF POLYMER AND HYDROGEL FROM ACRYLAMIDE MONOMER

    Institute of Scientific and Technical Information of China (English)

    M. M. Alam; M. F. Mina; F. Akhtar

    2003-01-01

    The formation of polymer and hydrogel from aqueous solutions having 20, 30 and 40% concentrations of acrylamide monomer by γ-ray irradiation processing in the dose range 0.06-30 kGy using a Co-60 source and their characterization have been observed. Polymer conversion and gel fraction are found to depend on radiation doses. Polymer conversion increases with the increase of dose, depending on the solution concentration, where maximum conversion is achieved at 0.18, 0.16 and 0.10 kGy for 20%, 30% and 40% concentrations, respectively. On the other hand, gel fraction increases with dose from the gel point (0.12 kGy) for all concentrations, where 100% conversion of gel occurs at doses ≥ 5 kGy. Tensile strength, viscosity and molecular weight (Mw) of polymer samples increase with both the dose and the concentration, showing a high value of Mw up to ≈108. Swelling of hydrogels under water with respect to time varies due to the variation of cross-linking density formed in the gels and the maximum swelling mainly occurs within 24 h. A remarkable change of surface morphology reveals characteristic features of monomer, polymer and hydrogel films.

  20. Bespoke cationic nano-objects via RAFT aqueous dispersion polymerisation

    OpenAIRE

    Williams, M.; Penfold, NJW; Lovett, JR; Warren, NJ; Douglas, CWI; Doroshenko, N; Verstraete, P; Smets, J; Armes, SP

    2016-01-01

    A range of cationic diblock copolymer nanoparticles are synthesised via polymerisation-induced self-assembly (PISA) using a RAFT aqueous dispersion polymerisation formulation. The cationic character of these nanoparticles can be systematically varied by utilising a binary mixture of two macro-CTAs, namely non-ionic poly(glycerol monomethacrylate) (PGMA) and cationic poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride (PQDMA), with poly(2-hydroxypropyl methacrylate) (PHPMA) being selected...

  1. Development of Recombinant Cationic Polymers for Gene Therapy Research

    OpenAIRE

    Canine, Brenda F.; Hatefi, Arash

    2010-01-01

    Cationic polymers created through recombinant DNA technology have the potential to fill a void in the area of gene delivery. The recombinant cationic polymers to be discussed here are amino acid based polymers synthesized in E.coli with the purpose to not only address the major barriers to efficient gene delivery but offer safety, biodegradability, targetability and cost-effectiveness. This review helps the readers to get a better understanding about the evolution of recombinant cationic poly...

  2. Versatile Tandem Ring-Opening/Ring-Closing Metathesis Polymerization: Strategies for Successful Polymerization of Challenging Monomers and Their Mechanistic Studies.

    Science.gov (United States)

    Park, Hyeon; Kang, Eun-Hye; Müller, Laura; Choi, Tae-Lim

    2016-02-24

    Tandem ring-opening/ring-closing metathesis (RO/RCM) results in extremely fast living polymerization; however, according to previous reports, only monomers containing certain combinations of cycloalkenes, terminal alkynes, and nitrogen linkers successfully underwent tandem polymerization. After examining the polymerization pathways, we proposed that the relatively slow intramolecular cyclization might lead to competing side reactions such as intermolecular cross metathesis reactions to form inactive propagating species. Thus, we developed two strategies to enhance tandem polymerization efficiency. First, we modified monomer structures to accelerate tandem RO/RCM cyclization by enhancing the Thorpe-Ingold effect. This strategy increased the polymerization rate and suppressed the chain transfer reaction to achieve controlled polymerization, even for challenging syntheses of dendronized polymers. Alternatively, reducing the reaction concentration facilitated tandem polymerization, suggesting that the slow tandem RO/RCM cyclization step was the main reason for the previous failure. To broaden the monomer scope, we used monomers containing internal alkynes and observed that two different polymer units with different ring sizes were produced as a result of nonselective α-addition and β-addition on the internal alkynes. Thorough experiments with various monomers with internal alkynes suggested that steric and electronic effects of the alkyne substituents influenced alkyne addition selectivity and the polymerization reactivity. Further polymerization kinetics studies revealed that the rate-determining step of monomers containing certain internal alkynes was the six-membered cyclization step via β-addition, whereas that for other monomers was the conventional intermolecular propagation step, as observed in other chain-growth polymerizations. This conclusion agrees well with all those polymerization results and thus validates our strategies. PMID:26878670

  3. Molecular Design, Graft Polymerization and Performance Evaluation of Radiation Curable Flame Retardant Monomers Derived from Phosphorus-Nitrogen Systems

    Science.gov (United States)

    Edwards, Brian Tyndall

    The textile industry is constantly seeking new technologies to make its production more efficient, economical and environmentally friendly. An exciting new strategy to impart value-added functional finishes to textiles is the use of radiation, such as ultraviolet (UV) light, to drive the polymerization of monomers onto the surface of the substrates. These grafted polymeric layers provide the fiber or fabric with interesting new properties, such as antimicrobial behavior, water and oil repellency or flame retardancy. With the aid of a photoinitiator, UV curing can take place very rapidly and the process is waterless and uses less energy than traditional textile wet processing. With these thoughts in mind, this research explores the molecular design, synthesis, UV induced graft polymerization and performance evaluation of nine phosphorus-based flame retardant monomers for cellulosic cotton substrates. All monomers in this work were easily prepared using one-pot reactions procedures. With the assistance of Irgacure 819 photoinitiator, seven of the nine monomers were shown to simultaneously graft and polymerize onto the surface of cotton fabrics under UV radiation. JMPRTM Pro 10 software was used to explore the effect of variables, such as monomer concentration, photoinitiator concentration and UV exposure time, on the yield of the grafted polymeric layer. Burn testing of the treated fabrics in the vertical, 45° and horizontal orientations showed that all nine monomers were effective flame retardants that function via the condensed phase mechanism by encouraging the formation of nonflammable char. These burn test results were validated by thermogravimetric analysis, which demonstrated quantitatively that all nine monomers strongly promote the generation of a protective char. Finally, scanning electron microscopy was used to examine the surface morphology of the treated fabrics and visualize the grafted polymeric layer.

  4. Hydration Structure of the Quaternary Ammonium Cations

    KAUST Repository

    Babiaczyk, Wojtek Iwo

    2010-11-25

    Two indicators of the hydropathicity of small solutes are introduced and tested by molecular dynamics simulations. These indicators are defined as probabilities of the orientation of water molecules\\' dipoles and hydrogen bond vectors, conditional on a generalized distance from the solute suitable for arbitrarily shaped molecules. Using conditional probabilities, it is possible to distinguish features of the distributions in close proximity of the solute. These regions contain the most significant information on the hydration structure but cannot be adequately represented by using, as is usually done, joint distance-angle probability densities. Our calculations show that using our indicators a relative hydropathicity scale for the interesting test set of the quaternary ammonium cations can be roughly determined. © 2010 American Chemical Society.

  5. Univalent-cation-elicited acidification by yeasts.

    Science.gov (United States)

    Kotyk, A; Georghiou, G

    1994-08-01

    Addition of univalent cations to sugar-metabolizing Saccharomyces cerevisiae, Schizosaccharomyces pombe and Lodderomyces elongisporus brought about a powerful acidification of the external medium with rates up to nearly 20 nmol H+ per min per mg dry wt. in S. cerevisiae, over 15 nmol in S. pombe, and 4.7 nmol in L. elongisporus. These rates were as much as 20 times, 5.5 times and 10.3 times, respectively. higher than in the absence of K+. Use of galactose-induced cells, of H(+)-ATPase-deficient mutants and observations over the entire growth curve indicated that the K+ effect on H+ extrusion is not connected with the H(+)-ATPase function as such but rather depends on metabolic reactions producing ATP. The effect has apparently nothing to do with the electrical potential across the plasma membrane. PMID:7804140

  6. Retention of Cationic Starch onto Cellulose Fibres

    Science.gov (United States)

    Missaoui, Mohamed; Mauret, Evelyne; Belgacem, Mohamed Naceur

    2008-08-01

    Three methods of cationic starch titration were used to quantify its retention on cellulose fibres, namely: (i) the complexation of CS with iodine and measurement of the absorbency of the ensuing blue solution by UV-vis spectroscopy; (ii) hydrolysis of the starch macromolecules followed by the conversion of the resulting sugars to furan-based molecules and quantifying the ensuing mixture by measuring their absorbance at a Ι of 490 nm, using the same technique as previous one and; finally (iii) hydrolysis of starch macromolecules by trifluoro-acetic acid and quantification of the sugars in the resulting hydrolysates by high performance liquid chromatography. The three methods were found to give similar results within the range of CS addition from 0 to 50 mg per g of cellulose fibres.

  7. Capturing dynamic cation hopping in cubic pyrochlores

    Science.gov (United States)

    Brooks Hinojosa, Beverly; Asthagiri, Aravind; Nino, Juan C.

    2011-08-01

    In direct contrast to recent reports, density functional theory predicts that the most stable structure of Bi2Ti2O7 pyrochlore is a cubic Fd3¯m space group by accounting for atomic displacements. The displaced Bi occupies the 96g(x,x,z) Wyckoff position with six equivalent sites, which create multiple local minima. Using nudged elastic band method, the transition states of Bi cation hopping between equivalent minima were investigated and an energy barrier between 0.11 and 0.21 eV was determined. Energy barriers associated with the motion of Bi between equivalent sites within the 96g Wyckoff position suggest the presence of dielectric relaxation in Bi2Ti2O7.

  8. Interaction of actinide cations with synthetic polyelectrolytes

    International Nuclear Information System (INIS)

    The binding of Am+3, Th+4 and UO2+2 to polymaleic acid, polyethylenemaleic acid and polymethylvinylethermaleic acid has been measured by a solvent extraction technique at 250C and either 0.02 or 0.10 M ionic strength. The solutions were buffered over a pH range such that the percent of carboxylate groups ionized ranged from 25 to 74%. The binding was described by two constants, β1 and β2, which were evaluated after correction for complexation of the actinide cations by acetate and hydrolysis. For comparable degrees of ionization, all three polyelectrolytes showed similar binding strengths. In general, these results indicated that the binding of actinides to these synthetic polyelectrolytes is basically similar to that of natural polyelectrolytes such as humic and fulvic acids. (orig.)

  9. Antiviral effect of cationic compounds on bacteriophages

    Directory of Open Access Journals (Sweden)

    Mai Huong eChatain-Ly

    2013-03-01

    Full Text Available The antiviral activity of several cationic compounds - cetytrimethylammonium (CTAB, chitosan, nisin and lysozyme - was investigated on the bacteriophage c2 (DNA head and non-contractile tail infecting Lactococcus strains and the bacteriophage MS2 (F-specific RNA infecting E.coli. Firstly, these activities were evaluated in a phosphate buffer pH 7- 10 mM. The CTAB had a virucidal effect on the Lactococcus bacteriophages, but not on the MS2. After 1 min of contact with 0.125 mM CTAB, the c2 population was reduced from 6 log(pfu/mL to 1,5 log(pfu/mL and completely deactivated at 1 mM. On the contrary, chitosan inhibited the MS2 more than it did the bacteriophages c2. No antiviral effect was observed for the nisin or the lysozyme on bacteriophages after 1 min of treatment. A 1 and 2.5 log reduction was respectively observed for nisin and lysozyme when the treatment time increased (5 or 10 min. These results showed that the antiviral effect depended both on the virus and structure of the antimicrobial compounds. The antiviral activity of these compounds was also evaluated in different physico-chemical conditions and in complex matrices. The antiviral activity of CTAB was impaired in acid pH and with an increase of the ionic strength. These results might be explained by the electrostatic interactions between cationic compounds and negatively charged particles such as bacteriophages or other compounds in a matrix. Milk proved to be protective suggesting the components of food could interfere with antimicrobial compounds.

  10. Role of extracellular cations in cell motility, polarity, and chemotaxis

    Directory of Open Access Journals (Sweden)

    Soll D

    2011-04-01

    Full Text Available David R Soll1, Deborah Wessels1, Daniel F Lusche1, Spencer Kuhl1, Amanda Scherer1, Shawna Grimm1,21Monoclonal Antibody Research Institute, Developmental Studies, Hybridoma Bank, Department of Biology, University of Iowa, Iowa City; 2Mercy Medical Center, Surgical Residency Program, Des Moines, Iowa, USAAbstract: The concentration of cations in the aqueous environment of free living organisms and cells within the human body influence motility, shape, and chemotaxis. The role of extracellular cations is usually perceived to be the source for intracellular cations in the process of homeostasis. The role of surface molecules that interact with extracellular cations is believed to be that of channels, transporters, and exchangers. However, the role of Ca2+ as a signal and chemoattractant and the discovery of the Ca2+ receptor have demonstrated that extracellular cations can function as signals at the cell surface, and the plasma membrane molecules they interact with can function as bona fide receptors that activate coupled signal transduction pathways, associated molecules in the plasma membrane, or the cytoskeleton. With this perspective in mind, we have reviewed the cationic composition of aqueous environments of free living cells and cells that move in multicellular organisms, most notably humans, the range of molecules interacting with cations at the cell surface, the concept of a cell surface cation receptor, and the roles extracellular cations and plasma membrane proteins that interact with them play in the regulation of motility, shape, and chemotaxis. Hopefully, the perspective of this review will increase awareness of the roles extracellular cations play and the possibility that many of the plasma membrane proteins that interact with them could also play roles as receptors.Keywords: extracellular cations, chemotaxis, transporters, calcium, receptors

  11. Effects of monomer functionality on performances of scaffolding morphologic transmission gratings recorded in polymer dispersed liquid crystals

    International Nuclear Information System (INIS)

    The effects of monomer functionality on performances of holographic polymer dispersed liquid crystal (HPDLC) transmission gratings are systematically investigated. Acrylate monomers with an average functionality ranging from 2.0 to 5.0 are used to prepare these samples. We find scaffolding morphologic transmission gratings (characterized by a high phase separation degree, a well alignment of LCs and low scattering loss) can be obtained irrespective of the monomer functionality, although the exact optimal curing intensity varies. The temporal evolution of the grating formation is studied and the onset time of the LC phase separation decreases significantly with the increase in average monomer functionality. It is also shown that the gratings prepared from low average functionality monomers require a comparatively low switch-off electric field (∼8 V μm−1) whilst suffering from mechanical fragility and long-term instability. Our results not only provide a complete understanding of scaffolding morphologic gratings in terms of the material composition effect, but also provide insight into the formation mechanisms of non-droplet morphologic HPDLC gratings. (paper)

  12. The Effect of Hydration on the Cation-π Interaction Between Benzene and Various Cations

    Indian Academy of Sciences (India)

    VIKASH DHINDHWAL; N SATHYAMURTHY

    2016-10-01

    The effect of hydration on cation-π interaction in Mq+ BmWn (B = benzene; W = water; Mq+ =Na⁺, K⁺, Mg²⁺, Ca²⁺, Al³⁺, 0 ≤ n,m ≤ 4, 1≤ m + n ≤ 4) complexes has been investigated using ab initio quantum chemical methods. Interaction energy values computed at the MP2 level of theory using the 6-31G(d,p) basis set reveal a qualitative trend in the relative affinity of different cations for benzene and water in these complexes. The π–cloud thickness values for benzene have also been estimated for these systems.

  13. Cationic Mucic Acid Polymer-Based siRNA Delivery Systems.

    Science.gov (United States)

    Pan, Dorothy W; Davis, Mark E

    2015-08-19

    Nanoparticle (NP) delivery systems for small interfering RNA (siRNA) that have good systemic circulation and high nucleic acid content are highly desired for translation into clinical use. Here, a family of cationic mucic acid-containing polymers is synthesized and shown to assemble with siRNA to form NPs. A cationic mucic acid polymer (cMAP) containing alternating mucic acid and charged monomers is synthesized. When combined with siRNA, cMAP forms NPs that require steric stabilization by poly(ethylene glycol) (PEG) that is attached to the NP surface via a 5-nitrophenylboronic acid linkage (5-nitrophenylboronic acid-PEGm (5-nPBA-PEGm)) to diols on mucic acid in the cMAP in order to inhibit aggregation in biological fluids. As an alternative, cMAP is covalently conjugated with PEG via two methods. First, a copolymer is prepared with alternating cMAP-PEG units that can form loops of PEG on the surface of the formulated siRNA-containing NPs. Second, an mPEG-cMAP-PEGm triblock polymer is synthesized that could lead to a PEG brush configuration on the surface of the formulated siRNA-containing NPs. The copolymer and triblock polymer are able to form stable siRNA-containing NPs without and with the addition of 5-nPBA-PEGm. Five formulations, (i) cMAP with 5-nPBA-PEGm, (ii) cMAP-PEG copolymer both (a) with and (b) without 5-nPBA-PEGm, and (iii) mPEG-cMAP-PEGm triblock polymer both (a) with and (b) without 5-nPBA-PEGm, are used to produce NPs in the 30-40 nm size range, and their circulation times are evaluated in mice using tail vein injections. The mPEG-cMAP-PEGm triblock polymer provides the siRNA-containing NP with the longest circulation time (5-10% of the formulation remains in circulation at 60 min postdosing), even when a portion of the excess cationic components used in the formulation is filtered away prior to injection. A NP formulation using the mPEG-cMAP-PEGm triblock polymer that is free of excess components could contain as much as ca. 30 wt % siRNA. PMID

  14. In vivo toxicity of cationic micelles and liposomes

    DEFF Research Database (Denmark)

    Knudsen, Kristina Bram; Northeved, Helle; Ek, Pramod Kumar;

    2015-01-01

    This study investigated toxicity of nanocarriers comprised of cationic polymer and lipid components often used in gene and drug delivery, formulated as cationic micelles and liposomes. Rats were injected intravenously with 10, 25 or 100 mg/kg and sacrificed after 24 or 48 h, or 24 h after the las...

  15. Stable polyfluorinated cycloalkenyl cations and their NMR spectra

    International Nuclear Information System (INIS)

    New stable 1-methoxyperfluoro-2-ethylcyclobutenyl, 1-methoxyperfluoro-2-methylcyclo-pentenyl, and 1-methoxyperfluoro-2-ethylcyclohexenyl cations were obtained by the action of antimony pentafluoride on the corresponding olefins. The distribution of the charges in the investigated polyfluorinated cycloalkenyl cations was investigated by 13C NMR method

  16. Photodynamic Inactivation of Bacteria and Biofilms Using Cationic Bacteriochlorins

    Science.gov (United States)

    Meerovich, G. A.; Tiganova, I. G.; Makarova, E. A.; Meerovich, I. G.; Romanova Ju., M.; Tolordova, E. R.; Alekseeva, N. V.; Stepanova, T. V.; Yu, Koloskova; Luk'anets, E. A.; Krivospitskaya, N. V.; Sipailo, I. P.; Baikova, T. V.; Loschenov, V. B.; Gonchukov, S. A.

    2016-02-01

    This work is devoted to the study of two new synthetic bacteriochlorins with four and eight cationic substitutes as the photosensitizers in the photodynamic process. The spectral and antibacterial properties of these photosensitizers in saline solution were investigated. It is shown, that the aggregation ability decreases and the antibacterial efficiency grows as the cationic substitute number increases.

  17. Effects of metallic cations in the beryl flotation

    International Nuclear Information System (INIS)

    The beryl zeta potential in microelectrophoretic cell is studied in the presence of neutral electrolyte, cations of calcium, magnesium and iron. The petroleum sulfonate is used how collector in Hallimond tube. Hydroxy complex of metallic cations seems activate the ore and precipitates of colloidal metallic hidroxies seems lower him when added to the mixture. (M.A.C.)

  18. Formation of surface relief gratings with homeotropically oriented photopolymer from a photocross-linkable organic monomer.

    Science.gov (United States)

    Zhao, Dongyu; Xu, Zeda; Wang, Guojie; Cao, Hui; Li, Wenbo; He, Wanli; Huang, Wei; Yang, Zhou; Yang, Huai

    2010-02-21

    In this communication, we describe a simple process for the generation of surface relief gratings (SRG). SRG are fabricated from a photocross-linkable organic monomer PDACE (4-propyldiphenylacetylenecarboxylic acid cinnamyl ester) with cinnamyl ester and tolane groups, by using a patterned non-polarized UV light irradiation. The patterns of the surface relief structures can be easily controlled and the modulation depth can reach 130 nm. Moreover, it is interestingly observed that the photopolymer of the SRG exhibits distinctive characteristics including homeotropic orientation and fluorescence properties as a result of the photocross-linking of the dual photoreactive groups of PDACE. Finally, the mechanism of fabrication of SRG from PDACE is discussed with mean-field theory.

  19. Ethanol monomers and dimers revisited: a Raman study of conformational preferences and argon nanocoating effects.

    Science.gov (United States)

    Wassermann, Tobias N; Suhm, Martin A

    2010-08-19

    The gauche-trans conformational distribution in ethanol can be determined from the OH stretching Raman spectrum of seeded supersonic jet expansions, which thus provides a sensitive conformational thermometer. Depending on the rare gas mixture, one, two or four ethanol dimer conformations are abundant. Their conformational assignment is facilitated by the observation of hydrogen bond acceptor modes, which have similar Raman cross sections but much inferior infrared intensities than donor modes. Ethanol monomers and dimers can be progressively Ar-coated, and the resulting spectra may be compared with those in a bulk argon matrix. The low frequency range of torsional transitions provides some evidence for conformation-changing transitions in Raman jet spectra. PMID:20701332

  20. KINETIC ANALYSIS OF CO-CONDENSATION POLYMERIZATION OF AB2 AND AB MONOMERS

    Institute of Scientific and Technical Information of China (English)

    Min-qiang Yu; Zhi-ping Zhou; De-yue Yan

    2004-01-01

    This work deals with the kinetics of co-condensation polymerization of AB2 and AB monomers, giving expressions of the two-dimensional molecular weight distribution function and the number/weight average molecular weights of the resulting copolymers. The two-dimensional molecular weight distribution depends on two indices, n and l, which are the respective numbers of AB2 and AB units in a copolymer species. The evolution of the two-dimensional weight and z distributions during the co-condensation polymerization has been evaluated systematically. Finally, the two-dimensional distribution was transformed into a one-dimensional molecular weight distribution with only one variable (the molecular weight of the products instead of the degree of polymerization). The calculated results show that the highly branched copolymer has a very broad molecular weight distribution when the co-condensation polymerization approaches completion.

  1. Progress of Research in Treatment of Hyperlipidemia by Monomer or Compound Recipe of Chinese Herbal Medicine

    Institute of Scientific and Technical Information of China (English)

    DOU Xiao-bing; WO Xing-de; FAN Chun-lei

    2008-01-01

    Hyperlipidemia (HLP) is the No.1 risk factor for patients with atherosclerosis (AS) and is directly related to the occurrence of coronary artery disease (CAD) and cerebrovascular disease. Therefore, prevention and treatment of AS is of great importance and of practical significance in controlling the incidence and mortality of CAD. With its peculiar syndrome-dependent therapy, traditional Chinese medicine (TCM) has accumulated abundant practical experiences in this field and good clinical effects have been achieved. Chinese herbal medicine, with its particularly unique advantages and high potentials yet to be tapped, displays its huge strength in HLP prevention and treatment. The progress of studies concerning prevention and treatment of HLP by Chinese herbal medicines, in the form of monomers or compound recipes, is reviewed in this paper.

  2. Simulation research on monomer agglomeration of nonmetallic inclusions in steel with a diffusion limited aggregation model

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The monomer agglomeration of nonmetallic inclusions was simulated with a diffusion limited aggregation (DLA) model of the fractal theory.The simulation study with a random two-dimensional diffusion was carried out.The results indicate that the DLA model can be used for the simulation of agglomeration behavior of the cluster-type inclusions.The morphology of clusters was observed with SEM and compared with the simulated agglomerates.The modelling procedure of the DLA model is applicable for the agglomeration process.The uncertainty of agglomeration process and the persuasive average agglomerative ratio was analyzed.The factors about the agglomerative ratio with the collision path distance and the size of particles or seed were discussed.The adherence of the nonmetallic inclusions on the dam, the weir and the walls of a tundish, and the absorption of inclusions by stopper or nozzle were also discussed.

  3. Phase diagrams for the adsorption of monomers with non-additive interactions

    Science.gov (United States)

    Pinto, O. A.; Ramirez-Pastor, A. J.; Nieto, F.

    2016-09-01

    In several experimental systems phase diagrams coverage-temperature show a strong asymmetry. This behavior can be reproduced by including non-additive lateral interactions. In this work a Monte Carlo study on the canonical assembly of the criticality of monomer adsorption with non-additive interactions is presented. Traditional pairwise energies were replaced by other more general ones where the lateral interaction between two ad-atoms depends on the coverage at first sphere of coordination. This kind of energies includes multibody interactions like three-body interactions and four-body interactions, etc. These energies induce the formation of several non-additive ordered structures. Finite size scaling method was used to classify the order of phase transition of each non-additive phase. On the other hand, the corresponding phase diagrams are formed naturally, in which case the diagrams show strong asymmetries.

  4. Synergistic Hypergolic Ignition of Amino End Group in Monomers and Polymers

    Directory of Open Access Journals (Sweden)

    S. P. Panda

    1986-10-01

    Full Text Available A few monomers, oligomers and polymers with amino end groups have been discovered to undergo synergistic ignition with red fuming nitric acid (RFNA when mixed with large quantities of magnesium powder. Aluminium powder under similar conditions does not ignite the mixture while powders of Zn, Co and Cu cause the ignition. Amongst the polymers used in the experiment commercially available nylon 6 is the most important which may be used as a binder for rocket propellant fuel grains, hypergolic with RFNA. Degree of polymerisation or the chain length of the polymers does not drastically affect the synergistic ignition of the polymer mixture with magnesium powder but high molecular weight and fully aromatised polymers like Kevlar and Nomex fail to ignite under similar conditions. Based upon the earlier work of the authors, explanations for the phenomena oberved have been provided in terms of creation of hot spots leading to ignition at the amino end groups.

