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High Reactivity (high + reactivity)
Selected AbstractsNew Iron(II) Complexes for Atom-Transfer Radical Polymerization: The Ligand Design for Triazacyclononane Results in High Reactivity and Catalyst PerformanceADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Mitsunobu Kawamura Abstract Mononuclear cordinatively unsaturated iron(II) complexes having a triazacyclononane ligand were developed as highly efficient and environmentally friendly catalysts for the atom-transfer radical polymerization (ATRP). These iron catalysts showed high performance in the well-controlled ATRP of styrene, methacrylates, and acrylates. The high reactivity of these catalysts led to well-controlled polymerization and block copolymerization even with lower catalyst concentrations. [source] ChemInform Abstract: Bis-Carbene Adducts of Non-IPR La2@C72: Localization of High Reactivity Around Fused Pentagons and Electrochemical Properties.CHEMINFORM, Issue 2 2009Takeshi Akasaka Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] A General Approach to the Synthesis of ,2 -Amino Acid Derivatives via Highly Efficient Catalytic Asymmetric Hydrogenation of ,-AminomethylacrylatesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Yujuan Guo Abstract A new strategy was developed for the synthesis of a valuable class of ,-aminomethylacrylates via the Baylis,Hillman reaction of different aldehydes with methyl acrylate followed by acetylation of the resulting allylic alcohols and SN2,-type amination of the allylic acetates. Asymmetric hydrogenation of these diverse olefinic precursors using rhodium(Et-Duphos) catalysts provided the corresponding ,2 -amino acid derivatives with excellent enantioselectivities and exceedingly high reactivities (up to >99.5% ee and S/C=10,000). The first hydrogenation of (Z)-configurated substrates was studied for the synthesis of ,2 -amino acid derivatives. The high influence of the substrate geometry and steric hindrance on the reactivity and enantioselectivity was also disclosed for this reaction. This protocol provides a highly practical, facile and scalable method for the preparation of optically pure ,2 -amino acids and their derivatives under mild reaction conditions. [source] Influence of the starting powders on the synthesis of nickel ferriteCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2006F. Kenfack Abstract The thermal decomposition of freeze-dried nickel(II)-iron(III) formate was investigated by means of DTA, TG, mass spectrometry and X-ray powder diffractometry. For the preparation of homogeneous freeze-dried nickel(II)-iron(III) formate precursors, a rigorous control of nickel ion concentration in the precursor solution was required. The decomposition of the reactive nickel(II)-iron(III) formate does not only reflect aspects of single formates, but also an interaction between components which lowers the decomposition temperature. Crystalline nickel ferrite powders were obtained at 600-800°C. This temperature is quite lower than 1100°C employed for the ceramic method. In the presence of air, the regeneration of nickel ferrite from the taenite phase (,Ni,Fe) is accomplished at 800°C. This temperature is also 300°C below the temperature employed when the mixtures NiO:,-Fe2O3 or Ni:2Fe are the starting powders. The main reason for the high reactivity of the freeze-dried formates and the taenite alloy is the large homogeneity of these precursors. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and characterization of compounds LixMn1+xFe2,2xO4 with spinel structure in the quasiternary system "LiO0,5 , MnOx , FeOx"CRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2006C. Wende Abstract The thermal decomposition of freeze-dried Li-Mn(II)-Fe(III)-formate precursors was investigated by means of DTA, TG and mass spectroscopy. By the thermal treatment of the prefired precursors between 400 and 1000°C, single phase solid solutions LixMn1+xFe2,2xO4 (0 , x , 1) with cubic spinel structure were obtained. To get single phase spinels, special conditions concerning the temperature T and the oxygen partial pressure p(O2) during the synthesis are required. Because of the high reactivity of the freeze-dried precursors, in comparison with the conventional solid state reaction, the reaction temperature can be lowered by 200°C. The cation distribution and the properties of the Li-Mn-ferrites were studied by chemical analysis, X-ray powder diffraction and magnetization measurements. It was found that for high substitution rates, almost all lithium occupies the tetrahedral coordinated A-sites of the spinel lattice AB2O4, while at small x-values, lithium ions are distributed over the tetrahedral and octahedral sites. