Science.gov

Sample records for reactive functionality synthesis

  1. Construction of functional group reactivity database under various reaction conditions automatically extracted from reaction database in a synthesis design system.

    PubMed

    Tanaka, Akio; Okamoto, Hideho; Bersohn, Malcolm

    2010-03-22

    To be able to estimate the reactivity of functional groups under certain reaction conditions, we have stored three types of data: (1) data of change or destruction of the functional groups by the conditions of the reaction conditions; (2) data showing no influence of the reaction conditions on the functional groups; and (3) data showing the relative reactivity of two functional groups in the presence of certain reaction conditions. These three types of data, considered together, form entities that are referenced as "interaction data". These interaction data are used in a synthesis design system called SYNSUP. A new module in our system has been constructed that automatically generates interaction data from the reaction databases. From 15 265 reactions in the database, our program selected 2763 useful reactions with yields of > or =90% and one functional group change. From these useful reactions, data regarding 465 interferences, 815 cases of inert functional groups (under the reaction conditions), and 62 relative rate data could be extracted. In addition, with the use of multiple relative rate datasets, the reactivity of more than two functional groups could be deduced.

  2. Synthesis, Characterization, and Reactivity of Functionalized Trinuclear Iron–Sulfur Clusters – A New Class of Bioinspired Hydrogenase Models

    PubMed Central

    Kaiser, Manuel; Knör, Günther

    2015-01-01

    The air- and moisture-stable iron–sulfur carbonyl clusters Fe3S2(CO)7(dppm) (1) and Fe3S2(CO)7(dppf) (2) carrying the bisphosphine ligands bis(diphenylphosphanyl)methane (dppm) and 1,1′-bis(diphenylphosphanyl)ferrocene (dppf) were prepared and fully characterized. Two alternative synthetic routes based on different thionation reactions of triiron dodecacarbonyl were tested. The molecular structures of the methylene-bridged compound 1 and the ferrocene-functionalized derivative 2 were determined by single-crystal X-ray diffraction. The catalytic reactivity of the trinuclear iron–sulfur cluster core for proton reduction in solution at low overpotential was demonstrated. These deeply colored bisphosphine-bridged sulfur-capped iron carbonyl systems are discussed as promising candidates for the development of new bioinspired model compounds of iron-based hydrogenases. PMID:26512211

  3. Chiral hypervalent iodine reagents: synthesis and reactivity.

    PubMed

    Parra, Alejandro; Reboredo, Silvia

    2013-12-16

    Chiral hypervalent iodine chemistry has been steadily increasing in importance in recent years. This review catalogues enantioselective transformations triggered by chiral hypervalent iodine(III/V) reagents, in stoichiometric or catalytic quantities, highlighting the different reactivities in terms of yield and enantioselectivity. Moreover, the synthesis of the most remarkable and successful catalysts has been illustrated in detail.

  4. Functional Reactive Polymer Electrospun Matrix.

    PubMed

    Agarwal, Vipul; Ho, Dominic; Ho, Diwei; Galabura, Yuriy; Yasin, Faizah; Gong, Peijun; Ye, Weike; Singh, Ruhani; Munshi, Alaa; Saunders, Martin; Woodward, Robert C; St Pierre, Timothy; Wood, Fiona M; Fear, Mark; Lorenser, Dirk; Sampson, David D; Zdyrko, Bogdan; Luzinov, Igor; Smith, Nicole M; Iyer, K Swaminathan

    2016-02-01

    Synthetic multifunctional electrospun composites are a new class of hybrid materials with many potential applications. However, the lack of an efficient, reactive large-area substrate has been one of the major limitations in the development of these materials as advanced functional platforms. Herein, we demonstrate the utility of electrospun poly(glycidyl methacrylate) films as a highly versatile platform for the development of functional nanostructured materials anchored to a surface. The utility of this platform as a reactive substrate is demonstrated by grafting poly(N-isopropylacrylamide) to incorporate stimuli-responsive properties. Additionally, we demonstrate that functional nanocomposites can be fabricated using this platform with properties for sensing, fluorescence imaging, and magneto-responsiveness. PMID:26780245

  5. Synthesis and Reactivity of Triazaphenanthrenes.

    PubMed

    Fernandez, Sarah; Ganiek, Maximilian A; Karpacheva, Mariia; Hanusch, Fabian C; Reuter, Stephan; Bein, Thomas; Auras, Florian; Knochel, Paul

    2016-07-01

    Pyridonaphthyridines (triazaphenanthrenes) were prepared in 4 steps and in 13-52% overall yield using Negishi cross-couplings between iodopicolines and 2-chloro-pyridylzinc derivatives. After chlorination, Gabriel amination and spontaneous ring-closure, the final aromatization leading to the triazaphenanthrenes was achieved with chloranil. This heterocyclic scaffold underwent a nucleophilic addition at position 6 leading to further functionalized pyridonaphthyridines. The influence of these chemical modifications on the optical properties was studied by steady-state and time-resolved optical spectroscopy. While the thiophene-substituted heterocycles exhibited the most extended absorption, the phenyl- and furan-substituted compounds showed a stronger photoluminescence, reaching above 20% quantum yield and lifetimes of several nanoseconds. PMID:27321707

  6. Direct Laser Synthesis of Functional Coatings

    SciTech Connect

    P. Schaaf; Michelle D. Shinn; E. Carpene; J. Kaspar

    2005-06-01

    The direct laser synthesis of functional coatings employs the irradiation of materials with short intensive laser pulses in a reactive atmosphere. The material is heated and plasma is ignited in the reactive atmosphere. This leads to an intensive interaction of the material with the reactive species and a coating is directly formed on the materials surface. By that functional coatings can be easily produced a fast way on steel, aluminium, and silicon by irradiation in nitrogen, methane, or even hydrogen. The influence of the processing parameters to the properties of the functional coatings will be presented for titanium nitride coating produced on titanium with the free electron laser.

  7. Reactive Functionalized Membranes for Polychlorinated Biphenyl Degradation.

    PubMed

    Gui, Minghui; Ormsbee, Lindell E; Bhattacharyya, Dibakar

    2013-08-01

    Membranes have been widely used in water remediation (e.g. desalination and heavy metal removal) because of the ability to control membrane pore size and surface charge. The incorporation of nanomaterials into the membranes provides added benefits through increased reactivity with different functionality. In this study, we report the dechlorination of 2-chlorobiphenyl in the aqueous phase by a reactive membrane system. Fe/Pd bimetallic nanoparticles (NPs) were synthesized (in-situ) within polyacrylic acid (PAA) functionalized polyvinylidene fluoride (PVDF) membranes for degradation of polychlorinated biphenyls (PCBs). Biphenyl formed in the reduction was further oxidized into hydroxylated biphenyls and benzoic acid by an iron-catalyzed hydroxyl radical (OH•) reaction. The formation of magnetite on Fe surface was observed. This combined pathway (reductive/oxidative) could reduce the toxicity of PCBs effectively while eliminating the formation of chlorinated degradation byproducts. The successful manufacturing of full-scale functionalized membranes demonstrates the possibility of applying reactive membranes in practical water treatment.

  8. Design and synthesis of reactive separation systems

    SciTech Connect

    Doherty, M.F.

    1992-01-01

    During the last decade there has been a rapid upturn in interest in reactive distillation. The chemical process industry recognizes the favorable economics of carrying out reaction simultaneously with distillation for certain classes of reacting systems, and many new processes have been built based on this technology. Interest is also increasing by academics and software vendors. Systematic design methods for reactive distillation systems have only recently begun to emerge. In this report we survey the available design techniques and point out the contributions made by our group at the University of Massachusetts.

  9. Covalent functionalization of graphene with reactive intermediates.

    PubMed

    Park, Jaehyeung; Yan, Mingdi

    2013-01-15

    Graphene, a material made exclusively of sp(2) carbon atoms with its π electrons delocalized over the entire 2D network, is somewhat chemically inert. Covalent functionalization can enhance graphene's properties including opening its band gap, tuning conductivity, and improving solubility and stability. Covalent functionalization of pristine graphene typically requires reactive species that can form covalent adducts with the sp(2) carbon structures in graphene. In this Account, we describe graphene functionalization reactions using reactive intermediates of radicals, nitrenes, carbenes, and arynes. These reactive species covalently modify graphene through free radical addition, CH insertion, or cycloaddition reactions. Free radical additions are among the most common reaction, and these radicals can be generated from diazonium salts and benzoyl peroxide. Electron transfer from graphene to aryl diazonium ion or photoactivation of benzoyl peroxide yields aryl radicals that subsequently add to graphene to form covalent adducts. Nitrenes, electron-deficient species generated by thermal or photochemical activation of organic azides, can functionalize graphene very efficiently. Because perfluorophenyl nitrenes show enhanced bimolecular reactions compared with alkyl or phenyl nitrenes, perfluorophenyl azides are especially effective. Carbenes are used less frequently than nitrenes, but they undergo CH insertion and C═C cycloaddition reactions with graphene. In addition, arynes can serve as a dienophile in a Diels-Alder type reaction with graphene. Further study is needed to understand and exploit the chemistry of graphene. The generation of highly reactive intermediates in these reactions leads to side products that complicate the product composition and analysis. Fundamental questions remain about the reactivity and regioselectivity of graphene. The differences in the basal plane and the undercoordinated edges of graphene and the zigzag versus arm-chair configurations

  10. Functional cavitands: Chemical reactivity in structured environments

    PubMed Central

    Purse, Byron W.; Rebek, Julius

    2005-01-01

    Container-shaped molecules provide structured environments that impart geometric bounds on the motions and conformations of smaller molecular occupants. Moreover, they provide “solvation” that is constrained in time and space. When inwardly directed functional groups are present, they can interact chemically with the occupants. Additionally, the potential for reactivity and catalysis is greatly enhanced. Deep cavitands, derived from resorcinarenes, nearly surround smaller molecules and have been one of the most successful platforms for elaboration with functional groups. Derivatives bearing organic and metal-binding functional groups have been shown to affect recognition properties and selectively accelerate diverse reactions. In this review, we examine recent examples of these systems with an emphasis on how and why ordered nanoenvironments impart changes in the properties and reactivity of their occupants. PMID:16043720

  11. Reactivity of functionalized indoles with rare-earth metal amides. Synthesis, characterization and catalytic activity of rare-earth metal complexes incorporating indolyl ligands.

    PubMed

    Feng, Zhijun; Wei, Yun; Zhou, Shuangliu; Zhang, Guangchao; Zhu, Xiancui; Guo, Liping; Wang, Shaowu; Mu, Xiaolong

    2015-12-21

    The reactivity of several functionalized indoles 2-(RNHCH2)C8H5NH (R = C6H5 (1), (t)Bu (2), 2,6-(i)Pr2C6H3 (3)) with rare-earth metal amides is described. Reactions of 1 or 2 with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Eu, Yb) respectively produced the europium complexes [2-(C6H5N[double bond, length as m-dash]CH)C8H5N]2Eu[N(SiMe3)2] (4) and [2-((t)BuN[double bond, length as m-dash]CH)C8H5N]Eu[N(SiMe3)2]2 (5), and the ytterbium complex [2-((t)BuN[double bond, length as m-dash]CH)C8H5N]2Yb[N(SiMe3)2] (6), containing bidentate anionic indolyl ligands via dehydrogenation of the amine to the imine. In contrast, reactions of the more sterically bulky indole 3 with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 afforded complexes [2-(2,6-(i)Pr2C6H3NCH2)C8H5N]RE[N(SiMe3)2](THF)2 (RE = Yb (7), Y (8), Er (9), Dy (10)) with the deprotonated indolyl ligand. While reactions of 3 with yttrium and ytterbium amides in refluxing toluene respectively gave the complexes [2-(2,6-(i)Pr2C6H3N[double bond, length as m-dash]CH)C8H5N]3Y (11) and [2-(2,6-(i)Pr2C6H3N[double bond, length as m-dash]CH)C8H5N]2Yb(II)(THF)2 (12), along with transformation of the amino group to the imino group, and also with a reduction of Yb(3+) to Yb(2+) in the formation of 12. Reactions of 3 with samarium and neodymium amides provided novel dinuclear complexes {[μ-η(5):η(1):η(1)-2-(2,6-(i)Pr2C6H3NCH2)C8H5N]RE[N(SiMe3)2]}2 (RE = Sm (13), Nd (14)) having indolyl ligands in μ-η(5):η(1):η(1) hapticities. The pathway for the transformation of the amino group to the imino group is proposed on the basis of the experimental results. The new complexes displayed excellent activity in the intramolecular hydroamination of aminoalkenes. PMID:26548974

  12. Reactive Functionalized Membranes for Polychlorinated Biphenyl Degradation

    PubMed Central

    Gui, Minghui; Ormsbee, Lindell E.; Bhattacharyya, Dibakar

    2014-01-01

    Membranes have been widely used in water remediation (e.g. desalination and heavy metal removal) because of the ability to control membrane pore size and surface charge. The incorporation of nanomaterials into the membranes provides added benefits through increased reactivity with different functionality. In this study, we report the dechlorination of 2-chlorobiphenyl in the aqueous phase by a reactive membrane system. Fe/Pd bimetallic nanoparticles (NPs) were synthesized (in-situ) within polyacrylic acid (PAA) functionalized polyvinylidene fluoride (PVDF) membranes for degradation of polychlorinated biphenyls (PCBs). Biphenyl formed in the reduction was further oxidized into hydroxylated biphenyls and benzoic acid by an iron-catalyzed hydroxyl radical (OH•) reaction. The formation of magnetite on Fe surface was observed. This combined pathway (reductive/oxidative) could reduce the toxicity of PCBs effectively while eliminating the formation of chlorinated degradation byproducts. The successful manufacturing of full-scale functionalized membranes demonstrates the possibility of applying reactive membranes in practical water treatment. PMID:24954974

  13. The 2-Arsaethynolate Anion: Synthesis and Reactivity Towards Heteroallenes.

    PubMed

    Hinz, Alexander; Goicoechea, Jose M

    2016-07-18

    The synthesis and isolation of the 2-arsaethynolate anion, AsCO(-) , and its subsequent reactivity towards heteroallenes is reported. Reactions with ketenes and carbodiimides afford four-membered anionic heterocycles in formal [2+2] cycloaddition reactions. By contrast, reaction with an isocyanate yielded a 1,4,2-diazaarsolidine-3,5-dionide anion and the unprecedented cluster anions As10 (2-) and As12 (4-) . These preliminary reactivity studies hint at the enormous potential synthetic utility of this novel anion, which may be employed as an arsenide (As(-) ) source. PMID:27093942

  14. Immune Function and Reactivation of Latent Viruses

    NASA Technical Reports Server (NTRS)

    Butel, Janet S.

    1999-01-01

    A major concern associated with long-duration space flight is the possibility of infectious diseases posing an unacceptable medical risk to crew members. One major hypothesis addressed in this project is that space flight will cause alterations in the immune system that will allow latent viruses that are endogenous in the human population to reactivate and shed to higher levels than normal, which may affect the health of crew members. The second major hypothesis being examined is that the effects of space flight will alter the mucosal immune system, the first line of defense against many microbial infections, including herpesviruses, polyomaviruses, and gastroenteritis viruses, rendering crew members more susceptible to virus infections across the mucosa. We are focusing the virus studies on the human herpesviruses and polyomaviruses, important pathogens known to establish latent infections in most of the human population. Both primary infection and reactivation from latent infection with these groups of viruses (especially certain herpesviruses) can cause a variety of illnesses that result in morbidity and, occasionally, mortality. Both herpesviruses and polyomaviruses have been associated with human cancer, as well. Effective vaccines exist for only one of the eight known human herpesviruses and available antivirals are of limited use. Whereas normal individuals display minimal consequences from latent viral infections, events which alter immune function (such as immunosuppressive therapy following solid organ transplantation) are known to increase the risk of complications as a result of viral reactivations.

  15. Function through synthesis-informed design.

    PubMed

    Wender, Paul A; Quiroz, Ryan V; Stevens, Matthew C

    2015-03-17

    In 1996, a snapshot of the field of synthesis was provided by many of its thought leaders in a Chemical Reviews thematic issue on "Frontiers in Organic Synthesis". This Accounts of Chemical Research thematic issue on "Synthesis, Design, and Molecular Function" is intended to provide further perspective now from well into the 21st century. Much has happened in the past few decades. The targets, methods, strategies, reagents, procedures, goals, funding, practices, and practitioners of synthesis have changed, some in dramatic ways as documented in impressive contributions to this issue. However, a constant for most synthesis studies continues to be the goal of achieving function with synthetic economy. Whether in the form of new catalysts, reagents, therapeutic leads, diagnostics, drug delivery systems, imaging agents, sensors, materials, energy generation and storage systems, bioremediation strategies, or molecules that challenge old theories or test new ones, the function of a target has been and continues to be a major and compelling justification for its synthesis. While the targets of synthesis have historically been heavily represented by natural products, increasingly design, often inspired by natural structures, is providing a new source of target structures exhibiting new or natural functions and new or natural synthetic challenges. Complementing isolation and screening approaches to new target identification, design enables one to create targets de novo with an emphasis on sought-after function and synthetic innovation with step-economy. Design provides choice. It allows one to determine how close a synthesis will come to the ideal synthesis and how close a structure will come to the ideal function. In this Account, we address studies in our laboratory on function-oriented synthesis (FOS), a strategy to achieve function by design and with synthetic economy. By starting with function rather than structure, FOS places an initial emphasis on target design

  16. Reactive Polyphenols: Adding a Function to DOM

    NASA Astrophysics Data System (ADS)

    Caldwell, B. A.; Lajtha, K.; Frentress, J.; Crow, S. E.

    2006-12-01

    Both the quantity and the quality of DOM changes dramatically as it moves in solution from plant detritus through the terrestrial landscape to rivers. In very N-limited ecosystems, ecosystem theory would suggest that DON would be efficiently retained, and yet DON export can be substantial and may comprise over 90 percent of total N export in many highly limited upland forested ecosystems. We are exploring the hypothesis that DOM contains reactive polyphenols that can bind significant amounts of otherwise highly labile proteinaceous matter and thus play a large role both in N export and the chemistry of DOM delivered to rivers. While polyphenols have been measured across a wide range of aqueous environments, results are usually limited to an estimate of total phenolics, commonly using the Folin-Ciocalteu reagent. We modified this general assay by adding a step where protein-complexing polyphenols are removed from a subsample by shaking with an insoluble protein. Measuring DOM polyphenols with and without the protein-binding step gives estimates of total phenolics and non-protein reactive phenolics. Protein-binding polyphenols are then calculated by difference. Preliminary measurements with soil lysimeter solutions, soil extracts and stream water collected from watersheds in western Oregon show that over 75 percent of the total polyphenols can bind to protein. Determining the protein-binding function of DOM under different climates, soil and vegetation can provide useful insight into the role of DOM into the N cycle and terrestrial-aquatic linkages.

  17. Synthesis of Reactive Polymers for Acrolein Capture Using AGET ATRP.

    PubMed

    Beringer, Laura T; Li, Shaohua; Gilmore, Gary; Lister, John; Averick, Saadyah

    2015-10-01

    Acrolein is a toxic metabolite of the anticancer agent cyclophosphamide (CP). Current strategies to mitigate acrolein toxicity are insufficient, and in this brief article, we report the synthesis of well-defined low molecular weight block copolymers using activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) capable of reacting with the cytotoxic small molecule acrolein. Acrolein reactivity was introduced into the block copolymers via incorporation of either (a) aminooxy or (b) sulfhydryl groups. The cytoprotective effect of the polymers was compared to sodium 2-sulfanylethanesulfonate (mesna) the current gold standard for protection from CP urotoxicity, and we found that the polymers bearing sulfhydryl moieties demonstrated superior cytoprotective activity.

  18. Function through Synthesis-Informed Design

    PubMed Central

    2016-01-01

    Conspectus In 1996, a snapshot of the field of synthesis was provided by many of its thought leaders in a Chemical Reviews thematic issue on “Frontiers in Organic Synthesis”. This Accounts of Chemical Research thematic issue on “Synthesis, Design, and Molecular Function” is intended to provide further perspective now from well into the 21st century. Much has happened in the past few decades. The targets, methods, strategies, reagents, procedures, goals, funding, practices, and practitioners of synthesis have changed, some in dramatic ways as documented in impressive contributions to this issue. However, a constant for most synthesis studies continues to be the goal of achieving function with synthetic economy. Whether in the form of new catalysts, reagents, therapeutic leads, diagnostics, drug delivery systems, imaging agents, sensors, materials, energy generation and storage systems, bioremediation strategies, or molecules that challenge old theories or test new ones, the function of a target has been and continues to be a major and compelling justification for its synthesis. While the targets of synthesis have historically been heavily represented by natural products, increasingly design, often inspired by natural structures, is providing a new source of target structures exhibiting new or natural functions and new or natural synthetic challenges. Complementing isolation and screening approaches to new target identification, design enables one to create targets de novo with an emphasis on sought-after function and synthetic innovation with step-economy. Design provides choice. It allows one to determine how close a synthesis will come to the ideal synthesis and how close a structure will come to the ideal function. In this Account, we address studies in our laboratory on function-oriented synthesis (FOS), a strategy to achieve function by design and with synthetic economy. By starting with function rather than structure, FOS places an initial emphasis on

  19. Synthesis, structure, spectra and reactivity of iron(III) complexes of imidazole and pyrazole containing ligands as functional models for catechol dioxygenases.

    PubMed

    Dhanalakshmi, Thirumanasekaran; Suresh, Eringathodi; Palaniandavar, Mallayan

    2009-10-21

    A series of new 1 : 1 iron(iii) complexes of the type [Fe()Cl(3)], where is a tridentate 3N donor ligand, has been isolated and studied as functional models for catechol dioxygenases. The ligands (1-methyl-1H-imidazol-2-ylmethyl)pyrid-2-ylmethyl-amine (), N,N-dimethyl-N'-(1-methyl-1H-imidazol-2-ylmethyl)ethane-1,2-diamine () and N-(1-methyl-1H-imidazol-2-ylmethyl)-N'-phenylethane-1,2-diamine () are linear while the ligands tris(1-pyrazolyl)methane (), tris(3,5-dimethyl-1-pyrazolyl)methane () and tris(3-iso-propylpyrazolyl)methane () are tripodal ones. All the complexes have been characterized by spectral and electrochemical methods. The X-ray crystal structure of the dinuclear catecholate adduct [Fe()(TCC)](2)O, where TCC(2-) is a tetrachlorocatecholate dianion, has been successfully determined. In this complex both the iron(iii) atoms are bridged by a mu-oxo group and each iron(iii) center possesses a distorted octahedral coordination geometry in which the ligand is facially coordinated and the remaining coordination sites are occupied by the TCC(2-) dianion. Spectral studies suggest that addition of a base like Et(3)N induces the mononuclear complex species [Fe()(TCC)Cl] to dimerize forming a mu-oxo-bridged complex. The spectral and electrochemical properties of the catecholate adducts of the complexes generated in situ reveal that a systematic variation in the ligand donor atom type significantly influences the Lewis acidity of the iron(iii) center and hence the interaction of the complexes with simple and substituted catechols. The 3,5-di-tert-butylcatecholate (DBC(2-)) adducts of the type [Fe()(DBC)Cl], where is a linear tridentate ligand (), undergo mainly oxidative intradiol cleavage of the catechol in the presence of dioxygen. Also, the extradiol-to-intradiol product selectivity (E : I) is enhanced upon removal of the coordinated chloride ion in these adducts to obtain [Fe()(DBC)(Sol)](+) and upon incorporating coordinated N-methylimidazolyl nitrogen in

  20. Carbasugars: Synthesis and Functions

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yoshiyuki

    It is well recognized that glycosidase inhibitors are not only tools to elucidate the mechanism of a living system manipulated by glycoconjugates but also potential clinical drugs and insecticides by inducing the failure of glycoconjugates to perform their function. In this chapter, the syntheses and functions of natural glycosidase inhibitors (cyclophelitol , allosamidine , and trehazoilin ), which possess highly oxygenated and functionalized cyclohexanes or cyclopentanes in their structures and are defined as carbasugars , and the structure and activity relationships (SAR) of their derivatives are described. Also, recently much attention has been focused on neuraminidase inhibitors as anti-influenza drugs since relenza , which was derived from sialic acid, and also, tamiflu , which is the artificial carbasugar designed as a transition state analogue in the hydrolysis pathway of substrates by neuraminidase, were launched in the market. Herein, the medicinal chemistry efforts to discover tamiflu and some efficient syntheses applicable to process chemistry are described. Finally, useful synthetic methodologies for carbasugar formation from sugars are also introduced in this chapter.

  1. Synthesis and processing of composites by reactive metal penetration

    SciTech Connect

    Loehman, R.E.; Ewsuk, K.G.; Tomsia, A.P.; Fahrenholtz, W.G.

    1996-07-01

    Ceramic-metal composites are being developed as engineering materials because of their high stiffness-to-weight ratios, good fracture toughness, and because their electrical and thermal properties can be varied through control of their compositions and microstructures. Wider use of ceramic-metal composites requires improvements in synthesis and processing so that high-performance parts can be produced more economically. Over the past three years reactive metal penetration has been shown to be a promising technique for making ceramic and metal-matrix composites to near-net-shape with control of both composition and microstructure. It appears that reactive metal penetration could be an economical process for manufacturing many of the advanced ceramic composites that are needed for light-weight structural and wear applications for transportation and energy conversion devices. Near-net-shape fabrication of parts has the additional advantage that costly and energy intensive grinding and machining operations are significantly reduced, and the waste generated from such finishing operations is minimized. The goals of this research and development program are: (1) to identify compositions favorable for making composites by reactive metal penetration; (2) to understand the mechanism(s) by which these composites are formed; and (3) to control and optimize the process so that composites and composite coatings can be made economically.

  2. Reactive oxygen species and boar sperm function.

    PubMed

    Awda, Basim J; Mackenzie-Bell, Meghan; Buhr, Mary M

    2009-09-01

    Boar spermatozoa are very susceptible to reactive oxygen species (ROS), but ROS involvement in damage and/or capacitation is unclear. The impact of exposing fresh boar spermatozoa to an ROS-generating system (xanthine/xanthine oxidase; XA/XO) on sperm ROS content, membrane lipid peroxidation, phospholipase (PL) A activity, and motility, viability, and capacitation was contrasted to ROS content and sperm function after cryopreservation. Exposing boar sperm (n = 4-5 ejaculates) to the ROS-generating system for 30 min rapidly increased hydrogen peroxide (H2O2) and lipid peroxidation in all sperm, increased PLA in dead sperm, and did not affect intracellular O2- (flow cytometry of sperm labeled with 2',7'-dichlorodihydrofluorscein diacetate, BODIPY 581/591 C11, bis-BODIPY-FL C11, hydroethidine, respectively; counterstained for viability). Sperm viability remained high, but sperm became immotile. Cryopreservation decreased sperm motility, viability, and intracellular O2- significantly, but did not affect H2O2. As expected, more sperm incubated in capacitating media than Beltsville thawing solution buffer underwent acrosome reactions and protein tyrosine phosphorylation (four proteins, 58-174 kDa); which proteins were tyrosine phosphorylated was pH dependent. Pre-exposing sperm to the ROS-generating system increased the percentage of sperm that underwent acrosome reactions after incubation in capacitating conditions (P < 0.025), and decreased capacitation-dependent increases in two tyrosine-phosphorylated proteins (P < or = 0.035). In summary, H2O2 is the major free radical mediating direct ROS effects, but not cryopreservation changes, on boar sperm. Boar sperm motility, acrosome integrity, and lipid peroxidation are more sensitive indicators of oxidative stress than viability and PLA activity. ROS may stimulate the acrosome reaction in boar sperm through membrane lipid peroxidation and PLA activation. PMID:19357363

  3. Concise Synthesis of Functionalized Benzocyclobutenones

    PubMed Central

    Chen, Peng-hao; Savage, Nikolas A.; Dong, Guangbin

    2014-01-01

    A concise approach to access functionalized benzocyclobutenones from 3-halophenol derivatives is described. This modified synthesis employs a [2+2] cycloaddition between benzynes generated from dehydrohalogenation of aryl halides using LiTMP and acetaldehyde enolate generated from n-BuLi and THF, followed by oxidation of the benzocyclobutenol intermediates to provide benzocyclobutenones. The [2+2] reaction can be run on a 10-gram scale with an increased yield. A number of functional groups including alkenes and alkynes are tolerated. Coupling of benzynes with ketene silyl acetals to give 8-substituted benzocyclobutenones is also demonstrated. PMID:24926108

  4. Silatranes: a review on their synthesis, structure, reactivity and applications.

    PubMed

    Puri, J K; Singh, Raghubir; Chahal, Varinder Kaur

    2011-03-01

    This critical review summarizes progress of the rapidly developing and very active field of silatrane chemistry. The first part of the review deals with general synthetic approaches used to synthesize different silatranes. The most interesting feature of silatranes, i.e., variation of Si-N bond length on the basis of the axial substituent of Si, and other structural features, are described in the second part with special emphasis on crystallographic and theoretical studies. It is followed by a discussion on the reactivity of various silatranes. Silatranes have now gained acceptance for a wide variety of applications which are summarized in the last section of review. Some of them have extensive interest due to their medical use to heal wounds or stimulate hair-growth (pilotropic activity), biological properties, pharmacological properties e.g. antitumor, anticancer, antibacterial, anti-inflammatory, fungicidal activity, stimulating effect in animal production and seed germination effects. The review focuses on the extended potential of silatranes in sol-gel processes, mesoporous zeotypes, atomic force microscopy, commercial products such as adhesion promoters, polymer formation and rubber compositions. This critical review will be helpful for general researchers, experts, advanced undergraduates and newcomers working on silatrane chemistry as this review presents greater emphasis on synthesis and characterization, structural properties, reactivity and applications of silatranes in the field of biology, material science, sol-gel chemistry, pharmaceutics, agriculture and medicine (311 references).

  5. Synthesis of cubic ruthenium nitride by reactive pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Moreno-Armenta, M. G.; Diaz, J.; Martinez-Ruiz, A.; Soto, G.

    2007-10-01

    The recent synthesis of platinum nitride opens the possibility of novel platinum-group metal nitrides to exist. In this work we report the synthesis of ruthenium nitride by reactive pulsed laser ablation. Several plausible structures have been evaluated by ab initio calculations using the full potential linearized augmented plane wave method, in order to investigate the ruthenium nitride structural and electronic properties. In fact, the predicted symmetry of stoichiometric RuN matches the experimental diffraction data. RuN crystallizes with NaCl-type structure at room temperature with cell-parameter somewhat larger than predicted by calculations. However we found a marginal chemical strength in these nitrides. The material is destroyed by mild acid and basic solutions. Under annealing RuN decomposes abruptly for temperatures beyond 100 °C. Since the thermal stability correlates directly with the mechanical properties our finding cast doubts than the latter transition metal nitrides can be ultra-hard materials at ambient conditions.

  6. Executive function and cerebrovascular reactivity in pediatric hypertension.

    PubMed

    Ostrovskaya, Maria A; Rojas, Mary; Kupferman, Juan C; Lande, Marc B; Paterno, Kara; Brosgol, Yuri; Pavlakis, Steven G

    2015-04-01

    Primary hypertension is associated with decreased performance on neurocognitive testing and a blunted cerebrovascular reactivity to hypercapnia. Parents of 14 children with hypertension and prehypertension completed the Behavior Rating Inventory of Executive Functions. Children underwent 24-hour ambulatory blood pressure monitoring and transcranial Doppler with reactivity measurement using time-averaged maximum mean velocity and end-tidal carbon dioxide during hypercapnia-rebreathing test. Comparing the reactivity slope for the patients to historical controls showed a statistically significant difference (t = -5.19, df = 13, P < .001), with lower slopes. Pearson correlations of the Behavior Rating Inventory of Executive Functions scores with the reactivity slopes showed a statistically significant inverse relationship with Behavioral Regulation Index (r = -.60, P = .02), Metacognition Index (r = -.40, P = .05), and the Global Executive Component (r = -.53, P = .05). Children with hypertension have decreased executive function, and this correlates to low transcranial Doppler-reactivity slopes, suggesting that the brain is a target organ in hypertensive children.

  7. Modulating executive functioning: trait motivational reactivity and resting HRV.

    PubMed

    Bailey, Rachel L; Potter, Robert F; Lang, Annie; Pisoni, David B

    2015-01-01

    This study assessed relationships among individual differences in trait motivational reactivity, executive functioning, and neurovisceral regulation of emotion and attention indexed via resting heart rate variability (rHRV). We derived predictions regarding these relationships according to neurovisceral neural network theory. Because lower rHRV has been suggested as an endophenotype of less adaptive behaviour, low rHRV individuals were predicted to have high aversive and low appetitive trait motivational reactivity, while high rHRV individuals were predicted to have high reactivity in both appetitive and aversive motivational systems. These predictions were supported. Motivational reactivity also was related to executive functioning deficits, although the pattern of results was not in the predicted direction. Results suggest that trait motivational reactivity scores are related to visceral responses proposed in the neurovisceral integration circuit as well as in the modulation of these responses by higher-order cognitive control systems related to executive function. PMID:24606341

  8. Negishi Cross-Coupling Is Compatible with a Reactive B-Cl Bond: Development of a Versatile Late-Stage Functionalization of 1,2-Azaborines and Its Application to the Synthesis of New BN Isosteres of Naphthalene and Indenyl.

    PubMed

    Brown, Alec N; Li, Bo; Liu, Shih-Yuan

    2015-07-22

    The compatibility of the Negishi cross-coupling reaction with the versatile B-Cl functionality has been demonstrated in the context of late-stage functionalization of 1,2-azaborines. Alkyl-, aryl-, and alkenylzinc reagents have been utilized for the functionalization of the triply orthogonal precursor 3-bromo-1-(tert-butyldimethylsilyl)-2-chloro-1,2-dihydro-1,2-azaborine (2) to furnish new 2,3-substituted monocyclic 1,2-azaborines. This methodology has enabled the synthesis of previously elusive BN-naphthalene and BN-indenyl structures from a common intermediate.

  9. Negishi Cross-Coupling Is Compatible with a Reactive B–Cl Bond: Development of a Versatile Late-Stage Functionalization of 1,2-Azaborines and Its Application to the Synthesis of New BN Isosteres of Naphthalene and Indenyl

    PubMed Central

    Brown, Alec N.; Li, Bo; Liu, Shih-Yuan

    2016-01-01

    The compatibility of the Negishi cross-coupling reaction with the versatile B–Cl functionality has been demonstrated in the context of late-stage functionalization of 1,2-azaborines. Alkyl-, aryl-, and alkenylzinc reagents have been utilized for the functionalization of the triply orthogonal precursor 3-bromo-1-(tert-butyldimethylsilyl)-2-chloro-1,2-dihydro-1,2-azaborine (2) to furnish new 2,3-substituted monocyclic 1,2-azaborines. This methodology has enabled the synthesis of previously elusive BN-naphthalene and BN-indenyl structures from a common intermediate. PMID:26148959

  10. Signaling functions of reactive oxygen species.

    PubMed

    Forman, Henry Jay; Maiorino, Matilde; Ursini, Fulvio

    2010-02-01

    We review signaling by reactive oxygen species, which is emerging as a major physiological process. However, among the reactive oxygen species, H(2)O(2) best fulfills the requirements of being a second messenger. Its enzymatic production and degradation, along with the requirements for the oxidation of thiols by H(2)O(2), provide the specificity for time and place that are required in signaling. Both thermodynamic and kinetic considerations suggest that among possible oxidation states of cysteine, formation of sulfenic acid derivatives or disulfides can be relevant as thiol redox switches in signaling. In this work, the general constraints that are required for protein thiol oxidation by H(2)O(2) to be fast enough to be relevant for signaling are discussed in light of the mechanism of oxidation of the catalytic cysteine or selenocysteine in thiol peroxidases. While the nonenzymatic reaction between thiol and H(2)O(2) is, in most cases, too slow to be relevant in signaling, the enzymatic catalysis of thiol oxidation by these peroxidases provides a potential mechanism for redox signaling.

  11. Measuring Memory Reactivation With Functional MRI: Implications for Psychological Theory.

    PubMed

    Levy, Benjamin J; Wagner, Anthony D

    2013-01-01

    Environmental cues often remind us of earlier experiences by triggering the reactivation of memories of events past. Recent evidence suggests that memory reactivation can be observed using functional MRI and that distributed pattern analyses can even provide evidence of reactivation on individual trials. The ability to measure memory reactivation offers unique and powerful leverage on theoretical issues of long-standing interest in cognitive psychology, providing a means to address questions that have proven difficult to answer with behavioral data alone. In this article, we consider three instances. First, reactivation measures can indicate whether memory-based inferences (i.e., generalization) arise through the encoding of integrated cross-event representations or through the flexible expression of separable event memories. Second, online measures of memory reactivation may inform theories of forgetting by providing information about when competing memories are reactivated during competitive retrieval situations. Finally, neural reactivation may provide a window onto the role of replay in memory consolidation. The ability to track memory reactivation, including at the individual trial level, provides unique leverage that is not afforded by behavioral measures and thus promises to shed light on such varied topics as generalization, integration, forgetting, and consolidation.

  12. Measuring Memory Reactivation With Functional MRI: Implications for Psychological Theory.

    PubMed

    Levy, Benjamin J; Wagner, Anthony D

    2013-01-01

    Environmental cues often remind us of earlier experiences by triggering the reactivation of memories of events past. Recent evidence suggests that memory reactivation can be observed using functional MRI and that distributed pattern analyses can even provide evidence of reactivation on individual trials. The ability to measure memory reactivation offers unique and powerful leverage on theoretical issues of long-standing interest in cognitive psychology, providing a means to address questions that have proven difficult to answer with behavioral data alone. In this article, we consider three instances. First, reactivation measures can indicate whether memory-based inferences (i.e., generalization) arise through the encoding of integrated cross-event representations or through the flexible expression of separable event memories. Second, online measures of memory reactivation may inform theories of forgetting by providing information about when competing memories are reactivated during competitive retrieval situations. Finally, neural reactivation may provide a window onto the role of replay in memory consolidation. The ability to track memory reactivation, including at the individual trial level, provides unique leverage that is not afforded by behavioral measures and thus promises to shed light on such varied topics as generalization, integration, forgetting, and consolidation. PMID:25484909

  13. Synthesis, Characterization and Reactivity of a Hexane-Soluble Silver Salt

    ERIC Educational Resources Information Center

    Stockland, Robert A. Jr.; Wilson, Brian D.; Goodman, Caton C.; Giese, Barret J.; Shrimp, Frederick L., II

    2007-01-01

    The connectivity of a hexane-soluble silver salt is established by using NMR spectroscopy to describe the synthesis, characterization and reactivity of the salt. The results found hexane-soluble silver to be an effective transfer agent.

  14. Glutathione (GSH) and the GSH synthesis gene Gclm modulate vascular reactivity in mice

    PubMed Central

    Weldy, Chad S.; Luttrell, Ian P.; White, Collin C.; Morgan-Stevenson, Vicki; Bammler, Theo K.; Beyer, Richard P.; Afsharinejad, Zahra; Kim, Francis; Chitaley, Kanchan; Kavanagh, Terrance J.

    2012-01-01

    Oxidative stress has been implicated in the development of vascular disease and in the promotion of endothelial dysfunction via the reduction in bioavailable nitric oxide (NO•). Glutathione (GSH) is a tripeptide thiol antioxidant that is utilized by glutathione peroxidase (GPx) to scavenge reactive oxygen species (ROS) such as hydrogen peroxide and phospholipid hydroperoxides. Relatively frequent single nucleotide polymorphisms (SNPs) within the 5’ promoters of the GSH synthesis genes GCLC and GCLM are associated with impaired vasomotor function as measured by decreased acetylcholine-stimulated coronary artery dilation and with increased risk of myocardial infarction. Although the influence of genetic knockdown of GPx on vascular function has been investigated in mice, no work to date has been published on the role of genetic knock down of GSH synthesis genes on vascular reactivity. We therefore investigated the effects of targeted disruption of Gclm in mice and the subsequent depletion of GSH on vascular reactivity, NO• production, aortic nitrotyrosine protein modification, and whole genome transcriptional responses as measured by DNA microarray. Gclm−/+ and Gclm−/− mice had 72% and 12%, respectively, of WT aortic GSH content. Gclm−/+ mice had a significant impairment in acetylcholine (ACh)-induced relaxation in aortic rings as well as increased aortic nitrotyrosine protein modification. Surprisingly, Gclm−/− aortas showed enhanced relaxation compared to Gclm−/+ aortas, as well as increased NO• production. Although aortic rings from Gclm−/− mice had enhanced ACh-relaxation, they have a significantly increased sensitivity to phenylephrine (PE)-induced contraction. Alternatively, the PE response of Gclm−/+ aortas was nearly identical to that of their WT littermates. In order to examine the role of NO• or other potential endothelium derived factors in differentially regulating vasomotor activity, we incubated aortic rings with the NO

  15. Synthesis, characterization, and reactivity of pentamethylcyclopentadienyl complexes of divalent cobalt and nickel

    SciTech Connect

    Smith, M.E.

    1993-10-01

    The thesis is divided into the following 4 chapters: synthesis, characterization, and reactivity of trinuclear pentamethylcyclopentadienyl cobalt and nickel clusters with triply-bridging methylidyne groups; chemical and physical properties of pentamethylcyclopentadienyl acetylacetonate complexes of Co(II) and Ni(II); synthesis, characterization, and reactivity of pentamethylcyclopentadienyl halide complexes of Co and Ni; and crystallographic studies of distortions in metallocenes with C{sub 5}-symmetrical cyclopentadienyl rings.

  16. Reactivity umpolung in intramolecular ring closure of 3,4-disubstituted butenolides: diastereoselective total synthesis of paeonilide.

    PubMed

    Deore, Prashant S; Argade, Narshinha P

    2013-11-15

    Remarkable reactivity reversal stratagem in 3,4-disubstituted butenolides under acidic conditions is described. Design of a suitably substituted multifunctional butenolide followed by an acid-catalyzed chemo- and diastereoselective intramolecular ring closure via the reactivity umpolung has been demonstrated to accomplish a concise total synthesis of paeonilide. Overall, the present protocol involves one-pot reduction of an α,β-unsaturated carbon-carbon double bond and intramolecular nucleophilic insertion of oxygen function at the electron-rich γ-position of butenolide. The involved mechanistic aspects have also been discussed. PMID:24175675

  17. Controlled reactivity tuning of metal-functionalized vanadium oxide clusters.

    PubMed

    Kastner, Katharina; Forster, Johannes; Ida, Hiromichi; Newton, Graham N; Oshio, Hiroki; Streb, Carsten

    2015-05-18

    Controlling the assembly and functionalization of molecular metal oxides [Mx Oy ](n-) (M=Mo, W, V) allows the targeted design of functional molecular materials. While general methods exist that enable the predetermined functionalization of tungstates and molybdates, no such routes are available for molecular vanadium oxides. Controlled design of polyoxovanadates, however, would provide highly active materials for energy conversion, (photo-) catalysis, molecular magnetism, and materials science. To this end, a new approach has been developed that allows the reactivity tuning of vanadium oxide clusters by selective metal functionalization. Organic, hydrogen-bonding cations, for example, dimethylammonium are used as molecular placeholders to block metal binding sites within vanadate cluster shells. Stepwise replacement of the placeholder cations with reactive metal cations gives mono- and difunctionalized clusters. Initial reactivity studies illustrate the tunability of the magnetic, redox, and catalytic activity.

  18. Sulfur-directed enantioselective synthesis of functionalized dihydropyrans.

    PubMed

    Fernández de la Pradilla, Roberto; Tortosa, Mariola; Lwoff, Nadia; del Aguila, Miguel A; Viso, Alma

    2008-09-01

    The highly selective base-promoted cyclization of enantiopure sulfinyl dienols affords allylic sulfinyl dihydropyrans. The scope of this methodology, including the preparation of seven-membered rings, has been studied in depth. The reactivity of our sulfinyl dihydropyrans toward oxidation, imination, and dihydroxylation has been explored, and thus several routes to densely functionalized pyran derivatives have been outlined. The reactivity of allylic dihydropyranyl sulfones and sulfoximines in S(N)2' processes with organocuprates has been examined. The displacement products were obtained with good regio- and stereoselectivity and fair to good yields. The reactivity of these products to dihydroxylation opens new possibilities to access enantiopure polyhydroxylated tetrahydropyrans that could be of interest for the synthesis of natural products.

  19. Relations among several nuclear and electronic density functional reactivity indexes

    NASA Astrophysics Data System (ADS)

    Torrent-Sucarrat, Miquel; Luis, Josep M.; Duran, Miquel; Toro-Labbé, Alejandro; Solà, Miquel

    2003-11-01

    An expansion of the energy functional in terms of the total number of electrons and the normal coordinates within the canonical ensemble is presented. A comparison of this expansion with the expansion of the energy in terms of the total number of electrons and the external potential leads to new relations among common density functional reactivity descriptors. The formulas obtained provide explicit links between important quantities related to the chemical reactivity of a system. In particular, the relation between the nuclear and the electronic Fukui functions is recovered. The connection between the derivatives of the electronic energy and the nuclear repulsion energy with respect to the external potential offers a proof for the "Quantum Chemical le Chatelier Principle." Finally, the nuclear linear response function is defined and the relation of this function with the electronic linear response function is given.

  20. Reactive Attachment Disorder: Implications for School Readiness and School Functioning

    ERIC Educational Resources Information Center

    Schwartz, Eric; Davis, Andrew S.

    2006-01-01

    School readiness and functioning in children diagnosed with Reactive Attachment Disorder (RAD) are important issues due to the dramatic impact RAD has on multiple areas of development. The negative impact of impaired or disrupted early relationships, characterized by extreme neglect, abuse, parental mental illness, domestic violence, and repeated…

  1. Electron driven processes in ices: Surface functionalization and synthesis reactions

    NASA Astrophysics Data System (ADS)

    Lafosse, A.; Bertin, M.; Azria, R.

    2009-05-01

    The ability to control and orientate chemical reactivity in the condensed phase is a major challenge of modern research. Upon interaction with condensed molecules electrons drive bond cleavage thus generating a population of very reactive species in the condensed medium. These reactive species may interact either within the volume leading to the synthesis of new molecules or with the substrate surface by forming strong chemical bonds. The former reaction is known as electron induced synthesis and the latter one as electron induced surface functionalization. High-energy electrons achieve only a low chemical specificity due to the large number of dissociating open channels. In contrast, electrons with energies below ionization threshold of the irradiated matter are capable of high selectivity because of the dissociative electron attachment mechanism. In this review recent studies of electron interaction with condensed molecules on hydrogenated diamond substrates will be described. In particular electron induced functionalization of diamond surfaces by CH 2CN groups, decarboxylation reactions in condensed films of pure organic acids RCOOH (R = H, CH 3, C 2H 5, CF 3), carbamic acid formation in CO 2:NH 3, HCOOH:NH 3 and CF 3COOH:NH 3 binary ice mixtures, and glycine formation in a CH 3COOD:NH 3 mixture are presented and discussed.

  2. Design and synthesis of reactive separation systems. Final report

    SciTech Connect

    Doherty, M.F.

    1992-12-31

    During the last decade there has been a rapid upturn in interest in reactive distillation. The chemical process industry recognizes the favorable economics of carrying out reaction simultaneously with distillation for certain classes of reacting systems, and many new processes have been built based on this technology. Interest is also increasing by academics and software vendors. Systematic design methods for reactive distillation systems have only recently begun to emerge. In this report we survey the available design techniques and point out the contributions made by our group at the University of Massachusetts.

  3. Sulfonyl Azoles in the Synthesis of 3-Functionalized Azole Derivatives.

    PubMed

    Palmieri, Alessandro; Petrini, Marino

    2016-06-01

    Sulfonyl indoles, as well as related azolyl derivatives, have been recently introduced in synthesis as stable precursors of reactive indolenine intermediates. This personal account reports on the discovery of sulfonyl azoles and their practical utilization in many synthetic processes for the preparation of functionalized 3-substituted indoles, indazoles, and pyrroles. The indolenine intermediates obtained by treatment of sulfonyl azoles with Brønsted bases or Lewis acids can be considered as vinylogous imino derivatives that can be made to react with different nucleophilic reagents. These include organometallic reagents, reducing agents, stabilized carbanions, and heteronucleophiles. The controlled and mild conditions for the generation of indolenines from sulfonyl azoles make these substrates particularly useful in asymmetric synthesis, exploiting organo- or metal-catalyzed processes. Although less exploited, sulfonyl indoles can also be involved in photochemical processes for the preparation of polycyclic derivatives. PMID:27147297

  4. Three-coordinate iron(IV) bisimido complexes with aminocarbene ligation: synthesis, structure, and reactivity.

    PubMed

    Wang, Lei; Hu, Lianrui; Zhang, Hezhong; Chen, Hui; Deng, Liang

    2015-11-11

    High-valent iron imido species are implicated as reactive intermediates in many iron-catalyzed transformations. However, isolable complexes of this type are rare, and their reactivity is poorly understood. Herein, we report the synthesis, characterization, and reactivity studies on novel three-coordinate iron(IV) bisimido complexes with aminocarbene ligation. Using our recently reported synthetic method for [LFe(NDipp)2] (L = IMes, 1; Me2-cAAC, 2), four new iron(IV) imido complexes, [(IPr)Fe(NDipp)2] (3) and [(Me2-cAAC)Fe(NR)2] (R = Mes, 4; Ad, 5; CMe2CH2Ph, 6), were prepared from the reactions of three-coordinate iron(0) compounds with organic azides. Characterization data acquired from (1)H and (13)C NMR spectroscopy, (57)Fe Mössbauer spectroscopy, and X-ray diffraction studies suggest a low-spin singlet ground state for these iron(IV) complexes and the multiple-bond character of their Fe-N bonds. A reactivity study taking the reactions of 1 as representative revealed an intramolecular alkane dehydrogenation of 1 to produce the iron(II) complex [(IMes)Fe(NHDipp)(NHC6H3-2-Pr(i)-6-CMe═CH2)] (7), a Si-H bond activation reaction of 1 with PhSiH3 to produce the iron(II) complex [(IMes)Fe(NHDipp)(NDippSiPhH2)] (8), and a [2+2]-addition reaction of 1 with PhNCNPh and p-Pr(i)C6H4NCO to form the corresponding open-shell formal iron(IV) monoimido complexes [(IMes)Fe(NDipp)(N(Dipp)C(NPh)(═NPh))] (9) and [(IMes)Fe(NDipp)(N(Dipp)C(O)N(p-Pr(i)C6H4))] (10), as well as [NDipp]-group-transfer reactions with CO and Bu(t)NC. Density functional theory calculations suggested that the alkane chain dehydrogenation reaction starts with a hydrogen atom abstraction mechanism, whereas the Si-H activation reaction proceeds in a [2π+2σ]-addition manner. Both reactions have the pathways at the triplet potential energy surfaces being energetically preferred, and have formal iron(IV) hydride and iron(IV) silyl species as intermediates, respectively. The low-coordinate nature and low d

  5. Synthesis of 5-bromopyridyl-2-magnesium chloride and its application in the synthesis of functionalized pyridines.

    PubMed

    Song, Jinhua J; Yee, Nathan K; Tan, Zhulin; Xu, Jinghua; Kapadia, Suresh R; Senanayake, Chris H

    2004-12-23

    [reaction: see text] The 5-bromopyridyl-2-magnesium chloride (2), which was not accessible previously, was efficiently synthesized for the first time via an iodo-magnesium exchange reaction with 5-bromo-2-iodopyridine (1). This reactive intermediate was allowed to react with a variety of electrophiles to afford a range of useful functionalized pyridine derivatives. Application of this methodology to 5-bromo-2-iodo-3-picoline provided a simple and economical synthesis of a key intermediate for the preparation of Lonafarnib, a potent anticancer agent.

  6. Synthesis and processing of composites by reactive metal penetration

    SciTech Connect

    Loehman, R.E.; Ewsuk, K.G.; Tomsia, A.P.

    1995-05-01

    Ceramic-metal composites are being developed because their high stiffness-to weight ratios, good fracture toughness, and variable electrical and thermal properties give them advantages over more conventional materials. However, because ceramic-metal composite components presently are more expensive than monolithic materials, improvements in processing are required to reduce manufacturing costs. Reactive metal penetration is a promising new method for making ceramic- and metal-matrix composites that has the advantage of being inherently a net-shape process. This technique, once fully developed, will provide another capability for manufacturing the advanced ceramic composites that are needed for many light-weight structural and wear applications. The lower densities of these composites lead directly to energy savings in use. Near-net-shape fabrication of composite parts should lead to additional savings because costly and energy intensive grinding and machining operations are significantly reduced, and the waste generated from such finishing operations is minimized. The goals of this research program are: (1) to identify feasible compositional systems for making composites by reactive metal penetration; (2) to understand the mechanism(s) of composite formation by reactive metal penetration; and (3) to learn how to control and optimize reactive metal penetration for economical production of composites and composite coatings.

  7. [Tetrahydrobiopterin Synthesis and Biological Function].

    PubMed

    Wang, Zhuo-fei; Chen Jin-Wen; Tie, Lu; Li, Xue-Jun

    2015-08-01

    Tetrahydrobiopterin (BH4) is an essential cofactor for aromatic amino acid hydroxylases and all three nitric oxide synthase (NOS) isoforms. It has protective effects as an antioxidant and scavenger of reactive nitrogen and oxygen species. It also serves as a cofactor in both normal physiologic and pathological states. In conditions of BH4 deficiency, endothelial nitric oxide synthase (eNOS) becomes 'uncoupled', which leads to endothelial dysfunction in diabetes, pulmonary hypertension and pathologic cardiac remodeling. In this review, we will discuss the pathophysiological role of BH4 in those diseases mentioned above. PMID:26669076

  8. Integrated reactive absorption process for synthesis of fatty esters.

    PubMed

    Kiss, Anton Alexandru; Bildea, Costin Sorin

    2011-01-01

    Reactive separations using green catalysts offer great opportunities for manufacturing fatty esters, involved in specialty chemicals and biodiesel production. Integrating reaction and separation into one unit provides key benefits such as: simplified operation, no waste, reduced capital investment and low operating costs. This work presents a novel heat-integrated reactive absorption process that eliminates all conventional catalyst related operations, efficiently uses the raw materials and equipment, and considerably reduces the energy requirements for biodiesel production--85% lower as compared to the base case. Rigorous simulations based on experimental results were carried out using Aspen Plus and Dynamics. Despite the high degree of integration, the process is well controllable using an efficient control structure proposed in this work. The main results are provided for a plant producing 10 ktpy fatty acid methyl esters from methanol and waste vegetable oil with high free fatty acids content, using sulfated zirconia as solid acid catalyst.

  9. Reactive gas condensation synthesis of aluminum nitride nanoparticles.

    PubMed

    Baker, Colin C; Ceylan, Abdullah; Shah, S Ismat

    2006-01-01

    Aluminum Nitride (AIN) nanoparticles were synthesized using a Reactive Gas Condensation (RGC) technique in which a mixture of ammonia (NH3) and nitrogen (N2) gases were used for the nitridation of aluminum. NH3 served as the reactive gas, while N2 served as both a carrier gas and the inert source for particle condensation. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that at reactive gas compositions greater than 10% NH3 in N2, samples were composed entirely of hexagonal AIN nanoparticles. Electron diffraction patterns showed single crystal hexagonal AIN structure. The particle size was controlled by varying the pressure of the gas mixture. AIN nanoparticles were dispersed in a liquid matrix to enhance thermal conductivity. Results showed that a minimal addition of AIN increased the thermal conductivity of hydrocarbon pump oil by approximately 27%. The thermal conductivity became constant after reaching a maximum above 0.01 wt% AIN. Temporal stability of AIN was studied by XRD. Samples exposed to air for extended periods of time and analyzed by XRD show no degradation of crystalline AIN nanoparticles.

  10. Unprecedented copper(I) bifluoride complexes: synthesis, characterization and reactivity.

    PubMed

    Vergote, Thomas; Nahra, Fady; Welle, Alexandre; Luhmer, Michel; Wouters, Johan; Mager, Nathalie; Riant, Olivier; Leyssens, Tom

    2012-01-16

    To be or not to bifluoride: Two synthetic pathways to unprecedented N-heterocyclic carbene copper(I) bifluoride complexes have been developed. Catalytic tests demonstrated that copper(I) bifluorides are very efficient catalysts, which do not require any additional activating agent. The first Cu-catalyzed diastereoselective allylation of (R)-N-tert-butanesulfinyl aldimines was also established. The method enables efficient, simple and general synthesis of enantiomerically enriched homoallylic amines at room temperature in high yields.

  11. Synthesis and processing of composites by reactive metal penetration

    SciTech Connect

    Loehman, R.E.; Ewsuk, K.G.; Tomsia, A.P.

    1997-04-01

    Achieving better performance in commercial products and processes often is dependent on availability of new and improved materials. Ceramic-metal composites have advantages over more conventional materials because of their high stiffness-to-weight ratios, good fracture toughness, and because their electrical and thermal properties can be varied through control of their compositions and microstructures. However, ceramic composites will be more widely used only when their costs are competitive with other materials and when designers have more confidence in their reliability. Over the past four years reactive metal penetration has been shown to be a promising technique for making ceramic and metal-matrix composites to near-net-shape with control of both composition and microstructure. It appears that, with sufficient development, reactive metal penetration could be an economical process for manufacturing many of the advanced ceramic composites that are needed for light-weight structural and wear applications for transportation and energy conversion devices. Near-net-shape fabrication of parts is a significant advantage because costly and energy intensive grinding and machining operations are substantially reduced, and the waste generated from such finishing operations is minimized. The most promising compositions to date consist of Al and Al{sub 2}O{sub 3}; thus, these composites should be of particular interest to the aluminum industry. The goals of this ceramic-metal composite research and development program are: (1) to identify compositions favorable for making composites by reactive metal penetration; (2) to understand the mechanism(s) by which these composites are formed; (3) to control and optimize the process so that composites and composite coatings can be made economically; and (4) to apply R&D results to problems of interest to the aluminum industry.

  12. Reactive multilayer synthesis of hard ceramic foils and films

    DOEpatents

    Makowiecki, Daniel M.; Holt, Joseph B.

    1996-01-01

    A method for synthesizing hard ceramic materials such as carbides, borides nd aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. The method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coild as a tape for later use.

  13. Reactive multilayer synthesis of hard ceramic foils and films

    DOEpatents

    Makowiecki, D.M.; Holt, J.B.

    1996-02-13

    A method is disclosed for synthesizing hard ceramic materials such as carbides, borides and aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. The method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coiled as a tape for later use.

  14. Synthesis of belite cement clinker of high hydraulic reactivity

    SciTech Connect

    Kacimi, Larbi Simon-Masseron, Angelique Salem, Souria Ghomari, Abdelhamid Derriche, Zoubir

    2009-07-15

    This study is concerned with the increase of the cooling rate of belite clinker, by using the water quenching for the chemical stabilization of reactive belite, which improves the hydraulic properties of this clinker. The addition of adequate mineralizers, as NaF and Fe{sub 2}O{sub 3}, contributes to the improvement of the clinker properties obtained at low burning temperature. X-ray fluorescence spectroscopy, X-ray diffraction analysis and optical microscopy were used to determine the chemical and mineralogical compositions of this clinker. The samples were analyzed by means of a scanning electronic microscope connected with an energy-dispersive X-ray spectrometer to detect the composition of the belite phase and its morphology. Physical and mechanical properties of this clinker cement were determined. The results show that the belite clinker obtained at 1150 {sup o}C, with lime saturation factor 0.67, is characterized by a great hydraulic reactivity, similar to that of the ordinary alite clinker. The addition of 2% of NaF and the water quenching improved the chemical, mineralogical and structural properties, while improving the cement hydraulic properties.

  15. Synthesis and Reactivity of 4′-Deoxypentenosyl Disaccharides

    PubMed Central

    2015-01-01

    4-Deoxypentenosides (4-DPs) are versatile synthons for rare or higher-order pyranosides, and they provide an entry for structural diversification at the C5 position. Previous studies have shown that 4-DPs undergo stereocontrolled DMDO oxidation; subsequent epoxide ring-openings with various nucleophiles can proceed with both anti or syn selectivity. Here, we report the synthesis of α- and β-linked 4′-deoxypentenosyl (4′-DP) disaccharides, and we investigate their post-glycosylational C5′ additions using the DMDO oxidation/ring-opening sequence. The α-linked 4′-DP disaccharides were synthesized by coupling thiophenyl 4-DP donors with glycosyl acceptors using BSP/Tf2O activation, whereas β-linked 4′-DP disaccharides were generated by the decarboxylative elimination of glucuronyl disaccharides under microwave conditions. Both α- and β-linked 4′-DP disaccharides could be epoxidized with high stereoselectivity using DMDO. In some cases, the α-epoxypentenosides could be successfully converted into terminal l-iduronic acids via the syn addition of 2-furylzinc bromide. These studies support a novel approach to oligosaccharide synthesis, in which the stereochemical configuration of the terminal 4′-DP unit is established at a post-glycosylative stage. PMID:24797640

  16. In Situ synthesis of self-assembled gold nanoparticles on glass or silicon substrates through reactive inkjet printing.

    PubMed

    Abulikemu, Mutalifu; Da'as, Eman Husni; Haverinen, Hanna; Cha, Dongkyu; Malik, Mohammad Azad; Jabbour, Ghassan Elie

    2014-01-01

    A facile and low cost method for the synthesis of self-assembled nanoparticles (NPs) with minimal size variation and chemical waste by using reactive inkjet printing was developed. Gold NPs with diameters as small as (8±2) nm can be made at low temperature (120 °C). The size of the resulting NPs can be readily controlled through the concentration of the gold precursor and oleylamine ink. The pure gold composition of the synthesized NPs was confirmed by energy-dispersive X-ray spectroscopy (EDXS) analysis. High-resolution SEM (HRSEM) and TEM (HRTEM), and X-ray diffraction revealed their size and face-centered cubic (fcc) crystal structure, respectively. Owing to the high density of the NP film, UV/Vis spectroscopy showed a red shift in the intrinsic plasmonic resonance peak. We envision the extension of this approach to the synthesis of other nanomaterials and the production of tailored functional nanomaterials and devices.

  17. Synthesis and Reactivity Studies of α,α-Difluoromethylphosphinates

    PubMed Central

    Abrunhosa-Thomas, Isabelle; Coudray, Laëtitia

    2010-01-01

    The preparation and reactivity of some α,α-difluorophosphinates is investigated. Alkylation of H-phosphinates with LiHMDS and ClCF2H gives the corresponding α,α-difluorophosphinates in good yield. Deprotonation of these reagents with alkyllithium or LDA is then studied. Subtle electronic effects translate into significant differences in the deprotonation/alkylation of the two “Ciba-Geigy reagents” (EtO)2CRP(O)(OEt)H (R = H, Me). On the other hand, attempted methylation of difluoromethyl-octyl-phosphinic acid butyl ester resulted in the exclusive alkylation of the octyl chain. Finally, reaction with carbonyl compounds results in the formation of 1,1-difluoro-2-phosphinoyl compounds. PMID:20725593

  18. Isolable aryl-substituted silyl radicals: synthesis, characterization, and reactivity.

    PubMed

    Taira, Kanako; Ichinohe, Masaaki; Sekiguchi, Akira

    2014-07-21

    Isolable aryl-substituted silyl radicals (tBu2 MeSi)2(Ar)Si(·) (Ar = C6H5, 4-tBuC6H4, 4-PhC6H4, 3,5-tBu2C6H3) were synthesized by the reaction of the corresponding iodosilane with an equimolar amount of potassium graphite (KC8 ) in tetrahydrofuran (THF). The crystal structure of 3,5-tBu2C6H3 derivative, which was determined by X-ray crystallography, showed a planar geometry around the Si atom for the radical center. EPR studies of all four radicals revealed the lack of the delocalization of the unpaired electron over the aromatic ring. Reactivity and spectroscopic studies of the less-hindered phenyl-substituted silyl radical showed that it exists as an equilibrium mixture of the radical and its silene-type dimer in solution. PMID:24909557

  19. Reactivity of Graphene Investigated by Density-Functional Theory

    NASA Astrophysics Data System (ADS)

    Soni, Himadri; Gebhardt, Julian; Görling, Andreas; Chair of Theoretical Chemistry Team

    Using spin-polarized density-functional theory, we study the adsorption and reaction of hydrogen and fluorine with graphene. Graphene has a bipartite lattice with two different sublattices and hence, due to Lieb's theorem, the inequality between two sublattices should lead to a net magnetic moment upon adsorption of hydrogen or fluorine. Our calculations using density-functional theory with the generalized gradient approximation predict a magnetic moment of 1 µB for a single hydrogen adsorbed on graphene but not for a single fluorine atom adsorbed on graphene. Switching to hybrid density-functional theory with the HSE functional, we obtain a magnetic moment of 1 µB for of a single fluorine atom adsorption on graphene. This is in line with work of Kim et al., who also found in density-functional theory calculations with the HSE exchange-correlation functional spin-polarization for a fluorine adatom on graphene. Here, we present a systematic study of the reactivity and relevant adsorption mechanism for single-sided graphene, i.e., a graphene sheet which is accessible by an adsorbate from only one side with hydrogen and fluorine using hybrid density-functional theory. German Research Council (DFG) by the Collaborative Research Center 953.

  20. Synthesis of α-Functionalized Trichloromethylcarbinols.

    PubMed

    Ram, Ram N; Soni, Vineet Kumar

    2015-09-01

    A new series of α-functionalized trichloromethylcarbinols have been synthesized from corresponding α-halomethyl ketones, esters, and amides in 48-78% overall yields. Reactivity of nitrates obtained in the first step was dependent on the electron-withdrawing nature of the functional groups, and increases with increasing electron deficiency. Synthetic applications of such trichloromethylcarbinols for the preparation of chloromethyl-α-diketones, trichloromethylated dihydrofurans, and enol acetates of α-functionalized acid chlorides have been demonstrated. The reaction of these compounds in the Jocic-Reeve reaction was also demonstrated. PMID:26263239

  1. Sterically demanding hetero-substituted [2]borametallocenophanes of group IV metals: synthesis, structure and reactivity.

    PubMed

    Braunschweig, Holger; Dörfler, Rainer; Mies, Jan; Oechsner, Andreas

    2011-10-17

    We report the synthesis and characterisation of unprecedented unstrained [2]diborametallocenophanes of zirconium and hafnium that bear the bulky octamethylfluorenyl (η(5)-C(29)H(36)) system, the proligands of which were pre-constructed by a two-step synthesis. The compounds were fully characterised by NMR spectroscopy, MALDI-TOF mass spectrometry and X-ray diffraction analysis. Typical reactivities relevant to olefin polymerisation such as methylation and chloride abstraction were also investigated. Finally, a sterically demanding bis(octamethylfluorenyl) metallocene was prepared.

  2. Water-free synthesis of polyurethane foams using highly reactive diisocyanates derived from 5-hydroxymethylfurfural.

    PubMed

    Neumann, Christopher N D; Bulach, Winfried D; Rehahn, Matthias; Klein, Roland

    2011-09-01

    This paper reports on the synthesis of a new highly reactive diisocyanate monomer based on hydroxymethylfurfural. It further describes its catalyst-free conversion to linear-chain thermoplastic polyurethanes as well as to cross-linked polyurethane foams. In addition, a novel strategy for the synthesis of polyurethane foams without the necessity of using water is developed. Nitrogen is utilized herein as blowing agent which is formed during Curtius rearrangement of a new furan based carboxylic azide into its corresponding diisocyanate. PMID:21842508

  3. The disulfide proteome and other reactive cysteine proteomes: analysis and functional significance.

    PubMed

    Lindahl, Marika; Mata-Cabana, Alejandro; Kieselbach, Thomas

    2011-06-15

    Ten years ago, proteomics techniques designed for large-scale investigations of redox-sensitive proteins started to emerge. The proteomes, defined as sets of proteins containing reactive cysteines that undergo oxidative post-translational modifications, have had a particular impact on research concerning the redox regulation of cellular processes. These proteomes, which are hereafter termed "disulfide proteomes," have been studied in nearly all kingdoms of life, including animals, plants, fungi, and bacteria. Disulfide proteomics has been applied to the identification of proteins modified by reactive oxygen and nitrogen species under stress conditions. Other studies involving disulfide proteomics have addressed the functions of thioredoxins and glutaredoxins. Hence, there is a steadily growing number of proteins containing reactive cysteines, which are probable targets for redox regulation. The disulfide proteomes have provided evidence that entire pathways, such as glycolysis, the tricarboxylic acid cycle, and the Calvin-Benson cycle, are controlled by mechanisms involving changes in the cysteine redox state of each enzyme implicated. Synthesis and degradation of proteins are processes highly represented in disulfide proteomes and additional biochemical data have established some mechanisms for their redox regulation. Thus, combined with biochemistry and genetics, disulfide proteomics has a significant potential to contribute to new discoveries on redox regulation and signaling.

  4. An experimental evaluation of the instrumented flux synthesis method for the real-time estimation of reactivity. Final report

    SciTech Connect

    Hughes, J.C.; Henry, A.F.; Lanning, D.D.; Bernard, J.A.

    1996-01-01

    One method of determining the flux density is flux synthesis which approximates the flux in the core by linear combinations of precomputed shape functions. In traditional flux synthesis, the unknown mixing coefficients are determined using a weighted residual method of solving the diffusion equation. In the instrumented synthesis method, the mixing coefficients are determined using count rates from neutron detectors in the core. In this way the mixing coefficients are linked to conditions in the reactor. Using the synthesized flux, kinetics parameters, notably reactivity, can be calculated in real time. An experimental evaluation has been performed in the Massachusetts Institute of Technology Reactor, MITR-II. Detector measurements have been collected using fission chambers placed at the periphery of the core. The reactor was put into a number of various conditions, both static and transient, and data were collected using a digital acquisition system for later combination with shape functions. Transients included increasing power, decreasing power, and a reactor scram. The shape functions were generated using Version 3.0 of the QUARTZ code, a quadratic nodal diffusion theory code in triangular-Z geometry. Supernodal analysis algorithms have been added to the original program, along with subroutines to guarantee diagonal dominance of the leakage matrix in the finite difference or quadratic current approximations in the coarse mesh. The agreement between coarse mesh and fine mesh in all cases is excellent, with finite difference coarse mesh solutions generally slightly better. The synthesis method has been shown to accurately reflect the changes from an initial condition by combining representative flux shapes. It can be concluded that, with proper calibration of the measurement system and inclusion of representative flux shapes, the instrumented synthesis method will properly predict the flux in the core under a number of conditions.

  5. Dithiolopyranthione Synthesis, Spectroscopy and an Unusual Reactivity with DDQ

    PubMed Central

    Pimkov, Igor V.; Nigam, Archana; Venna, Kiran; Solntsev, Pavlo V.; Nemykin, Victor N.

    2014-01-01

    The bicyclic pyran thiolone tetrahydro-3αH-[1,3]dithiolo[4,5-β]pyran-2-thione (3a) engages in a highly unusual fragmentation in the presence of DDQ. The pyran thiolone, 3a, was synthesized by chlorination of 3,4-dihydro-2H-pyran (1), followed by condensing with CS2 and NaSH. Reaction of 3a with DDQ generates the isomerized pyran thiolone tetrahydro-3αH-[1,3]dithiolo[4,5-β]pyran-2-thione (3b) and 4-benzyl-5-(3-hydroxypropyl)-1,3-dithiole-2-thione (4) via a deep-seated rearrangement. The identity of 3b was confirmed by single crystal X-ray analysis: P21/c, a=5.807(9) Å, b = 12.99(2) Å, c = 11.445(15), β=113.23(6)°. Mechanistic experiments and computational insight is used to explain the likely sequence of events in the highly unusual formation of 4. Collectively, these results establish fundamental reactivity patterns for further research in this area. PMID:25328243

  6. Synthesis and Regioselective Functionalization of Perhalogenated BODIPYs

    PubMed Central

    Zhao, Ning; Xuan, Sunting; Byrd, Brandon; Fronczek, Frank R.; Smith, Kevin M.

    2016-01-01

    Three perhalogenated BODIPYs (1b–3b), bearing chloro and bromo groups at all carbon positions, were synthesized and characterized. The reactivity of BODIPY 3b was investigated under Stille cross-coupling reactions, and single crystal X-ray analysis was used to confirm the regioselectivity of the reactions. Further substitution at the boron atom produced nona-functionalized BODIPYs 7a,b, which show 676 and 739 nm emissions with 91 and 100 nm Stokes shifts, respectively. PMID:27251595

  7. Cp*Co(IPr): synthesis and reactivity of an unsaturated Co(i) complex.

    PubMed

    Andjaba, John M; Tye, Jesse W; Yu, Pony; Pappas, Iraklis; Bradley, Christopher A

    2016-02-11

    Synthesis of coordinatively unsaturated Cp*Co(IPr) (2), is accomplished by addition of free N-heterocyclic carbene IPr to [(Cp*Co)2-μ-(η(4):η(4)-toluene)] (1). Stoichiometric reactivity is consistent with a 16 electron species, as 2 undergoes ligand addition/NHC displacement and reversible reaction with dihydrogen. Cp*Co(IPr) represents an elusive example of a stable Cp*CoL fragment.

  8. Low-reactive circulating fluidized bed combustion (CFBC) fly ashes as source material for geopolymer synthesis

    SciTech Connect

    Xu Hui; Li Qin; Shen Lifeng; Zhang Mengqun; Zhai Jianping

    2010-01-15

    In this contribution, low-reactive circulating fluidized bed combustion (CFBC) fly ashes (CFAs) have firstly been utilized as a source material for geopolymer synthesis. An alkali fusion process was employed to promote the dissolution of Si and Al species from the CFAs, and thus to enhance the reactivity of the ashes. A high-reactive metakaolin (MK) was also used to consume the excess alkali needed for the fusion. Reactivities of the CFAs and MK were examined by a series of dissolution tests in sodium hydroxide solutions. Geopolymer samples were prepared by alkali activation of the source materials using a sodium silicate solution as the activator. The synthesized products were characterized by mechanical testing, scanning electron microscopy (SEM), X-ray diffractography (XRD), as well as Fourier transform infrared spectroscopy (FTIR). The results of this study indicate that, via enhancing the reactivity by alkali fusion and balancing the Na/Al ratio by additional aluminosilicate source, low-reactive CFAs could also be recycled as an alternative source material for geopolymer production.

  9. Low-reactive circulating fluidized bed combustion (CFBC) fly ashes as source material for geopolymer synthesis.

    PubMed

    Xu, Hui; Li, Qin; Shen, Lifeng; Zhang, Mengqun; Zhai, Jianping

    2010-01-01

    In this contribution, low-reactive circulating fluidized bed combustion (CFBC) fly ashes (CFAs) have firstly been utilized as a source material for geopolymer synthesis. An alkali fusion process was employed to promote the dissolution of Si and Al species from the CFAs, and thus to enhance the reactivity of the ashes. A high-reactive metakaolin (MK) was also used to consume the excess alkali needed for the fusion. Reactivities of the CFAs and MK were examined by a series of dissolution tests in sodium hydroxide solutions. Geopolymer samples were prepared by alkali activation of the source materials using a sodium silicate solution as the activator. The synthesized products were characterized by mechanical testing, scanning electron microscopy (SEM), X-ray diffractography (XRD), as well as Fourier transform infrared spectroscopy (FTIR). The results of this study indicate that, via enhancing the reactivity by alkali fusion and balancing the Na/Al ratio by additional aluminosilicate source, low-reactive CFAs could also be recycled as an alternative source material for geopolymer production.

  10. Synthesis and Reactivity of Tripodal Complexes Containing Pendant Bases

    SciTech Connect

    Blacquiere, Johanna M.; Pegis, Michael L.; Raugei, Simone; Kaminsky, Werner; Forget, Amelie; Cook, Sarah; Taguchi, Taketo; Borovik, Andrew S.; Mayer, James M.

    2014-09-02

    The synthesis of a new tripodal ligand family is reported, with tertiary-amine groups in the second-coordination sphere. The ligands are tris(amido)amine derivatives, with the pendant amines attached via a peptide coupling strategy. They were designed to be used in new catalysts for the oxygen reduction reaction (ORR), in which the pendant acid/base group could improve catalyst performance. Two members of the new ligand family were each metallated with Co(II) and Zn(II) to afford trigonal monopyramidal complexes. Reaction of the cobalt complexes, [Co(L)]-, with dioxygen reversibly generates a small amount of a Co(III)-superoxo species, which was characterized by EPR. Protonation of the zinc complex Zn[N{CH2CH2NC(O)CH2N(CH2Ph)2}3)-– ([Zn(TNBn)]-) with one equivalent of acid occurs with displacement and dissociation of an amide ligand. Addition of excess acid to the any of the complexes [M(L)]- results in complete proteolysis and formation of the ligands H3L. This decomposition limits the use of these complexes as catalysts for the ORR. An alternative ligand with two pyridyl arms was also prepared but could not be metallated. These studies highlight the importance of stability of the primary-coordination sphere of ORR electrocatalysts to both oxidative and acidic conditions. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  11. Synthesis, characterization, and reactivity of sulfided hexanuclear molybdenum cluster compounds

    SciTech Connect

    Spink, D.

    1990-09-21

    Hexanuclear molybdenum clusters with mixed chloride and sulfide bridging ligands were prepared by reacting {alpha}-MoCl{sub 2} with sodium hydrosulfide in the presence of sodium butoxide. The resulting species, Mo{sub 6}Cl{sub (8-x)}S{sub x}{center dot}npy(x {congruent} 3.6, n {congruent} 4, py = pyridine), was pyrophoric and insoluble. The mixed sulfide chloride cluster species Mo{sub 6}S{sub 4}Cl{sub 4}{center dot}6OPEt{sub 3} and Mo{sub 6}S{sub {approximately}5}Cl{sub {approximately}3}{center dot}6PEt{sub 3} and Mo{sub 6}S{sub 8}{center dot}6PEt{sub 3} were isolated and characterized. Phosphorus-31 nuclear magnetic resonance, electron paramagnetic resonance, and UV/visible spectra were obtained for each fraction. The completely sulfided cluster, Mo{sub 6}S{sub 8}{center dot}6PEt{sub 3}, was prepared similarly and used in various experiments as a possible precursor to Chevrel phase materials of the type Mo{sub 6}S{sub 8}or M{sub n}Mo{sub 6}S{sub 8}. With the goal of removing all of the triethylphosphine ligands, Mo{sub 6}S{sub 8}{center dot}6PEt{sub 3} was reacted with the transition metal carbonyls molybdenum hexacarbonyl and dicobalt octacarbonyl. Reaction on the molecular sulfide cluster with copper(I) chloride in toluene gave a completely insoluble product. The reaction of Mo{sub 6}S{sub 8}{center dot}6PEt{sub 3} with propylene sulfide gave a product whose infrared spectra showed only very weak peaks associated with coordinated triethylphosphine. The elemental analysis of this product fit the formula Mo{sub 6}S{sub 8}{center dot}5SPEt{sub 3}. Reactivity of the outer ligands of the Mo{sub 6}S{sub 8}{center dot}npy and Mo{sub 6}S{sub 8}{center dot}(6{minus}x)PrNH{sub x} clusters were investigated. Crystalline Mo{sub 6}S{sub 8}{center dot}6THT was recovered from the reaction of the n-propylamine derivative with THT. A crystal structure determination was done. 87 refs., 12 fig., 15 tabs.

  12. Applications of the Conceptual Density Functional Theory Indices to Organic Chemistry Reactivity.

    PubMed

    Domingo, Luis R; Ríos-Gutiérrez, Mar; Pérez, Patricia

    2016-01-01

    Theoretical reactivity indices based on the conceptual Density Functional Theory (DFT) have become a powerful tool for the semiquantitative study of organic reactivity. A large number of reactivity indices have been proposed in the literature. Herein, global quantities like the electronic chemical potential μ, the electrophilicity ω and the nucleophilicity N indices, and local condensed indices like the electrophilic P k + and nucleophilic P k - Parr functions, as the most relevant indices for the study of organic reactivity, are discussed. PMID:27294896

  13. Applications of the Conceptual Density Functional Theory Indices to Organic Chemistry Reactivity.

    PubMed

    Domingo, Luis R; Ríos-Gutiérrez, Mar; Pérez, Patricia

    2016-06-09

    Theoretical reactivity indices based on the conceptual Density Functional Theory (DFT) have become a powerful tool for the semiquantitative study of organic reactivity. A large number of reactivity indices have been proposed in the literature. Herein, global quantities like the electronic chemical potential μ, the electrophilicity ω and the nucleophilicity N indices, and local condensed indices like the electrophilic P k + and nucleophilic P k - Parr functions, as the most relevant indices for the study of organic reactivity, are discussed.