  5. Environmental effects on the lignin model monomer, vanillyl alcohol, studied by raman spectroscopy

    DEFF Research Database (Denmark)

    Larsen, Kiki Lyster; Barsberg, Søren Talbro

    2011-01-01

    units, respectively. Raman spectroscopy gives valuable knowledge on lignin and has a large potential for further developments. Thus in the present work we show how the use of electronic structure theory can support the study of environmental effects on lignin Raman bands. Raman spectra of the lignin...... model monomer, vanillyl alcohol (G type), dissolved in different solvents were compared to investigate such effects on the Raman band shapes and positions. Density functional theory combined with the polarizable continuum model were applied to assign the observed bands and tested for prediction accuracy....... Two ring deformation modes at 1600 cm–1 showed strong dependency on solvent ability to act as hydrogen bond donor, and this has to be considered in addition to substitutional effects on these modes....

  6. Extraction, characterization of components, and potential thermoplastic applications of camelina meal grafted with vinyl monomers.

    Science.gov (United States)

    Reddy, Narendra; Jin, Enqi; Chen, Lihong; Jiang, Xue; Yang, Yiqi

    2012-05-16

    Camelina meal contains oil, proteins, and carbohydrates that can be used to develop value-added bioproducts. In addition to containing valuable polymers, coproducts generated during the production of biofuels are inexpensive and renewable. Camelina is a preferred oilseed crop for biodiesel production because camelina is easier to grow and provides better yields. In this research, the components in camelina meal were extracted and studied for their composition, structure, and properties. The potential of using the camelina meal to develop thermoplastics was also studied by grafting various vinyl monomers. Oil (19%) extracted from camelina meal could be useful for food and fuel applications, and proteins and cellulose in camelina meal could be useful in the development of films, fibers, and thermoplastics. Thermoplastic films developed from grafted camelina meal had excellent wet tensile properties, unlike thermoplastics developed from other biopolymers. Camelina meal grafted with butylmethacrylate (BMA) had high dry and wet tensile strengths of 53.7 and 17.3 MPa, respectively.

  7. Electrosynthesis and characterization of a conductive polythiophene deriving from a terthiophene monomer

    International Nuclear Information System (INIS)

    The electrochemical polymerization of the 3,3''-di[(S)-(+)-2-methylbutyl]-2,2':5',2''-terthiophene (DMBTT) monomer was carried out potentiodynamically on indium tin oxide (ITO), Pt or glassy carbon (GC) electrodes in anhydrous CH3CN with TBAPF6 as supporting electrolyte. Films with good adhesion were obtained for all the tested substrates and they were characterized by various analytical techniques including UV-Vis-NIR absorption spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM), and gel permeation chromatography (GPC). The most outstanding properties of the electrochemically synthesized polymer were compared with those of the same polymer obtained by a chemical method. The film obtained on ITO displayed a reversible electrochromic behavior under potential switching between -0.50 and +1.00 V vs. SCE.

  8. Electrosynthesis and characterization of a conductive polythiophene deriving from a terthiophene monomer

    Energy Technology Data Exchange (ETDEWEB)

    Cocchi, Valentina [Dipartimento di Chimica Industriale e dei Materiali, Universita di Bologna, V.le Risorgimento 4, 40136 Bologna (Italy); Guadagnini, Lorella; Mignani, Adriana [Dipartimento di Chimica Fisica ed Inorganica, UdR Bologna, V.le Risorgimento 4, 40136 Bologna (Italy); Salatelli, Elisabetta [Dipartimento di Chimica Industriale e dei Materiali, Universita di Bologna, V.le Risorgimento 4, 40136 Bologna (Italy); Tonelli, Domenica, E-mail: domenica.tonelli@unibo.it [Dipartimento di Chimica Fisica ed Inorganica, UdR Bologna, V.le Risorgimento 4, 40136 Bologna (Italy)

    2011-08-01

    The electrochemical polymerization of the 3,3''-di[(S)-(+)-2-methylbutyl]-2,2':5',2''-terthiophene (DMBTT) monomer was carried out potentiodynamically on indium tin oxide (ITO), Pt or glassy carbon (GC) electrodes in anhydrous CH{sub 3}CN with TBAPF{sub 6} as supporting electrolyte. Films with good adhesion were obtained for all the tested substrates and they were characterized by various analytical techniques including UV-Vis-NIR absorption spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM), and gel permeation chromatography (GPC). The most outstanding properties of the electrochemically synthesized polymer were compared with those of the same polymer obtained by a chemical method. The film obtained on ITO displayed a reversible electrochromic behavior under potential switching between -0.50 and +1.00 V vs. SCE.

  9. Microporous Polymers from a Carbazole-Based Triptycene Monomer: Synthesis and Their Applications for Gas Uptake.

    Science.gov (United States)

    Zhai, Tian-Long; Tan, Liangxiao; Luo, Yi; Liu, Jun-Min; Tan, Bien; Yang, Xiang-Liang; Xu, Hui-Bi; Zhang, Chun

    2016-01-01

    Two kinds of novel organic microporous polymers TCPs (TCP-A and TCP-B) were prepared by two cost-effective synthetic strategies from the monomer of tricarbazolyltriptycene (TCT). Their structure and properties were characterized by FT-IR, solid (13) C NMR, powder XRD, SEM, TEM, and gas absorption measurements. TCP-B displayed a high surface area (1469 m(2)  g(-1) ) and excellent H2 storage (1.70 wt % at 1 bar/77 K) and CO2 uptake abilities (16.1 wt % at 1 bar/273 K), which makes it a promising material for potential application in gas storage.

  10. Anhydrous trifluoroacetic acid pretreatment converts insoluble polyglutamine peptides to soluble monomers

    Directory of Open Access Journals (Sweden)

    Gunasekhar Burra

    2015-12-01

    Full Text Available The data provided in this article are related to the research article entitled “Unaided trifluoroacetic acid pretreatment solubilizes polyglutamine (polyGln peptides and retains their biophysical properties of aggregation” by Burra and Thakur (in press [1]. This research article reports data from size exclusion chromatography (SEC, reversed phase-high performance liquid chromatography (RP-HPLC and mass spectrometry (MS assays. This data show that trifluoroacetic acid (TFA has the ability to convert insoluble polyGln peptides to soluble monomers. The data also clarify the possibility of trifluoroacetylation modification caused due to TFA. We hope the data presented here will enhance the understanding of polyGln disaggregation and solubilization. For more insightful and useful discussions, see the research article published in Analytical Biochemistry: Methods in the Biological Sciences (Burra and Thakur, in press [1].

  11. Synthesis of fluorinated dimethacrylate monomer and its application in preparing Bis-GMA free dental resin.

    Science.gov (United States)

    Yin, Mei; Guo, Sen; Liu, Fang; He, Jingwei

    2015-11-01

    With the aim to reduce human exposure to Bis-phenol A derivatives, a novel fluorinated dimethacrylate monomer FUDMA was synthesized and mixed with triethyleneglycol dimethacrylate (TEGDMA) to prepare 2,2-bis[4-(2-hydroxy-3-methacryloy- loxypropyl)phenyl]propane (Bis-GMA) free dental resin system. Physicochemical properties, such as double bond conversion (DC), polymerization shrinkage (VS), water sorption (WS) and solubility (SL), flexural strength (FS) and modulus (FM), and fracture energy of FUDMA/TEGDMA resin system were investigated. Bis-GMA/TEGDMA resin system was used as a control. The results showed that, compared with Bis-GMA/TEGDMA resin system, FUDMA/TEGDMA had advantages like higher DC, lower VS, and higher fracture energy, but had no disadvantages. Therefore, FUDMA/TEGDMA resin system had better comprehensive physicochemical properties than Bis-GMA/TEGDMA resin system, and FUDMA had potential to be used as a substitute for Bis-GMA.

  12. Compensated Arrhenius formalism applied to a conductivity study in poly(propylene glycol) diacrylate monomers

    Science.gov (United States)

    Dubois, F.; Derouiche, Y.; Leblond, J. M.; Maschke, U.; Douali, R.

    2015-09-01

    The temperature dependence of the ionic conductivity is studied in a series of poly(propylene glycol) diacrylate monomers. The experimental data are analyzed by means of the approach recently proposed by Petrowsky et al. [J. Phys. Chem. B. 113, 5996 (2009), 10.1021/jp810095g]. This so-called compensated Arrhenius formalism (CAF) approach takes into account the influence of the dielectric permittivity on the exponential prefactor in the classical Arrhenius equation. The experimental data presented in this paper show a good agreement with the CAF; this means that the exponential prefactor is principally dielectric permittivity dependent. The compensated data revealed two conduction processes with different activation energies; they correspond to low and high temperature ranges, respectively.

  13. Surface reliefs on diacrylate monomer films by spatially controlled UV photopolymerization

    International Nuclear Information System (INIS)

    The non-uniform ultraviolet (UV) photopolymerization of acrylic films allows the formation of surface reliefs through a self-developing process. The parameters that influence the growth of the reliefs for polymer films made of bis-phenol-A-diglycidil-ether diacrylate (BGEDA), an aliphatic polyurethane diacrylate and an aromatic polyurethane diacrylate, mixed with tri-propylen-glycol diacrylate as promoter, have been investigated. The results show that the time of photopolymerization, the after-curing self-developing time, the mixture composition and the polymer film thickness influence the relief development in a complex way. The behaviours of the different monomers were explained on the basis of two main factors: the properties of the polymeric network and the diffusion phenomena which take place in the polymer bulk

  14. Monte Carlo simulation of star/linear and star/star blends with chemically identical monomers

    Energy Technology Data Exchange (ETDEWEB)

    Theodorakis, P E [Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina (Greece); Avgeropoulos, A [Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina (Greece); Freire, J J [Departamento de Ciencias y Tecnicas FisicoquImicas, Universidad Nacional de Educacion a Distancia, Facultad de Ciencias, Senda del Rey 9, 28040 Madrid (Spain); Kosmas, M [Department of Chemistry, University of Ioannina, 45110 Ioannina (Greece); Vlahos, C [Department of Chemistry, University of Ioannina, 45110 Ioannina (Greece)

    2007-11-21

    The effects of chain size and architectural asymmetry on the miscibility of blends with chemically identical monomers, differing only in their molecular weight and architecture, are studied via Monte Carlo simulation by using the bond fluctuation model. Namely, we consider blends composed of linear/linear, star/linear and star/star chains. We found that linear/linear blends are more miscible than the corresponding star/star mixtures. In star/linear blends, the increase in the volume fraction of the star chains increases the miscibility. For both star/linear and star/star blends, the miscibility decreases with the increase in star functionality. When we increase the molecular weight of linear chains of star/linear mixtures the miscibility decreases. Our findings are compared with recent analytical and experimental results.

  15. Water and acrylamide monomer transfer rates from a settling basin to groundwaters.

    Science.gov (United States)

    Binet, Stéphane; Bru, Kathy; Klinka, Thomas; Touzé, Solène; Motelica-Heino, Mickael

    2015-05-01

    The aim of this paper was to estimate the potential leakage of acrylamide monomer, used for flocculation in a settling basin, towards the groundwaters. Surface-groundwater interactions were conceptualized with a groundwater transport model, using a transfer rate to describe the clogged properties of the interface. The change in the transfer rate as a function of the spreading of the clogged layer in the settling basin was characterized with respect to time. It is shown that the water and the Acrylamide transfer rate are not controlled by the spreading of the clogged layer until this layer fully covers the interface. When the clogged layer spreads out, the transfer rate remains in the same order of magnitude until the area covered reaches 80 %. The main flux takes place through bank seepage. In these early stage conditions of a working settling basin, the acrylamide flux towards groundwaters remains constant, at close to 10 g/year (±5).

  16. Luminal and parenteral TFF2 and TFF3 dimer and monomer in two models of experimental colitis in the rat

    DEFF Research Database (Denmark)

    Poulsen, Steen Seier; Kissow, Hannelouise; Hare, Kristine;

    2005-01-01

    % dextran sodium sulphate in the drinking water or by one intraperitoneal injection of mitomycin C, 3.75 mg/kg. TFF peptides were administered as subcutaneous injections or directly into the lumen via a catheter placed in the proximal colon. Treatments were saline, TFF2, TFF3 monomer or TFF3 dimer 5 mg....../kg twice per day throughout the study [dextran sulphate sodium (DSS)] or from day 4 to 7 (mitomycin C). Colitis severity was scored in a stereomicroscope and histologically. RESULTS: Luminal treatment with TFF3 in its dimeric form significantly improved the colitis score in both colitis models, whereas TFF...... in both colitis models. CONCLUSIONS: Intracolonic administration of TFF3 dimer and TFF2 improves experimentally induced colitis in rats. The TFF3 monomer has no effect. Parenteral administration of TFF peptides aggravates the colitis especially the TFF3 monomer....

  17. Monomer Basis Representation Method For Calculating The Spectra Of Molecular Clusters I. The Method And Qualitative Models

    CERN Document Server

    Ocak, Mahir E

    2012-01-01

    Firstly, a sequential symmetry adaptation procedure is derived for semidirect product groups. Then, this sequential symmetry adaptation procedure is used in the development of new method named Monomer Basis Representation (MBR) for calculating the vibration-rotation-tunneling (VRT) spectra of molecular clusters. The method is based on generation of optimized bases for each monomer in the cluster as a linear combination of some primitive basis functions and then using the sequential symmetry adaptation procedure for generating a small symmetry adapted basis for the solution of the full problem. It is seen that given an optimized basis for each monomer the application of the sequential symmetry adaptation procedure leads to a generalized eigenvalue problem instead of a standard eigenvalue problem if the procedure is used as it is. In this paper, MBR method will be developed as a solution of that problem such that it leads to generation of an orthogonal optimized basis for the cluster being studied regardless of...

  18. Quantitation of oxidized triglyceride monomers and dimers as an useful measurement for early and advanced stages of oxidation

    Directory of Open Access Journals (Sweden)

    Márquez-Ruiz, G.

    1996-04-01

    Full Text Available Quantitation of oxidized triglyceride monomers and dimers is reported as a good measurement for early and advanced stages of oxidation. Applicability of this approach to follow-up oxidation was tested in samples of trilinolein and methyl linoleate stored at either room temperature or 60°C for different periods of time. Oxidized monomers, dimers and polymers were determined in 50 mg-samples by adding monostearin as internal standard and applying a combination of adsorption chromatography, using silica cartridges, followed by high-performance size-exclusion chromatography. Additionally, peroxide values and tocopherol contents were measured. Results showed that a significant rise of dimeric compounds denoted the end of the induction period while oxidized monomers were the only group of compounds showing a progressive increase during the early stages of oxidation.

  19. Structural effect of monomer type on properties of copolyimides and copolyimide-silica hybrid materials

    Directory of Open Access Journals (Sweden)

    Kizilkaya Canan

    2015-01-01

    Full Text Available In this work, the effect of two different diamine monomers, containing phosphine oxide, on thermal, mechanical and morphological properties of copolyimides and their hybrid materials was investigated. Gas separation properties of the synthesized copolyimides were also analysed. Two different diamine monomers with phosphine oxide were bis(3-aminophenyl phenylphosphine oxide (BAPPO and bis(3-aminophenoxy-4-phenyl phenylphosphine oxide (m-BAPPO. In the synthesis of copolyimides 3,3’-diamino-diphenyl sulfone (DDS was also used as the diamine, as well as 2,2’-bis(3,4-dicarboxyphenylhexafluoropropane dianhydride (6FDA. Copolyimide films were prepared by thermal imidization. Hybrid materials containing 5 % SiO2 were synthesised further by sol-gel technique. The Fourier-transform infrared spectroscopy (FTIR, Nuclear magnetic resonance spectroscopy (NMR confirmed the expected structure. Dynamic mechanical analysis (DMA demonstrated that m-BAPPO based copolyimides had lower glass transition temperatures (Tg than BAPPO based copolyimides. m-BAPPO containing copolyimide without silica shifted the thermal decomposition temperature to a higher value. The moduli and strength values of BAPPO diamine containing copolyimide and its hybrid were higher than those of m-BAPPO containing materials. The contact angle measurements showed the hydrophobicity. Scanning electron microscope (SEM analysis exhibited the silica particles dispersion in the copolyimides. These copolyimides may be used in the coating industry. The CO2 permeability and the permselectivity were the highest among the other values in this study, when m-BAPPO containing copolyimide in the absence of silica was used. The gas permeabilities obtained from this work were in this decreasing order: PCO2 > PO2 > PN2.

  20. Improvement of antithrombogenicity of a fluoro polymer by radiation-induced grafting of hydrophilic monomer

    International Nuclear Information System (INIS)

    Fluoro polymers have been used as biomaterials in medical field since they have good compatibility with both tissue and blood, and their biomaterial application are of variety. Blood compatibility of fluoro polymers, however, are not always enough for every applications. Especially, there is a large difficulty in the application for artificial vessel with small radius below than 4 mm. In the present study, grafting of a hydrophilic monomer onto a fluoro polymer has been carried out to improve blood compatibility of the fluoro polymer. The technique of grafting employed here was simultaneous irradiation method of gamma rays from a 60Co source. The fluoro polymer and the hydrophilic monomer used in the experiment were alternative copolymer of ethylene and tetrafluoethylene(AFLON) and N,N-dimethylacry lamide(DMAA), respectively. After grafting, it was found by in vitro tests that antithrombogenicity of AFLON was improved by grafting of DMAA. It was, however, also found that degree of the improvement is affected by grafting conditions. When ethyl acetate was used as a solvent for the graft copolymerization, the improvement was affected by dose rate. Blood compatibility of DMAA-g-AFLON obtained at a higher dose rate of 1 x 105 rad/h was not improved, while it was improved in the sample of DMAA-g-AFLON obtained at a lower dose rate of 1 x 104 rad/h. On the other hand, when acetone was used as a solvent for the grafting, the degree of grafting gave a significant effect on the improvement. Blood compatibility of all samples with grafting percent more than 20 % was improved by grafting of DMAA. (author)

  1. Association of Fibrin Monomer Polymerization Function, Cerebrovascular Risk Factors and Ischemic Cerebrovascular Disease in Old People

    Institute of Scientific and Technical Information of China (English)

    洪梅; 魏文宁; 李红戈; 杨锐; 杨焰

    2003-01-01

    Summary: In order to investigate the association of fibrin monomer polymerization function (FMPF)with traditional cerebrovascular risk factors and ischemic cerebrovascular disease in old people, 1 : 1paired case-control comparative study was performed for FMPF and traditional cerebrovascular riskfactors on 110 cases of old ischemic cerebrovascular disease and 110 controls matched on age, sex andliving condition. The results showed that cerebrovascular risk factors were more prevalent in casegroup than in control group. In the case group, FMPF was significantly higher than in controlgroup. There was a significant positive correlation between hypertension and fibrin monomer poly-merization velocity (FMPV), hypertension and fibrinogen (Fbg), alcohol consumption and Fbg, butno significant correlation between diabetic mellitus, smoking and FMPF was found. Among the pa-rameters of blood lipids, there were significant positive correlations between total cholesterol (TC)and parameters of FMPF to varying degrees, triglycerides (TG) and FMPV, TG and Fbg. Our re-sults also showed there were significant linear trends between TC and FMPV (P<0. 001), TC andFbg (P=0. 0087), TG and FMPV/Amax (maximum absorbance)(P=0. 0143) respectively. Multi-ple logistic regression analysis revealed that FMPF in case group remained significantly higher thancontrol group after adjustment of all risk factors that were significant in univariate analysis. It wasconcluded that there is a possible pathophysiological link between FMPF and cerebrovascular risk fac-tors. An elevated FMPF is associated with ischemic cerebrovascular disease and an independent riskfactor of this disease. In old people, detection of FMPF might be a useful screening to identify indi-viduals at increased cerebrothrombotic risk.

  2. Identification and quantification of monomers released from dental composites using HPLC

    Directory of Open Access Journals (Sweden)

    Lucí Regina Panka Archegas

    2009-08-01

    Full Text Available The aim of this study was to detect and quantify the main residual monomers released from composites, using high performance liquid chromatography (HPLC. Discs were made with dental composites (Herculite XRV, Tetric Ceram and Filtek Z250 and immersed in deionized water at 37ºC for 28 days, with water changes in 1, 7, 14 and 21 days. The mean concentration of residual monomers were subject to the Kruskal-Wallis test (pA liberação de monômeros residuais pode afetar o comportamento clínico e a biocompatibilidade dos materiais resinosos. O objetivo deste estudo foi detectar e quantificar os principais monômeros residuais liberados de resinas compostas, usando cromatografia líquida de alta performance (HPLC. Discos foram construídos de resinas compostas de uso odontológico (Herculite XRV, Tetric Ceram and Filtek Z250 e imersos em água deionizada a 37ºC durante 28 dias, com mudanças de água em 24 horas, 7, 14 e 21 dias. As concentrações médias dos monômeros residuais foram submetidas ao teste de Kruskal-Wallis (p<0,05. Tetric Ceram apresentou as maiores concentrações de monômeros lixiviados. Bis-GMA foi o monômero liberado em menores concentrações para todos os materiais. Não houve diferença estatística significante entre TEGDMA e UDMA. A maioria dos monômeros demonstrou máxima concentração no período de 7 dias. A análise por meio de HPLC identificou Bis-GMA, TEGDMA e UDMA em quantidades detectáveis para todas as resinas compostas testadas.

  3. Prediction of monomer reactivity in radical copolymerizations from transition state quantum chemical descriptors

    Directory of Open Access Journals (Sweden)

    Zhengde Tan

    2013-01-01

    Full Text Available In comparison with the Q-e scheme, the Revised Patterns Scheme: the U, V Version (the U-V scheme has greatly improved both its accessibility and its accuracy in interpreting and predicting the reactivity of a monomer in free-radical copolymerizations. Quantitative structure-activity relationship (QSAR models were developed to predict the reactivity parameters u and v of the U-V scheme, by applying genetic algorithm (GA and support vector machine (SVM techniques. Quantum chemical descriptors used for QSAR models were calculated from transition state species with structures C¹H3 - C²HR³• or •C¹H2 - C²H2R³ (formed from vinyl monomers C¹H²=C²HR³ + H•, using density functional theory (DFT, at the UB3LYP level of theory with 6-31G(d basis set. The optimum support vector regression (SVR model of the reactivity parameter u based on Gaussian radial basis function (RBF kernel (C = 10, ε = 10- 5 and γ = 1.0 produced root-mean-square (rms errors for the training, validation and prediction sets being 0.220, 0.326 and 0.345, respectively. The optimal SVR model for v with the RBF kernel (C = 20, ε = 10- 4 and γ = 1.2 produced rms errors for the training set of 0.123, the validation set of 0.206 and the prediction set of 0.238. The feasibility of applying the transition state quantum chemical descriptors to develop SVM models for reactivity parameters u and v in the U-V scheme has been demonstrated.

  4. Vulcanization Kinetics and Mechanical Properties of Ethylene Propylene Diene Monomer Thermal Insulation

    Directory of Open Access Journals (Sweden)

    Mohamad Irfan Fathurrohman

    2015-07-01

    Full Text Available The vulcanization kinetics of Ethylene-propylene diene monomer (EPDM rubber thermal insulation was studied by using rheometer under isothermal condition at different temperatures. The rheometry analysis was used to determining the cure kinetic parameters and predicting the cure time of EPDM thermal insulation. The experimental results revealed that the curing curves of EPDM thermal insulation were marching and the optimum curing time decreased with increasing the temperature. The kinetic parameters were determined from the autocatalytic model showed close fitting with the experimental results, indicating suitability of autocatalytic model in characterizing the cure kinetics. The activation energy was determined from the autocatalytic model is 46.3661 kJ mol-1. The cure time were predicted from autocatalytic model and the obtained kinetic parameter by using the relationship among degree of conversion, cure temperature, and cure time. The predictions of cure time provide information for the actual curing characteristic of EPDM thermal insulation. The mechanical properties of EPDM thermal insulation with different vulcanization temperatures showed the same hardness, tensile strength and modulus at 300%, except at temperature 70 °C, while the elongation at breaking point decreased with increasing temperature of vulcanization. © 2015 BCREC UNDIP. All rights reservedReceived: 8th April 2014; Revised: 7th January 2015; Accepted: 16th January 2015How to Cite: Fathurrohman, M.I., Maspanger, D.R., Sutrisno, S. (2015. Vulcanization Kinetics and Mechanical Properties of Ethylene Propylene Diene Monomer Thermal Insulation. Bulletin of Chemi-cal Reaction Engineering & Catalysis, 10 (2, 104-110. (doi:10.9767/bcrec.10.2.6682.104-110Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.2.6682.104-110 

  5. Ionization of cytosine monomer and dimer studied by VUV photoionization and electronic structure calculations

    Energy Technology Data Exchange (ETDEWEB)

    Kostko, Oleg; Bravaya, Ksenia; Krylov, Anna; Ahmed, Musahid

    2009-12-14

    We report a combined theoretical and experimental study of ionization of cytosine monomers and dimers. Gas-phase molecules are generated by thermal vaporization of cytosine followed by expansion of the vapor in a continuous supersonic jet seeded in Ar. The resulting species are investigated by single photon ionization with tunable vacuum-ultraviolet (VUV) synchrotron radiation and mass analyzed using reflectron mass spectrometry. Energy onsets for the measured photoionization efficiency (PIE) spectra are 8.60+-0.05 eV and 7.6+-0.1 eV for the monomer and the dimer, respectively, and provide an estimate for the adiabatic ionization energies (AIE). The first AIE and the ten lowest vertical ionization energies (VIEs) for selected isomers of cytosine dimer computed using equation-of-motion coupled-cluster (EOM-IP-CCSD) method are reported. The comparison of the computed VIEs with the derivative of the PIE spectra, suggests that multiple isomers of the cytosine dimer are present in the molecular beam. The calculations reveal that the large red shift (0.7 eV) of the first IE of the lowest-energy cytosine dimer is due to strong inter-fragment electrostatic interactions, i.e., the hole localized on one of the fragments is stabilized by the dipole moment of the other. A sharp rise in the CH+ signal at 9.20+-0.05 eV is ascribed to the formation of protonated cytosine by dissociation of the ionized dimers. The dominant role of this channel is supported by the computed energy thresholds for the CH+ appearance and the barrierless or nearly barrierless ionization-induced proton transfer observed for five isomers of the dimer.