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fructose-mediated non-enzymatic glycation: sweet coupling or bad modificationDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 5 2004Casper G. Schalkwijk Abstract The Maillard reaction is a process in which reducing sugars react spontaneously with amino groups in proteins to advanced glycation endproducts (AGEs). Although an elevated level of glucose had been thought to play a primary role in the Maillard reaction, on a molecular basis, glucose is among the least reactive sugars within biological systems. The formation of AGEs is now also known to result from the action of various metabolites other than glucose, which are primarily located intracellularly and participate in the non-enzymatic glycation reaction at a much faster rate, such as fructose, trioses and dicarbonyl compounds. In this review, we considered the glycation reaction with particular attention to the potential role of fructose and fructose metabolites. The two sources for fructose are an exogenous supply from the diet and the endogenous formation from glucose through the aldose reductase pathway. Despite its ,eightfold higher reactivity, the contribution of extracellular glycation by fructose is considerably less than that by glucose, because of the low plasma concentration of fructose (5 mmol/L glucose vs 35 µmol/L fructose). Intracellularly, fructose is elevated in a number of tissues of diabetic patients in which the polyol pathway is active. In the cells of these tissues, the concentrations of fructose and glucose are of the same magnitude. Although direct evidence is not yet available, it is likely that the high reactivity of fructose and its metabolites may substantially contribute to the formation of intracellular AGEs and may contribute to alterations of cellular proteins, dysfunction of cells and, subsequently, to vascular complications. Copyright © 2004 John Wiley & Sons, Ltd. [source] Chiral Primary Amine,Polyoxometalate Acid Hybrids as Asymmetric Recoverable Iminium-Based CatalystsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 26 2009Jiuyuan Li Abstract A new strategy for the immobilization of iminium organocatalysts through the acid,base assembly of multidentate chiral primary amines and solid polyacids is presented. A suitable structurally distinctive C2 -symmetric chiral primary amine (CPA) was identified in this study and the optimal CPA,POM hybrid obtained catalyzed the Diels,Alder cycloaddition of ,-substituted acroleins in high yields and fair-to-high selectivity under aqueous conditions. The primary amine in the metal,organic-framework (MOF)-like catalyst acted as the catalytic center as well as multidentate basic centers, whereas phosphotungstic acid played dual roles as both catalyst anchors and modulators of the activity and stereoselectivity. Furthermore, the MOF-like catalyst showed both high reactivity and physical stability and thus could be recycled and reused six times with only a small loss of activity and selectivity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Discontented people: reactivity and locus of control as determinants of subjective well-beingEUROPEAN JOURNAL OF PERSONALITY, Issue 1 2001Tatiana Klonowicz This study examines the effects of reactivity temperament and locus of control variables on subjective well-being (SWB). SWB is operationalized as positive affect, the absence of somatic concerns, and heightened life satisfaction. The study hypotheses were that (1) reactivity and locus of control influenced SWB and that (2) affect either mediated or moderated the influence of these traits on SWB. As expected, high reactivity and external locus of control were associated with lower SWB, whereas low reactivity and internal locus of control were associated with higher SWB. However, the data indicate that reactivity and locus of control influenced different components of SWB and that locus of control predicted SWB more consistently than reactivity. Somatic health is influenced by reactivity, locus of control and negative affect, but not positive affect. Current life satisfaction is influenced by locus of control,but not reactivity,and by both positive and negative affect. Hope is related to reactivity but not to either locus of control or affect. The data corroborate the expectation that affect serves as a mediator in the trait,SWB relations, whereas the view that affect moderates the effect of stable dispositions on SWB finds scant support. Copyright © 2001 John Wiley & Sons, Ltd. [source] Development of recombinant inhibitors specific to human kallikrein 2 using phage-display selected substratesFEBS JOURNAL, Issue 3 2004Sylvain M. Cloutier The reactive site loop of serpins undoubtedly defines in part their ability to inhibit a particular enzyme. Exchanges in the reactive loop of serpins might reassign the targets and modify the serpin,protease interaction kinetics. Based on this concept, we have developed a procedure to change the specificity of known serpins. First, reactive loops are very good substrates for the target enzymes. Therefore, we have used the phage-display technology to select from a pentapeptide phage library the best substrates for the human prostate kallikrein hK2 [Cloutier, S.M., Chagas, J.R., Mach, J.P., Gygi, C.M., Leisinger, H.J. & Deperthes, D. (2002) Eur. J. Biochem. 