  14. Synthesis, reactivity and application studies for different biolubricants

    PubMed Central

    2014-01-01

    Vegetable oils have different unique properties owing to their unique chemical structure. Vegetable oils have a greater ability to lubricate and have higher viscosity indices. Therefore, they are being more closely examined as base oil for biolubricants and functional fluids. In spite of their many advantages, vegetable oils suffer from two major drawbacks of inadequate oxidative stability and poor low-temperature properties, which hinder their utilization as biolubricant base oils. Transforming alkene groups in fatty acids to other stable functional groups could improve the oxidative stability, whereas reducing structural uniformity of the oil by attaching alkyl side chains could improve the low-temperature performance. In that light, the epoxidation of unsaturated fatty acids is very interesting as it can provide diverse side chains arising from the mono- or di-epoxidation of the unsaturated fatty acid. Oxirane ring opening by an acid-catalyzed reaction with a suitable reagent provides interesting polyfunctional compounds. PMID:24612780

  15. Acrolein stimulates the synthesis of IL-6 and C-reactive protein (CRP) in thrombosis model mice and cultured cells.

    PubMed

    Saiki, Ryotaro; Hayashi, Daisuke; Ikuo, Yukiko; Nishimura, Kazuhiro; Ishii, Itsuko; Kobayashi, Kaoru; Chiba, Kan; Toida, Toshihiko; Kashiwagi, Keiko; Igarashi, Kazuei

    2013-12-01

    Measurements of protein-conjugated acrolein (PC-Acro), IL-6, and C-reactive protein (CRP) in plasma were useful for identifying silent brain infarction with high sensitivity and specificity. The aim of this study was to determine whether acrolein causes increased production of IL-6 and CRP in thrombosis model mice and cultured cells. In mice with photochemically induced thrombosis, acrolein produced at the locus of infarction increased the level of IL-6 and then CRP in plasma. This was confirmed in cell culture systems - acrolein stimulated the production of IL-6 in mouse neuroblastoma Neuro-2a cells, mouse macrophage-like J774.1 cells, and human umbilical vein endothelial cells (HUVEC), and IL-6 in turn stimulated the production of CRP in human hepatocarcinoma cells. The level of IL-6 mRNA was increased by acrolein through an increase in phosphorylation of the transcription factors, c-Jun, and NF-κB p65. Furthermore, CRP stimulated IL-6 production in mouse macrophage-like J774.1 cells and HUVEC. IL-6 functioned as a protective factor against acrolein toxicity in Neuro-2a cells and HUVEC. These results show that acrolein stimulates the synthesis of IL-6 and CRP, which function as protecting factors against acrolein toxicity, and that the combined measurement of PC-Acro, IL-6, and CRP is effective for identification of silent brain infarction. The combined measurements of protein-conjugated acrolein (PC-Acro), IL-6, and C-reactive protein (CRP) in plasma were useful for identifying silent brain infarction. The aim of this study was to determine whether acrolein causes increased production of IL-6 and CRP, and indeed acrolein increased IL-6 synthesis and IL-6 in turn increased CRP synthesis. Furthermore, IL-6 decreased acrolein toxicity in several cell lines.

  16. Diversity-oriented synthesis leads to an effective class of bifunctional linchpins uniting anion relay chemistry (ARC) with benzyne reactivity.

    PubMed

    Smith, Amos B; Kim, Won-Suk

    2011-04-26

    In conjunction with the construction of a diversity-oriented synthesis library of 10-membered ring "natural product-like" macrolides, the design, synthesis, and validation of a unique class of bifunctional linchpins, uniting benzyne reactivity initiated by type II anion relay chemistry (ARC) has been achieved, permitting access to diverse [2+2], [3+2], and [4+2] cycloadducts.

  17. Zero Valent Iron: Impact of Anions Present during Synthesis on Subsequent Nanoparticle Reactivity

    SciTech Connect

    Moore, Kirsten; Forsberg, Brady; Baer, Donald R.; Arnold, William A.; Penn, R. Lee

    2011-10-01

    Zero-valent iron particles are an effective remediation technology for groundwater contaminated with halogenated organic compounds. In particular, nano-scale zero-valent iron is a promising material for remediation due to its high specific surface area, which results in faster rate constants and more effective use of the iron. An aspect of iron nanoparticle reactivity that has not been explored is the impact of anions present during iron metal nanoparticle synthesis. Solutions containing chloride, phosphate, sulfate, and nitrate anions and ferric ions were used to generate iron oxide nanoparticles. The resulting materials were dialyzed to remove dissolved byproducts and then dried and reduced by hydrogen gas at high temperature. The reactivity of the resulting zero valent iron nanoparticles was quantified by monitoring the kinetics as well as products of carbon tetrachloride reduction, and significant differences in reactivity and chloroform yield were observed. The reactivity of nanoparticles prepared in the presence of sulfate and phosphate demonstrated the highest reactivity and chloroform yield. Furthermore, substantial variations in the solid-state products of oxidation (magnetite, iron sulfide, and goethite, among others) were also observed.

  18. Reactivities of vinyl azides and their recent applications in nitrogen heterocycle synthesis

    PubMed Central

    Hu, Bao; DiMagno, Stephen G.

    2015-01-01

    Nitrogen heterocycles are abundant in natural products and pharmaceuticals. An emerging interest among synthetic chemists is to apply vinyl azides as a pivotal three-atom synthon for the construction of structurally complex and diverse N-heterocyclic skeletons. The unique features of the azide group connected to an alkene moiety permit vinyl azides to function as electrophiles, nucleophiles, or radical acceptors; their access to diverse reaction pathways provides great opportunities to generate highly reactive intermediates with often unusual or unconventional reactivities. This tutorial review will systematically illustrate the reactivities of vinyl azides and describe recent breakthroughs in the development of new transformations that create N-heterocycles. PMID:25731154

  19. Functional models of α-keto acid dependent nonheme iron oxygenases: synthesis and reactivity of biomimetic iron(II) benzoylformate complexes supported by a 2,9-dimethyl-1,10-phenanthroline ligand.

    PubMed

    Das, Oindrila; Chatterjee, Sayanti; Paine, Tapan Kanti

    2013-03-01

    Two biomimetic iron(II) benzoylformate complexes, [LFe(II)(BF)(2)] (2) and [LFe(II)(NO(3))(BF)] (3) (L is 2,9-dimethyl-1,10-phenanthroline and BF is monoanionic benzoylformate), have been synthesized from an iron(II)-dichloro complex [LFe(II)Cl(2)] (1). All the iron(II) complexes have been structurally and spectroscopically characterized. The iron(II) center in 2 is coordinated by a bidentate NN ligand (2,9-dimethyl-1,10-phenanthroline) and two monoanionic benzoylformates to form a distorted octahedral coordination geometry. One of the benzoylformates binds to the iron in 2 via both carboxylate oxygens but the other one binds in a chelating bidentate fashion via one carboxylate oxygen and the keto oxygen. On the other hand, the iron(II) center in 3 is ligated by one NN ligand, one bidentate nitrate, and one monoanionic chelating benzoylformate. Both iron(II) benzoylformate complexes exhibit the facial NNO donor environment in their solid-state structures. Complexes 2 and 3 are stable in noncoordinating solvents under an inert atmosphere, but react with dioxygen under ambient conditions to undergo oxidative decarboxylation of benzoylformate to benzoate in high yields. Evidence for the formation of an iron(IV)-oxo intermediate upon oxidative decarboxylation of benzoylformate was obtained by interception and labeling experiments. The iron(II) benzoylformate complexes represent the functional models of α-keto acid dependent oxygenases.

  20. Synthesis of Strophasterol A Guided by a Proposed Biosynthesis and Innate Reactivity.

    PubMed

    Heinze, Robert C; Lentz, Dieter; Heretsch, Philipp

    2016-09-12

    The synthesis of strophasterol A, a moderator of endoplasmatic reticulum (ER) stress in Alzheimer's disease, and the first member of a structurally unprecedented class of secosterols, was achieved through the implementation of a key step of its proposed biosynthesis and two C-H oxidations. Analysis of the innate reactivity of the intermediates enabled the identification of a novel way to prepare an α-chloro-γ-hydroxy-δ-keto enone, as well as its vinylogous α-ketol rearrangement to a δ-keto carboxylic acid. PMID:27530462

  1. Synthesis and reactivities of cubane-type sulfido clusters containing noble metals.

    PubMed

    Hidai, M; Kuwata, S; Mizobe, Y

    2000-01-01

    Cubane-type sulfido clusters containing noble metals are newcomers compared with the corresponding clusters of the first transition series metals and molybdenum, which have been extensively studied in relation to metalloenzymes and industrial hydrodesulfurization catalysts. This Account reviews the recent progress in studies on the synthesis and reactivities of these noble metal cubane-type clusters. One of the goals in this new area lies in development of the unique catalysis of the noble metals embedded in the robust and redox-active cubane-type cores. Rational synthetic approaches indispensable to the preparation of such effective cluster catalysts are discussed to a significant extent.

  2. Impact of C-reactive protein (CRP) on surfactant function

    SciTech Connect

    Li, J.J.; Sanders, R.L.; McAdam, K.P.; Hales, C.A.; Thompson, B.T.; Gelfand, J.A.; Burke, J.F. )

    1989-12-01

    Plasma levels of the acute-phase reactant, C-reactive protein (CRP), increase up to one thousand-fold as a result of trauma or inflammation. CRP binds to phosphorylcholine (PC) in a calcium-ion dependent manner. The structural homology between PC and the major phospholipid component of surfactant, dipalmitoyl phosphatidylcholine (DPPC), led to the present study in which we examined if CRP levels might be increased in patients with adult respiratory distress syndrome (ARDS), and subsequently interfere with surfactant function. Our results showed that CRP levels in the bronchoalveolar fluid (BALF) was increased in patients with ARDS (97.8 +/- 84.2 micrograms/mg total protein vs. 4.04 +/- 2.2 micrograms/mg total protein in normals). Our results show that CRP binds to liposomes containing DPPC and phosphatidylglycerol (PG). As a result of this interaction, CRP inhibits the surface activity of a PG-DPPC mixture when tested with a Wilhelmy surfactometer or with the Enhorning pulsating bubble apparatus. Furthermore, the surface activity of a clinically used surfactant replacement, Surfactant TA (2 mg/ml), was also severely impaired by CRP in a dose-dependent manner (doses used ranging from 24.5 to 1,175 micrograms/ml). In contrast, human serum albumin (HSA) at 500 and 900 micrograms/ml had no inhibitory effect on Surfactant TA surface activity. These results suggest that CRP, although not an initiating insult in ARDS, may contribute to the subsequent abnormalities of surfactant function and thus the pathogenesis of the pulmonary dysfunction seen in ARDS.

  3. Atherosclerosis-related functions of C-reactive protein

    PubMed Central

    Agrawal, Alok; Hammond, David J.; Singh, Sanjay K.

    2011-01-01

    C-reactive protein (CRP) is secreted by hepatocytes as a pentameric molecule made up of identical monomers, circulates in the plasma as pentamers, and localizes in atherosclerotic lesions. In some cases, localized CRP was detected by using monoclonal antibodies that did not react with native pentameric CRP but were specific for isolated monomeric CRP. It has been reported that, once CRP is bound to certain ligands, the pentameric structure of CRP is altered so that it can dissociate into monomers. Accordingly, the monomeric CRP found in atherosclerotic lesions may be a stationary, ligand-bound, by-product of a ligand-binding function of CRP. CRP binds to modified forms of low-density lipoprotein (LDL). The binding of CRP to oxidized LDL requires acidic pH conditions; the binding at physiological pH is controversial. The binding of CRP to enzymatically-modified LDL occurs at physiological pH; however, the binding is enhanced at acidic pH. Using enzymatically-modified LDL, CRP has been shown to prevent the formation of enzymatically-modified LDL-loaded macrophage foam cells. CRP is neither pro-atherogenic nor atheroprotective in ApoE−/− and ApoB100/100Ldlr −/− murine models of atherosclerosis, except in one study where CRP was found to be slightly atheroprotective in ApoB100/100Ldlr −/− mice. The reasons for the ineffectiveness of human CRP in murine models of atherosclerosis are not defined. It is possible that an inflammatory environment, such as those characterized by acidic pH, is needed for efficient interaction between CRP and atherogenic LDL during the development of atherosclerosis and to observe the possible atheroprotective function of CRP in animal models. PMID:20932269

  4. Synthesis, Characterization, and Reactivity Studies of Iron Complexes Supported by the Redox-Active [ONO] Ligand

    NASA Astrophysics Data System (ADS)

    Wong, Janice Lin

    The work reported herein primarily focuses on the development of new platforms for multi-electron reactivity using iron complexes supported by a redox-active pincer-type ligand. This dissertation details the synthesis, characterization, and reactivity of iron complexes coordinated to the redox-active [ONO] ([ONO]H3 = bis(3,5-di-tert-butyl-2-phenol)amine) ligand. Chapter 1 provides a general background on ligand-centered and metal-centered redox reactivity. Specifically, the characteristics of redox-active ligands and their ability to promote multi-electron reactivity at redox-inert metal centers is presented. In addition, iron-catalyzed organic transformations in which the metal center undergoes redox changes is also discussed. Finally, ligand-enabled redox reactions mediated by iron complexes containing redox-active ligands is described. Chapter 2 reports on the complexation of bis(3,5-di-tert-butyl-2-phenoxy)amine, [ONHO], and the redox-active [ONO] ligands by iron centers to afford a new family of iron complexes. Characterizations of each compound through a battery of analytical techniques reveal the oxidation states of the metal center and ligand. Furthermore, the electronic properties of each complex were investigated in order to evaluate their potential to facilitate multi-electron reactivity. Chapter 3 details the reactivity of the [ONO]Fe platform. Metathesis reactions are conducted with [ONOq]FeIIIX 2 (X = Cl, N[SiMe3]2) complexes, demonstrating the capability of the fully-oxidized [ONOq]1-- to act as a two-electron acceptor to generate the fully reduced [ONO cat]3-- that is coordinated to an iron(III) center. Similarly, oxidation of [ONOcat]FeIII(py) 3 (py = pyridine) using dihalogens result in two-electron oxidations of the tridentate ligand while the metal oxidation state remains the same. These redox reactions showcase the ability of the [ONO] ligand platform to undergo reversible two-electron oxidation state changes, allowing multi-electron reactivity

  5. Filtered density function approach for reactive transport in groundwater

    NASA Astrophysics Data System (ADS)

    Suciu, Nicolae; Schüler, Lennart; Attinger, Sabine; Knabner, Peter

    2016-04-01

    Spatial filtering may be used in coarse-grained simulations (CGS) of reactive transport in groundwater, similar to the large eddy simulations (LES) in turbulence. The filtered density function (FDF), stochastically equivalent to a probability density function (PDF), provides a statistical description of the sub-grid, unresolved, variability of the concentration field. Besides closing the chemical source terms in the transport equation for the mean concentration, like in LES-FDF methods, the CGS-FDF approach aims at quantifying the uncertainty over the whole hierarchy of heterogeneity scales exhibited by natural porous media. Practically, that means estimating concentration PDFs on coarse grids, at affordable computational costs. To cope with the high dimensionality of the problem in case of multi-component reactive transport and to reduce the numerical diffusion, FDF equations are solved by particle methods. But, while trajectories of computational particles are modeled as stochastic processes indexed by time, the concentration's heterogeneity is modeled as a random field, with multi-dimensional, spatio-temporal sets of indices. To overcome this conceptual inconsistency, we consider FDFs/PDFs of random species concentrations weighted by conserved scalars and we show that their evolution equations can be formulated as Fokker-Planck equations describing stochastically equivalent processes in concentration-position spaces. Numerical solutions can then be approximated by the density in the concentration-position space of an ensemble of computational particles governed by the associated Itô equations. Instead of sequential particle methods we use a global random walk (GRW) algorithm, which is stable, free of numerical diffusion, and practically insensitive to the increase of the number of particles. We illustrate the general FDF approach and the GRW numerical solution for a reduced complexity problem consisting of the transport of a single scalar in groundwater

  6. Synthesis and postmodification of functionally relevant organically modified silica particles

    NASA Astrophysics Data System (ADS)

    Brozek, Eric

    This thesis describes the synthesis and properties of organically modified silica (ORMOSIL) particles with possible applications in the field of drug delivery. Nanoparticle drug delivery methods take advantage of the unique physical properties of nanoscale architecture to deliver a large payload of drug to a targeted site. They are highly porous, contain many organic functionalities for covalent attachment, and their surfaces can be functionalized. A particle-based approach allows for the delivery of a large and localized payload in a single package. Initial study focused on the generation of submicron organically modified silica particles containing boron. This involved the synthesis of vinyl-enriched silica particles and the postmodification of the vinyl functionalities throughout the particle body. Hydroboration and bromination of the vinyl functionalities showed for the first time that the organic functionalities of ORMOSIL particles could be significantly modified. Next, new organically modified silica particle types were developed. These new particle types incorporated unique organic functionalities that may undergo additional functionalization. Organic functionalities included alkenyl-, cyano-, mercapto-, and isocyanto- throughout the particle body. The different organic functionalities were then modified to demonstrate their reactivity. Finally, a particle containing nuclei suitable for neutron capture therapy, a fluorescent tag, and targeting ligand was synthesized. Boron was the active nuclei, fluorescein was the fluorescent label, useful for in vitro studies, and folic acid is a broad field targeting ligand, useful in targeting a variety of cancer types. The particle containing the three unique motifs underwent early stages of in vitro studies against the OVCAR-3 cell line. This thesis has considerably advanced the field of ORMOSIL chemistry through the development and modification of new ORMOSIL products. While initial efforts were geared toward the

  7. Synthesis of functional materials in combustion reactions

    NASA Astrophysics Data System (ADS)

    Zhuravlev, V. D.; Bamburov, V. G.; Ermakova, L. V.; Lobachevskaya, N. I.

    2015-12-01

    The conditions for obtaining oxide compounds in combustion reactions of nitrates of metals with organic chelating-reducing agents such as amino acids, urea, and polyvinyl alcohol are reviewed. Changing the nature of internal fuels and the reducing agent-to-oxidizing agent ratio makes possible to modify the thermal regime of the process, fractal dimensionality, morphology, and dispersion of synthesized functional materials. This method can be used to synthesize simple and complex oxides, composites, and metal powders, as well as ceramics and coatings. The possibilities of synthesis in combustion reactions are illustrated by examples of αand γ-Al2O3, YSZ composites, uranium oxides, nickel powder, NiO and NiO: YSZ composite, TiO2, and manganites, cobaltites, and aluminates of rare earth elements.

  8. Synthesis of functional materials in combustion reactions

    SciTech Connect

    Zhuravlev, V. D. Bamburov, V. G.; Ermakova, L. V.; Lobachevskaya, N. I.

    2015-12-15

    The conditions for obtaining oxide compounds in combustion reactions of nitrates of metals with organic chelating–reducing agents such as amino acids, urea, and polyvinyl alcohol are reviewed. Changing the nature of internal fuels and the reducing agent-to-oxidizing agent ratio makes possible to modify the thermal regime of the process, fractal dimensionality, morphology, and dispersion of synthesized functional materials. This method can be used to synthesize simple and complex oxides, composites, and metal powders, as well as ceramics and coatings. The possibilities of synthesis in combustion reactions are illustrated by examples of αand γ-Al{sub 2}O{sub 3}, YSZ composites, uranium oxides, nickel powder, NiO and NiO: YSZ composite, TiO{sub 2}, and manganites, cobaltites, and aluminates of rare earth elements.

  9. Synthesis and reactivity of compounds containing ruthenium-carbon, -nitrogen, and -oxygen bonds

    SciTech Connect

    Hartwig, J.F.

    1990-12-01

    The products and mechanisms of the thermal reactions of several complexes of the general structure (PMe{sub 3}){sub 4}Ru(X)(Y) and (DMPM){sub 2}Ru(X)(Y) where X and Y are hydride, aryl, and benzyl groups, have been investigated. The mechanism of decomposition depends critically on the structure of the complex and the medium in which the thermolysis is carried out. The alkyl hydride complexes are do not react with alkane solvent, but undergo C-H activation processes with aromatic solvents by several different mechanisms. Thermolysis of (PMe{sub 3}){sub 4}Ru(Ph)(Me) or (PMe{sub 3}){sub 4}Ru(Ph){sub 2} leads to the ruthenium benzyne complex (PMe{sub 3}){sub 4}Ru({eta}{sup 2}-C{sub 6}H{sub 4}) (1) by a mechanism which involves reversible dissociation of phosphine. In many ways its chemistry is analogous to that of early rather than late organo transition metal complexes. The synthesis, structure, variable temperature NMR spectroscopy and reactivity of ruthenium complexes containing aryloxide or arylamide ligands are reported. These complexes undergo cleavage of a P-C bond in coordinated trimethylphosphine, insertion of CO and CO{sub 2} and hydrogenolysis. Mechanistic studies on these reactions are described. The generation of a series of reactive ruthenium complexes of the general formula (PMe{sub 3}){sub 4}Ru(R)(enolate) is reported. Most of these enolates have been shown to bind to the ruthenium center through the oxygen atom. Two of the enolate complexes 8 and 9 exist in equilibrium between the O- and C-bound forms. The reactions of these compounds are reported, including reactions to form oxygen-containing metallacycles. The structure and reactivity of these ruthenium metallacycles is reported, including their thermal chemistry and reactivity toward protic acids, electrophiles, carbon monoxide, hydrogen and trimethylsilane. 243 refs., 10 tabs.

  10. Synthesis and characterization of aryl phosphine oxide containing thermoplastic polyimides and thermosetting polyimides with controlled reactivity

    NASA Astrophysics Data System (ADS)

    Zhuang, Hong

    1998-11-01

    Phosphorus containing monomers, bis(3-aminophenyl)methyl phosphine oxide (m-DAMPO) and bis(3-aminophenyl)phenyl phosphine oxide (m-DAPPO), were synthesized and incorporated into a thermoplastic poly(arylene ether imide) based upon 2,2sp'-bis (4-(3,4-dicarboxyphenoxy)phenyl) propane dianhydride and 1,3-phenylene diamine, in order to study their influence on flame resistance and other properties. DAMPO or DAPPO were quantitatively incorporated in concentrations of 25, 50, 75 and 100 mole percent, using the "one pot" ester-acid method. The number average molecular weights of the prepared materials were controlled to 20,000g/mol by off-setting the stoichiometry and endcapping with phthalic anhydride. This strategy enabled one to distinguish the effects of the phosphine oxide incorporation from the influence of molecular weight. The resulting copolymers demonstrated a significant increase in char yield as a function of the phosphine oxide content, thus suggesting improved fire resistance. Glass transition temperatures similar to the control were determined by DSC analysis. Analysis of the mechanical behavior of the DAMPO system at room temperature showed that tensile strength and elongation at failure values were comparable to the control system, while the DAPPO containing copolymers were surprisingly brittle. The influence of the reactive endgroup on the synthesis, cure behavior and network properties of thermosetting polyetherimides was investigated. Reactive phenylacetylene, acetylene and maleimide terminated poly(ether imide) oligomers were prepared and characterized. Optimal reaction conditions were established to produce fully endcapped oligomers with imidized structures and controlled molecular weight. The phenylacetylene endcapped system was synthesized by a conventional ester-acid method. The acetylene endcapped system was prepared via modified ester-acid method and the maleimide endcapped system was fabricated utilizing an amic-acid route. It was determined

  11. Hyperbranched polyphosphates: synthesis, functionalization and biomedical applications.

    PubMed

    Liu, Jinyao; Huang, Wei; Pang, Yan; Yan, Deyue

    2015-06-21

    Hyperbranched polyphosphates (HBPPs) are newly emerged polymeric biomaterials with repeating phosphate bonds in a highly branched framework over the past 5 years. Due to the integration of the advantages of both hyperbranched polymers and polyphosphates, HBPPs are versatile in chemical structure, flexible in physicochemical properties, water soluble, biocompatible and biodegradable in biological features. On the basis of their excellent water solubility, biocompatibility, biodegradability and potential functionalization as well as their simple preparation in one-pot synthesis, HBPPs have fascinating biomedical applications, especially for drug delivery. In this tutorial review, the recent advances of HBPPs are summarized. HBPPs with different topological structures and various functionalities were synthesized via adjusting the side group of cyclic phosphate monomers, which have shown promising biomedical applications, for example, using as a macromolecular anticancer agent and constructing advanced drug delivery systems, including site-specific delivery systems, self-delivery systems, and stimuli-responsive delivery systems. Such progress may promote the further development of interdisciplinary research between polymer chemistry, material science and biomedicine.

  12. Polar red-emitting rhodamine dyes with reactive groups: synthesis, photophysical properties, and two-color STED nanoscopy applications.

    PubMed

    Kolmakov, Kirill; Wurm, Christian A; Meineke, Dirk N H; Göttfert, Fabian; Boyarskiy, Vadim P; Belov, Vladimir N; Hell, Stefan W

    2014-01-01

    The synthesis, reactivity, and photophysical properties of new rhodamines with intense red fluorescence, two polar residues (hydroxyls, primary phosphates, or sulfonic acid groups), and improved hydrolytic stability of the amino-reactive sites (NHS esters or mixed N-succinimidyl carbonates) are reported. All fluorophores contain an N-alkyl-1,2-dihydro-2,2,4-trimethylquinoline fragment, and most of them bear a fully substituted tetrafluoro phenyl ring with a secondary carboxamide group. The absorption and emission maxima in water are in the range of 635-639 and 655-659 nm, respectively. A vastly simplified approach to red-emitting rhodamines with two phosphate groups that are compatible with diverse functional linkers was developed. As an example, a phosphorylated dye with an azide residue was prepared and was used in a click reaction with a strained alkyne bearing an N-hydroxysuccinimid (NHS) ester group. This method bypasses the undesired activation of phosphate groups, and gives an amphiphilic amino-reactive dye, the solubility and distribution of which between aqueous and organic phases can be controlled by varying the pH. The presence of two hydroxyl groups and a phenyl ring with two carboxyl residues in the dyes with another substitution pattern is sufficient for providing the hydrophilic properties. Selective formation of a mono-N-hydroxysuccinimidyl ester from 5-carboxy isomer of this rhodamine is reported. The fluorescence quantum yields varied from 58 to 92% for free fluorophores, and amounted to 18-64% for antibody conjugates in aqueous buffers. The brightness and photostability of these fluorophores facilitated two-color stimulated emission depletion (STED) fluorescence nanoscopy of biological samples with high contrast and minimal background. Selecting a pair of fluorophores with absorption/emission bands at 579/609 and 635/655 nm enabled two-color channels with low cross-talk and negligible background at approximately 40 nm resolution.

  13. Polar red-emitting rhodamine dyes with reactive groups: synthesis, photophysical properties, and two-color STED nanoscopy applications.

    PubMed

    Kolmakov, Kirill; Wurm, Christian A; Meineke, Dirk N H; Göttfert, Fabian; Boyarskiy, Vadim P; Belov, Vladimir N; Hell, Stefan W

    2014-01-01

    The synthesis, reactivity, and photophysical properties of new rhodamines with intense red fluorescence, two polar residues (hydroxyls, primary phosphates, or sulfonic acid groups), and improved hydrolytic stability of the amino-reactive sites (NHS esters or mixed N-succinimidyl carbonates) are reported. All fluorophores contain an N-alkyl-1,2-dihydro-2,2,4-trimethylquinoline fragment, and most of them bear a fully substituted tetrafluoro phenyl ring with a secondary carboxamide group. The absorption and emission maxima in water are in the range of 635-639 and 655-659 nm, respectively. A vastly simplified approach to red-emitting rhodamines with two phosphate groups that are compatible with diverse functional linkers was developed. As an example, a phosphorylated dye with an azide residue was prepared and was used in a click reaction with a strained alkyne bearing an N-hydroxysuccinimid (NHS) ester group. This method bypasses the undesired activation of phosphate groups, and gives an amphiphilic amino-reactive dye, the solubility and distribution of which between aqueous and organic phases can be controlled by varying the pH. The presence of two hydroxyl groups and a phenyl ring with two carboxyl residues in the dyes with another substitution pattern is sufficient for providing the hydrophilic properties. Selective formation of a mono-N-hydroxysuccinimidyl ester from 5-carboxy isomer of this rhodamine is reported. The fluorescence quantum yields varied from 58 to 92% for free fluorophores, and amounted to 18-64% for antibody conjugates in aqueous buffers. The brightness and photostability of these fluorophores facilitated two-color stimulated emission depletion (STED) fluorescence nanoscopy of biological samples with high contrast and minimal background. Selecting a pair of fluorophores with absorption/emission bands at 579/609 and 635/655 nm enabled two-color channels with low cross-talk and negligible background at approximately 40 nm resolution. PMID:24338798

  14. Local and linear chemical reactivity response functions at finite temperature in density functional theory

    SciTech Connect

    Franco-Pérez, Marco E-mail: ayers@mcmaster.ca E-mail: avela@cinvestav.mx; Ayers, Paul W. E-mail: ayers@mcmaster.ca E-mail: avela@cinvestav.mx; Gázquez, José L. E-mail: ayers@mcmaster.ca E-mail: avela@cinvestav.mx; Vela, Alberto E-mail: ayers@mcmaster.ca E-mail: avela@cinvestav.mx

    2015-12-28

    We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model.

  15. Local and linear chemical reactivity response functions at finite temperature in density functional theory.

    PubMed

    Franco-Pérez, Marco; Ayers, Paul W; Gázquez, José L; Vela, Alberto

    2015-12-28

    We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model.

  16. Synthesis and Characterization of Reactive Powder Concrete for its Application on Thermal Insulation Panels

    NASA Astrophysics Data System (ADS)

    Chozas, V.; Larraza, Í.; Vera-Agullo, J.; Williams-Portal, N.; Mueller, U.; Da Silva, N.; Flansbjer, M.

    2015-11-01

    This paper describes the synthesis and characterization of a set of textile reinforced reactive powder concrete (RPC) mixes that have been prepared in the framework of the SESBE project which aims to develop facade panels for the building envelope. In order to reduce the environmental impact, high concentration of type I and II mineral additions were added to the mixtures (up to 40% of cement replacement). The mechanical properties of the materials were analysed showing high values of compression strength thus indicating no disadvantages in the compression mechanical performance (∼140 MPa) and modulus of elasticity. In order to enable the use of these materials in building applications, textile reinforcement was introduced by incorporating layers of carbon fibre grids into the RPC matrix. The flexural performance of these samples was analysed showing high strength values and suitability for their further utilization.

  17. Synthesis of novel amorphous calcium carbonate by sono atomization for reactive mixing.

    PubMed

    Kojima, Yoshiyuki; Kanai, Makoto; Nishimiya, Nobuyuki

    2012-03-01

    Droplets of several micrometers in size can be formed in aqueous solution by atomization under ultrasonic irradiation at 2 MHz. This phenomenon, known as atomization, is capable of forming fine droplets for use as a reaction field. This synthetic method is called SARM (sono atomization for reactive mixing). This paper reports on the synthesis of a novel amorphous calcium carbonate formed by SARM. The amorphous calcium carbonate, obtained at a solution concentration of 0.8 mol/dm(3), had a specific surface area of 65 m(2)/g and a composition of CaCO(3)•0.5H(2)O as determined using thermogravimetric/differential thermal analysis (TG-DTA). Because the ACC had a lower hydrate composition than conventional amorphous calcium carbonate (ACC), the ACC synthesized in this paper was very stable at room temperature.

  18. Lewis Acid Zeolites for Biomass Conversion: Perspectives and Challenges on Reactivity, Synthesis, and Stability.

    PubMed

    Luo, Helen Y; Lewis, Jennifer D; Román-Leshkov, Yuriy

    2016-06-01

    Zeolites containing Sn, Ti, Zr, Hf, Nb, or Ta heteroatoms are versatile catalysts for the activation and conversion of oxygenated molecules owing to the unique Lewis acid character of their tetrahedral metal sites. Through fluoride-mediated synthesis, hydrophobic Lewis acid zeolites can behave as water-tolerant catalysts, which has resulted in a recent surge of experimental and computational studies in the field of biomass conversion. However, many open questions still surround these materials, especially relating to the nature of their active sites. This lack of fundamental understanding is exemplified by the many dissonant results that have been described in recent literature reports. In this review, we use a molecular-based approach to provide insight into the relationship between the structure of the metal center and its reactivity toward different substrates, with the ultimate goal of providing a robust framework to understand the properties that have the strongest influence on catalytic performance for the conversion of oxygenates. PMID:27146555

  19. Peptide template effects on the synthesis and reactivity of metal nanoparticle networks

    NASA Astrophysics Data System (ADS)

    Bhandari, Rohit

    A bio-templated approach for the synthesis of multiple inorganic materials has been presented that correlates with the role of a 3-dimensional peptide template in controlling the overall reactivity of the fabricated materials for a variety of chemical reactions. The role of self-assembling R5 peptide for the formation of metallic nanoparticles including Pd, Au and Pt has been described. The materials were fully characterized using UV-vis spectroscopy, dynamic light scattering analysis, transmission electron microscopy and powder-X ray diffraction analysis. Also, the materials were employed as efficient catalysts for the Stille coupling reaction, 4-nitrophenol reduction as well as olefin hydrogenation reactions. These results are important as these template-based materials could potentially serve as candidates for a variety of applications ranging from bio- sensing tocatalysis to energy production.

  20. Synthesis and characterization of an isocyanate functionalized polyhedral oligosilsesquioxane and the subsequent formation of an organic-inorganic hybrid polyurethane.

    PubMed

    Neumann, Daniel; Fisher, Mark; Tran, Linh; Matisons, Janis G

    2002-11-27

    Organic-inorganic hybrids are an important class of new materials that offer improved thermal and mechanical properties over normal polymers. They may be produced by either the sol-gel route or through the use of inorganic compounds possessing reactive functional groups. Polyhedral oligosilsesquioxanes (POSS) are completely defined molecules of nanoscale dimensions that may be functionalized with reactive groups suitable for the synthesis of new organic-inorganic hybrids. Here we report the synthesis and characterization of a novel POSS possessing eight isocyanate groups via the hydrosilylation of octakis(hydridodimethylsiloxy)octasilsesquioxane (Q8M8H) and m-isopropenyl-alpha,alpha'-dimethylbenzyl isocyanate (m-TMI). The suitability of this new macromer to the synthesis of a organic-hybrids has been explored by forming a new type of highly cross-linked polyurethane elastomer via reaction of the macromer with poly(ethylene glycol) using dibutyltin dilaurate catalyst. PMID:12440890

  1. Polyamines function in stress tolerance: from synthesis to regulation

    PubMed Central

    Liu, Ji-Hong; Wang, Wei; Wu, Hao; Gong, Xiaoqing; Moriguchi, Takaya

    2015-01-01

    Plants are challenged by a variety of biotic or abiotic stresses, which can affect their growth and development, productivity, and geographic distribution. In order to survive adverse environmental conditions, plants have evolved various adaptive strategies, among which is the accumulation of metabolites that play protective roles. A well-established example of the metabolites that are involved in stress responses, or stress tolerance, is the low-molecular-weight aliphatic polyamines, including putrescine, spermidine, and spermine. The critical role of polyamines in stress tolerance is suggested by several lines of evidence: firstly, the transcript levels of polyamine biosynthetic genes, as well as the activities of the corresponding enzymes, are induced by stresses; secondly, elevation of endogenous polyamine levels by exogenous supply of polyamines, or overexpression of polyamine biosynthetic genes, results in enhanced stress tolerance; and thirdly, a reduction of endogenous polyamines is accompanied by compromised stress tolerance. A number of studies have demonstrated that polyamines function in stress tolerance largely by modulating the homeostasis of reactive oxygen species (ROS) due to their direct, or indirect, roles in regulating antioxidant systems or suppressing ROS production. The transcriptional regulation of polyamine synthesis by transcription factors is also reviewed here. Meanwhile, future perspectives on polyamine research are also suggested. PMID:26528300

  2. The Synthesis of Functional Mesoporous Materials

    SciTech Connect

    Fryxell, Glen E.

    2006-11-01

    The ability to decorate a silica surface with specific ligand fields and/or metal complexes creates powerful new capabilities for catalysis, chemical separations and sensor development. Integrating this with the ability to control the spacing of these complexes across the surface, as well as the symmetry and size of the pore structure, allows the synthetic chemist to hierarchically tailor these structured nanomaterials to specific needs. The next step up the “scale ladder” is provided by the ability to coat these mesoporous materials onto complex shapes, allowing for the intimate integration of these tailored materials into device interfaces. The ability to tailor the pore structure of these mesoporous supports is derived from the surfactant templated synthesis of mesoporous materials, an area which has seen an explosion of activity over the last decade.[1,2] The ability to decorate the surface with the desired functionality requires chemical modification of the oxide interface, most commonly achieved using organosilane self-assembly.[3-6] This manuscript describes recent results from the confluence of these two research areas, with a focus on synthetic manipulation of the morphology and chemistry of the interface, with the ultimate goal of binding metal centers in a chemically useful manner.

  3. An Approach to the Synthesis of Functionalized Polycyclic Aromatic Hydrocarbons

    PubMed Central

    Little, Mark; Lan, He; Raftery, James; Morrison, John J; McDouall, Joseph J W; Yeates, Stephen G; Quayle, Peter

    2013-01-01

    The application of a new benzannulation reaction for the regiocontrolled synthesis of functionalized chrysenes is reported. The initial benzannulation and the subsequent halogen displacement reactions are both highly regiospecific, which thereby enables the regiocontrolled synthesis of a variety of 4,10-disubstituted chrysenes from commercially available 1,5-dihydroxynaphthalene. PMID:25045320

  4. Amine-Reactive Fluorene Probes: Synthesis, Optical Characterization, Bioconjugation, and Two-Photon Fluorescence Imaging

    PubMed Central

    2008-01-01

    With the increasing demand for confocal and two-photon fluorescence imaging, the availability of reactive probes that possess high two-photon absorptivity, high fluorescence quantum yield, and high photostability is of paramount importance. To address the demand for better-performing probes, we prepared two-photon absorbing amine-reactive fluorenyl-based probes 2-(9,9-bis(2-(2-methoxyethoxy)ethyl)-2-isothiocyanato-9H-fluoren-7-yl)benzothiazole (1) and 2-(4-(2-(9,9-bis(2-(2-ethoxyethoxy)ethyl)-2-isothiocyanato-9H-fluoren-7-yl)vinyl)phenyl)benzothiazole (2), incorporating the isothiocyanate as a reactive linker. Probe design was augmented by integrating high optical nonlinearities, increased hydrophilicity, and coupling with reactive functional groups for specific targeting of biomolecules, assuring a better impact on two-photon fluorescence microscopy (2PFM) imaging. The isothiocyanate (NCS) derivatives were conjugated with cyclic peptide RGDfK and Reelin protein. The study of the chemical and photophysical properties of the new labeling reagents, as well as the conjugates, is described. The conjugates displayed high chemical stability and photostability. The NCS derivatives had low fluorescence quantum yields, while their bioconjugates exhibited high fluorescence quantum yields, essentially “lighting up” after conjugation. Conventional and 2PFM imaging and fluorescence lifetime imaging (FLIM) of HeLa, NT2, and H1299 cells, incubated with two-photon absorbing amine-reactive probe (1), RGDfK-dye conjugate (7), and Reelin-dye conjugate (6), was demonstrated. PMID:19090700

  5. The Development of Negative Reactivity in Irritable Newborns as a Function of Attachment

    PubMed Central

    Sherman, Laura J.; Stupica, Brandi; Dykas, Matthew J.; Ramos-Marcuse, Fatima; Cassidy, Jude

    2013-01-01

    This longitudinal study builds on existing research exploring the developmental course of infants’ negative reactivity to frustration in a sample of 84 irritable infants. We investigated whether infants’ negative reactivity to frustration differed during the first year as a function of infant attachment classification. Various elements of the designs of previous studies investigating negative reactivity and attachment preclude the strong conclusion that negative reactivity develops differently as a function of attachment. Thus, we utilized the same observational assessment of infant negative reactivity, conducted without parental involvement, at 5 and 12 months. One proposition, based in attachment theory (Bowlby, 1969/1982; Cassidy, 1994), is that relative to secure infants, insecure-avoidant infants come to minimize their negative emotional reactions, whereas insecure-ambivalent infants come to maximize their negative emotional reactions. As expected, we found that at 5 months, attachment groups did not differ in reactivity, but at 12 months, insecure-avoidant infants were the least reactive, followed by secure infants, and insecure-ambivalent infants were the most reactive. Results are discussed in terms of conceptualizing the development of emotion regulation and their implications for future research. PMID:23287637

  6. Situational reactivity of autonomic functions in schizophrenic patients.

    PubMed

    Albus, M; Ackenheil, M; Engel, R R; Müller, F

    1982-06-01

    In a study designed to evaluate the state of arousal and the autonomic reactivity to experimental conditions in schizophrenic patients, 12 acute, unmedicated schizophrenic patients with paranoid hallucinatory symptomatology and 63 healthy normal control subjects were administered four standardized tasks: cold pressor test, noise, mental arithmetic, and active relaxation. Biochemical (norepinephrine and cortisol) and physiological (electromyogram, electroencephalogram, skin and conductance response, skin conductance level, finger pulse amplitude, finger temperature, heart rate, respiratory volume, pulse wave velocity, and electrogastrogram) parameters were measured simultaneously. Schizophrenic patients showed elevated levels of cortisol and norepinephrine, as well as heightened responsivity on measures of electromyographic activity, skin conductance level, and heart rate, throughout the trial, and reduced responsivity to conditions of stress. It is concluded that schizophrenic patients show higher nonspecific activation and reduced ability to react to external stimulation, perhaps induced by lack of inhibition of the reticular formation by the limbic system.

  7. Exploring the surface reactivity of 3d metal endofullerenes: a density-functional theory study.

    PubMed

    Estrada-Salas, Rubén E; Valladares, Ariel A

    2009-09-24

    Changes in the preferential sites of electrophilic, nucleophilic, and radical attacks on the pristine C60 surface with endohedral doping using 3d transition metal atoms were studied via two useful reactivity indices, namely the Fukui functions and the molecular electrostatic potential. Both of these were calculated at the density functional BPW91 level of theory with the DNP basis set. Our results clearly show changes in the preferential reactivity sites on the fullerene surface when it is doped with Mn, Fe, Co, or Ni atoms, whereas there are no significant changes in the preferential reactivity sites on the C60 surface upon endohedral doping with Cu and Zn atoms. Electron affinities (EA), ionization potentials (IP), and HOMO-LUMO gaps (Eg) were also calculated to complete the study of the endofullerene's surface reactivity. These findings provide insight into endofullerene functionalization, an important issue in their application.

  8. Design and synthesis of supramolecular functional benzoxazines

    NASA Astrophysics Data System (ADS)

    Choi, Seong-Woo

    Dendritic macromolecules containing benzoxazine moieties are designed and synthesized using the Frechet type of ester dendritic building block via a convergent approach. Before proceeding with dendritic building synthesis, the compatibility of benzoxazine chemistry with four different types of 2,4-, 2,5-, 2,6-, and 3,5-dihydroxy benzoicacid isomers is evaluated using Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (NMR). Among isomers, 3,5-dihydroxybenzoic acid is the most compatible with benzoxazine chemistry and yields completely closed-ring benzoxazine monomer structure. Unlike 3,5-dihydroxybenzoic acid, the other three isomers show only partial ring closure or incompatibility with benzoxazine chemistry due to the existence of intramolecular hydrogen bonding between OH--O species. After finishing the model isomer study, dendritic macromolecules containing benzoxazine moieties are newly synthesized using various combinations of amine derivatives. Benzoxazine dendrimers show much lower maximum polymerization exotherm temperatures as the generation is increased as compared to ordinary benzoxazine monomers. Especially, it is revealed that the dendritic effect on benzoxazine curing temperature is more effective for the aromatic amine based benzoxazine dendrimer than for the aliphatic amine based system. By characterizing benzoxazine dendrimers, their self-catalyzed ring opening ability is elucidated and suggests their use as a curing initiator with other benzoxazine monomers. The dendritic multiplication effect on benzoxazine curing behavior and dynamic viscosity is further investigated using a combination of 6-[1-methyl-1-(3-phenyl(2H,4H-benzo[3,4-e]1,3-oxazaperhydroin-6-yl))ethyl]-3-phenyl-2H,4H-benzo[e]1,3-oxazine (abbreviated as BA-a) monomer with various phenolic derivatives. Another possibility is found for improving processibility by decreasing the polymerization temperature of ordinary benzoxazine monomer with

  9. Scar Functions, Barriers for Chemical Reactivity, and Vibrational Basis Sets.

    PubMed

    Revuelta, F; Vergini, E; Benito, R M; Borondo, F

    2016-07-14

    The performance of a recently proposed method to efficiently calculate scar functions is analyzed in problems of chemical interest. An application to the computation of wave functions associated with barriers relevant for the LiNC ⇄ LiCN isomerization reaction is presented as an illustration. These scar functions also constitute excellent elements for basis sets suitable for quantum calculation of vibrational energy levels. To illustrate their efficiency, a calculation of the LiNC/LiCN eigenfunctions is also presented.

  10. Investigation of PAA/PVDF-NZVI hybrids for metronidazole removal: synthesis, characterization, and reactivity characteristics.

    PubMed

    Yang, Jiacheng; Wang, Xiangyu; Zhu, Minping; Liu, Huiling; Ma, Jun

    2014-01-15

    For the first time, the removal process of metronidazole (MNZ) from aqueous solutions over nano zerovalent iron (NZVI) encapsulated within poly(acrylic acid) (PAA)/poly(vinylidene fluoride) (PVDF) membranes was reported. The resultant composite (PPN) demonstrated high reactivity, excellent stability and reusability over the reaction course. Such excellent performance might be attributed to the presence of the charged carboxyl groups in PVDF membrane support, which could enhance NZVI dispersion and improve its longevity. Results showed that a lower initial concentration and higher reaction temperature facilitated the removal of MNZ by PPN, and that the acidic and neutral conditions generally exhibited more favorable effect on MNZ removal than the alkaline ones. Kinetics of the MNZ removal by PPN was found to follow a two-parameter pseudo-first-order decay model well, and the activation energy of the MNZ degradation by PPN was determined to be 30.49kJ/mol. The presence of chloride ions slightly enhanced the reactivity of PPN with MNZ, whereas sulfate ions inhibited its reactivity. In addition, MNZ degradation pathways by PPN were proposed based on the identified intermediates. This study suggests that PPN composite possessing excellent performance may be a promising functional material to pretreat antibiotic wastewaters.

  11. Reaction design, discovery, and development as a foundation to function-oriented synthesis.

    PubMed

    Micalizio, Glenn C; Hale, Sarah B

    2015-03-17

    Convergent C-C bond-forming reactions define the fabric of organic synthesis and, when applied in complex molecule synthesis, can have a profound impact on efficiency by decreasing the longest linear sequence of transformations required to convert simple starting materials to complex targets. Despite their well-appreciated strategic significance, campaigns in natural product synthesis typically embrace only a small suite of reactivity to achieve such bond construction (i.e., nucleophilic addition to polarized π-bonds, nucleophilic substitution, cycloaddition, and metal-catalyzed "cross-coupling"), therefore limiting the sites at which convergent coupling chemistry can be strategically employed. In our opinion, it is far too often that triumphs in the field are defined by chemical sequences that do not address the challenges associated with discovery, development, and production of natural product-inspired agents. We speculated that advancing an area of chemical reactivity not represented in the few well-established strategies for convergent C-C bond formation may lead to powerful new retrosynthetic relationships that could simplify approaches to the syntheses of a variety of different classes of natural products. Our studies ultimately embraced the pursuit of strategies to control the course of metallacycle-mediated "cross-coupling" between substrates containing sites of simple π-unsaturation (ubiquitous functionality in organic chemistry including alkenes, alkynes, allenes, aldehydes, and imines, among others). In just eight years since our initial publication in this area, we have defined over 20 stereoselective intermolecular C-C bond-forming reactions that provide access to structural motifs of relevance for the synthesis of polyketides, fatty acids, alkaloids, and terpenes, while doing so in a direct and stereoselective fashion. These achievements continue to serve as the foundation of my group's activity in natural product and function-oriented synthesis

  12. Reaction Design, Discovery, and Development as a Foundation to Function-Oriented Synthesis

    PubMed Central

    Micalizio, Glenn C.; Hale, Sarah B.

    2015-01-01

    CONSPECTUS Convergent C–C bond-forming reactions define the fabric of organic synthesis and, when applied in complex molecule synthesis, can have a profound impact on efficiency by decreasing the longest linear sequence of transformations required to convert simple starting materials to complex targets. Despite their well-appreciated strategic significance, campaigns in natural product synthesis typically embrace only a small suite of reactivity to achieve such bond construction (i.e. nucleophilic addition to polarized π-bonds, nucleophilic substitution, cycloaddition, and metal-catalyzed “cross-coupling”), therefore limiting the sites at which convergent coupling chemistry can be strategically employed. In our opinion, it is far too often that triumphs in the field are defined by chemical sequences that do not address the challenges associated with discovery, development and/or production of natural product-inspired agents. We speculated that advancing an area of chemical reactivity not represented in the few well-established strategies for convergent C–C bond formation may lead to powerful new retrosynthetic relationships that could simplify approaches to the syntheses of a variety of different classes of natural products. Our studies ultimately embraced the pursuit of strategies to control the course of metallacycle-mediated “cross-coupling” between substrates containing sites of simple π-unsaturation (ubiquitous functionality in organic chemistry including alkenes, alkynes, allenes, aldehydes and imines, among others). In just eight years since our initial publication in this area, we have defined over twenty stereoselective intermolecular C–C bond-forming reactions that provide access to structural motifs of relevance for the synthesis of polyketides, fatty acids, alkaloids, and terpenes, while doing so in a direct and stereoselective fashion. These achievements continue to serve as the foundation of my group’s activity in natural product and

  13. Linkage of functional and structural anomalies in the left amygdala of reactive-aggressive men.

    PubMed

    Bobes, María A; Ostrosky, Feggy; Diaz, Karla; Romero, Cesar; Borja, Karina; Santos, Yusniel; Valdés-Sosa, Mitchell

    2013-12-01

    Amygdala structural and functional abnormalities have been associated to reactive aggression in previous studies. However, the possible linkage of these two types of anomalies has not been examined. We hypothesized that they would coincide in the same localizations, would be correlated in intensity and would be mediated by reactive aggression personality traits. Here violent (n = 25) and non-violent (n = 29) men were recruited on the basis of their reactive aggression. Callous-unemotional (CU) traits were also assessed. Gray matter concentration (gmC) and reactivity to fearful and neutral facial expressions were measured in dorsal and ventral amygdala partitions. The difference between responses to fearful and neutral facial expressions was calculated (F/N-difference). Violent individuals exhibited a smaller F/N-difference and gmC in the left dorsal amygdala, where a significant coincidence was found in a conjunction analysis. Moreover, the left amygdala F/N-difference and gmC were correlated to each other, an effect mediated by reactive aggression but not by CU. The F/N-difference was caused by increased reactivity to neutral faces. This suggests that anatomical anomalies within local circuitry (and not only altered input) may underlie the amygdala hyper-reactivity to social signals which is characteristic of reactive aggression.

  14. Linkage of functional and structural anomalies in the left amygdala of reactive-aggressive men

    PubMed Central

    Ostrosky, Feggy; Diaz, Karla; Romero, Cesar; Borja, Karina; Santos, Yusniel; Valdés-Sosa, Mitchell

    2013-01-01

    Amygdala structural and functional abnormalities have been associated to reactive aggression in previous studies. However, the possible linkage of these two types of anomalies has not been examined. We hypothesized that they would coincide in the same localizations, would be correlated in intensity and would be mediated by reactive aggression personality traits. Here violent (n = 25) and non-violent (n = 29) men were recruited on the basis of their reactive aggression. Callous-unemotional (CU) traits were also assessed. Gray matter concentration (gmC) and reactivity to fearful and neutral facial expressions were measured in dorsal and ventral amygdala partitions. The difference between responses to fearful and neutral facial expressions was calculated (F/N-difference). Violent individuals exhibited a smaller F/N-difference and gmC in the left dorsal amygdala, where a significant coincidence was found in a conjunction analysis. Moreover, the left amygdala F/N-difference and gmC were correlated to each other, an effect mediated by reactive aggression but not by CU. The F/N-difference was caused by increased reactivity to neutral faces. This suggests that anatomical anomalies within local circuitry (and not only altered input) may underlie the amygdala hyper-reactivity to social signals which is characteristic of reactive aggression. PMID:22956672

  15. Effects of reactive oxygen species on sperm function.

    PubMed

    Guthrie, H D; Welch, G R

    2012-11-01

    Reactive oxygen species (ROS) formation and membrane lipid peroxidation have been recognized as problems for sperm survival and fertility. The precise roles and detection of superoxide (SO), hydrogen peroxide (HP), and membrane lipid peroxidation have been problematic, because of the low specificity and sensitivity of the established chemiluminescence assay technologies. We developed flow cytometric assays to measure SO, HP, membrane lipid peroxidation, and inner mitochondrial transmembrane potential in boar sperm. These methods were sufficiently sensitive to permit detection of early changes in ROS formation in sperm cells that were still viable. Basal ROS formation and membrane lipid peroxidation in the absence of ROS generators were low in viable sperm of both fresh and frozen-thawed boar semen, affecting less than 4% of the sperm cells on average. However, this is not the case in other species, as human, bovine, and poultry sperm have large increases in sperm ROS formation, lipid peroxidation, loss of motility, and death in vitro. Closer study of the effects of ROS formation on the relationship between sperm motility and ATP content in boar sperm was conducted using menadione (mitochondrial SO generator) and HP treatment. Menadione or HP caused an immediate disruption of motility with delayed or no decrease in sperm ATP content, respectively. Overall, the inhibitory effects of ROS on motility point to a mitochondrial-independent mechanism. The reduction in motility may have been due to a ROS-induced lesion in ATP utilization or in the contractile apparatus of the flagellum. PMID:22704396

  16. Shear stress, reactive oxygen species, and arterial structure and function.

    PubMed

    Matlung, Hanke L; Bakker, Erik N T P; VanBavel, Ed

    2009-07-01

    Shear stress is well known to be a key factor in the regulation of small-artery tone and structure. Although nitric oxide is a major endothelium-derived factor involved in short- and long-term regulation of vascular caliber, it is clear that other mechanisms also can be involved. This review discusses the evidence for endothelium-derived reactive oxygen species (ROS) as mediators for shear-dependent arterial tone and remodeling. The work focuses on resistance vessels, because their caliber determines local perfusion. However, work on large vessels is included where needed. Attention is given to the shear-stress levels and profiles that exist in the arterial system and the differential effects of steady and oscillating shear on NO and ROS production. We furthermore address the relation between microvascular tone and remodeling and the effect of ROS and inflammation on the activity of remodeling enzymes such as matrix metalloproteinases and transglutaminases. We conclude that future work should address the role of H(2)O(2) as an endothelium-derived factor mediating tone and influencing structure of small arteries over the long term.

  17. Exploration of Visible-Light Photocatalysis in Heterocycle Synthesis and Functionalization: Reaction Design and Beyond.

    PubMed

    Chen, Jia-Rong; Hu, Xiao-Qiang; Lu, Liang-Qiu; Xiao, Wen-Jing

    2016-09-20

    Visible-light photocatalysis has recently received increasing attention from chemists because of its wide application in organic synthesis and its significance for sustainable chemistry. This catalytic strategy enables the generation of various reactive species, frequently without stoichiometric activation reagents under mild reaction conditions. Manipulation of these reactive intermediates can result in numerous synthetically useful bond formations in a controllable manner. In this Account, we describe our recent advances in the rational design and strategic application of photocatalysis in the synthesis of various synthetically and biologically important heterocycles. Our main research efforts toward this goal can be classified into four categories: formal cycloaddition and cyclization reactions, radical-mediated olefin functionalization/cyclization cascades, photocatalytic generation and cyclization of N-centered radicals, and photocatalytic functionalization of heterocycles by visible-light-induced dual catalysis. Inspired by the wide application of tertiary amines as reductive additives in photoredox catalysis, we exploited a series of readily accessible or rationally designed tertiary amines with reactive sites in a range of photocatalytic formal cycloaddition and cyclization reactions, providing efficient access to diverse nitrogen heterocycles. Employing various photogenerated radical species, we further developed a series of radical-mediated olefin functionalization/cyclization cascade reactions to successfully assemble various five- and six-membered heterocycles. We have also achieved for the first time the direct catalytic conversion of recalcitrant N-H bonds into neutral N-centered radicals through a visible-light-photocatalytic oxidative deprotonation electron transfer. Using this generic strategy, we have devised several types of radical cyclizations of unsaturated hydrazones, leading to the construction of diversely functionalized pyrazoline and

  18. A highly reactive chalcogenide precursor for the synthesis of metal chalcogenide quantum dots

    NASA Astrophysics Data System (ADS)

    Jiang, Peng; Zhu, Dong-Liang; Zhu, Chun-Nan; Zhang, Zhi-Ling; Zhang, Guo-Jun; Pang, Dai-Wen

    2015-11-01

    Metal chalcogenide semiconductor nanocrystals (NCs) are ideal inorganic materials for solar cells and biomedical labeling. In consideration of the hazard and instability of alkylphosphines, the phosphine-free synthetic route has become one of the most important trends in synthesizing selenide QDs. Here we report a novel phase transfer strategy to prepare phosphine-free chalcogenide precursors. The anions in aqueous solution were transferred to toluene via electrostatic interactions between the anions and didodecyldimethylammonium bromide (DDAB). The obtained chalcogenide precursors show high reactivity with metal ions in the organic phase and could be applied to the low-temperature synthesis of various metal chalcogenide NCs based on a simple reaction between metal ions (e.g. Ag+, Pb2+, Cd2+) and chalcogenide anions (e.g. S2-) in toluene. In addition to chalcogenide anions, other anions such as BH4- ions and AuCl4- ions can also be transferred to the organic phase for synthesizing noble metal NCs (such as Ag and Au NCs).Metal chalcogenide semiconductor nanocrystals (NCs) are ideal inorganic materials for solar cells and biomedical labeling. In consideration of the hazard and instability of alkylphosphines, the phosphine-free synthetic route has become one of the most important trends in synthesizing selenide QDs. Here we report a novel phase transfer strategy to prepare phosphine-free chalcogenide precursors. The anions in aqueous solution were transferred to toluene via electrostatic interactions between the anions and didodecyldimethylammonium bromide (DDAB). The obtained chalcogenide precursors show high reactivity with metal ions in the organic phase and could be applied to the low-temperature synthesis of various metal chalcogenide NCs based on a simple reaction between metal ions (e.g. Ag+, Pb2+, Cd2+) and chalcogenide anions (e.g. S2-) in toluene. In addition to chalcogenide anions, other anions such as BH4- ions and AuCl4- ions can also be transferred to

  19. Scar Functions, Barriers for Chemical Reactivity, and Vibrational Basis Sets.

    PubMed

    Revuelta, F; Vergini, E; Benito, R M; Borondo, F

    2016-07-14

    The performance of a recently proposed method to efficiently calculate scar functions is analyzed in problems of chemical interest. An application to the computation of wave functions associated with barriers relevant for the LiNC ⇄ LiCN isomerization reaction is presented as an illustration. These scar functions also constitute excellent elements for basis sets suitable for quantum calculation of vibrational energy levels. To illustrate their efficiency, a calculation of the LiNC/LiCN eigenfunctions is also presented. PMID:26905100

  20. Hardness and softness reactivity kernels within the spin-polarized density-functional theory

    SciTech Connect

    Chamorro, Eduardo; De Proft, Frank; Geerlings, Paul

    2005-10-15

    Generalized hardness and softness reactivity kernels are defined within a spin-polarized density-functional theory (SP-DFT) conceptual framework. These quantities constitute the basis for the global, local (i.e., r-position dependent), and nonlocal (i.e., r and r{sup '}-position dependents) indices devoted to the treatment of both charge-transfer and spin-polarization processes in such a reactivity framework. The exact relationships between these descriptors within a SP-DFT framework are derived and the implications for chemical reactivity in such context are outlined.

  1. Iron complexes of a bidentate picolyl-NHC ligand: synthesis, structure and reactivity.

    PubMed

    Liang, Qiuming; Janes, Trevor; Gjergji, Xhoana; Song, Datong

    2016-09-21

    The synthesis, structure and reactivity of bidentate picolyl N-heterocyclic carbene (NHC) iron compounds were studied. Compounds [FeBr(HL)2]Br (1), [FeBr(HL)(HMDS)] (2) and [FeBr2(HL)] (3) (HL = 1-mesityl-3-(pyridin-2-ylmethyl)imidazol-1-ylidene, HMDS = hexamethyldisilazide) were prepared from H2LBr with suitable amounts of Fe(HMDS)2 or in situ prepared [Fe(HMDS)Br]. The deprotonation of 1 with 2 eq. of LiHMDS gave [FeL2] (4), featuring dearomatized pyridine moieties with exocyclic C-C double bonds. The protonation of 4 with 2 eq. of PPh3·HBr results in the formation of 1. Attempted deprotonation of 3 using benzyl Grignard as the base resulted in transmetalation products [FeBnBr(HL)] (5) and [FeBn2(HL)] (6). Exposure of 6 to CO resulted in the formation of diamagnetic compound [Fe(CO)3(HL)] (7) and dibenzyl ketone. Prolonged exposure of 7 to CO with heating induces pyridine dissociation, affording [Fe(CO)4(HL-κC)] (8). Treatment of compound 6 with an equimolar amount of p-methoxybenzyl bromide yielded homo- and cross-coupling products. PMID:27513216

  2. Development of a new graded-porosity FeAl alloy by elemental reactive synthesis

    SciTech Connect

    Shen, P Z; He, Y H; Gao, H Y; Zou, J; Xu, N P; Jiang, Y; Huang, B; Lui, C T

    2009-01-01

    A new graded-porosity FeAl alloy can be fabricated through Fe and Al elemental reactive synthesis. FeAl alloy with large connecting open pores and permeability were used as porous supports. The coating was obtained by spraying slurries consisting of mixtures of Fe powder and Al powder with 3 5 m diameter onto porous FeAl support and then sintered at 1100 C. The performances of the coating were compared in terms of thickness, pore diameter and permeability. With an increase in the coating thickness up to 200 m, the changes of maximum pore size decreased from 23.6 m to 5.9 m and the permeability decreased from 184.2 m3m 2kPa 1h 1 to 76.2 m3m 2kPa 1h 1, respectively, for a sintering temperature equal to 1100 C. The composite membranes have potential application for excellent filters in severe environments.

  3. Synthesis Of Reactive Nano-Fe/Pd Bimetallic System-Impregnated Activated Carbon For The Simultaneous Adsorption And Dechlorination Of PCBs

    EPA Science Inventory

    Synthesis and use of reactive metal particles have shown significant environmental implications for the remediation of groundwater and sediment contaminated with chlorinated compounds. Herein, we have developed an effective strategy, employing a series of innovative granular act...

  4. Computational Study of Chemical Reactivity Using Information-Theoretic Quantities from Density Functional Reactivity Theory for Electrophilic Aromatic Substitution Reactions.

    PubMed

    Wu, Wenjie; Wu, Zemin; Rong, Chunying; Lu, Tian; Huang, Ying; Liu, Shubin

    2015-07-23

    The electrophilic aromatic substitution for nitration, halogenation, sulfonation, and acylation is a vastly important category of chemical transformation. Its reactivity and regioselectivity is predominantly determined by nucleophilicity of carbon atoms on the aromatic ring, which in return is immensely influenced by the group that is attached to the aromatic ring a priori. In this work, taking advantage of recent developments in quantifying nucleophilicity (electrophilicity) with descriptors from the information-theoretic approach in density functional reactivity theory, we examine the reactivity properties of this reaction system from three perspectives. These include scaling patterns of information-theoretic quantities such as Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy and information gain at both molecular and atomic levels, quantitative predictions of the barrier height with both Hirshfeld charge and information gain, and energetic decomposition analyses of the barrier height for the reactions. To that end, we focused in this work on the identity reaction of the monosubstituted-benzene molecule reacting with hydrogen fluoride using boron trifluoride as the catalyst in the gas phase. We also considered 19 substituting groups, 9 of which are ortho/para directing and the other 9 meta directing, besides the case of R = -H. Similar scaling patterns for these information-theoretic quantities found for stable species elsewhere were disclosed for these reactions systems. We also unveiled novel scaling patterns for information gain at the atomic level. The barrier height of the reactions can reliably be predicted by using both the Hirshfeld charge and information gain at the regioselective carbon atom. The energy decomposition analysis ensued yields an unambiguous picture about the origin of the barrier height, where we showed that it is the electrostatic interaction that plays the dominant role, while the roles played by exchange-correlation and

  5. Computational Study of Chemical Reactivity Using Information-Theoretic Quantities from Density Functional Reactivity Theory for Electrophilic Aromatic Substitution Reactions.

    PubMed

    Wu, Wenjie; Wu, Zemin; Rong, Chunying; Lu, Tian; Huang, Ying; Liu, Shubin

    2015-07-23

    The electrophilic aromatic substitution for nitration, halogenation, sulfonation, and acylation is a vastly important category of chemical transformation. Its reactivity and regioselectivity is predominantly determined by nucleophilicity of carbon atoms on the aromatic ring, which in return is immensely influenced by the group that is attached to the aromatic ring a priori. In this work, taking advantage of recent developments in quantifying nucleophilicity (electrophilicity) with descriptors from the information-theoretic approach in density functional reactivity theory, we examine the reactivity properties of this reaction system from three perspectives. These include scaling patterns of information-theoretic quantities such as Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy and information gain at both molecular and atomic levels, quantitative predictions of the barrier height with both Hirshfeld charge and information gain, and energetic decomposition analyses of the barrier height for the reactions. To that end, we focused in this work on the identity reaction of the monosubstituted-benzene molecule reacting with hydrogen fluoride using boron trifluoride as the catalyst in the gas phase. We also considered 19 substituting groups, 9 of which are ortho/para directing and the other 9 meta directing, besides the case of R = -H. Similar scaling patterns for these information-theoretic quantities found for stable species elsewhere were disclosed for these reactions systems. We also unveiled novel scaling patterns for information gain at the atomic level. The barrier height of the reactions can reliably be predicted by using both the Hirshfeld charge and information gain at the regioselective carbon atom. The energy decomposition analysis ensued yields an unambiguous picture about the origin of the barrier height, where we showed that it is the electrostatic interaction that plays the dominant role, while the roles played by exchange-correlation and

  6. Substrate reactivity as a function of the extent of reaction in the enzymatic hydrolysis of lignocellulose

    SciTech Connect

    Desai, S.G.; Converse, A.O.

    1997-12-20

    In an effort to better understand the role of the substrate in the rapid fall off in the rate of enzymatic hydrolysis of cellulose with conversion, substrate reactivity was measured as a function of conversion. These measurements were made by interrupting the hydrolysis of pretreated wood at various degrees of conversion; and, after boiling and washing, restarting the hydrolysis in fresh butter with fresh enzyme. The comparison of the restart rate per enzyme adsorbed with the initial rate per enzyme adsorbed, both extrapolated back to zero conversion, provides a measurement of the substrate reactivity without the complications of product inhibition or cellulase inactivation. The results indicate that the substrate reactivity falls only modestly as conversion increases. However, the restart rate is still higher than the rate of the uninterrupted hydrolysis, particularly at high conversion. Hence the authors conclude that the loss of substrate reactivity is not the principal cause for the long residence time required for complete conversion.

  7. Study of curcumin immunomodulatory effects on reactive astrocyte cell function.

    PubMed

    Seyedzadeh, Mir Hadi; Safari, Zohreh; Zare, Ahad; Gholizadeh Navashenaq, Jamshid; Razavi, Seyed Alireza; Kardar, Gholam Ali; Khorramizadeh, Mohammad Reza

    2014-09-01

    Multiple sclerosis (MS) is considered an inflammatory and neurodegenerative disease of the central nervous system (CNS) which most often presents as relapsing-remitting episodes. Recent evidence suggests that activated astrocytes play a dual functional role in CNS inflammatory disorders such as MS. In this study, we tried to induce anti-inflammatory functions of astrocytes by curcumin. The effects of curcumin were examined on human a astrocyte cell line (U373-MG) induced by lipopolysaccharide (LPS) in vitro. Matrix metalloproteinase (MMP)-9 activity was assessed by gelatin zymography. Cytokine levels were evaluated by quantitative ELISA method and mRNA expression was measured by real-time PCR. We found that curcumin decreased the release of IL-6 and reduced MMP-9 enzyme activity. It down-regulated MCP-1 mRNA expression too. However, curcumin did not have significant effects on the expression of neurotrophin (NT)-3 and insulin-like growth factor (IGF)-1 mRNAs. Results suggest that curcumin might beneficially affect astrocyte population in CNS neuroinflammatory environment lean to anti-inflammatory response and help to components in respects of CNS repair. Our findings offer curcumin as a new therapeutic agent with the potential of regulating astrocyte-mediated inflammatory diseases in the CNS. PMID:24998635

  8. Tactic, reactive, and functional droplets outside of equilibrium.

    PubMed

    Lach, Sławomir; Yoon, Seok Min; Grzybowski, Bartosz A

    2016-08-22

    Under non-equilibrium conditions, liquid droplets coupled to their environment by sustained flows of matter and/or energy can become "active" systems capable of various life-like functions. When "fueled" by even simple chemical reactions, such droplets can become tactic and can perform "intelligent" tasks such as maze solving. With more complex chemistries, droplets can support basic forms of metabolism, grow, self-replicate, and exhibit evolutionary changes akin to biological cells. There are also first exciting examples of active droplets connected into larger, tissue-like systems supporting droplet-to-droplet communication, and giving rise to collective material properties. As practical applications of droplets also begin to appear (e.g., in single-cell diagnostics, new methods of electricity generation, optofluidics, or sensors), it appears timely to review and systematize progress in this highly interdisciplinary area of chemical research, and also think about the avenues (and the roadblocks) for future work.

  9. On the nature of Parr functions to predict the most reactive sites along organic polar reactions

    NASA Astrophysics Data System (ADS)

    Chamorro, Eduardo; Pérez, Patricia; Domingo, Luis R.

    2013-09-01

    Very recently, local electrophilic and nucleophilic “Parr functions” were empirically introduced (L.R. Domingo, P. Pérez, J.A. Saez RSC Adv. 3 (2013) 1486) in order to properly characterize the most reactive sites along polar chemical reactions. This Letter reports a theoretical advance to the new methodology by identifying these quantities with key Fukui descriptors of the spin-polarized density functional theory. Given such framework properly incorporates the treatment of both charge-transfer and spin-polarization, this finding provides a significant insight and substantial step forward within the field of a chemical reactivity theory based on the conceptual framework of density functional theory.

  10. Deficient cardiovascular stress reactivity predicts poor executive functions in adults with attention-deficit/hyperactivity disorder.

    PubMed

    Hirvikoski, Tatja; Olsson, Erik M G; Nordenstrom, Anna; Lindholm, Torun; Nordstrom, Anna-Lena; Lajic, Svetlana

    2011-01-01

    Associations between cardiovascular stress markers, subjective stress reactivity, and executive functions were studied in 60 adults (30 with attention-deficit/hyperactivity disorder, ADHD, and 30 controls) using the Paced Auditory Serial Addition Test (PASAT, a test of executive functions) as a cognitive stressor. Despite higher self-perceived stress, the adults with ADHD showed lower or atypical cardiovascular stress reactivity, which was associated with poorer performance on PASAT. Using cardiovascular stress markers, subjective stress, and results on PASAT as predictors in a logistic regression, 83.3% of the ADHD group and 86.9% of the controls could be classified correctly.

  11. Highly reactive {001} facets of TiO2-based composites: synthesis, formation mechanism and characterization.

    PubMed

    Ong, Wee-Jun; Tan, Lling-Lling; Chai, Siang-Piao; Yong, Siek-Ting; Mohamed, Abdul Rahman

    2014-02-21

    Titanium dioxide (TiO2) is one of the most widely investigated metal oxides due to its extraordinary surface, electronic and catalytic properties. However, the large band gap of TiO2 and massive recombination of photogenerated electron-hole pairs limit its photocatalytic and photovoltaic efficiency. Therefore, increasing research attention is now being directed towards engineering the surface structure of TiO2 at the most fundamental and atomic level namely morphological control of {001} facets in the range of microscale and nanoscale to fine-tune its physicochemical properties, which could ultimately lead to the optimization of its selectivity and reactivity. The synthesis of {001}-faceted TiO2 is currently one of the most active interdisciplinary research areas and demonstrations of catalytic enhancement are abundant. Modifications such as metal and non-metal doping have also been extensively studied to extend its band gap to the visible light region. This steady progress has demonstrated that TiO2-based composites with {001} facets are playing and will continue to play an indispensable role in the environmental remediation and in the search for clean and renewable energy technologies. This review encompasses the state-of-the-art research activities and latest advancements in the design of highly reactive {001} facet-dominated TiO2via various strategies, including hydrothermal/solvothermal, high temperature gas phase reactions and non-hydrolytic alcoholysis methods. The stabilization of {001} facets using fluorine-containing species and fluorine-free capping agents is also critically discussed in this review. To overcome the large band gap of TiO2 and rapid recombination of photogenerated charge carriers, modifications are carried out to manipulate its electronic band structure, including transition metal doping, noble metal doping, non-metal doping and incorporating graphene as a two-dimensional (2D) catalyst support. The advancements made in these aspects are

  12. Increasing CRTC1 function in the dentate gyrus during memory formation or reactivation increases memory strength without compromising memory quality.

    PubMed

    Sekeres, Melanie J; Mercaldo, Valentina; Richards, Blake; Sargin, Derya; Mahadevan, Vivek; Woodin, Melanie A; Frankland, Paul W; Josselyn, Sheena A

    2012-12-01

    Memory stabilization following encoding (synaptic consolidation) or memory reactivation (reconsolidation) requires gene expression and protein synthesis (Dudai and Eisenberg, 2004; Tronson and Taylor, 2007; Nader and Einarsson, 2010; Alberini, 2011). Although consolidation and reconsolidation may be mediated by distinct molecular mechanisms (Lee et al., 2004), disrupting the function of the transcription factor CREB impairs both processes (Kida et al., 2002; Mamiya et al., 2009). Phosphorylation of CREB at Ser133 recruits CREB binding protein (CBP)/p300 coactivators to activate transcription (Chrivia et al., 1993; Parker et al., 1996). In addition to this well known mechanism, CREB regulated transcription coactivators (CRTCs), previously called transducers of regulated CREB (TORC) activity, stimulate CREB-mediated transcription, even in the absence of CREB phosphorylation. Recently, CRTC1 has been shown to undergo activity-dependent trafficking from synapses and dendrites to the nucleus in excitatory hippocampal neurons (Ch'ng et al., 2012). Despite being a powerful and specific coactivator of CREB, the role of CRTC in memory is virtually unexplored. To examine the effects of increasing CRTC levels, we used viral vectors to locally and acutely increase CRTC1 in the dorsal hippocampus dentate gyrus region of mice before training or memory reactivation in context fear conditioning. Overexpressing CRTC1 enhanced both memory consolidation and reconsolidation; CRTC1-mediated memory facilitation was context specific (did not generalize to nontrained context) and long lasting (observed after virally expressed CRTC1 dissipated). CREB overexpression produced strikingly similar effects. Therefore, increasing CRTC1 or CREB function is sufficient to enhance the strength of new, as well as established reactivated, memories without compromising memory quality.

  13. Synthesis of Orthogonally Reactive FK506 Derivatives via Olefin Cross Metathesis

    PubMed Central

    Marinec, Paul S.; Evans, Christopher G.; Gibbons, Garrett S.; Tarnowski, Malloree A.; Overbeek, Daniel L.; Gestwicki, Jason E.

    2009-01-01

    Chemical inducers of dimerization (CIDs) are employed in a wide range of biological applications, to control protein localization, modulate protein-protein interactions and improve drug lifetimes. These bifunctional chemical probes are assembled from two synthetic modules, which each provide affinity for a distinct protein target. FK506 and its derivatives are often employed as modules in the syntheses of these bifunctional constructs, owing to the abundance and favorable distribution of their target, FK506-binding protein (FKBP). However, the structural complexity of FK506 necessitates multi-step syntheses and/or multiple protection-deprotection schemes prior to installation into CIDs. In this work, we describe an efficient, one-step synthesis of FK506 derivatives through a selective, microwave-accelerated, cross metathesis diversification step of the C39 terminal alkene. Using this approach, FK506 is modified with an array of functional groups, including primary amines and carboxylic acids, which make the resulting derivatives suitable for the modular assembly of CIDs. To illustrate this idea, we report the synthesis of a heterobifunctional HIV protease inhibitor. PMID:19643614

  14. Molecular architectures and functions of radical enzymes and their (re)activating proteins.

    PubMed

    Shibata, Naoki; Toraya, Tetsuo

    2015-10-01

    Certain proteins utilize the high reactivity of radicals for catalysing chemically challenging reactions. These proteins contain or form a radical and therefore named 'radical enzymes'. Radicals are introduced by enzymes themselves or by (re)activating proteins called (re)activases. The X-ray structures of radical enzymes and their (re)activases revealed some structural features of these molecular apparatuses which solved common enigmas of radical enzymes—i.e. how the enzymes form or introduce radicals at the active sites, how they use the high reactivity of radicals for catalysis, how they suppress undesired side reactions of highly reactive radicals and how they are (re)activated when inactivated by extinction of radicals. This review highlights molecular architectures of radical B12 enzymes, radical SAM enzymes, tyrosyl radical enzymes, glycyl radical enzymes and their (re)activating proteins that support their functions. For generalization, comparisons of the recently reported structures of radical enzymes with those of canonical radical enzymes are summarized here.

  15. Effects of nitrogen dioxide exposure on pulmonary function and airway reactivity in normal humans.

    PubMed

    Frampton, M W; Morrow, P E; Cox, C; Gibb, F R; Speers, D M; Utell, M J

    1991-03-01

    Nitrogen dioxide (NO2) is a product of combustion that has become recognized as a significant component of indoor air in some homes. Despite extensive study, it remains unresolved whether exposures to low levels of NO2 affect airway function or reactivity. These studies were designed to assess effects of various levels and patterns of NO2 exposure on pulmonary function and airway reactivity in normal humans. Normal volunteers screened for the absence of airway hyperreactivity were exposed for 3 h in an environmental chamber to purified air or NO2, separated by at least 2 wk, according to three protocols: (1) continuous 0.60 ppm NO2, (2) baseline 0.05 ppm NO2 with intermittent peaks of 2.0 ppm, and (3) continuous 1.5 ppm NO2. Subjects exercised for 10 min of each 30 min at a level sufficient to result in a minute ventilation near 40 L/min. Pulmonary function was measured before, during, and after exposure. Airway reactivity to increasing doses of carbachol was assessed 30 min after exposure. NO2 did not directly alter pulmonary function in any of the exposure protocols. In addition, airway reactivity was not altered by continuous exposure to 0.60 ppm or intermittent peaks of 2.0 ppm NO2. In contrast, continuous exposure to 1.5 ppm NO2 resulted in a greater fall in FVC and FEV1 in response to carbachol than after exposure to air (percent decrease in FVC: 1.5% after air, 3.9% after NO2, p less than 0.01). We conclude that for subjects without airway hyperreactivity, exposure to 1.5 ppm NO2 for 3 h increases airway reactivity, whereas repeated 15-min exposures to 2.0 ppm NO2 do not alter airway reactivity. PMID:2001061

  16. Solvent effect on the reactivity of CIS-platinum (II) complexes: A density functional approach

    NASA Astrophysics Data System (ADS)

    Sarmah, Pubalee; Deka, Ramesh C.

    The structure and chemical reactivity of some selected cis-platinum(II) complexes, including clinically used drug molecules, cisplatin, carboplatin, and oxaliplatin are investigated using density functional theory (DFT) calculations. Calculated geometries of the complexes are in agreement with their available X-ray data. The global and local reactivity descriptors, such as hardness, chemical potential, electrophilicity index, Fukui function, and local philicity are calculated to investigate the usefulness of these descriptors for understanding the reactive nature and reactive sites of the complexes. Inclusion of solvent effect shows that both global and local descriptors change the trend of reactivity with respect to their trend in the gas phase. The stability of the complexes increases with the inclusion of water molecules. Simple regression analysis is applied to build up a quantitative structure-activity relationship (QSAR) model based on DFT derived electrophilicity index for the Pt(II) complexes against A2780 human ovarian adenocarcinoma cell line to establish the importance of the descriptor in predicting cytotoxicity.

  17. Cortisol Reactivity is Positively Related to Executive Function in Preschool Children Attending Head Start

    ERIC Educational Resources Information Center

    Blair, Clancy; Granger, Douglas; Razza, Rachel Peters

    2005-01-01

    This study examined relations among cortisol reactivity and measures of cognitive function and social behavior in 4- to 5-year-old children (N=169) attending Head Start. Saliva samples for the assay of cortisol were collected at the beginning, middle, and end of an approximately 45-min testing session. Moderate increase in cortisol followed by…

  18. Emotional Reactivity and Regulation in Infancy Interact to Predict Executive Functioning in Early Childhood

    ERIC Educational Resources Information Center

    Ursache, Alexandra; Blair, Clancy; Stifter, Cynthia; Voegtline, Kristin

    2013-01-01

    The relation of observed emotional reactivity and regulation in infancy to executive function in early childhood was examined in a prospective longitudinal sample of 1,292 children from predominantly low-income and rural communities. Children participated in a fear eliciting task at ages 7, 15, and 24 months and completed an executive function…

  19. Dislocation-driven synthesis and bioinspired assembly of functional nanomaterials

    NASA Astrophysics Data System (ADS)

    Morin, Stephen A.