  6. Do Cation-π Interactions Exist in Bacteriorhodopsin

    Institute of Scientific and Technical Information of China (English)

    HU Kun-Sheng; WANG Guang-Yu; HE Jin-An

    2001-01-01

    Metal ions are essential to the structure and physiological functions of bacteriorhodopsin. Experimental evidence suggests the existence of specific cation binding to the negatively charged groups of Asp85 and Asp212 via an electrostatic interaction. However, only using electrostatic force is not enough to explain the role of the metal cations because the carboxylate of Asp85 is well known to be protonated in the M intermediate. Considering the presence of some aromatic amino acid residues in the vicinity of the retinal pocket, the existence of cation-π interactions between the metal cation and aromatic amino acid residues is suggested. Obviously, introduction of this kind of interaction is conducive to understanding the effects of the metal cations and aromatic amino acid residues inside the protein on the structural stability and proton pumping of bacteriorhodopsin.

  7. Effect of microwave postpolymerization treatment on residual monomer content and the flexural strength of autopolymerizing reline resin

    Directory of Open Access Journals (Sweden)

    Patil Padmakar

    2009-01-01

    Full Text Available Background : Microwave postpolymerization has been suggested as a method to improve the flexural strength of an autopolymerizing denture reline resin. However, the effect of microwave postpolymerization on the residual monomer content and its influence on flexural strength have not been investigated. Objectives : This study analyzed the effect of microwave postpolymerization on the residual monomer content and its influence on the flexural strength of an autopolymerizing reline resin (Denture Liner. Materials and Methods : A total of 70 specimens (64 Χ 10 Χ 3.3 mm were polymerized according to the manufacturer′s instructions and divided into 7 groups (n = 10. Control group specimens were not subjectedto any further processing. Before testing, the specimens were subjected to postpolymerization in a microwave oven using different power (550 and 650 W and time (3, 4, and 5 min settings. Two specimens of each group were then manually ground into fine powder and samples extracted from the specimens using reflux method. The samples were then subjected to gas chromatography for residual monomer determination in area%. Eight specimens were subjected to a three-point bending device with a span of 50 mm and crosshead speed of 5 mm/min, and the flexural strength was determined in MPa. Data analyses included Student′s t-test and one-way analysis of variance. Results : For the Denture Liner reline resin, the residual monomer content decreased and the flexural strength increased significantly with the application of microwave irradiation using different time/power combinations. The specimens with the lowest residual monomer content were the similar specimens which presented with the highest flexural strength. Conclusion : Microwave postpolymerization irradiation can be an effective method for increasing the flexural strength of denture liner (at 650 W for 5 min by reducing the residual monomer content by further polymerization at free radical sites.

  8. Application of Nuclear Radiation to Textile Materials and Processes. Radiation-induced graft copolymerization of vinyl monomers and fibrous polymers

    International Nuclear Information System (INIS)

    A technique has been developed that permits the radiation grafting of volatile vinyl monomers to fibrous polymers in a uniform manner. It involves the addition of the organic compound from the vapour phase, and the process may be done by either a mutual or a pre-irradiation process using cobalt-60. Systems that accelerate the rate of graft copolymerization have been studied, and it is possible to add significant amounts of several of the monomers without radiation damage to the fibre substrate. The fibrous materials that are relatively unstable toward radiation are the ones that add the vinyl compounds the most readily. These are the celluloses, celluloseesters, polyamides, and polypropylene. The addition of the monomer to the fibre substrate apparently takes place by a free-radical mechanism and, as already indicated above, it is possible to irradiate the material first and subsequently obtain grafting by exposure of the irradiated material to the monomer vapour. Attempts have been made to determine the life of the free-radicals and while it has been difficult to obtain exact figures, it has been demonstrated that they may continue to exist in some fibres for15 to 20 hr after irradiation, even at room temperature. Preliminary experimental evidence has also suggested that the diffusion time of the monomer to free-radical sites in post-irradiation grafting proceeds at different rates in the different fibres. The modification of cotton by the addition of polyacrylonitrile results in a fibre almost completely resistant to micro-organisms. Only 3.5% deposition is required and the material retains the appearance and feel of untreated cotton. The product is superior to that made by the addition of acrylonitrile using the ironperoxide catalyst system. Polypropylene may be grafted with several different monomers to produce a fibre that is dyeable by commonly-used dyeing procedures. At the present stage of development, however, the wash fastness of the grafted and dyed

  9. Evaluation of level of impregnation monomers in hydrotalcite; Avaliacao do grau de impregnacao de monomeros em hidrotalcita

    Energy Technology Data Exchange (ETDEWEB)

    Carmo, Danieli M. do, E-mail: danielimcarmo@hotmail.com [Instituto de Macromoleculas Professora Eloisa Mano - IMA, Universidade Federal do Rio de Janeiro - UFRJ, RJ (Brazil); Machado, Jacson S.C.; Oliveira, Marcelo F.L.; Oliveira, Marcia G. [Instituto Nacional de Tecnologia - INT, Rio de Janeiro, RJ (Brazil); Soares, Bluma G. [Instituto de Macromoleculas Professora Eloisa Mano - IMA, Universidade Federal do Rio de Janeiro - UFRJ, RJ (Brazil)

    2011-07-01

    To evaluate the impregnation degree of 1,6-hexamethylene diisocyanate and 1,4-butanediol monomers in hydrotalcite clays it was prepared dispersions with mixing ratio 1:100 (clay/monomer), using the Ultraturrax and Ultrasound. Subsequently the samples were characterized by Fourier Transform Infrared Spectroscopy and X-ray Diffraction. Swelling tests and Tyndall effect were used to illustrate the different dispersions. The results indicated a strong interaction between the hydrotalcite with 1,6-hexamethylene diisocyanate, favoring the formation of intercalated structures. (author)

  10. Synthesis and Ring-Opening Metathesis Polymerization of Second-Generation Dendronized Poly(ether Monomers Initiated by Ruthenium Carbenes

    Directory of Open Access Journals (Sweden)

    Guzmán Pablo E.

    2016-03-01

    Full Text Available The Ring-Opening Metathesis Polymerization (ROMP of second-generation dendronized monomers is described. Using the highly active and fast-initiating third-generation ruthenium complex [(H2IMes(pyr2Cl2RuCHPh], moderate to high molecular weight polymers (430-2230 kDa are efficiently synthesized with low dispersities (Ð = 1.01-1.17. This study highlights the power of the metathesis approach toward polymer synthesis in a context where monomer structure can significantly impede polymerization.

  11. Single stranded DNA translocation of E. coli UvrD monomer is tightly coupled to ATP hydrolysis

    OpenAIRE

    Tomko, Eric J.; Fischer, Christopher J.; Lohman, Timothy M.

    2012-01-01

    E. coli UvrD is an SF1A helicase/translocase that functions in several DNA repair pathways. A UvrD monomer is a rapid and processive single-stranded (ss) DNA translocase, but is unable to unwind DNA processively in vitro. Based on data at saturating ATP (500 μM) we proposed a non-uniform stepping mechanism in which a UvrD monomer translocates with biased (3′ to 5′) directionality while hydrolyzing 1 ATP per DNA base translocated, but with a kinetic step-size of 4–5 nucleotides/step, suggestin...

  12. Formation of a cyclic dimer containing two mirror image monomers in the solid state controlled by van der Waals forces.

    Science.gov (United States)

    Zhang, Zibin; Yu, Guocan; Han, Chengyou; Liu, Jiyong; Ding, Xia; Yu, Yihua; Huang, Feihe

    2011-09-16

    Two new copillar[5]arenes were prepared. They are arranged in two completely different motifs, a cyclic dimer containing two monomers with two different conformations that are mirror images of each other and linear supramolecular polymers in the solid state. Not only has it been shown that to form this kind of dimer is a unique feature associated with pillar[5]arene macrocycles but also it was demonstrated that weak van der Waals forces can be used to control the self-organization of monomers during their supramolecular polymerization process.

  13. Repurposing Cationic Amphiphilic Antihistamines for Cancer Treatment

    DEFF Research Database (Denmark)

    Ellegaard, Anne-Marie; Dehlendorff, Christian; Vind, Anna C.;

    2016-01-01

    Non-small cell lung cancer (NSCLC) is one of the deadliest cancers worldwide. In search for new NSCLC treatment options, we screened a cationic amphiphilic drug (CAD) library for cytotoxicity against NSCLC cells and identified several CAD antihistamines as inducers of lysosomal cell death. We the...... of loratadine, astemizole and ebastine sensitized NSCLC cells to chemotherapy and reverted multidrug resistance in NSCLC, breast and prostate cancer cells. Thus, CAD antihistamines may improve the efficacy of cancer chemotherapy...... then performed a cohort study on the effect of CAD antihistamine use on mortality of patients diagnosed with non-localized cancer in Denmark between 1995 and 2011. The use of the most commonly prescribed CAD antihistamine, loratadine, was associated with significantly reduced all-cause mortality among patients...... with non-localized NSCLC or any non-localized cancer when compared with use of non-CAD antihistamines and adjusted for potential confounders. Of the less frequently described CAD antihistamines, astemizole showed a similar significant association with reduced mortality as loratadine among patients with any...

  14. Repurposing Cationic Amphiphilic Antihistamines for Cancer Treatment

    Directory of Open Access Journals (Sweden)

    Anne-Marie Ellegaard

    2016-07-01

    Full Text Available Non-small cell lung cancer (NSCLC is one of the deadliest cancers worldwide. In search for new NSCLC treatment options, we screened a cationic amphiphilic drug (CAD library for cytotoxicity against NSCLC cells and identified several CAD antihistamines as inducers of lysosomal cell death. We then performed a cohort study on the effect of CAD antihistamine use on mortality of patients diagnosed with non-localized cancer in Denmark between 1995 and 2011. The use of the most commonly prescribed CAD antihistamine, loratadine, was associated with significantly reduced all-cause mortality among patients with non-localized NSCLC or any non-localized cancer when compared with use of non-CAD antihistamines and adjusted for potential confounders. Of the less frequently described CAD antihistamines, astemizole showed a similar significant association with reduced mortality as loratadine among patients with any non-localized cancer, and ebastine use showed a similar tendency. The association between CAD antihistamine use and reduced mortality was stronger among patients with records of concurrent chemotherapy than among those without such records. In line with this, sub-micromolar concentrations of loratadine, astemizole and ebastine sensitized NSCLC cells to chemotherapy and reverted multidrug resistance in NSCLC, breast and prostate cancer cells. Thus, CAD antihistamines may improve the efficacy of cancer chemotherapy.

  15. Repurposing Cationic Amphiphilic Antihistamines for Cancer Treatment.

    Science.gov (United States)

    Ellegaard, Anne-Marie; Dehlendorff, Christian; Vind, Anna C; Anand, Atul; Cederkvist, Luise; Petersen, Nikolaj H T; Nylandsted, Jesper; Stenvang, Jan; Mellemgaard, Anders; Østerlind, Kell; Friis, Søren; Jäättelä, Marja

    2016-07-01

    Non-small cell lung cancer (NSCLC) is one of the deadliest cancers worldwide. In search for new NSCLC treatment options, we screened a cationic amphiphilic drug (CAD) library for cytotoxicity against NSCLC cells and identified several CAD antihistamines as inducers of lysosomal cell death. We then performed a cohort study on the effect of CAD antihistamine use on mortality of patients diagnosed with non-localized cancer in Denmark between 1995 and 2011. The use of the most commonly prescribed CAD antihistamine, loratadine, was associated with significantly reduced all-cause mortality among patients with non-localized NSCLC or any non-localized cancer when compared with use of non-CAD antihistamines and adjusted for potential confounders. Of the less frequently described CAD antihistamines, astemizole showed a similar significant association with reduced mortality as loratadine among patients with any non-localized cancer, and ebastine use showed a similar tendency. The association between CAD antihistamine use and reduced mortality was stronger among patients with records of concurrent chemotherapy than among those without such records. In line with this, sub-micromolar concentrations of loratadine, astemizole and ebastine sensitized NSCLC cells to chemotherapy and reverted multidrug resistance in NSCLC, breast and prostate cancer cells. Thus, CAD antihistamines may improve the efficacy of cancer chemotherapy. PMID:27333030

  16. Therapeutic potential of cationic steroid antibacterials.

    Science.gov (United States)

    Salmi, Chanaz; Brunel, Jean M

    2007-08-01

    Antibiotics were one of the great health successes of the 20th century. Antibiotics, both naturally derived and synthetic, have resulted in huge decreases in both morbidity and mortality from bacterial infections. As a consequence, the 'antibiotic age' has changed public expectations about the results of infectious disease. However, this has led to high levels of inappropriate prescribing, where antibiotics may be administered to fulfil patient expectations rather than for clinical benefit. Along with unwise uses in agriculture and elsewhere, this has contributed to recent rises in numbers of antibiotic-resistant bacteria. As a result, many commentators have described this as the end of the antibiotic age and the term 'superbug' has entered the common vocabulary for multi-drug-resistant bacteria such as vancomycin-resistant Enterococcus, multi-drug-resistant Staphylococcus aureus and multi-drug-resistant Pseudomonas aeruginosa. In this context, an attractive approach for the development of antibacterial agents is the use of a new class of cationic steroidal compounds mimicking polymyxin activities. The permeabilization properties of these agents of the outer membranes of Gram-negative bacteria are reported in this review, as well as a discussion of literature results. PMID:17685865

  17. Competitive Effects of 2+ and 3+ Cations on DNA Compaction

    CERN Document Server

    Tongu, C; Yoshikawa, Y; Zinchenko, A A; Chen, N; Yoshikawa, K

    2016-01-01

    By using single-DNA observation with fluorescence microscopy, we observed the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA with 166 kbp). It was found that divalent cations, such as Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)). On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA. These experimental observations are inconsistent with the well-established Debye-Huckel scheme regarding the shielding effect of counter ions, which is given as the additivity of contributions of cations with different valences. We interpreted the competition between 2+ and 3+ cations in terms of the change in the translational entropy of the counter ions before and after the folding transition of DNA. For the compaction with SPD(3+), we considered the increase in translational entropy due to the ion-exchange of the intrinsic monovalent cations condensing on a highly-charged polyelectrolyte, double-st...

  18. Dimeric WH2 repeats of VopF sequester actin monomers into non-nucleating linear string conformations: An X-ray scattering study.

    Science.gov (United States)

    Avvaru, Balendu Sankara; Pernier, Julien; Carlier, Marie-France

    2015-05-01

    VopF and VopL are highly similar virulence-factors of Vibrio cholerae and Vibrio parahaemolyticus respectively that disrupt the host's actin cytoskeleton, using a unique organization in dimerized WH2 repeats. Association of dimerized WH2 domains with the barbed face of actin confers multifunctional activities to VopF in vitro, including G-actin sequestration and filament nucleation, barbed end tracking and uncapping. Here, small angle X-ray scattering (SAXS) measurements of complexes of VopF with actin and structural modeling reveal that VopF stabilizes linear actin-strings that differ from canonical actin filament architectures but represent non-polymerizable sequestered forms of actin. The results exclude that VopL binds the pointed end of actin filaments in the template filament nucleation mechanism derived from crystallographic studies. PMID:25818509

  19. Cations bind only weakly to amides in aqueous solutions.

    Science.gov (United States)

    Okur, Halil I; Kherb, Jaibir; Cremer, Paul S

    2013-04-01

    We investigated salt interactions with butyramide as a simple mimic of cation interactions with protein backbones. The experiments were performed in aqueous metal chloride solutions using two spectroscopic techniques. In the first, which provided information about contact pair formation, the response of the amide I band to the nature and concentration of salt was monitored in bulk aqueous solutions via attenuated total reflection Fourier transform infrared spectroscopy. It was found that molar concentrations of well-hydrated metal cations (Ca(2+), Mg(2+), Li(+)) led to the rise of a peak assigned to metal cation-bound amides (1645 cm(-1)) and a decrease in the peak associated with purely water-bound amides (1620 cm(-1)). In a complementary set of experiments, the effect of cation identity and concentration was investigated at the air/butyramide/water interface via vibrational sum frequency spectroscopy. In these studies, metal ion-amide binding led to the ordering of the adjacent water layer. Such experiments were sensitive to the interfacial partitioning of cations in either a contact pair with the amide or as a solvent separated pair. In both experiments, the ordering of the interactions of the cations was: Ca(2+) > Mg(2+) > Li(+) > Na(+) ≈ K(+). This is a direct cationic Hofmeister series. Even for Ca(2+), however, the apparent equilibrium dissociation constant of the cation with the amide carbonyl oxygen was no tighter than ∼8.5 M. For Na(+) and K(+), no evidence was found for any binding. As such, the interactions of metal cations with amides are far weaker than the analogous binding of weakly hydrated anions.

  20. Novel polymeric materials from vegetable oils and vinyl monomers: preparation, properties, and applications.

    Science.gov (United States)

    Lu, Yongshang; Larock, Richard C

    2009-01-01

    Veggie-based products: Vegetable-oil-based polymeric materials, prepared by free radical, cationic, and olefin metathesis polymerizations, range from soft rubbers to ductile or rigid plastics, and to high-performance biocomposites and nanocomposites. They display a wide range of thermophysical and mechanical properties and may find promising applications as alternatives to petroleum-based polymers.Vegetable oils are considered to be among the most promising renewable raw materials for polymers, because of their ready availability, inherent biodegradability, and their many versatile applications. Research on and development of vegetable oil based polymeric materials, including thermosetting resins, biocomposites, and nanocomposites, have attracted increasing attention in recent years. This Minireview focuses on the latest developments in the preparation, properties, and applications of vegetable oil based polymeric materials obtained by free radical, cationic, and olefin metathesis polymerizations. The novel vegetable oil based polymeric materials obtained range from soft rubbery materials to ductile or rigid plastics and to high-performance biocomposites and nanocomposites. These vegetable oil based polymeric materials display a wide range of thermophysical and mechanical properties and should find useful applications as alternatives to their petroleum-based counterparts. PMID:19180601

  1. Competitive Solvation of the Imidazolium Cation by Water and Methanol

    CERN Document Server

    Chaban, Vitaly

    2014-01-01

    Imidazolium-based ionic liquids are widely used in conjunction with molecular liquids for various applications. Solvation, miscibility and similar properties are of fundamental importance for successful implementation of theoretical schemes. This work reports competitive solvation of the 1,3-dimethylimidazolium cation by water and methanol. Employing molecular dynamics simulations powered by semiempirical Hamiltonian (electronic structure level of description), the local structure nearly imidazolium cation is described in terms of radial distribution functions. Although water and methanol are chemically similar, water appears systematically more successful in solvating the 1,3-dimethylimidazolium cation. This result fosters construction of future applications of the ternary ion-molecular systems.

  2. Pyridine radical cation and its fluorine substituted derivatives

    Science.gov (United States)

    Bondybey, V.E.; English, J.H.; Shiley, R.H.

    1982-01-01

    The spectra and relaxation of the pyridine cation and of several of its fluorinated derivatives are studied in low temperature Ne matrices. The ions are generated by direct photoionization of the parent compounds. Of the compounds studied, laser induced → and → fluorescence is observed only for the 2, 6‐difluoropyridine cation. The analysis of the spectrum indicates that the ion is planar both in the and states. The large variety in the spectroscopic and relaxation behavior of fluoropyridine radical cations is explained in terms of their electronic structure and of the differential shifts of the individual electronic states caused by the fluorine substitution.

  3. Microtubule +TIP protein EB1 binds to GTP and undergoes dissociation from dimer to monomer on binding GTP.

    Science.gov (United States)

    Gireesh, K K; Sreeja, Jamuna S; Chakraborti, Soumyananda; Singh, Puja; Thomas, Geethu Emily; Gupta, Hindol; Manna, Tapas

    2014-09-01

    The +TIP protein EB1 autonomously tracks the growing plus end of microtubules and regulates plus-end dynamics. Previous studies have indicated that EB1 can recognize GTP-bound tubulin structures at the plus end, and it localizes on the microtubule surface at a site close to the exchangeable GTP-binding site of tubulin. Although the GTP-dependent structural change in tubulin has been demonstrated to be a critical determinant for recognition of plus ends by EB1, the effect of GTP on the structure of EB1 has remained unclear. Here, we have used spectroscopic, calorimetric, and biochemical methods to analyze the effect of GTP on EB1 in vitro. Isothermal titration calorimetry and tryptophan fluorescence quenching experiments demonstrated that EB1 binds to GTP with a dissociation constant ~30 μM. Circular dichroism measurements showed that EB1 undergoes changes in its secondary structure on binding GTP. Size-exclusion chromatography and urea-induced unfolding analyses revealed that GTP binding induces dissociation of the EB1 dimer to monomers. Size-exclusion chromatography followed by biochemical analysis further determined that EB1-GTP binding involves association of approximately one molecule of GTP per EB1 monomer. The results reveal a hitherto unknown GTP-dependent mechanism of dimer-to-monomer transition in EB1 and further implicate its possible role in regulating the stability of the EB1 dimer vs monomer as well as plus-end regulation in cells. PMID:25111064

  4. Solvent-free synthesis, coating and morphogenesis of conductive polymer materials through spontaneous generation of activated monomers.

    Science.gov (United States)

    Muramatsu, Ryo; Oaki, Yuya; Kuwabara, Kento; Hayashi, Kosei; Imai, Hiroaki

    2014-10-14

    Synthesis, coating, and morphogenesis of conductive polymers were achieved on a variety of substrates through spontaneous generation of activated monomer vapors under ambient pressure and low temperature conditions. The present approach facilitates the generation of complex hierarchical morphologies and the conductive coating for improvement of electrochemical properties. PMID:25145680

  5. Novel polymer composites from waste ethylene-propylene-diene-monomer rubber by supercritical CO2 foaming technology.

    Science.gov (United States)

    Jeong, Keuk Min; Hong, Yeo Joo; Saha, Prosenjit; Park, Seong Ho; Kim, Jin Kuk

    2014-11-01

    In this study, a composite has been prepared by mixing waste rubber, such as ethylene-propylene-diene-monomer and low-density poly ethylene foaming, with supercritical carbon dioxide. In order to optimise the foaming process of the waste ethylene-propylene-diene-monomer-low-density poly ethylene composite, the variations of pressure and temperature on the foamed Microcell formation were studied. As indicated in scanning electron microscope photographs, the most uniform microcellular pattern was found at 200 bar and 100 °C using 30% by weight of waste ethylene-propylene-diene-monomer. Carbon dioxide could not be dissolved uniformly during foaming owing to extensive cross-linking of the waste ethylene-propylene-diene-monomer used for the composite. As a result the presence of un-uniform microcells after foaming were observed in the composite matrix to impart inferior mechanical properties of the composite. This problem was solved with uniform foaming by increasing the cross-link density of low-density poly ethylene using 1.5 parts per hundred dicumyl peroxide that enhances composite tensile and compressive strength up to 57% and 15%, respectively. The composite has the potential to be used as a foaming mat for artificial turf.

  6. Oligonucleotides containing a piperazino-modified 2'-amino-LNA monomer exhibit very high duplex stability and remarkable nuclease resistance

    DEFF Research Database (Denmark)

    Lou, Chenguang; Vester, Birte; Wengel, Jesper

    2015-01-01

    Incorporation of a piperazino-modified 2'-amino-LNA monomer (PipLNA-T) into oligonucleotides conferred very high affinity and base-pairing selectivity towards complementary DNA and RNA strands. Furthermore, one PipLNA-T modification provided a robust nuclease resistance that safeguarded three nei...

  7. The role of monomer fraction data in association theories—Can we improve the performance for phase equilibrium calculations?

    DEFF Research Database (Denmark)

    Tsivintzelis, Ioannis; Bøgh, David; Karakatsani, Eirini;

    2014-01-01

    Monomer fraction (fraction of non-hydrogen bonded molecules) data obtained from spectroscopy are available for a few associating compounds. Such data can be used for testing the performance of association models like CPA and SAFT or alternatively be employed in the model development. But how accu...