269, 2747,2754]. Selected substrates were then transplanted into the reactive site loop of ,1-antichymotrypsin to generate new variants of this serpin, able to inhibit the serine protease. Thus, we have developed some highly specific ,1-antichymotrypsin variants toward human kallikrein 2 which also show high reactivity. These inhibitors might be useful to help elucidate the importance of hK2 in prostate cancer progression. [source] Effects of aluminum on activity of Krebs cycle enzymes and glutamate dehydrogenase in rat brain homogenateFEBS JOURNAL, Issue 10 2000P. Zatta Aluminum is a neurotoxic agent for animals and humans that has been implicated as an etiological factor in several neurodegenerative diseases and as a destabilizer of cell membranes. Due to its high reactivity, Al3+ is able to interfere with several biological functions, including enzymatic activities in key metabolic pathways. In this paper we report that, among the enzymes that constitute the Krebs cycle, only two are activated by aluminum: ,-ketoglutarate dehydrogenase and succinate dehydrogenase. In contrast, aconitase, shows decreased activity in the presence of the metal ion. Al3+ also inhibits glutamate dehydrogenase, an allosteric enzyme that is closely linked to the Krebs cycle. A possible correlation between aluminum, the Krebs cycle and aging processes is discussed. [source] Sensing of Alkylating Agents Using Organic Field-Effect TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Yair Gannot Abstract Alkylating agents are simple and reactive molecules that are commonly used in many and diverse fields, such as organic synthesis, medicine, and agriculture. Some highly reactive alkylating species are also being used as blister chemical warfare agents. The detection and identification of alkylating agent is not a trivial issue because of their high reactivity and simple structure. Here, a novel polythiophene derivative that is capable of reacting with alkylating agents is reported, along with its application in direct electrical sensing of alkylators using an organic field-effect transistor, OFET, device. Upon reacting with alkylators, the OFET containing the new polythiophene analogue as its channel becomes conductive, and the gate effect is lost; this is in marked contrast to the response of the OFET to "innocent" vapors, such as alcohols and acetone. By following the drain,source current under gate bias, one can easily follow the processes of absorption of the analyte to the polythiophene channel and their subsequent reaction. [source] Magnetic Multi-Functional Nano Composites for Environmental ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Jie Dong Abstract A novel concept is proposed to synthesize a new class of composites featuring magnetic, molecular sieve and metallic nanoparticle properties. These multi-functional materials have potential applications as recyclable catalysts, disinfectants and sorbents. The magnetic property enables effective separation of the spent composites from complex multiphase systems for regeneration and recycle, safe disposal of the waste and/or recovery of loaded valuable species. The zeolite molecular sieve provides a matrix which supports a remarkably new, simple, efficient and economical method to make stable, supported silver nanoparticles by silver ion exchange and controlled thermal reduction. The silver nanoparticles generated in this way have excellent properties such as high reactivity and good thermal stability without aggregation, which act as nano reactors for desired functionality in a wide range of applications. Magnetic component (Fe3O4), molecular sieve matrix (zeolite) and silver nanoparticles generated by ion exchange followed by controlled reduction, together form this unique novel composite with designed functions. It represents a practically operational, economical, sustainable and environmentally friendly new advanced functional material. This paper focuses on the novel synthesis and characterization of the composite, with an example of applications as sorbents for the removal of vapor-phase mercury from the flue gas of