    Nanomaterial-based technologies demand the ability to precisely and simultaneously control the synthesis and assembly of inorganic materials at the nanoscale. Motivated by this challenge, my research has focused on the fundamental nucleation and growth processes of functional nanomaterials and the variables we can manipulate to control them for rational synthesis and assembly. In particular, by combining fundamental concepts of crystal growth theory with crystal growth principles derived from natural biomineralization processes this work has yielded new nanomaterial synthesis and assembly strategies. Specifically, this dissertation describes the solution-based growth of nanowires (NWs), nanotubes (NTs), and nanoplates that is driven by screw dislocations and offers new methods for the bottom-up fabrication of hybrid nanostructures, which together enable the formation of tailored functional nanomaterials for a variety of useful applications in diverse areas such as renewable energy and nanoelectronics.

  20. Cationic methyl complexes of the rare-earth metals: an experimental and computational study on synthesis, structure, and reactivity.

    PubMed

    Kramer, Mathias U; Robert, Dominique; Arndt, Stefan; Zeimentz, Peter M; Spaniol, Thomas P; Yahia, Ahmed; Maron, Laurent; Eisenstein, Odile; Okuda, Jun

    2008-10-20

    Synthesis, structure, and reactivity of two families of rare-earth metal complexes containing discrete methyl cations [LnMe(2-x)(thf)n]((1+x)+) (x = 0, 1; thf = tetrahydrofuran) have been studied. As a synthetic equivalent for the elusive trimethyl complex [LnMe3], lithium methylates of the approximate composition [Li3LnMe6(thf)n] were prepared by treating rare-earth metal trichlorides [LnCl3(thf)n] with 6 equiv of methyllithium in diethyl ether. Heteronuclear complexes of the formula [Li3Ln2Me9L(n)] (Ln = Sc, Y, Tb; L = Et2O, thf) were isolated by crystallization from diethyl ether. Single crystal X-ray diffraction studies revealed a heterometallic aggregate of composition [Li3Ln2Me9(thf)n(Et2O)m] with a [LiLn2Me9](2-) core (Ln = Sc, Y, Tb). When tris(tetramethylaluminate) [Ln(AlMe4)3] (Ln = Y, Lu) was reacted with less than 1 equiv of [NR3H][BPh4], the dimethyl cations [LnMe2(thf)n][BPh4] were obtained. The coordination number as well as cis/trans isomer preference was studied by crystallographic and computational methods. Dicationic methyl complexes of the rare-earth metals of the formula [LnMe(thf)n][BAr4]2 (Ln = Sc, Y, La-Nd, Sm, Gd-Lu; Ar = Ph, C6H4F-4) were synthesized, by protonolysis of either the ate complex [Li3LnMe6(thf)n] (Ln = Sc, Y, Gd-Lu) or the tris(tetramethylaluminate) [Ln(AlMe4)3] (Ln = La-Nd, Sm, Dy, Gd) with ammonium borates [NR3H][BAr4] in thf. The number of coordinated thf ligands varied from n = 5 (Ln = Sc, Tm) to n = 6 (Ln = La, Y, Sm, Dy, Ho). The configuration of representative examples was determined by X-ray diffraction studies and confirmed by density-functional theory calculations. The highly polarized bonding between the methyl group and the rare-earth metal center results in the reactivity pattern dominated by the carbanionic character and the pronounced Lewis acidity: The dicationic methyl complex [YMe(thf)6](2+) inserted benzophenone as an electrophile to give the alkoxy complex [Y(OCMePh2)(thf)5](2+). Nucleophilic addition of

  1. Synthesis and properties of arsenic(III)-reactive coumarin-appended benzothiazolines: a new approach for inorganic arsenic detection.

    PubMed

    Ezeh, Vivian C; Harrop, Todd C

    2013-03-01

    The EPA has established a maximum contaminant level (MCL) of 10 ppb for arsenic (As) in drinking water requiring sensitive and selective detection methodologies. To tackle this challenge, we have been active in constructing small molecules that react specifically with As(3+) to furnish a new fluorescent species (termed a chemodosimeter). We report in this contribution, the synthesis and spectroscopy of two small-molecule fluorescent probes that we term ArsenoFluors (or AFs) as As-specific chemodosimeters. The AFs (AF1 and AF2) incorporate a coumarin fluorescent reporter coupled with an As-reactive benzothiazoline functional group. AFs react with As(3+) to yield the highly fluorescent coumarin-6 dye (C6) resulting in a 20-25-fold fluorescence enhancement at λem ∼ 500 nm with detection limits of 0.14-0.23 ppb in tetrahydrofuran (THF) at 298 K. The AFs also react with common environmental As(3+) sources such as sodium arsenite in a THF/CHES (N-cyclohexyl-2-aminoethanesulfonic acid) (1:1, pH 9, 298 K) mixture resulting in a modest fluorescence turn-ON (1.5- to 3-fold) due to the quenched nature of coumarin-6 derivatives in high polarity solvents. Bulk analysis of the reaction of the AFs with As(3+) revealed that the C6 derivatives and the Schiff-base disulfide of the AFs (SB1 and SB2) are the ultimate end-products of this chemistry with the formation of C6 being the principle photoproduct responsible for the As(3+)-specific turn-ON. It appears that a likely species that is traversed in the reaction path is an As-hydride-ligand complex that is a putative intermediate in the proposed reaction path.

  2. Synthesis of neoglycosphingolipid from methoxyamino-functionalized ceramide.

    PubMed

    Ishida, Junya; Hinou, Hiroshi; Naruchi, Kentaro; Nishimura, Shin-Ichiro

    2014-02-15

    An efficient approach for the synthesis of a methoxyamino-functionalized ceramide was established from phytosphingosine using specific Nβ→Nα acyl migration of the octadecanoyl group during the removal of Nα-Fmoc protective group. One step glycoblotting reaction of the ceramide mimic with lactose afforded a neoglycosphingolipid showing potent inhibitory activity against recombinant endoglycoceramidase II from Rhodococcus sp. PMID:24461288

  3. Synthesis and characterization of functionalized magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Biswal, Dipti; Peeples, Brianna N.; Spence, Destiny D.; Peeples, Caryn; Bell, Crystal N.; Pradhan, A. K.

    2012-04-01

    Magnetic nanoparticles have been used in a wide array of industrial and biomedical applications due to their unique properties at the nanoscale level. They are extensively used in magnetic resonance imaging (MRI), magnetic hyperthermia treatment, drug delivery, and in assays for biological separations. Furthermore, superparamagnetic nanoparticles are of large interest for in vivo applications. However, these unmodified nanoparticles aggregate and consequently lose their superparamagnetic behaviors, due to high surface to volume ratio and strong dipole to dipole interaction. For these reasons, surface coating is necessary for the enhancement and effectiveness of magnetic nanoparticles to be used in various applications. In addition to providing increased stability to the nanoparticles in different solvents or media, stabilizers such as surfactants, organic/inorganic molecules, polymer and co-polymers are employed as surface coatings, which yield magnetically responsive systems. In this work we present the synthesis and magnetic characterization of Fe3O4 nanoparticles coated with 3-aminopropyltriethoxy silane (APS) and citric acid. The particles magnetic hysteresis was measured by a superconducting quantum interference device (SQUID) magnetometer with an in-plane magnetic field. The uncoated and coated magnetic nanoparticles were characterized by using fourier transform infrared (FTIR), UV-vis, X-ray diffraction, transmission electron microscopy, and thermo-gravimetric analysis.

  4. Function of reactive oxygen species during animal development: passive or active?

    PubMed

    Covarrubias, Luis; Hernández-García, David; Schnabel, Denhí; Salas-Vidal, Enrique; Castro-Obregón, Susana

    2008-08-01

    Oxidative stress is considered causal of aging and pathological cell death, however, very little is known about its function in the natural processes that support the formation of an organism. It is generally thought that cells must continuously protect themselves from the possible damage caused by reactive oxygen species (ROS) (passive ROS function). However, presently, ROS are recognized as physiologically relevant molecules that mediate cell responses to a variety of stimuli, and the activities of several molecules, some developmentally relevant, are directly or indirectly regulated by oxidative stress (active ROS function). Here we review recent data that are suggestive of specific ROS functions during development of animals, particularly mammals.

  5. Synthesis and Surface Reactivity of Vinylized Macroporous Silica Monoliths: One-Pot Hybrid versus Postsynthesis Grafting Strategies.

    PubMed

    El-Debs, Racha; Cadoux, Franck; Bois, Laurence; Bonhommé, Anne; Randon, Jérôme; Dugas, Vincent; Demesmay, Claire

    2015-10-27

    Different synthesis routes have been implemented to prepare macroporous monoliths with vinyl pendant groups and micrometric skeletons and through-pore sizes. A standard process combining the synthesis of a widely used (methyltrimethoxysilane/tetramethoxysilane) (MTMS/TMOS) hybrid silica monolith and the postsilanization with vinyltrimethoxysilane (VTMS) was used as reference material (Vgr-MTMS). An alternative "one-pot" procedure was used to obtain vinylized hybrid monoliths. Two VTMS/TMOS hybrid based monoliths were successfully prepared starting from 20% (w) and 80% (w/w) of VTMS, respectively, called 20-VTMS and 80-VTMS. Monoliths were characterized by SEM, nitrogen-adsorption isotherm, and (29)Si MAS NMR spectroscopy. One-pot synthesis allowed to obtain higher vinyl contents (15.9 and 61.5 mol % of Si atoms bonded to vinyl groups respectively for 20-VTMS and 80-VTMS) than for the postgrafted one (7.1%). Accessibility of vinyl groups was determined by the extent of bromination reactions followed by FTIR-ATR spectroscopy. Bromination with reaction yields were higher than 80% for all materials (80%, 85%, and 100% for 80-VTMS, 20-VTMS, and Vgr-MTMS respectively), with no diffusion issues The chemical reactivity of the pendant vinyl groups was investigated through radical-mediated thiol-ene reaction and radical-initiated bisulfite addition. Reaction yields for the two VTMS hybrid monoliths were quite lower (4-6%) than those obtained (about 50%) for the Vgr-MTMS monolith. The difference in reactivity was attributed to the steric hindrance of the vinyl moieties at the surface of hybrid materials. However, the lower reactivity of vinyl groups is compensated by their considerably higher surface density. Thus, hybrid monoliths are advantageous over their grafted counterparts, due to their higher hydrolytic stability and to the greater simplicity of the one-pot process. A chromatographic application exemplifies their interest and performances in separation science. PMID

  6. Synthesis and Surface Reactivity of Vinylized Macroporous Silica Monoliths: One-Pot Hybrid versus Postsynthesis Grafting Strategies.

    PubMed

    El-Debs, Racha; Cadoux, Franck; Bois, Laurence; Bonhommé, Anne; Randon, Jérôme; Dugas, Vincent; Demesmay, Claire

    2015-10-27

    Different synthesis routes have been implemented to prepare macroporous monoliths with vinyl pendant groups and micrometric skeletons and through-pore sizes. A standard process combining the synthesis of a widely used (methyltrimethoxysilane/tetramethoxysilane) (MTMS/TMOS) hybrid silica monolith and the postsilanization with vinyltrimethoxysilane (VTMS) was used as reference material (Vgr-MTMS). An alternative "one-pot" procedure was used to obtain vinylized hybrid monoliths. Two VTMS/TMOS hybrid based monoliths were successfully prepared starting from 20% (w) and 80% (w/w) of VTMS, respectively, called 20-VTMS and 80-VTMS. Monoliths were characterized by SEM, nitrogen-adsorption isotherm, and (29)Si MAS NMR spectroscopy. One-pot synthesis allowed to obtain higher vinyl contents (15.9 and 61.5 mol % of Si atoms bonded to vinyl groups respectively for 20-VTMS and 80-VTMS) than for the postgrafted one (7.1%). Accessibility of vinyl groups was determined by the extent of bromination reactions followed by FTIR-ATR spectroscopy. Bromination with reaction yields were higher than 80% for all materials (80%, 85%, and 100% for 80-VTMS, 20-VTMS, and Vgr-MTMS respectively), with no diffusion issues The chemical reactivity of the pendant vinyl groups was investigated through radical-mediated thiol-ene reaction and radical-initiated bisulfite addition. Reaction yields for the two VTMS hybrid monoliths were quite lower (4-6%) than those obtained (about 50%) for the Vgr-MTMS monolith. The difference in reactivity was attributed to the steric hindrance of the vinyl moieties at the surface of hybrid materials. However, the lower reactivity of vinyl groups is compensated by their considerably higher surface density. Thus, hybrid monoliths are advantageous over their grafted counterparts, due to their higher hydrolytic stability and to the greater simplicity of the one-pot process. A chromatographic application exemplifies their interest and performances in separation science.

  7. Resting State Functional Connectivity within the Cingulate Cortex Jointly Predicts Agreeableness and Stressor-Evoked Cardiovascular Reactivity

    PubMed Central

    Ryan, John P.; Sheu, Lei K.; Gianaros, Peter J.

    2010-01-01

    Exaggerated cardiovascular reactivity to stress confers risk for cardiovascular disease. Further, individual differences in stressor-evoked cardiovascular reactivity covary with the functionality of cortical and limbic brain areas, particularly within the cingulate cortex. What remains unclear, however, is how individual differences in personality traits interact with cingulate functionality in the prediction of stressor-evoked cardiovascular reactivity. Accordingly, we tested the associations between (i) a particular personality trait, Agreeableness, which is associated with emotional reactions to conflict, (ii) resting state functional connectivity within the cingulate cortex, and (iii) stressor-evoked blood pressure (BP) reactivity. Participants (N=39, 19 men, aged 20–37 yrs) completed a resting functional connectivity MRI protocol, followed by two standardized stressor tasks that engaged conflict processing and evoked BP reactivity. Agreeableness covaried positively with BP reactivity across individuals. Moreover, connectivity analyses demonstrated that a more positive functional connectivity between the posterior cingulate (BA31) and the perigenual anterior cingulate (BA32) covaried positively with Agreeableness and with BP reactivity. Finally, statistical mediation analyses demonstrated that BA31–BA32 connectivity mediated the covariation between Agreeableness and BP reactivity. Functional connectivity within the cingulate appears to link Agreeableness and a risk factor for cardiovascular disease, stressor-evoked BP reactivity. PMID:21130172

  8. Organometallic synthesis, reactivity and catalysis in the solid state using well-defined single-site species

    PubMed Central

    Pike, Sebastian D.; Weller, Andrew S.

    2015-01-01

    Acting as a bridge between the heterogeneous and homogeneous realms, the use of discrete, well-defined, solid-state organometallic complexes for synthesis and catalysis is a remarkably undeveloped field. Here, we present a review of this topic, focusing on describing the key transformations that can be observed at a transition-metal centre, as well as the use of well-defined organometallic complexes in the solid state as catalysts. There is a particular focus upon gas–solid reactivity/catalysis and single-crystal-to-single-crystal transformations. PMID:25666064

  9. New one-pot synthesis of Au and Ag nanoparticles using green rust reactive particle as a micro-reactor.

    PubMed

    Ayadi, Sondra; Perca, Cristian; Legrand, Ludovic

    2013-01-01

    A new, simple, and fast one-pot synthesis of supported Au or Ag nanoparticles is implemented, for which a reactive Fe(II)-bearing green rust inorganic particle is used as an individual micro-reactor acting as both the reducing agent and support for the resulting metal nanoparticles. The mechanism involves both the solid-state oxidation of the green rust support (sulfate or carbonate) and the reduction-precipitation of soluble metal precursor. The resulting nanohybrids have a platy inorganic part supporting about one to ten nanoparticles with sizes in the 20 to 120 nm range. PMID:23433071

  10. New one-pot synthesis of Au and Ag nanoparticles using green rust reactive particle as a micro-reactor

    NASA Astrophysics Data System (ADS)

    Ayadi, Sondra; Perca, Cristian; Legrand, Ludovic

    2013-02-01

    A new, simple, and fast one-pot synthesis of supported Au or Ag nanoparticles is implemented, for which a reactive Fe(II)-bearing green rust inorganic particle is used as an individual micro-reactor acting as both the reducing agent and support for the resulting metal nanoparticles. The mechanism involves both the solid-state oxidation of the green rust support (sulfate or carbonate) and the reduction-precipitation of soluble metal precursor. The resulting nanohybrids have a platy inorganic part supporting about one to ten nanoparticles with sizes in the 20 to 120 nm range.

  11. New one-pot synthesis of Au and Ag nanoparticles using green rust reactive particle as a micro-reactor.

    PubMed

    Ayadi, Sondra; Perca, Cristian; Legrand, Ludovic

    2013-02-22

    A new, simple, and fast one-pot synthesis of supported Au or Ag nanoparticles is implemented, for which a reactive Fe(II)-bearing green rust inorganic particle is used as an individual micro-reactor acting as both the reducing agent and support for the resulting metal nanoparticles. The mechanism involves both the solid-state oxidation of the green rust support (sulfate or carbonate) and the reduction-precipitation of soluble metal precursor. The resulting nanohybrids have a platy inorganic part supporting about one to ten nanoparticles with sizes in the 20 to 120 nm range.

  12. New one-pot synthesis of Au and Ag nanoparticles using green rust reactive particle as a micro-reactor

    PubMed Central

    2013-01-01

    A new, simple, and fast one-pot synthesis of supported Au or Ag nanoparticles is implemented, for which a reactive Fe(II)-bearing green rust inorganic particle is used as an individual micro-reactor acting as both the reducing agent and support for the resulting metal nanoparticles. The mechanism involves both the solid-state oxidation of the green rust support (sulfate or carbonate) and the reduction-precipitation of soluble metal precursor. The resulting nanohybrids have a platy inorganic part supporting about one to ten nanoparticles with sizes in the 20 to 120 nm range. PMID:23433071

  13. Clear microstructure-performance relationships in Mn-containing perovskite and hexaaluminate compounds prepared by activated reactive synthesis.

    PubMed

    Laassiri, Said; Bion, Nicolas; Duprez, Daniel; Royer, Sébastien; Alamdari, Houshang

    2014-03-01

    Microstructural properties of mixed oxides play essential roles in their oxygen mobility and consequently in their catalytic performances. Two families of mixed oxides (perovskite and hexaaluminate) with different microstructural features, such as crystal size and specific surface area, were prepared using the activated reactive synthesis (ARS) method. It was shown that ARS is a flexible route to synthesize both mixed oxides with nano-scale crystal size and high specific surface area. Redox properties and oxygen mobility were found to be strongly affected by the material microstructure. Catalytic activities of hexaaluminate and perovskite materials for methane oxidation were discussed in the light of structural, redox and oxygen mobility properties. PMID:24448203

  14. Centrifugally-assisted combustion synthesis of functionally-graded materials

    SciTech Connect

    Lai, W.; Munir, Z.A.; McCoy, B.J.; Risbud, S.H.

    1997-02-01

    Functionally graded materials (FGM`s) have been prepared by a variety of techniques, including combustion synthesis, and the use of a centrifugal force in this method of synthesis has been demonstrated previously. However, in the earlier work, a centrifugal force was applied to investigate the changes in the dynamics of self-propagating combustion waves or to deposit coatings on the inside surfaces of pipes. The use of a centrifugal force to investigate the formation of FGM`s has not been reported previously and is the focus of this communication. In this work, the authors have chosen thermite reactions to investigate the feasibility of FGM formation by centrifugally-assisted combustion synthesis.

  15. Reactivation of peptidoglycan synthesis in ether-permeabilized Escherichia coli after inhibition by beta-lactam antibiotics.

    PubMed Central

    Talbot, M K; Schaefer, F; Brocks, V; Christenson, J G

    1989-01-01

    The recovery of peptidoglycan-synthesizing activity after inhibition by beta-lactam antibiotics was investigated in ether-permeabilized cells of Escherichia coli B. Such cells synthesize sodium dodecyl sulfate-insoluble peptidoglycan when provided with UDP-linked precursors and Mg2+. The ability of beta-lactam antibiotics to inhibit the synthesis of peptidoglycan was correlated with their affinity for penicillin-binding proteins 1A and 1Bs. Penicillin-binding protein 1Bs is thought to be the major peptidoglycan synthetase in E. coli and is a major lethal target for beta-lactam antibiotics. Ether-treated bacteria were preincubated with concentrations of beta-lactams sufficient to completely inhibit peptidoglycan synthesis and then treated with beta-lactamases to inactivate free antibiotic prior to measurement of peptidoglycan synthesis. At 40 min after beta-lactamase treatment, the rate of peptidoglycan synthesis was about 74% of the control rate in cells pretreated with ampicillin, but only 15% of the control in cells pretreated with penicillin G or azlocillin. Reversal of inhibition by several other antibiotics fell between these extremes. When cross-linking of peptidoglycan was measured specifically, reversal of inhibition by ampicillin also occurred more readily than that by penicillin G. Reactivation of peptidoglycan synthesis was not due to de novo synthesis of penicillin-binding proteins since it occurred under conditions that did not allow incorporation of [14C]leucine. We conclude that there is considerable variation in the stability of the inactive acyl enzymes formed between various beta-lactams and penicillin-binding protein 1Bs, with those formed by penicillin G being relatively long-lived. Images PMID:2515794

  16. Synthesis and adsorption of functionalized polystyrenes

    SciTech Connect

    Iyengar, D.R.

    1992-12-31

    The effect of specifically interacting functional groups located at the chain ends of polystyrene on the absorption rate, adsorbance, graft density and surface excess are discussed from cyclohexane, a theta solvent and toluene. Polystyrenes with hydroxyl and carboxylic acid-end-groups in narrow molecular weight distribution are synthesized by anionic polymerization of styrene followed by suitable termination reactions. Thin layer chromatography (TLC) is developed as an analytical technique to predict trends in the adsorption of the polymers in a range of solvents. In particular the information about the localization of the end-group and therefore different chain architectures at the interface are inferred from this simple technique. Adsorption isotherms are obtained for each of the functionalized polymers of four different molecular weights, the selection of which was based on the TLC results. Kinetics of adsorption and the adsorbance data are determined by liquid counting of tritium labelled polymers. Graft density and surface excess data are calculated from the adsorbance data and other known parameters. It is shown, from these data, that polystyrenes with a carboxylic acid end-group form weakly stretched brushes at the glass-cyclohexane interface and mushrooms at the glass-toluene interface a result consistent with the higher osmotic repulsions towards packing in good solvents. Polystyrenes with function groups at both the chain ends are hypothesized to form a range of structures from those dominated by tails at higher concentrations to those dominated by loops and trains at lower solution concentrations. At higher molecular weights it is shown that functionalized a result consistent with the TLC predictions. Hydroxyl end-group is shown to be an ineffective sticky foot from its adsorbance vis-a-vis polystyrene.

  17. Synthesis of diethylamine-functionalized soybean oil.

    PubMed

    Biswas, Atanu; Adhvaryu, Atanu; Gordon, Sherald H; Erhan, Sevim Z; Willett, Julious L

    2005-11-30

    Specialty chemicals based on renewable resources are desirable commodities due to their eco-friendly nature and "green" product characteristics. These chemicals can demonstrate physical and chemical properties comparable to those of conventional petroleum-based products. Suitably functionalized amines in the triacylglycerol structure can function as an antioxidant, as well as an antiwear/antifriction agent. In addition, the amphiphilic nature of seed oils makes them an excellent candidate as base fluid. The reaction of amine and epoxidized seed oils in the presence of a catalyst almost always leads to different intra/intermolecular cross-linked products. In most cases, the triacylglycerol structure is lost due to disruption of the ester linkage. Currently, there is no reported literature describing the aminolysis of vegetable oil without cross-linking. Here the epoxy group of the epoxidized soybean oil has been selectively reacted with amines to give amine-functionalized soybean oil. The optimization procedure involved various amines and catalysts for maximum aminolysis, without cross-linking and disruption of the ester linkage. Diethylamine and ZnCl2 were found to be the best. NMR, IR, and nitrogen analysis were used to characterize the products. PMID:16302766

  18. Synthesis of a novel small diameter polyurethane vascular graft with reactive binding sites.

    PubMed

    Dempsey, D J; Phaneuf, M D; Bide, M J; Szycher, M; Quist, W C; Logerfo, F W

    1998-01-01

    Development of a small diameter (4 mm inner diameter [ID]) prosthetic vascular graft with functional groups accessible for covalent binding of recombinant hirudin (a potent anticoagulant) should create a more hemocompatible surface. The purpose of this study was to develop a technique for generating carboxylic acid groups on the surface of precast 4 mm ID poly-(carbonate urea)-urethane vascular grafts and to evaluate the accessibility of these groups. A polycarbonate based urethane with the chain extender 2,2-bis(hydroxymethyl)propionic acid was synthesized. A precast 4 mm ID poly(carbonate urea)-urethane vascular graft (Chronoflex [CF]; CardioTech International, Woburn, MA) was then placed into a 4% carboxylated polyurethane (cPU) solution (in 1% dimethyl acetamide) and incubated for 30 minutes (cPU graft). To determine the accessibility of the carboxylic acid groups, a standard textile technique using methylene blue dye was used. Macroscopic cross-sections, which were cut and evaluated for dye penetration, showed greatest concentration of carboxylic acid groups at the luminal and capsule surfaces, with minimal penetration into the mid-portion of the graft. Analysis of dye baths for absorbance reduction resulted in the cPU grafts having 3.7-fold and 5.4-fold more accessible carboxylic acid groups compared with untreated and dimethyl acetamide dipped CF grafts. Thus, a novel small diameter vascular graft has been developed that contains reactive carboxylic acid groups accessible for protein binding. PMID:9804482

  19. Examining Endothelial Function and Platelet Reactivity in Patients with Depression before and after SSRI Therapy.

    PubMed

    Dawood, Tye; Barton, David A; Lambert, Elisabeth A; Eikelis, Nina; Lambert, Gavin W

    2016-01-01

    Although it is recognized that patients with major depressive disorder (MDD) are at increased risk of developing cardiovascular disease (CVD) the mechanisms responsible remain unknown. Endothelial dysfunction is one of the first signs of CVD. Using two techniques, flow-mediated dilatation in response to reactive hyperemia and laser Doppler velocimetry with iontophoresis, we examined endothelial function in the forearm before and after serotonin-specific reuptake inhibitor (SSRI) treatment in 31 patients with MDD. Measurement of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, soluble P-selectin, and noradrenaline in plasma was also performed. Prior to treatment, markers of endothelial and vascular function and platelet reactivity were within the normal range. Following SSRI therapy (95 ± 5 days) symptoms of depression were reduced (paired difference between pre- and post-treatment Hamilton rating -18 ± 1, P < 0.001) with 19 patients recovered and 4 remitted. There occurred no significant change in markers of endothelial or vascular function following SSRI therapy. The improvement in Hamilton depression rating in response to therapy could be independently predicted by the baseline arterial plasma noradrenaline concentration (r (2) = 0.36, P = 0.003). In this cohort of patients with MDD, SSRI therapy did not influence endothelial function or markers of vascular or platelet reactivity. Patient response to SSRI therapy could be predicted by the initial circulating level of noradrenaline, with noradrenaline levels being lower in responders. PMID:26924994

  20. Examining Endothelial Function and Platelet Reactivity in Patients with Depression before and after SSRI Therapy

    PubMed Central

    Dawood, Tye; Barton, David A.; Lambert, Elisabeth A.; Eikelis, Nina; Lambert, Gavin W.

    2016-01-01

    Although it is recognized that patients with major depressive disorder (MDD) are at increased risk of developing cardiovascular disease (CVD) the mechanisms responsible remain unknown. Endothelial dysfunction is one of the first signs of CVD. Using two techniques, flow-mediated dilatation in response to reactive hyperemia and laser Doppler velocimetry with iontophoresis, we examined endothelial function in the forearm before and after serotonin-specific reuptake inhibitor (SSRI) treatment in 31 patients with MDD. Measurement of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, soluble P-selectin, and noradrenaline in plasma was also performed. Prior to treatment, markers of endothelial and vascular function and platelet reactivity were within the normal range. Following SSRI therapy (95 ± 5 days) symptoms of depression were reduced (paired difference between pre- and post-treatment Hamilton rating −18 ± 1, P < 0.001) with 19 patients recovered and 4 remitted. There occurred no significant change in markers of endothelial or vascular function following SSRI therapy. The improvement in Hamilton depression rating in response to therapy could be independently predicted by the baseline arterial plasma noradrenaline concentration (r2 = 0.36, P = 0.003). In this cohort of patients with MDD, SSRI therapy did not influence endothelial function or markers of vascular or platelet reactivity. Patient response to SSRI therapy could be predicted by the initial circulating level of noradrenaline, with noradrenaline levels being lower in responders. PMID:26924994

  1. A parametric transfer function methodology for analyzing reactive transport in nonuniform flow.

    PubMed

    Luo, Jian; Cirpka, Olaf A; Fienen, Michael N; Wu, Wei-min; Mehlhorn, Tonia L; Carley, Jack; Jardine, Philip M; Criddle, Craig S; Kitanidis, Peter K

    2006-02-01

    We analyze reactive transport during in-situ bioremediation in a nonuniform flow field, involving multiple extraction and injection wells, by the method of transfer functions. Gamma distributions are used as parametric models of the transfer functions. Apparent parameters of classical transport models may be estimated from those of the gamma distributions by matching temporal moments. We demonstrate the method by application to measured data taken at a field experiment on bioremediation conducted in a multiple-well system in Oak Ridge, TN. Breakthrough curves (BTCs) of a conservative tracer (bromide) and a reactive compound (ethanol) are measured at multi-level sampling (MLS) wells and in extraction wells. The BTCs of both compounds are jointly analyzed to estimate the first-order degradation rate of ethanol. To quantify the tracer loss, we compare the approaches of using a scaling factor and a first-order decay term. Results show that by including a scaling factor both gamma distributions and inverse-Gaussian distributions (transfer functions according to the advection-dispersion equation) are suitable to approximate the transfer functions and estimate the reactive rate coefficients for both MLS and extraction wells. However, using a first-order decay term for tracer loss fails to describe the BTCs at the extraction well, which is affected by the nonuniform distribution of travel paths.

  2. Acute functional reactivation of the language network during awake intraoperative brain mapping.

    PubMed

    Spena, Giannantonio; Costi, Emanuele; Panciani, Pier Paolo; Roca, Elena; Migliorati, Karol; Fontanella, Marco Maria

    2015-01-01

    Acute brain plasticity during resection of central lesions has been recently described. In the cases reported, perilesional latent networks, useful to preserve the neurological functions, were detected in asymptomatic patients. In this paper, we presented a case of acute functional reactivation (AFR) of the language network in a symptomatic patient. Tumor resection allowed to acutely restore the neurological deficit. Intraoperative direct cortical stimulation (DCS) and functional neuroimaging showed new epicentres of activation of the language network after tumor excision. DCS in awake surgery is mandatory to reveal AFR needful to improve the extent of resection preserving the quality of life.

  3. Applications of C–H Functionalization Logic to Cyclobutane Synthesis

    PubMed Central

    2015-01-01

    The application of C–H functionalization logic to target-oriented synthesis provides an exciting new venue for the development of new and useful strategies in organic chemistry. In this article, C–H functionalization reactions are explored as an alternative approach to access pseudodimeric cyclobutane natural products, such as the dictazole and the piperarborenine families. The use of these strategies in a variety of complex settings highlights the subtle geometric, steric, and electronic effects at play in the auxiliary guided C–H functionalization of cyclobutanes. PMID:24548142

  4. Cellulose nanocrystals: synthesis, functional properties, and applications.

    PubMed

    George, Johnsy; Sabapathi, S N

    2015-01-01

    Cellulose nanocrystals are unique nanomaterials derived from the most abundant and almost inexhaustible natural polymer, cellulose. These nanomaterials have received significant interest due to their mechanical, optical, chemical, and rheological properties. Cellulose nanocrystals primarily obtained from naturally occurring cellulose fibers are biodegradable and renewable in nature and hence they serve as a sustainable and environmentally friendly material for most applications. These nanocrystals are basically hydrophilic in nature; however, they can be surface functionalized to meet various challenging requirements, such as the development of high-performance nanocomposites, using hydrophobic polymer matrices. Considering the ever-increasing interdisciplinary research being carried out on cellulose nanocrystals, this review aims to collate the knowledge available about the sources, chemical structure, and physical and chemical isolation procedures, as well as describes the mechanical, optical, and rheological properties, of cellulose nanocrystals. Innovative applications in diverse fields such as biomedical engineering, material sciences, electronics, catalysis, etc, wherein these cellulose nanocrystals can be used, are highlighted. PMID:26604715

  5. Cellulose nanocrystals: synthesis, functional properties, and applications

    PubMed Central

    George, Johnsy; Sabapathi, SN

    2015-01-01

    Cellulose nanocrystals are unique nanomaterials derived from the most abundant and almost inexhaustible natural polymer, cellulose. These nanomaterials have received significant interest due to their mechanical, optical, chemical, and rheological properties. Cellulose nanocrystals primarily obtained from naturally occurring cellulose fibers are biodegradable and renewable in nature and hence they serve as a sustainable and environmentally friendly material for most applications. These nanocrystals are basically hydrophilic in nature; however, they can be surface functionalized to meet various challenging requirements, such as the development of high-performance nanocomposites, using hydrophobic polymer matrices. Considering the ever-increasing interdisciplinary research being carried out on cellulose nanocrystals, this review aims to collate the knowledge available about the sources, chemical structure, and physical and chemical isolation procedures, as well as describes the mechanical, optical, and rheological properties, of cellulose nanocrystals. Innovative applications in diverse fields such as biomedical engineering, material sciences, electronics, catalysis, etc, wherein these cellulose nanocrystals can be used, are highlighted. PMID:26604715

  6. Electrochemical synthesis and reactivity screening of a ternary composition gradient for combinatorial discovery of fuel cell catalysts

    NASA Astrophysics Data System (ADS)

    Jayaraman, S.; Hillier, A. C.

    2005-01-01

    This paper describes a method for synthesis of multi-component gradient libraries for combinatorial catalyst discovery. A 'gel-transfer' synthesis method is demonstrated that involves localized diffusion of aqueous precursor metal salts into a hydrated gel to establish spatially varying concentration fields. Electrodeposition is then used to transfer the gradient in metal precursors to a surface. To illustrate the utility of this method, a platinum-ruthenium-rhodium (PtxRuyRhz) catalyst gradient was constructed, and its reactivity towards several fuel cell reactions evaluated. An optical screening technique based upon the pH-sensitive fluorescence of quinine was used to visualize the spatial onset of reactivity on the ternary catalyst gradient. The evolution of protons from several reactions of interest for low temperature fuel cells was visualized by quinine fluorescence. The oxidation of hydrogen, carbon monoxide, methanol and ethanol were tested on the catalyst library. Catalyst regions that exhibited fluorescence (and hence the onset of activity) at lowest potentials were identified for each of the above reactions.

  7. Scaling properties of information-theoretic quantities in density functional reactivity theory.

    PubMed

    Rong, Chunying; Lu, Tian; Ayers, Paul W; Chattaraj, Pratim K; Liu, Shubin

    2015-02-21

    Density functional reactivity theory (DFRT) employs the electron density and its related quantities to describe reactivity properties of a molecular system. Quantities from information theory such as Shannon entropy, Fisher information, and Ghosh-Berkowitz-Parr entropy are natural descriptors within the DFRT framework. They have been previously employed to quantify electrophilicity, nucleophilicity and the steric effect. In this work, we examine their scaling properties with respect to the total number of electrons. To that end, we considered their representations in terms of both the electron density and the shape function for isolated atoms and neutral molecules. We also investigated their atomic behaviors in different molecules with three distinct partitioning schemes: Bader's zero-flux, Becke's fuzzy atom, and Hirshfeld's stockholder partitioning. Strong linear relationships of these quantities as a function of the total electron population are reported for atoms, molecules, and atoms in molecules. These relationships reveal how these information-theoretic quantities depend on the molecular environment and the electron population. These trends also indicate how these quantities can be used to explore chemical reactivity for real chemical processes.

  8. Dissecting molecular descriptors into atomic contributions in density functional reactivity theory

    NASA Astrophysics Data System (ADS)

    Rong, Chunying; Lu, Tian; Liu, Shubin

    2014-01-01

    Density functional reactivity theory (DFRT) employs the electron density of a molecule and its related quantities such as gradient and Laplacian to describe its structure and reactivity properties. Proper descriptions at both molecular (global) and atomic (local) levels are equally important and illuminating. In this work, we make use of Bader's zero-flux partition scheme and consider atomic contributions for a few global reactivity descriptors in DFRT, including the density-based quantification of steric effect and related indices. Earlier, we proved that these quantities are intrinsically correlated for atomic and molecular systems [S. B. Liu, J. Chem. Phys. 126, 191107 (2007); ibid. 126, 244103 (2007)]. In this work, a new basin-based integration algorithm has been implemented, whose reliability and effectiveness have been extensively examined. We also investigated a list of simple hydrocarbon systems and different scenarios of bonding processes, including stretching, bending, and rotating. Interesting changing patterns for the atomic and molecular values of these quantities have been revealed for different systems. This work not only confirms the strong correlation between these global reactivity descriptors for molecular systems, as theoretically proven earlier by us, it also provides new and unexpected changing patterns for their atomic values, which can be employed to understand the origin and nature of chemical phenomena.

  9. Dissecting molecular descriptors into atomic contributions in density functional reactivity theory

    SciTech Connect

    Rong, Chunying; Lu, Tian; Liu, Shubin

    2014-01-14

    Density functional reactivity theory (DFRT) employs the electron density of a molecule and its related quantities such as gradient and Laplacian to describe its structure and reactivity properties. Proper descriptions at both molecular (global) and atomic (local) levels are equally important and illuminating. In this work, we make use of Bader's zero-flux partition scheme and consider atomic contributions for a few global reactivity descriptors in DFRT, including the density-based quantification of steric effect and related indices. Earlier, we proved that these quantities are intrinsically correlated for atomic and molecular systems [S. B. Liu, J. Chem. Phys. 126, 191107 (2007); ibid. 126, 244103 (2007)]. In this work, a new basin-based integration algorithm has been implemented, whose reliability and effectiveness have been extensively examined. We also investigated a list of simple hydrocarbon systems and different scenarios of bonding processes, including stretching, bending, and rotating. Interesting changing patterns for the atomic and molecular values of these quantities have been revealed for different systems. This work not only confirms the strong correlation between these global reactivity descriptors for molecular systems, as theoretically proven earlier by us, it also provides new and unexpected changing patterns for their atomic values, which can be employed to understand the origin and nature of chemical phenomena.

  10. Effects of protein synthesis inhibitors during reactivation of associative memory in the common snail induces reversible and irreversible amnesia.

    PubMed

    Solntseva, S V; Nikitin, V P; Kozyrev, S A; Shevelkin, A V; Lagutin, A V; Sherstnev, V V

    2007-11-01

    The effects of protein synthesis inhibitors on the reactivation of an associative skill consisting of refusing a particular food by common snails were studied. Animals were given single injections of a protein synthesis inhibitor (cycloheximide at 0.6 mg/snail or anisomycin at 0.4 mg) 24 h after three days of training, and were then presented with a "reminding" stimulus (the "conditioned reflex" food-banana) and tested for retention of the skill. Observations revealed an impairment of reproduction of the acquired skill 2.5 h after the "reminder," with spontaneous restoration at 4.5-5.5 h. Other snails were given single 1.8-mg doses of cycloheximide or three 0.6-mg doses with intervals of 2 h. "Reminders" were presented after each injection. In these conditions, impairment of reproduction of the conditioned reflex also appeared 2.5 h after the first "reminder," though amnesia lasted at least 30 days and repeat training of the animals produced only partial recovery of the skill. Thus, we have provided the first demonstration that recovery of a long-term memory "trace" on exposure to relatively low doses of protein synthesis inhibitors produces transient and short-lived amnesia, lasting 2-3 h, while long-term, irreversible amnesia occurs after longer-lasting or more profound suppression of protein synthesis. These results suggest that the "reminding" process induces reconsolidation of the " initial" memory, suppression of which by protein synthesis inhibitors leads to "erasure" of the memory "trace" and impairs consolidation on repeat training. PMID:17955385

  11. Facile Synthesis of Functionalized Carbene Metal Complexes from Coordinated Isonitriles.

    PubMed

    Lothschütz, Christian; Wurm, Thomas; Zeiler, Anna; Freiherr V Falkenhausen, Alexander; Rudolph, Matthias; Rominger, Frank; Hashmi, A Stephen K

    2016-02-01

    The scope and limitations of the isonitrile-based NHC template synthesis were investigated with a series of precursors containing a nucleophilic amine in combination with tethered electrophiles. In the case of alkynes and phosphonic esters as electrophiles no ring closure was observed and new functionalized NAC gold complexes were obtained. By the use of unsaturated esters and phosphonic esters as Michael acceptors in the amine precursors, ester-modified gold and palladium NHC complexes were accessible in high efficiency. PMID:26033484

  12. Toward the Synthesis of More Reactive S = 2 Non-Heme Oxoiron(IV) Complexes

    PubMed Central

    2016-01-01

    cleave substrate C–H bonds. The second strategy entailed introducing weaker-field equatorial ligands in six-coordinate oxoiron(IV) complexes to decrease the dx2–y2/dxy energy gap to the point where the S = 2 ground state is favored. These pseudo-octahedral S = 2 oxoiron(IV) complexes exhibit high H-atom transfer reactivity relative to their S = 1 counterparts and shed light on the role that the spin state may play in these reactions. Among these complexes is a highly reactive species that to date represents the closest electronic and functional model of the enzymatic intermediate, TauD-J. PMID:26176555

  13. Synthesis and in vitro reactivation study of isonicotinamide derivatives of 2-(hydroxyimino)-N-(pyridin-3-yl)acetamide as reactivators of Sarin and VX inhibited human acetylcholinesterase (hAChE).

    PubMed

    Karade, Hitendra N; Raviraju, G; Acharya, B N; Valiveti, Aditya Kapil; Bhalerao, Uma; Acharya, Jyotiranjan

    2016-09-15

    Previously (Karade et al., 2014), we have reported the synthesis and in vitro evaluation of bis-pyridinium derivatives of pyridine-3-yl-(2-hydroxyimino acetamide), as reactivators of sarin and VX inhibited hAChE. Few of the molecules showed superior in vivo protection efficacy (mice model) (Kumar et al., 2014; Swami et al., 2016) in comparison to 2-PAM against DFP and sarin poisoning. Encouraged by these results, herein we report the synthesis and in vitro evaluation of isonicotinamide derivatives of pyridine-3-yl-(2-hydroxyimino acetamide) (4a-4d) against sarin and VX inhibited erythrocyte ghost hAChE. Reactivation kinetics of these compounds was studied and the determined kinetic parameters were compared with that of commercial reactivators viz. 2-PAM and obidoxime. In comparison to 2-PAM and obidoxime, oxime 4a and 4b exhibited enhanced reactivation efficacy toward sarin inhibited hAChE while oxime 4c showed far greater reactivation efficacy toward VX inhibited hAChE. The acid dissociation constant and IC50 values of these oximes were determined and correlated with the observed reactivation potential. PMID:27450532

  14. Infant adrenocortical reactivity and behavioral functioning: relation to early exposure to maternal intimate partner violence.

    PubMed

    Levendosky, Alytia A; Bogat, G Anne; Lonstein, Joseph S; Martinez-Torteya, Cecilia; Muzik, Maria; Granger, Douglas A; von Eye, Alexander

    2016-01-01

    Prenatal stress negatively affects fetal development, which in turn may affect infant hypothalamic-pituitary-adrenal (HPA) axis regulation and behavioral functioning. We examined effects of exposure to a traumatic stressor in families [intimate partner violence (IPV)] on both infants' HPA axis reactivity to stress and their internalizing and externalizing behaviors. Infants (n = 182, 50% girls, x age = 11.77 months) were exposed to a laboratory challenge task designed to induce frustration and anger (i.e. arm restraint). Saliva samples were taken pre-task and 20 and 40 min post-task and then assayed for cortisol. Mothers reported on their pregnancy and postpartum IPV history, current mental health, substance use and their infants' behaviors. Structural equation modeling revealed that prenatal, but not postnatal, IPV was independently associated with infant cortisol reactivity and problem behavior. Maternal mental health predicted infant behavioral functioning but not infant HPA axis reactivity. These findings are consistent with the prenatal programing hypothesis; that is, early life stress affects later risk and vulnerability for altered physiological and behavioral regulation. PMID:26482431

  15. Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

    NASA Astrophysics Data System (ADS)

    Wu, Wei; He, Quanguo; Jiang, Changzhong

    2008-10-01

    Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed.

  16. Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

    PubMed Central

    2008-01-01

    Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed. PMID:21749733

  17. [Peptide synthesis aiming at elucidation and creation of protein functions].

    PubMed

    Futaki, S

    1998-11-01

    The recent development of molecular biology has been elucidating outlines of the cross-talk of biomolecules. The understanding of the function of these biomolecules from the viewpoint of chemistry is now demanded not only for the understanding of biological systems but also for the creation of novel functional molecules. Here two topics are described about peptide synthesis aiming at the elucidation and the creation of protein functions. The first topic is the development of approaches for the synthesis of Tyr (SO3H)-containing peptides. Tyrosine sulfation is one of the most popular protein post-translational modifications. Synthetic peptides are of great help for the elucidation of the biological significance of tyrosine sulfation. We have developed two approaches for the efficient synthesis of tyrosine sulfate [Tyr (SO3H)]-containing peptides. The first approach employs a dimethylformamide-sulfur trioxide (DMF-SO3) complex as a sulfating agent and safety-catch protecting groups for the selective sulfation of tyrosine in the presence of serine. The second approach employs the direct introduction of Tyr(SO3H) into the peptide chain in the form of Fmoc-Tyr(SO3Na) followed by deprotection at 4 degrees C in trifluoroacetic acid. These approaches were successfully applied for the synthesis of cholecystokinin (CCK)-related peptides. The second topic deals with new approaches for the creation of artificial proteins through assembling alpha-helical peptides via selective disulfide or thioether formation. Approaches to assemble individual peptide segments on a peptide template were also developed. Four peptides corresponding to the transmembrane segments of the sodium channel (S4 in repeat I-IV) were assembled on a peptide template to give a protein having ion channel activity with rectification.

  18. Pt-Catalyzed Synthesis of Functionalized Symmetrical and Unsymmetrical Disilazanes.

    PubMed

    Kuciński, Krzysztof; Szudkowska-Frątczak, Justyna; Hreczycho, Grzegorz

    2016-09-01

    In nearly every total synthesis, silylating agents are employed in synthetic steps to protect sensitive functional groups. A Pt-catalyzed hydrosilylation of various unsaturated substrates to prepare novel symmetrical and unsymmetrical disilazanes is described. The developed synthetic methodology is widely applicable and tolerates all manner of functional groups (e.g., amines, ethers, esters, halogens, silanes, etc.). To demonstrate the value of the described method, mono-substituted 1,1,3,3-tetramethyldisilazanes were further selectively converted to completely new unsymmetrical derivatives. PMID:27414042

  19. Structure, vibrational analysis, electronic properties and chemical reactivity of two benzoxazole derivatives: Functional density theory study

    NASA Astrophysics Data System (ADS)

    Zaater, Sihem; Bouchoucha, Afaf; Djebbar, Safia; Brahimi, Meziane

    2016-11-01

    In the present work we calculate structural parameters, vibrational spectra (IR, 1H NMR and UV-Visible Absorption) and corresponding mode of vibrational assignments of two ligands derived from benzoxazole; L1: 2-(5-(trifluoromethylpyridin-2-yl)-benzoxazole and L2: 2-(5-methylpyridin-2-yl)-benzoxazole at B3LYP/6-311++G** level, in the gas phase. The HOMO and LUMO study is used to determine the charge transfer within the molecules. Reactivity descriptors such as ionization energy, electronic affinity, global hardness, global softness, electrophilicity, nucleophilicity and condensed Fukui functions using NBO population analysis are also determined to predict the reactivity of L1 and L2. The calculated geometrical parameters are in good agreement with those of similar benzoxazole derivatives. Theoretical frequencies assignments confirmed the experimental ones of these benzoxazole derivatives.

  20. Rapid Microwave Synthesis of Perovskite Oxide Nanostructures with Enhanced Functionality

    NASA Astrophysics Data System (ADS)

    Salazar, Gregory; Datta, Anuja; Mukherjee, Pritish

    2015-03-01

    Perovskite oxides are an important class of materials having high dielectric and piezoelectric coefficients, switchable ferroelectric (FE) polarization and interesting optical and electrical properties. Realization of functional devices based on classic perovskite oxides such as Pb(Zr0.52Ti0.48) O3 (PZT), and emerging Pb-free noncentrosymmetric (NCS) oxides, such as, ZnSnO3, ZnTiO3 and CaTiO3 have reinforced the investigation of these materials in multiple dimensions and length scales. However, large-scale synthesis and integration of ordered low-dimensional structures is a challenge, due to their complicated methodologies, high-cost and difficulties with phase stability. We discuss a generalized, cost-effective, rapid microwave synthesis route for size and shape selective nanostructure growth of these functional perovskite oxides on industrially viable flexible and hard substrates, stabilized by an enhanced ionic covalence. The rational synthesis approach allowed improved tunability of the size, shape, and orientation of the structures with improved electrical and FE properties. The facile fabrication route of these nanostructures may expand the outreach of probes for understanding the structure-property relationships in these hitherto unexplored and technologically important materials.

  1. Design and synthesis of highly reactive dienophiles for the tetrazine-trans-cyclooctene ligation.

    PubMed

    Taylor, Michael T; Blackman, Melissa L; Dmitrenko, Olga; Fox, Joseph M

    2011-06-29

    Computation was used to design a trans-cyclooctene derivative that displays enhanced reactivity in the tetrazine-trans-cycloctene ligation. The optimized derivative is an (E)-bicyclo[6.1.0]non-4-ene with a cis-ring fusion, in which the eight-membered ring is forced to adopt a highly strained 'half-chair' conformation. Toward 3,6-dipyridyl-s-tetrazine in MeOH at 25 °C, the strained derivative is 19 and 27 times more reactive than the parent trans-cyclooctene and 4E-cyclooct-4-enol, respectively. Toward 3,6-diphenyl-s-tetrazine in MeOH at 25 °C, the strained derivative is 160 times more reactive than the parent trans-cyclooctene.

  2. Synthesis and application of polyepoxide cardanol glycidyl ether as biobased polyepoxide reactive diluent for epoxy resin

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Polyepoxide cardanol glycidyl ether (PECGE), a novel cardanol derivative, was synthesized and used as reactive diluent for petroleum-based epoxy resin in this work. The synthetic condition was first optimized, and the resultant PECGE diluent was characterized using Fourier transform infrared spectro...

  3. Gas-phase synthesis and reactivity of Cu(+)-benzyne complexes.

    PubMed

    Chai, Yunfeng; Shen, Shanshan; Weng, Guofeng; Pan, Yuanjiang

    2014-10-11

    Cu(+)-benzyne complexes bearing bidentate nitrogen ligands were synthesized in the gas phase for the first time using electrospray ionization mass spectrometry. The addition reactivity of copper-stabilized benzyne with amines was studied in the ion trap analyzer. The structures of products were identified by comparing their MS(n) data with authentic compounds obtained from another generation route.

  4. Monitoring Immune System Function and Reactivation of Latent Viruses in the Artificial Gravity Pilot Study

    NASA Technical Reports Server (NTRS)

    Mehta, Satish; Crusian, Brian; Pierson, Duane; Sams, Clarence; Stowe, Raymond

    2007-01-01

    Numerous studies have indicated that dysregulation of the immune system occurs during or after spaceflight. Using 21 day -6 deg. head-down tilt bed rest as a spaceflight analog, this study describes the effects of artificial gravity as a daily countermeasure on immunity, stress and reactivation of clinically important latent herpes viruses. The specific aims were to evaluate psychological and physiological stress, to determine the status of the immune system and to quantify reactivation of latent herpes viruses. Blood, saliva, and urine samples were collected from each participating subject at different times throughout the study. An immune assessment was performed on all treatment and control subjects that consisted of a comprehensive peripheral immunophenotype analysis, intracellular cytokine profiles and a measurement of T cell function. The treatment group displayed no differences throughout the course of the study with regards to peripheral leukocyte distribution, cytokine production or T cell function. Shedding of EBV and CMV was quantified by real time PCR in saliva and urine samples, respectively. There was no significant difference in CMV DNA in the treatment group as compared to the control group. EBV and VZV on the other hand showed a mild reactivation during the study. There were no significant differences in plasma cortisol between the control and treatment groups. In addition, no significant differences between antiviral antibody titers (EBV-VCA, -EA, -EBNA, CMV) or tetramer-positive (EBV, CMV) were found between the two groups. EBV DNA copies in blood were typically undetectable but never exceeded 1,500 copies per 10(exp 6) PBMCs. These data indicate that the artificial gravity countermeasure and the 21 day head-down tilt bed rest regimen had no observable adverse effect on immune function.

  5. Monitoring Immune System Function and Reactivation of Latent Viruses in the Artificial Gravity Pilot Study

    NASA Technical Reports Server (NTRS)

    Mehta, Satish K.; Crucian, Brian; Pierson, Duane L.; Sams, Clarence; Stowe, Raymond P.

    2007-01-01

    Numerous studies have indicated that dysregulation of the immune system occurs during or after spaceflight. Using 21 day -6 degrees head-down tilt bed rest as a spaceflight analog, this study describes the effects of artificial gravity (AG) as a daily countermeasure on immunity, stress and reactivation of clinically important latent herpes viruses. The specific aims were to evaluate psychological and physiological stress, to determine the status of the immune system, and to quantify reactivation of latent herpes viruses. Blood, saliva, and urine samples were collected from each participating subject at different times throughout the study. An immune assessment was performed on all treatment and control subjects that consisted of a comprehensive peripheral immunophenotype analysis, intracellular cytokine profiles and a measurement of T cell function. The treatment group displayed no differences throughout the course of the study with regards to peripheral leukocyte distribution, cytokine production or T cell function. Shedding of Epstein barr virus (EBV), Cytomegalovirus (CMV), and Varicella zoster virus (VZV) was quantified by real time PCR in saliva and urine samples, respectively. There was no significant difference in CMV DNA in the treatment group as compared to the control group. EBV and VZV on the other hand showed a mild reactivation during the study. There were no significant differences in cortisol between the control and treatment groups. In addition, no significant differences between antiviral antibody titers (EBV-VCA, -EA, -EBNA, CMV) or tetramer-positive (EBV, CMV) were found between the two groups. EBV DNA copies in blood were typically undetectable but never exceeded 1,500 copies per 106 PBMCs. Overall, these data indicate that the artificial gravity countermeasure and the 21 day head-down tilt bed rest regimen had no observable adverse effect on immune function.

  6. Electronic structure and reactivity of cobalt oxide dimers and their hexacarbonyl complexes: a density functional study.

    PubMed

    Uzunova, Ellie L; Mikosch, Hans

    2012-03-29

    The dimers of cobalt oxide (CoO)(2) with cyclic and open bent structure are studied with the B1LYP density functional; the ordering of states is validated by the CCSD(T) method. The D(2h)-symmetry rhombic dioxide Co(2)O(2) with antiferromagnetically ordered electrons on cobalt centers is the global minimum. The cyclic peroxide Co(2)(O(2)) with side-on-bonded dioxygen in (7)B(2) ground state is separated from the global minimum by an energy gap of 3.15 eV. The dioxide is highly reactive as indicated by the high value of proton affinity and chemical reactivity indices. The four-member ring structures are more stable than those with three-member ring or chain configuration. The thermodynamic stability toward dissociation to CoO increases upon carbonylation, whereas proton affinity and reactivity with release of molecular oxygen also increase. The global minimum of Co(2)O(2)(CO)(6) corresponds to a triplet state (3)A" with oxygen atoms shifted above the molecular plane of the rhombic dioxide Co(2)O(2). The SOMO-LUMO gap in the ground-state carbonylated dioxide is wider, compared to the same gap in the bare dicobalt dioxide. The peroxo-isomer Co(2)(O(2))(CO)(6) retains the planar Co(2)(O(2)) ring and is only stable in a high-spin state (7)A". The carbonylated clusters have increased reactivity in both redox and nucleophilic reactions, as a result of the increased electron density in the Co(2)O(2)-ring area. PMID:22397598

  7. Facile synthesis of fluorescent polymer nanoparticles by covalent modification-nanoprecipitation of amine-reactive ester polymers.

    PubMed

    Lee, Yeonju; Hanif, Sadaf; Theato, Patrick; Zentel, Rudolf; Lim, Jeewoo; Char, Kookheon

    2015-06-01

    Emission wavelength control in fluorescent nanoparticles (NPs) is crucial for their applications. In the case of inorganic quantum dots or dye-impregnated silica NPs, such a control is readily achieved by changing the size of the particles or choosing appropriate fluorescent dyes, respectively. A similar modular approach for controlling the emission wavelength of fluo-rescent polymer NPs, however, is difficult. This article reports on fluorescent polymer NPs, the synthesis of which provides a platform for a modular approach towards the preparation of fluorescent NPs of desired emission wavelength. Atom-transfer radical polymerization (ATRP) is employed to synthesize reactive ester polymers, which are then easily modified with a commercially available dye and subsequently subjected to nanoprecipitation. The resulting NPs, with low size polydispersity, show an enhanced emission quantum yield when compared with the same dye molecules in solution.

  8. Synthesis and reactivity of molybdenum and tungsten bis(dinitrogen) complexes supported by diphosphine chelates containing pendant amines

    SciTech Connect

    Weiss, Charles J.; Groves, Amy N.; Mock, Michael T.; Dougherty, William G.; Kassel, W. S.; Helm, Monte L.; DuBois, Daniel L.; Bullock, R. Morris

    2012-04-30

    In this study, we report the synthesis and characterization of molybdenum bis(dinitrogen) complexes supported by two PNP diphosphine ligands, Mo(N{sub 2}){sub 2}(PNP){sub 2}; PNP = [(R{sub 2}PCH{sub 2}){sub 2}N(R'), R = Et (ethyl), Ph (phenyl); R'= Me (methyl), Bn (benzyl)], and a series of tungsten bis(dinitrogen) complexes containing one or two PNP ligands, W(N{sub 2}){sub 2}(dppe)(PNP) and W(N{sub 2}){sub 2}(PNP){sub 2}, respectively, and the analogues complexes without pendant amines for comparison. These Mo- and W-N{sub 2} complexes were characterized by NMR, IR, spectroscopy, cyclic voltammetry and structurally characterized by X-ray crystallography. In addition, reactivity of the complexes with CO is described.

  9. Synthesis and reactivity of metal complexes with acyclic (amino)(ylide)carbene ligands.

    PubMed

    González-Fernández, Elisa; Rust, Jörg; Alcarazo, Manuel

    2013-10-18

    No cycle required: The straightforward synthesis of acyclic (amino)(ylide)carbene gold complexes was achieved by reaction of isocyanide gold complexes with phosphorus and arsenic ylides as well as electron-rich olefins. Their ability to form bimetallic species and to act as ligand-transfer reagents has also been established. PMID:24038894

  10. Synthesis and reactivity of metal complexes with acyclic (amino)(ylide)carbene ligands.

    PubMed

    González-Fernández, Elisa; Rust, Jörg; Alcarazo, Manuel

    2013-10-18

    No cycle required: The straightforward synthesis of acyclic (amino)(ylide)carbene gold complexes was achieved by reaction of isocyanide gold complexes with phosphorus and arsenic ylides as well as electron-rich olefins. Their ability to form bimetallic species and to act as ligand-transfer reagents has also been established.

  11. A Miniaturized Technique for Assessing Protein Thermodynamics and Function Using Fast Determination of Quantitative Cysteine Reactivity

    PubMed Central

    Isom, Daniel G.; Marguet, Philippe R.; Oas, Terrence G.; Hellinga, Homme W.

    2010-01-01

    Protein thermodynamic stability is a fundamental physical characteristic that determines biological function. Furthermore, alteration of thermodynamic stability by macromolecular interactions or biochemical modifications is a powerful tool for assessing the relationship between protein structure, stability, and biological function. High-throughput approaches for quantifying protein stability are beginning to emerge that enable thermodynamic measurements on small amounts of material, in short periods of time, and using readily accessible instrumentation. Here we present such a method, fast quantitative cysteine reactivity (fQCR), which exploits the linkage between protein stability, sidechain protection by protein structure, and structural dynamics to characterize the thermodynamic and kinetic properties of proteins. In this approach, the reaction of a protected cysteine and thiol-reactive fluorogenic indicator is monitored over a gradient of temperatures after a short incubation time. These labeling data can be used to determine the midpoint of thermal unfolding, measure the temperature dependence of protein stability, quantify ligand-binding affinity, and, under certain conditions, estimate folding rate constants. Here, we demonstrate the fQCR method by characterizing these thermodynamic and kinetic properties for variants of Staphylococcal nuclease and E. coli ribose-binding protein engineered to contain single, protected cysteines. These straightforward, information-rich experiments are likely to find applications in protein engineering and functional genomics. PMID:21387407

  12. TOPICAL REVIEW: Functionalized molecules studied by STM: motion, switching and reactivity

    NASA Astrophysics Data System (ADS)

    Grill, Leonhard

    2008-02-01

    Functionalized molecules represent the central issue of molecular nanotechnology. Scanning tunnelling microscopy (STM) is a powerful method to investigate such molecules, because it allows us to image them with sub-molecular resolution when adsorbed on a surface and can be used at the same time as a tool to manipulate single molecules in a controlled way. Such studies permit deep insight into the conformational, mechanical and electronic structure and thus functionalities of the molecules. In this review, recent experiments on specially designed molecules, acting as model systems for molecular nanotechnology, are reviewed. The presented studies focus on key functionalities: lateral rolling and hopping motion on a supporting surface, the switching behaviour of azobenzene derivatives by using the STM tip and the controlled reactivity of molecular side groups, which enable the formation of covalently bound molecular nanoarchitectures.

  13. Effects of gravity on combustion synthesis of functionally graded biomaterials

    NASA Astrophysics Data System (ADS)

    Castillo, M.; Moore, J. J.; Schowengerdt, F. D.; Ayers, R. A.; Zhang, X.; Umakoshi, M.; Yi, H. C.; Guigne, J. Y.

    2003-07-01

    Combustion synthesis, or self-propagating, high temperature synthesis is currently being used at the Colorado School of Mines to produce advanced materials for biomedical applications. These biomaterials include ceramic, intermetallic, and metal-matrix composites for applications ranging from structural to oxidation- and wear-resistant materials, e.g., TiC-Ti, TiC-Cr 3C 2, MOSi 2-SiC, NiAl-TiB 2, to engineered porous composites, e.g., B 4C-Al 2O 3, Ti-TiB x, Ni-Ti, Ca 3(P0 4) 2 and glass-ceramic composites, e.g., CaO-SiO 2-BaO-Al 2O 3-TiB 2. The goal of the functionally graded biomaterials project is to develop new materials, graded in porosity and composition, which will combine the desirable mechanical properties of implant, e.g., NiTi, with the bone-growth enhancement properties of porous biodegradable ceramics, e.g., Ca 3(PO 4) 2. Recent experiments on the NASA parabolic flight (KC-135) aircraft have shown that gravity plays an important role in controlling the structure and properties of materials produced by combustion synthesis. The results of these studies, which will be presented at the conference, will provide valuable input to the design of experiments to be done in Space-DRUMS TM, a containerless materials processing facility scheduled to be placed on the International Space Station in 2003.

  14. Effects of gravity on combustion synthesis of functionally graded biomaterials

    NASA Astrophysics Data System (ADS)

    Moore, J.; Schowengerdt, F.; Ayers, R.; Castillo, M.; Zhang, X.; Umakoshi, U.; Yi, C.; Guigne, J.

    Combustion synthesis, or self-propagating, high temperature synthesis (SHS) is currently being used at the Colorado School of Mines to produce advanced materials for biomedical applications. These biomaterials include ceramic, intermetallic, and metal-matrix composites for applications ranging from structural to oxidation- and wear-resistant materials, e.g., TiC-Ti, TiC-Cr3 C2 , MoSi2 - SiC, NiAl-TiB2 , to engineered porous composites, e.g., B4 C-A l2 O3 , Ti-TiBx , Ni-Ti, Ca 3 (PO4 )2 and glass- ceramic composites, e.g., CaO-SiO2 - B a O-A l2 O3 -T i B2 . The goal of the functionally graded biomaterials project is to develop new materials, graded in porosity and composition, which will combine the desirable mechanical properties of implant, e.g., NiTi, with the bone-growth enhancement properties of porous biodegradable ceramics, e.g., Ca 3 (PO4 )2 . Recent experiments on the NASA parabolic flight (KC- 135) aircraft have shown that gravity plays an important role in controlling the structure and properties of materials produced by combustion synthesis. The results of these studies, which will be presented at the conference, will provide valuable input to the design of experiments to be done in Space-DRUMSTM, a containerless materials processing facility scheduled to be placed on the International Space Station in 2003.

  15. Asymmetric Catalysis with Ethylene. Synthesis of Functionalized Chiral Enolates

    PubMed Central

    Biswas, Souvagya; Page, Jordan P.; Dewese, Kendra R.; RajanBabu, T. V.

    2016-01-01

    Trialkylsilyl enol ethers are versatile intermediates often used as enolate surrogates for the synthesis of carbonyl compounds. Yet there are no reports of broadly applicable, catalytic methods for the synthesis of chiral silyl enol ethers carrying latent functionalities useful for synthetic operations beyond the many possible reactions of the silyl enol ether moiety itself. Here we report a general procedure for highly catalytic (substrate:catalyst ratio up to 1000:1) and enantioselective (92% to 98% major enantiomer) synthesis of such compounds bearing a vinyl group at a chiral carbon at the β-position. The reactions, run under ambient conditions, use trialkylsiloxy-1,3-dienes and ethylene (1 atmosphere) as precursors, and readily available (bis-phosphine)-cobalt(II) complexes as catalysts. The silyl enolates can be readily converted into novel enantiopure vinyl triflates, a class of highly versatile cross-coupling reagents, enabling the syntheses of other enantiomerically pure, stereo-defined trisubstituted alkene intermediates not easily accessible by current methods. Examples of Kumada, Stille and Suzuki coupling reactions are illustrated. PMID:26529467

  16. Synthesis and Characterization of Functionalized Metal-organic Frameworks

    PubMed Central

    Karagiaridi, Olga; Bury, Wojciech; Sarjeant, Amy A.; Hupp, Joseph T.; Farha, Omar K.

    2014-01-01

    Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy. PMID:25225784

  17. Interfacial synthesis and functionality of self-stabilized polydiaminonaphthalene nanoparticles.

    PubMed

    Li, Xin-Gui; Zhang, Jia-Li; Huang, Mei-Rong

    2012-08-01

    A simple and effective template-free synthesis method for nanosized conducting polymers with self-stability and functionality is a main challenge. Herein, a strategy is reported for the facile synthesis of poly(1,5-diaminonaphthalene) nanospherical particles by an interfacial miniemulsion oxidative polymerization of 1,5-diaminonaphthalene at mobile microinterfaces between a stirred biphase without external emulsifiers. The size of the nanospheres was carefully optimized by controlling the polymerization conditions. Formation and self-stabilization mechanisms of the nanoparticles are proposed. The constantly movable and refreshed microinterface is a key to successful synthesis of the nanospheres, for significantly suppressing secondary growth leading to agglomerated particles because vigorous stirring makes as-formed self-stabilized nanospheres instantly leave the microinterfaces. The resulting nanospheres possess several advantages: clean surface, self-stability, redispersibility, semiconductivity, electroactivity, and fluorescence emission. The fluorescence emission can be quenched by specific quenchers, thus enabling low-cost, high-performance chemosensors to be obtained for the sensitive detection of Zn(II) ions in a wide linear concentration range of more than five orders of magnitude with a superior detection limit down to 1 nM.

  18. Synthesis of functional acetylene derivatives from calcium carbide.

    PubMed

    Lin, Zhewang; Yu, Dingyi; Sum, Yin Ngai; Zhang, Yugen

    2012-04-01

    AHA Erlebnis: CaC(2), used to produce acetylene until several decades ago, is re-emerging as a cheap, sustainable resource synthesized from coal and lignocellulosic biomass. We report efficient catalytic protocols for the synthesis of functional acetylene derivatives from CaC(2) through aldehyde, alkyne, and amine (AAA) as well as alkyne, haloalkane, and amine (AHA) couplings, and in addition demonstrate its use in click and Sonogashira chemistry, showing that calcium carbide is a sustainable and cost-efficient carbon source.

  19. Synthesis of fully functionalized aglycone of lycoperdinoside A and B.

    PubMed

    Chandrasekhar, Balla; Athe, Sudhakar; Reddy, P Purushotham; Ghosh, Subhash

    2015-01-01

    This article reported the synthesis of fully functionalized aglycone of lycoperdinoside A and B. Pd-catalyzed Stille-Migita cross coupling between E-vinyl iodide 6 and E-vinyl stannane 23 established the highly substituted E,E-diene unit present in lycoperdinoside A and B. The other two Z-olefins present in the molecule were introduced by means of cis-selective Horner-Wadsworth-Emmons reaction with Still-Gennari phosphonate. Evans syn- and anti-aldol reactions were utilized to fix six of the seven stereo centres present in the aglycone. PMID:25340961

  20. Boron-based nanostructures: Synthesis, functionalization, and characterization

    NASA Astrophysics Data System (ADS)

    Bedasso, Eyrusalam Kifyalew

    Boron-based nanostructures have not been explored in detail; however, these structures have the potential to revolutionize many fields including electronics and biomedicine. The research discussed in this dissertation focuses on synthesis, functionalization, and characterization of boron-based zero-dimensional nanostructures (core/shell and nanoparticles) and one-dimensional nanostructures (nanorods). The first project investigates the synthesis and functionalization of boron-based core/shell nanoparticles. Two boron-containing core/shell nanoparticles, namely boron/iron oxide and boron/silica, were synthesized. Initially, boron nanoparticles with a diameter between 10-100 nm were prepared by decomposition of nido-decaborane (B10H14) followed by formation of a core/shell structure. The core/shell structures were prepared using the appropriate precursor, iron source and silica source, for the shell in the presence of boron nanoparticles. The formation of core/shell nanostructures was confirmed using high resolution TEM. Then, the core/shell nanoparticles underwent a surface modification. Boron/iron oxide core/shell nanoparticles were functionalized with oleic acid, citric acid, amine-terminated polyethylene glycol, folic acid, and dopamine, and boron/silica core/shell nanoparticles were modified with 3-(amino propyl) triethoxy silane, 3-(2-aminoethyleamino)propyltrimethoxysilane), citric acid, folic acid, amine-terminated polyethylene glycol, and O-(2-Carboxyethyl)polyethylene glycol. A UV-Vis and ATR-FTIR analysis established the success of surface modification. The cytotoxicity of water-soluble core/shell nanoparticles was studied in triple negative breast cancer cell line MDA-MB-231 and the result showed the compounds are not toxic. The second project highlights optimization of reaction conditions for the synthesis of boron nanorods. This synthesis, done via reduction of boron oxide with molten lithium, was studied to produce boron nanorods without any

  1. Synthesis of functional nanocomposites based on solid-phase nanoreactors

    NASA Astrophysics Data System (ADS)

    Tretyakov, Yuri D.; Lukashin, Alexey V.; Eliseev, Andrei A.

    2004-09-01

    Approaches to the synthesis of functional nanocomposites based on zero-, one- and two-dimensional solid-state nanoreactors formed by zeolite cages, pores of mesoporous matrices, or interlayer cavities in layered compounds are considered. It is demonstrated that the use of solid-state nanoreactors opens up extensive opportunities for designing nanocomposites with specified physicochemical properties and makes it possible to avoid the aggregation of nanoparticles and to protect them from exposure to external factors, thus essentially facilitating the practical utility of these materials.

  2. Chronic Hindlimb Ischemia Impairs Functional Vasodilation and Vascular Reactivity in Mouse Feed Arteries

    PubMed Central

    Cardinal, Trevor R.; Struthers, Kyle R.; Kesler, Thomas J.; Yocum, Matthew D.; Kurjiaka, David T.; Hoying, James B.

    2011-01-01

    Vasodilation of lower leg arterioles is impaired in animal models of chronic peripheral ischemia. In addition to arterioles, feed arteries are a critical component of the vascular resistance network, accounting for as much as 50% of the pressure drop across the arterial circulation. Despite the critical importance of feed arteries in blood flow control, the impact of ischemia on feed artery vascular reactivity is unknown. At 14 days following unilateral resection of the femoral–saphenous artery–vein pair, functional vasodilation of the profunda femoris artery was severely impaired, 11 ± 9 versus 152 ± 22%. Although endothelial and smooth muscle-dependent vasodilation were both impaired in ischemic arteries compared to control arteries (Ach: 40 ± 14 versus 81 ± 11%, SNP: 43 ± 12 versus and 85 ± 11%), the responses to acetylcholine and sodium nitroprusside were similar, implicating impaired smooth muscle-dependent vasodilation. Conversely, vasoconstriction responses to norepinephrine were not different between ischemic and control arteries, −68 ± 3 versus −66 ± 3%, indicating that smooth muscle cells were functional following the ischemic insult. Finally, maximal dilation responses to acetylcholine, ex vivo, were significantly impaired in the ischemic artery compared to control, 71 ± 9 versus 97 ± 2%, despite a similar generation of myogenic tone to the same intravascular pressure (80 mmHg). These data indicate that ischemia impairs feed artery vasodilation by impairing the responsiveness of the vascular wall to vasodilating stimuli. Future studies to examine the mechanistic basis for the impact of ischemia on vascular reactivity or treatment strategies to improve vascular reactivity following ischemia could provide the foundation for an alternative therapeutic paradigm for peripheral arterial occlusive disease. PMID:22164145

  3. Oxygen precursor to the reactive intermediate in methanol synthesis by Cu-ZSM-5.

    PubMed

    Smeets, Pieter J; Hadt, Ryan G; Woertink, Julia S; Vanelderen, Pieter; Schoonheydt, Robert A; Sels, Bert F; Solomon, Edward I

    2010-10-27

    The reactive oxidizing species in the selective oxidation of methane to methanol in oxygen activated Cu-ZSM-5 was recently defined to be a bent mono(μ-oxo)dicopper(II) species, [Cu(2)O](2+). In this communication we report the formation of an O(2)-precursor of this reactive site with an associated absorption band at 29,000 cm(-1). Laser excitation into this absorption feature yields a resonance Raman (rR) spectrum characterized by (18)O(2) isotope sensitive and insensitive vibrations, νO-O and νCu-Cu, at 736 (Δ(18)O(2) = 41 cm(-1)) and 269 cm(-1), respectively. These define the precursor to be a μ-(η(2):η(2)) peroxo dicopper(II) species, [Cu(2)(O(2))](2+). rR experiments in combination with UV-vis absorption data show that this [Cu(2)(O(2))](2+) species transforms directly into the [Cu(2)O](2+) reactive site. Spectator Cu(+) sites in the zeolite ion-exchange sites provide the two electrons required to break the peroxo bond in the precursor. O(2)-TPD experiments with (18)O(2) show the incorporation of the second (18)O atom into the zeolite lattice in the transformation of [Cu(2)(O(2))](2+) into [Cu(2)O](2+). This study defines the mechanism of oxo-active site formation in Cu-ZSM-5.

  4. Versatile and Biomass Synthesis of Iron-based Nanoparticles Supported on Carbon Matrix with High Iron Content and Tunable Reactivity

    SciTech Connect

    Zhang, Dongmao; Shi, Sheldon Q; Jiang, Dongping; Che, Wen; Gai, Zheng; Howe, Jane Y; More, Karren Leslie; Arockiasamy, Antonyraj

    2012-01-01

    Iron-based nanoparticles supported on carbon (FeNPs{at}C) have enormous potential for environmental applications. Reported is a biomass-based method for FeNP{at}C synthesis that involves pyrolysis of bleached wood fiber pre-mixed with Fe{sub 3}O{sub 4} nanoparticles. This method allows synthesis of iron-based nanoparticles with tunable chemical reactivity by changing the pyrolysis temperature. The FeNP{at}C synthesized at a pyrolysis temperature of 500 C (FeNP{at}C-500) reacts violently (pyrophoric) when exposed to air, while FeNP{at}C prepared at 800 C (FeNP{at}C-800) remains stable in ambient condition for at least 3 months. The FeNPs in FeNP{at}C-800 are mostly below 50 nm in diameter and are surrounded by carbon. The immediate carbon layer (within 5-15 nm radius) on the FeNPs is graphitized. Proof-of-concept environmental applications of FeNPs{at}C-800 were demonstrated by Rhodamine 6G and arsenate (V) removal from water. This biomass-based method provides an effective way for iron-based nanoparticle fabrication and biomass utilization.

  5. [Inhibition of protein synthesis during associative memory reactivation produces reversible or irreversible amnesia in the snail Helix lucorum].

    PubMed

    Solntseva, S V; Nikitin, V P; Kozyrev, S A; Shevelkin, A V; Lagutin, A V; Sherstnev, V V

    2006-09-01

    Effects of protein synthesis inhibitors on reactivation processes of food aversion conditioning were inverstigated in snail Helix lucorum. Protein synthesis inhibitor (PSI, anisomycin, 0.4 mg, or cycloheximede, 0.6 mg) was injected into snail body cavity 24 hours after 3-day training; then conditioned stimulus (banana) was presented and memory was tested. It was found that 2.5-3 hours after first reminding, associative food conditioning was suppressed, recovering of the conditioning was observed 4.5-5.5 hours after first reminding. In other group of snails, PSI injections were single (1.8 mg) or triple (0.6 mg with 2-hour interval). Reminding stimulus was presented after each injection. In this case, suppression of food aversion conditioning was also observed 2.5-3 hours after first reminding, while amnesia in this case lasted over 30 days. Repeated training of the group of snails recovered the food aversion conditioning only partially. In control snails (saline instead of PSI or 3 injections of PSI without reminding), foot aversion conditioning was detected 30 days after first training. Thus we found that PSI effects during reminding of food aversion conditioning produced two phases amnesia: (1) the easily suppressed by PSI transient phase lasted 2-3 hours, and (2) irreversible phase, its suppression by high doses of PSI-initiated amnesia lasting over 1 month. Second phase of amnesia was not recovered after repeated training. It was suggested that reminding induced reconsolidation of initial memory. Its suppression by protein synthesis inhibitors results in erasing of memory trace and disturbs repeated consolidation. PMID:17290873

  6. Sulfur dioxide and ammonium sulfate effects on pulmonary function and bronchial reactivity in human subjects

    SciTech Connect

    Kulle, T.J.; Sauder, L.R.; Shanty, F.; Kerr, H.D.; Farrell, B.P.; Miller, W.R.; Milman, J.H.

    1984-03-01

    The effect of exposures to 1 ppm sulfur dioxide (SO/sub 2/) and 500 ..mu..g/m/sup 3/ respirable ammonium sulfate ((NH/sub 4/)/sub 2/SO/sub 4/) was studied in 20 nonsmoking subjects to determine if a response can be measured at these atmospheric levels and if the response is additive or synergistic. Four-hour separate and combined exposures were employed. Each subject acted as his or her own control and performed two light-to-moderate exercise stints (612 kg-m/min) for 15 minutes on each day's confinement in the environmental chamber. Pulmonary function tests (body plethysmography and spirometry) and bronchial reactivity to methacholine were performed to assess the response of these exposures. No significant changes in pulmonary function or bronchial reactivity were observed in the individual exposures ((NH/sub 4/)/sub 2/SO/sub 4/ or SO/sub 2/), the combined exposure ((NH/sub 4/)/sub 2/SO/sub 4/ and SO/sub 2/), or 24 hours post-exposure. This study design and the observed results did not demonstrate any readily apparent risk to healthy subjects with these exposures. Since no significant changes were measured, it was not possible to conclude if these two pollutants in combination produce an additive or synergistic response.

  7. The effect of oxime reactivators on muscarinic receptors: functional and binding examinations.

    PubMed

    Soukup, O; Kumar, U K; Proska, J; Bratova, L; Adem, A; Jun, D; Fusek, J; Kuca, K; Tobin, G

    2011-05-01

    The antidotal treatment of organophosphorus poisoning is still a problematic issue since no versatile antidote has been developed yet. In our study, we focused on an interesting property, which does not relate to the reactivation of inhibited acetylcholinesterase (AChE) of some oximes, but refers to their anti-muscarinic effects which may contribute considerably to their treatment efficacy. One standard reactivator (HI-6) and two new compounds (K027 and K203) have been investigated for their antimuscarinic properties. Anti-muscarinic effects were studies by means of an in vitro stimulated atrium preparation (functional test), the [(3)H]-QNB binding assay and G-protein coupled receptor assay (GPCR, beta-Arrestin Assay). Based on the functional data HI-6 demonstrates the highest anti-muscarinic effect. However, only when comparing [(3)H]-QNB binding results and GPCR data, K203 shows a very promising compound with regard to anti-muscarinic potency. The therapeutic impact of these findings has been discussed.