  8. Interaction potential for water dimer from symmetry-adapted perturbation theory based on density functional description of monomers

    NARCIS (Netherlands)

    Bukowski, R.; Szalewicz, K.; Groenenboom, G.C.; Avoird, A. van der

    2006-01-01

    A new six-dimensional interaction potential for the water dimer has been obtained by fitting interaction energies computed at 2510 geometries using a variant of symmetry-adapted perturbation theory (SAPT) based on density functional theory (DFT) description of monomers, referred to as SAPT(DFT). The

  9. PSEUDOMONAS-PUTIDA KT2442 CULTIVATED ON GLUCOSE ACCUMULATES POLY(3-HYDROXYALKANOATES) CONSISTING OF SATURATED AND UNSATURATED MONOMERS

    NARCIS (Netherlands)

    HUIJBERTS, GNM; EGGINK, G; DEWAARD, P; HUISMAN, GW; WITHOLT, B

    1992-01-01

    The biosynthesis of poly(3-hydroxyalkanoates) (PHAs) by Pseudomonas putida KT2442 during growth on carbohydrates was studied. PHAs isolated from P. putida cultivated on glucose, fructose, and glycerol were found to have a very similar monomer composition. In addition to the major constituent 3-hydro

  10. Dimer monomer transition and dimer re-formation play important role for ATM cellular function during DNA repair

    Energy Technology Data Exchange (ETDEWEB)

    Du, Fengxia [Laboratory of Genome Variations and Precision Bio-Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101 (China); Zhang, Minjie [Laboratory of Genome Variations and Precision Bio-Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Li, Xiaohua; Yang, Caiyun [Laboratory of Genome Variations and Precision Bio-Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101 (China); Meng, Hao; Wang, Dong; Chang, Shuang [Laboratory of Genome Variations and Precision Bio-Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xu, Ye [Department of Radiation Oncology, Division of Genomic Stability, Dana Farber Cancer Institute, Harvard Medical School, MA 02134 (United States); Price, Brendan, E-mail: Brendan_Price@dfci.harvard.edu [Department of Radiation Oncology, Division of Genomic Stability, Dana Farber Cancer Institute, Harvard Medical School, MA 02134 (United States); Sun, Yingli, E-mail: sunyl@big.ac.cn [Laboratory of Genome Variations and Precision Bio-Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101 (China)

    2014-10-03

    Highlights: • ATM phosphorylates the opposite strand of the dimer in response to DNA damage. • The PETPVFRLT box of ATM plays a key role in its dimer dissociation in DNA repair. • The dephosphorylation of ATM is critical for dimer re-formation after DNA repair. - Abstract: The ATM protein kinase, is a serine/threonine protein kinase that is recruited and activated by DNA double-strand breaks, mediates responses to ionizing radiation in mammalian cells. Here we show that ATM is held inactive in unirradiated cells as a dimer and phosphorylates the opposite strand of the dimer in response to DNA damage. Cellular irradiation induces rapid intermolecular autophosphorylation of serine 1981 that causes dimer dissociation and initiates cellular ATM kinase activity. ATM cannot phosphorylate the substrates when it could not undergo dimer monomer transition. After DNA repair, the active monomer will undergo dephosphorylation to form dimer again and dephosphorylation is critical for dimer re-formation. Our work reveals novel function of ATM dimer monomer transition and explains why ATM dimer monomer transition plays such important role for ATM cellular activity during DNA repair.

  11. Dimer monomer transition and dimer re-formation play important role for ATM cellular function during DNA repair

    International Nuclear Information System (INIS)

    Highlights: • ATM phosphorylates the opposite strand of the dimer in response to DNA damage. • The PETPVFRLT box of ATM plays a key role in its dimer dissociation in DNA repair. • The dephosphorylation of ATM is critical for dimer re-formation after DNA repair. - Abstract: The ATM protein kinase, is a serine/threonine protein kinase that is recruited and activated by DNA double-strand breaks, mediates responses to ionizing radiation in mammalian cells. Here we show that ATM is held inactive in unirradiated cells as a dimer and phosphorylates the opposite strand of the dimer in response to DNA damage. Cellular irradiation induces rapid intermolecular autophosphorylation of serine 1981 that causes dimer dissociation and initiates cellular ATM kinase activity. ATM cannot phosphorylate the substrates when it could not undergo dimer monomer transition. After DNA repair, the active monomer will undergo dephosphorylation to form dimer again and dephosphorylation is critical for dimer re-formation. Our work reveals novel function of ATM dimer monomer transition and explains why ATM dimer monomer transition plays such important role for ATM cellular activity during DNA repair

  12. Folding Landscape of Mutant Huntingtin Exon1: Diffusible Multimers, Oligomers and Fibrils, and No Detectable Monomer.

    Directory of Open Access Journals (Sweden)

    Bankanidhi Sahoo

    Full Text Available Expansion of the polyglutamine (polyQ track of the Huntingtin (HTT protein above 36 is associated with a sharply enhanced risk of Huntington's disease (HD. Although there is general agreement that HTT toxicity resides primarily in N-terminal fragments such as the HTT exon1 protein, there is no consensus on the nature of the physical states of HTT exon1 that are induced by polyQ expansion, nor on which of these states might be responsible for toxicity. One hypothesis is that polyQ expansion induces an alternative, toxic conformation in the HTT exon1 monomer. Alternative hypotheses posit that the toxic species is one of several possible aggregated states. Defining the nature of the toxic species is particularly challenging because of facile interconversion between physical states as well as challenges to identifying these states, especially in vivo. Here we describe the use of fluorescence correlation spectroscopy (FCS to characterize the detailed time and repeat length dependent self-association of HTT exon1-like fragments both with chemically synthesized peptides in vitro and with cell-produced proteins in extracts and in living cells. We find that, in vitro, mutant HTT exon1 peptides engage in polyQ repeat length dependent dimer and tetramer formation, followed by time dependent formation of diffusible spherical and fibrillar oligomers and finally by larger, sedimentable amyloid fibrils. For expanded polyQ HTT exon1 expressed in PC12 cells, monomers are absent, with tetramers being the smallest molecular form detected, followed in the incubation time course by small, diffusible aggregates at 6-9 hours and larger, sedimentable aggregates that begin to build up at 12 hrs. In these cell cultures, significant nuclear DNA damage appears by 6 hours, followed at later times by caspase 3 induction, mitochondrial dysfunction, and cell death. Our data thus defines limits on the sizes and concentrations of different physical states of HTT exon1 along the

  13. Pseudomonas syringae evades host immunity by degrading flagellin monomers with alkaline protease AprA.

    Science.gov (United States)

    Pel, Michiel J C; van Dijken, Anja J H; Bardoel, Bart W; Seidl, Michael F; van der Ent, Sjoerd; van Strijp, Jos A G; Pieterse, Corné M J

    2014-07-01

    Bacterial flagellin molecules are strong inducers of innate immune responses in both mammals and plants. The opportunistic pathogen Pseudomonas aeruginosa secretes an alkaline protease called AprA that degrades flagellin monomers. Here, we show that AprA is widespread among a wide variety of bacterial species. In addition, we investigated the role of AprA in virulence of the bacterial plant pathogen P. syringae pv. tomato DC3000. The AprA-deficient DC3000 ΔaprA knockout mutant was significantly less virulent on both tomato and Arabidopsis thaliana. Moreover, infiltration of A. thaliana Col-0 leaves with DC3000 ΔaprA evoked a significantly higher level of expression of the defense-related genes FRK1 and PR-1 than did wild-type DC3000. In the flagellin receptor mutant fls2, pathogen virulence and defense-related gene activation did not differ between DC3000 and DC3000 ΔaprA. Together, these results suggest that AprA of DC3000 is important for evasion of recognition by the FLS2 receptor, allowing wild-type DC3000 to be more virulent on its host plant than AprA-deficient DC3000 ΔaprA. To provide further evidence for the role of DC3000 AprA in host immune evasion, we overexpressed the AprA inhibitory peptide AprI of DC3000 in A. thaliana to counteract the immune evasive capacity of DC3000 AprA. Ectopic expression of aprI in A. thaliana resulted in an enhanced level of resistance against wild-type DC3000, while the already elevated level of resistance against DC3000 ΔaprA remained unchanged. Together, these results indicate that evasion of host immunity by the alkaline protease AprA is important for full virulence of strain DC3000 and likely acts by preventing flagellin monomers from being recognized by its cognate immune receptor. PMID:24654978

  14. Effect of Rhizopus oryzae Fermentation on Kenaf-Based Polylactic Acid’s Monomer

    Directory of Open Access Journals (Sweden)

    Nur Aimi Mohd Nasir

    2011-12-01

    Full Text Available Kenaf biomass is the potential as raw materials used to produce polylactic acid's monomer which is lactic acid via fermentation by Rhizopus oryzae. Kenaf biomass' structure is complex due to its lignin and cellulose content. This matter had encouraged it to undergo pre- treatment process as the initial step before fermentation process can be done. In this paper, kenaf biomass was treated with dilute sulphuric acid (H2SO4 to hydrolyze the cellulose content in it as well as to convert the cellulose into glucose- a carbon source for Rhizopus to grow. Then, the fermentation process was carried out in shake flask for 3 days at pH 6. Several conditions for fermentation process had been chosen which were 25oC at 150 rpm, 25 oC at 200 rpm, 37 oC at 150 rpm and 37oC at 200 rpm. In this fermentation process, 0.471 g/L, 0.428 g/L, 0.444 g/L and 0.38 g/L of lactic acid was produced respectively. Sample at 25oC at 200 rpm produced maximum amount of lactic acid compared to others.ABSTRAK: Biojisim kenaf berpotensi sebagai bahan mentah dalam penghasilan monomer asid polylactic (poliester alifatik termoplastik diterbitkan daripada sumber boleh diperbaharu seperti kanji jagung yang merupakan asid laktik menerusi penapaian oleh Rhizopus oryzae (sejenis fungus yang hidup dalam jirim organik yang telah mati. Struktur biojisim kenaf adalah kompleks disebabkan kandungan lignin dan selulosanya. Hal ini menyebabkan ia perlu melalui proses pra-rawatan sebagai langkah awal sebelum proses penapaian dijalankan. Dalam kertas ini, biojirim kenaf dirawat dengan asid sulfurik (H2SO4 yang dicairkan untuk menghidrolisis kandungan selulosa di dalamnya di samping menukar selulosa menjadi glukosa - sumber karbon bagi tumbesaran Rhizopus. Kemudian, proses penapaian dijalankan di dalam kelalang goncang selama 3 hari pada pH 6. Beberapa ciri proses penapaian telah dipilih iaitu 25 oC pada 150 rpm, 25 oC pada 200 rpm, 37 oC pada 150 rpm dan 37 oC pada 200 rpm. Dalam proses penapaian

  15. Triblock and pentablock terpolymers by sequential base-assisted living cationic copolymerization of functionalized vinyl ethers

    KAUST Repository

    Bouchekif, Hassen

    2015-01-01

    A series of novel, well-defined triblock (PnBVE-b-PCEVE-b-PSiDEGVE) and pentablock (PSiDEGVE-b-PCEVE-b-PnBVE-b-PCEVE-b-PSiDEGVE) terpolymers of n-butyl vinyl ether (nBVE), 2-chloroethyl vinyl ether (CEVE) and tert-butyldimethylsilyl ethylene glycol vinyl ether (SiEGVE) were synthesized by sequential base-assisted living cationic polymerization. The living character of the homopolymerization of the three VE monomers and the crossover reaction resulting in the formation of well-defined block copolymers were investigated in various solvents (toluene, dichloromethane and n-hexane) using either a monofunctional [nBVE-acetic acid adduct (nBEA), CEVE-acetic acid adduct (CEEA) and SiDEGVE-acetic acid adduct (SiDEGEA)] or a difunctional [1,4-cyclohexane-1,4-diyl bis(2-methoxyethyl acetate) (cHDMEA)] initiator. All initiators are structurally equivalent to the dormant species of the corresponding monomers in order to achieve fast initiation. The optimal conditions of polymerization were achieved in n-hexane at -20 °C, in the presence of 1 M AcOEt (base). Good control over the number average molecular weight (Mn) and the polydispersity index (PDI) was obtained only at [Et3Al2Cl3]0 = [Chain-end]0 ≤ 10 mM. 2,6-Di-tert-butylpyridine (DtBP) was used as a non-nucleophilic proton trap to suppress any protonic initiation from moisture (i.e., Et3Al2Cl3·H2O). Well-defined PnBVEn-b-PCEVEp-b-PSiDEGVEq and PSiDEGVEq-b-PCEVEp-b-PnBVEn-b-PCEVEp-b-PSiDEGVEq terpolymers with a high crossover efficiency, no PCEVE-induced physical gelation, and predictable Mn and PDI < 1.15 were synthesized successfully provided that the targeted DPCEVE/DPnBVE ratio (i.e., p/n) did not exceed 2 and 0.2, respectively. The quantitative desilylation of the PSiEGVE by n-Bu4N+F- in THF at 0 °C led to triblock and pentablock terpolymers in which the PCEVE is the central block and the polyalcohol is the outer block. The thermal properties of the synthesized materials were examined by differential scanning

  16. Isomerization of propargyl cation to cyclopropenyl cation: Mechanistic elucidations and effects of lone pair donors

    Indian Academy of Sciences (India)

    Zodinpuia Pachuau; Kiew S Kharnaior; R H Duncan Lyngdoh

    2013-03-01

    This ab initio study examines two pathways (one concerted and the other two-step) for isomerization of the linear propargyl cation to the aromatic cyclopropenyl cation, also probing the phenomenon of solvation of this reaction by simple lone pair donors (NH3, H2O, H2S and HF) which bind to the substrate at two sites. Fully optimized geometries at the B3LYP/6-31G(d) level were used, along with single point QCISD(T)/6-311+G(d,p) and accurate G3 level calculations upon the DFT optimized geometries. For the unsolvated reaction, the two-step second pathway is energetically favoured over the one-step first pathway. Lone pair donor affinity for the various C3H$^{+}_{3}$ species follows the uniform order NH3 > H2S>H2O>HF. The activation barriers for the solvated isomerizations decrease in the order HF>H2O>H2S>NH3 for both pathways. The number of lone pairs on the donor heteroatom as well as the heteroatom electronegativity are factors related to both these trends. Compared to the unsolvated cases, the solvated reactions have transition states which are usually ‘later’ in position along the reaction coordinate, validating the Hammond postulate.

  17. DFT study on the cycloreversion of thietane radical cations.

    Science.gov (United States)

    Domingo, Luis R; Pérez-Ruiz, Raúl; Argüello, Juan E; Miranda, Miguel A

    2011-06-01

    The molecular mechanism of the cycloreversion (CR) of thietane radical cations has been analyzed in detail at the UB3LYP/6-31G* level of theory. Results have shown that the process takes place via a stepwise mechanism leading to alkenes and thiobenzophenone; alternatively, formal [4+2] cycloadducts are obtained. Thus, the CR of radical cations 1a,b(•+) is initiated by C2-C3 bond breaking, giving common intermediates INa,b. At this stage, two reaction pathways are feasible involving ion molecule complexes IMCa,b (i) or radical cations 4a,b(•+) (ii). Calculations support that 1a(•+) follows reaction pathway ii (leading to the formal [4+2] cycloadducts 5a). By contrast, 1b(•+) follows pathway i, leading to trans-stilbene radical cation (2b(•+)) and thiobenzophenone.

  18. Degradation Mechanism of Cationic Red X-GRL by Ozonation

    Institute of Scientific and Technical Information of China (English)

    Wei Rong ZHAO; Xin Hua XU; Hui Xiang SHI; Da Hui WANG

    2003-01-01

    The degradation mechanism of Cationic Red X-GRL was investigated when the intermediates, the nitrate ion and the pH were analyzed in the ozonation. The degradation of the Cationic Red X-GRL includes the de-auxochrome stage, the decolour stage, and the decomposition of fragment stage. During the degradation process, among the six nitrogen atoms of Cationic Red X-GRL, one is transferred into a nitrate ion, one becomes the form of an amine compound, and the rest four are transformed into two molecules of nitrogen. In the course of the ozonation of Cationic Red X-GRL, the direct attack of ozone is the main decolour effect.

  19. Condensation of nonstochiometric DNA/polycation complexes by divalent cations.

    Science.gov (United States)

    Budker, Vladimir; Trubetskoy, Vladimir; Wolff, Jon A

    2006-12-15

    This study found that divalent cations induced the further condensation of partially condensed DNA within nonstochiometric polycation complexes. The addition of a few mmol of a divalent cation such as calcium reduced by half the inflection point at which DNA became fully condensed by poly-L-lysine (PLL) and a variety of other polycations. The effect on DNA condensation was initially observed using a new method, which is based on the concentration-dependent self-quenching of fluorescent moieties (e.g., rhodamine) covalently linked to the DNA backbone at relatively high densities. Additional analyses, which employed ultracentrifugation, dynamic light scattering, agarose gel electrophoresis, and atomic force microscopy, confirmed the effect of divalent cations. These results provide an additional accounting of the process by which divalent cations induce greater chromatin compaction that is based on the representation of chromatin fibers as a nonstoichiometric polyelectrolyte complex. They also offer a new approach to assemble nonviral vectors for gene therapy.

  20. Microbial monomers custom-synthesized to build true bio-derived aromatic polymers.

    Science.gov (United States)

    Fujita, Tomoya; Nguyen, Hieu Duc; Ito, Takashi; Zhou, Shengmin; Osada, Lisa; Tateyama, Seiji; Kaneko, Tatsuo; Takaya, Naoki

    2013-10-01

    Aromatic polymers include novel and extant functional materials although none has been produced from biotic building blocks derived from primary biomass glucose. Here we screened microbial aromatic metabolites, engineered bacterial metabolism and fermented the aromatic lactic acid derivative β-phenyllactic acid (PhLA). We expressed the Wickerhamia fluorescens gene (pprA) encoding a phenylpyruvate reductase in Escherichia coli strains producing high levels of phenylalanine, and fermented optically pure (>99.9 %) D-PhLA. Replacing pprA with bacterial ldhA encoding lactate dehydrogenase generated L-PhLA, indicating that the produced enzymes converted phenylpyruvate, which is an intermediate of phenylalanine synthesis, to these chiral PhLAs. Glucose was converted under optimized fermentation conditions to yield 29 g/l D-PhLA, which was purified from fermentation broth. The product satisfied the laboratory-scale chemical synthesis of poly(D-PhLA) with M w 28,000 and allowed initial physiochemical characterization. Poly(D-PhLA) absorbed near ultraviolet light, and has the same potential as all other biomass-derived aromatic bioplastics of phenylated derivatives of poly(lactic acid). This approach to screening and fermenting aromatic monomers from glucose exploits a new era of bio-based aromatic polymer design and will contribute to petroleum conservation and carbon dioxide fixation. PMID:23949992

  1. Synthesis and optical properties of chlorin monomer, dimer and trimer on an amino nitrogen atom.

    Science.gov (United States)

    Tamiaki, Hitoshi; Nagai, Tomoaki; Tanaka, Takuya; Tatebe, Tomohiro

    2015-09-01

    Naturally occurring chlorophyll-a was chemically modified to methyl 3-aminomethyl-pyropheophorbides-a including primary, secondary, and tertiary amines. Reductive amination of methyl pyropheophorbide-d possessing the 3-formyl group with ammonia efficiently gave a chlorin dimer covalently linked with CH2NHCH2 at the 3-position, which was transformed into a trimer through the substitution at the amino group. Conformational analyses by (1)H NMR spectroscopic observation and molecular modeling estimation indicated that the dimer and trimer were apt to form closely packed structures. Chlorin chromophores in the dimer and trimer were weakly interacted in dichloromethane to shift their Qy absorption bands to longer wavelengths by 4-6nm than the maxima of the corresponding monomer. In the red-shifted Qy region, the trimer gave an S-shaped circular dichroism band by exciton coupling of composite chlorin units. All the semi-synthetic chlorophyll derivatives were highly fluorescent and no intramolecular quenching was observed even in the trimer. The behaviors would be ascribable to the formation of compact conformers and suppression of intramolecular motion, which are important to construct light-harvesting antenna complexes in phototrophs and their model systems.

  2. Trends in water monomer adsorption and dissociation on flat insulating surfaces.

    Science.gov (United States)

    Hu, Xiao Liang; Carrasco, Javier; Klimeš, Jiří; Michaelides, Angelos

    2011-07-21

    The interaction of water with solid surfaces is key to a wide variety of industrial and natural processes. However, the basic principles that dictate how stable and in which state (intact or dissociated) water will be on a given surface are not fully understood. Towards this end, we have used density functional theory to examine water monomer adsorption on the (001) surfaces of a broad range of alkaline earth oxides, alkaline earth sulfides, alkali fluorides, and alkali chlorides. Some interesting general conclusions are arrived at: (i) on all the surfaces considered only a few specific adsorption structures are favoured; (ii) water becomes more stable upon descending the oxide and fluoride series but does not vary much upon going down the chloride and sulfide series; (iii) water is stabilised both by an increase in the lattice constant, which facilitates hydrogen bonding to the substrate, and by the flexibility of the substrate. These are also factors that favour water dissociation. We hope that this study is of some value in better understanding the surface science of water in general, and in assisting in the interpretation and design of future experiments.

  3. Vegetable oil-derived epoxy monomers and polymer blends: A comparative study with review

    Directory of Open Access Journals (Sweden)

    T. P. Schuman

    2013-03-01

    Full Text Available Glycidyl esters of epoxidized fatty acids derived from soybean oil (EGS and linseed oil (EGL have been synthesized to have higher oxirane content, more reactivity and lower viscosity than epoxidized soybean oil (ESO or epoxidized linseed oil (ELO. The EGS and ESO, for comparison, were used neat and in blends with diglycidyl ether of bisphenol A (DGEBA. Thermosetting resins were fabricated with the epoxy monomers and either BF3 catalyst or anhydride. The curing behaviors, glass transition temperatures, crosslink densities and mechanical properties were tested. The results indicated that polymer glass transition temperatures were mostly a function of oxirane content with additional influence of glycidyl versus internal oxirane reactivity, pendant chain content, and chemical structure and presence of saturated components. EGS provided better compatibility with DGEBA, improved intermolecular crosslinking and glass transition temperature, and yielded mechanically stronger polymerized materials than materials obtained using ESO. Other benefits of the EGS resin blend systems were significantly reduced viscosities compared to either DGEBA or ESO-blended DGEBA counterparts. Therefore, EGS that is derived from renewable sources has improved potential for fabrication of structural and structurally complex epoxy composites, e.g., by vacuum-assisted resin transfer molding.

  4. A study of normoxic polymer gel using monomer 2-hydroxyethyl methacrylate (HEMA)

    Energy Technology Data Exchange (ETDEWEB)

    Ishak, Siti Atiqah; Mustafa, Iskandar Shahrim; Rahman, Azhar Abdul [School of Physics, Universiti Sains Malaysia, Pulau Pinang (Malaysia); Moktar, Mohd; Min, Ung Ngie [Radiotherapy Department, University Malaya Medical Centre, Kuala Lumpur (Malaysia)

    2015-04-24

    The aim of this study is to determine the sensitivity of HEMA-polymer gel mixture consist of monomer 2-hydroxyethyl methacrylate (HEMA) with different types of composition. Several composition of HEMA-polymer gel were fabricated and the gels were irradiated with radiation dose between 10 cGy to 100cGy by using x-ray machine and 100 cGy to 1400 cGy by using 6 MV photon beam energy of linear accelerator. The degree of polymerization was evaluated by using magnetic resonance imaging (MRI) with dependence of R2-dose response. Polymer gel consists of cross-linker, anti-oxidant Tetrakis(Hydroxymethyl)phosphonium chloride solution (THPC) and oxygen scavenger hydroquinone shows a stable sensitivity with highest dose dependency. Besides, the results shows the stage polymerization consist of induction, propagation, termination, and chain transfer were dependence with type of chemical mixture and radiation dose. Thus, normoxic HEMA-polymer gel with the different gel formulations can have a better dose resolution and an appropriate recipe must be selected to increase of the sensitivity required and the stability of the dosimeter.

  5. Papain-Catalyzed Synthesis of Polyglutamate Containing a Nylon Monomer Unit

    Directory of Open Access Journals (Sweden)

    Kenjiro Yazawa

    2016-05-01

    Full Text Available Peptides have the potential to serve as an alternative for petroleum-based polymers to support a sustainable society. However, they lack thermoplasticity, owing to their strong intermolecular interactions. In contrast, nylon is famous for its thermoplasticity and chemical resistance. Here, we synthesized peptides containing a nylon unit to modify their thermal properties by using papain-catalyzed chemoenzymatic polymerization. We used l-glutamic acid alkyl ester as the amino acid monomer and nylon 1, 3, 4, and 6 alkyl esters as the nylon unit. Papain catalyzed the copolymerization of glutamic acid with nylon 3, 4, and 6 alkyl esters, whereas the nylon 1 unit could not be copolymerized. Other proteases used in this study, namely, bromelain, proteinase K, and Candida antarctica lipase (CALB, were not able to copolymerize with any nylon units. The broad substrate specificity of papain enabled the copolymerization of l-glutamic acid with a nylon unit. The peptides with nylon units demonstrated different thermal profiles from that of oligo(l-glutamic acid. Therefore, the resultant peptides with various nylon units are expected to form fewer intermolecular hydrogen bonds, thus altering their thermal properties. This finding is expected to broaden the applications of peptide materials and chemoenzymatic polymerization.