coal-fired power plants. [source] On the Enantioselectivity of Transition Metal-Catalyzed 1,3-Cycloadditions of 2-Diazocyclohexane-1,3-dionesHELVETICA CHIMICA ACTA, Issue 9 2003Paul Müller The formal 1,3-cycloaddition of 2-diazocyclohexane-1,3-diones 1a,1d to acyclic and cyclic enol ethers in the presence of RhII -catalysts to afford dihydrofurans has been investigated. Reaction with a cis/trans mixture of 1-ethoxyprop-1-ene (13a) yielded the dihydrofuran 14a with a cis/trans ratio of 85,:,15, while that with (Z)-1-ethoxy-3,3,3-trifluoroprop-1-ene (13b) gave the cis -product 14b exclusively. The stereochemical outcome of the reaction is consistent with a concerted rather than stepwise mechanism for cycloaddition. The asymmetric cycloaddition of 2-diazocyclohexane-1,3-dione (1a) or 2-diazodimedone (=2-diazo-5,5-dimethylcyclohexane-1,3-dione; 1b) to furan and dihydrofuran was investigated with a representative selection of chiral, nonracemic RhII catalysts, but no significant enantioselectivity was observed, and the reported enantioselective cycloadditions of these diazo compounds could not be reproduced. The absence of enantioselectivity in the cycloadditions of 2-diazocyclohexane-1,3-diones is tentatively explained in terms of the Hammond postulate. The transition state for the cycloaddition occurs early on the reaction coordinate owing to the high reactivity of the intermediate metallocarbene. An early transition state is associated with low selectivity. In contrast, the transition state for transfer of stabilized metallocarbenes occurs later, and the reactions exhibit higher selectivity. [source] Infiltration pattern in a regolith,fractured bedrock profile: field observation of a dye stain patternHYDROLOGICAL PROCESSES, Issue 2 2006Jae Gon Kim Abstract We examined the infiltration pattern of water in a regolith,bedrock profile consisting of two overburdens (OB1 and OB2), a buried rice paddy soil (PS), two texturally distinctive weathered materials (WM1 and WM2) and a fractured sedimentary rock (BR), using a Brilliant Blue FCF dye tracer. A black-coloured coating in conducting fractures in WM1, WM2 and BR was analysed by X-ray diffraction and scanning electron microscopy. The dye tracer penetrated to greater than 2 m depth in the profile. The macropore flow and saturated interflow were the major infiltration patterns in the profile. Macropore flow and saturated interflow were observed along fractures in WM1, WM2 and BR and at the dipping interfaces of PS,WM1, PS,WM2 and PS,BR respectively. Heterogeneous matrix flow occurred in upper overburden (OB1) and PS. Compared with OB1, the coarser textured OB2 acted as a physical barrier for vertical flow of water. The PS with low bulk density and many fine roots was another major conducting route of water in the profile. Manganese oxide and iron oxide were positively identified in the black coating material and had low crystallinity and high surface area, indicating their high reactivity with conducting contaminants. Copyright © 2006 John Wiley & Sons, Ltd. [source] The role of chlorine atoms and hydroxyl radicals in the formation of PCDDs from the oxidative pyrolysis of 2,4,6-trichlorophenolINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2010Lavrent Khachatryan A 132-step gas-phase reaction kinetic model has been combined with a four-step surface model for the formation of 1,3,6,8-tetrachlorodibenzo- p -dioxin (1,3,6,8-TCDD) from the oxidation of 2,4,6-trichlorophenol (2,4,6-TCP) in the presence of hexane. The revised model is based on a simpler model previously published in the literature and modified by adding Cl-releasing and the surface submodels, recalculating polynomial functions for thermodynamic parameters, and updating gas-phase submodels for (i) 1,3,6,8-TCDD formation, (ii) hydrogen oxidation, and (iii) hexane oxidation. The roles of the potential chain carriers, OH and Cl, in the formation of 1,3,6,8-TCDD were specifically addressed. In spite of the reported high reactivity of Cl, it was found that OH:Cl , 1, and OH is the dominant chain carrier from the apparent onset of purely gas-phase reactions at 750 K to 99% conversion of 2,4,6-TCP and hexane at 1075 K. This suggests that oxidation reactions are always dominant in realistic combustion systems, even where there are high concentrations of chlorine and relatively rich burning conditions. The update of the three gas-phase submodels as well as incorporation of Cl-releasing and the surface submodels resulted in improved agreement between calculated and experimental yields of 1,3,6,8-TCDD yields at temperatures as low as 800 K. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 90,97, 2010 [source] Highly Enantioselective Hydrogenation of Quinoline and Pyridine Derivatives with Iridium-(P-Phos) CatalystADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010Wei-Jun Tang Abstract The use of a chiral iridium catalyst generated in situ from the (cyclooctadiene)iridium chloride dimer, [Ir(COD)Cl]2, the P-Phos ligand [4,4,-bis(diphenylphosphino)-2,2,,6,6,-tetramethoxy-3,3,-bipyridine] and iodine (I2) for the asymmetric hydrogenation of 2,6-substituted quinolines and trisubstituted pyridines [2-substituted 7,8-dihydroquinolin-5(6H)-one derivatives] is reported. The catalyst worked efficiently to hydrogenate a series of quinoline derivatives to provide chiral 1,2,3,4-tetrahydroquinolines in high yields and up to 96% ee. The hydrogenation was carried out at high S/C (substrate to catalyst) ratios of 2000,50000, reaching up to 4000,h,1 TOF (turnover frequency) and up to 43000 TON (turnover number). The catalytic activity is found to be additive-controlled. At low catalyst loadings, decreasing the amount of additive I2 was necessary to maintain the good conversion. The same catalyst system could also enantioselectively hydrogenate trisubstituted pyridines, affording the chiral hexahydroquinolinone derivatives in nearly quantitative yields and up to 99% ee. Interestingly, increasing the amount of I2 favored high reactivity and enantioselectivity in this case. The high efficacy and enantioselectivity enable the present catalyst system of high practical potential. [source] Silver Acetate/TF-BiphamPhos-Catalyzed endo -Selective Enantioselective 1,3-Dipolar Cycloaddition of Azomethine Ylides with Vinyl Phenyl SulfoneADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Gang Liang Abstract The first catalytic endo -selective 1,3-dipolar cycloaddition of azomethine ylides and vinyl phenyl sulfone has been developed successfully. The highly efficient silver acetate (AgOAc)/TF-BiphamPhos catalytic system exhibited high reactivity, excellent diastereoselectivity (>98:2), good enantioselectivity (67,92% ee) and broad substrate scope under mild conditions. [source] Homogeneous Hydrogenation of Tri- and Tetrasubstituted Olefins: Comparison of Iridium-Phospinooxazoline [Ir-PHOX] Complexes and Crabtree Catalysts with Hexafluorophosphate (PF6) and Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF) as CounterionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2008Bettina Wüstenberg Abstract Four iridium complexes with achiral phosphino-oxazoline (PHOX) ligands were readily prepared in two steps starting from commercially available phenyloxazolines. The air-stable complexes with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF) as counterion showed high reactivity in the hydrogenation of a range of tri- and tetrasubstituted olefins. The best results were obtained with an iridium complex (11) derived from a dicyclohexylphosphino-oxazoline ligand bearing no additional substituents in the oxazoline ring. With several substrates, which gave only low conversion with the Crabtree catalyst, [Ir(Py)(PCy3)(COD)]PF6, full conversion was observed. The productivity of the Crabtree catalyst could be strongly increased by replacing the hexafluorophosphate anion with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. In one case, in the hydrogenation of a tetraalkyl-substituted CC bond, [Ir(Py)(PCy3)(COD)]BArF gave higher conversion than catalyst 11. However, with several other substrates complex 11 proved to be superior. [source] Synthesis and characterization of high thermally-stable and good soluble PVK-based polymers with perylene moietyJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Jianli Hua Abstract Three new poly(N -vinylcarbazole) (PVK)-based copolymers containing N -(n -butyl)- N -ethyl-1,6,7,12-tetra-(4- tert -butyl-phenoxy)-3,4,9,10-perylene tetracarboxylic bisimides were successfully synthesized by partially formylated by the standard Vilsmeier reaction, and the formyl groups of high reactivity are condensed with cyanoacetylated perylene to afford PVK-based polymers. The copolymers containing different percentage of perylene were obtained through the percentage of cyanoacetylated perylene unit being controlled by the initial feed ratio. The structures and properties of three copolymers were characterized and evaluated by FT-IR, NMR, UV,vis, FL spectroscopy, gel permeation chromatography, and thermogravimetric analysis measurements. The polymers were highly soluble in conventional solvents such as toluene, CHCl3, THF, DMF etc., and they were thermally stable up to 442,445°C. Three copolymers have emission spectra with characteristic features of the perylene unit, and fluorescence quantum yields of polymers are higher than that of perylene bisimide, which may be caused by singlet,singlet energy transfer from PVK backbone to