  8. Origin of molecular conformational stability: perspectives from molecular orbital interactions and density functional reactivity theory.

    PubMed

    Liu, Shubin; Schauer, Cynthia K

    2015-02-01

    To have a quantitative understanding about the origin of conformation stability for molecular systems is still an unaccomplished task. Frontier orbital interactions from molecular orbital theory and energy partition schemes from density functional reactivity theory are the two approaches available in the literature that can be used for this purpose. In this work, we compare the performance of these approaches for a total of 48 simple molecules. We also conduct studies to flexibly bend bond angles for water, carbon dioxide, borane, and ammonia molecules to obtain energy profiles for these systems over a wide range of conformations. We find that results from molecular orbital interactions using frontier occupied orbitals such as the highest occupied molecular orbital and its neighbors are only qualitatively, at most semi-qualitatively, trustworthy. To obtain quantitative insights into relative stability of different conformations, the energy partition approach from density functional reactivity theory is much more reliable. We also find that the electrostatic interaction is the dominant descriptor for conformational stability, and steric and quantum effects are smaller in contribution but their contributions are indispensable. Stable molecular conformations prefer to have a strong electrostatic interaction, small molecular size, and large exchange-correlation effect. This work should shed new light towards establishing a general theoretical framework for molecular stability.

  9. Origin of molecular conformational stability: Perspectives from molecular orbital interactions and density functional reactivity theory

    SciTech Connect

    Liu, Shubin E-mail: schauer@unc.edu; Schauer, Cynthia K. E-mail: schauer@unc.edu

    2015-02-07

    To have a quantitative understanding about the origin of conformation stability for molecular systems is still an unaccomplished task. Frontier orbital interactions from molecular orbital theory and energy partition schemes from density functional reactivity theory are the two approaches available in the literature that can be used for this purpose. In this work, we compare the performance of these approaches for a total of 48 simple molecules. We also conduct studies to flexibly bend bond angles for water, carbon dioxide, borane, and ammonia molecules to obtain energy profiles for these systems over a wide range of conformations. We find that results from molecular orbital interactions using frontier occupied orbitals such as the highest occupied molecular orbital and its neighbors are only qualitatively, at most semi-qualitatively, trustworthy. To obtain quantitative insights into relative stability of different conformations, the energy partition approach from density functional reactivity theory is much more reliable. We also find that the electrostatic interaction is the dominant descriptor for conformational stability, and steric and quantum effects are smaller in contribution but their contributions are indispensable. Stable molecular conformations prefer to have a strong electrostatic interaction, small molecular size, and large exchange-correlation effect. This work should shed new light towards establishing a general theoretical framework for molecular stability.

  10. Unscheduled DNA Synthesis: The Clinical and Functional Assay for Global Genomic DNA Nucleotide Excision Repair

    PubMed Central

    Latimer, Jean J.; Kelly, Crystal M.

    2016-01-01

    The unscheduled DNA synthesis (UDS) assay measures the ability of a cell to perform global genomic nucleotide excision repair (NER). This chapter provides instructions for the application of this technique by creating 6-4 photoproducts and pyrimidine dimers using UV-C irradiation. This procedure is designed specifically for quantification of the 6-4 photoproducts. Repair is quantified by the amount of radioactive thymidine incorporated during repair synthesis after this insult, and radioactivity is evaluated by grain counting after autoradiography. The results are used to clinically diagnose human DNA repair deficiency disorders and provide a basis for investigation of repair deficiency in human tissues or tumors. No other functional assay is available that directly measures the capacity to perform NER on the entire genome without the use of specific antibodies. Since live cells are required for this assay, explant culture techniques must be previously established. Host cell reactivation (HCR), as discussed in Chapter 37, is not an equivalent technique, as it measures only transcription-coupled repair (TCR) at active genes, a small subset of total NER. PMID:24623250

  11. Synthesis of Highly Reactive Subnano-sized Zero-valent Iron using Smectite Clay Templates

    PubMed Central

    Gu, Cheng; Jia, Hanzhang; Li, Hui; Teppen, Brian J.; Boyd, Stephen A.

    2010-01-01

    A novel method was developed for synthesizing subnano-sized zero-valent iron (ZVI) using smectite clay layers as templates. Exchangeable Fe(III) cations compensating the structural negative charges of smectites were reduced with NaBH4, resulting in the formation of ZVI. The unique structure of smectite clay, in which isolated exchangeable Fe(III) cations reside near the sites of structural negative charges, inhibited the agglomeration of ZVI resulting in the formation of discrete regions of subnanoscale ZVI particles in the smectite interlayer regions. X-ray diffraction revealed an interlayer spacing of ~ 5 Å. The non-structural iron content of this clay yields a calculated ratio of two atoms of ZVI per three cation exchange sites, in full agreement with the XRD results since the diameter of elemental Fe is 2.5 Å. The clay-templated ZVI showed superior reactivity and efficiency compared to other previously reported forms of ZVI as indicated by the reduction of nitrobenzene; structural Fe within the aluminosilicate layers was nonreactive. At a 1:3 molar ratio of nitrobenzene:non-structural Fe, a reaction efficiency of 83% was achieved, and over 80% of the nitrobenzene was reduced within one minute. These results confirm that non-structural Fe from Fe(III)-smectite was reduced predominantly to ZVI which was responsible for the reduction of nitrobenzene to aniline. This new form of subnano-scale ZVI may find utility in the development of remediation technologies for persistent environmental contaminants, e.g. as components of constructed reactive domains such as reactive caps for contaminated sediments. PMID:20446730

  12. Non-Pincer-Type Mononuclear Scandium Alkylidene Complexes: Synthesis, Bonding, and Reactivity.

    PubMed

    Wang, Chen; Zhou, Jiliang; Zhao, Xuefei; Maron, Laurent; Leng, Xuebing; Chen, Yaofeng

    2016-01-22

    The first non-pincer-type mononuclear scandium alkylidene complexes were synthesized and structurally characterized. These complexes exhibited short Sc-C bond lengths and even one of the shortest reported to date (2.1134(18) Å). The multiple character of the Sc-C bond was highlighted by a DFT calculation. This was confirmed by experimental reactivity study where the complex underwent [2+1] cycloaddition with elemental selenium and [2+2] cycloaddition with imine. DFT calculation also revealed a strong nucleophilic behavior of the alkylidene complex that was experimentally demonstrated by the C-H bond activation of phenylacetylene.

  13. Synthesis of peptide nucleic acids containing a crosslinking agent and evaluation of their reactivities.

    PubMed

    Akisawa, Takuya; Ishizawa, Yuki; Nagatsugi, Fumi

    2015-03-13

    Peptide nucleic acids (PNAs) are structural mimics of nucleic acids that form stable hybrids with DNA and RNA. In addition, PNAs can invade double-stranded DNA. Due to these characteristics, PNAs are widely used as biochemical tools, for example, in antisense/antigene therapy. Interstrand crosslink formation in nucleic acids is one of the strategies for preparing a stable duplex by covalent bond formation. In this study, we have synthesized PNAs incorporating 4-amino-6-oxo-2-vinylpyrimidine (AOVP) as a crosslinking agent and evaluated their reactivities for targeting DNA and RNA.

  14. Non-Pincer-Type Mononuclear Scandium Alkylidene Complexes: Synthesis, Bonding, and Reactivity.

    PubMed

    Wang, Chen; Zhou, Jiliang; Zhao, Xuefei; Maron, Laurent; Leng, Xuebing; Chen, Yaofeng

    2016-01-22

    The first non-pincer-type mononuclear scandium alkylidene complexes were synthesized and structurally characterized. These complexes exhibited short Sc-C bond lengths and even one of the shortest reported to date (2.1134(18) Å). The multiple character of the Sc-C bond was highlighted by a DFT calculation. This was confirmed by experimental reactivity study where the complex underwent [2+1] cycloaddition with elemental selenium and [2+2] cycloaddition with imine. DFT calculation also revealed a strong nucleophilic behavior of the alkylidene complex that was experimentally demonstrated by the C-H bond activation of phenylacetylene. PMID:26617412

  15. Solvent-Free Synthesis and Fluorescence of a Thiol-Reactive Sensor for Undergraduate Organic Laboratories

    PubMed Central

    Patterson, Anastasia L.; May, Mary D.; Visser, Bryan J.; Kislukhin, Alexander A.; Vosburg, David A.

    2013-01-01

    A green organic laboratory experiment was developed in which students synthesize a sensor for thiols using a microscale, solventless Diels–Alder reaction at room temperature or 37 °C. The molecular probe is easily purified by column chromatography in a Pasteur pipet and characterized by thin-layer chromatography and NMR spectroscopy. The thiol-reactive sensor becomes intensely fluorescent upon exposure to thiols from N-acetylcysteine, bovine serum albumin, or human hair (pretreated with a reducing agent to reveal cysteine thiols in α-keratin). This fluorescence is observable even with micrograms of probe. PMID:24415795

  16. Density functional theory of chemical reactivity indices in some ion-molecule reaction systems

    SciTech Connect

    Tachibana, Akitoma; Kawauchi, Susumu; Nakamura, Koichi; Inaba, Hideyuki

    1996-02-15

    Three isoelectronic reactions, proton transfer (PT), hydrogen abstraction (HA), and electron transfer (ET), of NH{sub 3}{sup +} with NH{sub 3}, H{sub 2}O, and HF have been studied using ab initio molecular orbital calculations. For the reaction of NH{sub 3}{sup +} + H{sub 2}O, the energy of the transition state (TS) is higher than that of the reactants. This is consistent with the experimental observation that the rate constant is less than the average dipole orientation (ADO) rate constant. It seems reasonable that the reaction rate for the reaction NH{sub 3}{sup +} + H{sub 2}O would hardly depend on the V{sub 2} mode of NH{sub 3}{sup +} at least for low-lying excited states (E{sub int}{le} 0.714 eV) of the V{sub 2} mode, because the V{sub 2} contributes mainly to the normal mode orthogonal to the reaction coordinate at the TS. This is consistent with experimental observation. A similiar prediction can be made for the NH{sub 3}{sup +} + HF reaction. The electron transfer processes for the HA reactions have been examined in terms of the intrinsic reaction coordinate (IRC). The order of reactivity with NH{sub 3}{sup +} is NH{sub 3}>H{sub 2}O>HF. It is found that the degree of the electron transfer and the reactivity are correlated with the absolute hardness {eta} of NH{sub 3}, H{sub 2}O, and HF. this is accord with the softness as the chemical reactivity index in the density functional theory. 25 refs., 6 fig., 4 tab.

  17. Density functional reactivity theory study of SN2 reactions from the information-theoretic perspective.

    PubMed

    Wu, Zemin; Rong, Chunying; Lu, Tian; Ayers, Paul W; Liu, Shubin

    2015-10-28

    As a continuation of our recent efforts to quantify chemical reactivity with quantities from the information-theoretic approach within the framework of density functional reactivity theory, the effectiveness of applying these quantities to quantify electrophilicity for the bimolecular nucleophilic substitution (SN2) reactions in both gas phase and aqueous solvent is presented in this work. We examined a total of 21 self-exchange SN2 reactions for the compound with the general chemical formula of R1R2R3C-F, where R1, R2, and R3 represent substituting alkyl groups such as -H, -CH3, -C2H5, -C3H7, and -C4H9 in both gas and solvent phases. Our findings confirm that scaling properties for information-theoretic quantities found elsewhere are still valid. It has also been verified that the barrier height has the strongest correlation with the electrostatic interaction, but the contributions from the exchange-correlation and steric effects, though less significant, are indispensable. We additionally unveiled that the barrier height of these SN2 reactions can reliably be predicted not only by the Hirshfeld charge and information gain at the regioselective carbon atom, as previously reported by us for other systems, but also by other information-theoretic descriptors such as Shannon entropy, Fisher information, and Ghosh-Berkowitz-Parr entropy on the same atom. These new findings provide further insights for the better understanding of the factors impacting the chemical reactivity of this vastly important category of chemical transformations.

  18. Cardiorespiratory fitness, pulmonary function and C-reactive protein levels in nonsmoking individuals with diabetes

    PubMed Central

    Francisco, C.O.; Catai, A.M.; Moura-Tonello, S.C.G.; Lopes, S.L.B.; Benze, B.G.; Del Vale, A.M.; Leal, A.M.O.

    2014-01-01

    The objective of this study was to evaluate cardiorespiratory fitness and pulmonary function and the relationship with metabolic variables and C-reactive protein (CRP) plasma levels in individuals with diabetes mellitus (DM). Nineteen men with diabetes and 19 age- and gender-matched control subjects were studied. All individuals were given incremental cardiopulmonary exercise and pulmonary function tests. In the exercise test, maximal workload (158.3±22.3 vs 135.1±25.2, P=0.005), peak heart rate (HRpeak: 149±12 vs 139±10, P=0.009), peak oxygen uptake (VO2peak: 24.2±3.2 vs 18.9±2.8, P<0.001), and anaerobic threshold (VO2VT: 14.1±3.4 vs 12.2±2.2, P=0.04) were significantly lower in individuals with diabetes than in control subjects. Pulmonary function test parameters, blood pressure, lipid profile (triglycerides, HDL, LDL, and total cholesterol), and CRP plasma levels were not different in control subjects and individuals with DM. No correlations were observed between hemoglobin A1C (HbA1c), CRP and pulmonary function test and cardiopulmonary exercise test performance. In conclusion, the results demonstrate that nonsmoking individuals with DM have decreased cardiorespiratory fitness that is not correlated with resting pulmonary function parameters, HbA1c, and CRP plasma levels. PMID:24760118

  19. Synthesis and Reactivity of a Mono-σ-Aryl Palladium(IV) Fluoride Complex

    PubMed Central

    Ball, Nicholas D.; Sanford, Melanie S.

    2009-01-01

    This communication describes the rational design and synthesis of a remarkably stable PdIV mono-aryl fluoride complex (t-Bu-bpy)PdIV(p-FC6H4)(F)2(FHF) (t-Bu-bpy = 4,4′-di-tert-butyl-2,2′-bipyridine). This and related complexes undergo Ar-F bond formation in the presence of “F+” sources. This work serves as a foundation for the development of a PdII/IV catalyzed coupling reactions to form aryl fluorides. PMID:19249867

  20. Synthesis and characterisation of ruthenium dihydrogen complexes and their reactivity towards B-H bonds.

    PubMed

    Choi, Jong-Hoo; Schloerer, Nils E; Berger, Josefine; Prechtl, Martin H G

    2014-01-01

    In this paper the synthesis and characterisation of ruthenium dihydrogen complexes bearing rigid aliphatic PNP pincer-type ligands are described. As one result hydride complexes were synthesised in good to high yields by a one-pot direct hydrogenation reaction. As another finding the dihydrogen complex, stabilised with a N-Me group in the ligand frame, can be converted with dimethylamine borane into a rare σ-boron complex [RuH2(BH3)(Me-PNP)] with rapid B-N decoupling. Additionally, we present the first mass spectrometric analysis of the synthesised σ-complexes via liquid injection field desorption/ionisation technique (LIFDI-MS).

  1. Synthesis and characterization of core-shell acrylate based latex and study of its reactive blends.

    PubMed

    Liu, Xiang; Fan, Xiao-Dong; Tang, Min-Feng; Nie, Ying

    2008-03-01

    Techniques in resin blending are simple and efficient method for improving the properties of polymers, and have been used widely in polymer modification field. However, polymer latex blends such as the combination of latexes, especially the latexes with water-soluble polymers, were rarely reported. Here, we report a core-shell composite latex synthesized using methyl methacrylate (MMA), butyl acrylate (BA), 2-ethylhexyl acrylate (EHA) and glycidyl methacrylate (GMA) as monomers and ammonium persulfate and sodium bisulfite redox system as the initiator. Two stages seeded semi-continuous emulsion polymerization were employed for constructing a core-shell structure with P(MMA-co-BA) component as the core and P(EHA-co-GMA) component as the shell. Results of Transmission Electron Microscopy (TEM) and Dynamics Light Scattering (DLS) tests confirmed that the particles obtained are indeed possessing a desired core-shell structural character. Stable reactive latex blends were prepared by adding the latex with waterborne melamine-formaldehyde resin (MF) or urea-formaldehyde resin (UF). It was found that the glass transition temperature, the mechanical strength and the hygroscopic property of films cast from the latex blends present marked enhancements under higher thermal treatment temperature. It was revealed that the physical properties of chemically reactive latexes with core-shell structure could be altered via the change of crosslinking density both from the addition of crosslinkers and the thermal treatment.

  2. Synthesis of novel reactive N-halamine precursors and application in antimicrobial cellulose

    NASA Astrophysics Data System (ADS)

    Jiang, Zhiming; Ma, Kaikai; Du, Jinmei; Li, Rong; Ren, Xuehong; Huang, T. S.

    2014-01-01

    2,4,6-Trichloro-s-triazine has been used as one of the important linkers of reactive dyes for textiles such as cellulosic fibers. N-Halamine precursors could be bonded to a triazine-based linker by the chloride displacement reaction, and the synthesized compounds could attach to cotton fabrics by covalent bonds through a reactive dyeing process. In this study, two novel antimicrobial N-halamine precursors, 2,2,6,6-tetramethyl-4-piperidinol-s-trizine (TMPT) and 4-(4-(2,2,6,6-tetramethyl-4-piperidinol)-6-chloro-1,3,5-triazinylamino)-benzenesulfonate (BTMPT), were synthesized and used to coat cotton fabrics. The synthesized s-triazine-based N-halamine precursors react with cellulose to produce biocidal cellulosic fibers upon exposure to diluted household bleach. The coated fabrics were characterized by FT-IR and SEM. The chlorinated treated cotton swatches demonstrated excellent antimicrobial properties against S. aureus (Gram-positive) and E. coli O157:H7 (Gram-negative) with short contact times. Washing test and UVA light test showed that chlorinated BTMPT-coated cotton fabrics were more stable than TMPT-coated cotton fabrics. Compared to the traditional pad-dry-cure technique to produce antimicrobial textiles, the novel process in this study has advantages of saving energy and maintaining tensile strength of fabrics.

  3. Synthesis and Characterization of Core-Shell Acrylate Based Latex and Study of Its Reactive Blends

    PubMed Central

    Liu, Xiang; Fan, Xiao-Dong; Tang, Min-Feng; Nie, Ying

    2008-01-01

    Techniques in resin blending are simple and efficient method for improving the properties of polymers, and have been used widely in polymer modification field. However, polymer latex blends such as the combination of latexes, especially the latexes with water-soluble polymers, were rarely reported. Here, we report a core-shell composite latex synthesized using methyl methacrylate (MMA), butyl acrylate (BA), 2-ethylhexyl acrylate (EHA) and glycidyl methacrylate (GMA) as monomers and ammonium persulfate and sodium bisulfite redox system as the initiator. Two stages seeded semi-continuous emulsion polymerization were employed for constructing a core-shell structure with P(MMA-co-BA) component as the core and P(EHA-co-GMA) component as the shell. Results of Transmission Electron Microscopy (TEM) and Dynamics Light Scattering (DLS) tests confirmed that the particles obtained are indeed possessing a desired core-shell structural character. Stable reactive latex blends were prepared by adding the latex with waterborne melamine-formaldehyde resin (MF) or urea-formaldehyde resin (UF). It was found that the glass transition temperature, the mechanical strength and the hygroscopic property of films cast from the latex blends present marked enhancements under higher thermal treatment temperature. It was revealed that the physical properties of chemically reactive latexes with core-shell structure could be altered via the change of crosslinking density both from the addition of crosslinkers and the thermal treatment. PMID:19325753

  4. Revisiting the chemical reactivity indices as the state function derivatives. The role of classical chemical hardness

    SciTech Connect

    Malek, Ali; Balawender, Robert

    2015-02-07

    The chemical reactivity indices as the equilibrium state-function derivatives are revisited. They are obtained in terms of the central moments (fluctuation formulas). To analyze the role of the chemical hardness introduced by Pearson [J. Am. Chem. Soc. 105, 7512 (1983)], the relations between the derivatives up to the third-order and the central moments are obtained. As shown, the chemical hardness and the chemical potential are really the principal indices of the chemical reactivity theory. It is clear from the results presented here that the chemical hardness is not the derivative of the Mulliken chemical potential (this means also not the second derivative of the energy at zero-temperature limit). The conventional quadratic dependence of energy, observed at finite temperature, reduces to linear dependence on the electron number at zero-temperature limit. The chemical hardness plays a double role in the admixture of ionic states to the reference neutral state energy: it determines the amplitude of the admixture and regulates the damping of its thermal factor.

  5. Seed birth to death: dual functions of reactive oxygen species in seed physiology

    PubMed Central

    Jeevan Kumar, S. P.; Rajendra Prasad, S.; Banerjee, Rintu; Thammineni, Chakradhar

    2015-01-01

    Background Reactive oxygen species (ROS) are considered to be detrimental to seed viability. However, recent studies have demonstrated that ROS have key roles in seed germination particularly in the release of seed dormancy and embryogenesis, as well as in protection from pathogens. Scope This review considers the functions of ROS in seed physiology. ROS are present in all cells and at all phases of the seed life cycle. ROS accumulation is important in breaking seed dormancy, and stimulating seed germination and protection from pathogens. However, excessive ROS accumulation can be detrimental. Therefore, knowledge of the mechanisms by which ROS influence seed physiology will provide insights that may not only allow the development of seed quality markers but also help us understand how dormancy can be broken in several recalcitrant species. Conclusions Reactive oxygen species have a dual role in seed physiology. Understanding the relative importance of beneficial and detrimental effects of ROS provides great scope for the improvement and maintenance of seed vigour and quality, factors that may ultimately increase crop yields. PMID:26271119

  6. Coordination chemistry of cyclopropenylidene-stabilized phosphenium cations: synthesis and reactivity of Pd and Pt complexes.

    PubMed

    Kozma, Agnes; Deden, Tobias; Carreras, Javier; Wille, Christian; Petuškova, Jekaterina; Rust, Jörg; Alcarazo, Manuel

    2014-02-17

    A straightforward synthesis of cyclopropenylidene-stabilized phosphenium cations 1 a-g through the reaction of [(iPr2N)2C3(+)Cl]BF4 with secondary phosphines is described. Their donor ability was evaluated by analysis of the CO stretching frequency in Rh complexes [RhCl(CO)L2](BF4)2 and electrochemical methods. The cyclopropenium ring induces a phosphite-type behavior that can be tuned by the other two substituents attached to the phosphorus atom. Despite of the positive charge that they bear, phosphenium cations 1 a-g still act as two-electron donor ligands, forming adducts with Pd(II) and Pt(II) precursors. Conversely, in the presence of Pd(0) species, an oxidative insertion of the Pd atom into the Ccarbene-phosphorus bond takes place, providing dimeric structures in which each Pd atom is bonded to a cyclopropenyl carbene while two dialkyl/diaryl phosphide ligands serve as bridges between the two Pd centers. The catalytic performance of the resulting library of Pt(II) complexes was tested; all of the cationic phosphines accelerated the prototype 6-endo-dig cyclization of 2-ethynyl-1,1'-biphenyl to afford pentahelicene. The best ligand 1 g was used in the synthesis of two natural products, chrysotoxene and epimedoicarisoside A.

  7. Cued Reactivation of Motor Learning during Sleep Leads to Overnight Changes in Functional Brain Activity and Connectivity

    PubMed Central

    Cousins, James N.; El-Deredy, Wael; Parkes, Laura M.; Hennies, Nora; Lewis, Penelope A.

    2016-01-01

    Sleep plays a role in memory consolidation. This is demonstrated by improved performance and neural plasticity underlying that improvement after sleep. Targeted memory reactivation (TMR) allows the manipulation of sleep-dependent consolidation through intentionally biasing the replay of specific memories in sleep, but the underlying neural basis of these altered memories remains unclear. We use functional magnetic resonance imaging (fMRI) to show a change in the neural representation of a motor memory after targeted reactivation in slow-wave sleep (SWS). Participants learned two serial reaction time task (SRTT) sequences associated with different auditory tones (high or low pitch). During subsequent SWS, one sequence was reactivated by replaying the associated tones. Participants were retested on both sequences the following day during fMRI. As predicted, they showed faster reaction times for the cued sequence after targeted memory reactivation. Furthermore, increased activity in bilateral caudate nucleus and hippocampus for the cued relative to uncued sequence was associated with time in SWS, while increased cerebellar and cortical motor activity was related to time in rapid eye movement (REM) sleep. Functional connectivity between the caudate nucleus and hippocampus was also increased after targeted memory reactivation. These findings suggest that the offline performance gains associated with memory reactivation are supported by altered functional activity in key cognitive and motor networks, and that this consolidation is differentially mediated by both REM sleep and SWS. PMID:27137944

  8. Effects of various physical stress factors on mitochondrial function and reactive oxygen species in rat spermatozoa

    PubMed Central

    Kim, Suhee; Agca, Cansu; Agca, Yuksel

    2013-01-01

    The aim of the present study was to evaluate the effects of various physical interventions on the function of epididymal rat spermatozoa and determine whether there are correlations among these functional parameters. Epididymal rat spermatozoa were subjected to various mechanical (pipetting, centrifugation and Percoll gradient separation) and anisotonic conditions, and sperm motility, plasma membrane integrity (PMI), mitochondrial membrane potential (MMP) and intracellular reactive oxygen species (ROS) were evaluated. Repeated pipetting caused a loss in motility, PMI and MMP (P < 0.05). Minimal centrifugation force (200g) had no effect on motility, PMI and MMP, whereas an increase in the centrifugation force to 400g or 600g decreased sperm function (P < 0.005). Percoll gradient separation increased total motility, PMI and MMP (P < 0.05). However, the spermatozoa that were subjected to mechanical interventions showed high susceptibility to a ROS stimulant (P < 0.005). Anisotonic conditions decreased motility, PMI and MMP, and hypotonic conditions in particular increased basal ROS (P < 0.05). In correlation tests, there were strong positive correlations among total motility, PMI and MMP, whereas ROS showed no or negatively weak correlations with the other parameters. In conclusion, the physical interventions may act as important variables, affecting functional parameters of epididymal rat spermatozoa. Therefore, careful consideration and proper protocols for handling of rat spermatozoa and osmotic conditions are required to achieve reliable results and minimise damage. PMID:23140582

  9. Path integrals for electronic densities, reactivity indices, and localization functions in quantum systems.

    PubMed

    Putz, Mihai V

    2009-11-10

    The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI) development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr's quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions - all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving) many-electronic systems.

  10. Path Integrals for Electronic Densities, Reactivity Indices, and Localization Functions in Quantum Systems

    PubMed Central

    Putz, Mihai V.

    2009-01-01

    The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI) development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr’s quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions – all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving) many-electronic systems. PMID:20087467

  11. Amine Functionalization via Oxidative Photoredox Catalysis: Methodology Development and Complex Molecule Synthesis

    PubMed Central

    2016-01-01

    Conspectus While the use of visible light to drive chemical reactivity is of high importance to the development of environmentally benign chemical transformations, the concomitant use of a stoichiometric electron donor or acceptor is often required to steer the desired redox behavior of these systems. The low-cost and ubiquity of tertiary amine bases has led to their widespread use as reductive additives in photoredox catalysis. Early use of trialkylamines in this context was focused on their role as reductive excited state quenchers of the photocatalyst, which in turn provides a more highly reducing catalytic intermediate. In this Account, we discuss some of the observations and thought processes that have led from our use of amines as reductive additives to their use as complex substrates and intermediates for natural product synthesis. Early attempts by our group to construct key carbon–carbon bonds via free-radical intermediates led to the observation that some trialkylamines readily behave as efficient hydrogen atom donors under redox-active photochemical conditions. In the wake of in-depth mechanistic studies published in the 1970s, 1980s and 1990s, this understanding has in turn allowed for a systematic approach to the design of a number of photochemical methodologies through rational tuning of the amine component. Minimization of the C–H donicity of the amine additive was found to promote desired C–C bond formation in a number of contexts, and subsequent elucidation of the amine’s redox fate has sparked a reevaluation of the amine’s role from that of reagent to that of substrate. The reactivity of tertiary amines in these photochemical systems is complex, and allows for a number of mechanistic possibilities that are not necessarily mutually exclusive. A variety of combinations of single-electron oxidation, C–H abstraction, deprotonation, and β-scission result in the formation of reactive intermediates such as α-amino radicals and iminium ions

  12. Synthesis, conformational, spectroscopic and chemical reactivity analysis of 2-cyano-3-(1H-pyrrol-2-yl)acrylohydrazide using experimental and quantum chemical approaches

    NASA Astrophysics Data System (ADS)

    Rawat, Poonam; Singh, R. N.

    2015-02-01

    This paper describes the synthesis, spectroscopic (1H and 13C NMR, UV-Visible, FT-IR and ESI Mass), conformational analysis, chemical reactivity and non-linear optical (NLO) properties of newly synthesized pyrrole derivative 2-cyano-3-(1H-pyrrol-2-yl)acrylohydrazide (2CPA) C8H8N4O using experimental and quantum chemical techniques. The presence of signal at δ 8.010 ppm due to vinyl proton as well as NH and NH2 protons signals at 11.054 and 2.499 ppm in experimental 1H NMR spectrum indicate that 2CPA contain sbnd CHdbnd CCNsbnd and sbnd NHsbnd NH2 frame. The combined experimental and theoretical symmetric (3194 cm-1) and asymmetric (3221 cm-1) stretching wavenumber analysis confirms free NH2 group in the solid phase FT-IR spectrum of the synthesized compound. The interaction energies of dimer formation using density functional theory (DFT) and Quantum theory of Atoms in Molecules (QTAIM) calculations are found to be 20.210, 19.683 kcal/mol, respectively. The maximum values of the electrophilic reactivity descriptors at C6 indicate that this site is more prone to nucleophilic attack and favoring the formation of heterocyclic derivatives. A natural bond orbital (NBOs) analysis has been carried out to investigate intramolecular charge transfer, conjugative and hyperconjugative interactions within molecule. The calculated first hyperpolarizability (β0) of 2CPA, indicates that investigated molecule will show non-linear optical response and might be used as non-linear optical (NLO) material.

  13. Alphavirus RNA synthesis and non-structural protein functions

    PubMed Central

    Rupp, Jonathan C.; Sokoloski, Kevin J.; Gebhart, Natasha N.

    2015-01-01

    The members of the genus Alphavirus are positive-sense RNA viruses, which are predominantly transmitted to vertebrates by a mosquito vector. Alphavirus disease in humans can be severely debilitating, and depending on the particular viral species, infection may result in encephalitis and possibly death. In recent years, alphaviruses have received significant attention from public health authorities as a consequence of the dramatic emergence of chikungunya virus in the Indian Ocean islands and the Caribbean. Currently, no safe, approved or effective vaccine or antiviral intervention exists for human alphavirus infection. The molecular biology of alphavirus RNA synthesis has been well studied in a few species of the genus and represents a general target for antiviral drug development. This review describes what is currently understood about the regulation of alphavirus RNA synthesis, the roles of the viral non-structural proteins in this process and the functions of cis-acting RNA elements in replication, and points to open questions within the field. PMID:26219641

  14. Molybdenum(0) Dinitrogen Complexes Supported by Pentadentate Tetrapodal Phosphine Ligands: Structure, Synthesis, and Reactivity toward Acids.

    PubMed

    Hinrichsen, Svea; Kindjajev, Andrei; Adomeit, Sven; Krahmer, Jan; Näther, Christian; Tuczek, Felix

    2016-09-01

    The syntheses of two pentadentate tetrapodal phosphine (pentaPod(P)) ligands, P2(Ph)PP2(Ph) and P2(Me)PP2(Ph), are reported, which derive from the fusion of a tripod and a trident ligand. Reaction of the ligand P2(Ph)PP2(Ph) with [MoCl3(THF)3] followed by an amalgam reduction under N2 does not lead to well-defined products. The same reactions performed with the ligand P2(Me)PP2(Ph) afford the mononuclear molybdenum dinitrogen complex [MoN2(P2(Me)PP2(Ph))]. Because of the unprecedented topology of the pentaphosphine ligand, the Mo-P bond to the phosphine in the trans position to N2 is significantly shortened, explaining the very strong activation of the dinitrogen ligand (ν̃NN = 1929 cm(-1)). The reactivity of this complex toward acids is investigated. PMID:27526268

  15. Synthesis and reactivity of aliphatic sulfur pentafluorides from substituted (pentafluorosulfanyl)benzenes

    PubMed Central

    Vida, Norbert; Václavík, Jiří

    2016-01-01

    Summary Oxidation of 3- and 4-pentafluorosulfanyl-substituted anisoles and phenols with hydrogen peroxide and sulfuric acid provided a mixture of SF5-substituted muconolactone, maleic, and succinic acids. A plausible mechanism for the formation of the aliphatic SF5 compounds was presented and their chemical reactivity was investigated. SF5-substituted para-benzoquinone was synthesized; its oxidation led to an improved yield of 2-(pentafluorosulfanyl)maleic acid. The reaction of SF5-substituted maleic anhydride and para-benzoquinone with cyclopentadiene afforded the Diels–Alder adducts. Decomposition of 3-(pentafluorosulfanyl)muconolactone in acidic, neutral and basic aqueous media was investigated and the decarboxylation of 2-(pentafluorosulfanyl)maleic acid provided 3-(pentafluorosulfanyl)acrylic acid. PMID:26877813

  16. Synthesis and reactivity of aliphatic sulfur pentafluorides from substituted (pentafluorosulfanyl)benzenes.

    PubMed

    Vida, Norbert; Václavík, Jiří; Beier, Petr

    2016-01-01

    Oxidation of 3- and 4-pentafluorosulfanyl-substituted anisoles and phenols with hydrogen peroxide and sulfuric acid provided a mixture of SF5-substituted muconolactone, maleic, and succinic acids. A plausible mechanism for the formation of the aliphatic SF5 compounds was presented and their chemical reactivity was investigated. SF5-substituted para-benzoquinone was synthesized; its oxidation led to an improved yield of 2-(pentafluorosulfanyl)maleic acid. The reaction of SF5-substituted maleic anhydride and para-benzoquinone with cyclopentadiene afforded the Diels-Alder adducts. Decomposition of 3-(pentafluorosulfanyl)muconolactone in acidic, neutral and basic aqueous media was investigated and the decarboxylation of 2-(pentafluorosulfanyl)maleic acid provided 3-(pentafluorosulfanyl)acrylic acid. PMID:26877813

  17. Synthesis, characterization and reactivity of early transition metal neo-pentoxides

    SciTech Connect

    Boyle, T.J.; Alam, T.M.; Scott, B.; Ziller, J.W.

    1997-12-31

    Titanium neo-pentoxide was isolated by the alcoholysis exchange between Ti(OCHMe{sub 2}){sub 4} and ONep. The molecule, [Ti(ONep){sub 4}]{sub 2}, was characterized using X-ray analysis and solution {sup 17}O, and {sup 47},{sup 49}Ti NMR spectroscopy. This dinuclear complex is the smallest Ti(OR){sub 4} isolated wherein each metal center is 5-coordinated. The molecule is highly soluble in standard solvents and volatile. The reactivity of this compound has been undertaken to compare with the ubiquitous Ti(O-I-Pr){sub 4}. The various compounds isolated and further NMR studies will be reported. Analogous routes to other M(ONep){sub n} will be reported as well.

  18. Two-coordinate terminal zinc hydride complexes: synthesis, structure and preliminary reactivity studies.

    PubMed

    Dawkins, Michael J C; Middleton, Ewart; Kefalidis, Christos E; Dange, Deepak; Juckel, Martin M; Maron, Laurent; Jones, Cameron

    2016-08-18

    The first examples of essentially two-coordinate, monomeric zinc hydride complexes, LZnH (L = -N(Ar)(SiR3)) (Ar = C6H2{C(H)Ph2}2R'-2,6,4; R = Me, R' = Pr(i) (L'); R = Pr(i), R' = Me (L*); R = Pr(i), R' = Pr(i) (L(†))) have been prepared and shown by crystallographic studies to have near linear N-Zn-H fragments. The results of computational studies imply that any PhZn interactions in the compounds are weak at best. Preliminary reactivity studies reveal the compounds to be effective for the stoichiometric hydrozincation and catalytic hydrosilylation of carbonyl compounds. PMID:27499232

  19. Functionalized Silicone Nanospheres: Synthesis, Transition Metal Immobilization, and Catalytic Applications

    SciTech Connect

    Bradley, Christopher A.; Yuhas, Benjamin D.; McMurdo, Meredith J.; Tilley, T. D.

    2008-12-11

    Silicone nanospheres containing a variety of functional groups (pyridines, phosphines, thiols, amines, etc.) have been prepared by emulsion copolymerization of methyltrimethoxysilane, MeSi(OMe)3, and the functionalized monomer of interest, RSi(OMe)3. This procedure provides a reproducible synthesis of spherical particles in the 12-28 nm size regime as determined by transmission electronSilicone nanospheres containing a variety of functional groups (pyridines, phosphines, thiols, amines, etc.) have been prepared by emulsion copolymerization of methyltrimethoxysilane, MeSi(OMe)₃, and the functionalized monomer of interest, RSi(OMe)₃. This procedure provides a reproducible synthesis of spherical particles in the 12-28 nm size regime as determined by transmission electron microscopy (TEM). The presence of the functional groups is supported by a combination of spectroscopic methods including DRUV-vis, DRIFTS, and NMR spectroscopy. Comonomer dispersity within the nanospheres was probed using elemental mapping techniques, and these support a homogeneous distribution of functional groups within the particles. Palladium(0) immobilization on phosphine-substituted nanospheres also results in a random distribution of the transition metal throughout the particles. Nanospheres containing multiple acid/base functionalities were also prepared, and these demonstrate functional group cooperativity based on enhanced conversions in the base-catalyzed Henry reaction, relative to nanosphere catalysts containing only basic groups. The diversity of functional groups that may be incorporated into the spheres suggests that these materials hold considerable promise as ligand supports and catalysts.Graphene nanoribbons (GNRs) have been suggested as a promising material for its use as nanoelectromechanical reasonators for highly sensitive force, mass, and charge detection. Therefore the accurate determination of the size-dependent elastic properties of GNRs is desirable for the design of

  20. Enzymatic synthesis of lignin-siloxane hybrid functional polymers.

    PubMed

    Prasetyo, Endry Nugroho; Kudanga, Tukayi; Fischer, Roman; Eichinger, Reinhard; Nyanhongo, Gibson S; Guebitz, Georg M

    2012-02-01

    This study combines the properties of siloxanes and lignin polymers to produce hybrid functional polymers that can be used as adhesives, coating materials, and/or multifunctionalized thin-coating films. Lignin-silica hybrid copolymers were synthesized by using a sol-gel process. Laccases from Trametes hirsuta were used to oxidize lignosulphonates to enhance their reactivity towards siloxanes and then were incorporated into siloxane precursors undergoing a sol-gel process. In vitro copolymerization studies using pure lignin monomers with aminosilanes or ethoxytrimethylsilane and analysis by ²⁹Si NMR spectroscopy revealed hybrid products. Except for kraft lignin, an increase in lignin concentration positively affected the tensile strength in all samples. Similarly, the viscosity generally increased in all samples with increasing lignin concentration and also affected the curing time.

  1. N-benzoylimido complexes of palladium. Synthesis, structural characterisation and structure-reactivity relationship.

    PubMed

    Besenyei, Gábor; Párkányi, László; Szalontai, Gábor; Holly, Sándor; Pápai, Imre; Keresztury, Gábor; Nagy, Andrea

    2004-07-01

    Benzoyl azides, ArC(O)N3, 2, (Ar = phenyl or substituted phenyl), react with [Pd2Cl2(dppm)2], 1, [dppm = bis(diphenylphosphino)methane] with the formation of novel [Pd2Cl2(mu-NC(O)Ar)(dppm)2], 3, benzoylnitrene complexes that were structurally characterised by multinuclear magnetic resonance and IR spectroscopy and, in several instances, by single crystal X-ray diffraction. As shown by crystallographic studies, the C2P4Pd2 rings adopt extended twist-boat conformations with methylene groups bending towards the bridging benzoylimido moieties. X-ray diffraction studies have revealed the chiral nature of the imido complexes, the chiral element being the propeller-like C2P4Pd2 ring. Structural data accumulated on complexes 3 such as short C-N distances (1.32 A), elongated C=O bonds (1.30 A) as well as the outstandingly high barrier to internal rotation around the N-C(O) linkage (88.3 kJ mol(-1)) are in line with extensive ppi-ppi interaction between the bridging nitrogen and the carbonyl carbon atoms. Theoretical calculations indicate an electron shift from the dimer towards the apical nitrogen atom, which, in turn, facilitates the donation of electrons towards the carbonyl moiety. To elucidate the structure-reactivity relationship of benzoyl azides towards 1, crystallographic and solution IR spectroscopic studies were carried out on a series of para-substituted benzoyl azides. The reaction obeys the Hammett equation. The large positive value of the reaction constant indicates that the azides act as electrophiles in the reaction studied. The enhanced reactivity of 2-nitrobenzoyl azide has been attributed to a decreased conjugation of the phenyl and carbonyl moieties in this reagent.

  2. Fatty acid synthesis: from CO2 to functional genomics.

    PubMed

    Ohlrogge, J; Pollard, M; Bao, X; Focke, M; Girke, T; Ruuska, S; Mekhedov, S; Benning, C

    2000-12-01

    For over 25 years there has been uncertainty over the pathway from CO(2) to acetyl-CoA in chloroplasts. On the one hand, free acetate is the most effective substrate for fatty acid synthesis by isolated chloroplasts, and free acetate concentrations reported in leaf tissue (0.1-1 mM) appear adequate to saturate fatty acid synthase. On the other hand, a clear mechanism to generate sufficient free acetate for fatty acid synthesis is not established and direct production of acetyl-CoA from pyruvate by a plastid pyruvate dehydrogenase seems a more simple and direct path. We have re-examined this question and attempted to distinguish between the alternatives. The kinetics of (13)CO(2) and (14)CO(2) movement into fatty acids and the absolute rate of fatty acid synthesis in leaves was determined in light and dark. Because administered (14)C appears in fatty acids within < 2-3 min our results are inconsistent with a large pool of free acetate as an intermediate in leaf fatty acid synthesis. In addition, these studies provide an estimate of the turnover rate of fatty acid in leaves. Studies similar to the above are more complex in seeds, and some questions about the regulation of plant lipid metabolism seem difficult to solve using conventional biochemical or molecular approaches. For example, we have little understanding of why or how some seeds produce >50% oil whereas other seeds store largely carbohydrate or protein. Major control over complex plant biochemical pathways may only become possible by understanding regulatory networks which provide 'global' control over these pathways. To begin to discover such networks and provide a broad analysis of gene expression in developing oilseeds, we have produced microarrays that display approx. 5000 seed-expressed Arabidopsis genes. Sensitivity of the arrays was 1-2 copies of mRNA/cell. The arrays have been hybridized with probes derived from seeds, leaves and roots, and analysis of expression ratios between the different tissues

  3. Novel imidazolium and imidazolinium salts containing the 9-nickelafluorenyl anion--synthesis, structures and reactivity.

    PubMed

    Buchalski, Piotr; Pacholski, Roman; Chodkiewicz, Krzysztof; Buchowicz, Włodzimierz; Suwińska, Kinga; Shkurenko, Aleksander

    2015-04-28

    Investigation of the properties of carbene complexes is one of the most important fields of modern coordination chemistry. In this paper, we propose the convenient synthesis of NHC-nickel compounds. The 9-nickelafluorenyllithium complex reacts with imidazolium or imidazolinium salts to afford 9-nickelafluorenyl-NHC salts via ionic metathesis with very good yields (66-92%). These compounds can be isomerised at elevated temperatures to give Ni-NHC complexes with excellent yields (88-91%), probably via nickel mediated hydrogen transfer to the biphenyl moiety. In this reaction, the nickelacyclic ring itself serves as a base in the deprotonation of the carbene precursor. DFT calculations show the thermodynamic instability of the synthesized salts, with Gibbs free energy differences for 1 of -84 kJ mol(-1) at 298 K and -167 kJ mol(-1) at 374 K. The obtained salts and carbene complexes are relatively air and moisture stable in the solid state. PMID:25786198

  4. Structure and reactivity of alumina-supported iron catalysts for ammonia synthesis

    SciTech Connect

    Sueiras, J.E.; Homs, N.; Ramirez de la Piscina, P.; Gracia, M.; Fierro, J.L.G.

    1986-04-01

    Alumina-supported iron catalysts, obtained either by impregnation of iron from a K/sub 4/(Fe(CN)/sub 6/) aqueous solution upon several acid-modified ..gamma..-Al/sub 2/O/sub 3/ samples or by the incipient wetness method, were characterized and their activities for ammonia synthesis at atmospheric pressure and 593 K were studied. Characterization was carried out by temperature-programmed reduction (TPR), kinetics of hydrogen reduction, CO chemisorption, X-ray photoelectron spectroscopy (XPS), IR spectroscopy, and Moessbauer spectroscopy, resulting in the degree of reduction and the dispersion of the metallic phase dependent on the previous acid modification of the ..gamma..-Al/sub 2/O/sub 3/. The XPS surface composition expressed as M 2p/Al 2p (M = Fe, K) gave K 2p/Al 2p > Fe 2p/Al 2p. IR experiments, with NO as probe molecules, exhibited bands for reduced catalysts at 1778 and 1712 cm/sup -1/ whose intensity and position depended on the protonation degree of ..gamma..-Al/sub 2/O/sub 3/ and promoter content, respectively. Moessbauer spectra of the reduced samples showed the presence of surface ..cap alpha..-Fe, superparamagnetic Fe/sup 0/, Fe/sup 2 +/, Fe/sup 3 +/, and ..cap alpha..-Fe/sub 2/O/sub 3/ depending on the catalyst. Finally, the catalytic activity for ammonia synthesis was found to be dependent on the surface structure of the catalyst and hence on the method of preparation.

  5. New insights into ferritin synthesis and function highlight a link between iron homeostasis and oxidative stress in plants

    PubMed Central

    Briat, Jean-Francois; Ravet, Karl; Arnaud, Nicolas; Duc, Céline; Boucherez, Jossia; Touraine, Brigitte; Cellier, Francoise; Gaymard, Frederic

    2010-01-01

    Background Iron is an essential element for both plant productivity and nutritional quality. Improving plant iron content was attempted through genetic engineering of plants overexpressing ferritins. However, both the roles of these proteins in plant physiology, and the mechanisms involved in the regulation of their expression are largely unknown. Although the structure of ferritins is highly conserved between plants and animals, their cellular localization differs. Furthermore, regulation of ferritin gene expression in response to iron excess occurs at the transcriptional level in plants, in contrast to animals which regulate ferritin expression at the translational level. Scope In this review, an overview of our knowledge of bacterial and mammalian ferritin synthesis and functions is presented. Then the following will be reviewed: (a) the specific features of plant ferritins; (b) the regulation of their synthesis during development and in response to various environmental cues; and (c) their function in plant physiology, with special emphasis on the role that both bacterial and plant ferritins play during plant–bacteria interactions. Arabidopsis ferritins are encoded by a small nuclear gene family of four members which are differentially expressed. Recent results obtained by using this model plant enabled progress to be made in our understanding of the regulation of the synthesis and the in planta function of these various ferritins. Conclusions Studies on plant ferritin functions and regulation of their synthesis revealed strong links between these proteins and protection against oxidative stress. In contrast, their putative iron-storage function to furnish iron during various development processes is unlikely to be essential. Ferritins, by buffering iron, exert a fine tuning of the quantity of metal required for metabolic purposes, and help plants to cope with adverse situations, the deleterious effects of which would be amplified if no system had evolved to

  6. Synthesis and Functions of Ag2S Nanostructures

    NASA Astrophysics Data System (ADS)

    Cui, Chunyan; Li, Xiaoru; Liu, Jixian; Hou, Yongchao; Zhao, Yuqing; Zhong, Guocheng

    2015-11-01

    The paper presents a review about synthesis and applications of Ag2S nanostructures. As the modern photoelectric and biological materials, Ag2S nanomaterials are potentially useful for both structure and function purposes. Ag2S is a direction narrow band gap semiconductor with special properties. Ag2S nanostructures have been widely researched in chemistry and biochemistry fields because of their unusual optical, electrical, and mechanical properties. It can also be used in many fields, such as photovoltaic cells and infrared detector. In the past few years, Ag2S nanostructures have been synthesized by various methods. The article mainly discusses the four types of preparation methods. Moreover, this article shows a detailed review on the new properties, fabrication, and applications of Ag2S nanocrystals.

  7. Synthesis and Functions of Ag2S Nanostructures.

    PubMed

    Cui, Chunyan; Li, Xiaoru; Liu, Jixian; Hou, Yongchao; Zhao, Yuqing; Zhong, Guocheng

    2015-12-01

    The paper presents a review about synthesis and applications of Ag2S nanostructures. As the modern photoelectric and biological materials, Ag2S nanomaterials are potentially useful for both structure and function purposes. Ag2S is a direction narrow band gap semiconductor with special properties. Ag2S nanostructures have been widely researched in chemistry and biochemistry fields because of their unusual optical, electrical, and mechanical properties. It can also be used in many fields, such as photovoltaic cells and infrared detector. In the past few years, Ag2S nanostructures have been synthesized by various methods. The article mainly discusses the four types of preparation methods. Moreover, this article shows a detailed review on the new properties, fabrication, and applications of Ag2S nanocrystals. PMID:26525702

  8. Synthesis, characterization, and controlled assembly of functional nanostructures

    NASA Astrophysics Data System (ADS)

    Patete, Jonathan M.

    Nanomaterials represent a particularly interesting class of materials for research, as they bridge the gap between bulk materials and atomic or molecular structures, and often exhibit both novel chemical and physical properties. These properties may be altered not only by the chemical composition of the material but also by the size and shape of the nanoparticle. More specifically, the inherent anisotropy of one-dimensional nanostructures renders them as particularly efficient for electron transport applications. These materials are also highly sought after, because their distinctive shape allows for facile incorporation into functional device configurations. My graduate research has spanned several stages of nanotechnology from the synthesis and characterization of one-dimensional metal oxide nanostructures to the assembly of metal nanoparticles for practical device engineering. In particular, I have investigated the effect of the nanoscale size regime on the electronic, magnetic, and optical properties of as-prepared nanowires composed of hexagonal yttrium manganese oxide and olivine lithium iron phosphate. As a multiferroic material, h-YMnO3 is predominately sought after for applications in data storage devices. Alternatively, nanoscale LiFePO4 has shown a lot of promise as a cathode material in advanced lithium ion battery systems. The synthesis of both materials was achieved through template-directed methods, thereby allowing for precise control over the size and morphology of the as-obtained product. Finally, purposeful, directed methods for controlling the deposition pattern of metallic nanoparticles on a two-dimensional surface will be presented, and their viability as functional optical sensors will be explored.

  9. Organic functional group transformations in water at elevated temperature and pressure: Reversibility, reactivity, and mechanisms

    NASA Astrophysics Data System (ADS)

    Shipp, Jessie; Gould, Ian R.; Herckes, Pierre; Shock, Everett L.; Williams, Lynda B.; Hartnett, Hilairy E.

    2013-03-01

    Many transformation reactions involving hydrocarbons occur in the presence of H2O in hydrothermal systems and deep sedimentary systems. We investigate these reactions using laboratory-based organic chemistry experiments at high temperature and pressure (300 °C and 100 MPa). Organic functional group transformation reactions using model organic compounds based on cyclohexane with one or two methyl groups provided regio- and stereochemical markers that yield information about reversibility and reaction mechanisms. We found rapidly reversible interconversion between alkanes, alkenes, dienes, alcohols, ketones, and enones. The alkane-to-ketone reactions were not only completely reversible, but also exhibited such extensive reversibility that any of the functional groups along the reaction path (alcohol, ketone, and even the diene) could be used as the reactant and form all the other groups as products. There was also a propensity for these ring-based structures to dehydrogenate; presumably from the alkene, through a diene, to an aromatic ring. The product suites provide strong evidence that water behaved as a reactant and the various functional groups showed differing degrees of reactivity. Mechanistically-revealing products indicated reaction mechanisms that involve carbon-centered cation intermediates. This work therefore demonstrates that a wide range of organic compound types can be generated by abiotic reactions at hydrothermal conditions.

  10. Combining bifunctional chelator with (3 + 2)-cycloaddition approaches: synthesis of dual-function technetium complexes.

    PubMed

    Braband, Henrik; Imstepf, Sebastian; Benz, Michael; Spingler, Bernhard; Alberto, Roger

    2012-04-01

    A new concept for the synthesis of dual-functionalized technetium (Tc) compounds is presented, on the basis of the reactivity of fac-{Tc(VII)O(3)}(+) complexes. The concept combines the "classical" bifunctional chelator (BFC) approach with the new ligand centered labeling strategy of fac-{TcO(3)}(+) complexes with alkenes ((3 + 2)-cycloaddition approach). To evidence this concept, fac-{(99)TcO(3)}(+) model complexes containing functionalized 1,4,7-triazacyclononane (tacn) derivatives N-benzyl-2-(1,4,7-triazonan-1-yl)acetamide (tacn-ba) and 2,2',2″-(1,4,7-triazonane-1,4,7-triyl)triacetic acid (nota·3H) were synthesized and characterized. Whereas [(99)TcO(3)(tacn-ba)](+) [2](+) can be synthesized following a established oxidation procedure starting from the Tc(V) complex [(99)TcO(glyc)(tacn-ba)](+) [1](+), a new synthetic pathway for the synthesis of [(99)TcO(3)(nota)](2-) [5](2-) had to be developed, starting from [(99)Tc(nota·3H)(CO)(3)](+) [4](+) and using sodium perborate tetrahydrate (NaBO(3)·4H(2)O) as oxidizing reagent. While [(99)TcO(3)(nota)](2-) [5](2-) is a very attractive candidate for the development of trisubstituted novel multifunctional radioprobes, (3 + 2)-cycloaddition reactions of [(99)TcO(3)(tacn-ba)](+) [2](+) with 4-vinylbenzenesulfonate (styrene-SO(3)(-)) demonstrated the suitability of monosubstituted tacn derivatives for the new mixed "BFC-(3 + 2)-cycloaddition" approach. Kinetic studies of this reaction lead to the conclusion that the alteration of the electronic structure of the nitrogen donors by, e.g., alkylation can be used to tune the rate of the (3 + 2)-cycloaddition.

  11. The synthesis, characterization and reactivity of high oxidation state nickel fluorides

    SciTech Connect

    Chacon, L.C. |

    1997-12-01

    The research described in this thesis has mainly addressed the challenge of the synthesis of thermodynamically unstable nickel fluorides, which cannot be made by traditional thermal methods. A low-temperature approach towards the synthesis of such transition metal fluorides exploits the greater thermodynamic stability of high oxidation states in anions and involves the use of anhydrous hydrogen fluoride (aHF) as a solvent. The general method consists of combining an aHF soluble starting material (e.g., K{sub 2}NiF{sub 6}) with a Lewis fluoroacid (e.g., BF{sub 3}), which precipitates a neutral polymeric solid state fluoride: 2 K{sup +} + NiF{sub 6}{sup 2{minus}} + BF{sub 3} {r_arrow} NiF{sub 4} + 2 BF{sub 4}{sup {minus}} + 2 K{sup +}. At room temperature, this reaction yields a different structural phase, with composition K{sub x}NiF{sub 3} (x {approx} 0.18). This material has a pseudo-hexagonal tungsten bronze structure (H{sub 0}-K{sub x}NiF{sub 3}), and is an ionic conductor, probably due to K{sup +} ions hosted in the lattice channels. R-NiF{sub 3} is capable of fluorinating a wide range of inorganic and organic substrates. These reactions have probably shed light on the mechanism of the Simons Electrochemical Fluorination (ECF) Process, an important industrial method of fluorinating organic compounds. It has long been speculated that NiF{sub 3} plays a role in the ECF process, which uses nickel electrodes in aHF solvent. K{sub 2}NiF{sub 6} also fluorinates organic compounds in aHF, but interestingly, yields different fluorinated products. The reduction of R-NiF{sub 3} and K{sub 2}NiF{sub 6} during fluorination reactions yields NiF{sub 2}. A method has been developed to regenerate NiF{sub 6}{sup 2{minus}} from NiF{sub 2}.

  12. Synthesis and characterization of nanocrystalline Ti(1-x)Al(x)N by reactive magnetron sputtering.

    PubMed

    Jose, Feby; Ramaseshan, R; Dash, S; Dasgupta, Arup; Saroja, S; Tyagi, A K

    2009-09-01

    Ti(1-x)Al(x)N metastable films were synthesized by reactive magnetron co-sputtering with different Ti to Al ratios. XRD studies showed that as-deposited films were crystalline for concentrations of Al (35, 40, 55 and 64%) and become amorphous at 81% Al. These films were annealed at 1073 K to study the phase separation. Films up to 55% Al did not show any phase separation after annealing. But films with 64% Al splits into c-TiAIN and c-AIN, whereas films with 81% Al split into cubic-TiN and hex-AIN. Distribution of crystallites and their size were analyzed by TEM. High density of crystallites with dimensions between 3-11 nm was dispersed in amorphous matrix for 64% Al films. Nanoindentation technique was used to determine the mechanical properties of these films without substrate effect. Maximum hardness obtained for as deposited and annealed films (64% Al) were 35 GPa and 38 GPa, respectively.

  13. Synthesis and microstructure observation of titanium carbonitride nanostructured coatings using reactive plasma spraying in atmosphere

    NASA Astrophysics Data System (ADS)

    Zhu, Lin; He, Jining; Yan, Dianran; Xiao, Lisong; Dong, Yanchun; Zhang, Jianxin; Liao, Hanlin

    2011-08-01

    In the present study, nanostructured titanium carbonitride (TiCN) coatings were successfully deposited by reactive plasma spraying (RPS) technology using a self-designed gas tunnel mounted on a normal plasma spray torch. The phase composition and microstructure of the TiCN coatings were characterised by XRD, SEM and TEM. The results indicated that the main phase of the coatings was FCC TiC 0.2N 0.8 with a small amount of Ti 3O. The coating that was deposited using 35 kW displayed better microstructure and properties. The coating exhibited a typical nanostructure including 90 nm diamertrical equiaxed grains and 400 nm long columnar grains by TEM images. The SEM observation further revealed that the equiaxed grains in parallel direction to the substrate surface in TEM images were actually the columnar grains perpendicular to the substrate surface. The formation mechanism of the nanostructured coatings was also discussed. The measured microhardness value of the coating was approximately 1659 Hv 100 g , and the calculated crack extension force was about 34.9 J/m 2.

  14. Synthesis and characterization of petal type CZTS by stacked layer reactive sputtering

    NASA Astrophysics Data System (ADS)

    Singh, Om Pal; Parmar, R.; Gour, K. S.; Dalai, M. K.; Tawale, Jai; Singh, S. P.; Singh, Vidya Nand

    2015-12-01

    Here we present a method to grow the petal type structure of CZTS thin film on soda lime glass substrate using the stacked layer reactive sputtering and post-depostion annealing in N2 atmosphere. Optical bandgap of the petal type structure of CZTS was determined using UV-VIS spectroscopy and the value was 1.5 eV. In XRD analysis, (112) plane having highest intensity and other supporting planes with low intensity peaks corresponding to (200), (220) and (312) revealed the presence of CZTS phase. It was further confirmed by the Raman analysis, where the Raman peaks at 288 cm-1, 335 cm-1 and 353 cm-1 revealed the presence of CZTS phase. Petal type growth was observed in the scanning electron microscopy analysis. Elemental analysis was done by the EDAX. In EDAX analysis, It is observed that sample was Sn rich which may be responsible for petal type growth. Petal type growth of CZTS may be helpful in increasing the performance of the CZTS based thin film solar cell by phenomena of light scattering and enhanced surface area.

  15. Synthesis of copper nitride films doped with Fe, Co, or Ni by reactive magnetron sputtering

    SciTech Connect

    Yang, Jianbo; Huang, Saijia; Wang, Zhijiao; Hou, Yuxuan; Shi, Yuyu; Zhang, Jian; Yang, Jianping Li, Xing'ao

    2014-09-01

    Copper nitride (Cu{sub 3}N) and Fe-, Co-, and Ni-doped Cu{sub 3}N films were prepared by reactive magnetron sputtering. The films were deposited on silicon substrates at room temperature using pure Cu target and metal chips. The molar ratio of Cu to N atoms in the as-prepared Cu{sub 3}N film was 2.7:1, which is comparable with the stoichiometry ratio 3:1. X-ray diffraction measurements showed that the films were composed of Cu{sub 3}N crystallites with anti-ReO{sub 3} structure and adopted different preferred orientations. The reflectance of the four samples decreased in the wavelength range of 400–830 nm, but increased rapidly within wavelength range of 830–1200 nm. Compared with the Cu{sub 3}N films, the resistivity of the doped Cu{sub 3}N films decreased by three orders of magnitude. These changes have great application potential in optical and electrical devices based on Cu{sub 3}N films.

  16. Green synthesis of iron nanoparticles by various tea extracts: Comparative study of the reactivity

    NASA Astrophysics Data System (ADS)

    Huang, Lanlan; Weng, Xiulan; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra

    2014-09-01

    Iron nanoparticles (Fe NPs) are often synthesized using sodium borohydride with aggregation, which is a high cost process and environmentally toxic. To address these issues, Fe NPs were synthesized using green methods based on tea extracts, including green, oolong and black teas. The best method for degrading malachite green (MG) was Fe NPs synthesized by green tea extracts because it contains a high concentration of caffeine/polyphenols which act as both reducing and capping agents in the synthesis of Fe NPs. These characteristics were confirmed by a scanning electron microscope (SEM), UV-visible (UV-vis) and specific surface area (BET). To understand the formation of Fe NPs using various tea extracts, the synthesized Fe NPs were characterized by SEM, X-ray energy-dispersive spectrometer (EDS), and X-ray diffraction (XRD). What emerged were different sizes and concentrations of Fe NPs being synthesized by tea extracts, leading to various degradations of MG. Furthermore, kinetics for the degradation of MG using these Fe NPs fitted well to the pseudo first-order reaction kinetics model with more than 20 kJ/mol activation energy, suggesting a chemically diffusion-controlled reaction. The degradation mechanism using these Fe NPs included adsorption of MG to Fe NPs, oxidation of iron, and cleaving the bond that was connected to the benzene ring.

  17. Green synthesis of iron nanoparticles by various tea extracts: comparative study of the reactivity.

    PubMed

    Huang, Lanlan; Weng, Xiulan; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra

    2014-09-15

    Iron nanoparticles (Fe NPs) are often synthesized using sodium borohydride with aggregation, which is a high cost process and environmentally toxic. To address these issues, Fe NPs were synthesized using green methods based on tea extracts, including green, oolong and black teas. The best method for degrading malachite green (MG) was Fe NPs synthesized by green tea extracts because it contains a high concentration of caffeine/polyphenols which act as both reducing and capping agents in the synthesis of Fe NPs. These characteristics were confirmed by a scanning electron microscope (SEM), UV-visible (UV-vis) and specific surface area (BET). To understand the formation of Fe NPs using various tea extracts, the synthesized Fe NPs were characterized by SEM, X-ray energy-dispersive spectrometer (EDS), and X-ray diffraction (XRD). What emerged were different sizes and concentrations of Fe NPs being synthesized by tea extracts, leading to various degradations of MG. Furthermore, kinetics for the degradation of MG using these Fe NPs fitted well to the pseudo first-order reaction kinetics model with more than 20 kJ/mol activation energy, suggesting a chemically diffusion-controlled reaction. The degradation mechanism using these Fe NPs included adsorption of MG to Fe NPs, oxidation of iron, and cleaving the bond that was connected to the benzene ring.

  18. Template-mediated synthesis and bio-functionalization of flexible lignin-based nanotubes and nanowires

    NASA Astrophysics Data System (ADS)

    Caicedo, Hector M.; Dempere, Luisa A.; Vermerris, Wilfred

    2012-03-01

    Limitations of cylindrical carbon nanotubes based on the buckminsterfullerene structure as delivery vehicles for therapeutic agents include their chemical inertness, sharp edges and toxicological concerns. As an alternative, we have developed lignin-based nanotubes synthesized in a sacrificial template of commercially available alumina membranes. Lignin is a complex phenolic plant cell wall polymer that is generated as a waste product from paper mills and biorefineries that process lignocellulosic biomass into fuels and chemicals. We covalently linked isolated lignin to the inner walls of activated alumina membranes and then added layers of dehydrogenation polymer onto this base layer via a peroxidase-catalyzed reaction. By using phenolic monomers displaying different reactivities, we were able to change the thickness of the polymer layer deposited within the pores, resulting in the synthesis of nanotubes with a wall thickness of approximately 15 nm or nanowires with a nominal diameter of 200 nm. These novel nanotubes are flexible and can be bio-functionalized easily and specifically, as shown by in vitro assays with biotin and Concanavalin A. Together with their intrinsic optical properties, which can also be varied as a function of their chemical composition, these lignin-based nanotubes are expected to enable a variety of new applications including as delivery systems that can be easily localized and imaged after uptake by living cells.

  19. Template-mediated synthesis and bio-functionalization of flexible lignin-based nanotubes and nanowires.

    PubMed

    Caicedo, Hector M; Dempere, Luisa A; Vermerris, Wilfred

    2012-03-16

    Limitations of cylindrical carbon nanotubes based on the buckminsterfullerene structure as delivery vehicles for therapeutic agents include their chemical inertness, sharp edges and toxicological concerns. As an alternative, we have developed lignin-based nanotubes synthesized in a sacrificial template of commercially available alumina membranes. Lignin is a complex phenolic plant cell wall polymer that is generated as a waste product from paper mills and biorefineries that process lignocellulosic biomass into fuels and chemicals. We covalently linked isolated lignin to the inner walls of activated alumina membranes and then added layers of dehydrogenation polymer onto this base layer via a peroxidase-catalyzed reaction. By using phenolic monomers displaying different reactivities, we were able to change the thickness of the polymer layer deposited within the pores, resulting in the synthesis of nanotubes with a wall thickness of approximately 15 nm or nanowires with a nominal diameter of 200 nm. These novel nanotubes are flexible and can be bio-functionalized easily and specifically, as shown by in vitro assays with biotin and Concanavalin A. Together with their intrinsic optical properties, which can also be varied as a function of their chemical composition, these lignin-based nanotubes are expected to enable a variety of new applications including as delivery systems that can be easily localized and imaged after uptake by living cells. PMID:22362196

  20. Reactive processing and characterization of nickel aluminide-alumina functionally gradient composites

    NASA Astrophysics Data System (ADS)

    Zhu, Hexiang

    The reactive hot compaction (RHC) technique was successfully utilized to produce bulk in-situ nickel aluminide (NiAl)-alumina (Al 2O3) functionally gradient composites (FGCs) as well as thin FGC coating. The FGCs consisted of four or five layers with alumina content increasing from less than 3vol.% to about 35vol.%. The composites were fabricated via reactive processing of the powder mixtures of nickel, aluminum, partially oxidized aluminum (Al*) and/or nickel oxide (NiO). The technique resulted in a gradual transition of the microstructure and properties along the thickness of the FGC, and led to reduced residual stresses and a strong bonding between the NiAl substrate and the FGC coating. The FGC also had higher fracture toughness than the corresponding composites. The phase and microstructural development for the three powder mixture systems (Ni-Al, Ni-Al*, and NiO-Al), which occurred during reactive processing of the composites, were systematically studied. The reaction process of Ni + Al powder mixtures was found to be strongly affected by pressure, heating rates, heat loss and diffusion barrier. It was found that the formation of NiAl occurred rapidly via combustion reaction at high heating rates and with small heat loss. At slow heating rates, however, the reaction process was slow and controlled by solid-state diffusion. The phase formation sequence for the slow solid-state reaction was determined to be: NiAl3 → Ni2Al3 → NiAl (Ni3Al) → NiAl. An Al2O3 particle network was produced during RHC of Ni + Al* powders, while an interpenetrating Al2O3 skeleton formed for NiO + Al powders. The formation of Al2O 3 phases during RHC of NiO + Al powders was a three-stage process, with the Al2O3 phases coming from both the liquid and the solid state reactions. The solid state displacement reaction between NiO and nickel-aluminides (NiAl3, Ni2Al3, NiAl) is believed to lead to the formation of an interpenetrating Al2O 3 network in the final product. The in

  1. Synthesis of ferrocene-labeled steroids via copper-catalyzed azide-alkyne cycloaddition. Reactivity difference between 2β-, 6β- and 16β-azido-androstanes.

    PubMed

    Fehér, Klaudia; Balogh, János; Csók, Zsolt; Kégl, Tamás; Kollár, László; Skoda-Földes, Rita

    2012-06-01

    Copper-catalyzed cycloaddition of steroidal azides and ferrocenyl-alkynes were found to be an efficient methodology for the synthesis of ferrocene-labeled steroids. At the same time, a great difference between the reactivity of 2β- or 16β-azido-androstanes and a sterically hindered 6β-azido steroid toward both ferrocenyl-alkynes and simple alkynes, such as phenylacetylene, 1-octyne, propargyl acetate and methyl propiolate, was observed.

  2. Synthesis of Self-Assembled Multifunctional Nanocomposite Catalysts with Highly Stabilized Reactivity and Magnetic Recyclability

    NASA Astrophysics Data System (ADS)

    Yu, Xu; Cheng, Gong; Zheng, Si-Yang

    2016-05-01

    In this paper, a multifunctional Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite catalyst with highly stabilized reactivity and magnetic recyclability was synthesized by a self-assembled method. The magnetic Fe3O4 nanoparticles were coated with a thin layer of the SiO2 to obtain a negatively charged surface. Then positively charged poly(ethyleneimine) polymer (PEI) was self-assembled onto the Fe3O4@SiO2 by electrostatic interaction. Next, negatively charged glutathione capped gold nanoparticles (GSH-AuNPs) were electrostatically self-assembled onto the Fe3O4@SiO2@PEI. After that, silver was grown on the surface of the nanocomposite due to the reduction of the dopamine in the alkaline solution. An about 5 nm thick layer of polydopamine (PDA) was observed to form the Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite. The Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite was carefully characterized by the SEM, TEM, FT-IR, XRD and so on. The Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite shows a high saturation magnetization (Ms) of 48.9 emu/g, which allows it to be attracted rapidly to a magnet. The Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite was used to catalyze the reduction of p-nitrophenol (4-NP) to p-aminophenol (4-AP) as a model system. The reaction kinetic constant k was measured to be about 0.56 min‑1 (R2 = 0.974). Furthermore, the as-prepared catalyst can be easily recovered and reused for 8 times, which didn’t show much decrease of the catalytic capability.

  3. Synthesis of Self-Assembled Multifunctional Nanocomposite Catalysts with Highly Stabilized Reactivity and Magnetic Recyclability

    PubMed Central

    Yu, Xu; Cheng, Gong; Zheng, Si-Yang

    2016-01-01

    In this paper, a multifunctional Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite catalyst with highly stabilized reactivity and magnetic recyclability was synthesized by a self-assembled method. The magnetic Fe3O4 nanoparticles were coated with a thin layer of the SiO2 to obtain a negatively charged surface. Then positively charged poly(ethyleneimine) polymer (PEI) was self-assembled onto the Fe3O4@SiO2 by electrostatic interaction. Next, negatively charged glutathione capped gold nanoparticles (GSH-AuNPs) were electrostatically self-assembled onto the Fe3O4@SiO2@PEI. After that, silver was grown on the surface of the nanocomposite due to the reduction of the dopamine in the alkaline solution. An about 5 nm thick layer of polydopamine (PDA) was observed to form the Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite. The Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite was carefully characterized by the SEM, TEM, FT-IR, XRD and so on. The Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite shows a high saturation magnetization (Ms) of 48.9 emu/g, which allows it to be attracted rapidly to a magnet. The Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite was used to catalyze the reduction of p-nitrophenol (4-NP) to p-aminophenol (4-AP) as a model system. The reaction kinetic constant k was measured to be about 0.56 min−1 (R2 = 0.974). Furthermore, the as-prepared catalyst can be easily recovered and reused for 8 times, which didn’t show much decrease of the catalytic capability. PMID:27147586

  4. Synthesis, structure, and reactivity of high oxidation state silver fluorides and related compounds

    SciTech Connect

    Lucier, G.M.

    1995-05-01

    This thesis has been largely concerned with defining the oxidizing power of Ag(III) and Ag(II) in anhydrous hydrogen fluoride (aHF) solution. Emphasis was on cationic species, since in a cation the electronegativity of a given oxidation state is greatest. Cationic Ag(III) solv has a short half life at ordinary temperatures, oxidizing the solvent to elemental fluorine with formation of Ag(II). Salts of such a cation have not yet been preparable, but solutions which must contain such a species have proved to be effective and powerful oxidizers. In presence of PtF{sub 6}{sup {minus}}, RuF{sub 6}{sup {minus}}, or RhF{sub 6}{sup {minus}}, Ag(III) solv effectively oxidizes the anions to release the neutral hexafluorides. Such reactivity ranks cationic Ag(III) as the most powerfully oxidizing chemical agent known as far. Unlike its trivalent relative Ag (II) solv is thermodynamically stable in acid aHF. Nevertheless, it oxidizes IrF{sub 6}{sup {minus}} to IrF{sub 6} at room temperature, placing its oxidizing potential not more than 2 eV below that of cationic Ag(III). Range of Ag{sup 2+} (MF{sub 6}{sup {minus}}){sub 2} salts attainable in aHF has been explored. An anion must be stable with respect to electron loss to Ag{sup 2+}. The anion must also be a poor F{sup {minus}} donor; otherwise, either AgF{sup +} salts or AgF{sub 2} are generated.

  5. Synthesis and characterization of delafossite thin films by reactive RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Asmat Uceda, Martin Antonio

    This work presents a comparative study on optical and electrical properties of CuAlO2 thin films on sapphire (0001) substrates deposited with two different growth conditions using reactive RF-magnetron sputtering technique from metallic Cu and Al targets. CuAlO2 is a very promising material for transparent electronic applications, it is intended that comparison of results obtained from both approaches, could lead to optimization and control of the physical properties of this material, namely its electrical conductivity and optical transmittance. All samples were heat treated at 1100°C using rapid thermal annealing with varying time and rate of cooling. The effect of sputtering conditions and different annealing time on phase formation and evolution is studied with X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that for most of the samples CuAlO2 phase is formed after 60 min of annealing time, but secondary phases were also present that depend on the deposition conditions. However, pure CuAlO2 phase was obtained for annealed CuO on sapphire films with annealing time of 60 min. The optical properties obtained from UV-Visible spectroscopic measurement reveals indirect and direct optical band gaps for CuAlO2 films and were found to be 2.58 and 3.72 eV respectively. The films show a transmittance of about 60% in the visible range. Hall effect measurements indicate p-type conductivity. Van der Pauw technique was used to measure resistivity of the samples. The highest electrical conductivity and charge carrier concentration obtained were of 1.01x10-1S.cm -1 and 3.63 x1018 cm-3 respectively.

  6. Synthesis and Reactivity of Oxo-Peroxo-Vanadium(V) Bipyridine Compounds

    PubMed Central

    Waidmann, Christopher R.; DiPasquale, Antonio G.

    2010-01-01

    The vanadium(IV) compound [VIVO(OH)(tBu2bpy)2]BF4 (VIVO(OH)) (tBu2bpy = 4,4′-di-tert-butylbipyridine) is slowly oxidized by O2 in ethereal solvents to give the oxo-peroxo compound [VVO(O2)(tBu2bpy)2]BF4 (VVO(O2)) in excellent yield. This and related compounds were fully characterized by NMR, IR, and optical spectroscopies, mass spectrometry, elemental analyses, and an X-ray crystal structure of the 4,4′-dimethylbipyridine analog, [VVO(O2)(Me2bpy)2]BF4. Monitoring the reaction of VIVO(OH) with O2 in THF/acetonitrile mixtures by 1H NMR and optical spectroscopies surprisingly shows that the initial product is the cis-dioxo compound [VV(O)2(tBu2bpy)2]BF4 (VVO2), which then converts to VVO(O2). Reaction of VIVO(OH) with 18O2 gives ca. 60% triply 18O labeled VVO(O2). The mechanism of formation of VVO(O2) is complex and may occur via initial reduction of O2 at vanadium(IV) to give a superoxo-vanadium(V) intermediate, autoxidation of the THF solvent, or both. That VVO2 is generated first appears to be due to the ability of VIVO(OH) to act as a hydrogen atom donor. For instance, VIVO(OH) reacts with VVO(O2) give VVO2. VVO(O2) is also slowly reduced to VIVO(OH) by the organic hydrogen atom donors hydroquinone and TEMPOH (2,2,6,6-tetramethylpiperidin-1-ol) as well as by triphenylphosphine. Notably, the peroxo complex VVO(O2) is much less reactive with these substrates than the analogous dioxo compound VVO2. PMID:20108930

  7. Synthesis, Structure, and Reactivity of Co(II) and Ni(II) PCP Pincer Borohydride Complexes

    PubMed Central

    2015-01-01

    The 15e square-planar complexes [Co(PCPMe-iPr)Cl] (2a) and [Co(PCP-tBu)Cl] (2b), respectively, react readily with NaBH4 to afford complexes [Co(PCPMe-iPr)(η2-BH4)] (4a) and [Co(PCP-tBu)(η2-BH4)] (4b) in high yields, as confirmed by IR spectroscopy, X-ray crystallography, and elemental analysis. The borohydride ligand is symmetrically bound to the cobalt center in η2-fashion. These compounds are paramagnetic with effective magnetic moments of 2.0(1) and 2.1(1) μB consistent with a d7 low-spin system corresponding to one unpaired electron. None of these complexes reacted with CO2 to give formate complexes. For structural and reactivity comparisons, we prepared the analogous Ni(II) borohydride complex [Ni(PCPMe-iPr)(η2-BH4)] (5) via two different synthetic routes. One utilizes [Ni(PCPMe-iPr)Cl] (3) and NaBH4, the second one makes use of the hydride complex [Ni(PCPMe-iPr)H] (6) and BH3·THF. In both cases, 5 is obtained in high yields. In contrast to 4a and 4b, the borohydride ligand is asymmetrically bound to the nickel center but still in an η2-mode. [Ni(PCPMe-iPr)(η2-BH4)] (5) loses readily BH3 at elevated temperatures in the presence of NEt3 to form 6. Complexes 5 and 6 are both diamagnetic and were characterized by a combination of 1H, 13C{1H}, and 31P{1H} NMR, IR spectroscopy, and elemental analysis. Additionally, the structure of these compounds was established by X-ray crystallography. Complexes 5 and 6 react with CO2 to give the formate complex [Ni(PCPMe-iPr)(OC(C=O)H] (7). The extrusion of BH3 from [Co(PCPMe-iPr)(η2-BH4)] (4a) and [Ni(PCPMe-iPr)(η2-BH4)] (5) with the aid of NH3 to yield the respective hydride complexes [Co(PCPMe-iPr)H] and [Ni(PCPMe-iPr)H] (6) and BH3NH3 was investigated by DFT calculations showing that formation of the Ni hydride is thermodynamically favorable, whereas the formation of the Co(II) hydride, in agreement with the experiment, is unfavorable. The electronic structures and the bonding of the borohydride ligand in [Co

  8. Synthesis, characterization, and reactivity of Ti(IV)-monosubstituted Keggin polyoxometalates.

    PubMed

    Kholdeeva, Oxana A; Trubitsina, Tatiana A; Maksimov, Gennadii M; Golovin, Anatolii V; Maksimovskaya, Raisa I

    2005-03-01

    Ti(IV)-monosubstituted Keggin-type polyoxometalates (Ti-POMs), mu-oxo dimer [Bu4N]8[(PTiW11O39)2O] (1), and three monomers [Bu4N]4[PTi(L)W11O39], where L = OH (2), OMe (3), and OAr (4, ArOH = 2,3,6-trimethylphenol (TMP)), have been prepared starting from mu-hydroxo dimer [Bu4N]7[(PTiW11O39)2OH] (5) or heteropolyacid H5PW11TiO40 or both. The compounds have been characterized by elemental analysis, IR, UV-vis, and multinuclear (31P, 1H, 183W) NMR. The interaction of 1 and 3-5 with H2O in MeCN produces 2. The hydrolysis constants, estimated from 31P and 1H NMR data, are 0.006 and 0.04 for 1 and 3, respectively. Studies by 31P NMR, IR, potentiometric titration, and cyclic voltammetry revealed that 1-3 and 5 afford the same protonated titanium peroxo complex [Bu4N]4[HPTi(O2)W11O39] (I) upon interaction with aqueous H2O2 in MeCN. The rates of formation of I correlate with the rates of hydrolysis of the Ti-POMs and follow the order of 5 > 1 > 3. A two-step mechanism of the reaction of Ti-POMs with H2O2, which involves hydrolysis of the Ti-L bonds to yield 2 followed by fast interaction of 2 with hydrogen peroxide producing I, is suggested. The equilibrium constant for the reaction of 2 with H2O2 to yield I and H2O, estimated using 31P NMR, is 10. The interaction of the Ti-POMs with TMP follows the trends similar to their interaction with H2O) and requires preliminary hydrolysis of the Ti-L bonds. All of the Ti-POMs catalyze the oxidation of TMP with H2O2 in MeCN to give 2,3,5-trimethyl-p-benzoquinone and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol. The product distribution is similar for all of the Ti-POMs. The catalytic activities of the Ti-POMs correlate with the rates of formation of I and follow the order of 2 > 5 > 1 > 3. The findings lay a basis for a better understanding of the nature of the reactivity of titanium in Ti-catalyzed oxidations. PMID:15733007

  9. Surface functionalization of titanium dioxide nanoparticles: Photo-stability and reactive oxygen species (ROS) generation

    NASA Astrophysics Data System (ADS)

    Louis, Kacie M.