  6. Alternate fuels and chemicals from synthesis gas: Vinyl acetate monomer. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Richard D. Colberg; Nick A. Collins; Edwin F. Holcombe; Gerald C. Tustin; Joseph R. Zoeller

    1999-01-01

    There has been a long-standing desire on the part of industry and the U.S. Department of Energy to replace the existing ethylene-based vinyl acetate monomer (VAM) process with an entirely synthesis gas-based process. Although there are a large number of process options for the conversion of synthesis gas to VAM, Eastman Chemical Company undertook an analytical approach, based on known chemical and economic principles, to reduce the potential candidate processes to a select group of eight processes. The critical technologies that would be required for these routes were: (1) the esterification of acetaldehyde (AcH) with ketene to generate VAM, (2) the hydrogenation of ketene to acetaldehyde, (3) the hydrogenation of acetic acid to acetaldehyde, and (4) the reductive carbonylation of methanol to acetaldehyde. This report describes the selection process for the candidate processes, the successful development of the key technologies, and the economic assessments for the preferred routes. In addition, improvements in the conversion of acetic anhydride and acetaldehyde to VAM are discussed. The conclusion from this study is that, with the technology developed in this study, VAM may be produced from synthesis gas, but the cost of production is about 15% higher than the conventional oxidative acetoxylation of ethylene, primarily due to higher capital associated with the synthesis gas-based processes.

  7. Production of bone cement composites: effect of fillers, co-monomer and particles properties

    Energy Technology Data Exchange (ETDEWEB)

    Santos Junior, J.G.F.; Melo, P.A.; Pinto, J.C., E-mail: jjunior@peq.coppe.ufrj.b, E-mail: melo@peq.coppe.ufrj.b, E-mail: pinto@peq.coppe.ufrj.b [Coordenacao dos Programas de Pos-Graduacao de Engenharia. (PEQ/COPPE/UFRJ), RJ (Brazil). Programa de Engenharia Quimica; Pita, V.J.R.R., E-mail: vjpita@ima.ufrj.b [Universidade Federal do Rio de Janeiro (IMA/UFRJ), RJ (Brazil). Inst. de Macromoleculas Eloisa Mano; Nele, M. [Universidade Federal do Rio de Janeiro (EQ/UFRJ), RJ (Brazil). Escola de Quimica

    2011-04-15

    Artificial bone cements (BCs) based on poly(methyl methacrylate) (PMMA) powders and methyl methacrylate (MMA) liquid monomer also present in their formulation small amounts of other substances, including a chemical initiator compound and radiopaque agents. Because inadequate mixing of the recipe components during the manufacture of the bone cement may compromise the mechanical properties of the final pieces, new techniques to incorporate the fillers into the BC and their effect upon the mechanical properties of BC pieces were investigated in the present study. PMMA powder composites were produced in situ in the reaction vessel by addition of X-ray contrasts to the reacting MMA mixture. It is shown that this can lead to much better mechanical properties of test pieces, when compared to standard bone cement formulations, because enhanced dispersion of the radiopaque agents can be achieved. Moreover, it is shown that the addition of hydroxyapatite (HA) and acrylic acid (AA) to the bone cement recipe can be beneficial for the mechanical performance of the final material. It is also shown that particle morphology can exert a tremendous effect upon the performance of test pieces, indicating that the suspension polymerization step should be carefully controlled when optimization of the bone cement formulation is desired. (author)

  8. Characterization of a Low Shrinkage Dental Composite Containing Bismethylene Spiroorthocarbonate Expanding Monomer

    Directory of Open Access Journals (Sweden)

    Jing Fu

    2014-02-01

    Full Text Available In this study, a novel dental composite based on the unsaturated bismethylene spiroorthocarbonate expanding monomer 3,9-dimethylene-1,3,5,7-tetraoxa-spiro[5,5]undecane (BMSOC and bisphenol-S-bis(3-meth acrylate-2-hydroxypropylether (BisS-GMA was prepared. CQ (camphorquinone of 1 wt % and DMAEMA (2-(dimethylaminoethyl methacrylate of 2 wt % were used in a photoinitiation system to initiate the copolymerization of the matrix resins. Distilled water contact angle measurements were performed for the wettability measurement. Degree of conversion, volumetric shrinkage, contraction stress and compressive strength were measured using Fourier Transformation Infrared-FTIR spectroscopy, the AccuVol and a universal testing machine, respectively. Within the limitations of this study, it can be concluded that the resin composites modified by bismethylene spiroorthocarbonate and BisS-GMA showed a low volumetric shrinkage at 1.25% and a higher contact angle. The lower contraction stress, higher degree of conversion and compressive strength of the novel dental composites were also observed.

  9. Stability of functionalized C{sub 60} paramagnetic dimers and monomers

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Michael [Armament Research Development and Engineering Center, Picatinny, NJ 07806-5000 (United States); Owens, Frank J., E-mail: owensfj@gmail.com [Department of Physics, Hunter College, City University of New York, 695 Park Ave., NY 10065 (United States)

    2012-02-06

    Highlights: Black-Right-Pointing-Pointer DFT is used to calculate the bond dissociation energy of functionalized C{sub 60} dimers. Black-Right-Pointing-Pointer The results show the dimers would not be stable above room temperature. Black-Right-Pointing-Pointer The calculations indicate the observed magnetism cannot be due to C{sub 60} dimers. Black-Right-Pointing-Pointer Because of their higher stability the ferromagnetism is likely due to X-C{sub 60} monomers. - Abstract: Density functional theory is used to calculate the bond dissociation energy to cleave the C{sub 60}=C{sub 60} bond of the paramagnetic X-C{sub 60}=C{sub 60}-X and X-C{sub 60}=C{sub 60} dimers where X is F, OH, O and H. The results show that these dimers would not be stable much above room temperature and therefore cannot constitute the paramagnetic phase needed to form the observed ferromagnetism which has been shown to be stable up to 800 K. The calculated bond dissociation energies to remove an F, OH or H from a single C{sub 60} are large suggesting that they could be the source of the unpaired spin needed for the high temperature ferromagnetism.

  10. Synthesis of antibacterial methacrylate monomer derived from thiazole and its application in dental resin.

    Science.gov (United States)

    Luo, Weixun; Huang, Qiting; Liu, Fang; Lin, Zhengmei; He, Jingwei

    2015-09-01

    A non-quaternary ammonium antibacterial methacrylate monomer MEMT derived from thiazole was synthesized and applied into UDMA/TEGDMA dental resin with a series of mass fraction (10 wt%, 20 wt%, and 30 wt%). Double bond conversion, polymerization shrinkage, water sorption, solubility, flexural strength and modulus, and antibacterial activity of MEMT containing resin formulations were investigated with UDMA/TEGDMA as control resin. The results showed that MEMT containing dental resin had higher double bond conversion than control resin. Compared with control polymer, all MEMT containing polymer had comparable or lower polymerization shrinkage, water sorption and solubility, except for the polymer with 30 wt% of MEMT which had higher water sorption and solubility than control polymer. The MEMT had no influence on flexural strength and modulus before water immersion, but all MEMT containing polymers had lower flexural strength and modulus than control polymer after water immersion. The MEMT could endow dental polymer with obvious antibacterial activity by immobilizing MEMT into the polymeric network.

  11. Response of hydroponically grown head lettuce on residual monomer from polyacrylamide.

    Science.gov (United States)

    Mroczek, E; Konieczny, P; Kleiber, T; Waśkiewicz, A

    2014-01-01

    The aim was to assess acrylamide monomer (AMD) uptake by hydroponically grown lettuce. Lettuce was cultivated by applying plant tissue testing in a recycled system by the use of nutrient solutions prepared with two water-soluble flocculants F3 and F4 containing 176 and 763 mg kg(-1) of AMD, respectively. The effects on growth, fresh weight and plant leaf quality were evaluated by comparing these treatments and one control standard nutrient solution typically recommended for lettuce hydroponic cultivation. To assess the nutritional status of lettuce, samples were collected and lyophilised before determination of the selected micro- and macro-element contents. An HPLC with photodiode array detector method was applied to determine AMD in both selected flocculants and dried plant samples. Results show that lettuces cultivated under the conditions described above absorb AMD from nutrient solutions into their leaves. The AMD presence in recycled nutrient solutions has a negative influence on the growth of lettuce, reducing their average fresh weight and average number of leaves. The study confirmed that the problem of AMD mobility and its accumulation risk in plants should to be an important topic with respect to safe polyacrylamide (PAM) handling in the agro food area. PMID:24916210

  12. Determination of Residual Monomers Released from Soft Lining Materials with the use of HPLC

    Directory of Open Access Journals (Sweden)

    Afrodite Sofou

    2007-12-01

    Full Text Available A study was carried out to examine the post polymerized leachability of three non phthalic and four phthalic residual monomers, from twelve commercially available soft lining materials, using HPLC. Specimens of equal dimensions were constructed from each brand of material following a standardized procedure and were stored in three different conditions of storage i.e. distilled water, artificial saliva and a binary mixture of ethanol-water, with the resulting liquids providing samples for analysis in the HPLC apparatus. Three different experiments were performed for each brand of material and each condition of storage, in order to examine the parameters time and temperature. The results obtained from this study suggest that a wide spectrum of residues is diffusing out of the twelve examined soft lining materials. The non phthalic compounds were leaching at high concentrations while all the phthalates examined exhibited different degrees of elusion commensurate with the storage condition, brand of material and type of experiment. The main non phthalic component extracted from all the materials was methyl methacrylate, while the mainly extracted phthalic compound was different from each material. The level of elusion seems to be increasing dependent on time, medium of storage, and temperature as well.

  13. Enzymatic Polymerization of an Ibuprofen-Containing Monomer and Subsequent Drug Release.

    Science.gov (United States)

    Stebbins, Nicholas D; Yu, Weiling; Uhrich, Kathryn E

    2015-08-01

    Novel ibuprofen-containing monomers comprising naturally occurring and biocompatible compounds were synthesized and subsequently polymerized via enzymatic methods. Through the use of a malic acid sugar backbone, ibuprofen was attached as a pendant group, and then subsequently polymerized with a linear aliphatic diol (1,3-propanediol, 1,5-pentanediol, or 1,8-octanediol) as comonomer using lipase B from Candida antarctica, a greener alternative to traditional metal catalysts. Polymer structures were elucidated by nuclear magnetic resonance and infrared spectroscopies, and thermal properties and molecular weights were determined. All polymers exhibited sustained ibuprofen release, with the longer chain, more hydrophobic diols exhibiting the slowest release over the 30 d study. Polymers were deemed cytocompatible using mouse fibroblasts, when evaluated at relevant therapeutic concentrations. Additionally, ibuprofen retained its chemical integrity throughout the polymerization and in vitro hydrolytic degradation processes. This methodology of enzymatic polymerization of a drug presents a more environmentally friendly synthesis and a novel approach to bioactive polymer conjugates. PMID:25879779

  14. Synergistic inhibition of Haemonchus contortus exsheathment by flavonoid monomers and condensed tannins

    Directory of Open Access Journals (Sweden)

    Chaweewan Klongsiriwet

    2015-12-01

    Full Text Available This study investigated the separate and combined anthelmintic (AH effects of different phenolic compounds, including condensed tannins and flavonoids, all of which are known to occur in willow leaves, a potentially valuable dry season feed. A range of contrasting model tannins, which span the whole range of willow tannins, were isolated from tilia flowers, goat willow leaves, black currant leaves and red currant leaves. All together, the tested compounds represented the major tannin types (procyanidins and prodelphinidins and flavonoid types (flavonols, flavones and flavanones. The larval exsheathment inhibition assay (LEIA was used to assess their in vitro effects on Haemonchus contortus third stage larvae. Arbutin, vanillic acid, and taxifolin proved to be ineffective whereas naringenin, quercetin and luteolin were highly effective at 250 μM concentrations. Procyanidin (PC tannins tended to be less active than prodelphinidin tannins (PD. Experiments with combinations of tannins and quercetin or luteolin revealed for the first time the existence of synergistic AH effects between tannins and flavonoid monomers. They also provided evidence that synergistic effects appear to occur at slightly lower concentrations of PC than PD. This suggests that the AH activity of condensed tannins can be significantly enhanced by the addition of quercetin or luteolin. This information may prove useful for plant breeding or selection and for designing optimal feed mixtures.

  15. Elution of monomers from three different bonding systems and their antibacterial effect.

    Science.gov (United States)

    Polydorou, Olga; Rogatti, Philipp; Bolek, Richard; Wolkewitz, Martin; Kümmerer, Klaus; Hellwig, Elmar

    2013-07-01

    The aim of the present study was to evaluate the release of monomers from three bonding systems and to correlate it with their antibacterial effect. Three bonding systems (Optibond FL(®), Xeno III(®) and Clearfil™ Protect Bond) were tested after storage in ethanol 75 % and human saliva. Twenty samples (n = 10/medium) of each bonding material were prepared and polymerized according to the manufacturers' instructions. Each sample was stored in 1 ml of the respective storage medium. The medium was renewed after 24 h, 7 days, and 28 days and was analysed by LC-MS/MS for the release of substances. Additionally, the antibacterial effect of the unpolymerized components of each bonding system and their polymerized mixture was tested using agar disc-diffusion test with Streptococcus mutans. Only HEMA was found to be released. The amount of HEMA detected in the ethanol samples was significantly higher compared to the saliva samples (p Optibond FL(®) < Xeno III(®.) According to the agar disc-diffusion test, all materials exhibited certain antibacterial activity. The release of HEMA from all tested materials even after storing in human saliva increases the concerns about their toxicity. Their antibacterial effect seems not be due to the release of substances. PMID:22684585

  16. Polyethylene with Reverse Co-monomer Incorporation: From an Industrial Serendipitous Discovery to Fundamental Understanding.

    Science.gov (United States)

    Cicmil, Dimitrije; Meeuwissen, Jurjen; Vantomme, Aurélien; Wang, Jian; van Ravenhorst, Ilse K; van der Bij, Hendrik E; Muñoz-Murillo, Ara; Weckhuysen, Bert M

    2015-10-26

    A triethylaluminium(TEAl)-modified Phillips ethylene polymerisation Cr/Ti/SiO2 catalyst has been developed with two distinct active regions positioned respectively in the inner core and outer shell of the catalyst particle. DRIFTS, EPR, UV-Vis-NIR DRS, STXM, SEM-EDX and GPC-IR studies revealed that the catalyst produces simultaneously two different polymers, i.e., low molecular weight linear-chain polyethylene in the Ti-abundant catalyst particle shell and high molecular weight short-chain branched polyethylene in the Ti-scarce catalyst particle core. Co-monomers for the short-chain branched polymer were generated in situ within the TEAl-impregnated confined space of the Ti-scarce catalyst particle core in close proximity to the active sites that produced the high molecular weight polymer. These results demonstrate that the catalyst particle architecture directly affects polymer composition, offering the perspective of making high-performance polyethylene from a single reactor system using this modified Phillips catalyst.

  17. Polyethylene with Reverse Co-monomer Incorporation: From an Industrial Serendipitous Discovery to Fundamental Understanding

    Science.gov (United States)

    Cicmil, Dimitrije; Meeuwissen, Jurjen; Vantomme, Aurélien; Wang, Jian; van Ravenhorst, Ilse K; van der Bij, Hendrik E; Muñoz-Murillo, Ara; Weckhuysen, Bert M

    2015-01-01

    A triethylaluminium(TEAl)-modified Phillips ethylene polymerisation Cr/Ti/SiO2 catalyst has been developed with two distinct active regions positioned respectively in the inner core and outer shell of the catalyst particle. DRIFTS, EPR, UV-Vis-NIR DRS, STXM, SEM-EDX and GPC-IR studies revealed that the catalyst produces simultaneously two different polymers, i.e., low molecular weight linear-chain polyethylene in the Ti-abundant catalyst particle shell and high molecular weight short-chain branched polyethylene in the Ti-scarce catalyst particle core. Co-monomers for the short-chain branched polymer were generated in situ within the TEAl-impregnated confined space of the Ti-scarce catalyst particle core in close proximity to the active sites that produced the high molecular weight polymer. These results demonstrate that the catalyst particle architecture directly affects polymer composition, offering the perspective of making high-performance polyethylene from a single reactor system using this modified Phillips catalyst. PMID:26349452

  18. TUNG OIL BASED MONOMER FOR THERMOSETTING POLYMERS: SYNTHESIS, CHARACTERIZATION AND COPOLYMERIZATION WITH STYRENE

    Directory of Open Access Journals (Sweden)

    Chengguo Liu,

    2011-11-01

    Full Text Available A tung oil (TO based monomer for rigid thermosetting polymer was synthesized, characterized, and copolymerized with styrene in this study. Tung oil was alcoholyzed with pentaerythritol (PER to get tung oil pentaerythritol alcoholysis products (TOPER, and the optimized conditions were explored according to the yields of TOPER analyzed by gas chromatography-mass spectrometry (GC-MS. The resulting alcoholysis products were maleinated to form tung oil maleate half ester (TOPERMA, and the reaction conditions were determined by monitoring the reaction extents of TOPER and maleic anhydride (MA with 1HNMR spectroscopy. The TO alcoholysis and maleinization reaction products were characterized by IR, 1HNMR, and electrospray ionization-mass spectrometry (ESI-MS techniques. At last, the TOPERMA mixture was cured with styrene (St, and the initiator tert-butyl peroxy benzoate (TPB. Differential scanning calorimetry (DSC was employed to characterize the curing process. Mechanical properties of the cured TOPERMA/St resin further confirmed the best procedure for the maleinization reaction. The loading of TO reached about 30% weight of the resulting thermosetting polymer. This promising material from renewable resources can be a potential substitution for petroleum products when used as sheet molding compounds.

  19. Synergistic inhibition of Haemonchus contortus exsheathment by flavonoid monomers and condensed tannins.

    Science.gov (United States)

    Klongsiriwet, Chaweewan; Quijada, Jessica; Williams, Andrew R; Mueller-Harvey, Irene; Williamson, Elizabeth M; Hoste, Hervé

    2015-12-01

    This study investigated the separate and combined anthelmintic (AH) effects of different phenolic compounds, including condensed tannins and flavonoids, all of which are known to occur in willow leaves, a potentially valuable dry season feed. A range of contrasting model tannins, which span the whole range of willow tannins, were isolated from tilia flowers, goat willow leaves, black currant leaves and red currant leaves. All together, the tested compounds represented the major tannin types (procyanidins and prodelphinidins) and flavonoid types (flavonols, flavones and flavanones). The larval exsheathment inhibition assay (LEIA) was used to assess their in vitro effects on Haemonchus contortus third stage larvae. Arbutin, vanillic acid, and taxifolin proved to be ineffective whereas naringenin, quercetin and luteolin were highly effective at 250 μM concentrations. Procyanidin (PC) tannins tended to be less active than prodelphinidin tannins (PD). Experiments with combinations of tannins and quercetin or luteolin revealed for the first time the existence of synergistic AH effects between tannins and flavonoid monomers. They also provided evidence that synergistic effects appear to occur at slightly lower concentrations of PC than PD. This suggests that the AH activity of condensed tannins can be significantly enhanced by the addition of quercetin or luteolin. This information may prove useful for plant breeding or selection and for designing optimal feed mixtures. PMID:26199861

  20. Microscopic Theory of Cation Exchange in CdSe Nanocrystals

    OpenAIRE

    Ott, Florian D.; Spiegel, Leo L.; Norris, David J.; Erwin, Steven C.

    2014-01-01

    Although poorly understood, cation-exchange reactions are increasingly used to dope or transform colloidal semiconductor nanocrystals (quantum dots). We used density-functional theory and kinetic Monte Carlo simulations to develop a microscopic theory that explains structural, optical, and electronic changes observed experimentally in Ag-cation-exchanged CdSe nanocrystals. We find that Coulomb interactions, both between ionized impurities and with the polarized nanocrystal surface, play a key...

  1. Migration of Cations and Anions in Amorphous Polymer Electrolytes

    Institute of Scientific and Technical Information of China (English)

    N.A.Stolwijk; S.H.Obeidi; M.Wiencierz

    2007-01-01

    1 Results Polymer electrolytes are used as ion conductors in batteries and fuel cells.Simple systems consist of a polymer matrix complexing an inorganic salt and are fully amorphous at the temperatures of interest.Both cations and anions are mobile and contribute to charge transport.Most studies on polymer electrolytes use the electrical conductivity to characterize the ion mobility.However,conductivity measurements cannot discriminate between cations and anions.This paper reports some recent results fr...

  2. Mercury release from deforested soils triggered by base cation enrichment.

    Science.gov (United States)

    Farella, N; Lucotte, M; Davidson, R; Daigle, S

    2006-09-01

    The Brazilian Amazon has experienced considerable colonization in the last few decades. Family agriculture based on slash-and-burn enables millions of people to live in that region. However, the poor nutrient content of most Amazonian soils requires cation-rich ashes from the burning of the vegetation biomass for cultivation to be successful, which leads to forest ecosystem degradation, soil erosion and mercury contamination. While recent studies have suggested that mercury present in soils was transferred towards rivers upon deforestation, little is known about the dynamics between agricultural land-use and mercury leaching. In this context, the present study proposes an explanation that illustrates how agricultural land-use triggers mercury loss from soils. This explanation lies in the competition between base cations and mercury in soils which are characterized by a low adsorption capacity. Since these soils are naturally very poor in base cations, the burning of the forest biomass suddenly brings high quantities of base cations to soils, destabilizing the previous equilibrium amongst cations. Base cation enrichment triggers mobility in soil cations, rapidly dislocating mercury atoms. This conclusion comes from principal component analyses illustrating that agricultural land-use was associated with base cation enrichment and mercury depletion. The overall conclusions highlight a pernicious cycle: while soil nutrient enrichment actually occurs through biomass burning, although on a temporary basis, there is a loss in Hg content, which is leached to rivers, entering the aquatic chain, and posing a potential health threat to local populations. Data presented here reflects three decades of deforestation activities, but little is known about the long-term impact of such a disequilibrium. These findings may have repercussions on our understanding of the complex dynamics of deforestation and agriculture worldwide. PMID:16781764

  3. Statistical properties of linear-hyperbranched graft copolymers prepared via "hypergrafting" of AB(m) monomers from linear B-functional core chains: A molecular dynamics simulation.

    Science.gov (United States)

    Rabbel, Hauke; Frey, Holger; Schmid, Friederike

    2015-12-28

    The reaction of ABm monomers (m = 2, 3) with a multifunctional Bf-type polymer chain ("hypergrafting") is studied by coarse-grained molecular dynamics simulations. The ABm monomers are hypergrafted using the slow monomer addition strategy. Fully dendronized, i.e., perfectly branched polymers are also simulated for comparison. The degree of branching of the molecules obtained with the "hypergrafting" process critically depends on the rate with which monomers attach to inner monomers compared to terminal monomers. This ratio is more favorable if the ABm monomers have lower reactivity, since the free monomers then have time to diffuse inside the chain. Configurational chain properties are also determined, showing that the stretching of the polymer backbone as a consequence of the "hypergrafting" procedure is much less pronounced than for perfectly dendronized chains. Furthermore, we analyze the scaling of various quantities with molecular weight M for large M (M > 100). The Wiener index scales as M(2.3), which is intermediate between linear chains (M(3)) and perfectly branched polymers (M(2)ln(M)). The polymer size, characterized by the radius of gyration Rg or the hydrodynamic radius Rh, is found to scale as Rg,h ∝ M(ν) with ν ≈ 0.38, which lies between the exponent of diffusion limited aggregation (ν = 0.4) and the mean-field exponent predicted by Konkolewicz and co-workers [Phys. Rev. Lett. 98, 238301 (2007)] (ν = 0.33). PMID:26723610

  4. Statistical properties of linear-hyperbranched graft copolymers prepared via "hypergrafting" of ABm monomers from linear B-functional core chains: A molecular dynamics simulation

    Science.gov (United States)

    Rabbel, Hauke; Frey, Holger; Schmid, Friederike

    2015-12-01

    The reaction of ABm monomers (m = 2, 3) with a multifunctional Bf-type polymer chain ("hypergrafting") is studied by coarse-grained molecular dynamics simulations. The ABm monomers are hypergrafted using the slow monomer addition strategy. Fully dendronized, i.e., perfectly branched polymers are also simulated for comparison. The degree of branching of the molecules obtained with the "hypergrafting" process critically depends on the rate with which monomers attach to inner monomers compared to terminal monomers. This ratio is more favorable if the ABm monomers have lower reactivity, since the free monomers then have time to diffuse inside the chain. Configurational chain properties are also determined, showing that the stretching of the polymer backbone as a consequence of the "hypergrafting" procedure is much less pronounced than for perfectly dendronized chains. Furthermore, we analyze the scaling of various quantities with molecular weight M for large M (M > 100). The Wiener index scales as M2.3, which is intermediate between linear chains (M3) and perfectly branched polymers (M2ln(M)). The polymer size, characterized by the radius of gyration Rg or the hydrodynamic radius Rh, is found to scale as Rg,h ∝ Mν with ν ≈ 0.38, which lies between the exponent of diffusion limited aggregation (ν = 0.4) and the mean-field exponent predicted by Konkolewicz and co-workers [Phys. Rev. Lett. 98, 238301 (2007)] (ν = 0.33).

  5. The effect of the polymerization initiator and light source on the elution of residual Bis-GMA and TEGDMA monomers: A study using liquid chromatography with UV detection.