perylene in the polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Using anionic polymerizable surfactants in ultrasonically irradiated emulsion polymerization to prepare polymer nanoparticlesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Yuhui He Abstract An ionic polymerizable surfactant, sodium sulfopropyl-laurylmaleate (M12), was synthesized and used as an emulsifier, an initiator, and a comonomer in ultrasonically irradiated emulsion polymerization. FTIR spectra and gravimetric method results indicated that copolymers P(Styrene-M12) and P(Butylacrlate-M12) were prepared successfully by ultrasonically irradiated emulsion polymerization and the composition of M12 elevated with the increasing concentration of M12 added. TEM photographs of P(St-M12) showed that the nanoparticles with small diameters (20,45 nm) were prepared. With the increase of M12 concentration, the particle size became smaller and the size distribution became wider. The P(BA-M12) particles size was also small (<100 nm) but the size distribution was wide due to the high reactivity of BA. Because surfmer M12 was chemically bonded with the latex particles, the stability of the copolymer latex prepared by ultrasonically irradiated emulsion polymerization was much better than that of the homopolymer latex (PSt or PBA) prepared by the same way. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Upregulation of genes orchestrating keratinocyte differentiation, including the novel marker gene ID2, by contact sensitizers in human bulge-derived keratinocytesJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 1 2010Yoshie Yoshikawa Abstract In the epidermis, keratinocytes are involved in physical and first-line immune protection of the host. In this study, we analyzed the molecular responses to certain contact sensitizers (2,4-dinitrochlorobenzene and NiSO4) and irritants (sodium dodecyl sulfate and benzalkonium chloride) in cultured human keratinocytes from the bulge region of a plucked hair follicle (bulge-derived keratinocytes [BDKs]) and compared these molecular responses to those with the human monocytic leukemia cell line, THP-1. The BDKs, individually established without invasive biopsies, showed high reactivity to these stimulants. As a primary response to the contact sensitizers, the NRF2-mediated signaling pathway was upregulated in BDKs and THP-1. The expression of IL1B and IL8 genes was not induced by the irritants but by the sensitizers in THP-1. However, the expression of the IL1B and IL8 genes was induced at higher levels by the irritants in BDKs than by the sensitizers. Many genes orchestrating keratinocyte differentiation, including ID2, were significantly upregulated in response to the sensitizers in BDKs but not those in THP-1. The use of the ID2 gene to discriminate between sensitizers and irritants might be effective as a novel marker for application during in vitro sensitization with BDKs. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 24:10,20, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20307 [source] Activation barriers for DNA alkylation by carcinogenic methane diazonium ionsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2006Kaushalya S. Ekanayake Abstract Methylation reactions of the DNA bases with the methane diazonium ion, which is the reactive intermediate formed from several carcinogenic methylating agents, were examined. The SN2 transition states of the methylation reactions at N7, N3, and O6 of guanine; N7, N3, and N1 of adenine; N3 and O2 of cytosine; and O2 and O4 of thymine were calculated using the B3LYP density functional method. Solvation effects were examined using the conductor-like polarizable continuum method and the combined discrete/SCRF method. The transition states for reactions at guanine N3, adenine N7, and adenine N1 are influenced by steric interactions between the methane diazonium ion and exocyclic amino groups. Both in the gas phase and in aqueous solution, the methylation reactions at N atoms have transition states that are looser, and generally occur earlier along the reaction pathways than reactions at O atoms. The forming bonds in the transition states in water are 0.03 to 0.13 Å shorter than those observed in the gas phase, and the activation energies are 13 to 35 kcal/mol higher. The combined discrete/SCRF solvation energy calculations using base-water complexes with three water molecules yield base solvation energies that are larger than those obtained from the CPCM continuum method, especially for cytosine. Reactivities calculated using barriers obtained with the discrete/SCRF method are consistent with the experimentally observed high reactivity at N7 of guanine. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 277,286, 2006 [source] Synthesis of new 1,2,3-triazolo[1,5-a]quinazolinonesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2010Nazariy T. Pokhodylo Synthesis of novel 3-substituted-1,2,3-triazolo[1,5-a]quinazolinones in high yields was performed via anionic hetero-domino reaction of appropriate substituted 2-azidobenzoates prepared from isatines and acetonitriles activated by 1,3-thiazole, 1,3-benzothiazole, 1,3,4-oxadiazole, and 1,2,4-oxadiazole rings. It was shown that acetonitriles exhibited high reactivity and were convenient methylenic compounds for such reactions providing rapid structural variation. J. Heterocyclic Chem., (2010). [source] Radiosyntheses and reactivities of novel [18F]2-fluoroethyl arylsulfonatesJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 10 2005John L. Musachio Abstract [18F]2-Fluoroethyl tosylate ([18F]FEOX, X=Ts) is widely used for labeling radiotracers for positron emission tomography (PET). Little work has been reported on syntheses of other [18F]2-fluoroethyl arylsulfonates ([18F]FEOX) that bear a less electron-rich aryl group, even though these might offer enhanced reactivities. Thus, a series of novel [18F]FEOX (X=benzenesulfonyl, brosyl, nosyl, 3,4-dibromobenzenesulfonyl) were synthesized and reactivities compared to [18F]FEOTs. Precursors for radiolabeling (bis -ethylene glycol arylsulfonates) and reference FEOX were synthesized (alcohol+arylsulfonyl chloride+KOSiMe3 in THF). Regardless of substitution pattern, [18F]FEOX (110°C, 5 min, acetonitrile) were obtained in similar decay-corrected isolated radiochemical yields (RCY; 47,53%). All [18F]FEOX gave excellent RCYs (64,87%) of the dopamine uptake radioligand, [18F]FECNT (130°C, 10 min, acetonitrile). The 3,4-dibromobenzensulfonate gave the highest RCY of [18F]FECNT (87%) and this HPLC-purified labeling agent was used directly for efficient [18F]FECNT production. When the secondary aniline of an amyloid probe (HM-IMPY) or p -nitrophenol was reacted with [18F]FEOX, RCYs were appreciably higher for brosylate and nosylate than for tosylate, while 3,4-dibromobenzenesulfonate again gave the highest RCY. Owing to the high reactivity of the new [18F]FEOX and their ease of syntheses via stable precursors, such agents (particularly 3,4-dibromobenzenesulfonate) should be considered as alternatives to [18F]FEOTs. Copyright © 2005 John Wiley & Sons, Ltd. [source] Formation and photodissociation of M+,C6H6 (M+ = V+ and Ta+) and Ta+,C6H4 complexes in a time-of-flight mass spectrometerJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2001Hsiu-Fang Lee Abstract A series of cyclic hydrocarbons were introduced to react with V+ and Ta+ using a pulsed beam expansion source in a time-of-flight mass spectrometer. The third-row metal Ta+ displayed high reactivity in dehydrogenation to form benzyne complexes, whereas benzene complexes were the terminal products for V+. M+,C6H6 (M+ = V+ and Ta+) and Ta+,C6H4 were selected to perform the photodissociation experiments. In contrast to the V+ fragment formation via simple cleavage of the V+,C6H6 bond, a photoinduced loss of C2H2 occurred in both the Ta+,C6H6 and Ta+,C6H4 complexes. Plausible explanations involved in the formation of Ta+,C6H6 and Ta+,C6H4 complexes are given for observing such photo-induced dissociation. The observed photodissociation in Ta+,C6H6 is analogous to the dissociative process previously investigated in metal ion,molecule reactions. The photodissociation spectrum of Ta+,C6H4 was obtained by recording the appearance of Ta+,C4H2 as a function of wavelength and yielded a dissociation energy of 91 ± 1 kcal mol,1. Copyright © 2001 John Wiley & Sons, Ltd. [source] Atom transfer radical polymerization and copolymerization of vinyl acetate catalyzed by copper halide/terpyridineAICHE JOURNAL, Issue 3 2009Huadong Tang Abstract Copper-mediated atom transfer radical polymerization (ATRP) is versatile for living polymerizations of a wide range of monomers, but ATRP of vinyl acetate (VAc) remains challenging due to the low homolytic cleavage activity of the carbon-halide bond of the dormant poly(vinyl acetate) (PVAc) chains and the high reactivity of growing PVAc radicals. Therefore, all the reported highly active copper-based catalysts are inactive in ATRP of VAc. Herein, we report the first copper-catalyst mediated ATRP of VAc using CuBr/2,2,:6,,2,-terpyridine (tPy) or CuCl/tPy as catalysts. The polymerization was a first order reaction with respect to the monomer concentration. The molecular weights of the resulting PVAc linearly increased with the VAc conversion. The living character was further proven by self-chain extension of PVAc. Using polystyrene (PS) as a macroinitiator, a well-defined diblock copolymer PS-b-PVAc was prepared. Hydrolysis of the PS-b-PVAc produced a PS-b-poly(vinyl alcohol) amphiphilic diblock copolymer. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Copolymerization of norbornene and styrene catalyzed by a novel anilido,imino nickel complex/methylaluminoxane systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2006Haiyang Gao Abstract Copolymerizations of norbornene with styrene were carried out with a catalytic system of anilido,imino nickel complex (ArNCHC6H4NAr)NiBr (Ar = 2,6-dimethylphenyl) and methylaluminoxane in toluene. The influence of the comonomer feed content and polymerization temperature on the conversion and composition of the copolymers with (ArNCHC6H4NAr)NiBr/methylaluminoxane was investigated. An increase in the initial styrene feed content led to an increase in the incorporated styrene content of the resulting copolymer. The determination of the reactivity ratios showed a much high reactivity for norbornene (reactivity ratio for styrene = 0.26, reactivity ratio for norbornene = 20.78), which was consistent with a coordination mechanism. NMR analysis of the end groups further confirmed that the chain was initiated through a styrene secondary insertion or a norbornene insertion into NiH and terminated through ,-H elimination from an inserted styrene unit. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5237,5246, 2006 [source] Synthesis and second-order nonlinear optical properties of multifunctional polysiloxanes with sulfonyl-based chromophoresJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2005Jianli Hua Abstract Two new polysiloxanes (P1 and P2) with a high density of sulfonyl-based chromophores were prepared by a new two-step method. Poly[methyl-3-(9-carbazolyl)propyl siloxane] was partially formulated by the standard Vilsmeier reaction, and formyl groups of high reactivity were condensed with cyanoacetylated chromophores; this yielded polysiloxanes P1 and P2 in almost complete conversions. Their structures were verified with 1H NMR, IR, and ultraviolet,visible spectra. P1 and P2 exhibited good solubility in common organic solvents and were thermally stable. The maximum absorptions appeared at about 452 and 390 nm for P1 and P2, respectively, in tetrahydrofuran; they were blueshifted about 42 and 8 nm, respectively, in comparison with those of the corresponding chromophores with a nitro acceptor and resulted in a wider transparency window. The P1 values of the nonlinear optical coefficient (d33), measured by in situ second harmonic generation, was 16.2 pm/V. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1317,1324, 2005 [source] Mechanical Activation of Tetracalcium PhosphateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2004Uwe Gbureck It was found that prolonged high-energy ball-milling of Hilgenstokite (tetracalcium phosphate, TTCP) resulted in a decrease in both particle and crystallite size, leading to a mechanical activation of the compound. This mechanically activated material demonstrated a high reactivity such that, in contrast to highly crystalline TTCP, a setting reaction with water to nanocrystalline hydroxyapatite (HA) and Ca(OH)2 could be achieved at 37°C. However, crystalline TTCP is practically unreactive at physiologic temperatures because of the formation of a thin HA layer on the particle surface preventing further reaction. [source] Cardiac Troponin I in Pastured and Race-Training Thoroughbred HorsesJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 4 2003Wade Phillips Cardiac troponin I (cTnI), a myocardial polypeptide, is a highly sensitive and specific biomarker of myocardial injury in people and dogs. The structure of cTnI is highly conserved across species, and equine myocardium has high reactivity with human immunoassays. The purpose of this study was to describe cTnI concentrations in normal pastured and race-training Thoroughbred horses. Ten horses on pasture and 10 horses in race training were studied. Horses were considered normal on the basis of physical examination, training performance, electrocardiography (ECG), and echocardiography. Serum cTnI concentrations were determined with a colorimetric immunoassay. The assay has an analytical sensitivity of 0.04 ng/mL. Serum cTnI concentrations in race-training horses were not significantly different from those of pastured horses. When groups were combined, mean cTnI concentration (±SD) was 0.047 ± 0.085 ng/mL, and the median was 0 (range, 0-0.35 ng/mL). The 90th percentile for both groups combined was 0.11 ng/mL. This study establishes a preliminary reference range for serum cTnI in normal Thoroughbred horses. Key words: Cardiac disease; Cardiac markers; Creatine kinase; Myocarditis. [source] | ||||||||||||||||||||||||||||||||||||||||