    Metal oxide nanoparticles are becoming increasingly prevalent in society for applications of sunscreens, cosmetics, paints, biomedical imaging, and photovoltaics. Due to the increased surface area to volume ratio of nanoparticles compared to bulk materials, it is important to know the health and safety impacts of these materials. One mechanism of toxicity of nominally "safe" materials such as TiO 2 is through the photocatalytic generation of reactive oxygen species (ROS). ROS production and ligand degradation can affect the bioavailability of these particles in aqueous organisms. We have investigated ROS generation by functionalized TiO2 nanoparticles and its influence on aggregation and bioavailability and toxicity to zebrafish embryos/larvae. For these studies we investigated anatase TiO2 nanoparticles. For application purposes and solution stability, the TiO2 nanoparticles were functionalized with a variety of ligands such as citrate, 3,4-dihydroxybenzaldehyde, and ascorbate. We quantitatively examined the amount of ROS produced in aqueous solution using fluorescent probes and see that more ROS is produced under UV light than in the dark control. Our measurements show that TiO2 toxicity reaches a maximum for nanoparticles with smaller diameters, and is correlated with surface area dependent changes in ROS generation. In an effort to reduce toxicity through control of the surface and surface ligands, we synthesized anatase nanoparticles of different sizes, functionalized them with different ligands, and examined the resulting ROS generation and ligand stability. Using a modular ligand containing a hydrophobic inner region and a hydrophilic outer region, we synthesized water-stable nanoparticles, via two different chemical reactions, having much-reduced ROS generation and thus reduced toxicity. These results suggest new strategies for making safer nanoparticles while still retaining their desired properties. We also examine the degradation of the different ligands

  10. Hypothalamic Pituitary Adrenal Axis Functioning in Reactive and Proactive Aggression in Children

    ERIC Educational Resources Information Center

    Lopez-Duran, Nestor L.; Olson, Sheryl L.; Hajal, Nastassia J.; Felt, Barbara T.; Vazquez, Delia M.

    2009-01-01

    The purpose of this study was to examine the association between hypothalamic-pituitary-adrenal axis (HPA-axis) reactivity and proactive and reactive aggression in pre-pubertal children. After a 30-min controlled base line period, 73 7-year-old children (40 males and 33 females) were randomly assigned to one of two experimental tasks designed to…

  11. Children's Patterns of Emotional Reactivity to Conflict as Explanatory Mechanisms in Links between Interpartner Aggression and Child Physiological Functioning

    ERIC Educational Resources Information Center

    Davies, Patrick T.; Sturge-Apple, Melissa L.; Cicchetti, Dante; Manning, Liviah G.; Zale, Emily

    2009-01-01

    Background: This paper examined children's fearful, sad, and angry reactivity to interparental conflict as mediators of associations between their exposure to interparental aggression and physiological functioning. Methods: Participants included 200 toddlers and their mothers. Assessments of interparental aggression and children's emotional…

  12. Ventral striatum dysfunction in children and adolescents with reactive attachment disorder: functional MRI study

    PubMed Central

    Takiguchi, Shinichiro; Fujisawa, Takashi X.; Mizushima, Sakae; Saito, Daisuke N.; Okamoto, Yuko; Shimada, Koji; Koizumi, Michiko; Kumazaki, Hirokazu; Jung, Minyoung; Kosaka, Hirotaka; Hiratani, Michio; Ohshima, Yusei; Teicher, Martin H.

    2015-01-01

    Background Child maltreatment is a major risk factor for psychopathology, including reactive attachment disorder (RAD). Aims To examine whether neural activity during reward processing was altered in children and adolescents with RAD. Method Sixteen children and adolescents with RAD and 20 typically developing (TD) individuals performed tasks with high and low monetary rewards while undergoing functional magnetic resonance imaging. Results Significantly reduced activity in the caudate and nucleus accumbens was observed during the high monetary reward condition in the RAD group compared with the TD group (P=0.015, family-wise error-corrected cluster level). Significant negative correlations between bilateral striatal activity and avoidant attachment were observed in the RAD and TD groups. Conclusions Striatal neural reward activity in the RAD group was markedly decreased. The present results suggest that dopaminergic dysfunction occurs in the striatum of children and adolescents with RAD, leading towards potential future risks for psychopathology. Declaration of interest None. Copyright and usage © The Royal College of Psychiatrists 2015. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence.

  13. Lung function and bronchial reactivity in asthmatics during exposure to volatile organic compounds

    SciTech Connect

    Harving, H.; Dahl, R.; Molhave, L. )

    1991-04-01

    The purpose of the present study was to investigate whether vapors of organic solvents at low concentrations could exert an adverse effect in the lower airways. Under controlled conditions in a climate chamber, 11 persons with bronchial hyperreactivity to histamine and bronchial asthma were exposed for 90 min to a mixture of organic solvents at levels of zero, 2.5, and 25 mg/m3. During exposure to 25 mg/m3 a decrease in FEV1 to 90.7% of baseline value was measured. This was significantly different from the initial value (p less than 0.05), but not significantly different from the value found after sham exposure (FEV1, 97.4% of initial value). The decline in FEV1 during exposure to 25 mg/m3 was most pronounced in persons with high bronchial sensitivity. No changes were found in histamine reactivity after exposure, and no late reactions were registered. Ratings of discomfort showed different individual patterns ranging from no response to reactions towards both of the concentrations. The ratings indicated development of tolerance during exposure. Volatile organic compounds in concentrations found in both the work and the home environments may influence lung function and are probably of importance as bronchial irritants.

  14. Theoretical studies of structure, function and reactivity of molecules— A personal account

    PubMed Central

    Morokuma, Keiji

    2009-01-01

    Last few decades theoretical/computational studies of structure, function and reactivity of molecules have been contributing significantly in chemistry by explanation of experimental results, better understanding of underlying principles and prediction of the unknown experimental outcome. Accuracy needed in chemistry has long been established, but due to high power dependency of such accurate methods on the molecular size, it has been a major challenge to apply theoretical methods to large molecular systems. In the present article we will review some examples of such applications. One is theoretical study of growth/formation of carbon nanostructures such as fullerenes and carbon nanotubes, using quantum mechanical molecular dynamics method. For growth of single walled carbon nanotube from transition metal cluster, we have demonstrated continued growth of attached nanotube, cap formation and growth from small carbon fragments. For homogeneous catalysis we presented results of studies on N2 activation by Zr complexes. For biomolecular reactions we use active site and protein models and show that in some catalyses the protein environment is involved in reactions and changes the preferred pathway, and in some other case the effect is modest. The review is concluded with a perspective. PMID:19444009

  15. Ligation of Glycophorin A Generates Reactive Oxygen Species Leading to Decreased Red Blood Cell Function

    PubMed Central

    Khoory, Joseph; Estanislau, Jessica; Elkhal, Abdallah; Lazaar, Asmae; Melhorn, Mark I.; Brodsky, Abigail; Illigens, Ben; Hamachi, Itaru; Kurishita, Yasutaka; Ivanov, Alexander R.; Shevkoplyas, Sergey; Shapiro, Nathan I.; Ghiran, Ionita C.

    2016-01-01

    Acute, inflammatory conditions associated with dysregulated complement activation are characterized by significant increases in blood concentration of reactive oxygen species (ROS) and ATP. The mechanisms by which these molecules arise are not fully understood. In this study, using luminometric- and fluorescence-based methods, we show that ligation of glycophorin A (GPA) on human red blood cells (RBCs) results in a 2.1-fold, NADPH-oxidase-dependent increase in intracellular ROS that, in turn, trigger multiple downstream cascades leading to caspase-3 activation, ATP release, and increased band 3 phosphorylation. Functionally, using 2D microchannels to assess membrane deformability, GPS-ligated RBCs travel 33% slower than control RBCs, and lipid mobility was hindered by 10% using fluorescence recovery after photobleaching (FRAP). These outcomes were preventable by pretreating RBCs with cell-permeable ROS scavenger glutathione monoethyl ester (GSH-ME). Our results obtained in vitro using anti-GPA antibodies were validated using complement-altered RBCs isolated from control and septic patients. Our results suggest that during inflammatory conditions, circulating RBCs significantly contribute to capillary flow dysfunctions, and constitute an important but overlooked source of intravascular ROS and ATP, both critical mediators responsible for endothelial cell activation, microcirculation impairment, platelet activation, as well as long-term dysregulated adaptive and innate immune responses. PMID:26784696

  16. Molecular Differentiated Initiator Reactivity in the Synthesis of Poly(caprolactone)-Based Hydrophobic Homopolymer and Amphiphilic Core Corona Star Polymers.

    PubMed

    Deng, Eileen; Nguyen, Nam T; Hild, Frédéric; Hamilton, Ian E; Dimitrakis, Georgios; Kingman, Samuel W; Lau, Phei-Li; Irvine, Derek J

    2015-11-09

    Macromolecules that possess three-dimensional, branched molecular structures are of great interest because they exhibit significantly differentiated application performance compared to conventional linear (straight chain) polymers. This paper reports the synthesis of 3- and 4-arm star branched polymers via ring opening polymerisation (ROP) utilising multi-functional hydroxyl initiators and Sn(Oct)2 as precatalyst. The structures produced include mono-functional hydrophobic and multi-functional amphiphilic core corona stars. The characteristics of the synthetic process were shown to be principally dependent upon the physical/dielectric properties of the initiators used. ROP's using initiators that were more available to become directly involved with the Sn(Oct)₂ in the "in-situ" formation of the true catalytic species were observed to require shorter reaction times. Use of microwave heating (MWH) in homopolymer star synthesis reduced reaction times compared to conventional heating (CH) equivalents, this was attributed to an increased rate of "in-situ" catalyst formation. However, in amphiphilic core corona star formation, the MWH polymerisations exhibited slower propagation rates than CH equivalents. This was attributed to macro-structuring within the reaction medium, which reduced the potential for reaction. It was concluded that CH experiments were less affected by this macro-structuring because it was disrupted by the thermal currents/gradients caused by the conductive/convective heating mechanisms. These gradients are much reduced/absent with MWH because it selectively heats specific species simultaneously throughout the entire volume of the reaction medium. These partitioning problems were overcome by introducing additional quantities of the species that had been determined to selectively heat.

  17. Synthesis, Structure, and Reactivity ofbis(1,2,4-tri-t-butylcyclopentadienyl) Complexes of Cerium

    SciTech Connect

    Werkema, Evan L.

    2005-05-19

    The sterically demanding 1,2,4-tri-t-butylcyclopentadienylligand (1,2,4-(Me3C)3C5H2, hereafter Cp') has been used to preparemonomeric cerium metallocenes, Cp 2CeX (X = Cl, I, OSO2CF3), which areused to synthesize the benzyl, Cp'2CeCH2C6H5. The benzyl is a usefulstarting material for preparing other complexes in the Cp'2CeZ system (Z= BF4, F, NH2, C6H5, H). X-ray crystal structures of Cp'2CeOSO2CF3,Cp'2CeF, Cp'2CeCH2C6H5, and Cp'2CeH are presented. The benzyl slowlydecomposes in solution to toluene and a metallacycle,[Cp'][(Me3C)2C5H2(CMe2CH2)]Ce. The ring CMe3 groups of both themetallacycle and the hydride, Cp'2CeH, can be fully deuterated byprolonged exposure to C6D6, providing a useful labeling tool inmechanistic studies.The hydride activates C-F and/or C-H bonds influorobenzenes, C6HxF6-x , x = 0-5. The reactions are selective, with theselectivity depending on the presence of two fluorines ortho to thereaction site more than on the type of bond activated. Complexes of thetype Cp'2CeC6HxF5-x , x = 0-4, are formed as intermediates, which slowlydecompose in solution to Cp'2CeF and fluorobenzynes, C6HxF4-x, x = 0-4,which are trapped. The rate at which Cp'2CeC6HxF5-x complexes decomposeincreases as the number of fluorines decreases. Complexes with oneortho-fluorine decompose much faster than those with two ortho-fluorines.The metallacycle activates only C-H bonds in fluorobenzenes, permittingthe synthesis of specific Cp'2

  18. Radical coupling reactions in lignin synthesis: a density functional theory study.

    PubMed

    Sangha, Amandeep K; Parks, Jerry M; Standaert, Robert F; Ziebell, Angela; Davis, Mark; Smith, Jeremy C

    2012-04-26

    Lignin is a complex, heterogeneous polymer in plant cell walls that provides mechanical strength to the plant stem and confers resistance to degrading microbes, enzymes, and chemicals. Lignin synthesis initiates through oxidative radical-radical coupling of monolignols, the most common of which are p-coumaryl, coniferyl, and sinapyl alcohols. Here, we use density functional theory to characterize radical-radical coupling reactions involved in monolignol dimerization. We compute reaction enthalpies for the initial self- and cross-coupling reactions of these monolignol radicals to form dimeric intermediates via six major linkages observed in natural lignin. The 8-O-4, 8-8, and 8-5 coupling are computed to be the most favorable, whereas the 5-O-4, 5-5, and 8-1 linkages are less favorable. Overall, p-coumaryl self- and cross-coupling reactions are calculated to be the most favorable. For cross-coupling reactions, in which each radical can couple via either of the two sites involved in dimer formation, the more reactive of the two radicals is found to undergo coupling at its site with the highest spin density.

  19. Testosterone improves erectile function through inhibition of reactive oxygen species generation in castrated rats

    PubMed Central

    Li, Rui; Meng, Xianghu; Zhang, Yan; Wang, Tao; Yang, Jun; Niu, Yonghua; Cui, Kai; Wang, Shaogang

    2016-01-01

    Testosterone is overwhelmingly important in regulating erectile physiology. However, the associated molecular mechanisms are poorly understood. The purpose of this study was to explore the effects and mechanisms of testosterone in erectile dysfunction (ED) in castrated rats. Forty male Sprague-Dawley rats were randomized to four groups (control, sham-operated, castration and castration-with-testosterone-replacement). Reactive oxygen species (ROS) production was measured by dihydroethidium (DHE) staining. Erectile function was assessed by the recording of intracavernous pressure (ICP) and mean arterial blood pressure (MAP). Protein expression levels were examined by western blotting. We found that castration reduced erectile function and that testosterone restored it. Nitric oxide synthase (NOS) activity was decrease in the castrated rats, and testosterone administration attenuated this decrease (each p < 0.05). The testosterone, dihydrotestosterone, cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) concentrations were lower in the castrated rats, and testosterone restored these levels (each p < 0.05). Furthermore, the cyclooxygenase-2 (COX-2) and prostacyclin synthase (PTGIS) expression levels and phospho-endothelial nitric oxide synthase (p-eNOS, Ser1177)/endothelial nitric oxide synthase (eNOS) ratio were reduced in the castrated rats compared with the controls (each p < 0.05). In addition, the p40phox and p67phox expression levels were increased in the castrated rats, and testosterone reversed these changes (each p < 0.05). Overall, our results demonstrate that testosterone ameliorates ED after castration by reducing ROS production and increasing the activity of the eNOS/cGMP and COX-2/PTGIS/cAMP signaling pathways. PMID:27168996

  20. Lactate Regulates Rat Male Germ Cell Function through Reactive Oxygen Species

    PubMed Central

    Galardo, María Noel; Regueira, Mariana; Riera, María Fernanda; Pellizzari, Eliana Herminia; Cigorraga, Selva Beatriz; Meroni, Silvina Beatriz

    2014-01-01

    Besides giving structural support, Sertoli cells regulate the fate of germ cells by supplying a variety of factors. These factors include hormones, several pro- and anti-apoptotic agents and also energetic substrates. Lactate is one of the compounds produced by Sertoli cells, which is utilized as an energetic substrate by germ cells, particularly spermatocytes and spermatids. Beyond its function as an energy source, some studies have proposed a role of lactate in the regulation of gene expression not strictly related to the energetic state of the cells. The general hypothesis that motivated this investigation was that lactate affects male germ cell function, far beyond its well-known role as energetic substrate. To evaluate this hypothesis we investigated: 1) if lactate was able to regulate germ cell gene expression and if reactive oxygen species (ROS) participated in this regulation, 2) if different signal transduction pathways were modified by the production of ROS in response to lactate and 3) possible mechanisms that may be involved in lactate stimulation of ROS production. In order to achieve these goals, cultures of germ cells obtained from male 30-day old rats were exposed to 10 or 20 mM lactate. Increases in lactate dehydrogenase (LDH) C and monocarboxylate transporter (MCT)2 expression, in Akt and p38-MAPK phosphorylation levels and in ROS production were observed. These effects were impaired in the presence of a ROS scavenger. Lactate stimulated ROS production was also inhibited by a LDH inhibitor or a NAD(P)H oxidase (NOX) inhibitor. NOX4 expression was identified in male germ cells. The results obtained herein are consistent with a scenario where lactate, taken up by germ cells, becomes oxidized to pyruvate with the resultant increase in NADH, which is a substrate for NOX4. ROS, products of NOX4 activity, may act as second messengers regulating signal transduction pathways and gene expression. PMID:24498241

  1. Evolution of New Enzymatic Function by Structural Modulation of Cysteine Reactivity in Pseudomonas fluorescens Isocyanide Hydratase*

    PubMed Central

    Lakshminarasimhan, Mahadevan; Madzelan, Peter; Nan, Ruth; Milkovic, Nicole M.; Wilson, Mark A.

    2010-01-01

    Isocyanide (formerly isonitrile) hydratase (EC 4.2.1.103) is an enzyme of the DJ-1 superfamily that hydrates isocyanides to yield the corresponding N-formamide. In order to understand the structural basis for isocyanide hydratase (ICH) catalysis, we determined the crystal structures of wild-type and several site-directed mutants of Pseudomonas fluorescens ICH at resolutions ranging from 1.0 to 1.9 Å. We also developed a simple UV-visible spectrophotometric assay for ICH activity using 2-naphthyl isocyanide as a substrate. ICH contains a highly conserved cysteine residue (Cys101) that is required for catalysis and interacts with Asp17, Thr102, and an ordered water molecule in the active site. Asp17 has carboxylic acid bond lengths that are consistent with protonation, and we propose that it activates the ordered water molecule to hydrate organic isocyanides. In contrast to Cys101 and Asp17, Thr102 is tolerant of mutagenesis, and the T102V mutation results in a substrate-inhibited enzyme. Although ICH is similar to human DJ-1 (1.6 Å C-α root mean square deviation), structural differences in the vicinity of Cys101 disfavor the facile oxidation of this residue that is functionally important in human DJ-1 but would be detrimental to ICH activity. The ICH active site region also exhibits surprising conformational plasticity and samples two distinct conformations in the crystal. ICH represents a previously uncharacterized clade of the DJ-1 superfamily that possesses a novel enzymatic activity, demonstrating that the DJ-1 core fold can evolve diverse functions by subtle modulation of the environment of a conserved, reactive cysteine residue. PMID:20630867

  2. Linear response function of the Mayer bond order: an indicator to describe intrinsic chemical reactivity of molecules

    NASA Astrophysics Data System (ADS)

    Yamanaka, Shusuke; Mitsuta, Yuki; Okumura, Mitsutaka; Yamaguchi, Kizashi; Nakamura, Haruki

    2015-02-01

    We here formulate and implement linear response function (LRF) of the Mayer bond order (MBO), which is expected to be a new indicator to describe intrinsic chemical reactivity of molecules. We calculate LRFs of the MBOs of para-substituted benzoic acids, and compare the results with the Hammett substituent constants and computational results of acid dissociation constants that were previously reported. The results are discussed from the viewpoint of the applicability of LRF of the MBO to estimate the relative reactivity of the substituted benzoic acids.

  3. Reactive combinatorial synthesis and characterization of a gradient Ag-Ti oxide thin film with antibacterial properties.

    PubMed

    Unosson, Erik; Rodriguez, Daniel; Welch, Ken; Engqvist, Håkan

    2015-01-01

    The growing demand for orthopedic and dental implants has spurred researchers to develop multifunctional coatings, combining tissue integration with antibacterial features. A possible strategy to endow titanium (Ti) with antibacterial properties is by incorporating silver (Ag), but designing a structure with adequate Ag(+) release while maintaining biocompatibility has been shown difficult. To further explore the composition-structure-property relationships between Ag and Ti, and its effects against bacteria, this study utilized a combinatorial approach to manufacture and test a single sample containing a binary Ag-Ti oxide gradient. The sample, sputter-deposited in a reactive (O2) environment using a custom-built combinatorial physical vapor deposition system, was shown to be effective against Staphylococcus aureus with viability reductions ranging from 17 to above 99%, depending on the amount of Ag(+) released from its different parts. The Ag content along the gradient ranged from 35 to 62 wt.%, but it was found that structural properties such as varied porosity and degree of crystallinity, rather than the amount of incorporated Ag, governed the Ag(+) release and resulting antibacterial activity. The coating also demonstrated in vitro apatite-forming abilities, where structural variety along the sample was shown to alter the hydrophilic behavior, with the degree of hydroxyapatite deposition varying accordingly. By means of combinatorial synthesis, a single gradient sample was able to display intricate compositional and structural features affecting its biological response, which would otherwise require a series of coatings. The current findings suggest that future implant coatings incorporating Ag as an antibacterial agent could be structurally enhanced to better suit clinical requirements.

  4. Ytterbium amides of linked bis(amidinate): synthesis, molecular structures, and reactivity for the polymerization of L-lactide.

    PubMed

    Wang, Junfeng; Cai, Tao; Yao, Yingming; Zhang, Yong; Shen, Qi

    2007-12-01

    The steric effect of an amide group on the synthesis, molecular structures and reactivity of ytterbium amides supported by linked bis(amidinate) L (L = [Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3]) is reported. Reaction of LYbCl(THF)2 with equimolar NaNHAr' and NaNHAr (Ar' = 2,6-Me2C6H3; Ar = 2,6-iPr2C6H3), respectively, gave the corresponding monometallic amide complexes LYb(NHAr')(DME) 1 and LYb(NHAr)(DME) 2, in which the linked bis(amidinate) is coordinated to the metal center as a chelating ligand. The similar reaction with NaN(SiMe3)2 afforded a bimetallic amide complex (TMS)2NYb(L)2YbN(TMS)2 3 formed through the rearrangement reaction of L induced by the bulky N(SiMe3)2 group. In complex 3 the two linked bis(amidinate)s act as bridging ancillary ligands to link two YbN(TMS)2 species in one molecule. The definite molecular structures of 1-3 were provided by single-crystal X-ray analysis. Complexes 1-3 are efficient initiators for the polymerization of L-lactide, and their catalytic performance is highly dependent on the amido groups and molecular structures. The polymerizations initiated by complexes 1 and 2 proceeded in a living fashion as evidenced by the narrow polydispersities of the resulting polymers, together with the linear natures of the number average molecular weight versus conversion plots, while the polymerization system with complex 3 provided polymers with rather broad molecular weight distributions.

  5. The N cycle in Earth subsurface. Reactivity of functional genes to anthropogenic CO2 injections.

    NASA Astrophysics Data System (ADS)

    Trias, Rosalia; Gérard, Emmanuelle; Le Campion, Paul; Gíslason, Sigurður R.; Aradóttir, Edda S.; Alfreðsson, Helgui A.; Mesfin, Kiflom G.; Snæbjörnsdóttir, Sandra Ó.; Ménez, Bénédicte

    2014-05-01

    The Nitrogen cycle has been widely studied in surface ecosystems, due to the importance of this nutrient for the organisms' development, and to the impact in the environment of most of the N forms, many of them being considered pollutants. However, little is known about the importance of the N-related metabolisms in subsurface systems now recognized to host diverse and active microbial life. In this study, we have periodically sampled the subsurface aquifers of the Icelandic pilot site for CO2 storage associated with the geothermal plant of Hellisheidi (operated by Reykjavik Energy; http://www.or.is/en/projects/carbfix). With the aim of understanding the dynamics of N-cycle in the subsurface, and its reactivity to CO2 injections, we quantified through qPCR the functional genes amoA (archaea), amoA (bacteria), nirK, nirS, nosZ, nifH, and the 16SrRNA genes of the anammox, total archaea and total bacteria. The 16SrRNA gene quantification provided values of around 107 gene copies/l at non injection periods. CO2 injection caused first a slight decrease probably due to pH decrease or toxicity by oxygen contamination during the injections. Two months after injection, the copy numbers increased up to 109 gene copies/l, and slowly returned to pre-injection values. The archaeal 16S rDNA copy numbers showed a similar reaction, with higher toxicity effects, and a lower increase afterwards. Due to the high reactivity of the microbial populations to CO2 injections, all the N cycle quantifications were related to the total 16S rDNA copies for normalization. Nitrifying genes (amoA) were mainly represented by the ammonia oxidizing archaea, and were apparently not affected by CO2 injections. Anammox bacteria were present in a very low percentage, and the obtained copy numbers tended to decrease after the injection. These results were surprising due to the autotrophic character of ammonia oxidizers, but could be explained by a competitive exclusion. On the contrary, N-fixation (nif

  6. Synthesis of Co(II)-NO(-) Complexes and Their Reactivity as a Source of Nitroxyl.

    PubMed

    Walter, Melody R; Dzul, Stephen P; Rodrigues, Andria V; Stemmler, Timothy L; Telser, Joshua; Conradie, Jeanet; Ghosh, Abhik; Harrop, Todd C

    2016-09-28

    Metal-nitroxyl (M-HNO/M-NO(-)) coordination units are found in denitrification enzymes of the global nitrogen cycle, and free HNO exhibits pharmacological properties related to cardiovascular physiology that are distinct from nitric oxide (NO). To elucidate the properties that control the binding and release of coordinated nitroxyl or its anion at these biological metal sites, we synthesized {CoNO}(8) (1, 2) and {CoNO}(9) (3, 4) complexes that contain diimine-dipyrrolide supporting ligands. Experimental (NMR, IR, MS, EPR, XAS, XRD) and computational data (DFT) support an oxidation state assignment for 3 and 4 of high spin Co(II) (SCo = 3/2) coordinated to (3)NO(-) (SNO = 1) for Stot = 1/2. As suggested by DFT, upon protonation, a spin transition occurs to generate a putative low spin Co(II)-(1)HNO (SCo = Stot = 1/2); the Co-NO bond is ∼0.2 Å longer, more labile, and facilitates the release of HNO. This property was confirmed experimentally through the detection and quantification of N2O (∼70% yield), a byproduct of the established HNO self-reaction (2HNO → N2O + H2O). Additionally, 3 and 4 function as HNO donors in aqueous media at pH 7.4 and react with known HNO targets, such as a water-soluble Mn(III)-porphyrin ([Mn(III)(TPPS)](3-); TPPS = meso-tetrakis(4-sulfonatophenyl)porphyrinate) and ferric myoglobin (metMb) to quantitatively yield [Mn(TPPS)(NO)](4-) and MbNO, respectively. PMID:27562882

  7. Synthesis of Co(II)-NO(-) Complexes and Their Reactivity as a Source of Nitroxyl.

    PubMed

    Walter, Melody R; Dzul, Stephen P; Rodrigues, Andria V; Stemmler, Timothy L; Telser, Joshua; Conradie, Jeanet; Ghosh, Abhik; Harrop, Todd C

    2016-09-28

    Metal-nitroxyl (M-HNO/M-NO(-)) coordination units are found in denitrification enzymes of the global nitrogen cycle, and free HNO exhibits pharmacological properties related to cardiovascular physiology that are distinct from nitric oxide (NO). To elucidate the properties that control the binding and release of coordinated nitroxyl or its anion at these biological metal sites, we synthesized {CoNO}(8) (1, 2) and {CoNO}(9) (3, 4) complexes that contain diimine-dipyrrolide supporting ligands. Experimental (NMR, IR, MS, EPR, XAS, XRD) and computational data (DFT) support an oxidation state assignment for 3 and 4 of high spin Co(II) (SCo = 3/2) coordinated to (3)NO(-) (SNO = 1) for Stot = 1/2. As suggested by DFT, upon protonation, a spin transition occurs to generate a putative low spin Co(II)-(1)HNO (SCo = Stot = 1/2); the Co-NO bond is ∼0.2 Å longer, more labile, and facilitates the release of HNO. This property was confirmed experimentally through the detection and quantification of N2O (∼70% yield), a byproduct of the established HNO self-reaction (2HNO → N2O + H2O). Additionally, 3 and 4 function as HNO donors in aqueous media at pH 7.4 and react with known HNO targets, such as a water-soluble Mn(III)-porphyrin ([Mn(III)(TPPS)](3-); TPPS = meso-tetrakis(4-sulfonatophenyl)porphyrinate) and ferric myoglobin (metMb) to quantitatively yield [Mn(TPPS)(NO)](4-) and MbNO, respectively.

  8. Synthesis, characterization, and reactivity of ruthenium diene/diamine complexes including catalytic hydrogenation of ketones.

    PubMed

    Morilla, M Esther; Rodríguez, Pilar; Belderrain, Tomas R; Graiff, Claudia; Tiripicchio, Antonio; Nicasio, M Carmen; Pérez, Pedro J

    2007-10-29

    Thermal reactions between [RuCl2(diene)]n (diene = 2,5-norbornadiene, nbd; 1,5-cyclooctadiene, cod) with an excess of N,N,N',N'-tetramethylethylene diamine (tmeda) afforded derivatives [RuCl2(diene)(tmeda)] (diene = nbd, 1; cod, 2) as a mixture of cis and trans isomers. When thermolysis was performed under H2 mixtures of hydride species [RuCl(H)(diene)(tmeda)] (diene = nbd, 3; cod, 4) and the bis-tmeda adduct trans-[RuCl2(tmeda)2] (5) were obtained in different ratios depending upon the reaction conditions and reaction times. Heating polymeric Ru(II) precursors in toluene in the presence of a 5-fold excess of the bulkier N,N,N',N'-tetraethylethylene diamine (teeda) resulted in a rare diamine dealkylation process with formation of trans-[RuCl2(nbd)(Et2NCH2CH2NHEt)] (6) and trans-[RuCl2(cod)(EtHNCH2CH2NHEt)] (7) in high yields. The presence of N-H functionalities in the coordinated diamine ligands of 6 and 7 was unambiguously established by single-crystal X-ray diffraction studies. The dealkylation process of the teeda ligand seems to proceed intramolecularly as shown by solution NMR studies performed with the soluble Ru(II) precursors trans-[RuCl2(amine)2(diene)] (diene = nbd, amine = morpholine, 9; diene = cod, amine = Et2NH, 10). The above complexes [RuCl2(diene)(diamine)] have been tested as precatalysts in the hydrogenation of ketones both for transfer as well as direct hydrogenation, the latter route being the most effective.

  9. Functionalized alkoxysilane mediated controlled synthesis of noble metal nanoparticles dispersible in aqueous and non-aqueous medium.

    PubMed

    Pandey, Prem C; Pandey, Ashish K; Pandey, G

    2014-09-01

    The synthesis of amphiphilic noble metal nanoparticles involving the functional role of 3-aminopropyltrimethoxysilane (3-APTMS) and 3-glycidoxypropyltrimethoxy-silane (3-GPTMS) is reported herein. The mechanistic approach on the reactivity of these functional alkoxysilane for the typical controlled synthesis of AuNPs as evidenced from UV-visible spectroscopy and transmission electron microscopy (TEM) is reported. The experimental findings demonstrate the followings; (1) Methanolic solution of 3-GPTMS undergo interaction with 3-APTMS and the same is facilitated in the presence of 3-APTMS treated noble metal ions, (2) The molar ratio of 3-GPTMS/3-APTMS control the nanogeometry as well as the dispersibility of AuNPs in both aqueous and non-aqueous media, (3) the dispersion ability of nanoparticles is found to be based on the hydrophobic alkyl chain of the reaction product of 3-GPTMS and 3-APTMS, and (4) AuNPs shows absorption maxima as a function of polarity and refractive index of the medium. A typical application of as synthesized AuNPs as peroxidase mimetic is reported.

  10. Lead-chromium carbonyl complexes incorporated with group 8 metals: synthesis, reactivity, and theoretical calculations.

    PubMed

    Shieh, Minghuey; Chu, Yen-Yi; Hsu, Miao-Hsing; Ke, Wei-Ming; Lin, Chien-Nan

    2011-01-17

    The trichromium-lead complex [Pb{Cr(CO)5}3](2-) (1) was isolated from the reaction of PbCl2 and Cr(CO)6 in a KOH/MeOH solution, and the new mixed chromium-iron-lead complex [Pb{Cr(CO)5}{Fe(CO)4}2](2-) (3) was synthesized from the reaction of PbCl2 and Cr(CO)6 in a KOH/MeOH solution followed by the addition of Fe(CO)5. X-ray crystallography showed that 3 consisted of a central Pb atom bound in a trigonal-planar environment to two Fe(CO)4 and one Cr(CO)5 fragments. When complex 1 reacted with 1.5 equiv of Mn(CO)5Br, the Cr(CO)4-bridged dimeric lead-chromium carbonyl complex [Pb2Br2Cr4(CO)18](2-) (4) was produced. However, a similar reaction of 3 or the isostructural triiron-lead complex [Pb{Fe(CO)4}3](2-) (2) with Mn(CO)5Br in MeCN led to the formation of the Fe3Pb2-based trigonal-bipyramidal complexes [Fe3(CO)9{PbCr(CO)5}2](2-) (6) and [Fe3(CO)9{PbFe(CO)4}2](2-) (5), respectively. On the other hand, the Ru3Pb2-based trigonal-bipyramidal complex [Ru3(CO)9{PbCr(CO)5}2](2-) (7) was obtained directly from the reaction of PbCl2, Cr(CO)6, and Ru3(CO)12 in a KOH/MeOH solution. X-ray crystallography showed that 5 and 6 each had an Fe3Pb2 trigonal-bipyramidal core geometry, with three Fe(CO)3 groups occupying the equatorial positions and two PbFe(CO)4 or PbCr(CO)5 units in the axial positions, while 7 displayed a Ru3Pb2 trigonal-bipyramidal geometry with three equatorial Ru(CO)3 groups and two axial PbCr(CO)5 units. The complexes 3-7 were characterized spectroscopically, and their nature, formation, and electrochemistry were further examined by molecular orbital calculations at the B3LYP level of density functional theory.

  11. Synthesis and nucleophilic reactivity of a series of glutathione analogues, modified at the gamma-glutamyl moiety.

    PubMed Central

    Adang, A E; Duindam, A J; Brussee, J; Mulder, G J; van der Gen, A

    1988-01-01

    A series of GSH analogues with modifications at the gamma-glutamyl moiety was synthesized and purified by following peptide chemistry methodology. Benzyl, benzyloxycarbonyl and t-butyloxycarbonyl protective groups were used to protect individual amino acid functional groups. The formation of peptide bonds was accomplished through coupling of free amino groups with active esters, generated by reaction of the carboxylate functions with dicyclohexylcarbodi-imide and 1-hydroxybenzotriazole. The protecting groups in the tripeptides were removed in a single step by using Na in liquid NH3. Precautions were taken in order to prevent oxidation of the thiol function in the cysteine residue. Thus GSH analogues containing both L- and D-glutamic acid and L- and D-aspartic acid, coupled to cysteinylglycine through both the alpha- and the omega-carboxylate group, were synthesized. Also, decarboxy-GSH and deamino-GSH, lacking one functional group in the glutamate moiety, were prepared. The spontaneous non-enzyme-catalysed nucleophilic reaction of these GSH analogues with the electrophilic model substrate 1-chloro-2,4-dinitrobenzene showed appreciable rate differences, indicating the importance of intramolecular interactions in determining the nucleophilic reactivity of the thiol function in the cysteine residue. In particular, the free amino group in the gamma-L-glutamic acid residue appears to play a crucial role in activating the thiol group in GSH. In an adjacent paper [Adang, Brussee, Meyer, Coles, Ketterer, van der Gen & Mulder (1988) Biochem. J. 255, 721-724] these results are compared with those obtained in a study on the ability of these GSH analogues to act as a co-substrate in the glutathione S-transferase-catalysed conjugation reaction with 1-chloro-2,4-dinitrobenzene. PMID:2904808

  12. Highly luminescent half-lantern cyclometalated platinum(II) complex: synthesis, structure, luminescence studies, and reactivity.

    PubMed

    Sicilia, Violeta; Forniés, Juan; Casas, José Ma; Martín, Antonio; López, José A; Larraz, Carmen; Borja, Pilar; Ovejero, Carmen; Tordera, Daniel; Bolink, Henk

    2012-03-19

    The half-lantern compound [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)}(2)]·Me(2)CO (1) was obtained by reaction of equimolar amounts of potassium 2-mercaptobenzothiazolate (KC(7)H(4)NS(2)) and [Pt(bzq)(NCMe)(2)]ClO(4). The Pt(II)···Pt(II) separation in the neutral complex [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)}(2)] is 2.910 (2) Å, this being among the shortest observed in half-lantern divalent platinum complexes. Within the complex, the benzo[h]quinoline (bzq) groups lie in close proximity with most C···C distances being between 3.3 and 3.7 Å, which is indicative of significant π-π interactions. The reaction of 1 with halogens X(2) (X(2) = Cl(2), Br(2), or I(2)) proceeds with a two-electron oxidation to give the corresponding dihalodiplatinum(III) complexes [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)X}(2)] (X = Cl 2, Br 3, I 4). Their X-ray structures confirm the retention of the half-lantern structure and the coordination mode of the bzq and the bridging ligand μ-C(7)H(4)NS(2)-κN,S. The Pt-Pt distances (Pt-Pt = 2.6420(3) Å 2, 2.6435(4) Å 3, 2.6690(3) Å 4) are shorter than that in 1 because of the Pt-Pt bond formation. Time dependent-density functional theory (TD-DFT) studies performed on 1 show a formal bond order of 0 between the metal atoms, with the 6p(z) contribution diminishing the antibonding character of the highest occupied molecular orbital (HOMO) and being responsible for an attractive intermetallic interaction. A shortening of the Pt-Pt distance from 2.959 Å in the ground state S(0) to 2.760 Å in the optimized first excited state (T(1)) is consistent with an increase in the Pt-Pt bond order to 0.5. In agreement with TD-DFT calculations, the intense, structureless, red emission of 1 in the solid state and in solution can be mainly attributed to triplet metal-metal-to-ligand charge transfer ((3)MMLCT) [dσ*(Pt-Pt) → π*(bzq)] excited states. The high quantum yields of this emission measured in toluene (44%) and solid state (62%) at room temperature indicate

  13. Highly luminescent half-lantern cyclometalated platinum(II) complex: synthesis, structure, luminescence studies, and reactivity.

    PubMed

    Sicilia, Violeta; Forniés, Juan; Casas, José Ma; Martín, Antonio; López, José A; Larraz, Carmen; Borja, Pilar; Ovejero, Carmen; Tordera, Daniel; Bolink, Henk

    2012-03-19

    The half-lantern compound [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)}(2)]·Me(2)CO (1) was obtained by reaction of equimolar amounts of potassium 2-mercaptobenzothiazolate (KC(7)H(4)NS(2)) and [Pt(bzq)(NCMe)(2)]ClO(4). The Pt(II)···Pt(II) separation in the neutral complex [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)}(2)] is 2.910 (2) Å, this being among the shortest observed in half-lantern divalent platinum complexes. Within the complex, the benzo[h]quinoline (bzq) groups lie in close proximity with most C···C distances being between 3.3 and 3.7 Å, which is indicative of significant π-π interactions. The reaction of 1 with halogens X(2) (X(2) = Cl(2), Br(2), or I(2)) proceeds with a two-electron oxidation to give the corresponding dihalodiplatinum(III) complexes [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)X}(2)] (X = Cl 2, Br 3, I 4). Their X-ray structures confirm the retention of the half-lantern structure and the coordination mode of the bzq and the bridging ligand μ-C(7)H(4)NS(2)-κN,S. The Pt-Pt distances (Pt-Pt = 2.6420(3) Å 2, 2.6435(4) Å 3, 2.6690(3) Å 4) are shorter than that in 1 because of the Pt-Pt bond formation. Time dependent-density functional theory (TD-DFT) studies performed on 1 show a formal bond order of 0 between the metal atoms, with the 6p(z) contribution diminishing the antibonding character of the highest occupied molecular orbital (HOMO) and being responsible for an attractive intermetallic interaction. A shortening of the Pt-Pt distance from 2.959 Å in the ground state S(0) to 2.760 Å in the optimized first excited state (T(1)) is consistent with an increase in the Pt-Pt bond order to 0.5. In agreement with TD-DFT calculations, the intense, structureless, red emission of 1 in the solid state and in solution can be mainly attributed to triplet metal-metal-to-ligand charge transfer ((3)MMLCT) [dσ*(Pt-Pt) → π*(bzq)] excited states. The high quantum yields of this emission measured in toluene (44%) and solid state (62%) at room temperature indicate

  14. Synthesis of nine-atom deltahedral Zintl ions of germanium and their functionalization with organic groups.

    PubMed

    Gillett-Kunnath, Miriam M; Sevov, Slavi C

    2012-01-01

    Although the first studies of Zintl ions date between the late 1890's and early 1930's they were not structurally characterized until many years later. Their redox chemistry is even younger, just about ten years old, but despite this short history these deltahedral clusters ions E9(n-) (E = Si, Ge, Sn, Pb; n = 2, 3, 4) have already shown interesting and diverse reactivity and have been at the forefront of rapidly developing and exciting new chemistry. Notable milestones are the oxidative coupling of Ge9(4-) clusters to oligomers and infinite chains, their metallation, capping by transition-metal organometallic fragments, insertion of a transition-metal atom at the center of the cluster which is sometimes combined with capping and oligomerization, addition of main-group organometallic fragments as exo-bonded substituents, and functionalization with various organic residues by reactions with organic halides and alkynes. This latter development of attaching organic fragments directly to the clusters has opened up a new field, namely organo-Zintl chemistry, that is potentially fertile for further synthetic explorations, and it is the step-by-step procedure for the synthesis of germanium-divinyl clusters described herein. The initial steps outline the synthesis of an intermetallic precursor of K4Ge9 from which the Ge9(4-) clusters are extracted later in solution. This involves fused-silica glass blowing, arc-welding of niobium containers, and handling of highly air-sensitive materials in a glove box. The air-sensitive K4Ge9 is then dissolved in ethylenediamine in the box and then alkenylated by a reaction with Me3SiC≡CSiMe3. The reaction is followed by electrospray mass spectrometry while the resulting solution is used for obtaining single crystals containing the functionalized clusters [H2C=CH-Ge9-CH=CH2](2-). For this purpose the solution is centrifuged, filtered, and carefully layered with a toluene solution of 18-crown-6. Left undisturbed for a few days, the so

  15. Synthesis of Nine-atom Deltahedral Zintl Ions of Germanium and their Functionalization with Organic Groups

    PubMed Central

    Gillett-Kunnath, Miriam M.; Sevov, Slavi C.

    2012-01-01

    Although the first studies of Zintl ions date between the late 1890's and early 1930's they were not structurally characterized until many years later.1,2 Their redox chemistry is even younger, just about ten years old, but despite this short history these deltahedral clusters ions E9n- (E = Si, Ge, Sn, Pb; n = 2, 3, 4) have already shown interesting and diverse reactivity and have been at the forefront of rapidly developing and exciting new chemistry.3-6 Notable milestones are the oxidative coupling of Ge94- clusters to oligomers and infinite chains,7-19 their metallation,14-16,20-25 capping by transition-metal organometallic fragments,26-34 insertion of a transition-metal atom at the center of the cluster which is sometimes combined with capping and oligomerization,35-47 addition of main-group organometallic fragments as exo-bonded substituents,48-50 and functionalization with various organic residues by reactions with organic halides and alkynes.51-58 This latter development of attaching organic fragments directly to the clusters has opened up a new field, namely organo-Zintl chemistry, that is potentially fertile for further synthetic explorations, and it is the step-by-step procedure for the synthesis of germanium-divinyl clusters described herein. The initial steps outline the synthesis of an intermetallic precursor of K4Ge9 from which the Ge94- clusters are extracted later in solution. This involves fused-silica glass blowing, arc-welding of niobium containers, and handling of highly air-sensitive materials in a glove box. The air-sensitive K4Ge9 is then dissolved in ethylenediamine in the box and then alkenylated by a reaction with Me3SiC≡CSiMe3. The reaction is followed by electrospray mass spectrometry while the resulting solution is used for obtaining single crystals containing the functionalized clusters [H2C=CH-Ge9-CH=CH2]2-. For this purpose the solution is centrifuged, filtered, and carefully layered with a toluene solution of 18-crown-6. Left

  16. Exposing a Hidden Functional Site of C-reactive Protein by Site-directed Mutagenesis*

    PubMed Central

    Singh, Sanjay K.; Thirumalai, Avinash; Hammond, David J.; Pangburn, Michael K.; Mishra, Vinod K.; Johnson, David A.; Rusiñol, Antonio E.; Agrawal, Alok

    2012-01-01

    C-reactive protein (CRP) is a cyclic pentameric protein whose major binding specificity, at physiological pH, is for substances bearing exposed phosphocholine moieties. Another pentameric form of CRP, which exists at acidic pH, displays binding activity for oxidized LDL (ox-LDL). The ox-LDL-binding site in CRP, which is hidden at physiological pH, is exposed by acidic pH-induced structural changes in pentameric CRP. The aim of this study was to expose the hidden ox-LDL-binding site of CRP by site-directed mutagenesis and to generate a CRP mutant that can bind to ox-LDL without the requirement of acidic pH. Mutation of Glu42, an amino acid that participates in intersubunit interactions in the CRP pentamer and is buried, to Gln resulted in a CRP mutant (E42Q) that showed significant binding activity for ox-LDL at physiological pH. For maximal binding to ox-LDL, E42Q CRP required a pH much less acidic than that required by wild-type CRP. At any given pH, E42Q CRP was more efficient than wild-type CRP in binding to ox-LDL. Like wild-type CRP, E42Q CRP remained pentameric at acidic pH. Also, E42Q CRP was more efficient than wild-type CRP in binding to several other deposited, conformationally altered proteins. The E42Q CRP mutant provides a tool to investigate the functions of CRP in defined animal models of inflammatory diseases including atherosclerosis because wild-type CRP requires acidic pH to bind to deposited, conformationally altered proteins, including ox-LDL, and available animal models may not have sufficient acidosis or other possible modifiers of the pentameric structure of CRP at the sites of inflammation. PMID:22158621

  17. Synthesis of functionalized fluorescent gold nanoclusters for acid phosphatase sensing

    NASA Astrophysics Data System (ADS)

    Sun, Jian; Yang, Fan; Yang, Xiurong

    2015-10-01

    A novel and convenient one-pot but two-step synthesis of fluorescent gold nanoclusters, incorporating glutathione (GSH) and 11-mercaptoundecanoic acid (MUA) as the functionalized ligands (i.e. AuNCs@GSH/MUA), is demonstrated. Herein, the mixing of HAuCl4 and GSH in aqueous solution results in the immediate formation of non-fluorescent GSH-Au+ complexes, and then a class of ~2.6 nm GSH-coated AuNCs (AuNCs@GSH) with mild orange-yellow fluorescence after several days. Interestingly, the intense orange-red emitting ~1.7 nm AuNCs@GSH/MUA can be synthesized within seconds by introducing an alkaline aqueous solution of MUA into the GSH-Au+ complexes or AuNC@GSH solution. Subsequently, a reliable AuNC@GSH/MUA-based real-time assay of acid phosphatase (ACP) is established for the first time, inspired by the selective coordination of Fe3+ with surface ligands of AuNCs, the higher binding affinity between the pyrophosphate ion (PPi) and Fe3+, and the hydrolysis of PPi into orthophosphate by ACP. Our fluorescent chemosensor can also be applied to assay ACP in a real biological sample and, furthermore, to screen the inhibitor of ACP. This report paves a new avenue for synthesizing AuNCs based on either the bottom-up reduction or top-down etching method, establishing real-time fluorescence assays for ACP by means of PPi as the substrate, and further exploring the sensing applications of fluorescent AuNCs.A novel and convenient one-pot but two-step synthesis of fluorescent gold nanoclusters, incorporating glutathione (GSH) and 11-mercaptoundecanoic acid (MUA) as the functionalized ligands (i.e. AuNCs@GSH/MUA), is demonstrated. Herein, the mixing of HAuCl4 and GSH in aqueous solution results in the immediate formation of non-fluorescent GSH-Au+ complexes, and then a class of ~2.6 nm GSH-coated AuNCs (AuNCs@GSH) with mild orange-yellow fluorescence after several days. Interestingly, the intense orange-red emitting ~1.7 nm AuNCs@GSH/MUA can be synthesized within seconds by

  18. Synthesis of functionalized fluorescent gold nanoclusters for acid phosphatase sensing.

    PubMed

    Sun, Jian; Yang, Fan; Yang, Xiurong

    2015-10-21

    A novel and convenient one-pot but two-step synthesis of fluorescent gold nanoclusters, incorporating glutathione (GSH) and 11-mercaptoundecanoic acid (MUA) as the functionalized ligands (i.e. AuNCs@GSH/MUA), is demonstrated. Herein, the mixing of HAuCl4 and GSH in aqueous solution results in the immediate formation of non-fluorescent GSH-Au(+) complexes, and then a class of ∼2.6 nm GSH-coated AuNCs (AuNCs@GSH) with mild orange-yellow fluorescence after several days. Interestingly, the intense orange-red emitting ∼1.7 nm AuNCs@GSH/MUA can be synthesized within seconds by introducing an alkaline aqueous solution of MUA into the GSH-Au(+) complexes or AuNC@GSH solution. Subsequently, a reliable AuNC@GSH/MUA-based real-time assay of acid phosphatase (ACP) is established for the first time, inspired by the selective coordination of Fe(3+) with surface ligands of AuNCs, the higher binding affinity between the pyrophosphate ion (PPi) and Fe(3+), and the hydrolysis of PPi into orthophosphate by ACP. Our fluorescent chemosensor can also be applied to assay ACP in a real biological sample and, furthermore, to screen the inhibitor of ACP. This report paves a new avenue for synthesizing AuNCs based on either the bottom-up reduction or top-down etching method, establishing real-time fluorescence assays for ACP by means of PPi as the substrate, and further exploring the sensing applications of fluorescent AuNCs. PMID:26391420

  19. Children’s Patterns of Emotional Reactivity to Conflict as Explanatory Mechanisms in Links Between Interpartner Aggression and Child Physiological Functioning

    PubMed Central

    Davies, Patrick T.; Sturge-Apple, Melissa L.; Cicchetti, Dante; Manning, Liviah G.; Zale, Emily

    2009-01-01

    Background This paper examined children’s fearful, sad, and angry reactivity to interparental conflict as mediators of associations between their exposure to interparental aggression and physiological functioning. Methods Participants included 200 toddlers and their mothers. Assessments of interparental aggression and children’s emotional reactivity were derived from maternal surveys and a semi-structured interview. Cortisol levels and cardiac indices of sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) activity were used to assess toddler physiological functioning. Results Results indicated that toddler exposure to interparental aggression was associated with greater cortisol levels and PNS activity and diminished SNS activity. Toddler angry emotional reactivity mediated associations between interparental aggression and cortisol and PNS functioning. Fearful emotional reactivity was a mediator of the link between interparental aggression and SNS functioning. Conclusions The results are interpreted within conceptualizations of how exposure and reactivity to family risk organizing individual differences in physiological functioning. PMID:19744183

  20. Surface reactivity of Ge[111] for organic functionalization by means of a radical-initiated reaction: A DFT study

    NASA Astrophysics Data System (ADS)

    Rubio-Pereda, Pamela; Takeuchi, Noboru

    2016-08-01

    The study of interfacial chemistry at semiconductor surfaces has become an important area of research. Functionalities such as molecular recognition, biocompatibility of surfaces, and molecular computing, could be achieved by the combinations of organic chemistry with the semiconductor technology. One way to accomplish this goal is by means of organic functionalization of semiconductor surfaces such as the bulk-terminated germanium surfaces, more specifically the Ge[111]. In this work, we theoretically study, by applying density functional theory, the surface reactivity of the bulk-terminated Ge[111] surface for organic functionalization by means of a radical-initiated reaction of unsaturated molecules such as acetylene, ethylene and styrene with a hydrogen vacancy on a previously hydrogen-terminated Ge[111] surface. Results derived from this work are compared with those obtained in our previous calculations on the germanene surface, following the same chemical route. Our calculations show an accumulation of electronic charge at the H-vacancy having as a result electron pairing due to strong lattice-electron coupling and therefore a diminished surface reactivity. Calculation of the transition states for acetylene and ethylene indicates that the surface reactivity of the hydrogen-terminated Ge[111] surface is less promising than its two-dimensional analogue, the hydrogen-terminated germanene.

  1. Chemically functionalized gold nanoparticles: Synthesis, characterization, and applications

    NASA Astrophysics Data System (ADS)

    Daniel, Weston Lewis

    This thesis focuses on the development and application of gold nanoparticle based detection systems and biomimetic structures. Each class of modified nanoparticle has properties that are defined by its chemical moieties that interface with solution and the gold nanoparticle core. In Chapter 2, a comparison of the biomolecular composition and binding properties of various preparations of antibody oligonucleotide gold nanoparticle conjugates is presented. These constructs differed significantly in terms of their structure and binding properties. Chapter 3 reports the use of electroless gold deposition as a light scattering signal enhancer in a multiplexed, microarray-based scanometric immunoassay using the gold nanoparticle probes evaluated in Chapter 2. The use of gold development results in greater signal enhancement than the typical silver development, and multiple rounds of metal development were found to increase the resulting signal compared to one development. Chapter 4 describes an amplified scanometric detection method for human telomerase activity. Gold nanoparticles functionalized with specific oligonucleotide sequences can efficiently capture telomerase enzymes and subsequently be elongated. Both the elongated and unmodified oligonucleotide sequences are simultaneously measured. At low telomerase concentrations, elongated strands cannot be detected, but the unmodified sequences, which come from the same probe particles, can be detected because their concentration is higher, providing a novel form of amplification. Chapter 5 reports the development of a novel colorimetric nitrite and nitrate ion assay based upon gold nanoparticle probes functionalized with Griess reaction reagents. This assay takes advantage of the distance-dependent plasmonic properties of the gold nanoparticles and the ability of nitrite ion to facilitate the cross coupling of novel nanoparticle probes. The assay works on the concept of a kinetic end point and can be triggered at the EPA

  2. Baseline Functioning and Stress Reactivity in Maltreating Parents and At-Risk Adults

    PubMed Central

    Reijman, Sophie; Bakermans-Kranenburg, Marian J.; Hiraoka, Regina; Crouch, Julie L.; Milner, Joel S.; van IJzendoorn, Marinus H.

    2016-01-01

    We reviewed and meta-analyzed 10 studies (N = 492) that examined the association between (risk for) child maltreatment perpetration and basal autonomic activity, and 10 studies (N = 471) that examined the association between (risk for) child maltreatment and autonomic stress reactivity. We hypothesized that maltreating parents/at-risk adults would show higher basal levels of heart rate (HR) and skin conductance (SC) and lower levels of HR variability (HRV) and would show greater HR and SC stress reactivity, but blunted HRV reactivity. A narrative review showed that evidence from significance testing within and across studies was mixed. The first set of meta-analyses revealed that (risk for) child maltreatment was associated with higher HR baseline activity (g = 0.24), a possible indication of allostatic load. The second set of meta-analyses yielded no differences in autonomic stress reactivity between maltreating/at-risk participants and nonmaltreating/low-risk comparison groups. Cumulative meta-analyses showed that positive effects for sympathetic stress reactivity as a risk factor for child maltreatment were found in a few early studies, whereas each subsequently aggregated study reduced the combined effect size to a null effect, an indication of the winner’s curse. Most studies were underpowered. Future directions for research are suggested. PMID:27462035

  3. Synthesis, solubilization, and surface functionalization of highly fluorescent quantum dots for cellular targeting through a small molecule

    NASA Astrophysics Data System (ADS)

    Galloway, Justin F.

    To achieve long-term fluorescence imaging with quantum dots (QDs), a CdSe core/shell must first be synthesized. The synthesis of bright CdSe QDs is not trivial and as a consequence, the role of surfactant in nucleation and growth was investigated. It was found that the type of surfactant used, either phosphonic or fatty acid, played a pivotal role in the size of the CdSe core. The study of surfactant on CdSe synthesis, ultimately led to an electrical passivation method that utilized a short-chained phosphonic acid and highly reactive organometallic precursors to achieve high quantum yield (QY) as has been previously described. The synthesis of QDs using organometallic precursors and a phosphonic acid for passivation resulted in 4 out of 9 batches of QDs achieving QYs greater than 50% and 8 out of 9 batches with QYs greater than 35%. The synthesis of CdSe QDs was done in organic solutions rendering the surface of the particle hydrophobic. To perform cell-targeting experiments, QDs must be transferred to water. The transfer of QDs to water was successfully accomplished by using single acyl chain lipids. A systematic study of different lipid combinations and coatings demonstrated that 20-40 mol% single acyl chained lipids were able to transfer QDs to water resulting in monodispersed, stable QDs without adversely affecting the QY. The advantage to water solubilization using single acyl chain lipids is that the QD have a hydrodynamic radius less than 15 nm, QYs that can exceed 50% and additional surface functionalization can be down using the reactive sites incorporated into the lipid bilayer. QDs that are bright and stable in water were studied for the purpose of targeting G protein-coupled Receptors (GPCR). GPCRs are transmembrane receptors that internalize extracellular cues, and thus mediate signal transduction. The cyclic Adenosine Monophosphate Receptor 1 of the model organism Dictyostelium disodium was the receptor of interest. The Halo protein, a genetically

  4. Specificity, cross-reactivity, and function of antibodies elicited by Zika virus infection.

    PubMed

    Stettler, Karin; Beltramello, Martina; Espinosa, Diego A; Graham, Victoria; Cassotta, Antonino; Bianchi, Siro; Vanzetta, Fabrizia; Minola, Andrea; Jaconi, Stefano; Mele, Federico; Foglierini, Mathilde; Pedotti, Mattia; Simonelli, Luca; Dowall, Stuart; Atkinson, Barry; Percivalle, Elena; Simmons, Cameron P; Varani, Luca; Blum, Johannes; Baldanti, Fausto; Cameroni, Elisabetta; Hewson, Roger; Harris, Eva; Lanzavecchia, Antonio; Sallusto, Federica; Corti, Davide

    2016-08-19

    Zika virus (ZIKV), a mosquito-borne flavivirus with homology to Dengue virus (DENV), has become a public health emergency. By characterizing memory lymphocytes from ZIKV-infected patients, we dissected ZIKV-specific and DENV-cross-reactive immune responses. Antibodies to nonstructural protein 1 (NS1) were largely ZIKV-specific and were used to develop a serological diagnostic tool. In contrast, antibodies against E protein domain I/II (EDI/II) were cross-reactive and, although poorly neutralizing, potently enhanced ZIKV and DENV infection in vitro and lethally enhanced DENV disease in mice. Memory T cells against NS1 or E proteins were poorly cross-reactive, even in donors preexposed to DENV. The most potent neutralizing antibodies were ZIKV-specific and targeted EDIII or quaternary epitopes on infectious virus. An EDIII-specific antibody protected mice from lethal ZIKV infection, illustrating the potential for antibody-based therapy.

  5. Specificity, cross-reactivity, and function of antibodies elicited by Zika virus infection.

    PubMed

    Stettler, Karin; Beltramello, Martina; Espinosa, Diego A; Graham, Victoria; Cassotta, Antonino; Bianchi, Siro; Vanzetta, Fabrizia; Minola, Andrea; Jaconi, Stefano; Mele, Federico; Foglierini, Mathilde; Pedotti, Mattia; Simonelli, Luca; Dowall, Stuart; Atkinson, Barry; Percivalle, Elena; Simmons, Cameron P; Varani, Luca; Blum, Johannes; Baldanti, Fausto; Cameroni, Elisabetta; Hewson, Roger; Harris, Eva; Lanzavecchia, Antonio; Sallusto, Federica; Corti, Davide

    2016-08-19

    Zika virus (ZIKV), a mosquito-borne flavivirus with homology to Dengue virus (DENV), has become a public health emergency. By characterizing memory lymphocytes from ZIKV-infected patients, we dissected ZIKV-specific and DENV-cross-reactive immune responses. Antibodies to nonstructural protein 1 (NS1) were largely ZIKV-specific and were used to develop a serological diagnostic tool. In contrast, antibodies against E protein domain I/II (EDI/II) were cross-reactive and, although poorly neutralizing, potently enhanced ZIKV and DENV infection in vitro and lethally enhanced DENV disease in mice. Memory T cells against NS1 or E proteins were poorly cross-reactive, even in donors preexposed to DENV. The most potent neutralizing antibodies were ZIKV-specific and targeted EDIII or quaternary epitopes on infectious virus. An EDIII-specific antibody protected mice from lethal ZIKV infection, illustrating the potential for antibody-based therapy. PMID:27417494

  6. Rheology at the Interface and the Role of the Interphase in Reactive Functionalized Multilayer Polymers in Coextrusion Process

    NASA Astrophysics Data System (ADS)

    Lamnawar, Khalid; Maazouz, Abderrahim

    2008-07-01

    Coextrusion technologies are commonly used to produce multilayered composite sheets or films for a large range of applications from food packaging to optics. The contrast of rheological properties between layers can lead to interfacial instabilities during flow. Important theoretical and experimental advances regarding the stability of compatible and incompatible polymers have, during the last decades, been made using a mechanical approach. However, few research efforts have been dedicated to the physicochemical affinity between the neighboring layers. The present study deals with the influence of this affinity on interfacial instabilities for functionalized incompatible polymers. Polyamide (PA6)/polyethylene grafted with glycidyl methacrylate (PE-GMA) was used as a reactive system and PE/PA6 as a non reactive one. Two grades of polyamide (PA6) were used in order to change the viscosity and elasticity ratios between PE (or PE-GMA) and PA6. It was experimentally confirmed, in this case, that weak disturbance can be predicted by considering an interphase of non-zero thickness (corresponding to an interdiffusion/reaction zone) instead of a purely geometrical interface between the two reactive layers. According to the rheological investigations from previous work which the interphase effect can be probed, an experimental strategy was here formulated to optimize the process by listing the parameters that controlled the stability of the reactive multilayer flows. Hence, based on this analysis, guidelines for a stable coextrusion of reactive functionalized polymers can be provided coupling the classical parameters (viscosity, elasticity and layer ratios) and the physicochemical affinity at the polymer/polymer interface.

  7. Function and regulation of self-reactive marginal zone B cells in autoimmune arthritis

    PubMed Central

    Palm, Anna-Karin E; Friedrich, Heike C; Mezger, Anja; Salomonsson, Maya; Myers, Linda K; Kleinau, Sandra

    2015-01-01

    Polyreactive innate-type B cells account for many B cells expressing self-reactivity in the periphery. Improper regulation of these B cells may be an important factor that underlies autoimmune disease. Here we have explored the influence of self-reactive innate B cells in the development of collagen-induced arthritis (CIA), a mouse model of rheumatoid arthritis. We show that splenic marginal zone (MZ), but not B-1 B cells exhibit spontaneous IgM reactivity to autologous collagen II in naïve mice. Upon immunization with heterologous collagen II in complete Freund's adjuvant the collagen-reactive MZ B cells expanded rapidly, while the B-1 B cells showed a modest anti-collagen response. The MZ B cells were easily activated by toll-like receptor (TLR) 4 and 9-ligands in vitro, inducing proliferation and cytokine secretion, implying that dual engagement of the B-cell receptor and TLRs may promote the immune response to self-antigen. Furthermore, collagen-primed MZ B cells showed significant antigen-presenting capacity as reflected by cognate T-cell proliferation in vitro and induction of IgG anti-collagen antibodies in vivo. MZ B cells that were deficient in complement receptors 1 and 2 demonstrated increased proliferation and cytokine production, while Fcγ receptor IIb deficiency of the cells lead to increased cytokine production and antigen presentation. In conclusion, our data highlight self-reactive MZ B cells as initiators of the autoimmune response in CIA, where complement and Fc receptors are relevant in controlling the self-reactivity in the cells. PMID:25958842

  8. Unprecedented influence of remote substituents on reactivity and stereoselectivity in Cu(I)-catalysed [2 + 2] photocycloaddition. An approach towards the synthesis of tricycloclavulone.

    PubMed

    Mondal, Sujit; Yadav, Ram Naresh; Ghosh, Subrata

    2011-07-01

    Cu(I)-catalysed [2 + 2] photocycloaddition of 1,6-dienes embedded in a furano sugar is described in connection to a synthetic approach to an abnormal marine prostanoid tricycloclavulone. An unprecedented influence of remote substituents on the reactivity and stereoselectivity of the photocycloaddition reaction has been uncovered during this investigation. While an alkene substituent inhibits cycloaddition through steric effects, a substituent having a hydroxyl or alkoxy group at the same location facilitates cycloaddition exclusively from its own side. This investigation has led to the synthesis of a functionalised 5,4-fused core unit of tricycloclavulone. PMID:21573291

  9. Triple-bond reactivity of an AsP complex intermediate: synthesis stemming from molecular arsenic, As(4).

    PubMed

    Spinney, Heather A; Piro, Nicholas A; Cummins, Christopher C

    2009-11-11

    While P(4) is the stable molecular form of phosphorus, a recent study illustrated the possibility of P(2) generation for reactions in organic media under mild conditions. The heavier group 15 element arsenic can exist as As(4) molecules, but As(4) cannot be stored as a pure substance because it is both light-sensitive and reverts thermally to its stable, metallic gray form. Herein we report As(4) activation giving rise to a mu-As(2) diniobium complex, serving in turn as precursor to a terminal arsenide anion complex of niobium. Functionalization of the latter provides the new AsPNMes* ligand, which when complexed with tungsten pentacarbonyl elicits extrusion of the (AsP)W(CO)(5) molecule as a reactive intermediate. Trapping reactions of the latter with organic dienes are found to furnish double Diels-Alder adducts in which the AsP unit is embedded in a polycyclic organic framework. Thermal generation of (AsP)W(CO)(5) in the presence of the neutral terminal phosphide complex P identical withMo(N[(i)Pr]Ar)(3) leads to the cyclo-AsP(2) complex (OC)(5)W(cyclo-AsP(2))Mo(N[(i)Pr]Ar)(3). The (AsP)W(CO)(5) trapping products were crystallized and characterized by X-ray diffraction methods, and computational methods were applied for analysis of the As-As and As-P bonds in the complexes.

  10. Data synthesis and display programs for wave distribution function analysis

    NASA Technical Reports Server (NTRS)

    Storey, L. R. O.; Yeh, K. J.

    1992-01-01

    At the National Space Science Data Center (NSSDC) software was written to synthesize and display artificial data for use in developing the methodology of wave distribution analysis. The software comprises two separate interactive programs, one for data synthesis and the other for data display.

  11. Function of SREBP1 in the milk fat synthesis of dairy cow mammary epithelial cells.

    PubMed

    Li, Nan; Zhao, Feng; Wei, Chenjie; Liang, Mengyao; Zhang, Na; Wang, Chunmei; Li, Qing-Zhang; Gao, Xue-Jun

    2014-09-23

    Sterol regulatory element-binding proteins (SREBPs) belong to a family of nuclear transcription factors. The question of which is the most important positive regulator in milk fat synthesis in dairy cow mammary epithelial cells (DCMECs) between SREBPs or other nuclear transcription factors, such as peroxisome proliferator-activated receptor γ (PPARγ), remains a controversial one. Recent studies have found that mTORC1 (the mammalian target of rapamycin C1) regulates SREBP1 to promote fat synthesis. Thus far, however, the interaction between the SREBP1 and mTOR (the mammalian target of rapamycin) pathways in the regulation of milk fat synthesis remains poorly understood. This study aimed to identify the function of SREBP1 in milk fat synthesis and to characterize the relationship between SREBP1 and mTOR in DCMECs. The effects of SREBP1 overexpression and gene silencing on milk fat synthesis and the effects of stearic acid and serum on SREBP1 expression in the upregulation of milk fat synthesis were investigated in DCMECs using immunostaining, Western blotting, real-time quantitative PCR, lipid droplet staining, and detection kits for triglyceride content. SREBP1 was found to be a positive regulator of milk fat synthesis and was shown to be regulated by stearic acid and serum. These findings indicate that SREBP1 is the key positive regulator in milk fat synthesis.

  12. Synthesis of Highly Functionalized Decalins via Metallacycle-Mediated Cross-Coupling.

    PubMed

    Mizoguchi, Haruki; Micalizio, Glenn C

    2015-05-27

    Bridged bicyclic metallacyclopentenes generated from the [4 + 2] cycloaddition of metallacyclopentadienes with alkenes have been proposed as reactive intermediates in the course of [2 + 2 + 2] annulation reactions. Recently a collection of alkoxide-directed Ti-mediated [2 + 2 + 2] annulation reactions have been discovered for the synthesis of densely functionalized hydrindanes, where the bridged bicyclic metallacyclopentenes from intramolecular [4 + 2] were treated as fleeting intermediates en route to cyclohexadiene products formed by formal cheletropic extrusion of Ti(Oi-Pr)2. In studies aimed at understanding the course of these organometallic cascade reactions it was later discovered that these bridged bicyclic intermediates can be trapped by various elimination processes. Here, we have realized metallacycle-mediated annulation reactions for the assembly of angularly substituted decalins--structural motifs that are ubiquitous in natural products and molecules of pharmaceutical relevance. In addition to defining the basic annulation reaction we have discovered a surprising stability associated with the complex organometallic intermediates generated in the course of this coupling process and document here the ability to control the fate of such species. Ligand-induced cheletropic extrusion of the titanium center delivers cyclohexadiene-containing products, while several distinct protonation events have been identified to realize polycyclic products that contain three new stereocenters (one of which is the angular quaternary center that is a hallmark of alkoxide-directed titanium-mediated [2 + 2 + 2] annulation reactions). Examples of this metallacycle-mediated annulation reaction are provided to demonstrate that a range of stereodefined fused bicyclo[4.4.0]decanes are accessible, including those that contain aromatic and aliphatic substituents, and an empirical model is presented to accompany the observations made. PMID:25930967

  13. Development of new methods in modern selective organic synthesis: preparation of functionalized molecules with atomic precision

    NASA Astrophysics Data System (ADS)

    Ananikov, V. P.; Khemchyan, L. L.; Ivanova, Yu V.; Bukhtiyarov, V. I.; Sorokin, A. M.; Prosvirin, I. P.; Vatsadze, S. Z.; Medved'ko, A. V.; Nuriev, V. N.; Dilman, A. D.; Levin, V. V.; Koptyug, I. V.; Kovtunov, K. V.; Zhivonitko, V. V.; Likholobov, V. A.; Romanenko, A. V.; Simonov, P. A.; Nenajdenko, V. G.; Shmatova, O. I.; Muzalevskiy, V. M.; Nechaev, M. S.; Asachenko, A. F.; Morozov, O. S.; Dzhevakov, P. B.; Osipov, S. N.; Vorobyeva, D. V.; Topchiy, M. A.; Zotova, M. A.; Ponomarenko, S. A.; Borshchev, O. V.; Luponosov, Yu N.; Rempel, A. A.; Valeeva, A. A.; Stakheev, A. Yu; Turova, O. V.; Mashkovsky, I. S.; Sysolyatin, S. V.; Malykhin, V. V.; Bukhtiyarova, G. A.; Terent'ev, A. O.; Krylov, I. B.

    2014-10-01

    The challenges of the modern society and the growing demand of high-technology sectors of industrial production bring about a new phase in the development of organic synthesis. A cutting edge of modern synthetic methods is introduction of functional groups and more complex structural units into organic molecules with unprecedented control over the course of chemical transformation. Analysis of the state-of-the-art achievements in selective organic synthesis indicates the appearance of a new trend — the synthesis of organic molecules, biologically active compounds, pharmaceutical substances and smart materials with absolute selectivity. Most advanced approaches to organic synthesis anticipated in the near future can be defined as 'atomic precision' in chemical reactions. The present review considers selective methods of organic synthesis suitable for transformation of complex functionalized molecules under mild conditions. Selected key trends in the modern organic synthesis are considered including the preparation of organofluorine compounds, catalytic cross-coupling and oxidative cross-coupling reactions, atom-economic addition reactions, methathesis processes, oxidation and reduction reactions, synthesis of heterocyclic compounds, design of new homogeneous and heterogeneous catalytic systems, application of photocatalysis, scaling up synthetic procedures to industrial level and development of new approaches to investigation of mechanisms of catalytic reactions. The bibliography includes 840 references.

  14. Listening to music and physiological and psychological functioning: the mediating role of emotion regulation and stress reactivity.

    PubMed

    Thoma, M V; Scholz, U; Ehlert, U; Nater, U M

    2012-01-01

    Music listening has been suggested to have short-term beneficial effects. The aim of this study was to investigate the association and potential mediating mechanisms between various aspects of habitual music-listening behaviour and physiological and psychological functioning. An internet-based survey was conducted in university students, measuring habitual music-listening behaviour, emotion regulation, stress reactivity, as well as physiological and psychological functioning. A total of 1230 individuals (mean = 24.89 ± 5.34 years, 55.3% women) completed the questionnaire. Quantitative aspects of habitual music-listening behaviour, i.e. average duration of music listening and subjective relevance of music, were not associated with physiological and psychological functioning. In contrast, qualitative aspects, i.e. reasons for listening (especially 'reducing loneliness and aggression', and 'arousing or intensifying specific emotions') were significantly related to physiological and psychological functioning (all p = 0.001). These direct effects were mediated by distress-augmenting emotion regulation and individual stress reactivity. The habitual music-listening behaviour appears to be a multifaceted behaviour that is further influenced by dispositions that are usually not related to music listening. Consequently, habitual music-listening behaviour is not obviously linked to physiological and psychological functioning.

  15. The Dual Function of Reactive Oxygen/Nitrogen Species in Bioenergetics and Cell Death: The Role of ATP Synthase

    PubMed Central

    Kaludercic, Nina

    2016-01-01

    Reactive oxygen species (ROS) and reactive nitrogen species (RNS) targeting mitochondria are major causative factors in disease pathogenesis. The mitochondrial permeability transition pore (PTP) is a mega-channel modulated by calcium and ROS/RNS modifications and it has been described to play a crucial role in many pathophysiological events since prolonged channel opening causes cell death. The recent identification that dimers of ATP synthase form the PTP and the fact that posttranslational modifications caused by ROS/RNS also affect cellular bioenergetics through the modulation of ATP synthase catalysis reveal a dual function of these modifications in the cells. Here, we describe mitochondria as a major site of production and as a target of ROS/RNS and discuss the pathophysiological conditions in which oxidative and nitrosative modifications modulate the catalytic and pore-forming activities of ATP synthase. PMID:27034734

  16. Synthesis, structure and reactivity of cyclopropenyl-1-ylidene stabilized S(II), Se(II) and Te(II) mono- and dications.

    PubMed

    Kozma, Ágnes; Petuškova, Jekaterina; Lehmann, Christian W; Alcarazo, Manuel

    2013-05-14

    The syntheses and structural characterization of carbene-stabilized chalcogen centred mono- and dications employing a reverse electron demand onio-substitutent transfer strategy are reported. The electronic structures of these compounds were determined by density functional calculations and their reactivity towards Pd(0) centres was evaluated.

  17. Selection of functional human sperm with higher DNA integrity and fewer reactive oxygen species

    PubMed Central

    Asghar, Waseem; Velasco, Vanessa; Kingsley, James L.; Shoukat, Muhammad S.; Shafiee, Hadi; Anchan, Raymond M.; Mutter, George L.; Tüzel, Erkan; Demirci, Utkan

    2014-01-01

    Fertilization and reproduction are central to the survival and propagation of a species. Couples who cannot reproduce naturally have to undergo in vitro clinical procedures. An integral part of these clinical procedures includes isolation of healthy sperm from raw semen. Existing sperm sorting methods are not efficient and isolate sperm having high DNA fragmentation and reactive oxygen species, and suffer from multiple manual steps and variations between embryologists. Inspired by in vivo natural sperm sorting mechanisms where vaginal mucus becomes less viscous to form microchannels to guide sperm towards egg, we present a chip that efficiently sorts healthy, motile and morphologically normal sperm without centrifugation. Higher percentage of sorted sperm show significantly lesser reactive oxygen species and DNA fragmentation than the conventional swim-up method. The presented chip is an easy-to-use high throughput sperm sorter that provides standardized sperm sorting assay with less reliance on embryologist’s skills, facilitating reliable operational steps. PMID:24753434

  18. Intermatrix Synthesis as a rapid, inexpensive and reproducible methodology for the in situ functionalization of nanostructured surfaces with quantum dots

    NASA Astrophysics Data System (ADS)

    Bastos-Arrieta, Julio; Muñoz, Jose; Stenbock-Fermor, Anja; Muñoz, Maria; Muraviev, Dmitri N.; Céspedes, Francisco; Tsarkova, Larisa A.; Baeza, Mireia

    2016-04-01

    Intermatrix Synthesis (IMS) technique has proven to be a valid methodology for the in situ incorporation of quantum dots (QDs) in a wide range of nanostructured surfaces for the preparation of advanced hybrid-nanomaterials. In this sense, this communication reports the recent advances in the application of IMS for the synthesis of CdS-QDs with favourable distribution on sulfonated polyetherether ketone (SPEEK) membrane thin films (TFs), multiwall carbon nanotubes (MWCNTs) and nanodiamonds (NDs). The synthetic route takes advantage of the ion exchange functionality of the reactive surfaces for the loading of the QDs precursor and consequent QDs appearance by precipitation. The benefits of such modified nanomaterials were studied using CdS-QDs@MWCNTs hybrid-nanomaterials. CdS-QDs@MWCNTs has been used as conducting filler for the preparation of electrochemical nanocomposite sensors, which present electrocatalytic properties. Finally, the optical properties of the QDs contained on MWCNTs could allow a new procedure for the analytical detection of nanostructured carbon allotropes in water.

  19. Precision synthesis, structure and function of helical polymers

    PubMed Central

    OKAMOTO, Yoshio

    2015-01-01

    Helical structures are chiral, which means that if we can synthesize a polymer having a stable one-handed helicity, the polymer is optically active. In 1979, we succeeded in the synthesis of a one-handed helical polymer from an optically inactive achiral monomer, triphenylmethyl methacrylate (TrMA). This is the first example of the asymmetric synthesis of an optically active one-handed helical polymer. The polymer (PTrMA) exhibited an unexpected high chiral recognition ability and afforded a practically useful chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) by coating it on silica gel. In addition, we also succeeded in the development of very useful CSPs for HPLC using the phenylcarbamate derivatives of polysaccharides, cellulose and amylose. These CSPs can efficiently resolve a broad range of chiral compounds, and have been used all over the world for separating and analyzing chiral compounds. PMID:26062738

  20. Precision synthesis, structure and function of helical polymers.

    PubMed

    Okamoto, Yoshio

    2015-01-01

    Helical structures are chiral, which means that if we can synthesize a polymer having a stable one-handed helicity, the polymer is optically active. In 1979, we succeeded in the synthesis of a one-handed helical polymer from an optically inactive achiral monomer, triphenylmethyl methacrylate (TrMA). This is the first example of the asymmetric synthesis of an optically active one-handed helical polymer. The polymer (PTrMA) exhibited an unexpected high chiral recognition ability and afforded a practically useful chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) by coating it on silica gel. In addition, we also succeeded in the development of very useful CSPs for HPLC using the phenylcarbamate derivatives of polysaccharides, cellulose and amylose. These CSPs can efficiently resolve a broad range of chiral compounds, and have been used all over the world for separating and analyzing chiral compounds. PMID:26062738

  1. A comparison of the chemical reactivity of naringenin calculated with the M06 family of density functionals

    PubMed Central

    2013-01-01

    Background Chemicals generically referred to as flavonoids belong to the group of phenolic compounds and constitute an important group of secondary metabolites due to their applications as well as their biochemical properties. Flavonoids, which share a common benzo- γ-pyrone structure, constitute a kind of compound which are highly ubiquitous in the plant kingdom. Findings The M06 family of density functionals has been assessed for the calculation of the molecular structure and properties of the Naringenin flavonoid. The chemical reactivity descriptors have been calculated through Conceptual DFT. The active sites for nucleophilic and electrophilic attacks have been chosen by relating them to the Fukui function indices and the dual descriptor f(2)(r). A comparison between the descriptors calculated through vertical energy values and those arising from the Koopmans’ theorem approximation have been performed in order to check for the validity of the last procedure. Conclusions The M06 family of density functionals (M06, M06L, M06-2X and M06-HF) used in the present work leads to the same qualitatively and quantitatively similar description of the chemistry and reactivity of the Naringenin molecule, yielding reasonable results. However, for the case of the M06-2X and M06-HF density functionals, which include a large portion of HF exchange, the calculations considering the validity of the Koopmans’ theorem lead to negative electron affinities. PMID:24041114

  2. Reactive Intermediates: Molecular and MS-Based Approaches to Assess the Functional Significance of Chemical:Protein Adducts1

    PubMed Central

    Monks, Terrence J.; Lau, Serrine S.