    Science.gov (United States)

    Denis, Aline B; Diagone, Cristina A; Plepis, Ana M G; Viana, Rommel B

    2015-12-01

    A method for the extraction and quantification of two residual monomers, bisphenol glycidyl dimethacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA), that were evaluated using high efficiency liquid chromatography with UV detection was developed and validated in this study. Three types of solvents were applied in the extraction of the monomers (methanol, ethanol and acetonitrile), where the highest extraction efficiency was obtained using acetonitrile. The different resins were prepared by photoactivation of Bis-GMA and TEGDMA monomers. Additionally, the effects of the addition of two photoinitiators (camphorquinone (CQ) and phenyl propanodione (PPD) and that of a co-initiator (N,N-dimethyl-p-toluidine) were also analyzed. When only the CQ photoinitiator was used, a smaller amount of residual monomers was obtained, whereas a larger amount was obtained with PPD. When the two photoinitiators were used in the same matrix, however, no significant changes were observed in relation to the amount of residual TEGDMA monomers. For the addition of the co-initiator, there were no large changes in the extraction of residual monomers. The effect of the two photoactivation sources (halogen lamp and LED) led to small differences in the elution of the two monomers, although all of the resins differed significantly when photoactivated with a LED. Quantum chemical calculations using Density Functional Theory were carried out to characterize several molecular properties of each monomer. PMID:26184476

  6. Modulatory role of bivalent cations on reward system.

    Science.gov (United States)

    Nechifor, M; Chelărescu, D

    2008-01-01

    Bivalent cations (Ca, Mg, Zn, Mn etc.) modulate activity of reward system (RS). At physiologic levels they may influence all components of RS. There are influenced behavioral reactions at physiological stimuli and all essential elements of drug dependence (compulsive intake of substance, craving, reinforcement, withdrawal syndrom, relapse and reinstatement of intake) The fact that some cations (e.g. calcium) enhance some of the aspects of drug dependence and others (e.g. magnesium, zinc) decrease intensity of this process show that ratio between intra- and extracellular in the brain of these cations is important for the function of RS. Among actions of different cations at the level of RS there are important differences. Their mecahanism of action are common in part and specific in other. It is important the fact that modulatory action appear at physiologic cation concentrations (that could be reached at therapeutic doses). Modulatory action is related to ratio between concetrations of different bivalent cations and is exerted both in normal or pathologic conditions.

  7. Complexation Between Cationic Diblock Copolymers and Plasmid DNA

    Science.gov (United States)

    Jung, Seyoung; Reineke, Theresa; Lodge, Timothy

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

  8. Tunable states of interlayer cations in two-dimensional materials

    Energy Technology Data Exchange (ETDEWEB)

    Sato, K.; Numata, K. [Department of Environmental Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501 (Japan); Dai, W. [Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of Chemistry, Nankai University, Tianjin 300071 (China); Hunger, M. [Institute of Chemical Technology, University of Stuttgart, 70550 Stuttgart (Germany)

    2014-03-31

    The local state of cations inside the Ångstrom-scale interlayer spaces is one of the controlling factors for designing sophisticated two-dimensional (2D) materials consisting of 2D nanosheets. In the present work, the molecular mechanism on how the interlayer cation states are induced by the local structures of the 2D nanosheets is highlighted. For this purpose, the local states of Na cations in inorganic 2D materials, in which the compositional fluctuations of a few percent are introduced in the tetrahedral and octahedral units of the 2D nanosheets, were systematically studied by means of {sup 23}Na magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) and {sup 23}Na multiple-quantum MAS (MQMAS) NMR spectroscopy. In contrast with an uniform distribution of Na cations expected so far, various well-defined cation states sensitive to the local structures of the 2D nanosheets were identified. The tunability of the interlayer cation states along with the local structure of the 2D nanosheets, as the smallest structural unit of the 2D material, is discussed.

  9. Development of methacrylate/silorane hybrid monomer system: Relationship between photopolymerization behavior and dynamic mechanical properties.

    Science.gov (United States)

    Song, Linyong; Ye, Qiang; Ge, Xueping; Singh, Viraj; Misra, Anil; Laurence, Jennifer S; Berrie, Cindy L; Spencer, Paulette

    2016-07-01

    Resin chemistries for dental composite are evolving as noted by the introduction of silorane-based composites in 2007. This shift in the landscape from methacrylate-based composites has fueled the quest for versatile methacrylate-silorane adhesives. The objective of this study was to evaluate the polymerization behavior and structure/property relationships of methacrylate-silorane hybrid systems. Amine compound ethyl-4-(dimethylamino) benzoate (EDMAB) or silane compound tris(trimethylsilyl) silane (TTMSS) was selected as coinitiators. The mechanical properties of the copolymer were improved significantly at low concentrations (15, 25, or 35 wt %) of silorane when EDMAB was used as coinitiator. The rubbery moduli of these experimental copolymers were increased by up to 260%, compared with that of the control (30.8 ± 1.9 MPa). Visible phase separation appeared in these formulations if the silorane concentrations in the formulations were 50-75 wt %. The use of TTMSS as coinitiator decreased the phase separation, but there was a concomitant decrease in mechanical properties. In the neat methacrylate formulations, the maximum rates of free-radical polymerization with EDMAB or TTMSS were 0.28 or 0.06 s(-1) , respectively. In the neat silorane resin, the maximum rates of cationic ring-opening polymerization with EDMAB or TTMSS were 0.056 or 0.087 s(-1) , respectively. The phase separation phenomenon may be attributed to differences in the rates of free-radical polymerization of methacrylates and cationic ring-opening polymerization of silorane. In the hybrid systems, free-radical polymerization initiated with EDMAB led to higher crosslink density and better mechanical properties under dry/wet conditions. These beneficial effects were, however, associated with an increase in heterogeneity in the network structure. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 841-852, 2016. PMID:25953619

  10. Progress on Preparation and Application of Cationic Polymer Microsphere%阳离子聚合物微球的制备和应用进展

    Institute of Scientific and Technical Information of China (English)

    李光辉; 葛际江; 蒋平; 申金伟

    2012-01-01

    Herein, the conventional preparation methods of cationic polymer microsphere, highlighting the progress of (emulsifier-free) emulsion polymerization, dispersion polymerization, microemulsion polymerization, as well as the application in profile conformation, electrorheology fluid, biomedicine, are reviewed, and origin of cationic charges in the microsphere surface and cationic monomers used in world-wide published works are systematically summed up. Moreover, the specifications of various processes for preparation are elucidated. Recently, a number of new methods like clicking chemistry, atom transfer radical polymerization for this use have paved a way for the control of surface property of microsphere. Thus, the outline on the future directions and challenges come with the design and engineering of cationic polymer particles is concluded.%全面介绍了合成阳离子微球的常用方法,着重阐述了(无皂)乳液聚合、分散聚合、微乳聚合的研究进展及阳离子微球在油田调剖、电流变液、生物医药领域的应用,系统归纳了阳离子微球表面电荷来源和国内外文献报道的常用阳离子单体,并总结了不同合成工艺的应用特点。最近,许多新的合成方法如点击化学、原子转移自由基聚合等应用于阳离子微球的合成,为控制微球的表面性能提供了新的途径。在此基础上,展望了阳离子聚合物微球未来发展方向和面临挑战。

  11. Separation of proteins by cation-exchange sequential injection chromatography using a polymeric monolithic column.

    Science.gov (United States)

    Masini, Jorge Cesar

    2016-02-01

    Since sequential injection chromatography (SIC) emerged in 2003, it has been used for separation of small molecules in diverse samples, but separations of high molar mass compounds such as proteins have not yet been described. In the present work a poly(glycidyl methacrylate-co-ethylene dimethacrylate) (GMA-co-EDMA) monolithic column was prepared by free radical polymerization inside a 2.1-mm-i.d. activated fused silica-lined stainless steel tubing and modified with iminodiacetic acid (IDA). The column was prepared from a mixture of 24% GMA, 16% EDMA, 20% cyclohexanol, and 40% 1-dodecanol (all% as w/w) containing 1% of azobisisobutyronitrile (AIBN) (in relation to monomers). Polymerization was done at 60 °C for 24 h. The polymer was modified with 1.0 M IDA (in 2 M Na2CO3, pH 10.5) at 80 °C for 16 h. Separation of myoglobin, ribonuclease A, cytochrome C, and lysozyme was achieved at pH 7.0 (20 mM KH2PO4/K2HPO4) using a salt gradient (NaCl). Myoglobin was not retained, and the other proteins were separated by a gradient of NaCl created inside the holding coil (4 m of 0.8-mm-i.d. PTFE tubing) by sequential aspiration of 750 and 700 μL of 0.2 and 0.1 M NaCl, respectively. As the flow was reversed toward the column (5 μL s(-1)) the interdispersion of these solutions created a reproducible gradient which separated the proteins in 10 min, with the following order of retention: ribonuclease A < cytochrome C < lysozyme. The elution order was consistent with a cation-exchange mechanism as the retention increased with the isoelectric points.

  12. A Low Protein Binding Cationic Poly(2-oxazoline) as Non-Viral Vector

    KAUST Repository

    He, Zhijian

    2015-04-02

    © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Developing safe and efficient non-viral gene delivery systems remains a major challenge. We present a new cationic poly(2-oxazoline) (CPOx) block copolymer for gene therapy that was synthesized by sequential polymerization of non-ionic 2-methyl-2-oxazoline and a new 2-oxazoline monomer, 2-(N-methyl, N-Boc-amino)-methyl-2-oxazoline, followed by deprotection of the pendant secondary amine groups. Upon mixing with plasmid DNA (pDNA), CPOx forms small (diameter ≈80 nm) and narrowly dispersed polyplexes (PDI <0.2), which are stable upon dilution in saline and against thermal challenge. These polyplexes exhibited low plasma protein binding and very low cytotoxicity in vitro compared to the polyplexes of pDNA and poly(ethylene glycol)-b-poly(L-lysine) (PEG-b-PLL). CPOx/pDNA polyplexes at N/P = 5 bound considerably less plasma protein compared to polyplexes of PEG-b-PLL at the same N/P ratio. This is a unique aspect of the developed polyplexes emphasizing their potential for systemic delivery in vivo. The transfection efficiency of the polyplexes in B16 murine melanoma cells was low after 4 h, but increased significantly for 10 h exposure time, indicative of slow internalization of polyplexes. Addition of Pluronic P85 boosted the transfection using CPOx/pDNA polyplexes considerably. The low protein binding of CPOx/pDNA polyplexes is particularly interesting for the future development of targeted gene delivery.

  13. Common molecular weight of the androgen receptor monomer in different target tissues

    International Nuclear Information System (INIS)

    Previously reported molecular weights for the monomeric steroid binding subunit of the androgen receptor protein have ranged from 25,000 to 167,000. The molecular weight appeared to vary among different species and target organs, as well as between different investigators. This study has examined androgen receptors from a diverse group of organs and species to determine whether these tissues share a common monomeric form. Gel filtration revealed peaks of specific [3H]dihydrotestosterone binding activity corresponding to Stokes radii of 54, 33, and 20 A in cytosols from several tissues. Phosphocellulose chromatography diminished the appearance of the smaller androgen receptor forms and facilitated the appearance of the larger 54-A form. Mixing experiments suggested that phosphocellulose was stabilizing the 54-A form by binding putative proteases which cleave this larger form. Methods were developed to generate homogeneous preparations of a given androgen receptor size for comparative study. Sucrose density gradient analysis showed sedimentation coefficients of 4.5-5.0, 3.5-4.0, and 2.5-3.0 S, respectively. The corresponding calculated molecular weights were 109,000-121,000, 52,000-59,000, and 22,000-27,000. Scatchard analysis of each of these androgen receptor forms demonstrated very similar affinity for [3H]dihydrotestosterone. Extensively purified preparations of androgen receptor from R3327 tumor contained varying amounts of the three receptor forms even though molybdate and phosphocellulose were used to stabilize the androgen receptor protein during purification. It is concluded that androgen receptors from a variety of tissues share a common monomeric subunit and that stabilization is necessary during analytical and purification procedures to prevent cleavage of the monomer by endogenous proteases

  14. Optical transition energies of isolated molecular monomers and weakly interacting two-dimensional aggregates

    Science.gov (United States)

    Forker, Roman; Dienel, Thomas; Krause, Andreas; Gruenewald, Marco; Meissner, Matthias; Kirchhuebel, Tino; Gröning, Oliver; Fritz, Torsten

    2016-04-01

    The optical excitation energies of organic dye molecules are often said to depend sensitively on the polarizability of the utilized substrate. To this end, we employ differential reflectance spectroscopy (DRS) to analyze the S0→S1 fundamental transition energies observed for 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) as a function of coverage on various surfaces, such as sp2-bonded insulating layers [graphene and hexagonal boron nitride (h-BN)], and noble metals pre-covered by a molecular wetting layer which prevents hybridization of the second-layer molecules with the metal states. We elucidate the optical absorbance behavior of PTCDA layers grown on h-BN/Rh(111) and on h-BN/Pt(111) and characterize their structures by means of scanning tunneling microscopy. Surprisingly, although the dielectric properties of the employed substrates differ substantially, only two main transition energies are observed: (i) PTCDAHE essentially mimics the behavior of isolated monomers on surfaces (particularly at submonolayer coverage), while (ii) PTCDALE, red-shifted by ≈70 meV (≈560 cm-1 ), is attributed to two-dimensional densely packed aggregates. This red-shift is in remarkable accordance with previous investigations for PTCDA on NaCl(100) and, therefore, likely arises from the same physical effects, namely the formation of two-dimensional excitonic bands and the polarizability of neighboring molecules within the monolayer. In distinction from earlier studies, we conclude that the polarizabilities of the employed substrates do not constitute the dominant contribution to the molecular S0→S1 transition energies observed here.

  15. Final Report: Investigation of Catalytic Pathways for Lignin Breakdown into Monomers and Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Gluckstein, Jeffrey A [ORNL; Hu, Michael Z. [ORNL; Kidder, Michelle [ORNL; McFarlane, Joanna [ORNL; Narula, Chaitanya Kumar [ORNL; Sturgeon, Matthew R [ORNL

    2010-12-01

    Lignin is a biopolymer that comprises up to 35% of woody biomass by dry weight. It is currently underutilized compared to cellulose and hemicellulose, the other two primary components of woody biomass. Lignin has an irregular structure of methoxylated aromatic groups linked by a suite of ether and alkyl bonds which makes it difficult to degrade selectively. However, the aromatic components of lignin also make it promising as a base material for the production of aromatic fuel additives and cyclic chemical feed stocks such as styrene, benzene, and cyclohexanol. Our laboratory research focused on three methods to selectively cleave and deoxygenate purified lignin under mild conditions: acidolysis, hydrogenation and electrocatalysis. (1) Acidolysis was undertaken in CH2Cl2 at room temperature. (2) Hydrogenation was carried out by dissolving lignin and a rhodium catalyst in 1:1 water:methoxyethanol under a 1 atm H2 environment. (3) Electrocatalysis of lignin involved reacting electrically generated hydrogen atoms at a catalytic palladium cathode with lignin dissolved in a solution of aqueous methanol. In all of the experiments, the lignin degradation products were identified and quantified by gas chromatography mass spectroscopy and flame ionization detection. Yields were low, but this may have reflected the difficulty in recovering the various fractions after conversion. The homogeneous hydrogenation of lignin showed fragmentation into monomers, while the electrocatalytic hydrogenation showed production of polyaromatic hydrocarbons and substituted benzenes. In addition to the experiments, promising pathways for the conversion of lignin were assessed. Three conversion methods were compared based on their material and energy inputs and proposed improvements using better catalyst and process technology. A variety of areas were noted as needing further experimental and theoretical effort to increase the feasibility of lignin conversion to fuels.

  16. Coxibs interfere with the action of aspirin by binding tightly to one monomer of cyclooxygenase-1

    Energy Technology Data Exchange (ETDEWEB)

    Rimon, Gilad; Sidhu, Ranjinder S.; Lauver, D. Adam; Lee, Jullia Y.; Sharma, Narayan P.; Yuan, Chong; Frieler, Ryan A.; Trievel, Raymond C.; Lucchesi, Benedict R.; Smith, William L. (Michigan)

    2010-02-11

    Pain associated with inflammation involves prostaglandins synthesized from arachidonic acid (AA) through cyclooxygenase-2 (COX-2) pathways while thromboxane A{sub 2} formed by platelets from AA via cyclooxygenase-1 (COX-1) mediates thrombosis. COX-1 and COX-2 are both targets of nonselective nonsteroidal antiinflammatory drugs (nsNSAIDs) including aspirin whereas COX-2 activity is preferentially blocked by COX-2 inhibitors called coxibs. COXs are homodimers composed of identical subunits, but we have shown that only one subunit is active at a time during catalysis; moreover, many nsNSAIDS bind to a single subunit of a COX dimer to inhibit the COX activity of the entire dimer. Here, we report the surprising observation that celecoxib and other coxibs bind tightly to a subunit of COX-1. Although celecoxib binding to one monomer of COX-1 does not affect the normal catalytic processing of AA by the second, partner subunit, celecoxib does interfere with the inhibition of COX-1 by aspirin in vitro. X-ray crystallographic results obtained with a celecoxib/COX-1 complex show how celecoxib can bind to one of the two available COX sites of the COX-1 dimer. Finally, we find that administration of celecoxib to dogs interferes with the ability of a low dose of aspirin to inhibit AA-induced ex vivo platelet aggregation. COX-2 inhibitors such as celecoxib are widely used for pain relief. Because coxibs exhibit cardiovascular side effects, they are often prescribed in combination with low-dose aspirin to prevent thrombosis. Our studies predict that the cardioprotective effect of low-dose aspirin on COX-1 may be blunted when taken with coxibs.

  17. Enzyme-catalyzed synthesis of saccharide acrylate monomers from nonedible biomass.

    Science.gov (United States)

    Kloosterman, Wouter M J; Brouwer, Sander G M; Loos, Katja

    2014-08-01

    Various cellulase preparations were found to catalyze the transglycosidation between cotton linters and 2-hydroxyethyl acrylate. The conversion and enzyme activity were found to be optimal in reaction mixtures that contained 5 vol % of the acrylate. The structures of the products were revealed by using TLC and (1) H and (13) C NMR spectroscopy. The enzyme-catalyzed reaction resulted in two products. The minor product originated from transglycosidation to hemicellulose and was found to be 2-(β-xylosyloxy)-ethyl acrylate. The major product was identified as 2-(β-glucosyloxy)-ethyl acrylate and the yield of the product was 5 wt % based on the amount of consumed cellulose. Glycosidation products with oligosaccharide moieties could not be detected in the reaction mixture. This result can be explained by the hydrolytic activities of the used cellulase preparation. Cellulase from Trichoderma reesei was found to possess, in addition to endoglucanase activity, cellobiosidase and β-glucosidase activities. Five other cellulase preparations from different origins were tested as well for catalysis of oligosaccharide acrylate synthesis. For most cellulase preparations the major transglycosidation product appeared to be 2-(β-glucosyloxy)-ethyl acrylate. Nevertheless, the endo-β-(1,4)-glucanase from Trichoderma longibrachiatum was found to catalyze the synthesis of 2-(β-cellobiosyloxy)-ethyl acrylate. Unlike the other cellulase preparations, endo-β-(1,4)-glucanase from T. longibrachiatum showed no detectable β-glucosidase activity and therefore oligosaccharide acrylate monomers were not further hydrolyzed into the monosaccharide acrylate 2-(β-glucosyloxy)-ethyl acrylate. PMID:24866837

  18. Synthesis and characterization of new dimethacrylate monomer and its application in dental resin.

    Science.gov (United States)

    He, Jingwei; Liu, Fang; Vallittu, Pekka K; Lassila, Lippo V J

    2013-01-01

    In this study, a dimethacrylate monomer, 1,4-Bis[2-(4-(2'-hydroxy-3'-methacryloyloxy-propoxy)phenyl)-2propyl]benzene (BMPPB) was synthesized to replace 2,2-bis[4-(2'-hydroxyl-3'-methacryloyloxy-propoxy)phenyl]propane (Bis-GMA) as one component of dental restorative materials. The structure of BMPPB and its intermediate product 1,4-bis[2-(4-(oxiranylmethoxy)phenyl)-2propyl]benzene (BOPPB) were confirmed by Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance spectroscopy ((1)H-NMR), and elemental analysis. In order to evaluate the possibility of replacing Bis-GMA with BMPPB in dental resin, double bond conversion (DC), polymerization shrinkage, contact angle, water sorption (WS) and solubility (SL), and flexural strength (FS) and modulus of BMPPB/tri(ethylene glycol)dimethacrylate (TEGDMA) (50/50 wt) resin system and Bis-GMA/BMPPB/TEGDMA (25/25/50 wt) resin system were studied. Commercially used Bis-GMA/TEGDMA (50/50 wt) dental resin system was used as reference. The results showed that BMPPB-contained copolymer had higher DC, higher WS and SL than the copolymer that only contained Bis-GMA (p0.05). BMPPB/TEGDMA resin system had lower polymerization shrinkage, higher FS and modulus (p0.05) between Bis-GMA/BMPPB/TEGDMA resin system and Bis-GMA/TEGDMA resin system. Before and after water immersion, both FS and modulus of every copolymer did not change significantly (p>0.05). Therefore, BMPPB had potential to be used to replace Bis-GMA as base resin in dental restorative materials, but many studies should be undertaken further.

  19. Quantitative monitoring of dermal and inhalation exposure to 1,6-hexamethylene diisocyanate monomer and oligomers.

    Science.gov (United States)

    Fent, Kenneth W; Jayaraj, Karupiah; Ball, Louise M; Nylander-French, Leena A

    2008-04-01

    Respiratory sensitization and occupational asthma are associated with exposure to 1,6-hexamethylene diisocyanate (HDI) in both monomeric and oligomeric forms. The monomer and polymers of diisocyanates differ significantly in their rates of absorption into tissue and their toxicity, and hence may differ in their contribution to sensitization. We have developed and evaluated a liquid chromatography/mass spectrometry (LC-MS) method capable of quantifying HDI and its oligomers (uretidone, biuret, and isocyanurate) in air, tape-stripped skin, and paint samples collected in the automotive refinishing industry. To generate analytical standards, urea derivatives of HDI, biuret, and isocyanurate were synthesized by reaction with 1-(2-methoxyphenyl)piperazine and purified. The urea derivatives were shown to degrade on average by less than 2% per week at -20 degrees C over a 2 month period in occupational samples. The average recovery of HDI and its oligomers from tape was 100% and the limits of detection were 2 and 8 fmol microl(-1), respectively. Exposure assessments were performed on 13 automotive spray painters to evaluate the LC-MS method and the sampling methods under field conditions. Isocyanurate was the most abundant component measured in paint tasks, with median air and skin concentrations of 2.4 mg m(-3) and 4.6 microg mm(-3), respectively. Log-transformed concentrations of HDI (r = 0.79, p < 0.0001) and of isocyanurate (r = 0.71, p < 0.0001) in the skin of workers were correlated with the log-transformed product of air concentration and painting time. The other polyisocyanates were detected on skin for less than 25% of the paint tasks. This LC-MS method provides a valuable tool to investigate inhalation and dermal exposures to specific polyisocyanates and to explore relative differences in the exposure pathways. PMID:18385871

  20. Generation and characterization of a transgenic pig carrying a DsRed-monomer reporter gene.

    Directory of Open Access Journals (Sweden)

    Chih-Jen Chou

    Full Text Available Pigs are an optimal animal for conducting biomedical research because of their anatomical and physiological resemblance to humans. In contrast to the abundant resources available in the study of mice, few fluorescent protein-harboring porcine models are available for preclinical studies. In this paper, we report the successful generation and characterization of a transgenic DsRed-Monomer porcine model.The transgene comprised a CMV enhancer/chicken-beta actin promoter and DsRed monomeric cDNA. Transgenic pigs were produced by using pronuclear microinjection. PCR and Southern blot analyses were applied for identification of the transgene. Histology, blood examinations and computed tomography were performed to study the health conditions. The pig amniotic fluid progenitor/stem cells were also isolated to examine the existence of red fluorescence and differentiation ability.Transgenic pigs were successfully generated and transmitted to offspring at a germ-line transmission rate of 43.59% (17/39. Ubiquitous expression of red fluorescence was detected in the brain, eye, tongue, heart, lung, liver, pancreas, spleen, stomach, small intestine, large intestine, kidney, testis, and muscle; this was confirmed by histology and western blot analyses. In addition, we confirmed the differentiation potential of amniotic fluid progenitor stem cells isolated from the transgenic pig.This red fluorescent pig can serve as a host for other fluorescent-labeled cells in order to study cell-microenvironment interactions, and can provide optimal red-fluorescent-labeled cells and tissues for research in developmental biology, regenerative medicine, and xenotransplantation.

  1. DEPENDENCE OF THE DISTRIBUTION OF ACTIVE CENTERS ON MONOMER IN SUPPORTED ZIEGLER-NATTA CATALYSTS

    Institute of Scientific and Technical Information of China (English)

    Le-tian Zhang; Zhi-qiang Fan; Zhi-sheng Fu

    2008-01-01

    Distribution of active centers(ACD)of ethylene or 1-hexene homopolymerization and ethylene-1-hexene copolymerization with a MgCl2/TiCl4 type Z-N catalyst were studied by deconvolution of the polymer molecular weight distribution into multiple Flory components.Each Flory component is thought to be formed by a certain type of active center.ACD of ethylene-1-hexene copolymer with very low 1-hexene incorporation was compared with that of ethylene homopolymer to see the effect of introducing a-olefin on ethylene polymerization.On the other hand.ACD of ethylene-1-hexene copolymer with very low ethylene incorporation was compared with that of 1-hexene homopolymer.Adding small amount of 1-hexene in ethylene polymerization caused marked activation of all the Flory components of the polymer.in which the low molecular weight components are activated more than the high molecular weight components.In 1-hexene polymerization system,the activity can also be greatly enhanced by introducing small amount of ethylene.but the different Flory components(or active centers) are activated with similar extent,except a newly emerged active center producing polymer with the lowest molecular weight.The total number of active centers is markedly increased by adding small amount of ethylene in 1-hexene polymerization,but the average catalysis efficiency of the active centers decreased.The broad composition distribution of the ethylene-1-hexene copolymer Can be well understood from the ACD of catalyst and is dependence on the monomer.