    2014-01-01

    Biologically reactive intermediates formed as endogenous products of various metabolic processes are considered important factors in a variety of human diseases, including Parkinson’s disease and other neurological disorders, diabetes and complications thereof, and other inflammatory-associated diseases. Chemical-induced toxicities are also frequently mediated via the bioactivation of relatively stable organic molecules to reactive electrophilic metabolites. Indeed, chemical-induced toxicities have long been known to be associated with the ability of electrophilic metabolites to react with a variety of targets within the cell, including their covalent adduction to nucleophilic residues in proteins, and nucleotides within DNA. Although we possess considerable knowledge of the various biochemical mechanisms by which chemicals undergo metabolic bioactivation, we understand far less about the processes that couple bioactivation to toxicity. Identifying specific sites within a protein that are targets for adduction can provide the initial information necessary to determine whether such adventitious post-translational modifications significantly alter either protein structure and/or function. To address this problem we have developed MS-based approaches to identify specific amino acid targets of electrophile adduction (electrophile-binding motifs), coupled with molecular modeling of such adducts, to determine the potential structural and functional consequences. Where appropriate, functional assays are subsequently conducted to assess protein function. PMID:23222993

  3. Functional Metal Oxide Nanostructures: Their Synthesis, Characterization, and Energy Applications

    NASA Astrophysics Data System (ADS)

    Iyer, Aparna

    This research focuses on studying metal oxides (MnO 2, Co3O4, MgO, Y2O3) for various applications including water oxidation and photocatalytic oxidation, developing different synthesis methodologies, and presenting detailed characterization studies of these metal oxides. This research consists of three major parts. The first part is studying novel applications and developing a synthesis method for manganese oxide nanomaterials. Manganese oxide materials were studied for renewable energy applications by using them as catalysts for water oxidation reactions. In this study, various crystallographic forms of manganese oxides (amorphous, 2D layered, 1D 2 x 2 tunnel structures) were evaluated for water oxidation catalysis. Amorphous manganese oxides (AMO) were found to be catalytically active for chemical and photochemical water oxidation compared to cryptomelane type tunnel manganese oxides (2 x 2 tunnels; OMS2) or layered birnessite (OL-1) materials. Detailed characterization was done to establish a correlation between the properties of the manganese oxide materials and their catalytic activities in water oxidation. The gas phase photocatalytic oxidation of 2-propanol under visible light was studied using manganese oxide 2 x 2 tunnel structures (OMS-2) as catalysts (Chapter 3). The reaction is 100% selective to acetone. As suggested by the photocatalytic and characterization data, important factors for the design of active OMS-2 photocatalysts are synthesis methodology, morphology, mixed valency and the release of oxygen from the OMS-2 structure. Manganese oxide octahedral molecular sieves (2 x 2 tunnels; OMS-2) with self-assembled dense or hollow sphere morphologies were fabricated via a room temperature ultrasonic atomization assisted synthesis (Chapter 4). The properties and catalytic activities of these newly developed materials were compared with that of OMS-2 synthesized by conventional reflux route. These materials exhibit exceptionally high catalytic activities

  4. Surface decoration through electrostatic interaction leading to enhanced reactivity: Low temperature synthesis of nanostructured chromium borides (CrB and CrB{sub 2})

    SciTech Connect

    Menaka,; Kumar, Bharat; Kumar, Sandeep; Ganguli, A.K.

    2013-04-15

    The present study describes a novel low temperature route at ambient pressure for the synthesis of nanocrystalline chromium borides (CrB and CrB{sub 2}) without using any flux or additives. The favorable and intimate mixing of nanoparticles of chromium acetate (Cr source) and boron forms an active chromium–boron precursor which decomposes at much lower temperature (400 °C) to form CrB (which is ∼1000 °C less than the known ambient pressure synthesis). The chromium acetate nanoparticles (∼5 nm) decorate the larger boron particles (150–200 nm) due to electrostatic interactions resulting from opposing surface charges of boron (zeta potential:+48.101 mV) and chromium acetate (zeta potential:−4.021 mV) in ethanolic medium and is evident in the TEM micrographs. The above method leads to the formation of pure CrB film like structure at 400 °C and nanospheres (40–60 nm) at 600 °C. Also, chromium diboride (CrB{sub 2}) nanoparticles (25 nm) could be obtained at 1000 °C. - Graphical abstract: Variation of surface charge of reactants, precursor and the products, chromium borides (CrB and CrB{sub 2}). Highlights: ► Novel borothermal reduction process for synthesis of chromium boride. ► Significant lowering of reaction temperature to obtain nanocrystalline chromium boride. ► Enhanced reactivity due to appropriate surface interactions.

  5. Functional implications of mitochondrial reactive oxygen species generated by oncogenic viruses

    PubMed Central

    Choi, Young Bong; Harhaj, Edward William

    2014-01-01

    Between 15–20% of human cancers are associated with infection by oncogenic viruses. Oncogenic viruses, including HPV, HBV, HCV and HTLV-1, target mitochondria to influence cell proliferation and survival. Oncogenic viral gene products also trigger the production of reactive oxygen species which can elicit oxidative DNA damage and potentiate oncogenic host signaling pathways. Viral oncogenes may also subvert mitochondria quality control mechanisms such as mitophagy and metabolic adaptation pathways to promote virus replication. Here, we will review recent progress on viral regulation of mitophagy and metabolic adaptation and their roles in viral oncogenesis. PMID:25580106

  6. Synthesis and functionalization of magnetite nanoparticles with different amino-functional alkoxysilanes

    NASA Astrophysics Data System (ADS)

    Bini, Rafael A.; Marques, Rodrigo Fernando C.; Santos, Francisco J.; Chaker, Juliano A.; Jafelicci, Miguel

    2012-02-01

    Superparamagnetic iron oxide (SPIO) nanoparticles show great promise for many biotechnological applications. This paper addresses the synthesis and characterization of SPIO nanoparticles grafted with three different alkoxysilanes: 3-aminopropyl-triethoxysilane (APTES), 3-aminopropyl-ethyl-diethoxysilane (APDES) and 3-aminopropyl-diethy-ethoxysilane (APES). SPIO nanoparticles with an average particle diameter of 10 nm were prepared by chemical sonoprecipitation. As confirmed by Fourier transform infrared (FTIR) spectroscopy, silylation of these nanoparticles occurs through a two-step process. Decreasing the number of alkoxide groups reduced the concentration of free amino groups on the SPIO surface ([SPIO-NH2]-APTES>APDES>APES). This phenomenon results from steric contributions and the formation of H-bonded amines provided by the ethyl groups present in the APDES and APES molecules. A simulation of SPIO nanoparticles in a saline physiologic solution shows that the ethyl groups impart larger steric stability onto the ferrofluids, which reduces aggregation. The magnetization (M) versus magnetic field (H) curves show that the synthesized iron oxide nanoparticles display superparamagnetic behavior. The zero-field cooling (ZFC) and field cooling (FC) curves show that the changes in the blocking temperature depend on the alkoxysilane-functionalized particle surface.

  7. A robust platform for functional microgels via thiol-ene achemistry with reactive polyether-based nanoparticles

    PubMed Central

    Fleischmann, Carolin; Gopez, Jeffrey; Lundberg, Pontus; Ritter, Helmut; Killops, Kato L.

    2015-01-01

    We herein report the development of crosslinked polyether particles as a reactive platform for the preparation of functional microgels. Thiol-ene crosslinking of poly(allyl glycidyl ether) in miniemulsion droplets - stabilized by a surface active, bio-compatible polyethylene glycol block copolymer - resulted in colloidal gels with a PEG corona and an inner polymeric network containing reactive allyl units. The stability of the allyl groups allows the microgels to be purified and stored before a second, subsequent thiol-ene functionalization step allows a wide variety of pH- and chemically-responsive groups to be introduced into the nanoparticles. The facile nature of this synthetic platform enables the preparation of microgel libraries that are responsive to different triggers but are characterized by the same size distribution, surface functionality, and crosslinking density. In addition, the utilization of a crosslinker containing cleavable ester groups renders the resulting hydrogel particles degradable at elevated pH or in the presence of esterase under physiological conditions. PMID:26005499

  8. Changes in pulmonary function and airway reactivity due to prolonged exposure to typical ambient ozone (O/sub 3/) levels

    SciTech Connect

    Horstman, D.; McConnell, W.; Folinsbee, L.; Abdul-Salaam, S.; Ives, P.

    1988-05-01

    Daily ambient ozone levels between 0.08 and 0.12 ppm for periods exceeding 6 hours often occur in many urban, suburban, and rural areas of the United States and Europe. Substantial decrements in pulmonary functions, moderate to severe respiratory symptoms, and increased airway reactivity have been observed in young men performing moderate to heavy exercise. This study evaluates pulmonary responses of 22 healthy nonsmoking males, resulting from exposures to 0.08, 0.10, and 0.12 ppm ozone.

  9. Extracellular Redox Regulation of Intracellular Reactive Oxygen Generation, Mitochondrial Function and Lipid Turnover in Cultured Human Adipocytes

    PubMed Central

    Oliveira, Marcus F.; Burritt, Nathan; Corkey, Barbara E.

    2016-01-01

    Background Many tissues play an important role in metabolic homeostasis and the development of diabetes and obesity. We hypothesized that the circulating redox metabolome is a master metabolic regulatory system that impacts all organs and modulates reactive oxygen species (ROS) production, lipid peroxidation, energy production and changes in lipid turnover in many cells including adipocytes. Methods Differentiated human preadipocytes were exposed to the redox couples, lactate (L) and pyruvate (P), β–hydroxybutyrate (βOHB) and acetoacetate (Acoc), and the thiol-disulfides cysteine/ cystine (Cys/CySS) and GSH/GSSG for 1.5–4 hours. ROS measurements were done with CM-H2DCFDA. Lipid peroxidation (LPO) was assessed by a modification of the thiobarbituric acid method. Lipolysis was measured as glycerol release. Lipid synthesis was measured as 14C-glucose incorporated into lipid. Respiration was assessed using the SeaHorse XF24 analyzer and the proton leak was determined from the difference in respiration with oligomycin and antimycin A. Results Metabolites with increasing oxidation potentials (GSSG, CySS, Acoc) increased adipocyte ROS. In contrast, P caused a decrease in ROS compared with L. Acoc also induced a significant increase in both LPO and lipid synthesis. L and Acoc increased lipolysis. βOHB increased respiration, mainly due to an increased proton leak. GSSG, when present throughout 14 days of differentiation significantly increased fat accumulation, but not when added later. Conclusions We demonstrated that in human adipocytes changes in the external redox state impacted ROS production, LPO, energy efficiency, lipid handling, and differentiation. A more oxidized state generally led to increased ROS, LPO and lipid turnover and more reduction led to increased respiration and a proton leak. However, not all of the redox couples were the same suggesting compartmentalization. These data are consistent with the concept of the circulating redox metabolome as a

  10. Arterial stiffness, endothelial function and microcirculatory reactivity in healthy young males.

    PubMed

    Wright, C I; Scholten, H J; Schilder, J C M; Elsen, B M; Hanselaar, W; Kroner, C I; Draijer, R; Kastelein, J J P; Stok, W; Karemaker, J; de Groot, E

    2008-09-01

    Large (C1) and small (C2) arterial stiffness has been suggested to parallel endothelial reactivity and has led researchers to suggest parameters of arterial stiffness may be alternative measures to brachial sonographic assessments of flow-mediated dilatation (FMD). However, past studies comparing these measures can be criticized. In addition to %FMD responses, we recorded concurrent hyperaemic responses of the microcirculation and both were compared with C1 and C2. Twenty-nine subjects 18-30 years of age were investigated. Radial blood pressure was recorded with a tonometer. Pulse waveform analysis was performed to calculate C1 and C2. These were compared with %FMD responses and responses of finger flux measured by laser Doppler fluxmetry (LDF); pulsatile finger volume measured by photoplethysmography (PPG); and palm skin temperature measured by infrared thermography (Tpalm) (i.e. microcirculatory responses). Responses were determined as % changes from control. We only found weak relationships between C1 and %FMD (r=0.4, P=0.04); C2 and %PPG (r=0.38, P=0.07); and C2 and %LDFdorsal (r=-0.38; P=0.04). Responses of %FMD weakly parallel those of C1. Neither C2 nor C1 are viable indicators of endothelial or microcirculatory reactivity (i.e. hyperaemic or venous constriction) in healthy, resting young males. These findings refute the claims that C1 and C2 are substitute measures to sonographic assessments of brachial FMD. PMID:18445071

  11. Parameter manipulation in the Synthesis of Ti-Cd-C Films via Reactive Sputtering in a Magnetized Sheet Plasma Facility

    NASA Astrophysics Data System (ADS)

    Villanueva, Matthew Bryan; Ramos, Henry

    2013-09-01

    Titanium-cadmium-carbon (Ti-Cd-C) deposits were achieved through reactive sputtering in a magnetized sheet plasma facility (MSPF). Titanium and cadmium metals (99.9% purity) were used as sputter targets, and high purity methane as the reactive gas. Parameters investigated were target bias, deposition duration, filling pressure, gas ratio, gas type such as acetylene, and magnetic configuration. Through X-ray diffractometry, peak signals at 2 θ = 23.3° for the treatment which implemented an independent sputtering step at -200 V target bias, and 2 θ = 12.34° for direct reactive sputtering only with -800 V target bias were recorded. Both XRD results are indicative of the formation of Ti2CdC, a theorized solid solution of Mn+1AXn phase variety. Department of Science and Technology for the project grant.

  12. Synthesis of 2-Nickela(II)oxetanes from Nickel(0) and Epoxides: Structure, Reactivity, and a New Mechanism of Formation.

    PubMed

    Desnoyer, Addison N; Bowes, Eric G; Patrick, Brian O; Love, Jennifer A

    2015-10-14

    2-Nickelaoxetanes have been frequently invoked as reactive intermediates in catalytic reactions of epoxides using nickel, but have never been isolated or experimentally observed in these transformations. Herein, we report the preparation of a series of well-defined nickelaoxetanes formed via the oxidative addition of nickel(0) with epoxides featuring ketones. The stereochemistry of the products is retained, which has not yet been reported for nickelaoxetanes. Theoretical calculations support a bimetallic ring-opening/closing pathway over a concerted oxidative addition. Initial reactivity studies of a nickelaoxetane demonstrated protonolysis, oxidatively induced reductive elimination, deoxygenation, and elimination reactions when treated with the appropriate reagents.

  13. Pentaerythritol Tetranitrate Targeting Myocardial Reactive Oxygen Species Production Improves Left Ventricular Remodeling and Function in Rats With Ischemic Heart Failure.

    PubMed

    Fraccarollo, Daniela; Galuppo, Paolo; Neuser, Jonas; Bauersachs, Johann; Widder, Julian D

    2015-11-01

    Reduced nitric oxide bioavailability contributes to progression of cardiac dysfunction and remodeling in ischemic heart failure. Clinical use of organic nitrates as nitric oxide donors is limited by development of nitrate tolerance and reactive oxygen species formation. We investigated the effects of long-term therapy with pentaerythritol tetranitrate (PETN), an organic nitrate devoid of tolerance, in rats with congestive heart failure after extensive myocardial infarction. Seven days after coronary artery ligation, rats were randomly allocated to treatment with PETN (80 mg/kg BID) or placebo for 9 weeks. Long-term PETN therapy prevented the progressive left ventricular dilatation and improved left ventricular contractile function and relaxation in rats with congestive heart failure. Mitochondrial superoxide anion production was markedly increased in the failing left ventricular myocardium and nearly normalized by PETN treatment. Gene set enrichment analysis revealed that PETN beneficially modulated the dysregulation of mitochondrial genes involved in energy metabolism, paralleled by prevention of uncoupling protein-3, thioredoxin-2, and superoxide dismutase-2 downregulation. Moreover, PETN provided a remarkable protective effect against reactive fibrosis in chronically failing hearts. Mechanistically, induction of heme oxygenase-1 by PETN prevented mitochondrial superoxide generation, NOX4 upregulation, and ensuing formation of extracellular matrix proteins in fibroblasts from failing hearts. In summary, PETN targeting reactive oxygen species generation prevented the changes of mitochondrial antioxidant enzymes and progressive fibrotic remodeling, leading to amelioration of cardiac functional performance. Therefore, PETN might be a promising therapeutic option in the treatment of ischemic heart diseases involving oxidative stress and impairment in nitric oxide bioactivity.

  14. Monoamines and sexual function in rats bred for increased catatonic reactivity.

    PubMed

    Klochkov, D V; Alekhina, T A; Kuznetsova, E G; Barykina, N N

    2009-07-01

    Body weight, ovary and uterus weight, the nature of estral cycles, and hypothalamus dopamine and noradrenaline levels and plasma testosterone levels were studied in female GC rats, bred for increased catatonic reactivity, at different stages of the estral cycle (estrus, proestrus). The outbred Wistar strain served as controls. On the background of decreased body weight, GC females showed impairments to the morphological cyclical changes in the ovaries and uterus, with a reduction in ovary weight in diestrus (p < 0.01) and a smaller estrogen-dependent increase in uterus weight in estrus as compared with Wistar females. On the background of decreases in dopamine and noradrenaline contents in the hypothalamus, GC rats showed higher levels of these monoamines in estrus and lower levels in diestrus. Plasma testosterone levels in female GC rats were higher in diestrus than in estrus and in Wistar rats.

  15. Synthesis and solvent dependent reactivity of chelating bis-N-heterocyclic carbene complexes of Fe(II) hydrides.

    PubMed

    Zlatogorsky, Sergey; Ingleson, Michael J

    2012-03-01

    The synthesis and isolation of low coordinate methylenebis-(N-DIPP-imidazole-2-ylidene)iron((II))hydrides, (((DIPP)C)(2)CH(2))FeH(2-y)I(y) ((DIPP = 2,6-di-isopropylphenyl, y = 1 or 0), was complicated by competitive reactions with solvent, rapid reductive elimination of H(2) and/or dissociation of the bis-N-heterocyclic carbene ligand. Addition of KH to (((DIPP)C)(2)CH(2))FeI(2) in THF/haloalkane mixtures enabled a short lived mono-hydride to be trapped by reaction with CH(2)Cl(2) or cyclo-heptylbromide to form (((DIPP)C)(2)CH(2))FeI(X) (X = Cl or Br, respectively). Toluene coordination stabilises iron-mono hydride complexes as (((DIPP)C)(2)CH(2))Fe(II)H{η(6)-(toluene)} species, which can be isolated in low yield from combination of borohydride salts and (((DIPP)C)(2)CH(2))FeI(2) in toluene, including an imidazole C4 deprotonated carbene-borane, methylene(N-DIPP-imidazole-2-ylidene)(N-DIPP-4-triethyl-borane-imidazole-2-ylidene)](hydrido)(η(6)-toluene)iron. In the absence of toluene, or at short reaction times compounds with empirical formula (((DIPP)C)(2)CH(2))Fe(H)(HB(R)(3))·LiI (R = Et or sec-Bu) that function as a masked Fe((II))-dihydride are isolated. Whilst (((DIPP)C)(2)CH(2))Fe(H)(HB(R)(3))·LiI was stable for days in Et(2)O, more polar solvents (MeCN, THF) led to formation of the carbene borane adducts (((DIPP)C)(2)CH(2))(BR(3))(2). The addition of CO or cyclo-heptylbromide to (((DIPP)C)(2)CH(2))Fe(H)(HB(R)(3))·LiI formed (((DIPP)C)(2)CH(2))Fe(CO)(3) and (((DIPP)C)(2)CH(2))FeBr(2), respectively with BR(3) evolved from both reactions as a by-product.

  16. Total Synthesis of Ellagitannins through Regioselective Sequential Functionalization of Unprotected Glucose.

    PubMed

    Takeuchi, Hironori; Mishiro, Kenji; Ueda, Yoshihiro; Fujimori, Yusuke; Furuta, Takumi; Kawabata, Takeo

    2015-05-18

    Short total syntheses of natural glycosides (ellagitannins) were performed through sequential and regioselective functionalization of the hydroxy groups of unprotected glucose. The key reactions are β-selective glycosidation of a gallic acid derivative by using unprotected glucose as a glycosyl donor and catalyst-controlled regioselective introduction of a galloyl group into the inherently less reactive hydroxy group of the glucoside.

  17. Site-specific covalent modifications of human insulin by catechol estrogens: Reactivity and induced structural and functional changes

    NASA Astrophysics Data System (ADS)

    Ku, Ming-Chun; Fang, Chieh-Ming; Cheng, Juei-Tang; Liang, Huei-Chen; Wang, Tzu-Fan; Wu, Chih-Hsing; Chen, Chiao-Chen; Tai, Jung-Hsiang; Chen, Shu-Hui

    2016-06-01

    Proteins, covalently modified by catechol estrogens (CEs), were identified recently from the blood serum of diabetic patients and referred to as estrogenized proteins. Estrogenization of circulating insulin may occur and affect its molecular functioning. Here, the chemical reactivity of CEs towards specific amino acid residues of proteins and the structural and functional changes induced by the estrogenization of insulin were studied using cyclic voltammetry, liquid chromatography-mass spectrometry, circular dichroism spectroscopy, molecular modeling, and bioassays. Our results indicate that CEs, namely, 2- and 4-hydroxyl estrogens, were thermodynamically and kinetically more reactive than the catechol moiety. Upon co-incubation, intact insulin formed a substantial number of adducts with one or multiple CEs via covalent conjugation at its Cys 7 in the A or B chain, as well as at His10 or Lys29 in the B chain. Such conjugation was coupled with the cleavage of inter-chain disulfide linkages. Estrogenization on these sites may block the receptor-binding pockets of insulin. Insulin signaling and glucose uptake levels were lower in MCF-7 cells treated with modified insulin than in cells treated with native insulin. Taken together, our findings demonstrate that insulin molecules are susceptible to active estrogenization, and that such modification may alter the action of insulin.

  18. Site-specific covalent modifications of human insulin by catechol estrogens: Reactivity and induced structural and functional changes

    PubMed Central

    Ku, Ming-Chun; Fang, Chieh-Ming; Cheng, Juei-Tang; Liang, Huei-Chen; Wang, Tzu-Fan; Wu, Chih-Hsing; Chen, Chiao-Chen; Tai, Jung-Hsiang; Chen, Shu-Hui

    2016-01-01

    Proteins, covalently modified by catechol estrogens (CEs), were identified recently from the blood serum of diabetic patients and referred to as estrogenized proteins. Estrogenization of circulating insulin may occur and affect its molecular functioning. Here, the chemical reactivity of CEs towards specific amino acid residues of proteins and the structural and functional changes induced by the estrogenization of insulin were studied using cyclic voltammetry, liquid chromatography-mass spectrometry, circular dichroism spectroscopy, molecular modeling, and bioassays. Our results indicate that CEs, namely, 2- and 4-hydroxyl estrogens, were thermodynamically and kinetically more reactive than the catechol moiety. Upon co-incubation, intact insulin formed a substantial number of adducts with one or multiple CEs via covalent conjugation at its Cys 7 in the A or B chain, as well as at His10 or Lys29 in the B chain. Such conjugation was coupled with the cleavage of inter-chain disulfide linkages. Estrogenization on these sites may block the receptor-binding pockets of insulin. Insulin signaling and glucose uptake levels were lower in MCF-7 cells treated with modified insulin than in cells treated with native insulin. Taken together, our findings demonstrate that insulin molecules are susceptible to active estrogenization, and that such modification may alter the action of insulin. PMID:27353345

  19. Synthesis of a highly reactive (benzyne)ruthenium complex: C-C, C-H, N-H, and O-H activation reactions

    SciTech Connect

    Hartwig, J.F.; Andersen, R.A.; Bergman, R.G. )

    1989-03-29

    The authors report here the synthesis and chemistry of an exceptionally reactive ruthenium benzyne complex, (PMe{sub 3}){sub 4}Ru({eta}{sup 2}-C{sub 6}H{sub 4}) (1). The ruthenium-carbon bond in this molecule reacts with a wide range of organic substrates that are typically inert toward late transition-metal-carbon bonds, including those in benzyne complexes. For example, complex 1 reacts cleanly with arylamine N-H bonds, water O-H bonds, and benzyl and aryl C-H bonds. It reacts with acetophenone to yield an O-bound enolate complex, inserts benzaldehyde cleanly, and cleaves the C-C bond of acetone.

  20. A concise and scalable strategy for the total synthesis of dictyodendrin B based on sequential C-H functionalization.

    PubMed

    Pitts, Andrew K; O'Hara, Fionn; Snell, Robert H; Gaunt, Matthew J

    2015-04-27

    A sequential CH functionalization strategy for the synthesis of the marine alkaloid dictyodendrin B is reported. Our synthesis begins from commercially available 4-bromoindole and involves six direct functionalizations around the heteroarene core as part of a gram-scale strategy towards the natural product.

  1. Mechanical and electrical properties of functionalized graphene nanoribbon: A study of reactive molecular dynamic simulation and density functional tight-binding theory

    NASA Astrophysics Data System (ADS)

    Zaminpayma, Esmaeil; Nayebi, Payman

    2015-02-01

    Graphene has novel electronic structure, such as unusual transport properties, high carrier mobility and excellent mechanical properties like high Young's modulus. These properties can be modified by many methods, such as functionalized with adding chemical groups, cutting graphene as a nanoribbon and Appling a stress along graphene. In this work, we studied the mechanical and electrical properties of functionalized graphene nanoribbon with -NH2, -CH3, -OH, -C5H6 groups. In mechanical section, we calculated Young's modulus of functionalized graphene nanoribbon as a function of temperature by method of reactive molecular dynamic simulation. Our results show that Young's modulus decrease by increasing temperature. Also we studied the effect of functionalized groups on Young's modulus. We show that Young's modulus decreases by adding these groups. It is in the order of Y (nanoribbon)>Y (NH2)>Y (C6H5)>Y (OH)>Y (CH3). In electrical section, we calculated current-voltage curve for functionalized nanoribbon with density functional tight-binding method at two different 0% and 5% strain. We found for both strains, the functionalized groups decrease the electrical resistance of nanoribbon and increase its current. The relationship of the current is in the order of I(CH3) >I(C5H6) >I(NH2) >I(OH) >I (nanoribbon).

  2. Synthesis of Specifically Modified Oligonucleotides for Application in Structural and Functional Analysis of RNA

    PubMed Central

    Rublack, Nico; Nguyen, Hien; Appel, Bettina; Springstubbe, Danilo; Strohbach, Denise; Müller, Sabine

    2011-01-01

    Nowadays, RNA synthesis has become an essential tool not only in the field of molecular biology and medicine, but also in areas like molecular diagnostics and material sciences. Beyond synthetic RNAs for antisense, aptamer, ribozyme, and siRNA technologies, oligoribonucleotides carrying site-specific modifications for structure and function studies are needed. This often requires labeling of the RNA with a suitable spectroscopic reporter group. Herein, we describe the synthesis of functionalized monomer building blocks that upon incorporation in RNA allow for selective reaction with a specific reporter or functional entity. In particular, we report on the synthesis of 5′-O-dimethoxytrityl-2′-O-tert-butyldimethylsilyl protected 3′-O-phosphoramidites of nucleosides that carry amino linkers of different lengths and flexibility at the heterocyclic base, their incorporation in a variety of RNAs, and postsynthetic conjugation with fluorescent dyes and nitroxide spin labels. Further, we show the synthesis of a flavine mononucleotide-N-hydroxy-succinimidyl ester and its conjugation to amino functionalized RNA. PMID:22013508

  3. A Synthesis of the Peer-Reviewed Differential Bundle Functioning Research

    ERIC Educational Resources Information Center

    Banks, Kathleen

    2013-01-01

    The purpose of this article was to present a synthesis of the peer-reviewed differential bundle functioning (DBF) research that has been conducted to date. A total of 16 studies were synthesized according to the following characteristics: tests used and learner groups, organizing principles used for developing bundles, DBF detection methods used,…

  4. Low frequency sonochemical synthesis of nanoporous amorphous manganese dioxide (MnO{sub 2}) and adsorption of remazol reactive dye

    SciTech Connect

    Hasan, Siti Zubaidah; Yusop, Muhammad Rahimi; Othman, Mohamed Rozali

    2015-09-25

    Nanoporous amorphous-MnO{sub 2} was synthesized by sonochemical process (sonication) on the solid manganese (II) acetate tetrahydrate (Mn(CH{sub 3}COO){sub 2}.4H{sub 2}O) in 0.1 M KMnO{sub 4}. The product was characterized by X-ray diffraction (XRD), morphology of the material was scanned by Field Emission Scanning Electron Microscopy (FE-SEM) and absorptions of MnO{sub 2} bonding was characterized by Fourier Transform Infra-Red Spectrometer (FT-IR). Remazol reactive dye or Red 3BS, was used in the adsorption study using nanoporous amorphous-MnO{sub 2}. In batch experiment, 10 ppm of Remazol reactive dye was used and experiment was carried out at room temperature. Adsorption of Remazol dye on 0.2g synthesized nanoporous amorphous-MnO{sub 2} showed 99 – 100% decolorization.

  5. Endothelial Microparticle-Derived Reactive Oxygen Species: Role in Endothelial Signaling and Vascular Function

    PubMed Central

    Burger, Dylan; Turner, Maddison; Munkonda, Mercedes N.; Touyz, Rhian M.

    2016-01-01

    Endothelial microparticles are effectors of endothelial damage; however mechanisms involved are unclear. We examined the effects of eMPs on cultured endothelial cells (ECs) and isolated vessels and investigated the role of eMP-derived reactive oxygen species (ROS) and redox signaling in these processes. eMPs were isolated from EC media and their ability to directly produce ROS was assessed by lucigenin and liquid chromatography. Nicotinamide adenine dinucleotide phosphate oxidase (Nox) subunits were probed by Western blot. ECs were treated with eMPs and effects on kinase signaling, superoxide anion (O2∙−) generation, and nitric oxide (NO) production were examined. Acetylcholine-mediated vasorelaxation was assessed by myography in eMP-treated mesenteric arteries. eMPs contained Nox1, Nox2, Nox4, p47phox, p67phox, and p22phox and they produced ROS which was inhibited by the Nox inhibitor, apocynin. eMPs increased phosphorylation of ERK1/2 and Src, increased O2∙− production, and decreased A23187-induced NO production in ECs. Pretreatment of eMPs with apocynin diminished eMP-mediated effects on ROS and NO production but had no effect on eMP-mediated kinase activation or impairment in vasorelaxation. Our findings identify a novel mechanism whereby eMP-derived ROS contributes to MP bioactivity. These interactions may be important in conditions associated with vascular injury and increased eMP formation. PMID:27313830

  6. C-Reactive Protein: An In-Depth Look into Structure, Function, and Regulation

    PubMed Central

    Salazar, Juan; Martínez, María Sofía; Chávez-Castillo, Mervin; Núñez, Victoria; Añez, Roberto; Torres, Yaquelin; Toledo, Alexandra; Chacín, Maricarmen; Silva, Carlos; Pacheco, Enrique; Rojas, Joselyn; Bermúdez, Valmore

    2014-01-01

    Cardiovascular disease is the leading cause of morbidity and mortality in the adult population worldwide, with atherosclerosis being its key pathophysiologic component. Atherosclerosis possesses a fundamental chronic inflammatory aspect, and the involvement of numerous inflammatory molecules has been studied in this scenario, particularly C-reactive protein (CRP). CRP is a plasma protein with strong phylogenetic conservation and high resistance to proteolysis, predominantly synthesized in the liver in response to proinflammatory cytokines, especially IL-6, IL-1β, and TNF. CRP may intervene in atherosclerosis by directly activating the complement system and inducing apoptosis, vascular cell activation, monocyte recruitment, lipid accumulation, and thrombosis, among other actions. Moreover, CRP can dissociate in peripheral tissue—including atheromatous plaques—from its native pentameric form into a monomeric form, which may also be synthesized de novo in extrahepatic sites. Each form exhibits distinct affinities for ligands and receptors, and exerts different effects in the progression of atherosclerosis. In view of epidemiologic evidence associating high CRP levels with cardiovascular risk—reflecting the biologic impact it bears on atherosclerosis—measurement of serum levels of high-sensitivity CRP has been proposed as a tool for assessment of cardiovascular risk. PMID:27433484

  7. Endothelial Microparticle-Derived Reactive Oxygen Species: Role in Endothelial Signaling and Vascular Function.

    PubMed

    Burger, Dylan; Turner, Maddison; Munkonda, Mercedes N; Touyz, Rhian M

    2016-01-01

    Endothelial microparticles are effectors of endothelial damage; however mechanisms involved are unclear. We examined the effects of eMPs on cultured endothelial cells (ECs) and isolated vessels and investigated the role of eMP-derived reactive oxygen species (ROS) and redox signaling in these processes. eMPs were isolated from EC media and their ability to directly produce ROS was assessed by lucigenin and liquid chromatography. Nicotinamide adenine dinucleotide phosphate oxidase (Nox) subunits were probed by Western blot. ECs were treated with eMPs and effects on kinase signaling, superoxide anion (O2 (∙-)) generation, and nitric oxide (NO) production were examined. Acetylcholine-mediated vasorelaxation was assessed by myography in eMP-treated mesenteric arteries. eMPs contained Nox1, Nox2, Nox4, p47(phox), p67(phox), and p22(phox) and they produced ROS which was inhibited by the Nox inhibitor, apocynin. eMPs increased phosphorylation of ERK1/2 and Src, increased O2 (∙-) production, and decreased A23187-induced NO production in ECs. Pretreatment of eMPs with apocynin diminished eMP-mediated effects on ROS and NO production but had no effect on eMP-mediated kinase activation or impairment in vasorelaxation. Our findings identify a novel mechanism whereby eMP-derived ROS contributes to MP bioactivity. These interactions may be important in conditions associated with vascular injury and increased eMP formation. PMID:27313830

  8. Reactive-oxygen-species-mediated P. aeruginosa killing is functional in human cystic fibrosis macrophages.

    PubMed

    Cifani, Noemi; Pompili, Barbara; Anile, Marco; Patella, Miriam; Diso, Daniele; Venuta, Federico; Cimino, Giuseppe; Quattrucci, Serena; Di Domenico, Enea Gino; Ascenzioni, Fiorentina; Del Porto, Paola

    2013-01-01

    Pseudomonas aeruginosa is the most common pathogen for chronic lung infection in cystic fibrosis (CF) patients. About 80% of adult CF patients have chronic P. aeruginosa infection, which accounts for much of the morbidity and most of the mortality. Both bacterial genetic adaptations and defective innate immune responses contribute to the bacteria persistence. It is well accepted that CF transmembrane conductance regulator (CFTR) dysfunction impairs the airways-epithelium-mediated lung defence; however, other innate immune cells also appear to be affected, such as neutrophils and macrophages, which thus contribute to this infectious pathology in the CF lung. In macrophages, the absence of CFTR has been linked to defective P. aeruginosa killing, increased pro-inflammatory cytokine secretion, and reduced reactive oxygen species (ROS) production. To learn more about macrophage dysfunction in CF patients, we investigated the generation of the oxidative burst and its impact on bacterial killing in CF macrophages isolated from peripheral blood or lung parenchyma of CF patients, after P. aeruginosa infection. Our data demonstrate that CF macrophages show an oxidative response of similar intensity to that of non-CF macrophages. Intracellular ROS are recognized as one of the earliest microbicidal mechanisms against engulfed pathogens that are activated by macrophages. Accordingly, NADPH inhibition resulted in a significant increase in the intracellular bacteria survival in CF and non-CF macrophages, both as monocyte-derived macrophages and as lung macrophages. These data strongly suggest that the contribution of ROS to P. aeruginosa killing is not affected by CFTR mutations.

  9. Synthesis and reactivity of a conveniently prepared two-coordinate bis(amido) nickel(II) complex.

    PubMed

    Lipschutz, Michael I; Tilley, T Don

    2012-07-21

    A strictly two-coordinate nickel(II) bis(amido) complex has been prepared and its reactivity towards a variety of small molecules is described. Ni[N(SiMe(3))(DIPP)](2) reacts with DMAP and acetonitrile to form T-shaped three-coordinate complexes, and preliminary results show that Ni[N(SiMe(3))(DIPP)](2) is a catalyst for the hydrosilation of olefins with secondary silanes at ambient temperature.

  10. Boryl (Hetero)aryne Precursors as Versatile Arylation Reagents: Synthesis through C–H Activation and Orthogonal Reactivity

    PubMed Central

    Demory, Emilien; Devaraj, Karthik; Orthaber, Andreas; Gates, Paul J; Pilarski, Lukasz T

    2015-01-01

    (Pinacolato)boryl ortho-silyl(hetero)aryl triflates are presented as a new class of building blocks for arylation. They demonstrate unique versatility by delivering boronate or (hetero)aryne reactivity chemoselectively in a broad range of transformations. This approach enables the unprecedented postfunctionalization of fluoride-activated (hetero)aryne precursors, for example, as substrates in transition-metal catalysis, and offers valuable new possibilities for aryl boronate postfunctionalization without the use of specialized protecting groups. PMID:26270451

  11. Synthesis of Azide-Functionalized Hydroxyl-Terminated Polybutadiene

    NASA Astrophysics Data System (ADS)

    Shekhar Pant, Chandra; Santosh Mada, S. S. N. M.; Mehilal; Banerjee, Shaibal; Khanna, Pawan K.

    2016-10-01

    This article reports ways to functionalize hydroxyl-terminated polybutadiene (HTPB) by azide groups to impart energetic properties to the polymer. Two different synthetic approaches were explored to synthesize azide-functionalized hydroxyl-terminated polybutadiene (azide-HTPB). The functionalized polymer was analyzed for structural confirmation and determination of important physical and thermal properties. Azide-HTPB obtained by azidation of 10% double bonds of HTPB showed viscosity of 11 Pa.s and a glass transition temperature of -66°C.

  12. General Method for Functionalized Polyaryl Synthesis via Aryne Intermediates

    PubMed Central

    2015-01-01

    A method for base-promoted arylation of arenes and heterocycles by aryl halides and aryl triflates is described. Additionally, in situ electrophilic trapping of ArLi intermediates generated in the reaction of benzyne with deprotonated arenes or heterocycles has been developed, providing rapid and easy access to a wide range of highly functionalized polyaryls. Base-promoted arylation methodology complements transition-metal-catalyzed direct arylation and allows access to structures that are not easily accessible via other direct arylation methods. The reactions are highly functional-group tolerant, with alkene, ether, dimethylamino, trifluoromethyl, ester, cyano, halide, hydroxyl, and silyl functionalities compatible with reaction conditions. PMID:24893069

  13. Enhanced neuropeptide Y synthesis during intermittent hypoxia in the rat adrenal medulla: role of reactive oxygen species-dependent alterations in precursor peptide processing.

    PubMed

    Raghuraman, Gayatri; Kalari, Apeksha; Dhingra, Rishi; Prabhakar, Nanduri R; Kumar, Ganesh K

    2011-04-01

    Intermittent hypoxia (IH) associated with recurrent apneas often leads to cardiovascular abnormalities. Previously, we showed that IH treatment elevates blood pressure and increases plasma catecholamines (CAs) in rats via reactive oxygen species (ROS)-dependent enhanced synthesis and secretion from the adrenal medulla (AM). Neuropeptide Y (NPY), a sympathetic neurotransmitter that colocalizes with CA in the AM, has been implicated in blood pressure regulation during persistent stress. Here, we investigated whether IH facilitates NPY synthesis in the rat AM and assessed the role of ROS signaling. IH increased NPY-like immunoreactivity in many dopamine-β-hydroxylase-expressing chromaffin cells with a parallel increase in preproNPY mRNA and protein. IH increased the activities of proNPY-processing enzymes, which were due, in part, to elevated protein expression and increased proteolytic processing. IH increased ROS generation, and antioxidants reversed IH-induced increases in ROS, preproNPY, and its processing to bioactive NPY in the AM. IH treatment increased blood pressure and antioxidants and inhibition of NPY amidation prevented this response. These findings suggest that IH-induced elevation in NPY expression in the rat AM is mediated by ROS-dependent augmentation of preproNPY mRNA expression and proNPY-processing enzyme activities and contributes to IH-induced elevation of blood pressure.

  14. Functional Information: Towards Synthesis of Biosemiotics and Cybernetics

    PubMed Central

    Sharov, Alexei A.

    2012-01-01

    Biosemiotics and cybernetics are closely related, yet they are separated by the boundary between life and non-life: biosemiotics is focused on living organisms, whereas cybernetics is applied mostly to non-living artificial devices. However, both classes of systems are agents that perform functions necessary for reaching their goals. I propose to shift the focus of biosemiotics from living organisms to agents in general, which all belong to a pragmasphere or functional universe. Agents should be considered in the context of their hierarchy and origin because their semiosis can be inherited or induced by higher-level agents. To preserve and disseminate their functions, agents use functional information - a set of signs that encode and control their functions. It includes stable memory signs, transient messengers, and natural signs. The origin and evolution of functional information is discussed in terms of transitions between vegetative, animal, and social levels of semiosis, defined by Kull. Vegetative semiosis differs substantially from higher levels of semiosis, because signs are recognized and interpreted via direct code-based matching and are not associated with ideal representations of objects. Thus, I consider a separate classification of signs at the vegetative level that includes proto-icons, proto-indexes, and proto-symbols. Animal and social semiosis are based on classification, and modeling of objects, which represent the knowledge of agents about their body (Innenwelt) and environment (Umwelt). PMID:22368439

  15. Functional Information: Towards Synthesis of Biosemiotics and Cybernetics.

    PubMed

    Sharov, Alexei A

    2010-04-27

    Biosemiotics and cybernetics are closely related, yet they are separated by the boundary between life and non-life: biosemiotics is focused on living organisms, whereas cybernetics is applied mostly to non-living artificial devices. However, both classes of systems are agents that perform functions necessary for reaching their goals. I propose to shift the focus of biosemiotics from living organisms to agents in general, which all belong to a pragmasphere or functional universe. Agents should be considered in the context of their hierarchy and origin because their semiosis can be inherited or induced by higher-level agents. To preserve and disseminate their functions, agents use functional information - a set of signs that encode and control their functions. It includes stable memory signs, transient messengers, and natural signs. The origin and evolution of functional information is discussed in terms of transitions between vegetative, animal, and social levels of semiosis, defined by Kull. Vegetative semiosis differs substantially from higher levels of semiosis, because signs are recognized and interpreted via direct code-based matching and are not associated with ideal representations of objects. Thus, I consider a separate classification of signs at the vegetative level that includes proto-icons, proto-indexes, and proto-symbols. Animal and social semiosis are based on classification, and modeling of objects, which represent the knowledge of agents about their body (Innenwelt) and environment (Umwelt).

  16. Reactivity of Heteropolytungstate and Heteropolymolybdate Metal Transition Salts in the Synthesis of Dimethyl Carbonate from Methanol and CO2

    PubMed Central

    Aouissi, Ahmed; Al-Deyab, Salem S.; Al-Owais, Ahmad; Al-Amro, Amro

    2010-01-01

    A series of Keggin-type heteropoly compounds (HPC) having different countercations (Co, Fe) and different addenda atoms (W, Mo) were synthesized and characterized by means of Fourier-Transform Infrared Spectrometer (FT-IR) and X-ray powder diffraction (XRD). The catalytic properties of the prepared catalysts for the dimethyl carbonate (DMC) synthesis from CO2 and CH3OH were investigated. The experimental results showed that the catalytic activity is significantly influenced by the type of the countercation and addenda atoms transition metal. Among the catalysts examined, Co1.5PW12O40 is the most active for the DMC synthesis, owing to the synergetic effect between Co and W. Investigating the effect of the support showed that the least acidic one (Al2O3) enhanced the conversion but decreased the DMC selectivity in favor of that of methyl formate (MF), while that of dimethoxy methane remained stable. PMID:20717536

  17. Aqueous synthesis of Cu-doped ZnCdS/ZnS core/shell nanocrystals with a new and highly reactive sulfur source.

    PubMed

    Zeng, Ruosheng; Shen, Rongan; Zhao, Yunqiang; Li, Xingsheng; Sun, Zhiguo; Shen, Yayun

    2014-04-01

    A new sulfur precursor with a highly reactive chemical nature was prepared with S powder and NaBH₄ at the high temperature of 180 °C in a closed autoclave and made it possible to carry out the synthesis of high quality metal sulfide nanocrystals (NCs) with diverse composition and structure. Using this new sulfur source, we demonstrated aqueous synthesis of colloidal Cu-doped ZnCdS NCs (d-dots) with pure, color-tunable photoluminescence (PL) in a wide spectral range (from 517 to 650 nm) based on the 'co-nucleation doping' strategy. The influences of the various experimental variables, including Cd/Zn ratio, Cu-doping concentration, pH value and amount of mercaptopropionic acid (MPA), on the optical properties of Cu-doped ZnCdS NCs were systematically investigated. Furthermore, highly efficient and stable dopant emission from Cu:ZnCdS/ZnS core/shell d-dots with PL quantum yield as high as 40% was achieved by the deposition of a ZnS shell around the bare Cu:ZnCdS cores; this is the highest reported to date for aqueous doped NCs. The optical properties and structure of the d-dots were characterized by UV-vis absorption spectra, PL spectra, x-ray photoelectron spectroscopy, powder x-ray diffraction, and transmission electron microscopy. The experimental results indicated that this facile synthesis route would provide a versatile approach for the preparation of other water-soluble sulfide NCs. PMID:24583650

  18. Aqueous synthesis of Cu-doped ZnCdS/ZnS core/shell nanocrystals with a new and highly reactive sulfur source

    NASA Astrophysics Data System (ADS)

    Zeng, Ruosheng; Shen, Rongan; Zhao, Yunqiang; Li, Xingsheng; Sun, Zhiguo; Shen, Yayun

    2014-04-01

    A new sulfur precursor with a highly reactive chemical nature was prepared with S powder and NaBH4 at the high temperature of 180 °C in a closed autoclave and made it possible to carry out the synthesis of high quality metal sulfide nanocrystals (NCs) with diverse composition and structure. Using this new sulfur source, we demonstrated aqueous synthesis of colloidal Cu-doped ZnCdS NCs (d-dots) with pure, color-tunable photoluminescence (PL) in a wide spectral range (from 517 to 650 nm) based on the ‘co-nucleation doping’ strategy. The influences of the various experimental variables, including Cd/Zn ratio, Cu-doping concentration, pH value and amount of mercaptopropionic acid (MPA), on the optical properties of Cu-doped ZnCdS NCs were systematically investigated. Furthermore, highly efficient and stable dopant emission from Cu:ZnCdS/ZnS core/shell d-dots with PL quantum yield as high as 40% was achieved by the deposition of a ZnS shell around the bare Cu:ZnCdS cores; this is the highest reported to date for aqueous doped NCs. The optical properties and structure of the d-dots were characterized by UV-vis absorption spectra, PL spectra, x-ray photoelectron spectroscopy, powder x-ray diffraction, and transmission electron microscopy. The experimental results indicated that this facile synthesis route would provide a versatile approach for the preparation of other water-soluble sulfide NCs.

  19. Azide-Reactive Liposome for Chemoselective and Biocompatible Liposomal Surface Functionalization and Glyco-Liposomal Microarray Fabrication

    PubMed Central

    Ma, Yong; Zhang, Hailong; Gruzdys, Valentinas; Sun, Xue-Long

    2011-01-01

    A chemically selective liposomal surface functionalization and liposomal microarray fabrication using azide-reactive liposome are described. First, liposome carrying PEG-triphenylphosphine was prepared for Staudinger ligation with azide-containing biotin, which was conducted in PBS buffer (pH 7.4) at room temperature without catalyst. Then, immobilization and microarray fabrication of the biotinylated liposome onto streptavidin-modified glass slide via specific streptavidin/biotin interaction were investigated by comparing with direct-formed biotin-liposome, which was prepared by conventional liposome formulation of lipid-biotin with all other lipid components. Next, covalent microarray fabrication of liposome carrying triphenylphosphine onto an azide-modified glass slide and its further glyco-modification with azide-containing carbohydrate were demonstrated for glyco-liposomal microarray fabrication via Staudinger ligation. Fluorescence imaging confirmed the successful immobilization and protein binding of the intact immobilized liposomes and arrayed glyco-liposomes. The azide-reactive liposome provides a facile strategy for a membrane-mimetic glycoarray fabrication, which may find important biological and biomedical applications such as studying carbohydrate-protein interaction and toxin and antibody screening. PMID:21928859

  20. [Covalent chloramine inhibitors of blood platelet functions: computational indices for their reactivity and antiplatelet activity].

    PubMed

    Roshchupkin, D I; Murina, M A; Sergienko, V I

    2011-01-01

    The quantum mechanics computation of the reactivities of chloramine derivatives of amino acids and taurine has been accomplished. A pair of computational indices that reflect a predisposition of alpha amino acid chloramines to chemical decay have been revealed. One of the indices was the dihedral angle for the chain of four atoms: carbons at beta- and alpha-positions, carbon of the carboxyl group, and carbonyl oxygen. The second index was the sum of partial charges for three or two carbon atoms in the chain. The amino acid chloramines with high values of the indices showed enhanced stability. Partial charges for active chlorine in known chloramines having different structures have been computed. The charges correlate with the rate constants of the reaction between chloramines and the thiol group of reduced glutathione. New derivatives of taurine chloramines have been constructed via the introduction of different substituents into the chloramine part. Among them, the amidoderivatives had the greatest charges of active chlorine (0.19-0.23). It was found in the study of the reactions of N-acetyl-N-chlorotaurine and N-propyonyl-N-chlorotaurine with amino acids and peptides possessing the thiol, thioester, or disulphide groups that the amidoderivatives manifested the thiol chemoselectivity. N-Acetyl-N-chlorotaurine and N-propionyl-N-chlorotaurine suppress the aggregation activity of blood platelets under their activation by the agonists ADP and collagen. It is not excluded that the amidoderivatives studied prevent platelet aggregation by a modification of the critical thiol group in the purine receptor P2Y12. PMID:22117450

  1. The composite nodule. A structural and functional unit of the reactive human lymph node.

    PubMed Central

    van den Oord, J. J.; de Wolf-Peeters, C.; Desmet, V. J.

    1986-01-01

    The relationship between T nodules and adjacent B-lymphoid follicles was investigated in 37 reactive lymph nodes by light microscopy and combined enzyme immunohistochemistry. In 16 cases (43%), T nodules and adjacent B-lymphoid follicles were unified in an ovoid, distinct nodular structure termed a "composite nodule." The composite nodule comprises two separate domains. The peripheral, subcapsular B domain contains all stationary and migratory elements of the B-lymphoid follicle, ie, B1+ B-cells, OKT4+, Leu 3a+ helper/inducer T cells, HLA-DR+ dendritic reticulum cells, and ANAE+, AcPhase+ tangible body macrophages and is surrounded by a B1+, HLA-DR+ lymphocytic corona displaying focal adenosine triphosphatase (ATPase) and alkaline phosphatase (AlkPhase) activity. The deep, paracortical T-domain contains all elements of the T nodule, ie, OKT4+, Leu3a+ helper/inducer T cells, high endothelial venules and HLA-DR+, ATPase+ interdigitating reticulum cells. The composite nodule is surrounded by a rim of ATPase+, AlkPhase+ high endothelial venules. Both domains are subject to changes in volume; thus, in follicular hyperplasia, the B domain enlarges at the cost of the T domain, and the reverse may occur in T-zone hyperplasia. Based on the striking resemblance between the composite nodule and the white pulp of the spleen, it is suggested that the composite nodule plays a major role in the triggering, helper-T-cell-dependent stimulation and subsequent maturation of antigen-responsive B cells into antibody-secreting plasma cells. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:2934988

  2. Effect of Obesity on Acute Ozone-Induced Changes in Airway Function, Reactivity, and Inflammation in Adult Females

    PubMed Central

    Bennett, William D.; Ivins, Sally; Alexis, Neil E.; Wu, Jihong; Bromberg, Philip A.; Brar, Sukhdev S.; Travlos, Gregory; London, Stephanie J.

    2016-01-01

    We previously observed greater ozone-induced lung function decrements in obese than non-obese women. Animal models suggest that obesity enhances ozone-induced airway reactivity and inflammation. In a controlled exposure study, we compared the acute effect of randomized 0.4ppm ozone and air exposures (2 h with intermittent light exercise) in obese (N = 20) (30reactivity to inhaled methacholine (3h post-exposure). Inflammation and obesity markers were assessed in the blood (pre, 4h post, and 20h post exposures) and induced-sputum (4h post-exposures and on 24h pre-exposure training day, no exercise): measures of C reactive protein (CRP) (blood only), leptin (blood only), adiponectin, interleukins IL-6, IL-1b, and IL-8, and tumor necrosis factor alpha, and sputum cell differential cell counts. The pre- to post-exposure decrease in forced vital capacity after ozone (adjusted for the change after air exposure) was significantly greater in the obese group (12.5+/-7.5 vs. 8.0+/-5.8%, p<0.05). Post ozone exposure, 6 obese and 6 non-obese subjects responded to methacholine at ≤ 10mg/ml (the maximum dose); the degree of hyperresponsiveness was similar for the two groups. Both BMI groups showed similar and significant ozone-induced increases in sputum neutrophils. Plasma IL-6 was increased by exercise (4 hr post air exposure vs. pre) only in the obese but returned to pre-air exposure levels at 20hr post-exposure. Plasma IL-6 was significantly increased at 4hr post ozone exposure in both groups and returned to pre-exposure levels by 20h post-exposure. These results confirm our previous findings of greater post-ozone spirometric decrements in obese young women. However, acute ozone-induced airway reactivity to methacholine and airway inflammation did not differ by obesity at the exposure and exercise levels used. PMID:27513854

  3. Effect of Obesity on Acute Ozone-Induced Changes in Airway Function, Reactivity, and Inflammation in Adult Females.

    PubMed

    Bennett, William D; Ivins, Sally; Alexis, Neil E; Wu, Jihong; Bromberg, Philip A; Brar, Sukhdev S; Travlos, Gregory; London, Stephanie J

    2016-01-01

    We previously observed greater ozone-induced lung function decrements in obese than non-obese women. Animal models suggest that obesity enhances ozone-induced airway reactivity and inflammation. In a controlled exposure study, we compared the acute effect of randomized 0.4ppm ozone and air exposures (2 h with intermittent light exercise) in obese (N = 20) (30reactivity to inhaled methacholine (3h post-exposure). Inflammation and obesity markers were assessed in the blood (pre, 4h post, and 20h post exposures) and induced-sputum (4h post-exposures and on 24h pre-exposure training day, no exercise): measures of C reactive protein (CRP) (blood only), leptin (blood only), adiponectin, interleukins IL-6, IL-1b, and IL-8, and tumor necrosis factor alpha, and sputum cell differential cell counts. The pre- to post-exposure decrease in forced vital capacity after ozone (adjusted for the change after air exposure) was significantly greater in the obese group (12.5+/-7.5 vs. 8.0+/-5.8%, p<0.05). Post ozone exposure, 6 obese and 6 non-obese subjects responded to methacholine at ≤ 10mg/ml (the maximum dose); the degree of hyperresponsiveness was similar for the two groups. Both BMI groups showed similar and significant ozone-induced increases in sputum neutrophils. Plasma IL-6 was increased by exercise (4 hr post air exposure vs. pre) only in the obese but returned to pre-air exposure levels at 20hr post-exposure. Plasma IL-6 was significantly increased at 4hr post ozone exposure in both groups and returned to pre-exposure levels by 20h post-exposure. These results confirm our previous findings of greater post-ozone spirometric decrements in obese young women. However, acute ozone-induced airway reactivity to methacholine and airway inflammation did not differ by obesity at the exposure and exercise levels used. PMID:27513854

  4. Dichlorocarbene-Functionalized Fluorographene: Synthesis and Reaction Mechanism.

    PubMed

    Lazar, Petr; Chua, Chun Kiang; Holá, Kateřina; Zbořil, Radek; Otyepka, Michal; Pumera, Martin

    2015-08-01

    Halogen functionalization of graphene is an important branch of graphene research as it provides opportunities to tailor the band gap and catalytic properties of graphene. Monovalent C-X bond obviates pitfalls of functionalization with atoms of groups 13, 15, and 16, which can introduce various poorly defined groups. Here, the preparation of functionalized graphene containing both fluorine and chlorine atoms is shown. The starting material, fluorographite, undergoes a reaction with dichlorocarbene to provide dichlorocarbene-functionalized fluorographene (DCC-FG). The material is characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy with X-ray dispersive spectroscopy. It is found that the chlorine atoms in DCC-FG are distributed homogeneously over the entire area of the fluorographene sheet. Further density functional theory calculations show that the mechanism of dichlorocarbene attack on fluorographene sheet is a two-step process. Dichlorocarbene detaches fluorine atoms from fluorographene sheet and subsequently adds to the newly formed sp(2) carbons. Halogenated graphene consisting of two (or eventually three) types of halogen atoms is envisioned to find its way as new graphene materials with tailored properties.

  5. Production and characterization of thermoplastic cassava starch, functionalized poly(lactic acid), and their reactive compatibilized blends

    NASA Astrophysics Data System (ADS)

    Detyothin, Sukeewan

    Cassava starch was blended with glycerol using a co-rotating twin-screw extruder (TSE). Thermoplastic cassava starch (TPCS) at a ratio of 70/30 by weight of cassava/glycerol was selected and further blended with other polymers. TPCS sheets made from compression molding had low tensile strength (0.45 +/- 0.05 MPa) and Young's modulus (1.24 +/- 0.58 MPa), but moderate elongation at break (83.0 +/- 0.18.6%), medium level of oxygen permeability, and high water vapor permeability with a very high rate of water absorption. TPCS was blended with poly(lactic acid) (PLA) at various ratios by using a TSE. The blend resins exhibited good properties such as increased thermal stability (Tmax) and crystallinity of PLA, and improved water sensitivity and processability of TPCS. PLA and TPCS exhibited a high interfacial tension between the two phases of 7.9 mJ·m -2, indicating the formation of an incompatible, immiscible blend. SEM micrographs showed a non-homogeneous distribution of TPCS droplets in the PLA continuous phase. TEM micrographs of the blend films made by cast-film extrusion showed coalescence of the TPCS droplets in the PLA continuous phase of the blend, indicating that the compatibility between the polymer pair needs to be improved. A response surface methodology (RSM) design was used to analyze the effects of maleic anhydride (MA) and 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (Luperox or L101) contents, and TSE screw speed on the degree of grafted MA and number average molecular weight (Mn) of functionalized PLA (PLA-g-MA), a reactive compatibilizer. PLA-g- MA made by reactive extrusion had an array of colors depending on the content of L101 and MA used. New FTIR peaks suggested that MA was grafted onto the PLA backbone and oligomeric MA may occur. Increasing L101 increased the degree of grafting and decreased Mn, but the Mn of the PLA-g-MA's produced with a high amount of L101 was stable during storage. MA exhibited an optimum concentration for maximizing the

  6. Synthesis of nanoparticle-cored dendrimers by convergent dendritic functionalization of monolayer-protected nanoparticles.

    PubMed

    Shon, Young-Seok; Choi, Daeock; Dare, Jonathan; Dinh, Tuong

    2008-06-01

    This article presents a synthesis method for nanoparticle-cored dendrimers (NCDs), which have dendritic architectures around a monolayer-protected gold nanoparticle. The synthesis method is based on a strategy in which the synthesis of monolayer-protected nanoparticles is followed by adding dendrons on functionalized nanoparticles by a single coupling reaction. NMR spectroscopy, IR spectroscopy, and thermogravimetric analysis (TGA) characterizations confirmed the successful coupling reaction between dendrons with different generations ([G1], [G2], and [G3]) and COOH-functionalized nanoparticles ( approximately Au201L71). The dendrimer wedge density also could be controlled by reacting nanoparticles having different loading of COOH groups ( approximately 60 and approximately 10% COOH of the 71 ligands per gold nanoparticle) with functionalized dendrons. Transmission electron microscope results showed that this synthesis strategy maintains the average size of the nanoparticle core during dendron coupling reactions. This control over the composition and core size makes the systematic study of NCDs with different generations possible. The chemical stability of NCDs was found to be affected by dendron generation around the nanoparticle core. The current-potential response of NCD films on microelectrode arrays exhibited better electrical conductivity for NCDs with lower dendron generation.

  7. One pot synthesis of Curcumin-NSAIDs prodrug, spectroscopic characterization, conformational analysis, chemical reactivity, intramolecular interactions and first order hyperpolarizability by DFT method

    NASA Astrophysics Data System (ADS)

    Srivastava, Sangeeta; Gupta, Preeti; Sethi, Arun; Singh, Ranvijay Pratap

    2016-08-01

    A novel Curcumin-NSAIDs prodrug 4-((1E, 3Z, 6E)-3-hydroxy-(4-hydroxy-3-methoxyphenyl)-5-oxohepta-1,3,3-trienyl)-2-methoxyphenyl-2-(4-isobutylphenyl) propanoate (2) derivative was synthesized by Steglich esterification in high yield and characterized with the help of 1H, 13C NMR, 1H-1H COSY, UV, FT-IR spectroscopy and mass spectrometry. The molecular geometry of synthesized compound was calculated in ground state by Density functional theory (DFT/B3LYP) using two different basis set 6-31G (d, p) and 6-311G (d, p). Conformational analysis of 2 was carried out to determine the most stable conformation. Stability of the molecule as a result of hyperconjugative interactions and electron delocalization were analysed using Natural bond orbital (NBO) analysis. Intramolecular interactions were analysed by AIM (Atom in molecule) approach. Global and local reactivity descriptors were calculated to study the reactive site within molecule. The electronic properties such as HOMO and LUMO energies were calculated using time dependent Density Functional Theory (TD-DFT). The vibrational wavenumbers were calculated using DFT method and assigned with the help of potential energy distribution (PED). First hyperpolarizability value has been calculated to describe the nonlinear optical (NLO) property of the synthesized compound. Molecular electrostatic potential (MEP) for synthesized compounds have also been determined to check their electrophilic or nucleophilic reactivity.

  8. Instrumental and Reactive Functions and Overt and Relational Forms of Aggression: Developmental Trajectories and Prospective Associations during Middle School

    ERIC Educational Resources Information Center

    Ojanen, Tiina; Kiefer, Sarah

    2013-01-01

    This study examined the development of adolescent self-reported instrumental-overt, instrumental-relational, reactive-overt, and reactive-relational aggression during middle school ("N" = 384; 12-14 years; 53% boys). Growth modeling indicated average increases in instrumental-relational aggression, and decreases in reactive-overt and…

  9. Fischer-Tropsch synthesis on functionalized carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Pokhrel, Sewa

    The aim of this research was to investigate the role of chemical functionalization on carbon nanotubes surfaces and its effect on FT catalysis. Multi walled carbon nanotubes (MWNT) were first treated with acid (HCl) to remove the residual metal particles and were then functionalized using H2O2 and HNO3 to introduce oxygen-containing groups to the MWNT surface. These treatments also add defects on MWNT surface. Morphological analyses were performed on the MWNT samples with TEM and it was found that the peroxide and acid treated MWNTs showed an increase oxygen functional groups and created additional surface defects on the MWNTs. Results of FT experiments showed enhanced CO conversion, FT activity and product selectivity towards liquid hydrocarbons due to functionalization. The liquid selectivity was found to be significantly high for H2O 2 treated catalyst. HNO3 treated catalyst had highest activity although selectivity to methane and CO2 was found higher than the H2O2 treated catalyst. It was observed that the chemical treatments increase the carbon chain length of the produced hydrocarbons. While comparing hydrocarbon distribution of as-produced and H2O2 treated MWNT, it was found that carbon-chain length increases for peroxide treated catalyst. Along with as-produced and functionalized nanotube, FT experiments were also conducted using B-doped sponge, un-doped sponge and N-doped CNT catalyst. B-doped sponge showed enhanced CO conversion and FT activity as compared to un-doped sponge. Conversion and product selectivity were found to be affected by temperature when test was conducted with N-CNT. Operating conditions like temperature, syngas feed flow rate and syngas ratio were also to impact the FT performance.

  10. Gas-Phase Reactivity of Carboxylic Acid Functional Groups with Carbodiimides

    PubMed Central

    Prentice, Boone M.; Gilbert, Joshua D.; Stutzman, John R.; Forrest, William P.; McLuckey, Scott A.

    2012-01-01

    Gas-phase modification of carboxylic acid functionalities is performed via ion/ion reactions with carbodiimide reagents [N-cyclohexyl-N′-(2-morpholinoethyl)carbodiimide (CMC) and [3-(3-Ethylcarbodiimide-1-yl)propyl]trimethylaminium (ECPT). Gas-phase ion/ion covalent chemistry requires the formation of a long-lived complex. In this instance, the complex is stabilized by an electrostatic interaction between the fixed charge quaternary ammonium group of the carbodiimide reagent cation and the analyte dianion. Subsequent activation results in characteristic loss of an isocyanate derivative from one side of the carbodiimide functionality, a signature for this covalent chemistry. The resulting amide bond is formed on the analyte at the site of the original carboxylic acid. Reactions involving analytes that do not contain available carboxylic acid groups (e.g., they have been converted to sodium salts) or reagents that do not have the carbodiimide functionality do not undergo a covalent reaction. This chemistry is demonstrated using PAMAM generation 0.5 dendrimer, ethylenediaminetetraacetic acid (EDTA), and the model peptide DGAILDGAILD. This work demonstrates the selective gas-phase covalent modification of carboxylic acid functionalities. PMID:23208744

  11. Synthesis, characterization and application of functional carbon nano materials

    NASA Astrophysics Data System (ADS)

    Chu, Jin

    The synthesis, characterizations and applications of carbon nanomaterials, including carbon nanorods, carbon nanosheets, carbon nanohoneycombs and carbon nanotubes were demonstrated. Different growth techniques such as pulsed laser deposition, DC/RF sputtering, hot filament physical vapour deposition, evaporative casting and vacuum filtration methods were introduced or applied for synthesizing carbon nanomaterials. The morphology, chemical compositions, bond structures, electronic, mechanical and sensing properties of the obtained samples were investigated. Tilted well-aligned carbon micro- and nano- hybrid rods were fabricated on Si at different substrate temperatures and incident angles of carbon source beam using the hot filament physical vapour deposition technique. The morphologic surfaces and bond structures of the oblique carbon rod-like structures were investigated by scanning electron microscopy, field emission scanning electron microscopy, transmission electron diffraction and Raman scattering spectroscopy. The field emission behaviour of the fabricated samples was also tested. Carbon nanosheets and nanohoneycombs were also synthesized on Si substrates using a hot filament physical vapor deposition technique under methane ambient and vacuum, respectively. The four-point Au electrodes are then sputtered on the surface of the nanostructured carbon films to form prototypical humidity sensors. The sensing properties of prototypical sensors at different temperature, humidity, direct current, and alternative current voltage were characterized. Linear sensing response of sensors to relative humidity ranging from 11% to 95% is observed at room temperature. Experimental data indicate that the carbon nanosheets based sensors exhibit an excellent reversible behavior and long-term stability. It also has higher response than that of the humidity sensor with carbon nanohoneycombs materials. Conducting composite films containing carbon nanotubes (CNTs) were prepared in

  12. A XAFS study of the local environment and reactivity of Pt- sites in functionalized UiO-67 MOFs

    NASA Astrophysics Data System (ADS)

    Borfecchia, E.; Øien, S.; Svelle, S.; Mino, L.; Braglia, L.; Agostini, G.; Gallo, E.; Lomachenko, K. A.; Bordiga, S.; Guda, A. A.; Soldatov, M. A.; Soldatov, A. V.; Olsbye, U.; Lillerud, K. P.; Lamberti, C.

    2016-05-01

    We synthesized UiO-67 Metal Organic Frameworks (MOFs) functionalized with bpydcPt(II)Cl2 and bpydcPt(IV)Cl4 complexes (bpydc = bipyridine-dicarboxylate), as attractive candidates for the heterogenization of homogeneous catalytic reactions. Pt L3-edge XAFS experiments allowed us to thoroughly characterize these materials, in the local environment of the Pt centers. XAFS studies evidenced the rich reactivity of UiO-67-Pt(II) MOFs, including reduction to bpydcPt(0) under H2 flow in the 600-700 K range, room-temperature oxidation to bpydcPt(IV)Br4 through oxidative addition of liquid Br2 and ligand exchange between 2 Cl- and even bulky ligands such as toluene-3,4-dithiol. Preliminary XANES simulations with ADF code provide additional information on the oxidation state of Pt sites.

  13. Patterns of Sensitivity to Emotion in Children with Williams Syndrome and Autism: Relations between Autonomic Nervous System Reactivity and Social Functioning

    ERIC Educational Resources Information Center

    Järvinen, Anna; Ng, Rowena; Crivelli, Davide; Neumann, Dirk; Grichanik, Mark; Arnold, Andrew J.; Lai, Philip; Trauner, Doris; Bellugi, Ursula

    2015-01-01

    Williams syndrome (WS) and autism spectrum disorder (ASD) are associated with atypical social-emotional functioning. Affective visual stimuli were used to assess autonomic reactivity and emotion identification, and the social responsiveness scale was used to determine the level social functioning in children with WS and ASD contrasted with typical…

  14. Selecting for Function: Solution Synthesis of Magnetic Nanopropellers

    PubMed Central

    2013-01-01

    We show that we can select magnetically steerable nanopropellers from a set of carbon coated aggregates of magnetic nanoparticles using weak homogeneous rotating magnetic fields. The carbon coating can be functionalized, enabling a wide range of applications. Despite their arbitrary shape, all nanostructures propel parallel to the vector of rotation of the magnetic field. We use a simple theoretical model to find experimental conditions to select nanopropellers which are predominantly smaller than previously published ones. PMID:24127909

  15. Fluoroalkyl-functionalized silica particles: synthesis, characterization, and wetting characteristics.

    PubMed

    Campos, Raymond; Guenthner, Andrew J; Haddad, Timothy S; Mabry, Joseph M

    2011-08-16

    Fluoroalkyl-functionalized silica particles for use in nonwetting surfaces were prepared by treatment of silica particles with fluoroalkyl-functional chlorosilanes. Both fumed and precipitated silica were studied, as well as the efficiency of surface coverage using mono-, di-, and trifunctional chlorosilanes. The most effective surface treatment was accomplished via the surface grafting of monofunctional chlorosilanes in the presence of preadsorbed dimethylamine under anhydrous conditions at room temperature. Confirmation of covalent attachment was accomplished via Fourier transform infrared (FT-IR) spectroscopy, while elemental analysis, thermogravimetric analysis, and nitrogen adsorption isotherms were used to determine grafting densities and additional key geometric characteristics of the grafted layer. The effect of residual silanol content on the moisture uptake properties of the modified silica particles was determined by measuring the water uptake of unbound particles, while liquid wetting properties were determined by dynamic contact angle analysis of elastomeric composites. Although residual silanol content was shown to effect wetting properties, results suggest that surface geometry dominates the performance of liquid-repellent surfaces. The potential use of fluoroalkyl-functionalized silica particles for hydrophobic and oleophobic applications is discussed. PMID:21728328

  16. Fluoroalkyl-functionalized silica particles: synthesis, characterization, and wetting characteristics.

    PubMed

    Campos, Raymond; Guenthner, Andrew J; Haddad, Timothy S; Mabry, Joseph M

    2011-08-16

    Fluoroalkyl-functionalized silica particles for use in nonwetting surfaces were prepared by treatment of silica particles with fluoroalkyl-functional chlorosilanes. Both fumed and precipitated silica were studied, as well as the efficiency of surface coverage using mono-, di-, and trifunctional chlorosilanes. The most effective surface treatment was accomplished via the surface grafting of monofunctional chlorosilanes in the presence of preadsorbed dimethylamine under anhydrous conditions at room temperature. Confirmation of covalent attachment was accomplished via Fourier transform infrared (FT-IR) spectroscopy, while elemental analysis, thermogravimetric analysis, and nitrogen adsorption isotherms were used to determine grafting densities and additional key geometric characteristics of the grafted layer. The effect of residual silanol content on the moisture uptake properties of the modified silica particles was determined by measuring the water uptake of unbound particles, while liquid wetting properties were determined by dynamic contact angle analysis of elastomeric composites. Although residual silanol content was shown to effect wetting properties, results suggest that surface geometry dominates the performance of liquid-repellent surfaces. The potential use of fluoroalkyl-functionalized silica particles for hydrophobic and oleophobic applications is discussed.

  17. Synthesis of an Al{sub 2}O{sub 3}/Al co-continuous composite by reactive melt infiltration

    SciTech Connect

    Wu, C.M.L. . E-mail: Lawrence.Wu@cityu.edu.hk; Han, G.W.

    2007-05-15

    The route for the fabrication of an Al{sub 2}O{sub 3}/Al co-continuous composite by reactive melt infiltration was investigated using scanning electron microscopy, energy dispersive X-ray microanalysis and X-ray diffraction analysis. It was found that in the process of molten aluminium infiltration into the SiO{sub 2} preform, the chemical reaction of 3SiO{sub 2} + 4Al {sup {yields}} 2Al{sub 2}O{sub 3} + 3Si occurred at the infiltration front, and generated a transition zone containing a new type of continuous porosity about 100 {mu}m in width. The reaction continued with further infiltration of molten aluminium alloy into this porosity which reacted with the residual SiO{sub 2} until all the SiO{sub 2} was transformed into Al{sub 2}O{sub 3}. A comparison was made between this route and that by direct infiltration of molten aluminium alloy into the open porosity of an Al{sub 2}O{sub 3} preform. As a result of the increased wetting ability of the molten aluminium alloy by the chemical reaction, reactive melt infiltration took place at a higher rate for the SiO{sub 2} preform than that for the direct infiltration of the Al{sub 2}O{sub 3} preform. A fracture surface examination demonstrated a toughening effect provided by the continuous aluminium alloy in the composite.

  18. Ligand redox effects in the synthesis, electronic structure, and reactivity of an alkyl-alkyl cross-coupling catalyst.

    PubMed

    Jones, Gavin D; Martin, Jason L; McFarland, Chris; Allen, Olivia R; Hall, Ryan E; Haley, Aireal D; Brandon, R Jacob; Konovalova, Tatyana; Desrochers, Patrick J; Pulay, Peter; Vicic, David A

    2006-10-11

    The ability of the terpyridine ligand to stabilize alkyl complexes of nickel has been central in obtaining a fundamental understanding of the key processes involved in alkyl-alkyl cross-coupling reactions. Here, mechanistic studies using isotopically labeled (TMEDA)NiMe(2) (TMEDA = N,N,N',N'-tetramethylethylenediamine) have shown that an important catalyst in alkyl-alkyl cross-coupling reactions, (tpy')NiMe (2b, tpy' = 4,4',4' '-tri-tert-butylterpyridine), is not produced via a mechanism that involves the formation of methyl radicals. Instead, it is proposed that (terpyridine)NiMe complexes arise via a comproportionation reaction between a Ni(II)-dimethyl species and a Ni(0) fragment in solution upon addition of a terpyridine ligand to (TMEDA)NiMe(2). EPR and DFT studies on the paramagnetic (terpyridine)NiMe (2a) both suggest that the unpaired electron resides heavily on the terpyridine ligand and that the proper electronic description of this nickel complex is a Ni(II)-methyl cation bound to a reduced terpyridine ligand. Thus, an important consequence of these results is that alkyl halide reduction by (terpyridine)NiR(alkyl) complexes appears to be substantially ligand based. A comprehensive survey investigating the catalytic reactivity of related ligand derivatives suggests that electronic factors only moderately influence reactivity in the terpyridine-based catalysis and that the most dramatic effects arise from steric and solubility factors.

  19. Synthesis and Reactivity of Low-Coordinate Titanium Synthons Supported by a Reduced Redox-Active Ligand.

    PubMed

    Clark, Kensha Marie

    2016-07-01

    To further explore the reactivity and redox capability of the bis-arylimino acenaphthylene ligand (BIAN) in early transition metal complexes, the coordinatively unsaturated titanium synthons, [(dpp-BAAN)Ti(R)2] ([dpp-BAAN](2-) = N,N'-bis(2,6-diisopropylphenylamido)acenaphthylene and R = O(t)Bu (2) or CH2C(CH3)3 (3)), in which the BAAN ligand is reduced by two electrons, were isolated in good yields via sterically induced radical elimination reactions. Addition of p-tolyl azide to complex 3 initiated reductive elimination of the neopentyl ligands to generate a putative imido species. The imido species was trapped by a second oxidative addition of chloride ligands to yield the titanium imido complex, [(dpp-BIAN)Ti[═N(4-C6H4Me)]Cl2 (4). These reactions demonstrate that the BAAN ligand can provide redox equivalents for enhanced reactivity that includes oxidative addition and reductive elimination at d(0) metal centers. PMID:27304996

  20. Synthesis and Reactivity of Low-Coordinate Titanium Synthons Supported by a Reduced Redox-Active Ligand.

    PubMed

    Clark, Kensha Marie

    2016-07-01

    To further explore the reactivity and redox capability of the bis-arylimino acenaphthylene ligand (BIAN) in early transition metal complexes, the coordinatively unsaturated titanium synthons, [(dpp-BAAN)Ti(R)2] ([dpp-BAAN](2-) = N,N'-bis(2,6-diisopropylphenylamido)acenaphthylene and R = O(t)Bu (2) or CH2C(CH3)3 (3)), in which the BAAN ligand is reduced by two electrons, were isolated in good yields via sterically induced radical elimination reactions. Addition of p-tolyl azide to complex 3 initiated reductive elimination of the neopentyl ligands to generate a putative imido species. The imido species was trapped by a second oxidative addition of chloride ligands to yield the titanium imido complex, [(dpp-BIAN)Ti[═N(4-C6H4Me)]Cl2 (4). These reactions demonstrate that the BAAN ligand can provide redox equivalents for enhanced reactivity that includes oxidative addition and reductive elimination at d(0) metal centers.

  1. Disentangling the web of fear: amygdala reactivity and functional connectivity in spider and snake phobia.

    PubMed

    Ahs, Fredrik; Pissiota, Anna; Michelgård, Asa; Frans, Orjan; Furmark, Tomas; Appel, Lieuwe; Fredrikson, Mats

    2009-05-15

    The objective was to study effects of fear on brain activity, functional connectivity and brain-behavior relationships during symptom provocation in subjects with specific phobia. Positron emission tomography (PET) and (15)O water was used to measure regional cerebral blood flow (rCBF) in 16 women phobic of either snakes or spiders but not both. Subjects watched pictures of snakes and spiders serving either as phobic or fear-relevant, but non-phobic, control stimuli depending on phobia type. Presentation of phobic as compared with non-phobic cues was associated with increased activation of the right amygdala and cerebellum as well as the left visual cortex and circumscribed frontal areas. Activity decreased in the prefrontal, orbitofrontal and ventromedial cortices as well as in the primary somatosensory cortex and auditory cortices. Furthermore, amygdala activation correlated positively with the subjective experience of distress. Connectivity analyses of activity in the phobic state revealed increased functional couplings between voxels in the right amygdala and the periamygdaloid area, fusiform gyrus and motor cortex. During non-phobic stimulation, prefrontal activity correlated negatively with amygdala rCBF, suggesting a phobia-related functional decoupling. These results suggest that visually elicited phobic reactions activate object recognition areas and deactivate prefrontal areas involved in cognitive control over emotion-triggering areas like the amygdala, resulting in motor readiness to support fight or flight.

  2. Correlation functions for fully or partially state-resolved reactive scattering calculations

    SciTech Connect

    Manthe, Uwe Welsch, Ralph

    2014-06-28

    Flux correlation functions and the quantum transition state concept are important tools for the accurate description of polyatomic reaction processes. Combined with the multi-configurational time-dependent Hartree approach, they facilitate rigorous full-dimensional calculations of cumulative and initial-state selected reaction probabilities for six atom reactions. In recent work [R. Welsch, F. Huarte-Larrañaga, and U. Manthe, J. Chem. Phys. 136, 064117 (2012)], an approach which allows one to calculate also state-to-state reaction probabilities within the quantum transition state concept has been introduced. This article presents further developments. Alternative generalized flux correlation functions are introduced and discussed. Equations for the calculation of fully state-resolved differential cross section using arbitrary definitions of the body fixed frame are derived. An approach for the efficient calculation of partially state-resolved observables as a function of the collision energy is introduced. Finally, numerical test studying the D + H{sub 2} reaction illustrate important aspects of the formalism.

  3. Photoelectron spectroscopic and electronic structure studies of CH(2)O bonding and reactivity on ZnO surfaces: steps in the methanol synthesis reaction.

    PubMed

    Jones, P M; May, J A; Reitz, J B; Solomon, Edward I

    2004-05-31

    Adsorption of CH(2)O on ZnO(0001) has been investigated using XPS, NEXAFS, variable-energy photoelectron spectroscopy (PES), and density functional theory (DFT) calculations. CH(2)O is chemisorbed on the (0001) surface at 130 K. Its C1s XPS peak position at 292.7 eV and NEXAFS sigma shape resonance at 302.6 eV are consistent with an eta(1) bound surface geometry. Geometry optimized DFT calculations also indicate that CH(2)O is bound to the Zn(II) site in an eta(1) configuration through its oxygen atom. The variable-energy PES of the eta(1) bound CH(2)O/ZnO(0001) complex exhibits four valence band features at 21.2, 16.4, 13.8, and 10.7 eV below the vacuum level providing an experimental and theoretical description of this surface interaction. Annealing the ZnO(0001)/CH(2)O surface complex to 220 K decomposes the chemisorbed CH(2)O, producing formyl (291.5 eV), methoxide (290.2 eV), and formate (293.6 eV) intermediates. Thus this reaction coordinate involves the conversion of an oxygen bound formaldehyde to a carbon bound formyl species on ZnO(0001). Only formate is formed on the ZnO(100) surface. DFT is used to explore surface intermediates and the transition state in the methanol synthesis reaction (MSR). The bonding interactions of H(2), CO, CH(3)O(-), HCO(-), and trans-HCOH to the ZnO(0001) surface are elucidated using geometry optimization. H(2) was found to be heterolytically cleaved on the ZnO(0001) surface, and carbon monoxide, formyl, and methoxide are calculated to be eta(1) bound. These results are consistent with observed metal oxide surface reactivity where heterolytic bond cleavage is dominant. The oxygen atom in the bound formyl was found to be activated for attack by a proton. This results in the planar eta(1) bound trans-HCOH surface species. The transition state in the gas phase rearrangement of trans-HCOH to formaldehyde was calculated to have a barrier of 31 kcal/mol. The correlation diagram for this rearrangement in the gas phase indicates that

  4. Absence of insulin signalling in skeletal muscle is associated with reduced muscle mass and function: evidence for decreased protein synthesis and not increased degradation

    PubMed Central

    O’Neill, Elaine D.; Wilding, John P. H.; Kahn, C. Ronald; Van Remmen, Holly; McArdle, Anne; Jackson, Malcolm J.

    2010-01-01

    Loss of skeletal muscle mass and function is observed in many insulin-resistant disease states such as diabetes, cancer cachexia, renal failure and ageing although the mechanisms for this remain unclear. We hypothesised that impaired insulin signalling results in reduced muscle mass and function and that this decrease in muscle mass and function is due to both increased production of atrogenes and aberrant reactive oxygen species (ROS) generation. Maximum tetanic force of the extensor digitorum longus of muscle insulin receptor knockout (MIRKO) and lox/lox control mice was measured in situ. Muscles were removed for the measurement of mass, histological examination and ROS production. Activation of insulin signalling pathways, markers of muscle atrophy and indices of protein synthesis were determined in a separate group of MIRKO and lox/lox mice 15 min following treatment with insulin. Muscles from MIRKO mice had 36% lower maximum tetanic force generation compared with muscles of lox/lox mice. Muscle fibres of MIRKO mice were significantly smaller than those of lox/lox mice with no apparent structural abnormalities. Muscles from MIRKO mice demonstrated absent phosphorylation of AKT in response to exogenous insulin along with a failure to phosphorylate ribosomal S6 compared with lox/lox mice. Atrogin-1 and MuRF1 relative mRNA expression in muscles from MIRKO mice were decreased compared with muscles from lox/lox mice following insulin treatment. There were no differences in markers of reactive oxygen species damage between muscles from MIRKO mice and lox/lox mice. These data support the hypothesis that the absence of insulin signalling contributes to reduced muscle mass and function though decreased protein synthesis rather than proteasomal atrophic pathways. PMID:20431988

  5. Emotion reactivity and regulation are associated with psychological functioning following the 2011 earthquake, tsunami, and nuclear crisis in Japan.

    PubMed

    Cavanagh, Sarah R; Fitzgerald, Erin J; Urry, Heather L

    2014-04-01

    Frequent and successful use of cognitive reappraisal, an emotion regulation strategy that involves rethinking the meaning of an emotional event in order to change one's emotional response, has been linked in everyday life to positive outcomes such as higher well-being. Whether we should expect this association to be maintained in a strong, temporally and spatially close emotional context is an unexplored question that might have important implications for our understanding of emotion regulation and its relations to psychological functioning. In this study of members of the U. S. Embassy Tokyo community in the months following the March 2011 earthquake, tsunami, and nuclear crisis in Japan, self-reported use of cognitive reappraisal was not related to psychological functioning, but demonstrated success using cognitive reappraisal to decrease feelings of unpleasantness in response to disaster-related pictures on a performance-based task was associated with fewer symptoms of depression and posttraumatic stress. Moreover, emotional reactivity to these pictures was associated with greater symptomatology. These results suggest that situational intensity may be an important moderator of reappraisal and psychological functioning relationships.

  6. Emotion reactivity and regulation are associated with psychological functioning following the 2011 earthquake, tsunami, and nuclear crisis in Japan.

    PubMed

    Cavanagh, Sarah R; Fitzgerald, Erin J; Urry, Heather L

    2014-04-01

    Frequent and successful use of cognitive reappraisal, an emotion regulation strategy that involves rethinking the meaning of an emotional event in order to change one's emotional response, has been linked in everyday life to positive outcomes such as higher well-being. Whether we should expect this association to be maintained in a strong, temporally and spatially close emotional context is an unexplored question that might have important implications for our understanding of emotion regulation and its relations to psychological functioning. In this study of members of the U. S. Embassy Tokyo community in the months following the March 2011 earthquake, tsunami, and nuclear crisis in Japan, self-reported use of cognitive reappraisal was not related to psychological functioning, but demonstrated success using cognitive reappraisal to decrease feelings of unpleasantness in response to disaster-related pictures on a performance-based task was associated with fewer symptoms of depression and posttraumatic stress. Moreover, emotional reactivity to these pictures was associated with greater symptomatology. These results suggest that situational intensity may be an important moderator of reappraisal and psychological functioning relationships. PMID:24708504

  7. Buffalo (Bubalus bubalis) interleukin-12: analysis of expression profiles and functional cross-reactivity with bovine system.

    PubMed

    Premraj, Avinash; Sreekumar, E; Jain, Mamta; Rasool, T J

    2006-03-01

    Interleukin-12, a heterodimeric pro-inflammatory cytokine, from water buffaloes (Bubalus bubalis) was analyzed for its for its tissue specific expression and functionality. Concanavalin A stimulated splenocytes displayed an up-regulation of the IL-12 p40 subunit 8-24h post-stimulation, whereas the p35 subunit did not show any quantitative variation at different time intervals. Basal level expressions of both the subunits were observed by RT-PCR in spleen. In addition p40 transcripts could be detected in liver and p35 in brain and muscle tissues as well in very low levels. Functional recombinant buffalo IL-12 was expressed in HEK 293T cells as a heterodimer using foot-and-mouth disease virus 2A polypeptide as a linker. Culture supernatants from transfected cells contained a hetero-dimeric p70 subunit as revealed in western blot of the proteins separated by native polyacrylamide gel electrophoresis (PAGE) using a monoclonal antibody against bovine IL-12 p40. IL-12 containing culture supernatant induced production of nitric oxide in cultured splenocytes of both buffalo and bovine origin. Our study reveals that buffalo IL-12, which shares a high-level sequence identity with bovine IL-12, also has functional cross-reactivity with the bovine immune cells.

  8. Synthesis of onion-peel nanodendritic structures with sequential functional phosphorus diversity.

    PubMed

    Katir, Nadia; El Brahmi, Nabil; El Kadib, Abdelkrim; Mignani, Serge; Caminade, Anne-Marie; Bousmina, Mosto; Majoral, Jean Pierre

    2015-04-20

    The preparation of novel families of phosphorus-based macromolecular architectures called "onion peel" phosphorus nanodendritic systems is reported. This construct is based on the versatility of methods of synthesis using several building blocks and on the capability of these systems to undergo regioselective reactions within the cascade structure. Sustainable metal-free routes such as the Staudinger reaction or Schiff-base condensation, involving only water and nitrogen as byproducts, allow access to several dendritic macromolecules bearing up to seven different phosphorus units in their backbone, each of them featuring specific reactivity. The presence of the highly aurophilic P=N-P=S fragment enables selective ligation of Au(I) within the dendritic framework. PMID:25754619

  9. Acetate functions as an epigenetic metabolite to promote lipid synthesis under hypoxia

    PubMed Central

    Gao, Xue; Lin, Shu-Hai; Ren, Feng; Li, Jin-Tao; Chen, Jia-Jia; Yao, Chuan-Bo; Yang, Hong-Bin; Jiang, Shu-Xia; Yan, Guo-Quan; Wang, Di; Wang, Yi; Liu, Ying; Cai, Zongwei; Xu, Ying-Ying; Chen, Jing; Yu, Wenqiang; Yang, Peng-Yuan; Lei, Qun-Ying

    2016-01-01

    Besides the conventional carbon sources, acetyl-CoA has recently been shown to be generated from acetate in various types of cancers, where it promotes lipid synthesis and tumour growth. The underlying mechanism, however, remains largely unknown. We find that acetate induces a hyperacetylated state of histone H3 in hypoxic cells. Acetate predominately activates lipogenic genes ACACA and FASN expression by increasing H3K9, H3K27 and H3K56 acetylation levels at their promoter regions, thus enhancing de novo lipid synthesis, which combines with its function as the metabolic precursor for fatty acid synthesis. Acetyl-CoA synthetases (ACSS1, ACSS2) are involved in this acetate-mediated epigenetic regulation. More importantly, human hepatocellular carcinoma with high ACSS1/2 expression exhibit increased histone H3 acetylation and FASN expression. Taken together, this study demonstrates that acetate, in addition to its ability to induce fatty acid synthesis as an immediate metabolic precursor, also functions as an epigenetic metabolite to promote cancer cell survival under hypoxic stress. PMID:27357947

  10. Synthesis and psychotropic activity of functionally substituted diaziridines and bisdiaziridines

    SciTech Connect

    Kostyanovskii, R.G.; Shustov, G.V.; Nabiev, O.G.; Denisenko, S.N.; Sukhanova, S.A.; Lavretskaya, E.F.

    1987-04-01

    The authors examine the psychotropic activity of diaziridines which differ considerable in their structures and the C- and N-substituents. Diaziridines are monoamine oxidase inhibitors in the brain and, thus, are potential antidepressants. The acute toxicities and some pharmacological effects of diaziridines are shown. Mice were used in the experiments. The bisdiaziridines obtained differ in their /sup 1/H and /sup 13/C NMR spectra. The effect is presented of functionally substituted diaziridines on the effects of reserpine, 5-hydroxytryptophan, tryptamine, corazole, and apomorphine hypothermia.

  11. Synthesis of functionalized ZnS:Mn/ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Li, Dongmei; Wang, Yiqiang; Yang, Guowei; Xu, Zhen

    2008-02-01

    ZnS:Mn/ZnS core/shell nanoparticles were pre-synthesized by microemulsions technique. To prepare water-soluble and biocompatible nanoparticles, thioglycolic acid was directly added into the same reverse microemulsion system to modify the surface of ZnS:Mn/ZnS nanoparticles. The functionalized ZnS:Mn/ZnS nanoparticles were coupled with carboxyl and revealed farther luminescence enhancement at 600nm. The experiment results indicated that passivating of the organic molecules and the polynuclear complex of Zinc may be the possible mechanism leading to enhancement of luminescence.

  12. Functionalized Polymers-Emerging Versatile Tools for Solution-Phase Chemistry and Automated Parallel Synthesis.

    PubMed

    Kirschning, Andreas; Monenschein, Holger; Wittenberg, Rüdiger

    2001-02-16

    As part of the dramatic changes associated with the need for preparing compound libraries in pharmaceutical and agrochemical research laboratories, industry searches for new technologies that allow for the automation of synthetic processes. Since the pioneering work by Merrifield polymeric supports have been identified to play a key role in this field however, polymer-assisted solution-phase synthesis which utilizes immobilized reagents and catalysts has only recently begun to flourish. Polymer-assisted solution-phase synthesis has various advantages over conventional solution-phase chemistry, such as the ease of separation of the supported species from a reaction mixture by filtration and washing, the opportunity to use an excess of the reagent to force the reaction to completion without causing workup problems, and the adaptability to continuous-flow processes. Various strategies for employing functionalized polymers stoichiometrically have been developed. Apart from reagents that are covalently or ionically attached to the polymeric backbone and which are released into solution in the presence of a suitable substrate, scavenger reagents play an increasingly important role in purifying reaction mixtures. Employing functionalized polymers in solution-phase synthesis has been shown to be extremely useful in automated parallel synthesis and multistep sequences. So far, compound libraries containing as many as 88 members have been generated by using several polymer-bound reagents one after another. Furthermore, it has been demonstrated that complex natural products like the alkaloids (+/-)-oxomaritidine and (+/-)-epimaritidine can be prepared by a sequence of five and six consecutive polymer-assisted steps, respectively, and the potent analgesic compound (+/-)-epibatidine in twelve linear steps ten of which are based on functionalized polymers. These developments reveal the great future prospects of polymer-assisted solution-phase synthesis.

  13. Exercise improves endothelial function: a local analysis of production of nitric oxide and reactive oxygen species.

    PubMed

    Tanaka, Leonardo Yuji; Bechara, Luiz Roberto Grassmann; dos Santos, Adriana Marques; Jordão, Camila Paixão; de Sousa, Luís Gustavo Oliveira; Bartholomeu, Teresa; Ventura, Laura Inês; Laurindo, Francisco Rafael Martins; Ramires, Paulo Rizzo

    2015-02-15

    This study aimed at investigating the acute effects of aerobic exercise on endothelium-dependent vasomotor function of rat aorta, as well as mechanisms involved in endothelial nitric oxide (NO) bioactivity. Wistar rats were assigned to either a resting control (C, n = 21) or acutely exercised (E, n = 21) groups (60 min, 55-60% of maximum speed). After exercise, thoracic aorta was excised and cut into rings. Two rings were promptly applied to evaluate vasomotor function and the rest of aorta was used for additional measurements. Acute exercise significantly improved maximum ACh-induced relaxation (C, 91.6 ± 1.2 vs. E, 102.4 ± 1.7%, p < 0.001) and sensitivity to ACh (C, -7.3 ± 0.06 vs. E, -7.3 ± 0.02 log M, p < 0.01), and was accompanied by significantly increases on serine1177 eNOS phosphorylation, reflecting its enhanced activation. However, acute exercise also enhanced both superoxide and hydrogen peroxide production, as assayed by dihydroethidium oxidation, lucigenin chemiluminescence and Amplex Red assays. We also provided evidence for Nox2 NADPH oxidase (Nox) activation through gp91dstat-mediated inhibition of superoxide signals. Enhanced arterial relaxations associated with acute exercise were nearly-completely prevented by catalase, suggesting a role for paracrine hydrogen peroxide. Despite increased detectable oxidant generation, cellular oxidative stress was not evident, as suggested by unaltered GSH:GSSG ratio and lipid hydroperoxides. Collectively, these results demonstrate that one bout of moderate aerobic exercise improves endothelial function by increasing NO bioavailability, while superoxide and hydrogen peroxide are generated in a controlled fashion. PMID:25619203

  14. Synthesis of a base-free hafnium nitride from N2 cleavage: a versatile platform for dinitrogen functionalization.

    PubMed

    Semproni, Scott P; Chirik, Paul J

    2013-07-31

    The synthesis and characterization of a metastable, base-free isocyanato dihafnocene μ-nitrido complex from CO-induced dinitrogen cleavage is described. The open coordination site at hafnium suggested the possibility of functionalization of the nitrogen atom by cycloaddition and insertion chemistry. Addition of the strained, activated alkyne, cyclooctyne, resulted in N-C bond formation by cycloaddition. The alkyne product is kinetically unstable engaging the terminal hafnocene isocyanate and promoting deoxygenation and additional N-C bond formation resulting in a substituted cyanamide ligand. Group transfer between hafnium centers was observed upon treatment with Me3SiCl resulting in bridging carbodiimidyl ligands. Amidinato-type ligands, [NC(R)N](3-) were prepared by addition of either cyclohexyl or isobutyronitrile to the base free dihafnocene μ-nitrido complex, which also engages in additional N-C bond formation with the terminal isocyanate to form bridging ureate-type ligands. Heterocummulenes also proved reactive as exposure of the nitride complex to CO2 resulted in deoxygenation and N-C bond formation to form isocyanate ligands. With substituted isocyanates, cycloaddition to the dihafnocene μ-nitrido was observed forming ureate ligands, which upon thermolysis isomerize to bridging carbodiimides. Taken together, these results establish the base free dihafnocene μ-nitrido as a versatile platform to synthesize organic molecules from N2 and carbon monoxide.

  15. Circadian clock functioning is linked to acute stress reactivity in rats.

    PubMed

    Weibel, L; Maccari, S; Van Reeth, O

    2002-10-01

    At least two major physiological systems are involved in the adaptation of the organism to environmental challenges: the circadian system and the stress reaction. This study addressed the possibility that interindividual differences in stress sensitivity and in the functioning of the circadian system are related. At 2 months of age, corticosterone secretion in response to a 20-min restraint stress was assessed in 9 Sprague-Dawley rats for which running wheel activity was recorded as a rhythmic behavioral marker of the circadian clock. Two weeks later, the adaptive response of the circadian system to an abrupt shift in the light:dark (LD) cycle was assessed in those rats using a jet-lag paradigm. Finally, after resynchronization to the new LD cycle, rats were transferred to constant darkness to assess the free-running period of their circadian rhythm of running-wheel activity. Results indicate that stress-induced corticosterone secretion was (1) positively correlated with the number of days to resynchronize the circadian activity rhythm to the new LD cycle, and with the value of its free-running period, and (2) negatively correlated with the intensity of daily locomotor activity. Those data, emphasizing the interactions between the stress response of an organism and the functioning of its circadian system, could explain interindividual differences in humans' susceptibility to shift work or other circadian-related disorders. PMID:12375620

  16. Synthesis and characterization of a pH responsive folic acid functionalized polymeric drug delivery system.

    PubMed

    Li, Xia; McTaggart, Matt; Malardier-Jugroot, Cecile

    2016-01-01

    We report the computational analysis, synthesis and characterization of folate functionalized poly(styrene-alt-maleic anhydride), PSMA for drug delivery purpose. The selection of the proper linker between the polymer and the folic acid group was performed before conducting the synthesis using Density Functional Theory (DFT). The computational results showed the bio-degradable linker 2, 4-diaminobutyric acid, DABA as a good candidate allowing flexibility of the folic acid group while maintaining the pH sensitivity of PSMA, used as a trigger for drug release. The synthesis was subsequently carried out in multi-step experimental procedures. The functionalized polymer was characterized using InfraRed spectroscopy, Nuclear Magnetic Resonance and Dynamic Light Scattering confirming both the chemical structure and the pH responsiveness of PSMA-DABA-Folate polymers. This study provides an excellent example of how computational chemistry can be used in selection process for the functional materials and product characterization. The pH sensitive polymers are expected to be used in delivering anti-cancer drugs to solid tumors with overly expressed folic acid receptors. PMID:27183249

  17. Synthesis, thermal stability and reactivity towards 9-aminoellipticine of double-stranded oligonucleotides containing a true abasic site.

    PubMed Central

    Bertrand, J R; Vasseur, J J; Rayner, B; Imbach, J L; Paoletti, J; Paoletti, C; Malvy, C

    1989-01-01

    A 13 mers abasic oligonucleotide was synthetized. It was therefore possible to compare thermal stability and reactivity of duplex oligonucleotides either with an apurinic/apyrimidinic site or without any lesion. An important decrease in the melting temperature appeared for duplexes with an abasic site. The chemical reaction of these modified oligonucleotides with the intercalating agent 9-aminoellipticine was studied by gel electrophoresis and by fluorescence. The formation of a Schiff base between 9-aminoellipticine and abasic sites was rapid and complete with duplexes at 11 degrees C. Schiff base related fluorescence and beta-elimination cleavage were more important with the apyrimidinic sites than with the apurinic ones. When compared to previous results obtained with the model d(TprpT) some unexpected behaviours appeared with longer and duplex oligonucleotides. For instance only partial beta-elimination cleavage was observed. It is likely that stacking parameters in the double helix play a great role in the studied reaction. Images PMID:2602153

  18. Synthesis and reactivity of a transition metal complex containing exclusively TEMPO ligands: Ni(η2-TEMPO)2.

    PubMed

    Isrow, Derek; Captain, Burjor

    2011-07-01

    The reaction of Ni(COD)(2) with two equivalents of the TEMPO radical at 68 °C affords the 16 e(-) "bow-tie" complex Ni(η(2)-TEMPO)(2), 1, in 78% yield. Compound 1 reacts with tert-butyl isocyanide and phenylacetylene at room temperature to yield the 16 e(-) distorted square planar nickel complexes Ni(η(2)-TEMPO)(η(1)-TEMPO)(CN(t)Bu), 2, and Ni(η(2)-TEMPO)(η(1)-TEMPOH)(CCPh), 4, respectively. The facile reactivity of 1 is aided by the transition of the TEMPO ligand from an η(2) to η(1) binding mode. Complex 4 is an unusual example of hydrogen atom transfer from phenylacetylene to a coordinated TEMPO ligand.

  19. Synthesis and Function of Apocarotenoid Signals in Plants.

    PubMed

    Hou, Xin; Rivers, John; León, Patricia; McQuinn, Ryan P; Pogson, Barry J

    2016-09-01

    In plants, carotenoids are essential for photosynthesis and photoprotection. However, carotenoids are not the end products of the pathway; apocarotenoids are produced by carotenoid cleavage dioxygenases (CCDs) or non-enzymatic processes. Apocarotenoids are more soluble or volatile than carotenoids but they are not simply breakdown products, as there can be modifications post-cleavage and their functions include hormones, volatiles, and signals. Evidence is emerging for a class of apocarotenoids, here referred to as apocarotenoid signals (ACSs), that have regulatory roles throughout plant development beyond those ascribed to abscisic acid (ABA) and strigolactone (SL). In this context we review studies of carotenoid feedback regulation, chloroplast biogenesis, stress signaling, and leaf and root development providing evidence that apocarotenoids may fine-tune plant development and responses to environmental stimuli. PMID:27344539

  20. One-step continuous synthesis of functionalized magnetite nanoflowers

    NASA Astrophysics Data System (ADS)

    Thomas, G.; Demoisson, F.; Chassagnon, R.; Popova, E.; Millot, N.

    2016-04-01

    For the first time, functionalized magnetite nanoparticles (Fe3O4 NPs) that form aggregates with a nanoflower morphology were synthesized using a rapid (11 s) one-step continuous hydrothermal process, which was recently modified, and their application as a T 2 magnetic resonance imaging (MRI) contrast agent was evaluated. The nanoparticles functionalized with 3,4-dihydroxy-L-phenylalanine (LDOPA) or 3,4-dihydroxyhydrocinnamic acid (DHCA) consisted of small crystallites of approximately 15 nm of diameter that assembled to form flower-shaped aggregate structures. The Fe3O4-LDOPA nanoflowers exhibited a high transverse relaxivity, r 2 of 418 ± 10 l mmolFe -1 s-1 at 3 T owing to magnetic dipolar interactions, which is twice as that of the commercial Feridex®/Endorem®. The prepared nanostructures were compared with bare Fe3O4 NPs and citrated Fe3O4 NPs. DHCA, LDOPA, and citric acid (CA) were found to have an anti-oxidizing effect and to influence the crystallite size and the lattice parameter of the NPs. DHCA and LDOPA increased the crystallite size, whereas CA decreased it. Surface modification increased the colloidal stability of NPs as compared to bare NPs. Nanoflower suspensions of Fe3O4-LDOPA NPs were found to be stable in the phosphate-buffered saline, saline medium, and minimal essential medium and formed aggregates of sizes smaller than 120 nm. All samples were found to be superparamagnetic in nature and the highest saturation magnetization was obtained for the Fe3O4-LDOPA samples. These NPs can bind to polymers such as PEG, and to fluorescent and chelating agents owing to the presence of free -NH2 or -COOH groups on the surface of NPs, allowing their use in dual imaging applications.

  1. Childhood poverty and stress reactivity are associated with aberrant functional connectivity in default mode network.

    PubMed

    Sripada, Rebecca K; Swain, James E; Evans, Gary W; Welsh, Robert C; Liberzon, Israel

    2014-08-01

    Convergent research suggests that childhood poverty is associated with perturbation in the stress response system. This might extend to aberrations in the connectivity of large-scale brain networks, which subserve key cognitive and emotional functions. Resting-state brain activity was measured in adults with a documented history of childhood poverty (n=26) and matched controls from middle-income families (n=26). Participants also underwent a standard laboratory social stress test and provided saliva samples for cortisol assay. Childhood poverty was associated with reduced default mode network (DMN) connectivity. This, in turn, was associated with higher cortisol levels in anticipation of social stress. These results suggest a possible brain basis for exaggerated stress sensitivity in low-income individuals. Alterations in DMN may be associated with less efficient cognitive processing or greater risk for development of stress-related psychopathology among individuals who experienced the adversity of chronic childhood poverty.

  2. 2,4,6-Triphenylphosphinine and 2,4,6-triphenylposphabarrelene revisited: synthesis, reactivity and coordination chemistry.

    PubMed

    Rigo, M; Sklorz, J A W; Hatje, N; Noack, F; Weber, M; Wiecko, J; Müller, C

    2016-02-01

    The synthesis of 2,4,6-triphenylphosphinine has been revisited and a general protocol for the preparation of such low-coordinate phosphorus compounds in good to excellent yields could be established. This allows to investigate several aspects of the chemistry of 2,4,6-triarylphosphinine, such as the reaction with in situ generated benzyne to give 2,4,6-triphenylphosphabarrelene. The corresponding 2,4,6-triphenylphosphabarrelene-selenide could be characterized crystallographically for the first time and the structural and electronic properties of this cage-compound in comparison to classical triarylphosphines could be evaluated. Moreover, [(L)W(CO)5)] complexes of both 2,4,6-triphenylphosphinine and 2,4,6-triphenylphosphabarrelene were prepared and characterized by means of X-ray crystallography. This allowed for the first time a direct structural comparison of these related phosphorus compounds, coordinated to the same metal fragment.

  3. One-Pot Synthesis of Aza-Diketopiperazines Enabled by Controlled Reactivity of N-Isocyanate Precursors.

    PubMed

    Ivanovich, Ryan A; Vincent-Rocan, Jean-François; Elkaeed, Eslam B; Beauchemin, André M

    2015-10-01

    A one-pot sequence for the synthesis of aza-diketopiperazines is reported, involving carbazate acylation with chloroacetyl chloride, SN2 with a primary amine, N-isocyanate formation, and cyclization. Nitrogen-substituted isocyanates (N-isocyanates) are a rare class of amphoteric isocyanate with high, but severely underdeveloped synthetic potential. This approach highlights that βN-acyl carbazates can act as blocked (masked) N-isocyanates, thus allowing a challenging intermolecular SN2 reaction of a primary amine to proceed while the N-isocyanate is "protected", and then cyclization once it is unmasked. Control experiments show that the alternate pathway--N-isocyanate substitution and then cyclization by an intramolecular SN2 reaction--is not operating.

  4. A paramagnetic heterobimetallic polymer: synthesis, reactivity, and ring-opening polymerization of tin-bridged homo- and heteroleptic vanadoarenophanes.

    PubMed

    Braunschweig, Holger; Damme, Alexander; Demeshko, Serhiy; Dück, Klaus; Kramer, Thomas; Krummenacher, Ivo; Meyer, Franc; Radacki, Krzysztof; Stellwag-Konertz, Sascha; Whittell, George R

    2015-02-01

    The synthesis of the first tin-bridged bis(benzene) vanadium and trovacene sandwich compounds and the investigation of their oxidative addition and insertion behavior are reported. The vanadoarenophanes and the corresponding platinum insertion products were fully characterized including electrochemical and electron paramagnetic resonance (EPR) measurements. Controllable ring-opening polymerization of the heteroleptic tin-bridged [1]trovacenophane using Karstedt's catalyst yields a high molecular weight polymer (up to M(n) = 89 200 g·mol(-1)) composed of d(5)-vanadium metal centers in the main chain, making it a rare example of a spin-carrying macromolecule. Magnetic susceptibility measurements (SQUID) confirm the paramagnetic scaffold with repeating S = 1/2 centers in the main chain and suggest antiferromagnetic interactions between adjacent spin sites (Weiss constant Θ = -2.9 K). PMID:25565127

  5. Computational chemistry of natural products: a comparison of the chemical reactivity of isonaringin calculated with the M06 family of density functionals.

    PubMed

    Glossman-Mitnik, Daniel

    2014-07-01

    The M06 family of density functionals has been assessed for the calculation of the molecular structure and properties of the Isonaringin flavonoid that can be an interesting material for dye-sensitized solar cells (DSSC). The chemical reactivity descriptors have been calculated through chemical reactivity theory within DFT (CR-DFT). The active sites for nucleophilic and electrophilic attacks have been chosen by relating them to the Fukui function indices and the dual descriptor f ((2))(r). A comparison between the descriptors calculated through vertical energy values and those arising from the Janak's theorem approximation have been performed in order to check for the validity of the last procedure.

  6. Computational chemistry of natural products: a comparison of the chemical reactivity of isonaringin calculated with the M06 family of density functionals.

    PubMed

    Glossman-Mitnik, Daniel

    2014-07-01

    The M06 family of density functionals has been assessed for the calculation of the molecular structure and properties of the Isonaringin flavonoid that can be an interesting material for dye-sensitized solar cells (DSSC). The chemical reactivity descriptors have been calculated through chemical reactivity theory within DFT (CR-DFT). The active sites for nucleophilic and electrophilic attacks have been chosen by relating them to the Fukui function indices and the dual descriptor f ((2))(r). A comparison between the descriptors calculated through vertical energy values and those arising from the Janak's theorem approximation have been performed in order to check for the validity of the last procedure. PMID:24992989

  7. Synthesis of functionally graded materials via electrophoretic deposition and sintering

    NASA Astrophysics Data System (ADS)

    Wang, Xuan

    In this research, both the experiments and the modeling aspects of the net-shape fabrication of Functionally Graded Materials (FGM) by Electrophoretic Deposition (EPD) and consecutive sintering have been investigated. In order to obtain FGMs with desired final shape and properties, the issues regarding the shape evolution during sintering, the optimization of initial properties and composition profiles, and the fabrication of green components by EPD have been analyzed. In order to fabricate FGMs by the proposed technological sequence (EPD with the following sintering), the initial shape has to be optimized prior to sintering. In this research, the formulations to simulate sintering of an FGM were developed based on the continuum theory of sintering. A finite element sintering-modeling subroutine has been created and linked to the commercial finite element package ABAQUS. The shape changes of FGM disks during sintering were simulated. In order to obtain the desired final shape after sintering, an inverse modeling methodology was developed to optimize the initial shape. In order to fabricate the optimized initial shape of a green FGM specimen determined by the inverse continuum modeling of sintering, EPD of a number of FGMs was investigated. The FGM green specimens made of Al2O 3 and ZrO2 with the initial shape predicted by the inverse modeling, were deposited using self-designed equipments. The acetone-based suspension with n-butylamine as a particle-charging additive was used. The comparison of the shape between the sintered and the green FGM indicated that the developed experimental-theoretical methodology provided a reliable solution for near net shaping of complex 3-D FGM components. Other applications of EPD, such as in electronic packaging materials and zeolites, were also investigated. In order to fabricate functionally graded materials based on aligned porous structures, unidirectional freezing followed by freeze-drying and sintering has been investigated

  8. Synthesis of a bis(indenyl) Co(I) anion: a reactive source of a 14 electron indenyl Co(I) equivalent.

    PubMed

    Hung-Low, Fernando; Bradley, Christopher A

    2013-03-01

    Alkali metal reduction of (η(5)-C9H5-1,3-(SiMe3)2)2Co (1) in tetrahydrofuran (THF) permits isolation of the unusual and reactive 20 electron Co(I) anion [Na(THF)6][(η(5)-C9H5-1,3-(SiMe3)2)2Co] (2). Crystallographic characterization of both 1 and 2 provide support for the one electron reduction from Co(II) to Co(I). Reactivity studies of 2 are further consistent with a Co(I) equivalent, based on both one electron chemical oxidation to reform 1 and reaction with a variety of σ and π donors. Upon addition of pyridines or vinyltrimethylsilane to 2, known dimer [(C9H5-1,3-(SiMe3)2)2Co2] (3) is formed, likely through 16 electron (η(5)-C9H5-1,3-(SiMe3)2)Co(L) intermediates. Ethylene addition to 2 establishes an equilibrium between (η(5)-C9H5-1,3-(SiMe3)2)Co(η(2)-H2C═CH2)2 (8) and 2, suggestive of reversible ligand ejection from 2. Crossover experiments between a related metal indenide salt and 2 confirm ligand extrusion from the anion, even in the absence of strong supporting donors. Reaction of 2 with PMe3 results in formation of 3, (η(5)-C9H5-1,3-(SiMe3)2)Co(PMe3)2 (13), and a paramagnetic species, with the product ratios being highly dependent on the conditions of synthesis. Collectively, 2 demonstrates an alternative entry point into the chemistry of 14 electron Co(I) equivalents when compared to typical ligand loss from neutral 18 electron cyclopentadienyl cobalt bis(ligand) complexes, perhaps permitting generation of low electron count species more effective for small molecule activation. PMID:23427933

  9. Synthesis of a bis(indenyl) Co(I) anion: a reactive source of a 14 electron indenyl Co(I) equivalent.

    PubMed

    Hung-Low, Fernando; Bradley, Christopher A

    2013-03-01

    Alkali metal reduction of (η(5)-C9H5-1,3-(SiMe3)2)2Co (1) in tetrahydrofuran (THF) permits isolation of the unusual and reactive 20 electron Co(I) anion [Na(THF)6][(η(5)-C9H5-1,3-(SiMe3)2)2Co] (2). Crystallographic characterization of both 1 and 2 provide support for the one electron reduction from Co(II) to Co(I). Reactivity studies of 2 are further consistent with a Co(I) equivalent, based on both one electron chemical oxidation to reform 1 and reaction with a variety of σ and π donors. Upon addition of pyridines or vinyltrimethylsilane to 2, known dimer [(C9H5-1,3-(SiMe3)2)2Co2] (3) is formed, likely through 16 electron (η(5)-C9H5-1,3-(SiMe3)2)Co(L) intermediates. Ethylene addition to 2 establishes an equilibrium between (η(5)-C9H5-1,3-(SiMe3)2)Co(η(2)-H2C═CH2)2 (8) and 2, suggestive of reversible ligand ejection from 2. Crossover experiments between a related metal indenide salt and 2 confirm ligand extrusion from the anion, even in the absence of strong supporting donors. Reaction of 2 with PMe3 results in formation of 3, (η(5)-C9H5-1,3-(SiMe3)2)Co(PMe3)2 (13), and a paramagnetic species, with the product ratios being highly dependent on the conditions of synthesis. Collectively, 2 demonstrates an alternative entry point into the chemistry of 14 electron Co(I) equivalents when compared to typical ligand loss from neutral 18 electron cyclopentadienyl cobalt bis(ligand) complexes, perhaps permitting generation of low electron count species more effective for small molecule activation.

  10. Facile and green synthesis of highly stable L-cysteine functionalized copper nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumar, Nikhil; Upadhyay, Lata Sheo Bachan

    2016-11-01

    A simple eco-friendly method for L-cysteine capped copper nanoparticles (CCNPs) synthesis in aqueous solution has been developed. Glucose and L-cysteine were used as reducing agent and capping/functionalizing agent, respectively. Different parameters such as capping agent concentration, pH, reaction temperature, and reducing agent concentration were optimized during the synthesis. The L-cysteine capped copper nanoparticle were characterized by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, Particle size and zeta potential analyser, and high resolution transmission electron microscopy. Spherical shaped cysteine functionalized/capped copper nanoparticles with an average size of 40 nm were found to be highly stable at room temperature (RT) for a period of 1 month

  11. Ligands for FKBP12 Increase Ca2+ Influx and Protein Synthesis to Improve Skeletal Muscle Function*

    PubMed Central

    Lee, Chang Seok; Georgiou, Dimitra K.; Dagnino-Acosta, Adan; Xu, Jianjun; Ismailov, Iskander I.; Knoblauch, Mark; Monroe, Tanner O.; Ji, RuiRui; Hanna, Amy D.; Joshi, Aditya D.; Long, Cheng; Oakes, Joshua; Tran, Ted; Corona, Benjamin T.; Lorca, Sabina; Ingalls, Christopher P.; Narkar, Vihang A.; Lanner, Johanna T.; Bayle, J. Henri; Durham, William J.; Hamilton, Susan L.

    2014-01-01

    Rapamycin at high doses (2–10 mg/kg body weight) inhibits mammalian target of rapamycin complex 1 (mTORC1) and protein synthesis in mice. In contrast, low doses of rapamycin (10 μg/kg) increase mTORC1 activity and protein synthesis in skeletal muscle. Similar changes are found with SLF (synthetic ligand for FKBP12, which does not inhibit mTORC1) and in mice with a skeletal muscle-specific FKBP12 deficiency. These interventions also increase Ca2+ influx to enhance refilling of sarcoplasmic reticulum Ca2+ stores, slow muscle fatigue, and increase running endurance without negatively impacting cardiac function. FKBP12 deficiency or longer treatments with low dose rapamycin or SLF increase the percentage of type I fibers, further adding to fatigue resistance. We demonstrate that FKBP12 and its ligands impact multiple aspects of muscle function. PMID:25053409

  12. Stem cell function and stress response are controlled by protein synthesis.

    PubMed

    Blanco, Sandra; Bandiera, Roberto; Popis, Martyna; Hussain, Shobbir; Lombard, Patrick; Aleksic, Jelena; Sajini, Abdulrahim; Tanna, Hinal; Cortés-Garrido, Rosana; Gkatza, Nikoletta; Dietmann, Sabine; Frye, Michaela

    2016-06-15

    Whether protein synthesis and cellular stress response pathways interact to control stem cell function is currently unknown. Here we show that mouse skin stem cells synthesize less protein than their immediate progenitors in vivo, even when forced to proliferate. Our analyses reveal that activation of stress response pathways drives both a global reduction of protein synthesis and altered translational programmes that together promote stem cell functions and tumorigenesis. Mechanistically, we show that inhibition of post-transcriptional cytosine-5 methylation locks tumour-initiating cells in this distinct translational inhibition programme. Paradoxically, this inhibition renders stem cells hypersensitive to cytotoxic stress, as tumour regeneration after treatment with 5-fluorouracil is blocked. Thus, stem cells must revoke translation inhibition pathways to regenerate a tissue or tumour.

  13. Stem cell function and stress response are controlled by protein synthesis.

    PubMed

    Blanco, Sandra; Bandiera, Roberto; Popis, Martyna; Hussain, Shobbir; Lombard, Patrick; Aleksic, Jelena; Sajini, Abdulrahim; Tanna, Hinal; Cortés-Garrido, Rosana; Gkatza, Nikoletta; Dietmann, Sabine; Frye, Michaela

    2016-06-16

    Whether protein synthesis and cellular stress response pathways interact to control stem cell function is currently unknown. Here we show that mouse skin stem cells synthesize less protein than their immediate progenitors in vivo, even when forced to proliferate. Our analyses reveal that activation of stress response pathways drives both a global reduction of protein synthesis and altered translational programmes that together promote stem cell functions and tumorigenesis. Mechanistically, we show that inhibition of post-transcriptional cytosine-5 methylation locks tumour-initiating cells in this distinct translational inhibition programme. Paradoxically, this inhibition renders stem cells hypersensitive to cytotoxic stress, as tumour regeneration after treatment with 5-fluorouracil is blocked. Thus, stem cells must revoke translation inhibition pathways to regenerate a tissue or tumour. PMID:27306184

  14. Towards a filtered density function approach for reactive transport in groundwater

    NASA Astrophysics Data System (ADS)

    Suciu, N.; Schüler, L.; Attinger, S.; Knabner, P.

    2016-04-01

    Evolution equations for probability density functions (PDFs) and filtered density functions (FDFs) of random species concentrations weighted by conserved scalars are formulated as Fokker-Planck equations describing stochastically equivalent processes in concentration-position spaces. This approach provides consistent numerical PDF/FDF solutions, given by the density in the concentration-position space of an ensemble of computational particles governed by the associated Itô equations. The solutions are obtained by a global random walk (GRW) algorithm, which is stable, free of numerical diffusion, and practically insensitive to the increase of the number of particles. The general FDF approach and the GRW numerical solution are illustrated for a reduced complexity problem consisting of the transport of a single scalar in groundwater. Randomness is induced by the stochastic parameterization of the hydraulic conductivity, characterized by short range correlations and small variance. The objective is to infer the statistics of the random concentration sampled at the plume center of mass, integrated over the transverse dimension of a two-dimensional spatial domain. The PDF/FDF problem can therefore be formulated in a two-dimensional domain as well, a spatial dimension and one in the concentration space. The upscaled drift and diffusion coefficients describing the PDF transport in the physical space are estimated on single-trajectories of diffusion in velocity fields with short-range correlations, owing to their self-averaging property. The mixing coefficients describing the PDF transport in concentration spaces are parameterized by the trend and the noise inferred from the statistical analysis of an ensemble of simulated concentration time series, as well as by classical mixing models. A Gaussian spatial filter applied to a Kraichnan velocity field generator is used to construct coarse-grained simulations (CGS) for FDF problems. The purposes of the CGS simulations are

  15. Functional imaging of emotion reactivity in opiate-dependent borderline personality disorder.

    PubMed

    Smoski, Moria J; Salsman, Nicholas; Wang, Lihong; Smith, Veronica; Lynch, Thomas R; Dager, Stephen R; LaBar, Kevin S; Linehan, Marsha M

    2011-07-01

    Opiate dependence (OD) and borderline personality disorder (BPD), separately and together, are significant public health problems with poor treatment outcomes. BPD is associated with difficulties in emotion regulation, and brain-imaging studies in BPD individuals indicate differential activation in prefrontal cingulate cortices and their interactions with limbic regions. Likewise, a similar network is implicated in drug cue responsivity in substance abusers. The present, preliminary study used functional MRI to examine activation of this network in comorbid OD/BPD participants when engaged in an "oddball" task that required attention to a target in the context of emotionally negative distractors. Twelve male OD/BPD participants and 12 male healthy controls participated. All OD/BPD participants were taking the opiate replacement medication Suboxone, and a subset of participants was positive for substances of abuse on scan day. Relative to controls, OD/BPD participants demonstrated reduced activation to negative stimuli in the amygdala and anterior cingulate. Unlike previous studies that demonstrated hyperresponsivity in neural regions associated with affective processing in individuals with BPD versus healthy controls, comorbid OD/BPD participants were hyporesponsive to emotional cues. Future studies that also include BPD-only and OD-only groups are necessary to help clarify the individual and potentially synergistic effects of these two conditions. PMID:22448769

  16. Light and Dark of Reactive Oxygen Species for Vascular Function: 2014 ASVB (Asian Society of Vascular Biology).

    PubMed

    Shimokawa, Hiroaki; Satoh, Kimio

    2015-05-01

    Vascular-derived hydrogen peroxide (H2O2) serves as an important signaling molecule in the cardiovascular system and contributes to vascular homeostasis. H2O2 is a second messenger, transducing the oxidative signal into biological responses through posttranslational protein modification. The balance between oxidant and antioxidant systems regulates intracellular redox status, and their imbalance causes oxidative or reductive stress, leading to cellular damage in cardiovascular systems. Excessive H2O2 deteriorates vascular functions and promotes vascular disease through multiple pathways. The RhoA/Rho-kinase pathway plays an important role in various fundamental cellular functions, including production of excessive reactive oxygen species, leading to the development of cardiovascular diseases. Rho-kinase (ROCK1 and ROCK2) belongs to the family of serine/threonine kinases and is an important downstream effector of the small GTP-binding protein RhoA. Rho-kinase plays a crucial role in the pathogenesis of vasospasm, arteriosclerosis, ischemia/reperfusion injury, hypertension, pulmonary hypertension, stroke, and heart failure. Thus, Rho-kinase inhibitors may be useful for the treatment of cardiovascular diseases in humans. In this review, we will briefly discuss the roles of vascular-derived H2O2 and review the recent progress in the translational research on the therapeutic importance of the Rho-kinase pathway in cardiovascular medicine.

  17. Luminescent Rare-earth-based Nanoparticles: A Summarized Overview of their Synthesis, Functionalization, and Applications.

    PubMed

    Escudero, Alberto; Carrillo-Carrión, Carolina; Zyuzin, Mikhail V; Parak, Wolfgang J

    2016-08-01

    Rare-earth-based nanoparticles are currently attracting wide research interest in material science, physics, chemistry, medicine, and biology due to their optical properties, their stability, and novel applications. We present in this review a summarized overview of the general and recent developments in their synthesis and functionalization. Their luminescent properties are also discussed, including the latest advances in the enhancement of their emission luminescence. Some of their more relevant and novel biomedical, analytical, and optoelectronic applications are also commented on. PMID:27573400

  18. A Copper-Catalyzed Decarboxylative Amination/Hydroamination Sequence: Switchable Synthesis of Functionalized Indoles.

    PubMed

    Li, Tian-Ren; Cheng, Bei-Yi; Wang, Ya-Ni; Zhang, Mao-Mao; Lu, Liang-Qiu; Xiao, Wen-Jing

    2016-09-26

    A copper-catalyzed decarboxylative amination/hydroamination sequence of propargylic carbamates with various nucleophiles is described for the first time. It features an earth-abundant metal catalyst, mild reaction conditions, and high efficiency. Further treatments of the resultant key intermediates using an acid or a base in one pot enable the controllable and divergent synthesis of two types of functionalized indoles. Moreover, experiments to demonstrate the synthetic potential of this methodology are performed. PMID:27593696

  19. Luminescent Rare-earth-based Nanoparticles: A Summarized Overview of their Synthesis, Functionalization, and Applications.

    PubMed

    Escudero, Alberto; Carrillo-Carrión, Carolina; Zyuzin, Mikhail V; Parak, Wolfgang J

    2016-08-01

    Rare-earth-based nanoparticles are currently attracting wide research interest in material science, physics, chemistry, medicine, and biology due to their optical properties, their stability, and novel applications. We present in this review a summarized overview of the general and recent developments in their synthesis and functionalization. Their luminescent properties are also discussed, including the latest advances in the enhancement of their emission luminescence. Some of their more relevant and novel biomedical, analytical, and optoelectronic applications are also commented on.

  20. Lipid Peroxidation-Derived Reactive Aldehydes Directly and Differentially Impair Spinal Cord and Brain Mitochondrial Function

    PubMed Central

    Vaishnav, Radhika A.; Singh, Indrapal N.; Miller, Darren M.

    2010-01-01

    Abstract Mitochondrial bioenergetic dysfunction in traumatic spinal cord and brain injury is associated with post-traumatic free radical–mediated oxidative damage to proteins and lipids. Lipid peroxidation by-products, such as 4-hydroxy-2-nonenal and acrolein, can form adducts with proteins and exacerbate the effects of direct free radical–induced protein oxidation. The aim of the present investigation was to determine and compare the direct contribution of 4-hydroxy-2-nonenal and acrolein to spinal cord and brain mitochondrial dysfunction. Ficoll gradient–isolated mitochondria from normal rat spinal cords and brains were treated with carefully selected doses of 4-hydroxy-2-nonenal or acrolein, followed by measurement of complex I– and complex II–driven respiratory rates. Both compounds were potent inhibitors of mitochondrial respiration in a dose-dependent manner. 4-Hydroxy-2-nonenal significantly compromised spinal cord mitochondrial respiration at a 0.1-μM concentration, whereas 10-fold greater concentrations produced a similar effect in brain. Acrolein was more potent than 4-hydroxy-2-nonenal, significantly decreasing spinal cord and brain mitochondrial respiration at 0.01 μM and 0.1 μM concentrations, respectively. The results of this study show that 4-hydroxy-2-nonenal and acrolein can directly and differentially impair spinal cord and brain mitochondrial function, and that the targets for the toxic effects of aldehydes appear to include pyruvate dehydrogenase and complex I–associated proteins. Furthermore, they suggest that protein modification by these lipid peroxidation products may directly contribute to post-traumatic mitochondrial damage, with spinal cord mitochondria showing a greater sensitivity than those in brain. PMID:20392143

  1. Probability density function of non-reactive solute concentration in heterogeneous porous formations.

    PubMed

    Bellin, Alberto; Tonina, Daniele

    2007-10-30

    Available models of solute transport in heterogeneous formations lack in providing complete characterization of the predicted concentration. This is a serious drawback especially in risk analysis where confidence intervals and probability of exceeding threshold values are required. Our contribution to fill this gap of knowledge is a probability distribution model for the local concentration of conservative tracers migrating in heterogeneous aquifers. Our model accounts for dilution, mechanical mixing within the sampling volume and spreading due to formation heterogeneity. It is developed by modeling local concentration dynamics with an Ito Stochastic Differential Equation (SDE) that under the hypothesis of statistical stationarity leads to the Beta probability distribution function (pdf) for the solute concentration. This model shows large flexibility in capturing the smoothing effect of the sampling volume and the associated reduction of the probability of exceeding large concentrations. Furthermore, it is fully characterized by the first two moments of the solute concentration, and these are the same pieces of information required for standard geostatistical techniques employing Normal or Log-Normal distributions. Additionally, we show that in the absence of pore-scale dispersion and for point concentrations the pdf model converges to the binary distribution of [Dagan, G., 1982. Stochastic modeling of groundwater flow by unconditional and conditional probabilities, 2, The solute transport. Water Resour. Res. 18 (4), 835-848.], while it approaches the Normal distribution for sampling volumes much larger than the characteristic scale of the aquifer heterogeneity. Furthermore, we demonstrate that the same model with the spatial moments replacing the statistical moments can be applied to estimate the proportion of the plume volume where solute concentrations are above or below critical thresholds. Application of this model to point and vertically averaged bromide

  2. Template synthesis of novel carboxamide dinuclear copper (II) complex: spectral characterization and reactivity towards calf-thymus DNA.

    PubMed

    Mathur, Suvigya; Tabassum, Sartaj

    2008-06-01

    Dinuclear complexes Bis [aqua 1,8-(1,2-dicarboxamido benzene) 3,6-diazaoctane copper (II)/nickel (II)] tetrachloride (1 and 2) were synthesized by a two component one-pot metal template condensation between phthalic anhydride and 1,8-diamino 3,6-diazaoctane. Elemental analysis, molar conductance measurements, electronic absorption, infra-red, electron paramagnetic resonance, nuclear magnetic resonance, atomic absorption, and electron spray mass spectral studies have been performed to probe the nature and structure of the complexes. The interaction of copper (II) complex with calf thymus (CT-DNA) has been studied by using absorption, emission and circular dichoric spectral methods, viscometry, and cyclic voltammetry. A strong hyperchromism along with a red shift in UV bands and hypochromism in the ligand field band of the complex 1 on interaction with CT-DNA imply a covalent mode of DNA binding. This is further confirmed by studying the reactivity of complex 1 using circular dichroism and viscosity measurements. The variation in relative emission intensity of DNA-bound ethidium bromide observed upon treatment with the complex 1 parallel the trend of DNA binding studies. Cyclic voltammetry studies reveal that the complex 1 prefers to bind to DNA in Cu(II) rather than Cu(I) oxidation state.

  3. Synthesis of composite particles through emulsion polymerization based on silica/fluoroacrylate-siloxane using anionic reactive and nonionic surfactants.

    PubMed

    Qu, Ailan; Wen, Xiufang; Pi, Pihui; Cheng, Jiang; Yang, Zhuoru

    2008-01-01

    The composite particles with core/shell structure resulting from the combination of silica seed and hydrophobic copolymer (dodecafluoroheptyl methacrylate (DFMA), gamma-methacryloxypropyltriisopropoxidesilane (MAPTIPS), methyl methacrylate, butyl acrylate) were synthesized by emulsion polymerization. The amount of the silica seeds, concentration of reactive surfactant, as well as the addition of DFMA and MAPTIPS, have strong influences on the morphology of composite particles. It has been shown that it would be possible to produce stable organic/inorganic composite particles with inhomogeneous core/shell structure encapsulated by hydrophobic fluorinated acrylate even though using unmodified silica particles and admixture of anionic and nonionic surfactants. However, there was an obvious difference on the morphologies of core-shell structure whether the DFMA and MAPTIPS were added or not. It was concluded that two kinds of polymerization approaches might coexist in the presence of DFMA and MAPTIPS for raw silica. One clear advantage of this process is that there is only one silica bead for each composite particle. This kind of stable core-shell structural hybrid latex is useful for preparing high performance hydrophobic coating.

  4. Synthesis, Molecular Structure, DNA/Protein Binding, Cytotoxicity, Apoptosis, Reactive Oxygen Species, and Mitochondrial Membrane Potential of Dibenzoxanthenes Derivatives.

    PubMed

    Yang, Hui-Hui; Han, Bing-Jie; Li, Wei; Liu, Yun-Jun; Wang, Xiu-Zhen

    2015-12-01

    Two dibenzoxanthene isomers 3 and 4 were synthesized and characterized. The crystal structures of the two compounds were solved by single-crystal X-ray diffraction. Binding of two compounds with calf thymus DNA (CT DNA) and BSA (bovine serum albumin) has been thoroughly investigated by UV-Vis and fluorescence spectroscopy. The DNA-binding constants were determined to be 2.51 (± 0.09) × 10(3) for compound 3 and 4.55 (± 0.10) × 10(3) for compound 4. Two compounds can cleave pBR322 DNA upon irradiation. Significant nuclear damages of BEL-7402 cells were observed with compound treatment in a comet assay. The cytotoxicity in vitro was investigated by MTT method. These compounds have been found to induce nuclear condensation and fragmentation in BEL-7402 cells. The two compounds can enhance intracellular reactive oxygen species and decrease the mitochondrial membrane potential. The compounds activated caspase-3 and caspase-7, down-regulated the expression levels of anti-apoptotic protein Bcl-2, and up-regulated the expression levels of pro-apoptotic protein Bax. These compounds induce apoptosis of BEL-7402 cells through an ROS-mediated mitochondrial dysfunction pathway.

  5. Synthesis, Structure, and Reactivities of Iminosulfane- and Phosphane-Stabilized Carbones Exhibiting Four-Electron Donor Ability.

    PubMed

    Morosaki, Tomohito; Wang, Wei-Wei; Nagase, Shigeru; Fujii, Takayoshi

    2015-10-19

    Iminosulfane(phosphane)carbon(0) derivatives (iSPCs; Ar3 P→C←SPh2 (NMe); Ar=Ph (1), 4-MeOC6 H4 (2), 4-(Me2 N)C6 H4 (3)) have been successfully synthesized and the molecular structure of 3 characterized. Carbone 3 is the first thermally and hydrolytically stable carbone stabilized by phosphorus and sulfur ligands. DFT calculations reveal the electronic structures of 1-3, which have two lone pairs of electrons at the carbon center. First and second proton affinity values are theoretically calculated to be in the range of 286.8-301.1 and 189.6-208.3 kcal mol(-1) , respectively. Cyclic voltammetry measurements reveal that the HOMO energy levels follow the order of 3>2>1 and the HOMO of 3 is at a higher energy than those of bis(chalcogenane)carbon(0) (BChCs). The reactivities of these lone pairs of electrons are demonstrated by the C-diaurated and C-proton-aurated complexes. These results are the first experimental evidence of phosphorus- and sulfur-stabilized carbones behaving as four-electron donors. In addition, the reaction of hydrochloric salts of the carbones with Ag2 O gives the corresponding Ag(I) complexes. The resulting silver(I) carbone complexes can be used as carbone transfer agents. This synthetic protocol can also be used for moisture-sensitive carbone species. PMID:26471447

  6. Synthesis, Structure, and Reactivities of Iminosulfane- and Phosphane-Stabilized Carbones Exhibiting Four-Electron Donor Ability.

    PubMed

    Morosaki, Tomohito; Wang, Wei-Wei; Nagase, Shigeru; Fujii, Takayoshi

    2015-10-19

    Iminosulfane(phosphane)carbon(0) derivatives (iSPCs; Ar3 P→C←SPh2 (NMe); Ar=Ph (1), 4-MeOC6 H4 (2), 4-(Me2 N)C6 H4 (3)) have been successfully synthesized and the molecular structure of 3 characterized. Carbone 3 is the first thermally and hydrolytically stable carbone stabilized by phosphorus and sulfur ligands. DFT calculations reveal the electronic structures of 1-3, which have two lone pairs of electrons at the carbon center. First and second proton affinity values are theoretically calculated to be in the range of 286.8-301.1 and 189.6-208.3 kcal mol(-1) , respectively. Cyclic voltammetry measurements reveal that the HOMO energy levels follow the order of 3>2>1 and the HOMO of 3 is at a higher energy than those of bis(chalcogenane)carbon(0) (BChCs). The reactivities of these lone pairs of electrons are demonstrated by the C-diaurated and C-proton-aurated complexes. These results are the first experimental evidence of phosphorus- and sulfur-stabilized carbones behaving as four-electron donors. In addition, the reaction of hydrochloric salts of the carbones with Ag2 O gives the corresponding Ag(I) complexes. The resulting silver(I) carbone complexes can be used as carbone transfer agents. This synthetic protocol can also be used for moisture-sensitive carbone species.

  7. A method of synthesis magnetotelluric time-series combining interstation transfer functions and a reference site

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Campanyà, Joan

    2016-04-01

    A new method to Synthesis magnetotelluric (MT) data is proposed whereby the MT Time-series of local site are derived using an Inverse Fourier transform of electric and magnetic fields spectrum of local site, which are computed by Combining Interstation transfer functions and a Reference horizontal magnetic time series (STICIR). The method is based on the stability of interstation transfer function, assuming that the geoelectrical structures of the subsurface independent of time. Applying the suggested method, two interstation transfer functions need to be estimated: the quasi-MT impedance tensor and the interstation geomagnetic transfer functions, which are used to compute the horizontal electric fields and the vertical magnetic field at the local site, respectively. The interstation transfer functions can be estimated by single site robust or remote reference (RR) method if another reference site existed. STICIR provides a new way to synthesis MT time-series at the local site combining interstation transfer functions and the magnetic fields at a reference site. Due to this property, STICIR provides significant improvements processing MT data when time-series at the local site are affected by local noise or are truncated. A test with good quality of MT data shows that synthetic time-series are similar to natural electric and magnetic time series. For contaminated data example, when this method is used to remove noise present at the local site, the scatter of MT sounding curves are clear reduced, and the low frequency data quality are improved.

  8. Synthesis of a reactive polymethacrylate capillary monolith and its use as a starting material for the preparation of a stationary phase for hydrophilic interaction chromatography.

    PubMed

    Kip, Çiğdem; Erkakan, Damla; Gökaltun, Aslıhan; Çelebi, Bekir; Tuncel, Ali

    2015-05-29

    Poly(3-chloro-2-hydroxypropyl methacrylate-co-ethylene dimethacrylate), poly(HPMA-Cl-co-EDMA) capillary monolith was proposed as a reactive starting material with tailoring flexibility for the preparation of monolithic stationary phases. The reactive capillary monolith was synthesized by free radical copolymerization of 3-chloro-2-hydroxypropyl methacrylate (HPMA-Cl) and ethylene dimethacrylate (EDMA). The mean pore size, the specific surface area and the permeability of poly(HPMA-Cl-co-EDMA) monoliths were controlled by adjusting porogen/monomer volume ratio, porogen composition and polymerization temperature. The porogen/monomer volume ratio was found as the most effective factor controlling the porous properties of poly(HPMA-Cl-co-EDMA) monolith. Triethanolamine (TEA-OH) functionalized polymethacrylate monoliths were prepared by using the reactive chloropropyl group of poly(HPMA-Cl-co-EDMA) monolith via one-pot and simple post-functionalization process. Poly(HPMA-Cl-co-EDMA) monolith reacted with TEA-OH was evaluated as a stationary phase in nano-hydrophilic interaction chromatography (nano-HILIC). Nucleotides, nucleosides and benzoic acid derivatives were satisfactorily separated with the plate heights up to 20μm. TEA-OH attached-poly(HPMA-Cl-co-EDMA) monolith showed a reproducible and stable retention behaviour in nano-HILIC runs. However, a decrease in the column performance (i.e. an increase in the plate height) was observed with the increasing retention factor. Hence "retention-dependent column efficiency" behaviour was shown for HILIC mode using the chromatographic data collected with the polymer based monolith synthesized.

  9. Polymer/organosilica nanocomposites based on polyimide with benzimidazole linkages and reactive organoclay containing isoleucine amino acid: Synthesis, characterization and morphology properties

    SciTech Connect

    Mallakpour, Shadpour; Dinari, Mohammad

    2012-09-15

    Highlights: ► A reactive organoclay was formed using L-isoleucine amino acid as a swelling agent. ► Polyimide was synthesized from benzimidazole diamine and pyromellitic dianhydride. ► Imide and benzimidazole groups assured the thermal stability of the nanocomposites. ► Nanocomposite films were prepared by an in situ polymerization reaction. ► The TEM micrographs of nanocomposites revealed well-exfoliated structures. -- Abstract: Polyimide–silica nanocomposites are attractive hybrid architectures that possess excellent mechanical, thermal and chemical properties. But, the dispersion of inorganic domains in the polymer matrix and the compatibility between the organic and inorganic phases are critical factors in these hybrid systems. In this investigation, a reactive organoclay was prepared via ion exchange reaction between protonated form of difunctional L-isoleucine amino acid as a swelling agent and Cloisite Na{sup +} montmorillonite. Amine functional groups of this swelling agent formed an ionic bond with the negatively charged silicates, whereas the remaining acid functional groups were available for further interaction with polymer chains. Then organo-soluble polyimide (PI) have been successfully synthesized from the reaction of 2-(3,5-diaminophenyl)-benzimidazole and pyromellitic dianhydride in N,N-dimethylacetamide. Finally, PI/organoclay nanocomposite films enclosing 1%, 3%, 5%, 7% and 10% of synthesized organoclay were successfully prepared by an in situ polymerization reaction through thermal imidization. The synthesized hybrid materials were subsequently characterized by Fourier transform infrared spectroscopy, X-ray diffraction, electron microscopy, and thermogravimetric analysis techniques. The PI/organoclay nanocomposite films have good optical transparencies and the mechanical properties were substantially improved by the incorporation of the reactive organoclay.

  10. Design and synthesis of diverse functional kinked nanowire structures for nanoelectronic bioprobes.

    PubMed

    Xu, Lin; Jiang, Zhe; Qing, Quan; Mai, Liqiang; Zhang, Qingjie; Lieber, Charles M

    2013-02-13

    Functional kinked nanowires (KNWs) represent a new class of nanowire building blocks, in which functional devices, for example, nanoscale field-effect transistors (nanoFETs), are encoded in geometrically controlled nanowire superstructures during synthesis. The bottom-up control of both structure and function of KNWs enables construction of spatially isolated point-like nanoelectronic probes that are especially useful for monitoring biological systems where finely tuned feature size and structure are highly desired. Here we present three new types of functional KNWs including (1) the zero-degree KNW structures with two parallel heavily doped arms of U-shaped structures with a nanoFET at the tip of the "U", (2) series multiplexed functional KNW integrating multi-nanoFETs along the arm and at the tips of V-shaped structures, and (3) parallel multiplexed KNWs integrating nanoFETs at the two tips of W-shaped structures. First, U-shaped KNWs were synthesized with separations as small as 650 nm between the parallel arms and used to fabricate three-dimensional nanoFET probes at least 3 times smaller than previous V-shaped designs. In addition, multiple nanoFETs were encoded during synthesis in one of the arms/tip of V-shaped and distinct arms/tips of W-shaped KNWs. These new multiplexed KNW structures were structurally verified by optical and electron microscopy of dopant-selective etched samples and electrically characterized using scanning gate microscopy and transport measurements. The facile design and bottom-up synthesis of these diverse functional KNWs provides a growing toolbox of building blocks for fabricating highly compact and multiplexed three-dimensional nanoprobes for applications in life sciences, including intracellular and deep tissue/cell recordings.

  11. Carbonated hydroxyapatite starting from calcite and different orthophosphates under moderate hydrothermal conditions: Synthesis and surface reactivity in simulated body fluid

    SciTech Connect

    Pham Minh, Doan Nzihou, Ange; Sharrock, Patrick

    2014-12-15

    Highlights: • Carbonated apatite (CAP) could be easily obtained from CaCO{sub 3} and orthophosphates. • Highest CaCO{sub 3} dissolution and apatitic carbonate content were obtained with H{sub 3}PO{sub 4}. • A-B-type CAP was formed. • The synthesized CAP was thermally stable up to 1000 °C. • This CAP showed high biomineralization activity before and after thermal treatment. - Abstract: The one-step synthesis of carbonated hydroxyapatite (CAP) using calcite and different orthophosphates was investigated in a closed batch reactor. Only orthophosphoric acid could lead to the complete decomposition of calcite particles, when the reaction temperature was set at 80 °C. On the other hand, the reaction time and the dilution of the initial calcite suspension had no significant influence on the formation of the solid products. CAP was formed as the main crystalline calcium phosphate with the carbonate content in the range of 4.2–4.6 wt.%. The thermal decarbonation of the synthesized CAP started at 750 °C but it was only significant at 1000 °C under air atmosphere. This thermal decarbonation was total at 1200 °C or above. All CAP samples and products following thermal treatments were found bioactive in the test using simulated body fluid (SBF) solution.

  12. Control of vascular smooth muscle function by Src-family kinases and reactive oxygen species in health and disease

    PubMed Central

    MacKay, Charles E; Knock, Greg A

    2015-01-01

    Abstract Reactive oxygen species (ROS) are now recognised as second messenger molecules that regulate cellular function by reversibly oxidising specific amino acid residues of key target proteins. Amongst these are the Src-family kinases (SrcFKs), a multi-functional group of non-receptor tyrosine kinases highly expressed in vascular smooth muscle (VSM). In this review we examine the evidence supporting a role for ROS-induced SrcFK activity in normal VSM contractile function and in vascular remodelling in cardiovascular disease. VSM contractile responses to G-protein-coupled receptor stimulation, as well as hypoxia in pulmonary artery, are shown to be dependent on both ROS and SrcFK activity. Specific phosphorylation targets are identified amongst those that alter intracellular Ca2+ concentration, including transient receptor potential channels, voltage-gated Ca2+ channels and various types of K+ channels, as well as amongst those that regulate actin cytoskeleton dynamics and myosin phosphatase activity, including focal adhesion kinase, protein tyrosine kinase-2, Janus kinase, other focal adhesion-associated proteins, and Rho guanine nucleotide exchange factors. We also examine a growing weight of evidence in favour of a key role for SrcFKs in multiple pro-proliferative and anti-apoptotic signalling pathways relating to oxidative stress and vascular remodelling, with a particular focus on pulmonary hypertension, including growth-factor receptor transactivation and downstream signalling, hypoxia-inducible factors, positive feedback between SrcFK and STAT3 signalling and positive feedback between SrcFK and NADPH oxidase dependent ROS production. We also discuss evidence for and against the potential therapeutic targeting of SrcFKs in the treatment of pulmonary hypertension. PMID:25384773

  13. Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment.

    PubMed

    Su, Yiming; Adeleye, Adeyemi S; Huang, Yuxiong; Zhou, Xuefei; Keller, Arturo A; Zhang, Yalei

    2016-01-01

    Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) is of great technical and scientific interest because of its promising application in groundwater remediation, although its synthesis is still a challenge. We develop a new nanoparticle seeding method to obtain a novel and reactive nanohybrid, which contains an Fe(0) core covered by a highly sulfidized layer under high extent of sulfidation. Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe(2+) to Fe(0) by 19%. X-ray adsorption near edge structure (XANES) spectroscopy and extended X-ray absorption fine structure analyses demonstrate the hexahedral Fe-Fe bond (2.45 and 2.83 Å) formation through breaking down of the 1.99 Å Fe-O bond both in crystalline and amorphous iron oxide. The XANES analysis also shows 24.2% (wt%) of FeS with bond length of 2.4 Å in final nanohybrid. Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe(0) crystals. Nano-SiO2 seeding brings down the size of single Fe(0) grain from 32.4 nm to 18.7 nm, enhances final Fe(0) content from 5.9% to 55.6%, and increases magnetization from 4.7 to 65.5 emu/g. The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water.

  14. Synthesis of 1-(β-D-Galactopyranosyl)Thymine-6'-O-Triphosphate - A Potential Probe to Generate Reactive Dialdehyde for DNA-Enzyme Cross-Linking.

    PubMed

    Kore, Anilkumar R; Yang, Bo; Srinivasan, Balasubramanian

    2015-01-01

    Concise, facile, and efficient synthesis of 1-(β-D-galactopyranosyl)thymine-6'-O-triphosphate, a potential probe that can generate reactive dialdehyde for DNA-enzyme cross-linking applications, was described starting from O,O'-bis(trimethylsilyl)thymine. Stannic chloride promoted glycosylation of 1,2,3,4,6-penta-O-acetyl-α-D-galactopyranose with O,O'-bis(trimethylsilyl)thymine, resulting in the formation of 1-(2,3,4,6-O-tetraacetyl-β-D-galactopyranosyl)thymine in 91% yield. Acetyl deprotection using methanolic ammonia afforded 1-(β-D-galactopyranosyl)thymine in 98% yield. The modified one-pot methodology was used to convert 1-(β-D-galactopyranosyl)thymine into 1-(β-D-galactopyranosyl)thymine-6'-O-triphosphate in 72% yield, which involves the formation of 1-(β-D-galactopyranosyl)thymine dichlorophosphoridate using POCl3 as the reagent at the monophosphorylation step followed by reaction with tributylammonium pyrophosphate and hydrolysis of resulting cyclic intermediate.

  15. Sulfide Oxidation by O2: Synthesis, Structure and Reactivity of Novel Sulfide-Incorporated Fe(II) Bis(imino)pyridine Complexes

    PubMed Central

    Widger, Leland R.; Siegler, Maxime A.

    2013-01-01

    The unsymmetrical iron(II) bis(imino)pyridine complexes [FeII(LN3SMe)(H2O)3](OTf)2 (1), and [FeII(LN3SMe)Cl2] (2) were synthesized and their reactivity with O2 was examined. Complexes 1 and 2 were characterized by single crystal X-ray crystallography, LDI-MS, 1H-NMR and elemental analysis. The LN3SMe ligand was designed to incorporate a single sulfide donor and relies on the bis(imino)pyridine scaffold. This scaffold was selected for its ease of synthesis and its well-precedented ability to stabilize Fe(II) ions. Complexes 1 and 2 ware prepared via a metal-assisted template reaction from the unsymmetrical pyridyl ketone precursor 2-(O=CMe)-6-(2,6-(iPr2-C6H3N=CMe)-C5H3N. Reaction of 1 with O2 was shown to afford the S-oxygenated sulfoxide complex [Fe(LN3S(O)Me)(OTf)]2+(3), whereas compound 2, under the same reaction conditions, afforded the corresponding sulfone complex [Fe(LN3S(O2)Me)Cl]2+ (4). PMID:23878411

  16. Synthesis and non-covalent functionalization of carbon nanotubes rings: new nanomaterials with lectin affinity

    NASA Astrophysics Data System (ADS)

    Assali, Mohyeddin; Pernía Leal, Manuel; Fernández, Inmaculada; Khiar, Noureddine

    2013-03-01

    We present a mild and practical carbon nanotubes rings (CNRs) synthesis from non-covalent functionalized and water-soluble linear single-wall carbon nanotubes. The hemi-micellar-supramolecular self-organization of lactose-based glycolipid 1 on the ring surface, followed by photo-polymerization of the diacetylenic function triggered by UV light afforded the first water-soluble and biocompatible CNRs. The obtained donut-like nanoconstructs expose a high density of lactose moieties on their surface, and are able to engage specific interactions with Arachis hypogea lectin similar to glycoconjugates on the cell membrane.

  17. Design, synthesis and characterization of functionalized SCK nanoparticles and functionalized biocompatible surfaces: Construction platforms for nanoparticle assembly and biomacromolecule immobilization

    NASA Astrophysics Data System (ADS)

    Qi, Kai

    This dissertation focuses on the design, synthesis and characterization of biotin-functionalized shell crosslinked knedel-like (SCK) nanoparticles, biotin-functionalized polymer brush surfaces, and their utilization as construction platforms for the study of streptavidin-mediated nanoparticle assembly. SCKs are a class of nano-objects, originating from the self-assembly of amphiphilic block copolymers. Their synthesis and functionalization were accomplished beginning from the synthesis of block copolymers via living radical polymerization techniques, and extending to supramolecular assembly and polymer modification reactions. The regioselective placement of biotin units on the surface of SCK nanoparticles was achieved via two synthetic methods: mixed micelle formation with chain-end biotinylated block copolymers and their non-biotinylated analog followed by shell crosslinking reactions; and post-preparation functionalization reactions of SCKs with biotinylated molecules. Both methods enabled facile control of the degree of biotinylation. The resulting SCK nanoparticles were characterized thoroughly and the bioavailability of the biotin moieties present on the SCK surface was determined. These biotinylated SCK nanoparticles were used as building blocks for the preparation of streptavidin-mediated nanoparticle assemblies upon well-defined biotinylated substrates. Chain-end biotinylated polymer brushes served as well-defined substrates for nanoparticle assembly. These functionalized polymer brush surfaces were prepared by a grafting-from technique utilizing nitroxide mediated polymerization (NMP). Functionalized initiators were synthesized and covalently immobilized on the surface in patterns by contact molding that allowed for the preparation of nano-patterned polymer brush surfaces via NMP. The biotinylated polymer brush surfaces were characterized thoroughly and used to immobilize streptavidin. Subsequent attachment of biotinylated SCKs led to the formation of

  18. Gas phase studies of the Pesci decarboxylation reaction: synthesis, structure, and unimolecular and bimolecular reactivity of organometallic ions.

    PubMed

    O'Hair, Richard A J; Rijs, Nicole J

    2015-02-17

    promoting the formation of the organometallic ion. Where isomeric organometallic ions are generated and normal MS approaches cannot distinguish them, we describe approaches to elucidate the decarboxylation mechanism via determination of their structure. These "unmasked" organometallic ions, [RM(L)n](x), can also be structurally interrogated spectroscopically or via CID. We have thus compared the gas-phase structures and decomposition of several highly reactive and synthetically important organometallic ions for the first time. Perhaps the most significant aspect of this work is the study of bimolecular reactions, which provides experimental information on mechanistically obscure bond-formation and cross-coupling steps and the intrinsic reactivity of ions. We have sought to understand transformations of substrates including acid-base and hydrolysis reactions, along with reactions resulting in C-C bond formation. Our studies also allow a direct comparison of the performance of different metal catalysts in the individual elementary steps associated with protodecarboxylation and decarboxylative alkylation cycles. Electronic structure (DFT and ab initio) and dynamics (RRKM) calculations provide further mechanistic insights into these reactions. The broad implications of this research are that new reactions can be discovered and that the performance of metal catalysts can be evaluated in terms of each of their elementary steps. This has been particularly useful for the study of metal-mediated decarboxylation reactions.

  19. Gas phase studies of the Pesci decarboxylation reaction: synthesis, structure, and unimolecular and bimolecular reactivity of organometallic ions.

    PubMed

    O'Hair, Richard A J; Rijs, Nicole J

    2015-02-17

    promoting the formation of the organometallic ion. Where isomeric organometallic ions are generated and normal MS approaches cannot distinguish them, we describe approaches to elucidate the decarboxylation mechanism via determination of their structure. These "unmasked" organometallic ions, [RM(L)n](x), can also be structurally interrogated spectroscopically or via CID. We have thus compared the gas-phase structures and decomposition of several highly reactive and synthetically important organometallic ions for the first time. Perhaps the most significant aspect of this work is the study of bimolecular reactions, which provides experimental information on mechanistically obscure bond-formation and cross-coupling steps and the intrinsic reactivity of ions. We have sought to understand transformations of substrates including acid-base and hydrolysis reactions, along with reactions resulting in C-C bond formation. Our studies also allow a direct comparison of the performance of different metal catalysts in the individual elementary steps associated with protodecarboxylation and decarboxylative alkylation cycles. Electronic structure (DFT and ab initio) and dynamics (RRKM) calculations provide further mechanistic insights into these reactions. The broad implications of this research are that new reactions can be discovered and that the performance of metal catalysts can be evaluated in terms of each of their elementary steps. This has been particularly useful for the study of metal-mediated decarboxylation reactions. PMID:25594228

  20. Synthesis, Characterization and Preliminary Biological Evaluation of P(HPMA)-b-P(LLA) Copolymers: A New Type of Functional Biocompatible Block Copolymer.

    PubMed

    Barz, Matthias; Wolf, Florian K; Canal, Fabiana; Koynov, Kaloian; Vicent, Maria J; Frey, Holger; Zentel, Rudolf

    2010-09-01

    We describe a synthetic pathway to functional P(HPMA)-b-P(LLA) block copolymers. The synthesis relies on a combination of ring-opening polymerization of L-lactide, conversion into a chain transfer agent (CTA) for the RAFT polymerization of pentafluorophenyl methacrylate. A series of block copolymers was prepared that exhibited molecular weights $\\overline M _{\\rm n}$ ranging from 7 600 to 34 300 g · mol(-1) , with moderate PDI between 1.3 and 1.45. These reactive precursor polymers have been transformed into biocompatible P(HPMA)-b-P(LLA) copolymers and their fluorescently labeled derivatives by facile replacement of the pentafluorophenyl groups. The fluorescence label attached to this new type of a partially degradable amphiphilic block copolymer was used to study cellular uptake in human cervix adenocarcinoma (HeLa) cells as well as aggregation behavior by fluorescence correlation spectroscopy (FCS).

  1. Highly functionalized dispiro oxindole-pyrrolo[1,2-c]thiazole-piperidone hybrid: Synthesis, characterization and theoretical investigations on the regiochemistry

    NASA Astrophysics Data System (ADS)

    Suresh Kumar, Raju; Almansour, Abdulrahman I.; Arumugam, Natarajan; Soliman, Saied M.; Ranjith Kumar, Raju; Ghabbour, Hazem A.

    2016-10-01

    The synthesis of highly functionalized dispiro oxindole-pyrrolo[1,2-c]thiazole-piperidone hybrid has been achieved regioselectively employing microwave-assisted three-component 1,3-dipolar cycloaddition. Structural elucidation of the compound has been accomplished using NMR spectroscopy and further confirmed by single crystal X-ray crystallographic studies. The molecular structure of the compound crystallized in monoclinic, P21/c, a = 11.6182 (2) Å, b = 12.2466 (2) Å, c = 21.7061 (3) Å, β = 103.018 (1)°, V = 3009.04 (8) Å3, Z = 4. The cycloaddition was found to proceed by normal electronic demand (NED) character with a significant high charge transfer (0.1247 eV) from the 1,3-dipole to the dipolarophile. The regiochemistry has been explained using the local reactivity descriptors obtained from the DFT calculations. The DFT optimized molecular structure agreed well with the X-ray results.

  2. Vanadium(V) complex with Schiff-base ligand containing a flexible amino side chain: Synthesis, structure and reactivity.

    PubMed

    Nica, Simona; Rudolph, Manfred; Lippold, Ines; Buchholz, Axel; Görls, Helmar; Plass, Winfried

    2015-06-01

    The Schiff-base ligand (H2salhyhNH3)Cl (1) derived from salicylaldehyde and 6-aminohexanoic acid hydrazide hydrochloride reacts with ammonium metavanadate in methanol solution to yield the dioxidovanadium(V) complex [VO2(salhyhNH3)] (2). The utilized hydrazone ligand contains a flexible and protonated amino side chain. Crystallization from methanol affords complex 2 in the monoclinic space group P21/n, whereas crystallization from a methanol/water mixture 1:1 yields crystals, containing a water molecule of crystallization per two formula units (2⋅1/2H2O), in the orthorhombic space group Pbcn. In both cases the protonated amino group compensates the negative charge on the dioxidovanadium moiety and is involved in an extensive hydrogen bonding network particularly including the oxido groups from neighboring vanadium complexes. The reactivity of complex 2 toward protonation in aqueous solution has been investigated by spectrophotometric titrations and is characterized by two subsequent protonation steps at the hydrazide nitrogen atom of the ligand system and an oxido group leading to the formation of an oxidohydroxidovanadium(V) species with corresponding pKa values of 3.2 and 2.9, respectively. With larger excess of acid the oxidohydroxidovanadium(V) species starts to form the corresponding anhydride. The formation of the anhydride is strongly favored in the presence of methanol. The reaction of complex 2 with hydrogen peroxide in methanol solution leads to the formation of an oxidoperoxidovanadium(V) species, whereas in aqueous solution the addition of one equivalent of acid is required. Complex 2 catalyzes the oxidation of methylphenylsulfane to the corresponding sulfoxide in methanol/dichloromethane mixture using hydrogen peroxide as oxidant at room temperature.