  2. Phase separation of monomer in liquid crystal mixtures and surface morphology in polymer-stabilized vertical alignment liquid crystal displays

    Energy Technology Data Exchange (ETDEWEB)

    Lyu, Jae Jin; Lee, Jun Hyup; Kim, Kyeong Hyeon [Development Center, LCD Business, SAMSUNG Electronics Co. LTD., Tangjeong-Myeon, Asan, Chungnam 336-741 (Korea, Republic of); Kikuchi, Hirotsuku; Higuchi, Hiroki [Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-Koen, Kasuga 816-8580 (Japan); Kim, Dae Hyun; Lee, Seung Hee, E-mail: jsquare.lyu@samsung.com, E-mail: lsh1@chonbuk.ac.kr [Department of BIN Fusion Technology and Department of Polymer-Nano Science and Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of)

    2011-08-17

    The polymer-stabilized vertically aligned (PS-VA) liquid crystal display (LCD) driving mode has high potential for manufacturing low power consuming displays due to the higher transmittance and fast response as compared with the existing patterned vertically aligned and multi-domain vertically aligned modes. In this paper we have investigated the reaction mechanisms of monomer-liquid crystal blends to form a surface pre-tilt angle of liquid crystal in vertical alignment LCD associated with a fishbone electrode structure. The observed sizes of polymer bumps formed on the substrates were found to be dependent on the exposed UV wavelength and were almost equal in both top and bottom substrates. When a large UV wavelength was used, the phase separation mechanism of monomer in PS-VA mode was found nearly isotropic rather than anisotropic in contrast to the previous studies.

  3. Control of particle size by feed composition in the nanolatexes produced via monomer-starved semicontinuous emulsion copolymerization.

    Science.gov (United States)

    Sajjadi, Shahriar

    2015-05-01

    Conventional batch and semicontinuous emulsion copolymerizations often produce large particles whose size cannot be easily correlated with the comonomer feed compositions, and are to some degree susceptible to composition drift. In contrast, we found that copolymer nanolatexes made via semicontinuous monomer-starved emulsion copolymerizations are featured with an average nanoparticle size being controlled by the feed composition, a high conversion achieved, and a high degree of particle composition uniformity. This was achieved because the rate of particle growth, during nucleation, was controlled by the rate of comonomer addition, and the copolymer composition, surfactant parking area on the particles, and nucleation efficiency determined by the comonomer feed composition. Two model systems, methyl methacrylate/styrene and vinyl acetate/butyl acrylate, with significant differences in water solubility were studied. Monomers were added to the aqueous solution of sodium dodecylsulfate and potassium persulfate at a low rate to achieve high instantaneous conversions. PMID:25617612

  4. Effect of the hardener to epoxy monomer ratio on the water absorption behavior of the DGEBA/TETA epoxy system

    Directory of Open Access Journals (Sweden)

    Ayrton Alef Castanheira Pereira

    2016-02-01

    Full Text Available Abstract The water absorption behavior of the DGEBA/TETA epoxy system was evaluated as a function of the epoxy monomer to amine hardener ratio. Weight gain versus immersion time curves were obtained and the experimental points were fitted using Fickian and Non-Fickian diffusion models. The results obtained showed that for all epoxy monomer to hardener ratios analyzed water diffusion followed non-Fickian behavior. It was possible to correlate the water absorption behavior to the macromolecular structure developed when the epoxy/ hardener ratio was varied. All epoxy/hardener ratios present a two-phase macromolecular structure, composed of regions with high crosslink density and regions with lower crosslinking. Epoxy rich systems have a more open macromolecular structure with a lower fraction of the dense phase than the amine rich systems, which present a more compact two-phase structure.

  5. Comparison of calculated and experimentally resolved rate constants for excitation energy transfer in C-phycocyanin. 1. Monomers

    Energy Technology Data Exchange (ETDEWEB)

    Debreczeny, M.P.; Sauer, K. [Lawrence Berkeley Lab., CA (United States); Zhou, J.; Bryant, D.A. [Pennsylvania State Univ., University Park, PA (United States)

    1995-05-18

    Rate constants for excitation energy transfer in light-harvesting protein, C-phycocyanin (PC), in the monomeric aggregation state, isolated from the cyanobacterium cynechococcus sp. PCC 7002, are calculated, using Foerster theory and compared with the results of time-resolved fluorescence measurements. The assignments of the energy-transfer rate constants in PC monomers are confirmed here by time-resolved fluorescence anisotropy measurements of the PC monomers isolated from both the wild-type and a mutant strain (cpcB/C155S) whose PC is missing the {beta}{sub 155} chromophore. It is concluded that the Foerster model of resonant energy transfer in the weak coupling limit successfully describes the dominant energy-transfer processes in this protein in the monomeric state. 31 refs., 3 figs., 4 tabs.

  6. Catalytical oxidation of styrene by molecularly imprinted polymer with phenylacetic acid as template and hemin as co-monomer

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This letter used the molecular imprinting technology to build up the microenvironment around co-monomer hemin to mimic the cytochrome P450 catalyzing the epoxidation of styrene. The results showed that the conversion rates of products were obviously enhanced by molecularly imprinted polymers, compared to free hemin solution, using three kinds of oxidants. The used axial ligand in polymers synthesis also improved the total conversion rates.

  7. Alport familial nephritis. Absence of 28 kilodalton non-collagenous monomers of type IV collagen in glomerular basement membrane.

    OpenAIRE

    Kleppel, M M; Kashtan, C. E.; Butkowski, R J; Fish, A. J.; Michael, A. F.

    1987-01-01

    Alport-type familial nephritis (FN), a genetic disorder, results in progressive renal insufficiency and sensorineural hearing loss. Immunochemical and biochemical analyses of the non-collagenous (NC1) domain of type IV collagen isolated from the glomerular basement membranes (GBM) of three males with this disease demonstrate absence of the normally occurring 28-kilodalton (kD) NC1 monomers, but persistence of the 26- and 24-kD monomeric subunits derived from alpha 1 and 2 (both type IV) colla...

  8. Monomer-dimer model explains the results of radiation inactivation: binding characteristics of insulin receptor purified from human placenta

    International Nuclear Information System (INIS)

    The technique of radiation inactivation has been used on highly purified human placental insulin receptor in order to determine the functional molecular size responsible for the insulin binding and to evaluate the affinity regulator hypothesis, which has been proposed to explain the increase in specific insulin binding to rat liver membranes observed at low radiation does. Three different types of inactivation curves were observed: (1) biphasic with an enhanced binding activity after exposure to low radiation doses, (2) nonlinear with no change in binding activity after exposure to low radiation doses, and (3) linear with a loss in the binding activity with increasing radiation exposures. A monomer-dimer model was the simplest model that best described the three types of radiation inactivation curves observed. The model predicts that an increase in insulin binding activity would result after exposure to low radiation doses when the initial dimer/monomer ratio is equal to or greater than 1 and a monomer is more active than a dimer. The monomer size of the binding activity was estimated to be 227,000 daltons by this model. To substantiate this model, the purified receptor was fractionated by Sepharose CL-6B chromatography. The insulin binding profile of this column indicated two peaks. These studies suggest that the affinity regulator does not exist as a separate structural protein but is due to the dimeric form of the receptor. The dimeric form (α2β2) possesses a much lower specific activity for insulin binding than does the monomeric αβ form (under the standard conditions), but the dimeric structure is necessary to observe the negative cooperative binding isotherm

  9. Degree of conversion and leached monomers of urethane dimethacrylate-hydroxypropyl methacrylate-based dental resin systems.

    Science.gov (United States)

    Zhang, Meng; Puska, Mervi A; Botelho, Michael G; Säilynoja, Eija S; Matinlinna, Jukka P

    2016-01-01

    The degree of conversion (DC) and monomer leaching of three experimental urethane dimethacrylate (UEDMA)-hydroxypropyl methacrylate (HPMA)-based resin systems were studied. Three experimental resins (E1: 70.6 wt% UEDMA + 27.4 wt% HPMA, E2: 80.6 wt% UEDMA + 17.4 wt% HPMA, E3: 90.6 wt% UEDMA + 7.4 wt% HPMA) and one control resin [C: 70.6 wt% bis-phenol A glycidyl methacrylate (bis-GMA) + 27.4 wt% methyl methacrylate (MMA)] were prepared. For the DC test, cylindrical specimens [1.5 mm (h) × 6 mm (d)] were scanned with an ATR-FTIR instrument before and after light-curing (n = 5). For the monomer leaching test, block-shaped specimens [5.67 mm (l) × 2.00 mm (w) × 2.00 mm (h)] were light-cured (n = 6), stored in a 75% ethanol:water solution for 3 days, and then analyzed with HPLC. The UEDMA-HPMA-based experimental groups showed higher DC (62-78%) than the bis-GMA-MMA-based control group (58-66%), and the DC decreased as the UEDMA content increased (P < 0.05). Amongst the four groups, E3 exhibited the lowest leaching of both mono methacrylate (0.1% HPMA) and dimethacrylate (<0.043% UEDMA) monomers after 30 or 40 s of curing. The UEDMA-HPMA-based resins, therefore, exhibited higher DC and less monomer leaching compared to the bis-GMA-MMA-based resin. (J Oral Sci 58, 15-22, 2016).

  10. Optoelectronic and Photovoltaic Performances of Pyridine Based Monomer and Polymer Capped ZnO Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Singh, Satbir; Raj, Tilak; Singh, Amarpal; Kaur, Navneet

    2016-06-01

    The present research work describes the comparative analysis and performance characteristics of 4-pyridine based monomer and polymer capped ZnO dye-sensitized solar cells. The N, N-dimethyl-N4-((pyridine-4yl)methylene) propaneamine (4,monomer) and polyamine-4-pyridyl Schiff base (5, polymer) dyes were synthesized through one step condensation reaction between 4-pyridinecarboxaldehyde 1 and N, N-dimethylpropylamine 2/polyamine 3. Products obtained N, N-dimethyl-N4-((pyridine-4yl)methylene)propaneamine (4) and polyamine-4-pyridyl Schiff base (5) were purified and characterized using 1H, 13C NMR, mass, IR and CHN spectroscopy. Both the dyes 4 and 5 were further coated over ZnO nanoparticles and characterized using SEM, DLS and XRD analysis. Absorption profile and emission profile was monitored using fluorescence and UV-Vis absorption spectroscopy. A thick layer of these inbuilt dye linked ZnO nanoparticles of dyes (4) and (5) was pasted on one of the conductive side of ITO glass followed with a liquid electrolyte and counter electrode of the same conductive glass. Polyamine-4-pyridyl Schiff base polymer (5) decorated dye sensitized solar cell has shown better exciting photovoltaic properties in the form of short circuit current density (J(sc) = 6.3 mA/cm2), open circuit photo voltage (V(oc) = 0.7 V), fill factor (FF = 0.736) than monomer decorated dye sensitized solar cell. Polymer dye (5) based ZnO solar cell has shown a maximum solar power to electrical conversion efficiency of 3.25%, which is enhanced by 2.16% in case of monomer dye based ZnO solar cell under AM 1.5 sun illuminations.

  11. Optoelectronic and Photovoltaic Performances of Pyridine Based Monomer and Polymer Capped ZnO Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Singh, Satbir; Raj, Tilak; Singh, Amarpal; Kaur, Navneet

    2016-06-01

    The present research work describes the comparative analysis and performance characteristics of 4-pyridine based monomer and polymer capped ZnO dye-sensitized solar cells. The N, N-dimethyl-N4-((pyridine-4yl)methylene) propaneamine (4,monomer) and polyamine-4-pyridyl Schiff base (5, polymer) dyes were synthesized through one step condensation reaction between 4-pyridinecarboxaldehyde 1 and N, N-dimethylpropylamine 2/polyamine 3. Products obtained N, N-dimethyl-N4-((pyridine-4yl)methylene)propaneamine (4) and polyamine-4-pyridyl Schiff base (5) were purified and characterized using 1H, 13C NMR, mass, IR and CHN spectroscopy. Both the dyes 4 and 5 were further coated over ZnO nanoparticles and characterized using SEM, DLS and XRD analysis. Absorption profile and emission profile was monitored using fluorescence and UV-Vis absorption spectroscopy. A thick layer of these inbuilt dye linked ZnO nanoparticles of dyes (4) and (5) was pasted on one of the conductive side of ITO glass followed with a liquid electrolyte and counter electrode of the same conductive glass. Polyamine-4-pyridyl Schiff base polymer (5) decorated dye sensitized solar cell has shown better exciting photovoltaic properties in the form of short circuit current density (J(sc) = 6.3 mA/cm2), open circuit photo voltage (V(oc) = 0.7 V), fill factor (FF = 0.736) than monomer decorated dye sensitized solar cell. Polymer dye (5) based ZnO solar cell has shown a maximum solar power to electrical conversion efficiency of 3.25%, which is enhanced by 2.16% in case of monomer dye based ZnO solar cell under AM 1.5 sun illuminations. PMID:27427659

  12. 阳离子醚化改性聚乙烯醇干强剂的合成及应用%Preparation and Application of Styrene-acrylic Emulsion Modified by Cationic-etherified PVA as a Dry Strength Additive

    Institute of Scientific and Technical Information of China (English)

    曹辉波; 肖舒; 何静

    2012-01-01

    With poly (vinyl alcohol) (PVA) , styrene (St) , ethyl acrylate (BA) , and acrylamide (AM)as main monomers, hydroxy propyl methacrylate ( HPMA) as functional monomer, methacroylcholine chloride ( DMC) as cationic-functional monomer, and glycidyl-trimethyl-ammonium chloride ( GTMAC) as cationic etherifying agent, the dry strength additive was prepared by semi-continuous emulsifier-free emulsion polymerization technique. The morphology of the emulsion particles and the treated paper were characterized by transmission electron microscopy and scanning electron microscopy. The result indicated that the Zeta potential of the emulsion has maximum and the dispersion system would be more stable when the dosage of DMC was 1. 5% on the whole monomers. When the amount of GTMAC was 1. 5% , the increase of dry strength was 24. 7% and folding endurance was 36 times. When the amount of HPMA was 1. 5% ~ 2. 0% on the whole monomers , the paper possessed higher dry tensile strength and folding endurance.%以聚乙烯醇(PVA)、苯乙烯(St)、丙烯酸丁酯(BA)、丙烯酰胺(AM)为基础单体,甲基丙烯酸羟丙酯(HPMA)为功能单体,甲基丙烯酰氧乙基三甲基氯化铵(DMC)为阳离子功能单体,2,3-环氧丙基三甲基氯化铵(GTMAC)为阳离子醚化剂,采用无皂乳液聚合法合成了阳离子醚化改性聚乙烯醇干强剂乳液;通过透射电镜(TEM)和扫描电镜(SEM)分别对干强剂乳液颗粒形态和纸张纤维形态进行表征和检测.结果表明,当HPMA用量为1.5%(对单体总质量而言,下同)时,干强剂乳液Zeta电位最大,体系较稳定;当GTMAC用量为1.5%时,纸张抗张强度的增幅为24.7%,耐折度的增幅为157%;当HPMA用量为1.5%~2.0%时,纸张的抗张强度和耐折度均较高.

  13. Fragment distribution of thermal decomposition for lignin monomer by QMD calculations using the excited and charged model molecules

    Energy Technology Data Exchange (ETDEWEB)

    Endo, Kazunaka [Department of Chemistry (Faculty of Science), Graduate School of Natural Science and Technology, Kanazawa University, Kakumamachi, Kanazawa 920-1192 (Japan)], E-mail: endo@wriron1.s.kanazawa-u.ac.jp; Matsumoto, Daisuke; Kato, Kenichi; Takagi, Yusuke; Ida, Tomonori; Mizuno, Motohiro [Department of Chemistry (Faculty of Science), Graduate School of Natural Science and Technology, Kanazawa University, Kakumamachi, Kanazawa 920-1192 (Japan); Saito, Kaori; Fukushima, Kazuhiko [Graduate School of Bioagricultural Sciences and Technical Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Kato, Nobuhiko [Applied Physics, Seikei University, Musashino-city, Tokyo 180-8633 (Japan)

    2008-12-15

    Simulations with a quantum molecular dynamics (QMD) method (MD with MO) were demonstrated on the thermal decomposition of lignin monomer at the ground state including excited and positive charged states. Geometry and energy optimized results of the lignin monomer at the singlet and triplet states in single excitation, and at (+2) positive charged state by semi-empirical AM1 MO calculations were used as the initial MD step of QMD calculations. In the QMD calculations, we controlled the total energy of the system using Nose-Hoover thermostats in the total energy range of 0.69-0.95 eV, and the sampling position data with a time step of 0.5 fs were carried out up to 5000 steps at 50 different initial conditions. The calculated neutral, positive and negative charged fragment distributions of the monomer model with 0.82 eV energy control were obtained as 90.6, 3.5, and 5.9% to the total fragments, respectively. The ratios seem to correspond well with to the values observed experimentally in SIMS.

  14. Molecular and quantum mechanical studies on the monomer recognition of a highly-regular β-helical antifreeze protein

    Institute of Scientific and Technical Information of China (English)

    YANG; Zuoyin; JIA; Zongchao; LIU; Ruozhuang; CHEN; Guangj

    2004-01-01

    The possible interaction models for an antifreeze protein from Tenebrio molitar (TmAFP) have been systematically studied using the methods of molecular mechanics, molecular dynamics and quantum chemistry. It is hoped that these approaches would provide insights into the nature of interaction between protein monomers through sampling a number of interaction possibilities and evaluating their interaction energies between two monomers in the course of recognition. The results derived from the molecular mechanics indicate that monomer's β-sheets would be involved in interaction area and the side chains on two β-faces can match each other at the two-dimensional level. The results from molecular mechanics and ONIOM methods show that the strongest interaction energy could be gained through the formation of H-bonds when the two β-sheets are involved in the interaction model. Furthermore, the calculation of DFT and analysis of van der Waals bond charge density confirm further that recognition between the two TCTs mainly depends on inter-molecular hydroxyls. Therefore, our results demonstrate that during the course of interaction the most favorable association of TmAFPs is via their β-sheets.

  15. High-flexibility combinatorial peptide synthesis with laser-based transfer of monomers in solid matrix material.

    Science.gov (United States)

    Loeffler, Felix F; Foertsch, Tobias C; Popov, Roman; Mattes, Daniela S; Schlageter, Martin; Sedlmayr, Martyna; Ridder, Barbara; Dang, Florian-Xuan; von Bojničić-Kninski, Clemens; Weber, Laura K; Fischer, Andrea; Greifenstein, Juliane; Bykovskaya, Valentina; Buliev, Ivan; Bischoff, F Ralf; Hahn, Lothar; Meier, Michael A R; Bräse, Stefan; Powell, Annie K; Balaban, Teodor Silviu; Breitling, Frank; Nesterov-Mueller, Alexander

    2016-06-14

    Laser writing is used to structure surfaces in many different ways in materials and life sciences. However, combinatorial patterning applications are still limited. Here we present a method for cost-efficient combinatorial synthesis of very-high-density peptide arrays with natural and synthetic monomers. A laser automatically transfers nanometre-thin solid material spots from different donor slides to an acceptor. Each donor bears a thin polymer film, embedding one type of monomer. Coupling occurs in a separate heating step, where the matrix becomes viscous and building blocks diffuse and couple to the acceptor surface. Furthermore, we can consecutively deposit two material layers of activation reagents and amino acids. Subsequent heat-induced mixing facilitates an in situ activation and coupling of the monomers. This allows us to incorporate building blocks with click chemistry compatibility or a large variety of commercially available non-activated, for example, posttranslationally modified building blocks into the array's peptides with >17,000 spots per cm(2).

  16. Synthesis and characterization of a new trimethacrylate monomer with low polymerization shrinkage and its application in dental restoration materials.

    Science.gov (United States)

    He, Jingwei; Luo, Yuanfang; Liu, Fang; Jia, Demin

    2010-09-01

    In this study, a new trimethacrylate monomer alpha,alpha,alpha'-tri[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)phenyl]-1-ethyl-4-isopropylbenzene (alpha,alpha,alpha'-THMPEIB) with a molecular weight of 850 and a large molecular volume was designed and synthesized. The structure of monomer alpha,alpha,alpha'-THMPEIB was confirmed by FT-IR, (1)H NMR, and elemental analysis. Degree of double-bond conversion, volume shrinkage, water sorption and solubility, diffusion coefficient value, and flexure strength of alpha,alpha,alpha'-THMPEIB/tri(ethylene glycol) dimethacrylate- (TEGDMA) based resin were measured. 2,2-Bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)-phenyl]-propane (bis-GMA)/TEGDMA monomer mixture was used as reference. The result showed that the alpha,alpha,alpha'-THMPEIB/TEGDMA-based resin had the lower double-bond conversion, polymerization shrinkage, and water solubility than bis-GMA/TEGDMA-based resin. Water sorption and diffusion coefficient value of alpha,alpha,alpha'-THMPEIB/TEGDMA-based resin were nearly the same as those of bis-GMA/TEGDMA-based resin. Flexural strength of alpha,alpha,alpha'-THMPEIB/TEGDMA-based resin was higher than that of bis-GMA/ TEGDMA-based resin.

  17. Comparison of sampling methods for monomer and polyisocyanates of 1,6-hexamethylene diisocyanate during spray finishing operations.

    Science.gov (United States)

    England, E; Key-Schwartz, R; Lesage, J; Carlton, G; Streicher, R; Song, R

    2000-06-01

    A comparison study of isocyanate sampling methods for 1,6-hexamethylene diisocyanate (HDI) monomer and HDI-based polyisocyanates was conducted in spray painting environments. This study compared the performance of the Iso-chek sampler against existing and proposed National Institute of Occupational Safety and Health (NIOSH) and Occupational Safety and Health Administration (OSHA) monitoring methods for HDI-based isocyanates. Six methods for monitoring HDI monomer and polyisocyanate levels were compared. Fifty-eight sampling sets were collected during spray painting of aircraft and aircraft parts at four U.S. Air Force bases. Impinger and cassette samplers were mounted side-by-side on a mannequin located in paint overspray areas. For HDI monomer sampling results, there were no significant differences between NIOSH 5521, NIOSH 5522, OSHA 42, MAP (the proposed NIOSH method), and the Iso-Chek. For HDI-based polyisocyanates, NIOSH 5522, NIOSH 5521, Iso-Chek, and the Total Aerosol Mass Method (TAMM) were significantly different from one another. There was no significant difference between MAP and the NIOSH 5522 polyisocyanate sampling results. This study suggests the Iso-Chek and MAP sampling methods compare favorably with established methods for monitoring in HDI spray painting environments and the Total Aerosol Mass Method provides a reasonable upper boundary for estimating HDI polyisocyanate concentrations. The results also reemphasize aerosol sampling physics and sampler geometries must be carefully considered and appropriate samplers used when measuring exposures in spray paint environments where particulates are of the inhalable size. PMID:10853287

  18. The diffusion of hydrogen monomers on hole-doped graphitic lattices: over-barrier transition and quantum tunneling.

    Science.gov (United States)

    Huang, Liang Feng; Ni, Mei Yan; Zeng, Zhi

    2011-11-01

    The diffusion of hydrogen and deuterium monomers on hole-doped graphene (a planar graphitic lattice), the outside wall and the inside wall of hole-doped (6, 0) single-walled carbon nanotubes (a curved graphitic lattice) was investigated using density functional theory and density functional perturbation theory. The jump frequencies for the over-barrier transition and phonon-assisted quantum tunneling were calculated by transition state theory and small-polaron theory, respectively. The effects of the local curvature of the surface and the hole doping on the thermodynamic and kinetic properties of a hydrogen monomer on these graphitic lattices are discussed. Our results demonstrate that it is sufficient to judge the diffusional mobility of a hydrogen monomer on graphitic lattices from just the over-barrier transition, no matter how much it is curved and hole doped, while the quantum tunneling can be safely neglected because it is significantly suppressed by the covalent bonding of hydrogen with the graphitic lattice. PMID:21971019

  19. High-flexibility combinatorial peptide synthesis with laser-based transfer of monomers in solid matrix material

    Science.gov (United States)

    Loeffler, Felix F.; Foertsch, Tobias C.; Popov, Roman; Mattes, Daniela S.; Schlageter, Martin; Sedlmayr, Martyna; Ridder, Barbara; Dang, Florian-Xuan; von Bojničić-Kninski, Clemens; Weber, Laura K.; Fischer, Andrea; Greifenstein, Juliane; Bykovskaya, Valentina; Buliev, Ivan; Bischoff, F. Ralf; Hahn, Lothar; Meier, Michael A. R.; Bräse, Stefan; Powell, Annie K.; Balaban, Teodor Silviu; Breitling, Frank; Nesterov-Mueller, Alexander

    2016-06-01

    Laser writing is used to structure surfaces in many different ways in materials and life sciences. However, combinatorial patterning applications are still limited. Here we present a method for cost-efficient combinatorial synthesis of very-high-density peptide arrays with natural and synthetic monomers. A laser automatically transfers nanometre-thin solid material spots from different donor slides to an acceptor. Each donor bears a thin polymer film, embedding one type of monomer. Coupling occurs in a separate heating step, where the matrix becomes viscous and building blocks diffuse and couple to the acceptor surface. Furthermore, we can consecutively deposit two material layers of activation reagents and amino acids. Subsequent heat-induced mixing facilitates an in situ activation and coupling of the monomers. This allows us to incorporate building blocks with click chemistry compatibility or a large variety of commercially available non-activated, for example, posttranslationally modified building blocks into the array's peptides with >17,000 spots per cm2.

  20. Reactivity of free radical intermediates that form spontaneously during molecular chlorine action on acetylene and vinyl monomers at low temperatures

    International Nuclear Information System (INIS)

    In this study ESR, UV, VIS and IR spectroscopy, chromatography, calorimetry, and elemental analysis were employed to show the spontaneous formation of free radicals under low-temperature action of molecular chlorine on acetylene monomer p-diethynylbenzene, and vinyl monomer acrylamide. These radicals are able to initiate chain reaction of polymerization of monomers at low temperatures. This reaction results in a completely soluble polymer with a yield of 25 %, while an insoluble cross-linked polymer has been obtained during polymerization of p-diethynylbenzene initiated by other means. For example, under radiolysis by 1000 kGy the soluble fraction of obtained polymer was ∼ 1% while the overall yield was ∼ 10%. p-Diethynylbenzene polymerizes at temperatures close to chlorine melting (170 K). Polymerization of acrylamide takes place in the temperature range of 180-210 K with an yield of polymer ∼ 10%. The low-temperature chlorination of a 20%-solution of acrylamide in glycerol enables a twofold increase of the polymer yield, and a tenfold decrease of the chlorine content in it.

  1. A new approach to the synthesis of monomers and polymers incorporating furan/maleimide Diels-Alder adducts

    Science.gov (United States)

    Banella, Maria Barbara; Gioia, Claudio; Vannini, Micaela; Colonna, Martino; Celli, Annamaria; Gandini, Alessandro

    2016-05-01

    The Diels-Alder reaction between furan and maleimide moieties is a well-known and widely used strategy to build bio-based macromolecular structures with peculiar properties. The furan-maleimide adducts are thermally reversible because they can be broken above about 120°C and recombined at lower temperatures. At the moment only the monomers exhibiting the furan or the maleimide moieties on their extremity are used in order to get linear or cross-linked polymeric structures. The innovative idea described here consists in using a monomer bearing two carboxylic acidic groups on its extremities and a furan-maleimide Diels-Alder adduct within its structure. This monomer can give rise to classical polycondensation reactions leading to polymers. These polymers (which are polyesters in the present case) can be broken at high temperatures in correspondence of the furane-maleimide Diels-Alder adduct leading to segments exhibiting furan or maleimide moieties at their extremities, which at lower temperature recombine leading to random or block copolymers.

  2. Synthesis of biodegradable chiral poly(ester-imide)s derived from valine-, leucine- and tyrosine-containing monomers.

    Science.gov (United States)

    Mallakpour, Shadpour; Asadi, Parvin; Sabzalian, Mohammad R

    2011-11-01

    The present demand for a drastic reduction in environmental pollution is extended to qualitative change in the approach to development of biodegradable polymers. The aim of this article is to focus on the synthesis of biodegradable optically active poly(ester-imide)s (PEI)s, which compose of different amino acids in the main chain as well as in the side chain. These polymers were synthesized by polycondensation of diacid monomers such as 5-(2-phthalimidyl-3-methyl butanoylamino) isophthalic acid (1), 5-(4-methyl-2-phthalimidyl pentanoylamino)isophthalic acid (2) with N,N'-(pyromellitoyl)-bis-L: -tyrosine dimethyl ester (3) as a phenolic diol. The direct polycondensation reaction was carried out in a system of tosyl chloride, pyridine and N,N-dimethylformamide as a condensing agent under conventional heating conditions. The optically active PEIs were obtained in good yield and moderate inherent viscosity. The synthesized polymers were characterized by means of FT-IR, (1)H-NMR, elemental and thermo gravimetric analysis techniques. In addition, in vitro toxicity and soil burial test were employed for assessing the sensitivity of these compounds to microbial degradation. To this purpose, biodegradability behavior of the monomers and polymers were investigated in culture media and soil condition. The results of this study revealed that synthesized monomers and their derived polymers are biologically active and probably microbiologically biodegradable.

  3. Second-order-like cluster-monomer transition within magnetic fluids and its impact upon the magnetic susceptibility.

    Science.gov (United States)

    Zhong, Jing; Xiang, Qing; Massa, Letícia O; Qu, Fanyao; Morais, Paulo C; Liu, Wenzhong

    2012-01-01

    The low-field (below 5 Oe) ac and dc magnetic response of a magnetic fluid [MF] sample in the range of 305 to 360 K and 410 to 455 K was experimentally and theoretically investigated. We found a systematic deviation of Curie's law, which predicts a linear temperature dependence of inverse initial susceptibility in the range of our investigation. This finding, as we hypothesized, is due to the onset of a second-order-like cluster-to-monomer transition with a critical exponent which is equal to 0.50. The susceptibility data were well fitted by a modified Langevin function, in which cluster dissociation into monomers, at the critical temperature [T*], was included. In the ac experiments, we found that T* was reducing from 381.8 to 380.4 K as the frequency of the applied field increases from 123 to 173 Hz. In addition, our ac experiments confirm that only monomers respond for the magnetic behavior of the MF sample above T*. Furthermore, our Monte Carlo simulation and analytical results support the hypothesis of a thermal-assisted dissociation of chain-like structures.PACS: 75.75.-C; 75.30.Kz; 75.30.Cr. PMID:22390618

  4. Immunoglobulin-free light chain monomer-dimer patterns help to distinguish malignant from premalignant monoclonal gammopathies: a pilot study.

    Science.gov (United States)

    Kaplan, Batia; Golderman, Sizilia; Aizenbud, Boris; Esev, Konstantin; Kukuy, Olga; Leiba, Merav; Livneh, Avi; Ben-Zvi, Ilan

    2014-09-01

    Multiple myeloma (MM) and AL amyloidosis (AL) are two malignant forms of monoclonal gammopathies. For the purposes of prognosis and treatment, it is important to distinguish these diseases from the premalignant forms of monoclonal gammopathies, such as monoclonal gammopathy of unknown significance (MGUS) and smoldering myeloma (SMM). Routine serum/urine tests for monoclonal protein are insufficient for differential diagnosis. Thus, invasive procedures, such as tissue aspiration or biopsy, are applied. In this study, we aimed at characterization of serum-free light chain (FLC) monomer-dimer patterns to distinguish the malignant from the premalignant forms of monoclonal gammopathies. A quantitative Western blotting was applied to estimate the FLC monomer and dimer levels in AL, MM, MGUS, and SMM patients, and in control subjects (healthy individuals and patients with AA amyloidosis). AL and MM patients displayed an abnormally increased dimerization of monoclonal FLC, accompanied by higher clonality values of FLC dimers, as compared to that of monomers. These abnormalities of FLC patterns were not observed in patients with MGUS, SMM, AA amyloidosis, and healthy individuals. Analysis of FLC patterns helped to differentiate AL and MM from MGUS and SMM, a goal difficult to achieve using routine serum tests. Also, our technique might serve as a complimentary diagnostic tool in the cases with suspected AL amyloidosis, where the diagnosis of MM is excluded, while the results of amyloid typing by routine immunohistochemical techniques are inconclusive. PMID:24866208

  5. State-of-the-art applications of cyclodextrins as functional monomers in molecular imprinting techniques: a review.

    Science.gov (United States)

    Lay, Sovichea; Ni, Xiaofeng; Yu, Haining; Shen, Shengrong

    2016-06-01

    As a versatile tool in separation science, cyclodextrins and their derivatives, known as emerging functional monomers, have been used extensively in molecular imprinting techniques. The attributes of cyclodextrins and their derivatives are widely known to form host-guest inclusion complex processes between the polymer and template. The exploitation of the imprinting technique could produce a product of molecularly imprinted polymers, which are very robust with long-term stability, reliability, cost-efficiency, and selectivity. Hence, molecularly imprinted polymers have gained popularity in chemical separation and analysis. Molecularly imprinted polymers containing either cyclodextrin or its derivatives demonstrate superior binding effects for a target molecule. As noted in the previous studies, the functional monomers of cyclodextrins and their derivatives have been used in molecular imprinting for selective separation with a wide range of chemical compounds, including steroidals, amino acids, polysaccharides, drugs, plant hormones, proteins, pesticides, and plastic additives. Therefore, the main goal of this review is to illustrate the exotic applications of imprinting techniques employing cyclodextrins and their derivatives as single or binary functional monomers in synthesizing molecularly imprinted polymers in areas of separation science by reviewing some of the latest studies reported in the literature. PMID:27324352

  6. Copolymers of N-cyclohexylacrylamide and n-butyl acrylate: synthesis, characterization, monomer reactivity ratios and mean sequence length

    Directory of Open Access Journals (Sweden)

    2007-06-01

    Full Text Available Copolymerization of N-cyclohexylacrylamide (NCHA and n-butyl acrylate (BA was carried out in dimethylformamide at 55±1°C using azobisisobutyronitrile as a free radical initiator. The copolymers were characterized by 1H-NMR spectroscopy and the copolymer compositions were determined by 1H-NMR analysis. The reactivity ratios of the monomers were determined by both linear and non-linear methods. The reactivity ratios of monomers determined using linear methods like Fineman-Ross (r1 = 0.37 and r2 = 1.77 , Kelen-Tudos (r1 = 0.38 and r2 = 1.77, ext. Kelen-Tudos (r1 = 0.37 and r2 = 1.75 Yezrieler-Brokhina-Roskin (r1 = 0.37 and r2 = 1.77 and non-linear methods like Tidwell-Mortimer (r1 = 0.37 and r2 = 1.76, ProCop (r1 = 0.36 and r2 = 1.82. The Q and e values for NCHA are 0.67 and 0.68 respectively. Mean sequence lengths of copolymers are estimated from r1 and r2 values. It shows that the BA units increases in a linear fashion in the polymer chain as the concentration of BA increases in the monomer feed.

  7. Influence of the angle between two crown ether moieties on supramolecular copolymerization of bis(crown ether)s and bisparaquat homoditopic monomers

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Bis(crown ether) homoditopic monomers containing two bis(p-phenylene)-34-crown-10 moieties with different angles(180° for monomer 3,120°for monomer 4,and 60°for monomer 5) and a complementary bisparaquat homoditopic monomer(7) were designed and synthesized.The three bis(crown ether) monomers could organize into linear supramolecular polymers in concentrated solutions in CHCl3/CH3CN with the bisparaquat monomer 7,as demonstrated by 1 H NMR and viscosity studies. The pseudorotaxanes or supramolecular polymers formed from 3+7 and 4+7 had larger values of Ka,p,n,slope 1,and slope 2 than those of 5+7.This result was attributed to the greater steric hindrance of compound 5 than that of 3 and 4,which resulted in less effective formation of linear supramolecular polymers from 5 with compound 7 than those from compounds 3 and 4 with compound 7,as also demonstrated by UV-vis method.

  8. Preparation of Quaternized Cationic Waterborne Polyurethane and its Fixative Performance on Reactive Dyes%季胺化阳离子水性聚氨酯制备及其对活性染料的固色性能

    Institute of Scientific and Technical Information of China (English)

    张梦月; 刘俊琦; 刘玉峰; 权衡

    2014-01-01

    A set of silicon-modified cationic waterborne polyurethane reactive dyes wet rubbing fastness agent having high activity is prepared by isophorone diisocyanate, 1,4-butanediol, N-butyl diethanolamine as hard monomer, mixed polyether as soft monomer, hydroxyl alkyl polysiloxane as modified monomers. The effects that quaternary amination degree of the reactive polyurethane polymer have on the wet rubbing fastness ascend agent are studied. The results prove that quaternary ammonium salt structure make polyurethane macromolecules show excellent resistance to acid and alkali stability;however, the polyurethane macromolecules of strong cationic strength are not conducive to improve the fixation textile wet rubbing fastness.%以异佛尔酮二异氰酸酯、1,4-丁二醇、N-丁基二乙醇胺为硬单体,混合聚醚为软单体,羟烃基聚硅氧烷为改性单体,制备了一组具有较高化学活性的有机硅改性阳离子水性聚氨酯活性染料湿摩擦牢度提升剂,研究了活性聚氨酯高分子的季铵化程度对湿摩擦牢度提升剂性能的影响。研究结果表明:季铵盐结构使得聚氨酯大分子表现出优异的耐酸、耐碱稳定性;较高阳离子强度的聚氨酯大分子并不利于其固色纺织品湿摩擦牢度的改善。

  9. The effects of paeoniflorin monomer of a Chinese herb on cardiac ion channels

    Institute of Scientific and Technical Information of China (English)

    WANG Rong-rong; LI Ning; ZHANG Yin-hui; RAN Yu-qin; PU Jie-lin

    2011-01-01

    Background Because of the potential proarrhythmic effect of current antiarrhythmic drugs, it is still desirable to find safer antiarrhythmic drugs worldwide. Paeoniflorin is one of the Chinese herb monomers that have different effects on many ion channels. The present study aimed to determine the effects of paeoniflorin on cardiac ion channels.Methods Whole-cell patch-clamp technique was used to record ion channel currents. L-type calcium current (/Ca-L),inward rectifier potassium current (/K1), and transient outward potassium current (/to1) were studied in rat ventricular myocytes and sodium current (/Na), slow delayed rectifier current (/Ks), and HERG current (/Kr) were investigated in transfected human embryonic kidney 293 cells.Results One hundred μmol/L paeoniflorin reduced the peak /ca-L by 40.29% at the test potential of ±10 mV (from (-9.78±0.52) pA/pF to (-5.84±0.89) pA/pF, n=5, P=0.028). The steady-state activation curve was shifted to more positive potential in the presence of the drug. The half activation potentials were (-11.22±0.27) mV vs. (-5.95±0.84) mV (n=5,P=0.007), respectively. However, the steady-state inactivation and the time course of recovery from inactivation were not changed. One hundred μmol/L paeoniflorin completely inhibited the peak /Na and the effect was reversible. Moreover,paeoniflorin inhibited the /K1 by 30.13% at the test potential of -100 mV (from (-25.26±8.21) pA/pF to (-17.65±6.52)pA/pF, n=6, F=0.015) without effects on the reversal potential and the rectification property. By contrast, 100 μmol/L paeoniflorin had no effects on/to1, /Ks or /Kr channels.Conclusions The study demonstrated that paeoniflorin blocked /Ca-L, /Na, and /Kf without affecting /to1, /Ks, or /Kr. The multi-channel block effect may account for its antiarrhythmic effects with less proarrhythmic potential.

  10. A covalent attraction between two molecular cation TTF·~+

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The optimized structure of the tetrathiafulvalence radical-cation dimer(TTF·+-TTF·+) with all-real frequencies is obtained at MP2/6-311G level,which exhibits the attraction between two molecular cation TTF·+.The new attraction interaction is a 20-center-2-electron intermolecular covalent π /π bonding with a telescope shape.The covalent π /π bonding has the bonding energy of about -21 kcal·mol-1 and is concealed by the Coulombic repulsion between two TTF·+ cations.This intermolecular covalent attraction also influences the structure of the TTF·+ subunit,i.e.,its molecular plane is bent by an angle θ=5.6°.This work provides new knowledge on intermolecular interaction.

  11. Cationic lipids delay the transfer of plasmid DNA to lysosomes.

    Science.gov (United States)

    Wattiaux, R; Jadot, M; Laurent, N; Dubois, F; Wattiaux-De Coninck, S

    1996-10-14

    Plasmid 35S DNA, naked or associated with different cationic lipid preparations was injected to rats. Subcellular distribution of radioactivity in the liver one hour after injection, was established by centrifugation methods. Results show that at that time, 35S DNA has reached lysosomes. On the contrary, when 35S DNA was complexed with lipids, radioactivity remains located in organelles whose distribution after differential and isopycnic centrifugation, is clearly distinct from that of arylsulfatase, lysosome marker enzyme. Injection of Triton WR 1339, a specific density perturbant of lysosomes, four days before 35S DNA injection causes a density decrease of radioactivity bearing structures, apparent one hour after naked 35S DNA injection but visible only after more than five hours, when 35S DNA associated with a cationic lipid is injected. These observations show that cationic lipids delay the transfer to lysosomes, of plasmid DNA taken up by the liver.

  12. Cationization of Alpha-Cellulose to Develop New Sustainable Products

    Directory of Open Access Journals (Sweden)

    Ana Moral

    2015-01-01

    Full Text Available Papermaking has been using high quantities of retention agents, mainly cationic substances and organic compounds such as polyamines. The addition of these agents is related to economic and environmental issues, increasing contamination of the effluents. The aim of this work is to develop a cationic polymer for papermaking purposes based on the utilization of alpha-cellulose. The cationization of mercerized alpha-cellulose with 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC is governed by a pseudo-second-order reaction. The initial amorphous fraction of cellulose is reacted with CHPTAC until the equilibrium value of nitrogen substitution is reached. Nitrogen is incorporated as a quaternary ammonium group in the polymer. Also, the kinetic constant increased with decreasing crystallinity index, showing the importance of the previous alkalization stage. The use of modified natural polysaccharides is a sustainable alternative to synthetic, nonbiodegradable polyelectrolytes and thus is desirable with a view to developing new products and new processes.

  13. Theoretical Studies on the Interactions of Cations with Diazine

    Institute of Scientific and Technical Information of China (English)

    CHEN Xing; WU Wen-Peng; ZHANG Jing-Lai; CAO Ze-Xing

    2006-01-01

    Density functional theory and MP2 calculations have been used to determine the geometries, stabilities, binding energies, and dissociative properties of cation-diazine complexes Mn+-C4H4N2 (Mn+ = Li+, B+, Al+, Be2+, Mg2+, Ca2+). The calculated results indicate that most complexes are stable except the π complexes of Ca2+-pyridazine, Ca2+-pyrazine, Al+-pyrimidine and Al+-pyrimidine. The σ complexes are generally much more stable than their π counterparts. Among the π complexes, the cation-pyrazine π complexes have slightly higher stability. The nature of the ion-molecule interactions has been discussed by the natural bond orbital analysis and frontier molecular orbital interactions. In these σ complexes, there is stronger covalent interaction between B+ and diazine. In the selected π complexes, B+ and Be2+ have stronger covalent interaction with diazine, while the other cations mainly have electrostatic interaction with diazine.

  14. Surface hopping investigation of the relaxation dynamics in radical cations

    Energy Technology Data Exchange (ETDEWEB)

    Assmann, Mariana; Matsika, Spiridoula, E-mail: smatsika@temple.edu [Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122 (United States); Weinacht, Thomas [Department of Physics, Stony Brook University, Stony Brook, New York 11794 (United States)

    2016-01-21

    Ionization processes can lead to the formation of radical cations with population in several ionic states. In this study, we examine the dynamics of three radical cations starting from an excited ionic state using trajectory surface hopping dynamics in combination with multiconfigurational electronic structure methods. The efficiency of relaxation to the ground state is examined in an effort to understand better whether fragmentation of cations is likely to occur directly on excited states or after relaxation to the ground state. The results on cyclohexadiene, hexatriene, and uracil indicate that relaxation to the ground ionic state is very fast in these systems, while fragmentation before relaxation is rare. Ultrafast relaxation is facilitated by the close proximity of electronic states and the presence of two- and three-state conical intersections. Examining the properties of the systems in the Franck-Condon region can give some insight into the subsequent dynamics.

  15. Strong and specific effects of cations on lysozyme chloride solubility.

    Science.gov (United States)

    Bénas, Philippe; Legrand, Laurent; Riès-Kautt, Madeleine

    2002-10-01

    The influence of salt nature and concentration on tetragonal lysozyme chloride crystal solubility is presented for a set of mono-, di- and trivalent cations (Cs(+), Rb(+), Mn(2+), Co(2+) and Yb(3+)). The results show that cations have as strong an effect on protein solubility as anions and that they present their own particular effects as co-ions. Indeed, after decreasing at low ionic strength, lysozyme solubility increases with high concentration of polyvalent cations, probably due to co-ion binding and therefore the concomitant increase of the net charge of the protein-salt complex. These new results are discussed in order to progress in the understanding of the crystallisation process at the atomic level. PMID:12351866

  16. A covalent attraction between two molecular cation TTF·~+

    Institute of Scientific and Technical Information of China (English)

    WANG FangFang; WANG Yi; WANG BingQiang; WANG YinFeng; MA Fang; Li ZhiRu

    2009-01-01

    The optimized structure of the tetrathiafulvalence radical-cation dimer (TTF·~+-TTF·~+) with all-real frequencies is obtained at MP2/6-311G level,which exhibits the attraction between two molecular cation TTF·~+.The new attraction interaction is a 20-center-2-electron intermolecular covalent π/π bonding with a telescope shape.The covalent π/π bonding has the bonding energy of about-21 kcal·mol~(-1) and is concealed by the Coulombic repulsion between two TTF·~+ cations.This intermolecular covalent attraction also influences the structure of the TTF·~+ subunit,I.e.,its molecular plane is bent by an angle θ=5.6°.This work provides new knowledge on intermolecular interaction.

  17. Low-Temperature Cationic Rearrangement in a Bulk Metal Oxide.

    Science.gov (United States)

    Li, Man-Rong; Retuerto, Maria; Stephens, Peter W; Croft, Mark; Sheptyakov, Denis; Pomjakushin, Vladimir; Deng, Zheng; Akamatsu, Hirofumi; Gopalan, Venkatraman; Sánchez-Benítez, Javier; Saouma, Felix O; Jang, Joon I; Walker, David; Greenblatt, Martha

    2016-08-16

    Cationic rearrangement is a compelling strategy for producing desirable physical properties by atomic-scale manipulation. However, activating ionic diffusion typically requires high temperature, and in some cases also high pressure in bulk oxide materials. Herein, we present the cationic rearrangement in bulk Mn2 FeMoO6 at unparalleled low temperatures of 150-300 (o) C. The irreversible ionic motion at ambient pressure, as evidenced by real-time powder synchrotron X-ray and neutron diffraction, and second harmonic generation, leads to a transition from a Ni3 TeO6 -type to an ordered-ilmenite structure, and dramatic changes of the electrical and magnetic properties. This work demonstrates a remarkable cationic rearrangement, with corresponding large changes in the physical properties in a bulk oxide at unprecedented low temperatures. PMID:27203790

  18. Modeling cation exchange using EQ3/6

    International Nuclear Information System (INIS)

    Geochemical modeling codes must be able to predict solid-solution and ion-exchange behavior of zeolites and smectites in order to design and assess strategies for containing and cleaning up toxic and/or radioactive wastes. Cation-exchange and solid-solution models have been implemented in the EQ3/6 geochemical modeling package and used to predict the composition of clinoptilolite under a variety of conditions. Published free energies of cation exchange on clinoptilolite at 25 degrees C were combined with the calorimetric data for clinoptilolite to derive free energies of formation of the component end members of a solid solution in which mixing is allowed only on the exchange site. The solid-solution model and component end-member data were incorporated into EQ3/6 and its data base. An option to treat cation exchange independently of the solid-solution model was also developed and implemented in EQ3/6. This option allows the user to model mixed-phase exchangers, multisite exchangers, and systems in which the exchanger is not in overall equilibrium with the solution. Two open-quotes idealclose quotes cation-exchange conventions [Vanselow (mole fraction) and Gapon (equivalent fraction)] are currently implemented in the code. A description of the cation-exchange models and their implementation into EQ3/6 is presented, and the relationship between the exchange formalisms and the solid-solution models is discussed. The advantages and limitations of the models and currently available thermodynamic data are addressed by comparing cation-exchange compositions of clinoptilolites with (1) published binary exchange data; (2) compositions of coexisting clinoptilolites and formation waters at Yucca Mountain; and (3) experimental sorption isotherms of Cs and Sr on zeolitized tuff

  19. THE APPLICATION OF CATIONIC POLYACRYLAMIDE AS DRAINAGE AND RETENTION AIDS

    Institute of Scientific and Technical Information of China (English)

    Jin Wang; Kefu Chen; Fushan Chen; Chuanshan Zhao; Rendang Yang

    2004-01-01

    Cationic polyacrylamide (CPAM) which was prepared through complex initiation system in laboratory and cationic polyacrylamide (Ciba) were used as retention and drainage aids for bleached wheat straw pulp. The influences of (polydiallyldimethlammonium chloride) PDADMAC and PDADMAC/CPAM on Zeta potential and drainability of pulp was investigated. The dual drainage and retention systems such as CPAM/modified bentonite, CPAM/colloidal SiO2,as well as their comparison between the two systems were discussed, and the optimal dosages of additives were determined. The results showed that: the complex systems can further enhance filler retention,drainability of pulp and strength properties of paper.

  20. Combining material characterization with single and multi-oxyanion adsorption for mechanistic study of chromate removal by cationic hydrogel

    Institute of Scientific and Technical Information of China (English)

    Irene M. C. Lo; Ke Yin; Samuel C. N. Tang

    2011-01-01

    Cationic hydrogel with magnetic property was synthesized via radical polymerization and its removal capacity of chromate from contaminated water was found to be 200 mg/g.Using Fourier transform infrared spectroscopy (FT-IR) study, the mechanism of chromate removal by hydrogel was found to be non-specific adsorption, mainly due to ion exchange, as evidenced by the positively charged functional group, trimethyl ammonium -N+(CH3)3.in the monomer.Verifications were accordingly determined by testing different oxyanion adsorption onto the hydrogel.The results of the chromate adsorption experiments illustrated that the amount of chromate adsorbed was nearly equal to that of the chloride released from the hydrogel, which is part of the evidence for ion exchange.Single and multi-oxyanion adsorption experiments were also performed, and it was demonstrated that ion removal was species independent, but charge dependent, another characteristic of the ion exchange process.It was found that the same Langmuir model can be applied to best fit the findings of single and multi-oxyanion adsorption, which further indicates the mechanism of chromate removal is attributed to ion exchange.In view of the above, the background anions compete for adsorption sites with chromate,evidenced by inhibitive chromate removal in the presence of background electrolytes in the batch studies, further echoing the ion exchange mechanism.