  3. Synthesis, stereochemistry and reactivity of the highly mutagenic bay-region diol epoxides from benzo(c)phenanthrene

    SciTech Connect

    Sayer, J.M.; Yagi, H.; Croisy-Delcey, M.; Jerina, D.M.

    1980-08-01

    Within the past six years, epoxides on saturated benzo-rings in which the epoxide group forms part of a sterically hindered bay-region of the polycyclic aromatic hydrocarbon molecule have been identified as ultimate carcinogenic metabolites of a number of hydrocarbons. Several of these observations led to the formulation of the bay-region theory, which predicts that bay-region epoxides which yield stable benzylic carbonium ions (as indicated by large values of ..delta..E/sub deloc/..beta.. is for the formation of these carbonium ions) will be active as tumorigens and/or mutagens when derived from carcinogenic hydrocarbons. This prediction is in good qualitative agreement with the decreasing order of tumorigenicity and mutagenicity for the biologically active diastereomers of the bay-region diol eoxides derived from benzo(a)pyrene, benzo(a)anthracene and its derivatives, and chrysene. Factors, in addition to carbonium ion stability, also play an essential role in determining the chemical and biological activity of these molecules; namely, S/sub N/2 reactivity, steric, stereoelectronic and conformational effects, hydrogen bonding, size, shape and hydrophobic character of the aromatic moiety, and possible complexation effects with biological macromolecules. As part of studies to assess the importance of these factors, we have investigated the diastereomeric diol epoxides (+)-3..cap alpha.., 4..beta..-dihydroxy-1..beta.., 2..beta..-epoxy-1,2,3,4,-tetrahydrobenzo(c)phenanthrene, 1 and (+)-3..cap alpha.., 4..beta..-dihydroxy-1..cap alpha.., 2..cap alpha..-epoxy-1,2,3,4-tetrahydrobenzo(c)phenanthrene, 2.

  4. Continued functioning of the secretory pathway is essential for ribosome synthesis.

    PubMed Central

    Mizuta, K; Warner, J R

    1994-01-01

    To explore the regulatory elements that maintain the balanced synthesis of the components of the ribosome, we isolated a temperature-sensitive (ts) mutant of Saccharomyces cerevisiae in which transcription both of rRNA and of ribosomal protein genes is defective at the nonpermissive temperature. Temperature sensitivity for growth is recessive and segregates 2:2. A gene that complements the ts phenotype was cloned from a genomic DNA library. Sequence analysis revealed that this gene is SLY1, encoding a protein essential for protein and vesicle transport between the endoplasmic reticulum and the Golgi apparatus. In the strain carrying our ts allele of SLY1, accumulation of the carboxypeptidase Y precursor was detected at the nonpermissive temperature, indicating that the secretory pathway is defective. To ask whether the effect of the ts allele on ribosome synthesis was specific for sly1 or was a general result of the inactivation of the secretion pathway, we assayed the levels of mRNA for several ribosomal proteins in cells carrying ts alleles of sec1, sec7, sec11, sec14, sec18, sec53, or sec63, representing all stages of secretion. In each case, the mRNA levels were severely depressed, suggesting that this is a common feature in mutants of protein secretion. For the mutants tested, transcription of rRNA was also substantially reduced. Furthermore, treatment of a sensitive strain with brefeldin A at a concentration sufficient to block the secretion pathway also led to a decrease of the level of ribosomal protein mRNA, with kinetics suggesting that the effect of a secretion defect is manifest within 15 to 30 min. We conclude that the continued function of the entire secretion pathway is essential for the maintenance of ribosome synthesis. The apparent coupling of membrane synthesis and ribosome synthesis suggest the existence of a regulatory network that connects the production of the various structural elements of the cell. Images PMID:8139552

  5. A general and highly regioselective synthesis approach to multi-functionalized organoimido derivatives of Polyoxometalates

    PubMed Central

    Huang, Yichao; Zhang, Jiangwei; Hao, Jian; Wei, Yongge

    2016-01-01

    Organoimidoylization of Polyoxometalates (POMs) can dramatically modify the electronic structures of POMs and gives rise to novel “value-adding” properties of the POMs for promising material applications including photo-electronic transformation and catalysis. To date, the preparation of multi-functionalized organoimido derivatives of POMs is generally conducted under strict condition and is time-consuming with limited yields. Herein, a series of regioselective polyorganoimido derivatives of POMs, ocatant- [Mo6O13(NAr)3(μ2-NAr)3]2− (Ar = phenyl (1), p-methoxyphenyl (2) and p-ethylphenyl (3)), were synthesized with high selectivity and in good yields via a general and highly regioselective synthesis method, called as the one-octant synthesis protocol. The reaction was monitored by ESI-MS and the as-prepared products were studied by ESI-MS, IR, UV-Vis, EA, 1HNMR, single crystal XRD analysis and DFT calculations. The one-octant synthesis protocol here may serve as an idea method to design novel nanoscale POM-based organic-inorganic multi-functional hybrids. PMID:27108955

  6. Functionalization of SBA-15 mesoporous silica by Cu-phosphonate units: Probing of synthesis route

    SciTech Connect

    Laskowski, Lukasz; Laskowska, Magdalena

    2014-12-15

    Mesoporous silica SBA-15 containing propyl-copper phosphonate units was investigated. The structure of mesoporous samples was tested by N{sub 2} isothermal sorption (BET and BHJ analysis), TEM microscopy and X-Ray scattering. Quantitative analysis EDX has given information about proportions between component atoms in the sample. Quantitative elemental analysis has been carried out to support EDX. To examine bounding between copper atoms and phosphonic units the Raman spectroscopy was carried out. As a support of Raman scattering, the theoretical calculations were made based on density functional theory, with the B3LYP method. By comparison of the calculated vibrational spectra of the molecule with experimental results, distribution of the active units inside silica matrix has been determined. - Graphical abstract: The present study is devoted to mesoporous silica SBA-15 containing propyl-copper phosphonate units. The species were investigated to confirm of synthesis procedure correctness by the micro-Raman technique combined with DFT numerical simulations. Complementary research was carried out to test the structure of mesoporous samples. - Highlights: • SBA-15 silica functionalized with propyl-copper phosphonate units was synthesized. • Synthesis efficiency probed by Raman study supported with DFT simulations. • Homogenous distribution of active units was proved. • Synthesis route enables precise control of distance between copper ions.

  7. A general and highly regioselective synthesis approach to multi-functionalized organoimido derivatives of Polyoxometalates

    NASA Astrophysics Data System (ADS)

    Huang, Yichao; Zhang, Jiangwei; Hao, Jian; Wei, Yongge

    2016-04-01

    Organoimidoylization of Polyoxometalates (POMs) can dramatically modify the electronic structures of POMs and gives rise to novel “value-adding” properties of the POMs for promising material applications including photo-electronic transformation and catalysis. To date, the preparation of multi-functionalized organoimido derivatives of POMs is generally conducted under strict condition and is time-consuming with limited yields. Herein, a series of regioselective polyorganoimido derivatives of POMs, ocatant- [Mo6O13(NAr)3(μ2-NAr)3]2- (Ar = phenyl (1), p-methoxyphenyl (2) and p-ethylphenyl (3)), were synthesized with high selectivity and in good yields via a general and highly regioselective synthesis method, called as the one-octant synthesis protocol. The reaction was monitored by ESI-MS and the as-prepared products were studied by ESI-MS, IR, UV-Vis, EA, 1HNMR, single crystal XRD analysis and DFT calculations. The one-octant synthesis protocol here may serve as an idea method to design novel nanoscale POM-based organic-inorganic multi-functional hybrids.

  8. Acid synthesis of luminescent amine-functionalized or erbium-doped silica spheres for biological applications.

    PubMed

    Enrichi, Francesco; Trave, Enrico; Bersani, Marco

    2008-03-01

    In this work we discuss and investigate the morphological and optical properties of luminescent silica spheres which can have interesting applications in bioimaging and biosensing. The spheres are synthesized following an acid route by the hydrolysis and condensation of tetraethylortosilicate (TEOS) and can be functionalized by incorporation of aminopropyl-triethoxysilane (APTES) during the synthesis, inducing a significant luminescence that can be attributed to a recombination mechanism from localized organic defects related to -NH(2) groups. It is shown that the acid synthesis route produces very regular spherical particles, but their diameter vary in the range of 200-4,000 nm. The luminescence properties have been investigated and optimized by variation of the annealing temperature for the functionalized spheres, obtaining the most efficient PL emission after a thermal treatment of 1 h at 600 degrees C in air. Moreover, the possibility to introduce rare earths like erbium in the spheres was also studied and the corresponding Er(3) luminescence emission at 1.53 microm is reported in terms of intensity and lifetime, pointing out that erbium can be easily and efficiently incorporated during the acid synthesis giving high PL intensity with a good lifetime of 3.9 ms.

  9. Halogen bonding from a hard and soft acids and bases perspective: investigation by using density functional theory reactivity indices.

    PubMed

    Pinter, Balazs; Nagels, Nick; Herrebout, Wouter A; De Proft, Frank

    2013-01-01

    Halogen bonds between the trifluoromethyl halides CF(3)Cl, CF(3)Br and CF(3)I, and dimethyl ether, dimethyl sulfide, trimethylamine and trimethyl phosphine were investigated using Pearson's hard and soft acids and bases (HSAB) concept with conceptual DFT reactivity indices, the Ziegler-Rauk-type energy-decomposition analysis, the natural orbital for chemical valence (NOCV) framework and the non-covalent interaction (NCI) index. It is found that the relative importance of electrostatic and orbital (charge transfer) interactions varies as a function of both the donor and acceptor molecules. Hard and soft interactions were distinguished and characterised by atomic charges, electrophilicity and local softness indices. Dual-descriptor plots indicate an orbital σ hole on the halogen similar to the electrostatic σ hole manifested in the molecular electrostatic potential. The predicted high halogen-bond-acceptor affinity of N-heterocyclic carbenes was evidenced in the highest complexation energy for the hitherto unknown CF(3) I·NHC complex. The dominant NOCV orbital represents an electron-density deformation according to a n→σ*-type interaction. The characteristic signal found in the reduced density gradient versus electron-density diagram corresponds to the non-covalent interaction between contact atoms in the NCI plots, which is the manifestation of halogen bonding within the NCI theory. The unexpected C-X bond strengthening observed in several cases was rationalised within the molecular orbital framework.

  10. Changes in pulmonary function and airway reactivity due to prolonged exposure to typical ambient ozone (O sub 3 ) levels

    SciTech Connect

    Horstman, D.; McDonnell, W.; Folinsbee, L.; Abdul-Salaam, S.; Ives, P.

    1989-01-01

    Previously observed (JAPCA 38:28-35, 1988) pulmonary responses of delta FEV1 (-13%), moderate to severe pain upon inspiration, and a doubling of PD100 for methacholine following prolonged moderate exercise at 0.12 ppm O3 were of sufficient magnitude to warrant the assessing of responses at a lower range of concentrations, i.e., 0.08, 0.10 and 0.12 ppm O3. Exposures consisted of six 50-min exercises (VE approximately equals 40 L/min), each followed by 10-min rest; a 35-min lunch break was included. When compared with exposures to 0.00 ppm, substantial pulmonary function decrements, respiratory symptoms and increases in nonspecific airway reactivity were observed at all three O3 concentrations. For example, decreases in FEV1 (P < 0.01) of 7%, 7% and 12% were observed at 0.08, 0.10 and 0.12 ppm O3, respectively. The ratios (P < 0.005) of PD100 observed in 0.00 ppm to that in O3 were 1.56 at 0.08 ppm, 1.89 at 0.10 ppm, and 2.21 at 0.12 ppm O3. It is concluded that exercise representative of a day of moderate to heavy work or play performed during exposures to O3 at levels and pattern often found in ambient air induced clinically meaningful pulmonary responses.

  11. Halogen bonding from a hard and soft acids and bases perspective: investigation by using density functional theory reactivity indices.

    PubMed

    Pinter, Balazs; Nagels, Nick; Herrebout, Wouter A; De Proft, Frank

    2013-01-01

    Halogen bonds between the trifluoromethyl halides CF(3)Cl, CF(3)Br and CF(3)I, and dimethyl ether, dimethyl sulfide, trimethylamine and trimethyl phosphine were investigated using Pearson's hard and soft acids and bases (HSAB) concept with conceptual DFT reactivity indices, the Ziegler-Rauk-type energy-decomposition analysis, the natural orbital for chemical valence (NOCV) framework and the non-covalent interaction (NCI) index. It is found that the relative importance of electrostatic and orbital (charge transfer) interactions varies as a function of both the donor and acceptor molecules. Hard and soft interactions were distinguished and characterised by atomic charges, electrophilicity and local softness indices. Dual-descriptor plots indicate an orbital σ hole on the halogen similar to the electrostatic σ hole manifested in the molecular electrostatic potential. The predicted high halogen-bond-acceptor affinity of N-heterocyclic carbenes was evidenced in the highest complexation energy for the hitherto unknown CF(3) I·NHC complex. The dominant NOCV orbital represents an electron-density deformation according to a n→σ*-type interaction. The characteristic signal found in the reduced density gradient versus electron-density diagram corresponds to the non-covalent interaction between contact atoms in the NCI plots, which is the manifestation of halogen bonding within the NCI theory. The unexpected C-X bond strengthening observed in several cases was rationalised within the molecular orbital framework. PMID:23169478

  12. Highly functionalized organic nitrates in the southeast United States: Contribution to secondary organic aerosol and reactive nitrogen budgets.

    PubMed

    Lee, Ben H; Mohr, Claudia; Lopez-Hilfiker, Felipe D; Lutz, Anna; Hallquist, Mattias; Lee, Lance; Romer, Paul; Cohen, Ronald C; Iyer, Siddharth; Kurtén, Theo; Hu, Weiwei; Day, Douglas A; Campuzano-Jost, Pedro; Jimenez, Jose L; Xu, Lu; Ng, Nga Lee; Guo, Hongyu; Weber, Rodney J; Wild, Robert J; Brown, Steven S; Koss, Abigail; de Gouw, Joost; Olson, Kevin; Goldstein, Allen H; Seco, Roger; Kim, Saewung; McAvey, Kevin; Shepson, Paul B; Starn, Tim; Baumann, Karsten; Edgerton, Eric S; Liu, Jiumeng; Shilling, John E; Miller, David O; Brune, William; Schobesberger, Siegfried; D'Ambro, Emma L; Thornton, Joel A

    2016-02-01

    Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part of the Southern Oxidant and Aerosol Study. A large fraction of pONs is highly functionalized, possessing between six and eight oxygen atoms within each carbon number group, and is not the common first generation alkyl nitrates previously reported. Using calibrations for isoprene hydroxynitrates and the measured molecular compositions, we estimate that pONs account for 3% and 8% of total submicrometer organic aerosol mass, on average, during the day and night, respectively. Each of the isoprene- and monoterpenes-derived groups exhibited a strong diel trend consistent with the emission patterns of likely biogenic hydrocarbon precursors. An observationally constrained diel box model can replicate the observed pON assuming that pONs (i) are produced in the gas phase and rapidly establish gas-particle equilibrium and (ii) have a short particle-phase lifetime (∼2-4 h). Such dynamic behavior has significant implications for the production and phase partitioning of pONs, organic aerosol mass, and reactive nitrogen speciation in a forested environment.

  13. Highly functionalized organic nitrates in the southeast United States: Contribution to secondary organic aerosol and reactive nitrogen budgets

    PubMed Central

    Mohr, Claudia; Lopez-Hilfiker, Felipe D.; Lutz, Anna; Hallquist, Mattias; Lee, Lance; Romer, Paul; Cohen, Ronald C.; Iyer, Siddharth; Kurtén, Theo; Hu, Weiwei; Day, Douglas A.; Campuzano-Jost, Pedro; Jimenez, Jose L.; Xu, Lu; Ng, Nga Lee; Guo, Hongyu; Weber, Rodney J.; Wild, Robert J.; Brown, Steven S.; Koss, Abigail; de Gouw, Joost; Olson, Kevin; Goldstein, Allen H.; Seco, Roger; Kim, Saewung; McAvey, Kevin; Shepson, Paul B.; Starn, Tim; Baumann, Karsten; Edgerton, Eric S.; Liu, Jiumeng; Shilling, John E.; Miller, David O.; Brune, William; Schobesberger, Siegfried; D'Ambro, Emma L.; Thornton, Joel A.

    2016-01-01

    Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part of the Southern Oxidant and Aerosol Study. A large fraction of pONs is highly functionalized, possessing between six and eight oxygen atoms within each carbon number group, and is not the common first generation alkyl nitrates previously reported. Using calibrations for isoprene hydroxynitrates and the measured molecular compositions, we estimate that pONs account for 3% and 8% of total submicrometer organic aerosol mass, on average, during the day and night, respectively. Each of the isoprene- and monoterpenes-derived groups exhibited a strong diel trend consistent with the emission patterns of likely biogenic hydrocarbon precursors. An observationally constrained diel box model can replicate the observed pON assuming that pONs (i) are produced in the gas phase and rapidly establish gas–particle equilibrium and (ii) have a short particle-phase lifetime (∼2–4 h). Such dynamic behavior has significant implications for the production and phase partitioning of pONs, organic aerosol mass, and reactive nitrogen speciation in a forested environment. PMID:26811465

  14. Highly functionalized organic nitrates in the southeast United States: Contribution to secondary organic aerosol and reactive nitrogen budgets.

    PubMed

    Lee, Ben H; Mohr, Claudia; Lopez-Hilfiker, Felipe D; Lutz, Anna; Hallquist, Mattias; Lee, Lance; Romer, Paul; Cohen, Ronald C; Iyer, Siddharth; Kurtén, Theo; Hu, Weiwei; Day, Douglas A; Campuzano-Jost, Pedro; Jimenez, Jose L; Xu, Lu; Ng, Nga Lee; Guo, Hongyu; Weber, Rodney J; Wild, Robert J; Brown, Steven S; Koss, Abigail; de Gouw, Joost; Olson, Kevin; Goldstein, Allen H; Seco, Roger; Kim, Saewung; McAvey, Kevin; Shepson, Paul B; Starn, Tim; Baumann, Karsten; Edgerton, Eric S; Liu, Jiumeng; Shilling, John E; Miller, David O; Brune, William; Schobesberger, Siegfried; D'Ambro, Emma L; Thornton, Joel A

    2016-02-01

    Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part of the Southern Oxidant and Aerosol Study. A large fraction of pONs is highly functionalized, possessing between six and eight oxygen atoms within each carbon number group, and is not the common first generation alkyl nitrates previously reported. Using calibrations for isoprene hydroxynitrates and the measured molecular compositions, we estimate that pONs account for 3% and 8% of total submicrometer organic aerosol mass, on average, during the day and night, respectively. Each of the isoprene- and monoterpenes-derived groups exhibited a strong diel trend consistent with the emission patterns of likely biogenic hydrocarbon precursors. An observationally constrained diel box model can replicate the observed pON assuming that pONs (i) are produced in the gas phase and rapidly establish gas-particle equilibrium and (ii) have a short particle-phase lifetime (∼2-4 h). Such dynamic behavior has significant implications for the production and phase partitioning of pONs, organic aerosol mass, and reactive nitrogen speciation in a forested environment. PMID:26811465

  15. One-step synthesis and functionalization of hydroxyl-decorated magnetite nanoparticles.

    PubMed

    Mondini, Sara; Cenedese, Simone; Marinoni, Giorgio; Molteni, Giorgio; Santo, Nadia; Bianchi, Claudia L; Ponti, Alessandro

    2008-06-01

    Magnetite nanoparticles covered by a layer of omega-hydroxycarboxylic acid were synthesized in one step by high-temperature decomposition of iron(III) omega-hydroxycarboxylates in tri- and tetra-ethylene glycol. The nanoparticles were characterized by TEM, XRD, IR, XPS and NMR techniques in order to show that they comprise a crystalline magnetite core and actually bear on the outer surface terminal hydroxy groups. The latter ones are convenient "handles" for further functionalization as opposed to the chemically-inert aliphatic chains which cover conventionally synthesized nanoparticles. This was shown by several examples in which the hydroxy groups on the nanoparticle surface were easily transformed in other functional groups or reacted with other molecules. For instance, the hydroxyl-decorated nanoparticles were made water soluble by esterification with a PEGylated acetic acid. The reactive behavior of the surfactant monolayer was monitored by degrading the nanoparticles with aqueous acid and isolating the surfactant for NMR characterization. In general, the reactivity of the terminal hydroxyl groups on the nanoparticle surface parallels that observed in the free surfactants. The reported hydroxyl-decorated magnetite nanoparticles can be thus considered as pro-functional nanoparticles, i.e., a convenient starting material to functionalized magnetic nanoparticles.

  16. Synthesis of surface bound silver nanoparticles on cellulose fibers using lignin as multi-functional agent.

    PubMed

    Hu, Sixiao; Hsieh, You-Lo

    2015-10-20

    Lignin has proven to be highly effective "green" multi-functional binding, complexing and reducing agents for silver cations as well as capping agents for the synthesis of silver nanoparticles on ultra-fine cellulose fibrous membranes. Silver nanoparticles could be synthesized in 10min to be densely distributed and stably bound on the cellulose fiber surfaces at up to 2.9% in mass. Silver nanoparticle increased in sizes from 5 to 100nm and became more polydispersed in size distribution on larger fibers and with longer synthesis time. These cellulose fiber bound silver nanoparticles did not agglomerate under elevated temperatures and showed improved thermal stability. The presence of alkali lignin conferred moderate UV absorbing ability in both UV-B and UV-C regions whereas the bound silver nanoparticles exhibited excellent antibacterial activities toward Escherichia coli. PMID:26256169

  17. Synthesis of surface bound silver nanoparticles on cellulose fibers using lignin as multi-functional agent.

    PubMed

    Hu, Sixiao; Hsieh, You-Lo

    2015-10-20

    Lignin has proven to be highly effective "green" multi-functional binding, complexing and reducing agents for silver cations as well as capping agents for the synthesis of silver nanoparticles on ultra-fine cellulose fibrous membranes. Silver nanoparticles could be synthesized in 10min to be densely distributed and stably bound on the cellulose fiber surfaces at up to 2.9% in mass. Silver nanoparticle increased in sizes from 5 to 100nm and became more polydispersed in size distribution on larger fibers and with longer synthesis time. These cellulose fiber bound silver nanoparticles did not agglomerate under elevated temperatures and showed improved thermal stability. The presence of alkali lignin conferred moderate UV absorbing ability in both UV-B and UV-C regions whereas the bound silver nanoparticles exhibited excellent antibacterial activities toward Escherichia coli.

  18. Enantioselective Synthesis of (−)-Maoecrystal V by Enantiodetermining C–H Functionalization

    PubMed Central

    2015-01-01

    The evolution of a program directed at the enantioselective total synthesis of maoecrystal V, a highly modified ent-kauranoid, is described. An early stage chiral auxiliary-directed asymmetric C–H functionalization for the construction of a key benzofuran intermediate enabled the first asymmetric synthesis of the natural enantiomer of maoecrystal V, confirming the assigned stereochemistry. A divergent course of the central intramolecular Diels–Alder reaction, which is dependent on the nature of the dienophile, initially led to the development of an unanticipated and previously unknown isomer of maoecrystal V, which we named maoecrystal ZG. In light of the reported selective and potent cytotoxic activity of maoecrystal V, the cytotoxic properties of maoecrystal ZG were also investigated. PMID:25409033

  19. Synthesis of gold nanorods and their functionalization with bovine serum albumin for optical hyperthermia.

    PubMed

    Zhang, Liming; Xia, Kai; Bai, Ying-Ying; Tang, Yongjun; Deng, Yan; Chen, Juan; Qian, Weiping; Shen, He; Zhang, Zhijun; Ju, Shenghong; He, Nongyue

    2014-08-01

    Although gold nanorods (GNRs) have been investigated extensively for optical hyperthermia therapies, the synthesis of rods is far from ideal. In this report, we optimized the synthesis of gold nanorods using hydroquinone as a reducing agent. Compared with the GNRs prepared by traditional ways, the as-synthesized rods have a flexibly tunable size and wider range of longitudinal surface plasmon resonance (LSPR). Furthermore, a series of small-length gold nanorods with length ranging from 30 to 90 nm were synthesized and they are more suitable for in vivo biomedical applications. Finally, we exploited a convenient approach for preparing water-soluble GNRs with less toxicity, better dispersion and flexible functionalization by exchanging hexadecyltrimethylammonium bromide (CTAB) on the surface of the rods with carboxylated bovine serum albumin (BSA) derivative, the BSA modified GNRs showed significant anticancer efficacy through near infrared (NIR) hyperthermia. We believe that the as-prepared gold nanorods will find promising applications in biomedical fields, especially in cancer therapy.

  20. Mechanistic study of synthesis of gold nanoparticles using multi-functional polymer

    NASA Astrophysics Data System (ADS)

    Yu, Taekyung; Kim, Rayoung; Park, Hoseok; Yi, Jonghyup; Kim, Woo-Sik

    2014-01-01

    This Letter presents a mechanistic study of the large-scale synthesis of Au nanoparticles when using branched polyethyleneimine (BPEI) as a multi-functional reducing agent, capping agent, and stabilizer. During the synthesis, the molar ratio of BPEI/HAuCl4, reaction temperature, and pH of the reacting solution were all found to be important factors in the formation, size control, and stabilization of the Au nanoparticles. The proposed synthetic route provided a highly concentrated product of Au nanoparticles (above 40 g/L), at least 10- to 200-fold more than previous methods, and can be readily applied to a large-scale process due to its simple and mild reaction conditions.

  1. Synthesis and Functionalization of Carbon and Boron Nitride Nanomaterials and Their Applications

    NASA Astrophysics Data System (ADS)

    Erickson, Kristopher John

    Carbon and boron-nitride based nanomaterials possess many exciting properties making them suitable for numerous applications spanning from electronics to advanced composites. However, these materials when synthesized often differ significantly from the idealized crystals usually considered theoretically. A thorough understanding of the structure of the materials as synthesized and how the resultant materials can be utilized for specific application purposes is required such that these applications can be effectively realized. To this end, the synthesis and characterization of carbon and boron-nitride based nanomaterials is undertaken with specific application purposes in mind. As a potential scalable synthetic route for graphene, graphene oxide (GO) and reduced graphene oxide are synthesized and characterized using atomic resolution electron microscopy. This elucidates their underlying structures revealing that the reduced form of GO does not resemble pristine graphene. The long-standing debate over the structure of GO is successfully ended with this study given the direct observation of the atomic structure of this material. To develop advanced composite materials, the functionalization of carbon and boron nitride nanotubes is undertaken. The characterization of their functionalization and incorporation within composite materials, specifically within a Kevlar polymer matrix, is presented to allow for the development of composites with significantly enhanced mechanical properties. Given a significant body of theoretical work paired with a single previous synthetic success, the synthesis of boron nitride nanoribbons is outlined. The first scalable synthesis of boron nitride nanoribbons is demonstrated resulting in long, consistent width, narrow, few-layer boron nitride nanoribbons which could be ideal for addressing these theoretical considerations. To establish a method for the synthesis of thin hexagonal-boron nitride (h-BN), the design of a specialized CVD system

  2. Heart function in magnetic resonance imaging and the mesenteric artery reactivity in rats receiving lead-contaminated drinking water.

    PubMed

    Skoczynska, A; Skórka, T; Wojakowska, A; Nowacki, D; Turczyn, B; Poręba, R; Tyrankiewicz, U; Byk, K; Szuba, A

    2014-05-01

    The aim of this study was to evaluate the effect of lead (Pb)-contaminated drinking water on magnetic resonance imaging (MRI)-estimated cardiac function, vascular reactivity, and serum lipids in rats. For 3 months, male Wistar rats, aged 4-6 weeks, were given drinking water with the addition of lead acetate at a concentration of 100 ppm Pb (10 rats) or water free from Pb (8 control rats). The cardiac MRI was performed at rest and under β-adrenergic stimulation on a 4.7 T scanner using electrocardiogram-triggered gradient echo (FLASH) cine sequence. After 1-2 weeks of the MRI test, experiments were performed ex vivo. After stabilization of perfusion pressure (PP), norepinephrine at doses from 0.01 to 5.0 μg was dissolved in Krebs solution, injected in a volume of 100 μl, and next infused at a concentration of 0.5 μg/ml into the isolated mesenteric artery. In this manner, preconstricted mesenteric bed was used to determine PP changes induced by acetylcholine, given at doses from 0.05 to 5.0 μg, before and during the infusion of nitric oxide synthase inhibitor (1.0 μg/ml). At the end, dobutamine (5 mg), followed by potassium chloride (10.5 mg), was injected. Lipid levels were determined enzymatically, blood Pb level was measured by the atomic absorption spectrophotometer. This study showed that Pb impairs the left ventricular systolic and diastolic function. Pb-induced changes in response to resistance of vessels to vasoactive agents may be secondary to the reduced left ventricular ejection fraction. The high-density lipoprotein subfraction 2 (HDL2) is involved in the cardiovascular effect of Pb.

  3. Synthesis and Characterization of Thiol-Ene Functionalized Siloxanes and Evaluation of their Crosslinked Network Properties

    PubMed Central

    Cole, Megan A.; Bowman, Christopher N.

    2012-01-01

    Three types of linear thiol-functionalized siloxane oligomers and three types of ene-functionalized oligomers were synthesized and subsequently photopolymerized. Within each type of thiol-functionalized oligomer, the ratio of mercaptan repeat units to non-reactive phenyl repeat units was varied to manipulate both the crosslink density and the degree of secondary interactions through pi-pi stacking. Similarly, the repeat units of the three ene-functionalized oligomers are composed of allyl-functional monomers, benzene-functional monomers, and octyl-functional monomers in varying ratios of benzene:octyl but with a constant fraction of allyl moieties. The structural composition of the siloxane oligomers plays a pivotal role in the observed material properties of networks formed through thiol-ene photopolymerization. Networks with a high concentration of thiol functionalities exhibit higher rubbery moduli, ultimate strengths, and Young’s moduli than networks with lower thiol concentrations. Moreover, the concentration of functionalities capable of participating in secondary interactions via hydrogen bonding or pi-pi stacking directly impacts the network glass transition temperature and elasticity. The combination of low crosslink density and high secondary interactions produces networks with the greatest toughness. Finally, the fraction of octyl repeats correlates with the hydrophobic nature of the network. PMID:23162209

  4. Thymic function failure and C-reactive protein levels are independent predictors of all-cause mortality in healthy elderly humans.

    PubMed

    Ferrando-Martínez, Sara; Romero-Sánchez, María Concepción; Solana, Rafael; Delgado, Juan; de la Rosa, Rafael; Muñoz-Fernández, Ma Angeles; Ruiz-Mateos, Ezequiel; Leal, Manuel

    2013-02-01

    Relationship between thymic function and elderly survival has been suspected, despite the fact that formal proof is elusive due to technical limitations of thymic function-related markers. The newly described sj/β-TREC ratio allows now, by overcoming these limitations, an accurate measurement of thymic output in elderly humans. Thus, the aim of this study was to determine the impact of thymic function and inflammatory markers on healthy elderly human survival. Healthy volunteers (n = 151), aged over 65, were asked to participate (CARRERITAS cohort). Subjects were excluded if diagnosed of dementia or, during the last 6 months, had clinical data of infection, hospital admission, antitumor therapy, or any treatment that could influence the immune status. Thymic function (sj/β-TREC ratio), CD4:CD8 T cell ratio, C-reactive protein, interleukin-6, and neutrophilia were determined from basal samples. All basal variables and age were associated with 2-year all-cause mortality. Multivariate analysis showed that only thymic function and C-reactive protein were independently associated with time to death. In conclusion, we show, for the first time, the direct role of thymic function in human survival. C-reactive protein raise is also a marker of mortality in the healthy elderly, in a thymic-independent way.

  5. Applications of Click Chemistry Reactions to the Synthesis of Functional Materials

    NASA Astrophysics Data System (ADS)

    Accurso, Adrian A.

    This body of work focuses on the production of functional materials using the most reliable carbon-hetoratom bond-forming processes available, which are widely termed "click chemistry" reactions in the literature. This focus on function is enabled by a basis in synthetic chemistry, and where appropriate, brings in techniques from the related fields of materials science and biology to address current needs in those areas. Chapter 1 concerns the in situ production of azide and alkyne-based click chemistry adhesive polymers. Screening of a library of multivalent azides and alkynes was accomplished on a custom-built highthroughput instrument and followed up on a lap-shear testing apparatus. The conductivity of composites made of the adhesive was also explored according to standard methods. The second and third chapters explore the synthesis and function of a family of related [3.3.1]-bicyclononane dichlorides, which we have termed "WCL" electrophiles, and their potential applications for surface functionalization, the synthesis of polycations, and candidate membrane disruptive compounds. The rates of consumption of dichlorides and hydrolysis of model compounds were also explored using NMR, GC-MS, and HPLC-based methods.

  6. Recent Advances in the Synthesis and Functions of Reconfigurable Interlocked DNA Nanostructures.

    PubMed

    Lu, Chun-Hua; Cecconello, Alessandro; Willner, Itamar

    2016-04-27

    Interlocked circular DNA nanostructures, e.g., catenanes or rotaxanes, provide functional materials within the area of DNA nanotechnology. Specifically, the triggered reversible reconfiguration of the catenane or rotaxane structures provides a means to yield new DNA switches and to use them as dynamic scaffolds for controlling chemical functions and positioning functional cargoes. The synthesis of two-ring catenanes and their switchable reconfiguration by pH, metal ions, or fuel/anti-fuel stimuli are presented, and the functions of these systems, as pendulum or rotor devices or as switchable catalysts, are described. Also, the synthesis of three-, five-, and seven-ring catenanes is presented, and their switchable reconfiguration using fuel/anti-fuel strands is addressed. Implementation of the dynamically reconfigured catenane structures for the programmed organization of Au nanoparticle (NP) assemblies, which allows the plasmonic control of the fluorescence properties of Au NP/fluorophore loads associated with the scaffold, and for the operation of logic gates is discussed. Interlocked DNA rotaxanes and their different synthetic approaches are presented, and their switchable reconfiguration by means of fuel/anti-fuel strands or photonic stimuli is described. Specifically, the use of the rotaxane as a scaffold to organize Au NP assemblies, and the control of the fluorescence properties with Au NP/fluorophore hybrids loaded on the rotaxane scaffold, are introduced. The future prospectives and challenges in the field of interlocked DNA nanostructures and the possible applications are discussed. PMID:27019201

  7. Differential effects of rumination and distraction on ketamine induced modulation of resting state functional connectivity and reactivity of regions within the default-mode network.

    PubMed

    Lehmann, Mick; Seifritz, Erich; Henning, Anke; Walter, Martin; Böker, Heinz; Scheidegger, Milan; Grimm, Simone

    2016-08-01

    Distraction and rumination are distinct response styles that determine how an individual deals with negative thoughts and feelings. Rumination is accompanied by an elevated self-focus, which is associated with increased resting state functional connectivity and decreased reactivity within the default mode network. Interestingly, the NMDA receptor antagonist ketamine reduces functional connectivity in this network, while its effects on blood oxygenation level-dependent (BOLD) responses during stimulus perception are not known. Ketamine might lead to a more variable processing of the external world with an attenuated self-focus by reducing the resting state connectivity. Here, we used an emotional picture-viewing task in combination with functional magnetic resonance imaging to test the hypothesis that a single ketamine administration to healthy subjects increases BOLD reactivity to negative stimuli. We found a region specific increase in BOLD reactivity in the pregenual anterior cingulate cortex and not in a posterior control region after ketamine compared with placebo administration. Moreover, a linear regression revealed that the increase in BOLD reactivity was more pronounced for subjects with a low ability to apply distraction during negative experiences. Our results implicate that ketamine attenuates a potentially pathological increased self-focus during negative experiences. PMID:27075438

  8. Structure and chemical reactivity of the polar three-fold surfaces of GaPd: a density-functional study.

    PubMed

    Krajčí, M; Hafner, J

    2013-03-28

    The polar threefold surfaces of the GaPd compound crystallizing in the B20 (FeSi-type) structure (space group P2(1)3) have been investigated using density-functional methods. Because of the lack of inversion symmetry the B20 structure exists in two enantiomorphic forms denoted as A and B. The threefold {111} surfaces have polar character. In both nonequivalent (111) and (111) directions several surface terminations differing in structure and chemical composition are possible. The formation of the threefold surfaces has been studied by simulated cleavage experiments and by calculations of the surface energies. Because of the polar character of the threefold surfaces calculations for stoichiometric slabs permit only the determination of the average energy of the surfaces exposed on both sides of the slab. Calculations for nonstoichiometric slabs performed in the grand canonical ensemble yield differences of the surface energies for the possible terminations as a function of the chemical potential in the reactive atmosphere above the surface and predict a transition between Ga- and Pd-terminated surfaces as a function of the chemical potential. The {100} surfaces are stoichiometric and uniquely defined. The calculated surface energies are identical to the average energies of the {100} surfaces of the pure metals. The {210} surfaces are also stoichiometric, with an energy very close to that of the {100} surfaces. Assuming that for the {111} surfaces the energies of different possible terminations are in a proportion equal to that of the concentration-weighted energies of the {111} surfaces of the pure metals, surface energies for all possible {111} terminations may be calculated. The preferable termination perpendicular to the A<111> direction consists of a bilayer with three Ga atoms in the upper and three Pd atoms in the lower part. The surface energy of this termination further decreases if the Pd triplet is covered by additional Ga atom. Perpendicular to the A<111

  9. Synthesis, Radical Reactivity, and Thermochemistry of Monomeric Cu(II) Alkoxide Complexes Relevant to Cu/Radical Alcohol Oxidation Catalysis.

    PubMed

    Porter, Thomas R; Capitao, Dany; Kaminsky, Werner; Qian, Zhaoshen; Mayer, James M

    2016-06-01

    with (t)Bu3ArO(•) gives no reaction, despite evidence that overall ligand oxidation and formation of 1/2[Tp(tBuMe)Cu(I)]2 is significantly exoergic. The origin of this lack of reactivity may be due to insufficient weakening of the alcohol α-C-H bond upon complexation to copper. PMID:27171230

  10. Synthesis and Exploratory Catalysis of 3d Metals: Group-Transfer Reactions, and the Activation and Functionalization of Small Molecules Including Greenhouse Gases

    SciTech Connect

    Mindiola, Daniel J.

    2014-05-07

    Our work over the past three years has resulted in the development of electron rich and low-coordinate vanadium fragments, molecular nitrides of vanadium and parent imide systems of titanium, and the synthesis of phosphorus containing molecules of the 3d transition metal series. Likewise, with financial support from BES Division in DOE (DE-FG02-07ER15893), we now completed the full characterization of the first single molecular magnet (SMM) of Fe(III). We demonstrated that this monomeric form of Fe(III) has an unusual slow relaxation of the magnetization under zero applied field. To make matters more interesting, this system also undergoes a rare example of an intermediate to high-spin transition (an S = 3/2 to S = 5/2 transition). In 2010 we reported the synthesis of the first neutral and low-coordinate vanadium complexes having the terminal nitride functionality. We have now completed a full study to understand formation of the nitride ligand from the metastable azide precursor, and have also explored the reactivity of the nitride ligand in the context of incomplete and complete N-atom transfer. During the 2010-2013 period we also discovered a facile approach to assemble low-coordinate and low-valent vanadium(II) complexes and exploit their multielectron chemistry ranging from 1-3 electrons. Consequently, we can now access 3d ligand frameworks such as cyclo-P3 (and its corresponding radical anion), nitride radical anions and cations, low-coordinate vanadium oxo’s, and the first example of a vanadium thionitrosyl complex. A cis-divacant iron(IV) imido having some ligand centered radical has been also discovered, and we are in the process of elucidating its electronic structure (in particular the sign of zero field splitting and the origin of its magnitude), bonding and reactivity. We have also revisited some paramagnetic and classic metallocene compounds with S >1/2 ground states in order to understand their reactivity patterns and electronic structure. Lastly

  11. Synthesis of a mononuclear, non-square-planar chromium(ii) bis(alkoxide) complex and its reactivity toward organic carbonyls and CO2.

    PubMed

    Yousif, Maryam; Cabelof, Alyssa C; Martin, Philip D; Lord, Richard L; Groysman, Stanislav

    2016-06-14

    In this paper, we report the synthesis and reactivity of a rare mononuclear chromium(ii) bis(alkoxide) complex, Cr(OR')2(THF)2, that is supported by a new bulky alkoxide ligand (OR' = di-t-butyl-(3,5-diphenylphenyl)methoxide). The complex is prepared by protonolysis of square-planar Cr(N(SiMe3)2)2(THF)2 with HOR'. X-ray structure determination disclosed that Cr(OR')2(THF)2 features a distorted seesaw geometry, in contrast to nearly all other tetra-coordinate Cr(ii) complexes, which are square-planar. The reactivity of Cr(OR')2(THF)2 with aldehydes, ketones, and carbon dioxide was investigated. Treatment of Cr(OR')2(THF)2 with two equivalents of aromatic aldehydes ArCHO (ArCHO = benzaldehyde, 4-anisaldehyde, 4-trifluorbenzaldehyde, and 2,4,6-trimethylbenzaldehyde) leads cleanly to the formation of Cr(iv) diolate complexes Cr(OR')2(O2C2H2Ar2) that were characterized by UV-vis and IR spectroscopies and elemental analysis; the representative complex Cr(OR')2(O2C2H2Ph2) was characterized by X-ray crystallography. In contrast, no reductive coupling was observed for ketones: treatment of Cr(OR')2(THF)2 with one or two equivalents of benzophenone forms invariably a single ketone adduct Cr(OR')2(OCPh2) which does not react further. QM/MM calculations suggest the steric demands prevent ketone coupling, and demonstrate that a mononuclear Cr(iii) bis-aldehyde complex with partially reduced aldehydes is sufficient for C-C bond formation. The reaction of Cr(OR')2(THF)2 with CO2 leads to the insertion of CO2 into a Cr-OR' bond, followed by complex rearrangement to form a diamagnetic dinuclear paddlewheel complex Cr2(O2COR')4(THF)2, that was characterized by NMR, UV-vis, and IR spectroscopy, and X-ray crystallography. PMID:27073074

  12. Synthesis of a mononuclear, non-square-planar chromium(ii) bis(alkoxide) complex and its reactivity toward organic carbonyls and CO2.

    PubMed

    Yousif, Maryam; Cabelof, Alyssa C; Martin, Philip D; Lord, Richard L; Groysman, Stanislav

    2016-06-14

    In this paper, we report the synthesis and reactivity of a rare mononuclear chromium(ii) bis(alkoxide) complex, Cr(OR')2(THF)2, that is supported by a new bulky alkoxide ligand (OR' = di-t-butyl-(3,5-diphenylphenyl)methoxide). The complex is prepared by protonolysis of square-planar Cr(N(SiMe3)2)2(THF)2 with HOR'. X-ray structure determination disclosed that Cr(OR')2(THF)2 features a distorted seesaw geometry, in contrast to nearly all other tetra-coordinate Cr(ii) complexes, which are square-planar. The reactivity of Cr(OR')2(THF)2 with aldehydes, ketones, and carbon dioxide was investigated. Treatment of Cr(OR')2(THF)2 with two equivalents of aromatic aldehydes ArCHO (ArCHO = benzaldehyde, 4-anisaldehyde, 4-trifluorbenzaldehyde, and 2,4,6-trimethylbenzaldehyde) leads cleanly to the formation of Cr(iv) diolate complexes Cr(OR')2(O2C2H2Ar2) that were characterized by UV-vis and IR spectroscopies and elemental analysis; the representative complex Cr(OR')2(O2C2H2Ph2) was characterized by X-ray crystallography. In contrast, no reductive coupling was observed for ketones: treatment of Cr(OR')2(THF)2 with one or two equivalents of benzophenone forms invariably a single ketone adduct Cr(OR')2(OCPh2) which does not react further. QM/MM calculations suggest the steric demands prevent ketone coupling, and demonstrate that a mononuclear Cr(iii) bis-aldehyde complex with partially reduced aldehydes is sufficient for C-C bond formation. The reaction of Cr(OR')2(THF)2 with CO2 leads to the insertion of CO2 into a Cr-OR' bond, followed by complex rearrangement to form a diamagnetic dinuclear paddlewheel complex Cr2(O2COR')4(THF)2, that was characterized by NMR, UV-vis, and IR spectroscopy, and X-ray crystallography.

  13. Synthesis of highly functionalized macrocycles by the peripheral functionalization of macrocyclic diimines.

    PubMed

    Sierra, Miguel A; Pellico, Daniel; Gómez-Gallego, Mar; Mancheño, María José; Torres, Rosario

    2006-11-10

    The easily available macrocyclic diimines 4-7 can be stereoselectively transformed to macrocyclic bis-beta-amino acids 13-17, macrocyclic bisazetidines 18-20, and macrocyclic bisamides 21 and 22 by means of the corresponding bis-beta-lactam scaffolds 8-12. These key intermediates are available through standard Staudinger reaction and obtained as the cis-cis diastereomers, exclusively. An interesting relation between the proximity of the reactive C=N bonds and the selectivity in the formation of the bis-beta-lactams 8-12 is observed. Thus, diimine 4 leads to low selectivities, producing a 1:1 mixture of cis-syn-cis and cis-anti-cis diastereomers, while diimines 5-7 having the diimine sites more separated lead almost exclusively to the cis-anti-cis diastereomers. The stereochemistry of all the products was unambiguously assigned by X-ray diffraction analysis of compounds cis-syn-cis 8 and cis-anti-cis 12-Co2CO6 complex.

  14. Biological sensitivity to context: I. An evolutionary-developmental theory of the origins and functions of stress reactivity.

    PubMed

    Boyce, W Thomas; Ellis, Bruce J

    2005-01-01

    Biological reactivity to psychological stressors comprises a complex, integrated, and highly conserved repertoire of central neural and peripheral neuroendocrine responses designed to prepare the organism for challenge or threat. Developmental experience plays a role, along with heritable, polygenic variation, in calibrating the response dynamics of these systems, with early adversity biasing their combined effects toward a profile of heightened or prolonged reactivity. Conventional views of such high reactivity suggest that it is an atavistic and pathogenic legacy of an evolutionary past in which threats to survival were more prevalent and severe. Recent evidence, however, indicates that (a) stress reactivity is not a unitary process, but rather incorporates counterregulatory circuits serving to modify or temper physiological arousal, and (b) the effects of high reactivity phenotypes on psychiatric and biomedical outcomes are bivalent, rather than univalent, in character, exerting both risk-augmenting and risk-protective effects in a context-dependent manner. These observations suggest that heightened stress reactivity may reflect, not simply exaggerated arousal under challenge, but rather an increased biological sensitivity to context, with potential for negative health effects under conditions of adversity and positive effects under conditions of support and protection. From an evolutionary perspective, the developmental plasticity of the stress response systems, along with their structured, context-dependent effects, suggests that these systems may constitute conditional adaptations: evolved psychobiological mechanisms that monitor specific features of childhood environments as a basis for calibrating the development of stress response systems to adaptively match those environments. Taken together, these theoretical perspectives generate a novel hypothesis: that there is a curvilinear, U-shaped relation between early exposures to adversity and the development

  15. Synthesis, reactivity studies, structural aspects, and solution behavior of half sandwich ruthenium(II) N,N',N''-triarylguanidinate complexes.

    PubMed

    Singh, Taruna; Kishan, Ram; Nethaji, Munirathinam; Thirupathi, Natesan

    2012-01-01

    [(η(6)-C(10)H(14))RuCl(μ-Cl)](2) (η(6)-C(10)H(14) = η(6)-p-cymene) was subjected to a bridge-splitting reaction with N,N',N''-triarylguanidines, (ArNH)(2)C═NAr, in toluene at ambient temperature to afford [(η(6)-C(10)H(14))RuCl{κ(2)(N,N')((ArN)(2)C-N(H)Ar)}] (Ar = C(6)H(4)Me-4 (1), C(6)H(4)(OMe)-2 (2), C(6)H(4)Me-2 (3), and C(6)H(3)Me(2)-2,4 (4)) in high yield with a view aimed at understanding the influence of substituent(s) on the aryl rings of the guanidine upon the solid-state structure, solution behavior, and reactivity pattern of the products. Complexes 1-3 upon reaction with NaN(3) in ethanol at ambient temperature afforded [(η(6)-C(10)H(14))RuN(3){κ(2)(N,N')((ArN)(2)C-N(H)Ar)}] (Ar = C(6)H(4)Me-4 (5), C(6)H(4)(OMe)-2 (6), and C(6)H(4)Me-2 (7)) in high yield. [3 + 2] cycloaddition reaction of 5-7 with RO(O)C-C≡C-C(O)OR (R = Et (DEAD) and Me (DMAD)) (diethylacetylenedicarboxylate, DEAD; dimethylacetylenedicarboxylate, DMAD) in CH(2)Cl(2) at ambient temperature afforded [(η(6)-C(10)H(14))Ru{N(3)C(2)(C(O)OR)(2)}{κ(2)(N,N')((ArN)(2)C-N(H)Ar)}]·xH(2)O (x = 1, R = Et, Ar = C(6)H(4)Me-4 (8·H(2)O); x = 0, R = Me, Ar = C(6)H(4)(OMe)-2 (9), and C(6)H(4)Me-2 (10)) in moderate yield. The molecular structures of 1-6, 8·H(2)O, and 10 were determined by single crystal X-ray diffraction data. The ruthenium atom in the aforementioned complexes revealed pseudo octahedral "three legged piano stool" geometry. The guanidinate ligand in 2, 3, and 6 revealed syn-syn conformation and that in 4, and 10 revealed syn-anti conformation, and the conformational difference was rationalized on the basis of subtle differences in the stereochemistry of the coordinated nitrogen atoms caused by the aryl moiety in 3 and 4 or steric overload caused by the substituents around the ruthenium atom in 10. The bonding pattern of the CN(3) unit of the guanidinate ligand in the new complexes was explained by invoking n-π conjugation involving the interaction of the NHAr/N(coord)Ar lone

  16. Reactivity studies of plasma-synthesized aluminum trifluoride and electrochemical synthesis of non-stoichiometric silver selenide nanowire arrays

    NASA Astrophysics Data System (ADS)

    Hajime, Evan Koon Lun Yuuji

    A high surface area aluminum trifluoride material ("plasma-AIF3 ") has previously been synthesized in our laboratory by decomposition of zeolitic precursors in fluorine-containing, low-temperature plasmas. The characterization of the halogen exchange reactivity of this unique fluoride material is presented in Part 1 of the dissertation. A gas flow reactor was designed and built to study the isothermal and temperature-dependent halogen exchange activity of plasma-AIF3, with comparisons being made to the well-known halogen exchange catalyst beta-AIF3. Isothermal experiments showed that plasma-AIF3 is an active halogen exchange catalyst for the dismutation of dichlorodifluoromethane, while temperature-programmed reaction (TPR) experiments revealed a lower temperature onset of activity with plasma-AIF3 when compared to beta-AIF3. The existence of two distinct active sites for halogen exchange on aluminum fluoride is proposed, with sites characteristic of plasma-AIF3 and R-AIF3 having lower and higher temperature onsets of activity, respectively. TPR data for hydrated plasma-AIF3 showed a significant attenuation of the lower temperature active sites, while the higher temperature site remained relatively unchanged in activity. Temperature-programmed X-ray diffraction of plasma-AIF3 revealed the existence of beta-AIF 3 crystallites at temperatures between 225 and 500°C, thus rationalizing the existence of the higher temperature active site (associated with beta-AIF 3) in plasma-AIF3 during heating. Plasma-AIF3 also displayed a high affinity for crystalline hydrate formation with extended exposure to moist air, and TPR experiments performed on commercially available AIF3·3H2O produced plots similar in shape and features when compared to plasma-AIF3. The thermal transformation processes of the trihydrate suggest the origin of the lower temperature active site to be associated with an amorphous bulk AIF3 structure. Part 2 of the dissertation summarizes the current efforts

  17. Comparative effects of three popular diets on lipids, endothelial function, and C-reactive protein during weight maintenance.

    PubMed

    Miller, Michael; Beach, Valerie; Sorkin, John D; Mangano, Charles; Dobmeier, Christine; Novacic, Danica; Rhyne, Jeffrey; Vogel, Robert A

    2009-04-01

    Although popular diets focus on weight loss and their favorable biochemical and physiological effects, fewer investigations have evaluated the biological impact of these diets during weight maintenance. To study this issue, three popular diets-Atkins, South Beach, and Ornish-were tested in a randomized and counterbalanced crossover study between January and December 2006. Participants completed each of the three 4-week isocaloric dietary intervention phases followed by a 4-week washout period. They were weighed weekly and caloric adjustments made if weight change exceeded 1 kg. At the completion of each dietary phase, 3-day food records were analyzed, fasting blood sampled, and brachial artery reactivity testing performed. Eighteen adults completed all three isocaloric dietary phases. During the South Beach and Ornish maintenance phase, there were significant reductions in low-density lipoprotein cholesterol (11.8%; P=0.01, 16.6%; P=0.0006, respectively) compared to prediet baseline. In addition, in contrast to the Atkins maintenance phase, significant reductions in low-density lipoprotein cholesterol and apolipoprotein B levels were observed after the South Beach (P=0.003, P=0.05; repeated measures analyses of variance) and Ornish maintenance phases (P=0.0004, P=0.006, repeated measures analyses of variance). Brachial artery testing revealed an inverse correlation between flow-mediated vasodilatation and intake of saturated fat (r=-0.33; P=0.016). These data suggest that during weight maintenance, less favorable biological effects are observed during a simulated, high-fat Atkins diet when compared to the South Beach and Ornish diet. The findings support additional study in subjects with visceral obesity and the metabolic syndrome, in whom an increased risk of coronary disease at baseline may be accentuated with chronic consumption of a diet that exhibits unfavorable effects on lipids and endothelial function.

  18. Environmental enrichment and social interaction improve cognitive function and decrease reactive oxidative species in normal adult mice.

    PubMed

    Doulames, Vanessa; Lee, Sangmook; Shea, Thomas B

    2014-05-01

    Environmental stimulation and increased social interactions stimulate cognitive performance, while decrease in these parameters can exacerbate cognitive decline as a function of illness, injury, or age. We examined the impact of environmental stimulation and social interactions on cognitive performance in healthy adult C57B1/6J mice. Mice were housed for 1 month individually or in groups of three (to prevent or allow social interaction) in either a standard environment (SE) or an enlarged cage containing nesting material and items classically utilized to stimulate exploration and activity ("enriched environment"; EE). Cognitive performance was tested by Y maze navigation and Novel Object Recognition (NOR; which compares the relative amount of time mice spent investigating a novel vs. a familiar object). Mice maintained for 1 month under isolated conditions in the SE statistically declined in performance versus baseline in the Y maze (p < 0.02; ANOVA). Performance under all other conditions did not change from baseline. Maintenance in groups in the SE statistically improved NOR (p < 0.01), whereas maintenance in isolation in the SE did not alter performance from baseline. Maintenance in the EE statistically improved performance in NOR for mice housed in groups and individually (p < 0.01). Maintenance under isolated conditions slightly increased reactive oxygen/nitrogen species (ROS/RNS) in brain. Environmental enrichment did not influence ROS/RNS. These findings indicate that environmental and social enrichment can positively influence cognitive performance in healthy adult mice, and support the notion that proactive approaches may delay age-related cognitive decline.

  19. Molecular Design of Bioinspired Nanostructures for Biomedical Applications: Synthesis, Self-Assembly and Functional Properties

    NASA Astrophysics Data System (ADS)

    Xu, Hesheng Victor; Zheng, Xin Ting; Mok, Beverly Yin Leng; Ibrahim, Salwa Ali; Yu, Yong; Tan, Yen Nee

    2016-08-01

    Biomolecules are the nanoscale building blocks of cells, which play multifaceted roles in the critical biological processes such as biomineralization in a living organism. In these processes, the biological molecules such as protein and nucleic acids use their exclusive biorecognition properties enabled from their unique chemical composition, shape and function to initiate a cascade of cellular events. The exceptional features of these biomolecules, coupled with the recent advancement in nanotechnology, have led to the emergence of a new research field that focuses on the molecular design of bioinspired nanostructures that inherit the extraordinary function of natural biomaterials. These “bioinspired” nanostructures could be formulated by biomimetic approaches through either self-assembling of biomolecules or acting as a biomolecular template/precursor to direct the synthesis of nanocomposite. In either situation, the resulting nanomaterials exhibit phenomenal biocompatibility, superb aqueous solubility and excellent colloidal stability, branding them exceptionally desirable for both in vitro and in vivo biomedical applications. In this review, we will present the recent developments in the preparation of “bioinspired” nanostructures through biomimetic self-assembly and biotemplating synthesis, as well as highlight their functional properties and potential applications in biomedical diagnostics and therapeutic delivery. Lastly, we will conclude this topic with some personal perspective on the challenges and future outlooks of the “bioinspired” nanostructures for nanomedicine.

  20. Cell-free synthesis, functional refolding, and spectroscopic characterization of bacteriorhodopsin, an integral membrane protein.

    PubMed

    Sonar, S; Patel, N; Fischer, W; Rothschild, K J

    1993-12-21

    Bacteriorhodopsin (bR) is an integral membrane protein which functions as a light-driven proton pump in Halobacterium halobium (also known as Halobacterium salinarium). The cell-free synthesis of bR in quantities sufficient for FTIR and NMR spectroscopy and the ability to selectively isotope label bR using aminoacylated suppressor tRNAs would provide a powerful approach for studying the role of specific amino acid residues. However, no integral membrane protein has yet been expressed in a cell-free system in quantities sufficient for such biophysical studies. We report the cell-free synthesis of bacterioopsin, its purification, its refolding in polar lipids from H. halobium, and its regeneration with all-trans-retinal to yield bacteriorhodopsin in a form functionally similar to bR in purple membrane. Importantly, the yields obtained from in vitro and in vivo expression are comparable. Functionality of the cell-free expressed bR is established using static and time-resolved absorption spectroscopy and FTIR difference spectroscopy.

  1. Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment

    NASA Astrophysics Data System (ADS)

    Su, Yiming; Adeleye, Adeyemi S.; Huang, Yuxiong; Zhou, Xuefei; Keller, Arturo A.; Zhang, Yalei

    2016-04-01

    Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) is of great technical and scientific interest because of its promising application in groundwater remediation, although its synthesis is still a challenge. We develop a new nanoparticle seeding method to obtain a novel and reactive nanohybrid, which contains an Fe(0) core covered by a highly sulfidized layer under high extent of sulfidation. Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe2+ to Fe0 by 19%. X-ray adsorption near edge structure (XANES) spectroscopy and extended X-ray absorption fine structure analyses demonstrate the hexahedral Fe-Fe bond (2.45 and 2.83 Å) formation through breaking down of the 1.99 Å Fe-O bond both in crystalline and amorphous iron oxide. The XANES analysis also shows 24.2% (wt%) of FeS with bond length of 2.4 Å in final nanohybrid. Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe0 crystals. Nano-SiO2 seeding brings down the size of single Fe0 grain from 32.4 nm to 18.7 nm, enhances final Fe0 content from 5.9% to 55.6%, and increases magnetization from 4.7 to 65.5 emu/g. The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water.

  2. Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment

    PubMed Central

    Su, Yiming; Adeleye, Adeyemi S.; Huang, Yuxiong; Zhou, Xuefei; Keller, Arturo A.; Zhang, Yalei

    2016-01-01

    Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) is of great technical and scientific interest because of its promising application in groundwater remediation, although its synthesis is still a challenge. We develop a new nanoparticle seeding method to obtain a novel and reactive nanohybrid, which contains an Fe(0) core covered by a highly sulfidized layer under high extent of sulfidation. Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe2+ to Fe0 by 19%. X-ray adsorption near edge structure (XANES) spectroscopy and extended X-ray absorption fine structure analyses demonstrate the hexahedral Fe-Fe bond (2.45 and 2.83 Å) formation through breaking down of the 1.99 Å Fe-O bond both in crystalline and amorphous iron oxide. The XANES analysis also shows 24.2% (wt%) of FeS with bond length of 2.4 Å in final nanohybrid. Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe0 crystals. Nano-SiO2 seeding brings down the size of single Fe0 grain from 32.4 nm to 18.7 nm, enhances final Fe0 content from 5.9% to 55.6%, and increases magnetization from 4.7 to 65.5 emu/g. The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water. PMID:27095387

  3. Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment.

    PubMed

    Su, Yiming; Adeleye, Adeyemi S; Huang, Yuxiong; Zhou, Xuefei; Keller, Arturo A; Zhang, Yalei

    2016-01-01

    Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) is of great technical and scientific interest because of its promising application in groundwater remediation, although its synthesis is still a challenge. We develop a new nanoparticle seeding method to obtain a novel and reactive nanohybrid, which contains an Fe(0) core covered by a highly sulfidized layer under high extent of sulfidation. Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe(2+) to Fe(0) by 19%. X-ray adsorption near edge structure (XANES) spectroscopy and extended X-ray absorption fine structure analyses demonstrate the hexahedral Fe-Fe bond (2.45 and 2.83 Å) formation through breaking down of the 1.99 Å Fe-O bond both in crystalline and amorphous iron oxide. The XANES analysis also shows 24.2% (wt%) of FeS with bond length of 2.4 Å in final nanohybrid. Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe(0) crystals. Nano-SiO2 seeding brings down the size of single Fe(0) grain from 32.4 nm to 18.7 nm, enhances final Fe(0) content from 5.9% to 55.6%, and increases magnetization from 4.7 to 65.5 emu/g. The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water. PMID:27095387

  4. Design, Synthesis and Characterization of Nucleic Acid-Functionalized Gold Surfaces for Biomarker Detection

    PubMed Central

    Adams, Nicholas M.; Jackson, Stephen R.; Haselton, Frederick R.; Wright, David W.

    2014-01-01

    Nucleic acid-functionalized gold surfaces have been used extensively for the development of biological sensors. The development of an effective biomarker detection assay requires careful design, synthesis and characterization of probe components. In this feature article, we describe fundamental probe development constraints and provide a critical appraisal of the current methodologies and applications in the field. We discuss critical issues and obstacles that impede the sensitivity and reliability of the sensors to underscore the challenges that must be met to advance the field of biomarker detection. PMID:21905721

  5. Boron Nitride Nanotubes: Recent Advances in Their Synthesis, Functionalization, and Applications.

    PubMed

    Lee, Chee Huei; Bhandari, Shiva; Tiwari, Bishnu; Yapici, Nazmiye; Zhang, Dongyan; Yap, Yoke Khin

    2016-01-01

    A comprehensive overview of current research progress on boron nitride nanotubes (BNNTs) is presented in this article. Particularly, recent advancements in controlled synthesis and large-scale production of BNNTs will first be summarized. While recent success in mass production of BNNTs has opened up new opportunities to implement the appealing properties in various applications, concerns about product purity and quality still remain. Secondly, we will summarize the progress in functionalization of BNNTs, which is the necessary step for their applications. Additionally, selected potential applications in structural composites and biomedicine will be highlighted. PMID:27428947

  6. Synthesis of functionalized indole- and benzo-fused heterocyclic derivatives through anionic benzyne cyclization.

    PubMed

    Barluenga, José; Fañanás, Francisco J; Sanz, Roberto; Fernández, Yolanda

    2002-05-01

    The development of a new method for the regioselective synthesis of functionalized indoles and six-membered benzo-fused N-, O-, and S-heterocycles is reported. The key step involves the generation of a benzyne-tethered vinyl or aryllithium compound that undergoes a subsequent intramolecular anionic cyclization. Reaction of the organolithium intermediates with selected electrophiles allows the preparation of a wide variety of indole, tetrahydrocarbazole, dihydrofenantridine, dibenzopyran, and dibenzothiopyran derivatives. Finally, the application of this strategy to the appropriate starting materials allows the preparation of some tryptamine and serotonin analogues.

  7. Synthesis of Functionalized Furans via Chemoselective Reduction/Wittig Reaction Using Catalytic Triethylamine and Phosphine.

    PubMed

    Lee, Chia-Jui; Chang, Tzu-Hsiu; Yu, Jhen-Kuei; Madhusudhan Reddy, Ganapuram; Hsiao, Ming-Yu; Lin, Wenwei

    2016-08-01

    An efficient protocol for the synthesis of highly functionalized furans via intramolecular Wittig reaction has been developed using catalytic amounts of phosphine and triethylamine. Silyl chloride served as the initial promoter to activate the phosphine oxide. Reduction of the activated phosphine oxide by hydrosilane resulted in generation of phosphine, while decomposition of Et3N·HCl resulted in regeneration of base, which mediated formation of phosphorus ylide. Remarkably, the in situ generated byproduct, Et3N·HCl, also catalyzes reduction of phosphine oxide. PMID:27434727

  8. (Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

    PubMed Central

    Koutoulogenis, Giorgos; Kaplaneris, Nikolaos

    2016-01-01

    Summary Organocatalysis, now running its second decade of life, is being considered one of the main tools a synthetic chemist has to perform asymmetric catalysis. In this review the synthesis of six-membered rings, that contain multiple chiral centers, either by a ring closing process or by a functionalization reaction on an already existing six-membered ring, utilizing bifunctional (thio)ureas will be summarized. Initially, the use of primary amine-thioureas as organocatalysts for the above transformation is being discussed, followed by the examples employing secondary amine-thioureas. Finally, the use of tertiary amine-thioureas and miscellaneous examples are presented. PMID:27340441

  9. Laser synthesis of functional graded filter elements from metal-polymer powder compositions

    NASA Astrophysics Data System (ADS)

    Petrov, Alexei L.; Snarev, A. I.; Shishkovsky, Igor V.; Scherbakov, V. I.

    2002-04-01

    Perspectives of laser synthesis of functional graded materials (FGM) with controlled pores and chemical mixture are discussed. Filter elements from metal-polymer powder compositions were fabricated by the selective laser sintering method. It was shown that physical properties of the composited 3D part can change from layer to layer and have no nature analogy. In particular, permeability and porosity coefficients of synthesized 3D parts were determined depending on laser influence parameters and a polymer quantity. Wide opportunities of preliminary computer modeling of the porous space structure, the forecast filtration characteristics are discussed.

  10. A new synthesis of brassinosteroids with a cholestane framework based on a highly functionalized starting material.

    PubMed

    Alshakova, Irina D; Ermolovich, Yuri V; Zhabinskii, Vladimir N; Khripach, Vladimir A

    2015-05-01

    A new route to the synthesis of minor brassinosteroids with a cholestane framework (28-norcastasterone and 28-norbrassinolide) has been proposed. It makes use of commercially available 24-epicastasterone as a starting material. In addition, [26,26,26-(2)H3]-28-norcastasterone and [26,26,26-(2)H3]-28-norbrassinolide have been prepared as tools for analytical applications. The key steps were regioselective manipulations of functional groups in 24-epicastasterone, oxidative cleavage of 22,23-diol group and Claisen rearrangement.

  11. One-Pot, Four-Step Organocatalytic Asymmetric Synthesis of Functionalized Nitrocyclopropanes.

    PubMed

    Zaghi, Anna; Bernardi, Tatiana; Bertolasi, Valerio; Bortolini, Olga; Massi, Alessandro; De Risi, Carmela

    2015-09-18

    The asymmetric synthesis of functionalized nitrocyclopropanes has been achieved by a one-pot, four-step method catalyzed by (S)-diphenylprolinol TMS ether, which joins two sequential domino reactions, namely a domino sulfa-Michael/aldol condensation of α,β-unsaturated aldehydes with 1,4-dithiane-2,5-diol, and a domino Michael/α-alkylation reaction of the derived chiral dihydrothiophenes with bromonitromethane. The title compounds were obtained in 27-45% yields, with high levels of diastereoselectivity (93:7 to 100:0 dr) and generally good enantioselectivities (up to 95:5 er). PMID:26317611

  12. Metal-ligand synergistic effects in the complex Ni(η(2)-TEMPO)2: synthesis, structures, and reactivity.

    PubMed

    Isrow, Derek; DeYonker, Nathan J; Koppaka, Anjaneyulu; Pellechia, Perry J; Webster, Charles Edwin; Captain, Burjor

    2013-12-16

    In the current investigation, reactions of the "bow-tie" Ni(η(2)-TEMPO)2 complex with an assortment of donor ligands have been characterized experimentally and computationally. While the Ni(η(2)-TEMPO)2 complex has trans-disposed TEMPO ligands, proton transfer from the C-H bond of alkyne substrates (phenylacetylene, acetylene, trimethylsilyl acetylene, and 1,4-diethynylbenzene) produce cis-disposed ligands of the form Ni(η(2)-TEMPO)(κ(1)-TEMPOH)(κ(1)-R). In the case of 1,4-diethynylbenzene, a two-stage reaction occurs. The initial product Ni(η(2)-TEMPO)(κ(1)-TEMPOH)[κ(1)-CC(C6H4)CCH] is formed first but can react further with another equivalent of Ni(η(2)-TEMPO)2 to form the bridged complex Ni(η(2)-TEMPO)(κ(1)-TEMPOH)[κ(1)-κ(1)-CC(C6H4)CC]Ni(η(2)-TEMPO)(κ(1)-TEMPOH). The corresponding reaction with acetylene, which could conceivably also yield a bridging complex, does not occur. Via density functional theory (DFT), addition mechanisms are proposed in order to rationalize thermodynamic and kinetic selectivity. Computations have also been used to probe the relative thermodynamic stabilities of the cis and trans addition products and are in accord with experimental results. Based upon the computational results and the geometry of the experimentally observed product, a trans-cis isomerization must occur.

  13. Influenza virus-like particle vaccines made in Nicotiana benthamiana elicit durable, poly-functional and cross-reactive T cell responses to influenza HA antigens.

    PubMed

    Landry, Nathalie; Pillet, Stéphane; Favre, David; Poulin, Jean-François; Trépanier, Sonia; Yassine-Diab, Bader; Ward, Brian J

    2014-10-01

    Cell-mediated immunity plays a major role in long-lived, cross-reactive protection against influenza virus. We measured long-term poly-functional and cross-reactive T cell responses to influenza hemagglutinin (HA) elicited by a new plant-made Virus-Like Particle (VLP) vaccine targeting either H1N1 A/California/7/09 (H1) or H5N1 A/Indonesia/5/05 (H5). In two independent clinical trials, we characterized the CD4(+) and CD8(+) T cell homotypic and heterotypic responses 6 months after different vaccination regimens. Responses of VLP-vaccinated subjects were compared with placebo and/or a commercial trivalent inactivated vaccine (TIV:Fluzone™) recipients. Both H1 and H5 VLP vaccines elicited significantly greater poly-functional CD4(+) T cell responses than placebo and TIV. Poly-functional CD8(+) T cell responses were also observed after H1 VLP vaccination. Our results show that plant-made HA VLP vaccines elicit both strong antibody responses and poly-functional, cross-reactive memory T cells that persist for at least 6 months after vaccination. PMID:25128897

  14. Multiscale Theoretical and Computational Modeling of the Synthesis, Structure and Performance of Functional Carbon Materials

    NASA Astrophysics Data System (ADS)

    Mushrif, Samir Hemant

    2010-09-01

    Functional carbon-based/supported materials, including those doped with transition metal, are widely applied in hydrogen mediated catalysis and are currently being designed for hydrogen storage applications. This thesis focuses on acquiring a fundamental understanding and quantitative characterization of: (i) the chemistry of their synthesis procedure, (ii) their microstructure and chemical composition and (iii) their functionality, using multiscale modeling and simulation methodologies. Palladium and palladium(II) acetylacetonate are the transition metal and its precursor of interest, respectively. A first-principles modeling approach consisting of the planewave-pseudopotential implementation of the Kohn-Sham density functional theory, combined with the Car-Parrinello molecular dynamics, is implemented to model the palladium doping step in the synthesis of carbon-based/supported material and its interaction with hydrogen. The electronic structure is analyzed using the electron localization function and, when required, the hydrogen interaction dynamics are accelerated and the energetics are computed using the metadynamics technique. Palladium pseudopotentials are tested and validated for their use in a hydrocarbon environment by successfully computing the experimentally observed crystal structure of palladium(II) acetylacetonate. Long-standing hypotheses related to the palladium doping process are confirmed and new fundamental insights about its molecular chemistry are revealed. The dynamics, mechanism and energy landscape and barriers of hydrogen adsorption and migration on and desorption from the carbon-based/supported palladium clusters are reported for the first time. The effects of palladium doping and of the synthesis procedure on the pore structure of palladium-doped activated carbon fibers are quantified by applying novel statistical mechanical based methods to the experimental physisorption isotherms. The drawbacks of the conventional adsorption-based pore

  15. Anionic synthesis of in-chain and chain-end functionalized polymers

    NASA Astrophysics Data System (ADS)

    Roy Chowdhury, Sumana

    The objective of this work was to anionically synthesize well-defined polymers having functional groups either at the chain-end or along the polymer chain. General functionalization methods (GFM) were used for synthesizing both kinds of polymers. Chain-end functionalized polymers were synthesized by terminating the anionically synthesized, living polymer chains using chlorodimethylsilane. Hydrosilation reactions were then done between the silyl-hydride groups at the chain-ends and the double bonds of commercially available substituted alkenes. This produced a range of well-defined polymers having the desired functional groups at the chain-ends. In-chain functionalized polymers were synthesized by anionically polymerizing a silylhydride functionalized styrene monomer: (4-vinylphenyl)dimethysilane. Polymerizations were done at room temperature in hydrocarbon solvents to produce well-defined polymers. Functional groups were then introduced into the polymer chains by use of hydrosilation reactions done post-polymerization. The functionalized polymers produced were characterized using SEC, 1H and 13C NMR, FTIR, MALDI TOF mass spectrometry and DSC. The monomer reactivity ratios in the copolymerization of styrene with (4-vinylphenyl)dimethylsilane were also measured. A series of copolymerizaions was done with different molar ratios of styrene(S) and (4-vinylphenyl)dimethylsilane(Si). Three different methods were used to determine the values of the monomer reactivity ratios: Fineman-Ross, Kelen-Tudos and Error-In-Variable (EVM) methods. The average values of the two monomer reactivity ratios obtained were: r Si = 0.16 and rS = 1.74. From these values it was observed that in the copolymerization of styrene with (4-vinylphenyl)dimethylsilane, the second monomer was preferentially incorporated into the copolymer chain. Also, rSirS = 0.27, which shows that the copolymer has a tendency to have an alternating structure. Amino acid-functionalized polymers (biohybrids) were

  16. Click dendrimers and triazole-related aspects: catalysts, mechanism, synthesis, and functions. A bridge between dendritic architectures and nanomaterials.

    PubMed

    Astruc, Didier; Liang, Liyuan; Rapakousiou, Amalia; Ruiz, Jaime

    2012-04-17

    One of the primary recent improvements in molecular chemistry is the now decade-old concept of click chemistry. Typically performed as copper-catalyzed azide-alkyne (CuAAC) Huisgen-type 1,3-cycloadditions, this reaction has many applications in biomedicine and materials science. The application of this chemistry in dendrimer synthesis beyond the zeroth generation and in nanoparticle functionalization requires stoichiometric use of the most common click catalyst, CuSO(4)·5H(2)O with sodium ascorbate. Efforts to develop milder reaction conditions for these substrates have led to the design of polydentate nitrogen ligands. Along these lines, we have described a new, efficient, practical, and easy-to-synthesize catalytic complex, [Cu(I)(hexabenzyltren)]Br, 1 [tren = tris(2-aminoethyl)amine], for the synthesis of relatively large dendrimers and functional gold nanoparticles (AuNPs). This efficient catalyst can be used alone in 0.1% mol amounts for nondendritic click reactions or with the sodium-ascorbate additive, which inhibits aerobic catalyst oxidation. Alternatively, catalytic quantities of the air-stable compounds hexabenzyltren and CuBr added to the click reaction medium can provide analogously satisfactory results. Based on this catalyst as a core, we have also designed and synthesized analogous Cu(I)-centered dendritic catalysts that are much less air-sensitive than 1 and are soluble in organic solvents or in water (depending on the nature of the terminal groups). These multivalent catalysts facilitate efficient click chemistry and exert positive dendritic effects that mimic enzyme activity. We propose a monometallic CuAAC click mechanism for this process. Although the primary use of click chemistry with dendrimers has been to decorate dendrimers with a large number of molecules for medicinal or materials purposes, we are specifically interested in the formation of intradendritic [1,2,3]-triazole heterocycles that coordinate to transition-metal ions via their

  17. Taming reactive phenol tautomers and o-quinone methides with transition metals: a structure-reactivity relationship.

    PubMed

    Amouri, Hani; Le Bras, Jean

    2002-07-01

    Quinone methides act as important intermediates in organic syntheses, as well as in chemical and biological processes; however, examples of such isolated species are scarce as a result of their high reactivity. Phenol tautomers (keto form of phenol) are also important intermediates in several organic and organometallic reactions; nevertheless, isolated complexes are rare. This Account reviews the recent progress on the synthesis and reactivity of iridium and rhodium o-quinone methide complexes as well as on iridium-mediated ortho functionalization of phenols. This reaction was at the origin of the discovery of a general synthetic procedure to prepare the first metal-stabilized o-quinone methide.

  18. SYNTHESIS AND CHARACTERIZATION OF SMART FUNCTIONAL COATINGS BY CHEMICAL SOLUTION DEPOSITION METHODS

    SciTech Connect

    Mendez-Torres, A.

    2011-07-19

    New coating technology enables the fabrication of low cost structural health monitoring (SHM) and tamper indication devices that can be employed to strengthen national and international safeguards objectives. In particular, such innovations could serve the safeguards community by improving both the timeliness of detection and confidence in verification and monitoring. This work investigates the synthesis of functional surface coatings using chemical solutions deposition methods. Chemical solution deposition has recently received attention in the materials research community due to its unique advantages such as low temperature processing, high homogeneity of final products and the ability to fabricate materials with controlled surface properties and pore structures. The synthesis of functional coatings aimed at modifying the materials conductivity and optical properties was investigated by the incorporation of transition element (e.g. Cr{sup +3}) and rare earth (e.g. Er{sup +3}) serving as dopants in a polymer or gel matrix. The structural and morphological investigation of the as-deposited films was carried out using UV/Vis and photoluminescence (PL) spectroscopy. The as deposited coating was further investigated by scanning electron microscopy and energy dispersive x-ray microscopy.

  19. Synthesis and characterization of cysteine functionalized silver nanoparticles for biomolecule immobilization.

    PubMed

    Upadhyay, Lata Sheo Bachan; Verma, Nishant

    2014-11-01

    A facile method for the aqueous phase synthesis of cysteine-functionalized silver nanoparticles by potato extract has been reported in the present work. These functionalized nanoparticles were then used for the covalent immobilization of a biomolecule, alkaline phosphatase, on its surface through carbodiimide coupling. Different reaction parameters such as cysteine concentration, reducing agent concentration, temperature, pH and reaction time were varied during the nanoparticles' formation, and their effects on plasmon resonance were studied using Ultraviolet-visible spectroscopy. Fourier transform infrared spectroscopy was used to confirm the surface modification of silver nanoparticles by cysteine and the particle size analysis was done using particle size analyzer, which showed the average nanoparticles' size of 61 nm for bare silver nanoparticles and 201 nm for the enzyme-immobilized nanoparticles. The synthesized nanoparticles were found to be highly efficient for the covalent immobilization of alkaline phosphatase on its surface and retained 67% of its initial enzyme activity (9.44 U/mg), with 75% binding efficiency. The shelf life of the enzyme-nanoparticle bioconjugates was found to be 60 days, with a 12% loss in the initial enzyme activity. With a simple synthesis strategy, high immobilization efficiency and enhanced stability, these enzyme-coated nanoparticles have the potential for further integration into the biosensor technology. PMID:24760173

  20. Room-temperature solution synthesis of Ag nanoparticle functionalized molybdenum oxide nanowires and their catalytic applications

    NASA Astrophysics Data System (ADS)

    Dong, Wenjun; Huang, Huandi; Zhu, Yanjun; Li, Xiaoyun; Wang, Xuebin; Li, Chaorong; Chen, Benyong; Wang, Ge; Shi, Zhan

    2012-10-01

    A simple chemical solution route for the synthesis of large-scale high-quality Ag nanoparticle functionalized molybdenum oxide nanowire at room temperature has been developed. In the synthesis, the protonated amine was intercalated into the molybdenum bronze layers to reduce the electrostatic force of the lamellar structures, and then the Ag nanoparticle functionalized long nanowires could be easily induced by a redox reaction between a molybdenum oxide-amine intermediate and Ag+ at room temperature. The intercalation lamellar structures improved the nucleation and growth of the Ag nanoparticles, with the result that uniform Ag nanoparticles occurred on the surface of the MoO3 nanowire. In this way Ag nanoparticles with average sizes of around 6 nm, and high-purity nanowires with mean diameter of around 50 nm and with typical lengths of several tens to hundreds of micrometers were produced. The heteronanostructured nanowires were intricately and inseparably connected to each other with hydrogen bonds and/or bridge oxygen atoms and packed together, forming a paper-like porous network film. The Ag-MoO3 nanowire film performs a promoted catalytic property for the epoxidation of cis-cyclooctene, and the heteronanostructured nanowire film sensor shows excellent sensing performance to hydrogen and oxygen at room temperature.